Comparative Evaluation of Sliding Mode and PI-Based PWM Current Control for Six-Phase Induction Machine Drives

Six-phase induction machines offer inherent fault tolerance capability, reduced torque ripple, and improved reliability compared to a classical three-phase configuration. However, they impose demanding requirements on current control strategies. This study presents a comparative evaluation of Sliding Mode Control (SMC) and the well-established Proportional Integral regulator with Pulse Width Modulation (PI+PWM), both modelled and implemented in MATLAB/Simulink using the same system and identical test condition profiles to ensure a fair comparison. The mentioned controllers are evaluated using speed reversal tests at ±500 rpm (8 kHz sampling) and ±1000 rpm (12 kHz sampling), and further assessed under ±50% variations in magnetising inductance to analyse robustness. The results show that PI+PWM achieves significantly lower steady-state current tracking error, with root mean square error (RMSE) typically below 0.02 A, compared to 0.05 – 0.08 A for SMC. In terms of current quality, SMC maintains a total harmonic distortion (THD) of approximately 1.3% at low speed and 1.05% at high speed. In comparison, PI+PWM consistently remains below 1.1% and 0.9%, respectively, demonstrating stable performance across both operating conditions. Consequently, PI+PWM emerges as a low-complexity and effective solution for industrial applications with limited computational resources. In contrast, SMC remains advantageous in scenarios requiring strong disturbance rejection and robustness to significant parameter variations.