A Stabilized Doubly Fed Motor with a Separately Controlled Current Source Converter

A speed-control system with a separately controlled current source converter is proposed for a doubly fed synchronous motor. Conventional systems with a voltage-source converter develop negative damping torques and become unstable. The theoretical analysis for a linearized model shows that the proposed system eliminates negative damping torques. The digital simulation of a nonlinear model and experiments using a laboratory machine verify the theoretical predictions. The system has the advantages of a simple frequency converter construction and a wide-range speed control capability from standstill to supersynchronous speeds.