17,928 research outputs found
Graphene Conductivity near the Charge Neutral Point
Disordered Fermi-Dirac distributions are used to model, within a
straightforward and essentially phenomenological Boltzmann equation approach,
the electron/hole transport across graphene puddles. We establish, with
striking experimental support, a functional relationship between the graphene
minimum conductivity, the mobility in the Boltzmann regime, and the steepness
of the conductivity parabolic profile usually observed through gate-voltage
scanning around the charge neutral point.Comment: 5 pages, 2 figures - Accepted for publication in Physical Review
P-resonant control for the neutral point of three phase inverter
In this project, a Proportional resonant (PR) current controller is proposed to
maintain a balanced neutral point for a three-phase four wire inverter, which can be
used in microgrid applications. The neutral-point circuit consists of a conventional
neutral leg and a split DC link. The neutral point is balanced with respect to the two
DC source terminals (as required, in neutral-point clamped three-level converters)
even when the neutral current is large so that the inverter can be connected to an
unbalanced load. The controller, designed by using the Proportional resonant control
techniques, which attain eliminate for the current flowing through the split
capacitors. This leads to very small variation of the neutral point from the mid-point
of the DC source, in spite of the possibly large neutral current. The simulation of
inverter circuit, neutral-point and P-resonant has been performed using
MATLAB/SIMULINK software. The simulation results confirm the validity of the
proposed method, which can be seen as a promising that ensure P-resonant control
suitable for microgrid applications
Approximate neutral point of a subsonic canard aircraft
An approximate formula is derived for the position of the neutral point in canard aircraft. This formula accounts for the aerodynamic interference between the wing (rear wing) and the canard (forward wing). Topics covered include determination of the canard downwash derivative, determination of the canard and wing liftslopes including the aerodynamic interference, and calculation of the neutral point position
An On-line Diagnostic Method for Open-circuit Switch Faults in NPC Multilevel Converters
On-line condition monitoring is of paramount importance for multilevel converters used in safety-critical applications. A novel on-line diagnostic method for detecting open-circuit switch faults in neutral-point-clamped (NPC) multilevel converters is introduced in this paper. The principle of this method is based on monitoring the abnormal variation of the dc-bus neutral-point current in combination with the existing information on instantaneous switching states and phase currents. Advantages of this method include simpler implementation and faster detection speed compared to other existing diagnostic methods in the literature. In this method, only one additional current sensor is required for measuring the dc-bus neutral-point current, therefore the implementation cost is low. Simulation and experimental results based on a lab-scale 50 kVA adjustable speed drive (ASD) with a three-level NPC inverter validate the efficacy of this novel diagnostic method
Classical neutral point particle in linearly polarized EM plane wave field
We study a covariant classical model of neutral point particles with magnetic
moment interacting with external electromagnetic fields. Classical dynamical
equations which reproduce a correct behavior in the non-relativistic limit are
introduced. We also discuss the non-uniqueness of the covariant torque
equation. The focus of this work is on Dirac neutrino beam control. We present
a full analytical solution of the dynamical equations for a neutral point
particle motion in the presence of an external linearly polarized EM plane wave
(laser) fields. Neutrino beam control using extremely intense laser fields
could possibly demonstrate Dirac nature of the neutrino. However, for linearly
polarized ideal laser waves we show cancellation of all leading beam control
effects.Comment: 9 pages, 2 figure
Comparison between two VSC-HVDC transmission systems technologies : modular and neutral point clamped multilevel converter
The paper presents a detail comparison between two voltage source converter high voltage dc transmission systems, the first is based on neutral point-clamped (also known as HVDC-Light) and the second is based on innovative modular multilevel converter (known as HVDC-Plus). The comparison focuses on the reliability issues of both technologies such as fault ride-through capability and control flexibility. To address these issues, neutral point-clamped and three-level modular converters are considered in both stations of the dc transmission system, and several operating conditions are considered, including, symmetrical and asymmetrical faults. Computer simulation in Matlab-Simulink environment has been used to confirm the validity of the results
Analysis of variation of neutral point potential in neutral-point-clamped voltage source PWM inverters
The authors present the analysis of the neutral-point potential variation of the neutral-point-clamped voltage source PWM (pulse-width-modulation) inverter (NPC-VSI) for AC motor drives and static VAr compensators (SVC). The potential variation is analyzed with the focus on the current flowing out of or into the neutral point of the DC link. The theoretical minimum capacity of the DC link capacitors is discussed for its application to both a vector-controlled induction motor system of 2.2 kW and a SVC system of 10 MVA, 6.6 kV, 60 Hz. It is shown that the proposed control scheme makes it possible to suppress the neutral-point potential variation within a few percent, so that the total capacity of the DC link capacitors in the NPC-VSI is almost the same as that in the conventional voltage source inverter</p
Neutral /zero/ Points of Magnetic Fields
Geometry of force-free magnetic field in vicinity of neutral point
- …