LAUSR

This article proposes a fundamental frequency estimation technique for three-phase voltage systems under unbalanced and harmonic conditions. It is based on the Clarke transformation, recursive discrete Fourier transform, and Teager energy operator. The proposed technique is computationally efficient and relatively simple to implement, thus suitable for low-cost applications. It does not require real-time evaluation of the computationally demanding inverse trigonometric functions. The proposed method does not suffer from the accumulation error and is also not affected when the voltage signal is sampled at zero or close to zero. It is immune to various voltage harmonics and can produce quick transient response with a time of less than 75% of one fundamental period. When compared with the competing techniques based on phase-locked loops and three consecutive samples, the proposed method can produce faster response under dynamic conditions. The advantages of the proposed technique are confirmed by simulated and experimental results in the laboratory.