CN-115656795-B - Switch abnormality detection method and device, photovoltaic direct-driven power system and photovoltaic air conditioner

CN115656795BCN 115656795 BCN115656795 BCN 115656795BCN-115656795-B

Abstract

The invention discloses a switch abnormality detection method and device, a photovoltaic direct-driven power system and a photovoltaic air conditioner. The method is applied to a photovoltaic direct-drive power system with a photovoltaic cell and a DC/AC converter, wherein a first switch is arranged between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch is arranged between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter. According to the invention, the abnormal switching in the photovoltaic direct-drive power system can be automatically and accurately realized, and the abnormal operation of the photovoltaic direct-drive power system caused by the abnormal switching is avoided.

Inventors

CUI YU
HUANG MENG
SUN YUXIN
HUANG SONGRU

Assignees

珠海格力电器股份有限公司
国创能源互联网创新中心(广东)有限公司

Dates

Publication Date: 20260505
Application Date: 20221014

Claims (10)

1. A switching abnormality detection method applied to a photovoltaic direct-drive power system having a photovoltaic cell and a DC/AC converter, a first switch being provided between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch being provided between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter, characterized in that the method comprises: Judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter; After the first switch is judged to detect no abnormality, judging whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage, wherein the method comprises the steps of controlling the first switch to be opened, then acquiring the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage respectively under the condition that the second switch is opened and closed, judging whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage is within a second preset range after the second switch is closed, judging that the second switch is normally closed if the second switch is normally opened, judging whether the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the DC bus voltage is within the second preset range if the second switch is normally opened, and judging whether the second switch is normally opened if the second switch is normally opened.
2. The method of claim 1, wherein determining whether the first switch is abnormal based on an insulation resistance of a negative terminal of the DC/AC converter comprises: controlling the second switch to be opened, and then detecting insulation resistance of a negative terminal of the DC/AC converter under the condition that the first switch is opened and closed respectively; And judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter.
3. The method of claim 2, wherein determining whether an abnormality has occurred in the first switch based on an insulation resistance of a negative terminal of the DC/AC converter comprises: after the first switch is disconnected, judging whether the deviation of the insulation impedance of the negative terminal of the DC/AC converter and the insulation impedance of the negative terminal of the photovoltaic cell is in a first preset range or not; if yes, judging that the first switch is disconnected abnormally; If not, the first switch is judged to be normally disconnected.
4. The method of claim 2, wherein determining whether an abnormality has occurred in the first switch based on an insulation resistance of a negative terminal of the DC/AC converter, further comprises: After the first switch is closed, judging whether the deviation of the insulation impedance of the negative terminal of the DC/AC converter and the insulation impedance of the negative terminal of the photovoltaic cell is in a first preset range or not; if yes, judging that the first switch is normally closed; if not, the first switch is judged to be closed abnormally.
5. The method of claim 1, wherein before determining whether the first switch is abnormal based on an insulation resistance of a negative terminal of the DC/AC converter, the method further comprises: Judging whether the insulation resistance of the photovoltaic cell is in a normal range or not; and if so, triggering to judge whether the first switch is abnormal according to the insulation impedance of the negative terminal of the DC/AC converter.
6. The method of claim 1, wherein after determining whether the second switch is abnormal based on the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the dc bus voltage, the method further comprises: and if the second switch is not abnormal, controlling the photovoltaic cell to cut into the photovoltaic direct-drive power system.
7. A switching abnormality detection apparatus for implementing the switching abnormality detection method according to any one of claims 1 to 6, characterized in that the apparatus includes: A first detection module for judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter; And the second detection module is used for judging whether the second switch is abnormal according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the direct current bus voltage after judging that the first switch detects no abnormality.
8. A photovoltaic direct-drive power system comprising the switching abnormality detection apparatus according to claim 7.
9. A photovoltaic air conditioner comprising the photovoltaic direct-drive power system of claim 8.
10. A computer readable storage medium, on which a computer program is stored, characterized in that the program, when being executed by a processor, implements the method according to any one of claims 1 to 6.

Description

Switch abnormality detection method and device, photovoltaic direct-driven power system and photovoltaic air conditioner Technical Field The invention relates to the technical field of electronic power, in particular to a method and a device for detecting abnormal switching, a photovoltaic direct-driven power system and a photovoltaic air conditioner. Background The high-speed development of modern society, the energy consumption is huge, environmental pollution is increasingly serious, clean and pollution-free solar energy has become the focus of new energy development, and the photovoltaic power generation technology corresponding to the solar energy is deeply emphasized. The photovoltaic power generation technology utilizes the photovoltaic effect of a semiconductor interface of a solar photovoltaic panel to convert clean pollution-free solar energy into electric energy, and the generated direct current is converted into alternating current through a DC/AC converter so as to be consumed and utilized. Wherein a switch (e.g., contactor, relay) acts as a medium for the connection of the photovoltaic cell to the DC/AC converter, switching the photovoltaic cell into and out of the DC/AC converter. At present, most of inverters in the market use mechanical direct current isolating switches, faults are easy to occur, if photovoltaic cells cannot be cut out of a power system in time due to the switching faults, the photovoltaic cells can continuously charge bus capacitors in a power utilization device stopping state, and accordingly damage is caused. However, in the existing photovoltaic direct-driven power system, the existing switch fault detection method is generally manual detection, the detection process is complicated, automatic and accurate fault detection cannot be realized, and the switch fault cannot be found in time. Aiming at the problems that in the prior art, the switch fault detection process of a photovoltaic direct-driven power system is complicated, automatic and accurate fault detection cannot be realized, and the switch fault cannot be found timely, no effective solution is proposed at present. Disclosure of Invention The embodiment of the invention provides a method and a device for detecting abnormal switching, a photovoltaic direct-driven power system and a photovoltaic air conditioner, and aims to solve the problems that in the prior art, the switching fault detection process of the photovoltaic direct-driven power system is complicated, automatic and accurate fault detection cannot be realized, and switching faults cannot be found timely. In order to solve the above technical problems, the present invention provides a switching abnormality detection method applied to a photovoltaic direct-drive power system having a photovoltaic cell and a DC/AC converter, a first switch being disposed between a negative terminal of the photovoltaic cell and a negative terminal of the DC/AC converter, and a second switch being disposed between a positive terminal of the photovoltaic cell and a positive terminal of the DC/AC converter, the method comprising: Judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter; And judging whether the second switch is abnormal or not according to the voltage difference between the positive terminal and the negative terminal of the photovoltaic cell and the direct current bus voltage after judging that the first switch detects no abnormality. Further, determining whether the first switch is abnormal according to an insulation resistance of a negative terminal of the DC/AC converter includes: Controlling the second switch to be opened, and then detecting insulation resistance of a negative terminal of the DC/AC converter under the condition that the first switch is opened and closed respectively; And judging whether the first switch is abnormal or not according to the insulation impedance of the negative terminal of the DC/AC converter. Further, determining whether an abnormality occurs in the first switch according to an insulation resistance of a negative terminal of the DC/AC converter includes: after the first switch is disconnected, judging whether the deviation of the insulation impedance of the negative terminal of the DC/AC converter and the insulation impedance of the negative terminal of the photovoltaic cell is in a first preset range or not; if yes, judging that the first switch is disconnected abnormally; If not, the first switch is judged to be normally disconnected. Further, determining whether an abnormality occurs in the first switch according to an insulation resistance of a negative terminal of the DC/AC converter, further includes: After the first switch is closed, judging whether the deviation of the insulation impedance of the negative terminal of the DC/AC converter and the insulation impedance of the negative terminal of the photovoltaic cell is in a first preset ran