DC Fault Ride Through Strategy of a PWM-CSC Based Hybrid HVDC Transmission System

Abstract

An improved pulse width modulated current source converter (PWM-CSC) based hybrid high voltage direct current (HVDC) transmission system is proposed in this paper. The system adopts a line commutated converter (LCC) at the rectifier side and an improved PWM-CSC at the inverter side. The system has the capability of dc fault protection and rapid dc fault recovery. The dc fault characteristics of the system is analyzed and a dc fault ride through strategy is proposed. The control mode is switched from dc voltage close-loop control to dc current close-loop control when the dc fault is detected. The dc fault recovery process is presented. With the proposed method, the reactive power at the inverter side can be controllable during dc fault period. Finally, a $400kV/1250$ MW system is built using PSCAD/EMTDC software. The simulation results verify the correctness and effectiveness of the proposed strategy.