فصلنامه روشهای هوشمند در صنعت برق
پیاپی 46 (تابستان 1400)

Path planning of mobile robots is one of the important issues in the field of robotics. Also, optimizing the path length and crossing the local minima traps are the basic and up-to-date challenges in this field. One of the important methods in path planning of these robots is the artificial potential field method. Because it is based on simple mathematical calculations. One of the most important disadvantages of this method is getting trapped in local minima situations. One approach for solving the problem of local minima is to use optimization methods to find suitable coefficients (attractive and repulsive) and step length that can solve local minima and optimize the path length. The Harris Hawks algorithm is a powerful and new meta-heuristic algorithm in the field of optimization that is based on population and inspired by the life of Harris Hawks in nature. This algorithm has been able to prove its superiority over similar optimization methods in finding the optimal solution, faster convergence, lower computational time and not trapping in local minima. This method has not been used in the path planning of mobile robots. In order to eliminate the disadvantages of the artificial potential field method and to optimize the path length, the Harris Hawks algorithm has been used in this paper. The simulation results showed that the combination of the artificial potential field method and the Harris Hawks algorithm can solve the local minima problem and optimize the path length, increase the path efficiency and reduce the convergence time.

The presence of the inverter distributed generations in the power systems can bring about incoordination in the protection system performance while enjoying various advantages. In this paper, a suitable solution, independent of relay settings, is presented in order to solve the protection problems of inverter island microgrids with circular arrangement. The presence of distributed inverter generation sources causes a change in the direction and amplitude of the fault current at the microgrid level. This problem is more visible in microgrids with circular arrangement. Therefore, conventional protection schemes that consider a single path and a high fault current level compared to load current may be problematic. An important factor for the proper design of a protective system for microgrids is the contribution of the injecting fault current of the inverter sources. In this paper, a protection strategy based on the inverter control of sources is presented and ordinary overcurrent relays with the same characteristic curve are used. When a short circuit fault occurs in the microgrid, an adaptive current limiting strategy is applied using the virtual impedance loop. In this case, the share of fault current of each source is controlled according to the position of the fault, and sources closer to the fault produce a larger fault current. Therefore, the current passing through the protective equipment is closer to the fault than other equipment in the micro grid. And without the need for making connection between protective equipment, the protective coordination is guaranteed.

Today, solar arrays, fuel cells and wind energy are highly regarded as sources of clean energy. These sources can deliver their energy to the grid or directly to the consumer. Usually the voltage level produced in these sources is low and the need to increase the voltage level is. To solve this problem, high voltage gain converters can be used as single-port and multi-port. In the proposed converter to increase the voltage gain, the voltage multiplier circuit, the switched inductors and the switched capacitor are used, and also the clamp circuit is used to solve the problem of energy stored in the leakage inductor. One of the features of this converter is to share the components of the converter in different modes. This is important to reduce the number of semiconductor elements in the construction of the converter. In the proposed converter, the power transfer can be from solar array to load or from solar array to battery or both. Also, in peak moments, solar array and battery consumption can provide load power at the same time. In this paper, theoretical analysis has been used to evaluate the performance of the proposed converters and the results of the converter simulation in Orcad software have been presented to evaluate the accuracy of the theoretical analysis. Finally, a laboratory sample of the proposed converter with a power of 200 watts and a frequency of 100 kHz has been implemented,

The multi-path transmission is an appropriate transmission method for high data rate packets like video streaming. To provide video streaming with high quality, the video packets are divided into different frames for transmitting through various paths. Nevertheless, regarding the results of numerous inherent features of vehicular ad-hoc networks (VANETs), designing an efficient and stable routing protocol is difficult for various applications of VANETs. In particular, the dynamic nature of topology and intermittent connectivity make maintaining the quality of service (QoS) task very difficult. To provide QoS to entertainment applications and traffic safety in VANET, we offer a routing protocol based on the adaptive intersection with QoS support regarding delay, packet delivery ratio (PDR), and connectivity probability. To establish the best QoS routes, we considered the equivalent routing problem as the optimization problem and then proposed an algorithm based on ant colony optimization (ACO) for solving it. Furthermore, a fuzzy logic-based algorithm was employed to select the best next-hop vehicle by incorporating multiple metrics associated with the vehicle’s position, link quality, and vehicle mobility. According to the simulation results, the proposed approach achieves the average PDR of more than 84.2%, the end-to-end delay of less than 3.58 s, the overhead of less than 15.65%, and the peak signal to noise ratio (PSNR) of more than 20.82 dB. It is understandable from the result analysis that the performance of the proposed approach is excellent.

Human life and the economy of a country are becoming more and more dependent on electricity. However, events that occur due to various factors in the power grids, affect the quality of electrical energy delivered to subscribers. The human error of maintenance teams is one of the most important causes of automatic outputs of electrical equipment. Human error, in addition to the economic consequences of not transiting electrical energy due to equipment outages, may also cause health damage to personnel. The purpose of this study is to propose a method for analyzing the human reliability of maintenance teams in power transmission grids, which has been implemented as a case study on power transmission grids teams in Fars. The first step is to identify the roots of human error. So far, no comprehensive studies have been conducted on the root causes of human error in power transmission grids. Therefore, in this article, the actual and potential roots of various aspects such as organization, individual moods, supervision, etc. are identified and predicted in the framework of the method of human factors analysis and classification system. Then, a method is proposed to estimate the probability of the root event to use its results to prioritize the necessary control and corrective measures to reduce human error.

In recent years, low-power transceivers have found wide applications in medical engineering. In this paper, the system design and simulation of a low-power implantable receiver are presented for the case of stimulating brain cells. The receiver shows a high data rate in the industrial scientific and medical (ISM) band for being used in a bidirectional wireless full-duplex link and communication between the implanted system and the outside world. The proposed receiver has a non-coherent structure and operates at a frequency of 2.4 GHz with on-off keying (OOK) modulation. This receiver has a bit error rate (BER) of less than 0.001 and a data rate of 100 Mbps. The simulation results of the proposed circuit show a 26.4 dB gain (S21), a -39 dB input return loss (S11) and a 5.22 dB noise figure (NF). The simulation results are in good agreement with the analytical calculations.