A New Third-Order Continuous Sliding Mode Speed and DC-Link Voltage Controllers for a PMSG-based Wind Turbine with Energy Storage System

This article presents a novel approach for regulating a wind energy conversion system (WECS) that features a permanent magnet synchronous generator (PMSG) and an energy storage system (ESS). The WECS topology includes two converters on both the machine and grid sides. To maximize power production at varying wind speeds, the machine side converter uses an outer loop to control rotor speed and an inner loop to regulate generator current. Concurrently, the grid side converter employs dual control loops, with the outer loop regulating DC-link voltage and the inner loop regulating grid current. A new third-order continuous sliding mode control (TOCSMC) strategy is introduced for controlling the PMSG rotor speed and DC-bus voltage. The key innovation is extending the conventional sliding surface to a third-order sliding mode by increasing its time derivatives and ensuring smoother transitions by replacing the discontinuous switching term with a continuous smooth function. TOCSMC addresses issues such as settling time, overshoot, and steady-state error in PMSG speed and DC-link voltage. Comparisons with a proportional–integral (PI) controller and a conventional second-order sliding mode controller (SOSMC) demonstrate that TOCSMC performs better, increasing system efficiency to 96.5%, compared to 92% for SOSMC and 89% for PI. Additionally, TOCSMC reduces grid current total harmonic distortion (THD) by about 55.32% compared to SOSMC. A test involving the integration of the ESS verifies the system's capability to deliver smooth power and maintain high current quality for consumers. The proposed system's effectiveness is evaluated through MATLAB software simulations.