【作者】 马亚辉；

【导师】 李欣然；

【作者基本信息】 湖南大学 ， 电气工程， 2013， 博士

【摘要】 分布式发电以其安装灵活、投资少、清洁高效等优点及其对传统集中式电网性能改善的巨大潜力得以快速发展。分布式电源接入容量的不断增大，使得原本呈放射状的配电网络逐步演变成一种遍布电源和用户互联的网络，配电网潮流将不再由变电站母线单向流向负荷。电网结构及潮流流向的改变将不可避免地影响配电网运行特性和综合负荷特性。原有的综合负荷模型可能已不再能很好地描述该区域的负荷特性。基于此，本文依托国家自然科学基金资助课题“考虑分布式发电的电力系统广义综合负荷建模关键理论与技术研究”，就含分布式电源的配电网综合负荷特性及其模型结构与建模方法展开研究，以期为电力系统仿真计算提供必要的模型支持。本文深入研究了典型分布式电源的运行特性，提出了光伏发电、燃料电池发电、微型燃气轮机发电、风力发电等分布式电源的等效描述模型；在深入分析逆变并网型分布式电源的结构及其等效外特性所具有的共同特点的基础上，提出了逆变型分布式电源的统一等效模型；研究了逆变并网型分布式电源接入容量对传统机理负荷模型描述能力的影响，提出了能够描述逆变型分布式电源高渗透率水平下配电网综合负荷特性的广义综合负荷模型结构；研究了双馈式风力发电系统的功率特性，构建了面向负荷建模的风力发电系统的等效描述模型；基于数值相似度和趋势相似度，提出了一种以数值处理和权重分配为核心的负荷模型准确性评估方法。具体工作如下：构建了典型分布式电源等效模型，包括光伏发电、燃料电池发电、微型燃气轮机发电、直驱式风力发电。在系统研究分布式电源发电原理和运行特性的基础上，基于Matlab/Simulink仿真平台，构建了典型分布式电源的详细数字仿真模型。通过研究其在暂态过程中的动态行为，建立了光伏阵列的受控电流源模型、燃料电池的电压源模型、微型燃气轮机及整流器的受控电流源模型、直驱式风力发电机及整流器的受控电流源模型，进而结合通用的控制策略，建立了上述分布式电源的外特性等效模型，并通过不同故障程度条件下的建模仿真分析，验证了等效模型的有效性。提出了逆变型分布式电源的统一模型。根据分布式电源与电网的连接方式，将功率全部通过逆变器馈入电网的分布式电源统称为逆变型分布式电源，主要包括光伏发电、燃料电池发电、微型燃气轮机发电、直驱式风力发电。通过分析逆变型分布式电源在拓扑结构和控制特性上的相似性，结合其运行特征，提出了逆变型分布式电源的统一模型，并给出模型完整的数学解析及模型参数的辨识策略，并通过不同故障程度条件下的仿真实验，验证了统一模型对各逆变型分布式电源外特性描述的适用性。提出了含逆变型分布式电源的配电网广义综合负荷模型。首先系统分析了逆变型分布式电源接入对传统机理模型在区域配电网综合负荷特性描述能力方面的影响，指出在逆变型分布式电源高渗透率条件下，传统机理负荷模型将不能很好地反映区域配电网综合负荷特性。为准确描述逆变型分布式电源高渗透率条件下区域配电网的综合负荷特性，基于逆变型分布式电源统一模型，提出了考虑逆变型分布式电源影响的配电网广义综合负荷模型结构，并在不同故障程度和不同逆变型分布式电源容量配比条件下，检验了该广义综合负荷模型的有效性。提出了面向负荷建模的双馈式风力发电机的等效描述模型。通过系统分析双馈式风力发电机的稳态运行特性及其在暂态过程中的动态行为，以三阶感应电机模型为基础，结合双馈式风机的转子电压调整机制，构建了双馈式风力发电机的等效描述模型——感应电机并联受控功率源模型。在此基础上，通过在模型的输出方程中引入一阶差分环节，构建了DFIG风电系统的改进等效模型，解决了由于模型降阶带来的暂态特性逼近能力不足的问题，有效地提高了模型对暂态过程的描述能力。提出了一种基于趋势相似度和数值相似度的模型准确性评估方法。首先将数据序列按事态发展进行分段，并依据重视程度对各段分配相应的权重，有效削弱了常规数值评估方法存在的评估结果与序列长度强相关的不利影响。数值相似度评估方法以稳态值为基准值构建数据序列的相对差值序列，避免了由于序列间相对应元素之间差值过大造成的数值相似度为负的错误，并根据层次分析法，确定相对差值序列元素的权重。趋势相似度采用规范变换法，有效降低了序列的幅值、偏移及噪声等因素对趋势相似度评估带来的不良影响。通过基于实测数据和基于仿真数据的模型准确性评估算例，验证了该方法的可行性。更多还原

【Abstract】 Distributed generation (DG) has won a rapid development for its flexible installation, less investment, cleanliness and efficiency as well as its ability to improve the function of traditional centralized grid. Accompanied with the ever increasing generation capacity, the original radial distribution networks have gradually evolved into an interconnected network of users and generations in which load flow is no longer unidirectional from substation bus lines to the load. Unavoidably, the change of grid structure and direction of load flow would have an impact on the operational characteristics of the distribution network and that of the composite load. As a result, the former composite model may fail to offer a suitable depiction of regional load characteristics. Under Such Background, relying on the National Natural Science Foundation project “Critical Theory and Technology of Power System Generalized Composite Load Modeling Considering Distributed Generation”, this paper studies the composite load characteristics of distribution network with DG and its model structure in an effort to provide model to support power system simulation.This paper has carried out in-depth research on the operational characteristics of typical DG, proposed equivalent description models for DGs such as PV, fuel cell, micro-gas turbine generator, etc. With analysis of the similarities among structure and equivalent characteristics of different inverter-based grid-connecting DGs, a unified model for this kind of DG is put forward. This paper also studies the impact of inverter-based DG’s penetration levels on descriptive ability of traditional mechanism model, and proposes a generalized composite load model structure that can represent the distribution network’s composite load characteristics with high penetration of inverter-based DGs. After thoroughly studying the output characteristics of doubly-fed wind generation system, a modeling-oriented equivalent description model of wind generation system is constructed. Then, based on numerical and trend similarity, an assessment method for load model accuracy centered on numerical processing and weight distribution is put forward. Detailed works are as follow:In the first place, equivalent models for typical DGs including PV, fuel cell, micro-gas turbine generator, direct-drive wind generator are constructed. Based on systematic research on DG’s generating principles and operational characteristics, using Matlab/Simulink, specific digital simulation models for typical DGs are established. By studying their dynamic behaviors in transient process, controlled current source model of PV array, voltage source model of fuel cell, controlled current source model of micro-gas turbine generator and its rectifier as well as that of direct-drive wind generator and its rectifier are set up. These models are then combined with general control strategy to construct their external characteristic equivalent models. With simulation and analysis of those models under different fault degrees, their effectiveness is testified.Secondly, a unified model for inverter-based DGs is proposed. From the connection mode between DGs and the grid, it defines the DG which feeds its power through inverter into the grid as inverter-based DG This category includes generation systems of PV, fuel cell, micro-gas turbine generator and direct-drive wind generator. Through analyzing the similarities of inverter-based DG on topological structure and control characteristics, and considering their operational characteristics, a unified model for inverter-based DG has come into being with complete mathematical analysis and identification strategy of model parameters. The unified model’s adaptability to depict the external characteristics of different inverter-based DGs is verified by running numerous simulations under different fault degrees.Then, the generalized composite load model of distribution network considering the impact of inverter-based DG is constructed. After systematic analysis of the impact of inverter-based DG’s penetration on the traditional mechanism model’s descriptive ability over regional composite load characteristics of the distribution network, it is pointed out that the traditional one is incapable to offer a well depiction of composite load characteristics of the distribution network under high penetration of inverter-based DG. Therefore, in a pursuit to conquer this problem, a generalized composite load model of distribution network considering the impact of inverter-based DG is proposed on the basis of the unified model of those DGs. The validity of the proposed model is testified under different fault degrees as well as varied capacity configuration ratios of different inverter-based DGs.Also, an equivalent description model of load modeling-oriented doubly-fed wind generator is built. Through systematic analysis of steady-state operational characteristics of doubly-fed wind generator (DFIG) as well as its dynamic behavior in transient state, its corresponding equivalent description model is constructed based on three-order induction motor model—an induction motor in serial connection with controlled power source. Moreover, an equivalent description model of DFIG wind generation system is proposed, that is, an internal feedback expressed by a first-order difference equation is introduced into the output equation of the model, to solve the problem of inadequate approximation capability resulted from order reduction of the model and strengthen its depiction ability of transient state.Finally, a model accuracy assessment method is proposed based on trend and numerical similarity. The data sequence is divided at the beginning according to its development. Their corresponding weight is distributed according to their importance. By doing so, the negative impact of strong relation between assessment results and sequence length occurred in regular numerical assessment is effectively curbed. Numerical similarity assessment method bases its relative deviation sequence of data sequence on steady-state value, thus avoiding the mistakes of negative numerical similarity due to large gap between corresponding elements of the sequence. Weight of relative deviation sequence’s elements is set in line with analytic hierarchy process. Trend similarity has adopted gauge transformation method to reduce the negative impact of sequence amplitude, deviation as well as noise on trend similarity assessment. By test carried out on examples based on measured and simulation data, the new assessment method is proved to be effective.更多还原