Research On Power Quality Monitoring And Evaluation System In Distributed Power System

The combination of distributed power system with large power grids is recognized by many energy and electrical experts as the main mode to save investment, reduce energy consumption, and improve the stability and flexibility of the power system. It is one of the most important developments in the power industry during the 21st century. Besides, the distributed power generation is compatible with the environment and has the advantage of using renewable energy effectively, which makes contribution to ease the continued tension and pressure in world energy and environment problems. As a result, the distributed power generation technology has developed rapidly in recent years. But at the same time, the introduction of this technology will have a bad effect on the grid's power quality. For the safe and stable operation of the distributed power supply system and the gird, it becomes very important to accurately grasp and assess the power quality of the system.First, this paper analyzes the power quality problems brought by the distributed generation technology. And a study of the existing power quality standards in our country is made. Meanwhile, the commonly used power quality detection methods were analyzed and compared, including the methods to detect harmonics, frequency deviation, voltage deviation and so on. In addition, the windowed interpolation base-2 FFT is used to detect the frequency and harmonics in high accuracy.Then, the current main evaluation methods are studied and their advantages and disadvantages are analyzed. And based on it, a comprehensive evaluation method has been proposed, which combines the advantages of analytic hierarchy process, probability statistics and fuzzy comprehensive evaluation methods. As a result, the level of power quality is able to be accurately assessed.In the end, by using Visual Studio 2008, SQL Server 2000, data acquisition card and other hardware, an experimental system of power quality monitoring and evaluation is developed. It can not only achieve the inverted output of power quality, but also monitor the operating status of distributed power and energy storage devices in real time. Besides, it can evaluate the system's power quality and running status at any historical time period.