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Y. H. Song - One of the best experts on this subject based on the ideXlab platform.
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Steady‐state power flow and voltage control by unified power‐flow controllers, part 2: Applications
European Transactions on Electrical Power, 2007Co-Authors: Y. H. Song, J.y. LiuAbstract:The unified power-flow controller (UPFC) is a powerful device for the relief of transmission constraints. Part 1 of the paper proposes novel steady-state modelling and control algorithms for the study of UPFC, which use power-injection models to derive control parameters for UPFC to achieve the required line active power control and bus-voltage support. The proposed method does not change the symmetrical structures of Jacobian matrix, avoids the initialisations of control parameters and can cover a wide control range of UPFC due to the characteristics of Optimal Multiplier power-flow algorithms employed. This paper describes in detail the applications of the proposed theory in a 28-node system. The convergence of controlled power flow is analysed. Control performance has been evaluated. The numerical results presented clearly illustrate the effectiveness of the proposed approach.
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Steady‐state power flow and voltage control by unified power‐flow controllers, part 1: Modelling and algorithms
European Transactions on Electrical Power, 2007Co-Authors: Y. H. Song, J.y. LiuAbstract:The unified power-flow controller (UPFC), with its unique combination of fast shunt and series compensation, offers a versatile device for the relief of transmission constraints. However, in order to realise this potential benefit, appropriate local and global power-system control strategies must first be developed. UPFC steady-state model and its implementation in normal (open-loop) power flow has been investigated by a number of investigators. This paper further develops the power-injection method based on Optimal Multiplier power flow for the steady-state control of UPFC for power-flow control and voltage support. The proposed power injection power-flow control can be effectively used to derive UPFC control parameters to achieve the required control objectives.
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Power flow studies of a large practical power network with embedded facts devices using improved Optimal Multiplier newton‐raphson method
European Transactions on Electrical Power, 2001Co-Authors: Y. Xiao, Y. H. SongAbstract:In this paper, an improved Optimal Multiplier Newton-Raphson (OMNR) power flow method is presented for power flow studies of ill-conditioned large power system with embedded Flexible AC Transmission Systems (FACTS) devices. Power injection models (PIMs) of two typical FACTS devices, Phase Shifter (PS) and Unified Power Flow Controller (UPFC), are derived in rectangular form. After detailed analysis, a defect of the original OMNR method is identified and an improved version is presented. Incorporating the derived FACTS power injection models into the improved OMNR power flow program, the impacts of FACTS devices on power system control have been fully tested on the U.K. National Grid Company (NGC) system. The results clearly illustrate the effectiveness of the proposed approach.
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Steady-state analysis and control
Flexible AC Transmission Systems (FACTS), 1999Co-Authors: Y. H. SongAbstract:This chapter focuses on the steady state analysis and control of systems with FACTS devices with particular reference to the UPFC. A steady-state UPFC model is proposed and its power injection transformation is derived in rectangular form. The Optimal Multiplier power flow method for ill-conditioned system is applied to implement the UPFC model. Then a novel method for the steady state control of UPFC for power flow control and voltage support is presented. Essentially, it is based on a power injection model and Optimal Multiplier power flow. The proposed power injection power flow control can be effectively used to derive UPFC control parameters to achieve the required control objectives. A number of internal limits imposed on the UPFC have been considered, including series injection voltage magnitude, line current through the series inverter, real power transfer between the shunt inverter and series inverter, shunt side current and shunt injection voltage magnitude. The proposed constrained control strategies can co-ordinate the available control freedom to achieve an efficient usage of the UPFC when constrained by the internal limits. The comparison of rating and control flexibility of three major FACTS devices is also included in the numerical examples. The proposed UPFC model and power flow control algorithms have been vigorously tested in a number of systems. The results on two practical systems clearly illustrate the effectiveness of the proposed algorithms.
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Power injection modeling and Optimal Multiplier power flow algorithm for steady-state studies of unified power flow controllers
Electric Power Systems Research, 1999Co-Authors: Y. H. Song, J.y. Liu, P.a. MehtaAbstract:Abstract This paper presents an Optimal Multiplier based Newton-Raphson power flow algorithm for reliably and efficiently handling power systems with embedded flexible AC transmission systems (FACTS) devices such as unified power flow controllers (UPFCs). A power injection transformation of a two voltage source UPFC model is derived in rectangular form. After detailed analyses of issues in implementation of UPFCs in power flow programmes by various power flow algorithms, the Optimal Multiplier power flow method for ill-conditioned systems is adopted. The proposed UPFC model and power flow algorithm have been programmed and vigorously tested in a number of systems. The results on the IEEE 30-bus test system and a 306-bus practical system are reported and compared with conventional user defined model type programmes, which clearly illustrate the effectiveness of the proposed algorithm.
J.y. Liu - One of the best experts on this subject based on the ideXlab platform.
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Steady‐state power flow and voltage control by unified power‐flow controllers, part 1: Modelling and algorithms
European Transactions on Electrical Power, 2007Co-Authors: Y. H. Song, J.y. LiuAbstract:The unified power-flow controller (UPFC), with its unique combination of fast shunt and series compensation, offers a versatile device for the relief of transmission constraints. However, in order to realise this potential benefit, appropriate local and global power-system control strategies must first be developed. UPFC steady-state model and its implementation in normal (open-loop) power flow has been investigated by a number of investigators. This paper further develops the power-injection method based on Optimal Multiplier power flow for the steady-state control of UPFC for power-flow control and voltage support. The proposed power injection power-flow control can be effectively used to derive UPFC control parameters to achieve the required control objectives.
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Steady‐state power flow and voltage control by unified power‐flow controllers, part 2: Applications
European Transactions on Electrical Power, 2007Co-Authors: Y. H. Song, J.y. LiuAbstract:The unified power-flow controller (UPFC) is a powerful device for the relief of transmission constraints. Part 1 of the paper proposes novel steady-state modelling and control algorithms for the study of UPFC, which use power-injection models to derive control parameters for UPFC to achieve the required line active power control and bus-voltage support. The proposed method does not change the symmetrical structures of Jacobian matrix, avoids the initialisations of control parameters and can cover a wide control range of UPFC due to the characteristics of Optimal Multiplier power-flow algorithms employed. This paper describes in detail the applications of the proposed theory in a 28-node system. The convergence of controlled power flow is analysed. Control performance has been evaluated. The numerical results presented clearly illustrate the effectiveness of the proposed approach.
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Power injection modeling and Optimal Multiplier power flow algorithm for steady-state studies of unified power flow controllers
Electric Power Systems Research, 1999Co-Authors: Y. H. Song, J.y. Liu, P.a. MehtaAbstract:Abstract This paper presents an Optimal Multiplier based Newton-Raphson power flow algorithm for reliably and efficiently handling power systems with embedded flexible AC transmission systems (FACTS) devices such as unified power flow controllers (UPFCs). A power injection transformation of a two voltage source UPFC model is derived in rectangular form. After detailed analyses of issues in implementation of UPFCs in power flow programmes by various power flow algorithms, the Optimal Multiplier power flow method for ill-conditioned systems is adopted. The proposed UPFC model and power flow algorithm have been programmed and vigorously tested in a number of systems. The results on the IEEE 30-bus test system and a 306-bus practical system are reported and compared with conventional user defined model type programmes, which clearly illustrate the effectiveness of the proposed algorithm.
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DETERMINING MAXIMUM REGULATING CAPABILITY OF UPFC BASED ON PREDICTING FEASIBILITY LIMIT OF POWER SYSTEMS
Electric Machines & Power Systems, 1998Co-Authors: J.y. Liu, Y. H. SongAbstract:ABSTRACT This paper presents a novel procedure to determine the maximum regulating capability of a unified power flow controller (UPFC) by using Optimal Multiplier power flow. The capabilities of flexible ac transmission systems (FACTS) equipment are not only constrained by their thermal limits and the steady-state security limits, but also limited by their feasibility limits. After the detailed analyses have been made on the use of Optimal Multiplier u as a new predictor to estimate the boundary point of the feasibility region, an algorithm for deteiTnirung the UPFC regulating capability is proposed. The approach is then compared with minimum singular value decomposition on the IEEE 30 bus system. The results clearly demonstrate the effectiveness of the proposed approach.
Fernando Pereira - One of the best experts on this subject based on the ideXlab platform.
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Optimal Lagrange Multipliers for dependent rate allocation in video coding
Signal Processing: Image Communication, 2018Co-Authors: Ana De Abreu, Pascal Frossard, Gene Cheung, Fernando PereiraAbstract:Abstract In a typical video rate allocation problem, the objective is to Optimally distribute a source rate budget among a set of (in)dependently coded data units to minimize the total distortion. Conventional Lagrangian approaches convert the lone rate constraint to a linear rate penalty scaled by a Multiplier in the objective, resulting in a simpler unconstrained formulation. However, the search for the “Optimal” Multiplier – one that results in a distortion-minimizing solution among all Lagrangian solutions that satisfy the original rate constraint – remains an elusive open problem in the general setting. To address this problem, we are the first in the literature to construct a computation-efficient search strategy to identify this Optimal Multiplier numerically in the general dependent coding scenario. Specifically, we first formulate a general rate allocation problem where each data unit can be dependently coded at different quantization parameters (QP) using a previous unit as predictor, or left uncoded at the encoder and subsequently interpolated at the decoder using neighboring coded units. After converting the original rate-constrained problem to the unconstrained Lagrangian counterpart, we design an efficient dynamic programming (DP) algorithm that finds the Optimal Lagrangian solution for a fixed Multiplier. In extensive monoview and multiview video coding experiments, we show that for fixed target rate constraints, our algorithm is able to find the Optimal Multipliers in a distortion minimum sense among all Lagrangian solutions. Moreover, we show that our simple solution is able to compete with complex rate control (RC) solutions used in video compression standards such as HEVC and 3D-HEVC, which outlines the importance of the proper choice of the Lagrangian Multipliers.
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Optimal Lagrange Multipliers for Dependent Rate Allocation in Video Coding
arXiv: Multimedia, 2016Co-Authors: Ana De Abreu, Pascal Frossard, Gene Cheung, Fernando PereiraAbstract:In a typical video rate allocation problem, the objective is to Optimally distribute a source rate budget among a set of (in)dependently coded data units to minimize the total distortion of all units. Conventional Lagrangian approaches convert the lone rate constraint to a linear rate penalty scaled by a Multiplier in the objective, resulting in a simpler unconstrained formulation. However, the search for the "Optimal" Multiplier, one that results in a distortion-minimizing solution among all Lagrangian solutions that satisfy the original rate constraint, remains an elusive open problem in the general setting. To address this problem, we propose a computation-efficient search strategy to identify this Optimal Multiplier numerically. Specifically, we first formulate a general rate allocation problem where each data unit can be dependently coded at different quantization parameters (QP) using a previous unit as predictor, or left uncoded at the encoder and subsequently interpolated at the decoder using neighboring coded units. After converting the original rate constrained problem to the unconstrained Lagrangian counterpart, we design an efficient dynamic programming (DP) algorithm that finds the Optimal Lagrangian solution for a fixed Multiplier. Finally, within the DP framework, we iteratively compute neighboring singular Multiplier values, each resulting in multiple simultaneously Optimal Lagrangian solutions, to drive the rates of the computed Lagrangian solutions towards the bit budget. We terminate when a singular Multiplier value results in two Lagrangian solutions with rates below and above the bit budget. In extensive monoview and multiview video coding experiments, we show that our DP algorithm and selection of Optimal Multipliers on average outperform comparable rate control solutions used in video compression standards such as HEVC that do not skip frames in Y-PSNR.
Swapan Kumar Goswami - One of the best experts on this subject based on the ideXlab platform.
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Handling inequalities and discrete variables in newton Optimal power flow using Optimal Multiplier and fuzzy based limit enforcement and relaxation technique
International Journal of Electrical Power & Energy Systems, 2012Co-Authors: S. Patra, Swapan Kumar GoswamiAbstract:Abstract This paper makes contributions in the Newton’s Optimal power flow in two ways, in the handling of inequalities and the discrete variables. The problem of identification of binding inequalities is handled by controlled correction of the variables during iterations through the use of separate optimum Multipliers for active and reactive variables. Convergence of the OPF is improved by enforcing the limit on the inequalities that oscillate around their limiting values. A fuzzy based limit enforcement and relaxation technique is used for this purpose. The problem of handling discrete variables with large step sizes is also solved using the optimum Multipliers. Optimal Multipliers are selected in such a way that corrections of the discrete variables automatically correspond to their available tap values. Numerical test results for standard IEEE test systems and a real power system are produced in support of the claims of the authors.
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Multiple low voltage power flow solutions using hybrid PSO and Optimal Multiplier method
Expert Systems with Applications, 2010Co-Authors: Swapan Kumar Goswami, Parimal AcharjeeAbstract:In this paper a method for computing multiple power flow solutions of power system is proposed. The proposed method determines the multiple solutions in pairs. Particle Swarm Optimization (PSO) technique is used to find the starting values of the rectangular Newton-Raphson power flow. From these starting values, the rectangular Newton-Raphson load flow determines a low voltage solution close to the first one. Optimal Multipliers are then used to determine a second low voltage solution. Test results of standard IEEE 14 bus system have been shown.
Ana De Abreu - One of the best experts on this subject based on the ideXlab platform.
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Optimal Lagrange Multipliers for dependent rate allocation in video coding
Signal Processing: Image Communication, 2018Co-Authors: Ana De Abreu, Pascal Frossard, Gene Cheung, Fernando PereiraAbstract:Abstract In a typical video rate allocation problem, the objective is to Optimally distribute a source rate budget among a set of (in)dependently coded data units to minimize the total distortion. Conventional Lagrangian approaches convert the lone rate constraint to a linear rate penalty scaled by a Multiplier in the objective, resulting in a simpler unconstrained formulation. However, the search for the “Optimal” Multiplier – one that results in a distortion-minimizing solution among all Lagrangian solutions that satisfy the original rate constraint – remains an elusive open problem in the general setting. To address this problem, we are the first in the literature to construct a computation-efficient search strategy to identify this Optimal Multiplier numerically in the general dependent coding scenario. Specifically, we first formulate a general rate allocation problem where each data unit can be dependently coded at different quantization parameters (QP) using a previous unit as predictor, or left uncoded at the encoder and subsequently interpolated at the decoder using neighboring coded units. After converting the original rate-constrained problem to the unconstrained Lagrangian counterpart, we design an efficient dynamic programming (DP) algorithm that finds the Optimal Lagrangian solution for a fixed Multiplier. In extensive monoview and multiview video coding experiments, we show that for fixed target rate constraints, our algorithm is able to find the Optimal Multipliers in a distortion minimum sense among all Lagrangian solutions. Moreover, we show that our simple solution is able to compete with complex rate control (RC) solutions used in video compression standards such as HEVC and 3D-HEVC, which outlines the importance of the proper choice of the Lagrangian Multipliers.
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Optimal Lagrange Multipliers for Dependent Rate Allocation in Video Coding
arXiv: Multimedia, 2016Co-Authors: Ana De Abreu, Pascal Frossard, Gene Cheung, Fernando PereiraAbstract:In a typical video rate allocation problem, the objective is to Optimally distribute a source rate budget among a set of (in)dependently coded data units to minimize the total distortion of all units. Conventional Lagrangian approaches convert the lone rate constraint to a linear rate penalty scaled by a Multiplier in the objective, resulting in a simpler unconstrained formulation. However, the search for the "Optimal" Multiplier, one that results in a distortion-minimizing solution among all Lagrangian solutions that satisfy the original rate constraint, remains an elusive open problem in the general setting. To address this problem, we propose a computation-efficient search strategy to identify this Optimal Multiplier numerically. Specifically, we first formulate a general rate allocation problem where each data unit can be dependently coded at different quantization parameters (QP) using a previous unit as predictor, or left uncoded at the encoder and subsequently interpolated at the decoder using neighboring coded units. After converting the original rate constrained problem to the unconstrained Lagrangian counterpart, we design an efficient dynamic programming (DP) algorithm that finds the Optimal Lagrangian solution for a fixed Multiplier. Finally, within the DP framework, we iteratively compute neighboring singular Multiplier values, each resulting in multiple simultaneously Optimal Lagrangian solutions, to drive the rates of the computed Lagrangian solutions towards the bit budget. We terminate when a singular Multiplier value results in two Lagrangian solutions with rates below and above the bit budget. In extensive monoview and multiview video coding experiments, we show that our DP algorithm and selection of Optimal Multipliers on average outperform comparable rate control solutions used in video compression standards such as HEVC that do not skip frames in Y-PSNR.