• Journal of Power Electronics
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• v.15 no.3
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• pp.587-601
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• 2015

A high step-up dc-dc converter is proposed for photovoltaic power systems in this paper. The proposed converter consists of an input current doubler, a symmetrical switched-capacitor doubler and an active-clamp circuit. The input current doubler minimizes the input current ripple. The symmetrical switched-capacitor doubler is composed of two symmetrical quasi-resonant switched-capacitor circuits, which share the leakage inductance of the transformer as a resonant inductor. The rectifier diodes (switched-capacitor circuit) are turned off at the zero current switching (ZCS) condition, so that the reverse-recovery problem of the diodes is removed. In addition, the symmetrical structure results in an output voltage ripple reduction because the voltage ripples of the charge/pump capacitors cancel each other out. Meanwhile, the voltage stress of the rectifier diodes is clamped at half of the output voltage. In addition, the active-clamp circuit clamps the voltage surges of the switches and recycles the energy of the transformer leakage inductance. Furthermore, pulse-width modulation plus phase angle shift (PPAS) is employed to control the output voltage. The operation principle of the converter is analyzed and experimental results obtained from a 400W prototype are presented to validate the performance of the proposed converter.

• Journal of IKEEE
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• v.22 no.3
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• pp.630-637
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• 2018

To supply a high voltage to an inverter, a motor control unit (MCU) generally employs a front-end boost converter. Because it generates a high output voltage, the converter needs an output capacitor, which has a high working voltage resulted in cost increasing. To solve this problem, we present a bidirectional dc-to-dc converter, which can decrease a working voltage of the output capacitor. Basic characteristic of the proposed converter is similar to a conventional boost converter. A difference comes from the structure of the output terminal connecting an output capacitor and an input battery in series. Owing to this circuit configuration, the working voltage of the output capacitor becomes lower than that of a conventional boost converter. After theoretical analysis, we carry out simulations and experiments to verify the validity and performance comparing with a conventional boost converter.

• Journal of Electrical Engineering and Technology
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• v.7 no.3
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• pp.320-329
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• 2012

The Load Tap Changing (LTC) transformer and Shunt Capacitor (SC) bank are major devices for voltage and reactive power control in a distribution substation. Thus, the coordination operation of a LTC transformer and a SC bank is required to achieve better voltage and reactive power compensation at a distribution substation in the same time. This paper proposes coordinate control method of LTC transformer and SC bank to achieve better voltage and reactive power compensation and operation times of these two devices in the same time. The mathematical formulations of the proposed coordinate control method are introduced. Sample case studies are shown to verify the effectiveness of the proposed coordinate control method.

• Journal of Biosystems Engineering
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• v.43 no.2
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• pp.94-102
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• 2018

Purpose: In this study, a maintenance free super-capacitor battery charging system based on the photovoltaic module, to be used in agricultural electric carriers, was developed and its charging characteristics were studied in detail. Methods: At first, the electric carrier system configuration is introduced and the electric control components are presented. The super-capacitor batteries and photovoltaic module used in the experiment are specified. Next, the developed charging system consisting of a constant current / constant voltage Buck converter as the charging device and a super-capacitor cell as a balancing device are initiated. The proposed circuit design, a developed PCB layout of each device and a proportional control to check the current and voltage during the charging process are outlined. An experiment was carried out using a developed prototype to clarify the effectiveness of the proposed system. A power analyzer was used to measure the current and voltage during charging to evaluate the efficiency of the energy storage device. Finally, the conclusions of this research are presented. Results: The experimental results show that the proposed system successfully controls the charging current and balances the battery voltage. The maximum voltage of the super-capacitor battery obtained by using the proposed battery charger is 16.2 V, and the maximum charging current is 20 A. It was found that the charging time was less than an hour through the duty ratio of 95% or more. Conclusions: The developed battery charging system was successfully implemented on the agricultural electric carriers.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.55-60
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• 2017

Capacitor Charging Power Supply(CCPS) is one of the most important components of a pulsed power system. The CCPS is widely used in source of lasers, accelerators and plasma generators. This paper presents design of a dead time control circuit and operation characteristics for stable high repetition rate of high voltage CCPS. The CCPS consists of battery, high voltage transformer and controller with a dead time control circuit. A dead time control circuit was simulated by PSpice. The performance test of the CCPS was carried out with a 7[nF] load capacitor at output voltage of 50[kV] and a pulse repetition frequency of 100[Hz]. As a result, we can verify that charging and discharging waveform is stable at 100[Hz]. The experiment results indicate that 3[ms] dead time made it possible for stable high repetition rate of 100[Hz]. This paper paves the way for designing an advanced CCPS which is more applicable outside experiments.

• Journal of Power Electronics
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• v.17 no.5
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• pp.1173-1185
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• 2017

In this paper, a new single phase multilevel inverter topology with a single DC source is presented. The proposed topology is developed based on the concepts of the L-Z source inverter and the switched capacitor multilevel inverter. The input voltage to the proposed inverter is boosted by two steps: the first step by an impedance network and the second step by switched capacitor units. Compared to other existing topologies, the presented topology can produce a higher boosted multilevel output voltage while using a smaller number of components. In addition, it provides more flexibility to control boosting factor, size, cost and complexity of the inverter. The proposed inverter possesses all the advantages of the L-Z source inverter and the switched capacitor multilevel inverter like controlling the start-up inrush current and capacitor voltage balancing using a simple switching strategy. The operating principle and general expression for the different parameters of the proposed topology are presented in detail. A phase disposition pulse width modulation strategy has been developed to switch the inverter. The effectiveness of the topology is verified by extensive simulation and experimental studies on a 7-level inverter structure.

• Journal of Power Electronics
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• v.19 no.4
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• pp.869-880
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• 2019

Due to the inherent feedforward of load current, capacitor current (CC) control shows a fast transient response that makes it suitable for the power supplies used in various portable electronic devices. However, considering the effect of the outer voltage loop, the stable range of the duty-cycle is significantly diminished in CC controlled buck converters. To investigate the stability effect of the outer voltage loop on buck converters, a CC controlled buck converter with a proportion-integral (PI) compensator is taken as an example, and its second-order discrete-time model is established. Based on this model, the instability caused by the duty-cycle is discussed with consideration of the outer voltage loop. Then the dynamical effects of the feedback gain of the PI compensator and the equivalent series resistance (ESR) of the output capacitor on the CC controlled buck converter with a PI compensator are studied. Furthermore, the design-oriented closed-loop stability criterion is derived. Finally, PSIM simulations and experimental results are supplied to verify the theoretical analyses.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1103-1105
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• 2002

A conventional AC-DC boost converter has much variation of input current as more increased the load or output voltage by the hysterical control method that is comparing area of current pulse by using PWM method and integration to sinusoidal input current. To improve the problems. in this paper, we propose the single-phase voltage doubler AC-DC converter circuit using the capacitor for boost:confirm characteristics of normal and transition state by using simulation, be stabilized voltage of doubler capacitor for boost, and Identify to get the sinusoidal input current with unity power factor.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.914-919
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• 1998

A Capacitor Commutated Converter (CCC) has less difficulty of commutation failure in comparison to the conventional line commutated converter. This paper proposes the Ar1R control of the CCC in the inverter operation, which deserves as the Ar1R of the conventional converter. The CCC can be operated in high power factor area by using the proposing Ar1R control. The voltage stability at an AC bus connected the CCC inverter is investigated and estimated its ability of preventing the AC voltage collapse. To estimate the voltage stability, this paper developed the simplified converter mathematical model and led the VSF index. The results shows that the AC voltage stability is guaranteed and enables the interconnection to an weak AC system, when compensation factor of the compensation capacitor is higher than 200%.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.329-331
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• 1998

This paper presents a modified Learning Vector Quantization rule to control shunt capacitor banks and feeder voltage regulators in electric distribution systems with Kohonen Neural Network(KNN). The objective of the KNN is on-line decision of the optimal state of shunt capacitor banks and feeder voltage regulators which minimize $I^{2}R$ losses of the distribution system while maintaining all the bus voltages within the limits. The KNN is tested on a distribution system with 30 buses, 5 on-off switchable capacitor banks and a nine tap line voltage regulator.