Analysis of strategies of modulation voltage of the active rectifier based on the modular multilevel converters

The article deals with multilevel converters based on a modular design (MMC), intended for high-voltage networks as active rectifiers controlled AC drives and static var compensator. The structure of the MMC, a distinctive feature of which is that each phase contains a number of series-connected sub-modules of the same. The typical topology submodule consisting of a capacitor, bypassed anti-parallel connection of diodes and transistors. Possible operating states submodule affecting the level of the voltage at the input terminals. Analyzed in detail three known modulation method voltage MMC: method pulse amplitude modulation method with the purpose of dial-submodule and the method of comparison with a reference voltage.Powered harmonic content in the output line voltage MMC for these three modulation techniques. It is shown that the method of comparison with the reference voltage level THD voltage at the input terminals of the converter is of the order of 4 % when the switching frequency of power switches 300 Hz.