Abstract
This study proposes a novel fractional-order sliding-mode control strategy with robust switching gain to achieve reliable and high quality of wind-powered microgrid systems. Three fractional-order sliding mode controllers are designed to generate continuous control signals and regulate the outer DC-link voltage loop and inner current loop in the grid-side inverters. High robustness and stability of the grid-side inverter can be guaranteed even in the presence of parameter variations and external disturbances. Owing to the fractional-order sliding manifold and fractional-order integral control law, the chattering is attenuated. The fractional-order robust adaptive switching gain is designed to avoid overestimating the upper bound of matched/unmatched uncertainties, save the control energy, and guarantee the rapidity and robustness of the convergence. Simulations validate the proposed method.
Highlights
Distributed generation (DG) has paid more and more attention because of its advantages, such as low investment, clean environment protection, high reliability of power supply, and flexible power generation [1]
To give full play to the efficiency of the distributed generation systems, the most effective way is to combine the distributed generation and loads to form a microgrid connecting to the main grid. e active power and reactive power between the microgrid and the main grid can be flexibly exchanged
Compared with traditional integral order calculus, fractional calculus increases the variability of differential and integral degrees of freedom, which brings new flexibility to the design of control systems [21, 22], so that it has both advantages of fractional calculus and the Sliding mode control (SMC). e memorial and genetic traits are the typical characteristics of fractional-order SMC (FOSMC), which can predict the control behavior of the system to a certain extent, reduce the switching probability of the control behavior in the reaching process, and improve the continuity of the control [23, 24]
Summary
Distributed generation (DG) has paid more and more attention because of its advantages, such as low investment, clean environment protection, high reliability of power supply, and flexible power generation [1]. In the wind-powered microgrid system, the voltage source inverters (VSIs) are widely used as grid-side inverters This type of converter has a characteristic that the high-frequency harmonics exist in the voltage waveform. Ere are many uncertainties existed in the wind powered microgrid system, such as parameter variations of LCL filters, grid voltage sag, and frequency fluctuation. Compared with traditional integral order calculus, fractional calculus increases the variability of differential and integral degrees of freedom, which brings new flexibility to the design of control systems [21, 22], so that it has both advantages of fractional calculus and the SMC. To achieve higher performances of wind-powered microgrid systems, this study proposes a fractional-order SMC method with robust adaptive switching gain for GSI. Fractional-order sliding mode controllers are designed for the outer DC-link voltage loop and inner current loop in GSI.
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