Due to a rising share of power electronic devices in power networks and the consequent rise in harmonic distortion, impedance resonances are an important issue. Nowadays, the frequency scan method is used for resonance phenomena identification and analysis. The main disadvantage of the method is its inability to decouple different resonance phenomena. This means that the method is also unable to provide sufficient information about the effects that the parameters of network elements have on different resonance phenomena. Furthermore, it was also noted that despite the fact that the harmonic resonance mode analysis is well described in the literature, there is a lack of systematic approach to the analysis procedure. Thus the main objective of this paper is to address this disadvantage and to propose a systematic approach to harmonic resonance analysis and mitigation, utilizing modal analysis. In the first part of the paper, dominant network nodes in terms of resonance amplification of harmonics are determined. This is done by analysis of the eigenvalues of the network admittance matrix. Using the eigenvalue analysis results, key parameters of network elements involved in a specific resonance are determined next. This is performed by calculating the critical mode (i.e., the mode that experiences resonance) sensitivity coefficients with respect to network parameters. In the second part of the paper, the procedure for modal resonance frequency shift is presented. The shift is performed by changing the value of a selected parameter so that the modal resonance frequency matches the desired resonance frequency value. The parameter value is calculated with the Newton–Rhapson method. Presented analysis considers both parallel and series resonances. The effectiveness of the proposed method is demonstrated on an actual industrial-network model.
Harmonic Resonance Identification and Mitigation in Power System Using Modal Analysis
