摘要 该文研究孤岛交流微电网二次电压和频率的固定时间精确控制问题,基于多智能体一致性方法,提出考虑状态受限的自适应模糊固定时间二次电压控制器和基于控制障碍函数的二次频率控制器。在多智能体一致性控制中,将每一个分布式电源视为一个非线性智能体,智能体之间通过稀疏网络进行通信。在电压控制器设计中,采用反馈线性化后未知变量的自适应模糊估计提高控制器的自适应能力,并引入新的滑模面使电压控制器在固定时间内收敛。考虑到系统状态受限问题,分别采用障碍Lyapunov函数和控制障碍函数设计电压与频率控制器,使系统状态在预设的约束范围内。频率控制器的设计还考虑了有功功率的精确分配问题,给出了严格的固定时间收敛及稳定性证明。在Matlab/Sim Power System环境下,对微电网负载变化及大干扰下的仿真验证了所提控制器的有效性。
Abstract：Microgrid is one of the most effective and flexible means to manage and control the distributed generation. In microgrid control, the convergence rate of closed-loop system is considered as one of the performance indexes of the control system design. Therefore, it is necessary to analyze the influence of the convergence rate in the control system on the system performance. Finite time convergence can make the error converge to zero in a finite time. However, finite time convergence is related to the initial state of the system. In practical application, because the initial state of the system cannot be obtained in advance, so the specific convergence time cannot be obtained. Meanwhile, the state constrained problem is common in real systems. If the constrained condition does not be met in a system, it will cause the security performance of the system to decline, even may make the whole system unstable. In the microgrid, the physical states such as voltage and frequency are usually constrained to a certain extent. For example, the change of bus voltage should not exceed 10% and the change of frequency should not exceed 2%, otherwise it will seriously affect the stable operation of the system. So, in this paper, based on the multi-agent consensus method, an adaptive fuzzy practical fixed time secondary voltage controller considering state constraints and the secondary frequency controller based on control barrier function are proposed. First of all, the microgrid is regarded as a distributed multi-agent system, and each agents communicate with each other through a sparse network. To solve the deviation problem caused by droop control, based on the multi-agent consensus protocol, secondary control is used to adjust the output voltage, frequency and active power. Secondly feedback linearization is applied to the microgrid system, for the system uncertainty and internal disturbance, adaptive fuzzy estimation is designed to improve the adaptive ability of the controller. A new sliding surface is introduced to design the voltage controller, which makes it converge in practical fixed time, so as to accelerate the convergence speed of the system. The fixed time convergence does not depend on the initial state of the system, but only depends on the parameters of the designed controller, which is conducive to the calculation of convergence time. Finally, considering the problem of system state constraints, the barrier Lyapunov function is used to design the voltage controller, so that the system voltage is constrained within the preset range. The fixed time frequency controller is designed based on cooperative control method of consensus protocol and the control barrier function, and the accurate sharing of active power is realized. The following conclusions can be drawn from the simulation analysis: In the case of load variation, impedance line fault and large disturbance, the proposed controller makes the voltage and frequency follow the reference input quickly and accurately in a fixed time, and the adaptive fuzzy system has a good approximation effect on the system uncertainty and internal disturbance. Compared with the traditional secondary control, the maximum errors of voltage and frequency are within the preset constraint range using the proposed controller, which have the ability of state constraint and strong robustness, at the same time the stability of the system is improved.
吴忠强, 程洪强. 考虑状态受限的微电网二次电压与频率固定时间控制[J]. 电工技术学报, 2023, 38(15): 4107-4119.
Wu Zhongqiang, Cheng Hongqiang. Fixed-Time Secondary Voltage and Frequency Control for Microgrid Considering State-Constrained. Transactions of China Electrotechnical Society, 2023, 38(15): 4107-4119.
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