Hae-Kon Nam

A new eigen-sensitivity theory of augmented matrix and its applications to power system stability analysis

Wang, L.; Li, X. Author Affiliation: University of New Orleans, LA Abstract: A robust fast decoupled power flow method (RFDPFM) is presented. It can effectively handle the systems with high r/x ratio lines andor depressed bus voltages to yield fast and better convergence. Tkt results show significant improvement on the convergence in the case that there are high r/x ratios andor low bus voltages in power sys- tems. Abstract: A new second-order eigen-sensitivity and perturbation theory of the augmented matrix is developed using of only dominant eigenvalues and their left and right-eigenvectors. Eigen-sensitivities on various system and control parameters are computed for analysis of small signal and voltage stability of the New Engl.md system. It is shown that the sensitivity analysis may be used as an i ivaluable tool for analysis, planning, and operation of power systems: identification of the cause of the stability problems and weak lines; optimal tuning of control parameters; determining locations of compensating devices for stability enhancement such as capacitor compcnsatio I and FACTS de- Acha, E.; Ambriz-Perez, H.; Fuerte-Esquivel, C.R. Author A4ffiliation: University of Glasgow, Scotland, UK; Institute Tecnologico de Morelia, Mexico bation. Abstract: This paper reports on advanced transformer modeling fa- cilities suitable for large-scale optimal power flow studies. The new transformer models are developed from first principles and incorpo- rated into an existing Newton-based optimal power flow computer pro- gram for highly robust iterative solutions. A three-winding transformer model with tap ratios in all three windings is shown to be a general case for existing two-winding transformer models and the classic load tap-changing and phase-shifting transformer models. The newly devel-

A Practical Approach to HVDC System Control for Damping Subsynchronous Oscillation Using the Novel Eigenvalue Analysis Program

This paper presents a practical approach for supplementary control of high voltage direct current (HVDC) system to damp subsynchronous oscillation (SSO) involving HVDC converters and turbine-generator shaft systems. A novel eigenvalue analysis (NEA) program, HVDC system modeling to consider steady-state and dynamic conditions in a combined ac/dc system, and an appropriate control scheme have been utilized. The design method proposed facilitates the design of a subsynchronous oscillation damping controller (SODC) to provide positive damping torque for the dominant torsional mode in combined ac/dc systems. The suggested SODC design method has been applied to an ac/dc system to verify its practicality using the EMTDC simulation program.

Development of photovoltaic simulator based on DC-DC converter

This paper introduces the photovoltaic (PV) simulator for the inverter of PV energy system. In order to embody the PV simulator, the conventional solar cell is numerically modeled based on the one-diode equivalent circuit. With the P-V relationships, we find the maximum and minimum power which is needed during the inverter performs the MPPT algorithm and design the parameter based on the maximum and minimum power. Finally, this paper verifies design parameters numerically through the PSIM and analyzes the PV simulator in the frequency domain using matlab.

Contingency ranking for transient stability via eigen-sensitivity analysis of small signal stability model

This paper presents a new systematic contingency screening and ranking method for transient stability. The modal synchronizing torque coefficient (MSTC) is computed using eigen-sensitivity analysis of the electromechanical oscillation modes in a small signal stability model and contingencies are ranked in decreasing order of the sensitivities of the MSTC. The relevant clusters are identified using the eigenvector or participating factor. The proposed algorithm is tested on the New England 10-machine 39-bus system. Ranking obtained by eigen-sensitivity analysis is consistent with the time simulation results.

Adaptive protection schemes of Distributed Generation at distribution network for automatic reclosing and voltage sags

In this paper, the adaptive protection schemes of utility interconnected distributed generation (DG) units for distribution automatic reclosing and voltage sag are proposed. Based on the general transient responses of DG units with synchronous generator during a fault by the reclosing types, i.e. radial reclosing and passive reclosing, classifying algorithms of reclosing types with varying fault resistance are proposed. Also, mathematical formulation of adaptive protection coordination schemes for reclosing types and voltage sags are introduced. The proposed algorithms are evaluated by the case study using PSCAD/EMTDC simulation tool.

Development of wide area measurement and dynamic security assessment systems in Korea

This paper describes the effort of the Korea Electric Power Co. to develop a wide area monitoring system (WAMS) and online transient and voltage security assessment tools. The master system of the WAMS at the Control Center monitors at a 10 Hz sampling rate the important system conditions transmitted from 24 local measurement units installed at major generating stations and substations. Each local unit monitors two 3-phase bus voltages and 3-phase currents of fourteen feeders at the 7680 Hz sampling rate.

Fast contingency screening for on-line transient stability monitoring of the KEPCO system

In this paper, a fast contingency screening algorithm using SIME for the transient stability monitoring of the KEPCO system is implemented. This method evaluates the first-swing stability of a large number of contingencies in a short time with reliable accuracy. The salient feature of the proposed screening algorithm is as follows. First, critical cluster of generators is identified by a new index in the early stage of the time domain simulation. Thus, the computational time required for finding the equivalent one machine infinite bus system can be reduced significantly. Second, clustering critical machines can perform even in very stable cases. It allows us to avoid extra calculation of the time trajectory that is needed in the SIME for classifying the stable cases. Third, the screening capability is improved using the power-angle trajectory and subdividing the contingency classification.

Application results of the eigen-sensitivity theory of augmented matrix to small signal stability analysis of large power systems

This paper presents briefly the application results of the eigen-sensitivity theory of an augmented matrix to small signal and transient stability problems of the large Korea Electric Power Co. (KEPCO) system. First, the real parts of the eigen-sensitivity of the inter-area mode for changes in line parameters are found to be negligibly small. It may be concluded from this result that adding a new transmission line will not improve damping of the inter-area mode significantly. Second, the eigen-sensitivity of the inter-area mode for changes in line reactance is equivalent to controllability of the mode with TCSC as input. Hence, the lines having large sensitivity may be selected as the best candidates for installing TCSC for the purpose of improving damping of the inter-area oscillation. An H/sub /spl infin// controller of TCSC installed at the selected lines damps successfully the inter-area oscillation. Thirdly, critical contingencies for transient stability are identified systematically by computing the modal synchronizing torque coefficient with use of eigen-sensitivity analysis of small signal stability model.

The Coordinate Control Method of LTC Transformer and Capacitor Banks at Distribution Substation

The Load Tap Changing (LTC) transformer and Shunt Capacitor (SC) bank are major devices for voltage and reactive power control in a distribution substation. Thus, the coordination operation of a LTC transformer and a SC bank is required to achieve better voltage and reactive power compensation at a distribution substation in the same time. This paper proposes coordinate control method of LTC transformer and SC bank to achieve better voltage and reactive power compensation and operation times of these two devices in the same time. The mathematical formulations of the proposed coordinate control method are introduced. Sample case studies are shown to verify the effectiveness of the proposed coordinate control method.

A New Simplified Doubly Fed Induction Generator Model for Transient Stability Studies

This paper proposes a new simplified model of a doubly fed induction generator (DFIG) that is integrated with a rotor-side converter for studies of large-scale transient stability. This model accurately considers the rotor field dynamics of an induction generator to yield simulation results that are more accurate in terms of voltage stability, as well as angle stability. The purpose of this paper is to provide a simple but effective DFIG model for the study of large-scale transient stability, and to examine the important aspects of rotor voltage and rotor slip power. This new simplified DFIG model with an electric/turbine control system was tested against a six-machine and 23-bus system, and the responses obtained in case studies of transient stability were compared with those of a PSS/E program. Finally, the proposed DFIG model was also validated by comparing the simulation results for a single-machine and infinite-bus system with those of PSCAD/EMTDC.