• ETRI Journal
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• v.31 no.3
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• pp.298-303
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• 2009

A single-switch parallel resonant converter for induction heating is implemented. The circuit consists of an input LC-filter, a bridge rectifier, and a controlled power switch. The switch operates in soft commutation mode and serves as a high frequency generator. The output power is controlled via the switching frequency. A steady state analysis of the converter operation is presented. A closed-loop circuit model is also presented, and the experimental results are compared with the simulation results.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2208-2218
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• 2017

To resolve overload in a distribution system, a distribution system operator (DSO) often performs a load transfer using normally open tie points and switches in the distribution line. During this process, the distribution system is momentarily operated in closed-loop operation. A closed-loop current in the distribution system can cause a power failure due to excess breaking current in the circuit breakers and reclosers. Therefore, it is necessary to calculate the closed-loop current exactly. However, if there are a large number of distributed generation (DG) systems in the distribution system, such as energy storage systems (ESS), they might obstruct the closed-loop operation based on bidirectional power flow. For quick and precise operation of a closed-loop system, the ESS has to regulate the power generation while satisfying closed-loop operation in the worst cases. We propose a strategy for balanced power regulation of an ESS. Simulations were carried out using PSCAD/EMTDC, and the results were compared with calculation results.

• Journal of Power Electronics
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• v.12 no.5
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• pp.800-812
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• 2012

This paper analyses the mathematical model and control strategies of a Hybrid Active Power Filter with Injection Circuit (IHAPF). The control strategy based on the load harmonic current detection is selected. A novel control method for a IHAPF, which is based on the analyzed control mathematical model, is proposed. It consists of two closed-control loops. The upper closed-control loop consists of a single fuzzy logic controller and the IHAPF model, while the lower closed-control loop is composed of an Adaptive Network based Fuzzy Inference System (ANFIS) controller, a Neural Generalized Predictive (NGP) regulator and the IHAPF model. The purpose of the lower closed-control loop is to improve the performance of the upper closed-control loop. When compared to other control methods, the simulation and experimental results show that the proposed control method has the advantages of a shorter response time, good online control and very effective harmonics reduction.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2753-2756
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• 2003

A convenient, tunable loop-gain negative impedance circuit that increases input impedance of a front-end in a bioimpedance measurement has been proposed. Since the proposed circuit comprises wide-band operational amplifiers, selecting operational amplifiers is easy, while an operational amplifier of proper bandwidth should be chosen to use conventional circuit. Also, since loop-gain can be controlled by a feedback resistor connected serially with a feedback capacitor, loop-gain is tunable with a potentiometer. The input impedance of the proposed circuit is two times larger than that of the conventional circuit. Furthermore, closed loop phase response of the proposed circuit is better than that of the conventional circuit or without a negative capacitance circuit. The implemeted, proposed circuit showed stable operation and a zero input capacitance.

• IEIE Transactions on Smart Processing and Computing
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• v.5 no.1
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• pp.22-28
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• 2016

Multi-loop control of a boost converter needs a current-sensing circuit to detect the inductor current. Current sensorless multi-loop control reduces the cost, size and weight of the converter. The Luenberger observer (LO) is widely used to estimate the inductor current for current sensorless control of a switching converter. However, the design of the LO-based sensorless multi-loop control has not been well presented, so far. In this paper, a closed-loop characteristics evaluation method is proposed to design an LO-based current sensorless multi-loop control for boost converters. Simulations show evaluations of the closed-loop characteristics. Practical experiments on a digital processor confirm the simulations.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.229-230
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• 2015

This paper presents practical details about control-loop design and dynamic analysis for a voltage-mode controlled isolated double step-down DC-DC converter. Graphical loop gain method is used to design the feedback compensation and analyze the closed-loop performance of isolated double step-down DC-DC converter. The results of the control design and closed-loop analysis are validated by experiments on a prototype converter.

• Journal of Power Electronics
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• v.14 no.5
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• pp.1038-1046
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• 2014

Lithium-ion batteries are widely used in hybrid and pure electric vehicles. State-of-charge (SOC) estimation is a fundamental issue in vehicle power train control and battery management systems. This study proposes a novel model-based SOC estimation method that applies closed-loop state observer theory and a comprehensive battery model. The state-space model of lithium-ion battery is developed based on a three-order resistor-capacitor equivalent circuit model. The least square algorithm is used to identify model parameters. A multi-state closed-loop state observer is designed to predict the open-circuit voltage (OCV) of a battery based on the battery state-space model. Battery SOC can then be estimated based on the corresponding relationship between battery OCV and SOC. Finally, practical driving tests that use two types of typical driving cycle are performed to verify the proposed SOC estimation method. Test results prove that the proposed estimation method is reasonably accurate and exhibits accuracy in estimating SOC within 2% under different driving cycles.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1701-1705
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• 2004

This paper presents a design and analysis of electromechanical sigma-delta modulator for MEMS gyroscope, which enables us to control the proof mass and to obtain an exact digital output without additional A/D conversion. The system structure and the circuit realization of the sigma-delta modulation are simpler than those of the analog sensing and feedback circuit. Based on the electrical sigma-delta modulator theory, a compensator is designed to improve the closed loop resolution of the sensor. With the designed compensator, we could obtain enhanced closed-loop performances of the gyroscope such as larger bandwidth, lower noise, and digital output comparing with the results of analog open-loop system.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.718-719
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• 2011

Lately, the demand for electrical power has been significantly increased. As a result a power transmission system has been improved. On the other hand fault current increased more than past. Superconducting fault current limiter (SFCL) is one of the solutions to limit fault current. However, SFCL's research has not advanced in a power transmission system fully. Therefore, we studied effect of SFCL in a power transmission system. The power distribution system is open-loop circuit, but a power transmission system is closed-loop system. Consequently, Fault current in a power transmission system is larger than fault current in a power distribution system. we exerimented a simple closed-loop power transmission system circuit.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1843-1845
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• 1998

Gyroscope is a very important core sensor as a rotation sensor in inertial space, in inertial guidance and navigation system on aeronautics. Plane, vessel and so on for civilian and millitary applications. Research and development of fiber optic gyroscope began in 1976 and focused on improving the gyroscope's sensitivity to rotation. bias performance and reducing noise. We have developed a Interferometric Fiber Optic' Gyroscope using a integrated-optic-circuit (IOC), which is operating with closed-loop electronic circuit. This paper describes the scheme of optical part and electronic part and also test results of this fiber optic gyroscope using a integrated-optic-circuit (IOC). The performance have been achieved as long-term bias drift of $1.73^{\circ}/h$.