Determination of design parameters for direct-drive wind turbines

Starting with rotor blade performance and permanent magnet synchronous machine data, a series of equations for determining preliminary aerodynamic and electrical design parameters of a direct-drive wind turbine with a given converter topology is presented in this paper. Serving as a case study, these equations, derived based on aerodynamic, circuit analysis and electric machine theories, can determine blade radius, expected cut-in, rated, and cut-out wind speeds, sizes of inline inductors on machine and grid sides and the DC capacitor, and controller limits accurately. The efficacy of the method is demonstrated by modeling and simulating a complete Type 4 wind turbine based on the derived design parameters. It is shown that performance and response of the simulated wind turbine model meet the design criteria.