An online optimization algorithm for coordinated control of VSC-HVDC link and DFIGs for offshore wind applications

The aim of this paper is to find out an optimization algorithm for wind power plants, where the wind turbines are equipped by DFIG, connected to on-shore grid by means VSC-HVDC link. The off-shore grid frequency is assumed variable under a fixed range and the wind power tracking characteristic of the DFIG has to be extended to consider the additional grid frequency dependence. The highly non linear problem is solved by means of a interior point algorithm and a sequential quadratic programming algorithm. The methodology has been tested on a wind park composed by 50 turbines. Results show that the best operation point is quickly reached, demonstrating the effectiveness of the tool for online operations.