Inverter control device

Abstract

The purpose of the present invention is to reduce a voltage difference caused by dead time. An inverter control device 100 comprises: a modulated wave generating unit 120 that generates a modulated wave signal on the basis of a voltage command value in an output voltage of an inverter 10; and a PWM pulse generating unit 150 that, on the basis of the modulated wave signal, generates a PWM pulse signal for controlling a switching operation of the inverter 10. The modulated wave generating unit 120 includes: a modulation factor command computing unit 121 that computes a modulation factor command value that indicates a voltage command value as a modulation factor of an output voltage; an actual modulation factor estimating unit 124 that estimates an actual modulation factor that is a modulation factor for which a dead time of the inverter 10 is considered; and a correction coefficient computing unit 125 that computes a correction coefficient of the voltage command value on the basis of the modulation factor command value and the actual modulation factor. The modulated wave generating unit 120 generates a modulated wave signal on the basis of the voltage command value corrected with the correction coefficient.

Description

Technical Field

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

Background Art

[0002] In order to increase the output of a motor, it is necessary to increase the output voltage of an inverter that supplies power to the motor. On the other hand, when the output voltage of the inverter is increased, the switching frequency may decrease. Therefore, when operating the inverter in the overmodulation region, the inverter control device uses a modulation wave with a low switching frequency such as a rectangular wave. The overmodulation region is an operating region of the inverter where the voltage command value in the output voltage of the inverter exceeds the maximum output level in a sine wave.

[0003] The inverter is provided with a dead time, which is a section where both the upper and lower arms are turned off to prevent short circuits when switching 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. Therefore, the inverter control device generally has a dead time compensation function.

[0004] The voltage error generated by the dead time varies with the decrease in the switching frequency. Patent Document 1 discloses a technique for obtaining an output voltage corresponding to the voltage command value in the overmodulation region by performing dead time compensation in consideration of the variation of the voltage error with the voltage command value.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the technology disclosed in Patent Document 1, a dead time is added to the rising or falling edge (hereinafter also referred to as "pulse edge") of the PWM waveform. However, for example, if a dead time compensation value is added in advance to the voltage command value in the overmodulation region, the duty cycle of the modulated wave signal may exceed 100%, and switching may not occur. When the duty cycle of the modulated wave signal exceeds 100%, there is no pulse edge to add dead time, so no dead time occurs, and the pre-added dead time compensation value becomes overcompensated. As a result, the intended inverter output voltage may not be obtained.

[0007] This invention has been made in view of the above, and aims to reduce voltage errors caused by dead time. [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 an inverter that converts a DC voltage to an AC voltage and applies it to an AC motor, and comprises a modulation wave generation unit that generates a modulated wave signal based on a voltage command value at the output voltage of the inverter, and a PWM pulse generation unit that generates a PWM pulse signal for controlling the switching operation of the inverter based on the modulated wave signal, wherein the modulation wave generation unit comprises a modulation rate command calculation unit that calculates a modulation rate command value in which the voltage command value is expressed as the modulation rate of the output voltage, an actual modulation rate estimation unit that estimates the actual modulation rate which is the modulation rate considering the dead time of the inverter, and a correction coefficient calculation unit that calculates a correction coefficient for the voltage command value based on the modulation rate command value and the actual modulation rate, and generates the modulated wave signal based on the voltage command value corrected by the correction coefficient. [Effects of the Invention]

[0009] According to the present invention, it is possible to reduce voltage errors caused by dead time. 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] Figure 1 shows the configuration diagram of the modulated wave generation unit. [Figure 3] A flowchart of the process performed by the modulated wave generation unit shown in Figure 2. [Figure 4] A diagram showing the waveform of a PWM pulse signal corresponding to a modulated wave signal. [Figure 5] A diagram showing the configuration of the modulated wave generation unit included in the inverter control device of Embodiment 2. [Figure 6] A diagram showing the configuration of the modulated wave generation unit included in the inverter control device of Embodiment 3. [Figure 7] A flowchart of the process performed by the modulated wave generation unit shown in Figure 6. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. In each embodiment, components denoted by the same reference numerals have the same function in each embodiment unless otherwise specified, and their descriptions will be omitted.

[0012] [Embodiment 1] The inverter control device 100 of Embodiment 1 will be described using Figures 1 to 4. Figure 1 is a configuration diagram of the motor drive system 1 equipped with the inverter control device 100 of Embodiment 1.

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

[0014] Battery 2 is the DC voltage source for inverter 10. The DC voltage Vdc of battery 2 (hereinafter also referred to as "power supply voltage Vdc") is converted by inverter 10 into a variable voltage and variable frequency three-phase AC voltage and applied to motor 3. Motor 3 is a synchronous motor that is driven to rotate by the application of the three-phase AC voltage. A rotational position sensor 4 is attached to motor 3 to control the phase of the three-phase AC voltage applied from inverter 10 to match the phase of the induced voltage of motor 3. The rotational position sensor 4 is composed of, for example, a resolver consisting of an iron core and windings. Alternatively, the rotational position sensor 4 may be composed of a GMR sensor or a rotational position sensor using 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 control unit 110, a modulated wave generation unit 120, a current detection unit 130, a rotational position detection unit 140, a PWM pulse generation unit 150, and a drive signal generation unit 160.

[0017] The rotation position detection unit 140 detects the rotation position θp of the rotor in 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 control unit 110 compares the dq-axis current detection value Idq detected by the current detection unit 130 with the dq-axis current command value Idq * (Id * , Iq * ) and calculates the dq-axis voltage command value Vdq * (Vd * , Vq * ) as the voltage command value of the output voltage of the inverter 10. The current control unit 110 outputs the calculated dq-axis voltage command value Vdq * to the modulation wave generation unit 120.

[0020] The modulation wave generation unit 120 calculates a modulation wave based on the voltage command value of the output voltage of the inverter 10 and generates a modulation wave signal indicating the calculated modulation wave. Specifically, the modulation wave generation unit 120 uses the rotational 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 110 to calculate the three-phase voltage command value Vuvw * (Vu * , Vv * , Vw * ). Among the three-phase voltage command values 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. Then, the modulation wave generation unit 120 generates a modulation wave signal Dv indicating the modulation wave represented by the three-phase voltage command value Vuvw * and outputs it to the PWM pulse generation unit 150. At this time, the modulation wave generation unit 120 may select a modulation method other than sine wave modulation to represent the three-phase voltage command value Vuvw * by a waveform other than a sine wave, such as a trapezoidal wave or a waveform obtained by superimposing harmonics of a predetermined order on a sine wave.

[0021] In addition, the modulation wave generation unit 120 uses the power supply voltage Vdc and the dq-axis voltage command value Vdq output from the current control unit 110* Based on this, the modulation rate MF of the output voltage of the inverter 10 may be calculated and output to the PWM pulse generation unit 150 instead of the modulated wave signal Dv. Furthermore, the modulated wave generation unit 120 may calculate both the modulated wave signal Dv and the modulation rate MF and output them to the PWM pulse generation unit 150. That is, the modulated wave generation unit 120 can calculate at least one of the modulated wave signal Dv and the modulation rate MF and output them to the PWM pulse generation unit 150.

[0022] The PWM pulse generation unit 150 performs three-phase pulse width modulation (PWM) based on the modulated wave signal Dv or modulation index MF output from the modulated wave generation unit 120 to generate 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 wave that changes periodically with the carrier frequency fc with the modulated wave signal Dv. 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 each pulse edge 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 wave and modulated wave signal Dv. Alternatively, the PWM pulse generation unit 150 may generate a PWM pulse signal P by yet another method. In any case, the PWM pulse generation unit 150 only needs to be able to generate a 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 used.

[0023] The drive signal generation unit 160 outputs a drive signal DR to the inverter 10. 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.

[0024] In the above, the dq axis current command value Idq is from the higher-level control device. * Figure 1 illustrates an example configuration of the motor drive system 1 when controlling the current of motor 3 accordingly, but the configuration in Figure 1 can also be applied when other control methods are employed. For example, when controlling the rotational speed of 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 current command value that matches the speed command value from the higher-level control device. Also, when controlling the output torque of motor 3, the inverter control device 100 can use a relationship formula or map between motor current (Idq) and motor torque to create a current command value (Idq * ) can be created.

[0025] Figure 2 is a diagram showing the configuration of the modulated wave generation unit 120 shown in Figure 1.

[0026] The modulated wave generation unit 120 includes a modulation rate command calculation unit 121, a modulated wave calculation unit 122, a dead time compensation unit 123, an actual modulation rate estimation unit 124, and a correction coefficient calculation unit 125.

[0027] The modulation rate command calculation unit 121 calculates a modulation rate command value MF, which represents the voltage command value at the output voltage of the inverter 10 as the modulation rate of said output voltage. * The modulated wave generation unit 120 calculates the three-phase voltage command value Vuvw calculated as described above. * This is normalized by dividing it by the power supply voltage Vdc. The modulation rate command calculation unit 121 calculates the normalized 3-phase voltage command value Vuvw * From, modulation rate command value MF * The modulation rate command calculation unit 121 calculates the normalized three-phase voltage command value Vuvw. * The vector is converted to αβ coordinates, and the vector length is calculated using the square root of the sum of squares. Then, the modulation rate command calculation unit 121 converts the calculated vector length to the modulation rate command value MF * Let's assume that.

[0028] The modulated wave calculation unit 122 calculates the normalized voltage command value Vuvw * From, the modulated wave Dv before dead time compensation. pre The modulated wave is calculated. The modulated wave may be a third harmonic or a two-phase modulated wave. The dead time compensation unit 123 indicates a dead time compensation value that compensates for the voltage error caused by the dead time provided in the inverter 10. dt The modulated wave generation unit 120 outputs the dead time compensated modulated wave Dv output from the dead time compensation unit 123. dt The modulated wave Dv calculated by the modulated wave calculation unit 122 pre This is added to generate the modulated wave signal Dv.

[0029] The actual modulation rate estimation unit 124 estimates the actual modulation rate MF, which is the modulation rate that takes dead time into consideration. Specifically, the actual modulation rate estimation unit 124 estimates the dead time compensated modulated wave Dv dt Based on the modulated wave signal Dv, the actual modulation rate MF is estimated. The details of the method for estimating the actual modulation rate MF will be described later using Figure 3.

[0030] The correction coefficient calculation unit 125 calculates the modulation rate command value MF * And it calculates a correction coefficient for the voltage command value based on the actual modulation rate MF. Specifically, the correction coefficient calculation unit 125 calculates the modulation rate command value MF * The difference between this value and the actual modulation rate MF is calculated by integrating, proportional-integral (PI control), or using a moving average to obtain the 3-phase voltage command value Vuvw * The correction coefficient is calculated. When calculating the moving average of the difference, the correction coefficient calculation unit 125 requires a sample over one period of the motor 3's electrical angle.

[0031] When the correction coefficient calculation unit 125 calculates the correction coefficient by integrating or proportionally integrating the above difference value, the modulated wave generation unit 120 generates the normalized three-phase voltage command value Vuvw * The correction coefficient is multiplied by the above difference value. When the correction coefficient calculation unit 125 calculates the correction coefficient by moving average the above difference value, the modulated wave generation unit 120 generates the normalized three-phase voltage command value Vuvw *The correction coefficient is subtracted from '. In this way, the modulated wave generation unit 120 generates the normalized three-phase voltage command value Vuvw * It can correct '.

[0032] The modulated wave generation unit 120 then generates a modulated wave signal Dv based on the voltage command value corrected by the correction coefficient. Specifically, the modulated wave generation unit 120 generates a three-phase voltage command value Vuvw corrected by the correction coefficient. * Modulated wave Dv before dead time compensation calculated from '' pre In addition, dead time compensated modulated wave Dv dt The modulated wave signal Dv is generated by adding these values. The modulated wave generation unit 120 then outputs the generated modulated wave signal Dv to the PWM pulse generation unit 150.

[0033] Figure 3 is a flowchart of the processing performed by the modulated wave generation unit 120 shown in Figure 2. Figure 4 is a diagram showing the waveform of the PWM pulse signal corresponding to the modulated wave signal.

[0034] In step S1, the modulation wave generation unit 120 receives the dq-axis voltage command value Vdq output from the current control unit 110. * By converting between two phases and three phases, the three-phase voltage command value Vuvw * The modulated wave generation unit 120 calculates the three-phase voltage command value Vuvw. * The normalized 3-phase voltage command value is Vuvw, obtained by dividing it by the power supply voltage Vdc. * Let's assume that.

[0035] In step S2, the modulated wave generation unit 120 sets the normalized three-phase voltage command value to Vuvw * The vector is converted to αβ coordinates, and the vector length is calculated using the square root of the sum of squares. Then, the modulated wave generation unit 120 sets the calculated vector length to the modulation rate command value MF * Let's assume that.

[0036] In step S3, the modulated wave generation unit 120 sets the normalized three-phase voltage command value to Vuvw *The normalized 3-phase voltage command value Vuvw is obtained by multiplying (or subtracting) ' by the correction coefficient calculated in the previous step. * ' is corrected. The 3-phase voltage command value corrected by the correction coefficient is Vuvw * Let's assume it's ''.

[0037] In step S4, the modulated wave generation unit 120 generates the corrected three-phase voltage command value Vuvw * From '', the modulated wave Dv of the third harmonic or two-phase modulated wave. pre The modulated wave generation unit 120 then calculates the modulated wave Dv. pre Dead time compensated modulated wave Dv dt These are added together to generate the modulated wave signal Dv.

[0038] In step S5, the modulated wave generation unit 120 determines whether the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more. As shown in Figure 4, if the duty cycle of the modulated wave signal Dv is greater than 0% and less than 100%, pulse edges exist in the waveform of the PWM pulse signal corresponding to the modulated wave signal Dv (also referred to as the "PWM waveform"), so a dead time can be added. On the other hand, if the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more, pulse edges do not exist in the PWM waveform corresponding to the modulated wave signal Dv, so a dead time cannot be added. Therefore, the modulated wave generation unit 120 changes the method for estimating the actual modulation rate MF depending on whether the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more. If the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more, the modulated wave generation unit 120 proceeds to step S6. If the duty cycle of the modulated wave signal Dv is greater than 0% and less than 100%, the modulated wave generation unit 120 proceeds to step S7.

[0039] In step S6, the modulated wave generation unit 120 converts the modulated wave signal Dv into an actual modulation index MF. Specifically, the modulated wave generation unit 120 converts the modulated wave signal Dv into αβ coordinates and calculates the vector length using the root of the sum of squares. The modulated wave generation unit 120 then uses the calculated vector length as the actual modulation index MF. That is, if the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more, the actual modulation index estimation unit 124 of the modulated wave generation unit 120 estimates the actual modulation index MF using the modulated wave signal Dv, which has not had the dead time compensation value subtracted. After step S6, the modulated wave generation unit 120 proceeds to step S8.

[0040] In step S7, the modulated wave generation unit 120 generates a dead-time compensated modulated wave Dv from the modulated wave signal Dv. dt It subtracts and converts the subtracted modulated wave signal Dv into the actual modulation rate MF. Specifically, the modulated wave generation unit 120 converts the modulated wave signal Dv to a dead time compensated modulated wave Dv dt The modulated wave generation unit 120 then subtracts the dead time compensation value. The modulated wave generation unit 120 converts the corrected modulated wave signal Dv into αβ coordinates and calculates the vector length using the square root of the sum of squares. The modulated wave generation unit 120 then sets the calculated vector length as the actual modulation rate MF. That is, if the duty cycle of the modulated wave signal Dv is greater than 0% and less than 100%, the actual modulation rate estimation unit 124 of the modulated wave generation unit 120 estimates the actual modulation rate MF using the modulated wave signal Dv from which the dead time compensation value has been subtracted.

[0041] In step S8, the modulation wave generation unit 120 generates a modulation rate command value MF * The correction coefficient is calculated by integrating (or proportionally integrating or using a moving average) the difference between the actual modulation rate MF and the actual modulation rate MF. If the actual modulation rate MF used here is the value estimated in step S7, then the modulation rate command value MF *The difference between this value and the actual modulation rate MF becomes zero. This means that, when estimated in step S7, since a dead time can be added, there is no overcompensation for the dead time, and therefore the voltage command value is not substantially corrected. The modulated wave generation unit 120 stores the calculated correction coefficient in a predetermined memory area. The correction coefficient calculated in step S8 is used the next time the process shown in Figure 3 is performed. After step S8, the modulated wave generation unit 120 terminates the process shown in Figure 3.

[0042] As described above, the inverter control device 100 of Embodiment 1 is a device that controls an inverter 10 that converts a DC voltage to an AC voltage and applies it to a motor 3. The inverter control device 100 of Embodiment 1 includes a modulation wave generation unit 120 that generates a modulated wave signal based on a voltage command value at the output voltage of the inverter 10, and a PWM pulse generation unit 150 that generates a PWM pulse signal to control the switching operation of the inverter 10 based on the modulated wave signal. The modulation wave generation unit 120 includes a modulation rate command calculation unit 121 that calculates a modulation rate command value expressed as the modulation rate of the output voltage, an actual modulation rate estimation unit 124 that estimates the actual modulation rate, which is the modulation rate considering the dead time of the inverter 10, and a correction coefficient calculation unit 125 that calculates a correction coefficient for the voltage command value based on the modulation rate command value and the actual modulation rate. The modulation wave generation unit 120 generates a modulated wave signal based on the voltage command value corrected by the correction coefficient.

[0043] As a result, the inverter control device 100 of Embodiment 1 can correct the voltage command value to prevent overcompensation for dead time when an error occurs between the actual modulation rate and the modulation rate command value. In addition, when no error occurs between the actual modulation rate and the modulation rate command value, the inverter control device 100 of Embodiment 1 can substantially eliminate the need to correct the voltage command value because the dead time is appropriately compensated. In other words, the inverter control device 100 of Embodiment 1 can correct the voltage command value in a timely manner so that the dead time compensation value is added only when it should be added. Therefore, the inverter control device 100 of Embodiment 1 can reduce the voltage error caused by dead time.

[0044] If an error occurs between the actual modulation rate and the modulation rate command value, when the modulated wave is switched using the modulation rate, the torque of the motor 3 fluctuates faster than the response of the current flowing through the motor 3, resulting in a deterioration of torque control accuracy. The inverter control device 100 of Embodiment 1 can reduce the voltage error caused by dead time, thereby reducing the error between the actual modulation rate and the modulation rate command value, and suppressing torque fluctuations that occur when switching modulated waves using the modulation rate.

[0045] When voltage errors occur due to dead time, the rotor position estimation method, which estimates the rotor position according to the phase of the induced voltage calculated from the dq-axis voltage command value, as described in Japanese Patent Publication No. 3411878, presents the following problem: In this rotor position estimation method, the voltage error caused by dead time is superimposed as an error on the phase of the induced voltage, degrading the accuracy of rotor position estimation. The inverter control device 100 of Embodiment 1 can reduce the voltage error caused by dead time, thereby improving the accuracy of rotor position estimation in this rotor position estimation method. The same applies to magnetic flux estimation and torque estimation of the motor 3 using the dq-axis voltage command value, and the inverter control device 100 of Embodiment 1 can improve the estimation accuracy of magnetic flux estimation and torque estimation of the motor 3 using the dq-axis voltage command value.

[0046] Furthermore, in the inverter control device 100 of Embodiment 1, the actual modulation rate estimation unit 124 estimates the actual modulation rate using a modulated wave signal from which the dead time compensation value has been subtracted when the duty cycle of the modulated wave signal is greater than 0% and less than 100%. The actual modulation rate estimation unit 124 estimates the actual modulation rate using a modulated wave signal from which the dead time compensation value has not been subtracted when the duty cycle of the modulated wave signal is 0% or less or 100% or more.

[0047] As a result, the inverter control device 100 of Embodiment 1 can promptly correct the voltage command value so that the dead time compensation value is not added when it should not be added, such as in the overmodulation region. Therefore, the inverter control device 100 of Embodiment 1 can reliably reduce the voltage error caused by dead time in the overmodulation region.

[0048] Furthermore, in the inverter control device 100 of Embodiment 1, the correction coefficient calculation unit 125 calculates the correction coefficient by integrating, proportionally integrating, or moving average the difference between the modulation rate command value and the actual modulation rate.

[0049] As a result, the inverter control device 100 of Embodiment 1 can calculate the correction coefficient using a relatively simple method. Therefore, the inverter control device 100 of Embodiment 1 can easily reduce the voltage error caused by dead time.

[0050] [Embodiment 2] The inverter control device 100 of Embodiment 2 will be described using Figure 5. The same configuration and operation as in Embodiment 1 will not be described in the inverter control device 100 of Embodiment 2. Figure 5 is a configuration diagram of the modulation wave generation unit 120 included in the inverter control device 100 of Embodiment 2.

[0051] The actual modulation rate estimation unit 124 of Embodiment 1 calculates the dead time compensated modulation wave Dv dtThe actual modulation rate MF was estimated using the modulated wave signal Dv. The actual modulation rate estimation unit 124 of Embodiment 2 estimates the actual modulation rate MF based on the detected value of a sensor that detects the voltage applied to the motor 3.

[0052] Specifically, the actual modulation rate estimation unit 124 of Embodiment 2 estimates the actual modulation rate MF using the phase voltage Vuvw (Vu, Vv, Vw) of the motor 3 and the power supply voltage Vdc. The phase voltage Vuvw is a value calculated from the line voltage applied to the motor 3. The line voltage can be detected by a known sensor. More specifically, the actual modulation rate estimation unit 124 of Embodiment 2 calculates the voltage amplitude Vamp of the phase voltage Vuvw, and the value obtained by dividing the calculated voltage amplitude Vamp by (Vdc / 2) is defined as the actual modulation rate MF.

[0053] As described above, the actual modulation rate estimation unit 124 of Embodiment 2 estimates the actual modulation rate MF based on the detected value of a sensor that detects the voltage applied to the motor 3.

[0054] Therefore, the inverter control device 100 of Embodiment 2 can estimate the actual modulation rate MF without performing the determination shown in step S5 of Figure 3, thus simplifying the control logic compared to Embodiment 1. Furthermore, since the inverter control device 100 of Embodiment 2 can estimate the actual modulation rate MF based on the sensor's detected value, it can estimate the actual modulation rate MF more accurately than Embodiment 1. Thus, the inverter control device 100 of Embodiment 2 can easily and reliably reduce the voltage error caused by dead time.

[0055] [Embodiment 3] The inverter control device 100 of Embodiment 3 will be described with reference to Figures 6 and 7. The same configuration and operation as in Embodiments 1 and 2 will not be described in this description. Figure 6 is a configuration diagram of the modulation wave generation unit 120 included in the inverter control device 100 of Embodiment 3.

[0056] The modulation wave generation unit 120 of Embodiment 1 includes a modulation rate command calculation unit 121 and an actual modulation rate estimation unit 124, and the three-phase voltage command value Vuvw * The correction coefficient was calculated. The modulation wave generation unit 120 of Embodiment 3 includes a two-phase to three-phase conversion unit 126 and a voltage estimation value calculation unit 127, and the dq axis voltage command value Vdq * Calculate the correction factor.

[0057] The voltage estimation calculation unit 127 calculates a voltage estimate, which is an estimated value of the output voltage, based on the dead time compensation value of the inverter 10. Specifically, the voltage estimation calculation unit 127 calculates the dead time compensation modulated wave Dv dt The dq-axis voltage estimate Vdq(Vd,Vq) is calculated using the modulated wave signal Dv. Details of how to calculate the dq-axis voltage estimate Vdq will be described later using Figure 7.

[0058] The correction coefficient calculation unit 125 of Embodiment 3 calculates a correction coefficient for the voltage command value based on the voltage command value and the estimated voltage value. Specifically, the correction coefficient calculation unit 125 of Embodiment 3 calculates a correction coefficient for the dq axis voltage command value Vdq * The difference between the dq-axis voltage command value Vdq and the estimated dq-axis voltage Vdq is calculated by integrating or proportionally integrating (PI control). * The correction coefficient Kdq(Kd,Kq) is calculated.

[0059] Furthermore, the correction coefficient calculation unit 125 of Embodiment 3 calculates the dq axis voltage command value Vdq as follows: * It is also possible to calculate the correction coefficient Kdq. That is, the correction coefficient calculation unit 125 of Embodiment 3 calculates the dq axis voltage command value Vdq * The dq-axis voltage estimated value Vdq is converted into amplitude and phase, respectively. The correction coefficient calculation unit 125 of Embodiment 3 calculates the dq-axis voltage command value Vdq * The difference between the amplitude and the estimated dq-axis voltage Vdq, and the dq-axis voltage command value Vdq * The difference between the phase of and the phase of the estimated dq-axis voltage Vdq is calculated. Then, the correction coefficient calculation unit 125 of Embodiment 3 calculates the dq-axis voltage command value Vdq by integrating or proportionally integrating (PI control) the difference in amplitude and the difference in phase, respectively. *It is also possible to calculate the correction coefficient Kdq.

[0060] The modulated wave generation unit 120 of Embodiment 3 generates a dq-axis voltage command value Vdq * By subtracting the correction coefficient Kdq from the dq axis voltage command value Vdq, * Correct it.

[0061] The 2-phase to 3-phase conversion unit 126 converts the corrected dq-axis voltage command value Vdq * The 3-phase voltage command value Vuvw * Converts to the following. The modulated wave generation unit 120 of Embodiment 3 converts the converted three-phase voltage command value Vuvw * The value is normalized by dividing it by the power supply voltage Vdc. The modulated wave generation unit 120 of Embodiment 3 generates the normalized three-phase voltage command value Vuvw, similar to Embodiment 1. * 'From modulated wave Dv pre Calculate the dead-time compensated modulated wave Dv dt By adding these values, a modulated wave signal Dv is generated.

[0062] Figure 7 is a flowchart of the processing performed by the modulated wave generation unit 120 shown in Figure 6.

[0063] In step S11, the modulation wave generation unit 120 receives the dq-axis voltage command value Vdq output from the current control unit 110. * By subtracting the previously calculated correction coefficient Kdq from this, the dq-axis voltage command value Vdq is obtained. * Correct it.

[0064] In step S12, the modulated wave generation unit 120 generates a dq-axis voltage command value Vdq corrected by the correction coefficient Kdq. * Convert the two-phase to three-phase signal, and correct the three-phase voltage command value Vuvw. * Perform the calculation.

[0065] In step S13, the modulated wave generation unit 120 generates the corrected three-phase voltage command value Vuvw * This is normalized by dividing it by the power supply voltage Vdc.

[0066] In step S14, the modulated wave generation unit 120 generates the corrected three-phase voltage command value Vuvw * From '', the modulated wave Dv of the third harmonic or two-phase modulated wave. pre The modulated wave generation unit 120 then calculates the modulated wave Dv. pre Dead time compensated modulated wave Dv dt These are added together to generate the modulated wave signal Dv.

[0067] In step S15, the modulated wave generation unit 120 determines whether the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more. If the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more, the modulated wave generation unit 120 proceeds to step S16. If the duty cycle of the modulated wave signal Dv is greater than 0% and less than 100%, the modulated wave generation unit 120 proceeds to step S17.

[0068] In step S16, the modulated wave generation unit 120 converts the modulated wave signal Dv into a dq-axis voltage estimate Vdq. Specifically, the modulated wave generation unit 120 multiplies the modulated wave signal Dv by the power supply voltage Vdc to calculate a three-phase voltage estimate Vuvw. Then, the modulated wave generation unit 120 converts the calculated three-phase voltage estimate Vuvw into a three-phase to two-phase conversion to calculate a dq-axis voltage estimate Vdq. That is, if the duty cycle of the modulated wave signal Dv is 0% or less or 100% or more, the voltage estimation calculation unit 127 of the modulated wave generation unit 120 calculates the dq-axis voltage estimate Vdq using the modulated wave signal Dv, which has not had the dead time compensation value subtracted. After step S16, the modulated wave generation unit 120 proceeds to step S18.

[0069] In step S17, the modulated wave generation unit 120 generates a dead-time compensated modulated wave Dv from the modulated wave signal Dv. dt It subtracts and converts the subtracted modulated wave signal Dv into a dq-axis voltage estimate Vdq. Specifically, the modulated wave generation unit 120 converts the modulated wave signal Dv into a dead-time compensated modulated wave Dv dtSubtract it, multiply the subtracted modulation wave signal Dv by the power supply voltage Vdc, and calculate the three-phase voltage estimated value Vuvw. Then, the modulation wave generation unit 120 performs three-phase to two-phase conversion on the calculated three-phase voltage estimated value Vuvw to calculate the dq-axis voltage estimated value Vdq. That is, when the duty ratio of the modulation wave signal Dv is greater than 0% and less than 100%, the voltage estimation unit 127 of the modulation wave generation unit 120 calculates the dq-axis voltage estimated value Vdq using the modulation wave signal Dv from which the dead time compensation value has been subtracted.

[0070] In step S18, the modulation wave generation unit 120 * calculates the correction coefficient Kdq by integrating (or proportional-integrating) the difference value between the dq-axis voltage command value Vdq

[0071] and the dq-axis voltage estimated value Vdq. The modulation wave generation unit 120 stores the calculated correction coefficient Kdq in a predetermined storage area. The correction coefficient calculated in step S18 is used when the process shown in FIG. 7 is performed next time. After step S18, the modulation wave generation unit 120 ends the process shown in FIG. 7.

[0071] As described above, the modulation wave generation unit 120 of Embodiment 3 includes a voltage estimation unit 127 that calculates the dq-axis voltage estimated value Vdq, which is an estimated value of the output voltage, based on the dead time compensation value of the inverter 10, and a dq-axis voltage command value Vdq * and calculates the correction coefficient Kdq of the dq-axis voltage command value Vdq * based on the dq-axis voltage estimated value Vdq. The modulation wave generation unit 120 of Embodiment 3 generates the modulation wave signal Dv based on the dq-axis voltage command value Vdq * corrected by the correction coefficient Kdq.

[0072]

[0073] As a result, the inverter control device 100 of Embodiment 3 can appropriately correct the voltage command value so that the dead time compensation value is added only when it should be added, similar to Embodiment 1. Therefore, the inverter control device 100 of Embodiment 3 can reduce the voltage error caused by the dead time, similar to Embodiment 1.Furthermore, the inverter control device 100 of Embodiment 3 adjusts the dq-axis voltage command value Vdq, which has been corrected by the correction coefficient Kdq. * If you wish to use this in other functions of the inverter control device 100, such as rotor position estimation, magnetic flux estimation, and torque estimation of motor 3, use the corrected dq axis voltage command value Vdq. * It can be used easily.

[0074] [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.

[0075] 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.

[0076] 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]

[0077] 3...Motor (AC motor), 10...Inverter, 100...Inverter control device, 120...Modulation wave generation unit, 121...Modulation rate command calculation unit, 124...Actual modulation rate estimation unit, 125...Correction coefficient calculation unit, 127...Voltage estimate calculation unit, 150...PWM pulse generation unit

Claims

1. An inverter control device that controls an inverter that converts a DC voltage to an AC voltage and applies it to an AC motor, A modulation wave generation unit that generates a modulated wave signal based on the voltage command value of the output voltage of the inverter, The system includes a PWM pulse generation unit that generates a PWM pulse signal to control the switching operation of the inverter based on the modulated wave signal, The modulated wave generation unit is A modulation rate command calculation unit calculates a modulation rate command value that expresses the voltage command value as the modulation rate of the output voltage, An actual modulation rate estimation unit estimates the actual modulation rate, which is the modulation rate taking into account the dead time of the inverter, It includes a correction coefficient calculation unit that calculates a correction coefficient for the voltage command value by integrating, proportionally integrating, or moving average the difference between the modulation rate command value and the actual modulation rate, The modulated wave signal is generated based on the voltage command value corrected by the correction coefficient. An inverter control device characterized by the following:

2. The actual modulation rate estimation unit, If the duty cycle of the modulated wave signal is greater than 0% and less than 100%, the actual modulation rate is estimated using the modulated wave signal from which the dead time compensation value has been subtracted. If the duty cycle is 0% or less or 100% or more, the actual modulation rate is estimated using the modulated wave signal from which the dead time compensation value has not been subtracted. The inverter control device according to feature 1.

3. The actual modulation rate estimation unit estimates the actual modulation rate based on the detected value of a sensor that detects the voltage applied to the AC motor. The inverter control device according to feature 1.

4. An inverter control device that controls an inverter that converts a DC voltage to an AC voltage and applies it to an AC motor, A modulation wave generation unit that generates a modulated wave signal based on the voltage command value of the output voltage of the inverter, The system includes a PWM pulse generation unit that generates a PWM pulse signal to control the switching operation of the inverter based on the modulated wave signal, The modulated wave generation unit is A voltage estimation calculation unit calculates a voltage estimation value, which is an estimated value of the output voltage, using a dead time compensation modulated wave that indicates the dead time compensation value of the inverter and a modulated wave calculated from the voltage command value. It includes a correction coefficient calculation unit that calculates a correction coefficient for the voltage command value by integrating or proportionally integrating the difference between the voltage command value and the estimated voltage value, The modulated wave signal is generated based on the voltage command value corrected by the correction coefficient. An inverter control device characterized by the following:

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