JP2001086784A - Motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor control method, which can avoid decline in the output DC voltage of an active filter due to load increase. SOLUTION: An AC power supply 1 voltage is converted into a DC voltage by a rectifying unit 2, and the DC voltage is transformed into a prescribed voltage by an active filter unit 3 and supplied to an inverter unit 5 which controls the inverter of a motor 6. A control circuit 20 turns on/off the switching device 3b of an active filter unit 3 for making an input AC current waveform of approximately sinusoidal in form, while controlling the inverter unit 5 to control the rotation of the motor 6. At this time, if the switching device 3b is driven with a certain chopping duty ratio to make the output DC voltage of the active filter unit 3 constant, a primary current which is an input AC current is detected by a current detection sensor 10. However, if the primary current is increased by the increase in the motor current, the on-width of the chopping duty is increased according to the increased value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technique for controlling a motor (brushless DC motor) of a home appliance or the like by an inverter, and more particularly to a control method of a motor for controlling an output DC voltage of an active filter of a power supply circuit. It is about.

[0002]

2. Description of the Related Art When a motor is controlled by an inverter, a DC voltage is switched and applied to the motor, and the DC voltage is controlled by an active filter so that an input AC current waveform is substantially sinusoidal. As this control device, for example, there is one having a configuration shown in FIG.

In FIG. 4, this control device converts an AC power supply 1 into a DC voltage by a rectifying unit 2 of a diode bridge circuit and inputs the DC voltage to an active filter unit 3. Then, the input DC voltage is switched by a plurality of switching elements of the inverter unit 5, converted into, for example, three-phase AC, and applied to the motor 6.

The active filter section 3 includes a choke coil 3a connected in series to the positive terminal of the rectifier section 2;
The other terminal (output side) of the choke coil 3a and the rectifier 2
Switching element (IGB) connected between the negative terminal of
T; insulated gate transistor) 3b.

Further, the control device includes a control circuit 7 for turning on and off the switching element of the inverter section 5 and controlling on and off of the switching element 3b of the active filter section 3 and a base amplifier circuit 8. . Although not shown, the control circuit 7 is a microcomputer for controlling the motor, and controls input and output signals to and from various circuits necessary for the operation of the motor to control various parts of the motor.

The control device further includes a position detection circuit 9 for detecting the position of the rotor of the motor 6, and a position detection signal from the position detection circuit 9 is input to the control circuit 7, and the armature of the motor 6 The energization of the winding is switched, and the rotation control is performed appropriately.

Furthermore, a current detection sensor (CT: current transformer) 10 and a primary current detection circuit 11 are provided for detecting the input AC current (primary current), and the detection current from the primary current detection circuit 11 is controlled. The switching element 3b of the active filter unit 3 is input to the circuit 7 and is controlled to a predetermined command (chopping duty ratio) in accordance with the detected current to turn on and off the switching element 3b to make the input AC current waveform substantially a sine wave.

As described above, by making the input AC current waveform substantially a sine wave and reducing the distortion of the input AC current waveform, it is possible to reduce the harmonic current and improve the power factor.

[0009]

However, in the above-described motor control method, the output DC voltage of the active filter unit 3 fluctuates depending on the magnitude of the motor current. When the current flowing through the motor 6 increases due to an increase in the load of the motor 6, the output DC voltage of the active filter unit 3 is correspondingly increased because the chopping duty ratio is fixed. Is relatively reduced, and the operating efficiency of the motor is reduced.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to reduce the output DC voltage of an active filter due to an increase in the load of a motor, thereby enabling efficient motor operation. Is to provide a control method.

[0011]

In order to achieve the above object, the present invention converts an input AC power supply into a DC voltage by a rectifier and converts the DC voltage to a predetermined voltage by an active filter including at least a switching element. Supply the motor to inverter means for inverter control,
A motor control method for controlling the rotation of the motor by driving the inverter means while turning on and off the switching element to make the input AC current waveform substantially a sine wave, wherein the switching element is fixed. When the output DC voltage of the active filter is constant, the primary current as the input AC current is detected, and the amount of increase of the primary current is calculated. The on-width of the chopping duty ratio is increased accordingly.

According to the present invention, an input AC power supply is converted into a DC voltage by a rectifier, and the DC voltage is supplied to an inverter for controlling the motor as an inverter by an active filter including at least a switching element. A method for controlling a motor, wherein the switching element is turned on and off so as to make an alternating current waveform substantially a sine wave, and the inverter means is PWM-controlled to control the motor at a target rotation speed. Is driven at a constant chopping duty ratio, and when the output DC voltage of the active filter is constant, the amount of increase in the ON width of the PWM duty ratio for performing the PWM control is calculated. So that the ON width of the chopping duty ratio is increased accordingly. It is characterized in that was.

[0013]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In FIG. 1,
The same parts as those in FIG.

In FIG. 1, the control device to which the control method of the motor is applied is such that when the switching element 3b of the active filter section 3 is driven at a constant chopping duty ratio, the input of the motor 6 is increased. Judgment is made based on the increase amount of the alternating current (primary current) or the increase amount of the ON width of the PWM duty ratio for controlling the inverter unit 5, and calculates the increase amount, and chops the switching element 3b according to the increase amount. A control circuit (microcomputer) 2 for increasing the ON width of the duty ratio
0 is provided. Note that the control circuit 20 also has the function of the control circuit 7 shown in FIG.

As shown in FIG. 2, as the increase amount of the primary current increases, the decrease amount of the output DC voltage of the active filter unit 3 increases (corresponding to the broken arrow in FIG. 2). That is, the chopping duty ratio of the switching element 3b is a constant value, and when the output DC voltage of the active filter unit 3 is constant and the primary current is larger than usual, the current of the motor 6 is larger than usual. This is because the output DC voltage decreases.

As shown in FIG. 3, the larger the increase of the ON width of the PWM duty ratio is, the larger the decrease of the output DC voltage of the active filter unit 3 is (as indicated by the dashed arrow in FIG. 3). That is, when the chopping duty ratio of the switching element 3b is a constant value and the output DC voltage of the active filter unit 3 is constant and the ON width of the PWM duty ratio becomes larger than usual, the current of the motor 6 Is higher than usual and the output DC voltage is reduced, so that the voltage applied to the motor 6 is corrected and the speed control is corrected.

Next, the operation of the control device having the above configuration will be described. First, the control circuit 20 drives the switching element 3b of the active filter section 3 at a constant chopping duty ratio, and controls the motor 6 at a target rotation speed. It is assumed that

When the chopping duty ratio is constant, the primary current is detected to determine whether or not the current is larger than usual. For example, after detecting a primary current and storing it in a memory as a primary current at a normal time, a primary current is detected every predetermined time, and the detected primary current is compared with the primary current of the memory to determine a primary current. Is determined to be increasing.

Here, when the load of the motor 6 becomes heavy for some reason and the current of the motor 6 increases, the output DC voltage of the active filter unit 3 may decrease. In such a state, that is, when the primary current increases, the increase (increase amount) is calculated based on the currently detected primary current and the primary current of the memory, and the switching element 3b is chopped according to the calculated increase amount. Increase the duty ratio ON width. At this time, since the ON width of the chopping duty ratio is increased, a decrease in the output DC voltage of the active filter unit 3 is corrected, and a decrease in the output DC voltage is prevented. The amount by which the on-width of the chopping duty ratio is increased with respect to the amount of increase in the primary current may be determined in advance empirically.

When the motor 6 is under PWM control, if the rotation speed of the motor 6 deviates from the target rotation speed, the rotation speed is corrected, the ON width of the PWM duty ratio is increased, and the rotation speed of the motor 6 is adjusted to the target rotation speed. The number of rotations. Therefore, when the decrease in the output DC voltage of the active filter unit 3 is corrected, the rotation speed of the motor 6 becomes higher than the target rotation speed. However, in this case, by the PWM control, the ON width of the PWM duty ratio is reduced to the original value, that is, the control of setting the rotation speed of the motor 6 to the target rotation speed is performed.

In addition to the increase in the primary current, the PWM
The decrease in the output DC voltage of the active filter unit 3 can also be determined based on the increase amount of the ON width of the duty ratio. In this case, when the chopping duty ratio is kept constant, the ON width of the PWM duty ratio is stored in the memory as a normal value, and then the current pulse width is changed every predetermined time.
The ON width of the WM duty ratio is compared with the ON width of the memory, and it is determined whether the ON width of the PWM duty ratio has increased.

At this time, if the load of the motor 6 becomes heavy for some reason, that is, if the current of the motor 6 increases, the output DC voltage of the active filter unit 3 may decrease. In such a state, that is, when the ON width of the PWM duty ratio increases, an increase (increase amount) is calculated based on the current PWM duty ratio and the ON width of the memory, and the chopping duty of the switching element 3b is calculated according to the increase amount. Increase the ON width of the ratio. Then, the drop of the output DC voltage of the active filter unit 3 is corrected, and the drop of the output DC voltage is prevented. The amount by which the on-width of the chopping duty ratio is increased with respect to the increase in the on-width of the PWM duty ratio may be empirically determined in advance.

In the PWM control, when the rotation speed of the motor 6 deviates from the target rotation speed, the rotation speed is corrected and the PWM speed is corrected.
The ON width of the duty ratio is increased, and the rotation speed of the motor 6 is set as the target rotation speed. Therefore, when the decrease in the output DC voltage of the active filter unit 3 is corrected, the rotation speed of the motor 6 becomes higher than the target rotation speed. However, in this case, by the PWM control, the ON width of the PWM duty ratio is reduced to the original value, and control is performed to set the rotation speed of the motor 6 to the target rotation speed.

As described above, when the switching element 3b of the active filter section 3 is driven at a constant chopping duty ratio, the motor current increases and the output DC voltage of the active filter section 3 decreases. The amount of decrease in DC voltage is the amount of increase in primary current or PWM.
Judgment is made based on the increase amount of the ON width of the duty ratio, and the ON width of the chopping duty ratio for controlling the switching element 3b is increased according to the increase amount.

Accordingly, it is possible to correct the amount of decrease in the output DC voltage of the active filter section 3 and return it to the original constant value, thereby preventing the decrease in the output DC voltage. Further, the output DC voltage of the active filter unit 3 is divided by a resistance circuit,
Although a decrease in the output DC voltage can be detected from the divided voltage, as described above, the present invention does not require such a voltage dividing circuit, so that the cost does not increase.

[0026]

According to the present invention described above, the following effects can be obtained. The present invention relates to a motor control in which a DC voltage is supplied as a predetermined voltage by an active filter to an inverter means for driving the motor, wherein the switching element of the active filter is driven at a constant chopping duty ratio, and the output DC of the active filter is controlled. When the voltage is constant, the primary current as the input AC current is detected, the amount of increase of the primary current is calculated, and the ON width of the chopping duty ratio is increased in accordance with the calculated amount of increase. Is larger, the ON width of the chopping duty ratio becomes larger. For example, even when the current increases due to an increase in the motor load, it is possible to prevent the output DC voltage of the active filter from decreasing. It is possible to drive the motor stably with voltage There is an effect that efficient operation is possible.

When the motor is subjected to PWM control, the switching element of the active filter is driven at a constant chopping duty ratio by using the increase amount of the ON width of the PWM duty ratio instead of the increase amount of the primary current. When the output DC voltage of the filter is constant, the amount of increase in the on-width of the PWM duty ratio is calculated, and the on-width of the chopping duty ratio is increased in accordance with the calculated amount of increase. It has the same effect.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device according to an embodiment of the present invention, to which a motor control method is applied;

FIG. 2 is a schematic graph for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic graph for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic block diagram of a conventional motor control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input AC power supply 2 Rectification part 3 Active filter part 3a Choke coil 3b Switching element (IGBT) 4 Inverter part 5 Motor 7, 20 Control circuit (microcomputer) 10 Current detection sensor (CT) 11 Primary current detection circuit

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H007 AA02 BB06 CA01 CB05 CC12 CC23 DB07 DC02 DC07 EA02 5H560 AA10 BB04 BB12 DC12 EB01 GG04 SS03 SS07 TT08 UA02 UA06 XA12

Claims (2)

[Claims] 1. An input AC power source is converted into a DC voltage by a rectifier, and the DC voltage is supplied to an inverter for inverter-controlling the motor as a predetermined voltage by an active filter including at least a switching element.
A motor control method for controlling the rotation of the motor by driving the inverter means while turning on and off the switching element to make the input AC current waveform substantially a sine wave, wherein the switching element is fixed. When the output DC voltage of the active filter is constant, the primary current as the input AC current is detected, and the amount of increase of the primary current is calculated. A method for controlling a motor, wherein the on-width of the chopping duty ratio is increased accordingly. 2. An input AC power source is converted into a DC voltage by a rectifier, and the DC voltage is supplied to an inverter for controlling the motor as an inverter by an active filter including at least a switching element.
A method of controlling a motor, wherein the switching element is turned on and off to make the input AC current waveform substantially a sine wave, and the inverter means is PWM-controlled to control the motor to a target rotation speed, When the switching element is driven at a constant chopping duty ratio and the output DC voltage of the active filter is constant, the amount of increase in the ON width of the PWM duty ratio for performing the PWM control is calculated, and the calculated increase A method for controlling a motor, wherein an on-width of the chopping duty ratio is increased in accordance with the amount.