Rotor-Position Estimation of Switched Reluctance Motors Based on Damped Voltage Resonance

Abstract

Abstract-This paper proposes a method to obtain the rotor position of switched reluctance motors by means of voltage measurements. It is shown that the combination of motor and power-electronic converter defines a resonant circuit, comprised by the motor phase inductances and the parasitic capacitance of converter switches, power cables and motor phase windings. For salient machines in general, the associated resonance frequency of the circuit depends on the rotor position. In the position estimation method, an initial voltage distribution is imposed over the impedances of the resonance circuit, after which the circuit is let to oscillate freely. During this phase of free oscillation, the induced voltage over a phase winding exhibits a damped oscillatory behaviour, from which position information can be retrieved.An overview is given of different possibilities to trigger the voltage resonance. It is shown that the proposed position estimation method has favourable characteristics such as measurement of large-amplitude voltages, robustness against temperature deviations of motor and power semiconductors, very high update rates for the estimated position and absence of sound and disturbance torque. Experimental results are given for a sensorless commutation scheme of a switched reluctance motor under small load.

Influence of converter capacitance in resonance-based sensorless switched reluctance drives

“…In switched reluctance drives, the rotor position can be obtained by observation of the unforced oscillation of a resonant circuit comprising the inductance and parasitic capacitance associated with an idle motor phase [4]. Fig.…”

“…From this part of the waveform, rotor position can be estimated e.g. by measuring the damped oscillation period, or by a single voltage measurement at a fixed time after the start of the test pulse [4].…”

“…A rotor position estimation method based on electrical resonance, but without the need for an external excitation circuit, is proposed in [4]. The method is characterized by the fact that very short voltage pulses are used to trigger resonance between the magnetic energy stored in the phase inductances and the energy stored in parasitic capacitances associated with the power semiconductor devices, power cables and motor phase windings.…”

Mitigation of cross-saturation effects in resonance-based sensorless switched reluctance drives

“…In switched reluctance drives, the rotor position can be obtained by observation of the oscillation of a resonant circuit comprising the inductance and parasitic capacitance associated with an idle motor phase [6]. Fig.…”

“…This paper discusses the influence of cross-saturation on a resonance-based sensorless method for SRMs [6]. If the trailing phase with respect to the torque-producing phase is used to extract position information, the position error leads to an advanced phase commutation.…”