JP2012147571A - Inverter apparatus and motor drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter apparatus that can discharge a charge stored in a smoothing capacitor without utilizing a special discharge circuit even if a loading motor is not connected or if there are any failed elements in a plurality of switching elements constituting a power conversion section.SOLUTION: An inverter apparatus 101 includes: a smoothing capacitor 2 for smoothing DC power from a DC voltage supply 1; a power conversion section 3 for converting the DC power from the smoothing capacitor 2 to AC power by means of a plurality of switching elements 31; and a switching control section 4 for, when interrupting the DC power supply 1, discharging a charge stored in the smoothing capacitor through a switching pattern of repeated switching, excluding, if there are any failed elements in the plurality of switching elements 31, the failed elements and opposite arm elements.

Description

  The present invention relates to an inverter device and an electric motor drive system.

  2. Description of the Related Art Conventionally, an electric motor drive control device that controls a switch unit of a buck-boost converter and discharges electric charges accumulated in a capacitor while maintaining a state in which voltage is not boosted or boosted is known (see, for example, Patent Document 1). ).

  In the above-mentioned Patent Document 1, when discharge cannot be performed using an electric motor, the time required to turn on the lower arm switching element of the buck-boost converter provided in the electric motor drive control device is shortened, and the upper arm switching element is turned on. By extending the time for the state, the charge accumulated in the capacitor is discharged by switching loss without providing a discharge circuit.

Japanese Patent Laid-Open No. 2005-229689

  However, the electric motor drive control device described in Patent Document 1 has a problem that it cannot be applied when a step-up / down converter including a switching element is not provided.

  Therefore, the present invention provides a smoothing capacitor without a special discharge circuit, even if a motor as a load is not connected, or even if there are failed elements in a plurality of switching elements constituting the power converter. An object of the present invention is to provide an inverter device capable of discharging the electric charge accumulated in the battery.

  In order to achieve the above object, an inverter device according to a first aspect of the present invention includes a smoothing capacitor that smoothes DC power input from a DC voltage source, DC power output from the smoothing capacitor, and a plurality of switching elements. An inverter device having a function of detecting the presence / absence of a failure of a plurality of switching elements, comprising: a power conversion unit that converts the AC power into AC power; and a switching control unit that controls a plurality of switching elements. When switching off the DC voltage source, if there are faulty switching elements in the plurality of switching elements, except for the faulty switching element and the switching element of the reverse arm and the reverse arm, a switching pattern that is repeatedly switched, Configured to discharge the charge accumulated in the smoothing capacitor It has been.

  An electric motor drive system according to a second aspect of the present invention is a smoothing capacitor that smoothes DC power input from a DC voltage source, and converts DC power output from the smoothing capacitor into AC power using a plurality of switching elements. An inverter device including a power conversion unit and a switching control unit that controls a plurality of switching elements, and having a function of detecting the presence or absence of a failure of the plurality of switching elements, and an electric motor connected to the inverter device, and switching When the control unit shuts off the DC voltage source and there is a faulty switching element in the plurality of switching elements, the switching unit repeatedly switches except the faulty switching element and the switching element of the faulty switching element and the reverse arm. And the charge accumulated in the smoothing capacitor It is configured to electricity.

  According to the present invention, when the DC voltage source is shut off and the electric charge accumulated in the smoothing capacitor is discharged, a discharge process is performed by selecting an element that switches according to a failure of a plurality of switching elements constituting the power conversion unit. Therefore, even when an element fails, the charge accumulated in the smoothing capacitor can be discharged without causing secondary breakdown of the power conversion unit. In addition, since the discharge process is performed by switching loss generated by repeatedly switching a plurality of switching elements constituting the power conversion unit, smoothing can be performed without providing a special discharge circuit even if a motor as a load is not connected. The electric charge stored in the capacitor can be discharged.

It is a block diagram which shows the structure of the inverter apparatus by one Embodiment of this invention. It is the figure which showed the 1st switching pattern used when the inverter apparatus by one Embodiment of this invention specifies the switching element of a short circuit failure. It is a signal waveform diagram for demonstrating the switching operation | movement by a 1st switching pattern. It is the figure which showed the 2nd switching pattern used when the inverter apparatus by one Embodiment of this invention specifies the switching element of an open fault. It is a signal waveform diagram for demonstrating the switching operation | movement by a 2nd switching pattern. It is the figure which showed the 3rd switching pattern.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same structure, the same code | symbol is attached | subjected and duplication description is abbreviate | omitted suitably.

  First, with reference to FIG. 1, the structure of the inverter apparatus 101 of the electric motor drive system 100 by one Embodiment of this invention is demonstrated.

  As shown in FIG. 1, the inverter device 101 includes a DC voltage source 1, a smoothing capacitor 2, a power conversion unit 3, a switching control unit 4, a current detector 5, and a voltage detector 7. An electric motor 6 is connected to the output side of the inverter device 101.

  The DC voltage source 1 includes an AC power source 11 and a rectifier circuit 12 including a plurality of diodes. One electrode of the smoothing capacitor 2 is connected to the positive electrode side of the DC voltage source 1. The other electrode of the smoothing capacitor 2 is connected to the negative electrode side of the DC voltage source 1.

  The smoothing capacitor 2 smoothes the DC voltage from the DC voltage source 1 and supplies the smoothed DC voltage to the power converter 3. Although not shown, the DC voltage source 1 is cut off by turning off the contactor provided between the DC voltage source 1 and the smoothing capacitor 2.

  The power conversion unit 3 includes a plurality of switching elements 31 (S1 to S6) and is driven by a gate signal from the switching control unit 4. The switching element S1 includes a transistor Up made of an IGBT (insulated gate bipolar transistor) and a diode Bup. Similarly, the switching element S2 (S3, S4, S5, S6) includes a transistor Aun (Avp, Avn, Awp, Awn) and a diode Bun (Bvp, Bvn, Bwp, Bwn).

  Switching elements S 1, S 3 and S 5 constitute the upper arm of power conversion unit 3, and one terminal is connected to the positive electrode side of DC voltage source 1. The switching elements S2, S4, and S6 constitute a lower arm of the power conversion unit 3, and one terminal is connected to the negative electrode side of the DC voltage source 1. The other terminals of the switching elements S1, S3, and S5 are connected to the other terminals of the switching elements S2, S4, and S6 and the electric motor 6, respectively.

  The switching elements S1 and S2 are configured to perform power conversion of the U phase of the electric motor 6, the switching elements S3 and S4 are respectively converted to the V phase of the electric motor 6, and the switching elements S5 and S6 are configured to perform electric power conversion of the W phase of the electric motor 6. .

The switching control unit 4 is configured to control the six switching elements 31 (S1 to S6) constituting the power conversion unit 3, and outputs a gate signal to the switching elements 31 (S1 to S6). Such a switching control unit 4 is generally provided in the inverter device 101, and is not shown when driving the electric motor 6. However, for example, the voltage command Vu generated by performing speed control, current control, etc. A gate signal for driving the switching elements 31 (S1 to S6) is generated by PWM control based on ^* , Vv ^* , and Vw ^* .

  The current detector 5 is connected between the power conversion unit 3 and the electric motor 6 and detects U-phase, V-phase, and W-phase currents Iu, Iv, and Iw supplied from the power conversion unit 3 to the electric motor 6. , Output to the switching control unit 4. In FIG. 1, three current detectors 5 are shown for each phase. However, for example, one phase can be omitted by calculating Iw = −Iu−Iv.

  The voltage detector 7 is configured to detect the voltage of the smoothing capacitor 2 and output the detected voltage value to the switching control unit 4 when the DC voltage source 1 is shut off.

  Next, for reference, with reference to FIG. 2 to FIG. 5, a failure (short circuit failure and open failure) of the switching element 31 (S1 to S6) by the switching control unit 4 of the inverter device 101 according to the embodiment of the present invention. The determination operation and the specific operation of the failed switching element 31 will be briefly described. FIG. 2 is a diagram showing a first switching pattern used for specifying a switching element having a short-circuit failure, FIG. 3 is a signal waveform diagram for explaining a switching operation in the first switching pattern, and FIG. 4 is an open circuit. FIG. 5 is a diagram showing a second switching pattern used when specifying a faulty switching element, FIG. 5 is a signal waveform diagram for explaining the switching operation in the second switching pattern, and FIGS. Each switching pattern shown in FIG. 6 corresponds to a gate signal output to each switching element 31 (S1 to S6). Here, the function of detecting a failure of the switching element 31 is described as being included in the switching control unit 4, but is not limited thereto.

(Specific operation of switching element with short circuit failure)
First, the determination of the short circuit failure of the switching element 31 (S1 to S6) and the identification of the switching element having the short circuit failure are performed. At this time, the switching control unit 4 turns on one switching element 31 among the six switching elements 31 (S1 to S6) and sets the other switching element 31 in the OFF state (first switching pattern ( 6 is used to switch the six switching elements 31 and sequentially switch one switching element 31 to be in the ON state (switching at every time t1 (see FIG. 3)). The time t1 is a length of time that prevents the switching element 31 from being destroyed even when a large current (for example, a short-circuit current between the upper and lower arms) flows through the switching element 31. FIG. 3 shows a principle switching pattern in which dead time is not taken into consideration.

(Specific operation of switching element with open failure)
Next, the determination of the open failure of the switching element 31 (S1 to S6) and the identification of the switching element having the open failure are performed. At this time, the switching control unit 4 turns on one switching element 31 of the upper arm or the lower arm of one of the three phases (U phase, V phase, and W phase) and switches the other The element 31 is turned off, the two switching elements 31 of the upper arm or the lower arm other than the one phase are turned off, and the other two switching elements 31 are turned on. To do. In other words, the switching control unit 4 performs six switching operations in the second switching pattern (see FIG. 4) in which the arm on the side in which one of the three phases is turned on is different from the other two phases. The element 31 is switched. Then, one phase in which the arm on the side to be turned on is different from the other two phases, and the arm on the side in which the one phase is turned on are sequentially switched (switched at every time t2 (FIG. 5). reference)). FIG. 5 shows a principle switching pattern in which dead time is not taken into consideration.

  Next, the discharge operation of the electric charge accumulated in the smoothing capacitor 2 when the DC voltage source 1 is shut off in the inverter device 101 according to the embodiment of the present invention will be described.

(Discharge operation when there is a switching element determined to be faulty)
Of the switching elements 31 (S1 to S6), when there is a switching element 31 that has been determined to be a short circuit failure, the switching pattern used in the determination operation and the specific operation of the switching element 31 described up to the above reference (second) Of the switching patterns (patterns B1 to B6) (see FIG. 4)), the short-circuit faulty switching element 31 is turned ON, the short-circuit faulty switching element 31 and the reverse-arm switching element 31 are OFF, and the rest An operation of repeatedly switching is performed with a switching pattern that does not simultaneously turn on the upper and lower arms of the four switching elements 31 (for example, patterns B1, B5, and B6 when the switching element S1 is short-circuited).

  Moreover, when there exists the switching element 31 determined to be an open failure among the switching elements 31 (S1 to S6), the second switching pattern (patterns B1 to B6) shown in FIG. A switching pattern (for example, switching the failure switching element 31 to the OFF state, switching the switching element 31 opposite to the open failure switching element 31 to the ON state, and setting the upper and lower arms of the remaining four switching elements 31 to the ON state simultaneously (for example, When the switching element S1 has an open failure, a switching operation is performed in which switching is repeatedly performed with the patterns B2, B3, and B4).

  Note that setting the ON state for the switching element 31 that is in a short circuit failure and turning the OFF state for the switching element 31 that is in an open failure state that there is a switching element 31 that is not completely short-circuited or opened. It is very effective when considered.

  Thereby, the switching control part 4 discharges the electric charge accumulated in the smoothing capacitor 2 by the switching loss due to the switching element 31 using only the switching element 31 that is not in failure.

(Discharge operation when there is no switching element determined to be faulty)
When there is no switching element 31 determined to be a short circuit failure or an open failure in the switching element 31 (when all the switching elements 31 are normal), the switching pattern of the switching element 31 described above for the reference (second) In this switching pattern (patterns B1 to B6) (see FIG. 4)), the operation of repeatedly switching all six switching elements 31 is performed.

  Thereby, the switching control unit 4 discharges the electric charge accumulated in the smoothing capacitor 2 due to the switching loss caused by the six switching elements 31. Of the six switching elements 31, the state of some of the switching elements 31 may be fixed and the discharge process may be performed.

  In addition, when discharging the accumulated charge of the smoothing capacitor 2, if the switching element 31 that has failed as described above is not used, the second switching pattern (B1 to B6) shown in FIG. A pattern based on the first switching pattern (A1 to A6) shown in FIG. 2 and the third switching pattern (C1, C2) shown in FIG. 6 may be repeatedly switched.

  Next, the abnormality determination operation of the smoothing capacitor 2 when the DC voltage source 1 is shut off in the inverter device 101 according to the embodiment of the present invention will be described.

  The voltage detector 7 outputs the voltage detection value of the smoothing capacitor 2 to the switching control unit 4 every predetermined time when the DC voltage source 1 is shut off. The switching control unit 4 measures the time when the voltage detection value is changed from the predetermined value 1 to the predetermined value 2 as the discharge time of the accumulated charge of the smoothing capacitor 2. When the measured discharge time is less than or equal to a predetermined value, it is determined that the smoothing capacitor 2 has an abnormality (for example, the capacity of the capacitor is missing).

  Note that the predetermined value to be compared with the discharge time is stored in advance as a discharge time in a state before deterioration due to life such as a measured value or a design value when the smoothing capacitor 2 is replaced with a normal smoothing capacitor 2. It is like that. Further, the predetermined value to be compared with the discharge time is determined in consideration of at least one of the switching frequency per unit time of all the switching elements 31 and the switching frequency. Note that the predetermined value 1 and the predetermined value 2 that determine the potential of the voltage detection value may be any predetermined value.

  Further, although the time when the voltage detection value becomes the predetermined value 2 from the predetermined value 1 is defined as the discharge time of the accumulated charge of the smoothing capacitor 2, the smoothing capacitor 2 is abnormal. The change amount of the detected voltage value may be compared.

  In the above embodiment, the DC voltage source 1 supplies the direct current by rectifying the alternating current power supply using the rectifier circuit. However, the DC voltage source 1 may be a PWM converter instead of the rectifier circuit, or a direct current power supply such as a battery. Direct current may be supplied by Moreover, although the example which outputs three-phase alternating current using a three-phase alternating current power supply was shown, it is applicable to the inverter apparatus using alternating current power supplies of the number of phases other than three phases, and alternating current of the number of phases other than three phases It is also applicable to an inverter device that outputs

  Since the embodiment of the present invention is configured as described above, the inverter device 101 according to the present embodiment uses the switching element 31 that does not fail, and discharges the electric charge accumulated in the smoothing capacitor 2 only by switching loss. Since it can be performed quickly, it is not necessary to connect the electric motor 6 as a load, and secondary breakdown of the power conversion unit due to unconditional switching of the failed switching element 31 can be prevented. For this reason, it is not necessary to provide a separate discharge circuit.

  Furthermore, the abnormality of the smoothing capacitor 2 can be easily determined by simply measuring the discharge time of the accumulated charge of the smoothing capacitor 2 and the voltage of the smoothing capacitor 2. This can be performed more easily than the case where the capacitance of the smoothing capacitor 2 is calculated and the abnormality of the smoothing capacitor 2 is determined based on the capacitance obtained by the calculation.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the above embodiment, an example in which a switching element including an IGBT is used as the switching element has been described. Moreover, although the example which connects an electric motor as a load to an inverter apparatus was shown, you may connect loads other than an electric motor to an inverter apparatus.

DESCRIPTION OF SYMBOLS 1 DC voltage source 2 Smoothing capacitor 3 Power conversion part 4 Switching control part 6 Electric motor 7 Voltage detector 31, S1, S2, S3, S4, S5, S6 Switching element

Claims (8)

A smoothing capacitor for smoothing the DC power input from the DC voltage source;
A power converter that converts the DC power output from the smoothing capacitor into AC power using a plurality of switching elements;
A switching control unit for controlling the plurality of switching elements,
An inverter device having a function of detecting the presence or absence of failure of the plurality of switching elements,
When the switching control unit shuts off the DC voltage source,
When there is a faulty switching element in the plurality of switching elements, except for the faulty switching element and the switching element of the reverse arm and the faulty switching element, a switching pattern for repeated switching,
An inverter device configured to discharge the electric charge accumulated in the smoothing capacitor. The switching pattern is:
The short-circuit fault switching element is turned ON, and the short-circuit fault switching element and the reverse arm switching element are turned OFF,
The switching element of the open failure is turned off, and the switching element of the reverse arm and the switching element of the reverse arm are turned on,
2. The inverter device according to claim 1, wherein the other switching elements are switching patterns in which the upper and lower arms of the plurality of switching elements are not simultaneously turned on. When the switching control unit shuts off the DC voltage source,
When there is no faulty switching element in the plurality of switching elements, a switching pattern that repeatedly switches all of the plurality of switching elements,
The inverter device according to claim 1, wherein the inverter device is configured to discharge the electric charge accumulated in the smoothing capacitor. A voltage detector that detects the voltage of the smoothing capacitor and outputs it as a voltage detection value,
The switching control unit, when discharging the charge accumulated in the smoothing capacitor, sets a time during which the voltage detection value changes to a predetermined magnitude as a discharge time, and when the discharge time is equal to or less than a predetermined value, The inverter device according to claim 1, wherein the inverter device is configured to determine that there is an abnormality in the capacitor.   The inverter according to claim 4, wherein the predetermined value for determining that the smoothing capacitor is abnormal is determined in consideration of at least one of a switching frequency per unit time of all the switching elements and a switching frequency. apparatus. A voltage detector that detects the voltage of the smoothing capacitor and outputs it as a voltage detection value,
The switching control unit determines that the smoothing capacitor is abnormal when the amount of change in the voltage detection value is less than or equal to a predetermined value when the charge accumulated in the smoothing capacitor is discharged for a predetermined time. The inverter device according to claim 1, wherein the inverter device is configured as follows.   The inverter according to claim 6, wherein the predetermined value for determining that the smoothing capacitor is abnormal is determined in consideration of at least one of a switching frequency per unit time of all the switching elements and a switching frequency. apparatus. A smoothing capacitor for smoothing the DC power input from the DC voltage source;
A power converter that converts the DC power output from the smoothing capacitor into AC power using a plurality of switching elements;
A switching control unit that controls the plurality of switching elements,
An inverter device having a function of detecting the presence or absence of failure of the plurality of switching elements;
An electric motor connected to the inverter device,
When the switching control unit shuts off the DC voltage source,
When there is a faulty switching element in the plurality of switching elements, except for the faulty switching element and the switching element of the reverse arm and the faulty switching element, a switching pattern for repeated switching,
An electric motor drive system configured to discharge electric charges accumulated in the smoothing capacitor.

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