Proceedings of the Tomsk Polytechnic Institute Named after S. M. Kirov, Holder of the Order of the October Revolution and the Order of the Red Banner of Labor

Volume 299　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1976

Organization of Dynamic Data Exchange in the Creation of an Automated Control System for a Power System

A. A. Tereshchenko, V. I. Zhulmin

(Presented by the scientific and technical seminar of the Department of PM)

In creating an automated control system for a power system, taking into account the principal specific features of power engineering, a number of problems arise, for the solution of which research of both a theoretical and a practical nature must be carried out. Attention must be paid to questions of organizing the system, algorithms for communication with the object, data-processing algorithms, software tools, and technical means, including both means for processing and storing information and means for communication with the object and with personnel. A systems approach presupposes the unification of all the listed subsystems into a single integrated system. Such research must include, among other things, the creation of methods for organizing and processing data that are organically incorporated into the system, consistent with the requirements imposed on the automated control system and with the methods and principles for organizing other subsystems, their links, and their interaction. The theoretical foundations of representing an object and the forms of its connection with the computer, developed in works [1, 2, 3], create the basic concept on which the entire integrated information system can be developed and elaborated. The methodology for investigating the object and the methods of analysis and synthesis of the information system is based on a concept whose main core is the notion of the structural component of information flows and of the relations among them, which create the “skeleton” of the flow—its structural scheme.

The main supplier of information under the conditions of an automated control system should be the communication channels with the enterprises and power stations of the power system. Therefore, this information is naturally to be “attached” to the terminal devices from which it is obtained, by assigning certain memory areas to the terminal devices. The “place” (or attached area) carries information about the terminal device to which the data refer. Belonging to a particular terminal device can determine the method of coding the data, the structure of the array, and can partially determine the object described by these data. As indicated above, only the structural component of information flows can prove to be the basis for integrated processing of information in the control system. Therefore, the basis for creating a dynamic memory structure under the conditions of an automated control system was the concept of structural

components. It must not be forgotten that the memory structure being created must satisfy the condition of the system’s further development by increasing the number of tasks. Therefore, newly created tasks must be easily adapted to this structure without any substantial change in the system’s software. Taking into account the basic requirements imposed on the memory structure being created, the entire system of processing programs consists of processors, system subroutines, and auxiliary subroutines. The processors include one or several ordinary subroutines (depending on the number of subtasks included in the task) and are intended for solving specific concrete problems. When solving problems, the program structures are composed of individual processors in the required sequence with the aid of control programs. Such a system for constructing programs when solving problems makes it possible to become well acquainted with separate parts of a program through a description of the processors and of the packages that it uses and creates; i.e., it considerably simplifies the use of large processing programs. Data exchange between different processors is carried out by special system subroutines through packages in dynamically distributed memory. Each processor finds in the packages the data it needs and creates new packages with the results of computations. In turn, the information placed in these packages serves as initial information for other processors. Packages are placed and created in dynamic memory by system subroutines. Dynamic memory is a common block whose length is specified by the user, depending on the volume of information for the problems being solved. The system makes it possible to use this block dynamically in the course of program operation. Packages in dynamic memory are linked into “data structures,” for which the structural components of the model of the controlled object are used. A data structure is such a sequence of packages in which the address of the first package is located in a place in dynamic memory directly accessible to the program, the address of the second is in the first package, the address of the third is in the second, and so on. Data structures make it possible to express the relationship among the various data used by the program. Knowing the address of a package and the arrangement of data in it, the system can easily identify it and extract the required information from it. A package with data that have already been used and are no longer needed is discarded by the system subroutines from the dynamic-memory block; i.e., memory is cleared. Thus, the proposed structure for constructing the system memory takes into account the basic property of integration of the initial information and ensures the adaptation of added tasks in the course of system development without substantial changes in the software.

LITERATURE

1. V. L. Enshtein. The structure of the informational representation of industrial objects. — Avtomatika i telemekhanika, 1971, No. 8.

2. V. L. Enshtein. A mathematical model of information flows and the definition of the information base of an ACS. Report at the Third All-Union Conference on Automatic Control and Engineering Cybernetics. Odessa, September 1965.

3. L. B. Nisnevich, V. L. Enshtein. On certain methods for studying information flows and designing automated control systems. — In: Studies of Economic Information Flows. Moscow, “Nauka,” 1968.