A novel scheme based on equivalent instantaneous leakage inductance (EILI) to distinguish inrush currents from internal fault currents in power transformers is proposed, which is derived from the circuit differential equation. First, the EILI that represents different characteristics between the inrush current and an internal fault is defined, and its calculation methods and the criteria of two-winding and three-winding transformers are derived. This method does not require B-H curve data and the parameters of leakage inductances obtained from the transformer manufacturer. A total of 147 experimental cases verify that the EILI calculated in real time is able to clear internal fault even light fault rapidly and correctly.
{"title":"A Novel Algorithm for Discrimination Between Inrush Currents and Internal Faults Based on Equivalent Instantaneous Leakage Inductance","authors":"Ma Jing, Wang Zeng-ping","doi":"10.1109/PES.2007.385714","DOIUrl":"https://doi.org/10.1109/PES.2007.385714","url":null,"abstract":"A novel scheme based on equivalent instantaneous leakage inductance (EILI) to distinguish inrush currents from internal fault currents in power transformers is proposed, which is derived from the circuit differential equation. First, the EILI that represents different characteristics between the inrush current and an internal fault is defined, and its calculation methods and the criteria of two-winding and three-winding transformers are derived. This method does not require B-H curve data and the parameters of leakage inductances obtained from the transformer manufacturer. A total of 147 experimental cases verify that the EILI calculated in real time is able to clear internal fault even light fault rapidly and correctly.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127811549","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In algebraic geometry, the concept of Grobner basis allows a systematic study of the solution of a system of polynomial equations. This concept can be applied to find the global (and all local optima) optimum of a nonlinear, not necessarily convex function, the only restriction being that the objective function be polynomial. The method is based on computing a lexicographic (lex) ordered Grobner basis for the ideal generated by the first order necessary conditions defined by the Lagrangian. Computing the optimal solution is then equivalent to computing the variety corresponding to this ideal. By virtue of the (lex) ordering, the system is transformed in to set of polynomials which can be solved successively to obtain the solutions. Here, we illustrate the application of the method on a non-convex function and identify the global optimum from the set of fifteen stationary points (6 local minima, 2 local maxima and 7 saddles). Then we apply the method to solve the classical economic dispatch problem including a combined cycle heat plant (CCHP) whose piecewise linear cost function is approximated by a smooth tenth order polynomial. Interestingly, the the method yields two possible solutions from which the least cost solution can be picked. While the work reported here is only preliminary, we find the results encouraging and hope that the method will find applicability in identifying the global optimum of non-convex power systems optimization problems.
{"title":"A Computational Algebraic Geometry Based Global Optimization Technique to Address Economic Dispatch","authors":"R. Kavasseri, Parthasarathi Nag","doi":"10.1109/PES.2007.386198","DOIUrl":"https://doi.org/10.1109/PES.2007.386198","url":null,"abstract":"In algebraic geometry, the concept of Grobner basis allows a systematic study of the solution of a system of polynomial equations. This concept can be applied to find the global (and all local optima) optimum of a nonlinear, not necessarily convex function, the only restriction being that the objective function be polynomial. The method is based on computing a lexicographic (lex) ordered Grobner basis for the ideal generated by the first order necessary conditions defined by the Lagrangian. Computing the optimal solution is then equivalent to computing the variety corresponding to this ideal. By virtue of the (lex) ordering, the system is transformed in to set of polynomials which can be solved successively to obtain the solutions. Here, we illustrate the application of the method on a non-convex function and identify the global optimum from the set of fifteen stationary points (6 local minima, 2 local maxima and 7 saddles). Then we apply the method to solve the classical economic dispatch problem including a combined cycle heat plant (CCHP) whose piecewise linear cost function is approximated by a smooth tenth order polynomial. Interestingly, the the method yields two possible solutions from which the least cost solution can be picked. While the work reported here is only preliminary, we find the results encouraging and hope that the method will find applicability in identifying the global optimum of non-convex power systems optimization problems.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134456798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Regis, T. Soubdhan, R. Calif, M. Abadi, R. Blonbou
Solar energy converter devices such as photovoltaic cells are very sensitive to instantaneous solar radiation fluctuations. Thus rapid variation of solar radiation due to changes in the local meteorological condition can induce large amplitude fluctuations of the produced electrical power and reduce the overall efficiency of the system. When large amount of photovoltaic electricity is send into a weak or small electricity network such as island network; the electric grid security can be in jeopardy due to these power fluctuations. To palliate these difficulties, it is essential to identify the characteristic of these fluctuations in order to anticipate the eventuality of power shortage or power surge. The detection of singularity in solar radiation signal allows separating the signal in different sequences, as a function of the different meteorological conditions encountered at the measurement site. Thereby, the different sequences could be analyzed separately. For instance, a statistical analysis could be conducted in order to classify these sequences as a function of their effect on the overall efficiency of a photovoltaic system. The objective of this paper is to present an approach that uses wavelet transform analysis to detect singularities in solar radiation signal. This preliminary work set the basis for further investigation dedicated to classification of solar energy fluctuation.
{"title":"Singularity detection in Solar Radiation Signal using wavelet transform","authors":"S. Regis, T. Soubdhan, R. Calif, M. Abadi, R. Blonbou","doi":"10.1109/PES.2007.386160","DOIUrl":"https://doi.org/10.1109/PES.2007.386160","url":null,"abstract":"Solar energy converter devices such as photovoltaic cells are very sensitive to instantaneous solar radiation fluctuations. Thus rapid variation of solar radiation due to changes in the local meteorological condition can induce large amplitude fluctuations of the produced electrical power and reduce the overall efficiency of the system. When large amount of photovoltaic electricity is send into a weak or small electricity network such as island network; the electric grid security can be in jeopardy due to these power fluctuations. To palliate these difficulties, it is essential to identify the characteristic of these fluctuations in order to anticipate the eventuality of power shortage or power surge. The detection of singularity in solar radiation signal allows separating the signal in different sequences, as a function of the different meteorological conditions encountered at the measurement site. Thereby, the different sequences could be analyzed separately. For instance, a statistical analysis could be conducted in order to classify these sequences as a function of their effect on the overall efficiency of a photovoltaic system. The objective of this paper is to present an approach that uses wavelet transform analysis to detect singularities in solar radiation signal. This preliminary work set the basis for further investigation dedicated to classification of solar energy fluctuation.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133836681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Summary form only given.This paper presents results from an analysis of voltage stability following severe contingencies in the PJM system. The analyses involved the use of steady-state (OPF) and short and long-term simulation tools. The results highlight the importance of adequate load modeling in assessing the performance of and solutions to voltage instability. UVLS is shown to be beneficial in arresting instability. Optimal Power Flow (OPF) analyses (supplemented with dynamic simulation results) provide valuable insight into the best locations and required minimum levels of UVLS. However, UVLS may not be able to address the serious scenarios where fast voltage dynamics develop immediately after an outage.
{"title":"Voltage Stability Study of the PJM System Following Extreme Disturbances","authors":"R. Koessler, Wenzheng Qiu, M. Patel, H. Clark","doi":"10.1109/PES.2007.385705","DOIUrl":"https://doi.org/10.1109/PES.2007.385705","url":null,"abstract":"Summary form only given.This paper presents results from an analysis of voltage stability following severe contingencies in the PJM system. The analyses involved the use of steady-state (OPF) and short and long-term simulation tools. The results highlight the importance of adequate load modeling in assessing the performance of and solutions to voltage instability. UVLS is shown to be beneficial in arresting instability. Optimal Power Flow (OPF) analyses (supplemented with dynamic simulation results) provide valuable insight into the best locations and required minimum levels of UVLS. However, UVLS may not be able to address the serious scenarios where fast voltage dynamics develop immediately after an outage.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115184413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper demonstrates the possibility to enhance the damping of inter-area oscillations using wide area measurement (WAM) based adaptive supervisory controller (ASC).. A damping controller based on the mixed-sensitivity linear matrix inequality (LMI) approach with pole-placement restriction is designed. The ASC uses the input information from conveniently located phase measurement units (PMU) in the system and dispatches supplementary control signals to the available local controllers. Different input signals to the ASC, i.e., frequency and active power generators are used and corresponding ASC performances compared. The design of the ASC is explained in detail and its performance validated by frequency and time domain simulations on a 4- machine 2-area test system.
{"title":"Damping of Inter-area Oscillations by WAM Based Supplementary Controller","authors":"Zhijian Hu, J. Milanović","doi":"10.1109/PES.2007.386095","DOIUrl":"https://doi.org/10.1109/PES.2007.386095","url":null,"abstract":"The paper demonstrates the possibility to enhance the damping of inter-area oscillations using wide area measurement (WAM) based adaptive supervisory controller (ASC).. A damping controller based on the mixed-sensitivity linear matrix inequality (LMI) approach with pole-placement restriction is designed. The ASC uses the input information from conveniently located phase measurement units (PMU) in the system and dispatches supplementary control signals to the available local controllers. Different input signals to the ASC, i.e., frequency and active power generators are used and corresponding ASC performances compared. The design of the ASC is explained in detail and its performance validated by frequency and time domain simulations on a 4- machine 2-area test system.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115487594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Power system stabilizers (PSSs) are used to provide damping torque for the synchronous generators to suppress low frequency oscillations present in the power system by generating supplementary control signals for the excitation system. Strong nonlinearity and dynamics exist in the power system. Numerous previous techniques have been proposed to design PSSs but many of them are synthesized based on a linearized model. This paper presents a nonlinear power system stabilizer based on synergetic control theory. Synergetic synthesis of the PSS is based fully on a simplified nonlinear model of the power system. The synergetic control law provides asymptotic stability with respect to the required operating modes, invariance to the load variations, and robustness to variations of the input variables and power system parameters. The dynamic characteristics of the proposed PSS are studied in a typical single-machine infinite-bus power system and compared with the cases with a conventional PSS and without a PSS. Simulation results show the proposed PSS is robust for such nonlinear dynamic system and achieves better performance than the conventional PSS in damping oscillations.
{"title":"Design of Power System Stabilizers Using Synergetic Control Theory","authors":"Zhenhua Jiang","doi":"10.1109/PES.2007.385651","DOIUrl":"https://doi.org/10.1109/PES.2007.385651","url":null,"abstract":"Power system stabilizers (PSSs) are used to provide damping torque for the synchronous generators to suppress low frequency oscillations present in the power system by generating supplementary control signals for the excitation system. Strong nonlinearity and dynamics exist in the power system. Numerous previous techniques have been proposed to design PSSs but many of them are synthesized based on a linearized model. This paper presents a nonlinear power system stabilizer based on synergetic control theory. Synergetic synthesis of the PSS is based fully on a simplified nonlinear model of the power system. The synergetic control law provides asymptotic stability with respect to the required operating modes, invariance to the load variations, and robustness to variations of the input variables and power system parameters. The dynamic characteristics of the proposed PSS are studied in a typical single-machine infinite-bus power system and compared with the cases with a conventional PSS and without a PSS. Simulation results show the proposed PSS is robust for such nonlinear dynamic system and achieves better performance than the conventional PSS in damping oscillations.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115555464","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As wind penetration increases, the adverse impact of wind power fluctuations on the system frequency becomes significant. Especially for isolated or weakly connected small- scale power systems, the wind power induced system frequency deviations might exceed beyond the safe range set by utilities. Coupling energy storage system (ESS) to wind energy can smooth the wind power. The ESS in a wind farm can be either aggregated or distributed configured. This paper examines the performance differences of the two ESS configurations. The evaluation of the ESS performance is based on the fluctuation harmonic content (FHC) which quantitatively describes how fluctuant the power is. The system frequency deviations induced by untreated and filtered wind powers are investigated in a study system with different generation mixes. This research shows the distributed ESS configuration is as effective as its aggregated counterpart in wind power smoothing and system frequency deviation reduction.
{"title":"Performance Comparison of Aggregated and Distributed Energy Storage Systems in a Wind Farm For Wind Power Fluctuation Suppression","authors":"Wei Li, G. Joós","doi":"10.1109/PES.2007.386249","DOIUrl":"https://doi.org/10.1109/PES.2007.386249","url":null,"abstract":"As wind penetration increases, the adverse impact of wind power fluctuations on the system frequency becomes significant. Especially for isolated or weakly connected small- scale power systems, the wind power induced system frequency deviations might exceed beyond the safe range set by utilities. Coupling energy storage system (ESS) to wind energy can smooth the wind power. The ESS in a wind farm can be either aggregated or distributed configured. This paper examines the performance differences of the two ESS configurations. The evaluation of the ESS performance is based on the fluctuation harmonic content (FHC) which quantitatively describes how fluctuant the power is. The system frequency deviations induced by untreated and filtered wind powers are investigated in a study system with different generation mixes. This research shows the distributed ESS configuration is as effective as its aggregated counterpart in wind power smoothing and system frequency deviation reduction.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"52 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115637887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper discusses the use of trajectory sensitivity analysis (TSA) in assessing the effects of a thyristor controlled series compensator (TCSC) on the stability condition of a power system. TSA has been used to find suitable controller parameters for the effective use of the TCSC in improving stability margin. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. Security assessment through TSA is carried out in systems with part of the network reduced by Ward-PV method. This increases the computation speed without much loss of accuracy. The study is carried out in IEEE 16- machine 68-bus system.
{"title":"Using Trajectory Sensitivity for Stability Assessment of a Ward-PV Equivalent Power System","authors":"D. Chatterjee, A. Ghosh","doi":"10.1109/PES.2007.385911","DOIUrl":"https://doi.org/10.1109/PES.2007.385911","url":null,"abstract":"This paper discusses the use of trajectory sensitivity analysis (TSA) in assessing the effects of a thyristor controlled series compensator (TCSC) on the stability condition of a power system. TSA has been used to find suitable controller parameters for the effective use of the TCSC in improving stability margin. The TCSC is modeled by a variable capacitor, the value of which changes with the firing angle. Security assessment through TSA is carried out in systems with part of the network reduced by Ward-PV method. This increases the computation speed without much loss of accuracy. The study is carried out in IEEE 16- machine 68-bus system.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115697217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper proposes a statistical distribution of blackouts for power systems through the employment of statistical theory. Two groups of factors involved in the cascading events leading to blackouts are explored and explained. The mechanism of blackouts is proposed based on these two factors so that the statistical law of blackouts can be derived by using statistical and probability theory. The theoretical proofs are given in obtaining the statistical law of blackouts. Sequential Monte Carlo simulation method is utilized to perform the numerical tests on different power systems to justify the proposed law for blackouts.
{"title":"Probability Distribution of Power System Blackouts","authors":"B. Gou, Hui Zheng, Weibiao Wu, X. Yu","doi":"10.1109/PES.2007.385471","DOIUrl":"https://doi.org/10.1109/PES.2007.385471","url":null,"abstract":"This paper proposes a statistical distribution of blackouts for power systems through the employment of statistical theory. Two groups of factors involved in the cascading events leading to blackouts are explored and explained. The mechanism of blackouts is proposed based on these two factors so that the statistical law of blackouts can be derived by using statistical and probability theory. The theoretical proofs are given in obtaining the statistical law of blackouts. Sequential Monte Carlo simulation method is utilized to perform the numerical tests on different power systems to justify the proposed law for blackouts.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115841071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Distributed generation (DG) is playing an increasing role not only in electric power generation, as backup sources to increase the supply reliability, but also as a possible source providing ancillary services for grid support. The penetration level of DG in some particular power systems is high and growing, leading to a great concern how to employ DG in an efficient and effective way for network control and support. This paper aims to give an overview of technical, economical and environmental aspects when integrating DG to the power system. The contribution ability of DG to ancillary services is also investigated.
{"title":"Benefits and Impact of Using Small Generators for Network Support","authors":"V. V. Thong, J. Driesen, R. Belmans","doi":"10.1109/PES.2007.385933","DOIUrl":"https://doi.org/10.1109/PES.2007.385933","url":null,"abstract":"Distributed generation (DG) is playing an increasing role not only in electric power generation, as backup sources to increase the supply reliability, but also as a possible source providing ancillary services for grid support. The penetration level of DG in some particular power systems is high and growing, leading to a great concern how to employ DG in an efficient and effective way for network control and support. This paper aims to give an overview of technical, economical and environmental aspects when integrating DG to the power system. The contribution ability of DG to ancillary services is also investigated.","PeriodicalId":380613,"journal":{"name":"2007 IEEE Power Engineering Society General Meeting","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124255735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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