Abstract：Carrier phase-shifted PWM (CPS-PWM) of cascaded multilevel converter has a good control and output performance, but has low utilization of DC voltage, higher switching frequency of the device and more switching loss. Combined the idea about controlling freedom degrees of DPWM and the CPS-PWM, an optimal CPS-PWM strategy more suitable for high-power cascaded multilevel converter is proposed in this paper. The principle of optimization CPS-PWM is given, and the relationship between power-factor angle, switching frequency, carrier-phase and switching loss is amalyzed, and the output voltage formulas in frequency domain both in-phase mode and inter-phase mode are deduced. DC voltage can be increased by 1.154 times when in-phase mode, and can eliminate the output common-mode voltage component when inter-phase mode, and both modes can reduce 1/3 switching frequency, and still maintains the waveform quality and the control performance. The experimental results on the cascaded multilevel inverter and cascaded STATCOM platform are given to demonstrate the correctness and feasibility of the optimization CPS-PWM method.
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