voltage control and frequency control
Power factor control is largely due to the dominant motor loads one industrial machines.

There are many methods of utility power generation system power factor and phase-frequency control systems to adjust  supply to meet demand.

Since the grid cannot store much energy except for brief intevals, the system must supply the load in real-time.

Nuclear reactors are run at 100% output while being only 50% efficient with heat loss transferred to available water at a temperature about 5’C above the body of water. While all the other sources must make up the difference in demand load with power factor being one of the variables..

Adapting + or - reactance to by phase control to maximize pf correction comes at a cost of conduction losses reducing the generators output.  Passive L and LC harmonic tuned filters are common place to optimize pf depending on harmonic content.

A method uses passive (manual or ) auto-switched Cap banks made of polypropylene dielectric while older versions were oil filled capacitors. 


  The concept is to provide conjugate matching of the grid and distribution source reactance to the load reactance while have a resistive impedance relative to rated load impedance measure in Z per unit or Zpu (%) of about 10 in order to limit fault currents to 10x rated load.
   But since it is dynamic, diurnal and seasonal it is a fairly complex control system. 


Shunt Reactors and Cap banks both rated in kVARs to shift phase.  Both can be fixed with tap switches or remote switched depending on location dynamics.

Generators can be electro-mechanically remote-controlled to increase current phaser angle as coordinated by the utilities and Regional Power Authority by also adjusting frequency down if supply cannot meet demand but then need to make up for lost cycles in low demand periods with higher frequency over the regional specified tolerances.

Governors may be electromechanical, or electronic Grid Tied Inverters (GTI) which usually pf =1 but can be remote programmed to adapt if necessary.  

There are libraries full of books, magazines and papers on the web thru Archive.gov, Google Scholar and MIcrosoft Research that are better read for the details on all the factors that must be considered for stability, optimization and more cost effective ways to control line reactance, load reactance and fault protection.

Here in Toronto, we have the luxury of state-of-the art control systems with remote monitors for each distribution line for power, balance, power factor, fault, redundancy control, instant fault re-routing, service isolation protection, and realtime home power utilization every minute with charts available to each consumer thru our Alectra home page to look for patterns per hour or day of the week or month of the year to examine energy use.