Maximum power point tracking controlled boost converter design for battery charger

 MPPT controlled DC-DC converters are crucial in power systems which are supplied by PV panels. They extract maximum available power of PV panel irrespective of variable environmental conditions; thus increase the conversion efficiency of PV panels. In addition, especially in stand-alone PV system, they can control charging process of rechargable batteries in a way that reduces charging time and increases cycle life of battery. In this reseach, the design of MPPT controlled DC-DC boost converter and its application as solar battery charger are presented. In this design, in order to meet the requirments of MPPT tracker and battery charger systems, an expanded MPPT algorithm is developed. The developed algorithm comprises Incremental conductance MPPT algorithm which is expanded to incorporate CC-CV charging algorithm. This developed algorithm adjusts directly the duty cycle of boost converter, which operates in 25 KHz,in order to control the operating point of PV panel. Depending on developed algorithm, the designed MPPT boost converter charges battery through three stages. These stages are pre-charging, in MPPT-CC charging and CV charging stages. Designed system operates as MPPT controller in MPPT-CC charging stages; whereas operates as charger controller in pre-charging and CV charging stages. The implementation of CV charging stage is performed by using voltage regulating device which is Zener diode. In addition, the designed system provides end of charge detection method which depends on measuring PV power instead of battery charging current. The functionality and performance of designed, MPPT controlled DC-DC boost converter are simulated and validated by SIMULINK-MATLAB program.The simulation process is performed under two different cases of environmental conditions which are standard test condition (STC) and variable environmental condition.The simulation results show the proper operation of designed system in the three stages of charging process. They show that the designed system has an averaged tracking efficiency of 99.444% over the simulated variable levels of irradiance for MPPT-CC charging, and an averaged conversion efficiency of 96,66%, 99,28%, and 98,3% over the simulated variable levels of irradiance for pre-charging, MPPT-CC charging and CV charging stages respectively. In addition, the designed system ensures input current ripples and output voltage ripples of 10mA and 100µV repectively, which are within the allowable limits of this designed. These simulation results prove the proper functionality and high performance of designed, MPPT controlled DC-DC boost converter as MPPT controller and charge controller.