JP2005027395A - Controller of permanent magnetic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cover a wide rotational frequency range for increased maximum rotational frequency and increased nominal efficiency, using a single rotor magnetic pole position detecting circuit. <P>SOLUTION: A method for controlling a sensorless permanent magnet motor comprises a position detecting circuit 10 which acquires a differential voltage between a virtual neutral point potential acquired from the resistor connected parallel to a stator coil and a motor neutral point potential of the stator coil, and outputs a position detection signal acquired by subtracting the signal other than third harmonics component from the signal of differential voltage. A control circuit 11 controls switching timing for energizing the stator coil based on the position detection signal from the position detecting circuit 10, and switches PWM energization pattern from sine wave driving to square wave driving according to operation states. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a sensorless permanent magnet motor (brushless DC motor). More specifically, the present invention is suitable for compressor motors and fan motors such as air conditioners and electric refrigerators that can further increase the maximum rotation speed. The present invention relates to a control device for a permanent magnet motor.
[0002]
[Prior art]
In the past, when controlling the rotation speed of a permanent magnet motor, it was controlled based on the optimal phase relationship while detecting the magnetic pole position of the rotor using a sensor, but it was used for home appliances such as air conditioners and electric refrigerators. In this case, high-priced sensors are avoided due to demands for cost reduction, and compressor motors are used in severe environments of high temperature and high pressure. It is difficult to build in because it tends to occur.
[0003]
Therefore, at present, a sensorless system that detects and estimates the magnetic pole position of the rotor by using the electrical characteristics of the motor without using a sensor and optimally controls the motor has become the mainstream, and a brushless DC motor motor based on the sensorless system An example of the control device is shown in FIG.
[0004]
This control device is an inverter drive control device that converts a voltage Vdc of a predetermined DC power source 1 into an arbitrary AC voltage by an inverter circuit 2 composed of, for example, a six-element bridge circuit, and applies it to the permanent magnet motor 3. And a position detection circuit 4 for switching the winding current of the stator.
[0005]
The position detection circuit 4 detects a zero-cross point of an induced voltage waveform included in a virtual neutral point potential by resistance star connection (not shown), and outputs a position detection signal including the detection point to a control circuit (microcomputer) 5.
[0006]
The control circuit 5 estimates the magnetic pole position of the rotor from the position detection signal and outputs the drive signal to the inverter circuit 2 via the driver circuit 6 in order to drive the predetermined switching element of the inverter circuit 2. The energization of the winding is switched and the PWM duty is adjusted to control the rotation speed to the target rotation speed.
[0007]
However, since it becomes difficult to accurately detect the zero crossing of the induced voltage when the rotational speed of the motor is in a high speed region, the maximum rotational speed is limited. In order to solve this point, Patent Document 1 proposes an invention including two magnetic pole position detection circuits.
[0008]
That is, in Patent Document 1, the first and second magnetic pole position detection circuits are used in combination, and one of the first magnetic pole position detection circuit and the second magnetic pole position detection circuit is changed depending on the energization angle or the rotation speed. The magnetic pole position of the rotor is detected based on the signal from the selected magnetic pole position detection circuit.
[0009]
The first magnetic pole position detection circuit detects an induced voltage generated in the non-energized phase, compares the induced voltage waveforms with each other to obtain a signal having a frequency three times the electric rotation speed, and detects the rotor magnetic pole position from this signal. . The second magnetic pole position detection circuit is the difference between the intermediate point (virtual neutral point voltage) of the resistance element (Y star connection) connected in parallel with the motor winding and the neutral point (motor neutral point voltage) of the motor winding. (Potential difference fluctuation) is detected, and the rotor magnetic pole position is detected by this potential difference fluctuation.
[0010]
When the motor is operated at a conduction angle of 120 °, the rotor magnetic pole position is detected by the first magnetic pole position detection circuit. When the energization angle is wider than 120 °, it is difficult to detect the magnetic pole position by the first magnetic pole position detection circuit. Therefore, the magnetic pole position is detected by the second magnetic pole position detection circuit.
[0011]
Thus, according to Patent Document 1, the rotor magnetic pole position is properly detected in the low rotation region to the high rotation region, and the conduction angle is used from 120 ° to 180 °, so that the power supply voltage is effectively used. Thus, high speed rotation can be achieved.
[0012]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-186274
[Problems to be solved by the invention]
However, the invention of Patent Document 1 is not preferable in terms of cost because it requires two magnetic pole position detection circuits for the low rotation region and the high rotation region. Accordingly, an object of the present invention is to realize an increase in the maximum rotational speed and an improvement in rated efficiency by using one magnetic pole position detection circuit.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention detects a magnetic pole position of a rotor without a sensor, and switches the energization of a stator winding based on the position detection signal to control the rotational speed of the rotor. In this case, the differential voltage signal between the virtual neutral point potential obtained through the resistors connected to the terminals of the stator winding and the neutral point potential of the stator winding is passed through a filter to obtain a component other than the third harmonic component. And a position detection means for outputting a position detection signal mainly including the third harmonic component, and the energization switching timing of the stator winding is controlled based on the position detection signal from the position detection means. In addition, the PWM energization pattern is switched from sinusoidal wave driving to rectangular wave driving according to the operating state.
[0015]
The switching of the PWM energization pattern adopts a sine wave driving method at the time of starting the operation and in the rotation speed region until the PWM waveform modulation rate becomes 1, and the rotation speed is changed when the PWM waveform modulation rate becomes 1. In the case of further increase, it is preferable to switch to the rectangular wave driving method.
[0016]
Further, immediately after switching from the sine wave driving method to the rectangular wave driving method, driving is performed by 120-degree energization, and when the rotational speed is further increased, driving is preferably performed by a predetermined energization angle and ignition phase. .
[0017]
In the present invention, a second-order bandpass filter or a bandpass filter in which a second-order high-pass filter and a second-order low-pass filter are combined can be used as the filter. The above-described filter may include at least one of a primary high-pass filter, a primary low-pass filter, a secondary high-pass filter, and a secondary low-pass filter. Can be inexpensively supported.
[0018]
In addition, it is preferable that a predetermined energization angle and firing phase pattern is tabulated according to load conditions, or the pattern is obtained by an approximate expression, and driven under optimum conditions according to the operation mode. The present invention is particularly suitable as a control device for a compressor motor or a fan motor of an air conditioner or an electric refrigerator because the operating range of the motor can be widened and the rated efficiency can be improved.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 to 9, but the present invention is not limited thereto. The inverter circuit 2 and its driver circuit 6 in FIG. 1 may be the same as the prior art of FIG. 10 described above.
[0020]
In FIG. 1, the control device of the present invention detects a difference voltage between a virtual neutral point potential and a motor neutral point potential obtained by inserting resistances in the bridges of motor winding terminals, respectively. A position detection circuit 10 that passes a filter to reduce frequency components other than the third harmonic component and outputs a rotor position detection signal based on the third harmonic component, and a position detection signal from the position detection circuit 10 makes the rotor While detecting and estimating the magnetic pole position to obtain the energization switching timing, the permanent magnet motor 3 is PWM-controlled, and the PWM energization pattern is changed from sine wave driving to rectangular wave driving according to the operating state during the operation of the permanent magnet motor 3 A switching control circuit (microcomputer) 11 is provided.
[0021]
As shown in FIG. 2, the position detection circuit 10 includes a resistance bridge circuit 10a in which one end is connected to each winding terminal of the permanent magnet motor and Y connection (star connection), and the resistance bridge circuit 10a. The difference voltage between the obtained virtual neutral point potential and the motor neutral point potential is taken, and at least a capacitor 10b having a predetermined capacity for suppressing a surge voltage included in the difference voltage, and a signal of the difference voltage for suppressing the surge voltage A voltage follower circuit 10c using an open amplifier with low impedance and a signal of a difference voltage via the voltage follower circuit 10c, which is unnecessary for magnetic pole position detection (high-order harmonics, fundamental wave) is removed. A filter circuit 10d for obtaining a necessary signal component (third harmonic component), and a signal of the third harmonic component by the filter circuit 10d; Composed of a comparator 10e for outputting a position detection signal by detecting the zero-cross point by comparison with the standard value M.
[0022]
The filter circuit 10d may be composed of a second-order bandpass filter (BPF) circuit 20, for example, as shown in FIG. The BPF circuit 20 can be a secondary multiple-feedback band-pass filter including an operational amplifier 20a, resistors R1, R2, and R3 and capacitors C1 and C2 having the same capacitance to realize a single amplifier.
[0023]
For example, given the bandpass gains Ho, Q and the center frequency (third harmonic) ωo = 2πf, the resistors R1, R2, and R3 have R1 = Q / (Ho · ωo · C) and R2 = Q / ( 2 · (Q squared) −Ho) · ωo · C), R3 = 2 · Q / ωo · C. The pass band is a frequency band in the vicinity of at least the third harmonic (a harmonic that is three times the fundamental wave), and cuts a frequency lower than the third harmonic and a frequency higher than the third harmonic.
[0024]
In place of the BPF circuit 20, a filter combining a secondary high-pass filter (HPF) 21 shown in FIG. 4 and a secondary low-pass filter (LPF) circuit 22 shown in FIG. 5 may be used.
[0025]
The HPF circuit 21 is a high-pass active filter including an inverting operational amplifier 21a, resistors R4 and R5, and capacitors C3, C4, and C5. The LPF circuit 22 is a secondary filter including non-inverting operational amplifiers 22a and 22b, resistors R6 and R7, and capacitors C6 and C7. This is a VCVS (voltage control source) type filter.
[0026]
The HPF circuit 21 and the LPF circuit 22 determine the resistors R4, R5 and C3, C4, C5 so as to have the same function as the BPF circuit 20, and the resistors R6, R7 and capacitors C6, C7. decide. In the determination, it is assumed that the cut in the high region is the same as that of the conventional low-pass filter, and that the cut in the low region is at least a frequency lower than the third harmonic (three times the harmonic of the fundamental wave). .
[0027]
For example, for the HPF circuit 21, the values of R4, R5, C3, C4, and C5 are determined when Ho, Q and ωc = 2πf are given. For convenience, assuming that C3 = C4, the resistors R4 and R5 are determined by R4 = 1 / (Q · ωc · C1 (2Ho + 1), R5 = (Q / ωc · C1) · (2Ho + 1), and the capacitor C5 is C5. = C4 / Ho).
[0028]
Further, in place of the secondary HPF circuit 21 and the LPF circuit 22 described above, a low-cost primary HPF circuit 23 shown in FIG. 6 and a primary LPF circuit 24 shown in FIG. 7 may be used. The HPF circuit 23 includes a circuit including a capacitor C8 and a resistor R8, and the LPF circuit 24 includes a CR circuit including a resistor R9 and a capacitor C9. Note that only one filter circuit of the HPF circuits 21, 23 and the LPF circuits 22, 24 may be used, that is, a frequency component lower than the third harmonic component is cut, or a frequency higher than the third harmonic component is used. Just cut the ingredients.
[0029]
By the above filter, the signal of the difference voltage between the virtual neutral point potential and the motor neutral point potential is removed from the signal in the region higher than the third harmonic, and the signal in the region lower than that is removed. That is, the harmonic component and the fundamental component due to the nonlinearity of the inductance of the stator winding are greatly reduced, and at least the required third-order harmonic component signal can be obtained. Thus, since the required third harmonic component is extracted, the accuracy of position detection is improved, and position detection in a wide operation range is possible.
[0030]
The control circuit 11 switches the PWM energization pattern of the permanent magnet motor 3, and adopts a sine wave drive method at the time of starting and in the rotation speed range until the PWM duty reaches the full duty (PWM waveform modulation factor 1). When the modulation rate of the PWM waveform reaches 1, in order to increase the rotation speed, the PWM pattern is switched to the rectangular wave driving method to increase the rotation speed.
[0031]
The operation of this control apparatus will be described with reference to FIGS. 8 and 9. The control circuit 11 starts the permanent magnet motor 3, and then applies a 180-degree sine wave drive method (sine wave PWM drive). The rotation is controlled (see solid line arrow A in FIG. 8). In addition, 180 degrees sine wave drive is performed at the time of starting of the permanent magnet motor 3, but a motor applied voltage is generated in the inverter circuit 2 using a preset PWM waveform.
[0032]
Regarding the position information at this time, since the position detection signal from the position detection circuit 10 is input, the motor magnetic pole position can be appropriately detected. Since the motor magnetic pole position is detected appropriately, in other words, detailed position information can be obtained. In sinusoidal PWM driving, the PWM duty is adjusted, that is, the PWM waveform modulation rate is sequentially adjusted to sine the motor applied voltage. Wave.
[0033]
By this sine wave PWM drive, the rotational speed of the permanent magnet electric motor 3 is increased to the target rotational speed. Since control is possible by sinusoidal PWM drive until the PWM waveform reaches full duty (PWM waveform modulation factor 1), the rotational speed of the permanent magnet electric motor 3 exceeds the normal motor rating and increases to f1. It is possible.
[0034]
If the rotational speed of the permanent magnet motor 3 does not reach the target rotational speed even if the target rotational speed is higher than f1 and the modulation rate of the PWM waveform becomes 1, the PWM pattern of the motor is driven in a rectangular wave (120 to 180 degrees). (See solid arrow B in FIG. 8).
[0035]
Immediately after switching from the sine wave drive to the rectangular wave drive, the motor voltage is increased by the PWM rectangular wave of the 120-degree energization method so that the rotation speed of the permanent magnet motor 3 becomes the target rotation speed. In the 120-degree energization rectangular wave drive, even if the PWM duty becomes 100%, if the rotation speed does not reach the target rotation speed, for example, if the rotation speed is f2 (<target rotation speed) shown in FIG. The permanent magnet motor 3 is driven using a predetermined energization angle (wide angle; 120 ° to 180 ° rectangular wave) and a firing phase pattern (see solid arrow C in the figure).
[0036]
The motor voltage rises by making the energization angle wide, and the ignition phase is a lead phase, and is used for field weakening control. As the pattern of the conduction angle and the ignition phase, for example, the pattern shown in FIG. The pattern shown by the solid line arrow D in the figure is a pattern in which the advance phase angle is increased without increasing the energization angle so much, that is, the field weakening control is emphasized.
[0037]
The pattern indicated by the wavy arrow E in the figure is a pattern in which the energization angle is increased and the advance phase angle is increased, and PWM rectangular wave driving and field weakening control are used in combination. The pattern indicated by the dotted arrow F in the figure does not advance the phase so much and increases the energization angle, and emphasizes PWM rectangular wave driving.
[0038]
Here, the position detection circuit 10 can reliably detect the rotor magnetic pole position from the position detection signal obtained by the difference voltage between the virtual neutral point potential and the motor neutral point potential. The wide angle control of the conduction angle becomes possible. These field-weakening control and wide angle control of the energization angle further increase the rotational speed of the permanent magnet motor 3 and increase the rated efficiency.
[0039]
As described above, since one position detection circuit 11 is used as the position detection means, the cost can be reduced. In addition, a sine wave drive system is adopted when the permanent magnet motor 3 is rated, and a rectangular wave drive system and a lead phase control system are adopted at points above the rating, so that the speed can be increased, and the maximum rotational speed is increased. The motor efficiency can be maximized by increasing the rated efficiency.
[0040]
For example, in applying to a compressor motor of an air conditioner, assuming load patterns according to various modes such as heating operation and cooling operation, the rotor position is used as a reference (for example, the true rotor position phase is used as a reference), The optimum firing phase angle and energization angle (data corresponding to FIG. 9) are determined empirically according to the load pattern, and these firing phase angle and energization angle patterns may be tabulated.
[0041]
The patterns of the ignition phase angle and the conduction angle included in the pattern shown in FIG. 9 are each represented by an approximate expression, and for example, the advance phase and the conduction angle may be calculated from the approximate expression for each detection of the rotor magnetic pole position. The table and approximate expression may be stored in the memory in a form corresponding to the solid arrow D, the wavy arrow E, or the dotted arrow F in FIG.
[0042]
Then, an advanced ignition phase angle is obtained by referring to a predetermined table in accordance with each load pattern, and a PWM voltage signal according to the ignition phase angle is provided every time the rotor magnetic pole position is detected. In addition, the PWM voltage signal also includes the conduction angle, so that the rotational speed is further increased even under the condition that the motor voltage is limited by controlling the lead phase angle and the conduction angle (PWM duty 100%). The rating is increased. Thereby, cost reduction of compressor motors and fan motors such as an air conditioner and an electric refrigerator, an increase in the maximum rotation speed, and an improvement in rated efficiency of the air conditioner and the refrigerator can be achieved.
[0043]
【The invention's effect】
As described above, according to the present invention, a virtual neutral point obtained from a resistor connected in parallel with a stator winding in a control apparatus for a permanent magnet motor that employs a PWM control method and controls a permanent magnet motor by inverter. A position detecting means for obtaining a difference voltage between the electric potential and the motor neutral point potential and obtaining a position detection signal of the third harmonic component by reducing other than the third harmonic component of the difference voltage signal; While switching the energization of the stator winding based on the position detection signal from the position detection means, the PWM energization pattern is switched from sine wave drive to rectangular wave drive according to the motor operation state. The rotor magnetic pole position can be detected from the rotation range to the high rotation range with a single position detection circuit, and the maximum motor speed and rated efficiency can be increased without increasing costs. .
[Brief description of the drawings]
FIG. 1 is a schematic block diagram showing a control device of the present invention.
FIG. 2 is a circuit diagram showing a position detection circuit of the control device.
FIG. 3 is a circuit diagram of a filter used in the position detection circuit.
FIG. 4 is a circuit diagram of a filter suitably used as the filter.
FIG. 5 is a circuit diagram of a filter suitably used as the filter.
FIG. 6 is a circuit diagram of a filter suitably used as the filter.
FIG. 7 is a circuit diagram of a filter suitably used as the filter.
FIG. 8 is a schematic graph illustrating the operation of the present invention.
FIG. 9 is a schematic graph illustrating the operation of the present invention.
FIG. 10 is a schematic block diagram showing a conventional motor control device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 DC power supply 2 Inverter circuit 3 Permanent magnet motor 10 Position detection circuit 10a Resistance bridge circuit 10b Capacitor (surge voltage suppression circuit)
10c Voltage follower circuit 10d Filter circuit 10e Comparator unit 11 Control circuit 20a Secondary band pass filters 20a, 21a, 22a, 22b Operational amplifier 21 Secondary high pass filter 22 Secondary low pass filter 23 Primary high pass filter 24 Primary primary Low pass filter

Claims (7)

In the control device of the permanent magnet motor that detects the magnetic pole position of the rotor without a sensor and switches the energization of the stator winding based on the position detection signal to control the rotation speed of the rotor.
A differential voltage signal between a virtual neutral point potential obtained through a resistor connected to each terminal of the stator winding and a neutral point potential of the stator winding is passed through a filter to obtain a signal other than the third harmonic component. A position detection means for outputting a position detection signal mainly including the third harmonic component,
A permanent magnet that controls energization switching timing of the stator winding based on a position detection signal from the position detection means and switches the PWM energization pattern from sinusoidal wave driving to rectangular wave driving according to an operating state. Electric motor control device. A sine wave drive method is adopted at the time of start-up and the rotation speed range until the PWM waveform modulation factor becomes 1, and a rectangular wave is used when the rotation rate is further increased when the PWM waveform modulation factor becomes 1. The control device for a permanent magnet motor according to claim 1, wherein the control method is switched to a drive system. Immediately after switching from the sine wave driving method to the rectangular wave driving method, driving is performed by 120 ° energization, and when the rotational speed is further increased, driving is performed by a predetermined energization angle and ignition phase. The control apparatus for the permanent magnet motor according to claim 2. 4. The control apparatus for a permanent magnet motor according to claim 1, wherein the filter is a secondary band pass filter or a band pass filter in which a secondary high pass filter and a secondary low pass filter are combined. . 4. The filter according to claim 1, wherein the filter includes at least one of a primary high-pass filter, a primary low-pass filter, a secondary high-pass filter, and a secondary low-pass filter. Permanent magnet motor control device. 6. The method according to any one of claims 1 to 5, wherein a predetermined energization angle and firing phase pattern is tabulated according to load conditions, or the pattern is obtained by an approximate expression, and the driving is performed under an optimum condition according to an operation mode. The control apparatus of the permanent magnet motor of description. The permanent magnet motor control device according to any one of claims 1 to 6, wherein the permanent magnet motor is used as a compressor motor or a fan motor of an air conditioner or an electric refrigerator.

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