bluuebunny/crossref_metadata_2025 huggingface dataset:
Extreme learning machine‐based alleviation for overloaded power system
Authors: Labed Imen , Labed Djamel
Published: October 2019

The present study proposes a corrective method of electric system overload provided that the wind farm is integrated into the distribution system, taking into account the congestion cost. The authors attempted to mitigate the overload and to monitor flow over transmission lines. Unified power flow controller device was the first suggestion utilised to solve this problem, then due to its extremely fast training and the excellent generalisation performance, extreme learning machine algorithm is employed. The fundamental point is the transmission line alleviation. In addition, other targets are realised: the load shedding avoidance, minimisation of losses and congestion cost. This study is also designed to utilise PowerWorld Simulator and MATLAB software to demonstrate methods for relieving transmission overloads. The accuracy of the proposed approach has been tested for Algerian (Adrar) 22‐bus system. Obtained results showed an improvement in power system behaviour. Simulation results are exposed, discussed and compared at the end of this study.
Multi‐objective optimisation operation of thermostatically controllable appliances for voltage management in low‐voltage distribution networks
Authors: Zhou Lai , Zhang Yongjun , Chen Boda , Li Canbing , Xie Xiaoyu , Fan Suchun , Tang Wenhu , Yi Yingqi
Published: October 2019

The development of residential demand response (RDR) programs opens up another perspective for mitigating the problems of voltage magnitude and unbalance limit violation (VMULV) in the low‐voltage distribution network (LVDN). Under this background, this study introduces thermostatically controllable appliances (TCAs) including electric water heater (EWH) and air conditioner (AC) to tackle the VMULV problems in LVDN based on the incentive RDR. Firstly, the response characteristics of TCA in LVDN voltage management are analysed. Then, a voltage management model incorporating EWHs and ACs in residents is established as a multi‐objective optimisation model that jointly minimises the RDR cost, network loss, and customer dissatisfaction. In this model, the discomfort index associated with hot water and indoor temperature is employed to reflect users' discomfort. The proposed modelling method is examined on a 6‐resident network and a 28‐resident network in Sweden with considerable unbalanced and distributed generations. Moreover, the impacts on the optimisation result from different objective functions, photovoltaic (PV) penetration levels, and the tolerable temperature ranges set by users are also investigated. The results indicate that the proposed method effectively alleviates voltage amplitude and imbalance limit violation, and improves the capability of LVDN to integrate PV.
Design of a DSO‐TSO balancing market coordination scheme for decentralised energy
Authors: Edmunds Calum , Galloway Stuart , Elders Ian , Bukhsh Waqquas , Telford Rory
Published: October 2019

The proliferation of distributed generation and the electrification of heat and transport pose significant challenges to distribution system operators (DSOs) and transmission system operators (TSOs). These challenges include the choice between network upgrades or operating increasingly constrained networks, with a reliance on the flexibility of distributed energy resources (DERs). This study presents a novel market‐based coordination scheme, which allows both the DSO and TSO to access DER flexibility, while respecting distribution system limits. The DSO's objective in this work is to minimise the cost incurred by DSO adjustments to DERs, required to ensure stable distribution network operation. The methodology presented has the advantages of being compatible with existing TSO balancing market operation, and scalable enough to include multiple DSO markets coordinating with the TSO. The approach is demonstrated on a section of Great Britain distribution network, using high DER growth scenario data for the year 2030. The case studies demonstrate the proposed DSO market mechanism to maintain thermal and voltage limits during periods of peak demand and DER output. The DSO is given priority in using DERs to solve distribution network constraints, however, significant flexibility remains for the TSO even during periods of peak demand and maximum export.
SUGAMAN: describing floor plans for visually impaired by annotation learning and proximity‐based grammar
Authors: Goyal Shreya , Bhavsar Satya , Patel Shreya , Chattopadhyay Chiranjoy , Bhatnagar Gaurav
Published: October 2019

In this study, the authors propose a framework SUGAMAN (Supervised and Unified framework using Grammar and Annotation Model for Access and Navigation). SUGAMAN is a Hindi word meaning ‘easy passage from one place to another’. SUGAMAN synthesises textual description from a given floor plan image, usable by visually impaired to navigate by understanding the arrangement of rooms and furniture. It is the first framework for describing a floor plan and giving direction for obstacle‐free movement within a building. The model learns five classes of room categories from 1355 room image samples under a supervised learning paradigm. These learned annotations are fed into a description synthesis framework to yield a holistic description of a floor plan image. Authors demonstrate the performance of various supervised classifiers on room learning and provided a comparative analysis of system generated and human‐written descriptions. The contribution of this study includes a novel framework for description generation from document images with graphics while proposing a new feature representing the floor plans, text annotations for a publicly available data set, and an algorithm for door to door obstacle avoidance navigation. This work can be applied to areas like understanding floor plans and design of historical monuments, and retrieval.
Welding defect detection based on local image enhancement
Authors: Lin Zhang , Yingjie Zhang , Bochao Dai , Bo Chen , Yangfan Li
Published: October 2019

Welding defect detection in a radiographic image is an important topic in the field of industrial non‐destructive testing. To improve the accuracy of welding defect segmentation, a local image enhancement approach is proposed. In this algorithm, the requirement of contrast enhancement is considered when extracting the weld seam and segmenting the weld defect. The whole defect detection is conducted by three procedures: image enhancement, welding seam extraction, and defect segmentation. Firstly, a method for determining the Localised Pixel Inhomogeneity Factor (LPIF) is proposed. Then, based on the results of LPIF, the Otsu method is applied to segment the welding seam and defects are, identified by region growing algorithm. The authors compared LPIF with histogram equalisation, adaptive histogram equalisation, and contrast‐limited adaptive histogram equalisation algorithms and assessed its performance by using indicators such as image contrast, image definition, and edge intensity. Moreover, the authors compared the segmentation results of the enhanced defect images with the original image to further study the method's effect on weld defect segmentation. More than 70 images containing various types of defects are tested. The experimental results demonstrate that the quality of enhanced defect images is improved significantly, and has a high relative segmentation accuracy of more than 92%.
Pansharpening with transform‐based gradient transferring model
Authors: Liu Pengfei
Published: October 2019

As one of the most popular kinds of the component substitution (CS)‐based pansharpening methods, the intensity‐hue‐saturation (IHS) method can produce the pan‐sharpened images with high spatial quality while causing some spectral distortion, mainly owing to it cannot estimate an accurate intensity image in the IHS space. To solve this issue in the IHS method, in this study, the authors propose a new pansharpening method with gradient transferring in the generalised IHS transform space, which aims at estimating a more accurate intensity image. More specifically, the novelty of the proposed method consists of building a novel variational gradient transferring model to transfer the spatial gradient information of the panchromatic image into the new intensity image as well as preserve the local spectral information from the low resolution multispectral image. Finally, they compare the proposed method with some CS methods using the Pleiades, QuickBird, and GeoEye‐1 satellite datasets from both the subjective and objective aspects. Specifically, the experimental results show that the proposed method yields better pansharpening results than the other methods in terms of higher spatial and spectral qualities.
Improved image segmentation algorithms for detecting types of acute lymphatic leukaemia
Authors: Al‐Tahhan F.E. , Sakr Ali A. , Aladle Doaa A. , Fares M.E.
Published: October 2019

A modified digital image processing technique is presented to accurately investigate the types of the acute lymphatic leukaemia (ALL). In this technique, three complementary steps are performed. In the first one, a colour segmentation procedure is used to obtain images including only the white blood cell. In the second step, the histogram equalisation and linear contrast stretching procedures are utilised to obtain images for the nucleus. In the third step, images for the cytoplasm only may be reconstructed from which the vacuoles may be detected. For accurate detection for ALL types, significant and discriminative parameters are introduced such as geometric shape of nucleus membrane, equivalent sizes for the nucleus and cytoplasm and their ratio when the shapes of nucleuses are regular or irregular. This method is applied to a blood smear images for real cases of ALL. To validate the present technique, a comparison is made between present results with their counterparts obtained by expert (manual) technique. Another assessment is performed by comparing the average accuracy of the present technique and the average accuracy of different image processing techniques in the literature. The assessment confirms the high efficiency of the present technique in detecting all types of ALL.
Defect inspection research on fabric based on template correction and primitive decomposition
Authors: Liu Wei , Chang Xingzhi , Liang Jiuzhen , Hou Zhenjie , Xu Li
Published: October 2019

To accurately detect defects in patterned fabrics, a novel detection algorithm combining template correction with primitive decomposition (TCPD) method is proposed in this study. First of all, the fabric image is segmented into lattices according to variation regularity. Then, the authors propose an effective anisotropy correction method to reduce the interference of stretching and distortion between lattices. On the basis of the proposed PD method, the corrected lattice is further divided into graphic elements with smaller particle size. The smaller primitives make the boundary of the detection results more accurate. Moreover, a self‐supervised threshold selection strategy is presented, which utilises the defect‐free regions to obtain threshold. Furthermore, this strategy makes each primitive has corresponding criteria for judging defects. Extensive experiments demonstrate that TCPD method achieves 0.8127 true positive rate, 0.3889 positive predictive value and 0.5261 f value in star‐patterned fabrics.
Heat diffusion embedded level set evolution for infrared image segmentation
Authors: Wei Ziwei , Qiao Yulong , Lu Xiao
Published: October 2019

In this study, the authors present a novel level set method for infrared image segmentation. Local region‐based models can fit intensity inhomogeneity partly but they are sensitive to local window scale. To deal with it, they embed an heat diffusion process in conventional level set evolution and convert heat to a part of data term in level set energy function. Besides, bias field model can extract the local intensity clustering property of the image. Therefore, the proposed method can deal with the interference of intensity inhomogeneity and complex background if appropriate seeded pixels are selected. Finally, the energy functional is minimised by a combinatorial optimal algorithm in a graph model to get a global optimal solution and accelerate the level set evolution implementation. The experiments show that the proposed method is robust to parameter setting, noise, and initial contour position. The comparisons on a large quantity of infrared image datasets with standard level set methods also demonstrate the efficiency of the proposed method.
Automatic optical‐to‐SAR image registration using a structural descriptor
Authors: Paul Sourabh , Pati Umesh C.
Published: October 2019

Optical‐to‐synthetic aperture radar (SAR) image registration is a challenging task in remote sensing as the images have significant non‐linear intensity variations as well as large geometric differences. Moreover, the influence of speckle noise in the SAR image further affects the registration result. The structural descriptors are very effective to handle the non‐linear intensity variations between optical and SAR images. Although a number of optical‐to‐SAR image registration methods have been proposed in the past few years based on the structural information of image, most of them are ineffective for the images having large geometric differences. To address these problems, a novel optical‐to‐SAR image registration algorithm is proposed by using a new structural descriptor. Initially, the corner features are extracted from the optical and SAR images. Then, the proposed structural descriptor is constructed for the extracted features. Finally, feature matching is performed between the optical and SAR images and the correct match are identified. The proposed method is very effective to register the optical and SAR images having significant intensity variations and large geometric differences. It can increase the number of correct match between the images. Experiments on six sets of optical and SAR image pairs demonstrate the effectiveness of the proposed method.
New over‐relaxed monotone fast iterative shrinkage‐thresholding algorithm for linear inverse problems
Authors: Zhu Tao
Published: October 2019

The over‐relaxed monotone fast iterative shrinkage‐thresholding algorithm (OMFISTA) needs to satisfy a complex convergence condition with respect to its additional parameters. To simplify the convergence condition, this study proposes a new OMFISTA, termed OMFISTAv2, using a parameter setting strategy which will derive a simple sufficient condition with respect to the additional parameters to guarantee the convergence of OMFISTAv2. Moreover, the authors find experimentally that OMFISTAv2 can accelerate MFISTA in some cases where the system matrix is ill‐conditioned or rank‐deficient, while OMFISTA cannot.
Forced‐node route guidance system: incorporating both user equilibrium and system optimal benefits
Authors: Rahimi‐Farahani Hossein , Rassafi Amir Abbas , Mirbaha Babak
Published: October 2019

Route guidance systems (RGSs), due to recent advances in technology, are emerging as a low‐cost and fast solution to the congestion problem in urban areas. Route guidance with the aim of minimising total travel time (system optimum) causes longer paths, and consequently, more unfairness between individual users. Moreover, more congestion is created when guiding the users to their shortest paths (user equilibrium) to provide fairness among them. Therefore, an RGS that is able to combine these two inconsistent objectives, i.e. minimising total congestion of the network, and travel unfairness between individual travellers, would be of great value. To this end, a forced‐node RGS is proposed in this study. The guidance task is delegated to some of the network nodes (e.g. intersections and roundabouts) in a distributed and autonomous way, similar to the routing operation in computer networks. Then, by applying a novel idea in transforming the demand rates, a non‐recursive algorithm is proposed and compared with well‐known traffic assignment methods; i.e. the classic user equilibrium and system optimal traffic assignment methods. Computational results affirmed the applicability of the forced‐node RGS through the incorporation of both system and users’ benefits in different proportions.
Fuzzy hybrid framework with dynamic weights for short‐term traffic flow prediction by mining spatio‐temporal correlations
Authors: Ma Dongfang , Sheng Bowen , Ma Xiaolong , Jin Sheng
Published: October 2019

Forecasting short‐term traffic flows is crucial in designing intelligent transportation systems. There has been significant research on this topic; however, no single model can maintain optimality under all conditions. This study analysed the complementarity of non‐parametric regression and deep learning in terms of prediction accuracy. Then, a mixed prediction method, combining two sub‐models based on a fuzzy logic system, was constructed. First, the two sub‐models based on long‐short‐term memory) and K‐nearest neighbour were improved, by extracting more features that consider the spatial–temporal correlations of traffic flow and the influences of specific contextual factors to the traffic flow. Second, a fusion mechanism with dynamic weights was presented to optimise the mix predictor. A compensation term was added based on the deviations. Finally, the new method was tested using real data in Seattle, Washington. The results show that the proposed model predicts the flow for the next 5 min across the verification set, with a 6.42% mean absolute percentage error and 31.49 standard error. These results are more accurate and robust than those achieved with other state‐of‐the‐art models.
Improvement of safe stopping distance and accident risk coefficient based on active driver sight field on real road conditions
Authors: Gürbüz Habib , Buyruk Serhat
Published: October 2019

In this paper, a new model based on factors of driver, vehicle and environment was developed to determine the ‘safe stopping distance’ of the vehicles, and tested on real road conditions by using equipment placed on the vehicle. The new stopping distance model has been developed based on the stopping distance formula commonly used in the literature. Then, an ‘active driver sight field’ was created considering effect of factors of driver, vehicle and environment. The safe field of view of driver, the safe escape area and safe stopping distance value of vehicle was transferred continuously during driving to the driver through the driver information screen positioned on front console in vehicle cockpit. In addition, a new approach has been developed to evaluate possible accident risks by using relationship between the safe escape area of the vehicle and the safe field of view of the driver. As a result, generalised stopping distance formula was yielded results closer to the actual road results, when expanded by using factors of driver, vehicle and environment. It was determined that obtained accident risk coefficients could be used to detection of accident risk with minor errors that especially at low speeds up to 60 km/h.
Analyses on the heterogeneity of car‐following behaviour: evidence from a cross‐cultural driving simulator study
Authors: Cheng Qian , Jiang Xiaobei , Wang Wuhong , Dietrich André , Bengler Klaus , Qin Yong
Published: October 2019

Driving behaviours have been proved sensitive to the cultural background. This study aims to investigate the heterogeneity of car‐following behaviour between and within Chinese and German driver groups. A driving simulator‐based experiment was designed and conducted. Participants were asked to drive through two scenarios: (i) Leading vehicle with high speed; braking after a specific distance. (ii) Leading vehicle with a frequently changing speed; braking after a specific distance. Totally 41 participants’ (20 Chinese; 21 German) car‐following behaviours were recorded. Desired safety margin (DSM) model was used to conclude each participant's driving character in car following. Heterogeneity between and within participant groups was investigated through statistical analysis of five driving behaviour parameters. Results showed that Chinese participants had a higher degree of heterogeneity for acceleration sensitivity parameter in Scenario 2. German participants had a higher value of the lower limit of DSM in Scenario 1. The authors also found that four out of five driving behaviour parameters were observed sensitive to the scenario. This study may provide support for researches on the traffic flows’ cross‐cultural difference and the technique transferring from developed country to developing country.
Distributed coalition formation game for enhancing cooperative spectrum sensing in cognitive radio ad hoc networks
Authors: Rajendran Muthukkumar , Duraisamy Manimegalai
Published: October 2019

Cooperative spectrum sensing (CSS) among secondary users (SUs) in cognitive radio ad hoc networks exhibits an essential trade‐off minimising the misdetection probability of the primary user and maintaining a reasonable false alarm probability to obtain efficient spectrum utilisation. In this study, distributed coalition formation game with a genetic algorithm is proposed to select the optimal coalitional head. It provides an incentive to SUs that improve their detection performance and cooperation among SUs. Since spectrum sensing will incur a cost for SUs, an incentive mechanism is necessary to motivate active participation. Consider the CSS problem as a non‐transferable coalition game and it is used to allow the SUs to self‐organise into disjoint coalitions while accounting for the CSS. The authors calculate payoff for each SU to form minimum winning coalition and to analyse their strategy profile for joining in coalition based on its utility maximisation. Simulation results reveal that the proposed algorithm has significantly improved sensing accuracy, minimised energy consumption and thereby enhanced CSS.
Nano‐scale multifunctional logic gate based on graphene/hexagonal boron nitride plasmonic waveguides
Authors: Rezaei Mir Hamid , Boroumandi Rahim , Zarifkar Abbas , Farmani Ali
Published: October 2019

The concept and analysis of a nano‐scale multifunctional logic gate based on graphene/hexagonal boron nitride (h‐BN) plasmonic waveguides at a wavelength of 7.5µm are presented. By using graphene as a metamaterial with outstanding electro‐optical properties, various logical operations including AND, OR, and XOR are implemented. The proposed multifunctional structure supports surface plasmons (SPs) whose dispersion properties can be controlled by applying an electrical field to graphene. The effects of the incident polarisation and the substrate of graphene on the transmission of SPs are investigated. Simulations by finite difference time domain method show that the extinction ratios for the presented logical operations are higher than 15dB. Also, the structure has a compact footprint of 1.12µm2 which is suitable for using in integrated photonic circuits. This provides a path for the development of novel nano‐scale practical on‐chip applications such as plasmonic memory devices.
Three‐phase thyristor controlled reactor using two sets of delta connected switches with low current harmonics
Authors: Maiti Dipten , Mukhopadhyay Susovan , Biswas Sujit K.
Published: October 2019

This work presents a three‐phase thyristor‐controlled reactor (TCR), which makes use of two constituent banks of controlled reactors, with coordinated control of the triggering angle of both the banks. The first reactor bank has a set of ‘delta’ connected back‐to‐back thyristor switches with a balanced set of reactors in series with each switch, while the second reactor bank also has back‐to‐back thyristor switches in ‘delta’ connection but with a balanced set of reactors in series with each line. It is demonstrated that this arrangement prevents some major current harmonics in the supply line by proper choice of the maximum kVAr ratio between the two reactor banks. The use of delta connected switches in both banks reduces the current rating of the switches. Hence, without using any phase‐shifting isolation transformer or filters, the proposed technique permits control of reactive power over a reasonable range, with a low current total harmonic distortion meeting existing harmonics standards. Simple construction and operation of the proposed TCR make it an attractive and cheaper solution. The modelling, analysis and performance assessment of the new TCR are presented.
Single‐stage single‐switch high power factor driving circuit for lighting applications
Authors: Pan Shangzhi , Lam John C.W. , Jain Praveen
Published: October 2019

Although compact fluorescent lamps (CFLs) have been in the market for a long time, many of them do not achieve the same power factor as the incandescent lamps do, which appears to be a significant problem for the utility with the current widespread use of CFLs for household lightings. A single‐stage single‐switch electronic ballast with active power factor correction is presented in this study for CFL applications. Unlike other single‐switch ballast circuits, the presented integrated dual‐boost converter circuit can produce a symmetric bipolar square‐wave voltage, thus generating a near‐pure high‐frequency sinusoidal voltage on the lamp, which is beneficial to the CFL lifetime. Moreover, its soft‐switching variant can achieve the ZVZC turn‐on and ZV turn‐off for the MOSFET to improve the conversion efficiency. Detailed operating principles and circuit analysis of the proposed circuit have been provided in this study. Simulation and experimental results on a prototype of a 15 W CFL validate the theoretical analysis and highlight the merits of the presented work.
Quadratic buck–boost converter with reduced input current ripple and wide conversion range
Authors: García‐Vite Pedro Martín , Rosas‐Caro Julio C. , Martínez‐Salazar Ana Lidia , Chavez Jose de Jesus , Valderrábano‐González Antonio , Sánchez‐Huerta Victor M.
Published: October 2019

This study introduces an advanced DC–DC power converter with two main objectives, (i) to achieve a wide range of voltage gain, which means the converter may work over a wide range of input voltage for a fixed desired output voltage and (ii) to achieve a reduced input current ripple. Those features are highly desired in renewable energy applications, for example with photovoltaic panels and fuel cells. The proposed converter was designed in a structure in which the input voltage is composed by the difference of two inductor currents, the currents through inductors are driven with transistors that may have different duty cycle, this allows the current ripple cancellation. In addition, the structure of the converter provides a quadratic type voltage gain, which leads to a wide range of operation voltage. The converter achieves both the wire range of voltage gain and current ripple cancellation, nonetheless, the buck–boost capability is also provided. The input current ripple reduction helps preserve the renewable energy sources since they suffer deterioration when current with considerable ripple is drawn from them. Dynamic and steady‐state analysis are performed along with the components sizing. Simulation and experimental results are provided to demonstrate the principle of the proposition.
Design and implementation of a novel nine‐level MT‐MLI with a self‐voltage‐balancing switching technique
Authors: Naik Banavath Shiva , Suresh Yellasiri , Venkataramanaiah Jammala , Panda Anup Kumar
Published: October 2019

In this study, a novel nine‐level modified T‐type multilevel inverter (MT‐MLI) with a simple capacitor balancing technique is proposed. The proposed MT‐MLI circuit can generate higher levels with a single DC source and the minimum number of switching components. Each phase of the proposed topology contains ten switches and one flying capacitor (FC). The DC source voltage is divided into two parts with the help of capacitors. Phase disposition‐sine pulse‐width modulation technique is employed to regulate the DC‐link capacitors and FC voltages. To reduce the control complexity of FC‐based circuits, quarter‐cycle selector is introduced to control the FC voltage within the given half fundamental cycle using redundant states, so an external capacitor charging setup is not required. Furthermore, to highlight the potential merits of the proposed MT‐MLI, the comparison is made among state‐of‐the‐art MLIs. Simulation verification of the MT‐MLI is done using MATLAB/Simulink, and then hardware verifications are done using the laboratory prototype setup with Opal‐RT controller. Finally, adequate results are presented to validate the proposed MT‐MLI.
Comparison of matrix converter stabilisation techniques based on the damping resistor and digital filter approaches for bidirectional power flow control
Authors: Malekjamshidi Zahra , Jafari Mohammad , Zhu Jianguo , Xiao Dan
Published: October 2019

The matrix converter is becoming a mature technology with its specific advantages and limitations and can be effectively used as interface link in the future smart grids. In this context, the stability of the converter under different power flow conditions is highly important and needs more clarification. The input inductor–capacitor filter can significantly impact the stability of the converter when the output is tightly regulated, especially in bidirectional power flow control applications where a low‐impedance source is connected to the converter output. This study investigates the matrix converter stability for bidirectional power flow control, considering the input filter and other parameters of the system. A detailed analysis of two commonly used active and passive stabilisation techniques known as digital filter and damping resistor approaches is presented, and a combination of these two methods is suggested as a better choice. The converter stability region for the proposed technique is determined by using the small‐signal model of the converter. The converter performance for the methods is compared in terms of the efficiency, stability, transients, and quality of the input and output currents. Numerical simulations and experimental tests are conducted on a prototype direct matrix converter to validate the proposed method.
Integrated step‐up non‐isolated inverter with leakage current elimination for grid‐tied photovoltaic system
Authors: Hu Xuefeng , Liang Wenjuan , Gao Benbao , Ma Penghui , Zhang Yubo
Published: October 2019

This study presents a non‐isolated step‐up inverter without leakage current for low‐voltage renewable energy generation such as photovoltaic (PV) cells grid connection. From the structure of the proposed inverter, the negative terminal of the PV array is directly linked with the grid neutral, so the common mode voltage of the parasitic capacitance can be kept constant and the leakage current will not be generated in theory. Moreover, this transformerless inverter can produce an AC output voltage higher than the input DC voltage, which will reduce the sizes of the generation system. A switching modulation strategy carrier‐based is analysed in detail when the input inductor current is operated in discontinuous conduction mode. The operation modes of the proposed inverter are also discussed, respectively, in positive and negative half line cycles. Finally, a digital experimental prototype is tested in the laboratory, and the experimental results are consistent with the theoretical analysis.
Energy regeneration technique for electric vehicles driven by a brushless DC motor
Authors: Bahrami Mansour , Mokhtari Hossein , Dindar Amin
Published: October 2019

The development of energy regeneration capability in electric vehicles can extend their driving range making them a competent alternative for conventional internal combustion engine vehicles. In this study, a novel energy regeneration technique, called a two‐boost method, for electric vehicles driven by a brushless DC (BLDC) motor, a widely used motor in vehicular technology, is proposed. Based on this technique, the BLDC motor driver, which is selected to be a three‐phase inverter, is converted into two simultaneous boost converters during energy regeneration periods in order to transfer energy from the BLDC motor into the battery and provide the braking force. Also, this method is compared with the single‐boost method. The simulation and experimental results show that the amount of regenerated energy in this method is more than twice of that in the single‐boost method. Moreover, it is observed that in the two‐boost method, the motor speed changes linearly without any control of the electrical torque. In addition, since the amount of regenerated energy in this method as compared to the single‐boost method is higher, the energy regeneration efficiency in this method is increased significantly.
Grid‐interfaced solar PV powered electric vehicle battery system with novel adaptive digital control algorithm
Authors: Chauhan Shubhra , Singh Bhim
Published: October 2019

This study deals with the control of a three‐phase grid‐tied solar photovoltaic (PV) powered electric vehicle battery (EVB) system. The perturb and observe technique is used to obtain the peak power of a solar PV array. The EVB is connected through a DC–DC buck–boost converter at the DC link of voltage source converter (VSC), which is charged in base load periods and discharged at high load periods. This converter also maintains the DC link voltage to its maximum power point tracking and the EVB capacity is reduced in comparison to a system, where it is directly assimilated at the DC link. An adaptive recursive digital filter is used in an economical and efficient single‐stage grid‐connected solar PV‐EVB system for the evaluation of the fundamental current constituent of non‐linear load current, subsequently the grid current is sinusoidal and has unity power factor. The system with recursive filter control is adaptable at solar insolation variation and load change. VSC works as an active power filter under no solar power generation and compensates the load reactive power. The operation of scheme is validated with test results on a prototype developed in steady‐state and dynamic conditions.
Displacement damage and total ionisation dose effects on 4H‐SiC power devices
Authors: Hazdra Pavel , Popelka Stanislav
Published: October 2019

A comprehensive study of displacement damage and total ionisation dose effects on 4H‐silicon carbide power devices is presented. Power diodes and transistors produced by different manufacturers were irradiated by high‐energy particles (protons, alphas, electrons and neutrons). The influence of radiation on device characteristics was determined, the introduced radiation defects were identified, and the main degradation mechanisms were established. Results show that radiation leads to the creation of acceptor traps in the lightly doped drift regions of irradiated devices. Devices then degrade due to the removal of the carriers and the decrease in carrier mobility and lifetime. For unipolar devices, the gradual increase of the forward voltage is typical while the blocking characteristics remain nearly unchanged. In bipolar devices, high introduction rates of defects cause a sharp reduction of carrier lifetime. This results in shorter carrier diffusion lengths and subsequent loss of conductivity modulation leading to a sharp increase of the forward voltage drop. The irradiation also shifts the threshold voltage of power switches. That is critical, namely for metal–oxide–semiconductor field‐effect transistors. According to the authors’ study, the junction barrier Schottky diode and junction field‐effect transistor (JFET) can be considered the most radiation‐resistant SiC power devices.
Design and development of isolated snubber based bidirectional DC–DC converter for electric vehicle applications
Authors: Bhatt Kunalkumar , Gupta Ram Avtar , Gupta Nitin
Published: October 2019

Particularly, in the classical dual‐active‐bridge (DAB) converter, the current difference between the source and leakage inductance of high‐frequency transformer potentially results in circulating current. This circulating current further causes the increased voltage stress, voltage overshoots, and conduction losses in the circuit. In view of this, a combination of dual‐switch‐forward (DSF) snubber and pre‐charging method assisted isolated bi‐directional DC–DC (BDC) converter is described in this study for electric vehicle application. The proposed configuration effectively diminishes the adverse impact of circulating current while reducing conduction loss, as well as switching stress. The working principle and corresponding circuit configurations are extensively discussed during both modes of operation. The control‐to‐output transfer functions have been obtained, and it has been confirmed that the system is stable for both modes of operation. The experimental prototype of 480 W for 20 kHz application has been developed using DSP TMS320F28335 to verify the practicality of the proposed converter. The experimental results assure that the voltage spike is successfully alleviated when the converter is operated with the proposed configuration. Finally, the comparative loss analysis has been carried out, which determines that the DSF snubber circuit with pre‐charging method provides a better solution compared to classical converters/techniques.
Automated tool for 3D planar magnetic temperature modelling: application to EE and E/PLT core‐based components
Authors: Bakri Reda , Margueron Xavier , Ngoua Teu Magambo Jean Sylvio , Le Moigne Philippe , Idir Nadir
Published: October 2019

Thermal performance of power converters is a key issue for the power integration. Temperatures inside the active and passive devices can be determined using thermal models. Modelling the temperature distribution of high‐frequency magnetic components is quite complex due to the diversity of their geometries and used materials. This study presents a thermal modelling method based on lumped elements thermal network model, applied to planar magnetic components made of double planar E shaped cores (EE) and planar E core combined with plate one (E/PLT). The 3D model is automatically generated from the component's geometry. The computation enables to obtain 3D temperature distribution inside windings and core of planar transformers or inductors, in steady state or in transient case. This study details the proposed modelling method as well as the automated tool including the problem definition and the solving process. The obtained temperature distributions are compared with finite‐element simulation results and measurements on different planar transformers.
Novel DC–AC inverter based on phase‐shift shoot‐through controlled dual‐active‐bridge and high‐frequency pulse DC link
Authors: Song Zhanfei , Chen Wu
Published: October 2019

Bidirectional isolated DC–AC inverters are widely used in industrial applications, such as grid‐connected uninterruptible power supply, renewable power energy system, electric vehicles and so on. In order to improve the conversion efficiency, realising soft switching will become the essential technology in the research of DC–AC inverters. Based on the commonly used two‐stage isolated inverter, this study proposed a novel DC–AC inverter that combines dual‐active‐bridge (DAB) converter, switched capacitor and full‐bridge inverter. Utilising the strategy of phase‐shift shoot‐through control, DAB will generate a high‐frequency pulse DC link cooperated with switched capacitor. As a result, during the shoot‐through period, when the DC link is in zero‐voltage‐stage, the full‐bridge inverter could realise zero‐voltage switching (ZVS) through discrete pulse modulation. Principles, characteristics and implementations of the proposed inverter and its control strategy are analysed in detail. A further analysis on the operation modes and ZVS constraint of DAB's secondary bridge and switched capacitor is completed. A 250 VDC to 150 VAC (peak value) 1.13 kW simulation and experimental prototype is presented to validate the ZVS of full‐bridge inverter and the analysis of DAB converter and switched capacitor.
Method for the calculation of coupling coefficient between two arbitrary‐shaped coils
Authors: Dehui Wu , Fan Yang , Chao Huang , Fang Cheng
Published: October 2019

A new analytic method to calculate the coupling coefficient including self‐inductances and mutual inductance between two arbitrary‐shaped coils is proposed. The proposed method is applicable for all common coil geometries such as rectangular, square, polygonal, circular coils etc. In the formula, the coil function, which is a completely a new type of function, is defined. The differences in shape and position of the coils are only on the choice of the coil function and its complex conjugate. The layouts of the two coils including separation change and lateral misalignment are discussed. An experimental setup has been built to validate the analytic calculations. Theoretical and experimental results are then compared to be in good agreement, which verify the effectiveness of the proposed method.
Voltage and frequency regulation in an islanded microgrid with PEM fuel cell based on a fuzzy logic voltage control and adaptive droop control
Authors: Shafiee Roudbari Elham , Beheshti Mohammad Taghi Hamidi , Rakhtala Seyed Mehdi
Published: October 2019

Nowadays, the demand for electrical energy is increasing, and conventional power systems will face major problems in the future if they cannot generate extra demand for electrical energy. One of the best solutions for solving extra demand for electrical energy is the use of renewable resources to produce energy. The main aim of this study is designing and controlling the microgrid voltage and frequency. This study proposed the voltage and frequency control of an islanded microgrid based on fuzzy logic controller. The system considered for this study consists of Proton‐Exchange Membrane Fuel Cell (PEMFC) that connected to parallel inverters to convert DC voltage to AC voltage. The control structure is based on adaptive droop control and fuzzy voltage control loop. Also, the proposed structure controls active and reactive powers and decreases power losses of the microgrid. Simulation results are presented to show the effectiveness and robustness of the proposed control structure over the conventional proportional–integral controller. It is shown that the proposed controller has good transient response under the output voltage PEMFC variation and load changes as disturbance.
Stability analysis of modular multilevel converter based on harmonic state‐space theory
Authors: Ma Yajun , Lin Hua , Wang Zhe , Ze Zuyao
Published: October 2019

Modular multilevel converter (MMC) is regarded as one of the most potential topologies for high‐voltage direct current transmission system. However, the multi‐frequency behaviour and complex control structure of MMC bright great challenges to the stability analysis, identification of factors affecting stability, and controller design. To address this problem, the harmonic state‐space (HSS) theory is applied to MMC in this study. First, the small‐signal HSS model is established to describe the multi‐frequency behaviour of MMC. Capacitor voltage control, circulating current control, and output current control are also taken into account in the modelling. On this basis, the stability analysis is performed by evaluating the eigenvalues of the HSS model, and participation factor is introduced to identify the factors affecting stability. In addition, the proposed approach reveals the influence of different controllers on the system stability, providing guidance for the tuning of multiple controller parameters. Finally, the effectiveness and accuracy of the proposed approach are verified by simulation and experiment results.
Analytical calculations of self‐ and mutual inductances for rectangular coils with lateral misalignment in IPT
Authors: Dehui Wu , Chao Huang , Fan Yang , Qisheng Sun
Published: October 2019

Rectangular coils are widely used in inductive power transfer (IPT), and the self‐ and mutual inductances of them are key system parameters. However, the study of the rectangular coil is not enough. In this study, a series of unified analytical formulae for the self‐ and mutual inductance calculations of a variety of rectangular coils including filamentary coils, pancake coils and thin‐ or thick‐walled solenoids are presented. Various positions of the rectangular coils above are discussed, and the mutual inductance formulae in the case of co‐axis, co‐plane, misalignment and even overlapping are given. Finally, the experimental measurements are carried out on various types of rectangular coils. The experimental results agree well with the calculated ones, which indicate the effectiveness of the proposed method. Therefore, this study provides an interesting tool for designing the transceiver of rectangular coils in IPT system.
Acoustic Noise of Axial Flux Permanent Magnet Generators in Locally Manufactured Small Wind Turbines
Authors: Latoufis Kostas , Matzakos Alexandros , Katsambiris Ilias , Vassilakis Athanasios , Hatziargyriou Nikos
Published: October 2019

During the last decade, the local manufacturing of small wind turbines has become a common approach in rural electrification applications, especially among international networks of renewable energy practitioners. Locally manufactured small wind turbines (LMSWTs) used in off‐grid battery based renewable energy systems, typically utilize coreless axial flux permanent magnet generators (AFPMGs) due to their simple manufacturing. Typically, low cost three phase uncontrolled diode bridge rectifiers are used for the direct coupling of the AFPMG to the battery bank, which increases significantly the total harmonic distortion (THD) content in the stator current. LMSWT users have occasionally reported AFPMG noise as contributing to the overall acoustic noise emissions of the small wind turbine, especially during low wind speeds. In this paper the relation between current harmonics and acoustic noise emissions in AFPMGs is investigated and verified experimentally, while appropriate passive filtering techniques are utilized in order to reduce their effect. Furthermore, the overall acoustic noise emissions of a LMSWT are measured experimentally in the field and are compared to noise standards for residential areas. Finally, electromagnetic and aerodynamic sources of acoustic noise are investigated experimentally in the field, while design recommendations are developed for LMSWTs towards the reduction of acoustic noise emissions.
Impact of low (zero) carbon power systems on power system protection: a new evaluation approach based on a flexible modelling and hardware testing platform
Authors: Li Ruiqi , Zhu Jiebei , Hong Qiteng , Booth Campbell , Dyśko Adam , Roscoe Andrew , Urdal Helge
Published: October 2019

This study presents a flexible model and testing arrangement that can be used to mimic the fault infeed characteristics of power electronics converters and evaluate the performance of transmission protection schemes to faults when the system is ‘converter‐dominated’. That is sources (e.g. renewables) and infeeds (e.g. HVDC interconnectors) that are interfaced to the main power system via converters. Actual protection relays are injected, in real‐time, using the outputs of the various fault simulations. A range of potential protection issues, including slow tripping, erroneous discrimination and non‐operation, are illustrated for particular scenarios. The main contributions of the study include knowledge of how different protection schemes may be affected by converter‐interfaced sources and guidance on possible solutions to the observed problems. Two solution options are highlighted: changes to the fault detection methods used within relays, and/or defining the fault‐response elements of future grid codes (and therefore future converter fault responses) to ensure that existing protection schemes will not be adversely affected in future low‐carbon, converter‐dominated systems.