Modified PWM Direct Instantaneous Torque Control System for SRM

Yong Cheng,Xiaodong Sun

doi:10.1155/2021/1158360

Abstract

Torque ripple is a defect of switched reluctant motors. DITC (direct instantaneous torque control) is harnessed to solve the problem as a traditional method, which is superior to TSF (torque sharing function). In this paper, a new controller is proposed with modified hysteresis and PWM in DITC. With the modified algorithm, the torque error will be reduced with PWM in DITC. The proposed algorithm is effective to improve sample and 0 status in a period. The modified algorithm is based on application of zero in the asymmetric half bridge, which is implemented as the buffer zone. In case of big torque error, hysteresis will mitigate error under the characteristic of fast responding. In case of small errors, the modified PWM will solve torque error in the equivalent strategy, which has adopted the essence of the impulse equivalent method. The modified controller is designed to reduce responding time and minimize the torque ripple under the proposed algorithm, which has been designed to harness different functions in different torque errors. Based on final simulation and experimental results, responding speed and reduction of output torque ripple are enhanced effectively.

Highlights

Switched reluctant motors [1] (SRMs) have special features such as high tolerance, robustness, low cost with no permanent magnet, and high efficiency without winding in simple and double salient. e torque is stimulated by tendency of rotor poles to align with excited stator pole
In direct instantaneous torque control (DITC) hysteresis control system, the torque is between 23 Nm and 24.9 Nm, and the torque ripple is 1.9 Nm; when the load is reduced as modified PWM-direct instantaneous torque control (MP-DITC), the time required is 2 s; when the load is 19 Nm, the torque is between 19.5 Nm and 21.3 Nm, and the torque ripple is 1.8 Nm. e performance of MP-DITC strategy is superior to hysteresis DITC control strategy (Table 2)
Aiming at the large torque ripple of SRM, with analysis of SRM theory, a control method combining direct instantaneous torque hysteresis control and pulse width modulation is proposed. e traditional hysteresis DITC is compared and analyzed. e simulation model and experimental platform of motor control are built based on Matlab/ Simulink

Summary

Introduction

Switched reluctant motors [1] (SRMs) have special features such as high tolerance, robustness, low cost with no permanent magnet, and high efficiency without winding in simple and double salient. e torque is stimulated by tendency of rotor poles to align with excited stator pole. E voltage control vector is employed by calculating torque error and hysteresis, which reduces the further torque ripple under DITC. In terms of the analysis of torque characteristics of SRM, modified PWM-direct instantaneous torque control (MP-DITC) algorithm is introduced with asymmetric half bridge power converter. In MP-DITC, a new buffering scheme is proposed to mitigate torque error, which is based on asymmetric half bridge. Both theoretical analysis and experimental results reflect that the strategy is an effective method to relieve torque ripple. E paper is arranged as follows: Section 2 is the main part discussing torque character and comparing with different classical torque control schemes for further analysis of the proposed algorithm.

Theoretical Background

Basic Characteristic of SRMs

Direct Instantaneous Torque Controlling Strategy

Units Analysis of Simulation

Conclusion