JP2014180068A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device capable of preventing erroneous detection of the short-circuiting of a coil without the need for adding a current detector.SOLUTION: The motor drive device is configured with a permanent magnet synchronous motor 1, an inverter 2 having a converter 23 and a current detector 24, a DC power source 3, and a controller 4. The controller 4 has: a current detection unit 46 for converting the output signal of the current detector 24 into a current detection value of a prescribed level; a short-circuit detection unit 47 for detecting, when the converter 23 stops for a fault while the permanent magnet synchronous motor 2 is rotating at or above a prescribed speed, the short-circuiting of a coil due to a short-circuit fault of a switching element on the basis of the current detection value; and a current detector fault detection unit 48 for detecting, when the converter 23 stops for a fault while the permanent magnet synchronous motor 2 is rotating at or above the prescribed speed, a fault in the current detector 24 on the basis of the current detection value being periodically in a state equal to or less than a threshold, if the current detector 24 is normal, and on the basis of the current detection value being continuously in the state equal to or greater than the threshold, if the current detector 24 is faulty.

Description

  The present invention relates to an electric motor drive device having a function of preventing erroneous detection of a winding short circuit due to a switching element short circuit failure of an inverter.

  As a recent trend of electric motor drive devices, examples of driving a permanent magnet synchronous motor by an inverter are increasing. Permanent magnet synchronous motors (hereinafter simply referred to as “motors”) are characterized by high efficiency, but there may be a problem that an induced voltage is always generated by rotation. If the field is an electromagnet type, no induced voltage is generated if the excitation is turned off. However, if the field magnet is a permanent magnet type, the excitation cannot be turned off and an induced voltage is generated. Therefore, when the switching element of the inverter is short-circuited, even if an OFF signal is given to all the switching elements, if the motor is rotated by an external force or its own inertia, the switching element that is short-circuited by an induced voltage generated by the motor A short-circuit current flows through the freewheeling diode. Since the induced voltage has a magnitude proportional to the speed of the electric motor, the higher the speed, the larger the short-circuit current. If this short-circuit current is larger than the maximum allowable current of the motor winding, the motor winding may be burned out due to overheating. In this case, it is conceivable to protect by connecting a fuse in series with the winding of the motor, but depending on the magnitude of the short circuit current, protection by the fuse is not possible and the motor winding is damaged. Occurs. Therefore, when a short circuit failure occurs in the switching element, it is important to detect whether a short circuit of the winding has occurred before restarting the operation of the inverter. As this detection method, there is a method of detecting whether or not a current of a specified value or more flows in a motor for a predetermined time or longer in a state where an ON command is given to all switching elements of the upper arm or lower arm of the inverter (see, for example, Patent Document 1). .)

JP 2012-16281 A (Overall)

  The technique disclosed in Patent Document 1 has a problem that a winding short circuit is erroneously detected when a detected current value is not correct due to a failure of a current detector or the like. Although there is a method of installing another current detector and comparing the current values in order to judge the failure of the current detector itself, it has a large outer shape and is disadvantageous in terms of cost. In addition, in a motor drive device that drives multiple motors and multiphase motors with multiple inverters, even if a failure occurs in the inverter, the other inverters continue to operate and do not stop the motor operation as much as possible. There may be. In this configuration, if the switching element really short-circuits and a winding short-circuit occurs, when the motor is operated with the remaining inverter, an excessive current flows in the short-phase winding due to the induced voltage of the motor. To prevent it, the motor drive must be stopped. On the other hand, if the current value is not correct due to the failure of the current detector, if a short-circuit is detected by mistake, the motor is driven even though only the relevant inverter can be stopped and operation can continue with other inverters. The device stops.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an electric motor driving device that can prevent erroneous detection of a winding short-circuit without adding a current detector.

  In order to achieve the above object, an electric motor drive device of the present invention flows through a permanent magnet synchronous motor, a converter that drives the permanent magnet synchronous motor, and a bridge connection of a switching element, and a winding of the permanent magnet synchronous motor. An inverter provided with a current detector for detecting current; a DC power supply for supplying DC power to the inverter; and a control device for supplying a drive signal to the inverter and controlling the permanent magnet synchronous motor, The apparatus includes: a current detection unit that converts an output signal of the current detector into a current detection value of a predetermined level; and when the converter has failed and stopped while the permanent magnet synchronous motor is rotating at a predetermined speed or more, A short-circuit detecting unit for detecting a winding short-circuit due to a short-circuit failure of the switching element based on a current detection value, and the permanent magnet synchronous motor When the converter has failed and stopped, if the current detector is normal, the current detection value periodically falls below a predetermined threshold, and if the current detector fails, the current detection value exceeds the threshold. It has a current detector failure detection unit that detects a failure of the current detector based on continuing the state.

  According to the present invention, it is possible to provide an electric motor drive device that can prevent erroneous detection of a winding short circuit without adding a current detector.

The block block diagram of the electric motor drive device which concerns on Example 1 of this invention. The figure explaining the path | route through which a short circuit current flows, when the switching element QU of a three-phase inverter carries out a short circuit failure. The figure which shows the schematic waveform of the induced voltage and electric current of each phase when the switching element QU of a three-phase inverter has a short circuit failure. The circuit block diagram of the winding short circuit detection based on Example 1 of this invention, and a current detector failure detection. The figure for demonstrating the method of performing failure detection of the electric current detection value in the electric motor drive device which concerns on Example 1 of this invention. The flowchart for demonstrating control of the electric motor drive device which concerns on Example 1 of this invention. The block block diagram of the electric motor drive device which concerns on Example 2 of this invention. The block block diagram of the electric motor drive device which concerns on Example 3 of this invention.

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

  FIG. 1 is a block configuration diagram of an electric motor drive device according to Embodiment 1 of the present invention. The motor drive device includes a permanent magnet synchronous motor 1, an inverter 2 that drives the permanent magnet synchronous motor 1, a DC power source 3 that supplies a DC voltage to the inverter 2, a control device 4 that controls the inverter 2, and a permanent magnet synchronous motor 1. A position detector 5 for detecting the rotational position is provided.

  The permanent magnet synchronous motor 1 is a three-phase synchronous motor having a three-phase star-connected stator winding of U phase, V phase, and W phase. The inverter 2 has an overcurrent protection fuse 21 and a smoothing capacitor 22 on the input side, and includes switching elements QU, QV, QW, QX, QY, QZ, and free-wheeling diodes DU, DV, DW, DX, DY, DZ. The converter 23 comprising: These switching elements are bridge-connected, and the converter 23 is a voltage source converter. On the output side, a current detector 24 and an overcurrent protection fuse 25 are provided. Although the switching elements constituting the converter 23 are illustrated as IGBTs, other switching elements such as MOS-FETs may be used. The DC voltage of the DC power supply 3 is smoothed by the smoothing capacitor 22, and the converter 23 converts the DC voltage into an AC voltage and supplies it to the permanent magnet synchronous motor 1. The current detector 24 detects U-phase and W-phase currents IU and IW.

  The control device 4 includes a speed controller 41, a current controller 42, a drive signal generator 43, a phase angle detector 44, a speed detector 45, a current detector 46, a short circuit detector 47, and a current detector failure detector 48. Have. The position detector 5 attached to the permanent magnet synchronous motor 1 detects the rotational position of the motor and converts it into a phase angle by the phase angle detector 44, and the speed detector 45 differentiates this phase angle into the speed. Convert. The speed control unit 41 performs speed control so that this speed matches a speed command given from the outside, and gives a current command to the current control unit 42. The current detector 46 calculates the V-phase current IV from the U-phase current IU and the W-phase current IW detected by the current detector 24 and performs signal level conversion. The current control unit 42 performs current control so that these currents coincide with the current command, and gives a command for switching operation to the drive signal generating unit 43. The drive signal generator 43 gives an ON signal or an OFF signal to the switching elements QU, QV, QW, QX, QY, QZ of the converter 23 based on the given switching operation command.

  The drive signal generator 43 normally stops all the switching elements by supplying an OFF signal while detecting the failure of the inverter 2. As will be described in detail later, the short-circuit detection unit 47 detects a winding short-circuit due to a short-circuit failure of the switching element based on the current, and the current detector failure detection unit 48 detects a failure of the current detector 24 based on the current.

  The permanent magnet synchronous motor 1 is characterized in that an induced voltage is generated by rotation by an external force. When the switching element of the inverter 2 is short-circuited, even if an OFF signal is given to all the switching elements, if the permanent magnet synchronous motor 1 is rotated by an external force or its own inertia, the switching element is short-circuited by the generated induced voltage. And a short-circuit current flows through the reflux diode. Since the induced voltage has a magnitude proportional to the speed of the permanent magnet synchronous motor 1, the higher the speed, the larger the short circuit current. If this short-circuit current is larger than the maximum allowable current of the winding of the permanent magnet synchronous motor 1, overheating will cause burnout of the motor winding. In this case, it is necessary that the fuse 25 connected to the winding of the permanent magnet synchronous motor 1 is blown to cut off the short-circuit current, or the entire system of the motor drive device is stopped to stop the rotation of the permanent magnet synchronous motor 1. is there.

  FIG. 2 is a diagram illustrating a path through which a short-circuit current flows when the switching element QU is short-circuited while the permanent magnet synchronous motor 1 is rotating at a predetermined speed or more. A short-circuit current flows through the switching element QU and the free-wheeling diodes DV and DW that are short-circuited due to the induced voltage generated in the permanent magnet synchronous motor 1. If the short-circuit current is sufficiently large, the short-circuit current is interrupted by fusing the fuse 25.

  The current of each phase is detected by the current detector 24 and sent to the current detection unit 46 in the control device 4. A Hall CT is often used for the current detector 24 used for detecting the main circuit current of the inverter. The Hall CT is composed of a Hall element and an electronic circuit (not shown), operates by applying a control power supply from the outside, and outputs a voltage having a magnitude proportional to the current passing through the Hall CT. Although there are various failure modes of the current detector 24, most of the failure modes result in the output voltage being fixed to a constant value. If the current detector 24 fails during operation of the electric motor drive device, current control is not executed correctly, and a protective operation such as overcurrent or overvoltage is activated in the control device 4 and the inverter 2 stops.

  FIG. 3 shows the permanent magnet synchronous motor 1 at a predetermined speed (that is, a predetermined minimum rotation frequency, and if it is lower than this speed, it means a speed that does not cause a problem even if a winding short-circuit occurs due to a switching element failure). It is a figure which shows the schematic waveform of the induced voltage and electric current of each phase when the switching element QU carries out a short circuit failure during rotation. An off signal is given to all the switching elements, the phase order of the induced voltage is U-phase, V-phase, and W-phase, and the direction in which the current flows into the permanent magnet synchronous motor 1 is positive. As shown in the figure, the phase difference between the induced voltages of the respective phases is 120 °. As shown in FIG. 2, in this case, the current flows only in the direction in which the current flows into the U-phase winding.

  On the other hand, if all switching elements are healthy and an OFF signal is given to all the switching elements, the current remains zero even if the permanent magnet synchronous motor 1 is rotating. Therefore, it can be determined that the switching element is short-circuited when a current exceeding a specified value flows for a certain period of time in a state where an OFF signal is applied to all the switching elements. However, if the current detector 24 fails and detects a value different from the actual current value, it may be erroneously determined as a short circuit failure of the switching element. In order to prevent this, a failure of the current detector 24 is detected as follows.

  FIG. 4 is a circuit configuration diagram of winding short-circuit detection and current detector failure detection. First, the winding short circuit detection circuit 47 will be described.

  The detected current value IU is input to the effective value calculation circuit 471, and the effective value IURMS is calculated. This effective value IURMS is input to the comparator 472, and if this is greater than or equal to the specified value, the output B_A of the comparator 472 is set to 1 and if less than the specified value, it is set to 0. This signal B_A is input to the on-delay circuit 473. If B_A = 1 continues for the specified time T1 or longer in the on-delay circuit 473, the output B_SHORT changes from 0 to 1. As a result, it is determined that a winding short circuit has occurred due to a short circuit failure of the switching element. Here, the reason why the effective value IURMS is used for detection is that, as shown in FIG. 3, the polarity of the current that flows intermittently differs depending on the short-circuited switching element. The calculation time of the effective value IURMS is set to a value sufficiently shorter than the half cycle of the current, that is, the electrical angle half cycle of the rotation frequency of the permanent magnet synchronous motor 1. Further, the specified time T1 is set to be equal to or shorter than the time when the winding is damaged by the short-circuit current and longer than the electrical angle half cycle of the rotation frequency of the permanent magnet synchronous motor 1.

  Next, the failure detection circuit 48 of the current detector will be described. 5A and 5B are diagrams for explaining a method of detecting a failure of the current detector using the failure detection circuit 48 of FIG. 4, in which FIG. 5A is a stop and FIG. 5B is a normal operation. 5 (c) shows a waveform of each part at the time of a short circuit failure of one switching element, FIG. 5 (d) shows a time of a short circuit fault of two switching elements, and FIG. . The signal names given to the respective parts in FIG. 5 correspond to the signal names given to the outputs of the respective parts in FIG. This will be described below with reference to both the drawings.

  In FIG. 4, the current detection value IU is input to the absolute value calculation circuit 481, and the absolute value IUABS is calculated. This absolute value IUABS is input to the comparator 482, and if this is greater than or equal to the threshold, the output B_NZ is set to 1 and if less than the threshold, it is set to 0. This signal B_NZ is input to the on-delay circuit 483. If B_NZ = 1 continues for the specified time T2 or longer in the on-delay circuit 483, the output B_S changes from 0 to 1. When B_S is 1, the current detector is in a failure detection state. The specified time T2 depends on the rotation frequency and is set longer than the time when the current zero-crosses at the minimum rotation frequency. If the specified time T2 is long, the failure detection of the current detector is delayed, so the specified time T2 needs to be set sufficiently shorter than the specified time T1.

  Normally, failure of the current detector can be detected by the signal B_S. However, when the current detection sampling period is long, the absolute value IUA of the current detection value is predetermined even if the current detector is in a normal state. There is an exception that does not become less than the time threshold, and in this case, there is a risk that the fault detection of the current detector is erroneously performed. This exception applies to normal operation and two switching element short-circuit faults. When one switching element is short-circuited, there is a section that is 0 for half a period as shown in FIG.

  Therefore, during normal operation and when two switching elements are short-circuited, the current detection value IU is periodically alternated between a positive threshold and a negative threshold as shown in FIGS. 5 (b) and 5 (d). Utilizing the change, the current detector determines that it is normal when it is alternately changing periodically. This determination is made by the normal check circuit 49. Hereinafter, the configuration of the normal check circuit 49 will be described.

  The current detection value IU is input to the rising detector 485 and the falling detector 487, and when the current detection value IU changes from negative to positive and passes the positive threshold (+ threshold), the output B_L1 1 and the one-shot circuit 486 changes the output B_M1 from 0 to 1 for a specified time T3. Similarly, in the falling detector 487, when the current detection value IU changes from positive to negative and passes the negative threshold value (−threshold value), the output B_L2 is set to 1, and the one-shot circuit 488 outputs only for the specified time T3. B_M2 is changed from 0 to 1. B_L1 and B_L2 are input to the OR circuit 489, and if either one is 1, the output B_R is set to 1. The specified time T3 is set based on the same concept as the specified time T2.

  The output of the normal check circuit 49 being “1” indicates that the current detector is normal. Therefore, B_S output from the on-delay circuit 483 and B_R output from the normal check circuit 49 circuit are respectively input to the set terminal and reset terminal of the reset priority flip-flop, and when the output signal B_ERR is 1, the current is Judged as failure detection of the detector. Therefore, even if the output B_S of the on-delay circuit 483 is erroneously set to 1 due to a detection error, if the output B_R of the OR circuit 489 is 1, the current detector is determined to be normal. FIG. 5 shows signals of respective parts in each case when a failure of the current detector occurs, and as a result, the failure detection is performed after a specified time T3 after the failure has occurred. ing.

  FIG. 6 is a flowchart for explaining the control of the electric motor drive device according to the first embodiment of the present invention. While operating the permanent magnet synchronous motor 1 at a predetermined speed or more, it is checked whether or not a failure is detected by the inverter (S01). If a failure is detected, the operation of the inverter is stopped (S02). It is determined whether the absolute value of the current detection value is periodically below the threshold value in the stopped inverter (S03), and if it is not below the threshold value, it is checked whether the current is alternately changing (S03A). If the current does not change alternately, it is determined that the current detector has failed (S04). If it is less than or equal to the threshold value in step S03, or if the current changes alternately in step S03A, it is determined that the current detector is normal. Then, in order to determine whether or not there is a winding short-circuit due to a switching element failure, it is determined whether or not the current detection value is longer than a specified value and continues for a specified time (S05). (S06), and the entire system of the motor drive device is stopped (S07).

  As described above, according to the first embodiment, it is possible to prevent erroneous detection of the winding short circuit due to the failure of the current detector. Note that step S03A in the above can be omitted if no erroneous detection can occur.

  FIG. 7 is a block diagram of an electric motor drive device according to the second embodiment of the present invention. Regarding the respective parts of the second embodiment, the same parts as those in the block configuration diagram of the motor drive device according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The second embodiment is different from the first embodiment in that the permanent magnet synchronous motor 1 is a multiple synchronous motor 1A having two three-phase windings, and one three-phase winding is supplied with power from the inverter 2 and the other one The three-phase winding is configured to be fed from the inverter 2A.

  The multiple synchronous motor 1A is a three-phase permanent magnet synchronous motor in which U-phase, V-phase, and W-phase windings are three-phase and the star connection is doubled. The multiple synchronous motor 1A is driven by voltage-type inverters 2 and 2A. Such a multi-synchronous motor drive device has a feature that even if one of the inverters fails, the motor can be driven only by the remaining healthy inverters. In this embodiment, a two-winding multiplex synchronous motor is driven by two inverters. However, even if there are three or more windings, the same configuration can be achieved by increasing the number of inverters.

  The control device 4A has the same configuration as the control device 4. In FIG. 7, the same speed control is performed for both of the control devices 4 and 4 </ b> A, but it is also possible to add control that makes the load sharing the same. The winding short-circuit detection and the current detector failure detection described in the first embodiment are individually performed in the control devices 4 and 4A.

  FIG. 8 is a block diagram of an electric motor drive device according to Embodiment 3 of the present invention. Regarding the respective parts of the third embodiment, the same parts as those of the block configuration diagram of the electric motor drive device according to the first embodiment of FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. The second embodiment is different from the first embodiment in that the permanent magnet synchronous motor 1 is a multiphase synchronous motor 1B, and single-phase inverters 6 and 6A are used for windings of M phases of the multiphase synchronous motor 1B. ,..., 6L.

  The multi-phase synchronous motor 1B is an M-phase permanent magnet synchronous motor composed of M-phase windings from the first phase to the M-th phase. The voltage-type single-phase inverters 6, 6A,..., 6L are connected to the first to M-th windings of the multiphase synchronous motor 1B, respectively, and drive the multiphase synchronous motor 1B. Even if one of the single-phase inverters 6, 6 </ b> A,..., 6 </ b> L fails, such a multi-phase synchronous motor drive device can drive the motor with only the remaining healthy single-phase inverter. There are features that can be done.

  The single-phase inverter 6 includes an input fuse 21, a smoothing capacitor 22, a converter 23A composed of switching elements QU, QV, QX, QY and free-wheeling diodes DU, DV, DX, DY, a current detector 24A, and a fuse 25. have. Although the switching element is illustrated as an IGBT, other switching elements such as a MOS-FET may be used. The DC voltage of the DC power supply 3 is smoothed by the smoothing capacitor 22, and the converter 23A converts the DC power into single-phase AC power and supplies it to each winding of the multiphase synchronous motor 1B. The current detector 24A detects a U-phase current IU. The single-phase inverters 6A, 6B,..., 6L have the same configuration as the single-phase inverter 6.

  The control device 7 is basically the same as the control device 4 of FIG. 1 except that the current detection unit 46A is configured to detect a one-phase current. That is, the current detection unit 46A performs only signal level conversion. The control devices 7A,..., 7L have the same configuration as the control device 7.

  As mentioned above, although Example 1 thru | or Example 3 was demonstrated, these Examples are shown as an example and are not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  For example, as described above, the normality check circuit 49 can be omitted in some cases. Further, if the threshold value in the comparator 482 is changed approximately in proportion to the magnitude of the detection signal IUABS, it is possible to reduce false detection. This is also true for the prescribed value of the comparator 472.

  In addition, the effective value calculation circuit 471 is used for detecting the winding short-circuit, and the absolute value calculation circuit 481 is used for detecting the current detector failure. It can also be used.

  In the first to third embodiments, the position detector 5 is attached to the permanent magnet synchronous motor and the control device performs the speed feedback control. However, the speed feedback control is not necessarily performed. Obviously, torque control or open loop control may be used.

  Further, the fuses 21 and 25 in the first to third embodiments may be omitted.

1, 1A, 1B Permanent magnet synchronous motor 2, 2A Inverter 3 DC power supply 4, 4A Control device 5 Position detector 6, 6A,..., 6L Single phase inverter 7, 7A,. 22 Smoothing capacitor 23, 23A Converter 24, 24A Current detector 25 Fuse 41 Speed control unit 42 Current control unit 43 Drive signal generation unit 44 Phase angle detection unit 45 Speed detection unit 46, 46A Current detection unit 47 Winding short circuit detection unit 48 Current detector failure detection unit 471 RMS value calculation circuit 472 Comparator 473 On-delay circuit 481 Absolute value calculation circuit 482 Comparator 483 On-delay circuit 484 Reset priority type flip-flop 485 Rise detection circuit 486 One-shot circuit 487 Fall detection circuit 488 One-shot circuit 489 OR circuit

Claims (6)

A permanent magnet synchronous motor,
An inverter provided with a converter that drives the permanent magnet synchronous motor and bridge-connects a switching element and a current detector that detects a current flowing through the winding of the permanent magnet synchronous motor;
A DC power supply for supplying DC power to the inverter;
Providing a drive signal to the inverter, and controlling the permanent magnet synchronous motor,
The controller is
A current detector for converting the output signal of the current detector into a current detection value of a predetermined level;
When the converter fails and stops while the permanent magnet synchronous motor is rotating at a predetermined speed or higher,
A short-circuit detecting unit that detects a winding short-circuit due to a short-circuit failure of the switching element based on the current detection value;
When the converter fails and stops while the permanent magnet synchronous motor is rotating at a predetermined speed or higher,
If the current detector is normal, the current detection value periodically falls below a predetermined threshold, and if the current detector fails, the current detection value continues to be above the threshold. An electric motor drive device comprising: a current detector failure detection unit that detects a failure of the current detector. The permanent magnet synchronous motor is a multiple synchronous motor having N (N is an integer of 2 or more) three-phase winding, and the inverter is supplied with DC power from the DC power source, and the output is the N It consists of N individual inverters connected to each of the three-phase windings,
2. The motor driving device according to claim 1, wherein each of the N control devices controls each of the N individual inverters. The permanent magnet synchronous motor is a multi-phase synchronous motor having M (M is an integer of 3 or more) single-phase windings, and the inverter is supplied with DC power from the DC power source, and the output is the M outputs. Consisting of M single-phase inverters connected to each of the single-phase windings of
2. The motor driving device according to claim 1, wherein each of the M control devices controls each of the M single-phase inverters. The short circuit detector is
When the effective value or absolute value of the current of any one phase detected by the current detection value exceeds a predetermined threshold for a predetermined time or more, it is determined that the winding is short-circuited due to a short-circuit failure of the switching element. The electric motor drive device according to any one of claims 1 to 3. The current detector failure detection unit is
When the effective value or absolute value of any one-phase current detected by the current detection value does not periodically fall below a predetermined threshold, it is determined that the current detector has failed. The electric motor drive device according to any one of claims 1 to 4. The current detector failure detection unit is
Even if the effective value or absolute value of any one-phase current detected by the current detection value does not periodically become a predetermined threshold value or less, the detection value of the current changes periodically alternately. 6. The electric motor drive device according to claim 5, wherein the current detector is determined to be normal if it is.

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