Abstract
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.
Highlights
The meshed 3-T modular multilevel converter (MMC) HVDC simulation system shown in Figure 1 was built via an real-time digital simulator (RTDS) to validate the effectiveness of the theoretical analysis and the control system
The main contribution of this article is the establishment of a small-signal model of a 3-T meshed DC grid including a DC current flow controller (CFC) and the design of parameters for the control system of the CFC
A control system that satisfies both stability and dynamic performance requirements has been designed based on the established small-signal models
Summary
There are three terminals, namely T1, T2, and T3. The AC systems of the three terminals have the same structures and parameters. The DC system is a ±160-kV, 640-MVA meshed system
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