Implementation and analysis of a control scheme for damping of oscillations in VSC-based HVDC grids

This paper proposes a simple method for damping of oscillations in dc grids based on Voltage Source Converters (VSCs). The damping effect is achieved by a control loop for counteracting measured dc voltage oscillations by acting on the active current reference of the ac-side VSC controller. The design of the damping method is supported by participation factor analysis and parametric sensitivities of a small-signal model representing an investigated test case. This investigated system is consisting of a single HVDC converter station connected to a dc cable equivalent and an ac grid. The validity of the developed small-signal model is verified by comparison to a simulation model including nonlinear effects of the investigated converter configuration. The small-signal model is then used to analyze the stability and dynamic characteristics of the system with and without the proposed active damping and to identify a suitable tuning of the damping controller.