JP2677686B2 - Drive device for brushless motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a drive device for a brushless motor using an inverter circuit.

(Prior Art) In a brushless motor, the relative position of the stator winding and the permanent magnet type rotor is determined by the terminal voltage including the induced voltage generated in the stator winding without using a position detecting element such as a Hall element. The method of detecting by utilizing is becoming popular.

This conventional example is shown in FIG. That is, 1 is a DC power supply, 2
Is an inverter circuit for energizing the stator windings 3U, 3V and 3W of the brushless motor 3, and 4, 5 and 6 are stator windings 3U,
Terminal voltage UV, VV and WV including induced voltage generated at 3V and 3W
, 90 is a filter circuit for shifting the phase by 90 °, 7 is a detection circuit for obtaining the neutral point voltage NV from the output signals of these filter circuits 4 to 6, and 8, 9 and 10 are filter circuits 4, 5 and 6 which are first-order lag elements. A comparator for comparing the output signal and the neutral point voltage NV, respectively,
Reference numeral 11 is a control circuit. FIG. 6 is a time chart showing the operation of the conventional example, and the U phase will now be considered with reference to this. The terminal voltage UV (see FIG. 6 (a)) generated in the stator winding 3U includes a spike-shaped voltage component generated by conduction of the anti-arm return diode during commutation of the inverter circuit 2. In order to eliminate the influence of this spike-shaped voltage component, the terminal voltage UV is phase-shifted by 90 ° by the filter circuit 4 to obtain the phase shift voltage DUV as shown in FIG. 6 (b). Thereafter, the phase shift voltage DUV and the neutral point voltage NV shown in FIG. 6 (b) are compared by the comparator 8,
The position detection signal PSU is obtained as shown in FIG. The same applies to the other V and W phases, and the terminal voltages VV and WV
6 (d) and (e) from the comparators 9 and 10 based on FIG.
Position detection signals PSV and PSW are obtained as indicated by. These position detection signals PSU, PSV and PSW are signals of 180 ° energization and different in 120 ° phase, and when these are supplied to the control circuit 11, the control circuit 11 outputs six commutation signals and outputs the inverter circuit. It is applied to the base of the transistor which is the second switching element.

(Problems to be Solved by the Invention) However, in the above conventional configuration, the terminal voltages UV, VV and W
90 to remove spike-like voltage components contained in V
Since the filter circuits 4 to 6 having the delay phase characteristic are provided, the time constants of the filter circuits 4 to 6 are large, which causes a problem that rapid acceleration / deceleration cannot be followed.
There is a problem that it becomes difficult to detect the position in the low speed region. Further, the magnitudes of spike-shaped voltage components included in the terminal voltages UV, VV and WV vary depending on the currents of the stator windings 3U, 3V and 3W, that is, the magnitude of the load. A phase error will occur in the signal waveforms of 4 to 6 and thereafter, and there is a problem in stability.

The present invention has been made in view of the above circumstances, and an object of the present invention is to perform control based on a current flowing in a DC side portion of an inverter circuit without using a terminal voltage of a stator winding, thereby performing a rapid acceleration / deceleration. And good response to load changes,
(EN) Provided is a brushless motor drive device capable of improving stability.

[Means for Solving the Problems] (Means for Solving the Problems) The present invention relates to a stator having a permanent magnet type rotor and a plurality of phases of stator windings for applying a magnetic field to give a rotational force to the rotor. In a brushless motor provided with, an inverter circuit for converting a direct current voltage from a direct current power supply into an alternating current voltage and supplying the stator winding with a switching element is provided, and a DC side portion of the inverter circuit is provided. The power factor signal is calculated by providing the current detecting means for detecting the current and obtaining the difference between the values immediately before and after each predetermined electrical angle based on the output frequency of the inverter circuit in the DC current signal of the current detecting means. Providing power factor calculation means,
A voltage frequency calculation means for calculating a voltage signal and a frequency signal from the calculation result of the power factor calculation means and the command value is provided, and a drive signal is given to the switching element of the inverter circuit based on the calculation result of the voltage frequency calculation means. It is characterized by doing so.

(Operation) According to the brushless motor drive device of the present invention, the current flowing in the direct current side portion of the inverter circuit, that is, the direct current signal of the current detection means, the predetermined electrical angle of the output frequency of the inverter circuit (for example, three phases). For example, the power factor calculation means calculates the power factor signal by the difference between the values immediately before and after each electrical angle 60 °), and the voltage frequency calculation means calculates the voltage signal and the frequency signal based on the power factor signal and the command value. Since the brushless motor is controlled by means of the brushless motor, it is not necessary to obtain the position detection signal by the terminal voltage of the stator winding of the brushless motor, and therefore it is not necessary to use a filter circuit having a 90 ° delay characteristic. It is possible to improve the responsiveness to rapid acceleration / deceleration and load fluctuation.

(Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

First, the overall configuration will be described with reference to FIG.
Reference numeral 21 is a three-phase AC power supply, and its three-phase AC voltage is a full-wave rectifier circuit in which six diodes are connected in a three-phase bridge.
It is designed to be applied to the AC input terminal of. The DC output voltage of this full-wave rectifier circuit 22 is the same as the DC power supply 23.
Through the smoothing capacitor 24 that composes
Is to be given. Reference numeral 27 is an inverter circuit in which transistors, which are six switching elements, are connected in a three-phase bridge, and its input terminals are DC buses 25 and 26.
A DC voltage between them is applied. 28 is a three-phase, four-pole brushless motor, which comprises a stator 29 having U, V and W phase stator windings 29U, 29V and 29W, and a permanent magnet rotor 30. . And stator winding
29U, 29V, and 29W are star-connected, and the AC output voltage from the output terminal of the inverter circuit 27 is supplied to them. Reference numeral 31 is a current detector composed of a Hall CT, which is provided on the DC bus 25 which is the DC side portion of the inverter circuit 27. Reference numeral 32 denotes a DC amplification circuit, which constitutes a current detection means 33 together with the current detector 31. The DC current signal Idc detected by the current detector 31 is supplied to the input terminal of the power factor calculation circuit 34, which is the power factor calculation means, via the DC amplification circuit 32. As will be described later, the power factor calculation circuit 34 uses the direct current signal Idc to calculate the power factor signal ΔIdc and the current change amount Δ.
Idc ′ is calculated, and the power factor signal ΔIdc and current change amount ΔIdc ′ are output as signals from the output terminal and given to the input terminal of the V / F calculation circuit 35 which is the voltage frequency (V / F) calculation means. It is like this. This V / F arithmetic circuit 35
As will be described later, the power factor signal ΔIdc and the current change amount ΔId
c'and the speed command value ω given from the setter not shown
^The voltage signal V and the frequency signal F are calculated based on ^* , and these are output from the output terminal to drive circuit 36.
It is designed to be applied to the input terminal of. The drive circuit 36 outputs six drive signals PWM-controlled on the basis of the voltage signal V and the frequency signal F from the output terminal and supplies the drive signals to the bases of the six transistors of the inverter circuit 27. As a result, the rotor 30 of the brushless motor 28 is rotated at the rotation speed indicated by the speed command value ω ^* .

Now, a specific configuration of the V / F arithmetic circuit 35 will be described with reference to FIG. The speed command value ω ^* is applied to each input terminal of the integration element 38 and the V / F control element 39 via the acceleration / deceleration time element 37, and the integration element 38 outputs the frequency command signal F ^* from the output terminal. The V / F control element 39 outputs the voltage command signal V ^* from the output terminal and outputs it to one positive (+) input terminal of the adder 41. It has become. The power factor signal ΔIdc is supplied to one input terminal of the power calculation element 42, and the voltage command signal V ^* is supplied to the other input terminal of the power calculation element 42 via the voltage calculation element 43. The power calculation element 42 calculates the power value W and outputs it from the output terminal. This calculated power value W is the first
Is provided to the other positive (+) input terminal of the adder 41 via the control element 44 of the above, and one positive (+) input terminal of the adder 46 is provided via the second control element 45. To be given to. Then, the current change amount ΔId
c'is given to the other positive (+) input terminal of the adder 46 via the third control element 47, and the addition result of the adder 46 is output from the output terminal to the negative (-) side of the speed reducer 40. It is designed to be applied to the input terminal.

Next, the operation of this embodiment will be described with reference to FIG.

FIG. 3 shows a current detection means for a change in power factor when the inverter circuit 27 does not perform power factor control.
33 shows the waveform of the DC current signal Idc of 33. That is, when the power factor is delayed, as shown in FIG.
The waveform changes every 6 cycles (60 electrical degrees), and the change is to the upper right. On the contrary, when the power factor advances, the waveform changes in each same cycle as shown in FIG. 7C, and the change is downward rightward. When the power factor becomes approximately 1, the waveform has almost no change as shown in FIG. Therefore, the waveform of the DC current signal Idc is 60 in electrical angle.
Since it changes repeatedly every °°, pay attention to the time points (0 °, 60 °, 120 °, 180 °… 360 °) at every 60 ° electrical angle, and find the current value Ia at point A just before each time point. Immediately after the current value at point B
The difference from Ib (Ib-Ia) is detected and this difference is zero, that is, the current value I
By controlling so that a and Ib are equal, Fig. 3 (b)
Brushless motor 28 so that the power factor is approximately 1 as shown in
Can be driven. That is, it is possible to perform an operation equivalent to that of the conventional brushless motor system in which the magnetic pole position is detected from the terminal voltage of the stator winding.

Thus, the power factor calculation circuit 34 detects the DC current signal Idc supplied from the current detection means 33 at a constant sampling cycle, and calculates the current value Id immediately after each electrical angle 60 ° from the current value Id immediately before.
The value obtained by subtracting Ia (Ib-Ic) is calculated as the power factor signal ΔIdc, and the amount of current change ΔIdc ′ during the electrical angle of 60 ° is calculated.
Is also calculated. Here, the power factor signal ΔIdc indicates a positive (+) or negative (−) current value, and does not indicate the power factor itself.

On the other hand, in the V / F arithmetic circuit 35, when the speed command value ω ^* is given to the acceleration / deceleration time element 37, the output of the acceleration / deceleration time element 37 is such that the speed command value ω ^* rises at any acceleration / deceleration time. , Which is integrated by the integration element 38 and output as the frequency command signal F ^* , and the V / F control element 39
The voltage command signal V is compared with an arbitrary V / F pattern by
It is output as ^* . Then, the voltage command signal V ^* is applied to the power calculation element 42 as a voltage value after being multiplied by an appropriate coefficient by the voltage calculation element 43. This power calculation element 42
Then, the voltage value from the voltage calculation element 43 described above is multiplied by the power factor signal ΔIdc and the coefficient K and output as the power value W. Therefore, the power value W is W = V ^* × ΔIdc × K (1) In the first control element 44 to which the power value W is given, the voltage component value Vdc of the power value W is calculated and W × K _P (where K _P is a constant) (2) (Vdc) _N = (Vdc) _N-1 + W × K _I (where K _I is a coefficient, N ≥ 1 and an integer) …… (3) From formula (1) + (2) (Vdc) _N + W × K _P …… The proportional-plus-integral processing of (4) is performed, and this is given to the adder 41.
Therefore, in the adder 41, the above formula (4) and the voltage command signal V
By converting ^* and, the voltage signal V is calculated as V = V ^* + (Vdc) _N + W × K _P (5). The above equation (4) is a so-called proportional integral (PI) control equation. (5)
As is clear from the equation, when the power value W is positive, that is, when the power factor signal ΔIdc is positive, the current value Ib at point B in FIG. 2 is larger than the current value Ia at point A, so When the power value W is negative, that is, when the power factor signal ΔIdc is negative, the current value Ib at point B in the figure is smaller than the current value Ia at point A. Is the delay power factor, and the voltage signal V is lowered. Incidentally, in this voltage control, PI control is performed as shown in equation (4), but proportional-integral-derivative (PID) control may be performed depending on the application.
Further, the second control element 45 to which the electric power value W is given is for multiplying W × K ₁ (where K ₁ is a coefficient) (6), which is controlled at every 60 ° electrical angle. Is an element that is Further, the third control element 47 to which the current change amount ΔIdc ′ is given is for multiplying ΔIdc ′ × K ₂ (where K ₂ is a coefficient) (7), which is always controlled. Is an element. Then, the outputs of these control elements 45 and 47 represented by the equations (6) and (7) are added by the adder 46 and then given to the subtractor 40. Therefore, in the subtractor 40, F = F ^* − (W × K _I + ΔIdc ′ × K ₂ ) (8) is subtracted and the frequency signal F is output. That is,
When the current value W or the current change amount ΔIdc ′ increases, the frequency signal F decreases and the output frequency of the inverter circuit 27 decreases, and conversely, the power value W or the current change amount ΔIdc ′.
When c'decreases, the frequency signal F becomes large and the output frequency of the inverter circuit 27 rises, and phase control is performed in response to an increase / decrease in current, that is, load fluctuation, resulting in a sudden load fluctuation. Also provides stable control. As described above, in the V / F arithmetic circuit 35, the voltage command signal V ^* determined by the speed command value ω ^{*, the} frequency command signal F ^*, and the increment determined by the feedback amount according to the change of the direct current signal Idc or The voltage signal V and the frequency signal F are output by performing the calculation with the decrement, and accordingly, the drive circuit 36 and the inverter circuit are output.
The operation of the brushless motor 28 is controlled via 27 so that the power factor becomes approximately 1.

According to this embodiment, the following effects can be obtained.

That is, the DC bus 25 which is the DC side portion of the inverter circuit 27.
Is detected by the current detecting means 33, the power factor signal ΔIdc and the current change amount ΔIdc ′ are calculated by the power factor calculating circuit 34 from the change in the detected direct current signal Idc, and the calculation result and the speed command The voltage signal V and the frequency signal F are calculated from the value ω ^* by the V / F calculation circuit 35, and the power factor of the brushless motor 28 is set through the drive circuit 36 and the inverter circuit 27 based on the voltage signal V and the frequency signal F. Since the operation is controlled so that the output voltage becomes approximately 1, unlike the conventional method in which the terminal voltage of the stator winding is used, it is not necessary to use a filter circuit that is a first-order lag element, and therefore rapid acceleration / deceleration is performed. Also, it has good responsiveness to load fluctuations and can improve stability. It also has excellent responsiveness to external disturbances, can detect even in a low speed range, and can take a wide control range. .

In addition, the DC current signal Idc of the current detection means 33 can be shared for overcurrent and overload detection protection and measurement for output display. Therefore, one current detection means 33 can control the speed and The various objectives of current and overload protection and measurement can be achieved, and it is not necessary to provide a dedicated current detection means for each, and the cost is reduced accordingly, and the installation space is small.

FIG. 4 shows a second embodiment of the present invention, and the same parts as those in FIG. 2 are designated by the same reference numerals. The difference from FIG. 2 is that the output of the integrating element 38 and the output of the first control element 44 are given to the positive (+) input terminal and the negative (-) input terminal of the subtractor 50 respectively, and the V / F control element 39 is supplied. 2 and the output of the adder 46 are applied to one and the other positive (+) input terminals of the adder 51, respectively.

As a result, the voltage signal V output from the adder 51 becomes V = V ^* + (W × K _I + ΔIdc ′ × K ₂ ) (9), and the frequency signal F output from the subtractor 50 is F = F ^* -[(Vdc) _N + W x K _P ] (10), and the frequency signal F becomes PI control.

Therefore, in the first embodiment, voltage control is mainly performed with respect to load fluctuation, whereas in the second embodiment,
Phase control is mainly performed for load fluctuations.

In the above-mentioned respective embodiments, the drive device is shown as a block diagram for each function, but for example, the power factor calculation circuit 34 and
It is also possible to configure the V / F arithmetic circuit 35 with a microcomputer.

In addition, the present invention is not limited to the embodiments described above and shown in the drawings, and is appropriately modified within a range not departing from the gist such as applicable to general brushless motors of a plurality of phases without being limited to three phases. Of course, you can do that.

[Effects of the Invention] As described above, the brushless motor drive device of the present invention detects the current flowing in the DC side portion of the inverter circuit and obtains the power factor signal from the change in the detected DC current signal. Since the brushless motor is operated and controlled so that the power factor becomes approximately 1 based on the calculation result of the power factor signal and the command value, it is not necessary to use a filter circuit which is a first-order lag element, and therefore a rapid acceleration / deceleration is performed. In addition, the responsiveness to the load fluctuation is good, the stability can be improved, and a wide range of control can be achieved, which is an excellent effect.

[Brief description of the drawings]

1 to 3 show a first embodiment of the present invention.
FIG. 1 is a block diagram showing the overall electrical configuration, FIG. 2 is a block diagram showing the specific configuration of a voltage frequency calculation circuit, and FIG. 3 is a waveform diagram of a DC current signal in a state where the power factor is different. FIG. 4 is a view corresponding to FIG. 2 showing a second embodiment of the present invention, and FIG. 5 is an electrical configuration diagram of a conventional example, and FIG.
The figure is a signal waveform diagram of each part for explaining the same operation. In the drawing, 23 is a DC power supply, 25 is a DC bus (DC side part),
27 is an inverter circuit, 28 is a brushless motor, 29 is a stator, 29U, 29V and 29W are stator windings, 30 is a rotor, 33 is a current detection means, 34 is a power factor calculation circuit (power factor calculation means), Reference numeral 35 denotes a voltage frequency calculation circuit (voltage frequency calculation means).

Claims (1)

(57) [Claims] 1. A brushless motor having a permanent magnet type rotor and a stator having stator windings of a plurality of phases for applying a magnetic field to give a rotational force to the rotor, the brushless motor having a switching element. An inverter circuit for converting a DC voltage from a DC power supply into an AC voltage and supplying the AC voltage to the stator winding, a current detecting means for detecting a current in a DC side portion of the inverter circuit, and a current detecting means of the current detecting means. Power factor calculating means for calculating the power factor signal by obtaining the difference between the values immediately before and after each predetermined electrical angle based on the output frequency of the inverter circuit in the direct current signal, and the calculation result of this power factor calculating means. A voltage frequency calculating means for calculating a voltage signal and a frequency signal from a command value, and a switch of the inverter circuit based on a calculation result of the voltage frequency calculating means. Drive device for a brushless motor which is characterized in that so as to provide a drive signal to the grayed element.