Full Bridge Converter based SRM Drive with Extended Conduction Strategy

A Switched Reluctance Motor (SRM) is traditionally controlled using an Asymmetric Half-Bridge (AHB) converter. Unlike Full-Bridge (FB) converters, which are widely used in AC motor drives, the AHB converter is not available as an Intelligent Power Module (IPM) since its application is primarily limited to SRMs. Consequently, conventional SRM drives struggle to compete with AC motor drives. Recent studies have shown that an FB converter can also be used to control an SRM in a manner similar to an AHB converter. However, the FB converter has limited conduction period for each phase to avoid short-circuiting the power supply. This limited conduction period is insufficient to minimize large torque ripples that arise from the nature of the SRM. Therefore, torque control performance of the FB converter for the SRM is usually not satisfactory. In this research, a switching strategy that allows extending conduction period of each phase has been proposed to improve torque control capability of the FB converter for the SRM. The validity of the proposed method has been applied to a 12/8 SRM. A complete system structure has been constructed in Finite Element Analysis (FEA) software to test the effectiveness of the approach. The FEA analysis has demonstrated Direct Torque Control accompanied by extended conduction strategy has significant capacity to mitigate torque ripples in FB based SRM drive.