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Showing 3 results for High Frequency
Graphene Nano-Ribbon Field Effect Transistor under Different Ambient Temperatures
M. Akbari Eshkalak,
Volume 12, Issue 2 (6-2016)
Abstract

This paper is the first study on the impact of ambient temperature on the electrical characteristics and high frequency performances of double gate armchair graphene nanoribbon field effect transistor (GNRFET). The results illustrate that the GNRFET under high temperature (HT-GNRFET) has the highest cut-off frequency, lowest sub-threshold swing, lowest intrinsic delay and power delay product compared with low-temperature GNRFET (LT-GNRFET) and medium-temperature GNRFET (MTGNRFET). Besides, the LT-GNRFET demonstrates the lowest off-state current and the highest ratios of Ion/Ioff, average velocity and mobile charge. In addition, the LT-GNRFET has the highest gate and quantum capacitances among three aforementioned GNRFETs.


Sensorless Model Reference Adaptive Control of DFIG by Using High Frequency Signal Injection and Fuzzy Logic Control
R. Pour Ebrahim, S. Tohidi, A. Younesi,
Volume 14, Issue 1 (3-2018)
Abstract
In this paper, a new sensorless model reference adaptive method is used for direct control of active and reactive power of the doubly fed induction generator (DFIG). In order to estimate the rotor speed, a high frequency signal injection scheme is implemented. In this study, to improve the accuracy of speed estimation, two methods are suggested. First, the coefficients of proportional-integral (PI) blocks are optimized by using Krill Herd algorithm. In the second method, the fuzzy logic control method is applied in the estimator structure instead of PI controllers. The simulation results for the proposed methods illustrate that the estimated speed perfectly matches the actual speed of the DFIG. In addition, the desired slip value is achieved due to the accurate response. On the other hand, the active and reactive power responses have fast dynamics and relatively low oscillations. Moreover, the fuzzy controller shows more robustness against the variations of machine parameters.

Two-Stage Islanding Detection Method via High Frequency Impedance and Harmonic Distortion Evaluation in Multi-DG Networks
M. Mohiti, S. Sabzevari, P. Siano,
Volume 17, Issue 3 (9-2021)
Abstract
Islanding detection is essential for reliable and safe operation of systems with distributed generations (DG). In systems with multiple DGs, the interaction between DGs can make the islanding detection process more challenging. To address this concern, this paper proposes a two-stage islanding detection method for power systems equipped with multiple-DGs through estimation of high frequency impedance (Zf) and determination of the total harmonic distortion (THD). The impedances of the DGs are estimated at distinct frequencies to avoid interval overlaps. The concept of different frequency bands makes the proposed method applicable to multiple DG systems. To evaluate the effectiveness of the proposed method, a test system with multiple DGs is simulated through several case studies in PSCAD/EMTDC. The simulation results demonstrate the accuracy of the proposed islanding detection method in both single and multi-DG systems. It is also shown that the proposed method remains robust under different operating conditions and events.

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© 2022 by the authors. Licensee IUST, Tehran, Iran. This is an open access journal distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license.