Photovoltaic panel cathode grounding detection and protection device

Abstract

The invention relates to a photovoltaic panel negative electrode grounding detection and protection device which comprises fuses,voltage and current sampling and signal isolation units, a controller and a control unit of a photovoltaic inverter. The fuses are connected in series with photovoltaic panel group strings in a one-to-one correspondence manner; the voltage and current sampling and signal isolation units are arranged in one-to-one correspondence with the photovoltaic panel group strings and are used for detecting voltages and short-circuit currents at the two ends of the corresponding fuses, isolating the voltages and the short-circuit currents and then outputting corresponding detection signals; the controller is respectively in communication connection with each voltage and current sampling and signal isolation unit and a control unit of the photovoltaic inverter, and is used for judging the photovoltaic panel group string with the negative electrode grounded according to the detection signal output by the voltage and current sampling and signal isolation unit and sending a corresponding control signal; and the control unit of the photovoltaic inverter closes the MPPT control unit corresponding to the photovoltaic panel string with the negative electrode grounded based on the control signal. The system can timely detect grounding of the negative electrode of the photovoltaic panel and disconnect the corresponding loop, protects the inverter, and reduces the power generation loss caused by the shutdown of the whole machine.

Description

technical field [0001] The invention relates to the field of power electronics technology and the field of electrical equipment technology, in particular to a photovoltaic panel negative electrode grounding detection and protection device in the solar photovoltaic power generation system industry. Background technique [0002] Photovoltaic power generation technology, as a renewable energy power generation technology, is booming all over the world. During the initial installation and construction of the photovoltaic power station, the negative cable of the photovoltaic panel may be broken and grounded, or the negative cable of the photovoltaic panel may be grounded due to aging and poor insulation after the long-term operation of the photovoltaic power station. When this grounding occurs, there is a current loop between the photovoltaic panel, inverter and transformer, which makes the current flowing through the inverter relatively large and damages the inverter. Now relyin...

AI Technical Summary

Problems solved by technology

Now relying on the insulation monitoring circuit and leakage current detection circuit integrated in the current photovoltaic inverter, it is impossible to quickly cut off the circuit between the inverter and the transformer, resulting in damage to the inverter and unable to protect the inverter. The specific performance is as follows: (1) The current technology requires the photovoltaic inverter controller to first sample the ground fault signal, extract the fault signal and issue a relay to disconnect the output side of the photovoltaic inverter. The entire action time is relatively long, and the inverter cannot be protected. (2) The existing technology has no way to determine which string of photovoltaic panels connected to the inverter is grounded; (3) For inverters with multiple MPPT inputs, when there is a string of photovoltaic panels After the negative cable of the power station is grounded, the entire inverter stops grid-connected power generation, which brings more loss of power generation to the power station owner

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