Abstract：A three-phase four-wire energy storage type low-voltage control device with the function of grid

voltage unbalance compensation was designed. Firstly，a control method based on active voltage droop and constant power factor was introduced in detail to solve the problem of low voltage at the terminal of substation area power grid，which can compensate the low voltage at the terminal of substation area power grid. Secondly，a three-phase unbalance voltage compensation method based on negative sequence and zero sequence virtual impedance was proposed，which directly controls negative sequence and zero sequence voltage and omits the application of current sensor. Finally，a Matlab/Simulink simulation model and a 50 kW mid-point capacitor three-phase four-wire T-type three-level energy storage converter experiment platform were built，and the effectiveness of the proposed control scheme was verified through simulation and experiments.

      Key words：three-phase four-wire；low-voltage control；grid voltage unbalance control；negative sequence and zero sequence virtual impedance