In Iraq the problem of electricity shutdown in the main supply still exists and the cuts may last for hours. This shutdown causes problems in lectures and students experiments in the colleges because all electrical devices are off. PV system is a good alternative source to overcome such a problem; therefore a stand-alone photovoltaic power system is presented in this paper to supply department laboratories to ensure power continuity. A stand-alone PV system is presented to supply three laboratories selected as a case study, these laboratories belong to the electronic and communications engineering department, Al-Nahrain University, Baghdad. The loads for these laboratories were calculated based on what are exists already from electrical devices assuming that they were fully on during work time. The Pvsyst6 software package is used for simulation purposes in this work.
One drawback of PVs is their low efficiency. As the PVs have a unique maximum Power Point for a specified irradiation level, there must be an effective method for extracting maximum power from the PV module to raise the efficiency. Conventional Perturbation and Observation (P&O) is a simple algorithm for maximum power point tracking (MPPT) but it suffers from oscillation during steady state conditions and is deviated from the maximum power point during slow and rapid irradiation level change. This paper presents a modified P&O by adding variation in PV current as a third in addition to the voltage and power variation parameters. This new algorithm is capable of eliminating the MPPT deviation. To increase the perturbation speed, a double step is taken as the tracking is deviated from the MPP. The modified P&O algorithm is used to control the duty cycle of DC-DC buck converter. The simulation shows that the modified P&O is faster than the conventional. The power loss due to oscillation before attaining the steady state is less for modified P&O. For slow irradiation level change (ramp up 600 to 1000 and ramp down 1000-800) W/m2, the modified P&O shows less tracking diverge. As the irradiation level changes rapidly from 800 to 200 W/m2, it's shown that the modified algorithm attains the steady state faster than the conventional P&O and the average efficiency increased by 4.34%.
In the photovoltaic (PV) system some problems happen causes a substantial reduction in power generation, one of these problems are Partial shading (PS), and (PS) happen when some obstacles block the sun's rays on the photovoltaic (PV) cells in a PV array, panel, or module in the PV system. Therefore, this paper suggests a method for reducing the effects of partial shading and increasing output power by reconfiguring a solar photovoltaic array using a new shade dispersion strategy (NSDS). The improvements achieved in maximum power point MPP when the shadows are angled or have a significant size, NSDS is also suitable for any photovoltaic array size. The simulation in this study was done by using MATLAB-software Simulink. Different shapes for shades were taken like Short and Wide (SW), Short and Narrow (SN), Long and Wide (LW), and Long and Narrow (LN) partial shading in addition to diagonal shade (DI). The suggested method was used on 6x3 photovoltaic panels to solve the partial shadow problem that cannot be solved by some previous shadow dispersion methods like so du Ku and stepwise. Also, it is applied to a 4x2 PV array which is considered difficult to spread the shadows to all PV panels because of its small size. Analysis and comparisons of the output characteristic were done using Cadmium telluride (CdTe) F-4112-3 PV panels and it was found that the increment in the generated power is more than 30% in comparison with the typical series-parallel (SP) for the SW and LW shades while it is more than 30% and 20% in comparison with the Total-Cross-Tied (TCT) configuration for the SW and LW shades respectively.
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