Load frequency fractional‐order controller design for shipboard microgrids using direct search alghorithm

Abstract

Load frequency control (LFC) is one of the controversial topics in power systems, especially in shipboard microgrids (SMG). In such applications, renewable energies such as wind, solar, or wave energies provide the power supply. However, changes in the weather conditions or loads can disrupt the frequency. To have a constant frequency in the presence of such turbulence in SMG, a fractional‐order dynamic output feedback controller (FDOFC) is proposed. As a result, the closed‐loop system is extended to a non‐identical fractional‐order system in the state space model. First, the non‐identical fractional‐order system is transformed into an identical one using the least common multiple techniques to determine control parameters. Subsequently, using a direct search algorithm, a considered initial design space is divided into smaller totally stable (TS) sub‐spaces. Then, among all TS controller parameters, the H∞$H_{\infty }$ controller is designed to reduce the effects of disturbances. The study is carried out on a practical SMG system to show the practicality of the proposed FDOFC. Finally, to evaluate the proposed method's efficiency, the SMG results are compared with the results obtained with μ synthesis, H∞$H_{\infty }$, Bilinear Matrix Inequality (BMI)‐based, and fuzzy fractional optimization methods. Compared to the state‐of‐the‐art approaches, more promising results are obtained for H∞$H_{\infty }$‐norm of the closed‐loop system about ten times smaller, that is, false|false|normalΔffalse|false|∞=0.00026$||\Delta f||_\infty = 0.00026$ which is such a negligible norm that concludes perfect disturbance rejection. Moreover, in more scenarios, the robustness of the designed framework is evaluated under parameter variations and time delays in communication. The results show that the maximum frequency deviation is 2.5×10−3$2.5 \times 10^{-3}$, which is very small. Therefore, the controller also works impressively under deviations of SMG system parameters, and communication time delays.

Optimal Observer-Based Power Imbalance Allocation for Frequency Regulation in Shipboard Microgrids

“…Our proposal stands out from existing solutions in the literature. Most significantly, existing solutions focus predominantly on predefined SMG setups with specific known ESSs and components [5,7,22]. On the contrary, we propose a generalised approach that can be tailored to different SMGs.…”

“…This article focusses only on LFC. This is a conventional approach that is generally adopted in the literature [6,22,23].…”

Cases of PD-CFPID selector for frequency adjustment of integrated power grid

“…To upgrade the command performances under involved work conditions, a new partially decentralized combined fuzzy PID (PD-CFPID) regulators are planned. While domestic outlooks regularly hurt if there is a single failure, decentralized plans are associated with demanding practical implementations and costly communication demands [11]- [15]. The chief contributions of study are to examine the efficacy of the proposed control structure.…”

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“…If the frequency cannot be kept within an acceptable range, the system could become unstable. Therefore, a reliable frequency controller is anxiously anticipated [10].…”