Yasuyuki Tada

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.

Evaluation of Battery System for Frequency Control in Interconnected Power System with a Large Penetration of Wind Power Generation

Recently, a lot of distributed generations such as wind power generation are going to be installed into power systems. However, the fluctuation of these generator outputs affects the system frequency. Therefore, introduction of battery system to the power system has been considered in order to suppress the fluctuation of the total power output of the distributed generation. For frequency analysis, we use the interconnected 2-area power system model. It is assumed that a small control area with a large penetration of wind power plants is interconnected into a large control area. In this system, the tie line power fluctuation is very large as well as the system frequency fluctuation. It is shown that the installed battery can suppress these fluctuations and that the effect of battery on suppression of fluctuations depends on the battery capacity. Then, the required battery capacity for suppressing the tie line power deviation within a given level is calculated.

Optimal reconfiguration of transmission systems with transient stability constraints

This paper focuses on theoretically proposing a method based on the decomposition technique to solve the optimal reconfiguration of transmission systems (ORTS) constrained by transient stability restrictions. That is, by taking a large number of contingencies into consideration and further exploiting the characteristics of ORTS, this paper adopts the Benders decomposition to divide the ORTS into an OPF subproblem with the stability constraints and a line switching master problem. Moreover, the active set technique is used to improve the efficiency for the subproblem while the relaxation method is applied to the master problem to cope with mixed integer variables. Since the ORTS directly involves the manipulations of transmission lines, it can be expected to apply to not only operations of power systems, but also the evaluations of transactions and wheeling under competitive environment.

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.

Reconfiguration of transmission systems with transient stability constraints

This paper focuses on theoretically proposing a method based on the decomposition technique to solve the optimal reconfiguration of transmission systems (ORTS) constrained by the transient stability restrictions. The authors first adopt the Benders decomposition to divide the ORTS into an OPF subproblem with the stability constraints and a line switching master problem, by exploiting the characteristics of ORTS. Then, the active set technique is used to improve the efficiency for the subproblem while relaxation method is applied to the master problem to deal with mixed integer variables. Since the ORTS directly involves the manipulations of transmission lines, it can be expected to apply to not only operations of power systems, but also the evaluations of transactions and wheeling under competitive environment.

On-Line Transient Stability Screening of a Practical 14,500-Bus Power System: Methodology and Evaluations

This paper describes an effective methodology for on-line screening and ranking of a large set of contingencies. An evaluation study of the on-line methodology in a real-time environment as a transient stability analysis (TSA) screening tool is presented. Requirements for an on-line screening and ranking tools are presented. The methodology of BCU classifiers implemented in the TEPCO-BCU package was evaluated on the PJM system as a fast screening tool to improve on-line performance of the PJM TSA system. This evaluation study is the largest in terms of system size, 14,500-bus, 3000 generators, for a practical application of direct methods for on-line TSA. The total number of contingencies involved in this evaluation is about 5.3 million. The evaluation results were very promising and confirm the practicality of the methodology based on direct methods, in particular the BCU method for on-line TSA of large-scale systems with a large set of contingencies.

On-line transient stability screening of 14,000-bus models using TEPCO-BCU: Evaluations and methods

PJM Interconnection has successfully designed and implemented a Transient Stability Analysis & Control (TSA&C) system. This is the first on-line transient stability analysis ever performed in the control center of a large power network. TEPCO-BCU was selected as a leading fast screening tool to improve the performance of PJMs TSA system. This paper will present an evaluation of TEPCO-BCU in a real time environment as a transient stability analysis screening tool. This evaluation represents the largest practical application of the theory of a stability region in terms of the system size (14,000-bus), the number of contingencies (a total of 5,293,691 contingencies), and over a wide range of operating conditions. This extensive numerical study reveals that TEPCO-BCU is an effective tool for performing on-line dynamic contingency screening of large-scale power systems‥

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.

Development of an integrated power system analysis package

With the present de-regulation in the electric power market, powerful analytical tools are required for the planning and evaluation of feasibility of wheeling of electrical power. A major role for power system engineers is confirming the stable operation of power systems in order to maintain dynamic stability voltage stability, etc. under a wide variety of constraints. Conventional computer software used in power system analysis is, however, not convenient or friendly because it requires that data be input in text form, including even the data for modeling generators, their controllers, loads and so on. In this paper, the authors present a new integrated power system package named Impact (Integrated and Multi-purpose Package of Advanced Computational Tools for power system engineering). This package was developed to provide a fully graphical user interface (GUI). Impact is a package of several useful integrated analytical applications. Users can easily handle bus configurations from the powerful GUI. The power of the GUI coupled with full integration of the application is demonstrated in many attractive themes.

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