HARMONIC ANALYSIS OF SERIES HYBRID MODULAR MULTILEVEL CONVERTER
Keywords:High voltage DC transmission, Modular Multilevel Converter, Series-Hybrid Modular Multilevel Converter, Wave-Shaping circuit, Sub-Module
Recent research on modular multilevel converter (MMC) have brought numerous advantages of it in high power applications. However, main drawback of MMC is lack of DC fault blocking. Hence, hybrid configurations consist of MMC and two-level converters are investigated to overcome the drawbacks of MMC. These converters offer the advantages of both these configurations and also help in blocking DC fault. In this paper harmonic analysis of series hybrid MMC is presented. Series hybrid MMC consists of two-level converter and series connections of fullbridge modules on ac side. The two-level converters gives square wave output which operates at fundamental frequency and series connections of full bridge modules act as filters and absorbs the difference of square wave and required multilevel waveform. The series modules are operated with pulse width modulation and hence the harmonic spectrum of output voltage waveform is improved.