Analysis of voltage sag transient characteristics in photovoltaic distribution systems based on generalized load model

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With the rapid growth of distributed photovoltaic (PV) capacity, traditional transient simulations that rely on detailed distribution network models face increasing computational challenges. To address this issue, this paper proposes a physics-based PV-integrated generalized load model (GLM) that simplifies load-side representation while explicitly incorporating the low-voltage ride-through (LVRT) reactive power support capability of distributed PV systems. To quantitatively evaluate the transient voltage impact of PV support, macroscopic performance indices, including voltage deviation energy and reactive support efficiency, are analytically linked to key physical mechanisms such as induction motor slip dynamics and inverter current limits. Extensive electromagnetic transient simulations are conducted under various fault locations, voltage sag depths, and dynamic load ratios. The results reveal strongly nonlinear and spatially dependent characteristics of PV reactive power support. Faults associated with larger equivalent network reactance exhibit greater voltage improvement from PV reactive injection, resulting in increased voltage recovery and reduced voltage deviation energy. In contrast, under severe voltage sags, decelerating induction motor loads may absorb a large portion of the available reactive power, which significantly reduces the observable benefit of PV support. In addition, as the dynamic load proportion increases, PV reactive injection can suppress slip acceleration during the disturbance, smoothly reshaping the recovery trajectory and fundamentally restricting the integral voltage deviation energy, thereby mitigating the impact of heavy motor loads. By capturing these coupled dynamics between distributed PV systems and dynamic loads, the proposed GLM together with the quantitative evaluation framework provides a physically grounded basis for LVRT control coordination, transient protection design, and planning analysis in distribution networks with high PV penetration.

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