Lifetime and reliability improvements in modular multilevel converters using controlled circulating current

Abstract Circulating current has been an inherent feature of modular multilevel converters (MMC), which results in second-order harmonics on the arms currents. If not properly controlled, circulating can affect lifetime and reliability a converter by increasing loading, loss distribution, junction temperature its semiconductor devices. This paper proposes controlled injection as means improving MMC. The proposed method involves modifying reference modulating signals to include differential voltage offset. devices obtained from electro-thermal simulation is processed deduce converter. are benchmarked against case where control incorporated. incorporation 68.25% increase expected 3.06% index. Experimental scaled down laboratory prototype validate effectiveness approach.