Study On New Protection Schemes For Distribution Network With Distributed Generation

Considering the economics and security of power grid, distributed generation generally is connected to low and medium voltage distribution network. The most of current Chinese distribution network adopted the radiant structure with single source. Therefore, the unidirectional power flow contributes to simple protection methods with no regarding of directionality. Since the integration of distributed generation, the distribution network becomes a system with multi-power sources. Moreover, the uncertainties of renewable energy has great possibility to result in uncertain bidirectional power flow under the normal operation. Thus the traditional protection methods can't meet the requirements of the stability and security of distribution network integrated with distributed generation. In order to resolve these problems, this paper studies the new protection scheme for the smart distribution network with high permeability of distributed generation. The main research of this paper is organized as follows:First, this paper introduces the basic over-current protection and automatic reclosing of traditional distribution network. Furthermore, to provide reference for the design of new protection scheme, the impacts of different interconnected location and capacity of distributed network on fault current is analyzed theoretically and simulated.Further, based on the wide area protection ideologies of transmission network, a novel distributed protection method based on regional fault information is proposed, to resolve the practical difficulties and requirements attributed to the access of distributed generation. This method can precisely locate and quickly isolate fault relying on the cooperation of smart terminals, consequently, it can resolve the protection of distribution network with distributed generation.Based on the big data of smart distribution network, this paper proposes a centralized state monitoring and fault processing mehod. This method fuses several fault characteristics into a integrated fault characteristic, therefore, it can improve the accuracy and reliability of state recognition comparing to the traditional protection methods. Moreover, the proposed method removes the complicated relay setting computation because of the analytical result based on big data.Finally, with great concern of the development tendency and protection requirements of future smart distribution network, this paper puts forward a hierarchy hybrid protection method based on the combination of distributed protection method and centralized protection method. This method combines the distributed protection method based on regional fault information and the centralized state monitoring and fault processing mehod based on big data analyzing. Thus, this method greatly improves the performance of fault processing, possessing the fast fault processing capability of distributed protection and the overall importance and high fault tolerance of centralized protection.This paper studies the novel protection method for smart distribution network with distributed generation, including the distributed protection method based on regional fault information, the centralized state monitoring and fault processing mehod based on big data analyzing, and the hierarchy hybrid protection method. Furthermore, the proposed method is validated on static experiment platform. The studies of this paper can provide reference for the protection and control of distribution network with distributed generation, and great practical significance for the development of smart distribution network.