25 Maximizing Output Power of Photovoltaic Power System with Maximum Power Point Tracking via Innovation of Low Loss Buck Converter and Sun Tracking

This paper, the design and experimental implementation of a low cost and high efficiency photovoltaic system based on a new quasi-square wave resonant switch (QSW) dc-dc soft-switching buck converter operating in discontinuous conduction mode (DCM) that controlled by a maximum power point tracking (MPPT) was proposed. Due to the power switch of the converter in the proposed system was turned-on and turned-off by softswitching technique. The power circuit implementation in the proposed system is very simple and it was comparable with the conventional QSW converter because it required only one power switching device and one inductor coil. Analytical model was built from the PV system and the developed QSW dc-dc buck converter. It was verified by the basis of the normalized state-plane trajectory method and the principle of energy conservation. The control circuit of the proposed system was realized by a DSC single-chip microcontroller with MC56F8323EVM based on the P&O method. The MPPT was implemented in a software program with a self-tuning function, which automatically adjusts the array reference voltage and voltage step size to achieve the maximum power tracking under changing irradiations. A proportional integral (PI) controller was used in the forward path for adjusting the duty cycle of converter.. From the simulation and experimental results, the overall efficiency of the MPP-tracking was about 97.543%. In additional, at same 60 Watts of output power.