The research of control algorithm and topology for high voltage frequency converter based on modular multilevel converter

The new type of high voltage frequency converter has been gradually applied in coal mine enterprises production. This paper first describes the fundamental concepts of the high voltage frequency converter which mainly constituted by modular multilevel converter (MMC). The mathematical model was built through the analysis of the topological structure and working mechanism for MMC which based on switching function. After that, the model was controlled by carrier phase disposition pulse width modulation (POD-PWM) with capacitor voltage stabilization and balancing control based on modeling-sequencing algorithm. Through the comparison for different modulations, the advantage of POD-PWM is proved. Last, the simulation has been carried out in the software Matlab-Simulink and RT-Lab. The result shows that the converter works properly and the capacitor voltage keeps steady state. The output waveform contains few harmonic waves. It also proves that POD-PWM and voltage stabilization and balancing control algorithm is effective.