An Operating Mode Based on Variable DC Voltage and Current for Enlarging P–Q Capability Range of Unidirectional Current H-Bridge Submodule-Based MMC

Modular multilevel converters (MMCs) are widely utilized in dc applications. With the development of MMCs, many applications require MMCs to have additional functions and characteristics, such as fault clearing capability low submodule capacitance. A unidirectional current H-bridge (UCH-SM) has been proposed, which uses capacitance possesses capability. However, reactive power is limited during active because inadequate bias arm currents caused by current. Although retaining a rated even at zero it results increasing losses large This study proposes new operating mode based on variable voltage (VVVCM) for point-to-point systems. The basic idea that both vary basis lower limit set provide adequate exchange. Analysis shows UCH-MMC VVVCM an enlarged P–Q range still retains capacitor usage. Simulation verify effectiveness proposed mode.