JP2000050689A - Drive control equipment of ac motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce difference between a torque command value and actual output torque in a drive control of an AC motor. SOLUTION: A torque detecting means 14 is constituted by using a torque sensor or the like, and torque feedback control is performed. A voltage phase ψis set so as to reduce a torque deviation ΔT, and the range of ψ is restricted in a specified phase range. As a result, actual output torque can be made to approach a torque command value, without breaking control.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a drive control device for an AC motor.

[0002]

2. Description of the Related Art When an AC motor is driven using a DC power supply, it is widely used to apply a pulse width modulation (PWM) waveform voltage using an inverter. However, applying a PWM waveform voltage to an AC motor has a limitation in voltage utilization. Therefore, for example, there is a problem that a sufficiently high output cannot be obtained in a high rotation range.

In this regard, there is a technique in which a rectangular wave voltage is applied to an AC motor to rotate the AC motor. According to this technique, the output in the high rotation range can be improved, and at this time, it is not necessary to flow a large field weakening current, and the copper loss can be reduced. Further, since the number of times of switching in the inverter can be reduced, switching loss can be suppressed.

A control technique for applying such a rectangular wave voltage to an AC motor has been disclosed, for example, in the 1997 JEVA Electric Vehicle Forum entitled "High-performance control system of drive system using surface magnet structure PM motor". ing.
FIG. 6 is a diagram illustrating an example of a motor drive control system employing the same technology.

In FIG. 1, an inverter 106 is connected to a motor 108 which is a permanent magnet synchronous AC motor. A rectangular wave generator 104 is connected to the inverter 106.
02 based on the voltage phase ψ supplied from the motor 102 and the rotor angle θ output from the resolver 110 provided adjacent to the motor 108 so that a rectangular wave voltage having the voltage phase ψ is applied to the motor 108. For switching control.

The phase calculation unit 102 receives a torque command value T generated by an electronic control unit (ECU) (not shown), and also outputs a voltage Vdc of a battery (not shown) connected to the inverter 106. Has been entered. The phase calculator 102 calculates and outputs a voltage phase ψ corresponding to the torque command value T using these input values.

That is, a voltage equation in a steady state of the system can be expressed by the following equation.

[0008]

Vd = R * Id−ω * Lq * Iq (1) Vq = R * Iq + ω * Ld * Id + ω * Φ (2) where Vd and Vq are the d-axis and q-axis voltage values, respectively. . Further, Id and Iq are current values of the d-axis and the q-axis, respectively. Furthermore, Ld and Lq are d-axis and q-axis inductances, and ω is the angular velocity of the motor 108. Φ is the number of magnetic flux linkages.

Here, when Vd and Vq are represented using the magnitude | V | of the voltage vector and the phase ψ with respect to the q axis, the following equation is obtained.

[0010]

Vd = − | V | * sinψ (3) Vq = | V | * cosψ (4) In the following, for simplicity of description, it is assumed that the motor 108 is a non-salient motor (Ld = Lq = L). Assume. However, in principle, salient pole motors can be applied in a similar manner.

First, the torque of the motor 108 can be expressed by the following equation.

[0012]

T = p * Φ * Iq + p * (Ld−Lq) * Id * Iq (5) where T represents torque, and p represents the number of pole pairs. In the above equation, the first term on the right side represents the torque by the permanent magnet, and the second term on the right side represents the reluctance torque. However,
Here, the second term is 0 to explain the non-salient pole motor.
It is.

When the relational expression between the torque and the voltage vector is derived from the above expression, the following expression is obtained.

[0014]

T = p * Φ * | V | * sinψ / (ω * L) (6) where the magnitude | V | of the voltage vector is the battery voltage V
It can be expressed as follows using dc.

[0015]

| V | = (√6 / π) * Vdc (7) That is, the phase calculation unit 102 shown in FIG.
Using the equation (7), the voltage phase ψ can be calculated based on the battery voltage Vdc and the torque command value T.

As described above, according to the conventional motor drive system shown in FIG. 6, the motor 108 is driven at a desired torque.

[0017]

However, the battery voltage Vdc decreases with the power consumption of the motor 108, and the inductance L also decreases due to magnetic saturation at a high load. Further, the number of magnetic flux linkages Φ changes with a change in magnet temperature. Therefore, even if the phase calculation unit 102 calculates the equation (6), it is difficult to output the required torque from the motor 108.

The situation described above is not limited to the drive control of an AC motor using a rectangular wave voltage, but also to the drive control of an AC motor using a PWM sine wave voltage having a variable voltage amplitude.
Equally valid.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide a drive control device capable of reducing an error between a torque command value and an actual output torque when driving an AC motor. It is in.

[0020]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a drive control device for rotating an AC motor by a rectangular wave voltage, wherein a torque detecting means for detecting an output torque value of the AC motor is provided. Means for generating a torque deviation representing a difference between a detected torque value and a given torque command value, and phase setting means for setting a phase of the rectangular wave voltage so as to eliminate the torque deviation. And

According to another aspect of the present invention, there is provided a drive control device for rotating an AC motor by applying an AC voltage to the AC motor, wherein a torque detecting means for detecting an output torque value of the AC motor is provided. It is characterized by including means for generating a torque deviation representing a difference from a command value, and phase setting means for setting a phase of the AC voltage so as to eliminate the torque deviation.

That is, in the present invention, unlike the voltage phase control according to the prior art, the output torque value of the AC motor is fed back, and the phases of the rectangular wave voltage and the AC voltage are set so as to eliminate the torque deviation. By doing so, the actual output torque and the torque command value can be output without being affected by the fluctuation of the motor constant, as compared with the conventional method of calculating the voltage phase based on the motor constant so that a torque corresponding to the torque command value can be output. Can be approached.

In one embodiment of the present invention, the phase setting means sets the phase of the rectangular wave voltage within a predetermined phase range. The voltage phase-torque curve of the AC motor has an extreme value. For example, a non-salient pole type AC motor has an extreme value of the voltage phase-torque curve at a point where the voltage phase is ± 90 °. For this reason, if the phase set by the phase setting means is performed without limitation, the torque feedback control is broken. According to this aspect, since the phase set by the phase setting means is restricted within the predetermined phase range, control failure can be prevented.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing an overall configuration of a drive control device for an AC motor according to an embodiment of the present invention. In the figure, an adder 13 has an electronic control unit (E
CU), the torque command value generated by the torque detector 14 is also input to the adder 13. The torque detecting means 14 can be configured using a torque sensor, but can also be calculated based on the following equation.

[0026]

T = Pin / ω = (iu × vu + Iv × vv + iw × vw) / ω (8) Here, Pin represents electric power supplied to the motor 24.
Ω represents the angular velocity of the motor 24. Furthermore, iu, i
v and iw represent values of each phase of the three-phase alternating current supplied to the motor 24, and vu, vv and vw represent voltages of each phase.

Note that vu, vv, and vw are inverters 22
May be used, or an actual value supplied from the inverter 22 to the motor 24 may be detected by a sensor and used.

Alternatively, the torque detecting means 14 can calculate from the DC current and DC voltage as shown in the following equation.

[0029]

T = Pin / ω = (IB × VB) / ω (9) Here, IB and VB represent DC current and DC voltage of a battery (not shown) connected to the inverter 22.

The adder 13 subtracts the torque value supplied from the torque detecting means 14 from the torque command value supplied from the ECU to generate a torque deviation ΔT. Then, the torque deviation ΔT is supplied to the compensator 12. Compensator 12
Now, the torque deviation Δ after compensation based on the torque deviation ΔT
Generate T '.

That is, when both sides of the above equation (6) are differentiated by the voltage phase ψ, and the voltage amplitude | V | is erased using the equation (7), the following equation (10) is obtained.

[0032]

DT / dψ = p * Φ * (√6 / π) * Vdc * cosψ / (ω * L) (10) As can be seen from equation (10), the slope of the voltage phase-torque curve is It is proportional to the battery voltage Vdc and cosψ, and inversely proportional to the angular velocity ω of the motor 24. FIG. 2 shows how the voltage phase-torque curve changes due to the change in the battery voltage Vdc. As shown in the figure, when the battery voltage Vdc increases, a large torque T can be exerted even when the voltage phase 小 さ く is small. Therefore, the compensator 12 generates a compensated torque deviation ΔT ′ using the torque deviation ΔT according to the following equation (11).

[0033]

ΔT ′ = ω / (Vdc * cosψ) * ΔT (11) In this case, the expression (10) becomes the following expression (12), and the torque deviation ΔT ′ and the voltage phase difference Δψ are proportional to each other. Can be provided. As a result, good control characteristics can be obtained.

[0034]

DT ′ / dψ = p * Φ * (√6 / π) / L (12) The torque deviation ΔT ′ generated by the compensator 12 is supplied to the PI calculator 16 where the torque deviation ΔT ′ is obtained. Is set to 0, and the voltage phase ψ is output. This voltage phase ψ is then input to a phase limiter 18. The phase limiter 18 changes the value of the voltage phase ψ supplied from the PI calculator 16 from -90 ° to +
This is a means for limiting the range to 90 °. For example,
When the voltage phase ψ output from the PI calculator 16 exceeds 90 °, the value is clipped and corrected to 90 °, and then the value is supplied to the subsequent rectangular wave generator 20.

FIG. 3 is a diagram showing the relationship between the voltage phase ψ and the torque of the motor 24. As shown in the figure, when the voltage phase ψ is in the range of −90 ° to + 90 °, the torque T increases as the voltage phase 増 加 increases, but when the voltage phase 超 え る exceeds the range, the voltage phase 増 加 increases. Accordingly, the torque T decreases. Therefore, the phase limiter 18 limits the voltage phase ψ output from the PI calculator 16 within the phase control range indicated by the arrow 28. For this reason, as shown in FIG. 4, the end point of the voltage vector is limited to be located only on the locus 30 on the dq plane. In this way, it is possible to effectively prevent the control failure in the drive control device 10 that performs the torque feedback.

The rectangular wave generator 20 supplies a switching signal for generating a rectangular wave voltage to the inverter 22 based on the voltage phase ψ output from the phase limiter 18 and the rotor angle θ supplied from the resolver 26.
Thus, the motor 24 can be driven by the rectangular wave voltage having the voltage phase ψ.

FIG. 5 is a diagram showing a rectangular wave voltage supplied to the motor 24. FIG. 3 shows, as an example, a voltage waveform applied to the U-phase among the three-phase AC voltages applied to the motor 24. The winding of the motor 24 is star-connected, so that the difference between the maximum value and the minimum value in the rectangular wave matches the battery voltage Vdc. The voltage phase ψ corresponds to the difference between the timing when the rotor angle θ is 0 ° and the falling timing of the rectangular wave in FIG.

Drive control device 1 for AC motor described above
According to 0, the torque detection means 14 is provided to set the voltage phase ψ such that the torque deviation ΔT, which is the difference between the actual output torque and the torque command value, becomes 0, and the rectangular wave voltage having the voltage phase ψ is set. Since the voltage is applied to the motor 24, it is possible to prevent the torque accuracy from deteriorating due to the fluctuation of the motor constant.

The AC motor drive control device 10 described above can be modified in various ways. For example, in the above description, a rectangular wave voltage is applied to the motor 24. However, the present invention can be similarly applied to a case where a PWM sine wave voltage having a variable voltage amplitude is applied to the motor 24. That is, if the torque feedback control is performed by providing the torque detecting means 14, the difference between the torque command value and the actual output torque can be reduced even when the motor constant fluctuates.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a drive control device for an AC motor according to an embodiment of the present invention.

FIG. 2 is a diagram showing how a voltage phase-torque characteristic changes according to a change in battery voltage.

FIG. 3 is a diagram showing a voltage phase-torque characteristic and a limit range of a voltage phase.

FIG. 4 is a diagram illustrating a locus of a voltage vector.

FIG. 5 is a diagram showing a relationship between a voltage waveform supplied to a motor, a battery voltage, and a voltage phase.

FIG. 6 is a diagram showing an overall configuration of a drive control device for an AC motor according to the related art.

[Explanation of symbols]

10 drive control device, 12 compensator, 13 adder, 1
4 Torque detecting means, 16 PI calculator, 18 phase limiter, 20 rectangular wave generator, 22 inverter, 24
Motor, 26 resolver.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Inakuma 41-cho, Yokomichi, Nagakute-cho, Aichi-gun, Aichi Prefecture Inside Toyota Central Research Laboratory Co., Ltd. No. 41 at Yokomichi 1 Toyota Central Research Laboratory Co., Ltd. F-term (reference) LL58

Claims (3)

[Claims] 1. A drive control device for applying a rectangular wave voltage to an AC motor to rotate and drive the AC motor, comprising: a torque detecting means for detecting an output torque value of the AC motor; And a phase setting means for setting a phase of the rectangular wave voltage so as to eliminate the torque deviation. 2. The drive control device for an AC motor according to claim 1, wherein the phase setting means sets the phase of the rectangular wave voltage within a predetermined phase range. . 3. A drive control device for rotating an AC motor by applying an AC voltage to drive the AC motor, comprising: a torque detector for detecting an output torque value of the AC motor; A drive control device for an AC motor, comprising: means for generating a torque deviation representing a difference; and phase setting means for setting a phase of the AC voltage so as to eliminate the torque deviation.