Category Archives: Fără categorie

Rehabilitation of Wastewater Treatment Plant Gardabani

8 January 2020Fără categoriecburada

Abstract

In this project, the problem was the realization of a SCADA (Supervisory Control and Data Acquisition) system and automation system that will reduce the costs of maintenance, will increase energy efficiency and will help to improve the quality of wastewater that drains into the river and which comes directly from the sewerage system of Tbilisi and Gardabani cities. The automated station will work non-stop, with high efficiency in water quality and cleaning. The warranty of this station is 25 years without mechanical defects, from which comes the decrease on the maintenance expenses towards a non-automated station.

Operational Aspects of an Auxiliary Converter Used in Railway Applications

8 January 2020Fără categoriecburada

Abstract

This paper presents operational aspects of an auxiliary converter for rail traction which was designed, simulated and realized by authors under the frame of an academia-industry project based partnership. The general technical and functional characteristics of the equipment are described. Data representing electrical waveforms ac-quired from the realized converter’s key test points are pre-sented. High harmonic orders (exceeding the 70-th rank) had to be removed through original programs in order to reveal the significant low harmonic order components. The instantaneous values representing the pollution with har-monic orders were evaluated, along with the components oscillating at the fundamental frequency. Highly variable levels of noise were revealed. Unlike the current waveforms from the analyzed converter’s output, the phase voltages preserved a significant content of harmonic distortions after the removal of harmonics higher than 70. Therefore an analysis based on the Fast Fourier Transform was per-formed. Most significant power quality indices were com-puted for cutoff frequencies corresponding to the harmonics from the set {40, 70 and 80}. Harmonic spectra for phase currents, voltages, active and reactive powers were also rep-resented, along with the phasor diagram. Filtering of all frequencies over the 40-th harmonic was revealed to be a good solution for electromagnetic compatibility compliance.

Harmonics Based Clustering Patterns Featured by the Final Nodes of a WPT tree

8 January 2020Fără categoriecburada

Abstract

Decompositions1 of electric waveforms relying on the Wavelet Package Transform (WPT) provide numerous advantages but require a significant amount of computa-tional resources (runtime and memory). A tree topology with 7 levels, relying on a wavelet mother from Daubechies family with a filter of 28 components was studied. Studies on artificial waveforms polluted with a single harmonic were made firstly, revealing interesting aspects relative to clusters of nodes affected by the same group of harmonic orders. Different pairing patterns of odd and even harmonics were revealed, along with decisions on nodes being more relevant for certain harmonics. Nodes clustering patterns with re-spect to the most significant odd harmonic orders were de-duced as well. These patterns consist in sequences of 4, 8 and 32 nodes. Similarities in harmonic weights associated to node clustering patterns based on the most significant har-monic orders were also derived and discussed. The harmon-ics-nodes clustering properties were afterward tested with respect to capabilities related to time-frequency identifica-tion of most common harmonic orders magnitudes modifi-cation. Multi-harmonic artificial test signals, similar to those from power applications were used to validate the original WPT based algorithms relying on the special clustering and patterns-related properties derived by authors. The results were commented and conclusions were drawn.

Sensorless Adaptive and Predictive Control of PMSM Based

8 January 2020Fără categoriecburada

Abstract

This article presents a sensorless control structure for a PMSM (Permanent Magnet Synchronous Motor), with a MRAC (Model Reference Adaptive Controller) type speed controller, FOC (Field Oriented Control) type overall con-trol strategy, and d-q axis type reference system, for which the Id current reference set to zero is selected for reasons of torque maximization, and the current reference is supplied by the MRAC adaptive controller output. The numerical simulations results obtained in the case of parameter varia-tion and rapidly varying load torque with a random compo-nent, plus an adjustment mechanism described by first-order differential equations recommend the implementation of this structure in an embedded system in real time. Also, presents a sensorless MPC (Model Predictive Control) for a PMSM in which the rotor speed is provided by a MRAS (Model Reference Adaptive System) observer. The results of the numerical simulations show the superiority of the MPC control system compared to FOC type control system in the case of parameter variation and rapidly varying torque load with a random component. The relatively low complexity of the number of arithmetic operations required to implement the estimation and control algorithms recommends the im-plementation of an embedded system in real time in future works.

Deploying Renewable Energy Sources and Energy Storage Systems to Achieve Energy Security in the R. of Moldova

8 January 2020Fără categoriecburada

Abstract

100% RES scenario to improve energy security of R. Moldova is analyzed. Economic simulations are used. The paper shows that only about 70% of the demand could be covered directly from wind farms (WF) and photovoltaic (PV) energy sources (WPES). The remained 30% of energy (RE) – by energy storage system (ESS) with a capacity (kWh) of 32% from RE and a power (MW) of 87% from maximum power demand. As country doesn’t have its own hydro reserves, Li-ion batteries are considered for ESS. The investment in such SSE would exceed 3-52 times national GDP and that makes unrealistic 100% RES scenario for R. Moldova. As analysis showed, there are more than 1400 episodes within the year when energy to cover daily demand cannot be accumulated during 1 to 4 days. By reducing SSE capacity to a value equal to the daily energy demand and maintaining ESS power, it was found that the levelised tariff of WPES+ESS scenario exceeds, however, those of traditional scenarios. Only 5% of energy produced by WPES can be accumulated in such ESS, the remaining 25% – by importing night electricity, at negligible price in the calculations.

On the Thermographic Analysis and Thermal Re-sistance Estimation of the Capacitor-Run Single-Phase Induction Motors

8 January 2020Fără categoriecburada

Abstract

The real-time estimations of heating of the elec-tromechanical converters are important for both overheat-ing prevention and overall efficiency optimization during operation. The two-phased induction motors with capacitor-run capacitors onto the auxiliary phase are sensitive to the capacitance variations of the capacitor. In this respect, the optimization of the two-phased induction motors with elec-tronically-switched, capacitor-run, supplied from frequency inverters may be achieved if the elliptical magnetic motion field into the machine is controlled such as the ratio between the maximum and the minimum of its amplitude is reduced to unity. Observations of the heat of the machine’s body and an appropriate thermal model may provide information about the eccentricity of the magnetic motion field in the machine. In this work, the authors investigated the impact of the capacitor-run capacitance onto the characteristics of the thermal field of the machine. In this perspective, the authors implemented a method based on the image analysis techniques that allows estimating: (a) the geometric features of the machine from the boundaries of the thermal field, and (b) the temperature distribution onto the cross-section of the body in correlation with the main components of the ma-chine and (c) the thermal resistance of the machine’s body.

Determining Idle Running and Short-Circuit Operating Characteristics of an Asynchronous Traction Motor

8 January 2020Fără categoriecburada

Abstract

Abstract – It is proposed the possibility to simulate the idle running and short-circuit characteristics of an asynchro-nous traction motor. Based on the results, the motor pa-rameters can be determined. In the modern design of asyn-chronous motors, the simulation of these characteristics is required as a mandatory stage. On this basis, the electro-magnetic stresses and the constructive solutions are finally established, so that the engine corresponds in operation. The tests are important, as they allow for a computation of the motor parameters. There still exists the possibility to simu-late the stationary and dynamic modes, in order to deter-mine the behavior of the motor while running. The compari-sons between the simulated and the data provided in the motor datasheet proves that the occurring errors are under the 2.1 % level accepted as precision level. The correctness of the simulations performed is important in operation, be-cause with the parameters and the results obtained we can anticipate the behavior of the machine in the dynamic or stationary modes. The operating, starting and speed charac-teristics of the asynchronous traction motor must meet the high demands imposed by the complex equipment used in modern transport vehicles. Concerns related to the devel-opment of new methods and procedures to optimize the construction of the asynchronous motors used in traction, to find new mathematical models for the correct simulation of the operating characteristics, are a permanent activity. The simulations and experimental tests were carried out consid-ering a traction motor from a diesel electric locomotive.

Identification and Sensorless Control Using Embedded System of PMSM Based on FOC Strategy and Power Factor Correction

8 January 2020Fără categoriecburada

Abstract

This article presents the procedure for identifying the electrical and mechanical parameters of the PMSM (Permanent Magnet Synchronous Motor). The parameter identification procedure is required in the event that the motor’s electrical and mechanical parameters are unknown, or in industrial applications at the beginning of a drive cycle due to variations of the PMSM parameters with the tem-perature. The parameter identification procedure is imple-mented in the Matlab/Simulink environment. This proce-dure was also implemented in an embedded system and the results of the two (offline and online) identification methods of the nominal parameters of the PMSM are presented comparatively to the parameters in the datasheet. It pre-sents the block structure of the PFC together with the nu-merical simulations achieved in Matlab/Simulink, on the improvement of the PF (Power Factor) of the supply circuit. It also presents the block structures of the FOC (Field Ori-ented Control) strategy and of the back-EMF (back Elec-tromotive Force) sliding mode, MRAS (Model Reference Adaptive System), and PLL (Phase Locked Loop) type ob-servers. The numerical simulations show the superiority of rotor speed estimation when using the back-EMF sliding mode observer compared to the rotor speed estimate pro-vided by MRAS and PLL observers.

Contactless Power Transfer – Theoretical Principles and Fields of Applications

9 January 2019Fără categoriecburada

Abstract

Contactless energy transfer 1 has indubitable advantages in modern technique given by the lack of electro-mechanical contacts predisposed to pitting and failure: use in aggressive or explosive (no sparks) environments, application to mechanisms with translation or rotation move-ments (robotics), high efficiency on relatively short distances a.s.o. Recent researches carried out in Romania demonstrate the feasibility of these systems for a wide power range, from a few watts up to tens of kW, suitable for the expansion of the electro-mobility and proliferation of multimedia and mobile communication devices. Such systems impose storing the energy in batteries requiring frequent charging. The concept of high frequency transformer with separable windings, as well as a capacitor with separable electrodes working in near field regime, the use of resonance and magnetic flux concentrators for increasing the transfer efficiency, some practical achievements and also maintaining of electromagnetic compatibility within well-defined limits are presented. The paper aims to draw the attention of users and also of prospective investors on the applications and advantages of these systems and to encourage national partnerships for developing theoretical and applied research in this field.

Wireless Power Transfer Analysis Using Scattering Parameters

9 January 2019Fără categoriecburada

Abstract

Wireless power transfer systems (WPTS) can be made more efficient from the emitter-receiver and from the active power transfer efficiency point of view by using the scattering parameters S. Using electrical circuit theory and starting from the correct formulation of scattering parame-ters, S parameters are computed in an automated manner based on modified nodal equations corresponding to WPTS. Advanced computation software (ADS, Ansoft Extractor Q3D, Cadence, etc.) is used to compute the parameters cor-responding to the magnetically coupled coils. The magneti-cally coupled coils can be described by the parameters of the resulting equivalent circuit, such as: impedance and admit-tance matrices, transfer coefficients matrix and the scatter-ing parameters matrix. This paper presents on one hand the correct formulation of S parameters and on the other hand the practical use of these parameters to streamline the wire-less energy transfer. To generate the analyzed parameters, dedicated function were developed in MATLAB and exist-ing routines from the Microwave toolbox (MATLAB) have been used. The frequency variation of S has been studied using graphical representation and Smith diagram. The accuracy in defining the scattering parameters S, based on analog circuit theory in harmonic state, in complex domain, is confirmed by the results obtained using the program ADS, that contains routines specific for generating S parameters.