Inverter control apparatus and inverter control method

• US 7,049,778 B2
• Filed: 02/09/2005
• Issued: 05/23/2006
• Est. Priority Date: 02/09/2004
• Status: Expired due to Fees

• Current Assignee: Nippon Yusoki Company Limited (Mitsubishi Heavy Industries, Ltd.)
• Original Assignee: Nippon Yusoki Company Limited (Mitsubishi Heavy Industries, Ltd.)
• Inventors: Katanaya, Ikuya
• Primary Examiner(s): Martin, David
• Assistant Examiner(s): HORN, ROBERT WAYNE
• Application Number:
  US11/052,813
• Publication Number:
  US 20050174076A1
• Time in Patent Office: 468 Days
• Field of Search: 318/139, 318/811, 318800-802, 318437-439, 318599-608, 318/254, 318/700
• US Class Current: 318/400.04
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 29/0241 the fault being an overvoltage

Abstract

An interrupt signal is generated at each of rising timings of PWM signals which are produced on the basis of phase-shifted triangular wave carrier signals for phases, and voltage command values for the phases. At timings of the interrupt signals, A/D conversion of motor currents of the phases detected by a shunt is started. Interrupt signals are also produced at timings of valleys of the triangular wave carrier signals. Additionally, peak interrupt signals and valley interrupt signals are respectively produced at timings of peaks and valleys of triangular wave carrier signals for phases. Based on each of the peak interrupt signals, normality/abnormality of a switching element of an upper side of the phase corresponding to the interrupt signal is checked, and, based on each of the valley interrupt signals, normality/abnormality of a switching element of a lower side of the phase corresponding to the interrupt signal is checked.

Claims

1. An inverter control apparatus comprising:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multiphase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively;

a current detection means, disposed in series with the inverter circuit, for detecting a motor current flowing through the motor; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit, wherein

the control section comprises;

an A/D converter which A/D converts the motor current detected by the current detection means;

a control means for controlling an operation of the A/D converter;

a carrier signal generation section which generates triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases; and

a signal production means for producing PWM signals respectively for the switching elements on the basis of a comparison between the triangular wave carrier signals for the phases output from the carrier signal generation section, and the command values for the phases,

the signal production means produces interrupt signals for the control method respectively at timings when the PWM signals cause ON/OFF states of the switching elements to be switched over, and

the control means controls the A/D converter to start A/D conversion, based on the interrupt signals.

2. The inverter control apparatus according to claim 1, wherein the signal production means produces the interrupt signals for the control means respectively at rising timings of the PWM signals when the switching elements are switched from the OFF state to the ON state.

3. The inverter control apparatus according to claim 1, wherein

the control means obtains a time period from timing when one interrupt signal is produced to timing when a next interrupt signal is produced,

when the time period is equal to or larger than a fixed value, the control means makes values of motor currents, which are A/D-converted during the time period, effective, and

when the time period is smaller than the fixed value, the control means makes values of motor currents, which are A/D-converted during the time period, ineffective.

4. The inverter control apparatus according to claim 1, wherein

the control means obtains a time period from timing when one interrupt signal is produced to timing when a next interrupt signal is produced,

when the time period is equal to or larger than a fixed value, the control means controls the A/D converter to conduct A/D conversion during the time period, and

when the time period is smaller than the fixed value, the control means inhibits A/D conversion during the time period.

5. The inverter control apparatus according to claim 1, wherein

the control means sets one of the triangular wave carrier signals as a reference triangular wave carrier signal,

when A/D conversion is conducted plural times on a motor current of the same phase in one cycle of the reference triangular wave carrier signal, the control means obtains an average of the A/D-converted motor currents, and sets the average as the motor current of the phase in the one cycle.

6. The inverter control apparatus according to claim 1, wherein

the carrier signal generation section is disposed in each of the phases, each of the carrier signal generation sections comprises:

a counting means for counting clock signals and outputting a triangular wave carrier signal by incrementing or decrementing a count value;

a first detection means for detecting that the count value of the counting means reaches a predetermined upper limit;

a second detection means for detecting that the count value of the counting means reaches a predetermined lower limit; and

a command means giving a subtraction command for conducting a decrementing calculation to the counting means based on a detection output of the first detection means and giving an addition command for conducting an incrementing calculation to the counting means based on a detection output of the second detection means, wherein

the counting means for one phase outputs a triangular wave carrier signal which has a predetermined phase difference with respect to triangular wave carrier signals output from the counting means of the other phases.

7. An inverter control method for an inverter control apparatus, which comprises:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multi-phase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively;

a current detection method, disposed in series with the inverter circuit, for detecting a motor current flowing through the motor; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit,

the control method comprising the steps of;

generating triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases,

producing the PWM signals on the basis of a comparison between the triangular wave carrier signals and command values for the phases,

producing the interrupt signals at timings when the PWM signals cause ON/OFF states of the switching elements to be switched over, and

starting A/D conversion of the motor current detected by the current detection method on the basis of the interrupt signals.

8. The inverter control method according to claim 7, wherein the interrupt signals are produced respectively at rising timings of the PWM signals when the switching elements are switched from the OFF state to the ON state.

9. An inverter control apparatus comprising:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multi-phase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively;

current detection means, connected in series with the series connections respectively, for detecting a motor current flowing through the motor for each phase; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit, wherein

the control section comprises;

an A/D converter which A/D-converts the motor currents of the phases detected respectively by the current detection means;

a control means for controlling an operation of the A/D converter;

a carrier signal generation section which generates triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases; and

a signal production means for producing PWM signals respectively for the switching elements on the basis of a comparison between the triangular wave carrier signals for the phases output from the carrier signal generation section, and the command values for the phases,

the carrier signal generation section produces interrupt signals for the control method respectively at timings of peaks or valleys of the triangular wave carrier signals for the phases, and

the control means controls the A/D converter to start A/D conversion of the motor current of the phase corresponding to the interrupt signal on the basis of each of the interrupt signals.

10. The inverter control apparatus according to claim 9, wherein

each of the PWM signals is configured by:

an ON-period signal which maintains corresponding one of the switching elements to an ON state, and which has a variable time width; and

an OFF-period signal which maintains the switching element to an OFF state, and which has a variable time width,

the control means obtains a time width of the ON-period signal which maintains one of the switching elements of the series connection for the phases to an ON state,

when the time width is equal to or larger than a fixed value, the control means makes values of motor currents which are A/D-converted on the basis of interrupt signals that are produced during the time period, effective, and

when the time width is smaller than the fixed value, the control means makes values of motor currents which are A/D-converted on the basis of interrupt signals that are produced during the time period, ineffective.

11. The inverter control apparatus according to claim 9, wherein

each of the PWM signals is configured by:

an ON-period signal which maintains corresponding one of the switching elements to an ON state, and which has a variable time width; and

an OFF-period signal which maintains the switching element to an OFF state, and which has a variable time width,

the control means obtains a time width of the ON-period signal which maintains one of the switching elements of the series connection for the phases to an ON state,

when the time width is equal to or larger than a fixed value, the control method controls the A/D converter to conduct A/D conversion based on interrupt signals that are produced during the time period, and

when the time width is smaller than the fixed value, the control means inhibits A/D conversion during the time period.

12. The inverter control apparatus according to claim 9, wherein

the carrier signal generation section is disposed in each of the phases, each of the carrier signal generation sections comprises:

a counting means for counting clock signals, and outputting a triangular wave carrier signal by incrementing or decrementing a count value;

a first detection means for detecting that the count value of the counting means reaches a predetermined upper limit, and producing a first interrupt signal corresponding to a peak of the triangular wave carrier signal at timing when the count value reaches the upper limit;

a second detection means for detecting that the count value of the counting means reaches a predetermined lower limit, and producing a second interrupt signal corresponding to a valley of the triangular wave carrier signal at timing when the count value reaches the lower limit; and

a command means for giving a subtraction command for conducting the decrementing calculation to the counting means based on a detection output of the first detection method, and giving an addition command for conducting the incrementing calculation to the counting method, based on a detection output of the second detection means, and

the counting means for one phase outputs a triangular wave carrier signal which has a predetermined phase difference with respect to triangular wave carrier signals output from the counting means of the other phases.

13. An inverter control method for an inverter control apparatus, which comprises:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multiphase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively;

a current detection method, connected in series with the series connections, respectively, for detecting a motor current flowing through the motor for each phase; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit,

the control method comprising the steps of;

in the control section,

generating triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases,

producing the PWM signals on the basis of a comparison between the triangular wave carrier signals and command values for the phases,

producing the interrupt signals at timings of peaks or valleys of the triangular wave carrier signals, and

starting the A/D conversion of the motor currents of the phases corresponding to the interrupt signals detected by the detection method, on the basis of the interrupt signals.

14. An inverter control apparatus comprising:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multi-phase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit, wherein

the control section comprises;

a carrier signal generation section which generates triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases;

a signal production means for producing PWM signals respectively for the switching elements on the basis of a comparison between the triangular wave carrier signals for the phases output from the carrier signal generation section, and the command values for the phases; and

a judging means for judging normality and abnormality of the switching elements operating on the basis of the PWM signals,

the carrier signal generation section produces interrupt signals for the judging means respectively at timings of peaks or valleys of the triangular wave carrier signals for the phases, and

on the basis of each of the interrupt signals, the judging means judges normality and abnormality of the switching elements of the series connection for the phase corresponding to the interrupt signal.

15. The inverter control apparatus according to claim 14, wherein

each of the PWM signals is configured by:

an ON-period signal which maintains corresponding one of the switching elements to an ON state, and which has a variable time width; and

an OFF-period signal which maintains the switching element to an OFF state, and which has a variable time width, and

on the basis of the interrupt signals, the judging means judges whether the time width of the ON-period signal which maintains the switching element for the phase corresponding to the interrupt signal is equal to or larger than a fixed value or not, and

when the time width is equal to or larger than the fixed value, the judging means reads a voltage of the phase at a junction, and judges normality and abnormality of the switching elements on the basis of the voltage.

16. The inverter control apparatus according to claim 14, wherein

the carrier signal generation section produces a peak interrupt signal for the judging means at timings of peaks of the triangular wave carrier signals for the phases, and a valley interrupt signal for the judging means at timings of valleys, and

on the basis of the peak interrupt signal of the interrupt signals, the judging means judges normality and abnormality of one of the switching elements of the series connection for the phase corresponding to the interrupt signal, and

on the basis of the valley interrupt signal, the judging means judges normality and abnormality of another one of the switching elements of the series connection for the phase corresponding to the interrupt signal.

17. The inverter control apparatus according to claim 16, wherein

the judging means sets one of the triangular wave carrier signals as a reference triangular wave carrier signal, and

in one cycle of the reference triangular wave carrier signal, the judging means judges normality and abnormality of all the switching elements on the basis of the peak and valley interrupt signals for the phases.

18. The inverter control apparatus according to claim 14, wherein

the carrier signal generation section is disposed in each of the phases, and each of the carrier signal generation sections comprises:

a counting means for counting clock signals, and outputting a triangular wave carrier signal by incrementing or decrementing a count value;

a first detection means for detecting that the count value reaches a predetermined upper limit, and producing a peak interrupt signal corresponding to a peak of the triangular wave carrier signal at timing when the count value reaches the upper limit;

a second detection means for detecting that the count value reaches a predetermined lower limit, and producing a valley interrupt signal corresponding to a valley of the triangular wave carrier signal at timing when the count value reaches the lower limit; and

a command means for giving a subtraction command for conducting a decrementing calculation to the counting means, based on a detection output of the first detection means, and giving an addition command for conducting an incrementing calculation to the counting means, based on a detection output of the second detection means, and

the counting means for one phase outputs a triangular wave carrier signal which has a predetermined phase difference with respect to triangular wave carrier signals output from the counting means of the other phases.

19. An inverter control method for an inverter control apparatus, which comprises:

an inverter circuit in which series connections of a pair of switching elements are connected in parallel, the series connections being disposed correspondingly with respective phases of a multi-phase alternating current motor, and phase voltages for driving the motor are taken out from junctions of the switching elements in the series connections, respectively; and

a control section which outputs PWM signals based on command values for the phases to control ON/OFF operations of the switching elements of the inverter circuit,

the control method comprising the steps of;

in the control section,

generating triangular wave carrier signals respectively corresponding to the phases forming a predetermined phase difference among the carrier signals for the phases,

producing interrupt signals at timings of peaks or valleys of the triangular wave carrier signals for the phases, and

judging normality and abnormality of the switching elements of the series connection for the phase corresponding to the interrupt signal on the basis of each of the interrupt signals.

20. The inverter control method according to claim 19, wherein, in the control section,

a peak interrupt signal is produced at timings of peaks of the triangular wave carrier signals for the phases,

a valley interrupt signal is produced at timings of valleys,

normality and abnormality of one of the switching elements of the series connection for the phase corresponding to the interrupt signal is judged on the basis of the peak interrupt signal, and

normality and abnormality of another one of the switching elements of the series connection for the phase corresponding to the interrupt signal is judged on the basis of the valley interrupt signal.