JP3636344B2 - Control method of brushless DC motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a brushless DC motor driven via an inverter.
[0002]
[Prior art]
FIG. 15 is a block diagram showing a first conventional example, and FIG. 16 is a block diagram showing a second conventional example.
In these figures, 1 is an AC power source, 2 is a rectifier circuit, 3 is a chopper circuit for boosting DC voltage, 4 and 5 are electrolytic capacitors for smoothing DC voltage, and 6 is a semiconductor switch formed by connecting a transistor and a diode in antiparallel. An inverter circuit composed of four sets (Ta to Td), 7 is a brushless DC motor (M: also simply referred to as a motor) fed from the inverter main circuit 6.
[0003]
Further, in FIG. 15 as a control unit for controlling the motor, the magnetic pole position of the motor is detected from the signal from the magnetic pole sensor or the output voltage signal of the inverter, and the magnetic pole position detection signal is output every 60 degrees (°) of the motor. Based on the magnetic pole position detection circuit 9, a signal generation circuit 10 that generates switching signals (Ta1 to Td1 signals) to the semiconductor switch based on the detection signal, and a signal from the magnetic pole position detection circuit 9, the speed of the motor is detected and controlled. A speed detection / control circuit 11, a DC voltage command calculation circuit 12, a DC intermediate voltage control circuit, a control circuit 13 including an input current control circuit, and the like are included.
In FIG. 16, in addition to FIG. 15, 60 ° of the conduction angle of 120 ° includes an oscillator 18 for performing pulse width modulation (PWM) and a signal generation circuit 19 for PWM signals (Ta4 to Td4 signals). Yes. Each numerical value of the term “conduction angle 120 ° and 60 ° therein” is a theoretical value, but in practice it is allowed to include some errors (± 2, 3 degrees). The same shall apply.
In the configuration as described above, the motor 7 can be rotated in a desired manner by controlling the DC intermediate voltage value based on the motor speed command value and the magnetic pole position detection signal every 60 °, and the switching command signal to each of the semiconductor switches Ta to Td. Number and output torque can be given.
[0004]
FIG. 17 shows an example of switching signals to the semiconductor switches Ta to Td in FIG. FIG. 17 shows an example of a 120 ° conduction square switching pattern. Further, the current waveform is characterized in that a large current flows in the U phase and the W phase in the vicinity of times T4 and T7. This is because the voltage applied to the motor 7 is three-phase unbalanced.
FIG. 18 shows an example of switching signals (Ta4 to Td4) to the semiconductor switches Ta to Td in FIG. In the figure, 60 ° of the conduction angle of 120 ° for each semiconductor switch is a switching pattern for performing PWM with an on-duty of 75%, for example, and this control method is fundamental. In addition, the current waveform is a PWM waveform between times T3 and T4 and in the vicinity of T6 to T7, and has a characteristic that it is approximately equal on average to the current flowing in other sections (T2 to T3, T5 to T6, etc.). This is because the voltage applied to the motor 7 is three-phase balanced.
[0005]
[Problems to be solved by the invention]
In the system shown in FIG. 16, in order to increase the maximum number of revolutions of the motor, the DC voltage of the electrolytic capacitors 4 and 5 may be increased by the DC chopper circuit 3. At this time, the semiconductor switch and the inverter main circuit in the chopper circuit are connected. The voltage rating of the constituent semiconductor switches Ta to Td is increased, which hinders downsizing and cost reduction. Further, in the case of the method of FIG. 15, higher speed operation is possible than in the case of FIG. 16, but there are problems in torque ripple and efficiency.
Accordingly, an object of the present invention is to lower the voltage rating of the semiconductor switch as compared with the conventional one and to realize the high performance operation of the brushless DC motor.
[0006]
[Means for Solving the Problems]
In order to solve such problems, in the invention of claim 1, a series circuit in which a plurality of capacitors are connected in series between a DC voltage source and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are provided. When connecting in parallel and controlling a power supply by connecting a brushless DC motor to the intermediate potential point of the series circuit and each AC output point of the two-phase bridge circuit,
The on / off control is performed by a switching signal in which a conduction angle of each semiconductor switch generated from a position detection signal of the brushless DC motor is set to 108 °.
In the first aspect of the invention, the semiconductor switch can be turned on / off by advancing the switching signal of the conduction angle of 108 ° by a predetermined phase (invention of the second aspect).
[0007]
In the invention of claim 3, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel between the DC voltage sources, When performing control while connecting a brushless DC motor to the potential point and each AC output point of the two-phase bridge circuit and supplying power,
When either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor reaches a predetermined value, the semiconductor switch is set to 60 ° out of the conduction angle of 120 °. From the first control for on / off control based on a 120 ° conduction type switching signal that performs pulse width modulation, to the second control for on / off control using a switching signal for setting the conduction angle of each semiconductor switch to 108 °. And switching.
[0008]
In a fourth aspect of the present invention, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel between DC voltage sources, When performing control while connecting a brushless DC motor to the potential point and each AC output point of the two-phase bridge circuit and supplying power,
Depending on the speed command value and detection value of the brushless DC motor or the DC voltage command value and detection value of the capacitor, each semiconductor switch is subjected to pulse width modulation for 60 ° of the conduction angle of 120 °. The first control for on / off control based on the 120 ° conduction type switching signal to be performed, and each semiconductor switch based on the switching signal having a conduction angle and a pulse width modulation conduction ratio different from those of the 120 ° conduction type switching signal. The second control for on / off control and the third control for on / off control by a switching signal for setting the conduction angle of each semiconductor switch to 108 ° are sequentially performed.
[0009]
In the invention of claim 5, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel between the DC voltage sources, When performing control while connecting a brushless DC motor to the potential point and each AC output point of the two-phase bridge circuit and supplying power,
A switching signal for setting the conduction angle of each semiconductor switch to 108 ° when either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor reaches a predetermined value. The control is switched from the first control for on / off control to the second control for on / off control based on a switching signal for setting the conduction angle of each semiconductor switch to 120 °.
[0010]
In the invention of claim 6, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel between the DC voltage sources, When performing control while connecting a brushless DC motor to the potential point and each AC output point of the two-phase bridge circuit and supplying power,
On / off control with a switching signal that sets the conduction angle of each semiconductor switch to 108 ° in accordance with either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor. A first control for controlling the semiconductor switch based on a switching signal having a conduction angle different from that of the switching signal, a second control for controlling on / off of each semiconductor switch, and a switching signal for setting the conduction angle of each semiconductor switch to 120 °. Based on this, the control is sequentially switched to the third control for on / off control.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of the present invention.
This is for the circuit shown in FIG. 15 by calculating the following formulas (1) and (2) from the speed detection value or the speed command value (n) to calculate time data corresponding to 12 ° and 48 °. It is characterized in that a time data calculation circuit 14 and a signal generation circuit 15 are added.
12 ° time data = 1 / (speed detection value or speed command value) * (12/360) = 1 / 30n (1)
48 ° time data = 1 / (speed detection value or speed command value) * (48/360) = 2 / 15n (2)
[0012]
The signal generation circuit 15 generates 108 ° conduction type switching signals Ta2 to Td2 based on the output from the time data calculation circuit 14 and the switching signals Ta1 to Td1 from the signal generation circuit 10. For example, a counter can be used as a specific circuit for delaying the rise and fall of the signal by a time corresponding to 12 ° and 48 °.
FIG. 2 shows a time chart of each signal in the case of FIG. The signal Ta2 rises at time T3 and the signal Tc2 rises at a time delay of 12 ° with respect to the rise of the signals Ta1 and Tc1 at time T6, and the signals Tb2 and Td2 take 48 ° minutes from the times T6 and T3, respectively. So that it will fall after a certain amount of time. It can also be seen that the current flowing through the motor has a reduced peak current value of iu and iw compared to the first conventional example.
[0013]
FIG. 3 is a block diagram showing a second embodiment of the present invention. Only the control part is shown, and a phase shift amount calculation circuit 16 and a signal generation circuit 17 are added to FIG. The phase shift amount calculation circuit 16 obtains time data (Δt) corresponding to the phase (Δθ) amount by which the 108 ° conduction type switching signals Ta2 to Td2 are advanced, so that the speed detection data from the speed detection / control circuit 11 is obtained. Or based on the speed command data (n ′), the following equation (3) is calculated.
Δt = Δθ / 360n ′ (3)
Based on the output from the phase shift amount calculation circuit 16, the signal generation circuit 17 advances the 108 ° conduction type switching signals Ta <b> 2 to Td <b> 2 from the signal generation circuit 15 by Δθ.
[0014]
FIG. 4 shows a time chart of each signal in the case of FIG.
That is, since it is not usually possible to advance the phase by Δθ, for example, the rise of the Ta3 signal is delayed by time data corresponding to (72 ° −Δθ) from time T2, and the fall of the Ta3 signal is caused at time T4. To (60 [deg.]-[Delta] [theta]) corresponding to each other by delaying the time data, and this also applies to the other signals Tb, Tc, Td.
[0015]
FIG. 5 is a block diagram showing a third embodiment of the present invention. Only the control portion is shown, and is configured by adding an oscillator 18, signal generation circuits 19, 20 and a comparator 21 to FIG. As in the second conventional example shown in FIG. 16, the oscillator 18 and the signal generating circuit 19 apply 120 ° conduction type switching signals Ta4 to Td4 that perform pulse width modulation to 60 ° of the conduction angle of 120 ° for each semiconductor switch. create. The signal generation circuit 20 has a built-in switch, and switches and outputs the signals Ta2 to Td2 from the signal generation circuit 15 and the signals Ta4 to Td4 from the signal generation circuit 19, and the comparator 21 has speed detection data or speed command data, The switching speed data set in advance is compared, and a signal for switching the switch in the signal generating circuit 20 is generated.
FIG. 6 is an explanatory diagram of the operation of FIG. In the figure, the switching signal Ta5 to the semiconductor switch Ta with the switching speed n1 as a boundary is from a 120 ° conduction type in which the conduction angle is 60 ° out of 120 ° to 108 ° conduction type. The state of switching to is shown. The same applies to the other signals Tb, Tc, Td.
[0016]
FIG. 7 is a block diagram showing a fourth embodiment of the present invention. Only the control portion is shown, and an on-duty calculation circuit 22, a conduction angle calculation circuit 23, and a signal generation circuit 24 are added to the second conventional example.
The on-duty calculation circuit 22 and the conduction angle calculation circuit 23 calculate an on-duty (conduction rate) and conduction angle during the period in which the signals Ta4 to Td4 are output based on the speed detection data or speed command data, and a signal generation circuit 24 generates switching signals Ta6 to Td6 according to the conductivity and the conduction angle.
[0017]
FIG. 8 shows an example of the signal Ta6 when the motor speed changes stepwise. That is, a switching signal with a conduction angle of 120 ° and duty 75% at a low speed, a switching signal with a conduction angle of 114 ° and duty 87.5% at a medium speed, and a switching signal with a conduction angle 108 ° and duty 100% at a high speed. Is shown.
FIG. 9 shows an example of the relationship between speed, conduction angle, and duty.
That is, between a certain set speeds n1 and n2, the duty is x and the conduction angle is y, so that the following relationship is satisfied.
y = 90 + 45 / (4x-1.5) (4)
[0018]
FIG. 10 is a block diagram showing a fifth embodiment of the present invention, which is configured by adding a signal generating circuit 25 and a comparator 26 to the control portion of FIG.
The signal generation circuit 25 has a built-in switch, and switches and outputs signals Ta1 to Td1 from the signal generation circuit 10 and signals Ta2 to Td2 from the signal generation circuit 15 according to the speed of the motor. The detection data or speed command data is compared with preset switching speed data, and a signal for switching the switch in the signal generating circuit 25 is generated.
FIG. 11 is an explanatory diagram of the operation of FIG. In the figure, the switching signal Ta7 to the semiconductor switch Ta is switched from the 108 ° conduction type to the 120 ° conduction type at the switching speed n3. The same applies to the other signals Tb, Tc, Td.
[0019]
FIG. 12 is a block diagram showing a sixth embodiment of the present invention, which is configured by adding a conduction angle calculation circuit 27 and a signal generation circuit 28 to the control portion of FIG.
That is, the conduction angle calculation circuit 27 calculates the conduction angle based on the speed detection data or the speed command data, and the signal generation circuit 28 generates the switching signals Ta8 to Td8 according to the calculated conduction angle.
FIG. 13 shows an example of the signal Ta8 when the motor speed changes stepwise.
That is, a switching signal with a conduction angle of 108 ° at a low speed, a switching signal with a conduction angle of 114 ° at a medium speed, and a switching signal with a conduction angle of 120 ° at a high speed is shown. The same applies to the other signals Tb, Tc, Td.
[0020]
FIG. 14 is an explanatory diagram of the relationship between speed and conduction angle. This shows an example in which the conduction angle is 108 ° to 120 ° between the speeds n5 and n6.
In the above description, the speed command value and the detected value are used for switching the control. However, it goes without saying that the DC voltage command value and the detected value of the capacitors 4 and 5 may be used.
[0021]
【The invention's effect】
According to the first invention, the voltage utilization rate is improved as compared with the second conventional example. Therefore, when the same semiconductor switch is used, the motor can be operated at a high speed, and the maximum rotational speed of the motor is the same. If so, the voltage rating of the semiconductor switch can be reduced. Further, since the low-order harmonics flowing in the motor are reduced with respect to the first conventional example, the torque ripple of the motor can be reduced and the efficiency can be improved. According to the second invention, the lower harmonics flowing through the motor are reduced as compared with the first invention, and the torque ripple of the motor can be reduced and the efficiency can be improved.
[0022]
According to the third aspect of the invention, since the driving method is the same as that of the second conventional example during the low speed operation of the motor, the torque ripple can be reduced and the efficiency can be improved during the low speed operation of the motor.
According to the fourth invention, since the rapid acceleration / deceleration operation due to the switching of the control method is eliminated with respect to the third invention, a smooth motor operation with less shock is possible.
[0023]
According to the fifth aspect of the invention, since the same operation as the first aspect of the invention is performed at the time of low speed operation of the motor with respect to the first conventional example, the torque ripple of the motor at the time of low speed operation can be reduced and the efficiency can be improved.
According to the sixth invention, since the rapid acceleration / deceleration operation due to the switching of the control method is eliminated with respect to the fifth invention, a smooth motor operation with less shock is possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention;
FIG. 2 is an operation explanatory diagram of FIG. 1;
FIG. 3 is a block diagram showing a second embodiment of the present invention.
4 is an operation explanatory diagram of FIG. 3; FIG.
FIG. 5 is a block diagram showing a third embodiment of the present invention.
6 is an operation explanatory diagram of FIG. 5. FIG.
FIG. 7 is a block diagram showing a fourth embodiment of the present invention.
8 is an operation explanatory diagram of FIG. 7. FIG.
9 is a diagram for explaining the relationship between the speed, the conduction angle, and the on-duty in FIG.
FIG. 10 is a block diagram showing a fifth embodiment of the present invention.
11 is an operation explanatory diagram of FIG. 10;
FIG. 12 is a block diagram showing a sixth embodiment of the present invention.
13 is an operation explanatory diagram of FIG. 12. FIG.
14 is an explanatory diagram of the relationship between the speed and the conduction angle in FIG. 13;
FIG. 15 is a block diagram showing a first conventional example.
FIG. 16 is a block diagram showing a second conventional example.
FIG. 17 is an operation explanatory diagram of FIG. 15;
18 is an operation explanatory diagram of FIG. 16. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power supply, 2 ... Rectifier circuit, 3 ... Chopper circuit, 4, 5 ... Electrolytic capacitor, 6 ... Inverter circuit, 7 ... Brushless DC motor (M), 9 ... Magnetic pole position detection circuit 10, 15, 17, 19, 20, 24, 25, 28 ... signal generation circuit, 11 ... speed detection / control circuit, 12 ... DC voltage command calculation circuit, 13 ... control circuit, 14 ... time data calculation circuit, 16 ... phase shift amount calculation circuit, 18 ... Oscillator, 21, 26... Comparator, 22... On duty operation circuit, 23, 27.

Claims (6)

Between a DC voltage source, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel, and an intermediate potential point of the series circuit and a two-phase bridge circuit When performing control while supplying power by connecting a brushless DC motor to each AC output point,
A control method for a brushless DC motor, wherein on / off control is performed with a switching signal for setting a conduction angle of each semiconductor switch generated from a position detection signal of the brushless DC motor to 108 °. 2. The method of controlling a brushless DC motor according to claim 1, wherein the semiconductor switch is turned on / off by advancing a switching signal having a conduction angle of 108 [deg.] By a predetermined phase. Between a DC voltage source, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel, and an intermediate potential point of the series circuit and a two-phase bridge circuit When performing control while supplying power by connecting a brushless DC motor to each AC output point,
When either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor reaches a predetermined value, the semiconductor switch is set to 60 ° out of the conduction angle of 120 °. From the first control for on / off control based on a 120 ° conduction type switching signal that performs pulse width modulation, to the second control for on / off control using a switching signal for setting the conduction angle of each semiconductor switch to 108 °. And a method for controlling the brushless DC motor. Between a DC voltage source, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel, and an intermediate potential point of the series circuit and a two-phase bridge circuit When performing control while supplying power by connecting a brushless DC motor to each AC output point,
Depending on the speed command value and detection value of the brushless DC motor or the DC voltage command value and detection value of the capacitor, each semiconductor switch is subjected to pulse width modulation for 60 ° of the conduction angle of 120 °. The first control for on / off control based on the 120 ° conduction type switching signal to be performed, and each semiconductor switch based on the switching signal having a conduction angle and a pulse width modulation conduction ratio different from those of the 120 ° conduction type switching signal. A control method for a brushless DC motor, wherein the second control for on / off control and the third control for on / off control are sequentially performed by a switching signal for setting the conduction angle of each semiconductor switch to 108 °. . Between a DC voltage source, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel, and an intermediate potential point of the series circuit and a two-phase bridge circuit When performing control while supplying power by connecting a brushless DC motor to each AC output point,
A switching signal for setting the conduction angle of each semiconductor switch to 108 ° when either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor reaches a predetermined value. The control of the brushless DC motor is switched from the first control for on / off control to the second control for on / off control based on a switching signal for setting the conduction angle of each semiconductor switch to 120 °. Method. Between a DC voltage source, a series circuit in which a plurality of capacitors are connected in series and a two-phase bridge circuit in which four sets of semiconductor switches are connected in a two-phase bridge are connected in parallel, and an intermediate potential point of the series circuit and a two-phase bridge circuit When performing control while supplying power by connecting a brushless DC motor to each AC output point,
On / off control with a switching signal that sets the conduction angle of each semiconductor switch to 108 ° in accordance with either the speed command value or detection value of the brushless DC motor or the DC voltage command value or detection value of the capacitor. A first control for controlling the semiconductor switch based on a switching signal having a conduction angle different from that of the switching signal, a second control for controlling on / off of each semiconductor switch, and a switching signal for setting the conduction angle of each semiconductor switch to 120 °. A control method for a brushless DC motor, wherein the control is sequentially switched to a third control that performs on / off control based on the control.

Images