JPH10164707A - Hybrid primemover and its controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to efficiently limit the rotational change (torque ripple) to a lower level with a system as simple as possible. SOLUTION: The output shafts of a motor 6 and an engine 7 are connected so as to satisfy an equation, p=L/(2N), which makes both torque ripples anti- phase; where p = number of paired poles of the motor 6, L = number of cylinders of the engine 7 and N = rotational speed ratio of the output shafts of the motor 6 and engine 7. A DC brushless motor is used as the motor 6. A switched reluctance motor can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hybrid prime mover and a control device thereof, and more particularly, to a technique for reducing rotation fluctuation and torque pulsation of the hybrid prime mover.

[0002]

2. Description of the Related Art A gasoline / diesel engine generally used as a motor of an automobile generates torque due to the combustion pressure of intermittent combustion, so that torque pulsation occurs, and the torque pulsation causes fluctuations in the rotational speed. In the idle state, in order to prevent the stall due to the rotation speed fluctuation, the idle rotation speed is set to be high, or the engine mount is devised so that the driver does not feel uncomfortable vibration. However, increasing the idling rotational speed causes an increase in fuel consumption, and it is difficult to completely suppress the vibration only by the engine mount.

[0003] Recently, research on a parallel hybrid vehicle combining a gasoline / diesel engine and an electric motor as a prime mover has been conducted with the aim of improving total performance, such as a demand for low fuel consumption, improvement in power performance and comfort, etc. In this technique, a rotation speed is detected and rotation speed control is performed to suppress the rotation speed fluctuation (see Japanese Patent Application Laid-Open No. 6-247186). The crank angle position of the engine is detected and torque pulsation is detected. Japanese Patent Application Laid-Open No. 7-208228 discloses a method in which a torque command for canceling is created, and torque pulsation of the engine is canceled by controlling the motor torque to absorb torque fluctuation.

[0004] Since durability is required for the motor of the hybrid vehicle, an AC motor is generally used, and the AC motor is also used in the above-mentioned conventional example.

[0005]

However, in such a conventional hybrid prime mover, various problems occur when suppressing torque pulsation. First, in order to suppress pulsation using an AC motor, it is necessary to control the rotating magnetic field of the AC motor so as to have a predetermined relationship with the rotation angle of the rotor. Therefore, means for detecting the rotation angle phase of the motor is required.

Further, in order to control the torque of the motor, it is necessary to perform coordinate conversion between a three-phase AC coordinate system and a dq-axis coordinate system which is a rotating coordinate system that rotates in synchronization with the motor rotor. It is necessary to perform two coordinate conversion calculations using the rotational position detection value until the motor application voltage is calculated. Such control is necessary in order to synchronize the rotating magnetic field between the rotor and the stator when the motor is an AC motor, but there is a delay in controlling the current. That is, in terms of performance, the response of the output torque is delayed due to the delay of the current control, and the fluctuation of the rotation speed (torque pulsation) cannot be suppressed to a low level.

In order to pulsate the motor torque with an AC motor, the current and the voltage applied to the motor must be greatly changed as shown in FIGS. And it is difficult to make the current follow the command. The present invention has been made in view of such conventional problems, and has a hybrid prime mover that can efficiently suppress the rotation fluctuation (torque pulsation) of a synchronous motor and an internal combustion engine to a low level with a system as simple as possible. It is an object to provide the control device.

[0008]

According to a first aspect of the present invention, there is provided a hybrid prime mover comprising a synchronous motor and an internal combustion engine, wherein an output shaft of the synchronous motor and an output shaft of the internal combustion engine are connected. Are connected at a rotational phase and a rotational speed at which both torque pulsations have opposite phases.

According to this configuration, the torque pulsations (rotation fluctuations) of the synchronous motor and the internal combustion engine are in opposite phases, and the torque pulsations of both are canceled. In the hybrid prime mover according to the second aspect of the present invention, the output shaft of the synchronous motor and the output shaft of the internal combustion engine are connected so as to satisfy the relationship of Expression (1). p = L / (2N) (1) where p: number of pole pairs of the synchronous motor L: number of cylinders of the internal combustion engine N: output of the synchronous motor and the internal combustion engine According to such a configuration, the cycle of the torque pulsation of the engine and the cycle of the torque pulsation of the synchronous motor generated while keeping the armature current constant are equal. That is, the torque pulsation of the internal combustion engine occurs half the number of cylinders per rotation of the output shaft of the internal combustion engine. On the other hand, when the output shaft is rotated while the armature current of the synchronous motor is kept constant, torque pulsation having a frequency corresponding to the number of pole pairs is generated. Therefore, by connecting the output shaft of the synchronous motor and the output shaft of the internal combustion engine so as to satisfy the relationship of Expression (1), the periods of both torque pulsations coincide.

According to a third aspect of the present invention, the synchronous motor is a DC brushless motor. According to such a configuration, the output shaft of the DC brush race motor and the output shaft of the internal combustion engine are connected with a rotational phase and a rotational speed such that the torque pulsation has an opposite phase. In the hybrid prime mover according to the invention of claim 4, the synchronous motor is a reluctance motor.

According to this configuration, the output shaft of the reluctance motor and the output shaft of the internal combustion engine are connected with a rotational phase and a rotational speed at which the torque pulsation has an opposite phase. In the hybrid prime mover according to the fifth aspect of the present invention, the reluctance motor is connected to the internal combustion engine such that the phase of the self-inductance is advanced by １ ／ cycle from the phase at which the maximum value of the torque pulsation of the internal combustion engine occurs. I have.

According to this configuration, the torque of the reluctance motor decreases when its self-inductance decreases, and increases when its self-inductance increases. Is 1/4 of the phase at which the maximum value of
When advanced by the period, both torque pulsations have opposite phases.

According to a sixth aspect of the present invention, there is provided the hybrid prime mover control device according to the third aspect, wherein current command value generating means for generating a current command value for each phase in accordance with equation (2); Power supply control means for controlling the power supply of the DC brushless motor in accordance with the current command value. ^{_{i n * = Icos (θ 0}} + 2π × (n-1) / N) ······ (2) where, N: number of phases (N ≧ 1) n: Phase (n = 1,2, ·· ^{_{·, n) i n *:}} n -phase electric current command value I: electric current command value amplitude theta _0: according to the rotation angle generated by the internal combustion engine maximum torque configuration in n-phase coordinate system of the brushless DC motor, wherein ( In 2), the phase of the output torque of the DC brushless motor becomes opposite to the phase of the output torque of the internal combustion engine due to the rotation angle θ ₀ , and the amplitude of the generated torque of the DC brushless motor is adjusted by adjusting the current command value amplitude I. And the same amplitude as the torque of the internal combustion engine.
Since the phase θ ₀ is a constant value, the current command value of each phase is a DC amount. Therefore, the total value of the output torques of the DC brushless motor and the internal combustion engine becomes substantially constant, and both torque pulsations are canceled.

According to a seventh aspect of the present invention, there is provided a control device for a hybrid prime mover according to the fifth aspect, wherein a current command value for generating a current command value for each phase according to the equations (3) and (4). And a power supply control means for controlling the power supply of the reluctance motor in accordance with the current command value. i _X ^* = I (3) i _Y ^* = 0 (4) where i _X ^* is the current command value of the phase (X) in which the phase of the self-inductance is advanced by １ ／ cycle from the phase at which the maximum value of the torque pulsation of the internal combustion engine occurs. i _Y ^* : current command value of a phase other than the X phase I: current command value amplitude According to this configuration, the reluctance motor is connected so that its torque pulsation is in the opposite phase to the torque pulsation of the internal combustion engine. By setting the current command value amplitude I to a value such that the amplitude of the fundamental wave component of the torque pulsation of the internal combustion engine and the amplitude of the torque pulsation of the reluctance motor are equal, both torque pulsations are canceled.

[0015]

According to the hybrid prime mover of the first aspect, both output shafts are connected so that the torque pulsation of the synchronous motor and the torque pulsation of the internal combustion engine are in opposite phases. Are canceled, and torque pulsation can be easily suppressed without detecting the rotation angle of the synchronous motor or the internal combustion engine.

According to the hybrid prime mover of the present invention, the rotational speed of the synchronous motor and the rotational speed of the internal combustion engine can be matched, and the torque pulsation can be reversed by matching the rotational phases of both. Can be. According to the hybrid prime mover according to the third aspect of the present invention, by using a DC brushless motor for the synchronous motor,
The torque pulsation of the internal combustion engine and the DC brushless motor can be suppressed to a low level.

According to the hybrid motor of the fourth aspect, by using the reluctance motor for the synchronous motor, the torque pulsation of the reluctance motor and the torque pulsation of the internal combustion engine can be suppressed to a low level. According to the hybrid prime mover according to the fifth aspect of the present invention, both the torque pulsations can be set in opposite phases.

According to the control apparatus for a hybrid prime mover according to the sixth aspect of the present invention, the two torque pulsations are set in opposite phases,
Both amplitudes can be the same. In addition, since it is only necessary to control the current supplied to the DC brushless motor to a constant value, torque responsiveness is improved and energy in the motor control system is improved as compared with the conventional control in which the supplied current is changed. Loss can be reduced.

According to the control apparatus for a hybrid prime mover of the present invention, the amplitude of the torque pulsation generated in the reluctance motor by adjusting the amplitude of the current command value is made equal to the amplitude of the torque pulsation of the internal combustion engine. And both torque pulsations can be offset.

[0020]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. First, a first embodiment will be described. FIG. 1 is a diagram showing a first embodiment of the present invention. Note that this embodiment shows a configuration example in which the function is limited only to suppression of engine rotation fluctuation (torque pulsation). In this figure, the engine 7 is a gasoline (reciprocating) engine. The motor 6 is a DC brushless motor which is one of synchronous motors, and here, a three-phase motor is used.

The output shaft of the engine 7 and the output shaft of the motor 6 are connected so as to satisfy the following equation (1). p = L / (2N) (1) where p: number of motor poles L: number of engine cylinders N: ratio of rotation speed of motor 6 to engine 7 In the embodiment, the number of cylinders of the engine 7 is four,
Is two. Therefore, the output shaft of the engine 7 and the output shaft of the motor 6 are connected such that the rotation speed ratio between them becomes 1: 1. The connection is made directly or via a gear or the like. Note that the rotation phases of both output shafts at this time may be arbitrary.

The motor 6 is provided with current sensors 5-1 and 5-2 for detecting U-phase and V-phase current values, respectively. The current command generation device 1 is a current command value generation unit that generates a command value of a current supplied to the motor 6. The current control device 2 inputs a current command value from the current command generation device 1, inputs a motor current detection value from the current sensors 5-1 and 5-2, and based on the current command value and the motor current detection value. command value of the voltage applied to the motor 6 v _U ^* to v _W computes a ^*.

The inverter 3 converts the DC voltage of the battery 4 into a PWM (pulse) based on a voltage command value from the current control means.
It is a PWM inverter that converts to AC voltage by width modulation. The current control device 2 and the inverter 3
Corresponds to the energization control means. Next, the operation will be described.

FIG. 2 shows the output torque of a gasoline (reciprocating) engine in a low rotation range. As shown in this figure, the gasoline engine is an intermittent combustion engine,
Torque pulsation occurs. The current command generation device 1 generates current command values such as the following equations (5) to (7).

[0025] ^{_{i u * = Icos θ 0 ············}} (5) i v * = Icos (θ 0 + 2π / 3) ············ ( ^{_{6) i w * = Icos (}} θ 0 -2π / 3) ············ (7) However, i _u ^*: _u-phase current command value i _v ^*: _v-phase current command value i _w ^* : w-phase current command value I: current command value amplitude θ ₀ : phase angle of the motor 6 when the torque pulsation of the engine 7 reaches a peak (based on the U-phase shaft position) Expressions (5) to (7) Is set to a value such that the amplitude of the fundamental frequency component of the torque pulsation of the engine 7 and the amplitude of the torque pulsation of the motor 6 become the same.

The reference axis position of the phase angle θ ₀ is not limited to the U-phase, but may be the V-phase and W-phase axis positions. Since this phase angle θ ₀ is a constant value, the current command values i _u ^{* to} i
_w ^* is a DC amount. Energizing current i _u , i of motor 6
_V is detected by the current sensors 5-1 and 5-2, and is input to the current control device 2. And the current control device 2
Controls the inverter 3 based on the detected motor currents i _u , i _V , so that the motor currents i _{u to} i _w are equal to the current command value i
I would like to follow the _u ^* _{~i w} ^*.

With the motor currents i _{u to} i _w , the motor 6 generates a torque as shown in FIG. That is,
By instructing the motor currents represented by the equations (5) to (7), the phase of the torque pulsation of the motor 6 becomes opposite to the phase of the torque pulsation of the engine 7 (phase difference 180 °), and the amplitude thereof becomes , And the amplitude of the output torque of the engine 7. Therefore, the total value of the output torque of the engine 7 and the output torque of the motor 6 is substantially constant.

Although the actual pulsation waveform of the output torque of the engine is not always a sine wave, if the fundamental frequency component is canceled by the output torque of the motor 6, the torque pulsation and the fluctuation of the engine rotation do not matter. It can be reduced to the level. According to such a configuration, the output shafts of the engine 7 and the motor 6 are connected so as to satisfy the relationship of Expression (1), and the current that satisfies the relationship of Expressions (5) to (7) is supplied to the motor 6.
, The torque pulsation of the engine 7 and the torque pulsation of the motor 6 are in opposite phases, and both torque pulsations are cancelled, and rotation fluctuation of the hybrid prime mover can be suppressed.

Further, since it is only necessary to control the current to a constant value, the means for detecting the rotation angle of the motor 6 or the engine 7 becomes unnecessary, the control is easy, and the current responsiveness and drive loss can be reduced. In the present embodiment, a three-phase motor has been described. However, the present invention is not limited to this, and can be applied to a multi-phase motor. In the case of a polyphase motor, the current command value of each phase is represented by Expression (2).

[0030] ^{_{i n * = Icos (θ 0}} + 2π × (n-1) / N) ······ (2) where, N: number of phases (N ≧ 1) n: Phase (n = 1, 2 ^{_{, ···, n) i n *}} : n -phase electric current command value I: electric current command value amplitude theta _0: rotation angle then the second embodiment engine 7 to generate the maximum torque at the n-phase coordinate system of the motor 6 The embodiment will be described.

In this motor, both torque pulsations are reversed in phase using a switch reluctance motor (hereinafter referred to as an SR motor). FIG. 4 shows a second embodiment. In this embodiment, a configuration example in which the function is limited only to the suppression of engine rotation fluctuation is shown. The motor 11 is an SR motor and has three phases a, b, and c. The number of poles of the rotor is 4 and the motor 11
A speed reducer 8 having a rotation speed ratio of the output shaft of the motor 11 and the engine 7 set to 2: 1 is connected between the motor and the engine 7. As a result, the relationship of equation (1) is maintained.

In the motor 11, the phase of the self-inductance of the a-phase is １ ／ of the phase of the output torque of the engine 7.
It is connected to the engine 7 so as to advance by the period. Next, the operation will be described. FIG. 5 shows the relationship between the output torque of the engine 7 and the self-inductance of the motor 11.

By satisfying the relationship of equation (1), the cycle of the self-inductance of the motor 11 and the cycle of the output torque of the engine 7 match. Incidentally, the output torque T of the SR motor is represented by the following equation (8). T = (1/2) (dL _a / dθ) i _a ² + (1/2) (dL _b / _d θ) i _b ² + (1/2) (dL _b / _d θ) i _c ² + (dM _{ab / dθ) i a i b +} (dM bc / dθ) i b i c + (dM ca / dθ) i c i a ·············· (8) L a: a phase self Intakutansu i _a: a-phase motor current L _b: b phase self Intakutansu i _b: b-phase motor current L _c: c-phase self Intakutansu i _c: c-phase motor current M _ab: ab-phase self Intakutansu θ : Motor rotor phase M _bc : bc phase self-inductance M _ca : ca phase self-inductance In SR motors, the phase differential of self inductance (dL / dθ) is generally the phase differential of mutual inductance (dM /
dθ), it is often not a problem to ignore the mutual inductance term. If the mutual inductance is neglected, the output torque is expressed by Expression (9).

T = (1/2) (dL _a / dθ) i _a ² + (1/2) (dL _b / _d θ) i _b ² + (1/2) (dL _b / _d θ) i _c ² · (9) In other words, the output torque of the motor 11 is expressed in the form of the sum of the torques T _k (k = a, b, c) generated by the respective phases. Is proportional to the product of the phase derivative of the self-inductance (dL / dθ) and the square of the current (i ² ).

Since the phase of the self-inductance of the a-phase is advanced by １ ／ cycle from the phase of the torque pulsation of the engine 7, the current command generation device 1 uses the current command as shown in the equations (10) to (12). Generate a value. ^{_{i a * = I ····················· (10}} ) i b * = 0 ················ ^{_{····· (11) i c * =}} 0 ····················· (12) where, i _a ^*: _a phase current command value i _b ^* : B-phase current command value _ic ^* : c-phase current command value I: current command value amplitude The current command value of the a-phase is a constant value I.
The amplitude of the fundamental wave component of the output torque of the motor 11 is
Is set so as to be equal to the amplitude of the fundamental wave component of the torque pulsation.

A current that follows the current command value I is supplied to the motor 11 by the current control system of the current control device 2, the inverter 3, and the current sensors 5-1 and 5-2. This current generates a torque as shown in FIG. That is, the torque generated in the a-phase is proportional to the product of the phase differential of the self-inductance and the square of the current, and increases as the self-inductance of the motor 11 increases, as shown in FIG. It decreases when the inductance decreases.

Since the phase of the self-inductance of the a-phase is advanced by 1/4 cycle from the phase of the torque pulsation of the engine 7, the phase of the torque pulsation of the motor 11 is
Has the opposite phase to the phase of the torque pulsation. Since the current command value amplitude I is set as described above, the engine 7
When the output torque of the motor 7 and the output torque of the motor 11 are summed, the fundamental frequency component of the torque pulsation of the engine 7 is almost canceled. Although the pulsation waveform of the output torque of the engine 7 and the output torque of the motor 11 do not become sinusoidal, if the fundamental frequency component is canceled, the torque pulsation and the fluctuation of the engine rotation are reduced to a level that does not cause a problem.

As described above, even if an SR motor is used, torque pulsation can be suppressed, and the structure is extremely simplified. Further, in addition to the merit in the configuration, the responsiveness of the current, that is, the responsiveness of the torque in terms of performance is also extremely good. Hereinafter, the reason will be described. The circuit equation of the SR motor is described by equations (13) to (15).

[0039] _{v a = Ri a + ω (} i a (dL a / dθ) + i b (dM ab / dθ) + i c (dM ca / dθ)) + (L a (di a / dt) + M ab (di b _{/ dt) + M ca (di} c / dt)) ········· (13) v b = Ri b + ω (i b (dL b / dθ) + i c (dM bc / dθ) + i a ( _{dM ab / dθ)) + (} L b (di b / dt) + M bc (di c / dt) + M ab (di a / dt)) ········· (14) v c = Ri c _{+ ω (i c (dL c} / dθ) + i a (dM ca / dθ) + i b (dM bc / dθ)) + (L c (di c / dt) + M ca (di a / dt) + M bc (di b / dt)) ········· (15) where, v _{a: a} phase voltage applied v _b: b-phase applied voltage
v _c: c-phase applied voltage i _a: a-phase current i _b: b-phase current i _c: c-phase current R: winding resistance value omega: The motor speed this embodiment, a predetermined current of a predetermined 1-phase Since it is only necessary to control the currents of the other phases to zero, the term of the voltage caused by the time change of the current becomes zero. Therefore, the circuit equation of the SR motor is represented by equations (16) to (18).

[0040] _{v a = Ri a + ω (} i a (dL a / dθ)) ········· (16) v b = ω (i a (dM ab / dθ)) ····· _{···· (17) v c = ω} (i a (dM ca / dθ)) ········· (18) That is, as can be seen from these equations (16) - (18) Since the current only needs to be controlled to a constant value, a voltage for changing the current with time is not required, and the applied voltage can be small. In other words, a large torque can be obtained with a small voltage, and the responsiveness is also improved as compared with the conventional control device.

Next, a third embodiment will be described.
In this system, the same control as that of the second embodiment is performed in a low rotation region where the torque pulsation (rotational speed fluctuation) of the engine is easily felt. The control is performed. FIG. 7 shows the third embodiment. In the third embodiment, a current command switching device 12 is provided, and a rotation angle sensor 13 is also used.

[0042] Here, when the rotational speed of the engine 7 is lower than the predetermined speed, the current command generator 1, similar current command value and the second embodiment i _a ^* ~i _c ^* is computed Output to the current control device 2. Further, when the rotational speed of the engine 7 is higher than a predetermined speed, the electric current patterns are switched by the current command switcher 12, the torque command and rotation angle theta _m current command value is calculated from the i of the motor 11
_a ^{* to} _ic ^* are output to the current control device 2.

According to the configuration of the third embodiment,
Although the rotation angle sensor 13 is used and the control device is not simple, the torque response is good and the loss is small in the low rotation range where torque pulsation is easily felt. There is an advantage that the motor can be controlled with a high degree of freedom in the same manner as described above. In the first to third embodiments, the DC brushless motor and the SR motor have been described. However, the present invention is not limited to this. For example, even if another synchronous motor such as a step motor is used, the The torque pulsation can be suppressed by setting the phase opposite to the torque pulsation. However, a DC brushless motor and an SR motor are most suitable for suppressing torque pulsation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between an output torque of the engine of FIG. 1 and a rotation angle of a motor.

FIG. 3 is an explanatory diagram showing a relationship between an engine output torque and a motor output torque of FIG. 1;

FIG. 4 is a block diagram showing a configuration according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing the relationship between the output torque of the engine of FIG. 4 and the self-inductance of the motor.

FIG. 6 is an explanatory diagram showing the relationship between the output torque of the motor in FIG. 4 and the self-inductance of the motor.

FIG. 7 is a block diagram showing a configuration according to a third embodiment of the present invention.

FIG. 8 is a conventional explanatory diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Current command generator 2 Current controller 6, 11 Motor 7 Engine

Claims (7)

[Claims] 1. A hybrid motor having a synchronous motor and an internal combustion engine, wherein an output shaft of the synchronous motor and an output shaft of the internal combustion engine are connected at a rotational phase and a rotational speed at which both torque pulsations are in opposite phases. A hybrid prime mover. 2. The hybrid prime mover according to claim 1, wherein an output shaft of the synchronous motor and an output shaft of the internal combustion engine are connected so as to satisfy a relationship represented by Expression (1). p = L / (2N) (1) where p: number of pole pairs of the synchronous motor L: number of cylinders of the internal combustion engine N: synchronous motor and internal combustion Rotational speed ratio of output shaft to engine 3. The hybrid motor according to claim 1, wherein the synchronous motor is a DC brushless motor. 4. The hybrid motor according to claim 1, wherein the synchronous motor is a reluctance motor. 5. The reluctance motor is connected to the internal combustion engine such that the phase of the self-inductance is advanced by １ ／ cycle from the phase at which the maximum value of torque pulsation of the internal combustion engine occurs. Item 6. A hybrid prime mover according to Item 4. 6. A hybrid motor according to claim 3, wherein current command value generating means for generating a current command value for each phase according to equation (2), and energizing control of the DC brushless motor according to the current command value. A control device for a hybrid prime mover, comprising: an energization control unit. ^{_{i n * = Icos (θ 0}} + 2π × (n-1) / N) ······ (2) where, N: number of phases (N ≧ 1) n: Phase (n = 1,2, ·· ^{_{·, n) i n *:}} n -phase electric current command value I: electric current command value amplitude theta _0: rotation angle generated by the internal combustion engine maximum torque at n-phase coordinate system of the brushless DC motor 7. A hybrid motor according to claim 5, wherein a current command value generating means for generating a current command value for each phase according to the equations (3) and (4), and a reluctance motor according to the current command value. A control device for a hybrid prime mover, comprising: an energization control unit that controls energization. i _X ^* = I (3) i _Y ^* = 0 (4) where i _X ^* is the current command value of the phase (X) in which the phase of the self-inductance is advanced by １ ／ cycle from the phase at which the maximum value of the torque pulsation of the internal combustion engine occurs. i _Y ^* : Current command value of phases other than X phase I: Current command value amplitude