【作者】 瞿寒冰；

【导师】 刘玉田；

【作者基本信息】 山东大学 ， 电力系统及其自动化， 2012， 博士

【摘要】 由于现代社会对电力供应的依存度越来越高,大规模、长时间的停电事故将给社会、经济带来严重的负面影响,合理可行的系统恢复方案能有效加快恢复进程,减少停电损失。作为系统恢复控制的重要优化目标之一,负荷恢复贯穿于整个恢复过程,系统恢复的每一阶段都存在负荷投入的优化问题,负荷的全面快速恢复不仅能减少社会经济损失,而且能加速整个系统的重构过程。在认真学习和借鉴已有研究工作的基础上,本文从单点负荷恢复的基础理论研究入手,深入到实际恢复过程中各阶段负荷投入的优化问题,并详细研究了负荷投入与其他恢复目标的协调控制策略流程,构成了大停电后负荷恢复研究的整体框架。整个研究涉及了模型建立、算法求解、约束校验、策略流程、交互协调控制等多个具体方面的内容,针对负荷恢复问题建立了系统的研究体系和详细的分析方法,完善了系统恢复控制的研究框架。论文的研究工作和创新成果如下：1)针对系统恢复过程中具体变电站的负荷恢复能力进行研究,综合考虑系统频率约束、暂态电压下降约束、冷负荷启动特性和系统潮流等影响因素,建立了确定变电站单次最大负荷恢复量的通用模型。针对负荷投入时的频率跌落问题,提出用经验估算公式和平均系统频率模型进行计算；针对暂态电压下降约束,根据对精度和速度不同的要求,提出了两种校验方法；针对冷负荷启动特性,通过建立考虑温控负荷特性的计算公式来确定故障后实际接入的负荷量。根据实际的恢复进程和系统状态,所建立的通用模型可简化影响因素个数或选择简化的计算方法以提高计算速度。为提高搜索寻优时的收敛速度,提出用一种改进的二分法对模型进行求解。算例仿真验证了所建模型和算法的有效性。2)结合系统恢复前期机组启动过程中的特点,分析了该时期负荷恢复的作用和主要内容,提出了与该时期其他恢复目标相协调的恢复流程；针对平衡机组出力的负荷恢复问题,建立了一种多目标的数学模型,并根据贪心算法的基本思想,提出了一种基于重要性优先的求解算法。线路充电时的负荷恢复问题包括两种不同的情况,针对最优负荷量的确定问题,基于二分法的搜索思想,提出了相应的负荷量优化流程；针对最优负荷点的选择问题,首先确定了负荷点选择的基本原则,在此基础上提出了相应的优化策略。所提出的优化策略和协调流程使得相应的负荷恢复能够与机组启动和相关网架恢复过程安全、有序、协调进行。3)系统恢复后期,随着主力机组的并网和主干网架的形成,需要进行大规模的负荷投入,实际多个负荷点的总体恢复应在满足系统各种等式和不等式约束的前提下,根据各负荷点的大小、位置和重要性分阶段顺序进行的。本文将该问题构建成考虑多负荷点投入顺序的组合优化模型,即在目标函数中引入了负荷投入顺序的影响,并综合考虑了不同顺序下频率、电压、机组出力限值以及稳态潮流等多个约束的满足情况,即从频率约束和电压约束的角度,考虑了先投入负荷对后续负荷投入的影响；结合该阶段负荷恢复的实际特点,提出用一种自适应的粒子群优化算法对模型进行求解,通过分析个体极值的优劣实现优化过程中参数的自适应调整。实际算例验证了所建模型和方法的有效性。4)为实现各恢复操作或优化策略的功能模块化,将恢复控制中的各种问题从不同的层面进行分类；提出将某阶段的整体优化恢复目标分割为多个局部对象,通过局部的恢复控制方法实现对某一个或几个操作的优化,在此基础上提出了大停电后协调恢复控制的系统框架；基于不同的判断标志,对系统恢复状态进行划分和识别,确定不同局部恢复控制优化策略方法的实施时机；根据不同的恢复状态,提出相应的局部恢复控制策略,包括机组恢复策略、网架恢复策略、负荷恢复策略、并列合环恢复策略以及直流恢复策略等,并结合已有的协调恢复控制框架提出了各策略具体的实施流程。在时间和空间维度上实现了交互式的并行协调恢复控制,提高了恢复控制优化方案的实用性和可操作性,能有效应对电网各种突发性大停电事故。更多还原

【Abstract】 As modern society is dependent on the power supply excessively, the widespread blackout has a serious negative effect to the social economy. In order to speed up the restoration process and reduce outage cost, proper scheme for system restoration should be determined in a reasonable way. As one of the optimization objectives in system restoration, load pickup should be focused on which exists in each stage of restorion process. The effective load reatoration is in favor of the unit start-up and network reconfiguration. Based on current researches, a detail study on load restoration has been carried out in this dissertation, which includes maximizing the restorable load amount for specific substation, load pickup optimization for different stages in practical restoration, coordination strategies for multi objectives and etc. The whole research refers to many specific aspects, such as mathematical model, sovling algorithms, checking constraints, restoration strategies and coordinative control. The dissertation presents a fully study on load restoration, which perfects the whole framework for power system restoration. Main contributions and innovations are described as following:1) During power system restoration, the maximum load amount that a substation can pick up at one time is a critical parameter to be determined. Many factors should be considered, such as frequency constraint, transient voltage-dip constraint, cold load pickup and steady-state voltage constraint. A general model is proposed for calculating the maximum restorable load amount, in which proper checking methods are presented to deal with these constraints. Frequency deviation is calculated by the average system frequency model or an estimation formula. The transient voltage-dip constraint can be dealt with by two checking methods according to different requirements of calculation speed and precision.Cold load pickup characteristics are addressed using derived formulas. The proposed model is adaptive to various scenarios and can speedup computations by neglecting unnecessary simulation. A modified bisection algorithm is proposed to solve the complex problem efficiently. The effectiveness is demonstrated by case studies performed on the IEEE14-bus system and a practical power system.2) After a major blackout, the primary units of system should be restarted first. In this process, it is necessary to pick up reasonable loads to keep system stability and improve restoration efficiency. According to characteristics of this stage, this dissertation presents detailed contents of load restoration and related restoration strategies, which are coordinated with unit start-up. For load restoration of stabilizing generators, a multi-objective model is established. According to the principle of greedy algorithm, a method based on load priority is proposed to solve the problem efficiently. For load restoration during energizing high voltage line, two different situations are discussed. The optimization strategy based on bisection algorithm is described for determining reasonable load amount and a basic principle is given for choosing different load feeders. The effectiveness is demonstrated by case studies performed on the IEEE9-bus system and a practical black-start test system.3) During last stage of network reconfiguration after major blackout, loads should be picked up in sequence with considering certain constraints, which is a multi-constraint, non-linearity, integer programming problem. A combinatorial optimization model is proposed with considering the sequencing problem of load pickup, in which effects of pickup sequence are taken into consideration in both objective function and constraints. As the large optimization scale of restorable loads during last stage of network reconfiguration, a new adaptive particle swarm optimization algorithm is adopted to solve the proposed model. The adaptive strategy of parameters is carried out by comparing individual optimum in iterative process. Case studies performed on the actual Shandong power system demonstrate that the proposed model effectively reflects sequencing problem and the adopted algorithm can satisfy the practical requirement on computation speed.4) In order to achieve independent modules for different restoration actions or strategies, issues during system restoration are classified from different aspects. The whole optimization goal in certain stage is divided into many local objectives, in which one or several operation actions can be optimized by local restoration strategies. And a cooperation framework for system restoration is established in an interactive way. According to specific criterion, different system restoration states are defined with employing the corresponding local restoration strategies, which include unit start-up, network reconfiguration, load restoration, paralleling operation, DC restoration and etc. The implementation flow corresponding to specific local restoration strategy is also given in the proposed cooperation framework. From the perspective of both space and time dimensions, the present strategy can be carried out in a parallel processing way, which improves the availability and feasibility of restoration schemes. Case studies demonstrate that the proposed framework and strategies can deal with different emergency blackouts effectively.更多还原