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Once the wind data is measured, the values are processed, based on statistic approach, as accurately as possible, to provide a clear over-view of the locations wind potential, being the basis of any wind farm project, representing the go or no-go in further subsequent design steps. The probability density distributions are derived from time-series data, identifying the associated distributional parameters. The wind energy potential of the locations is studied based on the Rayleigh and Weibull models, implemented with the help of Excel computations, and representing tools, to understand the wind characteristics. Based on the statistical analysis of wind conditions presented here, the results of current study can be used to make a sustainable energy yield for any location.

The methods currently used for frequency estimation do not provide accurate results as the obtained values depend on the acquisition time. To increase the estimates’ accuracy, the authors propose a pseudo-sinc function that is dependent on the acquisition time but better reflect the physical phenomenon. The paper provides a new interpolation method developed to take into account more maximizer, obtained by iteratively cropping the source signal. The maximizer obtained in this way corresponds to an asymmetric pseudo-sinc function, which does not coincide with the assumptions generated by the commonly used interpolation methods. The method of interpolation using the pseudo-sinc function, developed by the authors, has as a direct practical application, the detection of changes in the mechanical characteristics of the engineering structures.

The operation at maximum power in condition of rapid wind velocity modifications poses a challenge for wind power plants. Based on measured data, the authors determine for generator and turbine, the mathematical models. Also, with current measured values for mechanical angular speed, ω, and wind speed, v, the authors determine the mathematical model in a timely manner and, on its basis, compute the optimal mechanical angular speed ωOPTIM, at which the value of the wind turbine power is maximum. We determine the dependence of the optimal / ideal mechanical angular speed, ωOPTIM, to the wind speed, v, and bring the wind turbine into optimal operating area by modification of the generators load. By measuring the wind velocity and monitoring the electric energy flowing from the permanent magnets synchronous generator (PMSG), we compute the wind turbine power. Based on those remarks, to get maximum power out from a wind turbine, it is necessary that between wind velocity and mechanical angular speed should always exist a correlation, according to the wind velocity changes and the inertia moment, J.

The purpose of the present paper is to determine the values of the real power of the WT, P WT-REAL , to observe, if the operation of the wind turbine is in the optimal area, in terms of captured wind energy. The real values of the wind turbine power are determined based on experimental data from a wind power plant. The value of the inertia moment, J, is calculated based on the real power values of the WT. Based on the values of mechanical angular velocity, MAV, and the power produced through the permanent magnet synchronous generator PMSG, we compute the real value of the WT power, which represents the basis of the recalculation of the mathematical model of WT, MM-WT. We determine the coordinates of the maximum power point, MPP, the maximum power, P WT-MAX and speed, n OPTIM as the values of the proportionality factors k O for optimal MAV, and k P factor for P WT-MAX are recalculated. The paper analyzes the evolution of the real powers of the WT in time. Knowing the real power of the WT, P WT-REAL , at the same wind speed, at different moments, we obtain useful information related to the optimal operation from the energy point of view.

The main target of this paper is to develop and implement structures of fuzzy control in the continuous casting process (in the secondary cooling) capable of eliminating the surface flaws and casting rejects, to increase the quality of continuously cast products and implicitly to increase the productivity of the installation by controlling the water flow rate in the secondary cooling circuit. In order to achieve this objective, a solution will be developed and implemented, meant to control the casting process by a fuzzy system, allowing the control of the water flow rate in the secondary cooling, by appropriate distribution along the cooling area. This necessity is imposed by the fact that actual control systems do not correlate in real time the variations of the multiple variables related to the continuous casting process and stick to a rigid distribution of the water flow rate on each cooling area.

The present paper determines the optimum energy operation area of an electric wind power system, under time varying wind speed conditions. The determinations of the optimal area, from the energy point of view, is done based on experimental values from the Romanian black sea cost, Dobrogea area. The optimum operation area is defined by the optimal mechanical velocity, ω OPTIM . For this, the dependence between the wind speed, v, and ω OPTIM are computed based on the current wind speed and the current mechanical velocity ω. Due to the high inertia of the wind turbine (WT), the generators speed is not able to follow the changes of the wind speed. Knowing the optimum value ω OPTIM , the solution is to determine the load at the permanent magnet synchronous generator (PMSG) in order that the mechanical speed should timely reach his optimum.

SMA-based (Shape Memory Alloy) actuators with thermal activation are widely implemented in a large area of equipments and devices, but they have an important limitation in the low force produced. The force increases with the dimension, which gives new issues in the control of the requested energy for activation. This happens more often when the SMA actuator is driven by electrical current intensity. Here, a solution for SMA control at low voltage and high intensity is proposed, involving pretty usual devices in handy schematics. The solution was tested and proved as effective in such cases.

This paper presents an application of digital cascade control implemented in Scilab / Xcos environment, using a P type regulator for the position adjustment circuit, a PI controller for the speed circuit adjustment; the current respectively moments control circuits are rendered by elements of PT1 type. On this basis the program is done in Scilab and the related signal block diagram implemented in Xcos; through simulation, the step response of the system is analyzed for different sampling times.

To optimise the diagnosis process for Romanian railroad traffic safety installations a series of diagnosis charts were devised on which a diagnosis software package was created. In the first part of the paper we explain the installation’s operation mode. At this point, the installation diagnosis is classically done at its sequence of operation steps, without detailing the actual failure cause. That is, only the schema where the failure appears is identified. In our work, through the diagnosis charts and the afferent software we can determine the actual failure cause. The software is written in Visual Basic. The maintenance staff using this software are quick and correct in reaching a decision about failure causes. Thus, train traffic delays caused by lengthy and problematic failure diagnosis is kept to a minimum. At the same time wrong maintenance decisions are eliminated and serious traffic events avoided

The paper presents the computing of digital control circuits using Scilab environment. It exemplifies the influence of the sampling time in case of a transfer system described by a PT3 element composed of one PT1 and one PT2 element. For a continuous control system, the transfer function in z is computed and replaced with a digital control system. The presented calculation, done in Scilab, highlights the test responses of the process evidencing the systems performances.

The paper proposes to render the mathematic relations between the mathematic ideal of a generating polynomial from GF (2), the generating matrix of the type 4 x 7 associated to this ideal and the generating polynomial g(x), as well as the relations between the generating matrix H of the type 3 x 7, associated to a second mathematic ideal and to a second generating polynomial h(x). These generating polynomials as well as the generating matrixes G and H are not randomly selected, they being part of an associative general linear algebra generated by a polynomial f(x) from GF(2) that has as dividends the polynomials g(x) and h(x). All these we shall concretely exemplify in the proposed paper. Much more, we shall observe, also by a concrete example furnished in this paper, the connecting relations that exist between the matrixes G and H and that are very important in the mathematic theory of encodings. Practically, in the theory of encodings by redundant symbols, if between two matrixes there is no total relation of orthogonally, than the decoding cannot be realized. Therefore a property of the two matrixes is strictly necessary, this fact being also exemplified and demonstrated in this article.

Mathematics is often considered difficult by students, consequently it appears as an unattractive curricular element and a kind of blockage occurs in the learning process. This happens because some aspects are (at least) presented in an abstract way, the students having not the possibility to visualize the results or to interpret/link these results with known aspects from the real life. A good way to visualize results of mathematical concepts and results is their presentation in a graphical way; this is possible to be realized using different dedicated software, but also by constructing virtual instruments. The use of these last tools is motivated by the fact that the experience reveals the attractiveness of computers and programming languages in education. This is amplified by the fact that programming develops the ability of thinking and structural organizing of activities and actions, and involves in our case the use of functions and relations in a logical sentence. While the results are visible and the facility to simply modify the input parameters is assured, the effect on outputs is clearly shown by the Virtual Instrument. This approach is proven as successful in enhancing mathematical skills for students in the engineering domains, the target of our research group being the development of Virtual Instruments for all topics taught in mathematics. Some of them are presented at the end of the paper.

Frequency and magnitude evaluation are two of the main signal analysis tasks in the electrical power systems. This paper presents a simple and robust algorithm which enables an accurate estimation of the harmonic parameters of signals with unknown frequency. Differing from the existing approaches, frequency and magnitude of harmonic waves are simultaneously and precisely identified. The proposed algorithm can be applied in spectral estimation as well as in system identification, signal reconstruction, and other important signal processing issues. Algorithm operational efficiency was proved by frequency and amplitude estimation of generated signals with known frequency achieved their aim.

The paper presents the computing of control circuits in the frequency domain, starting from the mathematical model of the frequency response H(j) obtained from the transfer function H(s) where the operational variable keeps just the image part. For PT1 and PT2 elements, using Scilab, the geometrical place is illustrated and the frequency diagrams are determinate for different duping constants (PT2). The logarithmic frequency diagrams (Bode), determine the amplitude and phase reserve for a control circuits with three PT1 elements.

This paper present a solution for improving efficiency of solar photovoltaic installation, realized with fixed solar photovoltaic modules, placed in solar parks or individual installations. The proposed solution to increase the radiation on the solar photovoltaic panels is to use some thin plates covered with a reflective blanket, mounted in front of the solar photovoltaic modules, with the possibility of their adjustment.

The main target of this paper is to develop and implement structures of intelligent control of the continuous casting process (in the secondary cooling area) capable of eliminating the surface flaws and casting rejects, to increase the quality of continuously cast products and implicitly to increase the productivity of the installation by controlling the water flow rate in the secondary cooling circuit. In order to achieve this objective, a solution will be developed and implemented, meant to control the casting process by an intelligent fuzzy-type system, allowing the control of the water flow rate in the secondary cooling, by appropriate distribution along the cooling area. This necessity is imposed by the fact that actual control systems do not correlate in real time the variations of the multiple variables related to the continuous casting process and stick to a rigid distribution of the water flow rate on each cooling area.

In practice, vector control methods are widely used offering the possibility to reach high performance. Certain application areas need optimum control in at limit operating conditions, as, operation at maximum torque. The paper presents how through the proposed control scheme at the output of the flux and the voltage controllers, provide direct the frequency and voltage values for an asynchronous machine (ASM) operating at variable speed. The simulation analyses for the considered control structure are based on the use of two controllers: flux regulator for determining the stator flux and the speed regulator for determining the stator frequency. The dynamic analysis of the system is done highlighting the tuning process for the two controllers, which enables conclusions on the proposed method with different applications, as the ASM in wind turbines.

TEM Journal; Vol 5, No 3, 2016. ISSN 2217-8309, This paper introduces a robust method for vibration-based damage assessment, which is based on a mathematical relation contrived by the authors that involves the frequency shifts, the damage size and position. Databases containing damage indicators for all possible damage scenarios, for three types of beams, were developed by involving this mathematical relation. The proposed damage indicator is expressed using the relative frequency shifts. The damage location and severity can be assessed if the relative frequency shifts are derived from measurements at the initial state and periodically afterwards. The paper investigates the effectiveness of several dissimilarity estimators, to find damage involving frequencies measured without and in the presence of noise.

The Wigner Ville distribution offers a visual display of quantitative information about the way a signal’s energy is distributed in both, time and frequency. Through that, this distribution embodies the fundamentally concepts of the Fourier and time-domain analysis. The energy of the signal is distributed so that specific frequencies are localized in time by the group delay time and at specifics instants in time the frequency is given by the instantaneous frequency. The net positive volum of the Wigner distribution is numerically equal to the signal’s total energy. The paper shows the application of the Wigner Ville distribution, in the field of signal processing, using Scilab environment.

For an accurate prediction of the production for windpowerplants and to chose the rigth location for such investments, the main information are given through long time and punctual windmeasurements. That's why the accuracy of a proper wind resource assesment and the rigth data management give the necesary information about the wind shear, turbulance and variability (temporal and spatial). The paper presents the main windmeasurement technics to identify the vertical wind profil, wind speed, wind rose and the time distribution of those parameters.

This paper presents a complex technical solution for implementing renewable energy, namely: wind, solar photovoltaic and hydraulics. Because wind and solar photovoltaic energy habe a highly random character, it is required to find solution to store the product energy for unfavorable periods, without wind or solar radiations. This could be achieved using the third type of renewable energy, the hydraulic one, obtained from an hydroelectric pumped storage plant (HPSP), located in the imediate vicinity of the wind and solar photovoltaic plant.

The paper presents an application of a solar photovoltaic plant for the 'Eftimie Murgu' University, with an estimation of the yearly medium energy production. The substantiation of the plant designed is based on the many years measurements obtained in the laboratory for monitoring the solar photovoltaic energy of the university and the favorable conditions of promoting the energy production from renewable sources, assured in the new legislation.

The paper presents method’s and a testing stand for electronic controller using for this a signal generator and a digital oscilloscope respectively the virtual instrumentation and the signal acquisitions from the controllers input and output through an data acquisition board and an PC on that Lab View program runs.

The paper presents a PID controller made with LM741 operational amplifier that implement the PID controllers laws and allow for a widerange of applications of in the field of automatic control of technicalprocesses and systems.

The paper presents an overwiev of the performances of the grid connectedphotovoltaik plant at the University ”Eftimie Murgu��� Resita, Romaniarealised on the monitoriesed wheather and installations datastored in a on-line data base during one year.

This paper presents the actual state of research in the field of solarphotovoltaic conversion at the «Eftimie Murgu» University Resita, forthe location Resita, a location with following geographic coordinates:450 30’ Nordic latitude and 210 59’ east longitudes. The principal monitoriesed parameters are: solar radiation, module and ambient temperature, wind direction and speed, humidity, atmospheric pressure [2], a.o., in on-line mode, recorded in a data base with the possibility to view them on the Internet; added to this, the produced energy, from different types of photovoltaic modules, is counted and injected in the public grid to persuade the quality indicators of the installation.

The paper presents an experimental method to determine the skin effectin comparison to the theoretically one and the influence on the rotorparameters of the asynchronous machine with short-circuited rotorwinding.

The solution of simulation requires the construction of a system model composed of equivalents of the real elements, which must simulate those characteristics, which are relevant to the real behaviour. In this paper the simulation is realised by a designed network analyser represented the electrical line by a connection of three-phase ?-inductors represent units, which are symmetric, and the mutual inductive coupling between phases only.

The present paper wants to be a first contact in analyzing and knowing the solar photovoltaic potential from Resita, this, in fact means, the 45 parallel in our country. This issue will be obtained through monitoring the produced electric energy and injected in the public grip. The research studies are extended over a period of two years to have a more exact evolution of the monitories parameters. These researches results will be then directly used in planning of photovoltaic plants in our country.

The paper presents the major steps that have to be gone for the implementation of the mathematical model of the asynchronous machine in SciLab / Scicos. This implemented ASM model, will be used to check the dynamic behavior of the system, the current diagrams as well as the behavior motor speed and the torque, if the input signal has a pulsation form. This implementation’s are made in Scilab / Scicos environment, a clone of the MATLAB, which provides number-crunching power similar to MATLAB, at a much better cost/performance ratio. The implemented model offers the possibility to analyze the behaviors of the asynchronous machine in different dynamic situations: speed, torques, current in motor or generator regime and to study its behavior in different possible control schemes.

This paper analyzes the behavior of wind power systems at significantly variable wind speeds in time. That’s the reason why we have to determine the angular reference speed, so as to achieve a maximum capture of wind energy over a longer period of time. This paper determines the behavior of the system wind turbine (WT) synchronous generator (SG), considering the speed/mechanical angular velocity n ref/ω ref as reference in the control system. The control structure is based on the instantaneous wind speed measurement using an original model for the wind turbine. As the WT & SG system is nonlinear, the regulator tuning is done through numerical simulation.

This paper presents a control method for a wind turbine with a synchronous generator with permanent magnet (SGPM), to achieve optimal function in the optimal energy field at variable wind speed. The wind speed and the angular speed of the SGPM impose the value of the generator load in the optimal energy area. Based on energy balances, done with speed and power measurements, the generator load is determined so that the system can be brought into the optimal energy area. The operation at maximum power of a wind turbine (WT) is analyzed by modifying the generators load, under the terms of a significant wind speed variation in time. The coordinates of the maximum power point (MPP) change in time being determined by the instantaneous values of the wind speed and the mechanical inertia, not in every case the wind turbine can be brought, in a timely manner, in the MPP area. The rapidity of the wind speed variation in time as well as the inertial value, are two fundamental elements upon which the operation in MPP depends. Prescribing the value of the DC current, Icc, from the intermediate converter circuit, a simple and useful control of the wind turbine system can be achieved. The control method that allows the WT to function in the optimal energy area is based on knowing the value of Icc, which is determinate from wind speed and the angular mechanical velocity (AMV).

The paper presents the influence of time discretization on the results of simulations of technical systems. In this sense the systems are mod-eled using the SciLab/SCICOS environment, using different time inter-vals. Ulterior the processes are simulated and the results are com-pared.

This paper presents the results of research based on real data taken from the installation process at Arcelor Mittal Hunedoara. Using Matlab Simulink an intelligent system is made that takes in data from the process and makes real time adjustments in the rate of flow of the cooling water and the speed of casting that eliminates fissures in the poured material from the secondary cooling of steel. Using Matlab Simulink simulation environment allowed for qualitative analysis for various real world situations. Thus, compared to the old method of approach for the problem of cracks forming in the crust of the steel in the continuous casting, this new method, proposed and developed, brings safety and precision in this complex process, thus removing any doubt on the existence or non-existence of cracks and takes the necessary steps to prevent and correct them.

The modern, developed society becomes aware of the necessity to conserve and protect the environment, increasing the gained benefits from a rational use of the natural resources. The pollution and the limitation of the fossil fuels, associated with the political situation worldwide that affects direct the energy strategies, have opened opportunities in the area of operation renewable energy sources. The development of the exploitation of renewable energy sources is directly linked to the energy politic, which, in terms of Romania, has the focus to integrate into the European Union energy strategy. The year 2014 brought in Romania many legislative changes to the renewable support scheme, that proves, once again, the legislative unpredictability and limitations introduced by the legislator "during the game" that overthrew all economic profitability calculation of the existent and planned investments in this sector. The actual stage of the wind energy across Europe and the particular situation in Romania are highlighted; also a 2020 forecast for Romania tries to evaluate the perspective for the wind, and general, renewable energy market. The actual Romanian renewable energy support scheme, mainly regulated by "Law 220/2008" ends December 2016. The so-called "ready to build" projects especially wind- or hydropower, can't be finalized until this deadline, being unable to qualify to the existing, mainly to inoperable, support scheme. Another legislation that has to clarify how investments in renewable energy will be supported is still not in place, blocking any project development, implementation and economical benefit of the producer. The paper presents in this respect an updated overview of the Romanian renewable energy sector and its perspective.

Based on experimental measurements, this paper presents the vibration analysis of a hydro generator that equips a Kaplan hydraulic turbine of a Hydropower plant in Romania. This analysis means vibrations measurement to different operating regimes of the hydro generator respectively before installing it and into operation, namely putting off load mode (unexcited and excited) respectively putting on load mode. By comparing, through the experimental results obtained before and after the operation of hydro aggregates are observed vibrations improvements.

Vector control methods offer the possibility to gain high performance, being widely used. Certain applications require an optimum control in limit operating conditions, as, at maximum torque, that is not always satisfied. The paper presents how the voltage and the frequency for an asynchronous machine (ASM) operating at variable speed are determinate, with an accent on the method that keeps the rotor flux constant. The simulation analyses consider three load types: variable torque and speed, variable torque and constant speed, constant torque and variable speed. The final values of frequency and voltage are obtained through the proposed control schemes with one controller using the simulation language based on the Maple module. The dynamic analysis of the system is done for the case with P and PI controller and allows conclusions on the proposed method, which can have different applications, as the ASM in wind turbines.

This paper presents an intelligent system capable of eliminating the surface flaws and casting rejects, to increase the quality of continuously cast products and implicitly to increase the productivity of the installation.This method contains a fuzzy controller which requires changes of the water flow value at the secondary cooling. Fuzzy system controlling in real time the distribution of the water flow rate according to the real situation in the installation and working as an adaptive. The simulations results show us that the control strategy proposed is a very efficient method for the water flow control in the secondary cooling stage.

This paper presents an enhanced method that accurately identifies natural frequencies of structures, via an important improvement of spectral lines density. Spectral lines density increases due to the superposition of many spectra, each spectrum being accomplished by subtracting certain number of samples from the original signal and using the power spectral density analysis. The newly achieved overlapped-spectrum shows important additions to spectral line number and makes more accurately identification of frequencies in the peak position of relevant amplitudes. In this way, modal analysis becomes more reliable and efficient. Method application assumes small frequency changes and the advantage of establishing more precisely the position and dimension of damage. The analysis of all results explicitly indicates an important assessment in the evaluation of frequency. Considering relevant aspects, it can be appreciated that the approached method offers a new development way in the vibration-based damage detection, allowing de possibility to perform more accurate evaluation of frequencies and introducing new features into the domain.

To do an analysis of the phenomena that lead to cracks in continuous casting process is necessary to study the heat exchange and steel solidification. Thus, this paper proposes a modeling of semi-finished product solidification during continuous cast, based on finite difference method. To validate the model, we have developed a simulation program, which had obtained important results by running comparable with the experimental results. The proposed method of modeling and simulation allows a sufficiently accurate analysis of the phenomenon of crust formation and hence the formation of solidification cracks. Although we can use it only off-line, it derives essential information necessary for designing neural system for detection of cracks and the drawing up fuzzy decision system bases rules to determine the weight correction for the cooling water flow rate and primary casting.