Deterioration estimation device and deterioration estimation program for power conversion device

1. A deterioration estimation device for a power conversion device outputting an AC current, the deterioration estimation device comprising:

calculating means for calculating a variation of characteristics of switching elements for power conversion in the power conversion device from a voltage command treated as a target for an output voltage of the power conversion device and an output voltage value of the power conversion device, the calculating means comprising a subtracting means for calculating a difference between the voltage command and the output voltage value;

determining means for determining whether the variation of the characteristics calculated by the calculating means has changed from an initial state by a threshold value or greater, the determining means comprising a first unit for receiving a variation of characteristics signal from a first integrating means, and a second unit for receiving a variation of characteristics signal from a second integrating means; and

notifying means for issuing a warning when the determining means has determined that the change in the variation of the characteristics is equal to or greater than the threshold value, wherein

the calculating means includes polarity determining means for determining a polarity of the AC current outputted from the power conversion device including an upper arm comprising a first switching element among the switching elements and a lower arm comprising a second switching element among the switching elements, and switching means configured to switch the signal from the subtracting means to the first integrating means when the switching signal from the polarity determining means indicates that a positive polarity of the AC current is detected, and switch the signal from the subtracting means to the second integrating means when the switching signal from the polarity determining means indicates that a negative polarity of the AC current is detected, and

the determining means includes a pair of units each of which is respectively configured to determine the variation of the characteristics switched by the switching means.

2. The deterioration estimation device according to claim 1 , wherein the determining means stores and treats is configured to store the variation of the characteristics corresponding to the output voltage value of the power conversion device, the stored variation of the characteristics being treated as an initial state, and the determining means is configured to determine the threshold value on a basis of the initial state.

3. The deterioration estimation device according to claim 1 , wherein the first and second integrating means are configured to output an integral value from a definite integral over a predetermined interval as the differential integral value.

4. The deterioration estimation device according to claim 1 , wherein the calculating means includes first averaging means for calculating an average value of an input voltage value into the power conversion device at respective time intervals synchronized with a carrier signal, multiplying means for multiplying the average value of the input voltage value from the first averaging means by a modulation ratio to calculate and output the voltage command to the subtracting means, and second averaging means for calculating and outputting, to the subtracting means, an average value of the output voltage value of the power conversion device at respective time intervals synchronized with the carrier signal.

5. A non-transitory computer-readable medium storing thereon a deterioration estimation program for a power conversion device outputting an AC current, the deterioration estimation program causing a computer to function as:

calculating means for calculating a variation of characteristics of switching elements for power conversion in the power conversion device from a voltage command treated as a target for an output voltage of the power conversion device and an output voltage value of the power conversion device, the calculating means comprising a subtracting means for calculating a difference between the voltage command and the output voltage value;

determining means for determining whether the variation of the characteristics calculated by the calculating means has changed from an initial state by a threshold value or greater, the determining means comprising a first unit for receiving a variation of characteristics signal from a first integrating means, and a second unit for receiving a variation of characteristics signal from a second integrating means; and

notifying means for issuing a warning when the determining means has determined that the change in the variation of the characteristics is equal to or greater than the threshold value, wherein

the calculating means includes polarity determining means for determining a polarity of the AC current outputted from the power conversion device including an upper arm comprising a first switching element among the switching elements and a lower arm comprising a second switching element among the switching elements, and switching means configured to switch the signal from the subtracting means to the first integrating means when the switching signal from the polarity determining means indicates that a positive polarity of the AC current is detected, and switch the signal from the subtracting means to the second integrating means when the switching signal from the polarity determining means indicates that a negative polarity of the AC current is detected, and

the determining means includes a pair of units each of which is respectively configured to determine the variation of the characteristics switched by the switching means.