Research Of Related Problem For Disconnection Criteria And The Selection Of Disconnection Point In Micro Source Intensively Connected Area

The world is facing increasing energy and environmental pollution. Micro source generation is clean and environmentally friendly, large-scale use of micro source can reduce the air pollution and the use of fossil fuels compared with traditional power plant, which makes the micro source popular over the world. The micro source supply has the advantages of short construction period, flexible installation location, high reliability and high energy utilization rate. Micro grid as an effective carrier of micro source, can take full advantages of micro power, improve the power quality and reliability of the demand side. When the fault occurs in power distribution system or the power quality can not meet the needs of users, the condition of the micro-grid and the distribution network split islanding. Therefore, it is important to study the distribution network with micro source supply. The main contents of this paper are as follows:(1)The composition and characteristics of the micro grid are introduced, and the typical micro power supply is described as following:photovoltaic power generation, wind turbine, fuel cell and micro gas turbine. In the view of the power quality of distribution network, the safety and reliability of the system operation and the protection of the system, the influence of micro source supply on the distribution network is analyzed.(2) For photovoltaic and wind power generation, it is required to have a low voltage ride through capability when the grid voltage drops. When faults occur in different locations, the changes of the voltage digs at monitoring point is analyzed. The fault line splitting criterion of distribution network considering the low voltage ride through capability of the micro power supply is proposed.(3)The different strategies for the different levels of the load are proposed when micro source has to operate in the islanding mode. For important loads, the strategy consists with offline supply path selection and online confirmation, and the energy storage device is used to provide reliable power supply. For the average loads, the Kruskal algorithm is applied to generate the minimum spanning tree of micro grid connected graph according to the structure of the distribution network. According to the scale of the micro power generation and load power consumption, the loads may be added to the island as much as possible. At last, the final strategy is proposed with consideration of the important loads.