Electrical and Electronics

Nowadays, phasor measurement units are used in power networks for different purposes, such as Linearization of state estimation equations and speed improvement of controlling and protecting systems. Optimization of position and number of these equipments is considerably important because of their high costs. Effective parameters on position and number of PMUs optimization are: Network topology and zero injection buses in power networks. In this paper an objective function based on integer linear programming (ILP) is presented to determine the number and optimized position of PMUs, in order to complete observability of power systems. The effect of zero injection buses on objective function in power networks is evaluated. Simulation results are implemented in MATLAB software on the IEEE 14 buses system, and also 230kv and 400kv networks in Khouzestan province.

The four quadrant analog multiplier proposed by Rathor and Bhattacharya is reanalysed and modified in a different way for simple and low cost multiplication applications without using any reference waveforms. Verification of the feasibility of the circuit configuration is established by way of test results.

Improving distribution systems performance has become a significant issue as a result of large increase in electrical power consumption during recent years. The system operators aim to enhance efficiency of the distribution system in both dynamic and static modes. While DFACTS has commonly been employed to promote distribution systems capability in dynamic mode, this paper proposes a new static technique based on using interline dynamic voltage restorer (IDVR) to make a virtual smooth load duration curve for the adjacent loads having different load curves. Such a technique can be used for peak shaving and help the operator postpones the system expansion necessity. Furthermore, as a result of virtual smoothing load duration curve, voltage security margin and system reliability which are two important topics in static performance of the distribution systems will be enhanced. The simulation results demonstrate the suitability of the proposed technique.

Modern semiconductor switching devices are being utilized more and more in a wide range of applications These power electronics devices offer economical and reliable solutions to better manage and control the use of electric energy. However, the characteristics of most power electronics circuits, those semiconductor devices present nonlinear operational characteristics, which introduce contamination to voltage and current waveforms at the point of common coupling (PCC) of industrial loads. These devices, aggregated in thousands, have become the main polluters, the main distorters, of the modern power systems. At the Same time rapid development of semiconductor devices in power and control circuits, a new generation of equipments that help maintaining a good level of power quality, namely active power filters, has been developed. Theirs advantages over conventional means are more flexibility and very fast control response. The paper aim is to present the actual Power Quality Problems and solutions by active filters based on state-of-the-art power electronics technology and also their future prospects and directions.

Various phenomena occur in Air dielectric when a voltage is applied. When low voltage is applied, small current flows between the electrodes and the insulation retains its electrical properties. If the applied voltage is large, the current flowing through the insulation increases very sharply and an electrical breakdown occur. A strongly conducting spark formed during breakdown, practically produces a short circuit between the electrodes. The maximum voltage applied to the insulation at the moment of breakdown is called the breakdown voltage. For a uniform gap, the effect of humidity on the breakdown voltage is negligible. For non-uniform gaps such as rod-sphere, point-sphere like gaps the influence of humidity is found to be of significant. A correction procedure recommended by IEC is commonly used for converting the measured voltage or the test voltage from non-standard to standard reference atmosphere. So the result in analysis is then corrected into the standard reference conditions [in STP].

With the rapidly growing interest in smart grid technology, plug-in electric vehicles (PEVs) are expected to become more popular as low emission replacement for the petroleum based vehicles. Significant PEVs charging activities will mostly take place in customer’s premises, public or corporate car parks and electric charging stations. Therefore, utilities are concern about the possible detrimental impacts of these sizeable and unpredictable loads on the performance of distribution grids. Based on a recently proposed real-time smart load management (RT-SLM) control strategy, this paper focuses on the impact of uncoordinated and coordinated PEVs charging on substation transformer loading, system losses and voltage profile. Detailed simulations are performed on a 449 node smart grid system consisting of the modified IEEE 23 kV distribution system serving 4 charging stations and 22 low voltage residential networks populated with PEVs.

The paper presents an optimal fuzzy logic controller – controlled shunt active power filter (SAPF) used to compensate for harmonic distortion in three-phase systems. A optimal fuzzy logic controller based current controller strategy is used to regulate the filter current and hence ensure harmonic free supply current. The optimal adjustment of the membership functions and normalization gains are realized by using Ant Colony Optimization. Simulations results show the best dynamic behavior and performance control compared with traditional Fuzzy controller. as well as effective in reducing harmonic. The validity of the presented approach in harmonic mitigation is verified via simulation results of the proposed test system under different loading conditions.

A dual-band characteristic of multilayer aperture coupled microstrip log-periodic dipole antenna is studied. Further loading of patches is performed and its effects are investigated. It is a probe fed antenna for impedance matching with 50? coaxial cable. This antenna works well in the frequency range 4.3 GHz to 8.5 GHz. It is basically a low cost, light weight medium gain antenna, which is used for wireless communication. The multilayer microstrip antenna structure involves addition of multiple layers one over the other. When a microstrip antenna is stacked with a superstrate dielectric layer, its properties like resonance frequency, gain and bandwidth are changed, which may affect the system performance. With proper choice of the thickness of substrate and superstrate layers, significant increase in bandwidth and return loss can be achieved for practical applications. This structure uses stacked configuration of three different substrates. One dielectric substrate as a feeding plane, one dielectric substrate as aperture plane and a dielectric substrate as a LPDA. The simulated antenna yields -29.16 dB return loss with 33% bandwidth with a size of 24x26x6mm3. The proposed antennas present an excellent candidate for compact and low-cost microwave integrated systems.

A circuit which accepts two sinusoidal waveforms with phase difference Ø and provides two dc output voltages in which one dc output voltage is proportional to the quadrature component SinØ and the another is proportional to the in phase component CosØ, by position sampling of the reference quadrature waveforms, is described in this letter.

Increasing need for energy and limited fossil resources, increasing environmental pollution resulting from the burning of these resources, the effects of global warming and the greenhouse effects, acid rain and the need to balance the propagation of CO2, all call for the necessity of saving fossil resources and increased attention to the use of renewable energy sources. Wind energy is one of the main types of renewable energies that have always attracted the human mind so that man is always thinking of using this energy in the industry. The human had been used wind to move boats and sailing ships and windmills. In the current situation with regard to the above mentioned terms and economic justification of wind energy compared to other energy sources, wind energy seems to be vital and essential. This article firstly provides an introduction to the field installation locations of wind turbines in the power system and then various methods for predicting wind speed and power of wind farms are expressed. After that Modeling of wind powerhouses are explained. Finally, wind powerhouse modeling methods are fully described and the equations of each model are given.