Research On Islanding Detection Methods Of Micro-Grid

Compared to the traditional grid, the micro-grid has the advantages of less investment, pollution-free, the reliability of power supply and without the need of long distance power transmission. Micro-grid not only provided power separately but also grid-connected to the main grid. The micro-grid is a good supplement of the main grid when the system is grid-connected. It is an important trend in the development of electric power now. Though a lot of advantages the micro-grid has, some important things, such as islanding detection, cannot be solve.The islanding detection method of micro-grid can be divided into two categories as passive islanding detection method and active islanding detection method. Both of the two categories methods have the advantages and disadvantages. For the passive method, its structure is very simple and has a good power quality, but it also has a big no-detection-zone. Active method has the advantages of shorter detection time and narrow no-detection-zone, but has a bad power quality. So it is very important to find out a better method to justice whether islanding is happen.Firstly, we discuss the basic knowledge of micro-grid such as the different definition of micro-grid by different countries, the history, structure and the benefits of research of micro-grid; we also discuss the basic knowledge of the islanding detection, such as the definition, the standard, no-detection-zone and so on. After that we gave the advantage and disadvantage of both the passive method and active method.Secondly provided a new method based on the discussion of the existence method. This method based on injecting three harmonic to the modulation wave of the inverter drive signal, we can check the voltage and total harmonic distortion (THD) of the point of common coupling (PCC). Then discussed the theory of the new method.And the paper also show the simulation of ISE software based on FPGA. Mainly introduce how to generate all kinds of waveform using ISE software. The waveform include triangle, sine waveform, SPWM and so on. This paper not only give the main program but also show out the schematic diagram and simulation waveform. And designed the FPGA program that used to the smallest system at last. Finally, we build a small experiment system using FPGA to decide whether the method of islanding detection is probability. This part is the most important in this paper. Firstly, we introduce the basic knowledge of FPGA, and other module that make the FPGA work safely. This module is very important and has been design very well. Secondly, we gave the module of islanding detection method simulation module. Use the Matlab/Simulink to build the simulation module and gave the final result simulation wave of the new method. At last, the paper gave the implement of IGBT drive signal by FPGA and the implement of the small system.Set up a simulation module using Matlab/Simulink to analyze and verify the new method and use the small system to get the experiment wave. All of the results demonstrate that the proposed islanding detection method is effective.