Study Of A New Background Harmonic Damping Method For Closed-loop Distribution Power Systems

Numbers of electronic-based appliances generate a large amount of harmonic currentin power systems. Background harmonic voltage in power grid may damage IHAPF andmay also cause the harmonic current on PCC to exceed the criterion value. The harmonicvoltage standing wave is severely complicated, and the voltage distortion on the feedermay become much worse in closed-loop distribution networks on certain locations if anunmatched active filter is switched on. To solve this problem in the colsed-loopdistribution systems, this paper proposed an infinite transmission line active power filterwhich can be used to closed-loop distribution power systems for the background harmonicdamping.The main work of this paper is as follows:(1) Three arrangements of closed-loop feeders are Described in this paper, thelumped-parameter model and the distributed-parameter model of closed-loop feeders ofType I are established as well. Based on these two models, two electromagnetic wavepropagation equations in a closed loop transmission line are established. These twoequations proven that the distributed parameter models and the lumped parameter modelcan replace each other when analyzing the harmonic voltage on the closed-looptransmission line.(2) Based on the analysis of harmonic propagation characteristics of the closed-looptransmission line, the Infinite closed-loop transmission line is proposed in this paper.Adopt the infinitely long transmission line APF to achieve the infinite closed-looptransmission line. Two structures infinite transmission line, that is, single and dualtransformer transformer infinite APF are proposed. The dual transformer infinite APF hastwo implementations: Dual Transformer infinite series-parallel-series APF and doubleparallel passive transformer series active hybrid APF. The control parameters and thecontrol method of the proposed APF were given in detial.(3) Operation principles are explained in detail, and builds up a simulation modelbased on actual parameters, the simulation results show the compensation waveforms and effects which proves the project is feasible and effective.