【作者】 陈海焱；

【导师】 段献忠； 陈金富；

【作者基本信息】 华中科技大学 ， 电力系统及其自动化， 2007， 博士

【摘要】 作为集中式发电的补充,分布式发电(Distributed Generation,简称DG)能起到削峰填谷,改善电压水平,减少网络损耗,延缓或减少输配电设备扩建,以及减轻环境污染等作用,近年来在全球范围内引起了人们极大的关注。由于DG自身的一些特殊性,含DG的系统分析方法与传统方法不完全一致,结合DG的特点研究DG并网系统的相关分析方法是当前电力研究领域的热点之一。本文致力于对该领域的关键技术问题进行研究,其内容涉及到DG系统的稳态分析、规划分析、优化分析以及动态分析等方面。在稳态分析方面,本文首先建立了不同类型的DG在潮流计算中的数学模型,提出了包含多种DG的配电网潮流双层迭代算法和灵敏度补偿算法,对两种算法的收敛性能进行了分析和比较,算例测试表明基于灵敏度补偿的算法具有收敛快、对迭代初值不敏感的优点;接着,利用提出的算法分析了DG对配网电压分布的影响,发现不同类型的DG对系统电压支撑能力不一样;然后,在灵敏度补偿算法的基础上,结合配电网电压稳定指标定量地研究了不同类型和不同安装位置的DG对配网静态电压稳定性的影响,得到了若干重要结论。在规划分析方面,根据电压稳定分析的结论提出了一种快速的、启发式的DG选址方法,该方法具有简单实用的特点,对实际电力系统中的DG规划具有较好的参考意义。另外,本文还研究了DG位置和容量的综合规划方法,建立了考虑经济性和安全性的DG多目标规划模型,其中目标函数由DG投资成本最小、系统网损最小和静态电压稳定裕度最大三个子目标构成,由于DG的并网增大了系统的短路电流,为了防止规划方案出现短路电流超标现象,在建立的模型中还考虑了短路电流约束。在求解方法上,引入模糊理论将不同量纲的多目标优化问题转化为单一目标的优化问题。43节点系统的测试结果表明在DG规划模型中计及短路电流约束是必要的,且按本文模型得到的DG规划方案较大地改善了系统的静态电压稳定性,使得系统能在较高的电压稳定水平下承受更大的负荷增长,这对解决规划过程中因负荷的不确定性引起的问题具有较大的意义。在优化分析方面,主要结合DG中发展较为成熟的风力发电技术开展了研究。首先研究了含大型风电场的电力系统多时段动态优化潮流问题。为了考虑风电场风速随机变化的特点,在风速预测的基础上提出了分时段策略,结合异步发电机的无功电压特性,提出了风电系统最优潮流的改进内点算法。IEEE30节点系统的测试结果表明提出的多时段动态优化潮流对风速的随机性和间歇性具有一定的适应性。接着,研究了风电系统的经济调度问题,为了解决风速预测误差较大带来的困难,引入了模糊理论,采用模糊梯形隶属度函数来表示风电场输出功率的不确定性,在此基础上建立了风电系统动态经济调度的模糊模型。在求解方法方面,通过引入下降搜索算子对传统的粒子群优化算法(PSO)进行了改进,算例结果表明提出的改进PSO算法收敛性优于传统PSO算法,在搜索过程中具有跳出局部最优解的潜力。然后,考虑到风速具有统计特征,应用基于概率的场景决策法建立了含风电的配网无功优化模型,结合风电机组输出功率特性提出了风电系统典型场景的选取策略,并采用基于自适应权重的遗传算法来求解提出的问题,算例表明基于场景的无功优化模型在风速随机变化的条件下能够获得期望值意义上的最优方案。最后,设计了若干典型仿真算例,通过这些算例分析了不同类型、不同穿透水平的DG对系统暂态稳定性和小扰动稳定性的影响,得到了一些有价值的结论,可以为工程实际提供参考。更多还原

【Abstract】 As the complementarity of centralized generation, distributed generation (DG) has been widely concerned in the world in recent years because it can be reducing power losses and on-peak operating costs, improving voltage profiles, deferring or eliminating for system upgrades, and mitigating environment pollution. Due to some particularities of DG, analysis methods in power systems with DG are not completely consistent with traditional methods. Therefore, study on analysis methods for power grids connected DG is one of the hotspots in the power engineering research field. This thesis concentrates on studying critical problems in this field, including the steady-state and dynamic stability analysis methods for the systems with DG, optimal planning methods for DG, optimal operation methods under the condition of uncertain DG output.In the aspect of the steady-state analysis for the system with DG, at first the models of various kinds of DGs are developed in power flow calculations, and two algorithms available to calculate the power flow of distribution system with multi-type DGs are presented. One includes a two-layer iterance process, and the other is based on constructing a sensitivity matrix. The convergence characteristics of the two algorithms is compared and analyzed. An example of 90-node system gives an illustration of the feasibility of the presented method. After that, the impacts of DG on voltage profiles of distributed network are analyzed using the presented algorithm based a sensitivity matrix. Then, two main scenarios are investigated to evaluate the impacts of DGs on the system static voltage stability. These impacts are quantified by a voltage stability index introduced in this thesis. Some important conclusions are obtained.In the aspect of the optimal planning for DG, a heuristic method for selecting the sites of DG is presented according to the above obtained conclusions. This method is easy to be applied in practice, which is in favor of the planning engineers to site DGs in distribution systems. In addition, this thesis also studies the integrated planning method for siting and sizing of DG. A multi-objective fuzzy optimal model is proposed that takes into account minimizing the investment cost of DG and the power loss of distribution networks and maximizing the static voltage stability margin. The multi-objective planning is transformed into single objective planning by employing the fuzzy optimization theory. Owing to an increase of short-circuit current level (SCL) due to DG, the maximum SCL limit is taken into account in the constraints. The fault calculation principle in the distribution network with DG is analyzed. As DG has the intermission characteristic, a spinning reserve constraint is included in the model, that is, the distribution substation can supply sufficient power to meet load demands should any DG unit quit. The feasibility of the method proposed is shown by an example of a 43-bus distribution system.Wind power generation is one of DG technologies. Large wind farms connected to power grid bring new challenges to optimal operation of power systems. In this thesis, the optimal power flow (OPF) problems in wind power integrated systems are researched and a multi-period dynamic OPF model is presented. In order to consider the wind speed random behavior, a dividing-stage strategy is developed. Based on the Q-V equation of the induction generator, an improved interior point method for the multi-period dynamic OPF is presented. The effectiveness and computation performance of the proposed method are verified in the IEEE 30-bus system.However, wind speed is difficult to be forecasted accurately. In order to overcome the difficulty, fuzzy theory is applied to represent the random variation of wind power output. The dynamic economic dispatch (DED) problem including wind farms is discussed and a fuzzy modeling for DED is then presented, which could make the dispatch result reflect the willingness of decision-makers and hereby adapt the random wind power output better. Moreover, the conventional particle swarm optimization (PSO) is improved by using the descending search and then adopted to solve the proposed dynamic economic dispatch. The example testing result indicates the feasibility of the proposed method.Reactive power optimization problem in distribution system with wind power generators is also analyzed. A compositive index based on scenario analysis is presented. Power loss and static voltage stability margin are taken into considered in this index. A new model including the index for reactive power optimization is proposed. The strategy for selecting typical scenarios of wind power output is discussed from the view point of probability. A genetic algorithm based on self-adaptive weight is proposed and applied to solve the reactive power optimization problem. The samples show that the proposed method is feasible.Finally, influences of DG on the dynamic stability are discussed in some scenarios. A comparison between the network performance with different sites and different contributions of DG is made. Some important conclusions are obtained, which provides a reference value for the operation of practical system.更多还原