High Voltage Wind Turbine Conversion System with Dual DC Converter for MVDC Grids

This paper proposes an isolated dual DC-DC output converter (IDOC) for a wind generation application to connect to an HVDC grid. The IDOC has two outputs, (i) A leading output that processes wind turbine (WT) power/current and controls connection of WT to a medium voltage DC (MVDC) collector grid, and (ii) a further output that provides DC current for wound field (WF) of a dual-field excitation generator (DFEG) resulting in control over MVDC collector grid voltage. The DFEG has a two-rotor topology that facilitates the control over the WT output using combination of a permanent magnet (PM) and WF rotor. The DFEG output is rectified using a passive rectifier whose output provides a variable-voltage input to the IDOC. The paper proposes two controllers, a dual-closed-loop leading controller that maintains maximum power point tracking (MPPT) for the WT, and a dual-closed-loop further controller that adjusts the DFEG WF current. Simulation results from electrical model in MATLAB verify the functionality of IDOC and its controllers.