Online detection method of insulating resistance to ground of photovoltaic grid-connected inverter

Abstract

The invention relates to the technology of photovoltaic grid-connected inverter, in particular to an online detection method of insulating resistance to ground of a photovoltaic grid-connected inverter. The method comprises the following steps of: by sampling an output voltage VPV of a photovoltaic cell and enabling a switch S1 in a resistance switch circuit to be in opening or closing state, disconnecting or connecting a resistor R5 from or to an upper bridge arm, and then sampling a voltage signal of a dividing voltage output end of a lower bridge arm to obtain a voltage ratio equation of anode to ground of photovoltaic cell and cathode to ground of the photovoltaic cell, thereby online calculating a insulating resistance R+ of anode to ground of the photovoltaic cell and an insulating resistance R- of cathode to ground of the photovoltaic cell in real-time and accurately. The method has simple calculation process and high detecting precision; by adopting the method, the online and real-time detection of anode-to-ground resistance of the photovoltaic cell and the cathode-to-ground resistance of the photovoltaic cell is achieved, the photovoltaic grid-connected inverter is guaranteed to work safely and reliably.

Description

technical field [0001] The invention relates to the photovoltaic grid-connected inverter technology, in particular to an online detection method for the ground insulation resistance of the photovoltaic grid-connected inverter. Background technique [0002] In photovoltaic grid-connected inverters, the output voltage of photovoltaic cells is relatively high. For example, in high-power photovoltaic grid-connected inverters, the output voltage of photovoltaic cells can be as high as 600V or more. At the same time, since the photovoltaic cell panels of photovoltaic cells are placed in the open air, weather factors such as dust, rain, snow, and heavy fog will affect the positive and negative electrodes of photovoltaic cells to the ground (hereinafter referred to as "to the ground" refers to "to the earth") , ie Earth) insulation changes. As a high-voltage system, a key indicator of the safety of photovoltaic grid-connected inverters is the degree of insulation. The insulation re...

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Problems solved by technology

However, when R+ and R- drop equally, this detection method based on the bridge balance principle cannot accurately detect the actual insulation resistance of the positive electrode of the photovoltaic cell to the ground and the actual insulation resistance of the negative electrode of the photovoltaic cell to the ground. , that is, it cannot accurately detect the change of the positive and negative electrodes of the photovoltaic cell to the ground insulation

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