Transactions on Environment and Electrical Engineering

Online ISSN: 2450-5730
Publications
Article
Safety is an essential issue for processes that present high risk for human beings and environment. An acceptable level of risk is obtained both with actions on the process itself (risk reduction) and with the use of special safety systems that switch the process into safe mode when a fault or an abnormal operation mode happens. These safety systems are today based on digital devices that communicate through digital networks. The IEC 61508 series specifies the safety requirements of all the devices that are involved in a safety function, including the communication network. Also electrical generation and distribution systems are processes that may have a significant level of risk, so the criteria stated by the IEC 61508 applies. Starting from this consideration, the paper analyzes the safety requirement for the communication network and compare them with the services of the communication protocol IEC 61850 that represents the most used protocol for automation of electrical plants. The goal of this job is to demonstrate that, from the technical point of view, IEC 61850 can be used for implementing safety-related functions, even if a formal safety certification is still missing.
 
Article
Proper synchronization of Distributed Generator with grid and its performance in grid-connected mode relies on fast and precise estimation of phase and amplitude of the fundamental component of grid voltage. However, the accuracy with which the frequency is estimated is dependent on the type of grid voltage abnormalities and structure of the phase-locked loop or frequency locked loop control schemes. Among various control schemes, second-order generalized integrator based frequency- locked loop (SOGI-FLL) is reported to have the most promising performance. It tracks the frequency of grid voltage accurately even when grid voltage is characterized by sag, swell, harmonics, imbalance, frequency variations etc. However, estimated frequency contains low frequency oscillations in case when sensed grid-voltage has a dc offset. This paper presents a modified dual second-order generalized integrator frequency-locked loop (MDSOGI-FLL) for three-phase systems to cope with the non-ideal three-phase grid voltages having all type of abnormalities including the dc offset. The complexity in control scheme is almost the same as the standard dual SOGI-FLL, but the performance is enhanced. Simulation results show that the proposed MDSOGI-FLL is effective under all abnormal grid voltage conditions. The results are validated experimentally to justify the superior performance of MDSOGI-FLL under adverse conditions.
 
Article
The partial discharge diagnosis is an established instrument for the condition assessment of high voltage insulations and equipment. Under AC voltage stress the phase resolved pattern is of great significance in order to become aware of the type of fault. As a result of the inapplicability for DC voltage stress, approaches for alternative interpretation techniques such as the time domain analysis of partial discharges were identified in recent investigations. In these different types of fault are taken into account as well as different insulating media. The purpose of this paper is to investigate whether an analysis of the pulse shape is also applicable for the defect identification under AC voltage stress. By focussing on gaseous insulating media, contact noise and surface discharges are emulated in ambient air, whereas corona discharges are emulated in ambient air and oxygen. A method for analysing discharges, occurring in the negative and the positive half-wave of the test voltage, is proposed and discussed.
 
Article
This paper represents the overall electrical energy profile and access in Bangladesh. In the recent past Bangladesh has been experiencing shortage of electricity, and about 42 % of population no access to the electricity. The electricity consumption has rapidly increased over last decade. The demand and consumption will intensify in the remote future as overall development and future growth. To set “vision 2021” of Bangladesh; government of Bangladesh has devoted to ensuring access of affordable and reliable electricity for all by 2021. In the modern time, energy is the vital ingredient for socioeconomic growth in the developing country i.e., alleviating poverty. Along with electricity access in Bangladesh strived to become middle income country by 2021. Bangladesh has experienced that energy consumption inclines to increase rapidly when per capita income researches between US$ 1,000 and US$ 10,000, and a country’s
 
Bode plot of inverter output impedance and grid impedance (a) proportional gain changes (top) (b) integral gain changes (bottom) 
The inverter output impedance sensitivity to inductance variation
Article
Explored in this paper is the grid impedance effect on the stability of a single-phase grid connected inverter with an LC filter based on an analysis of the inverter output impedance. For a single-phase grid connected inverter, a PI controller is often used to regulate the current injected into the grid. However, the control performance can be influenced when the inverter is connected to a weak grid. Also, the utility grid has background harmonic noise, which can make the injected current distorted. Therefore, analysis of the output impedance of a single-phase grid connected inverter is important for the robustness and stability of the system. By modeling the output impedance of inverter, it can be determined that the proportional gain and integral gain of the controller have an effect on the output impedance. Analytical results show that by adjusting the PI controller parameters, the ability for harmonic reduction and stability of the system can be improved. Simulation and experiments using a 1 kW single-phase grid connected inverter verify the effectiveness of the theoretical analysis.
 
Article
The objective of this work is to investigate the influence of slotted air gap constructive parameters on magnetic flux density of rotating machines. For this purpose, different approaches were used to solve the air gap field diagram using finite element method and the magnetic field distribution uniformity was evaluated by Carter's factor calculation on two-dimensional and three-dimensional models. Sensitivity analysis of slot constructive parameters was performed and results show that slot geometry modifies the magnetic flux on air gap and shifts the air gap magnetic equipotential midline of double slotted machines. Finally, minimization of Carter’s factor on two-dimensional model presents an optimized slot geometry with a near uniform magnetic flux density distribution.
 
PD measuring circuit according to IEC 60270 to determine the PD inception voltage and to capture the pulse shape. 
Medians of the pulse width (left) and the fall time (right) for positive corona discharges in dependence of the absolute humdity. 
Box plots for the pulse shape parameters rise time (top left), pulse width (top right), fall time (bottom left) and the apparent charge (bottom right) of positive corona discharges occuring under a varying temperature level for relative humidity levels of 40 % and 80 %. 
Box plots for the pulse shape parameters rise time (top left), pulse width (top right), fall time (bottom left) and the apparent charge (bottom right) of positive corona discharges occuring under a varying relative humidity level for temperature levels of 20 °C and 50 °C. 
Article
The increasing importance of HVDC transmission systems requires the development and evaluation of suitable basic approaches regarding the partial discharge diagnosis. Although diverse promising approaches are identified, recent research is focused on standard atmospheric conditions. Due to the fact that this is just partly consistent to real operating conditions, additional research is required. Focusing on the time domain analysis of corona discharges, occurring under positive DC voltage stress in air, a measurement method for investigating the influence of varying atmospheric quantities is presented. Measurements are carried out for five different relative humidity levels in the range of 20 % to 95 % and for four different temperature levels in the range of 20 °C to 65 °C. As characterizing pulse shape parameters, the rise time, the pulse width and the fall time are determined as well as the apparent charge. The gained values are compared to each other and reconciled with physical processes.
 
Article
In this paper we proposes a synthesis of different mathematical models of power electronic converters based on Thevenin/Norton equivalent circuits. Those models, composed by impedances and harmonic noise sources, are helpful to predict the conducted ElectroMagnetic Interferences (EMI) generated by converters connected to the electrical network. Moreover, the extracted impedances are determining for sizing EMC filters. The proposed analytical model is tested with PSpice simulations and validated by experimental measurements, from DC frequency until 30MHz.
 
ROUTE THAT CAN BE REMOVED FROM SYSTEM WHILE MAINTAING 80% LOADING CONDITION 
BUS DATA OF DEHRADUN SYSTEM IN 2015 
Article
Planning for expanding a power system under different scenarios is one of the major challenge for power engineers hence, it is very important and essential to implement a well-balanced and feasible system over a time horizon under suitable assumptions and available constraints. Transmission expansion planning is one of this task. Here it is important to develop a suitable planning structure. In this paper some analytical approaches have been implemented for specific load condition with variations in generation.
 
Article
Since its launch in February 2012, the LAser RElativity Satellite (LARES) of the Italian Space Agency experienced four close approaches with space debris. LARES orbits at an altitude of 1450 km, in a region where the density of space debris has a peak. However, the probability of an impact with a debris during the operational life of the satellite was reasonably low. The analysis of the close approaches identified three of the objects, that are from two peculiar population of objects. This paper discusses the problem of space debris in low orbit, the approaches occurred with LARES, and some possible scenarios related to space regulations and space law in case of an impact.
 
Unconventional grid.
Surface Potential.
Surface Potential. 
Surface Potential. 
Article
This paper deals with the computation of ground resistance, surface voltage, touch voltage and step voltage, to mesh with horizontal wires arranged in different angles. The computer program implemented used in the mathematical modeling is based on the method proposed by Heppe, which allows obtaining the grounding parameters for homogeneous soil and soil stratified in two layers. The results obtained with the proposed method will be compared with other methods in literature. Also will be presented the results of a grounding grid using wires at various angles.
 
Zoomed waveforms: (a) voltages of tie-1 and tie-2, (b) input current of boost converter, (c) PV array voltage Each row of Table-II shows maximum output power of PV array with different shading pattern. G_PVij indicates the irradiance on PV module PVij, while Po_wo_fc stands for maximum power obtained in absence of flyback converters. Po_CC represents the maximum power tracked with TCT-CC method and Po_GCC represents the maximum power tracked with TCT-GCC method. It is observed that the GCC method significantly enhances the amount of output power of the array under partially shaded conditions compared to TCT-CC method.
Article
Non-uniform conditions on the modules of the PV array, especially, partial shading reduces the output of the PV array to a large extent. The shaded module in a string limits the current of the entire string and hence, the output power of the string. The output power under such conditions is reported to be higher for total-cross-tied (TCT) configuration. This paper describes two different approaches, one based on current compensation (current equalization) and another based on voltage equalization, to extract higher power from the partially shaded total-cross-tied photovoltaic array. The TCT configuration is considered to minimize the number of converters, sensors, cost and complexity involved. The additional converters in the two distinct approaches evaluated here operate only when the partial shading occurs and are controlled to minimize the current and voltage miss-matches. The analysis and the control algorithm are presented. Simulation results obtained in MATLAB/Simulink are included to demonstrate the effectiveness of both methods and the relative merits and demerits of these approaches are highlighted.
 
Article
The increase of renewable non-programmable production and the necessity to locally self-consume the produced energy led to utilize ever more storage systems. To correctly utilize storage systems, an opportune management method has to be utilized. This paper implements a multi-period management method for storage systems, using different management strategies. The method aims to minimize the total absorbed and supplied energy or the peak power exchanged with the grid. The results show the effectiveness of the method in diminishing the energy exchanged with the grid and also the possibility to optimize the performance of the storage systems
 
Article
Electric vehicles (EV) have brought promising technologies for future mobility solutions. As one of the key components of EVs, battery systems have fundamental functions which disconnect the battery during parking and in case of failure. To provide a safe system, specialized high voltage (HV) electromechanical switches are used to perform these major functions such as switch on, switch off or pre-charging. Due to these components can be easily damaged, expensive, heavy and bulky, a solution based on pure semiconductors may be desired to accomplish these operations. Many studies were exhibited on EV battery systems regarding developing solid-state systems for HV switchgear. Developing technology on semiconductor devices allows to make a safety concept based on only solidstate components. This study presents a comprehensive analysis off pre-charge sequences between conventional and semiconductor switchgear to be used in electric vehicle battery systems. Spice simulations are presented to investigate advantages and drawbacks of these systems.
 
Wholesale Pricing used for 48 periods
MAS with HDBMS Fig.14 shows the overall communication of the MultiAgent System (MAS) for HDBMS using JADE. It shows the importance of the interactions in the communication based network.
Overall MAS communication 
Article
Smart Buildings is a modern building that allows residents to have sustainable comfort with high efficiency of electricity usage. These objectives could be achieved by applying appropriate, capable optimization algorithms and techniques. This paper presents a Housing Development Building Management System (HDBMS) strategy inspired by Building Energy Management System (BEMS) concept that will integrate with smart buildings using Supply Side Management (SSM) and Demand Side Management (DSM) System. HDBMS is a Multi-Agent System (MAS) based decentralized decision making system proposed by various authors. MAS based HDBMS was created using JAVA on a IEEE FIPA compliant multi-agent platform named JADE. It allows agents to communicate, interact and negotiate with energy supply and demand of the smart buildings to provide the optimal energy usage and minimal electricity costs. This results in reducing the load of the power distribution system in smart buildings which simulation studies has shown the potential of proposed HDBMS strategy to provide the optimal solution for smart building energy management.
 
Article
This paper focuses mainly on performance analysis for three biogas stations situated within the territory of the Czech Republic. This paper contains basic details of the individual biogas stations as well as description of their types. It also refers to the general description of the measurement gauge involved, with specifications of its potential use. The final part of this paper deals with the analysis of course data obtained, with special regard to voltage, current, active power and reactive power data.)
 
Ranking and failure distrbution of power electronic components in power converters [1]. 
Aspects in power electronics reliability assessment [2]. 
Article
Boost converters are needed in many applications which require the output voltage to be higher than the input voltage. Recently, boost type converters have been applied for industrial applications, and hence it has become an interesting topic of research. Many researchers proposed different impedance source converters with their unique advantages as having a high voltage gain in a small range of duty cycle ratio. However, the thermal behaviour of the semiconductor devices and passive elements in the impedance source converter is an important issue from a reliability point of view and it has not been investigated yet. Therefore, this paper presents a comparison between the conventional boost, the Z-source, and the Y-source converters based on a thermal evaluation of the semiconductors. In addition, the three topologies are also compared with respect to their efficiency. In this study the results show that the boost converter has higher efficiency than the Zsource and Y-source converter for these specific voltage gain of 2 and 4. The operational principle, mathematical derivations, simulation results and final comparisons are presented in this paper.
 
Article
The purpose of the present study is to simulate and analyze an isolated full-bridge DC/DC boost converter, for photovoltaic panels, running a modified perturb and observe maximum power point tracking method. The zero voltage switching technique was used in order to minimize the losses of the converter for a wide range of solar operation. The efficiency of the power transfer is higher than 90% for large solar operating points. The panel enhancement due to the maximum power point tracking algorithm is 5.06%.
 
Article
This paper proposes a methodology based on system connections to calculate its complexity. Two study cases are proposed: the dining Chinese philosophers’ problem and the distribution center. Both studies are modeled using the theory of Discrete Event Systems and simulations in different contexts were performed in order to measure their complexities. The obtained results present i) the static complexity as a limiting factor for the dynamic complexity, ii) the lowest cost in terms of complexity for each unit of measure of the system performance and iii) the output sensitivity to the input parameters. The associated complexity and performance measures aggregate knowledge about the system.
 
Article
The aim of this research project is the architecture and the design of an electronic system for controlling domestic tactile switches to be integrated into a home automation system based on the KNX standard. All the steps that led to the fulfillment of the finished prototype are reported, from the study and design of the capacitive tactile sensors and the electronic control board according to the specifications imposed by KNX standard. The touch event detection is reached as a trade-off with the footprint requirements of the switch. Experimental results of the fabricated prototype are presented to demonstrate the feasibility of this device
 
b: Block diagram of alternative potential multi-source renewable energy ship powering network with parallel AC and DC grid 
Generation and load profile for tanker operation during cargo unloading at port 
a: Block diagram of potential multi-source renewable energy ship powering network with DC grid 
Article
The paper discusses the feasibility of installing renewable energy generation technologies on sea-going transport, taking into account the additional weight and power consumption. This study in based on the power management of a 26,198 tonne commercial chemical tanker. The management system would aim at reducing the number of generators as well as the power required from burning fossil fuels. After a process of elimination of potential technologies based on feasibility of the project and shipboard application, the work is focused towards photovoltaic and wind energy generation in combination with fossil fueled engines and Li-ion battery storage covering the higher energy density needs, and the intermittent nature of renewables. The network architecture is optimized in order to have the highest efficiency, and reduced system weight. The results show that successful management of the system can lead to reduction in generator requirement, and energy despite the weight of extra installations of photovoltaic and wind energy generation systems. By reducing the number of generators and allowing each remaining one to operate near their maximum power, the specific fuel consumption is improved, the efficiency is increased, resulting in significant fuel and cost saving, along with the mass of fuel to be carried on-board.
 
General Structure of a TEM 
Figure of merit ZT of different thermoelectric materials performing a function of temperature 
Electro-thermal model of a TEM 
Identification of internal and contact thermal resistances of the TEM 
Article
The efficiency of a Thermoelectric Module (TEM) is not only influenced by the material properties, but also by the heat losses due to the internal and contact thermal resistances. In the literature, the material properties are mostly discussed, mainly to increase the well-known thermoelectric figure of merit ZT. Nevertheless, when a TEM is considered, the separate characterization of the materials of the p and n elements is not enough to have a suitable TEM electrical model and evaluate more precisely its efficiency. Only a few recent papers deal with thermal resistances and their influence on the TEM efficiency; mostly, the minimization of these resistances is recommended, without giving a way to determine their values. The aim of the present paper is to identify the internal and contact thermal resistances of a TEM by electrical characterization. Depending on the applications, the TEM can be used either under constant temperature gradient or constant heat flow conditions. The proposed identification approach is based on the theoretical electrical modeling of the TEM, in both conditions. It is simple to implement, because it is based only on open circuit test conditions. A single electrical measurement under both conditions (constant-temperature and constant-heat) is needed. Based on the theoretical electrical models, one can identify the internal and thermal resistances.
 
The size of e-bus fleet in European region and USA [7].
Article
Today, climate change is a significant effect on population growth, especially in big cities. Transport in metropolitan cities is the most important reason for climate change with the contribution of CO2 pollution that threatens human health and the environment. Electrified transport systems can, therefore, provide a suitable solution to air pollution and health problems. This study investigates the feasibility of applying electric buses to the Metrobus line in Istanbul. Initially, Metrobus line data regarding the number of vehicles, number of stops, route length is gathered from the official Istanbul transportation system to define how much energy is needed for the routes. Then, it is analyzed how to re-charge proposed batteries for the allocation of chargers on the stations where it is applicable. It is observed that the electrification of each line is not possible.
 
Proposal for a new definition of the SP: Case Study. Note: The Scarcity prices were converted into USD using the same ECR of SP t f . 
Article
The Colombian government introduced a capacity market in order to promote the diversification in the energy matrix, and protect users from high prices derived from dry seasonal events. Unfortunately, the flaws in the scarcity price definition- a mechanism that activates the capacity market obligation and sets a cap price for the spot market- have led into a market failure. Specifically, some generation plants have been forced to be unavailable because their variable costs are significantly higher than the scarcity price. This paper presents a qualitative and quantitative analysis of the Colombian Electricity system, with a particular emphasis on the definition of the scarcity price. Results present lessons and recommendations for policy makers based on the experience of the Colombian Electricity Market, highlighting the need of a new Scarcity price definition and a different focus on the energy planning scheme.
 
Schematic diagram of the Electromagnetic Voltage Regulator. Adapted from [11].
Undervoltage magnitudes compensated by the EVR according to the autotransformer tap for a 10 MVA load.
System implemented in the MATLAB Simulink.
Load voltage profile for Case 01.
Load voltage profile for Case 02.
Article
Although there currently exists a wide range of voltage regulators that are commercially available, the search for devices with a simpler physical design remains the focus of research studies. Following this line, an electromagnetic voltage regulator (EVR) arrangement has been proposed. The EVR is constituted of an autotransformer that supplies, via discrete taps, a series transformer that injects voltage for regulating the feeder voltage. Even though its operating principle is shown as being similar to that of other devices on the market, the physical arrangement and operating strategy of EVR show novelties which result in properties such as: economic attractiveness, constructive simplicity, and operational reliability. Moreover, when installing voltage regulators, efficacy studies must be carried out to optimize equipment design. In this context, this paper aims at evaluating the factors that influence the effectiveness of the EVR in restoring voltage variations according to the determinations imposed by regulatory agencies. The ultimate goal of this study is to determine the voltage deviation range that the EVR is able to restore. To achieve this goal, a mathematical modeling of the EVR is given and study cases are computationally carried out to investigate its performance when connected to a typical distribution feeder.
 
Article
This paper describes a new approach and methodology of quantitative assessment of the fault tolerance of electric power drive consisting of the multi-phase traction electric motor and multilevel electric inverter. It is suggested to consider such traction drive as a system with several degraded states. As a comprehensive parameter for evaluating of the fault tolerance, it is proposed to use the criterion of degree of the fault tolerance. For the approbation of the proposed method, the authors carried out research and obtained results of its practical application for evaluating the fault tolerance of the power train of an electrical helicopter.
 
Article
This work study the influence of concrete, plaster, clay and others buried structures in grounding systems. Comparison of soil characteristics between dry and rainy seasons on different grounding systems. The study includes comparison of six different grounding system on dry season and wet season. Simulations in finite element method was performed for tree layer stratified soil and the electrostatic equipotential surfaces were mapped into the region of interest.
 
Comparison between Surge Values Obtained 
Article
The purpose of this work is to calculate Surge and Swab pressure in oil wells with eccentricity between drill string and wellbore or casing string. Analysis of this phenomenon, in which the fluid is confined between two eccentric cylinders, are made. The conformal mapping is used to lead the eccentric domain into the concentric domain, since the usual models correspond to concentric geometries. The results of this study, using the proposed methodology, are presented and discussed.
 
Article
This paper proposes a Model Predictive Controller (MPC) for control of a P2AT mobile robot. MPC refers to a group of controllers that employ a distinctly identical model of process to predict its future behavior over an extended prediction horizon. The design of a MPC is formulated as an optimal control problem. Then this problem is considered as linear quadratic equation (LQR) and is solved by making use of Ricatti equation. To show the effectiveness of the proposed method this controller is implemented on a real robot. The comparison between a PID controller, adaptive controller, and the MPC illustrates advantage of the designed controller and its ability for exact control of the robot on a specified guide path.
 
Fault diagnosis principle for a T-type converter
Open switch fault diagnosis in State 2 (i(t)>0).
Article
In this paper, an open-switch fault diagnosis method for five-level H-Bridge Neutral Point Piloted (HB-NPP) or T-type converters is proposed. While fault tolerant operation is based on three steps (fault detection, fault localization and system reconfiguration), a fast fault diagnosis, including both fault detection and localization, is mandatory to make a suitable response to an open-circuit fault in one of the switches of the converter. Furthermore, fault diagnosis is necessary in embedded and safety critical applications, to prevent further damage and perform continuity of service. In this paper, we present an open-switch fault diagnosis method, based on the switches control orders and the observation of the converter output voltage level. In five-level converters such as HB-NPP and T-type topologies, some switches are mostly 'on' at the same time. Therefore, the fault localization is quite complicated. The fault diagnosis method we proposed is capable to detect and localize an open-switch fault in all cases. Computer simulations are carried out by using Matlab Simulink and SimPowerSystem toolbox to validate the proposed approach.
 
Article
Recently, the use of electrolyzers for hydrogen production through water electrolysis is of great interest in the industrial field to replace current hydrogen production pathways based on fossil fuels (e.g. oil, coal). The electrolyzers must be supplied with a very low DC voltage in order to produce hydrogen from the deionized water. For this reason, DC-DC step-down converters are generally used. However, these topologies present several drawbacks from output current ripple and voltage gain point of view. In order to meet these expectations, interleaved DC-DC step-down converters are considered as promising and interesting candidates to supply proton exchange membrane (PEM) electrolyzers. Indeed, these converters offer some advantages including output current ripple reduction and reliability in case of power switch failures. In addition, over the last decade, many improvements have been brought to these topologies with the aim to enhance their conversion gain. Hence, the main goal of this paper is to carry out a thorough state-of-the-art of different interleaved step-down DC-DC topologies featuring a high voltage gain, needed for PEM electrolyzer applications.
 
Operating diagram of the system.  
Developed laboratory bench.  
Thermal image of the photovoltaic panel when the water flow is 2 L/min.  
Effect of water flow rate in the current produced.  
Article
This paper presents the development of a cooling apparatus using water in a commercial photovoltaic panel in order to analyze the increased efficiency through decreased operating temperature. The system enables the application of reuse water flow, at ambient temperature, on the front surface of PV panel and is composed of an inclined plane support, a perforated aluminum profile and a water gutter. A luminaire was specially developed to simulate the solar radiation over the module under test in a closed room, free from the influence of external climatic conditions, to carry out the repetition of the experiment in controlled situations. The panel was submitted to different rates of water flow. The best water flow rate was of 0.6 L/min and net energy of 77.41Wh. Gain of 22.69% compared to the panel without the cooling system.
 
Photo of the air-wound coils used in the WPT system prototype with four magnetically coupled resonators. 
Article
We present a procedure for system identification and tuning of a wireless power transfer (WPT) system with four magnetically coupled resonators, where each resonator consists of a coil and a capacitor bank. The system-identification procedure involves three main steps: 1) individual measurement of the capacitor banks in the system; 2) measurement of the frequency-dependent two-port impedance matrix of the magnetically coupled resonators; and 3) determining the inductance of all coils and their corresponding coupling coefficients using a Bayesian approach. The Bayesian approach involves solving an optimization problem where we minimize the mismatch between the measured and simulated impedance matrix together with a penalization term that incorporates information from a direct measurement procedure of the inductance and losses of the coils. This identification procedure yields an accurate system model which we use to tune the four capacitance values to recover high system-performance and account for, e.g., manufacturing tolerances and coil displacement. For a prototype WPT system, we achieve 3.3~kW power transfer with 91\% system efficiency over an air-gap distance of approximately 20~cm.
 
DC motor controlled by DMC tuned by deterministic method (ωref = 50 rad/s). Analyzing Fig. 5 is noted similarity to Fig. 4. Is noted higher values for armature voltage and armature current in early moments of the experiment and stabilization of these values with the stabilization of motor speed. Is noted the perturbation of system due to insertion of load with value of 1.0 N at time t = 10 s, similar to the previous experiment, it is evident the increase of armature voltage and armature current values aiming to return and the stabilization of speed developed by DC motor to reference speed. Fig. 5 yet present the integral of absolute error between reference speed and speed developed by DC motor being IAEω = 5.9936. Tab. II presents the total error found during the experiments and the optimal values for parameters of DMC controller obtained using the deterministic Quasi-Newton method.
Speed of DC motor controlled by DMC tuned by heuristic method (ωref = 100 rad/s). Analyzing Fig. 6 is noted higher values for armature voltage and armature current in early moments of the experiment, DC motor starting. Is noted also that with the stabilization of speed developed by DC motor in speed reference both the armature voltage and the armature current remain stable. In instant t = 10 s the insertion of load with value 2.0 N causes disturbance to system slowing DC motor speed developed and making it necessary the increase of armature voltage and armature current values to that the speed developed reaches reference speed. Again, with stabilization of DC motor speed in speed reference both the armature voltage as the armature current remains stable. Fig. 6 yet present the integral of absolute error between reference speed and speed developed by DC motor being IAEω = 12.2551. Fig. 7 present values of speed, armature current and armature voltage developed by DC motor controlled by DMC with parameters values obtained by Genetic Algorithm method. It considered the set-point speed at 50 rad/s and inserted load of 1.0 N · m applied at time t = 10 s.
DC motor controlled by DMC tuned by heuristic method (ωref = 50 rad/s). Analyzing Fig. 7 is noted similarity to Fig. 6. Is noted higher values for armature voltage and armature current in early moments of the experiment and stabilization of these values with the stabilization of speed. Is noted the perturbation of system due to insertion of load with value of 1.0 N at time t = 10 s, similar to the previous experiment, it is evident the increase of armature voltage and armature current values aiming to return and the stabilization of speed developed by DC motor to reference speed. Fig. 7 yet present the integral of absolute error between reference speed and speed developed by DC motor being IAEω = 2.7503. With the results obtained using the heuristic method, it is possible to observe the improvement in curves presented in relation to deterministic method. Tab. III presents the total error found during the experiments and the optimal values for parameters of DMC controller obtained using the heuristic Genetic Algorithm method.
DC motor controlled by DMC tuned by hybrid method (ωref = 100 rad/s). Operation of DC motor controlled by DMC tuned by hybrid optimization method, Fig. 8, is similar to operation presented with optimization by heuristic method, Fig. 6. In speed developed by DC motor could be noted reduction of overshoot before speed stabilization. Note also, reduction in speed decrease caused by insertion of load with value 2.0 N at t = 10s. Characteristics evidenced in Fig. 8 illustrate reduction in integral of absolute error between reference speed and speed developed by DC motor, resulting in IAEw = 10.8909. Fig. 9 present values of speed, armature current and armature voltage developed by DC motor controlled by DMC with parameters values obtained by Hybrid method. It considered the set-point speed at 50 rad/s and inserted load of 1.0 N · m applied at time t = 10 s.
DC motor controlled by DMC tuned by hybrid method (ωref = 50 rad/s).
Article
This paper presents study about Dynamic Matrix Control (DMC) controller applied to speed control of DC motor. DMC controller parameters (prediction horizon, control horizon and damping rate of reference) are obtained through optimization methods employing heuristic, deterministic and hybrid strategies. The use of advanced control technique combined with using of optimization methods aims to achieve highly efficient control, reducing the transient state period and variations in steady state. These methods were applied on a simulation model in order to verify which one provides better control results. Index Terms—Predictive Control, Deterministic Optimization, Heuristic Optimization, Hybrid Optimization, DC motor.
 
Article
Dissolved gas-in-oil analysis (DGA) is a sensitive and reliable technique for the detection of incipient fault condition within oil-immersed transformers. When the mineral oil is subjected to high thermal or/and electrical stresses, it decomposes and, as a result, gases are generated. This paper presents modification of Duval triangle DGA diagnostic graph to numerical method that is easy to use for diagnosing and the possibility to use for a Matlab program. The evaluation is carried out on DGA data obtained from three different groups of transformers. A Matlab program was developed to automate the evaluation of Duval Triangle graph to numerical modification, Also the fault gases can be generated due to oil decomposing effected by transformer over excitation which increasing thetransformer exciting current lead to rising the temperature inside transformer core beside the other causes.
 
Article
In many countries, the grid-code or standards do not allow the Photovoltaic (PV) inverters to exchange reactive power with the grid. Recently, some countries have relaxed the standards. Hence, capacity of the inverters to control reactive power must be utilized. However, the reactive power that a PV inverter can supply is constrained by the maximum power that a PV array generates and changes with the environmental conditions. A reactive power sharing algorithm is proposed that not only ensures proper distribution of reactive power amongst the inverters, but also ensures that the maximum power generated by PV is supplied to the grid. In case of identical PV inverters, the algorithm operates all inverters at nearly equal apparent power leading to nearly equal percentage utilization of the inverters, thereby achieving uniform heating of the similar devices of the inverters. The algorithms are further investigated for power sharing amongst PV inverters of unequal ratings. It is highlighted that the proposed algorithm results into the least change in the utilization factor of a PV inverter, whose power changes due to the change in environmental conditions. The effectiveness of the algorithm over other algorithms in sharing power amongst inverters is displayed through MATLAB/Simulink simulations.
 
Average Estonian 2014 Electricity Spot Price during a day. III. IMPROVEMENT OF VALUE STREAM MAPPING METHODOLOGY FOR EVALUATION OF LOAD SCHEDULING POSSIBILITIES  
VSM with Energy Consumption and Storage Overview.  
Article
The aim of this paper is to provide a solution for load scheduling by implementing value stream mapping, which is a straightforward enough for production management. Decision makers in the industry should have a clear understanding about positive effect from load scheduling and its effect to production outcome and process availability. Value stream mapping is a well-known process optimization tool from lean production philosophy. The aim of value stream mapping is to shorten the lead time of industrial processes and to reduce the intermediate stock amounts. By complementing value stream map with process energy intensity and energy stored in intermediate stocks, we can promote load scheduling possibilities. Our methodology provides a tool that is understandable and traceable for industry-minded decision makers. Finally, we present a real life test example for the new methodology, which is based on the production process of a district heating plant.
 
IA corresponding to remove first imf normal condition of signal 
IF corresponding to remove first imf normal condition of signal 
IA corresponding to remove first imf voltage sag condition of signal 
IF corresponding to remove first imfs voltage sag condition of signal 
Article
Identification of system disturbances and detection of them guarantees smart grids power quality system reliability and long lasting life of the power system. The key goal of this study is to generate non - time consuming features for CPU, for recognizing different types of non-stationary and non-linear smart grid faults based on signal processing techniques. This paper proposes a new solution for real time power system monitoring against power quality faults focusing on voltage sag and noise. EEMD is used for noise reduction with first intrinsic mode function (imf1). Hilbert Huang Transform (HHT) is used for generating instantaneous amplitude (IA) and instantaneous frequency (IF) feature of real time voltage sag power signal. The proposed power system monitoring system is able to detect power system voltage sag disturbances and capable of recognize and remove EMI (Electromagnetic Interference)-Noise. In this study based on experimental studies, Hilbert Huang based pattern recognition technique was used to investigate power signal to diagnose voltage sag in power grid. SVM and Decision Tree (C4.5) were operated and their achievements were matched for calculation error and CPU time. According to the analysis, decision tree algorithm without dimensionality reduction produces the best solution.
 
Article
This paper presents the study of the relationship between electrical properties and physical characteristics of the soil. Measures of apparent electrical resistivity of the soil were made for different types of soil, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. Development of a correlation surface is proposed in order to identify granulometry of the soil from moisture and compaction measurements. For the study of spatial variability, two areas were chosen to allow the change of moisture content and compaction in order to verify the measurement capacity of apparent electrical resistivity of the soil as methodology to identify change in soil dynamics. Results obtained show correlations among apparent electrical resistivity of the soil, moisture, soil compaction and clay content.
 
Article
Today’s companies are able to automate the enforcement of Environmental, Health and Safety (EH&S) duties through the use of workflow management technology. This approach requires to specify activities that are combined to workflow models for EH&S enforcement duties. In order to meet given safety regulations these activities are to be completed correctly and within given deadlines. Otherwise, activity failures emerge which may lead to breaches against safety regulations. A novel domain-specific workflow meta data model is proposed. The model enables a system to detect and predict activity failures through the use of data about the company, failure statistics, and activity proxies. Since the detection and prediction methods are based on the evaluation of constraints specified on EH&S regulations, a system approach is proposed that builds on the integration of a Workflow Management System (WMS) with an EH&S Compliance Information System. Main principles of the failure detection and prediction are described. For EH&S managers the system shall provide insights into the current failure situation. This can help to prevent and mitigate critical situations such as safety enforcement measures that are behind their deadlines. As a result a more reliable enforcement of safety regulations can be achieved.
 
Iteration of transmitting power over signal behavior VII. CONCLUSIONS 
Article
The high demand for network coverage in an indoor setting brought about the acceptance of femtocell technology as a solution using the backhaul connectivity in the existing network. The quality of signal, voice calling, Internet, security and data are improved through the use femtocell at the indoor environment. Here the service provider attempts to reduce their operation cost by presenting self-organizing mechanisms for optimization of the network. The remarkable part is that, femtocells improves coverage, enhances the data rate at the indoor environment. Therefore, the challenges of the femtocell also known as interference deteriorates the capacity and quality performance of the whole cellular network. In this paper we simulate the bit error rate against signal behaviour at the indoor environment and we also simulate the transmitting power over signal for both macrocells and femtocells. We focus on the transmitting power that might cause interference within the cellular network.
 
The results of the measuring and evaluation of the 15 th and 21 st voltage harmonics in the LV distribution network  
The results of the measuring of flicker – Spring 2014  
The results of the measuring of flicker – Autumn 2014  
5 th harmonic and flicker (Plt) in MV network OS-8  
Article
In 1997 cooperation began between the Faculty of Electrical Engineering and Computer Science and the power company CEZ on a joint project that involved monitoring selected voltage quality parameters. Over the course of several years measurements were carried out at 59 points of the distribution system at a low voltage (LV) level and their power supply nodes at medium voltage (MV) and high voltage (HV) levels, which constituted more than 100 measured points. The measurements continued until 2012 (with a one-year break in 2009) and with a total scope of five cycles of three-year measurements. The last phase of the measurements was focused, inter alia, on the evaluation of 15th and 21st voltage harmonics. From 2013, the cooperation focused again on monitoring flicker in localities with the occurrence of elevated levels of this voltage quality parameter. At these sites, the monitoring of flicker was carried out for two weeks in spring and autumn for a period of three years. The basis for evaluating the quality parameters is the standard EN 50160.
 
Article
This paper presents a novel method for data analysis and visualization, including real-time visual monitoring and proposal for combined area PQ indices on the example of the developed and operational comprehensive system of registration, archiving and data processing for the wide-area monitoring of power quality in a separated part of real power grid with distributed renewable generation. Real case studies related to power quality disturbances are presented. (Archived by WebCite® at http://www.webcitation.org/6ex7AUlDN)
 
Article
Pulverizing system is an important part in the clean and efficient utilization of coal in thermal power plant, and the optimal control of the system is an important way to achieve this goal. This paper presents a stair-like multivariable generalized predictive control scheme for a pulverizing system. This control scheme focuses on the problem of predictive control algorithm in practical application, and integrates the feedforward experience in traditional control schemes of pulverizing system. Simulation results showed that the scheme are able to realize the decoupling control of the pulverizing system, avoid the problem of matrix inversion, reduce the amount of calculation, and has certain engineering application value.
 
Article
This article introduces the switched reluctance machine operating as a generator. This kind of electrical machine delivers CC power at the output and the energy generated can be controlled through several variables. In this work, the switching angles of the machine's power converter are optimized using deterministic and heuristic techniques so that the output power is kept constant via PI controller while guaranteeing maximum value for machine performance, even for different excitation values and mechanical power on the shaft.
 
Interconnected electrical power system-IEPS for Case Study 1. 
Equipments utilized in laboratory tests. 
Interconnected electrical power system-IEPS for Case Study 2. 
Article
The purpose of this paper is to compare mathematical modeling and practical bench in order to validate the electrical interactions between an induction generator and a synchronous generator. Two generators was connected to a common bus in steady state, subject to non-linear load. The results comparing modeling and bench tests show that the induction generator besides the active power increasing, has a better way for harmonic currents flowing in common bus. It was concluded that the induction generator repowering and attenuates current harmonic components present at the connection point, improving the network voltage profile.
 
A superconducting multi-pole generator. Reproduced from Courtesy of Converteam.  
Article
Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends to introduce the basic concept and principle of superconductivity, and compare form traditional wind turbine to obtain superiority, then to summary three proposed machine concept.While superconductivity have difficulty in modern technology and we also have proposed some challenges in achieving superconducting wind turbine finally.
 
Spectrogram of the current LCD TV 
The representation of the EEMD algorithm[16] 
IMF components of PV current signal 
Article
Nowadays supra-harmonic distortion studies are gaining attention day by day in power quality research area. When handling communication systems especially Power Line Carrier (PLC) systems in frequency range 2- 150 kHz, they are suitable for causing electromagnetic interference (EMI) to other systems. This study shows results of analysis employing advanced method called ensemble empirical mode decomposition (EEMD) to describe supra-harmonic distortion. Unlike the traditional method (short time fourier transform- STFT), EEMD gives extensive representation for supra-harmonic components
 
Article
The purpose of the present study is to evaluate gains through measurement and verification methodology adapted from the International Performance Measurement and Verification Protocol, from case studies involving Energy Efficiency Projects in the Goias State, Brazil. This paper also presents the stochastic modelling for the generation of future scenarios of electricity saving resulted by these Energy Efficiency Projects. The model is developed by using the Geometric Brownian Motion Stochastic Process with Mean Reversion associated with the Monte Carlo simulation technique. Results show that the electricity saved from the replacement of electric showers by solar water heating systems in homes of low-income families has great potential to bring financial benefits to such families, and that the reduction in peak demand obtained from this Energy Efficiency Action is advantageous to the Brazilian electrical system. Results contemplate also the future scenarios of electricity saving and a sensitivity analysis in order to verify how values of some parameters influence on the results, once there is no historical data available for obtaining these values.
 
Article
This paper presents the complete analysis of Linear Induction Motor (LIM) under VVVF. The complete variation of LIM air gap flux under ‘blocked Linor’ condition and starting force is analyzed and presented when LIM is given VVVF supply. The analysis of this data is important in further understanding of the equivalent circuit parameters of LIM and to study the magnetic circuit of LIM. The variation of these parameters is important to know the LIM response at different frequencies. The simulation and application of different control strategies such as vector control thus becomes quite easy to apply and understand motor’s response under such strategy of control.
 
Top-cited authors
Oluwafemi Oni
  • University of KwaZulu-Natal
Inno Davidson
  • Durban University of Technology
Wesley Pacheco Calixto
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Muhammad Taheruzzaman
  • Uttara University
Przemyslaw Janik
  • Wroclaw University of Science and Technology