Two-stage deadbeat-based predictive torque control strategy for modular multilevel converter-fed three-phase induction motors

Abstract

Recently, Modular Multilevel Converters (MMC) are considered to be extensively used in medium-voltage AC drives A two-stage deadbeat-based strategy is developed by the authors to make the implementation of Predictive Torque Control (PTC) technique for an induction motor that is fed by a three-phase MMC possible . Despite various benefits of PTC strategy, it has not been widely employed for multilevel topologies due to the huge number of switching states of these converters, and the complex internal dynamics of topologies such as MMC. The proposed control scheme results in significant reduction of the computational burden, using an initial reference voltage that is determined at the first stage of the strategy by the deadbeat technique. Next, the predictive evaluation process is conducted at the second stage to simultaneously control the stator flux, electromagnetic torque and circulating current. The number of admissible vectors that should be evaluated in the cost function is effectively limited by only considering some adjacent vectors of the reference voltage in the first stage. Moreover, the circulating current control capability, which is necessary for effective operation of MMC, is also considered in the developed scheme. Finally, the satisfactory performance of the proposed strategy is validated through various experimental tests.