Coordinated control of HVDC sending system with large-scale DFIG-based wind farm under mono-polar blocking fault

Abstract When the mono-polar blocking fault occurs at the line-commutated converter (LCC)-based high voltage direct current (HVDC) transmission system, due to the long switch time of the installed mechanical switching type VAR compensations, the reactive power of the sending alternating current (AC) system will be surplus. Consequently, the voltage of sending AC system will be sharply increased during the switch process of VAR compensations, which may trip off the connected doubly fed induction generator (DFIG)-based wind farm. For ensuring the sending system can operate in stability and security, the power flow and the overvoltage mechanism of sending AC system under mono polar blocking have been investigated firstly. Furthermore, the power controllable operation area of the DFIG system as well as the transient response of the synchronous compensator (SC) and static synchronous compensator (STATCOM) have been researched. Then, a fault ride through control strategy by coordinating the VAR compensations, DFIG-based wind farm, HVDC system converter and SC is designed. The simulation results show that the proposed scheme can significantly restrain the sending AC system’s overvoltage during the switch process of the installed VAR compensators under mono-polar blocking fault, thus, the transient stability of the HVDC sending system can be effectively enhanced.