Comparative Performance Study of Dynamic Reactive Power Compensators on Operating Characteristics of LCC Based UHVDC System Under Hierarchical Connection Mode

This paper compares the performance of different dynamic reactive power compensators (DRPCs) on transient characteristics of LCC based UHVDC system under hierarchical connection mode (LCC-UHVDC-HCM). The different DRPCs considered are Synchronous Condenser (SC), STATCOM and combination of both SC and STATCOM (hybrid dynamic reactive power compensator, HDRPC). Various transient indices like commutation failure immunity index (CFII), commutation failure probability index (CFPI) and fault recovery time (FRT) of LCC-UHVDC-HCM system are undertaken in order to evaluate the comparative performance of various DRPCs. The LCC-UHVDC-HCM system along with different DRPCs is developed in PSCAD/EMTDC and numerous simulations are done to observe the transient phenomena. The results indicate that performance of DRPCs changes during various AC disturbances such as single phase to ground fault and three phase to ground fault for different fault severity. It is examined that STATCOM is better than other dynamic compensators in improving CFII and CFPI. SC and HDRPC show almost same behavior in improving CFII. However, in case of CFPI, HDRPC is superior to SC. The performance of SC is better than STATCOM and HDRPC in improving FRT under severe fault conditions. However, under low fault conditions, all DRPCs have equal performance in reducing FRT.