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A robust backstepping high-order sliding mode control strategy for grid-connected DG units with harmonic/interharmonic current compensation capability
, Article IEEE Transactions on Sustainable Energy ; Volume 8, Issue 2 , 2017 , Pages 561-572 ; 19493029 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2017
Abstract
This paper presents a new nonlinear current control strategy based on backstepping control and high-order sliding mode differentiator in order to employ distributed generation (DG) unit interfacing converters to actively compensate harmonics/interharmonics of local loads. The converter-based DG unit is connected to a weak grid (with uncertain impedance) and local load (that can be parametrically uncertain and topologically unknown) through an LCL filter. The proposed strategy robustly regulates the inverter output currents and delivers pure sinusoidal, three-phase balanced currents to the grid. The new controller demonstrates the robust performance and robust stability of the DG unit system...
A backstepping high-order sliding mode voltage control strategy for an islanded microgrid with harmonic/interharmonic loads
, Article Control Engineering Practice ; Volume 58 , 2017 , Pages 150-160 ; 09670661 (ISSN) ; Sadati, N ; Hamzeh, M ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
This paper presents a new nonlinear voltage control strategy based on backstepping control and a high-order sliding mode differentiator for an islanded microgrid. The microgrid consists of multiple distributed generation (DG) units with an arbitrary configuration that can be parametrically uncertain or topologically unknown. The proposed controller robustly regulates the microgrid voltages in the presence of parametric uncertainties, unmodeled dynamics, load imbalances, and nonlinear loads with harmonic/interharmonic currents. In contrast to existing methods, the controller does not need to know the frequency of harmonic and interharmonic current of microgrid loads that lead to the reduction...
Adaptive Estimation of Components of a Three-Phase Signal Polluted with Sinusoidal Disturbance
, M.Sc. Thesis Sharif University of Technology ; Karimi, Houshang (Supervisor)
Abstract
This thesis proposes a new method for estimation of parameters of a multi-component signal. The signal is composed of several sinusoidal components whose frequencies and magnitudes are unknown. Moreover, the signal is polluted with white noise. The estimated parameters are frequency, amplitude, and phase-angle of each component. The proposed method is able to adaptively decompose the multi-component signal into its constituting sinusoidal components. The core unit of the proposed method comprises an adaptive band-pass and an adaptive notch filter. The proposed method consists of parallel connection of several core units. The band pass filter rejects all components except the one whose...
Stabilization of Subsynchronous Oscillations of ILAM Refinery Gas Turbine Units in Islanded Operations
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Ilam refinery has three synchronous generator units each with a capacity of 26.5 MVA and two six-phase LCI-fed synchronous compressors, each with a capacity of 8 MW. Generators of Ilam gas refinery have instability issue in case of island operation. With launching one generator unit and then connecting two compressors the instability problem and tripping of the generators appear. Given the importance of this issue, various tests and corresponding measurements in both electrical and mechanical aspects were carried out at the plant in on-grid and island operations to analyze the cause of instability phenomena. The mechanical part of tests analyses the frequency of oscillations and vibration in...
A distortion-free phase-locked loop system for FACTS and power electronic controllers
, Article Electric Power Systems Research ; Volume 77, Issue 8 , 2007 , Pages 1095-1100 ; 03787796 (ISSN) ; Sharif University of Technology
2007
Abstract
This paper presents a single-phase phase-locked loop (PLL) system which is primarily free from the double-frequency ripples from which the conventional PLL system suffers. The proposed PLL is then extended to reject the harmonic components from the input signal and to estimate the phase-angle and frequency of the distorted input signal with no error. Three units of the proposed PLL can be used in three-phase power systems, such as FACTS and HVDC converters, to estimate the phase-angles of the individual phases with no double-frequency ripples and without sensitivity to the presence of harmonics and inter-harmonics. This makes the proposed PLL unique and desirable for applications which...
Study and Improvement of Stability of Generator-based Distributed Generation units Inpresence of Large Nonlinear Loads
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Hyderogels are hydrophilic polymers with three dimensional network structure, due to their high water absoption, their application to life and industry is increasing from day to day, such as tissue engineering, actuators and sensors, drug delivery and therapeutic treatment. In this project, it has been attempted to produce polyacrylamide/alginate double network hydrogels with the use of graphene oxide nanosheets to indicate that it is possible to combine toughness and self-healing in a hydrogel with the opposite nature of each other. To evaluate mechanical properties, uniaxial tensile test and loading-unloading test were used. The results indicate that increase the weight ratio of acrylamide...
Active damping of torsional vibrations due to the sub-harmonic instability on a synchronous generator
, Article 20th European Conference on Power Electronics and Applications, EPE 2018 ECCE Europe, 17 September 2018 through 21 September 2018 ; 2018 ; 9789075815283 (ISBN) ; Azizi, A ; Mokhtari, H ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018
Abstract
Sub-harmonic stability issues due to the interaction between a load-commutated motor drive and a synchronous turbo-generator train in a Liquefied Natural Gas (LNG) station are studied in this paper. The sub-harmonic current injected by motor drives may excite the mechanical torsional modes of turbogenerator train. In this paper, the electro-mechanical interaction phenomenon is investigated and an active damper is proposed to absorb the sub-harmonic currents of motor drives and increase the damping of the electro-mechanical system. Simulations and experiments validate the instability problem and effectiveness of the proposed solution. © 2018 EPE Association
Application of the unified power quality conditioner for mitigating electric arc furnace disturbances
, Article International Journal of Power and Energy Systems ; Volume 28, Issue 4 , 2008 , Pages 363-371 ; 10783466 (ISSN) ; Parniani, M ; Emadi, A ; Mokhtari, H ; Sharif University of Technology
2008
Abstract
This paper discusses the application of unified power quality conditioner (UPQC) for improving power quality of a system supplying an electric arc furnace (EAF). The UPQC includes combined series and shunt active filters sharing a common DC link. It is used to mitigate voltage disturbances and compensate for reactive power, harmonics and interharmonics. A novel control strategy for the UPQC is presented. As voltages at the point of common coupling contain low-frequency interharmonics, conventional methods cannot be used for extracting voltage reference signals. In the proposed method, voltage references are extracted using a phase-locked loop to generate sinusoidal waveforms. Current...