JP2005218299A - Drive control device of alternating current motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive control device of an alternating current capable of efficiently driving an alternating current motor by performing control switching without using a map which necessitates many experiments. <P>SOLUTION: A PWM current control mode and a rectangular wave voltage phase control mode are selectively used by a switch 28. In this state, in the case of operating in the rectangular wave voltage phase mode, when an absolute value ¾ϕi¾ of the real current phase supplied to a motor 38 turns into under an absolute value ¾ϕ0¾ of a predetermined switching current phase, control is switched to a PWM current control mode. The predetermined switching current phase phase ϕ0 is set so that the phase may make the ratio of torque/current to the maximum, for example. On the contrary, in the case of operating in the PWM current control mode, when a voltage amplitude ¾V¾ supplied to a PWM circuit 30 from a current controller 14 exceeds a predetermined switching voltage amplitude V0, the control is switched to the rectangular wave voltage phase control mode. For example, in the predetermined switching voltage amplitude V0, a critical voltage is set so as to perform stably the PWM current control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a drive control device for an AC motor, and more particularly to a device capable of selectively driving voltage phase control such as rectangular wave voltage phase control and PWM voltage phase control and PWM current control to drive the AC motor.

  An inverter is used to drive the AC motor using a DC power source. Such an inverter is switching-controlled by an inverter drive circuit, which generally applies a pulse width modulation (PWM) waveform voltage to the AC motor.

  In PWM current control in which a PWM waveform voltage is applied to an AC motor, smooth rotation can be obtained even in a low rotation range, but there is a problem that the voltage utilization rate of the DC power supply is limited. For this, there is a method of obtaining a high rotation speed by applying a field weakening current to the AC motor, but this is not appropriate because the copper loss increases.

  On the other hand, there is also a method of applying a rectangular wave voltage to the AC motor for driving control of the AC motor. In this control method, the voltage utilization factor of the DC power supply can be improved, and as a result, the output in the high rotation range can be improved. Moreover, since the field weakening current can be reduced, the generation of copper loss can be suppressed and the energy efficiency can be improved. Furthermore, since the frequency | count of switching in an inverter can be decreased, there also exists an advantage that a switching loss can also be suppressed.

  For this reason, it is desirable that both the PWM waveform voltage and the rectangular wave voltage be configured to be applied to the AC motor, and that they are properly used according to the situation, and in particular, the output of the motor in a high rotation range is improved. . Japanese Patent Application Laid-Open No. 55-49996 discloses a technique for selectively applying a PWM waveform voltage and a rectangular wave voltage to an AC motor to improve its output.

JP 55-49996 A

  In such prior art, when the rotational speed of the AC motor exceeds a predetermined value, the AC motor is driven with a rectangular wave voltage, and when it is less than that, the AC motor is driven with a PWM waveform voltage. However, simply switching both controls based on the rotational speed alone cannot always drive an efficient AC motor, and in order to achieve efficient control switching, torque and DC power supply in addition to the rotational speed. The control switching timing must be measured with the voltage taken into account. For this purpose, it is necessary to prepare a three-dimensional map that gives the optimum number of revolutions for control switching by giving torque and a DC power supply voltage, but many experiments are necessary to prepare this map, There is a problem that a lot of time is required.

  The present invention has been made in view of the above-described problems, and the object of the present invention is to provide an AC motor that can perform control switching and drive an efficient AC motor without using a map that requires many experiments. To provide a drive control device.

(1) In order to solve the above-mentioned problem, the present invention includes a PWM current control means for supplying a sine wave current having a predetermined amplitude and a predetermined phase corresponding to a torque command to an AC motor, and the predetermined phase corresponding to the torque command. Voltage phase control means for supplying an alternating current having a phase out of phase to the alternating current motor, and when the alternating current motor is driven by the voltage phase control means, the current phase of the alternating current supplied to the alternating current motor and the predetermined phase A control switching means for starting driving of the AC motor by the PWM current control means instead of the voltage phase control means if the relationship between the advance and delay with the control switching phase corresponding to the phase is reversed. Features.

  According to the present invention, smooth AC motor drive can be obtained by the PWM current control means in the low rotation range, and torque command can be obtained by the voltage phase control means such as PWM voltage phase control and rectangular wave voltage phase control in the high rotation range. The current phase is adjusted with respect to a predetermined phase corresponding to, and field weakening control can be performed to obtain a high output. For this reason, an efficient alternating current motor can be driven. If the relationship between the advance and delay of the current phase and the control switching phase corresponding to the predetermined phase is reversed during driving or braking, the AC motor is switched from the voltage phase control means to the PWM current control means by the control switching means. The control means is switched. Although the control switching phase can vary depending on the torque, the map can be made smaller than the conventional three-dimensional map, and experiments for preparing the map can be reduced.

(2) Further, according to one aspect of the present invention, the predetermined phase corresponding to the torque command is determined such that a torque / current ratio is increased. In this way, the AC motor can be driven with higher efficiency.

(3) Further, in one aspect of the present invention, the switching control unit is configured such that when the AC motor is driven by the PWM current control unit, the amplitude of the AC voltage applied to the AC motor exceeds a predetermined amplitude. The driving of the AC motor by the voltage phase control means is started instead of the PWM current control means. In this way, it is possible to realize efficient control switching from the PWM current control means to the voltage phase control means by setting the predetermined amplitude to the maximum amplitude that can be stably controlled by PWM current control, for example.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing an overall configuration of an AC motor drive control device according to an embodiment of the present invention. The drive control apparatus 10 shown in the figure is mounted on, for example, an electric vehicle, and has two control modes, a PWM current control mode and a rectangular wave voltage phase control mode.

  Here, the PWM current control mode is a control mode executed when the switch 28 is switched to the upper side in the figure, and the current controller 14 is fed back with the current value of the alternating current output from the inverter 36. The voltage amplitude | V | and the voltage phase ψ are set so that it approaches the current amplitude command value | I | and the current phase command value φ, and the pseudo sine wave voltage is supplied to the motor 38 by the PWM circuit 30 and the inverter 36. Apply to.

  On the other hand, the rectangular wave voltage phase control mode is a control mode that is executed when the switch 28 is switched to the lower side in the figure. In this mode, a rectangular wave voltage is applied to the motor 38. The voltage amplitude | V | is determined by the power supply voltage Vdc of the DC power supply of the inverter 36 (not shown), and the voltage phase ψ is set according to the torque command value.

  In the drive control device 10 shown in the figure, a torque command value is generated according to an accelerator opening degree and a brake depression angle by an electronic control unit (ECU) (not shown), and the torque command value is added to the current command generation unit 12. The signal is input in parallel to the device 13. The current command generation unit 12 generates a current amplitude | I | and a current phase φ based on the input torque command value. The current controller 14 performs proportional-integral control, where a voltage amplitude | V | and a voltage phase ψ are generated. Here, the voltage phase ψ is an angle of a voltage vector with respect to the q axis. These voltage amplitude | V | and voltage phase ψ are supplied to the PWM circuit 30. Although not particularly illustrated, a current value is fed back from the current sensor 40 to the current controller 14.

  The PWM circuit 30 generates a switching command by comparing a sine wave having a voltage amplitude | V | and a voltage phase ψ supplied from the current controller 14 with a triangular wave prepared in advance. This switching command is supplied to the inverter 36 via the switch 28. The inverter 36 is a voltage type inverter, and generates a pseudo sine wave voltage based on a switching command supplied from the PWM circuit 30. The pseudo sine wave voltage is supplied to the motor 38.

  The motor 38 is a permanent magnet synchronous (PM) motor. A current sensor 40 is mounted on the power supply line from the inverter 36 to the motor 38, and the real-time actual current phase φi detected there is supplied to the current phase determination unit 22. Although not shown, the current sensor 40 detects a real-time current value and feeds it back to the current controller 14.

  Next, as described above, the torque command value generated by the ECU (not shown) is also input to the adder 13. The adder 13 also receives a real-time torque value detected by the torque detector 20, and generates a torque deviation ΔT that is the difference between the two values. The torque detection unit 20 can be configured using a known torque sensor, but can also be configured to generate torque by executing the calculation shown in the following equation (1).

(Equation 1)
T = Pin / ω
= (Iu × vu + iv × vv + iw × vw) / ω (1)

  Here, Pin represents the power supplied to the motor 38. ω represents the angular velocity of the motor 38. iu, iv, and iw represent the current value of each phase supplied to the motor 38, and vu, vv, and vw represent the voltage value of each phase supplied to the motor 38. For vu, vv, and vw, a voltage command value set in the inverter 36 may be used, or an actual value supplied from the inverter 36 to the motor 38 may be detected by a voltage sensor.

  Alternatively, as shown in the following equation (2), the input power of the inverter 36 may be calculated from the DC current and the DC voltage, and the torque may be calculated and generated.

(Equation 2)
T = Pin / ω
= (IB × VB) / ω (2)

  Here, IB and VB represent the current and voltage of a DC power supply (not shown) connected to the inverter 36.

  The torque deviation ΔT generated by the adder 13 is supplied to the voltage phase controller 18. The voltage phase controller 18 generates a voltage phase ψ according to the torque deviation ΔT. This voltage phase ψ is a phase of a rectangular wave applied to the motor 38. Specifically, the voltage phase controller 18 uses a voltage Vdc of a DC power source (not shown) connected to the inverter 36 and an angular velocity ω of the motor 38 as a parameter when generating the voltage phase ψ, together with the torque deviation ΔT. They are substituted into a predetermined arithmetic expression (or an equivalent process is performed) to generate a necessary voltage phase.

  The rectangular wave generating unit 32 issues a switching command to generate a rectangular wave voltage based on the voltage phase ψ output from the voltage phase controller 18. This switching command is supplied to the inverter 36 via the switch 28. When the switch 28 is switched to the lower side in the figure, a rectangular wave voltage is applied from the inverter 36 to the motor 38. Yes.

  The voltage amplitude determination unit 16 and the current phase determination unit 22 are configured to switch between the PWM current control mode and the rectangular wave voltage phase control mode by switching the switch 28. The voltage amplitude determination unit 16 is configured such that the voltage amplitude | V | supplied from the current controller 14 to the PWM circuit 30 is larger than the predetermined switching voltage amplitude V0 when the drive control device 10 is operating in the PWM current control mode. If it becomes larger, the switch 28 is switched to the lower side in the figure, and the control is switched to the rectangular wave voltage phase control mode. For this predetermined switching voltage amplitude V0, for example, a value obtained by multiplying the voltage of a DC power source (not shown) connected to the inverter 36 by the modulation rate of the inverter 36 is used.

  On the other hand, the current phase determination unit 22 is the absolute value of the phase (actual current phase) φi of the alternating current supplied from the inverter 36 to the motor 38 when the drive control device 10 is operating in the rectangular wave voltage phase control mode. Is smaller than the absolute value of the predetermined switching current phase φ0 (differing between driving and braking), and if it becomes smaller, the switch 28 is switched to the upper side in the figure to enter the PWM current control mode. Switch control. As this predetermined switching current phase φ0, for example, a current phase necessary for realizing the current torque command with the smallest current value, that is, a phase with the largest torque / current ratio is used. A plurality are prepared according to time. The distinction between driving and braking may be determined by, for example, the sign of a torque command.

  Next, the operation of the AC motor drive control device 10 will be described.

  FIG. 2 is a flowchart for explaining the control switching of the drive control apparatus 10. As shown in the figure, the drive control device 10 determines whether the current control is performed under the PWM current control mode or the rectangular wave voltage phase control mode (S101).

  When it is determined that the motor 38 is driven in the PWM current control mode, the voltage amplitude determination unit 16 next outputs the voltage amplitude | V | output from the current controller 14 is equal to or greater than the predetermined switching voltage amplitude V0 described above. Whether or not (S102). Here, if it is determined that the switching voltage amplitude is equal to or greater than the predetermined switching voltage amplitude V0, the voltage amplitude determination unit 16 switches the switch 28 to the lower side in the figure and shifts the control mode to the rectangular wave voltage phase control mode (S105). On the other hand, if it is determined that it is less than the predetermined switching voltage amplitude V0, the voltage amplitude determination unit 16 maintains the state of the switch 28 and continues the operation in the PWM current control mode as it is (S104).

  If it is determined in S101 that the current control mode is the rectangular wave voltage phase control mode, then the current phase determination unit 22 determines that the absolute value | φi | of the actual current phase is the absolute value of the predetermined switching current phase described above. It is determined whether it is less than | φ0 | (S103). If it is determined that the absolute value | φ0 | of the predetermined switching current phase is equal to or larger than the predetermined value, the current phase determination unit 22 maintains the state of the switch 28 and continues the operation in the rectangular wave voltage phase control mode as it is ( S105). Further, when it is determined that the absolute value | φi | of the actual current phase is less than the absolute value | φ0 | of the predetermined switching current phase, the current phase determination unit 22 switches the switch 28 to the upper side in the figure, and the control mode is set to PWM. The process proceeds to the current control mode (S104).

  FIGS. 3-6 is a figure explaining the state of the drive control apparatus 10 before and behind control switching. In these figures, the voltage amplitude | V | is a predetermined initial voltage amplitude Vinit, the absolute value of the current phase | φi | is | φ0 |, the current value is B, and the rotation speed of the motor 38 is zero. . The voltage amplitude | V | is a predetermined switching voltage amplitude V0, the current phase absolute value | φi | is | φ0 |, the current value is B, and the motor rotation speed is N0. Further, let Z be a state where the voltage amplitude | V | is a predetermined switching voltage amplitude V0, the current phase absolute value | φi | is greater than the absolute value | φ0 | of the predetermined switching current phase, and the rotational speed is increased from N0. In these drawings, a solid line connecting the states X to Z represents a constant torque state.

  FIG. 3 shows the relationship between the rotation speed and the voltage amplitude | V | when the operation mode of the drive control device 10 shifts from the PWM current control mode to the rectangular wave voltage phase control mode with a constant torque. In the figure, when the rotational speed gradually increases from the state X, the back electromotive force of the motor 38 increases accordingly. To counter this, the voltage amplitude | V | At this time, the drive control device 10 is in the PWM current control mode, and the current phase φ is set to a value that maximizes the torque / current ratio (this value corresponds to the predetermined switching current phase φ0).

  FIG. 4 is a diagram showing the current-torque characteristics of the PM motor. In the figure, the broken lines indicate the absolute value of torque and the absolute value of current phase | φi | at current values A to C (A> B> C), respectively. Represents the relationship. However, the phase | φi | indicates that the phase angle of the permanent magnet magnetic flux complex number of the winding at no load is 0 °. A curve 51 formed by connecting the tops of the broken lines represents a current phase for achieving a certain motor torque with a minimum current value. Here, since the states X and Y are plotted on the curve 51, in the PWM current control mode until the state changes from X to Y, the motor 38 is driven in the state where the energy efficiency is the best. I understand that.

  Returning to FIG. 3, when the voltage amplitude | V | and the absolute value | φi | of the current phase gradually increase from the state X, the voltage amplitude | V | reaches the predetermined switching voltage amplitude V0. In this drive control device 10, the switch 28 is switched at this timing, and the control mode is shifted to the rectangular wave voltage phase control mode. FIG. 5 is a diagram showing the current-voltage characteristics of the PM motor, where the horizontal axis represents the absolute value of the current phase | φi |, and the vertical axis represents the voltage constant (motor voltage per rotation of the motor 38). Also, in the figure, the wavy line represents the relationship between the absolute value of the current phase | φi | As shown in FIGS. 5 and 4, after reaching the state Y from the state X, the absolute value of the current phase is increased while gradually increasing the current value from B to A in order to increase the rotational speed of the motor 38. φi | is gradually increased from the absolute value | φ0 | of the predetermined switching current phase. Thereby, even if the rotation speed increases, the voltage amplitude can be suppressed to V0. The state of the drive control device 10 reaches Z.

  Next, the case where the torque is changed from the state Z in the rectangular wave voltage phase control mode to the state X in the PWM current control mode will be described. FIG. 6 is a diagram showing the relationship between the rotational speed of the motor 38 and the absolute value | φi | of the current phase when shifting from the state Z to the state X with a constant torque. In this figure, the state Z is under the rectangular wave voltage phase control mode, and the absolute value | φi | of the current phase is larger than the absolute value | φ0 | of the predetermined switching current phase. When the rotational speed gradually decreases from the state Z to the state Y and the absolute value | φi | of the current phase becomes small and reaches the same value as the absolute value | φ0 | of the predetermined current phase, The phase determination unit 22 switches the switch 28 to shift the operation of the drive control device 10 to the PWM current control mode. Thereafter, as described above, in the PWM current control mode, the current phase φi is maintained at a value at which the torque / current ratio is maximum, that is, the predetermined switching current phase φ0, and the rotational speed is reduced to zero.

  According to the AC motor drive control device 10 described above, the time for preparing a map for determining the switching timing can be reduced. In the PWM current control mode, the motor 38 is operated in a state where the motor current is minimum. In the rectangular wave voltage phase control mode, the motor voltage is maximized, so that the output can be improved and the output efficiency can be maintained. Since the optimum control method is automatically selected according to the operating state of the motor 38, the motor 38 can always be operated efficiently and high output can be obtained.

  The AC motor drive control device 10 described above can be variously modified. For example, in the above description, rectangular wave voltage phase control is adopted as voltage phase control, but PWM voltage phase control may be adopted.

  FIG. 7 is a diagram showing an overall configuration of an AC motor drive control device 50 operable in both the PWM current control mode and the PWM voltage phase control mode. In the figure, the same components as those of the drive control apparatus 10 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted here.

  The main difference from the drive control device 10 shown in FIG. 1 is that the voltage amplitude | V | and the voltage phase ψ supplied to the PWM circuit 30 are supplied from the current controller 14, the voltage amplitude controller 15 and the voltage phase. The state supplied from the controller 18 is switched by the switch 35. Here, when the voltage amplitude controller 15 shifts from the PWM current control mode to the PWM voltage phase control mode, the voltage amplitude | V | Output, and thereafter the value is increased or decreased to supply the voltage amplitude | V | to the switch 35.

  Even when the drive control device 50 according to this modification is used, the optimum control method is automatically selected according to the operation state of the motor 38, and the motor 38 can be operated efficiently.

  In addition, in the above description, the predetermined switching voltage amplitude V0 and the predetermined switching current phase φ0 that define the control switching timing are set to the optimum values in consideration of the operation efficiency of the motor 38. Even if it deviates to some extent from the value, there is no practical problem.

It is a figure which shows the whole structure of the drive control apparatus of the alternating current motor which concerns on embodiment of this invention. It is a flowchart explaining the control switching in the drive control apparatus of the alternating current motor which concerns on embodiment of this invention. It is a figure explaining the state of the drive control apparatus before and behind control switching. It is a figure explaining the state of the drive control apparatus before and behind control switching. It is a figure explaining the state of the drive control apparatus before and behind control switching. It is a figure explaining the state of the drive control apparatus before and behind control switching. It is a figure which shows the whole structure of the drive control apparatus of the alternating current motor which concerns on a modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,50 Drive control apparatus, 12 Current command production | generation part, 13 Adder, 14 Current controller, 15 Voltage amplitude controller, 16 Voltage amplitude determination part, 18 Voltage phase controller, 20 Torque detection part, 22 Current phase determination part , 28, 35 switch, 30 PWM circuit, 36 inverter, 38 motor, 40 current sensor, 51 (optimum phase) curve.

Claims (3)

PWM current control means for supplying a sine wave current having a predetermined amplitude and a predetermined phase according to the torque command to the AC motor;
Voltage phase control means for supplying an alternating current having a phase out of the predetermined phase according to a torque command to the alternating current motor;
When the AC motor is driven by the voltage phase control means, if the relationship between the advance and delay between the current phase of the AC current supplied to the AC motor and the control switching phase corresponding to the predetermined phase is reversed, Control switching means for starting driving of the AC motor by the PWM current control means instead of the voltage phase control means;
A drive control device for an AC motor, comprising: In the drive control apparatus of the alternating current motor according to claim 1,
The drive control device for an AC motor, wherein the predetermined phase corresponding to the torque command is determined so that a torque / current ratio is increased. In the drive control apparatus of the alternating current motor according to claim 1 or 2,
When the AC motor is driven by the PWM current control means, the switching control means replaces the PWM current control means with the voltage phase when the amplitude of the AC voltage applied to the AC motor exceeds a predetermined amplitude. A drive control device for an AC motor, wherein the drive of the AC motor by a control means is started.

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