Electric power converter and motor driving system

Abstract

An electric power converter which has improved accuracy in compensation of a dead time. A motor driving system employing the electric power converter is also provided. A power module includes a plurality of switching devices connected in series and converts DC power to AC power. A control circuit produces a voltage command value in accordance with a control command inputted from the exterior, and produces gate signals to drive the switching devices of the power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation. A dead time compensation logic circuit calculates a final dead time compensation voltage based on a change rate of the voltage command value, a gain (dead time compensation voltage value), and a polarity of a current, the gain being calculated from a DC voltage value supplied to the electric power converter, a dead time, and a switching frequency.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a motor driving system using an inverter which is an electric power converter according to one embodiment of the present invention;

FIG. 2 is charts showing waveforms for explaining a PWM signal used in the inverter which is the electric power converter according to the one embodiment of the present invention;

FIG. 3 is a block diagram of a control circuit in the electric power converter according to the one embodiment of the present invention;

FIG. 4 is a block diagram of a dead time compensation logic circuit in the electric power converter according to the one embodiment of the present invention;

FIG. 5 is a chart showing the waveform of a final voltage command value produced by the electric power converter according to the one embodiment of the present invention when the power factor is 1; and

FIG. 6 is a chart showing the waveform of the final voltage command value produced by the electric power converter according to the one embodiment of the present invention when the power factor is other than 1.

Claims

1. An electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for producing the final voltage command value which takes a maximum value approximately at a phase π/2 of the voltage command value on both sides thereof and a minimum value approximately at a phase 3π/2 of the voltage command value on both sides thereof.

2. The electric power converter according to claim 1, wherein said dead time compensation means sets a dead time compensation voltage to 0 at the phase π/2 and the phase 3π/2 of the voltage command value.

3. The electric power converter according to claim 2, wherein said dead time compensation means calculates the dead time compensation voltage based on a change rate of the voltage command value and a polarity of a current, and calculates the final voltage command value by adding the calculated dead time compensation voltage to the voltage command value.

4. The electric power converter according to claim 3, wherein said dead time compensation means calculates a gain based on a DC voltage value supplied to said electric power converter, a dead time and a switching frequency, and sets, as an absolute value of the dead time compensation voltage, an absolute value of the product obtained by multiplying the calculated gain by a differentiated value of the voltage command value.

5. An electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for calculating the final voltage command value by applying the dead time compensation to the voltage command value.

6. An electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for calculating a dead time compensation voltage based on a change rate of the voltage command value, a gain, and a polarity of a current, the gain being calculated from a DC voltage value supplied to said electric power converter, a dead time, and a switching frequency.

7. A motor driving system comprising an electric power converter for converting DC power to AC power, and an AC motor driven with supply of the AC power converted by said electric power converter, said electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for producing the final voltage command value which takes a maximum value approximately at a phase π/2 of the voltage command value on both sides thereof and a minimum value approximately at a phase 3π/2 of the voltage command value on both sides thereof.

8. A motor driving system comprising an electric power converter for converting DC power to AC power, and an AC motor driven with supply of the AC power converted by said electric power converter, said electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for calculating the final voltage command value by applying the dead time compensation to the voltage command value.

9. A motor driving system comprising an electric power converter for converting DC power to AC power, and an AC motor driven with supply of the AC power converted by said electric power converter, said electric power converter comprising: a power module including a plurality of switching devices connected in series and converting DC power to AC power; andcontrol means for producing a voltage command value in accordance with a control command inputted from the exterior, and producing gate signals to drive the switching devices of said power module corresponding to a final voltage command value which is obtained from the voltage command value with dead time compensation,said control means including dead time compensation means for calculating a dead time compensation voltage based on a change rate of the voltage command value, a gain, and a polarity of a current, the gain being calculated from a DC voltage value supplied to said electric power converter, a dead time and a switching frequency.