Analysis of SVPWM with Minimum Switching Losses for Multi-Modular Converter

The classic voltage space vector PWM (SVPWM) is a kind of symmetrical regular-sampled PWM with zero sequence component added to its modulating wave. The technique of carrier phase shifted SPWM (CPS-PWM), which combines the multilevel with SPWM technique, is characteristic of high equivalent switching frequency of the output wave. A technique named sample time staggered SVPWM which combines SVPWM with CPS-PWM is presented in this paper. In order to reduce the maximum switching current, the zero sequence component added into the individual converter units can be adjusted dynamically according to the phase of the load current. Thus, the non-switching sectors can be arranged close to the period of the maximum load current. So the maximum switching current in each element can be reduced effectively and the minimum switching losses of the multi-modular converter are achieved. Simulation results implemented by PSCAD/EMTDC show the validity of the proposed approach.