ABSTRACT
The purpose of maximum power point tracking (MPPT) is to match the current and voltage characteristics of the load to the PV module's maximum power point, automatically for any given illumination. There are several ways to accomplish MPPT. One way is to have a large database containing the PV panel's output voltage and current values at different illumination levels at Te maximum power point stored in the MPPT module. A second way to accomplish MPPT is to use a dynamic system that tracks the maximum power point continuously. This system tracks the maximum power point by use of short-term memory. In this method the relative maximum power level of the PV module is dynamically tracked. This control method will constantly move the operational power point around the maximum power point. This method has several advantages and was chosen by the PEARL research team. The PEARL research team designed and developed a digital (microprocessor controlled), as well as an analog version of a novel MPPT battery charging controller. Both systems use a unique dynamic-relative-maximum algorithm. A high power buck switcher was used to alter the apparent impedance of the load as seen by the PV module. The power from the module is calculated using analog circuitry and is then digitized for the microprocessor. The micro-controller then increases and decreases the PV module output voltage to maximize the power delivered by the module. Both systems obtained efficiencies of approximately 94%.
