Switched Reluctance Motor Drives 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° compared with the conventional method without variable-sampling and variable-hysteresis-band current control.