Synchronization of different frequency power grids by back-to-back modular multilevel converter with CSMC-SPWM algorithm

This paper presents a control process and the functioning of Back-to-Back Modular Multilevel Converter (MMC) in connecting asynchronous grids of high-voltage DC transmission system. CSMC-SPWM algorithm is used to generate gate pulses of the switching devices of back-to-back MMC for running, shifting the system from higher to any other lower level of operation and connecting of two different frequencies power grids. In this research two power grids having different frequencies of 50Hz and 60Hz are connected. The simulation results shows that the MMC operates well and synchronized properly with asynchronous grids and power can transmitted in both direction. A tap changing transformer is used to step up the output voltage of the converter during reduced number of level operation.