You can design device which will include: 3 current transformers for 3-phase current sensing, 3 transformers for missing phase sensing, Microcontroller with A/D, LCD display, buttons or pot to adjust current and 3-phase SSR module (can be controlled directly from micro) or 3-pole contactor.
This is not very complicated circuit so almost any microcontroller can be used. If you fill comfortable with AVR use it!