一种直驱风电场中换流器控制系统间动态交互引起系统的失稳机理分析

Mechanism Analysis of Instability Caused by Dynamic Interactions Between Converter Control Systems in PMSG Based Wind Farms

主要分析了换流器控制系统间动态交互对直驱风电场并网系统稳定性的影响。通过构建闭环互联系统模型,其中锁相环环节作为其反馈子系统,研究了开环子系统间动态交互与开、闭环系统模式分析结果间的联系。基于此模型,以期从开环模式谐振角度为直驱风电机组间动态交互,及其引起系统失稳提供一种机理解释。在开环模式谐振条件下,即开环锁相环模式与另一子系统开环模式在复平面上较为接近,因子系统间的强交互作用导致系统阻尼水平降低。最后,通过直驱风电场仿真系统对所提模型和分析方法的有效性进行了验证,并分析了系统运行条件（电网连接强度、风机注入功率）及无功控制结构与参数对开环模式谐振的影响。

Impact of dynamic interactions between converter control systems on stability of permanent magnet synchronous generator（PMSG） based wind farms is investigated in this paper. A closed-loop interconnected model is established, wherein the phase locked loop（PLL） is treated as a feedback subsystem, and then correlations of dynamic interactions between the subsystems are examined with modal analysis of open-loop and closed-loop system. Based on the established model, an instability mechanism caused by dynamic interactions between PMSGs is revealed from the perspective of open-loop modal resonance. Under the condition of open-loop modal resonance, i.e., an open-loop PLL mode in the feedback subsystem close to an oscillation mode of open-loop plant subsystem on complex plane, strong interactions between the subsystems may degrade system damping. Finally, a power system with PMSG based wind farms is used as an example to demonstrate and validate analysis and conclusions obtained in this paper. Meanwhile, impact of many factors on open-loop mode resonance is also explored, including system operation conditions（such as connection strength with the grid, PMSG injected power level）, and reactive power control structures and parameters.