JP2021078262A - Control apparatus for drive system - Google Patents

Abstract

To provide a control apparatus for a drive system capable of suppressing an increase of ripple current flowing through a capacitor without increasing a dimension of the drive system.SOLUTION: A control apparatus 30 determines whether or not an operation point of a rotary electric machine 10 is within a ripple occurrence range in which ripple current flowing through a capacitor 25 becomes equal to or more than a predetermined value in a period when an invertor 20 is operated by a PWM control. When it is determined that the operation point is within the ripple occurrence range, a stronger field control is performed to d axis command current Id* and q axis command current Iq*. The control apparatus 30 calculates a voltage command value used by the PWM control based on the d axis command current Id* and q axis command current Iq*.SELECTED DRAWING: Figure 7

Description

The present invention relates to a control device for a drive system that drives a rotary electric machine.

A drive system is known that includes an inverter that converts a DC voltage into an AC voltage and drives a rotary electric machine by the AC voltage converted by the inverter. The drive system is equipped with a capacitor to suppress fluctuations in the current flowing through the inverter. When the switch of the inverter is switched by PWM control, the ripple current component due to the carrier wave used in PWM control may be superimposed on the current flowing through the capacitor, and the ripple current may flow through the capacitor. Since the ripple current increases the calorific value of the capacitor, it is necessary to increase the heat resistance of the capacitor in consideration of the calorific value when the ripple current flows. The improvement in heat resistance is a factor that increases the physique of the capacitor.

Patent Document 1 discloses a power conversion device including a converter that supplies a voltage to a capacitor and suppresses an increase in a ripple current flowing through the capacitor due to a voltage applied to the converter. Specifically, the power conversion device includes an observer that generates an AC command value for canceling the ripple current based on a parameter when operating the inverter. By superimposing the AC command value generated by the observer on the voltage command value of the converter, the converter supplies a voltage to the capacitor that cancels the ripple current.

Japanese Unexamined Patent Publication No. 2009-17662

In the invention disclosed in Patent Document 1, since a converter that supplies a voltage to a capacitor is indispensable, it cannot be applied to a drive system that does not have a converter. Further, when a converter is added to the drive system in order to suppress an increase in the ripple current, there is a concern that the physique of the drive system will be increased by the amount of the added converter.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for a drive system capable of suppressing an increase in a ripple current flowing through a capacitor without increasing the physique of the drive system.

In order to solve the above problems, in the present invention, a rotary electric machine having an armature winding and a switch are provided, and the DC voltage from the DC power supply is converted into an AC voltage by the switching operation of the switch to convert the armature winding. The present invention relates to a drive system control device applied to a drive system including an inverter supplied to a line and a capacitor connected to the input side of the inverter. The control device includes a command information generator that generates command current vector information for controlling the current flowing through the armature winding based on the torque command value of the rotary electric machine, and a command information generator based on the command current vector information. The operation unit that performs the switching operation of the switch by the PWM control based on the magnitude comparison between the voltage command value supplied from the inverter to the armature winding and the carrier, and the period during which the PWM control is performed, said. Based on the torque command value and the speed command value of the rotary electric machine, the operating point determination for determining whether or not the operating point of the rotary electric machine is included in the ripple generation range in which the ripple current flowing through the capacitor is equal to or higher than a predetermined value. When it is determined that the unit and the operating point of the rotary electric machine are included in the ripple generation range, the absolute value of the d-axis current determined from the generated command current vector information is reduced and generated. A command value changing unit that changes the command current vector information so as to increase the magnitude of the command current vector determined from the command current vector information is provided, and the operation unit uses the changed command current vector information. Based on this, the voltage command value used in the PWM control is calculated.

The ripple current flowing through the capacitor is dominated by the secondary component of the carrier wave used in PWM control. The secondary component G2 of the ripple current can be calculated by the following formula (1).

Ｉｍは、回転電機の電機子巻線に流れる電流の振幅であり、Ｊ１は、１次のベッセル関数である。ａは、変調率である。１次のベッセル関数は、駆動システムで取り得る変調率ａの範囲において変調率ａとの間に負の相関があるため、変調率ａを増加させることにより、リプル電流の２次成分Ｇ２を低下させることができ、ひいてはリップル電流の増加を抑制することができる。

Im is the amplitude of the current flowing through the armature winding of the rotating electric machine, and J1 is a first-order Bessel function. a is the modulation factor. Since the first-order Bessel function has a negative correlation with the modulation factor a in the range of the modulation factor a that can be taken by the drive system, the secondary component G2 of the ripple current is lowered by increasing the modulation factor a. As a result, the increase in ripple current can be suppressed.

In the above configuration, during the period when PWM control is performed, the operating point of the rotary electric machine is within the ripple generation range in which the ripple current flowing through the capacitor is equal to or higher than a predetermined value based on the torque command value and the speed command value for the rotary electric machine. Whether or not it is included is determined. When it is determined that the operating point of the rotary electric machine is included in the ripple generation range, the absolute value of the d-axis current determined from the generated command current vector information is reduced, and it is determined from the generated command current vector information. The command current vector information is changed so as to increase the magnitude of the command current vector. As the magnitude of the command current vector increases, the command voltage increases, and the modulation rate in PWM control increases. As a result, the increase in the ripple current flowing through the capacitor can be suppressed without applying a voltage for suppressing the increase in the ripple current to the capacitor, so that the current flows through the capacitor without increasing the physique of the drive system. The increase in ripple current can be suppressed.

Configuration diagram of the drive system. The figure explaining the operating area of a rotary electric machine. Functional block diagram of the control device. The figure explaining the minimum current maximum torque control. The figure explaining the operating area of a rotary electric machine. The figure explaining the strong field control. A flowchart illustrating a procedure for operating an inverter. The figure explaining the action effect of this embodiment. The block diagram of the drive system which concerns on 2nd Embodiment. A flowchart illustrating a procedure for operating an inverter.

<First Embodiment>
Hereinafter, a first embodiment in which the drive system according to the present invention is applied to a vehicle will be described with reference to the drawings.

As shown in FIG. 1, the drive system 100 includes a rotary electric machine 10, an inverter 20, and a capacitor 25. The rotary electric machine 10 is a three-phase synchronous machine, and includes U, V, and W phase windings 11U, 11V, and 11W as stator windings. In the present embodiment, the rotary electric machine 10 is used as an in-vehicle main engine that powers a vehicle.

The inverter 20 includes a series connection body of the upper arm switches SUp, SVp, SWp and the lower arm switches SUn, SVn, SWn for three phases. In the present embodiment, voltage-controlled semiconductor switching elements are used as the switches SUp, SUn, SVp, SVn, SWp, and SWn, and more specifically, IGBTs are used. Freewheel diodes DUp, DUn, DVp, DVn, DWp, and DWn are connected in antiparallel to each switch SUp, SUn, SVp, SVn, SWp, and SWn.

The collector of the U-phase lower arm switch SU is connected to the emitter of the U-phase upper arm switch SUP. The collector of the V-phase lower arm switch SVn is connected to the emitter of the V-phase upper arm switch SVp. The collector of the W phase lower arm switch SWn is connected to the emitter of the W phase upper arm switch SWp. The collectors of the U, V, and W phase upper arm switches SUp, SVp, and SWp are connected to the high voltage side line 21 connected to the first terminal 23 of the inverter 20. The emitters of the U, V, and W phase lower arm switches SUn, SVn, and SWp are connected to the low voltage side line 22 connected to the second terminal 24 of the inverter 20.

The first terminal 23 of the inverter 20 is connected to the positive electrode side terminal of the storage battery 200, which is a DC power source, and the second terminal 24 is connected to the negative electrode side terminal of the storage battery 200.

A capacitor 25 is connected to the input side of the inverter 20. Specifically, one terminal of the capacitor 25 is connected to a wiring connecting the first terminal 23 and the positive electrode side terminal of the storage battery 200, and the other terminal connects the second terminal 24 and the negative electrode side terminal of the storage battery 200. It is connected to the connecting wiring. As a result, the capacitor 25 is connected in parallel to the inverter 20. The capacitor 25 may be built in the inverter 20 by connecting the high voltage side line 21 and the low voltage side line 22.

The first end of the U-phase conductive member 21U is connected to the connection point between the U-phase upper arm switch SUP and the U-phase lower arm switch SUn. The second end of the U-phase conductive member 21U is connected to the first end of the U-phase winding 11U. The first end of the V-phase conductive member 21V is connected to the connection point between the V-phase upper arm switch SVp and the V-phase lower arm switch SVn. The second end of the V-phase conductive member 21V is connected to the first end of the V-phase winding 11V. The first end of the W-phase conductive member 21W is connected to the connection point between the W-phase upper arm switch SWp and the W-phase lower arm switch SWn. The second end of the W-phase conductive member 21W is connected to the first end of the W-phase winding 11W. The second ends of the U, V, W phase windings 11U, 11V, 11W are connected to each other at a neutral point.

The drive system 100 includes a first current sensor 31u, a second current sensor 31v, a third current sensor 31w, a rotation angle sensor 32, and a voltage sensor 33. The first current sensor 31u detects the U-phase current flowing through the U-phase conductive member 21U. The second current sensor 31v detects the V-phase current flowing through the V-phase conductive member 21V. The third current sensor 31w detects the W-phase current flowing through the W-phase conductive member 21W. The rotation angle sensor 32 detects the electric angle θ, which is the angle of the rotating magnetic field of the rotating electric machine 10. The voltage sensor 33 detects the input voltage VINV from the storage battery 200 input to the inverter 20. In this embodiment, each current sensor may be provided so as to be able to detect currents for at least two phases.

The drive system 100 includes a control device 30. The control device 30 is mainly composed of a microcomputer, and switches each switch constituting the inverter 20 in order to feedback-control the control amount of the rotary electric machine 10 to the command value thereof. In this embodiment, the control amount is torque.

The control device 30 selects and executes any of PWM control, overmodulation control, and rectangular control according to the operating point of the rotary electric machine 10. First, the operating region of the rotary electric machine 10 will be described with reference to FIG.

FIG. 2 shows an operating region of the rotary electric machine 10 when the horizontal axis is the rotation speed Nm and the vertical axis is the torque Trq. In the rotary electric machine 10, there is a first range B1 which is a speed range in which the upper limit value of the torque that can be output by the rotary electric machine 10 does not change regardless of the rotation speed Nm on the lower rotation side than the base rotation speed N1. Hereinafter, in the first range B1, the range of the operating point defined by connecting the maximum torque Tmax which is the upper limit value of the torque that can be output is referred to as a constant torque line Lmax. The rotary electric machine 10 has a second range B2, which is a speed range in which the upper limit of the torque that can be output by the rotary electric machine 10 becomes smaller as the rotation speed Nm is increased on the higher rotation side than the base rotation speed N1. ..

The control device 30 acquires the torque command value Trq * and the speed command value Nm * of the rotary electric machine 10 from the upper control device. The control device 30 selects one of PWM control, overmodulation control, and rectangular control based on the operating point determined from the acquired torque command value Trq * and speed command value Nm *. The control device 30 switches the operation mode for the inverter 20 in the order of PWM control, overmodulation control, and rectangular control as the speed command value Nm * of the rotary electric machine 10 shifts from the low rotation side to the high rotation side.

PWM control is a carrier signal (carrier wave) such as a triangular wave signal and U, V, W phase command voltages Vu *, Vv *, Vw that determine the phase voltage applied to the U, V, W phase windings 11U, 11V, 11W. Based on the magnitude comparison with *, it is a control to generate an operation signal for turning on / off each of the upper arm switches SUp to SWp and each lower arm switch SUn to SWn. Each operation signal consists of an on command instructing the on operation of the switch and an off command instructing the off operation of the switch. In the present embodiment, the U, V, and W phase command voltages Vu *, Vv *, and Vw * are sinusoidal signals whose phases are 120 degrees out of phase with the electric angle θ. In PWM control, the modulation factor a, which is the ratio of the amplitudes of the U, V, and W phase command voltages Vu *, Vv *, and Vw * to the amplitude of the carrier signal, is set to 1 or less. In this embodiment, the U, V, W phase command voltages Vu *, Vv *, Vw * correspond to the voltage command values.

The overmodulation control is a control that generates each operation signal based on a magnitude comparison between the U, V, W phase command voltages Vu *, Vv *, Vw * having an amplitude larger than the amplitude of the carrier signal and the carrier signal. Is. In the overmodulation control, the modulation factor a is made larger than 1.

In the rectangular control, in each U, V, and W phase, the upper arm switch is turned on and the lower arm switch is turned off, and the upper arm switch is turned off and the lower arm switch is turned on. Each of the states is a control for generating each operation signal so that each of them is realized once in one cycle of the electric angle θ of the rotary electric machine 10. In the rectangular control, for example, the modulation factor a is 1.2 or more.

Here, when the control device 30 operates the switches SUp to SWp and Sun to SWn of the inverter 20 by PWM control, a ripple current of a predetermined value or more may flow through the capacitor 25. Therefore, it is necessary to improve the heat resistance of the capacitor 25 in consideration of the amount of heat generated when a ripple current of a predetermined value or more flows. The improvement in heat resistance is a factor that increases the physique of the capacitor 25.

It is generally known that the ripple current flowing through the capacitor 25 is dominated by the secondary component of the carrier signal in PWM control, and this secondary component G2 is approximated by the following equation (2).

Ｉｍは、回転電機１０の各Ｕ，Ｖ、Ｗ相巻線１１Ｕ，１１Ｖ，１１Ｗに流れる各相電流の振幅であり、Ｊ１は、１次のベッセル関数である。

Im is the amplitude of each phase current flowing through each U, V, W phase winding 11U, 11V, 11W of the rotary electric machine 10, and J1 is a first-order Bessel function.

Since the first-order Bessel function has a negative correlation with the modulation factor a in the range of the modulation factor a that can be taken by the drive system 100, the secondary component G2 is lowered by increasing the modulation factor a. As a result, the increase in ripple current can be suppressed. Therefore, in the present embodiment, when the PWM control is being executed and the ripple current of a predetermined value or more flows through the capacitor 25, the control device 30 suppresses the increase of the ripple current by increasing the modulation factor a. To do.

Next, among the functions of the control device 30, the functions related to PWM control will be described in detail with reference to the functional block diagram of FIG. The control device 30 includes a two-phase conversion unit 40, a command information generation unit 41, an operating point determination unit 42, a command value change unit 43, and an operation unit 44.

The two-phase conversion unit 40 uses the U, V, W phase currents in the three-phase fixed coordinate system based on the phase currents Iu, Iv, Iw detected by the current sensors 31u, 31v, 31w and the electric angle θ. Is converted into a d-axis current Idr and a q-axis current Iqr in the dq coordinate system, which is a two-phase rotation coordinate system.

The command information generation unit 41 calculates the d and q-axis command currents Id * and Iq * according to the torque command value Trq *. In the present embodiment, the command information generation unit 41 calculates d, q-axis command currents Id *, Iq * that minimize the loss of the rotary electric machine 10 while satisfying the torque command value Trq * by the minimum current maximum torque control. To do.

The minimum current and maximum torque control performed by the command information generation unit 41 will be described with reference to FIG. As shown in FIG. 4, in the dq coordinate system, the constant current circles C1, C2, and C3 defined by connecting the d, q-axis currents Idr, and Iqr are shown by broken lines. In the dq coordinate system, the equal torque lines TL1, TL2, TL3 defined by connecting the d, q-axis currents Idr, Iqr corresponding to the output torques T1, T2, T3 of the rotary electric machine 10 are shown by solid lines. Each output torque T1, T2, T3 has a relationship of T1 <T2 <T3.

In the minimum current and maximum torque control, among the d, q-axis currents Idr and Iqr on the equal torque line corresponding to the torque command value Trq *, the current that minimizes the distance from the origin 0 is the d, q-axis command current Id *. , Iq *. For example, when the torque corresponding to the torque command value Trq * is T2, the origin 0 of the d, q-axis currents Idr and Iqr, which are the intersections of the equal torque line TL2 and the constant current circles C1, C2, and C3. The value at which the distance between the two is the minimum is calculated as the d, q-axis command currents Id *, Iq *. In the minimum current and maximum torque control, the d, q-axis command currents Id * and Iq * calculated as the d and q-axis command currents Id * and Iq * satisfy the following equations (3) and (4).

βは、ｑ軸を基準とした場合のｄ，ｑ軸指令電流Ｉｄ＊，Ｉｑ＊により規定される指令電流ベクトルの位相角である。Ψａは鎖交磁束［ｗｂ］であり、Ｌｄはｄ軸インダクタンス［Ｈ］であり、Ｌｑはｑ軸インダクタンス［Ｈ］である。

β is the phase angle of the command current vector defined by d, the q-axis command currents Id *, and Iq * when the q-axis is used as a reference. Ψa is the interlinkage magnetic flux [wb], Ld is the d-axis inductance [H], and Lq is the q-axis inductance [H].

In the present embodiment, the storage unit included in the control device 30 contains the torque command value Trq * and the d, q-axis command currents Id *, Iq * that satisfy the relationship represented by the above equations (3) and (4). A map showing the relationship is stored. By referring to this map, the command information generation unit 41 can calculate the d, q-axis command currents Id * and Iq * according to the torque command value Trq *.

The operating point determination unit 42 determines whether or not the operating point of the rotary electric machine 10 is included in the ripple generation range based on the torque command value Trq * and the speed command value Nm *. The ripple generation range is the operating range of the rotary electric machine 10 in which the ripple current flowing through the capacitor 25 is equal to or greater than a predetermined value.

The relationship between the operating region of the rotary electric machine 10 and the ripple generation range will be described with reference to FIG. The ripple current flowing through the capacitor 25 becomes maximum when the output torque of the rotary electric machine 10 reaches the maximum torque Tmax, and decreases as the torque Trq decreases. In the constant torque line Lmax, the maximum ripple operating point P1 at which the ripple current flowing through the capacitor 25 is maximized exists on the lower rotation side than the speed determination value N2. The speed determination value N2 is a speed command value Nm * when the control device 30 switches the operation on the inverter 20 between PWM control and overmodulation control when the operating point of the rotary electric machine 10 is on the constant torque line Lmax. It is a judgment value of. Further, in the constant torque line Lmax, the operating point defined by the base rotation speed N1 is the maximum load operating point P2 at which the allowable heat load in the inverter 20 is maximized. The maximum ripple operating point P1 is an operating point on the lower rotation side than the maximum load operating point P2 on the constant torque line Lmax. This is because in PWM control, the number of times per unit time for turning on and off each switch of the inverter 20 is larger than in overmodulation control and rectangular control. Therefore, in the constant torque line Lmax, the capacitor is used at the operating point where PWM control is performed. This is because the harmonic component is likely to be superimposed on the current flowing through the 25.

In the present embodiment, in the operating region shown in FIG. 5, the torque Trq is equal to or greater than the torque determination value Ts lower than the maximum torque Tmax and equal to or less than the maximum torque Tmax, and the rotation speed Nm is greater than 0 and the speed determination value N2. The following range is defined as the ripple generation range. The operating point determination unit 42 determines whether or not the operating point of the rotary electric machine 10 is included in this ripple generation range (0 <Nm * ≦ N2, Ts ≦ Trq * ≦ Tmax). By setting the ripple generation range to the operating range of the speed determination value N2 or less on the constant torque line Lmax, the operating point of the rotary electric machine 10 can be changed to the maximum load operating point P2. The degree of freedom can be increased.

Returning to FIG. 3, when the operation point determination unit 42 determines that the operation point of the rotary electric machine 10 is included in the ripple generation range, the command value change unit 43 is generated by the command information generation unit 41. The d, q-axis command currents Id *, Iq * so as to increase the magnitude | Ia | of the command current vector determined from the q-axis command currents Id *, Iq * and decrease the absolute value of the d-axis command current Id *. To change.

The change of the d and q-axis command currents Id * and Iq * by the command value changing unit 43 will be described with reference to FIG. In FIG. 6, the d and q-axis currents determined by the d and q-axis command currents Id * and Iq * before the change are indicated by Id1 and Iq1, and the d and q-axis command currents Id *, after the change by the command value changing unit 43. The d and q-axis currents determined by Iq * are indicated by Id2 and Iq2. On the same torque line TL11, the absolute value of the d-axis command current Id * is reduced by reducing (degrading) the phase angle β of the command current vector Ia determined by the d, q-axis command currents Id *, Iq *. While making it smaller, increase the magnitude | Ia | of the command current vector. Hereinafter, the change of the d and q-axis command currents Id * and Iq * by the command value changing unit 43 is referred to as field control by strengthening. In FIG. 6, the command current vector is changed from Ia1 to Ia2 by reducing the phase angle of the command current vector Ia1 from β1 to β2 by the field strengthening field control. As a result, the absolute value of the d-axis command current Id * decreases from | Id1 | to | Id2 |, and the magnitude of the command current vector increases from | Ia1 | to | Ia2 |.

In the present embodiment, the storage unit included in the control device 30 stores a map showing the relationship between the d, q-axis command currents Id *, Iq * and the retardation amount of the phase angle β. By referring to this map, the command value changing unit 43 can calculate the amount of change in the phase angle β according to the d and q-axis command currents Id * and Iq *.

Returning to FIG. 3, the d and q-axis command currents Id * and Iq * from the command value changing unit 43 are input to the operation unit 44. The operation unit 44 calculates the U, V, W phase command voltages Vu *, Vv *, Vw * based on the d, q-axis command currents Id *, Iq *. Then, the switches SUp to SWp and Sun to SWn of the inverter 20 are turned on and off by PWM control using the calculated U, V, W phase command voltages Vu *, Vv *, Vw * and the carrier signal.

The U, V, W phase command voltage Vu *, calculated by the operation unit 44 as the magnitude | Ia | of the command current vector determined by the changed d, q-axis command currents Id *, Iq * increases. Vv * and Vw * increase. Therefore, in the PWM control performed by the operation unit 44, the modulation factor a, which is the ratio of the U, V, and W phase command voltages Vu *, Vv *, and Vw * to the carrier signal, becomes large.

In the present embodiment, the operation unit 44 includes a d-axis deviation calculation unit 44a, a q-axis deviation calculation unit 44b, a d-axis command voltage calculation unit 44c, a q-axis command voltage calculation unit 44d, and a three-phase conversion unit 44e. , The PWM control unit 44f is provided.

The d-axis deviation calculation unit 44a calculates the d-axis current deviation ΔId, which is a value obtained by subtracting the d-axis current Idr from the d-axis command current Id *. The q-axis deviation calculation unit 44b calculates the q-axis current deviation ΔIq, which is a value obtained by subtracting the q-axis current Iqr from the q-axis command current Iq *.

The d-axis command voltage calculation unit 44c calculates the d-axis command voltage Vd * based on the speed command value Nm * and the d-axis current deviation ΔId. Specifically, the d-axis command voltage calculation unit 44c calculates the d-axis command voltage Vd * as an operation amount for controlling the d-axis current deviation ΔId to zero. At this time, the speed command value Nm * is taken into consideration so that the actual rotation speed Nm of the rotary electric machine 10 does not deviate from the speed command value Nm *.

The q-axis command voltage calculation unit 44d calculates the q-axis command voltage Vq * based on the speed command value Nm * and the q-axis current deviation ΔIq. Specifically, the q-axis command voltage calculation unit 44d calculates the q-axis command voltage Vq * as an operation amount for controlling the q-axis current deviation ΔIq to zero. At this time, the speed command value Nm * is taken into consideration so that the actual rotation speed Nm of the rotary electric machine 10 does not deviate from the speed command value Nm *.

The three-phase conversion unit 44e sets the d, q-axis command voltages Vd *, Vq * in the three-phase fixed coordinate system based on the d, q-axis command voltages Vd *, Vq *, the input voltage VINV, and the electric angle θ. Converts to U, V, W phase command voltage Vu *, Vv *, Vw *. In the present embodiment, the U, V, and W phase command voltages Vu *, Vv *, and Vw * have sinusoidal waveforms whose phases are 120 ° out of phase with each other at the electric angle θ.

The PWM control unit 44f is used to turn on / off the switches SUp to SWp and Sun to SWn based on the U, V, W phase command voltages Vu *, Vv *, and Vw * output from the three-phase conversion unit 44e. Operation signals gUp, gUn, gVp, gVn, gWp, gWn are generated. The operation signals gUp to gWp and gUn to gWp are generated based on the magnitude comparison between the carrier signal and the U, V, W phase command voltages Vu *, Vv *, and Vw *.

Next, the procedure for operating the switches SUp to SWp and Sun to SWn of the inverter 20 will be described with reference to FIG. 7. The process of FIG. 7 is repeatedly executed by the control device 30 at a predetermined control cycle.

In step S11, the torque command value Trq * and the speed command value Nm * are acquired. In step S12, it is determined whether or not PWM control is performed as an operation on the inverter 20. When PWM control is performed as an operation for the inverter 20, the process proceeds to step S13, and the d, q-axis command currents Id * and Iq * are calculated by the minimum current and maximum torque control described with reference to FIG. 4 and the like.

In step S14, it is determined whether or not the operating point of the rotary electric machine 10 is included in the ripple generation range based on the torque command value Trq * and the speed command value Nm * acquired in step S11. Specifically, if it is determined that the torque command value Trq * is equal to or greater than the torque determination value Ts and the maximum torque Tmax or less, and the speed command value Nm * is greater than 0 and equal to or less than the speed determination value N2, the rotary electric machine 10 It is determined that the operating point of is included in the ripple generation range.

When the affirmative determination is made in step S14, the process proceeds to step S15, and as described with reference to FIG. 5 and the like, the d and q-axis command currents Id * and Iq * calculated in step S13 are changed by the field strengthening control. As a result, the d, q-axis command currents Id * and Iq * are changed so that the absolute value of the d-axis command current Id * is reduced and the magnitude | Ia | of the command current vector is increased.

In step S16, the U, V, W phase command voltages Vu *, Vv *, Vw * are calculated using the d, q-axis command currents Id *, Iq * changed in step S15. In step S18, the inverter 20 is operated by PWM control using the U, V, W phase command voltages Vu *, Vv *, Vw * calculated in step S16. As a result, the modulation factor a in the PWM control increases as compared with the case where the d and q-axis command currents Id * and Iq * are not changed, so that the increase in the ripple current flowing through the capacitor 25 is suppressed.

Returning to step S14, if it is determined that the operating point of the rotary electric machine 10 is not included in the ripple generation range, the process proceeds to step S17, and the d, q-axis command currents Id *, Iq * calculated in step S13 are used as they are for U, The V and W phase command voltages Vu *, Vv *, and Vw * are calculated. When proceeding from step S17 to step S18, the inverter 20 is operated by PWM control using the U, V, W phase command voltages Vu *, Vv *, Vw * calculated in step S17.

If a negative determination is made in step S12, the process proceeds to step S19. In step S19, rectangular control or overmodulation control is performed as the control of the inverter 20. Then, the process of FIG. 7 is temporarily terminated.

Next, the effect of suppressing the increase in the ripple current in the present embodiment will be described with reference to FIG.

8 (a) to 8 (d) show the values of Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and this Example. Specifically, FIG. 8A shows the phase angle β of the command current vector with reference to the q-axis in Comparative Examples 1 to 4 and this example. FIG. 8B shows the effective values of the U, V, and W phase currents Iu, Iv, and Iw in Comparative Examples 1 to 4 and this example. FIG. 8C shows the ripple currents in Comparative Examples 1 to 4 and this example. FIG. 8D shows the system loss in Comparative Examples 1 to 4 and this example.

The d, q-axis command currents Id * and Iq * of Comparative Example 3 are calculated by the minimum current and maximum torque control (MTPA). Therefore, as shown in FIG. 8D, Comparative Example 3 has the lowest system loss value among Comparative Examples 1 to 4 and this Example. In the following, the phase angle of the command current vector defined by the d, q-axis command currents Id * and Iq * in Comparative Example 3 will be referred to as a reference phase angle βs.

Comparative Examples 1 and 2 show each value when the d, q-axis command currents Id * and Iq * of Comparative Example 3 are changed to the field weakening side. Specifically, in Comparative Examples 1 and 2, the d and q-axis commands of Comparative Example 3 are increased so that the absolute value of the d-axis command current Id * is increased while increasing the magnitude | Ia | of the command current vector. These are the values when the currents Id * and Iq * are changed. In Comparative Example 1, the magnitude | Ia | of the command current vector is larger than that in Comparative Example 2, and the absolute value of the d-axis command current Id * is larger.

In Comparative Examples 1 and 2, the phase angle β is larger than the reference phase angle βs, and in Comparative Example 1, the phase angle β is larger than that of Comparative Example 2. Further, in Comparative Example 1, the effective values of the U, V, and W phase currents Iu, Iv, and Iw are larger than those in Comparative Example 2. As the effective values of the U, V, and W phase currents Iu, Iv, and Iw increase, the ripple currents in Comparative Examples 1 and 2 are larger than those in Comparative Example 3. This is because in Comparative Examples 1 and 2, the magnitude of the command current vector | Ia | increased and the absolute value of the d-axis command current Id * became larger than that of Comparative Example 3, so that the rotation was larger than that of Comparative Example 3. This is because the counter electromotive force due to the interlinkage magnetic flux of the electric machine 10 is suppressed and the modulation factor a is lowered. In Comparative Examples 1 and 2, the system loss is larger than in Comparative Example 3 because the effective values of the U, V, and W phase currents Iu, Iv, and Iw are larger.

In this embodiment and Comparative Example 4, each value when the d, q-axis command currents Id * and Iq * of Comparative Example 3 are strengthened and changed to the field side is shown. Specifically, in this embodiment and Comparative Example 4, d, q of Comparative Example 3 are made so that the absolute value of the d-axis command current Id * is reduced while increasing the magnitude | Ia | of the command current vector. These are the values when the shaft command currents Id * and Iq * are changed. In this embodiment, the magnitude | Ia | of the command current vector is smaller and the absolute value of the d-axis command current Id * is smaller than that of Comparative Example 4.

In this example and Comparative Example 4, the phase angle β is smaller than the reference phase angle βs, and in Comparative Example 4, the phase angle β is smaller than that in this example. Further, in this embodiment, the effective values of the U, V, and W phase currents Iu, Iv, and Iw are smaller than those in Comparative Example 4. In this embodiment, the ripple current is smaller than that in Comparative Example 3 as the effective values of the U, V, and W phase currents Iu, Iv, and Iw increase. This is due to the interlinkage magnetic flux of the rotary electric machine 10 as compared with Comparative Example 3 because the absolute value of the d-axis command current Id * became smaller as the magnitude | Ia | of the command current vector increased in this embodiment. This is because the modulation factor a has increased due to the increase in the back electromotive force. In this example, the system loss is larger than that of Comparative Example 3 because the effective values of the U, V, W phase currents Iu, Iv, and Iw are larger than those of Comparative Example 3. Further, if the phase angle β is made too small, the ripple current becomes larger than that of this embodiment as in Comparative Example 4.

The following effects can be achieved by the present embodiment described above.

Whether or not the control device 30 includes the operating point of the rotary electric machine 10 within the ripple generation range in which the ripple current flowing through the capacitor 25 is equal to or greater than a predetermined value during the period in which PWM control is performed on the inverter 20. To judge. When it is determined that the operating point of the rotary electric machine 10 is included in the ripple generation range, the absolute value of the d-axis current Idr determined from the d and q-axis command currents Id * and Iq * is reduced, and the command current vector The d and q-axis command currents Id * and Iq * are changed so as to increase the magnitude | Ia |. As a result, the modulation factor a in the PWM control for the inverter 20 increases, and the increase in the ripple current can be suppressed without using a converter that applies a voltage to the capacitor 25.

In the control device 30, the torque command value Trq * is equal to or greater than the torque determination value Ts, the maximum torque is Tmax, the speed command value Nm * is greater than 0, and the speed determination value N2 or less is smaller than the base rotation speed N1. In this case, it is determined that the operating point of the rotary electric machine 10 is included in the ripple generation range. Thereby, in the range of the operating point where the ripple current is likely to be generated, the increase of the ripple current can be suppressed within the range not exceeding the allowable heat load of the inverter 20.

The control device 30 generates d, q-axis command currents Id *, Iq * by minimum current maximum torque control based on the torque command value Trq *. As a result, it is possible to suppress an increase in the ripple current flowing through the capacitor 25 without significantly reducing the loss of the drive system 100.

The control device 30 brings the command current vector Ia defined by the d, q-axis command currents Id *, Iq * closer to the q-axis side on the same torque line corresponding to the torque command value Trq * in the dq-axis coordinate system. As described above, the d and q-axis command currents Id * and Iq * are changed. As a result, it is possible to suppress an increase in the ripple current flowing through the capacitor 25 while maintaining the torque of the rotary electric machine 10 at the torque command value Trq *.

<Modified example of the first embodiment>
The ripple current becomes maximum at the maximum ripple operating point P1 on the constant torque line Lmax. Therefore, in the operating region of the rotary electric machine 10, the constant torque line Lmax may be defined as the ripple generation range. Specifically, in the operating range of the rotary electric machine 10, the range in which the torque Trq is the maximum torque Tmax, the rotation speed Nm is larger than 0 and the speed determination value N2 or less may be defined as the ripple generation range. ..

<Second Embodiment>
In the second embodiment, a configuration different from that of the first embodiment will be mainly described. The configurations with the same reference numerals as those in the first embodiment show the same configurations, and the description thereof will not be repeated.

In the present embodiment, the d, q-axis command currents Id * and Iq * are changed by the field strengthening control on the condition that the temperature of the capacitor 25 is higher than the predetermined temperature. This is because when the temperature of the capacitor 25 is low, the adverse effect of heat generation of the capacitor 25 due to the flow of the ripple current is smaller than when the temperature is high.

As shown in FIG. 9, the drive system 100 of the present embodiment includes a temperature sensor 50 that detects the temperature of the capacitor 25. The capacitor temperature F, which is the temperature of the capacitor 25 detected by the temperature sensor 50, is input to the control device 30. In this embodiment, the control device 30 corresponds to the temperature acquisition unit.

Next, the PWM control procedure according to the present embodiment will be described with reference to FIG. The process shown in FIG. 10 is repeatedly performed by the control device 30 at a predetermined cycle.

After calculating the d, q-axis command currents Id * and Iq * by the minimum current and maximum torque control in step S13, in step S20, is the capacitor temperature F detected by the temperature sensor 50 higher than the temperature determination value Tc? Judge whether or not. The temperature determination value Tc is set to a value equal to or lower than the allowable upper limit temperature (heat resistant temperature) of the capacitor 25 that can maintain the reliability of the capacitor 25, and specifically, for example, is set to the allowable upper limit temperature.

If a negative determination is made in step S20, the process proceeds to step S17, and the d, q-axis command currents Id *, Iq * calculated in step S13 are used as they are to generate the U, V, W phase command voltages Vu *, Vv *, Vw *. calculate. On the other hand, if an affirmative determination is made in step S20, the process proceeds to step S14.

The present embodiment described above can exert the following effects.

When the control device 30 determines that the temperature of the capacitor 25 is higher than the temperature determination value Tc and the operating point of the rotary electric machine 10 is included in the ripple generation range, the control device 30 sets the d, q-axis command currents Id * and Iq *. change. Therefore, the increase in the ripple current is suppressed only when the adverse effect on the temperature rise of the capacitor 25 due to the ripple current is large. As a result, it is possible to suppress an increase in the ripple current while suppressing a decrease in efficiency of the drive system 100 due to an increase in the modulation factor a as much as possible.

<Other Embodiments>
The command information generation unit 41 may calculate the magnitude and phase angle of the command current vector as the command current vector information instead of the d and q-axis command currents Id * and Iq *. In this case, the command value changing unit 43 shown in FIG. 3 increases the magnitude of the command current vector and decreases the phase angle when the operating point of the rotary electric machine 10 is included in the ripple generation range. Then, the d and q-axis command currents Id * and Iq * may be calculated based on the magnitude and phase angle of the changed command current vector.

-The control device 30 may perform only PWM control without performing overmodulation control and rectangular control as operations on the inverter 20.

10 ... rotary electric machine, 11U, 11V, 11W ... U-phase winding, V-phase winding, W-phase winding, 20 ... inverter, 25 ... capacitor, 30 ... control device, 100 ... drive system.

Claims (5)

A rotating electric machine (10) having armature windings (11U, 11V, 11W) and
With an inverter (20) having switches (SUP to SWp, Sun to SWn) and converting the DC voltage from the DC power supply (200) into an AC voltage and supplying it to the armature winding by the switching operation of the switch. ,
A drive system control device (30) applied to a drive system (100) including a capacitor (25) connected to the input side of the inverter.
A command information generation unit (41) that generates command current vector information for controlling the current flowing through the armature winding based on the torque command value of the rotary electric machine.
An operation unit (44) that performs a switching operation of the switch by PWM control based on a magnitude comparison between a voltage command value supplied from the inverter to the armature winding and a carrier wave based on the command current vector information.
During the period in which the PWM control is performed, the operating point of the rotary electric machine is the ripple generation range in which the ripple current flowing through the capacitor is equal to or higher than a predetermined value based on the torque command value and the speed command value of the rotary electric machine. The operating point determination unit (42) that determines whether or not it is included in
When it is determined that the operating point of the rotary electric machine is included in the ripple generation range, the absolute value of the d-axis current determined from the generated command current vector information is reduced, and the generated command current is generated. A command value changing unit (43) that changes the command current vector information so as to increase the magnitude of the command current vector determined from the vector information is provided.
The operation unit is a control device of a drive system that calculates the voltage command value used in the PWM control based on the changed command current vector information. When the rotation speed of the rotary electric machine is equal to or lower than a predetermined base rotation speed, the maximum torque of the rotary electric machine is constant regardless of the rotation speed, and when the rotation speed is larger than the base rotation speed, the rotation is performed. The higher the speed, the smaller the maximum torque.
When the speed command value is equal to or less than the speed determination value lower than the base rotation speed, the operation unit performs a switching operation of the switch by the PWM control, and the speed command value is larger than the speed determination value. In this case, the switching operation of the switch is performed by the control having a modulation rate larger than that of the PWM control.
In the operating point determination unit, when the torque command value is equal to or greater than the determination torque of the maximum torque or less and the speed command value is equal to or less than the speed determination value, the operating point of the rotary electric machine generates the ripple. The control device for a drive system according to claim 1, which is determined to be included in the range. The control device for a drive system according to claim 1 or 2, wherein the command information generation unit generates command current vector information by minimum current maximum torque control based on the torque command value. In the dq coordinate system, the command value changing unit changes the command current vector determined by the generated command current vector information so as to approach the q-axis side on the same torque line as the torque command value. The control device for a drive system according to any one of claims 1 to 3, which changes the command current vector information. A temperature acquisition unit for acquiring the temperature of the capacitor is provided.
A claim that the command value changing unit changes the command current vector information when it is determined that the temperature of the capacitor is higher than a predetermined temperature and the operating point of the rotary electric machine is included in the ripple generation range. The control device for a drive system according to any one of 1 to 4.

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