Co-ordinated hierarchical control strategy for multi-infeed HVDC systems

A co-ordinated hierarchical control strategy for multi-infeed HVDC systems is presented. The control law of the HVDC system´s transfer power can be derived using optimal control theory with the HVDC system being treated as a variable admittance connected at the commutation busbars. A two-level hierarchical control structure is assumed for the rectifier and inverter side AC system, respectively. The control of constituent HVDC subsystems can be better co-ordinated by the consideration of the AC commutation voltage included in the optimised performance index, and the performance of both rectifier and inverter side AC systems is considered