Ground insulation impedance detection circuit and method of photovoltaic inverter

Abstract

The invention discloses an improved ground insulation impedance detection circuit and method for a photovoltaic inverter. The ground insulation impedance detection circuit further comprises a disturbance resistor and a voltage sampling device; the inverter bridge at least comprises a first bridge arm closest to the bus capacitor; the first bridge arm comprises a first switch and a second switch which are connected in series; one end of the first switch is electrically connected to the positive direct-current bus; one end of the second switch is electrically connected to the negative direct-current bus; the first end of the disturbance resistor is grounded; the second end of the disturbance resistor is electrically connected to the middle point of the first switch and the second switch; andthe voltage sampling device is electrically connected between the positive direct-current bus and the disturbance resistor. The ground insulation impedance detection circuit further comprises a controller, and the controller is used for driving all switches of the inverter bridge to be switched off in the first state and driving the second switch to be switched on and other switches to be switched off in the second state. According to the method, the insulation impedance can be rapidly solved, and the hardware cost is relatively low.

Description

technical field [0001] The invention belongs to the field of photovoltaic inverter insulation resistance detection, and relates to a ground insulation resistance detection circuit and method of a photovoltaic inverter. Background technique [0002] In the photovoltaic inverter system, the protection of the photovoltaic inverter's insulation resistance to ground is very important. Each region or country has made very clear regulations on it, and it can only be used if the insulation resistance of the input terminal to the earth (chassis) is less than the specified threshold standard. There are also many ways to detect insulation resistance, and most of them are obtained based on Kirchhoff's law. These methods also involve the solution of equivalent infinity, which is relatively complicated. Moreover, the circuit design adopts the signal quantity at the input side of the panel, and the hardware cost is relatively high. [0003] Chinese patent CN105548719B promptly discloses ...

AI Technical Summary

Problems solved by technology

However, in this insulation resistance detection circuit and method, the insulation resistance to ground is obtained by solving the equivalent calculation formula. At least one switch needs to be assisted on the hardware, and the equivalent formula is solved by the opening and closing of the switch and the voltage on the input side. In photovoltaic Switches and other devices are added to the original circuit of the inverter, the hardware cost is high, and the algorithm is complex and the calculation amount is large

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