Efficiency-optimizing direct torque control of interior permanent magnet synchronous machines with fastest start up

Direct torque control (DTC) appears as an effective and practical control scheme for AC motor drive, including permanent magnet synchronous (PMS) motor drives. The DTC performance can be even improved by adding an efficiency optimization method and a fast start up solution. The main contribution of this paper is to apply simultaneously, an off line control method for optimization of steady state efficiency of permanent magnet synchronous machines under DTC and a method resulting in rapid torque response. In the proposed DTC approach, the flux command is obtained based on an optimization procedure to yield a maximum efficiency over a wide motor operating range. Since this flux is not an optimum value for the fastest torque response, the selection of proper amplitude and angle of flux vector during start up is also required. It is done by applying an optimal voltage vector in each sampling time. Simulation results confirm the effectiveness of the proposed DTC.