Calculation of Series Resonance Frequencies in Electrical Grids Using Resonance Mode Analysis

The ongoing structural changes of electrical grids come with changes in their harmonic behaviour. Thus, the resonance frequencies change and harmonic analysis and calculations are necessary for reliable operation of energy transmission and supply. Frequency scan is a simple and helpful tool to find resonance frequencies of the system. With modal analysis, these resonances can be interpreted as decoupled resonance circuits. Thereby, the definition of the most participating electrical components of the system on the particular resonance is feasible. In the literature, the dummy branch method is introduced to apply modal analysis for calculation of series resonance frequencies. Therefore, the loop matrix representation of the system is used. In this paper, the dummy branch method is discussed and improved. Two types of series resonance frequencies are defined for electrical grids with corresponding calculation methods. The methods are calculated on a simple test grid, and results are presented.