An Adaptive Frequency-Fixed Second-Order Generalized Integrator-Quadrature Signal Generator Using Fractional-Order Conformal Mapping Based Approach

The frequency-fixed second-order generalized integrator-based quadrature signal generator (FFSOGI-QSG) has been widely used in grid synchronization applications. The major limitations of using this technique are the unequal amplitudes of in-phase and quadrature-phase signals under grid frequency variation, which causes double-frequency oscillatory and offset errors in FFSOGI-based phase-locked loop output. To overcome the issues, in this letter, a modified complex analysis of FFSOGI-QSG using fractional-order-based conformal mapping approach has been presented, and an adaptive FFSOGI-QSG (AFFSOGI-QSG) is proposed. The proposed AFFSOGI-QSG can adapt itself to the grid frequency variations through the adjustment of single tuning parameter, i.e., fractional-order gain. The proposed structure is also found to inherit the simplicity of the FFSOGI-QSG without changing the order of the system while demonstrating an improved disturbance rejection capability under various grid disturbances. Performance of the proposed AFFSOGI-QSG is finally validated against some well-known SOGI-QSGs using numerical results obtained from the MATLAB and experimental results from the dSPACE DS1104 hardware.