• Journal of IKEEE
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• v.12 no.1
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• pp.59-64
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• 2008

In this paper, a new efficient SMPS has been designed and implemented. It can replace the existing product that is widely used in industry. To investigate the performance of the conventional SMPS, the output voltage changes due to variations in the input voltage and the load conditions, and the ripple and noise voltages have been measured and analyzed. As a result, it has been confirmed that the noise in the conventional SMPS is severe due to the deficiency of patterns for current. This is because the conventional SMPS draw out all outputs using one transformer and the alarm logic exists in the output path. To solve this problem, the switching frequency is increased from 17KHz to 70KHz and the current patterns are fully guaranteed by separating the alarm circuit and PWM circuit as a sub-board from the main board. Measurement results shows that the output noise of the designed SMPS decreases below 32% of the conventional SMPS noise for various test conditions, and both the line and load regulations are improved.

• Nuclear Engineering and Technology
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• v.52 no.12
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• pp.2699-2708
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• 2020

Helical-coil steam generator (HCSG) technology is a major design candidate for small modular reactors due to its compactness and capability to produce superheated steam with high generation efficiency. In this paper, we investigate the feasibility of the passively autonomous power maneuvering by coupling the 3-D transient multi-physics of a soluble-boron-free (SBF) core with a time-dependent HCSG model. The predictor corrector quasi-static method was used to reduce the cost of the transient 3-D neutronic solution. In the numerical system simulations, the feedwater flow rate to the secondary of the HCSGs is adjusted to extract the demanded power from the primary loop. This varies the coolant temperature at the inlet of the SBF core, which governs the passively autonomous power maneuvering due to the strongly negative coolant reactivity feedback. Here, we simulate a 100-50-100 load-follow operation with a 5%/minute power ramping speed to investigate the feasibility of the passively autonomous load-follow in a 450 MW_th SBF PWR. In addition, the passively autonomous frequency control operation is investigated. The various system models are coupled, and they are solved by an in-house Fortran-95 code. The results of this work demonstrate constant steam temperature in the secondary side and limited variation of the primary coolant temperature. Meanwhile, the variations of the core axial shape index and the core power peaking are sufficiently small.

• Journal of IKEEE
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• v.24 no.4
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• pp.1104-1108
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• 2020

This paper propose a variable proportional resonant feedforward algorithm for reducing the speed ripple of a three-phase permanent magnet synchronous motor. In general, the torque ripples can be generated by electrical pulsation due to current measurement errors and dead time and mechanical pulsation because of rotor eccentricity and eccentric load. These torque pulsations can cause speed pulsations of the motor and degrade the operating performance of the motor drive system. Therefore, in this paper, the factors of the speed ripple is analyzed and an algorithm to reduce the speed ripple is proposed. The proposed algorithm applied a variable proportional resonant controller in order to reduce the specific operating frequency included in the speed pulsation, and utilized a feedforward compensation controller structure to perform the compensation operation. The proposed algorithm is verified through various experiments.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.3
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• pp.433-441
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• 2022

In general, in an emergency generator system for an electric facility including an induction motor load, an emergency power generation facility larger than the facility load capacity is built due to the initial starting current of the induction motor. In order to reduce this economic burden, various methods to reduce the inrush current of induction motors are applied to suppress the additional expansion of generators due to the reduction of power generation facilities and the increase in electrical facilities. Among these methods, when a system with a built-in soft start function of an induction motor using an inverter is built, it is the best way to reduce the inrush current of the induction motor to less than the rated current. However, in this case, the installation cost of the inverter to drive the induction motor increases. This paper proposes a soft start method of an induction motor by expanding the frequency and voltage control operation area of an emergency generator. In addition, proposed a speed calculation method based on power factor information, which is essential information for stable soft start of an induction motor, and a method for generating a speed command value of the governor for starting with maximum torque.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.1
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• pp.26-32
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• 2022

This paper proposes a power system that includes a 120k W fuel cell DC-DC converter (FDC) and 30 kW bidirectional DC-DC converter (BHDC) for a 150 kW fuel-cell vehicle. With a high DC link voltage of 800 V, the efficiency and power density of the power electronic components are improved. Through the modular design of FDC and BHDC, electric components are shared, resulting in reduced mass production costs. The switching frequency of 30 kHz of full SiC devices and optimal design of coupled inductor reduce the volume, achieving a power density of 8.3 kW/L. Furthermore, a synergetic operation strategy using variable limiter control of FDC and BHDC was proposed to efficiently operate the fuel cell vehicle considering the fuel cell stack efficiency according to the load. Finally, the performance of the prototype was verified by Highway Fuel Economy Driving Schedule testing, EMI test, and the linked operation between FDC and BHDC. The full load efficiencies of the FDC and BHDC prototypes are 98.47% and 98.74%, respectively.

• Journal of Korean Society of Transportation
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• v.34 no.3
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• pp.263-277
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• 2016

Traffic safety in freeway work zones is of keen interest since both crash frequency and severity are much higher than those in general freeway sections. The lane closure in work zones results in greater work load of drivers due to compulsory lane changes and speed reduction. Therefore, traffic merging control is an effective countermeasure for enhancing work zone safety. This study proposed an integrated framework based on driving and traffic simulations to evaluate traffic merging control methods in terms of traffic safety. In addition to the conventional merging method using the taper, joint merge and chicane-type merge were evaluated by the proposed methodology. Chicane-type merge outperformed other methods under level of service (LOS) A and B. On the other hand, it was identified that joint merge showed the best safety performance under LOS C traffic conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.1
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• pp.48-56
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• 2006

This paper studies particularly applicable method for sensorless PM BLDC motor drive system. The waveform of the motor internal voltages(or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonic component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition. Also because of low resolution of estimated signal obtained by the proposed sensorless algorithm, to improve the wide range of speed response characteristic more exactly, we propose the rotor position signal synthesizer using PLL circuit based on estimated signals. Some experimental results are provided to demonstrate the validity of the proposed control method.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.486-494
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• 2012

In this paper, we proposes the three-phase embedded Z-source inverter consisting of the three embedded Z-source converters and it's the output voltage control method. Each embedded Z-source converter can produce the bipolar output capacitor voltages according to duty ratio D such as single-phase PWM inverter. The output AC voltage of the proposed system is obtained as the difference in the output capacitor voltages of each converter, and the L-C output filter is not required. Because the output AC voltage can be stepped up and down, the boost DC converter in the conventional two-stage inverter is unnecessary. To confirm the validity of the proposed system, PSIM simulation and a DSP based experiment were performed under the condition of the input DC voltage 38V, load $100{\Omega}$, and switching frequency 30kHz. Each converter is connected by Y-connection for three-phase loads. In case that the output phase voltage is the same $38V_{peak}$ as the input DC voltage and is the 1.5 times($57V_{peak}$), the simulation and experimental results ; capacitor voltages, output phase voltages, output line voltages, inductor currents, and switch voltages were verified and discussed.

• Journal of IKEEE
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• v.15 no.4
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• pp.319-323
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• 2011

In this paper presents a new model of dual-mode synchronous buck converter with dynamic control for mobile applications was proposed. The proposed circuit can operate at 2.5MHz with supply voltage 2.5V to 5V for low ripple and minimum inductor and capacitor size, which is suitable for single-cell lithium-ion battery supply mobile applications. For high efficiency, the proposed circuit adopts synchronous type and dynamic control. The proposed circuit is designed by using the device parameter of TSMC 0.18um BCD process and the performance is evaluated by Cadence spectre. Experimental board level results show the maximum conversion efficiency is 96% at 100mA load current.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.691-700
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• 1994

A power line in not so good in characteristics for communication, because it is a media to transfer the commercial electrical power, and its load noise and high frequency noise are so much. Thus, a simple method to transfer a remote control signal on the power line is studied. The already-existing method is that two signals with upper part eliminated is transmitted every N step. But the method is investigated which the transmitter sends a period signal eliminated in arbitrary phase. Thus the transmission power loss due to elimination of signal can be reduced to the minimum. To implement it, a timer calculating the time from zero-crossing point to the phase is required. The micro-controller, 87C51, precisely calculates the phase using one of two built-in timers. As a result, a remote control signal tramsmitter and receiver using a partially eliminated signal, which is better than the conventional technique using half-eliminated signal in a efficiency of power transmission, is realized, and its characteristics are analyzed.