Photovoltaic system, relay detection method, and power supply system

Patent metadata

Field	Value
Publication number	US-12537374-B2
Application number	US-202418598117-A
Country	US
Kind code	B2
Filing date	Mar 7, 2024
Priority date	Sep 16, 2021
Publication date	Jan 27, 2026
Grant date	Jan 27, 2026

Abstract

A photovoltaic system, a relay detection method, and a power supply system. When a fault, for example, sticking of the relay is detected, the controller stops sending a PWM driver gating signal to the inverter, and stops driving of a switch transistor in the inverter, and the inverter stops outputting power, and then determines whether a voltage difference between two ends of the relay is greater than a preset value, to determine whether the relay is faulty. The controller stops sending the PWM driver gating signal to the inverter only within a preset phase range of a voltage of the filter capacitor, to ensure that the voltage of the filter capacitor has a large value. Because the voltage of the filter capacitor is large, an alternating current grid-to-ground voltage is pulled up, to avoid detecting the fault as an alternating current grid-to-ground short circuit.

First claim

What is claimed is:

1 . A photovoltaic system, comprising:
an inverter and a relay, wherein an input of the inverter is configured to be connected to a photovoltaic array, an output of the inverter is connected to a first end of the relay, and a second end of the relay is configured to be connected to an alternating current grid; a filter capacitor, wherein the output of the inverter is connected to the filter capacitor; and a controller, wherein the controller is configured to:
send a turn-off instruction to the relay when a voltage of the filter capacitor and an alternating current grid voltage have a same frequency and a same phase, stop driving of an action of a switch transistor in the inverter when the phase of the voltage of the filter capacitor falls within a preset phase range, and
send fault alarm information of the relay when detecting that a valid value of a difference between the voltage of the filter capacitor and the alternating current grid voltage is less than a preset value, wherein the voltage of the filter capacitor is greater than or equal to a preset threshold when the phase of the voltage of the filter capacitor falls within the preset phase range.

2 . The photovoltaic system according to claim 1 , wherein the controller is further configured to obtain the phase of the voltage of the filter capacitor based on the phase of the alternating current grid voltage.

3 . The photovoltaic system according to claim 2 , wherein the controller is further configured to perform phase locking on a phase voltage of any phase of the alternating current grid, to obtain the phase of the alternating current grid voltage.

4 . The photovoltaic system according to claim 1 , wherein the controller is further configured to stop driving of the action of the switch transistor in the inverter when the phase of the voltage of the filter capacitor is at a peak of the voltage of the filter capacitor.

5 . The photovoltaic system according to claim 1 , wherein the relay comprises a first-level relay and a second-level relay;
the first-level relay and the second-level relay are connected in series between the output of the inverter and the alternating current grid; and the controller is further configured to: send a turn-off instruction to the second-level relay when sending a turn-on instruction to the first-level relay, and send fault alarm information of the second-level relay when the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value.

6 . The photovoltaic system according to claim 1 , wherein the relay comprises a first-level relay and a second-level relay;
the first-level relay and the second-level relay are connected in series between the output of the inverter and the alternating current grid; and the controller is further configured to: send a turn-on instruction to the second-level relay when sending a turn-off instruction to the first-level relay, and send fault alarm information of the first-level relay when the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value.

7 . The photovoltaic system according to claim 1 , wherein, when any phase in three phases of the alternating current grid is grounded, the controller is further configured to:
drive an action of a switch transistor of the any phase in the inverter after the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value, and send fault alarm information of a relay of the any phase when determining that the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is still less than the preset value.

8 . The photovoltaic system according to claim 1 , wherein the controller is further configured to:
drive an action of a switch transistor of any phase in three phases in the inverter after the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value, and send fault alarm information of a relay of the any phase when determining that the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is still less than the preset value.

9 . A method, wherein the method is applied to a photovoltaic system, the photovoltaic system comprises an inverter, a filter capacitor, and a relay, an input of the inverter is configured to be connected to a photovoltaic array, an output of the inverter is connected to a first end of the relay, a second end of the relay is connected to an alternating current grid, the output of the inverter is connected to the filter capacitor, the method comprising:
sending a turn-off instruction to the relay when a voltage of the filter capacitor and an alternating current grid voltage have a same frequency and a same phase; stopping driving of an action of a switch transistor in the inverter within a preset phase range of the voltage of the filter capacitor, wherein the voltage of the filter capacitor is greater than or equal to a preset threshold when the phase of the voltage of the filter capacitor falls within the preset phase range; and sending fault alarm information of the relay when it is detected that a valid value of a difference between the voltage of the filter capacitor and the alternating current grid voltage is less than a preset value.

10 . The method according to claim 9 , further comprising: obtaining the phase of the voltage of the filter capacitor based on the phase of the alternating current grid voltage.

11 . The method according to claim 10 , wherein obtaining the phase of the voltage of the filter capacitor based on the phase of the alternating current grid voltage comprises: performing phase locking on a phase voltage of any phase of the alternating current grid, to obtain the phase of the alternating current grid voltage.

12 . The method according to claim 9 , wherein stopping driving of the action of the switch transistor in the inverter within a preset phase range of the voltage of the filter capacitor comprises:
stopping driving of the action of the switch transistor in the inverter when the phase of the voltage of the filter capacitor corresponds to a peak of the voltage of the filter capacitor.

13 . The method according to claim 9 , wherein the relay comprises a first-level relay and a second-level relay;
the first-level relay and the second-level relay are connected in series between the output of the inverter and the alternating current grid; sending the turn-off instruction to the relay comprises:
sending a turn-off instruction to the second-level relay when sending a turn-on instruction to the first-level relay; and
sending fault alarm information of the relay when it is detected that the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value comprises:
sending fault alarm information of the second-level relay when the valid value of the difference between the voltage of the filter capacitor and the alternating current grid voltage is less than the preset value.

14 . The method according to claim 9 , wherein the relay comprises a first-level relay and a second-level relay;
the first-level relay and the second-level relay are connected in series between the output of the inverter and the alternating current grid; sending the turn-o

Assignees

• Huawei Digital Power Tech Co Ltd

Inventors

• Lu Li
• Xin Kai
• Yu Xinyu
• Liu Yunfeng

Classifications

• H02J2300/24

  Electricity · mapped topic

• 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

• H02J3/38

  Arrangements for feeding a single network from two or more generators or sources in parallel; Arrangements for feeding already energised networks from additional generators or sources in parallel · CPC title

• H02J3/001

  Arrangements for handling faults or abnormalities, e.g. emergencies or contingencies · CPC title

• G01R19/1658

  AC voltage or recurrent signals · CPC title