• 대한전기학회논문지
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• 제43권6호
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• pp.927-935
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• 1994

Detailed analysis of the commutation circuit of the proposed wide-frequency current source inverter is given. In this inverter a spike-limit circuit and a precommutation circuit are used. The spike-limit circuit is intended to limit spike voltage which is arising during commutation time in a current source inverter, and the precommutation circuit to reuse the energy which flows from main inverter to spike-limit circuit during commutation time to aid commutation. Thus voltage stress of main thyristor is minimized. Since this inverter can be made up of thyristors for phase control, it has some advantage in high voltage and high power application.

• 대한전기학회논문지
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• 제41권2호
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• pp.144-155
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• 1992

A design of a highly stable current-controlled power supply combining the phase-controlled rectifier (PCR), passive filter and active filter is investigated. A digital phase-looked voltage control (PLVC) with a capability of compensating the thyristor firing angles under unvalanced power source is proposed` otherwise the PCR output voltage has low-order subharmonics whose suppression requires a bulky passive filter. The digital PLVC has a fast dynamic characteristics as an inner control loop of the PCR. To suppress further the output ripple, an active filter using a transformer is introduced and its design is described through the frequency domain analysis. An optimal integral, proportional and measurable variable feedback (IPM) controller is designed using the time-weighted performance index based on the time domain analysis. The design method based on the time-weighted performance index gives better response characteristics than that based on the conventional performance index. It is also shown via experimental results that the proposed scheme gives better response characteristics than that based on the conventional performance index. It is also shown via experimental results that the proposed scheme gives good dynamic and static performances.

• 전기학회논문지P
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• 제57권3호
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• pp.231-235
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• 2008

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. Joos presented a topology and a control technique for a hybrid large-power high-precision magnet power supply in 1996. The system consists of a phase controlled rectifier (PCR) connected in series with a high-frequency PWM converter. This paper improves the power circuit of the PWM converter using interphase transformer. Simulation result proves effect of the proposed system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 B
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• pp.540-542
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• 1999

We develop jumping ring system with sensor and control system using dynamic neural networks. Jumping ring, sensor and control system are controlled by 586 PC using Turbo C program. Sensor system is composed of 20 optical sensors and encoder. The control circuits are consisted of thyristor, FET and phase controller. A/D converter and optical sensor acquire real time motion data of the jumping ring system. The information of acquired jumping ring Position is estimated by using dynamic neural networks. Estimated control signals are sent to control circuits and D/A converter to track desired position of the jumping ring system. Experiment results are given to verify that proposed dynamic controller is useful in real jumping ring system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.539-545
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• 2001

This paper proposes a static synchronous series compensator based on multi-bridge inverter. The proposed system consists of 6 H-bridge modules per phase, which generate 13 pulses for each half period of power frequency. The dynamic characteristic was analyzed by simulations with EMTP code, assuming that it is inserted in the 154-kV transmission line of one-machine-infinite-bus power system. The feasibility of hardware implementation was verified through experimental works using a scaled model. The proposed system does not require a coupling transformer for voltage injection, and has flexibility in expanding the operation voltage by increasing the number of H-bridge modules.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.464-469
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• 1998

In the conventional wire feeder drives of welding machine, one thyristor or MOSFET device was used for half-wave phase control circuit and direct EMF measurement was used for sensing the wire feed rate. But the method using one switching device has poor response for sudden disturbance and it has latent speed ripple. It can affect some welding performance such as spatter generation and irregular bead formming. Therefore, the welding performance using full-bridge PWM speed control scheme was compared with conventional driving scheme was compared with conventional driving scheme and experimented in this paper. The results of experiment confirm the posibility of welding performance improvement by proposed constant speed control scheme in wire feeding drive of welding machine.

• Journal of Welding and Joining
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• 제32권1호
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• pp.102-107
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• 2014

SCR(Thyristor) type $CO_2$ welders have widely used for the welding process of heavy industries such as shipbuilding and plant. Since the industrial fields of shipbuilding and plant are usually exposed to severe welding condition with lots of dust, extreme temperature, high humidity and vibration, it is not recommended to use inverter type welder despite its state-of-the-art technology. Many sophisticated functions in the inverter welder may not work due to malfunction of its sensitive components. Hence this study focused on digitalization of SCR $CO_2$ welder by making use of microprocessor for SCR phase control. By this application, fine control of output of the $CO_2$ welding systems is achieved. Also pulse output mode of operation is realized and its verification is carried out with aluminum sample welding. The experimental results showed sound weld bead. The front operation panel provide user with numerical parameter settings and monitors. It will help precise weld process monitoring and control with digital value.

• 전력전자학회논문지
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• 제9권2호
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• pp.97-104
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• 2004

회생차량에서 직류전원단으로 회생되는 에너지를 교류전원측으로 반환하여 활용하기 위한 장치로서 사이리스터 인버터가 널리 사용되고 있다 기존의 사이리스터 인버터는 단방향의 위상제어방식으로 출력의 역률제어가 불가능하고, 고조파 함유율이 높아 별도의 필터를 필요로 한다. 본 연구에서는 이러한 문제점을 해결하고자 스위칭 소자로서 양방향 제어가 가능한 IGBT를 채용하여 Space vector PWM 제어를 함으로서 유효전력 및 무효전력 제어가 가능한 인버터를 개발하였다. 개발한 인버터는 상업용으로 실계통에 바로 적용이 가능하도록 경제성 및 신뢰성을 제고하여 전체 제어시스템을 디지털 형식으로 구현하였고, 저대역 필터를 내장하여 고조파 발생을 억제하였으며, 전체 부피를 콤팩트하게 하였다. 본 논문에서는 전기철도 직류급전계통에 적합한 회생 인버터의 설계기준, 기술사양, 전력회로, 인버터 및 계통연계 제어기법, 개발시스템, 시험결과 및 특성 등을 기술하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.718-722
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• 2001

This paper proposes an SSSC based on multi-bridge inverters in PWM scheme. The proposed system consists of 6 H-bridge inverter modules per phase. The dynamic characteristic of proposed system was analyzed by simulation with EMTP codes, assuming that the SSSC is inserted in the 154-kV transmission line of one-machine-infinite-bus power system. The feasibility of hardware implementation was verified through experimental works with a scaled-model. The proposed system can be directly inserted in the transmission line without coupling transformers, and has flexibility in expanding the operation voltage by increasing the number of H-bridges.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1370-1372
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• 2004

At present. distance relay and ${\Delta}I$ current increment relay are used as primary and secondary protection in the AC feeder system. However. electric railway vehicles according to power electronic's development had developed resistance control, thyristor phase control and PWM control system. and operation of train is increasing in a feeder section. Therefore this paper analyzes the load characteristics and situation of relay's maloperation caused by load current increase, harmonics, regenerative braking current and operation of the different vehicles in same feeder section. Based on this analysis. this paper proposes consideration items for relay correction and advanced adaptive relay that can change operation area according to load current.