直驱风电机组全运行区域的次同步振荡特性分析

针对直驱风电机组(direct-drive permanent magnet synchronous generator,D-PMSG)并入弱交流电网的次同步振荡(subsynchronous oscillation,SSO)问题,现有研究多是在风机处于最大功率跟踪运行区域的情况下进行分析,未考虑恒输出功率等运行区域。建立了D-PMSG并入弱交流电网的小信号模型,进而采用特征值法对全运行区域下不同风速、不同输出功率时的次同步振荡特性进行分析,并建立了D-PMSG并入弱交流电网的PSCAD/EMTDC时域仿真模型,验证理论分析结果的正确性。结果表明:在最大功率跟踪运行区域,风速增大且输出功率为最大值时,次同步振荡阻尼增大;在恒输出功率运行区域,输出功率一定,风速增大,次同步振荡阻尼和频率基本不变;在全运行区域,相同风速下,输出功率越小,阻尼越小;在实际运行中,若电网限制D-PMSG的输出功率,降低系统的输出功率更适合采用切机措施,使得系统在发生次同步振荡现象时有更大的阻尼。

Sub-Synchronous Oscillation Characteristics of Direct-Drive PMSG under All Operation Regions when Wind Farms Connected to Weak AC System

In view of the sub-synchronous oscillation (SSO) characteristics of direct-drive wind farms incorporating weak AC grids， the existing research mostly analyzes the situation that the direct-drive permanent magnet synchronous generator (D-PMSG) in the maximum power tracking operation area without considering the constant output power and other operation areas. In this paper， a small signal model of D-PMSG connected into weak AC power network is established， and then the eigenvalue method is used to analyze the sub-synchronous oscillation characteristics under different wind speeds and output power in the full operating region. A time-domain simulation model of a direct-drive wind farm connected to a weak AC grid was established in PSCAD/EMTDC to verify the correctness of the conclusions. The results show that， in the maximum power tracking operation area， when the wind speed increases and the output power is the maximum， the damping increases； In the running area of constant output power， when the wind speed increases， the damping is basically unchanged； In the whole operation area， at the same wind speed， the lower the output power， the smaller the damping and the worse the system stability； In actual operation， if the power grid limits the output power of wind farm， in order to reduce the power output of wind farm， more suitable measure is cutting off some D-PMSGs， thus the system has greater damping when sub-synchronous oscillation occurs.