Aiming at the lack of modeling of large-scale centralized photovoltaic power generation systems in the study of the existing multi-inverter grid-connected systems

the Norton and Thevenin equivalent methods are used for equivalent modeling of power generation units

boost transformers

transmission lines and power grid for centralized photovoltaic grid-connected systems

and the impedance model of grid-connected power system is established. On this basis

the relationship between harmonics and system impedances is derived

and the frequency domain analysis is used to study the amplification mechanism of harmonics in the transmission process. The influence of equivalent power coefficient and equivalent coupling admittance of the impedance model on harmonic current amplification factor is given by the simulation results

which provides a theoretical basis for the subsequent research on harmonic suppression strategies.