• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.256-260
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• 2001

This paper presents boost and buck and buck-boost DC-DC converter circuit topologies of high-frequency soft switching transition PWM chopper type DC-DC high power converters with a single auxiliary passive resonant snubber. In the proposed boost power converter circuits operating under a principle of ZCS turn-on and ZVS turn-off commutation schemes, the capacitor and inductor in the auxiliary passive resonant circuit works as the loss less resonant snubber. In addition to this, the switching voltage and current peak stresses as well as EMI and RFI noises can be basically reduced by this single passive resonant snubber. Moreover, it is proved that converter circuit topologies with a passive resonant snubber are capable of solving some problems of the conventional hard switching PWM processing based on high-ferquency pulse modulation operation principle. The simulation results of this converter are discussed as compared with the experimental ones. The effectiveness of this power converter with a single passive resonant snubber is verified by the 5kW experimental breadboad set up.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.860-868
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• 2016

A bidirectional DC-DC converter (BDC) is an indispensable electrical unit for the electric vehicles (EVs). High efficiency, high power density, isolation, light weight and reliability are all essential requirements for BDC. In this paper, a 3 kW BDC for the battery charger of EVs is proposed. The proposed converter consists of a half-bridge structure on the primary side and an isolation transformer and a synchronous rectifier structure on the secondary side. With this topology, minimum number of switching devices are required for bidirectional power flow between the two dc buses of EVs. The easy implementation of the synchronous rectification gives advantages in terms of efficiency, cost and flexibility. The proposed BDC achieves high efficiency when operating in both modes (step-up and step-down). A 3 kW prototype is implemented to verify theoretical analysis and the performance of the proposed converter.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1004-1013
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• 2017

This paper presents an interleaving scheme for parallel-connected power systems to reduce the DC-link current ripple. A paralleled generator system generates current ripple by the Pulse Width Modulation (PWM) of each generator side converter. The current ripple in the DC-link degrades the efficiency of the whole generator system and decreases the lifetime of the DC-link capacitors. To mitigate these issues, the expression of the DC-link current is derived by a double-integral Fourier analysis while considering the modulation schemes. Optimized interleaving angles for the parallel generator system are obtained based on an analysis to minimize the dominant current harmonics component. Finally, the proposed interleaving scheme reduces the RMS value of the DC-link current ripple. Simulation and experimental results verify the effectiveness of the proposed interleaving scheme.

• Proceedings of the KIEE Conference
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• 2001.07e
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• pp.17-19
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• 2001

In this paper, we constitute H/W systems for the accurate control of DC servo motor. This H/W systems are designed by applying a simple genetic algorithm (SGA) to the robust $H_{\infty}$ control system and the intelligent Fuzzy control system of DC motor, respectively. To verify the effectiveness of the proposed systems, the characteristics of this systems are analysed and simulated.

• Journal of Power Electronics
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• v.12 no.1
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• pp.157-163
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• 2012

Internet Data Centers (IDCs), which are essential facilities in the modern IT industry, typically have scores of MW of concentrated electric loads. The provision of an Uninterruptible Power Supply (UPS) is necessary for the power feed system of IDCs owing to the need for stable power. Thus, conventional IDC AC power feed systems have three cascaded power conversion stages, (AC-DC), (DC-AC), and (AC-DC), resulting in a very low conversion efficiency. In comparison, DC power feed systems require only a single power conversion stage (AC-DC) to supply AC main power to DC server loads, resulting in comparatively high conversion efficiency and reliability [4-11]. This paper compares the efficiencies of a 220V AC power feed system with those of a 300V DC power feed system under equal load conditions, as established by the Mok-Dong IDC of Korea Telecom Co. Ltd. (KT). Experimental results show that the total operation efficiency of the 300V DC power feed system is approximately 15% higher than that of the 220V AC power feed system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.4
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• pp.763-769
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• 2009

A series voltage compensation(SVC) system is a power-electronics controller that can protect sensitive loads from disturbance in the supply system. Especially, voltage sags are considered the dominant disturbances affecting the power quality. This paper dealt with a system of off-line type voltage sag compensation by using a bi-directional DC/DC converter of environmentally friendly ultra-capacitor. This capacitor is attached to the DC link of SVC through the high-efficiency DC/DC converter in order to compensate the DC link voltage drop during short-term power interruption as voltage sags. Therefore, in this paper, a DC/DC converter to control high-efficiency energy of ultra-capacitor and voltage sag detection algorithm of off-line type SVC systems are newly introduced. According to the results of experimental of prototype system, it is verified that the proposed system has effectiveness of voltage sag compensation using an ultra-capacitor.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.1
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• pp.77-84
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• 2007

In this paper, Takagi-Sugeno (TS) fuzzy integral control is investigated to regulate the output voltage of an asymmetric half-bridge (AHB) DC/DC converter; First, we model the dynamic characteristics of the AHB DC/DC converter with state-space averaging method and small perturbation at an operating point. After introducing an additional integral state of the output regulation error, we obtain the $5^{th}$-order TS fuzzy model of the AHB DC/DC converter. Second, the concept of the parallel distributed compensation is applied to design the fuzzy integral controller, in which the state feedback gains are obtained by solving the linear matrix inequalities (LMIs). Finally, simulation results are presented to show the performance of the considered design method as the output voltage regulator and compared to the results for which the conventional loop gain method is used.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.10
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• pp.879-885
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• 2013

By performing interval analysis on the system transfer function, we propose an improved method of control loop design for a DC/DC converter. In conventional design methods, the effect of system parameter change due to the specified range of operating conditions and production tolerances in power components should be checked a posteriori, because this may result in a transfer function shift and performance degradation. In the proposed method, a possible parameter change is considered a priori in the design step in order that the desired crossover frequency and sufficient phase margin can be achieved even in the worst case condition. As an illustrative example, a buck dc/dc converter is designed by two different methods and performance comparisons are performed to verify the feasibility of the proposed scheme.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.2
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• pp.133-141
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• 2020

The use of high-gain-voltage step-up converters for distributed power generation systems is being popularized because of the need for new energy generation and power conversion technologies. In this study, a new constructed high-gain-boost DC-DC converter was proposed to coordinate low voltage output DC sources, such as PV or fuel cell systems, with high DC bus (380 V) lines. Compared with traditional boost DC-DC converters, the proposed converter can create higher gain and has wider input voltage range and lower voltage stress for power semiconductors and passive elements. Moreover, the proposed topology produces multilevel DC voltage output, which is the main advantage of the proposed topology. Steady-state analysis in continuous conduction mode of the proposed converter is discussed in detail. The practicability of the proposed DC-DC converter is presented by experimental results with a 300 W prototype converter.

• Journal of Electrical Engineering and Technology
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• v.11 no.4
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• pp.791-800
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• 2016

Optimal Power Flow (OPF) is an important operational and planning problem in minimizing the chosen objective functions of the power systems. The recent developments in power electronics have enabled introduction of dc links in the AC power systems with a view of making the operation more flexible, secure and economical. This paper formulates a new OPF to embrace dc link equations and presents a heuristic optimization technique, inspired by the behavior of fireflies, for solving the problem. The solution process involves AC/DC power flow and uses a self adaptive technique so as to avoid landing at the suboptimal solutions. It presents simulation results of IEEE test systems with a view of demonstrating its effectiveness.