HVDC换相失败引发次同步振荡现象分析

Analysis of subsynchronous oscillation caused by HVDC commutation failure

建立了适用于次同步振荡分析的汽轮发电机组轴系扭振数学模型,介绍了发电机组轴系扭振的机理,重点分析了发电机组与HVDC之间的机电扭振作用。受端电网故障导致逆变站换相失败,会引起整流站附近的汽轮发电机组轴系扰动,并引起发电机电磁转矩的变化,而HVDC控制系统的快速作用为扰动提供了负阻尼,从而形成一种正反馈性质的扭振相互作用,助增轴系扰动幅值,最终导致汽轮发电机组次同步振荡现象的发生。在PSCAD/EMTDC上搭建相应模型,仿真再现了由HVDC换相失败引起的次同步振荡现象,并对其产生机理进行验证。

The mathematical model of HVDC transmission system and its control system for subsynchronous oscillation analysis is established. Based on the torsional vibration model of generator shaft, the mechanism of generator shaft torsional vibration is introduced;the generator set and HVDC transmission are mainly analyzed. When the commutation failure occurs in the inverter station, it will cause the turbine generator shaft system disturbance near the rectifier station, which will cause problems in the HVDC system control and provide negative damping for the disturbance, thus forming a torsional vibration interaction with positive feedback properties. Eventually, the generator is subjected to shaft torsional vibration. Finally, the corresponding simulation model is built on PSCAD/EMTDC, the simulation reproduces the phenomenon of subsynchronous oscillation caused by the failure of HVDC commutation and verifies its mechanism.