Shoichi Takeda

An Efficient Eigenvalue Estimation Technique for Multimachine Power System Dynamic Stability Analysis

A practical method is proposed to analyze the dynamic stability of multimachine power system. Complex eigenvalues associated with generator oscillations are estimated by iterative calculations

Measurements of Synchronous Machines Parameters under Operating Condition

A practical method for deriving operational impedances from on load tests is proposed. This method differs from well-known frequency response methods from stator or rotor circuit [3-5]. The operational impedances are calculated from the data of small perturbations of the generator voltage, current and rotor angle during system disturbances using Laplace transforms. They include the saturation effect and are suited for dynamic stability studies.

Fast Transient Stability Solution Using An Array Processor

A fast transient stability program for an array processor (FPS AP-120B) connected to a host computer (DEC VAX-11/780) has been developed by using unique technique for improving the speed of transient stability studies. They are solving techniques of differential equations using a modified Euler method, effective use of vector operation, and programming techniques adapted to the array processor.

Development of a Generator Tripping System for Transient Stability Augmentation Based on the Energy Function Method

This paper proposes a new algorithm for an emergency control system which prevents transient instability by generator tripping. The algorithm is based on the energy function method, and it precisely can determine the amount of generation to be tripped. A prototype of the proposed system has been made, and it has been confirmed that the algorithm has been easily implemented in a microcomputer. Furthermore, test results show that the algorithm works well in an ATL (Artificial Transmission Line) System. This paper describes theoretical aspects of the algorithm, implementation and test results.

Analysis of Overvoltages Caused by Self-Excitation in a Separated Power System with Heavy Load and Large Shunt Capacitance

This paper deals with overvoltages caused by self-excitation in a separated power system, which has some generators, heavy load and large shunt capacitance of underground cables and/or shunt capacitors. The condition of stability in a separated power system is analyzed and a comparison with the experimental result is presented.

Laboratory Test and Feasibility Study of Two Countermeasures to Subsynchronous Resonance

This paper presents two countermeasures to subsynchronous resonance. One is a dynamic resistor which is controlled by thyristor switches based on shaft torsional oscillations. The other is a new dynamic compensator. Two types, called a dynamic current compensator and a dynamic voltage compensator, have been developed. Laboratory tests were conducted to investigate their damping forces against subsynchronous resonance. Results indicate that they can damp torsional interactions sufficiently; especially, a dynamic resistor has an excellent damping force. Analytical studies suggest that dynamic compensators can also stabilize induction generator effects. Stability analysis and transient simulations have good agreement with tested results.

A NEW EFFICIENT METHOD FOR INTEGRATED CONTROL OF VOLTAGE AND REACTIVE POWER IN POWER SYSTEMS

This paper presents an efficient method for the integrated control of voltage and reactive power in power systems. This method is able to maintain the bus voltages in their permissible limits while simultaneously realizing well-balanced operation of VAR sources and a reduction in active transmission losses. The proposed method has the following features compared with the conventional methods. (1) Voltage and reactive power control is divided into two parts: control of the switchable VAR sources and control of the load tap-changing transformers. This decomposition technique can realize well-balanced operation of VAR sources.

Operation Support System for Water Supply Systems Using Knowledge Based Method

Abstract This paper presents an attempt to improve the operation support system for real water supply systems. The conventional systems based on mathematical programming are not satisfactory, since operators cannot understand how solutions are derived. We propose an operation support system based on the operators own heuristic knowledge for problem solving processes, from which we can expect smooth interaction with the operator. This concept was examined through a prototype system which is constructed based on the heuristics of operators in charge of actual operation. As a result, we conclude that this approach can realize a human-friendly and effective support system. The outline of the system structure, composition of knowledge base, and flow of execution are included. This study is concerned with the application of knowledge engineering and cognitive science to a real world.

DESIGN AND VERIFICATION OF SEQUENCE CONTROL SYSTEMS WITH TIMED PETRI NETS

Abstract An interactive design support system “INDEED” for industrial sequence control is developed at an engineering work-station. The main features of the system are a user-friendly man-machine interface, a timed Petri nets based simulator and an intelligent verifier for the design modification. An integrated graphic editor/simulator is operated by a menu and a mouse. After a controller is designed as a logic diagram with the editor, a simulation can be carried out on the same logic diagram and a timing chart appears upon the diagram by means of a multi-window system. The timed Petri nets based simulator converts the logic diagram into a timed Petri net. The whole system (the controller and the controlled devices) is simulated. The properties of Petri nets, such as liveness, conflict and reachability, can be used for analyzing and improving the design. As a design is often carried out by the modification of an old design, a verifier for the design modification is developed. The verifier extracts different portions of the timed Petri nets of these designs and converts them into automata, and the detected difference is shown as state-transition maps.

Design and Verification of Sequence Control Systems with Timed Petri Nets

Abstract An interactive design support system “INDEED” for industrial sequence control is developed at an engineering work-station. The main features of the system are a user-friendly man-machine interface, a timed Petri nets based simulator and an intelli-gent verifier for the design modification. An integrated graphic editor/simulator is operated by a menu and a mouse. After a controller is designed as a logic diagram with the editor, a simulation can be carried out on the same logic diagram and a timing chart appears upon the diagram by means of a multi-window system. The timed Petri nets based simulator converts the logic diagram into a timed Petri net. The whole system (the controller and the controlled devices) is simulated. The properties of Petri nets, such as liveness, conflict and reachability, can be used for analyzing and improving the design. As a design is often carried out by the modification of an old design, a verifier for the design modification is developed. The verifier extracts different portions of the timed Petri nets of these designs and converts them into automata, and the detected difference is shown as state-transition maps.