Reduction of Torque and Flux Ripples in Space Vector Modulation-Based Direct Torque Control of Asymmetric Permanent Magnet Synchronous Machine.

Due to asymmetric three-phase system and influence of inverter nonlinearity, large torque, and stator flux harmonics would exist in the space vector modulation-based direct torque controlled (DTC-SVM) three-phase permanent magnet synchronous machines (PMSMs). A general expression for electromagnetic torque is derived for DTC of asymmetric three-phase PMSMs considering the influence of inverter nonlinearity. To mitigate the influence of the undesired harmonics, a compensation method is developed by enhancing the standard proportional-integral (PI)-regulator in the torque and flux loops with appropriate resonant controllers. Since the 2nd- and 6th-order harmonics are the most dominant components, two resonant controllers tuning at the 2nd and 6th of stator angular frequency, respectively, are utilized. The proposed method can achieve good steady-state performance in terms of low torque and flux ripples, while keeping the merits of the conventional DTC-SVM strategy such as good dynamic torque response and machine parameter independence. The experimental results validate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]