A new approach to HVDC grid voltage control based on generalized state feedback

In this paper, a new approach to DC voltage control in a High Voltage Direct Current (HVDC) grid is introduced. In an HVDC grid, the power sharing after a converter outage can be influenced by the droop control values. However, when relying on a local feedback signal, the DC voltage drops in the system hamper a straight-forward definition of the power sharing. The use of a common DC voltage signal for the control can solve some of the problems. However, it disregards some of the benefits that are associated with the use of a local voltage control, such as the tendency of a controller using local voltage feedback signals to solve problems locally which can reduce the stress on the AC system. Furthermore, it provides no direct means to obtain different system responses for different converter outages. The control approach presented in this paper aims at improving the DC voltage droop control by combining the local voltage signal available at the converter terminals with remote voltage signals at different locations in the DC system by means of communication. The local voltage feedback control is used for a fast, reliable system response. The introduction of the remote voltage signals in the control allows to differentiate the system response for different converter outages. Simulation results show the validity of the proposed control scheme.