微电网建模与短路故障特性仿真分析

发布时间：2018-05-19 14:02

本文选题：微网 + 电磁暂态　；参考：《安徽工程大学》2016年硕士论文

【摘要】：在世界各地,传统电力系统正面临着化石能源的枯竭、能源转化效率地下以及生态环境污染的问题。微网是一种将不同的分布式电源、储能装置、负荷联系起来的主动配电网,能够进行孤岛和并网双模式的运行以及相互的切换。微电源大都是一些可再生能源构成,这些可再生能源主要包括天然气、沼气、风力发电、太阳能光伏电池、燃料电池等等。对这些微电源的特性分析是实现控制目标的前提。在微网中,不同的控制策略对微电源的输出有不同的影响,这些控制策略主要包括恒压恒频控制、恒功率控制、下垂控制。本文主要对光伏微电源、蓄电池储能的结构及工作原理进行研究分析,进而对微电源、储能装置进行数学建模,最后构建了微电网模型。本文利用仿真软件分析了微网三相短路故障及不对称短路故障下电压电流变化情况,为微网研究提供了理论上的支持。本文进行了如下方面的工作：首先,本文对光伏微电源及其逆变器模型、储能模型进行了数学建模,进而建立了微网模型。其次,本文依据三相短路故障理论,即系统发生三相短路故障时,采用正序网络图进对三相短路故障电压电流进行计算分析,利用仿真软件对微电源进行三相短路故障研究,仿真结果表明：故障切除后,微电源采取恒压恒频控制,进入孤岛运行时电压突变较大,谐波较多,说明采取恒压恒频策略并不能有效地对电压突变进行抑制；故障切除后恒功率控制的微电源与储能装置继续并网运行时电压突变小,谐波较少,可以发现带上储能装置能够在一定程度上改善电压的突变情况和对电压的谐波抑制能力有所提升。最后,本文基于不对称短路故障理论,即根据不对称短路故障时的边界条件可以得到两相短路,单相接地短路和两相接地短路的复合序网络图,利用复合序网络图对不对称短路故障下的电压电流进行计算分析。利用仿真软件对微电源进行不对称短路故障仿真,由仿真结果可以验证相间短路故障时的短路电流最大,可知相间短路对电网和负荷威胁最高。不对称短路故障的研究为微网电能质量理论研究提供了支持,为微网保护提供了理论依据。
[Abstract]:All over the world, the traditional power system is facing the problems of fossil energy depletion, energy conversion efficiency underground and ecological environment pollution. Microgrid is an active distribution network which connects different distributed power sources, energy storage devices and loads, and can operate and switch with each other in isolated and grid-connected mode. Micro power sources are mostly composed of renewable energy sources, such as natural gas, biogas, wind power, solar photovoltaic cells, fuel cells and so on. The analysis of the characteristics of these micro-power sources is the premise to achieve the control objectives. In microgrid, different control strategies have different effects on the output of micro-power supply. These control strategies mainly include constant voltage and constant frequency control, constant power control and droop control. In this paper, the structure and working principle of photovoltaic micro-power supply and storage battery are studied and analyzed, and then the mathematical model of micro-power supply and energy storage device is established. Finally, the micro-grid model is constructed. In this paper, the variation of voltage and current in microgrid three-phase short-circuit fault and asymmetric short-circuit fault is analyzed by using simulation software, which provides theoretical support for microgrid research. The work of this paper is as follows: firstly, the model of photovoltaic micro-power supply and its inverter and the model of energy storage are modeled by mathematics, and then the model of micro-grid is established. Secondly, according to the theory of three-phase short-circuit fault, that is, when the system occurs three-phase short-circuit fault, the voltage and current of three-phase short-circuit fault are calculated and analyzed by using positive sequence network diagram, and the three-phase short-circuit fault of micro-power supply is studied by simulation software. The simulation results show that the micro-power supply adopts constant voltage and constant frequency control after fault removal, the voltage mutation is larger and the harmonics are more when entering the isolated island, which indicates that the constant voltage and constant frequency strategy can not effectively suppress the voltage mutation. After the fault is removed, the constant power controlled micro-power supply and the energy storage device continue to run in grid-connected operation. The voltage mutation is small and the harmonics are less. It can be found that the energy storage device can improve the voltage mutation and harmonic suppression ability to some extent. Finally, based on the theory of asymmetric short-circuit fault, the complex sequence network diagram of two-phase short-circuit, single-phase grounding short-circuit and two-phase earthing short-circuit can be obtained according to the boundary conditions of asymmetric short-circuit fault. The voltage and current under asymmetric short circuit fault are calculated and analyzed by using compound sequence network diagram. Using the simulation software to simulate the asymmetric short-circuit fault of the micro-power supply, the simulation results can verify that the short-circuit current of the inter-phase short-circuit fault is the largest, and the threat of the inter-phase short-circuit to the power network and load is the highest. The research of asymmetric short circuit fault provides the support for the research of microgrid power quality theory and provides the theoretical basis for microgrid protection.
【学位授予单位】：安徽工程大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM713

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