An induction motor is the most frequently used electric machine in high-performance drive applications. Control schemes of such drives require an exact knowledge of at least some of the induction motor parameters. Any mismatch between the parameter values used within the controller and actual parameter values in the motor leads to a deterioration in the drive performance. Numerous methods for induction machine on-line and off-line parameter estimation have been developed exclusively for application in high-performance drives. This paper aims at providing a review of the major techniques used for the induction motor parameter estimation. The paper is illustrated throughout with experimental and simulation examples related to various parameter estimation techniques.

A review of RFO induction motor parameter estimation techniques

For a reliable dynamic system and significant amount of savings in energy usage, adjustable speed drives (ASD) can play a vital role. The proper control of motor drives can give a good system response and also increase the efficacy of the drive. Recently the direct torque control (DTC) strategy has drawn great attention for motor drives due to its simplicity, insensitivity to the motor parameters, high reliability and improved dynamic response. Many control strategies have been developed for the improvement of conventional DTC drives focusing specifically on torque and flux. A number of techniques have been formulated and successfully implemented for induction motor (IM) control. This paper aims to provide a substantial updated review, albeit by no means complete, for those who are interested in keeping track of the present state-of-the-art in this field and working further. The review focuses on different control algorithms of DTC IM drives and their applications to minimize the energy losses and improve the system efficacy.

A review of reliable and energy efficient direct torque controlled induction motor drives

A three-phase squirrel-cage induction motor is used as the 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 pattem producing low harmonics The operating flux of the motor is chosen optimally for both loss 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

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Sensorless direct torque control of induction motors used in electric vehicle

The first and the most important step in solving the environmental problems created by cars with internal combustion engines is research and development of electric vehicles. Selection of a proper drive and optimal control strategy of electric vehicles are the major factors to obtain optimal energy management in order to extend the running distance per battery charge. This paper presents a brief review of direct torque control (DTC) of induction motors (IM) as well as its implementation for electric vehicle (EV) applications. First, the basic DTC technique based on hysteresis controllers will be introduced, and then an overview of the major problems in a basic DTC scheme will be presented and explained, as well as some efforts for improving the technique. The main section presents a critical review of DTC for EV applications, taking into consideration the vehicle mechanics and aerodynamics of electric vehicles. The review is very important to provide guidelines and insights for future research and development on the DTC of IM drives for sustainable reliability and energy efficient EV applications.

A review of direct torque control of induction motors for sustainable reliability and energy efficient drives

Four different techniques for rotor resistance estimation in sensorless direct torque control (DTC) are studied and compared. Since the input voltage contains harmonics, many available techniques cannot be applied in the DTC. Three of the four above-mentioned techniques are the generalization of the previous methods. The fourth technique is a new one, which is applied by the authors. The speed of motor is estimated based on the governing equations of the induction motor and DTC. The resistance is estimated above rated speeds, which were required in electric vehicles (EVs). Although the four techniques enable to estimate the rotor resistance in real time, the new technique and TE (torque-error) method have some advantages over two other techniques.

S.H. Hossieni

Papers

Direct torque control of induction motors for electric propulsion systems