Paralleling method and control for a VSCF system

Abstract

Prior variable speed constant frequency (VSCF) system controls which operate the VSCF system while it is coupled in parallel with an external AC source across a load have controlled inverter output voltage based only upon the reactive current level supplied by the inverter. This has in turn resulted in the possibility of unstable system operation under load. In order to overcome the foregoing problem, a control for controlling the supply of power to a load from an inverter coupled in parallel with an AC power source across the load senses the real and reactive components of the current supplied by the inverter and the phase displacement of the power developed by the inverter relative to the power developed by the AC power source to derive an angular displacement signal. The frequency and phase of the inverter output are controlled in dependence upon the real current component supplied by the inverter and the angular displacement signal while the magnitude of the inverter output is controlled in dependence upon the real and reactive current components. The present control is capable of operating a VSCF inverter in a stable fashion under load.

Dependencies are inferred from the claim text.