Direct Virtual Torque Control for Doubly Fed Induction Generator Grid Connection

This paper presents a grid-connection control strategy of doubly fed induction generator wind system based on the direct control of both a virtual torque and rotor flux of the generator. This control is achieved with no proportional-integral regulator and requires the measurement of only grid voltages, rotor currents, and rotor position. The same switching table is used for grid synchronization and for running process. A field-programmable-gate-array-based design of the proposed control is developed and tested on a 4-kW experimental prototype. Experimental results are provided to show the effectiveness of the fast and soft grid-connection method developed.