iosr-JEEE   Volume-8 ~ Issue-2

Abstract: Photovoltaic (PV) power systems have been widely applied in commercial and domestic facilities. Electrical Energy Storage (EES) systems are mandatory in standalone PV systems for continuous power supply. In this paper the efficiency and robustness enhancement methods for PV systems under partial shading have been investigated. Partial shading due to moving clouds and shadows of nearby obstacles on the PV module array causes significant efficiency degradation, since shaded and non-shaded PV modules have large discrepancy in their maximum power points. Use of by-pass diodes for each PV module may mitigate the negative effect from partial shading. However, this method alone may still face severe energy efficiency degradation caused by the energy loss due to parasitic effects in the EES elements under variable incoming power from the PV modules. Hence, this paper investigates the effect of shading on photovoltaic cells.

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Abstract: Use of by-pass diodes for each PV module may mitigate the negative effect from partial shading. However, this method alone may still face severe energy efficiency degradation caused by the energy loss due to parasitic effects in the EES elements under variable incoming power from the PV modules. Hence, this paper proposes methods to enhance the PV system efficiency and robustness under partial shading. Here, by-pass diodes are connected parallel to a number of solar cells. Under normal operating conditions, the diodes are blocked compared to the voltage generated by the cells. When shading occurs, the reverse of the voltage was observed in that specific section which enables the by-pass diode in parallel to conduct the current. It was observed that; the current of the un-shaded flows through the by-pass diode and the power/voltage characteristics shows a second local maximum. Also, the shaded cell was only loaded with that fraction of power produced by the un-shaded cells of that section.

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Abstract: Renewable energy sources like solar and fuel cells are emerging as a promising supplementary power sources due to their merits of cleanness, high efficiency, and high reliability. But the output levels of these are low. An isolated bidirectional full-bridge dc–dc converter can be used for interfacing battery to the system. Because of the presence of leakage inductance of the isolation transformer voltage spikes are produced. An isolated bidirectional converter with a flyback snubber can reduce voltage spike caused by the current difference between the current-fed inductor and leakage inductance of the isolation transformer. In this work an isolated bidirectional full bridge dc-dc converter with and without flyback snubber is simulated using MATLAB SIMULINK Tool and compared the simulation results . Also implemented the hardware of boost mode operation of the same converter with input as 10V and compared it with the simulation results.

Keywords: Clamping capacitor, Flyback snubber, , Isolated bidirectional Dc-Dc converter, Leakage inductance, Voltage spikes

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