Voltage Stabililty Analysis in Three-Phase Unbalanced PV Rich Distribution Systems

With the growth of global energy demand and the intensification of environmental problems, renewable energy, especially solar photovoltaic power generation, has received extensive attention because of its clean and renewable characteristics, so more and more small residential and commercial areas will connect distributed photovoltaic to low voltage power system. Nevertheless, in addition to above-mentioned advantages, the access of many distributed generation systems is not considered in the traditional power system. As the continuous improvement of photovoltaic penetration, the inherent three-phase unbalance of distribution power system because of the connection of distributed photovoltaic grid is aggravated, besides node voltage exceeds the upper limit. In this paper, from the perspectives of mathematical model and simulation model, the reasons for the voltage violation of unbalanced three-phase power system under high photovoltaic permeability are analyzed and proved in detail. In addition, to address voltage regulation issues in three-phase unbalanced power system due to the integration of distributed photovoltaic systems, various voltage control techniques are implemented. These include the application of on-load tap changer transformers, constant power factor correction, and reactive power droop control. The optimal strategy is identified by evaluating the comparative performance of these methods in maintaining voltage stability.