Study On Fault Analysis And Relay Protection Of Distribution Network With Distributed Photovoltaic

In recent years, with the vigorous development of new energy industry and preferential policies support from the government, the PV installed capacity in China increase year by year, and it will reach 60 GW by the year 2020.With increasing PV installed capacity into grid, A large number of Distributed Photovoltaic will change the structure and power flow distribution Of traditional Distributed network, make the distributed network fault characteristics change. Therefore, traditional distributed network Relay protection is no longer suitable for distributed PV generation. This may easily result in tripping missing or maloperation of traditional Relay protection, which produce a somewhat unfavorable effect on the safe and stable operation of Power System. This paper analyzed theoretically the impact on the traditional distributed network, and put forward the improvement measures on the original protection scheme on the basis of simulation verification, which make it adapt to the access of distributed photovoltaic generation.First of all, the model of distributed PV system was developed, the pq control strategy and limiting current protection behavior of inventer were taken into account. Then, this paper analyzed the fault characteristics of distributed PV generation compared with the Synchronous generator When a fault occurs.Secondly, this paper analyzed theoretically the influence of the location and capacity of distributed PV generation to Relay protection and Automatic reclosing by formula derivation. Then, the model of a lOkV distributed network injected with distributed PV generation was built. This paper simulated and analyzed power network failure of the Different locations, and converted the results into Graphics with fault current data and setting calculation results. Afterwards, quantitative analysis of the impact on the reliability, sensitivity and selective of the original Three-step current protection was made.Finally, in view of Network Synchronization Modes of distributed PV generation, an improved method of setting calculation thinking of current limiting protection was put forward. By reducing the protection range and sensitivity appropriately,misoperation caused by excessive extension of protection range can be avoid. Furthermore, this method Make downstream protection Automatically adapt to the change of DG capacity. In order to judge the effectiveness of improved method, this paper run the simulation of the specific example and calculate the adaptive setting value. Through the analysis of the results, a conclusion can be drawn that the improved setting calculation has the advantages of Automatic adaptive.