Control device of AC rotating electrical machine

1. A control device of an AC rotating electrical machine that controls, via an inverter circuit, an AC rotating electrical machine provided with polyphase armature windings,

the inverter circuit being made up of respective upper switching elements and lower switching elements provided corresponding to each phase of the AC rotating electrical machine, and receiving supply of power from a DC power supply to drive the AC rotating electrical machine,

the control device comprising:

a midpoint potential detection unit comprising a plurality of comparators that respectively detects, for each phase, whether a midpoint potential between the upper switching element and the lower switching element of the inverter circuit is equal to or greater than a threshold voltage, a number of the plurality of comparators being equal to a number of the phases of the AC rotating electrical machine;

a phase current detection unit that detects a phase current of each phase of the AC rotating electrical machine; and

a control unit that calculates a current estimated value of DC current that is input from the DC power supply to the inverter circuit, on the basis of the midpoint potential of each phase detected by the midpoint potential detection unit and the phase current of each phase detected by the phase current detection unit,

wherein the control unit includes an actual ON time calculation unit that calculates an actual ON time during which voltage is actually applied to each phase of the AC rotating electrical machine, on the basis of time from rising to falling of the midpoint potential of each phase detected by the midpoint potential direction unit, and

wherein the midpoint potential detection unit is configured to output a HI signal to the control unit if the midpoint potential of each of the phase is determined to be equal to or greater than the threshold voltage, and output a LOW signal to the control unit if the midpoint potential of each of the phase is detected to be lower than the threshold voltage.

2. The control device of an AC rotating electrical machine according to claim 1 ,

wherein the control unit includes:

a DC current estimation unit that calculates the current estimated value on the basis of the actual ON time for each phase as calculated by the actual ON time calculation unit, each phase current detected by the phase current detection unit, and a cycle of a carrier wave that is used when modulating a phase voltage command value, for each phase of the AC rotating electrical machine, to driving pulses for the upper switching elements and the lower switching elements.

3. The control device of an AC rotating electrical machine according to claim 1 ,

wherein the DC current estimation unit uses previous values of phase current acquired by the phase current detection unit in a previous cycle of the carrier wave, present values of phase current acquired by the phase current detection unit in a present cycle of the carrier wave, and a weighted correction value, to calculate the current estimated value through weighting, by the weighted correction value, of the previous values of phase current and the present values of phase current.

4. The control device of an AC rotating electrical machine according to claim 3 ,

wherein the weighted correction value is calculated on the basis of a frequency of the carrier wave and a frequency of the phase current.

5. The control device of an AC rotating electrical machine according to claim 3 ,

wherein the weighted correction value is calculated on the basis of at least any one of a rotational speed of the AC rotating electrical machine and an actual ON time Duty of phase voltage.

6. The control device of an AC rotating electrical machine according to claim 3 ,

wherein the weighted correction value takes on a value in the range of 0 to 1.