CN113271026A - Power conversion device - Google Patents
Power conversion device Download PDFInfo
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- CN113271026A CN113271026A CN202110002230.1A CN202110002230A CN113271026A CN 113271026 A CN113271026 A CN 113271026A CN 202110002230 A CN202110002230 A CN 202110002230A CN 113271026 A CN113271026 A CN 113271026A
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- output current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
- H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
- H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/06—Control, e.g. of temperature, of power
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Inverter Devices (AREA)
- General Induction Heating (AREA)
Description
Technical Field
The present invention relates to a power conversion device, and more particularly, to a power conversion device including a control unit that controls an inverter unit.
Background
Conventionally, a power conversion device including a control unit that controls an inverter unit is known. Such a power conversion device is disclosed in, for example, japanese patent laid-open No. 2016 and 194993.
Japanese patent application laid-open No. 2016-. In the induction melting furnace, a current detector is provided between the power conversion unit and the heating coil, and the current detector detects the current supplied from the power conversion unit to the heating coil. In addition, the control circuit is provided with a Current constant controller (ACR). The ACR performs proportional-integral feedback control based on the current detected by the current detector. Then, based on the output from the ACR, a gate signal for controlling on/off of the switching element of the power conversion unit is generated. Then, the switching element of the power conversion unit is driven based on the generated gate signal. Thereby, the current supplied from the power conversion unit to the heating coil is controlled to be constant.
Here, in the induction melting furnace as described in japanese patent application laid-open No. 2016 and 194993, when the load impedance of the heating coil changes rapidly, the current flowing through the heating coil may change rapidly. That is, the current flowing through the heating coil may become an overcurrent. However, in general, the response speed of ACR is relatively slow. Therefore, in the control (proportional-integral feedback control) using the ACR, there is a problem in that: when the current flowing through the heating coil becomes an overcurrent, it is difficult to quickly make the current supplied to the heating coil (load) constant (fall within a predetermined range).
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a power conversion device capable of quickly converging a current supplied to a load within a predetermined range even when the current flowing through the load becomes an overcurrent.
In order to achieve the above object, a power conversion device according to one aspect of the present invention includes: a rectifying unit that rectifies alternating-current power supplied from a power supply into direct-current power; a smoothing unit provided on an output side of the rectifying unit, for smoothing the DC power rectified by the rectifying unit; an inverter unit that converts the dc power smoothed by the smoothing unit into ac power; and a control unit that controls on/off of the switching element of the inverter unit, wherein the control unit is configured to adjust a gate signal for turning on/off the switching element based on a difference between a waveform command for outputting a current of a desired waveform from the inverter unit and an output current output from the inverter unit to the load and a value corresponding to a magnitude of an overcurrent when the output current is the overcurrent.
In the power conversion device according to the aspect of the present invention, as described above, the control unit is configured to adjust the gate signal for turning on and off the switching element based on the difference between the waveform command for outputting the current of the desired waveform from the inverter unit and the output current output from the inverter unit to the load and the value corresponding to the magnitude of the overcurrent when the output current is the overcurrent. Thus, unlike the case where the feedback control is performed by the difference (deviation) between the waveform command and the output current fed back, the gate signal is adjusted in consideration of the value corresponding to the magnitude of the overcurrent in addition to the deviation. That is, the deviation for feedback control can be adjusted using a value corresponding to the magnitude of the overcurrent. As a result, even when the current flowing through the load becomes an overcurrent, the current supplied to the load can be quickly converged within a predetermined range.
In the power conversion device according to the above aspect, preferably, the control unit is configured to: the gate signal is adjusted by subtracting a value corresponding to the magnitude of the overcurrent from a value based on the difference between the waveform command and the output current. With this configuration, the value corresponding to the magnitude of the overcurrent is subtracted from the value based on the difference between the waveform command and the output current (the deviation for feedback control), and therefore the deviation for feedback control is immediately reduced. This makes it possible to more quickly converge the current supplied to the load within a predetermined range even when the current flowing through the load becomes an overcurrent.
In this case, preferably, the control unit is configured to: when the output current exceeds a predetermined threshold value, the gate signal is adjusted by subtracting an amount corresponding to the difference between the output current and the predetermined threshold value from a value based on the difference between the waveform command and the output current. With this configuration, a value corresponding to the magnitude of the output current (the magnitude of the overcurrent) is subtracted from a value based on the difference between the waveform command and the output current (the deviation for feedback control). As a result, the current supplied to the load can be quickly converged within a predetermined range according to the magnitude of the overcurrent.
In the power conversion device according to the above aspect, the waveform command preferably includes a sine wave command that starts from a phase of a zero-cross point of the output current of the inverter unit, which is calculated based on the frequency of the gate signal, the phase of the output current of the inverter unit, and an effective value of a current command for outputting a desired current from the inverter unit. Here, the frequency (carrier frequency) of the appropriate gate signal changes with the fluctuation of the load. Therefore, as described above, the sine wave command is configured with the phase of the zero-crossing point of the output current as the starting point based on the frequency of the gate signal, the phase of the output current, and the effective value of the current command, and thus the sine wave command can be set in accordance with the carrier frequency.
In this case, it is preferable that the inverter further includes a first filter for attenuating a desired frequency component of the output current of the inverter, and the control unit is configured to: the phase of the zero-cross point of the output current is acquired based on the output current of the inverter section acquired by the first filter. Here, oscillation (oscillation of the output current) may occur in the vicinity of the zero cross point of the output current. Therefore, by attenuating a desired frequency component of the output current of the inverter unit by the first filter, the phase of the zero-cross point of the output current can be appropriately acquired.
In the power conversion device including the first filter, it is preferable that the power conversion device further includes a second filter for attenuating a desired frequency component of a difference between the waveform command and the output current, and the first filter and the second filter are configured to attenuate the same frequency component. With this configuration, the first filter for obtaining the phase of the zero-cross point and the second filter for obtaining the difference between the waveform command and the output current (the deviation for feedback control) have the same characteristics, and therefore, control for converging the current supplied to the load within a predetermined range can be performed with high accuracy.
In the power conversion device according to the above aspect, preferably, the control unit is configured to: the frequency of the gate signal is adjusted based on the difference between the waveform command and the output current and a value corresponding to the magnitude of the overcurrent when the output current is the overcurrent. With this configuration, in Pulse Frequency Modulation (PFM) control in which the switching element is controlled to be turned on and off by changing the Frequency of the gate signal, even when the current flowing through the load becomes an overcurrent, the current supplied to the load can be quickly converged within a predetermined range.
In the power conversion device according to the above aspect, the load preferably includes a heating coil that is provided on an output side of the inverter unit and heats the object to be heated. Here, in the heating coil that heats the object to be heated, the load impedance of the heating coil is likely to change rapidly due to a change in the shape of the object to be heated that is melted by being heated. Therefore, the current flowing through the heating coil easily becomes an overcurrent. Therefore, in the power converter that supplies power to the heating coil that heats the object to be heated, it is particularly effective to quickly converge the current supplied to the load within a predetermined range by the configuration of the power converter according to the above aspect.
According to the present invention, as described above, even when the current flowing through the load becomes an overcurrent, the current supplied to the load can be quickly converged within a predetermined range.
Drawings
Fig. 1 is a circuit diagram of an induction heating device (power conversion device) according to an embodiment.
Fig. 2 is a block diagram for explaining generation of a reference waveform of the power conversion device according to the embodiment.
Fig. 3 is a control block diagram of a control unit of the power conversion device according to the embodiment.
Fig. 4 is a graph showing a relationship between the frequency of the gate signal and the output current.
Fig. 5 is a graph showing the relationship of frequency to output current.
Detailed Description
Hereinafter, embodiments embodying the present invention will be described based on the drawings.
The structure of the induction heating apparatus 1 of the present embodiment will be described with reference to fig. 1 to 5.
As shown in fig. 1, the induction heating device 1 includes a power conversion device 100, a current detector 2, and a resonant capacitor C1And C2An induction heating coil 3 and a resistor 4. The induction heating coil 3 is an example of the "load" and the "heating coil" in the claims.
The power conversion device 100 includes a rectifier 10. The rectifier unit 10 is configured to rectify ac power supplied from the three-phase commercial power supply 200 into dc power. Specifically, the rectifying unit 10 includes a plurality of diodes constituting a three-phase full-wave rectifying circuit. Commercial power supply 200 is an example of the "power supply" in the claims.
Further, the power conversion device 100 includes a smoothing capacitor 20. The smoothing capacitor 20 is provided on the output side of the rectifying unit 10. The smoothing capacitor 20 is configured to smooth dc power rectified by the rectifying unit 10. The smoothing capacitor 20 is an example of the "smoothing portion" in the claims.
The power conversion device 100 includes an inverter unit 30 (high-frequency inverter circuit). The inverter unit 30 is configured to convert the dc power smoothed by the smoothing capacitor 20 into ac power. The inverter section 30 includes a plurality of switching elements S (semiconductor switching elements). The plurality of switching elements S include a switching element S constituting an upper arm1And a switching element S3And a switching element S constituting a lower arm2And a switching element S4。
The power conversion device 100 further includes a control unit 40. The control unit 40 is configured to control the switching elements S of the inverter unit 301～S4On/off of the switch. The detailed configuration of the control unit 40 will be described later.
In the induction heating device 1, a plurality of (two in the present embodiment) sets of the rectifying unit 10 and the inverter unit 30 are provided in parallel with each other.
The current detector 2 is configured to detect the ac output side of the inverter unit 30 toward the resonant capacitor C1The current flowing.
Resonant capacitor C1And C2Is provided on the ac output side of inverter unit 30. By a resonant capacitor C1And C2The induction heating coil 3 and the metal as the object to be heated constitute a resonance circuit.
In the present embodiment, the induction heating coil 3 is provided on the output side of the inverter unit 30, and is configured to heat and melt an object to be heated (metal). For example, the metal is an aluminum ingot. In addition, the ac output side of the inverter unit 30 and the resonant capacitor C1(resonant capacitor C)2) Is connected to one electrode of the first electrode. In addition, a resonant capacitor C1(resonant capacitor C)2) Is connected to the induction heating coil 3.
The induction heating coil 3 is connected to a resistor 4. A resistor 4 disposed between the induction heating coil 3 and the resonant capacitor C2In the meantime.
(detailed construction of control section)
Next, the detailed configuration of the control unit 40 will be described.
First, generation of a reference waveform by the control unit 40 will be described with reference to fig. 2. The reference waveform is a normalized waveform (sine wave). Further, the sine wave command is generated by multiplying the reference waveform by the execution value of the current command flowing through the induction heating coil 3. The sine wave command is used to generate a gate signal for controlling on/off of the switching element S included in the inverter unit 30. When the frequency (carrier frequency) of the gate signal changes, the reference waveform needs to be changed so as to correspond to the frequency of the gate signal after the change. This will be explained in detail below.
The current value of the output current of the inverter unit 30 detected by the current detector 2 is input to the control unit 40. The current value detected by the current detector 2 is input to the control unit 40 after analog-to-digital conversion. In addition, analog/digital conversion is performed at higher speeds. The current detector 2 detects the output current of the inverter unit 30 at predetermined sampling intervals.
Here, the output current may oscillate (vibrate) at least in the vicinity of the zero-crossing point of the output current. Therefore, a filter 41 is provided between the current detector 2 and the control unit 40. The filter 41 is configured to attenuate a desired frequency component of the output current of the inverter unit 30. The filter 41 is constituted by, for example, an LPF (Low-pass filter). Then, the current value passed through the filter 41 is input to the control unit 40. The filter 41 is an example of the "first filter" in the claims.
In the present embodiment, the control unit 40 is configured to acquire the phase of the zero cross point of the output current based on the output current of the inverter unit 30 acquired through the filter 41. Specifically, the phase of the zero-cross point is acquired from the current value of the output current acquired by the filter 41.
In the present embodiment, the control unit 40 calculates the sine wave command based on the frequency of the gate signal, the phase of the output current of the inverter unit 30 (the phase of the zero-cross point of the output current), and the effective value of the current command for outputting a desired current from the inverter unit 30, starting from the phase of the zero-cross point of the output current of the inverter unit 30. Specifically, the frequency of the gate signal, the detection period (sampling period) of the output current of the inverter unit 30, and the phase of the zero-cross point of the output current are input to the reference waveform generating unit 42 of the control unit 40. Here, the frequency of the gate signal is the frequency of the gate signal driving the switching element S at the current time point. The frequency of the current time point of the gate signal is taken as the frequency of the generated reference signal. Note that the phase of the zero-cross point of the acquired output current is counted by a counter (not shown) every detection period (sampling period) of the output current of the inverter unit 30. The reference waveform generating unit 42 calculates the phase position of the reference waveform from the count value counted by the counter. Then, the reference waveform generating unit 42 generates a reference waveform (sin θ) starting from the phase of the zero-crossing point of the output current.
Then, as shown in fig. 3, the generated reference waveform is multiplied by an effective value (target value, a) of a current command for outputting a desired current from the inverter section 30 by a multiplier 43. The effective value (a) of the current command is input to the control unit 40 from an ARP (alternating current power regulator), not shown. The sine wave command (a × sin θ) is generated by multiplying the reference waveform (sin θ) by the command value (a) of the output power. By generating the sine wave command as described above, the sine wave command corresponding to the change in the frequency (carrier frequency) of the gate signal is generated.
Then, the subtractor 44 calculates a difference (deviation) between the generated sine wave command and the current value (fed-back current value) detected by the current detector 2. After analog/digital conversion of the current value detected by the current detector 2, a desired frequency component is attenuated by the filter 41.
In the present embodiment, a filter 45 is provided, and the filter 45 attenuates a desired frequency component of a difference (deviation) between the sine wave command and the output current. The filter 41 and the filter 45 are configured to attenuate the same frequency component. Then, a desired frequency component of the output (offset) of the subtractor 44 is attenuated by the filter 45. Then, the deviation attenuated by the desired frequency component by the filter 45 is multiplied by the gain. The filter 45 is an example of the "second filter" in the claims.
Here, in the present embodiment, the control unit 40 is configured based on a sine wave command for outputting a current of a desired waveform from the inverter unit 30 and an output current (I) output from the inverter unit 30 to the induction heating coil 31) Difference (deviation, I)2) And adjusting a gate signal for turning on/off the switching element S according to the magnitude of the overcurrent when the output current is the overcurrent. Specifically, the control unit 40 subtracts a value corresponding to the magnitude of the overcurrent from a value based on the difference between the sine wave command and the output current. More specifically, when the output current exceeds a predetermined threshold value (I)TH) Under the condition of (1), controlThe unit 40 subtracts an amount (I) corresponding to the difference between the output current and a predetermined threshold value from a value based on the difference between the sine wave command and the output current1-ITH). Although not shown, the amount (I) corresponding to the difference between the output current and the predetermined threshold value may be subtracted1-ITH) The value obtained by multiplying the gain may be obtained by subtracting the amount (I) corresponding to the difference between the output current and a predetermined threshold value from the deviation after the desired frequency component is attenuated by the filter 451-ITH) And then multiplied by the gain.
That is, the subtractor 46 subtracts a predetermined threshold value from the current value of the output current detected by the current detector 2. Then, the desired frequency component is attenuated from the filtered signal 45 by the subtractor 47 (as a deviation I)2') and a deviation (kI) multiplied by a gain k2') subtracting the output of the subtractor 46 (by an amount I corresponding to the difference between the output current and a predetermined threshold value1-ITH). Moreover, only values equal to or greater than 0 among the values subtracted by the subtractor 46 are input to the subtractor 47. Thus, when the current output from the inverter unit 30 is an overcurrent, a value corresponding to the overcurrent (the output value of the subtractor 46) is immediately subtracted from the deviation multiplied by the gain. The predetermined threshold value is, for example, a value 1.1 times the rated current of the power conversion device 100. Further, the deviation (kI) obtained by multiplying the desired frequency component by the gain k is attenuated by the filter 452') is an example of the claim "value based on the difference between the sine wave command and the output current".
Then, the output (kI) of the subtractor 472’-(I1-ITH) Is input to the PI adjuster 48. That is, even when the current output from the inverter unit 30 is an overcurrent, a value obtained by subtracting a value corresponding to the overcurrent (the output value of the subtractor 46) from the deviation is input to the PI regulator 48.
Then, the output of the PI adjuster 48 is input to the frequency converter 49. That is, in the present embodiment, the control unit 40 is configured to instruct the output current based on the sinusoidal waveform and the difference I between the output current and the sinusoidal waveform2And the magnitude phase of the overcurrent when the output current is the overcurrentCorresponding value (I)1-ITH) To adjust the frequency of the gate signal. That is, in the power conversion device 100, Pulse Frequency Modulation (PFM) control is performed to control on/off of the switching element S by changing the Frequency of the gate signal.
Then, a gate signal for controlling on/off of the switching element S is generated by the frequency converter 49. As described above, even when the current output from the inverter unit 30 is an overcurrent, the value corresponding to the overcurrent (the output value (I) from the subtractor 46) is subtracted therefrom1-ITH) The obtained value is input to the PI regulator 48, and therefore the gate signal generated by the frequency converter 49 takes into account the value corresponding to the overcurrent. This can quickly suppress the output current of inverter unit 30 from becoming an overcurrent.
Next, the relationship between the frequency of the gate signal and the output current of the inverter unit 30 will be described with reference to fig. 4 and 5.
As the frequency of the gate signal becomes smaller, the magnitude (amplitude) of the output current of the inverter unit 30 becomes larger. In addition, in the induction heating device 1, the induction heating coil 3 and the resonant capacitor C are passed through1And C2And resonance occurs. As shown in fig. 5, at the resonant frequency f1Here, the output current of the inverter section 30 becomes maximum. In the induction heating device 1, the gate signal is controlled to be at the specific resonance frequency f1Large frequency f2～f3Within the range of (1). Thus, the gate signal has a specific resonant frequency f1The high frequency can suppress the breakdown of the switching element S due to the through current flowing through the switching element S.
[ Effect of the present embodiment ]
In the present embodiment, the following effects can be obtained.
In the present embodiment, as described above, the control unit 40 is configured to adjust the gate signal for turning on and off the switching element S based on the difference between the sine wave command for outputting the current of the desired waveform from the inverter unit 30 and the output current output from the inverter unit 30 to the induction heating coil 3 and the value corresponding to the magnitude of the overcurrent when the output current is the overcurrent. Thus, unlike the case where the feedback control is performed by the difference (deviation) between the sine wave command and the output current fed back, the gate signal is adjusted in consideration of the value according to the magnitude of the overcurrent in addition to the deviation. That is, the deviation for feedback control can be adjusted using a value corresponding to the magnitude of the overcurrent. As a result, even when the current flowing through the induction heating coil 3 becomes an overcurrent, the current supplied to the induction heating coil 3 can be quickly converged within a predetermined range.
In the present embodiment, as described above, the control unit 40 is configured to: the gate signal is adjusted by subtracting a value corresponding to the magnitude of the overcurrent from a value based on the difference between the sine wave command and the output current. Thus, the value corresponding to the magnitude of the overcurrent is subtracted from the value based on the difference between the sine wave command and the output current (the deviation for feedback control), and therefore the deviation for feedback control is immediately reduced. This makes it possible to more quickly converge the current supplied to the induction heating coil 3 within a predetermined range even when the current flowing through the induction heating coil 3 becomes an overcurrent.
In the present embodiment, as described above, the control unit 40 is configured to: when the output current exceeds a predetermined threshold value, the gate signal is adjusted by subtracting an amount corresponding to the difference between the output current and the predetermined threshold value from a value based on the difference between the sine wave command and the output current. Thus, a value corresponding to the magnitude of the output current (the magnitude of the overcurrent) is subtracted from a value based on the difference between the sine wave command and the output current (the deviation for feedback control). As a result, the current supplied to the induction heating coil 3 can be quickly converged within a predetermined range according to the magnitude of the overcurrent.
In the present embodiment, the sine wave command includes a sine wave command starting from the phase of the zero-cross point of the output current of the inverter unit 30, which is calculated based on the frequency of the gate signal, the phase of the output current of the inverter unit 30, and the effective value of the current command for outputting a desired current from the inverter unit 30, as described above. Here, the frequency (carrier frequency) of the appropriate gate signal changes with the fluctuation of the load (load impedance of the induction heating coil 3). Therefore, as described above, the sine wave command is configured with the phase of the zero-crossing point of the output current as the starting point based on the frequency of the gate signal, the phase of the output current, and the effective value of the current command, and thus the sine wave command can be set in accordance with the carrier frequency.
In the present embodiment, as described above, the control unit 40 is configured to acquire the phase of the zero-cross point of the output current based on the output current of the inverter unit 30 acquired through the filter 41. Here, oscillation (oscillation of the output current) may occur in the vicinity of the zero cross point of the output current. Therefore, by attenuating a desired frequency component of the output current of the inverter unit 30 by the filter 41, the phase of the zero-cross point of the output current can be appropriately acquired.
In the present embodiment, as described above, the filter 41 and the filter 45 are configured to attenuate the same frequency component. Thus, the filter 41 for obtaining the phase of the zero-cross point and the filter 45 for obtaining the difference between the sine wave command and the output current (the deviation for the feedback control) have the same characteristics, and therefore, the control for converging the current supplied to the induction heating coil 3 within the predetermined range can be performed with high accuracy.
In the present embodiment, as described above, the control unit 40 is configured to: the frequency of the gate signal is adjusted based on the difference between the sine wave command and the output current and a value corresponding to the magnitude of the overcurrent when the output current is the overcurrent. Thus, in the Pulse Frequency Modulation (PFM) control in which the on/off of the switching element S is controlled by changing the frequency of the gate signal, even when the current flowing through the induction heating coil 3 becomes an overcurrent, the current supplied to the induction heating coil 3 can be quickly converged within a predetermined range.
In the present embodiment, as described above, the induction heating coil 3 for heating the object to be heated is provided on the output side of the inverter unit 30. Here, in the induction heating coil 3 that heats the object to be heated, the load impedance of the induction heating coil 3 is likely to change rapidly due to a change in the shape of the object to be heated that is heated and melted. Therefore, the current flowing through the induction heating coil 3 easily becomes an overcurrent. Therefore, in the power converter 100 that supplies power to the induction heating coil 3 that heats an object to be heated, it is particularly effective to quickly converge the current supplied to the induction heating coil 3 within a predetermined range by configuring the power converter 100 according to the present embodiment.
[ modified examples ]
The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and includes all modifications (variations) within the meaning and scope equivalent to the claims.
For example, in the above-described embodiment, the example in which the present invention is applied to the power conversion device 100 used in the induction heating device 1 is shown, but the present invention is not limited thereto. The present invention can also be applied to the power conversion device 100 used in devices other than the induction heating device 1.
In the above-described embodiment, the gate signal is adjusted by subtracting a value corresponding to the magnitude of the overcurrent (the difference between the sine wave command and the predetermined threshold value) from a value based on the difference between the sine wave command and the output current, but the present invention is not limited to this. In the present invention, the gate signal may be adjusted by a method other than the subtraction based on a value corresponding to the magnitude of the overcurrent. For example, a value obtained by multiplying a difference between the sine wave command and a predetermined threshold by a predetermined constant may be subtracted from a difference between the sine wave command and the output current.
In the above-described embodiment, the sine wave command is generated based on the frequency of the gate signal, the phase of the output current of the inverter unit 30, and the effective value of the current command, with the phase of the zero-cross point of the output current of the inverter unit 30 as the starting point. Further, a command other than the sine wave command may be used as a command for outputting a current of a desired waveform from the inverter unit 30.
In the above embodiment, the filter 41 and the filter 45 are configured by the LPF, but the present invention is not limited to this. For example, the filter 41 and the filter 45 may be configured by a filter other than the LPF.
In the above-described embodiment, an example in which Pulse Frequency Modulation (PFM) control is used as control for turning on and off the switching element S has been described, but the present invention is not limited to this. For example, Pulse Width Modulation (PWM) control may be used as the control for turning on and off the switching element S.
In the above-described embodiment, the example in which the induction heating coil 3 is used as the "load" of the present invention is shown, but the present invention is not limited to this. The present invention can also be applied to a power converter that supplies power to a load other than the induction heating coil 3. In addition, a heating coil other than the induction heating coil 3 may be used.
Claims (8)
1. A power conversion device is provided with:
a rectifying unit that rectifies alternating-current power supplied from a power supply into direct-current power;
a smoothing unit provided on an output side of the rectifying unit, the smoothing unit smoothing the direct-current power rectified by the rectifying unit;
an inverter unit that converts the dc power smoothed by the smoothing unit into ac power; and
a control unit that controls on/off of the switching elements of the inverter unit,
the control unit is configured to adjust a gate signal for turning on and off the switching element based on a difference between a waveform command for outputting a current of a desired waveform from the inverter unit and an output current output from the inverter unit to a load and a value corresponding to a magnitude of an overcurrent when the output current is the overcurrent.
2. The power conversion apparatus according to claim 1,
the control unit is configured to: adjusting the gate signal by subtracting the value corresponding to the magnitude of the overcurrent from a value based on a difference between the waveform command and the output current.
3. The power conversion apparatus according to claim 2,
the control unit is configured to: when the output current exceeds a predetermined threshold value, the gate signal is adjusted by subtracting an amount corresponding to a difference between the output current and the predetermined threshold value from a value based on a difference between the waveform command and the output current.
4. The power conversion device according to any one of claims 1 to 3,
the waveform command includes a sine wave command that is calculated based on a frequency of the gate signal, a phase of the output current of the inverter unit, and an effective value of a current command for outputting a desired current from the inverter unit, and that starts from a phase of a zero-cross point of the output current of the inverter unit.
5. The power conversion apparatus according to claim 4,
further comprising a first filter for attenuating a desired frequency component of the output current of the inverter unit,
the control unit is configured to: a phase of a zero-cross point of the output current is acquired based on the output current of the inverter section acquired by means of the first filter.
6. The power conversion apparatus according to claim 5,
further comprising a second filter for attenuating a desired frequency component of a difference between the waveform command and the output current,
the first filter and the second filter are configured to attenuate the same frequency component.
7. The power conversion device according to any one of claims 1 to 3,
the control unit is configured to: the frequency of the gate signal is adjusted based on a difference between the waveform command and the output current and a value corresponding to the magnitude of an overcurrent when the output current is an overcurrent.
8. The power conversion device according to any one of claims 1 to 3,
the load includes a heating coil provided on an output side of the inverter unit and configured to heat an object to be heated.
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| Application Number | Priority Date | Filing Date | Title |
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| JP2020-023576 | 2020-02-14 | ||
| JP2020023576A JP7419863B2 (en) | 2020-02-14 | 2020-02-14 | power converter |
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| CN113271026A true CN113271026A (en) | 2021-08-17 |
| CN113271026B CN113271026B (en) | 2025-08-05 |
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| JP7036270B1 (en) | 2021-09-03 | 2022-03-15 | 富士電機株式会社 | Power converter and power converter for induction furnace |
| JP7631168B2 (en) * | 2021-10-21 | 2025-02-18 | 株式会社Tmeic | Power Conversion Equipment |
| CN118382975A (en) * | 2022-07-28 | 2024-07-23 | 株式会社Tmeic | Power supply unit |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63268467A (en) * | 1987-04-24 | 1988-11-07 | Fuji Electric Co Ltd | Control method of PWM inverter |
| JP2005142097A (en) * | 2003-11-10 | 2005-06-02 | Mitsubishi Electric Corp | Induction heating cooker |
| JP2008251440A (en) * | 2007-03-30 | 2008-10-16 | Mitsui Eng & Shipbuild Co Ltd | Induction heating method and induction heating apparatus |
| CN103444260A (en) * | 2011-03-23 | 2013-12-11 | 三井造船株式会社 | Induction heating device, control method for induction heating device, and control program |
| CN103959631A (en) * | 2011-11-28 | 2014-07-30 | 三菱电机株式会社 | Auxiliary power supply device for vehicle and overcurrent protection method thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3598850B1 (en) * | 2018-07-18 | 2020-12-16 | LG Electronics Inc. -1- | Induction heating device performing container sensing function |
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- 2021-01-04 CN CN202110002230.1A patent/CN113271026B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63268467A (en) * | 1987-04-24 | 1988-11-07 | Fuji Electric Co Ltd | Control method of PWM inverter |
| JP2005142097A (en) * | 2003-11-10 | 2005-06-02 | Mitsubishi Electric Corp | Induction heating cooker |
| JP2008251440A (en) * | 2007-03-30 | 2008-10-16 | Mitsui Eng & Shipbuild Co Ltd | Induction heating method and induction heating apparatus |
| CN103444260A (en) * | 2011-03-23 | 2013-12-11 | 三井造船株式会社 | Induction heating device, control method for induction heating device, and control program |
| CN103959631A (en) * | 2011-11-28 | 2014-07-30 | 三菱电机株式会社 | Auxiliary power supply device for vehicle and overcurrent protection method thereof |
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| Publication number | Publication date |
|---|---|
| JP7419863B2 (en) | 2024-01-23 |
| CN113271026B (en) | 2025-08-05 |
| JP2021129452A (en) | 2021-09-02 |
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