Abstract

Wavelet analysis is characterized by filters with irrational coefficients and runtimes increasing with filters order. The terminal nodes of Wavelet Packet decomposition trees exhibit good harmonics’ selectivity when implemented with Daubechies wavelet mothers with filters of length 28 and respectively of length 40 (denoted in MATLAB by ‘db14’ and ‘db20’). Therefore they can be used for power quality (PQ) analysis of electric signals. When rounded to 4 decimal places, certain coefficients from these filters become 0. In the “rounded” context, the number of iterations sup-porting the convolution products involved by the Wavelet analysis is restricted. Based on the number of neglected co-efficients and length of wavelet filter, a formula is deduced for the percent runtime savings strictly associated to the wavelet decompositions. Statistical evaluations (considering sets of 20 consecutive programs executions) were performed considering full operational contexts, where all types of studied wavelets were involved in complex operations like evaluating PQ indices and harmonic spectra. The mean runtime savings proved to be 20.4% for ‘db14’ and respec-tively 23.2% for ‘db20’. The impact of rounding over the PQ analysis’s accuracy was evaluated considering three-phase waveforms acquired from a power group. The follow-ing quantities were considered: harmonic spectra and ener-gies of the Wavelet Packet tree’s terminal nodes, instanta-neous values corresponding to the fundamental frequency, vectors of details and approximations yielded by the Dis-crete Wavelet Transform and signals reconstructed from the vectors of details and approximations. Highly acceptable small errors were obtained, recommending the rounding to 4 decimal places of the analyzed wavelet filters as a faster reliable wavelet based analysis method.

Abstract

In this paper we propose an approach for the de-termination of static force characteristic of a plunger-type AC electromagnet using 2D numerical model developed in QuickField software and the determination of the thermal field. The attraction electromagnetic force is calculated us-ing Maxwell stress tensor method. The magnetic numerical model is an AC magnetics problem coupled with the coil electric circuit. The magnetic numerical model has been experimentally validated. The thermal field is determined in steady-state regime. The source term in the thermal model equation is calculated from the magnetic model data.

Abstract

In the DC-traction substations, the diode rectifi-ers are commonly used to provide the needed DC-voltage for vehicles. Unfortunately, they attract important issues of power quality, of which the most significant is the injection of harmonic currents into the AC power supply. Withal, the feedback of the recovered braking energy into the power supply is not possible. This paper is focused on the trans-forming a DC-traction substation with six-pulse uncon-trolled rectifier into an active substation, leading to substan-tially improved power quality and energy efficiency. These effects are obtained through an IGBT-based voltage source inverter with a proper control, connected between the DC-traction line and the power supply via a dedicated trans-former and specific interfacing circuits. The indirect current control is based on the concepts of the p-q theory of the powers and intermediate use of the synchronous reference frame, so that perfect harmonic cancellation is imposed even under distorted supply voltages. The conceived Matlab-Simulink model of the system for active filtering and regen-eration is presented and the simulation results illustrate very good performance in both operating regimes of the system. Experiments on a 30 kVA reduced-scale laboratory setup controlled and monitored by a dSPACE 1103 based platform verify the feasibility and effectiveness of the pro-posed scheme. Both the harmonic distortion of the current upstream the point of common coupling and the power fac-tor are significantly improved.

Abstract

The paper has three main objectives: the presen-tation of a laboratory model of a system for active filtering and regeneration (SISFREG) developed through an applied research collaborative project in the frame of Partnerships in priority area programme during 2014-2016; the presenta-tion of the methodology and design of recuperative testing structure and the presentation of few experimental results. SISFREG allows the conversion of the DC traction substa-tions into “active substations”. The laboratory model is composed of one configurable voltage source inverter (input voltage range 200-560 V DC; output voltage 3×400 V AC; rated power 30 kVA) adequately interfaced with the DC-line and properly controlled in closed loop. The control algo-rithm was implemented on the dSPACE 1103 system that allows the monitoring of the system too. The methodology and the testing structure configuration started from the actual conditions existed in a substation for DC traction. The experimental structure is based on the equipment avail-able in the laboratory and it contains: the equivalent of the transformer-rectifier traction group; the equivalent of the DC traction motors; the possibility of system to be con-nected, on the one hand, in the connection point of the trac-tion transformer, and, on the other hand, with the DC line (equivalent catenary). Finally, the paper presents several experiments conducted in accordance with the testing pro-tocol, the analysis of the experimental results and the re-sulted performance of the system, during both active filter-ing and regeneration operation modes.

Abstract

In this paper is proposed an optimal geometrical shape for a DC electromagnet by combining the design of experiments (DOE) and 2-D FEM. The optimization prob-lem takes into account four geometrical parameters (the coil shape ratio, the support thickness ratio, the support height ratio and the support top ratio) and consists in maximiza-tion of the acting force related to the largest air-gap, pre-serving the global dimensions of the device (the external radius, the height of carcass, the height of plunger with sup-port) and the cross-section of the winding. Before optimiza-tion, the technique of screening was applied to verify the influence of the four geometrical parameters on the acting force. The experiments were performed by numerical tool FEMM in relation to the LUA language. The acting force was computed by Maxwel Stress Tensor principle. Best in-fluence was observed for all the four parameters, especially for the support top ratio, with 99% confidence. The method by zooms without computation of models was applied to increase with 21.20% the acting force related to the air-gap of 41 mm. The cost of this improvement is the reduction of electromagnetic force for lower air-gaps which can be com-pensated by eliminating the economy resistor in this range.

Abstract

The paper is focused on physical phenomena that degrade the effectiveness of the energy transfer in electrical systems when voltages and currents are nonsinusoidal and asymmetrical. The Currents’ Physical Components (CPC) – based power theory provides fundamentals for the analysis of the electric energy flow. This analysis identifies seven distinctive physical phenomena that affect this flow. Accord-ing to the CPC concept, seven current components are asso-ciated with these phenomena. Only one of them contributes to the useful transfer of the energy. Remaining six compo-nents only degrade the effectiveness of this transfer. They could be reduced by various compensators and the CPC-based power theory provides fundamentals for their synthe-sis and control. The results presented in the paper are valid for electrical systems of any complexity, meaning for single- and for three-phase systems and for any loads, meaning for linear and for nonlinear loads.

Content

CPC−Founded Clarification of Decline of the Effectiveness of the Energy Transfer in Power Systems – Leszek S. Czarnecki

Optimal Shape of DC Electromagnet – Alin-Iulian Dolan

Testing a Filtering and Regeneration System on a Recuperative Stand – Alexandru Bitoleanu, Mihaela Popescu and Vlad Constantin Suru

DC-Traction Substation with Improved Power Quality and Regeneration Capability – Mihaela Popescu, Alexandru Bitoleanu, Constantin Vlad Suru, and Mircea Dobriceanu

Static Force Characteristic and Thermal Field for a Plunger-Type AC Electromagnet – Ioan C. Popa, Alin-Iulian Dolan, Constantin Florin Ocoleanu

Diminishing the Computational Burden when Analyzing Electrical Signals with Long Wavelet Filters – Ileana-Diana Nicolae, Petre-Marian Nicolae, Ionuţ Daniel Smărăndescu

Hybrid Systems Modeling Approach with Petri Nets – Mircea  Adrian Drighiciu

Estimation of Certain Power in Single-phase Network and DC Circuits – Constantin Daniel Oancea

Dynamic State of Low Power Asynchronous Motors in Direct-on-Line Starting – Ion Vlad, Aurel Campeanu, Sorin Enache, Monica-Adela Enache

Aspects Regarding Operation of Power Supply System of Cars – Sorin Enache, Aurel Campeanu, Ion Vlad and Monica-Adela Enache

Design Optimization of an Asynchronous Motor Used in Light Railway Traction – Presură Raluca-Cristina, Nicolae Marian-Ştefan, Vlad Ion, Nicolae Petre-Marian

Contributions to the Development of Complementary Equipment for the Romanian Anti-Hail System – Gheorghe Manolea, Laurentiu Alboteanu, Sorin Stepan

Analysis of Crimped Connections Heat Transfer Coefficient Using Experimental and Numerical Determinations – Constantin Florin Ocoleanu, Ioan C. Popa

Modelling and Synthesis of Printed Circuit Boards Testing Systems based on Timed Hard Petri Nets – Sudacevschi Viorica, Ababii Victor, Calugari Dmitri, Bordian Dimitrie

Concerning the Automatic Computation of the Electrical Stresses in the High Voltage Substations during the Transient Regimes – Maria Brojboiu, Virginia Ivanov

Analyzing Signals from a Primary Winding of a Locomotive Transformer with Three Types of Wavelet-Based Transforms – Ileana-Diana Nicolae, Radu-Florin Marinescu, Petre-Marian Nicolae  and Diana-Cristina Marinescu

Shielding Effectiveness Measurement Using a DTEM Cell – Viorica Voicu, Ion Pătru, Livia-Andreea Dina, Petre-Marian Nicolae, Relu Aipu, Ionuţ Daniel Smărăndescu

Synthesis of the PID Algorithm for Control the Thermal Regime in the 3D Printer – Irina Cojuhari, Bartolomeu Izvoreanu, Ion Fiodorov, Dumitru Moraru, Sorin Botnaru

Analysis of Direct Current Motors in Dynamic Regimes Using Numerical Techniques – Ioana-Gabriela Sîrbu and Lucian Mandache

Control of Flow and Pressure in the Cooling Water Circuit of a Thermal Power Plant Using Fuzzy Logic – Radu Cristian Dinu, Cristian Bratu and Daniela Popescu

The Influence of the Output Current Deforming Regime on the Input Current Harmonics for a Three-Phase Rectifier Bridge – Mitică Iustinian Neaca

Theoretical and Practical Aspects Regarding Radiated Emission Testing in Semi-Anechoic Chambers – Livia-Andreea Dina, Viorica Voicu, Petre-Marian Nicolae, and Ionuţ Daniel Smărăndescu

Optimization of the Aerodynamics Airfoils Placed in Supersonic Viscous Flow – Victoriţa Rădulescu

Monitoring System for Reducing the Electric Equipment Stress in Transport and Distribution Lines – Virginia Ivanov, Maria Brojboiu and Sergiu Ivanov

Technical and Economic Analysis of Thermal Energy Storage in the Biomass CHP Plants with ORC Technology – Pavel Atănăsoae, Radu Pentiuc, Crenguţa Bobric, Elena Olariu and Valentin Martin

The Implementation and Validation of a Bidirectional PWM Boost Rectifier Control Algorithm – Ionuţ Deaconu, Constantin Vlad Suru, Mihăiţă Lincă, Cristina Alexandra Preda