JP5218818B2 - DC brushless motor parallel drive circuit - Google Patents

Description

  The present invention relates to a parallel drive circuit for driving a plurality of DC brushless motors connected in parallel by a single power converter in order to operate a plurality of fans, pumps, and the like as motor loads at the same speed. It is.

As this type of parallel drive circuit, for example, the one described in Patent Document 1 is known. This parallel drive circuit is intended to reduce noise when operation is started from an asynchronous state in which the rotors of a plurality of motors are not stopped at the same position.
FIG. 9 shows the overall configuration of the above-described prior art, in which two DC brushless motors MA and MB connected in parallel are driven by one power converter.

  In FIG. 9, E is a DC power source, T1 to T6 are semiconductor switching elements constituting a three-phase voltage source inverter as a power converter, MA and MB are coils connected to AC output terminals U, V, and W of the inverter. DC brassless motors having a stator 11 and a rotor 12, HU, HV, HW are Hall elements arranged for each phase in order to detect the rotor position of each motor MA, MB, 21, 22 are each motor MA , MB hall element HU, HV, HW connected to the rotor position detection circuit, 30 is a signal selection circuit for selecting one of the rotor position detection signals and outputs a control signal for each phase of the inverter, 50 is the operation A speed setting circuit for setting the rotational speeds of the motors MA and MB according to the command 40, and a speed control 60 for rotating the motors MA and MB according to the set speed. 70 is a switching signal generation circuit that generates switching signals of the switching elements T1 to T6 in accordance with the control signal from the signal selection circuit 30 and the speed control signal from the speed control circuit 60, and 80 is an operation command 40. The DC current setting circuit sets the DC current that flows through the stator coils CU, CV, and CW of the motors MA and MB, and the output is applied to the speed control circuit 60.

As described above, the speed control circuit 60 receives the set speed from the speed setting circuit 50 and the DC current set value from the DC current setting circuit 80. The speed control circuit 60 generates a switching signal according to the input. A speed control signal is sent to the circuit 70 to control the rotational speed and current of the motors MA and MB.
During the operation of the DC current setting circuit 80, the output of the speed setting circuit 50 is held at zero by a command from the DC current setting circuit 80.

Here, when the rotor positions of the motors MA and MB are stopped while being shifted, if a direct current is passed through the stator coils CU, CV, and CW of the motors MA and MB, the permanent magnets of the rotor 12 become the stator coils CU and CV. , CW is drawn to a predetermined position. Therefore, the positional relationship between the stator 11 and the rotor 12 of each motor MA, MB is the same, and a synchronized state can be realized.
This prior art pays attention to the above points, and for a certain period of time at start-up, a direct current is passed through the stator coils CU, CV, CW of the motors MA, MB to synchronize the rotor position, and then accelerate to a predetermined speed. It is what.

FIG. 10 shows outputs of the operation command 40, the speed setting circuit 50, and the direct current setting circuit 80 in FIG.
In FIG. 10, when the operation command 40 is input at time t ₁ , the direct current setting circuit 80 outputs the direct current setting value to the speed control circuit 60 for a fixed time from time t ₁ to time t ₂ , and switching is performed. A direct current is passed through the stator coils CU, CV, CW of the motors MA, MB via the signal generation circuit 70. As a result, the permanent magnets of the rotors 12 are attracted to the stator coils CU, CV, and CW as described above, and the positional relationship between the stators 11 and the rotors 12 of the motors MA and MB is equalized and synchronized. During this time, the output of the speed setting circuit 50 is held at zero.

Then, at the same time to zero the output of the DC current setting circuit 80 in time t _2, the subsequent, gradually increasing the output of the speed setting circuit 50, it is accelerated to the set speed V _2.
As a result, since the motors MA and MB can be accelerated in a synchronized state, the generation of noise can be prevented in advance.

Japanese Patent Laying-Open No. 2004-15980 (paragraphs [0020] to [0025], FIG. 1, FIG. 2, etc.)

According to the above prior art, a plurality of motors in a stopped state can be started in synchronization.
However, even if the motor is not driven, the motor may be free-running due to external wind power or water pressure. In such a case, it is difficult to align the rotor positions of a plurality of motors with the above prior art. In addition, if a direct current is passed through the stator coil while the motor is free running, a large current flows without matching the phase of the counter electromotive force generated in the stator coil, and a large noise is generated from the motor. was there.

For example, as shown in FIG. 11 (a), when the speed of the motor is coasting is low before time t _1, the direct current to the stator coils of the motor during the time t ₁ ~t ₂ as previously described By passing the current, the permanent magnets of the rotor are attracted to a predetermined position, so that the positions of the rotors of the two motors are stopped.
However, as shown in FIG. 11 (b), when the speed of the motor is coasting prior to time t ₁ is high, the DC current supplied between times t ₁ ~t ₂ to the stator coil motor A fixed magnetic field is formed in the rotor, but the rotor rotates at a high speed and there is inertia due to the rotor itself and its load, so the rotor rotates past the position attracted to the fixed magnetic field and repels the fixed magnetic field. The speed will increase and decrease repeatedly without stopping.
In such a case, there has been a problem that the motor cannot be started quickly, a large current flows through the stator coil, and the generated noise increases.

  SUMMARY OF THE INVENTION Accordingly, a problem to be solved by the present invention is to provide a DC brushless motor parallel drive circuit that can start a plurality of motors in a surely synchronized manner even when the motors are in a free-run state, and can reduce noise. There is.

In order to solve the above-mentioned problem, the invention according to claim 1 is a parallel drive circuit for driving a plurality of DC brushless motors connected in parallel with each other by a single power converter composed of a plurality of semiconductor switching elements. Rotor position detection means for detecting the rotor position of each motor, signal selection means for outputting a signal selected from the rotor position detection signal output from the detection means as a control signal, and the switching using the control signal In a parallel drive circuit of a DC brushless motor having switching signal generating means for generating a switching signal for the element,
Error detection means for each rotor position detection signal, rotation speed detection means for each rotor, rotation direction detection means for each rotor, and output signals from the error detection means, rotation speed detection means, and rotation direction detection means are input. Determining means; speed control means for controlling the rotational speed of each motor by the output signal of the determining means; and direct current from the power converter to the stator coil of each motor as required by the output signal of the determining means. DC current flow means for flowing
Before starting the motor by the power converter, based on the output signals of the error detection means, the rotation speed detection means, and the rotation direction detection means, the discrimination means determines the rotation speeds of all the motors in a free-run state. If the motor speed is higher than the specified speed, it is determined that all motors are synchronized. If the rotational speed of at least one motor in the free-run state is lower than the specified speed, the DC coil is passed through the stator coils of all motors. It is determined that all motors are synchronized by passing direct current through the flow means,
After these synchronization determinations, all the motors are started by the power converter via the speed control means and the switching signal generation means.

  According to a second aspect of the present invention, in the first aspect, the signal selection means switches the rotor position detection signal between the motors within a period in which the rotor position detection signal of each motor does not change, and the rotor position after the switching. The detection signal is output as a control signal to the switching signal generating means.

  According to a third aspect of the present invention, in the first aspect, the signal selecting means outputs a logical sum or logical product of the rotor position detection signals of the respective motors as a control signal to the switching signal generating means.

  According to a fourth aspect of the present invention, in the first, second, or third aspect, the square wave PWM control is performed for the entire region of the control of the power converter, and the fifth aspect of the invention provides a control of the power converter. The sine wave PWM control is performed for the entire region.

  According to a sixth aspect of the present invention, in the first, second, or third aspect, the control of the power converter at the time of reverse rotation of each motor is a square wave PWM control, and the control of the power converter at the time of forward rotation of each motor is a sine wave. This is PWM control.

According to the present invention, even when the motor is in a free-run state, a plurality of DC brushless motors can be reliably started in synchronization, and a parallel drive circuit that generates less noise can be realized.
Moreover, since the parallel drive circuit of the present invention can be configured by only a single power converter and its controller other than a plurality of motors, it can be provided at a low cost with a relatively simple configuration. is there.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the principle of the present invention is as follows.
As shown in FIG. 9, when the terminals of the stator coils CU, CV, and CW of the two DC brushless motors MA and MB are connected to each other, the motors MA and MB are free running by, for example, wind power. The following can be considered.

(1) Situation 1
Two motors MA and MB are rotated by a strong wind. In this case, both units generate electric power by the rotation of the rotor (permanent magnet) inside the motor, the current generated by the generated power circulates between the two motors, and the two motors rotate synchronously.

(2) Situation 2
One motor is rotated by strong wind, and the other one motor is not exposed to excessive wind. In this case, the motor rotating by the strong wind generates power, but the motor that is not exposed to excessive wind has a small amount of power generation. Therefore, the electric power generated by the motor rotating by the strong wind is consumed by the other motor.
Since the motor that is not exposed to the excessive wind simply turns when a current is passed through the stator coil, the two motors can rotate in synchronization.

(3) Situation 3
The two motors MA and MB are not hit by too much wind and are turning very slowly or stopped. In this case, since the power generation amount of the two motors MA and MB is small, the current flowing between the two motors is small and not synchronized. Therefore, it can be considered in the same manner as in FIG. 11A and FIG. 10 described above, and the motors MA and MB are easily synchronized when a direct current is passed through the stator coil.

As described above, in the case of the situation 1 or the situation 2, the two motors are rotating or rotatable in synchronization even though they are free running, and in the case of the situation 3, the stator coil If a direct current is passed through the circuit, synchronization can be easily achieved.
The present invention pays attention to this point, detects the rotor position error, rotation speed, and rotation direction from each rotor position detection signal when a plurality of motors are free running, and when the speed is sufficiently high, Start after confirming the synchronization state. If the rotational speed is low and the rotor position is not aligned, direct current is passed through the stator coil, and then the motor is started by the normal method when synchronization is confirmed. It is.

Here, FIG. 1 is a block diagram showing the configuration of the present embodiment, and the same components as those in FIG. 9 are denoted by the same reference numerals. Below, it demonstrates centering on a different part from FIG.
In FIG. 1, the rotor position detection signals (substantially equal to the output signals of the Hall elements HU, HV, HW) output from the rotor position detection circuits 21, 22 corresponding to the motors MA, MB are signal selection circuits 30. Is input to the position signal error detection circuit 101, the speed detection circuit 102, and the rotation direction detection circuit 103.

For example, as described in Japanese Patent Application Laid-Open No. 2003-37987, the signal selection circuit 30 is a rotor position detection signal used for generating a switching signal within a period in which the rotor position detection signals of the motors MA and MB do not change. Are switched between the motors MA and MB, and the rotor position detection signal after the switching is output as a control signal to the switching signal generation circuit 70.
In FIG. 2, the signal selection circuit 30 outputs the rotor position detection signal selected (switched) according to the rotor position detection signals of the motors MA and MB as control signals for the U phase, V phase, and W phase. It is a timing chart which shows the operation | movement to perform.

As a function of the signal selection circuit 30, in addition to the above, as described in, for example, Japanese Patent Application Laid-Open No. 2004-173361, a logical sum or logical product of the rotor position detection signals of the motors MA and MB is used as a control signal. May be output.
FIG. 3 shows an operation when the logical sum (OR circuit output in the figure) of the rotor position detection signals of the motors MA and MB is used as a control signal by the technique described in Japanese Patent Application Laid-Open No. 2004-173361. It is a timing chart.

The position signal error detection circuit 101 detects an error between the two rotor position detection signals, the speed detection circuit 102 detects the speeds of the motors MA and MB, and the rotation direction detection circuit 103 detects the speeds of the motors MA and MB. It has a function of detecting the direction of rotation.
The output signals of these detection circuits 101, 102, 103 are input to the discrimination circuit 104, and the output signals are input to the speed setting circuit 50, the speed control circuit 60, and the direct current setting circuit 80. The operation command 40 is input to the speed setting circuit 50 and the determination circuit 104.

  The discriminating circuit 104 performs various discriminating operations to be described later based on the output signals of the detection circuits 101, 102, 103, and using the results, the speed setting circuit 50, the direct current setting circuit 80, and the speed control circuit 60. Is to control. The determination circuit 104 always performs a determination operation not only when the operation command 40 is input.

  The speed control circuit 60 controls forward / reverse rotation of the motors MA, MB and DC current application based on the output of the discrimination circuit 104, and the motors MA, MB at a speed according to the speed set value by the speed setting circuit 50. A speed control signal is output to the switching signal generation circuit 70 so as to rotate the motor, and a DC current (or DC voltage) set by the DC current setting circuit 80 is supplied to the stator coils CU, CV, CW of the motors MA, MB. It controls to do.

Next, the operation of this embodiment will be described with reference to the flowchart of FIG. First, the operation of the entire circuit is started by the operation command 40 of FIG.
In FIG. 4, the rotor position and speed are detected from the rotor position detection signal for each of the motor MA side and the motor MB side (steps S1 and S9). Here, the rotor position detection signal is input to the signal selection circuit 30 of FIG. 1 to be used for the generation of the control signal described above, and is also input to the position signal error detection circuit 101 to detect the position signal error of both rotors. Used. At the same time, the rotor position detection signal is used by the speed detection circuit 102 to detect the rotation speeds of the motors MA and MB, and is also used by the rotation direction detection circuit 103 to detect the rotation direction.

The determination circuit 104 in FIG. 1 determines whether or not the motor MA side has rotated at a speed equal to or higher than the specified speed V _a [r / m] for at least _Ta seconds (step S2) and the motor MB side. In step S10, it is determined whether the speed is equal to or higher than the specified speed V _a [r / m] and continuously rotated for T _b seconds or more.
If the determination results in steps S2 and S10 are both “YES”, it can be considered that, for example, the two motors MA and MB are continuously rotating by strong wind as in the above-described situation 1. 4 moves to step S3.

  Further, when the determination result in step S2 or S10 is “NO”, as in the situation 2 and situation 3 described above, either or both of the motors MA and MB are not subjected to excessive wind and the power generation amount is small. Since it is considered that there is, a direct current is passed through the stator coils CU, CV, CW of the motors MA, MB (step S11). This DC current flow is performed by the discrimination circuit 104 controlling the DC current setting circuit 80 and the speed control circuit 60 and turning on predetermined switching elements T1 to T6 by the switching signal generation circuit 70.

On the other hand, if the determination results in steps S2 and S10 are both “YES”, it is determined from the output signals of the detection circuits 101, 102, and 103 whether the motors MA and MB are synchronized (step S3). That is, it is determined that the motors MA and MB are synchronized when the position signal error is within the specified value, the speed detection values are substantially equal, and the rotation directions are the same.
This synchronization determination is the same when a direct current is passed in step S11 described above (step S12).
If the determination result in step S3 is “NO”, the process from step S1 is repeated. If the determination result in step S12 is “NO”, the process in step S11 is repeated.

When the determination result in step S3 is “YES”, that is, when it is determined that the motors MA and MB are synchronized, the forward / reverse rotation is determined from the rotation direction of the motors MA and MB (step S4).
If both the motors MA and MB are rotating in the normal direction, the motor MA and MB are accelerated in the normal rotation state according to a predetermined speed pattern via the speed control circuit 60 (step S8).
If both the motors MA and MB are reversely rotated, the speed control circuit 60 is controlled so as to perform the reverse rotation operation based on the rotor position detection signal (step S5). At that time, the vehicle is decelerated according to the deceleration pattern set by the speed setting circuit 50 (step S6).

The next step S7 is a process in which a direct current is passed through the stator coils CU, CV, CW in order to position the rotor reliably while switching from reverse rotation to forward rotation, and is generally necessary when wind power is weak or small. Absent.
After that, the normal rotation acceleration process (step S8) described above is performed, and then the operation shifts to a steady operation (step S15).

Further, after step S12 described above, it is determined whether _Tc seconds have elapsed after the motors MA and MB are synchronized (step S13). This step is for confirming that the motors MA and MB are reliably synchronized. If _Tc seconds have not elapsed, the processes after steps S1 and S9 are repeated.
When _Tc seconds have passed since the synchronization, the speed control circuit 60 is controlled so as to accelerate forward from the phase (time) after the direct current is passed (step S14), and then the operation shifts to the steady operation. (Step S15).

5 to 8 are timing charts showing the operation of this embodiment, and showing the operation of each circuit in accordance with various situations of the two motors MA and MB.
First, FIG. 5 shows a case where the two motors MA and MB are both free running. In this example, from the previous run command 40 is generated at time t _1, the motor MA, MB is reversed at a specified speed V _a more identical speed. The error of the rotor position detection signal is also within a specified value.

In this case, from time _{t 1} time _(T a + T _b) motor MA at the time of the lapse of, MB that are synchronized is determined by the determination circuit 104, at time _{t 2, the} reversal operation in step S5, the aforementioned Be started. Thus, the time _{t 2} after the motor MA, MB is gradually decelerated gradually in step S6.
Then, after the speed becomes zero at time t _3, switch to forward acceleration operation by the step S8 mentioned above.
In this example, since the two motors MA and MB are rotating in synchronization with strong wind, for example, it is not necessary to pass a direct current to the stator coils CU, CV and CW.

Next, in FIG. 6, after the discrimination circuit 104 confirms the synchronization of the motors MA and MB, the speed control circuit 60 performs the reverse deceleration operation in step S6, and then the DC current to the stator coil in step S7. it is a flowchart in the case of performing flowing over time _t 3 ~t _6.

FIG. 7 shows a case where the motor MA is free running and the motor MB is stopped.
In this case, only the motor MA is rotating at a lower than the specified speed V _a speed, position error detection signal from the time t ₁ earlier is output periodically. From time _{t 2, the} motor MA by step S11 via the speed control circuit 60, MB stator coil CU, CV, when a DC current flows through the CW, also stops motor MA which has been free running, the magnetic flux of the stator by the rotor of the motor MA is drawn, the motor MA, MB of the rotor position will coincide at time t _5. Motor MA the discrimination circuit 104 in this state, MB synchronization is determined by step S13, S14, time _{t 3} after from the time _{t 5} after the elapse of time _{T c,} the motor MA, forward acceleration operation MB is started Is.

Further, FIG. 8 shows a case where the two motors MA and MB are both stopped.
In this case, operation after which flowed a direct current from time t ₂ is substantially repeated with 7, the motor MA from time t _3, the forward acceleration operation MB is started.

As a method for controlling the inverter composed of the switching elements T1 to T6, the square wave PWM control is generally simple, but the generated noise from the motor during operation is large, and the sine wave PWM control is complicated in control. Noise generated from the motor during operation is small.
Therefore, in the flowchart shown in FIG. 4, the reverse deceleration operation (step S6) is square wave PWM control, the forward rotation acceleration (steps S8 and S14) and the steady operation (step S15) are sine wave PWM control. Is practically preferable.
Of course, only the square wave PWM control or only the sine wave PWM control may be performed for the entire control range of the inverter in consideration of the advantages and disadvantages.

The control contents according to the present embodiment can be realized relatively easily by using a microcomputer.
In the above-described embodiment, the case where two DC brushless motors are driven in parallel has been described. Needless to say, the present invention can be similarly applied to a case where three or more DC brushless motors are driven in parallel.

It is a block diagram which shows the structure of embodiment of this invention. 2 is a timing chart showing the operation of the signal selection circuit in FIG. 2 is a timing chart showing the operation of the signal selection circuit in FIG. It is a flowchart which shows operation | movement of embodiment. It is a timing chart which shows operation of an embodiment. It is a timing chart which shows operation of an embodiment. It is a timing chart which shows operation of an embodiment. It is a timing chart which shows operation of an embodiment. It is a block diagram which shows the structure of a prior art. It is explanatory drawing which shows operation | movement of a prior art. It is explanatory drawing of the motor speed at the time of a free run.

Explanation of symbols

11: stator 12: rotor 21, 22: rotor position detection circuit 30: signal selection circuit 40: operation command 50: speed setting circuit 60: speed control circuit 70: switching signal generation circuit 80: DC current setting circuit 101: position signal error Detection circuit 102: Speed detection circuit 103: Rotation direction detection circuit 104: Discrimination circuit E: DC power sources T1 to T6: Semiconductor switching elements U, V, W: AC output terminals MA, MB: DC brassless motors CU, CV, CW : Stator coils HU, HV, HW: Hall elements

Claims (6)

A parallel drive circuit for driving a plurality of DC brushless motors connected in parallel to each other by a single power converter composed of a plurality of semiconductor switching elements, and a rotor position detection means for detecting the rotor position of each motor, respectively A signal selection unit that outputs a signal selected from the rotor position detection signal output from the detection unit as a control signal; and a switching signal generation unit that creates a switching signal for the switching element using the control signal. In parallel drive circuit of DC brushless motor,
Error detection means for each rotor position detection signal, rotation speed detection means for each rotor, rotation direction detection means for each rotor, and output signals from the error detection means, rotation speed detection means, and rotation direction detection means are input. Determining means; speed control means for controlling the rotational speed of each motor by the output signal of the determining means; and direct current from the power converter to the stator coil of each motor as required by the output signal of the determining means. DC current flow means for flowing
Before starting the motor by the power converter, based on the output signals of the error detection means, the rotation speed detection means, and the rotation direction detection means, the discrimination means determines the rotation speeds of all the motors in a free-run state. If the motor speed is higher than the specified speed, it is determined that all motors are synchronized. If the rotational speed of at least one motor in the free-run state is lower than the specified speed, the DC coil is passed through the stator coils of all motors. It is determined that all motors are synchronized by passing direct current through the flow means,
A parallel drive circuit for a DC brushless motor, wherein after the synchronization determination, all the motors are started by the power converter via the speed control means and the switching signal generation means.
In the parallel drive circuit of the DC brushless motor according to claim 1,
The signal selection means includes
Each rotor position detection signal is switched between the motors within a period in which the rotor position detection signal of each motor does not change, and the rotor position detection signal after the switching is output as a control signal to the switching signal generating means. DC brushless motor parallel drive circuit. In the parallel drive circuit of the DC brushless motor according to claim 1,
The signal selection means includes
A parallel drive circuit for a DC brushless motor, wherein a logical sum or logical product of rotor position detection signals of each motor is output to a switching signal generating means as a control signal. In the parallel drive circuit of the DC brushless motor according to claim 1, 2, or 3,
A parallel drive circuit for a DC brushless motor, wherein square wave PWM control is performed for the entire control range of the power converter. In the parallel drive circuit of the DC brushless motor according to claim 1, 2, or 3,
A parallel drive circuit for a DC brushless motor, wherein sinusoidal PWM control is performed for the entire control range of the power converter. In the parallel drive circuit of the DC brushless motor according to claim 1, 2, or 3,
Parallel driving of DC brushless motors characterized in that control of the power converter during reverse rotation of each motor is square wave PWM control, and control of the power converter during forward rotation of each motor is sinusoidal PWM control circuit.

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