Grid Connection Power Converter and Speed Controller for Slip-Synchronous Wind Generators

The process of connecting small-scale wind turbine synchronous generators directly to the grid is not prevalent in literature. A wind turbine generator system not connected to the grid is a non-self-regulating system that has to be actively loaded and speed controlled prior to grid connection. In this paper, a grid connection power converter and a speed controller is proposed and developed for connecting a fixed-speed slip-synchronous permanent magnet generator (SS-PMG) to the grid. The power converter consists of a diode rectifier and Buck dc-dc converter with a resistive dump load, however, the diode rectifier and Buck converter are only active prior to grid connection, after which they are disconnected and the generator is directly connected to the grid. The proposed power converter is shown to provide acceptable and smooth grid connection performance as per the relevant grid codes. The proposed speed controller results in a single set of controller gains which are shown to be capable of controlling the SS-PMG drivetrain's speed at synchronous speed from rest, regardless of the magnitude of the input conditions.