Research On The Protection Scheme For Distribution Network With Distributed Generation

Distributed generation becomes an effective method to improve energy efficiency and solve energy shortage problem today. The protection system's correctly operation can ensure the safety of power system with distributed generation. However, the distributed generation will change the power grid from the single power supply and the radiation structure to double-power or multi-power network. Since the current protection system of distribution network is designed according to the single power supply and radiation structure, these small capacity generations will change the protective performance, so the original protection system need to make appropriate adjustments. This article mainly studies the types and characteristics of distributed generation, analyzes the distributed generations'impact on the protection device, and proposes improved protection scheme. The main works in this dissertation are as following:(1) Analyze squirrel-cage asynchronous, driect-drive synchronous and double-fed asynchronous wind generator, according to that, establishes the mathematical model of wind speed, wind turbine, drive gear and generator. The diagram of distribution network with wind generation is obtained, and the impact of wind generator to the distribution network is then analyzed .(2) A typical distribution network model with distributed generation is established with PSCAD. The influence of distributed generation to the distribution network's protection system is summarized considering the short-circuited. The increasing current, decreasing current and opposite current impact of distributed generation to the distribution network are compared, and and the count–measures to improve protection performance of distribution network with distributed generation are presented.(3) The distribution network with distributed generation becomes dual-power or multi-power supply system. When the protection device acts, the reclosing device will reclose to make the transimission line supply the power again. The optimal reclosing methods and reclosing time are studied and suggested.At the end of this dissertation, a systematical summary is given. Further work to be studied is pointed out.