Voltage regulation using a permanent magnet synchronous condenser with a series compensator

Wind power plant (WPP) is often operated at unity power factor, and the utility host where the WPP connected prefers to regulate the voltage. While this may not be an issue in a stiff grid, the connection to a weak grid can be problematic. This paper explores the advantages of having voltage regulation capability via reactive power control. Another issue in wind power generation is that not all turbines are able to control its reactive power due to technical reason or contractual obligations. A synchronous condenser (SC) using a permanent magnet synchronous generator (PMSG) is proposed for providing necessary reactive power for regulating voltage at a weak grid connection. A PMSG has the advantage of higher efficiency and reliability. Because of its lack of a field winding, a PMSG is typically controlled by a full-power converter, which can be costly. In the proposed system, the reactive power of the SC is controlled by a serially connected compensator operating in a closed-loop configuration. The compensator also damps the PMSG's tendency to oscillate. The compensator's VA rating is only a fraction of the rating of the SC and the PMSG. In this initial investigation, the proposed scheme is shown to be effective by computer simulations.