Studies On Reliability Algorithm Of Distribution Network Considering Distribution Generation

With the continuous development of economy and society of our country, the demand on power quality is further more. Distribution system is the tip of power system and connects to the consumers. More and more attention and regard are paid to the reliability of distribution system, which is one of the key factors of power quality. At the same time along with the development of power technology, distributed generation (DG) has been connected to power system widely, which led to rapid increase of DG application in distribution systems. DG which improves the reliability of the system also brings new problems for reliability analysis, so it is important to study the impact of DG on the reliability of distribution networks.Currently the study of the reliability of distribution system has been relatively mature, but DG makes the calculation of reliability changes. Reliability assessment results will defer greatly due to the variation of DGs' interconnection position, interconnection way and operation manner. Island is a new kind of operation mode when the distribution network is incorporated with DG. Intentional islanding can reduce outage area and improve the power supply reliability. Islanding is the primary job for calculating the reliability of distribution system including DG. At first, several factors affecting the distribution reliability results are analyzed; three kinds of DG models are discussed. And then, the principle and mathematical model of an islanding algorithm is given while the fault occurs in distribution network with distributed generations, and the process of islanding is introduced.With a large number of DG interconnects to distribution system, distribution network becomes a network with a lot of power from a radial network, and the model and method of reliability analysis is changed. Due to the randomness of DC output and fluctuation of load, it is hard to establish the reliability evaluation model. Existing methods can't solve this problem, however, Monte Carlo method with high accuracy takes a long time for simulation.A new analysis algorithm based on "time section" is presented for calculating reliability index of distribution network with DG. The algorithm uses connection matrix expression structure change of the distribution system accessing DG. The load of the year is divided into different period of time according to the load duration curve and DG output under different probability. The reliability data of these periods are calculated respectively, and added to each other. Then we can get the reliability index of the load. The algorithm considering load and DG output changing over time in the process of calculating, could calculate reliability index of distribution network accurately. Compared with the Monte-Carlo simulation method, the algorithm based on "time section" is correct and effective. Practical example proves that the distributed generation can improve the reliability index of distribution network and improve quality of energy of abundant.