To improve the stability of renewable energy power systems, the response characteristics of two-level voltage-source converter (VSC) to disturbances are analyzed, and some suppression strategies for oscillation problems are further proposed in this paper. Based on the balance principle of frequency components, the response characteristics of two-level VSC to its AC-side disturbances are investigated in detail, considering its complete control system. Specially, the coupling effect among disturbances with different frequencies are illustrated by the time-domain phasor and space vector analysis. Subsequently, the impedance model describing the port-characteristics of two-level VSC is established and verified through electro-magnetic transient simulation in PSCAD/EMTDC. On the basis, the conditions about oscillation problems caused by negative-resistance effect are concluded and verified in a two-level VSC test system. Finally, by analyzing the influence of controller parameters on impedance characteristics, the controller parameters adjustment based suppression strategy is proposed and verified. From case studies, it indicates that the oscillation instability is related to the resonance frequency and the negative-resistance effect of two-level VSC, and it could be improved by adjusting controller parameters.

为了提高可再生能源电力系统的稳定性，分析了两电平电压源变换器（VSC）对扰动的响应特性，并提出了一些抑制振荡问题的策略。基于频率分量的平衡原理，考虑了其完整的控制系统，详细研究了两级VSC对交流侧干扰的响应特性。特别地，通过时域相量和空间矢量分析来说明不同频率的干扰之间的耦合效应。随后，建立了描述两级VSC端口特性的阻抗模型，并通过PSCAD / EMTDC中的电磁瞬态仿真对其进行了验证。基本上来说，在两级VSC测试系统中总结并验证了由负电阻效应引起的振荡问题的条件。最后，通过分析控制器参数对阻抗特性的影响，提出并验证了基于控制器参数调整的抑制策略。通过实例研究表明，振荡不稳定性与谐振频率和两级VSC的负阻效应有关，可以通过调整控制器参数来改善。