On the load demand changing, {HEAD ~ the controller} signals {TAIL ~ the frequency converter} to give a changed new power output to meet the changed demand 
On the load demand changing , { HEAD ~ the controller } signals { TAIL ~ the frequency converter } to give a changed new power output to meet the changed demand
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH