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Electricity Distributions Networks (DNs) are changing from a once passive to an active electric power system element. This change, driven by several European Commission Directives and Regulations in the energy sector prompts the proliferated integration of new network elements, which can actively participate in network operations if adequately utilized. This paper addresses the possibility of using these active DN elements for optimization of a time-discrete network operation in terms of minimization of power losses while ensuring other operational constraints (i.e., voltage profiles and line currents). The active elements considered within the proposed optimization procedure are distributed generation units, capable of reactive power provision; remotely controlled switches for changing the network configuration; and an on-load tap changer-equipped substation, supplying the network. The proposed procedure was tested on a model of an actual medium voltage DN. The results showed that simultaneous consideration of these active elements could reduce power losses at a considered point of operation while keeping the voltage profiles within the permitted interval. Furthermore, by performing a series of consecutive optimization procedures at a given time interval, an optimization of network operations for extended periods (e.g., days, months, or years) could also be achieved.
Nevena Srećković; Miran Rošer; Gorazd Štumberger. Utilization of Active Distribution Network Elements for Optimization of a Distribution Network Operation. Energies 2021, 14, 3494 .
AMA StyleNevena Srećković, Miran Rošer, Gorazd Štumberger. Utilization of Active Distribution Network Elements for Optimization of a Distribution Network Operation. Energies. 2021; 14 (12):3494.
Chicago/Turabian StyleNevena Srećković; Miran Rošer; Gorazd Štumberger. 2021. "Utilization of Active Distribution Network Elements for Optimization of a Distribution Network Operation." Energies 14, no. 12: 3494.
When it comes to the proliferation of photovoltaic (PV) systems, technological solutions have to go hand in hand with optimized policy approaches and regulatory frameworks. This paper proposes a new application of state-of-the-art PV potential estimation method based on Light Detection And Ranging (LiDAR) data targeted toward individual household self-supply. The performance of the proposed general approach is demonstrated in the case of Slovenian PV based self-supply (yearly net self-sufficient energy supply) scheme and related policy. The results obtained by PV potential assessment method show drawbacks of the current policy solution in Slovenia, which limits the installed peak power of the PV systems to 80% of the rated power supply. The paper proposes to change the policy in a way that increases the yearly energy production of the PV system and assures proper voltage profiles in the electricity network. The paper is novel in terms of considering PV potential over LiDAR data by also considering self-sustainability, in using such techno-economic analysis to validate the merits and demerits of a policy approach and is the first such case study used in the context of Slovenian self-supply policy. The proposed PV potential estimation method is generally applicable for any location and can be easily adjusted to the local regulatory framework.
Luka Tomažič; Niko Lukač; Gorazd Štumberger. A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia. Sustainability 2021, 13, 1290 .
AMA StyleLuka Tomažič, Niko Lukač, Gorazd Štumberger. A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia. Sustainability. 2021; 13 (3):1290.
Chicago/Turabian StyleLuka Tomažič; Niko Lukač; Gorazd Štumberger. 2021. "A New Regulatory Approach for PV-Based Self-Supply, Validated by a Techno-Economic Assessment: A Case Study for Slovenia." Sustainability 13, no. 3: 1290.
In this paper, a method for induction machine (IM) torque/speed tracking control derived from the 3-D non-holonomic integrator including drift terms is proposed. The proposition builds on a previous result derived in the form of a single loop non-linear state controller providing implicit rotor flux linkage vector tracking. This concept was appropriate only for piecewise constant references and assured minimal norm of the stator current vector during steady-states. The extended proposition introduces a second control loop for the rotor flux linkage vector magnitude that can be either constant, programmed, or optimized to achieve either maximum torque per amp ratio or high dynamic response. It should be emphasized that the same structure of the controller can be used either for torque control or for speed control. Additionally, it turns out that the proposed controller can be easily adapted to meet different objectives posed on the drive system. The introduced control concept assures stability of the closed loop system and significantly improves tracking performance for bounded but arbitrary torque/speed references. Moreover, the singularity problem near zero rotor flux linkage vector length is easily avoided. The presented analyses include nonlinear effects due to magnetic saturation. The overall IM control scheme includes cascaded high-gain current controllers based on measured electrical and mechanical quantities together with a rotor flux linkage vector estimator. Simulation and experimental results illustrate the main characteristics of the proposed control.
Bojan Grčar; Anton Hofer; Gorazd Štumberger. Induction Machine Control for a Wide Range of Drive Requirements. Energies 2019, 13, 175 .
AMA StyleBojan Grčar, Anton Hofer, Gorazd Štumberger. Induction Machine Control for a Wide Range of Drive Requirements. Energies. 2019; 13 (1):175.
Chicago/Turabian StyleBojan Grčar; Anton Hofer; Gorazd Štumberger. 2019. "Induction Machine Control for a Wide Range of Drive Requirements." Energies 13, no. 1: 175.
This paper proposes measures to improve the protection of MV distribution networks operating with feeders in a closed-loop arrangement. Bi-directional overcurrent relays (OCRs) are discussed, the selectivity of which is achieved through the timing coordination of their operation. The classic approach is formulated as a minimization of the operating times of all the OCRs. The proposed approach enhances the selectivity by considering the maximum operating time of substation OCRs and the unwanted trips of inloop OCRs. Moreover, the sensitivity is also increased by introducing an objective function that minimizes the pickup-current settings of all the OCRs together with their operating times. Furthermore, to fulfill the demanding requirements for operating times, variable penalties are introduced. Thus, the optimization procedure is forced towards the region with viable solutions for the optimization problem. Two variants of self-adaptive differential evolution have been used that both show better convergence when compared to the classic differential evolution. Moreover, ten mutation strategies were tested, where “rand/1/bin” showed the best results. A comparison with other methods for timing coordination shows that the proposed optimization results in a comparable value for the OCRs’ operating times. In order to further reduce the operating times, GOOSE communications between the OCRs are adopted. The proposed measures for improved protection operation are fully confirmed through dynamic simulations of the faults in the discussed 20-kV network. Moreover, the proposed protection design is already implemented and permanently operates in a 20-kV network with more than 5000 customers, whereas the field results show selective and reliable protection operation.
Bostjan Polajzer; Matej Pintaric; Miran Roser; Gorazd Stumberger. Protection of MV Closed-Loop Distribution Networks With Bi-Directional Overcurrent Relays and GOOSE Communications. IEEE Access 2019, 7, 165884 -165896.
AMA StyleBostjan Polajzer, Matej Pintaric, Miran Roser, Gorazd Stumberger. Protection of MV Closed-Loop Distribution Networks With Bi-Directional Overcurrent Relays and GOOSE Communications. IEEE Access. 2019; 7 (99):165884-165896.
Chicago/Turabian StyleBostjan Polajzer; Matej Pintaric; Miran Roser; Gorazd Stumberger. 2019. "Protection of MV Closed-Loop Distribution Networks With Bi-Directional Overcurrent Relays and GOOSE Communications." IEEE Access 7, no. 99: 165884-165896.
This paper deals with rotary and linear synchronous reluctance machines and synchronous permanent magnet machines. It proposes a general method appropriate for determining the two-axis dynamic models of these machines, where the effects of slotting, mutual interaction between the slots and permanent magnets, saturation, cross-saturation, and—in the case of linear machines—the end effects, are considered. The iron core is considered to be conservative, without any losses. The proposed method contains two steps. In the first step, the dynamic model state variables are selected. They are required to determine the model structure in an arbitrarily chosen reference frame. In the second step, the model parameters, described as state variable dependent functions, are determined. In this way, the magnetically nonlinear behavior of the machine is accounted for. The relations among the Fourier coefficients of flux linkages and electromagnetic torque/thrust are presented for the models written in dq reference frame. The paper presents some of the experimental methods appropriate for determining parameters of the discussed dynamic models, which is supported by experimental results.
Štumberger; Tine Marčič; Gorazd Štumberger; Bojan Štumberger; Bojan Štumberger. Magnetically Nonlinear Dynamic Models of Synchronous Machines and Experimental Methods for Determining their Parameters. Energies 2019, 12, 3519 .
AMA StyleŠtumberger, Tine Marčič, Gorazd Štumberger, Bojan Štumberger, Bojan Štumberger. Magnetically Nonlinear Dynamic Models of Synchronous Machines and Experimental Methods for Determining their Parameters. Energies. 2019; 12 (18):3519.
Chicago/Turabian StyleŠtumberger; Tine Marčič; Gorazd Štumberger; Bojan Štumberger; Bojan Štumberger. 2019. "Magnetically Nonlinear Dynamic Models of Synchronous Machines and Experimental Methods for Determining their Parameters." Energies 12, no. 18: 3519.
This paper presents the efficiency improvement in a speed closed-loop controlled permanent magnet synchronous machine (PMSM) sensorless drive. The drive efficiency can be improved by minimizing the inverter and the PMSM losses. These can be influenced by proper selection of DC-bus voltage and switching frequency of the inverter. The direct (d-) and quadrature (q-) axis current references generation methods, discussed in this paper, further improve the efficiency of the drive. Besides zero d-axis current reference control, the maximum torque per ampere (MTPA) characteristic is normally applied to generate the d- and q-axis current references in vector controlled PMSM drives. It assures control with maximum torque per unit of current but cannot assure maximum efficiency. In order to improve efficiency of the PMSM drive, this paper proposes the generation of d- and q-axis current references based on maximum efficiency (ME) characteristic. In the case study, the MTPA and ME characteristics are theoretically evaluated and determined experimentally by measurements on discussed PMSM drive. The obtained characteristics are applied for the d- and q-axis current references generation in the speed closed-loop vector controlled PMSM drive. The measured drive efficiency clearly shows that the use of ME characteristic instead of MTPA characteristic or zero d-axis current in the current references generation improves the efficiency of PMSM drive realizations with position sensor and without it—sensorless control.
Željko Plantić; Tine Marčič; Miloš Beković; Gorazd Štumberger. Sensorless PMSM Drive Implementation by Introduction of Maximum Efficiency Characteristics in Reference Current Generation. Energies 2019, 12, 3502 .
AMA StyleŽeljko Plantić, Tine Marčič, Miloš Beković, Gorazd Štumberger. Sensorless PMSM Drive Implementation by Introduction of Maximum Efficiency Characteristics in Reference Current Generation. Energies. 2019; 12 (18):3502.
Chicago/Turabian StyleŽeljko Plantić; Tine Marčič; Miloš Beković; Gorazd Štumberger. 2019. "Sensorless PMSM Drive Implementation by Introduction of Maximum Efficiency Characteristics in Reference Current Generation." Energies 12, no. 18: 3502.
This paper deals with the Differential Evolution (DE) based method for identification of the heat equation parameters applied for the estimation of a bare overhead conductor`s temperature. The parameters are determined in the optimization process using a dynamic model of the conductor; the measured environmental temperature, solar radiation and wind velocity; the current and temperature measured on the tested overhead conductor; and the DE, which is applied as the optimization tool. The main task of the DE is to minimise the difference between the measured and model-calculated conductor temperatures. The conductor model is relevant and suitable for the prediction of the conductor temperature, as the agreement between measured and model-calculated conductor temperatures is exceptional, where the deviation between mean and maximum measured and model-calculated conductor temperatures is less than 0.03 °C.
Mirza Sarajlić; Jože Pihler; Nermin Sarajlić; Gorazd Štumberger. Identification of the Heat Equation Parameters for Estimation of a Bare Overhead Conductor’s Temperature by the Differential Evolution Algorithm. Energies 2018, 11, 2061 .
AMA StyleMirza Sarajlić, Jože Pihler, Nermin Sarajlić, Gorazd Štumberger. Identification of the Heat Equation Parameters for Estimation of a Bare Overhead Conductor’s Temperature by the Differential Evolution Algorithm. Energies. 2018; 11 (8):2061.
Chicago/Turabian StyleMirza Sarajlić; Jože Pihler; Nermin Sarajlić; Gorazd Štumberger. 2018. "Identification of the Heat Equation Parameters for Estimation of a Bare Overhead Conductor’s Temperature by the Differential Evolution Algorithm." Energies 11, no. 8: 2061.
Clouds moving at a high speed in front of the Sun can cause step changes in the output power of photovoltaic (PV) power plants, which can lead to voltage fluctuations and stability problems in the connected electricity networks. These effects can be reduced effectively by proper short-term cloud passing forecasting and suitable PV power plant output power control. This paper proposes a low-cost Internet of Things (IoT)-based solution for intra-minute cloud passing forecasting. The hardware consists of a Raspberry PI Model B 3 with a WiFi connection and an OmniVision OV5647 sensor with a mounted wide-angle lens, a circular polarizing (CPL) filter and a natural density (ND) filter. The completely new algorithm for cloud passing forecasting uses the green and blue colors in the photo to determine the position of the Sun, to recognize the clouds, and to predict their movement. The image processing is performed in several stages, considering selectively only a small part of the photo relevant to the movement of the clouds in the vicinity of the Sun in the next minute. The proposed algorithm is compact, fast and suitable for implementation on low cost processors with low computation power. The speed of the cloud parts closest to the Sun is used to predict when the clouds will cover the Sun. WiFi communication is used to transmit this data to the PV power plant control system in order to decrease the output power slowly and smoothly.
Primož Sukič; Gorazd Štumberger. Intra-Minute Cloud Passing Forecasting Based on a Low Cost IoT Sensor—A Solution for Smoothing the Output Power of PV Power Plants. Sensors 2017, 17, 1116 .
AMA StylePrimož Sukič, Gorazd Štumberger. Intra-Minute Cloud Passing Forecasting Based on a Low Cost IoT Sensor—A Solution for Smoothing the Output Power of PV Power Plants. Sensors. 2017; 17 (5):1116.
Chicago/Turabian StylePrimož Sukič; Gorazd Štumberger. 2017. "Intra-Minute Cloud Passing Forecasting Based on a Low Cost IoT Sensor—A Solution for Smoothing the Output Power of PV Power Plants." Sensors 17, no. 5: 1116.
This paper deals with the evaluation of various dynamic models for modeling of three-limb core power transformers. Due to the specific construction of such transformers, the magnetic fluxes in individual core limbs are interdependent. For applications, such as simulations and testing protection devices and algorithms, adequate prediction of inrush currents waveforms is crucial and indispensable. In this paper, various different dynamic models are tested where the limitations of standard models that are available in commercial program packages are pointed out. Two groups of models are evaluated separately: standard three-phase models composed of three-single phase transformer models and advanced three-phase models, where the topology of the magnetic circuit is considered. Furthermore, in both transformer model groups, three different material descriptions are evaluated, where linear, non-linear, and hysteretic material properties are considered. The comparison between measured and calculated waveforms of inrush currents is used to evaluate individual models. The comparison of evaluated models shows that standard dynamic models cannot provide proper waveforms of inrush currents regardless of which magnetically non-linear behavior of the iron core is considered. For adequate modeling of discussed transformers the consideration of the topology of the magnetic circuit is crucial.
Klemen Deželak; Martin Petrun; Miran Rošer; Drago Dolinar; Gorazd Štumberger. The Impact of Iron Core Model on Dynamic Behavior of Three-Phase Power Transformer Dynamic Model. IEEE Transactions on Magnetics 2015, 51, 1 -4.
AMA StyleKlemen Deželak, Martin Petrun, Miran Rošer, Drago Dolinar, Gorazd Štumberger. The Impact of Iron Core Model on Dynamic Behavior of Three-Phase Power Transformer Dynamic Model. IEEE Transactions on Magnetics. 2015; 51 (1):1-4.
Chicago/Turabian StyleKlemen Deželak; Martin Petrun; Miran Rošer; Drago Dolinar; Gorazd Štumberger. 2015. "The Impact of Iron Core Model on Dynamic Behavior of Three-Phase Power Transformer Dynamic Model." IEEE Transactions on Magnetics 51, no. 1: 1-4.
This paper deals with determining the parameters of a resistance spot welding (RSW) transformer dynamic model. To obtain an efficient, accurate, and reliable dynamic model of an electromagnetic device, accurate determination of its model's parameters is crucial. In regard to an RSW transformer, determining of the dynamic model's parameters presents a big challenge. This paper presents a new methodology for determining such parameters, which can be used where other methods are not applicable or they give inaccurate results. It is based on a stochastic optimization algorithm called differential evolution (DE). Using the presented dynamic model of the device, the parameters of the model are determined by DE in such a way that the deviation between the measured and the calculated values is minimal.
Martin Petrun; Klemen Deželak; Drago Dolinar; Gorazd Štumberger. Determining the Parameters of a Resistance Spot Welding Transformer Using Differential Evolution. IEEE Transactions on Magnetics 2014, 50, 1 -4.
AMA StyleMartin Petrun, Klemen Deželak, Drago Dolinar, Gorazd Štumberger. Determining the Parameters of a Resistance Spot Welding Transformer Using Differential Evolution. IEEE Transactions on Magnetics. 2014; 50 (4):1-4.
Chicago/Turabian StyleMartin Petrun; Klemen Deželak; Drago Dolinar; Gorazd Štumberger. 2014. "Determining the Parameters of a Resistance Spot Welding Transformer Using Differential Evolution." IEEE Transactions on Magnetics 50, no. 4: 1-4.
This paper describes three different ways of transformer modeling for inrush current simulations. The developed transformer models are not dependent on an integration step, thus they can be incorporated in a state-space form of stiff differential equation systems. The eigenvalue propagations during simulation time cause very stiff equation systems. The state-space equation systems are solved by usingA- andL-stable numerical differentiation formulas (NDF2) method. This method suppresses spurious numerical oscillations in the transient simulations. The comparisons between measured and simulated inrush and steady-state transformer currents are done for all three of the proposed models. The realized nonlinear inductor, nonlinear resistor, and hysteresis model can be incorporated in the EMTP-type programs by using a combination of existing trapezoidal and proposed NDF2 methods.
Amir Tokic; Ivo Uglesic; Gorazd Stumberger. Simulations of Transformer Inrush Current by Using BDF-Based Numerical Methods. Mathematical Problems in Engineering 2013, 2013, 1 -10.
AMA StyleAmir Tokic, Ivo Uglesic, Gorazd Stumberger. Simulations of Transformer Inrush Current by Using BDF-Based Numerical Methods. Mathematical Problems in Engineering. 2013; 2013 (4):1-10.
Chicago/Turabian StyleAmir Tokic; Ivo Uglesic; Gorazd Stumberger. 2013. "Simulations of Transformer Inrush Current by Using BDF-Based Numerical Methods." Mathematical Problems in Engineering 2013, no. 4: 1-10.
Gorazd Štumberger; Bojan Štumberger; David Stojan; Željko Plantic; Klemen Deželak; Matjaž Cemažar; Drago Dolinar. Evaluating performances of electric machines supplied by the sinusoidal and pulse width modulated voltages. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 2013, 32, 1315 -1325.
AMA StyleGorazd Štumberger, Bojan Štumberger, David Stojan, Željko Plantic, Klemen Deželak, Matjaž Cemažar, Drago Dolinar. Evaluating performances of electric machines supplied by the sinusoidal and pulse width modulated voltages. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering. 2013; 32 (4):1315-1325.
Chicago/Turabian StyleGorazd Štumberger; Bojan Štumberger; David Stojan; Željko Plantic; Klemen Deželak; Matjaž Cemažar; Drago Dolinar. 2013. "Evaluating performances of electric machines supplied by the sinusoidal and pulse width modulated voltages." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 32, no. 4: 1315-1325.
Klemen Deželak; Drago Dolinar; Gorazd Štumberger. Comparison between the simplified and the Jiles‐Atherton model when accounting for the hysteresis losses of a transformer. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 2013, 32, 1393 -1403.
AMA StyleKlemen Deželak, Drago Dolinar, Gorazd Štumberger. Comparison between the simplified and the Jiles‐Atherton model when accounting for the hysteresis losses of a transformer. COMPEL - The international journal for computation and mathematics in electrical and electronic engineering. 2013; 32 (4):1393-1403.
Chicago/Turabian StyleKlemen Deželak; Drago Dolinar; Gorazd Štumberger. 2013. "Comparison between the simplified and the Jiles‐Atherton model when accounting for the hysteresis losses of a transformer." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 32, no. 4: 1393-1403.
This paper proposes an induction machine torque control derived from the model in the stator current vector reference frame. The required torque is produced by simultaneously manipulating the magnitude and the rotation speed of the stator current vector, thus forcing the rotor flux linkage vector to change implicitly in such a way that overall stability is preserved. Additional control features include maximal torque-per-ampere ratio in steady state and almost perfect command tracking even if the machine is magnetically saturated. The control adopts a cascaded structure and is based on a partial dynamic inversion of the reduced model that assures existence and uniqueness of the inverse mapping between the required torque, the rotor flux linkage vector, and the stator current vector. Singularity at zero rotor flux linkage represents no restriction for the control performance in the admissible machine operating range. The implementation of the proposed control requires the estimation of the torque-producing rotor flux component and cascaded stator current controllers. Experimental results confirm the key expectations and show the potential and benefits of the proposed control schemes.
Bojan Grcar; Gorazd Stumberger; Anton Hofer; Peter Cafuta. IM Torque Control Schemes Based on Stator Current Vector. IEEE Transactions on Industrial Electronics 2013, 61, 126 -138.
AMA StyleBojan Grcar, Gorazd Stumberger, Anton Hofer, Peter Cafuta. IM Torque Control Schemes Based on Stator Current Vector. IEEE Transactions on Industrial Electronics. 2013; 61 (1):126-138.
Chicago/Turabian StyleBojan Grcar; Gorazd Stumberger; Anton Hofer; Peter Cafuta. 2013. "IM Torque Control Schemes Based on Stator Current Vector." IEEE Transactions on Industrial Electronics 61, no. 1: 126-138.
In this paper a three-dimensional non-holonomic integrator (NI) with drift terms is considered. For this type of plant, the question how to obtain desired piecewise constant output functions with minimum norm control inputs is explored. It is shown that this can be achieved by a nonlinear controller that provides simultaneous modulation of both the amplitude and the frequency of the harmonic input vector. The internal states are implicitly forced to follow natural periodic orbits satisfying the non-holonomic constraints of the plant. Global asymptotic stability and high dynamics in the output response are achieved. The problem of singularity at zero initial state is solved by a time optimal control scheme for the internal states. By combining the nonlinear controller and the time-optimal controller using an appropriate switching strategy, a powerful control concept can be established. The torque control of an induction machine is considered as an illustrative example for the application of the control scheme. Experimental results of the closed loop feedback control system are presented.
Bojan Grčar; Anton Hofer; Peter Cafuta; Gorazd Štumberger. A contribution to the control of the non-holonomic integrator including drift. Automatica 2012, 48, 2888 -2893.
AMA StyleBojan Grčar, Anton Hofer, Peter Cafuta, Gorazd Štumberger. A contribution to the control of the non-holonomic integrator including drift. Automatica. 2012; 48 (11):2888-2893.
Chicago/Turabian StyleBojan Grčar; Anton Hofer; Peter Cafuta; Gorazd Štumberger. 2012. "A contribution to the control of the non-holonomic integrator including drift." Automatica 48, no. 11: 2888-2893.
This paper presents a novel voltage-angle-based field-weakening control scheme appropriate for the operation of permanent-magnet synchronous machines over a wide range of speed. At high rotational speed, the stator voltage is limited by the inverter dc bus voltage. To control the machine torque above the base speed, the proposed method controls the angle of the limited stator voltage by the integration of gain-scheduled q-axis current error. The stability of the drive is increased by a feedback loop, which compensates dynamic disturbances and smoothes the transition into field weakening. The proposed method can fully utilize the available dc bus voltage. Due to its simplicity, it is robust to the variation of machine parameters. Excellent performance of the proposed method is demonstrated through the experiments performed with and without speed and position sensors.
David Stojan; Dušan Drevensek; Željko Plantic; Bojan Grcar; Gorazd Stumberger. Novel Field-Weakening Control Scheme for Permanent-Magnet Synchronous Machines Based on Voltage Angle Control. IEEE Transactions on Industry Applications 2012, 48, 2390 -2401.
AMA StyleDavid Stojan, Dušan Drevensek, Željko Plantic, Bojan Grcar, Gorazd Stumberger. Novel Field-Weakening Control Scheme for Permanent-Magnet Synchronous Machines Based on Voltage Angle Control. IEEE Transactions on Industry Applications. 2012; 48 (6):2390-2401.
Chicago/Turabian StyleDavid Stojan; Dušan Drevensek; Željko Plantic; Bojan Grcar; Gorazd Stumberger. 2012. "Novel Field-Weakening Control Scheme for Permanent-Magnet Synchronous Machines Based on Voltage Angle Control." IEEE Transactions on Industry Applications 48, no. 6: 2390-2401.
Boštjan Polajžer; Gorazd Štumberger; Drago Dolinar. Impedance-Based Methods for Detection of Voltage Sag Sources. Renewable Energy and Power Quality Journal 2012, 1255 -1258.
AMA StyleBoštjan Polajžer, Gorazd Štumberger, Drago Dolinar. Impedance-Based Methods for Detection of Voltage Sag Sources. Renewable Energy and Power Quality Journal. 2012; ():1255-1258.
Chicago/Turabian StyleBoštjan Polajžer; Gorazd Štumberger; Drago Dolinar. 2012. "Impedance-Based Methods for Detection of Voltage Sag Sources." Renewable Energy and Power Quality Journal , no. : 1255-1258.
This paper deals with the acoustic noise emissions caused by a welding transformer (WT) operating as part of a middle-frequency direct current resistance spot welding system (RSWS). The WT consists of an iron core, one primary winding, and two secondary windings. The primary winding is supplied by the voltage from the input converter while the full-wave diode output rectifier is connected to the two secondary windings in order to generate a direct welding current. In the case study, the alternating current primary voltage is generated in two different ways, by applying a pulse width modulation and two hysteresis controllers. The aim of this paper is to analyze how the voltage generation method influences the acoustic noise emissions caused by the WT. The analysis is based on the values of the supply current, the welding current, and the iron core flux density measured on a 160 kW industrial WT operating as a part of laboratory RSWS where the supply voltage is generated in two different ways. The results presented in the paper show that proper voltage generation method can substantially reduce the acoustic noise emissions caused by a WT.
Gorazd Stumberger; Klemen Dezelak; Beno Klopcic; Drago Dolinar. The Impact of the Voltage Generation Method on Acoustic Noise Emissions Caused by a Welding Transformer. IEEE Transactions on Magnetics 2012, 48, 1669 -1672.
AMA StyleGorazd Stumberger, Klemen Dezelak, Beno Klopcic, Drago Dolinar. The Impact of the Voltage Generation Method on Acoustic Noise Emissions Caused by a Welding Transformer. IEEE Transactions on Magnetics. 2012; 48 (4):1669-1672.
Chicago/Turabian StyleGorazd Stumberger; Klemen Dezelak; Beno Klopcic; Drago Dolinar. 2012. "The Impact of the Voltage Generation Method on Acoustic Noise Emissions Caused by a Welding Transformer." IEEE Transactions on Magnetics 48, no. 4: 1669-1672.
This paper deals with a dual-axis sun tracking system for a photovoltaic system. Its trajectories are determined by an optimization procedure. The optimization goal is the maximization of the electrical energy production within a photovoltaic system, by considering the tracking system consumption. The procedure used for determining the tilt angle and azimuth angle trajectories is described as a nonlinear and bounded optimization problem. Since an explicit form of the objective function is unavailable, a stochastic search algorithm called Differential Evolution is applied as the optimization tool. In order to evaluate the objective function, models for calculating the available solar radiation and tracking system consumption are applied together with the efficiencies of solar cells, a DC/DC converter and inverter. A new algorithm is introduced for the time dependent prediction of available solar radiation. It is based on the length of a sunbeam’s path through the atmosphere and the statistical data of a pyranometer measured total and diffuse solar radiation at a given location on the Earth. The optimization bounds are given in the form of angular speed, lower and upper bounds for both angles and angle quantization. The results presented in this paper show, that the optimal trajectories can help to increase the electrical energy production within photovoltaic systems by sun tracking.
Sebastijan Seme; Gorazd Štumberger. A novel prediction algorithm for solar angles using solar radiation and Differential Evolution for dual-axis sun tracking purposes. Solar Energy 2011, 85, 2757 -2770.
AMA StyleSebastijan Seme, Gorazd Štumberger. A novel prediction algorithm for solar angles using solar radiation and Differential Evolution for dual-axis sun tracking purposes. Solar Energy. 2011; 85 (11):2757-2770.
Chicago/Turabian StyleSebastijan Seme; Gorazd Štumberger. 2011. "A novel prediction algorithm for solar angles using solar radiation and Differential Evolution for dual-axis sun tracking purposes." Solar Energy 85, no. 11: 2757-2770.
Klemen Deželak; Gorazd Štumberger; Drago Dolinar; Beno Klopcic; Gorazd Štumberger Klemen Deželak. Artificial Neural Network Applied for Detecting the Saturation Level in the Magnetic Core of a Welding Transformer. Artificial Neural Networks - Industrial and Control Engineering Applications 2011, 1 .
AMA StyleKlemen Deželak, Gorazd Štumberger, Drago Dolinar, Beno Klopcic, Gorazd Štumberger Klemen Deželak. Artificial Neural Network Applied for Detecting the Saturation Level in the Magnetic Core of a Welding Transformer. Artificial Neural Networks - Industrial and Control Engineering Applications. 2011; ():1.
Chicago/Turabian StyleKlemen Deželak; Gorazd Štumberger; Drago Dolinar; Beno Klopcic; Gorazd Štumberger Klemen Deželak. 2011. "Artificial Neural Network Applied for Detecting the Saturation Level in the Magnetic Core of a Welding Transformer." Artificial Neural Networks - Industrial and Control Engineering Applications , no. : 1.