A Low Computational Cost ROGI-based Frequency-Locked Loop

This letter proposes a reduced-order generalized integrator-based frequency-locked loop (ROGI-FLL) without discretization errors and trigonometric function (tr-f) calculations. The transfer function expression of discrete-time ROGI is converted to be implicit on tr-f. The FLL is then constructed to estimate the parameter of this expression rather than frequency. When the harmonics detection is considered, the estimated parameter directly implements the additional ROGIs without knowing the frequency. Thus, the proposed FLL features a low computational cost without compromising discretization accuracy. By the tests in DSP TMS320F28335, the proposed FLL can reduce more than 50% computational time of the discrete-time FLL with harmonics detection (up to the 19 order). Compared with the FLL discretized by the commonly-used methods, the proposed FLL improves the detection accuracy with similar or less computational time.