This paper presents results in the design of an adaptive algorithm for real‐time estimation of voltage phasor, frequency and its rate of change. The new algorithm, separated in two stages, is based on the non‐recursive “Least Error Squares Technique” (LS Technique). The estimation of the unknown parameters of the voltage signal is improved by means of an update procedure in the first stage. The update procedure is iteratively provided by the algorithm adaptation to the actual estimated frequency so that the frequency measurement range and accuracy are significantly improved and sensibility to the noise is reduced. The rate of change of frequency, estimated in the second stage using a common LS Technique, is represented by the linearly time‐dependent observation model. To demonstrate the performance of the algorithm developed, computer simulated, experimentally obtained and real‐life data records tests are presented.