JP2015142462A - Inverter control device and refrigerator employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a failure in any one of a plurality of switch elements within an inverter circuit during operation of the inverter circuit.SOLUTION: An inverter control device is connected to an inverter circuit which includes a plurality of switch elements and converts DC power into three-phase AC power by changing opening/closing states of the plurality of switch elements and supplies the converted power to a synchronous motor, and includes: a current calculation part which calculates output currents of three phases to flow from the inverter circuit to the synchronous motor on the basis of a current flowing in the inverter circuit; a voltage command calculation part which calculates voltage command values of three phases instructing a voltage to be applied from the inverter circuit to the synchronous motor on the basis of the output currents; and an abnormality detection part which determines a plurality of determination timings on the basis of the voltage command values of three phases and determines failures in the plurality of switch elements, respectively, on the basis of the output currents in the plurality of timings.

Description

  The present invention relates to a technique for detecting an abnormality of an inverter.

  The problem that the synchronous motor vibrates when the synchronous motor continues to be driven with only one phase of the motor wiring supplying three-phase alternating current from the inverter to the synchronous motor in a phase-open state where current does not flow due to disconnection or poor connection. In addition, there is a problem that the current of the phase that is not in phase increases in the inverter, which may cause a secondary failure of the synchronous motor or the inverter.

  Patent Document 1 discloses a motor control device including a three-phase inverter that outputs a three-phase AC voltage for driving a synchronous motor, and a current detection unit that detects a current flowing in each phase of the synchronous motor. Describes a motor control device having phase loss detection means for detecting phase loss based on the current value detected in step (1).

JP 2013-106424 A

  The technique for detecting an open phase as disclosed in Patent Document 1 cannot detect a failure when any one of a plurality of switch elements in the inverter circuit fails.

  In order to solve the above-described problem, an inverter control device according to one aspect of the present invention is an inverter circuit including a plurality of switch elements, and converts DC power to three-phase AC by changing an open / close state of the plurality of switch elements. Based on the output current, a current calculation unit that is connected to an inverter circuit that converts to electric power and supplies the synchronous motor, calculates a three-phase output current that flows from the inverter circuit to the synchronous motor based on the current flowing through the inverter circuit, A voltage command calculation unit for calculating a three-phase voltage command value for instructing a voltage to be applied to the synchronous motor from the inverter circuit, and determining a plurality of determination timings based on the three-phase voltage command value, and outputting at the plurality of determination timings And an abnormality detection unit that determines a failure of each of the plurality of switch elements based on the current.

  According to one embodiment of the present invention, a failure of any one of a plurality of switch elements in an inverter circuit can be detected during operation of the inverter circuit.

The structure of the freezing apparatus of Example 1 is shown. The structure of the motor drive device 10 is shown. The operation of the PWM control unit 14 is shown. The operation of the inverter 13 in the energization modes M2 and M6 is shown. The operation of the inverter 13 in the energization modes M3 and M5 is shown. The structure of the motor control part 19 is shown. Indicates the startup sequence. The relationship between the voltage command value, determination period, and motor current is shown. The structure of the motor drive device 10 of Example 2 is shown.

  Embodiments of the present invention will be described below with reference to the drawings.

  In this embodiment, a refrigeration apparatus to which the present invention is applied will be described. The refrigeration apparatus is, for example, an air conditioner or a refrigerator.

(Configuration of refrigeration equipment)

  FIG. 1 shows the configuration of the refrigeration apparatus of the first embodiment.

  The refrigeration apparatus 1 includes an outdoor unit 1a and an indoor unit 1b connected to the outdoor unit 1a by piping. The outdoor unit 1 a includes a compressor 2, an outdoor heat exchanger 4, and an accumulator 6. The indoor unit 1b includes an indoor expansion valve 5 and an indoor heat exchanger 3. The compressor 2, the outdoor heat exchanger 4, the indoor expansion valve 5, the indoor heat exchanger 3, and the accumulator 6 are connected in order, and form a refrigeration cycle by circulating the refrigerant. The indoor unit 1b further includes a fan motor 7 that blows air to the indoor heat exchanger 3. The outdoor unit 1a further includes a fan motor 8 that blows air to the outdoor heat exchanger 4, a permanent magnet synchronous motor 9 that is disposed inside the compressor 2 and drives the compressor 2, and a motor that drives the permanent magnet synchronous motor 9. A drive device 10 and a host device 11 that controls the motor drive device 10 are included. In this embodiment, a permanent magnet synchronous motor 9 is used as the synchronous motor.

  The motor driving device 10 controls the operating frequency (rotational speed) of the permanent magnet synchronous motor 9 according to the capacity of the compressor 2 required for the refrigeration cycle. The host device 11 sends an instruction to the motor drive device 10. The motor drive device 10 and the host device 11 share the operation state of the motor drive device 10 by communicating with each other. When the motor drive device 10 detects an abnormality of the motor drive device 10, the upper device 11 displays the detected abnormality on the display unit of the upper device 11.

(Configuration of motor driving device 10)

  FIG. 2 shows a configuration of the motor drive device 10 of the first embodiment.

  The motor drive device 10 includes a DC power source 12 that supplies DC power, an inverter 13 that converts DC power from the DC power source 12 into AC power, a shunt resistor 43 provided on the DC side of the inverter 13, and a shunt resistor 43. A bus current detector 15 that detects a DC bus current (input current) Idc by amplifying the voltage of the controller, and a controller 16 that controls the permanent magnet synchronous motor 9 according to an instruction from the host device 11 and the DC bus current Idc. Prepare.

  The inverter 13 has six semiconductor power elements Up, Un, Vp, Vn, Wp, and Wn. Semiconductor power devices include IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), bipolar transistors and other switch elements (self-extinguishing elements), and reflux connected to the switch elements in antiparallel. Including a diode. The two semiconductor power elements of each phase are connected in series to form one upper and lower arm, and the three upper and lower arms are connected in parallel. Here, the semiconductor power elements Up, Un, Vp, Vn, Wp, and Wn are respectively the U-phase upper arm, the U-phase lower arm, the V-phase upper arm, the V-phase lower arm, and the W-phase upper arm, Corresponds to the lower arm of the W phase. In each phase, the middle terminal of the upper and lower arms and the terminal of the permanent magnet synchronous motor 9 are connected by a motor wiring 44. The motor wiring 44 supplies the three-phase AC power output from the inverter 13 to the permanent magnet synchronous motor 9.

  The DC power source 12 is a converter (rectifier) or a battery that converts AC power supplied from an external AC power source into DC power, and supplies DC power to the DC side of the inverter 13. The controller 16 is realized by a semiconductor arithmetic element such as a microcomputer or a DSP (digital signal processor). The controller 16 includes a current calculation unit 17, an abnormality detection unit 18, a motor control unit 19, and a PWM control unit 14. The current calculation unit 17 calculates three-phase motor currents (output currents) Iu, Iv, and Iw from the DC bus current Idc detected by the bus current detector 15. The three-phase motor current flows from the inverter 13 to the permanent magnet synchronous motor 9 through the motor wiring 44. The motor control unit 19 calculates a voltage command value indicating a three-phase voltage supplied to the permanent magnet synchronous motor 9 based on the calculated motor current and an instruction from the host device 11. Based on the voltage command value, the PWM control unit 14 generates a PWM signal that is a gate signal for on / off control of each of the semiconductor power elements Up, Un, Vp, Vn, Wp, and Wn of the inverter 13. Output. The abnormality detector 18 detects an abnormality in the inverter 13, the motor wiring 44, and the permanent magnet synchronous motor 9 based on the three-phase motor current and the voltage command value.

(Calculation of motor current)

  FIG. 3 shows the operation of the PWM control unit 14.

  A carrier signal that is a triangular wave having a frequency sufficiently higher than the AC frequency is generated by the timer of the controller 16 and supplied to the PWM controller 14. This figure shows the relationship between the voltage command value, the power element drive signal, and the DC bus current in one cycle of the carrier signal.

  Here, among the three phases, the phase with the maximum voltage command value is called the maximum phase, the phase with the minimum voltage command value is called the minimum phase, and the phase with the middle voltage command value is called the intermediate phase. The voltage command values 20a, 20b, and 20c are respectively a maximum phase voltage command value Vmax * that is a maximum phase voltage command value, an intermediate phase voltage command value Vmid * that is an intermediate phase voltage command value, and a minimum phase voltage command value. A certain minimum phase voltage command value Vmin * is shown. The PWM control unit 14 compares the voltage command value 20a with the carrier signal, and generates and outputs the result as the power element drive signal 21a. Here, the power element driving signal 21a indicates a level of either Hi or Lo. When the voltage command value 20a is higher than the value of the carrier signal, the PWM control unit 14 sets the power element drive signal 21a to Hi. The same applies to the power element drive signals 21b and 21c based on the voltage command values 20b and 20c, respectively. A level Hi of a phase indicates that the upper arm signal is on (lower arm signal is off), and a level Lo of the phase indicates that the upper arm signal is off (lower arm signal is on).

  The inverter 13 sequentially shifts to energization modes M1, M2, M3, M4, M5, M6, and M7 according to the combination of the levels of the power element drive signals 21a, 21b, and 21c. Here, the case where the U phase, the V phase, and the W phase are the maximum phase, the intermediate phase, and the minimum phase, respectively, will be described. In the energization modes M1, M4, and M7, all upper arms are turned on or all lower arms are turned on, and the DC bus current Idc does not flow through the shunt resistor 43.

  FIG. 4 shows the operation of the inverter 13 in the energization modes M2 and M6. In the energization modes M2 and M6, the upper phase U phase and the intermediate phase V phase upper arm are turned on, and the W phase lower arm is turned on, and the DC bus current Idc is minimized in the shunt resistor 43. Phase current Iw flows in the opposite direction

  FIG. 5 shows the operation of the inverter 13 in the energization modes M3 and M5. Here, the maximum phase is the U phase. In the energization modes M3 and M5, the upper arm of only the U phase, which is the maximum phase, is turned on, the lower arm of the V phase, which is the intermediate phase, and the lower arm of the W phase, which is the minimum phase, is turned on. Phase current Iu flows in the positive direction.

  Hereinafter, the combination of turning on or off the semiconductor power elements in the maximum phase, intermediate phase, and minimum phase of each phase is referred to as a switching pattern. The current calculation unit 17 can calculate the current of the maximum phase or the minimum phase from the DC bus current based on the switching pattern, and can calculate other two-phase currents.

(Vector control)

  FIG. 6 shows the configuration of the motor control unit 19.

  The motor control unit 19 calculates a voltage command value to be applied to the permanent magnet synchronous motor 9 by dq coordinate system vector control. The motor control unit 19 includes a PLL (Phase Locked Loop) controller 22, a phase calculator 24, a voltage command controller 25, a 2-axis / 3-phase converter 27, an axis error calculator 26, a 3-phase / A biaxial converter 28, a switch 23, and a first-order lag filter 42 are included.

  As described above, the current calculation unit 17 calculates the DC bus current Idc detected by the bus current detector 15 and the three-phase voltage command values Vu *, Vv *, and Vw * calculated by the motor control unit 19. Use to calculate (reproduce) the motor currents Iu, Iv, and Iw.

  The three-phase / two-axis converter 28 outputs the dc-axis current Idc and the qc-axis current Iqc based on the calculated motor currents Iu, Iv, Iw and the control system phase θdc calculated by the phase calculator 24. Calculate based on the formula. Here, the dc-qc axis is defined as the control system axis, the dq axis is defined as the motor rotor axis, and the axis error between the dc-qc axis and the dq axis is defined as Δθc.

  The voltage command controller 25 outputs a preset dc-axis current command value Id *, a qc-axis current command value Iq * obtained by passing the qc-axis current Iqc through the first-order lag filter 42, and the host device 11. Using the rotation speed command value ω1 * set based on the command and the motor constant setting values r *, Ld *, Lq *, Ke * set in advance, the dc-axis voltage command value as shown in the following equation: Vdc * and qc-axis voltage command value Vqc * are calculated. Here, r * is the motor winding resistance setting value of the control system, Ld * is the d-axis inductance setting value of the motor, Lq * is the q-axis inductance setting value of the motor, and Ke * is the control system Motor induced voltage constant setting value.

  The 2-axis / 3-phase converter 27 converts the dc-axis voltage command value Vdc * and qc-axis voltage command value Vqc * calculated by the voltage command controller 25 and the control system phase θdc calculated by the phase calculator 24. Based on the following equation, the three-phase voltage command values Vu *, Vv *, Vw * of the permanent magnet synchronous motor 9 are calculated and output to the PWM control unit 14.

(Position sensorless control)

  Here, a rotational speed and phase estimation method for realizing position sensorless control will be described.

  The axis error calculator 26 is a dc-axis voltage command value Vdc * and qc-axis voltage command value Vqc * calculated by the voltage command controller 25, and a dc-axis current value Idc calculated by the three-phase / 2-axis converter 28. Then, the axis error Δθc is calculated from the qc-axis current value Iqc using the following equation.

Δθc = tan ⁻¹ {
(Vdc * -r * Idc + ω1 * Lq * Iqc)
/ (Vqc * -r * Iqc-ω1 * Lq * Idc)}

  The PLL controller 22 calculates an estimated value ωm of the rotational speed of the permanent magnet synchronous motor 9 based on the axis error Δθc calculated by the axis error calculator 26. The phase calculator 24 calculates the control system phase θdc by integrating the estimated rotational speed ωm. With such a configuration, the estimated axis error Δθc between the motor rotor shaft (dq axis) and the dc-qc axis of the control system coincides with a preset axis error command value Δθc * (usually near 0). Control to do.

  The above is the vector control and the position sensorless control in the position sensorless mode by the motor control unit 19.

(Startup sequence)

  Since the induced voltage of the permanent magnet synchronous motor 9 is small when the permanent magnet synchronous motor 9 is started and rotated at a low speed, the control system may become unstable due to the influence of the axis error Δθc.

  FIG. 7 shows an activation sequence.

  This figure shows the transition of the operation mode at the time of starting of the permanent magnet synchronous motor 9, and also shows the time change of the current command Id *, the current command Iq *, and the rotational speed command ω1 *. The operation modes include a positioning mode, a synchronous operation mode, and a position sensorless mode. In the positioning mode, a direct current is gradually applied to a predetermined motor winding of the permanent magnet synchronous motor 9 to fix the motor rotor at a predetermined position. The synchronous operation mode controls the voltage applied to the permanent magnet synchronous motor 9 according to a predetermined dc-axis current command value Idc *, qc-axis current command value Iqc *, and rotation speed command ω1 *. In the position sensorless mode, the current command value and the operation frequency are adjusted so that the axis error Δθc becomes a predetermined value.

  The motor driving device 10 changes any one of the dc-axis current command value Id *, the qc-axis current command value Iq * set in advance to the motor control unit 19, and the rotational speed input to the phase calculator 24, or Transition to another operation mode is performed by switching the switch 23 in the motor control unit 19. The switch 23 has a switch 23a and a switch 23b that are linked to each other. When the switch 23 is designated on the upper side, the switch 23a outputs the rotational speed command ω1 * set based on the command output from the host device 11 to the phase calculator 24, and the switch 23b outputs a preset current. Command values Iq * and Id * are output to the voltage command controller 25. On the other hand, when the switch 23 is designated as the lower side, the switch 23a outputs the rotational speed ωm output from the PLL controller 22 to the phase calculator 24, and the switch 23b is output from the primary delay filter 42. Qc-axis current command value Iq * is output to the voltage command controller 25.

  In the initial positioning mode and the synchronous operation mode of the startup sequence, the switch 23 is set to the upper side. That is, the phase calculator 24 calculates the control system phase θdc based on the rotation speed command ω1 *. The voltage command controller 22 calculates a voltage command value by changing the dc-axis current command value Id * and the qc-axis current command Iq * to a voltage command controller 25 by changing them into a preset current pattern. For example, the dc axis current command value Id * is increased in the positioning mode, and the dc axis current command value Id * is made constant in the synchronous operation mode. Further, the qc-axis current command value Iq * _start is set to zero in the positioning mode and the synchronous operation mode. The host device 11 sets the rotational speed command ω1 * to zero in the positioning mode and gradually increases the rotational speed command ω1 * in the synchronous operation mode.

  At the time point t1 when the operating frequency of the permanent magnet synchronous motor 9 reaches a predetermined frequency that enables position sensorless control, the host device 11 shifts to the position sensorless mode with the switch 23 on the lower side. Accordingly, the motor control unit 19 adjusts the rotational speed ωm * by the PLL controller 22 so that the axis error Δθc becomes zero. The qc-axis current command value Iq * is given by performing a first-order lag filter operation on the qc-axis current value Iqc. When the load torque increases, the phase of the motor rotor shaft shifts and the qc-axis current value Iqc increases, so that the qc-axis current command value Iq * corresponding to the load is obtained.

(Abnormality detection method)

  Based on the power element drive signals 21a, 21b, and 21c output from the PWM control unit 14, the abnormality detection unit 18 includes, for each phase, a maximum phase period that is the maximum phase and a minimum phase period that is the minimum phase. Is determined in the determination period, the determination timing is determined within the determination period, and it is determined whether or not the motor current calculated at the determination timing satisfies a predetermined abnormal condition. For a certain phase, the abnormal condition in the maximum phase period is a positive maximum phase current threshold (predetermined at the maximum phase determination timing (first determination timing) that is the determination timing within the maximum phase period. The abnormal condition in the minimum phase period is a negative phase in which the motor current of the phase is set in advance at the minimum phase determination timing (second determination timing) that is the determination timing in the minimum phase period. Exceeding the minimum phase current threshold (second current threshold).

  The abnormal condition in the maximum phase period may be that the motor current of the phase falls below the maximum phase current threshold over the maximum phase period, and the abnormal condition in the minimum phase period is that the motor current of the phase is minimum. It may be above the minimum phase current threshold over the phase period. Further, the abnormal condition in the maximum phase period may be that all of the motor currents of the phases at a plurality of determination timings in the maximum phase period are below the maximum phase current threshold, and the abnormal condition in the minimum phase period is the minimum All of the motor currents of the phase at a plurality of determination timings within the phase period may be such that the motor current of the phase exceeds the minimum phase current threshold. In addition, the abnormality detection unit 18 sets the maximum phase determination timing within a period in which only the maximum phase voltage command value exceeds the carrier signal among the three phase voltage command values, and sets the minimum phase among the three phase voltage command values. The minimum phase determination timing may be set within a period in which only the voltage command value is lower than the carrier signal.

  When it is determined that at least one of the motor currents of the maximum phase determination timing and the minimum phase determination timing set for each phase satisfies the abnormal condition, the abnormality detection unit 18 synchronizes the inverter 13, the motor wiring 44, and the permanent magnet. It is determined that an abnormality has occurred in the motor 9. Abnormalities in the inverter 13, the motor wiring 44, and the permanent magnet synchronous motor 9 include an open failure of one semiconductor power element in the inverter 13 and an open phase. An open failure of a semiconductor power element indicates that no current flows through the semiconductor power element. An open phase indicates that no current flows through the motor wiring 44 of one phase.

  FIG. 8 shows the relationship between the voltage command value, the determination period, and the motor current.

  This figure shows an example of the U phase. The anomaly detection unit 18 is configured so that the U phase is divided into a U phase maximum phase period Pa in which the U phase is the maximum phase and a U phase minimum phase period Pb in which the U phase is the minimum phase. It is determined whether the motor current satisfies the abnormal condition. For example, if an open failure occurs in which the U-phase upper arm side semiconductor power element Up remains open, the U-phase motor current Iu does not flow through the semiconductor power element Up during the U-phase maximum phase period. Iu becomes zero. The abnormality detector 18 determines whether or not the U-phase motor current Iu falls below the maximum phase current threshold at the maximum phase determination timing within the U-phase maximum phase period, and the U-phase motor current Iu falls below the maximum phase current threshold. Is determined, based on the switching pattern of the semiconductor power element in the U-phase maximum phase period, it is determined that an open failure of the semiconductor power element Up of the U-phase upper arm has occurred. Similarly, the abnormality detection unit 18 determines whether or not the U-phase motor current Iu exceeds the minimum phase current threshold at the minimum phase determination timing within the U-phase minimum phase period, and the U-phase motor current Iu is the minimum phase current. When it is determined that the threshold value is exceeded, the abnormality detection unit 18 determines that an open failure has occurred in the semiconductor power element Un of the U-phase lower arm based on the switching pattern of the semiconductor power element in the U-phase minimum phase period.

  The abnormality detection unit 18 determines an abnormality for the V phase and the W phase in the same manner as the U phase. The U-phase maximum phase period, the V-phase maximum phase period, and the W-phase maximum phase period appear in order during one electrical angle cycle of the AC power output from the inverter 13. Further, during one electrical angle cycle, a U-phase minimum phase period, a V-phase minimum phase period, and a W-phase minimum phase period appear in order.

  As described above, when the abnormality detection unit 18 determines that the motor current of the phase falls below the maximum phase current threshold at the maximum phase determination timing of a certain phase, the abnormality detection unit 18 It is determined that an open failure of the semiconductor power element has occurred. Similarly, when it is determined at the minimum phase determination timing of a certain phase that the motor current of that phase exceeds the minimum phase current threshold, the abnormality detection unit 18 indicates that an open failure of the semiconductor power element of the lower arm of that phase occurs. Judge that it occurred.

  The magnitudes of the maximum phase current threshold and the minimum phase current threshold are set to values sufficiently smaller than the current command values in the U phase maximum phase period and the U phase minimum phase period in consideration of circuit noise and the like. The abnormality detection unit 18 determines the motor current in the maximum phase period and the minimum phase period for each of the three phases during one electrical angle cycle, whereby the current path in the inverter 13 at the time of determination can be specified. In the maximum phase period, a failure is determined when the motor current of the target phase falls below the positive maximum phase current threshold.In the minimum phase period, the motor current of the target phase has a negative minimum phase current threshold. If it is determined that there is a failure, it is possible to determine whether the upper arm or the lower arm of the target phase is a failure.

  In order to reduce erroneous detection, the abnormality detection unit 18 is configured such that a motor current of a specific phase at a determination timing within a specific determination period continuously satisfies an abnormality condition over a predetermined number of electrical angle cycles. In addition, it may be determined that an abnormality has occurred.

  In the position sensorless mode, when the motor current is small, the motor current may satisfy the abnormal condition even if the inverter 13 is normal. Therefore, the abnormality detection unit 18 may perform abnormality determination when any of the dc-axis current command value Id * and the qc-axis current command value Iq * exceeds a predetermined current command threshold value. Thereby, it is possible to prevent erroneous detection even if an abnormality is determined in the position sensorless mode. In addition, the abnormality detection unit 18 may perform the determination in the synchronous operation mode in which the magnitude of the dc axis current command value Id * is large and constant.

  According to this activation sequence, an abnormality is detected in the synchronous operation mode or the position sensorless mode in which the permanent magnet synchronous motor 9 is operating without adding an abnormality detection process before the permanent magnet synchronous motor 9 is activated. Can do.

  When both U-phase upper and lower arm power elements Up and Un have an open failure, or when the U-phase motor wiring 44 is disconnected or poorly connected, both the U-phase maximum phase period and the U-phase minimum phase period Thus, the U-phase motor current becomes zero. When it is determined that the U-phase motor current satisfies the abnormal condition in both the U-phase maximum phase period and the U-phase minimum phase period, the abnormality detection unit 18 determines that the U-phase is missing. The abnormality detection unit 18 determines the missing phases of the V phase and the W phase in the same manner as the U phase.

  As described above, when it is determined that the motor current of the phase satisfies the abnormal condition in both the maximum phase period and the minimum phase period of the certain phase, the abnormality detection unit 18 determines that the phase is missing. Thereby, it is possible to distinguish a failure and a phase failure of one semiconductor power element.

  If the abnormality detection unit 18 determines that there is an abnormality, the normal motor drive cannot be performed, and thus the drive of the inverter 13 is immediately stopped. Thereby, the secondary failure of the permanent magnet synchronous motor 9 and the inverter 13 can be prevented. Further, the abnormality detection unit 18 may notify the abnormality to the display unit of the higher-level device 11 or the like. As a result, prompt analysis of failure analysis and repair becomes possible.

  The host device 11 may display the content of the abnormality on the display unit. The content of the abnormality may indicate an open failure or an open phase, may indicate an identifier of a semiconductor power element in which an open failure has occurred, or may indicate an identifier of a phase that has become an open phase.

  As in Patent Document 1, when the absolute value of the current of a certain phase to the synchronous motor is continuously below the threshold value over the half period of the electrical angle, When a failure occurs in one power element, the absolute value of a current of a certain phase does not continuously fall below the threshold over the electrical angle half cycle, and thus an abnormality cannot be detected. Even if an abnormality due to a failure of one power element is detected by any method, the cause of the abnormality cannot be specified, and all of the inverter 13, the motor wiring 44, and the compressor 2 are inspected, repaired, replaced, etc. There is a case.

  On the other hand, according to the present embodiment, the abnormality of the inverter 13 can be detected based on the motor current in each determination period of each phase, and the cause of the abnormality can be specified. Further, when one of the power elements in the inverter 13 fails, the failure can be detected and the failed power element can be specified. It can be determined whether or not the abnormality is a failure of one power element, and can be dealt with quickly. For example, in the refrigeration apparatus 1, when the abnormality detection unit 18 determines that one power element has failed, the motor wiring 44 and the compressor 2 are not inspected, and both the inverter 13 and the compressor 2 are replaced. Also disappear. Thereby, the time and cost of repair of the refrigeration apparatus 1 can be suppressed.

  In this embodiment, instead of the DC bus current on the DC side of the inverter 13, the motor current on the AC side of the inverter 13 is measured. In the present embodiment, differences from the first embodiment will be mainly described.

  FIG. 9 shows a configuration of the motor drive device 10 of the second embodiment.

  Compared to the first embodiment, the motor driving apparatus 10 of the present embodiment has a phase current detector 33 instead of the bus current detector 15 and a current calculation section 34 instead of the current calculation section 17. The phase current detector 33 directly measures the motor current. The phase current detector 33 measures a specific two-phase motor current. The current calculation unit 34 calculates the remaining one-phase motor current using the relationship of the following equation, and outputs the motor currents Iu, Iv, and Iw to the motor control unit 19.

  Iu + Iv + Iw = 0

  As in the first embodiment, the abnormality detection unit 18 determines that the motor current satisfies the abnormality condition at the determination timing within each determination period, and determines whether the failure is an open failure or a phase failure.

  According to the present embodiment, by measuring the two-phase motor current, the three-phase motor current can be calculated by a simple calculation as compared with the current calculation section 17 of the first embodiment. Thereby, the abnormality of the inverter 13 can be detected based on the motor current in each determination period of each phase, and the cause of the abnormality can be specified.

  The inverter control device of the present invention may be used for a pump, a ventilation fan, etc. in addition to a refrigeration device.

  Terms in one embodiment of the present invention will be described. The inverter control device corresponds to the controller 16 and the like. The inverter circuit corresponds to the inverter 13 or the like. The plurality of switch elements correspond to semiconductor power elements Up, Un, Vp, Vn, Wp, Wn, and the like. The synchronous motor corresponds to the permanent magnet synchronous motor 9 or the like. The current calculation unit corresponds to the current calculation unit 17, the current calculation unit 34, and the like. The voltage command calculation unit corresponds to the motor control unit 19 and the like. The abnormality detection unit corresponds to the abnormality detection unit 18 and the like. The compressor corresponds to the compressor 2 and the like. The heat exchanger corresponds to the indoor heat exchanger 3, the outdoor heat exchanger 4, and the like.

  The present invention is not limited to the above embodiments, and can be modified in various other forms without departing from the spirit of the present invention.

1: Refrigeration equipment 1a: Outdoor unit 1b: Indoor unit 2: Compressor 3: Indoor heat exchanger 4: Outdoor heat exchanger 5: Indoor expansion valve 6: Accumulator 7: Fan motor 8: Fan motor 9: Permanent magnet synchronous motor DESCRIPTION OF SYMBOLS 10: Motor drive device 11: High-order apparatus 12: DC power supply 13: Inverter 14: PWM control part 15: Bus current detector 16: Controller 17: Current calculation part 18: Abnormality detection part 19: Motor control part 33: Phase current Detector 34: Current calculation unit

Claims (8)

An inverter circuit including a plurality of switch elements, wherein the inverter circuit is connected to the inverter circuit that converts DC power into three-phase AC power by changing an open / closed state of the plurality of switch elements and supplies the three-phase AC power to the synchronous motor. A current calculation unit for calculating a three-phase output current flowing from the inverter circuit to the synchronous motor based on a current flowing through the circuit;
Based on the output current, a voltage command calculation unit that calculates a three-phase voltage command value that indicates a voltage to be applied to the synchronous motor from the inverter circuit;
An abnormality detection unit that determines the plurality of determination timings based on the three-phase voltage command values, and determines a failure of each of the plurality of switch elements based on an output current at the plurality of determination timings;
An inverter control device comprising: The abnormality detection unit selects each of the three phases as a target phase, determines a first determination timing at which the voltage command value of the target phase is maximum among the voltage command values of the three phases, Determining a second determination timing at which the voltage command value of the target phase is minimum among the voltage command values, and based on the output current of the target phase at the first determination timing and the second determination timing, Determine each failure of the switch element,
The inverter control device according to claim 1. The plurality of switch elements correspond to the three-phase upper arm and the lower arm in the inverter circuit,
The abnormality detection unit determines whether the output current of the target phase at the first determination timing is below a positive first current threshold, and the output current of the target phase at the first determination timing is the first When it is determined that the current threshold value is below the threshold value, it is determined that the switch element of the upper arm of the target phase is out of the plurality of switch elements, and the output current of the target phase at the second determination timing is negative. If the output current of the target phase at the second determination timing is determined to exceed the second current threshold, the target among the plurality of switch elements is determined. Determining that the switch element of the lower arm of the phase has failed,
The inverter control device according to claim 2. The abnormality detection unit determines that the output current of the target phase at the first determination timing is lower than the first current threshold, and the output current of the target phase at the second determination timing satisfies the second current threshold. If it is determined that the output current of the target phase is not flowing,
The inverter control device according to claim 3. The current calculation unit measures a DC input current to the inverter circuit, and calculates the three-phase output current based on the input current and the three-phase voltage command value.
The inverter control device according to claim 4. The current calculation unit measures at least two-phase output currents of the three-phase output currents.
The inverter control device according to claim 4. The abnormality detection unit determines whether the magnitude of the current command value given to the voltage command calculation unit exceeds a predetermined current command threshold value, and determines that the current command value exceeds the current command threshold value And determining a failure of each of the plurality of switch elements based on the output current at the determination timing.
The inverter control device according to claim 3. An inverter control device according to any one of claims 1 to 7,
The inverter circuit;
A compressor that includes the synchronous motor and compresses the refrigerant by the operation of the synchronous motor;
A heat exchanger that performs heat exchange of the refrigerant from the compressor;
A refrigeration apparatus comprising:

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