Analysis of Capacitor Voltage Ripple Minimization in Modular Multilevel Converter Based on Average Model

摘要

This paper investigates reduction of submodulernvoltage ripple in modular multilevel converter (MMC). Thernreduction is achieved by injecting the optimum amount ofrncirculating current across the phase leg of the converter. Thernmagnitude and phase angle of arm currents and submodulernvoltage quantities are calculated via an average model derivedrnfor the MMC topology. Then based on the derived equations forrnsubmodule voltage components at different ac frequencies, anrneffort is done to calculate and inject the optimum magnitude ofrncirculating current in order to minimize the voltage fluctuationrnacross submodule capacitors. Also in this paper, the effect ofrnnatural and optimized circulating currents on converter lossesrnand efficiency is investigated via calculating semiconductorrnlosses.