摘要
目前,随着能源危机的逐渐加剧和环保呼声的日益高涨,一场以能源变革为核心的全球产业竞争大幕已经拉开,探索新能源发电技术迫在眉睫,与之相应的分布式发电技术得到了国家的高度重视和快速发展。分布式电源的发展给传统电网注入活力的同时,也给电力系统提出了新的挑战,传统的配电网潮流计算方法和故障计算方法已经不能满足未来分布式发电系统的需求。为此,本文针对含分布式电源的弱环配电网三相潮流计算和故障计算进行了研究,主要工作如下：
首先,针对配电网三相不平衡比较突出以及线路参数比值R/X比较大的问题,建立了配电网相关元件的三相模型,为配电网的三相潮流计算奠定了基础。
其次,基于前推回代法,推导出了一种计算辐射状配电网络潮流的有效算法。该算法利用配电网络的道路矩阵,推导建立了节点电压与注入电流的关系矩阵,使节点电压和注入电流满足精确的线性关系。在网络结构不变的情况下,该关系矩阵为常数,潮流计算过程清晰简单,便于编程,计算速度快。针对配电网在网络重构和故障恢复计算等实际运行情况下出现的弱环网问题,在所提出的基本潮流算法的基础上,通过利用叠加原理,并结合多端口补偿技术,解决了弱环配电网的潮流计算的问题。
由于分布式电源种类繁多,在进行潮流计算时,不能简单将其全部视为PQ节点。本文根据几种典型分布式电源与电网互联的接口方式及其运行和控制方式,划分了不同的节点类型,提出了各自在潮流计算中的处理方法,其本质是将各类节点转换为传统方法能够处理的PQ节点,进而实现了含多种分布式电源的弱环配电网的潮流计算。
最后,利用对各种故障具有统一形式的故障补偿电路,使配电网的潮流计算在正常和故障两种情况下具有统一的计算公式和迭代步骤,最终将算法完善为能同时处理多种分布式电源、多环网和多故障的潮流故障统一计算方法。同时,采用33节点算例对该算法进行了测试,算例结果证明了本文算法的可行性和有效性。
With the supply of energy sources becomes emergency and more emphasis on the environmental protection, global industrial competition is already and the energy revolution is the core of the competition. Developing smart grid is the inevitable trend of our country and the other countries, so the distributed generation technology attracts great recognition and gets rapid development. The development of distributed generation has brought new advantages to traditional power systems, it has also brought challenges. Traditional distribution power flow will not meet the requirement of distributed generation systems. This paper focuses on load flow and short-circuits current calculation for distribution systems containing DGs. The main works of this paper include as below:
At first, as the three-phase is unbalanced and the line parameter r/X is very large in the distribution system, the traditional methods for power flow calculation are no longer applicable. Three-phase power flow calculation is needed and three-phase model is established.
Secondly, based on the improved backward-forward sweep, an efficient method for calculating the load flow solution of distribution system is presented. In this algorithm, by using path matrix of the distribution network, the incident matrix of node voltages an load injection currents is established based on circuit fundamental laws.Based on network branch equation, according to the weakly meshed structure characteristic of a distribution network, the nodal impedance matrices are calculated directly by line impedance matrices, avoiding constitute the nodal impedance matrices of the networks. The method can be adaptable to network changes in topology.
There are many kinds of distribute generation, all the DG can not only be seen as PQ nodes. Depending on the different characteristics of the DG, four models are presented and their respective features and treatments in the flow calculation were mentioned in details. The essence of the method is to transform all kinds of nodes into PQ node.
At last, By using a uniform compensation, circuit model given for all kind of faults, the algorithm can be applied in both normal and short circuit conditions, and their computation formulas and iteration steps are basically the same. Finally, this paper presents a uniform approach for power flow and fault analysis of asymmetrical three-phase, as well as weakly meshed distribution system with DGs.An example of33-node system is used to test the method proposed. Test result verifies the feasibility of the proposed algorithm.
引文
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