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stability-margins
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Power System Voltage Stability Margin Assessment Using Synchronous Wide Area Measurement System (WAMS)
, M.Sc. Thesis Sharif University of Technology ; Parniani, Mostafa (Supervisor)
Abstract
Although voltage control and stability issues are not new to the electricity industry, but nowadays, in most modern power systems, special attention has been paid to this issue. Once, only weak systems with long lines were involved in voltage instability, while today due to heavy loading, voltage stability is a serious concern even in developed networks. Over tim, with increasing demand for electricity and emergence of electricity market and economic constraints, power systems are more exposed to voltage instability and even voltage collapse. Therefore, reliable operation of the system in such circumstances requires evaluating voltage stability of the network at both stages of planning and...
Gain and Phase Margins in a Class of Nonlinear Systems
, M.Sc. Thesis Sharif University of Technology ; Haeri, Mohammad (Supervisor)
Abstract
The stability of dynamic systems has long been discussed in the theory of control and many people and experts have researched in this field and important results have been obtained from their research. In the real world, systems stability is the premise of controlling their behavior. In fact, systems that are unstable will not be controllable without stability. Therefore, the stability of the systems is discussed and at the same time the control expectations of the system will be raised. The systems of the surrounding world behave nonlinearly; Therefore, their exact stability is not debatable with linear approaches and requires stronger mathematics and attention to specific behaviors of...
Numerical Investigation of Fuid Injection Effects on Improving the Stability of Centrifugal Compressors
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Increasing the surge margin of compressors and preventing surge and stall phenomena have always been one of the main concerns of gas turbine engines. This research aims to numerically investigate the fluid injection effects on the surge margin in centrifugal compressors. In this regard, the NASA CC3 compressor is selected for validation purposes. Considering the available geometrical data, a simulation is performed by using Ansys software, and results are compared with those available from public literature.After the performance and accuracy of the fluid injection simulation results are validated, fluid injection is implemented in the newly selected location and its impact on the compressor...
Effects of bleed position on the stability of a supersonic inlet
, Article Journal of Propulsion and Power ; Volume 32, Issue 5 , 2016 , Pages 1153-1166 ; 07484658 (ISSN) ; Daliri, A ; Younsi, J. S ; Farahani, M ; Sharif University of Technology
American Institute of Aeronautics and Astronautics Inc
2016
Abstract
Effects of various boundary-layer bleed locations on the stability of an axisymmetric supersonic inlet has been investigated experimentally. The bleeds were located on the inlet compression cone and were designed to improve the stability margin of the inlet. The main objective of the study was to identify the boundary-layer bleed location and its effectsonthe improvementofthestability marginofthe inlet.Inaddition,a buzz precursordetection methodology based on the rms level has been introduced. Experiments have been carried out on a mixed-compression inlet with a design Mach number of 2.0 and three different bleed locations at three freestream Mach numbers of 1.8, 2.0, and 2.2. All tests were...
A global Particle Swarm-Based-Simulated Annealing Optimization technique for under-voltage load shedding problem
, Article Applied Soft Computing Journal ; Volume 9, Issue 2 , 2009 , Pages 652-657 ; 15684946 (ISSN) ; Amraee, T ; Ranjbar, A. M ; Sharif University of Technology
2009
Abstract
In this paper, a new approach based on hybrid Particle Swarm-Based-Simulated Annealing Optimization technique (PSO-B-SA) is proposed for solving under-voltage load shedding (UVLS) problem. Under-voltage load shedding (UVLS) is one of the most important tools for avoiding voltage instability. In this paper, the UVLS problem is formulated based on the concept of the static voltage stability margin and its sensitivity at the maximum loading point or the collapse point. The voltage stability criterion is modeled directly into the load-shedding scheme. In any UVLS scheme finding the global point is very important for having cost effective economy. The proposed PSO-B-SA methodology is implemented...
Reduced multiple model predictive control of an heating, ventilating, and air conditioning system using gap metric and stability margin
, Article Building Services Engineering Research and Technology ; Volume 43, Issue 5 , 2022 , Pages 589-603 ; 01436244 (ISSN) ; Haeri, M ; Sharif University of Technology
SAGE Publications Ltd
2022
Abstract
In this paper, a reduced multiple-model predictive controller based on gap metric and stability margin is presented to control heating, ventilating, and air conditioning (HVAC) systems. To tackle the strong nonlinearity and large number of degrees of freedom in HVAC system, two approaches, called Reduced Order Model Bank-Multiple Model (ROMB-MM) and Multiple Model-Reduced Order Model (MM-ROM), are introduced. In the first approach, the order reduction is performed prior to multiple models selection and in the second one multiple models selection is implemented before the model order reduction. Furthermore, soft switching is employed to enhance the closed-loop performance as well as to gain...
Optimal reactive power dispatch for improving voltage stability margin using a local voltage stability index
, Article Energy Conversion and Management ; Volume 59 , 2012 , Pages 66-73 ; 01968904 (ISSN) ; Vanouni, M ; Parniani, M ; Sharif University of Technology
2012
Abstract
Management of reactive power resources is vital for stable and secure operation of power systems in the view point of voltage stability. This paper deals with the management of on-load tap changers (OLTCs) and dynamic VAR sources (including synchronous generators, synchronous condensers, and shunt reactive power compensators) to improve voltage stability margin (VSM) of power systems. This problem is usually called optimal reactive power dispatch (ORD) in the literature. The main contribution of the paper is to introduce a new objective function for the ORD problem. The proposed objective function is derived based on a local voltage stability index, called DSY, and has a strong correlation...
Optimal reactive power dispatch using the concept of dynamic VAR source value
, Article 2009 IEEE Power and Energy Society General Meeting, PES '09, 26 July 2009 through 30 July 2009, Calgary, AB ; 2009 ; 9781424442416 (ISBN) ; Parniani, M ; Sharif University of Technology
Abstract
Voltage stability is the ability of a power system to maintain acceptable voltages at all buses in the system under normal conditions and after being subjected to a disturbance. This paper employs the management of reactive power generation to improve the voltage stability margin (VSM), in the framework of optimal reactive power dispatch (ORD) problem. Scheduling of VAR sources is performed using the concept of relative value of VAR sources. The proposed methodology has been tested on the IEEE 14-bus test system. Simulation results show that after the optimal reactive power scheduling, VSM of the systems is increased considerably. In addition, it is observed that reactive power reserve is...
MVAR management using generator participation factors for improving voltage stability margin
, Article Journal of Applied Sciences ; Volume 9, Issue 11 , 2009 , Pages 2123-2129 ; 18125654 (ISSN) ; Sharif University of Technology
2009
Abstract
This study assesses the management of reactive power generation to improve the voltage stability margin using modal analysis technique. The simulation results show that after the optimal reactive power re-scheduling, the voltage stability margin of the system is improved and the active/reactive power losses are decreased. Improving the voltage stability margin of power system without adding new VAR (Volt Ampere Reactive) sources and changing the active power dispatch, is the most important advantage of proposed method. © 2009 Asian Network for Scientific Information
An approach for under voltage load shedding using particle swarm optimization
, Article International Symposium on Industrial Electronics 2006, ISIE 2006, Montreal, QC, 9 July 2006 through 13 July 2006 ; Volume 3 , 2006 , Pages 2019-2024 ; 1424404975 (ISBN); 9781424404971 (ISBN) ; Amraee, T ; Ranjbar, A. M ; Sharif University of Technology
2006
Abstract
Under voltage load shedding (UVLS) is one of the most powerful countermeasure and somehow an economical solution to sustain voltage stability especially for double or severe contingencies in power systems. In this paper the concept of dynamic security-constrained OPF is employed to develop a model for optimal UVLS. Considering dynamic voltage security, the presented model attempts to provide sufficient voltage stability margin for post contingency condition. This is done by means of interruption some portion of loads at minimum cost. The voltage stability margin, which is measured as a MW distance to the collapse point, is incorporated into the power flow equations. Although some powerful...
Design of an H∞-optimal FOPID controller using particle swarm optimization
, Article 26th Chinese Control Conference, CCC 2007, Zhangjiajie, 26 July 2007 through 31 July 2007 ; October , 2007 , Pages 435-440 ; 7900719229 (ISBN); 9787900719225 (ISBN) ; Masoud, K. G ; Nasser, S ; Sharif University of Technology
2007
Abstract
This paper proposes a novel method to design an H∞-optimal Fractional Order PLD (FOPLD) controller with ability to control the transient, steady-state response and stability margins characteristics. The method uses particle swarm optimization algorithm and operates based on minimizing a general cost function. Minimization of the cost function is carried out subject to the H∞-norm; this norm is also included in the cost function to achieve its lower value. The method is applied to a phase-locked-loop motor speed system and an electromagnetic suspension system as two examples to illustrate the design procedure and verify performance of the proposed controller. The results show that the...
Voltage stability improvement through centralized reactive power management on the Smart Grid
, Article 2012 IEEE PES Innovative Smart Grid Technologies, ISGT 2012, 16 January 2012 through 20 January 2012 ; 2012 ; 9781457721588 (ISBN) ; Abbaspour-Tehrani Fard, A ; Dobakhshari, A. S ; Ranjbar, A. M ; Sharif University of Technology
2012
Abstract
With the increasing penetration of renewable energies as distributed generation (DG) in power systems, technical problems arise in both distribution and transmission system level. Voltage rise is the main barrier for connection of DGs in rural areas, while excessive reactive power demand from transmission system is the major concern for Transmission System Operators (TSO). Here, a centralized control scheme based on the Smart Grid is proposed to reduce the impact on the transmission system voltages and improve its stability, while mitigating the voltage rise issue in the distribution network. Reactive power output of DGs, substation capacitors and tap setting of transmission transformer are...
The Flexural instability of spinning flexible cylinder partially filled with viscous liquid
, Article Journal of Applied Mechanics, Transactions ASME ; Volume 77, Issue 1 , September , 2010 , Pages 1-9 ; 00218936 (ISSN) ; Haddadpour, H ; Sharif University of Technology
2010
Abstract
This paper deals with the flexural instability of flexible spinning cylinders partially filled with viscous fluid. Using the linearized Navier-Stokes equations for the incompressible flow, a two-dimensional model is developed for fluid motion. The resultant force exerted on the flexible cylinder wall as the result of the fluid motion is calculated as a function of lateral acceleration of the cylinder axis in the Laplace domain. Applying the Hamilton principle, the governing equations of flexural motion of the rotary flexible cylinder mounted on general viscoelastic supports are derived. Then combining the equations describing the fluid force on the flexible cylinder with the structural...
Robust flutter analysis and control of a wing
, Article Aircraft Engineering and Aerospace Technology ; Volume 84, Issue 6 , 2012 , Pages 423-438 ; 00022667 (ISSN) ; Moghaddam, M ; Rahim, M ; Sharif University of Technology
2012
Abstract
Purpose - The purpose of this paper is to present a novel approach in aeroservoelastic analysis and robust control of a wing section with two control surfaces in leading-edge and trailing-edge. The method demonstrates how the number of model uncertainties can affect the flutter margin. Design/methodology/approach - The proposed method effectively incorporates the structural model of a wing section with two degrees of freedom of pitch and plunge with two control surfaces on trailing and leading edges. A quasi-steady aerodynamics assumption is made for the aerodynamic modeling. Basically, perturbations are considered for the dynamic pressure models and uncertainty parameters are associated...
Dynamic instability of cantilevered composite pipe conveying flow with an end nozzle
, Article 21st International Congress on Sound and Vibration 2014, ICSV 2014 ; Vol. 4, issue , 13- 17 July , 2014 , pp. 3564-3571 ; ISBN: 9781634392389 ; Abtahi, H ; Haddadpour, H ; Sharif University of Technology
Abstract
In this paper, the instability of cantilevered horizontal composite pipes is investigated. To this aim, the lateral flow forces are modelled as a distributed lateral force and the nozzle effect is modelled as a compressive axial follower force and a concentrated end mass. The coupled bending-torsional equations of motion are derived using Hamilton's principal and Galerkin method. In order to obtain the stability margin of the pipe, the standard Eigen value problem is solved. Finally, effects of elastic coupling parameter and nozzle aspect ratio are considered on the stability margin of the pipe and some conclusions are drawn
An enhanced under-voltage load-shedding scheme to provide voltage stability
, Article Electric Power Systems Research ; Volume 77, Issue 8 , 2007 , Pages 1038-1046 ; 03787796 (ISSN) ; Ranjbar, A. M ; Mozafari, B ; Sadati, N ; Sharif University of Technology
2007
Abstract
Under-voltage load shedding is one of the most important tools for avoiding voltage instability. In this paper, an optimal load-shedding algorithm is developed. This approach is based on the concept of the static voltage stability margin and its sensitivity at the maximum loading point or the collapse point. The traditional load-shedding objective is extended to incorporate both technical and economic effects of load shedding. The voltage stability criterion is modeled directly into the load-shedding scheme. The proposed methodology is implemented over the IEEE 14 and 118 bus test systems and solved using a mathematical (GAMS/CONOPT) and two heuristic (PSO and GA) methods. The heuristic...
A new structured multimodel control of nonlinear systems by integrating stability margin and performance
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 139, Issue 9 , 2017 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
Abstract
This paper deals with a new systematic multimodel controller design for nonlinear systems. The design of local controllers based on performance requirements is incorporated with the concept of local models selection as an optimization problem. Gap metric and stability margin are used as measuring tool and operation space dividing criterion, respectively. The developed method provides support to design a simple structured multiple proportional-integral (PI) controller which guarantees both robust stability and time-domain performance specifications. The main advantages of the proposed method are avoiding model redundancy, not needing a priori knowledge about system, having simple structure,...
An integrated performance and robust stability based multi-model control of nonlinear systems: a PH neutralization reactor
, Article 2017 25th Iranian Conference on Electrical Engineering, ICEE 2017, 2 May 2017 through 4 May 2017 ; 2017 , Pages 679-684 ; 9781509059638 (ISBN) ; Haeri, M ; Sharif University of Technology
Abstract
This paper presents a new multi-model control scheme which integrates the stability and performance requirements to determine the nominal local models. Gap metric and stability margin concepts are applied to measure the distance between the local models and to grid the operation range of nonlinear system, respectively. The minimization of the integral of time absolute error is included as performance criterion. Furthermore, the multi-model decomposition and local controllers design are integrated in an optimization problem which provides avoidance of the redundancy issue. A fixed PI structure is considered as the local controllers to simplify the global multi-model controller structure....
Multimodel control of nonlinear systems: An improved gap metric and stability margin-based method
, Article Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME ; Volume 140, Issue 8 , 2018 ; 00220434 (ISSN) ; Haeri, M ; Sharif University of Technology
American Society of Mechanical Engineers (ASME)
2018
Abstract
This paper presents a new multimodel controller design approach incorporating stability and performance criteria. The gap metric is employed to measure the distance between local models. An efficient method based on state feedback strategy is introduced to improve the maximum stability margin of the local models. The proposed method avoids local model redundancy, simplifies the multimodel controller structure, and supports employing of many linear control techniques, while does not rely on a priori experience to choose the gridding threshold value. To evaluate the proposed method, three benchmark nonlinear systems are studied. Simulation results demonstrate that the method provides the...
An integrated best–worst decomposition approach of nonlinear systems using gap metric and stability margin
, Article Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering ; 2020 ; Haeri, M ; Sharif University of Technology
SAGE Publications Ltd
2020
Abstract
This article uses gap metric method to design a multi-model controller for nonlinear systems. In order to decompose the nonlinear system into a reduced nominal local models bank as much as possible, and assure the closed-loop robust stability and performance, the decomposition and designing of local controllers are integrated. To this end, robust stability, performance, and gap metric are incorporated to build a binary distance matrix that supports defining the driving and dependence powers for each local model. Then a best–worst analysis is employed considering the driving and dependence powers to find out the nominal local models. The proposed approach screens the value of all local models...