This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Estimation of Amplitude, instantaneous phase and frequency of single-phase grid voltage signal have been studied in this paper. The proposed approach uses a novel circular limit cycle oscillator (CLO) coupled with frequency-locked loop (FLL). Due to the nonlinear structure of the CLO, the proposed frequency adaptive CLO technique is robust against various perturbations faced in the practical settings e.g. discontinuous jump of phase, frequency and amplitude. Global stability analysis of the CLO and local stability analysis of the frequency adaptive CLO has been performed. Experimental results demonstrate the effectiveness of the proposed technique over a very recent technique proposed in the literature.

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This Letter proposes demodulation type PLL for phase and frequency estimation of single-phase system that can reject DC offset. Using results from the adaptive estimation literature, this Letter proposes a linear parametric model-based initial phase angle estimation approach. Then by using differentiation and integration operation on the estimated initial phase angle, the frequency is estimated. This avoids the use of any low-pass filter unlike conventional demodulation-based technique. Moreover, unlike existing demodulation-based technique, the proposed technique can completely reject DC offset. Comparative experimental results, provided with state-of-the-art DC offset rejection-based enhanced phase locked-loop, clearly demonstrate the suitability of the proposed technique.

This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.