Design of power supply for pollution flashover test under superimposed AC/DC voltage

Insulators are critical components in power systems, and pollution flashover presents a significant threat to their operational safety. Historically, research on pollution flashover has focused on conditions involving a single voltage type. However, with the rapid development and widespread adoption of flexible Direct Current (DC) transmission systems, insulators are increasingly exposed to complex operating conditions involving Alternating Current (AC)-DC composite voltages. This study investigates the flashover behavior of insulators under AC-DC composite voltage conditions. To achieve this, a novel AC-DC superimposed power supply system was developed, capable of generating varying 1:3 and 1:1 ratios of AC and DC components. The system's dynamic output characteristics were analyzed through theoretical calculations and simulation, with a focus on steady-state and transient-state behaviors. The power supply system was then utilized to conduct artificial pollution flashover tests on insulators. Results indicate that the inclusion of a DC component in the AC voltage significantly lowers the AC voltage required to initiate flashover, with larger DC components resulting in greater reductions. These findings offer valuable insights for the design and selection of insulators operating under AC-DC composite voltage conditions and establish a foundation for further research into insulator performance under mixed voltage environments.