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Standalone and Parallel Operation Optimization of Uninterruptible Power Supplies
, Ph.D. Dissertation Sharif University of Technology ; Mokhtari, Hossein (Supervisor) ; Karimi, Masoud (Supervisor)
Abstract
Increase of sensitive customers to power quality has raised concerns in industries regarding requirements of quality power supply. Uninterruptible Power Supplies (UPSs) are known as efficient tools in providing reliable power supply to sensitive customer. However, in a UPS, getting a desired output requires appropriate structural implementation and successful output voltage control. On the other hand, due to the increase in sensitive loads in customers, the output power range of UPSs has increased. Consequently, design and producing high power UPSs is not economical. In addition, tendency to have high reliability power supplies disrespect of their physical locations has moved researcher...
nvestigating and Using of an Optimal Controller for Parallel 3-Phase UPS
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
In this thesis first of all the different approaches of control and parallel of multi-modular inverter system were investigated. These methods have been categorized and examined separately, and they were compared with each other in terms of quality and quantity. Afterwards, Active current sharing technique due to its high reliability was selected as the fundamental control approach. Among different ways for active current sharing, Avarage load sharing was chosen for its acceptable stability compared with other method. Approaching this goal, for the first time optimal control strategy and LQR method was proposed to parallel 3-phase inverters.At first, the problem was edited to be compatible...
The effects of excitation control systems on parallel operation of DG with the main grid
, Article International Journal of Power and Energy Systems ; Volume 28, Issue 4 , 2008 , Pages 438-447 ; 10783466 (ISSN) ; Parniani, M ; Rasouli, M ; Sharif University of Technology
2008
Abstract
This paper presents actual cases of steady reactive power oscillation of distributed generations (DGs) during parallel operation with the main grid. The cause of the problem was found to be the adverse effects of excitation system voltage regulation. It is shown, through preliminary investigation and detailed simulation studies, that how the excitation control system can be modified to overcome this problem. On-site test results verify the analysis results and effectiveness of the remedial actions. Finally, general practical recommendations are offered for excitation control of synchronous generator-based DG, such that it performs properly, both in grid connected and in islanding conditions
Proposal of a Modular Structure and a Load Sharing Strategy among Back to Back Converters for Wind Turbines
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
The utilization of wind power has been increasing in recent years which lead to enhance the the usage of wind power capacity in the range of MegaWatt. However, due to the limitation ofswitching devices capacity, which exists in power electronic converters, improving the capacity of wind power generation is not accessible. Thus, a feasible solution for this problem is paralleling power electronics converters, which increases both the capacity of power generation and the reliability of wind turbine systems. Nevertheless, paralleling converters may cause a circulating-current which brings current discrepancy, current waveform distortion, power losses, increase in THD of currents, and reduction...
Effecive & efficient DSM configuration guidelines for low-cost development of complex systems
, Article Gain Competitive Advantage by Managing Complexity - Proceedings of the 14th International Dependency and Structure Modelling Conference, DSM 2012, 13 September 2012 through 14 September 2012 ; 2012 , Pages 125-137 ; 9783446433540 (ISBN) ; Sharif University of Technology
Institution of Engineering Designers
2012
Abstract
With the proliferation of more complex systems has come the need to find better solutions in both technical and management domains. Such complex systems are usually larger in size, have more parallel operations and contain more complex interfaces (Eisner, 2005). The Design Structure Matrix is a very useful tool in handling such complexities, provided that the system designer can use it properly. This paper addresses how effectiveness & efficiency are defined for a DSM and how these two important characteristics can be achieved. The importance of understanding the solution space in constructing an effective & efficient DSM is discussed and general guidelines are given on configuring the DSM...
Using optimal controller to parallel three-phase 4-leg inverters with unbalance loads
, Article 1st IEEE International Conference on Power Electronics, Intelligent Control and Energy Systems, ICPEICES 2016, 4 July 2016 through 6 July 2016 ; 2017 ; 9781467385879 (ISBN) ; Mokhtari, H ; Amiri, E ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
In this paper; control and parallel operation of multi-modular 3-phase inverters are investigated. Active current sharing approach is selected as the fundamental control technique for parallel operation of inverters due to its high reliability. Among different methods for active current sharing; average load sharing is employed due to its acceptable stability. For this purpose; optimal control strategy and Linear Quadratic Regulator (LQR) method is proposed to parallel 3-phase 4-leg inverters. The system is modeled to be compatible and solvable with LQR equations. Using dq technique; 3-phase inverters are paralleled and controlled. The proposed method obtains both current sharing and voltage...
An FPGA based implementation of G.729
, Article IEEE International Symposium on Circuits and Systems 2005, ISCAS 2005, Kobe, 23 May 2005 through 26 May 2005 ; 2005 , Pages 3571-3574 ; 02714310 (ISSN) ; Vahdat, B ; Radfar, M. H ; Sharif University of Technology
2005
Abstract
Main objective of this article is to present the implementation and simulation of a Conjugate Structure Algebraic Code Excited Linear Prediction speech coder (CSACELP) based upon ITU-T's G.729 recommendation and to optimize it for real-time implementation on an FPGA. The suggested architecture is characterized by pipelining and parallel operation of functional units; using fixed point two's complement representation for integers. The design was functionally verified by utilizing the ModelSim software package from Mentor Graphics Corporation Company and then synthesized by Xilinx Integrated Software Environment (ISE) 6.1 software. Preliminary results show that the overall system delay is less...