Enhanced Hybrid Synchronization Method to Improve Transient Stability of Grid-Forming Inverter Under Current Limitation

초록

This paper proposes an enhanced hybrid synchronization control (EHSC) method to improve the transient stability of grid-forming (GFM) inverters under current limitation. The proposed scheme utilizes the point of common coupling (PCC) voltage to adjust the contributions of power synchronization control (PSC) and phase-locked loop (PLL) in the active power loop, as well as the power references. This coordination enhances system damping and mitigates instability induced by current saturation. The output characteristics of GFM inverters are first analyzed under current limitation, and the mechanisms of transient instability caused by voltage sag, frequency disturbance, and phase angle jump are identified. A cascaded control structure is then designed, where the upper loop incorporates an active power controller combining PSC and PLL, as well as a reactive power controller with integral and droop control. The lower loops regulate inverter voltage and current according to reference signals from the upper loop. The sensitivity of the HSC and power adjustment terms is examined through phase portrait analysis. EMT simulations further validate the enhanced stability of the proposed EHSC under voltage sags, frequency disturbances, and phase angle jumps. © 2013 IEEE.

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