JP7578041B2 - Motor Control Device - Google Patents

Description

This disclosure relates to a motor control device.

A motor control device that controls the drive of a motor has a switching module that generates a three-phase AC voltage (hereinafter sometimes referred to as a "three-phase voltage") that is applied to the motor. The switching module is composed of multiple switching elements. The switching module is sometimes called an inverter.

When vector control is used for the motor control device, the motor control device generates a d-axis current command value and a q-axis current command value so that the motor rotation speed matches the speed command value (target speed), and generates a d-axis voltage command value and a q-axis voltage command value from the d-axis current command value and the q-axis current command value. Furthermore, the motor control device converts the d-axis voltage command value and the q-axis voltage command value into three-phase voltage command values.

PWM (Pulse Width Modulation) is known as a technique for controlling a switching module based on three-phase voltage command values. PWM is a technique for changing the output voltage (i.e., three-phase voltage) of a switching module by adjusting the on/off time of multiple switching elements that make up the switching module. A signal (hereinafter sometimes referred to as a "PWM signal") that controls the on/off of the switching elements is generated based on the result of comparing a carrier signal, which is the carrier wave of the PWM, with a comparison value. By controlling the on/off of the switching elements according to the PWM signal, a three-phase voltage is applied to the motor, controlling the drive of the motor.

There is also known a technology (hereinafter sometimes referred to as the "position sensorless method") that controls the drive of a motor without using a sensor (hereinafter sometimes referred to as the "position sensor") for detecting the rotational position of the motor rotor (hereinafter sometimes referred to as the "rotor position"). In the position sensorless method, the rotor position is estimated without using a position sensor by detecting the three-phase current (hereinafter sometimes referred to as the "motor current") that flows through the motor.

The "single-shunt detection method" is also known as a method for detecting motor current. In the single-shunt detection method, two phases of the motor current are detected based on the bus current flowing between the DC power supply and the switching module that generates the three-phase voltage, and the remaining one phase of current is calculated from the two phases of current using Kirchhoff's law.

Here, a prior art has been proposed in which a first connection line that transmits an amplified voltage obtained by amplifying the voltage generated across a shunt resistor for detecting a bus current to a first A/D converter and a second connection line that transmits an offset voltage generated by an offset voltage generating unit to a second A/D converter are arranged so as to be as equally affected by noise as possible. In this prior art, when noise is superimposed on the first connection line, noise is also superimposed on the second connection line, so that a determination is made as to whether or not a large noise is superimposed on the bus current (hereinafter, sometimes referred to as "noise determination") by determining whether or not the offset voltage is a voltage outside a predetermined range. In addition, in this prior art, when the offset voltage is a voltage outside a predetermined range, it is determined that the influence of noise is large, and the amplified voltage as the bus current detected simultaneously with the offset voltage is discarded, and when the offset voltage is within a predetermined range, a PWM signal is generated based on the bus current detected simultaneously with the offset voltage. In this way, it becomes possible to control the motor using a current value that is less affected by noise (i.e., a current value with high accuracy).

JP 2015-126555 A

In the above prior art, when making a noise judgment, it is necessary to sample the offset voltage at the same time as sampling the amplified voltage, so a separate circuit for acquiring the offset voltage and a second A/D converter for sampling the offset voltage are required. For this reason, in the above prior art, when controlling the motor using a highly accurate current value, the number of parts in the motor control device increases.

Therefore, this disclosure proposes a technology that can control a motor using highly accurate current values while minimizing an increase in the number of parts in a motor control device.

The motor control device of the present disclosure includes a switching module, a detection unit, a first calculation unit, a conversion unit, a prediction unit, and a determination unit. The switching module converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor. The detection unit detects a bus current of the switching module using a resistor connected between the DC power source and the switching module. The first calculation unit calculates a three-phase current of a fixed coordinate system in the motor based on the bus current. The conversion unit converts the three-phase current into a two-phase current of a rotating coordinate system. The prediction unit calculates a predicted value of the two-phase current according to a motor model formula of the motor. The determination unit determines whether the two-phase current or the predicted value is to be used to control the motor based on the two-phase current and the predicted value.

The disclosed technology makes it possible to control a motor using highly accurate current values while minimizing an increase in the number of parts in a motor control device.

FIG. 1 is a diagram illustrating a configuration example of a motor control device according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating an example of the configuration of a noise determination unit according to the first embodiment of the present disclosure. FIG. 3 is a diagram illustrating a configuration example of a noise determination unit according to the second embodiment of the present disclosure. FIG. 4 is a diagram illustrating an example of the operation of the noise component extraction unit according to the second embodiment of the present disclosure.

Below, examples of the present disclosure will be described with reference to the drawings. In the following examples, the same components are given the same reference numerals.

[Example 1]
<Configuration of the motor control device>
FIG. 1 is a diagram showing a configuration example of a motor control device according to a first embodiment of the present disclosure. The motor control device 100 shown in FIG. 1 controls the driving of a motor M using a position sensorless method, a one-shunt detection method, and PWM. In FIG. 1, the motor control device 100 includes subtraction units 46, 47, and 52, a d-axis current setting unit 48, a speed control unit 49, a d-axis and q-axis voltage setting unit 45, a dq/3φ conversion unit 43, a PWM unit 41, a switching module 10, a DC power supply E _DC , and a shunt resistor Rs. The motor control device 100 also includes a DC voltage detection unit 31, a current detection unit 21, AD conversion units 71 and 72, a 3φ current calculation unit 61, a DC voltage calculation unit 32, a 3φ/dq conversion unit 42, a position and speed estimation unit 44, a 1/Pn processing unit 51, and a noise determination unit 80.

The subtraction units 46, 47, 52, the d-axis current setting unit 48, the speed control unit 49, the d-axis/q-axis voltage setting unit 45, the dq/3φ conversion unit 43, the PWM unit 41, the DC voltage detection unit 31, the current detection unit 21, the AD conversion units 71, 72, the 3φ current calculation unit 61, the DC voltage calculation unit 32, the 3φ/dq conversion unit 42, the position/speed estimation unit 44, the 1/Pn processing unit 51, and the noise determination unit 80 are realized as hardware, for example, by an MCU (Micro Control Unit).

The switching module 10 also has upper arm switching elements SWup, SWvp, and SWwp, and lower arm switching elements SWun, SWvn, and SWwn.

In the motor control device 100, the d-axis current setting unit 48 outputs a predetermined d-axis current command value id ^* to the subtraction unit 46.

The subtraction unit 46 receives the d-axis current command value id ^* from the d-axis current setting unit 48, and receives the d-axis current id from the noise determination unit 80. The subtraction unit 46 calculates the d-axis current deviation Δid by subtracting the d-axis current id from the d-axis current command value id ^* , and outputs the calculated d-axis current deviation Δid to the d-axis/q-axis voltage setting unit 45.

The speed control unit 49 calculates the q-axis current command value iq ^* so that the speed deviation Δω input from the subtraction unit 52 approaches zero, and outputs the calculated q-axis current command value iq ^* to the subtraction unit 47.

The subtraction unit 47 receives the q-axis current command value iq ^* from the speed control unit 49 and the q-axis current iq from the noise determination unit 80. The subtraction unit 47 calculates the q-axis current deviation Δiq by subtracting the q-axis current iq from the q-axis current command value iq ^*, and outputs the calculated q-axis current deviation Δiq to the d-axis/q-axis voltage setting unit 45.

The d-axis/q-axis voltage setting unit 45 receives the d-axis current deviation Δid from the subtraction unit 46, the q-axis current deviation Δiq from the subtraction unit 47, and the d-axis current id and the q-axis current iq from the noise determination unit 80. The d-axis/q-axis voltage setting unit 45 calculates a d-axis voltage command value Vd ^* and a q-axis voltage command value Vq ^* so that the d-axis current deviation Δid and the q-axis current deviation Δiq approach zero, and outputs the calculated d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* to the position/speed estimation unit 44, the dq/3φ conversion unit 43, and the noise determination unit 80. The d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* also change according to the U-phase current iu, the V-phase current iv, and the W-phase current iw, which are the motor currents calculated by the 3φ current calculation unit 61.

The position/speed estimator 44 receives the d-axis current id and the q-axis current iq from the noise determiner 80, and receives the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* from the d-axis/q-axis voltage setting unit 45. The position/speed estimator 44 estimates the electrical angular velocity ωe of the motor M and the rotational phase angle θdq of the motor M in the rotating coordinates (dq coordinates ⁾ based on the d-axis current id, the q-axis current iq, the d-axis voltage command value Vd ^* , and the q-axis voltage command value Vq*. The position/speed estimator 44 outputs the estimated angular velocity ωe to the 1/Pn processor 51 and the noise determiner 80, and outputs the estimated rotational phase angle θdq to the 3φ/dq converter 42 and the dq/3φ converter 43.

The 1/Pn processing unit 51 converts the electrical angular velocity ωe into the mechanical angular velocity ωm of the rotor of the motor M by dividing the angular velocity ωe by the number of pole pairs of the motor M, and outputs the converted angular velocity ωm to the subtraction unit 52.

The subtraction unit 52 receives the angular velocity ωm from the 1/Pn processing unit 51, and receives a speed command value ωm ^* from outside the motor control device 100 (for example, from a higher-level controller of the motor control device 100). The subtraction unit 52 calculates a speed deviation Δω by subtracting the angular velocity ωm from the speed command value ωm ^* , and outputs the calculated speed deviation Δω to the speed control unit 49.

The dq/3φ conversion unit 43 converts the two-phase d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* in the rotating coordinates into three-phase voltage command values Vu ^* , Vv ^* , Vw ^* in the fixed coordinates (UVW coordinates) using the rotation phase angle θdq. The dq/3φ conversion unit 43 outputs the converted voltage command values Vu ^* , Vv ^* , Vw ^* to the PWM unit 41.

The PWM unit 41 receives the voltage command values Vu ^* , Vv ^* , Vw ^* from the dq/3φ conversion unit 43 and receives the DC voltage Vdc from the DC voltage calculation unit 32. A carrier signal, which is a PWM carrier wave, is also input to the PWM unit 41 from outside the motor control device 100 (for example, from a higher-level controller of the motor control device 100). The PWM unit 41 generates three-phase PWM signals Up, Un, Vp, Vn, Wp, Wn based on the voltage command values Vu ^* , Vv ^* , Vw ^* , the DC voltage Vdc, and the carrier signal, and outputs the generated PWM signals Up, Un, Vp, Vn, Wp, Wn to the switching module 10 and the 3φ current calculation unit 61.

The switching module 10 is supplied with a DC voltage from a DC power supply E _DC , and receives PWM signals Up, Un, Vp, Vn, Wp, and Wn from a PWM unit 41. The switching module 10 converts the DC voltage supplied from the DC power supply E _DC into a three-phase AC voltage in accordance with the PWM signals Up to Wn, and applies the converted three-phase AC voltage to a motor M. The motor M is driven by applying the three-phase AC voltage to the motor M. In the switching module 10, the switching elements SWup, SWun, SWvp, SWvn, SWwp, and SWwn are turned on/off in accordance with the PWM signals Up, Un, Vp, Vn, Wp, and Wn, thereby converting the DC voltage into a three-phase voltage. Freewheeling diodes Dup, Dun, Dvp, Dvn, Dwp, and Dwn are connected to both ends of each of the switching elements SWup, SWun, SWvp, SWvn, SWwp, and SWwn.

The current detection unit 21 detects the bus current Is of the switching module 10 by using a shunt resistor Rs connected between the DC power supply E _DC and the switching module 10. The shunt resistor Rs is arranged on an N line _LN which is a DC line between an N-side terminal of the DC power supply E _DC and the switching module 10. The shunt resistor Rs may be arranged on a P line _LP which is a DC line between a P-side terminal of the DC power supply E _DC and the switching module 10. A bus current Is corresponding to a U-phase current, a V-phase current, and a W-phase current which are motor currents and a PWM signal flows through the shunt resistor Rs, and when the bus current Is flows through the shunt resistor Rs, a voltage drop occurs across the shunt resistor Rs. The current detection unit 21 detects the bus current Is flowing through the shunt resistor Rs from the magnitude of this voltage drop and the resistance value of the shunt resistor Rs. Furthermore, the current detection unit 21 calculates an analog voltage VA1 expressed by equation (1) based on the shunt resistance Rs and the bus current Is, and outputs the calculated analog voltage VA1 to the AD conversion unit 72. "k" in equation (1) represents a predetermined amplification factor.
VA1=k×(Rs・Is)…(1)

The AD conversion unit 72 samples the analog voltage VA1 to convert it into a digital voltage value VA2, and outputs the converted digital voltage value VA2 to the 3φ current calculation unit 61.

The 3φ current calculation unit 61 calculates the motor current using a single shunt detection method. The 3φ current calculation unit 61 calculates the motor currents U-phase current iu, V-phase current iv, and W-phase current iw based on the resistance value of the shunt resistor Rs, the amplification factor k, the digital voltage value VA2, and the PWM signals Up to Wn, and outputs the calculated motor currents iu, iv, and iw to the 3φ/dq conversion unit 42.

The 3φ/dq conversion unit 42 converts the motor currents iu, iv, and iw, which indicate the three-phase current vector of the fixed coordinate system, into d-axis current and q-axis current, which indicate the two-phase current vector of the rotating coordinate system, using the rotation phase angle θdq input from the position and speed estimation unit 44. Hereinafter, the d-axis current after conversion by the 3φ/dq conversion unit 42 may be referred to as the "detected d-axis current," and the q-axis current after conversion by the 3φ/dq conversion unit 42 may be referred to as the "detected q-axis current." The 3φ/dq conversion unit 42 outputs the detected d-axis current id_det and the detected q-axis current iq_det to the noise determination unit 80.

The noise determination unit 80 receives the detected d-axis current id_det and the detected q-axis current iq_det from the 3φ/dq conversion unit 42, the angular velocity ωe from the position/speed estimation unit 44, and the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* from the d-axis/q-axis voltage setting unit 45. The noise determination unit 80 performs noise determination, and determines the d-axis current id to be output to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, and the subtraction unit 46, and the q-axis current iq to be output to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, and the subtraction unit 47, based on the result of the noise determination. Details of the noise determination unit 80 will be described later.

The DC voltage detection unit 31 detects a bus voltage between the P line _LP and the N line _LN , and outputs the detected analog bus voltage VB1 to the AD conversion unit 71.

The AD conversion unit 71 samples the analog bus voltage VB1 to convert it into a digital bus voltage value VB2, and outputs the converted digital bus voltage value VB2 to the DC voltage calculation unit 32.

The DC voltage calculation unit 32 calculates the DC voltage Vdc from the digital bus voltage value VB2 and outputs the calculated DC voltage Vdc to the PWM unit 41.

<Configuration of Noise Determination Unit>
2 is a diagram showing a configuration example of a noise determination unit according to the first embodiment of the present disclosure. In FIG. 2, the noise determination unit 80 includes a current prediction unit 81, a difference calculation unit 82, and a current determination unit 83. The current prediction unit 81 receives the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* from the d-axis/q-axis voltage setting unit 45, and receives the angular velocity ωe from the position/speed estimation unit 44. The difference calculation unit 82 and the current determination unit 83 receive the detected d-axis current id_det and the detected q-axis current iq_det from the 3φ/dq conversion unit 42.

Here, the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* are expressed by the motor model formulas shown in formulas (2.1) and (2.2). In formulas (2.1) and (2.2), "R" is the winding resistance of the motor M, "id" is the d-axis current output from the current determination unit 83 at the previous control timing (hereinafter may be referred to as the "previous d-axis current"), "p" is the differential operator of (d/dt), "Ld" is the d-axis inductance of the motor M, "ωe" is the angular velocity input from the position/speed estimation unit 44, "Lq" is the q-axis inductance of the motor M, "iq" is the q-axis current output from the current determination unit 83 at the previous control timing (hereinafter may be referred to as the "previous q-axis current"), and "Ψ" is the flux linkage of the motor M. The winding resistance R, the d-axis inductance Ld, the q-axis inductance Lq, and the flux linkage Ψ are parameters that determine the characteristics of the motor M (hereinafter, may be referred to as “motor parameters”).
Vd ^* = R・id+p・Ld・id−ωe・Lq・iq…(2.1)
Vq ^* = R・iq+p・Lq・iq+ωe・Ld・id+ωe・Ψ…(2.2)

Furthermore, when the carrier frequency fc in the motor control device 100 is used, formulas (2.1) and (2.2) can be transformed into formulas (3.1) and (3.2). In formulas (3.1) and (3.2), "ΔId" is the amount of change (hereinafter sometimes referred to as "d-axis current change") in the d-axis current predicted to be output from the current determination unit 83 at the current control timing (hereinafter sometimes referred to as "predicted d-axis current") relative to the previous d-axis current, and "ΔIq" is the amount of change (hereinafter sometimes referred to as "q-axis current change") in the q-axis current predicted to be output from the current determination unit 83 at the current control timing (hereinafter sometimes referred to as "predicted q-axis current") relative to the previous q-axis current.
Vd ^* =R・id+Ld・ΔId・fc−ωe・Lq・iq…(3.1)
Vq ^* = R・iq+Lq・ΔIq・fc+ωe・Ld・id+ωe・Ψ…(3.2)

By solving equations (3.1) and (3.2) for the d-axis current change amount and the q-axis current change amount, equations (4.1) and (4.2) are obtained.
ΔId=(Vd ^* -R・id+ωe・Lq・iq)/(Ld・fc)…(4.1)
ΔIq=(Vq ^* -R・iq−ωe・Ld・id−ωe・Ψ)/(Lq・fc)
…(4.2)

Therefore, the current prediction unit 81 calculates the predicted d-axis current id_pre and the predicted q-axis current iq_pre according to equations (5.1) and (5.2) using the previous d-axis current id determined by the current determination unit 83 at the previous control timing and input from the current determination unit 83, and the previous q-axis current iq determined by the current determination unit 83 at the previous control timing and input from the current determination unit 83.
id_pre=id+ΔId...(5.1)
iq_pre=iq+ΔIq...(5.2)

In this way, the current prediction unit 81 calculates the predicted d-axis current id_pre and the predicted q-axis current iq_pre that are theoretically derived according to the motor model equation of the motor M, and outputs the calculated predicted d-axis current id_pre and the predicted q-axis current iq_pre to the difference calculation unit 82 and the current determination unit 83.

The difference calculation unit 82 calculates the difference id_dif between the detected d-axis current id_det and the predicted d-axis current id_pre (hereinafter sometimes referred to as the “d-axis difference”) and the difference iq_dif between the detected q-axis current iq_det and the predicted q-axis current iq_pre (hereinafter sometimes referred to as the “q-axis difference”) in accordance with equations (6.1) and (6.2). The difference calculation unit 82 outputs the calculated d-axis difference id_dif and q-axis difference iq_dif to the current determination unit 83.
id_dif=id_det-id_pre...(6.1)
iq_dif=iq_det−iq_pre…(6.2)

The d-axis difference id_dif and the q-axis difference iq_dif are the differences between the detected values and the predicted values of the d-axis current and the q-axis current. If the detected values and the predicted values differ greatly, it is possible that noise is superimposed on the detected values of the d-axis current and the q-axis current. In addition, the d-axis difference id_dif and the q-axis difference iq_dif may become positive or negative depending on the superimposed noise. The current determination unit 83 performs noise determination by comparing the d-axis difference id_dif and the q-axis difference iq_dif with a predetermined first threshold TH1, which is a negative value, and a predetermined second threshold TH2, which is a positive value, to determine the d-axis current id and the q-axis current iq at the current control timing.

The first threshold value TH1 is set to a negative value smaller than the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif can be obtained in advance by testing. When the bottom values of the steady d-axis difference id_dif and q-axis difference iq_dif are -0.8 [A], the first threshold value TH1 is set to a negative value smaller than the bottom values, for example, -1 [A].

Similarly, the second threshold value TH2 is set to a positive value larger than the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif can be obtained in advance by testing. When the peak values of the steady d-axis difference id_dif and q-axis difference iq_dif are 0.8 [A], the second threshold value TH2 is set to a positive value larger than the peak values, for example 1 [A].

When the d-axis difference id_dif is greater than or equal to the first threshold TH1 and less than the second threshold TH2, the current determination unit 83 determines that no noise is superimposed on the detected d-axis current id_det or that the noise superimposed on the detected d-axis current id_det is small, and determines the detected d-axis current id_det as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the detected d-axis current id_det of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis/q-axis voltage setting unit 45, the subtraction unit 46, and the current prediction unit 81. On the other hand, when the d-axis difference id_dif is less than the first threshold TH1 or equal to or greater than the second threshold TH2, the current determination unit 83 determines that the noise superimposed on the detected d-axis current id_det is large, determines the predicted d-axis current id_pre as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the predicted d-axis current id_pre of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 46, and the current prediction unit 81.

In addition, when the q-axis difference iq_dif is greater than or equal to the first threshold value TH1 and less than the second threshold value TH2, the current determination unit 83 determines that no noise is superimposed on the detected q-axis current iq_det or that the noise superimposed on the detected q-axis current iq_det is small, and determines the detected q-axis current iq_det as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the detected q-axis current iq_det, of the detected q-axis current iq_det and the predicted q-axis current iq_pre, to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 47, and the current prediction unit 81. On the other hand, when the q-axis difference iq_dif is less than the first threshold value TH1 or greater than or equal to the second threshold value TH2, the current determination unit 83 determines that the noise superimposed on the detected q-axis current iq_det is large, determines the predicted q-axis current iq_pre as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the predicted q-axis current iq_pre of the detected q-axis current iq_det and the predicted q-axis current iq_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, the subtraction unit 47, and the current prediction unit 81.

The above explains Example 1.

[Example 2]
<Configuration of Noise Determination Unit>
Fig. 3 is a diagram showing a configuration example of a noise determination unit according to the second embodiment of the present disclosure. In Fig. 3, a noise determination unit 80 includes a current prediction unit 81, a difference calculation unit 82, a current determination unit 83, and a noise component extraction unit 84. The operations of the current prediction unit 81 and the difference calculation unit 82 are similar to those of the first embodiment, and therefore will not be described.

The difference calculation unit 82 outputs the calculated d-axis difference id_dif and q-axis difference iq_dif to the noise component extraction unit 84.

Here, the d-axis difference id_dif and the q-axis difference iq_dif include noise components and components other than noise (hereinafter sometimes referred to as "non-noise components"). The noise component extraction unit 84 extracts the d-axis noise components id_no and q-axis noise components iq_no from the d-axis difference id_dif and the q-axis difference iq_dif by removing the non-noise components from the d-axis difference id_dif and the q-axis difference iq_dif, and outputs the extracted d-axis noise components id_no and q-axis noise components iq_no to the current determination unit 83. The d-axis noise components id_no and q-axis noise components iq_no may be positive or negative values.

The current determination unit 83 performs noise determination by comparing the d-axis noise component id_no and the q-axis noise component iq_no with a predetermined third threshold TH3, which is a negative value, and a predetermined fourth threshold TH4, which is a positive value, to determine the d-axis current id and the q-axis current iq at the current control timing.

Here, the third threshold TH3 has a value different from the first threshold TH1. For example, the third threshold TH3 is set to a negative value smaller than the bottom values of the stationary d-axis noise components id_no and q-axis noise components iq_no when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the bottom values of the stationary d-axis noise components id_no and q-axis noise components iq_no can be obtained in advance by testing. When the bottom values of the stationary d-axis noise components id_no and q-axis noise components iq_no are -0.3 [A], the third threshold TH3 is set to a negative value smaller than the bottom values, for example, -0.5 [A].

Similarly, the fourth threshold TH4 has a value different from the second threshold TH2. For example, the fourth threshold TH4 is set to a positive value larger than the peak values of the stationary d-axis noise components id_no and q-axis noise components iq_no when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small. For example, the peak values of the stationary d-axis noise components id_no and q-axis noise components iq_no can be obtained in advance by testing. When the peak values of the stationary d-axis noise components id_no and q-axis noise components iq_no are 0.3 [A], the fourth threshold TH4 is set to a positive value larger than the peak values, for example, 0.5 [A].

The third threshold TH3 and the fourth threshold TH4 may be updated as needed based on the d-axis noise component id_no and the q-axis noise component iq_no. For example, when no noise is superimposed on the detected d-axis current id_det and the detected q-axis current iq_det, or when the noise superimposed on the detected d-axis current id_det and the detected q-axis current iq_det is small, the peak value and bottom value of the d-axis noise component id_no and the q-axis noise component iq_no may be updated as needed, a value with a margin set to the larger of the absolute values of the peak value and the bottom value may be calculated, the calculated value may be set as the fourth threshold TH4, and a value with a negative sign added to the calculated value may be set as the third threshold TH3.

When the magnitude of the d-axis noise component id_no is greater than or equal to the third threshold TH3 and less than the fourth threshold TH4, the current determination unit 83 determines that no noise is superimposed on the detected d-axis current id_det or that the noise superimposed on the detected d-axis current id_det is small, determines the detected d-axis current id_det as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the detected d-axis current id_det of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, and the subtraction unit 46. On the other hand, when the magnitude of the d-axis noise component id_no is less than the third threshold TH3 or equal to or greater than the fourth threshold TH4, the current determination unit 83 determines that the noise superimposed on the detected d-axis current id_det is large, determines the predicted d-axis current id_pre as the d-axis current id to be used for controlling the motor M at the current control timing, and outputs the predicted d-axis current id_pre of the detected d-axis current id_det and the predicted d-axis current id_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, and the subtraction unit 46.

In addition, when the magnitude of the q-axis noise component iq_no is greater than or equal to the third threshold TH3 and less than the fourth threshold TH4, the current determination unit 83 determines that no noise is superimposed on the detected q-axis current iq_det or that the noise superimposed on the detected q-axis current iq_det is small, determines the detected q-axis current iq_det as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the detected q-axis current iq_det, of the detected q-axis current iq_det and the predicted q-axis current iq_pre, to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, and the subtraction unit 47. On the other hand, when the magnitude of the q-axis noise component iq_no is less than the third threshold TH3 or equal to or greater than the fourth threshold TH4, the current determination unit 83 determines that the noise superimposed on the detected q-axis current iq_det is large, determines the predicted q-axis current iq_pre as the q-axis current iq to be used for controlling the motor M at the current control timing, and outputs the predicted q-axis current iq_pre of the detected q-axis current iq_det and the predicted q-axis current iq_pre to the position/speed estimation unit 44, the d-axis and q-axis voltage setting unit 45, and the subtraction unit 47.

Here, examples of non-noise components include frequency components (hereinafter sometimes referred to as "rotation order components") that depend on the order of the rotation frequency of the motor M (hereinafter sometimes referred to as "rotation order"), frequency components (hereinafter sometimes referred to as "calculation delay components") that occur due to a delay in the calculation of the predicted d-axis current id_pre and the predicted q-axis current iq_pre, and components (hereinafter sometimes referred to as "parameter error components") that occur due to errors in the motor parameters. An example of a rotation order component is pulsation due to cogging torque. Below, extraction of the d-axis noise component id_no and the q-axis noise component iq_no from the d-axis difference id_dif and the q-axis difference iq_dif will be explained using three extraction examples, extraction examples 1, 2, and 3.

<Extraction Example 1>
In extraction example 1, the noise component extraction unit 84 extracts the d-axis noise component id_no and the q-axis noise component iq_no from the d-axis difference id_dif and the q-axis difference iq_dif by removing the rotation order components from the d-axis difference id_dif and the q-axis difference iq_dif.

The rotational order components include harmonic components, and the order of the frequency at which the rotational order components appear is determined by the number of poles of motor M, the number of slots of motor M, and the rotational speed of motor M. For example, if motor M is an X-pole Y-slot motor with the rotational speed of motor M as the fundamental frequency, the rotational order components appear at the frequency of the least common multiple of X and Y, as shown in Figure 4. Furthermore, rotational order components also appear at frequencies of orders of half, two, three, ..., n times the least common multiple of X and Y. For example, if motor M is a 6-pole 9-slot motor, in addition to the 18th order frequency, which is the least common multiple of 6 and 9, the 9th order frequency, which is half the least common multiple of 6 and 9, and the 18 x n order frequencies of 36th, 54th, ... Therefore, for example, when the rotation speed of the motor M is 30 [rps], the rotation order components appear at frequencies of 270 [Hz], 540 [Hz], 1080 [Hz], 1620 [Hz], ..., 540 x n [Hz]. In this way, the rotation order components appear at specific frequencies. Figure 4 is a diagram for explaining an example of the operation of the noise component extraction unit of the second embodiment of the present disclosure.

Therefore, in extraction example 1, the noise component extraction unit 84 removes the rotational order components from the d-axis difference id_dif and the q-axis difference iq_dif by filtering the d-axis difference id_dif and the q-axis difference iq_dif using a notch filter capable of removing specific frequency components. This allows the d-axis noise component id_no and the q-axis noise component iq_no to be extracted after the rotational order components have been removed from the d-axis difference id_dif and the q-axis difference iq_dif.

<Extraction Example 2>
In extraction example 2, the noise component extraction unit 84 extracts the d-axis noise component id_no and the q-axis noise component iq_no from the d-axis difference id_dif and the q-axis difference iq_dif by removing the calculation delay components from the d-axis difference id_dif and the q-axis difference iq_dif.

Since the calculation delay component is a frequency component that occurs due to the calculation of the predicted d-axis current id_pre and the predicted q-axis current iq_pre, as shown in FIG. 4, the calculation delay component appears at a specific frequency that is the same as the rotation speed of the motor M. For example, when the rotation speed of the motor M is 30 [rps], the calculation delay component appears at a frequency of 30 [Hz].

Therefore, in extraction example 2, the noise component extraction unit 84 removes the calculation delay components from the d-axis difference id_dif and the q-axis difference iq_dif by filtering the d-axis difference id_dif and the q-axis difference iq_dif using a notch filter capable of removing specific frequency components. This allows the d-axis noise component id_no and the q-axis noise component iq_no to be extracted after the calculation delay components have been removed from the d-axis difference id_dif and the q-axis difference iq_dif.

<Extraction Example 3>
In extraction example 3, the noise component extraction unit 84 extracts the d-axis noise component id_no and the q-axis noise component iq_no from the d-axis difference id_dif and the q-axis difference iq_dif by removing parameter error components from the d-axis difference id_dif and the q-axis difference iq_dif.

The actual motor parameters are not fixed values, but values that change depending on the state of the motor M, so an error occurs between the fixed motor parameters set in equations (2.1) and (2.2) and the actual motor parameters. As described above, the predicted d-axis current id_pre and the predicted q-axis current iq_pre are calculated based on equations (2.1) and (2.2) in which fixed motor parameters are set, so that a steady error occurs between the detected d-axis current id_det and the predicted d-axis current id_pre, and between the detected q-axis current iq_det and the predicted q-axis current iq_pre due to the error between the motor parameters. In other words, the parameter error components are so-called offset components that do not have frequency components, as shown in FIG. 4.

Therefore, in extraction example 3, the noise component extraction unit 84 first extracts parameter error components from the d-axis difference id_dif and the q-axis difference iq_dif by filtering the d-axis difference id_dif and the q-axis difference iq_dif using a low-pass filter. Next, the noise component extraction unit 84 removes the extracted parameter error components from the d-axis difference id_dif and the q-axis difference iq_dif. As a result, the d-axis noise component id_no and the q-axis noise component iq_no are extracted after the parameter error components have been removed from the d-axis difference id_dif and the q-axis difference iq_dif.

Extraction examples 1, 2, and 3 have been explained above.

The noise component extraction unit 84 may also remove one or more of the rotation order components, the calculation delay components, and the parameter error components from the d-axis difference id_dif and the q-axis difference iq_dif.

The above explains Example 2.

As described above, the motor control device (motor control device 100 of the embodiment) of the present disclosure has a switching module (switching module 10 of the embodiment), a detection unit (current detection unit 21 of the embodiment), a first calculation unit (3φ current calculation unit 61 of the embodiment), a conversion unit (3φ/dq conversion unit 42 of the embodiment), a prediction unit (current prediction unit 81 of the embodiment), and a determination unit (current determination unit 83 of the embodiment). The switching module converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor (motor M of the embodiment). The detection unit detects the bus current of the switching module using a resistor (shunt resistor Rs of the embodiment) connected between the DC power source and the switching module. The first calculation unit calculates the three-phase current of the fixed coordinate in the motor based on the bus current. The conversion unit converts the three-phase current of the fixed coordinate into two-phase current of the rotating coordinate (detected d-axis current id_det, detected q-axis current iq_det of the embodiment). The prediction unit calculates the predicted values of the two-phase currents (predicted d-axis current id_pre, predicted q-axis current iq_pre in the embodiment) according to the motor model formula of the motor. The determination unit determines whether to use the two-phase currents or the predicted values for motor control based on the two-phase currents of the rotating coordinates and the predicted values of the two-phase currents.

For example, the motor control device of the present disclosure has a second calculation unit (difference calculation unit 82 in the embodiment) that calculates the difference between the two-phase currents and the predicted value (d-axis difference id_dif and q-axis difference iq_dif in the embodiment). The decision unit decides to use the two-phase currents to control the motor when the difference is equal to or greater than a first threshold (first threshold TH1 in the embodiment) and less than a second threshold (second threshold TH2 in the embodiment), and decides to use the predicted value to control the motor when the difference is less than the first threshold or equal to or greater than the second threshold.

In this way, when controlling a motor using a highly accurate current value, the offset voltage required by the above-mentioned prior art is no longer necessary, and therefore a circuit for acquiring the offset voltage and an A/D converter for sampling the offset voltage are no longer necessary. Therefore, it is possible to control a motor using a highly accurate current value while suppressing an increase in the number of parts in a motor control device. In addition, because an A/D converter for sampling the offset voltage is no longer necessary, the A/D converter used to sample the offset voltage can be used for another purpose.

The motor control device of the present disclosure also has an extraction unit (noise component extraction unit 84 in the embodiment) that extracts noise components contained in the difference by removing non-noise components contained in the difference from the difference. The determination unit determines that the two-phase current is used to control the motor when the magnitude of the noise component is equal to or greater than a third threshold (fourth threshold TH3 in the embodiment) and less than a fourth threshold (fourth threshold TH4 in the embodiment), and determines that the predicted value is used to control the motor when the magnitude of the noise component is less than the third threshold or equal to or greater than the fourth threshold.

This can further improve the accuracy of the current values used to control the motor.

For example, the extraction unit extracts the noise components contained in the difference by removing frequency components that depend on the rotational order of the motor from the difference.

For example, the extraction unit also extracts noise components contained in the difference by removing frequency components caused by a delay in the calculation of the predicted value from the difference.

For example, the extraction unit extracts an offset component between the motor parameters included in the motor model formula and the actual motor parameters of the motor from the difference, and extracts the noise component included in the difference by removing the offset component from the difference.

This allows the noise components to be extracted accurately.

REFERENCE SIGNS LIST 100 Motor control device 10 Switching module 21 Current detection section 42 3φ/dq conversion section 61 3φ current calculation section 80 Noise determination section 81 Current prediction section 82 Difference calculation section 83 Current determination section 84 Noise component extraction section

Claims (4)

a switching module that converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor;
a detection unit that detects a bus current of the switching module using a resistor connected between the DC power source and the switching module;
a first calculation unit that calculates three-phase currents of a fixed coordinate system in the motor based on the bus currents;
A conversion unit for converting the three-phase current into a two-phase current in a rotating coordinate system;
a prediction unit that calculates a predicted value of the two-phase current according to a motor model equation of the motor;
a determination unit that determines whether the two-phase currents or the predicted value is to be used for control of the motor based on the two-phase currents and the predicted value;
a second calculation unit that calculates a difference between the two-phase currents and the predicted values;
Equipped with
the determination unit determines that the two-phase currents are to be used for control of the motor when the difference is equal to or greater than a negative first predetermined value that is smaller than a bottom value of the steady difference and is less than a positive second predetermined value that is larger than a peak value of the steady difference, and determines that the predicted value is to be used for control of the motor when the difference is less than the first predetermined value or equal to or greater than the second predetermined value.
Motor control device. a switching module that converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor;
a detection unit that detects a bus current of the switching module using a resistor connected between the DC power source and the switching module;
a first calculation unit that calculates three-phase currents of a fixed coordinate system in the motor based on the bus currents;
A conversion unit for converting the three-phase current into a two-phase current in a rotating coordinate system;
a prediction unit that calculates a predicted value of the two-phase current according to a motor model equation of the motor;
a determination unit that determines whether the two-phase currents or the predicted value is to be used for control of the motor based on the two-phase currents and the predicted value;
a second calculation unit that calculates a difference between the two-phase currents and the predicted values;
an extracting unit that extracts a noise component included in the difference by removing a frequency component that depends on a rotation order of the motor from the difference;
Equipped with
the determination unit determines whether to use the two-phase currents or the predicted value for controlling the motor based on a magnitude of the noise component.
Motor control device. a switching module that converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor;
a detection unit that detects a bus current of the switching module using a resistor connected between the DC power source and the switching module;
a first calculation unit that calculates three-phase currents of a fixed coordinate system in the motor based on the bus currents;
A conversion unit for converting the three-phase current into a two-phase current in a rotating coordinate system;
a prediction unit that calculates a predicted value of the two-phase current according to a motor model equation of the motor;
a determination unit that determines whether the two-phase currents or the predicted value is to be used for control of the motor based on the two-phase currents and the predicted value;
a second calculation unit that calculates a difference between the two-phase currents and the predicted values;
an extraction unit that extracts a noise component included in the difference by removing a frequency component caused by a delay in calculation of the predicted value from the difference;
Equipped with
the determination unit determines whether to use the two-phase current or the predicted value for controlling the motor based on a magnitude of the noise component.
Motor control device. a switching module that converts a DC voltage supplied from a DC power source into an AC voltage and applies the AC voltage to a motor;
a detection unit that detects a bus current of the switching module using a resistor connected between the DC power source and the switching module;
a first calculation unit that calculates three-phase currents of a fixed coordinate system in the motor based on the bus currents;
A conversion unit for converting the three-phase current into a two-phase current in a rotating coordinate system;
a prediction unit that calculates a predicted value of the two-phase current according to a motor model equation of the motor;
a determination unit that determines whether the two-phase currents or the predicted value is to be used for control of the motor based on the two-phase currents and the predicted value;
a second calculation unit that calculates a difference between the two-phase currents and the predicted values;
an extraction unit that extracts an offset component between a motor parameter included in the motor model formula and an actual motor parameter of the motor from the difference, and extracts a noise component included in the difference by removing the offset component from the difference;
Equipped with
the determination unit determines whether to use the two-phase current or the predicted value for controlling the motor based on a magnitude of the noise component.
Motor control device.

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