Hybrid inductive and active filtering method for damping harmonic resonance in distribution network with non-linear loads

In this study, a hybrid inductive and active filtering (HIAF) method is proposed to dampen the harmonic resonance in distribution network with non-linear loads. At a first, a new topology of energy conversion system with active technique, which includes an inductively filtered converter transformer, fully-tuned branches and a controlled voltage source inverter (VSI), is proposed for large-power non-linear loads. The working principle of such a new topology is described, and the advantage of damping harmonic resonance of the distribution network is revealed by means of mathematical modelling and theoretical analysis. Then, the control system of VSI is designed with the multiple purposes of damping harmonic resonance from the grid side and isolating harmonic currents from the non-linear load side. A case study is carried out to validate theoretical results. By comparing with the traditional hybrid active filtering method and the passive filtering method, it indicates that the proposed HIAF method is more effective to dampen harmonic resonance in the distribution network and at the same time is able to significantly reduce the harmonic contents in the grid winding, which is good to both the public network and the energy conversion system connected with large-power non-linear loads.