Experimental Validation and Reliability Analyses of Minimum Voltage Control in Modular Multilevel Converter-Based STATCOM

The application of modular multilevel converters (MMCs) as medium voltage static synchronous compensators (STATCOMs) has aroused interest in recent years. Nevertheless, the implementation of this converter is still expensive. Consequently, improvements in the efficiency and reliability of MMC-STATCOM are essential to reduce operational costs and enable the use of this technology. The recently proposed minimum voltage control (MVC) can potentially improve converter reliability and reduce losses by controlling the submodule (SM) voltage as the minimum required at each operational condition. Nevertheless, the evaluation of MVC during transients and with different insulated-gate bipolar transistor (IGBT) blocking voltages is still missing in the literature. This work aims to fulfill this gap by experimentally validating MVC in an MMC setup platform in steady-state and during transient conditions. Moreover, it also analyzes the role of the IGBT blocking voltage and modulation strategy on the reliability and the reduction of losses of an MMC-STATCOM when MVC is employed. The experimental results demonstrated a slower power response and lower SM voltage for all operational conditions with MVC, compared with the conservative approach. The reliability results demonstrate that MVC can reduce the wear-out of semiconductor devices and capacitors (around 53%) in all cases studied.