JP6661423B2 - Motor drive - Google Patents

Description

  The present invention relates to a motor driving device for driving a motor.

  A high-precision control is required for a motor drive device that drives an electric motor by supplying an AC voltage to the electric motor by a voltage-type inverter that converts a DC voltage to an AC voltage. It is required that position sensorless control for controlling driving of the electric motor be possible without using a position sensor for detecting a rotational position.

  Position sensorless control requires information on the motor terminal voltage and the current flowing through the motor. Since the inverter is usually provided with a current sensor for current control and overcurrent protection, it is easy to obtain information on the current flowing through the motor. On the other hand, a technique using a voltage command for instructing an output voltage of an inverter is widely used for acquiring information on a motor terminal voltage. However, an error (voltage error) occurs between the voltage command and the actual output voltage of the inverter due to a voltage drop of a switching element in the inverter and an influence of a dead time described later. Therefore, a technique of compensating for a voltage error by adding a compensation amount of the voltage error to a voltage command is widely used (for example, see Patent Document 1).

Patent No. 3372436

  FIG. 6 is a diagram showing a configuration of a conventional electric motor driving device 30.

  The motor driving device 30 shown in FIG. 6 includes an inverter 1, an output voltage detection circuit 31, a current detector 32, a current detection circuit 33, a subtractor 34, a current control calculator 35, an adder 36, It includes a PWM (Pulse Width Modulation) circuit 37, a voltage error calculator 38, a dead time compensation amount storage unit 39, and a dead time compensation amount operation unit 40.

  The inverter 1 includes a DC power supply and a plurality of switching elements, converts a DC voltage (DC power supply voltage) output from the DC power supply into an AC voltage (three-phase AC voltage) by switching of the plurality of switching elements, and converts the DC voltage into a motor 2. It is a voltage type inverter to output. More specifically, in the inverter 1, a series body in which two switching elements are connected in series is provided for each of the U phase, the V phase, and the W phase, and each series body is connected in parallel to a DC power supply. An AC voltage having a desired voltage and frequency is output by controlling (PWM control) the on / off ratio of the switching elements constituting each series member. Although details will be described later, there is a period during which both switching elements constituting each phase are turned off, and this period is called a dead time.

  The output voltage detection circuit 31 detects the voltage value of the output voltage from the inverter 1 to the electric motor 2 and outputs the detection result (output voltage detection value) to the voltage error calculator 38. The current detector 32 and the current detection circuit 33 detect the current value of the current (output current) flowing from the inverter 1 to the motor 2, and subtract the detection result (the output current detection value) into the subtractor 34 and the dead time compensation amount storage unit 39. And the dead time compensation amount calculation unit 40.

The current command value i ^* indicating the output current of the inverter 1 is input to the subtractor 34 and the dead time compensation amount calculating section 40. The subtractor 34 calculates an error (current error) between the current command value i ^* and the output current detection value by the current detection circuit 33, and outputs the calculated current error to the current control calculator 35. The current control calculator 35 generates a voltage command indicating the output voltage of the inverter 1 according to the current error output from the subtractor 34, and outputs the voltage command to the adder 36.

  The adder 36 adds a voltage command output from the current control calculator 35 and a dead time compensation amount for compensating for a voltage error due to dead time, output from a dead time compensation amount calculator 40 described later. Then, a correction voltage command is generated and output to the PWM circuit 37 and the voltage error calculator 38.

  The PWM circuit 37 controls on / off of the switching element of the inverter 1 according to the correction voltage command output from the adder 36. The voltage error calculator 38 calculates an error (voltage error) between the correction voltage command output from the adder 36 and the output voltage detection value of the output voltage detection circuit 31, and stores the calculated voltage error in a dead time compensation amount. Output to the unit 39.

The dead time compensation amount storage unit 39 stores data of the dead time compensation amount corresponding to the output current of the inverter 1, and detects the output current detection value of the current detection circuit 33 and the voltage error output from the voltage error calculator 38. Based on the above, the data is corrected. The dead time compensation amount calculator 40 calculates the dead time compensation amount based on the data stored in the dead time compensation amount storage unit 39 according to the current command value i ^* or the output current detection value of the current detection circuit 33. , And outputs the calculated dead time compensation amount to the adder 36.

FIG. 7 is a diagram showing a circuit configuration for outputting a U-phase voltage of inverter 1. As shown in FIG. 7, switching elements S11 and S14 are connected in series, and a series body of switching elements S11 and S14 is connected to a DC power supply (not shown). Voltage E _u at the connection point of the switching elements S11, S14 are outputted to the electric motor 2 as a U-phase voltage (U-phase output voltage). Each of the switching elements S11 and S14 is configured by an IGBT (Insulated Gate Bipolar Transistor), and a reflux diode is connected to each IGBT in anti-parallel. The IGBT has an output capacitance _Coes represented by a minute capacitor between the drain and the source due to its structure.

  If the upper switching element S11 and the lower switching element S14 constituting the U phase are turned on at the same time, the DC power supply is short-circuited, an overcurrent flows, and the circuit may be damaged. In order to prevent this phenomenon, there is provided a period during which both the switching elements S11 and S14 are turned off at the timing when the switching elements S11 and S14 are turned on and off. This period is generally called a dead time (dead time period).

  Since the output voltage of the inverter 1 during the dead time period changes depending on the polarity and magnitude of the output current, a voltage error occurs between the voltage command and the output voltage of the inverter 1. Hereinafter, the reason why the voltage error occurs due to the dead time will be described with the direction in which the current flows from the inverter 1 to the electric motor 2 as the positive direction.

  FIG. 8 is a diagram for describing an output voltage (U-phase voltage) output from inverter 1.

In FIG. 8, a signal Su is a PWM signal obtained by comparing a U-phase corrected voltage command value with a triangular wave, and at a certain timing, the logic level transitions from Low to High (rising), and a time t ₀ from the transition. Elapses, the logic level changes from High to Low (falls). Signal Sup is a gate signal of the switching element S11, the rise is delayed from the rising edge of the signal Su by the dead time t _d, it falls at the same timing as the falling of the signal Su. Signal Sun is the gate signal of the switching element S14, standing at the same timing as the rise of the signal Su down, it rises with a delay from the falling of the signal Su by the dead time t _d.

The switching elements S11 and S14 are turned on with a delay of a time t _ON from the rise of the signals Sup and Sun, and are turned off with a delay of a time t _OFF from the fall of the signals Sup and Sun. Therefore, only those delay amount, U-phase output voltage E _u is the signal Sup, varies with a delay from the logic level of the transition of the Sun.

When the switching element S11 is turned on, the switching element S14 is turned off, the output capacitance C _OES1 switching element S11 is discharged, the output capacitance C _OES2 switching element S14 voltage of the DC power supply voltage corresponding to charge. When the switching element S11 is turned off in this state, the switching elements S11 and S14 are both turned off and a dead time state is set.

At this time, if the direction U-phase current i _u is positive, the discharge voltage that is charged in the output capacitor C _OES2 is, U-phase output voltage E _u becomes 0V. If U-phase current i _u is sufficiently large in the positive direction (i _u >> 0), discharge of output capacitance _Coes2 is performed instantaneously. If the U-phase current i _u is small (i _u > 0, i _u ≒ 0), the amount of discharge is small, and as the U-phase current i _u approaches 0, the U-phase output voltage _Eu during the dead time period becomes smaller than the DC power supply. Approach voltage. If the U-phase current is a negative direction, the output capacitance C _OES2 remains charged, U-phase output voltage E _u is the DC power supply voltage corresponding.

On the other hand, when the switching element S11 is off and the switching element S14 is on, the output capacitance _Coes2 is discharged, and the output capacitance _Coes1 is charged with a voltage equivalent to the DC power supply voltage. When the switching element S14 is turned off in this state, the switching elements S11 and S14 are both turned off and a dead time state is set.

At this time, if the U-phase current i _u is a positive direction, the output capacitance C _OES1 remains charged, U-phase output voltage E _u becomes 0V. If the U-phase current i _u is a negative direction, the voltage charged in the output capacitor C _OES1 discharge, the voltage is charged in the output capacitor C _OES2, U-phase output voltage E _u is a DC power supply voltage corresponding Become. If the U-phase current iu is sufficiently large in the negative direction (i _u << 0), the discharge of the output capacitance C _OES1 is instantaneous. If the U-phase current i _u is small (i _u <0, i _u ≒ 0), the amount of charge is small, and as the U-phase current approaches 0, the U-phase output voltage _Eu during the dead time period also approaches 0V.

That is, in the dead time period, when the U-phase current i _u is in the positive direction, the average of the U-phase output voltage _Eu is 0 V, but as the U-phase current i _u approaches 0, the U-phase output voltage E _u becomes zero. The average of _u approaches half of the DC power supply voltage, and when the U-phase current i _u goes in the negative direction, the average of the U-phase output voltage _Eu becomes the DC power supply voltage. As described above, since the output voltage in the dead time period changes according to the output current, a voltage error occurs with respect to the voltage command.

  In the motor drive device 30, the output voltage of the inverter 1 is detected by the output voltage detection circuit 31, the difference (voltage error) between the correction voltage command value and the output voltage detection value is calculated, and dead time compensation corresponding to the output current is performed. The amount is stored in the dead time compensation amount storage unit 39 as an amount.

FIG. 9 is a diagram illustrating an example of a relationship between the output current stored in the dead time compensation amount storage unit 39 and the dead time compensation amount. As shown in FIG. 9, the dead time compensation amount storage unit 39, the current i _x of a certain phase _{(x = u, v, w} ) to a horizontal axis, the current i dead time compensation amount corresponding to the _x E _d (i _The initial value of _x ) represented by the vertical axis is stored while being corrected according to the output current detection value and the voltage error. Then, the voltage error according to the output current is compensated by calculating the dead time compensation amount based on the data stored in the dead time compensation amount storage unit 39 according to the current command value i ^* or the output current detection value. can do.

  The relationship between the output current and the amount of dead time compensation differs depending on the variation of the switching element, and also changes due to heat generation of the switching element. The output current of the inverter 1 can be controlled with high accuracy by correcting the relationship between the output current and the dead time compensation amount even for such a variation or change in the dead time compensation amount.

  In the motor drive device 30, an output voltage detection circuit is used for detecting the output voltage. As described above, a current sensor is generally provided for current control and overcurrent protection of the inverter, but a voltage detection circuit is often not provided. Further, the output voltage of the inverter is higher than the power supply voltage of the control system circuit, and in order to take in the output voltage to the control system circuit, an insulation distance must be secured, and it is difficult to reduce the size of the voltage detection circuit. Therefore, providing the voltage detection circuit causes an increase in cost such as an increase in the size of the device and an increase in the number of components.

  An object of the present invention is to provide an electric motor drive device that can solve the above-described problems and can perform high-precision electric motor drive control while suppressing an increase in cost.

In order to solve the above problem, a motor driving device according to the present invention is a motor driving device that controls driving of a motor, the device including a plurality of switching elements, and the switching of the plurality of switching elements converts a DC voltage into an AC voltage. A power converter for converting and outputting to the motor, a voltage estimator for estimating an output voltage of the power converter based on an output current of the power converter and a characteristic equation of the motor, and the power converter An error calculator that calculates a voltage error between a voltage command indicating an output voltage of the power converter and an output voltage of the power converter estimated by the voltage estimator, and compensates for an output current of the power converter and the voltage error. And the relationship between the dead time compensation amount and the dead time compensation amount, based on the voltage error calculated by the error calculator. A dead time compensator that corrects the relationship and outputs a dead time compensation amount corresponding to the output current of the power converter based on the relationship, and a dead time compensation that outputs the voltage command from the dead time compensator. A command compensator that outputs a correction voltage command corrected by the amount, and a generator that generates a control signal that controls switching of the plurality of switching elements based on the correction voltage command output from the command compensator , The dead time compensator selects a plurality of integrators and any one of the plurality of integrators according to an output current of the power converter, and calculates a voltage error calculated by the error calculator. And a selector for inputting the selected integrator to the selected integrator, wherein the integrator is output from the error calculator when selected by the selector. Outputting an integrated value obtained by integrating a voltage error as the dead time compensation amount, when not being selected by the selector, that holds the accumulated value.

Further, in order to solve the above-described problem, an electric motor driving device that controls driving of an electric motor includes a plurality of switching elements, and converts a DC voltage into an AC voltage by switching of the plurality of switching elements, so that the electric motor has A power converter to be output, a voltage estimator for estimating an output voltage of the power converter based on an output current of the power converter and a characteristic equation of the electric motor, and a voltage indicating an output voltage of the power converter. An error calculator that calculates a voltage error between the command and the output voltage of the power converter estimated by the voltage estimator, and an output current of the power converter and a dead time compensation amount for compensating the voltage error. And correcting the relationship between the output current of the power converter and the dead time compensation amount based on the voltage error calculated by the error calculator. A dead time compensator that outputs a dead time compensation amount corresponding to the output current of the power converter based on the relationship, and a correction voltage that corrects the voltage command with the dead time compensation amount output from the dead time compensator. A command compensator that outputs a command, and a generator that generates a control signal that controls switching of the plurality of switching elements based on a correction voltage command output from the command compensator, the error calculator includes: Calculating, as the voltage error, an error between the correction voltage command and the output voltage of the power converter estimated by the voltage estimator; the dead time compensator includes a plurality of low-pass filters; Selecting one of the plurality of low-pass filters according to the output current of the filter, and selecting the low-pass filter calculated by the error calculator. A selector for inputting an error to the selected low-pass filter, wherein the low-pass filter filters the voltage error output from the error calculator when selected by the selector. It was carried out, and outputs as the dead time compensation amount, when not being selected by the selector, that holds the previous output.

  ADVANTAGE OF THE INVENTION According to the motor drive device which concerns on this invention, the drive control of a highly accurate electric motor can be performed, suppressing increase in cost.

It is a figure showing an example of composition of a motor drive device concerning a 1st embodiment of the present invention. FIG. 2 is a diagram illustrating an example of a configuration of an ab-axis dead time compensator illustrated in FIG. 1. FIG. 2 is a diagram illustrating an example of a relationship between an output current stored by an ab-axis dead time compensator illustrated in FIG. 1 and a dead time compensation amount. It is a figure showing an example of the composition of the electric motor drive concerning a 2nd embodiment of the present invention. FIG. 5 is a diagram illustrating an example of a configuration of an ab-axis dead time compensator illustrated in FIG. 4. FIG. 9 is a diagram illustrating an example of a configuration of a conventional motor drive device. FIG. 3 is a diagram illustrating a circuit configuration of a U-phase of an inverter. 5 is a time chart for describing an output voltage of an inverter. FIG. 4 is a diagram illustrating an example of a relationship between an output current of an inverter and a dead time compensation amount.

  Hereinafter, embodiments of the present invention will be described.

(First embodiment)
FIG. 1 is a diagram illustrating an example of a configuration of a motor drive device 10 according to a first embodiment of the present invention.

  The motor driving device 10 shown in FIG. 1 includes an inverter 1 (power converter), an adding unit 11, a PWM generator 12 (generator), a current detector 13, three-phase two-phase converters 14, 16, , Observer 15 (voltage estimator), first subtractor 17, second subtractor 18 (error calculator), ab-axis dead time compensator 19 (dead time compensator), two-phase three-phase And a converter 21.

  The inverter 1 is a voltage-type inverter that converts a DC voltage to an AC voltage and supplies the AC voltage to the electric motor 2, and includes a DC power supply E1, a capacitor C1, and switching elements S11 to S16.

  Each of the switching elements S11 to S16 is configured by, for example, an IGBT, and a freewheeling diode is connected to each IGBT in anti-parallel. Switching elements S11 and S14 are connected in series, switching elements S12 and S15 are connected in series, and switching elements S13 and S16 are connected in series. A series body of switching elements S11 and S14, a series body of switching elements S12 and S15, a series body of switching elements S13 and S16, and a capacitor C1 for smoothing the output of DC power supply E1 are connected in parallel to DC power supply E1. It is connected.

  The voltage at the connection point between the switching elements S11 and S14, the voltage at the connection point between the switching elements S12 and S15, and the voltage at the connection point between the switching elements S13 and S16 are a U-phase output voltage, a V-phase output voltage, and a W-phase output, respectively. The voltage is output to the electric motor 2. By controlling the on / off ratio (PWM control) of the switching elements constituting each series body, a three-phase AC voltage having a desired magnitude and frequency can be supplied to the electric motor 2.

The adder 11 receives a voltage command (U-phase voltage command v _u , V-phase voltage command v _v , W-phase voltage command v _w ) indicating the output voltage of the three-phase inverter 1, and The three-phase dead time compensation amounts (the U-phase dead time compensation amount E _du , the V-phase dead time compensation amount E _dv , and the W-phase dead time compensation amount E _dw ) output from the two-phase to three-phase converter 21 described later. By adding, a three-phase correction voltage command (U-phase correction voltage command v _uc , V-phase correction voltage command v _vc , W-phase voltage command v _wc ) is generated.

Specifically, the adding unit 11 includes adders 11u, 11v, and 11w. The adder 11u adds the U-phase voltage command v _u and the U-phase dead time compensation amount E _du to generate a U-phase correction voltage command v _uc . Adder 11v adds the V-phase voltage command v _v and V-phase dead time compensation amount E _dv, generates a V-phase corrected voltage command v _vc. Adder 11w adds the W-phase voltage command v _w and W-phase dead time compensation amount E _dw, generates a W-phase corrected voltage command v _wc.

The voltage commands (U-phase voltage command v _u , V-phase voltage command v _v , W-phase voltage command v _w ) are calculated by, for example, current feedback control such that the output current of inverter 1 follows the current command. It is limited by the voltage of the DC power supply E1 (DC power supply voltage) V _dc so as not to exceed the output voltage range of the inverter 1. The DC power supply voltage _Vdc is obtained by a voltage detection circuit and setting parameters not shown in FIG.

The adder 11 outputs the generated correction voltage commands (U-phase correction voltage command v _uc , V-phase correction voltage command v _vc , W-phase voltage command v _wc ) to the PWM generator 12 and the three-phase two-phase converter 16. I do.

  The PWM generator 12 generates a PWM signal (control signal) for controlling the switching of the switching elements S11 to S16 of the inverter 1 by comparing the three-phase correction voltage commands with each other with a triangular wave.

The current detector 13 detects the output current of the inverter 1 (three-phase currents flowing from the inverter 1 to the motor 2 (U-phase current i _u , V-phase current i _v , W-phase current i _w )), and Output to the three-phase to two-phase converter 14 and the ab-axis dead time compensator 19.

The three-phase / two-phase converter 14 converts the output currents (U-phase current i _u , V-phase current _iv , W-phase current i _w ) of the inverter 1 detected by the current detector 13 into an a-axis primary of a two-phase coordinate system. The current i _1a and the b-axis primary current i _1b are converted. Specifically, three-to-two phase converter 14, in the following equation (1), the value in _u of U-phase and the U-phase current i _u, the values in _v of the V-phase and V-phase current i _v, Using the W-phase value in _w as the W-phase current i _w , the a-axis primary current i _1a is calculated as the a-axis value out _a , and the b-axis primary current i _1b is calculated as the b-axis value out _b .

The three-phase / two-phase converter 14 outputs the calculated primary current (a-axis primary current i _1a , b-axis primary current i _1b ) to the observer 15.

The observer 15 outputs the output voltage (2) of the inverter 1 based on the primary current (a-axis primary current i _1a , b-axis primary current i _1b ) output from the three-phase to two-phase converter 14 and the characteristic equation of the motor 2. Estimate the phase primary voltage (a-axis primary voltage v _1a , b-axis primary voltage v _1b ). Here, the observer 15 assumes that the electric motor 2 is an induction motor, and constructs a characteristic expression of the electric motor 2 based on a voltage equation of the induction motor. The following equation (2) is an example of the voltage equation of the induction machine. In equation (2), i _2a is an a-axis secondary current, i _2b is a b-axis secondary current, R ₁ is a primary self-resistance, R ₂ is a secondary self-resistance, and L ₁ is L ₂ is the secondary self inductance, M is the mutual inductance, ω _m is the rotor rotation angle, and p is the differential operator.

The mathematical expression for calculating the output voltage from the output current of the inverter 1 depends on the coordinate system and the degree of modeling, and is not limited to the expression (2). For example, if the operating range of the motor 2 is low and the output frequency of the inverter 1 is sufficiently low (for example, 1 Hz or less), the interference term of the equation (2) can be omitted. Such a simple expression using the primary resistance R ₁ and the primary self inductance L ₁ can be expressed.

The observer 15 outputs the calculated primary voltages (a-axis primary voltage v _1a , b-axis primary voltage v _1b ) to the second subtraction unit 18.

The three-phase to two-phase converter 16 converts the three-phase correction voltage commands (the U-phase correction voltage command v _uc , the V-phase correction voltage command v _vc , and the W-phase correction voltage command v _wc ) output from the addition unit 11 by 2 It is converted into a phase coordinate system correction voltage command (a-axis correction voltage command _vac , b-axis correction voltage command _vbc ). Specifically, the three-phase to two-phase converter 16 sets the U-phase value in _u to the U-phase correction voltage command v _uc and _sets the V-phase value in _v to the V-phase correction voltage based on the above equation (1). A command v _vc , a W-phase value in _w is a W-phase correction voltage command v _wc , an a-axis correction voltage command v _ac is calculated as an a-axis value out _a , and a b-axis correction voltage is calculated as a b-axis value out _b Calculate the command _vbc .

The three-phase to two-phase converter 16 outputs the calculated correction voltage command (a-axis correction voltage command _vac , b-axis correction voltage command _vbc ) to the first subtraction unit 17.

The first subtraction unit 17 outputs a correction voltage command (a-axis correction voltage command _vac , b-axis correction voltage command _vbc ) output from the three-phase two-phase converter 16 and outputs the correction voltage command from the ab-axis dead time compensator 19. The obtained dead time compensation amounts (a-axis dead time compensation amount E _da and b-axis dead time compensation amount E _db ) are subtracted to obtain two-phase voltage commands (a-axis voltage command v _a ′ and b-axis voltage command v _b). ') Generate.

Specifically, the first subtraction unit 17 includes subtractors 17a and 17b. The subtracter 17a subtracts the a-axis dead time compensation amount E _da from the a-axis correction voltage command v _ac to generate an a-axis voltage command v _a ′. Subtractor 17b from the b-axis compensating voltage command v _bc by subtracting the b axis dead time compensation amount E _db, generates a b-axis voltage command v _b '.

The first subtraction unit 17 outputs the generated voltage commands (a-axis voltage command v _a ′, b-axis voltage command v _b ′) to the second subtraction unit 18.

The second subtraction unit 18 converts the voltage command (a-axis voltage command v _a ′, b-axis voltage command v _b ′) output from the first subtraction unit 17 into a primary voltage (a-axis voltage command v a ′) output from the observer 15. primary voltage v _1a, by subtracting the b-axis primary voltage v _1b), a shaft error value Delta] v _a, and generates a b-axis error value Delta] v _b.

Specifically, the second subtraction unit 18 includes subtracters 18a and 18b. Subtracter 18a subtracts the a-axis primary voltage v _1a from the a-axis voltage command v _a ', to generate the a-axis error value Delta] v _a. The subtracter 18b subtracts the b-axis primary voltage v _1b from the b-axis voltage command v _b ′ to generate a b-axis error value Δv _b .

The second subtracting unit 18, resulting a-axis error value Delta] v _a, a b-axis error value Delta] v _b, and outputs to the ab axis dead time compensator 19.

The ab-axis dead time compensator 19 stores the relationship between the output current of the inverter 1 and the dead time compensation amount (a-axis dead time compensation amount E _da , b-axis dead time compensation amount E _db ), and stores the second relationship. based on the a-axis error value Delta] v _a and the b-axis error value Delta] v _b output from the subtraction unit 18 to correct the relationship between the output current and the dead time compensation amount of the stored and the inverter 1. The ab-axis dead time compensator 19 stores the detection result of the output current (U-phase current i _u , V-phase current _iv , W-phase current i _w ) of the inverter 1 from the current detector 13. Based on the relationship between the output current and the dead time compensation amount, dead time compensation amounts (a-axis dead time compensation amount E _da and b-axis dead time compensation amount E _db ) corresponding to the detected output current are obtained. Output to the two-phase three-phase converter 21 and the first subtraction unit 17.

The two-phase three-phase converter 21 converts the two-phase dead time compensation amounts (a-axis dead time compensation amount E _da and b-axis dead time compensation amount E _db ) output from the ab-axis dead time compensator 19 into three-phase signals. (The U-phase dead time compensation amount E _du , the V-phase dead time compensation amount E _dv , and the W-phase dead time compensation amount E _dw ). Specifically, the three-phase to two-phase converter 21 sets the a-axis value in _a to the a-axis dead time compensation amount E _da and sets the b-axis value in _b to the b-axis dead based on the following equation (4). As the time compensation amount _Edb , the U-phase dead time compensation amount E _du is calculated as the U-phase value out _u , the V-phase dead time compensation amount E _dv is calculated as the V-phase value out _v , and the W-phase value out is calculated. _{The w-} phase dead time compensation amount _Edw is calculated as _w .

As described above, the three-phase correction voltage commands (U-phase correction voltage command v _uc , V-phase correction voltage command v _vc , W-phase voltage command v _wc ) are three-phase voltage commands (U-phase voltage command v _u , V-phase voltage command v _v , W-phase voltage command v _w ) and three-phase dead time compensation amounts (U-phase dead time compensation amount E _du , V-phase dead time compensation amount E _dv , W-phase dead time compensation amount E _dw ) And is generated by adding By converting the three-phase correction voltage command into a two-phase coordinate system, two-phase correction voltage commands (a-axis correction voltage command _vac and b-axis correction voltage command _vbc ) are generated.

Therefore, the voltage command two-phase output from the first subtracting unit 17 (a-axis voltage command v _a ', b-axis voltage command v _b'), the voltage command of the three-phase (U-phase voltage command v _u, V The phase voltage command v _v and the W-phase voltage command v _w ) correspond to two-phase coordinate systems. Further, a shaft error value Delta] v _a and the b-axis error value Delta] v _b output from the second subtracting unit 18, the voltage command and the error (voltage error between the output voltage of the inverter 1 estimated from the output current of the inverter 1 ). Based on this voltage error, the relationship between the output current of the inverter 1 and the amount of dead time compensation is corrected, and the dead time compensation amount is determined based on this relationship, so that more accurate drive control of the motor 2 is performed. Can be. In addition, since the output voltage is estimated from the output current of the inverter 1, there is no need to provide a voltage detection circuit for detecting the output voltage, and it is possible to suppress an increase in cost due to an increase in the size of the device and an increase in the number of components.

In FIG. 1, the three-phase correction voltage command is converted into a two-phase correction voltage command, and the two-phase dead time compensation amount is subtracted from the two-phase correction voltage command to obtain a two-phase voltage command. (A-axis voltage command v _a ′, b-axis voltage command v _b ′) are generated, but the present invention is not limited to this. Three-phase voltage commands are directly converted to two-phase voltage commands (a-axis voltage commands v _a ′, b-axis voltage command v _b ′).

  Next, the configuration of the ab-axis dead time compensator 19 will be described.

  FIG. 2 is a block diagram illustrating an example of the configuration of the ab-axis dead time compensator 19.

  The ab axis dead time compensator 19 shown in FIG. 2 includes multipliers 191a and 191b, integrator groups 192a and 192b, switches 193 to 196, and a selector 197.

The multiplier 191a is supplied with the a-axis error value Delta] v _a, is multiplied by a gain K and outputs the inputted a-axis error value Delta] v _a. The multiplier 191b receives the b-axis error value Δv _b , multiplies the input b-axis error value Δv _b by a gain K, and outputs the result.

  Each of the integrator groups 192a and 192b includes a plurality of integrators that integrate the input values and output the integrated values.

The switch 193 connects the multiplier 191a and any one of a plurality of integrators included in the integrator group 192a under the control of the selector 197. The connected integrators and a multiplier 191a via a switch 193, a value obtained by multiplying the gain K in the a-axis error value Delta] v _a is input, the integrator integrates the output value from the multiplier 191a , And hold the integrated value.

Under the control of the selector 197, the switch 194 outputs one of the plurality of integrators forming the integrator group 192a and the output of the a-axis dead time compensation amount E _da of the ab-axis dead time compensator 19. Connect to the end. The integrator connected to the output terminal of the a-axis dead time compensation amount E _da via the switch 194 outputs the held integrated value as the a-axis dead time compensation amount E _da .

The switch 195 connects the multiplier 191b and any one of the plurality of integrators forming the integrator group 192b according to the control of the selector 197. A value obtained by multiplying the b-axis error value Δv _b by the gain K is input to the integrator connected to the multiplier 191b via the switch 195, and the integrator integrates the value output from the multiplier 191b. , And hold the integrated value.

Under the control of the selector 197, the switch 196 outputs any one of the plurality of integrators constituting the integrator group 192b and the output of the b-axis dead time compensation amount _Edb of the ab-axis dead time compensator 19. Connect to the end. The integrator connected to the output terminal of the b-axis dead time compensation amount _Edb via the switch 196 outputs the held integrated value as the b-axis dead time compensation amount _Edb .

The selector 197 receives the detection results of the output currents of the inverter 1 (U-phase current i _u , V-phase current _iv , W-phase current i _w ), and forms an integrator group 192a based on the input detection results. One of the plurality of integrators is selected. Then, the selector 197 controls the switch 193 so that the selected integrator and the multiplier 191a are connected, so that the selected integrator is connected to the output terminal of the a-axis dead time compensation amount _Eda. To control the switch 194. Further, the selector 197 selects any one of the plurality of integrators forming the integrator group 192b based on the detection result of the output current of the inverter 1. Then, the selector 197 controls the switch 195 so that the selected integrator and the multiplier 191b are connected, so that the selected integrator is connected to the output terminal of the b-axis dead time compensation amount _Edb. The switch 196 is controlled.

  As described above, the selector 197 selects one of the plurality of integrators constituting each of the integrator groups 192a and 192b according to the value of the output current of the inverter 1. When each integrator is selected by the selector 197, the integrator accumulates the voltage error at the corresponding output current, holds as a dead time compensation amount, and outputs the amount. That is, each integrator stores the dead time compensation amount corresponding to each value of the output current, and when selected by the selector 197, outputs the stored dead time compensation amount and is not selected by the selector 197. In such a case, the integrated value thus far is kept.

That is, each of the plurality of integrators functions as a memory for storing the dead time compensation amount corresponding to the output current. Therefore, the ab-axis dead time compensator 19 uses a plurality of integrators to determine the relationship between the output current and the dead time compensation amount (a-axis dead time compensation amount E _da , b-axis dead time compensation amount E _db ) (dead time). Time table). The initial value of the dead time compensation amount stored in the integrators constituting the integrator groups 192a and 192b is a measured value or a theoretical value obtained by automatic tuning in advance.

  As a measuring method by auto-tuning, an arbitrary DC current is applied to the motor 2, and a voltage drop represented by a product of a primary resistance and a current of the motor 2 and a voltage drop due to a switching element or a return diode are subtracted from the voltage command. Then, a voltage error is calculated, and a dead time compensation amount is obtained from the voltage error. With this method, the initial value of the dead time table can be obtained by sequentially calculating the dead time compensation amount while changing the magnitude of the DC current.

  Next, the switching operation of the integrator by the selector 197 will be described.

  FIG. 3 is a diagram illustrating an example of the dead term table.

In FIG. 3, the horizontal axis indicates the number of an integrator (integrator number n) that constitutes each of the integrator groups 192a and 192b. 3, it is assumed that each of the integrator groups 192a and 192b is composed of 600 integrators S _n (n is an integer from 0 to 599). The vertical axis represents the currents (U-phase current i _u , V-phase current i _v , W-phase current i _w ) flowing through the motor 2 at the time of the measurement by the auto tuning, and the dead time compensation amount (a axis) obtained by the auto tuning. The dead time compensation amount E _da and the b-axis dead time compensation amount E _db are shown.

In FIG. 3, the current indicated by the dotted line means that a sufficient current such as the currents i _max and −i _max shown in FIG. Size is not important. Therefore, it can be divided into six regions A to F according to the magnitude relation of the output current of each phase.

Hereinafter, a region where the U-phase current i _u is the largest and the W-phase current i _w is the smallest is defined as a region A, and a region where the V-phase current i _v is the largest and the W-phase current i _w is the smallest is defined as a region. B, the area where the V-phase current _iv is the largest positively and the U-phase current _iu is the smallest is area C, and the area where the W-phase current _iw is the largest positively and the U-phase current _iu is the smallest is area D, the region where the W-phase current i _w is the largest positively and the V-phase current _iv is the smallest region is the region E, and the region where the U-phase current _iu is the largest positively and the V-phase current _iv is the smallest is the region F.

  When each of the integrator groups 192a and 192b is composed of 600 integrators, an integrator is assigned to each area as follows.

In the region A, the integrator S ₉₉ is allocated from the integrator S _0. Each integrator S ₀ to S _99, the dead time compensation corresponding to the -i _max i _max -i _max / 50 to i _max / 50 each the V-phase current i _v, in increments, corresponding to each the V-phase current i _v, Remember the amount.

In the region B, the integrator S ₁₉₉ is allocated from the integrator S _100. Integrator S ₁₀₀ to S _199, respectively, correspond to the -i _max + i _max / 50 to i _max / 50 each U-phase current i _u in increments from i _max, the dead time compensation amount corresponding to the U-phase current i _u Is stored.

In the area C, the integrators _S200 to _S299 are assigned. Each integrator S ₂₀₀ to S ₂₉₉ corresponds from -i _max to i _max -i _max / 50 to i _max / 50 each W-phase current i _w of the increments, the dead time compensation corresponding to each W-phase current i _w Remember the amount.

The region D, the integrator S ₃₉₉ is allocated from the integrator S _300. Integrator S ₃₀₀ to S _399, respectively, correspond to the -i _max + i _max / 50 to i _max / 50 each the V-phase current i _v, in increments from i _max, the dead time compensation amount corresponding to the respective the V-phase current i _v, Is stored.

In the region E, the integrator S ₄₉₉ is allocated from the integrator S _400. Each integrator S ₄₀₀ to S ₄₉₉ correspond from -i _max to i _max -i _max / 50 to i _max / 50 each U-phase current i _u of increments, the dead time compensation corresponding to each U-phase current i _u Remember the amount.

In the region F, the integrator S ₅₉₉ is allocated from the integrator S _500. Integrator S ₅₀₀ to S _599, respectively, correspond to the -i _max + i _max / 50 to i _max / 50 each W-phase current i _w in increments from i _max, the dead time compensation amount corresponding to the W-phase current i _w Is stored.

The selector 197 selects, from the areas A to F, an area that matches the magnitude relationship between the U-phase current i _u , the V-phase current _iv , and the W-phase current i _w . Then, in the selected region, the integrator corresponding to the current value of the current having the smallest absolute value among the U-phase current i _u , the V-phase current i _v , and the W-phase current i _w is selected. If the current having the smallest absolute value among the U-phase current i _u , the V-phase current i _v , and the W-phase current i _w is equal to or more than i _max , the selector 197 sets the current value of the current having the smallest absolute value to i _max as select integrator, also the smallest current absolute value if -i _max below selects the integrator current value of the absolute value is smallest current as -i _max.

As described above, since each of the integrators accumulates the error voltage, the dead time compensation amount output according to the dead time table is corrected, and the error voltage decreases. In other words, the ab-axis dead time compensator 19 has an automatic integration function of the dead time compensation amount, and the voltage command (U-phase voltage command v _u , V-phase voltage command v _v , W-phase voltage command) The error between the voltage command v _w ) and the voltage applied to the electric motor 2 decreases. Thereby, the voltage command (U-phase voltage command v _u , V-phase voltage command v _v , W-phase voltage command v _w ) and the current flowing through motor 2 (U-phase current i _u , V-phase current i _v , W-phase current) _iw ), the speed estimation error is improved in the speed sensorless control for calculating the speed of the electric motor 2, so that the speed ripple can be reduced.

  As described above, according to the present embodiment, the motor driving device 10 includes the plurality of switching elements S11 to S16, converts the DC voltage into the AC voltage by switching the plurality of switching elements S11 to S16, and outputs the motor 2 Inverter 1 (power converter), observer 15 (voltage estimator) for estimating the output voltage of inverter 1 based on the output current of inverter 1 and the characteristic equation of motor 2, and the output voltage of inverter 1 are specified. A second subtractor 18 (error calculator) for calculating a voltage error between the voltage command and the output voltage of the inverter 1 estimated by the observer 15; and dead time compensation for compensating the output current and the voltage error of the inverter 1 The relationship between the output current of the inverter 1 and the dead time compensation amount is corrected based on the calculated voltage error. At the same time, based on the stored relationship, the ab-axis dead time compensator 19 (dead time compensator) for outputting the dead time compensation amount corresponding to the output current of the inverter 1 and the voltage command are corrected with the dead time compensation amount. An adder 11 (command compensator) that outputs a correction voltage command, and a PWM generator (generator) that generates a control signal for controlling switching of the plurality of switching elements S11 to S16 based on the correction voltage command.

  The output voltage of the inverter 1 is estimated from the output current of the inverter 1 and the characteristic formula of the electric motor 2, and the relationship between the output current and the dead time compensation amount is determined based on the error (voltage error) between the estimated output voltage and the voltage command. Is corrected, and the dead time compensation amount is determined based on this relationship, so that more accurate drive control of the electric motor 2 can be performed. In addition, since the output voltage is estimated from the output current of the inverter 1, there is no need to provide a voltage detection circuit for detecting the output voltage, and it is possible to suppress an increase in cost due to an increase in the size of the device and an increase in the number of components.

(Second embodiment)
FIG. 4 is a diagram illustrating an example of a configuration of a motor drive device 10A according to a second embodiment of the present invention. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

  The electric motor driving device 10A according to the present embodiment is different from the electric motor driving device 10 according to the first embodiment in that the first subtraction unit 17 is omitted and the second subtraction unit 18 performs the second subtraction. The difference is that the unit is changed to the unit 18A and that the ab-axis dead time compensator 19 is changed to the ab-axis dead time compensator 19A.

The three-phase / two-phase converter 16 converts correction voltage commands (a-axis correction voltage command _vac , b-axis correction voltage command _vbc ) obtained by converting the three-phase correction voltage commands into a two-phase coordinate system into a second subtraction unit 18A. Output to The second subtraction unit 18A converts the correction voltage command (a-axis correction voltage command _vac , b-axis correction voltage command _vbc ) output from the three-phase / two-phase converter 16 into a primary voltage (from the observer 15). a shaft primary voltage v _1a, by subtracting the b-axis primary voltage v _1b), produces an a-axis voltage error value Delta] v _a 'and b-axis voltage error value Delta] v _b'.

Specifically, the second subtraction unit 18A includes subtractors 18a and 18b. Subtracter 18a subtracts the a-axis primary voltage v _1a from the a-axis compensating voltage command v _ac, generates the a-axis voltage error value Delta] v _a '. The subtracter 18b subtracts the b-axis primary voltage v _1b from the b-axis voltage command v _bc to generate a b-axis voltage error value Δv _b ′.

Second subtraction section 18A is generated a-axis voltage error value Delta] v _a 'and b-axis voltage error value Delta] v _b', and outputs the ab axis dead time compensator 19A. In the first embodiment, the second subtraction unit 18 calculates the voltage error between the voltage command and the estimated output voltage of the inverter 1, that is, the dead time compensation amount stored in the ab axis dead time compensator 19. The error from the voltage error due to the dead time generated in the inverter 1 was output. On the other hand, in the present embodiment, the second subtraction unit 18A outputs a voltage error due to the dead time generated in the inverter 1.

The ab-axis dead time compensator 19A stores the relationship between the output current of the inverter 1 and the amount of dead time compensation (a-axis dead time compensation amount E _da , b-axis dead time compensation amount E _db ), and a second subtraction unit. based on has been a-axis voltage error value Delta] v _a 'and b-axis voltage error value Delta] v _b' output from the 18A, correcting the relationship between the output current and the dead time compensation amount of the stored and the inverter 1. The ab-axis dead time compensator 19A outputs the output currents of the inverter 1 (U-phase current i _u , V-phase current i _v , W-phase current i _w) based on the relationship between the output current of the inverter 1 and the amount of dead time compensation. ) Is obtained (a-axis dead time compensation amount E _da , b-axis dead time compensation amount E _db ) and output to the two-phase to three-phase converter 21.

  FIG. 5 is a diagram illustrating an example of the configuration of the ab-axis dead time compensator 19A. 5, the same components as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted.

  The ab-axis dead time compensator 19A shown in FIG. 5 is different from the ab-axis dead time compensator 19 shown in FIG. 2 in that the multipliers 191a and 191b are eliminated and the integrator groups 192a and 192b are replaced by a filter group 198a. , 198b, and that the selector 197 is changed to the selector 197A.

The filter group 198a includes a plurality of low-pass filters (LPF: Low Pass Filter). Among the plurality of low-pass filter constituting the filter group 198a, either a low-pass filter, the switch 193 is connected to the second subtracting unit 18A, a-axis voltage error value Delta] v _a 'is input At the same time, the switch 194 is connected to the output terminal of the a-axis dead time compensation amount _Eda . The low-pass filter to which the a-axis voltage error value Δv _a ′ is input performs a filtering process on the a-axis voltage error value Δv _a ′, and outputs the result as the a-axis dead time compensation amount _Eda . The other low-pass filters retain the previous output.

The filter group 198b includes a plurality of low-pass filters. One of the plurality of low-pass filters constituting the filter group 198b is connected to the second subtraction unit 18A by the switch 195, and the b-axis voltage error value Δv _b ′ is input. At the same time, the switch 196 is connected to the output terminal of the b-axis dead time compensation amount _Edb . The low-pass filter to which the b-axis voltage error value Δv _b ′ is input performs a filtering process on the b-axis voltage error value Δv _b ′, and outputs the result as a b-axis dead time compensation amount _Edb . The other low-pass filters retain the previous output.

The selector 197A receives detection results of the output currents (U-phase current i _u , V-phase current i _v , W-phase current i _w ) of the inverter 1 and, based on the input detection results, forms a plurality of filters 198a. , One of the low-pass filters is selected. Then, the selector 197A controls the switch 193 so that the selected low-pass filter and the second subtractor 18A are connected, and outputs the selected low-pass filter and the a-axis dead time compensation amount _Eda . The switch 194 is controlled so that the end is connected. Further, the selector 197A selects any one of the plurality of low-pass filters constituting the filter group 198b based on the detection result of the output current of the inverter 1. Then, the selector 197A controls the switch 195 so that the selected low-pass filter and the second subtractor 18A are connected, and outputs the selected low-pass filter and the b-axis dead time compensation amount _Edb . The switch 196 is controlled so that the end is connected.

As described above, the selector 197A selects one of the plurality of low-pass filters forming the filter groups 198a and 198b according to the value of the output current of the inverter 1. When each of the low-pass filters is selected by the selector 197A, the low-pass filter performs a filtering process on a voltage error (a-axis voltage error value Δv _a ′, b-axis voltage error value Δv _b ′) in a corresponding output current, and performs a dead time. The value is output as the compensation amount and the value is held. That is, each low-pass filter stores the amount of dead time compensation corresponding to each value of the output current, outputs the amount of dead time compensation when selected by the selector 197A, and outputs the amount of dead time compensation when not selected by the selector 197. Keeps the output dead time compensation amount.

That is, each of the plurality of low-pass filters functions as a memory that stores the amount of dead time compensation according to the output current. Therefore, the ab-axis dead time compensator 19A uses a plurality of low-pass filters to determine the relationship between the output current and the dead time compensation amount (a-axis dead time compensation amount E _da , b-axis dead time compensation amount E _db ). (Dead time table). As the initial value of the dead time compensation amount stored in the low-pass filters constituting the filter groups 198a and 198b, a measured value or a theoretical value obtained by automatic tuning in advance is given as in the first embodiment.

  Next, the switching operation of the low-pass filter by the selector 197A will be described.

The ab-axis dead time compensator 19A stores a dead time table as described with reference to FIG. 3, as in the first embodiment. However, in the first embodiment, the numbers of the integrators constituting each of the integrator groups 192a and 192b and the dead time compensation amounts (a-axis dead time compensation amount E _da and b-axis dead time compensation amount E _db ) are included. In this embodiment, the numbers of the low-pass filters constituting the filter groups 198a and 198b and the dead time compensation amount (a-axis dead time compensation amount E _da , b-axis dead time compensation amount) are stored. E _db ) are stored in association with each other.

Then, similarly to the first embodiment, the output current is divided into six areas A to F according to the magnitude relation of the output currents of each phase (U-phase current i _u , V-phase current i _v , W-phase current i _w ), A low-pass filter forming filter groups 198a and 198b is assigned to each area. Then, in each region, a low-pass filter is assigned to each value of the output current, and each low-pass filter stores a dead time compensation amount in the assigned output current.

The selector 197A selects a region that matches the magnitude relationship between the U-phase current i _u , the V-phase current i _v , and the W-phase current i _w from the regions A to F. In the selected region, the U-phase current i _u , V-phase current _iv and W-phase current i _w , a low-pass filter corresponding to the current value of the current having the smallest absolute value is selected. If the current having the smallest absolute value among the U-phase current i _u , the V-phase current i _v , and the W-phase current i _w is equal to or more than i _max , the selector 197A sets the current value of the current having the smallest absolute value to i _max as selecting a low pass filter, also the smallest current absolute value if -i _max or less, selects the low-pass filter the current value of the absolute value is smallest current as -i _max.

  As described above, in the motor driving device 10A according to the present embodiment, the second subtraction unit 18A calculates the error between the correction voltage command and the output voltage of the inverter 1 estimated by the observer 15 as a voltage error, and The time compensator 19A selects one of the plurality of low-pass filters and one of the plurality of low-pass filters in accordance with the output current of the inverter 1, and the second subtractor 18A And a selector 197A for inputting the voltage error calculated by the above to the selected low-pass filter. When the low-pass filter is selected by the selector 197A, the low-pass filter outputs a value obtained by performing a filtering process on the voltage error output from the second subtraction unit 18A as a dead time compensation amount. If not selected, the previous output is retained.

  By doing so, it is possible to control the driving of the electric motor 2 with higher accuracy. In addition, since the output voltage is estimated from the output current of the inverter 1, there is no need to provide a voltage detection circuit for detecting the output voltage, and it is possible to suppress an increase in cost due to an increase in the size of the device and an increase in the number of components.

  In the above-described first and second embodiments, the case where the electric motor 2 is an induction machine has been described as an example. However, the present invention is not limited to this, and is applicable to a case where a synchronous machine is driven. It is possible to In addition, by appropriately performing coordinate conversion, the form of the dead time compensation amount stored in the ab dead time compensators 19 and 19A can be arbitrarily changed.

  Although the present invention has been described with reference to the drawings and embodiments, it should be noted that those skilled in the art can easily make various changes or modifications based on the present disclosure. Therefore, it should be noted that these variations or modifications are included in the scope of the present invention. For example, functions included in each block and the like can be rearranged so as not to be logically inconsistent, and a plurality of blocks can be combined into one or divided.

DESCRIPTION OF SYMBOLS 1 Inverter 2 Motor 10 Motor drive device 11 Adder 11u, 11v, 11w Adder 12 PWM generator 13 Current detector 14, 16 Three-phase two-phase converter 15 Observer 17 First subtractor 17a, 17b, 18a, 18b Subtractors 18, 18A Second subtractors 19, 19A Ab-axis dead time compensator 21 Two-phase three-phase converter E1 DC power supply C1 Capacitors S11 to S16 Switching elements 191a, 191b Multipliers 192a, 192b Integrator groups 193, 194 , 195, 196 Switch 197, 197A Selector 198a, 198b Filter group

Claims (2)

An electric motor driving device that controls driving of the electric motor,
A power converter that includes a plurality of switching elements, converts a DC voltage into an AC voltage by switching the plurality of switching elements, and outputs the AC voltage to the motor.
A voltage estimator that estimates an output voltage of the power converter based on an output current of the power converter and a characteristic equation of the electric motor;
An error calculator that calculates a voltage error between a voltage command indicating the output voltage of the power converter and the output voltage of the power converter estimated by the voltage estimator;
The relationship between the output current of the power converter and the dead time compensation amount for compensating the voltage error is stored, and based on the voltage error calculated by the error calculator, the output current of the power converter and the dead time are stored. A dead time compensator that corrects the relationship with the time compensation amount and outputs a dead time compensation amount corresponding to the output current of the power converter based on the relationship.
A command compensator that outputs a correction voltage command obtained by correcting the voltage command with the dead time compensation amount output from the dead time compensator,
A generator that generates a control signal that controls switching of the plurality of switching elements based on a correction voltage command output from the command compensator,
Equipped with a,
The dead time compensator,
Multiple integrators,
A selector for selecting any one of the plurality of integrators according to the output current of the power converter and inputting the voltage error calculated by the error calculator to the selected integrator; Prepare,
When the integrator is selected by the selector, the integrator outputs an integrated value obtained by integrating the voltage errors output from the error calculator as the dead time compensation amount, and when the selector is not selected by the selector, , electric motor drive device characterized that you hold the integrated value. An electric motor driving device that controls driving of the electric motor,
A power converter that includes a plurality of switching elements, converts a DC voltage into an AC voltage by switching the plurality of switching elements, and outputs the AC voltage to the motor.
A voltage estimator that estimates an output voltage of the power converter based on an output current of the power converter and a characteristic equation of the electric motor;
An error calculator that calculates a voltage error between a voltage command indicating the output voltage of the power converter and the output voltage of the power converter estimated by the voltage estimator;
The relationship between the output current of the power converter and the dead time compensation amount for compensating the voltage error is stored, and based on the voltage error calculated by the error calculator, the output current of the power converter and the dead time are stored. A dead time compensator that corrects the relationship with the time compensation amount and outputs a dead time compensation amount corresponding to the output current of the power converter based on the relationship.
A command compensator that outputs a correction voltage command obtained by correcting the voltage command with the dead time compensation amount output from the dead time compensator,
A generator that generates a control signal that controls switching of the plurality of switching elements based on a correction voltage command output from the command compensator,
With
The error calculator calculates, as the voltage error, an error between the corrected voltage command and the output voltage of the power converter estimated by the voltage estimator,
The dead time compensator,
A plurality of low-pass filters;
One of the plurality of low-pass filters is selected according to the output current of the power converter, and the voltage error calculated by the error calculator is applied to the selected low-pass filter. And a selector for inputting,
When the low-pass filter is selected by the selector, the low-pass filter performs a filtering process on the voltage error output from the error calculator, outputs the result as the dead time compensation amount, and is selected by the selector. An electric motor driving device characterized by holding the previous output when there is no output.

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