Study Of A Equivalent Mode Of A Closed-loop Distribution Feeder And A Harmonic Suppression Strategy Based On LFS-APF

Harmonic resonance between system inductors and power-factor correction capacitors may lead to significant harmonic amplification phenomenon in a radial or closed-loop power distribution feeder. The harmonic amplification phenomenon may cause serious voltage distortion in power distribution feeders, which not only deteriorates power quality, but also causes significant operating loss of the power system and even threatens the safe operation of electrical equipment.Firstly, in order to introduce the equivalent model of a closed-loop feeder and the novel approach of analyzing harmonics, this paper analyzes the harmonic resonance law and the traditional RAPF in a radial power distribution feeder. The traditional RAPF only suppresses harmonic resonance, rather than attenuates harmonic voltages effectively. Therefore, to overcome this shortcoming, this paper improves the theoretical analysis of the D-RAPF system and analyzes the relationship about rated power capacity between the D-RAPF system and the traditional RAPF.Secondly, this paper proposes an equivalent model between a closed-loop distribution feeder and a radial distribution feeder. Based on the equivalent model and the harmonic resonance law in a radial feeder, this paper proposes a novel approach of analyzing harmonics, which can analyze harmonic propagation law in a closed-loop distribution feeder and theoretically points out the best installation point and the best control parameters of an active power filter in a closed-loop distribution feeder.Finally, this paper points out that the harmonic suppression effect of the traditional RAPF is unsatisfactory especially in response to variations of non-linear loads, power-factor correction capacitors, and the installation location of an active power filter in a closed-loop feeder. Therefore, this paper proposes the LFS-APF and analyzes the operation principle of the LFS-APF. Moreover, simulation and experiment results demonstrate and clarify the effectiveness of the equivalent model of a closed-loop distribution feeder, the proposed approach of analyzing harmonics, and the proposed LFS-APF.A single-phase radial feeder and a single-phase closed-loop feeder are constructed on the basis of the lumped parameter modle. And experiment platforms of the traditional RAPF, the D-RAPF system, and the proposed LFS-APF are built with TMS320F2812 DSP to clarify the effectiveness of these proposed strategies in this paper.