Abstract 

The paper deals with techniques which use the predictive concepts in order to obtain both the pulse width modulation strategy of a voltage fed inverter and the predictive control of the induction motor drive. Concerning the PWM technique, it is applied for the case when the inverter supplies an induction motor, the reference values of the currents being obtained from a classical vector control scheme. The described technique is then simulated and the waveforms are compared with ones obtained with preset currents (bang-bang) pulse width modulation, as the behavior of the two strategies is similar. The results are also compared with the ones resulted when a classical DTC controls the induction motor, as the both determine, during each sampling period, the next stator voltage phasor, but considering different criteria. Concerning the control of the drive, the vector control and the predictive control of the induction motor are compared. For the vector control, the rotor flux oriented one is pointed out, with highlight on the voltage source inverter type. A simple (and practical) method for avoiding the influences of the stator resistance variations when a voltage source inverter is used is presented, based on proper simulation models. For the predictive control of the induction motor, a sensorless diagram is considered. Finally, further actions are proposed for the work continuation.

Abstract

The control circuit of an Electronically Controlled Capacitor (ECC) for the optimization of the Single Phase Induction Motor (SPIM) with auxiliary winding is presented. The control circuit is based on a fixed value AC capacitor within a full bidirectional switches bridge PWM controlled at much higher than line frequency (in kHz range). The power bridge circuit and its embedded pulse driver circuit are presented within the theoretical sections of the paper. In the experimental section, using a small electric motors test bench and a two speed SPIM with auxiliary winding, are analyzed the main influences of the pulse drive circuit over the ECC. Firstly, being considered that the optimum is reached at the maximum motor torque, the optimal pulses frequency has been established around 4 kHz. Secondly, the switches over-voltages at the ommutations moments being a serious drawback of the ECC, are analyzed the influence of the fixed capacitor value and the dead time of the pulse shape over the MOS-FET power transistors of the bidirectional switches over-voltages. The overvoltages diminish as both the capacitor value and the dead time diminish. More than that, in contrast with some authors, there are no disadvantages as dead time became zero. These issues are the main contributions of this paper.

Abstract

The main objective of this paper is represented by analysis and modeling of the transformer windings stressed by over-voltage with direct impact on voltage distribution across the winding. The authors considered both approaches in modeling the winding: windings with distributed electrical parameters respectively composed from disk coils with concentrated parameters. Both types of voltages applied across the transformer winding will generate free oscillations which are analyzed further on. According to the model, the transformer’s windings are divided in several disk coils with concentrated known parameters. This results in a complete electrical network used for simulations. All simulations have been performed using the software package SYSEG (SYmbolic State Equation Generation).

Content

Modelling of Transformer Windings and Computation of Very Fast Transient Over-Voltages – Gloria Ciumbulea, Sorin Deleanu, Mihai Iordache, Ciprian Curteanu, Neculai Galan, Anton Anastasie Moscu

Control circuit of an Electronically Controlled Capacitor for the Optimization of the Single Phase Induction Motor – Radu Câmpeanu, Adrian Danila

Predictive versus Classic Control of the Induction Motor Drives – Sergiu Ivanov, Vladimir Răsvan, Eugen Bobaşu, Dan Popescu, Florin Stîngă, Virginia Ivanov

Analytical-Numerical Method for Design of a Single-Phase AC Inductors with Ferromagnetic Core – Ioan Popa, Alin-Iulian Dolan, Florian Ştefănescu, Constantin Florin Ocoleanu

Optimal Heating Time for Cylindrical Items Removal from the Shaft – Grigore A. Cividjian

Analytical Algorithms for Synthesis of Modal Controllers by the Maximum Stability Degree Criterion – Ion Fiodorov, Bartolomeu Izvoreanu, Irina Cojuhari, Dumitru Moraru

Analysis of a Step-Down DC-DC Converter: Linear Versus Nonlinear Circuit – Ioana-Gabriela Sîrbu, Marius Voinea, Mihai Iordache

Designing a Simultaneous Control of Several Motors with a VHL Programming Language for a Single Microcontroller – Dan Mihai

Hardware Experiments for Simultaneous Control of Several Motors by a Microcontroller and a VHL Programming Language – Dan Mihai

Study of Low Power Alternating Current Motors by Functional and Energy Aspect – Ion Vlad, Aurel Campeanu, Sorin Enache, Monica-Adela Enache

Performance of an Active DC-Traction Substation with 12-Pulse Parallel Rectifier and Indirect Current Control – Mihaela Popescu, Alexandru Bitoleanu, Alexandra Preda

The Online Temperature Control – Florin Ravigan, Niculae Boteanu, Laurenţiu Alboteanu

Numerical Determination of Inductance of a SMES Device Using the Response Surface Methodology Applied on FEM Modeling – Alin-Iulian Dolan, Florian Stefanescu

Hybrid Petri Nets in Modeling the Packing Processes: Case Study – Mircea Adrian Drighiciu, Daniel Cristian Cismaru

Electromagnetic Field Coupling Between Over-Head Power Lines and Nearby Metallic Pipelines in Case of Direct Lightning – Denisa Stet, Levente Czumbil, Dan D. Micu

Modern Techniques for Monitoring Circuit Breakers by using Microcontroller System – Virginia Ivanov, Maria Brojboiu, Sergiu Ivanov

About the Analytical Methods Applying for Fault Diagnosis of the Static Converters from the Electric Locomotive – Maria Brojboiu, Ivanov Virginia, Andrei Savescu

Aspects Regarding Influences of Voltage and Resistant Torque on Asynchronous Motors Operation – Sorin Enache, Aurel Campeanu, Ion Vlad, Monica-Adela Enache

Lead Acid Battery Pack Charging Optimization – Constantin-Daniel Oancea, Florin Călin

Management of Renewable Energy Sources Integrated in a Micro Smart Grid – Laurenţiu Alboteanu, Gheorghe Manolea, Sergiu Ivanov

Factors Involved in Choosing LEDs for General Lighting Applications: a Critical Review – Dorin Dumitru Lucache, Cătălin Daniel Gălăţanu, Elena Dănilă

Transversal Shape Optimization of a Brushless DC Motor for Electric Vehicles – Ion Vlad, Sorin Enache, Lucian Mandache, Monica-Adela Enache

Information and Communication Technology in Urban Electric Transportation – Ilie Nucă, Iurie Nucă, Alexandr Motroi, Vitalie Eşanu

Study of Indirect Current Control Methods for Urban Traction Active DC Substations – Constantin Vlad Suru, Mihaela Popescu, Ionut Deaconu

Energetic Influence of Motor Power in Drive Systems with Space-Vector Static Converters and Induction Motors – Mihăiţă Lincă, Constantin Vlad Suru, Alexandru Bogdan Lupu

Increasing Safety of the Tests Carried Out in Laboratories by Using Electronic Devices – Marinel Popescu

Virtual Synchronoscope for Connecting Synchronous Generator on the Grid – Gheorghe-Eugen Subtirelu, Mircea Dobriceanu, Monica-Adela Enache

Use of Modern Computing Technique to Improve the Energy Indicators of Drive Motors of the Coal Mills – Silvia-Maria Digă, Daniela Popescu, Nicolae Digă

Estimation of the Heat Cumulated Inside a Wall with Cylindrical Symmetry – Mitică Iustinian Neacă, Andreea Maria Neacă

Fuzzy Control of Centrifugal Pumps Flow – Daniela Popescu, Jenica-Ileana Corcău

Object Oriented Video Retrieval System based on Domain Ontologies – Ion Eugen Ganea

Evolution of the Electric Power Components Definitions – Adrian A. Adăscăliţei, Alexander E. Emanuel

Active Power Filter Study Using Dedicated Matlab GUI – Cristina Alexandra Preda, Mihăiţă Lincă, Constantin Vlad Suru

Abstract 

A complex-envelope finite difference time domain (CE-FDTD) algorithm has been proposed in the literature as one of FDTD formulations that is very general. However, this method, didn’t receive a lot of scientific attention, since the introduced complexity wasn’t quite justified by the obtained gain in maximum time step size. Nevertheless, there is still a strong motivation to study this formulation, since it can potentially be, in combination with high order accuracy FDTD approaches, a significant tool to combat the accuracy deterioration due to numerical dispersion. A method of choice for termination of CE-FDTD computational domain was the convolutional perfectly matched layer (CPML), since it is considered to be superior over other commonly used techniques. Yet, the application of CPML in CE-FDTD environment isn’t straightforward. In this paper a modification of conventional CPML is performed in order to be used for termination of CE-FDTD computational domain. The modified CPML, along with CE-FDTD algorithm has been implemented in an own developed simulation environment and tested through various simulation cases. The functionality of the proposed CPML is illustrated on the example of a dipole antenna. The observed behavior of the boundary region fully corresponds to the propagation through the free space, without any undesirable reflections.

Abstract 

Voltage controlled microwave oscillators are used in digital communication systems. Pairs of coupled and synchronized voltage controlled oscillators are used to control the phase in microwave antenna arrays as an alternative to other methods. A particular phase shift can be obtained by choosing the free-running frequencies of the oscillators in the array. The aim of this paper is to analyze such a pair of coupled oscillators by targeting the phase shift between their output voltages, the coupling circuit being a passive two-port passive network. For this purpose, we use our computer-aided analysis tool ANCSYAP (ANalog Circuit Symbolic Analysis Program) capable to build the symbolic expressions of desired network functions or global parameters (as input/output/transfer impedances and admittances, fundamental or hybrid parameters) and to find the resonant frequencies of any two-port network as function of global parameters. The analysis is performed both in time domain and in frequency domain and in this way we can compute the shift phase analytic expression. To prove the procedure, we include two relevant examples.

Abstract 

Harmonics analysis is established by international standards as well as national norms [6], [7]. There are also definitions and calculus relationships for the indicators considered representative for this non quality aspect of the electric power. Among the harmonics analysis methods, the authors have dealt with application of DFT, given the fact that were to be analyzed acquired waves experimentally, using data acquisition boards. Experiences in using DFT, difficulties and highlighted errors as well are materialized in this paper, which is of great use to practitioners in this field. Next, there is made a distinction between the a.c. and d.c. current waves in defining the harmonics indicators, which gives accuracy and expressivity to the harmonic analysis.

Abstract 

The blend of geometry and numerical analysis that is taking place in the present material produces a subject with can gives a lots of detail and richness for the case of dynamical models arising in mathematics, science and engineering. The goal of this paper is the geometrical and numerical study of the main sizes of the mathematical models of the multispecies interactions which are important in determining long-time dynamics, based on the application of various notions from the theory of  dynamical systems to the numerical approximation of initial value problems over long-time intervals.  The numerical methods are widely used for the study of complicated temporal behavior of dynamical systems, in order to approximate different types of invariants sets or invariant manifolds and also to extract statistical information on the dynamical behavior in the computation of natural invariant measures or almost invariants sets. The present study is a interplay between dynamical systems geometrical theory and computational calculus of dynamical systems, knowing that the theory provides a framework for interpreting numerical observations and foundations for efficient numerical algorithms. We perform a computational study for the case of four important examples: prey-predator 2D Lotka-Volterra system, Bailey model for the evolution of epidemics, classical Kermack-McKendrick model of evolution of epidemics and the  prey-predator 3D Lotka-Volterra system.

Abstract 

For a proper operation of the shunt active power filters, the current reference detection method must be robust. This means it must extract correctly the fundamental frequency even if the grid has distorted and unbalanced voltages at the point of common connection. The most used reference current detection methods for shunt active power filters are analyzed and compared in this article, theoretically and through simulations in MATLAB/Simulink. One used criteria like settling time, transient performance, THD of reference and compensated grid current, overshoot and unbalance. Some practical aspects of hardware implementation and shunt active power filter design considerations are also discussed. Measured data, acquired with a dedicated data acquisition system provides the parameters required for a non-ideal real system simulation, namely a static excitation system of a power generator group. The simulated system consists of a transformer which feeds a Silicon Controlled Rectifier bridge. The Matlab/Simulink models allows for testing of the reference current detection methods implementation and improvement for dealing with problems arising with distortion and unbalance of mains voltages. Because the active power filter is a complex system, the reference current detection methods are studied with their dependencies, for example the different strategy to deal with voltage distortion and unbalance. The current controller and hardware setup are preserved. The study contributes to the existing comparisons in specialized literature by testing their weaknesses in distorted and unbalanced PCC voltages and may be useful in future hardware implementation.

Abstract 

In this paper, we propose an approach for the magnetic and thermal modeling of an encapsulated busbars system, in three-phase execution, for high voltage using QuickField software. The paper proposes a numerical model developed by coupling of the magnetic field problem with the stationary and transient heat field problems for the geometry of a three-phase execution busbars system with common shield. The coupling of problems is realized by importing specific losses from the magnetic field problem as heat sources for thermal field problem. The magnetic field problem is also coupled to the electrical circuit. The electrodynamic forces that occur between conductors in the presence of the ferromagnetic shield have different values compared to those that occur in an unshielded system. In the model it was taken into account the variation of electrical conductivity with the temperature. The global heat transfer coefficient by convection and radiation used in thermal model was estimated using the power losses computed by magnetic model. When evaluating the global heat transfer coefficient was taken into account the temperature dependence of the physical properties of the air. There is a good agreement between numerical and analytical temperature values. The paper analyzes the results for two materials used to build the shield, iron and aluminum. The presented model can be used for analysis, design and optimization of three-phase busbars system with common shield.