Grid-forming inverters (GFMIs) are anticipated to play a leading role in future power systems. In contrast to their counterpart grid-following inverters, which employ phase-locked loops for synchronization with the grid voltage and rely on stable grid connections, GFMIs primarily employ the power-based synchronization concept to form the voltage. Hence, they can not only stably operate in regions of the grid characterized by low strength but also provide critical ancillary services to power systems, including voltage, frequency, and inertia support. Several control strategies have been employed for GFMIs, making it crucial to comprehend their stability characteristics for the analysis of small-signal stability and low-frequency oscillations. This article examines the performance of GFMIs when equipped with four different control strategies, namely, droop-based GFMI, virtual synchronous generator (VSG)-based GFMI, compensated generalized VSG (CGVSG)- based GFMI, and adaptive VSG (AVSG)-based GFMI. The comparative analysis assesses the performance and robustness of these four control strategies across various operational scenarios in frequency and time domains. Initially, the impedance-based stability analysis method is employed to evaluate these control strategies across different case studies in terms of grid strengths, grid impedance ratios, the dynamics with/without virtual impedance and inner voltage and current loops, and variations in the inverter's operating points. Subsequently, time-domain verification using the electromagnetic transient models is conducted for these case studies as well as to assess the power tracking capability of these control strategies in response to changes in power references. Finally, the robustness of these four controllers is explored against external grid disturbances, including grid frequency deviations, phase jumps, and voltage sags, considering varying levels of disturbance magnitudes in both weak and strong grid connections. In conclusion, the evaluation of these control techniques in various operational scenarios reveals their strengths and weaknesses, offering valuable guidance for the selection of the most appropriate control technique to suit desired practical applications.

中文翻译：

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并网逆变器：频域和时域不同控制策略的比较研究

并网逆变器（GFMI）预计将在未来电力系统中发挥主导作用。与采用锁相环与电网电压同步并依赖稳定的电网连接的并网逆变器相比，GFMI 主要采用基于功率的同步概念来形成电压。因此，它们不仅可以在电网强度较低的地区稳定运行，还可以为电力系统提供关键的辅助服务，包括电压、频率和惯量支持。 GFMI 采用了多种控制策略，因此了解其稳定性特性对于分析小信号稳定性和低频振荡至关重要。本文研究了 GFMI 在配备四种不同控制策略时的性能，即基于下垂的 GFMI、基于虚拟同步发电机 (VSG) 的 GFMI、基于补偿广义 VSG (CGVSG) 的 GFMI 和基于自适应 VSG (AVSG) 的 GFMI。 GFMI。比较分析评估了这四种控制策略在频域和时域的各种操作场景中的性能和鲁棒性。最初，采用基于阻抗的稳定性分析方法来评估不同案例研究中的这些控制策略，包括电网强度、电网阻抗比、有/没有虚拟阻抗和内部电压和电流环路的动态以及逆变器运行的变化。点。随后，使用电磁瞬态模型对这些案例研究进行时域验证，并评估这些控制策略响应功率参考变化的功率跟踪能力。最后，考虑到弱电网连接和强电网连接中不同程度的扰动幅度，探讨了这四个控制器针对外部电网扰动的鲁棒性，包括电网频率偏差、相位跳变和电压暂降。总之，在各种操作场景中对这些控制技术的评估揭示了它们的优点和缺点，为选择最合适的控制技术以满足所需的实际应用提供了宝贵的指导。