مجله مهندسی برق و الکترونیک ایران
سال پانزدهم شماره 4 (زمستان 1397)

Reliability of gas turbine power plant is related to the blade normal operation. In this paper, a new on-line condition monitoring method has been presented to evaluate two important factors affecting the turbine blades that are the tip clearance and tip deformation.
A K band’s microwave sensor has been simulated and optimized in CST Microwave Studio software. Scattering parameters of the near field sensor has been used as a finger print for the turbine blade. A set of measuring indices has been introduced to compare the amplitude and phase of the scattering parameters and received power. The simulation results show that the proposed indices can effectively detect deformation of the blade tip and tip clearance extent can also be estimated.

Monopulse radarsare one of the most accurate tracking radars used to guide various platforms. Detection and tracking of surface targets with these radars are performed in order to point strike targets. Sea clutter presents challenges for detecting floated targets and in addition to affecting detection height, it can cause errors in monopulse angle finding. In this paper, the airborne monopulse radar with high squint angle has been considered. The radar platform has a curved path. Under conditions of ragged sea, sea clutter has been modeled with k distribution and simulation of return signal from sea surface with big size targets has been performed for the first time. Also, we have analyzed the detection heights in various platforms grazing angles in this paper. The results indicated that by increasing the grazing angle, the height of detecting floated targets decreases due to the increase in the clutter power in comparison with the power of returned signal from targets. Due to the significant changes in the simulation parameters of sea Clutter at the angles i.e. gamma function and Omega parameter, the novelty of this paper is simulation of the sea clutter in range and in high grazing angle (55 to 75 degrees), which has not been reported literatures. Sea clutter simulation using the cumulative distribution function (CDF) k is another novelty. Detection of moving target on sea surface with given curved path of the radar platform and real parameters for the simulation have also been performed for the first time.

In this paper, using theory of sheets, the deflection of suspended diaphragm has been obtained under uniform and circular loading. This type of diaphragm, unlike other diaphragms, has a central support which is recommended to be used in MEMS applications. The relationship between diaphragm deflection and static analysis of this diaphragm enjoys a great significance in investigating and understanding its behavior and calculating its other practical parameters both in dynamic and static fields. Here, using the thin sheet Kirchhoff-Law theory these issues are addressed. The results of analysis and simulation have been compared with each other, representing the 1% accuracy of the obtained statements, suggesting accuracy of the obtained results. The results show that the suspended diaphragm has greater deflection compared to simple flat diaphragm, which is considered important in sensors and micro electromechanical devices.

An efficient resource allocation is important to guarantee the best performance with a fair distribution of multi-beam satellite capacity to provide satellite multimedia and broadcasting services. In this way, available bandwidth and capacity problems in new satellite system likes Multi-Input-Multi-Output (MIMO), exploring new techniques for enhancing spectral efficiency in satellite communication has become an important research challenge. In this aspect, multi-beam or frequency reuse can be considered as a promising solution to solve spectrum scarcity problem. In this paper, a new bandwidth sharing algorithm for satellite systems under multi-beam technique is proposed. Furthermore, by using the above framework, capacity of multi-beam satellite system based the number of antenna was simulated and compared them to obtain a solution for designing the next generation satellite systems. Therefore, by using the multi-beam and multi antennas satellite parameters considered in the first step, the bit error rate was achieved by 4-QAM and 4-PSK modulations based on the number of antennas.

In this paper a new patch-based digital signature (DS) is proposed. The proposed approach similar to steganography methods hides the secure message in a host image. However, it uses a patch-based key to encode/decode the data like cryptography approaches. Both the host image and key patches are randomly initialized. The proposed approach consists of encoding and decoding algorithms. The encoding algorithm converts the characters stream of the secret message to the patches stream of the DS image. The final image is further distorted by noise to hide the source patches. Nevertheless, the decoding algorithm uses a similarity measure to decode the DS image. Experimental results demonstrated that it is significantly robust against noise. The proposed approach has been successfully used for digital signature generation/verification and software copyright protection

Nowadays, the usage of load emulators, is the best method for implementation and analysis of different electrical load change scenarios in laboratories. This paper presents an improved programmable load emulator which can emulate both reference active and reactive power simultaneously. The proposed control system can track the dynamic load changes rapidly and accurately in addition to pulse change emulation. So it is completely suitable for both dynamic and transient stability analysis. The emulator topology is made up of an inverter and a buck converter. Simple PI controller because of its coefficients dependence to operating point is not suitable especially for this application in which the operating point is constantly changing in a wide range. The usage of a Feed-Forward controller for grid side inverter increases the DC bus voltage stability and on the other hand the usage of the hysteresis current controller for buck converter improves the rate and accuracy of the reference active power tracking. Simulation results in SIMULINK verify the performance of the proposed control system.

Multilevel inverters have been developed due to limitations of the conventional two-level voltage source inverters (VSIs). Most of the topologies of multilevel inverters that have been presented in the literature are based on the sharing of the rated voltage between the switches so that the switches with lower voltage ratings can be used. In these topologies, the current rating of all of the switches is equal to the rated output current. Therefore, they may have limitations in high-current application. Recently, the coupled-inductor based multilevel inverter topologies have been presented to overcome the mentioned problem. In these topologies, the current rating of the switches is lower than the rated output current. In other words, these topologies can increase output current in comparison with the switches current. In this paper, a new generalized coupled-inductor based multilevel inverter is presented. The proposed topology consists of various coupled cells and can be extended to any number of voltage levels. This gives the generality and design flexibility for the proposed topology. If cells are used in the proposed topology, the switches operate at the rated current equal to of the rated output current. This shows a considerable in the switches current ratings. The number of voltage levels can be increased so that switches with lower current ratings can be used and at the same time, the quality of output voltage and current improves considerably. For the proposed topology, the pulse width modulation (PWM) method is also presented. The simulation results of the proposed 9-level inverter (in both single-phase and three-phase conditions) are presented to demonstrate the performance of the proposed topology.

A non-isolated DC/DC converter with high transfer gain is proposed in this paper. The presented converter consists of the switched inductor and three-level converters. The DC/DC power converter is three-level boost converter to convert the output voltage of the DC source into two voltage sources. The main advantages of DC/DC converter are using low voltage semiconductors and high gain voltage. The steady-state operation of the suggested converter is analyzed. A prototype is developed and tested to verify the performance of the proposed converter. To sum up, the MATLAB simulation results and the experimental results have transparently approved high efficiency of proposed converter as well as its feasibility.

The growing rate of energy consumption is a reason for establishment of new power plants which leads to increment in fault current level. One of the solutions to overcome this problem is utilization of fault current limiters (FCLs). Another concerning issue in energy generation is the satisfactory voltage quality in grid and to deal with it, a power electronic based device, known as dynamics voltage restorer (DVR), is introduced. However, in power grids FCL and DVR are independent devices. In this paper, a novel topology is proposed which linking DVR and FCL, provides substantial benefits. According to grid state, the DVR-FCL has four operating modes. Moreover, for appropriate operation of the presented topology, a suitable control method is proposed. The DVR-FCL and the control method are verified considering the simulation results.

In this paper, a customer incentive scheme is proposed for retailers to build an effective demand response program over the peak demand period to minimize the financial risk. Firstly, an objective function is formulated based on the market operation and an optimal incentive price is derived from this objective function. Secondly, the incentive price is employed as a part of an incentive scheme to encourage customers to reduce their electricity demand to a certain level during peak hours. Two typical customer response scenarios are studied to investigate the impact of customer response sensitivity on the loss of utilities’ and customers’ profit. Finally, a dataset for the state of New South Wales, Australia is employed as a case study to examine the effectiveness of the proposed scheme. The obtained results show that the proposed scheme can help to improve the elasticity of demand significantly thereby reducing the associated financial risk greatly. Moreover, the proposed scheme allows customers to get involved voluntarily and maximize their profits with minimum reduction of their comfort levels.

This paper provides a novel hierarchical control for VSI-based microgrids. The advantage of the provided control scheme is to maintain the frequency and voltage stability and load sharing against large-signal disturbances. A hierarchical control, consisting of three levels, is described. A new control loop based on PI controller, is presented. The new control loop has a great impact on increasing the stability margins, by moving the poles. In next steps, secondary and tertiary control levels are described. Then, the voltage droop equation is improved by a fuzzy controller. This controller generates a floating reactive power reference value, by a fuzzy logic. The role of floating reactive power reference value is to compensate the drastic changes in the voltage amplitude by changing the reactive power reference value. To verify the performance of the provided control scheme, a microgrid including four VSI-based DGs is simulated in islanded and grid-connected modes, by MATLAB/ SIMULINK. The simulation results show that the micogrid can maintain the frequency and voltage stability, in term of large-signal disturbances such as 3-phase and 1-phase short circuits. With this method microgrid load sharing is not altered after disturbances.

After occurrence of some disturbances in power system that causes the sever imbalance between generation power and electrical load, the power system frequency begins to decrease. To prevent power system frequency instability and stop the frequency decay below the power system allowable frequency limitation, load shedding schemes should be utilized by applying under frequency load shedding relays. In this paper, power system behavior is modeled as a mathematical mixed integer programing (MIP), moreover the parameters that are required for UFLS relays setting are determined optimally in order to minimize the load shedding amount throughout power system in compliance with certain restrictions. The obtained results have been verified by Simulation studies.

This paper proposes a methodology for practical siting and sizing of Hybrid energy systems (HESs) consist of: wind turbine (WT), photovoltaic (PV) and combined heat and power (CHP) units. In this method, the interaction of Plug-in Electric Vehicles (PIEVs) in the electric distribution system is considered. Electric Vehicle are seen to have some negative impacts on electric distribution system performance, such as increasing power losses, voltage variations and even customer energy prices. An important issue is that high penetration of electric vehicle (EVs) brings heavy electricity demand to the power grid. One effective way to alleviate the impact is to integrate local power generation such as Hybrid Energy Systems (HESs) into charging infrastructure. In this paper at the first stage, candidate buses for installation of Hybrid Energy Systems (PV-WT-CHP) and EV charging station. Then, the heat selling possibility of the buses is determined through the Bus Heating Factor (BHF) using a fuzzy method. Utilizing this factor and the electrical power to heat ratio of the units, the HESs placement proposal is suggested at the second stage. Moreover, the financial benefit of investors obtained from heat selling of the CHP units (in Hybrid Energy System) is determined through an economic analysis (EA) at this stage. Studying the interaction between EVs and HESs in the distribution system and the frequency regulation process of candidate buses at the third stage, the financial benefit of the distribution company obtained from loss reduction and the voltage profile improvement is evaluated through a technical analysis (TA). Finally considering the distribution company and investors as players, the best location and capacity of HESs and EV charging station will be achieved for installing in the distribution buses using a nash equilibrium point in game theory (GT) approach. The applicability of the proposed method is examined on a sample distribution feeder in the city of Hamadan.

In this paper multi objective optimization problem for partitioning process of VLSI circuit optimization is solved using IPO algorithm. The methodology used in this paper is based upon the dynamic of sliding motion along a frictionless inclined plane. In this work, modules and elements of the circuit are divided into two smaller parts (components) in order to minimize the cutsize and area imbalance. The algorithm is implemented to test real case study named RC6 block cipher circuit. The multi objective IPO algorithm (MOIPO) will give better results in comparison with the multi objective particle swarm optimization algorithm (MOPSO) with the same evaluation function.