Power quality enhancement in wind energy applications through E2PLL-based DSTATCOM control.

The distribution static compensator (DSTATCOM) is widely employed to regulate the voltage of self-excited induction generators (SEIGs) in wind energy systems. It supplies the reactive power demanded by both the SEIG and the connected load, drawing on the DC bus voltage for this purpose. Effective operation requires maintaining the DC bus voltage at a constant reference value and accurately determining the reactive power demand. This, in turn, depends on precise estimation of the reference source currents. Under nonlinear and unbalanced loading conditions, inadequate filtering of load currents can lead to errors in separating their active and reactive components, thereby degrading system performance. To address this challenge, this paper proposes an extended enhanced phase-locked loop (E2PLL)-based control algorithm for DSTATCOM-supported SEIGs operating with nonlinear and unbalanced loads. The proposed E²PLL achieves an effective balance between structural complexity and filtering capability, enabling accurate estimation of load current magnitude and frequency. This allows the DSTATCOM to maintain balanced and sinusoidal source currents even under nonlinear and unbalanced loading conditions. The proposed approach is comprehensively validated through real-time hardware-in-the-loop system (OPAL-RT) under these adverse conditions. In addition, robustness evaluations under practical operating disturbances, including wind-speed variations, measurement noise, and DC-link voltage ripple, further demonstrate the reliability of the proposed controller. The results demonstrate its effectiveness in ensuring accurate current estimation and stable system operation.