Improvement of the Torque-Speed Performance and Drive Efficiency in an SRM Using an Optimal Torque Sharing Function

Abstract

In this paper, by evaluating the extreme value of the qth-power current, a torque sharing function (TSF) family for reducing the torque ripples in the switched reluctance motor (SRM) is proposed. The optimization criteria of the TSF has two secondary objectives, including the maximization of the torque-speed range and the minimization of copper loss. The evaluation indices in terms of the peak phase current, the rms (root mean square) phase current, and the torque ripple factor are compared between the proposed TSF family and four conventional TSFs including linear, sinusoidal, exponential, and cubic TSFs. An optimization objective function that combines the maximum absolute value of the rate-of-change of the flux linkage (MAV-RCFL) and the qth-power of current is proposed and a weighting factor is used to balance the influence of the two optimization objectives. An optimal TSF can be easily obtained by solving the optimization problem from the TSF family. The proposed TSF is validated by using simulations and experiments with a three-phase 6/4 SRM with 7.5 kW, 3000 rpm, and 270 V DC-link voltage. The dynamic simulation model is implemented in Matlab/Simulink. The results demonstrate the validity and superiority of the proposed control method; the optimal TSF provides better torque-speed performance, and a better reduction in copper loss and torque ripples at high speed, as compared to conventional TSFs.

Influence of the Rotor Geometry on Efficiency and Torque Ripple of Switched Reluctance Motor Controlled by Optimized Torque Sharing Functions

“…There are two ways to achieve these goals. One is to optimize the structure and magnetic circuit design of the motor [3,[8][9][10][11][12], and the other is to implement sophisticated motor control [4,[13][14][15][16][17][18][19][20]. Authors in [8] changed the stator and rotor geometry by attaching feet to the poles to improve the average torque production with ripple minimization.…”

Comparison of an Off-Line Optimized Firing Angle Modulation and Torque Sharing Functions for Switched Reluctance Motor Control

“…Torque ripples that occur during the transition from one winding to another are the major drawback of SRMs. The main goal of ongoing research is a torque ripple reduction and efficiency improvement by the optimization of the structure and magnetic design of the motor [6][7][8][9][10], and by adopting advanced motor control [9,[11][12][13][14][15][16][17].…”

“…A minimum effective rate-of-change of flux linkage was used in [11,21] as an objective function that should be minimized by selected TSF to extend the torque-speed range. Research results in [11,13,[20][21][22][23] show that different objective functions lead to different TSF. Therefore, multi-objective optimization with weighted criterion [11,13,19] or the Pareto-optimal approach [22] are used.…”

“…Research results in [11,13,[20][21][22][23] show that different objective functions lead to different TSF. Therefore, multi-objective optimization with weighted criterion [11,13,19] or the Pareto-optimal approach [22] are used.…”

“…Many published works [6][7][8]11,13,[19][20][21][22][23] use two to four objective functions to compare or optimize control methods or the structural design of the motor. This reduction of problem formulation is necessary to handle the complexity of a full industrial design process and can be considered as one stage in the multi-stage optimization process.…”