JPH07236295A - Drive control method for inner magnet type brushless DC motor - Google Patents

Abstract

(57) [Summary] [Structure] When the torque command increases or the inverter input voltage decreases, the inverter output phase voltage effective value is V
_When it is attempted to exceed _dc / 2 (2) ^1/2 , the inverter output voltage monitoring unit 7 detects the output voltage command V ₁ , and the two changeover switches 6 are used to control the d-axis current commands I _d ^* and q.
The axis current command I _q ^* is directly input to the dq / 3-phase converter 44. [Effect] Along with being able to prevent a sudden decrease in torque,
It is possible to increase the inverter output voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control method for a so-called inner magnet type brushless DC motor in which a permanent magnet is arranged inside a rotor core.

[0002]

2. Description of the Related Art Conventionally, a so-called inner magnet type brushless DC motor (hereinafter referred to as a motor) in which a permanent magnet is disposed inside a rotor core has a rotation coordinate as shown in FIG. In the above, in the direction of the magnetic flux of the permanent magnet, d
Taking the axis and taking the q axis in the direction orthogonal to the d axis, the negative d
A current I _d is applied to the stator winding so that a magnetomotive force is generated in the axial direction.
If it is flowed, it is possible to perform control equivalent to so-called field weakening control in which the field current of the shunt DC motor is weakened by the d-axis reaction, and it is difficult for the shunt DC motor to have a brush and a commutator. The output range can be expanded to the high speed range. FIG. 4 shows a voltage vector diagram when a negative d-axis current is passed. However, in the high speed region, the voltage drop due to the resistance is sufficiently smaller than the voltage drop due to the inductance, and therefore is omitted. However, in the region where this motor is rotating at high speed, the induced voltage of the motor becomes high, and
As shown in, the maximum voltage (A
Point), the inverter output voltage saturates (strictly speaking, since there is a voltage drop due to the resistance and inductance of the motor, the inverter output voltage saturates before the induced voltage reaches point A). In such a case, in the conventional example, as shown in FIG.
As shown in FIG. 3, the DC power from the DC power supply 1 is converted into a voltage output of a PWM waveform controlled by the inverter main circuit 2 and supplied to the armature winding of the inner magnet type motor 3. . The inverter main circuit is controlled by the inverter control unit 4. The d-axis current command I _d ^* and the q-axis current command I _q ^* are the d-axis current controller 41 and the q-axis current controller 4 respectively.
2 are input respectively. Also, of the three-phase armature windings of the motor 3, two-phase armature currents i _u ,
i _w is input to the three-phase / d-q axis converter 43, and its outputs are input to the d-axis (excitation) current controller 41 and the q-axis (torque) current controller 42, respectively, and the excitation voltage command V _d and The torque voltage command _Vq is output, and its output is input to the dq / 3-phase converter 44. With respect to the rotor position of the motor 3, an electric angle is detected as a phase signal θ _e by the position detector 5 and is input to the dq / 3-phase converter 44 to generate three-phase sine wave signals V _u , V _v , Output V _w . The sine wave signals V _u , V _v , and V _w , along with the triangular wave e _T from the triangular wave generating circuit 45, are comparators 46, 47,
A gate signal is input to 48 and a gate signal is output to the inverter main circuit 2 via the gate circuit 49. The voltage equation of the inner magnet type brushless DC motor is given by the following equation (1).

[0003]

[Equation 2] … (1)

However, V _d is the d-axis excitation voltage command, V _q is the q-axis torque voltage command, R is the winding resistance of the armature winding, and L _d
Is the d-axis inductance, L _q is the q-axis inductance, ω
Is an angular velocity, p is a differential operator, and K _E is an induced voltage constant. Here, in the case where the voltage and the current on the stationary coordinate of the armature winding of the motor 3 are converted into the d-axis, that is, the excitation component and the q-axis, that is, the torque component on the rotational coordinate for control, d-axis excitation When the current command I _d is constant, for example, when an excessive torque command is input and the q-axis torque current command I _q becomes excessive, the q-axis torque voltage command V _q is saturated, and further the following equation (2), The output voltage command V ₁ calculated by V ₁ = (V _d ² + V _q ² ) ^1/2 (2) is saturated. Further, the output voltage phase angle command θ ₁ calculated by the following equation (3) θ ₁ = tan ⁻¹ (V _d / V _q ) (3) reaches a certain saturation value and the motor output until just before saturation is reached. There is a problem that the torque drops sharply. Although an example in which the torque command becomes excessive is given, the same problem occurs when the input voltage of the inverter drops. In order to solve this problem, the d-axis current controller 41 and the q-axis current controller 42 are respectively connected via the limiter L to the d-axis current command I _d ^* and the q-axis current so that the inverter output voltage is not saturated. Command I _q ^*
Was input to limit the torque command (for example, Japanese Patent Laid-Open No. 5-130709). In a region where the output voltage of the inverter is not saturated, a method of operating the current control system, disconnecting the current control system when approaching saturation, and switching to the voltage control system has been adopted (for example,
JP-A-5-91785).

[0005]

By the way, FIG. 6 shows the PW.
Although the principle of generating the M waveform is shown, limiting the torque command so that the output voltage of the inverter is not saturated means that the peak of the voltage command e _c does not exceed the peak E _p of the triangular wave e _T. is there. However, in the prior art, although a rapid torque decrease can be prevented, the output voltage of the inverter is limited to a range in which a sine wave can be output. Therefore, for example, in an electric vehicle using a battery as an inverter power supply, the voltage of the battery is If it drops, there is a problem that the output of the inverter also drops. It is an object of the present invention to provide a drive control method for a motor that prevents the output of the inverter from decreasing when the d-axis current controller and the q-axis current controller are saturated.

[0006]

In order to solve the above problems, the present invention comprises an inverter control section for controlling the output voltage of an inverter to which a DC voltage is applied, and torque components (q Axial component) and excitation component (d
In the drive control method of the inner magnet type brushless DC motor, in which the torque current command and the excitation current command are input to the inverter control unit separately for the axis component), the torque current command and the rotation obtained from the position detector mounted on the motor It is obtained from a q-axis current controller that obtains a torque voltage command from a deviation from a torque current feedback signal obtained by coordinate conversion based on the child position information, and an exciting current command and a position detector mounted on the motor. A q-axis current controller or a d-axis current controller, which comprises a d-axis current controller that obtains an excitation voltage command from a deviation from an excitation current feedback signal obtained by coordinate conversion based on rotor position information. when approaching saturation, disconnect the q-axis current controller and the d-axis current controller from the inverter controller, the d-axis current command I _d ^*, the q-axis current command and I _q ^* The following equation of time

[Equation 3] The d-axis voltage command and the q-axis voltage command are obtained by the voltage equation of the inner magnet type brushless DC motor shown by, and the output voltage command V ₁ of the inverter is expressed by the formula: V ₁ = (V _d ² +
V _q ² ) ^1/2 and the output voltage phase angle command are expressed as θ ₁ = t
It is obtained by an ⁻¹ (V _d / V _q ) and is input to the inverter control unit to control the output voltage of the inverter.

[0007]

With the above means, when the torque command is increased or the inverter input voltage is decreased so that the effective value of the inverter output phase voltage exceeds V _dc / 2 (2) ^1/2 , the inverter output The voltage monitor detects the output voltage command V ₁ , and the two changeover switches directly input the d-axis current command I _d ^* and the q-axis current command I _q ^* to the dq / 3-phase converter. That is, the d-axis current controller 41 and the q-axis current controller 42 are disconnected, and the d-axis voltage command V is calculated from the equation (1) using the d-axis current command I _d ^* and the q-axis current command I _q ^*.
_{The d} and q-axis voltage commands V _q are obtained and are substituted into the formulas (2) and (3) to calculate the output voltage command V ₁ and the output voltage phase angle command θ ₁ . Therefore, even if the d-axis current controller and the q-axis current controller are disconnected, the output voltage command V
_Since the continuity of ₁ can be maintained and the amplitude of the output voltage command V ₁ can be made larger than the triangular wave peak, the output voltage can be expanded to approximately V _dc / 2. further,
When the effective value of the inverter output phase voltage reaches V _dc / 2, that is, when the inverter output voltage becomes a square wave, the output voltage phase angle command θ ₁ is fixed to the value immediately before it.
Maintain the output voltage at approximately V _dc / 2.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the figure, the DC power from the DC power supply 1 is converted into a voltage output of a PWM waveform controlled by the inverter main circuit 2 and supplied to the armature winding of the inner magnet type motor 3.
The d-axis current command I _d ^* and the q-axis current command I _q ^* are input to the d-axis current controller 41 and the q-axis current controller 42 of the inverter control unit 4, respectively, and at the same time through the changeover switch 6, d- It is connected to the q / 3-phase converter 44. In addition, two of the three-phase armature windings of the motor 3
The phase armature currents i _u and i _w are three-phase / dq axis converter 43.
Are input to the d-axis current controller 41 and the q-axis current controller 42, respectively, and the excitation voltage command V _d and the torque voltage command V _q are input via the changeover switch 6.
Is output, and the output is input to the dq / 3-phase converter 44. The rotor position of the motor 3 is detected by the position detector 5 as a phase signal θ _e , and d−q
The three-phase AC voltage command V is input to the three-phase converter 44.
Output _u , V _v , and V _w . Sine wave signals V _u , V _v , V
_w is input to the comparators 46, 47 and 48 together with the triangular wave e _T from the triangular wave generating circuit 45, and the gate circuit 49
A gate signal is output to the inverter main circuit 2 via the. Further, the inverter output voltage monitoring unit 7 is connected to the dq / 3-phase converter 44, and the relationship between the output voltage command V ₁ and the voltage V _dc of the DC power supply 1 expressed by the above-mentioned formula 1 is V ₁ ≦ When V _dc / 2 (2) ^1/2 , d-axis current controller 41 and q-axis current controller 42
And dq / 3-phase converter 44 are connected, and when V ₁ > V _dc / 2 (2) ^1/2 , d-axis current command I _d ^* and q-axis current command I _q ^* are d
The changeover switch 6 is switched so as to input directly to the −q / 3-phase converter 44.

Now, the effective value of the inverter output phase voltage is V _dc
/ 2 (2) ^1/2 or less, that is, in a region where the d-axis current controller 41 and the q-axis current controller 42 are not saturated,
As is conventionally done, the d-axis current controller 41 and q
From the d-axis voltage command V _d , the q-axis voltage command V _q , which are the outputs of the shaft current controller 42, and the phase signal θ _{e of the} electrical angle obtained from the position detector 5 mounted on the motor 3, the three-phase AC voltage command V
Convert to _u , V _v , V _w . Torque command increases,
When the inverter input voltage drops or the inverter output phase voltage effective value tries to exceed V _dc / 2 (2) ^1/2 , the inverter output voltage monitoring unit 7 detects the output voltage command V ₁ , By the changeover switch 6, the d-axis current command I
_{The d} ^* and the q-axis current command _Iq ^* are directly input to the dq / 3-phase converter 44. That is, the d-axis current controller 41 and the q-axis current controller 42 are disconnected, and the d-axis current commands I _d ^* and q
The d-axis voltage command V _d and the q-axis voltage command V _q are obtained from the formula (1) using the shaft current command I _q ^*, and the obtained d-axis voltage command V _d and the q-axis voltage command V _q are obtained by the formula (2) {V ₁ = (V _d ² + V _q ² ). ^1/2 } and the expression (3) {θ ₁ = tan ⁻¹ (V _d / V _q )} are substituted to calculate the output voltage command V ₁ and the output voltage phase angle command θ ₁ . In this way, even detach the d-axis current controller 41 and the q-axis current controller 42, it is possible to maintain the continuity of the output voltage command V _1, the amplitude of the output voltage command V ₁ of the said Since it can be made larger than the triangular wave peak, the output voltage can be expanded to approximately V _dc / 2. Furthermore, when the inverter output phase voltage effective value reaches V _dc / 2, that is,
When the inverter output voltage becomes a square wave, the output voltage phase angle command θ ₁ is fixed to the value immediately before it and the output voltage is maintained at approximately V _dc / 2.

[0010]

As described above, according to the present invention, when the inner magnet type brushless DC motor is driven, the torque generated when the input voltage of the inverter is lowered or when an excessive torque command is input. It is possible to prevent a sharp drop and to increase the inverter output voltage.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a conventional example.

FIG. 3 is a configuration diagram showing a two-pole inner magnet type brushless DC motor.

FIG. 4 is a voltage vector diagram of an inner magnet type brushless DC motor.

FIG. 5 is an explanatory diagram showing a relationship between a motor induced voltage and an inverter output voltage.

FIG. 6 is an explanatory diagram showing a relationship among a voltage command, a triangular wave, and an inverter output voltage.

[Explanation of symbols]

1 DC power supply, 2 inverter main circuit, 3 motor, 4
Inverter controller, 41 d-axis current controller, 42 q
Axis current controller, 43 3 phase / dq converter, 44 d-
q / 3-phase converter, 45 triangular wave generation circuit, 46, 47,
48 comparators, 49 gate circuits, 5 position detectors, 6 changeover switches, 7 voltage monitoring section

Claims (1)

[Claims] 1. An output of an inverter to which a DC voltage is applied
Equipped with an inverter control unit that controls the voltage,
Torque component (q-axis component) and excitation component (d
(Axial component) and torque current command to the inverter controller
And an internal magnet type brushless DC
In the drive control method of the motor, the torque current command and the motor
Of the rotor position obtained from the position detector mounted on the rotor.
Torque current feed obtained by coordinate conversion based on information
Q-axis current to obtain torque voltage command from deviation from back signal
Controller, exciting current command and position attached to the motor
Coordinate conversion based on rotor position information obtained from the detector
From the deviation from the excitation current feedback signal obtained by
A d-axis current controller for obtaining an excitation voltage command, and the q-axis
When the current controller or d-axis current controller approaches saturation,
The q-axis current controller and the d-axis current controller are connected to the above-mentioned inverter.
Disconnect from the control unit and set the d-axis current command to I_d ^*, Q-axis current
Command I_q ^*Then, the following mathematical expressionIn the voltage equation of the inner magnet type brushless DC motor shown by
Therefore, the d-axis voltage command and the q-axis voltage command are obtained, and
Output voltage command V₁ Is the formula, V₁ = (V_d ²+ V
_q ²)^1/2 , And the output voltage phase angle command are mathematical expressions, θ₁ = T
an^-1(V_d / V _q ), Said inverter
Input to the control unit to control the output voltage of the inverter
Drive control of inner magnet type brushless DC motor characterized by
Way.