Study on an Optimum Design for DC and Doubly-Controlled DFIG System

This paper proposed a two-level optimum design for DC and doubly-controlled DFIG system to lower the gearbox ratio and improve the DFIG system economic benefit in the DC grid. Two voltage source converters consisting of a rotor side converter (RSC) and a stator side converter (SSC) interface DFIG with DC grid, which could regulate DFIG system synchronous speed, current and voltage flexibly. Without the limitation of AC grid, a regulation scheme of system current and generator poles is presented by two-level optimum strategy on the basis of the system costs model. The first level optimum strategy is carried out to regulate the generator poles and lower the gearbox ratio. And the second level optimum strategy is adopted to regulate the system current and lower the gearbox ratio. Finally, simulations are carried out to verify the system design effectiveness.