Utility scale renewable energy system controls for ramp-rate, voltage, and frequency management

Patent metadata

Field	Value
Publication number	US-2016190810-A1
Application number	US-201414585835-A
Country	US
Kind code	A1
Filing date	Dec 30, 2014
Priority date	Dec 30, 2014
Publication date	Jun 30, 2016
Grant date	—

Abstract

An energy system includes renewable energy sources each including an inverter. The renewable source inverters are coupled to a distribution line in a manner wherein power combines additively. The system also includes an energy storage source including an energy storage inverter coupled to the distribution line between the point of interconnection and the renewable source inverters. Finally, a control system is structured to: (i) control a voltage at the point of interconnection by controlling a renewable source reactive power output by the renewable source inverters and an energy storage reactive power output by the energy storage inverter, and (ii) provide power ramp rate control for the renewable energy system by controlling at least one of a renewable source real power output by each of the renewable source inverters and a first energy storage real power output by the energy storage inverter.

First claim

What is claimed is:

1 . A renewable energy system coupled to a point of interconnection of an electrical distribution system, comprising:
a number of renewable energy sources each including a renewable source inverter structured to output a renewable source power, the renewable source inverter of each of the renewable energy sources being coupled to a distribution line in a manner wherein the renewable source powers of the renewable source inverters combine additively; and an energy storage source including an energy storage device coupled to an energy storage inverter, wherein the energy storage inverter is coupled to the distribution line between the point of interconnection and the renewable source inverters; and a control system operatively coupled to the energy storage source and the number of renewable energy sources, wherein the control system is structured to: (i) control a voltage at the point of interconnection by controlling a renewable source reactive power output by each of the renewable source inverters and an energy storage reactive power output by the energy storage inverter, and (ii) provide power ramp rate control for the renewable energy system by controlling at least one of a renewable source real power output by each of the renewable source inverters and a first energy storage real power output by the energy storage inverter.

2 . The renewable energy system according to claim 1 , wherein the control system is further structured to control a frequency response of the renewable energy system by controlling a second energy storage real power output by the energy storage inverter.

3 . The renewable energy system according to claim 1 , further comprising a generator, wherein the control system is further structured to control a frequency response of the renewable energy system by controlling a first generator real power output by the generator.

4 . The renewable energy system according to claim 1 , wherein each renewable energy source is a photovoltaic source including a photovoltaic array coupled to the renewable source inverter of the renewable energy source.

5 . The renewable energy system according to claim 1 , wherein the energy storage device is a battery.

6 . The renewable energy system according to claim 1 , wherein the control system includes a processing device coupled to a controller of the energy storage inverter and a controller of each renewable source inverter.

7 . The renewable energy system according to claim 1 , wherein the control system is structured to control the voltage at the point of interconnection by determining a voltage drop along the distribution line associated with each renewable source inverter and using the voltage drop to control the renewable source reactive power output by the renewable source inverter.

8 . The renewable energy system according to claim 7 , wherein the control system is further structured to control the voltage at the point of interconnection by first determining that each of the PV inverters has reached a maximum reactive power and then using the energy storage reactive power output by the energy storage inverter to also control the voltage at the point of interconnection.

9 . The renewable energy system according to claim 1 , wherein the control system is structured to control the voltage at the point of interconnection by:
determining a distribution line voltage associated with each renewable source inverter; determining a voltage deviation associated with each renewable source inverter based on a voltage set point associated with the renewable source inverter and the distribution line voltage associated with the renewable source inverter and a real power output by the renewable source inverter; determining a renewable reactive power command for each renewable source inverter based on at least the voltage deviation associated with the renewable source inverter; determining a voltage at the point of interconnection; determining a system voltage deviation based on the voltage at the point of interconnection and a system voltage set point; and determining a reactive power command for the energy storage inverter based on the system voltage deviation and the system voltage set point.

10 . The renewable energy system according to claim 9 , wherein the control system is further structured to curtail real power output by one or more of the renewable energy sources when the energy storage source is no longer able to absorb additional power from the renewable energy sources.

11 . The renewable energy system according to claim 2 , wherein the control system is structured to control the frequency response of the renewable energy system by determining a frequency at the point of interconnection, determining a frequency deviation based on a predetermined reference and the frequency at the point of interconnection, causing the energy storage inverter to output real power based on a predetermined droop characteristic and following a predetermined ramp rate limitation if a size of the frequency deviation is determined to be less than a predetermined value, and causing the energy storage inverter to immediately output real power at a predetermined level is the size of the frequency deviation is determined to be greater than or equal to the predetermined value.

12 . The renewable energy system according to claim 2 , wherein the control system is structured to control the frequency response of the renewable energy system based on a measured frequency or a signal received from a utility supervisory control and data acquisition system.

13 . The renewable energy system according to claim 3 , wherein the control system is structured to control the frequency response of the renewable energy system based on a measured frequency or a signal received from a utility supervisory control and data acquisition system.

14 . The renewable energy system according to claim 13 , wherein the control system is further structured to curtail real power output by one or more of the renewable energy sources when the energy storage source is no longer able to absorb additional power from the renewable energy sources or when the renewable energy system employs a diesel or natural gas generator and the measured frequency is greater than a dead band.

15 . The renewable energy system according to claim 1 , wherein the control system in energy storage inverter is structured to provide power ramp rate control for the renewable energy system by determining that a total real power output of the renewable source inverters is decreasing and in response thereto causing the energy storage inverter to output real power in a manner such that a rate of change of a total real power output by the renewable energy system at the point of interconnection does not exceed a predetermined maximum ramp rate or by determining that a total real power output of the renewable source inverters is increasing and in response thereto causing the energy storage inverter to absorb real power in a manner such that a rate of change of a total real power output by the renewable energy system at the point of interconnection does not exceed a predetermined maximum ramp rate.

16 . A method of controlling a renewable energy system coupled to a point of interconnection of an electrical distribution system, the renewable energy system including a number of renewable energy sources each including a renewable source inverter and an energy storage source including an energy storage device coupled to an energy storage inverter, the method comprising:
controlling a voltage at the point of inter

Assignees

• Eaton Corp

Inventors

• Bhavaraju Vijay
• Fu Qiang
• Familiant Yakov L
• Thompson Christopher S

Classifications

• H02J3/28

  Arrangements for balancing of the load in networks by storage of energy · CPC title

• Y02E70/30

  Systems combining energy storage with energy generation of non-fossil origin · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02J2101/20

  Dispersed power generation using renewable energy sources · CPC title

• H02J2101/10

  Dispersed power generation using fossil fuels, e.g. diesel generators · CPC title