JP2023092165A - Control device for electric motor - Google Patents

Abstract

To provide a control device for controlling operation of an electric motor, which is improved in accuracy of estimating a resistance value of the electric motor.SOLUTION: A resistance value R^ of an electric motor M is estimated in accordance with Expression 1: id(n)-id(n-1)=Ts×{-R^/Ld×id(n-1)+ω×Lq/Ld×iq(n-1)}, where Ts represents a prescribed time period in a time period during which switching elements of upper arms/lower arms in respective phases of an inverter circuit 2 are all in an on state, id(n) represents a d-axis current Id at time t1 in the prescribed time period Ts, id(n-1) represents a d-axis current Id at time t0 that is prior to the time t1 in the prescribed time period Ts, iq(n-1) represents a q-axis current Iq at the time t0, R^ represents the resistance value of the electric motor M, Ld represents a d-axis inductance Ld of the electric motor M, Lq represents a q-axis inductance Lq of the electric motor M, and ω represents the number of rotations ω^ of a rotor.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device that controls the operation of an electric motor.

2. Description of the Related Art As a control device for a motor, there is a device that estimates the resistance value of the motor by substituting parameters such as a voltage command value and a current flowing through the motor into a voltage equation corresponding to a model of the motor. As a related technology, there is Patent Document 1.

By the way, the voltage command value may contain an error due to an operation delay of a switching element of an inverter circuit that drives the electric motor.

Therefore, in the control device described above, there is a possibility that the accuracy of estimating the resistance value is lowered due to the error included in the voltage command value.

JP 2013-146155 A

An object of one aspect of the present invention is to improve the accuracy of estimating the resistance value of an electric motor in a control device that controls the operation of the electric motor.

An electric motor control apparatus, which is one embodiment of the present invention, includes an inverter circuit that rotates a rotor of the electric motor by turning on and off a plurality of switching elements, and a d-axis current and a q-axis current that flow through the electric motor. and estimating the resistance value of the motor, and turning on and off the plurality of switching elements by vector control using at least the d-axis current, the q-axis current, and the resistance value.

The control circuit sets a predetermined period Ts during which all the switching elements of the upper arm or the lower arm of each phase of the inverter circuit are turned on, and sets the d-axis current at a first time within the predetermined period to Ts. id(n), the d-axis current at a second time earlier than the first time within the predetermined period is id(n-1), the q-axis current at the second time is iq(n-1 ), the resistance value of the electric motor is R^, the d-axis inductance of the electric motor is Ld, the q-axis inductance of the electric motor is Lq, and the rotation speed of the rotor is ω, use the following formula 1 to estimate the resistance value of the motor.

id(n)−id(n−1)=Ts×{−R^/Ld×id(n−1)+ω×Lq/Ld×iq(n−1)} Equation 1

In this manner, the resistance value is estimated using the d-axis current and the q-axis current during a predetermined period of the period in which all the switching elements of the upper arm or the lower arm of each phase of the inverter circuit are turned on. Since the parameter of the voltage command value is not included in Equation 1, the resistance value can be estimated without being affected by the error included in the voltage command value due to the operation delay of the switching element of the inverter circuit. In addition, since all the terms on the right and left sides of Equation 1 above include the parameters of the d-axis current and the q-axis current, respectively, can be canceled and the resistance value can be estimated without being affected by the error. In addition, since Equation 1 does not include the parameter of the induced voltage, the resistance value can be estimated without being affected by fluctuations in the induced voltage due to temperature changes. Thereby, the estimation accuracy of the resistance value of the electric motor can be improved.

The inverter circuit turns on and off the plurality of switching elements according to a comparison result between the voltage value of the carrier wave and the voltage command value, and the control circuit uses the resistance value to determine the position of the rotor of the electric motor. a position estimator for estimating; a current converter for converting the current flowing in the electric motor into the d-axis current and the q-axis current using the position; and the rotation speed of the rotor and the rotation speed command value. A current command value output unit for outputting a d-axis current command value and a q-axis current command value according to a difference, and calculating a d-axis voltage command value so that the difference between the d-axis current and the d-axis current command value becomes small. and a voltage command value calculation unit for calculating a q-axis voltage command value so that a difference between the q-axis current and the q-axis current command value becomes small, and the d-axis voltage command value and the q-axis command value using the position and a voltage command value conversion unit that converts a voltage command value into the voltage command value.

Further, the control circuit calculates a moving average of a plurality of resistance values obtained as the first time and the second time, which are two times adjacent to each other among the three or more times within the predetermined period, to the electric motor. may be configured to have a resistance value of

As a result, the resistance value of the electric motor can be estimated while suppressing the influence of the errors included in each of the plurality of resistance values before the average is calculated, so that the estimation accuracy of the resistance value of the electric motor can be further improved.

According to the present invention, it is possible to improve the accuracy of estimating the resistance value of the electric motor in the control device that controls the operation of the electric motor.

It is a figure which shows an example of the control apparatus of the electric motor in embodiment. It is a figure for demonstrating an example of the estimation method of the resistance value of an electric motor. FIG. 5 is a diagram for explaining another example of a method of estimating the resistance value of an electric motor; It is a figure which shows the other example of the control apparatus of the electric motor in embodiment.

Embodiments will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an example of a control device for an electric motor according to an embodiment.

A control device 1 shown in FIG. 1 controls the operation of an electric motor M mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle, and includes an inverter circuit 2 and a control circuit 3 . The electric motor M is, for example, an embedded magnet type motor or a surface magnet type motor.

The inverter circuit 2 drives the electric motor M with power supplied from the power source P, and includes a capacitor C, switching elements SW1 to SW6 (eg, IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 and Se2. and That is, one terminal of the capacitor C is connected to the positive terminal of the power supply P and the collector terminals of the switching elements SW1, SW3 and SW5, and the other terminal of the capacitor C is connected to the negative terminal of the power supply P and the switching elements SW2, SW4 and SW6. Connected to the emitter terminal. A connection point between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to the U-phase input terminal of the electric motor M via the current sensor Se1. A connection point between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to the V-phase input terminal of the electric motor M via the current sensor Se2. A connection point between the emitter terminal of the switching element SW5 and the collector terminal of the switching element SW6 is connected to the W-phase input terminal of the electric motor M. FIG.

The capacitor C smoothes the voltage output from the power supply P and input to the inverter circuit 2 .

The switching element SW1 is turned on or off based on the driving signal S1 output from the control circuit 3. FIG. The switching element SW2 is turned on or off based on the driving signal S2 output from the control circuit 3. FIG. The switching element SW3 is turned on or off based on the driving signal S3 output from the control circuit 3. FIG. The switching element SW4 is turned on or off based on the driving signal S4 output from the control circuit 3. FIG. The switching element SW5 is turned on or off based on the drive signal S5 output from the control circuit 3. FIG. The switching element SW6 is turned on or off based on the drive signal S6 output from the control circuit 3. FIG. By turning ON or OFF the switching elements SW1 to SW6 respectively, the DC voltage output from the power supply P is converted into three AC voltages having phases different from each other by 120 degrees. The rotor of the electric motor M is rotated by being applied to the input terminals of phase and W phase. That is, the inverter circuit 2 rotates the rotor of the electric motor M by turning on and off the switching elements SW1 to SW6.

The current sensor Se<b>1 includes a Hall element, a shunt resistor, and the like, detects a U-phase current Iu flowing in the U-phase of the electric motor M, and outputs the detected U-phase current Iu to the control circuit 3 . The current sensor Se2 is composed of a Hall element, a shunt resistor, and the like, detects a V-phase current Iv flowing in the V-phase of the electric motor M, and outputs the detected V-phase current Iv to the control circuit 3 .

The control circuit 3 includes a storage section 4 , a drive circuit 5 and a calculation section 6 .

The storage unit 4 is configured by RAM (Random Access Memory), ROM (Read Only Memory), or the like.

The drive circuit 5 is configured by an IC (Integrated Circuit) or the like, and includes a voltage value of a carrier wave (triangular wave, sawtooth wave, reverse sawtooth wave, etc.), a U-phase voltage command value Vu* output from the calculation unit 6, and a V-phase voltage value. The voltage command value Vv* and the W-phase voltage command value Vw* are compared, and drive signals S1 to S6 corresponding to the comparison results are output to respective gate terminals of the switching elements SW1 to SW6.

For example, when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs the high-level drive signal S1 and the low-level drive signal S2, and outputs the U-phase voltage command value When Vu* is smaller than the voltage value of the carrier wave, it outputs a low-level drive signal S1 and a high-level drive signal S2. Further, when the V-phase voltage command value Vv* is equal to or higher than the voltage value of the carrier wave, the drive circuit 5 outputs the high-level drive signal S3 and the low-level drive signal S4, and outputs the V-phase voltage command value. When Vv* is smaller than the voltage value of the carrier wave, it outputs the drive signal S3 of low level and the drive signal S4 of high level. Further, when the W-phase voltage command value Vw* is equal to or higher than the voltage value of the carrier wave, the drive circuit 5 outputs the high-level drive signal S5 and the low-level drive signal S6, and outputs the W-phase voltage command value. When Vw* is smaller than the voltage value of the carrier wave, it outputs the drive signal S5 of low level and the drive signal S6 of high level.

The computing unit 6 is configured by a microcomputer or the like, and includes a current converting unit 7, a resistance estimating unit 8, a temperature estimating unit 9, a position estimating unit 10, a subtracting unit 11, a torque command value calculating unit 12, and a current A command value output unit 13 , a subtraction unit 14 , a subtraction unit 15 , a voltage command value calculation unit 16 , and a voltage command value conversion unit 17 are provided. For example, when the microcomputer executes a program stored in the storage unit 4, the current converting unit 7, the resistance estimating unit 8, the temperature estimating unit 9, the position estimating unit 10, the subtracting unit 11, the torque command value calculating unit 12 , a current command value output unit 13, a subtraction unit 14, a subtraction unit 15, a voltage command value calculation unit 16, and a voltage command value conversion unit 17 are configured.

The current converter 7 obtains the W-phase current Iw flowing through the W-phase of the electric motor M using the U-phase current Iu detected by the current sensor Se1 and the V-phase current Iv detected by the current sensor Se2.

Further, the current conversion unit 7 uses the rotor position θ (phase angle) of the electric motor M estimated by the position estimation unit 10 to convert the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into It is converted into a d-axis current Id (a current component for causing the motor M to generate a weakened field) and a q-axis current Iq (a current component for causing the motor M to generate torque).

For example, the current converter 7 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into the d-axis current Id and the q-axis current Iq using the conversion matrix C1 shown in Equation 2 below.

Note that the current detected by the current sensors Se1 and Se2 is not limited to the combination of the U-phase current Iu and the V-phase current Iv, but the combination of the V-phase current Iv and the W-phase current Iw, or the combination of the U-phase currents Iu and W A combination of the phase currents Iw may be used. When the current sensors Se1 and Se2 detect the V-phase current Iv and the W-phase current Iw, the current converter 7 uses the V-phase current Iv and the W-phase current Iw to obtain the U-phase current Iu. When the current sensors Se1 and Se2 detect the U-phase current Iu and the W-phase current Iw, the current converter 7 uses the U-phase current Iu and the W-phase current Iw to obtain the V-phase current Iv.

Further, when the inverter circuit 2 further includes a current sensor Se3 for detecting the current flowing through the W phase of the electric motor M in addition to the current sensors Se1 and Se2, the current conversion unit 7 detects the position estimated by the position estimation unit 10. θ^ may be used to convert the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensors Se1 to Se3 into the d-axis current Id and the q-axis current Iq. .

The resistance estimator 8 estimates the resistance value (resistance component) R̂ of the electric motor M using Equation 1 below. Note that Ts is a predetermined period of the period T0 during which the upper arm switching elements SW1, SW3, and SW5 or the lower arm switching elements SW2, SW4, and SW6 of each phase of the inverter circuit 2 are all turned on. , as shown in FIG. 2(a), at least the period during which the d-axis voltage command value Vd* becomes zero. The predetermined period Ts is the same period as the period T0 or a period shorter than the period T0. Note that in the example shown in FIG. 2 and the example shown in FIG. 4 described later, the predetermined period Ts is the same period as the period T0. id(n) and id(n-1) are d-axis currents Id output from the current converter 7. For example, as shown in FIG. Let d-axis current Id at time t1 (first time) within period Ts, and let id(n-1) be the d-axis current Id at time t0 (second time) before time t1 within period Ts. In FIG. 2, the time t1 is the timing immediately before the d-axis voltage command value Vd* changes from zero to a negative value, but it may be set at any time within the period Ts. Further, the time t0 is the timing immediately after the d-axis voltage command value Vd* changes from a negative value to zero, but it can be set to any time before the time t1 within the predetermined period Ts. good. Also, iq(n-1) is the q-axis current Iq output from the current conversion unit 7, for example, the q-axis current Iq at time t0 as shown in FIG. 2(c). Also, R̂ is the resistance value of the electric motor M, and ω is the rotational speed (angular velocity) of the rotor estimated by the position estimator 10 ̂. Also, Ld is the d-axis inductance of the electric motor M, and Lq is the q-axis inductance of the electric motor M. It is also assumed that the d-axis inductance Ld and the q-axis inductance Lq do not fluctuate as the temperature of the electric motor M changes.

id(n)−id(n−1)=Ts×{−R^/Ld×id(n−1)+ω×Lq/Ld×iq(n−1)} Equation 1

It should be noted that Equation 1 above is derived by the following process.

First, the voltage equation corresponding to the model of the electric motor M is given by Equation 3 below. Vd is the d-axis voltage command value Vs* calculated by the voltage command value calculator 16, and Vq is the q-axis voltage command value Vq* calculated by the voltage command value calculator 16. R^ is the resistance value of the electric motor M, p is the differential operator, Ld is the d-axis inductance of the electric motor M, Lq is the q-axis inductance of the electric motor M, and ω is the position estimation unit 10. Let the rotational speed ω^ be estimated by Further, id is the d-axis current Id output from the current converter 7 and iq is the q-axis current Iq output from the current converter 7 . Also, L is the inductance of the motor M, and Ψa is the induced voltage of the motor M.

Next, Equation 3 above is transformed into Equation 4 below by time-differentiating Equation 3 over a predetermined period Ts.

Equation 1 is obtained by converting the equation shown in Equation 5 below, which is related to the d-axis current Id in Equation 4 above, into a difference equation. Note that the equation related to the q-axis current Iq in Equation 4 above is not used because it includes the induced voltage Ψa that fluctuates with temperature changes.

In this way, the predetermined period Ts (that is, at least During the period in which the d-axis voltage command value Vd* is zero), the resistance value R^ is estimated using the d-axis current Id and the q-axis current Iq, and the d-axis voltage command value Vd* and Since the parameter of the q-axis voltage command value Vq* is not included, the effects of errors included in the d-axis voltage command value Vd* and the q-axis voltage command value Vq* due to the operation delays of the switching elements SW1 to SW6 of the inverter circuit 2, etc. It is possible to estimate the resistance value R^ without undergoing Further, since all the terms on the right side and the left side of Equation 1 above include the parameters of the d-axis current Id and the q-axis current Iq, respectively, the d-axis current Id and q The error included in the parameter of the shaft current Iq can be canceled, and the resistance value R^ can be estimated without being affected by the error. In addition, since the parameter of the induced voltage Ψa is not included in Equation 1, the resistance value R̂ can be estimated without being affected by fluctuations in the induced voltage Ψa due to temperature changes. Thereby, the estimation accuracy of the resistance value R̂ of the electric motor M can be improved.

For example, the resistance estimator 8 estimates the resistance value R^ using system identification. That is, the resistance estimating unit 8 calculates the following formula 6 when the left side of the above formula 1 is Q, the right side of the above formula 1 is Q, γ is the identification gain, and R is the resistance value of the electric motor M. is set to the resistance value R^ of the electric motor M when the difference between Q and Q becomes zero by repeating the above.

R ^ = γ × ∫ (Q - Q ^) dt Equation 6

The resistance value R^ may be estimated by calculating the following formula 7 obtained by modifying the above formula 1 with respect to R^, and the method of estimating the resistance value R^ is not particularly limited.

R^=ω×Lq×iq(n−1)/id(n−1)−Ld/id(n−1)×{(id(n)−id(n−1))/Ts} . Equation 7

Further, the temperature estimator 9 shown in FIG. 1 estimates the temperature T̂ of the electric motor M using the resistance value R̂ estimated by the resistance estimator 8 . Note that the temperature T^ may be obtained by calculation using the resistance value R^ and a coefficient, or information in which the temperature and the resistance value of the electric motor M stored in advance in the storage unit 4 are associated with each other is referred to. , and the method for estimating the temperature T^ is not particularly limited. Further, the temperature T^ estimated by the temperature estimator 9 may be used for correcting various command values such as a torque command value T* described later that fluctuate with temperature changes.

The position estimator 10 estimates the rotational speed ω̂ and the position θ̂.

For example, the position estimation unit 10 calculates the d-axis current Id and the q-axis current Iq output from the current conversion unit 7 and the d-axis voltage command value Vd* and the q-axis voltage command value calculated by the voltage command value calculation unit 16. ω obtained by substituting Vq* and the resistance value R̂ estimated by the resistance estimating section 8 into the voltage equation shown in Equation 3 above is estimated as the rotational speed ω̂. Further, the position estimating unit 10 estimates the result of multiplying the number of rotations ω̂ by a unit time (for example, the clock cycle of the calculating unit 6) as the position θ̂.

Note that the position estimating unit 10 obtains the extended induced voltage excited by superimposing the high-frequency voltage on the d-axis voltage command value Vd* calculated by the voltage command value calculating unit 16 using the resistance value R^ and the like. The rotor position θ may be estimated from the phase of the extended induced voltage. In this configuration, the position estimator 10 estimates the result of dividing the position θ̂ by the unit time (for example, the clock cycle of the calculator 6) as the rotation speed ω̂.

The subtraction unit 11 calculates a rotation speed difference Δω between the rotation speed command value ω* input from the outside and the rotation speed ω ̂ estimated by the position estimation unit 10 .

The torque command value calculator 12 uses the rotational speed difference Δω output from the subtractor 11 to calculate the torque command value T*. For example, the torque command value calculation unit 12 refers to information (not shown) in which the rotation speed of the rotor of the electric motor M and the torque of the electric motor M are associated with each other, which is stored in the storage unit 4. A torque corresponding to a rotation speed corresponding to the rotation speed difference Δω is obtained as a torque command value T*. The torque command value calculator 12 may increase the torque command value T* as the temperature T^ estimated by the temperature estimator 9 increases. As a result, it is possible to suppress the decrease in the torque generated in the electric motor M due to the fact that the higher the temperature T^, the more difficult it is for the current to flow through the electric motor M and the lower the strength of the magnetic field of the permanent magnet.

A current command value output unit 13 outputs a d-axis current command value Id* and a q-axis current command value Iq* using the torque command value T*. For example, the current command value output unit 13 outputs information (non- ) to obtain the d-axis current command value Id* and the q-axis current command value Iq* corresponding to the torque command value T*.

That is, the current command value output unit 13 outputs the d-axis current command value Id* and the q-axis current command value Iq* based on the rotation speed difference Δω between the rotor rotation speed ω̂ and the rotation speed command value ω*.

The subtraction unit 14 calculates a difference ΔId between the d-axis current command value Id* output from the current command value output unit 13 and the d-axis current Id output from the current conversion unit 7 .

The subtraction unit 15 calculates a difference ΔIq between the q-axis current command value Iq* output from the current command value output unit 13 and the q-axis current Iq output from the current conversion unit 7 .

The voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* by PI control using the difference ΔId output from the subtraction unit 14 and the difference ΔIq output from the subtraction unit 15. calculate. For example, the voltage command value calculator 16 obtains the d-axis voltage command value Vd* by calculating the following equation 8, and obtains the q-axis voltage command value Vq* by calculating the following equation 9. Kp is the constant of the proportional term of the PI control, Ki is the constant of the integral term of the PI control, Lq is the q-axis inductance of the electric motor M, Ld is the d-axis inductance of the electric motor M, and ω is the position estimation unit 10. and Ψa is the induced voltage.

d-axis voltage command value Vd*=Kp×difference ΔId+∫(Ki×difference ΔId)−ωLqIq Equation 8

q-axis voltage command value Vq*=Kp×difference ΔIq+∫(Ki×difference ΔIq)+ωLdId+ωΨa Equation 9

That is, the voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* so that the difference ΔId between the d-axis current Id and the d-axis current command value Id* becomes small, and the q-axis current Iq and the q-axis current The q-axis voltage command value Vq* is calculated so that the difference ΔIq from the command value Iq* becomes small.

The voltage command value conversion unit 17 uses the position θ ̂ estimated by the position estimation unit 10 to convert the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu* and the V-phase voltage command value Vu*. It is converted into a voltage command value Vv* and a W-phase voltage command value Vw*. For example, the voltage command value conversion unit 17 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu*, the V-phase voltage The command value Vv* is converted into the W-phase voltage command value Vw*.

That is, the control circuit 3 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw flowing through the electric motor M into a d-axis current Id and a q-axis current Iq, and estimates the resistance value R^ of the electric motor M. , the switching elements SW1 to SW6 are turned on and off by vector control using at least the d-axis current Id and the q-axis current Iq and the resistance value R̂.

As described above, according to the control device 1 for the electric motor M of the embodiment, the resistance value R̂ of the electric motor M can be accurately estimated while the electric motor M is being driven.

Further, according to the control device 1 for the electric motor M of the embodiment, the resistance value R^ of the electric motor M can be estimated with high accuracy. Accuracy can be improved.

Further, in the control device 1 for the electric motor M of the embodiment, since the temperature T^ of the electric motor M can be estimated, there is no need to provide a temperature sensor for detecting the temperature of the electric motor M. can be improved.

The present invention is not limited to the above embodiments, and various improvements and modifications are possible without departing from the gist of the present invention.

<Modification 1>
FIG. 3 is a diagram showing another example of the motor control device according to the embodiment. In addition, the same code|symbol is attached|subjected to the same structure as the structure shown in FIG. 1, and the description is abbreviate|omitted.

The control device 1 shown in FIG. 3 differs from the control device 1 shown in FIG. and a rotational speed calculator 18 instead of the position estimator 10 of the calculator 6 .

The rotation speed calculation unit 18 calculates the rotation speed ω̂ using the position θ̂ detected by the position detection unit Sp. For example, the rotational speed calculation unit 18 obtains the rotational speed ω̂ by dividing the position θ̂ by a predetermined time (for example, the clock cycle of the arithmetic unit 6).

Also in the control device 1 configured in this way, the resistance value R^ is estimated by the resistance estimation unit 8, so that the resistance value R^ of the electric motor M can be accurately estimated while the electric motor M is being driven.

<Modification 2>
The resistance estimating unit 8 (control circuit 3) calculates a moving average of a plurality of resistance values obtained by setting two times adjacent to each other among three or more times within the predetermined period Ts to time t1 and time t0, to the electric motor M may be configured to have a resistance value R ^ of .

For example, as shown in FIG. 4, an arbitrary time within a predetermined period Ts is t _α , a time before time t _α is t _β , a time before time t _β is t _γ , and at time t _α The corresponding d-axis current is id _α , the d-axis current corresponding to time _tβ is _idβ , the d-axis current corresponding to time _tγ is _idγ , and the q-axis current corresponding to time _tβ is _iqβ. and the q-axis current corresponding to time t _γ is iq _γ .

First, _the resistance estimation unit 8 sets the d-axis current id _β to id(n) and the d-axis current id _γ to _id (n−1), the q-axis current iq _γ is iq(n−1), and the resistance value R^ _βγ is estimated using the above equation (1).

Next, _{the resistance} estimator 8 sets the d-axis current id _α to id(n) and the d-axis current id _β to id(n−1), the q-axis current _iqβ is iq(n−1), and the resistance value _R̂αβ is estimated using Equation 1 above.

Then, the resistance estimating unit 8 divides the sum of the resistance value _R̂βγ and the resistance value _R̂αβ by 2 to obtain the resistance value R̂.

As a result, the resistance value R^ of the electric motor M can be estimated while suppressing the influence of errors included in the plurality of resistance values R^ (resistance value R^ _βγ and resistance value R^ _αβ ) before calculating the average. Therefore, the estimation accuracy of the resistance value R̂ of the electric motor M can be further improved.

1 Control device 2 Inverter circuit 3 Control circuit 4 Storage unit 5 Drive circuit 6 Calculation unit 7 Current conversion unit 8 Resistance estimation unit 9 Temperature estimation unit 10 Position estimation unit 11 Subtraction unit 12 Torque command value calculation unit 13 Current command value output unit 14 Subtraction unit 15 Subtraction unit 16 Voltage command value calculation unit 17 Voltage command value conversion unit 18 Rotation speed calculation unit P Power supply C Capacitor Se1 Current sensor Se2 Current sensor Sp Position detection unit

Claims (3)

an inverter circuit that rotates a rotor of an electric motor by turning on and off a plurality of switching elements;
converting a current flowing through the motor into a d-axis current and a q-axis current, estimating a resistance value of the motor, and performing vector control using at least the d-axis current, the q-axis current, and the resistance value to perform the plurality of switching operations; a control circuit that turns the element on and off;
with
The control circuit defines a predetermined period of time Ts during which all the switching elements of the upper arm or the lower arm of each phase of the inverter circuit are turned on, and sets the d-axis current at a first time within the predetermined period to Ts. Let id(n) be the d-axis current at a second time before the first time within the predetermined period, id(n-1) be the d-axis current, and iq(n-1) be the q-axis current at the second time. ), the resistance value of the electric motor is R^, the d-axis inductance of the electric motor is Ld, the q-axis inductance of the electric motor is Lq, and the rotation speed of the rotor is ω, the following equation 1 is used: id(n)-id(n-1)=Ts×{-R^/Ld×id(n-1)+ω×Lq/Ld×iq(n-1)} ・..Formula 1
An electric motor control device characterized by: The electric motor control device according to claim 1,
The inverter circuit turns on and off the plurality of switching elements according to a comparison result between the voltage value of the carrier wave and the voltage command value,
The control circuit is
a position estimating unit that estimates the position of the rotor of the electric motor using the resistance value;
a current conversion unit that converts the current flowing in the electric motor into the d-axis current and the q-axis current using the position;
a current command value output unit that outputs a d-axis current command value and a q-axis current command value based on a difference between the rotation speed of the rotor and the rotation speed command value;
A d-axis voltage command value is calculated so that the difference between the d-axis current and the d-axis current command value is small, and a q-axis voltage is calculated so that the difference between the q-axis current and the q-axis current command value is small. a voltage command value calculation unit that calculates a command value;
a voltage command value conversion unit that converts the d-axis voltage command value and the q-axis voltage command value into the voltage command value using the position;
A control device for an electric motor, comprising: The electric motor control device according to claim 1 or claim 2,
The control circuit calculates a moving average of a plurality of resistance values obtained as the first time and the second time, which are two times adjacent to each other among the three or more times within the predetermined period, as the resistance of the electric motor. A motor control device characterized by:

Images