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A new practical technique for simultaneous local system frequency, magnitude, and active and reactive power estimation from voltage and current signals is presented. The technique consists of two phases using decoupled modules: the first phase estimates the frequency, and the second one estimates the magnitudes and the active and reactive power. The third important part is the adaptive bandpass and low-pass finite-impulse-response (FIR) filters that extract the fundamental and dc components, respectively. The most important point of this paper is the mathematical model that transforms the problem of estimation into an overdetermined set of linear equations. A very suitable algorithm for the aforementioned parameter estimation has been obtained. The algorithm showed a very high level of robustness and high measurement accuracy over a wide range of frequency changes. The algorithm convergence provided a fast response and adaptability. This technique provides accurate frequency estimates with errors in the range of 0.002 Hz and magnitude and power estimates with errors in the range of 0.03% for SNR = 60 dB in about 25 ms and requires reduced computations.