JP2007014115A - Motor control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device with enhanced high-speed operation capability. <P>SOLUTION: The motor control device includes: direct current-to-alternating current conversion means for converting direct-current voltage into alternating-current voltage through a switching element and supplying it to a three-phase brushless DC motor; induced voltage detection means for detecting motor induced voltage; first voltage control means for outputting a first voltage waveform with a conduction angle of less than 180° based on its magnetic pole position; PWM control means for converting the first voltage waveform into a PWM signal; induced voltage selection means for selecting (6-n) magnetic pole positions in one period of electrical angle and outputs magnetic pole position selection information; and second voltage control means for outputting a second voltage waveform in arbitrary shape to the PWM control means based on magnetic pole position selection information. In unselected n time domains, the second voltage control means outputs a predetermined second voltage waveform. The motor control device further includes: phase angle setting means for controlling the phase angle of alternating-current voltage based on magnetic pole position and magnetic pole position selection information; and pulsating voltage detection means for detecting pulsating voltage in direct-current voltage. The phase angle setting means controls the phase angle of alternating-current voltage based on this pulsating voltage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a motor control device that controls the frequency of a brushless DC motor.

  Conventionally, there are a 120 ° energization control method and a sine wave 180 ° energization control as motor control devices for controlling the rotational speed of a brushless DC motor.

  The 120 ° energization method is a method of directly detecting the zero-cross signal of the induced voltage, and is obtained by comparing the inverter phase voltage with the reference voltage in order to detect it. The commutation signal is changed based on this zero cross signal. This zero cross signal is generated 12 times during one rotation of the motor, and is generated every mechanical angle 30 °, that is, every electrical angle 60 ° (see Patent Documents 1 and 2).

The 180 ° energization method amplifies the differential voltage between the neutral point potential of the motor winding and the neutral point potential of the three-phase Y-connected resistor to the three-phase inverter output voltage, and inputs it to the integration circuit The position detection signal corresponding to the induced voltage is obtained by comparing the output signal of the integration circuit with the low-pass signal obtained by processing the output signal with 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 30 ° mechanical angle, that is, every 60 ° electrical angle. In this method, phase correction control is required because an integration circuit is passed (see Patent Document 3).
Japanese Patent No. 2642357 JP 7-245982 A Japanese Patent Laid-Open No. 7-337079

  Problems in the conventional configuration will be described.

  FIG. 8 is a control block diagram of a conventional motor control device. Since this 120 ° energization method compares the zero crossing of the induced voltage part, if the motor load sudden change or the power supply voltage sudden change occurs, the induced voltage zero crossing signal will be hidden in the inverter output voltage region and detected. It may not be possible. In such a state, first, a step-out phenomenon occurs and the inverter system stops. In addition, at 120 ° energization, the induced voltage per phase can be confirmed continuously for 60 ° electrical angle, but in order to reduce the noise and vibration during motor operation, the energization angle is set to about 150 ° for operation. As a result, the induced voltage per phase can only be confirmed continuously for an electrical angle of 30 °, the risk of stepping out during normal operation increases, and unstable phenomena such as turbulence tend to occur. It was. Further, this configuration has a problem that an operation close to 180 ° energization is impossible. FIG. 9A is a relationship diagram between the phase current waveform and the induced voltage waveform of 120 ° energization control. During normal operation, the position is set at the position of the phase current 20 with respect to the induced voltage 10, and the angle is advanced to the position of the phase current 21 when the maximum rotational speed is increased. However, since it is difficult to advance the position from the position of the phase current 21, there is a problem that the maximum number of revolutions is lowered and the driving can be performed only in a limited speed range.

FIG. 9B is a relationship diagram between the phase current waveform and the induced voltage waveform in the 180 ° energization control. Since the 180 ° energization method passes through the integration circuit, the zero cross position of the induced voltage cannot be accurately grasped with an absolute value, and the phase difference between the zero cross position and the position detection signal varies greatly depending on the operating state. Complicated control such as phase correction is required, and the phase correction adjustment is difficult, and the control calculation is complicated. Further, the motor requires a neutral point output terminal, and uses the third harmonic component of the induced voltage waveform, and therefore has a problem that it cannot be used in a motor using a sine wave magnetized magnet.

  In addition, in the sensorless sine wave 180 ° energization drive control by the current feedback method, the motor magnetic pole position is estimated and calculated by the motor current and the motor electrical constant, so the calculation error becomes large, and the limit point of the motor current advance control is There was a problem that the maximum number of rotations was not far from control with a position sensor. Also in the case of 180 ° energization control, the phase current 22 is set to the position of the induced voltage 10 during normal operation, and the phase current 23 is advanced to increase the maximum rotational speed.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to apply a 180 ° sine wave with a position sensor by a new method of induced voltage feedback control that does not require a mechanical electromagnetic pickup sensor. An object of the present invention is to provide an inexpensive and highly reliable motor control device that achieves high speed performance at the same level.

The motor control device according to the present invention includes a plurality of switching elements, a DC / AC conversion means that converts a DC voltage into an AC voltage based on a PWM signal by opening and closing the switching elements and supplies the AC voltage to a three-phase brushless DC motor, and the brushless DC An induced voltage detecting means for detecting an induced voltage of the motor, and a first voltage waveform for outputting a first voltage waveform having an energization angle of less than 180 ° based on six magnetic pole positions output from the induced voltage detecting means in one electrical angle cycle. In the motor control device having the voltage control means and the PWM control means for converting the first voltage waveform into the PWM signal,
Inductive voltage selection means that operates within a predetermined frequency region and selects the magnetic pole positions in one cycle of electrical angle (6-n (defined as m ≧ 0)) and outputs magnetic pole position selection, and magnetic pole position selection Second voltage control means for outputting a second voltage waveform of an arbitrary shape to the PWM control means based on the second voltage control means, and the second voltage control means is a predetermined second in each of n time regions that are not selected. The voltage waveform is output, and either the first voltage control means or the second voltage control means is operated by authenticity determination within the predetermined frequency region, and the magnetic pole position and the magnetic pole position selection are performed. A phase angle setting means for controlling a phase angle of the AC voltage based on the pulsating voltage detection means for detecting a pulsating voltage of the DC voltage, and the phase angle setting based on the pulsating voltage from the pulsating voltage detection means. The means is the phase angle of the AC voltage Control to.

  The pulsation voltage detection means is constituted by a low-pass filter group having a predetermined cut frequency calculated in advance from the voltage pulsation frequency of the DC voltage.

  The pulsating voltage is derived from the difference between the DC voltage and the output voltage of the low-pass filter group.

  Further, the phase angle of the AC voltage is controlled according to the pulsation voltage every 60 ° electrical angle section. When the pulsation voltage> 0, the phase angle is retarded, and when the pulsation voltage <0, the phase angle is increased. Advance.

  The phase angle of the AC voltage is given by a linear function expression of the pulsating voltage.

  Further, the linear coefficient or constant of the above linear function formula is individually set for each 60 ° electrical angle section.

  The first order coefficient is set to a monotonically increasing function with respect to the electrical angle.

  According to the motor control device of the present invention, the phase angle of the armature current flowing through the brushless DC motor can be freely controlled, so that the driving performance, driving characteristics, and high-speed performance corresponding to the driving application can be extracted.

  In addition, since the pulsation component of the DC voltage is taken into consideration, the motor control system can be stably constructed, and the motor current waveform can be further smoothed, and the operation sound and resonance sound of the motor control device can be suppressed as much as possible.

  In addition, the zero cross signal of the induced voltage can be accurately and reliably detected, so that extremely high control stability can be secured, and the motor control device has excellent operational reliability with no step-out, turbulence, abnormal vibration, or abnormal noise. Can be provided at low cost.

In addition, since the current waveform applying the phase angle change is supplied, the motor vibration component is dispersed, and a motor control device that balances low vibration, low noise, low heat generation, and low input in a high dimension can be constructed.

(Embodiment 1)
Hereinafter, embodiments of a motor control device according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a control block diagram of the motor control device of the present embodiment. The motor control device of the present embodiment is a motor control device that controls the rotation speed of the three-phase brushless DC motor 7. In this figure, the motor control device converts a DC voltage 8 into an AC voltage and outputs it to a three-phase brushless DC motor (hereinafter abbreviated as BLM) 7 and an induction for detecting an induced voltage of the BLM 7. Voltage detection means 1, first voltage control means 3 that outputs a first voltage waveform based on the magnetic pole position output from the induced voltage detection means 1, and PWM control that converts the first voltage waveform into a PWM signal Means 5; induced voltage selecting means 2 for selecting magnetic pole positions (6-n (defined as m)) for one electrical angle period and outputting magnetic pole position selection; and second voltage based on magnetic pole position selection. A second voltage control means 4 for outputting a waveform to the PWM control means 5, and the second voltage control means 4 is selected for each of n number of magnetic pole positions that are not selected from the voltage phase in each of the m time domains. Predetermined voltage phase in time domain Outputting a second voltage waveform is angularly.

  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 converting means 6 comprises six switching elements that open and close at high speed.

  First, the roles of the induced voltage detection means 1, the first voltage control means 3, and the PWM control means 5 will be described sequentially in FIG. This portion is the same as the operation of the control block diagram of the conventional motor control device in FIG.

  In FIG. 1, the induced voltage detection means 1 drops the induced voltage of the BLM 7, detects the zero cross signal, and outputs the zero cross signal as the magnetic pole position to the first voltage control means 3. Based on the magnetic pole position, the first voltage control means 3 calculates a voltage waveform for driving the BLM 7 and outputs it to the PWM control means 5 as a first voltage waveform. Based on the first voltage waveform, the PWM control means 5 outputs a PWM signal to the DC / AC conversion means 6. In the motor control apparatus 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 conversion means 6. .

  In the case of 120 ° energization control, the PWM control unit 5 outputs six types of PWM signals for opening and closing the switching elements of the DC / AC conversion unit 6, and the switching elements are opened and closed by the six types of PWM signals. The inverter frequency output from the AC conversion means 6 is controlled.

  Six kinds of PWM signals will be described. The six types of 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.

  Actually, the method for changing the rotation speed of the BLM 7 is that the PWM control means 5 controls the rotation speed of the BLM 7 while changing the inverter frequency of the DC / AC conversion means 6.

  The DC / AC converting means 6 has six switching elements, and includes one switching element on the upper arm and one switching element on the lower arm for the U phase, the V phase, and the W phase, respectively.

  In PTN1, the U-phase upper arm switching element and the V-phase lower arm switching element are energized. In PTN2, the U-phase upper arm switching element and the W-phase lower arm switching element are energized. In PTN3, the V-phase upper arm switching element and the W-phase lower arm switching element are energized.

  In PTN4, the V-phase upper arm switching element and the U-phase lower arm switching element are energized. In PTN5, the W-phase upper arm switching element and the U-phase lower arm switching element are energized. In PTN6, the W-phase upper arm switching element and the V-phase lower arm switching element are energized.

  The commutation switching of the PWM signal is performed based on the first voltage waveform output of the first voltage control means 3. The detailed operation of the induced voltage detection means 1 will be described with reference to the operation explanatory diagram of the induced voltage detection means of FIG. The induced voltage zero cross signal of the BLM 7 is generated six times during one electrical angle cycle. FIG. 3 describes 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 detection means 1 is the induced voltages 10a and 10b in FIGS. 3A and 3B if the negative side of the DC voltage 8 is the GND potential N. This means that the line voltage of the BLM 7 is observed. If the induced voltage in the vicinity of the zero cross signal is considered, a waveform in which the PWM voltage component is superimposed on the voltage waveform of the induced voltage 10 is obtained. Basically, the intersection of the induced voltage 10a (10b) which is half of the DC voltage 8VDC (= VDC / 2) and the conduction point of the upper arm element and the lower arm element of the DC / AC conversion means 6 one by one. The positive zero-cross signal 11 (reverse zero-cross signal 12) can be detected during the arcing period (TON portion in FIG. 3).

The induced voltage detection means 1 detects the positive zero cross signal 11 and the reverse zero cross signal 12 in the figure, and outputs them to the first voltage control means 3 as magnetic pole positions. Based on the zero-cross signal, the first voltage control means 3 calculates a first voltage waveform that is substantially similar to the phase current 9, and the PWM control means 5 calculates each electrical voltage based on the information on the first voltage waveform. A base PTN of the PWM signal corresponding to the corner is created. Electrical angles X1 to X2 and X3 to X4 are current cut sections. 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, it is necessary to make the conduction angle less than 180 °.

  When the conduction angle> 120 °, in addition to the six PWM signals described in the 120 ° conduction control, a three-phase sine wave drive PWM signal is added. Basically, a PWM signal for 120 ° energization control is used in a section where the current is OFF in any one of the three phases. In the section where the phase current flows in all three phases, the PWM signal for three-phase sine wave drive is used. Since this PWM signal is already known as three-phase sine wave PWM control, detailed description thereof is omitted here.

  Although the first voltage waveform is almost 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 text, for the sake of simplicity, the phase difference is assumed to be zero. That is, the phase current 9 is defined as the first voltage waveform.

  FIG. 7 is an equivalent circuit diagram of the BLM7. 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 a magnet (field) when the BLM 7 rotates in a non-energized state. FIG. 4 is a field induced voltage waveform relationship diagram of a three-phase brushless DC motor. In the figure, U1 represents the positive zero cross position of Eu, and U2 represents the reverse zero cross position. Similarly, the other phases are also shown, and the interval between the zero cross positions is ideally generated 6 times every 60 ° and one cycle of the electrical angle. These zero-cross positions are named as the true magnetic pole positions of the BLM7.

The true magnetic pole position of the BLM 7 cannot be determined directly from the zero cross signal of the induced voltage 10 due to the influence of the armature reaction, and a phase difference occurs between the two. Further, since this phase difference depends on the operating load, it is difficult to specify 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 preferable to control by the induced voltage. In the present embodiment, description will be made assuming that the phase difference between the two is zero. That is,
True magnetic pole position = induced voltage zero cross position. That is, 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. In addition,
Eu ≠ induced voltage 10
It is. The above equation is generated because the voltage waveform amplitudes of both are different due to the influence of the armature reaction.

Next, operations of the induced voltage selection unit 2 and the second voltage control unit 4 will be described. This part is a new control mechanism according to the present invention. The induced voltage selection means 2 selects the magnetic pole position that is the output of the induced voltage detection means 1. As the selection operation,
Thinning out n pieces in one cycle of electrical angle (select (6-n) (= m) pieces)
It is. Where n and m are
n ≧ 0 and m ≧ 0; n + m = 6
It is a natural number that satisfies Note that the variable need not be a constant value, and may be changed every cycle or more. Alternatively, it may be changed even with a period of less than one period. The selected magnetic pole position is output to the second voltage control means 4 as a magnetic pole position selection.

The second voltage control means 4 creates a second voltage waveform having an arbitrary shape based on the magnetic pole position selection. Based on the second voltage waveform, the PWM control means 5 calculates the PWM signal in the same way as creating a PWM signal from the first voltage waveform. The PWM control means 5 selects the first voltage waveform or the second voltage waveform according to the operating state of the motor control device. The second voltage waveform will be described with reference to FIG. 2 showing the relationship between the phase current waveform and the induced voltage waveform of the present embodiment.

FIGS. 2A and 2B show the case where n = 4 (m = 2) is set and the zero cross U1 and the zero cross U2 are selected. A combination of zero cross V1 and zero cross V2, or zero cross W1 and zero cross W2 may be used. Since the positive zero cross signal 11 and the reverse zero cross signal 12 are inputted as magnetic pole position selections every 180 °, the second voltage waveform can be made 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, currents are 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 °
It is a real number satisfying 330 ° ≦ X5 ≦ 360 °.

FIG. 2B shows current waveforms when X3 and X5 are set smaller (advance angle setting) than FIG. 2A. The phase current 9b apparently advances with respect to the induced voltage 10, and the rotational speed of the BLM 7 can be improved. Note that the above settings of n and m are an example, and over two cycles of electrical angle depending on the operating state of the motor control device,
n = 6 (m = 0)
But you can. In addition, even if the rotational speed of the BLM7 changes suddenly due to sudden accidental or inevitable disturbance, motor control is possible if n (or m) is controlled in real time (n changes several times within one electrical angle cycle). Since n can be made large while sufficiently ensuring the control stability and responsiveness of the apparatus, the degree of freedom of the waveform 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 the BLM 7.

  Next, the operation of the pulsating voltage detection means 32 will be described with reference to FIG. The pulsation voltage detection means 32 is configured by a low-pass filter group having a predetermined cut frequency calculated in advance from the voltage pulsation frequency of the DC voltage 8. When the DC voltage waveform 33 is input to the pulsation voltage detection means 32, a DC average voltage waveform 34 is first generated. Then, the pulsation voltage waveform 35 is obtained by performing the following calculation.

Pulsating voltage waveform 35 = DC voltage waveform 33-DC average voltage waveform 34
The pulsating voltage waveform 35 thus obtained is output to the phase angle setting means 14.

Next, the operation of the phase angle setting means 14 will be described with reference to FIG. The phase angle setting means 14 has an equal or different phase angle for each electrical angle 60 ° × integer multiple, and outputs the phase angle to the second voltage control means 4 for each electrical angle. The phase angle setting means 14 defines the maximum and minimum values of the phase angles, and can also set different maximum and minimum values for each electrical angle of 60 ° × integer multiple. The phase angle setting unit 14 outputs the phase angle for each electricity corresponding to the induced voltage zero cross signal to the second voltage control unit 4 based on the induced voltage zero cross signal of the induced voltage detection unit 1. Further, based on the magnetic pole position selection output of the induced voltage selection means 2, a phase angle corresponding to the magnetic pole position selection is set, and the phase angle value is output to the second voltage control means 4. These image diagrams are shown in FIG. FIG. 5 shows the operation of the phase angle setting means 14, and the phase angle set by the phase angle setting means 14 is set for each electrical angle corresponding to the zero cross signal output from the induced voltage detection means 1. To express. If the phase angle value is increased, the armature current of the brushless DC motor 7 advances to the induced voltage, and this state is defined as the current advance angle (advance angle). Conversely, if the phase angle value is decreased, a lag phase is obtained and a current delay angle (retard angle). The phase angle 15 corresponding to each electrical angle is determined in the induced voltage selection means 2 by
n = 5, m = 1
If the phase angle setting number in the phase angle setting means 14 is n0,
n0 = 6
It is what. A section is divided for each electrical angle corresponding to each zero-cross signal, and a phase angle 15φi is defined for each rotation section i (natural number satisfying 0 ≦ i ≦ 5 in this figure). As shown in the figure, φi is
U phase current 16, V phase current 17, W phase current 18
The phase angle is determined. The phase angle here represents the phase angle with respect to the induced voltage zero-cross signal. In this figure, the setting of the induced voltage selection means 2 is
An example is shown in which an induced voltage zero cross signal is selected for each electrical angle of 360 ° * natural number.

The phase angle setting unit 14 individually sets an initial phase angle constant as indicated by the phase angle 13φi ′, and performs a predetermined calculation based on the pulsation voltage waveform 35 that is the output of the pulsation voltage detection unit 32. The phase angle 15φi is set again. here,
Pulsating voltage ΔV = Pulsating voltage waveform 35
Then, the equation is as follows.

φi = φi′−Ki · ΔV: Ki is a variable constant (≧ 0)
Therefore, the phase angle φi ′ is retarded when the pulsating voltage ΔV> 0, and the phase angle φi ′ is advanced when the pulsating voltage ΔV <0. In other words, the electrical characteristics of a general brushless DC motor are applied. Increasing (advancing) the phase angle has the same effect as increasing the voltage value supplied to the brushless DC motor. Therefore, in order to suppress the torque fluctuation due to the pulsating voltage ΔV, the phase angle φi may be controlled as in the above equation. If Ki is appropriately set in the above equation, the torque fluctuation of BLM7 due to pulsation voltage waveform 35 can be offset, and a motor control device that can greatly contribute to low vibration, low noise, high efficiency, and low cost. Can be built.

The second voltage control means 4 has a sinusoidal internal current command and is made based on the magnetic pole position selection information from the induced voltage selection means 2. This is shown in FIGS. 2 (c) and 2 (d). In the figure, the internal current command 9 d advances the phase angle with respect to the induced voltage 10. That is, if the zero point electrical angle of the internal current command 9d is X1, X3, X5
X1 <0 °, X3 <180 °, and X5 <360 °. The second voltage control means 4 performs voltage control so that the phase current 9c follows the internal current command 9d. Since FIG. 2C corresponds to the U phase, the current selection unit 32 selects the current detection unit 30 and outputs current information to the second voltage control unit 4. This figure describes a case where the phase current 9c is cut at the electrical angle X1, and the phase current 9c is controlled to follow the internal current command 9d at the electrical angle of 0 °.

FIG. 2D is an example when the current frequency of the internal current command 9f is changed during one electrical angle cycle. Specifically, if the average frequency of the internal current command 9f is f9f and the frequency at the electrical angle X is f (X),
f (X) ≧ f9f; 0 ≦ X ≦ X5
f (X) ≦ f9f; X5 <X <360
It is. In this way, the phase current 9e in the vicinity of X> 0 becomes smoother while the phase angle advance effect similar to that shown in FIG. I think it is possible. However, the internal current command 9d in FIG. 2 (c) only advances the phase angle fixedly, whereas the internal current command 9f needs to change the frequency dynamically. FIG. 2C may be useful as a total, and an internal current command system that is optimal for the motor control system may be selected or newly created.

  In the above description, the magnetic pole position selection of the induced voltage selection means 2 is a description based on the zero-cross signal (U1) for one phase. Of course, any zero-cross signal over two to three phases may be selected. The zero cross signal can be selected / deselected as appropriate.

  If the PWM control means 5 selects the first voltage waveform during the low-speed to medium-speed rotation of the BLM 7 and selects the second voltage waveform during the high-speed rotation, all the magnetic pole positions are used at the low and medium speeds. 120 ° energization control to 150 ° energization control with improved driving efficiency and good driving efficiency can be utilized. In the high-speed range, advance angle control using sinusoidal current, trapezoidal wave, or arc-shaped current can be used, so high-speed performance improves.

  The induced voltage selection unit 2 may output a magnetic pole position selection in which the magnetic pole position is selected once every electrical angle (number of magnet poles / 2) in terms of the electrical angle period 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) with periodic and regular speed fluctuations is driven every rotation, a 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 takes a substantially constant value. In this case, the motor control device is hardly affected by the speed fluctuation and can construct a very stable speed control system.

  Although the present embodiment has been described by taking a three-phase brushless DC motor as an example, the concept is the same for application to a single-phase brushless DC motor, and the scope does not depart from the spirit, concept, and claims of the present invention. Of course, it is possible to change, add, or delete the embodiment as appropriate.

  The motor control device according to the present invention can be applied to applications such as an inverter air conditioner and a general-purpose inverter device because a brushless DC motor can be operated at high speed with less noise and vibration.

Control block diagram of motor control apparatus in Embodiment 1 of the present invention Relationship diagram between phase current waveform and induced voltage waveform in Embodiment 1 of the present invention Operation explanatory diagram of the induced voltage detection means in Embodiment 1 of the present invention Field induced voltage waveform relationship diagram of three-phase brushless DC motor in Embodiment 1 of the present invention Operational explanatory diagram of phase angle setting means in Embodiment 1 of the present invention Operation explanatory diagram of the pulsation voltage detection means in the first embodiment of the present invention. Equivalent circuit diagram of three-phase brushless DC motor common to the present invention and the prior art Control block diagram of a conventional motor control device Relationship diagram between conventional phase current waveform and induced voltage waveform

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Induced voltage detection means 2 Induced voltage selection means 3 1st voltage control means 4 2nd 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 13 phase angle 14 phase angle setting means 15 phase angle 16 U phase current 17 V phase current 18 W phase current 20 phase current 21 phase current 22 phase current 23 Phase current 32 Pulsating voltage detection means 33 DC voltage waveform 34 DC average voltage waveform 35 Pulsating voltage waveform

Claims (7)

DC-AC conversion means that includes a plurality of switching elements, 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, and an induced voltage for detecting the induced voltage of the brushless DC motor Detection means; first voltage control means for outputting a first voltage waveform with a conduction angle of less than 180 ° based on the magnetic pole positions output from the induced voltage detection means in six periods of electrical angle; and In a motor control device having a PWM control means for converting the voltage waveform into the PWM signal,
Inductive voltage selection means that operates within a predetermined frequency range and selects (6-n) magnetic pole positions (n is a natural number of 0 or more) for one electrical angle period, and outputs magnetic pole position selection. Second voltage control means for outputting a second voltage waveform of an arbitrary shape to the PWM control means based on the second voltage control means, and the second voltage control means is a predetermined second in each of n time regions that are not selected. The voltage waveform is output, and either the first voltage control means or the second voltage control means is operated by authenticity determination within the predetermined frequency region, and the magnetic pole position and the magnetic pole position selection are performed. A phase angle setting means for controlling a phase angle of the AC voltage based on the pulsating voltage detection means for detecting a pulsating voltage of the DC voltage, and the phase angle setting based on the pulsating voltage from the pulsating voltage detection means. The means is the level of the AC voltage. Motor control device and controls the corners. 2. The motor control apparatus according to claim 1, wherein the pulsation voltage detection means is constituted by a low-pass filter group having a predetermined cut frequency calculated in advance from the voltage pulsation frequency of the DC voltage. 3. The motor control device according to claim 2, wherein the pulsating voltage is derived from a difference between the DC voltage and an output voltage of the low-pass filter group. The phase angle of the AC voltage is controlled in accordance with the pulsation voltage every 60 ° electrical angle section. When the pulsation voltage> 0, the phase angle is retarded, and when the pulsation voltage <0, the phase angle is advanced. The motor control device according to claim 1, wherein 5. The motor control device according to claim 4, wherein the phase angle of the AC voltage is given by a linear function expression of a pulsating voltage. 6. The motor control device according to claim 5, wherein the linear coefficient or constant of the linear function equation is individually set for each 60 [deg.] Electrical angle section. 7. The motor control device according to claim 6, wherein the linear coefficient is set to a monotonically increasing function with respect to the electrical angle.

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