Control system for photovoltaic power plant

Abstract

A control system for a photovoltaic (“PV”) power plant that includes a plant-level control system for implementing plant-level control functions at power generation sites of the plant, a supervisory system for supervisory control and data acquisition of the plant, and a communications network connecting the plant-level control system, the supervisory system, and plant devices is described. Methods of controlling a PV plant using the plant-level control system and the supervisory system and methods of regulating power characteristics in power generation sites are also described.

What is claimed as new and desired to be protected by Letters Patent of the United States is: 
     
         1 . A control system for regulating operation of a photovoltaic (“PV”), power plant which includes a plurality of power generation sites, the control system comprising:
 a plant-level control system for receiving information on the power supplied to a grid from the PV power plant and for controlling functions at the plurality of power generation sites; 
 a plurality of monitoring and communication devices coupled to the plant level control system, each monitoring and communication device being associated with at least one power generation site for collecting measured direct-current and alternating current information from the associated power generation site, including information regarding the alternating-current output of the power generation site, and sending the collected information to the plant-level control system; and 
 at least one controllable device at respective power generation sites responsive to commands of the plant-level control system for adjusting the outputs of the power generation sites. 
 
     
     
         2 . The control system as in  claim 1 , wherein the controllable device is an inverter configured to adjust its AC output in response to commands from the plant level control system. 
     
     
         3 . The control system as in  claim 1 , wherein each power generation site comprises at least one plant device and wherein the controllable device is configured to generate and transmit instructions to the at least one plant device to adjust voltage output properties of a respective power generating site. 
     
     
         4 . The control system as in  claim 3 , wherein the plant device comprises at least one of a DC voltage combiner, a solar panel mounting mechanism, and a PV solar panel. 
     
     
         5 . The control system as in  claim 3 , wherein each power generation site includes at least one controllable inverter as the controllable device. 
     
     
         6 . The control system as in  claim 1 , wherein the plant level control system provides control functions which include at least one of attaining a set point control of the power output to the grid, attaining a set point control of the DC current input to at least one inverter of a power generation site, attaining ramp-up and ramp-down control of the power output by the PV power plant to the grid, voltage regulating of the power output to the grid, regulating a power factor of the power output to the grid, and frequency control of power output to the grid. 
     
     
         7 . The control system as in  claim 6 , wherein the plant level control system, in response to a set point power output parameter which is higher than a measured power output to the grid, takes no action with respect to a power generation site. 
     
     
         8 . The control system as in  claim 6 , wherein the plant level control system, in response to a set point power output parameter which is lower than a measured power output to the grid instructs the at least one controllable device to reduce power supplied by a respective power generation site. 
     
     
         9 . The control system as in  claim 8 , wherein the respective power generation site includes an inverter and the controllable device instructs the inverter to reduce the AC power output of the inverter. 
     
     
         10 . The control system as in  claim 8 , wherein the respective power generation site includes at least one DC voltage combiner and the controllable device instructs the at least one DC combiner to reduce the DC power output of the power generation site. 
     
     
         11 . The control system as in  claim 8 , wherein the respective power generation site includes a mounting mechanism for moving solar panels and the controllable device instructs the mounting mechanism to reduce the DC power output of the respective power generation site by moving the solar panels. 
     
     
         12 . The control system as in  claim 1 , wherein the power generation sites include respective inverters and the controllable device regulates the DC current input to an inverter of a power generation site. 
     
     
         13 . The control system as in  claim 12 , wherein the inverter is regulated by the plant level control system in response to at least one of an input from a user and a command generated by the inverter. 
     
     
         14 . The control system as in  claim 1 , wherein each power generation site includes a respective inverter and the plant level control system has a DC threshold current input parameter and if the DC threshold current input parameter is lower than a measured DC input current to the inverter, the plant level control system instructs the controllable device to reduce the DC output of the respective power generation site. 
     
     
         15 . The control system as in  claim 14 , wherein the controllable device controls a DC voltage combiner within the respective power generation site. 
     
     
         16 . The control system as in  claim 14 , wherein the controllable device controls a mounting mechanism for moving a solar panel of a respective power generate site. 
     
     
         17 . The control system as in  claim 1 , wherein the plant level control system provides ramp-up and ramp-down control of an output of the PV power plant. 
     
     
         18 . The control system as in  claim 17 , wherein output of the PV power plant is measured at a connection to the grid and if the output of the PV power plant is increasing at a greater rate than a specified ramp-up rate the plant level control system instructs one or more controllable devices to reduce the output power of a respective power generating site. 
     
     
         19 . The control system as in  claim 17 , wherein output of the PV power plant is measured at a connection to the grid and if the output of the PV power plant is decreasing at a rate greater than a specified ramp-down rate the plant level control system instructs one or more controllable devices to increase the output power of a respective power generating site. 
     
     
         20 . The control system as in  claim 1 , wherein the plant level control system regulates the PV power plant output voltage to the grid. 
     
     
         21 . The control system as in  claim 20 , wherein the plant level control system receives a desired parameter for the PV power plant voltage to be supplied to the grid, determines the voltage supplied to the grid, and sends instructions to one or more controllable devices to achieve a closed loop voltage feedback control of the voltage supplied to the grid. 
     
     
         22 . The control system as in  claim 1 , wherein the plant level control system provides power factor regulation of voltage supplied to the grid. 
     
     
         23 . The control system as in  claim 22 , wherein the plant level control system receives a power factor parameter and a ratio of real power to apparent power as measured at the connection of the PV power plant to the grid and if the measured real power to apparent power is not within a specified limit the plant-level control system instructs one or more controllable devices to achieve power factor regulation of their respective power generate sites to within the specified limit. 
     
     
         24 . The control system as in  claim 1 , wherein the plant-level control system provides regulation of the frequency of power droop at the output of the PV power plant to the grid. 
     
     
         25 . The control system as in  claim 24 , wherein the controllable device is response to instructions from the plant-level control system to perform down-power regulation of one or more inverters provided in a respective power generation site when the output frequency at the point of connection between the PV power plant and grid is higher than a desired value. 
     
     
         26 . The control system as in  claim 24 , wherein the controllable device is responsive to instructions from the plant-level control system to perform up-power regulation of one or more inverters provided in a respective power generation site when the output frequency at the point of connection of the PV power plant to the grid is lower than a desired value. 
     
     
         27 . The control system as in  claim 1 , wherein each power generation site includes one or more inverters and circuitry to provide the one or more inverters with low voltage and high voltage ride through capabilities. 
     
     
         28 . The control system as in  claim 27 , wherein the circuitry is integrated into the one or more inverters. 
     
     
         29 . The control system as in  claim 1 , further comprising a supervisory system for the PV power plant, the supervisory system communicating with the plant-level control system for instructing operations to be performed by the plant-level control system and for monitoring operation and performance indicators of the PV power plant, and status and operating conditions of components of the power generation sites. 
     
     
         30 . The control system as in  claim 29 , wherein the supervisory system is configured to control components of the power generation sites. 
     
     
         31 . The control system as in  claim 29 , wherein the supervisory system is configured to set the plant level control system into different operating modes including normal operational start up, normal operational shut down, in service and out of service modes. 
     
     
         32 . The control system as in  claim 29 , wherein the supervisory system collects real time data from one or more components of the PV power plant. 
     
     
         33 . The control system as in  claim 32 , wherein real time data is stored in one or more storage devices associated with a power generation site for collection by the supervisory system. 
     
     
         34 . The control system as in  claim 29 , wherein the supervisory system collects data from the plant level control system. 
     
     
         35 . The control system as in  claim 29 , wherein the supervisory system collects data from the point of connection of the PV power plant to the grid. 
     
     
         36 . The control system as in  claim 29 , wherein the supervisory system captures and stores historical data on the operation of the PV power plant. 
     
     
         37 . The control system as in  claim 9 , wherein the supervisory system is configured to identify warning and alarm conditions which occur during operation of the PV power plant.