JP2004222366A - Motor control device - Google Patents

Abstract

A motor control device with improved high-speed operation performance is provided.
A DC / AC converter for supplying an AC voltage to a three-phase brushless DC motor, an induced voltage detector for detecting an induced voltage of the motor, a first voltage controller for outputting a first voltage waveform, Induced voltage selection means having PWM control means for converting the first voltage waveform into a PWM signal, selecting and outputting (6-n) pieces (defined as m) of magnetic pole position information in one electrical angle cycle, And a second voltage control means for outputting a second voltage waveform to the PWM control means based on the magnetic pole position selection information, wherein the second voltage control means comprises n number of non-selected magnetic pole position selection information. In the time domain, a predetermined second voltage waveform is output.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor control device that controls the frequency of a brushless DC motor.
[0002]
[Prior art]
Conventional motor control devices for controlling the number of revolutions of a brushless DC motor include a 120 ° conduction control method and a sine wave 180 ° conduction control method.
[0003]
In the 120 ° conduction method, there is a method of directly detecting a zero-cross signal of an induced voltage. In order to detect the signal, a comparison is made between an inverter phase voltage and a reference voltage. The commutation signal is changed based on the zero cross signal. This zero-cross signal is generated 12 times during one rotation of the motor, and is generated every mechanical angle of 30 °, that is, every electrical angle of 60 ° (for example, see Patent Document 1).
[0004]
In the 180 ° energization method, the difference voltage between the neutral point potential of the motor winding and the neutral point potential of the three-phase Y-connected resistor with respect to the three-phase inverter output voltage is amplified, and the amplified voltage is integrated into an integrating circuit. In some cases, a position detection signal corresponding to the induced voltage is obtained by comparing the output signal of the integration circuit with a low-pass signal obtained by processing the output signal by a filter circuit and cutting the direct current. This position detection signal is generated 12 times during one rotation of the motor, and is generated every mechanical angle of 30 °, that is, every electrical angle of 60 °. In this method, phase correction control is necessary because the signal passes through an integration circuit (for example, see Patent Documents 2 and 3).
[0005]
[Patent Document 1]
Japanese Patent No. 2642357
[Patent Document 2]
Japanese Patent Application Laid-Open No. 7-245982
[Patent Document 3]
JP-A-7-337079
[0006]
[Problems to be solved by the invention]
A conventional problem will be described.
[0007]
FIG. 5 is a control block diagram of a conventional motor control device. In this 120 ° energization method, the zero crossing of the induced voltage part is compared. Therefore, when the motor load suddenly changes or the power supply voltage suddenly changes, the zero crossing signal of the induced voltage is hidden in the inverter output voltage area, and the detection is performed. May not be possible. In such a state, a step-out phenomenon occurs first, and the inverter system stops. In addition, when the motor is driven at 120 °, the induced voltage per phase can be continuously confirmed at an electrical angle of 60 °. However, in order to reduce the noise and vibration during motor operation, the motor is operated at an energization angle set to about 150 °. In such a case, the induced voltage per phase can be continuously confirmed only for an electrical angle of 30 °, the risk of step-out increases even during normal operation, and unstable phenomena such as turbulence tend to occur easily. Was. In addition, this configuration has a problem that operation near 180 ° energization is impossible at first. FIG. 6A is a relationship diagram between the phase current waveform and the induced voltage waveform of the 120 ° conduction control. At the time of normal operation, the position is set to the position of the phase current 20 with respect to the induced voltage 10, and when the maximum rotation speed is increased, the angle is advanced to the position of the phase current 21. However, since it is difficult to advance the phase from the position of the phase current 21, the maximum rotation speed is also low, and there is a problem that the vehicle can be operated only in a limited speed range.
[0008]
FIG. 6B is a relationship diagram between the phase current waveform and the induced voltage waveform of the 180 ° conduction control. In the 180 ° energization method, since the zero-cross position of the induced voltage cannot be accurately grasped by an absolute value because it passes through an integration circuit, and the phase difference between the zero-cross position and the position detection signal greatly changes depending on the operation state. Complex control such as phase correction is required, making it difficult to adjust the phase correction and complicating the control calculation. Further, there is a problem that the motor requires a neutral point output terminal and cannot be used in a motor using a sine wave magnetized magnet because the third harmonic component of the induced voltage waveform is used.
[0009]
In addition, in the sensorless sine wave 180 ° energization drive control using the current feedback method, a calculation error increases because the magnetic pole position of the motor is estimated and calculated from the motor current and the motor electrical constant, and the limit point of the advance control of the motor current is increased. There was a problem that the maximum number of revolutions was far from the control with the position sensor. Also in the case of the 180 ° energization control, the phase current 22 is set at the position of the phase current 22 with respect to the induced voltage 10 during normal operation, and the phase angle is advanced in the direction of the phase current 23 when the maximum rotation speed is increased.
[0010]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a sine wave 180 ° energization with a position sensor with a new method of induced voltage feedback control that does not require a mechanical electromagnetic pickup sensor. It is an object of the present invention to provide an inexpensive and highly reliable motor control device that achieves the same level of high-speed performance.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a DC-AC converter that includes a switching element, converts a DC voltage into an AC voltage based on a PWM signal by opening and closing the switching element, and supplies the AC voltage to a three-phase brushless DC motor; Induced voltage detecting means for detecting an induced voltage of a DC motor, first voltage control means for outputting a first voltage waveform based on magnetic pole position information output from the induced voltage detecting means, and the first voltage In a motor control device having a PWM control means for converting a waveform into the PWM signal, (6-n) pieces (defined as m) of the magnetic pole position information are selected in one electrical angle cycle and magnetic pole position selection information is output. An induced voltage selection means, and a second voltage control means for outputting a second voltage waveform to the PWM control means based on the magnetic pole position selection information, The voltage control means is a time each n-number unselected area is characterized in that for outputting a predetermined second voltage waveform.
[0012]
Further, n is a natural number satisfying m ≧ 0.
[0013]
In addition, m is changed every one cycle of the electrical angle or at one or more cycles.
[0014]
Further, the induced voltage selecting means selects magnetic pole position information for one phase.
[0015]
In addition, a sine-wave-shaped second voltage waveform is output in the n non-selected time regions.
[0016]
Further, in the n non-selected time regions, a trapezoidal or arc-shaped second voltage waveform is output.
[0017]
The PWM control means selects the first voltage waveform when the brushless DC motor rotates at a low speed to a medium speed, and selects the second voltage waveform when the brushless DC motor rotates at a high speed.
[0018]
Further, the PWM control means selects the second voltage waveform at a rotational speed (fmin × 6 / m) or more, where fmin is the minimum operable rotational speed of the motor control device.
[0019]
Further, the second voltage control means is configured to advance a voltage phase of each of n time domains which are not selected from a voltage phase in each of m time domains of the magnetic pole position selection information by a predetermined value. Is output.
[0020]
Further, the induced voltage selection means converts the electric angle cycle of the three-phase brushless DC motor into magnetic angle position information and selects magnetic pole position information once every electric angle (number of magnet poles / 2) cycle.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
(Embodiment 1)
FIG. 1 is a control block diagram of the motor control device according to the first embodiment of the present invention. The motor control device according to the present embodiment is a motor control device that controls the rotation speed of the three-phase brushless DC motor 7. In FIG. 1, a motor control device converts a DC voltage 8 into an AC voltage, and outputs the DC voltage to an three-phase brushless DC motor (hereinafter abbreviated as BLM) 7. Voltage detection means 1, first voltage control means 3 for outputting a first voltage waveform based on magnetic pole position information output from induced voltage detection means 1, and PWM for converting the first voltage waveform into a PWM signal Control means 5, induced voltage selecting means 2 for selecting (6-n) pieces (defined as m) of magnetic pole position information in one electrical angle cycle and outputting magnetic pole position selection information, And a second voltage control means 4 for outputting the second voltage waveform to the PWM control means 5, wherein the second voltage control means 4 is not selected from the voltage phases in the respective m time domains of the magnetic pole position selection information. N time domains each Outputting a second voltage waveform and the voltage phase by a predetermined NeSusumu angle.
[0022]
The PWM control means 5 outputs a PWM signal for controlling the applied voltage, frequency and phase for controlling the rotation speed of the BLM 7. The DC / AC converter 6 is composed of six switching elements that open and close at a high speed.
[0023]
First, the roles of the induced voltage detecting means 1, the first voltage control means 3, and the PWM control means 5 in FIG. This part is the same as the operation of the control block diagram of the conventional motor control device in FIG.
[0024]
In FIG. 1, the induced voltage detecting means 1 lowers the induced voltage of the BLM 7, detects the zero cross signal, and outputs the zero cross signal to the first voltage control means 3 as magnetic pole position information. The first voltage control means 3 calculates a voltage waveform for driving the BLM 7 based on the magnetic pole position information, and outputs it to the PWM control means 5 as a first voltage waveform. The PWM control means 5 outputs a PWM signal to the DC / AC conversion means 6 based on the first voltage waveform.
[0025]
In the motor control device configured as described above, the rotation speed of the BLM 7 is controlled by changing the frequency and phase (hereinafter, referred to as “inverter frequency”) of the AC voltage output from the DC / AC converter 6. .
[0026]
In the case of 120 ° energization control, the PWM control means 5 outputs six types of PWM signals for opening and closing the switching elements of the DC / AC conversion means 6, and the switching elements are opened and closed by the six types of PWM signals. The inverter frequency output from the AC converter 6 is controlled.
[0027]
Six types of PWM signals will be described. The six PWM signals are pulse signals for driving the switching elements of the DC / AC converter 6. The PWM signal has six basic patterns PTN1 to PTN6 in one cycle of the inverter electrical angle, and the reciprocal of one cycle of the PWM signal is the inverter frequency.
[0028]
In fact, as a method for changing the rotation speed of the BLM 7, the PWM control unit 5 controls the rotation speed of the BLM 7 while changing the inverter frequency of the DC / AC conversion unit 6.
[0029]
The DC / AC converter 6 has six switching elements, and has one switching element on the upper arm and one switching element on the lower arm for each of the U, V, and W phases.
[0030]
In PTN1, the U-phase upper arm switching element and the V-phase lower arm switching element are energized.
[0031]
In PTN2, the U-phase upper arm switching element and the W-phase lower arm switching element are energized.
[0032]
In PTN3, the V-phase upper arm switching element and the W-phase lower arm switching element are energized.
[0033]
In PTN4, the V-phase upper arm switching element and the U-phase lower arm switching element are energized.
[0034]
In PTN5, the W-phase upper arm switching element and the U-phase lower arm switching element are energized.
[0035]
In the PTN 6, the W-phase upper arm switching element and the V-phase lower arm switching element are energized.
[0036]
The commutation switching of the PWM signal is performed based on the first voltage waveform output of the first voltage control means 3.
[0037]
The detailed operation of the induced voltage detecting means 1 will be described with reference to FIG. The induced voltage zero cross signal of the BLM 7 occurs six times in one cycle of the electrical angle. FIG. 3 shows the induced voltage zero cross signal per phase. FIG. 3A is a relationship diagram between the phase current waveform and the induced voltage waveform, and shows the induced voltage 10, the phase current 9, its positive zero-cross signal 11, and the reverse zero-cross signal 12. The positive zero cross signal 11 is generated at an electrical angle of 0 °, and the reverse zero cross signal 12 is generated at an electrical angle of 180 °. The induced voltage that can be actually observed by the induced voltage detecting means 1 is like the induced voltages 10a and 10b in FIG. 3B, and has a waveform in which the PWM voltage component is superimposed on the voltage waveform of the induced voltage 10. A positive zero crossing occurs when the half point of the DC voltage VDC (= VDC / 2) and the induced voltage 10a (10b) intersect, and the upper arm element and the lower arm element of the DC / AC converter 6 are each fired one by one. The signal 11 (the reverse zero-cross signal 12) can be detected.
[0038]
A positive zero cross signal 11 and a reverse zero cross signal 12 in the figure are detected, and the magnetic pole position information is output to the first voltage control means 3. The first voltage control means 3 calculates a first voltage waveform substantially similar to the phase current 9 on the basis of the zero-cross signal, and the PWM control means 5 calculates each electrical signal based on the information of the first voltage waveform. Create a base PTN of the PWM signal corresponding to the corner. The electric angles X1 to X2 and X3 to X4 are current cut sections.
[0039]
Further, the first voltage control means 3 can create a first voltage waveform having a 120 ° to 180 ° conduction waveform. However, in order to observe the induced voltage, the conduction angle needs to be less than 180 °. In consideration of the control stability of the motor control device, it is actually preferable to set the conduction angle to 150 ° or less.
[0040]
If the energization angle is greater than 120 °, a three-phase sine wave drive PWM signal is added in addition to the six PWM signals described in the 120 ° energization control. Basically, in a section where the current is turned off in any one of the three phases, the PWM signal for 120 ° conduction control is used. In a section in which phase currents flow in all three phases, a three-phase sine wave driving PWM signal is used. Since the PWM signal is a known technique as three-phase sine wave PWM control, a detailed description thereof is omitted here.
[0041]
Although the first voltage waveform is substantially similar to the phase current 9, the phase difference is actually slightly advanced with respect to the phase current 9. In the description of the present invention, the phase difference will be described as zero for simplification. That is, the phase current 9 is defined as the first voltage waveform.
[0042]
FIG. 7 is an equivalent circuit diagram of the BLM 7. R1 is the primary resistance of the winding, Lu, Lv, Lw is the inductance of each phase, and Eu, Ev, Ew is the field induced voltage of each phase. Here, the field induced voltage means an induced voltage generated only by the magnet (field) when the BLM 7 rotates. FIG. 4 is a diagram showing a field induced voltage waveform of the three-phase brushless DC motor. In the drawing, U1 represents the positive zero-cross position of Eu, and U2 represents the reverse zero-cross position. Similarly, other phases are also described, and the intervals between the zero cross positions are ideally generated every 60 ° and six times per one cycle of the electrical angle.
[0043]
The true magnetic pole position of the BLM 7 cannot be directly determined from the zero-cross signal of the induced voltage due to the effect of the armature reaction, and a phase difference occurs between the two. Further, since this phase difference depends on the operation load, it is difficult to identify the true magnetic pole position from the induced voltage zero cross signal. However, even if the true magnetic pole position cannot be specified, it is sufficiently possible to control the rotation speed of the BLM 7 only by the induced voltage zero cross signal, and it may be more desirable to control the BLM 7 by the induced voltage. In the present invention, description will be made on the assumption that the phase difference between the two is zero.
[0044]
That is, the true magnetic pole position = the induced voltage zero cross position. If the induced voltage 10 in FIG. 3A corresponds to the U phase,
Zero cross U1 = positive zero cross signal 11
Zero cross U2 = reverse zero cross signal 12
It is. However,
Eu ≠ induced voltage 10
It is. The above expression means that the voltage waveform amplitudes of the two are different.
[0045]
Next, the operation of the induced voltage selection means 2 and the second voltage control means 4 will be described. This part is a new control mechanism according to the present invention. The induced voltage selecting means 2 selects magnetic pole position information which is an output of the induced voltage detecting means 1. As the selection operation,
N is thinned out in one cycle of electrical angle ((6-n) (defined as m) is selected)
It is. Where n and m are
n ≧ 0 and m ≧ 0; n + m = 6
Is a natural number that satisfies The variable need not be a constant value, and may be changed every cycle or more. Alternatively, it may be changed even in a cycle shorter than one cycle. The selected magnetic pole position information is output to the second voltage control means 4 as magnetic pole position selection information.
[0046]
The second voltage control means 4 creates a second voltage waveform based on the magnetic pole position selection information. The operation of the PWM control means 5 on the basis of the second voltage waveform to calculate the PWM signal is equivalent to the method of creating a PWM signal from the first voltage waveform. Note that the PWM control means 5 selects the first voltage waveform or the second voltage waveform according to the operation state of the motor control device. The second voltage waveform will be described with reference to FIG.
[0047]
FIG. 2 is a diagram showing the relationship between the phase current waveform and the induced voltage waveform of the present embodiment.
[0048]
FIGS. 2A and 2B show a case where n = 4 (m = 2) is set and zero cross U1 and zero cross U2 are selected. Note that a combination of the zero cross V1 and the zero cross V2, or a combination of the zero cross W1 and the zero cross W2 may be used. Since the positive zero-cross signal 11 and the reverse zero-cross signal 12 are input as magnetic pole position selection information at every 180 °, the second voltage waveform can be formed like the phase current 9a based on this. In order to detect the positive zero-cross signal 11 and the reverse zero-cross signal 12, the current is set to zero in the sections X1 to X2 and X3 to X4. here,
−30 ° ≦ X1 ≦ 0 °, 0 ° ≦ X2 ≦ 30 °, 150 ° ≦ X3 ≦ 180 °,
180 ° ≦ X4 ≦ 210 °, 330 ° ≦ X5 ≦ 360 °
Is a real number that satisfies
[0049]
FIG. 2B shows a current waveform when X3 and X5 are set smaller (advance setting) than in FIG. 2A. Apparently, the phase current 9b is advanced with respect to the induced voltage 10, so that the rotation speed of the BLM 7 can be improved.
[0050]
FIGS. 2C to 2H show a case where n = 5 (m = 1) and the zero cross U1 is selected as the magnetic pole position selection information. In FIG. 2C, since there is no magnetic pole position selection information of the zero cross U2,
X3 = X4 = 180 °
It is what it was. In the electrical angle region excluding X1 to X2 and X5 to 360 °, since there is no magnetic pole position selection information, any second voltage waveform may be output, and an arbitrary waveform can be created. Since the zero cross U1 is detected every 360 electrical degrees, the second voltage waveform can be created based on this. FIG. 2C shows that the phase current 9c is sinusoidal in the time domain where there is no magnetic pole position selection information. In this way, partial sinusoidal drive becomes possible, and low-vibration and low-noise operation can be realized as compared with 120 ° energization and 150 ° wide-angle energization.
[0051]
FIG. 2 (d)
X2 ≦ X3 = X4 ≦ 180 °, 180 ° ≦ X5 ≦ 360 °
Since the phase current 9d is further advanced with respect to the induced voltage 10, higher speed performance can be improved. In this drawing, the phase current 9d1 is zero, but the current that flows through this portion is the phase current 9e in FIG. 2 (e). Since the current flows up to the electric angle X5 ', the high-speed performance can be further improved. In addition,
X5 ≦ X5 ′ ≦ 360 °
Meet.
[0052]
FIG. 9 (f)
X5 = X3 + 180 ° = X1 + 360 °, 0 ° ≦ X2 ≦ 30 °
Since the control parameters are reduced, the control calculation is simplified, and the second voltage control means 4 can be configured by a simple calculation.
[0053]
FIGS. 9 (g) and 9 (h) show the second voltage waveform output of the second voltage control means 4 so that the phase current 9g becomes trapezoidal and the phase current 9h becomes arc based on FIG. 9 (d). Is adjusted. Driving the motor with such a current waveform further increases the voltage applied to the BLM 7, so that the maximum rotation speed can be further increased.
[0054]
FIG. 9 (i)
n = 5 (m = 1); electrical angle 0 to 360
n = 6 (m = 0); electrical angle 360-720 °
Select zero cross U1
And the electrical angle is changed every one cycle.
[0055]
The phase current 9i can realize an arbitrary waveform over two cycles of the electrical angle. In particular, in the case of a sinusoidal waveform, lower vibration and lower noise operation can be achieved. In addition, in the case of a trapezoidal wave shape or an arc shape, the maximum rotation speed can be further improved. Note that the above settings of n and m are examples, and depending on the operation state of the motor control device, the electrical angle may be two or more cycles,
n = 6 (m = 0)
May be. Even when the rotation speed of the BLM 7 is suddenly changed due to a sudden accidental or inevitable disturbance, if n (or m) is controlled in real time (n is changed several times within one electrical angle cycle), the motor control is performed. Since n can be increased while ensuring sufficient control stability and responsiveness of the device, the degree of freedom of the second voltage waveform, which is the output of the second voltage control means 4, can be improved. A current waveform can be supplied to BLM7.
[0056]
In the above description, the description is based on the zero-cross signal (U1, U2, etc.) for one phase as the magnetic pole position selection information. The signal can be selected / non-selected as appropriate.
[0057]
If the PWM control means 5 selects the first voltage waveform during low to medium speed rotation of the BLM 7 and selects the second voltage waveform during high speed rotation, all the magnetic pole position information is used at low to medium speed. Stability is improved, and 120 ° energization control to 150 ° energization control with good driving efficiency can be utilized. In the high-speed range, the advanced angle control using the sine wave current, trapezoidal wave or arc current can be used, so that the high-speed performance is improved.
[0058]
Further, in the PWM control means 5, if the minimum operable rotation speed of the motor control device is fmin, the first voltage waveform is formed below the rotation speed (fmin × 6 / m), and the second voltage waveform is formed above the rotation speed. If it is set to select, the number of times of obtaining the zero cross signal per unit time can be secured to a predetermined value or more, so that the response speed of the control system can be sufficiently secured even after the voltage waveform switching, and the control switching can be performed smoothly.
[0059]
The induced voltage selection means 2 may output the magnetic pole position selection information in which the magnetic pole position information is selected once for each electric angle (number of magnet poles / 2) period in terms of the electric angle cycle of the BLM 7. As a result, the induced voltage zero-cross signal is detected once per rotation of the motor. Therefore, even when a load (for example, a rotary compressor) having a periodic and regular speed fluctuation is driven for each rotation, the constant speed is detected. -In the steady operation region, the motor rotation speed at the moment when the induced voltage zero cross signal is detected becomes substantially constant.
[0060]
In this case, the motor control device can construct a very stable speed control system which is hardly affected by the speed fluctuation.
[0061]
Although the first embodiment of the present invention has been described with reference to a three-phase brushless DC motor as an example, the concept of application to a single-phase brushless DC motor is the same, and the gist of the present invention is as follows. Modifications, additions, and deletions of the embodiments can be made as appropriate without departing from the concept.
[0062]
【The invention's effect】
According to the present invention, a DC / AC converting means including a switching element, converting a DC voltage into an AC voltage based on a PWM signal by opening and closing the switching element and supplying the AC voltage to a three-phase brushless DC motor, and an induced voltage of the brushless DC motor. Induced voltage detecting means for detecting, first voltage control means for outputting a first voltage waveform based on magnetic pole position information output from the induced voltage detecting means, and converting the first voltage waveform to the PWM signal. An induced voltage selecting means for selecting (6-n) pieces (defined as m) of said magnetic pole position information in one electrical angle cycle and outputting magnetic pole position selection information; And a second voltage control means for outputting a second voltage waveform to the PWM control means based on the magnetic pole position selection information, wherein the second voltage control means selects In this case, a predetermined second voltage waveform is output in each of the n time domains that are not performed, whereby the phase current waveform of the brushless DC motor can be set more freely than before, and the characteristics of the motor control device Optimal current waveform setting can be realized according to the application.
[0063]
According to the present invention, n is a natural number satisfying m ≧ 0. As a result, it is possible to select current lead angle control with a higher degree of freedom, and to achieve optimal control performance for motor characteristics, load characteristics, and voltage characteristics of the motor control device.
[0064]
Further, according to the present invention, m is changed at every one cycle of the electrical angle or at a cycle of one cycle or more, so that even if the load characteristic of the motor control device changes abruptly, it follows the load change. Thus, stable operation can be continued without step-out.
[0065]
Further, according to the present invention, the induced voltage selection means selects magnetic pole position information for one phase, and thereby, even if an inter-phase imbalance occurs in the motor electrical characteristics of the motor control device, the other causes. Since it is not affected by the phase, the fluctuation of the motor rotation speed is small and the operation can be extremely stable.
[0066]
Further, according to the present invention, a sine-wave-shaped second voltage waveform is output in the n non-selected time regions, whereby the current waveform can be changed to a partial sine wave, so that high-speed rotation can be achieved. Sometimes, the sound and vibration are reduced and smooth operation is possible.
[0067]
According to the present invention, a trapezoidal or arc-shaped second voltage waveform is output in the n non-selected time regions. As a result, the motor applied voltage increases as compared with the sinusoidal voltage, so that higher speed can be easily realized and the high speed performance can be further improved.
[0068]
Further, according to the present invention, the PWM control means selects the first voltage waveform when the brushless DC motor is rotating at low speed to medium speed, and selects the second voltage waveform when rotating at high speed. Thus, at low to medium speeds, the 120 ° energizing control to the 150 ° energizing control with good stability and driving efficiency can be selected, so that low input, low cost, and low heat generation of the motor control device can be achieved at the same time.
[0069]
Further, according to the present invention, the PWM control means selects the second voltage waveform at a rotation speed (fmin × 6 / m) or more, where fmin is a minimum operable rotation speed of the motor control device. is there. As a result, the response speed of the control system can be sufficiently ensured even after the waveform switching of the present invention, and the control switching can be performed smoothly, so that the motor having extremely high operation reliability without step-out, irregular tuning, abnormal vibration, and abnormal sound. A control device can be provided.
[0070]
Further, according to the present invention, the second voltage control means advances the voltage phases of each of the n time domains which are not selected from the voltage phase of each of the m time domains of the magnetic pole position selection information by a predetermined value. And outputs the second voltage waveform. As a result, the phase current waveform of the brushless DC motor can be advanced more than before, and higher-speed rotation than before can be realized.
[0071]
Further, according to the present invention, the induced voltage selecting means converts the electric angle cycle of the three-phase brushless DC motor into magnetic pole position information once every electric angle (number of magnet poles / 2) cycle. It is. As a result, the induced voltage zero-cross signal is detected once per rotation of the motor. Therefore, even when a load (for example, a rotary compressor) having periodic and regular speed fluctuations is driven for each rotation, constant-speed / steady-state operation is performed. In the region, the motor rotation speed at the moment when the induced voltage zero-cross signal is detected has a substantially constant value, so that a very stable speed control system can be constructed which is hardly affected by the speed fluctuation. For this reason, the advanced angle control value can be set larger in the high-speed operation region, and the high-speed control performance can be dramatically improved.
[Brief description of the drawings]
FIG. 1 is a control block diagram of a motor control device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a relationship between a phase current waveform and an induced voltage waveform according to the embodiment of the present invention.
FIG. 3 is a diagram illustrating the operation of an induced voltage detecting means.
FIG. 4 is a relationship diagram of a field induced voltage waveform of a three-phase brushless DC motor.
FIG. 5 is a control block diagram of a conventional motor control device.
FIG. 6 is a relationship diagram between a conventional phase current waveform and an induced voltage waveform.
FIG. 7 is an equivalent circuit diagram of a three-phase brushless DC motor.
[Explanation of symbols]
1 Induced voltage detection means
2 Induced voltage selection means
3 First voltage control means
4. Second voltage control means
5 PWM control means
6 DC / AC conversion means
7 Brushless DC motor (BLM)
8 DC voltage
9-phase current
10 Induced voltage
11 Positive zero cross signal
12 Reverse zero cross signal
20-phase current
21-phase current
22-phase current
23-phase current

Claims (10)

DC / AC converting means including a switching element, converting a DC voltage into an AC voltage based on a PWM signal by opening and closing the switching element, and supplying the AC voltage to a three-phase brushless DC motor; First voltage control means for outputting a first voltage waveform based on magnetic pole position information output from the induced voltage detection means, and PWM control means for converting the first voltage waveform into the PWM signal. An induced voltage selecting means for selecting (6-n) pieces (defined as m) of the magnetic pole position information in one electrical angle cycle and outputting the magnetic pole position selection information; Second voltage control means for outputting a second voltage waveform to the PWM control means on the basis of the second voltage control means, wherein each of the n second voltage control means is not selected. Motor control device and outputs a predetermined second voltage waveform in the time domain. 2. The motor control device according to claim 1, wherein n is a natural number satisfying m ≧ 0. 3. The motor control device according to claim 1, wherein m is changed every one cycle of the electrical angle or at least one cycle. 4. The motor control device according to claim 1, wherein the induced voltage selecting means selects magnetic pole position information for one phase. 5. The motor control device according to claim 1, wherein a sine-wave-shaped second voltage waveform is output in n non-selected time domains. 5. The motor control device according to claim 1, wherein a trapezoidal or arc-shaped second voltage waveform is output in n non-selected time domains. 7. The motor control device according to claim 1, wherein the PWM control means selects the first voltage waveform when the brushless DC motor is rotating at low speed to medium speed, and selects the second voltage waveform when rotating at high speed. . 8. The motor according to claim 7, wherein the PWM control means selects the second voltage waveform at a rotation speed (fmin × 6 / m) or more, where fmin is a minimum operable rotation speed of the motor control device. Control device. The second voltage control means outputs a second voltage waveform obtained by advancing a voltage phase in each of n time domains that are not selected from a voltage phase in each of the m time domains of the magnetic pole position selection information by a predetermined value. 9. The motor control device according to claim 1, wherein: 5. The motor according to claim 4, wherein the induced voltage selecting means converts magnetic pole position information once every electric angle (number of magnet poles / 2) cycles by converting into an electric angle cycle of the three-phase brushless DC motor. Control device.

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