JPH08186984A - Fail-safe apparatus for inverter - Google Patents

Abstract

PURPOSE: To prevent the destruction of transistors by stopping the combinations of PWM driving signals that turn on a switching element forming a counterpart to a transistor in case of an ON fault in the transistor, and those of PWM driving signals that turn on switching in case of an OFF fault. CONSTITUTION: A fault detecting circuit 20 detects the combinations of outputs from delay circuits 31, 36 and voltage detecting circuits 33, 38 (A combination of H and H represents an OFF fault in a transistor Q, and that of L and L represents an ON fault in the transistor) through AND circuits 34, 35, 39, 40 from the output from the delay circuits and voltage detecting circuits. The data on Q1's ON fault, Q4's OFF fault, Q1's OFF fault and Q4's On fault requiring a corrective action, is complied through OR circuits 42, 41, and stored In latch circuits 44, 43. If Q1 Is at ON fault or if Q4 is at OFF fault, the latch circuit 44 outputs Q4INH; if Q1 is at OFF fault or if Q4 is at ON fault, the latch circuit 43 outputs Q1INH.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter fail-safe device, and more particularly to an inverter fail-safe device used in a variable speed drive system for a synchronous motor using a permanent magnet as a field.

[0002]

2. Description of the Related Art A synchronous motor is used, for example, as a driving force source for an electric vehicle, and an inverter is used to drive it. That is, the DC power is converted into AC by the inverter and then supplied to the winding of the synchronous motor.
A synchronous motor that uses a permanent magnet for the field does not require an exciting current because the field is supplied by the permanent magnet.
As the number of revolutions increases, the induced electromotive force generated by the field of the permanent magnet increases in proportion to the number of revolutions, and at a certain number of revolutions, it exceeds the output voltage of the inverter, and the inverter drives the drive current. Cannot be generated, and torque cannot be generated in the synchronous motor. In an electric vehicle or the like, the rotation speed is relatively high, or the motor may be rotated to a high rotation speed range, for example, when descending a slope. Therefore, in the control in the high rotation range where the induced electromotive force exceeds the output voltage of the inverter, it is necessary to suppress the induced electromotive force within the maximum output voltage of the inverter. Field weakening is performed on this.

FIG. 13 shows changes in the output torque T of the synchronous motor, the output voltage E of the inverter, and the output current I in the low rotation range N1 where the field weakening is not required and the high rotation range n where the field weakening is performed. Show. In the figure, Em is the maximum output voltage of the inverter, I1 is the maximum torque current, and In is the inverter output current when field weakening is performed.

In the region up to the rotational speed N1, only the torque component current Iq (q-axis current) flows as the output current I of the inverter, and the product Xq · Iq of Iq and the q-axis reactance Xq is vectored to the induced electromotive force Eo. Since the summed voltage is equal to or less than the inverter maximum output voltage Em, the constant torque characteristic as shown in FIG. 13 can be realized. However, when the rotation speed rises to N1, the induced electromotive force Eo becomes Eo1 as shown in FIG. 14, and the vector sum of the product Xq1 · Iq1 of the maximum torque current I1 and the q-axis reactance Xq1 becomes Em,
If it exceeds this, the synchronous motor cannot produce torque. Therefore, at higher rotation speeds than this, it becomes necessary to weaken the field. FIG. 15 shows changes in voltage and current in this rotation range. That is, the induced electromotive force of Eon is generated at the rotation speed n, and the vector sum of the induced electromotive force Eon and Xqn · Iqn exceeds Em. At this time, the field weakening current Idn (d
Shaft) to a synchronous motor, so that Eon and Xqn
* Iqn and d-axis reactance Xdn, product Xdn * I
The vector sum of dn becomes Em or less, and the synchronous motor can output torque.

[0005]

However, in an inverter for driving a synchronous motor whose rotation range is widened by performing the field weakening as described above, for example, "Inverter Application Manual" (edited by Mitsubishi Electric Corp., With the overcurrent detection circuit connected to each arm of the three-phase inverter as introduced on page 362), a fail-safe device that turns off all the transistors when an overcurrent flows through even one transistor is applied. Attempting to do so, at a rotation speed of N1 or more, the field is weakened by a current from the outside. Therefore, when the transistor is turned off, the excitation current does not flow and a large induced electromotive force is generated in the excitation winding. There was a problem that it would cause transistor destruction. Therefore, the present invention has been made by paying attention to such a conventional problem. Even when a transistor failure occurs in the inverter, the synchronous motor is continuously operated, a large induced voltage is not generated, and the transistor is destroyed. It is an object of the present invention to provide a fail-safe device that does not prevent it.

[0006]

For this reason, the invention according to claim 1 is a failure detection circuit for detecting a failure of a switching element for performing power conversion in an inverter for driving a synchronous motor using a permanent magnet as a field. When the detected failure is an ON failure in which the switching element continues to turn on, the combination of PWM drive signals for turning on the switching element paired with the switching element is stopped, and the failure continues in which the switching element remains off. In the case of a failure, it is constituted by a failure processing means for stopping the combination of PWM drive signals for turning on the switching.

According to a second aspect of the present invention, a switch for cutting off a torque command to the inverter is provided, and the switch is operated when the failure processing means stops the combination of PWM signals related to the failed switching element. And Further, the invention according to claim 3 is provided with means for detecting the number of rotations of the synchronous motor, and the failure processing means stops the combination of the PWM signals relating to the switching element which has failed only when the synchronous motor is in the field weakening rotation range. It was supposed to be. Furthermore, the invention according to claim 4 is characterized in that a switch for cutting off the power supply to the synchronous motor is provided, and the switch is operated when the failure processing means stops the combination of the PWM signals relating to the failed switching element. did.

[0008]

According to the first aspect of the invention, the failure detection device detects a failure of the switching element, and when the failure processing device has an ON failure due to the failure of the switching element, a PWM signal for turning on the switching element which is paired with the failure is provided. The combination is stopped, the other PWM signal combinations are continuously output, and in the case of the OFF failure, the PWM signal combinations that turn on the failed switching element are stopped, and the other PWM signal combinations are continuously output. As a result, even if the switching element fails, the controllable switching element continues to be driven, and field weakening prevents the switching element from being damaged by high induced electromotive force.

If the torque command to the inverter is cut off when the combination of the PWM signals related to the faulty switching element is stopped, the synchronous motor can be stopped promptly without generating further torque when the fault occurs. . Further, when the combination of the PWM signals related to the faulty switching element is stopped, if it is performed only in the field weakening rotation range, it is possible to prevent the destruction of the switching element and to prevent unnecessary power consumption. If the power supply to the synchronous motor is stopped when the combination of the PWM signals related to the failed switching element is stopped, the effect that the induced voltage generated in the synchronous motor is not reliably applied to the inverter is obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
FIG. 1 shows the configuration of the first embodiment of the present invention. The synchronous motor (SM) 1 is a permanent magnet 3-phase synchronous motor.
It is driven by a three-phase inverter 2 composed of a phase bridge circuit or the like. The synchronous motor 1 has an encoder 3 on the output shaft, and the rotation angle θre of the synchronous motor 1 is a trigonometric function generator 4.
Given to. The AC coordinate converter 5 uses the current commands id ^* , i
Two sin θ given by q ^* from the trigonometric function generator 4
The signals of re and sin (θre−2π / 3) are converted into three-phase current commands iu and iv. id ^* is encoder 3
Obtained from id ^* arithmetic circuit 15 by the rotational angle θre rotational speed of the synchronous motor 1 calculated by from and iq ^*
Is obtained from the torque command.

The converted three-phase current commands iu and iv are input to the adders 6 and 7, and the PI compensators 10 and 1 are obtained by taking the difference from the actual phase current obtained by the current sensors 8 and 9.
Input to 1. The outputs of the PI compensators 10 and 11 are PW
It is input to the positive terminals of the comparators A and B of the M generator 13, and the sum of which the sign is inverted by the adder 12 is taken and input to the positive terminal of the comparator C. The output of the triangular wave generator 14 is input to the negative terminals of the comparators A, B and C. The PWM generator 13 produces PWM signals a, b, c of the three-phase inverter 2 from the comparators A, B, C.

The PWM signals a, b and c are sent to the failure processing circuit 19
Is input to the failure processing circuit 19 as negative theoretical PWM signals a *, b *, and c *. Here, the PWM signals a, b, c and a *, b *, c * are selected by the failure detection signals Q1INH to Q6INH from the failure detection circuit 20 and output to the failure detection circuit 20. The failure detection circuit 20 is a built-in drive circuit according to the output of the failure processing circuit 19 and includes transistors Q1, Q2, Q3, Q4, Q5, Q of the three-phase inverter 2.
6 is driven, and the failure of each transistor is detected, and failure detection signals Q1INH to Q6INH are output. Figure 2
3 shows a simplified connection between the transistor of the three-phase inverter 2 and the corresponding PWM signal and the synchronous motor 1.

FIG. 3 shows a fault detection circuit 20 and an inverter 2.
It is a figure which shows a part (U phase part) of in detail. PWM signal a
Is input to the delay circuit 31 and the isolated driver 3
2 drives the base of Q1. The voltage detection circuit 33 outputs a logic signal according to the collector-emitter voltage of Q1. The output of the delay circuit 31 and the output of the voltage detection circuit 33 are the AND circuit 34 and the AND of the negative logic input, respectively.
It is input to the circuit 35.

On the other hand, the PWM signal a * is input to the driver 37 via the delay circuit 36 in the same manner as described above to drive Q4. The voltage detection circuit 38 outputs a logical output according to the collector-emitter voltage of Q4, and the delay circuit 36
The outputs of and 38 are input to the AND circuit 39 and the negative logic input AND circuit 40. The outputs of the AND circuit 34 and the negative logic AND circuit 40 are input to the OR circuit 41, and the latch circuit 4
It becomes the fault detection signal Q1INH via the signal line 3. The outputs of the negative logic AND 35 and the AND circuit 39 are input to the OR circuit 42, and the failure detection signal Q4INH is input via the latch circuit 44.
Becomes

FIG. 4 shows details of the failure processing circuit 19.
The PWM signal a is input to the AND circuits 51 and 58. Similarly, a * is AND circuits 52 and 59, b is 53 and 60, b * is 54 and 61, and c is 55 and 62.
, C * is input to 56 and 63, respectively. The failure detection signal Q1INH is AND circuit 51, and Q4INH is AND circuit.
The circuit 52 and Q3INH are AND circuits 53, and Q6INH is AN.
D circuit 54 and Q5INH are AND circuits 55 and Q2INH is A
It is input to each ND circuit 56. AND circuit 5
The outputs of 1, 52, 53, 54, 55 and 56 are inputs to the NOR circuit 57, and the outputs of the NOR circuit 57 are inputs to the AND circuits 58, 59, 60, 61, 62 and 63.
The outputs of the AND circuits 58, 59, 60, 61, 62, 63 become the PWM signals a, a *, b, b *, c, c * supplied to the failure detection circuit 20, respectively.

Next, the operation will be described. FIG. 5 shows FIG. 1 or 2.
The vector of the output voltage of the 3-phase inverter shown in FIG.
FIG. 6 shows an operational combination of the transistors Q1 to Q6 when generating the vector voltage as shown in FIG. Considering, for example, the case where Q1 fails, in FIG. 2, in the case of ON failure where Q1 continues to turn on, if Q4 of the same U-phase arm is turned on, a short circuit between Q1 and Q4 occurs, Do not generate an output voltage vector that turns on Q4. That is, vector voltages V0, V3, V4, V5 as shown by the dotted lines in FIG.
It is necessary to control not to generate.

On the other hand, in the case of an OFF failure in which Q4 continues to be turned off, Q4 cannot be turned ON, so that V0, V3, V4, and V5 cannot be generated as in the ON failure of Q1. Q4 is O
In the case of FF failure, short circuit of Q1 and Q4 does not occur even if Q1 is turned on, but as shown in FIG. 6, V0, V3, V
When switching corresponding to 4 and V5 is performed, a voltage vector different from the original direction is generated, and abnormal torque is generated. Therefore, like an ON failure, V0, V3, V
4, it is necessary to control so that V5 is not generated.

In FIG. 3, the failure detection circuit 20 has a combination of the outputs of the delay circuits 31 and 36 and the voltage detection circuits 33 and 38 and the outputs of the delay circuit and the voltage detection circuit (H and H indicate an OFF failure of the transistor Q). Equivalent, L, L
Corresponds to ON failure of the transistor) and the AND circuit 34,
35, 39, 40. The ON failure of Q1 and the OFF failure of Q4, the OFF failure of Q1 and the ON failure of Q4, which need to be dealt with at the time of failure, are collected by the OR circuits 42 and 41 and stored in the latch circuits 44 and 43. When Q1 has an ON failure or Q4 has an OFF failure, the latch circuit 44 outputs Q
Outputs 4INH, Q1 is OFF failure, or Q4 is ON
When there is a failure, the latch circuit 43 outputs Q1INH.

In the failure processing circuit 19 of FIG. 4, for example, Q1
When INH is output, when PWM signal a is input, Q1INH is set to a, Q so that all output is not performed.
4INH is a *, Q3INH is b, Q6INH is b *, Q5IN
AND circuit 51NO corresponding to H = c and Q6INH = c *
R circuit 57, AND circuits 58, 59, 60, 61, 6
The output of the signal is masked by 2, 63.

This embodiment is configured as described above, detects a failure of the transistors Q1 to Q6, masks the output of the PWM signal including the driving of the transistor in the same phase as that of the ON failure and masks the OFF failure. In this case, the output of the PWM signal including driving of the defective transistor is masked. As a result, even if the transistor fails, the synchronous motor continues to operate, and it is possible to prevent the transistor from being destroyed by the induced electromotive force of the synchronous motor due to the stop of the drive signal.

8 and 9 show a second embodiment according to the present invention. In this embodiment, as shown in FIG. 8, a switch 25 is further provided between the torque command and the AC coordinate converter 5 in the first embodiment shown in FIG.
Is used. Other configurations are similar to those of the first embodiment. As shown in FIG. 9, the failure processing circuit 19A has the same configuration as in FIG.
In addition to the failure processing circuit 19 shown in, Q1INH to Q6INH
A NOR circuit 64 for taking the logical sum of the above is provided, and other configurations are similar to those of the first embodiment shown in FIG.
The TINH signal is generated by the Q1INH to Q6INH signals generated when a transistor fails. The switch 25 is thereby turned off to cut off the torque command. As a result, the same effect as that of the first embodiment can be obtained, and an effect of generating no extra torque at the time of failure can be obtained.

10 and 11 show a third embodiment according to the present invention. In this embodiment, as shown in FIG. 10, an F / V converter 22, a comparator 23 and a reference power supply 24 are further provided in the first embodiment shown in FIG. 1, and 19B is used instead of the failure processing circuit 19. is there. Failure processing circuit 19
B is a NAND between the output of the NOR circuit 57 and the AND circuits 58, 59, 60, 61, 62, 63 as shown in FIG.
The circuit 65 is provided, and other configurations are similar to those of the first embodiment. The rotational speed of the synchronous motor 1 is compared with the reference power source 24 by the F / V converter 22 and the comparator 23, and when the synchronous motor rotational speed is within the field weakening region, the fail safe signal FWL is output. Figure 11
The failure processing circuit 19B masks the PWM signal based on the Q1INH to Q6INH signals and when the FWL signal is input. As a result, the same effect as that of the first embodiment is obtained, and when the field weakening is not performed, the inverter is not operated, so that it is possible to quickly attain the fail-safe state without wasting power. The effect is obtained.

FIG. 12 shows a fourth embodiment according to the present invention. In this embodiment, instead of the switch 25 provided in the second embodiment shown in FIG. 8, a switch 21 for cutting off the driving power source is provided between the inverter 2 and the synchronous motor 1. The other structure is similar to that of the second embodiment. When the TINH signal is output from the failure processing circuit 19A, the switch 21 cuts off the power supply to the synchronous motor, which has the same effect as that of the first embodiment and, at the time of transistor failure, induces the synchronous motor. Since it is possible to reliably apply no voltage to the inverter, it is possible to cut off the power supply to the synchronous motor and prevent the transistor from being damaged by the induced electromotive force.

[0024]

As described above, according to the present invention,
A PW that detects the failure of a switching element and, when the failure is an ON failure, includes the driving of the switching element that is paired with it.
The combination of the M signals is stopped, the other combinations of the PWM signals are continuously output, and in the case of the OFF failure, the combinations of the PWM signals including the driving of the failed switching element are stopped and the other combinations of the PWM signals are output. Even if the switching element fails, the controllable switching element continues to drive the synchronous motor, and the field weakening prevents the destruction of the switching element due to high induced electromotive force.

If the torque command to the inverter is cut off when the combination of the PWM signals relating to the failed switching element is stopped, no extra torque is generated at the time of failure, so that the synchronous motor can be stopped quickly. . In addition, the P related to the failed switching element
When the combination of the WM signals is stopped, if it is performed only in the field weakening rotation region, it is possible to prevent destruction of the switching element and to obtain an effect of not wasteful power consumption. If the power supply to the synchronous motor is cut off when the combination of the PWM signals related to the faulty switching element is stopped, the induced voltage generated in the synchronous motor cannot be reliably applied to the inverter, and the synchronous motor is stopped. At times, the effect of preventing destruction of the switching element is obtained.

[Brief description of drawings]

FIG. 1 is an overall view showing a configuration of a first embodiment.

FIG. 2 shows the connection between the inverter and the synchronous motor in the first embodiment.

FIG. 3 is a diagram showing a configuration of a failure detection circuit in the first embodiment.

FIG. 4 is a diagram showing a configuration of a failure processing circuit in the first embodiment.

FIG. 5 is a vector diagram of a drive voltage.

FIG. 6 is a diagram showing a relationship between a switching mode and a transistor which is turned on.

FIG. 7 is a diagram showing voltage vectors that can be output when a U-phase transistor fails.

FIG. 8 is an overall view showing a configuration of a second exemplary embodiment.

FIG. 9 is a diagram showing a configuration of a failure detection circuit according to a second embodiment.

FIG. 10 is an overall diagram showing a configuration of a third exemplary embodiment.

FIG. 11 is a diagram showing a configuration of a failure detection circuit according to a third embodiment.

FIG. 12 is an overall diagram showing a configuration of a fourth exemplary embodiment.

FIG. 13 is a diagram showing a relationship among a drive voltage, a current, an output torque, and a rotation speed of a permanent magnet synchronous motor.

FIG. 14 is a diagram showing vectors of voltage and current in a rotation region where field weakening is unnecessary.

FIG. 15 is a diagram showing vectors of voltage and current in a high rotation region where field weakening is required.

[Explanation of symbols]

1 Permanent magnet synchronous motor 2 Inverter 3 Encoder 4 Trigonometric function generator 5 AC coordinate converter 6, 7 Adder 8, 9 Current sensor 10, 11 PI circuit 12 Inverting adder 13 PWM generator 14 Triangular wave generator 15 id ^* current Operation circuit 16, 17, 18 Inverter 19, 19A, 19B Fault processing circuit 20 Fault detection circuit 21, 25 Switch 22 F / V converter 23 Comparator 24 Reference power supply 31, 36 Delay circuit 32, 37 Insulated driver 33, 38 Voltage detection circuit 34, 39, 51, 52, 53 AND circuit 54, 55, 56, 58, 59 AND circuit 60, 61, 62, 63 AND circuit 35, 40 Negative logic AND circuit 41, 42 OR circuit 43, 44 Latch Circuit 57, 64 NOR circuit 65 NAND circuit a, b, c PWM signal Q1 to Q6 transistors

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Yanase 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. No. 1 inside Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. In an inverter for driving a synchronous motor using a permanent magnet as a field, a failure detection circuit for detecting a failure of a switching element that performs power conversion, and the detected failure keeps the switching element turned on. In the case of a failure, the combination of the PWM drive signals for turning on the switching element paired with the switching element is stopped, and the failure keeps the switching element off.
PWM for turning on the switching element in case of F failure
A fail-safe device for an inverter, comprising: a failure processing means for stopping a combination of drive signals. 2. In an inverter for driving a synchronous motor using a permanent magnet as a field, a switch for interrupting a torque command to the inverter, a failure detection circuit for detecting a failure of a switching element for power conversion, and the detection. When the failure is an ON failure in which the switching element continues to be turned on, the combination of PWM drive signals for turning on the switching element paired with the switching element is stopped,
When the failure is an OFF failure in which the switching element continues to be turned off, a failure processing unit that stops the combination of the PWM drive signals that turn on the switching element and actuates the switch is provided. Fail-safe device. 3. In an inverter for driving a synchronous motor using a permanent magnet as a field, a failure detection circuit for detecting a failure of a switching element that performs power conversion, a means for detecting the rotational speed of the synchronous motor, and the synchronization. When the detected fault is an ON fault in which the switching element continues to turn on when the motor is in the field weakening rotation range, the combination of the PWM drive signals for turning on the switching element paired with the switching element is stopped, When the failure is an OFF failure in which the switching element keeps turning off,
A fail-safe device for an inverter, comprising: failure processing means for stopping a combination of PWM drive signals for turning on the switching elements. 4. An inverter for driving a synchronous motor using a permanent magnet as a field, a failure detection circuit for detecting a failure of a switching element for converting power, a switch for interrupting power supply to the synchronous motor, and When the detected failure is an ON failure in which the switching element continues to be turned on, the combination of PWM drive signals for turning on the switching element paired with the switching element is stopped,
When the failure is an OFF failure in which the switching element continues to be turned off, a failure processing unit that stops the combination of the PWM drive signals that turn on the switching element and actuates the switch is provided. Fail-safe device.