Position sensorless step-wise freewheeling control method for switched reluctance motor

A position sensorless step-wise freewheeling control method for a switched reluctance motor, including a power supply, windings of a switched reluctance motor, and a power converter including a main switch and diodes with an upper tube S1 and a lower tube S2 in the power converter of the main switch of a phase in an OFF state and the winding of the phase in the switched reluctance motor in DC negative voltage forced freewheeling state, comprising the steps of:

• setting a threshold for a winding current of the phase, and detecting the winding current i of the phase;
• switching on either the lower tube S2 or the upper tube S1 in the power converter of the main switch of the phase when the winding current i of the phase drops to a preset threshold, so that the winding of the phase in the switched reluctance motor changes into a zero voltage natural freewheeling state and the winding current i of the phase begins to rise up;
• and
• when the rotor position of the switched reluctance motor is a start position b of minimum phase inductance of the phase when the winding current i of the phase rises up to a peak value, acquiring the start position b of minimum phase inductance of the phase, taking the acquired value as the switch-on position θ1 of the main switch of the phase in the power converter of switched reluctance motor, and switching on the upper tube S1 and lower tube S2 of the main switch in the power converter.