Reactive power control strategy for a wind farm with a doubly fed induction generator (DFIG) is investigated. Under stator flux-oriented (SFO) vector control, the real power of the DFIG is controlled by the q-axis rotor current Iqr and the reactive power is mainly affected by the d-axis rotor current Idr. To examine the effect of Idr on stator reactive power Qs and rotor reactive power Qr, the DFIG is operated under five different operating modes, i.e, the maximum Qs absorption mode, the rotor unity power factor mode, the minimum DFIG loss mode, the stator unity power factor mode, and the maximum Qs generation mode. In pervious works, stator resistance Rs was usually neglected in deriving the d-axis rotor currents Idr for different DFIG reactive power operating modes. In the present work, an iterative algorithm is presented to compute the d-axis rotor currents Idr for the five reactive power control modes. To demonstrate the effectiveness of the proposed iterative algorithm, the rotor current, rotor voltage, stator current, real power and reactive power of a 2.5 MW DFIG operated under the five different operating modes are computed.
- Reactive power;
- Induction generator;
- Maximum power tracking
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