Sensorless control of the switched reluctance motor drive based on back EMF estimation

Due to its several inherent advantages, the Switched Reluctance Motor (SRM) drive is considered an attractive candidate for variable speed motor drive applications.; Position information is essential for a high performance SRM drive. Mechanical position sensors are often used to provide rotor position information for the SRM drive. However, these mechanical position sensors add to the cost and dimension and lower the reliability of the SRM drive.; Several sensorless SRM control methods have been proposed. Most of these methods utilize the functional relationship between the stator flux linkage or phase inductance, phase current, and rotor position to estimate the rotor position. Depending on the way of phase flux linkage or inductance estimation, each of these published sensorless SRM control methods is suitable for a specific speed range. Furthermore, most of them suffer from computational complexity, need for huge memory space or extra hardware.; This dissertation proposes a novel sensorless control method to drive the Switched Reluctance Motor up to rated speed. The basis of the proposed sensorless control method is the estimation of the Back Electro Motive Force, BEMF. A novel approach to online estimation of the developed Back EMF is proposed. Then an analytical model of the phase incremental inductance is introduced. In order to commutate the motor phase at the right rotor position, the active phase incremental inductance is determined based on the estimated Back EMF, phase voltage and current and then it is compared to the desired threshold that is determined based on the model and desired commutation angles. In order to solve the ambiguity problem of the phase incremental inductance encoded position information, the incremental inductance of each phase is used for rotor position estimation only when it monotonically increases as the rotor moves from the unaligned position to the aligned position. In addition, a closed loop speed control system has been designed.; The proposed algorithm can be implemented on low cost processors like fixed-point Digital Signal Processors or micro-controllers and it does not need any extra circuitry. Furthermore, it benefits computational simplicity.; Simulation and experimental results are presented to verify the proposed sensorless control method. As the final step, several factors affecting the accuracy of the proposed sensorless control method are discussed.