A fixed-time fractional-order sliding mode control strategy for power quality enhancement of PMSG wind turbine

Abstract This paper proposes a fixed-time fractional-order sliding mode controller (FTFOSMC) for the permanent magnet synchronous generator (PMSG) wind turbine to enhance the power quality. The FTFOSMC is implemented in the rotor side converter (RSC) and the grid side converter (GSC) to stabilize the PMSG wind turbine within an upper limited convergence time and to improve the dynamic performances. The fractional-order calculus is taken to devise fractional-order controller and the expression of the FTFOSMC is a continuous description, which can better weaken the chattering phenomenon of conventional SMC. Meanwhile, fixed-time stability is adopted to ensure the stabilization of the PMSG wind turbine within an upper limited convergence time irrelated with the initial states. The detailed proof is presented to validate that the proposed FTFOSMC can ensure the PMSG wind turbine stable and estimate the upper limited convergence time through Lyapunov function. Finally, several cases, including peak power tracking and reactive power control, variable wind speeds, grid voltage disturbances and experimental verification, are studied to show the effectiveness, robustness and superiority of the FTFOSMC than the PI control. Simulation and experimental results show that the FTFOSMC can achieve superior dynamic performances than the PI control with shorter convergence time, less vibration, higher tracking accuracy and stronger robustness, thus improving power quality of the PMSG wind turbine.