PSASP_UPI can combine PSASP and Simulink to make up for the disadvantages of PSASP in PV modeling. However, PSASP cannot control the simulation step size of UP, which may resulting in incomplete utilization of Simulink model and even distortion. In view of the problem, a hybrid step size simulation method based on improved UP is proposed in this paper. The photovoltaic grid connected model is compiled into C code through Simulink Code and embedded to UP. The UP is improved in VC to calculate one hundred times step-by-step every time it receiving PSASP"s calculations at one time, saving each calculation result and passing the last calculation to the PSASP at the next time. The simulation example of CEPRI 36 nodes PV grid connected model built in PSASP shows that the improved UP hybrid step simulation method is more accurate and feasible compared with the fixed step size simulation method,
