JP2020120513A - Synchronous motor control device - Google Patents

Abstract

To drive a synchronous motor stably during phase control of an inverse converter by a position detector by providing a synchronous motor control device capable of automatically correcting a detection of a rotor magnetic pole position by the position detector.SOLUTION: The synchronous motor control device includes: an electrical phase detection unit for detecting a phase from an induced voltage in an armature winding of a synchronous motor; a mechanical phase detection unit for detecting a phase from an output signal of a position detector of the synchronous motor; and a phase correction unit for correcting an output of the mechanical phase detection unit. The phase correction unit calculates a correction value based on outputs of a phase difference calculation unit for calculating a difference between an output of the electrical phase detection unit and an output of the mechanical phase detection unit and the phase difference calculation unit during turning operation of the synchronous motor and corrects the output of the mechanical phase detection unit based on the correction value.SELECTED DRAWING: Figure 1

Description

The present invention relates to a synchronous motor control device.

Patent Document 1 discloses a control device for a synchronous motor. According to the control device, the device can be stopped without causing torque pulsation.

JP2012-200109A

However, in the control device described in Patent Document 1, the detection of the rotor magnetic pole position, that is, the mechanical rotation phase of the synchronous motor by the mechanical position detector (eg, position sensor or resolver) is different from the actual electrical phase. Then, the ignition timing of the thyristor of the inverse converter is deviated. In this case, commutation failure may occur and the synchronous motor may not be stably controlled. Further, when the synchronous motor is inspected, the synchronous motor and the mechanical position detector are separated from each other, and a difference may occur during reassembly, and it may be necessary to readjust the phase after the inspection.

The present invention has been made to solve the above problems. An object of the present invention is to provide a synchronous motor control device capable of automatically correcting the detection of the rotor magnetic pole position by the position detector, thereby stabilizing the synchronous motor during phase control of the inverse converter by the position detector. To drive.

A control device for a synchronous motor according to the present invention is a mechanical phase detection unit for detecting a phase from an output signal of an electric phase detection unit for detecting a phase from an induced voltage of an armature winding of the synchronous motor and a position detector for the synchronous motor. And a phase correction unit that corrects the output of the mechanical phase detection unit, and the phase correction unit calculates the difference between the output of the electrical phase detection unit and the output of the mechanical phase detection unit. A correction value is calculated based on the output of the phase difference calculation unit and the phase difference calculation unit during the turning operation of the synchronous motor, and the output of the mechanical phase detection unit is corrected based on the correction value.

According to the present invention, the synchronous motor can be stably driven during phase control of the inverse converter by the position detector.

1 is a configuration diagram of a system to which a control device for a synchronous motor according to a first embodiment is applied. FIG. 3 is a diagram for explaining an outline of control of the synchronous motor by the control device for the synchronous motor in the first embodiment. FIG. 3 is an equivalent circuit diagram of a synchronous motor to which the synchronous motor control device according to the first embodiment is applied. FIG. 5 is a diagram for explaining a method of calculating an error by the control device for the synchronous motor in the first embodiment. FIG. 5 is a diagram for explaining a method of calculating an error by the control device for the synchronous motor in the first embodiment. FIG. 3 is a block diagram of a main part of the control device for the synchronous motor in the first embodiment. FIG. 3 is a hardware configuration diagram of the synchronous motor control device according to the first embodiment.

Embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In each figure, the same or corresponding parts are designated by the same reference numerals. Overlapping description of the part is appropriately simplified or omitted.

Embodiment 1.
FIG. 1 is a configuration diagram of a system to which the control device for a synchronous motor according to the first embodiment is applied.

In FIG. 1, the power supply 1 is provided so as to be able to output AC power. For example, the power source 1 is a commercial power source. The load 2 is a roller or the like of a rolling mill. The output part of the synchronous motor 3 is connected to the input part of the load 2. The output of the small electric motor 4 is connected to the input of the load 2. The position detector 5 is provided in the synchronous motor 3. The position detector 5 is provided so as to output a rotor magnetic pole position detection signal when the magnetic pole position of the rotor of the synchronous motor 3 is detected. The exciting coil 6 is a field winding coil of the synchronous motor 3. The exciting device 7 is provided so that the exciting coil 6 of the synchronous motor 3 can be supplied with DC power from a power source (not shown). The LCI device 8 is a load commutated inverter device. The LCI device 8 converts the commercial frequency AC power supplied from the power supply 1 into a variable frequency AC power and supplies the variable frequency AC power to the armature winding of the synchronous motor 3 to drive the synchronous motor 3 at a variable speed.

The LCI device 8 includes a forward converter 9, a DC reactor 10, an inverse converter 11, a current detector 12, a voltage detector 13, and a controller 14.

The forward converter 9 is provided so as to be able to convert the AC power output from the power supply 1 into DC power. The DC reactor 10 is provided so as to smooth the DC power output by the forward converter 9. The inverse converter 11 is provided so that the DC power smoothed by the DC reactor 10 can be converted into AC power. The current detector 12 is provided so as to detect an alternating current input from the power supply 1 to the LCI device 8. The voltage detector 13 is provided so as to detect the armature winding voltage of the synchronous motor 3.

The control device 14 includes a speed control unit 15, a current control unit 16, a mechanical phase detection unit 17, an electrical phase detection unit 18, a switching unit 19, a speed detection unit 20, a current interruption control unit 21, a β calculation unit 22, and α. The phase controller 23, the β phase controller 24, the induced voltage calculator 25, and the phase corrector 27 are provided.

The speed control unit 15 is provided so as to be able to output the current command based on the deviation between the detected value of the speed of the synchronous motor 3 which is the output of the speed detection unit 20 and the speed reference given from the outside. The current control unit 16 is provided so as to be able to output the ignition phase of the forward converter 9 based on the deviation between the current command output by the speed control unit 15 and the detection value of the current detector 12.

The mechanical phase detector 17 is provided so as to detect the phase of the synchronous motor 3 based on the rotor magnetic pole position detection signal output by the position detector 5. The electrical phase detector 18 is provided so as to detect the phase of the synchronous motor 3 based on the AC voltage detected by the voltage detector 13. The electrical phase detector 18 is configured by, for example, a PLL (Phase Locked Loop) circuit. The switching unit 19 is provided so as to be able to output either one of the input from the mechanical phase detection unit 17 and the input from the electrical phase detection unit 18. The speed detection unit 20 is provided so as to be able to calculate the detected value of the speed of the synchronous motor 3 based on the output of the switching unit 19.

The current interruption control unit 21 is provided so as to be able to output a current interruption control command based on the output of the switching unit 19. The β calculator 22 is provided so as to be able to calculate β based on the output of the switching unit 19, the output of the induced voltage calculator 25, and the output of the current detector 12.

The α phase control unit 23 is provided so as to perform α phase control for the thyristor of the forward converter 9 based on the output of the current control unit 16, the output of the current interruption control unit 21, and the phase signal (not shown) of the power supply 1. The β phase control unit 24 is provided so as to perform β phase control for the thyristor of the inverse converter 11 based on the output of the current interruption control unit 21, the output of the β calculation unit 22, and the output of the switching unit 19.

The induced voltage calculator 25 is provided so that the induced voltage of the synchronous motor 3 can be calculated from the detection value of the voltage detector 13. The phase corrector 27 is based on the result of comparison between the phase θe of the induced voltage detected by the electrical phase detector 18 and the mechanical phase signal θm detected by the mechanical phase detector 17 during the turning operation of the synchronous motor 3. The phase error between the induced voltage of the synchronous motor 3 and the detection by the position detector 5 is calculated, and the phase of the detection by the position detector 5 can be corrected.

The control device 14 includes a control unit 28.

The control unit 28 is provided so as to control the operation of each unit of the control device 14. For example, the control unit 28 is provided so that a turning signal indicating a turning operation period is input from the outside and the operation timing of the phase correction unit 27 can be controlled. Further, for example, the control unit 28 is provided so as to be able to output a command for outputting a strong field command to the exciter 7.

Next, the outline of control of the synchronous motor 3 will be described with reference to FIG.
FIG. 2 is a diagram for explaining the outline of the control of the synchronous motor by the control device for the synchronous motor in the first embodiment.

The induced voltage E of the synchronous motor 3 is expressed by the following equation (1).

However, k is a constant. Φ is a field of the synchronous motor 3. ω is the rotation speed of the synchronous motor 3.

In the formula (1), when the rotation speed ω of the synchronous motor 3 is 0, the induced voltage E is not generated. From time t1 to time t5 is a period in which the turning operation is performed, and the synchronous motor is driven by the small electric motor 4. The LCI device is not operated until time t5. The rotation speed ω of the synchronous motor 3 is increased to a speed ω1 which is about 1% of the rated rotation speed, and is kept in this state for a predetermined time (time t2 to time t5). For example, the rotation speed ω1 of the synchronous motor 3 is about 30 rpm. This state is maintained for 30 to 60 minutes.

From time t5 to time t7, the LCI device 8 drives the synchronous motor 3 to accelerate the rotation speed from ω1 to the rated rotation speed ω3. When the rotation speed ω of the synchronous motor 3 is low, the value of the induced voltage E is small. Therefore, commutation of the inverse converter 11 due to the induced voltage may be difficult.

Therefore, in the low speed region (for example, a region lower than the rotation speed ω2), the current interruption control unit 21 of the control device 14 performs the current interruption control. If the induced voltage E is low, the electrical phase detector 18 may not operate stably. Therefore, specifically, the current interrupting control unit 21 of the control device 14 sequentially advances, for example, every 60° based on the corrected mechanical phase signal θme which is the output of the phase correction unit 27 selected by the switching unit 19. The DC current output by the converter 9 is interrupted, and a preset thyristor of the inverse converter 11 is fired.

After that, when the rotation speed ω of the synchronous motor 3 increases, the control unit 28 of the control device 14 applies a reverse voltage to the thyristor energized up to that point by the load commutation action using the induced voltage E of the synchronous motor 3. Control to turn it off. Further, when the induced voltage E increases and the electrical phase detection unit 18 operates stably, the switching unit 19 switches its output to the electrical phase θe.

After that, when the rotation speed ω of the synchronous motor 3 reaches the rated rotation speed ω3, for example, when the rotation speed ω3 of the synchronous motor 3 reaches 3000 rpm, the synchronous motor 3 is synchronized with the power source 1 by the switch device (not shown), The synchronous motor 3 may be directly driven by the power supply 1.

Next, a method of calculating the induced voltage E will be described with reference to FIG.
FIG. 3 is an equivalent circuit diagram of a synchronous motor to which the synchronous motor control device according to the first embodiment is applied. The left side of FIG. 3 is an equivalent circuit. The right side of FIG. 3 is a vector diagram.

The induced voltage of the synchronous motor 3 is expressed by the following equation (2).

However, in the equation (2), V is a terminal voltage. X _s is a synchronous reactance. Ia is an electric current.

The current Ia is 0 during the turning operation. Therefore, the induced voltage E of the synchronous motor 3 becomes the same as the terminal voltage V. Specifically, the induced voltage E is represented by the following equation (3).

Next, a method of calculating the phase error will be described with reference to FIGS. 4 and 5.
FIG. 4 and FIG. 5 are waveform diagrams of respective parts for explaining the error calculation method by the control device for the synchronous motor in the first embodiment. 4 and 5, (a) is the induced voltage of the synchronous motor 3, (b) is the rotor magnetic pole position detection signal, (c) is the electrical phase signal θe, and (d) is the mechanical phase signal θm.

The position detector 5 is a proximity sensor. Therefore, the rotor magnetic pole position detection signal becomes a rectangular wave. On the other hand, the induced voltage E of the synchronous motor 3 becomes a sine wave. The electrical phase signal θe and the mechanical phase signal θm are triangular waves that periodically change from 0 to 2π.

When there is no phase error between the induced voltage E of the synchronous motor 3 and the rotor magnetic pole position detection signal, the rotor magnetic pole position detection signal is at the zero-cross position of the induced voltage E of the synchronous motor 3 as shown in FIG. Turns on and off. The waveform of (c) and the waveform of (d) are synchronized.

When there is a phase error between the induced voltage E of the synchronous motor 3 and the rotor magnetic pole position detection signal, the rotor magnetic pole position detection signal is output from the zero-cross position of the induced voltage E of the synchronous motor 3 as shown in FIG. Turns on and off at offset positions. Similarly, the waveforms of (c) and (d) are also shifted in timing of zero.

For example, when the rotor magnetic pole position detection signal is turned on and off at a time deviating from the time when the zero cross of the induced voltage E of the synchronous motor 3 occurs by Δt, the phase error Δθ is calculated by the following equation (4). expressed.

However, in the equation (4), T is a cycle obtained from the rotation speed of the synchronous motor 3.
Therefore, it is understood that Δθ should be corrected for the mechanical phase signal θm.

Next, the details of the correction of the detection phase by the position detector 5 will be described with reference to FIG.
FIG. 6 is a block diagram of essential parts of the phase correction unit 27 and the control unit 28 in the first embodiment.

For example, the phase correction unit 27 includes a subtraction unit 271, a latch circuit 272, an addition unit 273, a normalization circuit 274, a comparator 275, a comparator 276, and a 3-input AND circuit unit 277. For example, the control unit 28 includes a delay unit 281, a one-shot circuit 283, an AND circuit unit 284, and the like.

The turning signal from the outside is input to the AND circuit unit 284 which is a logical product of the delay unit 282 in the control unit 28 and the two inputs. The output of the delay unit 282 is input to the one-shot circuit 283. The output of the one-shot circuit 283 is input to the AND circuit unit 284. The output of the AND circuit unit 284 is input to the AND circuit unit 277 in the phase correction unit 27 and is also output to the exciter 7 as a strong field command.

The delay unit 282 is a circuit that changes its output from L level to H level with a delay of a predetermined time T1 when the input signal changes from L level to H level. The one-shot circuit 283 is a circuit whose output becomes H level only during a predetermined time T2 when the input signal changes from L level to H level.

The electrical phase signal θe, which is the output of the electrical phase detection unit 18, is connected to the first input of the subtraction unit 271. The mechanical phase signal θm output from the mechanical phase detector 17 is connected to the second input of the subtractor 271 and the first input of the adder 273. The subtraction unit 271 outputs the difference Δθ between the electrical phase signal θe that is the first input and the mechanical phase signal θm that is the second input to the signal input terminal of the latch circuit 272. The output of the latch circuit 272 is connected to the second input of the adder 273.

The mechanical phase signal θm, which is the output of the mechanical phase detection unit 17, is input to the input of the comparator 275. The comparator 275 is configured so that the output is at the H level when the input signal is in the range from the first set value to the second set value, and is at the L level otherwise. The output of the comparator 275 is input to the AND circuit unit 277.

The electrical phase signal θe, which is the output of the electrical phase detector 18, is input to the input of the comparator 276. The comparator 276 is configured so that the output is at the H level when the input signal is in the range of the third set value to the fourth set value, and is at the L level otherwise. The output of the comparator 276 is input to the AND circuit unit 277.

The output of the AND circuit unit 277 is input to the control terminal of the latch circuit 272. The latch circuit 272 outputs the same value as the input signal when the signal at the control terminal is at the H level, and holds the previous value when the control terminal input changes from the H level to the L level. It is a latch circuit. The output of the adder 273 is input to the normalization circuit 274. The output of the normalization circuit 274 is output to the switching unit 19 as a corrected mechanical phase signal θme. The normalization circuit 274 is a circuit that normalizes and outputs the input signal as a periodic signal of 0 or more and less than 2π.

The operation of the first embodiment will be described with reference to FIGS. 1, 2 and 6. Here, for simplification, it is assumed that the outputs of the comparators 275 and 276 are always at the H level.

It is assumed that turning is started at time t1. When the turning is started, the turning signal changes from the L level to the H level. The synchronous motor 3 is driven by the small electric motor 4 and stably rotates at the rotation speed ω1 from time t2 to time t5. At time t3 when time T1 has elapsed from time t1 after time t2, the output of the delay unit 282 changes from L level to H level. Further, the one-shot circuit 283 is set to the H level for the period T2 from the time t3 to the time t4. Therefore, during the period from time t3 to time t4, the output of the AND circuit unit 284 also becomes H level. Therefore, while the output of the one-shot circuit 283 is at the H level, the output of the latch circuit 272 is the output of the subtraction unit 271 itself. Here, in the period from time t3 to time t4, since the rotation speed of the synchronous motor 3 is stable at ω1, the difference Δθ which is the output of the subtraction unit 271 is also stable. When the output of the one-shot circuit 283 changes from the H level to the L level at time t4, the latch circuit 272 holds the value immediately before that, Δθt4. That is, the output of the latch circuit 272 after time t4 becomes Δθt4. Since Δθt4 is the difference between the mechanical phase detection and the electrical phase detection, the addition unit 273 corrects the output of the mechanical phase detection unit 17 by adding θm and Δθt4 to obtain a highly accurate phase of the synchronous motor. be able to. Therefore, from time t5 to time t6, it is possible to use a highly accurate phase signal in the drive period of the synchronous motor 3 by the LCI device 8 using mechanical phase detection.

Further, when the one-shot circuit 283 accepts the input of the delay signal from the delay unit 282, the one-shot circuit 283 outputs the field strengthening signal of the constant time width T2 to the H level via the AND circuit unit 283 and outputs it.

The exciter 7 increases the current flowing through the exciting coil 6 from the rated value when the input of the field strengthening signal is at the H level. As a result, field strengthening control is performed, and the field becomes large according to the equation (1) described above, so that the induced voltage becomes high and the electrical phase can be detected more accurately even at a low rotation speed. Therefore, the phase error Δθ can be accurately detected. Further, since the field strengthening control is performed for a relatively short period of time T2, it is possible to reduce the influence of stress on the exciting device 7, the exciting coil 6, and the like.

Here, the operation of the comparator 275 and the comparator 276 will be described. As can be seen from (c) and (d) of FIG. 5, the electrical phase signal θe and the mechanical phase signal θm are triangular waves, and their values increase in the range of 0 to 2π (strictly, less than 2π). However, it suddenly changes from 2π to 0. Therefore, since Δθ changes abruptly at this timing, it is not preferable that the latch circuit 272 holds the suddenly changed Δθ and corrects with that value. Therefore, the control terminal of the latch circuit 272 is always L in the regions where θm and θe are close to 0 and 2π, which are timings when Δθ is expected to change suddenly in the comparators 275 and 276 and the AND circuit unit 277. It is configured to reach the level.

The maximum phase difference between the mechanical phase signal θm and the electrical phase signal θe can be predicted from the mechanical accuracy of the synchronous motor 3 and the position detector 5 and the assembly error. If this maximum phase difference is ±ΔθMAX, it is desirable that the first and third set values be larger than ΔθMAX and the second and fourth set values be smaller than 2π−θMAX. Further, either one of the comparator 275 and the comparator 276 may be omitted and the AND circuit unit 277 may have two inputs.

Further, the AND circuit unit 284 is an interlock circuit for outputting the control signal only when the signal indicating the turning operation and the field strengthening signal are simultaneously input, and may be omitted if necessary.

According to the first embodiment described above, during the turning operation, control device 14 calculates the phase from the induced voltage of synchronous motor 3 detected by voltage detector 13 to obtain the electrical phase signal. The control device 14 calculates the phase error between the induced voltage of the synchronous motor 3 and the detection by the position detector 5 based on the comparison result of the electrical phase signal and the mechanical phase signal by the induced voltage. The controller 14 corrects the mechanical phase signal from the position detector 5 based on the calculated phase error, and uses the corrected value when the LCI device 8 is turned after the turning operation. Therefore, the mechanical phase detection by the position detector 5 can be automatically corrected. As a result, the ignition timing of the LCI device 8 can be made appropriate in the low speed region of the synchronous motor in the current interrupt control or the like. Therefore, the synchronous motor can be stably driven during the phase control of the inverse converter by the mechanical position detector.

At this time, precise adjustment of the position detector 5 is not necessary. Therefore, it is not necessary to send a specialized coordinator to the site. As a result, the adjustment time and the adjustment cost of the position detector 5 can be eliminated.

Further, the control device 14 performs field strengthening control of the synchronous motor 3 at the detection timings of the voltage detector 13 and the position detector 5 when the detection phase of the position detector 5 is corrected. Therefore, the phase detection by the position detector 5 can be corrected more accurately in a state where the induced voltage of the synchronous motor 3 is increased.

The phase of detection by the position detector 5 may be continuously corrected while the synchronous motor 3 rotates at least once. If the correction value changes during one cycle, a means such as averaging may be added.

Next, an example of the control device 14 will be described with reference to FIG. 7.
FIG. 7 is a hardware configuration diagram of the synchronous motor control device according to the first embodiment.

Each function of the control device 14 can be realized by a processing circuit. For example, the processing circuit comprises at least one processor 100a and at least one memory 100b. For example, the processing circuit comprises at least one dedicated hardware 200.

When the processing circuit includes at least one processor 100a and at least one memory 100b, each function of the control device 14 is realized by software, firmware, or a combination of software and firmware. At least one of software and firmware is described as a program. At least one of software and firmware is stored in at least one memory 100b. At least one processor 100a realizes each function of the control device 14 by reading and executing a program stored in at least one memory 100b. The at least one processor 100a is also called a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, and a DSP. For example, the at least one memory 100b is a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, or an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD, or the like.

If the processing circuit comprises at least one dedicated hardware 200, the processing circuit may be implemented, for example, in a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. It For example, each function of the control device 14 is realized by a processing circuit. For example, each function of the control device 14 is collectively realized by a processing circuit.

Part of each function of the control device 14 may be realized by the dedicated hardware 200, and the other part may be realized by software or firmware. For example, the function of the control unit 28 is realized by a processing circuit as the dedicated hardware 200, and for the function other than the function of the control unit 28, at least one processor 100a reads a program stored in at least one memory 100b. It may be realized by executing.

As such, the processing circuit implements each function of the control device 14 by the hardware 200, software, firmware, or a combination thereof.

1 power source, 2 load, 3 synchronous motor, 4 small electric motor, 5 position detector, 6 exciting coil, 7 exciting device, 8 LCI device, 9 forward converter, 10 DC reactor, 11 reverse converter, 12 current detector, 13 voltage detector, 14 control device, 15 speed control unit, 16 current control unit, 17 mechanical phase detection unit, 18 electrical phase detection unit, 19 switching unit, 20 speed detection unit, 21 current interruption control unit, 22 β Arithmetic unit, 23 α phase control unit, 24 β phase control unit, 25 induced voltage calculation unit, 27 phase correction unit, 28 control unit, 271 subtraction unit, 272 latch circuit, 273 addition unit, 274 normalization circuit, 275 comparator, 276 comparator, 277 AND circuit unit, 281 delay unit, 283 one-shot circuit, 284 AND circuit unit, 100a processor, 100b memory, 200 hardware

Claims (4)

An electrical phase detection unit that detects a phase from an induced voltage of an armature winding of a synchronous motor, a mechanical phase detection unit that detects a phase from an output signal of a position detector of the synchronous motor, and an output of the mechanical phase detection unit. A phase correction unit for correction,
Equipped with
The phase correction unit,
Compute a correction value based on the output of the phase difference calculator during the turning operation of the synchronous motor and the phase difference calculator that calculates the difference between the output of the electrical phase detector and the output of the mechanical phase detector, A control device for a synchronous motor that corrects the output of the mechanical phase detector based on the correction value. A control unit that performs field strengthening control of the synchronous motor at the time of calculating the correction value,
The control device for the synchronous motor according to claim 1, further comprising: The control device for the synchronous motor according to claim 1, wherein the timing for calculating the correction value is a period during which the output of the mechanical phase detection unit falls within a range of a first predetermined value and a second predetermined value. The control device for the synchronous motor according to claim 1, wherein the timing for calculating the correction value is a period during which the output of the electrical phase detection unit falls within a range between a third predetermined value and a fourth predetermined value.

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