An Enhanced Single-Phase Self-Tuning Filter based Open-Loop Frequency Estimator for Weak Grid

This article proposes an enhanced single-phase self-tuning pre-filter for estimating the fundamental grid voltage frequency. The known extended self-tuning filter (STF) adheres to an increased structural complexity, which may consume memory in the digital hardware to estimate the fundamental grid voltage signal. The proposed STF, which relies on a simple non-adaptive comb filter, may address this issue. Consequently, the introduction of imaginary zeros ensures better rejection of the DC-offset and the harmonic components while keeping the proposed filter structure simpler to implement. Furthermore, a simple open-loop frequency estimator is proposed, which does not involve any inverse trigonometric function to estimate the fundamental frequency. This entire proposal is cost-effective and has good frequency tracking abilities with a reduced computational load. The experimental results imply the suitability of the proposed scheme for weak inertia power grid networks where synthetic inertia controllers require a rapid frequency information to control the injected power under adverse grid voltage conditions.