• Proceedings of the KIPE Conference
• /
• 2003.07b
• /
• pp.987-993
• /
• 2003

The module UPS can flexibly implement expansion of power system capacities. Furthermore, it can be used to build up the parallel redundant system to improve the reliability of power system operation. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. In this paper, the three-arm converter/inverter is compared with the general full-bridge and half-bridge topology from a practical point of view and chosen as the module UPS topology. The switching control approaches based on a pulse width modulation of the converter and inverter of the system are presented independently The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. Two prototype 3kVA modules are designed and implemented to confirm the effectiveness of the proposed approaches. Experimental results show that the three-arm UPS system has a high power factor, a low distortion of output voltage and input current, and good load sharing characteristic.

• KSBB Journal
• /
• v.23 no.1
• /
• pp.31-36
• /
• 2008

The use of L-carbohydrates and their corresponding nucleosides in medicinal application has greatly increased. For example L-ribose has been much in demand as the starting material for curing hepatitis B. High performance liquid chromatography (HPLC) method was studied for the analysis of ribose and arabinose fractions from ion exchange chromatography (IEC). Dowex Monosphere 99 Ca/320 resin was packed in IEC to separate ribose and arabinose under various operating conditions. $NH_{2}$ and sugar HPLC columns were then used to analyze the fractions from the IEC column. Pulse input method (PIM) was also used to measure adsorption isotherms of ribose and arabinose in the Dowex column and HPLC columns. Experimental results and simulations by ASPEN chromatography were compared with fair agreement.

• Proceedings of the KIEE Conference
• /
• 1994.07a
• /
• pp.43-45
• /
• 1994

This paper proposes the new method to calculate the static thrust and normal force of a hybrid type double-sided linear pulse motor by the coenergy which considered the magnetic nonlinealities. In the process of the computation, the nonlinear characteristics of the magnetic material were interpolated by the cubic spline method. And, to investigate the characteristics of the hybrid type DLPM, the static thrust and the normal force is shown as a function of displacement, input current and air airgap length. Also the simulation values are compared with the experimental ones obtained from a hybrid type DLPM.

• Journal of the Korean Society for Railway
• /
• v.10 no.1 s.38
• /
• pp.51-56
• /
• 2007

In this paper, control schemes are developed for a propulsion system(Converter/Inverter) in electrical train. A robust controller for PWM converter is proposed. The converter controller consists of a PI controller for DC output voltage and a current controller using error-space approach for maintaining the sinusoidal current waveform and unity power factor. This proposed method is based on characteristic ratio assignment(CRA) method which has the advantage to design the optimal gain to meet the referenced response and overshoot within the limit range. Inverter system is controlled by vector control and slip frequency control. At low speed region, vector control scheme is applied to control instantaneous torque and slip frequency control is performed under overmodulation region and one pulse mode. Because output voltage of converter contains harmonics ripple at twice input ac line frequency, control scheme is developed to reduce the pulsating torque current. The performance of propulsion system will be verified by simulation and prototype experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1997.11a
• /
• pp.381-384
• /
• 1997

This paper describes the method of diagnosing the degradation by void defects of insulator inside in operation. Needle-shape void specimens, made from LDPE, were used to generate an electrical tree under ac voltage. The method uses a neural network system with input signal of AE patterns. AE pattern consists of the pulse count and average amplitude according to the phase angle. After the learning process was over, unknown emission patterns were put into the network. It was shown that the network discriminates the void deflects well. The effectiveness of the neural network system for partial discharge recognition was shown.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.1211-1213
• /
• 2003

A pulse width modulation(PWM) method for single-phase Sepic-type rectifier is introduced in this paper. The characteristics of the proposed PWM system are high performance high power factor with low input current harmonic distortion. The proposed control method is based on the average-current-mode using the dedicated integrated circuit UC3854 this technique it is possible to implement a very simple control circuit for unitary power-factor in CCM operation and also to provide over-current protection.

• Proceedings of the KIPE Conference
• /
• 2008.10a
• /
• pp.16-18
• /
• 2008

A novel general direct duty ratio pulse width modulation strategy is proposed to modulate matrix converters. By using average concept over one switching period, the modulation algorithm and the required equations are derived to synthesize the desired output voltage and to achieve the controlled input power factor. The proposed method use continuous carrier and the predetermined duty ratio signal for directly generating gating signals an thus is named "direct duty ratio PWM(DDPWM)". The feasibility and validity of the proposed strategy are verified by experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.17 no.2
• /
• pp.73-80
• /
• 2003

This Paper Proposes instantaneous following control method to control pulse modulation switching converter by using principle that reset time of integrator is inverse proportion in size of integrator input voltage. proposed control method acts of fixed frequency and control switch calculates time of become turn on and turn off using analog integrator. Duty ratio that express switching time of converter is depended on mean value of switching variable and following time consists in one cycle. Follow to do order exactly stationary state as well as transition state, and controller corrects mean value of control variable and control reference value and control as control error gets into zero. Proposed control method could experimented and know that experiment result and theory are agreeing well through this using the buck converter.

• The Journal of the Acoustical Society of Korea
• /
• v.19 no.2E
• /
• pp.8-13
• /
• 2000

In this paper, we present an adaptive formant tracking algorithm for speech using closed phase WRLS-VFF-VT method. The pitch synchronous closed phase methods is known to give more accurate estimates of the vocal tract parameters than the pitch asynchronous method. However the use of a pitch-synchronous closed phase analysis method has been limited due to difficulties associated with the task of accurately isolating the closed phase region in successive periods of speech. Therefore we have implemented the pitch synchronous closed phase WRLS-VFF-VT algorithm for speech analysis, especially for formant tracking. The proposed algorithm with the variable threshold(VT) can provide a superior performance in the boundary of phone and voiced/unvoiced sound. The proposed method is experimentally compared with the other method such as two channel CPC method by using synthetic waveform and real speech data. From the experimental results, we found that the block data processing techniques, such as the two-channel CPC, gave reasonable estimates of the formant/antiformant. However, the data windows used by these methods included the effects of the periodic excitation pulses, which affected the accuracy of the estimated formants. On the other hand the proposed WRLS-VFF-VT method, which eliminated the influence of the pulse excitation by using an input estimation as part of the algorithm, gave very accurate formant/bandwidth estimates and good spectral matching.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.38 no.2
• /
• pp.191-198
• /
• 2001

As a method to compensate the deterioration of the picture quality which was caused by beam profile characteristic in the CRT and the projection screen of HD projection TV, a linear scan velocity modulation(SVM) method has been employed, whose modulation velocity is linearly proportional to the variation in the video signal amplitude. However, the effect of picture quality improvement is not uniform with video signal amplitude in the linear SVM. In this paper, for the optimum SVM effect, we analyze the beam profile characteristic on the HD projection screen and we analyze the SVM effect as function of the differentiated pulse width, the differentiated pulse amplitude and the input signal amplitude. Finally we confirm that the nonlinear SVM method is necessary to get uniform image compensation in the HD projection TV, and we implement the nonlinear SVM circuit. The performance of the realized SVM circuit with nonlinear amplitude transfer characteristic is confirmed as uniform improvements in picture quality.