Design of non-negatively interactive FACTS-based stabilizers in multi-machine power systems

In this paper, a method is proposed for the design of a non-negatively interactive FACTS-based stabilizer in a multi-machine power system. It is demonstrated in the paper that the FACTS-based stabilizer can be designed to impose positive interactions upon other stabilizers in the power system through the correct selection of non-negatively interactive installing locations and feedback signals of the FACTS-based stabilizer and the proper setting of the phase angle of the FACTS-based stabilizer. An example power system is presented in the paper, where a TCSC-based stabilizer is designed, which is not only able to damp the target inter-area oscillation mode effectively but also imposes a positive interaction with a PSS in the power system to damp a local oscillation mode.     

基于进化策略的多机系统PSS参数优化

该文提出了一种基于进化策略的多机系统PSS参数优化的新方法。在这种方法中，目标函数设定为度量所有机电振荡模态性能的函数，将PSS的参数优化表示为带不等式约束的非光滑优化问题。进化策略用于该优化问题的求解，从而找出PSS的优化参数。进化策略属现代全局优化方法的一种，它对优化问题本身几乎无任何限制，冈其具有全局寻优能力，故可得到比常规优化方法更好的结果。且进化策略直接采用实型编码，因而可提高优化计算的效率。Anderson 3机系统和New England 10机系统的仿真结果表明，该方法是一种有效的参数优化方法，得到的优化参数对系统运行方式的变化具有良好的鲁棒性。     

基于多目标进化算法的统一潮流控制器稳定控制器鲁棒运行点选择

针对多机电力系统中UPFC稳定控制器鲁棒运行点的选择问题,提出了综合考虑UPFC装置向系统提供阻尼以及受控电力系统本身阻尼两个目标的选择方法,将该问题转化为一个多目标问题,并提出求解该问题的相应多目标进化算法（MOEA）,该算法基于Pareto排序选择方法,采取模糊修正、小生境算子、精英选种策略等技术,具有收敛速度快等优点.最后通过对新英格兰电力系统的仿真分析,验证了多目标进化方法在选取UPFC稳定控制器鲁棒运行点问题上的有效性.     

一种多运行方式下多机系统稳定器设计方法

本文介绍了一种应用非线性规划,同时考虑系统的多种运行方式,将多机电力系统稳定器(PSS)的最佳配置和参数协调问题统一进行求解的方法,并对其目标函数进行了修正.实例结果表明该方法十分有效。     

电网规划综合评判决策系统的设计与应用

提出了一种求解电力系统负荷经济分配问题的改进粒子群优化算法.该算法考虑了机组的爬坡约束、出力限制区约束、非光滑费用函数曲线等非线性特性,用保留可行解的方法处理负荷平衡约束条件,用自适应罚函数法处理爬坡和出力限制区约束条件,加快了算法的收敛速度,对不活动粒子的处理使算法避免了"早熟"现象.仿真计算表明,改进粒子群优化算法是一种求解负荷经济分配问题的有效方法.     

Pole placement technique for PSS and TCSC-based stabilizer design using simulated annealing

A pole placement technique for power system stabilizer (PSS) and thyristor controlled series capacitor (TCSC) based stabilizer using simulated annealing (SA) algorithm is presented in this paper. The proposed approach employs SA optimization technique to PSS (SAPSS) and TCSC-based stabilizer (SACSC) design. The design problem is formulated as an optimization problem where SA is applied to search for the optimal setting of the proposed SAPSS and SACSC parameters. A pole placement-based objective function to shift the dominant eigenvalues to the left in the s-plane is considered. The proposed SAPSS and SACSC have been examined on a weakly connected power system with different disturbances, loading conditions, and system parameter variations. Eigenvalue analysis and nonlinear simulation results show the effectiveness and the robustness of the proposed stabilizers and their ability to provide efficient damping of low frequency oscillations. In addition, the performance of the proposed stabilizers outperforms that of the conventional power system stabilizer (CPSS). It is also observed that the proposed SACSC improves greatly the voltage profile of the system under severe disturbances.     

自适应混沌粒子群算法在PSS设计中的应用

该文采用一种改进的粒子群算法PSO———自适应混沌粒子群算法ACPSO,对多机电力系统稳定器参数进行优化设计,以抑制系统低频振荡。该算法通过混沌初始化粒子群,在迭代计算过程中根据粒子的适应值自适应地调整算法惯性系数,从而可以获得更好的全局搜索能力和收敛速度。选取系统机电振荡模式最小阻尼比最大化为目标函数,将PSS参数优化转换为带不等式约束的非线性优化问题。以3机9节点系统为例,特征值和非线性仿真结果表明,运用该方法设计的PSS能够有效地抑制外界扰动引起的低频振荡。     

免疫算法及其在电力系统无功优化中的应用

提出一种用于电力系统无功优化的免疫算法(Immune Algorithm,IA).该算法是根据生物免疫原理提出的,与遗传算法相比,它具有抗原识别、记忆、抗体的抑制和促进等显著特点.IA将目标函数和约束条件比作抗原,将问题的解比作抗体.通过亲和度的计算来评价抗体并促进或抑制抗体的产生,减小了进化过程陷入局部最优解的可能性;通过抗原记忆,提高了局部搜索能力,加快了计算速度.将IA用于69节点实际电力系统的无功优化计算,并与传统遗传算法的计算结果进行了比较.结果表明IA能够以更快的速度得到最优解,其性能明显优于遗传算法.     

Design of a nonlinear power system stabilizer using synergetic control theory

Electromechanical oscillations of small magnitude and low frequency exist in the interconnected power system and often persist for long periods of time. Power system stabilizers (PSSs) are traditionally used to provide damping torque for the synchronous generators to suppress the oscillations by generating supplementary control signals for the generator excitation system. Numerous techniques have previously been proposed to design PSSs but many of them are synthesized based on a linearized model. This paper presents a nonlinear power system stabilizer based on synergetic control theory. Synergetic synthesis of the PSS is based fully on a simplified nonlinear model of the power system. The dynamic characteristics of the proposed PSS are studied in a typical single-machine infinite-bus power system and compared with the cases with a conventional PSS and without a PSS. Simulation results show the proposed PSS is robust for such nonlinear dynamic system and achieves better performance than the conventional PSS in damping oscillations.     

Location and design of stabilizers in multimachine power systems

A new procedure for the design of decentralized power system stabilizers (PSS) in multimachine power systems (MMPS) is presented in this paper. In the proposed approach, the generators most effective for stabilizer applications are first identified using participation factors and mode controllability matrix. The method determines the parameters of stabilizers by assigning mechanical modes at desired locations. The algorithm uses transfer function matrix between inputs and outputs, to assign the mechanical modes.     

Flexible generator maintenance scheduling based on subjective relaxation of constraints

This paper presents a fuzzy-based method for determining a flexible generator maintenance scheduling by means of subjective relaxation of constraints imposed on the maintenance scheduling problem. The constraints are divided into hard (crisp) constraint set and soft (fuzzy) constraint set according to reflecting conditions which surround power systems. The problem is formulated as a fuzzy mathematical programming problem and solved with the fuzzy branch-and-bound method using Bellman-Zadeh maximizing decision. The proposed approach provides not only a new flexible concept of planning problems in power systems, but also natural expansion of conventional approaches based on crisp set theory. The effectiveness and feasibility of the proposed approach are demonstrated on two typical power system models which consist of 15 generators and 60 generators, respectively.     

一种线路极限传输容量的在线计算方法

提出了一种电力系统在线极限传输容量的计算模型和实用化算法。这一模型基于发电计划和短期负荷预测来定义负荷发电增长方向，全面地考虑了系统在一个预想故障集下的暂态稳定约束、静态稳定约束、电压和支路潮流等静态运行约束。文中采用了一种考虑暂态稳定约束的连续潮流算法来求解，在充分利用连续潮流可以有效地计及静态稳定和安全约束的同时，采用快速时域仿真技术来处理暂态稳定约束。对一个300节点的实际系统和50个故障组成的故障集的应用表明，文中所提模型和算法是有效实用的。     

A knowledge based decision support algorithm for power transmission system vulnerability impact reduction

One of the main reasons for wide area blackouts is cascading failures due to critical contingencies. Since, several factors such as faults, misoperations, environmental effects and sabotage issues are involved; the analysis of such contingencies is a challenging process. Most available methods in literature deal mainly with a certain aspect of the problem. In this study, a more comprehensive methodology using operational and non-operational indices for power system vulnerability analysis is presented. The individual indices are defined for power system’s operational performance, terrorist attack and adverse weather conditions where a fuzzy inference system is used to obtain a single Total Vulnerability Index for each transmission system line. Additionally, a knowledge based decision support algorithm is proposed for the use of TSO’s defense activities in order to determine the weak points and counter measures like load shedding. The modeling approach is tested on IEEE reliability test network with imposed external constraints.     

Interconnected multi-machine powersystem stabilizer design using whaleoptimization algorithm

The role of Power System Stabilizer (PSS) in the power system is to provide necessary damping torque to the system in order to suppress the oscillations caused by a variety of disturbances that occur frequently and maintain the stability of the system. In this paper, a PSS design technique is proposed using Whale Optimization Algorithm (WOA) by considering eigenvalue objective function. Two bench mark multi machine test systems: three- generator nine- bus system, two- area four- generator inter connected system working on various operating conditions are considered as case studies and tested with the proposed technique. Extensive simulation results are obtained and effectiveness of proposed WOA-PSS are compared with well - known PSO and DE based stabilizers under several disturbances.     

A heuristic technique to determine corrective control actions for reactive power flows

This paper presents a sensitivity-based heuristic tool designed to help the system operator in the reactive power flow control problem. The objective of the proposed technique is to determine control actions to ensure that reactive power flows in transmission-subtransmission boundary transformers remain within specified limits, satisfying the new regulatory constraints imposed in most of deregulated markets. With this new constraint the utilities want to guarantee that the utility is able to satisfy its own reactive power requirements, avoiding reactive power flows through long distances in order to reduce the well known disadvantages that reactive power circulation has in the system.A 5-bus tutorial system is used to present the proposed algorithm. The results of the application of the proposed technique to the IEEE 118 buses system and to a regional subtransmission network of the South of Spain are reported and analyzed. In this last actual case, the aim is to maintain reactive power flows in transmission/distribution transformers between those limits set by the Spanish Regulation. A comparison between the proposed tool and a conventional OPF is discussed.     

Transient stability improvement by nonlinear controllers based on tracking

This paper deals with the control problem in multi-machine electric power systems, which represent complex great scale nonlinear systems. Thus, the controller design is a challenging problem. These systems are subjected to different perturbations, such as short circuits, connection and/or disconnection of loads, lines, or generators. Then, the utilization of controllers which guarantee good performance under those perturbations is required in order to provide electrical energy to the loads with admissible stability margins. The proposed controllers are based on a systematic strategy, which calculate nonlinear controllers for generating units in a power plant, both for voltage and velocity regulation. The formulation allows designing controllers in a multi-machine power system without intricate calculations. Results on a power system of the open research indicate the proposition’s suitability. The problem is formulated as a tracking problem. The designed controllers may be implemented in any electric power system.     

多组态电力系统稳定器

本文分析了多组态电力系统稳定器在不同输入信号下的特点,并介绍了其硬件结构、人机接口单元的设计和多组态的软件实现.通过仿真试验结果和现场应用情况,可以证明多组态电力系统稳定器组态灵活、方便,可以满足实验室培训需求,同时可应用于现场,满足多种电力系统稳定方案的实施需求.     

Robust control of electrical power systems using PSSs and Bilinear Matrix Inequalities

This work presents the application of Bilinear Matrix Inequalities to the robust adjustment of Power System Stabilizers with pre-defined structure. Results of some tests show that gain and zeros adjustments are sufficient to guarantee robust stability and performance with respect to various operating points. Making use of the flexible structure of BMIs, we propose an algorithm that guarantees a minimum damping factor specified for the closed loop system, always using a controller with flexible structure. The technique used here is the pole placement, whose objective is to place the poles of the closed loop system in a specific region of the complex plane. The BMIs are linearized using the homotopic method. Results of tests with a nine-machine system are presented and discussed, in order to validate the algorithm proposed.     

Design of decentralized variable structure stabilizers for multimachine power systems

Variable structure (VS) stabilizers possess the advantages of better transient response, insensitivity to plant parameter variations, etc. In general, variable structure controls involve measurements from all the states, which is not possible in a multimachine power system (MMPS). In this paper, the switching planes for the variable structure stabilizers are selected in such a way that computation of switching planes involves local state variables only. The coefficients of the switching plane equation are determined using the Riccati equation approach. Through the approximation of neglecting non-diagonal blocks of the state space matrix, at the design stage, a decentralized Variable Structure stabilizer (VS stabilizer) is obtained. To accept the switching plane so obtained, a check of the closed loop eigenvalues is made with the actual state space matrix. After computation of the switching plane, the variable gains are also selected in such a way that control signal computation involves only local state variables. This is possible as the gains of nonlocal state variables are small compared with local variables. The response of the system with variable structure stabilizers indicates that the system performance is improved.     

基于非线性互补问题函数的半光滑牛顿最优潮流算法

提出了一种新的基于非线性互补问题(NCP)函数的半光滑牛顿方法，以用于求解最优潮流(OPF)问题。通过引入NCP函数，将OPF模型KKT条件的互补松弛约束转化为等式约束，并采用非光滑牛顿法求解。算法的突出优势在于能够有效地处理OPF模型中的不等式约束，从而完全避免了OPF计算中起作用的不等式约束的识别问题。同时，文中利用电力系统的弱耦合特性，构造了牛顿分解算法。IEEE多个算例的数值试验表明：提出的算法具有很好的收敛特性和计算效果，有很好的实际应用前景。