Sectionalizing strategies for minimizing outage durations of critical loads in parallel power system restoration with bi-level programming

Fast restoration of critical loads and non-black-start generators can significantly reduce the economic losses caused by power system blackouts. In a parallel power system restoration scenario, the sectionalization of restoration subsystems plays a very important role in determining the pickup of critical loads before synchronization. Most existing research mainly focuses on the startup of non-black-start generators. The restoration of critical loads, especially the loads with cold load characteristics, has not yet been addressed in optimizing the subsystem divisions. As a result, sectionalized restoration subsystems cannot achieve the best coordination between the pickup of loads and the ramping of generators. In order to generate sectionalizing strategies considering the pickup of critical loads in parallel power system restoration scenarios, an optimization model considering power system constraints, the characteristics of the cold load pickup and the features of generator startup is proposed in this paper. A bi-level programming approach is employed to solve the proposed sectionalizing model. In the upper level the optimal sectionalizing problem for the restoration subsystems is addressed, while in the lower level the objective is to minimize the outage durations of critical loads. The proposed sectionalizing model has been validated by the New-England 39-bus system and the IEEE 118-bus system. Further comparisons with some existing methods are carried out as well.     

计及冷负荷效应时变特性的含风储联合系统负荷恢复策略

随着风电大规模接入电力系统,风电与储能结合构成的风储联合系统成为提高风电消纳能力的重要措施之一。在电力系统恢复阶段,如何构建合理的风储联合系统调度策略以加快系统恢复速度成为当前的研究热点。为此,提出了一种计及冷负荷效应时变特性的含风储联合系统负荷恢复策略。介绍了输电系统恢复后期的负荷恢复优化方案;提出了考虑冷负荷效应时变特性和风储联合系统运行约束的输电系统负荷恢复模型,将冷负荷效应描述为关于停电时间的函数,并在风储联合系统的运行约束中考虑了储能系统的寿命约束。为了提高模型的求解效率,提出了基于Benders分解的求解框架,所构建的主问题模型和子问题模型均为混合整数线性规划模型,可调用商业求解器进行高效求解。以IEEE 39节点系统为算例验证了所提模型和方法的有效性。     

Power system restoration by joint usage of expert system and mathematical programming approach

When electric power supply interruption is caused by a fault, it is imperative to restore the power system promptly to an optimal target configuration after the fault. The problem of obtaining a target system is referred to as power system restoration. Both mathematical programming (MP) and expert systems (ES) have been used to solve restoration problems. However, existing approaches based on either MP and ES alone have inherent limitations stemming from their own paradigms. Mathematical progressing can obtain an optimal configuration under specified operational constraints, but requires a relatively long solution time. Although ES are effective in that they can utilize expert knowledge, maintenance of large-scale ES requires inordinate effort. This paper proposes a new approach to power system restoration that utilizes both methodologies so as to exploit both systems' advantages. That is, a system under study is decomposed into a set of subsystems based on the knowledge of restoration experts, which is realized as an expert system. Then, MP is applied to each decomposed subsystem to obtain an optimal target configuration. A feasible operation sequence leading to the target configuration is generated by ES. This approach reduces significantly the computation time required to obtain target systems and is far less than would be the case if the total system is solved (as a unity). Moreover, the number of rules in the knowledge-base are greatly decreased.     

基于IGDT的网架重构过程中风电场出力调度

风电具有启动功率小、启动速度快等特点,在停电系统恢复过程中利用风电为其提供功率支持,可以加快系统负荷的恢复。由于风电出力的不确定性,需要对风电场出力进行调度,减小风电场出力的波动范围,在保证已恢复系统安全的前提下提高风电的利用效率。为此,文中提出了一种基于信息间隙决策理论(IGDT)的风电场出力调度方法。首先建立不考虑风电出力不确定性时的风电场出力参考值确定性模型,然后基于IGDT方法将确定性优化模型转变为考虑风电不确定性的风电场出力调度优化模型,再利用人工蜂群算法对优化模型进行求解,最后以IEEE 39节点系统和江苏实际系统为例验证了文中方法的有效性。     

A heuristic method for feeder reconfiguration and service restoration in distribution networks

A sequential switch opening method is proposed for minimum loss feeder reconfiguration in this paper. The algorithm is further extended for service restoration. The method is based on the branch power flow rather than the current flow as reported in earlier methods. The final algorithm arrives at opening of a branch in a loop carrying minimum resistive power flow to make the network radial causing minimum loss. The test results reveal that the proposed method yields optimal configuration with reduced computation burden and better restoration plan.     

Linking energy policy,electricity generation and transmission using strong sustainability and co-optimization

The design of a sustainable electricity generation and transmission system is based on the established science of anthropogenic climate change and the realization that depending on imported fossil-fuels is becoming a measure of energy insecurity of supply. A model is proposed which integrates generation fuel mix composition, assignment of plants and optimized power flow, using Portugal as a case study. The result of this co-optimized approach is an overall set of generator types/fuels which increases the diversity of Portuguese electricity supply, lowers its dependency on imported fuels by 21.30% and moves the country towards meeting its regional and international obligations of 31% energy from renewables by 2020 and a 27% reduction in greenhouse gas emissions by 2012, respectively. The quantity and composition of power generation at each bus is specified, with particular focus on quantifying the amount of distributed generation. Based on other works, the resultant, overall distributed capacity penetration of 11.88% of total installed generation is expected to yield positive network benefits. Thus, the model demonstrates that national energy policy and technical deployment can be linked through sustainability and, moreover, that the respective goals may be mutually achieved via holistic, integrated design.     

基于电网分区的负荷恢复智能优化策略

针对电力系统大停电后的负荷快速恢复问题,提出了一种基于电网分区的负荷恢复智能优化策略。提出了一种大停电事故后系统恢复的最优分区策略,并在所建立的优化模型中考虑了为恢复发电机而引入的架空线路充电无功以及为恢复负荷所引入的线路合闸操作次数等影响因素。在完成对大规模系统优化分区后,对各分区建立了一个统一的并计及网络重构因素的负荷恢复优化模型,实现各分区负荷的并行恢复。针对上述所提出的优化模型,通过结合传统图论理论和遗传算法,实现基于电网分区的负荷恢复优化问题的求解。解算中,对遗传算法进行了改进,并针对应用遗传算法时所产生的大量不可行解问题,提出了随机甩负荷和最短路径修补策略的处理方法,进一步提高了算法的寻优效率和全局优化能力。以IEEE30节点系统为算例进行仿真分析,验证了所提模型与方法的正确性和有效性。     

Development of restoration system based on human performance model

A stable power supply is required from power systems as the importance of electrical energy increases. Particularly, in the case of high-voltage systems (500-, 275-, 154-kV bulk power systems), this requirement is high. However, there are cases when power system faults cannot be avoided. Accordingly, it is very important to restore power systems quickly and safely if these failures occur. The characteristics of the power system restoration (its combinatorial aspects, use of knowledge from a wide variety of origins and of different types, number of criteria to satisfy) make it a difficult problem, for which the use of expert systems to generate restoration plans is being considered by many researchers, and promising results have already been obtained. However, most systems are still in the prototype stage [1]. One reason seems to be the lack of studies of a support system for knowledge-based behavior (unable to describe with any rule). This paper analyzes first power system restoration based on the human performance model [6] and discusses the knowledge-based behavior that is a high conceptual level of human performance to solve the problem from the combinatorial viewpoint. Then the application for the trunk line dispatching center is reported. Finally, the relations between knowledge-based behavior and the designed human interfaces are verified with a power networks restoration case-study.     

Data acquisition,power forecasting and coordinated dispatch of power systems with distributed PV power generation

The integration of photovoltaic (PV) power generation with highly random and intermittent characteristics has posed significant challenges to the safe and economic operations of power systems. This paper establishes an entire operation structure covering PV data acquisition, PV power forecasting, and coordinated dispatch of power systems with large-scale behind-the-meter distributed PV units. The PV data acquisition method provides training data for the power forecasting model, and then the forecasting results serve as the references for developing coordinated dispatch strategies. Real-world systems and numerical studies validate the effectiveness and superiority of the proposed operation structure.     

独立电力系统故障恢复现状及发展趋势

从独立电力系统与陆地互联电力系统的区别出发,较为全面地分析了独立电力系统的特点,综述了系统的计算方法,指出目前还没有对供配电网络统一考虑的快速、有效的计算方法。总结了故障恢复的数学模型,将其归类为多约束、非线性的组合优化问题,归纳了上述数学模型的各种解算方法,这些方法主要集中在启发式优化方法、传统的数学优化方法、现代随机优化方法及一些混合算法,分析了各种方法的优缺点。在此基础上提出了今后独立电力系统故障恢复研究的方向。     

Petri Nets算法在电力系统恢复中的应用

通过对电力系统恢复的不同恢复策略、方法和恢复阶段的研究，发现恢复过程中存在一系列的“普遍恢复动作”，而将这一系列的普遍恢复动作组织起来即可形成恢复方案。提出应用Peter Nets算法组织电力系统恢复过程中的普遍恢复动作。Peter Nets算法对系统恢复时各电力元件状态和恢复操作进行建模，可以在时域上直接仿真系统恢复的全过程。该算法考虑了不同恢复阶段的目标、每个操作措施的估计时间和操作员的经验，具有灵活的冲突处理机制和并行处理特性，形成的恢复方案准确而直观。对给定的一个电网算例进行了仿真计算。     

水电站黑启动方案及分析

黑启动是在电网发生大范围停电事故、电网崩溃瓦解的情况下迅速恢复供电的重要手段.本文介绍了南川鱼跳水电站黑启动方案,分析了成功黑启动的条件,并提出了水电站黑启动中存在的一些问题.     

面向恢复过程的环网并列合闸角两步调控方法

基于投入负荷和增加发电机有功出力之间的相互牵制关系,提出了一种面向恢复过程的环网并列合闸角两步调控方法。根据重要性和对减小合闸角的灵敏度确定负荷的恢复顺序,通过非线性规划求解得到与投入负荷相对应的有功发电增加量。两步调控策略能详细描述以投入负荷和增加发电机有功出力为控制变量的合闸角调控过程。在快速完成调控目标的同时,恢复了部分重要负荷,提高了系统恢复效率,加快了恢复进程,减小了停电损失。山东电网临沂—日照分区子系统的仿真结果表明,该方法能够得到与分支定界算法基本一致的调控策略,参与调整的发电机数量少,出力调整量小,可为系统运行人员提供面向恢复过程的决策支持。     

An investigation about the impact of the optimal reactive power dispatch solved by DE

With the advent of new technology based on power electronics, power systems may attain better voltage profile. This implies the proposition of careful strategies to dispatch reactive power in order to take advantage of all reactive sources, depending on size, location, and availability. This paper proposes an optimal reactive power dispatch strategy taking care of the steady state voltage stability implications. Two power systems of the open publications are studied. Power flow analysis has been carried out, which are the initial conditions for Transient Stability (TS), Small Disturbance (SD), and Continuation Power Flow (CPF) studies. Steady state voltage stability analysis is used to verify the impact of the optimization strategy. To demonstrate the proposal, PV curves, eigenvalue analyses, and time domain simulations, are utilized.     

Use of HVDC links for power system restoration

Power system restoration plans worldwide have often been based on black start units capable of supplying cranking power to bulk generation plants. The increase in the number and size of CCGT plants and other forms of generation with low regulating capacity and requiring a restless growing power for the cranking phase needs that new strategies and tools be developed for facing the unlucky event of a black-out. The study presents the possibility of using HVDC links with a synchronous compensator at the receiving end. Such systems have high regulating capacity and reliability which are precious characteristics during the critical phases of the restoration. A detailed stability analysis is developed for checking the correct size of the compensator. Electromagnetic simulations prove the validity of the solution.     

西电东送交流断面功率波动空间的分析及建议

为了确定南方电网西电东送交流断面功率波动预留空间的合理值,统计和分析了历年来西电东送主要交流断面功率波动及其裕度数据。结果显示：西电东送交流断面功率波动呈上升趋势;波动裕度应根据电网发展及西电的送电水平进行动态调整;进一步优化电网频率质量、减小正常情况下的频率波动幅值有助于降低交流联络线功率偏差。目前交流断面预留的波动空间是必要且合理的,但有需要开展深入的研究,规范预留波动空间值的计算和管理。     

Expert system for dispatch control in restoration of ehv power system after complete blackout

Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.     

专家系统在电力系统结构恢复中的应用

电力系统的恢复是一个多变量、多目标、多步骤、非线性的优化问题，以往预先大量的潮流和稳定计算而制定的系统恢复计划很难跟上系统的变化。而依靠智能性的专家系统在很大程度上可以解决这个难题。为了提高专家系统的搜索效率，在使用传统的深度优先搜索策略的基础上，结合启发式算法、关键路径算法，以及Petri网，Tabu search等优化算法短时间内给出一个最合适的方案。该专家系统由人工智能语言AMZI Prolog和C 混合编程实现，既考虑到传统智能语言的优越性，又兼顾到使用流行的面向对象语言实现友好的人机接口。     

Chaos embedded krill herd algorithm for optimal VAR dispatch problem of power system

Chaotic krill herd algorithm (KHA) (CKHA) is proposed in this paper to solve the optimal VAR dispatch problem of power system considering either minimization of real power loss or that of absolute value of total voltage deviation or improvements of voltage profile as an objective while satisfying all the equality and the inequality constraints of the power system network. Detailed studies of different chaotic maps are illustrated. Among these, Logistic map is considered in the proposed technique to improve the performance of the basic KHA. The performance of the proposed CKHA is implemented, successfully, on standard IEEE 14- and IEEE 118-bus test power systems in which the control of bus voltages, tap position of transformers and reactive power sources are involved. The results offered by the proposed CKHA are compared to other evolutionary optimization based techniques surfaced in the recent state-of-the-art literature. Simulation results indicate that the proposed CKHA approach yields better optimization efficacy over some other recent popular techniques in terms of results offered, effectiveness, quality of solution and convergence speed.     

大停电后含分布式电源的电网分区及负荷恢复方案

含有分布式电源(Distributed Generation,DG)的电网在发生大停电事故后,为提高系统恢复效率,一般将电网进行合理分区,并采用分区并行恢复的方案。首先运用灰色决策理论选取了各分区的黑启动电源,结合最短路径快速算法(Shortest Path Faster Algorithm,SPFA)搜索各黑启动电源到待恢复节点的最优恢复路径;然后据此建立了兼顾恢复时间性和安全性的最优分区多目标优化模型,并采用多目标粒子群优化算法(Multi-objective Particle Swarm Optimization,MOPSO)对模型进行了求解。基于所得的最优分区方案,以构建初步网架为目标,结合遗传算法对各分区内的负荷恢复问题进行了优化。IEEE 30节点算例验证了所提方案的有效性。