基于马尔柯夫模型的微网可靠性评估

发布时间：2018-06-06 13:24

本文选题：分布式电源 + 微网　；参考：《山东大学》2017年硕士论文

【摘要】：随着全球能源危机和环境问题的日渐突出,加之用户对供电可靠性要求的日益提高,可再生能源的开发和利用受到了世界各国越来越多的关注。微网作为一个单一可控单元,能够有效就地吸纳分布式电源出力,减少损耗,提高用户供电可靠性和缓解能源危机与环境污染压力。然而,微网的接入从根本上改变了传统配电网的单电源辐射状结构。另外,微网中的分布式电源多为风电、光伏发电等可再生能源发电,具有较强的随机性和波动性。传统配电网可靠性评估模型、方法和可靠性指标都难以适应新形势下的电网结构。本文针对以上问题,对含微网的配电网可靠性评估相关问题展开了研究。本文以国内外微网研究现状和现阶段微网可靠性研究中存在的问题为出发点展开研究。首先概述了微网的定义和结构,并分析了其运行特点。为全面分析含微网的配电网可靠性评估,文中对比分析了常用的可靠性评估方法,并最终选择最小路法来评估本文微网算例。文章的重点分为两部分,一部分是分布式电源建模,另一部分是微网可靠性分析。分别概括如下:(1)本文提出了基于改进的马尔柯夫链建立分布式电源的方法。文中仅考虑了风电、光伏和储能系统三种分布式电源。储能系统仅考虑充放电约束和能量约束。风电和光伏的建模思路如下:直接利用风电、光伏出力历史数据,基于一阶马尔柯夫链,综合考虑分布式电源出力的日特性、季节特性以及天气特性,统计得出多个转移矩阵,再根据气候特性以及时间属性来选择转移矩阵,最终生成各时刻的状态量。本文的建模方法,省去了风速和太阳辐照度建模以及能量转化过程,无需进行繁杂的2次或多次建模,使得风电、光伏出力模型更加准确和简洁。(2)解析法适用于结构简单的小型电力系统的可靠性评估。本文研究的微网结构简单,采用最小路法进行可靠性评估。另外,传统的配电系统可靠性指标不能直观地评估微网对整个配电网可靠性的贡献,本文提出了平均断电频率降低系数MSAIFI、平均运行可用率提升系数MASAI和电量不足期望降低系数MEENS这3个新的微网评估指标。文中对分布式电源不同接入容量和不同接入位置对微网内负荷和整个配电网的可靠性影响进行了分析,并以改进的IEEE RBTS Bus6测试系统进行了算例分析,从可靠性评估结果可以得到的结论有:①微网能够有效提高其内部负荷和整个配电系统的可靠性;②随着微网容量的增加,其内部负荷和整个配电系统可靠性都不断增加,但是增加的趋势越来越平缓;③微网接入位置对其内部负荷的可靠性影响比较明显,靠近分布式电源的负荷可靠性要明显高于距离分布式电源较远的同等级负荷。最后,通过算例验证了本文所提出的新评估指标能够更加直观准确地评估微网对配电系统可靠性的贡献,能够更加科学地指导微网的规划和建设。
[Abstract]:With the global energy crisis and environmental problems increasingly prominent, coupled with the increasing demand for the reliability of power supply, the development and utilization of renewable energy has been paid more and more attention in the world. As a single controllable unit, microgrid can effectively absorb the distributed power supply, reduce the loss, improve the reliability of power supply and alleviate the energy crisis and environmental pollution pressure. However, the access of microgrid fundamentally changes the single source radiation structure of traditional distribution network. In addition, most of the distributed power sources in the microgrid are wind power, photovoltaic power generation and other renewable energy generation, which has strong randomness and volatility. The traditional distribution network reliability evaluation model, method and reliability index are difficult to adapt to the new situation of power network structure. In order to solve the above problems, this paper studies the reliability evaluation of distribution network with microgrid. In this paper, the current situation of microgrid research at home and abroad and the existing problems in the research of microgrid reliability are taken as the starting point. Firstly, the definition and structure of microgrid are summarized, and its operation characteristics are analyzed. In order to analyze the reliability evaluation of distribution network with microgrid, this paper compares and analyzes the commonly used reliability evaluation methods, and finally selects the minimal path method to evaluate the microgrid in this paper. This paper is divided into two parts, one is modeling of distributed power supply, the other is reliability analysis of microgrid. In this paper, a method of building distributed power based on improved Markov chain is presented. Only wind power, photovoltaic and energy storage systems are considered in this paper. Only charge and discharge constraints and energy constraints are considered in the energy storage system. The modeling ideas of wind power and photovoltaic are as follows: based on the historical data of wind power and photovoltaic power generation, based on first-order Markov chain, the daily, seasonal and weather characteristics of distributed power generation are comprehensively considered, and several transfer matrices are statistically obtained. Then the transition matrix is selected according to the climate characteristic and the time attribute, and the state quantity of each time is generated finally. The modeling method in this paper eliminates the modeling of wind speed and solar irradiance and the process of energy conversion. The photovoltaic output model is more accurate and succinct. The analytical method is suitable for the reliability evaluation of small power systems with simple structure. The structure of the microgrid studied in this paper is simple, and the reliability evaluation is carried out by using the minimal path method. In addition, the traditional reliability index of distribution system can not directly evaluate the contribution of microgrid to the reliability of the whole distribution network. In this paper, three new evaluation indexes of microgrid, such as average power cut frequency reduction coefficient (MSAIFI), average operational availability coefficient (MASAI), and electricity shortage expected reduction coefficient (MEENS), are proposed. In this paper, the influence of different access capacity and different access location of distributed generation on the internal load of microgrid and the reliability of the whole distribution network is analyzed, and the example of the improved IEEE RBTS Bus6 test system is given. From the results of reliability evaluation, it can be concluded that: 1 microgrid can effectively increase its internal load and the reliability of the entire distribution system with the increase of the capacity of the microgrid, the internal load and the reliability of the entire distribution system increase continuously. However, the increasing trend is more and more gentle, and the influence of the access position of the microgrid on the reliability of the internal load is obvious. The load reliability near the distributed power supply is obviously higher than that of the same class load which is far away from the distributed power supply. Finally, an example is given to verify that the new evaluation index proposed in this paper can more directly and accurately evaluate the contribution of microgrid to the reliability of distribution system, and can guide the planning and construction of microgrid more scientifically.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM727

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