JP3419258B2 - Motor control device - Google Patents

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 for controlling the number of revolutions of a motor to a desired number of revolutions, and an air conditioner for driving a compressor driving motor using the motor control device to perform air conditioning in a room. Regarding the machine.

[0002]

2. Description of the Related Art Conventionally, as a motor control device for controlling the speed of a motor by combining a power supply circuit for controlling a DC voltage and a motor drive circuit, JP-A-61-10968 and 59-59.
There are methods described in Japanese Patent Laid-Open No. 181973 and Japanese Patent Laid-Open No. 63-224698, and PWM (Pulse Width Modulation) control for controlling the speed of the motor by varying the duty ratio of the motor drive circuit and supplying to the motor drive circuit The PAM (Pulse Amplitude Modulation) control for controlling the motor speed by controlling the DC voltage is switched according to certain conditions to control the motor speed.

Switching between the PWM control and the PAM control is as follows.
It is performed with a set value of a value related to the speed of the motor, a speed command (frequency or frequency command), an AC output voltage value, or a conduction ratio of the motor drive circuit.

[0004]

In the above-mentioned conventional method, when switching is performed by the motor speed, speed command (frequency or frequency command) or AC output voltage value, the switching point (set value) between PWM control and PAM control is set. ) Is predetermined, a shock such as a sudden change in motor speed occurs at the time of switching under a motor load or power supply conditions other than the set conditions. Also,
It is expected that the switching condition value cannot reach the set value depending on the load condition, the control method is not changed, and the motor speed control itself becomes impossible.

In particular, when applied to general equipment such as an inverter air conditioner, it is difficult to apply the above-mentioned conventional method because the load range is wide and the fluctuation range of the power source is large.

In addition, in the above-mentioned conventional methods including the method of switching by the duty factor of the motor drive circuit, while having a control system capable of changing two electric powers at the same time, two control systems are switched and the speed is always controlled by only one control system. Since the control is performed, the characteristics of the speed control device cannot be fully utilized for speed control. Here, comparing the PWM control and the PAM control, they have the following characteristics.

Since the PWM control uses pulse width modulation, the voltage response to the motor speed control is faster than the PAM control, and at the same time the control system is relatively simple.

Compared to PWM control, PAM control does not involve switching operation during one current flow period, so that loss of switching elements and iron loss due to current pulsation of a motor are suppressed.

An object of the present invention is to maximize the characteristics of a motor speed control device equipped with a PWM control system and a PAM control system to prevent a sudden change in the motor speed at the time of switching and an inability to switch. An object of the present invention is to provide an improved motor control acceleration / deceleration rate and a highly efficient motor control device.

[0010]

The above object is to provide a converter circuit for increasing and decreasing a DC voltage, an inverter circuit connected to the output of the converter circuit, and a DC circuit for detecting a DC voltage value on the output side of the converter circuit. A voltage detection circuit,
DC voltage control means for controlling the output voltage of the DC voltage detection circuit and the DC voltage command value so that the DC voltage value becomes the DC voltage command value, and an inverter control circuit for controlling the switching operation of the inverter circuit to drive the motor. A first speed control configuration for outputting a duty ratio signal to the inverter control circuit to control the speed of the motor; and a second speed control configuration for outputting a DC voltage command to the DC voltage control means to control the speed of the motor.
The speed deviation is defined by the difference between the commanded speed and the motor speed, and the speed deviation is positive. When the DC voltage is increased and the conduction ratio of the motor drive circuit is increased, on the contrary, when the speed deviation is negative, the DC voltage is decreased and the conduction ratio of the motor drive circuit is decreased, and the speed deviation is zero. In this case, the switching loss and the motor current are reduced by decreasing the DC voltage and at the same time increasing the duty ratio of the motor drive circuit by an amount equivalent to the power, suppressing the DC voltage and increasing the duty ratio of the motor drive circuit. This can be achieved by controlling the iron loss due to the pulsation.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an overall configuration diagram of a motor drive device of a first embodiment according to the present invention. In this embodiment, a commercial power source is used as the power source, and a boost converter is used to realize high-speed rotation of the motor. Therefore, this drive device uses a rectifier circuit and a step-up chopper circuit, a converter circuit 2 that controls the magnitude of the DC voltage, an inverter circuit 3 that converts the DC voltage into an AC power source of a desired voltage, and a speed command according to the speed command. Motor control means 8 for controlling the speed of the brushless DC motor 4, a position detection circuit 9 for detecting the magnetic pole position of the brushless DC motor 4, and a correction DC voltage signal and a converter ON / OFF signal from the motor control means 8 Converter control circuit 6 for controlling the converter circuit 2
A driver 5 for driving the inverter circuit 3 by a PWM signal and a drive signal from the motor control means 8, and a current detection circuit 7 for detecting a power supply current input from the AC power supply 1 and transmitting it to the motor control means 8. It is configured.

The motor control means 8 includes a position detection circuit 9
Of outputting a drive signal to the driver 5 based on the position detection signal from the controller, and a function of outputting a converter ON / OFF signal to be input to the converter control circuit 6 based on the input current value output from the current detection circuit 7. And a velocity deviation is calculated from the given command velocity and a velocity calculated based on the position detection signal from the position detection circuit 9, and the motor control means 8 outputs a PWM signal and a DC voltage command in accordance with the velocity deviation. A signal is output to each circuit to realize speed control of the brushless DC motor 4. Here, the motor control means 8 uses a microcomputer, and all the operations in the motor control means 8 can be realized by software processing.

FIG. 2 is a flow chart for determining the conduction ratio command Di ^* and the DC voltage command Ed ^* based on the speed deviation.

FIG. 3 shows the PWM in one embodiment of the present invention.
/ PAM control operation explanatory diagram, command speed = actual speed (speed deviation is zero) at t0 to t1, command speed> actual speed at t1 to t2 (speed deviation is positive), command speed = actual speed at t2 to t4 (Speed deviation is zero), command speed <actual speed (speed deviation is negative) at t4 to t5, command speed = actual speed after t5 = actual speed (speed deviation is zero), DC voltage at that time and conduction ratio of inverter circuit 3 Represents the change of.

2 and 3, changes in the duty ratio command Di ^* and the DC voltage command Ed ^* with the increase / decrease of the command speed, the DC voltage, the duty ratio of the inverter circuit 3, and the actual speed of the motor. The operation will be described. At this time, the maximum value of the duty ratio command Di ^* is 100% and the minimum value of the DC voltage command Ed ^* is 150V.
And

In the flowchart of FIG. 2, first, the speed deviation of (1) is determined as positive, negative, or zero. At this time, from t0 to t1 in FIG. 3, the command speed and the actual speed are the same and the speed deviation is zero, so the determination of FIG. Here, since the DC voltage command value is 150 V, which is the minimum, the conduction ratio command Di ^* and the DC voltage command Ed ^* are not changed and the arithmetic processing is ended. The voltage / current waveform applied to the motor at this time is equivalent to what is called PWM control. FIG. 4 shows PWM control and P
It is a diagram schematically showing a one-phase motor terminal voltage and a motor current in the AM control. During PWM control, the switching operation is repeated within one current flow period, and the current flowing through the motor pulsates accordingly. This switching operation causes loss of switching elements and current pulsation on the motor side causes iron loss. Occurs. On the other hand, in the PAM control, since there is no switching operation within one current flow period, there is no switching element loss due to the switching operation, and no iron loss occurs on the motor side due to current pulsation.

Next, at t1 in FIG. 3, when a command speed higher than the actual speed is given, the speed deviation becomes positive, and therefore the processing after (6) in FIG. 2 is performed. Here, the conduction ratio command Di ^* and the DC voltage command Ed ^* are increased so that the actual speed reaches the command speed. At this time, unless the respective command values are the maximum values, the motor speed is increased faster than the method of switching the PWM and PAM controls to speed control by simultaneously increasing the duty ratio command Di ^* and the DC voltage command Ed ^*. Therefore, the time required to reach the command speed can be shortened.

FIG. 3 (b) compares the operations of the present invention method and the PWM / PAM switching method with the addition / subtraction amounts of the DC voltage command Ed ^* and the duty ratio command Di ^* set to the same value. From this, it is understood that the method of the present invention can accelerate and decelerate faster than the switching method.

After that, at t2 in FIG. 3, when the command speed and the actual speed match and the speed deviation becomes zero, the DC voltage command E
At the same time that d ^* is reduced, the conduction ratio D corresponding to the reduced power
By increasing i ^* , the converter circuit 2 and the inverter circuit 3 are controlled so that the switching loss is reduced and the loss due to the pulsation of the motor current is reduced. The DC voltage command Ed ^* and the increase / decrease in the conduction ratio Di ^* at this time are shown in FIGS. 2 (4), (7), and (11) in order to improve the control stability.
And, (5) and (9), (13) are set to different values. The same effect can be obtained even if the increase / decrease values for the positive, negative, and zero speed deviations are the same.

At t3 in FIG. 3, the conduction ratio Di ^* becomes 100%, and after the determination in FIG. 2 (3), the flow is terminated and stable without changing the DC voltage command Ed ^* and the conduction ratio Di ^*. It becomes a state. The voltage / current waveform applied to the motor at this time is equivalent to what is called PAM control, and there is no switching operation within one flow period, and pulsation of the motor current does not occur.

At the time of deceleration after t4 in FIG. 3, the direct current voltage command Ed ^* and the conduction ratio Di ^* are simultaneously decreased in the opposite manner to the acceleration at t1 so that the arrival time to the command speed is shortened as in the acceleration. However, after t5, the DC voltage becomes the minimum value, and as a result, PWM control is performed.

By repeating the above operation, the acceleration / deceleration of the motor and the stable state are realized.

That is, the control system of the present invention shortens the acceleration / deceleration time by simultaneously increasing / decreasing the output power in the two speed control systems during acceleration / deceleration, and when the speed deviation becomes zero, one of the two speed control systems The speed control device realizes highly efficient speed control by reducing the loss as a speed control device by performing contradictory control such as decreasing the other and increasing the other.

When this algorithm is used, the DC voltage inevitably converges to the minimum voltage when the final conduction ratio is within 100% in the determination of FIG. 2 (2), and the DC voltage is not the minimum value. At times, the flow rate converges to 100%. Therefore, the method for determining the DC voltage command Ed ^* and the conduction ratio Di ^* is
The converter can be applied to all types of step-up type, step-down type, and buck-boost type, and similar operation and effects can be realized.

Further, if the control method of the present invention is applied to the compression motor of the air conditioner, the rising time during cooling / heating can be shortened and a highly efficient air conditioner can be realized in the steady state.

[0027]

According to the present invention, the PWM control configuration and the PA
It has two speed control configurations of M control configuration, and by controlling these two speed control configurations at the same time, the acceleration / deceleration time is shortened, and switching loss and iron loss of the motor are reduced in the steady state, thus achieving highly efficient motor control. Can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a motor drive device according to a first embodiment of the present invention.

FIG. 2 is a flowchart of a DC voltage command and a duty ratio calculation according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of PWM / PAM control operation according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram of motor terminal voltage and motor current during PWM control and PAM control of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC power supply, 2 ... Converter circuit, 3 ... Inverter circuit, 4 ... Motor, 5 ... Driver, 6 ... Converter control circuit, 7 ... Current detection circuit, 8 ... Motor control means, 9 ... Position detection circuit.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-105563 (JP, A) JP-A-7-15966 (JP, A) JP-A-9-149690 (JP, A) JP-A-8- 289582 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02P 6/06 H02M 7/48

Claims (3)

(57) [Claims] 1. A microcomputer, a converter circuit for increasing / decreasing a DC voltage, an inverter circuit connected to the output of the converter circuit, and a DC voltage value of the DC voltage based on a DC voltage command from the microcomputer. A direct current voltage control circuit for controlling, and an inverter control circuit for controlling a duty ratio of the inverter circuit based on a duty ratio signal from the microcomputer to drive a motor, wherein the microcomputer is a speed of the motor. And the speed deviation obtained from the command speed is positive, the DC voltage is increased in the direction of the maximum value, and the conduction ratio of the inverter drive circuit is increased in the direction of the maximum value. Is negative, the DC voltage is reduced to the minimum value and the conduction ratio of the inverter drive circuit is reduced to the minimum value. Decreasing direction, wherein when the speed deviation of the inverter drive circuit is zero, characterized by having a function of increasing the duty ratio of the inverter driver circuit to correspond to a reduced and less power is the DC voltage And the motor control device. 2. The motor control device according to claim 1, wherein the increase / decrease amount of the DC voltage and the conduction ratio at positive, negative and zero speed deviations are different values. 3. An air conditioner using the motor control device according to claim 1 as a control device for a compressor driving motor of an air conditioner.