The PV modelling is done in two parts at the moment.
1. defining it as a load. 'insert a final circuit and set is as a renewable source. this will help with cable sizing and protective device rating selection (the power of the inverter will not contribute to total power of the system)
2. Adding it as a source. insert a DC source and separately insert an AC/DC converter to the point you want to connect the PV system. insert a JB to the converter. Connect DC source to the JB.
Currently PV and grid cannot run simultaneously, I must admit that is not ideal. However, updates to this is at final stages and will be released as a Beta very soon.