Synthesis of Automatic Control System for Low-Temperature Separator

The gas produced from the well under high pressure is fed to a complex preparation unit, where solid impurities and water are removed. Purified natural gas contains valuable components such as condensate, as well as heavy hydrocarbons, butane and propane. To extract associated components from gas (condensate and heavy hydrocarbons) low-temperature separation is used. The temperature regime in the separator is maintained by the energy of the compressed gas. When the gas passes through the throttle, due to the Joule-Thomson effect, the pressure and temperature decrease. The technological regime in the separator is provided by the single-loop automatic control systems for pressure and condensate level control. As shown by the studies carried out by the authors of the paper, the low-temperature separation as a control object is characterized by internal cross-links. Their presence significantly reduces the efficiency of single-loop control systems. To improve the quality of the control process, an autonomous control system for the low-temperature separation process was synthesized. A cross-coupling compensator was included in the control circuit of such a system, resulting in two independent single-loop automatic control systems. Based on the developed mathematical model, the transfer function of the compensator is synthesized and a method for determining the parameters of PI controllers is developed. The essence of the method is that on the complex plane of the roots of the characteristic equation, the positions of the roots are determined, which should ensure the desired quality of the control process. The placement of the roots is selected from the condition of the minimum of the generalized quadratic criterion of the quality of the control process.