JP2017028827A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress flow of overcurrent through a motor when switching from PWM control to rectangular wave control is limited in an inverter device for switching the PWM control and the rectangular wave control to each other.SOLUTION: An inverter device 1 is configured by an inverter circuit 2, a drive circuit 3, a PWM control circuit 7, a rectangular wave control circuit 9, and a switching unit 10 for performing switching from the rectangular wave control to the PWM control when a current phase difference φi increases to a current phase difference threshold value φith or more, and also performing switching from the PWM control to the rectangular wave control when a percentage modulation M increases to a percentage modulation threshold value Mth1 or more. The PWM control circuit 7 limits a d-axis voltage command value Vd* and a q-axis voltage command value Vq* when the percentage modulation M increases to a percentage modulation threshold Mth2 which is smaller than the percentage modulation threshold Mth1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inverter device that drives a motor mounted on an electric vehicle or the like.

  With the widespread use of electric vehicles such as electric forklifts and plug-in hybrid vehicles that travel using the power of motors, improvements in the technology of inverter devices that drive motors mounted on electric vehicles have been attempted. For example, see Patent Document 1.

  As an example of the inverter device, the d-axis voltage command value and the q-axis voltage command value are obtained so that the actual current flowing through the motor follows the current command value, and the d-axis voltage command value and the q-axis voltage command value are obtained for each phase of the motor. Are converted into voltage command values corresponding to each, and based on the comparison result between the voltage command values and the reference wave, a pulse width modulation signal corresponding to each phase of the motor is obtained, and the pulse width modulation signal is used for the inverter circuit. Some motors are driven by controlling the ON / OFF of the switching elements provided to apply AC voltages with different phases to each phase of the motor (pulse width modulation control (PWM (Pulse Width Modulation) control)) .

  As another example of the inverter device, a rectangular wave control signal corresponding to each phase of the motor is obtained based on the voltage phase obtained from the torque difference value between the torque command value and the torque estimated value, and the rectangular wave control is performed. Some control devices turn on and off switching elements provided in an inverter circuit to apply AC voltages having different phases to each phase of the motor to drive the motor (rectangular wave control).

  As still another example of the inverter device, when the amount of change in the rotation speed of the motor increases and the current phase difference between the current command value and the actual current flowing through the motor exceeds the current phase difference threshold, In order to switch to control and drive the motor at high rotation and high output, when the modulation rate, which is the ratio of the input voltage of the motor to the input voltage of the inverter circuit, is equal to or higher than the modulation rate threshold value, there is one that switches from PWM control to rectangular wave control .

JP 2011-061887 A

  However, as described above, in the inverter device that switches between PWM control and rectangular wave control according to the modulation factor and current phase difference, when switching from PWM control to rectangular wave control is restricted (for example, an electric vehicle is wavy) Even if the motor should be driven by rectangular wave control, such as when accelerating the road at high speed, the motor is forcibly driven by PWM control due to an increase in the fluctuation amount of the motor rotation speed. If the d-axis voltage command value or the q-axis voltage command value increases and is fixed to a certain value as a result of increasing the integral term of PI control without reducing the difference from the command value, The flowing actual current cannot follow the current command value, and an overcurrent (for example, a current larger than the current flowing through the motor during rectangular wave control) may flow through the motor. Patent Document 1 attempts to stabilize PWM control by controlling a DC voltage that is a power source.

  An object of one aspect of the present invention is to suppress an overcurrent from flowing in a motor when switching from PWM control to rectangular wave control is limited in an inverter device that switches between PWM control and rectangular wave control. .

An inverter device according to one aspect of the present invention includes an inverter circuit, a drive circuit, a PWM control circuit, a rectangular wave control circuit, and a switching unit.
The inverter circuit drives a motor.

The drive circuit drives the inverter circuit.
The PWM control circuit is configured such that the driving of the motor is controlled by pulse width modulation control based on a voltage command value obtained by PI control using a current difference value between a current command value and an actual current flowing through the motor. The drive of the drive circuit is controlled.

The rectangular wave control circuit controls driving of the drive circuit so that driving of the motor is controlled by rectangular wave control.
The switching unit switches from the rectangular wave control to the pulse width modulation control when a current phase difference determined by the current command value and the actual current flowing through the motor is equal to or greater than a current phase difference threshold, and inputs the inverter circuit When the modulation rate, which is the ratio of the motor input voltage to the voltage, becomes equal to or higher than the first modulation rate threshold, the pulse width modulation control is switched to the rectangular wave control.

  Further, when the PWM control circuit restricts switching from PWM control to rectangular wave control, and the modulation factor is equal to or greater than a second modulation factor threshold smaller than the first modulation factor threshold The voltage command value is limited.

  According to the present invention, in an inverter device that switches between PWM control and rectangular wave control, when switching from PWM control to rectangular wave control is restricted, it is possible to suppress overcurrent from flowing through the motor.

It is a figure which shows the structural example of the inverter apparatus of embodiment. It is a flowchart which shows an example of operation | movement of a current control part. (A) is a figure which shows an example of a voltage phase. (B) is a figure which shows an example of the information which shows the correspondence of the rotation speed of the rotor of a motor, a torque command value, the input voltage of an inverter circuit, and a limiter value. (C) is a figure which shows an example of the information which shows the correspondence of a voltage phase and a sin value.

Hereinafter, embodiments will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of an inverter device according to an embodiment.
An inverter device 1 shown in FIG. 1 is an inverter device for driving a motor mounted on an electric vehicle such as an electric forklift or a plug-in hybrid vehicle, and includes an inverter circuit 2, a drive circuit 3, and voltage detection. Unit 4, current detection units 5 and 6, PWM control circuit 7, rotation angle detection unit 8, rectangular wave control circuit 9, switching unit 10, and storage unit 11. The storage unit 11 is a RAM (Random Access Memory), a ROM (Random Access Memory), or the like.

  The inverter circuit 2 drives the motor m and includes a capacitor C and switching elements 21 to 26 (for example, IGBT (Insulated Gate Bipolar Transistor)). That is, one end of the capacitor C is connected to the positive terminal of the DC power source P and the collector terminals of the switching elements 21 to 23, and the other end of the capacitor C is connected to the negative terminal of the DC power source P and the emitter terminals of the switching elements 24 to 26. It is connected to the. The emitter terminal of the switching element 21 is connected to the collector terminal of the switching element 24 and the U-phase input terminal of the motor m, and the emitter terminal of the switching element 22 is connected to the collector terminal of the switching element 25 and the V-phase input terminal of the motor m. The emitter terminal of the switching element 23 is connected to the collector terminal of the switching element 26 and the W-phase input terminal of the motor m.

Capacitor C smoothes the voltage output from DC power supply P and input to inverter circuit 2.
The switching elements 21 to 26 are turned on and off based on drive signals output from the drive circuit 3 and input to their gate terminals, respectively. When the switching elements 21 to 26 are turned on and off, respectively, the DC voltage output from the DC power source P is converted into three AC voltages having phases different from each other by 120 degrees, and these AC voltages are converted to the U phase of the motor m, The motor m is driven by being applied to the V-phase and W-phase input terminals.

  The drive circuit 3 drives the inverter circuit 2 in accordance with an input PWM control signal (pulse width modulation control signal) or a rectangular wave control signal. For example, when the input U-phase PWM control signal or U-phase rectangular wave control signal is at a high level, the drive circuit 3 sends a drive signal for turning on the switching element 21 and turning off the switching element 24 to each of the switching elements 21, 24. When the U-phase PWM control signal or the U-phase rectangular wave control signal input to the gate terminal is at a low level, the driving signal for turning off the switching element 21 and turning on the switching element 24 is sent to each gate of the switching elements 21 and 24. Input to the terminal. In addition, when the input V-phase PWM control signal or V-phase rectangular wave control signal is at a high level, the drive circuit 3 sends a drive signal for turning on the switching element 22 and turning off the switching element 25 to each of the switching elements 22 and 25. When the V-phase PWM control signal or the V-phase rectangular wave control signal input to the gate terminal is at a low level, the switching element 22 is turned off and the driving signal for turning on the switching element 25 is supplied to each gate of the switching elements 22 and 25. Input to the terminal. In addition, when the input W-phase PWM control signal or W-phase rectangular wave control signal is at a high level, the drive circuit 3 sends a drive signal for turning on the switching element 23 and turning off the switching element 26 to each of the switching elements 23, 26. When a W-phase PWM control signal or a W-phase rectangular wave control signal input to the gate terminal is at a low level, a driving signal for turning off the switching element 23 and turning on the switching element 26 is sent to each gate of the switching elements 23 and 26. Input to the terminal.

The voltage detector 4 is a voltage sensor, for example, and detects the input voltage Vdc of the inverter circuit 2.
The current detector 5 is, for example, a current sensor, and detects an actual current Iu flowing from the inverter circuit 2 to the U-phase input terminal of the motor m.

The current detector 6 is, for example, a current sensor, and detects an actual current Iw flowing from the inverter circuit 2 to the W-phase input terminal of the motor m.
The PWM control circuit 7 includes a torque / current command value conversion unit 71, a current coordinate conversion unit 72, subtraction units 73 and 74, a current control unit 75, a voltage coordinate conversion unit 76, and a PWM control unit 77. . Note that the PWM control circuit 7 is configured by, for example, a CPU (Central Processing Unit) and the like, and the CPU executes a program stored in the storage unit 11, whereby the torque / current command value conversion unit 71, current coordinate conversion is performed. The unit 72, the subtraction unit 73, the subtraction unit 74, the current control unit 75, the voltage coordinate conversion unit 76, and the PWM control unit 77 are realized.

  Torque / current command value conversion unit 71 converts torque command value Tref output from an external control unit or the like and input to inverter device 1 into d-axis current command value Id * and q-axis current command value Iq *. For example, the torque / current command value conversion unit 71 stores information indicating a correspondence relationship between the torque command value Tref, the d-axis current command value Id *, and the q-axis current command value Iq * stored in advance in the storage unit 11. Referring to this, the d-axis current command value Id * and the q-axis current command value Iq * corresponding to the input torque command value Tref are acquired.

  The current coordinate conversion unit 72 obtains the actual current Iv flowing in the V phase of the motor m from the actual current Iu detected by the current detection unit 5 and the actual current Iw detected by the current detection unit 6, and the actual current Iu, Iv and Iw are converted into d-axis actual current Id (current component for generating field weakening) and q-axis actual current Iq (current component for generating torque).

The subtracting unit 73 calculates a current difference value ΔId between the d-axis actual current Id and the d-axis current command value Id *.
The subtracting unit 74 calculates a current difference value ΔIq between the q-axis actual current Iq and the q-axis current command value Iq *.

The current control unit 75 obtains the d-axis voltage command value Vd * and the q-axis voltage command value Vq * by PI (Proportional Integral) control using the current difference values ΔId and ΔIq.
For example, the current control unit 75 calculates the d-axis voltage command value Vd * by calculating the following formula 1, and calculates the q-axis voltage command value Vq * by calculating the following formula 2. Kp is a constant of the proportional term of PI control, Ki is a constant of the integral term of PI control, ω is the angular velocity of the rotor of the motor m, Lq is the q-axis inductance of the motor m, and Ld is the motor m. The d-axis inductance is used, and Ke is an induced voltage constant.

d-axis voltage command value Vd * = Kp × current difference value ΔId + ∫ (Ki × current difference value ΔId) −ωLqIq Equation 1
q-axis voltage command value Vq * = Kp × current difference value ΔIq + ∫ (Ki × current difference value ΔIq) + ωLdId + ωKe Equation 2
The voltage coordinate conversion unit 76 converts the d-axis voltage command value Vd * and the q-axis voltage command value Vq * into voltage command values (U-phase voltage command value Vu *, V-phase voltage command value corresponding to each phase of the motor m). Vv * and W-phase voltage command value Vw *).

  The PWM control unit 77 controls driving of the drive circuit 3 based on voltage command values corresponding to the respective phases of the motor m. That is, the PWM control unit 77 obtains a U-phase PWM control signal based on the comparison result between the U-phase voltage command value Vu * and the reference wave (triangular wave), and V V based on the comparison result between the V-phase voltage command value Vv * and the reference wave. The phase PWM control signal is obtained, and the W phase PWM control signal is obtained from the comparison result between the W phase voltage command value Vw * and the reference wave.

  That is, the PWM control circuit 7 determines the d-axis voltage command value Vd * obtained by PI control using the current difference values ΔId, ΔIq between the current command values Id *, Iq * and the actual currents Id, Iq flowing through the motor m. The drive of the drive circuit 3 is controlled so that the drive of the motor m is controlled by pulse width modulation control based on the q-axis voltage command value Vq *.

The rotation angle detection unit 8 is, for example, a rotary encoder or a resolver, and detects the rotation angle θ of the rotor of the motor m.
The rectangular wave control circuit 9 includes a torque calculation unit 91, a subtraction unit 92, a voltage phase control unit 93, and a rectangular wave control unit 94. Note that the rectangular wave control circuit 9 is configured by, for example, a CPU, and the CPU executes a program stored in the storage unit 11 to thereby execute a torque calculation unit 91, a subtraction unit 92, a voltage phase control unit 93, and A rectangular wave control unit 94 is realized.

  The torque calculator 91 divides the difference Δθ between the electrical angle θ1 detected at the time t1 by the rotation angle detector 8 and the electrical angle θ2 detected at the time t2 by the difference Δt between the time t1 and the time t2. The angular velocity ω of the rotor of the motor m is obtained, and the estimated torque value Tdet is obtained by calculating the following formula 3.

Estimated torque value Tdet = (d-axis voltage command value Vd * × d-axis actual current Id + q-axis voltage command value Vq * × q-axis actual current Iq) / angular velocity ω Equation 3
The subtraction unit 92 calculates a torque difference value ΔT between the input torque command value Tref and the estimated torque value Tdet calculated by the torque calculation unit 91.

The voltage phase control unit 93 obtains the voltage phase φ so that the torque difference value ΔT becomes zero.
The rectangular wave control unit 94 generates a rectangular wave control signal in consideration of the voltage phase φ obtained by the voltage phase control unit 93 and the electrical angle of the rotor, and a U-phase rectangular wave control signal, a V-phase rectangular wave control signal, and The W-phase rectangular wave signal is set to high level or low level, respectively.

  That is, the rectangular wave control circuit 9 controls the drive circuit 3 so that the drive of the motor m is controlled by the rectangular wave control based on the voltage phase φ obtained from the torque difference value ΔT between the torque command value Tref and the estimated torque value Tdet. Control the drive.

  When the current phase difference φi becomes equal to or greater than the current phase difference threshold φith, the switching unit 10 uses a rectangular wave control signal (U-phase rectangular wave control signal, V-phase rectangular wave control signal, and W Switching from a phase rectangular wave signal) to a PWM control signal (U-phase PWM control signal, V-phase PWM control signal, and W-phase PWM control signal). The difference between the current phase obtained from the d-axis actual current Id and the q-axis actual current Iq and the threshold Ith obtained from the d-axis current command value Id * and the q-axis current command value Iq * is defined as a current phase difference φi. .

Further, when the modulation rate M, which is the ratio of the input voltage Vm of the motor m to the input voltage Vdc of the inverter circuit 2, becomes equal to or higher than the modulation rate threshold value Mth1 (first modulation rate threshold value), the switching unit 10 inputs to the drive circuit 3. As a control signal, a rectangular wave control signal (a U-phase rectangular wave control signal, a V-phase rectangular wave control signal, and a W-phase PWM control signal) from a PWM control signal (a U-phase PWM control signal, a V-phase PWM control signal, and a W-phase PWM control signal) Switch to phase square wave signal. It is assumed that √ ((d-axis voltage command value Vd *) ² + (q-axis voltage command value Vq *) ² ) is the input voltage Vm.

  That is, the switching unit 10 switches from the rectangular wave control to the pulse width modulation control when the current phase difference φi is equal to or greater than the current phase difference threshold φith, and when the modulation factor M is equal to or greater than the modulation factor threshold Mth1, Switch to wave control. Note that the switching unit 10 restricts switching from PWM control to rectangular wave control according to a change in the rotational speed n of the rotor of the motor m, for example, when traveling on a wavy road at high speed.

  In the embodiment, when the switching from PWM control to rectangular wave control is restricted, the modulation factor M is set to the modulation factor threshold Mth1 in the current controller 75 (PWM control circuit 7) in order to suppress overcurrent from flowing through the motor m. If it is equal to or greater than the smaller modulation factor threshold Mth2 (second modulation factor threshold), the d-axis voltage command value Vd * and the q-axis voltage command value Vq * are limited.

FIG. 2 is a flowchart showing an example of the operation of the current control unit 75. Note that the flowchart shown in FIG. 2 is repeatedly executed at each control timing.
First, when the modulation factor M is not equal to or greater than the modulation factor threshold Mth2 (S1: No), the current controller 75 turns off the voltage phase flag (S2), and proceeds to the process of S3.

  Further, the current control unit 75 is a case where the modulation factor M is equal to or greater than the modulation factor threshold Mth2 (S1: Yes), and the motor m is in a regenerative state instead of a power running state (S4: No). The voltage phase φ during regeneration is converted into the voltage phase φ during power running (S5).

  For example, the current control unit 75 converts the voltage phase φ during regeneration shown in FIG. 3A into a voltage phase φ during power running by performing calculation for rotating the voltage phase φ by a predetermined angle. If the motor m is not in a regenerative state depending on the type of the motor m, the processes of S4 and S5 can be omitted.

  Next, when the voltage phase φ is equal to or larger than the limiter value φth (voltage phase threshold) (S6: Yes), the current control unit 75 turns on the voltage phase flag (S7), and the voltage phase φ is smaller than the limiter value φth. If it is smaller (S6: No), the voltage phase flag is turned off (S2), and the process proceeds to S3.

  For example, in the process of S6, the current control unit 75 stores the rotation speed n (n1, n2,...) Of the rotor of the motor m shown in FIG. Value Tref (Tref1, Tref2,...), Input voltage Vdc (Vdc1, Vdc2,...) Of the inverter circuit 2, and limiter values φth (φth11, φth12,..., Φth21, φ22,. ) To obtain the limiter value φth corresponding to the rotation speed n, the torque command value Tref, and the input voltage Vdc at the current control timing. The rotational speed n (rpm) of the rotor of the motor m is set to 60 * angular velocity ω / 2π.

  Next, when the voltage phase flag is off (S3: No), the current control unit 75 performs PI control using the current difference values ΔId and ΔIq, that is, by calculating the above Equations 1 and 2. The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are obtained, and the obtained d-axis voltage command value Vd * and q-axis voltage command value Vq * are used as the d-axis voltage command value Vd * for PWM control and The q-axis voltage command value Vq * is output to the voltage coordinate conversion unit 76, and the obtained d-axis voltage command value Vd * and q-axis voltage command value Vq * are initialized to values used for low-pass filter processing described later. The values Vd1 * and Vq1 * are stored in the storage unit 11 (S8) and wait until the next control timing.

Further, when the voltage phase flag is ON (S3: Yes), the current control unit 75 obtains a sin value and a cos value corresponding to the limiter value φth acquired in the process of S6 (S9).
For example, the current control unit 75 refers to the information indicating the correspondence relationship between the limiter value φth and the sin value shown in FIG. 3C stored in the storage unit 11, so that the limiter value φth acquired in S <b> 6 is set. While acquiring the corresponding sin value, by referring to the information shown in FIG. 3C, the sin value corresponding to the value obtained by subtracting the limiter value φth acquired in the process of S6 from 90 ° was acquired in S6. Obtained as a cos value corresponding to the limiter value φth.

Next, the current control unit 75 calculates “the input voltage Vm of the motor m” by calculating the following expression 4 (S10).
“Input voltage Vm of motor m” = “input voltage Vdc of inverter circuit 2” × “modulation factor threshold Mth2” Equation 4
Next, the current control unit 75 calculates the “restricted d-axis voltage command value Vd *” by calculating the following formula 5 and calculates the “restricted q-axis voltage command value Vq * by calculating the following formula 6. Is obtained (S11).

“Restricted d-axis voltage command value Vd *” = “cos value obtained in the process of S9” × “the input voltage Vm of the motor m obtained in the process of S10” Expression 5
“Restricted q-axis voltage command value Vq *” = “sin value determined in the process of S9” × “input voltage Vm of the motor m determined in the process of S10” Expression 6
Next, the current control unit 75 performs a low-pass filter process on the “restricted d-axis voltage command value Vd *” and “restricted q-axis voltage command value Vq *” obtained in the process of S11 (S12).

For example, when the modulation factor M that is smaller than the modulation factor threshold value Mth2 at the previous control timing becomes equal to or greater than the modulation factor threshold value Mth2 at the current control timing, the current control unit 75 calculates “ The “d-axis voltage command value Vd *” is calculated, and the “q-axis voltage command value Vq * after low-pass filter processing” is calculated by calculating the following equation 8. For example, the predetermined value a is 2 ⁿ (n is a natural number).

“D-axis voltage command value Vd * after low-pass filter processing” = “initial value Vd1 * stored in the storage unit 11” + (“d-axis voltage command value Vd * limited at the current control timing” − “ Initial value Vd1 * ") stored in storage unit 11) / predetermined value a ... Formula 7
“Q-axis voltage command value Vq * after low-pass filter processing” = “initial value Vq1 * stored in storage unit 11” + (“q-axis voltage command value Vq * limited at the current control timing” − “ Initial value Vq1 * "stored in storage unit 11) / predetermined value a ... Equation 8
Further, for example, when the modulation factor M that is equal to or greater than the modulation factor threshold Mth2 at the previous control timing is equal to or greater than the modulation factor threshold Mth2 at the current control timing, for example, the current control unit 75 calculates “D-axis voltage command value Vd * after low-pass filter processing” is obtained, and “q-axis voltage command value Vq * after low-pass filter processing” is obtained by calculating the following equation 10.

“D-axis voltage command value Vd * after filtering” = “d-axis voltage command value Vd * after low-pass filtering at the previous control timing” + (“d-axis voltage command value Vd * limited at the current control timing” "-" D-axis voltage command value Vd * after low-pass filter processing at the previous control timing ") / predetermined value a (Equation 9)
“Q-axis voltage command value Vq * after filtering” = “q-axis voltage command value Vq * after low-pass filtering at the previous control timing” + (“q-axis voltage command value Vq * limited at the current control timing” "-" Q-axis voltage command value Vq * after low-pass filter processing at the previous control timing ") / predetermined value a ... Equation 10
Next, the current control unit 75 converts the d-axis voltage command value Vd * and the q-axis voltage command value Vq * after low-pass filter processing into the d-axis voltage command value Vd * and the q-axis voltage command value Vq * for PWM control. Is output to the voltage coordinate conversion unit 76 (S13).

  Next, the current control unit 75 obtains an initial value ∫d1 of an integral term of PI control for obtaining the d-axis voltage command value Vd * by calculating the following equation 11, and calculating q An initial value ∫q1 of the integral term of PI control for obtaining the shaft voltage command value Vq * is obtained, the initial values ∫d1 and ∫q1 are stored in the storage unit 11 (S14), and the system waits until the next control timing. Equation 11 below is modified so that Equation (11) can be solved for ∫ (Ki × current difference value ΔId), and ∫ (Ki × current difference value ΔId) of Equation 1 after deformation is changed to an initial value ∫d1. Equation 12 below is modified so that Equation 12 below can be solved for ∫ (Ki × current difference value ΔIq), and ∫ (Ki × current difference value ΔIq) of Equation 2 after deformation is modified. Is changed to the initial value ∫q1.

Initial value ∫d1 = d-axis voltage command value Vd * −Kp × current difference value ΔId + ωLqIq Equation 11
Initial value ∫q1 = q-axis voltage command value Vq * −Kp × current difference value ΔIq−ωLdId−ωKe Equation 12
For example, when the modulation factor M that is equal to or greater than the modulation factor threshold Mth2 at the previous control timing becomes smaller than the modulation factor threshold Mth2 at the current control timing, the current control unit 75 performs “ Substituting the initial value ∫d1 for (Ki × current difference value ΔId) ”and calculating Equation 1 thereof, the d-axis voltage command value Vd * is obtained, and“ ∫ (Ki × current difference value ΔIq) of Equation 2 is also obtained. ) "Is substituted for the initial value ∫q1 and the equation 2 is calculated to obtain the q-axis voltage command value Vqi *.

  In the inverter device 1 of the embodiment, in the current control unit 75 (PWM control circuit 7), when the modulation factor M is equal to or higher than the modulation factor threshold Mth2 smaller than the modulation factor threshold Mth1, the d-axis voltage command value Vd * and the q-axis The voltage command value Vq * is limited. As a result, even when switching from PWM control to rectangular wave control is restricted, the d-axis voltage command value Vd * and the q-axis voltage command value Vq * are increased and fixed to a certain value. Therefore, the actual currents Id and Iq flowing through the motor m can be made to follow the current command values Id * and Iq *, and the motor m is overcurrent (from the current flowing through the motor m during rectangular wave control). Large current) can be suppressed.

  Further, in the inverter device 1 of the embodiment, when the modulation factor M is equal to or greater than the modulation factor threshold Mth2, the PI control integral term using the limited d-axis voltage command value Vd * and the limited q-axis voltage command value Vq *. Initial values ∫d1 and ∫q1 are obtained and stored in the storage unit 11. When the modulation factor M becomes smaller than the modulation factor threshold Mth2 at the next control timing, the integral term stored in the storage unit 11 is stored. The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are obtained by performing PI control using the initial values ∫d1 and ∫q1. As a result, when the modulation factor M becomes smaller than the modulation factor threshold Mth2, as compared with the case where PI control is performed without using the initial values ∫d1 and ∫q1 of the integral terms stored in the storage unit 11. Variations in the d-axis voltage command value Vd * and the q-axis voltage command value Vq * obtained by PI control can be suppressed. Therefore, the motor m can be driven stably.

  Further, in the inverter device 1 of the embodiment, when the modulation factor M is smaller than the modulation factor threshold Mth2, the d-axis voltage command value Vd * and the q-axis voltage command value Vq * are stored in the storage unit 11, and the next time When the modulation factor M becomes equal to or greater than the modulation factor threshold Mth2 at the control timing, the d-axis voltage stored in the storage unit 11 with respect to the restricted d-axis voltage command value Vd * and the restricted q-axis voltage command value Vq *. The low-pass filter process is performed using the command value Vd * and the q-axis voltage command value Vq *, and the motor m is controlled by PWM control based on the d-axis voltage command value Vd * and the q-axis voltage command value Vq * after the low-pass filter process. The drive of the drive circuit 3 is controlled so that the drive is controlled. As a result, the modulation factor M is greater than or equal to the modulation factor threshold Mth2 as compared with the case where the low-pass filter process is performed without using the d-axis voltage command value Vd * and the q-axis voltage command value Vq * stored in the storage unit 11. Thus, fluctuations in the d-axis voltage command value Vd * and the q-axis voltage command value Vq * after the low-pass filter processing can be suppressed. Therefore, the motor m can be driven stably.

  The present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Inverter apparatus 2 Inverter circuit 3 Drive circuit 4 Voltage detection part 5, 6 Current detection part 7 PWM control circuit 8 Rotation angle detection part 9 Rectangular wave control circuit 10 Switching part 11 Memory | storage parts 21-26 Switching element 71 Torque / current command value Converter 72 Current coordinate converters 73, 74, 92 Subtractor 75 Current controller 76 Voltage coordinate converter 77 PWM controller 91 Torque calculator 93 Voltage phase controller 94 Rectangular wave controller

Claims (4)

An inverter circuit for driving the motor;
A drive circuit for driving the inverter circuit;
The drive circuit is driven such that the drive of the motor is controlled by pulse width modulation control based on a voltage command value obtained by PI control using a current difference value between a current command value and an actual current flowing through the motor. A PWM control circuit to control;
A rectangular wave control circuit for controlling the driving of the drive circuit so that the driving of the motor is controlled by the rectangular wave control;
When the current phase difference obtained by the current command value and the actual current flowing through the motor is equal to or greater than a current phase difference threshold, the rectangular wave control is switched to the pulse width modulation control, and the motor is controlled with respect to the input voltage of the inverter circuit. A switching unit that switches from the pulse width modulation control to the rectangular wave control when a modulation rate that is a ratio of input voltages is equal to or greater than a first modulation rate threshold;
With
When the PWM control circuit restricts switching from PWM control to rectangular wave control, and the modulation factor is equal to or higher than a second modulation factor threshold smaller than the first modulation factor threshold, An inverter device characterized by limiting a voltage command value. The inverter device according to claim 1,
The PWM control circuit is
When the modulation factor is equal to or greater than the second modulation factor threshold value, the initial value of the integral term of PI control is obtained using the limited voltage command value and stored in the storage unit;
When the modulation factor becomes smaller than the second modulation factor threshold at the next control timing, the voltage command value is obtained by performing PI control using the initial value stored in the storage unit. A featured inverter device. The inverter device according to claim 1 or 2,
The PWM control circuit is
When the modulation factor is smaller than the second modulation factor threshold, the voltage command value is stored in a storage unit,
When the modulation rate becomes equal to or higher than the second modulation rate threshold at the next control timing, low-pass filter processing is performed on the limited voltage command value using the voltage command value stored in the storage unit. The drive of the drive circuit is controlled so that the drive of the motor is controlled by pulse width modulation control based on the voltage command value after the low-pass filter processing. The inverter device according to any one of claims 1 to 3,
The PWM control circuit has a case where the modulation factor is equal to or greater than the second modulation factor threshold and a voltage phase obtained from a torque difference value between the torque command value and the torque estimated value is equal to or greater than the voltage phase threshold. The sin value and the cos value corresponding to the voltage phase threshold value are obtained, and the input voltage of the motor corresponding to the voltage phase threshold value is obtained by multiplying the input voltage of the inverter circuit and the second modulation factor threshold value. The d-axis voltage command value is obtained by multiplying the cos value and the input voltage of the motor corresponding to the voltage phase threshold, and the sin value and the input voltage of the motor corresponding to the voltage phase threshold are multiplied. Thus, the q-axis voltage command value is obtained, and the drive of the motor is controlled by pulse width modulation control based on the d-axis voltage command value and the q-axis voltage command value. , Inverter device and controls the driving of the drive circuit.

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