• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.6
• /
• pp.565-572
• /
• 2013

The sensorless speed control using the improved full-order flux observer for PMSM is proposed in this paper. A conventional full-order flux observer has a drawback that the estimated flux of this observer contains the ripple component at the low speed range due to the increased gains of the convectional full-order flux observer. The improved full-order flux observer with the modified gains guarantee the improved estimation performance without ripple component at the from zero to high speed range. To identify the performance of proposed observer, the simulation and experiment are conducted and this performance is compared with the conventional full-order observer.

• Proceedings of the KIEE Conference
• /
• 1996.07a
• /
• pp.553-555
• /
• 1996

This paper concerns with a method to improve the current and power waveforms of the variable speed $3{\Phi}$ AC motor system driven by the single-pulse PWM, and the current waveforms and $3{\Phi}$ power waveforms are analyzed by FFT under various running conditions. By the performance analysis through the experiments, the following results have been obtained. AC source of pseudo sine waveform can be obtained from the modulated alternating square voltage by means of the well designed LC filter. It is confirmed that current waveforms and $3{\Phi}$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order. Especially, current waveforms and $3{\Phi}$ power waveforms tan be much improved at low frequency domain. $3{\Phi}$ power waveforms have a smatter ripple and bigger power by utilizing the high order low pass LC filter than that of lower order. Also, the running condition of $3{\Phi}$ AC motor is good at low frequency domain.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.1025-1035
• /
• 2016

Luenberger observer (LO)-based sensorless multi-loop control of a converter requires an iterative trial-and-error design process, considering that many parameters should be determined, and loop gains are indirectly related to the closed-loop characteristics. Robust H∞ control adopts a compact sensorless controller. The algebraic Riccati equation (ARE)-based and linear matrix inequality (LMI)-based H∞ approaches need an exhaustive procedure, particularly for a low-order controller. Therefore, in this study, a novel robust H∞ synthesis approach is proposed to design a low-order sensorless controller for boost converters, which need not solve any ARE or LMI, and to parameterize the controller by an adjustable parameter behaving like a "knob" on the closed-loop characteristics. Simulation results show the straightforward closed-loop characteristics evaluation and better dynamic performance by the proposed H∞ approach, compared with the LO-based sensorless multi-loop control. Practical experiments on a digital processor confirmed the simulation results.

• Journal of Institute of Control, Robotics and Systems
• /
• v.6 no.5
• /
• pp.339-344
• /
• 2000

This paper is concerned with the simplification of complex linear time-invariant systems. A simple technique is suggested using the well-known least squares method in the frequency domain. Given a high-order transfer function in the s- or z-domain, the squared-gain function corresponding to a low-order model is computed by the least squares method. Then, the low-order transfer function is obtained through the factorization. Three examples are given to illustrate the efficiency of the proposed method.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.35 no.1
• /
• pp.8-16
• /
• 1986

For digital process control, a low order discrete time modeling method is suggested and a direct digital control algorithm has been developed. The modeling method maintains process order of 3, while the sampling rate is doubled for fast response. With easy calculation it is possible to compute the model parameters and the controller gains. Controller tuning is possible on the spot. Simulation results show that this method has better performance than the deadbeat control agorithm.

• Journal of the Korean Society of Industry Convergence
• /
• v.15 no.3
• /
• pp.71-77
• /
• 2012

This study gives the optimal reaction conditions, reaction mechanisms, reaction rates leaded from the oxidation of phenol by electron beam accelerator and ozone used for recent water treatment. It gives the new possibility of water treatment process to effectively manage industrial sewage containing toxic organic compounds and biological refractory materials. The high decomposition of phenol was observed at the low dose rate, but at this low dose rate, the reaction time was lengthened. So we must find out the optimal dose rate to promote high oxidation of reactants. The reason why the TOC value of aqueous solution wasn't decreased at the low dose was that there were a lot of low molecular organic acids as an intermediates such as formic acid or glyoxalic acid. In order to use both electron beam accelerator and biological treatment for high concentration refractory organic compounds, biological treatment is needed when low molecular organic compounds exist abundantly in sewage. In this experiment, the condition of making a lot of organic acids is from 5 kGy into 20 kGy dose. Decomposition rate of phenol by electron beam accelerator was first order reaction up to 300ppm phenol solution on the basic of TOC value and also showed first order reaction by using both air and ozone as an oxidants.

• Journal of Advanced Marine Engineering and Technology
• /
• v.19 no.3
• /
• pp.107-118
• /
• 1995

The characteristics of the current waveforms and 3$\Phi$ power waveforms of the variable speed 3$\Phi$ AC motor system driven by the single-pulse PWM investigated in this paper. The system is composed of a digital bridge inverter and low pass LC filter. It is confirmed that current waveforms and 3$\Phi$ power waveforms can be improved by utilizing the high order low pass LC filter than that of lower order through computer simulation. Also, we propose the low pass LC filter revised from the conventional LC filter.

• Proceedings of the IEEK Conference
• /
• 2000.11b
• /
• pp.257-260
• /
• 2000

In this paper, a Gm-C filter for low voltage and low power applications using a fully-differential transconductor is presented. The designed transconductor using the series composite transistors and the low voltage composite transistors has wide input range at low supply voltage. A negative resistor load (NRL) technology for high DC gain of the transconductor is employed with a common mode feedback (CMFB). As a design example, the third-order Elliptic lowpass filter is designed. The designed filter is simulated and examined by HSPICE using 0.25${\mu}{\textrm}{m}$ CMOS n-well parameters. The simulation results show 105MHz cutoff frequency and 2.4㎽ power dissipation with a 2.5V supply voltage.

• The Korean Journal of Community Living Science
• /
• v.23 no.4
• /
• pp.479-490
• /
• 2012

This research focuses on the self-concept in children of low-income families. A questionnaire was given to elementary school-aged children(grades 3-6). 454 children from low-income families were surveyed. The major findings were as follows: first, the variables that affected the self-concept among the low-income families children were relatively different. For boys, the major influential individual variables were in the following order: grade, stress, and the father's affective attitude. For girls, the major influential individual variables were in the following order: stress, support from friend, father's affective attitude, and grade. Second, through this comparison, this study examined the relative influence of variables that affected children's self-concept. This study proposes interventions to improve their self-concept mechanisms.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.5
• /
• pp.450-456
• /
• 2014

In HVDC converters that employ a line-commutated control, reactive power is absorbed by the rectifier and inverter terminals during AC/DC conversion. An AC filter usually consists of filters and large shunt capacitors to supply reactive power to the HVDC station. When STATCOM is used to supply reactive power to the HVDC system with AC filter, the low-order harmonics generated from STATCOM can result in a resonance between the shunt capacitor and AC network. Therefore, a control strategy based on selective harmonic elimination is adopted to minimize the low-order harmonics from STATCOM. The cancellation of harmonic instabilities is verified through simulations in PSCAD/EMTDC.