抄録
For extending self-commutated converter application to future trunk power system, it is important to develop stable operation scheme as well as to realize substantial cost reduction through coordinated system and control design. Suppression controls of converter overcurrent and dc overvoltage in various system fault conditions are essentially needed to ensure stable operation and cost reduction of HVDC system with voltage source type self-commutated converter. Converter control and protection schemes which include such suppression controls have been developed employing CRIEPI's AC•DC Power System Simulator test and EMTP analysis.
This paper first discusses the cause of converter overcurrent at ac system fault considering the effect of PWM pulse number and converter control speed. Continued operation has been achieved by adding a new overcurrent suppression scheme into the converter control. In a condition of dc line grounding fault, the selection of grounding circuit constant and the adoption of high speed converter control practically ensure the reduction of dc overvoltage while suppressing converter overcurrent. Converter block and restart sequence after de fault, which is coordinated with dc circuit breaker operation, enables stable recovery of HVDC transmission as fast as the usual line-commutated HVDC system.
