Cascade control of electrical drives of a pumping station based on an astatic fuzzy regulator

Abstract

The article discusses the main features of cascade pressure control in a water supply system with a controlled and additional uncontrolled pumps. The disadvantages of the existing control systems are formulated and it is proposed to control the pump station electric drives using correction of speed of the controlled pump depending on the mode of operation of the uncontrolled pump. A simplified mathematical model of the pressure control loop was developed, with the representation of the switching on of the additional pump as a disturbance effect of an aperiodic behavior. At the same time, the control algorithm of the additional pump is described in the form of unequivocal nonlinearities based on single step and signature functions, which allows to significantly simplify its implementation in the case of using microprocessor devices. To reduce the impact of disturbances in transient operating modes, namely when the additional pump is switched on, it is proposed to use the speed correction component for the main pump in the control algorithm. To avoid the formation of a static error, it is suggested to use a pressure regulator with integral component. Next, a refined mathematical model in the MATLAB environment was developed and an investigation of system operation using proportional-integral-derivative controller of pressure main pump speed control was carried out. It was determined that using of correction component allows to increase the accuracy of pressure control, but does not allow to compensate the presence of transport delay and nonlinearities of the system. Therefore, as a pressure regulator of the hydraulic system output, a combined astatic fuzzy regulator based on a proportional-integral control algorithm is used. The main difference of such a regulator is the automatic change of the gain factor when the error changes, which prevents the occurrence of unstable modes with large coefficients of the open system. The developed fuzzy control system provides a lot of benefits, such as increasing the reliability of the water supply network, improving the performance of the water supply system for consumers, reducing the wear and tear of pumping equipment, and reducing electricity consumption, which is confirmed by the results of numerical modeling.