• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.4
• /
• pp.251-260
• /
• 2020

A growing interest has emerged in recycling used automobile batteries into energy storage systems (ESSs) to prevent their harmful effects to the environment from improper disposal and to recycle such resources. To transform used batteries into ESSs, composing battery modules with similar performance by grading them is crucial. Imbalance among battery modules degrades the performance of an entire system. Thus, the selection of modules with similar performance and remaining life is the first prerequisite in the reuse of used batteries. In this study, we develop an instrument to measure the impedance spectrum of a battery module to predict the useful remaining life of the used battery. The developed hardware and software are used to apply the AC perturbation to the used battery module and measure its impedance spectrum. The developed instrument can measure the impedance spectrum of the battery module from 0.1 Hz to 1 kHz and calculate the equivalent circuit parameters through curve fitting. The performance of the developed instrument is verified by comparing the measured impedance spectra with those obtained by a commercial equipment.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.30 no.6
• /
• pp.366-371
• /
• 2017

In this paper, we introduce an electrocardiogram (ECG) system designed to solve problems caused by wetgels and motion artifacts in measuring active movement. The system is called a dry-contact ECG and was designed by considering impedance matching between skin and electrode as well as the frictional electricity between electrode and clothes. In order to create the system, we measured impedance on the skin-electrode interface, and the result was applied to the electronic circuit scheme. Moreover, we added an electrode on the back of the measurement electrode to make a flow path to ground the electrical noise. The final ECG circuit and novel electrode were used to detect real human cardiac signals from a subject who was tested while standing still and walking. The signals obtained from the two activities were nicely shaped, without any motion artifact noise. We took electrode size into account in this study because the impedance depended on the area of the electrode. An electrode of 50 mm diameter showed the best curve for the ECG signal without any electrical noise.

• Proceedings of the KOR-BRONCHOESO Conference
• /
• 1977.06a
• /
• pp.4.4-5
• /
• 1977

The vibratory energy introduced into the external ear canal is changed by the mechanical factors of eardrum itself, the motility of ossicles, and the air cushion of tympanic cavity and the like. This study was designed to investigate the volume of middle ear cavity and mastoid air cell system as a factor of determining the accoustic impedance of middle ear system. The author studied how the increase in air volume of middle ear cavity effects on the acoustic impedance of middle ear system with dogs' ears and researched the correlation between the degree of pneumatization of temporal bones and the acoustic impedance of middle ear system by comparing the radiological findings of pneumatization (Law's and Towne's projection) with the acoustic impedance measurements with Madsen ZO 70. The result is as follows: 1 The tympanometric findings in control state revealed the curves of type A, and did not change in its configuration by the increase in the air volume of dogs middle ear system. 2. The static compliance of middle ear revealed a distinct and linear increase in proportion to the increase in air volume of middle ear system; the rate of increase was $0.05{\pm}0.02$ cc of static compliance per cc of air volume. 3. Authenticated in the above result and the tendency to increase in static compliance in proportion to the increase in the degree of pneumatization of temporal bones, there was significant regression equation between the degree of pneumatization of temporal bones (x variable) and the static compliance of middle ear system; $y=0.19x{\pm}0.16{\pm}0.05$ It is suggested that the difference in volume of middle ear system plays an important role in the change of the static compliance of middle ear, and the author concludes that the measurement of static compliance of middle ear has clinical value as diagnostic means of evaluating the degree of pneumatization of temporal bones along with some radiological examination.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.8 no.2
• /
• pp.199-210
• /
• 2003

In this paper, the new Islanding detection method is studied for utility interactive photovoltaic system(UIPVS). It describes the brief of UIPV system and the features of islanding phenomenon. The new islanding detection method for improving the detection characteristics, HCIM(Harmonic Current Injection Method), is proposed and analyzed. The impedance curve of AC load is derived from the complex power equation for testing Islanding detection features. The proposed detection method and the derivation of islanding condition we verified by the simulation with ACSL and the laboratorial experiments.

• KEPCO Journal on Electric Power and Energy
• /
• v.2 no.4
• /
• pp.601-608
• /
• 2016

The electrical characteristics of the soil where a ground electrode is buried vary with regions, seasons and environmental factors. Electrical discharge in the vicinity of the ground electrode will occur differently and significantly affect the performance of the grounding system. It is necessary to analyze discharge and ionization characteristics of soils when the grounding system is designed. The aims of this investigation are to understand correlation between the soil ionization and the transient ground impedance. This paper presents the experimental results on the soil ionization parameters and the transient ground resistance due to the soil ionization around a hemispherical ground electrode stressed by lightning impulse voltages.

• Journal of IKEEE
• /
• v.19 no.1
• /
• pp.33-40
• /
• 2015

Inverse problem in electrical impedance tomography (EIT) is highly ill-posed therefore prior information is used to mitigate the ill-posedness. Regularization methods are often adopted in solving EIT inverse problem to have satisfactory reconstruction performance. In solving the EIT inverse problem, iterative Gauss-Newton method is generally used due to its accuracy and fast convergence. However, its performance is still suboptimal and mainly depends on the selection of regularization parameter. Although, there are few methods available to determine the regularization parameter such as L-curve method they are sometimes not applicable for all cases. Moreover, regularization parameter is a scalar and it is fixed during iteration process. Therefore, in this paper, a novel method is used to determine the regularization parameter to improve reconstruction performance. Conductivity norm is calculated at each iteration step and it used to obtain the regularization parameter which is a diagonal matrix in this case. The proposed method is applied to human thorax imaging and the reconstruction performance is compared with traditional methods. From numerical results, improved performance of proposed method is seen as compared to conventional methods.

• Journal of Power Electronics
• /
• v.11 no.1
• /
• pp.82-89
• /
• 2011

Differences in the frequency characteristic applied to a ripple current may shorten fuel cell life span and worsen the fuel efficiency. Therefore, this paper presents an experimental analysis of the ripple current applied variable frequency characteristic in a polymer electrolyte membrane fuel cell (PEMFC). This paper provides the first attempt to examine the impact of ripple current through immediate measurements on a single cell test. After cycling for hours at three frequencies, each polarization and impedance curve is obtained and compared with those of a fuel cell. Through experimental results, it can be absolutely concluded that low frequency ripple current leads to long-term degradation of a fuel cell. Three different PEMFC failures such as membrane dehydration, flooding and carbon monoxide (CO) poisoning that lead to an increase in the impedance magnitude at low frequencies are simply introduced.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.57 no.6
• /
• pp.932-937
• /
• 2008

The transformer inrush current can cause a voltage drop by source impedance. This current can impact sensitive loads by the voltage drop. Therefore, it is necessary to take measures to limit this inrush current. This study, described in this paper, analyzes the power quality affected by transformer inrush current using the X power system in Korea. The Electromagnetic Transients Program(EMTP) is used to analyze the transient phenomenon. We discuss a method to model the hysteresis curve of the transformer in EMTP. We carried out various simulations to analyze the power quality during transformer energization. The analysis results of voltage drop by the inrush current occurrence when certain requirements are met are presented.

• Proceedings of the KIEE Conference
• /
• 2007.11b
• /
• pp.95-97
• /
• 2007

Transformer inrush current can cause the voltage drop by source impedance. The accurate modeling and analysis for inrush current is first step to limit the inrush current and improve the power qualify. This paper presents the modeling of transformer inrush current by EMTP-RV using Jeju power system, Korea. The method to model the hysteresis curve of transformer in EMTP-RV is discussed. Simulations demonstrate the verification of modeling of inrush current by comparing the data recorded in field with simulation values and analyzing the harmonics of inrush current.

• Proceedings of the KIEE Conference
• /
• 2002.11b
• /
• pp.151-153
• /
• 2002

Using UPFC(Unified Power Flow Controlled), it is possible to control three parameters(voltage, impedance, and phase angle). The UPFC can generate or absorb reactive power rapidly so as to enhance the transient and voltage stability and also influence the power flow. In this paper, the effects of application of the UPFC to the power system are analyzed from a viewpoint of improving the total transfer capability by enhancing voltage stability. The IPLAN, which is a high level language used with PSS/E program, is employed for evaluating the total transfer capability from a f-V curve.