Short-circuit detection device for rotating electric machine, and short-circuit detection method
A short-circuit detection device for a rotating electric machine sets an order lower than a fundamental order of a slot harmonic wave as a threshold value, and reduces, among the plurality of frequency components, even-order frequency components having orders higher than the threshold value and odd-order frequency components, converts a plurality of frequency components output from the specific frequency component reduction unit into a voltage signal, generates a difference waveform of voltage signals respectively corresponding to adjacent magnetic poles, detects a short-circuit of a field winding based on a shape of the difference waveform, and estimates a short-circuit position of the field winding, and determines an estimation accuracy of the short-circuit position of the field winding based on a degree of symmetry of a waveform of a maximum wave with respect to a peak angle of the difference waveform serving as a center.
1 . A short-circuit detection device for a rotating electric machine, the short-circuit detection device comprising:
circuitry configured to:
as a process:
acquire a first voltage signal from a magnetic detector arranged opposed to a field winding provided in a plurality of slots of the rotating electric machine;
decompose the first voltage signal into a plurality of frequency components having orders different from each other;
set an order lower than a fundamental order of a slot harmonic wave being a harmonic wave having a correlation with a pitch of the plurality of slots as a threshold value;
reduce, among the plurality of frequency components, an even-order frequency component having an order higher than the threshold value and an odd-order frequency component;
convert the plurality of frequency components into a second voltage signal;
divide the second voltage signal into a divided voltage signal for each circumferential angle of the rotating electric machine corresponding to one of a plurality of magnetic poles of the rotating electric machine;
generate a difference waveform of voltage signals of the divided voltage signals respectively corresponding to adjacent magnetic poles among the plurality of magnetic poles;
detect a short-circuit of the field winding based on a shape of the difference waveform;
estimate at which position in a circumferential direction of the rotating electric machine the short-circuit of the field winding has occurred; and
determine an estimation accuracy of the position at which the short-circuit has occurred,
determine whether the estimation accuracy estimated in the process is lower than a determination threshold value, and
when the estimation accuracy estimated in the process is lower than a determination threshold value:
change an operation condition of the rotating electric machine; and
perform the process again after the change of the operation condition,
wherein, when one wave including a maximum value of an absolute value of a peak voltage in the difference waveform is defined as a maximum wave and a circumferential angle of the rotating electric machine corresponding to the maximum value is defined as a peak angle, the circuitry is configured to determine the estimation accuracy of the position at which the short-circuit has occurred based on a degree of symmetry of a waveform of the maximum wave with respect to the peak angle serving as a center.
2 . The short-circuit detection device for a rotating electric machine according to claim 1 , wherein the circuitry is configured to determine the estimation accuracy based on an angle difference between the peak angle and a center angle being a circumferential angle corresponding to a center of a width of the maximum wave at a determination voltage being a voltage smaller than the maximum value of the maximum wave.
3 . The short-circuit detection device for a rotating electric machine according to claim 2 , wherein the determination voltage is a voltage that is a half of the maximum value.
4 . The short-circuit detection device for a rotating electric machine according to claim 1 , wherein the circuitry is configured to estimate the fundamental order of the slot harmonic wave based on an amplitude of each of the plurality of frequency components.
5 . The short-circuit detection device for a rotating electric machine according to claim 1 , wherein the circuitry is configured to set an amplitude of an odd-order frequency component having an order equal to or lower than the threshold value to zero.
6 . The short-circuit detection device for a rotating electric machine according to claim 1 , wherein the circuitry is configured to output, to an outside, information on whether the short-circuit of the field winding has occurred, a position of a corresponding one of the plurality of slots in which the short-circuit has occurred, and the estimation accuracy of the position of the corresponding one of the plurality of slots in which the short-circuit has occurred.
7 . The short-circuit detection device for a rotating electric machine according to claim 1 , wherein the circuitry is configured to detect the short-circuit of the field winding based on a peak waveform appearing in the difference waveform, and to estimate that the short-circuit of the field winding has occurred in a slot corresponding to the peak angle.
8 . A short-circuit detection method for a rotating electric machine, the short-circuit detection method comprising:
as a process:
acquiring a first voltage signal from a magnetic detector arranged opposed to a field winding provided in a plurality of slots of a field system;
decomposing the first voltage signal into a plurality of frequency components having orders different from each other;
setting an order lower than a fundamental order of a slot harmonic wave being a harmonic wave having a correlation with a pitch of the plurality of slots as a threshold value;
reducing, among the plurality of frequency components, an even-order frequency component having an order higher than the threshold value and an odd-order frequency component;
converting the plurality of frequency components into a second voltage signal;
dividing the second voltage signal into a divided voltage signal for each circumferential angle of the field system corresponding to one of a plurality of magnetic poles of the field system;
generating a difference waveform of voltage signals of the divided voltage signals respectively corresponding to adjacent magnetic poles among the plurality of magnetic poles;
detecting a short-circuit of the field winding based on a shape of the difference waveform;
estimating at which position in a circumferential direction of the field system the short-circuit of the field winding has occurred; and
determining an estimation accuracy of the position at which the short-circuit has occurred,
determining whether the estimation accuracy estimated in the process is lower than a determination threshold value, and
when the estimation accuracy estimated in the process is lower than the determination threshold value:
changing an operation condition of the rotating electric machine; and
performing the process again after the changing of the operation condition,
wherein, when one wave including a maximum value of an absolute value of a peak voltage in the difference waveform is defined as a maximum wave and a circumferential angle of the field system corresponding to the maximum value is defined as a peak angle, the determining includes determining the estimation accuracy of the position at which the short-circuit has occurred based on a degree of symmetry of a waveform of the maximum wave with respect to the peak angle serving as a center.