Abstract
The electric energy storage system (EESS) is considered as an efficient and promising tool to alleviate the power imbalance of grid-connected microgrid with distributed generation (DG). This work develops a perturbation observer-based fractional-order control (POFOC) strategy for superconducting magnetic energy storage (SMES) system. Initially, a high-gain state and perturbation observer (HGSPO) is designed for reliable estimation of the combined impact of the nonlinearities, parameter uncertainties, unmodeled dynamics, and external disturbances of SMES. Then the storage function of an SMES system is designed, which takes favorable terms into serious consideration to sufficiently utilize the physical properties of the SMES system. Moreover, a fractional-order control framework is applied for complete compensation for the estimated perturbation and adopted as the attached input to boost its dynamical responses. Furthermore, a newly proposed jellyfish search algorithm (JSA) is utilized to realize optimization and tuning of control gains of the developed strategy, upon which high-quality global optimum can be obtained to ensure prominent controlling performance. Case studies, e.g., active power and reactive power supply and system restoration capability under power grid fault effectively validate the effectiveness and reliability of the POFOC strategy compared with traditional PID control and interconnection and damping assignment passivity-based controller (IDA-PBC). In particular, the overshoot of PID is 115.264% of the rated value, while POFOC has no overshoot.
Highlights
Large-scale exploitation and application of renewable energy are significant to our future energy transformation and sustainable development, thanks to their outstanding environment-friendly characteristics (Yan, 2020), which can effectively help in the global energy crisis and ecosystem deterioration (Zhang et al, 2021a)
4.2.1 Population initialization The initialization of population in jellyfish search algorithm (JSA) is conducted based on a logical graph (May 1976), which eliminates the negative effects of random initialization that are often adopted by traditional metaheuristic algorithms, e.g., low convergence rate and easy to fall into local optima due to the lack of population diversity
Compared with PID control, the proposed perturbation observer-based fractional-order control (POFOC) method can always maintain a relatively stable tracking performance, and the restore speed is much faster after the fault on the transmission line
Summary
Large-scale exploitation and application of renewable energy are significant to our future energy transformation and sustainable development, thanks to their outstanding environment-friendly characteristics (Yan, 2020), which can effectively help in the global energy crisis and ecosystem deterioration (Zhang et al, 2021a). It is worth noting that SMES receive vast research attention, thanks to their merits of high-energy conversion efficiency via superconductors, and low cost and high current intensity (Yang et al, 2016) It can achieve rapid regulation of active power/reactive power, which is beneficial to power transfer control (Shima et al, 2018). A novel jellyfish search algorithm (JSA) (Chou and Truong, 2021) is adopted to realize the optimization and tuning of control gains of the developed strategy, upon which highquality global optimum can be obtained to ensure a consistently remarkable performance. An HGPO is employed to estimate the perturbation, while the controller is adopted for FIGURE 1 | Pulse-width modulated current source converterPWMCSC)-based superconducting magnetic energy storage (SMES) system connected to an AC power grid.
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