Optimal Current Assignment Strategy for Maximum Torque Control of Induction Machines

摘要

A novel current optimization strategy which ensures maximum torque capability over the whole speed range for induction machines is presented in this paper. Considering the voltage ratings of the power inverter, the current constraint of the induction machine and the limit of the maximum slip frequency adequately, the trajectory of the optimal current vector for maximum torque operation is investigated by finding the extremum of the torque function, and the guidelines for the implementation of the current assignment strategy is summarized. Following the guidelines, an alternative approach that effectively combines the best attributes of the conventional flux-weakening method with modified voltage controller is proposed to realize the optimal current control. Finally, a complete solution of induction machine drive system including the proposed algorithm is fully implemented to evaluate the validity of the algorithm, which can achieve maximum torque operation and good dynamic response over a wide speed range.