Journal of Electrical Engineering and Technology
The Korean Institute of Electrical Engineers
- Bimonthly
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- 1975-0102(pISSN)
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- 2093-7423(eISSN)
Aim & Scope
Journal of Electrical Engineering & Technology (JEET), which is the official publication of the Korean Institute of Electrical Engineers (KIEE) being published bimonthly, released the first issue in March 2006.The journal is open to submission from scholars and experts in the areas of electrical engineering technologies. The scope of the JEET included the following: A-Electric Power Engineering - Power System Security & Risk Analysis - Power System Computational Analysis - Power System Dynamics & Control - Power System Economics & Markets - Power System Reliability - Power System Operations - Power System Planning & Implementation - Power System Relaying - Application of Power Electronics to Power Transmission - Power Distribution System B-Electric Machinery and Power Electronics - Electric Machinery I (Induction Motor) - Electric Machinery II (PM Machine and Special Machine) - Power Electronics - Advanced Technology for Electrical Transportation - Renewable Energy System - Motor Drive & Control C-Electrophysics & Applications - Electric Material and Semiconductor - High Power, High Voltage and Discharge - MEMS - Optical and EM Wave - Power Asset and Risk Management D-Information and Control - Control - Sensors and Systems - Robotics and Automation - Signal Processing - Information Technology - Biomedical Engineering E-Electrical Facilities - Technical Standard & Design and Supervision - Electric Construction Technology - Electric Safety Technology - Distribution Facilities Operation & Maintenance - Electric Railway System The scope of the journal includes issues in the field of Electrical Engineering and Technology. Included are techniques for electrical power engineering, electrical machinery and energy conversion systems, electrophysics and applications, information and controls, and electrical facilities. Papers based on novel methodologies and implementations, creative and innovative electrical engineering associated with the five scopes are particularly welcome but not restricted to the above topics.
http://home.jeet.or.kr/ KSCI KCI SCOPUSVolume 13 Issue 6
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Chintam, Jagadeeswar Reddy;Geetha, V.;Mary, D. 2145
Congestion Management (CM) is an attractive research area in the electrical power transmission with the power compensation abilities. Reconfiguration and the Flexible Alternating Current Transmission Systems (FACTS) devices utilization relieve the congestion in transmission lines. The lack of optimal power (real and reactive) usage with the better transfer capability and minimum cost is still challenging issue in the CM. The prediction of suitable place for the energy resources to control the power flow is the major requirement for power handling scenario. This paper proposes the novel optimization principle to select the best location for the energy resources to achieve the real-reactive power compensation. The parameters estimation and the selection of values with the best fitness through the Symmetrical Distance Travelling Optimization (SDTO) algorithm establishes the proper controlling of optimal power flow in the transmission lines. The modified fitness function formulation based on the bus parameters, index estimation correspond to the optimal reactive power usage enhances the power transfer capability with the minimum cost. The comparative analysis between the proposed method with the existing power management techniques regarding the parameters of power loss, cost value, load power and energy loss confirms the effectiveness of proposed work in the distributed renewable energy systems. -
Li, Hongfeng;Ma, Zigang;Han, Bing;Li, Bin;Li, Guidan 2158
This paper analyzed the magnetic field produced by the cylindrical stator coils of permanent magnet spherical motor (PMSM). The elliptic equations about the vector magnetic potential were given. Given that the eddy current effects are neglected, the magnet field of the PMSM is regarded as irrotational field, which can be calculated by scalar magnetic potential. The current density of cylindrical stator coil was proposed based on the definition of current density. The expression of current density of stator coil was obtained according to the double Fourier series decomposition and spherical harmonic functions. Then the magnetic flux density for scalar magnetic potential was derived. Further, the influence of different parameters on radial flux density was also analyzed. Finally, the results by the analytical method in this paper were validated by finite element analysis (FEA). -
Huang, Yu;Xu, Qingshan;Jiang, Xianqiang;Zhang, Tong;Liu, Jiankun 2168
The unavoidable forecast error of wind power is one of the biggest obstacles for wind farms to participate in day-ahead electricity market. To mitigate the deviation from forecast, installation of energy storage system (ESS) is considered. An accurate model of wind power forecast error is fundamental for ESS sizing. However, previous study shows that the error distribution has variable kurtosis and fat tails, and insufficient measurement data of wind farms would add to the difficulty of modeling. This paper presents a comprehensive way that makes the use of mixed skewness model (MSM) and copula theory to give a better approximation for the distribution of forecast error, and it remains valid even if the dataset is not so well documented. The model is then used to optimize the ESS power and capacity aiming to pay the minimal extra cost. Results show the effectiveness of the new model for finding the optimal size of ESS and increasing the economic benefit. -
Xia, Chen-Yang;Zhu, Wen-Ting;Ma, Nian;Jia, Ren-Hai;Yu, Qiang 2178
Online identification of load parameters is the premise of establishing a stable and highly-efficient ICPT (Inductive Coupled Power Transfer) system. However, compared with pure resistive load, precise identification of composite load, such as resistor-inductance load and resistance-capacitance load, is more difficult. This paper proposes a method for detecting the composite load parameters of ICPT system utilizing harmonics. In this system, the fundamental and harmonic wave channel are connected to the high frequency inverter jointly. The load parameter values can be obtained by setting the load equation based on the induced voltage of secondary-side network, the fundamental wave current, as well as the third harmonic current effective value received by the secondary-side current via Fourier decomposition. This method can achieve precise identification of all kinds of load types without interfering the normal energy transmission and it can not only increase the output power, but also obtain higher efficiency compared with the fundamental wave channel alone. The experimental results with the full-bridge LCCL-S type voltage-fed ICPT system have shown that this method is accurate and reliable. -
In order to realize the multi-objective control of single-input multi-output nonlinear differential algebraic system (NDAS) and to improve the dynamic characteristics and static accuracy, a design method of nonlinear control with multi-objective feedback (NCMOF) is proposed, the principium of this method to arrange system poles, as well as its nature to coordinate dynamic characteristics and static accuracy of the system are analyzed in detail. Through NCMOF design method, the multi-objective control of the system is transformed into linear space, and then it is effectively controlled under the nonlinear feedback control law, the problem to balance all control objectives caused by less input and more output of the system thus is solved. Applying NCMOF design method to generator excitation system, the nonlinear excitation control law with terminal voltage, active power and rotor speed as objective outputs is designed. Simulation results show that NCMOF can not only improve the dynamic characteristics of generator, but also damp the mechanical oscillation of a generator in transient process. Moreover, NCMOF can control the terminal voltage of the generator to the setting value with no static error under typical disturbances.
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Kim, Ji-Soo;Cho, Gyu-Jung;Song, Jin-Sol;Shin, Jae-Yun;Kim, Dong-Hyun;Kim, Chul-Hwan 2196
The conventional power system allowed only downstream power flow. Therefore, even if a fault occurs, only the forward current flow is considered. However, with the interest in distributed generation (DG), DGs such as Photovoltaic (PV), Wind Turbine (WT) are being connected to a power system. DGs have many advantages, but they also have disadvantage such as generation of reverse flow. Reverse flow can severely disrupt existing protection systems that only consider downstream power flow. The major problems that may arise from reverse power flow are blinding protection and sympathetic tripping. In order to solve such problems, the methods of installing a directional relay or a fault current limiter is proposed. However, this method is inconceivable because of the economics shortage. Therefore, in this paper, a distance relay installed in existing power system is used to solve the protection problem. Modeling of distance relay has been carried out using ElectroMagnetic Transients Program (EMTP), and it has been verified through simulations that the above problems can be solved by a distance relay. -
Kim, Hyoungtae;Lee, Sungwoo;Kim, Tae Hyun;Shin, Hansol;Kim, Wook 2203
Capacity payment mechanism has been adopted as the incentive scheme to achieve resource adequacy in Korean electricity market, however, the level of capacity price has been controversial due to its insufficient extent to incur financial loss for certain generators. Therefore, a new method is proposed to estimate the proper level of capacity price incorporating profitability of market participants and resource adequacy in this paper. The proposed method is successfully applied to test system based on Korean power system. -
This paper describes extended fault location algorithm using estimated remote source impedance. The method uses data only at the local end and the sequence current distribution factors for more accurate estimation. The proposed algorithm can respond to variation of the local and remote source impedance. Therefore, this method is especially useful for transmission lines interconnected to a wind farm that the source impedance varies continuously. The proposed algorithm is very insensitive to the variation in fault distance and fault resistance. The simulation results have shown the accuracy and effectiveness of the proposed algorithm.
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Yoon, Sung Hyun;Jin, Young Gyu;Yoon, Yong Tae 2220
Electric vehicles (EVs) are significant resources for demand response (DR). Thus, it is essential for EV aggregators to quantitatively evaluate their capability for DR. In this paper, a concept of dynamic equivalent battery (DEB) is proposed as a metric for evaluating the DR performance using EVs. The DEB is the available virtual battery for DR. The capacity of DEB is determined from stochastic calculation while satisfying the charging requirements of each EV, and it varies also with time. Further, a new indicator based on the DEB and time-varying electricity prices, named as value of DEB (VoDEB), is introduced to quantify the value of DEB coupled with the electricity prices. The effectiveness of the DEB and the VoDEB as metrics for the DR performance of EVs is verified with the simulations, where the difference of charging cost reduction between direct charging and optimized bidding methods is used to express the DR performance. The simulation results show that the proposed metrics accord well with the DR performance of an EV fleet. Thus, an EV aggregator may utilize the proposed concepts of DEB and VoDEB for designing an incentive scheme to EV users, who participate in a DR program. -
Kong, Junhyuk;Jufri, Fauzan Hanif;Kang, Byung O;Jung, Jaesung 2227
Under the current policies and compensation rules in South Korea, Photovoltaic (PV) generation supplier can maximize the profit by combining PV generation with Energy Storage System (ESS). However, the existing operational strategy of ESS is not able to maximize the profit due to the limitation of ESS capacity. In this paper, new ESS scheduling algorithm is introduced by utilizing the System Marginal Price (SMP) and PV generation forecasting to maximize the profits of PV generation supplier. The proposed algorithm determines the charging time of ESS by ranking the charging schedule from low to high SMP when PV generation is more than enough to charge ESS. The discharging time of ESS is determined by ranking the discharging schedule from high to low SMP when ESS energy is not enough to maintain the discharging. To compensate forecasting error, the algorithm is updated every hour to apply the up-to-date information. The simulation is performed to verify the effectiveness of the proposed algorithm by using actual PV generation and ESS information. -
Son, Seungwoo;Han, Sini;Roh, Jae Hyung;Lee, Duehee 2236
We make optimal consecutive offer curves for an energy storage system (ESS) integrated wind power producer (WPP) in the co-optimized day-ahead energy and regulation markets. We build the offer curves by solving multi-stage stochastic optimization (MSSO) problems based on the scenarios of pairs consisting of real-time price and wind power forecasts through the progressive hedging method (PHM). We also use the rolling horizon method (RHM) to build the consecutive offer curves for several hours in chronological order. We test the profitability of the offer curves by using the data sampled from the Iberian Peninsula. We show that the offer curves obtained by solving MSSO problems with the PHM and RHM have a higher profitability than offer curves obtained by solving deterministic problems. -
With the increase of electrical consumption and the unbalance of power demand and supply, power reserve rate is getting smaller and also the reliability of the power supply is getting deteriorated. Under this circumstance, the electrical energy storage (EES) System is considered as one of essential countermeasure for demand side management. This paper proposes efficient evaluation algorithms of multiple functions for EES systems, especially the secondary battery energy storage systems, in the case where they are interconnected with the power distribution systems. It is important to perform the economic evaluation for the new energy storage systems in a quantitative manner, because they are very costly right now. In this paper, the multiple functions of EES systems such as load levelling, effective utilization of power distribution systems and uninterruptible power supply are classified, and then the quantitative evaluation methods for their functions are proposed. From the case studies, it is verified that EES systems installed at distribution systems in a dispersed manner have multiple functions involved with direct and indirect benefits and also they can be expected to introduce to distribution systems with respects to economical point of view.
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This paper analyzes stability of current control in respect of four cases of battery energy storage system (BESS) in a stand-alone microgrid. The stand-alone microgrid is composed of BESS, diesel generator and controllable loads, where all of them have a rated power of 50kW. The four cases are considered as following: 1) BESS with a stiff grid 2) BESS with the diesel generator 3) BESS with passive damping + diesel generator 4) BESS with active damping + diesel generator, and their stabilities are analyzed in the frequency domain and discrete time domain. The comparative analysis for four cases are verified through simulation and experiments through demonstration site of the stand-alone microgrid, where the DC link is connected to a 115kW battery bank composed of 48 lead-acid batteries (400AH/12V). Experimental results show a good agreement with the analysis.
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Lee, Jae-Gil;Jung, Hyun-Kyo;Woo, Dong-Kyun 2262
In electric machine design, there is a large computation cost for finite element analyses (FEA) when analyzing nonlinear characteristics in the machine Therefore, for the optimal design of an electric machine, designers commonly use an optimization algorithm capable of excellent convergence performance. However, robustness consideration, as this factor can guarantee machine performances capabilities within design uncertainties such as the manufacturing tolerance or external perturbations, is essential during the machine design process. Moreover, additional FEA is required to search robust optimum. To address this issue, this paper proposes a computationally efficient robust optimization algorithm. To reduce the computational burden of the FEA, the proposed algorithm employs a useful technique which termed static analysis assisted technique (SAAT). The proposed method is verified via the effective robust optimal design of electric machine to reduce cogging torque at a reasonable computational cost. -
This paper presents a high-efficiency low-power permanent magnet (PM) generator for the power supply of the generator exciter. In the conventional generator system, the power for the exciter is fed by the generator output power or an emergency battery for the starting. The proposed low-power PM generator can generate the proper power and voltage to excite the exciter field winding. According to the starting of the generator, the designed PM generator can supply the constant voltage to the Automatic Voltage Regulator (AVR), then it can be used to control of exciter field current for the generator. Because of the designed PM generator which is placed inside the conventional generator system, the emergency battery and Potential Transducer(PT) for AVR can be removed. Thus, the total efficiency can be improved. The proposed generator system is tested in the practical system. And the efficiency characteristic is analyzed.
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Lumped-Parameter Thermal Analysis and Experimental Validation of Interior IPMSM for Electric VehicleA 50kW-4000rpm interior permanent magnet synchronous machine (IPMSM) applied to the high-performance electric vehicle (EV) is introduced in this paper. The main work of this paper is that a 2-D T-type lumped-parameter thermal network (LPTN) model is presented for IPMSM temperature rise calculation. Thermal conductance matrix equation is generated based on calculated thermal resistance and loss. Thus the temperature of each node is obtained by solving thermal conductance matrix. Then a 3-D liquid-solid coupling model is built to compare with the 2-D T-type LPTN model. Finally, an experimental platform is established to verify the above-mentioned methods, which obtains the measured efficiency map and current wave at rated load case and overload case. Thermocouple PTC100 is used to measure the temperature of the stator winding and iron core, and the FLUKE infrared-thermal-imager is applied to measure the surface temperature of IPMSM and controller. Test results show that the 2-D T-type LPTN model have a high accuracy to predict each part temperature.
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Lee, Byeong-Hwa;Park, Hyung-Il;Jung, Jae-Woo 2284
This paper deals with optimum design of surface mounted permanent magnet synchronous motor (SPMSM) for automotive component. For a compact system structure, it was designed as a motor with a 14-pole 12-slot concentrated winding and hollow shaft. The motor is a thin type structure which stator outer diameter is relatively large compared to its axial length and is designed to have a high magnetic saturation for increasing the torque density. Since the high magnetic saturation in the stator core increases the axial leakage flux, a 3-dimensional (3-D) finite element analysis (FEA) is indispensable for torque analysis. However, optimum designs using 3-D FEA is inefficient in terms of time and cost. Therefore, equivalent 2-D FEA which is able to consider axial leakage flux is applied to the optimization to overcome the disadvantages of 3-D FEA. The structure for cost reduction is proposed and optimum design using equivalent 2-D FEA has been performed. -
Zhou, Zhi-ting;Fan, Zhen-nan;Li, Jian-fu;Wen, Kun;Zhang, Bide;Wang, Tao;Xia, Yan-kun;Sun, Zhang;Yao, Bing 2292
A field-circuit coupling model of a typical faulty generator is established to correct through-bolt end-region overheating and breakdown failure in a tubular hydro-generator. Using the model, eddy current loss and electromagnetic forces on through bolts under normal and failure conditions are analyzed and compared and the natural frequency of a through bolt is determined. Based on the analysis results, the causative mechanism of failure is revealed and targeted improvement design measures are proposed. The numerical results are found to be consistent with the actual fault characteristics, validating the design measure improvements. The results are useful in improving the design and manufacturing standards and enhancing the operational reliability of large tubular hydro-generators. -
In a field-oriented vector-controlled permanent magnet synchronous motor (PMSM) control system, the d-axis current control loop can offer a free degree of freedom which can be used to improve control performances. However, in the industry the desired d-axis current command is usually set as zero without using the free degree of freedom. This paper proposes a method to use the degree of freedom for control performance improvement. It is assumed that both the inner loop proportional-integral (PI) current controller and the q-axis outer loop PI speed controller are tuned by the well-known tuning rules. This paper gives an optimal d-axis reference current command generator such that some useful performance indexes are minimized and/or a tradeoff between conflicting performance criteria is made. This paper uses a differential evolution algorithm to autotune the parameter values of the optimal d-axis reference current command generator. This paper implements the proposed control system in real time on a Texas Instruments TMS320F28335 floating-point DSP. This paper also gives experimental results showing the practicality and feasibility of the proposed control system, along with simulation results.
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Critical conduction mode (CRM) operation is more efficient than continuous conduction mode (CCM) operation at low power levels because of the valley switching of switches and elimination of the reverse recovery losses of boost diodes. When using a sensorless digital control method, an error occurs between the actual and the estimated current. Because of the error, it operates as CCM or discontinuous conduction mode (DCM) during CRM operation and also has an adverse effect on THD of input current. In this paper, a current sensorless technique is presented in an inverter system using a bridgeless boosted power factor correction converter, and a compensation method is proposed to reduce CRM calculation error. The validity of the proposed method is verified by simulation and experiment.
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Kim, Si-Hwan;Kim, June-Sung;Kim, Rae-Young;Cho, Jin-Tae;Kim, Seok-Woong 2319
This paper introduces a control method for a transformerless MMC-HVDC system. The proposed method can effectively control the grid currents of the MMC-HVDC system under unbalanced grid conditions such as a single line-to-ground fault. The proposed method controls the currents of the positive sequence component and the negative sequence component without separating algorithms. Therefore, complicated calculations for extracting the positive sequence and the negative sequence component are not required. In addition, a control method to regulate a zero sequence component current under unbalanced grid conditions in the transformerless MMC-HVDC system is also proposed. The validity of the proposed method is verified through PSCAD/EMTDC simulation. -
Luu, Phuong Thi;Lee, Ji-Young;Kim, Ji-Won;Chun, Yon-Do;Oh, Hong-Seok 2329
This paper discusses the thermal effect of the number of permanent-magnet (PM) layers in an outer rotor machine. Depending on the number of axial-layer of PM, the operating temperature is compared analytically and experimentally. The electromagnetic analysis is performed using 3-dimensional time varying finite element method to get the heat sources depending on axial-layered PM models. Then thermal analysis is conducted using the lumped-parameter-thermal-network method for each case. Two outer rotor machines, which have the different number of axial-layer of PM, are manufactured and tested to validate the analysis results. -
This paper proposes an optimal damping control algorithm of the DTI (Direct Two-level Inverter) to miniaturize and reduce the weight of auxiliary power supply for railway vehicles. The conventional auxiliary power supply for railway vehicles uses a DC-DC converter to maintain the inverter input power from the line voltage smoothly. The proposed topology does not use a DC-DC converter for reducing of manufacturing and maintenance costs. It also proposes a DTI topology removed damping resistors that generate ground signal noise in a certain period. At this time, a resonance phenomenon of DC-link voltage occurs due to variation of the inductive load, and a method of controlling the resonance phenomenon of DC-link voltage is required. In order to suppress the resonance phenomenon of the DC-link voltage, at a point before resonance occurs, this paper introduces an algorithm to suppress the resonance phenomenon of DC-link voltage by compensating the resonance component of the q axis voltage of the synchronous reference frame. The proposed algorithm verifies the effect through simulation and experiment.
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Wang, Yangding;Xu, Shen;Huang, Hai;Guo, Yiping;Jin, Hai 2344
A coupled recursive total least squares (CRTLS) algorithm is proposed for parameter estimation of permanent magnet synchronous machines (PMSMs). TLS considers the errors of both input variables and output ones, and thus achieves more accurate estimates than standard least squares method does. The proposed algorithm consists of two recursive total least squares (RTLS) algorithms for the d-axis subsystem and q-axis subsystem respectively. The incremental singular value decomposition (SVD) for the RTLS obtained by an approximate calculation with less computation. The performance of the CRTLS is demonstrated by simulation and experimental results. -
This paper proposed a novel double closed control strategy for single-phase voltage source pulse width modulation (PWM) rectifier based on active disturbance rejection control (ADRC) and dq current decoupling control. First, the mathematical model of the single-phase PWM rectifier in the d-q axis synchronous rotating reference frame is established by constructing a virtual component using a second-order generalized integrator (SOGI). Then, the mathematical model is simplified according to the active power conservation, and the first-order equation of single-phase PWM rectifier voltage outer loop is acquired. A linear auto-disturbance rejection controller is used to design the voltage outer loop according to the first-order equation. Finally, the proposed control strategy and the traditional PI control are compared and verified by simulation and physical experiments. Both simulation and experimental results confirm that the proposed control strategy has excellent dynamic performance and strong rejection ability to disturbances.
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Zhu, Yueying;Yang, Chuantian;Yue, Yuan;Zhao, Chengwen;Zhang, Yan 2364
Two-phase simultaneous excitation mode of the switched reluctance motor (SRM) has been shown to effectively improve the average torque output compared with traditional single-phase excitation mode. But the torque ripple of the two-phase excitation SRM with traditional winding distribution increases because of the inconsistent electromagnetic field. To reduce the torque ripple, a two-phase excitation 8/6 SRM with novel winding distribution is proposed in this paper. The static torques generated by various magnetic circuits are analyzed and obtained to verify the torque increase. Then the electromagnetic characteristics of the proposed SRM are investigated by the numerical calculation method in detail, including flux linkage, inductance, and torque. Finally, an experiment for measuring the SRM static electromagnetic characteristics and dynamic performance is designed and performed based on the novel mode, and the comparing results show that the proposed two-phase SRM is effective. -
To reduce the size and cost of motor driving systems, several methods for driving multiple parallel-connected motors with a single inverter have been proposed. However, dual PMSMs driven by a single inverter, unlike induction motors, have a problem with instability due to system resonance caused by disturbances such as load imbalance and tolerances between two motors. To drive dual SPMSMs fed by a single inverter, this paper proposes an active damping algorithm to effectively suppress resonance by using one-sided sensorless speed control and position difference estimation. By deriving rotor position difference from d-q current differences between two motors, the proposed method is affected less by position difference estimation errors and is simpler than dual sensorless position estimation.
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Cai, Fan-Yi;Tan, Dong-Xian;Zhou, Bai-Jie;Xue, Jian;Xiao, Deng-Ming 2385
This paper is devoted to detecting decomposition characteristics of Iodotrifluoromethane ($CF_3I$ ) under alternating current (AC) discharges or load current interruptions. The decomposition products are measured utilizing chromatography-mass spectroscopy. It is found that less than 1%$CF_3I$ gas decomposed after several interruptions at load current of 200 A or hundred times of AC discharges. However, under interruptions at a current of 400 A, more than 95%$CF_3I$ gas decomposed into carbon tetrafluoride ($CF_4$ ) and hexafluoroethane ($C_2F_6$ ). The equilibrium compositions based on Gibbs free energy minimization of$CF_3I$ was calculated to explain the decomposition mechanism. -
Javed, Hassan;LI, Kang;Zhang, Guoqiang;Plesca, Adrian Traian 2392
Creepage discharge faults in air on solid insulating material play a vital role in degradation and ageing of material which ultimately leads to breakdown of power equipment. And electric discharge decompose air in to its by-products such as Ozone and$NO_x$ gases. By analyzing air decomposition gases is a potential method for fault diagnostic in air. In this paper, experimental research has been conducted to study the effect of creepage discharge on rate of generation of air decomposition by-products using different insulating materials such as RTV, epoxy and fiberglass laminated sheet. Moreover XRF analysis has been done to analyze creepage discharge effect on these insulating materials. All experiments have been done in an open air test cell under constant temperature and pressure conditions. While analysis has been made for low and high humidity conditions. The results show that the overall concentration of air decomposition by-products under creepage discharge in low humidity is 4% higher than concentration measured in high humidity. Based on this study a mathematical relationship is also proposed for the rate of generation of air decomposition by-products under creepage discharge fault. This study leads to indirect way for diagnostic of creepage discharge propagation in air. -
Chen, Geng;Tu, Youping;Wang, Cong;Cheng, Yi;Jiang, Han;Zhou, Hongyang;Jin, Hua 2402
Fluoronitriles-$CO_2$ gas mixtures are promising alternatives to$SF_6$ in environmentally-friendly gas-insulated transmission lines (GILs). Insulating gas heat transfer characteristics are of major significance for the current-carrying capacity design and operational state monitoring of GILs. In this paper, a three-dimensional calculation model was established for a GIL using the thermal-fluid coupled finite element method. The calculated results showed close agreement with experimentally measured data. The temperature distribution of a GIL filled with the Fluoronitriles-$CO_2$ mixture was obtained and compared with those of GILs filled with$CO_2$ and$SF_6$ . Furthermore, the effects of the mixture ratio of the component gases and the gas pressure on the temperature rise and current-carrying capacity of the GIL were analyzed. Results indicated that the heat transfer performance of the Fluoronitriles-$CO_2$ gas mixture was better than that of$CO_2$ but worse than that of$SF_6$ . When compared with$SF_6$ , use of the Fluoronitriles-$CO_2$ gas mixture caused a reduction in the GIL's current-carrying capacity. In addition, increasing the Fluoronitriles gas component ratio or increasing the pressure of the insulating gas mixture could improve the heat dissipation and current-carrying capacity of the GIL. These research results can be used to design environmentally-friendly GILs containing Fluoronitriles-$CO_2$ gas mixtures. -
Wang, Can;Xie, Yaoheng;Pan, Hua;Wang, Youyuan 2412
The thermal degradation of low density polyethylene (LDPE) will accelerate the production of carbonyl groups (C=O), which can act as the induced dipoles under high voltage. In this paper, we researched the dielectric properties and space charge behavior of LDPE after thermal aging, which can help us to understand the correlation between carbonyl groups (C=O) and electrical properties of LDPE. The spectra results show that LDPE exhibit obvious thermooxidative reactions when the aging time is 35 days and the productions mainly contain carboxylic acid, carboxylic eater and carboxylic anhydride, whose amount increase with the increasing of aging time. The dielectric properties show that the real permittivity of LDPE is inversely proportional to temperature before aging and subsequently become proportional to temperature after thermal aging. Furthermore, both the real and imaginary permittivity increase sharply with the increasing of aging time. The fitting results of imaginary permittivity show that DC conductivity become more sensitive about temperature after thermal aging. On this basis, the active energies of materials calculated from DC conductivity increase first and then decrease with the increasing of aging time. In addition, the space charge results show that the heterocharges accumulated near electrodes in LDPE change to the homocharges after thermal aging and the mean volume charge density increase with the increasing of aging time. It is considered that the overlaps caused by electrical potential area is the main reason for the increase of DC conductivity. -
A direct measurement of an initiation carrier injection for a low voltage discharge is presented. A self-sustained pulsed discharge is utilized to characterize electrical responses of a glow discharge for varying amounts of injected initiation carriers. It is clearly demonstrated that the initiation carrier injection affects the ignition time and the breakdown voltage of the primary discharge. An abrupt reduction in the breakdown voltage for a
$300{\mu}m$ gap pin-plate discharge is observed when a threshold carrier density of$3{\times}10^{11}cm^{-3}$ is injected and the breakdown voltage continues to decrease to 250 V with increasing the initiation carrier injection beyond the threshold density. -
Trnka, Pavel;Mentlik, Vaclav;Harvanek, Lukas;Hornak, Jaroslav;Matejka, Libor 2425
This study investigates a new organic based material and its dielectric and mechanical properties. It is a comprehensive nanocomposite comprising a combination of various types of nanofillers with hydrophobic silica nanoparticles (AEROSIL R 974) as a matrix modifier and a polyamide nano nonwoven textile, Ultramid-Polyamide 6, pulped in the electrostatic field as a dielectric barrier. The polymer matrix is an epoxy network based on diglycidyl ether of bisphenol A (DGEBA) and cycloaliphatic diamine (Laromine C260). The designed nanocomposite material is an alternative to the conventional three-component composites containing fiberglass and mica with properties that exceed current electroinsulating systems (volume resistivity on the order of$10^{16}{\Omega}{\cdot}m$ , dissipation factor tan${\delta}=4.7{\cdot}10^{-3}$ , dielectric strength 39 kV/mm). -
Lim, Un-Hyun;Yoo, Jin-Hee;Kondalkar, Vijay;Lee, Keekeun 2434
A new type of piezoelectric micromachined ultrasonic transducer (pMUT) with high resonant frequency was developed by using a thin lead zirconate titanate (PZT) as an insulation layer on a floating$10{\mu}m$ silicon membrane. The PZT insulation layer facilitated acoustic impedance matching at active pMUT, leading to a high performance in the acoustic conversion property compared with the transducer using$SiO_2$ insulation layer. The fabricated ultrasonic devices were wirelessly measured by connecting two identical acoustic transducers to two separate ports in a single network analyzer simultaneously. The acoustic wave emitted from a transducer induced a$3.16{\mu}W$ on the other side of the transducer at a distance of 2 cm. The transducer performances in terms of device diameters, PZT thickness, annealings, and different DC polings, etc. were investigated. COMSOL simulation was also performed to predict the device performances prior to fabrication. Based on the COMSOL simulation, the device was fabricated and the results were compared. -
This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using
$0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current. -
Sujihelen, L.;Jayakumar, C.;Senthilsingh, C. 2447
Security is more important in many sensor applications. The node replication attack is a major issue on sensor networks. The replicated node can capture all node details. Node Replication attacks use its secret cryptographic key to successfully produce the networks with clone nodes and also it creates duplicate nodes to build up various attacks. The replication attacks will affect in routing, more energy consumption, packet loss, misbehavior detection, etc. In this paper, a Secure-Efficient Centralized approach is proposed for detecting a Node Replication Attacks in Wireless Sensor Networks for Static Networks. The proposed system easily detects the replication attacks in an effective manner. In this approach Secure Cluster Election is used to prevent from node replication attack and Secure Efficient Centralized Approach is used to detect if any replicated node present in the network. When comparing with the existing approach the detection ratio, energy consumption performs better. -
Wireless multimedia sensor networks (WMSNs) require real-time quality-of-service (QoS) guarantees to be provided by the network. The end-to-end delay is very critical metric for QoS guarantees in WMSNs. In WMSNs, due to the transmission errors incurred over wireless channels, it is difficult to obtain reliable delivery of data in conjunction with low end-to-end delay. In order to improve the end-to-end delay performance, the system has to drop few packets during network congestion. In this article, our proposal is based on optimization of end-to end delay for WMSNs. We optimize end-to-end delay constraint by assuming that each packet is allowed fixed number of retransmissions. To optimize the end-to-end delay, first, we compute the performance measures of the system, such as end-to-end delay and reliability for different network topologies (e.g., linear topology, tree topology) and against different choices of system parameters (e.g., data rate, number of nodes, number of retransmissions). Second, we study the impact of the end-to-end delay and packet delivery ratio on indoor and outdoor environments in WMSNs. All scenarios are simulated with multiple run-times by using network simulator-2 (NS-2) and results are evaluated and discussed.
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Kim, Sung Hee;Pae, Dong Sung;Kang, Tae-Koo;Kim, Dong W.;Lim, Myo Taeg 2468
We propose the Sparse Feature Convolutional Neural Network (SFCNN) to reduce the volume of convolutional neural networks (CNNs). Despite the superior classification performance of CNNs, their enormous network volume requires high computational cost and long processing time, making real-time applications such as online-training difficult. We propose an advanced network that reduces the volume of conventional CNNs by producing a region-based sparse feature map. To produce the sparse feature map, two complementary region-based value extraction methods, cluster max extraction and local value extraction, are proposed. Cluster max is selected as the main function based on experimental results. To evaluate SFCNN, we conduct an experiment with two conventional CNNs. The network trains 59 times faster and tests 81 times faster than the VGG network, with a 1.2% loss of accuracy in multi-class classification using the Caltech101 dataset. In vehicle classification using the GTI Vehicle Image Database, the network trains 88 times faster and tests 94 times faster than the conventional CNNs, with a 0.1% loss of accuracy. -
The filter bank multicarrier modulation (FBMC) technique is one of multicarrier modulation technique (MCM), which is mainly used to improve channel capacity of cognitive radio (CR) network and frequency spectrum access technique. The existing FBMC System contains serial to parallel converter, normal QAM modulation, Radix2 inverse FFT, parallel to serial converter and poly phase filter. It needs high area, delay and power consumption. To further reduce the area, delay and power of FBMC structure, a new clock gating technique is applied in the QAM modulation, radix2 multipath delay commutator (R2MDC) based inverse FFT and unified addition and subtraction (UAS) based FIR filter with parallel asynchronous self time adder (PASTA). The clock gating technique is mainly used to reduce the unwanted clock switching activity. The clock gating is nothing but clock signal of flip-flops is controlled by gate (i.e.) AND gate. Hence speed is high and power consumption is low. The comparison between existing QAM and proposed QAM with clock gating technique is carried out to analyze the results. Conversely, the proposed inverse R2MDC FFT with clock gating technique is compared with the existing radix2 inverse FFT. Also the comparison between existing poly phase filter and proposed UAS based FIR filter with PASTA adder is carried out to analyze the performance, area and power consumption individually. The proposed FBMC with clock gating technique offers low power and high speed than the existing FBMC structures.
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Wang, Yuehai;Ma, Yuying;Cui, Shiming;Yan, Yongzheng 2485
The rapid development of large-scale integrated circuits has brought great challenges to the circuit testing and diagnosis, and due to the lack of exact fault models, inaccurate analog components tolerance, and some nonlinear factors, the analog circuit fault diagnosis is still regarded as an extremely difficult problem. To cope with the problem that it's difficult to extract fault features effectively from masses of original data of the nonlinear continuous analog circuit output signal, a novel approach of feature extraction and dimension reduction for analog circuit fault diagnosis based on wavelet packet decomposition, local linear embedding algorithm, and clone selection algorithm (WPD-LLE-CSA) is proposed. The proposed method can identify faulty components in complicated analog circuits with a high accuracy above 99%. Compared with the existing feature extraction methods, the proposed method can significantly reduce the quantity of features with less time spent under the premise of maintaining a high level of diagnosing rate, and also the ratio of dimensionality reduction was discussed. Several groups of experiments are conducted to demonstrate the efficiency of the proposed method. -
Passive dynamic walking exhibits humanoid and energy efficient gaits. However, optimal design of passive walker at multi-variable level is not well studied yet. This paper presents a Chaotic Particle Swarm Optimization (CPSO) algorithm and applies it to the optimal design of flexible passive walker. Hip torsional stiffness and damping were incorporated into flexible biped walker, to imitate passive elastic mechanisms utilized in human locomotion. Hybrid dynamics were developed to model passive walking, and period-one gait was gained. The parameters global searching scopes were gained after investigating the influences of structural parameters on passive gait. CPSO were utilized to optimize the flexible passive walker. To improve the performance of PSO, multi-scroll Jerk chaotic system was used to generate pseudorandom sequences, and chaotic disturbance would be triggered if the swarm is trapped into local optimum. The effectiveness of CPSO is verified by comparisons with standard PSO and two typical chaotic PSO methods. Numerical simulations show that better fitness value of optimal design could be gained by CPSO presented. The proposed CPSO would be useful to design biped robot prototype.
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Actuator failures and the failures of controlled objects are often considered together. To overcome this limitation, a class of sliding mode observers for the fault diagnosis of nonlinear systems is designed in this paper. Due to the influence of the sliding mode function, the control strategy and the residual change of the observer exhibit certain trends governed by specific relations. Therefore, according to the changes in the control strategy and the observer residuals, the sensor and actuator faults in nonlinear systems can be determined. Finally, the effectiveness of the proposed method is verified based on simulations of a DC motor system.
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Wang, Zheng;Yang, Cheng;Oh, Sung-Kwun;Fu, Zunwei 2511
In this study, Multi-Radial Basis Function Support Vector Machine (Multi-RBF SVM) classifier is introduced based on a composite kernel function. In the proposed multi-RBF support vector machine classifier, the input space is divided into several local subsets considered for extremely nonlinear classification tasks. Each local subset is expressed as nonlinear classification subspace and mapped into feature space by using kernel function. The composite kernel function employs the dual RBF structure. By capturing the nonlinear distribution knowledge of local subsets, the training data is mapped into higher feature space, then Multi-SVM classifier is realized by using the composite kernel function through optimization procedure similar to conventional SVM classifier. The original training data set is partitioned by using some unsupervised learning methods such as clustering methods. In this study, three types of clustering method are considered such as Affinity propagation (AP), Hard C-Mean (HCM) and Iterative Self-Organizing Data Analysis Technique Algorithm (ISODATA). Experimental results on benchmark machine learning datasets show that the proposed method improves the classification performance efficiently. -
This paper deals with a sampled-data tracking control problem for the Takagi-Sugeno fuzzy system with external disturbances. We derive a stability condition guaranteeing both asymptotic stability and H-infinity tracking performance by employing a newly proposed time-dependent line-integral fuzzy Lyapunov-Krasovskii functional. A new integral inequality is also introduced, by which the proposed stability condition is formulated in terms of linear matrix inequalities. Finally, the effectiveness of the proposed method is demonstrated through a simulation example.
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Yoo, Joong-Sun;Kim, Do-Hyeong;Kim, Gon-Woo 2530
In this paper, we propose an enhanced LiDAR-camera calibration method that extracts the marker plane from 3D point cloud information. In previous work, we estimated the straight line of each board to obtain the vertex. However, the errors in the point information in relation to the z axis were not considered. These errors are caused by the effects of user selection on the board border. Because of the nature of LiDAR, the point information is separated in the horizontal direction, causing the approximated model of the straight line to be erroneous. In the proposed work, we obtain each vertex by estimating a rectangle from a plane rather than obtaining a point from each straight line in order to obtain a vertex more precisely than the previous study. The advantage of using planes is that it is easier to select the area, and the most point information on the board is available. We demonstrated through experiments that the proposed method could be used to obtain more accurate results compared to the performance of the previous method. -
Yuan, Zhikang;Tu, Youping;Wang, Cong;Qin, Sichen;Chen, Geng 2545
$SF_6$ has been widely used in high voltage power equipment, such as gas insulated switchgear (GIS) and gas insulated transmission line (GIL), because of its excellent insulation and arc extinguishing performance. However,$SF_6$ faces two environmental problems: greenhouse effect and high liquefaction temperature. Therefore, to find the$SF_6$ substitute gases has become a research hotspot in recent years. In this paper, the liquefaction characteristics of$SF_6$ substitute gases were studied. Peng-Robinson equation of state with the van der Waals mixing rule (PR-vdW model) was used to calculate the dew point temperature of the binary gas mixtures, with$SF_6$ ,$C_3F_8$ ,$c-C_4F_8$ ,$CF_3I$ or$C_4F_7N$ as the insulating gas and$N_2$ or$CO_2$ as the buffer gas. The sequence of the dew point temperatures of the binary gas mixtures under the same pressure and composition ratio was obtained.$SF_6/N_2$ <$SF_6/CO_2$ <$C_3F_8/N_2$ <$C_3F_8/CO_2$ <$CF_3I/N_2$ <$CF_3I/CO_2$ <$c-C_4F_8/N_2$ <$C_4F_7N/N_2$ <$c-C_4F_8/CO_2$ <$C_4F_7N/CO_2$ .$SF_6/N_2$ gas mixture showed the best temperature adaptability and$C_4F_7N/CO_2$ gas mixture showed the worst temperature adaptability. Furthermore, the dew point temperatures of the$SF_6$ substitute gases at different pressures and the upper limits of the insulating gas mole fraction at$-30^{\circ}C$ ,$-20^{\circ}C$ and$-10^{\circ}C$ were obtained. The results would supply sufficient data support for GIS/GIL operators and researchers. -
In Korea, there are no instances where a hydrogen fuel cell power generation system has been used in a railway vehicle. Only the basic topology has been studied. In the previous study, conventional converters using a single switch were applied to the fuel cell power generation system. Therefore, current stress on the switch at converter on-off transitions would be large when controlling a large-capacity railway vehicle. In addition, since the input side ripple is also large, there is a problem with a shortening of the lifetime of both the fuel cell power generation system and the inductor. In this paper, a soft-switching transformer inductor boost converter for fuel cell powered railway vehicles was proposed. A technique to reduce both the switching current stress generated during on-off transitions, and the input ripple current flowing in the inductor were studied. The soft-switching TIB converter uses a transformer-type inductor to configure the entire circuit in an interleaved method, and reduces both input current ripple and the current ripple of the inductor and switch.
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The extension of DC battery backup time in the DC power supply system of nuclear power plants (NPPs) remains a challenge. The lead-acid battery is the most popular at present. And it is generally the most popular energy storage device. However, extension of backup time requires too much space. The lithium-ion battery has high energy density and advanced gravimetric and volumetric properties. The aim of this paper is development of the sizing formula of stationary lithium-ion batteries. The ongoing research activities and related industrial standards for stationary lithium-ion batteries are reviewed. Then, the lithium-ion battery sizing calculation formular is proposed for the establishment of industrial design standard which is essential for the design of stationary batteries of nuclear power plants. An example of calculating the lithium-ion battery capacity for a medium voltage UPS is presented.