Fuzzy bang-bang control of static VAR compensators for damping system-wide low-frequency oscillations

Static VAR compensators (SVCs) have been widely used in power systems to keep terminal voltages within bounds. The other application is to improve power systems damping, especially for loosely connected power systems. In this paper, a scheme using fuzzy logic control (FLC) is connected in parallel with a conventional voltage regulation loop to form a supplementary damping loop for the SVC to increase the system's transmission capacity. The FLC is based on bang-bang control, and provides damping across each connected line to the SVC. Damping is of particular importance especially for weakly coupled power systems. Using rotor-angle signals that are estimated from voltage and power measurements at each connected line to the SVC, a fictitious generator at the remote end of each connected line is identified. The SVC receives control signals from all fictitious generators, which are competing and reacting differently at different phases of system oscillations. The final control for the SVC combines the control signals from all fictitious generators, which are scaled according to their individual contributions to damping. The proposed signal structure guarantees robustness and effectiveness of the final control with respect to different loading and fault conditions. The FLC design is based on Lyapunov function analysis, and is simulated on a three-generator power system for performance evaluation.     

STATCOM模糊控制的综合优化设计

针对严重非线性静止同步补偿器模糊逻辑控制隶属函数的参数和模糊控制规则调整困难的问题,根据微遗传算法,并利用模糊系统的逼近能力,提出了一种模糊控制综合优化设计方法.选择模糊控制器的输入/输出观测信号,应用MATLAB中的模糊控制工具箱快速地获得初始的模糊控制规则,再采用微遗传算法优化其隶属函数参数和模糊控制规则,并给出了模糊控制规则优化后的结果.对带有一个静止同步补偿器的四机电力系统,在三种不同的负荷和三种不同的控制方式下进行仿真实验,结果表明:在宽负荷变化范围内,该控制器的追踪控制能力和鲁棒性等比常规的超前滞后控制、未优化模糊控制都优越.     

Damping of low‐frequency oscillations using an SVC‐based supplementary controller

In this paper, the optimal tunning problem of parameters of a conventional lead–lag controller (LLC) and a fuzzy logic controller (FLC) based on the static Var compensator (SVC) is considered. The solution is obtained using an improved particle swarm optimization (IPSO) algorithm. The membership functions and scaling factors of the FLC and LLC parameters are optimized using the above‐mentioned technique. The proposed controllers are settled down to an SVC that is installed at the middle of a transmission line connecting a single machine to an infinite bus system. Simulation results show the superiority of the optimized FLC compared to the optimized LLC and also when the SVC is without the supplementary controller under different disturbances and loading conditions. The simulations and analyses are implemented in MATLAB environment. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A novel fuzzy state feedback controller for power system stabilization

A novel fuzzy logic controller (FLC) is developed for damping electromechanical modes of oscillations and enhancing power system synchronous stability. The proposed controller is based on state feedback control system. The input signals to the controller are the weighted sum of the mechanical states and the electrical states weighted sum, while its output signal is added to the conventional fixed-gain PI controller output signal to give the excitation control signal. The simulation results using the proposed controller are carried out on an synchronous machine infinite bus system. Moreover, a comparison between the conventional fixed-gain PI controller and the proposed FLC is presented. The results validate the effectiveness of the proposed FLC in terms of less overshoot/undershoot and enhancing the power system stability over a wide range variation of operating conditions.     

Coordinated fuzzy logic control between SVC and PSS to enhance stability of power systems

This paper presents a new switching control scheme for static var compensator (SVC) using fuzzy logic control rules to enhance the overall stability of electric power systems. In addition, the coordination with power system stabilizers (PSS) is also considered to achieve a wider stable region. An SVC is set on one of the busbars in the transmission system, where the real power flow signal is utilized at the location of the SVC to determine the firing angle of the thyristor switch. The switching control scheme is simple so as not to require heavy computation on the microcomputer based switching controller. The PSSs are also set on the generators in the study system. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme for the SVC. The coordination between SVC and PSS is also effective to enlarge the stable region.     

Fuzzy logic switching of thyristor controlled braking resistorconsidering coordination with SVC

This paper presents a new switching control scheme for braking resistors (BR) using fuzzy logic to enhance overall stability of electric power systems. In addition, the coordination with an SVC is also considered to achieve a wider stable region. The braking resistor is set on one of the generator busbars, where the real power output from the generator is measured to determine the firing-angle of the thyristor switch. The switching control scheme is simple so as not to require heavy computation on the microcomputer based switching controller. An SVC is set on one of the busbars in the system. The switching of the SVC uses a similar fuzzy logic control scheme to the one for the BR. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme     

SVC与发电机励磁的非线性变结构协调控制

针对电力系统的强非线性和不确定性特点及精确反馈线性化的不足,引入自抗扰控制技术设计了能同时改善电力系统功角稳定和电压动态特性的静止无功补偿(SVC)与发电机励磁的变结构协调控制器。扩张状态观测器的动态补偿作用不仅使励磁控制与SVC控制实现解耦,而且使二者均能实现当地信号控制。仿真结果表明提出的非线性鲁棒变结构协调控制器能有效地改善系统的动态稳定性。所设计的控制器对系统运行点和网络结构的变化具有良好的适应性和鲁棒性。     

基于遗传算法的窄间距隶属函数在模糊逻辑电力系统稳定器设计中的应用

提出了一种简单、高效的模糊逻辑电力系统稳定器的设计方案,其特点是采用了窄间距隶属函数(SSMFs).SSMFs是设计模糊逻辑控制器隶属函数的一种新方法.采用遗传算法选择SSMFs模糊逻辑控制器的最佳参数值,包括间距系数、重叠系数和增益系数等.通过单机无穷大系统验证所提方案的正确性.结果表明,所提出的SSMFs模糊逻辑电力系统稳定器在发电机负载和励磁增益大范围变化情况下,改善了电力系统的稳定性.     

A fuzzy logic-based adaptive damping controller for static VAR compensator

This paper presents an approach for designing a fuzzy logic-based adaptive SVC damping controller for damping low frequency power oscillations. The proposed approach uses linear optimal controllers and, in addition, a fuzzy signal tuner is introduced to achieve adaptiveness. Two linear damping controllers are designed to accommodate two extreme operating conditions and a fuzzy logic mechanism is used to generate one single control signal by properly combining the outputs of the linear controllers. The fuzzy controller is optimized using a least squares error criterion and, as a result, a higher-order adaptive controller is achieved. Simulation studies of the proposed fuzzy adaptive damping controller show that it provides satisfactory damping against low frequency oscillations under different operating conditions. Results are given for a one-machine infinite-bus and a four-machine two-area test system, which show improvement over the use of a fixed parameter controller.     

用于静止无功补偿器的非线性状态PI控制器

针对电力系统的强非线性和不确定性,运用非线性状态PI控制直接对其不确定对象进行设计,能同时改善电力系统功角稳定和装设点电压动态特性的静止无功补偿器（SVC）,避免了基于反馈线性化理论的非线性SVC控制器由于数学模型的误差而影响控制器性能的缺点,所得的控制规律与系统运行点和网络结构完全无关。仿真计算表明非线性状态PI型静止无功补偿控制器能有效地改善系统的动态特性。     

A stable self-tuning fuzzy logic control system for industrialtemperature regulation

A closed-loop control system incorporating fuzzy logic has been developed for a class of industrial temperature control problems. A unique fuzzy logic controller (FLC) structure with an efficient realization and a small rule base that can be easily implemented in existing industrial controllers was proposed. The potential of FLC in both software simulation and hardware tests in an industrial setting was demonstrated. This includes compensating for thermo mass changes in the system, dealing with unknown and variable delays, operating at very different temperature set points without retuning, etc. It is achieved by implementing, in the FLC, a classical control strategy and an adaptation mechanism to compensate for the dynamic changes in the system. The proposed FLC was applied to two different temperature processes and performance and robustness improvements were observed in both cases. Furthermore, the stability of the FLC is investigated and a safeguard is established     

Ant Colony Optimized Fuzzy Control Solution for Frequency Oscillation Suppression

This paper presents a novel approach in addressing a critical power system issue, i.e., automatic generation control (AGC) in a smart grid scenario. It proposes the design and implementation of an optimized fuzzy logic controller (FLC) for AGC of interconnected power network. There are three different sources of power generation considered in the two-area interconnected model of power system network. First area is equipped with a single reheat thermal unit and a superconducting magnetic energy storage (SMES) unit, while another area has a hydro-unit with SMES. A multi-stage optimization strategy for the optimal solution of FLC for tie-line and frequency oscillation suppression is proposed in this paper using an ant colony optimization technique. The optimization of FLC is carried out in four different stages. The first stage is the optimization of range of input and output variables; the second stage is the optimization of membership function; the third and fourth stages are the optimization for rule base and rule weight optimization, respectively. The performance of the proposed controller is also compared with another control approaches to stabilize P_tie-line and Δf oscillations; these are the Ziegler–Nichols-tuned proportional–integral–derivative (PID) controller and genetic algorithm optimized PID controller. A comprehensive analysis of the traditional techniques and proposed techniques is presented on the basis of major dynamic performance parameters, i.e., settling time and peak overshoot.     

Controlling chaos and voltage collapse using an ANFIS-based composite controller-static var compensator in power systems

Chaos and voltage collapse exist in power systems due to critical loading and disturbing of energy (DE). These phenomena cause instability in power system operation and must be avoided. In this paper, an ANFIS-based composite controller-static var compensator (CC-SVC) was proposed to control both chaotic oscillations and voltage collapse. The ANFIS-based CC-SVC was proposed because its computation was more efficient than Mamdani fuzzy logic controller. Adaptive network parameters were obtained through a training process. The controller parameters were automatically updated by off-line training. Both chaos and voltage collapse were able to control and suppress effectively by the proposed method. Furthermore, the load voltage was held to a set value by adjusting the supplied reactive power. When the reactive load was increased, the SVC susceptance and reactive power supplied by the SVC also increased. The proposed method was able to maintain the load voltage and to increase the loading margin.     

用于静止无功补偿器的变结构控制器的设计

本文提出了能同时改善电力系统功角稳定和装设点电压动态特性的用于静止无功补偿器的变结构控制器设计方法。控制器对系统工作点的变化具有鲁棒性。     

基于SVC的大型风电场次同步谐振抑制

当风电场通过含串联补偿电容线路提升外送功率时可能会发生次同步谐振。分析了风电场次同步谐振机理以及SVC在抑制大型风电场次同步谐振方面的作用,将SIMPLEX算法与单隶属度函数模糊控制技术相结合,设计了基于单隶属度函数模糊控制的SVC附加控制器。与常规模糊控制器相比较,论文提出的控制方案性能更优,能更快速抑制次同步谐振。仿真结果验证了所提出附加控制器的优越性。     

A novel SVC supplementary controller based on wide area signals

Static Var Compensator (SVC) is a kind of FACTS device which is used in power system primarily for the purpose of voltage and reactive power control. Based on wide area signals, this paper presents a systematic approach for designing SVC supplementary controller, which is used to improve the damping of power system oscillation. The principle for damping oscillation by SVC is first analyzed and the concept of synthetic residue index is then presented which is used to choose the proper input wide area signals. Parameters of the controller are determined by means of test signal method and residue root locus. Eigenvalue analysis and time domain simulations are performed on a two-area system and the results demonstrate the effectiveness of the proposed controller.     

基于扩张状态观测器的SVC非线性变结构控制

针对电力系统的强非线性和不确定性,将自抗扰控制技术引入变结构控制器的设计,设计了能同时改善电力系统功角稳定和装设点电压动态特性的静止无功补偿(SVC)控制器,所得的控制规律与系统运行点和网络结构完全无关。仿真结果表明所提出的非线性变结构SVC控制器能有效地改善系统的动态稳定性。     

基于瞬时无功功率理论和模糊控制的新型SVC控制算法

为满足不平衡三相配电网的无功功率实时补偿的要求,设计了一种新型的FC-TCR型静止无功补偿器(SVC)控制系统。该系统采用瞬时无功功率理论来精确检测基波正序和负序电压、电流,并推导出补偿导纳的表达式;SVC的整体控制采用了开环和闭环控制相结合的控制算法,并在闭环控制算法中,提出了基于智能规则的模糊-PI双模调节技术在无功补偿控制系统中的应用方案。该方案结合了模糊控制和PI控制2种方法的优点,根据系统状况改变PI控制器的参数,以达到更好的动态控制效果。仿真研究结果表明,该新型SVC控制系统对于提高功率因数和补偿三相不平衡,具有响应快、精度高的控制效果。     

An electronic dimming ballast with bifrequency and fuzzy logiccontrol

This paper presents the analysis and design of a series-resonant parallel-loaded inverter applied to electronic dimming ballasts with bifrequency and fuzzy logic control. The analysis of the ballast is carried out in conjunction with the fluorescent lamp represented in a plasma model. The component values of the power stage, as well as two switching frequencies, according to the desired maximum and minimum power levels are, therefore, determined. The power levels in between are controlled by varying the ratio between two time intervals for which the two frequencies last, respectively. This mechanism is achieved by using a fuzzy logic controller (FLC). A ballast prototype with the FLC which is implemented on an 8-bit microprocessor with a reduced instruction set computer architecture has been built. Experimental measurements have shown the feasibility of the ballast with the proposed control strategy     

基于模糊控制补偿的支持向量机逆模型控制

支持向量机(SVM)具有很强的非线性逼近能力与泛化能力,文章研究了基于SVM的非线性系统逆模型辨识,并设计了基于模糊控制补偿的SVM逆控制系统.由SVM辨识的逆模型作为前馈控制器,形成直接逆模型控制器.同时,设计模糊控制器构成反馈补偿控制,克服逆模型的建模误差,提高系统鲁棒稳定性.仿真研究表明,SVM具有优良的逆模型辨识能力,基于模糊控制补偿的支持向量机逆控制系统的动态性能好、跟踪精度高、鲁棒稳定性强.