Primary and secondary power control of multiterminal HVDC grids

The article introduces a hierarchical control structure for Multiterminal High Voltage Direct Current (M-HVDC) systems. The presented hierarchy is similar to the control structure of the classical AC systems divided in primary, secondary and tertiary control. The design and interaction between the secondary, or power control, and the primary controllers, or voltage control, are discussed. Furthermore, the operation characteristics and operation points are commented. Some scenarios have been simulated in order to test and verify the proposed method including a power reference change and a grid side converter disconnection.