Influence of noise on the IpDFT-based estimation of the grid frequency in renewable energy systems

Renewable energy systems have become very popular in recent years. The quality of power produced in such systems has to fulfill the requirements defined in the respective standards. The power control process is based on the frequency, amplitude and phase estimation of the grid signal. Recently, a fast and accurate estimation method was presented. The method is based on the FFT procedure and 3-point spectrum interpolation. It is not computationally complex and it reduces the impact of the conjugate component on the results. Estimates can be obtained in time that is much shorter than one cycle of the grid signal. This paper presents the variance expression of the normalized frequency estimator taking into consideration the conjugate component in the signal spectrum. The simulation results confirm the accuracy of the expression for different orders of the time windows used as a function of measurement time and SNR value. The results of the simulation show that the efficiency of the entire system can be increased using the method, which can be also applied in many other fields of science and technology.