Control System for Open-End Winding Surface PM Synchronous Machines with a Floating Capacitor Bridge

A speed control scheme is presented for a 3-phase permanent magnet synchronous machine with an open-end stator winding fed by a dual inverter system with a floating bridge. The floating bridge inverter is used to compensate the reactive power of the main inverter and, hence, to maximize the active power delivered to the motor in compliance with the constraints of a limited current and voltage. The DC-link voltage of the floating bridge varies depending on the operating condition of the motor in order to reduce the switching losses and ensure the controllability of the system. The experimental results show that a significant improvement in the width of the speed range at constant power is achievable in the flux weakening region.