Research On Background Harmonic Voltage Suppression In Branched Distribution Systems

Scholars have proposed various harmonic suppression methods for backgroundharmonic voltage propagation and magnification in distribution system, this methodsbased on the no branching radial transmission line or the ring line. Actually branchingtransmission line exists in distribution system, so the harmonic suppression methods basedon branching line is involved.Firstly, according to the uniform transmission line theory and the lumped-parametermodel, some theoretical derivations are made. At the same time, the causes of thebackground harmonic proliferation or magnification in transmission line are analyzed andR-APF approach is validated by simulation.Secondly, based on the radial line with no branching, the distributed-parameter modeland the lumped-parameter model of the radial transmission line with branching areestablished, the harmonic voltage propagation equation is derived, and harmonic voltageoscillation is analyzed. According to the terminal R-APF harmonic suppression methodwith no branching radial transmission line, two resistive active power filters are installedat branching terminal of an8km transmission line with a1km branch and a5km branchrespectively. The simulation and experiment results show that this method can restrain theharmonic voltage propagation of the branching line and maintain its magnification about1,but harmonic voltage suppression for the8km transmission line is not so obvious.Thirdly, to restrain harmonic voltage propagation on transmission line before thebranch node, a new control method APF installing at branch node is proposed. The APFoutput compensation current by sampling voltage and current of the branch node, as aresult, the branch node impedance and transmission line characteristic impedance arematching. Simulation and experiment validates that this method can restrain harmonicvoltage propagation in the transmission line before branch node.Finally, according to the lumped parameter model of the radial transmission line withbranch, this paper has built8km transmission line with a1km branch and a5km branchimitatively. For the purpose of filtering the harmonic in the transmission line, experiments platform based on TMS320F2812DSP have been set up and experiments have beenperformed to demonstrate and verify the feasibility and effectiveness of terminal R-APFand branch node APF.