JP7613352B2 - Motor control device - Google Patents

Description

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

There is a motor control device that estimates the resistance value of the motor by substituting parameters such as a voltage command value and the current flowing through the motor into a voltage equation that corresponds to a model of the motor. Related technology is disclosed in Patent Document 1.

However, there is a risk that errors may be included in the voltage command value due to operational delays in the switching elements of the inverter circuit that drives the electric motor.

Therefore, in the above control device, there is a risk that the accuracy of estimating the resistance value will decrease due to errors contained 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.

One embodiment of the motor control device according to the present invention includes an inverter circuit that rotates the rotor of the motor by turning on and off multiple switching elements, and a control circuit that converts the current flowing through the motor into a d-axis current and a q-axis current, estimates the resistance value of the motor, and turns on and off the multiple switching elements by vector control using at least the d-axis current, the q-axis current, and the resistance value.

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

id(n)-id(n-1)=Ts×{-R^/Ld×id(n-1)+ω×Lq/Ld×iq(n-1)}...Formula 1

In this way, the resistance value is estimated using the d-axis current and the q-axis current during a predetermined period during which all switching elements of the upper arm or lower arm of each phase of the inverter circuit are on. Since the above formula 1 does not include a parameter for the voltage command value, the resistance value can be estimated without being affected by errors contained in the voltage command value due to operational delays of the switching elements of the inverter circuit. In addition, since all terms on the right and left sides of the above formula 1 include parameters for the d-axis current and the q-axis current, respectively, the gain of the amplifier in the current sensor can offset errors contained in the parameters of the d-axis current and the q-axis current, and the resistance value can be estimated without being affected by these errors. In addition, since the above formula 1 does not include a parameter for the induced voltage, the resistance value can be estimated without being affected by fluctuations in the induced voltage due to temperature changes. This improves the accuracy of estimating the resistance value of the motor.

The inverter circuit may also be configured to turn on and off the multiple switching elements based on a comparison between the voltage value of the carrier wave and a voltage command value, and the control circuit may be configured to include a position estimation unit that estimates the position of the rotor of the motor using the resistance value, a current conversion unit that converts the current flowing through the 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 the difference in rotation speed between the rotor rotation speed and the rotation speed command value, a voltage command value calculation unit that calculates a d-axis voltage command value so that the difference between the d-axis current and the d-axis current command value is small, and calculates a q-axis voltage command value so that the difference between the q-axis current and the q-axis current command value is small, and 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.

The control circuit may also be configured to determine the resistance value of the motor as a moving average of multiple resistance values obtained by using two adjacent times among three or more times within the specified period as the first time and the second time.

This makes it possible to estimate the motor resistance value while reducing the influence of errors contained in each of the multiple resistance values before calculating the average, thereby further improving the accuracy of estimating the motor resistance value.

According to the present invention, it is possible 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.

FIG. 2 is a diagram illustrating an example of a control device for an electric motor according to an embodiment. FIG. 4 is a diagram for explaining an example of a method for estimating a resistance value of a motor. FIG. 10 is a diagram for explaining another example of a method for estimating a resistance value of a motor. FIG. 4 is a diagram illustrating another example of the control device for the electric motor in the embodiment.

The following describes the embodiment in detail with reference to the drawings.

Figure 1 shows an example of a motor control device in an embodiment.

The 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 motor or a surface magnet 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 (e.g., IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 and Se2. That is, one terminal of the capacitor C is connected to the positive terminal of the power source 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 source P and the emitter terminals of the switching elements SW2, SW4, and SW6. The 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. The 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. The connection point between the emitter terminal of switching element SW5 and the collector terminal of switching element SW6 is connected to the W-phase input terminal of motor M.

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

Switching element SW1 is turned on or off based on drive signal S1 output from control circuit 3. Switching element SW2 is turned on or off based on drive signal S2 output from control circuit 3. Switching element SW3 is turned on or off based on drive signal S3 output from control circuit 3. Switching element SW4 is turned on or off based on drive signal S4 output from control circuit 3. Switching element SW5 is turned on or off based on drive signal S5 output from control circuit 3. Switching element SW6 is turned on or off based on drive signal S6 output from control circuit 3. By switching elements SW1 to SW6 being turned on or off, respectively, the DC voltage output from power source P is converted into three AC voltages whose phases differ from each other by 120 degrees, and these AC voltages are applied to the input terminals of the U phase, V phase, and W phase of electric motor M, causing the rotor of electric motor M to rotate. 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.

Current sensor Se1 is composed of a Hall element, a shunt resistor, etc., and detects U-phase current Iu flowing through the U-phase of motor M and outputs it to control circuit 3. Current sensor Se2 is composed of a Hall element, a shunt resistor, etc., and detects V-phase current Iv flowing through the V-phase of motor M and outputs it to control circuit 3.

The control circuit 3 includes a memory unit 4, a drive circuit 5, and a calculation unit 6.

The memory unit 4 is composed of RAM (Random Access Memory) or ROM (Read Only Memory), etc.

The drive circuit 5 is composed of an IC (Integrated Circuit) and compares the voltage value of the carrier wave (triangular wave, sawtooth wave, inverse sawtooth wave, etc.) with the U-phase voltage command value Vu*, V-phase voltage command value Vv*, and W-phase voltage command value Vw* output from the calculation unit 6, and outputs drive signals S1 to S6 according to the comparison results to the 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 a high-level drive signal S1 and a low-level drive signal S2. When the U-phase voltage command value Vu* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S1 and a high-level drive signal S2. When the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S3 and a low-level drive signal S4. When the V-phase voltage command value Vv* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S3 and a high-level drive signal S4. When the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S5 and a low-level drive signal S6. When the W-phase voltage command value Vw* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S5 and a high-level drive signal S6.

The calculation unit 6 is configured by a microcomputer and includes a current conversion unit 7, a resistance estimation unit 8, a temperature estimation unit 9, a position estimation unit 10, a subtraction unit 11, a torque command value calculation 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. For example, the microcomputer executes a program stored in the storage unit 4 to configure the current conversion unit 7, the resistance estimation unit 8, the temperature estimation unit 9, the position estimation unit 10, the subtraction unit 11, the torque command value calculation unit 12, the current command value output unit 13, the subtraction unit 14, the subtraction unit 15, the voltage command value calculation unit 16, and the voltage command value conversion unit 17.

The current conversion unit 7 uses the U-phase current Iu detected by the current sensor Se1 and the V-phase current Iv detected by the current sensor Se2 to determine the W-phase current Iw flowing through the W-phase of the motor M.

The current converter 7 also converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw into a d-axis current Id (current component for generating a weakened field in the motor M) and a q-axis current Iq (current component for generating torque in the motor M) using the rotor position θ^ (phase angle) of the motor M estimated by the position estimator 10.

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 the following formula 2.

The currents detected by the current sensors Se1 and Se2 are not limited to the combination of U-phase current Iu and V-phase current Iv, but may be the combination of V-phase current Iv and W-phase current Iw, or the combination of U-phase current Iu and W-phase current Iw. When the current sensors Se1 and Se2 detect the V-phase current Iv and W-phase current Iw, the current conversion unit 7 uses the V-phase current Iv and W-phase current Iw to determine the U-phase current Iu. When the current sensors Se1 and Se2 detect the U-phase current Iu and W-phase current Iw, the current conversion unit 7 uses the U-phase current Iu and W-phase current Iw to determine the V-phase current Iv.

If the inverter circuit 2 further includes a current sensor Se3 that detects the current flowing through the W-phase of the motor M in addition to the current sensors Se1 and Se2, the current conversion unit 7 may be configured 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 a d-axis current Id and a q-axis current Iq using the position θ^ estimated by the position estimation unit 10.

The resistance estimation unit 8 estimates the resistance value (resistance component) R^ of the electric motor M using the following formula 1. Note that Ts is a predetermined period of the period T0 during which the upper arm switching elements SW1, SW3, SW5 or the lower arm switching elements SW2, SW4, SW6 of each phase of the inverter circuit 2 are all on, and is set to a period during which at least the d-axis voltage command value Vd* becomes zero, as shown in FIG. 2(a), for example. The predetermined period Ts is set to a period equal to or 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 set to the same period as the period T0. Also, id(n) and id(n-1) are d-axis currents Id output from the current converter 7. For example, as shown in FIG. 2B, id(n) is the d-axis current Id at time t1 (first time) in the predetermined period Ts, and id(n-1) is the d-axis current Id at time t0 (second time) before time t1 in the period Ts. In FIG. 2, time t1 is the timing immediately before the d-axis voltage command value Vd* changes from zero to a negative value, but may be set to any time within the period Ts. Also, time t0 is the timing immediately after the d-axis voltage command value Vd* changes from a negative value to zero, but may be set to any time within the predetermined period Ts as long as it is a time before time t1. Also, iq(n-1) is the q-axis current Iq output from the current converter 7. For example, as shown in FIG. 2C, id(n) is the q-axis current Iq at time t0. Furthermore, R^ is the resistance value of the motor M, and ω is the rotor rotation speed (angular velocity) ω^ estimated by the position estimation unit 10. Furthermore, Ld is the d-axis inductance of the motor M, and Lq is the q-axis inductance of the motor M. Furthermore, it is assumed that the d-axis inductance Ld and the q-axis inductance Lq do not vary with temperature changes of the motor M.

id(n)-id(n-1)=Ts×{-R^/Ld×id(n-1)+ω×Lq/Ld×iq(n-1)}...Formula 1

The above formula 1 is derived through the following process.

First, the voltage equation corresponding to the model of the electric motor M is expressed as the following formula 3. Note that Vd is the d-axis voltage command value Vs* calculated by the voltage command value calculation unit 16, and Vq is the q-axis voltage command value Vq* calculated by the voltage command value calculation unit 16. Furthermore, 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 rotation speed ω^ estimated by the position estimation unit 10. Furthermore, id is the d-axis current Id output from the current conversion unit 7, and iq is the q-axis current Iq output from the current conversion unit 7. Furthermore, L is the inductance of the electric motor M, and Ψa is the induced voltage of the electric motor M.

Next, the above formula 3 is transformed into the following formula 4 by time differentiation over a predetermined period Ts.

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

In this way, the resistance value R^ is estimated using the d-axis current Id and the q-axis current Iq during a predetermined period Ts (i.e., the period when at least the d-axis voltage command value Vd* is zero) within the period T0 when the upper arm switching elements SW1, SW3, SW5 or the lower arm switching elements SW2, SW4, SW6 of each phase of the inverter circuit 2 are all on. Since the above equation 1 does not include parameters for the d-axis voltage command value Vd* or the q-axis voltage command value Vq*, the resistance value R^ can be estimated without being affected by errors contained in the d-axis voltage command value Vd* or the q-axis voltage command value Vq* due to operational delays of the switching elements SW1 to SW6 of the inverter circuit 2. In addition, since all terms on the right and left sides of the above formula 1 include parameters for the d-axis current Id and the q-axis current Iq, the gain of the amplifiers in the current sensors Se1 and Se2 can offset errors contained in the parameters for the d-axis current Id and the q-axis current Iq, and the resistance value R^ can be estimated without being affected by these errors. In addition, since the above formula 1 does not include a parameter for the induced voltage Ψa, the resistance value R^ can be estimated without being affected by fluctuations in the induced voltage Ψa that accompany temperature changes. This improves the accuracy of estimating the resistance value R^ of the motor M.

For example, the resistance estimation unit 8 estimates the resistance value R^ using system identification. That is, 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, the resistance estimation unit 8 repeats the calculation of the following formula 6 to determine R^ as the resistance value R^ of the electric motor M when the difference between Q and Q^ becomes zero.

R^ = γ × ∫ (Q - Q^) dt ... Equation 6

The resistance value R^ may be estimated by calculating the following formula 7, which is obtained by modifying the above formula 1 with respect to R^, and the method for 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}... Formula 7

The temperature estimation unit 9 shown in FIG. 1 estimates the temperature T^ of the electric motor M using the resistance value R^ estimated by the resistance estimation unit 8. The temperature T^ may be calculated by a calculation using the resistance value R^ and a coefficient, or may be calculated by referring to information that corresponds the temperature and resistance value of the electric motor M to each other and is stored in advance in the memory unit 4; there is no particular limitation on the method of estimating the temperature T^. The temperature T^ estimated by the temperature estimation unit 9 may be used to correct various command values that vary with temperature changes, such as the torque command value T* described below.

The position estimation unit 10 estimates the rotation speed ω^ and the position θ^.

For example, the position estimation unit 10 estimates ω as the rotation speed ω^ by substituting the d-axis current Id and q-axis current Iq output from the current conversion unit 7, the d-axis voltage command value Vd* and q-axis voltage command value Vq* calculated by the voltage command value calculation unit 16, and the resistance value R^ estimated by the resistance estimation unit 8 into the voltage equation shown in the above formula 3. The position estimation unit 10 also estimates the result of multiplying the rotation speed ω^ by a unit time (for example, the clock period of the calculation unit 6) as the position θ^.

The position estimation unit 10 may be configured to use a resistance value R^ or the like to determine an extended induced voltage excited by superimposing a high-frequency voltage on the d-axis voltage command value Vd* calculated by the voltage command value calculation unit 16, and to estimate the rotor position θ^ from the phase of the extended induced voltage. When configured in this way, the position estimation unit 10 estimates the rotation speed ω^ by dividing the position θ^ by a unit time (for example, the clock period of the calculation unit 6).

The subtraction unit 11 calculates the 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 calculation unit 12 calculates the torque command value T* using the rotation speed difference Δω output from the subtraction unit 11. For example, the torque command value calculation unit 12 refers to information (not shown) stored in the memory unit 4 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, and determines the torque corresponding to the rotation speed equivalent to the rotation speed difference Δω as the torque command value T*. Note that the torque command value calculation unit 12 may increase the torque command value T* as the temperature T^ estimated by the temperature estimation unit 9 increases. This makes it difficult for a current to flow through the electric motor M as the temperature T^ increases, and the strength of the magnetic field of the permanent magnet decreases, thereby preventing a decrease in the torque generated in the electric motor M.

The current command value output unit 13 uses the torque command value T* to output the d-axis current command value Id* and the q-axis current command value Iq*. For example, the current command value output unit 13 refers to information (not shown) stored in the memory unit 4 in which the torque of the motor M is associated with the d-axis current command value Id* and the q-axis current command value Iq*, and determines the d-axis current command value Id* and the q-axis current command value Iq* that correspond 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 ω^ and the rotation speed command value ω*.

The subtraction unit 14 calculates the 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 the 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. For example, the voltage command value calculation unit 16 calculates the d-axis voltage command value Vd* by calculating the following formula 8, and calculates the q-axis voltage command value Vq* by calculating the following formula 9. Note that Kp is a constant for the proportional term of the PI control, Ki is a constant for the integral term of the PI control, Lq is the q-axis inductance of the motor M, Ld is the d-axis inductance of the motor M, ω is the rotation speed ω^ estimated by the position estimation unit 10, and Ψa is the induced voltage.

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

q-axis voltage command value Vq* = Kp x difference ΔIq + ∫ (Ki x 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* is small, and calculates the q-axis voltage command value Vq* so that the difference ΔIq between the q-axis current Iq and the q-axis current command value Iq* is small.

The voltage command value converter 17 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using the position θ^ estimated by the position estimator 10. For example, the voltage command value converter 17 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using a conversion matrix C2 shown in the following formula 10.

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

In this way, according to the embodiment of the control device 1 for the electric motor M, the resistance value R^ of the electric motor M can be accurately estimated while the electric motor M is being driven.

In addition, 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 accurately estimated, thereby improving the estimation accuracy of the temperature T^ of the electric motor M estimated using the resistance value R^.

In addition, in the embodiment of the control device 1 for the electric motor M, since the temperature T^ of the electric motor M can be estimated, there is no need to provide a temperature sensor to detect the temperature of the electric motor M, and therefore the control device 1 can be made smaller.

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

<Modification 1>
Fig. 3 is a diagram showing another example of the motor control device according to the embodiment. Note that the same components as those shown in Fig. 1 are given the same reference numerals, and the description thereof will be omitted.

The control device 1 shown in FIG. 3 differs from the control device 1 shown in FIG. 1 in that it includes a position detection unit Sp (such as a resolver) that detects the rotor position θ^ (phase angle) of the electric motor M and outputs the detected position θ^ to the control circuit 3, and that it includes a rotation speed calculation unit 18 instead of the position estimation unit 10 of the calculation unit 6.

The rotation speed calculation unit 18 calculates the rotation speed ω^ using the position θ^ detected by the position detection unit Sp. For example, the rotation speed calculation unit 18 obtains the rotation speed ω^ by dividing the position θ^ by a predetermined time (for example, the clock period of the calculation unit 6).

Even in a control device 1 configured in this manner, 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 estimation unit 8 (control circuit 3) may be configured to set the moving average of multiple resistance values obtained by setting two adjacent times, t1 and t0, among three or more times within a specified period Ts as the resistance value R^ of the motor M.

For example, as shown in FIG. 4 , assume that an arbitrary time within a predetermined period Ts is _tα , a time before time _tα is _tβ , a time before time _tβ is _tγ , the d-axis current corresponding to time _tα is _idα , the d-axis current corresponding to time _tβ is _idβ , the d-axis current corresponding to time _tγ is _idγ , the q-axis current corresponding to time _tβ is _iqβ , and the q-axis current corresponding to time _tγ is _iqγ .

First, the resistance estimation unit 8 sets two adjacent times t _β and t _γ to times t1 and t0, sets the d-axis current id _β to id(n), the d-axis current id _γ to id(n-1), and the q-axis current iq _γ to iq(n-1), and estimates the resistance value R^ _βγ using the above equation 1.

Next, the resistance estimation unit 8 sets two adjacent times t _α and t _β to times t1 and t0, sets the d-axis current id _α to id(n), the d-axis current id _β to id(n-1), and the q-axis current iq _β to iq(n-1), and estimates the resistance value R^ _αβ using the above equation 1.

Then, the resistance estimating unit 8 divides the sum of the resistance value R^ _βγ and the resistance value R^ _αβ by 2 to obtain the resistance value R^.

This makes it possible to estimate the resistance value R^ of the motor M while suppressing the influence of errors contained in each of the multiple resistance values R^ (resistance value R^ _βγ and resistance value R^ _αβ ) before calculating the average, thereby further improving the estimation accuracy of the resistance value R^ of the motor M.

REFERENCE SIGNS LIST 1 Control device 2 Inverter circuit 3 Control circuit 4 Memory 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 Rotational 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;
a control circuit that converts a current flowing through the motor into a d-axis current and a q-axis current, estimates a resistance value of the motor, and turns on and off the multiple switching elements by vector control using at least the d-axis current, the q-axis current, and the resistance value;
Equipped with
The control circuit estimates the resistance value of the motor using the following formula 1, where Ts is a predetermined period during which all switching elements of the upper arm or lower arm of each phase of the inverter circuit are on, id(n) is the d-axis current at a first time within the predetermined period, id(n-1) is the d-axis current at a second time prior to the first time within the predetermined period, iq(n-1) is the q-axis current at the second time, R^ is the resistance value of the motor, Ld is the d-axis inductance of the motor, Lq is the q-axis inductance of the motor, and ω is the rotation speed of the rotor: id(n)-id(n-1)=Ts×{-R^/Ld×id(n-1)+ω×Lq/Ld×iq(n-1)} ...Formula 1
A control device for an electric motor. The 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 a voltage value of a carrier wave and a voltage command value;
The control circuit includes:
a position estimating unit that estimates a position of a rotor of the electric motor using the resistance value;
a current converter for converting a current flowing through 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 according to a difference between a rotation speed of the rotor and a rotation speed command value;
a voltage command value calculation unit that calculates a d-axis voltage command value so as to reduce a difference between the d-axis current and the d-axis current command value, and calculates a q-axis voltage command value so as to reduce a difference between the q-axis current and the q-axis current 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 motor control device according to claim 1 or 2,
The control circuit determines, as the resistance value of the motor, a moving average of multiple resistance values obtained by setting two adjacent times among three or more times within the specified period as the first time and the second time.

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