Hill climbing digital control algorithm for maximum power point tracking of photovoltaic arrays.

摘要

The photovoltaic energy obtained from solar modules varies with external conditions like seasonal changes, time of day, geographical location on the earth and associated factors like irradiance, temperature, absolute air mass and solar angle of incidence. Hence, it is necessary to maximize the output power available from the photovoltaic (PV) module. Several MPPT (Maximum Power Point Tracking) techniques are used. In this thesis, we propose a novel method and control algorithm for MPPT.; We first study in depth the electrical model of a PV cell and compare this with that simulated by a commercially available Solar Array Simulator. Our model of a PV module is provided by the behavior described by Sandia parameters, ideal equations and a novel modified ideal equation. We then critically examine the MPPT algorithm and circuit used in a previous thesis and suggest improvements necessary for successful operation of the control system. We also test the circuit components used in a previous thesis to learn about what was not made right in the previously designed system and suggest improvements or modifications. The MPPT algorithm finally proposed in this thesis uses a combination of two modes, namely "Wait for Perturbation" and "Climb the Hill." In the new algorithm, firstly, maximum power point is attained for a particular irradiance value and then the system constantly monitors for any perturbation. When the system is found to leave the maximum power point due to variation in irradiance or other causes, the algorithm jumps into action. The present value of the output power on the power "hill" (which is one of all possible values of the output power for the allowable conditions) determines the direction to the new position of the maximum power point. The circuit then begins the "Climbing the Hill" steps using the "increase in load resistance" operation until the maximum power point is re-obtained.