A Control Strategy for a VSC HVDC System in Steady State Response

Voltage Source Converter (VSC) based HVDC is the most recent HVDC technology with extruded DC cables in small and medium power transmission. VSC-HVDC converters include Insulated Gate Bipolar Transistors (IGBT´S) and operated with high frequency Pulse Width Modulation (PWM) in order to get high speed control of both active and reactive power. With VSC-HVDC there is an addition degree of freedom. The reactive power can be control separately in each converter by the AC voltage or set manually. The active power flow can be controlled by the DC voltage, the variation of frequency at the AC side or set manually. In this paper ,a control strategy for the VSC-HVDC is proposed. This strategy is design to regulate the ac and dc voltage on the rectifier side and to control the ac voltage and frequency at the inverter side.