JP7059925B2 - Inverter controller - Google Patents

Description

The present invention relates to an inverter control device.

Conventionally, an inverter control device for operating a switching element provided in an inverter circuit based on the current of each phase flowing through a three-phase AC rotary electric machine is known (see Patent Document 1).
The inverter control device disclosed in Patent Document 1 includes a PWM control unit that PWM-controls a switching element, a square wave control unit that controls a square wave of a switching element, and a control switching unit that switches between PWM control and square wave control. I have. The control switching unit calculates the modulation factor Va based on the d-axis voltage command value and the q-axis voltage command value of the three-phase AC rotary electric machine. The control switching unit switches to a state in which the three-phase AC rotary electric machine is controlled by a square wave when the modulation factor Va exceeds the threshold value in the state where the three-phase AC rotary electric machine is PWM-controlled. Here, the d-axis voltage command value and the q-axis voltage command value are converted between the d-axis current command value and the q-axis current command value calculated based on the torque command value and the current of each phase flowing through the three-phase AC rotary electric machine. It is calculated by feedback-controlling the difference between the d-axis current value and the q-axis current value. The PWM control is a control performed in a low rotation region of a three-phase AC rotary electric machine, and a square wave control is a control performed in a high rotation region of a three-phase AC rotary electric machine.

Japanese Unexamined Patent Publication No. 2016-226191

By the way, since the d-axis current command value and the q-axis current command value are calculated by feedback-controlling the difference between the d-axis current command value and the q-axis current command value and the d-axis current value and the q-axis current value. For example, as shown in FIG. 5A, the modulation factor Va may fluctuate in the vicinity of the threshold value. Therefore, even if the modulation factor Va exceeds the threshold value, it may fluctuate so as to immediately fall below the threshold value. In this case, for example, if the state in which the modulation factor Va exceeds the threshold value continues for a predetermined time as shown in FIG. 5 (b), it is conceivable to switch from the PWM control to the rectangular control as shown in FIG. 5 (c). It is not possible to switch from PWM control to square wave control for a predetermined time. That is, since the PWM control cannot be switched to the rectangular wave control, the torque response of the three-phase AC rotary electric machine deteriorates.

An object of the present invention is to provide an inverter control device capable of improving the torque response of a three-phase AC rotary electric machine when switching from PWM control to square wave control.

The inverter control device that solves the above problems has a PWM control unit that PWM-controls a switching element that drives a three-phase AC rotary electric machine by outputting a PWM control signal, and a rectangular wave signal that outputs the switching element in a rectangular shape. An inverter control device including a square wave control unit for wave control and a control switching unit for switching between the PWM control and the square wave control by switching and outputting the PWM control signal and the square wave signal. The control switching unit includes an induced voltage calculation unit that calculates the induced voltage of the three-phase AC rotary electric machine based on the current value of each phase of the three-phase AC rotary electric machine and the rotation speed of the three-phase AC rotary electric machine. When the induced voltage exceeds the threshold while the PWM control signal is being output, the signal is switched to the square wave signal and output.

According to this, the induced voltage of the three-phase AC rotary electric machine is calculated based on the current value of each phase of the three-phase AC rotary electric machine and the rotation speed of the three-phase AC rotary electric machine. Then, the control switching unit outputs a rectangular wave signal when the induced voltage exceeds the threshold value in the state where the switching element is PWM controlled. That is, the inverter control device uses the induced voltage as an index when switching from PWM control to rectangular wave control. Compared with the case where the modulation factor calculated using the d-axis voltage command value and the q-axis voltage command value of the conventional three-phase AC rotary electric machine is used as an index, the induced voltage of the three-phase AC rotary electric machine is the three-phase AC. It is calculated by the current value and rotation speed that reflect the drive state of the rotary electric machine. Therefore, the induced voltage has little fluctuation near the threshold value. Then, the inverter control device switches from PWM control to square wave control depending on the drive state of the three-phase AC rotary electric machine by using the induced voltage of the three-phase AC rotary electric machine as an index. Therefore, when the induced voltage exceeds the threshold value, the PWM control can be immediately switched to the rectangular wave control. Therefore, it is possible to improve the torque response associated with the switching from the PWM control to the rectangular wave control.

The inverter control device includes a first coordinate conversion unit that converts the current value of each phase of the three-phase AC rotary electric machine into a d-axis current value and a q-axis current value, and the PWM control unit is a torque command value. Based on the above, the current command value calculation unit that calculates the d-axis current command value and the q-axis current command value of the three-phase AC rotary electric machine, the difference between the d-axis current command value and the d-axis current value, and the q-axis current. A current control unit that calculates the d-axis voltage command value and the q-axis voltage command value of the three-phase AC rotary electric machine by feedback-controlling the difference between the command value and the q-axis current value, the d-axis voltage command value, and the d-axis voltage command value. The second coordinate conversion unit that converts the q-axis voltage command value into a three-phase voltage command value, which is a target value of the voltage generated in each phase of the three-phase AC rotary electric machine, and the PWM based on the three-phase voltage command value. It has a PWM signal generation unit that generates a control signal, and an estimated induced voltage estimated to be generated in the three-phase AC rotary electric machine based on the d-axis current command value, the q-axis current command value, and the rotation speed. Further, the control switching unit may output the PWM control signal when the estimated induced voltage is lower than the threshold value in a state where the rectangular wave signal is output.

When switching from rectangular wave control to PWM control, if the control switching by the control switching unit is delayed, an excessive current may flow in the three-phase AC rotary electric machine.
In that respect, according to this, the estimated induced voltage estimated to be generated in the three-phase AC rotary electric machine is calculated based on the d-axis current command value, the q-axis current command value, and the rotation speed. Then, the control switching unit outputs a PWM control signal when the estimated induced voltage is lower than the threshold value in a state where the switching element is controlled by a square wave. That is, the inverter control device uses the estimated induced voltage as an index when switching from the rectangular wave control to the PWM control. Since it is calculated faster than the induced voltage calculated based on the current value and the rotation speed indicating the driving state of the three-phase AC rotary electric machine, it is possible to switch from the square wave control to the PWM control earlier. Therefore, it is possible to suppress the supply of an excessive current to the three-phase AC rotary electric machine due to the switching from the rectangular wave control to the PWM control.

According to the present invention, it is possible to improve the torque response of the three-phase AC rotary electric machine accompanying the switching from the PWM control to the rectangular wave control.

The block diagram which shows the structure of the inverter control device. The block diagram which shows the structure of the control switching part. (A) is a time chart showing the change of the induced voltage, and (b) is a time chart showing the switching of the control method. (A) is a time chart showing the change of the estimated induced voltage, and (b) is a time chart showing the switching of the control method. (A) is a time chart showing a change in the modulation factor, (b) is a time chart showing a timer count value, and (c) is a time chart showing switching of a control method.

Hereinafter, embodiments in which the inverter control device is embodied will be described with reference to FIGS. 1 to 4. The inverter control device of the present embodiment will be described on the premise that it is applied to an inverter device that controls the drive of a three-phase AC rotary electric machine.

As shown in FIG. 1, the inverter device 1 includes an inverter circuit 10 and an inverter control device 20. The inverter circuit 10 includes six switching elements Q1 to Q6 and six diodes D1 to D6. Insulated gate bipolar transistors (IGBTs) are used in the switching elements Q1 to Q6. Between the positive electrode bus and the negative electrode bus, the switching element Q1 constituting the upper arm connected to the U phase of the motor 60 as a three-phase AC rotary electric machine, and the switching element constituting the lower arm connected to the U phase. Q2 is connected in series. Further, the switching element Q3 constituting the upper arm connected to the V phase of the motor 60 and the switching element Q4 constituting the lower arm connected to the V phase are connected in series between the positive electrode bus and the negative electrode bus. ing. Further, the switching element Q5 constituting the upper arm connected to the W phase of the motor 60 and the switching element Q6 constituting the lower arm connected to the W phase are connected in series between the positive electrode bus and the negative electrode bus. ing. Diodes D1 to D6 are connected in antiparallel to the switching elements Q1 to Q6, respectively. A battery B is connected to the positive electrode bus and the negative electrode bus via a capacitor C. The inverter circuit 10 configured in this way drives the motor 60 by converting the DC voltage of the battery B into an AC voltage and supplying it to the motor 60 in accordance with the switching operation of the switching elements Q1 to Q6. The battery B is provided with a voltage sensor 65 to monitor the DC voltage Vdc of the battery B.

The inverter control device 20 includes a first coordinate conversion unit 21, a rotation speed calculation unit 22, a drive circuit 25, a PWM control unit 30, a square wave control unit 40, and a control switching unit 50.

The first coordinate conversion unit 21 converts the current values Iu, Iv, and Iw of each phase of the motor 60 into the d-axis current value Id and the q-axis current value Iq using the electric angle θe indicating the rotation position of the motor 60. The current values Iu, Iv, and Iw are detected via the current sensors 61, 62, and 63 provided on the connection wirings W1, W2, and W3, respectively. The electric angle θe is detected by the position detecting unit 64 provided in the motor 60.

The rotation speed calculation unit 22 calculates the rotation speed ω of the motor 60. The rotation speed calculation unit 22 calculates the rotation speed ω by differentiating the electric angle θe detected by the position detection unit 64.

The PWM control unit 30 PWM-controls the switching elements Q1 to Q6 of the inverter circuit 10 that drives the motor 60 by outputting the PWM control signal S1. The PWM control unit 30 includes a current command value calculation unit 31, subtraction units 32 and 33, a current control unit 34, a second coordinate conversion unit 35, and a PWM signal generation unit 36.

The current command value calculation unit 31 calculates the d-axis current command value Id * and the q-axis current command value Iq * of the motor 60 based on the torque command value Tref input from the outside. For example, the current command value calculation unit 31 uses a table in which the torque command value Tref stored in advance in the storage unit (not shown), the d-axis current command value Id *, and the q-axis current command value Iq * are opposed to each other. The d-axis current command value Id * and the q-axis current command value Iq * are calculated.

The subtraction unit 32 calculates the difference ΔId between the d-axis current command value Id * and the d-axis current value Id. The subtraction unit 33 calculates the difference ΔIq between the q-axis current command value Iq * and the q-axis current value Iq.
The current control unit 34 calculates the d-axis voltage command value Vd * and the q-axis voltage command value Vq * of the motor 60 based on the differences ΔId and ΔIq. Specifically, the current control unit 34 calculates the d-axis voltage command value Vd * and the q-axis voltage command value Vq * by performing feedback control so as to eliminate the differences ΔId and ΔIq.

The second coordinate conversion unit 35 converts the d-axis voltage command value Vd * and the q-axis voltage command value Vq * into the three-phase voltage command values Vu, Vv, Vw based on the electric angle θe detected by the position detection unit 64. .. The three-phase voltage command values Vu, Vv, and Vw are target values of voltage values generated in each phase of the motor 60.

The PWM signal generation unit 36 is a PWM control signal S1 for opening and closing each switching element Q1 to Q6 of the inverter circuit 10 based on the comparison result between the triangular wave as a reference and the three-phase voltage command values Vu, Vv, Vw by PWM control. To generate.

The square wave control unit 40 controls the switching elements Q1 to Q6 of the inverter circuit 10 that drives the motor 60 by outputting the square wave signal S2. The square wave control unit 40 includes a torque calculation unit 41, a subtraction unit 42, a voltage phase control unit 43, and a square wave signal generation unit 44. The electric angle θe detected by the position detection unit 64, the d-axis current value Id, and the q-axis current value Iq are input to the torque calculation unit 41. The torque calculation unit 41 calculates a torque estimation value Tdet that can be generated in the motor 60 based on the electric angle θe, the d-axis current value Id, and the q-axis current value Iq. In the torque estimated value Tdet, for example, the d-axis current value Id, the q-axis current value Iq, the electric angle θe, and the torque estimated value Tdet stored in advance in a storage unit (not shown) provided in the square wave control unit 40 face each other. It is calculated using the attached table.

The subtraction unit 42 calculates the torque difference value ΔT between the torque command value Tref and the torque estimation value Tdet input from the outside.
The voltage phase control unit 43 adjusts the voltage phase angle command value φi so as to reduce the torque difference value ΔT between the torque command value Tref calculated by the subtraction unit 42 and the torque estimation value Tdet. The voltage phase angle command value φi can be adjusted, for example, by feedback control so that the torque difference value ΔT becomes small. Therefore, it is possible to match the estimated torque value Tdet with the torque command value Tref.

The square wave signal generation unit 44 raises or lowers the square wave signal S2 at a timing after the target count value from the count value corresponding to the voltage phase angle command value φi output from the voltage phase control unit 43. Specifically, the rectangular wave signal S2 has a rectangular wave shape in which "Vdc / 2" and "-Vdc / 2" are alternately changed in the same cycle after the target count value from the count value corresponding to the voltage phase angle command value φi. It is a control signal of. That is, the square wave control unit 40 generates a square wave signal S2 for controlling the switching elements Q1 to Q6 in a square wave based on the torque difference value ΔT between the torque command value Tref and the torque estimated value Tdet of the motor 60.

The control switching unit 50 inputs the PWM control signal S1 generated by the PWM control unit 30 and the square wave signal S2 generated by the square wave control unit 40.
The control switching unit 50 switches between PWM control and square wave control by switching and outputting the PWM control signal S1 and the rectangular wave signal S2. Specifically, the control switching unit 50 selects and outputs one of the PWM control signal S1 and the square wave signal S2 as the control signal S for controlling the switching operation of the switching elements Q1 to Q6, thereby performing PWM control. And switch between square wave control. At the beginning of operating the motor 60, the control switching unit 50 outputs the PWM control signal S1 output from the PWM control unit 30 as the control signal S because the motor 60 is driven in the low rotation region.

The gate terminals of the switching elements Q1 to Q6 are connected to the drive circuit 25. Further, a control switching unit 50 is connected to the drive circuit 25. The drive circuit 25 switches the switching elements Q1 to Q6 of the inverter circuit 10 based on the control signal S output by the control switching unit 50.

Here, the control switching unit 50 will be described in more detail.
As shown in FIGS. 1 and 2, the control switching unit 50 has not only the PWM control signal S1 and the square wave signal S2, but also the d-axis current value Id and the q-axis current value output by the first coordinate conversion unit 21. Iq, the rotation speed ω output by the rotation speed calculation unit 22, and the d-axis current command value Id * and the q-axis current command value Iq * calculated by the current command value calculation unit 31 of the PWM control unit 30 are input. .. The control switching unit 50 controls switching from PWM control to rectangular wave control and switching from rectangular wave control to PWM control based on these input parameters.

As shown in FIG. 2, the control switching unit 50 outputs a signal switching unit 51 for switching the PWM control signal S1 and the square wave signal S2, and a switching command output unit for outputting a command for switching the signals S1 and S2 by the signal switching unit 51. It is equipped with 52. As described above, when the motor 60 is initially operated, the PWM control signal S1 is adopted as the control signal S, so that the switching command output unit 52 is the first command for outputting the PWM control signal S1 to the drive circuit 25. This is a state in which the signal Sc1 is output to the signal switching unit 51.

The switching command output unit 52 includes an induced voltage calculation unit 52a that calculates the induced voltage Vi of the motor 60 and an estimated induced voltage calculation unit 52b that calculates the estimated induced voltage Vie that is the induced voltage estimated to be generated in the motor 60. I have.

The calculation of the induced voltage Vi and the estimated induced voltage Vie will be described.
The induced voltage calculation unit 52a of the motor 60 is based on the d-axis current value Id and the q-axis current value Iq calculated based on the current values Iu, Iv, and Iw of each phase of the motor 60, and the rotation speed ω of the motor 60. The d-axis induced voltage Vod and the q-axis induced voltage Voq are calculated. Then, the induced voltage calculation unit 52a calculates the induced voltage Vi based on the d-axis induced voltage Vod and the q-axis induced voltage Voq. Specifically, it is calculated by the following formula.

Vod = R x Id-ω x Lq x Iq
Voq = R x Iq + ω x Ld x Id + ω x Ke
Vi = √ (Vod ^ 2 + Voq ^ 2)
R ... motor resistance value, Ld ... motor d-axis inductance, Lq ... motor q-axis inductance, Ke ... permanent magnet magnetic flux.

The estimated induced voltage calculation unit 52b is a d-axis estimated induced voltage Vod_est and q-axis of the induced voltage estimated to be generated in the motor 60 based on the d-axis current command value Id *, the q-axis current command value Iq *, and the rotation speed ω. Calculate the estimated induced voltage Voq_est. Then, the estimated induced voltage calculation unit 52b calculates the estimated induced voltage Vie based on the d-axis estimated induced voltage Vod_est and the q-axis estimated induced voltage Voxy_est. Specifically, it is calculated by the following formula.

Vod_est = R x Id * -ω x Lq x Iq *
Voq_est = R x Iq * + ω x Ld x Id * + ω x Ke
View = √ (Vod_est ^ 2 + Voxy_est ^ 2)
The switching command output unit 52 has a memory (not shown), and the memory stores data such as a program for executing the above equation, the resistance value of the motor 60, and the inductances Ld and Lq. ing.

As shown in FIG. 3A, the induced voltage Vi gradually increases in magnitude as the rotation speed of the motor 60 increases from the beginning when the motor 60 is operated. As the rotation speed of the motor 60 increases, the rotation speed ω of the motor 60, the d-axis current value Id of the motor 60, and the q-axis current value Iq of the motor 60 increase. That is, the induced voltage Vi increases as the rotation speed ω, the d-axis current value Id, and the q-axis current value Iq increase.

As shown in FIGS. 2 and 3A, the switching command output unit 52 is rectangular with respect to the signal switching unit 51 when the induced voltage Vi of the motor 60 calculated by the induced voltage calculation unit 52a exceeds the threshold Mth. The second command signal Sc2 for outputting the wave signal S2 to the drive circuit 25 is output. That is, in the signal switching unit 51, the PWM control signal S1 is switched to the square wave signal S2, and the square wave signal S2 is output as the control signal S. Therefore, as shown in FIG. 3B, the switching elements Q1 to Q6 of the inverter circuit 10 are switched from the PWM controlled state to the rectangular wave controlled state.

As shown in FIG. 4A, the estimated induced voltage Vie has the same tendency as the induced voltage Vi, and its magnitude gradually increases as the rotation speed of the motor 60 increases from the beginning when the motor 60 is operated. Will increase. As the rotation speed of the motor 60 increases, not only the rotation speed ω of the motor 60 but also the torque command value Tref input from the outside increases. That is, the d-axis current command value Id * of the motor 60 and the q-axis current command value Iq * of the motor 60 increase.

On the other hand, the magnitude of the estimated induced voltage Vie gradually decreases as the rotation speed ω, the d-axis current command value Id *, and the q-axis current command value Iq * decrease. The induced voltage Vi also has the same tendency.

As shown in FIGS. 2 and 4A, the switching command output unit 52 performs PWM control to the signal switching unit 51 when the estimated induced voltage View calculated by the estimated induced voltage calculation unit 52b is below the threshold value Mth. The first command signal Sc1 for outputting the signal S1 to the drive circuit 25 is output to the signal switching unit 51. Therefore, as shown in FIG. 4B, the switching elements Q1 to Q6 of the inverter circuit 10 are switched from the rectangular wave controlled state to the PWM controlled state.

In the control switching unit 50 configured in this way, the induced voltage Vi exceeds the threshold value Mth in a state where the PWM control signal S1 is output from the signal switching unit 51 (a state in which the switching elements Q1 to Q6 are PWM controlled). In this case, the switching command output unit 52 outputs the second command signal Sc2 to the signal switching unit 51 to switch to the rectangular wave signal S2 and output the signal. That is, when the induced voltage Vi exceeds the threshold value Mth, the control switching unit 50 switches the switching elements Q1 to Q6 of the inverter circuit 10 from the PWM controlled state to the rectangular wave controlled state.

Further, when the estimated induced voltage Vie is lower than the threshold Mth in the state where the rectangular wave signal S2 is output from the signal switching unit 51 (the state where the switching elements Q1 to Q6 are controlled by the square wave), the control switching unit 50 is used. By outputting the first command signal Sc1 from the switching command output unit 52 to the signal switching unit 51, the signal is switched to the PWM control signal S1 and output. That is, when the estimated induced voltage Vie is lower than the threshold value Mth, the control switching unit 50 switches the switching elements Q1 to Q6 of the inverter circuit 10 from the rectangular wave controlled state to the PWM controlled state.

Further, the threshold value Mth will be described.
For example, when the modulation factor Va (see FIG. 5) proposed in the prior art is used, generally when the modulation factor Va exceeds 4 / π (about 1.27) when the rotation speed of the motor 60 increases. It is known that the controllability of PWM control is extremely reduced. Therefore, in the conventional technique, when the modulation factor Va exceeds 4 / π, the switching elements Q1 to Q6 are controlled by a square wave, and when the modulation factor Va is lower than 4 / π, the switching elements Q1 to Q6 are PWM controlled. That is, if the motor 60 is driven in the high rotation region, rectangular wave control is performed, and if the motor 60 is driven in the low rotation region, PWM control is performed.

The threshold value Mth in the present embodiment is a threshold value for discriminating whether the motor 60 is driven in the low rotation region or the high rotation region, as in the case of the above-mentioned modulation factor Va. Therefore, the threshold value Mth is set to match when the modulation factor Va is 4 / π.

The modulation factor Va is calculated by the following equation.
Va = (√ (Vd * ^ 2 + Vq * ^ 2)) / Vdc
That is, the threshold Mth is the d-axis current value Id, the q-axis current value Iq, and the d-axis current corresponding to the d-axis voltage command value Vd * and the q-axis voltage command value Vq * when the modulation factor Va is 4 / π. It is set to match the induced voltage Vi and the estimated induced voltage Vie calculated based on the command value Id *, the q-axis current command value Iq *, and the rotation speed ω.

The operation of this embodiment will be described.
In the inverter control device 20 configured as described above, when the induced voltage Vi of the motor 60 calculated by the induced voltage calculation unit 52a exceeds the threshold value Mth while the PWM control signal S1 is output from the control switching unit 50. , Outputs the square wave signal S2. Further, in the inverter control device 20, the estimated induced voltage Vie estimated to be generated in the motor 60 calculated by the estimated induced voltage calculation unit 52b while the rectangular wave signal S2 is output from the control switching unit 50 sets the threshold value Mth. If it is lower than that, the PWM control signal S1 is output. Therefore, when the induced voltage Vi exceeds the threshold voltage Mth in the state where the switching elements Q1 to Q6 are PWM controlled, the inverter control device 20 switches from the PWM control to the square wave control, and the switching elements Q1 to Q6 are controlled by the square wave. When the estimated induced voltage Vie is lower than the threshold Mth in this state, the square wave control is switched to the PWM control.

In this embodiment, the following effects can be obtained.
(1) In the present embodiment, the induced voltage Vi of the motor 60 is calculated based on the current values Iu, Iv, Iw of each phase of the motor 60 and the rotation speed ω of the motor 60. Then, the control switching unit 50 outputs the rectangular wave signal S2 when the induced voltage Vi exceeds the threshold value Mth while the switching elements Q1 to Q6 are PWM controlled. That is, the inverter control device 20 uses the induced voltage Vi as an index when switching from PWM control to rectangular wave control. Compared with the case where the modulation factor Va calculated by using the d-axis voltage command value Vd * and the q-axis voltage command value Vq * of the conventional motor 60 is used as an index, the induced voltage Vi of the motor 60 is the motor 60. It is calculated by the current values Iu, Iv, Iw and the rotation speed ω that reflect the driving state. Therefore, the induced voltage Vi has little fluctuation in the vicinity of the threshold value Mth. Then, the inverter control device 20 switches from PWM control to square wave control depending on the drive state of the motor 60 by using the induced voltage Vi of the motor 60 as an index. Therefore, when the induced voltage Vi exceeds the threshold value Mth, the PWM control can be immediately switched to the rectangular wave control. Therefore, it is possible to improve the torque response associated with the switching from the PWM control to the rectangular wave control.

(2) When switching from rectangular wave control to PWM control, if the control switching by the control switching unit 50 is delayed, an excessive current may flow in the motor 60.
In that respect, in the present embodiment, the estimated induced voltage Vie estimated to be generated in the motor 60 is calculated based on the d-axis current command value Id *, the q-axis current command value Iq *, and the rotation speed ω. Then, the control switching unit 50 outputs the PWM control signal S1 when the estimated induced voltage View is lower than the threshold value Mth while the switching elements Q1 to Q6 are controlled by the rectangular wave. That is, the inverter control device 20 uses the estimated induced voltage View as an index when switching from the rectangular wave control to the PWM control. Since the calculated voltage is faster than the induced voltage Vi calculated based on the current values Iu, Iv, Iw and the rotation speed ω indicating the drive state of the motor 60, it is possible to switch from the square wave control to the PWM control earlier. can. Therefore, it is possible to suppress the supply of an excessive current to the motor 60 with the switching from the rectangular wave control to the PWM control.

In addition, this embodiment can be changed and carried out as follows. The present embodiment and the following modified examples can be implemented in combination with each other within a technically consistent range.
〇 In the present embodiment, the threshold value Mth is set to match the modulation factor Va (= √ (Vd * ^ 2 + Vq * ^ 2)), but the present invention is not limited to this. For example, the modulation factor Va may be appropriately multiplied by a coefficient depending on the product specifications. Therefore, when the modulation factor Va is calculated by multiplying the coefficient, it is preferable to set the threshold value Mth in consideration of the coefficient.

〇 In the present embodiment, the induced voltage calculation unit 52a and the estimated induced voltage calculation unit 52b are provided in the switching command output unit 52, so that the switching command output unit 52 has a function of calculating the induced voltage Vi and the estimated induced voltage Vie. It has a function of outputting the first command signal Sc1 and the second command signal Sc2 collectively, but the present invention is not limited to this. For example, the arrangement of the induced voltage calculation unit 52a and the estimated induced voltage calculation unit 52b may be changed so as to separate the functions for calculating the induced voltage Vi and the estimated induced voltage Vie from the switching command output unit 52.

Further, the control switching unit 50 may not have the induced voltage calculation unit 52a and the estimated induced voltage calculation unit 52b, and may be provided at any position in the inverter control device 20, for example.

〇 The inverter control device 20 may adopt a configuration in which the induced voltage calculation unit 52a is provided and the estimation induced voltage calculation unit 52b is not provided. Even if it is changed in this way, the effect of (1) of the present embodiment can be obtained.

〇 The first coordinate conversion unit 21 may be configured to be included in the PWM control unit 30 or the square wave control unit 40.
〇 The first coordinate conversion unit 21 may be changed so as to be calculated outside the inverter control device 20 and then input to the PWM control unit 30 and the square wave control unit 40 of the inverter control device 20.

〇 In this embodiment, the current value Iv of the V phase of the motor 60 was detected by the current sensor 62, but for example, the current value Iv is calculated from the current values Iu and Iw by the first coordinate conversion unit 21. You may.

10 ... Inverter circuit, 20 ... Inverter control device, 21 ... First coordinate conversion unit, 30 ... PWM control unit, 31 ... Current command value calculation unit, 34 ... Current control unit, 35 ... Second coordinate conversion unit, 36 ... PWM Signal generation unit, 40 ... rectangular wave control unit, 50 ... control switching unit, 52a ... induced voltage calculation unit, 52b ... estimated induced voltage calculation unit, Iu, Iv, Iw ... current value, Id ... d-axis current value, Iq ... q-axis current value, Id * ... d-axis current command value, Iq * ... q-axis current command value, ΔId, ΔIq ... difference, ω ... rotation speed, Vd * ... d-axis voltage command value, Vq * ... q-axis voltage command Value, Vu, Vv, Vw ... Three-phase voltage command value, Mth ... Threshold, Tref ... Torque command value, S1 ... PWM control signal, S2 ... Rectangular wave signal, Q1 to Q6 ... Switching element.

Claims (2)

A PWM control unit that PWM-controls the switching element that drives the three-phase AC rotary electric machine by outputting a PWM control signal.
A square wave control unit that controls the switching element by outputting a square wave signal, and a square wave control unit.
An inverter control device including a control switching unit that switches between PWM control and square wave control by switching and outputting the PWM control signal and the square wave signal.
It is provided with an induced voltage calculation unit that calculates the induced voltage of the three-phase AC rotary electric machine based on the current value of each phase of the three-phase AC rotary electric machine and the rotation speed of the three-phase AC rotary electric machine.
The control switching unit is an inverter control device characterized in that when the induced voltage exceeds a threshold value in a state where the PWM control signal is output, the control switching unit switches to the rectangular wave signal and outputs the signal. A first coordinate conversion unit that converts the current value of each phase of the three-phase AC rotary electric machine into a d-axis current value and a q-axis current value is provided.
The PWM control unit
A current command value calculation unit that calculates the d-axis current command value and the q-axis current command value of the three-phase AC rotary electric machine based on the torque command value, and
By feedback-controlling the difference between the d-axis current command value and the d-axis current value and the difference between the q-axis current command value and the q-axis current value, the d-axis voltage command value of the three-phase AC rotary electric machine and A current control unit that calculates the q-axis voltage command value,
A second coordinate conversion unit that converts the d-axis voltage command value and the q-axis voltage command value into a three-phase voltage command value that is a target value of the voltage generated in each phase of the three-phase AC rotary electric machine.
It has a PWM signal generation unit that generates the PWM control signal based on the three-phase voltage command value.
Further provided with an estimated induced voltage calculation unit for calculating an estimated induced voltage estimated to be generated in the three-phase AC rotary electric machine based on the d-axis current command value, the q-axis current command value, and the rotation speed.
The inverter control device according to claim 1, wherein the control switching unit outputs the PWM control signal when the estimated induced voltage is lower than the threshold value in the state of outputting the square wave signal.

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