text:
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Most popular at the top
The StormThe Floating Press 2014; US$ 3.99
British author Daniel Defoe is known as one of the early innovators of the book-length novel, especially in his works Moll Flanders and Robinson Crusoe. In The Storm, Defoe creates another literary landmark -- the first modern example of long-form journalism. In the book, Defoe, drawing on firsthand accounts, records the impact and aftermath of The... more...
Climate Change for Football FansUIT Cambridge Ltd. 2014; US$ 7.28
Climate policy hits Turf Moor: follow Burnley's adventure in Europe and their roller-coaster struggle for survival in the Premiership while racing through an unconventional take on climate policy. This is a funny book, written in the earthy and irreverent language of the terraces. But it has a serious subtext � about climate change. It's a series... more...
The Hartwell Approach to Climate PolicyTaylor and Francis 2014; US$ 50.95
The Hartwell Approach to Climate Policy presents a powerful critique of mainstream climate change policies and details a set of pragmatic alternatives based on the Hartwell Group?s collective writings from 1988-2010. Drawing on a rich history of heterodox but increasingly accepted views on climate change policy, this book brings together in a single... more...
Contemporary ClimatologyTaylor and Francis 2014; US$ 88.95
Now in its second edition, Climatology continues to provide an up-to-date stimulating and comprehensive guide to the nature of the earth's climate. It presents a synthesis of contemporary scientific ideas about atmospheric circulation. Topics covered include: -Energy systems-The hydrological cycle-General circulation, local and regional climate-Application... more...
Canned HeatTaylor and Francis 2014; US$ 110.00
Climate change is a key challenge in the contemporary world. This volume studies climate change through many lenses: politics, law, ethics, philosophy, religion, and contemporary art and culture. The essays explore alternatives for sustainable development and highlight oft-overlooked issues, such as climate change refugees and food justice. Designed... more...
Carbon Dioxide Emission in Maritime Container Transport and comparison of European deepwater ports: CO2 Calculation Approach, Analysis and CO2 Reduction MeasuresDiplomica Verlag 2014; US$ 46.96
Maritime container transport accounts for approximately 90 percent of global trade volumes. Largest container vessels represent challenges for container ports, such as the required draft of 15.5 meters. In order to be competitive, many ports try to integrate in global supply chains. Furthermore, environmental issues play a growing role in the maritime... more...
AirReaktion Books 2014; US$ 24.95
Outside of yoga class, we don?t pay too much attention to the air we take in every day. Long one of the essential elements to life on earth?from the atmospheric composition that gave life to the coal-forming forests some three hundred million years ago to the air that fuels our most important technologies today?we think little of its incredible properties.... more...
The Burning QuestionProfile Books 2013; US$ 13.31
The Burning Question reveals climate change to be the most fascinating scientific, political and social puzzle in history. It shows that carbon emissions are still accelerating upwards, following an exponential curve that goes back centuries. One reason is that saving energy is like squeezing a balloon: reductions in one place lead to increases elsewhere.... more...
Natur ? Nation ? Sicherheit.Traugott Bautz 2010; US$ 17.74
Im Verlauf des 18. Jahrhunderts wurde in wissenschaftlich interessierten Kreisen immer wieder der Wunsch laut, die �usserst heterogenen Masse und Gewichte zu homogenisieren. Die Gelehrten st�rten sich zunehmend an den gebr�uchlichen, �ber Jahrhunderte gewachsenen lokalen Masssystemen. Diese anthropomorphen Masse, wie der Fuss oder die Elle, behinderten... more...
Wetter, Klima, MenschheitsentwicklungKonrad Theiss Verlag 2013; US$ 33.03
Waldbr�nde, Flutkatastrophen, Erderw�rmung ? ein Ph�nomen des 21. Jahrhunderts? Oder bestimmt der Klimawandel nicht schon immer den Weg des Menschen? Mit dieser brandaktuellen Fragestellung befasst sich der Geowissenschaftler Frank Sirocko, doch nicht mit dem Ziel, die Zukunft vorherzusagen, sondern vielmehr um einen Blick weit zur�ck in die Vergangenheit... more...


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Best Of The Joy Of Painting
Oriental FallsSeries Website »
Episode Guide »
Bob Ross achieves some different effects on canvas, creating a light and easy beauty that looks almost like watercolor.
Vermont transplant and Guster frontman Ryan Miller seeks out far-fetched friends across the state! Available exclusively online.
A second HD broadcast service offering alternative programming and more content from local and regional producers.

subset: commoncrawl


text:
7168 Items
Art News from Elsewhere
Jarman's Garden
Via theguardian.com
Oct 7
Widely revered as a filmmaker, Derek Jarman was also a skilled gardener. The unique costumes and astute attention to color and detail in his movies translate to the beautifully curated plot, continually maintained in his memory, 20 years after his death.
Punking Out: Derek Jarman and Vivienne Westwood on Jubilee
Oct 7
On a white cotton sleeveless t-shirt, now housed in the V&A Collection in London, the following words are printed: Open T shirt to Derek Jarman from Vivienne Westwood JUBILEE I had been to see it once and thought it the most boring and therefore disgusting film I had ever seen. I went to see it […] On a white cotton sleeveless t-shirt, now housed in the V&A Collection in London, the following words are…
Art News from Elsewhere
Learning from Athens
Via artnews.com
Oct 7
Documenta 14 will be split between its original host city, Kassel, and the Greek capital Athens, a city the festival's artistic director sees as a curatorially relevant "portal or border or place where people coming from many, many other places can have visibility."
A Cornell Box… of Cake
Martin Friedman
Jan 2015
A visit to Joseph Cornell's home in Queens, chocolate cake in hand.
Art News from Elsewhere
Museum Interface
Via artinamericamagazine.com
Oct 7
As interactive technology "weighs heavily on our physical experience" of real life, a necessary but ever-complex assignment looms over our cultural institutions: create an engaging, meaningful digital interface that can bridge the real and the virtual.
A Seat at the Table
Nicole J. Caruth
Oct 7
The metaphor of the table evokes images of folks coming together to break bread or discuss personal and political issues. For Seitu Jones and Theaster Gates, the table is more than a metaphor; it's a medium. In the Twin Cities, their tables are provoking dialogue about systemic reform, in local foodways and cultural institutions. Can these conversations effect change? Or is the change the conversation itself?
Art News from Elsewhere
Op-Ed Rap
Via latimes.com
Oct 7
"If you needed evidence that [Ana] Tijoux is not your average rapper," writes Carolina Miranda, "the fact that she's penning op-eds about female objectification for the website of a major Minneapolis museum might be Exhibit A."
Art News from Elsewhere
Musical Metal
Via newyorker.com
Oct 7
"Repetition opens into something else and time starts to operate differently," says The Kitchen's Tim Griffin of Danh Vo's Metal—a performance in which a father and his son pound gold in tune with Xiu Xiu's percussion-based musical compositions.
Open Veins of Hip-Hop: Ana Tijoux at The Cedar
The Green Room
Oct 7
To spark discussion, the Walker invites local artists and critics to write overnight reviews of our performances. The ongoing Re:View Series shares a diverse array of independent voices and opinions; it doesn't reflect the views or opinions of the Walker or its curators. Today, Walker Performing Arts Intern and Radio K DJ Sam Segal shares his perspective on Ana Tijoux […] To spark discussion, the Walker…


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My images are not in the public domain. All images are copyright Elaine Teague. All rights reserved. They should not be published, transferred, reproduced, modified or used in any way or in any part thereof without my written permission. If you wish to purchase any of my images you may safely do so through this site.
Canon 450D (Tamron lens 10-24mm)
3 bracketed exps + 2 more processed in Photomatix and finished in Topaz Adjust.
Elephant Rocks is in the William Bay National Park
Destination Australia – 22 December 2013
You Got it, We Want it – 10 December 2013
RB's Explore Featured Photography – 29 August 2013
Everyday Women – 9 July 2013
Featured for a Challenge – 18 May 2012
Artists Universe – 18 May 2012
Australiana Challenges – 30 March 2012
WA Red Bubbles – 4 September 2011
High Quality Images – 27 August 2011
JPG Cast Offs – 24 August 2011
Landscapes of the World – 24 August 2011
looks good on the new Product Preview page
Really? Haven't seen this new page. Must take a peek. Thanks for the comment George.
– Elaine Teague
Another great capture
Thanks Chris.
– Elaine Teague
Excellent shot, great warmth and colour.
Thanks very much Glen.
– Elaine Teague
Very many thanks for this feature Bradley.
– Elaine Teague
A gorgeous shot sweetheART & great info * a fave ;~} Valz
Thanks so much Val for your kind words and the fave. xx
– Elaine Teague
Brilliant photography Elaine. We do live in the lucky country, to have so much beauty around us, aye?
Thanks Vicki. You're so right about being in the lucky country.
– Elaine Teague
great shot – they look so elephanty!
LOL! One of them particularly looks like an elephant Noni. Thanks for the comment.
– Elaine Teague
Thanks for the feature Lynne.
– Elaine Teague
Superb work Elaine, congrats on your HQI feature!
Thanks very much Chris.
– Elaine Teague


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2 coupon codes & deals for nseffect.com. The site highlights about the various apparels used in nigeria, canada and the United States. Shows Excellent collections of apparels based on fashion and culture.Online booking option is also available.
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February 20-22, 2015
registration: https://canadianopendataexperience.ca/register/?lang=en
main site: https://www.canadianopendataexperience.ca/?lang=en (scroll down on the site to see all info)
gov site: http://open.canada.ca/en/canadian-open-data-experience-code
PR: http://news.gc.ca/web/article-en.do?nid=907729
A 48-hour hackathon using Canadian federal open data from http://open.canada.ca/en/open-data
Hashtag #CODE2015
October 13, 2013 Canadian national app development competition - CODE 2014
Raw notes on presentation "Mind the Gap" by Geoff Bilder (@gbilder) at Shaking It Up 2014.
Scholarly cyberinfrastructure
Bilder uses ORCid as an example of some success in this area.
Ideas developed with Cameron Neylon & Jennifer Lin from PLoS
wikipedia - cyberinfrastructure
need to transcend individual institutions
can't actually do simple things, let alone grand transformation
there is a reluctance to address infrastructure
1) infrastructure is boring
2) associated with huge bureaucracy
anti-pattern: when we talk about infrastructure
funder invites - future of scholarly communication
but researchers don't want to think about infrastructure
funder -> money into A (infrastructure)
researcher -> studying B (research)
researcher tries to overlap A and B
but research projects don't actually produce sustainable infrastructure
when the grant runs out, the server goes down, and the "infrastructure" they built disappears
cloud makes this even worse (not even a hard drive in an office somewhere you can recover)
"open", "distributed", "lightweight", "framework" makes things sound reasonable
Distributed begets centralized, because otherwise it doesn't work.
People trying to punt difficult decisions about infrastructure.
If you don't acknowledge from the start that distributed will be centralized...
you don't realize that you can be co-opted
minimal distributed - need many shims and adapters
trust issues
(there were) big problems with trust and ORCid (that had to be addressed)
ORCid initially CrossRef author DOIs
approach to address trust: principles
10 ORCid principles
what would a scholarly infrastructure organisation be like?
transcending disciplines, geography, institutions, stakeholders
have to get beyond discipline silos
geography is an issue because funders are national
should be stakeholder-governed
non-discriminatory membership
transparent operations (within constraints of privacy)
organisation cannot lobby
- because people fear organisations that just try to keep themselves alive
infrastructure organisation should have a living will
formal incentives to fulfil mission & wind-down
time-limited funds are used only for time-limited activities
goal to generate surplus
- breakeven is an incredibly fragile position
goal to create contingency fund to support operations for 12 months
revenue based on services, not data
- need to ensure data remains open
revenue generation should be consistent with the mission
- open source: forkability
open source
open data (within constraints of privacy)
available data (within constraints of privacy)
insurance policy:
(with open data and open source) if you can bring the community with you (to a new location/organisation), you can win (control of your information and system)
patent non-assertion
Geoff says: if I were a funder, I would look for these principles
need to build foundation
stop asking researchers how to fund infrastructure
get people who are good at infrastructure to do infrastructure
get over the fear of directly funding infrastructure
thanks to
Minister Clement has announced the 2nd Open Government Action Plan (OGAP2). It covers the years 2014-2016.
Building on the first Open Government Action Plan (released April 2012), there are the following new developments relevant to Open Science:
For more information, including the complete text of the Open Science commitment, see the new portal at open.canada.ca
Departments must maximize the release of open data and open information by ensuring that all data and information resources specified [in Appendix B] are considered for release.
The directive covers all government data and information. In addition, the draft 2nd Open Government Action Plan lists some specific focus areas with deliverables, including C.1. Open Science.
Deliverables to be completed in 2014-2016:
C.1.1 Develop and publish a government-wide Open Science Implementation Plan which lays out strategies and milestones
C.1.2 Establish an online service to enable a one-stop search for publications and data resulting from federally-funded scientific activities.
C.1.3 Establish common Open Access requirements for federally funded scientific research.
C.1.4 Develop inventories of scientific data, and initiate the public release of data supporting scientific research publications.
C.1.5 Publish and maintain a consolidated online list of peer-reviewed articles by Government of Canada scientists dating back to 2012.
The draft is open for consultation until noon Eastern time, Monday October 20, 2014. You can contribute to the consultation by leaving a comment at the bottom of the draft document. (Note: this is the fourth and probably final phase of consultation on the 2nd Open Gov Action Plan.)
On February 22, 2013 the White House Office of Science and Technology Policy (OSTP) issued "Increasing Access to the Results of Federally Funded Scientific Research" (PDF)
2. Agency Public Access Plan
The Office of Science and Technology Policy (OSTP) hereby directs each Federal agency with over $100 million in annual conduct of research and development expenditures to develop a plan to support increased public access to the results of research funded by the Federal Government.
It is not clear to me how one is supposed to find these Public Access Plans.
So I'm making a list. Which currently is a list of one.
Why a policy about open access is a PDF in response to a PDF is a separate issue.
If you know of any other departmental public access plans, please let me know.
As of Monday September 15, 2014 I have joined Environment Canada for a one-year Interchange (a kind of temporary work assignment). I will be working on policy and planning related to the Open Science proposal for the 2nd Canadian Open Government Action Plan. The open science initiative includes open access and open research data. To quote from the proposal
The Government of Canada proposes to maximize the release of federal scientific data and make more federally funded, peer-reviewed scientific articles and research publicly available ... free of charge.
If you're a Government of Canada employee, you can find information and provide feedback on the government wiki GCpedia as well as joining the discussion group on GCconnex.
Members of the public and GC employees can also leave a comment about the proposed activities at http://data.gc.ca/eng/Open_Science
Sept 6, 2014 update on Open Science and Open Access for Government of Canada research
June 18, 2013 2013 G8 Science Ministers Statement
This is a post for me to gather information about the provision of live (real-time) election results open data in Canada. If you know of any examples, please let me know.
Elections data is one of the high-value datasets listed in the G8 Open Data Charter, in section 6 Technical Annex, subsection 6.2 Collective Actions, subitem Action 2: Release of high-value data:
Government Accountability and Democracy - Government contact points, election results, legislation and statutes, salaries (pay scales), hospitality/gifts
* Edmonton - provided through Socrata API - https://data.edmonton.ca/City-Administration/2013-Edmonton-Election-Unofficial-Results/7cfp-j3h7
"Provide a live stream of Election Results on Election Night. ... every 2 minutes as results are received from Voting Stations"
*Strathcona County - Live election night results - http://www.strathcona.ca/local-government/strathcona-county-elections/election-2013-open-data/#live
Appears to be results as XML files. File specification available: http://www.strathcona.ca/files/files/at-lls-2013election-results-specification.pdf
Quebec provides four formats, but I don't know if they're in real time.
I also found a standard from the UK but I don't know how widely used it is
Here's a story about elections data from the Guardian
If you have any information or expertise in this area, please let me know.
This is a bit of a complicated trail, but here goes:
Open science is in the Digital Canada 150 strategy.
Open science was a proposed idea in the phase 2 ideas consultation for the 2nd Open Government Action Plan.
Open science is now a proposed action (proposed commitment) in the phase 3 activitives consultation. This is the last phase of online consultation. The next step will be to issue the OGAP 2 plan.
The feedback on the proposed idea does not carry over to the proposed action. If you want to be heard again, you have to post comments on the proposed action: Open Science.
UPDATE 2014-09-20: The action consultation (phase 3 consultation) is now closed, as of Sept. 19, 2014. However, the data.gc.ca mailing list has announced that there will be a 4th phase of consultation "to request public input on the draft version of Canada's Action Plan on Open Government 2.0" from Oct. 6-17, 2014 Oct 9, 2014. ENDUPDATE
There are also still in-person consultations to be completed. You can read about them here and here.
I do not have the exact schedule. Contact firstname.lastname@example.com for the correct information.
It looks something like this, but there may be changes:
|Round Table #6
|September 11 – Halifax (1841 Argyle St., Halifax City Hall, Halifax Hall)
3 hour session
September 12 – Saint John, New Brunswick ?
|Round Table #7
|October – Edmonton (date and location to be confirmed)
|3 hour session
|October – Ottawa (details forthcoming)
|Round Table #8
|Lethbridge (date and location to be confirmed)
|3 hour session
Canada is doing a multi-part, multi-aspect consultation about the 2nd version of its Open Government Action Plan.
The three four parts are:
1. In-person consultations
2. Ideas generation
3. Discussion of proposed activities (proposed commitments)
4. Consultation on the draft complete Action Plan (NEW)
Part 3 is now running has completed, however activities are being posted progressively; not all proposed commitments will be posted at once. At the time of this writing, there are four proposed commitments posted
others will follow.
UPDATE 2014-08-21: Open Information (including Virtual Library and declassifying documents) added. ENDUPDATE
UPDATE 2014-08-29: Open Data Canada – Open Data Without Borders (unified open data across Canadian jurisdictions), Open Dialogue (consulting Canadians). ENDUPDATE
UPDATE 2014-09-06: Three new proposed activities (proposed commitments):
UPDATE 2014-09-20: The action consultation (phase 3 consultation) is now closed, as of Sept. 19, 2014. However, the data.gc.ca mailing list has announced that there will be a 4th phase of consultation "to request public input on the draft version of Canada's Action Plan on Open Government 2.0" from Oct. 6-17, 2014 Oct 9, 2014. ENDUPDATE
To try to clarify the stages - in part 2 the public is invited to submit ideas, in part 3 the public is invited to provide feedback on selected activities, and in part 4 the public is invited to provide feedback on the entire plan.
There is some information in a news release - New Action Plan on Open Government: Engaging Canadians on Draft Plan - August 11, 2014.
The UK Government Digital Service was formed in April 2011 (according to Wikipedia).
On August 11, 2014 the White House announced the formation of a US Digital Service, as reported in the Washington Post
The White House on Monday announced that is was formally launching a new U.S. Digital Service and that they've hired to lead it Mikey Dickerson ...
U.S. CIO Steve VanRoekel called it a "centralized, world-class capability...made up of our country's brightest digital talent," forming a team that will be "charged with removing barriers to exceptional Government service delivery and remaking the digital experiences that citizens and businesses have with their Government."
White House launches "U.S. Digital Service" - by Nancy Schola @nancyschola - August 11, 2014
The organisation will apparently be referred to as the USDS - I couldn't find a website yet. The Washington Post article points to a document on the CIO.gov site - U.S. Digital Services Playbook http://playbook.cio.gov/ that may give some ideas of the goals of the organisation. The article indicates the model will be for the service to be a centre of expertise on design and transformation of services for the digital environment.
The US Digital Services Playbook has some rough similarities to the UK GDS Digital Principles and Design Principles.
UPDATE: WhiteHouse.gov blog post - Delivering a Customer-Focused Government Through Smarter IT.
Another piece of the puzzle is 18F Digital Services Delivery https://18f.gsa.gov/ @18f which will be used more to provide developer expertise to implement changes across the government.
February 24, 2012 San Francisco Innovation - A startup called government
Open Knowledge Festival 2014 - July 16, 2014
Session "Open, Digital Science - moving beyond open access" by Celina Ramjoué and Silvia Luber.
Sched entry.
Etherpad https://pad.okfn.org/p/Open,_Digital_Science
Dr. Ramjoué and Dr. Luber presented the progress on open science in the EU to date
They presented a framework of the larger set of issues involved when you look at the impact of digital technologies on all of science:
The session was mainly group discussions; these are summarized in the Etherpad.
The question of what policy actions are needed to support this new scientific ecosystem is an interesting one; it's a complex system and we are still figuring out necessary pieces.
Open Knowledge Festival 2014 - July 16, 2014
Keynote - Eric Hysen @EricHysen - Google Civic Innovation
"Let's build the road network of civic technology."
Video of presentation http://youtu.be/0UNRZEsLxKc?t=57m20s
Interview video https://www.youtube.com/watch?v=jeyZxsQzes8
Excited by the great reaction to my talk at #OKFest14. I've posted the full talk https://t.co/fIBAWF3Zzm and slides https://t.co/p054R3uCqf
— Eric Hysen (@EricHysen) July 17, 2014
Text of talk.
Q: Andrew Clarke, Omidyar @andrew_c_clarke - What is the most needed (thing in this space)?
A: government (unique) identifiers
Open Knowledge Festival 2014 - July 16, 2014
Keynote - Neelie Kroes @NeelieKroesEU - European Commissioner for Digital Agenda
Video of presentation at http://youtu.be/0UNRZEsLxKc?t=29m45s
Interview video at http://www.youtube.com/watch?v=MGTLIfk-1BQ
Open Knowledge Festival 2014 - July 16, 2014
Keynote – Patrick Alley of Global Witness @Global_Witness
Video of presentation is not available. Interview with Patrick Alley at http://www.youtube.com/watch?v=znu9sSZ6ynM
csv,conf 2014 - July 15, 2014
14:00 The Content Mine by Peter Murray-Rust @petermurrayrust
Presentation: http://www.slideshare.net/petermurrayrust/csvconf
Peter is using the UK Exceptions to Copyright for Research (PDF), specifically the text and data mining exception.
csv,conf 2014 - July 15, 2014
12:20 Data-Hacking with Wikimedia Projects: Learn by Example, Including Wikipedia, WikiData and Beyond by Matt Senate @wrought and Max Klein @notconfusing
Matt and Max have clearly done a lot of thinking about how to make a project work within the WikiMedia context. The project they described is about automatically extracting information about open access content and then enriching multiple WikiMedia sites with the appropriate information.
Video available at https://www.youtube.com/watch?v=w5T6RoEckAQ
csv,conf 2014 - July 15, 2014
11:55 session CSV Validation by Adam Retter @adamretter
Video available at https://www.youtube.com/watch?v=9pIBG5iv5XI
See also UK National Archives blog: CSV validator – a new digital preservation tool.
csv,conf 2014 - July 15, 2014
10:35 session Data usability: the tabular data package and friends by Nick Stenning @nickstenning
Data publishers at #csvconf: my message to you today is "put it in a box." Publish your data as data packages: http://dataprotocols.org/
— Nick Stenning (@nickstenning) July 15, 2014
Slides at https://github.com/nickstenning/put-it-in-a-box
Introducing The Data Package, datapackage.json
See info at http://dataprotocols.org/data-packages/#specification
My question: What about BagIt?
Answer from Rufus Pollock (@rufuspollock): Other formats were examined, there is a white paper.
UPDATE 2014-08-01: Review of Existing Packaging Work via @rufuspollock
csv,conf 2014 introduction by Max Ogden and Rufus Pollock - @maxogden and @rufuspollock
July 15, 2014
(csv is Comma-Separated Values, a way of representing data.)
Hashtag #csvconf


text:
Photos and Description of this 2 bedroom holiday apartment in Montevarchi - Apartment In Chianti With Pool, Free Bike Rental, Wi-Fi, Terrace & Garden, Close Florence, Siena
Sleeps 6. 2 bedroom apartment in farmhouse Valleverde with two bedrooms, living room with kitchen and sofabed, two bathrooms, outdoor terrace with wineyard views. Ideal for 4 up to 6 guest. Close to the major tuscan cities, 30min from Florence,Arezzo and Siena, inside the Chianti areas. Pets are welcome.
The Valleverde (Green Valley) farmhouse is located in a beautiful valley, surrounded by woods and vineyards in the heart of the typical Tuscan landscape of the Chianti region; a true oasis of peace, ideal for a quiet and relaxing vacation. The pleasure of a traditional vacation to regenerate mind and body as you taste Tuscany's world famous cuisine, walk along winding country paths and discover the artistic treasures of nearby cities. The owners' hospitality is of the old fashioned variety and your every need will be cared for.
- Suitability:
- Pets
- pets considered
- children welcome
- suitable for elderly or infirm


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Discussion of the buttons, dials, wheels, switches, and menus found on cameras.
152 views
Why does my camera turn off after taking 2 to 3 shots?
My camera is acting weirdly these days... After putting fully charged batteries into it I was only able to take 2-3 shots before it turned off and showed the battery low symbol. So I took my camera to ...


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Today's Gazette
Hiding something
ADQ leader Mario Dumont claimed Saturday morning that Premier Jean Charest had ...
While Vick has dog days, his pit bulls are fine
10 of the animals taken from him brought together
Stu Cowan, The GazettePublished: Saturday, December 01 2012
"They live in the present moment, they value companionship, they mirror their owners' expectations, and despite our cruelties, they're incredibly forgiving by nature. I sometimes think dogs - pit bulls especially - are here to teach us all how to be better humans."
I also asked Reynolds what she thinks now when she sees Vick playing football on TV.
"That's a trick question," she responded. "We've stayed focused on the dogs since they're the true heroes. If you want to talk about making comebacks, the dogs from the Vick case are all Hall of Famers for their incredible resilience and outstanding performance in the real world."
To find out what BAD RAP director Donna Reynolds had to say about a recent opinion article published in The Gazette under the headline "No SPCA dogs for me" and to see a video of the BAD RAP reunion for Michael Vick's dogs, go to Stu Cowan's blog at montrealgazette.com/ stuonsports
firstname.lastname@example.com Twitter: @StuCowan1


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Dr. Nicholas A. Pawlowski, MD
Pediatric Allergy/Immunology, Childrens Hospital Of Philadelphia Specialty Care Center
- 210 Mall Blvd
King of Prussia, PA 19406
- 1 Office Location
- (610) 337-3232
Dr. Nicholas A. Pawlowski has been practicing medicine for 38 years. Dr. Pawlowski graduated from the Georgetown University School of Medicine in 1976. He practices medicine in King of Prussia, PA and specializes in Pediatric Allergy/Immunology. Dr. Pawlowski is affiliated with Childrens Hospital Of Philadelphia. He speaks English and Spanish.
Gender: Male
Years in Practice: 38 Years
Languages Spoken: English, Spanish
Medical School: Georgetown University School of Medicine
Graduation Date: 1976
Hospital Affiliations: Childrens Hospital Of Philadelphia
Specialties: Pediatric Allergy/Immunology


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74th out of 108 books — 20 voters
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Start by marking "Broken Pieces" as Want to Read:
Broken Pieces
by Carla Cassidy (Goodreads Author)
Mariah Sayers survived a brutal attack as a teenager, and ran away out of fear. Sixteen years later she returns with her daughter to make peace with her past. Just as she feels she is rekindling old friendships and even an old flame, she receives some shocking news; a girl has been killed in her town. Now, Mariah will have to confront the unthinkable—and reclaim the broken ...more
Paperback, 336 pages
Published September 2nd 2008 by Signet
(first published January 1st 2008)
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Best Romantic Suspense 2011
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Community Reviews
(showing 1-30 of 294)
Oct 06, 2008 Julie (jjmachshev) rated it 4 of 5 stars
Shelves: queuemyreview, 2008-reads
Reviewed for queuemyreview.com; book release Sep08
I have shivers running up and down my spine. I just finished "Broken Pieces" by Carla Cassidy and I really hope none of my stairs creak tonight or I'll likely have a heart attack screaming my head off. If you like books that scare you and have you looking over your shoulder, this one will fit the bill.
Mariah's childhood wasn't that great. Her fire and brimstone father was a firm believer in 'spare the rod and spoil the child'. So much so, that sh ...more
I have shivers running up and down my spine. I just finished "Broken Pieces" by Carla Cassidy and I really hope none of my stairs creak tonight or I'll likely have a heart attack screaming my head off. If you like books that scare you and have you looking over your shoulder, this one will fit the bill.
Mariah's childhood wasn't that great. Her fire and brimstone father was a firm believer in 'spare the rod and spoil the child'. So much so, that sh ...more
Sep 24, 2008 Sherry rated it 4 of 5 stars
Carla Cassidy has created a story that has the reader's attention at the very beginning. Mariah Sayers doesn't seem like a heroine at the beginning, just a woman with a traumatic start in life, yet as the plot unfolds you realize that indeed she is, simply by doing, being constant and overcoming; indeed more than a heroine, she is a strong survivor. This is a good read for those who like myself, enjoy reading books where the universe seems to finally right itself for individuals who not only de ...more
Apr 04, 2009 Blackbook rated it 4 of 5 stars
Shelves: 2009
I have a bunch half read books that I'm trying to finish up. Really glad I came back to this one. I am not always in the mood to want to read stories that have elements of sexual assault and healing past trauma. Not to mention teenage daughters, this is a topic I am always trying to get away from. This was a suspenseful, good read. I look forward to reading more of her work.
Oct 14, 2013 Jen_C rated it 4 of 5 stars · review of another edition
Shelves: abuse-addiction, single-parent, teacher-professor, tragic-past, veterinarian
Pretty good book. The rape & abuse was brutal but not graphically described. I was a bit frustrated with the h at times but not too much. The H is not alpha but was a really good guy. I figured out who the rapist was about 1/3 of the way in but was not truly bothered by that because I was anxiously awaiting the confrontation when Mariah figured it out and there was enough tension with other things going on. Worth a read.
Oct 26, 2011 Jacqueline rated it 3 of 5 stars
Nicely done romantic suspense. The plot made sense and moved right along. The author kept me guessing about the bad guy. I did guess but mostly because I picked one of the suspects and just stuck with him. A nice balance of romance and suspense. I liked the strong heroine and the nice guy hero.
Sep 04, 2011 Mic Tov rated it 4 of 5 stars
Shelves: own
I picked this up at one of the dollar stores for 1.50. It was well worth it. Everyone I have loaned out to thought it was a great read too. The story kept twisting. It kept you guessing right up to the end who the "bad guy" was. Loved the mother daughter relationship.
Jul 27, 2011 Jennifer rated it 5 of 5 stars
Great book. It was full of drama, intrigue, suspense, love, romance and friendship. A definite page turner that will keep you guessing till the end. Well written with a great writing style. Mariah and Dr Hot were just that HOT.
Jan 25, 2011 Carolina Perez rated it 5 of 5 stars
Recommends it for: anybody who loves mystery and suspense
Recommended to Carolina by: La'swanique Wesley
This book is definitley going down on one of my "treasure forever" books. It definitley has a lot of climax points and i am for sure that the end will be astonishing...I look forward to seeing who the killer is.
Dec 31, 2008 Mary Beth rated it 3 of 5 stars
Broken Pieces is very light reading. I have never read Carla Cassidy's work before, but it is very reminiscent in style to Mary Higgins Clark. A good mystery but a little heavy on the romance.
Apr 16, 2012 Pam rated it 5 of 5 stars
I never in a MILLION years expected the monster to be...........who it was! I was caught up in this book and read it in one day!!
Jun 11, 2009 Mom Taxi Julie rated it 3 of 5 stars
Just finished this book this morning. It felt like it took me forever to read but at the end I didn't want to put it down!
Jul 27, 2011 Hpitcher added it
i read this book in just hours of starting it and i adored it. i loved the entire idea and it shocked me and i loved it
Oct 16, 2008 Nicole rated it 5 of 5 stars
Carla Cassidy is an awesome author and I would recommend all of her books.
Apr 12, 2009 carla rated it 5 of 5 stars
another great story.. keeps you guessing right till the end.
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A method reducing transient overshoot of an output signal of an uninterruptable power supply, the uniterruptable power supply including: (a) an inverter having at least one power switch; (b) a digital controller that generates a pulse width modulated (PWM) signal for controlling the power switch, the PWM signal having a fixed period TPWM and (c) an analog to digital signal corresponding to the sampled output signal, the method comprising the steps of (1) operating the A/D converter to sample the output signal at a first time to generate a first sampled output value; (2) operating the A/D converter to sample the output signal at a second time to generate a second sampled output value, the period between the second time and the first time being equal to TPWM; (3) generating a control input value that is equal to 1.5 times the second sampled output value minus 0.5 times the first sampled output value; (4) computing a PWM signal at a third time, the PWM pulse having a duration equal to the PWM pulse duration, the period between the second time and the third time being equal to 0.5 TPWM.
1. A method reducing transient overshoot of an output signal of an uninerruptable power supply, the uniterruptable power supply including: (a) an inverter having at least one power switch; (b) a digital controller that generates a pulse width modulated (PWM) signal for controlling the power switch, the PWM signal having a fixed period TPWM and (c) an analog to digital signal corresponding to the sampled output signal, the method comprising the steps of:
i) operating the A/D converter to sample the output signal at a first time to generate a first sampled output value;
ii) operating the A/D converter to sample the output signal at a second time to generate a second sampled output value, the period between the second time and the first time being equal to Tpwm;
(iii) generating a control input value that is equal to 1.5 times the second sampled output value minus 0.5 times the first sampled output value;
(iv) computing a PWM pulse duration as a function of the control input value;
(v) initiating a pulse of the PWM signal at a third time, the PWM pulse having a duration equal to the PWM pulse duration, the period between the second time and the third time being equal to 0.5 TPWM.
This application claims the benefit of U.S. Provisional Application No. 60/182,394, filed Feb. 14, 2000.
Techniques for producing low Total Harmonic Distortion in PWM inverters (single-phase or three-phase) have been known to exist in several prior works. In the early days, the carrier-modulated PWM techniques such as the triangular wave comparison type PWM were very popular. For example such techniques are disclosed in: A. Schonung and Stemmler, "Static frequency changes with subharmonic control in conjunction with reversible variable speed drive," BBC RevI., pp. 555-557, August/September 1964; P. D. Ziogas, "Optimum voltage and harmonic control of PWM techniques for three phase static UPS systems," IEEE Trans. Ind. Appl., vol. IA-16, no. 4, pp. 542-446, July/August 1980; and B. K. Bose and H. A. Sutherland, "A high performance pulse-width modulator for an inverter-fed drive system using a microcomputer," in Conf. Rec. 1982 Ann. Meet. Ind. Appl. Soc., pp. 847-853.
Microcomputer based techniques using preprogrammed PWM patterns have also been utilized. For example in: H. S. Patel and R. G. Hoft, "Generalized technique of harmonic elimination and voltage control in thyristor inverter, Part I," IEEE Trans. Ind. Appl. vol. IA-9, no. 3, pp. 310-316, March/April 1973; and "Part II, "IEEE Trans. Ind. Appl., vol. LA-10, no. 5, pp. 666-673, September/October 1973; F. G. Turnbull, "Selected harmonic reduction in static dc-ac inverters, "IEEE Trans. Commun. Elec., vol. 83, pp. 374-478, July 1964; I. J. Pitel, S. N. Talukdar, and P. Wood, "Characterization of programmed-waveform pulse-width modulation," IEEE Trans. Ind. Appl., vol. IA-16, no. 5, pp. 707-715, September/October 1980; and G. S. Buja, "Optimum output waveforms in PWM inverters, "IEEE Trans. Ind. Appl., vol. IA-16, no. 6, pp. 830-836, November/December 1980.
In these techniques, the switching edges of the PWM pattern are computed to satisfy certain performance requirements; the most common of which is controlling the fundamental component and eliminating specified harmonics. Two main disadvantages of these techniques are: slow voltage regulation response due to average voltage control, and phase displacement between the reference sine wave and the filter output varies with the load.
More recent techniques include the time optimal response switching PWM, disclosed in, for example: A. Kernik, D.L. Stechshulte, and D.W. Shireman, "Static Inverter with synchronous output waveform synthesized by time-optimal response feedback" IEEE Trans. IECI, vol. IECI-24, no. 4, pp. 297-305, 1977; A. Kawamura and R. G. Hoft, "Instantaneous feedback controlled PWM inverter with adaptive hysteresis," IEEE Trans. Ind. Appl., vol. IA-20, no. 4, pp. 769-775, July/August 1984; and P. Ziogas, "Delta modulation technique in static PWM inverters," IEEE Trans. Ind. Appl., vol. IA-17, pp. 289-295, 1981. Other recent techniques include the real-time deadbeat-controlled PWM, disclosed in, for example: K. P. Gokhale, A. Kawamura, and R. G. Hoft, "Dead beat microprocessor control of PWM interter for sinusoidal output waveform synthesis," in Conf. Rec. IEEE Power Elect. Spec. Conf., 1985, pp. 28-36 and A. Kawamura, T. Haneyoshi, and R. G. Hoft, "Deadbeat controlled PWM inverter with parameter estimation using only voltage sensor," in Conf Rec. IEEE Power Elec. Spec. Conf, 1986. These techniques have very fast response for load disturbances, but it is also known that these systems have a high THD for non-linear load (crest-load).
The voltage control technique proposed in the present invention uses the perfect control of robust servomechanism problem (Perfect RSP) theory developed in Davison, E. J. and Scherzinger, B., "Perfect Control of the robust servomechanism problem", IEEE Trans. On Automatic Control, 32 (8), 689-702, 1987 ("Davison et al") to ensure perfect tracking of the output voltages under unknown load by providing means for eliminating errors at specified harmonic and at the same time ensuring good transient response. The theory is based on the internal model principle, proposed by Francis, B. A., and Wonham, W. M., "The internal mode principle for linear multivariable regulators", Appl. Math. Opt., vol. 2, pp. 170-194, which states that asymptotic tracking of controlled variables toward the corresponding references in the presence of disturbances (zero steady state tracking error) can be achieved if the models that generate these references and disturbances are included in the stable closed loop systems. In other words, if we include the frequency modes of the references and the disturbances to be eliminated in the control loop, then the steady state error will not contain these frequency modes.
Applying the internal model principle into the output voltages control in a three-phase PWM inverter means that the fundamental frequency mode (50 Hz or 60 Hz) has to be included in the controller since the references vary at this frequency. Elimination of the voltages errors due to the load currents at other harmonics frequency can then be achieved by including the frequency modes of these harmonics into the controller. The perfect RSP theory combines this internal model principle with the optimal state feedback to guarantee stability of the closed loop system and providing arbitrary good transient response.
Similar techniques that use the internal model principle to achieve very low THD output voltage in single-phase PWM inverters have been reported recently in T. Haneyoshi, A. Kawamura, and R. G. Hoft, "Waveform compensation of PWM inverter with cyclic fluctuating loads, IEEE Trans. Ind. Appl., vol. 24, pp. 582-589, 1988 ("Haneyoshi et al") and Y. Tzou, S. Jung, and H. Yeh, "Adaptive Repetitive Control of PWM Inverters for Very Low THD AC-Voltage Regulation with Unknown Loads ("Tzou et al"). In these papers, the control development follows the repetitive control theory developed in T. Inoue, M. Nakano, and S. Iwai, "High accuracy control of servomechanism for repeated contouring," in Proc 10th Annu. Symp. Incremental Motion Contr. Syst. Devices, 1981, pp. 258-292; T. Inoue and M. Nakano, "High accuracy control of a proton synchroton magnet power supply," in IFAC, vol. 20, 1981, pp. 216-221; and S. Hara, Y. Yamammoto, T. Omata, and M. Nakano, "Repetitive control system: A new type servo system for periodic exogenous signals," IEEE Trans. Automatic Contr., vol. 33, no. 7, pp. 659-666, 1988. Unlike the technique based on the perfect RSP that provides zero steady state error for references or disturbances only at finite specified frequencies, the repetitive control guarantees zero steady state error at all the harmonic frequencies less than half of the sampling period. However, the repetitive control is not easy to stabilize for all unknown load disturbances and cannot obtain very fast response for fluctuating load. In Haneyoshi et al, the latter problem is solved by including a "one sampling ahead preview controller", and Tzou et al enhances the stability result of Haneyoshi et al by providing an adaptive mechanism for unknown load disturbances.
The inventor would like to point out here that, although the perfect RSP used in this disclosure only eliminates voltage harmonic at a finite specified frequencies, the perfect RSP control is still a very suitable control for a three-phase PWM inverters. It is to be emphasized that in a three-phase system, most of the voltage harmonics, like the triplen harmonics (3rd, 6th, 9th, etc.), are either non-existent, uncontrollable, and/or negligible in values. Therefore, not too many harmonics are left for the control to handle. Moreover, the closed loop stability under unknown load is easier to achieve with the perfect RSP than the repetitive control, and the perfect RSP by itself already provides a good transient response.
The inventor has also successfully combined the perfect RSP control of the voltages harmonics with a fast current controller using a discrete time sliding mode controller, as disclosed in Utkin, V., Guldner, J., Shi, J., Sliding Mode Control in Electromechanical Systems, Taylor & Franci, Philadelphia, Pa., 1999, ("Utkin et al") for limiting the inverter currents under overload condition. This is one of the important features necessary for a UPS, which is not addressed in the repetitive control work of Haneyoshi et al and Tzou et al. The discrete sliding mode controller has been chosen because of the fast and no-overshoot response that it provides. The current controller acts as an inner loop to the perfect RSP control of the output voltages in the outer loop. In this case, the perfect RSP voltage control has been designed by accounting for the extra dynamic introduced by the discrete time sliding mode controller. This way, the stability and robustness of the overall control system are still guaranteed.
FIG. 1 diagrammatically illustrates a general controller that solves the robust servomechanism problem.
FIG. 2 illustrates a power converter system used with the present invention.
FIG. 3 illustrates each phase of the delta-wye transformer model used in the present invention.
FIGS. 4A-4E illustrate equivalent circuits of the inverter in the DQ0 stationary reference frame.
FIG. 5 illustrates a control strategy using a two-loop control structure, an inner inverter currents loop and an outer load voltages loop, in accordance with the present invention.
FIG. 6 shows the timing diagram of the PWM gating signals generation in relation with the A/D sampling time of the DSP.
FIG. 7 illustrates the robust servomechanism controller structure during current limit saturation.
FIGS. 8A-8D shows the waveforms of the load currents, load voltages, and inverter voltages under various linear loads: resistive, inductive, balanced, and unbalanced load.
FIG. 9 shows the load voltages, load currents, inverter voltages, and inverter currents under non-linear loads.
FIG. 10 illustrates a 0% to 100% resistive load transient.
FIG. 11 illustrates the load voltages when subjected to a 100% to 0% purely resistive load transient.
FIG. 12 illustrates the inverter currents during a short circuit.
FIG. 13 illustrates a schematic of a power system controlled in accordance with the present invention.
FIG. 14 illustrates the discrete state space implementation of the harmonic-eliminating transfer function for the fundamental frequency and the fifth and seventh harmonics.
FIG. 15 illustrates the overall sum for each axis derived by multiplying each state of the servo compensator states (xservo(k)) with the corresponding servo compensator gains.
FIG. 16 illustrates the current limiting accomplished by limiting the magnitude of the inverter current commands vector and maintaining its original direction.
The present invention relates to control techniques, and more particularly to techniques for digitally controlling uninterruptible power supplies. Specifically, the present invention relates to a method for reducing transient overshoot of the output of an uninterruptible power supply.
Particularly, the method of the claimed invention involves operating an analog to digital converter to sample the output signal, e.g., a voltage or a current, at a first time to generate a first sampled output value. The claimed invention further involves operating the analog to digital converter to sample the output signal at a second time to generate a second sampled output value. The period between the first operation of the analog to digital converter and the second analog to digital converter is equal the PWM period of the inverter; i.e., TPWM.
The method then involves generating a control input value for the inverter that is equal to 1.5 times the second sampled output value minus 0.5 times the first sampled output value. Once the control input value is determined, a PWM pulse duration is computed as a function of the control input value. A pulse having the computed pulse duration (i.e., a PWM signal) is initiated at a third time. The third time is one-half PWM period after the second sampling time.
Perfect Control of Robust Servomechanism Problem
Finding a solution to a Robust Servomechanism Problem (RSP) for a system involves finding a controller for the system such that: given a modeled class of unstable tracking/disturbance signals, exact asymptotic tracking/regulation occurs for all plant perturbations that do not produce instability. A perfect controller for the RSP solves the RSP and also provides arbitrarily good transient error, with no unbounded peaking in the error response of the system. Below some of the main results of the perfect RSP discussed in Davison et al are summarized.
Consider the plant to be regulated described by the following equations:
where xεRn, xεRm are the inputs, yεRr are the outputs to be regulated, ymεRrm are the measurable outputs, dεRδ are the disturbances, yrefεRr are the reference input signals, and eεRr are the error in the system. It is assumed that the disturbance d arises from the following class of systems:
{dot over (η)}1=Ψ1η1 , d=C 1η1, η1 εR n1 (2)
and the reference input signals yref arise from the following:
with eig(Θ1)⊂C+ and eig(Θ2)⊂C+, where eig( ) denotes the eigenvalues and C+ denotes the closed right complex half plane. This class of signals includes most classes of signals that occur in application problems, e.g., constant, polynomial, sinusoidal, polynomial-sinusoidal, etc. Let Λ={(λ1, λ2, . . . , λp} be the zeros of the least common multiple of minimal polynomial of Ψ1Ψ2 (multiplicities repeated), then a linear controller that solves the RSP for (1), consists of the following structure:
where ηεRrp is the outputs of a servo-compensator and ξεRm the output of a stabilizing-compensator S. The servo compensator has the form:
Ac=block diag (Ω,Ω, . . . ,Ω)
Bc=block diag(γ,γ, . . . ,γ)
where the coefficients σi,i=1,2, . . . , p are given by the coefficients of the polynomial
The servo compensator gain K1 in (4) and the stabilizing-compensator S should be found to stabilize and "give desired behavior" to the following stabilizable and detectable system:
A general controller that solves the robust servomechanism problem can be diagrammatically shown as in FIG. 1.
Note that, given a modeled class of references/disturbances, the servo-compensator is unique within the class of coordinate transformations and nonsingular input transformations. The stabilizing compensators S are, however, not unique; there are various classes of stabilizing compensators that can be used in a robust servomechanism controller. One of them is the complementary controller where the stabilizing compensator is given by:
where x can either be the measured states of the system, or the estimates found using an observer (if not all states are measurable). In this case, the control u is given by state feedback found to stabilize the augmented system of the plant and the servo-compensator:
A perfect controller for the robust servomechanism problem can be constructed using Cheap Control method, where the gains K=[K0 K1] are found by minimizing the following performance index:
where γ>0 is an arbitrarily small scalar. The optimal control gain K=Kopt, which minimizes this performance index, is given by: Kopt=−1/ε{tilde over (B)}′Popt, where Popt is the unique positive semi-definite solution to the algebraic Riccati equation.
Discrete-Time Sliding Mode Control
Discrete time sliding mode controller is an approach in the sliding mode control theory, which is suitable for digital implementation since it does not exhibit the chattering phenomena due to direct digital implementation of continuous time sliding mode control. See Utkin et al.
Consider a continuous linear time invariant system
with state vector x(t)εRn, control u(t)εRm, output to be regulated y(t), reference input yref(t), and disturbance d(t). System (12) can be transformed to discrete time system with sampling time Ts to yield.
A*=exp(A·TS) B*=∫0 T s eA·(Ts−τ)B dτ
E*=∫0 T s eA·(Ts−τ)E dτ
It is desired to control the output y(k) to follow the reference yref(k). For this purpose we can choose a sliding mode manifold in the form of: s(k)=Cx(k)−yref(k) such that when discrete-time sliding mode exists we have y(k)→yref(k). Discrete-time sliding mode exists if the control input u(k) is designed as the solution of:
The control law that satisfies (13) is called 'equivalent control' and is given by:
If the control is limited to a value u0 i.e. ∥u(k)∥≦u0 then the following modified control law can be applied:
With control law (16), the discrete-time sliding mode exists after a finite number of steps.
The Power Converter System
A power converter system to which the controller of the present invention may be applied comprises a typical three-phase PWM voltage inverter with LC output filter (Linv and Cinv) and a delta-wye transformer that act both as a potential transformer and electrical isolation to the load. FIG. 2 shows a circuit diagram of the system. Notice that the delta-wye transformer converts a three-wire (UVW) power system of the inverter to a four-wire (XYZ-N) system for the load. Small capacitors (denoted as Cgrass in FIG. 2) are added at the load side of the transformer to provide further harmonics filtering and stabilization of the load voltages. A DSP (Digital Signal Processor) system controls the operation of the power converter, providing required PWM gating signals to the power II devices. Voltages and currents measured by the DSP system for control purposes are shown labeled in FIG. 2. The line-to-neutral load voltages (at points xyz-n in FIG. 2) are denoted as: Vloadan, Vloadbn, and Vloadcn, the load phase currents as: Iloada, Iloadb, and Iloadc, the line-to-line inverter capacitor voltages (at points uvw in FIG. 2) as Vinvab, Vinvbc, and Vinvca., the inverter phase currents as: Iinva, Iinvb, and Iinvc.
For development of the control algorithm, a state space model of the system is needed. Each phase of the delta-wye transformer has been modeled as an ideal transformer with leakage inductance Ltrans and series resistance Rtrans on the secondary winding as shown in FIG. 3. The secondary transformer currents are denoted as Isnda, Isndb, and Isndc.
Using the transformer model in FIG. 3, the dynamic equations of the output filter circuit in FIG. 2 can be written as in equations (17.a)-(17.d):
where the voltages and currents vectors are defined as in (18).
Matrices Tri and Trv in equation (17.a) and (17.d) denote the currents and voltages transformations of the delta-wye transformer. Denoting the transformer's turn ratio as tr, these matrices are given by (19):
To obtain a state space model of the system, the dynamic equations in (17) are transformed to DQ0 stationary reference frame using the transformation:
where {right arrow over (f)}qd0 denotes the abc voltages and currents defined in (18), and {right arrow over (f)}qd0 the corresponding DQ0 stationary reference frame variables. The circuit dynamics can then be written as in (21):
where the matrices Triqd0 and Trvqd are defined as:
Notice that, due to the three-wire system of the inverter and filter, the zero components of the inverter voltages ({right arrow over (V)}invqd), the inverter currents ({right arrow over (I)}invqd) and the input PWM voltages ({right arrow over (V)}pwmqd) are trivial and they do not appear in (21).
Using the dynamic equations in (21), equivalent circuits can be drawn in the DQ0 stationary reference frame as shown in FIGS. 4A-4E. From FIGS. 4A-4E it can be seen that the 0-axis equivalent circuit of the load-side of the transformer is completely de-coupled from the qd-axis equivalent circuits. This shows that the zero components of the load voltages and the secondary transformer currents (Vload0 and Isnd0) are uncontrollable by the input PWM voltages ({right arrow over (V)}pwmqd). A linear controllability analysis performed to (21) can also be used to show this fact. The 0-component of the load currents will be non-zero under unbalanced load condition or under non-linear load in the form of triplen harmonics. Because these 0-components are uncontrollable, no action can be done by the control to compensate them. However, as is apparent from FIGS. 4A-4E, the small capacitor at the output along with the leakage inductance of the transformer act as an LC filter which can be tuned to provide attenuation to the effect of the 0-component of the load voltages. From FIGS. 4A-4E, the amount of this attenuation at steady state can be calculated from:
where ω=2 πf and f is a harmonic frequency of interest.
Control System Development
To achieve fast current limiting capability for the inverter, the control strategy uses a two-loop control structure; an inner inverter currents loop and an outer load voltages loop as shown in FIG. 5. The outer loop regulates the load voltages ({right arrow over (V)}loadqd) to follow 50/60 Hz balanced three-phase voltages references ({right arrow over (V)}refqd) and generates the inverter currents commands ({right arrow over (l)}cmdqd), which are limited. The inner loop in turn generates the PWM voltage commands to regulate the inverter currents to follow the inverter current command. A standard voltage space vector algorithm is then used to realize these PWM command voltages. Notice that the 0-components of the load voltages are not regulated by the control, since it is uncontrollable.
FIG. 6 shows the timing diagram of the PWM gating signals generation in relation with the A/D sampling time of the DSP. It can be seen that there is a one-half PWM period delay between the time the signals are sampled by the A/D and the time the PWM control action is applied.
The next two subsections summarize the development of the two control loops, the inner current loop using the discrete sliding mode controller and the voltage control loop using the robust servomechanism principles.
Discrete-Time Sliding Mode Current Controller
For designing the discrete time sliding mode current controller, consider the intverter and filter subsystem with no transformer and load dynamics:
Assuming the secondary transformer currents {right arrow over (I)}sndqd0 as disturbances, this subsystem can be written in state space form as:
where the states are {right arrow over (x)}=[{right arrow over (V)}invqd,{right arrow over (I)}invqd] the inputs {right arrow over (u)}={right arrow over (V)}pwmqd and disturbances {right arrow over (d)}1={right arrow over (I)}sndqd.
The discrete form 25 can be calculated as:
and TS is the A/D sampling time, which in this case is equal to the PWM period Tpwm
To force the inverter currents to follow their commands, the sliding mode surface is chosen as: {right arrow over (s)}(k)=C1·{right arrow over (x)}1(k)−{right arrow over (I)}cmd(k) where C1·{right arrow over (x)}1(k)={right arrow over (I)}invqd(k), so that when discrete sliding mode occurs, we have {right arrow over (s)}(k)=0 or {right arrow over (I)}inv(k)={right arrow over (I)}cmd(k). The existence of the discrete sliding mode can be guaranteed if the control is given:
where the equivalent control input {right arrow over (u)}eq(k) is calculated from:
and u0 denotes the maximum value of the PWM voltage command realizable by the space vector algorithm.
Note that the secondary transformer currents are needed for the control, but these currents are not measured in the system (see FIG. 2). A linear Luenberger observer can be easily designed to estimate these currents for control purposes. However, in most practical cases we can approximate these currents with the load currents (i.e., {right arrow over (I)}sndqd={right arrow over (I)}loadqd) because the currents through the output capacitor filters are small. According to the inventor's experience, the effect of using this approximation is unnoticeable in the control performance.
Due to the computation delay of the DSP, the control action given by (27) will result in undesirable overshoots during transients. This effect can be minimized, however, if the states {right arrow over (x)}1 (k) and disturbances {right arrow over (d)}1(k) are replaced with their first order one-half step ahead predicated values given by:
The equivalent control input {right arrow over (u)}eq(k) then becomes:
Voltage Controller Design Using Discrete Perfect RSP
The voltage control loop designed in this research is based on the discrete form of the technique developed in Davison et al discussed above. To design the load voltages controller, first consider the entire plant system with the 0-components of the voltages and currents omitted as given in (30). As explained in above, these 0-components are completely de-coupled and uncontrollable from the inputs, and therefore are not useful to be included in the design. In the system (30), an input delay of one-half the PWM period (0.5Tpwm) has been explicitly included to account for the computation delay of the DSP.
The states variables for the system (30) are chosen as {right arrow over (x)}p=[{right arrow over (V)}invqd,{right arrow over (I)}invqd, {right arrow over (V)}loadqd, {right arrow over (I)}sndqd], with the inputs as u={right arrow over (V)}pwmqd. System (30) can be transformed to a discrete-time system with sampling time Ts=Tpwm to yield:
Discrete time system (31) can be written in a standard discrete time state space equations by adding the extra states: {right arrow over (x)}a(k)={right arrow over (u)}(k−1)={right arrow over (V)}pwmqd(k−1) to yield:
so that the system can be written as:
To design the voltage controller, we need to consider the true plant (33) and the discrete time sliding mode current controller as the equivalent 'plant' as seen by the outer voltage loop. Using equation (27) and (33) the augmented true plant and discrete sliding mode current controller can be found as in (34).
with {right arrow over (u)}1(k)={right arrow over (I)}cmdqd*(k), and
Note that the augmented system given in (34) was found assuming the approximation {right arrow over (I)}sndqd≈{right arrow over (I)}loadqd has been used.
Now, assume ωi=2 πfi i=1,2, . . . n are frequencies of the reference voltages and harmonics to be eliminated. For a 60-Hz UPS system with desire to eliminate 5th and 7th harmonics, for example, we use ω1=2π·60, ω2=2π·5·60, and ω3=2π 7·60. We can then choose the servo-compensator to be of the form (35):
{right arrow over (η)}=[{right arrow over (η)}1,{right arrow over (η)}2, . . . {right arrow over (η)}n]T {right arrow over (η)}i εR 4 , i=1,2, . . . n A c=block diag[Ac1 ,Ac 2 , . . . ,Ac n ]B c =[Bc 1 ,Bc 2 , . . . ,Bc n]T
Note that each of the blocks {right arrow over ({dot over (η)})}i=Ac1{right arrow over (η)}i+Bci{right arrow over (e)}Vqd represents a state space implementation of the continuous transfer function 1/(s2+ωi2) for each of the qd-axis voltages errors.
The servo compensator (35) can be transformed to a discrete time system to yield:
Now that we have determined the 'plant' and the servo compensator, the control input for the perfect robust servomechanism controller is given by:
where the gains K [K0 K1] are found by minimizing the discrete performance index:
for the augmented 'equivalent plant' (34) and the servo compensator (36):
where ε>0 is an arbitrarily small scalar.
Current Limit and Control Saturation Handling
The current command {right arrow over (I)}cmdqd*(k) generated by the robust servomechanism voltage controller above is limited in magnitude as in (40) to yield the current command {right arrow over (I)}cmdqd*(k), which will be implemented by the inner loop current controller.
Imax represents the maximum allowable magnitude of the inverter currents. Equation (40) limits the magnitude of the current commands but maintains their vector directions in the qd space.
The states {right arrow over (η)}i of the servo-compensator can be seen as sine wave signal generators that get excited by the harmonic contents of the error signals at frequency ωi. When the control inputs of the robust servomechanism voltage controller saturate i.e., |{right arrow over (I)}cmdqd*(k)|>Imax the servo-compensator states will grow in magnitude due to the break in the control loop. This problem is similar to the integrator windup problem that occurs in an integral type controller. To prevent this, the servo-compensator in (36) can be modified as follows:
Using (41), during the current limit saturation, the servo compensator states will continue to oscillate at the harmonic frequency with constant magnitude. The resulting robust servomechanism controller structure is shown in FIG. 7.
Experimental Results
The effectiveness the proposed control strategy has been verified on an 80 kVA UPS unit with system parameters shown in Table 1. The DC bus voltage is obtained from a 6-pulse thyristor controlled rectifier in parallel with a 480V battery system. The DSP control system used is based on the TMS320F240 fixed point DSP with control timing diagram as given in FIG. 6. The PWM timing is calculated through a standard space vector PWM with switching frequency of 3.2 kHz Tpwm=Ts=320 μsec.
The experimental results presented in this report have been obtained using the proposed control strategy with the 5th and 7th harmonics being eliminated. Table 2 gives the steady state RMS output voltages regulation under different types of loads. It can be seen that the control strategy provides good output voltages regulation in all cases. Note that the deviations in the output voltages for unbalanced load are due to the uncontrollable 0-component of the load currents. However, as can be seen the effect is minimal showing the effectiveness of the LC filter at the output side of the transformer.
FIG. 8 shows the waveforms of the load currents, load voltages, and inverter voltages under various linear loads: resistive, inductive, balanced, and unbalanced load. FIG. 9 shows the load voltages, load currents, inverter voltages, and inverter currents under non linear crest load. The THD of the load voltages in FIG. 9 was measured at 2.8% with the load currents of 3:1 crest factor. Table 3 summarizes the output voltages THD under different types of loads showing the superior THD performance of the proposed control strategy. Better results may be obtained by including more harmonies to be eliminated into the robust servomechanism controller.
FIGS. 8A-8D the load currents, load voltages and inverter voltages for the experimental system loaded at steady state linear load as follows: (a) 100% resistive balanced; (b) 100% 0.8 pf load; (c) 100% resistive unbalanced (phase A unloaded) and; (d) 100 % resistive unbalanced (phase A&B). The top illustrates load currents. The middleindicates load voltages. The bottom indicates inverter voltages.
FIG. 9 illustrates the load voltages and load currents for a steady state non-linear load of 100% having 3:1 crest factor. The topillustrates phase A of load voltages and load currents, while the bottomillustrates phase A of inverter voltages and inverter currents.
FIG. 10 illustrates the load currents and load voltages for a 0 to 100% resistive load transient the topillustrates three-phase load currents, while the bottom illustrates three-phase load voltages.
FIG. 11 illustrates the load currents and load voltages for a 100% to 0% resistive load transient. The top illustrates three-phase load currents, and the bottom illustrates three-phase load voltages.
FIGS. 9 and 10 show the responses of the load voltages on resistive load transients. 0-100% and 100%-0 respectively. It can be seen that the load voltages recover within less than a cycle after the load is applied. In both cases, the output voltages magnitudes deviate less than 5% of the nominal. These result show that the perfect RSP controller provides fast transient recovery under load transients with minimal overshoot in the response. Finally, the effectiveness of the current controller was verified by applying a sudden three-phase short circuit on the output load terminals. The current limit was set at 300% level, and the inverter was shutdown deliberately after ten cycles of short circuit condition. The results are shown in FIG. 12. It can be seen that the discrete sliding mode controller provides a fast and minimal overshoot on the inverter currents. The top illustrates inverter currents; the middle illustrates load voltages; and the bottom illustrates inverter voltages.
Step-By-Step Control Flow for One Embodiment
The steps in operating the disclosed control system will now be described in sequence. A first step is, at each control sampling time k, sampling the following voltage and current signals: (1)the line-to-neutral voltages (at points xyz-n in FIG. 13) denoted as Vloadan, Vloadbn, and Vloadcn; (2) the load phase currents, denoted as Iloadb, Iloadb, and Iloadc; (3) the line-to-line inverter filter capacitor voltages (at points uvw in FIG. 13), denoted as Vinvab, Vinvbc, and Vincca; and (4) the inverter phase currents, denoted as Iinva, Iinvb, and Iinvc.
From the sampled values, the inverter voltage, inverter current, load voltage, and load current vectors are formed in abc reference frame:
Note that the inverter currents vectors are represented as line-to-line quantities. This is done to match the chosen state space equations and state variables used to derive the control. Inverter phase currents can also be used here with proper modification to the state space equations used.
The third step is to transform the sampled voltages and currents to the DQ0 stationary reference frame using the transformation:
The following voltages and currents variables in DQ stationary reference frame are obtained:
The 0-component of the inverter voltages and currents will always be zero and can be discarded due to the three-wire system of the inverter. The 0-components of the load voltages and currents can be non-zero, however, these components are non-controllable and have no use for control. Therefore only the DQ components need to be used and calculated:
Note that the DQ0 transformation used here is a standard transformation commonly used in three-phase power applications. The transformation puts the three-phase variables in the system into an orthogonal coordinate system. The use of an orthogonal coordinate system allows the identification of state variables and creation of the state space equations for control purposes.
The fourth step is to generate the sine waves references at discrete time k for the load voltages in the abc reference frame and perform the DQ transformation on them to obtain the references in DQ.
where Vmd is the voltage magnitude of reference AN, VmB is the voltage magnitude of reference BN, VmC is the voltage magnitude of reference CN, TS is the sampling period, and fref is the fundamental reference frequency.
These voltages are then transformed to DQ reference frame:
Again only the DQ components are needed for control:
The fifth step is then to compute the load voltage errors to be used by the voltage servo compensator, which are given by:eq=Vrefq−Vloadq and ed=Vrefd−Vloadd.
The sixth step is to calculate the next discrete states (time k+l) of the servo compensator for each of the harmonic frequency to be eliminated and the fundamental frequency and for each Q and D axis voltages errors. FIG. 14 shows the case when the 5th and 7th are to be eliminated. Each harmonic servo compensator block in FIG. 2 is the discrete state space implementation of the analog transfer function:
where T1=2Bθiθf,f is the fundamental frequency and i−f is the harmonic frequency (i.e., in the case of FIG. 14, i=1, 5, and 7). Specifically, the following continuous state space implementation of T(s) is used for each harmonic servo compensator block:
which is then discretized to obtain the a's and b's coefficients shown in FIG. 14. A standard discretization method like ZOH (Zero order hold) method is used in this case. Each harmonic servo compensator block in FIG. 14 ensures the elimination of the corresponding harmonic contents of the errors signals. This condition is guaranteed by the internal model principle that states that if frequency modes (poles) of the references and the disturbances to be eliminated are included in the control loop, then the steady state error will not contain these frequency contents. Each of these harmonic compensators can be viewed as signals generators that vary at the harmonic frequency and reacts only to the existence of the corresponding harmonic in the errors signals. It provides adjustment to the inverter current commands generated by the voltage control loop to force the corresponding harmonic content of the errors to zero.
The seventh step is to multiply each state of the servo compensator states (xservo(k)) with the corresponding servo compensator gain and get the overall sum for each axis as shown in FIG. 15. The plant states (consisting of the inverter voltages, inverter currents, load voltages, load currents, and the previous PWM voltage commands) are multiplied with the stabilizing compensator gains to get the summation for each axis. The sum of the servo compensator and the stabilizing compensator for each axis constitutes the inverter current commands generated by the voltage control loop i.e., Icmdq and Icmdd.
The servo compensator and the stabilzing compensator gains are designed to ensure the stability of the overall control loop i.e., the combined voltage control loop and the current control loop. The perfect RSP theory provides a way of calculating these gains using an OPTIMAL Control Technique. Using this technique, a cost function consisting of the weighted sum of squares of the servo compensator states, the plant states, and the control inputs (inverter current commands) is created. An optimization routine is then used to seek for the gains that minimize this cost function. The weighted sum of squares of the servo compensator states in this case can be viewed as the energy in the errors signals, while those of the plant states and the control inputs can be viewed as the fuel energy needed. Different weighting used can be used to obtain different behavior of the control system.
The eighth step in the control method is to perform the current limiting function. The purpose of this current limiting function is to limit the inverter currents commands generated by the voltage controller. At each sampling time the inverter currents commands generated by the voltage controller will be implemented by the inner current loop which will compute the necessary PWM command.
The current limiting is accomplished by limiting the magnitude of the inverter current commands vector and maintaining its original direction as shown in FIG. 16. The current limit appears as a circle in the DQ stationary reference frame. If the command vector generated by the voltage controller goes outside of this circle, its magnitude is limited to be within the circle with its direction unaltered. Limiting the inverter currents in this way ensures that at each time the magnitudes of the 3-phase inverter currents in the abc reference frame remain within the limit value but still provides the phase relations required by the voltage control loop. Mathematically, this limiting function can be written as:
where absolute value indicates square root of sum of the squares.
The ninth step in the control method is to compute the errors between the limited inverter current commands and the actual inverter commands as follows: elq=Icmdq−linvq and eld=Icmdd−linvd. The discrete sliding mode current controller will force these errors to zero at the next sampling time (k+1) by computing the necessary PWM voltage command.
The tenth step is to compute the one-half step ahead prediction of the inverter voltages and currents and the load currents. These predicted values of the voltages and currents are necessary to account for the delay in the application of the PWM voltage due to DSP computation time.
The eleventh step is to compute the necessary PWM voltages to implement the inverter current command using the Discrete sliding mode current controller. The Discrete Sliding Mode current controller ensures that at the next sampling time (k+1), the inverter current commands obtain the values of the command using the available DC bus voltage at the time. The necessary PWM voltages commands are given by:
Note the PWM voltage commands are limited by the amount of available DC bus voltage at that time. This limit value is denoted as u0 in the above equations.
The twelfth and final step involves implementation of the PWM voltage commands into an actual PWM voltages using a standard Space Vector PWM technique. The Space Vector PWM technique takes the PWM voltages commands Vpwmq and Vpwmd, and computes the necessary timing to switch on and off the power switches.
Having shown and described a preferred embodiment of the invention, those skilled in the art will realize that many variations and modifications may be made to II affect the described invention and still be within the scope of the claimed invention. Thus, many of the elements indicated above may be altered or replaced by different elements which will provide the same result and fall within the spirit of the claimed invention.
For example, it is appreciated that the present invention may be used with single-phase systems. It is also appreciated that various inverter systems may be used as well as other Uninterruptible Power Supplies. It is the intention, therefore, to limit the invention only as indicated by the scope of the claims.
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Happy Halloween! Today marks the official end of the University of Alberta's United Way campaign. A warm thank you to Chancellor Ralph Young for chairing the campaign—and to all staff and faculty who have organized special events over the last several weeks to help raise awareness for the annual campaign on campus, and of course, help bring in much-needed pledges.
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The focus of many of my activities this week was philanthropic stewardship. Two President's Society dinners were held, first in Calgary on Tuesday evening, followed by Edmonton on Wednesday.
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I write to you this week from London, England, where I have been engaged in informative discussions between the vice-chancellors from the Russell Group of Universities and the U15 Group of Universities' presidents and principals. The goal of this week's meeting has been to explore and advance new ways for Canada (U15) and the United Kingdom (Russell Group) to stimulate international joint research and development initiatives.
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University ranking season has now wrapped up with the results from the three international ranking bodies. I am proud to say that the University of Alberta has done well on a global scale. The first two, Academic Ranking of World Universities (ARWU) and Quacquarelli Symonds (QS), which measure research output from citations and other indicators, have placed us around 100th and 84th in the world, respectively. The third ranking, the Times Higher Education Ranking, attempts to rank teaching and research.
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Hockey, Fighting and Head Injuries
After a career that spanned Major Junior A, professional and university hockey, Chris Morehouse hung up his skates earlier this month. He was a hockey player, but he was also a veteran of more than a 100 on-ice brawls. The St. Thomas University journalism student now has time to reflect on what fighting and concussions mean for the game...and for the rest of his life.
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