A Hybrid Modulation Method for VSC Type High Voltage Direct Current System

A hybrid modulation method is proposed for the HVDC system using voltage sourced converter(VSC) technology,which performs satisfactorily both in steady state and in dynamic state.The system can be controlled in two different pulse width modulation(PWM) modes,i.e.sinusoidal PWM(SPWM) and minimum switching losses PWM.When the system is under disturbance or in the transient state,the SPWM control with a faster response speed is used;in the static state,the minimum switching losses PWM control is used to achieve best economic performances.The system status is monitored and the control mode is selected accordingly.Simulation results using PSCAD/EMTDC indicate that the proposed method has satisfactory control capability and minimum power losses,and suits for engineering applications.