POWER SYSTEM SERIES HARMONIC RESONANCE ASSESSMENT BASED ON IMPROVED MODAL ANALYSIS

Harmonic resonances in the grid network, both the parallel resonance and the series resonance, have been given more and more attention in modern power system operation and study. The modal analysis approach that based on the node impedance matrix has shown a promising way for the parallel resonance assessment in recent years. With regard to the series resonance, a novel approach, combining the modal analysis and the dummy branch method, is proposed in this paper to compute the series resonance frequency and the corresponding branch information. It is found here that the loop impedance matrix should be used in assessing the series resonance problem rather than the node impedance matrix that we used in assessing the parallel resonance. It is also illuminated that since the network topology changes constantly when analyzing the series resonance phenomenon, the dummy branch method should be embedded into this approach. The tests results and practical application show the correctness and effectiveness of this method. The results of this paper can serve as a parallel approach which can provide more sufficient information of harmonic resonance than the conventional widely used frequency scan analysis do, and this can also be used for the checkout of resonance frequency of filters.