• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1632-1642
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• 2014

This paper presents an interleaved resonant converter to reduce the voltage stress of power MOSFETs and achieve high circuit efficiency. Two half-bridge converters are connected in series at high voltage side to limit MOSFETs at $V_{in}/2$ voltage stress. Flying capacitor is used between two series half-bridge converters to balance two input capacitor voltages in each switching cycle. Variable switching frequency scheme is used to control the output voltage. The resonant circuit is operated at the inductive load. Thus, the input current of the resonant circuit is lagging to the fundamental input voltage. Power MOSFETs can be turn on under zero voltage switching. Two resonant circuits are connected in parallel to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is adopted to decrease the output ripple current. Finally, experiments are presented to demonstrate the performance of the proposed converter.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1888-1889
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• 2007

The power source of inverter welder stable power of low voltage and high current. Because if shouldn't be, it is caused to spark between the parent metal and the peak. So that, we designed to be base on high frequency transformer and reactor of DC part. Then, we optimized control of PWM, current rising slant, voltage, current, pulse current and 인버터 out-put voltage. Also we designed PCB for EMI and noises.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1582-1590
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• 2019

A new method for reducing the common-mode current generated by the voltage variations in a two-inverter air conditioner system by applying a synchronized pulse-width modulation (PWM) strategy is proposed. The PWM signals of the master-mode inverter are generated based on the reference voltage, while those of the slave-mode inverter are output in the opposite direction when the master-mode inverter changes its switching state. However, the slave-mode control results in a mismatch between the reference voltage and the actual output voltage that is modified by synchronized control operation. The proposed method is capable of reducing and controlling this voltage error by performing signal selection in the vector space of the slave-mode inverter, which mitigates the distortion of the phase current. The efficacy of this method in reducing conducted emissions has been validated both theoretically and experimentally.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.346-351
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• 1998

In design of a digital current controller for a 3-phase (3 ) voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulse-width modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3 VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. It represents no steady-state error in input current control and has the optimized transient responses. The validity of the proposed algorithm is proved by the computer simulation and experimental results.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1207-1216
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• 2015

In order to suppress the low frequency oscillation of the neutral-point voltage for three-level inverters, this paper proposes a new discontinuous pulse width modulation (DPWM) control method. The conventional sinusoidal pulse width modulation (SPWM) control has no effect on balancing the neutral-point voltage. Based on the basic control principle of DPWM, the relationship between the reference space voltage vector and the neutral-point current is analyzed. The proposed method suppresses the low frequency oscillation of the neutral-point voltage by keeping the switches of a certain phase no switching in one carrier cycle. So the operating time of the positive and negative small vectors is equal. Comparing with the conventional SPWM control method, the proposed DPWM control method suppresses the low frequency oscillation of the neutral-point voltage, decreases the output waveform harmonics, and increases both the output waveform quality and the system efficiency. An experiment has been realized by a neutral-point clamped (NPC) three-level inverter prototype based on STM32F407-CPLD. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the proposed DPWM method.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.683-686
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• 2001

This paper presents a novel prototype of the utility­interactive voltage source type sinewave pulse modulated power inverter using a high-frequency flyback transformer link. The proposed power conditioner circuit for the solar photovoltaic generation and small scale fuel cell has an isolation function due to the safety of the power processing system, which is more cost effective and acceptable for the small-scale distributed renewal energy conditioning and processing systems. The discontinuous current mode(DCM) of this power processing conversion circuit is applied to implement a simple circuit topology and pulse modulated control scheme. Its operation principle is described on the basis of simulation evaluations and theoretical considerations. The simulation results obtained herein prove that the proposed inverter outputs with sinusoidal waveforms and unity power factor currents are synchronized to the main voltage in utility power source grid. In this paper, the soft switching topology of high­frequency linked sinewave pulse modulation inverter is proposed and discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.6
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• pp.556-564
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• 2013

This paper proposes an initial rotor position detecting algorithm of a PM synchronous motor using an incremental encoder. The proposed algorithm estimates the phase offset between the rotor magnetic flux and the Z-pulse of the incremental encoder by applying six aligning mode current control. The absolute rotor position for driving a PM synchronous motor is calculated by using the phase offset of the Z pulse and A, B pulse signals of the encoder. The PMSM drives based on the estimated rotor position is applied to the elevator door system. The door length is measured on line at first setup of the elevator. The speed control for open, close, and reopen of the elevator door is also presented and the proposed algorithm for the elevator door system is verified by experiment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.6
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• pp.885-890
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• 2015

LLC resonant converter has been widely used because of its high efficiency and high energy density. In this paper, we designed a LLC resonant converter as the main power supply of the Nd:YAG pulse laser. First harmonic approximation (FHA) is used to model the LLC resonant converter. FHA equivalent circuit model and the transfer function of the LLC resonant converter is proposed. Soft start technology is also used to suppress the surge current. The laser output simulation test result is identical with the practical test, the laser energy of every pulse can reach up to 2.5J, and the pulse per second (PPS) can be adjusted from 6 to 18. The power system is verified stable and reliable by both of the simulation and experiment results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.6
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• pp.31-38
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• 2013

A pulse driven atmospheric plasma jet controlled by external ballast capacitor is developed. Unlike the most commonly use DBD sources, the proposed device utilizes bare metal electrode. The discharge energy per pulse can precisely be determined by changing voltage and capacitance of the ballast capacitor. It is shown that the device can provide wide range of plasma, from stable glow mode to near arc state. Current-voltage waveforms, optical emission spectra and discharge images are investigated as a function of an injection energy. The OES shows that He and oxygen lines are increased as a function of the external ballast capacitor. Ozone and rotational temperature have similar tendency with a power consumption. The feeding gas is He and the applied DC voltage is from 400V to 800V when the gap distance is $500{\mu}m$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.367-370
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• 2006

This paper deals with the modeling and simulation of the internal flowfield in a valveless airbreathing pulse detonation engine (PDE) currently under experimental development at the U.S. Naval Postgraduate School. The system involves no valves in the airflow path, and the isolation between the inlet and combustor is achieved through the gasdynamics in an isolator. The analysis accommodates the full conservation equations in axisymmetric coordinates, and takes into account variable properties for ethylene/oxygen/air system. Chemical reaction schemes with a single progress variable are implemented to minimize the computational burden. Detailed flow evolution during a full cycle is explored and propulsive performance is calculated. Effect of initiator mass injection rate is examined and results indicate that the mass injection rate should be carefully selected to avoid the formation of recirculation zones in the initial cold flowfield. Flow evolution results demonstrate a successful detonation transmission from the initiator to the combustor. However, strong pressure disturbance may propagate upstream to the inlet nozzle, suggesting the current configuration could be further refined to provide more efficient isolation between the inlet and combustor.