Analysis And Countermeasure Of Influence Of Photovoltaic Grid Connection On Distrirbution Network Relay Protection

As a technology of power generation from new energy sources,photovoltaic(PV)generation has been developing vigorously worldwide,whose application and innovation have promoted upstream technologies in the PV industry.Given the year-by-year increase in the run size of domestic PV stations,the access to numerous distributed PV supplies has exerted conspicuous influences on the flow distribution and relay protection of traditional distribution network.For such a network containing PV supplies,the complex characteristics of its fault may cause its relay protection's failure,and further decrease in the sensitivity of grid-connected protection,breaker's inaction,selective malfunction and other operation issues that may affect automatic safety devices.Thus,we shall reappraise the existing relay protection devices,settings and coordination to see if they can fit into the application of distribution network technologies under new circumstances,and shall “serve the people with public grid utilities” to contribute constantly to establishing the energy Internet with Chinese characteristics.In this paper,a brief description was made of the PV generation system's basic components,classification,grid-connection criteria and methods.Analyses were made of PV generation's MPPT with an aim to study the control strategies for PV grid-connected inverters,and also of the impacts of PV supplies' access locations and capacities on the distribution network's fault characteristics,through which the access was studied for its impacts on the relay protection's configuration.A simulation model for the network was set up using DIGSILENT/Power Factory simulation software,with pertinent simulation verification performed.A new scheme for adaptive current protection was raised to,based on symmetrical/unsymmetrical short-circuit faults' characteristic values,do well-matched setting calculations of protection adaptively to protect the network after the access to PV supplies.Data was simulated and verified based on the aforesaid model,and analyses were made of the protective effects before and after applying such scheme(cases selected from Feicheng,Tai'an).Simulation results and application cases all demonstrated the effectiveness of the new scheme.