This thesis proposes the direct torque control (DTC) of interior permanent magnet synchronous motors for fast dynamic response with constant switching frequency. The conventional DTC consists of the hysteresis torque and flux controllers with the torque and flux errors as input. The switching frequency of DTC with the hysteresis controllers is not fixed. In the DTC with constant switching frequency, a torque regulator with a constant switching frequency is applied instead of the hysteresis torque controller for the conventional DTC. As a result, the DTC with constant switching frequency overcome the problem that the switching frequency of conventional DTC is not constant. The DTC with constant switching frequency uses a torque regulator with a proportional-integral (PI) torque controller and a triangular carrier wave to realize a constant switching frequency. Compared to the conventional DTC, the dynamic response of DTC with constant switching frequency is slow because both voltage vectors increasing and decreasing torque are selected during the transient state. Therefore, the bandwidth of PI torque controller is varied to improve the dynamic response of the DTC with constant switching frequency. The effectiveness of the proposed DTC with constant switching frequency is validated through simulation results.
