Research on the Voltage Source Converter in VSC-HVDC

Voltage Source Converter (VSC) based High Voltage Direct Current (VSC-HVDC) transmission technology is a novel transmission technology on the basis of pulse width modulation (PWM) technology and fully-controlled power electronics devices. The output performance of VSC mainly depends on its modulation algorithm. A new kind of SVPWM algorithm based on 60° coordinate system for three-level VSC is introduced in this paper, and the neutral-point voltage imbalance problem is effectively solved by introducing an adjusting coefficient. And the high output voltage rating demand of VSC in VSC-HVDC can be achieved by connecting insulated gate bipolar transistors (IGBTs) in series. In order to solve the static and dynamic voltage unbalance problem associated with series-connected IGBTs, a new method combining with voltage clamp circuits and gate passive voltage balancing circuits is presented in this paper, and the effectiveness of the circuit is validated by simulation results.