Right-half-plain (RHP) zeros can significantly deteriorate a control system's dynamic performances as it exhibits non-minimum-phase behaviors. In this paper, we investigate the occurrence mechanism of RHP zeros in weak-grid-tied VSCs as well as provide guidance for minimizing their effects. A reduced-order multi-input multi-output (MIMO) transfer function of the weak-grid-tied VSC is firstly obtained. Then, the single-input single-output (SISO) transfer function to study the impact of the RHP zeros on the power response is further derived. The existence of RHP zeros is examined by applying the Routh criterion on the numerator of the SISO open-loop transfer function. We find that RHP zeros can exist either when the VSC works as an inverter or a rectifier. Furthermore, large grid impedance values as well as operation points with high active power values can result in a non-minimum-phase system. It is also shown that RHP zeros limit the minimum PLL bandwidth. Simulation results and RTDS experiments validate the correctness of the analysis and the conclusions obtained.

中文翻译：

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非最小相位零点对弱网格约束VSC的影响

右半平面（RHP）零会显着降低控制系统的动态性能，因为它表现出非最小相位行为。在本文中，我们研究了弱电网VSC中RHP零的发生机理，并为最大程度地减小其影响提供了指导。首先获得了弱网格VSC的降阶多输入多输出（MIMO）传递函数。然后，进一步推导了用于研究RHP零点对功率响应的影响的单输入单输出（SISO）传递函数。通过在SISO开环传递函数的分子上应用Routh准则来检查RHP零的存在。我们发现，当VSC用作逆变器或整流器时，RHP零可能存在。此外，较大的电网阻抗值以及具有高有功功率值的工作点都可能导致非最小相位系统。还表明，RHP零限制了最小PLL带宽。仿真结果和RTDS实验验证了分析和所得出结论的正确性。