New technologies of modular multilevel converter for VSC-HVDC application
摘要：LI Ke，ZHAO Cheng-yong．New technologies of modular multilevel converter for VSC-HVDC application[C]．APPEEC，Chengdu，Sichuan，China，2011 March 28．
This paper presents some new technologies of modular multilevel converter (MMC) forVSC-HVDC application. The origin of modular multilevel VSC and its essential working mechanism are clarified in detail. Then, the starting of MMC under de-energized condition is discussed and a simple but effective control scheme is proposed. Concerning the drawbacks of traditional PWM modulation technologies, i.e., SVPWM and SHPWM, an improved modulation control technology based on waveform approximation is presented. The proposed modulation technology makes the individual semiconductors have much lower switching frequency (50 Hz) resulting in lower switching losses and, consequently, lower total losses of the transmission system compared to 2 or 3-level VSC. The technologies and conclusions are validated by simulations in PSCAD/EMTDC. The theory analysis and simulation results indicate that these new technologies have great potentiality in the application of VSC-HVDCprojects in future.
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