Current sensorless three-phase NPC converter with less power switches

A three-phase NPC converter with less power switches is presented. Eight power switches and four clamped diodes with voltage stress of half DC bus voltage are used in the adopted circuit topology. A current sensorless control strategy is proposed to draw the balanced sinusoidal line currents in phase with phase voltages respectively. Bidirectional power flow operation is possible in the converter. A voltage-controlled scheme is employed to track the line current commands. The switching signals of the power switches are derived from the DC bus voltage controller and neutral point voltage compensator. A carrier-based PWM scheme is employed to draw the clean sinusoidal line currents with nearly unity power factor. The mathematical model of the converter is derived and the control strategy is provided. To verify the proposed operation scheme, performance characteristics are given by the simulation and experimental results.