Control and Performance of

The Modular Multilevel Converter (MMC) system has many advantages over conventional voltage source converters and therefore can be used in dc power transmission, micro grid, or renewable energy applications. While MMC’s distinctive topology offers many new features, it also necessitates a sophisticated controller to deal with extra control requirements. This paper presents a control scheme with multiple control objectives required by MMC, i.e. active and reactive power control, dc voltage control, sub-module capacitor voltage control and balancing, circulating current eliminating, and zero-sequence current eliminating. The system is modeled in an electromagnetic transients program, RT-LAB, and its dynamic performance is evaluated by time-domain studies using a real-time simulator, eMEGAsim. The results show the multiple control objectives are fulfilled and the system has fast response to control command and system dynamics.