Motor control method and motor control device

Abstract

To secure detection time of a three-phase current while suppressing generation of a voltage ripple in a DC bus unit.SOLUTION: With a method for controlling a motor, a three-phase current is acquired from a DC bus current. A first phase voltage command value is calculated from a predetermined torque command value with reference to the acquired three-phase current. Correction processing for securing detection time of the three-phase current is performed with respect to the first phase voltage command value. The motor is controlled based on a second phase voltage command value after correction. The correction processing includes: a correction target phase determination step of determining a size relation of an absolute value of respective phase current components in a three-phase current to determine a correction target phase in the first phase voltage command value based on the size relation; and a voltage correction step of correcting a phase voltage component of the correction target phase in the first phase voltage command value.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a motor control method and a motor control device. [Background technology]

[0002] Conventionally, there has been known a motor control method in which the current (three-phase current) of a three-phase AC motor is estimated using the current (DC bus current) detected in a DC power system, and a three-phase voltage command value for the motor is determined based on the estimated three-phase current. In such a motor control method, in a scene in which two or more phase voltage components of the three-phase voltage command value are substantially equal to each other, the time during which it is possible to separate the estimated values ​​of the phase current components of the three-phase current from the DC bus current (hereinafter also simply referred to as "detection time") becomes short, making the detection difficult.

[0003] In response to this, Patent Document 1 proposes a method for correcting each phase voltage component to ensure sufficient detection time while maintaining the average per carrier cycle of the three-phase voltage command value. In particular, the method described in Patent Document 1 corrects the maximum phase voltage component when the difference between two phase voltage components of the three-phase voltage command value is less than a predetermined value and one phase voltage component is the maximum among the phases (hereinafter, this phase will also be referred to simply as the "maximum phase"). Furthermore, the method proposed in Patent Document 1 corrects both the maximum and minimum phases in the motor operating region (low rotation and high torque region) where all phase voltage components are close to each other, thereby ensuring sufficient detection time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-327173 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 has a problem in that, in the above-mentioned motor operating range, voltage correction is performed on both the maximum phase and the minimum phase, which causes a DC current that coincides with the carrier period to flow through the DC bus, resulting in voltage ripple.

[0006] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a motor control method and a motor control device that can ensure the detection time for three-phase currents while suppressing the occurrence of voltage ripple in the DC bus section. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a motor control method comprising: acquiring three-phase currents from a DC bus current; calculating a first-phase voltage command value from a predetermined torque command value by referring to the acquired three-phase currents; correcting the first-phase voltage command value to ensure a detection time for the three-phase currents; and controlling the motor based on the corrected second-phase voltage command value.

[0008] In particular, the correction process includes a correction target phase determination step of determining the magnitude relationship between the absolute values ​​of the phase current components in the three-phase current and determining the phase to be corrected in the first phase voltage command value based on the magnitude relationship, and a voltage correction step of correcting the phase voltage component of the phase to be corrected in the first phase voltage command value. [Effects of the Invention]

[0009] According to the present invention, it is possible to ensure the detection time for three-phase currents while suppressing the occurrence of voltage ripples in the DC bus section. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing the configuration of a motor control system in which a motor control method according to a first embodiment of the present invention is executed. [Figure 2] FIG. 2 is a timing chart illustrating the processing of the phase current reproducing unit. [Figure 3]FIG. 3 is a block diagram illustrating the processing of the voltage command calculation unit according to the first embodiment. [Figure 4] FIG. 4 is a block diagram illustrating the processing of the voltage command correction unit according to the first embodiment. [Figure 5] FIG. 5 is a timing chart illustrating the process in the first voltage correction unit (correction in the voltage-based correction mode). [Figure 6] FIG. 6 is a flowchart showing a specific process of correction in the voltage-based correction mode. [Figure 7] FIG. 7 is a timing chart illustrating the process in the second voltage correction unit (correction in the current-based correction mode). [Figure 8] FIG. 8 is a flowchart showing a specific process of correction in the current-based correction mode. [Figure 9] FIG. 9 is a block diagram illustrating the processing of the correction mode signal generating unit. [Figure 10] FIG. 10 is a block diagram showing the configuration of a motor control system in which a motor control method according to the second embodiment is executed. [Figure 11] FIG. 11 is a block diagram illustrating the processing of the voltage command corrector according to the second embodiment. [Figure 12] FIG. 12 is a block diagram illustrating the processing of the current value magnitude relationship determination unit according to the second embodiment. [Figure 13] FIG. 13 is a block diagram showing the configuration of a motor control system in which a motor control method according to the third embodiment is executed. [Figure 14] FIG. 14 is a block diagram illustrating the processing of the voltage command corrector according to the third embodiment. [Figure 15] FIG. 15 is a block diagram illustrating the processing of the current value magnitude relationship determination unit according to the third embodiment. [Figure 16] FIG. 16 is a diagram illustrating the problems of each comparative example. [Figure 17] FIG. 17 shows the results of frequency analysis in the control of each comparative example and example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] [First embodiment] 1 is a block diagram showing the configuration of a motor control system 100 for executing a motor control method according to this embodiment. As shown in the figure, the motor control system 100 mainly includes a motor 9 configured as a three-phase synchronous motor or the like, and a torque command value T * and a power conversion device (inverter 6) that supplies desired power based on the three-phase command voltage from a battery (DC power source) to the motor 9. In particular, the motor control system 100 is mounted on a vehicle such as an electric vehicle or a hybrid vehicle that uses the motor 9 as a driving source.

[0013] The motor 9 is configured by, for example, an IPM (Interior Permanent Magnet) three-phase synchronous electric motor.

[0014] The motor control device is mainly composed of a voltage command calculation unit 1, a dq / uvw coordinate converter 2, a voltage command correction unit 3, a phase current reproduction unit 4, a PWM (Pulse Width Modulation) converter 5, a rotation speed calculation unit 11, and a uvw / dq coordinate converter 12.

[0015] The voltage command calculation unit 1 calculates the torque command value T * , the motor rotation speed N, the battery output voltage detected by the DC voltage sensor 7 (hereinafter referred to as "DC voltage V dc "), dq axis current detection value (i d ,i q ) is input, and the dq-axis voltage command value (v * d_fin ,v * q_fin) and outputs it. In particular, the voltage command calculation unit 1 calculates and outputs the torque command value T * The dq-axis current detection value (i d ,i q ) is fed back to obtain the dq-axis voltage command value (v * d_fin ,v * q_fin ) is calculated.

[0016] The dq / uvw coordinate converter 2 calculates the dq-axis voltage command value (v * d_fin ,v * q_fin ) to the first three-phase voltage command value (v * u1 ,v * v1 ,v * w1 ) and output.

[0017]

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[0018] The voltage command correction unit 3 calculates the dq-axis voltage command value (v * d_fin ,v * q_fin ), torque command value T * , motor rotation speed N, DC voltage V dc , the first three-phase voltage command value (v * u1 ,v * v1 ,v * w1 ), and dq axis current detection value (i d ,i q ) is input, and the DC bus current i dc to three-phase current (i u ,i v ,i w ) detection time (detection time), the second three-phase voltage command value (v *u2 ,v * v2 ,v * w2 ) is calculated. In particular, in this correction process, correction is performed so that the mutual difference between each phase voltage component becomes equal to or greater than a predetermined value in the first half cycle of one cycle of the carrier related to PWM control. On the other hand, in the second half cycle of the carrier, correction is performed so that the correction voltage amount in the first half cycle is canceled out. This correction maintains the average voltage per cycle of the carrier for each phase voltage component before and after correction. In other words, this correction shifts the pulse phase of the phase voltage component to be corrected. For simplicity's sake, this correction will be simply referred to as "pulse shift correction" below. Further details of the processing in the voltage command correction unit 3 will be described later.

[0019] The phase current reproducing unit 4 reproduces the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 ) and DC bus current i dc From the above, the phase reproduction current (i u_rep ,i v_rep ,i w_rep ) is calculated and output. dc is detected by the DC current detector 8. Here, the DC bus current i dc From this, current information for up to two phases can be obtained for each half cycle of the carrier. Therefore, by using the relationship in the following equation (2), the DC bus current i dc From the phase reproduction current (i u_rep ,i v_rep ,i w_rep ) can be calculated.

[0020]

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[0021] The processing in the phase current reproducing unit 4 will be described in further detail later.

[0022] The PWM converter 5 converts the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 ) and DC voltage V dc is input, and generates and outputs a high-power element drive signal for driving the switching elements of the inverter 6. The high-power element drive signal is a DC voltage V dc Each phase voltage component v * u2 , v * v2 , v * w2 The duty command value (D * u ,D * v ,D * w ) is determined based on the

[0023] The inverter 6 receives the high-voltage element drive signal and drives a power semiconductor element (not shown) to generate a second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 ) is supplied to the motor 9. As a result, the motor 9 supplies power according to the desired torque command value T * The actual torque according to the

[0024] The rotation speed calculator 11 calculates and outputs the motor rotation speed N from the amount of change per unit time of the detected electrical angle θ obtained from the rotor sensor 10.

[0025] The uvw / dq coordinate converter 12 converts the phase reproduced current (i u_rep ,i v_rep ,i w_rep ) to the dq axis current detection value (i d ,i q ) and output.

[0026]

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[0027] The motor control device described above is realized by a computer that includes a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and input / output interface (I / O interface) and is programmed to execute the above-mentioned components. The motor control device can also be configured by multiple computer hardware components that execute each process in a distributed manner.

[0028] The details of each part will be explained individually below.

[0029] (Phase current reproduction section) 2 is a timing chart illustrating the processing in the phase current reproducing unit 4. The phase current reproducing unit 4 generates trg1 by adding Δd1 to the duty command value of the phase (hereinafter simply referred to as the "middle phase") whose duty command value (i.e., phase voltage component) is intermediate, and generates trg2 by subtracting Δd2 from the duty command value. The phase current reproducing unit 4 then calculates the DC bus current i at the timings when the carrier wave C crosses trg1 and trg2. dc and use this as the phase reproduction current (i u_rep ,i v_rep ,i w_rep ) are two components. Δd1 is set to a predetermined value equal to or greater than 0, and Δd2 is the minimum duty difference D required to ensure the detection time. min It is set to a desired value above.

[0030] In particular, Fig. 2 shows the process at successive control timings k-1, k, and k+1, assuming that the w-phase is an intermediate phase. In the illustrated example, the phase current reproducing unit 4 reproduces the previous w-phase duty command value D * w Then, the phase current reproducing unit 4 determines trg1 and trg2 based on the DC bus current i detected at the previous control timing. dcThe DC bus current i at the timing when the carrier wave C crosses trg1 is dc From u phase reproduction current i u_rep , and the DC bus current i at the timing of crossing trg2 dc From v-phase reproduced current i v_rep are determined respectively.

[0031] More specifically, when the control timing k is the current time, the duty command value D calculated at the previous control timing k-1 is * w DC bus current i at the timing when trg1[k-1] based on [k-1] intersects with carrier wave C dc From the above, the u-phase reproduced current i obtained at the current control timing k u_rep On the other hand, the duty command value D at the previous control timing k-1 is * w DC bus current i at the timing when trg2[k-1] based on [k-1] and carrier wave C intersect dc From the above, the v-phase reproduced current i obtained at the current control timing k v_rep Define [k].

[0032] (Voltage command calculation unit) FIG. 3 is a block diagram illustrating the processing of the voltage command calculation unit 1. For the sake of simplicity, in FIG. 3, the d-axis voltage command value v * d_fin Only the calculation block in * q_fin The operation in can be performed similarly.

[0033] As shown in the figure, the voltage command calculation unit 1 includes a non-interference voltage calculator 101, a current target value calculator 102, and a current controller 103.

[0034] The decoupling voltage calculator 101 calculates the torque command value T * , motor rotation speed N, and DC voltage V dc is input, and the d-axis non-interacting voltage value v is calculated by referring to a predetermined table. * d_dcpl The current target value calculator 102 calculates and outputs the torque command value T* , motor rotation speed N, and DC voltage V dc is input, and the d-axis current target value i is calculated by referring to a specified table. * d Each table stores experimentally determined current values ​​that generate desired torque at maximum efficiency and corresponding interference voltage values.

[0035] The current controller 103 calculates the actual d-axis current as the d-axis current target value i * d In order to make it follow the d-axis current target value i * d and the d-axis current detection value i d The feedback calculation (equation (4) below) is performed to make the deviation of the current feedback d-axis voltage command value v di ´ is required.

[0036]

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[0037] The current controller 103 also calculates the d-axis non-interacting voltage value v * d_dcpl The corrected d-axis non-interacting voltage value v obtained by applying a low-pass filter with a time constant of the reference d-axis current response to d_dcpl_fit and the current feedback d-axis voltage command value v di The sum of ´ and is the d-axis voltage command value v * d_fin That is, the voltage command calculation unit 1 outputs the d-axis voltage command value v determined by the following equation (5): * d_fin Output.

[0038]

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[0039] (Voltage command correction unit) 4 is a block diagram illustrating the processing of the voltage command correction unit 3. The voltage command correction unit 3 generates a correction mode signal based on various input parameters, and calculates the first three-phase voltage command value (v * u1 ,v * v1 ,v * w1 ) by executing either the voltage-based correction mode or the current-based correction mode to obtain the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 ) is calculated.

[0040] Specifically, the voltage command correction unit 3 has a first voltage correction unit 301, a second voltage correction unit 302, a correction mode signal generation unit 303, a correction voltage command value generation unit 304, and a current value magnitude relationship determination unit 305.

[0041] The first voltage correction unit 301 calculates the first three-phase voltage command value (v * u1 ,v * v1 ,v * w1 ) to the voltage-based correction value (v * u2_v ,v * v2_v ,v * w2_v ) and output it.

[0042] 5 is a timing chart illustrating the processing (correction in the voltage-based correction mode) in the first voltage correction unit 301. As shown in the figure, the first voltage correction unit 301 performs correction to increase and decrease the maximum phase voltage component (u-phase voltage component shown by the dashed line in FIG. 5) and the minimum phase voltage component (v-phase voltage component shown by the dotted line in FIG. 5) in the first half of the carrier period, respectively, to correct the DC bus current i dc The detection time (in Fig. 5, the u-phase current component i u and v-phase current component i vOn the other hand, in the latter half of the carrier period, the phase voltage components of the maximum and minimum phases (the u-phase voltage component and the v-phase voltage component in Fig. 5) are corrected to cancel the correction amount in the first half. In other words, the phase voltage component of the maximum phase (u-phase voltage component) is decreased and the phase voltage component of the minimum phase (v-phase voltage component) is increased. This correction calculation maintains the average voltage command value per one carrier period while decreasing the DC bus current i dc Therefore, the detection time can be suitably secured.

[0043] 6 is a flowchart showing a specific process of correction in the voltage-based correction mode. min " is calculated by the following equation (6) as the minimum duty difference D min and DC voltage V dc It is determined from.

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[0044] The first voltage correction unit 301 calculates the phase voltage component v of the maximum phase after correction obtained through the processes of steps S101 to S111. 2max * , the phase voltage component of the minimum phase after correction v 2min * , and the phase voltage component of the intermediate phase v that remains unchanged 1mid * From the voltage base correction value (v * u2_v ,v * v2_v ,v * w2_v ) is established.

[0045] Next, the second voltage correction unit 302 will be described. The second voltage correction unit 302 refers to the maximum current phase information generated by the current value magnitude relationship determination unit 305, and calculates the first three-phase voltage command value (v * u1 ,v * v1 ,v * w1 ) to the current base correction value (v *u2_c ,v * v2_c ,v * w2_c ) and outputs it. The maximum current phase information includes at least information regarding the relative magnitude relationship of the absolute values ​​of the phase current components, in particular information regarding the phase in which the absolute value of the phase current component is maximum (hereinafter also simply referred to as the "maximum current phase").

[0046] 7 is a timing chart illustrating the processing (current-based correction mode) in the second voltage correction unit 302. As shown in the figure, the second voltage correction unit 302 refers to the maximum current phase information and calculates a voltage correction amount for two phases other than the maximum current phase such that the difference between the phase voltage components is equal to or greater than a predetermined value. Note that the example shown in FIG. 7 assumes that the maximum current phase is the v phase, and the other two phases are the u phase and the w phase.

[0047] Then, in the first half of the carrier period, the second voltage correction unit 302 corrects the phase voltage components (u-phase voltage component indicated by dashed lines and w-phase voltage component indicated by dotted lines) other than the maximum current phase (i.e., v-phase). In particular, the second voltage correction unit 302 increases the phase voltage component (u-phase voltage component in FIG. 7) of a phase other than the maximum current phase that has a relatively large phase voltage component (hereinafter simply referred to as the "first correction target phase"). On the other hand, the second voltage correction unit 302 decreases the phase voltage component (w-phase voltage component in FIG. 7) of a phase that has a relatively small phase voltage component (hereinafter simply referred to as the "second correction target phase"), thereby correcting the DC bus current i dc Ensure time for detection.

[0048] In the latter half of the carrier cycle, a correction is performed to cancel out the correction amount of each phase voltage component in the first half. That is, the phase voltage component of the first correction target phase (u-phase voltage component) is decreased, and the phase voltage component of the second correction target phase (w-phase voltage component) is increased. This correction calculation maintains the average voltage command value per carrier cycle while increasing the DC bus current i dc Therefore, the detection time can be suitably secured.

[0049] FIG. 8 is a flowchart showing a specific process of correction in the current-based correction mode. The second voltage correction unit 302 calculates the phase voltage component v of the first correction target phase after correction obtained through the processes of steps S201 to S212. c2mid * , the phase voltage component v of the second correction target phase after correction c2min * , and the phase voltage component v of the maximum current phase that remains unchanged c1max * From the current base correction value (v * u2_c ,v * v2_c ,v * w2_c ) is established.

[0050] Next, the correction mode signal generation unit 303 will be described. The correction mode signal generation unit 303 generates a correction mode signal based on the motor rotation speed N and the torque command value T * The correction mode signal is generated using the above as an input and output to the correction voltage command value generator 304.

[0051] 9 is a block diagram illustrating the processing of the correction mode signal generation unit 303. As shown in the figure, the correction mode signal generation unit 303 includes a rotation speed determination unit 3031, a torque command value determination unit 3032, and a determination signal generation unit 3033.

[0052] The rotation speed determination unit 3031 references the motor rotation speed N and generates a rotation speed determination signal according to the logic shown in Table 1.

[0053] [Table 1]

[0054] The torque command value determination unit 3032 determines the torque command value T * The torque command value determination signal is generated according to the logic shown in Table 2, with reference to the above.

[0055] [Table 2]

[0056] Then, the determination signal generating unit 3033 generates a correction mode signal according to the logic shown in Table 3, by referring to the rotation speed determination signal and the torque command value determination signal.

[0057] [Table 3]

[0058] Next, the correction voltage command value generator 304 will be described. The correction voltage command value generator 304 refers to the correction mode signal, selects either the voltage-based correction mode or the current-based correction mode, and generates the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 In particular, the corrected voltage command value generator 304 outputs the current-based correction value (v * u2_c ,v * v2_c ,v * w2_c ) to the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 ) otherwise, the correction voltage command value generator 304 outputs the voltage-based correction value (v * u2_v ,v * v2_v ,v * w2_v ) to the second three-phase voltage command value (v * u2 ,v * v2 ,v * w2 )

[0059] Next, the current value magnitude relation determination unit 305 will be described. The current value magnitude relation determination unit 305 determines the motor rotation speed N, the dq-axis voltage command value (v * d_fin ,v* q_fin ), dq axis current detection value (i d ,i q ), and the detected electrical angle θ are input to generate maximum current phase information. In particular, the current value magnitude relationship determination unit 305 determines the three-phase current (i u ,i v ,i w ) is the estimated three-phase current (i u_est ,i v_est ,i w_est ) is calculated. The current value magnitude relationship determination unit 305 calculates the estimated three-phase current (i u_est ,i v_est ,i w_est ) the phase that has the maximum value among the phase current components (i.e., the maximum current phase) is identified, and this is output to the second voltage correction unit 302 as maximum current phase information.

[0060] Here, ideally, the three-phase current (i u ,i v ,i w ) to specify the maximum current phase. However, in principle, it is possible to specify the maximum current phase by directly referring to the three-phase current (i u ,i v ,i w ) is unknown. Therefore, the three-phase current (i u ,i v ,i w ) equivalent to the estimated three-phase current (i u_est ,i v_est ,i w_est ) and generates maximum current phase information based on this.

[0061] Specifically, the current value magnitude relationship determination unit 305 calculates the estimated three-phase current (i u_est ,i v_est ,i w_est ) is calculated.

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[0062] In addition, "T com " represents the control period. a ” is the winding resistance of motor 9, “L d " is the d-axis inductance, "L q " is the q-axis inductance, and "φ a " represents magnetic flux.

[0063] Specifically, first, the dq-axis current change amount (Δi d ,Δi q ) is calculated. Here, the current value used at the current control timing k corresponds to the current value determined at the previous control timing k-1. Therefore, in order to estimate the current value at the next control timing k+1, the previous dq-axis current detection value (i d [k-1],i q The change in the voltage command value up to the current control timing k is estimated based on the current command value k [k-1], and the current change amount is determined according to this change.

[0064] More specifically, as shown on the right side of equation (8), the previous dq-axis voltage command value (v * d_fin [k-1],v * q_fin The difference between the voltage drop amount in the motor in a steady state at the previous control timing k-1 and the voltage drop amount in the inductance due to the change in current from the previous control timing k-1 to the current control timing k is calculated as the voltage drop amount in the inductance due to the change in current from the previous control timing k-1 to the current control timing k. In particular, as shown in the second term of each component of the vector on the right side of equation (8), the voltage drop amount in the motor in a steady state at the previous control timing k-1 is calculated based on the motor angular velocity ω determined from the motor rotation speed N by equation (7), and each parameter (winding resistance R a , each inductance L d ,L q , and magnetic flux φ a) is calculated based on the inductance matrix. The voltage drop in the inductance due to the current change calculated in this way is applied to calculate the current change, i.e., the dq axis current change (Δi d ,Δi q ) is found.

[0065] Then, based on equation (9), the previous dq-axis current detection value (i d [k-1],i q [k-1]) to the above dq axis current change amount (Δi d ,Δi q ) is added to obtain the estimated dq-axis current (i d_est ,i q_est On the other hand, based on the equation (10), the estimated electrical angle θ , which is the estimated value of the electrical angle at the next control timing k+1, is calculated from the electrical angle detection value θ and the electrical angular velocity ω acquired at the current control timing k. est Furthermore, based on equation (11), the estimated electrical angle θ est Using this, the estimated dq axis current (i d_est ,i q_est ) to obtain the estimated three-phase current (i u_est ,i v_est ,i w_est ) is calculated.

[0066] The estimated three-phase current (i u_est ,i v_est ,i w_est ), maximum current phase information is generated from the maximum current phase information, and pulse shift correction is performed in accordance with the current-based correction mode shown in FIG. 8 based on the generated maximum current phase information, thereby making it possible to correct the phase voltage components by targeting phases other than the maximum current phase at the next control timing k+1 as the correction target phases. In other words, it is possible to preferably exclude from the correction target phases that are expected to increase the current peak of the carrier frequency component in the DC bus section by correction, and perform correction on the other phase voltage components. Therefore, it is possible to eliminate the current peak flowing in the DC bus section and reduce voltage ripple, while increasing the three-phase current (i u ,i v ,iw ) detection time is ensured.

[0067] The configuration of the motor control method of the present embodiment described above and the resulting effects will now be described.

[0068] In this embodiment, the DC bus current i dc to three-phase current (i u ,i v ,i w ) and obtain the three-phase current (i u ,i v ,i w ) to obtain the specified torque command value T * to the first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) and calculates the first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) for three-phase current (i u ,i v ,i w ) detection time, the second phase voltage command value (v * u2 ,v * v2 ,v * w2 ) is used to control the motor 9.

[0069] The correction process is performed by using the three-phase current (i u ,i v ,i w ) and determines the magnitude relationship between the absolute values ​​of the phase current components in the first phase voltage command value (v * u1 ,v * v1 ,v * w1 a correction target phase determination step for determining a correction target phase in the first phase voltage command value (v* u1 ,v * v1 ,v * w1 and a voltage correction step of correcting the phase voltage component of the correction target phase in the phase voltage component of the phase to be corrected.

[0070] This allows the three-phase current (i u ,i v ,i w ) can be appropriately determined by referring to the magnitude relationship of each phase current component. Therefore, the DC bus current i dc Three-phase current (i u ,i v ,i w ) is estimated.

[0071] In particular, in the correction target phase determination step, the correction target phase is determined to be the minimum current phase and / or the intermediate current phase, which has the smallest absolute value among the phase current components. Then, in the voltage correction step, correction is performed to shift the pulse phase of the phase voltage component of the correction target phase (see especially FIG. 8).

[0072] This allows the three-phase current (i u ,i v ,i w ) is estimated.

[0073] Furthermore, in the correction target phase determination step of this embodiment, the correction target phase is determined based on the current information acquired at the previous control timing k-1.

[0074] As a result, at the current control timing k, the three-phase current (i u ,i v ,i w Even if ) is unknown, the phase to be corrected can be determined without requiring complicated calculations.

[0075] In particular, in the correction target phase determination step, a predicted value (estimated electrical angle θ) of the electrical angle detected value θ at the next control timing k+1 is determined based on the rotor angle (electrical angle detected value θ) of the motor 9 at the current control timing k. est ) and calculates the current information and estimated electrical angle θ est Based on this, the three-phase current (i u ,i v ,i w ) is the estimated three-phase current (i u_est ,i v_est ,i w_est ) and calculate the estimated three-phase current (i u_est ,i v_est ,i w_est ) to determine the phase to be corrected.

[0076] This allows for a reduction in the calculation load without requiring complicated calculations, and realizes a more specific control logic for determining the phase to be corrected.

[0077] More specifically, in the correction target phase determination step, the three-phase current (i u ,i v ,i w ) based on the previous dq-axis current detection value (i d [k-1],i q [k-1]) is obtained. In addition, the motor angular velocity ω is calculated based on the electrical angle detection value θ at the current control timing k (Equation (7)). Furthermore, the first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) based on the previous dq-axis voltage command value (v * d_fin [k-1],v * q_fin [k-1]), previous dq axis current detection value (i d [k-1],i q [k-1]), and the motor characteristic parameters (Ra ,L d ,L q ,φ a ), the dq axis current change amount (Δi d ,Δi q ) is calculated (Equation (8)). Then, the previous dq axis current detection value (i d [k-1],i q [k-1]), dq axis current change amount (Δi d ,Δi q ), and estimated electrical angle θ est Based on this, the estimated three-phase current (i u_est ,i v_est ,i w_est ) is calculated (Equations (9) to (11)).

[0078] This allows for a reduction in the calculation load without requiring complicated calculations, and also allows for a more specific control logic to be implemented for determining the phase to be corrected.

[0079] The correction process in the motor control method of this embodiment includes a current-based correction mode (second voltage correction unit 302, FIG. 8) consisting of a correction target phase determination step and a voltage correction step, and a voltage-based correction mode (first voltage correction unit 301, FIG. 6) in which a correction target phase is determined based on the relative magnitude of the phase voltage components and the phase voltage component of the correction target phase is corrected. Then, either the current-based correction mode or the voltage-based correction mode is selectively executed depending on the driving status of the motor 9, thereby obtaining a first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) is corrected to obtain the second phase voltage command value (v * u2 ,v * v2 ,v * w2 ) is calculated.

[0080] As already explained, the three-phase current (i u ,i v ,i wIn the current-based correction mode, which determines the phase to be corrected based on the magnitude relationship between the phase voltage components and performs correction, a reduction in current ripple in the DC bus is expected. On the other hand, in the voltage-based correction mode, which determines the phase to be corrected based on the magnitude relationship between the phase voltage components, harmonic components in the phase current can be reduced. Therefore, by employing control logic that appropriately switches between these modes depending on the driving status of the motor 9, it is possible to suitably adjust the balance between the effects of reducing voltage ripple and the effects of reducing harmonic components in the phase current depending on the situation.

[0081] In particular, the driving status of the motor 9 includes the rotation speed of the motor 9 (motor rotation speed N) and the torque command value T * On the other hand, any other parameter that can suggest the driving status of the motor 9 may be adopted instead of or in addition to these.

[0082] Furthermore, this embodiment provides a motor control device configured by a computer that functions as a voltage command calculation unit 1, a dq / uvw coordinate converter 2, a voltage command correction unit 3, a phase current reproduction unit 4, a PWM converter 5, a rotation speed calculation unit 11, and a uvw / dq coordinate converter 12. This realizes a motor control device configuration suitable for executing the above-described motor control method.

[0083] [Second embodiment] The second embodiment will be described below, with the same elements as those in the first embodiment being given the same reference numerals and their description being omitted.

[0084] Fig. 10 is a block diagram showing the configuration of a motor control system 200 that executes a motor control method according to this embodiment, and Fig. 11 is a block diagram illustrating the processing of voltage command corrector 3 of this embodiment.

[0085] As shown in the figure, in this embodiment, the current value magnitude relationship determination unit 305 of the voltage command correction unit 3 determines the torque command value T * , motor rotation speed N, dq axis voltage command value (v * d_fin ,v * q_fin), and the detected electrical angle θ are used as inputs to generate maximum current phase information. That is, the dq-axis current detection value (i d ,i q ) instead of the torque command value T * This embodiment differs from the first embodiment in that

[0086] 12 is a block diagram illustrating the processing of the current value magnitude relationship determination unit 305 according to this embodiment. As shown in the figure, the current value magnitude relationship determination unit 305 has a current command phase calculator 3051, a phase difference map 3052, and a maximum current phase determiner 3053.

[0087] The current command phase calculator 3051 calculates the dq-axis voltage command value (v * d_fin ,v * q_fin ) is used as an input, and the voltage phase command value α is calculated using the following equation (12).

[0088]

number

[0089] The phase difference map 3052 is a graph showing the relationship between the motor rotation speed N and the torque command value T * The phase difference Δθ between the voltage and current is calculated by taking the above into account and mapping the motor characteristics (magnetic flux resistance, winding resistance, etc.).

[0090] The current value magnitude relationship determination unit 305 determines the current phase θ from the electrical angle detection value θ, the voltage phase command value α, and the phase difference Δθ. c More specifically, the voltage phase θ is calculated by adding π / 2 to the detected electrical angle θ and then adding the voltage phase command value α. v Then, the voltage phase θ v By subtracting the phase difference Δθ between the voltage and current from c Calculate.

[0091] The maximum current phase determiner 3053 determines the current phase θ cThe maximum current phase information is generated using the logic shown in Table 4 below, referring to the above.

[0092] [Table 4]

[0093] According to the motor control method of the present embodiment described above, in the correction target phase determination step, the first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) as a voltage command parameter based on the dq-axis voltage command value (v * d_fin ,v * q_fin ), and the voltage phase θ from the rotor angle of the motor 9 (electrical angle detection value θ) v Also, the torque command value T * and the motor rotation speed N, the phase difference Δθ between the current and voltage is estimated by referring to the characteristics of the motor 9. Then, each phase current component i u , i v , i w The magnitude relationship of the absolute values ​​of (i.e., current maximum phase information) is calculated by the estimated current phase θ c The judgment is based on the following.

[0094] This results in a torque command value T * The motor rotation speed N is input, and the current phase θ is calculated by referring to the phase difference Δθ that is mapped in advance according to the characteristics of the motor 9. c The current phase θ c Therefore, the phase to be corrected can be determined by referring to the dq axis current detection value (i d ,i q ) the control logic is simplified and the calculation load can be further reduced.

[0095] [Third embodiment] The third embodiment will be described below, with the same elements as those in the first or second embodiment being given the same reference numerals and their description being omitted.

[0096] FIG. 13 is a block diagram showing the configuration of a motor control system 300 in which the motor control method according to this embodiment is executed.

[0097] In this embodiment, the voltage command calculation unit 1 calculates the torque command value T * , motor rotation speed N, and DC voltage V dc is input, and the dq axis current command value (i * d ,i * q ) and outputs it to the voltage command correction unit 3.

[0098] 14 is a block diagram illustrating the processing of the voltage command correction unit 3 of this embodiment. As shown in the figure, the current value magnitude relationship determination unit 305 of the voltage command correction unit 3 of this embodiment determines the magnitude relationship between the detected electrical angle value θ and the dq-axis current command value (i * d ,i * q ) is used as an input to generate maximum current phase information, which differs from the second embodiment.

[0099] 15 is a block diagram illustrating the processing of the current value magnitude relationship determination unit 305 according to this embodiment. As shown in the figure, the current value magnitude relationship determination unit 305 has a current command phase calculator 3054 and a maximum current phase determiner 3053.

[0100] The current command phase calculator 3054 calculates the dq axis current command value (i * d ,i * q ) is used as an input, and the current phase command value β is calculated using the following equation (13).

[0101]

number

[0102] The current value magnitude relationship determination unit 305 determines the current phase θ from the electrical angle detection value θ and the current phase command value β. cMore specifically, the current phase θ is calculated by adding π / 2 to the detected electrical angle θ and then adding the current phase command value β. c Ask for.

[0103] Then, the current command phase calculator 3054 calculates the current phase θ c and generates maximum current phase information using the logic shown in Table 4 above.

[0104] According to the motor control method of the present embodiment described above, in the correction target phase determination step, the torque command value T * and the dq-axis current command value (i * d ,i * q ) and calculates the current phase command value β from the electrical angle detection value θ and the current phase command value β. c Then, each phase current component i u , i v , i w The magnitude relationship of the absolute values ​​of (i.e., current maximum phase information) is calculated by the estimated current phase θ c The judgment is based on the following.

[0105] This results in a torque command value T * and the dq-axis current command value (i * d ,i * q ) to calculate the current phase θ c is estimated, and the current phase θ c Therefore, the phase to be corrected can be determined by using the dq axis current detection value (i d ,i q ) the control logic is simplified and the calculation load can be further reduced.

[0106] [Control results] Below, we will explain the control results of the motor control method of the above embodiment (Example) while comparing them with the control results of the motor control method of the comparative example. Note that to clarify the comparison, the same reference numerals are used to designate components that are common between the Example and the comparative example.

[0107] (Comparative Example 1) As Comparative Example 1, a motor control method employing three-phase current calculations is assumed, as described in "A Method for Calculating AC Current by Detecting DC Current in a Three-Phase PWM Inverter" (J. Electrical Engineering, Vol. 127, No. 2, 2007). In the control of Comparative Example 1, the shift method is changed according to the angle and magnitude of the voltage command vector on the αβ coordinate axes. Particularly in the control of Comparative Example 1, in the low modulation rate region (low rotation / high torque region), the voltage vector of the switching state adjacent to the switching state in the most dominant direction with respect to the voltage command vector is adopted, and a voltage vector that cancels the corrected amount is output after ensuring detection time. As a result, pulse shift correction is performed so that two-phase currents with similar voltage command values ​​are detected.

[0108] (Comparative Example 2) In Comparative Example 2, the first phase voltage command value (v * u1 ,v * v1 ,v * w1 ) is corrected.

[0109] FIG. 16 is a diagram illustrating the problems of Comparative Examples 1 and 2. As shown in the figure, in the control methods of Comparative Examples 1 and 2, excessive current components that approximately match the carrier frequency are generated in the DC bus section, causing voltage ripples in the smoothing capacitor. More specifically, particularly in the low modulation rate region (low rotation / high torque region) where pulse shift correction is performed on two-phase phase voltage components, the relationship between the maximum and minimum phases of the voltage command value is reversed between the first and second halves of the carrier cycle. As a result, a current with an inverted sign flows through the DC bus section, amplifying the component that approximately matches the carrier frequency and generating voltage ripples. At this time, the peak value of the current flowing through the DC bus section depends on the phase current component corresponding to the phase for which correction is performed. In both Comparative Examples 1 and 2, the phase to be corrected is determined based on the magnitude and phase of the voltage command value. Therefore, depending on the driving conditions (rotation speed and torque conditions) of the motor 9, correction is performed at the moment the phase current reaches its peak, causing excessive phase current to flow through the DC bus section and generating voltage ripples in the smoothing capacitor.

[0110] On the other hand, in the control of the embodiment, the above problem is solved by adopting the current-based correction mode. More specifically, the peak value of the phase current of each phase is the torque command value T * However, the phase current to be passed through the DC bus section depends on the phase to be corrected, so it can be changed. Therefore, by determining the phase to be corrected based on the current value, more specifically, by determining the phase to be corrected while avoiding the maximum current phase, it is possible to reduce the current of the carrier frequency component flowing through the DC bus section.

[0111] 17 shows the results of frequency analysis in the control of Comparative Examples 1 and 2 and the Example. As shown in the figure, the voltage component at the carrier frequency (5 kHz) is excessive in each of Comparative Examples 1 and 2. In contrast, it can be seen that the voltage component is significantly reduced in the control of the Example.

[0112] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0113] 1. Voltage command calculation section 2 dq / uvw coordinate converter 3 Voltage command correction section 4-phase current reproduction section 5 PWM converter 6 inverters 9 Motor 11. Rotation speed calculator 12 UVW / DQ Coordinate Transformer 100 Motor Control System 200 Motor Control System 300 Motor Control System

Claims

1. 1. A motor control method comprising: acquiring three-phase currents from a DC bus current; calculating a first-phase voltage command value from a predetermined torque command value by referring to the acquired three-phase currents; correcting the first-phase voltage command value to ensure a detection time for the three-phase currents; and controlling a motor based on the corrected second-phase voltage command value, The correction process includes: a correction target phase determination step of determining a magnitude relationship between absolute values ​​of phase current components of the three-phase currents and determining a phase to be corrected in the first phase voltage command value based on the magnitude relationship; a voltage correction step of correcting a phase voltage component of the correction target phase in the first phase voltage command value, Motor control methods.

2. 2. The motor control method of claim 1, In the correction target phase determination step, the correction target phase is determined to be a minimum current phase having a minimum absolute value among the phase current components and / or an intermediate current phase having an intermediate absolute value among the phase current components, In the voltage correction step, a correction is performed to shift a pulse phase of the phase voltage component of the correction target phase. Motor control methods.

3. 3. A motor control method according to claim 1 or 2, comprising: In the correction target phase determination step, The phase to be corrected is determined based on current information acquired at the previous control timing. Motor control methods.

4. 4. The motor control method according to claim 3, In the correction target phase determination step, calculating a predicted value of the rotor angle at a next control timing based on the rotor angle of the motor at a current control timing; calculating an estimated value of the three-phase current at the next control timing based on the current information and the predicted value of the rotor angle; determining the phase to be corrected based on the estimated values ​​of the three-phase currents; Motor control methods.

5. 5. The motor control method according to claim 4, In the correction target phase determination step, As the current information, previous values ​​of current parameters based on the three-phase currents acquired at the previous control timing are acquired; calculating a motor angular velocity based on the rotor angle at the current control timing; calculating a current parameter change amount from the previous control timing based on a previous value of a voltage command value parameter based on the first phase voltage command value, a previous value of the current parameter, the motor angular velocity, and a motor characteristic parameter according to a characteristic of the motor; calculating estimated values ​​of the three-phase currents based on previous values ​​of the current parameters, changes in the current parameters, and the predicted value of the rotor angle; Motor control methods.

6. 3. A motor control method according to claim 1 or 2, comprising: In the correction target phase determination step, calculating a voltage phase from a voltage command value parameter based on the first phase voltage command value and a rotor angle of the motor; estimating a phase difference between a current and a voltage from the torque command value and the rotation speed of the motor by referring to characteristics of the motor; estimating a current phase from the voltage phase and the phase difference; determining a magnitude relationship between the absolute values ​​of the phase current components based on the estimated current phases; Motor control methods.

7. 3. A motor control method according to claim 1 or 2, comprising: In the correction target phase determination step, calculating a current phase command value from the torque command value and a current command value based on the rotation speed of the motor; a current phase is estimated from the rotor angle of the motor and the current phase command value; determining a magnitude relationship between the absolute values ​​of the phase current components based on the estimated current phases; Motor control methods.

8. The motor control method according to any one of claims 1 to 7, the correction process includes a current-based correction mode including the correction target phase determination step and the voltage correction step, and a voltage-based correction mode in which the correction target phase is determined based on a magnitude relationship between the phase voltage components and the phase voltage component of the correction target phase is corrected, selectively executing either the current-based correction mode or the voltage-based correction mode according to a driving state of the motor to correct the first-phase voltage command value, thereby calculating the second-phase voltage command value; Motor control methods.

9. 9. A motor control method according to claim 8, comprising: The driving conditions include the rotation speed of the motor and the torque command value. Motor control methods.

10. 1. A motor control device that acquires three-phase currents from a DC bus current, calculates a first-phase voltage command value from a predetermined torque command value by referring to the acquired three-phase currents, performs a correction process on the first-phase voltage command value to ensure a detection time for the three-phase currents, and controls a motor based on the corrected second-phase voltage command value, In the correction process, determining a magnitude relationship between absolute values ​​of the phase current components of the three-phase currents, and determining a phase to be corrected in the first phase voltage command value based on the magnitude relationship; correcting the phase voltage component of the correction target phase; Motor control device.

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