• 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.

• 전력전자학회논문지
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• 제11권4호
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• pp.307-312
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• 2006

본 논문에서는 직류링크전류를 기반으로 SRM의 상전류를 추정하였고 이를 이용한 SRM 에 대한 속도제어법을 제안하였다. 또한 직류링크전류검출회로를 제안하여 전류검출분해능을 높일 수 있었으며 오프셋에 의한 영향을 최소화시킬 수 있는 장점을 가지고 있다. 상전류 정보를 이용한 SRM 구동방식과 직류링크전류정보를 이용한 SRM 구동방식을 실제실험을 통하여 비교함으로서 본 논문에서 제안한 상전류 추정알고리즘과 이에 관련된 직류링크전류 검출회로에 대한 유효성이 검증되었고 직류링크전류를 이용한 SRM 속도제어시스템은 속도응답이 3 상 전류정보를 이용한 시스템만큼 빠른 응답특성이 있음을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.304-307
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• 2001

This Paper describes a method for indirect sensing of the rotor position in switched reluctance motors(SRM's) using only current sensors. The detailed operation and simulation of this technique is shown. In particular, current waveform should have at least one peak and estimate the speed and rotor position by detecting position. The simulation result shows that the technique can gives the information of rotor position.

• Progress in Superconductivity
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• 제5권1호
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• pp.31-37
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• 2003

Wide-bandwidth SQUID current amplifier and its control electronics have been constructed for detecting pulse outputs of a superconducting microcalorimeter. The current amplifier made of a double relaxation oscillation SQUID (DROS) has a bandwidth of 1.2 MHz and typical white noise level of about 6 pA/(equation omitted) Hz. To increase the dynamic range of the current amplifier, the flux-locked loop (FLL) has additional circuits to reset the integrator and to count reset numbers which present the number of passed flux quanta. In this system, dynamic range covers from -65 mA to +65 mA. SQUID electronics are controlled by software to get the optimum FLL condition, and to control the current to bias the transition edge sensor (TES). The electronics are shielded from the outside electromagnetic noises by using an aluminum case of 66 mm ${\times}$ 25 mm ${\times}$ 100 mm, and consist of 2 separate printed-circuit-boards for the current amplifier and the control electronics, respectively. The SQUID current amplifier and its control electronics will be used in TESs for detecting photons such as UV and X-ray with high energy resolution.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.399-402
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• 1999

The single sensor technique reconstructing phase currents from the dc-link current without phase current sensors in proposed. When the duration of active vector is too short for the snubber current to reduce, the dc-link current including the snubber current gives large detection error. The solution is presented by analyzing the snubber current and modifying the switching sequences. This scheme is simple, requires only one sampling a period and has good results for detecting the phase currents.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권6호
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• pp.321-329
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• 2002

A protection scheme for series active compensator is presented and analyzed in this paper. The proposed series active compensator operated as a high impedance K($\Omega$) to the fundamentals when short-circuit faults occur in the power distribution system, and two control strategies are proposed in this paper The first is the method by detecting the fundamental source current through the p-q theory, the second is the method by detecting the fundamental component of load current in Synchronous Reference Frame(SRF). When the short-circuit faults occur in the power distribution system, the proposed scheme can protect the series active compensator without additional protection circuits. The validity of the Proposed Protection scheme was investigated through experimental results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 A
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• pp.64-66
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• 2000

This paper presents an algorithm for detecting current transformer (CT). At the instants of beginning and end of saturation, the increment of the secondary current is reduced significantly, depending on the residual flux and saturation time. Thus, the third difference of the current is used to detect saturation in this paper. If the third difference is less than threshold the CT is at the beginning/end of saturation. The proposed detection method is unaffected by the amount of residual flux. The results of various tests with residual flux from -80% to +80% indicate satisfactory performance of the method.

• 한국분말재료학회지
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• 제19권4호
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• pp.297-303
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• 2012

In this study, voltammetry system for realizing high sensitivity nano-labeled sensor of detecting heavy metals was designed, and optimal system operating conditions were determined. High precision digital to analog converter (DAC) circuit was designed to control applied unit voltage at working electrode and analog to digital converter (ADC) circuit was designed to measure the current range of $0.1{\sim}1000{\mu}A$ at counter electrode. Main control unit (MCU) circuit for controlling voltammetry system with 150 MHz clock speed, main memory circuit for the mathematical operation processing of the measured current value and independent power circuit for analog/digital circuit parts to reduce various noise were designed. From result of voltammetry system operation, oxidation current peaks which are proportional to the concentrations of Zn, Cd and Pb ions were found at each oxidation potential with high precision.

• 센서학회지
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• 제7권3호
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• pp.203-210
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• 1998

An experimental study of an eddy current nondestructive testing system to measure dimensions of cylindrical metallic rods, such as cross-sectional area or diameter, is presented. Impedance characteristics of a solenoid sensor, which are generally based on Maxwell's equations in electromagnetic field, are briefly discussed for inspecting geometrical parameters of the coil sensor and testing materials. A measurement system for detecting the diameter of the metallic rod is implemented. This instrument has capabilities for detecting the sensor output signals and estimating demensions of the testing material, continuously. As a result, it was shown that the eddy current sensor with an encircling coil could estimate the diameter of metallic rod. The implemented measurement system gives accurate information for inspecting the dimension of conducting rod with good sensitivity.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 B
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• pp.629-630
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• 2006

This paper describes a novel sensorless excitation position detecting method of Switched Reluctance Motor(SRM) drive. A suitable excitation pattern of each phases is determined by comparison of detecting current without an inductance estimation. The principle of the rotor position estimation is based on the detection of phase current according to rotor position. This sensorless method is very simple and gives efficient control of drive system. The suggested method is verified by experiments.