A multi-phase control system having multi-phase operation with single phase control includes a main control module, a lineman module, and an add-on lineman module. The main control module and the lineman module control, automatically or manually, the first phase and first phase tap changer of a multi-phase system. The add-on lineman module and the main control module control, automatically or manually, additional phases of the multi-phase system. In certain example embodiments, the multi-phase control system detects when a line voltage of an additional phase is de-energized and allows the tap changer of the additional phase to be powered by a line voltage of the first phase. In certain example embodiments, the tap changer of a de-energized phase is powered by an external power supply.