The impact of photovoltaic power estimation modeling on distribution grid voltages

As known, the photovoltaic (PV) systems play a key role in the worldwide energy transition towards a sustainable electrification. Unfortunately, the weather-related solar radiation variability may affect the actual amount of PV power injected into distribution systems, and consequently, affect grid stability if a significant mismatch between power supply and demand occurs. This problem is increasingly critical as PV penetration grows. To avoid the possible critical consequences of an excessive or wrong PV system sizing,(e.g., over-voltages or under-voltages at some bus of the feeder), accurate grid-level simulations under time-varying load and PV generation conditions (e.g., repeated power flow analyses as a function of time in quasi steady state scenarios) are needed. In this regard, an open issue is the selection of the model used for PV generation. Indeed, a variety of models of different complexity exist in the literature. In this work, the impact of three of such models on bus voltage fluctuations variability is analyzed. The reported simulation results obtained using a modified version of the IEEE 33-bus distribution system show that a basic PV model including just the PV performance ratio and the horizontal solar radiation pattern provides probably the best trade-off between simplicity and accuracy. More sophisticated models indeed make sense only when the PV penetration levels are extremely high.