Voltage Unbalance Probability Pre-Assessment of Electrified Railways With Uncertain Traction Load

Single-phase traction power supply systems (TPSSs) have caused severe voltage unbalance (VU) in the three-phase grid. VU pre-assessment provides a powerful approach to forecast the possible VU emission level in electrified railway planning. However, the uncertainty of traction load poses stringent challenges to the validity of the result. In this study, a modeling method including confidence interval prediction (CIP) and scenario generation is introduced to describe the power uncertainty of traction load. Furthermore, a probabilistic power flow (PPF) algorithm is proposed for the train–network system, especially considering the influence of the power supply scheme. Additionally, uniform VU propagation from TPSS to the power grid model is analyzed in detail. Finally, a novel VU probability pre-assessment process is developed to estimate the statistical features of VU. A real railway line case validates the effectiveness of the proposed methods and provides useful design information for electrified railway planning. The whole VU probability pre-assessment approach can be helpful for future VU assessment and compensation in electrified railway planning and operation.