جستجوی مقالات مرتبط با کلیدواژه « Frequency Response » در نشریات گروه « برق »

Wind power generation is making an increasingly significant contribution to global electricity production. The high penetration of wind power poses many operational and control challenges that affects the reliability and stability of power systems. In this Paper, the reported technical challenges caused by the grid integration of wind energy conversion system (WECS) and the proposed solutions methodologies represents. The wind-generating system components and architecture are investigated at the beginning of this article for analysis and stability studies purposes, then are addressed various technical challenges; each challenge is discussed individually, focusing on the bulk integration of wind energy into the power systems. Some solutions, including grids code, energy storage technologies, appropriate control strategies, and other methodologies employed to mitigate the effects of the integration, are also included. This review is ready-reckoner of essential topics for further research of wind energy and available technologies in this field. This review provides ready-reckoner of essential topics for grid integration of wind energy and available technologies in direction of overcome the related difficulties.

In this paper, the impedance of low voltage grids in frequency range of 2 kHz - 150 kHz is estimated using rectangular pulse injections and signal processing techniques. The grid impedance is defined as division of voltage signal to current signal in frequency domain. In noisy condition, the accuracy of impedance estimation is directly dependent to energy of injected signal. The injection signal must has sufficient energy in the frequency range of estimation for an accurate impedance estimation. In the proposed method, several injection signals with different widths are selected with the Genetic algorithm. The grid responses to the injected signals are measured and then denoised for an accurate impedance estimation. When the measurement duration is low, the whole transient state of the grid is not measured; hence the impedance estimation is not accurate. Therefore, in this paper a method is proposed for determining the best measurement duration for impedance estimation using Time-Frequency distributions. The proposed method is applied on several simulated grids and the results show the ability and accuracy of the proposed method in grid impedance estimation.

This paper deals with algebraic stability analysis and investigating the existence of proportional stabilizing controllers on the basis of frequency response data. Firstly, it is shown that using the available results in this subject may yield in inconsistent subsequences in the cases that there is a critical inflection point in phase diagram of the open-loop/process transfer function. Then, to solve this inconsistency problem some modifications are proposed. Finally, conditions for ensuring the existence of critical inflection point in phase diagram of a dynamical system are analytically found.

Atomic force microscopy is a powerful tool in imaging and detection of nanoscale materials. The performance of this device in liquid environment has a great advantage such as ability of imaging biological samples, reducing the van der Waals forces and elimination of capillary forces. Understanding of dynamic behavior of the device in liquid environment under various conditions is essential. Therefore in this paper the atomic force microscopy is modeled as a cantilever beam and its dynamic behavior is investigated using the analytical method of multiple scales. For this purpose the equation of motion of microcantilever is obtained using the continuous beam model. Subsequently the hydrodynamic force due of fluid incorporates into the equation using additional mass and damping. Then using the method of separation of variables and use of the Galerkin approximation method, partial differential equation of motion of the beam is turned to an ordinary differential equation. Finally, using the method of multiple scales, the frequency response of the micro-beam near its resonance frequencies is obtained. Moreover the effect of the fluid viscosity and beam dimensions on beam frequency response is studied. In addition, since in nonlinear systems, addition to the primary resonance, it is possible to there is another resonant frequencies, so in this paper the resonant frequencies other than the natural frequency of the linear system is studied and the existence of two resonant frequencies lower than the natural frequency is shown.

Analog multiplication of two signals is one of the most important applications in signal processing. The main motivation for choosing an analog current multiplier is its importance in the function of nonlinear analog signal processing. The multiplier is used as a programming element in systems such as filters, neural networks, and as mixers and modulators in a telecommunications system. And are widely used in end-of-life frequency modulation conversion control filters for fuzzy integrated systems and so on. Quadruple multiplication has a non-linear function in signal processing that is very useful for communication equipment and control systems, and CMOS technology is widely recognized as the most desirable technology for implementing integrated circuits. Therefore, comparison and evaluation of current quadruple multipliers in terms of power consumption, total THD harmonic distortion, frequency response, linearity, speed, input voltage range, input current range, noise, power supply, and other parameters affecting quadruple current multiplier circuits are necessary to achieve a multiplier with proper performance and use in specific applications.