Investigating the incorporation of a doubly fed induction machine as a shaft generator into a ship´s system: Application of a vector control scheme for controlling the doubly fed induction machine

In the following investigation the modeling and control strategy of a doubly fed induction machine is discussed for power production/electric propulsion purposes, when being incorporated as a shaft generator into a ship´s system. When the doubly fed induction machine serves as a power production machine, contributes to lower emission of CO2 and fuel saving. This is due to the fact that the doubly fed induction machine is capable of working at different speed (lower) than synchronous. This coincide with the enforcement with which the International Maritime Organization (IMO) and the EU demand reduction of Ship´s emissions. The system of the doubly fed induction machine is being controlled by implementing a practical form of a vector control technique which has been previous developed in the case of the control of variable speed wind energy systems. The electrical torque of the double fed induction machine is regulated to be constant and the doubly fed induction machine is allowed to perform within the range of zero to the twice of the synchronous speed. The relevant results demonstrate a very good regulation of the speed at various operational points either as in the motor or the generator mode.