• Journal of Electrical Engineering and Technology
• /
• 제10권2호
• /
• pp.504-510
• /
• 2015

Because wind generators (WGs) in a wind power plant (WPP) produce different active powers due to wake effects, the reactive power capability of each WG is different. This paper proposes a hierarchical voltage control scheme for a WPP that uses a WPP controller and WG controller. In the proposed scheme, the WPP controller determines a voltage error signal by using a PI controller and sends it to a doubly-fed induction generator (DFIG). Based on the reactive current-voltage ($I_Q-V$) characteristic of a DFIG, the DFIG injects an appropriate reactive power corresponding to the voltage error signal. To enhance the voltage recovery capability, the gains of the $I_Q-V$ characteristic of a DFIG are modified depending on its reactive current capability so that a DFIG with greater reactive current capability may inject more reactive power. The proposed scheme enables the WPP to recover the voltage at the point of common coupling (PCC) to the nominal value within a short time after a disturbance by using the adaptive $I_Q-V$ characteristics of a DFIG. The performance of the proposed scheme was investigated for a 100 MW WPP consisting of 20 units of 5 MW DFIGs for small and larger disturbances. The results show the proposed scheme successfully recovers the PCC voltage within a short time after a disturbance.

• Nuclear Engineering and Technology
• /
• 제51권8호
• /
• pp.1978-1982
• /
• 2019

The paper presents the electrical performance measurements of a prototype nuclear battery and two types of betavoltaic cells. The electrical performance was assessed by measuring current-voltage properties (I-V) and determining the short-circuit current and the open-circuit voltage. With ⁶³Ni as an irradiation source, the open-circuit voltage and the short-circuit current were determined as 1 V and 64 nA, respectively. The prototype consisted of 10 betavoltaic cells that were prepared using radioactive ⁶³Ni. Electroplating of the radioactive ⁶³Ni on an ohmic contact (Ti-Ni) was carried out at a current density of 20 mA/㎠. Two types of betavoltaic cells were studied: with an external ⁶³Ni source and a ⁶³Ni-covered source. Under irradiation of the ⁶³Ni source with an activity of 10 mCi, the open-circuit voltage V_oc of the fabricated cells reached 151 mV and 109 mV; the short-circuit current density J_sc was measured to be 72.9 nA/cm2 and 64.6 nA/㎠, respectively. The betavoltaic cells had the fill factor of 55% and 50%, respectively.

• E2M - 전기 전자와 첨단 소재
• /
• 제9권8호
• /
• pp.806-812
• /
• 1996

I-V characteristics of ground electrode fabricated using an aluminium scrap are presented. We fabricated several shapes of aluminium scraps and aluminium electrodes. The results show that the current of aluminium electrode increased linearly by the voltage increase. AC breakdown voltage of copper plate electrode was higher than that of aluminium electrode. AC breakdown current of aluminium electrode was higher than that of copper plate electrode. As applied voltage increased, grounding resistance of aluminum electrode decreased linearly.

• JSTS:Journal of Semiconductor Technology and Science
• /
• 제10권2호
• /
• pp.79-99
• /
• 2010

Pulsed current-voltage (I-V) methods are introduced to evaluate the impact of fast transient charge trapping on the performance of high-k dielectric transistors. Several pulsed I-V measurement configurations and measurement requirements are critically reviewed. Properly configured pulsed I-V measurements are shown to be capable of extracting such device characteristics as trap-free mobility, trap-induced threshold voltage shift (${\Delta}V_t$), as well as effective fast transient trap density. The results demonstrate that the pulsed I-V measurements are an essential technique for evaluating high-$\kappa$ gate dielectric devices.

• The Korean Journal of Physiology
• /
• 제28권2호
• /
• pp.215-224
• /
• 1994

The presence of a calcium current $(i_{Ca^{2+}})$ passed via a specific channel was examined in the unfertilized hamster egg using the whole-cell voltage clamp technique. Pure inward current was isolated using a $Ca^{2+}-rich$ pipette solution containing 10 mM TEA. This current was independent of external $Na^+$ and was highly sensitive to the $Ca^{2+}$ concentration in the bathing solution, indicating that the inward current is carried by $Ca^{2+}$. The maximal amplitude was $-4.12{\pm}0.58nA\;(n=12)$ with 10mM $Ca^{2+}$ at -3OmV from a holding potential of -8OmV. This current reached its maximum within 20ms beyond -3OmV and decayed rapidly with an inactivation time constant $({\tau})$ of 15ms. Activation and inactivation of this $i_{Ca^{2+}}$ was steeply dependent on the membrane potential. The $i_{Ca^{2+}}$ began to activate at the lower voltage of -55 mV and reached its peak at -35 mV, being completely inactivated at potentials more positive than -40 mV. These result suggest that $i_{Ca^{2+}}$ in hamster eggs passes through channels with electrical properties similar to low voltage-activated T-type channels. Other results from the present study support this suggestion; First, the inhibitory effect of $Ni^{2+}\;(IC_{50}=13.7\;{\mu}M)$ was more potent than $Cd^{2+}\;(IC_{50}=123\;{\mu}M)$. Second, $Ba^{2+}$ conductance was equal to or below that of $Ca^{2+}$. Third, $i_{Ca^{2+}}$ in hamster eggs was relatively insensitive to nifedipine $(IC_{50}=96.6\;{\mu}M)$, known to be a specific t-type blocker. The physiological role of $i_{Ca^{2+}}$ in the unfertilized hamster eggs remains unclear. Analysis from steady-state inactivation activation curves reveals that only a small amount of this current will pass in the voltage range $(-70{\sim}-30\;mV)$ which partially overlaps with the resting membrane potential. This current has the property that it can be easily activated by a weak depolarization, thus it may trigger a certain kind of a intracellular event following fertilization which may cause oscillations in the membrane potential.

• 한국재료학회지
• /
• 제31권10호
• /
• pp.586-591
• /
• 2021

This paper proposes a mathematical model that can calculate the luminescence characteristics driven by alternating current (AC) power using the current-voltage-luminance (I-V-L) properties of organic light emitting devices (OLED) driven by direct current power. Fluorescent OLEDs are manufactured to verify the model, and I-V-L characteristics driven by DC and AC are measured. The current efficiency of DC driven OLED can be divided into three sections. Region 1 is a section where the recombination efficiency increases as the carrier reaches the emission layer in proportion to the increase of the DC voltage. Region 2 is a section in which the maximum luminous efficiency is stably maintained. Region 3 is a section where the luminous efficiency decreases due to excess carriers. Therefore, the fitting equation is derived by dividing the current density and luminance of the DC driven OLED into three regions, and the current density and luminance of the AC driven OLED are calculated from the fitting equation. As a result, the measured and calculated values of the AC driving I-V-L characteristics show deviations of 4.7% for current density, 2.9 % for luminance, and 1.9 % for luminous efficiency.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.271-272
• /
• 2007

Displacement current $(I_{dis})$ and drain-to-source current $(I_{DS})$ are evaluated using the simultaneous measurements of source $(I_S)$ and drain $(I_D)$ currents during the application of a constant drain voltage and a triangular-wave gate voltage $(V_{GS})$ to top-contact pentacene thin-film transistors.

• The Korean Journal of Physiology
• /
• 제17권1호
• /
• pp.1-11
• /
• 1983

1) 토끼동방결절의 작은 절편에 미세 전극 두개로 voltage clamp를 하고 과분극에 의하여 활성화되는 내향전류, $i_f$의 동력학적 성상을 분석하였다. 2) 전류 $i_f$는 $10^{-7}g/ml$ TTX와 2 mM $Mn^{2+}$의 존재하에서 과분극 pulse에 의하여 활성화되었으며 그 범위는 $-45\;mV{\sim}-75\;mV$였다. 전류의 크기와 시간경과는 막전압이 과분극될수록 커지고 빨라졌다. 3) Envelope test결과 $i_f$전류는 단일 gate에 의하여 지수합수적 (exponential)으로 조절됨을 보였다. 4) 2 mM의 $Ba^{2+}$에 의하여$i_f$전류의 크기는 감소하고 시간경과도 느려졌으며 반응속도상수와 gating molecule의 열리고 닫히는 반응계수(rate coefficient; ${\alpha}_s$, ${\beta}_s$)와 막전압 관계곡선을 과분극쪽으로 이동시켰다. 이러한 $Ba^{2+}$의 효과는 24 mM $K^+$에 의하여 일부 상쇄되었다.

• 한국결정성장학회지
• /
• 제7권3호
• /
• pp.487-493
• /
• 1997

SiC(4H) 결정에 Ti을 열증착하여 Ti/SiC(4H) 쇼트키(Schottky) 장벽 다이오드를 만들었다. SiC(4H)의 주개농도(donor concentration)는 전기용량-전압(C-V) 측정으로부터 $2.0{\times}10^{15}{\textrm}{cm}^{-3}$이었으며, 내부전위(built-in potential)는 0.65 V이었다. 전류-전압(I-V) 특성으로 부터 다이오드의 이상계수(ideally factor)는 1.07이었으며, 역방향 항복전장(breakdown field)은 약 $1.7{\times}10^3V/{\textrm}{cm}$이었다. 상온에서 $140^{\circ}C$까지 온도변화에 따라 측정된 포화전류로 부터 구한 전위장벽(potential barrier)은 0.91 V이었는데, 이는 C-V 특성으로 부터 구한 전위장벽과 거의 같았다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
• /
• pp.3-4
• /
• 2008

Photovoltaic module consists of serially connected solar cell which has low voltage characteristics. But, the other way, the whole current flow of PV module is restricted by lowest current of one solar cell. For the experiment, we make PV module composing the solar cells that have short circuit current difference of 0%, 1%, 3% and 5%. Using Light I-V and Dark I-V measurements, electrical characteristic parameters like Isc(short-circuit current), Voc(open-circuit voltage), Rs(series resistance), Rsh(shunt resistance) are analyzed. PV module of low current characteristics has electrical stress from other modules. And, such a module has a tendency of hot-spot suffering which leads degradation.