Decoupled phase voltages control of three phase four-leg voltage source inverter via state feedback

The four-leg voltage source inverter (VSI) is becoming increasingly popular in power applications due to its superior performance characteristics such as relatively low dc-bus voltage and capability to handle unbalanced or nonlinear load currents. With unbalanced load condition, to balance such a system, a neutral connection is needed to control each phase voltage independently. Average large signal model in ABC coordinates is obtained and state space equation is presented. This paper presents new decoupled control strategy based on state feedback with simple proportional controller thus each phase is controlled independently in order to track references properly. Simulation results with MATLAB/Simulink show acceptable performance in unbalanced load conditions.