Hi,
With the above diagram. The Bridge Rectifier part from the AC mains turns it into an online UPS and needs to be controlled type for steady DC Bus Voltage. As already mentioned if the DC bus voltage is kept steady the output would also be steady.
Regarding PICbasic Pro, I learnt everything from this forum and owe all the contributors a lot. Best is take up one programming challenge at a time and get a grip on the concepts involved. This forum is a life-saver. I do not do basic much still while searching information this is the first place I take a peek.
Good Luck.