An on-grid and off-grid switching method and device for a microgrid cell energy storage system

Abstract

The invention provides an on-grid and off-grid switching method and device for a microgrid cell energy storage system. During on-grid running, a current value and a voltage value are calculated according to positive and negative sequence components of the voltage of an on-grid point and positive and negative sequence components of the output electric current of an inverter under a PQ control modem, so that the output power of the inverter is controlled; at the instant from the on-grid to the off-grid, a state following method is adopted by a VF control mode, the output power of a power grid istransferred to the inverter by increasing a power compensation control link, During on-grid running, the voltage and frequency support are provided for a system by a voltage outer ring under the VF control mode, and the device includes a PQ control module and a VF control module. The control of the negative sequence voltage is realized when the off-grid is switched through the provided technicalscheme, the reliability of power supply is assured, and the quality of the electric energy is improved.

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...

AI Technical Summary

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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