Part Of Admittance Research Articles

Self-Measurement of the Admittance Matrix of AC–DC Power Converter by Internal Harmonic Injection

Frequency-domain impedance or admittance model is widely applied to analyze harmonic stability of power electronic converters. Conventionally, the converter impedance is modeled holistically, without exhibiting the sole effect of different control and phase-locked loop (PLL). Besides, harmonic voltage or current injection external to the converter is usually adopted, which involves dedicated equipment and introduces unexpected inner impedance. In this paper, the response of voltage perturbation upon AC-DC power converter along various voltage signal flow paths is analyzed, based on superposition principle. Each part of admittance and its effect on stability can therefore be quantified explicitly. By injecting harmonic perturbation through the identified paths within the converter controller, each part of admittances, with and without the concerned control or PLL blocks, are measured and summed to be the total admittance. Harmonic voltage mitigation control implemented on a grid-forming converter creates an ideal grid with constant voltage and nearly zero inner impedance at the injected harmonic frequency. The proposed admittance analysis and measurement is successfully applied to power converter with different PLL, voltage feedforward, output power control, DC voltage control and grid-forming cascaded control. Effectiveness of the analysis and the proposed admittance measurement approach are validated by comprehensive simulation and hardware test.

Theoretical Analysis of Multilayer Surface Plasmon Resonance Sensors Using Thin-Film Optical Admittance Formalism

A theoretical analysis of surface plasmon resonance (SPR) behavior of conventional Ag sensor within the Kretschmann configuration is reported using thin-film optical admittance formalism. We examine the additional layer thickness and refractive index effects on optical admittance by considering Ag/SiO2, Ag/TiO2, and Ag/Si sensors. Theoretical results show that imaginary part of admittance is more sensitive to the sensing medium refractive index change than its real part, and a maximum of angular sensitivity reached by the sensors may be obtained simply by calculating the shift of the incident angle corresponding to the minimum of admittance imaginary parts.

Low Frequency AC Nonlinear Dynamic Admittance in Quantum Dot Structure

In the framework of scattering theory and in terms of the notion of local partial density of states(LPDOS), we derived the expressions of the linear and the second order nonlinear emittance, which is the imaginary part of admittance, for the quantum dot structure. With the help of discrete Hamiltonian model we obtained the linear and the second nonlinear partial density of states. By using the linear and the nonlinear emittance we could obtain expressions which can be used to detect the density of state(DOS) of the sample.

Frequency dependence of A.C. conductance of non-irradiated and neutron irradiated silicon detectors

The admittance-Y (real and imaginary) as a function of frequency (ω) and temperature (T) of silicon detectors, non-irradiated and neutron irradiated, were studied. An electric circuit model of Y(ω) was calculated. The experimentally measured data for real part of admittance G as a function of to have shown a quadratic dependence G∼ω 2 , for temperatures T≥40K. This experimental dependence was the same as resulted from the calculations based on the electric circuit model for the region of values T where G was proportional to the resistivity of the silicon detector (p). For temperatures T n (n a , a =2.3 for 170≤T≤ 270 K and a=1.8 for 50≤T≤ 150K). At T≤ 20K, due to the process of freeze-out of free carriers, the value G remains practically independent on to and on further decrease of T. Measurements on neutron irradiated samples at Φ >10 13 n/cm 2 , have shown important changes in the dependence of G as a function of co and T.

Nonequilibrium Green’s Function Approach to Dynamic Properties of Resonant-Tunneling through Double-Barrier Structures

In this paper, we review a recently developed approach to the dynamic properties of double barrier resonant tunneling systems, based on the nonequilibrium Green’s function technique and the Feynman path integral theory. The transient behavior of tunneling current, immediately after the switch-on of a dc bias voltage, is characterized by the building up process of tunneling electrons in the quantum well. The novel negative differential conductance demonstrates itself as a function of frequency of the small ac signal imposed upon a dc bias. The imaginary part of admittance is shown to be related to the conductance via a Kronig-Kramers relation. The noise characteristics clearly demonstrate a strong time correlation derived from the Pauli exclusion principle and have evident dependence upon the structure parameters and the bias voltage. All those theoretical results are compared with experiments and numerical simulations.