The main control system elements of Solar farms are inverters, power plant controllers, sun tracking controllers, harmonic controllers and various monitoring devices. Although these controllers are autonomous, solar farms require a central control system to enable the whole farm to be controlled from a central point.
We were engaged to write the software, commission and complete all acceptance testing on a 18MW solar farm used to power a treatment plant in Victoria.
The main control system of this plant consisted of a Siemens S7-1500 PLC, Siemens HMI and Red Lion protocol converters. There were 3 different sources of control of the plant, either local control of the plant via the HMI mounted on the control panel, remote control via an Ignition SCADA system or control via the existing plantwide control system. The solar farm control system steered the plant control from whichever source was selected.
Control of the plant consisted of obtaining the relevant point of control and sending setpoints, startup commands and various other commands to the power plant controllers, inverters, tracking devices and other devices. Communication to the various controllers was via Modbus TCP, Modbus RTU and Ethernet mostly via the Red Lion protocol converters that converted the Siemens TIA PLC protocol as required.
Monitoring information was obtained from all of the controllers, displayed on the HMI and also transmitted to the other points of control.
There were over 5000 data values used in the process being transmitted to and from the various devices to the points of control.
We saw this process through SAT testing and handover and the treatment plant are now successfully generating solar electricity to power the plant.
