Photovoltaic power generation system, photovoltaic inverter, and IV curve scanning method

Patent metadata

Field	Value
Publication number	US-12456869-B2
Application number	US-202318316387-A
Country	US
Kind code	B2
Filing date	May 12, 2023
Priority date	Nov 13, 2020
Publication date	Oct 28, 2025
Grant date	Oct 28, 2025

Abstract

The photovoltaic power generation system includes a controller and M groups of DC-DC circuits. Each group of DC-DC circuits include N DC-DC circuits, where M is a positive integer, and N is an integer greater than 1. An input end of each DC-DC circuit is connected to at least one photovoltaic unit, and each photovoltaic unit includes at least one photovoltaic module. The controller controls the N DC-DC circuits in each group of DC-DC circuits to sequentially start online IV curve scanning and controls a time interval at which two adjacent DC-DC circuits start online IV curve scanning to be less than duration of online IV curve scanning performed by one DC-DC circuit. The photovoltaic power generation system can reduce a fluctuation of a power output during online IV curve scanning, reduce duration of online IV curve scanning performed by the photovoltaic power generation system.

First claim

What is claimed is:

1. A photovoltaic power generation system, wherein the photovoltaic power generation system comprises a controller and M groups of DC-DC circuits, each group of DC-DC circuits comprise N DC-DC circuits, M is a positive integer, and N is an integer greater than 1;
an input end of each DC-DC circuit is configured to connect to at least one photovoltaic unit, and each photovoltaic unit comprises at least one photovoltaic module; and
the controller is configured to:
control the N DC-DC circuits in each group of DC-DC circuits to sequentially start online IV curve scanning, and
control a time interval at which two adjacent DC-DC circuits start online IV curve scanning to be less than duration of online IV curve scanning performed by one DC-DC circuit.

2. The photovoltaic power generation system according to claim 1 , wherein when controlling each DC-DC circuit to perform online IV curve scanning, the controller is further configured to:
increase an input voltage of the DC-DC circuit until an input current of the DC-DC circuit is zero, and
control the input voltage of the DC-DC circuit to gradually decrease to zero.

3. The photovoltaic power generation system according to claim 2 , wherein the controller is further configured to:
after controlling a first DC-DC circuit in each group of DC-DC circuits to start online IV curve scanning,
control a k th DC-DC circuit to start online IV curve scanning when an input voltage of a (k−1) th DC-DC circuit decreases to be less than a preset voltage threshold, wherein k=2, 3, . . . , N.

4. The photovoltaic power generation system according to claim 3 , wherein a duration of online IV curve scanning performed by all DC-DC circuits is the same, and the preset voltage threshold is a product of a first preset proportion and a sum of open-circuit voltages of all photovoltaic units connected to the (k−1) th DC-DC circuit.

5. The photovoltaic power generation system according to claim 3 , wherein the preset voltage threshold is a product of a first preset proportion and a sum of preset open-circuit voltages of photovoltaic units connected to the (k−1) th DC-DC circuit.

6. The photovoltaic power generation system according to claim 2 , wherein the controller is configured to:
after controlling a first DC-DC circuit in each group of DC-DC circuits to start online IV curve scanning,
control other DC-DC circuits to sequentially start online IV curve scanning at a preset time interval, wherein the preset time interval is less than the duration of online IV curve scanning performed by one DC-DC circuit.

7. The photovoltaic power generation system according to claim 6 , wherein the preset time interval is negatively correlated to a value of N.

8. The photovoltaic power generation system according to claim 6 , wherein the preset time interval is a product of a second preset proportion and the duration of online IV curve scanning performed by one DC-DC circuit.

9. The photovoltaic power generation system according to claim 1 , wherein the controller is further configured to controls the M groups of DC-DC circuits to synchronously perform online IV curve scanning.

10. The photovoltaic power generation system according to claim 1 , wherein the photovoltaic power generation system further comprises a DC-AC circuit, and the DC-AC circuit and the M groups of DC-DC circuits form an inverter; and
positive output ends of the M groups of DC-DC circuits are connected in parallel to a positive input end of the DC-AC circuit, and negative output ends of the M groups of DC-DC circuits are connected in parallel to a negative input end of the DC-AC circuit.

11. The photovoltaic power generation system according to claim 10 , wherein the controller is further configured to control a working status of the DC-AC circuit.

12. The photovoltaic power generation system according to claim 1 , wherein the M groups of DC-DC circuits form a DC combiner box;
positive output ends of the M groups of DC-DC circuits are connected in parallel to form a positive output end of the DC combiner box; and
negative output ends of the M groups of DC-DC circuits are connected in parallel to form a negative output end of the DC combiner box.

13. The photovoltaic power generation system according to claim 1 , wherein the DC-DC circuit is a photovoltaic optimizer, and N photovoltaic optimizers in each group of photovoltaic optimizers form a photovoltaic optimizer substring; and
a positive output end of an i th photovoltaic optimizer is connected to a negative output end of an (i−1) th photovoltaic optimizer, a negative output end of the i th photovoltaic optimizer is connected to a positive output end of an (i+1) th photovoltaic optimizer, a positive output end of a first photovoltaic optimizer is a positive output end of the photovoltaic optimizer substring, a negative output end of an N th photovoltaic optimizer is a negative output end of the photovoltaic optimizer substring, and i=2, 3, . . . , N−1.

14. A photovoltaic inverter, configured to connect to a photovoltaic unit, wherein the photovoltaic unit comprises at least one photovoltaic module, the photovoltaic inverter comprises a controller, a DC-AC circuit, and M groups of DC-DC circuits, each group of DC-DC circuits comprise N DC-DC circuits, M is a positive integer, and N is an integer greater than 1;
positive output ends of the M groups of DC-DC circuits are connected in parallel to a positive input end of the DC-AC circuit, negative output ends of the M groups of DC-DC circuits are connected in parallel to a negative input end of the DC-AC circuit, and an input end of each DC-DC circuit is connected to at least one photovoltaic unit;
the DC-DC circuit is configured to perform DC conversion on a DC obtained from the photovoltaic unit and then transmit a converted DC to the DC-AC circuit;
the DC-AC circuit is configured to convert the obtained DC into an AC; and
the controller is configured to:
control the N DC-DC circuits in each group of DC-DC circuits to sequentially start online IV curve scanning, and
control a time interval at which two adjacent DC-DC circuits start online IV curve scanning to be less than duration of online IV curve scanning performed by one DC-DC circuit.

15. The photovoltaic inverter according to claim 14 , wherein when controlling each DC-DC circuit to sequentially perform online IV curve scanning, the controller first increases an input voltage of the DC-DC circuit until an input current of the DC-DC circuit is zero, and then controls the input voltage of the DC-DC circuit to gradually decrease to zero.

16. The photovoltaic inverter according to claim 15 , wherein the controller is further—configured to:
after controlling a first DC-DC circuit in each group of DC-DC circuits to start online IV curve scanning,
control a k th DC-DC circuit to start online IV curve scanning when an input voltage of a (k−1) th DC-DC circuit decreases to be less than a preset voltage threshold, wherein k=2, 3, . . . , N.

17. The photovoltaic inverter according to claim 16 , wherein a duration of online IV curve scanning performed by all DC-DC circuits is the same, and the preset voltage threshold is a product of a first preset proportion and a sum of open-circuit voltages of all photovoltaic units connected to the (k−1) th DC-DC circuit.

18. The photovoltaic inverter according to claim 17 , wherein the preset voltage threshold is a product of a first preset proportion and a sum of preset open-circuit voltages of photovoltaic units connected to the (k−1) th DC-DC

Assignees

• Huawei Digital Power Tech Co Ltd

Inventors

• Yu Xinyu
• Xin Kai
• Wang Jianqiang
• Wan Song

Classifications

• H02J2101/25

  involving maximum power point tracking control for photovoltaic sources · CPC title

• H02J3/0014

  for preventing or reducing power oscillations in networks · CPC title

• H02J3/0012

  characterised by the contingency detection means in AC networks, e.g. using phasor measurement units [PMU], synchrophasors or contingency analysis · CPC title

• H02S50/10

  Testing of PV devices, e.g. of PV modules or single PV cells (testing of semiconductor devices during manufacturing {H10P74/00}) · CPC title

• H02J3/381 Primary

  Dispersed generators · CPC title