جستجوی مقالات مرتبط با کلیدواژه "تابع انتقال" در نشریات گروه "برق"

In this paper, the dynamic of a flyback converter is investigated by considering the effect of the output capacitor equivalent  series resistance (ESR) based on the calculation of the control input to output transfer function and based on the average value modeling method. The dynamic behavior of the non-minimum phase is an inherent behavior of the flyback converter, which by replacing it with the forward-flyback converter, for some values ​​of the parameters of the converter, it is possible to minimize the dynamic behavior. Calculating the transfer function of this converter is complicated due to the dependence of the state variables, so here a new method is used to calculate the transfer function by considering the effect of the series resistance of the output capacitor. The dynamic behavior of both flyback and forward-flyback converters have been compared by computer simulation results considering the effect of series resistance of the output capacitor. Also, a laboratory sample of both converters has been made and the results of laboratory measurements have shown the improvement of the dynamic response in the forward-flyback converter.

So far, comprehensive and extensive studies have been conducted on the brushless DC motor (BLDC), and a part of these studies focuses on the estimation of the parameters of the transfer function of this motor. Estimation of BLDC motor transfer function parameters is essential to study motor performance and predict its behavior. Therefore, an efficient, accurate and reliable parameter estimation method is needed. In this article, the problem of estimating the parameters of the transfer function of the inverter-fed BLDC motor set has been solved using particle swarm algorithms (PSO). The results of using this algorithm have been compared with the results of other optimization algorithms. The comparison of these results has shown that the PSO algorithm is an efficient, accurate and reliable method for solving the transfer function parameter estimation problem.

AAbstract: Transfer function of the InGaAs/GaAs SAQD laser is calculated using its rate equations. Using the calculated transfer function, time and frequency analysis can be implemented completely. In the time domain, the calculated transfer function can show the transient and steady state response of the laser. Also this transfer function can be used in circuit simulator such as SPICE in order for analyzing the electro-optical VLSI circuits. After the calculation of the transfer function, time domain together with Nyquist responses has been calculated. The effect of carrier dynamics on the output response of the laser is analyzed in this case. Nyquist diagram is selected in this analysis because one can predict the closed loop system using the open loop system. Unlike the systems such as interconnects and transistors that are analyzed before, the results reveal that in SAQDLs, the ratio of the transient peak overshoot in the output power to stable output power is very large. Accordingly in integrated circuits that use SAQDLs, amplification of each overshoots in output power of the laser can deteriorate the input of the next circuit module on the chip or shock to it. This increases the importance of the stability analysis in SAQDLs for more reliability.

Assessment of complex harmonic current contribution of each wind turbines at connection point of a wind farm to the grid (primary emission) is presented in this paper. Moreover, contribution of grid background harmonic voltage distortion on harmonic current distortion (secondary emission) of each turbine is also evaluated. Both assessments are represented based on primary and secondary transfer functions and modeling of wind farm components in frequency domain. In order to increase the accuracy of these transfer functions, wind turbine impedance must also be included in transfer functions while studying aggregation effect of complex harmonic current emissions. Accordingly, a new model of primary and secondary emission transfer functions for a type-III wind turbine is proposed to study aggregation effect of harmonic currents in a wind farm. This model is based on average modeling of back-to-back converters of a doubly-fed induction generator, in order to extract total impedance of a wind turbine in its linear working range. By applying this impedance into transfer function models, if turbines emit current with identical magnitude and phase angle, then the total primary emission aggregate less than the number of turbines, and if turbines emit current with identical magnitude but uniform phase angle distribution, then the total primary emission aggregate less than square root of the number of turbines and doesn't follow square root rule.

Application of power electronic converters in wind turbines results in generation of harmonic and interharmonic. Also, the switching of converters results in turbines active output power distortions. Harmonic interaction of wind farms with external grid, harmonic propagations in it and amplification of these propagations due to resonance of underground transmission cables, can leads to increase in power quality problems. This paper presents a method for study and classification of conventional current harmonic emissions in a wind farm. This method uses the concept of transfer function in order to evaluate the harmonic contributions of each wind turbines at point of connection as well as the contribution of external grid background harmonic voltage on each turbine current harmonic distortion. In this regard, extraction of voltage and current transfer functions, transfer admittance and impedance is done based on circuit theory and harmonic modeling of wind farm components from medium voltage (MV) side of turbine transformer in frequency domain. Two classification of harmonic propagation called as “primary emission” and “secondary emission” is evaluated based on these functions. With use of this method, the contribution of each turbine and also the contribution of external grid at overall wind farm emission can be decomposed. Also, the impact of transfer function of conventional LCL filter used in wind turbines, on each those transfer functions, is studied. The important conclusion is that the presence of this filter causes that the amplitude of primary harmonic transfer function from one turbine to another turbine, in special frequency range, be more than the amplitude of primary harmonic transfer function from one turbine to the grid.