Elimination of Mutual Flux Effect on Rotor Position Estimation of Switched Reluctance Motor Drives Considering Magnetic Saturation

In this letter, an approach to eliminate the mutual flux effect on the rotor position estimation of switched reluctance motor drives without a priori knowledge of mutual flux is proposed, while operating in both linear and saturated magnetic regions. Considering magnetic saturation, the incremental-inductance estimation using the phase current slope difference method can be classified into three modes: Modes I-III. At positive-current-slope and negative-current-slope sampling point of one phase, the sign of current slope of the other phase changes in Modes I and II, but does not change in Mode III. Theoretically, the incremental-inductance estimation error introduced by the mutual flux is both rotor position and phase current dependent, which is +/- 1% to +/- 7% for the studied motor in Modes I and II. However, in Mode III, the mutual flux effect does not exist. Therefore, two methods are proposed to ensure that the incremental-inductance estimation is working in Mode III exclusively. The first one is variable-sampling incremental-inductance estimation for the outgoing phase and the other is the variable-hysteresis-band current control for the incoming phase. Simulation and experimental results show that the proposed method improves position estimation accuracy by 2 degrees compared with the conventional method without variable-sampling and variable-hysteresis-band current control.