Optimal Control Strategy of a Series-Connected Multimachine System Supplied by a Single Inverter Using Third-Order Sliding-Mode Algorithm

Abstract

This paper presents a robust control strategy for multimachine systems (MMSs) composed of two five-phase permanent magnet synchronous motors (5Ph-PMSMs) connected in series through their stator windings. A single five-phase inverter can drive both machines while ensuring independent regulation using a phase transposition scheme. Conventional vector control with proportional-integral (PI) regulators is sensitive to parameter variations, whereas classical sliding mode control (SMC) suffers from chattering, transient errors, and reduced robustness. To address these issues, an advanced method based on third-order sliding mode control (TOSMC) is proposed for speed and current regulation. The approach was tested in MATLAB/Simulink, showing clear improvements. For 5Ph-PMSM1, the response time decreased by 45.29 % compared to MMS-SMC and 84.16 % compared to the PI-based control; for 5Ph-PMSM2, the reductions were 32.25 % and 81.73 %, respectively. Torque ripple was also reduced, reaching 9 % and 75.40 % for 5Ph-PMSM1, and 9.3 % and 76.03 % for 5Ph-PMSM2, relative to the MMS-PI and MMS-SMC technique. These results demonstrate the robustness and high efficiency of the proposed MMS-TOSMC method, which makes it suitable for demanding MMS drive applications.