Synthesis of an Invariant Automatic Control Systems with an Internal Model

The article is devoted to the modernization of typical cascade automatic control systems with stabilizing and corrective PI controllers. Such automatic control systems, in addition to the main signal (of adjustable value), use an additional leading signal that reacts to the disturbance faster than the main one. The leading signal effectively compensates for internal disturbances arising in the system by adjusting the stabilizing controller. The temperature control system of superheated steam boiler units of thermal power plants may be taken as an example. The task of determining the configuration parameters of such dual-circuit systems is quite difficult. With a relatively low inertia of the internal circuit, the speed of the stabilizing controller is quite high, and transients in it do not affect the quality of regulation in the external circuit with a corrective controller. This makes it possible to calculate the optimal settings of the latter only by the dynamic characteristics of the inertial section using conventional methods developed for single-circuit systems. The main disadvantage of such automatic control systems is that they do not allow, with close inertia of the contours, to significantly improve the quality of working out the main impacts during the jump of the task, internal and external disturbances. To eliminate this drawback, an invariant cascade automatic control system with an internal model is proposed that takes into account the dynamics of both the internal and external contours with an inertial section of the object when choosing the structure and setting up the corrective controller. In this case, the internal model is used to fully compensate for the main feedback of the system when working out the task signal, as well as to isolate an equivalent external disturbance, for which an invariance differentiator is used to compensate. The invariant cascade automatic control system makes it possible to significantly increase the speed and accuracy compared to the standard one.

1. Klyuev A. S., Lebedev A. T., Novoselov S. I. (1985) Adjustment of Automatic Control Systems of Steam Boilers. Moscow, Energoatomizdat Publ. 280 (in Russian).

2. Stefani E. P. (1972) Fundamentals of Calculating the Settings of Controllers of Heat and Power Processes. 2nd ed. Moscow, Energiya Publ. 376 (in Russian).

3. Solodovnikov V. V., Shramko L. S. (1972) Calculation and Design of Analytical Self-Adjusting Systems with Reference Models. Moscow, Mashinostroenie Publ. 270 (in Russian).

4. Rotach V. Ya. (2004) Theory of Automatic Control. Moscow, MEI. 396 (in Russian).

5. Shirokii D. K., Kurilenko O. D. (1972) Calculation of Settings of Industrial Control Systems. Kyiv, Tekhnika Publ. 232 (in Russian).

6. Rubashkin A. S. (1964) Methods for Determining the Settings of Fuel Controllers of Direct-Flow Boilers. Moscow – Leningrad, Energiya Publ. 112 (in Russian).

7. O’Dwyer A. (2006) Handbook of PI and PID Controller Tuning Rules. 3rd ed. Dublin: Institute of Technology; Ireland, Imperial College Press. 599. https://doi.org/10.1142/p424.

8. Kulakov G. T. (1984) Engineering Express Methods of Calculation of Industrial Control Systems: Reference Manual. Minsk, Vysheishaya Shkola Publ. 192 (in Russian).

9. Kulakov G. T. (1992) Theoretical Foundations of Express Methods of Structural-Parametric Optimization of Automatic Control Systems to Improve the Efficiency of the Use of Thermal Power Plants in Variable Modes. Kiev, KPI. 36 (in Russian).

10. Kuz’mitskii I. F., Kulakov G. T. (2010) Theory of Automatic Control. Minsk, BSTU. 574 (in Russian).

11. Fröhr F., Orttenburger F. (1970) Einführung in die Elektronische Regelungstechnik. Berlin – München, Siemens A.G. (in German).

12. Kulakov G. T., Kulakov A. T., Kukhorenko A. N., Kravchenko V. V. (2017) Theory of Automatic Control of Thermal Power Processes. Minsk, Vysheishaya Shkola Publ. 238 (in Russian).

13. Kulakov G. T., Kulakov A. T., Kukhorenko A. N., Kravchenko V. V. (2017) The Theory of Automatic Control. Minsk, BNTU. 135 (in Russian).

14. Khutskii G. I., Kulakov G. T. (1968) The System of Automatic Regulation of the Temperature of Superheated Steam with a Device for Correcting the Parameters of Dynamic Tuning. Teploenergetika = Thermal Engineering, (3), 64–67 (in Russian).

15. Kulakov G. T., Kulakov A. T., Artsiomenka K. I. (2018) Parametric Optimization for Automatic Control System of 300 MW Power Units at a Constant Steam Pressure Upstream of the Turbine. Enеrgеtika. Izvestiya Vysshikh Uchebnykh Zavedenii i Energeticheskikh Ob’edinenii SNG = Energetika. Proceedings of CIS Higher Education Institutions and Power Engineering Associations, 61 (5), 451–462. https://doi.org/10.21122/1029-7448-2018-61-5-451-462 (in Russian).

16. Kulakov G. T., Kulakov A. T., Artsiomenka K. I. (2018) Parametric Optimization for Automatic Control System of Power Units of 300 MW for the Mode of Variable Pressure of Turbine Inlet Steam. Enеrgеtika. Izvestiya Vysshikh Uchebnykh Zavedenii i Energeticheskikh Ob’edinenii SNG = Energetika. Proceedings of CIS Higher Education Institutions and Power Engineering Associations, 61 (6), 539–551. https://doi.org/10.21122/1029-7448-2018-61-6-539-551 (in Russian).