JP2003047272A - Controller for permanent-magnet motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use one control circuit both in low-speed operation and in high- speed operation in equipment wherein an inverter connected with a permanent- magnet motor is controlled by PWM based on position signals from a position sensor. SOLUTION: In the controller for permanent-magnet motor, a PWM control circuit 1 comprises a number of revolutions detection circuit 14 which detects the number ω of revolutions of a motor based on the position signal; a position computation circuit 13 which derives the rotational angle θ of the motor based on the position signal; a phase control circuit 12a which generates a voltage command signal based on a sine-wave function which represents the voltage command signal V* using the rotational angle θ of the motor as a variable; and a PWM signal generation circuit 12b which generates a PWM signal based on the voltage command signal. The position computation circuit 13 derives a rectangular-wave rotational angle based on the position signal during low- speed operation, and derives a rotational angle based on the position signal and further interpolates the rotational angle to derive a rectangular-wave rotational angle during high-speed operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for PWM controlling an inverter connected to a permanent magnet motor based on a position signal from a position sensor such as a Hall element.

[0002]

2. Description of the Related Art Conventionally, a permanent magnet motor has been used as a motor for driving a pulse eater of a washing machine. FIG. 5 shows the structure of a general permanent magnet motor,
As shown, the permanent magnet motor has a cylindrical stator (20).
A rotor (21) made of a cylindrical permanent magnet is rotatably housed in a space formed in the central portion of the. A plurality of slots (22) are provided on the inner peripheral surface of the stator (20), and the U-phase winding (23), the V-phase winding (24) and the W-phase winding are provided in the plurality of slots. (25) is wrapped around. In a permanent magnet motor, these multi-phase windings (23) (24) (25)
The rotor (21) is rotated by energizing the rotor.

The permanent magnet motor is controlled by, for example, the control device shown in FIG. FIG. 6 shows an overall configuration of a permanent magnet motor control device. AC power from a commercial power supply (4) is once converted to DC power by a rectifier circuit (5) and then converted by an inverter (6). The AC power is converted into AC power, and the AC power is supplied to the permanent magnet motor (2) to drive the motor. The permanent magnet motor (2) is provided with position sensors (3) consisting of Hall elements at three positions with a phase difference of 120 degrees on the circumference around the rotation axis. (3) (3) Three position signals (Hu, Hv, Hw) obtained from (3) are supplied to the inverter control circuit (7), and the inverter control circuit (7) controls the inverter (6). There is.

The drive system of the permanent magnet motor is a so-called 120-degree energization system in which two phases of the U-phase winding, the V-phase winding and the W-phase winding are sequentially energized, and a sinusoidal voltage. A so-called sinusoidal drive method is known in which three phases of U-phase winding, V-phase winding, and W-phase winding are energized simultaneously by PWM control using a command signal.

The inverter control circuit (7) can switch between a 120-degree conduction mode and a sine wave drive mode, and FIG. 7 shows a concrete configuration of the inverter control circuit (7). ing. The inverter control circuit (7) is
It is equipped with a 20-degree energizing rotation speed control circuit (71) and a sine wave driving rotation speed control circuit (72). These circuits (71) and (72) include positions obtained from the three position sensors. Signal (H
A rotation speed detection circuit (79) for detecting the rotation speed of the motor based on (u, Hv, Hw) is connected. Further, the target rotation speed signal is supplied from the microcomputer to the 120-degree energization rotation speed control circuit (71) and the sine wave driving rotation speed control circuit (72), and these circuits (71) and (72) Based on the target rotation speed signal and the rotation speed detection signal supplied from the rotation speed detection circuit (79), a signal necessary for generating a switching signal described later is created.

Further, the 120-degree energizing rotation speed control circuit (71) and the sine wave driving revolution speed control circuit (72) respectively include a 120-degree energizing switching signal generating circuit (73) and a sine wave driving switching signal. The generation circuit (74) is connected in series. The 120-degree energizing switching signal generation circuit (73) has a position signal (H) obtained from the three position sensors.
u, Hv, Hw) is connected to an energization pattern generation circuit (75) that generates a predetermined energization pattern based on (u, Hv, Hw), and the switching signal generation circuit (73) includes the 120-degree energization speed control circuit (73). ) And the energization pattern signal supplied from the energization pattern generation circuit (75), the switching signal SW for the inverter is generated. In this way, switching signals for the U phase, V phase, and W phase are created.

On the other hand, the sine wave driving switching signal generating circuit (74) calculates the rotational position of the rotor of the permanent magnet motor based on the position signals (Hu, Hv, Hw) obtained from the three position sensors. A position calculation circuit (78) is connected, and the switching signal generation circuit (74) supplies the signal supplied from the sine wave drive rotation speed control circuit (72) and the position calculation circuit (78). The switching signal SW for the inverter is generated based on the position calculation signal. In this way, switching signals for the U phase, V phase, and W phase are created.

Both switching signal generation circuits (73) (74)
Is connected to the inverter via one switch (77). The switch (77) is between a first state in which the 120-degree conduction switching signal generation circuit (73) is connected to the inverter and a second state in which the sine wave driving switching signal generation circuit (74) is connected to the inverter. The switch (77) includes a switching control circuit (a switching control circuit for controlling switching of the switch (77) based on position signals (Hu, Hv, Hw) obtained from the three position sensors. 76) is connected.

In the above inverter control circuit (7),
When the motor rotates at a low speed, the switch (77) is switched to the first state in which the 120-degree energizing switching signal generating circuit (73) is connected to the inverter, and is generated by the circuit (73) as described above. The U-phase, V-phase, and W-phase switching signals SW are supplied to the inverter. As a result, the permanent magnet motor is driven by the 120-degree energization method. On the other hand, when the motor rotates at high speed, the switch (77)
Is a switching signal of the U-phase, V-phase and W-phase generated as described above by the circuit (74) when the sine wave driving SW signal generation circuit (74) is switched to the second state connected to the inverter. SW is supplied to the inverter. As a result, the permanent magnet motor is driven by the sine wave driving method. As described above, the reason why the motor is controlled by the 120-degree conduction method during low-speed rotation of the motor is that if the motor is controlled by the sine wave drive method during low-speed rotation, the position signals (Hu, Hv, Hw) has a long switching cycle, and the position signals (Hu, Hv,
This is because the sinusoidal voltage command signal generated based on (Hw) contains a large error and the control accuracy is reduced.

[0010]

However, in the above-mentioned conventional inverter control circuit (7), two different control methods, a 120-degree energization method and a sine wave driving method, are used for low-speed rotation and high-speed rotation of the motor, respectively. As shown in FIG. 7, the rotation speed control circuits (71) and (72) and the switching signal generation circuit which are different between the low speed rotation and the high speed rotation are adopted.
(73) and (74) need to be configured, and a switch (77) for switching the circuit system needs to be provided, which causes a problem that the configuration of the device becomes complicated. Further, since the circuit system is switched between the low speed rotation and the high speed rotation, there is a problem that the control cannot be switched smoothly.

Therefore, an inverter for controlling the motor by PWM control using a rectangular wave voltage command signal when the motor rotates at a low speed, and controlling the motor by PWM control using a sinusoidal voltage command signal when the motor rotates at a high speed. A device has been proposed (Japanese Patent Laid-Open No. 10-164886 [H02P 6/1
Four]). However, even in such an inverter device, since the arithmetic expression for creating the rectangular wave voltage command signal at low speed rotation and the arithmetic expression for creating the sine wave voltage command signal at high speed rotation are different, the control There is a problem that switching cannot be performed smoothly. In addition, since a rectangular wave voltage command signal is created by logical operation,
Since the phase of the voltage command signal cannot be adjusted, a phase shift occurs between the current applied to the winding and the induced voltage generated in the winding, and the magnetic flux generated by the magnet is effectively used. However, there is a problem that the torque is reduced. Therefore, an object of the present invention is to provide a motor control that has a simple device configuration, can smoothly switch control between low speed rotation and high speed rotation of the motor, and can maximize the generated torque. It is to provide a device.

[0012]

A controller for a permanent magnet motor according to the present invention comprises an inverter for supplying AC power to the permanent magnet motor, and a rectangular wave having a constant phase relationship with the rotation angle of the permanent magnet motor. And a PWM control circuit for controlling the inverter based on the position signal obtained from the position sensor. Here, the PWM control circuit includes a speed detection unit that detects a rotation speed of the permanent magnet motor based on the position signal, a first calculation unit that derives a rotation angle of the permanent magnet motor based on the position signal, and a permanent calculation unit. A voltage command signal is generated from the derived rotation angle based on a sine wave function that represents a change in the voltage command signal with the rotation angle of the magnet motor as a variable, or a table that represents the relationship between the rotation angle of the permanent magnet motor and the voltage command signal. And a signal processing means for generating a PWM signal based on the generated voltage command signal and supplying the PWM signal to the inverter. The first calculation means derives a rotation angle that changes into a rectangular wave shape based on the phase of the position signal when the rotation speed of the permanent magnet motor is low, and a rotation speed derivation means at low speed, and rotation of the permanent magnet motor. At a high speed, when the speed is high, the rotation angle is derived based on the phase of the position signal, and the derived rotation angle is interpolated based on a sine wave to derive a rotation angle that changes in a sine wave shape. And a rotation angle deriving means.

In the above permanent magnet motor control device of the present invention, the basic data for deriving the rotation angle of the motor is switched between when the rotation speed of the permanent magnet motor is low and when it is high. That is, when the speed is low, the phase of the position signal is converted into a rotation angle in a one-to-one correspondence, and a rectangular wave-shaped rotation angle whose level changes with a coarser step size than that at the time of high speed is derived. On the other hand, at high speed,
The phase of the position signal is converted into a rotation angle in a one-to-one correspondence, and the rotation angle obtained by this is interpolated based on a sine wave, so that the level can be adjusted with a finer step size than at low speed. A varying sinusoidal rotation angle is derived. The rotation angle thus derived is subjected to calculation using a common sine wave function or table by the second calculation means regardless of whether the rotation angle is low speed or high speed, and the voltage command signal is generated. Is created. Therefore, the operation of the second arithmetic processing means does not change during the switching process between the low speed and the high speed. Further, the voltage command signal generated in this manner is subjected to common signal processing by the signal processing means regardless of whether it is at low speed or at high speed, and a PWM signal is generated to the inverter. Supplied.
Therefore, there is no change in the operation of the signal processing means during the switching process between low speed and high speed. As a result, control can be smoothly switched between low speed and high speed.

At a low speed, the cycle of switching the position signal is long, and the rotation angle derived based on the signal is
Since the level changes with a coarse step size, if a rotation angle that changes sinusoidally is derived by interpolation at low speed, a large error will be involved in the change of the rotation angle. Therefore, when the voltage command signal is generated based on the rotation angle with such a large error and the PWM control is performed, the control accuracy is rather low. In contrast,
In the present invention, the voltage command signal is generated from the rotation angle that changes in the rectangular wave shape by the second calculation means without interpolating the rotation angle of the rectangular wave shape that is derived at the time of low speed. There is no decrease in control accuracy due to. On the other hand, at a high speed, the switching cycle of the position signal is short, and the rotation angle derived based on the signal changes in level with a fine step size. Therefore, when a rotation angle that changes sinusoidally by interpolation is derived, A high degree of accuracy is obtained for the rotation angle, and thus a high degree of control accuracy is achieved.

Specifically, the second computing means has the following equations, where V * is the voltage command signal, Va is the voltage amplitude command, θ is the rotation angle of the permanent magnet motor, and ψ is a predetermined advance angle of zero or more. Two sinusoidal functions are specified.

[Expression 2] V * = Va · cos (θ + ψ)

According to this specific configuration, the phase (voltage phase) of the voltage command signal is advanced by giving a predetermined advance angle ψ, and the current supplied to the winding and the induction generated in the winding. It is possible to make the phase difference with the voltage zero, which allows the torque of the motor to be maximized.

Here, the voltage amplitude command Va is created based on the deviation between the detected rotation speed and the target rotation speed. As a result, the voltage amplitude command Va for causing the rotation angle of the permanent magnet motor to follow the target rotation speed is created, and the rotation angle of the permanent magnet motor is controlled.

[0018]

According to the control device for a permanent magnet motor of the present invention, a common control system is adopted at low speed and high speed, so that different control circuits are constructed for low speed and high speed as in the prior art. This makes it possible to simplify the apparatus and to smoothly switch the control. Further, since the relationship between the rotation angle of the permanent magnet motor and the voltage command signal is defined by a sine wave function or a table, it is possible to advance the phase of the voltage command signal by an arbitrary phase difference in the relationship.
This makes it possible to maximize the generated torque.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows the overall configuration of a controller for a permanent magnet motor according to the present invention. AC power obtained from a commercial power source (4) is a rectifier circuit.
After being converted into DC power by (5), it is converted into AC power by the inverter (6), and the AC power is supplied to the permanent magnet motor (2) to drive the motor. The permanent magnet motor (2) has a position sensor (3) consisting of a Hall element on the circumference around the rotation axis.
Three position signals are provided at three places with a phase difference of 0 degree, and these three position sensors (3) (3) (3) obtain
(Hu, Hv, Hw) is supplied to the PWM control circuit (1),
The PWM control circuit (1) controls the inverter (6).

FIG. 3 (a) shows the waveforms of the voltages (Eu, Ev, Ew) induced in the three-phase windings of the permanent magnet motor. Each voltage waveform is a sine wave with 360 degrees as one cycle. , And the three voltage waveforms have a phase difference of 120 degrees from each other. Further, FIG. 6B shows the waveforms of three position signals (Hu, Hv, Hw) obtained from the three position sensors. Each position signal is a rectangular wave that switches to high and low with 360 degrees as one cycle, and the three position signals have a phase difference of 120 degrees with each other.

FIG. 2 shows a concrete configuration of the PWM control circuit (1). The three position signals (Hu, Hv, Hw) obtained from the position sensors (3), (3) and (3) are supplied to the position calculation circuit (13) and the rotation speed detection circuit (14). It The rotation speed detection circuit (14) uses three position signals
The rotation speed of the motor is detected based on (Hu, Hv, Hw), and the result is the phase control circuit (12a), the position calculation circuit (13), and the mode switching control circuit (which configure the PWM control circuit (1). 15). The mode switching control circuit (15) determines whether the rotation speed ω supplied from the rotation speed detection circuit (14) is a low speed mode below a predetermined threshold value or whether the rotation speed ω is a high speed mode exceeding a predetermined threshold value. Judgment is made and the judgment result is supplied to the position calculation circuit (13).

In the low speed mode, the position calculation circuit (13) calculates the rotation angle θ of the motor from the phases of the three position signals (Hu, Hv, Hw). For example, Table 1 below shows three position signals (Hu, H) obtained with the rotation of the motor.
v, Hw) represents the relationship between the combination of high (“1”) and low (“0”) and the rotation angle θ. Based on this table, three position signals (Hu, Hv, Hw) The rotation angle θ of the motor corresponding to the phase can be derived. As a result, a rotation angle θ that changes in a rectangular wave shape with a step width of 60 ° is obtained.

[0023]

[Table 1]

In the high speed mode, as in the low speed mode, the rotation angle of the motor is derived from the phases of the three position signals (Hu, Hv, Hw) and the rotation angle θ is interpolated based on the sine wave. Thus, the rotation angle θ that changes sinusoidally with a step width (for example, 1 °) sufficiently smaller than 60 ° is calculated. The rotation speed detection circuit (14) shown in FIG.
The rotation angle ω obtained from the above is used for the interpolation processing. The rotation angle θ calculated as described above in the low speed mode or the high speed mode is supplied to the phase control circuit (12a).

Rotational speed ω obtained from the rotational speed detection circuit (14)
Is supplied to the rotation speed control circuit (11),
At (11), the voltage amplitude command Va is created based on the deviation of the motor rotation speed from the target value ω *. Voltage amplitude command Va
Is supplied to the phase control circuit (12a). In the phase control circuit (12a), the voltage amplitude command Va obtained from the rotation speed control circuit (11) and the rotation angle θ supplied from the position calculation circuit (13).
Based on the following, the voltage command signal Vu * for the U phase of the permanent magnet motor is calculated from Equation 3 below.

[0026]

## EQU3 ## Vu * = Va.cos (.theta. +. Psi.) Where .psi. Is the phase advance angle and is set to an appropriate value of zero or more according to the rotational speed .omega. Obtained from the rotational speed detection circuit (14). It

As a result, in the low speed mode, as shown in FIG. 3C, the voltage command signal Vu * which changes in a rectangular wave shape with a coarse step width of 60 ° is obtained. On the other hand, in the high speed mode, as shown in FIG. 4C, the voltage command signal Vu * that changes sinusoidally with a fine step size is obtained. And
By giving a phase difference of 120 ° to the U-phase voltage command signal Vu *, a V-phase voltage command signal Vu * is created, and further 120 ° to the V-phase voltage command signal Vv *. By giving the phase difference, the W-phase voltage command signal Vw * is created.

The three-phase voltage command signals (Vu *, Vv *, Vw *) calculated in this way are used in the PWM signal generating circuit which constitutes the sine wave / rectangular wave drive control circuit (12) shown in FIG. (1
2b), PWM for U phase, V phase, W phase
A signal is generated. That is, in the low speed mode, as shown in FIG.
As shown in (c), the U-phase voltage command signal Vu * is compared with a predetermined carrier wave (triangular wave), and based on the comparison result, the U-phase drive signal (PWM signal) shown in FIG. Is created. Similarly, the V-phase voltage command signal Vv * is compared with a predetermined carrier to create a V-phase drive signal, and the W-phase voltage command signal Vw * is compared with the predetermined carrier,
A W-phase drive signal is created. Similarly in the high-speed mode, as shown in FIG. 4C, the U-phase voltage command signal Vu *
Is compared with a predetermined carrier wave (triangular wave), and based on the comparison result, a U-phase drive signal (PWM signal) shown in FIG. Similarly, the V-phase voltage command signal Vv * is compared with a predetermined carrier to create a V-phase drive signal, and the W-phase voltage command signal Vw * is compared with the predetermined carrier to obtain W. A phase drive signal is created.

The U-phase, V-phase, and W-phase PWM signals thus created are supplied to the inverter (6) as shown in FIG. 1, and the inverter (6) is PWM-controlled. As a result, the permanent magnet motor (2) is driven based on the rectangular wave voltage command signal generated from the outputs of the three position sensors in the low speed mode, while it is driven from the outputs of the three position sensors in the high speed mode. It will be driven based on the created sine wave voltage command signal.

In the controller for the permanent magnet motor described above, the control in the low speed mode, that is, the three position signals (Hu,
Based on the phase difference of (Hv, Hw), coarse step width (60 °)
A control for deriving a rectangular wave-shaped rotation angle ω whose level changes at, and creating a voltage command signal based on the rotation angle ω,
High-speed mode control, that is, three position signals (Hu, H
v, Hw), the rotation angle is derived based on the phase difference, and these rotation angles are interpolated to derive a sinusoidal rotation angle whose level changes with a fine step size (for example, 1 °) and The control to generate the voltage command signal based on the angle ω can be switched according to the rotation speed of the permanent magnet motor (2). In any mode, the phase of the sine wave / rectangular wave drive control circuit (12) is changed. Since the control circuit (12a) performs the operation using the common sine wave function shown in the equation 3 to create the voltage command signal, the operation associated with the switching between the low speed mode and the high speed mode is performed. There is no change.

Further, P of the sine wave / rectangular wave drive control circuit (12)
In any mode, the WM signal generation circuit (12b)
Since the PWM signal is generated from the voltage command signal and supplied to the inverter, the operation does not change due to the switching between the low speed mode and the high speed mode.

Therefore, like the conventional inverter control circuit (7) shown in FIG. 7, two switching signal generation circuits (73) (7) are used.
4) and two rotation speed control circuits (71) and (72) are provided to switch the circuit system between low speed and high speed. Switching is done smoothly.

Further, in the phase control circuit (12a) of the sine wave / rectangular wave drive control circuit (12) shown in FIG. 2, the phase advance angle ψ defined in the sine wave function of the equation 3 is applied to the rotation speed ω. By setting the appropriate value according to
It is possible to set the phase difference between the current applied to the winding of (2) and the induced voltage generated in the winding to zero, whereby the torque of the motor can be maximized.

The configuration of each part of the present invention is not limited to the above embodiment, and various modifications can be made within the technical scope described in the claims. For example, in the above embodiment, the permanent magnet motor (2) has three position sensors (3) and (3).
Although (3) is provided, an arbitrary number of position sensors can be provided regardless of this. Permanent magnet motor
When the two position sensors are provided in (2), the rotation angle θ that changes in a rectangular wave shape with a step width of 90 ° can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of a permanent magnet motor control device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a PWM control circuit that constitutes the control device.

FIG. 3 is a waveform diagram of various signals created by the PWM control circuit at low speed.

FIG. 4 is a waveform diagram of various signals created by the PWM control circuit at high speed.

FIG. 5 is a diagram showing a structure of a permanent magnet motor.

FIG. 6 is a block diagram showing the overall configuration of a conventional permanent magnet motor control device.

FIG. 7 is a block diagram showing a conventional inverter control circuit.

[Explanation of symbols]

(1) PWM control circuit (2) Permanent magnet motor (3) Position sensor (4) Commercial power supply (5) Rectifier circuit (6) Inverter (11) Speed control circuit (12) Sine / square wave drive control circuit (12a) Phase control circuit (12b) PWM signal generation circuit (13) Position calculation circuit (14) Rotation speed detection circuit (15) Mode switching control circuit

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Claims (5)

[Claims] 1. An inverter for supplying alternating-current power to a permanent magnet motor, a position sensor for outputting a position signal composed of a rectangular wave having a constant phase relationship with a rotation angle of the permanent magnet motor, and a position sensor obtained from the position sensor. And a PWM control circuit for controlling the inverter based on the position signal, the PWM control circuit detects the rotational speed of the permanent magnet motor based on the position signal. A first computing means for deriving a rotation angle of the permanent magnet motor based on the position signal; a sine wave function representing a change in the voltage command signal with the rotation angle of the permanent magnet motor as a variable, or the rotation angle of the permanent magnet motor. And a voltage command signal based on a table representing the relationship between the voltage command signal and the second command means for generating a voltage command signal from the derived rotation angle. And a signal processing means for generating a PWM signal on the basis of the generated voltage command signal and supplying the PWM signal to an inverter, wherein the first computing means is: when the rotation speed of the permanent magnet motor is low. , A low-speed rotation angle deriving means for deriving a rotation angle that changes in a rectangular wave shape based on the phase of the position signal, and a rotation angle based on the phase of the position signal when the rotation speed of the permanent magnet motor is high. The permanent magnet motor is characterized in that it further comprises: a high-speed rotation angle deriving means for deriving a rotation angle that changes in a sine wave shape by performing interpolation based on a sine wave on the derived rotation angle. Control device. 2. The position sensor is provided at a plurality of locations on a circumference centered on the rotation axis of the permanent magnet motor, and the first calculation means calculates the phase difference between a plurality of position signals obtained from the plurality of position sensors. The control device according to claim 1, wherein the rotation angle is calculated based on the rotation angle. 3. The second computing means generates a plurality of phase voltage command signals for the windings of a plurality of phases of the permanent magnet motor, and the signal processing means generates a plurality of phases for the plurality of windings of the permanent magnet motor. Claim 1 or Claim 2 which produces the PWM signal of
The control device according to 1. 4. A voltage command signal V is supplied to the second calculation means.
4. The sine wave function of Formula 1 is defined, where * is the voltage amplitude command, Va is the rotation angle of the permanent magnet motor, and ψ is a predetermined phase advance angle of zero or more. The control device according to 1. [Equation 1] V * = Va · cos (θ + ψ) 5. The control device according to claim 4, further comprising speed control means for generating a voltage amplitude command Va based on a deviation between the detected rotation speed and a target rotation speed.