Inverter control device

Abstract

The purpose of the present invention is to readily reduce any voltage error that is caused by dead time, in order to suppress torque shock. This inverter control device 100 controls, through pulse width modulation, a switching operation of an inverter 10 that converts a DC voltage to an AC voltage and applies the AC voltage to a motor 3. The inverter control device 100 according to an embodiment 1 comprises a dead time compensation unit 183 that performs dead time compensation to compensate for an error in the output voltage of the inverter 10, the error being caused by dead time of the inverter 10. The dead time compensation unit 183 performs dead time compensation on the basis of a difference θvi between an electric current phase angle θi indicating a phase angle for outputting the electric current of the motor 3, and a voltage phase angle θv for outputting a voltage that corresponds to the electric current.

Description

Technical Field

[0001] The present invention relates to an inverter control device.

Background Art

[0002] An inverter control device that controls the switching operation of an inverter that converts a DC voltage into an AC voltage and applies it to an AC motor by pulse width modulation (hereinafter also referred to as "PWM") is widely used. In this type of inverter control device, in order to increase the rotational speed of the AC motor, a technique for operating the inverter in an overmodulation region where the voltage command value in the output voltage of the inverter exceeds the maximum output level in a sine wave is known. At this time, the inverter control device is operated in a one-pulse control mode or a three-pulse control mode that generates one pulse or three pulses per one cycle of the fundamental wave of the output voltage of the inverter. The inverter control device can switch these control modes according to the operating region of the AC motor.

[0003] The inverter is provided with a dead time, which is a section in which both the upper and lower arms are turned off to prevent short circuits during the switching of the upper and lower arms. As a result, an error (hereinafter also referred to as "voltage error") occurs between the output voltage of the inverter and its voltage command value. The voltage error generated by this dead time may cause a torque shock in which the commanded torque is not output from the motor when the inverter control device switches the control mode. Therefore, it is important to reduce the voltage error generated by this dead time to prevent the occurrence of torque shock.

[0004] Patent Document 1 discloses a technique for performing dead time compensation by correcting a phase threshold value used for generating a switch command for controlling the on / off of a switching element of an inverter with a dead time compensation phase in a phase reference type synchronous control mode.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-15566 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the technology disclosed in Patent Document 1, the dead time compensation phase is calculated from the detection signal of the current supplied from the inverter to the motor and the fundamental frequency of the voltage command value, which requires current polarity calculation at the switch timing. In other words, in the technology disclosed in Patent Document 1, high-speed current detection is essential for dead time compensation, and it is not easy to reduce the voltage error caused by the dead time.

[0007] The present invention has been made in view of the above, and aims to easily reduce voltage errors caused by dead time and suppress torque shock. [Means for solving the problem]

[0008] To solve the above problems, the inverter control device of the present invention is an inverter control device that controls the switching operation of an inverter that converts a DC voltage to an AC voltage and applies it to an AC motor by pulse width modulation, and comprises a dead time compensation unit that performs dead time compensation to compensate for an error in the output voltage of the inverter caused by the dead time of the inverter, and the dead time compensation unit performs the dead time compensation based on the difference between a current phase angle indicating the phase angle for outputting the current of the AC motor and a voltage phase angle for outputting a voltage corresponding to the current. [Effects of the Invention]

[0009] According to the present invention, voltage errors caused by dead time can be easily reduced, thereby suppressing torque shock. Other issues, configurations, and effects will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram illustrating the configuration of a motor drive system equipped with an inverter control device according to Embodiment 1. [Figure 2] Configuration diagram of the 3-pulse 1-pulse calculation unit when current phase angle and voltage phase angle are inputs. [Figure 3] A diagram illustrating the configuration of the 3-pulse 1-pulse calculation unit when current command values ​​and voltage command values ​​are inputs. [Figure 4] A diagram illustrating the voltage waveform when no voltage error occurs due to dead time. [Figure 5] (1) Diagram illustrating the calculation process of the dead time compensation unit when Δα < θvi < α. [Figure 6] (2) Diagram illustrating the calculation process of the dead time compensation unit when α + Δα < θvi < π - α is satisfied. [Figure 7] (3) Diagram illustrating the calculation of the dead time compensation unit when π-α+Δα<θvi<π is satisfied. [Figure 8] (4) Diagram illustrating the calculation process of the dead time compensation unit when π+Δα<θvi<π+α is satisfied. [Figure 9] (5) Diagram illustrating the calculation process of the dead time compensation unit 183 when π+α+Δα<θvi<2π-α is satisfied. [Figure 10] (6) Diagram illustrating the calculation process of the dead time compensation unit 183 when 2π-α+Δα<θvi<2π is satisfied. [Figure 11] A table showing the relationship between the difference between the voltage phase angle and the current phase angle, and the amplitude error and phase angle error. [Figure 12] Figure 1 is a diagram illustrating the operation and effects of the inverter control device. [Figure 13] A diagram showing the configuration of the 3-pulse 1-pulse calculation unit included in the inverter control device of Embodiment 2. [Figure 14] A table showing the relationship between the difference between the voltage phase angle and the current phase angle, and the phase angle error. [Figure 15] Configuration diagram of the inverter control device of Embodiment 3.

Best Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For components with the same reference numerals in each embodiment, unless otherwise specified, they have the same functions in each embodiment, and the description thereof will be omitted.

[0012] [Embodiment 1] The inverter control device 100 of Embodiment 1 will be described with reference to FIGS. 1 to 12. FIG. 1 is a configuration diagram of a motor drive system 1 including the inverter control device 100 of Embodiment 1.

[0013] The motor drive system 1 is connected to a battery 2 and includes an inverter 10 (inverter power unit), an inverter control device 100, and an AC motor 3 (hereinafter also referred to as "motor 3").

[0014] The battery 2 is a DC voltage source of the inverter 10. The DC voltage Vdc of the battery 2 (hereinafter also referred to as "power supply voltage Vdc") is converted by the inverter 10 into a three-phase AC voltage with a variable voltage and a variable frequency and applied to the motor 3. The motor 3 is a synchronous motor that is rotationally driven when a three-phase AC voltage is applied. A rotational position sensor 4 is attached to the motor 3 to control the phase of the three-phase AC voltage applied from the inverter 10 to match the phase of the induced voltage of the motor 3. The rotational position sensor 4 is constituted by, for example, a resolver composed of an iron core and a winding. Alternatively, the rotational position sensor 4 may be constituted by a rotational position sensor using a GMR sensor or a Hall element.

[0015] The inverter control device 100 is a device that controls the inverter 10. The inverter control device 100 is configured, for example, by a microcomputer. The inverter control device 100 can realize various functions by executing a predetermined program in the microcomputer. Alternatively, some or all of the functions of the inverter control device 100 may be realized using hardware circuits such as logic ICs or FPGAs.

[0016] The inverter control device 100 includes, as various functions, a current command unit 110, a current control unit 120, a current detection unit 130, a rotation position detection unit 140, a PWM pulse generation unit 150, a gate circuit 160, an SVPWM calculation unit 170, and a 3-pulse 1-pulse calculation unit 180.

[0017] The rotation position detection unit 140 detects the rotation position θp, which is the position of the rotor of the motor 3, based on the output signal of the rotation position sensor 4.

[0018] The current detection unit 130 acquires the three-phase current detection value Iuvw(Iu,Iv,Iw) flowing through the motor 3 from the current sensor Ict. Based on the rotation position θp detected by the rotation position detection unit 140, the current detection unit 130 converts these current detection values ​​from three phases to two phases to detect the dq-axis current detection value Idq(Id,Iq).

[0019] The inverter control device 100 has a current control function for controlling the output of the motor 3. The current command unit 110 calculates the dq-axis current command value Idq*(Id*,Iq*) based on the torque command value T* output from a higher-level control device (not shown). The current command unit 110 outputs the calculated dq-axis current command value Idq* to the current control unit 120, the SVPWM calculation unit 170, and the 3-pulse 1-pulse calculation unit 180. The current command unit 110 may also calculate the current phase angle θi, which indicates the phase angle of the dq-axis current command value Idq*, from the dq-axis current command value Idq*. The current command unit 110 may also output the calculated current phase angle θi to the current control unit 120, the SVPWM calculation unit 170, and the 3-pulse 1-pulse calculation unit 180.

[0020] The current control unit 120 calculates the dq-axis voltage command value Vdq*(Vd*,Vq*) as the voltage command value of the output voltage of the inverter 10 corresponding to the dq-axis current command value Idq* output from the current command unit 110. Specifically, the current control unit 120 calculates the dq-axis voltage command value Vdq* so that the dq-axis current command value Idq* output from the current command unit 110 matches the dq-axis current detection value Idq detected by the current detection unit 130. The current control unit 120 outputs the calculated dq-axis voltage command value Vdq* to the SVPWM calculation unit 170 and the 3-pulse 1-pulse calculation unit 180. The current control unit 120 may also calculate the voltage phase angle θv, which indicates the phase angle of the dq-axis voltage command value Vdq*, from the dq-axis voltage command value Vdq*. The current control unit 120 may output the calculated voltage phase angle θv to the SVPWM calculation unit 170 and the 3-pulse 1-pulse calculation unit 180.

[0021] The 3-pulse 1-pulse calculation unit 180 calculates a modulated wave based on the voltage command value at the output voltage of the inverter 10. In other words, the 3-pulse 1-pulse calculation unit 180 is a modulated wave calculation unit that calculates a modulated wave corresponding to the output voltage of the inverter 10. Specifically, the 3-pulse 1-pulse calculation unit 180 uses the rotation position θp to perform a 2-phase to 3-phase conversion on the dq-axis voltage command value Vdq* output from the current control unit 120, thereby calculating a 3-phase voltage command value Vuvw* (Vu*, Vv*, Vw*). Of the 3-phase voltage command value Vuvw*, Vu* is the U-phase voltage command value, Vv* is the V-phase voltage command value, and Vw* is the W-phase voltage command value. The 3-pulse 1-pulse calculation unit 180 then generates a modulated wave signal duvw, which represents the modulated wave expressed by the 3-phase voltage command value Vuvw*, and outputs it to the PWM pulse generation unit 150. In this case, the 3-pulse 1-pulse calculation unit 180 may express the 3-phase voltage command value Vuvw* using a waveform other than a sine wave, such as a trapezoidal wave or a waveform in which a predetermined order of harmonics is superimposed on a sine wave, by selecting a modulation method other than sine wave modulation.

[0022] Furthermore, the 3-pulse 1-pulse calculation unit 180 may calculate the modulation rate MF of the output voltage of the inverter 10 based on the power supply voltage Vdc and the dq-axis voltage command value Vdq* output from the current control unit 120, and output the modulation rate MF to the PWM pulse generation unit 150 instead of the modulated wave signal duvw. Moreover, the 3-pulse 1-pulse calculation unit 180 may calculate both the modulated wave signal duvw and the modulation rate MF and output them to the PWM pulse generation unit 150. In other words, the 3-pulse 1-pulse calculation unit 180 can calculate at least one of the modulated wave signal duvw and the modulation rate MF.

[0023] The PWM pulse generation unit 150 performs three-phase pulse width modulation (PWM) based on the modulated wave signal duvw or modulation index MF calculated by the three-pulse one-pulse calculation unit 180, and generates a PWM pulse signal P that controls the switching operation of the inverter 10. For example, the PWM pulse generation unit 150 compares a carrier that changes periodically with the carrier frequency fc with the modulated wave signal duvw. Then, based on this comparison result, the PWM pulse generation unit 150 can generate a PWM pulse signal P by determining the position (phase) of the rising edge and falling edge (hereinafter also referred to as "pulse edge") of each pulse using a well-known method. In this case, the PWM pulse generation unit 150 may keep the carrier frequency fc constant, or it may change the carrier frequency fc according to the rotation speed of the motor 3. Alternatively, the PWM pulse generation unit 150 may generate a PWM pulse signal P by directly calculating the position of each pulse edge based on the modulation index MF without using the carrier and the modulated wave signal duvw. Alternatively, the PWM pulse generation unit 150 may generate the PWM pulse signal P by yet another method. In any case, the PWM pulse generation unit 150 only needs to be able to generate the PWM pulse signal P for controlling the inverter 10 at predetermined control cycles according to the voltage command value of the output voltage of the inverter 10, and any method can be adopted.

[0024] The gate circuit 160 outputs a drive signal DR to the inverter 10 in accordance with the PWM pulse signal P. The inverter 10 has multiple semiconductor switch elements corresponding to each phase of the three-phase AC voltage, and each semiconductor switch element is controlled on / off by the drive signal DR. As a result, the output voltage of the inverter 10 is adjusted according to the control of the inverter control device 100.

[0025] The SVPWM calculation unit 170 calculates the modulated wave when using the Space Vector Pulse Width Modulation (SVPWM) control mode. In other words, the SVPWM calculation unit 170 is a modulated wave calculation unit that calculates the modulated wave corresponding to the output voltage of the inverter 10. Specifically, the SVPWM calculation unit 170 uses the rotation position θp to perform a two-phase to three-phase conversion on the dq-axis voltage command value Vdq* output from the current control unit 120, thereby calculating the three-phase voltage command value Vuvw*. The SVPWM calculation unit 170 then performs dead time compensation on the three-phase voltage command value Vuvw* using the dq-axis current command value Idq*. The SVPWM calculation unit 170 then calculates the duty cycle duvw by dividing the dead time-compensated three-phase voltage command value Vuvw* by the power supply voltage Vdc. The SVPWM calculation unit 170 then outputs the calculated duty cycle duvw to the PWM pulse generation unit 150.

[0026] In the above, an example configuration of the motor drive system 1 when controlling the current of the motor 3 according to the dq-axis current command value Idq* from the current command unit 110 was explained with reference to Figure 1. However, the configuration of Figure 1 can also be applied when other control methods are adopted. For example, when controlling the rotational speed of the motor 3, the inverter control device 100 can calculate the motor rotational speed ωr based on the time change of the rotational position θp and create a voltage command value or a current command value that matches the speed command value from the higher-level control device. Also, when controlling the output torque of the motor 3, the inverter control device 100 can create a current command value (Idq*) using a relationship formula or map between the motor current (Idq) and the motor torque.

[0027] Figure 2 is a diagram of the configuration of the 3-pulse 1-pulse calculation unit 180 when the current phase angle θi and voltage phase angle θv are inputs. Figure 3 is a diagram of the configuration of the 3-pulse 1-pulse calculation unit 180 when the current command value Idq* and voltage command value Vdq* are inputs.

[0028] As shown in Figures 2 and 3, the 3-pulse 1-pulse calculation unit 180 includes a dead time compensation unit 183, a firing angle calculation unit 184, a phase angle calculation unit 185, and a duty cycle calculation unit 186. Furthermore, the 3-pulse 1-pulse calculation unit 180 shown in Figure 3 includes a modulation rate / voltage phase angle calculation unit 181 and a current phase angle calculation unit 182.

[0029] Figure 2 shows an example in which the current phase angle θi, obtained by calculating the amplitude and phase angle in a table for a torque command, is directly input to the 3-pulse 1-pulse calculation unit 180, and the voltage phase angle θv, obtained using voltage phase control, is directly input to the 3-pulse 1-pulse calculation unit 180. Figure 3 shows an example in which the dq-axis current command value Idq* output from the current command unit 110 is input to the 3-pulse 1-pulse calculation unit 180, and the dq-axis voltage command value Vdq* output from the current control unit 120 is input to the 3-pulse 1-pulse calculation unit 180. The inverter control device 100 may employ either the 3-pulse 1-pulse calculation unit 180 shown in Figure 2 or the 3-pulse 1-pulse calculation unit 180 shown in Figure 3.

[0030] In the following explanation, we will use as an example a case in which the inverter control device 100 employs the 3-pulse 1-pulse calculation unit 180 shown in Figure 3 and controls the switching operation in 3-pulse control mode.

[0031] The modulation rate / voltage phase angle calculation unit 181 calculates the modulation rate MF and voltage phase angle θv based on the dq-axis voltage command value Vdq* of the output voltage of the inverter 10. Specifically, the modulation rate / voltage phase angle calculation unit 181 calculates the square root of the sum of the squares of the d-axis voltage command value Vd* and the q-axis voltage command value Vq* output from the current control unit 120. Then, the modulation rate / voltage phase angle calculation unit 181 calculates the modulation rate MF by dividing the calculated square root of the sum of squares by the power supply voltage Vdc.

[0032] The modulation rate / voltage phase angle calculation unit 181 calculates the voltage phase angle θv from the dq-axis voltage command value Vdq* using equation 1.

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[0033] The current phase angle calculation unit 182 calculates the current phase angle θi based on the dq-axis current command value Idq* of the current flowing through the motor 3. Specifically, the current phase angle calculation unit 182 calculates the current phase angle θi from the dq-axis current command value Idq* using equation 2.

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[0034] The current phase angle calculation unit 182 may calculate the current phase angle θi based on the detected dq-axis current value Idq, which is the detected value of the current flowing through the motor 3. Similarly, the modulation rate / voltage phase angle calculation unit 181 may calculate the modulation rate MF and voltage phase angle θv based on the detected value of the output voltage of the inverter 10.

[0035] The dead time compensation unit 183 performs dead time compensation to compensate for the output voltage error caused by the dead time Δα of the inverter 10. Specifically, the dead time compensation unit 183 performs dead time compensation when the switching operation of the inverter 10 is controlled by at least one of the 1-pulse control mode and the 3-pulse control mode.

[0036] The 1-pulse control mode generates one pulse per cycle of the fundamental frequency of the inverter 10's output voltage. The 1-pulse control mode is used in regions where the fundamental frequency of the inverter 10's output voltage is high. The 3-pulse control mode generates three pulses per cycle of the fundamental frequency of the inverter 10's output voltage. The 3-pulse control mode is used in regions where the fundamental frequency of the inverter's output voltage is medium. The SVPWM control mode generates pulses by comparing the carrier and the modulated wave and determining their relative magnitudes. The SVPWM control mode is used in regions where the fundamental frequency of the inverter 10's output voltage is low.

[0037] The dead time compensation unit 183 performs dead time compensation based on the difference θvi (=θv-θi) between the current phase angle θi, which indicates the phase angle for outputting current from the motor 3, and the voltage phase angle θv, which indicates the voltage for outputting a voltage corresponding to that current. Specifically, the dead time compensation unit 183 calculates at least one of the voltage errors caused by the dead time Δα, namely the amplitude error ΔA and the phase angle error Δθ of the output voltage, as the dead time compensation amount. The 3-pulse 1-pulse calculation unit 180 corrects the modulation rate MF used in the calculation of the firing angle α of the output voltage using the amplitude error ΔA calculated as the dead time compensation amount. The 3-pulse 1-pulse calculation unit 180 also corrects the phase angles θ1 and θ2 of the output voltage using the phase angle error Δθ calculated as the dead time compensation amount. In this way, the dead time compensation unit 183 can perform dead time compensation.

[0038] The firing angle α is the pulse width that needs to be adjusted when setting the number of pulses per cycle of the fundamental wave of the output voltage. There is a relationship between the firing angle α and the modulation index MF as shown in Equation 3.

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[0039] Therefore, the firing angle α can be expressed using the modulation rate MF as shown in Equation 4.

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[0040] The dead time compensation unit 183 calculates the amplitude error ΔA and the phase angle error Δθ as dead time compensation amounts, according to the relationship between the firing angle α and the difference θvi. The details of the calculation of the amplitude error ΔA and the phase angle error Δθ by the dead time compensation unit 183 will be explained using Figures 4 to 11.

[0041] Figure 4 is an explanatory diagram of the voltage waveform when no voltage error occurs due to dead time.

[0042] If no voltage error occurs due to dead time, the switch timings α1 to α4 in the interval [0, 2π] can be expressed as shown in Equation 5, with respect to the firing angle α.

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[0043] When the output voltage of inverter 10 is expanded into a Fourier series using the power supply voltage Vdc, firing angle α, and dead time Δα for switch timings α1 to α4, the Fourier coefficients an and bn can be expressed as shown in equation 6.

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[0044] The amplitude A of the output voltage of inverter 10 can be expressed as shown in equation 7, using the Fourier coefficients an and bn in equation 6.

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[0045] The phase angle error Δθ of the output voltage of inverter 10 can be expressed as shown in Equation 8, assuming no voltage error occurs due to dead time.

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[0046] The dead time compensation unit 183 calculates the amplitude error ΔA and phase angle error Δθ as dead time compensation amounts by determining the above equations 5 to 8 according to the relationship between the firing angle α and the difference θvi.

[0047] Figure 5 is an explanatory diagram of the calculation process of the dead time compensation unit 183 when (1) Δα < θvi < α is satisfied.

[0048] The upper part of Figure 5 (a) shows the voltage waveform before dead time compensation. For a given firing angle α, the switch timings α1 to α4 in the interval [0, 2π] of one fundamental wave period can be expressed as shown in Equation 9, from Figure 4 and Equation 5.

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[0049] In reality, there is a phase difference between the output voltage of the inverter 10 and the current flowing through the motor 3. The inventor focused on the fact that the amplitude error ΔA and the phase angle error Δθ vary depending on the range of the difference θvi between the voltage phase angle θv and the current phase angle θi. Specifically, for each of the cases (1) to (6) shown in Equation 10, the amplitude error ΔA and the phase angle error Δθ show different values. Therefore, the dead time compensation unit 183 calculates the amplitude error ΔA and the phase angle error Δθ separately for each of the cases (1) to (6) shown in Equation 10.

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[0050] (1) When Δα < θvi < α is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 5. (1) When Δα < θvi < α is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 5. The switch timings α0 to α5 shown in the lower section (c) of Figure 5 can be expressed using the firing angle α and the dead time Δα as shown in equation 11.

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[0051] The dead time compensation unit 183 calculates amplitude error ΔA and phase angle error Δθ, which are correction amounts for modulation rate and phase angle, so that the average modulation rate and phase angle in one cycle of the fundamental wave match the case where no voltage error occurs due to dead time during switch timings α0 to α5.

[0052] Specifically, the dead time compensation unit 183 can calculate the above-mentioned Fourier coefficients an and bn using the power supply voltage Vdc, firing angle α, and dead time Δα as shown in equation 12.

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[0053] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 12, as shown in equation 13.

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[0054] In comparison with equations 7 and 8 explained using Figure 4, which assume no voltage error due to dead time occurs, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (1) Δα < θvi < α as shown in equation 14.

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[0055] Figure 6 is an explanatory diagram of the calculations performed by the dead time compensation unit 183 when (2) α + Δα < θvi < π - α is satisfied.

[0056] (2) When α + Δα < θvi < π-α is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 6. (2) When α + Δα < θvi < π-α is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 6. The switch timings α0 to α5 shown in the lower section (c) of Figure 6 can be expressed using the firing angle α and the dead time Δα as shown in equation 15.

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[0057] The dead time compensation unit 183 can calculate the above Fourier coefficients an and bn as shown in equation 16.

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[0058] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 16, as shown in equation 17.

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[0059] In comparison with equations 7 and 8 explained using Figure 4, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (2) α + Δα < θvi < π - α is satisfied, as shown in equation 18.

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[0060] Figure 7 is an explanatory diagram of the calculation process of the dead time compensation unit 183 when (3)π-α+Δα<θvi<π is satisfied.

[0061] (3) When π-α+Δα<θvi<π is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 7. (3) When π-α+Δα<θvi<π is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 7. The switch timings α0 to α5 shown in the lower section (c) of Figure 7 can be expressed using the firing angle α and the dead time Δα as shown in equation 19.

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[0062] The dead time compensation unit 183 can calculate the above Fourier coefficients an and bn as shown in equation 20.

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[0063] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 20, as shown in equation 21.

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[0064] In comparison with equations 7 and 8 explained using Figure 4, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (3)π-α+Δα<θvi<π is satisfied, as shown in equation 22.

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[0065] Figure 8 is an explanatory diagram of the calculations performed by the dead time compensation unit 183 when (4)π+Δα<θvi<π+α is satisfied.

[0066] (4) When π+Δα<θvi<π+α is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 8. (4) When π+Δα<θvi<π+α is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 8. The switch timings α1 to α4 shown in the lower section (c) of Figure 8 can be expressed using the firing angle α and the dead time Δα as shown in equation 23.

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[0067] The dead time compensation unit 183 can calculate the above Fourier coefficients an and bn as shown in equation 24.

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[0068] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 24, as shown in equation 25.

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[0069] In comparison with equations 7 and 8 explained using Figure 4, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (4)π+Δα<θvi<π+α is satisfied, as shown in equation 26.

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[0070] Figure 9 is an explanatory diagram of the calculations performed by the dead time compensation unit 183 when (5)π+α+Δα<θvi<2π-α is satisfied.

[0071] (5) When π+α+Δα<θvi<2π-α is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 9. (5) When π+α+Δα<θvi<2π-α is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 9. The switch timings α1 to α4 shown in the lower section (c) of Figure 9 can be expressed using the firing angle α and the dead time Δα as shown in equation 27.

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[0072] The dead time compensation unit 183 can calculate the above Fourier coefficients an and bn as shown in equation 28.

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[0073] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 28, as shown in equation 29.

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[0074] In comparison with equations 7 and 8 explained using Figure 4, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (5)π+α+Δα<θvi<2π-α is satisfied, as shown in equation 30.

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[0075] Figure 10 is an explanatory diagram of the calculations performed by the dead time compensation unit 183 when (6) 2π-α+Δα<θvi<2π is satisfied.

[0076] (6) When 2π-α+Δα<θvi<2π is satisfied, the relationship between the output voltage of inverter 10 before dead time compensation and the current flowing through motor 3 is as shown in the middle section (b) of Figure 10. (6) When 2π-α+Δα<θvi<2π is satisfied, the output voltage after dead time compensation has the waveform shown in the lower section (c) of Figure 10. The switch timings α1 to α4 shown in the lower section (c) of Figure 10 can be expressed using the firing angle α and the dead time Δα as shown in equation 31.

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[0077] The dead time compensation unit 183 can calculate the above Fourier coefficients an and bn as shown in equation 32.

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[0078] Therefore, the dead time compensation unit 183 can calculate the amplitude A of the output voltage of the inverter 10 using the Fourier coefficients an and bn of equation 32, as shown in equation 33.

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[0079] In comparison with equations 7 and 8 explained using Figure 4, the dead time compensation unit 183 can calculate the amplitude error ΔA and phase angle error Δθ when (6) 2π-α+Δα<θvi<2π as shown in equation 34.

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[0080] Figure 11 is a table showing the relationship between the difference θvi between the voltage phase angle θv and the current phase angle θi, and the amplitude error ΔA and phase angle error Δθ. The table in Figure 11 summarizes the amplitude error ΔA and phase angle error Δθ calculated for each case in Figures 5 to 10.

[0081] In each of the cases (1) to (6) explained using Figures 5 to 10, the amplitude error ΔA and phase angle error Δθ show different values ​​as shown in Figure 11. The 3-pulse 1-pulse calculation unit 180 corrects the modulation rate MF used in calculating the firing angle α of the output voltage using the amplitude error ΔA corresponding to the range of difference θvi shown in Figure 11. The 3-pulse 1-pulse calculation unit 180 also corrects the phase angles θ1 and θ2 of the output voltage using the phase angle error Δθ corresponding to the range of difference θvi shown in Figure 11. As a result, the 3-pulse 1-pulse calculation unit 180 can output an output voltage from the inverter 10 that takes dead time into account for the required voltage. Note that, as shown in Figure 11, if the amplitude error ΔA is zero, the 3-pulse 1-pulse calculation unit 180 does not need to correct the modulation rate MF. Similarly, if the phase angle error Δθ is zero, the 3-pulse 1-pulse calculation unit 180 does not need to correct the phase angles θ1 and θ2 of the output voltage.

[0082] Furthermore, the dead time compensation unit 183 may calculate the amplitude error ΔA and phase angle error Δθ in the case between (6) 2π-α+Δα < θvi < 2π and (1) Δα < θvi < α, such as the interval [0, Δα], by linear interpolation from the amplitude error ΔA and phase angle error Δθ calculated in each range. Alternatively, since Δα is a small amount, the dead time compensation unit 183 may set the amplitude error ΔA and phase angle error Δθ in the case between (6) 2π-α+Δα < θvi < 2π and (1) Δα < θvi < α to zero.

[0083] The firing angle calculation unit 184 calculates the firing angle α of the output voltage of the inverter 10 based on the amplitude error ΔA calculated as a dead time compensation amount and the modulation rate MF. Specifically, the firing angle calculation unit 184 adds the amplitude error ΔA calculated as a dead time compensation amount to the modulation rate MF as a manipulated variable, and calculates the firing angle α from the modulation rate MF to which the amplitude error ΔA has been added. In detail, the firing angle calculation unit 184 can calculate the firing angle α using formula 35.

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[0084] The phase angle calculation unit 185 calculates the phase angles θ1 and θ2 of the output voltage of the inverter 10 based on the phase angle error Δθ calculated as a dead time compensation amount and the electrical angle θp of the motor 3. Phase angle θ1 indicates the phase angle of the output voltage at the next control timing. Phase angle θ2 indicates the phase angle of the output voltage at the control timing after that. Specifically, the phase angle calculation unit 185 uses the electrical angle deviation ωtc per carrier period, calculated from the electrical angular velocity ω of the motor 3 and the carrier period tc, as the one-sample delay of the phase angle. Then, the phase angle calculation unit 185 adds the phase angle error Δθ calculated as a dead time compensation amount to the previous voltage phase angle θv as a manipulated variable to calculate the phase angles θ1 and θ2. In detail, when the rotational speed of the motor 3 is positive, the phase angle calculation unit 185 can calculate the phase angles θ1 and θ2 using equation 36.

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[0085] When the rotational speed of motor 3 is negative, the phase angle calculation unit 185 can calculate the phase angles θ1 and θ2 by changing (+π / 2) to (-π / 2) on the right-hand side of equation 36. Equation 36 also shows the phase angles θ1 and θ2 of one of the three phase voltages (for example, the U phase). When calculating the phase angles θ1 and θ2 of another phase of the three phase voltages (for example, the V phase or W phase), the phase angle calculation unit 185 can calculate the phase angles θ1 and θ2 of that other phase by shifting the phase angles θ1 and θ2 calculated by equation 36 in units of 120 degrees.

[0086] The duty cycle calculation unit 186 calculates the duty cycle duvw for each phase of the three-phase voltage from the firing angle α of the output voltage calculated by the firing angle calculation unit 184 and the phase angles θ1 and θ2 of the output voltage calculated by the phase angle calculation unit 185, and determines the position (switch timing) of each pulse edge. The duty cycle calculation unit 186 then outputs the calculated duty cycle duvw and the position of each pulse edge to the PWM pulse generation unit 150.

[0087] The PWM pulse generation unit 150 generates a PWM pulse signal P corresponding to the calculated duty cycle duvw and the position of each pulse edge, and outputs it to the gate circuit 160. The gate circuit 160 outputs a drive signal DR corresponding to the PWM pulse signal P to the inverter 10. Each semiconductor switch element of the inverter 10 is controlled on / off by the drive signal DR. This adjusts the output voltage of the inverter 10.

[0088] Figure 12 is a diagram illustrating the operation and effects of the inverter control device 100 shown in Figure 1.

[0089] As described above, the inverter control device 100 of Embodiment 1 is a device that controls the switching operation of an inverter 10 that converts a DC voltage to an AC voltage and applies it to a motor 3 by pulse width modulation. The inverter control device 100 of Embodiment 1 includes a dead time compensation unit 183 that performs dead time compensation to compensate for errors in the output voltage of the inverter 10 caused by the dead time of the inverter 10. The dead time compensation unit 183 performs dead time compensation based on the difference θvi between the current phase angle θi, which indicates the phase angle for outputting the current of the motor 3, and the voltage phase angle θv, which is for outputting a voltage corresponding to the current.

[0090] As a result, the inverter control device 100 of Embodiment 1 can perform dead time compensation for the requested voltage, as shown in Figure 12, and can make the output voltage of the inverter 10 match the requested voltage. Therefore, the inverter control device 100 of Embodiment 1 can reduce voltage errors caused by dead time. Moreover, the dead time compensation unit 183 of Embodiment 1 can perform dead time compensation based on the difference θvi between the voltage phase angle θv, which can be calculated from the dq-axis voltage command value Vdq*, and the current phase angle θi, which can be calculated from the dq-axis current command value Idq*. Therefore, the inverter control device 100 of Embodiment 1 does not need to perform high-speed current detection as in the conventional method, and dead time compensation can be easily performed. Thus, the inverter control device 100 of Embodiment 1 can easily reduce voltage errors caused by dead time when switching from SVPWM control mode to 3-pulse control mode, and suppress torque shock.

[0091] Furthermore, the inverter control device 100 of Embodiment 1 includes a modulation rate / voltage phase angle calculation unit 181 that calculates the modulation rate MF and voltage phase angle θv of the output voltage, and a current phase angle calculation unit 182 that calculates the current phase angle θi. The inverter control device 100 of Embodiment 1 also includes a firing angle calculation unit 184 that calculates the firing angle α of the output voltage, and a phase angle calculation unit 185 that calculates the phase angles θ1 and θ2 of the output voltage. The dead time compensation unit 183 calculates at least one of the amplitude error ΔA and phase angle error Δθ of the output voltage generated by the dead time as a dead time compensation amount. The firing angle calculation unit 184 calculates the firing angle α based on the amplitude error ΔA and modulation rate MF calculated as the dead time compensation amount. The phase angle calculation unit 185 calculates the phase angles θ1 and θ2 based on the phase angle error Δθ calculated as the dead time compensation amount.

[0092] As a result, the inverter control device 100 of Embodiment 1 can calculate the firing angle α and phase angles θ1, θ2 in such a way that it corrects the amplitude error ΔA and phase angle error Δθ even if the amplitude error ΔA and phase angle error Δθ fluctuate within the range of the difference θvi. Therefore, the inverter control device 100 of Embodiment 1 can appropriately compensate for the voltage error that occurs due to dead time, even if the voltage error that occurs fluctuates according to the phase difference between the output voltage of the inverter 10 and the current flowing through the motor 3. Thus, the inverter control device 100 of Embodiment 1 can easily and reliably reduce the voltage error that occurs due to dead time and reliably suppress torque shock.

[0093] As a result, in the inverter control device 100 of Embodiment 1, the dead time compensation unit 183 performs dead time compensation when the switching operation is controlled by the 3-pulse control mode.

[0094] As a result, the inverter control device 100 of Embodiment 1 can easily reduce the voltage error caused by dead time when controlled by the 3-pulse control mode, thereby suppressing torque shock. In particular, the inverter control device 100 of Embodiment 1 can suppress the torque shock that occurred when switching from the SVPWM control mode to the 3-pulse control mode, as in the conventional method. Furthermore, the inverter control device 100 of Embodiment 1 can suppress the torque shock that occurs when switching from the 3-pulse control mode to the SVPWM control mode. Therefore, the inverter control device 100 of Embodiment 1 can stabilize the operation of the motor 3.

[0095] [Embodiment 2] The inverter control device 100 of Embodiment 2 will be described using Figures 13 and 14. The same configuration and operation as in Embodiment 1 will not be described in the inverter control device 100 of Embodiment 2. Figure 13 is a diagram of the configuration of the 3-pulse 1-pulse calculation unit 180 provided in the inverter control device 100 of Embodiment 2. Figure 14 is a table showing the relationship between the difference θvi between the voltage phase angle θv and the current phase angle θi, and the phase angle error Δθ.

[0096] Embodiment 2 will be explained using as an example the case in which the inverter control device 100 controls the switching operation in 1-pulse control mode.

[0097] Even in the case of a single-pulse control mode, if the Fourier coefficients an and bn are calculated in the same way as in the case of the three-pulse control mode described in Embodiment 1, the relationship between the range of the difference θvi and the phase angle error Δθ will be as shown in Figure 14. That is, as shown in Figure 14, in the case of a single-pulse control mode, there is no need to calculate the amplitude error ΔA as the dead time compensation amount, and there is no need to correct the modulation rate MF.

[0098] Therefore, the dead time compensation unit 183 of Embodiment 2 calculates only the phase angle error Δθ as the dead time compensation amount based on the difference θvi. The phase angle calculation unit 185 of Embodiment 2 calculates the phase angles θ1 and θ2 of the output voltage based on the phase angle error Δθ calculated as the dead time compensation amount and the electrical angle θp of the motor 3, similar to Embodiment 1. On the other hand, the firing angle calculation unit 184 of Embodiment 2 calculates the firing angle α of the output voltage based on the uncorrected modulation rate MF.

[0099] As a result, the inverter control device 100 of Embodiment 2 does not need to calculate the amplitude error ΔA as a dead time compensation amount, and does not need to correct the modulation rate MF, thus simplifying the control logic compared to Embodiment 1. Therefore, the inverter control device 100 of Embodiment 2 can more easily reduce the voltage error caused by dead time and suppress torque shock.

[0100] Furthermore, in the inverter control device 100 of Embodiment 2, the dead time compensation unit 183 performs dead time compensation when the switching operation is controlled by a 1-pulse control mode.

[0101] As a result, the inverter control device 100 of Embodiment 2 can easily reduce the voltage error caused by dead time when controlled in 1-pulse control mode, thereby suppressing torque shock. In particular, the inverter control device 100 of Embodiment 2 can suppress torque shock that occurs when switching from 3-pulse control mode to 1-pulse control mode. Furthermore, the inverter control device 100 of Embodiment 2 can suppress torque shock that occurs when switching from 1-pulse control mode to 3-pulse control mode. Therefore, the inverter control device 100 of Embodiment 2 can further stabilize the operation of the motor 3.

[0102] [Embodiment 3] The inverter control device 100 of Embodiment 3 will be described using Figure 15. The same configuration and operation as in Embodiment 1 will not be explained in the inverter control device 100 of Embodiment 3. Figure 15 is a configuration diagram of the inverter control device 100 of Embodiment 3.

[0103] In Embodiment 3, reducing the voltage error caused by dead time is used not only to suppress torque shock, but also to estimate the position of the rotor of the motor 3.

[0104] The inverter control device 100 of Embodiment 3 includes, instead of (or as part of) the rotational position detection unit 140, an induced voltage estimation shaft misalignment calculation unit 141 and a velocity phase estimation unit 142. The other configurations of the inverter control device 100 of Embodiment 3 are the same as those of Embodiment 1.

[0105] The induced voltage estimation axis misalignment calculation unit 141 estimates the induced voltage E0 of the motor 3 from the dq axis voltage command value Vdq*, the dq axis current detection value Idq, and the speed command value ωr* that commands the motor rotation speed. The induced voltage estimation axis misalignment calculation unit 141 then calculates the estimated axis misalignment value Δθp from the phase of the estimated induced voltage E0. The speed phase estimation unit 142 estimates the rotation position θp, which is the position of the rotor of the motor 3, from the magnitude |E0| of the induced voltage E0 and the estimated axis misalignment value Δθp.

[0106] A method for estimating the rotational position θp from the induced voltage E0 estimated using the dq-axis voltage command value Vdq* is disclosed in Japanese Patent No. 3411878. The inverter control device 100 of Embodiment 3 can utilize the method disclosed in Japanese Patent No. 3411878.

[0107] When a voltage error occurs due to dead time, the above method of estimating the rotational position θp using the dq-axis voltage command value Vdq* results in the voltage error caused by dead time being superimposed as an error on the phase of the induced voltage E0, thus degrading the accuracy of the rotational position θp estimation. However, the inverter control device 100 of Embodiment 3, like Embodiment 1, can reduce the voltage error caused by dead time, thereby improving the accuracy of the rotational position θp estimation. This is also true for the magnetic flux estimation and torque estimation of the motor 3 using the dq-axis voltage command value Vdq*, and the inverter control device 100 of Embodiment 3 can improve the estimation accuracy of the magnetic flux estimation and torque estimation of the motor 3 using the dq-axis voltage command value Vdq*.

[0108] [others] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0109] Furthermore, each of the above configurations, functions, processing units, and processing means may be implemented in hardware, either partially or entirely, by designing them, for example, using integrated circuits. Alternatively, each of the above configurations and functions may be implemented in software by having the processor interpret and execute programs that realize each function. Information such as programs, tapes, and files that realize each function can be stored in memory, recording devices such as hard disks and SSDs (solid state drives), or recording media such as IC cards, SD cards, and DVDs.

[0110] Furthermore, the control lines and information lines shown are those deemed necessary for explanatory purposes, and not all control lines and information lines are necessarily shown in the actual product. In reality, it is safe to assume that almost all components are interconnected. [Explanation of symbols]

[0111] 3…Motor (AC motor), 10…Inverter, 100…Inverter control device, 181…Modulation rate / voltage phase angle calculation unit, 182…Current phase angle calculation unit, 183…Dead time compensation unit, 184…Firing angle calculation unit, 185…Phase angle calculation unit

Claims

1. An inverter control device that controls the switching operation of an inverter that converts a DC voltage to an AC voltage and applies it to an AC motor by pulse width modulation, The inverter is equipped with a dead time compensation unit that performs dead time compensation to compensate for the error in the output voltage of the inverter caused by the dead time of the inverter. The aforementioned dead time compensation unit is Based on the difference between the current phase angle, which indicates the phase angle for outputting current from the AC motor, and the voltage phase angle, which indicates the voltage for outputting a voltage corresponding to the current, at least one of the amplitude error and phase angle error of the output voltage caused by the dead time is calculated as a dead time compensation amount. The firing angle and phase angle of the output voltage are corrected based on the calculated dead time compensation amount to perform the dead time compensation. An inverter control device characterized by the following:

2. A modulation rate / voltage phase angle calculation unit that calculates the modulation rate of the output voltage and the voltage phase angle, A current phase angle calculation unit that calculates the current phase angle, A firing angle calculation unit that calculates the firing angle of the output voltage, The system further comprises a phase angle calculation unit for calculating the phase angle of the output voltage, The firing angle calculation unit calculates the firing angle based on the amplitude error and modulation rate calculated as the dead time compensation amount, The phase angle calculation unit calculates the phase angle based on the phase angle error calculated as the dead time compensation amount. The inverter control device according to feature 1.

3. The dead time compensation unit performs the dead time compensation when the switching operation is controlled by at least one of the one-pulse control mode and the three-pulse control mode. The inverter control device according to feature 1.

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