JP2003209999A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a motor controller comprising a PAM circuit for boosting a power supply voltage and a PWM circuit performing PWM control, and being arranged to perform power conduction rate control by PWM control at the time of low rotation and to attain the large number of revolutions by boosting a voltage by PAM control at the time of high rotation in which a supplied voltage is controlled independently for each phase and efficiency is enhanced at the time of high rotation. <P>SOLUTION: An AC motor 4 is driven by a PAM circuit 2 for boosting the power supply voltage and a PWM circuit 3 for controlling an output power conduction rate. The PWM circuit comprises at least four switching elements for each phase of the AC motor wherein the output of each phase and the winding of each phase of the AC motor are connected independently. Furthermore, a means for detecting the voltage value of each phase of the AC motor is provided and, when the maximum value among detected voltage values of respective phases is lower than the power supply voltage but higher than a first predetermined reference voltage, the power supply voltage is applied while being boosted by the PAM circuit only for that phase. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device having a converter circuit and an inverter circuit for driving an AC motor.

[0002]

2. Description of the Related Art A conventional motor control device for driving an AC motor is disclosed in, for example, Japanese Patent Laid-Open No. 2000-7888. In this conventional example, a PAM circuit that boosts the power supply voltage and a PWM circuit that performs PWM control are provided,
At low speed, PWM (Pulse Width Modulation) control is used to control the electric current flow rate, and at high speed when PWM is at a predetermined flow rate (eg 100%), PAM (Pulse Amplitude Modulation) control is performed. The voltage is boosted to obtain a high rotation speed. In the motor control device as described above, each motor phase (U
Since the resistance value and the inductance are different depending on the winding length of the phase, the V phase, and the W phase, variations in the winding method, and the like, the voltage applied to each phase (hereinafter referred to as the phase voltage) is different. Therefore, if it is necessary to further increase the rotation speed of the motor when the phase voltage reaches the maximum value (Vbat) in any one of the three phases (for example, V phase), the above PAM circuit is used. The PWM circuit is operated to supply a voltage higher than the power supply voltage, thereby increasing the rotation speed.

[0003]

However, any one phase,
Alternatively, when the phase voltage reaches the maximum value (Vbat) in only two phases, the phase voltages of the phases other than that phase (for example, U phase and W phase) can still be increased to the power supply voltage. However, in the conventional example as described above, when the phase voltage reaches the maximum value in any one of the phases, it is necessary to boost the power supply voltage by the PAM circuit, so that there is a problem that the efficiency is deteriorated at a high rotation speed. It was

The present invention has been made to solve the problems of the prior art as described above, and a motor capable of independently controlling the applied voltage for each phase and improving the efficiency at high rotation speed. An object is to provide a control device.

[0005]

In order to achieve the above object, the present invention is constructed as described in the claims. That is, in claim 1, the AC motor is driven by the converter circuit for boosting the power supply voltage and the inverter circuit for controlling the duty ratio of the output power, and the inverter circuit is at least for each phase of the AC motor. Four switching elements are provided, and the output of each phase and the winding of each phase of the AC motor are configured to be independently connected for each phase. A second aspect of the present invention shows the configuration of the inverter circuit and the connection with each phase of the AC motor.

According to a third aspect of the present invention, the phase voltage detecting means for detecting the voltage value of each phase of the AC motor is provided, and the maximum value of the detected voltage values of each phase is lower than the power supply voltage. When the voltage becomes equal to or higher than the reference voltage of, the power supply voltage is boosted by the converter only for that phase and given.

According to a fourth aspect of the present invention, a power supply voltage detecting means for detecting the voltage value of the power supply is provided, and the first reference voltage is set based on the detected voltage value of the power supply. There is.

Further, in claim 5, the maximum value among the voltage values of the respective phases detected by the phase voltage detecting means is
When the voltage becomes equal to or higher than the second reference voltage which is higher than the first reference voltage, the field weakening control is performed.

Further, in the present invention, the second reference voltage is set to the maximum voltage value that can be output by the converter circuit.

[0010]

According to the first and second aspects of the present invention, since an independent circuit is formed for each phase and the voltage applied to each phase is independently applied, the voltage is applied to each phase. The voltage can be controlled independently, and the motor output can be controlled to increase even at high rotation speed.

In the third aspect, since only the phase voltage of the required phase can be boosted and applied individually, wasteful boosting can be eliminated and the efficiency as a whole at high speed can be improved.

According to the present invention, the first reference voltage for determining whether or not to boost the voltage is set according to the fluctuation of the power supply voltage. Corresponding control can be performed.

According to a fifth aspect of the present invention, the field weakening control is performed when the phase voltage becomes equal to or higher than the second reference voltage, so that the motor output is increased even at high rotation speed, and
The efficiency can be improved.

According to the sixth aspect of the present invention, the second reference voltage for determining whether or not the field weakening control is performed is set to the maximum output voltage of the converter circuit. If the magnetic field weakening control is performed when it becomes impossible to cope, the output of the motor can be efficiently increased.

[0015]

1 is a block diagram showing an embodiment of a motor control circuit of the present invention. The basic configuration of the circuit shown in FIG. 1 is a PAM converter circuit and a PWM.
However, the configuration of the inverter circuit by PWM and the method of connecting the windings of each phase of the motor are different from the conventional ones. In FIG.
Reference numeral 1 is a DC power source for driving a motor, 2 is a PAM converter circuit (hereinafter referred to as PAM circuit), 3 is a PWM inverter circuit (hereinafter referred to as PWM circuit), and 4 is a three-phase motor.

The PAM circuit 2 includes a coil L and a capacitor C.
Two switching elements connected in between (for example, power transistors with diodes connected in parallel)
By turning on and off, the voltage of the DC power supply 1 can be boosted and output to both ends of the capacitor C. The boost rate can be controlled by controlling the on / off timing. Further, if the two switching elements are held off, the output voltage across the capacitor C becomes substantially equal to the voltage of the DC power supply 1.

The PWM circuit 3 is provided with two series circuits in each of which two parallel circuits of a switching element and a diode are connected in series between the positive and negative terminals of the power source for each phase, and the middle point of each series circuit ( Connection point of two switching elements)
To three-phase motor 4 are connected to both ends of each phase winding.
In other words, the windings for each phase of U, V, W are independently P for each phase.
It is connected to the WM circuit 3. A positive-phase drive signal is applied to one gate terminal of the two switching elements in series, an inverted signal thereof is applied to the other gate terminal, and the two circuits for each phase are opposite to each other. The phase signal is given. For example, in the U-phase, two circuits, a series circuit with a switching element and a series circuit with a switching element, are provided, and are connected to both ends of the U-phase winding from the midpoint of each series circuit. Then, a drive signal is supplied such that when is on and is off, is off and is on, and when is off and is on, is on and is off. As a result, in the U-phase winding of the three-phase motor 4, from the left end to the right end of the figure (, is on, is off) or from the right end to the left end (, is on,
Is off), and current will flow. Therefore, the drive current of the motor can be controlled by controlling the pulse width (duty ratio) of the drive signal (PWM signal). Further, as described above, since the windings of each phase are connected independently of each other, the applied voltage can be controlled independently for each phase.

In the PWM circuit 3 shown in FIG. 1, one series circuit is composed of two switching elements, and four switching elements are provided for each phase. This configuration shows a configuration in which the number of switching elements is the minimum, and several switching elements may be connected in series, parallel connection, or serial / parallel connection as each switching element.

As described above, in the circuit of FIG.
It is also possible to control the M circuit 2 to apply a voltage boosted to the voltage of the DC power supply 1 or more, and to control the PWM circuit 3 to control the drive current supplied to the motor 4.
For example, when the duty ratio of the PWM circuit 3 does not reach 100%, the motor 4 is controlled only by the PWM circuit 3, but when the duty ratio of the PWM circuit 3 reaches 100%, the drive current is further increased. I can't let you do it. In such a high rotation range, the PAM circuit 2 is controlled so that the output voltage thereof is boosted to a DC power supply voltage or higher and is given, thereby enabling driving at a high rotation speed. At this time, since the windings of each phase are connected independently, the voltage applied to each phase can be controlled independently. For example, the boosted voltage can be applied only to the phase in which the maximum value of the phase voltage is equal to or higher than the power supply voltage, and the power supply voltage can be directly supplied to the phase in which the maximum value does not reach the power supply voltage (details will be described later).

Further, the counter electromotive force increases as the rotation speed increases, and when it exceeds the power supply voltage, the drive becomes impossible. Therefore, it is configured to perform so-called field weakening control in which the field current is weakened in the high rotation range so that the counter electromotive force does not exceed the power supply voltage. In the above configuration, the efficiency is controlled to maximize the efficiency in the steady state (low / medium speed rotation range), and the rotation speed is maximized in the high rotation range to achieve high efficiency operation in a wide range. Can be controlled so that

The PAM circuit 2 and the PWM circuit 3 are controlled as follows. Rotation angle detector (encoder) 5
Detects the rotation angle signal θ (rotation angle of the reference position) of the rotor of the motor 4. The position detector 6 calculates the rotation position (rotation angle θ ′) from the rotation angle signal θ. The speed detection unit 7 calculates the rotation angular speed ω (corresponding to the rotation speed rpm) from the rotation angle signal θ. The three-phase / two-phase conversion unit 8 inputs currents Iu and Iw of two phases (for example, u and w) of the three-phase currents of u, v, and w output from the PWM circuit 3, and outputs the three-phase current. Two-phase current I
It is converted into d and Iq and output. Since the total value of the three-phase currents is 0, if the two-phase currents are detected as described above, the three-phase currents can be calculated, and then Id and Iq are calculated.

The main control unit 9 has a torque command value T ^* given from the outside (for example, a torque controller) and a speed detection unit 7.
Rotation angular velocity ω given from the above, power supply voltage Vbat (voltage across DC power supply 1), output voltage Vdc of PAM circuit 2
(The voltage across the output of the PAM circuit 2) and the phase voltages Vu, Vv, and Vw of each phase are input, and the voltage value Vdc 'that is the control target of the PAM circuit 2 is output. The power supply voltage Vba
Power supply voltage detection means for detecting t and phase voltages Vu, V of each phase
Although not shown, the phase voltage detecting means for detecting v and Vw can be easily detected by a normal voltage detecting method. However, since the phase voltage is a PWM waveform, this voltage measurement is performed using a soft filter or a hard filter in order to capture only the primary component.

The voltage controller 10 drives the drive signal Vdc ^* for realizing the voltage value Vdc 'given by the main controller 9 ^.
To control the switching element of the PAM circuit 2 via the PAM signal generation circuit 15. As a result, the output voltage Vdc of the PAM circuit 2 is controlled so as to have the above voltage value Vdc '.

In addition, the current control unit 11 determines the torque command value T
^* , The rotational angular velocity ω given from the velocity detector 7, and P
A current value Id for realizing the torque instructed by the torque command value T ^* according to the output voltage Vdc of the AM circuit 2.
1 and Iq1 are calculated and output. The current control unit 11 has, for example, a current control map as shown in FIG. 4 described later. The current control map is a map corresponding to the rotational speed (corresponding to the rotational angular velocity ω) and the torque, and the torque command value T ^* and the rotational angular velocity ω are input, and the operating state at that time is in the maximum torque control region. It is in the field weakening control region, and the corresponding current value Id is determined.
1 and Iq1 are output.

The calculation unit 12 outputs from the current control unit 11.
Current values Id1 and Iq1 and the output of the 3-phase / 2-phase conversion unit 8
By obtaining the difference between Id and Iq, the current control target
Value Id^*, Iq^*To generate. The current-voltage conversion unit 13 has
Control target value Id of the above current^*, Iq^*The voltage value V
d ^*, Vq^*Convert to. The 2-phase / 3-phase converter 14 is
Voltage value Vd^*, Vq^*And rotation angle from the position detector 6
and the target value Vu of the three-phase voltage^*, V
v^*, Vw^*PWM signal generation circuit 1
Control the switching elements of the PWM circuit 3 via 6
It This controls the output current of the PWM circuit 3.

The main controller 9 and the current controller 11 will be described in detail below. The main controller 9 controls the torque command value T
^* , Three-phase voltages Vu, Vv, Vw of U-phase, V-phase, and W-phase output from the PWM circuit 3, the power supply voltage Vbat, and P
Based on the output voltage Vdc of the AM circuit 2 and the rotational angular velocity ω from the position / velocity detection unit 15, a voltage value Vdc ′ which is a control target value of the PAM circuit 2 is calculated and output to the voltage control unit 10, and , The torque command value T ^* to the current control unit 11,
The output voltage Vdc of the PAM circuit 2 is sent. Current control unit 11
Input the torque command value T ^* , the voltage Vdc, and the rotational angular velocity ω, determine whether the input Vdc is less than or equal to the maximum value Vdcmax of the voltage that can be boosted and output by the PAM circuit 2, and Vdc is Vdcmax. If it is less than the above, the torque command value T ^* and the map that stores the smallest d-axis and q-axis current values of the currents that satisfy the torque command value T ^* (see FIG. 4) are stored.
(Corresponding to the maximum torque control region of 1) is selected (maximum efficiency control). When Vdc is Vdcmax or higher, Vdc is Vdcmax or lower, and
A current value is selected from a map (corresponding to the field-weakening control region in FIG. 4) that stores d-axis and q-axis current values that generate a field-weakening current that satisfies the torque command value T ^* .
The selected d-axis and q-axis current values Id1 and Iq1 are output.

FIG. 2 is a flow chart showing the contents of arithmetic processing in the main controller 9. In FIG. 2, first, in step S1, three-phase voltage (U-phase voltage Vu, V-phase voltage Vu
v, W-phase voltage Vw) is read, and in step S2, the power supply voltage Vbat and the output voltage Vdc of the PAM circuit 2 are read. At this time, since Vu, Vv, and Vw are PWM waveforms, 1
To capture only the next component, measure the voltage using a soft filter or a hard filter.

Next, in step S3, the maximum value Vmax of the three-phase voltage is selected. Next, in step S4, the maximum value Vmax is compared with the first reference voltage (Vbat-α). However, α is a margin. In the comparison result, when Vmax ≦ (Vbat−α), the maximum value of the phase voltage is lower than the first reference voltage (value lower than the power supply voltage Vbat by the margin α) and can be sufficiently driven by the power supply voltage. Since it is in the state, the process goes to step S7 to turn off the boosting control of the PAM circuit 2. In this state, the boosting degree is 1, that is, Vdc = Vbat. This state is shown in FIG.

On the other hand, if NO in step S4, that is, if Vmax> (Vbat-α), the process proceeds to step S5 and is compared with the comparison voltage (Vbat-β). However,
β is the lowest limit (voltage drop due to the resistance of the switching element) in the PAM circuit 2, and β <α. As a result, (Vbat-β)>Vmax> (Vbat-α)
, The maximum value Vmax of the phase voltage is the power supply voltage V
Although it is lower than bat, since the margin is small, the process proceeds to step S8 and the drive signal Vdc ^{* is set} to Vdc ^*.
= Vbat + ΔVdc (where ΔVdc is a predetermined value smaller than β), the output voltage of the PAM circuit 2 is Vbat.
Boosting control is performed so that + ΔVdc is achieved. This state is shown in FIG. As described above, since the first reference voltage is set corresponding to the power supply voltage Vbat, even if the power supply voltage changes, the control corresponding to it can be performed.

If NO in step S5, that is, if Vmax> (Vbat-β), Vmax and (V
dc-α). As a result, Vmax> (Vd
c-α), that is, the maximum value Vmax of the phase voltage is P
If the output voltage Vdc of the AM circuit 2 is higher than the value obtained by subtracting the margin α from the output voltage Vdc, the process proceeds to step S9 to drive the drive signal Vd.
With c ^{* set} to Vdc ^* = Vmax + β, boosting control is performed so that the output voltage of the PAM circuit 2 becomes Vmax + β. This state is shown in FIG.

By controlling as described above, the PAM
Vdc is controlled so that the output voltage Vdc of the circuit 2 is maintained within the range of the margin α from the maximum value Vmax of the phase voltage, and appropriate boosting control can be performed according to the maximum value Vmax of the phase voltage. Further, in the above control, the PAM circuit 2 performs the boosting operation only when the maximum value Vmax of the phase voltage becomes higher than the first reference voltage (Vbat−α), so that the maximum value Vmax of the phase voltage is Only the phase voltage that is higher than the first reference voltage can be individually boosted (see FIG. 6 described later) and given. Therefore, it is possible to eliminate unnecessary boosting and improve the efficiency as a whole at the time of high rotation.

Next, FIG. 3 is a flow chart showing the contents of arithmetic processing in the current controller 11. In FIG. 3, in step S11, the torque command value T ^* , the output voltage Vdc of the PAM circuit 2 and the rotational angular velocity ω are read. In step S12, the current output voltage Vdc is compared with the maximum output voltage Vdcmax (second reference voltage). As a result, when Vdc = Vdcmax, that is, when the current output voltage has reached the maximum value, the voltage cannot be further boosted, so the routine proceeds to step S15, and the field weakening control map is selected.

On the other hand, if NO in step S12, that is, if Vdc <Vdcmax, the process proceeds to step S13, and the maximum torque control map (maximum efficiency control) is selected. Next, in step S14, the current values Id1 and Iq1 for the maximum torque control (maximum efficiency control) or the field weakening control are obtained using the selected map, and the calculated control target value Id for the current is calculated by the calculation unit 12 using the current values Id1 and Iq1. ^* , Iq ^* are generated.

FIG. 6 is a diagram showing the relationship between the phase voltage during operation in the circuit of FIG. 1 and the output voltage of the PAM circuit 2.
In FIG. 6, the thick solid line indicates the output voltage of the PAM circuit 2, and the straight line portion corresponds to the power supply voltage (battery voltage).
In FIG. 6A, the maximum value of the phase voltage of the U phase and the W phase is lower than the power supply voltage and there is a margin, and the maximum value of the phase voltage of the V phase is higher than the power supply voltage and the boosting operation is performed. Indicates that In FIG. 6B, the maximum value of the phase voltage of the W phase is lower than the power supply voltage and there is a margin, and the maximum value of the phase voltage of the U phase and the V phase is higher than the power supply voltage and the boosting operation is performed. Indicates that As described above, in the present invention, only the phase voltage of the phase in which the phase voltage exceeds the power supply voltage can be boosted, so that the output of the motor can be efficiently increased.

FIG. 7 is a diagram showing a comparison between the connection of each phase winding of the present invention shown in FIG. 1 and the conventional Y connection.
As is apparent from FIG. 7, in the conventional Y connection shown in (a), the output voltage (or power supply voltage) Vd of the PAM circuit 2 is Vd.
The voltage applied to the winding of each phase by c is (1 / √3)
It becomes Vdc. On the other hand, in the present invention shown in (b), the output voltage Vdc of the PAM circuit 2 is directly applied to the winding of each phase. Therefore, it is possible to drive the phase voltage of each phase to a value that is √3 times higher than the conventional value.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing the contents of arithmetic processing in a main control unit 9.

FIG. 3 is a flowchart showing the contents of calculation processing in the current control unit 11.

FIG. 4 is an example of a current control map.

FIG. 5 shows the maximum value Vmax of the phase voltage and the reference voltage and Vd.
The figure which shows the relationship with c.

6 is a diagram showing the relationship between the phase voltage during operation and the output voltage of the PAM circuit 2 in the circuit of FIG.

7 is a diagram showing a comparison between the connection of each phase winding of the present invention shown in FIG. 1 and a conventional Y connection.

[Explanation of symbols]

1 ... DC power source for driving a motor 2 ... PAM converter circuit (PAM circuit) 3 ... PWM inverter circuit (PWM circuit) 4 ... Three-phase motor 5 ... Rotation angle detector 6 ... Position detector 7 ... Speed detector 8 ... 3 Phase / 2 phase converter 9 ... Main controller 10 ... Voltage controller 11 ... Current controller 12 ... Calculator 13 ... Current / voltage converter 14 ... 2 phase / 3 phase converter

Continued front page    F term (reference) 5H007 BB06 CA01 CB02 CB05 CC12                       CC23 DB07 DC02 DC05 EA02                 5H560 AA08 BB04 DA07 DB07 DB20                       DC12 DC13 EB01 UA02 XA04                       XA12 XA13 XA17                 5H576 BB02 CC04 DD02 DD05 EE01                       EE02 EE11 FF08 GG02 GG04                       HA02 HB02 JJ03 LL07 LL22                       LL24 LL41

Claims (6)

[Claims] 1. A converter circuit connected to a power supply and capable of boosting and outputting a power supply voltage, an inverter circuit connected to an output of the converter circuit and controlling a conduction ratio of output power, and connected to the inverter circuit. And controlling the voltage boost rate by the converter circuit and the conduction rate by the inverter circuit based on an AC motor driven by electric power supplied from the inverter circuit and a torque command value given from the outside. A control unit that controls the generated torque of the motor to correspond to the torque command value, and the inverter circuit includes at least four switching elements for each phase of the AC motor, and outputs of each phase. And a winding for each phase of the AC motor are connected independently for each phase. 2. The inverter circuit includes a series circuit in which two switching elements are connected in series, which is connected between output terminals of the converter circuit, and two series circuits are provided for each phase. Each of the two circuits is provided with four switching elements, and is connected to both ends of each phase winding of the AC motor from the midpoint of each of the two circuits, and one gate terminal of the two series switching elements is driven in a positive phase. A signal is applied, the inverted signal is applied to the other gate terminal, and signals of opposite phases are applied to the two circuits for each phase, so that power is supplied independently for each phase. The motor control device according to claim 1, which is configured to: 3. A phase voltage detecting means for detecting a voltage value of each phase of the AC motor, wherein the control means has a maximum value among voltage values of each phase detected by the phase voltage detecting means. When the voltage becomes equal to or higher than the first reference voltage lower than the power supply voltage, the converter circuit boosts the voltage from the power supply and gives only the phase whose voltage value becomes equal to or higher than the first reference voltage. The motor control device according to claim 1 or 2, which is controlled. 4. A power supply voltage detecting means for detecting a voltage value of the power supply, wherein the control means sets the first reference voltage based on the voltage value of the power supply detected by the power supply voltage detecting means. The motor control device according to claim 3, wherein: 5. The control means, when the maximum value of the voltage values of the respective phases detected by the phase voltage detection means is equal to or larger than a second reference voltage larger than the first reference voltage. The field weakening control is performed on the first and second sides.
Alternatively, the motor control device according to claim 4. 6. The motor control device according to claim 5, wherein the second reference voltage is a maximum voltage value that can be output by the converter circuit.