A new switching charger for photovoltaic power system by soft-switching

This paper presents an intelligent control method for the maximum power point tracking(MPPT) of a photovoltaic powered water pump system for long tailed boat in Thailand by using DC-DC boost converter as switching charger, this system consisted of a solar array, a switching battery charger based on boost DC-DC converter, a battery and small water pump. The solar array had a specification as 75 watts of output power, 14-18 volts of output DC voltage, and 3A of output DC current. The output power of solar array was the input power for boost DC-DC converter as the switching charger. To control the boost converter, the pulse width modulation (PWM) was applied. The water pump was controlled by a microcontroller PIC 186627. When the water amount reaches the specified level, a sensor will send the signal to the microcontroller for controlling a relay to drive a motor in the water pump. To verify the proposed pump system, the prototype of water pump for small boat was built to experiment. From the results, to stabilize the output voltage of the boost DC-DC charger at 25.6 volts, the duty ratio was controlled at 35-50% with 100 kHz of switching frequency. The battery having rated voltage as 24 volts and rated current as 7 amps per hour was used in the system.