Osama A. Mohammed

Practical experiences with an adaptive neural network short-term load forecasting system

An adaptive neural network based short-term electric load forecasting system is presented. The system is developed and implemented for Florida Power and Light Company (FPL). Practical experiences with the system are discussed. The system accounts for seasonal and daily characteristics, as well as abnormal conditions such as cold fronts, heat waves, holidays and other conditions. It is capable of forecasting load with a lead time of one hour to seven days. The adaptive mechanism is used to train the neural networks when on-line. The results indicate that the load forecasting system presented gives robust and more accurate forecasts and allows greater adaptability to sudden climatic changes compared with statistical methods. The system is portable and can be modified to suit the requirements of other utility companies. >

Utilizing genetic algorithms for the optimal design of electromagnetic devices

A new technique for the design optimization of electromagnetic devices that adopts the genetic algorithms (GAs) as the search method is presented. The method is applied to the optimization of the shape of a pole face in an electric motor. The electromagnetic analysis of the devices implemented is performed using 2D finite elements. The results show an excellent promise and potential of using GAs as an efficient technique for the optimal design problem. >

Laboratory-Based Smart Power System, Part I: Design and System Development

This paper presents the design and development of a hardware-based laboratory smart grid test-bed. This system is developed at the Energy Systems Research Laboratory, Florida International University. The hardware/software based system includes implementation of control strategies for generating stations, and power transfer to programmable loads in a laboratory scale of up to 35 kilowatts in ac power and 36 kW in renewable sources and energy storages. Appropriate software was developed to monitor all system parameters as well as operate and control the various interconnected components in varying connectivity architectures. The interconnection of alternate energy such as wind emulators, PV arrays, and fuel cell emulators are implemented, studied and integrated into this system. Educational experiences were drawn during the design and system development of this laboratory-based smart grid. The real-time operation and analysis capability provides a platform for investigation of many challenging aspects of a real smart power system. The design, development, and hardware setup of this laboratory is presented here in Part I of this paper. This includes component development, hardware implementation, and control and communication capabilities. Part II of the paper presents the implementation of the monitoring, control, and protection system of the whole setup with detailed experimental and simulation results.

A phase variable model of brushless dc motors based on finite element analysis and its coupling with external circuits

This paper presents a fast and accurate brushless dc motor (BLDC) phase variable model for drive system simulations. The developed model was built based on nonlinear transient finite-element analysis to obtain the inductances, back electromotive force as well as the cogging torque. The model was implemented in a Simulink environment through the creation of an adjustable inductance component to account for the dependence of inductances on rotor position. Since no dq model for BLDC actually exists, the significance of this work is that it provides an accurate equivalent circuit model of BLDC motors for utilization in simulation environments. Using the developed model, the sensorless control and the torque ripple control issues were investigated and the simulation results show its practical effectiveness.

Physical modeling of PM synchronous motors for integrated coupling with Machine drives

A physical phase variable model for permanent magnet synchronous motors is proposed. This model is initiated to pursue an accurate and fast motor model for integrated motor drive simulation. Since the full finite element (FE) model may be time consuming and the direct- and quadratic-axis (dq)-model is inaccurate, the proposed physical phase variable model eliminates these deficiencies. The proposed model is a circuit model with inductance, back electromotive force (EMF), and cogging torque calculated from nonliner transient FE solutions. The main characteristics of this model are that it is as accurate as the full FE model while giving fast computational results. The Simulink implementation of the proposed model is studied. Comparisons of the proposed model with the full FE model and the dq-model are performed. The results verify the validity of the proposed model and show its practical superiority in drives applications.

Three Dimensional Finite Element Vector Potential Formulation of Magnetic Fields in Electrical Apparatus

The three dimensional magnetic vector potential (m.v.p.) variational formulation for magnetostatic field problems, with ideal current carrying conductors is given. An appropriate functional was chosen for this class of problems. Variational techniques were used to prove that the chosen functional is stationary whenever the partial differential equations, the Neumann, and the specified Dirichlet boundary conditions are satisfied, within and on the boundary of the volume under investigation, respectively. The finite element method is used to obtain a numerical approximation of the stationary point of the functional. A three dimensional discretization scheme involving first order tetrahedral elements was used to implement the method. The m. v. p. at each of the four tetrahedral vertices (nodes) has three degrees of freedom (or components) in the x, y and z directions due to the three dimensional nature of the field.

Real-Time Energy Management Algorithm for Mitigation of Pulse Loads in Hybrid Microgrids

This paper presents a real-time energy management algorithm for hybrid ac/dc microgrids involving sustainable energy and hybrid energy storage. This hybrid storage system consists of super capacitors (SC) for ultra-fast load matching beside lithium-ion batteries for relatively long term load buffering. The energy management algorithm aims mainly at managing the energy within the system such that the effect of pulsed (short duration) loads on the power system stability is minimized. Moreover, an average annual saving of around 7% is achieved by shifting loads to off-peak hours. The expected energy needed during a future peak, the time of its occurrence and the current state of charge of both elements of the hybrid storage system are all examples of the inputs to the algorithm. A nonlinear regression technique is used to obtain mathematical models for the uncertain quantities including load and sustainable energy curves. The results show a significant improvement for the system in terms of voltage and power stability by applying the proposed algorithm.

Design optimization of electrical machines using genetic algorithms

The application of genetic algorithms (GAs) to the design optimization of electromagnetic devices is presented in detail. The method is demonstrated on a magnetizer by optimizing its pole face to obtain the desired magnetic flux density distribution. The shape of the pole face is constructed from the control points by means of uniform nonrational b-splines. >

Modeling and Characterization of Induction Motor Internal Faults Using Finite-Element and Discrete Wavelet Transforms

This paper examines the behavior of three phase induction motors with internal fault conditions under sinusoidal supply voltages. Two types of induction machine internal faults are investigated, rotor broken bar, and stator shorted turns faults. Early detection and diagnosis of these faults are desirable for condition assessment, maintenance schedule and improved operational efficiency of induction motors. The terminal behavior of the induction motor was obtained by coupling the induction motor transient FE model and external electric circuit. Such a model would allow efficient representation of the induction machine with internal faults. A discrete wavelet transform (DWT) was then used to extract the different harmonic components of the stator currents. The key advantages of the DWT are its ability to provide a local representation of the nonstationary current signals for normal and faulty operating conditions.This paper examines the behavior of three phase induction motors with internal fault conditions under sinusoidal and nonsinusoidal supply. This includes rotor broken bar,and stator faults. The terminal behavior of the induction motor was investigated by coupling the induction motor FE model and external circuit. Discrete wavelet transform (DWT)was then used to study the harmonic behavior of the stator currents.

Internal Short Circuit Fault Diagnosis for PM Machines Using FE-Based Phase Variable Model and Wavelets Analysis

This paper presents a procedure using the finite-element (FE)-based phase variable model combined with wavelet analysis to facilitate the fault diagnostic study for permanent magnet machines with internal short circuit faults. Our efforts are dedicated to the aspects of fault modeling and fault extraction. The FE-based phase variable model is developed to describe the PM machine with internal short circuit faults. This model is built with the parameters [inductances and back Electromotive Force (EMF)] obtained from FE computations of the machine with the same type of fault. The developed model has two features. It includes the detailed information of the fault including the location of the shorted turns and the number of turns involved. It keeps the accuracy of the FE model by taking only a fraction of time needed by FE operation. This is particularly desired for diagnosing faults in machines connected to a control circuit. The wavelet transform is used to perform machine current/voltage signature analysis. Excellent results were obtained providing information that would not be otherwise available except by measurement