• 한국태양에너지학회 논문집
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• 제33권6호
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• pp.92-97
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• 2013

This paper proposes DC offset current compensation method of transformerless fuel cell/PV PCS. DC offset current is generated by the unbalanced internal resistance of the switching devices in full bridge topology. The other cause is the sensitivity of the current sensor, which is lower than DSP in resolution. If power converter system has these causes, the AC output current in the inverter will generate the DC offset. In case of transformerless grid-connected inverter system, DC offset current is fatal to grid-side, which results in saturating grid side transformer. Several simulation results show the difficulties of detecting DC offset current. Detecting DC offset current method consists of the differential amplifiers and PWM is compensated by the output of the Op amp circuit with integrator controller. PSIM simulation verifies that the proposed method is simpler and more effective than using low resolution current sensor alone.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.24-28
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• 2010

A simulation study of a current-mode direct current (DC)-DC buck converter is presented in this paper. The converter, with a fully integrated power module, is implemented by using sense method metal-oxide-semiconductor field-effect transistor (MOSFET) and bipolar complementary metal-oxide-semiconductor (BiCMOS) technology. When the MOSFET is used in a current sensor, the sensed inductor current with an internal ramp signal can be used for feedback control. In addition, the BiCMOS technology is applied in the converter for an accurate current sensing and a low power consumption. The DC-DC converter is designed using the standard $0.35\;{\mu}m$ CMOS process. An off-chip LC filter is designed with an inductance of 1 mH and a capacitance of 12.5 nF. The simulation results show that the error between the sensing signal and the inductor current can be controlled to be within 3%. The characteristics of the error amplification and output ripple are much improved, as compared to converters using conventional CMOS circuits.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.655-658
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• 1999

In this paper, Parallel operation of two DC-DC converters which we have ever done before need two CTs to do load current sharing. However, we have proposed a new method called ZCT method that can share load current with only a CT as doing parallel operation two converters with same converter capacity. To confirm parallel performance by a proposed DC-DC converter parallel operation method, we have done computer simulation and experiment. It is certain that we have showed to achieve two converters current sharing performance efficiently through simulation and experiment at result.

• Journal of Electrical Engineering and Technology
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• 제8권1호
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• pp.97-105
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• 2013

The control method of the bidirectional DC/DC converter for instantaneous regenerative current control is described in this paper. The general method to control the DC/DC converter is the output voltage control. However, the regenerative current cannot be controlled to be constant with this control method. To improve the performance of the conventional control method, the DC-link voltage of the inverter is controlled within the tolerance range by the instantaneous boost and buck operations of the bidirectional DC/DC converter. By the proposed control method, the battery current can be controlled to be constant regardless of the motor speed variation. The improved performance of the DC/DC converter controlled by the proposed control method is verified by the experiment and simulation of the system with the inverter and IPMSM(Interior Permanent Magnet Synchronous Motor) which is operated by the reduced practical speed profile.

• 대한전자공학회논문지SD
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• 제44권4호
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• pp.86-90
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• 2007

본 논문에서는 DC-DC 변환기에서 효율적으로 sensing 할 수 있는 센서 scheme을 제안하였다. DC-DC 변환기의 최종 출력전압을 되먹임하여 센서의 입력단에서 전류로 변환되며, 센서에 내장된 기준전류와의 전류비교를 통하여 목표전압에 도달했는지의 여부를 감지한다. 이때의 감지동작은 전류 push-pull 동작을 통해 전류 비교 방식을 수행한다. 센서에 내장된 기준전류도 고정된 기준전압을 변환함으로써 구현된다. 본 scheme의 특징은 전압을 전류로 변환하는 데 있어서의 파라미터가 코어 트랜지스터의 (W/L)의 비로써 결정되므로 비교적 정밀하고 기존의 전압 모드 방식과 비교했을 때, 전력소모 측면이나 칩 사이즈측면에서 효율적으로 구현되는 데에 있다. 본 논문에서는 입력 배터리 공급전압 2.2V${\sim}$3.6V에 대해 5V를 출력하는 DC-DC 변환기에 제안하는 센서를 적용하여 0.35um CMOS 공정으로써 구현하고 그 유용성을 확인하였다.

• 전기학회논문지
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• 제63권5호
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• pp.713-718
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• 2014

DC urban railway power system consists of DC power network and AC power network. The DC power network supplies electric power to railway vehicles and the AC power network supplies electric power to station electric equipment. Recently, because of power consumption reduction and peak load shaving, intelligent measurement of regenerative energy and renewable energy adapted on DC urban railway is required. For this reason, DC smart metering system for DC power network shall be developed. Therefore, in this paper, DC voltage sensor, current sensor, and DC smart meter were developed and evaluated by performance test. DC voltage sensor was developed for measuring standard voltage range of DC urban railway, and DC current sensor was developed as hall effect split core type in order to install in existing system. DC smart meter possesses function of general intelligent electric power meter, such as measuring electricity and wireless communication etc. And, DC voltage sensor showed average 0.17% of measuring error for 2,000V/50mA, and current sensor showed average 0.21% of measuring error for ${\pm}2,000V/{\pm}4V$ in performance test. Also DC smart meter showed maximum 0.92% of measuring error for output of voltage sensor and current sensor. In similar environment for real DC power network, measuring error rate was under 0.5%. In conclusion, accuracy of DC smart metering system was confirmed by performance test, and more detailed performance will be verified by further real operation DC urban railway line test.

• 한국초전도ㆍ저온공학회논문지
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• 제18권4호
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• pp.30-34
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• 2016

In this study, a SFCL-combined DC circuit breaker system was proposed by applying the current-limiting technology for DC circuit breaking. The SFCL-combined circuit breaker system consists of a mechanical DC circuit breaker combined with superconductors. To ensure the reliable structure and operation of the SFCL-combined circuit breaker system, a simulation grid was designed using the EMTDC/PSCAD program, and simulation was conducted. The results showed that the SFCL-combined DC circuit breaker system with superconductors limited the maximum fault current by 37%. In addition, the burden on the DC circuit breaker was decreased by 87%.

• 대한전자공학회논문지SD
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• 제43권9호
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• pp.23-30
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• 2006

본 논문은 전류 감지 feedback 기법을 사용한 고효율 CMOS DC-DC boost 변환기의 설계에 관한 것이다. 펄스-폭 변조 방식의 스위칭 동작을 위해 인덕터를 통해 흐르는 전류의 양을 감지하는 고해상도 전류 감지 회로를 설계하였다. 이를 통하여 외부 소자나 큰 면적을 차지하는 주파수 보상 회로 없이 안정적으로 동작하는 변환기 성능을 얻을 수 있다. 또한 외부 저항 열을 사용하여 다양한 입력/출력 전압 특성을 얻을 수 있다. 설계한 DC-DC 변환기는 thick gate oxide 옵션이 포함된 0.18-um CMOS 표준 공정으로 제작하였다. 부하 전류 200mA 이상에 대하여 3.3V의 출력을 얻는 변환기에서 최대 효율은 90% 이상, load regulation은 100mA의 변화에 대하여 1.15%의 특성을 나타낸다.

• 조명전기설비학회논문지
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• 제29권8호
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• pp.55-62
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• 2015

This paper deals with a switching method to minimize the current ripple component of 3-phase interleaved bidirectional DC-DC converter for charging and discharging of the battery. The characteristics of the output current ripple in 3-phase and 2-phase operation modes according to the variation of battery voltage is analyzed and a phase conversion method for minimizing the magnitude of the current ripple is proposed. The proposed method can extend the light load range because the switching frequency is lower than that of a 3-phase operating system. Simulation and experimental results show the usefulness of the proposed method.

• 조명전기설비학회논문지
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• 제29권6호
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• pp.42-48
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• 2015

DC distribution system is difficult to compose the single-system because of the capacity restriction of power semiconductors. Therefore, DC Distribution system needs parallel operation of AC/DC converters for increase to system capacity. However, this system generates the circulating current. This paper is reducing the circulating current and safely sharing the load using the proposed DC current droop control method when each other 3-phase AC/DC converter connected. This system confirms through the simulation and experiment. Also, when each other converter of parallel operate. it is compared the response characteristics