JP2005137120A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller in which operation performance is enhanced. <P>SOLUTION: A motor controller comprises: a DC/AC converting means 6 for supplying a three-phase brushless DC motor 7 with an AC voltage produced by converting a DC voltage through a switching element based on a PWM signal; a means 1 for detecting the induction voltage of the brushless DC motor; a means 2 for detecting the pole position of the brushless DC motor from the induction voltage; a voltage control means 3 outputting a voltage waveform based on the pole position outputted from the pole position detecting means 2; a PWM control means 5 for converting the voltage waveform into a PWM signal; a means 8 for detecting a regenerated voltage included in the induction voltage; a means 41 for detecting an operation load torque; and a torque gain control means 40 for controlling the torque gain amount based on the number of regeneration detecting times and on the operation load torque at a specified period, and for delivering it to the voltage control means 3, which has a phase correction function of torque gain amount. <P>COPYRIGHT: (C)2005,JPO&NCIPI

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 30 ° mechanical angle, that is, every 60 ° electrical angle (see, for example, Patent Document 1).

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 the integration circuit is passed (see Patent Document 2 and 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. If this is the case, the induced voltage per phase can only be confirmed continuously for an electrical angle of 30 °, and the risk of step-out increases due to the effect of the inverter regenerative voltage even during normal operation, and unstable phenomena such as turbulence occur. There was a tendency to occur easily. 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 phase current 20 is set to the position of the induced voltage 10 and when the maximum rotation speed is increased, the phase current 20 needs to be advanced, but the limit is fast and the high-speed rotation performance is inferior.

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.

  The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a 180 ° sine wave with a position sensor by applying 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 a motor control device that achieves a high speed performance of the same level, further improves the step-out limit torque in any operating load region, and is inexpensive and highly reliable.

  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 the induced voltage of the motor, a magnetic pole position detecting means for detecting the magnetic pole position of the brushless DC motor from the induced voltage, and a voltage waveform based on the magnetic pole position output from the magnetic pole position detecting means. In a motor control device having a voltage control means for outputting and a PWM control means for converting the voltage waveform into the PWM signal, a regenerative voltage detection means for detecting a regenerative voltage included in the induced voltage, and the detected regenerative voltage A magnetic pole position detecting means for determining the magnetic pole position based on the voltage and the induced voltage; A torque gain having a load torque detecting means for detecting torque, and controlling a torque gain amount at predetermined intervals based on the number of times of regenerative detection of the regenerative voltage detecting means and the operating load torque, and outputting the torque gain to the voltage control means Control means, and the torque gain control means has a phase correction function of the torque gain amount.

  The predetermined period is set so as to be synchronized with the PWM modulation period.

  The predetermined period is set to a value equal to or less than a value obtained by dividing a time corresponding to one rotation period of the brushless DC motor by a product of (number of motor poles × number of motor phases).

  The torque gain control means has a function of advancing the torque gain amount and correcting the phase based on a predetermined condition.

  The torque gain control means has a function of reducing the torque gain amount when the number of regeneration detections increases.

  According to the first invention, it is possible to control the torque control amount according to the motor characteristics and the driving application while avoiding the step-out phenomenon due to the regenerative voltage, so that it is possible to construct a motor control device corresponding to a wide range of driving load characteristics. Therefore, even when a load with periodic and regular speed fluctuations (for example, a rotary compressor) is driven every few revolutions, the induced voltage zero-cross signal can be detected accurately, so that it is extremely unaffected by speed fluctuation effects and regenerative voltage effects. A stable speed control system can be constructed.

According to the second invention, since frequency jitter and instability during torque control can be eliminated as much as possible, the frequency control performance can be further improved, and there is no out-of-step, turbulence or instability, and high reliability, high performance, and high durability.・ A low-cost motor control device can be provided.

  According to the third aspect of the invention, torque control can be smoothly and stably converged, so that the frequency stability of the control device is improved and a motor control device with very little driving noise, driving vibration and driving heat is built. it can.

  According to the fourth aspect of the invention, the phase delay of the inverter output torque can be made as small as possible, so that the performance of torque control can be brought out to the limit, an extremely stable motor control system can be realized, and high vibration suppression capability has been realized. A motor control device can be provided.

  According to the fifth aspect of the present invention, there is no need to set an excessive torque control gain, so that there is no operational trouble such as step-out, turbulence or instability, and there is provided a motor control device having high reliability and high durability. Can be provided.

(Embodiment 1)
Embodiments of a motor control device according to the present invention will be described below 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 4 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. A voltage detection means 1; a magnetic pole position detection means 2 for detecting the magnetic pole position of the brushless DC motor from the induced voltage; a voltage control means 3 for outputting a voltage waveform based on the magnetic pole position output from the magnetic pole position detection means 2; PWM control means 5 for converting a voltage waveform into a PWM signal, regenerative voltage detection means 8 for detecting a regenerative voltage included in the induced voltage, and a magnetic pole position for determining a magnetic pole position based on the detected regenerative voltage and the induced voltage And detecting means 2. The load torque detection means 41 detects the magnitude of the load torque from the magnetic pole position output of the magnetic pole position detection means 2 and outputs it to the torque gain control means 40. The torque gain control means 40 generates a torque gain substantially similar to the detected load torque and outputs it to the voltage control means 3. The voltage control means 3 controls the voltage waveform amplitude and the conduction angle for operating the DC / AC conversion means 6 based on the torque gain.

  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 includes six switching elements (FIG. 2A) that open and close at high speed.

  First, the roles of the induced voltage detection means 1, the magnetic pole position detection means 2, the voltage control means 3, and the PWM control means 5 will be described sequentially in FIG. This part is the same as the operation of the control block diagram of the conventional motor control device of FIG.

  In FIG. 1, the induced voltage detection means 1 lowers the induced voltage of the BLM 7, the magnetic pole position detection means 2 detects the induced voltage zero cross signal, and outputs the induced voltage zero cross signal to the voltage control means 3 as the magnetic pole position. Based on the magnetic pole position, the voltage control means 3 calculates a voltage waveform for driving the BLM 7 and outputs it to the PWM control means 5. Based on the 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.

  As shown in FIG. 2 (a), the DC / AC converting means 6 has six switching elements. For the U-phase, V-phase, and W-phase, one switching element is provided in the upper arm and the lower arm is switched. One element is provided.

  In PTN1, the U-phase upper arm switching element Tu and the V-phase lower arm switching element Ty are energized.

  In PTN2, the U-phase upper arm switching element Tu and the W-phase lower arm switching element Tz are energized.

  In PTN3, the V-phase upper arm switching element Tv and the W-phase lower arm switching element Tz are energized.

  In PTN4, the V-phase upper arm switching element Tv and the U-phase lower arm switching element Tx are energized.

  In PTN5, the W-phase upper arm switching element Tw and the U-phase lower arm switching element Tx are energized.

  In PTN6, the W-phase upper arm switching element Tw and the V-phase lower arm switching element Ty are energized.

  The commutation switching of the PWM signal is performed based on the voltage waveform output of the voltage control means 3.

  The detailed operation of the magnetic pole position detecting means 2 will be described with reference to FIG. 2B and FIGS. The induced voltage zero cross signal of the BLM 7 is generated six times during one electrical angle cycle. FIG. 3A shows the induced voltage zero-cross signal per phase. FIG. 3A is a relationship diagram of the phase current waveform and the phase induced voltage waveform, and shows the induced voltage 10, the phase current 9, the 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 magnetic pole position detecting means 2 is the induced voltage 10a in FIG. 3B and the induced voltage 10b in FIG. 4B if the negative side of the DC voltage 4 is the GND potential N. This means that the line voltage of the BLM 7 is observed. If the induced voltage near the zero cross signal is considered, the waveform of the induced voltage 10 is superimposed on the PWM voltage component. . Basically, the intersection of the half of the DC voltage VDC (= VDC / 2) and the induced voltage 10a (10b), and further the conduction point of each of the upper and lower arm elements of the DC / AC converting means 6 is one. The positive zero cross signal 11 (reverse zero cross signal 12) can be detected during the arcing period (TON portion in FIGS. 3 and 4).

  The magnetic pole position detection means 2 detects the positive zero cross signal 11 and the reverse zero cross signal 12 in the figure, and outputs them to the voltage control means 3 as the magnetic pole position. Based on the zero cross signal, the voltage control means 3 calculates a voltage waveform substantially similar to the phase current 9, and the PWM control means 5 creates a PWM signal base PTN corresponding to each electrical angle based on the voltage waveform. To do. The electrical angles X1 to X2 in FIG. 3 and the electrical angles X3 to X4 in FIG. 4 are current cut sections. Further, the voltage control means 3 can create a voltage waveform of a 120 ° to 180 ° energization 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 (= current cut section). 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.

  The voltage waveform output by the voltage control means 3 is almost similar to that of the phase current 9, but the phase difference is somewhat advanced with respect to the phase current 9. In the present embodiment, for simplification, the phase difference is described as zero. That is, voltage waveform = phase current 9 is defined.

  FIG. 10 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. 2B is a field induced voltage waveform relationship diagram of the 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, the detailed operation of the regenerative voltage detection means 8 will be described with reference to FIGS. Generally, as a condition for generating the regenerative voltage, the regenerative voltage is generated continuously for a predetermined time from the moment when the phase current of the BLM 7 is cut, and then the original induced voltage is generated. The output of the induced voltage detection means 1 includes both the regenerative voltage and the induced voltage, and both need to be distinguished. If this determination is wrong, the regenerative voltage portion is erroneously detected as a zero-cross signal of the induced voltage, and abnormal phenomena such as turbulence and step-out occur.

FIG. 3B and FIG. 4B show the relationship between the regenerative voltage and the induced voltage. FIG. 3 shows a case where the time differential value is positive as the induced voltage 10, and FIG. 4 shows a case where the time differential value is negative as the induced voltage 10. In the figure, the regenerative voltage 13 and the regenerative voltage 14 are generated from the moment when the phase current 9 is cut and continue to the regenerative voltage end point 19 and the regenerative voltage end point 22. As one of the necessary conditions for determining the positive zero cross signal 11,
Induced voltage 10a ≧ VDC / 2
As one of the necessary conditions for determining the reverse zero cross signal 12,
Induced voltage 10b ≦ VDC / 2
There is. However, since the voltage value of the regenerative voltage 13 is VDC before the positive zero cross signal 11 is detected, the relationship of the above equation is already satisfied and erroneous detection occurs. In order to prevent this, in the position detection in the figure, if the position detection result is ignored before the regenerative voltage end point 19 and the position detection determination is started after the regenerative voltage end point 19, the regenerative voltage 13 is supplied to the positive zero cross signal 11. As a false positive.

  Similarly, in the case of the reverse zero cross signal 12, the voltage value of the regenerative voltage 14 is 0 V, which already satisfies the relationship of the above equation and erroneously detects. In order to prevent this, the determination of the position detection section in the figure is started after the regenerative voltage end point 22. Thus, the regenerative voltage detecting means 8 outputs the regenerative voltage end point 19 and the regenerative voltage end point 22 to the magnetic pole position detecting means 2 as a regeneration end signal, and the magnetic pole position detecting means 2 receives the regenerative voltage until receiving the signal. 13. Ignore position detection of regenerative voltage 14. If the signal is received, determination of position detection is started, so that the original positive zero cross signal 11 and reverse zero cross signal 12 can be determined.

The regenerative voltage detection means 8 has a VTH1 regenerative determination reference voltage 17 and a VTH2 regenerative determination reference voltage 18 inside, and makes a determination by comparing the value with the regenerative voltage 13 and the regenerative voltage 14. Specifically, VTH 1 regeneration judgment reference voltage 17 = regenerative voltage coefficient * VDC
VTH2 regeneration judgment reference voltage 18 = regenerative voltage coefficient * VDC
And
0 ≦ Regenerative voltage coefficient ≦ 1
It is a real number that satisfies The regenerative voltage coefficient may be set appropriately. The regenerative voltage detection means 8 samples the regenerative voltage 13 and the regenerative voltage 14. That is, the regeneration detection point 15 and the regeneration detection point 16. The regenerative voltage detection means 8 performs voltage sampling from the electrical angles X1 and X3, which are current cut start points, and obtains the voltage Vij between the regenerative detection point 15 and the regenerative detection point 16. This voltage Vij will be described with reference to FIG.

FIG. 5 illustrates the voltage sampling operation of the regenerative voltage detection means 8. T = 0 in the figure corresponds to the electrical angles X1 and X3 of the current cut start point. From T = 0, the regenerative voltage detection means 8 starts sampling the induced voltage of the induced voltage detection means 1 (which is still the regenerative voltage at this time), and the regenerative voltage end point 19 and the regenerative voltage end point 22 at which the regenerative voltage ends. Thus, a regeneration end signal is generated for the magnetic pole position detecting means 2. From T = 0, a Vij regeneration detection point 30 that is a regenerative voltage acquisition at time Tij31 intervals is acquired,
V0j, V1j, V2j, ..., Vij
The regenerative voltage is determined every time. Here, i and j are arbitrary natural numbers. When judging the regenerative voltage,
Vi = Σ (Vip) / (j + 1); p = 0 → j
And the regenerative voltage is determined by comparing Vi with VTH1 or VTH2. That is, in the case of FIG.
Vi ≧ VTH1
In the case of FIG.
Vi ≦ VTH2
If so, Vi is regarded as a regenerative voltage. While the above condition is satisfied, the magnetic pole position detecting means 2 ignores all the position detection results. When the above condition is not satisfied, the regenerative voltage detection means 8 sends a regeneration end signal to the magnetic pole position detection means 2, and the magnetic pole position detection means 2 receives the signal and performs position detection. Start judgment. The magnetic pole position detection means 2 obtains the positive zero cross signal 11 and the reverse zero cross signal 12 according to the conventional determination criterion described above when the regeneration end signal is received. When the position determination is finished, the current cut is finished at the electrical angle X2 after the elapse of the wait time in FIGS. 3 and 4, and phase commutation (switching of the base PTN) is performed.

Next, the operation of the load torque detection means 41 will be described. Consider a case where a load device of a motor control device has a certain periodic load torque fluctuation element. The load torque detection means 41 specifies the operation load torque of the BLM 7 based on the magnetic pole position of the magnetic pole position detection means 2. The magnetic pole position of the magnetic pole position detection means 2 is a zero cross signal input every 60 ° electrical angle. If the magnetic pole position input at every electrical angle of 60 ° is measured at time intervals, it will fluctuate at the same cycle as the operating load. If a rotation division section is taken every electrical angle 60 °, the section cycle is a time interval every electrical angle 60 °. The reciprocal of the adjacent time interval (= section speed) is taken, and the difference value (current speed-previous speed) represents the differential torque obtained by subtracting the driving load torque from the inverter output torque. The operation load torque of the BLM 7 is detected by integrating each time independently and converging the differential torque integral value for each divided section to zero. The load torque detecting means 41 outputs this differential torque integral value to the torque gain control means 40 as a load torque (= torque gain). This load torque is output every 60 ° electrical angle, and is output m0 per rotation of the BLM7. This time,
m0 = number of motor poles × number of motor phases. In a normal control system, the number of section divisions per rotation is set to at least m0 or more.

Next, the operation of the torque gain control means 40 will be described. The torque gain control means 40 determines a torque gain based on the load torque of the load torque detection means 41 and basically generates a torque gain 35 having a similar shape and the same phase as the detected load torque. Further, the torque gain control means 40 has a function of changing the torque gain 35 for each PWM cycle, and in this case, a torque gain waveform as shown in FIG. In this case, it is assumed that the PWM period is sufficiently smaller than the section time for each rotation division section. When the torque gain G for each rotation division section is a natural number satisfying G = G (m); m <m0, the torque gain for each PWM cycle works to interpolate G (m)
G = G (m, n * Tc); n is a natural number. Here, Tc is a PWM cycle, and n is a permutation number obtained by dividing each divided section by the PWM cycle. Moreover, the torque gain control means 40 can also perform a phase advance shift like the torque gain 36 of FIG.6 (b). In this figure, the phase near the torque gain maximum value is advanced by Δm 0 (positive real number) with respect to the torque gain 34. In this way, the delay of the voltage waveform output from the DC / AC conversion means 6 can be corrected, and an optimum voltage waveform can be supplied to the BLM 7.

  Further, the torque gain control unit 40 adjusts the torque gain based on the number of regeneration detections NRCV determined by the regenerative voltage detection unit 8 and outputs the torque gain to the voltage control unit 3. The voltage control means 3 increases or decreases the current amplitude (voltage amplitude) in FIGS. 3 and 4 based on the torque gain. Specifically, the amplitude is increased when the torque gain value is increased, and the amplitude is decreased when the torque gain value is decreased. The voltage control means 3 outputs the voltage waveform thus obtained to the PWM control means 5.

The regeneration detection frequency NRCV will be described. As described above, from T = 0 in FIG. 5, the regenerative voltage is taken at time Tij31 intervals, and the regenerative detection point 30Vij is acquired. And
V0j, V1j, V2j, ..., Vij
The regenerative voltage is determined every time. Here, i and j are arbitrary natural numbers. When judging the regenerative voltage,
Vi = Σ (Vip) / (j + 1); p = 0 → j
And the regenerative voltage is determined by comparing Vi with VTH1 or VTH2. That is, in the case of FIG.
If Vi ≧ VTH1, add +1 to NRCV. In the case of FIG.
If Vi ≦ VTH2, +1 is added to NRCV. Further, NRCV ≧ 0 is satisfied. Then, it switches to the next base pattern, and again at time T = 0 after the start of the current cut start angle,
NRCV = 0
It becomes. The initial value after power-on is also NRCV = 0. It is assumed that the torque gain is controlled using this regenerative detection number NRCV. Basically, if the NRCV increases, the time region of the regenerative voltage 13 increases when taking FIG. 3 as an example. Accordingly, the time interval between the regenerative voltage end point 19 and the positive zero cross signal 11 is shortened. Needless to say, the regenerative voltage end point 19 cannot be detected accurately and accurately unless the position is advanced in time with respect to the positive zero cross signal 11, and exhibits an unstable behavior. Further, if a stable motor control device is constructed, it is necessary to secure a time interval from the regenerative voltage end point 19 to the positive zero cross signal 11 to some extent. As a method for realizing this, if NRCV is increased, the torque gain is decreased, and it may be accelerated. Further, if NRCV is reduced, the torque gain may be increased and delayed. That is,
NRCV large → torque gain small NRCV small → torque gain large. If the torque gain is G and the torque gain correction amount is ΔG (≧ 0),
G = G (m) −ΔG (NRCV)
It is. Here, ΔG is the torque gain correction amount 37 shown in FIG. 7, and the number of regeneration detections NRCV is used as a parameter.

  With the motor control device configuration as described above, the induced voltage zero cross signal can be accurately detected even when a load (for example, a rotary compressor) with periodic and regular speed fluctuations is driven every rotation. A very stable speed control system can be constructed with little influence from fluctuations and regenerative voltage.

  The present embodiment has been described by taking a three-phase brushless DC motor as an example. However, the concept of application to a single-phase brushless DC motor is the same, and 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 within the scope.

  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 of the present invention (A) Circuit diagram showing configuration of DC / AC conversion means (b) Waveform diagram showing relationship of field induced voltage waveform of three-phase brushless DC motor Operation explanatory diagram of regenerative voltage detection means Operation explanatory diagram of regenerative voltage detection means Operation explanatory diagram of regenerative voltage detection means Operation explanatory diagram of torque gain control means Operation explanatory diagram of torque gain control means Control block diagram of a conventional motor control device Relationship diagram between conventional phase current waveform and induced voltage waveform Equivalent circuit diagram of three-phase brushless DC motor

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Induced voltage detection means 2 Magnetic pole position detection means 3 Voltage control means 4 DC voltage 5 PWM control means 6 DC alternating current conversion means 7 Brushless DC motor (BLM)
8 Regenerative voltage detection means 9 Phase current 10 Induced voltage 11 Positive zero cross signal 12 Reverse zero cross signal 13 Regenerative voltage 14 Regenerative voltage 15 Regeneration detection point 16 Regeneration detection point 17 Regeneration determination reference voltage 18 Regeneration determination reference voltage 19 Regeneration voltage end point 22 Regeneration voltage Voltage end point 20 phase current 21 phase current 30 regeneration detection point 31 regeneration detection time interval 34 torque gain 35 torque gain 36 torque gain 37 torque gain correction amount 40 torque gain control means 41 load torque detection means

Claims (5)

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; magnetic pole position detection means for detecting the magnetic pole position of the brushless DC motor from the induced voltage; voltage control means for outputting a voltage waveform based on the magnetic pole position output from the magnetic pole position detection means; In a motor control device having a PWM control means for converting a waveform into the PWM signal, based on the regenerative voltage detection means for detecting a regenerative voltage included in the induced voltage, the detected regenerative voltage and the induced voltage. Magnetic pole position detection means for determining the magnetic pole position, and load torque detection for detecting an operating load torque based on the magnetic pole position. And a torque gain control means for controlling the torque gain amount at predetermined intervals based on the number of times of regenerative detection of the regenerative voltage detection means and the operating load torque, and outputting the torque gain to the voltage control means. The torque control means has a torque gain amount phase correction function. The motor control device according to claim 1, wherein the predetermined period is set so as to be synchronized with the PWM modulation period. 3. The predetermined period is set to be equal to or less than a value obtained by dividing a time corresponding to one rotation period of a brushless DC motor by a product of (number of motor poles × number of motor phases). Motor control device. 4. The motor control device according to claim 1, wherein the torque gain control means has a function of advancing the torque gain amount and correcting the phase based on a predetermined condition. 5. The motor control device according to claim 1, wherein the torque gain control means has a function of decreasing the torque gain amount when the number of regeneration detections increases.

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