Element Modeling And System Simulation For Power System Harmonics

People first paid attention to power system harmonics in the twenties of the twentieth century. As far as to the fifties and sixties, there came up many papers about the harmonics problem caused by the converter due to the development of HVDC. Since the seventies, the harmonics do more and more harm to people's life because of the increasing application of electronic devices in power system, industry, transportation and families. So the world cares much about this problem.This paper firstly introduces the basic concepts and main measurement indexes of power system harmonics. Then it makes a discussion about the model and application of harmonic analysis, clarifying the tough task and significant meaning of doing research on harmonics analysis.It is a natural result to use simulation in power system analysis with the development of computer techniques. In the second chapter, the author makes an introduction about a harmonic analysis software package PCFLO.There are two main points in this paper. First is the discussion of advantages and disadvantages of different model and its application in harmonic analysis. Second is using PCFLOH to do some system simulation for harmonics in frequency domain. There are two kinds model in harmonic analysis. One is for the modeling of conventional elements, such as generator, transformer, and transmission line. With the enhancement of the manufacture technique, these devices are no longer to be the main harmonic sources. So they can be expressed by equivalent impedance. However, on some specific conditions, they still generate harmonic current and are identified as a current source. The other is for power electronic equipment. With the development of power electronics, they now become the main factor in causing harmonics. So in order to express their frequency characteristics exactly, we should use current sources to represent these devices.In the forth chapter, the author lists criteria and rules established by some international and national academic organizations to limit the power system harmonics. In addition, the author gives an introduction of harmonics criteria according to our country' conditions.The test system is an 18 nodes distribution system. The distortion result is gained by PCFLOH. According to the result, the author discusses the effect of different model in harmonic analysis and solves the model selection problem during different conditions and different precisions.