• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1990년도 하계학술대회 논문집
• /
• pp.158-161
• /
• 1990

Recently, the phenomena of voltage instability have become major concern in power system. These phenomena are closely related to what are called multiple load flow solutions and calculation methods on these solutions have developed. But conventional methods require much run time. In this paper, by using sign of |J| and weighting factor considering system configuration, fast calculation method on the multiple load flow solutions is presented.

• 전기의세계
• /
• 제22권2호
• /
• pp.57-69
• /
• 1973

The aim of this study was to investigate the behaviors of plasma jet under coaxial magnetic field in paralled with it for controlling optical characteristics and input power of plasma jet without impurity and instability of arc plasma column. Because the discharge characteristics of plasma jet were so distinctively different according to the existence or non-existence of magnetic field, the input power, luminous intensity of plasma jet and thermal efficiency were comparatively studied in respect of such variables as arc current, gap of electrode, quantity of argon flow, magnetic flux density, diameter and length of nozzle, with the use of several materials which were different in diameter and length of nozzel. The results were as follows; 1) The voltage tends to show a drooping characteristic at law current and then rises gradually. The luminous intensity of plasma jet increases exponentially with arc current. 2) Arc voltage increases and luminous intensity tends to decrease gradually as gap of electrode increases. 3) Arc voltage and luminous intensity tends to decrease gradually as gap of electrode increases. 3) Arc voltage and luminous intensity increase in accordance with the quantity of argon flow. 4) At first step, arc voltage increases to maximum value with the growth of flux density and then tends to show a gradual decrease. Luminous intensity decreases with the growth flux density. 5) Arc voltage decreases as the constriction length of nozzle increases, maximum decrease is shown at the constriction length of 20(mm) and it increases beyond that value. The luminous intensity decreases as the constriction length grows. 6) Arc voltage and luminous in tensity increase with the growth of diameters of nozzle. 7) Thermal efficiency has values between 50% and 75%, being influenced by arc current, the quantity of argon flow, flux density, the length of electrode gap and the constriction length of nozzle.

• 전기학회논문지
• /
• 제59권12호
• /
• pp.2131-2134
• /
• 2010

In this paper, the on-line system schemes for coordinated control system of multiple FACTS were presented to enhance the voltage stability around the metropolitan areas. In order to coordinated control system of FACTS devices, MFC on-line system calculates the optimal set point(Vref, Qrev) of FACTS devices using the coordinated control algorithm with real time network data which is transferred from SCADA/EMS system. If the system is unstable after contingencies, the new operation set-point of FACTS would be determined using bus sensitivity from tangent vector at voltage instability point. Otherwise, we would determine the new operation set-point of FACTS for considering economical operation, like as active power loss minimization using Optimal Power Flow algorithm. As the test, MFC(Multiple FACTS Coordinated control) on-line system will be installed in Korea power system.

• 전기학회논문지P
• /
• 제58권4호
• /
• pp.404-409
• /
• 2009

A DC power system has many loads with various functions. In particular, these sizable loads take the form of power electronic converters. When they are tightly regulated, the loads appear as constant power loads and result in negative incremental input impedance. Under certain conditions the effect of such loads on the power system is causes instability. In this paper, converter with a large storage capacitor and a lag compensator is proposed as a DC bus conditioner to mitigate the voltage transients on the bus. In addition, the proposed control approach has the advantage of performing both the functions of mitigating the voltage bus transients and maintaining the level of energy stored. Simulation and experimental results showed that the proposed control method was operated well in a small-scale DC power system that contained subsystems with constant power characteristics, such as DC/DC converters and electrical drives.

• Smart Structures and Systems
• /
• 제22권3호
• /
• pp.327-334
• /
• 2018

In this paper, dynamic buckling of the smart subjected to blast load subjected to electric field is studied. The sandwich structure is rested on Pasternak foundation with springs and shear elements. Applying piezoelasticity theory and hyperbolic shear deformation beam theory (HSDBT), the motion equations are derived by energy method. For calculating the dynamic instability region (DIR) of the sandwich structure, differential quadrature method (DQM) along with Bolotin method is used. The aim of this study is to investigate the effects of applied voltage, geometrical parameters of structure and boundary conditions on the DIR of the structure. The results show that applying negative voltage, the DIR will be happened at higher excitation frequencies. In addition, the clamped-clamped beam leads to higher excitation frequency with respect to simply supported boundary condition.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
• /
• pp.719-722
• /
• 2003

This work investigates the device degradation p-channel PD SOI devices at various applied voltages as well as stress temperatures with respect to Body-Contact SOI (BC-SOI) and Floating-Body SOI (FB-SOI) MOSFETs. It is observed that the drain current degradation at the gate voltage of the maximum gate current is more significant in FB-SOI devices than in BC-SOI devices. For a stress at the gate voltage of the maximum gate current and elevated temperature, it is worth noting that the $V_{PT}$ Will be decreased by the amount of the HEIP plus the temperature effects. For a stress at $V_{GS}$ = $V_{DS}$ . the drain current decreases moderately with stress time at room temperature but it decreases significantly at the elevated temperature due to the negative bias temperature instability.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2003년도 추계학술발표대회 논문집
• /
• pp.3-6
• /
• 2003

In this work, poly(ethylene oxide) nanofibers were fabricated by electrospinning to prepare nanofibers-reinforced composites. And the PEO powders-impregnated composites were also prepared to compare with physicochemical properties of nanofibers-reinforced composites. Morphology and fiber diameter of PEO nanofibers were determined by SEM observation. Mechanical interfacial properties of the composites were investigated in fracture toughness tests and interlaminar shear strength (ILSS) test. As a result, the fiber diameter decreased in increasing applied voltage. However the optimum condition for the fiber formation was 15 ㎸, resulting from increasing of jet instability at high voltage and the prepared PEO nanofibers were useful in fiber reinforced composites. The PEO-based nanofibers-reinforced composites showed an improvement of fracture toughness factors ($K_{IC} and G_{ IC}$) and ILSS, compared to the composites impregnated with PEO powders. These results were noted that the nanofibers had higher specific surface area and larger aspect ratio than those of the powder, which played an important role in improving the mechanical interfacial properties of the composites.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
• /
• pp.898-902
• /
• 1998

Voltage and harmonic stability characteristics of capacitor commutated converters applied to a BTB (back to back) system (CCC-BTB) are analyzed and compared to characteristics of a BTB system composed of conventional line commutated converters (LCC-BTB). About 1.6 times larger safe operating regions can be obtained for the CCC-BTB system compared to the latter. The CCC-BTB system results in no harmonic instability problem as it has no shunt reactive compensators in the station and the adjoining AC system generates no low anti-res onance points.

• Coupled systems mechanics
• /
• 제4권3호
• /
• pp.251-262
• /
• 2015

The current paper aims at investigating the nonlinear dynamical behaviour of an electrically actuated microcantilever. The microcantilever is excited by a combination of AC and DC voltages. The nonlinear equation of motion of the microcantilever is obtained by means of force and moment balances. A high-dimensional Galerkin scheme is then applied to reduce the equation of motion to a discrete model. A numerical technique, based on the pseudo-arclength continuation method, is used to solve the discretized model. The electrostatic deflection of the microcantilever and static pull-in instabilities, due to the DC voltage, are analyzed by plotting the so-called DC voltage-deflection curves. At the simultaneous presence of the DC and AC voltages, the nonlinear dynamical behaviour of the microcantilever is analyzed by plotting frequency-response and force-response curves.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.1390-1395
• /
• 2004

Recently, the load increasement and new regenerative systems of electrified railway system make it a difficult to distinguish between the load current and fault current. The failure of traction system perhaps causes over-current to flow. The high current can collapse other railway systems. If failures of the traction system takes place, the failures are detected and protected lest it should provoke high current flow. The over current from such a traction system failure permit to charge high tension voltage and produces high temperature arc, voltage instability, current cutting, and break down railway systems. The traction system failures detect and the system has to immediately cut off from over-current flow. To isolate the failure, the system can distinguish failure current from current flows. It forces us to adapt such as a new intelligent protection system. The protective system in traction system play a role of detecting and isolating failure points. In this paper, we proposed intelligent algorithm for discriminating normal and abnormal situation instead of the system being operated abnormally.