Research On Application Of Adaptive Protection In DG Distribution Network

The use of traditional fossil fuels will cause serious environmental problems, coupled with the empolder of hundreds of years, this type of energy has been on the verge of exhaustion. At the same time, the centralized large power grid generation model also has various problems with the expansion of the power system. People’s eyes turned to the distributed generation technology based on renewable energy, and began to study the complementary role of distributed generation to the distribution system. However, the insert of a large number of distributed power supply will cause the traditional radiation based structure of the distribution network current protection not to meet the requirements, not to be fast and correct action. Therefore, this paper mainly studies the adaptive protection of the distribution network with DG in order to solve a series of problems caused by the DG access.First, the adaptive current protection methods used in several traditional distribution networks are studied, such as adaptive over current protection, adaptive current vector differential protection and so on. This paper briefly introduces the setting method, the protection scope and the realization process of these kinds of adaptive protection, and has a preliminary understanding of the idea of adaptive protection.With the distribution of a large number of distributed power access to the traditional distribution network, which will have a certain impact on the distribution network voltage, power flow, power quality and protection programs. According to the output characteristics of the distributed power supply, this paper analyzes the influence of the distributed generation access on the traditional current protection and automatic device from the type, capacity and access location of the DG inverter. On the basis of analyzing the fault characteristics and control method of the inverter type DG, the inverter type DG is equivalent to the constant power model, and the PSCAD/EMTDC simulation software is used to build a simple distribution network model with DG lOkV. The output capacity and the access position of the distributed power are kept unchanged, and the simulation results show that the DG has the influence on the traditional protection methods.Due to the change of output power of inverter interfaced distributed generators,the value setting of the traditional current protection becomes very difficult. Based on the existing adaptive current protection, the adaptive current fast fault protection for the distributed generation system with DG is studied. In order to calculate the adaptive current setting value which can adapt to the change of DG, the algorithm of calculating the equivalent impedance of the protection back is changed, and a more accurate calculation method is adopted. The analysis results show that, the adaptive setting expression of this method is invariant, but the parameters are more accurate than the previous calculation method, thus improving the adaptive current fast break protection method.In addition, the compound sequence network and simplified compound sequence network When a short circuit fault occurs are analyzed, the positive sequence fault current through the protection device is calculated, an adaptive sequence current inverter with DG distribution network quick break protection method is studied. At the same time, a simple model of distribution network with DG is built, and the effectiveness of the model is simulated and verified in the case of two-phase short circuit fault and three-phase short circuit fault.Adaptive protection is realized, which requires the integrated use of the local information of the power supply and distribution line adaptive protection device, the information and the centralized control center of the substation once, two times the state of the equipment information and topology connection. This paper introduces the realization process of adaptive protection in detail, combined with the specific work and operation process of various devices and network technology in the substation automation system and distribution network automation system.