EFFECT OF LOADING ON THE PERFORMANCE OF STANDALONE SOLAR PHOTOVOLTAIC SYSTEMS

Abstract

ABSTRACT The present master’s thesis seeks to develop a better understanding of the conventional solar photovoltaic systems and simultaneously using that understanding to improve the performance and efficiency of the system. The present Photovoltaic systems consist of solar PV modules/arrays and a power electronic converter stage to step up or step down the DC voltage of the PV array. The power electronic converter is controlled by a Maximum Power Point Tracking controller which ensures that the system operates at the maximum power point and delivers maximum power at all times. The MPPT is a well researched and a well established technology and a rich literature exists of the various MPPT techniques. But there are limitations to MPPT which prevent the system to transfer the maximum power from the input to the output stage of the power electronic converter. The thesis focuses on the effect of output resistance of the converter stage (which in this case is a buck converter) on the power which has been tracked by the MPPT and is being transferred to the output of the converter. The output resistance is an integral part of the converter stage and the thesis aims to explore the effects on the response and the limits that the resistance puts on the power transfer from the input to the output stage covering the limitations of the MPPT technique. Accurate mathematical models are developed in order to explain the behavior of the buck converter connected to the PV system and using them to deduce the best practices in order to improve the efficiency and dynamics of the system. Finally the ideas developed are applied to the practical application of battery charging which is commonly used in modern standalone PV systems. The ideas developed in this thesis are generic in nature and can be extended to grid connected PV systems also (or in any renewable energy system for that matter) to control the power which is to be injected in the grid at any point in time.