In this paper, the wavelet phase difference (WPD) approach is applied for the identification of power system areas with coherent generator groups. This approach allows observation, at different frequency bands, of movement of low frequency electromechanical oscillations (LFEO), identified at different parts of the power system and the identification of the inter-area components that move or do not move together. An illustration of the applied approach was performed on the New England (NE) 39-bus test system. The interesting results of WPD application are also presented in a real wide-area measurement data from European interconnected power system. By using the discrete wavelet transform (DWT) and Hilbert-Huang transform (HHT), the validation of results from WPD approach is also given.Index Terms-Discrete wavelet transform, generator coherency, Hilbert-Huang transform, power system, wavelet phase difference.
Study of harmonic propagation in transmission networks with high penetration of power electronics devices. In Study of harmonic propagation in transmission networks with high penetration of power electronics devices
A modified control algorithm of a variable speed wind generator (VSWG) for supporting power system frequency stabilization is presented in this paper. A comparison of the performance of this algorithm with active power control algorithms of VSWGs for supporting power system frequency stabilization, as published in the scientific literature, is also presented. A systematic method of analysis of the modified control algorithm is described in detail. It has been shown that by using the modified control algorithm, the VSWG "truly" emulates the inertial response of a conventional steam-generating unit with synchronous generators during the initial/inertial phase of primary frequency control, following loss of active power generation when wind speed is between cut-in (i.e. 4 m/s) and rated speed (i.e. 12 m/s). By the inclusion of a signal proportional to the frequency deviation as a power reference to the torque controller feedback loop of the modified control algorithm, it is ensured that the contribution of the VSWG to frequency stabilization is independent of the initial wind speed. This independence is kept as long as the wind speed is above the cut-in wind speed and slightly below the rated wind speed (i.e. 12 m/s). One of the important features of the modified control algorithm, namely a near-proportional relationship between the initial wind turbine speed and the maximum wind turbine speed variation during the inertial response, has been identified. The results of the analysis provide a solid basis for further research in the area of VSWG contribution to frequency stabilization.
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