Power Quality Control System

Nowadays, harmonic's contamination becomes more and more severe in power distribution system because of the ever-increasing nonlinear loads, such as converter, variable speed drivers, arc furnace, and so on. Active power filter, an effective solution, has been widely researched and developed in the recent years.A parallel hybrid active power filter is proposed in this paper based on the preventing harmonic currents. The theory of harmonic detecting and the control strategy is fully analysed. The main researching achievements of this paper are as the following:(1) A novel structure of parallel hybrid active power filter is proposed. It consists of Passive Filter (LC) and Active Power Filter (APF).Passive filter compensate majority of harmonic currents while APF can compensate a few harmonic current and prevent harmonic resonance. The capacity of APF is extremely small because of not withstanding basic voltage.(2) The problem of harmonic current amplied is analysed in passive filter system, the conditions of harmonic resonance as well as the circuit of harmonic resonance are discussed and analysed detailly in this paper, and the simulation results demonstrate that the problem of passive filter (LC) system resulting in harmonic currents amplied.(3) Two different methods of harmonic currents detecting, based on the fully analyzing instantaneous reative power theory, are introduced. These two harmonic currents detecting methods are compared in this paper.(4) An integrated control system of power quality is designed. It was made up of passive filter (LC) and active power filter (APF).(5) The simulation results of the whole system, which suggest that the integrated control system of power quality designed in this paper can not only eliminate the problem of harmonic resonance but also consumedly decrease the content of higher harmonic, are completed successfully.