JP2017184396A - Voltage inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a configuration capable of suppressing reduction in motor performance while reducing a switching loss and a current distortion factor of a current flowing in the motor, in a voltage inverter device.SOLUTION: A voltage inverter device 1 comprises: a current deviation vector calculation unit 21 that calculates a current deviation vector on the basis of current deviation between a current command at a plurality of phases and an output current of a motor 2; a voltage vector setting unit 23 that sets a voltage vector on the basis of the current deviation vector, and sets the voltage vector to a zero voltage vector in a case where a magnitude of the current deviation vector is equal to or less than a predetermined value; and a current command correction unit 60 that corrects the current command by a current command correction value so as to reduce an induction voltage generated at the motor 2 in a case where the voltage vector is the zero voltage vector.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a voltage source inverter device that outputs a voltage to a motor by driving a plurality of switching elements according to voltage vectors generated based on a plurality of phase current commands.

  2. Description of the Related Art Conventionally, a voltage-type inverter device that outputs a voltage to a motor by driving a switching element according to a voltage vector is known. As such a voltage source inverter device, for example, Patent Literature 1 discloses a current current deviation which is a difference between a current output voltage vector, a previous output voltage vector, an instantaneous value of an output current of the inverter device, and a command value. A configuration for selecting an optimum output voltage vector based on the vector is disclosed.

  Specifically, in the configuration disclosed in Patent Document 1, an output voltage vector (target voltage vector) required to make the output current coincide with the command value based on the current output voltage vector and the previous output voltage vector. And the switching element is driven and controlled by selecting an optimum output voltage vector based on the estimated output voltage vector region and the current deviation vector.

  With the configuration of Patent Document 1 as described above, it is not necessary to perform a differential operation, the configuration of the apparatus can be simplified, and control without being affected by noise or delay due to a filter can be performed.

Japanese Patent Laid-Open No. 1-259761

  By the way, in the configuration disclosed in Patent Document 1 described above, an optimum output voltage vector is selected based on the estimated output voltage vector region and a current deviation vector (current deviation vector). The switching element performs a switching operation. As described above, the switching element performs a switching operation according to the optimum output voltage vector, so that a voltage is always output to the motor. Therefore, the state where the voltage is applied to the motor continues. In this state, since the current flowing through the motor frequently changes, a switching operation corresponding to the optimum output voltage vector is performed each time. As a result, the frequency of the switching operation is increased, the loss (switching loss) due to this increases, and the current distortion rate of the current flowing through the motor is increased, resulting in distortion of the current waveform.

  On the other hand, instead of continuing to apply a voltage to the motor, it is conceivable to reduce the frequency of the switching operation of the switching element by setting the voltage applied to the motor to zero within a range that does not significantly affect the performance of the motor.

  However, when the motor is rotating, an induced voltage is generated in the motor. Therefore, even when the voltage applied to the motor is zero, a reflux current flows through the motor and the inverter device. Therefore, when the voltage applied to the motor is zero within a range that does not significantly affect the performance of the motor as described above, a reflux current flows through the motor while the voltage is zero. This reflux current is a sinusoidal current as shown in FIG. 12 and flows in each phase of the motor, so that an unintended torque is generated in the motor.

  Thus, when the return current flows through the motor, the torque generated in the motor is a regenerative torque (brake torque), which is a torque in a direction to stop the rotation of the motor. When such torque is generated in the motor, the motor rotation is affected, and the performance of the motor is reduced.

  An object of the present invention is to obtain a configuration capable of suppressing a decrease in control performance of a motor while reducing an inverter loss and a current distortion rate of a current flowing through the motor in a voltage source inverter device.

  A voltage source inverter device according to an embodiment of the present invention is a voltage source inverter device that outputs a voltage to a motor by driving a switching element according to a voltage vector generated based on a plurality of phase current commands. . The voltage source inverter device includes: a current deviation vector calculation unit that obtains a current deviation vector based on a current deviation between the current command and the output current of the motor in the plurality of phases; and the voltage vector based on the current deviation vector. When the magnitude of the current deviation vector is equal to or less than a predetermined value, a voltage vector setting unit that sets the voltage vector to a zero voltage vector; and A current command correction unit that corrects the current command with a current command correction value so as to reduce the generated induced voltage (first configuration);

  With the above configuration, when the magnitude of the current deviation vector is equal to or smaller than a predetermined value, the voltage vector is set to the zero voltage vector even if the current deviation vector changes. Therefore, the gradient of the current change becomes gentle, and it is easy to continue the state where the magnitude of the current deviation vector is equal to or less than a predetermined value. Thereby, the switching frequency of a switching element can be reduced and a switching loss can be reduced. Therefore, loss generated in the voltage source inverter device can be reduced, and the current distortion rate of the current flowing through the motor can be reduced. The number of times of switching means the amount of change when the switching state of the switching element output this time is compared with the switching state of the switching element output last time.

  As described above, by setting the voltage vector to the zero voltage vector, the voltage output from the voltage source inverter device to the motor becomes zero, but the motor has a reflux current due to the induced voltage generated by the rotation. Because it flows, regenerative torque is generated.

  On the other hand, by correcting the current command with the current command correction value so as to reduce the return current (regenerative current) generated in the motor when the voltage vector is a zero voltage vector as in the above-described configuration, The regenerative torque generated in the motor can be reduced.

  Therefore, it is possible to realize the configuration of the voltage source inverter device that can suppress the deterioration of the motor performance while reducing the switching loss and the current distortion rate of the current flowing through the motor.

  In the first configuration, the current command correction value is a power running torque command that cancels a torque generated in the motor when the voltage vector is a zero voltage vector (second configuration).

  Thereby, the regenerative torque which generate | occur | produces in this motor can be reduced in the state where the voltage is not applied to the motor. Therefore, it is possible to prevent the rotation of the motor from being inhibited by the regenerative torque due to the induced voltage generated in the motor.

  In the second configuration, the current command correction value is obtained by coordinate-transforming the predetermined value (third configuration).

  In this way, by setting the current command correction value in accordance with the current deviation vector range (below the predetermined value) that sets the voltage vector to the zero voltage vector, it is generated in the motor when the voltage vector is the zero voltage vector. The reflux current to be performed can be more reliably reduced.

  In the first configuration, the current command correction value is a field weakening command that weakens the field magnetic flux of the motor when the voltage vector is a zero voltage vector (fourth configuration).

  Thus, the induced voltage generated in the motor can also be reduced by using the field weakening command that weakens the field magnetic flux of the motor as the current command correction value.

  According to the voltage source inverter device of one embodiment of the present invention, in the configuration in which the voltage vector is set to the zero voltage vector when the magnitude of the current deviation vector is a predetermined value or less, the voltage vector is a zero voltage vector. The current command is corrected by the current command correction value so as to reduce the return current generated in the motor. As a result, it is possible to prevent a reduction in the control performance of the motor while reducing the switching loss and the current distortion rate of the current flowing through the motor.

FIG. 1 is a control block diagram illustrating a schematic configuration of the voltage source inverter device according to the embodiment. FIG. 2 is a circuit diagram showing a schematic configuration of the gate circuit. FIG. 3 is a diagram illustrating a voltage vector generated by the voltage source inverter device according to the embodiment. FIG. 4 is a diagram showing a coordinate system for converting a three-phase current deviation into two axes in the current deviation vector diagram. FIG. 5 is a diagram showing each region in the current deviation vector diagram. FIG. 6 is a diagram illustrating an example of a current deviation vector in the current deviation vector diagram. FIG. 7 is a voltage vector diagram showing an example of a voltage vector being output in the reflux mode, and (b) a voltage vector diagram showing an example of a voltage vector set by the voltage vector setting unit. FIG. 8 shows (a) a voltage vector diagram showing an example of a voltage vector determined in accordance with the voltage vector and the current deviation vector being output, and (b) a voltage vector set by the voltage vector setting unit in the steady mode. It is a voltage vector diagram which shows an example. 9A is a diagram illustrating an example of a current deviation vector, and FIG. 9B is a voltage vector diagram illustrating an example of a voltage vector set by a voltage vector setting unit. FIG. 10 is a flowchart showing the operation of the voltage vector setting unit. 11A is a diagram illustrating an example of a three-phase switching pattern and a motor current waveform in a conventional configuration, and FIG. 11B is a diagram illustrating an example of a three-phase switching pattern and a motor current waveform in the configuration of the present embodiment. FIG. FIG. 12 is a diagram illustrating an example of a waveform of a current flowing through the motor in a state where no voltage is applied to the motor. FIG. 13 shows an example of a current waveform that flows through the motor when no voltage is applied to the motor when (a) the current command value is not corrected and (b) the current command value is corrected. FIG. FIG. 14 is a diagram corresponding to FIG. 1 illustrating a schematic configuration of a voltage source inverter device according to another embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

(overall structure)
FIG. 1 is a control flow diagram showing a schematic configuration of a voltage source inverter device 1 according to an embodiment of the present invention. The voltage source inverter device 1 generates a voltage vector based on a plurality of phase current commands, and drives a plurality of switching elements 31, 32, 41, 42, 51, 52 in accordance with the voltage vector, thereby 2 is a device that outputs voltage. The motor 2 is a three-phase AC motor.

  The voltage source inverter device 1 includes a current command generation unit 11, a two-phase three-phase conversion unit 12, a voltage vector generation unit 13, a gate command generation unit 14, a gate circuit 15, and a three-phase two-phase conversion unit 16. The torque estimation unit 17 and the current command correction unit 60 are provided.

The current command generator 11 receives a torque command Trq ^* from the outside. The current command generator 11 generates d-axis and q-axis current commands Id ^* and Iq ^* based on the input torque command Trq ^* .

Current command correction unit 60, with respect to the current command Iq ^* of the q-axis output from the current command generation unit 11, by applying the current command correction value _{Iq oft,} corrects the current command Iq ^*. Current command correction unit 60, as will be described later in detail, the voltage vector so as to reduce the induced voltage generated in the motor 2 during the zero voltage vector, and corrects the current command Iq ^* by using the current command correction value Iq _oft . A detailed configuration of the current command correction unit 60 will be described later.

The two-phase / three-phase conversion unit 12 converts the d-axis and q-axis current commands corrected by the current command correction unit 60 into three-phase current commands Iu ^* , Iv ^* , and Iw ^* . Specifically, the two-phase / three-phase conversion unit 12 uses the corrected d-axis and q-axis current commands and the current phase angle output from the sensor 2a of the motor 2 to use the U-phase, V-phase, and W-phase. Current commands Iu ^* , Iv ^* , Iw ^* are generated.

The voltage vector generation unit 13 calculates a current deviation vector using the three-phase current commands Iu ^* , Iv ^* , Iw ^* and the three-phase output currents Iu, Iv, Iw of the motor 2, and A voltage vector is set according to the region to which the current deviation vector belongs. The voltage vector generation unit 13 outputs the set voltage vector as a voltage vector command Vect.

  The voltage vector generation unit 13 includes a current deviation calculation unit 20, a current deviation vector calculation unit 21, a current deviation vector region determination unit 22, a voltage vector setting unit 23, and a storage unit 24. The detailed configuration of the voltage vector generation unit 13 will be described later.

  The gate command generation unit 14 generates gate commands Up, Un, Vp, Vn, Wp, and Wn for driving the gate circuit 15 based on the voltage vector command Vect output from the voltage vector generation unit 13. The gate command generator 14 gives commands to switching elements 31, 32, 41, 42, 51, 52 of switching arms 30, 40, 50, which will be described later, of the gate circuit 15 in each phase of the U phase, the V phase, and the W phase. Generate.

  Specifically, the gate command generation unit 14 includes a gate command Up for the upper-arm switching element 31 in the U-phase switching arm 30, a gate command Un for the lower-arm switching element 32, and a V-phase switching arm 40. Gate command Vp for upper arm switching element 41, gate command Vn for lower arm switching element 42, gate command Wp for upper arm switching element 51 in W phase switching arm 50, and lower arm switching element 52 A gate command Wn is generated and output.

  Note that the gate commands Up, Un, Vp, Vn, Wp, and Wn generated by the gate command generation unit 14 include signals that turn each switching element on or off.

  The gate circuit 15 includes a plurality of switching elements 31, 32, 41, 42, 51, and 52 that constitute a three-phase bridge circuit. Specifically, as shown in FIG. 2, the gate circuit 15 includes switching arms 30, 40, and 50 connected to the U phase, V phase, and W phase of the motor 2, respectively. In the switching arm 30, a pair of switching elements 31 and 32 are connected in series. Similarly, in the switching arm 40, a pair of switching elements 41 and 42 are connected in series. Similarly, in the switching arm 50, a pair of switching elements 51 and 52 are connected in series.

  Note that one switching element 31, 41, 51 in the switching arm 30, 40, 50 corresponds to the upper arm of the switching arm 30, 40, 50, respectively. The other switching elements 32, 42, and 52 in the switching arms 30, 40, and 50 correspond to the lower arms of the switching arms 30, 40, and 50, respectively.

  In the present embodiment, the switching elements 31, 32, 41, 42, 51, 52 are, for example, IGBTs. Note that the switching elements 31, 32, 41, 42, 51, and 52 may be other switching devices such as MOSFETs.

  Diodes 31a, 32a, 41a, 42a, 51a, 52a are provided in parallel in the switching elements 31, 32, 41, 42, 51, 52, respectively. The diodes 31 a, 32 a, 41 a, 42 a, 51 a, 52 a are provided so as to allow a current flow in the direction opposite to the current flowing through the switching elements 31, 32, 41, 42, 51, 52. The diodes 31a, 32a, 41a, 42a, 51a, and 52a are so-called reflux diodes.

The switching elements 31, 32, 41, 42, 51, 52 of the gate circuit 15 are turned on or off according to the gate commands Up, Un, Vp, Vn, Wp, Wn output from the gate command generator 14, respectively. It is configured to be in an OFF state. FIG. 3 shows a voltage vector diagram of the output voltage of the gate circuit 15. In FIG. 3, V ₀ and V ₇ are zero voltage vectors in which no potential difference occurs in each phase. In FIG. 3, a voltage is generated in the U phase at V ₁ , a voltage is generated in the V phase at V ₂ , and a voltage is generated in the W phase at V ₄ .

  In the following description, when the ON / OFF state of the switching elements 31, 32, 41, 42, 51, 52 is indicated according to each voltage vector, the upper arm switching element is in the ON state, and the lower arm switching is performed. The element is in the OFF state “1”, the upper arm switching element is in the OFF state, and the lower arm switching element is in the “ON” state. Then, the voltage vector is expressed by a three-digit number in which the W-phase switching state is the third digit, the V-phase switching state is the second digit, and the U-phase switching state is the first digit.

For example, in the case of the voltage vector V ₁ , it is expressed as V ₁ = [001]. In this case, the switching element of each arm is such that the switching element of the upper arm of the W phase is OFF, the switching element of the lower arm of the W phase is ON, the switching element of the upper arm of the V phase is OFF, and The switching element of the lower arm of the V phase is in the ON state, the switching element of the upper arm of the U phase is in the ON state, and the switching element of the lower arm in the W phase is in the OFF state. The zero voltage vectors are for V ₀ and V ₇ , V ₀ = [000] (all switching elements of the lower arm of each phase are in the ON state), V ₇ = [111] (upper arm of each phase) The switching elements are all turned on).

  As shown in FIG. 1, the three-phase to two-phase converter 16 converts the output currents Iu and Iw of the motor 2 into a d-axis current Id and a q-axis current Iq. Specifically, the three-phase to two-phase converter 16 obtains a d-axis current Id and a q-axis current Iq based on the U-phase current Iu and the W-phase current Iw of the motor 2.

  The torque estimation unit 17 estimates the output torque of the motor 2 using the d-axis current Id and the q-axis current Iq output from the three-phase / two-phase conversion unit 16.

(Voltage vector generator)
Next, the configuration of the voltage vector generation unit 13 will be described in detail with reference to FIGS. 1 and 4 to 9.

  As described above, the voltage vector generation unit 13 includes a current deviation calculation unit 20, a current deviation vector calculation unit 21, a current deviation vector region determination unit 22, a voltage vector setting unit 23, and a storage unit 24. .

The current deviation calculation unit 20 uses the three-phase current commands Iu ^* , Iv ^* , Iw ^* and the three-phase output currents Iu, Iv, Iw of the motor 2 to calculate the current deviations Δiu, Δiv, Δiw of each phase. calculate.

Specifically, the current deviation calculation unit 20 obtains three-phase current deviations Δiu, Δiv, Δiw by the following formula.
Δiu = Iu ^* −Iu
Δiv = Iv ^* −Iv
Δiw = Iw ^* −Iw

  The current deviation vector calculation unit 21 obtains a current deviation vector using the current deviations Δiu, Δiv, Δiw of each phase calculated by the current deviation calculation unit 20. Specifically, the current deviation vector calculation unit 21 obtains the magnitude of the current deviation vector using the current deviations Δiu, Δiv, Δiw.

Specifically, the current deviation vector calculation unit 21 converts the three-phase current deviations Δiu, Δiv, Δiw into the biaxial current deviations Δiα, Δiβ as shown in FIG. By obtaining the sum of the squares, Δi ² corresponding to the magnitude of the current deviation vector is calculated.
Δiα = √ (3/2) × Δiu
Δiβ = √ (1/2) × (Δiv−Δiw)
Δi ² = (Δiα ² + Δiβ ² )

  The current deviation vector region determination unit 22 uses the three-phase current deviations Δiu, Δiv, Δiw calculated by the current deviation vector calculation unit 21 to determine which current deviation vector is in the current deviation vector diagram as shown in FIG. It is determined whether it belongs to the area. Here, as shown in FIG. 5, when the region is divided by 60 degrees in the current deviation vector diagram, it is determined which region A1 to A6 the current deviation vector belongs to.

  Specifically, the current deviation vector region determination unit 22 obtains a difference in absolute value of the current deviation between two phases among the three-phase current deviations Δiu, Δiv, Δiw, and determines whether the difference is 0 or more. After narrowing down the region to which the current deviation vector belongs, the region to which the current deviation vector belongs is specified according to whether the three-phase current deviations Δiu, Δiv, Δiw are 0 or more.

  For example, if | Δiu | − | Δiv | ≧ 0, | Δiv | − | Δiw | ≧ 0 and | Δiw | − | Δiu | <0, the current deviation vector is in the region A1 or the region A4 in FIG. Belongs. If Δiu ≧ 0, the current deviation vector belongs to the area A1 in FIG. 5, and if Δi <0, the current deviation vector belongs to the area A4 in FIG.

  The voltage vector setting unit 23 determines the switching mode when the switching elements 31, 32, 41, 42, 51, and 52 of the gate circuit 15 operate, and the current deviation vector in the determined mode and current deviation vector diagram. A voltage vector is set in accordance with the region to which.

  Specifically, the voltage vector setting unit 23 determines the switching mode using the magnitude of the current deviation vector X as shown in FIG. In the present embodiment, the voltage vector setting unit 23 determines whether or not the magnitude of the current deviation vector is equal to or smaller than a first predetermined value P (predetermined value) and is equal to or smaller than a second predetermined value Q that is larger than the first predetermined value P. Determine whether or not. In the example shown in FIG. 6, the current deviation vector X (thick line arrow in FIG. 6) is greater than or equal to the first predetermined value P and smaller than the second predetermined value Q.

  The first predetermined value P is set to the magnitude of the current deviation vector that does not significantly affect the output of the motor 2. Further, the second predetermined value Q is given to the switching loss and the current distortion ratio rather than the influence to the output of the motor 2 in consideration of the influence on the output of the motor 2 and the influence on the switching loss and the current distortion ratio. The magnitude of the current deviation vector is set such that the influence becomes larger.

When the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the voltage vector setting unit 23 sets the switching mode to the reflux mode. Specifically, when the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the voltage vector setting unit 23 sets the output voltage vector to one of zero voltage vectors V ₀ and V ₇ .

  When the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the difference between the current command and the output current of the motor 2 is not so large. In this state, when the voltage vector is generated to drive the switching elements 31, 32, 41, 42, 51, and 52 of the gate circuit 15, the number of times of switching increases, so that the switching loss increases and the current distortion rate also increases. Become.

On the other hand, as described above, the number of switching of the switching elements 31, 32, 41, 42, 51, and 52 can be reduced by setting the voltage vector to any one of the zero voltage vectors V ₀ and V _7. . Therefore, the switching loss can be reduced and the current distortion rate can be reduced.

As described above, by setting the voltage vector to one of the zero voltage vectors V ₀ and V ₇ , in the gate circuit 15, the switching elements 31, 32, 41, 42, 51, 52 have no potential difference between the phases. Operate. Specifically, the switching elements 31, 41, 51 on the upper arms of the switching arms 30, 40, 50 of the gate circuit 15 are all turned on or off. In this state, no voltage is output from the voltage source inverter device 1 to the motor 2. On the other hand, as described above, the switching elements 31, 32, 41, 42, 51, 52 of the gate circuit 15 are opposite to the direction of the current flowing through the switching elements 31, 32, 41, 42, 51, 52, respectively. Diodes 31a, 32a, 41a, 42a, 51a, 52a are connected in parallel so as to allow current flow in the direction. Therefore, a reflux current flows through the motor 2 and the gate circuit 15 due to an induced voltage generated as the motor 2 rotates.

As described above, by setting the voltage vector to one of the zero voltage vectors V ₀ and V ₇ when the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the switching elements 31, 32, 41, 42 are set. , 51, 52 can be reduced, and when the voltage output to the motor 2 is zero, a reflux current flows due to an induced voltage generated in the motor 2. Thereby, the waveform of the current flowing through the motor 2 becomes a waveform with less distortion due to the switching operation of the switching elements 31, 32, 41, 42, 51, 52. Therefore, with the above-described configuration, the current distortion rate of the current flowing through the motor 2 can be more effectively reduced.

In addition, when the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the voltage vector setting unit 23 selects the voltage vector to be output from the zero voltage vectors V ₀ and V ₇ as the voltage vector being output (finally When changing from the set voltage vector) to the zero voltage vector, the zero voltage vector is set such that the switching frequency of the switching elements 31, 32, 41, 42, 51, 52 is minimized. Information on the voltage vector being output is stored in the storage unit 24 described later. The voltage vector setting unit 23 reads information on the voltage vector being output from the storage unit 24 when setting the voltage vector to be output using the voltage vector being output.

For example, as shown in FIG. 7, when the voltage vector being output is V ₁ = [001] ((a) in FIG. 7), if the magnitude of the current deviation vector is equal to or less than the first predetermined value P, The output voltage vector is set to zero voltage vector V ₀ = [000] (FIG. 7B). Similarly, when the voltage vector being output is V ₃ = [011], if the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the output voltage vector is zero voltage vector V ₇ = [111]. ] Is set.

  In the present embodiment, the number of times of switching is defined as the number of times any one of the switching elements 31, 32, 41, 42, 51, 52 is switched from the ON state to the OFF state, or from the OFF state to the ON state. The total number of times of switching of all the switching elements 31, 32, 41, 42, 51, 52 of the gate circuit 15 is obtained.

  As described above, a zero voltage vector is selected such that the number of switching arms 30, 40, 50 operating in the gate circuit 15 (the number of times of switching) is minimized when the voltage vector being output is changed to the zero voltage vector. Thereby, the switching frequency of the switching elements 31, 32, 41, 42, 51, and 52 of the gate circuit 15 can be further reduced. Thereby, the loss caused by the switching operation can be further reduced, and the current distortion rate of the current flowing through the motor 2 can be further reduced.

  When the current deviation vector is larger than the first predetermined value P and equal to or smaller than the second predetermined value Q, the voltage vector setting unit 23 sets the switching mode to the steady mode. Specifically, when the magnitude of the current deviation vector is greater than the first predetermined value P and less than or equal to the second predetermined value Q, the voltage vector setting unit 23 includes a region to which the output voltage vector and the current deviation vector belong. Based on the above, a voltage vector is set.

  In the steady mode, the voltage vector setting unit 23 changes the voltage vector being output to a voltage vector determined according to the region to which the current deviation vector belongs (when the vector transitions) as follows. Set the output voltage vector.

In the voltage vector diagram of V _{0 to} V ₇ shown in FIG. 3, the voltage vector setting unit 23 permits vector transition when changing to an adjacent vector, and otherwise outputs a zero voltage vector once. And a transition to a desired voltage vector.

For example, when the voltage vector being output is V ₁ , the transitionable voltage vectors are V ₀ , V ₃ , V ₅ , and V ₇ . In this case, if the voltage vector determined according to the region to which the current deviation vector belongs is V ₃ or V ₅ , the voltage vector setting unit 23 sets the voltage vector as an output voltage vector. On the other hand, when the voltage vector determined in accordance with the region to which the current deviation vector belongs is another vector, for example, V ₄ , the voltage vector setting unit 23 outputs V ₀ instead of the voltage vector V _4. Set as a vector.

Here, since V ₀ and V ₇ are the same zero voltage vector, the voltage vector setting unit 23 is zero in which the change of the switching state is small when the voltage vector V ₁ in the output transitions to the zero voltage vector. Vector V ₀ is set as an output voltage vector.

  In other words, the voltage vector setting unit 23 changes the switching arms 30, 40, 50 of the gate circuit 15 when changing from the voltage vector being output to the voltage vector determined according to the region to which the current deviation vector belongs. When two or more must be operated (when the number of times of switching is a predetermined number or more), the output voltage vector is set to a zero voltage vector. The predetermined number of times is the number of times of switching when two of the switching arms 30, 40, 50 are operated.

For example, Figure 8 (a), the voltage vector V _{1 =} [001] in the output from the (thick solid line arrows in the figure), the voltage vector V ₄ which is determined according to the region where the current deviation vector belongs = When changing to [100] (broken line arrow in the figure), it is necessary to operate two or more switching arms 30, 40, 50 of the gate circuit 15. In this case, as shown in FIG. 8B, the voltage vector to be output is set to the one with the smaller number of switching times among the zero voltage vectors V ₀ and V ₇ .

Even in the steady mode, the voltage vector setting unit 23, when setting the output voltage vector to the zero voltage vector, of the zero voltage vectors V ₀ and V ₇ as in the above-described reflux mode, A zero voltage vector that minimizes the number of times of switching of 31, 32, 41, 42, 51, and 52 is selected.

On the other hand, as described above, in the steady mode, the voltage vector setting unit 23 changes the voltage vector being output to a voltage vector determined according to the region to which the current deviation vector belongs (when the vector transitions). In addition, in the voltage vector diagram of V _{0 to} V ₇ shown in FIG. 3, when changing to an adjacent vector, vector transition is permitted. For example, when the voltage vector being output is V ₁ and the voltage vector determined according to the region to which the current deviation vector belongs is V ₃ or V ₅ , the voltage vector setting unit 23 outputs the voltage vector. Set as a voltage vector.

  In other words, when the voltage vector setting unit 23 changes from the voltage vector being output to the voltage vector determined according to the region to which the current deviation vector belongs, the voltage vector setting unit 23 has one switching arm that operates in the gate circuit 15. When the number of times of switching is less than a predetermined number, the output voltage vector is set to a voltage vector determined according to the region to which the current deviation vector belongs.

  When the voltage vector being output is a zero voltage vector, the voltage vector setting unit 23 sets the output voltage vector to a voltage vector determined according to the region to which the current deviation vector belongs.

  Information on the voltage vector being output is stored in the storage unit 24 described later. When the voltage vector is set using the voltage vector being output, the voltage vector setting unit 23 reads information on the voltage vector being output from the storage unit 24.

  When the magnitude of the current deviation vector is larger than the second predetermined value Q, the voltage vector setting unit 23 sets the switching mode to the transient mode. Specifically, when the magnitude of the current deviation vector is larger than the second predetermined value Q, the voltage vector setting unit 23 changes the voltage vector to be output to a voltage vector determined according to the region to which the current deviation vector belongs. Set.

Specifically, the voltage vector setting unit 23 determines the voltage vector according to the region to which the current deviation vector belongs in the current deviation vector diagram. For example, as shown in FIG. 9A, when the current deviation vector Y belongs to the region A1 in the current deviation vector diagram, the voltage vector setting unit 23 outputs the output as shown in FIG. 9B. setting the voltage vector to the voltage vector V _1.

  Thus, in the transient mode, the voltage vector setting unit 23 sets the output voltage vector to a voltage vector corresponding to the region to which the current deviation vector belongs in the current deviation vector diagram.

  The storage unit 24 temporarily stores information regarding the voltage vector being output. The data stored in the storage unit 24 is used when the voltage vector setting unit 23 sets a voltage vector according to the switching mode.

  Specifically, when the switching mode is the reflux mode, the voltage vector setting unit 23 reads information on the voltage vector stored in the storage unit 24 and changes the voltage vector to the zero voltage vector. A zero voltage vector is set such that the switching arms 30, 40, 50 operating in the gate circuit 15 are minimized.

  In addition, when the switching mode is the steady mode, the voltage vector setting unit 23 reads information on the voltage vector stored in the storage unit 24, and converts the voltage vector to a voltage vector determined according to the current deviation vector. When changing, if there are two or more switching arms 30, 40, 50 operating in the gate circuit 15, a zero voltage vector is set as an output voltage vector.

(Voltage vector generation operation)
Next, the operation of voltage vector generation in the voltage vector generation unit 13 of the voltage source inverter device 1 having the above-described configuration will be described using the flow shown in FIG.

  When the flow shown in FIG. 10 starts (start), first, the voltage vector generation unit 13 inputs a three-phase current command and a current output from the motor 2 to the current deviation calculation unit 20 (step S1).

  The current deviation calculation unit 20 calculates the current deviation of each phase using the input three-phase current command and the output current of the motor 2 (step S2). In subsequent step S3, the current deviation vector calculation unit 21 calculates the magnitude of the current deviation vector based on the current deviation.

  Next, in step S4, the current deviation vector area determination unit 22 determines, based on the current deviation, which of the areas A1 to A6 of the current deviation vector diagram the current deviation vector belongs to. Specifically, the current deviation vector region determination unit 22 obtains the difference between the absolute values of the current deviation between the two phases, and determines the region to which the current deviation vector belongs in the current deviation vector diagram depending on whether the difference is 0 or more. In addition, the region to which the current deviation vector belongs is specified depending on whether the current deviation of the three phases is 0 or more.

  As described above, in this embodiment, after calculating the magnitude of the current deviation vector in step S3, the region to which the current deviation vector belongs is determined in step S4. However, the region determination in step S4 may be performed before step S3.

  In the subsequent step S5, the voltage vector setting unit 23 selects a switching mode performed in the gate circuit 15 based on the magnitude of the current deviation vector obtained in step S3. In the case of the present embodiment, the switching mode includes three modes of a reflux mode, a steady mode, and a transient mode.

  When the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the voltage vector setting unit 23 selects the reflux mode as the switching mode. In the reflux mode, the voltage vector setting unit 23 sets the output voltage vector to a zero voltage vector (step S6). At this time, the voltage vector setting unit 23 reads the voltage vector being output from the storage unit 24 and changes the voltage vector from the voltage vector to the zero voltage vector. A zero voltage vector that minimizes the number (number of times of switching) is selected.

  In step S5, when the magnitude of the current deviation vector is larger than the first predetermined value P and equal to or smaller than the second predetermined value Q, the voltage vector setting unit 23 selects the steady mode as the switching mode. In this steady mode, the voltage vector setting unit 23 changes the switching arm 30, 40, 50 of the gate circuit 15 when changing the voltage vector being output to the voltage vector determined according to the region to which the current deviation vector belongs. If two or more switching operations are performed (in the voltage vector diagram, the voltage vector is changed to a vector that is not adjacent), the output voltage vector is set to the zero voltage vector (step S6).

  On the other hand, when the voltage vector being output is changed to the voltage vector determined according to the region to which the current deviation vector belongs, when there is one switching arm 30, 40, 50 that performs the switching operation (in the voltage vector diagram, When the voltage vector is changed to an adjacent vector), the voltage vector setting unit 23 sets the output voltage vector to a voltage vector determined according to the region to which the current deviation vector belongs.

  Thereby, the frequency | count of switching of the switching elements 31, 32, 41, 42, 51, and 52 of the gate circuit 15 can be reduced. Therefore, the loss caused by the switching operation can be further reduced, and the current distortion rate of the current flowing through the motor 2 can be further reduced.

  When the magnitude of the current deviation vector is larger than the second predetermined value Q in step S5, the voltage vector setting unit 23 selects the transient mode as the switching mode. In this transient mode, the voltage vector setting unit 23 sets the output voltage vector to a voltage vector determined according to the region to which the current deviation vector belongs (step S6).

  Thereby, when the current deviation vector is large, it is possible to output a voltage vector that makes the current deviation small. Therefore, the output of the motor 2 can be quickly adjusted to a predetermined output.

  In step S <b> 7, the voltage vector setting unit 23 outputs the set voltage vector to the gate command generation unit 14 as the voltage vector command Vect. Thereafter, this flow is ended (END).

  With the above configuration, the voltage vector generation unit 13 outputs a zero voltage vector as a voltage vector when the magnitude of the current deviation vector is equal to or less than the first predetermined value P. Thereby, in the region where the current deviation vector is not so large, the number of times of switching of the gate circuit 15 can be reduced, and the switching loss can be reduced. Moreover, the waveform of the current flowing through the motor 2 can be made a waveform with less noise. Therefore, the current distortion rate of the current flowing through the motor 2 can be reduced.

  Here, FIG. 11 shows an example (FIG. 11A) of the three-phase switching pattern and the motor 2 current waveform in the conventional configuration, and the three-phase switching pattern and the motor 2 current waveform in the configuration of the present embodiment. An example (FIG. 11B) is shown. As can be seen from FIG. 11, in the configuration of the present embodiment, the number of times of switching can be reduced, and the current distortion rate of the current flowing through the motor 2 can be reduced. In FIG. 11, Up represents a U-phase gate command, Vp represents a V-phase gate command, and Wp represents a W-phase gate command.

(Current value command correction part)
Next, a current command correction unit 60 that corrects the q-axis current command Iq ^* will be described with reference to FIG.

The current command correction unit 60 reduces the return current generated in the motor 2 when the voltage applied to the motor 2 is zero (when the voltage vector generation unit 13 sets the output voltage vector to the zero voltage vector). Thus, the q-axis current command Iq ^* is corrected.

  As described above, when the voltage output from the voltage source inverter device 1 having the above-described configuration to the motor 2 becomes zero, an induced voltage is generated in the motor 2 due to rotation. When an induced voltage is generated in the motor 2, a reflux current flows through the motor 2 and the voltage source inverter device 1. The reflux current is a sinusoidal current as shown in FIG. 12 and flows in three phases of the voltage source inverter device 1. Then, regenerative torque is generated in the motor 2 by the return current. This regenerative torque is a torque that acts in a direction to stop the rotation of the motor 2.

  FIG. 12 shows, as an example, a waveform of a current flowing in the U phase of the motor 2 when the voltage applied to the motor 2 is zero.

  Therefore, as described above, when the magnitude of the current deviation vector is equal to or smaller than the first predetermined value P, the voltage vector output from the voltage vector generation unit 13 is set to the zero voltage vector, so that the switching loss and the motor 2 Even if the current distortion rate of the current flowing through the motor 2 is reduced, the induced voltage generated in the motor 2 adversely affects the rotation of the motor 2.

In contrast, in the present embodiment, the current command correction unit 60 corrects the q-axis current command Iq ^* so as to reduce the induced voltage generated in the motor 2. Specifically, the current command correction unit 60 includes a correction value generation unit 61 and an addition unit 62.

Correction value generation unit 61 generates a current command correction value Iq _oft for using a first predetermined value P used in performing the reflux mode in the voltage vector generating unit 13 corrects the current command Iq ^* of the q-axis To do. Correction value generation unit 61, using the following equation to calculate the current command correction value Iq _oft.
Iq _oft = Ia × cosβ
In this equation, Ia is a current amplitude, and is calculated by performing dq axis transformation (coordinate transformation) by multiplying √ (2/3) to the dead zone region width (first predetermined value P). Β is a current phase angle. β is set to zero in order to be in phase with the induced voltage (E = ψ × ω, ψ: rotor magnetic flux, ω: motor rotation speed) generated in the motor 2.

Thus, the correction value generation unit 61, as a current command correction value _{Iq oft,} to generate the Ia. The current command correction value Iq _oft is a power running torque command that causes the motor 2 to generate a power running torque that cancels the regenerative torque generated by the return current flowing through the motor 2.

Addition unit 62, a current command correction value _{Iq oft} generated by the correction value generation unit 61, adds to the current command Iq ^* of the q-axis.

FIG. 13 shows the effect of whether or not the current command value Iq ^* is corrected by the current command correction unit 60 when the voltage applied to the motor 2 is zero. Specifically, FIG. 13A shows an example of a current waveform flowing in the motor 2 without correcting the current command value Iq ^* , and FIG. 13B shows a current command value by the current command correction unit 60. An example of a waveform of a current flowing through the motor 2 when Iq ^* is corrected is shown.

As shown in FIG. 13, when the current command value Iq ^* is not corrected by the current command correction unit 60 (FIG. 13A), a sinusoidal current flows through the motor 2. On the other hand, when the current command value Iq ^* is corrected by the current command correction unit 60 (FIG. 13B), the current flowing through the motor 2 is not sinusoidal and has a value close to zero.

In this way, the current command correction unit 60 performs correction for adding the power running torque command that cancels the regenerative torque generated by the return current flowing through the motor 2 to the current command value Iq ^* , so that the voltage vector becomes zero voltage. When the vector is set, it is possible to prevent the rotation of the motor 2 from being hindered due to the induced voltage generated in the motor 2.

  Therefore, by reducing the number of times of switching by the configuration of the present embodiment, the switching loss and the current distortion rate of the current flowing through the motor 2 can be reduced, and the induction applied to the motor 2 when the voltage applied to the motor 2 is zero By reducing the voltage, it is possible to prevent the motor 2 from generating regenerative torque that inhibits rotation. Therefore, it is possible to prevent the motor performance from being lowered while reducing the switching loss and the current distortion rate.

Moreover, the current command correction value Iq _oft used in correcting the current command value Iq ^* by the current command correction unit 60, the upper limit of the range the reflux mode is applied in the size range of the current deviation vector (first predetermined value P). Therefore, it is possible to more reliably prevent the regenerative torque that inhibits the rotation of the motor 2 from occurring in the range of the reflux mode.

  The configuration of the present embodiment is particularly useful when the voltage source inverter device 1 is configured to operate at a high frequency (for example, 800 kHz or higher). That is, in the case of a high-frequency voltage source inverter device, since the switching operation of the switching element is fast, the switching loss tends to increase and the current distortion rate tends to increase accordingly. By applying the configuration of the present embodiment to such a high-frequency voltage source inverter device, a greater effect can be obtained with respect to reduction of switching loss and current distortion.

(Other embodiments)
While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented without departing from the spirit of the invention.

In the above embodiment, the current command correction unit 60, the current command value Iq ^* of the q-axis is corrected by the current command correction value _{Iq oft.} However, as shown in FIG. 14, the current command correction unit 70, a current command value Id ^* of the d-axis, may be corrected by the current command correction value _{Id oft.}

In this case, the current command correction unit 70, the current command correction value Id _oft weakening the field magnetic flux of the motor 2 so as not to generate an induced voltage in the motor 2, to correct the current command Id ^* of the d-axis. Specifically, the current command correction unit 70 includes a correction value generation unit 71 that generates a current command correction value Id _oft with rotor flux and the following equation.
Id _oft = Ib × sinβ
In this equation, Ib is a current amplitude, and is set to a current value that generates the rotor magnetic flux Ψ. That is, Ib = Ld / Ψ (Ld is d-axis inductance). Β is a current phase angle. β is set to 90 degrees in order to obtain a d-axis current.

Accordingly, the correction value generation unit 71, as a current command correction value _{Id oft,} to generate the Ia. The current command correction value Id _oft is a field weakening command weakening the magnetic field flux of the motor 2 so as not to cause an induced voltage to the motor 2.

In FIG. 14, reference numeral 72 is a current instruction correction value _{Id oft} generated by the correction value generation unit 71, an addition unit that adds the current command Id ^*.

In the above description, either the d-axis current command Id ^* or the q-axis current command Iq ^* is corrected. However, the present invention is not limited to this, and the d-axis and q-axis current commands Id ^* and Iq ^* are not limited thereto ^. and each current instruction correction value _{Id oft,} may be corrected by Iq _oft.

  In the embodiment, the current deviation vector region determination unit 22 obtains the difference in absolute value of the current deviation between the two phases among the current deviations Δiu, Δiv, Δiw of the three phases, and whether the difference is 0 or more, After narrowing down the region to which the current deviation vector belongs, the region to which the current deviation vector belongs is specified according to whether the three-phase current deviations Δiu, Δiv, Δiw are 0 or more. However, any method may be used as long as it can determine the region of the current deviation vector.

  In the embodiment, the voltage vector setting unit 23 selects the switching mode from the reflux mode, the steady mode, and the transient mode. However, the switching mode may have only one of the steady mode and the transient mode in addition to the return mode, or may have a mode other than the steady mode and the transient mode.

In the above-described embodiment, the voltage vector setting unit 23 outputs the voltage vector to be output in the reflux mode and the steady mode from among the zero voltage vectors V ₀ and V ₇ (the voltage vector set last). When changing from 0 to the zero voltage vector, the zero voltage vector is set so that the switching frequency of the switching elements 31, 32, 41, 42, 51, 52 is minimized. However, the voltage vector setting unit 23 may set the output voltage vector to a zero voltage vector having a large number of switching times.

  In the above-described embodiment, the configuration of the voltage source inverter device 1 that drives the three-phase AC motor 2 has been described. May be.

  The present invention is applicable to a voltage source inverter device that outputs a voltage to a motor by driving a switching element with a voltage vector obtained based on a current command.

DESCRIPTION OF SYMBOLS 1 Voltage type inverter apparatus 2 Motor 13 Voltage vector production | generation part 15 Gate circuit 20 Current deviation calculation part 21 Current deviation vector calculation part 22 Current deviation vector area determination part 23 Voltage vector setting part 30 Switching arm 31, 32, 41, 42, 51 , 52 Switching element 60, 70 Current command correction unit 61, 71 Correction value generation unit P First predetermined value (predetermined value)
X, Y Current deviation vector

Claims (4)

A voltage source inverter device that outputs a voltage to a motor by driving a switching element according to a voltage vector generated based on a current command of a plurality of phases,
A current deviation vector computing unit for obtaining a current deviation vector based on a current deviation between the current command and the motor output current in the plurality of phases;
A voltage vector setting unit that sets the voltage vector based on the current deviation vector and sets the voltage vector to a zero voltage vector when the magnitude of the current deviation vector is a predetermined value or less;
A voltage source inverter device comprising: a current command correction unit that corrects the current command with a current command correction value so as to reduce an induced voltage generated in the motor when the voltage vector is a zero voltage vector. In the voltage source inverter device according to claim 1,
The voltage command inverter device, wherein the current command correction value is a power running torque command that cancels a torque generated in the motor when the voltage vector is a zero voltage vector. The voltage source inverter device according to claim 2,
The voltage command inverter device, wherein the current command correction value is obtained by coordinate conversion of the predetermined value. In the voltage source inverter device according to claim 1,
The voltage command inverter device, wherein the current command correction value is a field weakening command for weakening a field magnetic flux of the motor when the voltage vector is a zero voltage vector.