Transient and steady state performance analysis of power flow control in a DFIG variable speed wind turbine

Cajethan M. Nwosu, Stephen E. Oti, Cosmas U. Ogbuka

   This paper presents transient and steady state performance analysis of power flow control in a 5.0 kW doubly-fed induction generator (DFIG) variable speed wind turbine (VSWT) under sub synchronous speed, super synchronous speed and synchronous speed modes of operation. Stator flux orientation is used for the control of the rotor-side converter (RSC) and DFIG whereas the grid (or stator) voltage orientation is the preferred choice for the control of the grid-side converter (GSC). In each of the three speeds modes, power is always supplied to the grid through the stator of the DFIG. The magnitude of net power (stator power plus rotor power) is less than stator power during the sub synchronous speed mode; it is greater than stator power during the super synchronous speed mode while it is equal to the stator power during the synchronous speed mode. In synchronous speed mode, the rotor power is zero indicating that power is neither supplied to the grid from the rotor nor supplied to the rotor from the grid; here the magnitude of net power is equal to stator power. The simulation results thus obtained in a MATLAB/SIMULINK environment laid credence to the controllability of power flow reversal in a DFIG-VSWT through back-to-back power electronic converter.

Keywords: doubly-fed induction generator, grid-side converter, rotor-side converter, bidirectional energy flow, decoupled control

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