نشریه فناوری های نوین مهندسی برق در سیستم انرژی سبز
پیاپی 4 (زمستان 1401)

Multi-input converters have different structures. These converters can be used in applications of power systems based on wind, photovoltaic, hybrid vehicles, etc. In a multi-input system, usually one of the inputs is connected to an AC source. Also, these converters use soft switching techniques to increase efficiency. In this paper, a non-insulated dual input soft-switching boost converter with power factor correction capability is proposed. This converter uses only an auxiliary circuit with simple operation. The operation modes of the proposed converter are described. All of the semiconductor elements in this converter turn on and off in soft switching conditions. The proposed controller circuit is presented with power factor correction capability. The converter is simulated with PSIM and THD and PF shows that the power factor correction in AC input is occurred correctly. The efficiency of the proposed converter is increased in comparison with the multi-input hard switching converter under the same conditions. The simulation results with PSpice for a 200-watt prototype converter confirm the theoretical analysis.

In this paper, we designed and simulated a new TFET. Due to the band-to-band tunneling current mechanism, the TFETs show a low current and subthreshold slope of less than 60mV/dec. As a result, they can be a suitable alternative to MOSFET for use in low-power switching circuits. But its main disadvantage is its low on-state current compared to MOSFET. In this article, an optimized two-gate-two-material tunnel transistor structure is proposed in which the tunneling rate of carriers increased by adding two regions with inherent impurity compared to the common two-gate TFET structures. We simulated the proposed TFET in two dimensions using Silvaco-Atlas software and analyzed its results. The results are as follows: the on-state current (Ion=5.49×10-6A/µm), off current (Ioff=2×10-18A/µm), Subthreshold slope (SS=15.02mV/dec), and the Ion/Ioff =2.74×1012. The calculated results show the improvement of the DC parameters of the device.

The use of electric vehicles is expanding as one of the essential solutions to reduce greenhouse gas emissions and save gasoline fuel consumption. Therefore, the modern transportation industry in many countries is changing and evolving under the influence of electric vehicles' economic and environmental benefits. To accelerate the process of this evolution, proper design and development of the charging infrastructure are crucial. In addition, equipping charging stations with renewable energy sources and managing the intermittent nature of the production of these sources can lead to the improvement of environmental goals. The design and development of the charging infrastructure and the increase in electric vehicles bring various challenges to the power and transportation networks. In this regard, it is essential to provide appropriate solutions for various key issues such as congestion management, determining the location and optimal capacity of charging stations, and managing charging demand, considering both networks' requirements. This paper comprehensively discusses the latest achievements and significant developments in this fascinating and rapidly developing research area by introducing the objectives, methods, and data used. By highlighting the existing challenges, we pave the way for revealing research gaps and helping researchers address the problems.

Machines with permanent magnet excitation have higher efficiency and more reliability than machines with electric excitation. Among the permanent magnet machines, the crossover machines have a higher ratio of power to volume and electric torque to volume, so that at the same power, their size is smaller than the usual permanent magnet machines. And this is the reason why researchers have paid attention to crossover machines in recent years. Cross-phase generators can be made with a smaller pole pitch than other machines. These features make these machines have a higher power density than other permanent magnet machines. The copper winding of the crossover generators is simple, and their passive copper winding is considerably less than other machines, so the mass of active materials required to produce power and electric torque can be less than other machines. In other words, a smaller volume of active materials per unit of electric torque can be obtained by these machines. Therefore, this generator creates high power and torque by creating a large number of poles and a small pole pitch, and it can be a suitable option for use in the production of electrical energy from wind power, especially at low wind speeds.  The lack of a suitable dynamic model and the application of this generator, dynamic modeling and simulation, are necessary to analyze its performance under different conditions. Therefore, this article presents a dynamic model for this generator to be connected to the wind turbine, and then simulates the wind turbine based on this generator by simulating the turbine-generator system.

In recent years, the Internet of Things (IoT) networks have extensively been used in various practical field, one of the most important of which is medical Internet of Things (MIoT). In these networks, radio frequency identification (RFID) is one of the main technologies in creating an authentication system that is able to efficiently identify and identify medical equipment and patients. Therefore, researchers in this field have proposed different authentication protocols for RFID-based MIOT systems and claimed that they are resistant to active and passive attacks. Contrary to their claims, most of these protocols are not resistant to conventional attacks. Fan et al. have recently proposed a lightweight RFID authentication scheme for cloud-based RFID health-care systems and claimed that it is sufficiently efficient and secure. In this paper , we analyzed the Fan et al protocole and demonstrated that their protocol is vulnerable to replay, reader impersonation, tag tracking, and de-synchronization attacks. Moreover, we show how the similarity of some of their protocol messages causes attack. Then, we propose an improved protocol (LRAMP) that is resistant to these and other known attacks in RFID authentication protocol. According to security analysis, we can see that the LRAPM protocol has a high level of security. This high security can only be achieved by adding a new message and changing other messages. A comparison of the performance of the LRAPM protocol shows that this protocol is comparable to similar protocols in terms of computational costs, storage costs and communication costs.

Maintaining the voltage profile of the power system within the appropriate bound has been a key factor for the proper operation of system equipment, especially during disturbances. However, due to the uncertainty of the load powers and the limitation in equipment ratings, achieving this goal has become a challenge. High voltage substations play an important role in voltage control, because these substations can be a primary connection point between the high voltage transmission network and the distribution system. The nature of local voltage control, the variety of control tools and the interaction between them, have made this type of control difficult. In this paper, a centralized voltage/reactive power control method is presented based on phasors measured by PMUs installed in grid substations. In this method, the tap changing of transformers and step switching of capacitor banks have been determined by the central controller based on system voltages and network equations. In addition, the appropriate values of the operating point of the generators have been carried out based on economic dispatch in each period of optimization. The consistent and efficiency of the proposed method have been investigated through simulation in MATLAB software environment.