A method and device for on-off and off-grid switching of a microgrid battery energy storage system

Abstract

The present invention provides a grid-connected and off-grid switching method and device for a battery energy storage system of a micro-grid, which includes, during grid-connected operation, according to the positive and negative sequence components of the grid-connected point voltage under the PQ control mode and the positive and negative sequence components of the inverter output current Sequence components are used to calculate the current and voltage values ​​of the inner loop of the current to control the output power of the inverter; at the moment when the grid is connected to the grid, the VF control mode adopts the state-following method, and the grid output power is transferred through the added power compensation control link to the inverter; when running off-grid, the voltage outer loop under VF control mode provides voltage and frequency support for the system; the device includes a PQ control module and a VF control module. The technical solution provided by the invention realizes the control of the negative sequence voltage during off-grid switching, ensures the reliability of power supply, and improves the quality of electric energy.

Description

technical field [0001] The invention relates to the field of electric power generation, in particular to a method and device for switching between on-grid and off-grid battery energy storage systems of a micro-grid. Background technique [0002] With the application of the microgrid system in the smart grid, the energy storage converter control technology has become an important research field. The energy storage converter can enhance the inertia and damping of the system by realizing the four-quadrant flexible operation of power control, and improve the efficiency of the microgrid. The stability of the grid system, but the load capacity in the microgrid is uncertain, and the single-machine operation is not convenient for system expansion, and if the energy storage system is out of operation due to a failure, the entire system will collapse and affect the off-grid operation of the microgrid reliability. [0003] Selecting an appropriate control strategy at the level of each...

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Problems solved by technology

[0004] The existing control strategies for active grid-connected and off-grid smooth switching between distribution networks and microgrids are based on the ideal sinusoidal three-phase voltage of the grid. Due to the grid line impedance and the uneven load of the three phases, there are often unbalanced three-phase voltages in the grid. Working conditions, if these control strategies are still used, seamless switching will not be achieved

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