Voltage Sag Assessment of Distribution Networks Considering Multiple Uncertainties of Distributed Photovoltaic Systems

During faults, distributed PV(photovoltaic) in distribution networks will enter different operating states. The uncertainty of PV output, the randomness of distribution network faults, and the uncertainty of PV disconnection will all affect the operating state of distributed PV inverters, leading to changes in the output characteristics of PV stations and influencing the assessment results of voltage sags in distribution networks. Therefore, this paper proposes a voltage sag assessment method for distribution networks considering multiple uncertainties. First, a PV output uncertainty model is established based on the Beta distribution function, and a random fault sampling model is built using the Monte Carlo method. Secondly, based on the determined PV output and fault scenarios, a PV disconnection probability model is developed based on the LVRT (Low Voltage Ride Through) curve and voltage tolerance curve, determining the final operating condition of distributed PV in the distribution network. Finally, the entropy weight method is used to calculate the severity set of voltage sags considering multiple uncertainties. Through case simulation and verification analysis, the rationality and effectiveness of the proposed method are verified.