Spikes frequently occur in power quality (PQ) disturbance signals due to various causes\nsuch as switching of the inductive loads and the energization of the capacitor bank. Such signals are\ndifficult to analyze using existing time-frequency (TF) methods as these signals have two orthogonal\ndirections in a TF plane. To address this issue, this paper proposes an adaptive TF distribution (TFD)\nfor the analysis of PQ signals. In the proposed adaptive method, the smoothing kernel�s direction\nis locally adapted based on the direction of energy in the joint TF domain, and hence an improved\nTF resolution can be obtained. Furthermore, the performance of the proposed adaptive technique\nin analyzing electrical PQ is thoroughly studied for both synthetic and real world electrical power\nsignals with the help of extensive simulations. The simulation results (specially for empirical data)\nindicate that the adaptive TFD method achieves high energy concentration in the TF domain for\nsignals composed of tones and spikes. Moreover, the local adaptation of the smoothing kernel in the\nadaptive TFD enables the extraction of TF signature of spikes from TF images, which further helps in\nmeasuring the energy of spikes in a given signal. This new measure can be used to both detect the\nspikes as well as to quantify the extent of distortion caused by the spikes in a given signal.
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