Influence Of Distributed Generator Integration On Fault Analysis Function Module Of Distribution Network Based On DMS System

In recent years,with the improvement of the level of distribution network automation and the increasing importance of distribution network,more functions based on the distribution network automation have been developed,and the distribution network fault analysis is one of the representatives.The application of the distribution network fault analysis function can quickly locate the fault point and reduce the repair time.It is an important way for the power supply companies to improve the reliability of power supply and customer satisfaction.With the development of society and the rapid development of distributed generation technology,large scale integration of distributed generators has become a general trend,and the impact brought by it cannot be ignored.Research on the impact of the operation of the distribution network fault analysis function module after distributed generation connected to the distribution network is necessary.This thesis introduces the DMS system-based distribution network fault analysis function module used by FZ power supply company.Its main functions are: 1.Determining the trip point according to the power outage distribution transformers out of power;2.Determining the fault zone according to the over-current signals and then offering the isolation and recovery strategy.The thesis sorts out the working process and working principle of the above functions in detail,and uses the doubly-fed induction generator as a representative of distributed generators to establish the model of a distributed generator connect to the actual distribution network of FZ power supply company in PSCAD system,simulates the operation of the distribution network fault analysis function under this circumstance.When earth fault happens,the original three-stage overcurrent protection of the distribution network operates normally to open the breaker,but the distributed generator continues to supply power to the distribution network,making the distribution transformer still electrified when the main power supply is cut off,which affects the distribution network fault analysis function module to determine the trip point.At the same time,after the main power trips,the distributed generator continues to transmit fault current to the fault point,causing the breakers and the fault indicators it flowing through to have an over-current signal,which affects the distribution network fault analysis function module’s determination of the fault zone.According to the simulation results,this paper proposes the protection scheme of the breaker installed in the point of common coupling and the optimization scheme of the distribution network fault analysis function module.Utilizing the characteristics of sudden changes in the voltage and current phase difference of the point of common coupling when the distribution network fails,the phase difference is used as the basis for the protection action to achieve that the distributed generator can be disconnected in time when the distribution network fails.Using the power directions of breakers installed between the main power supply and the distributed generator to obtain the real-time power supplier of the distribution transformer in the distribution network,mark it in the distribution network fault analysis function module,divide the signals into powered by the main power and powered by distributed generators when determining the trip point and the fault zone,so as to eliminate the adverse effects caused by the access of the distributed generators.Based on the study of the DMS-based fault analysis function module,and learning the working characteristics of distributed generators represented by doubly-fed wind turbines,this paper proposes a protection scheme depend on the voltage and current phase difference of the point of common coupling according to the simulation results.This protection scheme is valid,which is of great significance to the large number of distributed generators connected to the distribution network in the future,and lays the foundation for future practical work.