JP6589493B2 - Three-phase inverter device - Google Patents

Description

  The present invention relates to a three-phase inverter device having a failure detection function and limp home (emergency avoidance) function of an output current sensor.

FIG. 3 is a configuration diagram of a motor drive system described in Patent Document 1.
In FIG. 3, 101 is a DC power source, 102 is a three-phase inverter controlled by PWM, 103u, 103v, and 103w are current sensors that detect output currents i _u , i _v , and i _w of the inverter 102, and 201 is a position. / Speed sensor, 202 is a position measurement unit, 203 is a failure detection unit, 203a is a first estimation value calculation unit, 203b is a second estimation value calculation unit, 203c is a failure diagnosis unit, 204 and 206 are coordinate conversion units, and 205 is A PI control unit, 207 is a PWM conversion unit, 208 is a motor stop unit, and M is a motor.

In this system, as the operation when the current sensors 103u, 103v, 103w are normal, the coordinate conversion unit 204 detects the current detection values i _u ′, i _v ′, i of each phase output from the failure detection unit 203. Based on the phase angle θ measured by the position measurement unit 202, _w ′ is converted into current detection values i _d and i _q on the d and q axes. The PI control unit 205 sets the voltage command values v _d ^* and v _q ^* so that the deviations between the current command values i _d ^* and i _q ^* on the d and q axes and the detected current values i _d and i _q are eliminated. Then, the coordinate conversion unit 206 converts v _d ^* , v _q ^* into three-phase voltage command values v _u ^* , v _v ^* , v _w ^* .
The PWM conversion unit 207 generates PWM command values v _u ^** , v _v ^** , and v _w ^** based on the voltage command values v _u ^* , v _v ^* , and v _w ^*, and passes through the motor stop unit 208. Thus, the output voltage v _u , v _v , v _w of the inverter 102 is controlled according to the command value.

  Here, the first estimated value calculation unit 203a in the failure detection unit 203 has a function of estimating a current value of one phase from a current detection value by another two-phase current sensor, and a second estimated value calculation unit. 203b has a function of estimating a current value of one phase from a phase angle θ of a current flowing through the motor M and a current detection value by another two-phase current sensor. Further, the failure diagnosis unit 203c diagnoses a failure of the current sensor based on the current detection value by the current sensor and the current estimation value by the first estimated value calculation unit 203a and the second estimated value calculation unit 203b. When a phase current sensor failure occurs, it has a function of selecting an estimated current value of the phase and outputting it to the coordinate conversion unit 204.

  With the above configuration, in Patent Document 1, even if a single-phase current sensor fails, the estimated current value of the phase selected by the failure diagnosis unit 203c is used together with other two-phase current detection values, thereby driving the motor M. Continue. Further, when a current sensor of two or more phases breaks down, it is possible to operate the motor stop unit 208 by the failure diagnosis unit 203c and stop the operation of the inverter 102 and the motor M.

According to the technique described in Patent Document 1, even if a single-phase current sensor fails, the inverter 102 uses the estimated current value of the phase and another normal two-phase current detection value. The operation of the motor M can be continued.
However, in this prior art, since it is necessary to provide current sensors for three phases, there is a problem that the apparatus becomes large and the cost increases.
As a method for detecting a failure of a current sensor, a method is known in which current sensors are duplicated and the detection values of the respective sensors are compared. Inevitable.

On the other hand, Patent Document 2 discloses a technique for detecting a current of each phase by a semiconductor switching element with a so-called current sense without using a current sensor.
FIG. 4 is a configuration diagram of the motor drive system described in Patent Document 2. 300 is an inverter, 301 to 306 are semiconductor switching elements, 307 is a capacitor, 308a, 308b, 310a, 310b, 312a, and 312b are current detections. 309, 311 and 313 are adders, and 400 is a control circuit. In addition, as the switching elements 302, 304, and 306 in the lower arm of each phase of the inverter 300, elements having a current sense each having a sense emitter and a sense diode are used.

  In the inverter 300, currents flowing through the sense emitters and the sense diodes of the switching elements 302, 304, and 306 are detected by the current detectors 308a, 308b, 310a, 310b, 312a, and 312b, respectively, and the detected current values are added. By adding each phase at 309, 311, and 313, the output current of each phase of the inverter 300 is estimated as a discrete sine wave current.

Japanese Unexamined Patent Publication No. 2000-116176 (paragraphs [0012] to [0016], FIG. 1, FIG. 2, etc.) Japanese Patent No. 5304967 (paragraphs [0005] to [0007], FIG. 1, FIG. 10, etc.)

According to the technique described in Patent Document 2, the current sensors 103u, 103v, and 103w for each phase in Patent Document 1 are not required, and thus the apparatus can be reduced in size and cost.
However, in Patent Document 2, since it becomes difficult to estimate the output current when the width of the driving pulse for the switching elements 302, 304, and 306 of the lower arm becomes narrow, it is difficult to estimate the switching frequency and voltage amplitude command when the inverter 300 is PWM-controlled. The upper limit is constrained.
As described above, in Patent Document 2, since there are restrictions on the switching frequency and the like, for example, when a high-speed switching element using a wide band gap semiconductor material such as SiC (silicon carbide) is used, the high speed which is an advantage thereof, There is a problem that the advantages such as low loss cannot be fully utilized.

  Therefore, the problem to be solved by the present invention is that a three-phase inverter that can use a high-speed switching element without being restricted by a switching frequency or a voltage amplitude command, and that can be continuously operated even when a failure of the output current sensor occurs. To provide an apparatus.

In order to solve the above-mentioned problems, the invention according to claim 1 is provided with three phases of switching element series circuits for one phase each having semiconductor switching elements in the upper and lower arms, and the series connection point between the semiconductor switching elements of the upper and lower arms. An inverter main circuit connected to a load as an AC output terminal for each phase;
In a three-phase inverter device comprising a control circuit that generates a drive signal for the semiconductor switching element using an output current detection value of the inverter main circuit,
Current sensors that respectively detect two-phase output currents of the inverter main circuit;
A switching element with a current sense provided as the semiconductor switching element in the upper arm or the lower arm of one phase other than the phase in which the output current is detected by the current sensor;
Have
The control circuit includes:
Current estimating means for estimating a one-phase output current provided with the switching element with current sensing based on a detection signal from the switching element with current sensing;
A failure detection means for detecting a failure of the current sensor based on a current detection value by the current sensor and a current estimation value by the current estimation means;
A current detection value by other current sensors excluding the current sensor in which a failure is detected by the failure detection means is selected as a first current signal, and a current estimation value by the current estimation means is selected as a second current signal In addition, when a failure of the current sensor is not detected by the failure detection means, a current detection phase selection for selecting the two-phase current detection values by the current sensor as the first current signal and the second current signal, respectively. Means,
Drive signal generating means for generating the drive signal using the first current signal and the second current signal.

The invention according to claim 2 is provided with three phases of switching element series circuits for one phase each having semiconductor switching elements in the upper and lower arms, and the series connection point between the semiconductor switching elements of the upper and lower arms is an AC output terminal of each phase Inverter main circuit connected to each load as
In a three-phase inverter device comprising a control circuit that generates a drive signal for the semiconductor switching element using an output current detection value of the inverter main circuit,
Current sensors that respectively detect two-phase output currents of the inverter main circuit;
A switching element with current sensing provided as the semiconductor switching element in the upper arm or lower arm of the two phases in which the output current is detected by the current sensor;
Have
The control circuit includes:
Current estimation means for estimating two-phase output currents each provided with the current sensing switching element based on a detection signal from the current sensing switching element;
A failure detection means for detecting a failure of the current sensor based on a current detection value by the current sensor and a current estimation value by the current estimation means;
The current detection value by other current sensors excluding the current sensor in which the failure is detected by the failure detection means is selected as the first current signal, and the current estimation means of the phase having the current sensor in which the failure is detected When the current estimation value is selected as the second current signal and no failure of the current sensor is detected by the failure detection means, the two-phase current detection values by the current sensor are respectively set to the first current signal and the first current signal. Current detection phase selection means for selecting two current signals ;
Drive signal generating means for generating the drive signal using the first current signal and the second current signal.

  According to a third aspect of the present invention, in the three-phase inverter device according to the first or second aspect, the drive signal generating means is configured such that the switching frequency of the drive signal is detected when a failure of the current sensor is detected by the failure detection means. Is to lower.

In the present invention, when the current sensor is normal, the driving signal of the switching element is generated using the two-phase current detection value, so that the driving signal is generated based on the estimated current value by the switching element with current sensing. , It becomes difficult to be restricted by the switching frequency and the voltage amplitude command when the three-phase inverter device is PWM-controlled. Therefore, when high-speed and low-loss switching elements made of a wide band gap semiconductor material are used, the advantages of these elements can be fully exhibited.
Further, when a current sensor failure occurs, if the current estimated value by the switching element with current sense is used, the three-phase inverter device can be continuously operated, and the accuracy of the current estimated value is increased by lowering the switching frequency. You can also.

1 is a configuration diagram of a motor drive system to which a first embodiment of the present invention is applied. It is a block diagram of the motor drive system with which 2nd Embodiment of this invention is applied. 1 is a configuration diagram of a motor drive system described in Patent Document 1. FIG. It is a block diagram of the motor drive system described in patent document 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of a motor drive system to which the first embodiment of the present invention is applied. In FIG. 1, a three-phase inverter main circuit 31 is composed of a DC power supply 10 and a bridge circuit of semiconductor switching elements 1 to 3, 4A, 5 and 6 connected to both ends thereof. The series connection point of the switching elements 1 and 2 is a U-phase output terminal, the series connection point of the switching elements 3 and 4A is a V-phase output terminal, and the series connection point of the switching elements 5 and 6 is a W-phase output terminal. Connected to M. An angle sensor 8 for detecting the rotation angle of the rotor is attached to the motor M.

The U-phase output current i _u and the W-phase output current i _w are detected by current sensors 7 u and 7 w, respectively, and are input to the control circuit 20 described later. The switching elements 1 to 3, 4 </ b> A, 5 and 6 are controlled to be turned on / off by the gate signals G _{1 to} G ₆ generated by the control circuit 20 through the gate drive circuits 11 to 16, respectively.

  Here, a switching element with a current sense provided with a sense emitter 4e and a sense diode 4d is used for the switching element 4A of the lower arm of the V phase where no current sensor is provided. The sense emitter 4e and the sense diode 4d are connected to the sense detection signal processing circuit 17. Instead of the lower arm switching element 4A, the upper arm switching element 3 may be a switching element with a current sense.

  In this embodiment, the switching element with current sense is a lower arm or upper phase (also V phase) other than the two phases (U phase and W phase in the example of FIG. 1) in which the output current is detected by the current sensor. What is necessary is just to provide in an arm. As shown in FIG. 1, if the switching element 4A of the lower arm is an element with a current sense and its emitter potential is the same as the reference potential (ground potential) of the control circuit 20, the inverter main circuit 31 and the control circuit Therefore, it is not necessary to take measures to insulate from 20 and it is effective in reducing the cost and size of the apparatus.

  As the switching elements 1 to 3, 4 </ b> A, 5 and 6, it is desirable to use a low-loss element capable of high-speed operation using a wide band gap semiconductor material such as SiC. Further, the types of the switching elements 1 to 3, 4 </ b> A, 5 and 6 are not limited to IGBTs as illustrated, but may be FETs or bipolar transistors.

On the other hand, the control circuit 20 includes drive signal generation means 21, current estimation means 22 </ b> V, current sensor failure detection means 23, and current sensor selection means 24.
The output signal of the sense detection signal processing circuit 17 is input to the current estimation unit 22V. The current estimation unit 22V, for example, has the current information flowing in the sense emitter 4e and the reverse current (regenerative current) information flowing in the sense diode 4d, as in the functions of the current detection units 308a and 308b and the adder 309 in FIG. Based on the addition result, a discrete sinusoidal V-phase current estimation value i _va is obtained.

The current sensor failure detection means 23 determines the current sensor 7u or 7w based on the V-phase current estimation value i _va and the U-phase and W-phase current detection values i _u and i _w obtained by the current sensors 7u and 7w. Detect failure.
For example, when the sum of i _u , i _w , and i _va is not 0, it is determined that one of the current sensors 7 u and 7 w has failed. Alternatively, the average values of the current detection values i _u and i _w for one cycle may be obtained, respectively, and it may be determined that the current sensor of the phase whose average value is not 0 has failed.

From the current sensor failure detecting section 23 are output detection current selection signal _{i sel,} the detection current select signal _{i sel} is, V-phase current estimated value _{i va} and U-phase, W-phase current detection value _i u, i _The current detection phase selection means 24 is input together with _w .
The detection current selection signal i _sel has a function of designating a current detection value by a normal current sensor to be selected by the current detection phase selection means 24 when any of the current sensors 7u and 7w fails. For example, when the current sensor failure detection means 23 detects a failure of the U-phase current sensor 7u, the detection current selection signal i _sel causes the current detection phase selection means 24 to select the W-phase current detection value i _w. Have information.

The current detection phase selection means 24 is used to generate a drive signal based on the V phase current estimation value i _va , the U phase and W phase current detection values i _u and i _w , and the detection current selection signal i _sel. The first and second current signals i ₁ and i ₂ are selected and output to the drive signal generating means 21. These current signals _i 1, _{i 2,} the current sensor 7u, U-phase in the case 7w are normal, W-phase current detection value _i u, _{i w,} and the current sensor 7u, any failure of 7w In this case, the current detection value by the normal current sensor and the V-phase current estimation value i _va are obtained.
The current detection phase selection unit 24 outputs a carrier frequency change signal f _csel for reducing the carrier frequency for PWM control to the drive signal generation unit 21 when any of the current sensors 7u, 7w fails. .

Based on the first and second current signals i ₁ , i ₂ , the carrier frequency change signal f _csel , the angle detection value by the angle sensor 8, and the torque command, the drive signal generation unit 21, Gate signals G _{1 to} G ₆ for the switching elements 1 to 3, 4 A, 5 and ₆ are generated.

Next, the operation of this embodiment will be described.
Now, when the current sensors 7u and 7w are operating normally, the current detection phase selection means 24 uses the detection current selection signal i _sel output from the current sensor failure detection means 23 to cause the current detection phase selection means 24 to perform the first and second current signals. The U phase and W phase current detection values i _u and i _w are selected as i ₁ and i ₂ and output to the drive signal generation means 21. The drive signal generation means 21 uses these i _u , i _w and the V-phase current calculation value i _v obtained by i _v = − (i _u + i _w ) as current information, and further provides a torque command and an angle detection value. The gate signals G _{1 to} G ₆ are generated by performing a predetermined calculation based on the above.
At this time, since the current estimated value i _va by the switching element 4A with current sense is not used for generating the drive signal, there is no possibility that the switching frequency and voltage amplitude command at the time of PWM control are restricted. Further, the carrier frequency change signal f _csel is not activated.

When a failure occurs in any of the current sensors 7u and 7w, the current sensor failure detection means 23 determines that the total value of the U-phase current detection value i _u , the W-phase current detection value i _w , and the V-phase current estimation value i _va is Since it does not become 0, it is determined that one of the current sensors 7u and 7w has failed. Alternatively, the average value of one period of the current detection value i _u or i _w of the phase in which the current sensor has failed is not zero, it is determined that the corresponding phase of the current sensors 7u or 7w fails. In addition, it is possible to detect which of the current sensors 7u and 7w has failed based on the determination results of both of them.
The current sensor failure detection means 23 sends information indicating the current sensor that has failed (information indicating a normal current sensor) to the current detection phase selection means 24 by the detection current selection signal i _sel .

The current detection phase selection means 24 selects the V phase current estimation value i _va and the current detection value i _u or i _w of the phase in which the current sensor is normal, and these two pieces of current information are used as the first and second current information. The signals i ₁ and i ₂ are output to the drive signal generation means 21. At the same time, since the current estimated value i _va by the switching element 4A with current sensing is used for generating the drive signal in this case, the carrier frequency change signal f _csel is activated so that the switching frequency does not become too high. The generation means 21 reduces the frequency of the carrier used for generating the gate signals G _{1 to} G ₆ .
The drive signal generation means 21 uses the first and second current signals i ₁ and i ₂ described above and the current calculation value for the remaining one phase calculated using them to generate gate signals G _{1 to} G ₆ . Generate.

  Thus, in this embodiment, since the operation of the inverter can be continued even when the one-phase current sensor fails, a so-called limp home function can be achieved. In addition, the upper limit of the switching frequency is restricted only when the current sensor fails, and is not restricted when the current sensor is normal. Therefore, the advantages of high-speed, low-loss switching elements made of wide band gap semiconductor materials are maximized. It is possible to make use of it.

Next, FIG. 2 is a configuration diagram of a motor drive system to which the second embodiment of the present invention is applied. Parts having the same functions as those in FIG. 1 are denoted by the same reference numerals, and the following description will focus on the parts different from those in FIG.
In the inverter main circuit 32 shown in FIG. 2, the switching elements 2A and 6A in the lower arms of the U phase and the W phase are switching elements with current sensing, and the other switching elements 1, 3 to 5 have a current sensing function. Absent. In FIG. 2, 2e and 6e are sense emitters, 2d and 6d are sense diodes, and 18 and 19 are sense detection signal processing circuits.

Output signals of the sense detection signal processing circuits 18 and 19 are respectively input to current estimation units 22U and 22W in the control circuit 20A, and U-phase current estimation values i _ua and W output from these current estimation units 22U and 22W. The phase current estimated value i _wa is input to the current detection phase selection means 24A and the current sensor failure detection means 23A. As in FIG. 1, the U-phase current detection value i _u and the W-phase current detection value i _w are input to the current detection phase selection unit 24A and the current sensor failure detection unit 23A.
That is, in this embodiment, the phase using the switching element with current sense and the phase where the current sensors 7u and 7w are provided coincide (that is, the U phase and the W phase).

The operation of the drive signal generation means 21 in this embodiment is the same as that of FIG. 1, and is based on the first and second current signals i ₁ and i ₂ , the carrier frequency change signal f _csel as necessary, and the angle sensor 8. Based on the detected angle value and the torque command, the gate signals G _{1 to} G ₆ of the switching elements 1, 3 to 5, 2A, and 6A are generated.

The current sensor failure detection means 23A matches the U-phase current detection value i _u with the U-phase current estimation value i _ua and the W-phase current detection value i _w with the W-phase current estimation value i _wa to thereby match the current sensor 7u. , 7w is detected. Alternatively, the average value of one period of the current detection value i _u or i _w of the phase in which the current sensor has failed is not zero, whether appropriate current sensor phase 7u or 7w is normal You may judge.

When the current sensors 7u and 7w are operating normally, the current detection phase selection unit 24A performs the first operation based on the detection current selection signal i _sel from the current sensor failure detection unit 23A, as in the first embodiment. , The U-phase and W-phase current detection values i _u and i _w are selected as the second current signals i ₁ and i ₂ and output to the drive signal generation means 21. The drive signal generation means 21 uses these i _u , i _w and the V-phase current calculation value i _v obtained by i _v = − (i _u + i _w ) as current information, and further provides a torque command and an angle detection value. The gate signals G _{1 to} G ₆ are generated by performing a predetermined calculation based on the above.
In this case, the current estimation values i _ua and i _wa generated by the switching elements 2A and 6A with current sense are not used for generating the drive signal, so there is a possibility that the switching frequency or voltage amplitude command at the time of PWM control may be restricted. Absent. Further, the carrier frequency change signal f _csel is not activated.

When a failure occurs in any one of the current sensors 7u and 7w, the current sensor failure detection means 23A detects the failure phase current sensor by the above-described method, and at the same time, detects a failure current sensor by the detection current selection signal i _sel. (Information indicating a normal current sensor) is sent to the current detection phase selection means 24A.

The current detection phase selection means 24A selects the current detection value i _u or i _w of the phase in which the current sensor is normal and the current estimation value i _wa or i _{ua of the} phase in which the current sensor has failed, Two pieces of current information are output to the drive signal generation means 21 as _first and _second current signals i ₁ and i ₂ . At the same time, in this case, since the current estimation value i _wa or i _ua by the switching element 6A or 2A with current sense is used for generating the drive signal, the carrier frequency change signal f _csel is set so that the switching frequency does not become too high. The drive signal generation unit 21 reduces the carrier frequency used to generate the gate signals G _{1 to} G ₆ .
Similarly to the first embodiment, the drive signal generation means 21 uses the first and second current signals i ₁ and i ₂ described above and the current calculation value for the remaining one phase calculated using these, Gate signals G _{1 to} G ₆ are generated.

  As described above, also in the present embodiment, the operation of the inverter can be continued at the time of failure of the current sensor, and the upper limit value of the switching frequency is restricted only at the time of failure of the current sensor. It is possible to make the most of the advantages of.

It should be noted that when a failure is detected by the current sensor failure detection means 23 or 23A in each embodiment, measures such as generating an alarm and prompting the inspection of the current sensor may be taken.
Furthermore, the present invention is also applicable to the case where current sensors are provided in all phases of the three-phase inverter device.

  The present invention can be used for a three-phase inverter device for driving various AC loads in addition to the motor drive system.

1-6, 2A, 4A, 6A: semiconductor switching elements 2d, 4d, 6d: sense diodes 2e, 4e, 6e: sense emitters 7u, 7w: current sensors 8: angle sensors 11-16: gate drive circuits 17-19: Sense detection signal processing circuits 20, 20A: Control circuit 21: Drive signal generation means 22U, 22V, 22W: Current estimation means 23, 23A: Current sensor failure detection means 24, 24A: Current detection phase selection means 31, 32: Inverter main circuit

Claims (3)

Inverter comprising three-phase switching element series circuits for one phase each having semiconductor switching elements on the upper and lower arms, and a series connection point between the semiconductor switching elements of the upper and lower arms connected to a load as an AC output terminal of each phase The main circuit;
In a three-phase inverter device comprising a control circuit that generates a drive signal for the semiconductor switching element using an output current detection value of the inverter main circuit,
Current sensors that respectively detect two-phase output currents of the inverter main circuit;
A switching element with a current sense provided as the semiconductor switching element in the upper arm or the lower arm of one phase other than the phase in which the output current is detected by the current sensor;
Have
The control circuit includes:
Current estimating means for estimating a one-phase output current provided with the switching element with current sensing based on a detection signal from the switching element with current sensing;
A failure detection means for detecting a failure of the current sensor based on a current detection value by the current sensor and a current estimation value by the current estimation means;
A current detection value by other current sensors excluding the current sensor in which a failure is detected by the failure detection means is selected as a first current signal, and a current estimation value by the current estimation means is selected as a second current signal In addition, when a failure of the current sensor is not detected by the failure detection means, a current detection phase selection for selecting the two-phase current detection values by the current sensor as the first current signal and the second current signal, respectively. Means,
Drive signal generating means for generating the drive signal using the first current signal and the second current signal;
A three-phase inverter device comprising: Inverter comprising three-phase switching element series circuits for one phase each having semiconductor switching elements on the upper and lower arms, and a series connection point between the semiconductor switching elements of the upper and lower arms connected to a load as an AC output terminal of each phase The main circuit;
In a three-phase inverter device comprising a control circuit that generates a drive signal for the semiconductor switching element using an output current detection value of the inverter main circuit,
Current sensors that respectively detect two-phase output currents of the inverter main circuit;
A switching element with current sensing provided as the semiconductor switching element in the upper arm or lower arm of the two phases in which the output current is detected by the current sensor;
Have
The control circuit includes:
Current estimation means for estimating two-phase output currents each provided with the current sensing switching element based on a detection signal from the current sensing switching element;
A failure detection means for detecting a failure of the current sensor based on a current detection value by the current sensor and a current estimation value by the current estimation means;
The current detection value by other current sensors excluding the current sensor in which the failure is detected by the failure detection means is selected as the first current signal, and the current estimation means of the phase having the current sensor in which the failure is detected When the current estimation value is selected as the second current signal and no failure of the current sensor is detected by the failure detection means, the two-phase current detection values by the current sensor are respectively set to the first current signal and the first current signal. Current detection phase selection means for selecting two current signals ;
Drive signal generating means for generating the drive signal using the first current signal and the second current signal;
A three-phase inverter device comprising: In the three-phase inverter device according to claim 1 or 2,
The three-phase inverter device, wherein the drive signal generation means reduces the switching frequency of the drive signal when a failure of the current sensor is detected by the failure detection means.

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