Grid-connected and off-grid switching circuit and switching method of photovoltaic energy storage inverter

Abstract

The grid-connected and off-grid switching circuit comprises a first relay, a second relay, a non-delay switch unit, a filtering unit and a controller, after the non-delay switch unit is connected with the second relay in series, the first end of the non-delay switch unit is electrically connected with the N line of the inverter, and the second end of the non-delay switch unit is electrically connected with the N line of the inverter. The second end of the second relay is electrically connected with the second end of the power grid, the filtering unit is connected to the two ends of the non-delay switch unit in parallel, a load is connected between an L line and an N line of the inverter in series, and the non-delay switch unit comprises a first non-delay switch and a second non-delay switch which are reversely connected. The control ends of the first relay, the second relay, the first non-delay switch and the second non-delay switch are electrically connected with the controller. Grid connection and grid disconnection are instantly completed by controlling the conduction state of the non-delay switch unit, 0ms seamless switching of grid connection and grid disconnection is achieved, a load cannot be powered down, and uninterrupted power supply is achieved; no impact current exists when the relay is closed and opened, and the service life of the relay is prolonged.

Description

technical field [0001] The invention relates to the technical field of grid-connection and off-grid switching, in particular to a grid-connection and off-grid switching circuit and a switching method of a photovoltaic energy storage inverter. Background technique [0002] Photovoltaic energy storage inverters have two typical operating modes, grid-connected mode and off-grid mode. When the grid is normal, the photovoltaic energy storage inverter runs in the grid-connected mode; when the grid is abnormal, the photovoltaic energy storage inverter switches to the off-grid mode, and then switches back to the grid-connected mode when the grid returns to normal. In order to meet the safety requirements, multiple sets of relays are connected in series at the output end of the inverter and the input end of the grid, and multiple sets of relays are connected in series at the output end of the inverter and the input end of the load, so as to ensure that the inverter can be timely and ...

AI Technical Summary

Problems solved by technology

[0003] When switching between parallel and off-grid modes, different relays need to be disconnected or closed. When some relays need to be closed and other relays need to be disconnected, since the closing time of the relays is greater than the disconnecting time, when switching The load is actually in a power-off state. Usually, the closing time of the relay is about 10ms. As the use time goes by, the closing time of the relay contacts will be extended, and if the closing time of the relay is inconsistent, it will further prolong the power-off time of the load.

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