Fedoryshyn R. Step controllers of nonlinear control systems in thermal power engineering

The dissertation is devoted to the solution of the scientific and technical problem of control of nonlinear objects by means of step controllers for the purpose of increasing efficiency and reliability of work of both technological equipment and devices of automation systems for thermal objects, for heat generating equipment, as well as for the process of grinding of coal by means of ball drum mills at thermal power stations. The diagrams of step controllers working in conjunction with the actuators of the integrating action have been analyzed in the work. The following diagrams have been analyzed: step PID controller with double differentiation, PID controller with a differentiator and a pulse-width modulator, PID controller with a pulse converter, as well as PI-controller with a pulse generator. The accuracy of the step controllers has been analyzed. A new classification of diagrams of automatic controllers is proposed. Analysis of pulse-width modulation (PWM) algorithms has been performed. An improved PWM algorithm based on a sawtooth waveform generator is proposed. A methodology is developed to design the optimal filter of analog signal at the input of an automatic controller. Experimental studies were carried out for a thermal object (electric furnace) and a ball drum mill for coal grinding. Mathematical models of the controlled objects were built on the basis of the obtained experimental data. Automatic controllers were designed for these objects. An improved algorithm for automatic control of the ball drum mill operation is proposed. The accuracy of automated systems for measurement of flow rate and volume of fluid energy carriers (natural gas) has been analyzed. The influence of the inertia of a temperature transducer on the accuracy of gas metering in pulsed modes of the measurement system has been investigated. Heat exchange between the gas flow and a gas meter body has been studied. Measures have been developed to improve the accuracy of automated natural gas metering systems at heat-generating facilities.