Research of the Neutral-point Balancing Strategy for Three-level Rectifier

The neutral-point-clamped three-level PWM rectifier which can be used in four-quadrant operation field is investigated.A novel simplified space-vector pulse width modulation(SVPWM) method is proposed to simplify the spacevector diagram of a three-level inverter into that of a two-level inverter.The neutral-point balancing strategy of the neutral- point-clamped three-level rectifier is analyzed.Besides,a DC side’s power-flow direction judging method without DC current sensor is presented.Finally,the controlling strategies are verified by experimental results.