Sub-synchronous resonance mitigation via distributed power flow controller

Sub-synchronous resonance (SSR) is a frequent adverse phenomenon in series-compensated lines, threatening either or both mechanical facilities and power system stability. It is widely accepted that flexible AC transmission system (FACTS) can provide an effective solution to relieve the SSR. On the other hand, the advent of distributed FACTS (D-FACTS) technology has led to more economical deployment of the flexible devices in the power system control. This article focuses on verifying the capability of the distributed power flow controller (DPFC) to alleviate the SSR. As a member of the D-FACTS family, the DPFC operates in the same way as the unified power flow controller (UPFC). Compared with UPFC, the DPFC has some advantages like higher control capability, lower price, and more reliability. The DPFC impact on SSR mitigation is interrogated in various case studies, namely, with the SSR damping (SSRD) controller on the series converter, with SSRD controller on the shunt converter and with both simultaneously operating. The best case for SSR mitigation is achieved when the DPFC is supplied with two SSRD controllers concurrently. Simulations are carried out with Power Systems Computer Aided Design/ Electromagnetic Transients including DC (PSCAD/EMTDC) on the Institute of Electrical and Electronics Engineers (IEEE) first SSR benchmark model aggregated with DPFC on the transmission line. Furthermore, a comparison between the SSRD controller on DPFC converters and the supplementary excitation damping controller or the conventional power system stabilizer is also carried out.