Variable-speed generation with the series-resonant converter

Results of study and measurements are presented for a variable-speed generation (VSG) system that uses a series-resonant converter to excite the rotor windings of a doubly-fed generator. The capabilities of this system include maximum-efficiency operation and limited converter rating for a speed range from stand-still (zero RPM) to well beyond synchronous speed, as well as flexibility for line-voltage control, reactive power generation, and synchronization at zero RPM. Measurements of the harmonic distortion are provided showing the superiority of this converter as compared with a VSG system using a conventional cycloconverter or a DC-link converter. A convenient tool for analyzing the operating modes of the system is discussed that can be developed under varying resource conditions