Objective  In order to improve the charging efficiency, safety and speed of mobile online photovoltaic (PV) charging devices, a type of mobile online PV charging maximum power point tracking (MPPT) technology based on the variable step size disturbance approximation method is proposed.

  Methods  By combining a high-frequency inverter and isolation transformer as the MPPT carrier, the former DC/DC structure of traditional PV charging topology devices is removed, charging control is combined with the pulse modulation of the high-frequency inverter, and the three functions of high-frequency isolation, MPPT tracking and charging control are finally integrated into one. At the same time, according to the different states of the remaining power battery, a three-stage charging control strategy is proposed.

  Results  Simulation analysis and field test results show that this device can track the maximum power points of PV panels stably when their illumination intensity changes, and the battery can be charged efficiently in the three stages according to the set charging scheme. The measured overall charging efficiency can be maintained above 92%.

  Conclusion  This device and control strategy can improve PV panel-to-battery charging efficiency and meet the requirements of fast and safe charging.