Ahmed M. Ibrahim

LC compensators for power factor correction of nonlinear loads

A method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor, and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical examples.

Power conditioning using dynamic voltage restorers under different voltage sag types

Voltage sags can be symmetrical or unsymmetrical depending on the causes of the sag. At the present time, one of the most common procedures for mitigating voltage sags is by the use of dynamic voltage restorers (DVRs). By definition, a DVR is a controlled voltage source inserted between the network and a sensitive load through a booster transformer injecting voltage into the network in order to correct any disturbance affecting a sensitive load voltage. In this paper, modelling of DVR for voltage correction using MatLab software is presented. The performance of the device under different voltage sag types is described, where the voltage sag types are introduced using the different types of short-circuit faults included in the environment of the MatLab/Simulink package. The robustness of the proposed device is evaluated using the common voltage sag indices, while taking into account voltage and current unbalance percentages, where maintaining the total harmonic distortion percentage of the load voltage within a specified range is desired. Finally, several simulation results are shown in order to highlight that the DVR is capable of effective correction of the voltage sag while minimizing the grid voltage unbalance and distortion, regardless of the fault type.

Optimal sizing of C-type passive filters under non-sinusoidal conditions

Abstract In the literature, much attention has been focused on power system harmonics. One of its important effects is degradation of the load power factor. In this article, a C-type filter is used for reducing harmonic distortion, improving system performance, and compensating reactive power in order to improve the load power factor while taking into account economic considerations. Optimal sizing of the C-type filter parameters based on maximization of the load power factor as an objective function is determined. The total installation cost of the C-type filter and that of the conventional shunt (single-tuned) passive filter are comparatively evaluated. Background voltage and load current harmonics are taken into account. Recommendations defined in IEEE standards 519-1992 and 18-2002 are taken as the main constraints in this study. The presented design is tested using four numerical cases taken from previous publications, and the proposed filter results are compared with those of other published techniques. The results validate that the performance of the C-type passive filter as a low-pass filter is acceptable, especially in the case of lower short-circuit capacity systems. The C-type filter may achieve the same power factor with a lower total installation cost than a single-tuned passive filter.

Effect of connecting shunt capacitor on nonlinear load terminals

The use of terminal shunt capacitance has different effects on the displacement factor and distortion factor components of the power factor. These effects are considered for nonlinear loads with ideal supply, and also where the supply impedance exists but is small compared with the load impedance. Optimization of the displacement factor is found to result in reduction of the distortion factor to a minimum value.

Practical considerations regarding power factor for nonlinear loads

The choice of LC compensator may be constrained by the availability of manufacturers units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical examples.

Optimal sizing of different configurations of renewable distributed generation systems for a green building in Egypt

In this work, a comparative study of different configurations of renewable distributed generation (DG) for green building in Egypt is proposed. The considered DG systems are stand-alone photovoltaic (PV) system with an energy storage facility, wind system with an energy storage facility, a hybrid system of PV-Wind-Battery, with and without the use of diesel generators, where diesel generators are used for reliability and security requirements. A proper configuration that meets the considered buildings electric power demand with minimum cost over the lifetime of the system is proposed and discussed. The Hybrid Optimization Model for Multiple Energy Resources (HOMER) software is used to determine the optimal sizing of the considered renewable units. Additionally, due to the intermittent nature of these renewable resources, loss of power supply probability (LPSP) index has been taken in account while calculating the optimal sizing of the proposed DG system to assess the system reliability level.

Using solar photovoltaic at Egyptian airports: Opportunities and challenges

Using solar photovoltaic (PV) systems at airports is one of the complex tasks due to their impacts on pilots, air-traffic controllers, aircraft, and air navigation systems. Glare reflection, electromagnetic waves, and wildlife hazards are examples of the expected risks that may take place and potentially affect the safety of the air transportation system. On the other hand, airports have wide areas that could be used to install a solar PV project. In this paper, the possibility of using solar PV systems at Egyptian airports is presented and discussed, taking into account the security requirements as mandatory conditions for the airport environments. The expected problems and their possible solutions are discussed. Examples of international airports using solar PV systems are illustrated. Additionally, a pre-feasibility study for using a PV system at an Egyptian airport (Hurghada International Airport) is proposed. The results indicate that the Egyptian airports can play an effective role in producing renewable energy through the use of solar PV systems. Besides, economic and environmental benefits can be achieved under certain conditions.

Multiple-arm passive filters design based on different reactive power sharing approaches

In the literature, passive filters have been commonly used to mitigate the harmonic currents in industrial distribution systems because they are inexpensive, simple, and reliable. The aim of this paper is presenting different design methods for multiple-arm shunt passive filters based on various reactive power sharing approaches for an industrial distribution system of a petrochemical plant in Egypt. Eight techniques are presented, and their technical performance is assessed based on different indices such as power factor correction, filtering, voltage attenuation, distortion levels, and filter outage risks. Additionally, filters cost are considered in the comparison to decide the most economical technique. Modeling and simulation results of the case study are carried out in MATLAB and ETAP environments.

Assessment of a proposed hybrid photovoltaic array maximum power point tracking method

Abstract Photovoltaic arrays have limited conversion efficiency and thus, a maximum power point tracking technique is essential. This makes the maximum power point tracking (MPPT) require prior prediction of the mentioned point in spite of the undeniable changes in the environment. In this manuscript an introduction and assessment of the different techniques of MPPT is presented. The categorization scheme of the MPPT techniques is according to either the predefinition of operating points without system data update (offline methods) or continuous sampling of system variables, to update the PV module measurements (online methods). Whereas hybrid method is a combination of both. A number of techniques from each class were simulated in MATLAB/Simulink environment in order to compare their performance. Moreover, the hybrid method was simulated in two successive steps without pre-assumption of the output of the offline method. The results demonstrated the relevance of the hybrid method when applied to a photovoltaic system due to its good performance, fast response and less fluctuations, when subjected to sudden climatic changes.