三电平 NPC 型有源阻尼器直流侧主动均压方法研究

To maintain the midpoint potential at the time of resonance of a three-level NPC active damper in medium-voltage distribution network, an active voltage balancing method based on second harmonic is proposed. In a three-phase three-wire system, DC voltage balancing control is generally achieved by injecting zero-sequence component into the modulation signal. However, due to the output of small active current from the active damper, the traditional method is difficult to meet the DC voltage balancing requirements when resonance occurs. Therefore, the generation mechanism of offset adjustment current is analyzed, and the balance of midpoint potential is realized by using the inner product structure of secondary component in the absolute value of the modulation signal and the secondary current. Simulation results verify the effectiveness of the proposed method in a pure reactive environment, as well as the rapidity of DC-side voltage balancing control at the moment of resonance.