CN113251395B - Steam generator control device based on electromagnetic induction heating technology - Google Patents

Steam generator control device based on electromagnetic induction heating technology Download PDF

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CN113251395B
CN113251395B CN202110119290.1A CN202110119290A CN113251395B CN 113251395 B CN113251395 B CN 113251395B CN 202110119290 A CN202110119290 A CN 202110119290A CN 113251395 B CN113251395 B CN 113251395B
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CN113251395A (en
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杨波
周博文
杨东升
李广地
朱晓琳
贺志盈
唐庆志
王欢
魏宏岩
赵满红
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Qiyan Shenyang Technology Center Co ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/28—Methods of steam generation characterised by form of heating method in boilers heated electrically
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B35/00—Control systems for steam boilers
    • 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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Abstract

The invention discloses a control device of a steam generator based on an electromagnetic induction heating technology, which comprises a rectifying part, a filtering part, a direct-current voltage stabilizing part, an inversion part, a steam generating part, a driving part, a control part and a system power circuit, wherein the rectifying part is connected with the filtering part; the control part comprises a chopping control circuit, a control circuit of the inversion part, an IGBT driving circuit, a voltage detection circuit, a current detection circuit, a voltage and current protection circuit, a reset circuit and an output signal detection circuit; the control part not only controls the drive circuit to conduct and turn off the IGBT in the inversion part, but also controls the overcurrent, overvoltage and undervoltage protection of the IGBT. The invention adopts an AC-DC-AC circuit structure to ensure that the device has a better output power adjusting mode and higher working efficiency. In addition, the output medium-frequency alternating current is monitored in real time, and the stability of the output amplitude and frequency of the medium-frequency alternating current is ensured.

Description

Steam generator control device based on electromagnetic induction heating technology
Technical Field
The invention relates to the technical field of electromagnetic heating, in particular to a control device of a steam generator based on an electromagnetic induction heating technology.
Background
With the rapid development of industrial technology, steam generators are becoming more and more widely used, but steam generators using non-renewable energy sources such as coal as fuel still occupy a considerable proportion. Although the country has encouraged the improvement of the thermal efficiency of steam generation of the conventional boiler, the efficiency of steam generation is low, and the internal devices are complicated, maintenance is difficult, various pollutants are generated by combustion, and a number of environmental pollution problems are caused. New technologies with high energy utilization and environmental protection, one of which is induction heating technology, are being studied. The electromagnetic induction heating steam generator mainly uses the eddy current heating principle, and rapidly-changing alternating current passes through a coil which surrounds the outside of the steam generator to generate an alternating magnetic field, so that eddy current is generated on the metal surface for heating. Compared with the traditional steam generator, the electromagnetic induction heating type steam generator has the characteristics of energy conservation, high efficiency and no pollution, so that the electromagnetic induction heating type steam generator has great practical significance in research.
The steam generator based on electromagnetic induction heating technology is mainly focused on a control device thereof, and is mainly divided into low frequency, medium frequency and high frequency according to different application occasions, and most of applications are medium frequency control. The traditional induction heating control device adopts a parallel resonance type, the circuit design of the parallel resonance type controller is mature, but the control device is too complex, the connection line between the control device and a load cannot be too long, and the applicable occasion is limited. In order to make possible a wide range of applications of electromagnetic induction heating steam generators, an electromagnetic induction heating technology with high efficiency, low loss and wide application range is needed.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides a control device of a steam generator based on an electromagnetic induction heating technology.
In order to solve the technical problems, the invention adopts the following technical scheme: a control device of a steam generator based on electromagnetic induction heating technology, comprising: the device comprises a rectifying part, a filtering part, a direct-current voltage stabilizing part, an inversion part, a steam generating part, a driving part, a control part and a system power circuit;
the rectification part inputs three-phase alternating current and inputs the three-phase alternating current into the rectification part for rectification; after the rectification circuit works stably, the rectification circuit is short-circuited, and the output direct current is filtered by the filtering part; after filtering, the direct-current voltage stabilizing part, namely a chopper circuit, is connected to carry out chopper conversion of DC-DC; after being chopped, the chopper is connected with the inversion part to perform DC-AC conversion to generate intermediate frequency alternating current; connecting the medium-frequency alternating current generated by the inversion part to a surface coil wound on the steam generation part, namely the steam generator;
the control section includes (1) controlling a chopper circuit; (2) controlling the inversion portion; the control part controls the drive circuit to control the on-off of the IGBT in the inversion part on one hand and controls the over-current, over-voltage and under-voltage protection of the IGBT on the other hand.
The rectification part adopts a three-phase bridge type uncontrollable rectification circuit, and comprises 6 power diodes, namely VD1, VD2, VD3, VD4, VD5 and VD6; the common cathode of the VD1, the VD3 and the VD5 is connected, the common anode of the VD4, the common anode of the VD6 and the common anode of the VD2 are connected, the anode of the VD1 is connected with the cathode of the VD4, the anode of the VD3 is connected with the cathode of the VD6, and the anode of the VD5 is connected with the cathode of the VD 2;
when alternating current side line voltage U A ＞U B At the time, diodes VD1 and VD6 are conducted, and the DC side voltage is U AB The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U A ＞U C At the time, diodes VD1 and VD2 are conducted, and the voltage at the DC side is U AC The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U B ＞U C At the time, diodes VD3 and VD2 are conducted, and the voltage at the DC side is U BC The method comprises the steps of carrying out a first treatment on the surface of the I.e. the output dc voltage is the ac side voltage maximum.
The filtering part is characterized in that a direct-current voltage output end of a three-phase bridge type uncontrollable rectifying circuit is connected with two filtering capacitors C1 and C2, and the two resistors R2 and R3 are respectively connected in parallel on the filtering capacitors C1 and C2 to play a role in equalizing voltage, so that voltages applied to two ends of the capacitors C1 and C2 are the same; in addition, two voltage dividing resistors R4 and R5 are connected to the DC voltage output end of the three-phase bridge type uncontrollable rectifying circuit and are used for detecting the DC side voltage.
The direct-current voltage stabilizing part adopts a Sepic chopper circuit to regulate the output power of the direct-current side by regulating the voltage amplitude of the direct-current side of the input inversion part;
the voltage amplitude of the direct current side of the regulating input inversion part is regulated by regulating the duty ratio alpha of the chopper circuit, and the calculation formula of alpha is as follows:
Figure BDA0002921395150000021
Figure BDA0002921395150000022
wherein E is a rectified output voltage; u (U) 0 Outputting a voltage for the chopper circuit; t is t on And t off The on and off times of the IGBTs are respectively divided.
The inversion part adopts a single-phase bridge current type inversion circuit, an electromagnetic induction coil for heating and a series compensation capacitor C are connected in series to form a load of the single-phase bridge current type inversion circuit, and in order to ensure the stability of steam generation, the resonance frequency of a control system fluctuates in a set passband.
The control part comprises a chopping control circuit, a control circuit of the inversion part, an IGBT driving circuit, a voltage detection circuit, a current detection circuit, a voltage and current protection circuit, a reset circuit and an output signal detection circuit;
the output of the chopper control circuit is used as the input of a direct current chopper circuit to control the on and off of an IGBT in the chopper circuit;
the control circuit output of the inversion part is divided into two aspects: on one hand, the output is used as the input of the IGBT driving circuit, the inverter circuit is controlled to complete the inversion process, and the voltage and current protection circuit is controlled to protect the IGBT; on the other hand, the voltage detection circuit and the current detection circuit are controlled to detect the voltage and the current output by the inverter;
the IGBT driving circuit comprises two parts: one part is the IGBT drive of the chopper circuit, the other part is the IGBT drive of the inverter circuit, the IGBT drive of the chopper circuit is controlled by the SG3525 chip, and the IGBT drive of the inverter circuit is controlled by the DSP;
the IGBT driving circuit, the voltage detection circuit, the current detection circuit, the voltage and current protection circuit, the reset circuit and the output signal detection circuit of the inverter circuit are controlled by the DSP and are connected with the output of the DSP.
The pin 8 of the SG3525 chip is a soft start access end and is also an inverted input end of the PWM comparator; when the voltage at two ends of the capacitor cannot be suddenly changed, the reverse input end of the PWM comparator is also low level when the pin 8 is low level, the PWM comparator outputs high level, the PWM latch outputs high level, and the high level is applied to the output transistor through two NAND gates, so that the output transistor cannot be conducted; when the soft start capacitor is charged to enable the pin 8 of the SG3525 chip to be at a high level, the SG3525 is only operated;
the voltage is sent to a 1 pin of SG3525, the 1 pin is the reverse input end of the error amplifier, and a feedback signal is connected to the pin to form closed-loop control; PWM waves generated by SG3525 drive IGBT in a chopper circuit after passing through an isolation driving circuit; the reference voltage is connected to the same-direction input end of the error amplifier, namely the 2 pins, and the sampling voltage of the output voltage is added to the reverse input end of the error amplifier; when the output voltage rises, the output of the error amplifier becomes smaller, so that the high-level time of PWM output becomes longer, the conduction time of the IGBT tube becomes shorter, and the steady state is realized.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in:
1. the control device of the steam generator based on the electromagnetic induction heating technology provided by the invention adopts an AC-DC-AC circuit structure, so that the device has a better output power adjusting mode and higher working efficiency. The hardware control device monitors the output medium-frequency alternating current in real time, and ensures the stability of the output amplitude and frequency. Meanwhile, the safety and the stability of the device are greatly improved due to the protection and detection circuit.
2. The rectification part adopts three-phase alternating current input and a three-phase uncontrollable rectification circuit, is different from the traditional controllable rectification circuit, has higher circuit power factor, is connected with a current limiting resistor at the direct current side to prevent overlarge current at the direct current side, and is short-circuited after the rectifier works stably, and the output direct current is filtered through a filter capacitor.
3. The chopper circuit adopts the buck-boost chopper circuit, which has the main functions of providing direct current with stable amplitude for the inverter circuit to be transmitted to the inverter, and is different from the traditional steam generator power supply circuit which adopts alternating current power measurement and regulation. Meanwhile, the influence on a circuit caused by adding a power switch device into a chopper circuit is reduced as much as possible.
Drawings
FIG. 1 is a schematic diagram of a control device of a steam generator based on electromagnetic induction heating technology in an embodiment of the present invention;
FIG. 2 is a schematic diagram of an AC-DC rectifying and filtering circuit according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a DC-DC chopper circuit in an embodiment of the invention;
fig. 4 is a schematic diagram of an inverter working principle according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a power circuit according to an embodiment of the invention;
FIG. 6 is a schematic diagram of a chopper control circuit in accordance with an embodiment of the present invention;
FIG. 7 is a schematic diagram of an IGBT driving circuit according to an embodiment of the invention;
FIG. 8 is a schematic diagram of a voltage and current detection circuit according to an embodiment of the present invention;
FIG. 9 is a schematic diagram of an overvoltage and current protection circuit according to an embodiment of the invention;
FIG. 10 is a schematic diagram of an undervoltage circuit in accordance with an embodiment of the present invention;
FIG. 11 is a schematic diagram of a reset circuit according to an embodiment of the present invention;
FIG. 12 is a schematic diagram of a synchronous signal conversion circuit according to an embodiment of the present invention;
fig. 13 is a schematic circuit diagram of a steam generating part in an embodiment of the present invention.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
As shown in fig. 1, the structure of the control device of the steam generator based on the electromagnetic induction heating technology in the present embodiment includes: the device comprises a rectifying part, a filtering part, a direct-current voltage stabilizing part, an inversion part, a steam generating part, a driving part, a control part and a system power circuit;
the rectification part inputs three-phase alternating current and inputs the three-phase alternating current into the rectification part for rectification; after the rectification circuit works stably, the rectification circuit is short-circuited, and the output direct current is filtered by the filtering part; after filtering, the direct-current voltage stabilizing part, namely a chopper circuit, is connected to carry out chopper conversion of DC-DC; after being chopped, the chopper is connected with the inversion part to perform DC-AC conversion to generate intermediate frequency alternating current; connecting the medium-frequency alternating current generated by the inversion part to a surface coil wound on the steam generation part, namely the steam generator;
the control section includes (1) controlling a chopper circuit; (2) controlling the inversion portion; the control part controls the drive circuit to control the on-off of the IGBT in the inversion part on one hand and controls the over-current, over-voltage and under-voltage protection of the IGBT on the other hand.
In this embodiment, the rectification part adopts a three-phase bridge type uncontrollable rectification circuit, as shown in fig. 2, the three-phase half-control or full-control rectification circuit is not adopted, and the circuit controls the output voltage of the circuit by controlling the trigger angle, so that the power factor of the circuit is lower, the harmonic amplitude changes along with the trigger angle, and the circuit is easy to be polluted.
The three-phase bridge type uncontrollable rectifying circuit comprises 6 power diodes, namely VD1, VD2, VD3, VD4, VD5 and VD6; the common cathode of the VD1, the VD3 and the VD5 is connected, the common anode of the VD4, the common anode of the VD6 and the common anode of the VD2 are connected, the anode of the VD1 is connected with the cathode of the VD4, the anode of the VD3 is connected with the cathode of the VD6, and the anode of the VD5 is connected with the cathode of the VD 2;
when alternating current side line voltage U A ＞U B At the time, diodes VD1 and VD6 are conducted, and the DC side voltage is U AB The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U A ＞U C At the time, diodes VD1 and VD2 are conducted, and the voltage at the DC side is U AC The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U B ＞U C At the time, diodes VD3 and VD2 are conducted, and the voltage at the DC side is U BC The method comprises the steps of carrying out a first treatment on the surface of the I.e. the output dc voltage is the ac side voltage maximum.
The filtering part is characterized in that a direct-current voltage output end of a three-phase bridge type uncontrollable rectifying circuit is connected with two filtering capacitors C1 and C2, and as shown in fig. 2, the filtering part plays a role of direct-current side filtering. The filter capacitors C1 and C2 are respectively connected with two resistors R2 and R3 in parallel to play a role in equalizing voltage, so that voltages applied to two ends of the capacitors C1 and C2 are the same; in addition, two voltage dividing resistors R4 and R5 are connected to the DC voltage output end of the three-phase bridge type uncontrollable rectifying circuit and are used for detecting the DC side voltage. In fig. 2, R1 is a current limiting resistor, which limits the charging current of the capacitor and prevents the overcurrent of the rectifier. The switching action on the two sides of R1 is to short-circuit R1 after the current transformer stably works.
When the rectifying portion current is continuous, the rectifying portion outputs a voltage regardless of the switching tube loss:
U d ＝2.34U in (1)
U d ＝2.34×380＝889.2 (2)
wherein: u (U) d Representing the dc side voltage after rectification; u (U) in Representing the input three-phase ac phase voltage.
Figure BDA0002921395150000051
Wherein: the voltage peak value born by the diode is U FM 。
Considering the safety factor, a certain safety margin is generally selected, and the reverse voltage peak value is 3 times, so that:
U vd ＝3×537.32＝1611.96 (4)
in U vd Is in the opposite directionPeak voltage.
Because the circuit in this embodiment requires a final output power of 6K, U when switching tube losses are considered d Taking 880 and setting η of the circuit to 0.85, the output current is:
Figure BDA0002921395150000052
wherein I is d Is the rectified current output.
The current is:
Figure BDA0002921395150000061
wherein I is vd Is the current flowing through the diode;
also considering the safety margin, here again taking the diode current rating margin to be 3 times the current peak:
Figure BDA0002921395150000062
in summary, the rectifier diode in this embodiment should be selected to be 20A/1700V.
The direct-current voltage stabilizing part adopts a Sepic chopper circuit to regulate the output power of the direct-current side by regulating the voltage amplitude of the direct-current side of the input inversion part;
in this embodiment, fig. 3 shows the principle of the dc chopper circuit, since the rectifying circuit outputs dc power, which is shown as a dc power source for convenience, and since the final output is directly supplied to the input of the inverting section, the equivalent load section is not shown in fig. 3. The circuit is a Sepic chopper circuit, and the basic working principle is as follows: when V is in on state, the E-L1-V loop and the C1-V-L2 loop are simultaneously conducted, and L1 and L2 store energy. When V is in an off state, the E-L1-C-VD-load loop and the L2-VD-load loop are simultaneously conducted, and at the stage E and L1, power is supplied to a load and also charges C, and energy stored by C is transferred to L2 when V is in an on state.
The voltage amplitude of the direct current side of the regulating input inversion part is regulated by regulating the duty ratio alpha of the chopper circuit, and the calculation formula of alpha is as follows:
Figure BDA0002921395150000063
Figure BDA0002921395150000064
wherein E is a rectified output voltage; u (U) 0 Outputting a voltage for the chopper circuit; t is t on And t off The on and off times of the IGBTs are respectively divided.
In this embodiment, since the dc voltage output from the rectifying circuit is 880 and the voltage finally output to the inverter is 600, it is necessary to adjust the duty ratio α of the dc chopper circuit, and the above formula is used to derive the formula of α as:
Figure BDA0002921395150000065
so that only the duty cycle of the circuit needs to be adjusted to be set to 0.59 to generate a stable direct current with a magnitude of 600 to be supplied to the inverting section.
The inversion part adopts a single-phase bridge current type inversion circuit, as shown in fig. 4, an electromagnetic induction coil for heating and a series compensation capacitor C are connected in series to form a load of the single-phase bridge current type inversion circuit, and in order to ensure the stability of steam generation, the resonance frequency of a control system fluctuates in a set passband.
In this embodiment, as shown in fig. 4, the resistor R and the inductor L are connected in series to form an equivalent load of the induction coil. Since the power factor is low, the compensation capacitor C is connected in series. The capacitors C and L, R form a series resonant circuit. The four bridge arms are combined and can be seen as a combination of two half-bridge circuits. Bridge arms 1 and 4 are taken as a pair, bridge arms 2 and 3 are taken as another pair, two bridge arms in the pair are conducted simultaneously, and the two pairs are conducted alternately by 180 degrees. In the figure, VD1 and VD4, V1 and V4, VD2 and VD3, and V2 and V3 are alternately conducted successively.
In order to ensure that the resonant frequency of the system can fluctuate within a set range in the circuit, we usually use a passband to represent that the system frequency must be above 19kHz in order to ensure stability of steam generation, the resonant frequency of the circuit is 20kHz, and the bandwidth is 2kHz. So there are:
Figure BDA0002921395150000071
wherein: omega 0 Representing the resonant frequency of the circuit; Δω represents the bandwidth of the frequency band; q is the quality factor of the circuit.
The amplitude of the direct current voltage transmitted to the inverter circuit through the DC-DC chopper circuit is about 600, and at least a certain margin is selected when the circuit stably works, and the margin is uniformly set to be 2 times, namely about 1200, so that the method comprises the following steps:
Figure BDA0002921395150000072
Figure BDA0002921395150000073
can deduce I vt The expression of (2) is:
Figure BDA0002921395150000074
wherein: p is the power to be output; cos phi is the power factor of the circuit; u, I is the effective value of the output voltage and current of the inverter; i vt Is the effective value of the current flowing through the thyristor; u (U) l Is the effective value of the load voltage.
For safety reasons, the capacity is 2 times as large as that of the IGBT tube, and the model of MBQ40T120FDS, of 40A/1200V of Meguena company is finally determined and selected through the analysis.
In this embodiment, the system power supply circuit provides 15V for the overvoltage, overcurrent protection circuit and detection circuit, provides 5V for the IGBT driving circuit, designs a system power supply with different voltage output values, as shown in fig. 5, wherein the input voltage is an ac voltage, the positive electrode of the input terminal is connected with the fuse F, the negative electrode is connected with the switch S1, and when the input phase voltage fails such as short circuit, the input terminal can be disconnected in time, damage to the back-end circuit device is prevented, and the safety of the circuit is ensured. In the embodiment, a Jin Shengyang LH10-10A05 alternating current-direct current conversion power supply is adopted, capacitors C7, C9, C13 and C15 are connected for isolation with a rear-end circuit, the capacitors C2 and C5 are connected in parallel, resistors R3 and R4 are connected in parallel at two ends of the filter capacitors and the capacitors C2 and C5 at the same time, the effect of equalizing voltage of the filter capacitors is achieved, the principle of rear-end partial circuits is basically the same through inductors L1 and L2, and finally the voltage value required by a system is obtained through clamping diodes D1 and D2.
The control part comprises a chopping control circuit, a control circuit of the inversion part, an IGBT driving circuit, a voltage detection circuit, a current detection circuit, a voltage and current protection circuit, a reset circuit and an output signal detection circuit;
the output of the chopper control circuit is used as the input of a direct current chopper circuit to control the on and off of an IGBT in the chopper circuit;
the control circuit output of the inversion part is divided into two aspects: on one hand, the output is used as the input of the IGBT driving circuit, the inverter circuit is controlled to complete the inversion process, and the voltage and current protection circuit is controlled to protect the IGBT; on the other hand, the voltage detection circuit and the current detection circuit are controlled to detect the voltage and the current output by the inverter;
the IGBT driving circuit comprises two parts: one part is the IGBT drive of the chopper circuit, the other part is the IGBT drive of the inverter circuit, the IGBT drive of the chopper circuit is controlled by the SG3525 chip, and as shown in FIG. 6, the IGBT drive of the inverter circuit is controlled by the DSP;
the IGBT driving circuit, the voltage detection circuit, the current detection circuit, the voltage and current protection circuit, the reset circuit and the output signal detection circuit of the inverter circuit are controlled by the DSP and are connected with the output of the DSP.
In fig. 6, the power input terminal is 15V, and the pin 8 of the SG3525 chip is a soft start access terminal and an inverting input terminal of the PWM comparator; when the voltage at two ends of the capacitor cannot be suddenly changed, the reverse input end of the PWM comparator is also low level when the pin 8 is low level, the PWM comparator outputs high level, the PWM latch outputs high level, and the high level is applied to the output transistor through two NAND gates, so that the output transistor cannot be conducted; when the soft start capacitor is charged to enable the pin 8 of the SG3525 chip to be at a high level, the SG3525 is only operated;
the voltage is sent to a 1 pin of SG3525, the 1 pin is the reverse input end of the error amplifier, and a feedback signal is connected to the pin to form closed-loop control; PWM waves generated by SG3525 drive IGBT in a chopper circuit after passing through an isolation driving circuit; the reference voltage is connected to the same-direction input end of the error amplifier, namely the 2 pins, and the sampling voltage of the output voltage is added to the reverse input end of the error amplifier; when the output voltage rises, the output of the error amplifier becomes smaller, so that the high-level time of PWM output becomes longer, the conduction time of the IGBT tube becomes shorter, and the steady state is realized.
The IGBT driving circuit in this embodiment is an M57959L type IGBT driver of mitsubishi company, as shown in fig. 7, and has desaturation detection and protection links inside the driver, which can rapidly respond but slowly turn off the IGBT when an overcurrent occurs, and give a fault signal to an external circuit. The logic control signal is input by 13 pins, the resistance values of the resistors R1 and R2 are basically fixed, the diode D1 is a fast recovery diode, and the bidirectional voltage stabilizing diodes D2 and D3 prevent the grid electrode and the emitter electrode of the IGBT from breakdown to damage the circuit. The required input voltage of the driver is 5V, the positive driving voltage output outwards is +15V, and the negative driving voltage is-10V.
The voltage and current detection circuit diagram in this embodiment is shown in fig. 8, wherein the sampling circuit of the voltage detection circuit uses a hall voltage sensor CHV-25P/500V, and the sensor can electrically isolate the analog signal at the input end from the digital signal at the output end, and can output an output voltage of-5V to +5v. Since the DSP can only detect the voltage signal, the input signal is changed to a voltage of-2.5 to +2.5V by the sampling circuit constituted by the resistors R1, R2. The analog/digital conversion of the DSP allows voltages of 0-3V, so that in order to convert voltages of-2.5-2.5V to 0-3V, the operational amplifiers U1 and R3, R4, R5, R6 together constitute a voltage bias circuit.
Since some harmonic interference is included in the circuit, a filtering process is required in order to prevent noise generated by the harmonics from affecting the a/D sampling result. The operational amplifier U2, the capacitors C1 and C2 which are correspondingly configured and the resistor R7 form a first-order active filter together, the front-end input voltage is isolated from the sampling voltage by adopting a voltage tracking mode, and the cutoff frequency is further changed by changing the sizes of the R7 and the C1. In order to avoid damaging the digital/analog input interface due to excessive voltage, a 3V zener diode D1 is arranged at the interface.
The current detection circuit samples the current through the current transformer, and the sampled detection current flows into the current detection circuit shown in the figure. After the sampling current is filtered through a capacitor C6, the current input is changed into a voltage signal through sampling resistors R14 and R15, in order to prevent harmonic interference, the circuit comprises an operational amplifier TL028, capacitors C1 and C5 and resistors R7 and R17 together to form a second-order low-pass filter circuit, the voltage with the amplitude of +/-3V is obtained, the voltage can be identified by the A/D of the DSP, and two inverters are formed by the operational amplifiers TL0821 and TL0822, the resistors R1, R2, R3, R5 and R16 and the sliding rheostat R to obtain the voltage of 0-3V. Also, a zener diode D1 is designed at the interface for circuit safety.
As shown in fig. 9, the voltage-current protection circuit in this embodiment obtains ac voltage by feedback, and forms a diode uncontrollable rectifying circuit by four diodes D1, D2, D3, and D4 to become dc. Then the voltage drop is generated on the slide varistors R1 and R2 through the filtering of the capacitor C, and the voltage drop is transmitted to the operational amplifier TL082, and the reference voltage of the same-direction input end is 15V at the moment and the reference voltage of the opposite end is 3V. When the output voltage is too high, the voltage of the non-inverting input end of the comparator becomes small, when the voltage is smaller than the reference voltage of the inverting input end by 3V, the comparator will transmit low level, at the moment, the light emitting diode connected in series with R5 is used as a fault display lamp to be lightened, and then an interrupt signal is transmitted to the I/O port of the DSP through the operational amplifier TL 0821. The principle of the over-current protection is basically the same as that of the over-voltage protection, and will not be described in detail herein.
The undervoltage protection circuit in this embodiment is implemented by using an operational amplifier circuit, as shown in fig. 10, the input terminal voltage is 15V, the undervoltage protection circuit is connected to the zener diode D1 and then is fed to the 1 terminal of the comparator Ua, and the voltage drop of the forward input terminal starts to decrease when the undervoltage fault occurs, and the comparator outputs a low level when the undervoltage fault is lower than the reference voltage 3V of the reverse input terminal 2, the light emitting diode connected in series with the capacitor C2 is turned on, and the generated fault signal is transmitted to the DSP through the operational amplifier Ub and is processed accordingly.
In this embodiment, as shown in fig. 11, the reset signal is sent to the DSP by the low level signal, and is completed by the DSP interrupt subroutine. In the reset circuit, the resistors R4 and R7 charge the capacitor C2, and when the capacitor is charged to a certain value, the voltage at the 5 terminal is ensured to be always higher than the voltage at the 4 terminal, and the comparator U1 outputs a high level. When restart is pressed, the SR terminal is low, the capacitor C2 is discharged through the resistor R7 again, the voltage of the 5 terminal is reduced, and when the voltage is lower than the voltage of the 4 terminal, the comparator U1 outputs low level to be transmitted to the DSP.
In this embodiment, as shown in fig. 12, the synchronous signal conversion circuit is capable of tracking the frequency, and it is necessary to convert the current signal into a voltage signal having the same frequency in order to perform frequency tracking. In the figure, a current signal is converted into a voltage signal through sampling resistors R1 and R2, and the voltage signal is converted into square wave signals with the same frequency through a zener diode D1, capacitors C3, C4, C5, C6 and C7, and the resistors R3 and R4, and the square wave signals are transmitted to the AMC1200 for optocoupler isolation, so that an analog signal and a digital signal are isolated. And finally, filtering the signals generated by isolation through a first-order low-pass filter circuit formed by an operational amplifier, a capacitor C11 and a resistor R8, and sending the filtered signals to an eCAP module of the DSP for calculation.
In this embodiment, as shown in fig. 13, the schematic diagram of the steam generating part is that the medium frequency alternating current generated by the above part is sent to the high pressure boiler surrounded by the coil, and it is known from the law of electromagnetic induction that the high speed changing electric field generates a high speed changing magnetic field, so that eddy current is generated on the metal surface, the boiler is heated up rapidly, the air pressure in the boiler is higher than the standard air pressure, when the water in the boiler exceeds 100 ℃, vaporization starts to generate steam, and as long as the water inlet is opened and closed, and the flow rate of the water entering the high pressure boiler is controlled, whether steam is generated or not, and the flow rate of the generated steam can be controlled.

Claims (1)

1. A control device for a steam generator based on electromagnetic induction heating technology, comprising: the device comprises a rectifying part, a filtering part, a direct-current voltage stabilizing part, an inversion part, a steam generating part, a driving part, a control part and a system power circuit;
the rectification part inputs three-phase alternating current and inputs the three-phase alternating current into the rectification part for rectification; after the rectification circuit works stably, the rectification circuit is short-circuited, and the output direct current is filtered by the filtering part; after filtering, the direct-current voltage stabilizing part, namely a chopper circuit, is connected to carry out chopper conversion of DC-DC; after being chopped, the chopper is connected with the inversion part to perform DC-AC conversion to generate intermediate frequency alternating current; connecting the medium-frequency alternating current generated by the inversion part to a surface coil wound on the steam generation part, namely the steam generator;
the control section includes (1) controlling a chopper circuit; (2) controlling the inversion portion; the control part controls the drive circuit to control the on-off of the IGBT in the inversion part on one hand and controls the over-current, over-voltage and under-voltage protection of the IGBT on the other hand; the rectifying part adopts a three-phase bridge type uncontrollable rectifying circuit;
the rectification part adopts a three-phase bridge type uncontrollable rectification circuit, and comprises 6 power diodes, namely VD1, VD2, VD3, VD4, VD5 and VD6; the common cathode of the VD1, the VD3 and the VD5 is connected, the common anode of the VD4, the common anode of the VD6 and the common anode of the VD2 are connected, the anode of the VD1 is connected with the cathode of the VD4, the anode of the VD3 is connected with the cathode of the VD6, and the anode of the VD5 is connected with the cathode of the VD 2;
when alternating current side line voltage U A ＞U B At the time, diodes VD1 and VD6 are conducted, and the DC side voltage is U AB The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U A ＞U C At the time, diodes VD1 and VD2 are conducted, and the voltage at the DC side is U AC The method comprises the steps of carrying out a first treatment on the surface of the When alternating current side line voltage U B ＞U C At the time, diodes VD3 and VD2 are conducted, and the voltage at the DC side is U BC The method comprises the steps of carrying out a first treatment on the surface of the The output direct current voltage is the maximum value of the alternating current side line voltage;
the filtering part is characterized in that a direct-current voltage output end of a three-phase bridge type uncontrollable rectifying circuit is connected with two filtering capacitors C1 and C2, and the two resistors R2 and R3 are respectively connected in parallel on the filtering capacitors C1 and C2 to play a role in equalizing voltage, so that voltages applied to two ends of the capacitors C1 and C2 are the same; in addition, the direct-current voltage output end of the three-phase bridge type uncontrollable rectifying circuit is connected with two divider resistors R4 and R5 for detecting direct-current side voltage;
the control part comprises a chopping control circuit, a control circuit of the inversion part, an IGBT driving circuit, a voltage detection circuit, a current detection circuit, a voltage and current protection circuit, a reset circuit and an output signal detection circuit;
the output of the chopper control circuit is used as the input of a direct current chopper circuit to control the on and off of an IGBT in the chopper circuit;
the control circuit output of the inversion part is divided into two aspects: on one hand, the output is used as the input of the IGBT driving circuit, the inverter circuit is controlled to complete the inversion process, and the voltage and current protection circuit is controlled to protect the IGBT; on the other hand, the voltage detection circuit and the current detection circuit are controlled to detect the voltage and the current output by the inverter;
the IGBT driving circuit comprises two parts: one part is the IGBT drive of the chopper circuit, the other part is the IGBT drive of the inverter circuit, the IGBT drive of the chopper circuit is controlled by the SG3525 chip, and the IGBT drive of the inverter circuit is controlled by the DSP;
the IGBT driving circuit, the voltage detection circuit, the current detection circuit, the voltage and current protection circuit, the reset circuit and the output signal detection circuit of the inverter circuit are controlled by a DSP and are connected with the output of the DSP;
the direct-current voltage stabilizing part adopts a Sepic chopper circuit to regulate the output power of the direct-current side by regulating the voltage amplitude of the direct-current side of the input inversion part; the voltage amplitude of the direct current side of the regulating input inversion part is regulated by regulating the duty ratio alpha of the chopper circuit, and the calculation formula of alpha is as follows:
Figure QLYQS_1
Figure QLYQS_2
wherein E is a rectified output voltage; u (U) 0 Outputting a voltage for the chopper circuit; t is t on And t off The switching-on time and the switching-off time of the IGBT are respectively;
the inversion part adopts a single-phase bridge current type inversion circuit, an electromagnetic induction coil for heating and a series compensation capacitor C are connected in series to form a load of the single-phase bridge current type inversion circuit, and in order to ensure the stability of steam generation, the resonance frequency of a control system fluctuates in a set passband;
the pin 8 of the SG3525 chip is a soft start access end and is also an inverted input end of the PWM comparator; when the voltage at two ends of the capacitor cannot be suddenly changed, the reverse input end of the PWM comparator is also low level when the pin 8 is low level, the PWM comparator outputs high level, the PWM latch outputs high level, and the high level is applied to the output transistor through two NAND gates, so that the output transistor cannot be conducted; when the soft start capacitor is charged to enable the pin 8 of the SG3525 chip to be at a high level, the SG3525 is only operated;
the voltage is sent to a 1 pin of SG3525, the 1 pin is the reverse input end of the error amplifier, and a feedback signal is connected to the pin to form closed-loop control; PWM waves generated by SG3525 drive IGBT in a chopper circuit after passing through an isolation driving circuit; the reference voltage is connected to the same-direction input end of the error amplifier, namely the 2 pins, and the sampling voltage of the output voltage is added to the reverse input end of the error amplifier; when the output voltage is increased, the output of the error amplifier is reduced, so that the high-level time of PWM output is prolonged, the conduction time of the IGBT tube is shortened, and the steady state is realized;
the input voltage of the system power supply is alternating current voltage, a fuse F is connected to the positive electrode of the input end, a switch S1 is connected to the negative electrode of the input end, and when faults such as short circuit and the like occur in the input phase voltage, the input end can be disconnected in time, so that damage to a rear-end circuit device is prevented; adopting Jin Shengyang LH10-10A05 AC-DC conversion power supply, connecting capacitors C7, C9, C13 and C15 for isolation with a back-end circuit, connecting resistors R3 and R4 in parallel at two ends of the filter capacitor and C2 and C5 simultaneously through filter capacitors C2 and C5 to perform the function of equalizing voltage of the filter capacitor, and finally obtaining the voltage value required by the system through inductors L1 and L2 and clamping diodes D1 and D2;
the sampling circuit of the voltage detection circuit uses a Hall voltage sensor CHV-25P/500V, and the sensor electrically isolates an analog signal at an input end from a digital signal at an output end and outputs an output voltage of-5V to +5V; because the DSP can only detect voltage signals, the input signals are changed into voltages of-2.5 to +2.5V through a sampling circuit formed by resistors R1 and R2; the voltage allowed by the analog/digital conversion of the DSP is 0-3V, so in order to convert the voltage of-2.5-2.5V to 0-3V, the operational amplifier U1, R3, R4, R5 and R6 together form a voltage bias circuit;
since some harmonic interference is contained in the circuit, filtering processing is needed to prevent noise generated by harmonic waves from affecting the A/D sampling result; the operational amplifier U2, the capacitors C1 and C2 which are correspondingly configured and the resistor R7 form a first-order active filter together, the front-end input voltage is isolated from the sampling voltage by adopting a voltage tracking mode, and the cutoff frequency is changed by changing the sizes of the R7 and the C1; in order to avoid damaging the digital/analog input interface due to overhigh voltage, a 3V zener diode D1 is arranged at the interface;
the current detection circuit samples current through a current transformer, and sends the detected current obtained by sampling to the current detection circuit; after the sampling current is filtered through a capacitor C6, the current is input into a voltage signal through sampling resistors R14 and R15, in order to prevent harmonic interference, the circuit comprises an operational amplifier TL028, capacitors C1 and C5 and resistors R7 and R17 together to form a second-order low-pass filter circuit, so that a voltage with the amplitude of +/-3V is obtained, and the voltage can be identified by the A/D of a DSP, and two inverters are formed by the operational amplifiers TL0821 and TL0822, the resistors R1, R2, R3, R5 and R16 and a sliding rheostat R to obtain the voltage of 0-3V; also, for circuit safety, a zener diode D1 is designed at the interface;
the voltage and current protection circuit obtains alternating voltage through feedback, and a diode uncontrollable rectifying circuit is formed by four diodes D1, D2, D3 and D4 to be changed into direct current; then the voltage drop is generated on the slide varistors R1 and R2 through the filtering of the capacitor C, and the voltage drop is transmitted to the operational amplifier TL082, at the moment, the reference voltage of the same-direction input end is 15V, and the reverse end is 3V; when the output voltage is too high, the voltage of the non-inverting input end of the comparator becomes small, when the voltage is smaller than the reference voltage of the inverting input end by 3V, the comparator can transmit low level, at the moment, the light-emitting diode connected in series with R5 is used as a fault display lamp to be lightened, and then an interrupt signal is transmitted to an I/O port of the DSP through the operational amplifier TL 0821;
the reset signal of the reset circuit is completed by transmitting a low-level signal to the DSP and an interrupt subroutine of the DSP; in the reset circuit, resistors R4 and R7 charge a capacitor C2, when the capacitor is charged to a certain value, the voltage of the 5 terminal is ensured to be always higher than the voltage of the 4 terminal, and a comparator U1 outputs high level; when restart is pressed, the SR terminal is low level, the capacitor C2 is discharged through the resistor R7, the voltage of the 5 terminal is reduced, and when the voltage is lower than the voltage of the 4 terminal, the comparator U1 outputs low level and transmits the low level to the DSP;
the steam generating part is characterized in that the medium-frequency alternating current generated by the part is sent to a high-pressure boiler surrounded by a coil, a high-speed changing magnetic field is generated by an electric field which changes at high speed according to the law of electromagnetic induction, vortex is generated on the surface of metal, the boiler is heated up rapidly, the air pressure in the boiler is higher than standard air pressure, when the temperature of water in the boiler exceeds 100 ℃, vaporization is started to generate steam, and the water inlet is opened and the flow rate of water entering the high-pressure boiler is controlled, so that whether steam is generated and the flow rate of the generated steam can be controlled.
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