Improved Dual-Functional DVR with Integrated Auxiliary Capacitor for Capacity Optimization

Fault current-limiting dynamic voltage restorers (FCL-DVRs), also named as dual-functional DVRs, involving both the fault current-limiting (FCL) and the voltage compensation (VC) function, have attracted more attention. However, in case of the FCL-DVR operating in VC mode, either the high capacity of storage system in the dc-link or the oversizing of power converter is needed, and in case of the FCL-DVR operating in FCL mode both the high dc-link voltage and the oversizing of power converter are needed. Thus, in order to avoid these drawbacks, an improved FCL-DVR, which consists of a LC filter coupled with series coupling capacitor (LCC) at the ac side is proposed in this paper. The improved FCL-DVR using energy-optimized control strategy can not only perform the dual functions well, but also achieve the capacity optimization of FCL-DVR key components. The operating principle and performance of the proposed FCL-DVR under FCL and VC mode are elaborated, respectively. The optimal design of LCC and selection of FCL branch are studied in detail to ensure high stability and reliability for the proposed FCL-DVR operating in both modes. The simulation and experimental results clearly validate the effectiveness of the proposed topology and method.