Control Method for Overvoltage During Power Supply Loss in Medium-Voltage Flexible DC Sections Based on Guided Strategy Adaptive Particle Swarm Optimization

To address the challenge of overvoltage control during power loss in medium-voltage flexible DC sections under complex and variable operating conditions, a control method based on guided-strategy adaptive particle swarm optimization (GS-APSO) is proposed to ensure voltage stability. This method analyzes the overvoltage formation mechanism during faults according to the topology of the medium-voltage flexible DC section. Building on this analysis, an adaptive nearest-level modulation (ANLM) strategy with voltage-limiting functionality is employed. The strategy adjusts the DC voltage based on the changes in the average submodule capacitor voltage, constraining the voltage near the target value. Furthermore, to enhance the overvoltage suppression performance, the guided-strategy adaptive particle swarm algorithm optimizes the voltage-limiting coefficient, deriving the coefficient that minimizes the overvoltage decay ratio, thereby improving the overvoltage loss control in the medium-voltage flexible DC section. The experimental results demonstrate that under different unbalanced power conditions, the proposed method achieves overvoltage control within 1.5 s, enabling rapid voltage recovery and stabilization. Even under significant power fluctuations, it effectively restricts the peak voltage variation range. After control, the overvoltage decay ratio remains below 0.015 on average.