A Frequency and Angle Feedforward Estimator for Unbalanced and Distorted Three-Phase Electric Grids

This article presents an open-loop frequency estimator able to deal with typical disturbances, yet exhibiting fast dynamics. The proposal is tested and compared experimentally against the orthogonal voltage decomposition (OVD) approach, which is considered the state-of-the-art open-loop frequency estimator and the recently proposed adaptive feedforward frequency phase-locked loop (PLL). The results verify that the proposed approach operates correctly under unbalancing, harmonics, noise, and interharmonics, and after frequency, phase, and amplitude jumps, while exhibiting settling times about 25% better than the OVD, and a similar execution time. Furthermore, the proposed technique has a performance comparable to advanced frequency-locked loops ; it is easy to tune, and thus, it could be seamlessly applied in typical synchronization tasks where PLLs are usually employed.