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In this paper, a new algorithm is proposed to estimate amplitude and phase angle (and frequency) of load currents and source voltages in the presence of harmonics and frequency oscillation. Moreover, a comprehensive control strategy is introduced to extract the compensating signals for the control of series and shunt converters of the unified power-quality conditioner (UPQC). The basic approach used in this algorithm is to extract the fundamental component of load current and source voltage by using wavelet-transform decomposition. Then, the amplitude, phase angle, and frequency of fundamental component are calculated using the well-known LS algorithm, which is relatively simple and fast. The voltage and current references of UPQC active power filters are obtained using the positive sequence of three-phase system voltages and load currents. The proposed control strategy can extract the reference currents and voltages of UPQC fast and accurately in the presence of harmonics and/or frequency oscillation. Simulation results have been presented to show improvement of the UPQC performance in the presence of frequency and amplitude variation condition and various forms of current and voltage distortion. Index Terms--Frequency estimation, multiresolution analysis (MRA), power quality, unified power-quality conditioner (UPQC), wavelet transform.

Summary: Conventional under frequency and under voltage load shedding (UFLS and UVLS) schemes are generally independent than each other. Besides, in these schemes, the operating thresholds, amounts, and location of shed loads are settled in constant values for different disturbances. Due to these technical flaws, the conventional load shedding schemes fail to retrieve power system stability which outlines the necessity of devising improved adaptive mechanisms. To this end, the ongoing study proposes an adaptive UFLS scheme based on wide area measurement systems (WAMS). In contradiction to the existing methods, the proposed approach is featured with an adaptive manner. In other words, the frequency threshold of load shedding relays is adaptively tuned at each disturbance. Furthermore, a wide‐area index is proposed to select the amount of required shed loads. Extensive numerical studies conducted on a real‐world case study are involved to evaluate performance of the proposed approach. [ABSTRACT FROM AUTHOR]