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On the Local Identifiability of Load Model Parameters in Measurement-based Approach
Byoung-Kon Choi,Hsiao-Dong Chiang 대한전기학회 2009 Journal of Electrical Engineering & Technology Vol.4 No.2
It is important to derive reliable parameter values in the measurement-based load model development of electric power systems. However parameter estimation tasks, in practice, often face the parameter identifiability issue; whether or not the model parameters can be estimated with a given input-output data set in reliable manner. This paper introduces concepts and practical definitions of the local identifiability of model parameters. A posteriori local identifiability is defined in the sense of nonlinear least squares. As numerical examples, local identifiability of third-order induction motor (IM) model and a Z-induction motor (Z-IM) model is studied. It is shown that parameter illconditioning can significantly affect on reliable parameter estimation task. Numerical studies show that local identifiability can be quite sensitive to input data and a given local solution. Finally, several countermeasures are proposed to overcome ill-conditioning problem in measurement-based load modeling.
Development of Composite Load Models of Power Systems using On-line Measurement Data
Byoung-Kon Choi,Hsiao-Dong Chiang,Yinhong Li,Yung-Tien Chen,Der-Hua Huang,Mark G. Lauby 대한전기학회 2006 Journal of Electrical Engineering & Technology Vol.1 No.2
Load representation has a significant impact on power system analysis and control results. In this paper, composite load models are developed based on on-line measurement data from a practical power system. Three types of static-dynamic load models are derived: general ZIP-induction motor model, Exponential-induction motor model and Z-induction motor model. For the dynamic induction motor model, two different third-order induction motor models are studied. The performances in modeling real and reactive power behaviors by composite load models are compared with other dynamic load models in terms of relative mismatch error. In addition, numerical consideration of ill-conditioned parameters is addressed based on trajectory sensitivity. Numerical studies indicate that the developed composite load models can accurately capture the dynamic behaviors of loads during disturbance.
Trust-Tech based Parameter Estimation and its Application to Power System Load Modeling
Choi, Byoung-Kon,Chiang, Hsiao-Dong,Yu, David C. The Korean Institute of Electrical Engineers 2008 Journal of Electrical Engineering & Technology Vol.3 No.4
Accurate load modeling is essential for power system static and dynamic analysis. By the nature of the problem of parameter estimation for power system load modeling using actual measurements, multiple local optimal solutions may exist and local methods can be trapped in a local optimal solution giving possibly poor performance. In this paper, Trust-Tech, a novel methodology for global optimization, is applied to tackle the multiple local optimal solutions issue in measurement-based power system load modeling. Multiple sets of parameter values of a composite load model are obtained using Trust-Tech in a deterministic manner. Numerical studies indicate that Trust-Tech along with conventional local methods can be successfully applied to power system load model parameter estimation in measurement-based approaches.
On the Local Identifiability of Load Model Parameters in Measurement-based Approach
Choi, Byoung-Kon,Chiang, Hsiao-Dong The Korean Institute of Electrical Engineers 2009 Journal of Electrical Engineering & Technology Vol.4 No.2
It is important to derive reliable parameter values in the measurement-based load model development of electric power systems. However parameter estimation tasks, in practice, often face the parameter identifiability issue; whether or not the model parameters can be estimated with a given input-output data set in reliable manner. This paper introduces concepts and practical definitions of the local identifiability of model parameters. A posteriori local identifiability is defined in the sense of nonlinear least squares. As numerical examples, local identifiability of third-order induction motor (IM) model and a Z-induction motor (Z-IM) model is studied. It is shown that parameter ill-conditioning can significantly affect on reliable parameter estimation task. Numerical studies show that local identifiability can be quite sensitive to input data and a given local solution. Finally, several countermeasures are proposed to overcome ill-conditioning problem in measurement-based load modeling.
Trust-Tech based Parameter Estimation and its Application to Power System Load Modeling
Byoung-Kon Choi,Hsiao-Dong Chiang,David C. Yu 대한전기학회 2008 Journal of Electrical Engineering & Technology Vol.3 No.4
Accurate load modeling is essential for power system static and dynamic analysis. By the nature of the problem of parameter estimation for power system load modeling using actual measurements, multiple local optimal solutions may exist and local methods can be trapped in a local optimal solution giving possibly poor performance. In this paper, Trust-Tech, a novel methodology for global optimization, is applied to tackle the multiple local optimal solutions issue in measurement-based power system load modeling. Multiple sets of parameter values of a composite load model are obtained using Trust-Tech in a deterministic manner. Numerical studies indicate that Trust-Tech along with conventional local methods can be successfully applied to power system load model parameter estimation in measurement-based approaches.
Development of Composite Load Models of Power Systems using On-line Measurement Data
Choi Byoung-Kon,Chiang Hsiao Dong,Li Yinhong,Chen Yung Tien,Huang Der Hua,Lauby Mark G. The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.2
Load representation has a significant impact on power system analysis and control results. In this paper, composite load models are developed based on on-line measurement data from a practical power system. Three types of static-dynamic load models are derived: general ZIP-induction motor model, Exponential-induction motor model and Z-induction motor model. For the dynamic induction motor model, two different third-order induction motor models are studied. The performances in modeling real and reactive power behaviors by composite load models are compared with other dynamic load models in terms of relative mismatch error. In addition, numerical consideration of ill-conditioned parameters is addressed based on trajectory sensitivity. Numerical studies indicate that the developed composite load models can accurately capture the dynamic behaviors of loads during disturbance.
윤건탁 ( Kon Tak Yoon ),서인수 ( In Soo Seo ),김광봉 ( Kwang Bong Kim ),최병미 ( Byoung Mi Choi ),손민호 ( Min Ho Son ) 한국환경생물학회 2009 환경생물 : 환경생물학회지 Vol.27 No.1
본 연구는 한려해상국립공원 해역에 서식하는 대형저서동물의 군집구조를 파악하기 위하여 2005년 6월에 현장조사를 실시하였다. 현장조사는 거제·해금강지구에서 여수 오동도지구에 이르는 총 25개 정점을 대상으로 실시하였다. 조사 결과, 총 284종의 대형저서동물이 출현하였고, 단위면적당(m2) 개체수와 생체량은 각각 2,002개체와 154.92 gWWt이었다. 개체수와 생체량의 자료를 기초로 LeBris index (1988)를 이용하여 상위 20까지의 우점종을 선정하였다. 개체수에 있어서 상위 20위 우점종은 전체 출현 밀도의 47.64%를 점유하였고, 중요 우점종은 다모류의 긴자락송곳갯지렁이(S. longifolia), I. pulchella, M. californiensis, M. multibranchiata, Tharyx sp. 1 및 이매패류의 아기반투명조개(T. fragilis) 등이었다. 반면, 생체량에 있어서는 상위 20위 우점종들이 전체 중량의 70.47%를 점유하였고, 이 가운데 극피동물문의 염통성게(S. lacunosus), 연안거미불가사리(A. vadicola)와 이매패류의 새조개(Fulvia mutica)의 생체량이 높았다. 출현 종의 개체수 자료를 기초로 다변량분석(집괴분석과 다차원배열법)을 실시한 결과, 크게 2개의 정점(정점 1과 4)과 2개의 정점군으로 구분되었다. 이 중 정점군 1은 펄함량이 우세한 정점들로, 정점군 2는 죽은 패각과 모래함량이 높은 정점군으로 대별되었다. 특히, 펄함량이 높은 정점군에서는 다모류의 양손갯지렁이(M. japonica), 오뚜기갯지렁이(S. scutata), P. pinnata, Tharyx sp. 1과 절지동물문의 단각류(옆새우류)에 속하는 M. sinense 및 E. sechellensis 등이 우점하였다. 반면, 모래함량이 많은 그룹 2에서는 다모류의 I. pulchella, M. multibranchiata, 단각류의 두가시육질꼬리옆새우(M. acherusicum), 극동육질꼬리옆새우(G. japonicus) 및 연안거미불가사리가 특징적이었다. The study was performed to investigate the community structure of macrobenthic fauna during June 2005, in Hallyeohaesang National Park from Korea Strait. A total of 284 macrobenthic fauna were collected. The overall average macrobenthic density and biomass were 2,002 individuals m-2 and 154.92 gWWt m-2, respectively. Based on the Lebris (1988) index, there were 20 species accounting for approximately 47.64% of total individuals. And the highest densities were found in the polychaetes Scoletoma longifolia, Isolda pulchella, Mediomastus californiensis, Minuspio multibranchia, Tharyx sp. 1 and the bivalve Theora fragilis. On the other hand, the top twenty species made up 70.47% of the total biomass while the three most abundant, the echinoderms Schizaster lacunosus, Amphiura vadicola and the bivalve Fulvia mutica. The conventional multivariate statistics (cluster analysis and non-metric Multi-Dimensional Scaling) applied to assess spatial variation in macrobenthic assemblages. As a result of cluster analysis and nMDS ordination, this study area was divided into two different groups of stations and species. In case of station, there are two groups: one is a mud dominated station group and the other is dead shell and sand dominated group. And the 2 faunistic groups were established as follows: 1) a group of relatively higher abundances in mud dominated sediment. There were numerically dominated by the polychaetes Magelona japonica, Sternaspis scutata, Paraprionospio pinnata, Tharyx sp. 1 and the amphipods Monocorophium sinense and Eriopisella sechellensis. 2) a group of relatively higher densities dead shell and sand dominated sediment. These groups were characterized by the polychaetes I. pulchella, M. multibranchiata, the amphipods M. acherusicum, Gammaropsis japonicus and the echinoderm A. vadicola.