Simultaneous frequency and amplitude of sinusoidal signals estimation through maximum likelihood algorithm and adaptive filtering

A lot of literature is available on the amplitude and phase measurement techniques for power system applications. These methods show sensitivity on frequency variations. If the frequency is not known a priory, it becomes a very difficult task to measure the amplitude accurately. A new technique for simultaneous estimation of both local system frequency and amplitude from either a voltage or current signal is presented. There are two possibilities. The first one, simultaneous estimation of both frequency and amplitude, and the second one, the estimation of the frequency first and after that the estimation of the amplitude based of the estimated frequency. In the paper are presented both variants. Filtering of input signals of algorithms for measurement of electrical parameters of power system is very important. Filters are used to minimize the noise effect and to eliminate the presence of harmonics. An efficiency method for on-line designing of digital filters of sinusoidal signals is used in this paper described in [20]. A very suitable algorithm for frequency and amplitude estimation was obtained. This technique provides accurate frequency estimates with error in the range of 0.002 Hz and amplitude estimates with error in the range of 0.03% for SNR=60 dB in about 25 ms and requires modest computations. Theoretical basis and practical implementation of technique are described. To demonstrate the performance of the developed algorithm, computer simulated data records are processed. It has been found that the proposed algorithm is suitable for real-time applications.