Super-Twisting Sliding Mode Control for ANPC-Driven Permanent Magnet Synchronous Motor With Midpoint Voltage Balancing Strategy

The control system for permanent magnet synchronous motor (PMSM) driven by active neutral-point clamped (ANPC) three-level inverters faces challenges such as slow response of conventional PI controllers, significant chattering and insufficient disturbance rejection in traditional sliding mode control (SMC), and neutral-point (NP) voltage imbalance in the three-level inverter. To address these issues, this paper proposes a composite control strategy integrating second-order fast super-twisting sliding mode control (FSTA-SMC), a novel sliding mode disturbance observer (SMDO), and an improved zero-sequence voltage injection method. The speed loop employs the fast super-twisting algorithm, while the current loop utilizes the super-twisting algorithm, thereby preventing the issue of fast response in individual loops while overall system dynamics remain sluggish. Furthermore, a novel sliding mode disturbance observer is designed by formulating its sliding gain as a function of the disturbance estimation error. This enables precise observation of internal parameter variations and external load disturbances, which are then fed into the sliding mode controller via a feedforward compensation mechanism to enhance system robustness. Additionally, to mitigate the neutral-point voltage deviation, an improved zero-sequence voltage injection method is proposed, characterized by its computational simplicity and ease of engineering implementation. Simulation and experimental results demonstrate that the proposed control strategy achieves superior performance in enhancing dynamic response speed, improving robustness, and suppressing chattering, while also effectively balancing the neutral-point voltage and improving the overall performance of the drive system.