A new technique for stand-alone photovoltaic energy management system

This paper proposes the new technique for stand-alone PV (Photovoltaic) energy management system. The proposed technique utilizes the voltage controlled MPPT (Maximum Power Point Tracking) and the level-shifted PWM modulation. The MPPT tracks the maximum power point (MPP) of the PV by tracking the PV voltage. Then the output signal of the voltage controlled MPPT is modulated by the level-shifted PWM modulation. Each level of the level-shifted PWM is used for a particular energy storage element, for example, the highest level is used for charging the battery, whereas the lowest level is used for discharging the battery. The proposed technique makes the PV produce the power at its MPP while the load can draw the power from the system without interruption. The proposed system would have higher reliability, higher efficiency, and longer battery life-time than the conventional system. The design technique is presented in this paper. Then the proposed idea is verified by a 120-W experimental system.