Hisao Taoka

Real-time digital simulator for power system analysis on a hypercube computer

A digital simulator based on a hypercube-type massively parallel computer, the NCube2, has been developed. The simulator features: real-time simulation of a large power system which covers transient stability through long-term behavior with constant accuracy level in root mean square values; user-friendly man-machine interfaces which mimic the actual operating environment including interactive setting of several system parameters and real-time data presentation on a CRT; and high-speed A/D (analog to digital) converters, D/A (digital to analog) converters, and D/IO (digital input and digital output) interfaces are used to connect the digital simulator (power system dynamic model) to actual equipment. The authors describe the basic characteristics of the digital simulator and present results obtained in real-time simulations. >

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.

Fast Solution Method of Sparse Network Equations with an Array Processor

Taking full advantage of pipeline architecture, we propose a fast solution method of sparse network equations that consists of an improved node ordering and data storing scheme. The improved node ordering scheme enables overlapped operation of a series of multiply-and-subtract calculations in the substitution process by deriving parallelism in them. The new data storing scheme stores factorized data and the address of variables in vector. Using these new schemes in array processor AP-120B, the substitution process of solving network equations can be executed three times as fast as with the conventional method supplied in the AP-120Bs standard mathematical library.

On-Line Modeling for Emergency Control Systems

Abstract In a stabilizing system, control actions are determined through stability analysis or contingency analysis. Therefore the on-line modeling method is a key technology in these analysis, and is closely inseparable with emergency control systems which make power system stable after a fault. The difficulty of the on-line modeling of an external system is caused by the lack of on-line data from the external system. In this paper, we summarize several on-line modeling methods for emergency control systems, and propose a new on-line modeling method which uses only local information after the fault.

Distributed Power System Simulation on a Hypercube Computer

Abstract Distributed system is expected to realize characteristics of flexibility, high modularity, easy development, high speed processing and cost performance in the system of several fields. The use of distributed systems on parallel or distributed computers are studied for getting these characteristics. We developed a distributed simulation method of power systems to get high modularity such as easy attaching and detaching new components of power systems in the simulator for extension or maintenance. In this paper, we describe the detail of the distribution methods of power system simulation. First, we propose the distributed algorithm of solving network equations of power system simulation. Secondly, we describe the way to mapping tasks to be separated for distributed simulation to a hypercube computer. Thirdly, we show the flow of simulation including communication method with time stamp technique. Our approach is installed and evaluated in the hypercube computer, NCube/10. In the hypercube computer, each bus and each control circuit of generator in a power system are assigned to each processor. Finally, we show the result of installing and evaluating them.

A distributed simulator for power system analysis using a hypercube computer

Abstract The use of distributed systems is expected to realize characteristics of flexibility, high modularity, ease of development, high-speed processing and cost performance in several fields. Distributed systems on parallel or distributed computers are studied in order to obtain these characteristics. We have developed a distributed simulation method for the extension or maintenance of power systems in the simulator. In this paper, we describe the distribution methods of power system simulation. First, we propose a distributed algorithm for solving the network equations of power system simulation. Second, we describe a way of mapping tasks, which are to be separated for distributed simulation, to a hypercube computer, NCube/10. In the hypercube computer, each bus and control circuits of a generator in a power system are assigned to individual processors. Finally, we present the results of installing and evaluating the proposed algorithm and distributed simulation techniques on a hypercube computer.

Autonomous Distributed Network Architecture for Control System

Abstract With the advance of information technology, control system is going to be a large and complex one. We believe that key technology to solve it is distribution and autonomy. In this paper autonomous network architecture and its software design method for distributed control systems, with such autonomous functions as fault tolerance, flexibility, evolvability, extensibility, and conversely, partitionability, etc., are discussed. First, a network architecture is described. Then, the design method of network software with autonomous functions for distributed control systems is discussed. Autonomy of the system is realized in the network software, which is separated from the application software. Finally, the proposed network architecture and its software is installed in the distributed computer system composed of INMOS Transputers. Its autonomous functions, that is fault tolerance, etc., and the performance of control are evaluated in the distributed system, when a sorting algorithm and simple model of the load frequency control are applied.

An integrated approach to dynamic security assessment and control of power systems

This paper deals with security assessment and control for transient stability of a power system following a predefined disturbance. Different OMIB (one machine infinite bus) equivalent approaches, which are highly effective for directly estimating stability, are applied to the proposed method with the two function steps of contingency screening and detailed assessment. This method incorporates a suitable time domain simulation to compensate for the shortcomings resulting from OMIB prerequisites. It also provides a systematic procedure for positive identification of critical clusters, which is required for accurate assessment of stability limits and for generation rescheduling to improve dynamic security. Accordingly, all integrated form between assessment and control is described. Numerical results are obtained with a Japanese standard test system. They indicate that the method gives accurate assessment and control procedures by using appropriate energy margin sensitivity.

New 3-phase load flow program for steady state initialization of the EMTP

The new 3-phase load flow program, which will be used for the steady state initialization of the real-time electromagnetic transient simulator developed by Mitsubishi Electric Co., is described in this paper. The program uses the standard models and input file of the well-known EMTP, converts these 3-phase models into its equivalent 1 phase model. In order to have a better convergence for large scale power system simulation, it uses the Newton-Raphson algorithm instead of the Gauss-Seidal algorithm for 3-phase load flow calculation. The EMTP benchmarks and IEEE 14, 57, 118 bus load flow test systems have been used to test the proposed program in both balanced and unbalanced condition.