JP2022175151A - Power conversion device and control method for the same - Google Patents

Abstract

To control a current and a rotatable speed of a motor with high precision from a time of stopping to a high rotatable speed in a power conversion device.SOLUTION: An encoder switching processing unit 18 outputs a first encoder detection rotation speed ωenc1 as a detection rotation speed ω_det when the detection rotation speed ω_det is greater than a threshold value. The encoder switching processing unit 18 outputs a value obtained by adding a difference between a previous value of a first encoder detection phase θenc1 and a current value to a previous value of a control phase θ_det as a control phase θ_det. The encoder switching processing unit 18 outputs a second encoder detection rotation speed ωenc2 as the detection rotation speed ω_det when the detection rotation speed ω_det is less than the threshold value. The encoder switching processing unit 18 outputs a value obtained by adding a difference between a previous value of the second encoder detection phase θenc2 and the current value to the previous value of the control phase θ_det or the second encoder detection phase θenc2 as the control phase θ_det.SELECTED DRAWING: Figure 9

Description

The present invention relates to a power converter that switches the outputs of a plurality of position/rotation detectors (hereinafter referred to as encoders) during operation in order to control the current and rotation speed of an electric motor (hereinafter referred to as motor) with high accuracy.

Patent Literatures 1 and 2 disclose power conversion devices that control motors.

Patent Document 1 has sensorless magnetic pole position detection means and means for detecting the magnetic pole position with a sensor, and discloses a method of switching using a weighting circuit in a transition section (FIG. 15). In this system, the motor is operated in the low and medium speed ranges by sensorless control, and the magnetic pole position detected by the sensor is used in the high speed range. Patent Literature 1 aims at using an inexpensive sensor and driving the vehicle with high accuracy.

In Patent Document 2, the speed and angle of a motor controlled object are measured and used for control (FIG. 16). Patent Literature 2 aims at controlling an object to be controlled by a motor with high accuracy.

JP-A-2004-112939 JP 2019-34679 A

Patent Document 1 has sensorless magnetic pole position detection means and means for detecting the magnetic pole position with a sensor, and uses a weighting circuit in the transition section. However, sensorless control is known to be incapable of accurately detecting the magnetic pole position in the low speed range, so accuracy is poor. In addition, in the transition section, both types of phase information are mixed, so the characteristics of the phase information are not constant. For this reason, there is a possibility that the control accuracy will deteriorate.

Further, in Patent Document 2, the speed and angle of a motor controlled object are measured and used for control. In this case, the object to be controlled can be controlled with high accuracy, but the encoder detection accuracy of the motor itself is poor, so shaft misalignment occurs. As a result, an excessive current is generated, and there is a risk that the motor current will exceed the rated current (current that allows continuous operation), resulting in failure and stoppage of the device.

As described above, in the electric power conversion device, it becomes a problem to control the current and rotation speed of the motor with high accuracy from the time of stop to high rotation speed.

The present invention has been devised in view of the above-described conventional problems, and one aspect thereof is a power conversion device for driving a motor, comprising: a first position/rotation detector; A second position/rotation detector having a higher resolution per rotation of the motor but a slower detection cycle than the encoder, and a first encoder detecting rotation, which is the output of the first position/rotation detector when the detected rotation speed is greater than the threshold value. is output as the detected rotation speed, and the difference between the previous value and the current value of the first encoder detection phase, which is the output of the first position/rotation detector, is added to the previous value of the control phase as the control phase. When the detected rotational speed is smaller than the threshold, the second encoder detected rotational speed, which is the output of the second position/rotation detector, is output as the detected rotational speed, and the second position/rotation detector outputs the detected rotational speed. an encoder switching processing unit that outputs, as the control phase, a value obtained by adding the difference between the previous value and the current value of the second encoder detection phase, which is an output, to the previous value of the control phase, or the second encoder detection phase. It is characterized by

Further, as one aspect thereof, the encoder switching processing unit compares the detected rotational speed with the threshold value, outputs 1 as an encoder switching determination signal when the detected rotational speed is larger, and outputs 1 as an encoder switching determination signal. a threshold comparison unit that outputs 0 as the encoder switching determination signal when the encoder switching determination signal is smaller; a first switch for outputting the second encoder detected rotational speed as the detected rotational speed when 0; and a first subtractor for outputting a first difference, which is the difference between the previous value and the current value of the first encoder detected phase. a second subtractor for outputting a second difference between the previous value and the current value of the second encoder detection phase; and outputting the first difference when the encoder switching determination signal is 1 to determine the encoder switching. a second switch that outputs the second difference when the output of the signal is 0; and the first adder that adds the previous output value of the first adder to the output of the second switch and outputs the result as the control phase. , is provided.

Further, as one aspect thereof, the first position/rotation detector outputs a Z-phase pulse that is output one pulse for each rotation of the motor, and the encoder switching processing unit outputs one Z-phase pulse, and When the encoder switching determination signal is 1, the first encoder detection phase is set as the control phase.

In another aspect, the encoder switching processing unit compares the detected rotational speed with the threshold value, and outputs 1 as an encoder switching determination signal when the detected rotational speed is greater than the detected rotational speed. a threshold comparison unit that outputs 0 as the encoder switching determination signal when the encoder switching determination signal is smaller than A first switch that outputs the second encoder detected rotation speed as the detected rotation speed when the signal is 0, and a first subtractor that outputs a first difference that is the difference between the previous value and the current value of the first encoder detection phase. a second adder for adding the previous output value of the fourth switch to the first difference; outputting the second encoder detection phase during the detection cycle of the second position/rotation detector; the fourth switch that outputs the output of the second adder when the output of the encoder switching determination signal is 1; the output of the fourth switch is output as the control phase when the encoder switching determination signal is 1; and a fifth switch for outputting the second encoder detection phase as the control phase.

Further, as one aspect thereof, the encoder switching processing unit provides the threshold with hysteresis, and the threshold is set to the value of the first position/rotation detector when the encoder switching determination signal is switched from OFF to ON. A value obtained by adding the rotation speed detection accuracy to the rotation speed minimum resolution is set, and when the encoder switching determination signal is switched from ON to OFF, the rotation speed minimum resolution of the first position/rotation detector is set. Characterized by

Advantageous Effects of Invention According to the present invention, in a power conversion device, it is possible to control the current and rotation speed of a motor with high accuracy from the time of stop to the high rotation speed.

The block diagram which shows an example of a structure of a power converter device. FIG. 4 is a diagram showing an example of an A-phase pulse, a B-phase pulse, and a Z-phase pulse, which are INC output pulses; FIG. 4 is a diagram showing other examples of A-phase, B-phase, and Z-phase pulses that are output pulses of INC; FIG. 4 is a diagram showing other examples of A-phase, B-phase, and Z-phase pulses that are output pulses of INC; The figure which shows an example of the output signal of ABS. FIG. 4 is a diagram showing the relationship between INC and ABS output signals and detection phases; FIG. 10 is a diagram showing detection waveforms of INC and ABS at low speed in consideration of the detection cycle; FIG. 4 is a diagram showing INC and ABS detection waveforms at high speed in consideration of the detection cycle; 4 is a block diagram showing an encoder switching processing unit according to the first embodiment; FIG. 4A and 4B are diagrams showing first and second encoder detection phases and control phases according to the first embodiment; FIG. FIG. 4 is a diagram showing first and second encoder detection phases and control phases without an integrator; FIG. 8 is a block diagram showing an encoder switching processing unit according to the second embodiment; FIG. 11 is a block diagram showing an encoder switching processing unit according to the third embodiment; FIG. 11 is a diagram showing first and second encoder detection phases and control phases in Embodiment 3; The figure which shows the power converter device in the patent document 1. FIG. The figure which shows the power converter device in the patent document 2. FIG.

Embodiments 1 to 3 of the power converter according to the present invention will be described in detail below with reference to FIGS. 1 to 14. FIG.

[Embodiment 1]
An example of the power conversion device of Embodiment 1 is shown in FIG. In FIG. 1, the configuration is such that position control (hereinafter referred to as APR) for controlling the position as the main purpose is performed. In APR1, the phase command .theta._cmd and the control phase .theta._det are compared, and the rotational speed command .omega._cmd is output so as to eliminate the error. Next, the ASR 2 compares the rotational speed command ω_cmd and the detected rotational speed ω_det, performs speed control (hereinafter referred to as ASR) so as to eliminate the error, and outputs the torque command Trq_cmd.

The command conversion processing unit 3 converts the torque command Trq_cmd into a d-axis current command Id_cmd and a q-axis current command Iq_cmd by performing torque command→current command conversion processing.

The ACR 4 compares the d-axis current command Id_cmd with the d-axis current detection Id_det, compares the q-axis current command Iq_cmd with the q-axis current detection Iq_det, performs current control (hereinafter referred to as ACR) to eliminate errors, A voltage command Vd_cmd and a q-axis voltage command Vq_cmd are output.

Rotational coordinate conversion unit 5 performs coordinate conversion on d-axis voltage command Vd_cmd and q-axis voltage command Vq_cmd with control phase θ_det, and outputs α-axis voltage command Vα_cmd and β-axis voltage command Vβ_cmd.

The two-to-three-phase converter 6 converts the α-axis voltage command Vα_cmd and the β-axis voltage command Vβ_cmd into two-to-three phase, and outputs a U-phase voltage command Vu_cmd, a V-phase voltage command Vv_cmd, and a W-phase voltage command Vw_cmd.

The zero-phase modulation unit 7 zero-phase-modulates the U-phase voltage command Vu_cmd, the V-phase voltage command Vv_cmd, and the W-phase voltage command Vw_cmd to obtain the U-phase voltage command Vu after zero-phase modulation, the V-phase voltage command Vv after zero-phase modulation, A W-phase voltage command Vw is output after zero-phase modulation.

A carrier comparison unit 8 compares the U-phase voltage command Vu after zero-phase modulation, the V-phase voltage command Vv after zero-phase modulation, and the W-phase voltage command Vw after zero-phase modulation, and outputs a U-phase PWM modulation command Pu and a V-phase PWM modulation command. A modulation command Pv and a W-phase PWM modulation command Pw are output.

Gate signal generator 9 generates U-phase upper arm gate signal Gu, U-phase lower arm gate signal Gx, V-phase upper arm gate signal Gu, U-phase lower arm gate signal Gx, and V-phase upper arm gate signal Gu based on U-phase PWM modulation command Pu, V-phase PWM modulation command Pv, and W-phase PWM modulation command Pw. A gate signal Gv, a V-phase lower arm gate signal Gy, a W-phase upper arm gate signal Gw, and a W-phase lower arm gate signal Gz are generated to drive the inverter 10 . Further, in FIG. 1, reference numeral 19 denotes a three-phase AC power supply, and reference numeral 20 denotes a converter.

A three-phase to two-phase converter 11 converts the inverter U-phase output current Iu, the inverter V-phase output current Iv, and the inverter W-phase output current Iw into three-phase to two-phase, and outputs an α-axis current detection Iα_det and a β-axis current detection Iβ_det. do.

Rotational coordinate conversion unit 12 performs coordinate conversion of α-axis current detection Iα_det and β-axis current detection Iβ_det with control phase θ_det, and outputs d-axis current detection Id_det and q-axis current detection Iq_det.

Since the d-axis current detection Id_det and the q-axis current detection Iq_det obtained by coordinate transformation are used in the ACR 4, detection accuracy is required to control the permanent magnet synchronous motor (PM) 13 with high accuracy. . Therefore, the control phase θ_det is a very important signal.

The control phase θ_det can be obtained from the encoder. In FIG. 1, the first encoder 14 and the second encoder 15 output a first encoder signal Encsig1 and a second encoder signal Encsig2. Based on the first encoder signal Encsig1 and the second encoder signal Encsig2, the first and second encoder processing units 16 and 17 detect the first encoder detected phase θenc1 and the first encoder detected rotation speed ωenc1 (the signal of the first position/rotation detector). ), second encoder detected phase θenc2 and second encoder detected rotation speed ωenc2 (second position/rotation detector signal).

The encoder switching processing unit 18 selects which of the obtained first encoder detection phase θenc1 and first encoder detection rotation speed ωenc1 and the second encoder detection phase θenc2 and second encoder detection rotation speed ωenc2 to use, and performs control. It is output as phase θ_det and detected rotational speed ω_det.

An incremental encoder (hereinafter, INC) is applied to the first encoder 14 . This encoder has a pulse output signal. The resolution is low, but the output pulse has little delay.

For the second encoder 15, an encoder with high resolution but with detection delay is applied. In the power conversion device of FIG. 1, a high-resolution encoder is used, although detection cannot be performed at a cycle faster than the rotation coordinate conversion processing cycle. For example, it is a serial signal output type absolute encoder (hereinafter referred to as ABS). The signal format is a serial signal and there is a transmission delay. However, since one rotation has a resolution of several tens of bits, the resolution is very high. There is no problem even if the first encoder 14 and the second encoder 15 are interchanged.

In FIG. 1, PM vector control is described as the control that detects and uses the phase from encoder information. However, other control configurations can also be applied when the phase is detected from encoder information and used. Also, the control may be performed mainly for the number of revolutions or the current.

An example of the INC output pulse is shown in FIG. There are three types of signals, and hundreds of A-phase and B-phase pulses are output per rotation. A Z-phase pulse is a pulse that is output once per motor rotation. The A-phase pulse and the B-phase pulse are signals with a phase difference of 90°. Here, 360° is one pulse period. FIG. 2 is an example, and there are various forms such as FIG. 3 and FIG. 4 depending on the signal specifications of the encoder.

The ABS output is shown in FIG. The time required for transmission varies depending on the transmission speed per bit and the signal length.

FIG. 6 shows the relationship between INC and ABS output signals and detection phases. The detection phase of INC is detected by the rising edge/falling edge of the A-phase pulse and the rising edge/falling edge of the B-phase pulse (hereinafter referred to as the 4f method). When the Z-phase pulse rises, the phase is reset at the fall timing of the A-phase pulse. In reverse rotation, the phase is reset at the rising edge of the A-phase pulse while the Z-phase pulse is rising. This is the phase before origin correction.

If the inverter-driven motor is PM, the encoder origin position must be adjusted so that the detected phase is 0 when there is no phase difference between the rotor magnet and the stator U-phase winding. . In the case of INC, the deviation between the detection phase of the Z-phase pulse and the magnet position is corrected. In the case of ABS, the deviation between the 0 point of the encoder output detection phase and the magnet position is corrected. The phase after this correction is the phase after origin correction.

The ABS internal detection phase is sent by serial transmission. A transmission delay occurs due to serial transmission. The phase after this serial transmission is corrected for the origin. The phase obtained by compensating for the delay in serial transmission with respect to the origin-corrected value is the detected phase after ABS correction.

The encoder switching processing unit 18 performs encoder switching processing to switch each corrected phase.

FIG. 7 shows INC and ABS detection waveforms at low speeds, taking the detection cycle into consideration. (1) in FIG. 7 is the INC detection period, and (2) is the ABS detection period. As mentioned earlier, the ABS is serially transmitted, so transmission delays occur. Since it cannot be detected faster than the transmission time, the detection period is restricted by the transmission time. In the case of INC, there is no restriction on the detection cycle because the method is to detect pulses. When the speed is low, since the INC pulse is not input during the detection period, the INC detection phase is updated later than the ABS detection phase and the resolution is low. Also, since the ABS detection phase is periodically updated, it can be seen that the resolution is higher than that of INC.

Next, FIG. 8 shows INC and ABS detection waveforms at high speed in consideration of the detection cycle. (1) in FIG. 8 is an INC detection cycle, and (2) is an ABS detection cycle. At high speed, the INC pulse is input during the detection period, so the INC detection phase is updated faster than the ABS detection phase, resulting in higher resolution. Also, although the ABS detection phase is updated periodically, it can be seen that the resolution is low because the update is slower than the INC.

In the first embodiment, an encoder (ABS) with high resolution but large detection delay is used from the time of stop to low rotation speed, and an encoder (INC) with low resolution but little detection delay is used from low rotation speed to high rotation speed. do the driving.

The encoder switching processing unit 18 outputs the first encoder detected rotation speed ωenc1 as the detected rotation speed ω_det when the detected rotation speed ω_det is larger than the threshold value. Also, a value obtained by adding the difference between the previous value of the first encoder detection phase θenc1 and the current value to the previous value of the control phase θ_det is output as the control phase θ_det.

Further, the encoder switching processing unit 18 outputs the second encoder detected rotation speed ωenc2 as the detected rotation speed ω_det when the detected rotation speed ω_det is smaller than the threshold value. Further, a value obtained by adding the difference between the previous value of the second encoder detection phase θenc2 and the current value to the previous value of the control phase θ_det is output as the control phase θ_det.

FIG. 9 shows a block diagram of the encoder switching processing unit 18 in the first embodiment. In the first embodiment, the detected rotational speed ω_det is used for encoder switching determination. The threshold comparator 21 compares the detected rotational speed ω_det with a threshold and outputs an encoder switching determination signal. When the detected rotational speed ω_det is greater than the threshold, the encoder switching determination signal is 1, and when the detected rotational speed ω_det is less than the threshold, the encoder switching determination signal is 0. In addition, the threshold comparator 21 sets hysteresis to the threshold. This is to prevent 0 and 1 from being switched at a high speed when the detected rotation speed ω_det has an error corresponding to vibration and rotation speed detection accuracy, and the encoder cannot be stably switched. .

The first switch 22 outputs the first encoder detected rotation speed ωenc1 when the encoder switching determination signal is 1, and outputs the second encoder detection rotation speed ωenc2 when it is 0. The output of the first switch 22 becomes the detected rotational speed ω_det.

Next, phase processing at the time of encoder switching will be described. The buffer 23 outputs the previous value of the first encoder detection phase θenc1. The buffer 24 outputs the previous value of the second encoder detected phase θenc2. The first subtractor 25 outputs a first difference Δθenc1, which is the difference between the current value and the previous value of the first encoder detection phase θenc1. The second subtractor 26 outputs a second difference Δθenc2, which is the difference between the current value and the previous value of the second encoder detection phase θenc2.

The second switch 27 outputs the first difference Δθenc1 when the encoder switching determination signal is 1, and outputs the second difference Δθenc2 when it is 0. The output of the second switch 27 becomes the phase difference Δθenc. The phase difference Δθenc selected by the switching determination is input to the integrator. That is, the buffer 29 outputs the previous output value of the first adder 28 (previous value of the control phase θ_det). The adder 28 adds the previous output value (previous value of the control phase θ_det) of the first adder 28 to the phase difference Δθenc and outputs the result as the control phase θ_det.

The features of the first embodiment are summarized below.
- A process of obtaining the difference between the current value and the previous value of the phase detected by each encoder.
A process of integrating the phase obtained by taking the difference to obtain the control phase θ_det.

（２）式以上の回転数となるとＩＮＣ検出周期ごとにＩＮＣ検出位相が更新されていく。 Use ABS at low speeds and INC at high speeds. The minimum resolution for the detection time of each encoder is given by equations (1) and (2).

When the number of revolutions exceeds the formula (2), the INC detection phase is updated every INC detection cycle.

Here, A and B below are set for the hysteresis of encoder switching determination.
A: Rotational speed in formula (2) B: Rotational speed in formula (2) + rotational speed detection accuracy Encoder switching conditions are as follows.
1.0 ⇒ ABS is used for rotation speed + rotation speed detection accuracy of formula (2) or less.
2. (2) The INC is used after exceeding the number of rotations + the detection accuracy of the number of rotations in the formula.
3. After exceeding (2) the number of rotations + the detection accuracy of the number of rotations, INC is used until the number of rotations becomes smaller than the number of rotations of the expression (2).
4. ABS is used when the number of rotations is less than that of formula (2).
5.4 and later use ABS.

FIG. 10 shows waveforms of the first encoder detection phase θenc1, the second encoder detection phase θenc2, and the control phase θ_det when the first embodiment is adopted. Here, the first encoder detection phase θenc1 indicates the INC detection phase, and the second encoder detection phase θenc2 indicates the ABS detection phase.

It can be seen that the ABS detection phase is used when the rotational speed is equal to or less than the formula (2). It can be seen that the INC detection phase is applied after the ABS detection phase is updated beyond the number of revolutions of formula (2). Since the output of the integrator is fed back, even if there is a difference between the absolute value of the INC detection phase and the absolute value of the ABS detection phase, there is no difference in the control phase θ_det and the actual motor phase is followed. I understand. Thus, by calculating the control phase θ_det in the first embodiment, the phase can be detected with high accuracy from low speed to high speed, and torque accuracy can be achieved with high accuracy.

FIG. 11 shows waveforms of the first encoder detection phase θenc1, the second encoder detection phase θenc2, and the control phase θ_det when the first encoder detection phase θenc1 and the second encoder detection phase θenc2 are switched without an integrator. In this case, it can be seen that the control phase θ_det deviates from the actual motor phase when switching. In addition, the characteristics of the ABS detection phase and the INC detection phase are mixed, resulting in phase discontinuity. Therefore, it can be seen that by using the method of the first embodiment, there is no phase discontinuity and smooth switching is possible. Also, the actual phase of the motor can be detected with higher accuracy.

As described above, according to the first embodiment, an encoder with a high resolution but a large detection delay is used in the low speed range, and an encoder with a low resolution but a small detection delay is used in the high speed range. It is possible to control the current and rotation speed of the motor with high accuracy.

[Embodiment 2]
FIG. 12 shows a configuration diagram of the encoder switching processing unit 18 in the second embodiment. The encoder switching determination process is the same as in the first embodiment.

Basically, the encoder switching processing unit 18 outputs the first encoder detected rotation speed ωenc1 as the detected rotation speed ω_det when the detected rotation speed ω_det is greater than the threshold value. Also, a value obtained by adding the difference between the previous value of the first encoder detection phase θenc1 and the current value to the previous value of the control phase θ_det is output as the control phase θ_det.

Further, the encoder switching processing unit 18 outputs the second encoder detected rotation speed ωenc2 as the detected rotation speed ω_det when the detected rotation speed ω_det is smaller than the threshold value. Further, a value obtained by adding the difference between the previous value of the second encoder detection phase θenc2 and the current value to the previous value of the control phase θ_det is output as the control phase θ_det.

A feature of the second embodiment is that the encoder used is an INC, and when a Z-phase pulse that is output one pulse per motor rotation is detected as an encoder signal, the phase information of the INC is used as it is. It is to be.

When the encoder switching determination signal is 1 and the first difference Δθenc1 is selected as the phase difference Δθenc, and the Z-phase signal detection flag that detects the Z-phase pulse is turned ON, the control phase θ_det is set to the first encoder detection phase. Select θenc1.

Specifically, the AND element 30 outputs 1 when the encoder switching determination signal is 1 and the Z-phase detection flag is 1 (the Z-phase pulse is 1), and outputs 0 otherwise. The third switch 31 outputs the first encoder detection phase θenc1 when the output of the AND element 30 is 1, and outputs the output of the adder 28 when the output of the AND element 30 is 0. The output of the third switch 31 becomes the control phase θ_det. Other configurations are the same as those of the first embodiment.

For example, in the case of a permanent magnet synchronous motor (PMSM), there is a risk of stepping out if the position of the magnet cannot be detected. Therefore, the detection phase must also be able to detect the absolute position. If the phase difference .DELTA..theta.enc is integrated, errors continue to accumulate due to discretization errors and the like. For this reason, this error becomes a difference from the position of the magnet, and there is a risk of loss of synchronism due to continued rotation. In order to prevent the operation from stopping due to step-out due to this error, the first encoder detection phase θenc1 is set as the control phase θ_det without using the phase difference when detecting the Z-phase pulse.

As described above, according to the second embodiment, the same effects as those of the first embodiment can be obtained, and it can also be applied to motors such as PMSM, which must be able to detect absolute values.

[Embodiment 3]
FIG. 13 shows a configuration diagram of the encoder switching processing unit 18 in the third embodiment. The encoder switching determination process is the same as in the first embodiment.

Basically, the encoder switching processing unit 18 outputs the first encoder detected rotation speed ωenc1 as the detected rotation speed ω_det when the detected rotation speed ω_det is greater than the threshold value. Also, a value obtained by adding the difference between the previous value of the first encoder detection phase θenc1 and the current value to the previous value of the control phase θ_det is output as the control phase θ_det.

Further, the encoder switching processing unit 18 outputs the second encoder detected rotation speed ωenc2 as the detected rotation speed ω_det when the detected rotation speed ω_det is smaller than the threshold value. It also outputs the second encoder detection phase θenc2 as the control phase θ_det.

A feature of the third embodiment resides in phase processing after determination of encoder switching. In the detection period of the second encoder processing unit 17, the second encoder detection phase θenc2 is always set as the control phase θ_det. Until the next detection cycle of the second encoder process comes, the first difference Δθenc1 is added to obtain the control phase θ_det.

Specifically, the second adder 32 adds the previous output value of the fourth switch 33 (the previous value of the control phase θ_det), which is the output of the buffer 34 , to the output of the first subtractor 25 . The fourth switch 33 outputs the second encoder detection phase θenc2 when the pulse signal for each detection cycle of the second encoder processing section 17 is 1, and outputs the output of the second adder 32 when the pulse signal is 0. . The buffer 34 outputs the previous value of the fourth switch 33 . The fifth switch 35 outputs the output of the fourth switch 33 when the encoder switching determination signal is 1, and outputs the second encoder detection phase θenc2 when the signal is 0.

FIG. 14 shows the control phase θ_det in the third embodiment. In the processing after encoder switching, at the timing when the second encoder detection phase θenc2 is updated, the control phase θ_det also applies the second encoder detection phase θenc2. Although the second encoder detection phase θenc2 has a detection delay, the phase resolution is high, so the actual motor phase can be accurately detected. The first encoder detection phase θenc1 is used at the phase update timing which is not the ABS detection timing. While there is a detection delay in ABS detection, interpolation is performed with the first encoder detection phase θenc1 that has a low resolution but little delay.

As a result, the control phase θ_det can be accurately detected without detection delay. As shown in FIG. 13, when switching between the second encoder detection phase θenc2 and the first encoder detection phase θenc1 and interpolating with the first encoder detection phase θenc1, discontinuity does not occur due to the presence of the integrator. do not have.

As described above, according to the third embodiment, the high-resolution encoder information is used when the high-resolution encoder signal can be detected, and the encoder information with little detection delay is updated while the high-resolution encoder signal is not detected. By using low-resolution encoder information, high-resolution phase information with little detection delay can be detected. Therefore, it is possible to perform control with higher accuracy than in the first embodiment.

Although the present invention has been described in detail only with respect to the specific examples described above, it is obvious to those skilled in the art that various modifications and modifications are possible within the scope of the technical idea of the present invention. Such variations and modifications are, of course, covered by the claims.

14... First encoder (first phase/rotation detector)
15... Second encoder (second phase/rotation detector)
16 First encoder processing unit 17 Second encoder processing unit 18 Encoder switching processing unit 21 Threshold comparison unit 22 First switch 23, 24, 29, 34 Buffer 25, 26 First and second subtractors 27... Second switch 28... First adder 30... AND element 31... Third switch 32... Second adder 33... Fourth switch 35... Fifth switch

Claims (6)

A power conversion device that drives a motor,
a first position and rotation detector;
a second position/rotation detector having a higher resolution per rotation of the motor than the first position/rotation detector but a slower detection period;
When the detected rotational speed is greater than the threshold value, the first encoder detected rotational speed, which is the output of the first position/rotation detector, is output as the detected rotational speed, and the first encoder output, which is the output of the first position/rotation detector, is output as the detected rotational speed. A value obtained by adding the difference between the previous value of the encoder detection phase and the current value to the previous value of the control phase is output as the control phase, and when the detected rotation speed is smaller than the threshold value, the output of the second position/rotation detector. is output as the detected rotation speed, and the difference between the previous value and the current value of the second encoder detection phase, which is the output of the second position/rotation detector, is used as the previous value of the control phase. an encoder switching processing unit that outputs the added value or the second encoder detection phase as the control phase;
A power conversion device comprising: The encoder switching processing unit
The detected rotation speed is compared with the threshold value, and when the detected rotation speed is larger, 1 is output as an encoder switching determination signal, and when the detected rotation speed is smaller, 0 is output as the encoder switching determination signal. a threshold comparator;
When the encoder switching determination signal is 1, the first encoder detected rotation speed is output as the detection rotation speed, and when the encoder switching determination signal is 0, the second encoder detection rotation speed is output as the detection rotation speed. 1 switch;
a first subtractor that outputs a first difference that is the difference between the previous value and the current value of the first encoder detection phase;
a second subtractor that outputs a second difference that is the difference between the previous value and the current value of the second encoder detection phase;
a second switch that outputs the first difference when the encoder switching determination signal is 1 and outputs the second difference when the output of the encoder switching determination signal is 0;
the first adder for adding the previous output value of the first adder to the output of the second switch and outputting the result as the control phase;
The power converter according to claim 1, characterized by comprising: The first position/rotation detector outputs a Z-phase pulse that is output one pulse for each rotation of the motor,
The encoder switching processing unit
3. The power converter according to claim 2, wherein when said Z-phase pulse is 1 and said encoder switching determination signal is 1, said first encoder detection phase is set as said control phase. The encoder switching processing unit
When the detected rotational speed is compared with the threshold value, 1 is output as the encoder switching determination signal when the detected rotational speed is larger, and 0 is output as the encoder switching determination signal when the detected rotational speed is smaller. a threshold comparator for output;
When the encoder switching determination signal is 1, the first encoder detected rotation speed is output as the detection rotation speed, and when the encoder switching determination signal is 0, the second encoder detection rotation speed is output as the detection rotation speed. 1 switch;
a first subtractor that outputs a first difference that is the difference between the previous value and the current value of the first encoder detection phase;
a second adder that adds the previous output value of the fourth switch to the first difference;
the fourth switch for outputting the second encoder detection phase during the detection period of the second position/rotation detector and for outputting the output of the second adder otherwise;
A fifth switch that outputs the output of the fourth switch as the control phase when the encoder switching determination signal is 1, and outputs the second encoder detection phase as the control phase when the output of the encoder switching determination signal is 0. When,
The power converter according to claim 1, characterized by comprising: The encoder switching processing unit
The threshold is provided with hysteresis, and the threshold is a value obtained by adding the rotation speed detection accuracy to the rotation speed minimum resolution of the first position/rotation detector when the encoder switching determination signal is switched from OFF to ON. 5. The minimum resolution of the rotation speed of the first position/rotation detector is set when the encoder switching determination signal is switched from ON to OFF. power converter. A power converter for driving a motor, comprising a first position/rotation detector and a second position/rotation detector having a higher resolution per rotation of the motor than the first position/rotation detector but a slower detection period. A control method of
When the detected rotation speed is greater than the threshold value, the encoder switching processing unit outputs the first encoder detection rotation speed, which is the output of the first position/rotation detector, as the detection rotation speed, and outputs the detection rotation speed to the first position/rotation detector. A value obtained by adding the difference between the previous value and the current value of the first encoder detected phase, which is the output of , to the previous value of the control phase is output as the control phase, and when the detected rotation speed is smaller than the threshold value, the second position The second encoder detection rotation speed, which is the output of the rotation detector, is output as the detection rotation speed, and the difference between the previous value and the current value of the second encoder detection phase, which is the output of the second position/rotation detector, is calculated as the detection rotation speed. A control method for a power converter, wherein a value added to a previous value of a control phase or the second encoder detection phase is output as the control phase.

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