The Fast Detection And Compensation Method Of Microgrid Voltage Sag

Microgrid is an electric power generation and distribution network, which consisted by generators,energy storage units,control facilities and loads. It can solve the critical problem of how to provide increasing load with enough electric power and low environment harming effects. With the research and application of microgrid technology in the world, power quality of microgrid is gotten more and more attention.Compared to the traditional power system, the microgrid problem of voltage sag has new changes and new characteristics, which mainlyreflects on the access of distributed power supply. The system has the characteristics of "active network" and "two-way power flow”. The detailed analysis of the reason and harm of voltage sag is based on the result in traditional power system. The papermainly studied the voltage sag problems. The research on newdetection algorithm and compensation measures to improve the power quality of microgrid is of great significance. The main contents and related conclusions are outlined as follows:The paper analyzes the basic structure and operation of the microgrid and summarizes the new power quality problems brought by microgrid which accesses the system. The paper summarizes the reason of the voltage sags and analyzed the influence of the voltage sag to the microgrid and the influence of microgrid voltage sag to the user. The paper also summarizes the original voltage sag detection algorithm,and analyzes their advantages and disadvantages. On the basis of the traditional αβtransformation method of voltage sag,an improved αβ transformation method of voltage sag is proposed, which can achieve the purpose of testing considering the effects of harmonic without the filter. The improved αβ transformation method for voltage sag detection not only has good real-time performance but also has high accuracy. Compared with traditional alpha beta transformation method,the simulation results verify the improved αβ transformation method can rapidly and accurately detect the characteristic value of the voltage sag.Based on study on detection algorithm of voltage sag,this article analyzes the advantages and disadvantages of series compensation method and parallel compensation method. Combined with the characteristics of the microgrid, the series-parallel combined compensation method based on current limiter is proposed. The function of current limiter is to limit current, maintain voltage and increase the equivalent impedance of the system. This method can make full use of distributed power for voltage sag compensation and improve the voltage sag compensation scope.