Control interference of electrical machines with double-star winding systems driven by independent current controllers

This paper focuses on conditions leading to instability of digitally controlled double three-phase permanent magnet synchronous motors with standard PI controller based voltage source inverters. A first simplified motor model is derived to apprehend the problem. The model is then detailed further to get accurate stability limits. A validation of the analysis is done experimentally on a double star winding permanent magnet synchronous motor. To achieve stability and to fasten the system's dynamic, a new control scheme is proposed, using classical PI controllers with two interconnected inverters.