Research On Protection Of Distribution Network With Distributed Generation

With the development of distributed generator and increasing distributed generation capacity into grid, the impact of distributed generator bringing to grid can’t be ignored. This article studies the impact to grid protection after a large number of distributed generator accessed to grid. Its’ essence lies in that the access of distributed generator changes the structure of the original network and causes changes in the detection current of the protection, the ultimate impacts protection correct action.The paper studies on distributed generator model, mainly analyses the characteristics of typical distributed generator wind turbine, establishes wind turbine model, and discusses the voltage and current waveforms under normal operation and fault conditions. We research on control strategy of connecting to network, established equivalent model of distributed generator based on PQ control characteristics. And we verified by simulation that the double-loop control strategies of the outer power ring the inner current ring adopted can realize fast tracking control of the power, which can prove the effectiveness of distributed generator model established.The paper uses theory analyses the effect of distributed generator access locations, capacity to the line protection setting. Based on the theoretical analysis, we build IEEE7node system to verify the correctness of theoretical analysis. And we calculate the access capacity under different distributed generator access points. The results confirm the theoretical analysis consistent with the simulation.Based on the analysis of various impact on the distribution network, this paper proposes an adaptive protection scheme based on local information content. By adding an adaptive protection to the original line protect can largely improve the sensitivity of circuit protection, it tries to adapt to changes of various lines working state. The simulation shows that the algorithm can well cope with the over flow of distributed generator access to the grid, verifies the validity and correctness of the adaptive algorithm presented.Against the inadequate of the current protection, after analyzing the impact on distance protection with distributed generator, the paper proposes adaptive distance protection scheme. It mainly improves the tuning of section II of the protection distance, and makes simulation to verify the feasibility of the program.