Utilization of distributed generator inverters as statcom

Abstract

A method and system for operating an inverter based distributed power generation source as a reactive power compensator STATCOM—a Flexible AC Transmission System (FACTS) device. The inverter-based power generation source is a photovoltaic solar farm. The photovoltaic solar farm can provide various STATCOM functions both during nighttime and daytime in the power grid system to which the photovoltaic solar farm is coupled. STATCOM functions include reactive power compensation, voltage control, stability improvement, an increase in power transfer capacity, power oscillation damping, damping of subsynchronous oscillations, increasing voltage stability, etc. These STATCOM functions are provided when the photovoltaic solar farm is performing either of: i) not providing active power to said power grid system, or ii) providing active power less than said maximum inverter capacity to said power grid system.

What is claimed is: 
     
         1 . A control system for use in controlling an inverter based power generation source operatively coupled to a power grid system at a point of common coupling (PCC), said inverter based power generation source comprising at least one inverter, said control system enabling said inverter based power generation source to provide at least one of a plurality of static synchronous compensator (STATCOM) functions to said power grid system when said inverter based power generation source is performing at least one of:
 i) not providing active power to said power grid system; or   ii) providing active power to said power grid system where said active power is less than a maximum inverter capacity;   
       wherein said plurality of STATCOM functions includes:
 i) power oscillation damping; and 
 ii) damping of sub synchronous oscillations; 
 
       wherein said inverter-based power generation source is a photovoltaic solar farm; 
       wherein the power grid system is at least one of:
 i) a power transmission system, 
 ii) a power distribution system, 
 iii) a microgrid system, or 
 iv) any combination of the above. 
 
     
     
         2 . The control system according to  claim 1 , wherein said at least one of said plurality of STATCOM functions is provided by said at least one inverter of said inverter based power generation source. 
     
     
         3 . The control system according to  claim 1 , wherein said at least one of said plurality of STATCOM functions is provided by using an unutilized capacity of said at least one inverter of said inverter-based power generation source. 
     
     
         4 . The control system according to  claim 1 , wherein said at least one of said plurality of STATCOM functions, when provided to said power grid system, provides at least one of:
 i) an improvement in power grid system stability,   ii) an increase in power transmission capacity of said power grid system,   iii) a mitigation of subsynchronous resonance,   iv) an alleviation of subsynchronous control interactions,   v) an improvement in High Voltage Direct Current (HVDC) converter terminal performance,   vi) an increase of power output from existing power generation sources in said power grid system, and   vii) a facilitation of integration of additional power generation sources in said power grid system.   
     
     
         5 . The control system according to  claim 1 , wherein at least one input to said control system is derived from a characteristic of a signal passing through said power grid system. 
     
     
         6 . The control system according to  claim 1 , wherein at least one input to said control system is at least one of:
 i) at least one signal related to PCC voltage,   ii) at least one signal related to at least one bus voltage,   iii) at least one signal related to at least one line current,   iv) at least one signal related to at least one line power flow,   v) at least one signal related to at least one bus frequency,   vi) at least one signal related to rotor oscillations of at least one generator connected to said power grid,   vii) at least one signal related to power oscillations,   viii) at least one signal related to subsynchronous oscillations; and   ix) at least one power grid signal indicative of oscillations that need to be damped.   
     
     
         7 . The control system according to  claim 1 , wherein said control system is used to determine financial compensation to owners of said inverter based power generation source for providing said at least one of said plurality of STATCOM functions when said inverter based power generation source is performing at least one of: i) not providing active power to said power grid system, or ii) providing active power to said power grid system where said active power is less than a maximum inverter capacity. 
     
     
         8 . The control system according to  claim 1 , wherein said control system is used to determine financial compensation to owners of said inverter-based power generation source for providing said at least one of said plurality of STATCOM functions to said power grid system, wherein said at least one of said plurality of STATCOM functions, when provided to said power grid system, provides at least one of:
 i) an improvement in power grid system stability,   ii) an increase in power transmission capacity of said power grid system,   iii) a mitigation of subsynchronous resonance,   iv) an alleviation of subsynchronous control interactions,   v) an improvement in High Voltage Direct Current (HVDC) converter terminal performance,   vi) an increase of power output from existing power generation sources in said power grid system, and   vii) a facilitation in integration of additional power generation sources in said power grid system.   
     
     
         9 . A control system for use in controlling an inverter-based power generation source operatively coupled to a power grid system at a point of common coupling (PCC), said inverter based power generation source comprising at least one inverter, said control system enabling said inverter based power generation source to provide at least one of a plurality of static synchronous compensator (STATCOM) functions to said power grid system, said plurality of STATCOM functions including:
 i) reactive power compensation, and   ii) voltage control;   
       wherein said at least one of a plurality of STATCOM functions is provided to said power grid system when said inverter-based power generation source is performing at least one of:
 i) not providing active power to said power grid system, and when at least one other distributed power generation source also operatively connected to said power grid system produces an amount of power that is in excess of power required by one or more loads coupled to said power grid system, said at least one other distributed power generation source being different from said inverter-based power generation source; or 
 ii) providing active power to said power grid system where said active power provided is less than a maximum inverter capacity, and when at least one of:
 a) said inverter-based power generation source produces an amount of power that is in excess of power required by one or more loads coupled to said power grid system, or 
 
 b) one other distributed power generation source also operatively connected to said power grid system produces an amount of power that is in excess of power required by one or more loads coupled to said power grid system, said at least one other distributed power generation source being different from said inverter-based power generation source; 
 
       wherein said inverter-based power generation source is a photovoltaic solar farm; 
       wherein the power grid system is at least one of:
 i) a power transmission system, 
 ii) a power distribution system, 
 iii) a microgrid system, or 
 iv) any combination of the above. 
 
     
     
         10 . The control system according to  claim 9 , wherein said plurality of STATCOM function includes reactive power compensation and said reactive power compensation is dynamic. 
     
     
         11 . The control system according to  claim 9 , wherein said plurality of STATCOM functions includes voltage control and said voltage control is dynamic. 
     
     
         12 . The control system according to  claim 9 , wherein said at least one other distributed power generation source also operatively connected to said power grid system is one of:
 i) an inverter-based power generation source,   ii) a non-inverter-based power generation source.   
     
     
         13 . The control system according to  claim 9 , wherein said at least one of said plurality of STATCOM functions is provided by said at least one inverter of said inverter-based power generation source. 
     
     
         14 . The control system according to  claim 9 , wherein said at least one of said plurality of STATCOM functions is provided by using an unutilized capacity of said at least one inverter of said inverter-based power generation source. 
     
     
         15 . The control system according to  claim 9 , wherein said at least one of said plurality of STATCOM functions, when provided to said power grid system, provides at least one of:
 i) an improvement in power grid system stability,   ii) an increase in power transmission capacity of said power grid system,   iii) a mitigation of subsynchronous resonance,   iv) an alleviation of subsynchronous control interactions,   v) a regulation of system frequency,   vi) an improvement in High Voltage Direct Current (HVDC) converter terminal performance,   vii) an increase of power output from existing power generation sources in said power grid system,   viii) a facilitation of integration of additional power generation sources in said power grid system, and   ix) an increase in a hosting capacity for photovoltaic solar farms.   
     
     
         16 . The control system according to  claim 9 , wherein at least one input to said control system is derived from a characteristic of a signal passing through said power grid system. 
     
     
         17 . The control system according to  claim 9 , wherein at least one input of said control system is at least one of:
 i) at least one signal related to PCC voltage,   ii) at least one signal related to at least one bus voltage,   iii) at least one signal related to at least one line current,   iv) at least one signal related to at least one line power flow,   v) at least one signal related to at least one bus frequency,   vi) at least one signal related to rotor oscillations of at least one generator connected to said power grid,   vii) at least one signal related to power oscillations,   viii) at least one signal related to subsynchronous oscillations; and   ix) at least one power grid signal indicative of oscillations that need to be damped.   
     
     
         18 . The control system according to  claim 9 , wherein said control system is used to determine financial compensation to owners of said inverter-based power generation source for providing said at least one of said plurality of STATCOM functions to said power grid system, wherein said at least one of said plurality of STATCOM functions, when provided to said power grid system, provides at least one of:
 i) an improvement in power grid system stability,   ii) an increase in power transmission capacity of said power grid system,   iii) a mitigation of subsynchronous resonance,   iv) an alleviation of subsynchronous control interactions,   v) a regulation of system frequency   vi) an improvement in High Voltage Direct Current (HVDC) converter terminal performance,   vii) an increase of power output from existing power generation sources in said power grid system,   viii) a facilitation in integration of additional power generation sources in said power grid system, and   ix) an increase in a hosting capacity for photovoltaic solar farms.