Aiming at the problems of large power fluctuations and poor stability in photovoltaic and other new energy power generation systems, a step-up multiport converter (MPC) power converter that can simultaneously connect low-voltage photovoltaic cells, batteries, and loads (independent loads or power grids) is proposed in this manuscript. According to the possible operating conditions of the system, three modes of operating states are proposed and their working principles are explained in detail. Theoretical analysis based on different working modes has been presented and a hybrid modulation control method including pulse width modulation and phase shift modulation has been applied to realize energy transmission between photovoltaics, batteries, and power grids. A simulation model has been built in the PSIM environment to validate each working state of the system and mode switching function. System experiments were carried out on experimental platform using a dsPIC33FJ64GS606 digital microcontroller as the control center, and the experimental results successfully verified the system function and PWM+PSM control efficiency.