Dynamic Analysis and Stability Enhancement of a Weak Grid-Tied Hybrid System Integrating PV, Full-Scale Wind Turbine, and Battery Storage

Hybrid generation systems integrating photovoltaics (PV), full-scale wind turbines (WT), and battery energy storage systems (BESS) have garnered substantial interest for utility-scale grid-tied applications due to their enhanced efficiency and reliability. However, in a hybrid system integrating these resources at the dc-side of a voltage-source converter, the dc-link stability remains largely unexplored in existing literature, particularly under weak grid conditions and across different operational regions of the PV, WT, and BESS. This article presents a comprehensive small-signal stability analysis of a hybrid PV-WT-BESS system using detailed state-space and incremental impedance models. The analysis reveals that the hybrid system exhibits low-frequency oscillation instability in weak grid conditions when the PV operates in the current-limited region. A novel active damping strategy is introduced to mitigate these instabilities, effectively suppressing negative interaction dynamics and improving overall system stability; this is achieved by repositioning unstable eigenmodes and reshaping the dc-link dynamics to comply with the Nyquist stability criterion. The proposed compensation technique offers several key advantages: 1) it is simple yet effective and can be designed using linear analysis methods; 2) it ensures stable operation under varying grid conditions without altering steady-state performance; 3) it enhances the low-voltage ride-through capability; and 4) it eliminates the need for additional measurement sensors, thereby simplifying the implementation and reducing costs compared to alternative stabilization methods. Offline and real-time software-in-the-loop simulations validate the accuracy of the developed models and dynamic interactions, as well as the effectiveness of the proposed active stabilization approach across typical operating conditions.