Research Of Distribution Network Current Protection With Distributed Generation

Due to the access of distributed power, the structure of power distribution system changes the traditional single power supply radiation networks into a dual or multi power supply network with small and medium power supply, which affects the matching of relay protection device in the case of single power supply, and has a negative influence to the current protection on the distribution network.Firstly, introduce the principle of distributed power generation technology, advantages, classification, current research situations and current problems, in order to lay the groundwork for the later analysis. Study the standard of DG grid generation, select the inverter control method, current tracking way and phase lock module. Establish the simulation model of the equivalent single-phase distributed power grid system by means of the electromagnetic transient simulation software PSCAD/EMTDC.After that, establish the simulation model of the distributed power accessing to the distribution network, analyze the effect of distributed power as a constant voltage source and current source on the current protection of distribution network when accessing to it. The result proves that the changes of both the fault locations and distributed power supply capacity can affect the relay protection of distribution network when the distributed power supply is constant voltage source, and gives the conclusions;the changes of power supply capacity will not bring great influence on distribution network when the distributed power is a constant current source, the influence of the fault locations changes is similar to the constant voltage source.Finally, using 33 bus test system of IEEE standard, precede setting calculation to the distribution network current protection in both cases of constant voltage source and current source and not containing DG, and compare the results. The results proves that adding directional component at the terminal protection and verifying the setting value were needed for the upstream region of the distributed power; the directional component is not needed for the downstream region of the distributed power, but the setting value of protection is still needed to confirm, and gave out the result after setting.