Study on grid-connected PV inverter for grid synchronization based on virtual flux

When unbalanced fault occurs to power grid, it will distort sinusoidal PWM modulation and make grid tracking inaccurate etc. on grid-connected PV inverter. To solve these problems, an frequency-adaptive synchronization method based on Virtual Flux(VF)is proposed. It presents the virtues of VF estimation on voltage sensorlessly and Second Order Generalized Integrator(SOGI)without calculation of positive and negative sequences. VF can accurately estimate voltage oriented vector of PV inverters. SOGI can avoid delaying on computating negative sequence components. Frequency Locked Loop(FLL)can fast and accurately provide grid positive sequence frequency for VF estimation. The simulation and experiment results present the proposed method with synchronization tracking fast and accurately. © 2017, Editorial Board of Acta Energiae Solaris Sinica. All right reserved.