The requirements of a network equivalent to be used in a planning tool (such as the SuperOPF being developed at Cornell) for analyzing policy options, impacts on reliability, costs and emissions for networks as vast as the entire Eastern Interconnection, are very different from those assumed in the development of traditional equivalencing procedures. In this paper, a novel network equivalencing approach using bus aggregation techniques is proposed that shows promise for modeling such large systems in the context of analyzing policy options and emissions. This approach is superior to the existing bus aggregation methods in that a) under the base case, the equivalent-system inter-zonal power flows exactly match those calculated using the full-network-model b) as the operating conditions change, errors in line flows are minimized c) the method is more computationally efficient than other bus aggregation methods proposed heretofore. The proposed method is tested on an illustrative six-bus system and promising results are observed.

%B 2012 IEEE Power & Energy Society (PES) General Meeting %I IEEE %C San Diego, CA %P 1 - 8 %8 07/2012 %@ 978-1-4673-2727-5 %R 10.1109/PESGM.2012.6344668 %0 Conference Paper %B 2012 North American Power Symposium (NAPS) %D 2012 %T Optimal generation investment planning: Pt. 1: network equivalents %A Di Shi %A Daniel L. Shawhan %A Li, Nan %A Daniel J. Tylavsky %A John T. Taber %A Ray D. Zimmerman %A William D. Schulze %K CERTS %K Eastern Interconnection %K investment planning %K optimal power flow (OPF) %K Power system modeling %K reliability and markets %K RM11-005 %XThe requirements of a network equivalent to be used in new planning tools are very different from those used in traditional equivalencing procedures. For example, in the classical Ward equivalent, each generator in the external system is broken up into fractions. For newer long-term investment applications that take into account such things as greenhouse gas (GHG) regulations and generator availability, it is computationally impractical to model fractions of generators located at many buses. To overcome this limitation, a modified- Ward equivalencing scheme is proposed in this paper. The proposed scheme is applied to the entire Eastern Interconnection (EI) to obtain several backbone equivalents and these equivalents are tested for accuracy under a range of operating conditions. In a companion paper, the application of an equivalent developed by this procedure is used to perform optimal generation investment planning.

%B 2012 North American Power Symposium (NAPS) %I IEEE %C Champaign, IL, USA %P 1 - 6 %8 09/2012 %@ 978-1-4673-2306-2 %R 10.1109/NAPS.2012.6336375 %0 Conference Paper %B 2012 North American Power Symposium (NAPS) %D 2012 %T Optimal generation investment planning: Pt. 2: Application to the ERCOT system %A Li, Nan %A Di Shi %A Daniel L. Shawhan %A Daniel J. Tylavsky %A John T. Taber %A Ray D. Zimmerman %A William D. Schulze %K CERTS %K investment planning %K Power system modeling %K power system planning %K reliability and markets %K RM11-005 %XPower system planning and market behavioral analysis using the full model of a large-scale network, such as the entire ERCOT system, are computationally expensive. Reducing the full network into a small equivalent is a practical way to reduce the computational burden. In a companion paper, a modified-Ward equivalencing procedure has been proposed. In this paper, the proposed scheme is applied to the ERCOT system to obtain several backbone equivalents, the accuracy of which are tested under a range of operating conditions. The ERCOT equivalent is used in a system planning tool to perform optimal generation investment studies with promising results observed.

%B 2012 North American Power Symposium (NAPS) %I IEEE %C Champaign, IL, USA %P 1 - 6 %8 09/2012 %@ 978-1-4673-2306-2 %R 10.1109/NAPS.2012.6336374 %0 Journal Article %J European Transactions on Electrical Power %D 2011 %T Transmission line parameter identification using PMU measurements %A Di Shi %A Daniel J. Tylavsky %A Koellner, Kristian M. %A Logic, Naim %E Joe H. Chow %K AARD %K phasor measurement units (PMUs) %K RM11-005 %X Accurate knowledge of transmission line (TL) impedance parameters helps to improve accuracy in relay settings and power flow modeling. To improve TL parameter estimates, various algorithms have been proposed in the past to identify TL parameters based on measurements from Phasor Measurement Units (PMUs). These methods are based on the positive sequence TL models and can generate accurate positive sequence impedance parameters for a fully transposed TL when measurement noise is absent; however, these methods may generate erroneous parameters when the TLs are not fully transposed or when measurement noise is present. PMU field-measure data are often corrupted with noise and this noise is problematic for all parameter identification algorithms, particularly so when applied to short TLs. This paper analyzes the limitations of the positive sequence TL model when used for parameter estimation of TLs that are untransposed and proposes a novel method using linear estimation theory to identify TL parameters more reliably. This method can be used for the most general case: short/long lines that are fully transposed or untransposed and have balanced/unbalance loads. Besides the positive/negative sequence impedance parameters, the proposed method can also be used to estimate the zero sequence parameters and the mutual impedances between different sequences. This paper also examines the influence of noise in the PMU data on the calculation of TL parameters. Several case studies are conducted based on simulated data from ATP to validate the effectiveness of the new method. Through comparison of the results generated by this novel method and several other methods, the effectiveness of the proposed approach is demonstrated. %B European Transactions on Electrical Power %V 21 %P 1574 - 1588 %8 05/2011 %N 4 %! Euro. Trans. Electr. Power %R 10.1002/etep.522