• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1020-1022
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• 2001

because the output of solar cell is direct, it is necessary to install D/A converter system for A.C load, and in case of driving utility line system, it is possible to drive system relation when the system supplies sinusodal current ant voltage having unit power factor. As the characteristics of the soar cell output the is influenced by dailysunight charge, for more electric power it is essential to control the direction toward the san so that the driving point of solar cell can always operate near maximum output point. PWM modulation device among electric power converters must have stable modulation at anytime when it includes noise-factors such as noise-wave and noises on electric voltage wave, a synchronous signal system. In dealing with synchronous signal for control and control signal by microprocessor, it is necessary to compensate it because there is time difference between sample paint and carrier wave. On this papers, single phase PWM current type invertor controled the solar cell having typical voltage dropping character has optimun short current in short, reduces D.C reactance, composes controller for modulation and keeps lower harmonic and high power factor keeping maximum output of solar cell according daily sunlight charge variation.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1429-1437
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• 2015

A new parallel hybrid soft switching converter with low circulating current losses during the freewheeling state and a low output current ripple is presented in this paper. Two circuit modules are connected in parallel using the interleaved pulse-width modulation scheme to provide more power to the output load and to reduce the output current ripple. Each circuit module includes a three-level converter and a half-bridge converter sharing the same lagging-leg switches. A resonant capacitor is adopted on the primary side of the three-level converter to reduce the circulating current to zero in the freewheeling state. Thus, the high circulating current loss in conventional three-level converters is alleviated. A half-bridge converter is adopted to extend the ZVS range. Therefore, the lagging-leg switches can be turned on under zero voltage switching from light load to full load conditions. The secondary windings of the two converters are connected in series so that the rectified voltage is positive instead of zero during the freewheeling interval. Hence, the output inductance of the three-level converter can be reduced. The circuit configuration, operation principles and circuit characteristics are presented in detail. Experiments based on a 1920W prototype are provided to verify the effectiveness of the proposed converter.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1851-1860
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• 2016

The traction motors in electric multiple unit (EMU) trains are powered by AC-DC-AC converters, and the DC link voltage is generated by single phase PWM converters, with a fluctuation component under twice the frequency of the input catenary AC grid, which causes fluctuations in the motor torque and current. Traditionally, heavy and low-efficiency hardware LC resonant filters parallel in the DC side are adopted to reduce the ripple effect. In this paper, an analytical model of the ripple phenomenon is derived and analyzed in the frequency domain, and a ripple control scheme compensating the slip frequency of rotor vector control systems without a hardware filter is applied to reduce the torque and current ripple amplitude. Then a relatively simple discretization method is chosen to discretize the algorithm with a high discrete accuracy. Simulation and experimental results validate the proposed ripple control strategy.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1363-1371
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• 2017

In this paper, an improved Direct Power Control (DPC) algorithm is presented for grid connected three phase PWM rectifiers. The new DPC approach is based on two main tasks. First the optimization of the look-up table, which is well-known in conventional DPC, is outlined for selecting the optimum converter output voltage vectors. Secondly a very simple and effective method is used to directly calculate their duty cycles from the power errors. Therefore, the measured active and reactive powers are made to track their references using hysteresis controllers. Then two vectors are selected and applied during one control cycle to minimize both the active and reactive power ripples. The main advantages of this method are that there is no need of linear current controllers, coordinates transformations or modulators. In addition, the control strategy is able to operate at constant switching frequencies to ease the design of the power converter and the AC harmonic filter. The control exhibits a good steady state performance and improves the dynamic response without any overshoot in the line current. Theoretical principles of the proposed method are discussed. Both simulation and experimental results are presented to verify the performance and effectiveness of this control scheme.

• Journal of Power Electronics
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• v.14 no.3
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• pp.478-487
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• 2014

This study presents a new interleaved three-level zero-voltage switching (ZVS) converter for high-voltage and high-current applications. Two circuit cells are operated with interleaved pulse-width modulation in the proposed converter to reduce the current ripple at the input and output sides, as well as to decrease the current rating of output inductors for high-load-current applications. Each circuit cell includes one half-bridge converter and one three-level converter at the primary side. At the secondary side, the transformer windings of two converters are connected in series to reduce the size of the output inductor or switching current in the output capacitor. Based on the three-level circuit topology, the voltage stress of power switches is clamped at $V_{in}/2$. Thus, MOSFETs with 500 V voltage rating can be used at 800 V input voltage converters. The output capacitance of the power switch and the leakage inductance (or external inductance) are resonant at the transition interval. Therefore, power switches can be turned on under ZVS. Finally, experiments verify the effectiveness of the proposed converter.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1429-1439
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• 2019

Buck-Boost LLC (BBLLC) converters based on a PWM + phase control strategy are good candidates for high efficiency, high power density and wide input range applications. Nevertheless, they suffer from large computational complexity when it comes to calculating the optimal phase for ZVS of all the switches. In this paper, a method is proposed for a microcontroller unit (MCU) to calculate the optimal phase quickly and accurately. Firstly, a 2-D lookup table of the phase is established with an index of the input voltage and output current. Then, a bilinear interpolation method is applied to improve the accuracy. Meanwhile, simplification of the phase equation is presented to reduce the computational complexity. When compared with conventional curve-fitting and LUT methods, the proposed method makes the best tradeoff among the accuracy of the optimal phase, the computation time and the memory consumption of the MCU. Finally, A 350V-420V input, 24V/30A output experimental prototype is built to verify the proposed method. The efficiency can be improved by 1% when compared with the LUT method, and the computation time can be reduced by 13.5% when compared with the curve-fitting method.

• Journal of Power Electronics
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• v.19 no.4
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• pp.1034-1044
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• 2019

In medium-voltage and high-voltage high-power converters, the switching devices need to operate at a low switching frequency to reduce power loss and increase the power capacity. This increases the delay of the signal sampling and PWM. It also makes the cross-couplings of the d-q current components more severe. In addition, the LCL filter has three cross-coupling loops and is prone to resonance. In order to solve these problems, this paper establishes a complex vector model of an LCL type grid-connected converter. Based on this model, two multiple decoupling current control strategies with passive damping / notch damping are proposed for the LCL type grid-connected converter. The proposed strategies can effectively eliminate the cross-couplings of the converter, achieve independent control of the d-q current components, expand the stable region and suppress the resonance of the LCL filter. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategies.

• Journal of the Korean Society of Industry Convergence
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• v.26 no.6_2
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• pp.1097-1108
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• 2023

Recently, demand for technology for energy economy and stable supply is increasing due to the increase in power demand of loads. The amount of DC power generation using new and renewable energy is noticeably increasing, and the use of DC power supplies is also increasing due to the increase in electric vehicles and digital loads. During parallel operation to increase the capacity of the power converter, the module bus method or the method using Can communication and serial communication has significant difficulties in smooth operation due to communication time delay for information sharing. Synchronization of information sharing of each power converter is essential for smooth parallel operation, and minimization of communication time delay is urgently needed as a way to overcome this problem. In this paper, a new communication method using pulse width information is proposed as a communication method specialized for parallel operation of power converters to compensate for the disadvantage of communication transmission delay in the existing system. The proposed communication method has the advantage of being easily implemented using the PWM and Capture function of the microcomputer. In addition, the DC/DC converter for DC distribution was verified through simulation and experiment, and it has the advantage of easy capacity expansion when applied to parallel operation of various types of power converters as well as DC/DC converters.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.6
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• pp.57-65
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• 2007

This paper presents the design of single phase PFC(Power Factor Correction) using a DSP(TMS320F2812). In order to realize the proposed boost PFC converter in average current mode control, the DSP requires the A/D sampling values for a line input voltage, a inductor current, and the output voltage of the converter. Because of a FET switching noise, these sampling values contain a high frequency noise and switching ripple. The solution of A/D sampling keeps away from the switching point. Because the PWM duty is changed from 5% to 95%, we can#t decide a fixed sampling time. In this paper, the three A/D converters of the DSP are started using the prediction algorithm for the FET ON/OFF time at every sampling cycle(40 KHz). Implemented A/D sampling algorithm with only one timer of the DSP is very simple and gives the autostart of these A/D converters. From the experimental result, it was shown that the power factor was about 0.99 at wide input voltage, and the output ripple voltage was smaller than 5 Vpp at 80 Vdc output. Finally the parameters and gains of PI controllers are controlled by serial communication with Windows Xp based PC. Also it was shown that the implemented PFC converter can achieve the feasibility and the usefulness.