Abstract
The three-phase H-bridge or NPC converters are commonly adopted converter topologies for FACTS devices. Both the converters are classified as multilevel converters capable of producing a three-level AC voltage between the phase and the neutral terminals. Either topology is a good solution in the low voltage environment where it is possible to select a switch capable of blocking the required DC bus voltage. If the converter is designed for a high-voltage application, the design stage of these converters may be challenging due to making composite switches for voltage blocking requirements. Besides, there is a need for a large filter for interfacing these converters with the grid to meet the THD requirements as the operating frequency is the line frequency. Therefore, this paper adopts an MMC as an SSSC to enhance power flow in the transmission network and relieve the transmission line against abnormal situations. Besides, PR-based controllers are presented in αβ0 stationary reference frame to provide reliable operation under unbalanced grid conditions. The effectiveness of the MMC-based SSSC and its controller is modeled in FPGAs and integrated with the RTDS through fiber optic cables.