Search

A three-phase squirrel-cage induction motor is used as a propulsion system of an electric vehicle (EV). The motor is controlled at different operating conditions using a direct torque control (DTC) technique combined with a new switching pattern producing low harmonics. The operating flux of the motor is chosen optimally for losses minimization and good dynamic response. Since speed estimation is sensitive to rotor resistance variations, the rotor resistance value is calculated and modified in real time continuously. Simulation and experimental results show that the proposed DTC is able to follow the reference speed (which may be only input reference of the system) with a reasonable dynamic and relatively low error. Index Terms--DTC control technique, electrical vehicle.

A simple structure and a quick and robust response of the direct torque control (DTC) makes it attractive in ac drives. However, in sensorless applications, a precise estimation of the rotor speed is a crucial issue as along with the torque and flux estimation. In this paper an adaptive flux observer is introduced with a stator current and flux vector components as state variables and rotor speed as an unknown parameter which is estimated by using an adaptive scheme. A non-linear inverter model is proposed to obtain a more accurate response. Also, torque, flux and current pulsations, during the steady-state conditions, are considered as the disadvantages of the classical DTC method. A combined DTC and space vector modulation strategy is presented by using fuzzy logic control (FLC). FLCs are designed to obtain a fast response in the transients, and a high accuracy during the steady-state conditions. [ABSTRACT FROM AUTHOR]