If you mean one controller with multiple inputs to detect voltages imbalances and multiple outputs to switch the appropriate inter-phase capacitors in and out of service, of course just one can be used; but you must then ask, "What are the consequences of controller failure?" If they are unacceptable, a back-up controller with an appropriate auto-transfer scheme must be provided.
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
