فصلنامه روشهای هوشمند در صنعت برق
پیاپی 55 (پاییز 1402)

High step-up structures are commonly used to upgrade the low voltage levels generated by renewable energy sources. In this paper, a high step-up structure based on Quasi Z-Source network is presented, which has a simple yet functional structure consisting of two inductors and two capacitors. Due to the duty cycle of about 50% for this converter, the problems of reverse recovery of diodes and stability are solved. In addition, the common ground of the power switch and the input source simplifies the control circuit. Using the coupled inductor technique as well as the voltage multiplier cell, the converter voltage gain increases significantly. In addition, the stacked capacitor is used to limit the voltage stress on the switch. The use of the proposed structure increases the voltage gain of the converter. The proposed structure also reduces the level of voltage stress on the semiconductors of the circuit, which reduces the cost and increases the efficiency of the circuit. The converter designed with 25V/ 400V input/ output 100Wouput power is simulated in PSpice software and the results are presented.

In this paper, a sliding mode controller with an adjustable reactive power reference value is proposed. To improve the performance of the controller in a steady-state, an Integral Sliding Mode Control is designed and used. In addition, to improve the low-voltage ride-through capability in the fault condition, a reactive power controller with an adjustable reference value is proposed. The performance of this control system, during the power track, is compared with two other control systems that have a fixed reference for reactive power and are based on SMC and PI controllers in 9 different fault modes. These 9 different modes include one-phase, two-phase, and three-phase short circuit faults in the sub-synchronous, synchronous, and super-synchronous mode of operation for DFIG. The proposed method has been implemented in Simulink/MATLAB software. The simulation results confirm the capability and effectiveness of the proposed control system in comparison with two other aforementioned control systems.

Nowadays, the use of renewable resources has increased because of fossil fuel price growth, resource shortage, and environmental pollution. This study investigates a microgrid composed of wind and solar systems with battery storage sources and flywheel, diesel generator, and multi-carrier energy systems (MCH) as combined electricity and heat (CHP). The microgrid frequency is controlled based on the gas network and its consumption peak. In a multi-carrier network, the load distribution in the gas network is simultaneously considered with the electric charge distribution. Besides, the frequency is controlled nonlinearly. On the other hand, the growing trend of producing and using electric vehicles has generated new loads on the electricity network. In this regard, if these loads are not properly managed to charge them, the network’s frequency deviations will increase and cause the collapse of the electricity network.Therefore, electric vehicles (V2G) are considered in microgrid frequency tuning operations through ANFIS adaptive fuzzy control method. In order to compare the proposed method in the simulations, a fuzzy controller is used. The results of the simulations are examined in five studies that express the optimal performance of the proposed method in reducing frequency deviations, strength against disturbances and resistance Uncertainties in the system. The proposed method also has a more stable output power in microgrid production resources.

In this paper, an interleaved high step-up converter with a simple auxiliary circuit is presented. The proposed auxiliary circuit has the coupled inductor with the input inductors of the converter and provides zero voltage switching conditions for the main switches of the converter. On the other hand, auxiliary switches and diodes of auxiliary circuit operate under zero current condition and therefore do not impose significant losses on the converter. The auxiliary circuit is modular and can apply to more phases of the converter. Therefore, the converter can be easily designed for very high power applications. The proposed converter uses the cross-coupled inductors technique with series lift capacitors to increase the voltage gain and reduce the voltage stress on the main switches. Also, leakage inductance energy can be easily absorbed by the clamp capacitors and helps to increasing the voltage gain. The proposed high step-up converter has been analyzed in detail and a practical prototype has been implemented at 100W. The experimental results confirm the correctness of the operation of the circuit and the theoretical analysis.

In the islanded operation mode of microgrids, active and reactive powers sharing among sources is required. In order to provide this and based on decentralized approach, droop characteristics are used. The conventional droop characteristics of active power-frequency (P-ω) and reactive power-voltage (Q-V) are based on the assumption of inductive output impedance of sources. Since the dominant inductive output impedances are not provided, especially in low voltage microgrids, the virtual frequency-voltage frame droop characteristics, which include active power-virtual frequency (P-ωʹ) and reactive power-virtual voltage (Q-Vʹ) droop characteristics have been considered by researchers. By employing these droops, local property of both the virtual frequency and the virtual voltage leads to active power sharing error as well as reactive power sharing error. In addition, required small intended variation range of both virtual frequency and virtual voltage, results in big power sharing errors. In order to eliminate active and reactive power sharing errors, a decentralized control method is proposed in this paper. In the proposed method, instead of virtual frequency and virtual voltage of their terminal, sources droop virtual frequency and virtual voltage of point of common coupling (PCC) in order to a common parameter becomes in charge of active power generation as well as a common parameter becomes responsible for reactive power generation. Accordingly, the power sharing errors are resolved. Realization method of these droop characteristics will be explained in details. In order to confirm the performance of the proposed control method, simulation results of a test microgrid in PSIM software are presented.

The aim of this paper is to investigate the impact of second slot in stator tooth on performance of two commonly used rotor structures, namely Surface-type and Spoke-type, for a brushless direct current (BLDC) motor. The comparative results are reported for different closing slot conditions. Afterwards by inserting a direct current driven winding or permanent magnets (PMs) into the stator tooth slots of best performed model of previous stage, two hybrid-brushless direct current (HBLDC) motors are introduced and studied. The results demonstrated that slot-closing strategy has high impact on torque fluctuations while the torque produced remain almost constant. For HBLDC, the auxiliary Electro-Magnetic field, placed in stator slot, developed torque performance of the motors. The finite element method (FEM) is used in stages of study.

Standard PID controllers are one of the most desirable controllers for industrial automation and the most widely used control in feedback systems. However, linear controllers have limitations that represent tation controllers can be used to overcome these limitations. In this paper, a robust reset control based on optimal output feedback to control a robot with two degrees of freedom. In general, the behavior of reset controllers is similar to that of linear controllers, in other words, they are easy to implement. In this regard, in this paper, by introducing a special combination control called robust reset output feedback control, the disadvantages of the linear controller are eliminated and its main purpose is to reduce overexposure and increase the response speed and better stability of the controlled system. Therefore, this paper introduces a systematic method for reset optimal output feedback controller. To do this, an optimal output feedback controller is first designed without the reset action, so that the poles of the closed-loop system are located in a predefined area. This area is selected to ensure the stability of the exponential and the arrival time of the closed loop in a finite time. Then, the reset value at reset times is designed to minimize a cost-effective function for better performance. In this paper, for the first time, the reset value is specified only with the system output information and then the stability of the system will be guaranteed. The robot used in this article is a practical and industrial example that has two arms and two joints with separate control capability. The position and behavior of the arms based on the governing equations and mathematical relations indicate its direct effect on each other. Finally, to prove the proposed design, numerical simulation will be performed using Matlab software and a comparison between the proposed controller and a similar controller will be performed.

The supply of permanent electrical energy is of vital importance in modern life and its disruption can cause heavy damage to different areas in industry, commerce, transportation, sanitation and health, education, and management of the society. To prevent the network from short-circuiting to the ground, the amount of sag (drop) of the conductors must be within a standard range. Existing methods for sag measurement often require permanent installation of equipment - such as a camera, GPS receiver, and magnetic field sensor - on the line, the poles/towers, and/or around them. The method presented in this paper performs sag measurement based on a single image recorded from the conductor and poles/tow ers on its both sides. In addition, the distance between the two ends of the conductor from the camera needs to be measured using a laser rangefinder. First, the position of the two ends of the conductor in three-dimensional space is obtained with the help of rangefinder data. Then, from all the parabolas that pass through these two points, the one that best matches the visual observations and field assumptions is selected, and based on that, the three-dimensional conductor model is generated and the sag is calculated. The proposed measurement method can be done without interruption of the network and dangerous approach to the line and with the help of portable and inexpensive equipment. Evaluation on laboratory and field data showed that the proposed method is not sensitive to the shooting angle, works well in complicated backgrounds, and has an average error of less than 1% of the sag value.

In the modern era, the antennas with cosecant squared pattern play a significant role in radar applic ations. These applications are used to cover an airspace to search for targets and estimate their height. In this article, a method is proposed for the synthesis of cosecant squared pattern using leaky wave antenna. The principal mechanism in the leaky wave antennae is wave attenuation due to power leakage while the wave propagates through the structure. Thus, by controlling the leakage and phase constants along the length of the structure, one can synthesize the desired radiation patterns. We have used the genetic algorithm to optimize the leakage constant and obtain the desired cosecant squared pattern In the range of 10 to 30 degrees. Conformity in simulation results and measured results indicates accuracy in the design process. The proposed method obtains the desired pattern with a ripple of less than 2 dB in the designated area and side lobe level less than -18 dB, which makes the antenna suitable for radar applications.

Vehicular ad hoc networks are designed to provide safety and comfort for drivers and passengers. In these networks, many topological changes create many challenges for efficient data delivery. The data dissemination method can meet the needs of emergency message broadcasting. Disseminating data on these networks is a complex and vital task because the highly variable speeds of vehicles increase communication gaps. In these networks, fast and guaranteed high delivery of packets is essential. In this paper, a method is proposed in which the dedicated short range communication (DSRC) channel is divided into three different types of priorities for beacon messages. A dynamic receiver is defined for each class to broadcast the message. The technique of considering the intermediate condition between the source node and the sender node is used to prevent the broadcast of redundancy and the optimal use of bandwidth. The proposed method does not require any hardware or central controller. In order to analyze the efficiency, the proposed method is compared with ASPBT and aadaptive data dissemination protocol (AddP) methods. The analytical evaluation and simulation results show that our proposed method is superior to other methods in terms of efficiency.