Abstract: A controller (28) for a doubly fed induction generator (12,20) adjusts control signals to a rotor side converter (24) and line side converter (22) to adjust rotor current when a voltage transient on a utility grid (10) occurs, so that the doubly fed induction generator can ride through the transient. The controller can also turn off the transistors of the rotor side converter (24) to reduce rotor current and/or activate a crowbar (42) to reduce the voltage of the DC link (26) connecting the converters (22, 24) when significant voltage transients occur on the grid (10). This permits continued operation of the DFIG system without disconnecting from the grid.

Abstract: A method and apparatus for converting wind generated electricity to constant frequency electricity for supplying it to a utility grid. use a wind turbine generator having a doubly fed induction generator. Above the synchronous speed of the generator, the electricity from the rotor is converted to direct current (dc) electricity and the de electricity is converted back to alternating current (ac) electricity at a fixed unity power factor. Below synchronous speed, electricity flows to the rotor from the utility grid also at a fixed unity power factor. The current of the ac electricity is adjusted to be in phase with the utility grid voltage, wherein the ac electricity is maintained substantially at unity power factor.

Abstract: In a preferred embodiment, a motorized shed travels on a rail on two wheels thereof along a surface such as a roof while being adapted for spraying polyurethane foam from within a wind-diverter shed by a manual operator within, downwardly through a bottom port, and ventilation being through an upper open port having screen thereacross of a small mesh size which captures small droplets of polyurethane that might otherwise escape into exterior air and wind, from space within the shed. The walls of the shed are at an angle of preferably and typically about 55 degrees from a horizontal inclined inwardly as from a longer and wider base to a narrower top portion, and the shed has left and right sides of rectangular shape extending about 41/4 feet in length, a periphery along a lower edge of the shed being about 45 feet, and the shed has a height of preferably about 31/2 feet apart from the screen structure which may further increase the overall outer and inner height.

Abstract: A controller (28) for a doubly fed induction generator (12,20) adjusts control signals to a rotor side converter (24) and line side converter (22) to adjust rotor current when a voltage transient on a utility grid (10) occurs, so that the doubly fed induction generator can ride through the transient. The controller can also turn off the transistors of the rotor side converter (24) to reduce rotor current and/or activate a crowbar (42) to reduce the voltage of the DC link (26) connecting the converters (22, 24) when significant voltage transients occur on the grid (10). This permits continued operation of the DFIG system without disconnecting from the grid.