逆变型DG和异步DG对配电网过流保护的影响及应对策略

发布时间：2018-09-14 09:38

【摘要】：分布式发电在凭借其独特的经济和环境效益得到快速发展的同时,给配电网的运行带来了很大挑战,其中配电网保护问题尤为严重。随着分布式发电在配电网中渗透率显著增长,为维持电力系统的稳定,要求分布式发电具备低电压穿越能力,使得保护问题成为分布式发电接入下的配电网永远都回避不了的难题。而目前配电网一般配备三段式电流保护,因此深入研究分布式发电对配电网电流保护的影响及应对策略具有十分重要的意义。本文基于分布式发电对配电网保护的影响主要取决于其自身容量及其与配电网连接的电气接口的原理,将分布式发电类型分为逆变型DG、异步DG、同步DG、永磁同步DG,并研究了逆变型DG和异步DG在低电压穿越中输出电流特点及其对配电网电流保护的影响,通过对DG自身的调整来限制其故障电流以减小甚至避免其对配电网保护的不利影响。逆变型DG输出电流主要跟其控制策略有关。本文在逆变器模型研究现状的基础上提出一种广泛被认可的建模方式,从数学模型、低电压穿越策略、限流保护控制等出发,选取合理的仿真模型参数,搭建逆变型DG模型,观察其在电网故障期间输出电流的变化,据此提出了基于并网点电压实时动态调整逆变器限流保护参考电流的应对策略。理论计算和仿真实验验证了该方案的有效性。异步DG分为单馈异步DG、双馈异步DG。首先从理论计算和仿真结果两方面分析了单馈异步DG在电网故障期间输出电流的变化,基于转子的时间常数与转子外电阻有关的原理,提出了修改单馈异步DG转子外电阻的应对策略。然后在单馈异步DG的基础上理论分析了双馈异步DG的撬棒电阻和输出电流,理论计算和仿真实验验证了双馈异步DG对配电网电流保护没有影响。本文所提应对策略所依据的理论原理清晰,物理概念明确,为分布式发电接入下的配电网保护问题的解决提供了一种可行的方案。
[Abstract]:With the rapid development of its unique economic and environmental benefits, distributed generation has brought great challenges to the operation of distribution network, in which the distribution network protection problem is especially serious. With the increase of the permeability of distributed generation in distribution network, in order to maintain the stability of power system, distributed generation is required to have low voltage traversing capability. The protection problem has become a difficult problem for the distribution network under the distributed generation access. At present, the distribution network is generally equipped with three-segment current protection, so it is of great significance to study the impact of distributed generation on the distribution network current protection and countermeasures. In this paper, the influence of distributed generation on distribution network protection mainly depends on its own capacity and the principle of the electrical interface connected to the distribution network. The distributed generation type is divided into inverter DG, asynchronous DG, synchronous DG, permanent magnet synchronous DG, and the characteristics of output current of inverter DG and asynchronous DG in low voltage traversing and their influence on distribution network current protection are studied. The fault current of DG is limited by adjusting itself to reduce or even avoid its adverse effect on distribution network protection. The output current of inverter DG is mainly related to its control strategy. Based on the research status of inverter model, a widely accepted modeling method is proposed in this paper. Starting from mathematical model, low voltage traversing strategy, current limiting protection control and so on, reasonable simulation model parameters are selected to build inverter DG model. Based on the observation of the variation of the output current during the fault of the power network, a strategy to dynamically adjust the reference current of the inverter current limiting protection based on the parallel dot voltage is put forward. The effectiveness of the proposed scheme is verified by theoretical calculation and simulation experiments. Asynchronous DG is divided into single feed asynchronous DG, doubly-fed asynchronous DG. Firstly, the variation of output current of single-fed asynchronous DG during power network fault is analyzed from two aspects of theoretical calculation and simulation results, based on the principle that rotor time constant is related to rotor external resistance. A strategy for modifying the external resistance of a single feed asynchronous DG rotor is proposed. Then, based on the single-fed asynchronous DG, the crowbar resistance and output current of doubly-fed asynchronous DG are analyzed theoretically. The theoretical calculation and simulation results show that the doubly-fed asynchronous DG has no effect on the current protection of distribution network. The proposed strategy is based on a clear theory and clear physical concept, which provides a feasible solution to the distribution network protection problem under distributed generation access.
【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】：TM61;TM773

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