Inverter device and motor drive device

Abstract

To provide an inverter device capable of improving setting accuracy of a dead time compensation amount.SOLUTION: This inverter device (1) converts DC power into AC power, outputs the AC power to a load (3), and is controlled by a control unit (7) having a dead time compensation function. The control unit (7) generates a dead time compensation amount based on a third harmonic component included in the output current according to a sinusoidal current command of a predetermined frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an inverter device and a motor drive device using the inverter device.

Background Art

[0002] When the inverter device operates, a dead time is set to simultaneously turn off the semiconductor switching elements in the upper and lower arms so that the upper and lower arms do not short-circuit. When the dead time is set, an error voltage occurs between the voltage command value generated in the controller and the output voltage of the inverter device. Therefore, waveform distortion occurs in the output current of the inverter device. In order to reduce such waveform distortion, the controller performs dead time compensation.

[0003] In dead time compensation, a predetermined dead time compensation amount is added to the voltage command value according to the polarity of the output current. The magnitude of the dead time compensation amount is affected by the dead time, as well as the characteristics and variations of the semiconductor switching elements. Therefore, in order to set the dead time compensation amount, the characteristics of the semiconductor switching elements are investigated or measured in advance, or the error voltage associated with the dead time setting is measured.

[0004] On the other hand, as a conventional technique for setting the dead time compensation amount by a controller, for example, the technique described in Patent Document 1 is known. In this technique, the amplitude of the compensation voltage is corrected so that the difference between the value of the current pulsation generated in the motor current flowing from the power converter to the motor and the current command value becomes smaller than a predetermined reference value.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the conventional technology described above, the dead time compensation amount is set based on the sixth harmonic component in the motor current associated with dead time compensation. Therefore, it becomes difficult to ensure the accuracy of setting the dead time compensation amount due to sixth harmonic components in the motor current caused by distortion of the motor's induced voltage, magnetic saturation characteristics, and pulsation of the load torque.

[0007] Therefore, the present invention provides an inverter device that can improve the accuracy of setting the dead time compensation amount, and a motor drive device that uses such an inverter device. [Means for solving the problem]

[0008] To solve the above problems, the inverter device according to the present invention converts DC power to AC power and outputs AC power to the load. The dead time setting reduces waveform distortion of the output current caused by the error voltage between the voltage command value and the output voltage. Controlled by a control unit equipped with a dead time compensation function, In dead time compensation, the control unit adds a predetermined dead time compensation amount to the voltage command value according to the polarity of the output current. The control unit generates a dead time compensation amount based on the third harmonic component included in the output current corresponding to a sinusoidal current command of a predetermined frequency.

[0009] To solve the above problems, the motor drive device according to the present invention drives an AC motor with an inverter device, the inverter device converts DC power to AC power and outputs AC power to the AC motor, The dead time setting reduces waveform distortion of the output current caused by the error voltage between the voltage command value and the output voltage. Controlled by a control unit equipped with a dead time compensation function, In dead time compensation, the control unit adds a predetermined dead time compensation amount to the voltage command value according to the polarity of the output current. The control unit generates a dead time compensation amount based on the third harmonic component contained in the output current corresponding to a sinusoidal current command of a predetermined frequency. [Effects of the Invention]

[0010] According to the present invention, the accuracy of setting the dead time compensation amount is improved.

[0011] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0012] [Figure 1] It is a circuit diagram showing the configuration of the inverter device according to the first embodiment. [Figure 2] It is a functional block diagram showing the schematic configuration of the controller 7 (FIG. 1). [Figure 3] It is a functional block diagram showing the detailed configuration of the current command generator 10 (FIG. 2). [Figure 4] It is a functional block diagram showing the detailed configuration of the current controller 11 (FIG. 2). [Figure 5] It is a functional block diagram showing the detailed configuration of the dead time compensator 13 (FIG. 2). [Figure 6] It is a functional block diagram showing the detailed configuration of the dead time compensation amount identifier 15 (FIG. 2). [Figure 7] It is a waveform diagram showing the operation of the dead time compensation amount identifier 15 (FIG. 6). [Figure 8] It shows an example of the output waveform 33 of the low-pass filter 27 (FIG. 6) and an example of the waveform 34 of the corresponding dead time compensation amount during the operation of the dead time compensation amount identifier 15 (FIG. 6). [Figure 9] It is a circuit diagram showing the configuration of the inverter device according to the second embodiment. [Figure 10] It is a functional block diagram showing the schematic configuration of the controller 45 (FIG. 9). [Figure 11] It is a circuit diagram showing the overall configuration of the motor drive device according to the third embodiment.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the following first to third embodiments and the drawings. In each figure, components with the same reference numerals indicate the same components or components having similar functions.

[0014] As described below, in each embodiment, the dead time compensation amount is set based on the third harmonic component included in the current output by the inverter device.

Examples

[0015] Figure 1 is a circuit diagram showing the configuration of an inverter device according to Embodiment 1 of the present invention.

[0016] The inverter device 1 is connected between the DC power supply 2 and the load 3, and outputs a single-phase AC current to the load 3. In this embodiment 1, the load 3 is a series circuit of an inductor and a resistor, but it could be, for example, a motor winding.

[0017] The inverter device 1 includes a voltage detector 4, a plurality of arms 5, a current detector 6, and a controller 7.

[0018] Each of the multiple (four in this embodiment) arms 5 consists of a parallel circuit of a semiconductor switching element and a freewheeling diode. In this embodiment 1, the four semiconductor switching elements in the four arms 5 are connected in a full bridge configuration to form the main circuit of a single-phase inverter. In this embodiment 1, insulated-gate bipolar transistors (IGBTs) are used as the semiconductor switching elements.

[0019] The voltage detector 4 detects the DC power supply voltage of the DC power supply 2, that is, the DC input voltage to the single-phase inverter main circuit. The current detector 6 detects the single-phase AC output current from the single-phase inverter main circuit to the load 3 in the inverter device 1, that is, the load current.

[0020] Controller 7 receives a DC voltage detection signal from the voltage detector 4 and an output current detection signal from the current detector 6. Based on the DC voltage detection value and the AC output current detection value, Controller 7 generates and outputs a PWM (pulse width modulation) signal that controls the switching of the single-phase inverter main circuit. This PWM signal controls the on / off state of each semiconductor switching element constituting the single-phase inverter main circuit, thereby converting the DC power input from the DC power supply 2 into single-phase AC power.

[0021] Figure 2 is a functional block diagram showing the schematic configuration of the controller 7 (Figure 1).

[0022] As shown in Figure 2, the controller 7 comprises a current command generator 10, a current controller 11, a modulation rate calculator 12, a dead time compensator 13, a PWM controller 14, and a dead time compensation amount identifier 15.

[0023] The following describes the detailed configuration of each part.

[0024] Figure 3 is a functional block diagram showing the detailed configuration of the current command generator 10 (Figure 2).

[0025] The phase calculator 17 calculates the phase (θ1) by integral calculation based on the frequency (f1) that is pre-set in the current command frequency setting unit 16. Note that f1 is set based on the output frequency of the inverter device or the operating frequency of the load 3, etc. For example, f1 is set to the rated frequency.

[0026] The sine wave calculator 18A generates a sine wave signal (sin(θ1)) based on the phase (θ1) calculated by the phase calculator 17. The sine wave signal (sin(θ1)) generated by the sine wave calculator 18A is amplified by Iamp by the amplifier 19. As a result, the current command generator 10 generates a sine wave current command i_ref represented by equation (1). Iamp is the amplitude value of the current command.

[0027] The phase (θ1) calculated by the phase calculator 17 is amplified three times by the amplifier 20. The sine wave calculator 18A generates a sine wave signal (sin(3θ1)) based on the phase amplified three times. As a result, the current command generator 10 generates a sine wave signal sin_3, which is in phase with i_ref and has three times the frequency, as expressed by equation (2). The sine wave signal sin_3 is used in the dead time compensation amount identifyr 15 (Figure 2) to generate the dead time compensation amount dt_comp, as will be described later (Figure 6).

[0028]

number

[0029]

number

[0030] The current command generator 10 operates when the inverter device 1 is set to an operating mode that identifies the dead time compensation amount. In the normal operation of the inverter device 1, other current command generators operate to generate current commands in response to operating commands for the load 3, for example, speed commands and torque commands if the load 3 is a motor.

[0031] Furthermore, when the inverter device 1 is operated at a constant frequency f1, the current command generator 10 may be used both during dead time compensation amount identification and during normal operation.

[0032] Figure 4 is a functional block diagram showing the detailed configuration of the current controller 11 (Figure 2).

[0033] The current controller 11 generates a voltage command v_ref using the PI controller 21 and the S controller 22 such that the deviation (=i_ref-i_fb: see Figure 2) between the current command i_ref from the current command generator 10 (Figure 3) and the output current detection signal i_fb from the current detector 6 (Figure 1) is zero. The transfer function of the current controller 11 is expressed by equation (3). In equation (3), K P ,K I ,K S ,K T is the control gain, and s is the Laplace operator.

[0034]

number

[0035] In the right-hand side of equation (3), the first and second terms are the transfer functions of the PI controller 21, and the third term is the transfer function of the S controller 22. As this third term indicates, the S controller 22 exhibits a large gain for the signal component at frequency f1, thereby improving the accuracy of current control.

[0036] Alternatively, other controllers, such as a repetitive controller, may be used instead of the PI controller and S controller, to operate in a manner that reduces the deviation between the current command i_ref and the AC current detection signal i_fb to zero.

[0037] As shown in Figure 2, the modulation rate calculator 12 generates a modulation rate command, i.e., a modulated wave m_ref in PWM control, represented by equation (4), based on the voltage command v_ref generated by the current controller 11 (Figure 4) and the DC voltage signal Vdc from the voltage detector 4 (Figure 1).

[0038]

number

[0039] Figure 5 is a functional block diagram showing the detailed configuration of the dead time compensator 13 (Figure 2).

[0040] The dead time compensator 13 determines the polarity of the current command i_ref from the current command generator 10 (Figure 3) using the polarity determination unit 24. Furthermore, the dead time compensator 13 sets the sign of the dead time compensation amount dt_comp, described later, using the switch 23, according to the determined polarity of the current command i_ref. That is, depending on the polarity of i_ref, the switch 23 selects either dt_comp or -dt_comp. The dead time compensator 13 generates a dead time compensated modulated wave m_ref_dt by adding the dead time compensation amount, whose sign is set by the switch 23, to the modulated wave m_ref generated by the modulation rate calculator 12. In this way, the dead time compensator 13 performs dead time compensation.

[0041] As shown in Figure 2, the PWM controller 14 generates a PWM signal based on the modulated wave m_ref_dt, which has been dead-time compensated by the dead-time compensator 13. The PWM controller 14 generates the PWM signal by comparing the modulated wave m_ref_dt with a carrier wave (not shown).

[0042] Figure 6 is a functional block diagram showing the detailed configuration of the dead time compensation amount identifyr 15 (Figure 2).

[0043] The dead time compensation amount identifier 15 multiplies the AC current detection signal i_fb and the sine wave signal sin_3 from the current command generator 10 (Figure 3) using the multiplier 26. From the resulting multiplied value (=i_fb × sin_3 = i_fb × sin(3 × θ1)), the low-pass filter 27 extracts the DC component corresponding to the current waveform distortion caused by the dead time compensation error. The dead time compensation amount identifier 15 further generates a dead time compensation amount dt_comp using the integral controller 28, based on the deviation between zero and this DC component, so as to make this deviation zero, i.e., to eliminate the DC component.

[0044] According to the inventor's research, when the waveform of the output current of the inverter device 1 is distorted due to the dead time setting, there is a correlation between the DC component generated when the third harmonic component contained in the AC current detection signal i_fb is multiplied with the sine wave signal sin_3, and the dead time compensation amount. As this DC component approaches zero, the dead time compensation amount approaches an appropriate value.

[0045] In this embodiment 1, the DC component, which is one feature of the product of the AC current detection signal i_fb and the sine wave signal sin_3, is extracted. However, other features may be extracted if there is a correlation with the dead time compensation amount. For example, the amplitude of the frequency component generated when the third harmonic component contained in the AC current detection signal i_fb is multiplied with the sine wave signal sin_3 may also be extracted.

[0046] Next, we will explain the operation of the dead time compensation amount identifyr 15.

[0047] Figure 7 is a waveform diagram showing the operation of the dead time compensation amount identifyr 15 (Figure 6). This waveform diagram is based on the inventor's research.

[0048] Figure 7 shows the operation of the dead time compensation identifier 15 in the cases where the dead time compensation is excessive, insufficient, and appropriate. In each case, the waveforms shown from top to bottom in the figure are: the AC current detection value (i_fb), i.e., the output current; the waveform of the sine wave signal sin_3; the waveform of the multiplied value (=i_fb × sin_3) by the multiplier 26 (Figure 6); and the waveform of the DC component extracted from the multiplied value by the low-pass filter 27 (Figure 6).

[0049] When the dead time compensation is excessive (left diagram in Figure 7), the dead time compensation is set to 150% of the appropriate value. In this case, due to the excessive dead time compensation, the magnitude of the output current becomes larger than a sine wave around the time the polarity of the output current waveform 30 switches (for example, at time 2.58 sec) due to waveform distortion. As a result, the positive component of the multiplier value 32 increases, and the DC component extracted from the output waveform 33 of the low-pass filter 27 (Figure 6), i.e., the multiplier value 32, shows a positive value.

[0050] When the dead time compensation amount is insufficient (center diagram in Figure 7), the dead time compensation amount is set to 50% of the appropriate value. In this case, due to the insufficient dead time compensation amount, the magnitude of the output current becomes smaller than a sine wave around the time the polarity of the output current waveform 30 switches (for example, at time 2.58 sec) due to waveform distortion. As a result, the negative component of the multiplier value 32 increases, and the DC component extracted from the output waveform 33 of the low-pass filter 27 (Figure 6), i.e., the multiplier value 32, shows a negative value.

[0051] When the dead time compensation amount is at an appropriate value (right figure in Figure 7), the multiplication value 32 is close to zero. Therefore, the DC component extracted from the output waveform 33 of the low-pass filter 27 (Figure 6), i.e., the multiplication value 32, is approximately zero.

[0052] As shown in Figure 7, the magnitude of the DC component output by the low-pass filter is correlated with the dead time compensation amount. Therefore, the dead time compensation amount that makes the DC component output by the low-pass filter 27 (Figure 6) zero, i.e., the dead time compensation amount dt_comp output by the integrating controller 28 (Figure 6), has an appropriate value.

[0053] Figure 8 shows an example of the output waveform 33 of the low-pass filter 27 (Figure 6) and an example of the corresponding dead-time compensation waveform 34 when the dead-time compensation amount identifyr 15 (Figure 6) is in operation. The dashed line in Figure 8 indicates the appropriate value 35 for the dead-time compensation amount.

[0054] In the example shown in Figure 8, approximately 0.75 seconds after the dead time compensation amount identifyr 15 starts operating, the DC component of the output waveform 33 of the low-pass filter 27 becomes nearly zero, and the dead time compensation amount changes from the initial value (50% of the appropriate value) to the appropriate value.

[0055] The dead time compensation amount with an appropriate value, obtained by the operation of the dead time compensation amount identifier 15 (Figure 6), is stored in the memory unit (not shown) of the controller 7. Using the stored dead time compensation amount, the dead time compensator 13 (Figures 2, 5) performs dead time compensation.

[0056] Furthermore, the inverter device 1 is provided with a dead time compensation amount identification operation mode, and in the dead time compensation amount identification operation mode, the appropriate value of the dead time compensation amount is identified as described above.

[0057] The dead time compensation amount identification operation mode may be set in the inverter device 1 by a predetermined operation when the dead time compensation amount is identified, or it may be set each time the load 3 is started up.

[0058] Furthermore, the dead time compensation amount identifyr 15 may dynamically calculate the dead time compensation amount during load operation. This allows for highly accurate identification of the appropriate value of the dead time compensation amount, even when the temperature characteristics of the semiconductor switching elements affect the dead time compensation amount depending on the operating state and environment of the inverter device.

[0059] Furthermore, if the load is a motor, it is preferable to stop the motor and identify the appropriate value for the dead time compensation. This prevents the influence of harmonics associated with the motor's rotation, allowing for highly accurate identification of the appropriate value for the dead time compensation.

[0060] As described above, according to Example 1, the dead time compensation amount is set based on the third harmonic component contained in the output current corresponding to the sinusoidal current command. This improves the accuracy of setting the dead time compensation amount. Therefore, waveform distortion of the output current that occurs with the setting of the dead time is suppressed.

[0061] Furthermore, according to Example 1, the dead time compensation amount is set based on the DC component generated according to the third harmonic component contained in the output current by multiplying the AC current detection signal i_fb, i.e., the output current, by a sine wave signal (sin_3) with a frequency three times that of the current command frequency. This allows the dead time compensation amount to be set to an appropriate value with high accuracy.

[0062] In this embodiment 1, the current detector 6 used for current control is used in the dead time compensation, including the setting of the dead time compensation amount. Therefore, the number of detectors used in the inverter device does not increase with the dead time compensation. [Examples]

[0063] Figure 9 is a circuit diagram showing the configuration of an inverter device according to Embodiment 2 of the present invention.

[0064] The following mainly describes the differences from Example 1.

[0065] Unlike in Example 1 (single-phase inverter), the inverter device 41 is a three-phase inverter.

[0066] The inverter device 41 is connected between the DC power supply 40 and the load 42 and outputs a three-phase AC current to the load 42. In this embodiment 2, the load 42 consists of a series circuit (3) of inductors and resistors connected in a star configuration, for example, the three-phase winding of a three-phase AC motor.

[0067] The inverter device 41 includes a voltage detector 43, multiple arms, a current detector 44, and a controller 45.

[0068] Each of the multiple arms (six in this embodiment) consists of a parallel circuit of a semiconductor switching element and a freewheeling diode. In this embodiment 2, the six semiconductor switching elements in the six arms 5 are connected in a three-phase full bridge configuration to form the main circuit of a three-phase inverter.

[0069] The voltage detector 43 detects the DC power supply voltage of the DC power supply 40, that is, the DC input voltage to the three-phase inverter main circuit. The current detector 44 detects two phases of the three-phase AC output current from the three-phase inverter main circuit to the load 42 in the inverter device 41, that is, the three-phase load current.

[0070] The controller 45 receives a DC voltage detection signal from the voltage detector 43 and an output current detection signal from the current detector 44. Based on the DC voltage detection value and AC output current detection value indicated by the input DC voltage detection signal and output current detection signal, respectively, the controller 45 generates and outputs a PWM signal that controls the switching of the three-phase inverter main circuit. This PWM signal controls the on / off state of each semiconductor switching element constituting the three-phase inverter main circuit, thereby converting the DC power input from the DC power supply 2 into three-phase AC power.

[0071] Figure 10 is a functional block diagram showing the schematic configuration of the controller 45 (Figure 9).

[0072] As shown in Figure 10, the controller 45 comprises a current command generator 50, a dq-axis phase generator 51, a 3-phase 2-axis converter 52, a current controller 53, a 2-axis / 3-phase converter 54A, a 2-axis / 3-phase converter 54B, a modulation rate calculator 55, a dead time compensator 56, a PWM controller 57, and a dead time compensation amount identifyr 58. So-called vector control is applied in the controller 45.

[0073] The operation of each part will be explained below.

[0074] The current command generator 50 has the same configuration as the current command generator 10 in Example 1 (Figure 3). It generates a d-axis current command (Id*) and a sine wave signal (sin_3) with a frequency three times that of the fundamental frequency (f1). In addition, when identifying the dead time compensation amount, the q-axis current command (Iq*) is set to zero.

[0075] The dq-axis phase generator 51 generates the phase (θ) used for coordinate transformation in the 3-phase / 2-axis converter 52 and the 2-axis / 3-phase converters 54A and 54B. d ) generates the phase θ d In the dead time compensation amount identification mode, any phase is acceptable. For simplicity, the phase θ d You can set it to zero.

[0076] The 3-phase / 2-axis converter 52 converts the AC current detection signal (Iu, Iv) into a dq-axis current (Id, Iq). The conversion means is the same as that used in known vector control systems.

[0077] The current controller 53 comprises a d-axis current controller and a q-axis current controller. Each of the d-axis current controller and the q-axis current controller has the same configuration as the current controller 11 in Embodiment 1 (Figure 4). The dq-axis voltage commands (Vd*, Vq*) generated by the current controller 53 are converted into three-phase voltage commands (Vu*, Vv*, Vw*) by the two-axis / three-phase converter 54A. Furthermore, the three-phase voltage commands (Vu*, Vv*, Vw*) are converted into three-phase modulation rates (Mu, Mv, Mw) by the modulation rate calculator 55, in the same manner as in Embodiment 1 (see equation (4)).

[0078] The dead time compensator 56, similar to the dead time compensator 13 in Example 1 (Figure 5), adds or subtracts a dead time compensation amount dt_comp to the modulated wave (Mu, Mv, Mw) according to the polarity of the three-phase current command (Iu*, Iv*, Iw*) to generate a dead time compensated modulated wave (Mu_dt, Mv_dt, Mw_dt).

[0079] The PWM controller 57 uses the compensated modulated waves (Mu_dt, Mv_dt, Mw_dt) to create a PWM signal that controls the operation of the three-phase inverter.

[0080] The PWM controller 57 generates a PWM signal by comparing the modulated wave (Mu_dt, Mv_dt, Mw_dt) with a carrier wave (not shown).

[0081] The dead time compensation amount identifier 58, similar to the dead time compensation amount identifier 15 in Example 1 (Figure 6), multiplies the d-axis current detection value (Id) by the sine wave signal (sin_3) from the current command generator 50. From the multiplied value, a low-pass filter (not shown in Figure 10) extracts the DC component corresponding to the current waveform distortion caused by the dead time compensation error. Furthermore, based on the deviation between zero and this DC component, the dead time compensation amount identifier 58 generates a dead time compensation amount dt_comp using an integral controller (not shown in Figure 10) to make this deviation zero, i.e., to eliminate the DC component.

[0082] According to the above-described embodiment 2, the accuracy of setting the dead time compensation amount in a three-phase inverter device can be improved. Therefore, waveform distortion of the three-phase output current that occurs with the setting of the dead time is suppressed.

[0083] Furthermore, according to Example 2, the dead time compensation amount in the three-phase inverter device can be set to an appropriate value with high precision.

[0084] Furthermore, according to Example 2, when setting the dead time compensation amount, the d-axis current command value Iq* is set to 0, thereby suppressing the operation of the load 42, for example, a three-phase AC motor. This prevents the influence of harmonic components generated in conjunction with the driving of the load 42, thereby improving the accuracy of setting the dead time compensation amount.

[0085] Alternatively, instead of the above-described Embodiment 2, the semiconductor switching elements of the upper and lower arms of any one phase in the three-phase inverter main circuit may be turned off, and the dead time compensation amount setting means for the single-phase inverter in Embodiment 1 may be applied to the other two phases. [Examples]

[0086] Figure 11 is a circuit diagram showing the overall configuration of a motor drive device according to Embodiment 3 of the present invention.

[0087] As shown in Figure 11, the motor drive device according to this embodiment 3 comprises an AC power supply 60, a rectifier circuit 61, a smoothing capacitor 62 for removing voltage ripple, a three-phase inverter device 63 for converting DC power to AC power, a three-phase AC motor 64 to be driven, a mechanical load 65 driven by the three-phase AC motor 64, a controller 68 for controlling the three-phase inverter device 63, a current detector 66 for detecting the current flowing through the three-phase AC motor 64, and a voltage detector 67 for detecting the voltage across the smoothing capacitor 62.

[0088] Instead of the AC power supply 60, the rectifier circuit 61, and the smoothing capacitor 62, a DC power supply such as a stabilized power supply or a battery may be used.

[0089] Alternatively, instead of the current detector 66, a known current detection means that detects the DC bus current of the three-phase inverter device 63 to estimate the motor current may be used.

[0090] The controller 68 is the same as the controller 45 (Figure 10) in the aforementioned Embodiment 2. Therefore, the controller 68 sets the q-axis current command value to zero (Iq*=0), that is, identifies the dead time compensation amount when the three-phase AC motor 64 is stopped.

[0091] According to this embodiment 3, the controller 68 can set the dead time compensation amount in the three-phase inverter device to an appropriate value with high precision. As a result, the torque ripple generated by the three-phase AC motor 64 can be reduced, and the mechanical load 65 can be driven stably without vibration.

[0092] Furthermore, since the controller 68 generates a dead time compensation amount when the three-phase AC motor 64 stops, it can accurately identify the appropriate value of the dead time compensation amount without being affected by distortion of induced voltage or fluctuations in load torque.

[0093] 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. In addition, it is possible to add, delete, or replace some of the configurations in each embodiment with other configurations.

[0094] For example, the AC motor used as the load can be either an induction motor or a synchronous motor. [Explanation of Symbols]

[0095] 1... Inverter device, 2...DC power supply, 3... Load, 4…Voltage detector, 5... Arm, 6…Current detector, 7...Controller, 10...Current command generator, 11...Current controller, 12...Modulation rate calculator, 13...Dead time compensator, 14…PWM controller, 15...Dead time compensation amount identifyr, 16...Current command frequency setting unit, 17...Phase calculator, 18A,18B...Sine wave calculator, 19, 20… Amplifier, 21...PI controller, 22...S controller, 23…Switch, 24...Polarity determiner, 26... Multiplier, 27... Low-pass filter, 28... Integral controller, 40...DC power supply, 41... Inverter device, 42... Load, 43...Voltage detector, 44...Current detector, 45...Controller, 50...Current command generator, 51...dq axis phase generator, 52...3-phase / 2-axis converter, 53...Current controller, 54A, 54B... 2-axis / 3-phase converter, 55...Modulation rate calculator, 56...Dead time compensator, 57...PWM controller, 58...Dead time compensation amount identifyr, 60...AC power supply, 61... Rectifier circuit, 62... Smoothing capacitor, 63... Three-phase inverter device, 64... Three-phase AC motor, 65...mechanical load, 66... ​​Current detector, 67...Voltage detector, 68…Controller

Claims

1. In an inverter device that converts DC power to AC power and outputs the AC power to a load, and is controlled by a control unit equipped with a dead time compensation function that reduces waveform distortion of the output current caused by an error voltage between the voltage command value and the output voltage due to the setting of the dead time, the control unit adds a predetermined dead time compensation amount to the voltage command value according to the polarity of the output current, The control unit, An inverter device characterized by generating the dead time compensation amount based on the third harmonic component included in the output current corresponding to a sinusoidal current command of a predetermined frequency.

2. In the inverter device according to claim 1, The control unit, An inverter device characterized by generating a sinusoidal signal with a frequency three times that is in phase with the sinusoidal current command, calculating a characteristic quantity related to the third harmonic component from the product of the output current and the sinusoidal signal, and generating the dead time compensation amount based on the characteristic quantity.

3. In the inverter device according to claim 2, The control unit, An inverter device characterized by generating the dead time compensation amount in such a way as to reduce the aforementioned feature quantity.

4. In the inverter device according to claim 2, The inverter device is characterized in that the aforementioned feature quantity is the DC component in the multiplication value.

5. In the inverter device according to claim 1, The aforementioned AC power is three-phase AC power. The aforementioned sinusoidal current command is either a d-axis current command or a q-axis current command. The inverter device is characterized in that the output current is a d-axis current command or a q-axis current command.

6. An inverter device according to claim 1, When a three-phase inverter is used in the aforementioned inverter device, The aforementioned AC power is three-phase AC power. The inverter device is characterized in that the control unit turns off one of the three phases of the upper and lower arms in the main circuit to generate the dead time compensation amount.

7. In the inverter device according to claim 1, The control unit, The generated dead time compensation amount is stored in the storage unit. An inverter device characterized by performing dead time compensation using the dead time compensation amount stored in the memory unit.

8. In a motor drive system that drives an AC motor with an inverter device, The inverter device converts DC power to AC power and outputs the AC power to the AC motor. It is controlled by a control unit that has a dead time compensation function to reduce waveform distortion of the output current caused by error voltage between the voltage command value and the output voltage due to the setting of the dead time. In dead time compensation, the control unit adds a predetermined dead time compensation amount to the voltage command value according to the polarity of the output current. The control unit, A motor drive device characterized by generating the dead time compensation amount based on the third harmonic component included in the output current corresponding to a sinusoidal current command of a predetermined frequency.

9. In the motor drive device according to claim 8, The control unit, A motor drive device characterized by generating the dead time compensation amount when the AC motor stops.

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