JP6128016B2 - AC motor control device - Google Patents

Description

  The present invention relates to a control device for an AC motor that controls energization by current feedback control.

In the control of the AC motor, the current deviations ΔId, ΔIq between the d-axis, q-axis current Id, Iq and d-axis obtained by dq conversion of the phase current detection value, and the q-axis current command values Id ^* , Iq ^* are set to zero. , D-axis and q-axis voltage command values Vd ^* and Vq ^* are known as current feedback control for PI control calculation. In the conventional PI control calculation, generally, the d-axis and q-axis voltage deviations ΔId and ΔIq are added to the terms obtained by multiplying the proportional control gain and the integral control gain, respectively, to obtain the d-axis and q-axis voltage command values Vd ^* and Vq. ^* Is calculated.

In the voltage equation below, the d-axis voltage command value Vd ^* includes a component of the d-axis current Id and a component of the q-axis current Iq, and the q-axis voltage command value Vq ^* also includes a component of the d-axis current Id. And a component of the q-axis current Iq. That is, mutual interference occurs between the dq axes.
Vd ^* = R × Id−ω × Lq × Iq
Vq ^* = R × Iq + ω × Ld × Id + ω × φ
(R is an armature resistance, ω is an electrical angular velocity, Ld and Lq are d-axis and q-axis inductances, and φ is an armature interlinkage magnetic flux of a permanent magnet.)

In this specification, the above-mentioned “conventional PI control calculation” method is referred to as an “interference feedback method”. For example, the motor driving device disclosed in Patent Document 1 uses a d-axis voltage command correction value Vd0 (= ⁾ from the d-axis and q-axis voltage command values Vd ^* and Vq ^* calculated by the PI control calculation of the interference feedback method. The responsiveness is improved by subtracting ω × Lq × Iq ^* ) and q-axis voltage command correction value Vq0 (= −ω × Ld × Id ^* −ω × φ).
In the control of the responsiveness improvement disclosed in Patent Document 1, in the calculation of the terms including ω of the voltage equation (the second term of the d-axis voltage equation, the second term and the third term of the q-axis voltage equation), The values of the actual currents Id and Iq are to be calculated by substituting with the command currents Id ^* and Iq ^* , which is a concept close to feedforward control. Control combining this feedforward and the interference feedback method is generally known.

JP 2004-40861 A

Considering the interference feedback method, it is considered that the controllability is good in a low rotation region where the electrical angular velocity ω is relatively small and the ratio of the term including R (first term) in the voltage equation is dominant. However, in the high rotation region where the electrical angular velocity ω is relatively large, the error of the term including ω increases due to the difference between the actual currents Id and Iq and the command currents Id ^* and Iq ^*, and the control performance may be deteriorated.
In the first place, in the conventional interference feedback system, it is theoretically difficult in view of the voltage equation that the actual currents Id and Iq of the d-axis and q-axis continue to coincide with the command currents Id ^* and Iq ^* .

Therefore, for example, the conventional technology of Patent Document 1 is applied to control of an AC motor used over a wide rotation speed range from a low rotation range to a high rotation range, such as an AC motor that generates a driving force of a vehicle in a hybrid vehicle. Then, it may be difficult to ensure controllability.
The present invention has been made in view of such a point, and an object of the present invention is to provide a control device for an AC motor that improves the control performance of current feedback control over a wide rotational speed range.

The present invention relates to an “AC motor control device” that controls the voltage applied to the AC motor by controlling the drive of the inverter by current feedback control.
The control device includes a current command calculation unit that calculates a d-axis current command value (Id ^* ) and a q-axis current command value (Iq ^* ), a dq conversion of a phase current detection value of the AC motor, and a d-axis current detection value ( Id) and a q-axis current detection value (Iq), a dq converter that calculates a d-axis voltage command value (Vd ^* ) and q by a PI control calculation based on the d-axis current deviation (ΔId) and the q-axis current deviation (ΔIq) Based on the voltage command calculation unit for calculating the shaft voltage command value (Vq ^* ) and the control method of the voltage command calculation unit based on the rotational speed of the AC motor, the “non-interference feedback method” defined below and “interference” It is characterized by having a switching determination unit that switches between “feedback method”.

（但し、Ｋｐｄ／Ｋｐｑ：非干渉フィードバック方式のＰ（比例）制御項のゲイン、
Ｋｉｄ／Ｋｉｑ：非干渉フィードバック方式のＩ（積分）制御項のゲイン、
ΔＩｄ：ｄ軸電流偏差（ΔＩｄ＝Ｉｄ^*−Ｉｄ）、
ΔＩｑ：ｑ軸電流偏差（ΔＩｑ＝Ｉｑ^*−Ｉｑ）） The “non-interference feedback method” is defined as “a method in which the d-axis voltage command value is calculated from the q-axis current deviation and the q-axis voltage command value is calculated from the d-axis current deviation”. That is, it is expressed by the following formula 1.

(Where Kpd / Kpq: gain of P (proportional) control term of non-interference feedback system,
Kid / Kiq: Gain of I (integration) control term of non-interference feedback method,
ΔId: d-axis current deviation (ΔId = Id ^* −Id),
ΔIq: q-axis current deviation (ΔIq = Iq ^* −Iq))

（但し、Ｋ’ｐｄ／Ｋ’ｐｑ：干渉フィードバック方式のＰ（比例）制御項のゲイン、
Ｋ’ｉｄ／Ｋ’ｉｑ：干渉フィードバック方式のＩ（積分）制御項のゲイン） The “interference feedback method” is defined as “a method in which the d-axis voltage command value is calculated from the d-axis current deviation and the q-axis voltage command value is calculated from the q-axis current deviation”. That is, it is expressed by the following formula 2.

(Where K′pd / K′pq: gain of the P (proportional) control term of the interference feedback system,
K'id / K'iq: I (integral) control term gain of interference feedback system)

  The switching determination unit applies the interference feedback method in a region where the rotation speed of the AC motor is less than the predetermined switching rotation speed (A), and applies the non-interference feedback method in a region where the rotation speed of the AC motor is equal to or higher than the switching rotation speed. As described above, the control method of the voltage command calculation unit is switched.

（但し、Ｒ：電機子抵抗、Ｌｄ／Ｌｑ：ｄ軸インダクタンス／ｑ軸インダクタンス、
ω：電気角速度、φ：永久磁石の電機子鎖交磁束） In an example of the “non-interference feedback method”, the d-axis voltage command value and the q-axis voltage command value are calculated based on the following equation 4 using the voltage equation represented by the following equation 3.

(Where R: armature resistance, Ld / Lq: d-axis inductance / q-axis inductance,
(ω: electrical angular velocity, φ: armature flux linkage of permanent magnet)

  Here, Equation 4 includes an R term with respect to Equation 1. The R term of the d-axis voltage command value includes the d-axis current deviation, and the R term of the q-axis voltage command value includes the q-axis current deviation. There seems to be no. However, assuming that R in Equation 4 is relatively extremely small and close to 0, Equation 4 can be treated as an extended example of the “non-interference feedback method” in a practical sense.

According to the present invention, for example, the switching rotational speed is a predetermined value (α) in the rotational speed region where the “R term ratio”, which is the ratio of the value of the term including R in the voltage equation to the total value, is applied to the non-interference feedback method. It is set to be as follows.
In the high speed region, the influence of the R term ratio becomes substantially zero in the process of calculating the voltage command. Therefore, if the feedback gain is set appropriately in the non-interference feedback method in the high rotation range, the actual currents Id and Iq can theoretically be matched with the command currents Id ^* and Iq ^* , so that compared with the interference feedback method. Control performance. Therefore, in the current feedback control, by applying the non-interference feedback method in the high rotation region than the switching rotational speed, the control performance in the high rotation region can be improved.

On the other hand, in the low-rotation region where the R term ratio of the voltage equation is dominant, control performance may be obtained by applying the interference feedback method, so that there are few merits to apply the non-interference feedback method. Therefore, the control performance of the current feedback control can be improved over a wide rotation speed region by switching the control method of the voltage command calculation unit according to the rotation speed of the AC motor.
Due to such advantages, the present invention is particularly beneficial when applied to control of an AC motor that generates driving force in a hybrid vehicle, for example.

1 is a schematic configuration diagram of a drive system for a hybrid vehicle to which an AC motor control device according to an embodiment of the present invention is applied. It is a control block diagram of the control apparatus of the AC motor according to the embodiment of the present invention. It is a rotation speed-torque characteristic diagram explaining the control system switching process by 1st Embodiment of this invention. It is a flowchart of the control system switching process by 1st Embodiment of this invention. It is explanatory drawing which compares an interference feedback system and a non-interference feedback system by dq coordinate, and shows the case where (DELTA) id = 0 and (DELTA) iq <0. It is explanatory drawing same as the above, and shows the case where Δid = 0 and Δiq> 0. It is explanatory drawing same as the above, and shows the case where Δid <0 and Δiq = 0. It is explanatory drawing same as the above, and shows the case of (DELTA) id> 0 and (DELTA) iq = 0. It is explanatory drawing same as the above, It is a figure explaining that an actual current does not correspond to a command current in an interference feedback system. It is a rotation speed-torque characteristic diagram explaining the control system switching process by 2nd Embodiment of this invention. It is a flowchart of the control system switching process by 2nd Embodiment of this invention.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A control apparatus for an AC motor according to a first embodiment of the present invention will be described with reference to FIGS. The control device for an AC motor according to this embodiment is applied to a hybrid vehicle.
The hybrid vehicle shown in FIG. 1 is a so-called series-parallel hybrid vehicle, and includes an engine 6 and two motor generators as a driving force source of the vehicle.

A motor generator (hereinafter referred to as “MG”) has both a function as a generator that generates regenerative power by receiving torque and a function as a motor that generates torque by consuming electric power by a power running operation. In the present embodiment, the first MG 3 mainly functions as a generator, and the second MG 4 mainly functions as an electric motor. The first MG3 and the second MG4 are, for example, permanent magnet type synchronous three-phase AC motors.
In the present embodiment, the MG control device 20 that controls the energization of the first MG 3 and the second MG 4 corresponds to the “control device for an AC motor” of the present invention. As will be described in detail later, the MG control device 20 has a characteristic configuration of the present invention particularly in the control of the second MG 4 that mainly functions as an electric motor, and exhibits a specific operational effect.

The engine 6, the first MG 3, and the second MG 4 are connected by a power split mechanism 16. The engine 6 is, for example, a 4-cylinder gasoline engine. The power of the engine 6 is divided into two systems by a power split mechanism 16 connected to the crankshaft 15, and the wheels 14 are driven via the differential gear mechanism 19 and the axle 13 by one power, and the other power is used. The first MG 3 is caused to generate power.
The engine control device 60 acquires information such as the crank angle of the crankshaft 15 and the engine rotation speed based on a crank angle signal input from a crank angle sensor (not shown), and controls the operation of the engine 6.

  The battery 31 is a chargeable / dischargeable power storage device such as a nickel hydride or lithium ion battery. Boost converter 32 boosts the DC voltage of battery 31 and outputs the boosted voltage to inverters 33 and 34. The inverter 33 and the inverter 34 are composed of a plurality of bridge-connected switching elements, and convert DC power and three-phase AC power to each other.

The three-phase AC power generated by the first MG 3 is converted into DC power by the inverter 33 and regenerated to the battery 31 via the boost converter 33.
Second MG 4 uses the three-phase AC power converted by inverter 34 to output torque by a power running operation. The driving force by the second MG 4 is transmitted to the wheels 14 via the propeller shaft 17, the differential gear mechanism 19, and the axle 13.
The rotation angle sensors 51 and 52 are, for example, resolvers, provided near the rotors of the first MG3 and the second MG4, respectively, and detect the electrical angles of the first MG3 and the second MG4.

  The vehicle control circuit 10 is provided so as to be able to communicate with the MG control device 20 and the engine control device 60. The vehicle control circuit 10 receives an accelerator signal, a brake signal, a shift signal, a vehicle speed signal, and the like, and detects the driving state of the vehicle based on the acquired information. Then, a torque command value corresponding to the operating state is output to the MG control device 20 and the operation of the engine 6 is commanded to the engine control device 60.

The MG control device 20 includes a boost converter 32 and an inverter based on the torque command value from the vehicle control circuit 10, the current detection value by the current sensor (see FIG. 2), the electrical angle signal by the rotation angle sensors 51 and 52, and the like. The energization of the first MG 3 and the second MG 4 is controlled by controlling the switching operation of 33 and 34.
In the following description, the second MG 4 is referred to as “motor 4”, and the control of the motor 4 executed exclusively by the MG controller 20 will be described in detail.

Next, the configuration and operation of the MG control device 20 will be described with reference to FIGS. In the following figures, feedback is abbreviated as “FB”.
Here, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2010-88205 and the like, the MG control device 20 performs a sine wave PWM control mode, an overmodulation PWM according to the rotation speed and torque required for the output of the motor 4. The control mode and the rectangular wave control mode can be switched. That is, as shown in FIG. 3, when an output in a low rotation and low torque region is required, a current feedback control type sine wave PWM control mode is used. When output in a high rotation and high torque region is required, a torque feedback control type rectangular wave control mode is used. In the middle region, the current modulation control overmodulation PWM control mode is used.

Among them, in the sine wave PWM control mode and the overmodulation PWM control mode of the current feedback control method, the MG control device 20 executes characteristic control described below.
The control block shown in FIG. 2 corresponds to the sine wave PWM control mode. The MG control device 20 includes a current command calculation unit 21, a subtractor 22, a voltage command calculation unit 23, an inverse dq conversion unit 24, a PWM signal generation unit 25, a dq conversion unit 26, a rotation speed conversion unit 27, and a switching determination unit. 28.
In the overmodulation PWM control mode, a voltage amplitude correction unit is provided between the voltage command calculation unit 23 and the inverse dq conversion unit 24 to correct the amplitude of the three-phase voltage command so as to be distorted from the sine wave waveform.

Based on the torque command value Trq ^* acquired from the vehicle control circuit 10, the current command calculation unit 21 calculates the d-axis current command value Id ^* and the q-axis current command value Iq ^* using a map, a mathematical expression, or the like.
The subtractor 22 includes a d-axis current subtracter 221 and a q-axis current subtracter 222. The d-axis current subtracter 221 calculates a d-axis current deviation ΔId by subtracting the d-axis current detection value Id fed back from the dq converter 26 from the d-axis current command value Id ^* . The q-axis current subtractor 222 subtracts the q-axis current detection value Iq fed back from the dq converter 26 from the q-axis current command value Iq ^* to calculate a q-axis current deviation ΔIq.

The voltage command calculation unit 23 sets the d-axis and q-axis current deviations ΔId and ΔIq so that the d-axis and q-axis current detection values Id and Iq follow the d-axis and q-axis current command values Id ^* and Iq ^* , respectively. The d-axis and q-axis voltage command values Vd ^* and Vq ^* are calculated by PI control calculation so as to converge to zero.
The voltage command calculation unit 23 uses two control methods, “interference feedback method” and “non-interference feedback method”, in the PI control calculation. The meaning of these two control methods and the switching method of the control methods will be described later.

The inverse dq converter 24 converts the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* into the U-phase voltage command value Vu ^* and the V-phase voltage command value based on the electrical angle θ acquired from the rotation angle sensor 52. Vv ^* and W-phase voltage command value Vw ^* are converted.
The PWM signal generation unit 25 performs PWM related to on / off switching of the switching element of the inverter 34 based on the three-phase voltage command values Vu ^* , Vv ^* , Vw ^* and the system voltage VH applied to the inverter 34. Signals UU, UL, VU, VL, WU, WL are calculated.
On / off of the switching element of the inverter 34 is controlled based on the PWM signals UU, UL, VU, VL, WU, WL, and desired three-phase AC voltages Vu, Vv, Vw are generated. When the three-phase AC voltages Vu, Vv, and Vw are applied to the motor 4, the driving of the motor 4 is controlled so that torque according to the torque command value Trq ^* is output.

The dq converter 26 receives a phase current detection value from current sensors 35 and 36 provided on a power line connected from the inverter 34 to the motor 4. In this embodiment, detected values of the V-phase current Iv and the W-phase current Iw are input from the current sensors 35 and 36 provided in the V-phase and the W-phase, and the remaining U-phase current Iu is estimated based on Kirchhoff's law. doing. In other embodiments, any two-phase current may be detected, and a three-phase current may be detected. Or you may employ | adopt the technique which estimates the other two-phase electric current based on the electric current detection value of one phase.
The dq conversion unit 26 converts the three-phase current detection values Iu, Iv, and Iw into d-axis and q-axis current detection values Id and Iq based on the electrical angle θ acquired from the rotation angle sensor 52, and give feedback.

Next, the meanings of “interference feedback system” and “non-interference feedback system” will be described. In the past literature, the terms “interference” and “non-interference” are used in various different meanings. In the present specification, the terms “interference feedback” and “non-interference feedback” are used according to the definitions described below, without being bound by the terms of the past literature.
In the description of the embodiment, not the heading number of the formula but the formula number is described as in formula (1), and the formula overlapping with the formula of “means for solving the problem” is also renumbered. In addition, the formula related to the d-axis voltage and the formula related to the q-axis voltage are set as one set and expressed as formula (1) or the like.

記号は、以下のとおりである。
Ｒ：電機子抵抗
Ｌｄ／Ｌｑ：ｄ軸インダクタンス／ｑ軸インダクタンス
ω：電気角速度
φ：永久磁石の電機子鎖交磁束 First, the voltage equation of the motor is expressed by equation (1).

The symbols are as follows.
R: Armature resistance Ld / Lq: d-axis inductance / q-axis inductance ω: electrical angular velocity φ: armature linkage flux of permanent magnet

Subsequently, an interference feedback type voltage command arithmetic expression generally used in conventional current feedback control is defined by the following expression (2).

Here, K′pd and K′pq are gains of the P (proportional) control term, and K′id and K′iq are gains of the I (integral) control term. The subscript d indicates the gain used in the arithmetic expression of the d-axis voltage command value Vd ^* , and the subscript q indicates the gain used in the arithmetic expression of the q-axis voltage command value Vq ^* . In addition, “′” of “K ′” indicates a gain in the interference feedback method. In the interference feedback method, the d-axis voltage command value Vd ^* is calculated from the d-axis current deviation ΔId, and the q-axis voltage command value Vq ^* is calculated from the q-axis current deviation ΔIq.

「’」を付けないＫｐｄ、Ｋｐｑは、非干渉フィードバック方式のＰ（比例）制御項のゲインであり、Ｋｉｄ、Ｋｉｑは、非干渉フィードバック方式のＩ（積分）制御項のゲインである。非干渉フィードバック方式では、ｄ軸電圧指令値Ｖｄ^*をｑ軸電流偏差ΔＩｑから演算し、ｑ軸電圧指令値Ｖｑ^*をｄ軸電流偏差ΔＩｄから演算する。 Next, a non-interference feedback type voltage command arithmetic expression is defined by Expression (3).

Kpd and Kpq without “′” are gains of the P (proportional) control term of the non-interference feedback method, and Kid and Kiq are gains of the I (integration) control term of the non-interference feedback method. In the non-interference feedback method, the d-axis voltage command value Vd ^* is calculated from the q-axis current deviation ΔIq, and the q-axis voltage command value Vq ^* is calculated from the d-axis current deviation ΔId.

式（４）の非干渉フィードバック方式では、ｄ軸、ｑ軸電圧推定偏差ΔＶｄ、ΔＶｑに、それぞれ比例制御ゲイン及び積分制御ゲインを乗じた項を足し合わせて、ｄ軸、ｑ軸電圧指令値Ｖｄ^*、Ｖｑ^*を算出する。 The non-interfering feedback scheme may be combined with a feedforward term as described at the end of the specification. In the present embodiment, for simplification, the target to be referred to is limited to the feedback method, and Equation (4) using a voltage equation is shown as an example of the non-interference feedback method.

In the non-interference feedback method of Equation (4), d-axis and q-axis voltage command values Vd are added by adding terms obtained by multiplying the d-axis and q-axis voltage estimated deviations ΔVd and ΔVq by proportional control gain and integral control gain, respectively. ^{* And} Vq ^* are calculated.

Here, the derivation of Expression (4) will be described.
In the voltage equation of equation (1), the d-axis voltage Vd includes a component of the d-axis current Id and a component of the q-axis current Iq, and the q-axis voltage Vq also includes the component of the d-axis current Id and the q-axis current Iq. Of ingredients. That is, mutual interference occurs between the dq axes.

このΔＶｄ、ΔＶｑは、「電圧方程式（１）に基づいて推定した、電流偏差ΔＩｄ、ΔＩｑに対応する電圧の差分量」である。なお、ΔＶｄ、ΔＶｑを「電圧偏差」というと、あたかも実電圧と目標電圧とを直接比較したように誤解されるおそれがあるため、「電圧推定偏差」ということにする。 Substituting d-axis current deviation ΔId (= Id ^* −Id) and q-axis current deviation ΔIq (= Iq ^* −Iq) into d-axis current Id and q-axis current Iq in equation (1), respectively, When is deleted, the equation (5) is obtained.

These ΔVd and ΔVq are “a voltage difference amount corresponding to the current deviations ΔId and ΔIq estimated based on the voltage equation (1)”. Note that ΔVd and ΔVq are referred to as “voltage deviation” because they may be misunderstood as if the actual voltage and the target voltage were directly compared.

When formula (4) is expanded using formula (5), formula (6) is obtained. Further, when expression (6) is expanded, it is expressed as expression (6 ′).

On the right side of Equation (6) (or Equation (6 ′)), the term including the resistance R is referred to as “R term”, and the term including the product (ω · L) of the electrical angular velocity ω and the inductance L is defined as “ω · It is called "L term".
Further, the ratio of the value of the R term to the value of the entire right side of the expression (6) is referred to as “R term ratio”. The resistance R and the inductance L are constant if there is no temperature change or deterioration with time, and the R term ratio decreases as the electrical angular velocity ω increases, that is, as the rotational speed increases.

When “R << ω · L” in the equation (6), it is assumed that “R = 0” and the R term is ignored, and the d-axis and q-axis voltage command values Vd ^* and Vq ^* are obtained by the equation (7). , Ω · L terms only.

The above is the meaning of “interference feedback system” and “non-interference feedback system”. Next, a configuration related to switching between these two control methods will be described.
The rotation speed conversion unit 27 calculates the electric angular velocity ω [deg / s] of the motor 4 by differentiating the electric angle θ acquired from the rotation angle sensor 52 with respect to time, and further multiplies the electric angular velocity ω by a proportional constant. The rotational speed N [rpm] of 4 is calculated.
The switching determination unit 28 compares the rotation speed N acquired from the rotation speed conversion unit 27 with the switching rotation speed A, and determines a control method applied by the voltage command calculation unit 23. The switching rotational speed A is set to a rotational speed at which the R term ratio is a predetermined value α.

As shown in FIG. 3, the switching determination unit 28 applies the interference feedback method in a region where the rotational speed N of the motor 4 is less than the switching rotational speed A (R term ratio> α), and the rotational speed N of the motor 4 is switched. In the region where the rotational speed is A or more (R term ratio ≦ α), the control method of the voltage command calculation unit 23 is switched so that the non-interference feedback method is applied.
By defining the switching rotational speed A in units of the electrical angular speed ω, the rotational speed conversion unit 27 does not convert the electrical angular speed ω to the rotational speed N, and the switching determination unit 28 converts the electrical angular speed ω to the rotational speed. N may be handled as N and the switching determination may be performed.

The feedback control system switching process of this embodiment will be described with reference to the flowchart of FIG. In the description of the flowchart below, the symbol “S” means a step.
In S10, it is determined whether or not the rotational speed of the motor 4 is equal to or higher than a predetermined switching rotational speed A.
When the rotational speed N of the motor 4 is less than the switching rotational speed A (S10: NO), the process proceeds to S11, and d-axis and q-axis voltage command values Vd ^* and Vq ^* are calculated by the interference feedback method. On the other hand, when the rotation speed N of the motor 4 is equal to or higher than the switching rotation speed A (S10: YES), the process proceeds to S12, and d-axis and q-axis voltage command values Vd ^* and Vq ^* are calculated by a non-interference feedback method.

In S13 following S12, it is determined whether or not the rotational speed N of the motor 4 is equal to or greater than the simplified rotational speed B that is greater than the switching rotational speed A. When the rotation speed N of the motor 4 is equal to or higher than the simplified rotation speed B (S13: YES), the voltage command calculation unit 23 uses Expression (7) where R = 0 in the non-interference feedback calculation expression (6). Then, d-axis and q-axis voltage command values Vd ^* and Vq ^* are calculated. The simplified rotation speed B is set to, for example, a rotation speed at which the R term ratio is several percent or less.

(effect)
As an effect of the MG control device 20 of the present embodiment, in the non-interference feedback method using the voltage equation, if the feedback gain is set appropriately, the actual current can theoretically match the command current. Control performance is improved compared to the method.
This will be described with reference to FIGS. 5 to 9 showing current and voltage on the dq coordinate.
In the description of this part, the “current command value” is referred to as “command current” and the “current detection value” is referred to as “actual current” as appropriate depending on the context. A command current vector whose end point coordinates are (Id ^* , Iq ^* ) is represented as “command current Id ^* , Iq ^* ”, and an actual current vector whose end point coordinates are (Id, Iq) is represented by “actual current Id”. , Iq ”.

5 to 9, the actual currents Id and Iq in the dq coordinates are indicated by circles with an inclination of 45 °, and the command currents Id ^* and Iq ^* are indicated by dashed circles. The command currents Id ^* and Iq ^* are set, for example, on a maximum efficiency characteristic line ME that provides a maximum torque with respect to the absolute value of the current vector. 5 to 8 show cases where the actual currents Id and Iq are on the dq coordinate with respect to the command values Id ^* and Iq ^* , that is, according to the signs of the current deviations ΔId and ΔIq.

In the current feedback control, the voltage command values Vd ^* and Vq ^* are basically controlled so that the actual currents Id and Iq coincide with the command currents Id ^* and Iq ^* . However, the interference feedback method and the non-interference feedback method differ in how the actual currents Id and Iq change when the voltage command values Vd ^* and Vq ^* are moved.

The current voltage command value, that is, the coordinates Vd ^* and Vq ^* of the end point of the voltage command vector V ^* are indicated by a circle with an inclination of 45 °. The destinations where the voltage command values Vd ^* and Vq ^* move by the control of the interference feedback method are indicated by white circles, and the destinations of the voltage command values Vd ^* and Vq ^* by the control of the non-interference feedback method are hatched at an inclination of −45 °. Shown with a circle.
As a result of the control by the interference feedback method, the moving destination of the actual currents Id and Iq is indicated by white triangles, and as a result of the control by the non-interference feedback method, the moving destination of the actual currents Id and Iq is hatched at an inclination of −45 °. Indicated by a triangle.

As shown in FIG. 5, when ΔId = 0 and ΔIq <0, it is desired to move the q-axis current Iq in the minus direction (downward in the figure). At this time, in the interference feedback method, the q-axis voltage command value Vq ^* is moved in the minus direction based on the equation (2). On the other hand, in the non-interference feedback method, the d-axis voltage command value Vd ^* is moved in the plus direction based on Expression (7) regarded as “R = 0”. If you mark the point of interest in the formula with a circle, it will be as follows.

Next, paying attention to the second term of the voltage equation (1), in the interference feedback method, the q-axis voltage command value Vq ^* is moved in the minus direction, so that Vq ^* becomes minus → ω · Ld · Id becomes minus. The d-axis current Id moves in the negative direction. That is, the actual currents Id and Iq change in a direction different from the request for moving the q-axis current Iq in the minus direction.
On the other hand, in the non-interference feedback method, the d-axis voltage command value Vd ^* is moved in the plus direction, so that the Vd ^* is plus → ω · Lq · Iq is minus and the q-axis current Iq is moved in the minus direction. That is, the actual currents Id and Iq can be changed as required to move the q-axis current Iq in the negative direction, and the actual currents Id and Iq can be made to coincide with the command currents Id ^* and Iq ^* .

As shown in FIG. 6, when ΔId = 0 and ΔIq> 0, it is desired to move the q-axis current Iq in the plus direction (upward in the figure). Considering the same as in the example of FIG. 5, in the interference feedback method, the d-axis current Id moves in the positive direction by moving the q-axis voltage command value Vq ^* in the positive direction. That is, the actual currents Id and Iq change in a direction different from the request.
On the other hand, in the non-interference feedback method, the q-axis current Iq moves in the plus direction by moving the d-axis voltage command value Vd ^* in the minus direction. That is, the actual currents Id and Iq can be changed as required, and the actual currents Id and Iq can be matched with the command currents Id ^* and Iq ^* .

As shown in FIG. 7, when ΔId <0 and ΔIq = 0, it is desired to move the d-axis current Id in the minus direction (leftward in the figure). At this time, in the interference feedback method, the d-axis voltage command value Vd ^* is moved in the minus direction based on the equation (2). On the other hand, in the non-interference feedback method, the q-axis voltage command value Vq ^* is moved in the minus direction based on Expression (7) regarded as “R = 0”. If you mark the point of interest in the formula with a circle, it will be as follows.

Next, paying attention to the second term of the voltage equation (1), in the interference feedback method, the d-axis voltage command value Vd ^* is moved in the minus direction, so that Vd ^* becomes minus → ω · Lq · Iq becomes plus. Q-axis current Iq moves in the positive direction. That is, the actual currents Id and Iq change in a direction different from the request for moving the d-axis current Id in the minus direction.
On the other hand, in the non-interference feedback method, the q-axis voltage command value Vq ^* is moved in the minus direction, so that Vq ^* is minus → ω · Ld · Id is minus and the d-axis current Id is moved in the minus direction. That is, the actual currents Id and Iq can be changed as required to move the d-axis current Id in the minus direction, and the actual currents Id and Iq can be matched with the command currents Id ^* and Iq ^* .

As shown in FIG. 8, when ΔId> 0 and ΔIq = 0, it is desired to move the d-axis current Iq in the plus direction (rightward in the figure). Considering similarly to the example of FIG. 7, in the interference feedback method, the q-axis current Iq moves in the minus direction by moving the d-axis voltage command value Vd ^* in the plus direction. That is, the actual currents Id and Iq change in a direction different from the request.
On the other hand, in the non-interference feedback method, the d-axis current Id moves in the plus direction by moving the q-axis voltage command value Vq ^* in the plus direction. That is, the actual currents Id and Iq can be changed as required, and the actual currents Id and Iq can be matched with the command currents Id ^* and Iq ^* .

In short, in the interference feedback control, the actual currents Id and Iq move in a direction shifted by 90 ° from the desired movement direction. Referring to FIG. 9, for example, each time the control is repeated starting from the state of ΔId = 0 and ΔIq <0 shown in FIG. 5, the actual currents Id and Iq are the states of FIG. 5 → FIG. 8 → FIG. 6 → FIG. As shown in bold arrows, the current flows around the command currents Id ^* and Iq ^* . If the control cycle is fast, the radius of the circular locus drawn by the actual currents Id and Iq will be small, and if the number of synchronizations is small, the controllability will be poor.

On the other hand, in the non-interference feedback method, if the feedback gain is set appropriately, the actual currents Id and Iq can theoretically be matched with the command values Id ^* and Iq ^* . Therefore, in this embodiment, the control performance in the high rotation region can be improved by applying the non-interference feedback method in the rotation region higher than the switching rotational speed A.

  On the other hand, in the low-rotation region where the R term ratio of the voltage equation is dominant, control performance may be obtained by applying the interference feedback method, so that there are few merits to apply the non-interference feedback method. Therefore, the control performance of the current feedback control can be improved over a wide rotation speed region by switching the control method of the voltage command calculation unit according to the rotation speed of the motor 4. Therefore, the effect is particularly effectively exhibited as a control device for the motor 4 that generates the driving force of the hybrid vehicle.

  Further, supplementing with reference to FIG. 3, if switching is performed such that the interference feedback method is applied in the sine wave PWM control mode region and the non-interference feedback method is applied in the overmodulation PWM control mode region, the sine wave The effect of the non-interference feedback method cannot be obtained in the PWM control mode region. Therefore, the controllability in the region indicated by the broken line hatching in FIG. 3 can be improved by applying the non-interference feedback method in the higher rotation region based on the switching rotational speed A.

  Furthermore, in the present embodiment, when the rotational speed N is equal to or higher than the simplified rotational speed B in the region to which the non-interference feedback method is applied, it is assumed that “R = 0” and simplified formula (7) is used. Calculation load can be reduced.

(Second Embodiment)
A control apparatus for an AC motor according to a second embodiment of the present invention will be described with reference to FIGS. 10 and 11. The second embodiment is different from the first embodiment in that hysteresis characteristics are used in switching between the interference feedback method and the non-interference feedback method.
As shown in FIG. 10, in the second embodiment, the rotation speed N of the motor 4 increases, and the first switching rotation speed A1 used when switching from the interference feedback system to the non-interference feedback system and the rotation of the motor 4 are performed. The number N decreases, and the second switching rotation speed A2 used when switching from the non-interference feedback method to the interference feedback method is set separately. The first switching speed A1 (for example, 3000 rpm) is set to a value larger than the second switching speed A2 (for example, 2000 rpm).

The feedback control method switching process of the second embodiment will be described with reference to the flowchart of FIG. First, in S20, it is determined whether the interference feedback method is currently being applied or the non-interference feedback method is being applied.
While the interference feedback method is applied (S20: YES), when the rotational speed N increases (S21: YES), when the rotational speed becomes equal to or higher than the first switching rotational speed A1 (S22: YES), switching to the non-interference feedback method ( S23).
On the other hand, when the non-interference feedback method is being applied (S20: NO), while the rotation speed N is decreasing (S24: YES), when the second switching rotation speed A2 or less (S25: YES), the interference feedback method is switched to. Switching (S26).

In the second embodiment, when the rotation speed N of the motor 4 repeatedly increases and decreases across one switching rotation speed A, the feedback method is frequently switched to avoid the hunting phenomenon that may cause the control to become unstable. be able to.
As in the first embodiment, when the rotational speed N becomes equal to or greater than the simplified rotational speed B during application of the non-interference feedback method, the calculation is performed using the simplified formula (7) assuming that R = 0. You may do it.

(Other embodiments)
The control apparatus for the AC motor of the present invention is not limited to the hybrid vehicle including the two motor generators illustrated in FIG. 1 of the above embodiment, but in other hybrid vehicles and electric vehicles, or various devices other than the vehicle, current feedback. The present invention may be applied as a control device for any AC motor that performs control.

Moreover, the following formula | equation (8) combined with the feedforward term (Vdff, Vqff) may be used like the patent document 1 with respect to the formula (3) which is a definition formula of a non-interference feedback system.

  As mentioned above, this invention is not limited to the said embodiment at all, In the range which does not deviate from the meaning of invention, it can implement with a various form.

20 ... MG control device (control device for AC motor),
21 ... Current command calculation unit,
23 ... Voltage command calculation unit,
26 ... dq converter,
28 ... switching determination part,
34 ... second inverter (inverter),
4 ... 2nd MG, motor (AC motor).

Claims (5)

An AC motor control device (20) for controlling the voltage applied to the AC motor (4) by controlling the drive of the inverter (34) by current feedback control,
a current command calculation unit (21) for calculating a d-axis current command value (Id ^* ) and a q-axis current command value (Iq ^* );
A dq conversion unit (26) for performing dq conversion on the phase current detection value of the AC motor and calculating a d-axis current detection value (Id) and a q-axis current detection value (Iq);
A d-axis current deviation (ΔId) that is a deviation between the d-axis current command value (Id ^* ) and the d-axis current detection value (Id), and a q-axis current command value (Iq ^* ) and a q-axis current detection value (Iq). A voltage command calculation unit (23) that calculates a d-axis voltage command value (Vd ^* ) and a q-axis voltage command value (Vq ^* ) by a PI control calculation based on a q-axis current deviation (ΔIq) that is a deviation from ,
A switching determination unit (28) for switching the control method of the voltage command calculation unit based on the rotational speed of the AC motor,
The switching determination unit
A non-interference feedback method in which the d-axis voltage command value is calculated from the q-axis current deviation and the q-axis voltage command value is calculated from the d-axis current deviation according to Equation 1 below.

(Where Kpd / Kpq: gain of P (proportional) control term of non-interference feedback system,
Kid / Kiq: Gain of I (integration) control term of non-interference feedback method,
ΔId: d-axis current deviation (ΔId = Id ^* −Id),
ΔIq: q-axis current deviation (ΔIq = Iq ^* −Iq))
as well as,
An interference feedback method for calculating the d-axis voltage command value from the d-axis current deviation and calculating the q-axis voltage command value from the q-axis current deviation according to Equation 2 below:

(Where K′pd / K′pq: gain of the P (proportional) control term of the interference feedback system,
K'id / K'iq: I (integral) control term gain of interference feedback system)
The interference feedback method is applied in a region where the rotational speed of the AC motor is less than a predetermined switching rotational speed (A), and the non-interference feedback method is applied in a region where the rotational speed of the AC motor is equal to or higher than the switching rotational speed. Thus, the control system for the AC motor is characterized by switching the control method of the voltage command calculation unit. The non-interference feedback method calculates the d-axis voltage command value and the q-axis voltage command value based on the following equation 4 using the voltage equation shown in the following equation 3. The control apparatus for an AC motor according to claim 1.

(Where R: armature resistance, Ld / Lq: d-axis inductance / q-axis inductance,
(ω: electrical angular velocity, φ: armature flux linkage of permanent magnet)   The switching rotational speed is such that an R term ratio, which is a ratio of a value of a term including R in the voltage equation to a total value, is equal to or less than a predetermined value (α) in a rotational speed region to which the non-interference feedback method is applied. The AC motor control device according to claim 2, wherein the control device is set. In a rotation speed region equal to or greater than a predetermined simplified rotation speed (B) greater than the switching rotation speed,
4. The control apparatus for an AC motor according to claim 2, wherein the voltage command value is calculated by setting the value of R in the arithmetic expression of the non-interference feedback method to zero. The switching rotational speed includes a first switching rotational speed (A1) used when the rotational speed of the AC motor is increased and switching from the interference feedback system to the non-interference feedback system, and the rotational speed of the AC motor. Consisting of a second switching rotational speed (A2) that is used when switching from the non-interference feedback method to the interference feedback method.
5. The control device for an AC electric motor according to claim 1, wherein the first switching rotational speed is set to a value larger than the second switching rotational speed.

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