Dual-level ground insulation impedance detection circuit, and self-detection method and measuring method of detection circuit

Abstract

The invention discloses a dual-level ground insulation impedance detection circuit, and a self-detection method and a measuring method of the detection circuit. The detection circuit is low in cost, high in precision, perfect in self-detection, high in reliability and simple, can realize a wide impedance measuring range, and can avoid a detection dead zone caused by PV ground common mode voltage.The dual-level ground insulation impedance detection circuit is characterized in that a first resistor and a second resistor are connected in series to form a first branch; a first branch is connectedwith a BUS+; a third resistor and a fourth resistor are connected in series to form a second branch; a second branch is connected with a BUS-; the first branch and the second branch are connected, and then connected with a housing or the ground by a third controllable switch; a first partial pressure measuring resistor and a second partial pressure measuring resistor are connected in series to form a measuring partial pressure loop; a bus support capacitor is connected in parallel between the BUS+ and the BUS-; a first controllable switch is connected in parallel with the first resistor; a second controllable switch is connected in parallel with a third resistor; and a fifth resistor is connected with a housing of electrical energy equipment or the ground and a negative terminal of a photovoltaic module.

Description

technical field [0001] The invention belongs to the field of power electronic energy equipment, and relates to a dual-level ground-to-ground insulation resistance detection circuit and its self-inspection method and measurement method, in particular to a dual-level ground-to-ground of a photovoltaic inverter or an energy storage inverter Insulation resistance detection circuit and its self-test method and measurement method. Background technique [0002] The ground insulation resistance detection module is a type of safety circuit module widely used in power electronic energy equipment such as photovoltaic inverters and energy storage inverters. Taking the photovoltaic inverter as an example, when the photovoltaic inverter detects that the input voltage of the battery panel and the output voltage of the grid meet the operating requirements, it will prepare for grid connection. In order to meet the requirements of safety regulations, the insulation resistance between the pri...

AI Technical Summary

Problems solved by technology

[0004] 1. When there are multi-channel photovoltaic module inputs, switching elements and resistor networks equal to the number of inputs are required; otherwise, the specific impedance of each channel cannot be obtained, resulting in complicated circuits, high cost, difficult self-test, and low reliability;

[0005] 2. Using PV+ as the power supply source of the resistance network, the input voltage is unstable, which significantly affects the measurement accuracy, and the measured value at the protection threshold is fuzzy, which cannot reliably guarantee safety or cause false alarms for insulation detection errors due to measurement errors;

[0006] 3. Using PV+ as the power supply source of the resistor network, the input voltage variable of the resistor network is single, resulting in a measurement blind zone when the initial common-mode voltage of one of the multi-channel photovoltaic module inputs is close to the PV+ input voltage, and the real impedance value to ground cannot be measured, and Different measurement errors are generated due to different common-mode voltages, which significantly affect the measurement accuracy

Images