M.H. Shwehdi

Probabilistic assessment of photovoltaic (PV) generation systems

The sizing of photovoltaic (PV) power systems for remote offshore loads has been the concern of end users. This is because of the space constraints associated with the application and the expensive cost of panels and batteries. This paper evaluates the design of the PV system using three probabilistic methods. One is considering fixed days of battery back up and recharge and the other is based on loss of load probability (LOLP). The third is based on Markov chain modeling. LOLP distinctly shows reduction in the number of panels and size of batteries while providing a detailed view of the system performance.

A power line data communication interface using spread spectrum technology in home automation

Building automation technology is rapidly developing towards more reliable communication systems, devices that control electronic equipment. This equipment, if controlled, leads to efficient energy management, and savings on the monthly electricity bill. Power line communication (PLC) has been one of the dreams of the electronics industry for decades, especially for building automation. It is the purpose of this paper to demonstrate communication methods among electronic control devices through an AC power line carrier within the buildings for more efficient energy control. The paper outlines methods of communication over a power line, namely the X-10 and CE bus. It also introduces the spread spectrum technology as to increase speed to 100-150 times faster than the X-10 system. The power line carrier has tremendous applications in the field of building automation. The paper presents an attempt to realize a smart house concept, so called, in which all home electronic devices from a coffee maker to a water heater microwave to chaos robots will be utilized by an intelligent network whenever one wishes to do so. The designed system may be applied very profitably to help in energy management for both customer and utility.

Speed control of a three-phase induction motor based on robust optimal preview control theory

A synthesized method for speed control of a three-phase induction motor (IM) based on optimal preview control system theory is implemented in this article. An IM model comprises three-input variables and three-output variables that coincide with the synchronous reference frame that is implemented using the vector method. The input variables of this model are the stator angular frequency and the two components of the stator space voltage vector, whereas the output variables are the rotor angular speed and the two components of the stator space flux linkage. The objective of the synthesized control system is to achieve motor speed control, field orientation control, and constant flux control. A novel error system is derived and introduced into the control law to increase the robustness of the system. The preview feed-forward controller, which includes the desired and disturbance signals, is used to improve the transient response of the system. A space vector pulse-width modulation (PWM) control technique for voltage source-fed IM is prepared for microprocessor-based control. Spectral analysis of the output voltage is evaluated to predict the effect of the proposed space vector modulation technique on the dynamic performance of the IM. The optimal preview controlled system is implemented, and its applicability and robustness are demonstrated by computer simulation and experimental results.

Photoacoustic spectrometry for trace gas analysis and leak detection using different cell geometries

A photoacoustic (PA) spectrometer with high selectivity and sensitivity has been developed for trace gas analysis and for the detection of gas leak at part per trillion by volume (pptV) level. This PA system comprises of a resonant photoacoustic cell, a pulsed line tunable CO(2) laser as an excitation source and a sensitive electret microphone as a photoacoustic detector with an option to trigger the safety alarm system for early warning of gas leaks. In this work, three resonant PA cells with various geometries have been developed at our laboratory for the detection of photoacoustic signal using pulsed laser system and their comparative performance have been studied. As a special application of this PA system, the detection of sulfur hexa fluoride (SF(6)) gas using these three cells has been carried out for optimizing the sensitivity. Besides this, our PA system can very well be applied for pollution monitoring and detection of hazardous gases in a noisy environment.

A microprocessor-based digital wattmeter system design

A Digital Telewattmeter System (DTS) has been designed, developed and its prototype real time clock board has been tested according to a sponsoring agencys (utilities, manufacturing company, etc.) specifications. The DTS is a device that measures electrical energy consumption and reports via telephone. At a remote location, a microprocessor controlled wattmeter will sense current, voltage and time and convert this into kilowatt hours. For customer convenience, this information is displayed continuously. Every month, the remote location is polled by a main computer and the actual current value of kilowatt hours is read for its use by the billing department. This paper deals with the designing, assembling, and the operation of the DTS as an innovative design and its use as a load management device. Test results and specifications of the DTS showed that its basic properties conform with other available similar products and has more features.

Thunderstorm distribution and frequency in Saudi Arabia

A new average annual thunder day map for Saudi Arabia is presented. Based on this map, the distribution of thunderstorms over Saudi Arabia is analysed in terms of the factors related to the lightning performance of transmission lines such as thunderstorm days per year (Td/yr). Lightning activity continues for the present to be represented by thunderstorm frequency, which is routinely recorded at meteorological observation sites. Thunderstorm occurrence at a particular location is usually expressed as the number of days in a calendar year when thunder was heard, averaged over several years. This paper examines thunderstorm days in different areas of Saudi Arabia and specifically those areas where lightning strikes are more frequent; for this purpose, the software ArcGIS is used to produce contour maps which demonstrate areas of concern in Saudi Arabia in the period 1985–2003. Establishing the annual and seasonal Td/yr for Saudi Arabia enables transmission and distribution line engineers to calculate and better design a lightning protection system. Maps of thunder days/year (Td/yr) were constructed on the basis of the database records available on lightning incidence in Saudi Arabia at the Presidency of Meteorology and Environment (PME) (http://www.pme.gov.sa/). Annual thunderstorms are most frequent over the southwestern parts of the country, and generally decrease towards the west and east. Due to its low latitude and less temporal change, the west coast of the Red Sea recorded the lowest Td/yr. A secondary maximum Td/yr is apparent in the southeast to central part of the country. Thunderstorm frequency does not, in general, appear to vary in any consistent way with rainfall. There appears to be no evidence of any widespread temporal trend in thunderstorm frequency. The southern region in general, and especially the cities of Abha, Taif and Al-Baha, has shown greater numbers of thunderstorm days all year round. Similarly, this variation did show higher frequency throughout the year. The development of lightning incidence and the counting of Td/yr, as well as the establishment of annual and seasonal lightning maps of Saudi Arabia, are initiating a new era of producing and archiving thunderstorm maps and data records which serve the PME, the utilities, industry and the public.

Solving the harmonic problems produced from the use of adjustable speed drives in industrial oil pumping field

This paper investigates the application of different ASD models, 6-pulse, 12-pulse, and 18-pulse, in offshore oil field industry. The paper studies the harmonic distortion levels produced by each type and checks which one violates the IEEE-519 limits. The study considers the worst configuration of the system, that is when only one main transformer (50 MVA 115-13.8 kV) is supplying the whole system. A frequency scan analysis is conducted to study the effect of the submarine cables shunt capacitance in introducing resonance in the system. The effect of phase shift of the transformer is investigated and used as a method to reduce the harmonic distortion.

Voltage stability estimation and prediction using neural network

This paper proposes a neural network-based method for on-line voltage stability estimation, prediction and monitoring at each power system load bus. The training of the radial basis function neural network (RBFNN) was accomplished by using load flow voltage magnitude and phase as input information, and fast indicators of voltage stability information covering the whole power system and evaluated at each individual bus as output layer information. The generalization capability of the designed networks under a large number of random operation conditions and for several power systems has been tested. Fast performance, accurate evaluation and good prediction for the voltage stability margin have been obtained. Results of tests conducted on standard IEEE 14-bus test system are presented and discussed.

Reliable maps of lightning thunderstorms for Saudi Arabia

The main objective of this research is to develop reliable maps of isokeraunic level (thunderdays/year, TD) for the country on annual and seasonal bases. New annual thunder day maps for Saudi Arabia are presented. The results in this paper are based on data and records of thunderstorm incidences in Saudi Arabia recorded by the Presidency of Metrology and Environment. These are compared with data from power system fault records and with NASA satellite data. These new maps indicate the location, frequency, and intensity of thunderstorms. Such information is useful for engineers concerned with the design and operation of transmission and distribution lines in the country, and for the more general design of lightning protection systems. Thunderstorms are most frequent in the southwest mountains in the country, reaching a maximum TD of 97; the average TD for the whole country is 26.

Corona wind velocity: parametric approach

The paper presents briefly a laser Doppler Velocimetry that was designed and constructed to measure the corona wind velocity. It details the link of the discharge system geometrical parameters with the system variables such as, the applied voltage, the ion mobility, with the discharge medium characteristic such as permittivity and mass density, along with the measuring point position within the discharge system. A point to plane testing discharge system was constructed allowing the flow of air to pass, circulate and return to its initial status, when corona is initiated by the alternating applied voltage on the stressed electrode. Based on the experimental results, dimensional analysis is used to form a mathematical relation that estimates the corona wind velocity as function of the system geometrical parameters, the system electrical variables, and the discharge medium physical parameters. The developed relation was found to be sound when used within the range of the constructed geometrical system parameters. Research work is undergoing considering broader parameter ranges and for other electrode systems in order to investigate the validity and the generalization of the deduced relation.