Multilevel CSC System Based on Series–Parallel Connected Three-Phase Modules With Optimized Carrier-Shift SPWM

Current source converter (CSC) is widely used in high power applications. To increase the system power rating, both series and parallel connections can be adopted and implemented easily. In this article, a mixed series–parallel CSC structure is proposed for high power application. An optimized carrier-shift sinusoidal pulsewidth modulation (SPWM) is adopted for the mixed system to simultaneously improve the dc-link voltage quality and achieve multilevel ac output, which can potentially reduce the size of dc- and ac-side filters. Meanwhile, the system reliability can be significantly improved due to the modular design with carrier-shift SPWM and inherent short-circuit protection of CSC. With these advantages, the proposed mixed series–parallel CSC structure can be an attractive candidate for medium-voltage drives, high-voltage direct current, and offshore wind power applications. Simulation and experimental results verify the effectiveness of the novel mixed series–parallel CSC system with optimized carrier-shift SPWM.