Third-Harmonic Injection PWM Based Control Strategy for A Five-Phase Six-Leg Voltage Source Inverter With Unbalanced Loads

Compared to conventional n-phase topologies, the n-phase (n+1)-leg inverters are able to work under unbalanced loading conditions. This paper investigates the control strategy of a five-phase six-leg inverter system with unbalanced loads. Based on the third-harmonic injection pulse-width modulation (PWM) method, a double-closed loop control scheme with inner current loop and outer voltage loop is applied. Compared to an open five-phase five-leg inverter system, the designed system can balance the output multi-phase voltage with unbalanced loads, then realizing the required power distribution of different phases. Meanwhile, the generalized Park transformation is utilized in the controller to convert the referenced coordinate system to a rotating one from a natural coordinate system, which contributes to make the control system have a satisfied performance. Finally, the PLECS-based simulation verifies the designed strategy.