JP5321368B2 - Motor drive control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive controller capable of ideally protecting a switching element from overheat by properly reducing a loss of the switching element at the time of locking of an AC motor. <P>SOLUTION: Driving a three-phase AC motor M is controlled based on a conversion power, while a gate voltage is applied to each of switching element T1U, T3V, T5W, T2U, T4V, T6W of inverter equipment via a gate resistor. Then, a motor lock detection section 100 for detecting whether the three-phase AC motor M is in a locked state detects the locked state of the three-phase AC motor M, thus suppressing a system voltage of the inverter equipment, and changing a resistance value of the gate resistor to a small value. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a motor drive control device that protects a drive circuit from an overcurrent at the time of motor lock when driving an AC motor.

  An inverter device that converts DC power supplied from an in-vehicle battery into, for example, three-phase AC is widely used as a power conversion device for a motor such as a hybrid vehicle or an electric vehicle. Such a hybrid vehicle controls the driving of the motor by using three-phase AC power generated by a switching element constituting the inverter device as a power source. For this reason, when the motor is locked, an excessive direct current flows through the switching element, and the heat loss rapidly increases.

  Therefore, for example, a motor drive control device described in Patent Document 1 is known as a motor drive control device that prevents thermal destruction of a switching element due to such an increase in heat loss. FIG. 8 shows a schematic configuration of the motor drive control device described in Patent Document 1.

  As shown in FIG. 8, the DC voltage applied from the DC power supply B is smoothed between the positive bus bar BBP which is the positive bus of the DC power supply B and the negative bus bar BBN which is the negative bus in this inverter device. A smoothing capacitor C and an inverter circuit INV that converts the DC voltage into three-phase AC are connected. The inverter circuit INV is a three-phase bridge composed of three switching elements (IGBT: insulated gate bipolar transistor) T1U, T3V, T5W constituting the upper arm and three switching elements T2U, T4V, T6W constituting the lower arm. It is connected.

  The U-phase output electrode, the V-phase output electrode, and the W-phase output electrode, which are connection portions of the emitter electrodes of the switching elements T1U, T3V, and T5W and the collector electrodes of the switching elements T2U, T4V, and T6W, are output lines. It is connected to the U-phase coil, V-phase coil, and W-phase coil of the three-phase AC motor M via OWW, OWV, and OWW. On the other hand, between the switching elements T1U, T3V, T5W, and the emitter and collector electrodes of the switching elements T2U, T4V, T6W, free-wheeling diodes D1U, D3V, D5W and free-wheeling diodes D2U, which are rectifier elements, D4V and D6W are connected in reverse parallel.

  In the inverter device configured as described above, the current flowing through the three-phase AC motor M to be driven is detected by the current detection sensors 5 a to 5 c, and each detected current value is taken into the motor drive control device 10. . Further, the rotor rotation position of the three-phase AC motor M is detected by the position detection sensor 7, and the value is taken into the motor drive control device 10. The motor drive control device 10 generates switching patterns for the switching elements T1U, T3V, T5W, T2U, T4V, and T6W based on the current values and the rotor rotation position, and is built in the motor drive control device 10. The operation of each of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W is controlled by the gate driver circuit. FIG. 9 shows a schematic configuration of the gate driver circuit.

As shown in FIG. 9, the gate driver circuit receives the switching pattern signal, converts the potential level of the switching pattern signal into a signal having the same potential level as the switching element T1U, and generates the switching pattern signal. An insulating circuit 22 is provided to insulate the circuit side from the high voltage circuit side such as the switching element T1U. The signal whose potential is converted by the insulating circuit 22 is input to the first gate driver 23 and the second gate driver 24 for driving and controlling the gate of the switching element T1U. The first gate driver 23 and the second gate driver 24 are electrically connected in parallel, and the first gate driver 23 always operates when the motor is driven, while the second gate driver 24 is in the locked state of the motor M. Works only when The first gate driver 23 and the second gate driver 24 are connected to the switching element T1U via gate resistors 23a and 24a that limit their output current.

  Further, the lock detection circuit 25 detects whether or not the three-phase AC motor M is in a locked state. The logical product of the output of the lock detection circuit 25 and the output of the insulation circuit 22 is output to the second gate driver 24 via the logical product circuit 26. According to such a gate driver circuit, when the three-phase AC motor M is locked, the second gate driver 24 operates in synchronization with the first gate driver 23, and the gate resistor 23a and the gate resistor 24a are equivalent. In parallel.

  Next, the current flowing through the switching element T1U driven by such a gate driver circuit, the voltage between the emitter electrode and the collector electrode, and the loss will be described with reference to FIGS. 10 (a) to 10 (c), respectively. . 10A shows a transition example of the voltage, current, and loss when the switching element T1U is turned on when the three-phase AC motor M is not locked. FIG. 10B shows the three-phase AC. The transition example of the voltage, current, and loss when the switching element T1U is turned off when the motor M is not locked is shown. FIG. 10C shows a transition example of the voltage, current, and loss when the switching element T1U is turned on when the three-phase AC motor M is locked.

  First, when the switching element T1U is turned on when the three-phase AC motor M is not locked, as shown in FIG. 10A, t1 time (turn-on time) until the switching element T1U transitions from the off state to the on state. Is needed. For this reason, when the switching element T1U is turned on, a loss P1 proportional to the turn-on time t1 occurs as shown by the hatched line in FIG.

  When the switching element T1U is turned off when the three-phase AC motor M is not locked, as shown in FIG. 10B, t2 time (turn-off time) is required until the switching element T1U transitions from the on state to the off state. I need it. For this reason, when the switching element T1U is turned off, a loss P2 proportional to the turn-off time t2 occurs as shown by the hatched line in FIG.

  On the other hand, when the switching element T1U is turned on when the three-phase AC motor M is not locked, the first gate driver 23 and the second gate driver 24 operate together as described above, so that the gate resistors 23a and 24a are equivalent. Therefore, the time constant for the switching element T1U is reduced. As a result, the drive capability of the switching element T1U is enhanced, and as shown in FIG. 10C, the turn-on time t3 of the switching element T1U is shorter than the turn-on time t1 (t1> t3). Further, such a loss proportional to the turn-on time t3 also shortens the period in which the voltage and current are simultaneously present between the collector and the emitter as the switching time t3 is shortened, as shown in FIG. 10 (c). The loss P3 of the switching element is also reduced.

  As described above, according to the motor drive control device described in Patent Document 1, when the three-phase AC motor M is locked, the loss of the switching element T1U is reduced by reducing the gate resistance with respect to the switching element T1U. The overheating of the switching element T1U can be suppressed.

JP 2005-117758 A

  By the way, in the inverter device as described above, a surge voltage is generated due to the wiring inductance and the current change when the switching elements constituting the inverter device are turned on and off. Such a surge voltage becomes larger as the turn-on time and turn-off time of the switching element become steeper. That is, even if the gate resistance of each switching element is reduced when the three-phase AC motor M is locked as described above, the surge voltage increases in inverse proportion to the loss of each switching element. For this reason, the gate resistance must be set so that such a surge voltage falls within the range of the breakdown voltage of the switching element, and the loss reduction effect of the switching element through the adjustment of the gate resistance is not sufficient.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a motor that can suitably protect the switching element from overheating by accurately reducing the loss of the switching element when the AC motor is locked. To provide a drive control device.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
The invention according to claim 1 controls the driving of the AC motor based on the converted power while applying a gate voltage to each of the switching elements of the inverter device that performs power conversion to drive the AC motor via a gate resistor. The motor drive control device includes a motor lock detection unit that detects whether or not the AC motor is in a locked state, and the inverter device is based on detection of the locked state of the AC motor by the motor lock detection unit. And reducing the resistance value of the gate resistance to a small value in accordance with a margin of surge voltage generated in correlation with the resistance value of the gate resistance secured through the suppression of the system voltage. The gist.

  As described above, if the system voltage of the inverter device is suppressed and the resistance value of the gate resistance is changed to a small value when the locked state of the AC motor is detected, the system voltage of the inverter device is suppressed. Thus, a margin that can allow the generation of a surge voltage that occurs with the on / off operation of the switching element is secured. For this reason, the gate resistance correlated with the magnitude of the surge voltage can be changed to a small value by the amount that the surge voltage margin is secured. For this reason, the turn-on time or turn-off time of the switching element can be shortened in correlation with the change of the gate resistance of the switching element to a small value. In addition, it is possible to reduce power loss that occurs during turn-off. As a result, even if an excessive DC current flows through the switching element due to the locking of the AC motor, the loss of the switching element can be accurately reduced, and thus the switching element is preferably protected from overheating. To be able to protect.

  According to a second aspect of the present invention, in the motor drive control device according to the first aspect, the resistance value of the gate resistance that is changed based on detection of the lock state of the AC motor is equal to the withstand voltage reference voltage of the switching element. The gist is that the surge voltage generated in correlation with the value of the gate resistance in accordance with the difference from the suppressed system voltage is set to a value that can be maximized within the range of the withstand voltage reference voltage of the switching element.

  According to the above configuration, the resistance value of the gate resistance that is changed in the locked state of the motor is set so that the surge voltage is changed according to the difference between the withstand voltage reference voltage of the switching element and the suppressed system voltage. If it is set to a value that can be maximized within the range, the difference between the withstand voltage reference voltage of the switching element and the suppressed system voltage, in other words, according to the margin that the generation of the surge voltage is allowed. The resistance value of the gate resistance can be set to the minimum value. As a result, it is possible to generate the maximum surge voltage within the range of the withstand voltage reference voltage of the switching element, and consequently, further shortening of the turn-on time / turn-off time of the switching element is realized.

  Further, in order to reduce the power loss of the switching element through the change of the gate resistance, the voltage applied to the switching element can be suitably maintained within the range of the withstand voltage reference voltage of the switching element, The reliability as the motor drive control device is further improved.

  According to a third aspect of the present invention, in the motor drive control device according to the first or second aspect, the gate resistor is a first gate connected in parallel between the circuit for applying the gate voltage and the switching element. The first gate resistor is changed when the first gate resistor is always in a conductive state and the motor lock detecting unit detects the locked state of the AC motor. The gist of the present invention is that the resistor and the second gate resistor are both turned on.

  As in the above configuration, the change of the resistance value of the gate resistor when the AC motor is locked is a switching between the non-conducting state / conducting state of the second gate resistor connected in parallel with the first gate resistor that is always in the conducting state. If so, the switching element is always connected to the circuit for applying the gate voltage via the first gate resistor. For this reason, when changing the resistance value of the gate resistance when the AC motor is locked, the gate charge of the switching element can be reliably discharged through the gate resistance, and the operation as a switching element is achieved. Can be suitably maintained.

  According to a fourth aspect of the present invention, in the motor drive control device according to the first or second aspect, the gate resistance comprises a programmable volume whose resistance value can be adjusted in a plurality of stages, and the change of the gate resistance is as follows: The gist of the invention is that the motor lock detection unit performs a mode in which different resistance values are selected each time when the AC motor lock state is detected and when it is not detected.

  According to the above configuration, by configuring the gate resistor with the programmable volume whose resistance value can be adjusted in a plurality of stages, different resistance values are selected each time when the AC motor is locked and when it is not locked. For this reason, it is possible to selectively change the resistance value of the gate resistance in accordance with the difference between the withstand voltage reference voltage of the switching element and the suppressed system voltage, in other words, the allowance for the generation of the surge voltage. Thus, the resistance value of the gate resistance can be selected with a higher degree of freedom. This makes it easier to set a more desirable resistance value of the gate resistance in order to suppress power loss of the switching element.

  According to a fifth aspect of the present invention, in the motor drive control device according to the first or second aspect, the gate resistor is a first gate connected in parallel between the circuit for applying the gate voltage and the switching element. A second gate resistor having a resistance value lower than that of the first gate resistor, and changing the gate resistance causes the first gate resistor to be in a conductive state when the AC motor is not locked, and the second gate resistor. The resistance is set to a non-conductive state, and the first gate resistor is set to a non-conductive state and the second gate resistor is set to a conductive state when the lock state of the AC motor is detected by the motor lock detection unit. It is a summary.

  According to the above configuration, the change of the resistance value of the gate resistance when the AC motor is locked is performed by switching between the first gate resistance and the second gate resistance having a resistance value lower than the first gate resistance. As a result, the resistance value of the gate resistance can be changed more easily when the AC motor is locked, and the motor drive control device can be configured with a simpler configuration.

  According to a sixth aspect of the present invention, in the motor drive control device according to any one of the first to fifth aspects, the system voltage is suppressed by detecting the locked state of the AC motor by the motor lock detection unit. The gist of the present invention is to suppress the boosting by the boosting converter that boosts the system voltage of the inverter device.

  As in the above configuration, if the suppression of the system voltage of the inverter device when the AC motor is locked is performed as suppression of the boosting by the boost converter, the suppression of the system voltage of the inverter device when the AC motor is locked is suppressed to DC. It can be realized by an existing boost converter such as a DC converter. As a result, not only versatility as the motor drive control device but also structural simplification of the device can be achieved.

  Further, according to the above configuration, the value of the system voltage of the inverter device can be arbitrarily suppressed through the boosting by the boosting converter, so that the surge voltage can be allowed within the range of the withstand voltage reference voltage of the switching element. It is easier to secure. Thereby, in order to suppress the power loss of the switching element by reducing the resistance value of the gate resistance, it becomes possible to ensure the margin from both the change of the resistance value of the gate resistance and the suppression of the system voltage, The power loss of the switching element can be reduced with a higher degree of freedom.

  The invention according to claim 7 is the motor drive control device according to any one of claims 1 to 6, wherein the motor lock detector has a rotation speed of the AC motor in a stop rotation region, and The gist is to detect that the AC motor is in a locked state when the current supplied to the AC motor is equal to or higher than a reference current capable of driving the AC motor.

  Normally, when the AC motor is locked, the rotational speed of the motor is within the range of the stop rotation region even though a current higher than the reference current is supplied to the AC motor. Therefore, as described above, if the lock state of the AC motor is detected based on the rotational speed of the AC motor and the current value supplied to the AC motor, the lock state of the motor can be accurately detected. become able to. Thereby, when changing the resistance value of the said gate resistance at the time of the lock | rock of an alternating current motor, the reliability comes to be improved more.

  The invention according to claim 8 is summarized in that, in the motor drive control device according to any one of claims 1 to 7, the switching element of the inverter device is an insulated gate bipolar transistor.

  The present invention is particularly effective when an insulated gate bipolar transistor (IGBT) is used as a switching element as described above, and the resistance value of the gate resistor connected to the insulated gate bipolar transistor is changed. Through the suppression of the system voltage, the generation of the surge voltage is suppressed within the range of the reference withstand voltage, and the switching speed is improved, and the power loss of the switching element is preferably reduced.

A ninth aspect of the present invention is the motor drive control device according to any one of the first to eighth aspects, wherein the AC motor that is the target of the drive control is a three-phase AC motor that serves as a prime mover of the vehicle. This is the gist.

  In the three-phase AC motor that is the prime mover of the vehicle, the required electric power is particularly large, and at the time of locking, an excessive current flows through the switching element so that the element is overheated. The influence on controllability is also great. In this regard, according to the above configuration, even when the three-phase AC motor is locked, the switching element is improved through the suppression of the system voltage and the change of the gate resistance, and thus the power loss of the switching element is reduced. Thus, the three-phase AC motor can be driven and controlled with higher reliability. As a result, drivability of a vehicle such as an automobile can be well maintained even on a slope.

The block diagram which shows the structure about one Embodiment of the motor drive control apparatus concerning this invention. In the apparatus of the embodiment, (a) is a graph showing the relationship between the resistance value of the gate resistance for each suppressed system voltage and the inter-terminal voltage of the switching element. (B) is a graph showing a transition example of surge voltage generated in correlation with gate resistance. The block diagram which shows the structure about the gate resistance control part of the embodiment. The flowchart which shows the control procedure of the gate resistance by the apparatus of the embodiment. (A)-(c) contrasts the transition of the voltage applied between the terminals of the switching element by the apparatus of the embodiment with the voltage applied between the terminals of the switching element by the conventional motor drive control device. The figure shown under. (D)-(f) is a figure which shows the switching characteristic of the switching element by the apparatus of the embodiment based on contrast with the switching characteristic of the switching element by the conventional motor drive control apparatus. The block diagram which shows the structure of a gate resistance control part about the modification of the said embodiment. The block diagram which shows the structure of a gate resistance control part about the modification of the said embodiment. The block diagram which shows the structure about the conventional motor drive control apparatus. The block diagram which shows the structural example about the gate driver circuit which comprises the conventional motor drive control apparatus. (A)-(c) is a time chart which shows transition of the electric current supplied to the switching element in the conventional motor drive control apparatus, the voltage applied to the element, and the loss of the element.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a motor drive control device according to the present invention will be described below with reference to FIGS. In addition, the motor drive control apparatus of this Embodiment controls the drive of the three-phase alternating current motor which is mounted, for example in a hybrid vehicle etc. and becomes the prime mover similarly to the drive control apparatus of previous FIG.

  FIG. 1 shows a three-phase alternating current based on a conversion power by an inverter circuit INV that converts a direct-current power supplied from a vehicle-mounted battery into a three-phase alternating current or the like and performs power conversion for driving a motor in a hybrid vehicle or an electric vehicle. A schematic configuration of a motor drive control device that controls the drive of a motor M is shown.

As shown in FIG. 1, the applied DC voltage is smoothed between the positive bus bar BBP which is the positive bus and the negative bus bar BBN which is the negative bus in the inverter device constituting the motor drive control device. A smoothing capacitor C and an inverter circuit INV that converts the DC voltage into three-phase AC are connected. In the inverter circuit INV, three switching elements T1U, T3V, T5W constituting the upper arm and three switching elements T2U, T4V, T6W constituting the lower arm are connected in a three-phase bridge. In the present embodiment, insulated gate bipolar transistors are used as the switching elements T1U, T3V, T5W and the switching elements T2U, T4V, T6W.

  The U-phase output electrode, the V-phase output electrode, and the W-phase output electrode, which are connection portions of the emitter electrodes of the switching elements T1U, T3V, and T5W and the collector electrodes of the switching elements T2U, T4V, and T6W, are output lines. It is connected to the U-phase coil, V-phase coil, and W-phase coil of the three-phase AC motor M via OWW, OWV, and OWW. On the other hand, between the switching elements T1U, T3V, T5W, and the emitter and collector electrodes of the switching elements T2U, T4V, T6W, free-wheeling diodes D1U, D3V, D5W, and free-wheeling diodes D2U, which are rectifier elements, respectively. D4V and D6W are connected in reverse parallel.

  In the inverter device configured as described above, the current flowing through the three-phase AC motor M to be driven is detected by the current detection sensors Si1 to Si3, and each detected current value is the driving state of the three-phase AC motor M. Are input to a motor lock detection unit 100 that detects whether or not is in a locked state and an inverter control unit 110 that controls the operation of the inverter device. Further, the rotor rotation position of the three-phase AC motor M detected by the position detection sensor Sm is input to the motor lock detection unit 100 and the inverter control unit 110, respectively.

  Among these, the motor lock detection unit 100 monitors the driving state of the three-phase AC motor M based on the input current values flowing through the three-phase AC motor M and the rotor rotation position of the three-phase AC motor M. More specifically, in the motor lock detection unit 100, based on the detection values of the current detection sensors Si1 to Si3 and the position detection sensor Sm, the rotation speed of the three-phase AC motor M is in the stop rotation region, and the three-phase When the current flowing through the AC motor M is equal to or higher than a reference current that can drive the three-phase AC motor M, it is detected that the three-phase AC motor M is in the locked state. The driving information of the three-phase AC motor M detected by the motor lock detection unit 100 is in the inverter control unit 110 and the gate resistances of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W. Are respectively input to the gate resistance control unit 120 that makes the resistance value variable and the system voltage suppression unit 130 that suppresses boosting of the system voltage of the inverter device.

  On the other hand, in the inverter control unit 110, the switching elements T1U, T3V, T5W, T2U, T4V, T6W based on the current values detected by the current detection sensors Si1 to Si3 and the position detection sensor Sm and the rotor rotation position. Switching patterns are generated, and the operations of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are controlled based on the switching patterns. In the gate resistance control unit 120 constituting the inverter control unit 110, the driving information of the three-phase AC motor M input from the motor lock detection unit 100, that is, whether the three-phase AC motor M is in a locked state. Based on whether or not, the resistance values of the gate resistors of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are changed. That is, the gate resistance control unit 120 is changed so as to decrease the resistance value of each gate resistance when the motor lock detection unit 100 detects the locked state of the three-phase AC motor M.

Further, in the system voltage suppression unit 130 to which the driving information of the three-phase AC motor M from the motor lock detection unit 100 is input, the three-phase AC motor M is in a locked state based on the driving information by the motor lock detection unit 100. When detected, boosting by the boost converter 140 that boosts the system voltage of the inverter device is suppressed. Thus, when the lock state of the three-phase AC motor M is detected by the motor lock detection unit 100, the gate resistance control unit 120 changes the value of each gate resistance to a small value and the system voltage suppression unit 130 The system voltage of the inverter device is suppressed. Thus, when the three-phase AC motor M is locked, the suppressed system voltage is applied to the inverter circuit INV, and the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are changed to small values. Switching operation is performed according to the resistance value of the gate resistor.

  Next, the relationship between the resistance value of the gate resistance of each of the switching elements T1U, T3V, T5W, T2U, T4V, T6W and the inter-terminal voltage when the system voltage of the inverter device is appropriately reduced, and the gate resistance The transition of the surge voltage generated in this way will be described with reference to FIG. In FIG. 2A, curves L0 to L5 indicate terminals of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W when the system voltage of the inverter device is sequentially decreased by the system voltage suppression unit 130. It shows the transition of the inter-voltage. Further, the surge voltage shown in FIG. 2B is an example of the surge voltage generated in correlation with the value of each gate resistance exemplified in FIG.

  That is, as shown by curves L0 to L5 in FIG. 2A, the inter-terminal voltage including the surge voltage of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W has a small resistance value of the gate resistance. As the voltage increases, the surge voltage increases. For example, when the system voltage is not suppressed by the system voltage suppressing unit 130, the surge of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W is shown as a curve L0 in FIG. The inter-terminal voltage including the voltage increases as the resistance value of the gate resistance decreases. When the resistance value of the gate resistance is set to the resistance Ra [Ω], the switching elements T1U, T3V, T5W, T2U, T4V, T6W The withstand voltage reference voltage Vmax is reached. The switching characteristics of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W at this time are such that the maximum value of the surge voltage becomes the voltage Vsa [V] as shown by the solid line Lsa in FIG. Switching takes time Ta. Therefore, if the system voltage is not suppressed by the system voltage suppression unit 130, the voltage across the switching elements T1U, T3V, T5W, T2U, T4V, and T6W is suppressed within the range of the withstand voltage reference voltage Vmax. The shortest time required for switching correlated with the resistance value of the gate resistance is a time Ta as shown in FIG.

Next, when the system voltage is reduced by the system voltage suppression unit 130 by the voltage E1 [V], the inter-terminal voltages of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are also reduced in correlation with this. To come. As a result, as shown by a curve L1 in FIG. 2A, even if the resistance value of the gate resistance is the resistance Ra [Ω], the inter-terminal voltage V1 including the surge voltage of the switching element is equal to the withstand voltage reference voltage Vmax. (V1 <Vmax). For this reason, the difference α1 between the withstand voltage reference voltage Vmax and the inter-terminal voltage V1 (system voltage) suppressed by the system voltage suppressing unit 130 can further allow the generation of a surge voltage caused by the switching operation of the switching element. It can be used as a margin. For this reason, under the same conditions, the inter-terminal voltage including the surge voltage of the switching element is the breakdown voltage reference voltage when the gate resistance is a resistance Rb (Rb <Ra) having a resistance value smaller than the resistance Ra. Vmax is reached. For this reason, when the system voltage is lowered by the voltage E1 [V] along with the locking of the three-phase AC motor M, the gate resistance of the switching element is changed to the resistance Rb having a resistance value smaller than the resistance Ra. Is possible. As a result, the switching characteristics of the switching element when the system voltage is lowered by the voltage E1 [V] in accordance with the lock of the three-phase AC motor M are as shown by the solid line Lsb in FIG. The maximum value is the voltage Vsb [V], and switching takes time Tb. Therefore, the system voltage suppression unit 13
When the system voltage due to 0 is lowered by the voltage E1 [V], the gate resistance of the switching element is changed from the resistance Ra to the resistance Rb having a resistance value smaller than the resistance Ra, thereby reducing the voltage across the terminals of the switching element. The shortest time required for switching correlated with the resistance value of the gate resistance of the switching element while being suppressed within the range of the withstand voltage reference voltage Vmax can be shortened from time Ta to time Tb as shown in FIG. become able to. As described above, the power loss of the switching element is reduced by the increase in the switching speed when the three-phase AC motor M is locked, and consequently the overheating of the switching element is suppressed.

  Further, as shown by curves L2 to L5 in FIG. 2A, when the system voltage of the inverter device by the system voltage suppression unit 130 is further reduced, the withstand voltage reference voltage Vmax of the switching element and the system are accordingly changed. The difference from the voltage is further enlarged. For this reason, when the three-phase AC motor M is locked, the gate resistance is changed from the resistance Rb to the resistance Rc to the resistance in accordance with the difference between the withstand voltage reference voltage Vmax of the switching element and the system voltage that are sequentially expanded by the decrease in the system voltage. It becomes possible to change to a resistance having a small resistance value to Rd. As a result, as indicated by characteristics Lsb, Lsc, and Lsd in FIG. 2B, the maximum value of the surge voltage sequentially increases from voltage Vsb to voltage Vsd, while the time required for switching also increases from time Tb to Td. It will be shortened sequentially.

  Thus, in the present embodiment, when the three-phase AC motor M is locked, the resistance value of the gate resistor is determined according to the difference between the system voltage suppressed by the system voltage suppression unit 130 and the withstand voltage reference voltage of the switching element. Is set to a value that can maximize the surge voltage generated in correlation with the resistance value within the range of the withstand voltage reference voltage of the switching element.

Next, the configuration and operation of a part of the gate resistance control unit 120 constituting the motor drive control device based on the above premise will be described with reference to FIG.
As shown in FIG. 3, the gate resistance control unit 120 includes a gate driving circuit 121 that applies a gate voltage to each of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W and controls the operation thereof. ing. In FIG. 3, for the sake of convenience, the configuration of the switching element T1U among the switching elements T1U, T3V, T5W, T2U, T4V, and T6W is shown as an example. In such a gate drive circuit 121, a gate voltage is applied to the switching element T1U via a transistor M1 made of a P-channel MOSFET and a gate resistor R1, and switching is made via a transistor M2 made of an N-channel MOSFET and a gate resistor R2. The gate charge of the element T1U is discharged.

  In addition, the gate driving circuit 121 is connected to the switching element TIU through the AND circuit 122 in parallel with the transistor M1 and the gate resistor R1, and is connected to the transistor M3 and the gate resistor R3 made of a P-channel MOSFET. Has been. Similarly, a transistor M4 and a gate resistor R4 made of an N-channel MOSFET are connected to the gate driving circuit 121 in parallel with the transistor M2 and the gate resistor R2 through the AND circuit 123 between the switching element TIU. Has been.

On the other hand, the drive information of the three-phase AC motor M from the motor lock detector 100 is input to the input terminals of the AND circuits 122 and 123. Each of the AND circuits 122 and 123 receives a logic level “0” signal when the three-phase AC motor M is not locked, while the motor lock detection unit 100 determines whether the three-phase AC motor M is locked. When detected, a signal of logic level “1” is input. Thus, when the three-phase AC motor M is locked, the gate resistances R1 and R2 and the gate resistances R3 and R4 are in parallel, and the resistance value of the gate resistance with respect to the switching element T1U is equal to that of the three-phase AC motor M. It will be changed to a smaller value than when it is not locked. In the present embodiment, as described above, the resistance values of the gate resistors R1 to R4 depend on the difference between the withstand voltage reference voltage of the switching element TIU and the system voltage suppressed by the system voltage suppression unit 130. The surge voltage generated in correlation with the resistance value when the gate resistors R3 and R4 are in parallel with the gate resistors R1 and R2 is set to a value that can be maximized within the range of the withstand voltage reference voltage of the switching element TIU. ing. In the present embodiment, the switching element T1U is connected to the gate drive circuit 121 via the gate resistors R1 and R2 and the transistors M1 and M2 regardless of whether the three-phase AC motor M is locked or not. It is always connected. Thereby, even when the resistance value of the gate resistance of the switching element TIU is changed, the connection between the switching element T1U and the gate drive circuit 121 can be maintained at all times, and the switching element can be changed in changing the resistance value of the gate resistance. The switching operation of T1U can be guaranteed.

And if the locked state of the three-phase AC motor M is detected by such a motor drive control device,
(A) The system voltage of the inverter device is suppressed by the system voltage suppression unit 130, and the inter-terminal voltages of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are reduced.
(B) The amount of suppression of the inter-terminal voltage of each of the switching elements T1U, T3V, T5W, T2U, T4V, T6W is within the range of the withstand voltage reference voltage of each switching element T1U, T3V, T5W, T2U, T4V, T6W. As a margin for allowing the generation of the surge voltage, the resistance value of the gate resistance of each switching element T1U, T3V, T5W, T2U, T4V, T6W is changed to a small value.
In this manner, the switching elements T1U, T3V, T5W, T2U, T4V, and T6W are switched by the amount that the resistance value of the gate resistance of each switching element T1U, T3V, T5W, T2U, T4V, and T6W is changed to a small value. Increases speed. Thus, the power loss of each switching element T1U, T3V, T5W, T2U, T4V, T6W is reduced, and overheating of each switching element T1U, T3V, T5W, T2U, T4V, T6W is suppressed.

Next, the change mode of the gate resistance described above according to the present embodiment will be summarized with reference to FIG.
As shown in FIG. 4, first, when the three-phase AC motor M is driven, the gate resistors R1 and R2 are turned on, while the gate resistors R3 and R4 are turned off. In S101, the rotational speed N of the three-phase AC motor M is detected.

  When the detected rotation speed N is within the range of the stop rotation area NS, the current I flowing through the three-phase AC motor M is detected (steps S102: YES, S103). When the current I flowing through the three-phase AC motor M is detected in this way, whether or not the detected current I is equal to or greater than a reference current IS that can drive the three-phase AC motor M, that is, the three-phase AC motor M It is determined whether or not the lock state is established (step S104). As a result, when it is determined that the driving state of the three-phase AC motor M is in the locked state, first, the system voltage suppression unit 130 suppresses boosting of the system voltage by the boost converter 140 (step S105). Thus, when the system voltage of the inverter device is suppressed, the conduction state of the gate resistors R1 and R2 is maintained and the gate resistors R3 and R4 are turned on, and the switching elements T1U, T3V, T5W, The resistance value of the gate resistance with respect to T2U, T4V, and T6W is changed to a small value (step S106). On the other hand, when it is determined that the driving state of the three-phase AC motor M is in the unlocked state, only the conductive state of the gate resistors R1 and R2 is maintained, and the nonconductive state of the gate resistors R3 and R4 is maintained. It is maintained (step S107).

  Next, the transition of the voltage between the terminals of the switching element by the motor drive control device of the present embodiment is compared with the transition of the voltage between the terminals of the switching element by the conventional motor drive control device with reference to FIG. To explain. In FIG. 5, FIGS. 5A and 5B show the transition of the voltage across the terminals of the switching element by the conventional motor drive control device, and FIG. 5C shows the motor drive according to the present embodiment. The transition of the voltage between the terminals of the switching element by the control device is shown. 5 (d) and 5 (e) show the power loss of the switching element by the conventional motor drive control device, and FIG. 5 (f) shows the switching by the motor drive control device according to the present embodiment. The power loss of the element is shown.

  As shown in FIG. 5, the maximum value of the inter-terminal voltage including the surge voltage of the switching element during the switching operation of the switching element by a general motor drive control device is the case where the resistance value of the gate resistance is not changed. As shown in FIG. 5A, the voltage Vs1 is obtained. The switching speed of the switching element at this time is time T1 as shown in FIG. 5D, and during the switching operation of this switching element, the power loss P1 as shown by the hatched line in FIG. 5D. Comes to occur.

  Therefore, for example, even if the resistance value of the gate resistance is changed to a small value so as to reduce the loss P1 to the loss P2 (switching speed = time T2) shown in FIG. Since there is a margin that allows only the difference α2 between the system voltage Vsy of the inverter device and the withstand voltage reference voltage Vmax of the switching element to allow the generation of the surge voltage, the surge voltage that correlates with the resistance value of the gate resistance increases. Accordingly, the inter-terminal voltage Vs2 including the surge voltage of the switching element exceeds the withstand voltage reference voltage Vmax (FIG. 5B). For this reason, even if the power loss of the switching element is reduced by changing the resistance value of the gate resistance to a small value, in the end, the conventional motor drive control device has only a surge voltage within the range of the margin α2. The loss reduction effect of the switching element through the adjustment of the gate resistance cannot be said to be sufficient.

  On the other hand, according to the present embodiment, when the three-phase AC motor M is locked, the system voltage is suppressed by the system voltage suppression unit 130 as shown in FIG. The total α3 with α2 is a margin that can allow the generation of the surge voltage. Therefore, when the three-phase AC motor M is locked, it is possible to generate the maximum surge voltage correlated with the gate resistance within the margin α3 (FIG. 5 (f): power loss = P3, Switching speed = time T3), the loss reduction effect of the switching element through the adjustment of the gate resistance is further enhanced.

As described above, according to the motor drive control device according to the present embodiment, the following effects can be obtained.
(1) When the three-phase AC motor M is locked, the system voltage of the inverter device is suppressed, and the resistance value of the gate resistance is reduced by using the suppressed system voltage as a margin for allowing the generation of the surge voltage. It was decided to change the value. For this reason, when the three-phase AC motor M is locked, the switching elements T1U, T3V, T5W, T5W, T5W, T2U, T4V, and T6W are changed to the smaller resistance values of the switching elements T1U, T3V, T5W, T4V, and T6W. , T2U, T4V, T6W switching speed is increased. Thus, when the three-phase AC motor M is locked, even if an excessive current flows through each switching element T1U, T3V, T5W, T2U, T4V, T6W, each switching element T1U, T3V, T5W, T2U, The power loss of T4V and T6W is preferably reduced, and as a result, these elements can be suitably protected from overheating.

(2) The resistance values of the gate resistors R1 to R4 are changed according to the difference between the withstand voltage reference voltage Vmax and the system voltage suppressed by the system voltage suppression unit 130. The surge voltage generated in correlation with the resistance value in parallel with R2 is set to a value that can be maximized within the range of the withstand voltage reference voltage of each switching element T1U, T3V, T5W, T2U, T4V, T6W. . As a result, it is possible to generate the maximum surge voltage within the range of the withstand voltage reference voltage Vmax of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W. As a result, the switching elements T1U, T3V, T5W, T2U, T4V , T6W turn-on time / turn-off time can be further shortened. This also reduces the power loss of the switching elements T1U, T3V, T5W, T2U, T4V, T6W through the change of the resistance value of the gate resistance, and the switching elements T1U, T3V, T5W, T2U, T4V, The voltage applied to T6W can be suitably maintained within the range of the withstand voltage reference voltage Vmax, and the reliability as the motor drive control device can be further improved.

  (3) The change of the resistance value of the gate resistance when the three-phase AC motor M is locked is always in a conductive state between the gate drive circuit 121 and each of the switching elements T1U, T3V, T5W, T2U, T4V, T6W. The gate resistors R3 and R4 connected in parallel with the gate resistors R1 and R2 are switched between the non-conductive state / conductive state. Therefore, when the resistance value of the gate resistance is changed when the three-phase AC motor M is locked, the gate resistance R1 and R2 are used to connect the gate drive circuit 121 and each of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W. A constant connection will be maintained. Accordingly, in order to reduce the power loss of each switching element T1U, T3V, T5W, T2U, T4V, T6W through the change of the resistance value of the gate resistance, the switching elements T1U, T3V, T5W, T2U, T4V, The operation as T6W can be suitably maintained.

  (4) System voltage suppression when the three-phase AC motor M is locked is performed as suppression of boosting by the boost converter 140. For this reason, suppression of the system voltage of the inverter device when the three-phase AC motor M is locked can be realized by the existing boost converter 140 such as a DC-DC converter. As a result, not only versatility as the motor drive control device but also structural simplification of the device can be achieved. In addition, since the system voltage value of the inverter device can be arbitrarily suppressed through the boosting by the boosting converter 140 as described above, it is within the range of the withstand voltage reference voltage Vmax of each switching element T1U, T3V, T5W, T2U, T4V, T6W. Thus, it becomes easier to secure a margin for allowing the surge voltage. Thereby, in order to suppress the power loss of the switching element by reducing the resistance value of the gate resistance when the three-phase AC motor M is locked, both the change of the resistance value of the gate resistance and the suppression of the system voltage are described above. It is possible to ensure a margin and reduce the power loss of the switching element with a higher degree of freedom.

  (5) The driving state of the three-phase AC motor M is monitored based on the rotational speed N of the three-phase AC motor M and the current I flowing through the three-phase AC motor M, and the rotational speed N of the three-phase AC motor M is in the stop rotational range. When the current I supplied to the three-phase AC motor M is equal to or greater than the reference current IS, it is detected that the three-phase AC motor M is in the locked state. As a result, the locked state of the three-phase AC motor M can be accurately detected, and accordingly, the resistance value of the gate resistance can be suitably changed when the three-phase AC motor M is locked. become.

In addition, the said embodiment can also be implemented with the following forms.
The locked state of the three-phase AC motor M is detected based on the rotational speed N of the three-phase AC motor M and the current I supplied to the three-phase AC motor M. However, the temperature of each of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W is monitored, and the temperature increase rate of each of the switching elements T1U, T3V, T5W, T2U, T4V, and T6W monitored is three. It is also possible to detect that the three-phase AC motor M is in the locked state when the phase AC motor M is above the reference temperature increase rate when the phase AC motor M is not locked.

  The gate resistance is constituted by the gate resistance R1 and R2 and the gate resistances R3 and R4 connected in parallel between the gate driving circuit 121 and the switching elements T1U, T3V, T5W, T2U, T4V, and T6W. The change of the gate resistance when the AC motor M is locked is performed by switching between the conductive / nonconductive states of the gate resistors R3 and R4. For example, as shown in FIG. 6 as a diagram corresponding to FIG. 3, the gate resistance is configured by a programmable volume VR whose resistance value can be adjusted in a plurality of stages, and the three-phase AC motor M is locked. The gate resistance may be changed at different times depending on whether the motor lock detector 100 detects the locked state of the three-phase AC motor M or not. According to this configuration, as shown in FIG. 2 (a), the difference between the withstand voltage reference voltage of the switching element and the suppressed system voltage, in other words, the allowance for the generation of the surge voltage is allowed. Accordingly, the resistance value of the gate resistance can be selectively changed, and the resistance value of the gate resistance can be selected with a higher degree of freedom. This makes it easier to set a more desirable resistance value of the gate resistance in order to suppress power loss of the switching element.

  Further, as shown in FIG. 7 as a diagram corresponding to FIG. 3, for example, the gate resistor is connected between the gate drive circuit 121 and each of the switching elements T1U, T3V, T5W, T2U, T4V, T6W. And gate resistors R5 and R6 connected in parallel via SW2, and gate resistors R7 and R8 (R5> R7, R6> R8) having resistance values lower than those of the gate resistors R5 and R6. . That is, in this case, the gate resistance is changed when the three-phase AC motor M is locked, and the switches SW1 and SW2 are switched to the gate resistances R5 and R6 when the three-phase AC motor M is not locked. When the motor lock detection unit 100 detects the locked state of the three-phase AC motor M, the switches SW1 and SW2 are switched to the gate resistors R7 and R8.

  The suppression of the system voltage of the inverter device when the three-phase AC motor M is locked is performed by the boost converter 140 including a DC-DC converter. The present invention is not limited to this, and the motor drive control device may be configured to be able to suppress the system voltage of the inverter device when the three-phase AC motor M is locked, and may be a transformer provided separately from the boost converter 140. It is also possible to suppress the system voltage of the inverter device.

  Insulated gate bipolar transistors are used as the switching elements T1U, T3V, T5W, T2U, T4V, and T6W of the inverter device. In addition to this, as the switching element, it is also possible to use a power MOSFET, a thyristor, or the like.

  In the above embodiment, the target of the drive control is the three-phase AC motor M that is the prime mover of the vehicle, but the target of the drive control is an AC motor as a drive source such as a pump or a blower. May be. In short, the present invention can be applied to any AC motor that is driven and controlled based on the converted power while applying a gate voltage to each of the switching elements of the inverter device that performs power conversion via a gate resistor.

DESCRIPTION OF SYMBOLS 100 ... Motor lock | rock detection part, 110 ... Inverter control part, 120 ... Gate resistance control part, 121 ... Gate drive circuit, 122, 123 ... AND circuit, 130 ... System voltage suppression part, 140 ... Boost converter, M ... Three-phase alternating current Motor, M1, M3 ... transistor (P channel type MOSFET), M2, M4 ... transistor (N channel type MOSFET), R1 to R8 ... gate resistance (R1, R2, R5, R6: first gate resistance, R3, R4, R7, R8: second gate resistance), Sm ... position detection sensor, VR ... programmable volume, INV ... inverter circuit, T1U, T3V, T5W, T2U, T4V, T6W ... switching element (IGBT), Si1-Si3 ... current detection Sensor.

Claims (9)

In a motor drive control device for controlling the drive of the AC motor based on the converted power while applying a gate voltage to each of the switching elements of the inverter device that performs power conversion to drive the AC motor via a gate resistor,
A motor lock detection unit that detects whether or not the AC motor is in a locked state, and suppresses the system voltage of the inverter device based on the detection of the lock state of the AC motor by the motor lock detection unit. A motor drive control device, wherein the resistance value of the gate resistor is changed to a small value in accordance with a margin of a surge voltage generated in correlation with the resistance value of the gate resistor secured through suppression of the system voltage. . The resistance value of the gate resistance that is changed based on the detection of the lock state of the AC motor is correlated with the value of the gate resistance according to a difference between the withstand voltage reference voltage of the switching element and the suppressed system voltage. The motor drive control device according to claim 1, wherein the generated surge voltage is set to a maximum value within a range of a withstand voltage reference voltage of the switching element. The gate resistor includes a first gate resistor and a second gate resistor connected in parallel between the circuit for applying the gate voltage and the switching element, and the change of the gate resistor is performed by changing the first gate resistor. It is carried out in the aspect which makes it always a conduction | electrical_connection state and makes both the said 1st gate resistance and the said 2nd gate resistance a conduction | electrical_connection state, when the lock state of the said AC motor is detected by the said motor lock detection part. The motor drive control device described. The gate resistance is composed of a programmable volume whose resistance value can be adjusted in a plurality of stages, and the change of the gate resistance is detected when the motor lock detection unit detects the lock state of the AC motor and when it is not detected. The motor drive control device according to claim 1 or 2, wherein a different resistance value is selected each time. The gate resistor includes a first gate resistor connected in parallel between the circuit for applying the gate voltage and the switching element, and a second gate resistor having a resistance value lower than that of the first gate resistor. The change of the resistance is such that when the AC motor is not locked, the first gate resistor is turned on and the second gate resistor is turned off, and the lock state of the AC motor is detected by the motor lock detection unit. 3. The motor drive control device according to claim 1, wherein the motor drive control device is performed in such a manner that the first gate resistor is sometimes turned off and the second gate resistor is turned on. The suppression of the system voltage is performed as suppression of boosting by a boost converter that boosts the system voltage of the inverter device when the lock state of the AC motor is detected by the motor lock detection unit. The motor drive control device according to claim 1. The motor lock detection unit is configured such that the AC motor is in a locked state when the rotation speed of the AC motor is in a stop rotation region and the current supplied to the AC motor is equal to or higher than a reference current that can drive the AC motor. The motor drive control device according to any one of claims 1 to 6, wherein the motor drive control device is detected. The motor drive control device according to claim 1, wherein the switching element of the inverter device is an insulated gate bipolar transistor. The motor drive control device according to any one of claims 1 to 8, wherein the AC motor that is a target of the drive control is a three-phase AC motor that is a prime mover of a vehicle.

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