Improved Direct Power Control of Doubly Fed Induction Generator Without Phase-Locked Loop

Direct power control is widely used in renewable power generation, due to the advantages of simple implementation and fast dynamic response. This paper proposes an improved direct power control of doubly fed induction generator (DFIG) without phase-locked loop (PLL), which is implemented in the stationary reference frame. In order to deal with the time-varying voltage matrix-related dynamics of active and reactive powers for a DFIG in the stationary reference frame, the modulated active and reactive voltage are introduced. By this means, the time-varying voltage matrix-related dynamics of DFIG active and reactive powers are changed into a constant coefficient-related equation, thereby resulting in a simpler implementation. Meanwhile, the modulated rotor voltage can be obtained from the modulated active and reactive voltages based on DFIG rotor position. Then, a linear controller can be introduced to achieve the decoupling regulation and fast tracking of active and reactive powers. Finally, the experimental results are provided to confirm the effectiveness and frequency adaptability of the proposed method.