Power Electronics for Utility Interface
Technical Lecture Session
Controller and Filter Design for Utility Interface Converters
Modular multilevel converter (MMC),zero-sequence voltage,circulating current injection,capacitor voltage ripples,active power filter (APF)
This paper proposes an improved 3rd-order frequency zero-sequence voltage and circulating current injection control method to suppress the capacitor voltage ripples. The amplitude of injected voltage is 1/6 times that of the output voltage and the amplitude of injected circulating current is varying according to the instantaneous value of the output voltage and current. To further reduce the capacitor voltage ripples and power losses, an additional active power filter (APF) that diverts the phase pulsating powers is paralleled between the Nth SM of the upper arm and the 1st SM of the lower arm in each phase of traditional MMC.