Control Strategy for Cascaded Battery Energy Storage System under Unbalanced Grid Voltage

A control scheme for cascaded H-bridge battery storage converter operation under unbalanced grid voltage is proposed. The mathematic model of the converter is built under the two-phase coordinate, and the current instruction under the two-phase coordinate is deduced; the method of voltage feed-forward control based on the PR regulator is provided. Moreover, the output power of each phase of the converter is balanced by injecting zero-sequence voltage between phases, and the state of charge (SOC) of each converter cell in phase is balanced by adding fundamental voltage component on each converter cell in phase. The simulation results show that it can effectively solve the problem of unbalanced running of cascaded H-bridge battery storage converter under the unbalanced grid voltage by adopting the above control strategy.