JP7271480B2 - Power converter and power conversion system - Google Patents

Description

The present disclosure relates to power converters and power conversion systems.

Japanese Patent No. 6392708 discloses a power converter that outputs an AC voltage according to a control command, a phase detection device that detects the phase of the output voltage of the power converter, and a phase detector based on the detected phase detected by the phase detection device. a control device that generates and transmits a control command to the power converter.

Japanese Patent No. 6392708

In the power conversion system disclosed in Japanese Patent No. 6392708, when the calculation cycle of the control device and the detection cycle of the phase detection device are different, the detection phase recognized by the control device changes suddenly, and the power converter There is a concern that the output voltage waveform of the controller will be disturbed and the control will become unstable. Also, when the detection phase recognized by the control device changes suddenly due to the influence of noise, there is a concern that the control may similarly become unstable.

The present disclosure has been made to solve the above-described problems, and its purpose is to prevent the output voltage of the power converter from becoming unstable even if the detection phase recognized by the control device changes suddenly. It is to suppress.

A power conversion device according to the present disclosure is connected to a power converter that outputs an AC voltage according to a command phase, and a phase detection device that periodically detects the output phase of the power converter. and a controller for periodically calculating the commanded phase based on the phase. The control device calculates an estimated phase, which is an estimated value of the output phase, using the output frequency of the power converter and the previous value of the command phase, and the detected phase is higher than the first phase obtained by adding the first value to the estimated phase. If so, set the first phase to the current value of the commanded phase.

A power conversion system according to the present disclosure includes the power converter, the control device and the phase detection device described above, and a frequency detection device that detects the output frequency of the power converter.

In the power conversion device and the power conversion system according to the present disclosure, even if the detection phase recognized by the control device suddenly changes, it is possible to prevent the output voltage of the power converter from becoming unstable.

It is a circuit block diagram which shows the structure of a power conversion system. FIG. 10 is a diagram showing how a command phase changes according to a comparative example; FIG. 11 is a diagram (part 1) showing a method of setting a command phase; FIG. 11 is a diagram (part 2) showing a method of setting a command phase; FIG. 11 is a diagram (part 3) showing a method of setting a command phase; FIG. 5 is a diagram showing how a command phase changes; 10 is a flowchart (part 1) showing an example of a processing procedure of the control device; FIG. 10 is a diagram (part 4) showing a method of setting a command phase; 2 is a flowchart (part 2) showing an example of a processing procedure of a control device;

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[Embodiment 1]
<Overall composition>
FIG. 1 is a circuit block diagram showing the configuration of a power conversion system 1 according to this embodiment. The power conversion system 1 includes a power conversion device 10 , a phase detection device 40 and a frequency detection device 50 . The power converter 10 includes a power converter 20 and a control device 30 . The control device 30 includes a phase estimation section 31 , a command phase generation section 32 and a command output section 33 .

Power converter 20 outputs an AC voltage according to a control signal (instruction phase) from control device 30 . Specifically, the power converter 20 is controlled by a control signal from the control device 30, and uses the AC supplied from the commercial AC power supply 2 to generate AC with a voltage that can be used by the controlled object 3, Output to the controlled object 3. Note that the controlled object 3 is, for example, an AC motor.

The frequency detection device 50 detects the frequency of the AC voltage output from the power converter 20 to the controlled object 3 (hereinafter also referred to as “output frequency”). The output frequency detected by frequency detector 50 is output to phase estimator 31 of controller 30 .

The phase detection device 40 periodically detects the phase of the AC voltage output from the power converter 20 to the controlled object 3 (hereinafter also referred to as "output phase") at a predetermined detection cycle. The output phase detected by phase detection device 40 (hereinafter also referred to as “detection θ”) is output to command phase generation section 32 of control device 30 .

The control device 30 includes a CPU (Central Processing Unit), a memory and an input/output buffer (none of which are shown). Control device 30 periodically calculates a command phase (hereinafter also referred to as “command θ”) for controlling power converter 20 at a predetermined calculation cycle. Hereinafter, the command θ calculated by the control device 30 in the current calculation cycle is also referred to as the “current value of the command θ”, and the command θ calculated at the calculation timing one calculation cycle before the current calculation cycle is referred to as the “command "previous value of θ".

As described above, control device 30 includes phase estimator 31 , command phase generator 32 , and command output unit 33 .

Phase estimator 31 uses the output frequency input from frequency detection device 50 and the previous value of command θ to calculate an estimated value of the output phase (hereinafter also referred to as “estimated θ”). For example, the phase estimator 31 calculates the phase change amount Δθ of the output voltage for one calculation cycle from the output frequency and the calculation cycle of the control device 30, and adds the phase change amount Δθ to the previous value of the command θ. , is calculated as the estimated θ.

The command phase generator 32 generates the current value of the command θ using the estimated θ estimated by the phase estimator 31 and the detected θ input from the phase detector 40 , and outputs it to the command output unit 33 . The current value of the command θ is stored in the memory and used as the previous value of the command θ in the next calculation cycle.

The command output unit 33 outputs the command θ generated by the command phase generation unit 32 to the power converter 20 as a control signal. As a result, the power converter 20 outputs an AC voltage corresponding to the command θ to the controlled object 3 .

<Setting the command θ>
In the above configuration, if the control device 30 sets the detection θ from the phase detection device 40 as it is to the command θ, the difference between the calculation cycle of the control device 30 and the detection cycle of the phase detection device 40, or , the command θ calculated by the control device 30 may suddenly change due to the influence of noise, and the output voltage waveform of the power converter 20 may be disturbed, resulting in unstable control.

FIG. 2 is a diagram showing how the command θ changes when the control device 30 sets the detection θ from the phase detection device 40 as it is to the command θ (comparative example with respect to the present disclosure). In FIG. 2, the horizontal axis indicates time, and the vertical axis indicates phase θ. Note that FIG. 2 illustrates a case where the calculation cycle of the control device 30 is longer than the detection cycle of the phase detection device 40 .

Since the phase detection device 40 periodically detects the output phase at a predetermined detection cycle, the detection θ follows the actual phase of the output voltage step by step. Similarly, since the control device 30 periodically calculates the command θ at a predetermined calculation cycle, the command θ also changes stepwise.

At this time, as shown in FIG. 2, when the calculation cycle of the control device 30 is longer than the detection cycle of the phase detection device 40, the amount of change in the command θ at one time is equivalent to two detections θ (phase detection device 40 2 detection periods), and there may be a timing at which the command θ suddenly changes. If the command θ changes suddenly, there is concern that the control may become unstable due to an unexpected output.

Therefore, the control device 30 according to the present embodiment does not directly set the detected θ to the command θ, but calculates the estimated θ from the output frequency and the previous value of the command θ, and the current value of the command θ is calculated from the estimated θ. Set the current value of the command θ so as not to deviate too much. A method of setting the command θ according to the present embodiment will be described in detail below with reference to FIGS. 3 to 7. FIG.

FIG. 3 is a diagram showing a method of setting the command θ when the detected θ is much ahead of the estimated θ. The control device 30 (phase estimator 31) calculates a value obtained by adding the phase change amount Δθ for one calculation cycle to the previous value of the command θ as the estimated θ.

When the detected θ is much ahead of the estimated θ, specifically, when the detected θ is ahead of the first phase (=estimated θ+α) obtained by adding the first value α to the estimated θ, the control Device 30 (command phase generator 32) sets the first phase (=estimated θ+α) to the current value of command θ. As a result, compared to the case where the detected θ is directly set to the current value of the command θ, the amount of change in the command θ (the difference between the current value of the command θ and the previous value) can be reduced. θ can be changed smoothly. Also, since the first phase (= estimated θ + α), which is closer to the detected θ than the estimated θ, is set as the command θ, the current value of the command θ is more appropriate than when the estimated θ is directly set to the current value of the command θ. can be approximated to the detection θ. As a result, the command θ can smoothly and appropriately follow the detected θ.

FIG. 4 is a diagram showing a method of setting the command θ when the detected θ lags significantly behind the estimated θ. When the detected θ lags significantly behind the estimated θ, specifically, as shown in FIG. 4, a second phase (= When the detected θ lags behind the estimated θ−α), the control device 30 (command phase generator 32) sets the second phase (=estimated θ−α) to the current value of the command θ. As a result, compared to the case where the detected θ is directly set to the current value of the command θ, the amount of change in the command θ (the difference between the current value of the command θ and the previous value) can be reduced. θ can be changed smoothly. In addition, since the second phase (=estimated θ - α), which is closer to the detected θ than the estimated θ, is set as the command θ, compared to the case where the estimated θ is directly set to the current value of the command θ, the current value of the command θ can be appropriately brought close to the detection θ. As a result, the command θ can smoothly and appropriately follow the detected θ.

FIG. 5 is a diagram showing a method of setting the command θ when the detected θ is close to the estimated θ. When the detected θ is close to the estimated θ, specifically, as shown in FIG. 5, the detected θ is included in the range between the first phase (= estimated θ+α) and the second phase (= estimated θ−α). If so, set the estimated θ to the current value of the command θ. Thus, when the detected θ is close to the estimated θ, the current value of the command θ can be made to follow the detected θ by setting the estimated θ to the current value of the command θ. Also, since the current value of the command θ is set to the estimated θ instead of the detected θ itself, the command θ can be changed smoothly even if the detected θ has a minute detection error or variation.

By setting the command .theta. as described above, the command .theta. can smoothly and appropriately follow the detected .theta. in the present embodiment. Therefore, the output voltage waveform of power converter 20 is smoothed, and unstable control is suppressed.

In the present embodiment, the first value α used for setting the first phase and the second value α used for setting the second phase have the same magnitude. The magnitude of the binary α may be different. In either case, the magnitude of the first value α and the magnitude of the second value α are determined in advance by experiments or the like and stored in the memory within the control unit 30 .

FIG. 6 is a diagram showing how command θ set by control device 30 according to the present embodiment changes. 6, the horizontal axis represents time and the vertical axis represents phase .theta., as in FIG. 2 described above. exemplified.

In this embodiment, when the detected θ is ahead of the first phase (=estimated θ+α) obtained by adding the first value α to the estimated θ, the first phase (=estimated θ+α) is set to the command θ. be done. Therefore, compared to the case where the detected .theta. is set as the command .theta. as it is, sudden changes in the command .theta. Also, since the command θ is set to the first phase (=estimated θ+α) closer to the detected θ than the estimated θ, the command θ can be appropriately approximated to the detected θ.

FIG. 7 is a flowchart showing an example of a processing procedure performed by control device 30 when setting command θ. This flowchart is repeatedly executed for each calculation cycle of the control device 30 .

Control device 30 calculates estimated θ using the output frequency from frequency detection device 50 and the previous value of command θ (step S10). As described above, the control device 30 calculates, for example, the phase change amount Δθ for one calculation cycle from the output frequency and the calculation cycle of the control device 30, and adds the phase change amount Δθ to the previous value of the command θ. is calculated as the estimated θ.

Next, the controller 30 determines whether or not the detected θ input from the phase detector 40 leads the first phase (estimated θ+α) (step S12). If detected θ is ahead of the first phase (YES in step S12), control device 30 sets the first phase (estimated θ+α) to the current value of command θ (step S14).

If the detected θ is not ahead of the first phase (NO in step S12), control device 30 determines whether or not the detected θ is behind the second phase (estimated θ−α) (step S16). . If detected θ is behind the second phase (YES in step S16), control device 30 sets the second phase (estimated θ−α) to the current value of command θ (step S18).

If the detected θ is included between the first phase and the second phase (NO in step S12 and NO in step S16), control device 30 sets estimated θ to the current value of command θ (step S20). .

As described above, the power converter 10 according to the present embodiment includes the power converter 20 that outputs an AC voltage corresponding to the command θ and the phase detector 40 that periodically detects the output phase of the power converter 20. and a control device 30 which is connected and periodically calculates a command θ based on the detection θ detected by the phase detection device 40 . Control device 30 uses the output frequency of power converter 20 and the previous value of command θ to calculate estimated θ, which is an estimated value of the output phase. If it is ahead of the phase, the first phase (=estimated θ+α) is set to the current value of command θ. Accordingly, even if the detection θ recognized by the control device 30 changes suddenly due to the difference between the calculation cycle of the control device 30 and the detection cycle of the phase detection device 40 or the influence of noise, the command θ to be calculated does not change suddenly. while suppressing the command θ to be appropriately brought close to the detected θ. As a result, the command θ can be made to follow the detection θ smoothly and appropriately, so that it is possible to suppress the output voltage of the power converter 20 from becoming unstable in control.

[Modification]
In the above embodiment, when the detected θ is included in the range between the first phase (=estimated θ+α) and the second phase (=estimated θ−α), the "estimated θ" is the current value of the command θ. set to

On the other hand, in this modification, when the detected θ is included in the range between the first phase (=estimated θ+α) and the second phase (=estimated θ−α), instead of “estimated θ”, “ Detected θ” is set to the current value of command θ. Other configurations and processes of this modification are the same as those of the above-described embodiment, and thus detailed description thereof will not be repeated.

FIG. 8 is a diagram showing a method of setting the command θ when the detected θ is close to the estimated θ according to this modification. When the detected θ is close to the estimated θ, specifically, as shown in FIG. 8, the detected θ is included in the range between the first phase (= estimated θ+α) and the second phase (= estimated θ−α) If so, set the "detection θ" to the current value of the command θ. As a result, the command θ can more appropriately follow the detected θ than when the estimated θ is set to the current value of the command θ.

FIG. 9 is a flow chart showing an example of a processing procedure performed when control device 30 according to the present modification sets command θ. The flowchart shown in FIG. 9 is obtained by changing S20 of the flowchart shown in FIG. 7 above to S20A. Other steps in FIG. 9 (steps with the same numbers as those shown in FIG. 7) have already been described, and detailed description thereof will not be repeated here.

If detected θ is included between the first phase and the second phase (NO in step S12 and NO in step S16), control device 30 sets detected θ to the current value of command θ (step S20A). .

Even if modified as described above, the command θ can smoothly and appropriately follow the detection θ in the same manner as in the above-described embodiment. can be suppressed. Furthermore, in this modified example, when the detected θ is close to the estimated θ, the "detected θ" is set to the current value of the command θ. can be made

It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims rather than the above description, and is intended to include all modifications within the scope and meaning of equivalents of the scope of the claims.

Reference Signs List 1 power conversion system 2 commercial AC power supply 3 controlled object 10 power converter 20 power converter 30 controller 31 phase estimator 32 command phase generator 33 command output unit 40 phase detector 50 Frequency detector.

Claims (5)

a power converter that outputs an AC voltage according to the command phase;
a control device that is connected to a phase detection device that periodically detects the output phase of the power converter, and that periodically calculates the command phase based on the detected phase detected by the phase detection device;
The control device is
calculating an estimated phase, which is an estimated value of the output phase, using the output frequency of the power converter and the previous value of the command phase;
The power conversion device, wherein when the detected phase leads a first phase obtained by adding a first value to the estimated phase, the first phase is set to the current value of the command phase. 2. The control device according to claim 1, wherein when said detected phase lags behind a second phase obtained by subtracting a second value from said estimated phase, said control device sets said second phase to the current value of said command phase. Power converter. The power conversion according to claim 2, wherein the control device sets the estimated phase to the current value of the command phase when the detected phase is included in the range between the first phase and the second phase. Device. The power conversion according to claim 2, wherein when the detected phase is included in the range between the first phase and the second phase, the control device sets the detected phase to the current value of the command phase. Device. A power converter, a control device and a phase detection device according to any one of claims 1 to 4,
and a frequency detection device that detects an output frequency of the power converter.

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