A simulation system for the grid-connected photovoltaic(PV)power generation system is developed based on the MATLAB/Simulink and the physical mechanism of the PV cells. The influence of the grid-connected PV power generation system on the comprehensive load characteristic of distribution network is studied. And several equivalent models available to the PV power generation system are analyzed and compared. On this basis

a new equivalent model based on transfer functions for the PV power generation system is proposed. The model has a simple structure

less parameters

and can effectively describe the output limit of PV power generation system. At the same time

it is easy to implement in the power system simulation software. A generalized comprehensive load model is developed by paralleling the conventional comprehensive load model with the new equivalent model to describe the characteristic of the comprehensive load containing PV power generation systems. Simulation results show that the generalized comprehensive load model has good generalization ability and stable identification parameters

while meeting the need of engineering simulation.This work is supported by National Natural Science Foundation of China(No. 51277055)and National Basic Research Program of China(973 Program)(No. 2012CB215106).