A Slip Angle Computation Algorithm for Synchronization and Current Control of a Grid-Connected Doubly-Fed Induction Generator

In this paper, the computation of a slip position is introduced for the grid-flux oriented control of a grid-connected doubly fed induction generator. For the DC excitation process in the rotor-side converter, the stator voltage is built at the stator terminals, which is related to the shaft speed and magnetizing current. Therefore, the corrected rotor electrical and slip angular speeds are received. Again, for the AC excitation process, the condition of the synchronizing is proposed by checking the slip position between estimated and real slip angles. If it is matching at the zero angles, the DC excitation is changed to the AC excitation with the real slip angle; in addition, the induced stator voltage and frequency are completely synchronized with the utility grid. For the grid-connected operation, the dq-axes rotor currents are also proposed to regulate the grid-flux and to control the electromagnetic torque. To assess the performance of the proposed control algorithm, computer modeling is developed, the simulation results are provided.