The Comprehensive Treatmen Scheme Of Metro Power System Harmonic Current And Reactive Power

Increasing congestion in urban public transportation today, the metro is under increasing favour with its big advantage of fast, convenient, safety and stable, so the development of metro is very rapid. With the development of metro construction and accumulation of engineering experience, the power quality problems of power supply system become the focus of common attention. As the power supply system of metro ensure traction locomotive and subway station stable operation, it brought to power grid harmonic pollution and reactive power that can’t be ignored.Due to the DC traction, the metro traction substation set the rectifier device, and it will engender harmonic. Furthermore, all kinds of equipments including frequency conversion devices, Nonlinear electric light source, UPS, EPS power source and so on are popular in the dynamic lighting system of metro, and they will engender much3,5,7,11,13order harmonic. And the harmonic current will flee hither and thither even magnify. It will vibrate, noise, overheating, even burn electrical equipment, and cause failure or accident, causing serious pollution to power grid. On the other hand, the metro slathers perceptual Load. Especially the dynamic lighting system of metro will produce a lot of reactive power in peak time during the day, measured by the power factor less than0.9, not up to national standards. And at the night troughs time metro offstreams, so a lot of perceptual loads have been cut off. but the power supply cable will cause phenomenon of pouring capacitive reactive power send to grid owing to its charge effect. It will cause the power factor to decline seriously with only0.3～0.4. So it will waste seriously, the need to focus on management. In addition some metro still add the capacitance device for compensation reactive power of perceptual load compensation so that it will pour more capacitive reactive power to power system at night time for hugh car. And at present the capacitance device that we set to compensate for the perceptual reactive power will magnify harmonic on certain level, causing the second management problems. Therefore, macro perspective, the harmonic current and reactive power that the power supply system of metro produces will cause serious impact to the power grid. The problems that how to eliminate harmonic and at the same time compensate reactive power need to be solved urgently.Based on the particularity of power quality problems of the metro, in order to improve the environment of the power supply system, strengthen the power supply reliability and stability, reduce the bad influence to external power network, this paper puts forward a new dynamic compensation method that we can do the comprehensive treatment of the harmonic current and reactive power of the metro power supply system using the nowadays representative technology of the reactive power compensation field--------STATCOM(static synchronous compensator).The author of this paper expects that the research contents and results could provide theoretical basis to the construction plan and design research of the metro for future.