Power conversion device for induction heating device and induction heating device

Abstract

The present application relates to an inductive heating device power conversion device and an inductive heating device. The inductive heating device power conversion device includes a power control section that controls a current command value based on a power command value and a feedback value of output power; a current control section that controls a control signal for controlling an output current based on a feedback value of the output current and the current command value controlled by the power control section; and a calculation section that calculates the feedback value of the output power at intervals shorter than 1 cycle of the output current.

Description

Technical Field

[0001] This invention relates to a power conversion device for an induction heating device and an induction heating device, specifically a power conversion device for an induction heating device and an induction heating device for controlling the output current of a load including an induction heating coil. Background Technology

[0002] Previously, a power conversion device for an induction heating device was known that controls the output current of a load including an induction heating coil. For example, such a power conversion device is disclosed in Japanese Patent Application Publication No. 2016-194993.

[0003] Japanese Patent Application Publication No. 2016-194993 discloses a power conversion device (power conversion device for induction heating device) that controls the output current output to a load including an induction heating coil. The power conversion device described in the aforementioned Patent Document 1 includes a control circuit that performs feedback control on the output current based on the output current signal (feedback value of the output current).

[0004] Although not described in Japanese Patent Application Publication No. 2016-194993, in conventional power conversion devices as described in this publication, feedback control of the output power is sometimes performed based on the feedback value of the output power, and feedback control of the output current is performed based on the result of the output power feedback control. In this case, the output power feedback value is considered to be the effective power (power consumed by the load) calculated based on the effective value of the output current, the effective value of the output voltage, and the phase difference between the output current and the output voltage. In this case, calculating the effective value of the output current (effective value of the output voltage) requires data for one cycle of the output current (one cycle of the output voltage). Therefore, calculating the output power feedback value requires a longer time than one cycle of the output current (one cycle of the output voltage), resulting in a relatively long response time for the output power feedback control. Consequently, the response time of the output current feedback control based on the result of the output power feedback control is also relatively long. In this induction heating device, the output current changes drastically due to large variations in the impedance of the load (such as the induction heating coil). Therefore, when the response time of the output current feedback control is relatively long, the output current becomes unstable. For example, the output current may oscillate (fluctuate up and down like waves) or overshoot (rise sharply). Therefore, a power conversion device (power conversion device for induction heating device) and an induction heating device are desired that can suppress output current instability when feedback control of the output current is performed based on the result of feedback control of the output power. Summary of the Invention

[0005] The present invention was made to solve the problems described above. One of the objectives of the present invention is to provide a power conversion device for an induction heating device and an induction heating device that can suppress output current instability when the output current is controlled by feedback control based on the result of feedback control of output power.

[0006] To achieve the above objectives, the power conversion device for an induction heating device according to the first aspect of the present invention includes an induction heating coil and a power conversion device for melting metal by induction heating. The power conversion device for the induction heating device comprises: a power conversion unit that converts an input DC voltage into an AC voltage and outputs it to a load including the induction heating coil; a power control unit that controls a current command value based on a feedback value of the output power of the power conversion unit and a set power command value; a current control unit that controls a control signal for controlling the output current based on a feedback value of the output current of the power conversion unit and the current command value controlled by the power control unit; and a calculation unit that calculates the feedback value of the output power at intervals shorter than one cycle of the output current.

[0007] As described above, the power conversion device for the induction heating apparatus based on the first aspect of the present invention includes a calculation unit that calculates a feedback value of the output power at intervals shorter than one cycle of the output current. Therefore, since the calculation unit can calculate the feedback value of the output power at intervals shorter than one cycle of the output current (relatively short intervals), the response time of the feedback control of the output power can be shortened. Consequently, the response time of the feedback control of the output current based on the feedback control of the output power can also be shortened. As a result, when feedback control of the output current is performed based on the feedback control of the output power, output current instability (output current oscillation, overshoot) can be suppressed.

[0008] In the power conversion device for the induction heating apparatus based on the first aspect described above, it is preferable that the calculation unit calculates the feedback value of the output power based on an estimated value of the output power obtained at intervals shorter than one cycle of the output current. This configuration allows for the calculation of the feedback value of the output power at intervals shorter than one cycle of the output current by obtaining an estimated value of the output power at intervals shorter than one cycle of the output current.

[0009] In this case, it is preferable that the calculation unit calculates the feedback value of the output power based on the estimated value of the output voltage of the power conversion unit obtained at intervals shorter than one cycle of the output current and the output current obtained at intervals shorter than one cycle of the output current. Here, the product of the estimated value of the output voltage at intervals shorter than one cycle of the output current and the output current at intervals shorter than one cycle of the output current is the estimated value of the output power at intervals shorter than one cycle of the output current. Therefore, with the configuration described above, the estimated value of the output power at intervals shorter than one cycle of the output current can be easily calculated based on the estimated value of the output voltage at intervals shorter than one cycle of the output current and the output current at intervals shorter than one cycle of the output current.

[0010] In the aforementioned structure where the calculation unit calculates the feedback value of the output power based on the estimated value of the output voltage of the power converter obtained at intervals shorter than one cycle of the output current and the output current obtained at intervals shorter than one cycle of the output current, it is preferable that the calculation unit obtains the estimated value of the output voltage based on the DC voltage input to the power converter obtained at intervals shorter than one cycle of the output current and the control signal (for controlling the output current) obtained at intervals shorter than one cycle of the output current. Here, the product of the DC voltage input to the power converter at intervals shorter than one cycle of the output current and the control signal (high or low) for controlling the output current at intervals shorter than one cycle of the output current is the estimated value of the output voltage at intervals shorter than one cycle of the output current. Therefore, with the configuration described above, it is possible to easily obtain an estimated value of the output voltage at intervals shorter than one cycle of the output current based on the DC voltage input to the power conversion unit at intervals shorter than one cycle of the output current and the control signal at intervals shorter than one cycle of the output current.

[0011] In the aforementioned structure where the calculation unit calculates the feedback value of the output power based on the estimated value of the output voltage of the power conversion unit obtained at intervals shorter than one cycle of the output current and the output current obtained at intervals shorter than one cycle of the output current, it is preferable that the calculation unit calculates the feedback value of the output power based on the product of the estimated value of the output voltage and the output current, i.e., the estimated value of the output power. This configuration allows for the reliable calculation of the estimated value of the output power at intervals shorter than one cycle of the output current by multiplying the estimated value of the output voltage at intervals shorter than one cycle of the output current with the estimated value of the output current at intervals shorter than one cycle of the output current.

[0012] In the aforementioned structure where the calculation unit obtains an estimate of the output power at intervals shorter than one cycle of the output current to calculate the feedback value of the output power, it is preferable that the calculation unit filters the estimate of the output power through a low-pass filter over a predetermined period, thereby calculating the feedback value of the output power. This configuration, by filtering the estimate of the output power obtained at intervals shorter than one cycle of the output current through a low-pass filter over a predetermined period, allows the calculation of the effective power after averaging the estimate of the output power over a predetermined period (removing invalid power (power not consumed by the load)). As a result, the feedback value of the output power can be made to be effective power, thus improving the accuracy of the output power feedback control.

[0013] In the power conversion device for the induction heating apparatus based on the first aspect described above, it is preferable that the power control unit controls the current command value at intervals shorter than one cycle of the output current, based on the feedback value of the output power and the power command value. This configuration, by controlling the current command value at intervals shorter than one cycle of the output current, reliably shortens the response time of the feedback control of the output power.

[0014] In this case, it is preferable that the current control unit controls the control signal at intervals shorter than one cycle of the output current, based on the current command value and the feedback value of the output current obtained at intervals shorter than one cycle of the output current. This configuration, by controlling the control signal at intervals shorter than one cycle of the output current, reliably shortens the response time of the output current feedback control. Furthermore, since both the response time of the output power feedback control and the response time of the output current feedback control can be shortened, output current instability (output current oscillation, overshoot) can be effectively suppressed when output current feedback control is performed based on the result of the output power feedback control.

[0015] In the power conversion device for the induction heating apparatus based on the first aspect described above, it is preferable that the calculation unit calculates the feedback value of the output power at sampling intervals shorter than one cycle of the output current. With this configuration, since the calculation unit can calculate the feedback value of the output power at sampling intervals shorter than one cycle of the output current, the response time of the output power feedback control can be reliably shortened. Furthermore, the sampling period is the period during which the data used in calculating the feedback value of the output power is sampled.

[0016] Furthermore, in order to achieve the above-mentioned objective, an induction heating apparatus based on a second aspect of the present invention comprises: an induction heating apparatus body including an induction heating coil for melting metal by induction heating; a power conversion unit that converts an input DC voltage into an AC voltage and outputs it to the induction heating coil as a load; a power control unit that controls a current command value based on a feedback value of the output power of the power conversion unit and a set power command value; a current control unit that controls a control signal for controlling the output current based on a feedback value of the output current of the power conversion unit and the current command value controlled by the power control unit; and a calculation unit that calculates the feedback value of the output power at intervals shorter than one cycle of the output current.

[0017] In the induction heating apparatus based on the second aspect of the present invention, as described above, similar to the power conversion apparatus for the induction heating apparatus based on the first aspect, a calculation unit is provided that calculates the feedback value of the output power at intervals shorter than one cycle of the output current. Therefore, similar to the power conversion apparatus for the induction heating apparatus based on the first aspect, the calculation unit calculates the feedback value of the output power at intervals shorter than one cycle of the output current (relatively short intervals), thus enabling a shorter response time for the feedback control of the output power. Consequently, similar to the power conversion apparatus for the induction heating apparatus based on the first aspect, when feedback control of the output current is performed based on the result of the feedback control of the output power, output current instability (output current oscillation, overshoot) can be suppressed. Attached Figure Description

[0018] Figure 1 This is a diagram showing the overall structure of an induction heating device based on one embodiment of the present invention.

[0019] Figure 2 This is a block diagram illustrating the structure of a control unit for an induction heating device based on one embodiment of the present invention.

[0020] Figure 3 This is a diagram illustrating the calculation process of the feedback value of the output power in an induction heating device based on one embodiment of the present invention.

[0021] Figure 4 This is a graph showing the simulation results (theoretical values) obtained by table calculation software for calculating the feedback value of the output power in an induction heating device based on one embodiment of the present invention.

[0022] Figure 5 Therefore, compared Figure 4 Wide range (long period) indicates Figure 4 A waveform diagram.

[0023] Figure 6This is a graph showing the simulation results obtained by FPGA (Field-Programmable Gate Array) for calculating the feedback value of the output power in an induction heating device based on one embodiment of the present invention. Detailed Implementation

[0024] The embodiments embodied in the present invention will now be described with reference to the accompanying drawings.

[0025] Reference Figures 1-6 The structure of an induction heating device 100 based on one embodiment of the present invention will be described.

[0026] like Figure 1 As shown, the induction heating device 100 includes an induction heating device body 10 and a power conversion device 20. The induction heating device body 10 includes a load 11 and is configured to melt metal by induction heating. The load 11 includes an induction heating coil, a resistor, and a resonant capacitor. The power conversion device 20 converts the AC voltage (voltage, frequency, etc.) input from the AC power supply 200 and supplies it to the induction heating device body 10. Furthermore, the power conversion device 20 is an example of a "power conversion device for an induction heating device" in this invention.

[0027] The power conversion device 20 includes a rectifier circuit 21, a smoothing capacitor 22, and an inverter section 23. The rectifier circuit 21 converts the AC voltage input from the AC power supply 200 into a DC voltage before outputting it. The smoothing capacitor 22 receives the DC voltage (intermediate voltage V) output from the rectifier circuit 21. INT Smoothing. The DC voltage (intermediate voltage V) after being smoothed by smoothing capacitor 22. INT The input DC voltage (intermediate voltage V) is fed into the inverter section 23. The inverter section 23 converts the input DC voltage (intermediate voltage V) into DC voltage (intermediate voltage V). INT After being converted into AC voltage, it is output to the load 11, which includes the induction heating coil. Furthermore, the inverter section 23 is an example of the "power conversion section" in this invention. Additionally, the intermediate voltage V... INT This is an example of "(DC voltage input to the power conversion unit)" in the present invention.

[0028] The inverter section 23 includes a switching element 23a. The inverter section 23 has a full-bridge circuit structure composed of switching elements Q1, Q2, Q3, and Q4. The switching element 23a is an IGBT (Insulated Gate Bipolar Transistor). The inverter section 23 uses the switching element 23a to switch the input DC voltage (intermediate voltage V)... INT It is converted into AC voltage.

[0029] The power conversion device 20 includes a gate driver unit (GDU) 24 and a GDU power supply (not shown). The gate driver unit 24 is based on the gate signal S described later (see reference). Figure 2 The gate signal S is used to output a drive current for controlling the switching element 23a. The GDU power supply provides power for generating the drive current in the gate driver unit 24. Furthermore, the gate signal S is an example of a "control signal" in this invention.

[0030] The power conversion device 20 includes a control unit 25 for controlling various parts of the power conversion device 20. The control unit 25 is constructed using an FPGA. For example... Figure 2 As shown, the control unit 25 outputs a gate signal S to the gate driver unit 24 for generating a drive current. When the frequency of the gate signal S is changed, it controls the switching element 23a (see reference 23a). Figure 1 The drive current of the inverter section 23 (see reference 23a) varies with the output frequency of the switching element 23a. Furthermore, when the switching frequency of the switching element 23a changes, the inverter section 23 (see reference 23a)... Figure 1 Output current I OUT (Refer to Figure 1 The frequency change of ) (and thus the output current I) OUT (Change). That is, the gate signal S is used to control the output current I of the inverter section 23 by changing the frequency of the gate signal S. OUT The signal (gate frequency command value).

[0031] The control unit 25 includes an APR (Auto Power Regulator) 25a and an ACR (Auto Current Regulator) 25b. Furthermore, APR 25a and ACR 25b are examples of the "power control unit" and "current control unit" in this invention, respectively.

[0032] APR 25a is configured based on the set power command value P. COM And inverter section 23 (see reference) Figure 1 The feedback value P of the output power FB To control the current command value I COM That is, APR 25a performs feedback control on the output power of the inverter section 23. Power command value P COM For example, the user can set the desired electrical power to supply the main body 10 of the induction heating device.

[0033] ACR 25b is configured based on the current command value I after being controlled by APR 25a. COM and the output current I of inverter section 23 OUT Feedback value I FBThis controls the gate signal S. That is, ACR 25b controls the output current I of the inverter section 23. OUT Feedback control is performed. Furthermore, the control unit 25 is configured to control the output current I of the inverter section 23 based on the results of feedback control of the output power of the inverter section 23. OUT Implement feedback control.

[0034] In this embodiment, the power conversion device 20 includes an output power calculation unit 25c, which calculates power every sampling period T. S (Refer to Figure 4 Calculate the feedback value P of the output power. FB The sampling period T S It is compared to the output current I OUT One period T (refer to) Figure 4 Short intervals. Sampling period T S It is the feedback value P of the output power. FB The data used in the calculation (intermediate voltage V) INT Gate signal S, output current I OUT ) (refer to Figure 3 The sampling period is determined by using an FPGA and an AD (Analog-to-Digital) converter to perform high-speed feedback of the output power value P. FB The data used in the calculation is sampled. Furthermore, the output power calculation unit 25c is an example of a "calculation unit" in this invention.

[0035] like Figure 4 As shown, the sampling period T S For example, it can be a few μs to tens of μs. That is, the feedback value P of the output power. FB The data used in the calculations are approximate "instantaneous values". On the other hand, the output current I... OUT One cycle T is, for example, a few milliseconds to tens of milliseconds. Furthermore, when the output current I... OUT Under frequency variations, the output current I OUT The period T also changes.

[0036] In addition, such as Figure 2 As shown, in this embodiment, APR 25a is configured as follows: based on the power command value P COM And the output power calculation unit 25c every sampling period T S (Refer to Figure 4 The calculated feedback value P of the output power FB The control current command value I is obtained every APR feedback control cycle. COM The APR feedback control cycle is equal to the output current I. OUTThe interval is shorter than one cycle T. That is, APR 25a is every [time] compared to the output current I. OUT The output power of the inverter section 23 is controlled by feedback at intervals shorter than one period T (APR feedback control cycle). Furthermore, the APR feedback control cycle is longer than the sampling period T. S long.

[0037] Furthermore, in this embodiment, ACR 25b is configured to be based on the current command value I after being controlled by APR 25a every APR feedback control cycle. COM and every sampling period T S (Refer to Figure 4 The obtained output current I OUT Feedback value I FB The gate signal S is controlled every ACR feedback control cycle. The ACR feedback control cycle is equal to the output current I. OUT The interval is shorter than one cycle T. That is, the ACR 25b is activated every time the output current I... OUT The short interval T of one cycle (ACR feedback control cycle) affects the output current I of inverter section 23. OUT Feedback control is implemented. Furthermore, the ACR feedback control period is longer than the sampling period T. S It has a longer cycle than the APR feedback control cycle.

[0038] The following explains the feedback value P of the output power from the output power calculation unit 25c. FB The calculation.

[0039] like Figure 3 As shown, in this embodiment, the output power calculation unit 25c is configured to calculate power based on each sampling period T. S (Refer to Figure 4 The estimated value P of the obtained output power EST , to every sampling period T S Calculate the feedback value P of the output power. FB .

[0040] In detail, such as Figure 1 As shown, the output voltage V is when switching elements Q1 and Q4 are turned on. OUT Then the output intermediate voltage V INT The value of V. Additionally, if switching elements Q2 and Q3 are connected, the output voltage V... OUT Then the negative output intermediate voltage V INT The value of . That is, such as Figure 3 As shown, every sampling period T S (Refer to Figure 4 The intermediate voltage V INT With each sampling period T SThe product of the gate signal S (high or low) is the output voltage V of the gate signal S. OUT The estimated value V EST .

[0041] Therefore, the output power calculation unit 25c (refer to) Figure 2 By alternating sampling periods T S (Refer to Figure 4 The obtained intermediate voltage V INT With each sampling period T S The obtained gate signal S is multiplied to calculate the value every sampling period T. S Output voltage V OUT The estimated value V EST That is, in this embodiment, the output power calculation unit 25c is configured to calculate power based on each sampling period T. S The obtained intermediate voltage V INT and every sampling period T S The acquired gate signal S is used every sampling period T S Obtain the output voltage V OUT The estimated value V EST .

[0042] Moreover, every sampling period T S (Refer to Figure 4 Output voltage V OUT The estimated value V EST With each sampling period T S Output current I OUT The product is every sampling period T S The estimated output power P EST Therefore, the output power calculation unit 25c (refer to...) Figure 2 By alternating sampling periods T S (Refer to Figure 4 Output voltage V OUT The estimated value V EST With each sampling period T S Output current I OUT Multiply to calculate the interval T between sampling periods. S The estimated output power P EST That is, in this embodiment, the output power calculation unit 25c is configured to calculate power based on each sampling period T. S The obtained output voltage V OUT The estimated value V EST and every sampling period T S The obtained output current I OUT , to every sampling period T S Calculate the feedback value P of the output power. FBFurthermore, the output power calculation unit 25c is configured such that it calculates power based on a sampling period T. S The obtained output voltage V OUT The estimated value V EST With each sampling period T S The obtained output current I OUT The product is the estimated value P of the output power. EST , to every sampling period T S Calculate the feedback value P of the output power. FB .

[0043] Furthermore, in this embodiment, the output power calculation unit 25c is configured to perform calculations on each sampling period T by passing the low-pass filter (LPF) 25d over a predetermined period (e.g., a few milliseconds to tens of milliseconds). S (Refer to Figure 4 The estimated value P of the obtained output power EST Filtering is performed to calculate the feedback value P of the output power. FB .

[0044] In detail, such as Figure 4 As shown, the output current I OUT With output voltage V OUT (Refer to Figure 1 Between ) due to load 11 (refer to) Figure 1 This includes an induction heating coil and a resonant capacitor, which generate a phase difference θ. Therefore, every sampling period T... S (Refer to Figure 4 The estimated value P of the obtained output power EST In addition to including load 11 (refer to) Figure 1 The electricity consumed is the effective electricity P. ACT (Refer to Figure 4 In addition to the power consumed by load 11, it also includes power that is not consumed by load 11, i.e., ineffective power. Furthermore, it is desirable that the feedback value P of the output power... FB For effective power P ACT This is to avoid reducing the accuracy of feedback control of the output power.

[0045] Therefore, such as Figure 3 As shown, the output power calculation unit 25c (refer to) Figure 2 The low-pass filter is applied for 25 days over a specified period, and the sampling period T is applied at each sampling interval. S (Refer to Figure 4 The estimated value P of the obtained output power EST Filtering is performed to calculate an estimated value P of the output power. EST The effective power P obtained by averaging over a specified period (after removing invalid power) ACT (Refer to Figure 4 ).

[0046] In addition, such as Figure 5 and Figure 6 As shown, at the feedback value P of the output power FB In the simulation calculation, the initial value of the output power was set to 0W. Therefore, the estimated value P of the output power was obtained by passing through a low-pass filter for a specified period of 25d. EST The feedback value P of the output power obtained after filtering FB (Effective power P) ACT ), at the beginning of calculating the feedback value P of the output power FB At that time, the feedback value P of the output power is calculated. FB Previous period (estimated output power P) EST The period when the power is 0W is also averaged. Therefore, the feedback value P of the output power is calculated at the beginning. FB Feedback value P of the output power FB Gradually increase until the feedback value P of the output power is reached. FB Until it stabilizes.

[0047] In addition, Figure 6 The simulation results obtained through FPGA are shown below. Figure 5 The simulation results (theoretical values) obtained through the table calculation software shown represent the feedback value P of the output power. FB The time until stabilization is approximately consistent. That is, the time per sampling period T calculated by the output power calculation unit 25c has been confirmed. S Feedback value P of the output power FB (Effective power P) ACT The calculations are performed in practice according to the theory.

[0048] (Effects of the implementation method)

[0049] In this embodiment, the following effect can be obtained.

[0050] In this embodiment, as described above, the power conversion device 20 includes an output power calculation unit 25c, which calculates the output power every certain interval as the ratio of the output current I. OUT The sampling period T is one period T with a short interval. S Calculate the feedback value P of the output power. FB Therefore, since the output power calculation unit 25c can calculate the output power every sampling period T... S (Comparison of output current I) OUT The feedback value P of the output power is calculated using a short interval (T) within one cycle. FB Therefore, the response time of the feedback control of the output power can be relatively short. Consequently, the output current I based on the feedback control of the output power can be increased.OUT The response time of the feedback control is also relatively short. As a result, the output current I is determined based on the feedback control result of the output power. OUT Under feedback control, the output current I can be suppressed. OUT Unstable (output current I) OUT (This can cause oscillations and overshoot).

[0051] Furthermore, in this embodiment, as described above, the output power calculation unit 25c is based on every sampling period T S (Comparison of output current I) OUT The estimated output power P obtained from a short interval (T) within one period. EST , to every sampling period T S Calculate the feedback value P of the output power. FB Therefore, it is possible to achieve this by measuring every sampling period T. S Obtain an estimate of the output power P. EST , to every sampling period T S Calculate the feedback value P of the output power. FB .

[0052] Furthermore, in this embodiment, as described above, the output power calculation unit 25c is based on every sampling period T S (Comparison of output current I) OUT The output voltage V of inverter section 23 is obtained in one cycle (short interval T). OUT The estimated value V EST and every sampling period T S The obtained output current I OUT , to every sampling period T S Calculate the feedback value P of the output power. FB Therefore, it is possible to base the results on each sampling period T. S Output voltage V OUT The estimated value V EST and every sampling period T S Output current I OUT It is easy to calculate every sampling period T S The estimated output power P EST .

[0053] Furthermore, in this embodiment, as described above, the output power calculation unit 25c is based on every sampling period T S (Comparison of output current I) OUT The intermediate voltage V input to inverter section 23 is obtained during a short interval (T) of one cycle. INT and every sampling period T S The obtained (used to control the output current I) OUTThe gate signal S is used every sampling period T. S Obtain the output voltage V OUT The estimated value V EST Therefore, it is possible to base the results on each sampling period T. S The intermediate voltage V input to the inverter section 23 INT With each sampling period T S The gate signal S can be easily obtained every sampling period T. S Output voltage V OUT The estimated value V EST .

[0054] Furthermore, in this embodiment, as described above, the output power calculation unit 25c is configured to calculate power based on each sampling period T. S (Comparison of output current I) OUT The output voltage V obtained from one cycle T (short interval) OUT The estimated value V EST With each sampling period T S The obtained output current I OUT The product is the estimated value P of the output power. EST , to every sampling period T S Calculate the feedback value P of the output power. FB Therefore, it is possible to achieve this by sampling every T periods. S Output voltage V OUT The estimated value V EST With each sampling period T S Output current I OUT Multiply to reliably calculate every sampling period T S The estimated output power P EST .

[0055] Furthermore, in this embodiment, as described above, the output power calculation unit 25c is subjected to a predetermined period of time by the low-pass filter 25d for each sampling period T. S (Comparison of output current I) OUT The estimated output power P obtained from a short interval (T) within one period. EST Filtering is performed, and the feedback value P of the output power is calculated accordingly. FB Therefore, by passing a low-pass filter for 25d over a specified period, the sampling period T is... S The estimated value P of the obtained output power EST By performing filtering, an estimated value P of the output power can be calculated. EST The effective power P, obtained by averaging over a specified period (excluding invalid power (power not consumed by load 11)), is the power obtained from the average of the effective power P. ACT As a result, the feedback value P of the output power can be made... FBFor effective power P ACT Therefore, it can improve the accuracy of feedback control of output power.

[0056] Furthermore, in this embodiment, as described above, APR 25a is based on the power command value P. COM And the output power calculation unit 25c every sampling period T S The calculated feedback value P of the output power FB Every APR feedback control cycle (ratio of output current I) OUT The control current command value I is the short interval of one cycle T. COM Therefore, since the control current command value I is changed every APR feedback control cycle... COM Therefore, the response time of feedback control of output power can be reliably shortened.

[0057] Furthermore, in this embodiment, as described above, ACR 25b is based on APR 25a every APR feedback control cycle (ratio of output current I). OUT The current command value I after control of one cycle T (short interval) COM and every sampling period (ratio of output current I) OUT (1 period T short interval) T S The obtained output current I OUT Feedback value I FB Every ACR feedback control cycle (ratio of output current I) OUT The gate signal S is controlled by a short interval (T) of one cycle. Therefore, since the gate signal S is controlled every ACR feedback control cycle, the output current I can be reliably shortened. OUT The response time of the feedback control. Furthermore, since the response time of the feedback control of the output power and the output current I can be reduced... OUT The response time of feedback control is shortened, therefore, the output current I is determined based on the feedback control result of the output power. OUT Under feedback control, the output current I can be effectively suppressed. OUT Unstable (output current I) OUT (This can cause oscillations and overshoot).

[0058] [Variation Example]

[0059] All aspects of the embodiments disclosed herein should be considered illustrative rather than limiting. The scope of the invention is shown not by the description of the above embodiments but by the claims, and the scope of the invention also includes all modifications (variations) within the meaning and scope equivalent to the claims.

[0060] For example, in the above embodiment, it is shown that the ACR feedback control period is longer than the sampling period T. SExamples of ACR feedback control periods that are longer than the APR feedback control period exist, but the invention is not limited thereto. In this invention, the ACR feedback control period can also be equal to the sampling period, equal to the APR feedback control period, or longer than the APR feedback control period.

[0061] Furthermore, in the above embodiment, it is shown that the APR feedback control period is longer than the sampling period T. S This is a long example, but the invention is not limited thereto. In this invention, the APR feedback control period can also be equal to the sampling period.

[0062] Furthermore, in the above embodiment, the output power calculation unit 25c (calculation unit) is configured to estimate the output power P by passing the low-pass filter 25d over a predetermined period. EST Filtering is performed to calculate the feedback value P of the output power. FB Examples are given, but the present invention is not limited thereto. In the present invention, the calculation unit may also be configured to directly use the estimated value of the output power as the feedback value of the output power.

[0063] Furthermore, in the above embodiment, the output power calculation unit 25c (calculation unit) is configured to calculate power based on each sampling period T. S (Comparison of output current I) OUT The output voltage V obtained from one cycle T (short interval) OUT The estimated value V EST With each sampling period T S The obtained output current I OUT (The product is the estimated value P of the output power) EST ) every sampling period T S Calculate the feedback value P of the output power. FB (That is, output voltage V) OUT The estimated value V EST Acquisition interval, output current I OUT The acquisition interval and the feedback value P of the output power FB Examples of calculations with equal intervals are given, but the invention is not limited thereto. In this invention, the intervals for obtaining the estimated output voltage, the intervals for obtaining the output current, and the intervals for calculating the feedback value of the output power can also be different.

[0064] Furthermore, in the above embodiment, the output power calculation unit 25c (calculation unit) is configured to calculate power based on each sampling period T. S (Comparison of output current I) OUT The intermediate voltage V input to the inverter section 23 (power conversion section) is obtained during a short interval (T) of one cycle. INT (DC voltage) and sampling period T SThe acquired gate signal S(( is used to control the output current I) OUT The control signal is used every sampling period T S Obtain the output voltage V OUT The estimated value V EST (That is, the intermediate voltage V input to the inverter section 23 (power conversion section) INT The acquisition interval of (DC voltage) and the gate signal S (used to control the output current I) OUT The acquisition interval of the control signal and the output voltage V OUT The estimated value V EST Examples of acquisition intervals being equal to each other are not limited to this invention. In this invention, the acquisition intervals of the DC voltage input to the power conversion unit, the acquisition intervals of the control signal (for controlling the output current), and the acquisition intervals of the estimated output voltage may also be different.

[0065] Furthermore, in the above embodiment, the output power calculation unit 25c (calculation unit) is configured to calculate power based on each sampling period T. S (Comparison of output current I) OUT The estimated output power P obtained from a short interval (T) within one period. EST Every sampling period T S Calculate the feedback value P of the output power. FB (That is, the estimated value P of the output power) EST The acquisition interval and the feedback value P of the output power FB Examples of this invention include those where the acquisition intervals are equal, but the invention is not limited thereto. In this invention, the acquisition interval of the estimated output power value and the acquisition interval of the feedback output power value may also be different.

[0066] Furthermore, in the above embodiment, it is shown that the output power calculation unit 25c (calculation unit) is configured such that every interval of the output current I... OUT The sampling period T is one period T with a short interval. S Calculate the feedback value P of the output power. FB Examples are given, but the present invention is not limited thereto. In the present invention, the calculation unit may also be configured to calculate the feedback value of the output power at intervals other than the sampling period, where the intervals other than the sampling period are shorter than one cycle of the output current.

Claims

1. A power conversion device for an induction heating device, the induction heating device including an induction heating coil, for melting metal by induction heating, the power conversion device for the induction heating device comprising: The power conversion unit converts the input DC voltage into AC voltage and outputs it to the load including the induction heating coil. The power control unit controls the current command value at intervals shorter than one cycle of the output current of the power converter, based on the feedback value of the output power of the power converter and the set power command value. The current control unit controls the control signal for controlling the output current at intervals shorter than one cycle of the output current, based on the feedback value of the output current obtained at intervals shorter than one cycle of the output current and the current command value after being controlled by the power control unit. as well as The calculation unit calculates the feedback value of the output power at intervals shorter than one cycle of the output current.

2. The power conversion device for the induction heating device according to claim 1, characterized in that, The calculation unit calculates the feedback value of the output power based on the estimated value of the output power obtained at intervals shorter than one cycle of the output current.

3. The power conversion device for the induction heating device according to claim 2, characterized in that, The calculation unit calculates the feedback value of the output power based on the estimated value of the output voltage of the power conversion unit obtained at intervals shorter than one cycle of the output current and the output current obtained at intervals shorter than one cycle of the output current.

4. The power conversion device for the induction heating device according to claim 3, characterized in that, The calculation unit obtains an estimate of the output voltage based on the DC voltage input to the power conversion unit at intervals shorter than one cycle of the output current and the control signal obtained at intervals shorter than one cycle of the output current.

5. The power conversion device for the induction heating device according to claim 3, characterized in that, The calculation unit calculates the feedback value of the output power based on the product of the estimated value of the output voltage and the output current, which is the estimated value of the output power.

6. The power conversion device for the induction heating device according to claim 2, characterized in that, The calculation unit filters the estimated value of the output power through a low-pass filter over a specified period, thereby calculating the feedback value of the output power.

7. The power conversion device for the induction heating device according to claim 1, characterized in that, The calculation unit calculates the feedback value of the output power every sampling period, where the sampling period is shorter than one cycle of the output current.

8. An induction heating device, comprising: The main body of the induction heating device includes an induction heating coil, which melts metal through induction heating; The power conversion unit converts the input DC voltage into AC voltage and outputs it to the load including the induction heating coil. The power control unit controls the current command value at intervals shorter than one cycle of the output current of the power converter, based on the feedback value of the output power of the power converter and the set power command value. The current control unit controls the control signal for controlling the output current at intervals shorter than one cycle of the output current, based on the feedback value of the output current obtained at intervals shorter than one cycle of the output current and the current command value after being controlled by the power control unit. as well as The calculation unit calculates the feedback value of the output power at intervals shorter than one cycle of the output current.

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