Research of transient process on three-phase four-leg inverter with unbalanced load

For three-phase four-leg inverter, symmetrical component method and double closed-loop control is a traditional method to sustain the symmetry of three-phase output voltage in steady-state under unbalanced load, but asymmetrical output voltage is still generated in transient process. By analyzing the transient process after sudden load change, this paper illustrates the change law of the output voltage in the transient process after sudden load change and use dynamic feedforward compensation to restrain the load current disturbance, which greatly improves the symmetry of transient output voltage. In the end, simulation is made in Matlab/simulink platform and the simulation result proves the correctness of the theoretical analysis and the mentioning method.