Automatic detecting system and automatic detecting method for capacitance of photovoltaic grid-connected inverter bus capacitor

Abstract

The invention relates to an automatic detecting system and an automatic detecting method for capacitance of a photovoltaic grid-connected inverter bus capacitor. At night, an inverter is in a standby state; voltage of a DC bus reduces; a soft starting loop of the inverter is started for charging a bus capacitor, so that the voltage of the bus capacitor of the inverter is equal with the DC voltage. After charging is finished, soft starting is stopped. Hereon, an auxiliary resistance testing loop is started. The bus capacitor performs discharging through an auxiliary testing resistor, and the bus capacitor is in zero-state response. The capacitance of the capacitor can be obtained through bus voltage integration in a discharging time period and dividing the integrated result by the bus voltage drop and the auxiliary testing resistance. Furthermore the calculated capacitance is compared with a preset capacitance lower limit, thereby determining whether the capacitance of the capacitor is qualified. If the capacitance is unqualified, fault alarm is performed for reminding change of the bus capacitor, thereby preventing further damage caused by performance reduction or failure of the bus capacitor.

Description

technical field [0001] The invention relates to the field of photovoltaic grid-connected power generation, in particular to a system and method for automatically detecting the capacitance value of a bus bar of a photovoltaic grid-connected inverter. Background technique [0002] As one of the renewable energy sources, solar energy has the advantages of abundant reserves, wide distribution, clean and pollution-free, green and environmental protection, and is recognized as an alternative energy source. The direct current generated by the solar panels is converted into alternating current with the same amplitude, same frequency and same phase as the grid voltage by the inverter, and then sent to the grid. [0003] The photovoltaic grid-connected inverter is composed of key parts such as switching device unit and DC bus capacitor unit, and the DC bus capacitor is a crucial unit of the photovoltaic grid-connected inverter. In the process of exchanging with the AC side, it absorb...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide an automatic detection system for the bus capacitance of photovoltaic grid-connected inverters, and a detection method using the system to solve the problem that detection in the prior art affects the normal operation of the system

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