فصلنامه روشهای هوشمند در صنعت برق
پیاپی 60 (زمستان 1403)

This paper presents a fully differential operational transconductance amplifier (OTA) based on the dynamic threshold-voltage MOSFET and floating gate MOSFET (DT/FGMOS) inverter with a supply voltage of 0.5 V. The proposed inverter in the structure of this OTA is a combination of the dynamic threshold-voltage MOSFET (DTMOS) technique (for all PMOS transistors) and the floating gate MOSFET (FGMOS) (for all NMOS transistors) in n-well process. In this circuit, feedforward and feedback paths have been used to limit the common-mode gain. The first stage has feedforward paths to eliminate the common-mode and the second stage has the common-mode feedback to stabilize the common-mode output voltage on Vdd/2. Based on the post-layout simulation results, the proposed OTA showed a gain of 61 dB with a unity gain frequency (UGF) of 1.1 MHz under 13 pF load capacitors. With the studies performed by Monte Carlo analysis, it was found that the OTA based on the proposed inverter can perform well under process variations and device mismatches. The proposed circuit in 180 nm CMOS technology occupies an area of ​​0.182 mm2 from the chip. Its power consumption is 17 µW and it can be used in low voltage and low power applications including portable equipment. According to studies, the use of DTMOS and FGMOS techniques can lead to the effective reduction of the threshold voltage of transistors and the good performance of the proposed OTA at low voltage.

Since the electricity consumption’s prediction is one of the most important aspects of energy manage ment in each country, various methods based on artificial intelligence have been proposed to manage it. One of these methods is Artificial Neural Networks (ANN). To improve the performance of ANNs, an efficient algorithm is necessary to train it. Back Propagation (BP) algorithm is the most common algorithm employed in training ANNs, which is based on gradient descent. Since BP may fall in local optima, it cannot provide a good solution in some problems. To overcome this shortcoming, optimiz ation algorithms like meta-heuristic algorithms can be applied to train ANNs. In this study, a new meta-heuristic algorithm called Red Kite Optimization Algorithm (ROA) is introduced, which is inspired by the social life of red kites in nature. The ROA has several advantages such as simplicity in structure and implementation, having few parameters and good convergence rate. The perfprmance of ROA is compared with some recent metaheuristic algorithms on benchmark functions of CEC2018. Also, it is employed to train Multi-Layer Perceptron (MLP) for the electricity consumption prediction at peak load times in Iran. The results show the good performance of proposed algorithm compared with competitor algorithms in terms of solution accuracy and convergence speed.

Telecommunication networks are certainly one of the cornerstones of the modern information society and one of the main drivers of the economy and provide a basis on which many daily activities can rely. Also, new technologies such as the Internet of Things, artificial intelligence, self-driving cars, 5G, etc. will not reach their full potential unless an infrastructure communication network meets their needs. Security is critical to their infrastructure and services. On the other hand, the development of quantum computing technology in recent years and the construction of quantum computers with very high processing power and solving very complex problems faster than current computers has made cybersecurity, computer security and communication devices a vital and important issue for governments. However, with the advancement of quantum technology, these threats can be prevented by using quantum methods to distribute keys, so quantum cryptography is considered as an alternative to classical methods against quantum computers and cyberattacks. Quantum key distribution is the most popular sub-branch of quantum cryptography, and commercial examples are now available in the market. However, the implementation of quantum key distribution networks in fiber optics, which is discussed in this paper, is one of the solutions that provide unconditional security through quantum cryptography to establish secure communication. The distinguishing point of this article is to provide an overview of the latest research in the field of implementation of quantum key distribution networks in fiber optics. In addition, the quantum key distribution networks implemented in the world are reviewed and compared and the approach of different countries in this field is studied.

Fire is one of the dangers that can endanger human health in a short time and if it is not controlled in time, it will cause a lot of damage. Therefore, timely and accurate identification of the location of the fire can prevent the consequences of its expansion. In this research, a new method for fire detection is proposed based on the extraction of its temporal-spatial features in video frames. In the proposed algorithm, a multiscale convolutional neural network along with a YOLO (you only look once) network is used to extract spatial features and identify fire candidate regions. Then, fractal analysis based on the temporal blanket method is then used to remove non-moving textures similar to fire and to examine the temporal features of the candidate region. Finally, the fire region is separated from the other parts of the image by fusion the results of the two steps. The evaluation results of the proposed method on three data sets show that the accuracy of fire detection is about 96.1%, while the precision and recall values are 92% and 96.9%, respectively. Experimental results show that the proposed method performs better than existing algorithms and thus confirms the ability of this method for efficient use in the real world.

Interference Alignment is an efficient method of reducing interference in wireless networks, which can be used in radio cognitive networks. In the interference alignment, a suitable pre-encoder matrix will be found in each transmitter that all interferences are limited to a part of the signal subspace in each receiver, which causes the desired signal to be placed in the other part. Therefore, the desired signal can be easily received by a suitable interference removal filter. In this paper, an efficient method for using interference homogeneity in a cognitive radio network is presented. In the proposed method, the selection of radiation vectors for the formation of selection vectors based on adjacent vectors is done in equal steps. Selecting equal steps improves the convergence speed of the algorithm. The results show that computational efficiency and complexity have been greatly improved. To evaluate the proposed method of power allocation in the network, they are evaluated to maximize the network energy efficiency and the other to maximize the total rate of the cognitive radio network while keeping the initial user rate at the threshold level. The simulation results reveal the improvement of network performance using this method in both strategies.

Employing capacitance multipliers in low-frequency integrated circuits has a significant effect on reducing the chip size area. The main idea behind the proposed circuit in this paper is to use a folded current follower (FCF) structure to effectively reduce the equivalent series resistance (ESR) in the input stage. Furthermore, using an auxiliary circuit to adapt the bias current of the transistors and applying the necessary signals by the quasi-floating gate technique (QFG), are other approaches employed to reduce the static power consumption while properly increasing the linearity of the proposed circuit, which can be considered as other benefits of the proposed approach. On the other hand, to improve the linearity, negative feedback is used and necessary voltage is applied to the gate of the transistors in the current sampler. The “K” coefficient can be adjusted by the active method. Low input resistance and high output resistance as well as the reduced occupied silicon area are achieved based on the simulation results of the proposed circuit. The simulation results in 0.18 μm technology show that, with a 0.8 V power supply and base capacitor (Cb=1 pF), for 850 nW power consumption, a capacitor equivalent to 204 pF is achieved in the proposed approach. As another example, to realize the 101 pF capacitor with the supply as mentioned above and base capacitor, the proposed multiplier requires 6.3 times less area and 23 times more bandwidth than FCF, which shows the increased accuracy of the proposed design. In the proposed circuit, in the presence of a current adaptive circuit with an input signal range of 7 nA, the output current range is obtained as 1510 nA, While the output bias current is 100nA and the harmonic distortion value is obtained as 3.6%. The proposed circuit has the highest figure of merit 42.823 MHz/μW, which shows superiority in overall performance in comparison with other reported designs.

This paper proposes a new fuzzy control for photovoltaic static compensator (PV-STATCOM) system in order to improve voltage stability. The task of proposed system is the dynamic voltage control of a solar PV system connected to load bus in different operating modes as STATCOM and/or PV active power generation. In this strategy, in case of perturbation, the proposed fuzzy controller by detecting it and considering the severity of disturbance, when there is no or insufficient remaining capacity of the inverter to compensate the reactive power, stops the active power production of the PV solar system, and then the entire capacity of the inverter is used as a STATCOM to regulate the voltage at the load bus. Then, after fixing the problem, the system returns to the active power generation mode as before. To evaluate the performance of the proposed fuzzy controller, different modes are simulated with EMTDC/PSCAD software to prove the ability of the controller to improve the stability of the power system. The results confirm that the PV-STATCOM with the proposed controller can improve the dynamic performance of the system.

In general, the basis of operation of most fault current limiters is to reduce the short-circuit current by adding a large impedance to the system at the time of the fault. However, fault current limiters differ in the type of impedance and how the impedance adds and removes the system. In this paper, taking into account three different locations for installing fault current limiter in a sample power network, as well as changing the type (inductance or resistance) and its impedance value in an extensive range, the effects of these parameters on the stability of the power system have been investigated and analyzed. The criterion used for the first time in this article by the authors to examine and evaluate the transient stability of the power system is the method of the difference between the accelerating and decelerating area. The basis of this method is based on the equal area criterion. Other issues addressed in this paper are presenting a method for locating and determining the optimal value of fault current limiter impedance to improve the stability of the power system. Also, the effect of fault clearing time on transient stability has been studied when the fault current limiter is present in the power grid.

Unbalanced loads in the distribution grid can cause unbalanced supply voltage and reduce the power quality of the system. Besides, reactive power loads might create the voltage disturbances such as voltage sag/swell. In this paper, a four-wire distribution static synchronous compensator (DSTATCOM) integrated with Yy-transformer to compensate both the unbalanced voltage and reactive power is proposed. A DSTATCOM based on modular multilevel converter (MMC) connects to the group of taps in the primary windings of Yy-transformer to constitute an interconnected structure. The compensating currents flow through the taps. This structure is similar to an autotransformer. Compared to the conventional MMC-DSTATCOM, with proposed structure, The DSTATCOM connection point voltage decreases and one can trade-off between the capability of the power device's rated voltage and current. Therefore, it can be decreased the primary investment costs, the voltage stresses and the size of compensation system. Furthermore, a control algorithm based on measuring the point of common coupling (PCC) instantaneous voltage and current is presented that it is able to compensate the zero and negative sequence voltage due to unbalanced laod and grid. To compensate these components, voltage and current loops are used to track accurately the reference voltages of MMC-DSTATCOM by means of unbalanced algorithm. Simulation results verify the proposed method.

This paper presents a multi-objective optimization model for optimal placement of fixed capacitors and voltage regulators to manage the voltage profile of radial distribution networks, in which the realities of the distribution network of Ahvaz city (as representing the tropical regions of southern Iran) are considered. The objective functions include minimizing the investment cost, minimizing the sum of absolute value of the node’s voltage deviations from 1 p.u., and minimizing the cost of energy losses on the planning horizon. The optimization model is formulated by considering two different load patterns according to the warm and temperate periods of the year in Ahvaz city. The loads are modeled as a combination of constant power and constant impedance components and the share of each component in the warm and temperate periods of the year is considered in accordance with the actual conditions of the Ahwaz power distribution network. The cost of energy losses as well as the final profit of the project is calculated based on the current rules of Iranian power market for active and reactive powers. The optimization problem is solved using multi-objective non-dominated-sorting genetic algorithm-II (NSGA_II), and in order to choose the best answer among none-dominated Pareto front, a selection index is introduced. The proposed model is implemented on two 33 kV test feeders (i.e., a 33-bus test feeder and a real 123-bus feeder from Ahvaz distribution company) and the results are analyzed.