نشریه مهندسی برق
سال پنجاه و دوم شماره 1 (پیاپی 99، بهار 1401)

In this paper, a new adaptive fractional-order sliding mode controller is designed for a Permanent Magnet Synchronous Generator (PMSG) to track the maximum power point. The controller objective is to track the desired generator speed to extract the maximum power from the wind turbine system in the presence of parametric uncertainty and external disturbances. First, a new fractional order sliding surface is defined. To ensure the stability of the closed-loop system in the sliding model controller it is required to know the upper bounds of uncertainties and disturbances, where it is difficult to calculate these bounds for practical applications such as wind turbines. Therefore, the control signal parameters are estimated online by the proposed adaptive laws, in order to increase the convergence rate of the state variables to the reference value and reduce the chatting phenomenon, also to increase the system robustness against external disturbances and parametric uncertanity. On the other hand, due to the unknown disturbance dynamics, a disturbance observer is designed to estimate external disturbances and parametric uncertainty. Then, the stability of the general closed-loop system together with the disturbance observer is performed using Lyapunov's theory. Finally, the simulation results considering two different scenarios; first for step wind changes with external disturbance, second for changes in sine wind speed with parametric uncertainty. The results are compared with conventional sliding mode controller and results show the effective performance of the proposed controller in tracking the reference value, increasing its robustness against uncertainty and disturbance and reducing the chatting phenomenon.

In this paper, the load of the pulsed power generators is modeled using the impedance spectroscopy of human lung normal and cancer cells for electroporation. Due to the differences in the electrical behavior of normal and cancer cells, cell modeling can be used in cancer diagnosis and treatment selectivity (causing cell death in cancer tissues and not damaging the cells, and normal tissues) is effective. Also, due to the wide changes in cell impedance under different conditions and the dependence of pulse generator structures on load impedance, cell modeling can have a significant effect on the design of pulse generators and the creation of pulse parameters with the greatest effect. In this paper, the impedance of biological samples is measured at different frequencies. Finally, for quantitative analysis of the electrical properties of cells, an accurate electrical equivalent circuit is provided for the load. The proposed electrical model is not cell-focused but on the set of cuvette and its internal contents. This electrical model, taking into account the effect of the two-layer electrical capacitor and parasitic effects, and expanding the frequency range from 100 Hz to 500 MHz. The results show that the equivalent electrical circuit provided in most cases with an low error is consistent with the impedance measurements performed for different samples.

In this paper, the transistor level of single-ended and differential low-power sample-hold is presented based on carbon nanotube field effect transistor technology using the advantages of second generation current conveyor blocks. The switching operation in the proposed sampl and holds is based on the structure of the second generation current conveyor, which means that it has the same function as the analog current-conveyor switches.The implementation of the proposed the sample and hold blocks with using advantages of carbon nanotube field effect transistors improves the performance sampl and hold circuit. The proposed sample and hold circuits have very low power consumption and high operating speed, and it also does not require a non-overlapping clock pulse signal. These proposed circuits have been implemented and simulated in HSPICE software using 32-nanometer carbon nanotube field effect transistor technology. The simulation results show that the power consumption of the differential sample and hold circuit is 13.45 μW, also the ENOB value of the differential sample and hold circuit for the sampling frequency of 2 GHz and the input frequency of 20 MHz is 11 bits. The FOM index of the proposed circuit is 0.61×10-6 (nJ/Bit.Samples).

This paper proposes a 2.4 GHz active mixer without passive inductor for the transceiver system. Taking into account the design requirements of the mixer, a double-balanced down-conversion structure with active inductor and negative resistance is designed. The proposed mixer with 130 nm CMOS technology is designed and simulated using Cadence software at 1.5 V supply voltage. Although we had to compromise conversion gain with linearity, we were able to achieve very high conversion gain with average linearity. Based on the results of post-layout simulations, the conversion gain of 27.57 dB, IIP3 equal to -7.88 dBm, 1-dB compression point equal to -17.34 dBm and IIP2 equal to 44.22 dBm with power consumption of 2.5 mW was obtained for the proposed mixer. The chip size without input and output pads is 95.18 µm × 117.68 µm, which leads to a chip area of 0.0112mm2.

Monitoring and evaluation of transformers are essential to prevent their insulation failure. In this paper, the use of 2-furan-carboxaldehyde (2-FAL) and methanol (MeOH) concentrations as the main products of paper insulation degradation, and insulation condition markers, has been studied. In order to study the degradation process and production of degradation products, the thermal aging process of the transformer insulation system was implemented in laboratory conditions. The results of laboratory studies show that in the early stages of degradation the amount of MeOH is significant compared to 2-FAL. Also, the estimation of the degree of polymerization (DP) in the early stages of degradation (DP>800) through MeOH concentration and with decreasing DP (DP <800) through 2-FAL concentration is closer to the real value. The results of studies performed on 35 distribution transformers confirm the production of significant amounts of MeOH in the early stages of degradation. Also, the estimated DP values for the studied transformers were obtained through 2-FAL and MeOH concentration. The results show that estimating the amount of DP through MeOH concentration is associated with a probability of error of about 9% compared to estimating DP through 2-FAL concentration.

Non-cooperative intelligent control agents (ICAs) with dedicated cost functions, can lead the system to poor performance and in some cases, closed-loop instability. A robust solution to this challenge is to place the ICAs at the feedback Nash equilibrium point (FNEP) of the differential game between them. This paper introduces the designation of a robust decentralized infinite horizon LQR control system based on the FNEP for a linear time-invariant system. For this purpose, two control strategies are defined. The first one is a centralized infinite horizon LQR (CIHLQR) problem (i.e. a supervisory problem), and the second one is a decentralized control problem (i.e. an infinite horizon linear-quadratic differential game). Then, while examining the optimal solution of each of the above strategies on the performance of the other, the necessary and sufficient conditions for the equivalence of the two problems are presented. In the absence of the conditions, by using the least-squares error criterion, an approximated CIHLQR controller is presented. It is shown that the theorems could be extended from a two-agent control system to a multi-agent system. Finally, the results are evaluated using the simulation results of a Two-Area non-reheat power system.

High gain Balun-low-noise-amplifier (LNA) is proposed for tuner of digital televisions (DTVs). The proposed Balun-LNA is based on CS-CG (common-source-common-gate) structure. To improve the isolasion and frequency response, Balun-LNA has cascode transistors before load resistors. Balun-LNA uses current-bleeding circuit to increasie transconductance of CS transistor, so that current-bleeding transistor has transconductance of N-1 times larger than transconductance of cascode transistor. Thereby, transconductance and current of CS transistor are increased N times, as N-1 times of current pass to current-bleeding transistor. Therefore current of CG and CS stages stay identical. Also, Balun-LNA employs a positive feedback to satisfy input impedance matching and CG transistor has higher transconductance. By increasing transconductance of CS and CG transistors, the proposed Balun-LNA achieves to high voltage gain. Accordingly, CG and CS tansistors have symmetrical currents and loads at the differential output of the proposed Balun-LNA. Symmetrical loads cause the balanced differential outputs. This proposed Balun-LNA is designed in 90-nm CMOS technology and covers the frequency range of 40 MHz to 1GHz. This Balun-LNA achieves the voltage gain of 22.6 dB, S11 of less than -10 dB and the Minimum NF of 5 dB. This Balun-LNA operates at the nominal supply voltage of 2.2v.