Showing 41 results for Sa
H. Rezaie, H. Rastegar, M. Pichan,
Volume 14, Issue 1 (3-2018)
Abstract
An inherent problem of single-phase rectifiers is the existence of a pulsating portion in the input power, which pulsates at twice the grid frequency. If this pulsating power is transferred to the DC-link, it causes a significant amount of second-order harmonic at the output voltage. Since in many applications, such a high level of DC oscillation is not acceptable, so the pulsating power must be effectively filtered. A convenient solution to eliminate the output voltage oscillations is to use a capacitor with a relatively high capacity at the rectifier output. Due to the fact that the high capacity capacitors for this application usually have a short lifetime and occupy a lot of space, this solution cannot be considered as a proper one. In this paper, a new active method with the minimum of current and voltage stress is proposed to effectively eliminate the pulsating power and significantly reduce the required capacitance of the output filter. The proposed method is able to reduce the volume of the converter and increase its reliability and power density. The validity and effectiveness of the proposed method are confirmed by extensive simulations in the MATLAB/Simulink.
H. Faraji Baghtash, Kh. Monfaredi,
Volume 15, Issue 3 (9-2019)
Abstract
A novel active feedback frequency compensation scheme is presented in this work. Based on the proposed technique, an amplifier with two main poles in its frequency bandwidth can be easily compensated by introducing a pole-zero pair in a local feedback. The proposed method is mathematically analyzed and then based on the derived formulations, a design procedure is established. The capability of the proposed technique is examined considering a well-known two-stage amplifier, considering just a trivial modification on its input stage. To gain an analogous and fair insight, the performance of the proposed structure is compared with that is of the optimally designed miller-compensated two-stage amplifier. The post-layout simulations are accomplished with TSMC 180nm CMOS standard technology. The Spectre post-layout simulations show that the proposed structure outperforms the traditional structure in terms of power consumption and gain bandwidth product. The robustness of the design is checked with Monte Carlo simulations.
A. Kumar, P. Kumar,
Volume 15, Issue 4 (12-2019)
Abstract
This paper presents the three topologies of three-phase four-wire DSTATCOM for reduction of harmonics, reactive power compensation, increasing power factor, which occur due to a nonlinear load, environment problem and polluted grid. The performances of the above topologies have been compared for the magnitude of source current, power factor improvement, DC-link voltage regulation, and total harmonic distortion. This paper presents a novel work for the new young scientist /industrialist who working in the improvement of power quality in the grid. This paper helps to provide the application, designing constraints of shunt active filter in many fields. The First topology which is used in this paper is the three-phase four-wire four-pole voltage source converter based DSTATCOM. The second is the three-phase four-wire with three-leg voltage source converter based DSTATCOM with T-connected transformer and the third topology is the three H-bridge voltage source converter based DSTATCOM. The T-connected transformer in the second topology has been used to reduce the rating for voltage source converter. Synchronous reference frame theory based controller has been proposed to the generation of the reference current. Reference current generated from the synchronous frame theory is processed to hysteresis current controller loop which produces switching pulses for VSC based DSTATCOM. All these topologies have been implemented in MATLAB /Simulink platform by using different types of loading conditions such as resistive and power electronics load.
A. Amiri, S. Mirzakuchaki,
Volume 16, Issue 3 (9-2020)
Abstract
Watermarking has increased dramatically in recent years in the Internet and digital media. Watermarking is one of the powerful tools to protect copyright. Local image features have been widely used in watermarking techniques based on feature points. In various papers, the invariance feature has been used to obtain the robustness against attacks. The purpose of this research was based on local feature-based stability as the second-generation of watermarking due to invariance feature to achieve robustness against attacks. In the proposed algorithm, initially, the points were identified by the proposed function in the extraction and Harris and Surf algorithms. Then, an optimal selection process, formulated in the form of a Knapsack problem. That the Knapsack problem algorithm selects non-overlapping areas as they are more robust to embed watermark bits. The results are compared with each of the mentioned feature extraction algorithms and finally, we use the OPAP algorithm to increase the amount of PSNR. The evaluation of the results is based on most of the StirMark criterion.
M. Norianfar, S. Karimi, H. M. Cheshmehbeigi,
Volume 16, Issue 3 (9-2020)
Abstract
This paper suggests a new control method to modify the virtual impedance performance in unbalanced conditions. The proposed method compensates the voltage drop that occurred due to the virtual impedance and adjusts the voltage of the point of common coupling at a desirable level. To compensate the voltage drop, the reference voltage in the droop control varies according to the proposed algorithm. Moreover, a modified decoupled double synchronous reference frame is introduced to achieve appropriate active and reactive power sharing and voltage balancing, simultaneously. Finally, the simulation results in MATLAB/Simulink are provided to validate the accuracy and effectiveness of the proposed approach.
A. Rajabi, H. Lexian,
Volume 17, Issue 1 (3-2021)
Abstract
One of the important requirements in projectiles is to design a power supply for fuse consumption. In this study, an optimum design for the power supply, which includes a Miniaturized Inertia Generator (MIG), was introduced. The main objective of this research was to optimize the dimensions of the MIG with the aim of increasing energy. To achieve this, the design of experiment (DOE) was carried out through RSM-BBD to optimize six parts of the MIG. Numerical simulations were performed using Maxwell’s software. After analyzing of results by ANOVA and extracting the optimum result from the RSM, a Miniaturized Inertia Generator was fabricated with optimum dimensions. The results showed that the MIG with optimum dimensions at an acceleration of 800’g could generate 15.25V and stores the generated energy using an RLC circuit within 1ms. The experimental results which were obtained by the shock test system showed that 14.75V was charged on a capacitor within 1.1ms which has good conformity with the numerical results. The results indicated that the proposed design not only increased the MIG efficiency, but also determined the effect of each parameter on the produced energy and efficiency.
P. O. Oluseyi, J. A. Adeagbo, D. D. Dinakin, O. M. Babatunde,
Volume 17, Issue 1 (3-2021)
Abstract
The philosophy of efficient energy consumption is vitally crucial to profitable production cost in manufacturing industries. This is because the unit production cost is largely determined by the cost of unit energy supply; which is quite higher than the cost of raw materials in Nigeria. It has been established that the Nigerian industrial sector is responsible for 8.7% of the total energy consumption in the nation. Out of this chunk, the food and beverage industry appropriates approximately 2%. Meanwhile, it is observed that the energy consumption trend in most industrial electric motors is always high due to continuous operation even during the idle time/period in production. In this study, data gathered has a coefficient of determination of 99.7%. This is, thus, subjected to regression analysis which assists in predicting the energy consumption trend for a period of one year. Further to this, the capacity of control principles in efficient energy consumption is demonstrated by practical real time implementation of a smart energy saving in the food industries using PLClogicx software. In this sense, the developed programmable logic control (PLC) ladder diagram was further designed and implemented using fuzzy logic control (FLC). This is simulated using MATLAB/Simulink toolbox. By this arrangement; it is observed that there was a significant reduction in energy consumption. This is obviously revealed in the obtained results. In this case, there was an average electrical energy savings of 65.59% in the plant’s case sealing section while an energy saving of approximately 0.13% was achieved in reference to the overall energy consumption of the industrial plant’s processes. Finally, based on the mathematical calculations obtained from observations of typical production processes in the multinational food and beverage company, the FLC is discovered to provide 99.83% efficiency in optimizing energy consumption.
A. Jabbari, F. Dubas,
Volume 17, Issue 2 (6-2021)
Abstract
In this paper, we present a mathematical model for determining the optimal radius of the iron pole shape in spoke-type permanent-magnet (PM) machines (STPMM) in order to minimize the pulsating torque components. The proposed method is based on the formal resolution of the Laplace’s and Poisson’s equations in a Cartesian pseudo-coordinate system with respect to the relative permeability effect of iron core in a subdomain model. The effect of PM width on the optimal radius of the iron pole has been investigated. In addition, for initial and optimal machines, the effect of the iron core relative permeability on the STPMM performances was studied at no-load and on-load conditions considering three certain PM widths. Moreover, the effect of iron pole shape on pulsating torque components with respect to certain values of iron core relative permeability was studied by comparing cogging torque, ripple and reluctance torque waveforms. In order to validate the results of the proposed analytical model, three motors with different PM widths were considered as case studies and their performance results were compared analytically and numerically. Two prototype spoke-type machines were fabricated and the experimental results were compared to analytical results. It can be seen that the analytical modeling results are consistent with the numerical analysis and experimental results.
P. Gupta, S. K. Jana,
Volume 17, Issue 2 (6-2021)
Abstract
The advancement in the integrated circuit design has developed the demand for low voltage portable analog devices in the market. This demand has increased the requirement of the low-power RF transceiver. A low-power phase lock loop (PLL) is always desirable to fulfill the need for a low power RF transceiver. This paper deals with the designing of the low power transconductance- capacitance (Gm-C) based loop filter with the help of the gate-driven quasi bloating Bulk (GD-QFB) MOS technique. The GD-QFB MOS-based operational transconductance amplifier (OTA) has been proposed with a high dc gain of 82.41 dB and less power consumption of 188.72 µW. Further, Gm-C based active filter has been designed with the help of the proposed GD-QFB OTA. The simulation results of Gm-C filter attain a -3 dB cut-off frequency of 59.08 MHz and power consumption of 188.31µW at the supply voltage of 1V. The proposed Gm-C filter is suitable for the designing of 1-3 GHz low power PLL.
M. Khalaj-Amirhosseini,
Volume 17, Issue 2 (6-2021)
Abstract
Nonuniform Phased Sampling method is proposed to phase-only synthesize the power pattern of both linear and planar antenna arrays. This method modifies the conventional sampling method which is used for amplitude-phase synthesis. This method is based on assigning suitable phases to the sampling points of radiation pattern in order to reach desired amplitude of currents. Some examples are given to verify the effectiveness of the proposed method for both pencil-beam and shaped beam patterns.
F. Rezaee-Alam, B. Rezaeealam, S. M. M. Moosavi,
Volume 17, Issue 3 (9-2021)
Abstract
Poor modeling of air-gap is the main defect of conventional magnetic equivalent circuit (CMEC) model for performance analysis of electric machines. This paper presents an improved magnetic equivalent circuit (IMEC) which considers all components of air-gap permeance such as the mutual permeances between stator and rotor teeth, and the leakage permeances between adjacent stator teeth and adjacent rotor teeth in the air-gap. Since the conformal mapping (CM) method can accurately take into account the air-gap region, IMEC gets help from the CM method for calculating the air-gap permeance components. Therefore, the obtained model is a hybrid analytical model, which can accurately take into account the magnetic saturation in iron parts by using the CMEC, and the real paths of fringing flux, leakage flux, and the main flux in the air-gap by using the CM method. For a typical wound rotor induction motor, the accuracy of the results obtained by IMEC is verified by comparing them with the corresponding results determined through CMEC, improved conformal mapping (ICM), finite element method (FEM), and the experiment results.
M. Ahmadinia, J. Sadeh,
Volume 17, Issue 4 (12-2021)
Abstract
In this paper, an accurate fault location scheme based on phasor measurement unit (PMU) is proposed for shunt-compensated transmission lines. It is assumed that the voltage and current phasors on both sides of the shunt-compensated line have been provided by PMUs. In the proposed method, the faulted section is determined by presenting the absolute difference of positive- (or negative-) sequence current angles index, firstly. After determining faulted section, the voltage phasor at the shunt-compensator terminal is estimated via the sound section. The faulted section can be assumed as a perfect transmission line that synchronized voltage and current phasors at one end and voltage phasor at the other end are available. Secondly, a new fault location algorithm is presented to locate the precise fault point in the faulted section. In this algorithm, the location of the fault and the fault resistance are calculated simultaneously by solving an optimization problem, utilizing the heuristic Particle Swarm Optimization (PSO) method. The simulation results in MATLAB/SIMULINK platform demonstrate the high performance of the proposed method in finding the fault location in shunt-compensated transmission lines. The proposed scheme has high accuracy for both symmetrical and asymmetrical fault types and high fault resistance.
A. Zakipour, K. Aminzare, M. Salimi,
Volume 18, Issue 3 (9-2022)
Abstract
Considering the presence of different model parameters and controlling variables, as well as the nonlinear nature of DC to AC inverters; stabilizing the closed-loop system for grid current balancing is a challenging task. To cope with these issues, a novel sliding mode controller is proposed for the current balancing of local loads using grid-connected inverters in this paper. The closed-loop system includes two different controlling loops: a current controller which regulates the output current of grid-connected inverter and a voltage controller which is responsible for DC link voltage regulation. The main features of the proposed nonlinear controller are reactive power compensation, harmonic filtering and three-phase balancing of local nonlinear loads. The developed controller is designed based on the state-space averaged modelling its stability and robustness are proved analytically using the Lyapunov stability theorem. The accuracy and effectiveness of proposed controlled approach are investigated through the PC-based simulations in MATLAB/Simulink.
G. Vasudeva, B. V. Uma,
Volume 18, Issue 3 (9-2022)
Abstract
Successive approximation register (SAR) analog to digital converter (ADC) architecture comprises submodules such as comparator, digital to analog converters (DAC), and SAR logic. Each of these modules imposes challenges as the signal makes transition from analog to digital and vice-versa. Design strategies for optimum design of circuits considering 22nm FinFET technology meeting area, timing, power requirements, and ADC metrics are presented in this work. Operational Transconductance Amplifier (OTA) based comparator, 12-bit two-stage segmented resistive string DAC architecture, and low power SAR logic are designed and integrated to form the ADC architecture with a maximum sampling rate of 1 GS/s. Circuit schematic is captured in cadence environment with optimum geometrical parameters and performance metrics of the proposed ADC are evaluated in MATLAB environment. Differential nonlinearity and integral nonlinearity metrics for the 12-bit ADC are limited to +1.15/-1 LSB and +1.22/-0.69 LSB respectively. ENOB of 10.1663 with SNR of 62.9613 dB is achieved for the designed ADC measured for conversion of input signal of 100 MHz with 20dB noise. ADC with sampling frequency up to 1 GSps is designed in this work with low power dissipation of less than 10 mW.
A. Rahali, K. El Khadiri, A. Tahiri,
Volume 19, Issue 1 (3-2023)
Abstract
In this paper, a Li-Ion Battery Charger Interface (BCI) circuit with fast and safe charging for portable electronic devices is proposed. During the charging of Li-Ion battery, current spikes due to asynchronous control signals, and temperature are factors that greatly affect battery performances and life. This circuit has the following features: prevents current spikes and also incorporates a permanent battery temperature monitoring block. The BCI uses a dual current source and generates a constant current in a large current mode of 1.5 A, further reducing charging time. The proposed BCI was designed and simulated in Cadence Virtuoso using TSMC 180 nm technology. The simulation results of the control signals show that the proposed architecture was able to eliminate the current drifts and keep the battery temperature within the normal operating range.
A. Hamidi, S. Karimi, A. Ahmadi,
Volume 19, Issue 2 (6-2023)
Abstract
One of the problems in digital control of power converters is calculation time in each sampling instant which effect on cost and complexity of digital controller. In this paper, a formula is introduced for calculating the number of clock cycles in each sample then interaction between sampling frequency and implementation cost (number of functional units and word length) of FPGA-based digital controller of DC-AC converter (three-phase four-legs inverter) is verified. The digital architecture is built on finite set model predictive control, and implemented on the FPGA board based on fixed-point calculations. We consider two digital architectures for design the controller in this study. One with four functional units and another with six functional units. This study aims to develop a mathematical equation for the number of clock cycles in each time instant to select the best switching state in the control algorithm, which affects the sampling frequency and clock frequency. Based on the obtained results, the number of functional units, word-length, and the number of switches determine the maximum clock cycles. By knowing maximum clock cycles the maximum sampling frequency is determined. In structure with four functional units, the maximum sampling frequency is 71 kHz for WL=8 bits and 17.7 kHz for WL=32 bits, and in structure, with six functional units, the maximum sampling frequencies are 97.6 and 24.4 kHz for WL=8 and WL=32 bits, respectively. In architecture with more functional units, we have greater sampling frequency with more accuracy and cost. The results obtained from this paper can be a reference for digital controller design.
Mon Prakash Upadhyay, Arjun Deo, Ajitanshu Vedratnam ,
Volume 20, Issue 0 (12-2024)
Abstract
This paper provides an overview of the current innovations in Building Integrated Photovoltaic Thermal Systems. This paper briefly describes varying performance evaluation techniques, optimisation techniques, and the environmental impact and cost implication of Building Integrated Photovoltaic Thermal systems. The results reveal high energy-pin efficiency with Building Integrated Photovoltaic Thermal systems of over 50% and more efficient than when the two systems are incorporated separately. Exergy analysis is a more insightful means of analysing system effectiveness than energy analysis. The paper covers the current algorithms for various optimisation, algorithms such as Genetic Algorithms and Particle Swarm Optimisation, that provide enhanced utilisation improvements. An evaluation of the environmental impact of Building Integrated Photovoltaic Thermal in terms of carbon dioxide emission reduction and building energy optimisation is made. The results of the life cycle cost studies show that, even though the initial cost is higher than conventional solutions, the overall economic profit is more significant in the future. Some of the challenges described in the paper include increased initial costs and sophisticated integration procedures. In contrast, possible future developments include new materials, Building Integrated Photovoltaic Thermal system standardisation, and integration in smart grids. This review is intended to be a state-of-the-art source of information for researchers, engineers, architects, and policymakers involved in enhancing sustainable building technologies using building-integrated photovoltaic thermal systems.
Hossein Azizi Moghaddam, Arman Farhadi,
Volume 20, Issue 1 (3-2024)
Abstract
Dynamometers are equipment that has been widely used in the field of electric machines test benches. A dynamometer system has the ability to create intricate and unpredictable behaviours of mechanical loads according to a programmed manner. Extensive research into the characteristics of loads found in industrial settings has shown that non-linear and complex phenomena, including misalignment, mechanical friction, and others, are unavoidable in industrial drive systems. To assess the performance of motor and drive systems in industrial drives when subjected to these non-linear and complex loads, a fast and precise dynamic drive system must track high-frequency torque signals with precision. The suggested dynamometer, serving as an instrumental device, has the ability to emulate a wide torque response across various frequencies during both transient and steady-state conditions for the machine under test. Simulations and experimental results confirm the dynamometer's wide-ranging dynamic response, enabling the emulation of different linear and non-linear loads.
Priyanka Handa, Balkrishan Jindal ,
Volume 20, Issue 1 (3-2024)
Abstract
The potential adverse effects of maize leaf diseases on agricultural productivity highlight the significance of precise disease diagnosis using effective leaf segmentation techniques. In order to improve maize leaf segmentation, especially for maize leaf disease detection, a hybrid optimization method is proposed in this paper. The proposed method provides better segmentation accuracy and outperforms traditional approaches by combining enhanced Particle Swarm Optimisation (PSO) with Firefly algorithm (FFA). Extensive tests on images of maize leaves taken from the Plant Village dataset are used to show the algorithm's superiority. Experimental results show a considerable decrease in Hausdorff distances, indicating better segmentation accuracy than conventional methods. The proposed method also performs better than expected in terms of Jaccard and Dice coefficients, which measure the overlap and similarity between segmented sections. The proposed hybrid optimization method significantly contributes to agricultural research and indicates that the method may be helpful in real scenarios. The performance of proposed method is compared with existing techniques like K-Mean, OTSU, Canny, FuzzyOTSU, PSO and Firefly. The overall performance of the proposed method is satisfactory.
Ramin Safaeian, Mahmoud Tabandeh ,
Volume 20, Issue 2 (6-2024)
Abstract
Directed Acyclic Graphs stand as one of the prevailing approaches for representing causal relationships within a set of variables. With observational or interventional data, certain undirected edges within a causal DAG can be oriented. Performing intervention can be done in two different settings, passive and active. Here, we prove that an optimal intervention set can be obtained based on the minimum vertex cover of a graph. We propose an algorithm that efficiently identifies such an optimal intervention set for chordal graphs within polynomial time. Performing intervention on this optimal set recovers all the undirected edges in graph G, regardless of the underlying ground truth DAG. Furthermore, we present an algorithm for evaluating the performance of passive algorithms. This evaluation provides insights into how many intervention steps of a specific algorithm are required to recover all edges in the causal graph for any possible underlying ground truth in the equivalence class. Experimental findings underscore that the number of nodes in the optimal intervention set increases with growing the number of nodes in a graph, where the edge density is fixed, and also increases with the rising edge density in a graph with a fixed number of nodes.
