JPH11356081A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize stable start and rotation control even if ripple of load, input voltage, etc., exists. SOLUTION: This inverter device is equipped with a reference voltage storage means 15 which stores the reference value of the relation between the output voltage to be applied to a motor and the output frequency, and in this device a revolution control means 12 outputs the output voltage based on this reference voltage, and changes it on occasion whereby even in case that the operation conditions fluctuate, the revolutions of a motor quickly becomes stable, and it is controlled to be the desired objective revolutions. Furthermore, this is equipped with an input voltage detection means 14, and the revolution control means 12 smooths the start of the motor by changing the output pulse width according to the fluctuation, even if the detected input voltage fluctuates, and the revolutions is controlled stably. Furthermore, the compatibility of stable start and calm operation is materialized by switching the carrier frequency when the revolutions gets over the predetermined revolutions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in driving stability of an inverter device for driving a sensorless brushless motor at an arbitrary frequency and an improvement in accuracy of rotation speed control.

[0002]

2. Description of the Related Art Conventionally, in a rotation speed control method in an inverter device for driving a brushless motor such as a compressor of an air conditioner at an arbitrary frequency, a difference between a detected rotation speed of the motor and a given target rotation speed is determined. Generally, the number of rotations is controlled by calculating and increasing or decreasing the applied voltage according to the difference.

As a means for further improving the accuracy, for example, in a method of controlling a brushless motor disclosed in Japanese Patent Application Laid-Open No. H10-32994, when the applied voltage of the brushless motor is operated, its variable width is appropriately varied. In addition, the responsiveness of the rotation speed control was improved, and the accuracy of the rotation speed control was improved.

In a conventional inverter device for driving a brushless motor at an arbitrary frequency, a voltage applied to the motor is realized by performing pulse width chopping according to a predetermined duty ratio. In this case, a constant chopping frequency is used. (Hereinafter referred to as carrier frequency). In addition, in order to realize driving stability, for example, in a brushless motor control driving device disclosed in Japanese Patent Application Laid-Open No. 9-21991, prevention of start-up failure due to deterioration of duty ratio control resolution and ON duty In order to prevent the setting deviation of the overcurrent protection due to the decrease, the carrier frequency is changed according to the operation mode of the synchronous operation and the sensor operation.

[0005]

However, in such an inverter device, the applied voltage is operated while the target rotational speed is constant, and the voltage is changed at a predetermined rate during acceleration / deceleration. However, the convergence of the rotation speed during acceleration / deceleration was poor under the environment where the load was greatly different.

Further, since the power input voltage to the inverter device is not detected, when the power supply voltage fluctuates, the startup becomes unstable and the rotation speed becomes unstable.

Further, when the carrier frequency is increased in order to reduce noise, the pulse width decreases,
The phenomenon that rotation at the time of starting became unstable occurred.

Further, in the proposed motor control driving device, a synchronous operation for driving the motor with an alternating current having a constant period and a motor induced position generated by detecting the induced voltage generated by the rotation of the motor are used to estimate the rotor position of the motor. The aim was to achieve stable operation by changing the carrier frequency with the sensor operation that controls the period of the AC applied to the motor in accordance with the position. In such a case, there is a possibility that the operation may be unstable because the switching timing is too early.

The present invention solves the above-mentioned conventional problems, and realizes stable rotation speed control irrespective of the motor load, and also realizes stable startup and rotation speed control even when the power supply voltage fluctuates. The purpose is to:

[0010]

In order to solve the above-mentioned problems, an inverter device according to the present invention comprises: a reference voltage storage means for storing a reference relationship between an output voltage applied to a motor and an output frequency; Rotation speed detection means for detecting the number of rotations, and rotation for controlling an output voltage based on the reference voltage of the reference voltage storage means and controlling the rotation speed of the motor detected by the rotation speed detection means to a desired target rotation speed. Number control means.

[0011] Further, an input voltage detecting means for detecting an input voltage of the inverter device, and an input voltage detected by the input voltage detecting means is lower than a predetermined nominal voltage.
Alternatively, when the output voltage is high, a predetermined output voltage and output frequency relationship is realized by changing the output pulse width of the inverter device according to the input voltage, so that the brushless motor starts smoothly and the number of revolutions is controlled stably. The rotation speed control means is provided.

Further, the apparatus further comprises a carrier frequency control means having a function of switching a carrier frequency when the rotation speed detected by the rotation speed detection means exceeds a predetermined rotation speed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve the above-mentioned problems, an inverter device according to the present invention comprises: a reference voltage storage means for storing a relationship between an output voltage applied to a motor and a reference of an output frequency; Rotation speed detecting means for detecting,
Since the output voltage is controlled based on the reference voltage of the reference voltage storage means, and the rotation speed of the motor detected by the rotation speed detection means is controlled to a desired target rotation speed, the motor is provided with a rotation speed control means. According to the stored reference relationship between the output voltage to be applied and the output frequency, the motor speed is controlled to a desired target speed, and when the load of the motor changes, the output voltage and the output Since the relationship between the frequencies is automatically changed and stored, a smooth rotation speed change and stable rotation speed control are realized even when the load changes.

[0014] Further, an input voltage detecting means for detecting an input voltage of the inverter device, and an input voltage detected by the input voltage detecting means is lower than a predetermined nominal voltage.
Alternatively, when the output voltage is high, a predetermined output voltage and output frequency relationship is realized by changing the output pulse width of the inverter device according to the input voltage, so that the brushless motor starts smoothly and the number of revolutions is controlled stably. Since the rotation speed control means is provided, even if the input voltage of the inverter device changes, the output pulse width is corrected according to the value of the detected input voltage, so that a smooth start and stable rotation speed control are achieved. .

Further, when the rotation speed detected by the rotation speed detection means exceeds a predetermined rotation speed, there is provided a carrier frequency control means having a function of switching a carrier frequency. Even if it is desired to increase the carrier frequency during normal operation, the carrier frequency can be switched at the time of startup and at a certain rotational speed or more, so that stable startup can be achieved by increasing the pulse width.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the inverter device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an inverter device according to the present invention. AC power supply 1 to rectifier circuit 2
The DC power obtained by the rectification is input to the inverter device 3. The inverter device 3 drives the brushless motor 4 by outputting an AC such that the rotation speed of the brushless motor 4 matches the target rotation speed given from the outside.

The inverter device 3 includes switching elements (IGBT insulated gate bipolar transistors) 5a to 5f necessary for converting DC to AC, and flywheel diodes 6a to 6f connected in anti-parallel to the switching elements. It is composed of a three-phase inverter circuit formed by bridging these arms between the positive and negative sides of the DC bus, and outputs three-phase AC from three transistor series connection points. Is done. Further, a reference voltage generating circuit 7 for outputting a reference voltage from the voltage of the DC section
And a rotor voltage estimating means 9 for detecting the induced voltage of the brushless motor 4 from the motor voltage resistance circuit 8 for dividing the voltage of the motor winding and reducing the voltage, and estimating the position of the rotor. The switching elements 5a to 5f are driven through the driver circuit 11 in accordance with the position, in accordance with the switching element driving signal generated by the waveform generating means 10.

The rotation speed of the brushless motor 4 is controlled by providing the actual rotation speed of the brushless motor 4 obtained by the rotation speed detecting means 12 using the rotor position information obtained by the rotor position estimating means 9 and externally. The rotation speed control means 13 compares the target rotation speeds, and outputs a command to the waveform generation means 10 to increase the output voltage if acceleration is required and decrease the output voltage if acceleration is required. You. By performing such control, the motor can be stabilized at the target rotation speed.

The input voltage detecting means 14 detects the voltage input to the inverter device and outputs the information to the rotational speed control means 13. In the rotation speed control means 13, the output voltage of the inverter device 3 is controlled in accordance with the information, whereby stable operation is realized even when the input voltage fluctuates. The reference voltage storage means 15 stores the output frequency output from the inverter device 3 and the reference value of the output voltage, and controls the output voltage from the inverter device 3 according to this information during acceleration / deceleration.

The ON / OFF switching signal of the switching elements 5a to 5f generated by the waveform generating means 10 is a general PWM (Pulse Width Mod).
The method is performed in accordance with a method such as the above method, but detailed description is omitted here. The driving carrier frequency of this pulse signal is
The carrier frequency is controlled by the carrier frequency control means 16. The carrier frequency is low at the time of start-up in order to secure stability at the time of start-up. It is controlled to operate at the frequency.

Next, the operating principle of the reference voltage storage means 15 and the rotation speed control means 13 according to the present invention will be described.
The rotation speed control means 13 controls the output voltage according to the reference voltage value for the current output frequency stored in the reference voltage storage means 15 during acceleration / deceleration, and when the target rotation speed is constant, the actual speed of the brushless motor 4 is controlled. The number of revolutions is compared with a target number of revolutions given from the outside, and the output voltage is increased if it is necessary to accelerate, or decreased if it is necessary to decelerate. By performing such control, the motor can be stabilized at the target rotation speed.

FIG. 2 is a diagram showing an example of the reference voltage stored in the reference voltage storage means 15. The relationship between the output voltage and the output frequency is expressed and stored in the form of a general VF (voltage frequency) line that changes linearly. The rotation speed control means 13 outputs the target rotation speed at a constant timing.
The output voltage is increased or decreased so that the actual rotation speed of the motor is stabilized at the target rotation speed.
5 is reflected in the reference voltage information stored. For example, when the motor load is light, the target rotation speed can be realized at a low output voltage, so that the reference voltage straight line indicates a lower voltage than usual, and conversely, when the load is heavy, the output voltage is not high. Since the target rotation speed cannot be realized, the reference voltage straight line indicates a higher voltage than usual. As a result, smooth acceleration / deceleration is realized regardless of the motor load. For example,
When the reference voltage at the time of starting is the value of the straight line X0, the voltage V0 for the current output frequency f0 is output at first, but if the load of the motor fluctuates and the voltage needs to be changed. The rotation speed control means 13 lowers the output voltage to V1 and makes the rotation speed coincide with the target rotation speed. At that time,
The reference voltage information stored in the reference voltage storage means 15 is also changed to the reference voltage straight line X1. Thereafter, the rotation speed control is smoothly performed according to the reference voltage corresponding to the new load.

Next, the operating principle of the input voltage detecting means 14 and the rotation speed controlling means 13 according to the present invention will be described.
The input voltage detecting means 14 detects an input voltage supplied to the inverter device 3. The rotation speed control means 13 corrects the output voltage of the inverter device 3 according to the input voltage. FIGS. 3 and 4 show the principle. First, a case where there is no input voltage correction in the rotation speed control means 13 will be described. As described above, the value of the reference voltage with respect to the output frequency is given, for example, in the form of a general VF (voltage frequency) straight line in which the relationship between the output voltage and the output frequency changes linearly. Now, if the output frequency is f1
When the output voltage at that time is V1, the input voltage of the inverter device 3 is changed from a predetermined nominal voltage to Vh.
When it instantaneously rises to high, the inverter output voltage becomes V
It rises from 1 to V2. As a result, the motor rotation speed fluctuates due to the voltage rise.

On the other hand, in the rotation speed control means 13 of the present invention having the input voltage correction, the detected input voltage is compared with a predetermined nominal voltage, the deviation is reflected on the output voltage, and the output voltage is input. Suppress voltage fluctuations. For example, as shown in FIG. 4, in the case of the inverter output frequency f1, (V
By outputting a voltage command corrected by 2-V1) to the waveform generating means 10, a voltage is output in a form that compensates for the input voltage fluctuation, so that the inverter output voltage is affected by input voltage fluctuation and load fluctuation. On the other hand, it is kept constant (voltage V1). Therefore, the fluctuation of the rotation speed accompanying the fluctuation is very small, and stable inverter driving is possible. Further, since the voltage at the time of starting the motor is kept substantially constant even if the input voltage fluctuates, stable starting of the brushless motor is realized.

Next, the operation principle of the carrier frequency control means 16 according to the present invention will be described. First, the operation principle of the inverter device 3 will be described. The inverter device turns on the six switching elements 5a to 5f at high speed.
By turning OFF, DC can be changed to any frequency, voltage,
It is converted to phase alternating current. FIG. 5 shows ON-OFF of the switching element (hereinafter referred to as chopping).
Is a pattern of about one cycle. Thus, the six switching elements (U phase, V phase, W phase, X
(Phase, Y-phase, Z-phase) in a certain section, an arbitrary voltage is created by high-speed chopping.
This chopping frequency is called a carrier frequency.

The output pulse width is determined by the carrier frequency. For example, as shown in FIG. 6, when the carrier frequency is 2.5 KHz and when the carrier frequency is 5 KHz, the pulse width is 160 microseconds and 80 microseconds when the duty is 40% in order to output the same voltage. The pulse width changes as follows. When the rotation of the brushless motor is started, the voltage at the point A in FIG. 1 is low because the induced voltage is at a low level. Further, since the rotor position estimating means 9 has an analog filter element, the signal at the point A in FIG. 1 becomes as shown in FIG. 7 due to the pulse width. If the pulse width is small, it becomes difficult to detect the induced voltage. For this reason, it is difficult to start quickly at the time of startup.

On the other hand, in the carrier frequency control means 16 according to the present invention, after the brushless motor 4 is started, it operates at a relatively low carrier frequency while the rotation speed is lower than a predetermined rotation speed. When the number of rotations exceeds a predetermined switching speed, the frequency is switched to a relatively high carrier frequency. As shown in FIG. 8, by switching the carrier frequency, it is possible to perform a stable quick start-up at the time of startup with a low carrier frequency and an operation that achieves a quiet operation at the time of normal operation with a high carrier frequency.

[0029]

As described above, in the inverter device according to the present invention, the reference voltage storage means for storing the relationship between the output voltage applied to the motor and the output frequency, and the rotation speed detection for detecting the rotation speed of the motor. Means, and a rotation speed control means for controlling the rotation speed of the motor, by outputting an output voltage based on the reference voltage of the reference voltage storage means, even when operating conditions such as load fluctuate, Is controlled so that the desired rotation speed is quickly and stably attained.

Further, the apparatus further comprises input voltage detecting means for detecting an input voltage of the inverter device, wherein the rotational speed control means comprises:
When the input voltage detected by the input voltage detecting means is lower or higher than a predetermined nominal voltage, the pulse width output by the inverter device is changed according to the input voltage to thereby obtain a predetermined output voltage and output. By maintaining the frequency relationship, the brushless motor is started smoothly, and the rotation speed is controlled stably.

Further, when the number of revolutions detected by the number of revolutions detecting means exceeds a predetermined number of revolutions, a carrier frequency control means having a function of switching a carrier frequency is provided, so that the carrier frequency can be reduced for noise reduction. Even if it is desired to increase the frequency during normal operation, the carrier frequency can be switched between at startup and at a predetermined rotational speed or higher, so that stable startup can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an inverter device according to the present invention.

FIG. 2 is a characteristic diagram showing an operation principle of a reference voltage storage unit and a rotation speed control unit of the inverter device according to the present invention.

FIG. 3 is a characteristic diagram showing characteristics of the inverter device without input voltage correction.

FIG. 4 is a characteristic diagram showing characteristics when input voltage correction is performed in the rotation speed control means of the inverter device according to the present invention.

FIG. 5 is a diagram showing an example of a chopping method of the inverter device according to the present invention.

FIG. 6 is a diagram showing an example of a pulse width by chopping of the inverter device according to the present invention.

FIG. 7 is a diagram showing an example of an induced voltage signal of the inverter device according to the present invention.

FIG. 8 is a principle view showing the principle of an example of a carrier frequency switching method of the inverter device according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 AC power supply 2 Rectifier circuit 3 Inverter device 4 Brushless motor 5 a to 5 f Switching element 6 a to 6 f Flywheel diode 7 Reference voltage generating circuit 8 Motor voltage generating circuit 9 Rotor position estimating means 10 Waveform generating means 11 Driver circuit 12 Rotation speed detecting means 13 rotation speed control means 14 input voltage detection means 15 reference voltage storage means 16 carrier frequency control means

Claims (4)

[Claims] An inverter device for a brushless motor that switches a DC power supply to apply it to an armature winding of a brushless motor, and controls the applied voltage to control the number of revolutions. A reference voltage storage unit for storing a reference value of a frequency relationship, a rotation speed detection unit for detecting a rotation speed of the motor, and a rotation speed of the motor detected by the rotation speed detection unit by operating an output voltage. Rotation speed control means for controlling so as to be the target rotation speed of the motor, wherein the rotation speed control means sets an output voltage with a reference voltage value corresponding to the rotation speed of the motor stored in the reference voltage storage means as an initial value. The number of rotations is controlled by performing the increase / decrease operation, and the output voltage and the output frequency stored in the reference voltage storage means are further used by using the output voltage value obtained by the increase / decrease operation. Fixed number relationship, when the target rotational speed is changed, the inverter apparatus characterized by having modified output voltage, the function of determining the output voltage in accordance with the output frequency relationship. 2. An inverter device for a brushless motor, in which a DC power source is switched and applied to an armature winding of a brushless motor, and the applied voltage is operated to control the number of revolutions, wherein an input voltage of the inverter device is detected. Input voltage detection means, rotation number detection means for detecting the rotation number of the motor, and rotation number control means for increasing or decreasing the output voltage and controlling the rotation number of the motor to a desired target rotation number, Rotation speed control means, the input voltage detected by the input voltage detection means is lower than a predetermined nominal voltage,
Or, when the output voltage is high, the output pulse width of the inverter device is changed in accordance with the input voltage to realize a predetermined output voltage-output frequency relationship, and a function of stably controlling the rotation speed of the motor is provided. An inverter device characterized by the above-mentioned. 3. A brushless motor inverter device that switches a DC power supply to apply the voltage to an armature winding of a brushless motor and controls the applied voltage to control the number of rotations. Number detection means, and carrier frequency control means having a function of switching a drive carrier frequency of a voltage applied to the motor, and when the rotation number detected by the rotation number detection means exceeds a predetermined rotation number, the carrier An inverter device, wherein the frequency control means has a function of switching a carrier frequency. 4. The inverter device according to claim 3, wherein the carrier frequency is lowered in a region where the rotation speed of the brushless motor is low, and the carrier frequency is raised in a region where the rotation speed of the brushless motor is high.