Dynamic Equivalent Modeling of Distributed Photovoltaic Generation Systems in Microgrid Considering LVRT Active Power Response Difference

The integration of large-scale distributed photovoltaic (PV) units into a microgrid poses critical challenges to transient stability. Developing an effective model of distributed PV generation systems is essential for stability analysis. However, detailed modeling of individual PV units leads to prohibitive computational costs. To address this issue, this paper proposes an equivalent model for distributed PV generation systems in a microgrid. By thoroughly analyzing the PV units’ responses during the low voltage ride-through (LVRT) process, the dominant active power responses are identified, and two segmentation thresholds for clustering are analytically derived. To improve engineering applicability of the proposed clustering method, one voltage-dip-dependent segmentation threshold is approximated. Moreover, for PV units exhibiting post-fault active power ramp recovery, an additional clustering based on average pre-fault steady-state active power is introduced to better represent the dynamic behaviors of actual distributed PV generation systems. On this basis, a four-machine equivalent model is proposed, which captures key dynamic characteristics while ensuring both computational efficiency and modeling accuracy. Extensive simulations under various operating conditions and fault scenarios verify the effectiveness of the proposed equivalent model in reproducing transient behavior of distributed PV generation systems in a microgrid.