Dynamic Performance Evaluation of Third-Order SMC-Based Variable-Speed PHES in Single-phase Grid-Connected Hybrid Renewable Energy Systems

Renewable energy systems, such as wind and solar, are intermittent, necessitating energy storage systems with efficient controllers to improve performance. This work introduces a novel control technique to a 3-level neutral point clamped (3L-NPC) converter-based brushless direct current (BLDC) machine on a variable-speed pump hydro energy storage (PHES) system, which is connected to a grid-tied hybrid solar-wind energy network. A third-order sliding mode control (TOSMC)-based field-oriented control scheme is employed on both the outer and inner loops to control the 3L-NPC-powered BLDC machine prototype, ensuring an efficient control mechanism and an integrated bidirectional power flow. Also, the TOSMC-based voltage-oriented control scheme is employed to manage the single-phase grid converter. Furthermore, maximum power is extracted from the wind energy conversion system, solar photovoltaic array, and PHES system. To evaluate the dynamic performance of the variable-speed PHES system, a rigorous study based on wind speed, solar irradiation, and load variation is performed to observe the effectiveness in motoring, generating, and stopping modes of the PHES. Moreover, the proposed controller is compared with the traditional field-oriented proportional-integral control and second-order sliding mode control on a 3L-NPC-connected BLDC machine. The performance of the BLDC-based PHES system with a 3L-NPC converter is examined in MATLAB/Simulink and validated with a laboratory prototype, demonstrating its potential as a scalable solution for hybrid renewable integration in microgrids.