Operation of parallel three-phase converters as a motor drive

Key to more modular, redundant motor drives is the development of parallel three-phase voltage source converters which do not use either supervisory control or isolation between the converters. A drive with these characteristics is used to control a permanent-magnet synchronous machine load. Load-sharing is accomplished using a drooped-speed control and a novel 0-sequence controller is proposed to limit the circulating 0-sequence current. Simulation demonstrates the effectiveness of the controller and laboratory tests show circulating 0-sequence current is mitigated. Effective load-sharing is achieved both in steady state and under dynamic conditions.