A Discontinuous PWM Strategy to Control Neutral Point Voltage for Vienna Rectifier With Improved PWM Sequence

Vienna rectifier is a boost-type rectifier with unidirectional energy flow, which is widely used in industrial applications. To improve the power density of the Vienna rectifier, the high switching frequency is seen as an inevitable cause of larger switching losses. To reduce switching losses, discontinuous pulsewidth modulation (DPWM) is usually used. But this will cause dc offset and ac ripple on neutral point (NP) voltage. To overcome these problems, a carrier-based DPWM (CB_DPWM) method suitable for a Vienna rectifier with simple implementation is proposed to simultaneously reduce switching losses and control NP voltage. By selecting the proper clamping mode, NP voltage can be well controlled. To avoid unnecessary switching actions while switching clamping mode, an improved PWM sequence based on carrier type is given. The comparisons among space vector PWM, DPWM 1-3 presented by Zhang et al., and the proposed CB_DPWM are presented with the corresponding simulation and experimental results, and the superiority of the proposed strategy is verified in terms of reducing switching loss and controlling NP voltage.