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A novel configuration is studied where a doubly fed induction generator provides power to a squirrel-cage induction motor, and the speed of the motor is controlled through the rotor-side converter of the generator. Such topology could have applications in hybrid-electric propulsion and would require fewer and smaller power electronic converters than a system with an intermediate DC bus. An integrated motor/generator set model is developed to reflect the tightly connected dynamics of the combined electric machine. To simplify the derivations, a representation in complex variables is used. However, the control algorithm is based on proven field-oriented control principles for induction motors. Feedforward and feedback control algorithms of the induction motor integrated with the doubly fed induction generator are proposed, together with two methods to limit the rotor currents of the generator. Experimental data show excellent tracking performance of speed references, demonstrating the validity of the control methods proposed. Concepts are also presented for the management of a small energy storage component. [ABSTRACT FROM AUTHOR]

A traditional hybrid-electric propulsion system requires two full-rated converters to convert the electric power from the generator to motor. This brief proposes a method to control the speed of a permanent-magnet synchronous motor (PMSM) receiving power from a doubly fed induction generator (DFIG) and using the generator’s rotor-side converter. This technique can reduce the size and number of converters in a hybrid-electric propulsion system. An integrated model of the system is developed, which is then used to derive the control algorithm. The presentation is simplified by using a complex representation of the dynamic system and of the control law. A voltage and a current command mode are considered and limiting is incorporated to ensure the satisfaction of current constraints. Experimental data show excellent tracking performance of speed references and improved recovery from large load disturbances compared with operation using a synchronous generator. A storage element provides or recovers excess power through the rotor-side converter of the DFIG. [ABSTRACT FROM AUTHOR]

Cascading blackouts are the oldest major unsolved technical problem in power system engineering, highly visible since the Northeast Blackout of 1965 in North America. In this article, we review some cascading blackouts and past work on the problem. New metrics measure network stress to identify and reduce the risk of cascading failures. [ABSTRACT FROM AUTHOR]