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Empirical Mode Decomposition based Identification of Low Frequency Modes in Inverter based Microgrid

This paper shows the application of empirical mode decomposition (EMD) and prony analysis for identification of low frequency modes present in droop controlled inverter based microgrid for stability analysis. This method of EMD and prony analysis overcomes the requirement of a detailed small signal model which is widely used for the calculation of damping of low frequency oscillation (LFO) in inverter based microgrid. The small signal analysis requires solution of large number of differential and algebraic equations which makes it computationally difficult and time taking. Signal processing techniques have already been used in conventional power systems for frequency identification of LFO. This paper shows its application in inverter based microgrid to avoid the use of full order small signal model. EMD is used for decomposing the time varying signal into different intrinsic mode functions (IMFs) and then prony analysis is used to find the frequency and damping of individual mode. Comparison of calculated frequency of LFO with those obtained from eigen value analysis of small signal model is also presented for verification of the presented method.