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Chuck Landon: Traditional relations with OU changing
Pardon me for asking, but. ...
Is anybody hearing that Ohio University is dropping the basketball series with Marshall?
The rumors are true.
"They just said their schedule wouldn't allow us to play this coming year," said Marshall athletic director Mike Hamrick.
So, what gives? Why would a nearby rival drop a school it has played 100 times since 1954?
According to sources, the Bobcats offered the lame excuse that they ran out of room for another road game.
I call hogwash on that.
The crux of the matter is Ohio owed Marshall a game in Huntington after beating the Herd, 94-57, in Athens, Ohio, last season. But, now, the Bobcats are bailing on that obligation.
It sounds suspiciously like Ohio is blaming its non-conference schedule for not getting an at-large bid to the 2012 NCAA Tournament. And, of course, the Bobcats see Marshall and its 13-19 record as one of the culprits.
That leads to the real question in this controversy. Namely, is this a one-year hiatus or is the Marshall-Ohio basketball series over?
It could be kaput because Marshall's athletic officials definitely aren't happy with Ohio's stance. Nor should they be. This is a long-term rivalry with 100 meetings in basketball and 56 in football.
That's what makes Ohio's decision so unacceptable. I mean, these two schools aren't just casual rivals. But they soon could be.
I believe Marshall should tell Ohio that if the Bobcats aren't going to play the Herd in basketball, then MU is going to drop Ohio in football.
Don't let the door hit you in your stubby tail, Bobcats.
Sure, there are three games still remaining in the Marshall-Ohio football series, including a contest at Ohio at 8 p.m. on Sept. 14. Then, there are games at Marshall in 2014 and at Ohio in 2015.
But after that?
Unless Ohio revives the basketball series in 2014-15, Marshall needs to end this relationship.
What happened in the criminal case against Marshall's Angelo Jean-Louis?
The highly regarded wide receiver, who was arguably the No. 1 recruit in Marshall's 2013 football recruiting class, was arrested in early April. Jean-Louis was charged with three felonies and a misdemeanor for theft of a cell phone, credit card and fraudulent use of the credit card.
But, now, apparently the case has been resolved with Jean-Louis' punishment reduced to community service, according to sources with knowledge of the situation.
The Miami, Fla., native will be sitting out the upcoming football season as an academic non-qualifier.
Is Southern Miss turning into a "One Flew Over the Eagles' Nest" situation?
It seems that way.
New Southern Miss president Rodney Bennett recently chose not to renew the contract of athletic director Jeff Hammond. Why? Mostly, because Bennett appears upset that Southern Miss is still a member of Conference USA.
Golden Eagles' officials seem to believe the school should be competing in the Big 12 or, at least, the American Athletic Conference.
Talk about delusions of grandeur.
Southern Miss is located in only the 90th-ranked television market and all decent-sized airports are at least an hour away. Despite those pertinent problems, Hammond wasn't renewed after only one year on the job.
That means Southern Miss is looking for its third athletic director in 17 months. And it's clear what the new AD's mission will be.
Good luck with that, Cuckoos, oops, I mean, Eagles.
Chuck Landon is a sports columnist for The Herald-Dispatch. Contact him at 304-526-2827 or clandon@herald- dispatch.com.
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our neighborhoods: minneapolis
Thousands of years ago, receeding glaciers created the Great Lakes and Lake Itasca in Minnesota—the source of the Mississippi River.
Minneapolis—a combination of 'mni', Dakota Indian for water, and 'polis', Greek for city—this metropolitan area is not only divided by the river, it's combined with the state capital of Saint Paul giving it its Twin Cities nickname.
Various lakes, ponds, wetlands and rivers make up about six percent of the city, provide a livelihood and recreation for many residents—and in 1855, Henry Wadsworth Longfellow, the author of The Song of Hiawatha, named Hiawatha's wife in honor of the 53' Minnehaha Falls.
Abundant natural resources fueled the growth of Minneapolis—forests supplied wood, the vast landscape supplied wheat and fed livestock, and the great river supplied power to wool, flour, paper and saw mills.
Around the turn of the 20th century, the city saw remarkable growth as it became the world's capital of flour and a key resource for timber. In addition, railroads to Chicago opened in 1867—the year the city was incorporated—and provided easy distribution of these semi-processed raw materials across the country.
German and Scandanavian immigrants adapted comfortably to the climate and job prospects and today their descendants make up over 40% of the population. Its Native American community is also strong as descendants of Chippewa, Sioux and Dakota tribes not only make up sizable portion of the population, their heritage can be seen and felt in many aspects of the city.
During the 1950s and 60s, unfortunately the city's Gateway District was razed—along with many other architectural landmarks—however historic preservation of other buildings followed as a direct result.
And rebuilding has granted exciting opportunities for current architects to create modern works such as the Weisman Art Museum, or WAM. Designed by Frank Gehry it's a teaching museum for the University of Minnesota. The modern works wing of the Walker Art Center—designed by Michael Graves in 2006—is home to 100,000 works of art and the Minneapolis Institute of Arts.
Printing and publishing naturally came to the area as an extension to the paper milling industry and includes Open Book—the largest arts center of its kind in the US.
In other arts-related fields, Prince is not only Minneapolis's most famous musician, but with other local musicians he helped create venues which encourage musical experiences. Local listeners also support three not-for-profit public radio non-profit stations. And a statue of a fictional TV character—played by the real Mary Tyler Moore—commemorates the Emmy Award winning Mary Tyler Moore Show which was based here from 1970-73.
The perfect marriage of the city's strongest interests—the arts and sports—perhaps came about in 2004 when architect and hockey player Frank Gehry designed the World Cup trophy for the NHL.
Before moving to LA, the Minneapolis Lakers became the NBA's first dynasty during the 40s and 50s. In 1961, the Vikings—an NFL expansion team—and the Twins—the relocated Washington Senators—played outdoors in the Metropolitan Stadium until 1982.
Since 1982, the Metrodome is the only stadium in the country to have hosted championship games for football, baseball, and basketball. In addition, concerts, trade shows, community and religious activities are held throughout the year here.
Besides a form of exercise, biking is highly encouraged. Kiosks for bicycle sharing and pedicabs operate downtown thanks to Nice Ride Minnesota. In addition, many former railroad lines within the city have been converted for bicycle and pedestrian use—not to mention roller blading which began here as the Rollerblade company.

subset: commoncrawl


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Status: Six-time world champion boxer and 1992 Olympic gold medalist.
Ht: 5-11 Wt: 154
DOB: February 4, 1973 In: Los Angeles, CA
Childhood Heroes: "Alexis Arguello, Ray Leonard and Julio Cesar Chavez."
Age Started Boxing: "Seven."
Hobbies/Interests: "Golf. One thing about golf, you can never be too good. It's a challenge, the patience, the
frustration. I think golf is tougher than boxing actually."
Nicknames: "Golden Boy and The Hooker – because of my left hook."
Favorite Movies: "Pretty Woman and now, Rocky (6). Rocky was actually a pretty good movie. This last
Rocky movie, I actually enjoyed it. I was pleasantly surprised [smiles]."
Favorite TV Shows: "Favorite TV show, wow. Actually, American Idol. I have to admit I'm a big fan of American Idol [smiles]."
Musical Tastes: "All kinds, techno."
Last Book Read: "Swimming with the Sharks. Business. And The Ring [smiles]."
First Job: "Washing dishes at my aunt's Mexican restaurant (Tina's) in downtown Los Angeles when I was 10."
First Car: "1992 burgundy Camaro Z 28."
Childhood Ambition: "I always wanted to work at McDonalds – the register. And I still thought about doing that, even after I turned professional. To have that feeling of working and getting paid by the week."
Favorite Meal: "Has to be my wife's meatloaf. Amazing meatloaf [smiles]."
Favorite Breakfast Cereal: "Fruity Pebbles."
Favorite Ice Cream Flavor: "French vanilla."
First Boxing Memory: "When I was about seven, I had my first nosebleed. I took my gloves off and started crying. I wanted to get my mother [smiles]. I'll never forget that."
Pre-Fight Feeling: "Oh my, pre-fight feeling is everywhere…butterflies, nervous and anxious."
Greatest Sports Moment: "Olympic gold 1992, by far. That was the best feeling ever."
Most Painful Moment: "Probably the loss to Bernard Hopkins. Not because the body shot hurt or – just that frustration I felt afterwards. The fact that he paralyzed me for 10 seconds, and after 12 seconds I was fine. It's boxing. It's a body shot that was well-located, well-calculated. I mean, I went for history (the unified Middleweight title). I tried to fight the best, the bigger man, and I – at least I tried. I couldn't do it but I tried."
Worst Injury: "Fortunately just bruised around my eye."
Favorite Vacation Spot: "Cancun."
Funny Boxing Memory: "Yeah [laughs], I'm not sure who it was. I was fighting, we were in a clinch and all I hear is this guy just pass gas. And I didn't laugh but inside I was just cracking up and that was pretty funny."
Embarrassing Boxing Memory: "I gotta think about that one. In boxing you mean? (Or something from your life related to boxing or celebrity.) At a celebrity golf tournament in Lake Tahoe I was teeing off and I shanked the ball and hit somebody. And on TV. It's very embarrassing. All big celebrities, you have Jordan playing, everybody playing. And it's actually a serious tournament. And you had a hundred people there and I shank the ball. Luckily it only hit them on the shoulder."
Favorite Athletes To Watch: "Michael Jordan. Tiger Woods. Greg Norman. Jack Nicklaus. Chi Chi Rodriguez. I like that thing he does after he makes a good putt. Roy Jones was awesome to watch. Manny Pacquiao. Sugar Shane Mosley. Bernard Hopkins."
Favorite Fights: "Douglas-Tyson, Pryor-Arguello I and II."
Favorite Non-Boxing Sport To Watch: "Basketball."
Funniest Boxer Encountered: "Felix Savon (the great Cuban Olympic heavyweight champion). He's a funny guy. We were like buddies at the Olympics."
Early Boxing Memory: "I remember winning my first tournament. I had stopped this kid in the first round. I didn't know I'd win a trophy. Then they handed me one. I was like, Gosh, I want another one."
People Qualities Most Admired: "I like to see genuine people. I like to see people who are honest. I like those qualities."


text:
Walk-in health clinic offering a range of services, from immunization to treatment. Site presents service times and health links.
Serves as the main meeting and gathering place on the campus. Provides information about student activities, services, facility hours, and forms.
Focal point for TCU's academic services, facilities, resources, and initiatives. Serves as a comprehensive guide to the university's academic offerings.
Department of Geology and Environmental Sciences facility created to explore new technologies for mapping resources.
Dedicated to providing TCU with various professional and cost-effective solutions for the appropriate integration and use of instructional technologies.
Devoted to studying, preserving, sharing, and commemorating everything Texan.
Information on the center's staff, services, resources, and workshops. With news and contacts.
National research center for addiction treatment studies in communicate and correctional settings.
Research, training, and service facility dedicated to addressing the needs of families with at-risk children.
Site posts updates, resources, schedules, contacts, and links pertinent to the institute.
Support unit for teaching and learning at TCU. Develops and implements learning opportunities and thoughtful discourse on pedagogy and learning.


text:
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Best luck!
Edited by Diagomc, 14 February 2014 - 08:32 PM.


text:
A variable speed wind turbine is disclosed comprising a turbine rotor that drives a doubly-fed induction generator, a matrix converter which converts variable frequency output into constant frequency output, and a control unit and a protection circuit for the matrix converter. Power is circulated in the system allowing for sensorless detection of rotor position and better output ratios of power from the system.
1. A method for operating a variable speed wind turbine comprising:
configuring a generator for connection to a utility grid;
connecting a matrix converter with a plurality of switches connected to the generator;
supplying power from generator to the utility grid using the matrix converter; and
actively damping drive-train oscillations.
This application is a continuing application claiming benefit to U.S. application Ser. No. 09/862,316 filed May 23, 2001, now U.S. Pat. No. 6,566,764 and claims the benefit of U.S. Provisional Application No. 60/206,313, filed May 23, 2000, both of which are incorporated herein by reference.
The present invention relates to supplying a utility with power from a variable speed wind turbine, and, more particularly, to converting a variable frequency output from a generator directly into constant frequency using a matrix converter.
Wind speed fluctuates over time. Some wind turbines are not able to track these fluctuations and rotate only at a single speed (frequency). A way of operating at a fixed speed despite variations in wind speed is to use a synchronous generator or a directly connected induction (asynchronous) generator.
Since the maximum power available from the wind is a function of wind speed, and since the power captured by a propeller of a wind turbine is a function by rotor speed and wind speed, fixed speed wind turbines fail to recover this maximum power. Fixed speed turbines also suffer from noise, reliability problems and high stresses on the utility grid. Furthermore the lagging power factor of a grid-connected asynchronous generator demands a large capacitor battery to compensate for the lagging power factor. Accordingly, variable speed implementations have been proposed to recover the maximum power of the wind and better address these other problems of fixed speed turbines. Examples of these variable speed wind turbines are described in U.S. Pat. Nos. 5,083,039 and 5,225,712, and PCT Application US99/07996, each of which is incorporated by reference herein in its entirety.
A variable speed wind turbine 100 is also shown in FIG. 1. One or more wind turbine blades (not shown) drives rotor shaft 111 of asynchronous doubly-fed induction generator 110. Turbine 100 supplies power from rotor 112 and stator 113 of generator 110 when shaft 111 is rotating above synchronous speed. At speeds above synchronous speed, excitation power may be supplied to rotor 112 from rotor inverter 151 in order to achieve unity power factor at the stator side. At shaft speeds lower than synchronous speed, power is supplied from stator 113 and slip power along with the excitation power is supplied to rotor 112 from rotor inverter 151.
To supply power from stator 113, Y/Δ-contacter 130 shifts the three stator windings selectively into a Y-connection or a Δ-connection.
The output voltage and current from the stator are fed into a medium voltage transformer. The transformer may be located in the top of the turbine or elsewhere. When a transformer is located in the top of a turbine, the transformer can be constructed in at least two ways. The first way is with a primary winding (10 kV) and a secondary winding (690V) and a special tap on the secondary winding (480V). The second way is with a primary winding (10 kV) and a secondary winding (690V) and a tertiary winding (480V). When the medium voltage transformer is not in the top of the turbine, there is still a need for the converter voltage level (480V), and that can also be implemented in several ways, such as either having a transformer with primary winding (690V) and secondary winding (480V) or having a autotransformer with one active winding (690V) but a secondary tap (480V). The medium voltage transformer steps up the voltage to an amount, for example 10 kV at the primary side, required for a power supply, such as a utility grid. The contactor 113, however, is only exemplary and the stator windings can be directly connected to transformer 170 in either Y-connection or Δ-connection. Further, the output from stator 113 can be connected directly to the utility grid or to a separate transformer, instead of transformer 170.
To supply power to/from rotor 112, current induced in rotor 112 is passed through an output filter 140, which is designed to prevent large voltage changes across the generator windings and thereby increase the lifetime of the winding insulation, and then is passed to a back-to-back indirect power converter 150. Power converter 150 includes a converter stage 151, which converts the variable frequency output of generator 110 to a DC voltage, a DC link 152, including an electrolytic capacitance 153, and a converter stage 154, which converts the DC link voltage into a fixed frequency output. The output of converter 154 is fed to a filter 160, which smoothes the current to be supplied and boosts the DC-link voltage. To reduce the voltage ratings of the switches included in converters 151 and 154, the filtered fixed-frequency output is applied to the low-voltage, tertiary windings of transformer 170, for example 480 V.
In accordance with FIG. 1 and assuming ideal components:
The configuration of
An additional disadvantage of the
Matrix converters can also be called either venturini converters or direct frequency converters. Some wind turbines have used matrix converters to eliminate intermediate conversion using a DC link. These wind turbines, however, do not use an actively controlled matrix converter. Prototype wind turbines that have used matrix converters are designed to produce only about 7.5 kW of electricity. A viable design using a matrix converter in a wind turbine to produce electricity at higher power levels has yet to be achieved.
Other documents describe wind turbines and/or direct frequency converters. For example, U.S. Pat. No. 6,137,187 describes a variable speed system with a torque and pitch controller using field oriented control, U.S. Pat. No. 5,949,672 describes a three-phase matrix converter and method for operation thereof, U.S. Pat. No. 5,943,223 describes electric switches for reducing on-state power loss, U.S. Pat. No. 5,909,367 describes a modular AC-AC variable voltage and variable frequency power converter system and control, U.S. Pat. No. 5,892,677 describes an adaptive overlapping communication control of modular AC-AC converter and integration with a device module of multiple AC-AC switches, U.S. Pat. No. 5,852,559 describes power application circuits utilizing bidirectional insulated gate bipolar transistor, U.S. Pat. No. 5,798,631 describes performance optimization controller and control method for doubly-fed machines, U.S. Pat. No. 5,729,118 describes variable speed induction generator-motor with controllable excitation frequency, U.S. Pat. No. 5,669,470 describes a roadway-powered electric vehicle system, U.S. Pat. No. 5,289,041 describes a power converter using a predicted torque set point, U.S. Pat. No. 5,029,064 describes a phase-controlled reversible power conversion with equal duty cycle substantially constant amplitude square wave excitation of the power transformer, U.S. Pat. No. 4,648,022 describes a matrix converter control system, U.S. Pat. No. 4,468,725 describes a direct AC converter for converting a balanced AC polyphase input to an output voltage, U.S. Pat. No. 4,439,823 describes converting multiphase power from one frequency to another using current waveforms, U.S. Pat. No. 4,352,155 describes a variable speed constant frequency power converter with two modes of operation, and U.S. Pat. No. 3,832,625 describes an electrical power generating arrangement and method using an induction generator. Each of these U.S. patents are incorporated by reference herein in its entirety.
The present invention describes a variable speed wind turbine with a turbine rotor including at least one blade mounted to a rotatable turbine shaft. It includes a doubly-fed induction generator having a stator and a rotor coupled to the turbine shaft for rotation and a matrix converter with an array of switching elements. The matrix converter has a control unit to control the switching elements. Additionally the turbine may include, a voltage gradient limiting circuit located between the matrix converter and the generator rotor. Additionally the turbine may include, a transformer having at least three windings including a tertiary winding and means for adjusting voltage at the tertiary winding, wherein a ratio of the input potential to the output potential is greater than 0.866. Additionally the turbine may include, a generator having a winding ratio and means for adjusting the winding ratio of the generator wherein a reduced matrix converter gain is overcome, where a ratio of the input potential to the output potential is greater than 0.866 and where a current rating of the switching elements is increased. Additionally the turbine may include, a protection circuit for protecting the matrix converter against over voltages. Additionally the turbine may include, a protection circuit for protecting the matrix converter against over voltages and for retaining control after a grid disruption. Additionally the turbine may include, means for position sensorless detection of the position of said turbine rotor with the measurement of the current of said rotor, further including the circulation of reactive power. Additionally the turbine may include a power controller for circulating reactive energy. Additionally the turbine may include, a power controller for controlling the power factor of the turbine without impacting the circulation of reactive power. Additionally the switching elements may include a standard H-Bridge module. Additionally the stator may include a stator winding means for shifting between a Y-connection and a Δ-connection. Additionally the switching elements may be thermally rated to withstand a current at least √{square root over (2)}/√{square root over (3)}*707 A. Additionally the turbine may include a means for the facilitating the active damping of current harmonics. Additionally the turbine may include a means for facilitating the active damping of resultant drive-train oscillations.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the invention and together with the description, serve to explain the principles of the invention.
Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. The present invention is not limited to these particular implementations but may be realized by other implementations.
The present invention can provide an efficient source of electric power that is not harmful to the environment and does not utilize non-renewable natural resources. The present invention converts the kinetic energy of the wind into electric energy. A matrix converter is used to convert a variable frequency output of a generator into fixed-frequency output power. In one implementation, the matrix converter converts only a portion of the power produced by the generator. In another implementation, the matrix converter converts all of the power produced by the generator.
Systems and methods employing a matrix converter enable turbine operation at variable speed. They increase the energy efficiency of the blades, i.e., higher energy production; reduce noise from the blades at low wind speeds; provide dynamic and full control over the active power, both below and above synchronous speed; provide dynamic and full control over the reactive power, i.e., unitary cos φ can be obtained at the grid so as to avoid the need for large capacitor batteries; improve power quality since they can provide precise and accurate grid connection and disconnection, i.e., no inrush current during cut in or cut out; reduce the level of harmonics due to relatively high switching frequency in the converter; to some extent make it possible to include active control for the purpose of further reducing the level of lower harmonics, such as the 5th, 7th, and/or the slip harmonic component in the current; reduce power fluctuations (such as voltage variations and flicker); and reduce mechanical loading since operation at variable speeds makes it possible to control the wind turbine so that only a limited amount of stress from wind fluctuations is transferred through the drive-train components (the inertia in the drive train is utilized to absorb most of the power fluctuations). The system is also able to actively reduce the amplitude of lower frequency oscillations in the drive-train, which reduces the load in the gearbox and increases the lifetime of the drive-train components. This is done by inducing torque control signals with the same frequency as the measured speed oscillations and with an appropriate phase angle.
As compared to the back-to-back indirect voltage source conversion of
Systems without a large DC link capacitance also may have a longer life. Systems and methods consistent with the present invention also may have a higher power density due to the smaller semiconductor switches and absence of any large DC link capacitance. In addition, the present invention can be highly efficient by exhibiting lower switching losses, a simpler control structure, and less demanding controller hardware.
Typically, passive filters with relatively large components are provided in turbines to reduce the level of unwanted harmonics that have been generated together with electricity at the desired frequency. In the present invention, these passive filters can be designed with smaller components because the matrix converter has a lower content of high harmonics compared to back-to-back converter 150 of FIG. 1.
Although a matrix converter has a limited voltage transfer ratio, this characteristic is not a problem when the converter is implemented in a doubly-fed turbine. In such a turbine, the generator voltage, for example, is selected with the limited transfer ratio as a design criterion. In other fields, such as motor control, the motor voltage would not be selectable as a design criterion. Also, the voltage at the grid side of the matrix converter may be raised by increasing the number of turns on the tertiary winding of the transformer or a separate transformer.
In an implementation of the present invention, power control is achieved without the need for an input from an electromechanical sensor at the main generator shaft that detects the position of the shaft. Eliminating a position sensor makes the system mechanically more robust.
At light load, where rotor currents have low amplitude, an accurate position sensorless rotor angle detection might be difficult to obtain because the ripple due to switchings is very pronounced compared to the fundamental rotor current. To increase the accuracy of the rotor angle observation, the present invention uses the fact that circulation of reactive power (e.g. a reactive power is forced to circulate from the matrix converter through the rotor to the stator and back to the matrix converter) can be used to increase the rotor current amplitude without changing the overall power factor of the system. That is the power factor seen from the grid point of connection is maintained at unity (or any desired value). To improve the performance of the sensorless rotor position scheme, the reference QMG_REF, in
Compared to the present VCS-system, the matrix converter has a limited ability for circulating reactive power due to the fact that the voltage gain of the matrix converter decreases as the power factor of the matrix converter decreases (Vr=Vg*0.866*cos(φi)) where φi is the angle between current and voltage at the input of the matrix converter.
The protection circuit in practical matrix converter applications have useful, dual functions in wind turbine applications. For example, a matrix converter can include a clamp circuit for protection of the converter switches against over voltages caused from the inherent presence of stray inductances between the input filter and the matrix switching element array. This clamp circuit also can be used to supply power for the matrix converter controller circuitry, as shown in
In high-power implementations, the matrix converter preferably uses a power control procedure to permit control of both the real and reactive portions of power that is output from the wind turbine. The use of a matrix converter in a high-power wind turbine is contrary to the conventional wisdom in the field. In fact, matrix converters have been criticized because the output voltage (generator side in the present case) is limited to a percentage, 0.866, of the input voltage (grid side). Nevertheless, in the present system, this limitation on the voltage that is output from a matrix converter can be overcome by adjusting the voltage on the transformer or the generator.
The wind turbine of the present invention is more efficient due to lower switching losses. Lower switching losses are obtained because half of the switchings become natural switchings. Half of the switching can be natural communications, such as soft switching. A simpler control structure due to single-stage power conversion, lowers the level of undesirable harmonics by using more voltage levels, and increases the lifetime of the power conversion unit by providing equal thermal stress on the semiconductors in the conversion unit independent of the rotor frequency. The output harmonic content of a matrix converter can be made lower than the harmonic content of the wind turbine shown in
To prevent damages on the rotor windings insulation caused from flash over voltages and to increase the lifetime of the rotor windings, a voltage gradient limiting circuit is inserted between the matrix converter and the rotor of the generator. The voltage gradient circuit comprises, for example, a three phase inductance or a three phrase inductance-capacitor filter. By inserting the voltage gradient limiting circuit, the gradients of the applied voltages is shared between the rotor winding and the voltage gradient limiting circuit.
B. Architecture
1. Overall Configurations
A variable speed wind turbine 200 consistent with the present invention is shown in FIG. 2. One or more wind turbine blades (not shown) drives an doubly-fed induction generator 210 via rotor shaft 211. Turbine 200 supplies power from rotor 212 and stator 213 of generator 210 when generator shaft 211 is rotating at a speed higher than synchronous speed. At these shaft speeds above synchronous speed, excitation power may be supplied to the rotor of the generator. At shaft speeds lower than synchronous speed, power is supplied from stator 213 while the slip power and the excitation power is supplied to rotor 212 from converter 250.
By use of a Y/Δ-connector, the stator 213 winding can be selectively shifted into a Y-connection or a Δ-connection. The output of stator 213 is fed into a transformer 260, having a secondary voltage of 690 V, for example. The switch 230, however, is only exemplary and the stator can be directly connected to transformer 260 in a fixed Y- or Δ-connection. The transformer steps up the voltage to an amount, for example 10 kV, required for a power supply, such as a utility. Alternatively, the output from stator 213 can be connected directly to the utility grid or to a separate transformer, instead of transformer 260.
To supply power to/from rotor 212, current induced in rotor 212 is passed through a voltage gradient limiting circuit 220 to a power converter 250. Circuit 220 acts to prevent large voltage changes across the generator windings and thereby increases the lifetime of the winding insulation.
Power converter 250 directly converts the fixed frequency, fixed amplitude AC-voltage at the grid side of the converter to a variable frequency, variable amplitude AC voltage at the rotor side of the converter. As a result, power converter 250 does not include, among other components, the DC link 152 or capacitance 153 that must be provided in power converter 150 of FIG. 1.
To directly convert a fixed frequency, fixed amplitude AC-voltage to a variable frequency, variable amplitude AC voltage, power converter 250 includes a matrix converter. A matrix converter is an array of switching elements. By controlling the switches in the array with signals from a control unit (not shown in FIG. 2), the matrix converter converts a fixed frequency, fixed amplitude AC-voltage at the grid side to a variable frequency, variable amplitude AC voltage at the generator side. By a proper connection of the grid phases ua, ub and uc to the generator phases ux, uy and uz, both the grid currents and generator voltage can be controlled. The relationship between generator voltage vx,vy and vz and the grid voltages va, vb and vc of the matrix converter is calculated by:
The transfer matrix T represents the transfer function from the instantaneous input voltage to the instantaneous output voltage. Since no internal storage exists in the matrix converter, the grid currents are given as:
Consequently, the generator voltage and the grid currents are controllable parameters. On the other hand, the grid side voltage of the matrix converter is determined by the grid, while the generator currents are determined by the characteristics of the generator.
A filter 240 smoothes the switched AC-current from power converter 250, and passes the smoothed current to a tertiary winding of transformer 260. Transformer 260 steps up the voltage to an amount, for example 10 kV, required for a power supply, such as a utility. Of course, the output of filter 240 could be directly coupled to the grid without any transformer or a separate transformer could be used.
Another embodiment of a wind turbine 200A consistent with the present invention is shown in FIG. 2A. Wind turbine 200A differs from wind turbine 200 in that wind turbine 200A uses an induction generator 210A that does not have brushes (electrical connections) to rotor 212A. For example, induction generator 210A could be a squirrel-cage induction generator.
Since generator 210A does not have brushes, all of the power produced by generator 210A is output from the stator 213A. The three-phase output, for example, of stator 213A is connected to a voltage gradient limiting circuit 220A, which prevents large voltage changes across the generator windings. The output of this circuit is connected to a power converter 250A, which is similar to power converter 250 of FIG. 2 and includes a matrix converter for converting the constant frequency, constant amplitude voltage from the grid supply to a variable frequency, variable amplitude voltage at the stator side of generator 210A. Nevertheless, since the matrix converter of power converter 250A must handle all of the power of the generator, the components constituting the matrix converter must withstand higher voltages and/or currents.
A filter 240A smoothes the constant-frequency AC current from power converter 250A, and passes the smoothed current to a secondary winding of transformer 260A. Transformer 260A steps up the voltage to an amount, for example 10 kV, required for a power supply, such as a utility. Transformer 260A does not require a tertiary winding. Of course, the output of filter 240A could be directly coupled to the grid without any transformer.
In the doubly-fed variable-speed wind turbine system of
The voltage that is chosen for the tertiary windings of the transformer 260 is calculated in accordance with the desired speed range. For example, to achieve a dynamic speed range of ±30% around synchronous speed (i.e., maximum slip equals ±30%), the converter should be able to deliver an output voltage Vr at the rotor terminals which satisfies the following equation:
For example, when the standstill line-line voltage Vr0 is 1820 V, the rotor converter must be able to deliver a voltage of 546 V (1820 V×0.3) to achieve a speed range of ±30%. To achieve this voltage, the line-line voltage at the grid side of the matrix converter Vt3 has to be 630 V (546 V/0.866). On the other hand, the voltage at the tertiary winding should not be higher than necessary because that would require an increase in the voltage ratings of the switches in the converter. Ideally, the peak voltage across the switch {circumflex over (ν)}sw is:
For a tertiary winding voltage of 630 V, the switch voltage ratings are 892 V. When safety factors are included, the switch voltage ratings should be at least 1200V.
In the full scale converter of
2. Matrix Converter Architectures
Matrix converters 250 and 250A convert a fixed-frequency AC voltage into a variable-frequency AC voltage. Various architectures are available for a matrix converter used in a wind turbine consistent with the present invention. For example, in addition to the three-phase to three-phase matrix converters shown in
Given the engineering trade-offs identified above for a switch, a switch realized from the standard H-bridge module in
C. Architectural Operation
As shown in
Control system 700 is a power control system that controls the overall power of the wind turbine. Control system 700 does not directly control other parameters, such as generator torque. Nevertheless, to provide increased protection for the generator and wind turbine elements (such as the gearbox, not shown), control system 700 can be implemented as a torque control system. Examples of torque control systems are described in U.S. Pat. Nos. 5,083,039, 5,225,712, 6,137,187 and PCT Application US99/07996. Additionally, the control can be implemented as direct torque control to achieve faster response time for the real power P and reactive power Q. In this regard, see Domenico Casadei et al., "The Use of Matrix Converters in Direct Torque Control of Induction Machines," 2 IEEE Industrial Electronics Society 744-749 (1998) (incorporated by reference herein in its entirety).
The inputs to power control system 700 are desired amounts of total active power PMG_REF and reactive power QMG_REF. The desired amount of real power is based on the average power available in the wind at a given point in time. Various methods are available to estimate the amount of power available in the wind. For example, the estimate can be based on a direct measurement of wind speed or on a predicted wind speed, or on a combination of the above, as known to persons in the art. The desired amount of reactive power is not based on wind speed. Instead, the desired reactive power can be set to any level by the operator of the wind turbine. Also, the wind turbine can sense the power condition of the supply (utility grid) and determine the amount of reactive power needed to correct this condition. Power in the wind can also be predicted based on knowledge about power delivered to the grid, speed of the generator and the pitch angle of the blades, but other ways to predict power in the wind are also possible.
The real and reactive power references PMG_REF and QMG_REF shown in
A more detailed control algorithm for determining ura
In accordance with these inputs, angle and sector calculators 900 compute commands used in duty cycle calculators 910 to determine the duty cycles for the switches of the matrix converter. Once the duty cycles dα, dβ, dδ, and dγ of the switches are calculated, PWM generator 920 computes nine gate signals for controlling the switches. Commutation logic 930 converts the nine gate signals into eighteen gate signals to control the bidirectional switches in the matrix converter. The logic 930 uses an input of the direction of the three rotor currents in order to achieve safe phase commutations, as discussed above. Phase commutations occur, for example, when rotor phase x has to be shifted from being connected to grid phase a to grid phase b. In addition, a shut down signal is input to modulator 730 to shut down the matrix converter in any failure situation (for example, over voltage, over current, or over temperature).
For the functionality of the matrix converter in the wind turbine of
The system described by Zhang and Watthanasarn provides only simulation results and therefore does not realize many of the problems that have to be faced when an implementation is attempted, such as the use of protection circuits, voltage gradient limiting circuits, and sensorless operation. In the system, there is no implementation of adjusting the generator winding ratio or the voltage at the input side of the matrix converter to overcome the inherent voltage gain transfer ratio of the matrix converter. There is also no consideration of the control of the total (sum of the stator and rotor power) active power and reactive power, thereby preventing the system from achieving full control of active and reactive power. Further, the system described by Zhang and Watthanasarn can not use circulating reactive power (because only stator quantities are controlled) to increase the rotor currents and thereby improving the position sensorless control at light loads.
In sum, since control system 700 controls the matrix converter 250, rather than both the AC to DC converter 151 and the DC to AC converter 154 of
Referring to
One or more logic devices, such as an application specific integrated circuit (ASIC), can be used to reduce the processing burden on a DSP in control system 700. For example, an ASIC that handles phase commutations can reduce the number of gate signals of the matrix converter to be controlled. Phase commutation can be explained with reference to
R. R. Beasant, et al. and Charles L. Neft describe the simplest commutation strategies, but these strategies do not comply with the basic control rules. Nándor Burány and B. H. Kwon each describe strategies to reduce switching losses by making half of the switching become soft switching. The strategies of Jung G. Cho and H. L. Hey require a more complex hardware structure for the matrix converter.
For example, current io can be drawn from input phase a in one condition. In this stationary state, both switches Sa1 and Sa2 are turned on, i. e., the stationary switch state is 11-00-00. At an arbitrary time, having positive current io, according to
Based on this framework of how switching occurs, modulator 730 creates switching commands based on voltage references ura
Marco Venturini, "A New Sine Wave In, Sine Wave Out Conversion Technique Eliminates Reactive Elements" Powercont. P. E3-1-E3-15 (1980) (incorporated herein by reference) describes a direct transfer function approach. Modulation is based on solving the matrix equation using a sinusoidal reference for the input current and the output voltage. This approach, however, restricts the output voltage to 0.5 times the input voltage. The voltage transfer ratio can be increased to 0.866 times the input voltage by adding a harmonic component to the output reference voltage. See Alberto Alesina and Marco Venturini, "Intrinsic Amplitudes and Optimum Design of Direct PWM AC-AC Converters" IEEE Power Electronics Specialists Conference 1284-1291 (1988) (incorporated herein by reference). While the direct transfer function approach incorporates many desirable properties, i.e., maximum voltage transfer ratio, sinusoidal input/output, and adjustable power factor, the formulas for the computation of duty cycles are complicated and require considerable computational power to achieve real time implementation. See L. Zhang and C. Watthanasam, "An Efficient Space Vector Modulation Algorithm for AC-AC Matrix Converters" IEE Power Electronics and Variable Speed Drives 108-113, (Sep. 21-25, 1996) (incorporated herein by reference). In addition, the switching losses associated with this method are relatively high due to a high number of switch commutations per switching cycle. See C. Watthanasam et al., "Analysis and DSP-Based Implementation of Modulation Algorithms for AC-AC Matrix Converters" 2 IEEE Power Electronics Specialists Conf. 1053-1058 (Jun. 21-27, 1996) (incorporated herein by reference).
Y. Kim and M. Ehsani, "Control of Force-Commutated Direct Frequency Changers" IEEE Industrial Application Society Annual Meeting 1163-1170 (1990) (incorporated herein by reference) and Charles L. Neft and Colin D. Schauder, "Theory and Design of a 30-HP Matrix Converter" IEEE Industrial Application Society Annual Meeting 248-253 (1988) (incorporated herein by reference) each describe an indirect transfer function approach. In this approach, the matrix converter is theoretically separated into a rectifier part and an inversion part, which are modulated separately. Compared to the direct transfer function approach, the indirect transfer function approach requires less computational power. See L. Huber and D. Borojevic, "Space Vector Modulated Three-Phase to Three-Phase Matrix Converter with Input Power Factor Correction" 31 IEEE transactions on industry applications. No. 6, 1234-1246 (November/December 1995) (incorporated herein by reference).
Y. Kim and M. Ehsani, "New Modulation Methods for Force-Commutated Direct Frequency Changers" IEEE Power Electronics Specialists Conference 798-809 (1989) (incorporated herein by reference) and J. Oyama et al., "Effect of PWM Pulse Number on Matrix Converter Characteristics" 2 IEEE Power Electronics Specialists Conference 1306-1311 (Jun. 23-27, 1996) (incorporated herein by reference) each describe a carrier-based modulation approach. From applications in modulation of conventional converters, carrier-based modulation was adapted for use in matrix converters. Implementations can mainly focus on modulation of the output voltage to provide relatively simple modulation, or can also include modulation of the input current.
D. G. Holmes and T. A. Lipo, "Implementation of a Controlled Rectifier Using AC-AC Matrix Converter Theory" IEEE Power Electronics Specialists Conference 353-359 (1989) (incorporated herein by reference), P. Nielsen, D. Casadei, G. Serra and A. Tani, "Evaluation of the Input Current Quality by Three Different Modulation Strategies for SVM Controlled Matrix Converters with Input Voltage Unbalance" 2 IEEE International Conference on Power Electronics, Drives and Energy Systems for Industrial Growth, 794-800 (Jan.1996) (incorporated herein by reference), and D. O. Neascu, "Theory and Design of a Space-Vector Modulator for AC-AC Matrix Converter" 5 European Transactions on Electrical Power Engineering No. 4, 285-290 (July/August 1995) (incorporated herein by reference) describe space vector modulation. Both the space vector modulation approach and the indirect space vector modulation approach only use stationary vectors. The stationary vectors correspond to switch combinations where at least two of the generator phases are connected to one grid phase.
Lázló Huber and Dusan Borojevic, "Space Vector Modulation with Unity Input Power Factor for Forced Commutated Cycloconverters" IEEE Industrial Application Society Annual Meeting 1032-1041 (1991) (incorporated herein by reference) describe indirect space vector modulation, as did L. Huber and Borojevic, supra, and D. O. Neascu, supra. In one sense, indirect space vector modulation is the combination of principles from the indirect transfer function approach with principles from space vector modulation. In indirect space vector modulation, SVM is performed individually for rectification and inversion. In space vector modulation, the number of switchings is preferably optimized to achieve lower switching losses. See P. Nielsen and F. Blaabjerg and J. K. Pedersen; "Space vector modulated matrix converter with minimized number of switchings and a feedforward compensation of input voltage unbalance" IEEE international conference on power electronics, drives and energy systems for industrial growth, Vol. 2, pp. 833-839, January, 1996.
Hardware Interface and Protection Circuitry
As a reference, for a 850 kW system, a nominal rotor current can be 300 A. For a 2 MW system, the rotor current can be 800 A. At each of these power levels, the nominal rotor voltage at 100% slip can be 1850 V. The overcurrent and over voltage protection signals should be designed to be triggered in accordance with these values. Of course, these values are only examples, and the values would vary for different generator constructions.
Due to the removal of a DC-link from the present invention, there is no decoupling between the input and output of the matrix converter. In ideal designs, this is not a problem. In the case of unbalanced or distorted input voltages (or unbalanced loads), however, the input current and the output voltage will be distorted. Several papers have dealt with the problems of unbalanced input voltages. For example, D. Casadei et al., "Analysis of Space Vector Modulated Matrix Converters Under Unbalanced Supply Voltages" Symposium on Power Electronics, Electrical Drives, Advanced Electrical Motors, 39-44 (Jun. 8-10, 1994), D. Casadei, et al., "Reduction of the Input Current Harmonic Content in Matrix Converter Under Input/Output Unbalance" 1 IEEE International Conference on Industrial Electronics, Control and Instrumentation 457-462 (Nov. 9-14, 1995), D. Casadei, et al., "Performance of SVM Controlled Matrix Converter with Input and Output Unbalanced Conditions" 2 EPE 6th European Conference on Power Electronics and Applications 628-633 (Sep. 19-21, 1995), D. Casadei, et al., "A General Approach for the Analysis of the Input Power Quality in Matrix Converters" 2 IEEE Power Electronics Specialists Conference 1128-1134 (Jun. 21-27, 1996), P. Enjeti and X. Wang, "A Critical Evaluation of Harmonics Generated by Forced Commutated Cycloconverters (FFC's) under Unbalance" IEEE Industrial Application Society Annual Meeting 1162-1166 (1990), Peter Nielsen, "The Matrix Converter for an Induction Motor Drive." Ph.D. thesis, Aalborg University (August 1996), Nielsen et al., supra, Jun Oyama et al., "Displacement Angle Control of Matrix Converter" 2 IEEE Power Electronics Specialists Conference 1033-1039 (Jun. 22-27, 1997), and L. Zhang et al. "Analysis and Comparison of Control Techniques for AC-AC Matrix Converters" 145 IEE Proceedings on Electronic Power Application 284-294 (July 1998) describe strategies with various engineering trade-offs (input disturbance, line losses, controllability of the input power factor, etc.).
The wind turbines discussed above also provide protection to the matrix converter in fault situations. The snubber circuit 1710 is described in Nielsen, supra.
The protection of the matrix converter consists of a rotor circuit clamp 1700 and a snubber circuit 1710. The snubber 1710 acts as a diode clamp circuit across the matrix converter. This snubber performs two different functions. In normal operation, snubber 1710 clamps any over voltages across the switches in the matrix converter. Over voltages typically are caused by current changes across the leakage inductances of the power switch matrix during commutation. When the matrix converter receives an error signal, all the switches in the matrix converter are turned off. This action violates one of the basic control rules of the matrix converter, by interrupting the inductive generator current. If no current path is provided for this inductive current, the voltage across the switches in the matrix converter increases and the converter will be damaged. By inserting the diode snubber clamp, the diodes provide an alternative current path. Therefore, in a fault situation, the clamp circuit or snubber performs the additional function of absorbing the energy in the leakage inductances of the rotor circuit and the energy in the rotor filter.
Circuit 1720 in
This entire protection circuit requires inclusion of eighteen additional diodes, DC-link capacitor 1730, and switch 1710. The DC-link capacitor does not significantly impact the mean-time-between-failures for the wind turbine, since this DC-link capacitor is much smaller than the DC-link capacitor of FIG. 1. This DC-link capacitor voltage in the clamp circuit can be used as a power supply for the controller of the matrix converter. During a power grid disturbance, the DC-link capacitor can be energized from the energy stored in the generator to maintain the controller circuits active (as shown in
D. Conclusion
Wind turbines using matrix converters are described above. These wind turbines operate at high power and can provide reliable alternatives to fossil fuel generation of electricity for a utility grid.
While there has been illustrated and described what are at present considered to be a preferred implementation and method of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the true scope of the invention. Modifications may be made to adapt a particular element, technique, or implementation to the teachings of the present invention without departing from the spirit of the invention.
Also, the foregoing description is based on a client-server architecture, but those skilled in the art will recognize that a peer-to-peer architecture may be used consistent with the invention. Moreover, although the described implementation includes hardware and software, the invention may be implemented in hardware or software alone. Additionally, although aspects of the present invention are described as being stored in the memory of a microprocessor system, one skilled in the art will appreciate that these aspects can also be stored on other types of computer-readable media, such as secondary storage devices (e.g., hard disks, floppy disks, CD-ROM); a carrier wave from the Internet; or other forms of RAM or ROM.
Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.
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Diagnosing operation of an impulse piping line in an industrial process is provided. A vibration source transmits a vibration signal through the piping and a vibration signal receiver receives the vibration signal. The operation of the impulse piping line is diagnosed, such as failure or impending failures, based upon the received vibration signal.
1. A process variable transmitter for sensing a process variable of an industrial process, comprising:
a process variable sensor configured to sense the process variable;
an impulse piping line configured to couple the process variable sensor to a process fluid of an industrial process;
a vibration signal source configured to transmit an acoustic vibration signal into the industrial process and through the impulse piping line, the acoustic vibration signal having an acoustic signature, the vibration signal source providing the acoustic vibration signal in response to an input;
a vibration signal receiver acoustically coupled to the impulse piping configured to receive the vibration signal from the impulse piping line wherein the vibration signal is generated by the vibration signal source; and
diagnostic circuitry configured to provide the input to the vibration signal source and responsively diagnose condition of the impulse piping line based upon the received vibration signal.
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27. A method of sensing a process variable in an industrial process, comprising:
coupling a process variable sensor to the process fluid of the industrial process using impulse piping;
sensing a process variable of the process fluid using the process variable sensor;
controlling a vibration signal source with an input to the vibration signal source to generate a desired acoustic vibration signal having an acoustic signature response to the input and sending the vibration signal along the impulse piping;
receiving the vibration signal from the impulse piping line with a sensor acoustically coupled to the impulse piping; and
diagnosing condition of the impulse piping based upon the received vibration signal.
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The present invention relates to process devices. More particularly, the present invention relates to process devices which coupled to process fluid through process piping.
Various types of process devices are used to measure process variables and couple to process fluid through process piping. For example, fluid flow meters are used in industrial process control environments to measure fluid flow and provide outputs related to flow indicators and process controllers. Inferential flow meters measure fluid flow in a pipe by measuring a pressure drop near a discontinuity within the pipe. The discontinuity (primary element) can be an orifice, a nozzle, a venturi, a pitot tube, a vortex shedding bar, a target or even a simple bend in the pipe. Flow around the discontinuity causes both a pressure drop and increased turbulence. The pressure drop is sensed by a pressure transmitter (secondary element) placed outside the pipe and connected by impulse lines or impulse passageways to the fluid in the pipe. These connections are also referred to as impulse piping. Reliability depends on maintaining a correct calibration. Impulse lines can become plugged over time, which also adversely affects calibration.
Disassembly and inspection of the impulse lines is one method used to identify and correct plugging of lines. Another known method for detecting plugging is to periodically add a "check pulse" to the measurement signal from a pressure transmitter. This check pulse causes a control system connected to the transmitter to disturb the flow. If the pressure transmitter fails to accurately sense the flow disturbance, an alarm signal is generated indicating line plugging. Another known method for detecting plugging is sensing of both static and differential pressures. If there is inadequate correlation between oscillations in the static and differential pressures, then an alarm signal is generated indicating line plugging. Still another known method for detecting line plugging is to sense static pressures and pass them through high pass and low pass filters. Noise signals obtained from the filters are compared to a threshold, and if variance in the noise is less than the threshold, an alarm signal can be triggered which indicates that the line is blocked.
These known methods rely on providing static pressure sensors, disassembly of the flow meter or use of an external control system for diagnostics. The methods increase complexity and reduce reliability. There is thus a need for improved diagnostic technology that can provide more predictive, less reactive maintenance to reduce cost or improve reliability.
An apparatus and method for diagnosing operation of impulse piping lines in an industrial process is provided. A vibration source transmits a vibration signal through the piping to a receiver configured to receive the vibration signal. Operation of the piping is diagnosed based upon the received vibration signal.
Transmitter 102 couples to the process fluid through a process connection 110. The process connection provides impulse piping 112 which extends between the process fluid and a sensor, for example a pressure sensor 114. The impulse piping 112 can be a direct fluid connection which carries process fluid and, in some embodiments, can include an isolation diaphragm if desired to isolate a fill fluid which couples to the sensor 114 from the process fluid.
During operation, it is possible for impulse piping 112 to become clogged. The clogging can be either partial or complete. As discussed in the Background section, various techniques have been used to diagnose and identify such plugging of impulse piping 112. Partial plugging can be particularly difficult to identify because the impulse piping is not completely blocked, and the sensor 114 continues to report data which may be inaccurate.
The present invention provides a technique for identifying clogging or plugging of process impulse piping 112. In the embodiment illustrated in
In accordance with one embodiment of the present invention, transmitter 100 includes diagnostic circuitry 140 having memory 141. Diagnostic circuitry 140 couples to a transducer 142. Transducer 142 is physically connected to process impulse piping 112, for example by coupling to process connection 110 or by other connections. The transducer 142 can be a single transducer or can be two separate transducers formed by signal source 144 and signal receiver 146. In some embodiments, transducer 146 is a single element which provides both a send and receive function. The sending and receiving can be continuously operative or can be multiplexed.
In accordance with one embodiment, signal source 144 is a vibration signal source which sends a vibration signal into impulse piping line 112. The spectral content of the vibrations can be selected as desired. For example, the spectral content can comprise substantially random noise at relatively constant amplitude having frequencies which are lower than a selected upper limit. For reflected signal based diagnostics, a higher frequency acoustic frequency range is advantageous. Higher frequencies are more directional, and will reflect back more readily from build up sites along a partially plugged line. Since plugging sites create a low pass filter, a low frequency signal may not reflect from a plugging site, but rather may be transmitted, depending on the low pass filter characteristics. Also, short burst acoustic signals are more easily generated using higher frequencies, which can allow determining the position of the interface which provides the reflection. This is especially important in wet and dry leg level height diagnostics. Frequencies up to 40 KHz are useful for this type of burst mode signal. The burst mode signal also allows listening to the process noise spectrum for abnormal noise patterns between bursts. It is important that the burst noise frequency, or frequencies, not be masked by the process noise. In an optimal embodiment, the exact frequency, or frequencies of the transmitted interrogation signal would be changed for maximum signal to noise ratio versus the measured background noise spectrum.
The diagnostics of the present invention does not rely on ambient noise and instead utilizes source 144 to generate vibration noise. Receiver 146 is configured to receive vibration noise from impulse line 112 and provide a signal to diagnostic circuitry 140. Because the noise source 144 provides random noise with either a constant profile, or a profile adjusted as desired, diagnostic circuitry 140 can discriminate variations in the received signal and identify whether the source of the variations is due to changes in the plugging of impulse line 112 or is due to changes in the vibration signal applied by source 144. The transducer 146 can be coupled to a process manifold as a separate component or can be contained within the body of transmitter 102. Any appropriate transmitter and receiver configuration can be used. One type of transducing element is a piezoelectric element which is preferably adapted for high temperature installations. However, any technology can be used including electromechanical, etc. In order to improve efficiency, the piezoelectric element can be efficiently coupled to a manifold in the desired direction of acoustic energy travel, and decoupled in other directions. This configuration increases the applied noise signal and sensitivity in a desired direction.
According to one embodiment,
Pursuant to one embodiment, transducers 142 couple to the side of process coupling 110 and connect to diagnostic circuitry 140 (shown in
As illustrated in
During operation, the diagnostic circuitry 140 shown in
A plugged or partially plugged line condition can be detected based upon the received vibration signal. For example, a signal comprising a wide spectrum burst, or a swept signal, of acoustic noise is applied to the impulse piping 112 through noise source 144. The noise burst can be directionally coupled into the process connection 110 such that it travels along the process fluid in the impulse piping line 112. If a complete or partial interface exists in the line 112 due to plugging, a partially filled wet or dry leg, or other condition, a portion of the acoustic energy is reflected back to the receiver 146 of transducer 142. The transducer converts this received acoustic energy into an electrical signal which is provided to diagnostic circuitry 140. On the other hand, if no fault condition due to an obstruction exists, the only reflected signal will be due to fittings, bends, and normal obstructions in the line 112. These reflections are due to fixed sources. Thus, the acoustical profile of the process impulse line 112 in a nominal condition can be stored in memory 141 of diagnostic circuitry 140. During operation, the actual reflected signal can be compared with the stored profile. Variations between the stored profile and the received reflected signal are used by diagnostic circuitry 140 to identify a failure or impending failure in process line 112. Because the applied acoustic signal is known, the present invention is less susceptible to variations in the ambient noise for identifying line plugging than prior art techniques.
In some embodiments, the present invention is used to detect fault conditions in wet or dry legs of a process coupling. Wet legs are typically used in level measurement applications which are based upon differential pressure in which the top connection to a tank or other container is connected to a low pressure input of a transmitter with an impulse line that is intentionally kept filled with process fluid. However, maintenance may be required and performance can be degraded when the wet leg is only partially filled with fluid. A worst case scenario is one in which the wet leg fill level varies with time. This can lead to inaccurate measurements. A dry leg installation is similar, except that the impulse line is intentionally kept free of process fluid, i.e., the line is dry. Any fluid build up in a dry leg causes an apparent drift in the transmitter measurement. By sensing fluid levels in the wet or dry impulse lines, the present invention can detect when the levels are inappropriate and responsively provide a diagnostic output.
When an impulse line becomes plugged, the obstruction tends to act as a low pass filter. Higher frequencies of the transmitter signal are attenuated and partially reflected back to the transducer 142. The diagnostic circuitry 140 can identify a change in the spectral content of the reflected signal which can be an indication of line plugging. At a predetermined level of attenuation, for example, an early warning alarm can be communicated to a remote location by input/output circuitry 122 over process control loop 106.
In addition to detecting the reflected signal from source 144, receiver 146 can also be used to detect ambient process noise. This can be used to diagnose process conditions such as a pump failure, cavitation, etc. This can be coupled with other diagnostic techniques and used to diagnose other conditions in the process.
The vibration based diagnostics of the present invention can also be used to identify loss of isolation fluid in the process transmitter 102. As discussed above, typically isolation diaphragms are used which isolate process fluid from the sensor 114. Isolation fluid couples an isolation diaphragm to the sensor 114 such that variations in process pressure passed through the isolation diaphragm and isolation fluid oil to the process sensor. However, if the isolation fluid leaks, errors arise in sensor measurements and the sensor will ultimately fail. The oil/isolator/sensor form a low pass filter for audio signals. As fill fluid oil is lost in the transmitter, the characteristic of this low pass filter changes. The corner (i.e., frequency at which the signal is reduced by—3 dB) frequency of the low pass filter moves lower as the isolation fill fluid is lost. The transducer 142 of the present invention can be used to identify variations in this low pass filter and diagnose fill fluid loss conditions. The diagnostic circuitry 140 compares the reflected signal with a known profile to determine fill fluid loss.
Diagnostic circuitry 140 can also provide self diagnostics. For example, certain obstructions and configurations in the process impulse piping 112 provide a fixed or established time delay and amplitude of reflected pulses. Measuring the time delay and amplitudes over time, diagnostic circuitry 140 can identify a degradation or failure of the transducer 142.
The diagnostics of the present invention can be implemented using a single transducer or through multiple transducers. The diagnostic circuitry and transducer can be incorporated into transmitter electronics or can be part of a stand alone device. The transducer can couple to any type of process impulse piping including other manifold configurations. Various types of transmitters can include pressure, temperature, pH, flow, level, and other types. The diagnostic circuitry 140 can share components with other circuitry in the device, for example a microprocessor, memory, amplifier, analog to digital converter, digital to analog converter, etc. The diagnostic circuitry can be implemented in hardware, software, or their combination.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the vibration signal can be of any appropriate frequency or spectral content. The signal can be applied continuously, in bursts or pulses, or in other wave forms such as a ramped signal, etc. The diagnostic circuitry can compare the received vibration signal to a reference and can identify trends or abrupt changes in the signal. Additionally, the diagnostic circuitry can monitor background noise, for example when the vibration source is off, and compare monitored ambient noise to a stored noise spectrum or signature. The comparison can provide an indication of an anomaly or pending failure of the process equipment. In some embodiments, the frequency or spectral content of the vibration signal is adjusted as desired. For example, the spectral content can be adjusted to achieve a desired signal to noise ratio. The diagnostic circuitry of the present invention can also be configured to diagnose variations, such as failure modes, in impulse piping of the type which forms a filled capillary leg of the level measurement device. In such a configuration, the transmitter provides a level measurement output. Example failures include loss of oil, a ruptured or missing process isolator, or a kinked or broken capillary leg tube.
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Robert Reich: Obama must show America that the basic choice is between two fundamental views of this nation. Either we're all in this together, or we're a bunch of individuals who happen to live within these borders and are mainly on their own.
California GOP Targets Workers
WOLF! WOLF! WOLF!!! Cries the State Legislature
At the April meeting of Progressive Democrats of Los Angeles, we considered the initiatives on the upcoming May 19 ballot. We urge you to READ them as well as the analysis pieces. These were put onto the ballot at the end of the budget session in February when Republican Abel Maldonado, Santa Maria, cut a […]


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Michael E. ("Mick" or "Mike") Hazen, 70, a lifelong resident of Whitley County, died Thursday, March 31, 2011.
Mr. Hazen was born June 21, 1940 to Chalmers and Mildred Hazen. For 38 1/2-plus years he was employed at the General Electric Company in Fort Wayne.
During his lifetime he was an active citizen in both Whitley County and Churubusco community organizations. He was a member of the Faith Lutheran Church in Churubusco, and the Whitley County AARP Chapter. As a Cub Scout and Boy Scout leader for at least 50 years, he earned many awards, including the BSA Silver Beaver, and also the Lamb Award for religious affiliations.
Throughout his life he enjoyed Lionel model trains, and for 30 years he personally made sure that Santa Claus visited the Churubusco-area.
Surviving are his wife Bonnie; a son and daughter-in-law, Neal and Becky Hazen; two daughters, Christie Hazen and Heather Hazen; eight grandchildren; and a sister-in-law, Mary Ann Hazen.
He was preceded in death by his parents and by a brother, Leonard Hazen.
A Celebration of his life will be held at 10:30 a.m. Monday, at the Faith Lutheran Church in Churubusco. Visitation will be from 2 to 6 p.m. Sunday at the Sheets & Childs Funeral Home in Churubusco, or at the church one hour prior to the service. Interment will be in the Christian Chapel Cemetery, Merriam.
The family requests that memorials be directed to AWAC Boy Scouts of America, Indiana District LWML, Parkview Home Health & Hospice, or to the donor's choice.
To leave an online condolence for the family in Mr. Hazen's memory, log on to www.sheetsandchilds.net.


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Anne Marie Armstrong had a season-high 10 rebounds in the loss.
Feb. 28, 2013
STARKVILLE, Miss. --- Mississippi State raced to a 10-0 lead and withstood several rallies to upset No. 11 Georgia, 50-38, at Humphrey Coliseum on Thursday night.
Anne Marie Armstrong notched her first double-double of the season with 10 points and 10 boards in a losing effort for the Lady Bulldogs (23-5, 11-4 SEC). Jasmine Hassell grabbed 12 rebounds, her fifth double-digit rebound effort in the last six games.
Kendra Grant's 13 points, including an 8-of-10 night from the line, paced State (13-15, 5-10 SEC).
"Mississippi State outplayed us," Andy Landers said. "They played harder. They played with more intent. They knocked us on our heels in the first two three minutes of the game. We were passive from the onset. That said, we got behind 24-9 and fought our way back. When we did, we shot ourselves in the foot. We weren't running the break. We were hurrying the break. And because of that we missed some chances to get back in this basketball game."
Georgia opened its last two contests with 9-0 and 13-0 starts against Arkansas and Ole Miss, respectively, but had the tables turned in Starkville. State opened up a double-digit lead just 2:35 into the game before Jasmine James canned a 15-foot jumper to get the Lady Bulldogs on the board.
The margin grew to 19-4, forcing a Georgia timeout with 12:36 left in the period. Darriel Gaynor, State's lone senior, scored eight of the Lady Bulldogs' points during the surge. State maintained a 15-point edge at 24-9 before a Shacobia Barbee three ignited a 13-0 run to end the first half. Armstrong and Barbee did much of the damage during the surge, scoring six and five points, respectively.
State connected on 8-of-11 field goals en route to its first 19 points but then just hit 2-of-20 attempts from the floor over the remainder of the period. Georgia nearly took the lead on a Khaalidah Miller half-court buzzer beater that was slightly off target.
State regained an eight-point lead early in the second half, holding the Lady Bulldogs without a field goal until the 12:28 mark.
Georgia methodically cut into the margin and pulled within two at 35-33 on a James layup with 6:27 remaining. The Lady Bulldogs failed on four attempts to tie the game before Jerica James knocked down a three with 3:48 left.
State connected on 12-of-14 free throw attempts down the stretch to clinch the upset.
In addition to a season-low 38 points, the Lady Bulldogs also had their worst field goal shooting performance of the season both overall (18.2 percent) and from three-point range (9.1 percent).
The Lady Bulldogs will return home for their regular-season finale on Sunday when they host Vanderbilt at 1:30 p.m. at Stegeman Coliseum. The contest will be televised nationally on ESPNU. Georgia's seven seniors – Anne Marie Armstrong, Danielle Bennett, Jasmine Hassell, Jasmine James, Ebony Jones, Marisela Rodriguez and Tamika Willis – will be honored during pre-game ceremonies at approximately 12:15.
There are a host of promotions planned for Sunday's game. The first 1,000 fans will receive a Lady Bulldog "g" logo car decal, the first 300 kids 12 and under will get a Georgia Bulldogs superhero cape and the first 300 UGA students will receive "Real Dawgs Wear Red" t-shirts. In addition, students at select local elementary and middle schools have received a flyer good for one free admission to the game, and the school with the most students in attendance will receive $1,000.
Single-game reserved seat ticketsare $5 for adults and $3 for children. Single-game tickets are available at the UGA Ticket Office at the Butts-Mehre from 8:30-4:30 on Friday, via georgiadogs.com, by calling the UGA Ticket Office at 877-542-1621 or at the Stegeman Coliseum box office (closest to Sanford Drive) beginning 60 minutes before tip-off.
UGA students, faculty and staff are admitted to all Lady Bulldog games free of charge with a valid UGA Card. Faculty and staff should pick up tickets at the Coliseum box office. Students are admitted to the arena via the entrance to the left of the box office by showing their UGA Card.


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NEW YORK — After Le-Bron James won his second NBA championship this year, he talked about the improbability of his journey: ascending to world fame despite growing up with challenge after challenge in the inner city.
Now James plans to explore that theme as part of "Survivor's Remorse," a new show he's developing with Starz.
While he won't star in the half-hour sitcom, he'll be one of the executive producers of the show, which will explore the lives of two men from the streets who attain fame — one is an NBA star and one is not — and how they deal with friends and families in the wake of that success.
"I think the main thing for me is, first of all, making it out of a place where you're not supposed to. You're supposed to be a statistic and end up like the rest of the people in the inner city — (and) being one of the few to make it out and everyone looking at you to be the savior," the Miami Heat superstar said in a phone interview last week.
"When you make it out, everyone expects for — they automatically think that they made it out and it's very tough for a young, African-American 18-year-old kid to now hold the responsibility of a whole city, of a whole community. I can relate to that as well," said James, who was 18 when he came to the NBA and is now a 28-year-old veteran.
James is developing the show with his longtime friend and business partner, Maverick Carter; Tom Werner, the producer behind classic shows like "Roseanne" and "The Cosby Show"; and actor Mike O'Malley, who will be an executive producer and is the show's writer. Paul Wachter will be an executive producer.
"It's definitely not an autobiographical series about my life or LeBron's life; it's fictional characters living in a fictional world," said Carter, before adding with a laugh: "LeBron is actually too famous, he would screw the show up if I tried to make a show about him."
The show is based in North Philadelphia instead of Akron, Ohio, where the two are from: "More people can relate to it," explained Carter of Philadelphia. Still, Werner said the inspiration for the series started in part with conversations he had with Carter, and later James, about their lives.
"I think the juxtaposition of great wealth — and then you go back to your home in Akron and the neighborhood that you come from — the chasm is a fairly big one, and I think it's some very interesting story material," he said.
Werner, James and Carter have worked together since 2011. They are part of Fenway Sports Group, and Werner is the chairman of the organization, which combines sports, media and entertainment. Werner said they were "delighted" to bring the show, which is in development but has no firm timetable to air, to Starz.
Starz CEO Chris Albrecht said the show would be different for the channel, whose original programming includes the recently launched "The White Queen."
"It's a contemporary piece, which we've been trying to find," he said. "But mostly it's an opportunity to bring us into a world where guys as producers and a terrifically talented guy as a writer who I think are going to take the audience on an interesting, fun and I would bet funny ride."
However, there will be serious subjects tackled in the show. Werner compared "Survivor's Remorse" to shows like "Roseanne," which dealt with difficult situations with humor interspersed with serious moments.
"Nobody's getting killed, nobody's dying from cancer on this show," Carter said. "It's light-hearted, but its real-life stories."
James said though it's been years, survivor's remorse is still something he feels. "I live with that, knowing that I have to hold a huge burden and responsibility that a lot of people cannot even think about," he said.
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Spirited Chat
Stories of faith from your neighbors and faith leaders here in Houston
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Lakewood's reaction to Jay Bakker
Steve Ueckert : Chronicle Lakewood Church's Dodie Osteen. When Jay Bakker met with Joel Osteen at Lakewood Church on Mother's Day weekend, the two men agreed to disagree. But Lakewood spokesman Don Iloff said the visits and meetings went well. "Dodie Osteen, Joel's mother, wanted to meet Jay," Iloff told Chronicle reporter Claudia Feldman. "She […] [Read More]
Jay Bakker meets with Joel Osteen
Jay Bakker, the son of televangelists Jim Bakker and Tammy Faye Bakker Messner, said today that he met privately Sunday with Lakewood Church Pastor Joel Osteen and two senior Lakewood staff members. BRETT COOMER: Houston Chronicle Lakewood Pastor Joel Osteen. "Joel Osteen and his family were very kind and courteous," Bakker said in a statement […] [Read More]
A call for an inclusive day of prayer
The Council on Islamic-American Relations has joined the bandwagon calling for interfaith National Day of Prayer observances. In a news release Monday, CAIR said that in partnership with JewsOnFirst.org, it was "calling on American Muslims and members of other faith communities to contact … elected officials nationwide to ask that any government-sponsored National Day of […] [Read More]
Hempstead teens attend youth rally
On his third anniversary as pontiff, Pope Benedict XVI told cheering young Catholics that what matters most is their faith. Chronicle reporter Tara Dooley writes that the pope was the main act on a stage warmed up for him by American Idol star Kelly Clarkson. His address was the first directed particularly to young people […] [Read More]
Teens flock to youth rally with pope
About 25,000 young Catholics gathered on the grounds of St. Joseph's Seminary in Yonkers, N.Y., today for a rally with Pope Benedict XVI. But before the pope arrived, the vibe was that of a rock festival, according to the Religion News Service. American Idol star Kelly Clarkson and Christian artist Toby Mac were among the […] [Read More]
Cardinal DiNardo says pope's comments important for Houston
If you watched the prayer service at the Basilica of the National Shrine of the Immaculate Conception on television, you may have seen Cardinal Daniel N. DiNardo of the Archdiocese of Galveston-Houston singing with gusto on the front row. Photo by Matthew Barrick/Basilica via the Associated Press Houston's Cardinal Daniel N. DiNardo, left, joins other […] [Read More]
Papal Mass begins at Nationals Park
Chronicle reporter Tara Dooley has this update from the papal Mass: The crowd here at Nationals Park came to its feet as Pope Benedict XVI entered the stadium in the popemobile this morning: He traveled along the sides of the stadium smiling and waving to the cheering crowd. At 10 a.m. the Mass started with […] [Read More]
Crowds cheer Pope Benedict
Patrick Brendel of the Houston Chronicle's Washington Bureau filed this report today from the route of Pope Benedict's Popemobile. WASHINGTON – Thousands of people gravitated to the streets of the nation's capital today to catch a glimpse of Pope Benedict XVI traveling from the White House to the Vatican Embassy. AP Photo/Susan Walsh Crowds wave […] [Read More]
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am i hosed?
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Member Since: Feb 25, 2009
Posts: 2,109
Mac Specs: Late 2013 rMBP, i7, 750m gpu, OSX versions 10.9.3, 10.10
It reads to me that:
1) The auction claimed a New In Box Mac w/ 7200rpm drive
2) The item that arrived contained said 7200rpm drive, but the actual computer box itself had specs printed on it that stated the computer came with a 5400 rpm drive.
3) The screen cleaning cloth was missing.
So it seems that the OP is concerned that the laptop was really not New In Box because it appears that the hard drive, although specified as a 7200 in the auction (and what is in the system) was not the original drive from the manufacturer implying that the system is not really "new in box".
To the OP: There are several of possibilities.
It's possible he bought it at a store, bought a hard drive upgrade which was installed at the store, then later decided he didn't want it (as an example, I have a Mac Mini that I bought new, it came with 2 gig RAM, I had it upgraded at the store to 4 Gig (I didn't want to crack the case as getting into a mini is a pain) - technically since it was upgraded by the store one could argue it's still NIB since I hadn't opened it yet, but really since the box was opened, it's probably best to consider it LNIB).
It's possible he bought it, bought a bigger/better hard drive and installed it himself (really not a difficult task on current gen Macbook/Macbook Pro (not like a powerbook where you had to dig into it to get to the hard drive))
Either way, there aren't too many 500 GB 7200rpm laptop drives on the market, and from what it sounds, you got a seagate drive, which is - from reviews - a good drive.
You can always ask the seller why there was a discrepancy between what is printed on the box vs what was in the box - but it's not like there was something better that was made lesser, it was something lesser that was made better. At best case scenario - you're overreacting to a situation that isn't a problem. At worst case, the seller has a different interpretation of NIB then most people and should have listed it as LNIB (Like New In Box). Not knowing what you paid for it, I can only assume, either way, you probably got a decent deal otherwise you probably wouldn't have placed a bid on it?
My Macs: Late 2013 rMBP w/ 750m; Mac mini G4, 1.25 GHz, 512m ram (server); Late 2011 11" MBA, 1.8GHz i7, 4Gig Ram, 256Gig SSD, HD3000; Powerbook 12" G4 1.33GHz running Debian as a server; Apple TV (1080p version)
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Researchers have identified nanoscale changes in ageing lithium-ion batteries that could be responsible for their degradation over time.
Lithium-ion batteries are used in mobile phones, notebook computers and electric vehicles, and use lithium ions to carry the current from the negative to positive electrode.
They may then be recharged by an external electrical power source that forces ions to move in the reverse direction, from the positively charged cathode to the negative anode.
Giorgio Rizzoni and colleagues at the Ohio State University have dissected and examined batteries that had reached their end of life under experimental conditions.
They found that in dead batteries, a fraction of lithium was irreversibly lost from the cathode to the anode, and no longer participated in charging and discharging.
"We can clearly see that an aged sample versus and unaged sample has much lower lithium concentration in the cathode," Rizzoni explained.
"It has essentially combined with anode material in an irreversible way."
Using infrared thermal imaging and a range of microscopy techniques, the researchers discovered that finely-structured nanomaterials on dead batteries' electrodes had coarsened in size.
They suspected that the coarsening of the cathode may be responsible for the loss of lithium, although they have not yet proved this theory.
The study was being conducted in collaboration with Oak Ridge National Laboratory and the National Institute of Standards Technology.
Results were expected to increase batteries' longevity and improve their potential to power future electric vehicles.
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Forest Grove Campus Capital Improvements Planned for Summer
Updated May 19, 2015. Facilities Management will embark on several projects this summer to enhance the Forest Grove Campus and University Avenue.
Spring Commencement Brings Graduates, Families Together for Celebration
Pacific University held its 2015 spring commencement exercises on Saturday, May 16 at Hanson Stadium on the Forest Grove Campus.
Professor Jules Boykoff Receives Fulbright Award
Dr. Boykoff will travel to Brazil later this year to research the politics, economics and social issues of the 2016 Olympic Games in Rio de Janeiro.
Center for Peace & Spirituality Releases Annual Report
The Pacific University Center for Peace and Spirituality (CPAS) has released an Annual Report for the 2014-2015 academic year.
Updated Smoke-Free Tobacco Use Policy Goes Into Effect on May 31
In conjunction with World No Tobacco Day, Pacific University's updated Smoke-Free Tobacco Policy takes effect.
Important Information from the Student Health Center
A case of chickenpox has been identified in a resident student of the Forest Grove Campus. The Student Health Center advises students and employees to take appropriate precautions.
A Message from President Hallick
President Hallick is saddened to report that Lorelle Browning, professor of English, passed away on Sunday, April 26.
New Smoke-Free and Tobacco Use Policy Survey
Students, faculty and staff are asked to complete a short survey regarding the university's new smoking and tobacco use policy that will become effective May 31.
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