Closed loop control of a four leg inverter for unbalanced power networks

In this paper, a four leg inverter based compensator is proposed for unbalanced networks. The inverter is controlled in synchronously rotating reference frame consisting an outer voltage control and an inner current control. Zero sequence component of the system is also controlled in order to get a balanced output voltage when the system is distorted by neutral current. The inverter uses traditional Pulse Width Modulation technique combined with neutral voltage control technique. The system is proposed for hybrid power systems or stand-alone systems containing single phase or three phase loads. The inverter is modeled in `PSIM´ and the closed loop control system is verified for unbalanced network conditions.