Implementation of a PID Controller Using Siemens PLC

Due to growth of the population, the demand for food has increased lately and will continue to do on the next years. In this context, one of the most important matters is the control and monitorization of the irrigation systems, which help agriculture to be more productive. Any pumping station depends on the flow that is delivered to the end users. The electrical cabinets in a pumping station contain frequency converters and soft starters that actuate the pumps electric motors. In this paper, the control of a pumping station is analyzed and implemented with the help of a PID controller, where the water pressure must be maintained at the value of 6 bars. In this case, a solution is proposed with a frequency converter that will maintain the pressure at the specified value and if the flow rate increases, then additional pumps will be started, operated by the soft starter. To operate a pump, at a given time, a selector will switch the pump to either the frequency converter or the soft starter. When the station is switched to automatic mode, it will not be allowed to change the pump from the frequency converter to the soft starter or vice versa. To maintain the reference pressure, a PID controller implemented in the PLC program will be used. The pressure is referenced to 6 bars and will be managed by the PID controller designed in the PLC program. The performance results of the PID controller can be displayed on the running screen for different values of the controller parameters.