JP6540586B2 - Control device for AC motor - Google Patents

Description

  The present invention relates to a control device for an AC motor that controls energization of the AC motor.

Conventionally, in a control device for an AC motor that performs feedback control based on a phase current detection value detected by a current sensor, there is known a technique for reducing the influence of higher order components superimposed on the primary component of the phase current.
For example, the control device for an AC motor disclosed in Patent Document 1 performs Fourier control on the phase current detection value to extract a primary component, and performs feedback control based on the extracted primary current. At this time, Fourier coefficients are calculated by integrating the calculated values based on the phase current detection values sampled at sampling intervals obtained by dividing the electrical angle k period by the division number N.

Patent No. 5741966 gazette

  Patent Document 1 describes that the division number N may be changed according to the number of rotations or the electric frequency of the AC motor. Specifically, by decreasing the division number N as the number of rotations or the electric frequency increases, the time obtained by dividing one electrical cycle by the division number N falls below the processing time, preventing the control from being broken. Can. Further, the detection accuracy of the primary current can be secured by increasing the division number N as the rotation speed or the electric frequency decreases.

  By the way, in the calculation of the Fourier coefficient according to the prior art of Patent Document 1, the integrated value is calculated using N electrical angles and phase current detection values in the electrical angle k cycle, going back from the present. Therefore, from the time of change of division number to period of electrical angle k period, irregular operation using both phase current detection value by division number before change and phase current detection value by division number after change is executed. At this time, the calculated value of the primary current due to the Fourier series expansion may be suddenly changed, which may cause torque fluctuation and power fluctuation of the AC motor.

  The present invention has been made in view of such a point, and its object is to provide a control apparatus for an AC motor which prevents sudden change of the primary current calculation value by Fourier series expansion when the division number is changed. To provide.

The control device for an AC motor according to the present invention converts the DC power into AC power by the operation of the plurality of switching elements (21 to 26), and supplies the inverter (20) to the AC motor (80) with the phase current fed back. And an inverter control unit (30) for operating the inverter to control the energization of the AC motor.
In the present specification, "AC motor" includes an AC drive motor, a generator, and a motor generator, and is used as a main machine of a hybrid car or an electric car, for example, to generate torque for driving driving wheels. Motor generator corresponds. Further, for example, a control device that controls energization of the motor generator corresponds to “control device of AC motor”.

In the first aspect of the present invention, the inverter control unit includes a sampling unit (51), a Fourier coefficient calculation unit (53), a division number change unit (54), and a retrospective estimation unit (55).
The sampling unit samples the phase current detection value at sampling intervals obtained by dividing the electrical angle k period (k is a natural number) by “the number of divisions that is an integer of 2 or more”.
The Fourier coefficient operation unit integrates the calculated value based on the phase current detection value or the phase current estimated value over the electrical angle k period in a Fourier series expansion in which the phase current is extracted as a function of the electrical angle and the primary current of the phase is fed back. Calculate the Fourier coefficients by

The division number changing unit can change the number of divisions from the number before division (N) to the number after division (M) at any timing.
When the number of divisions is changed by the number-of-divisions change unit, the time point at which the Fourier coefficient calculation unit switches to the calculation based on the number of divisions after the change is taken as the operation switching time (tx). The retrospective estimation unit is a Fourier coefficient (a _sum , b _sum calculated using the division number before change as the electrical angle and the phase current value used for the calculation during the period of electrical angle k from the time of operation switching by the Fourier coefficient operation unit. The electric angle and the phase current estimated value corresponding to the post-change division number are reversely calculated from the time of operation switching based on

  As described above, the Fourier coefficient calculation unit does not use the electrical angle and phase current detection value according to the division number before change, and the electrical angle and phase current corresponding to the division number after change from the time of calculation switching Calculate the Fourier coefficients using the estimates. Thus, it is possible to execute a regular operation using only the number of divisions after the change. Therefore, it is possible to prevent the torque fluctuation and the power fluctuation of the AC motor from being suddenly changed due to the sudden change of the primary current operation value by the Fourier series expansion when the division number is changed.

In the second aspect of the present invention, the inverter control unit includes a plurality of sampling units (51, 52), a Fourier coefficient calculation unit (53), and a division number change unit (54).
The plurality of sampling units perform sampling of the phase current by the division number before change and sampling of the phase current by the division number after change in a transition period which is a period of k periods of electrical angle from when change of division number is notified. Run in parallel.
During the transition period, the Fourier coefficient operation unit calculates Fourier coefficients using the number of divisions before change, and switches the end of the transition period to the operation by the number of divisions after change as operation switching time (tx).
Also in this aspect, it is possible to prevent the sudden change of the primary current calculation value at the time of changing the number of divisions.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram of MG drive system to which the control apparatus of the alternating current motor by each embodiment is applied. FIG. 2 is a control block diagram of an inverter control unit of FIG. 1; The figure explaining the integration method (1) of the Fourier coefficient calculation by a prior art. The figure explaining the subject which arises at the time of division number change by integration method (1). The figure explaining the integration method (2) of the Fourier coefficient calculation by a prior art. A figure explaining a subject which arises at the time of division number change by integration method (2). FIG. 5 is a control block diagram of the current processing unit according to the first embodiment. FIG. 7 is a diagram for explaining an integration method of Fourier coefficient calculation according to the first embodiment. 4 is a flowchart of Fourier coefficient calculation processing according to the first embodiment. The time chart explaining the processing at the time of (a) normal operation processing and (b) division number change by a 1st embodiment. The figure which shows the element of (a) phase current detected value in the case of the number N of division | segmentation before change N = 6, and (b) Fourier coefficient. The figure which shows the element of (a) phase current estimated value in the case of division | segmentation number M = 10 after change, and (b) Fourier coefficient. The control block diagram of the current processing part by a 2nd embodiment. FIG. 10 is a control block diagram of a current processing unit according to a third embodiment. The time chart explaining the processing at the time of division number change by a 3rd embodiment.

Hereinafter, a plurality of embodiments of a control device for an AC motor will be described based on the drawings. Substantially the same configurations in the plurality of embodiments will be assigned the same reference numerals and descriptions thereof will be omitted. In addition, the following first to third embodiments are collectively referred to as “the present embodiment”.
The control apparatus for an AC motor according to the present embodiment is an apparatus for controlling energization of an MG, which is a three-phase AC motor, in a system for driving a motor generator (hereinafter referred to as "MG") that is a power source of a hybrid vehicle or an electric vehicle. . The “MG” and the “MG control device” in each embodiment correspond to the “AC motor” and the “control device for the AC motor” described in the claims.

[System configuration]
First, an entire configuration of an MG drive system to which the MG control device of each embodiment is applied will be described with reference to FIG. FIG. 1 illustrates a system comprising one MG.
The MG drive system 90 is a system that converts the DC power of the battery 11, which is a chargeable / dischargeable secondary battery, into three-phase AC power by the inverter 20 and supplies it to the MG 80. In the MG drive system 90, the MG control device 10 mainly includes an inverter 20 and an inverter control unit 30. The MG control apparatus 10 is similarly applicable to an MG drive system provided with two or more MGs.
MG control device 10 may be applied to an MG drive system including a converter that boosts the voltage of battery 11 and outputs the boosted voltage to inverter 20. In addition, the MG control device 10 is similarly applicable to an MG drive system provided with two or more MGs.

  The MG 80 is, for example, a permanent magnet synchronous three-phase AC motor. In the present embodiment, the MG 80 has a function as an electric motor that generates a torque for driving the drive wheels of the hybrid vehicle, and a function as a generator that recovers the energy transmitted from the engine and the drive wheels by power generation.

  The current path connected to at least one of the three-phase windings 81, 82, 83 of the MG 80 is provided with a current sensor for detecting a phase current. In the representative embodiment shown by the solid line in FIG. 1, a current sensor 87 for detecting the V-phase current Iv is provided in the current path connected to the V-phase winding 82, and the V-phase current is detected as one phase current. The inverter control unit 30 acquires Iv. In another embodiment, the U-phase current Iu or the W-phase current Iw may be acquired by the inverter control unit 30 as one-phase current. Further, as shown by a broken line in FIG. 1, in addition to the current sensor 87 for detecting the V-phase current Iv, a current sensor 88 for detecting the W-phase current Iw may be further provided. Alternatively, three-phase current may be detected.

The configuration of the arithmetic processing according to the number of phases of the current to be detected is appropriately applied by applying each embodiment disclosed in Patent Document 1 (Japanese Patent No. 5741966) or Patent Document 2 (Japanese Patent No. 5888567) described later. It is possible to design.
The electrical angle θ of the MG 80 is detected by, for example, a rotation angle sensor 85 such as a resolver.

  In the inverter 20, six switching elements 21 to 26 in upper and lower arms are bridge-connected. Specifically, switching elements 21, 22 and 23 are U-phase, V-phase and W-phase upper arm switching elements respectively, and switching elements 24, 25 and 26 are respectively below U-phase, V-phase and W-phase It is a switching element of an arm. The switching elements 21 to 26 are, for example, IGBTs, and parallel connection is made of reflux diodes that allow current from the low potential side to the high potential side.

The inverter 20 converts DC power into three-phase AC power by the switching elements 21 to 26 operating according to the gate signals UU, UL, VU, VL, WU, and WL from the inverter control unit 30. Then, phase voltages Vu, Vv, Vw according to the voltage commands calculated by inverter control unit 30 are applied to respective phase windings 81, 82, 83 of MG80. The smoothing capacitor 15 smoothes the system voltage Vsys input to the inverter 20.
The voltage sensor 27 detects a system voltage Vsys.

  The inverter control unit 30 is configured by a microcomputer or the like, and internally includes a CPU, a ROM, an I / O (not shown), and a bus line connecting these components. The microcomputer executes software processing by executing a program stored in advance by the CPU and control by hardware processing by a dedicated electronic circuit.

The inverter control unit 30 acquires the system voltage Vsys detected by each sensor, the two-phase phase currents Iv and Iw, and the electrical angle θ. Further, the inverter control unit 30 acquires an electrical angular velocity ω [deg / s] obtained by time-differentiating the electrical angle θ by the differentiator 86. The differentiator 86 may be provided inside the inverter control unit 30.
The electrical angular velocity ω is converted to the rotation speed Nr [rpm] by multiplying the proportional constant. In the present specification, “the number of revolutions obtained by converting the electrical angular velocity ω” is omitted, and is appropriately referred to as “the number of revolutions ω”, and “the number of revolutions ω” and “the number of revolutions Nr” are used in combination. In particular, the "rotational speed Nr" is used as information acquired by the division number changing unit in the current processing unit described later. In the description of motor control other than that, "rotational speed ω" is mainly used.

Further, the inverter control unit 30 receives the torque command Trq ^* from the host control circuit.
The inverter control unit 30 calculates gate signals UU, UL, VU, VL, WU, and WL for operating the inverter 20 based on the information. In response to gate signals UU, UL, VU, VL, WU and WL, inverter 20 operates switching elements 21 to 26 to convert DC power input from battery 11 into AC power and supplies it to MG 80.

[Configuration of inverter control unit]
Next, the configuration of inverter control unit 30 will be described with reference to FIG.
The inverter control unit 30 has a torque estimation unit 32, a torque feedback control unit 340, a current command calculation unit 35, a current feedback control unit 380, and a modulator 60 as a configuration of general feedback control ("FB control" in the figure). And a gate signal generation unit 79. In the present embodiment, the current processing unit 50 includes the function of converting the fixed coordinate system into the rotational coordinate system by vector control. In addition to including the current processing unit 50 which is the characteristic configuration, the inverter control unit 30 may include the spectrum calculation unit 40 as indicated by a broken line.

  First, a general feedback control configuration will be described. The present embodiment is established in a configuration in which at least one of the currents flowing through the three-phase windings 81, 82, 83 of the MG 80 is fed back. Therefore, inverter control unit 30 may include only current feedback control unit 380 and may not include torque feedback control unit 340. Alternatively, as shown in FIG. 2, only the torque feedback control unit 340 configured to calculate the torque estimated value Trq_est based on the feedback current may be provided.

However, as a configuration having both torque feedback control unit 340 and current feedback control unit 380 is general as a configuration that is actually applied to MG drive system 90 of a hybrid vehicle, the configuration is representative here. This embodiment will be described as a new embodiment.
In this configuration, the feedback method for calculating the voltage vector is switched according to the modulation factor calculated from the calculated amplitude Vr of the voltage vector and the system voltage Vsys. That is, there are a case where torque feedback control unit 340 and current feedback control unit 380 cooperate to calculate a voltage vector, and a case where current feedback control unit 380 independently calculates a voltage vector.

The torque feedback control unit 340 has a torque subtractor 33 and a controller 34.
The current feedback control unit 380 includes a current subtractor 36, a controller 37, a controller 38, and a voltage amplitude / phase operation unit 39. Among these, the controller 37, the controller 38 and the voltage amplitude / phase operation unit 39 are selectively provided in accordance with the above two feedback methods.

First, a configuration common to both feedback schemes will be described.
The current processing unit 50 feeds back the dq axis currents Id and Iq calculated based on the phase current detection value to the current subtractor 36.
The current command calculation unit 35 calculates the dq-axis current commands Id ^* and Iq ^* using a map or a mathematical expression based on the torque command Trq ^{* so} that, for example, the maximum torque per current can be obtained.
The current subtractor 36 of the current feedback control unit 380 calculates current deviations ΔId, ΔIq between the dq-axis current commands Id ^* , Iq ^* and the dq-axis currents Id, Iq fed back from the current processing unit 50.

Subsequently, a configuration in the case where torque feedback control unit 340 and current feedback control unit 380 cooperate to calculate a voltage vector will be described.
The torque estimation unit 32 calculates a torque estimated value Trq_est based on the dq-axis currents Id and Iq and the motor constant of the MG 80.

The torque subtractor 33 of the torque feedback control unit 340 calculates a torque deviation ΔTrq between the torque command Trq ^* and the torque estimated value Trq_est. The controller 34 calculates the voltage phase φ by PI calculation so that the torque deviation ΔTrq converges to 0, and outputs the voltage phase φ to the modulator 60.
Further, the controller 37 of the current feedback control unit 380 calculates the voltage amplitude Vr by PI calculation so as to cause the current deviations ΔId and ΔIq to converge to 0, and outputs the voltage amplitude Vr to the modulator 60.

Next, a configuration in the case where the current feedback control unit 380 independently calculates a voltage vector will be described.
The controller 38 of the current feedback control unit 380 calculates dq axis voltage commands Vd ^* and Vq ^* by PI calculation so that the current deviations ΔId and ΔIq converge to zero. Voltage amplitude / phase operation unit 39 converts dq axis voltage commands Vd ^* and Vq ^* into voltage amplitude Vr and voltage phase φ, and outputs the result to modulator 60. Although FIG. 2 shows an example in which the voltage phase φ is defined based on the d axis, the voltage phase may be defined based on the q axis.

Thus, the modulator 60 receives the voltage amplitude Vr and the voltage phase φ calculated by any feedback method. The modulator 60 also receives information such as the system voltage Vsys, the electrical angle θ, and the rotational speed ω. The modulator 60 outputs a voltage signal for operating the inverter 20 to the gate signal generation unit 79 based on the information.
The modulator 60 selects an appropriate pattern signal from among, for example, a plurality of pulse patterns stored in advance as a voltage signal. Alternatively, the PWM signal is generated by comparing the phase voltage and the carrier. Also, these signals may be switched according to the modulation factor or the like.
Gate signal generation unit 79 generates gate signals UU, UL, VU, VL, WU, and WL based on the pulse pattern or PWM signal output from modulator 60, and outputs the gate signals to switching element 21-26 of inverter 20. .

  Spectrum operation unit 40 detects or estimates the spectrum of one or more phase currents flowing to MG 80. For example, the spectrum operation unit 40 may acquire the V-phase current Iv and detect the spectrum of the phase current by means such as fast Fourier transform (FFT), or based on the voltage signal output from the modulator 60. Spectrum may be estimated.

[Configuration and action of current processing unit]
Next, the configuration and operation of the current processing unit 50 will be described. In the current processing unit 50, in addition to the V-phase current Iv detected by the current sensor 87, the electrical angle θ and the rotational speed Nr are input.
By the way, as it describes in patent document 1 which is a prior art, in a MG control device, a high-order component may be superimposed on a phase current to be fed back, or a phase current may be offset. Therefore, by performing feedback control using the primary current operation value extracted by Fourier series expansion of the phase current detection value, noise due to higher order components can be reduced, and torque fluctuation and power fluctuation due to offset of the phase current can be suppressed. It becomes.

The main functions of the current processing unit 50 of the present embodiment correspond to the combination of the “primary current calculation unit” and the “two-phase to three-phase conversion unit” disclosed in Patent Document 1. That is, the current processing unit 50 performs a Fourier series expansion of the phase current detection value detected by the current sensor 87 to extract a first order component, and further converts the first order component of the phase current into a dq axis current for feedback. Equipped with
In the prior art of Patent Document 1, in this Fourier series expansion, Fourier coefficients are calculated by integrating phase current detection values sampled at sampling intervals obtained by dividing an electrical angle k period by a division number N over the electrical angle k period. In Patent Document 1, "a sampling interval obtained by dividing an electrical angle k cycle by a division number N" is referred to as "an integration angle interval". The concept of the integration angle, the arithmetic expression of the Fourier coefficient, the arithmetic expression of the primary current using the Fourier coefficient, and the like conform to the disclosed contents of Patent Document 1, and the detailed description will be omitted in this specification.

In the second embodiment of the prior art, the interval of the integration angle is set to a constant interval Δ obtained by equally dividing the electrical angle k period by the division number N. In this configuration, the Fourier coefficients a1, b1 and, for example, the V-phase primary current Iv1s are calculated by the equations (1.1) to (1.3). Equations (1.2) and (1.3) represent integration operations in the integration period.
In the following equation, the variable "n" is used for sampled values. In addition, for the symbol "A" of the Fourier coefficient in the formula, in the specification and some of the drawings, the letter "a" is substituted for convenience.

Further, paragraph [0084] of Patent Document 1 describes as follows.
“When the division number N is fixed, the cycle of integration timing fluctuates according to the rotation speed Nr. Therefore, the division number N is determined by the rotation speed Nr of the AC motor or the electric frequency so that the accuracy of integration can be properly secured Specifically, the number of divisions N may be decreased as the number of rotations Nr or the electrical frequency is increased, and the number of divisions N may be increased as the number of rotations Nr or the electrical frequency is decreased.

Patent Document 1 does not describe at all immediately after changing the number of divisions, the integration calculation in the period of the electrical angle k period after switching the number of divisions used for the calculation of Fourier coefficients. However, the following problems may occur in the calculation when changing the number of divisions. This problem will be described on the assumption of two integration methods with reference to FIGS. 3 to 6.
Here, the cycle of the integration period is described as “k = 1”. Further, the integration period in the case of “k = 1” is described as “one cycle of electricity”.

The first integration method shown in FIG. 3 is a method of calculating the current integration value by subtracting the oldest value from the previous integration value for one cycle of electricity and adding the latest value. FIG. 3 (a) shows a control block, and FIG. 3 (b) shows a time change of the V-phase current Iv (θ) which is a function of the electrical angle θ.
<1> is “an integrated value of N (that is, one cycle) in the previous calculation”. The “Nth previous Iv cos θ and I v sin θ” of <2> correspond to the “discarded value” of FIG. Similarly, the “sampled Iv cos θ and I v sin θ” of <3> correspond to the “current value”. <4> is the “N (in other words, one cycle) integrated value in the current calculation”.
<4> is calculated by subtracting <2> from <1> and adding <3>.

FIG. 4 shows how the number of divisions is changed from N (e.g. 16) to M (e.g. 12) in the first integration method. Here, “Iv sin θ” is representatively shown as “I v cos θ” and “I v sin θ” integrated in Fourier coefficient calculation.
Assuming that the change timing of the division number coincides with the operation timing, the Fourier coefficient a1 calculated at the moment when the division number is changed has the same value as shown in the equation (2).

In the subsequent period of one cycle of electricity, since the primary current value to be calculated is not originally related to the division number, the integrated values a1 and b1 before and after the division number change must be the same value. Therefore, as shown in FIG. 4A, the processing is ideal in which the values of 16 points before the change of the division number are subtracted and the values of 12 points after the change of the division number are added. However, in the actual processing, only the 12 points corresponding to the 12 points added after the change of the division number are subtracted out of the values of 16 points before the change of the division number, and the value of 4 points remains.
Thus, due to the difference between the number of values to be added and the number of values to be subtracted, as shown in FIG. 4B, an offset occurs in the primary current calculation value after changing the number of divisions, and the amplitude increases. .

  Next, in the second integration method shown in FIG. 5, from the sampling time t [n-N] N times earlier to the current sampling time t [n-1], the electrical angle θ [n-N]. N phase current detection values Iv [n−N]... Iv [n−1] sampled at θ [n−1] are held. Then, at each calculation time, Fourier coefficients a1 and b1 are calculated by integrating the values of N pieces of Iv cos θ and I v sin θ retroactively from the present.

FIG. 6 shows how the number of divisions is changed from N (for example 16) to M (for example 8) in the second integration method. As shown in FIG. 6A, in this method, the period of one cycle of electricity after the number of divisions is changed, and the integration cycle of the number M of divisions after change does not become one cycle of electricity.
As a result, as shown in FIG. 4B, the primary current calculation value fluctuates in the period of one cycle of electricity after changing the number of divisions.

As described above, in the conventional integration method for calculating the Fourier coefficient, the phase current detection value by the division number N before change and the phase current detection by the division number M after change during the period of one electric cycle from the time of change of division number An irregular operation is performed using both the value and the value. At this time, there is a possibility that the primary current operation value Iv1s by the Fourier series expansion may be suddenly changed, and torque fluctuation and power fluctuation of the MG 80 may occur.
Therefore, the present embodiment is characterized in the configuration and operation of a current processing unit for preventing abrupt change of the primary current calculation value by Fourier series expansion when the number of divisions is changed.

Hereinafter, the detailed configuration of the current processing unit 50 will be described for each embodiment. As a code of the current processing unit of each embodiment, the third digit following “50” is given a number of the embodiment for distinction.
First Embodiment
As shown in FIG. 7, the current processing unit 501 of the first embodiment includes a sampling unit 51, a Fourier coefficient calculation unit 53, a division number change unit 54, a retrospective estimation unit 55, and a current vector calculation unit 56.

  When the integration period of the Fourier series expansion is generalized, the sampling unit 51 samples the phase current detection value at sampling intervals obtained by dividing the electrical angle k period (k is a natural number) by the "division number which is an integer of 2 or more". Do. Further, the Fourier coefficient calculation unit 53 electrically converts the calculated value based on the phase current detection value or the phase current estimated value in the “Fourier series expansion that extracts and feeds back the primary current of the phase as a function of the electric current as the phase current”. The Fourier coefficients are calculated by integrating over k periods.

However, in the first to third embodiments, the cycle of the integration period is “k = 1”, and the integration period in the case of “k = 1” is described as “one electricity cycle”. In the first to third embodiments, the V-phase current Iv detected by the one-phase current sensor 87 is input to the sampling unit 51.
Therefore, the sampling unit 51 according to the first to third embodiments obtains the electrical angle θ and the V-phase current Iv, and at sampling intervals obtained by dividing one cycle of electricity by “the number of divisions that is an integer of 2 or more”. The phase current detection value Iv [n] is sampled for each angle θ [n].

Hereinafter, the symbol of the division number uses "N" as a rule, and when referring to the change of the division number, it distinguishes the division number before change as "N" and the division number after change as "M". Moreover, in FIG. 9, FIG. 10, and numerical formula, "p" is used as a variable generally representing the number of divisions.
Although the number of divisions is conceptually defined as "an integer of 2 or more", it is preferable that the number of divisions in practice be set to 3 or more.

The division number changing unit 54 can change the number of divisions at an arbitrary timing according to the rotation speed Nr of the MG 80, the spectrum, and the like. For example, according to the knowledge of Patent Document 1, the division number changing unit 54 may change the number of divisions to be smaller as the rotation number Nr becomes higher and to increase the division number as the rotation number Nr becomes lower. Further, the division number changing unit 54 may prohibit the use of the specific number of divisions when the amplitude of the phase current spectrum of the specific frequency is equal to or greater than a predetermined threshold. For example, when the amplitude of the spectrum of the phase current of the 11th or 13th component is equal to or more than the threshold value, it may be considered to prohibit the use of “12” as the division number.
When the division number change unit 54 determines to change the division number N before change to the division number M after change, the division number change unit 54 notifies the sampling unit 51 and the Fourier coefficient calculation unit 53 of the division numbers N and M before and after the change. The number of post-divisions M is notified to the retrospective estimation unit 55.

The retrospective estimation unit 55 is the most characteristic configuration in the first and second embodiments.
Hereinafter, “when the number of divisions is changed by the number-of-divisions change unit 54, the time point at which the Fourier coefficient calculation unit 53 switches to calculation with the number of divisions M after change” is set as “operation switching time tx”. In the first and second embodiments, the delay time of control is ignored, and it is assumed that the change in division number and the operation switching time tx are substantially simultaneous.
The retrospective estimation unit 55 estimates the electrical angle and phase current corresponding to the number of divisions after change M as the electrical angle and phase current value used for computation by the Fourier coefficient computing unit 53 in the integration period of 1 cycle of electricity from the switching time tx. Calculating operation is performed from tx back when calculating switching.
At this time, the retrospective estimation unit 55 acquires from the Fourier coefficient calculation unit 53 the electrical angle θx at the time of operation switching and “Fourier coefficients a _sum and b _sum calculated using the division number N before change”. Perform "inverse operation" based on. Details of this inverse operation will be described later.

The Fourier coefficient calculation unit 53 always obtains the electrical angle θ [n] and the phase current detection value Iv [n] from the sampling unit 51. When the division number is changed, the electric angle θ [j] and the phase current estimated value Ivest [j] are acquired from the retrospective estimation unit 55 during the period of one electric cycle from the operation switching time tx. The variable "j" is used hereinafter for the estimated value.
Thus, the phase current detection value Iv [n] or the estimated value Ivest [j] and the corresponding electrical angles θ [n] and θ [j] are one set of information. However, since these will always be redundant, the description in the following specification mainly refers to the phase current detection value Iv [n] or the estimated value Ivest [j], and the corresponding electrical angle θ [n] The description of θ, j is omitted as appropriate. For example, when the phase current detection value Iv [n] or the estimated value Ivest [j] is acquired, it is interpreted that acquiring the information of the corresponding electrical angle simultaneously is obvious.

When the division number is not changed, the Fourier coefficient calculation unit 53 calculates Fourier coefficients a _sum and b _sum by integrating calculation values based on the phase current detection value Iv [n] acquired from the sampling unit 51 for one period of electricity. Do.
On the other hand, when the division number is changed, the Fourier coefficient calculation unit 53 calculates the calculated value based on the phase current detection value Iv [n] acquired from the sampling unit 51 and the phase current estimated value Ivest acquired from the retrospective estimation unit 55. Fourier coefficients a _sum and b _sum are calculated by integrating the calculated values based on [j] over one period of electricity.
Here, “computed value based on phase current detection value or estimated value” means elements a [n], b [n] or a [j], b [j] of Fourier coefficients in FIG.

The current vector calculation unit 56 directly calculates the dq-axis currents Id and Iq without calculating the primary component of the V-phase current based on the Fourier coefficients a _sum and b _sum calculated by the Fourier coefficient calculation unit 53.
The configuration of the current vector calculation unit 56 is the same as that disclosed in Japanese Patent No. 5888567. Hereinafter, this patent 5888567 gazette is called "patent documents 2". Since patent document 2 is not related to the subject of the whole this invention, it does not describe in the column of "the background art", but is mainly quoted by description of 1st Embodiment.

Paragraph [0064] of Patent Document 2 discloses a calculation formula for calculating the dq-axis currents Id and Iq based on the Fourier coefficient calculated from the V-phase current. The current vector calculator 56 of the first embodiment calculates the dq axis currents Id and Iq using this formula. That is, in the first embodiment, "the dq axis current calculation value obtained by coordinate converting the primary component of the phase current" is described in "the problem to be solved by the invention""the primary current calculation value by Fourier series expansion" It corresponds to
Note that, even in a configuration in which the dq-axis currents Id and Iq are calculated based on the Fourier coefficients calculated from the U-phase current or the W-phase current instead of the V-phase current, the corresponding calculation formulas in Patent Document 2 may be similarly used. it can.

FIG. 8 will be referred to for an integration method of Fourier coefficient calculation according to the first embodiment. FIG. 8 corresponds to FIG. 4 and FIG. 6 showing the problems of the above-described two accumulation methods.
For example, when the number of divisions is changed from “N = 16” to “M = 8”, the Fourier coefficient calculation unit 53 obtains sampling by the number of divisions before change N in Fourier coefficient calculation after tx at the time of operation switching. Not use the detected value. Instead, the post-change estimation unit 55 estimates the retrospective estimation unit 55 based on the “Fourier coefficients a _sum and b _sum calculated using the pre-change division number N” as the past value for one electric cycle before the change of the division number The estimated value corresponding to the division number M is used.

In short, the retrospective estimation unit 55 integrates the “estimated value before changing the number of divisions” and the “detected value after changing the number of divisions” over one period of electricity. In FIG. 8, estimated values are indicated by squares and detected values are indicated by circles. Also, the value when the current time is t4 is indicated by a solid line. The estimated values of the dashed square indicate the estimated values used at times t0 to t3 after the operation switching time tx.
Here, it is preferable that the retrospective estimation unit 55 use, as “the Fourier coefficients a _sum and b _sum calculated using the number of divisions before change N”, values calculated immediately before the operation switching time tx. This "immediately before" includes substantial "simultaneous".

  Next, with reference to FIG. 9 and FIG. 10, Fourier coefficient calculation processing according to the first embodiment will be described. The flowchart of FIG. 9 shows a routine of Fourier coefficient calculation processing. In the following description of the flow chart, the symbol "S" means a step. In S2 and S5 of the flowchart, reference is made to the time charts of FIGS. 10 (a) and 10 (b), respectively.

In S1, the Fourier coefficient calculation unit 53 acquires the phase current detection value Iv [p-1] newly sampled by the sampling unit 51 as a current value. The phase current detection values Iv [0],..., Iv [p-2] up to the previous time are acquired in the routine up to the previous time in a period of one cycle of electricity going back from the current time. Here, p indicates the number of divisions.
In S2, normal calculation processing according to equations (3.1) to (3.5) is performed. The unit of the electrical angle θ is [deg] in the following equation.

First, the current value of the electrical angle θ is set to θ [p−1] according to equation (3.1).
Hereinafter, a [n] and b [n] integrated in the equations (3.4) and (3.5) will be referred to as “elements of Fourier coefficients”. The Fourier coefficient calculation unit 53 calculates an element a [p based on the electric value θ [p−1] of the current value and the phase current detection value Iv [p−1] according to the equations (3.2) and (3.3). -1] and b [p-1] are calculated. Then, the Fourier coefficient calculation unit 53 integrates p elements a [n] and b [n] including the elements calculated in the routine up to the previous time according to the equations (3.4) and (3.5). Then, Fourier coefficients _asum and _bsum are calculated.

In S3, the division number changing unit 54 calculates the current value of the division number p based on the rotation speed of the MG 80 and the phase current spectrum.
In S4, it is determined whether the division number p is the same as the previous value. In the case of YES in S4, the process proceeds to S6, and in the case of NO, the process proceeds to the process of changing the number of divisions in S5.
In S5, the process at the time of division number change by Formula (4.1)-(4.4) is performed. The variable j takes p values of “j = 0,..., P−1” for the number of divisions p after change.

The retrospective estimation unit 55 calculates an electrical angle θ [j] corresponding to the post-change division number p according to equation (4.1) with reference to the electrical angle θx at the time of operation switching tx.
Further, the retrospective estimation unit 55 reverses the phase current estimated value Ivest [j] corresponding to the post-change division number p according to equation (4.2) using the Fourier coefficients a _sum and b _sum calculated in S2. Calculate

The Fourier coefficient calculation unit 53 uses the electrical angle θ [j] and the phase current estimated value Ivest [j] according to the equations (4.3) and (4.4) to generate elements a [j] and b [of Fourier coefficients. j] is calculated.
As shown in FIG. 10 (b), the data after changing the number of divisions includes the electrical angle θ [p-2], θ [p-1], and the phase current detection value Iv [p-2], Iv [p-1]. Etc. are used. In addition, the electrical angle θ [0], the phase current estimated value Ivest [0], and the like are used as the data before the division number change.

S6 is a step of value update processing. As shown in equations (5.1) to (5.3), the “n” th value in the current process is updated as the “n−1” th value in the next process.

Next, specific examples of the Fourier coefficient calculation process will be described with reference to FIGS. 11 and 12. Here, it is assumed that the division number p of one cycle of electricity is changed from 6 to 10 based on the V-phase current obtained by back calculation so that the dq axis current becomes “Id = −1, Iq = 1”.
When the V-phase current Iv in FIG. 11A is expressed in the form of “Iv = Asin (θ + α)”, A and α are expressed by the equations (6.1) and (6.2). The U-phase current Iu and the W-phase current Iw are illustrated only for reference and are not used for the calculation in this example.

When the division number p is 6, in FIG. 11A, six phase current detection values Iv [n] (n = 0,..., Per sampling interval 60 [deg] obtained by dividing one electric cycle into six. 5) is sampled.
The Fourier coefficient calculation unit 53 determines elements a [n] and b [n of Fourier coefficients according to equations (7.1) and (7.2) based on the electrical angle θ [n] and the phase current detection value Iv [n]. Calculate].

Formulas (8.1) and (8.2) are obtained by substituting “Iv = Asin (θ + α)” into formulas (7.1) and (7.2). Therefore, as shown in FIG. 11B, the locus of the elements a [n] and b [n] of the Fourier coefficient is a sine wave having a frequency twice that of the phase current.

The Fourier coefficient calculation unit 53 integrates the six elements a [n] and b [n] according to equations (9.1) and (9.2) to calculate Fourier coefficients a _sum and b _sum .

The current vector calculation unit 57 calculates the dq-axis currents Id and Iq according to the equations (10.1) and (10.2) based on the calculation equation disclosed in paragraph [0064] of Patent Document 2. The calculation result in this example is “Id = −1, Iq = 1”.

Subsequently, FIG. 12 will be referred to for the retrospective estimation operation when the number of divisions p is changed to 10. When the division number is 10, the sampling interval is (360/10) = 36 [deg].
The retrospective estimation unit 55 uses the Fourier coefficients a _sum and b _sum calculated based on the phase current detection value Iv [n] based on the division number 6 before the change, and calculates the phase current estimated value Ivest [ j] is estimated. Note that Ivest [j] is omitted and each current value in FIG. 12A is described as Iv [j].

こうしてフーリエ係数演算部５３は、遡及推定演算により求めた過去データと、演算切替時ｔｘ以後にサンプリングされたデータとを電気１周期にわたって積算し、フーリエ係数ａ_sum、ｂ_sumを算出する。以上で、フーリエ係数演算処理の具体例の説明を終わる。 The Fourier coefficient calculation unit 53 determines the element a [j of the Fourier coefficient according to the equations (12.1) and (12.2) based on the electrical angle θ [j] and the phase current estimated value Ivest [j] at the division number of 10. ], B [j] are calculated as past data.

Thus, the Fourier coefficient calculation unit 53 integrates the past data obtained by the retrospective estimation calculation and the data sampled after the operation switching time tx for one period of electricity to calculate Fourier coefficients a _sum and b _sum . This is the end of the description of the specific example of the Fourier coefficient calculation process.

Second Embodiment
The second embodiment will be described with reference to FIG.
The current processing unit 502 according to the second embodiment is configured to calculate the Fourier coefficient using the phase current detection value estimated by the retrospective estimation unit 55 when changing the number of divisions according to the first embodiment. And the current processing unit 501 of FIG. Further, the routine of Fourier coefficient calculation processing according to the second embodiment is the same as that in FIG.

On the other hand, the current processing unit 502 of the second embodiment has a primary current calculation unit 57, a three-phase to two-phase conversion unit 59, and the like, instead of the current vector calculation unit 56 of the first embodiment. Then, according to the configuration of Patent Document 1 instead of Patent Document 2, there is a difference in that the primary component of the phase current is once calculated from the Fourier coefficients a _sum and b _sum and then converted into dq axis current.
The primary current calculator 57 calculates, for example, the V-phase primary current Iv1s according to equation (13).

Further, as shown by the broken line, according to the seventh and eighth embodiments of Patent Document 1, for example, the primary current estimated value Iw1s_est of the W phase may be estimated by the other phase primary current estimation unit 58.
The three-to-two phase conversion unit 59 performs three-to-two phase conversion on the V-phase primary current Iv1s and the W-phase Iw1s_est to calculate dq axis currents Id and Iq.
As described above, the calculation process of the feedback current after the calculation of the Fourier coefficient may adopt any method depending on the processing capability of the control device, the relation with other control calculation, or the like.

(effect)
An effect common to the first embodiment and the second embodiment will be described.
(1) The Fourier coefficient calculation unit 53 does not use the electrical angle θ [n] and the phase current detection value Iv [n] according to the division number N before change, from the time tx of calculation switching to the period of one electric cycle, Fourier coefficients a _sum and b _sum are calculated using the electrical angle θ [j] corresponding to the number M and the phase current estimated value Ivest [j]. In this way, it is possible to execute a regular operation using only the number of divisions M after the change. Therefore, it is possible to prevent the torque fluctuation and the power fluctuation of MG 80 from being caused by the sudden change of the primary current operation value by the Fourier series expansion when the division number is changed.

(2) The retrospective estimation unit 55 can improve the calculation accuracy by using the values of the Fourier coefficients a _sum and b _sum calculated immediately before the switching time tx in the calculation of the phase current estimated value. In particular, when the current before the division number change is unstable, the effect becomes remarkable.
(3) The division number changing unit 54 changes the division number according to at least the rotation number Nr of the MG 80. Preferably, the number of divisions is decreased as the number of rotations Nr is increased, and the number of divisions is increased as the number of rotations Nr is decreased. As a result, it is possible to prevent the control from being broken in the high rotation region and to secure the detection accuracy of the primary current in the low rotation region.

Third Embodiment
A third embodiment will be described with reference to FIG. 14 and FIG. As shown in FIG. 14, the current processing unit 503 of the third embodiment includes two sampling units 51 and 52. The two sampling units 51 and 52 simultaneously perform sampling of the phase current by the division number before change and sampling of the phase current by the division number after change in the transition period of one cycle of electricity from when change of the division number is notified. And run.
In the example shown in FIG. 14, the current processing unit 503 includes the current vector calculation unit 56 similar to that of the first embodiment, but instead, a primary current calculation unit similar to that of the second embodiment. 57 and a three-phase to two-phase converter 59 may be provided.

When changing the division number from N to M, the division number change unit 54 notifies the first sampling unit 51 of the division number N before change, and notifies the second sampling unit 52 of the division number M after change.
The first sampling unit 51 samples the phase current detection value Iv [n] at the electrical angle θ [n] by the division number N before change, and outputs the sampled value to the Fourier coefficient calculation unit 53. The second sampling unit 52 samples the phase current detection value Iv [m] at the electrical angle θ [m] according to the post-change division number M, and outputs the phase current detection value Iv [m] to the Fourier coefficient calculation unit 53.

  As shown in FIG. 15, in the third embodiment, the division number change notification time tcom from the division number change unit 54 and the calculation switching time tx at which the Fourier coefficient calculation unit 53 switches the calculation are not simultaneous. The Fourier coefficient calculation unit 53 switches the calculation according to the number of divisions after the change as the calculation switching time tx when the change notification time tcom ends the "transition period equivalent to the period of one electric cycle".

For example, the first sampling unit 51 samples the phase current detection value Iv [n] by the division number N before change until the division number change notification tcom1. When the division number change notification is notified that the division number is changed to M at tcom1, the first sampling unit 51 continues sampling continuously, and the second sampling unit 52 detects the phase current according to the number of divisions after change M. Start sampling of the value Iv [m]. Thus, the transition period in which the two sampling units 51 and 52 sample the phase current in parallel is started.
During the transition period, the Fourier coefficient calculation unit 53 calculates Fourier coefficients based on the electrical angle θ [n] and the phase current detection value Iv [n] acquired from the first sampling unit 51 using the division number N before change .

  Then, from the operation switching time tx1 at which the transition period ends, the Fourier coefficient operation unit 53 uses the post-change division number M, and the electrical angle θ [m] and the phase current detection value Iv [m] obtained from the second sampling unit 52 The Fourier coefficient is calculated based on Also, the first sampling unit 51 ends sampling at tx1 at the time of operation switching.

  After that, it is notified that the division number is changed to L at the next division number change notification tcom2. Then, in the next transition period, phase current sampling with the division number M before change by the second sampling unit 52 and phase current sampling with the division number L after change by the first sampling unit 51 are performed in parallel. . During the next transition period, the Fourier coefficient calculation unit 53 calculates Fourier coefficients using the division number M before change. Then, at the operation switching time tx2 when the next transition period ends, the Fourier coefficient operation unit 53 switches to the operation with the post-change division number L.

Thus, the two sampling units 51 and 52 alternately execute sampling of the phase current by the division number before change and sampling of the phase current by the division number after change in parallel in the transition period. Thus, in the third embodiment, as in the first and second embodiments, it is possible to prevent a sudden change in the primary current calculation value due to the change in the number of divisions.
The “plurality of sampling units” is not limited to two, and three or more sampling units may alternately perform sampling of the phase current according to the number of divisions before and after the change.

(Other embodiments)
(A) In the above, although the embodiment in which the primary current is calculated based on the phase current detection value of one phase is mainly described, as disclosed in Patent Document 1 and Patent Document 2, The primary current may be calculated based on the phase current detection value of the phase or three phases. For example, in the first embodiment in which the dq axis current is calculated directly from the Fourier coefficient, the idea of the second embodiment of Patent Document 2 is applied, and the average value of the dq axis currents calculated from the two phase currents is calculated. May be

  (B) The "electrical angle k period (k is a natural number)" which is an integration period for calculating Fourier coefficients is not limited to "k = 1" but may be "kk2". The number of divisions may be changed, for example, by changing the value of k to a constant value, such as “16 divisions in 3 cycles” to “8 divisions in 3 cycles”. Alternatively, both the value of k and the number of divisions in the electrical angle k cycle may be changed, for example, “5 divisions in 2 cycles” to “7 divisions in 3 cycles”.

(C) The retrospective estimation unit 55 according to the first and second embodiments uses “the Fourier coefficients a _sum and b _sum calculated using the number of divisions before change N” due to the restriction of the processing time, etc. A value calculated several times earlier may be used. When the current before the division number change is stable, it is considered that the difference between the immediately preceding calculated value and the immediately preceding calculated value is small.

(D) The factor for changing the number of divisions in the present invention is not limited to the rotation speed of the MG 80 and the phase current spectrum, and may be due to any factor such as the driving state of the vehicle or the relation with other controls.
(E) The number of AC motor phases driven in the system to which the present invention is applied is not limited to three, and may be any number. The AC motor is not limited to a permanent magnet synchronous motor, and may be an induction motor or another synchronous motor.

(F) The control apparatus for an AC motor according to the present invention may be applied not only to the MG drive system of a hybrid car or an electric car, but also to a drive system of an AC motor for any application such as general machines.
As mentioned above, the present invention is not limited to the above-mentioned embodiment at all, and can be implemented in various forms in the range which does not deviate from the meaning of an invention.

10 ... MG control device (control device for AC motor),
20: Inverter, 21-26: Switching element,
30 · · · inverter control unit,
51, 52 ... sampling unit,
53 ··· Fourier coefficient operation unit,
54: Division number change unit,
55 ... retroactive estimation unit,
80 ... MG (AC motor).

Claims (4)

An inverter (20) which converts DC power into AC power by the operation of the plurality of switching elements (21-26) and supplies the AC power to the AC motor (80);
An inverter control unit (30) for operating the inverter based on the fed back phase current to control energization of the AC motor;
Equipped with
The inverter control unit
A sampling unit (51) for sampling the phase current detection value at sampling intervals obtained by dividing the electrical angle k period (k is a natural number) by a division number which is an integer of 2 or more;
In a Fourier series expansion that extracts and feeds back the primary current of the phase as a function of the electrical angle as a function of the phase current, the Fourier coefficient is integrated by integrating the calculated value based on the phase current detection value or the phase current estimated value over k periods A Fourier coefficient operation unit (53) for operation;
A division number changing unit (54) capable of changing the division number from the pre-change division number (N) to the post-change division number (M) at an arbitrary timing;
Assuming that the time point at which the Fourier coefficient operation unit switches to the operation after the change is the operation switching time (tx) when the division number is changed by the division number changing unit, then the Fourier coefficient operation unit performs the operation switching Corresponds to the post-modification division number based on the Fourier coefficients (a _sum , b _sum ) calculated using the pre-modification division number as the electrical angle and the phase current value used for calculation during the period from the time to the electrical angle k cycle A retrospective estimation unit (55) for performing an inverse operation of the estimated electrical angle and phase current value retroactively from the time of the operation switching;
Control device for an AC motor having:   The control device for an AC motor according to claim 1, wherein the retrospective estimation unit uses a value calculated immediately before the operation switching as the Fourier coefficient calculated using the division number before change. An inverter (20) which converts DC power into AC power by the operation of the plurality of switching elements (21-26) and supplies the AC power to the AC motor (80);
An inverter control unit (30) for operating the inverter based on the fed back phase current to control energization of the AC motor;
Equipped with
The inverter control unit
A plurality of sampling units (51, 52) for sampling phase current detection values at sampling intervals obtained by dividing an electrical angle k period (k is a natural number) by a division number which is an integer of 2 or more;
In Fourier series expansion that extracts and feeds back the primary current of the phase as a function of the electrical angle as a function of the electrical current, Fourier coefficient calculation is performed to calculate the Fourier coefficient by integrating the calculated value based on the phase current detection value over k electrical cycles Part (53),
A division number changing unit (54) capable of changing the division number from the pre-change division number (N) to the post-change division number (M) at an arbitrary timing;
Have
The plurality of sampling units perform sampling of the phase current by the division number before change and phase current by the division number after change in a transition period which is a period of k periods of electrical angle from when change of the division number is notified. Parallel to the sampling of the
The above-mentioned Fourier coefficient operation unit calculates a Fourier coefficient by the division number before change during the transition period, and switches an end time of the transition period to an operation by the division number after the change as operation switching time (tx) Control device.   The control device for an AC motor according to any one of claims 1 to 3, wherein the division number changing unit changes the division number according to at least a rotation speed of the AC motor.

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