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Permanent magnet synchronous motors (PMSMs) are known as highly efficient motors and are slowly replacing induction motors in diverse industries. PMSM systems are nonlinear and consist of time-varying parameters with high-order complex dynamics. High performance applications of PMSMs require their speed controllers to provide a fast response, precise tracking, small overshoot and strong disturbance rejection ability. Sliding mode control (SMC) is well known as a robust control method for systems with parameter variations and external disturbances. This paper investigates the current status of implementation of sliding mode control speed control of PMSMs. Our aim is to highlight various designs of sliding surface and composite controller designs with SMC implementation, which purpose is to improve controller’s robustness and/or to reduce SMC chattering. SMC enhancement using fractional order sliding surface design is elaborated and verified by simulation results presented. Remarkable features as well as disadvantages of previous works are summarized. Ideas on possible future works are also discussed, which emphasize on current gaps in this area of research.

This study presents selective harmonic elimination pulse width modulation technique-based hybrid asynchronous PSO-Newton-Raphson (APSO-NR) algorithm for the elimination of undesired harmonics in cascaded H-bridge multilevel inverter. The proposed algorithm is applicable to all levels of MLI having equal and non-equal DC sources. In the proposed method, ring topology-based APSO algorithm is hybrid with NR method. APSO worked as a global search technique and NR is used for the refinement of best solutions. APSO-NR is applied to the seven-level inverter to eliminate fifth and seventh harmonics. In simulations, the performance of the proposed algorithm is compared with genetic algorithm, bee algorithm and particle swarm optimisation. The results proved that the proposed algorithm is efficient, and gives more precise firing angles in less number of iterations with high capability of tackling local optima. For the 48% of modulation index range, APSO-NR minimised the fitness function value lower than (10 −25). The proposed algorithm is validated through the experimental implementation of the three-phase seven-level inverter.

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This paper investigates speed regulation of permanent magnet synchronous motor (PMSM) system based on sliding mode control (SMC). Sliding mode control has been vastly applied for speed control of PMSM. However, continuous SMC enhancement studies are executed to improve the performance of conventional SMC in terms of tracking and disturbance rejection properties as well as to reduce chattering effects. By introducing fractional calculus in the sliding mode manifold, a novel fractional order sliding mode controller is proposed for the speed loop. The proposed fractional order sliding mode speed controller is designed with a sliding surface that consists of both fractional differentiation and integration. Stability of the proposed controller is proved using Lyapunov stability theorem. The simulation and experimental results show the superiorities of the proposed method in terms of faster convergence, better tracking precision and better anti-disturbance rejection properties. In addition, chattering effect of this enhanced SMC is smaller compared to those of conventional SMC. Last but not least, a comprehensive comparison table summarizes key performance indexes of the proposed controller with respect to conventional integer order controller.