Low cost digital-analog hybrid controlled photovoltaic battery charger based on interleaved BCM boost converter and improved MPPT algorithm

Low cost digital-analog hybrid control for photovoltaic battery charger is studied in this paper. An interleaved boost circuit is used as the power converter. The interleaving control for the interleaved boost is realized with an analog IC. The change-discharge strategy for battery and an improved maximum power point tracking (MPPT) algorithm are realized with a low performance digital control chip. The digital control chip and the analog IC are connected through a conversion interface. The total cost of controller is reduced and the program work is also reduced. The maximum operation frequency under full load is up to 400kHz with this low cost control circuit. Variable step size incremental conductance method is introduced in this paper. By analyzing the disadvantage of this method, an improved method is proposed and the tracking oscillation in harsh environment is eliminated. The conventional method and the improved method were both simulated and compared with Matlab. Finally, a 120W experimental prototype with surface mounted inductors was built up to verify the theoretical analysis.