Centralized coordinated control of VSC-HVDC link and DFIGs in very large offshore wind power plants

The aim of this paper is to improve an optimization algorithm for coordinated management of VSC-HVDC link and DFIGs in variable frequency operation, presented by the authors in a previous work. The new features introduced in this paper concern different upper bounds on DFIG rotor and stator power flow and modified constraints on generator slips and AC offshore grid frequency. The upper bound on stator power flow is suitably set to allow an overload manageable for an electromechanical machine. The Central Optimizer procedure is followed by a Local one modifying (in dependence to real time measured wind speed) the optimization variables for each generators, taking constant the AC offshore grid frequency at the value previously found by the Central Optimizer. The highly non linear problem is solved by means of an interior point algorithm. Test results show the goodness of the proposed methodology.