Current gradient based rotor position detection of switched reluctance machines at low speed

Switched reluctance machines are an object of extensive research due to their low-cost potential and high reli­ability. Position sensorless control can contribute significantly to further improve these properties. Generally, position estimation by evaluation of the terminal quantities without additional signal injection in the idle phases is preferable. At medium and high speed a commonly applied technique is the flux-linkage method. At low speed and standstill however, flux linkage estimation suffers from offset integration and deterioration in quality. To avoid signal injection this work proposes a method that makes the application of the flux linkage at low speed and standstill possible. It estimates the incremental inductance from the current gradient and uses the additional information for rotor position detection and correction of the flux linkage method.