• Journal of the Korean Solar Energy Society
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• v.37 no.6
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• pp.1-12
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• 2017

The DC link of Grid-Connected 3-Phase 3-Level T-type Photovoltaic PCS (PV-PCS) consists of two series connected capacitors for using their neutral voltage. The mismatch between two capacitor characteristics and transient states happened in load change cause the imbalance of neutral voltage. As a result, PV-PCS performance is degraded and the system becomes unstable. In this paper, a mathematical model for analyzing the imbalance of neutral voltage is derived and a compensation method using offset voltage is proposed, where offset voltage adjusts the applying time of P-type and N-type small vectors. The validity of the proposed methods is verified by simulation and experiment.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1307-1312
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• 2007

This experiments are performed to investigate the effect of ventilation velocity on a high pressure water mist fire suppression in subway train. The experiment is conducted in half scale modeled train of a steel-welled enclosure (8.0m*2.4m*2.1m). The ventilation velocity is controlled by the ventilation duct through an inverter in the range of 0 to 2 m/s. The coverage-radius and an injection angle of an high pressure water mist system are measured. The mist nozzle with 7-injection holes is operated with pressure 80 bar. The heptane pool fires are used. The fire extinguishment times and the temperatures are measured for the ventilation velocities. In conclusion, because the momentum of injected water mist is more dominant than that of ventilation air, the characteristics of water mist, the fire extinguishment times and the temperatures are affected very little by ventilation velocity.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.629-638
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• 2016

This paper proposes a State-of-Charge (SOC) balancing control of Battery Power Modules (BPMs) for a modularized battery for Electric Vehicles (EVs) without additional balancing circuits. The BPMs are substituted with the single converter in EVs located between the battery and the inverter. The BPM is composed of a two-phase interleaved boost converter with battery modules. The discharge current of each battery module can be controlled individually by using the BPM to achieve a balanced state as well as increased utilization of the battery capacity. Also, an SOC balancing method is proposed to reduce the equalization time, which satisfies the regulation of a constant DC-link voltage and a demand of the output power. The proposed system and the SOC balancing method are verified through simulation and experiment.

• Journal of Electrical Engineering and Technology
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• v.3 no.4
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• pp.520-527
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• 2008

This work focuses on the evaluation of active power filter which is controlled by fuzzy logic and neural network based controller for harmonic mitigation and power factor enhancement. The APF consists of a variable DC voltage source and a DC/AC inverter. The task of an APF is to make the line current waveform as close as possible to a sinusoid in phase with the line voltage by injecting the compensation current. The compensation current is estimated using adaptive neural network. Using the estimated current, the proposed APF is controlled using neural network and fuzzy logic. Computer simulations of the proposed APF are performed using MATLAB. The results show that the proposed techniques for the evaluation of APF can reduce the total harmonic distortion less than 3% and improve the power factor of the system to almost unity.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1193-1194
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• 2008

본 논문은 주거환경 변화 및 공기 중 부유물질로 인한 피해를 보호하기 위해 제정된 공기질 관리법안에 적합한 대기 환경 조건을 구현하기 위한 고정압 환풍기용 모터 및 제어 알고리즘에 관한 논문이다. 외기에 압력이 변화하는 외란에도 일정한 풍량을 낼 수 있도록 하기 위해서 속도와 전류의 두 물리량을 곱의 형태로 취하여 profile을 만들고 이에 추종하는 방식을 본 논문에서 제안하였다. 제품의 상용화를 위해서 풍량센서가 없는 센서리스 방식을 구현하기 위해서 전류 값을 토대로 압력 변화량을 일정하게 제어하는 방식을 취하였다. 고정압제어를 위해서 Open-loop상태에서 모터의 P-Q(압력-풍량)data를 측정하고 이를 기초로 예상 구동 영역을 유추하고 이를 토대로 Profile을 만들고 이 Profile을 추종하는 제어를 통해서 고정압제어를 실현하였다. Reference로 속도를 기준으로 하였으며, 동일 속도에서 전류의 값을 비교하여 제어하고자 하는 전류 값이 되도록 함으로써 정압을 실현하였다.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1488-1490
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• 2008

The gyroscope is the sensor for detecting the rotation in inertial reference frame and constitute the navigation system together an accelerometer. As the inertial reference equipment for attitude determination and control in the satellite, the mechanical gyroscope has been used but it bring the disturbance for mass unbalance so the disturbance give a bad influence to the observation satellite mission because the mechanical gyroscope has the rotation parts. During the launch, The mechanical gyroscope is weak in vibration, shock and has the defect of narrow operating temperature range so it need the special design in integration. Recently the low orbit observation satellite for seeking the high pointing accuracy of image camera payload accept the FOG(Fiber Optic Gyro) or RLG(Ring Laser Gyro) for the attitude determination and control. The Ring Laser Gyro makes use of the Sanac effect within a resonant ring cavity of a He-Ne laser and has more accuracy than the other gyros. It need the 1000V DC to create the He-Ne plasma in discharge tube. In this paper, the design process of the High Voltage Power Supply for RLG(Ring Laser Gyroscope) is described. The specification for High Voltage Power Supply(HVPS) is proposed. Also, The analysis of flyback converter topology is explained. The Design for the HVPS is composed of the inverter circuit, feedback control circuit, high frequency switching transformer design and voltage doubler circuit.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.195-198
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• 2008

Recently, with the growth of photovoltaic system, many researchers and companies have concerned about the multi-level inverter which has an efficiency of boosting voltage. This paper implements a multi-level switching function based on the FPGA. It is efficient to implement the switching function based on the FPGA as a program able logic device. In order to implementation the switching function, this paper synchronized with the microprocessor through the clock and synchronous signal from the microprocessor.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.442-446
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• 1998

With the advent of the high-speed microprocessor and DSP, the possibility of executing a control strategy in digital domain has become a reality. By the use of the DSP and microprocessor controller, many high power converters such as especially inverter and motor drive system may be enhanced resulting in the improved robustness to EMI, the ability to communicate the operating conditions and the ease of adjusting the control parameters. But, the digital controller using DSP or microprocessor is not applied in the high frequency switching power supplies, especially full bridge dc/dc converter. So, this paper presents the method and realization of designing a digital-to-phase shift PWM circuit for full digital controlled phase-shifted full bridge dc/dc converter with zero voltage switching. The operating principles, simulation and experimental results will be presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.403-408
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• 2000

In this paper, voltage control APF(Active Power Filter) is introduced to improve power factor and reduce harmonics generated from nonlinear load. The voltage controlled APF which is consisted of inverter and passive filter operates with nonlinear load simultaneously. Real power supplies from main power to load and reactive power provides from APF to load. According to the results o experiment and simulation, it is proved that the proposed system has the performance of improving power factor and reducing harmonics.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.158-163
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• 2001

Current Source Inverter(CSI), operated in square wave mode, is more efficient thant the PWM CSI because of increased cost, greater complexity of control algorithm and substantial switching losses, EMI. But, the square wave output current of CSI, rich in low order harmonics produce motor torque ripples. Therefore, in this paper, describes active power filters for compensating square wave input current of current source induction motor. Also, notch filtering as compensation algorithm is employed. To confirm the validity of proposed system, PSIM simulation results are presented and discussed.