Photovoltaic power plant and primary frequency modulation control method therefor

Patent metadata

Field	Value
Publication number	US-11101770-B2
Application number	US-201816632331-A
Country	US
Kind code	B2
Filing date	May 10, 2018
Priority date	Dec 31, 2017
Publication date	Aug 24, 2021
Grant date	Aug 24, 2021

Abstract

Disclosed are a photovoltaic power plant and a primary frequency modulation control method therefor. The photovoltaic power plant comprises a photovoltaic power plant and an active power control system. The photovoltaic power plant comprises a photovoltaic array and a photovoltaic inverter, the photovoltaic inverter converting direct current electric energy generated by the photovoltaic array into alternating current electric energy. The active power control system is used for determining the variable quantity of active power of a single machine according to an operating state of the photovoltaic inverter when frequency values of grid connection points of the photovoltaic power plant meet a pre-set primary frequency modulation triggering condition, and regulating the active power output by the photovoltaic inverter. According to the disclosed photovoltaic power, the response speed and accuracy of primary frequency modulation of a generator set can be improved.

First claim

The invention claimed is:

1. A photovoltaic power plant, comprising a photovoltaic power station and an active power control system, wherein
the photovoltaic power station comprises a plurality of photovoltaic arrays and a plurality of photovoltaic inverters, and the photovoltaic inverters are configured to convert direct current electrical energy generated by the photovoltaic arrays to alternating current electrical energy; and
the active power control system is configured to determine, in a case that a frequency value at a grid connection point of the photovoltaic power plant satisfies a preset primary frequency modulation triggering condition, a single-unit active power variation according to an operating state of each of the photovoltaic inverters, to adjust an output active power of each of the photovoltaic inverters;
the active power control system comprises a field level controller and a plurality of single-unit frequency modulation modules, wherein
the field level controller is configured to, in a case that the frequency value at the grid connection point is determined to meet the primary frequency modulation triggering condition, calculate a total active power increment value at the grid connection point based on the frequency value at the grid connection point, and generate a single-unit primary frequency modulation command according to the operating state of each of the photovoltaic inverters; and
each of the single-unit frequency modulation modules is connected to a corresponding photovoltaic inverter, and each of the single-unit frequency modulation modules is configured to adjust an output active power of the corresponding photovoltaic inverter according to the single-unit primary frequency modulation command, wherein the single-unit primary frequency modulation command includes an output power target value of each of the photovoltaic inverters, a preset power adjustment step size of each of the photovoltaic inverters and an adjustment rate of each of the photovoltaic inverters.

2. The photovoltaic power plant according to claim 1 , wherein each of the single-unit frequency modulation modules comprises:
a single-unit communication interface connected to the field level controller, wherein the single-unit communication interface is configured to receive the single-unit primary frequency modulation command generated by the field level controller, and send the received single-unit primary frequency modulation command to a corresponding photovoltaic inverter to be frequency-modulated; and
a photovoltaic controller, which is configured to adjust, based on the output power target value, the preset power adjustment step size and the adjustment rate included in the single-unit primary frequency modulation command, the output active power of the photovoltaic inverter to be frequency-modulated to the output power target value according to the preset power adjustment step size and the adjustment rate.

3. The photovoltaic power plant according to claim 2 , wherein the field level controller comprises:
a primary frequency modulation triggering device of the photovoltaic power plant, which is configured to monitor the frequency value at the grid connection point, and adjust, in a case that the monitored frequency value at the grid connection point is offset from a preset fundamental frequency value and a frequency offset satisfies the primary frequency modulation triggering condition, the output active power of each of the photovoltaic inverters; the primary frequency modulation triggering condition comprises that the frequency value at the grid connection point is greater than a preset positive dead band threshold, or the frequency value at the grid connection point is smaller than a preset negative dead band threshold;
a determination device for determining the total active power increment value, which is configured to determine, in a case that the frequency offset satisfies the primary frequency modulation triggering condition, a total active power control target value at the grid connection point, and calculate the total active power increment value at the grid connection point according to the total active power control target value;
a single-unit primary frequency modulation triggering device, which is configured to determine, based on the operating state of each of the photovoltaic inverters and a single-unit active power allocation condition in the photovoltaic power station, photovoltaic inverters to be frequency-modulated that are allowed to participate in primary frequency modulation of the photovoltaic power station; and
a single-unit active power allocation device is configured to allocate the total active power increment value according to the operating state of each of the photovoltaic inverters to be frequency-modulated, to obtain the output power target value of each of the photovoltaic inverters to be frequency-modulated; and send a single-unit primary frequency modulation command comprising the output power target value of each of the photovoltaic inverters, the preset power adjustment step size of each of the photovoltaic inverters and the adjustment rate of each of the photovoltaic inverters to each of the photovoltaic inverters to be frequency-modulated.

4. The photovoltaic power plant according to claim 3 , wherein the determination device for determining the total active power increment value comprises:
a determination module for determining the total active power control target value, which is configured to determine, in a case that the frequency offset at the grid connection point satisfies the primary frequency modulation triggering condition, the total active power control target value at, the grid connection point according to an active power initial value of the photovoltaic power plant, the frequency value at the grid connection point, and an Automatic Generation Control (AGC) command value;
a setting module for setting a total active power target limit value, which is configured to set, in a case that an active power control target value at the grid connection point is lower than a preset active power lower threshold at the grid connection point, the active power control target value at the grid connection point to be the active power lower threshold at the grid connection point; and
a calculation module for calculating the total active power increment value, which is configured to take a difference between the total active power control target value and the active power initial value of the photovoltaic power plant as the total active power increment value at the grid connection point.

5. The photovoltaic power plant according to claim 4 , wherein the determination module for determining the total active power increment value comprises:
a calculation unit for calculating a primary frequency modulation active increment value, which is configured to calculate the frequency offset at the grid connection point according to the detected frequency value at the grid connection point, and calculate an active power increment value of the frequency offset at, the grid connection point according to the frequency offset at the grid connection point;
a calculation unit for calculating an AGC command active increment value, which is configured to take a difference between a current AGC command value and a previous AGC command value to be an active power increment value of the current AGC command;
a calculation unit for calculating a first total control target value, which is configured to set, in a case that a first active increment control condition is satisfied, the total active power control target value at the grid connection point to be an algebraic sum of adding the active power increment value of the current AGC command and the active power increment value of the frequency offset to the act

Assignees

• Beijing Goldwind Science & Creation Windpower Equipment Co Ltd
• Beijing Gold Wind Science & Creation Windpower Equipment Co Ltd

Inventors

• Zhang Yi
• Qiao Yuan
• Bao Xianwen

Classifications

• H02J2101/24

  Photovoltaics · CPC title

• H02J2101/22

  Solar energy · CPC title

• H02J3/00142 Primary

  Oscillations concerning frequency · CPC title

• H02J3/48

  Controlling the sharing of active power · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title