Small-signal stability analysis and control system design of a meshed multi-terminal high-voltage direct current grid with a current flow controller

A DC current flow controller can provide branch current control in a meshed multi-terminal high-voltage direct current (HVDC) grid. However, the introduction of a DC current flow controller may affect the stability of the multi-terminal HVDC. Hence, the dynamic characteristics of the multi-terminal HVDC with the DC current flow controller should be investigated. This article focuses on small-signal stability analysis of a current flow controller-equipped meshed three-terminal HVDC system. A small-signal model for the multi-terminal HVDC with the DC current flow controller is established. Based on the stability analysis of the small-signal model, a control system is designed for the DC current flow controller, fulfilling the system stability requirement. Finally, non-linear dynamic simulations on the real-time digital simulator are conducted, and simulation results are compared with a theoretical model to validate the proposed controller for the DC current flow controller. In addition, dynamic impacts of the DC current flow controller on the meshed multi-terminal HVDC grid are discussed.