A Novel Modular Multilevel Converter for Medium Voltage Variable Speed Induction Motor Drives

Now a days, Modular Multilevel Converter (MMC) attracts attention for medium voltage drive applications for several reasons. But, it has some issues, like circulating current and high capacitor voltage ripple at low frequency operation. In this paper, a novel configuration of MMC using Dual Active Bridge (DAB) is proposed where the aforesaid problems are overcome. The configuration performs direct ac-ac conversion and does not require any fundamental frequency transformer. For the same converter rating, the proposed configuration requires significantly less component count (less number of capacitors) and possess higher efficiency than the conventional topology (e.g. back-to-back MMC). The configuration is also suitable for bidirectional power flow which ensures regeneration. The relevant control techniques are applied for operation of the converter as per the requirements of medium voltage drives. The complete system is simulated in MATLAB/SIMULINK and the results show satisfactory performance.