Motor control device

Abstract

In this motor control device (100), an inverter (10) converts a DC voltage supplied from a DC power source into an AC voltage and applies the converted AC voltage to a motor (M), and a current detection unit (21) detects a bus current of the inverter (10) using a shunt resistor (Rs) connected between the DC power source and the inverter, and outputs the detected bus current to the motor (M). A 3 [phi] current calculation unit (61) calculates a motor current flowing through a motor (M) on the basis of a bus current, a first extraction unit (91) extracts a noise component included in the motor current from the motor current, and a noise amount determination unit (92) determines the magnitude of noise of the bus current on the basis of the extracted noise component.

Description

Technical Field

[0001] The present disclosure relates to a motor control device. Background Art

[0002] A motor control device for controlling the driving of a motor has an inverter for generating a three-phase AC voltage (hereinafter sometimes referred to as a “three-phase voltage”) to be applied to the motor. The inverter is composed of a plurality of switching elements.

[0003] In addition, if 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 in order to make the rotation speed of the motor consistent with the speed command value (target speed), and generates a d-axis voltage command value and a q-axis voltage command value based on 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.

[0004] As a technology for controlling an inverter based on a three-phase voltage command value, PWM (Pulse Width Modulation) is known. PWM is a technology that changes the output voltage (i.e., three-phase voltage) of an inverter by adjusting the on / off duration of multiple switching elements constituting the inverter. The signal for controlling the on / off of the switching elements (hereinafter sometimes referred to as a "PWM signal") is generated based on the comparison result between the PWM carrier and the modulation wave. By controlling the on / off of the switching elements according to the PWM signal, a three-phase voltage is applied to the motor to control the drive of the motor.

[0005] In addition, there is known a technique for controlling the driving of a motor without using a sensor (hereinafter sometimes referred to as a "position sensor") for detecting the rotational position of the motor rotor (hereinafter sometimes referred to as a "rotor position") (hereinafter sometimes referred to as a "position sensor"). In the position sensorless method, the rotor position is estimated by detecting the three-phase current (hereinafter sometimes referred to as a "motor current") flowing through the motor without using a position sensor.

[0006] In addition, as a method for detecting the motor current, a "single-shunt detection method" is known. In the single-shunt detection method, two-phase currents in the motor current are detected based on the bus current flowing between the inverter that generates the three-phase voltage and the DC power supply, and the remaining one-phase current is calculated from the two-phase current using Kirchhoff's law.

[0007] Here, the following prior art is proposed: the first connection line and the second connection line are configured to be equally affected by noise, the first connection line is used to transmit the amplified voltage generated by the voltage generated at both ends of the bus current detection shunt resistor to the first A / D converter, and the second connection line transmits the offset voltage generated by the offset voltage generating unit to the second A / D converter. In the prior art, if noise is superimposed on the first connection line, the same noise will also be superimposed on the second connection line, so by judging whether the offset voltage is a voltage outside the preset range, it is judged whether the bus current is superimposed with large noise (hereinafter sometimes referred to as "noise judgment"). In addition, in the prior art, when the offset voltage is a voltage outside the preset range, it is judged that the noise has a large influence on the detected bus current, and the amplified voltage detected at the same time as the offset voltage is discarded; when the offset voltage is within the preset range, a PWM signal is generated based on the bus current calculated according to the amplified voltage detected at the same time as the offset voltage. As a result, the motor can be controlled using a current value that is less affected by noise (i.e., a high-precision current value), thereby preventing the control from being unstable due to the use of a current value that is greatly affected by noise to control the motor.

[0008] Patent Document 1: Japanese Patent Application Publication No. 2015-126555 Summary of the invention

[0009] In the above-mentioned prior art, when performing noise determination, it is necessary to sample the offset voltage while sampling the amplified voltage, so a second connection line and a second A / D converter for acquiring the offset voltage are separately required. Therefore, in the above-mentioned prior art, when the motor is controlled using a high-precision current value, the number of components in the motor control device increases.

[0010] Therefore, the present disclosure proposes a technology capable of controlling a motor using a highly accurate current value while suppressing an increase in the number of components in a motor control device.

[0011] The motor control device disclosed in the present invention comprises an inverter, a detection unit, a calculation unit, a first extraction unit and a judgment unit. The inverter converts a DC voltage supplied from a DC power supply into an AC voltage and applies the AC voltage to the motor. The detection unit detects the bus current of the inverter using a resistor connected between the DC power supply and the inverter. The calculation unit calculates the motor current flowing through the motor based on the bus current. The first extraction unit extracts a noise component contained in the motor current from the motor current. The judgment unit judges the magnitude of the noise of the bus current based on the noise component.

[0012] According to the disclosed technology, it is possible to control a motor using a highly accurate current value while suppressing an increase in the number of components in a motor control device. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram showing a configuration example of a motor control device according to the first embodiment of the present disclosure.

[0014] Figure 2 It is a diagram showing a configuration example of a noise determination unit according to the first embodiment of the present disclosure.

[0015] Figure 3 It is a diagram showing a configuration example of a first extraction unit according to Embodiment 1 of the present disclosure.

[0016] Figure 4 This is a diagram showing an example of noise components and non-noise components included in the motor current according to the first embodiment of the present disclosure.

[0017] Figure 5 : is a diagram showing an example of the noise component extracted in the first embodiment of the present disclosure.

[0018] Figure 6 1 is a diagram showing an example of updating of a threshold used in noise determination in the first embodiment of the present disclosure.

[0019] Figure 7 It is a diagram showing a configuration example of a noise determination unit according to the second embodiment of the present disclosure.

[0020] Figure 8 It is a diagram showing a configuration example of a first extraction unit and a second extraction unit according to Embodiment 2 of the present disclosure.

[0021] Fig. 9 This is a flowchart showing an example of a processing procedure in the noise determination unit according to the second embodiment of the present disclosure. DETAILED DESCRIPTION

[0022] Hereinafter, embodiments of the present disclosure will be described based on the drawings. In the following embodiments, the same components are denoted by the same reference numerals.

[0023] Example 1

[0024] Structure of motor control device

[0025] Figure 1 It is a diagram showing a configuration example of a motor control device according to the first embodiment of the present disclosure. Figure 1 The motor control device 100 shown controls the driving of the motor M using a position sensorless method, a single shunt detection method, and PWM control. Figure 1The motor control device 100 includes subtraction units 46, 47, 52, a d-axis current setting unit 48, a speed control unit 49, a d-axis q-axis voltage setting unit 45, a dq / 3φ conversion unit 43, a PWM unit 41, an inverter 10, and a DC power supply E. DC The motor control device 100 includes a DC voltage detection unit 31, a current detection unit 21, AD conversion units 71, 72, a 3φ current calculation unit 61, a DC voltage calculation unit 32, a 3φ / dq conversion unit 42, a position-speed estimation unit 44, a 1 / Pn processing unit 51, a noise determination unit 80, and a current estimation unit 81.

[0026] 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, the noise judgment unit 80 and the current estimation unit 81 are implemented as hardware, for example, by an MCU (Micro Control Unit).

[0027] Inverter 10 also includes switching elements SWup, SWvp, and SWwp of an upper arm and switching elements SWun, SWvn, and SWwn of a lower arm.

[0028] In the motor control device 100, the d-axis current setting unit 48 sets the d-axis current command value id as a preset value. * The result is output to the subtraction unit 46 .

[0029] The d-axis current command value id is input from the d-axis current setting unit 48 to the subtraction unit 46. * The d-axis current id is input from the noise determination unit 80. The subtraction unit 46 obtains the d-axis current command value id by * The d-axis current deviation Δid is calculated by subtracting the d-axis current id, and the calculated d-axis current deviation Δid is output to the d-axis / q-axis voltage setting unit 45 .

[0030] 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 the calculated q-axis current command value iq * Output to the subtraction unit 47.

[0031] The q-axis current command value iq is input from the speed control unit 49 to the subtraction unit 47. * The q-axis current iq is input from the noise determination unit 80. The subtraction unit 47 obtains the q-axis current command value iq by* The q-axis current iq is subtracted to calculate a q-axis current deviation Δiq, and the calculated q-axis current deviation Δiq is output to the d-axis q-axis voltage setting unit 45 .

[0032] The d-axis q-axis voltage setting unit 45 receives the d-axis current deviation Δid from the subtraction unit 46, receives the q-axis current deviation Δiq from the subtraction unit 47, and receives 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 the d-axis voltage command value Vd such that the d-axis current deviation Δid and the q-axis current deviation Δiq are close to zero. * and q-axis voltage command value Vq * , and the calculated d-axis voltage command value Vd * and q-axis voltage command value Vq * Output to the position-speed estimating unit 44, the dq / 3φ conversion unit 43 and the current estimating unit 81. d-axis voltage command value Vd * and q-axis voltage command value Vq * It also changes according to the motor current calculated by the 3φ current calculation unit 61, that is, the U-phase current iu, the V-phase current iv, and the W-phase current iw.

[0033] The position-speed estimation unit 44 receives the d-axis current id and the q-axis current iq from the noise determination unit 80, and receives the d-axis voltage command value Vd from the d-axis and q-axis voltage setting unit 45. * and q-axis voltage command value Vq * The position-speed estimation unit 44 calculates the position-speed based on the d-axis current id, the q-axis current iq, and the d-axis voltage command value Vd. * and q-axis voltage command value Vq * , to estimate the electrical angular velocity ωe of the motor M and the rotation phase angle θdq of the motor M in the rotation coordinate (dq coordinate). The position-speed estimating unit 44 outputs the estimated angular velocity ωe to the 1 / Pn processing unit 51, the noise determination unit 80, and the current estimating unit 81, and outputs the estimated rotation phase angle θdq to the 3φ / dq conversion unit 42 and the dq / 3φ conversion unit 43.

[0034] The 1 / Pn processing unit 51 converts the electrical angular velocity ωe into a mechanical angular velocity ωm of a 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 .

[0035] The subtraction unit 52 receives an angular velocity ωm from the 1 / Pn processing unit 51 and 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 the speed command value ωm by *The speed deviation Δω is calculated by subtracting the angular velocity ωm, and the calculated speed deviation Δω is output to the speed control unit 49 .

[0036] The dq / 3φ conversion unit 43 converts the d-axis voltage command value Vd of the two phases of the rotation coordinate using the rotation phase angle θdq. * and q-axis voltage command value Vq * Convert the three-phase voltage command value Vu into fixed coordinates (UVW coordinates) * 、Vv * 、Vw * The dq / 3φ conversion unit 43 converts the converted voltage command value Vu * 、Vv * 、Vw * Output to the PWM unit 41.

[0037] The PWM unit 41 receives a voltage command value Vu from the dq / 3φ conversion unit 43. * 、Vv * 、Vw * The DC voltage Vdc is input from the DC voltage calculation unit 32. In addition, the PWM unit 41 receives a carrier signal as a carrier of the PWM 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 a voltage command value Vu based on the voltage command value Vu. * 、Vv * 、Vw * , DC voltage Vdc and a carrier signal, generate three-phase PWM signals Up, Un, Vp, Vn, Wp, Wn, and output the generated PWM signals Up, Un, Vp, Vn, Wp, Wn to the inverter 10 and the 3φ current calculation unit 61.

[0038] For the inverter 10, from the DC power source E DC The inverter 10 supplies a DC voltage and inputs PWM signals Up, Un, Vp, Vn, Wp, and Wn from the PWM unit 41. The inverter 10 converts the DC power supply E to a DC voltage according to the PWM signals Up to Wn. DC The supplied DC voltage is converted into a three-phase AC voltage, and the converted three-phase AC voltage is applied to the motor M. That is, the inverter 10 applies the AC voltage to the motor M through PWM control. The three-phase AC voltage is applied to the motor M so that the motor M is driven. In the inverter 10, each switching element SWup, SWun, SWvp, SWvn, SWwp, SWwn is turned on / off according to the PWM signal Up, Un, Vp, Vn, Wp, Wn, thereby converting the DC voltage into a three-phase voltage. Freewheeling diodes Dup, Dun, Dvp, Dvn, Dwp, Dwn are connected to both ends of each switching element SWup, SWun, SWvp, SWvn, SWwp, SWwn.

[0039] The current detection unit 21 uses a DC power supply E DC The shunt resistor Rs is arranged between the N line L and the inverter 10 to detect the bus current Is of the inverter 10. N On the N line L N is the DC power supply E DC The DC line between the N-side terminal of the inverter 10. In addition, the shunt resistor Rs can also be configured on the P line L P On the P line L P is the DC power supply E DC The DC line between the P-side terminal and the inverter 10. A bus current Is corresponding to the U-phase current, V-phase current, and W-phase current flows in the shunt resistor Rs. The U-phase current, V-phase current, and W-phase current are motor currents that flow according to the PWM signal. When the bus current Is flows through the shunt resistor Rs, a voltage drop will occur at both ends of the shunt resistor Rs. The current detection unit 21 detects the bus current Is flowing through the shunt resistor Rs based on the size of the voltage drop and the resistance value of the shunt resistor Rs. Furthermore, the current detection unit 21 calculates the analog voltage VA1 represented by formula (1) based on the shunt resistor Rs and the bus current Is, and outputs the calculated analog voltage VA1 to the AD conversion unit 72. "k" in formula (1) represents a preset gain.

[0040] VA1=k×(Rs·Is)…(1)

[0041] The AD converter 72 converts the analog voltage VA1 into a digital voltage value VA2 by sampling the analog voltage VA1 , and outputs the converted digital voltage value VA2 to the 3φ current calculator 61 .

[0042] The 3φ current calculation unit 61 calculates the motor current using a single shunt detection method. The 3φ current calculation unit 61 calculates the U-phase current iu, the V-phase current iv, and the W-phase current iw as the motor current 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.

[0043] The 3φ / dq conversion unit 42 uses the rotation phase angle θdq input from the position-speed estimation unit 44 to convert the motor currents iu, iv, iw of the three-phase current vector representing the fixed coordinates into the d-axis current and q-axis current of the two-phase current vector representing the rotating coordinates. Hereinafter, the d-axis current converted by the 3φ / dq conversion unit 42 is sometimes referred to as the "detected d-axis current", and the q-axis current converted by the 3φ / dq conversion unit 42 is sometimes referred to as the "detected q-axis current". The detected d-axis current and the detected q-axis current of the two phases are equivalent to the three-phase motor current calculated by the 3φ current calculation unit 61. 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. Hereinafter, the detected d-axis current id_det and the detected q-axis current iq_det are sometimes collectively referred to as the "detected current i_det".

[0044] The d-axis voltage command value Vd is input to the current estimation unit 81 from the d-axis and q-axis voltage setting unit 45. * and q-axis voltage command value Vq * The angular velocity ωe is input from the position-velocity estimation unit 44, and the d-axis current id and the q-axis current iq are input from the noise determination unit 80. The current estimation unit 81 determines the d-axis voltage command value Vd based on the d-axis voltage command value Vd. * , q-axis voltage command value Vq * , angular velocity ωe, d-axis current id, and q-axis current iq are used to estimate the current, and the estimated d-axis current id_est and the estimated q-axis current iq_est are output to the noise determination unit 80. Hereinafter, the d-axis current estimated by the current estimation unit 81 is sometimes referred to as "estimated d-axis current", and the q-axis current estimated by the current estimation unit 81 is sometimes referred to as "estimated q-axis current". In addition, the estimated d-axis current id_est and the estimated q-axis current iq_est are sometimes collectively referred to as "estimated current i_est".

[0045] The noise determination unit 80 receives the detection current i_det from the 3φ / dq conversion unit 42, the angular velocity ωe from the position-speed estimation unit 44, and the estimated current i_est from the current estimation unit 81. The noise determination unit 80 performs noise determination, and determines the d-axis current id output to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 46, and the current estimation unit 81, and the q-axis current iq output to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 47, and the current estimation unit 81 based on the determination result of the noise determination. The details of the noise determination unit 80 will be described below.

[0046] The DC voltage detection unit 31 detects the P line L P With N line L Nand outputs the detected analog bus voltage VB1 to the AD conversion unit 71.

[0047] The AD converter 71 converts the analog bus voltage VB1 into a digital bus voltage value VB2 by sampling the analog bus voltage VB1 , and outputs the converted digital bus voltage value VB2 to the DC voltage calculator 32 .

[0048] The DC voltage calculation unit 32 calculates the DC voltage Vdc based on the digital bus voltage value VB2 , and outputs the calculated DC voltage Vdc to the PWM unit 41 .

[0049] Configuration of the noise determination unit

[0050] Figure 2 It is a diagram showing a configuration example of a noise determination unit according to the first embodiment of the present disclosure. Figure 2 The noise determination unit 80a shown is equivalent to Figure 1 The noise determination unit 80 is shown. Figure 2 In the embodiment, the noise determination section 80 a includes a first extraction section 91 , a noise amount determination section 92 , and a current determination section 93 .

[0051] The first extraction unit 91 extracts the noise component contained in the motor current from the motor current, and outputs the extracted noise component to the noise amount determination unit 92. The noise component extracted by the first extraction unit 91 is formed by the d-axis noise component id_no and the q-axis noise component iq_no. Hereinafter, the d-axis noise component id_no and the q-axis noise component iq_no may be collectively referred to as "noise component i_no".

[0052] The noise amount determination unit 92 determines the magnitude of the noise of the bus current based on the noise component. The noise component may be a positive value or a negative value. Therefore, for example, the noise amount determination unit 92 determines that the noise of the bus current is large when at least one of the absolute value |id_no| of the d-axis noise component id_no or the absolute value |iq_no| of the q-axis noise component iq_no is greater than the absolute value |±THN| of the threshold value ±THN, and determines that the noise of the bus current is small when both |id_no| and |iq_no| are less than |±THN|. Furthermore, when the noise amount determination unit 92 determines that the noise of the bus current is large and the noise component has a positive value, it sets the determination flag DF to '+1' and outputs the determination flag DF set to '+1' to the current determination unit 93. On the other hand, when the noise amount determination unit 92 determines that the noise of the bus current is large and the noise component has a negative value, it sets the determination flag DF to '-1' and outputs the determination flag DF set to '-1' to the current determination unit 93. When determining that the noise of the bus current is small, the noise amount determination unit 92 sets the determination flag DF to '0' and outputs the determination flag DF set to '0' to the current determination unit 93 .

[0053] The current determination unit 93 receives the detection current i_det from the 3φ / dq conversion unit 42 , the estimated current i_est from the current estimation unit 81 , and the determination flag DF from the noise amount determination unit 92 .

[0054] When the flag DF is set to '0', the current determination unit 93 determines the detected d-axis current id_det as the d-axis current id for controlling the motor M in this carrier cycle, and outputs the detected d-axis current id_det of the detected d-axis current id_det and the estimated d-axis current id_est to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 46, and the current estimation unit 81. The carrier cycle is the reciprocal of the carrier frequency fc in the motor control device 100. On the other hand, when the flag DF is set to '+1' or '-1', the current determination unit 93 determines the estimated d-axis current id_est as the d-axis current id for controlling the motor M in this carrier cycle, and outputs the estimated d-axis current id_est of the detected d-axis current id_det and the estimated d-axis current id_est to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 46, and the current estimation unit 81.

[0055] In addition, when the determination flag DF is set to '0', the current determination unit 93 determines the detected q-axis current iq_det as the q-axis current iq for controlling the motor M in this carrier cycle, and outputs the detected q-axis current iq_det of the detected q-axis current iq_det and the estimated q-axis current iq_est to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 47, and the current estimation unit 81. On the other hand, when the determination flag DF is set to '+1' or '-1', the current determination unit 93 determines the estimated q-axis current iq_est as the q-axis current iq for controlling the motor M in this carrier cycle, and outputs the estimated q-axis current iq_est of the detected q-axis current iq_det and the estimated q-axis current iq_est to the position-speed estimation unit 44, the d-axis q-axis voltage setting unit 45, the subtraction unit 47, and the current estimation unit 81.

[0056] Estimation of current

[0057] Hereinafter, two estimation examples, namely, estimation example 1 and estimation example 2, will be described as examples of current estimation performed by the current estimating unit 81 .

[0058] Presumption Example 1

[0059] The d-axis voltage command value Vd is input from the d-axis and q-axis voltage setting unit 45 to the current estimating unit 81. * and q-axis voltage command value Vq * It is represented by the motor model formula shown in equation (2.1) and equation (2.2). In equation (2.1) and equation (2.2), "R" is the coil resistance of the motor M, "id" is the d-axis current input from the current determination unit 93 to the current estimation unit 81 in the previous carrier cycle (hereinafter sometimes referred to as "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 to the current estimation unit 81, "Lq" is the q-axis inductance of the motor M, "iq" is the q-axis current input from the current determination unit 93 to the current estimation unit 81 in the previous carrier cycle (hereinafter sometimes referred to as "previous q-axis current"), and "Ψ" is the flux of the motor M. The coil resistance R, the d-axis inductance Ld, the q-axis inductance Lq and the flux Ψ are parameters that determine the characteristics of the motor M (hereinafter sometimes referred to as "motor parameters").

[0060] Vd * =R·id+p·Ld·id-ωe·Lq·iq…(2.1)

[0061] V Q * =R·iq+p·Lq·iq+ωe·Ld·id+ωe·Ψ…(2.2)

[0062] In addition, if the carrier frequency fc in the motor control device 100 is used, the equations (2.1) and (2.2) can be transformed into equations (3.1) and (3.2). In equations (3.1) and (3.2), "ΔId" is the change amount of the d-axis current (hereinafter sometimes referred to as "the predicted d-axis current") predicted to be output from the current determination unit 93 in this carrier cycle relative to the previous d-axis current (hereinafter sometimes referred to as "the d-axis current change"), and "ΔIq" is the change amount of the q-axis current (hereinafter sometimes referred to as "the predicted q-axis current") predicted to be output from the current determination unit 93 in this carrier cycle relative to the previous q-axis current (hereinafter sometimes referred to as "the q-axis current change").

[0063] Vd * =R·id+Ld·ΔId·fc-ωe·Lq·iq…(3.1)

[0064] V Q * =R·iq+Lq·ΔIq·fc+ωe·Ld·id+ωe·Ψ…(3.2)

[0065] If equations (3.1) and (3.2) are solved for the d-axis current variation and the q-axis current variation, equations (4.1) and (4.2) can be obtained.

[0066] ΔId=(Vd * -R·id+ωe·Lq·iq) / (Ld·fc)…(4.1)

[0067] ΔIq=(Vq * -R·iq-ωe·Ld·id-ωe·Ψ) / (Lq·fc)…(4.2)

[0068] Therefore, in estimation example 1, the current estimation unit 81 uses the previous d-axis current id determined by the current determination unit 93 and input from the current determination unit 93 in the previous carrier cycle, and the previous q-axis current iq determined by the current determination unit 93 and input from the current determination unit 93 in the previous carrier cycle, to calculate the estimated d-axis current id_est and the estimated q-axis current iq_est according to equations (5.1) and (5.2).

[0069] id_est=id+ΔId…(5.1)

[0070] iq_est=iq+ΔIq…(5.2)

[0071] As described above, in estimation example 1, the current estimating unit 81 calculates the estimated d-axis current id_est and the estimated q-axis current iq_est theoretically derived from the motor model formula of the motor M, and outputs the calculated estimated d-axis current id_est and the estimated q-axis current iq_est to the current determining unit 93 .

[0072] Presumption Example 2

[0073] In estimation example 2, the current estimation unit 81 uses the previous d-axis current as the estimated d-axis current id_est, and uses the previous q-axis current as the estimated q-axis current iq_est.

[0074] Structure of the first extraction unit

[0075] Figure 3 FIG. 1 is a diagram showing a configuration example of a first extraction unit according to Embodiment 1 of the present disclosure. Figure 3 , the first extraction unit 91 includes a first notch filter 911, a second notch filter 912, and a first high-pass filter 913. The first notch filter 911 receives the detection current i_det from the 3φ / dq conversion unit 42, and receives the angular velocity ωe from the position-velocity estimation unit 44. The second notch filter 912 receives the angular velocity ωe from the position-velocity estimation unit 44.

[0076] Here, the detection current i_det includes a noise component and a component different from the noise component (hereinafter sometimes referred to as a “non-noise component”). The first extraction unit 91 extracts the noise component from the detection current i_det by removing the non-noise component from the detection current i_det, and outputs the extracted noise component to the noise amount determination unit 92.

[0077] Here, as an example of non-noise components, there can be cited load pulsation components, high-frequency components caused by the structure of the motor M (hereinafter sometimes referred to as "components caused by the motor structure"), and offset components. The load pulsation component is a component that appears due to load pulsation during one rotation of the motor M. The component caused by the motor structure is a frequency component including harmonic components depending on the rotation speed of the motor M, and as an example, pulsation caused by cogging torque can be cited. The offset component is equivalent to the average value of the motor current and has no frequency component.

[0078] In the first extraction unit 91 , first, the first notch filter 911 removes the load pulsation component, which is a non-noise component, from the detection current i_det.

[0079] The load pulsation component is a frequency component generated by the load pulsation of the motor M, and therefore appears at a specific frequency. In addition, the frequency at which the load pulsation component appears varies according to the rotation speed of the motor M.

[0080] Therefore, the first notch filter 911 performs filtering processing on the detection current i_det based on, for example, the carrier frequency "fc" and the specific frequency "ωn" at which the load pulsation component appears, and according to equations (6.1) to (6.7), thereby removing the load pulsation component from the detection current i_det. As a result, the noise component after the load pulsation component is removed from the detection current i_det is extracted. The specific frequency ωn at which the load pulsation component appears is calculated based on the angular velocity ωe. The first notch filter 911 outputs the noise component i_no after the load pulsation component is removed from the detection current i_det to the second notch filter 912.

[0081]

[0082] Here, "N0", "N1", "N2", "D0", "D1" and "D2" in equations (6.1) to (6.7) are preset filter constants of the notch filter, "d" is a parameter that determines the attenuation amount in the notch filter, and "σ" is a parameter that determines the bandwidth of the attenuation target in the notch filter. In addition, "x" in equations (6.1) to (6.7) is the detection current i_det, and "y" is the noise component extracted by the notch filter. In addition, "[k]" in equations (6.1) to (6.7) is the current carrier cycle, "[k-1]" is the previous carrier cycle, and "[k-2]" is the previous carrier cycle. Therefore, "x[k]" in equations (6.1) to (6.7) is the detection current i_det in the current carrier cycle, "x[k-1]" is the detection current i_det in the previous carrier cycle, "x[k-2]" is the detection current i_det in the previous carrier cycle, "y[k]" is the noise component i_no extracted in the current carrier cycle, "y[k-1]" is the noise component i_no extracted in the previous carrier cycle, and "y[k-2]" is the noise component i_no extracted in the previous carrier cycle.

[0083] Next, the second notch filter 912 removes a component caused by the motor structure, which is a non-noise component, from the detection current i_det.

[0084] The components caused by the motor structure include harmonic components, and the frequency of the components caused by the motor structure is determined by the number of poles of the motor M, the number of slots of the motor M, and the rotation speed of the motor M. For example, if the rotation speed of the motor M is set to the fundamental frequency, when the motor M is an X-pole Y-slot motor, the components caused by the motor structure appear at the frequency of the least common multiple of X and Y. Furthermore, the components caused by the motor structure also appear at frequencies of the order of 1 / 2 times, 2 times, 3 times, ..., n times the least common multiple of X and Y. For example, if the motor M is a 6-pole 9-slot motor, the components caused by the motor structure appear not only at the frequency of the least common multiple of 6 and 9, that is, the 18th order, but also at the frequency of 1 / 2 times the least common multiple of 6 and 9, that is, the 9th order, and the 36th order, 54th order, ..., and other 18×n-order frequencies. Therefore, for example, if the rotation speed of the motor M is 30 [rps], the components caused by the motor structure appear at frequencies of 270 [Hz], 540 [Hz], 1080 [Hz], 1620 [Hz], ..., 540 × n [Hz]. In this way, the components caused by the motor structure appear at a specific frequency determined by the rotation speed of the motor M.

[0085] Therefore, similarly to the first notch filter 911, the second notch filter 912 performs filtering processing on the detection current i_det based on, for example, the carrier frequency "fc" and the specific frequency "ωn" at which the component caused by the motor structure appears, and according to equations (6.1) to (6.7), thereby removing the component caused by the motor structure from the detection current i_det. Thus, the noise component after the component caused by the motor structure is removed from the detection current i_det is extracted. The specific frequency ωn at which the component caused by the motor structure appears is calculated based on the angular velocity ωe. The second notch filter 912 outputs the noise component i_no after the component caused by the motor structure is removed from the detection current i_det to the first high-pass filter 913.

[0086] Here, since the specific frequency ωn of the load pulsation component or the component caused by the motor structure varies according to the speed of the motor M, the preset filter constants N0, N1, N2, D0, D1, and D2 in equations (6.1) to (6.7) are determined according to the speed of the motor M.

[0087] Next, the first high-pass filter 913 removes an offset component, which is a non-noise component, from the detection current i_det.

[0088] For example, the first high-pass filter 913 performs filtering processing on the detection current i_det based on the carrier frequency "fc" and according to equations (7.1) to (7.6), thereby removing the offset component from the detection current i_det. Thus, the noise component after the offset component is removed from the detection current i_det is extracted as "y[k]" in equation (7.1). The first high-pass filter 913 outputs the noise component i_no after the offset component is removed from the detection current i_det to the noise amount determination unit 92. In equations (7.1) to (7.6), "a1" and "a0" are filter constants that determine the characteristics of the first high-pass filter 913.

[0089] y[k]=(A×x[k]+B×x[k-1]+C×x[k-2]-D×y[k-1]-E×y[k-2])…(7.1)

[0090]

[0091] like Figure 4 and Figure 5 As shown, the first extraction unit 91 extracts the noise component included in the motor current from the motor current by removing the load pulsation component, the component caused by the motor structure, and the offset component which are non-noise components from the detection current i_det as described above. Figure 4 FIG. 1 is a diagram showing an example of noise components and non-noise components included in the motor current according to the first embodiment of the present disclosure. Figure 5 : is a diagram showing an example of the noise component extracted in the first embodiment of the present disclosure.

[0092] In addition, the first extraction unit 91 may also remove one or more of the load pulsation component, the component caused by the motor structure, and the offset component from the detection current i_det. In addition, in the above, the first extraction unit 91 has a first notch filter 911, a second notch filter 912, and a first high-pass filter 913 as second-order filters. However, the filter to which the disclosed technology can be applied is not limited to the second-order filter.

[0093] Update of threshold ±THN

[0094] Hereinafter, three updating examples 1 to 3 will be described as examples of updating of the threshold value ±THN by the noise amount determination unit 92 .

[0095] Update Example 1

[0096] In update example 1, the noise amount determination unit 92 updates the threshold ±THN using the moving average of the latest n carriers of the noise component when it is determined that the noise of the bus current is small.

[0097] Update Example 2

[0098] In update example 2, the noise amount determination section 92 uses a low-pass filter to calculate the average value of the noise component when the noise of the bus current is determined to be small, and updates the threshold value ±THN using the calculated average value.

[0099] Update Example 3

[0100] In update example 3, the noise amount determination section 92 updates the threshold ±THN based on the noise component when it is determined that the noise of the bus current is small. Figure 6 1 is a diagram showing an example of updating of a threshold used in noise determination in the first embodiment of the present disclosure.

[0101] like Figure 6 As shown, for example, the noise amount determination unit 92 detects positive and negative peak values ​​P1, P2, and P3 in real time during the preset period Ia. The positive and negative peak values ​​P1, P2, and P3 are the values ​​of the maximum absolute value of the noise component i_no in the preset period Ia when it is determined that the noise of the bus current is relatively small. The value obtained by adding the margin to the absolute value of each peak value P1, P2, and P3 is used to update the threshold value ±THN. Figure 6 As shown, for example, when the cycles T1, T2, and T3 having the same preset period Ia are set, the noise amount determination unit 92 detects a negative peak value P1 in the cycle T1, sets a value obtained by adding a positive margin to the absolute value of the peak value P1 as the threshold value +THN in the cycle T2, and sets a value obtained by adding a negative margin to the absolute value of the peak value P1 as the threshold value -THN in the cycle T2. In addition, the noise amount determination unit 92 detects a positive peak value P2 in the cycle T2, sets a value obtained by adding a positive margin to the absolute value of the peak value P2 as the threshold value +THN in the cycle T3, and sets a value obtained by adding a negative margin to the absolute value of the peak value P2 as the threshold value -THN in the cycle T3. In addition, the margin is set in advance to a preset value obtained by experiments or the like in order to prevent the control of the motor M from becoming unstable.

[0102] Here, as an example of the preset period Ia, the period in which the load of the motor M pulsates as the motor M rotates, i.e., the "load pulsation period", can be cited. The peak of the steady-state noise that does not affect the accuracy of the current value appears periodically in the load pulsation period, so the threshold ±THN can be accurately set by updating the threshold ±THN for each load pulsation period. In other words, it is possible to prevent the situation where the bus current is mistakenly judged to have a large noise due to the steady-state noise that does not affect the accuracy of the current value. In addition, it is possible to prevent the bus current noise from being mistakenly judged to be a large noise (misjudged to be a small noise). Therefore, noise judgment can be performed accurately.

[0103] In the above, Example 1 has been described.

[0104] Example 2

[0105] When a second-order filter such as a notch filter is input with a non-periodic single signal such as noise, the output of the second-order filter will vibrate. The greater the noise input to the second-order filter, the greater the vibration generated by the output of the second-order filter, and the greater the vibration, the slower the vibration decreases. Therefore, if the noise amount judgment unit 92 judges that the noise of the bus current is large in this carrier cycle, then in the next and subsequent carrier cycles, even if the noise superimposed on the bus current is small, the noise amount judgment unit 92 may mistakenly judge that the noise of the bus current is large. Therefore, in Example 2, the noise judgment unit 80 adopts the following structure.

[0106] Configuration of the noise determination unit

[0107] Figure 7 It is a diagram showing a configuration example of a noise determination unit according to the second embodiment of the present disclosure. Figure 7 The noise determination unit 80b shown is equivalent to Figure 1 The noise determination unit 80 is shown. Figure 7 In the embodiment, the noise determination section 80 b includes a first extraction section 91 , a noise amount determination section 92 , a current determination section 93 , and a second extraction section 94 .

[0108] Configuration of the first extraction unit and the second extraction unit

[0109] Figure 8 It is a diagram showing a configuration example of a first extraction unit and a second extraction unit according to Embodiment 2 of the present disclosure.

[0110] Figure 8 In the embodiment, the first extraction unit 91 includes a first notch filter 911 , a second notch filter 912 , a first high-pass filter 913 and a data setting unit 914 .

[0111] in addition, Figure 8 , the second extraction unit 94 includes an input control unit 941, a third notch filter 942, a fourth notch filter 943, a second high-pass filter 944, and a data output unit 945. The input control unit 941 receives the detection current i_det from the 3φ / dq conversion unit 42, and receives the determination flag DF from the noise amount determination unit 92. The third notch filter 942 and the fourth notch filter 943 receive the angular velocity ωe from the position-velocity estimation unit 44. The data output unit 945 receives the determination flag DF from the noise amount determination unit 92.

[0112] Here, the third notch filter 942 is a filter having the same filter constant as the first notch filter 911, the fourth notch filter 943 is a filter having the same filter constant as the second notch filter 912, and the second high-pass filter 944 is a filter having the same filter constant as the first high-pass filter 913. That is, the third notch filter 942 performs filtering processing according to equations (6.1) to (6.7) in the same manner as the first notch filter 911, the fourth notch filter 943 performs filtering processing according to equations (6.1) to (6.7) in the same manner as the second notch filter 912, and the second high-pass filter 944 performs filtering processing according to equations (7.1) to (7.6) in the same manner as the first high-pass filter 913.

[0113] Operation of the noise determination unit

[0114] Hereinafter, an operation example of the noise determination unit 80b will be described for a case where the noise of the bus current is small and a case where the noise of the bus current is large.

[0115] When the bus current noise is small

[0116] When the noise amount determination unit 92 determines that the noise of the bus current is small, that is, when the determination flag DF set to '0' is input to the input control unit 941 and the data output unit 945, the input control unit 941 outputs the detection current i_det to the third notch filter 942 as an input to the third notch filter 942. On the other hand, the data output unit 945 does not operate, and the filter data FDa, FDb, and FDc are not output from the data output unit 945, so the data setting unit 914 does not operate either. In addition, the first notch filter 911, the second notch filter 912, and the first high-pass filter 913 perform the same filtering process as the filtering process described in the first embodiment. In addition, since the detection current i_det is input to the third notch filter 942, the third notch filter 942 performs the same filtering process as the first notch filter 911, the fourth notch filter 943 performs the same filtering process as the second notch filter 912, and the second high-pass filter 944 performs the same filtering process as the first high-pass filter 913.

[0117] When bus current noise is large

[0118] When the noise amount determination unit 92 determines that the noise of the bus current in the previous carrier cycle is large, that is, when the determination flag DF set to '+1' or '-1' is input to the input control unit 941 and the data output unit 945 in the previous carrier cycle, in the previous carrier cycle, the input control unit 941 calculates the current obtained by adding the stored detection current i_det in the previous carrier cycle to the preset addition value (hereinafter sometimes referred to as "virtual motor current"), and outputs the virtual motor current to the third notch filter 942 as an input to the third notch filter 942. When the determination flag DF input in the previous carrier cycle is set to '+1', the input control unit 941 adds the preset addition value +a to the detection current i_det in the previous carrier cycle, and when the determination flag DF input in the previous carrier cycle is set to '-1', the input control unit 941 adds the preset addition value -a to the detection current i_det in the previous carrier cycle. In addition, the absolute value |±a| of the preset addition value ±a is preferably smaller than the absolute value |±THN| of the threshold value ±THN. Since the vibration of the output of the second-order filter in this carrier cycle is smaller than that in the previous carrier cycle, if the absolute value |±a| of the preset addition value ±a is smaller than the absolute value |±THN| of the threshold value ±THN, the vibration of the output obtained by the filtering process described later by the first notch filter 911, the second notch filter 912 and the first high-pass filter 913 can be suppressed within the range not exceeding the threshold value ±THN in this carrier cycle. In other words, a virtual motor current can be obtained in which the influence of noise is reduced to the extent that the noise amount determination unit 92 does not mistakenly determine that the noise of the bus current is large. In addition, the preset addition value ±a can also be a variable value determined according to the updated threshold value ±THN. As described above, by adding the preset addition value ±a to the detection current i_det when it is determined that the noise of the bus current is large, a virtual motor current in which the influence of noise has been reduced can be obtained. In addition, the detection current i_det is stored in the noise amount determination unit 92 in time sequence for each carrier cycle.

[0119] In addition, when the noise amount judgment unit 92 determines that the noise of the bus current in the previous carrier cycle is large, in the previous carrier cycle, the third notch filter 942 and the fourth notch filter 943 are based on the virtual motor current in the previous carrier cycle and perform filtering according to equations (6.1) to (6.7), and the second high-pass filter 944 is based on the virtual motor current in the previous carrier cycle and performs filtering according to equations (7.1) to (7.6). That is, when the noise amount judgment unit 92 determines that the noise of the bus current in the previous carrier cycle is large, in the previous carrier cycle, the third notch filter 942, the fourth notch filter 943 and the second high-pass filter 944 replace the "x[k]" in equations (6.1) to (6.7) and (7.1) to (7.6) from the detected current i_det with the virtual motor current, and perform filtering processing based on the virtual motor current and according to equations (6.1) to (6.7) and (7.1) to (7.6), thereby extracting the noise component (hereinafter sometimes referred to as "virtual noise component") y[k] contained in the virtual motor current from the virtual motor current.

[0120] In addition, when the noise amount determination unit 92 determines that the noise of the bus current in the previous carrier cycle is large, in the current carrier cycle, the data output unit 945 outputs x[k-1] and y[k-1] in the third notch filter 942 as filter data FDa to the data setting unit 914, outputs x[k-1] and y[k-1] in the fourth notch filter 943 as filter data FDb to the data setting unit 914, and outputs x[k-1] and y[k-1] in the second high-pass filter 944 as filter data FDc to the data setting unit 914. In the current carrier cycle, the data setting unit 914 sets the filter data FDa input from the data output unit 945 to the first notch filter 911, sets the filter data FDb input from the data output unit 945 to the second notch filter 912, and sets the filter data FDc input from the data output unit 945 to the first high-pass filter 913. Therefore, in this carrier cycle, in the first extraction unit 91, x[k-1] and y[k-1] in the previous carrier cycle are replaced by x[k-1] and y[k-1] input from the data output unit 945 in this carrier cycle, and then filtering is performed using the first notch filter 911, the second notch filter 912 and the first high-pass filter 913.

[0121] Processing order in the noise determination unit

[0122] Fig. 9 This is a flowchart showing an example of a processing procedure in the noise determination unit according to the second embodiment of the present disclosure.

[0123] Fig. 9In step S100 , the first extraction unit 91 extracts the noise component i_no from the detection current i_det in the previous carrier cycle.

[0124] Next, in step S105, the noise amount determination unit 92 determines whether the absolute value of the noise component i_no is greater than the absolute value of the threshold ±THN in the previous carrier cycle, that is, whether the noise of the bus current is large. When it is determined that the noise of the bus current is large (step S105: Yes), the process proceeds to step S110, and when it is determined that the noise of the bus current is small (step S105: No), the process proceeds to step S125.

[0125] In step S110 , the input control section 941 calculates a virtual motor current by adding a preset addition value ±a to the detection current i_det in the previous carrier cycle, and inputs the virtual motor current to the third notch filter 942 instead of the detection current i_det.

[0126] Next, in step S115 , the third notch filter 942 , the fourth notch filter 943 , and the second high-pass filter 944 perform filtering processing in the previous carrier cycle based on the virtual motor current in the previous carrier cycle.

[0127] Next, in step S120, the data setting unit 914 replaces x[k-1] and y[k-1] in the first notch filter 911, the second notch filter 912 and the first high-pass filter 913 in this carrier cycle with x[k-1] and y[k-1] when the third notch filter 942, the fourth notch filter 943 and the second high-pass filter 944 performed filtering processing based on the virtual motor current in the previous carrier cycle, and the first notch filter 911, the second notch filter 912 and the first high-pass filter 913 use the replaced x[k-1] and y[k-1] to filter the detection current i_det.

[0128] On the other hand, in step S125 , the input control unit 941 inputs the detection current i_det to the third notch filter 942 .

[0129] Next, in step S130 , the third notch filter 942 , the fourth notch filter 943 , and the second high-pass filter 944 perform filtering processing based on the detection current i_det.

[0130] In the above, Example 2 has been described.

[0131] As described above, the motor control device of the present disclosure (motor control device 100 of the embodiment) has an inverter (inverter 10 of the embodiment), a detection unit (current detection unit 21 of the embodiment), a calculation unit (3φ current calculation unit 61 of the embodiment), a first extraction unit (first extraction unit 91 of the embodiment) and a judgment unit (noise amount judgment unit 92 of the embodiment). The inverter converts the DC voltage supplied from the DC power supply into an AC voltage, and applies the converted AC voltage to the motor (motor M of the embodiment). The detection unit uses a resistor (shunt resistor Rs of the embodiment) connected between the DC power supply and the inverter to detect the bus current of the inverter. The calculation unit calculates the motor current flowing through the motor based on the bus current. The first extraction unit extracts the noise component contained in the motor current from the motor current. The judgment unit judges the magnitude of the noise of the bus current based on the extracted noise component.

[0132] Thus, when the motor is controlled using a high-precision current value, the offset voltage required for determining the magnitude of the bus current noise in the above-mentioned prior art is no longer required. Therefore, a circuit for obtaining an offset voltage and an A / D converter for sampling the offset voltage are no longer required. Therefore, the motor can be controlled using a high-precision current value while suppressing an increase in the number of components in the motor control device. In addition, since an A / D converter for sampling the offset voltage is no longer required, the A / D converter previously used for sampling the offset voltage can be used for other purposes.

[0133] In addition, the first extraction unit extracts the noise component by removing a non-noise component different from the noise component from the motor current. For example, the first extraction unit extracts the noise component contained in the motor current from the motor current by removing a frequency component containing a harmonic component as a non-noise component from the motor current, wherein the harmonic component depends on the motor speed. For another example, the first extraction unit extracts the noise component contained in the motor current from the motor current by removing a frequency component caused by a load pulsation of the motor as a non-noise component from the motor current. For another example, the first extraction unit extracts the noise component contained in the motor current from the motor current by removing an average value of the motor current, i.e., an offset component, as a non-noise component from the motor current.

[0134] Thereby, the noise component can be accurately extracted.

[0135] In addition, the determination unit determines that the noise of the bus current is small when the noise component is less than the threshold value, and determines that the noise of the bus current is large when the noise component is greater than the threshold value. In addition, when the determination unit determines that the noise of the bus current is small, the threshold value is updated based on the noise component when the noise is determined to be small. On the other hand, when the determination unit determines that the noise of the bus current is large, the threshold value is not updated.

[0136] For example, the determination unit updates the threshold value based on the peak value of the noise component in the preset period when it is determined that the noise of the bus current is small in the preset period.

[0137] For another example, the preset period is a load pulsation period, that is, a period in which the load of the motor pulsates as the motor rotates.

[0138] This can prevent the bus current from being misjudged as having a large noise due to steady-state noise that does not affect the accuracy of the current value. In addition, it can prevent the bus current from being misjudged as having a large noise (misjudged as having a small noise) despite having a large noise. Therefore, noise judgment can be performed accurately.

[0139] In addition, the first extraction unit performs filtering processing based on the motor current calculated in the previous carrier cycle, the noise component extracted in the previous carrier cycle, and the motor current calculated in this carrier cycle, thereby removing non-noise components from the motor current and extracting the noise component contained in the motor current from the motor current.

[0140] Thereby, the noise component can be extracted more accurately.

[0141] In addition, the motor control device of the present disclosure has a second extraction unit (second extraction unit 94 of the embodiment). When the determination unit determines that the noise of the bus current is large in the previous carrier cycle, the second extraction unit outputs the virtual motor current whose noise influence has been reduced and the virtual noise component contained in the virtual motor current to the first extraction unit in the current carrier cycle.

[0142] For example, the first extraction unit performs filtering processing using a preset filter constant, and the second extraction unit uses the same filter constant as the preset filter constant in the first extraction unit and performs filtering processing based on the virtual motor current, thereby extracting the virtual noise component contained in the virtual motor current from the virtual motor current.

[0143] For another example, when the judgment unit determines that the noise of the bus current is large in the previous carrier cycle, the first extraction unit replaces the motor current calculated in the previous carrier cycle and the noise component extracted in the previous carrier cycle with the virtual motor current and virtual noise component input from the second extraction unit in the current carrier cycle for filtering.

[0144] For another example, the second extraction unit calculates the virtual motor current by adding a preset addition value to the motor current calculated in the previous carrier cycle. In addition, the preset addition value has the same sign as the sign of the noise component extracted by the first extraction unit, and the absolute value of the preset addition value is smaller than the absolute value of the threshold value of the noise component.

[0145] Thus, even if the determination unit determines that the bus current noise is large in this carrier cycle, the output vibration of the first extraction unit can be suppressed in the next and subsequent carrier cycles. Therefore, it is possible to prevent the situation where the noise superimposed on the bus current is small but the bus current noise is mistakenly determined to be large.

[0146] Explanation of symbols

[0147] 100 Motor control device

[0148] 10 Inverter

[0149] 21 Current detection unit

[0150] 61 3φ current calculation unit

[0151] 91 First Extraction Department

[0152] 92 Noise amount determination unit

[0153] 94 Second Extraction

Claims

1. A motor control device, characterized in that: have: an inverter for converting a DC voltage supplied from a DC power source into an AC voltage and applying the AC voltage to the motor; a detection unit that detects a bus current of the inverter using a resistor connected between the DC power supply and the inverter; a calculation unit that calculates a motor current flowing through the motor based on the bus current; a first extracting unit configured to extract a noise component included in the motor current from the motor current; as well as A determination unit determines the magnitude of the noise of the bus current based on the noise component.

2. The motor control device according to claim 1, characterized in that: The first extraction section extracts the noise component by removing a non-noise component different from the noise component from the motor current.

3. The motor control device according to claim 1, characterized in that: The determination unit determines that the noise of the bus current is small when the noise component is smaller than a threshold value, The threshold value is updated based on the noise component when it is determined that the noise of the bus current is relatively small.

4. The motor control device according to claim 3, characterized in that: The determination unit updates the threshold value based on a peak value of the noise component in a preset period when it is determined that the noise of the bus current is relatively small in the preset period.

5. The motor control device according to claim 4, characterized in that: The preset period is a load pulsation period, that is, a period during which the load of the motor pulsates as the motor rotates.

6. The motor control device according to claim 2, characterized in that: The first extraction unit extracts the noise component included in the motor current from the motor current by removing a frequency component including a harmonic component as the non-noise component from the motor current, wherein the harmonic component depends on a rotation speed of the motor.

7. The motor control device according to claim 2, characterized in that: The first extraction unit extracts the noise component included in the motor current from the motor current by removing a frequency component caused by a load pulsation of the motor as the non-noise component from the motor current.

8. The motor control device according to claim 2, characterized in that: The first extraction unit extracts the noise component included in the motor current from the motor current by removing an offset component, which is an average value of the motor current and is the non-noise component, from the motor current.

9. The motor control device according to claim 2, characterized in that: The inverter applies the AC voltage to the motor through PWM control, The determination unit determines that the noise of the bus current is large when the noise component is equal to or greater than a threshold value, The first extraction unit performs filtering processing based on the motor current calculated in the previous carrier cycle, the noise component extracted in the previous carrier cycle, and the motor current calculated in this carrier cycle, thereby removing the non-noise component from the motor current and extracting the noise component included in the motor current from the motor current. The motor control device also has a second extraction unit. When the judgment unit determines that the noise of the bus current is large in the previous carrier cycle, the second extraction unit outputs a virtual motor current in which the influence of the noise has been reduced and a virtual noise component contained in the virtual motor current to the first extraction unit in this carrier cycle.

10. The motor control device according to claim 9, characterized in that: The first extraction unit performs the filtering process using a preset filtering constant. The second extraction section performs filtering processing based on the virtual motor current using a filter constant that is the same as the preset filter constant, thereby extracting the virtual noise component included in the virtual motor current from the virtual motor current.

11. The motor control device according to claim 9, characterized in that: When the judgment unit determines that the noise of the bus current is large in the previous carrier cycle, the first extraction unit replaces the motor current calculated in the previous carrier cycle and the noise component extracted in the previous carrier cycle with the virtual motor current and the virtual noise component input from the second extraction unit in the current carrier cycle to perform the filtering process.

12. The motor control device according to claim 9, characterized in that: The second extracting unit calculates the virtual motor current by adding a preset addition value to the motor current calculated in the previous carrier cycle. The preset added value has the same sign as that of the noise component extracted by the first extracting section, and an absolute value of the preset added value is smaller than an absolute value of the threshold value.

Images