نشریه کارافن
سال هجدهم شماره 55 (پاییز 1400)

In addition to effects on the distribution network such as reducing loss, improving voltage profile, and increasing reliability, installing DGs can also indirectly affect the power system generation reliability. But unlike the transmission network, which is considered to be completely reliable when studying HLI level reliability studies, the distribution network, which contains most of the distributed power generation capacity, has high incidence, lower levels of automation, and radial structure that can lead to capacity closure. These units are crafted. Therefore, in this article, a method is proposed to combine the uncertainties of distribution network and forced outage rate of DG into “Equivalent Forced Outage Rate” or EFOR. Using this parameter, DGs can be moved from the distribution network to the sub-transmission bus to participate in forming the capacity outage probability table and calculating HLI reliability indices. The proposed method has a Single Contingency approach to distribution network events and therefore has a higher speed compared to methods such as Monte Carlo simulation.

Self-healing is used to automatically repair the distribution system in the event of a fault. One way to reduce without service customers is to operate the faulty area as an island. However, the island is formed optimally when the island is formed online after the fault. If the island is determined before the fault, the optimal margin of the island will not be formed and the number of customers without electricity might increase. In this article, island building is carried out online after the fault. One of the most important problems after a fault occurs is the quick solution of the problem. Since nonlinear models greatly increase the solving time, in the proposed method, the problem is transformed from a non-convex MINLP model to a convex model. As a result, the proposed model can be answered in a very short time. The second point in the problem of self-healing optimization is to achieve the optimal global solution. The optimization problem is carried out by the convex optimization method. Because in convex problems there is only one optimal, the proposed method ensures the achievement of the optimal global solution. A variety of dispatchable and non-dispatchable distributed generation sources were used. Load and production modeling was also undertaken in a probabilistic space because considering the uncertainty, it can be said that the proposed model can be resistant to such events. After determining the optimal microgrid, the optimal production of distributed generation resources and load shedding was carried out to balance the system power. The IEEE 33-bus system was used to demonstrate the efficiency of the proposed method.

Given the increasing importance of energy management, optimizing power generation systems and reducing their energy consumption are of great importance, particularly recognizing the parameters affecting the performance of these units. In the present study, ANSALDO unit was investigated as a combined cycle unit commonly applied in Iran. To this end, the ANSALDO unit of Yazd Combined Cycle Power Plants was modeled and analyzed. This was followed by obtaining the efficiency and production capacity of the power plant, determining the thermal balance of all power plant equipment and investigating the impact of effective parameters on gas and steam units. Based on the findings, each gas unit of this power plant had a thermal efficiency of 34% and a production capacity of 134 MW. When these units were coupled to the steam unit in the design, the total thermal efficiency of the power plant reached 50% and its production capacity reached 422 MW. An examination of the impact of effective parameters on thermal efficiency and production capacity showed that increasing ambient temperature decreased the thermal efficiency of power plant by 14%, which can be compensated by activating the evaporator system and total production by 10 to 15 MW.

This research paper aimed to design and manufacture a sample of motion recording gloves to measure angles and quantify the amount of vibration of the finger joints to obtain a suitable criterion for measuring the amount of hand vibration. This glove can record the intensity of vibration, and by connecting to a computer, it can provide motion and vibration signals in the form of diagrams. The device's hardware includes an ATmega32 microcontroller, an LCD, and six bending sensors used in gloves. The present research used LabVIEW software to show online charts. After repeated tests and optimization of the device, samples were taken from 13 people with hand tremors (patients) and 9 people without hand tremors (healthy). In this sampling method, patients were evaluated in three states of displacement, concentration, and position. After recording the samples, processes were performed to extract the hand movement signal diagrams and variables to differentiate between people in the best way. The classification performed in this study between the two groups of healthy and patients showed that experimentally this system had a difference of 2.5 to 3 times between patients and healthy people in 22 people using the average speed feature. This device will help physicians in clinical diagnoses. It was also found that the best diagnostic examination by this device occurs in the parameter of average speed and position.

In this paper, a single - axis satellite attitude control with reaction wheel actuator was analyzed in the presence of uncertainty and external disturbance. A proportional - integral - derivative (PID) controller was used to control when the control gains were achieved with evolutionary optimization algorithm. To increase robustness, robust optimization method was used in the presence of uncertainties and disturbances. In the robust optimization method, the statistical properties of the performance criterion, expected value and standard deviation were considered as the combined objective function of the optimization algorithm. For fair comparison, deterministic and robust optimization results were compared together versus uncertainties. Reaction wheel actuator was modeled with first - order equation and practical constraint in maximum and minimum generation momentum. Uncertainty was considered on moment of inertia, external disturbance, and reaction wheel with power spectral density function sampled with LHS algorithm. The graph of the mean value and performance criteria of the combined objective function shows small changes in the objective function in the face of uncertainties. Achieved numerical solution results indicated that the tuned controller with robust optimization performed better in the presence of uncertainties although tuned controller with deterministic optimization performed better assuming certain values.

One of the main challenges in island microgrids is the distribution of reactive power between distributed generation sources. The use of adaptive virtual impedance has been introduced as a method of improving the distribution of reactive power between distributed generation sources. Although the use of adaptive virtual impedance improves the reactive power distribution between the distributed generation sources and reduces the circulating current, it causes a voltage drop and the output voltage range of the distributed generation unit is reduced. In this paper, a control strategy for improving the adaptive virtual impedance method is proposed. In the proposed control strategy, the voltage drop across the output impedance of the distributed generation units is compensated due to the use of increased virtual impedance, and the load supply voltage is adjusted to the nominal value. The proposed control method, in addition to maintaining the advantages of using adaptive virtual impedance such as appropriate distribution of active and reactive capacities between distributed generation units and reducing circulating current, compensates for the voltage drop in the output impedance. In the proposed method, the output reference voltage of the drop control method is adjusted within the allowable range in proportion to the load change. To evaluate performance and efficiency, the proposed control method is implemented on an island microgrid consisting of two distributed generation units. The simulation results show the performance and efficiency of the proposed method.

One of the most important issues in image processing is to find algorithms that can determine the similarity and dissimilarity of a texture image with other images in a short time. Because texture images have repetitive patterns throughout the image, similarity algorithms for natural or non- texture images are not effective for texture images. Deep learning algorithms also require large amounts of data in the same group and for texture images that do not have much data volumes available, they do not work. In this paper, an algorithm was developed to rapidly search for tissue similarity using the Walsh-Hadamard transform. This algorithm consists of three steps. In the first step, the Gabor filter was used to extract the high-dimensional feature from each texture. Then, a randomized Walsh-Hadamard transform was used to convert high-dimensional feature from each texture into two-dimensional feature. In the third step, an earth mover distance (EMD) approximation algorithm was used to determine the similarity or dissimilarity between two textures that are represented by two-dimensional vectors. The results of the proposed algorithm proved that this approximation algorithm is relatively suitable for real tissues.

One The generation of sinusoidal voltage in terminal of synchronous generators is often non-sinusoidal due to the connection of non-linear loads to it. Under these conditions, the flowing current and voltage waveforms would considerably be affected. This would ultimately result in destructive effects such as increased losses, frequency fluctuations, reduced grid stability as well as reduced power quality of the load. Accordingly, this paper examines the various harmonic components and their impact on synchronous generators with conventional windings feeding nonlinear local loads. The consequences of the harmonic contents of the output waveforms by varying nonlinear loads were tested practically by implementing the single and triple layer winding synchronous generators. Then, the energy-saving lightbulb, the three-phase induction motor, and the incandescent lamp connected to the diode bridge (using power electronic components) were utilized as three non-linear electrical charges. Finally, the obtained results were evaluated by calculating the THD of the different states of the experiments performed on the two designs (three-layer winding design instead of one-layer winding). By comparing the experimental THD, the three-layer winding design was superior to the conventional one.

Marine simulators are effective tools for making a ship feel like driving by creating a similar environment using motion commands. The main problem with simulators is the limited workspace which does not allow them to generate accurate real-time floating movements, so they require a motion synchronization algorithm. Recently, the use of predictive control has become popular in marine simulators. Values of control horizon and future forecast affect the computational load. However, because the designer manually selects these horizons, they are lower than the optimal level. In this paper, a new method based on particle swarm algorithm was used to achieve the best control and forecast horizons by minimizing some periods such as sensory error, displacement and computational load. The proposed method eliminates the disadvantages of the MPC-MCA method such as time-consuming empirical estimation through trial and error for initial control and forecast horizons, while minimizing optimal cost performance and computational load. The simulation results showed the efficiency of the proposed method based on the improvement of performance output and computational load.

Using bidirectional parallel converters improves system reliability as they can bypass faults. Therefore, the bidirectional parallel converters structure is adopted for the DC micr ogrid connected to the grid. There is a circulating current between the bidirectional parallel converters that limits the overall capacity of the system and can damage switching devices. To solve this problem, in this paper, the mechanism of generating circulating current on the AC side when several bidirectional parallel converters work together was taken into consideration with the effect of constant power loads by the droop strategy Pdc-vdc2-f to share DC power and network frequency adaptation. The PI coefficients of the bidirectional parallel converters controller were optimized by online genetic algorithm and neural networks and updated with system conditions. Both the stable and dynamic relationships between Pdc and vdc2 are linear and did not create constant power loads of unstable poles for the system. The results indicated that compared with conventional idc-vdc droop control, the proposed Pdc-vdc2-f strategy can increase dc power control and system stability, consequently increasing the dc voltage regulation dynamics.

In the present work, the potential and capability of Iran's waters for acquiring and installing different types of wind turbines is discussed. For this purpose, various types of offshore wind turbines such as offshore float as the latest type of wind turbines as well as various types of base fixed offshore wind turbines were studied. In addition to reviewing the state of wind turbine technology in Iran according to oceanographic features, geographical coordinates, transportation costs and the possibility of assembly and ease of installation for the northern and southern seas of Iran, the amount of wind resources, water depth and available area were also taken into consideration. Based on the SWOT model, recommendations were made for the use of different types of turbines. In a part of the research, a comparison was made between Iran and leading countries in this field. For the Caspian Sea, the type of traction base of these turbines is not recommended due to the structural complexity, difficult installation and transportation and the need for deep water, while monopile structures and the third generation of gravity are suitable options for the shallow depths of lakes. In addition, near the southern coast of Iran, due to high tides and many changes in water depth during the day and night and the impact of the tension of the restraint lines of traction platforms, the use of this structure is not recommended. Due to the high depth of water in coastal areas and very good stability in various weather conditions, spar structures are introduced as a desirable option.

In recent years, intelligent control of entry/exit points particularly based on image processing extracted from surveillance cameras, has been developed. The information obtained from such systems is important for monitoring the traffic and passage of vehicles. It can play an effective role in maintaining public safety and obtaining traffic statistics such as counting traffic at the gates of cities, statistical estimation of clients to organizations, and detecting and tracking suspicious traffic. Vehicles that enter a busy organization are identified at the time of entry and exit and a traffic log including the vehicle image with the license plate number and the date and time of entry and exit are recorded. In this research, a new method for extracting the license plate area is presented. The proposed method uses a combination of Canny vertical edge detection method and examination of connected components to identify candidate areas for the license plate. Experiment results in real conditions (images were taken from surveillance cameras in the organization supporting this research) showed that the proposed method can identify the license plate area of different vehicles in different lighting conditions with accuracy and readability of more than 98% and presents better performance than other state of the art methods.

In clustering algorithms for wireless sensor networks, cluster heads close to the sink node usually encounter much more relay traffic and therefore lose energy rapidly. To address this problem in wireless sensor networks, distance-aware clustering approaches such as EEUC that adjust the cluster size according to the distance between the sink node and each cluster head have been proposed. However, the network lifetime of such approaches is highly dependent on the distribution of the sensor nodes because in randomly distributed sensor networks the approaches do not guarantee that the cluster energy consumption is commensurate with the cluster size. It might be necessary, for example, for sensors to be randomly distributed over the surveillance region (e.g., via aircraft). To solve this problem in wireless sensor networks, a new method called distribution based clustering algorithm (DBCA) was proposed in the present research which is not only aware of the distance but also the density of the sensor nodes. In DBCA, clusters have limited sensor nodes that are determined by the distance between the sink node and the cluster head. The simulation results show that DBCA is 25% to 45% more efficient than previous algorithms in terms of power consumption under different operating conditions.

In the present research, the non-uniform magnetic field effect on separation phenomenon in divergent channels was investigated numerically. The governing equations, including continuity and momentum equations, were presented and simplified for the laminar, steady, and incompressible flow; then, a non-uniform magnetic field was applied to the flow. Hence, the finite volume method using the OpenFOAM CFD toolbox was employed and a code for 3-D divergent channel flow under a non-uniform magnetic field developed. The effect of non-uniform magnetic field intensity on the boundary layer separation phenomenon on the divergent channel wall was investigated. The results show that the separation in the flow without applying a magnetic field occurs in Re=250 on the channel's upper (lower) wall. By applying the magnetic field and increasing the Hartmann, the boundary layer separation was delayed and in Ha equals 4, the separation is completely deleted and not observed. Under the same conditions, near the sidewalls, the separation occurs sooner than the channel entrance. Furthermore, by reducing the Reynolds to 208.33, the separation occurs late. In a 3-D channel that has a width ten times bigger than its height, the separation points far from the side walls are almost the same as a 2-D channel.

Tube hydroforming process is used widely in production of car structural parts. High strength to weight ratio is one of the properties of parts which is produced using this process. Low pressure tube hydroforming (LPTH) is one method recommended for solving problems of tube hydroforming such as requiring high pressure of fluid and sealing problems. LPTH method is similar to crushing a hollow solid body. Unlike high pressure tube hydroforming, upper die is not fixed in this process and it moves at the same time by applying internal pressure and squeezes the tube. Main defects in low pressure hydroforming are tube wall thinning and geometric errors at final form of the part. In this paper, LPTH of AA6063 aluminum tubes was carried out and circular cross section of tube was deformed to rectangular. Thickness distribution, formed corner radius and flatness of top surface of part was investigated under three different loading paths. Results show that lower corner radius can be achieved with higher internal pressure while thinning is increased. Maximum of flatness was obtained when moving of the upper die was carried out after reaching the maximum of internal pressure. Minimum of radius was formed at upper corner equal to 5.63mm and at lower corner equal to 5.62mm under internal pressure of 10MPa. Concavity of upper surface of part was decreased to 0.2mm by applying 10MPa internal pressure.

An ideal tire should be completely uniform in geometric dimension, mass distribution and stiffness coefficient. Under such conditions, the tire would rotate without any unwanted and harmful vibrations and/or force alterations delivered to the vehicle body as it moves. However, the ideal conditions are only theoretically possible and cannot be the case in actual conditions. Accordingly, a tire has some non-uniformities in actual conditions. This paper aims to study the lost energy of a non-uniform tire of a passenger car. To achieve this, the vertical force on the tire, which is due to initial loading and also each case of non-uniformity, was analytically calculated. Then, the equations were simulated in MATLAB software package. This was followed by comparing the frictional force between the tire and ground to the engine force to calculate the power loss. Finally, the value of power loss as a result of all kinds of tire non-uniformity was evaluated.

In this paper, the feasibility study of the production of PA6/NBR/Graphene nanocomposite by an internal mixer was investigated. The effect of nitrile and graphene content on modulus strength and hardness was studied by response surface methodology. Analysis of variance was used to study the effect of input parameters and mathematical models. The mechanical properties and microstructure were investigated by tensile test, hardness, and scanning electron microscopy. The comparison of the experimental results and response surface methodology results showed a small percentage of error. The results show that at the different percentage of NBR content, modulus strength and hardness increased with an increase in graphene content at 0 to 2 wt% and the maximum modulus strength (2354 MPa) and hardness (111 shore A) was obtained at the graphene content of 2 % and nitrile content of 20 %. At a low percentage of graphene nanoparticle, an increase in the NBR content lead to a higher decrease of modulus strength so that in graphene content of 0.5%, with increasing NBR content from 20 % to 40 %, modulus strength decreased from 2229 to 1859 MPa. However, for graphene content of 1.5 %, increasing the NBR content lead to decreases of modulus strength from 2354 to 2164 MPa.

The achievement of a desirable surface roughness with an efficient structure is a major challenge in machining of Polytetrafluoroethylene (PTFE) owing to its viscoelastic behavior. The aim of this research is to investigate the effect of gaseous coolants utilization on the roughness and structure of surfaces.  For this purpose, the effect of Argon noble and CO2 effective gases on the machining of PTFE were evaluated, taking into consideration the cutting and feed velocities as input factors. The surface roughness was measured by Ra criterion.  The microscopic structure of surfaces was investigated using optical and scanning electron microscopes. To measure the machining temperature, the operation was recorded by high accurate thermal camera. The results show that the utilization of CO2 due to decreasing local machining temperature to below -40°C can change the cutting behavior of material from viscoelastic to elastoplastic, and reduces the surface roughness up to Ra=0.2 µm. Microscopic studies indicate that the using of CO2 can govern the viscous behavior during cutting which causes the viscous-flowing of material and prevents the generation of surface cracks. CO2 also protects the surface from chemical interactions and creation of functional groups during the machining. Microscopic examination revealed that the use of carbon dioxide gas prevents separated chips from re-adhering to the surface.