Power electronic converters for medium and high power / voltage applications employ low frequency synchronous fundamental switching to minimize semiconductor switching losses. There are two major approaches to converter switching angles determination - Selective Harmonic Elimination (SHE) and Total Harmonic Distortion (THD) minimization. For the THD minimization, converter switching angles are found to assure minimum THD criterion without taking care of frequency spectrum. For the SHE approach, all degrees of freedom due to available amount of switching angles are spent on elimination of low order harmonics. Recently suggested combined approach suggests spending some degrees of freedom on certain harmonics elimination and the rest for minimizing THD. This generalized problem formulation includes classic minimal THD and SHE problems as special cases. The paper presents comprehensive results on combined SHE and THD minimization for a staircase modulation of a single-phase converter with 5, 6, 7 and 8 switching angles (6, 7, 8 and 9 non-negative voltage levels).
The paper presents a new prototype model car design devoted to provide a better study and research of the control techniques and navigation algorithms employed within vehicle platooning. The prototype car has a modular design and is equipped with various sensors. All the car parts were designed in a 3D CAD application and 3D printed. The embedded application designed to control the car behavior is developed in compliance with the FreeRTOS real-time operating system. The embedded system was designed to be highly customizable and is composed of a main board with a dsPIC33 microcontroller and an optional secondary one, namely STM32F3DISCOVERY board. The latest can implement a more powerful platoon controller whilst freeing the main board of this task.
This paper deals with the start-up analysis of a synchronous reluctance motors (SynRMs) with uniformly distributed cage bars in the rotor structure. Two SynRMs are modelled using 2D Finite Element Method (FEM). The rotors of both motors are built with stamped conventional steel laminations having flux barriers. The first motor model (SynRM1) has closed rotor slots above each flux barrier separated with magnetic bridges, and the second (SynRM2) is fitted with cage bars in the rotor air-barriers. The motors magnetic conditions are analysed under transients and steady-state operations. The Finite Element Analysis (FEA) results show that the SynRM2 has higher peak-to-peak accelerating torque, but has higher synchronization time. The results also provide that high steady-state average torque (Tave.) and lower torque ripple (Trip.) contents are achieved by the fitted with cage bars in the rotor air-barriers.
This study presents the direct torque controlled induction motor (IM) drive utilizing a novel extended Kalman filter (EKF) that simultaneously estimates stator stationary axis components of stator currents and stator fluxes in addition to rotor and stator resistances with the assumption of available stator voltages/currents and rotor speed. Thus, it is desired to show that the on-line estimations of rotor and stator resistances are possible by using a single EKF algorithm in the case with speed-sensor. Performances of the proposed EKF are tested under challenging scenarios generated in simulations. The obtained results confirm very satisfying performances of the introduced EKF algorithm and thus the IM drive.
This paper presents a toolbox created with the purpose of offering support for power engineering students to better understand the power system steady-state operation and active power flow control using a phase-shifting transformer (PST). The toolbox consists of a graphical user interface (GUI) that allows the user to define scenarios, run the load-flow calculation and select scenarios in order to compare the results.
The purpose of this paper is to estimate the efficiency of the inverter circuits used for the Photovoltaic (PV) systems. The analysis of a power electronics converter with the SPICE during the steady-state operation takes a long time and the results may not be obtained accurately due to convergence problem in the solver. The MATLAB package program is widely preferred to analyze the power electronics converters if the switching losses are not taken into account and efficiency of the converter is not main purpose of the study. Here, In order to perform a detailed efficiency analysis of converter with SPICE program, the gate signals of IGBTs have been generated as a text file in MATLAB simulation of the same converter and that data has been transferred into the SPICE. The simulation results are verified with experimental results. The algorithm developed here is applicable to all converters that can be simulated in the MATLAB and the SPICE. Hence this approach is very useful to compare the efficiencies of the power electronic converters which are alternative to each other.
Image segmentation has been and still is a challenge in computer vision. Regardless of the methods used to perform this task, almost always the result is the same: a set of areas representing locations of various items found in the image. If we wish to classify the areas into two types of data, the problem becomes separating foreground from background. Our proposed method starts with this supposition: that the image is segmented and as a result we obtain a mask where the white pixels represent foreground and the black ones are the background. Another supposition we make, is that the items have almost the same size and shape. The goal is to obtain the locations of all the items in the image. This algorithm has numerous applications such as item localization, measurement, validation, etc.
This paper is concerned with a portable automatic solar panel, mounted on a mobile trailer. The benefits of a mobile solar panel versus one mounted in a fixed position are highlighted. The paper focuses mostly on the efficiency of the solar panel, in relation to the sunlight angle with respect to the panel surface. The results of the analysis performed demonstrate the higher efficiency of the panel mounted on a sun tracking device with quantifiable differences reported in the paper.
In this paper, we introduce a real-time approach for object recognition, applying the Faster Region-based Convolutional Network (Faster-RCNN) concept in an affordable and open source simulator that can be used to train and test Deep Neural Networks (DNN) models. The objective is to provide the scientific community with a framework where the advantages and disadvantages of already published or new designed architectures and concepts for object detection can be validated. The framework proposes two available configurations for implementing DNN algorithms. Our framework provides an interface to the TORCS racing game simulator, where the deployed methods can be evaluated. Various ground truth information can be extracted from TORCS, like the traffic scene image, car position on the track, speed or distances between the traffic participants.
The purpose of this article is to perform a modal analysis for a three phase induction motor (11kW–1000 rpm), premium efficiency IE3 category. Modal analysis involves determining the frequencies and vibration modes. The analysis was accomplished on the main components of the motor and the entire assembly.
The paper presents the design of non-uniform linear antenna arrays with symmetrical elements, considering linear and parabolic variations for distances between elements and a non-uniform distribution of currents through the elements. Starting from an imposed radiation pattern the coefficients, which describe the linear and parabolic variations of the array antenna parameters, are determined using optimization with genetic algorithms. Using this approach, the number of variables of the fitness function is reduced from 2N to 2, which can be helpful in the implementation of real-time algorithms used in complex/dynamic adaptive arrays.
The paper subject is the modernization of two mobile wood processing equipment, a debarking and a chipping machine, working at the forest border and used to obtain wood chips for the pulp and paper industry, in order to work in tandem operating mode. Control hardware has been added and original software has been elaborated but with the wireless communications between the two machines established, the main goal of the work and the principal novelty is achieved, controlled tandem operation mode. The specific equipment hardware challenges and software implementation are presented. The control system design and online measurements allows optimization using simulations. The practical tests and experimental results are presented. The production efficiency has been improved by 25%. Having the experimental results, a correlation study of the debarking and chipping processes in tandem operating mode has shown a minimum fuel rate versus the processes time lag and a software module to watch it online has been added on, being a second novelty of the work.
The actual energy efficiency requirements generated a large usage of the power electronic converters for driving asynchronous motors in numerous industrial facilities. The associated power quality issues of these adjustable speed drives, especially harmonic currents, adversely affect the power distribution transformers by increasing their losses and decreasing their life time expectancy. Accordingly, the intentional reduction of the transformers apparent power rating (derating) becomes mandatory in order to preserve their rated losses and the equivalent admissible thermal stress. The paper investigates both theoretically and experimentally the transformers harmonic behavior by evaluating the additional losses and the corresponding maximal permissible supplied power. The transformer derating factors, according to different international standards, are also computed and critically analyzed in terms of their suitable usage. The study is illustrated on 160 kVA oil-type three-phase power distribution transformer that mainly supplies induction pump motors controlled by frequency converters. The transformer operating parameters are acquired at its low-voltage secondary windings by a portable power quality analyzer.
The hydropower plants have been one of the most important points in the secure operation of the system in the last period. The massive introduction of the renewable energy sources with a variable production, determined the hydropower plants to become a major player in the power system control, helping stabilize fluctuations between demand and supply. The availability, flexibility and reliability of power production and also the quality of energy in hydropower plants determine an appropriate control of the system behavior in normal operating conditions, and in the ones improper. An expert system for optimal power allocation into a dispatchable unit which include three hydropower plants is proposed in the paper. The obtained results have shown that the expert system can be used with success for a proper power allocation between plants inside of a hydropower dispatchable unit for the next day.
The paper presents the inductances and rotor resistance estimation - using FEM - for the closed slot induction machine. One presents the variations of inductances and rotor resistance as function on current and frequency for emphasizing their dependence upon the saturation level of the machine. So it is possible to estimate the machine parameters for a large area of the operating modes.
The analysis of disturbances transmission is a complex process that supposes the study of disturbances' sources, propagation and magnitude. The paper presents the results obtained within a research that aimed to assess the condition of low-voltage microgrids, relating to power quality, principally harmonic distortion and imbalance. For this goal, a careful investigation of the disturbances' sources was achieved. Further on, the propagation of harmonics and imbalance was performed using MATLAB/Simulink and the proper quality indices were traced. Therefore, a real microgrid was implemented using the three-phase models of the electric lines, power sources and consumers. This approach gave the opportunity to get an appropriate view of the power quality indices' actual situation in every node of the microgrid. Based on different loading regarding the energy sources and consumers i.e. day, night or evening, we considered various situations.
A spark discharge, which was produced between two electrodes made from a Ni3Al alloy, was applied in the production of hydrogen in the steam reforming of ethanol. The influence of the water: ethanol molar ratio and feed flow on the total conversion rate of ethanol, as well as the conversion of ethanol into hydrogen, energy efficiency and selectivity of ethanol conversion to hydrogen, carbon monoxide, carbon dioxide, methane, ethylene and acetylene were studied. The highest energy efficiency was 38 gH(2)/kWh. The highest selectivity of ethanol conversion to hydrogen was 89%. The highest conversion of ethanol was 78%.
High-Voltage DC (HVDC) transmission lines offer highly efficient transport of electric energy. If connected to comparatively weak AC grids, self-commutated converters are the proper choice, because they allow to stabilize the grid in case of faults by injecting reactive power. At high voltages of e.g. 400 kV Modular Multilevel Converters (MMC) fulfill all requirements. For testing all relevant aspects of a multiterminal HVDC transmission system, a scaled-down test bench has been built up. The associated real-life system "Ultranet" will use overhead lines. Weather-induced faults (lightning, conductor bouncing und strong wind) are expected and have to be mastered by the converter stations. This paper first introduces the system and the associated test bench and then presents the mitigation of faults caused by arcing.
The article presents a study to determine the thermal transmittance for buildings different walls structure. Thermal transmittance is used especially in western European countries to indicate the rate of heat transfer for different components of buildings: walls, ceilings, floors, windows, doors, etc. The first part of the article includes several thermal transmittance introductive notions. The second part of the article defines the global heat transfer and thermal transmittance and their calculating relationships. In the third part of the article is presented a comparison of thermal transmittance values for two different wall structures analyzed by numerical calculation so as MC 001/2009 and by measurements taken using specialized equipment Testo 435.
