Decentralized robust adaptive-output feedback controller for power system load frequency control

In this paper, a new model reference-decentralized robust adaptive-output feedback controller is proposed for the load frequency control (LFC) of large-scale power systems with unknown parameters. This control strategy requires only local input–output data and can follow random changes in the operating conditions. The controller is designed such that the trajectory errors and the control gains of each area remain uniformly bounded. In the proposed method, firstly an adaptive observer is designed to estimate the state variables and system parameters using local data only. Then a locally linear combination of the estimated states and the model reference states are used to design a robust adaptive-output feedback controller for each area. Simulation results for a three-area power system show that the proposed controller achieves good performance even in the presence of plant parameter changes and system non-linearities. Received: 18 October 2001/Accepted: 24 October 2001     

考虑电动汽车集群的互联电网负荷频率分散预测控制

随着大量电动汽车接入互联电网,其移动的充电模式会给电网带来一定的冲击,反过来,电动汽车作为一种移动式储能单元可参与互联电网调频,但目前的研究都是集中式或分散式的V2G控制上.在电动汽车储能电池动态模型的基础上,构建含电动汽车集群的多区域互联电网负荷频率控制模型,基于广域监测系统,结合模型预测控制实现了多区域电网负荷频率...     

Decentralized load frequency based on H∞ control

This paper presents a decentralized load frequency control (LFC) based on H_∞ optimal control theory with an observer. A few LFC schemes have been proposed based on the optimal control theory, but they have not considered the change of system parameters in operation and the characteristics of load disturbances in a target system. In this paper, H_∞ robust control is introduced to address such problems. Owing to its practical merit, the proposed control scheme is a decentralized LFC. Employing observer theory, the proposed method requires only frequency and tie‐line power deviation in each area. Numerical simulations are shown to demonstrate the effectiveness of the proposed method. H_∞ control was proven to show greater effectiveness of damping disturbance over the conventional optimal control by the design of control systems aimed at restricting the H_∞ norm of its transfer function. In particular, when a decentralized LFC is applied, by reducing the system size, H_∞ norm is easier to dampen; thus H_∞ control is more effective in the decentralized control. Future research topics include the design of H_∞ control system with a weight on frequency response. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 28–38, 2001     

Decentralized load frequency controller for a multi-area interconnected power system

This paper proposes a control scheme for the load frequency control (LFC) problem of multi-area power systems. These systems are treated as interconnected dynamical systems. In the design of the proposed controller, each local area network is overlapped with states representing the interconnections with the other local area networks in the global system. Then, a decentralized control scheme is developed as function of the local area state variables and those resulting from the overlapped states which represent an approximation of the interconnection variables. The proposed controller guarantees the asymptotic stability of the overall closed loop system.The simulation results indicate that the proposed control scheme works well. In addition, they show that the controlled system is robust to changes in the parameters of the power system and to bounded input disturbances acting on the system. Moreover, the simulation results show that the controlled system behaves well even when there is a maximum limit on the rate of change in power generation.     

Decentralized robust adaptive load frequency control using interactions estimation

In this paper, a new model reference decentralized adaptive output feedback controller is proposed for load-frequency control (LFC) of large-scale power systems with unknown parameters. The main problem with a decentralized robust LFC is that the interactions are treated as disturbances. This results in a conservative control action to maintain stability in the worst-case scenario. Furthermore, to improve the performance of the decentralized LFC, the proposed method estimates the interactions from other subsystems to modify the adaptive controller so that the interactions are effectively neutralized. The other important features of the proposed controller are: (1) no prior information about the system parameters is required, (2) random changes in the operating conditions are traced, (3) only the local input–output data are needed, (4) the robustness of the overall system against the system parameter uncertainties is guaranteed. To show the effectiveness of the proposed controller, a three-area power system is studied. The simulation results are promising and highlight the remarkable performance of the controller even in the presence of both plant parameter changes and high interactions.     

Effect of load characteristics on frequency control in power systems

The load-frequency control (LFC) problem is investigated on assumptions considered realistic for most power systems. Voltage and frequency dependence of system loads, and load inertia effects, are taken into account. Results include system dynamic response to changes in load, and effects of LFC parameter settings. Using a performance index based on squared tie-line flow error plus squared area frequency error, the effect of load representation on optimum integrator gain is examined.     

含双馈风电电力系统的采样负荷频率控制

针对含新能源的多区域电力系统频率稳定问题,提出一种考虑控制信号更新周期变化的采样负荷频率控制(load frequency control,LFC)方案。首先,在充分考虑系统采样特性的基础上,建立新型电力系统采样LFC模型,并将模型转化为一个采样数据网络控制系统。然后,利用整个采样区间[t _k,t _k+1)信息,构建一个新的双边闭环型Lyapunov泛函。结合所提出的泛函与自由矩阵不等式,导出系统的低保守性稳定准则。基于这个准则,提出确保系统镇定的采样控制器设计方法。最后,通过实例仿真验证了所提方法的有效性与优越性。     

Adaptive fuzzy logic load frequency control of multi-area power system

Based on indirect adaptive fuzzy control technique, a new load frequency control (LFC) scheme for multi-area power system is proposed. The power systems under study have the characterization of unknown parameters. Local load frequency controller is designed using the frequency and tie-line power deviations of each area. In the controller design, the approximation capabilities of fuzzy systems are employed to identify the unknown functions, formulate suitable adaptive control law and updating algorithms for the controller parameters. It is proved that the proposed controller ensures the boundedness of all variables of the closed-loop system and the tracking error. Moreover, in the proposed controller an auxiliary control signal is introduced to attenuate the effect of fuzzy approximation error and to mitigate the effect of external disturbance on the tracking performance. Simulation results of a three-area power system are presented to validate the effectiveness of the proposed LFC and show its superiority over a classical PID controller.     

考虑可控负荷的多区域电力系统分布式模型预测负荷频率控制

由于同步发电机的惯性较大,导致传统的集中式负荷频率控制模式反应不够迅速,而用户侧具有快速响应能力的可控负荷资源为系统的频率调节提供了新机遇。研究了考虑用户侧可控负荷资源主动参与系统频率调节的多区域互联电力系统分布式模型预测负荷频率控制问题。通过建立的含可控负荷的多区域互联电力系统负荷频率响应模型及自动发电控制模型,基于连续时域交替方向乘子法和分布式模型预测控制方法,提出了一种用户侧可控负荷资源主动参与的多区域互联电力系统分布式模型预测最优负荷频率控制模型。基于修改的IEEE39节点三区域互联电力系统进行仿真验证,结果表明所提考虑可控负荷的分布式模型预测控制策略可显著减少系统恢复至稳态所需的时间。分布式控制策略的控制自由度更高,增强了系统的可控性。     

考虑疲劳载荷的风电场分散式频率响应策略

风电场参与调频时会增加风机的疲劳载荷,导致风电场维护成本上升、运营效益下降.为此,提出一种考虑疲劳载荷的风电场分散式频率响应策略,可在维持风电场调频性能的同时,降低风机疲劳损伤.为实现该目标,首先分析风电场调频及有功控制结构,推导风机线性动力学模型,并构建考虑疲劳载荷的单机频率响应模型.然后基于Jensen尾流模型,推...     

拒绝服务攻击下的分布式弹性负荷频率控制

开放通信网络的大量应用,给电网带来了潜在安全隐患.文章研究了周期性拒绝服务攻击下的弹性负荷频率控制器的设计问题.给出了一种可检测的拒绝服务攻击模型,推导了网络攻击下的分布式负荷频率控制时滞切换系统模型.基于李亚普洛夫理论,分析了切换系统的稳定性,并进行了弹性控制器设计,所设计控制器对负荷扰动和网络攻击具备一定的鲁棒性....     

Decentralized voltage control in multiarea power system

This paper discusses the feasibility of a decentralized voltage control scheme for large-scale power systems. The algorithm is intended to apply to a reactive normal operating state from an emergency state caused by illcondition and also to keep the operating state away from approaching unstable boundaries in preventive control. The procedure for releasing voltage deviation (over/under voltage) is formulated as a multistage decision process over a certain time interval. The optimization problem is transformed into a two-point boundary value problem using the discrete maximum principle and is solved easily by using the discrete Riccati equation. For a large-scale power system, control values must be computed from a large number of state variables, and this inevitably prolongs the slow dynamics with controllers. The centralized control system in a large-scale system cannot be justified from the economical and technical viewpoints. To resolve the foregoing problems, a decentralized voltage control system incorporating slow voltage dynamics is presented.     

基于Ziegler-Nichols优化算法的火电机组负荷频率PID控制研究

随着风电和光伏接入电网的规模不断扩大,电网负荷峰谷差逐渐增加,电网的频率控制出现超调量过大、调节速度过慢等一系列问题。本文针对互联电力系统的负荷分配以及频率控制问题,提出考虑发电机组分配系数的互联电力系统负荷频率控制方法。首先,建立单个区域包含多个火电机组的两区域电网自动发电控制（AGC）系统仿真模型,根据各发电机组的煤耗特性建立经济性目标函数,并且获得最优的出力分配系数;然后,基于联络线功率和频率偏差控制（TBC-TBC）的控制模式,采用经Ziegler-Nichols相关算法优化后的PID控制,并对优化后PID控制器的鲁棒性进行分析研究;最后,基于两区域系统仿真模型,在一定的负荷扰动工况下进行仿真验证。仿真结果表明:该分配方法能够有效节省煤耗,本文算法优化后的PID控制器在频率恢复速度方面具有一定的优势,并且鲁棒性良好。     

Battery energy storage for load frequency control of an interconnected power system

This paper deals with load frequency control of an interconnected reheat thermal system considering battery energy storage (BES) system. Area control error (ACE) is used for the control of BES system. Time domain simulations are used to study the performance of the power system and BES system. Results reveal that BES meets sudden requirements of real power load and very effective in reducing the peak deviations of frequency and tie-power and also reduces the steady state values of time error and inadvertent interchange accumulations.     

基于变论域模糊逻辑的互联电力系统负荷频率控制

随着风电在电力系统中的渗透率不断提高,其出力不确定性对系统频率稳定造成威胁.针对风电接入系统后的频率波动问题,提出变论域模糊PI负荷频率控制策略.为克服传统模糊控制器由于论域固定导致自适应能力有限的缺点,设计的变论域模糊PI负荷频率控制器通过变论域方法实现输入、输出论域的动态调整.为满足风电接入系统后复杂的论域调整需求...     

应用于电厂鼓风机变频运行的MMC控制技术研究

鼓风机是发电厂锅炉的重要辅助设备,采用高压变频器对鼓风机进行变频调速能够极大提高效率,减小损耗。对一种基于MMC的高压变频器结构进行研究,提出了相应的控制策略,并对提出的控制策略进行了仿真和实验研究,仿真和实验结果验证了所提出控制策略的正确性和实用性。     

Optimal decentralized load frequency control

A new approach for optimal decentralized load frequency control of a multi-area interconnected power system is presented, which includes the optimal design of a decentralized load frequency controller, an observer for unmeasurable local states and load disturbances, and a quadratic estimator for tie-line power flow information transmitted at intervals. The optimal design of the decentralized controller is based on a modified application of the singular perturbation theory, and the decentralized Luenberger observer uses techniques of state augmentation for exponential disturbance functions and the representation of tie-line power flows as indirectly controlled inputs. The approach presented herein is tested numerically through a two-area load frequency system model, and the results demonstrate remarkable advantages over the conventional ones.