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Proposed Methods to Increase the Output Efficiency of a Photovoltaic (PV) System

Keywords: photovoltaic , MPPT , configuration , optimum power , switching

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Lately, the use of solar energy has seen considerable development.Transformation in electric energy is one of its applications which attracts considerableinterest, owing to the fact that it makes it possible to solve a major problem in isolatedcities that lack electrical supply networks. For solar energy use, the current drawbackremains its high cost. This problem can be resolved through different improvements interms of power production. For that, different axis of research can be explored [1-3].Over the past few years, solar cells arrays (SCA) have been connected to various loads in adirect coupled method. A PV module can produce the power at a point, called an operatingpoint, anywhere on the current- voltage (I-V) curve. The coordinates of the Operating pointare the operating voltage and current. There is a unique point near the knee of the I-Vcurve, called a maximum power point (MPP), at which the module operates with themaximum efficiency and produces the maximum output power. The point of maximumpower is the desired operating point for a PV array to obtain maximum efficiency. A PVarray is usually oversized to compensate for a low power yield during winter months. Thismismatching between a PV module and a load requires further over-sizing of the PV arrayand thus increases the overall system cost [3-5]. To mitigate this problem, differentmethods have been developed [6-12]. A maximum power point tracker (MPPT) can be usedto maintain the PV module’s operating point at the MPP. The system in a direct coupledmethod cannot always operate at maximum power point (MPP) of the solar array when theload, irradiance or temperature changes. A PV-load coupling system should be able tomaximize the energy output of the PV generator, which should operate always at itsmaximum power point (MPP) in order to achieve maximum global efficiency. Some authorshave supported the direct coupling between the PV generator and the load [2-3]. Severalmethods and algorithms to track the maximum power point have been developed [2-12].We focused our effort on improving the matching between PV sources and loads throughthe development of new performing methods. In this paper, a rapid approach for peakpower tracking is proposed. The system PV generator - load is optimized, when the workingpoint in direct coupling is quite near the MPP of the PV generator, so that the globalefficiency of the system is acceptable. Another method is proposed. It is based onreconfiguring on-line the SCA by changing the connections between different modules in order to minimize the losses due to load and ope


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