JP2012105393A - Pwm inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PWM inverter device which takes into account a fluctuation in a dead time error voltage in pulse width modulation in an overmodulation region as it compensates for the dead time, thereby producing an output voltage just as same as a directive value.SOLUTION: There is included dead time compensation means which generates a second AC voltage directive signal based on a dead time error voltage which is produced by a dead time used to prevent a switching element from getting shorted. The dead time compensation means, at least in an overmodulation region where the amplitude of the second AC voltage directive signal is larger than that of a carrier signal, generates the second AC voltage directive signal based on at least one of the second AC voltage directive signal or a second modulation rate directive k2indicating a proportion of the size of a fundamental wave component of the second AC voltage directive signal and the dead time error voltage which is produced according to a difference between a first AC voltage phase, or the phase of a first AC voltage directive signal, and a detected or a calculated phase of the output current of a PWM inverter device 10.

Description

  The present invention relates to a PWM inverter device that converts a DC voltage to an AC voltage by pulse width modulation, and more specifically, performs pulse width modulation in an overmodulation region in which the amplitude of an AC voltage command signal is larger than the amplitude of a carrier signal. The present invention relates to a PWM inverter device.

  In a PWM inverter device that converts a DC voltage into an AC voltage by turning on and off the switching element, a dead time is inserted in consideration of a turn-off time of the switching element in order to prevent a short circuit of the switching element. Due to this dead time, an error voltage (hereinafter referred to as a dead time error voltage) between the voltage command of the inverter and the output voltage is generated. Therefore, dead time compensation is generally performed to compensate for this.

  By the way, when performing pulse width modulation in a sinusoidal modulation region where the amplitude of the AC voltage command signal is equal to or less than the amplitude of the carrier signal, the dead time error voltage is a square wave voltage having an amplitude proportional to the carrier cycle. Patent Document 1 discloses a PWM inverter device that performs dead time compensation in proportion to a cycle.

  However, when increasing the magnitude of the fundamental component of the output voltage of the PWM inverter device, for example, when it is necessary to rotate the motor at a high speed, the overmodulation region in which the amplitude of the AC voltage command signal is larger than the amplitude of the carrier wave signal In some cases, pulse width modulation may be performed. In the overmodulation region, the average number of times of switching decreases as the amplitude of the AC voltage command signal increases, and therefore the amplitude of the dead time error voltage varies. For this reason, appropriate compensation cannot be performed by dead time compensation that is simply proportional to the carrier wave period as in Patent Document 1 described above.

  Patent Document 2 discloses a technique for suppressing a change in the influence of a dead time error voltage on an inverter output voltage when pulse width modulation is performed in an overmodulation region.

JP 2006-217776 A JP 2010-104151 A

  The technique disclosed in Patent Document 2 corrects the amplitude of the AC voltage command signal so as to suppress the change in the influence of the dead time due to the switching between the sine wave modulation region and the overmodulation region and the decrease in the number of switching in the overmodulation region. Thus, fluctuations in the inverter output voltage are suppressed.

  However, in the technique disclosed in Patent Document 2, since the dead time error voltage itself is not compensated, the inverter output voltage includes the dead time error voltage, and an appropriate inverter output voltage cannot be obtained.

  An object of the present invention is to provide a PWM inverter device that performs dead time compensation in consideration of fluctuations in dead time error voltage in pulse width modulation in an overmodulation region and obtains an output voltage according to a command value.

The PWM inverter device according to the present invention is a PWM inverter device that converts a DC voltage into an AC voltage by turning on and off a switching element based on a control command, and is a fundamental wave of the AC voltage that can be output by the DC voltage. First modulation rate command generation means for generating a first modulation rate command indicating a ratio of the magnitude of the fundamental wave component of the first AC voltage command signal to the size of the component; and the first AC voltage command signal A first phase generating means for generating a first phase used for generating the second AC voltage based on the first phase and a dead time error voltage generated by a dead time for preventing a short circuit of the switching element. The dead time compensation means for generating the command signal, and the control command by the pulse width modulation control based on the comparison between the second AC voltage command signal and the carrier signal. With a PWM control means for forming, a,
The dead time compensation means includes at least the second AC voltage command signal or the second AC voltage command signal in an overmodulation region where the amplitude of the second AC voltage command signal is larger than the amplitude of the carrier signal. At least one of the second modulation rate commands indicating the ratio of the magnitude of the fundamental wave component, the second AC voltage phase that is the phase of the second AC voltage command signal, and the output current of the PWM inverter device The second AC voltage command signal is generated based on the dead time error voltage generated according to the difference between the detected value or the phase of the calculated value.

  The PWM inverter device according to the present invention generates an AC voltage command signal that obtains a desired PWM inverter output voltage in consideration of a dead time error voltage change that occurs when an overmodulation region is used. Thereby, dead time compensation can be appropriately performed even in the overmodulation region.

It is a block block diagram which shows the control system of the synchronous motor containing the PWM inverter apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the inside of the alternating voltage generation means of FIG. It is a figure which shows the production | generation of the control command by the PWM control means of FIG. It is a figure which shows the voltage response characteristic of the PWM inverter apparatus which concerns on Embodiment 1 of this invention. It is a figure explaining the function of the phase compensation means of the PWM inverter apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the control system of the synchronous motor at the time of performing square wave type | mold dead time compensation in an overmodulation area | region by the PWM inverter apparatus which concerns on Embodiment 1 of this invention.

  Preferred embodiments of a PWM inverter device according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding parts are described with the same reference numerals, and the characters representing the commands are marked with *. Further, in each of the following embodiments, a case will be described in which this PWM inverter device is used as a magnetic pole position sensorless control device for a synchronous motor.

Embodiment 1 FIG.
1 is a block diagram showing a PWM inverter device according to Embodiment 1 of the present invention together with a synchronous motor.
In FIG. 1, the PWM inverter device 10 controls the driving of the synchronous motor 11. The synchronous motor 11 has a stator 12 and a rotor 13. The PWM inverter device 10 includes a subtractor 14, a frequency compensation unit 15, a first dq voltage command generation unit 16, an integrator 17 as a first phase generation unit, a three-phase-dq coordinate conversion unit 18, and a second phase conversion unit 18. Dq voltage command generation means 19, first AC voltage command signal generation means 20, phase compensation means 21, overmodulation region detection means 22, second AC voltage command signal generation means 23, PWM control means 24, AC voltage generation Means 25, first modulation rate command generation means 26, and second modulation rate command generation means 27 are provided. The dead time compensation means includes a second dq voltage command generation means 19, a first AC voltage command signal generation means 20, a phase compensation means 21, a second AC voltage command signal generation means 23, a second modulation factor. The command generation means 27 is comprised.

  As described above, the PWM inverter device 10 is a magnetic pole position sensorless control device and cannot know the dq axes. Therefore, the synchronous motor 11 is energized using the virtual dq axis set on the control side, and the total magnetic flux of the rotor magnetic flux and the armature reaction magnetic flux is maintained at a constant value. Use matching magnetic flux vector control. Thereby, the voltage can be controlled without losing sight of the magnetic pole position.

Subtractor 14 subtracts the amount of frequency compensation fc output from the frequency compensation means 15 from the rotational speed command omega ^*, and outputs the rotation speed after frequency compensation command .omega.1 ^*.

The frequency compensation unit 15 calculates and outputs a frequency compensation amount fc for compensating the frequency of the rotational speed command ω ^* based on the q-axis current Iq from the three-phase-dq coordinate conversion unit 18. The frequency compensation amount fc is expressed by the following equation (1).

    fc = (khpf × ωhpf) × s / (s + ωhpf) × Iq (1)

  In Equation (1), khpf is a frequency compensation gain, ωhpf is a high-pass filter passing frequency, and s is a Laplace operator.

The first dq voltage command generation means 16 includes the input field magnetic flux, the rotational speed command ω1 ^* after frequency compensation from the subtractor 14, the d-axis current Id from the three-phase-dq coordinate conversion means 18, and Based on the q-axis current Iq, the first d-axis voltage command Vd1 ^* and the first q-axis voltage command Vq1 ^* are generated and output. In this embodiment, a first dq voltage command value (first d-axis voltage command Vd1 ^* and first q-axis voltage is based on a magnetic flux vector control algorithm which is one of magnetic pole position sensorless control algorithms. The command Vq1 ^* ) is generated, but the first dq voltage command may be calculated based on another algorithm.

The integrator 17 calculates the phase (first phase) θ of the rotor 13 based on the rotational speed command ω1 ^* after frequency compensation from the subtractor 14, and outputs the phase θ of the rotor 13. Specifically, the integrator 17 adds the phase advance for the calculation period to the previous phase of the rotor 13 to calculate the phase θ of the rotor 13. This phase advance is obtained by multiplying the calculation cycle by the rotational speed command ω1 ^* after frequency compensation.

  Based on the phase θ of the rotor 13 from the integrator 17, the three-phase-dq coordinate conversion means 18 converts the dq current value (d-axis current Id and q-axis current from the three-phase current flowing through the stator 12 of the synchronous motor 11. Iq) is calculated and output. In this embodiment, the U-phase current Iu and the V-phase current Iv are detected from the three-phase currents, and the dq current value is calculated based on these detected currents. However, the present invention is not limited to this. The phase current to be detected may be any two of the three phases. The d-axis current Id and the q-axis current Iq calculated by the three-phase-dq coordinate conversion means 18 are used for the first dq voltage command generation means 16.

The first modulation rate command generation unit 26 generates a first modulation rate command k1 ^* from the first dq voltage command value output from the first dq voltage command generation unit 16. The first modulation factor command k1 ^* is obtained by dividing the square root of the sum of squares of Vd1 ^* and Vq1 ^* by the magnitude of the fundamental component of the AC voltage that can be output from the PWM inverter device 10, for example, the input DC voltage of the PWM inverter. calculate.

The second modulation rate command generation means 27 is configured to detect the amplitude Vtda of the dead time error voltage and the power factor (power factor of AC power exchanged between the PWM inverter device 10 and the synchronous motor 11 connected to the PWM inverter device 10). pf, dead time error voltage calculation means for calculating a dead time error voltage based on the first modulation factor command k1 ^* .

The power factor pf is an example of a difference between the second AC voltage phase, which is the phase of the second AC voltage command signal, and the phase of the output current of the PWM inverter device 10. It is defined by the cosine of the difference between the second AC voltage phase that is the phase of the voltage command signal and the phase of the output current of the PWM inverter device 10. The second modulation rate command generation means 27 is a second modulation that can obtain the output voltage of the PWM inverter device 10 equal to the first dq voltage command based on the dead time error voltage calculated by the dead time error voltage calculation means. A rate command k2 ^* is generated. The detailed function of the second modulation factor command generation means 27 will be described later.

The second dq voltage command generation means 19 obtains a value obtained by dividing the second modulation ratio command k2 ^* output from the second modulation ratio command generation means 27 by the first modulation ratio command k1 ^* , Vd1 ^* , Multiply each by Vq1 ^* and set the values as Vd2 ^* and Vq2 ^* . That is, Vd2 ^* and Vq2 ^* can be expressed by the following equations (2) and (3), respectively, where the value of the first modulation factor command is k1 ^* and the value of the second modulation factor command is k2 ^* .

Vd2 ^* = (k2 ^* / k1 ^* ). Vd1 ^* (2)

Vq2 ^* = (k2 ^* / k1 ^* ) · Vq1 ^* (3)

The first AC voltage command signal generation unit 20 outputs the first d-axis voltage command Vd ^* and the first q-axis voltage command Vq ^* from the first dq voltage command generation unit 16 and the integrator 17. The first U-phase voltage command Vu1 ^* , the first V-phase voltage command Vv1 ^*, and the first W-phase voltage command Vw1 ^* are generated and output based on the rotor phase θ. The first U-phase voltage command Vu1 ^* , the first V-phase voltage command Vv1 ^*, and the first W-phase voltage command Vw1 ^* are expressed by the following equations (4) to (6), respectively.

Vu1 ^* = (√2 / √3) Vd1 ^* · cos θ− (√2 / √3) Vq1 ^* · sin θ
... (4)

Vv1 ^* = (√2 / √3) Vd1 ^* · cos (θ + 240 °)
-(√2 / √3) Vq1 ^* · sin (θ + 240 °) (5)

Vw1 ^* = − (Vu1 ^* + Vv1 ^* ) (6)

The phase compensation unit 21 includes a power factor pf, an amplitude Vtda of a dead time error voltage, a second modulation rate command k2 ^* output from the second modulation rate command generation unit 27, and a first output from the integrator 17. Based on the phase θ, a second phase θc that compensates for the phase shift caused by the generation of the dead time error voltage is output. The detailed function of the phase compensation means 21 will be described later.

The overmodulation area detection means 22 is a sine wave when the sum of the amplitude Vamp of the first AC voltage command signal and the dead time compensation amount Vtdc used in the sine wave modulation area is equal to or less than the amplitude of the carrier signal in the PWM control means 24. A case where the modulation area is larger than the amplitude of the carrier signal is detected as an overmodulation area, and an overmodulation area detection signal Ov is generated and output. The amplitude Vamp of the first AC voltage command signal is multiplied by the first modulation factor command k1 ^* by the magnitude of the fundamental wave component of the AC voltage that can be output from the PWM inverter device 10, for example, the input DC voltage of the PWM inverter device 10. To calculate.

When the second AC voltage command signal generation means 23 is determined to be a sine wave modulation area by the overmodulation area detection signal Ov from the overmodulation area detection means 22, the dead time based on the dead time error voltage Vtd is determined. A value obtained by adding or subtracting the compensation amount Vtdc to or from the first AC voltage command signal according to the polarity of the output current of the PWM inverter device 10 (phase current flowing through the stator 12) is the second AC voltage command signal (second Output as a U-phase voltage command Vu2 ^* , a second V-phase voltage command Vv2 ^*, and a second W-phase voltage command Vw2 ^* ). In the present embodiment, among the phase currents flowing through the stator 12, the W-phase current Iw uses the relationship that the sum of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw becomes 0, It is calculated from the current Iu and the V-phase current Iv.

  The dead time error voltage in the sine wave modulation region can be expressed by the following equations (7) to (9), where Ip is the output current of the PWM inverter device 10 and Vtda is the amplitude of the dead time error voltage. As can be seen from the equations (7) to (9), the dead time error voltage Vtd is a square wave voltage that depends on the polarity of the output current Ip of the PWM inverter device 10. The phase θip of the output current Ip is determined as shown in the following equation (10) by the phase θp of the AC voltage signal and the power factor pf, for example.

    Vtd = Vtda (Ip <0) (7)

    Vtd = 0 (Ip = 0) (8)

    Vtd = −Vtda (Ip> 0) (9)

    θip = θp-arccos (pf) (10)

  The amplitude Vtda of the dead time error voltage can be expressed by using the input DC voltage E of the PWM inverter device 10, the carrier wave period f generated by the PWM control device 24, and the dead time td as shown in the following equation (11).

    Vtda = E · f · td (11)

  The dead time compensation amount Vtdc is added to or subtracted from the first AC voltage command signal so as to cancel the dead time error voltage Vtd expressed by the equations (7) to (11). Specifically, assuming that Vtdc = Vtda, Vtdc is subtracted from the first AC voltage command signal when Ip <0, and Vtdc is added to the first AC voltage command signal when Ip> 0. When Ip = 0, neither addition nor subtraction is performed on the first AC voltage command signal. In this way, a value obtained by adding or subtracting the dead time compensation amount Vtdc to or from the first AC voltage command signal is output as the second AC voltage command signal.

When the second AC voltage command signal generation unit 23 determines that the region is an overmodulation region based on the overmodulation region detection signal Ov from the overmodulation region detection unit 22, the second AC voltage command signal generation unit 23 receives the second dq voltage command from the second dq voltage command. An AC voltage command signal is generated and output. Specifically, the second AC voltage command signal is generated and output using the formulas in which Vd1 ^* and Vq1 ^* in the above formulas (2) to (4) are replaced with Vd2 ^* and Vq2 ^* , and θ is replaced with θc, respectively. To do.

  The AC voltage generator 25 outputs a three-phase AC voltage by turning on and off the switching element based on the DC voltage and the control command output from the PWM controller 24, and energizes the stator 12 of the synchronous motor 11.

  FIG. 2 is a diagram showing the inside of the AC voltage generation means 25. The AC voltage generation means 25 includes a U-phase upper and lower arm (U-phase upper arm and U-phase lower arm), a V-phase upper and lower arm (V-phase upper arm and V-phase lower arm), and a W-phase upper and lower arm (W-phase upper arm). , W-phase lower arm).

  The U-phase upper arm consists of a switching element Q1 and a diode D1, and the U-phase lower arm consists of a switching element Q2 and a diode D2. The V-phase upper arm is composed of a switching element Q3 and a diode D3, and the V-phase lower arm is composed of a switching element Q4 and a diode D4. Further, the W-phase upper arm consists of a switching element Q5 and a diode D5, and the W-phase lower arm consists of a switching element Q6 and a diode D6. The control command generated from the PWM control means 24 is input to the switching elements Q1 to Q6, and the switching elements are turned on / off.

  The PWM control unit 24 has a pulse width based on a comparison between the second AC voltage command signal output from the second AC voltage command signal generation unit 23 and a triangular wave carrier wave generated inside the PWM control unit 24. A control command is generated by modulation control.

  FIG. 3 is a diagram illustrating generation of a control command for one phase by the PWM control unit 24. When the second AC voltage command signal and the carrier wave signal are compared, and the second AC voltage command signal is equal to or greater than the carrier wave signal, the upper arm switching element, for example, Q1 is turned ON in the case of the U phase, and the lower arm switching is performed. In the case of an element, for example, U phase, Q2 is turned OFF. When the second AC voltage command signal <carrier wave signal, the upper arm switching element, for example, Q1 is turned off for the U phase, and the lower arm switching element, for example, Q2 is turned on for the U phase.

  Since the switching elements of the upper and lower arms (upper arm and lower arm) are connected in series, it is necessary to prevent a short circuit due to switching. For this reason, the timing at which the switching elements are turned on for both the upper arm and the lower arm is delayed by a predetermined time td. This time td is a dead time.

Next, the detailed function of the second modulation factor command generation unit 27 will be described along the flow of processing.
The second modulation factor command generation means 27 shows the relationship with the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 when the dead time error voltage Vtd is not compensated for the first modulation factor command k1 ^* . From the voltage response characteristic, a second modulation factor command k2 ^* is generated in which the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 is equal to the magnitude of the fundamental wave component of the first AC voltage command signal.

The magnitude of the fundamental wave component of the first AC voltage command signal is the magnitude of the fundamental wave component of the AC voltage that can be output from the PWM inverter device 10 according to the first modulation factor command k1 ^* , for example, the PWM inverter device 10 It can be calculated by multiplying the input DC voltage.

Next, voltage response characteristics used to generate the second modulation factor command k2 ^* from the first modulation factor command k1 ^* will be described. FIG. 4 is an illustrative example of voltage response characteristics, and also illustrates the relationship between the magnitude of the fundamental component of the first modulation rate command k1 ^* and the first AC voltage command signal.

The magnitude of the fundamental wave component of the first modulation rate command k1 ^* and the first AC voltage command signal is in a linear relationship, but when the pulse width modulation is performed by the PWM control unit 24, a certain first modulation rate command k1 Enters overmodulation range from above ^* value. In the overmodulation region, the relationship between the magnitudes of the fundamental wave components of the PWM inverter device 10 when the first modulation factor command k1 ^* and the first AC voltage command signal are input to the PWM control unit 24 is nonlinear. In addition, in the overmodulation region, the number of PWM switching operations decreases as the first modulation factor command k1 ^* increases, so that the influence of the dead time error voltage is reduced. Therefore, the voltage response characteristic is also nonlinear.

Vmax in FIG. 4 indicates the maximum value of the fundamental component of the output voltage of the PWM inverter device 10 when there is no dead time error voltage. Vcom1 indicates the magnitude of the fundamental component of the first AC voltage command signal when the first modulation factor command k1 ^* is a certain value kcom1. From the voltage response characteristic, the second modulation factor command k2 ^{* at} which the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 becomes Vcom1 can be obtained as shown in FIG.

As described above, it has been described that the second modulation factor command k2 ^* is obtained from the voltage response characteristics with reference to FIG. 4, but a method for obtaining the second modulation factor command k2 ^* will be described using mathematical formulas and the like.

Using the unknown number Vpa set to obtain the second modulation factor command k2 ^* , an equation of the AC voltage signal Vp assuming the second AC voltage command signal is established as in the following equation (12). θp indicates the phase of the AC voltage signal Vp.

    Vp = − (√2 / √3) Vpa · sin θp (12)

  When the AC voltage signal Vp deviates from the range of values that the carrier wave can take, the value of the AC voltage command signal Vp is determined as follows.

  Assuming that the value of the carrier wave amplitude is Vc, when the value of the AC voltage signal Vp is larger than Vc, the value of the AC voltage signal Vp is set to Vc. When the value of the AC voltage signal Vp is smaller than −Vc, the value of the AC voltage signal Vp is set to −Vc.

  The AC voltage after the dead time error voltage superposition is calculated by superimposing the dead time error voltage Vtd on the AC voltage signal Vp set as described above. When the value of the AC voltage signal Vp is equal to or lower than Vc and equal to or higher than −Vc, the dead time error voltage Vtd is expressed by equations (7) to (11) as in the case of the sine wave modulation region when the amplitude is Vtda. Can be expressed in different cases according to the polarity of the output current Ip of each phase of the PWM inverter device 10.

  Note that no switching occurs due to pulse width modulation in a section where the AC voltage signal Vp is held at Vc or -Vc, which occurs when pulse width modulation is performed in the overmodulation region, so that no dead time is generated. For this reason, the dead time error voltage Vtd does not occur in this section, and Vtd = 0 regardless of the equations (7) to (11).

  Since the interval in which the AC voltage signal Vp is held at Vc or −Vc depends on the value of the unknown Vpa in Equation (12), Vtd is also an unknown.

  The AC voltage after the dead time error voltage superposition is obtained by adding Vtd to the AC voltage signal Vp. What extracted the magnitude | size of the fundamental wave component of AC voltage after this dead time error voltage superimposition corresponds to the magnitude | size of the fundamental wave component of the output voltage of the PWM inverter apparatus 10. FIG. The magnitude of the fundamental wave component can be extracted by, for example, obtaining a Fourier coefficient corresponding to the magnitude of the fundamental wave component by Fourier series expansion.

  From the above steps, the relationship between the unknown Vpa in equation (12) and the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 is obtained. From this relationship, Vpa is obtained in which the magnitude of the fundamental wave component of the AC voltage after the dead time error voltage superposition is equal to Vcom1 in FIG.

In order to obtain the second modulation factor command k2 ^* from this Vpa, Vpa may be divided by the magnitude of the fundamental component of the AC voltage that can be output from the PWM inverter device 10, for example, the input DC voltage of the PWM inverter device 10. . Through the above steps, the second modulation factor command k2 ^* can be obtained by calculation from the first modulation factor command k1 ^* .

From the viewpoint of reducing the calculation load, a map capable of obtaining the second modulation factor command k2 ^* with the first modulation factor command k1 ^* and the power factor pf in the range to be used as arguments is prepared in the calculation device. Conceivable.

If there is no second modulation factor command k2 ^{* in} which the magnitude of the fundamental wave component of the first AC voltage command signal is equal to the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10, for example, The second modulation factor command k2 ^* that is closest to the magnitude of the fundamental component of one AC voltage command signal is selected.

Next, the detailed function of the phase compensation means 21 will be described. In this embodiment, since the dead time compensation using the dead time compensation amount in the sine wave modulation region can compensate the influence of the dead time error voltage including the phase, the phase compensation means 21 in the sine wave modulation region The first phase θ is output as it is as the second phase θc. The dead time compensation in the overmodulation region is to obtain only the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 by obtaining the second modulation rate command k2 ^* from the first modulation rate command k1 ^* . A phase shift occurs due to a dead time error voltage. In order to compensate for the phase shift due to the dead time error voltage, the phase compensation means 21 is required.

The phase compensation unit 21 is generated based on the second modulation rate command k2 ^* output from the second modulation rate command generation unit 27 when the overmodulation region is detected by the overmodulation region detection unit 22. When the second AC voltage command signal is output based on the second modulation factor command k2 ^* using the second dq voltage command, the dead time error voltage amplitude Vtda, and the power factor pf of the synchronous motor 11 The phase difference between the output voltage of the PWM inverter device 10 and the phase of the first AC voltage command signal is compensated.

  The U-phase output voltage Vu that does not include the dead time error voltage of the PWM inverter device 10 can be expressed by the following equation (13) when Vu is Vc or less and −Vc or more.

Vu = (√2 / √3) Vd2 ^* · cos θ− (√2 / √3) Vq2 ^* · sin θ
... (13)

  When Vu is larger than Vc, Vu = Vc, and when Vu is smaller than −Vc, Vu = −Vc.

  Vu_1 is obtained by extracting the magnitude of the fundamental wave component of the U-phase output voltage Vu expressed as described above by a technique such as Fourier series expansion.

  Next, the dead time error voltage Vtd is calculated based on the equations (7) to (11). However, as described above, in the section where the AC voltage signal Vp is held at Vc or −Vc, switching due to pulse width modulation does not occur, and therefore no dead time is generated. For this reason, the dead time error voltage Vtd does not occur in this section, and Vtd = 0 regardless of the equations (7) to (11).

  Vtd_1 obtained by extracting the magnitude of the fundamental component of the Vtd calculated as described above by a technique such as Fourier series expansion is defined as Vtd_1.

  FIG. 5 shows the first AC voltage command signal, the output voltage of the PWM inverter device 10 not including the dead time error voltage, the dead time error voltage, the output voltage of the PWM inverter device 10 including the dead time error voltage, and the PWM inverter device 10. Is a diagram illustrating an example of a vector of each fundamental wave component of the output current, and reference numerals 51, 52, 53, 54, and 55 are assigned to the vectors of the respective fundamental wave components. The circle in FIG. 5 has the radius of the size of the vector 51.

  The second modulation factor command generation means 27 obtains a vector 54 having a magnitude equal to the magnitude of the fundamental wave component of the first AC voltage command signal (corresponding to the magnitude of the vector 51 in FIG. 5). However, it can be seen that the direction of the vector 54 is shifted by α with respect to the vector 51 as shown in FIG. 5. The phase compensation means 21 compensates for this vector shift and performs phase compensation to match the direction of 54 vectors with the direction of 51 vectors.

  From FIG. 5, it can be seen that the three vectors 52, 53 and 54 form a triangle. Since the vector sizes of 52, 53, and 54 are known, α can be obtained by the cosine theorem. Assuming that the sizes of the vectors 52, 53, and 54 are a, b, and c, respectively, α can be calculated as the following equation (14).

α = arccos {(a ² + c ² −b ² ) / (2 · a · c)} (14)

  By subtracting the phase compensation amount α from the first phase θ, the direction of the vector 54 in FIG. The phase compensation means 21 outputs the second phase θc by subtracting the phase compensation amount α from the input first phase θ.

  The details of the function of the phase compensation means 21 have been described above using the U-phase output voltage Vu of the PWM inverter device 10 as a representative. The difference between the phases (U-phase, V-phase, W-phase) is the PWM inverter device 10. The phase of the output voltage is different, and there is no difference in the magnitude of the dead time error voltage and the output voltage of the PWM inverter device 10 in each phase. Therefore, the triangular shape does not change in each phase. Therefore, any phase can be described with reference to FIG. Therefore, the phase compensation amount α does not need to consider the difference between the phases.

From the viewpoint of reducing the calculation load, the extraction of the magnitude of the fundamental wave component of the output voltage not including the dead time error voltage of the PWM inverter device 10 is determined by the second modulation factor k2 ^* . In addition, since there is no need to consider the difference between the phases, it is conceivable that a map having the second modulation factor command k2 ^* as an argument is prepared in the arithmetic unit.

Similarly, from the viewpoint of reducing the calculation load, the extraction of the magnitude of the fundamental wave component of the dead time error voltage Vtd is determined by the dead time error voltage Vtda and the second modulation factor command k2 ^* . Therefore, it is conceivable that a map having the arguments of the amplitude Vtda of the dead time error voltage and the second modulation factor command k2 ^* is prepared in the arithmetic unit.

  Similarly, from the viewpoint of reducing the calculation load, the phase compensation amount α is calculated by using a map that uses the magnitude of the vectors 52, 53, and 54 as an argument, or a map that uses the value in the arccos on the right side of Expression (14) as an argument. It is conceivable to prepare and ask for.

  As described above, in the PWM inverter device 10 according to the first embodiment, the fundamental component of the output voltage of the PWM inverter device 10 is used as the first AC voltage command signal even when pulse width modulation is performed in the overmodulation region. Can be made equal to the fundamental wave component.

In this embodiment, from the first modulation factor command k1 ^* , the second modulation factor command generator 27 can perform dead time compensation by paying attention to the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10. I explained that.

  By the way, since the dead time error voltage Vtd is a square wave having the amplitude Vtda in the sine wave modulation region as described above, the dead time error voltage Vtd includes a harmonic component. In this embodiment, as described above, dead time compensation is performed in the sine wave modulation region by adding or subtracting the dead time compensation amount Vtdc in accordance with the polarity of the output current of the PWM inverter device 10. Performing dead time compensation by adding or subtracting the dead time compensation amount Vtdc in accordance with the polarity of the output current of the PWM inverter device 10 is hereinafter referred to as square wave type dead time compensation. When square wave dead time compensation is performed in the sine wave modulation region, the dead time compensation amount Vtdc is added or subtracted so as to cancel the square wave dead time error voltage Vtd. Therefore, the PWM inverter device 10 uses the dead time error voltage Vtd. Not only the influence of the output voltage on the fundamental wave component but also the influence of the harmonic component of the dead time error voltage Vtd can be eliminated.

  In this embodiment, the dead time compensation using the dead time compensation amount Vtdc is not performed in the overmodulation region, and attention is paid to the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 due to the dead time error voltage Vtd. Although the dead time compensation is performed, the influence of the harmonic component of the dead time error voltage Vtd can be reduced by performing the square wave type dead time compensation even in the overmodulation region.

  In the overmodulation region, in the interval where the second AC voltage command signal is larger than Vc or smaller than −Vc, switching due to pulse width modulation does not occur, and therefore no dead time occurs. Accordingly, the dead time error voltage Vtd becomes 0 in this interval.

  In addition, as a result of adding or subtracting the dead time compensation amount Vtdc to the first AC voltage command signal in the overmodulation region, the second AC voltage command signal may be larger than Vc or smaller than −Vc. The dead time error voltage Vtd becomes 0 even in a section in which the second AC voltage command signal generated in this case is larger than Vc or smaller than −Vc.

  Since the dead time error voltage is constant in the sine wave modulation region, square wave type dead time compensation can be performed using a constant dead time compensation amount. However, in the over modulation region, the dead time error voltage changes, so the constant time error voltage is constant. Square wave type dead time compensation using the amount of dead time compensation cannot be performed.

  In order to perform square wave type dead time compensation in the overmodulation region, this embodiment is changed as shown in FIGS. In FIG. 6, a dead time compensation amount generating unit 60 is provided instead of the second modulation factor command generating unit 27 and the second dq voltage command generating unit 19 in FIG. 1. From the amplitude Vtda of the dead time error voltage and the power factor pf, the dead time compensation amount calculating means 60 determines that the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 is the magnitude of the fundamental wave component of the first AC voltage command signal. A dead time compensation amount equal to the above is calculated.

  Next, a detailed function of the dead time compensation amount generating means 60 will be described. The AC voltage signal Vp assuming the second AC voltage command signal can be expressed by the following equations (15) to (17). Expressions (15) to (17) typically represent the case of the U phase. Vtdc is a dead time compensation amount to be obtained and is an unknown number.

Vp = (√2 / √3) Vd1 ^* · cos θ− (√2 / √3) Vq1 ^* · sin θ
-Vtdc (Ip <0) (15)

Vp = (√2 / √3) Vd1 ^* · cos θ− (√2 / √3) Vq1 ^* · sin θ
+ Vtdc (Ip> 0) (16)

Vp = (√2 / √3) Vd1 ^* · cos θ− (√2 / √3) Vq1 ^* · sin θ
(Ip = 0) (17)

  When Vp is larger than Vc or smaller than −Vc, Vp = Vc and Vp = −Vc, respectively.

  By adding the dead time error voltage Vtd to the AC voltage signal Vp set as described above, the AC voltage after the dead time error voltage is superimposed is calculated. Although the dead time error voltage Vtd is calculated based on the equations (7) to (11), it is set to 0 when the AC voltage Vp set as described above is larger than Vc or smaller than −Vc.

  The fundamental wave component is extracted from the AC voltage after the dead time error voltage superposition set as described above. The fundamental wave component can be extracted by obtaining a Fourier coefficient corresponding to the fundamental wave component by, for example, Fourier series expansion. Thereby, after extracting the fundamental wave component of the AC voltage after dead time error voltage superposition, the magnitude of the fundamental wave component after the dead time error voltage superposition becomes equal to the fundamental wave component of the first AC voltage command signal. The dead time compensation amount Vtdc can be obtained. The relationship between the dead time compensation amount and the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 is the compensation amount response characteristic.

From the viewpoint of reducing the calculation load, it is conceivable that the dead time compensation amount Vtdc is generated by preparing a map having the first modulation factor command k1 ^* and the power factor pf as arguments in the calculation device. .

  The detailed function of the dead time compensation amount generating means 60 has been described in consideration of the case of the U phase. However, the difference in each phase is only the difference in phase. A time compensation amount can be generated.

  The second AC voltage command signal generating means 23, when the overmodulation area detecting means 22 detects that it is an overmodulation area, converts the dead time compensation amount generated by the dead time compensation amount generating means 60 into a sine wave. When the modulation area is detected, the dead time compensation amount determined by the equation (10) is added to or subtracted from the first AC voltage command signal according to the polarity of the output current of the PWM inverter device 10. To generate a second AC voltage command signal.

  Next, a detailed function of the phase compensation means 21 when performing square wave type dead time compensation in the overmodulation region will be described. The output voltage of the PWM inverter device 10 not including the dead time error voltage can be calculated by substituting the dead time compensation amount Vtdc output from the dead time compensation amount generating means 60 into the equations (15) to (17). However, Vp is calculated as Vp = Vc when Vp is larger than Vc, and Vp = −Vc when Vp is smaller than −Vc. The fundamental wave component of the output voltage of the PWM inverter device 10 not including the dead time error voltage obtained in this way is extracted. For example, Fourier series expansion is used to extract the fundamental wave component.

  Next, the dead time error voltage Vtd is calculated. The dead time error voltage Vtd is calculated based on the equations (7) to (11), and is 0 when the AC voltage Vp set as described above is larger than Vc or smaller than −Vc. The fundamental wave component of the dead time error voltage Vtd thus obtained is extracted. For example, Fourier series expansion is used to extract the fundamental wave component.

  By using the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 not including the dead time error voltage obtained in the above steps and the magnitude of the fundamental wave component of the dead time error voltage, the phase compensation amount α is calculated. Ask. The phase compensation amount α is calculated based on the equation (14), and a value obtained by subtracting the phase compensation amount α from the first phase θ is output as the second phase θc.

From the viewpoint of reducing the calculation load, it is necessary to take into account that the equations (15) to (17) are determined by the first modulation factor command k1 ^* , the dead time compensation amount Vtdc, and the power factor pf, and the differences between the phases. Therefore, the extraction of the magnitude of the fundamental wave component of the output voltage that does not include the dead time error voltage of the PWM inverter device 10 uses the first modulation factor command k1 ^* , the dead time compensation amount Vtdc, and the power factor pf as arguments. It is conceivable to prepare and execute a map in the arithmetic unit.

Similarly, from the viewpoint of reducing the calculation load, since the dead time error voltage Vtd is determined by the amplitude Vtda of the dead time error voltage, the first modulation factor command k1 ^* , and the power factor pf, the fundamental wave component of the dead time error voltage Vtd It is conceivable that extraction of the magnitude of is performed by preparing a map in the arithmetic unit using the amplitude Vtda of the dead time error voltage, the first modulation factor command k1 ^* , and the power factor pf as arguments.

  Similarly, from the viewpoint of reducing the calculation load, the phase compensation amount α is calculated by using a map that uses the magnitude of the vectors 52, 53, and 54 as an argument, or a map that uses the value in the arccos on the right side of Expression (14) as an argument. It is conceivable to prepare and ask for.

  When there is no dead time compensation amount Vtdc in which the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 is equal to the magnitude of the fundamental component of the first AC voltage command signal, for example, the PWM inverter device The dead time compensation amount Vtdc in which the magnitude of the fundamental wave component of the output voltage of 10 is closest to the magnitude of the fundamental wave component of the first AC voltage command signal is selected and output.

  As described above, according to the PWM inverter device 10 according to the first embodiment, the dead time compensation means outputs the second AC voltage command signal and the dead time error voltage when performing pulse width modulation in the overmodulation region. Assume that a second AC voltage command signal is generated in which the magnitude of the fundamental wave component of the first AC voltage command signal is equal to the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10. Alternatively, assuming the second AC voltage command signal, dead time error voltage, and dead time compensation amount, the dead time when the magnitude of the output voltage of the PWM inverter device 10 becomes equal to the fundamental wave component of the first AC voltage command signal A compensation amount is generated, and a second AC voltage command signal is generated based on the dead time compensation amount. Therefore, in the overmodulation region, the relationship between the magnitude of the fundamental wave component of the first AC voltage command signal and the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 is non-linear, and a short circuit of the switching element is prevented. As a result, the difference in magnitude of the fundamental voltage component of the first AC voltage command signal and the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 is caused by the change in the magnitude of the error voltage due to the dead time. Even in the case of changing according to the AC voltage command signal, the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 equal to the magnitude of the fundamental wave component of the first AC voltage command signal can be obtained.

  Furthermore, according to the PWM inverter device 10 according to the first embodiment, the phase compensation means 21 is configured so that the output voltage not including the dead time error voltage of the PWM inverter device 10 and the magnitude of each fundamental wave component of the dead time error voltage are large. Using this, a phase compensation amount is calculated, and this is subtracted from the first phase to generate a second phase. Therefore, it is possible to compensate for a deviation between the phase of the output voltage of the PWM inverter device 10 caused by the dead time error voltage and the phase of the first AC voltage command signal.

  In the above embodiment, the case where the PWM inverter device 10 is a magnetic pole position sensorless control device has been described. However, a control device using a magnetic pole position detection sensor may be used. By using the magnetic pole position detection sensor for detecting the magnetic pole position, the integrator 17 shown in FIG. 1 is not necessary, and the actual rotational speed of the synchronous motor 11 can be calculated by using the differentiator. In addition, closed loop control of the motor rotation speed can be executed by feeding back the actual rotation speed.

  In the above-described embodiment, the configuration in which the vector control by the dq coordinate system is executed is shown, but the configuration in which the AC voltage itself is controlled without using the dq coordinate system may be used. In this case, the first dq voltage command generation unit 16 and the second dq voltage command generation unit 19 are not required.

  Moreover, in the said embodiment, although the number of alternating current phases was set to 3, the number of alternating current phases is not limited to this.

  In the above embodiment, the power factor is used to represent the difference between the phase of the second AC voltage command signal and the phase of the output current of the PWM inverter device 10, but the power factor is calculated by calculation. It may be used, or a value measured in advance may be used. More directly, the difference between the phase of the second AC voltage command signal and the phase of the PWM inverter output current may be calculated.

  In the above embodiment, the AC voltage command for each phase is represented by a sine wave. However, an AC voltage command that is not a sine wave, such as a waveform in which the third harmonic is superimposed on the sine wave, may be used.

  In the above embodiment, the voltage response characteristic is obtained by calculation. However, the magnitude of the fundamental wave component of the output voltage of the PWM inverter device 10 when the first modulation factor command and the dead time error voltage are not compensated in advance is calculated. The voltage response characteristic can also be obtained by obtaining the above relationship by measurement or the like.

  Further, in the above embodiment, the dead time compensation amount response characteristic is obtained by calculation. However, the dead time compensation amount and the dead time compensation amount are previously determined based on the detected value of the output current of the PWM inverter device 10 or the output current. The relationship with the magnitude of the fundamental component of the output voltage of the PWM inverter device 10 when adding or subtracting to the first AC voltage command signal according to the polarity of any one of the calculated values is obtained by measurement or the like. The dead time compensation amount response characteristic can also be obtained.

  In the above embodiment, the dead time compensation method is switched between the sine wave modulation area and the over modulation area by the over modulation area detection means 22, but the sine wave modulation is not performed without using the over modulation area detection means 22. Also in the region, the dead time compensation method in the overmodulation region shown in the above embodiment can be implemented. When the square wave type dead time compensation in the overmodulation region shown in the above embodiment is also executed in the sine wave region, the generated dead time compensation amount is the dead time in the sine wave modulation region shown in the above embodiment. Since it is equal to the dead time compensation amount used for time compensation, equivalent dead time compensation is performed.

  The scope of the present invention is not limited to the embodiments described above, but is defined by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. .

DESCRIPTION OF SYMBOLS 10 PWM inverter apparatus 11 Synchronous motor 12 Synchronous motor stator 13 Synchronous motor rotor 14 Subtractor 15 Frequency compensation means 16 1st dq voltage command generation means 17 Integrator 18 3 phase-dq coordinate conversion means 19 2nd dq voltage Command generation means 20 First AC voltage command signal generation means 21 Phase compensation means 22 Overmodulation region detection means 23 Second AC voltage command signal generation means 24 PWM control means 25 AC voltage generation means 26 First modulation rate command generation Means 27 Second modulation factor command generation means 51 Vector 52 representing fundamental wave component of first AC voltage command signal Vector 53 representing fundamental wave component of output voltage of PWM inverter 10 not including dead time error voltage Vector 54 representing fundamental wave component of error voltage PWM inverter device 10 including dead time error voltage 55 representing the fundamental wave component of the output voltage of the vector 60 representing the fundamental wave component of the output current of the PWM inverter device 10 Dead time compensation amount generating means

Claims (7)

A PWM inverter device that converts a DC voltage into an AC voltage by turning on and off a switching element based on a control command,
A first modulation factor that generates a first modulation factor command indicating a ratio of the magnitude of the fundamental wave component of the first AC voltage command signal to the magnitude of the fundamental wave component of the AC voltage that can be output by the DC voltage Command generation means;
First phase generating means for generating a first phase used for generating the first AC voltage command signal;
Dead time compensation means for generating a second AC voltage command signal based on a dead time error voltage generated by the first phase and a dead time for preventing a short circuit of the switching element;
PWM control means for generating the control command by pulse width modulation control based on the comparison between the second AC voltage command signal and the carrier wave signal,
The dead time compensation means includes at least the second AC voltage command signal or the second AC voltage command signal in an overmodulation region where the amplitude of the second AC voltage command signal is larger than the amplitude of the carrier signal. At least one of the second modulation rate commands indicating the ratio of the magnitude of the fundamental wave component, the second AC voltage phase that is the phase of the second AC voltage command signal, and the output current of the PWM inverter device A PWM inverter device, wherein the second AC voltage command signal is generated based on the dead time error voltage generated in accordance with a difference between a detected value or a calculated value and a phase. The dead time compensation means is configured to calculate a fundamental wave component magnitude of the output voltage of the PWM inverter device and the first modulation rate command when the dead time error voltage is not compensated for the first modulation rate command. From the voltage response characteristic indicating the relationship based on the dead time error voltage, the magnitude of the fundamental wave component of the output voltage of the PWM inverter device becomes equal to the magnitude of the fundamental wave component of the first AC voltage command signal. A second modulation factor command generating means for outputting a second modulation factor command;
2. The PWM inverter device according to claim 1, wherein the second AC voltage command signal is generated based on the second modulation factor command.   In the voltage response characteristic, when the second modulation factor command in which the magnitude of the fundamental component of the output voltage of the PWM inverter device is equal to the magnitude of the fundamental component of the first AC voltage command signal does not exist 3. The PWM inverter device according to claim 1, wherein the second modulation factor command is selected in accordance with the first modulation factor command. The dead time compensation means is configured to determine the dead time compensation amount and the dead time compensation amount according to the polarity of either the detected value of the output current or the calculated value of the output current of the PWM inverter device. From the compensation amount response characteristic indicating the relationship between the magnitude of the fundamental wave component of the output voltage of the PWM inverter device when added or subtracted to the command signal based on the dead time error voltage, the output voltage of the PWM inverter device is A dead time compensation amount generating means for outputting the dead time compensation amount in which the magnitude of the fundamental wave component is equal to the magnitude of the fundamental wave component of the first AC voltage command signal;
The second AC voltage command signal generation means sets the dead time compensation amount to the first AC voltage command signal according to the polarity of the detected value of the output current or the calculated value of the output current of the PWM inverter device. 2. The PWM inverter device according to claim 1, wherein the second AC voltage command signal is generated based on a value obtained by adding or subtracting to the second AC voltage command signal.   The dead time compensation amount generating means is the dead time in which the magnitude of the fundamental component of the output voltage of the PWM inverter device is equal to the magnitude of the fundamental component of the first AC voltage command signal in the compensation amount response characteristic. 5. The PWM inverter device according to claim 4, wherein when there is no time compensation amount, the dead time compensation amount is selected and output in accordance with the first modulation factor command. The dead time compensation means compensates for the phase shift of the output voltage of the PWM inverter device with respect to the phase of the first AC voltage command signal caused by the dead time error voltage with respect to the first phase. Phase compensation means for outputting as a second phase;
The PWM inverter device according to any one of claims 1 to 5, wherein the second AC voltage command signal is generated based on the second phase. The dead time compensation means includes a sinusoidal modulation region in which the amplitude of the second AC voltage command signal is equal to or less than the amplitude of the carrier signal, and the amplitude of the second AC voltage command signal is greater than the amplitude of the carrier signal. An overmodulation region detecting means for determining a large overmodulation region;
When the overmodulation region detecting means determines that the sine wave modulation region is present, the dead time compensation amount is calculated based on a ratio of the period of the carrier signal and the dead time, and the first AC voltage command signal is calculated. The second AC voltage command signal is obtained by adding or subtracting the dead time compensation amount according to the polarity of either the detected value of the output current of the PWM inverter device or the calculated value of the output current. The PWM inverter device according to any one of claims 1 to 6, wherein the PWM inverter device is any one of the above.

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