Atsushi Kurita

A method for identification of effective locations of variable impedance apparatus on enhancement of steady-state stability in large scale power systems

Variable impedance apparatus such as a static VAr compensator (SVC) and a variable series capacitor (VSC) can improve the steady-state stability of a power system if they are located appropriately. The present paper proposes an index for identifying the location of SVC and VSC in large scale power systems for effective damping. The index is called LIED (location index for effective damping) by the authors. Since LIED can be computed quickly for large scale power systems which have more than two hundred generators without conducting a number of digital simulations and eigenvalue analyses, it is valuable for the system planner who needs to identify the effective location of SVC and VSC. The proposed index is applied to the New England test system and its validity is demonstrated through digital simulations. >

Multiple time-scale power system dynamic simulation

A new program, EXSTAB (extended time-scale stability) has been developed for representing a wide variety of power system performance problems, from transient stability through long-term dynamics and voltage instability. The capability of the program includes multiple execution modes and automatic step size selection to address conflicting goals of accuracy and efficiency. The modeling includes a broad range of apparatus to provide the needed time-scale representation (four orders of magnitude). Models for automatic generation control, plant characteristics and control, voltage and reactive power control, static and dynamic loads, and protective relaying for apparatus and system connections are provided. Technologies were developed to perform analysis of voltage stability and prediction of peak power transfer to avoid voltage collapse. >

DC Flashover Voltage Characeteristics and Their Calculation Method for Oil-Immersed Insulation Systems in HVDC Transformers

The effects of the laminated paper layer direction on the conductivity and the dc breakdown strength in oil-impregnated paper were experimentally clarified. It was confirmed that not only oil and paper discharges through the laminated paper layers, but also paper discharges along them triggered total flashover in oil and oil-impregnated paper composite insulation. Analyses verified the usefulness of the dc flashover voltage calculation method, based on a non-linear directional field calculations and the lowest flashover voltage estimations between paper discharges along the laminated paper layers and oil and paper discharges through them.

Modeling combined-cycle power plant for simulation of frequency excursions

The maximum continuous power output of a combined-cycle power plant depends on the system frequency and the ambient temperature. The temperature control of a gas turbine limits the exhaust temperature by reducing the fuel flow as the air flow decreases with the shaft speed. A simple model of a combined-cycle power plant is derived from a detailed design model for an example plant. The model is suitable for long-term simulation of power system dynamic performance involving abnormal frequency conditions.

Functional design for a system-wide multivariable damping controller (for power systems)

A system-wide dynamic controller is designed to improve power system damping. Multivariable control techniques, involving many machines and associated measurements and controls, are applied on a large-scale system with realistic dynamics. An iterative design method with multiple tasks is presented. It uses eigenvector-based dynamic reduction, suboptimal state space control design, reconstitution of design to full system representation, and verification. The resulting hierarchical controller is shown, with time simulations and eigenvalues, to stabilize the system for heavy power transfer without adverse side effects. >

BCU-guided time-domain method for energy margin calculation to improve BCU-DSA system

On-line dynamic security assessment offers several significant engineering and financial benefits. However, Current EMS systems can not perform online dynamic security assessment (DSA) to ensure the ability of the power system to withstand some contingencies. We have designed and implemented a reliable and effective system, called BCU-DSA, for online dynamic security assessments and energy margin calculations of practical power systems. BCU-DSA system achieves high level of reliability and accuracy by effective exploration of the merits of both the improved BCU classifiers and the detailed time-domain simulation program. The system has been evaluated on practical power system models with promising results. The BCU-DSA system gives exact stability/instability assessments and accurate energy margin for every contingency of practical power systems.

Identification of low-order linear power system models from EMTP simulations using the Steiglitz-McBride algorithm

This paper presents the implementation of an efficient method for computing low order linear system models of power systems from time domain simulations. The method is the identification algorithm initially introduced by K. Steiglitz and L.E. McBride for calculating the transfer function of a linear system from samples of its input and output. The paper describes the original algorithm, added extensions, and issues addressed for its practical implementation. The applicability of the method is demonstrated by computing a low-order equivalent linear system of a detailed three-phase power system, modeled on an Electromagnetic Transients Program (EMTP). The paper discusses practical implementation issues.

Multivariable control design for damping interarea oscillations of bulk power systems using a modal reduction technique

A new technique for power system multivariable control design in order to raise precision and facilitate design procedures is described. The multivariable control scheme for damping improvement of power swings is based on the optimal feedback control theory, and in the design process, eigenvalues of a 2n/spl times/2n matrix for an n-th dimension state equation must be calculated in order to solve the Riccati equation. Hence, in order to apply this method to a bulk power system, the matrix size must be reduced. By using the modal reduction technique which is proposed in this paper, the matrix size can be reduced by about 75%. The multivariable control scheme is applied to a 164-machine power system. The result shows that the proposed technique enables multivariable control design for a bulk power system with simple procedures.

Suppression of Numerical Oscillation Caused by the EMTP-TACS Interface Using Filter Interposition

where xa is periodic with period Ta and xb is periodic with period Tb. If Ta/Tb is rational, x(t) is periodic; however, if Ta/Tb is not rational, x(t) is not periodic. We will refer to the latter case as quasi-periodic. If the state vector X(t) is composed of quasi-periodic states for t > Tpss, the system is in the quasi-periodic steady state. The analysis of distribution system loads usually includes (and is often focused on) the periodic or quasi-periodic steady state. In many applications, it is desired to know the spectrum of the demand current, the harmonic distortion of the load current or distribution bus voltage, or any number of several indices which quantify the voltage or current distortion. When the load is characterized by a time varying model