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.     

Bacteria foraging optimization algorithm based load frequency controller for interconnected power system

Social foraging behavior of Escherichia coli bacteria has recently been explored to develop a novel algorithm for distributed optimization and control. The Bacterial Foraging Optimization Algorithm (BFOA), as it is called now, is currently gaining popularity in the community of researchers, for its effectiveness in solving certain difficult real world optimization problems. This paper proposes BFOA based Load Frequency Control (LFC) for the suppression of oscillations in power system. A two area non-reheat thermal system is considered to be equipped with proportional plus integral (PI) controllers. BFOA is employed to search for optimal controller parameters by minimizing the time domain objective function. The performance of the proposed controller has been evaluated with the performance of the conventional PI controller and PI controller tuned by genetic algorithm (GA) in order to demonstrate the superior efficiency of the proposed BFOA in tuning PI controller. Simulation results emphasis on the better performance of the optimized PI controller based on BFOA in compare to optimized PI controller based on GA and conventional one over wide range of operating conditions, and system parameters variations.     

Decentralized stochastic adaptive control of interconnected systems

This paper considers the stochastic adaptive control problem for a class of large-scale systems formed by arbitrary interconnection of subsystems with unknown parameters and non-linearities. For the estimation of the unknown parameters of the local controllers, stochastic approximation algorithms are used. Conditions sufficient for global stability of the overall system are established. It is shown that the overall tracking error is bounded by a quantity depending on the size of interconnections.     

Age-of-information-aware PI controller for load frequency control

Open communication system in modern power systems brings concern about information staleness which may cause power system frequency instability. The information staleness is often characterized by communication delay. However, communication delay is a packet-centered metric and cannot refect the requirement of information freshness for load frequency control (LFC). This paper introduces the age of information (AoI), which is more compre-hensive and informative than the conventional communication delay modeling method. An LFC controller and com-munication are integrated into the design for LFC performance improvement. An AoI-aware LFC model is formulated frst, and considering each allowable update period of the smart sensor, diferent AoI-aware PI controllers are then designed according to the exponential decay rate. The right AoI-aware controller and update period are selected according to the degree of frequency fuctuation of the power system. Case studies are carried out on one-area and two-area power systems. The results show the superior performance of the AoI-aware controllers in comparison to the delay-dependent controllers.     

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.     

A robust adaptive LQG/LTR TCSC controller applied to damp power system oscillations

This paper investigates the use of self-tuning Linear Quadratic Gaussian control with Loop Transfer Recovery (LQG/LTR), applied in Thyristor Controlled Series Capacitors (TCSC) installed in interconnected power systems. The proposed robust adaptive controller can improve power system stability margins, damping properly the system's dominant electromechanical modes. Although this TCSC controller is designed mainly to identify and damp inter-area modes, it does not affect negatively the local modes damping, therefore enhancing the overall system performance. The proposed controller properties can be verified using non-linear simulations for a four-machine power system, in different operation conditions.     

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.     

Decentralized load frequency control on each power plant

This paper presents a load frequency control system using a refined controller for interconnected power systems. The controller consists of an integral compensator and state feedback. It has been proven that any transfer function between a reference input and a controlled output or between a disturbance and a controlled output is attained by this controller if it is attainable by realizable linear compensation. Parameters of the controller are determined by the optimal regulator theory and additional calculation. The controller can reduce time deviation and inadvertent interchange without information about tie-lines as well as deviations of frequency and net interchange power. This structural features makes it possible to design the control system for each regulating power plant instead of for the control center. If some state variables are not available, the control system can be designed with the remainder of state variables and a dynamic compensator. Simulation results show that the control system is superior to the TBC system.     

风力发电系统最大功率跟踪自适应鲁棒控制

为了提高风力发电系统最大功率跟踪(MPPT)运行的工作性能,针对系统未知建模误差和外部扰动等不确定问题,提出了一种MPPT自适应鲁棒控制方法。该方法建立在基于广义扰动的风力发电系统角速度跟踪动态模型基础上,不依赖于系统模型参数和外部扰动辨识。利用MPPT跟踪偏差的非线性状态反馈和扰动边界值的在线实时估计,自适应地调整切换控制项增益,以加快系统收敛的速度。实际控制律经过一阶积分输出,进一步削弱控制输出信号幅值的抖振,平滑发电转矩,提高跟踪精度。通过构造Lyapunov函数,验证了闭环系统的全局稳定性。通过与常规线性PID控制和非线性动态状态反馈控制(SFC)进行仿真比较,验证了该控制器实现最大功率跟踪控制的良好效果,具有较强的鲁棒性和自适应性。     

机器人的鲁棒自适应分散跟踪控制

提供了一种鲁棒自适应控制策略,用于不确定性机器人的发迹跟踪,该控制器由一个ＰＤ线性反馈、一个立方项偿和非线性项构成。控制律采用分散形式,通过对二自由度机器人的仿真,证明该方法能使跟踪误差快速趋近于零。     

Design of a robust variable structure controller for improving power system dynamic stability

This paper proposes a nonlinear robust controller for improving power system dynamic stability. The design procedure of the controller which uses a nonlinear transformation technique and the variable structure control (VSC) theory is discussed. A method of eliminating the chattering encountered in variable structure controllers is also presented. Performance of the proposed controller in a simple power system, a single machine connected to infinite bus, is investigated using computer simulations. Robust performance of the controller is verified using a number of studies.     

Comprehensive modelling of the unified power flow controller for power system control

In this paper, comprehensive modelling of the unified power flow controller (UPFC) for power flow, voltage, angle and impedance controls is presented. The control modes include some thirteen different power flow, voltage, angle and impedance control functions. The similarities and differences between some of the control modes and those of traditional transformers and series compensation devices are also discussed. The control modes were successfully implemented in a Newton power flow algorithm. Numerical examples are given on the IEEE 30-bus system and the IEEE 118-bus system to illustrate the feasibility and the performance of the Newton power flow algorithm.     

基于PDNN的含风电互联电网负荷频率Tube-RMPC设计

随着新能源大规模接入电网,为应对新能源随机性和波动性给互联系统负荷频率控制(Load Frequency Control, LFC)带来的不确定问题,实现新能源电力系统多约束条件下的优化运行,建立了含风电机组的LFC多胞模型,以减少模型参数不确定对控制系统的影响。设计了基于原对偶神经网络(Primal-Dual Neural Network, PDNN)的Tube鲁棒模型预测控制(Tube-Robust Model Predictive Control, Tube-RMPC)策略。将标称模型预测控制器与辅助反馈控制器结合,通过PDNN实时求解标称模型预测控制器以保证为LFC系统产生最优状态轨迹。设计辅助反馈控制器抵消外部干扰,使实际系统的状态维持在以标称轨迹为中心的Tube内。最后,对含风电的三区域负荷频率控制系统进行仿真研究,结果表明所提出的Tube-RMPC控制策略,不仅能够有效提高控制精度,还能增强系统鲁棒性,提高实时优化效率。     

电网调频型飞轮储能系统自适应鲁棒充电控制方法研究

飞轮储能系统对电网频率调节控制的效果优异,能够有效地提高电网频率稳定性,保证电网运行的可靠性和安全性。为了提高电网波动下的系统充电过程中系统性能和转速跟踪精度,并减小系统的振动和冲击,针对采用永磁同步电机的此类系统,基于矢量控制策略提出了转子转速自适应鲁棒控制(ARC)方法和连续参考转速曲线。通过建立的仿真模型,对推导的方法进行了验证。接着应用转速PID控制方法和等加速度参考转速曲线。仿真结果表明:基于转速ARC控制方法和连续参考转速曲线,系统的转速稳态误差为0.03%,角加速度稳态误差为0.7%,电网波动下的转速最大误差为0.8%;基于转速PID控制方法和等加速度参考转速曲线时,系统的转速稳态误差为0.08%,角加速度稳态误差为1.6%,电网波动下的转速最大误差为6.0%。因此,采用转速ARC控制方法和连续参考转速曲线的系统性能和转速跟踪误差明显优于采用转速PID控制方法和等加速度参考转速曲线。     

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...     

Quasi oppositional harmony search algorithm based controller tuning for load frequency control of multi-source multi-area power system

This paper deals with the load frequency control (LFC) study of single-area and interconnected two-area power system having diversified power sources. The two areas considered in the present study are identical. Each area is having thermal, hydro and gas based power plants. Split-shaft model of gas turbine is used in the present work as one of the diversified generating unit for the purpose of LFC study. Optimal gains of the classical controllers (like integral controller, proportional–integral controller and proportional–integral–derivative (PID) controller, one installed at a time in the studied models) are obtained by using a novel music-inspired metaheuristic harmony search algorithm (HSA) which incorporates quasi opposition based learning technique for memory initialization and also for generation jumping. Single-area power system with diverse power sources is considered and its optimal transient performances are obtained and compared for step load perturbation. The same approach is further extended to two-area interconnected power system consisting of diverse power sources with nominal values of area input parameters. The performance of PID controller is found to be the best one for the studied power system models. It is also revealed that the performance of the interconnected two-area power system with AC–DC tie line is better in comparison to AC tie line.     

多机系统发电机时滞反馈励磁与STATCOM的非线性鲁棒协调控制

广域反馈信号的时滞性使得包含广域信号的电力系统变成时滞动力系统。利用Pade近似逼近时滞环节,将时滞影响隐含在系统动态方程的系数中,静止同步补偿器(STATCOM)的动态特性用一阶微分方程形式的可控无功电流源表示,推导了含多台STATCOM的多机系统的电磁功率表达式。基于伪广义Hamilton系统理论,将包含STATCOM和时滞反馈励磁的多机系统表示成伪广义耗散Hamilton系统形式。利用L2干扰抑制控制方法得到考虑广域信号时滞性及转移电导的发电机励磁和STATCOM的协调控制策略。4机2区域系统的仿真结果表明,与传统的分散控制器相比,所提考虑时滞影响的非线性鲁棒协调控制器能够有效地抑制系统振荡,且具有一定的时滞不敏感性。     

Decentralized robust adaptive neural dynamic surface control for multi‐machine excitation systems with static var compensator

Focusing on solving the control problem of the multimachine excitation systems with static var compensator (SVC), this paper proposes a decentralized neural adaptive dynamic surface control (DNADSC) scheme, where the radial basis function neural networks are used to approximate the unknown nonlinear dynamics of the subsystems and compensate the unknown nonlinear interactions. The main advantages of the proposed DNADSC scheme are summarized as follows: (1) the strong nonlinearities and complexities are mitigated when the SVC equipment are introduced to the multimachine excitation systems and the explosion of complexity problem of the backstepping method is overcome by combining the dynamic surface control method with neural networks (NNs) approximators; 2) the tracking error of the power angle can be kept in the prespecified performance curve by introducing the error transformed function; (3) instead of estimating the weighted vector itself, the norm of the weighted vector of the NNs are estimated, leading to the reduction of the computational burden. It is proved that all the signals in the multimachine excitation system with SVC are semiglobally uniformly ultimately bounded.     

Decentralized adaptive output‐feedback control for stochastic interconnected systems with stochastic unmodeled dynamic interactions

In this paper, we consider the problem of decentralized adaptive output‐feedback regulation for stochastic nonlinear interconnected systems with unknown virtual control coefficients, stochastic unmodeled dynamic interactions. The main contributions of the paper are as follows: (1) This paper presents the first result on decentralized output‐feedback control for stochastic nonlinear systems with unknown virtual control coefficients; (2) For stochastic interconnected systems with stochastic integral input‐to‐state stable unmodeled dynamics, and more general nonlinear uncertain interconnections which depend upon the outputs of subsystems and the stochastic unmodeled dynamics, a decentralized output‐feedback controller is designed to drive the outputs and states to the origin almost surely. Copyright © 2011 John Wiley & Sons, Ltd.     

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