Operation range of HVDC-MMC with circulating current suppression and energy balancing control

Many control strategies have been proposed to optimize the operation of the Modular Multilevel Converter (MMC) in HVDC applications, including the suppression of the circulating current and the balancing of arm energies. Applying these control strategies, we present an analysis of the operation range of the MMC, visualized as P-Q-charts. The analysis is performed with three different parameters which limit the operation range of the MMC: submodule voltage ripple, minimum value of the voltage reference and converter losses. The first two parameters define the voltage limit, and the third one the current limit of the converter. They are therefore important parameters for the converter design.