07-12-2012, 11:34 AM
Solar Photovoltaic panel charging control with Maximum Power Point tracking algorithm for optimum charging of Lead Acid Storage batteries.
ABSTRACT
A maximum power point tracker (or MPPT) is a high efficiency DC to DC converter which functions as an optimal electrical load for a photovoltaic (PV) cell, most commonly for a solar panel or array, and converts
the power to a voltage or current level which is more suitable to
whatever load the system is designed to drive. PV cells have a single operating point where the values of the current (I) and Voltage (V) of the cell result in a maximum power output. These values correspond to a particular resistance, which is equal to V/I as specified by
Ohm's Law. A PV cell has an exponential relationship between current and voltage, and the maximum power point (MPP) occurs at the knee of the curve, where the resistance is equal to the negative of the differential resistance (V/I = -dV/dI). Maximum power point trackers
utilize some type of control circuit or logic to search for this point and thus to allow the converter circuit to extract the maximum power available from a cell. MPPT charge controllers are used to extract the maximum power from a PV array. The benefits of MPPT regulators are greatest during cold weather, on cloudy or hazy days or when the battery is deeply discharged. Solar MPPTs can also be used to drive motors directly from solar panels. The benefits seen are huge, especially if the motor load is continuously changing. The MPPT will switch the power to match the varying resistance.