Monitoring device of photovoltaic grid-connected inverter insulating resistor and electronic equipment

Abstract

The invention discloses a monitoring device of a photovoltaic grid-connected inverter insulating resistor and electronic equipment. The monitoring device comprises a main control board, a first-levelrelay, a second-level relay, a positive bus grounded bridge arm resistor set and a negative bus grounded bridge arm resistor set; when insulating resistance monitoring is conducted, firstly, the maincontrol board sends a first switch-on control instruction through a control port to the first-level relay, controls a switch channel in the first-level relay to be switched on and conducts acquisitionthrough a voltage sampling port to obtain a first voltage value; after the first voltage value is received, the main control board sends a second switch-on control instruction to the second-level relay, switches on a switch channel of the second-level relay and conducts acquisition through the voltage sampling port to obtain a second voltage value, according to the first voltage value and the second voltage value, a positive bus grounded insulating resistance value and a negative bus grounded insulating resistance value are obtained through calculation, and it is achieved that the positive bus grounded insulating resistance value and the negative bus grounded insulating resistance value are accurately monitored through a direct current method.

Description

technical field [0001] The invention relates to the field of insulation resistance detection, in particular to a monitoring device and electronic equipment for the insulation resistance of a photovoltaic grid-connected inverter. Background technique [0002] In the photovoltaic grid-connected power generation system, the photovoltaic grid-connected inverter is an important device, and it is very important to take necessary measures to ensure the safe operation of the photovoltaic grid-connected inverter. When a single-point grounding fault occurs on the DC voltage of the photovoltaic grid-connected inverter, the grounding resistance value is greater than 1 megohm. Generally, there will be no immediate harmful consequences. However, if two or more points simultaneously grounding resistance If the resistance value is not greater than 1 megohm, it may immediately cause the malfunction of the signal device and the control circuit, cause the DC circuit breaker to trip, or directl...

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Problems solved by technology

If there is a large capacitive element in the branch or the equivalent ground capacitance is large, this method must be compensated for the capacitive current before using this method, and the measurement accuracy is not high. In addition, the injected low-frequency carrier pulse signal is equivalent to the original system. Due to artificially increased external interference, the voltage ripple of the system becomes larger and affects the use of other equipment

For the frequency conversion detection method developed in recent years, the basic principle is to inject two sets of AC signals with the same amplitude and different frequencies into the DC bus, and then detect the low-frequency signals induced on the branch. When the insulation resistance of the system drops and a ground fault occurs, The amplitude of the detected low-frequency signal will change significantly, but this method, like the signal injection method, has the problem of interference with the ground capacitive current

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