• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.303-305
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• 1996

A strategy that can maximize the efficiency of the inverter system for the non-magnetic material is proposed. Frequency control and variable DC-Link voltage control are compared and analyzed by the experimental results. The experimental results show the variable DC-Link voltage control is superior to the frequency control with respect to improve the efficiency of the inverter system. MOSFETs and IGBTs are used as switching devices and IGBTs are considerable as better switching devices for improving the efficiency of the inverter system.

• 전력전자학회논문지
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• 제17권2호
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• pp.158-165
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• 2012

In this paper, the test bed using three-phase PWM converter connected with single phase inverter in series is set up to configure an active AC electric load. Since the two topologies, three-phase PWM converter and single-phase inverter, can be operated bidirectionally, the system not only re-generates surplus power to grid but also prevents power dissipation. However, the construction of system has a drawback. That is, ripple components two times of inverter operation frequency occur at DC-Link due to cascade connection, it can be cause of three phase unbalance Since the operational characteristic of the active AC electric load, the power frequency entered into the electric load can be varied, and the ripple of DC-Link is changed as well. In this paper, the three-phase PWM converter using a variable notch filter is proposed, and the reduction of three-phase current unbalance is presented. the validity of the proposed PWM converter using a variable notch filter is verified by the simulation and experimental results.

• 전력전자학회논문지
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• 제25권1호
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• pp.44-53
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• 2020

A bridgeless single-stage AC-DC converter for wireless power charging systems is proposed. This converter is composed of a PFC stage and a three-level hybrid DC-DC stage. The proposed converter can control the wide output voltage (200-450 V_DC) by the variable link voltage and the pulse-width voltage applied to the primary resonant circuit due to the phase-shifted modulation at a fixed switching frequency. Moreover, the input power factor and the total harmonic distortion can be improved by using the proposed converter. A 1 kW prototype was fabricated and validated through experimental results and analysis.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권2호
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• pp.48-54
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• 2002

In this study, a neuro-fuzzy controller which has the characteristic of fuzzy control and artificial neural network is designed. A fuzzy rule to be applied is automatically selected by the allocated neurons. The neurons correspond to fuzzy rules are created by an expert. To adapt the more precise model is implemented by error back-propagation learning algorithm to adjust the link-weight of fuzzy membership function in the neuro-fuzzy controller. The more classified fuzzy rule is used to include the property of dual mode method. In order to verify the effectiveness of the proposed algorithm designed above, an operating characteristic of a DC servo motor with variable load is investigated.

• Journal of international Conference on Electrical Machines and Systems
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• 제1권1호
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• pp.8-16
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• 2012

Fixed speed wind turbine generators system that uses induction generator as a wind generator has the stability problem similar to a synchronous generator. On the other hand, doubly fed induction generator (DFIG) has the flexibility to control its real and reactive powers independently while being operated in variable speed mode. This paper focuses on a scheme where IG is stabilized by using DFIG during grid fault. In that case, DFIG will be heavily stressed and a remedy should be found out to protect the frequency converter as well as to allow the independent control of real and reactive powers without loosing the synchronism. For that purpose, a crowbar protection switch or DC-link protecting device can be considered. This paper presents a comparative study between two protective schemes, a crowbar circuit connected across the rotor of the DFIG and a protective device connected in the DC-link circuit of the frequency converter. Simulation analysis by using PSCAD/EMTDC shows that both schemes could effectively protect the DFIG, but the latter scheme is superior to the former, because of less circuitry involved.

• 조명전기설비학회논문지
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• 제20권2호
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• pp.16-23
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• 2006

본 논문에서는 고역률을 가지고 영전압 스위칭으로 동작되는 새로운 단일 전력단 고주파 공진 인버터 링크형 DC-DC 컨버터 회로에 관하여 기술하고 있다. 제안된 토폴로지는 역률 교정기로써 하프 브리지형 부스트 컨버터와 하프 브리지 고주파 공진 컨버터를 단일 전력단으로 일체화 시켰다. 역률 보상용 부스트 컨버터의 부스트 인덕터 전류를 가변 스위칭 주파수와 일정 듀티비를 가지고 불연속 전류 모드(DCM)로 동작시킴으로써 부가적인 입력 전류제어기 없이 높은 입력 역률을 얻을 수 있다. 또 제안한 토폴로지의 이론해석을 무차원화 파라미터를 도입하여 범용성 있게 하여 회로 설계 전단계에서 필요한 특성값을 도식적으로 표현하다. 첨가해, 제안한 토폴로지의 상용화 가능성과 이론해석의 정당성을 입증하기 위해 스위칭 소자로 Power-MOSFET IRF 740을 제안회로 토폴로지의 스위칭 소자로 채용해 실험 장치를 구성하여 검토를 행하였다. 제안된 컨버터는 향후 통신용 DC/DC 컨버터의 전원장치, 방전등용 진원장치 등의 전원시스템에 유용히 사용될 것으로 사료된다.

• 전력전자학회논문지
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• 제26권2호
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• pp.141-149
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• 2021

In the field of electric vehicles and AGVs, wireless power transfer (WPT) charging systems have been developed recently because of its convenience, reliability, and positive environmental impact due to cable and cord elimination. In this study, we propose a WPT charging system using a single stage AC-DC converter that can be reduced in size and weight and thus can ensure convenience. The proposed single-stage AC-DC converter can control a wide output voltage (36-54 VDC) within coupling ranges by using the variable link voltage applied to the WPT resonant circuit through phase-shifted modulation at a fixed switching frequency. Moreover, the input power factor and total harmonic distortion can be improved by using the proposed converter. A 1 kW prototype that can operate with an air gap range of 40-50 mm is fabricated and validated through experimental results and analysis.

• 산업기술연구
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• 제25권B호
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• pp.203-210
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• 2005

The PWM(Pulse Width Modulated) converter for the AC to DC rectification has become attractive in the industrial variable-speed drive application and the electric utilities due to the following benefits: Nearly the sinusoidal input current with unity power factor; Controllable DC link voltage; Bidirectional power flow. This paper presents a quantitative analysis of single and three phase PWM converter's input and output characteristics as a function of the input filter inductance under balanced and unbalanced conditions. Also, its performance under the supply voltage including harmonics is investigated by simulation with Matlab Simlulink and experiments. These results provide a reference for selecting the reasonable converter's input filter inductance for given harmonics or power factor criterion.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1026-1029
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• 1993

Inherent speed-torque performance of Switched Reluctance Motor is similar to that of series wound DC motor. Thus, the speed of the motor is extremely regulated according to load torque. For the purpose of controlling the speed and torque of SRM it is necessary to change the applied DC link voltage or the switch-ON and switch-OFF angles which control the phase current of the motor. This paper describes speed-torque characteristics of an integral horse power Switched Reluctance Motor by adjusting the switch-ON and switch-OFF angles. Speed at rated load torque can be regulated by adjusting the switching angles and the control scheme is applied to 2kW, 3 phase, 6/4 SRM.

• 전력전자학회논문지
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• 제27권1호
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• pp.26-32
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• 2022

This paper proposes a power system that includes a 120k W fuel cell DC-DC converter (FDC) and 30 kW bidirectional DC-DC converter (BHDC) for a 150 kW fuel-cell vehicle. With a high DC link voltage of 800 V, the efficiency and power density of the power electronic components are improved. Through the modular design of FDC and BHDC, electric components are shared, resulting in reduced mass production costs. The switching frequency of 30 kHz of full SiC devices and optimal design of coupled inductor reduce the volume, achieving a power density of 8.3 kW/L. Furthermore, a synergetic operation strategy using variable limiter control of FDC and BHDC was proposed to efficiently operate the fuel cell vehicle considering the fuel cell stack efficiency according to the load. Finally, the performance of the prototype was verified by Highway Fuel Economy Driving Schedule testing, EMI test, and the linked operation between FDC and BHDC. The full load efficiencies of the FDC and BHDC prototypes are 98.47% and 98.74%, respectively.