Transient Analysis of a Modular Multilevel Converter With Coupled Arm Inductors

The influence of the coupling of the arm inductors of a modular multilevel converter has been investigated through transient simulations. In particular, positive, negative and zero coupling coefficient were considered for both steady-state and transient operating conditions. The effect of the coupling on the transient response, the capacitor voltage ripple, the circulating current, the DC short-circuit current and the switch power losses has been closely examined. The possibility to reduce either the circulating current or the DC short-circuit current has been demonstrated, opening the door to improved performances of modular multilevel converter with only minor modifications.