Sharif Digital Repository

The objective of the research done in this paper was to determine cost of the power and heat system with pressurized fluidized bed gasifier using exergoexonomic appraisal techniques. Exergetic efficiency maximization was approached with use of multi-objective evolutionary optimization methods which were designed such that the costs were minimized in line with the exergoeconomic plans. The results of this method were also compared to methods that employ iterative techniques. Results showed an almost 12.28% improvement in exergetic efficient that the system could reach through utilization of the multi-objective evolutionary algorithm  

Microwave power modules are the result of integration of vacuum tubes and their respective power supplies. In these modules, volume and weight are very important factors because the modules are used in many portable applications. There are many parameters that they affect the volume and weight of the microwave power module. High voltage issues are one of these factors because the required voltages of vacuum tubes are high voltage. Thermal management relates to the module volume directly. In high-voltage high-frequency converters as power supplies of vacuum tubes, parasitic elements of the transformer are dominant. Tuning the transformer parameters leads to variation in the volume of the... 

Renewable energy (RE) as a new player in the generation sector of power systems imposes new challenges to the system operators. The intermittent nature of REs for systems where are autonomous calls for new operational and planning strategies to reach more efficient power management. An autonomous hybrid green power system (HGPS) should be able to meet the load while keeping the cost of the HGPS as low as possible. Many studies have presented different un-optimal and optimal operational strategies, a few of which were optimally sized. In this regard, this paper develops a new thorough framework for designing and optimizing an autonomous HGPS. To reach this goal, the proposed model (a)... 

Fault detection (FD) in power electronic converters is necessary in embedded and safety critical applications to prevent further damage. Fast FD is a mandatory step in order to make a suitable response to a fault in one of the semiconductor devices. The aim of this study is to present a fast yet robust method for fault diagnosis in nonisolated dc-dc converters. FD is based on time and current criteria which observe the slope of the inductor current over the time. It is realized by using a hybrid structure via coordinated operation of two FD subsystems that work in parallel. No additional sensors, which increase system cost and reduce reliability, are required for this detection method. For... 

Electrospray technique is one of the commonly used methods for generating nanoparticles. In this method, the chemical solution which consists of a polymer and its solvent are injected into an electric field via a nozzle. At the end of this nozzle, due to electric forces, a certain part of this liquid is separated. Then, the separated part is divided into smaller particles and the solvent is evaporated and hence, the nanoparticles are acquired. Produced nanoparticales are collected in deionized water placed under the certain distant from nozzle. However, construction of this method is generally based on practical results. In this paper, modeling and performance evaluation of high voltage... 

Stray capacitance of transformer winding is an important parasitic element influencing the behavior of the switching power converters, especially for high-voltage transformers. There are various methods for calculating the stray capacitance in transformers and inductors with ordered windings. However, an ordered winding is less likely with an increased number of turns and layers. In this paper, it is shown that a slight disorderliness in winding leads to a considerable difference between the value of winding stray capacitance of the former ordered winding and its slightly disordered scheme. Therefore, regular methods for calculating the stray capacitance have significant errors in a... 

The transformer leakage inductance (TLI) is an important parameter in the design phase of the isolated power supplies. Hence, the TLI estimation before the transformer construction is very useful for the designers. The previous works considered an ordered winding turn arrangement (WTA) for the transformers. This assumption considers only ideal windings which may result in a significant error from what will be achieved after the construction of the transformer. This article concentrates on the transformers with nonideal windings in which the turns are not ordered. The uneven distribution of the turns in the layers is mainly due to the wrapping machine error. Hence, for a specific transformer... 

Line generators were attractive structures for high-power radio frequency (RF) pulse generation for two decades. Due to some disadvantages, there has been little attention to this type of generator for a relatively long time. In this paper, a nonuniform line generator is used which resolves some of the main shortcomings of conventional line generators. The considered generator can generate RF pulses at higher frequencies with considerably higher repetition rates. Furthermore, the implementation of nonuniform line generators is significantly easier than that of their conventional counterparts. Measurement results for three nonuniform line generators are presented. The possibility of... 

This paper presents several techniques for the processing of power system signals in a power system setup. The techniques exhibit a desirable performance against signal pollutions such as noise and distortions, signal unbalance (in three-phase applications), and Variations in the signal attributes (mainly its frequency). These features render them a promising set of options for modern power systems in which all or some of these undesired factors may be amplified depending on the case. Single-phase and three-phase applications are both examined and appropriate techniques are suggested for different scenarios. © 2007 IEEE  

This paper presents a stochastic model for optimal generating units' restoration planning. Restoration plans will be performed based on different objectives i.e. total system risk, total served energy in the period of restoration, and total restoration time. The proposed model is a multi objective stochastic program in which generating units' restoration plan is assumed to optimize different kinds of objective function. The proposed approach to the optimal restoration of generating units can be used by vertically integrated utilities as well as the ISOs in electricity markets. The approach coordinates the optimal start up of generating units within the restoration period. Physical... 

Most modern multi-core edge devices work in outdoor situations with limited power supplies like energy harvester and batteries. Therefore, energy consumption is a fundamental issue in which the memory subsystem has a significant role. Scratchpad memories (SPM) can provide a broad potential for energy saving. Still, due to the insufficient SPM capacity in such edge devices, a rigorous SPM data allocation scheme is necessary to reduce the energy consumption of the memory subsystem. Emerging non-volatile memories (NVMs) are very useful to reduce the energy consumption of the memory subsystem. Therefore, embedded and edge devices can take advantage of hybrid SPM composed of both NVM and SRAM to... 

In this paper, a low power receiver for medical implant communication service (MICS) is presented. Low power design is vital in the MICS applications since the implanted chip has to work for a long time without the need to change its battery. As a result, a merged N-path low noise amplifier (LNA) and mixer block is proposed. In this structure, the LNA and down-conversion mixer share a transconductance to lower the overall power consumption. An N-path feedback is utilized around the shared transconductance not only to improve the LNA selectivity and relax the linearity requirements but also to downconvert the radio frequency (RF) component and create the intermediate frequency (IF) signal. In... 

In switching power supplies, the transformer leakage inductance (TLI) is of considerable practical significance. Ordered winding is the certain assumption in previously reported works for the calculation of the TLI value. However, disordered windings are usually unavoidable in practice and their effect on the value of the TLI is considerable. The problem becomes more complex when the number of winding turns increases. In this paper, the effect of winding disorder on the TLI value is investigated. In disordered wrapping, the winding turns arrangement (WTA) of each produced transformer is different from the others. Thus, each produced transformer has an exclusive TLI value in a disordered... 

In this paper, we present an experimental evaluation of transient effects on an embedded system which uses SRAM-based FPGAs. A total of 7500 transient faults were injected into the target FPGA using Power Supply Disturbances (PSD) and a simple 8-bit microprocessor was implemented on the FPGA as the testbench. The results show that nearly 64 percent of faults cause system failures and about 63 percent of the faults lead to corruption of the configuration data of the FPGA chip. © 2005 IEEE  

Solid-State Drives (SSDs) are recently employed in enterprise servers and high-end storage systems in order to enhance performance of storage subsystem. Although employing high speed SSDs in the storage subsystems can significantly improve system performance, it comes with significant reliability threat for write operations upon power failures. In this paper, we present a comprehensive analysis investigating the impact of workload dependent parameters on the reliability of SSDs under power failure for variety of SSDs (from top manufacturers). To this end, we first develop a platform to perform two important features required for study: A) a realistic fault injection into the SSD in the... 

A huge amount of energy consumption, the cost of this usage and environmental effects have become serious issues for commercial cloud providers. Solar energy is a promising clean energy source, to provide some portion of the Internet data center's (IDC's) energy usage which can reduce environmental effects and total energy costs. Moreover, due to the high energy consumption of the cooling system, considering cooling power in job scheduling can provide efficient solutions to reduce total energy consumption. In this article, we investigate the problem of minimizing the energy cost of an IDC and propose an algorithm which schedules heterogeneous IDC workloads, by considering available renewable... 

This paper presents an experimental evaluation of transient effects on SRAM-based FPGAs. A total of 9000 transient faults were injected into the target FPGA using Power Supply Disturbances (PSD). The results show that nearly 60 percent of faults cause system failures and about 58 percent of the faults lead to corruption of the configuration data of the FPGA chip. © 2005 IEEE  

This paper presents an experimental evaluation of the effectiveness of the Master/Checker (M/C) architecture in a 32-bit Pentium® processor system using both power-supply disturbance (PSD) fault injection and software-implemented fault injection (SWIFI) methods. A total of 6000 faults were injected in the Master processor to measure the error detection coverage of the Checker processor. The results of the experiments with PSD fault injection show that the error detection coverage of the M/C architecture is about 66.13%, which is not quite effective. This low coverage depends on the high rate of Master processor hangs because of voltage fluctuation. The coverage increased to about 99.73% when... 

Proton Exchange Membrane (PEM) Fuel Cells are attracting most of the electricity consumers because of high efficiency, zero carbon emissions and high reliability. There are many parameters influencing on this power source's operation. A model of PEM fuel cell will be presented and the sensitivity of the fuel cell's parameters will be analyzed. Multi Parameters Sensitivity Analysis is used next to examine the relative importance of the influential parameters on the PEM fuel cell operation  

A major challenge for designers of competitive electricity markets is to devise market rules that limit the capability of electricity producers to exercise market power. Market power is the ability of a firm owning generation assets to raise the market price by its bidding behavior and to profit from this price increase. In addition, an important plan of market monitoring units in long term and competition policy framework is to persuade the participants to bid prices near to their marginal costs. Therefore, estimation of marginal cost function is important in way that Regulatory use it to increase competition in electricity markets. Bid price of the power plant to the power market contains...