CN212163754U

CN212163754U - Working circuit of transformer oil auxiliary heating device

Info

Publication number: CN212163754U
Application number: CN202020580040.9U
Authority: CN
Inventors: 张耘溢; 刘岩亮; 刘焱; 张海利; 王涛; 张华清; 张佳伟; 曾翔君; 骆一萍; 刘寅迪
Original assignee: State Grid Ningxia Electric Power Co Ltd
Current assignee: State Grid Ningxia Electric Power Co Ltd
Priority date: 2020-04-17
Filing date: 2020-04-17
Publication date: 2020-12-15
Anticipated expiration: 2030-04-17

Abstract

The utility model discloses a transformer oil auxiliary heating device's operating circuit, transformer oil auxiliary heating device includes: heating oil pipe, the working circuit includes: the device comprises a DSP controller, a power heating circuit, a voltage measuring circuit, a current measuring circuit and an analog-to-digital converter; the power heating circuit includes: single-phase full-bridge inverter, resonant capacitor and solenoid, voltage measurement circuit includes: the current measuring circuit comprises a voltage sensor, a first resistor, a first inverter, a first phase inverter, a first rectifier filter and a first differential amplifier, and comprises: the current sensor, second resistance, second inverter, second homophase ware, second rectifier filter and second differential amplifier. The utility model discloses the circuit is simple, safe and reliable, can real-time measurement power heating circuit's voltage and electric current to and, measure the transformer oil's of many places temperature.

Description

Working circuit of transformer oil auxiliary heating device

Technical Field

The utility model relates to a transformer oil auxiliary heating device technical field especially relates to a transformer oil auxiliary heating device's working circuit.

Background

When an alternating current or converter transformer in a power system is newly installed or overhauled, insulating oil needs to be filtered, oil products are heated to promote evaporation of moisture in the oil and separation of gas, moisture and impurities in the oil are removed, electric strength of the oil is improved, and paper insulation in the oil is protected.

The transformer oil auxiliary heating device based on electromagnetic induction has the advantages of high heating efficiency, high heating rate, uniform heating effect and accurate temperature control. The working circuit is used as a core part of the auxiliary heating device and mainly used for safely and reliably converting electric energy from a power grid into heat energy to achieve the function of energy conversion.

In order to master the working condition of the transformer oil auxiliary heating device in real time, the current and the voltage of the power heating circuit need to be measured. The error of measuring the current and the voltage of the power heating circuit in the prior art is large.

SUMMERY OF THE UTILITY MODEL

The embodiment of the utility model provides a transformer oil auxiliary heating device's working circuit to solve the great problem of error of prior art measured power heating circuit's electric current and voltage.

The embodiment of the utility model provides a concrete scheme as follows:

an operating circuit of a transformer oil auxiliary heating apparatus, the transformer oil auxiliary heating apparatus comprising: heating oil pipe, the working circuit includes: the device comprises a DSP controller, a power heating circuit, a voltage measuring circuit, a current measuring circuit and an analog-to-digital converter; the power heating circuit includes: the electromagnetic coil is wound on the surface of the heating oil pipe, the resonant capacitor and the electromagnetic coil are connected in series to form an equivalent load, the input end of the single-phase full-bridge inverter is electrically connected with the output end of the DSP controller, and the output end of the single-phase full-bridge inverter is connected to two ends of the equivalent load in parallel; the voltage measurement circuit includes: the input end of the voltage sensor is connected with two ends of the resonance capacitor in parallel, the output end of the voltage sensor is electrically connected with one end of the first resistor, the other end of the first resistor is grounded, the input ends of the first inverter and the first phase inverter are connected with two ends of the first resistor in parallel, the output ends of the first inverter and the first phase inverter are electrically connected with the input end of the first rectification filter, the output end of the first rectification filter is electrically connected with the input end of the first differential amplifier, and the output end of the first differential amplifier is electrically connected with the input end of the analog-to-digital converter; the current measurement circuit includes: the input end of the current sensor is connected with two ends of the electromagnetic coil in parallel, the output end of the current sensor is electrically connected with one end of the second resistor, the other end of the second resistor is grounded, the input ends of the second inverter and the second phase inverter are connected with two ends of the second resistor in parallel, the output ends of the second inverter and the second phase inverter are electrically connected with the input end of the second rectifier filter, the output end of the second rectifier filter is electrically connected with the input end of the second differential amplifier, and the output end of the second differential amplifier is electrically connected with the input end of the analog-to-digital converter; and the output end of the analog-to-digital converter is electrically connected with the input end of the DSP controller.

Further, the working circuit of the transformer oil auxiliary heating device further comprises: an isolation drive circuit, the isolation drive circuit comprising: the output end of the DSP controller is electrically connected with the four input ends of the single-phase full-bridge inverter through the four first optocouplers respectively.

Further, the working circuit of the transformer oil auxiliary heating device further comprises: a temperature measurement circuit, the temperature measurement circuit comprising: the system comprises a plurality of thermocouples, a plurality of temperature converters, a second optical coupler, three third optical couplers, a fourth optical coupler, a decoder and a data selector; the thermocouples are arranged at the points to be measured of the heating oil pipe, the output end of each thermocouple is electrically connected with the input end of each temperature converter, the output end of each temperature converter is respectively electrically connected with the input end of the data selector, the input end of the second optocoupler is electrically connected with the output end of the data selector, the output end of the second optocoupler is electrically connected with the input end of the DSP controller, the input end of each third optocoupler is electrically connected with the output end of the DSP controller, the output end of each third optocoupler is electrically connected with the input end of the decoder and the input end of the data selector, the input end of the fourth optical coupler is electrically connected with the output end of the DSP controller, the output end of the fourth optical coupler is electrically connected with the input end of each temperature converter, and the output end of the decoder is electrically connected with the input end of each temperature converter.

Further, the working circuit of the transformer oil auxiliary heating device further comprises: a maximum power tracking circuit, the maximum power tracking circuit comprising: a fifth optical coupler, a voltage comparator, an analog multiplier and a filter; the input end of the fifth optical coupler is electrically connected with the output end of the DSP controller, the output end of the fifth optical coupler is electrically connected with the input end of the voltage comparator, the output end of the voltage comparator and the output end of the second in-phase device are electrically connected with the input end of the analog multiplier, the output end of the analog multiplier is electrically connected with the input end of the filter, and the output end of the filter is electrically connected with the input end of the analog-to-digital converter.

Further, the working circuit of the transformer oil auxiliary heating device further comprises: a communication circuit, the communication circuit comprising: the input end and the output end of the optical fiber transceiver are electrically connected with the DSP controller, and the input end and the output end of the optical fiber transceiver are connected with the industrial personal computer through optical fiber communication.

The working circuit of the transformer oil auxiliary heating device provided by the embodiment of the utility model has the advantages of simple circuit, safety and reliability, and can measure the voltage and current of the power heating circuit in real time and the temperature of the transformer oil at multiple positions; according to the working characteristics of the heating device, the working circuit is divided into a weak current control circuit and a strong current power circuit, so that the weak current control part and the strong current power part are effectively and electrically isolated, and the reliability of the auxiliary heating device can be effectively improved; the resonance point of the auxiliary heating device is automatically tracked by adopting the maximum power tracking circuit, so that the auxiliary heating device always works near the resonance point in the heating process, the output power reaches the maximum, the energy conversion efficiency is high, and the heating efficiency can be obviously improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments of the present invention will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive labor.

Fig. 1 is a schematic diagram of an operating circuit of a transformer oil auxiliary heating device according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a DSP controller of an operating circuit of a transformer oil auxiliary heating apparatus according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a power heating circuit of an operating circuit of the transformer oil auxiliary heating apparatus according to the embodiment of the present invention;

fig. 4 is a schematic diagram of a voltage measuring circuit of an operating circuit of the transformer oil auxiliary heating apparatus according to the embodiment of the present invention;

fig. 5 is a schematic diagram of a current measuring circuit of an operating circuit of the transformer oil auxiliary heating apparatus according to the embodiment of the present invention;

fig. 6 is a schematic diagram of an analog-to-digital converter of an operating circuit of a transformer oil auxiliary heating apparatus according to an embodiment of the present invention;

fig. 7 is a schematic diagram of an isolation driving circuit of an operating circuit of a transformer oil auxiliary heating device according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a temperature measuring circuit of an operating circuit of the transformer oil auxiliary heating apparatus according to the embodiment of the present invention;

fig. 9 is a schematic diagram of a maximum power tracking circuit of an operating circuit of a transformer oil auxiliary heating apparatus according to an embodiment of the present invention;

fig. 10 is a schematic diagram of a communication circuit of an operating circuit of a transformer oil auxiliary heating device according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The embodiment of the utility model discloses transformer oil auxiliary heating device's working circuit. The transformer oil auxiliary heating device is based on electromagnetic induction. The transformer oil auxiliary heating device includes: the oil pipe is heated. As shown in fig. 1, the operating circuit includes: the device comprises a DSP controller 1, a power heating circuit 2, a voltage measuring circuit 3, a current measuring circuit 4 and an analog-to-digital converter 5.

Specifically, as shown in fig. 2, the DSP controller 1 may set four PWM wave output pins to output the control signals PWM1, PWM2, PWM3 and PWM4 of the four-way power heating circuit 2.

Specifically, as shown in fig. 3, the power heating circuit 2 includes: a single-phase full-bridge inverter 201, a resonant capacitor 202, and an electromagnetic coil 203. The electromagnetic coil 203 is wound on the surface of the heating oil pipe. The resonant capacitor 202 and the electromagnetic coil 203 are connected in series to form an equivalent load. The input end of the single-phase full-bridge inverter 201 is electrically connected with the output end of the DSP controller 1. The output end of the single-phase full-bridge inverter 201 is connected in parallel with two ends of the equivalent load.

Based on the above circuit design, the DSP controller 1 outputs the control signals PWM1, PWM2, PWM3 and PWM4 of the four-way power heating circuit 2 to the four power switching devices Q1, Q2, Q3 and Q4 of the single-phase full-bridge inverter 201, respectively, and controls the four power switching devices Q1, Q2, Q3 and Q4 to be turned on and off, respectively, so as to invert the direct current into a high-frequency alternating-current square-wave voltage and apply the high-frequency alternating-current square-wave voltage to both ends of the equivalent load.

As shown in fig. 4, the voltage measurement circuit 3 includes: a voltage sensor 301, a first resistor R1, a first inverter 302, a first inverter 303, a first rectifier filter 304, and a first differential amplifier 305. The input terminal of the voltage sensor 301 is connected in parallel across the resonant capacitor 202. The output terminal of the voltage sensor 301 is electrically connected to one terminal of the first resistor R1, and the other terminal of the first resistor R1 is grounded. The input terminals of the first inverter 302 and the first inverter 303 are connected in parallel to both ends of the first resistor R1. The output terminals of the first inverter 302 and the first inverter 303 are electrically connected to the input terminal of the first rectifying filter 304. The output of the first rectifier filter 304 is electrically connected to the input of the first differential amplifier 305. The output of the first differential amplifier 305 is electrically connected to the input of the analog-to-digital converter 5.

By the design of the voltage measuring circuit 3, the voltage + u across the resonant capacitor 202_cAnd-u_cA voltage signal u across the first resistor R1 input to the input terminal of the voltage sensor 301_cI.e. the output signal of the voltage sensor 301. Voltage signal u_cAfter passing through a first phase inverter 303, a voltage signal u is obtained_cF + voltage signal u_cAfter passing through the first inverter 302, a voltage signal u is obtained_cF-, apply the voltage signal u_cF + and voltage signal u_cF-is connected into the first rectifying filter 304, and the output signal of the first rectifying filter 304 is amplified by the first differential amplifier 305 to obtain a stable DC voltage analog signal u_c_Analog。

As shown in fig. 5, the current measurement circuit 4 includes: a current sensor 401, a second resistor R2, a second inverter 402, a second inverter 403, a second rectifier filter 404, and a second differential amplifier 405. The input terminal of the current sensor 401 is connected in parallel to both ends of the electromagnetic coil 203. The output terminal of the current sensor 401 is electrically connected to one terminal of the second resistor R2, and the other terminal of the second resistor R2 is grounded. The input terminals of the second inverter 402 and the second inverter 403 are connected in parallel to both ends of the second resistor R2. The output terminals of the second inverter 402 and the second inverter 403 are electrically connected to the input terminal of the second rectifier filter 404. The output of the second rectifier filter 404 is electrically connected to the input of a second differential amplifier 405. The output of the second differential amplifier 405 is electrically connected to the input of the analog-to-digital converter 5.

Through the design of the current measuring circuit 4, the currents + i and-i at the two ends of the electromagnetic coil 203 are input to the input end of the current sensor 401, and the current signal i at the two ends of the second resistor R2 is the output signal of the current sensor 401. The current signal i passes through the second phase inverter 403 to obtain a current signal i _ F +, the current signal i passes through the second inverter 402 to obtain a current signal i _ F-, the i _ F + and the i _ F-are connected to the second rectifying filter 404, and the output signal of the second rectifying filter 404 is amplified by the second differential amplifier 405 to obtain a stable direct current Analog quantity signal i _ Analog.

As shown in fig. 6, the output terminal of the analog-to-digital converter 5 is electrically connected to the input terminal of the DSP controller 1. Specifically, the DSP controller 1 may set a Digital voltage signal uc _ Digital input pin and a Digital current signal i _ Digital input pin.

By providing the Analog-to-Digital converter 5, the Analog signals i _ Analog and uc _ Analog received from the current measuring circuit 4 and the dc voltage Analog signal uc _ Analog of the voltage measuring circuit 3 are converted into Digital signals uc _ Digital and i _ Digital, and the Digital signals uc _ Digital and i _ Digital are transmitted to the DSP controller 1, so that the DSP controller 1 processes the Digital signals.

Through the circuit design, modules such as a phase inverter, a rectifier filter, a differential amplifier and the like are introduced, the input impedance of the phase inverter and the phase inverter is extremely large, the output impedance is extremely small, the influence of a voltage sensor and a current sensor on other working circuits can be greatly reduced, and the interference from a measuring point can be greatly weakened. The differential amplifier can compensate the measurement error to a certain extent, and the measurement accuracy is greatly improved. The rectifier filter can quickly and reliably convert the alternating current signal into the direct current signal, and the time of analog-digital conversion can be greatly shortened by aiming at the operation of the direct current quantity.

Preferably, as shown in fig. 7, the operating circuit of the transformer oil auxiliary heating apparatus further includes: the drive circuit 6 is isolated. The isolation drive circuit 6 includes: four first optocouplers 601. The output end of the DSP controller 1 is electrically connected to the four input ends of the single-phase full-bridge inverter 201 through four first optocouplers 601. Specifically, the DSP controller 1 outputs four control signals PWM1, PWM2, PWM3, and PWM4 to the four first optocouplers 601, respectively. The four first optocouplers 601 respectively isolate the four control signals to obtain isolated four control signals PWM1_ F, PWM2_ F, PWM3_ F and PWM4_ F. Four control signals PWM1_ F, PWM2_ F, PWM3_ F and PWM4_ F are respectively input to four power switching devices Q1, Q2, Q3 and Q4 of the single-phase full-bridge inverter 201, and control on and off of the power switching devices Q1, Q2, Q3 and Q4.

By arranging the isolation driving circuit 6, the purpose of electrically isolating the weak current part of the DSP controller 1 from the strong current part of the power heating circuit 2 is achieved, and the functions of protecting the DSP controller 1 and weakening electromagnetic interference are achieved.

Preferably, as shown in fig. 8, the operating circuit of the transformer oil auxiliary heating apparatus further includes: a temperature measuring circuit 7. The temperature measurement circuit 7 includes: a plurality of thermocouples 701, a plurality of temperature converters 702, a second optocoupler 703, three third optocouplers 704, a fourth optocoupler 705, a decoder 706, and a data selector 707.

The thermocouples 701 are arranged at the points to be measured of the heating oil pipe, and are used for measuring the temperature of the transformer oil at the points to be measured. The output of each thermocouple 701 is electrically connected to the input of each temperature transducer 702. The output terminal of each temperature converter 702 is electrically connected to the input terminal of the data selector 707. An input end of the second optocoupler 703 is electrically connected to an output end of the data selector 707. The output end of the second optocoupler 703 is electrically connected with the input end of the DSP controller 1. Specifically, the DSP controller 1 may set a Temperature input pin to be electrically connected to an output terminal of the second optocoupler 703. The input end of each third optical coupler 704 is electrically connected with the output end of the DSP controller 1. Specifically, the DSP controller 1 may SET output pins of the three chip select signals SET1, SET2, and SET3 to be electrically connected to an input terminal of each third optocoupler 704, respectively. An output terminal of each third optocoupler 704 is electrically connected to an input terminal of the decoder 706 and an input terminal of the data selector 707. An input end of the fourth optical coupler 705 is electrically connected with an output end of the DSP controller 1. Specifically, the DSP controller 1 may set an output pin of the clock signal SPICLKA to be electrically connected to an input end of the fourth optical coupler 705. The output end of the fourth optical coupler 705 is electrically connected with the input end of each temperature converter 702 respectively. The output of the decoder 706 is electrically connected to the input of each temperature converter 702.

The DSP controller 1 outputs three chip selection signals SET1, SET2 and SET3 and a clock signal SPICLKA. After the chip select signals SET1, SET2 and SET3 pass through the third optical coupler 704, signals SET1_ F, SET2_ F and SET3_ F are output. The output signals SET1_ F, SET2_ F and SET3_ F access the decoder 706 and the data selector 707. The clock signal spikalda passes through the fourth optocoupler 705 and then outputs a signal spikalda _ F. The output signal SPICLKA _ F is input to each of the temperature converters 702 to collectively provide a clock signal to the plurality of temperature converters 702, so that the temperature converters 702 can normally operate under the excitation of the clock signal. For example, when there are eight Temperature sensors 702, if SET1_ F is 0, SET2_ F is 0, and SET3_ F is 0, the decoder 706 outputs a valid signal MAX6675_1 (or, one of the output signals MAX6675_2 to MAX6675_8 is valid according to a combination of three chip selection signals), the first chip Temperature converter 702 is enabled, and at this time, the data selector 707 outputs a valid signal T _ OUT which is T1_ OUT (or, depending on the enabled Temperature sensor 702, the data selector 707 outputs a valid signal T _ OUT which is one of T2_ OUT to T8_ OUT), the signal T _ OUT is connected to the second optical coupler 703, and a signal Temperature is output through the second optical coupler 703 and is input to the DSP controller 1, so that the Temperature measurement circuit 7 transmits the first Temperature measurement value to the DSP controller 1. Similarly, according to different states of high and low levels of the 3-way chip select signals SET1, SET2, and SET3, temperature measurement values of other ways may be transmitted to the DSP controller 1.

Through the design of the temperature measuring circuit 7, the temperature of the transformer oil at a plurality of points to be measured can be measured in real time only by occupying five hardware pins of the DSP controller 1. The temperature measuring speed can be adjusted by changing the SET1, the SET2 and the SET3 and the SPICLKA signal frequency, and the temperature measuring device has great programmability. And interference can be greatly weakened by a circuit design with multiple isolated positions.

Preferably, as shown in fig. 9, the operating circuit of the transformer oil auxiliary heating apparatus further includes: a maximum power tracking circuit 8. The maximum power tracking circuit 8 includes: a fifth optical coupler 801, a voltage comparator 802, an analog multiplier 803, and a filter 804. The input end of the fifth optical coupler 801 is electrically connected with the output end of the DSP controller 1. Specifically, the DSP controller 1 may set a PWM wave output pin to output the control signal PWM5 to the input terminal of the fifth optocoupler 801. An output end of the fifth optical coupler 801 is electrically connected with an input end of the voltage comparator 802. The output terminal of the voltage comparator 802 and the output terminal of the second inverter 403 are both electrically connected to the input terminal of the analog multiplier 803. The output of the analog multiplier 803 is electrically connected to the input of the filter 804. The output of the filter 804 is electrically connected to the input of the analog-to-digital converter 5.

The DSP controller 1 generates a PWM5 signal having the same frequency and phase as the voltage at the output of the single-phase full-bridge inverter 201. It should be understood that the DSP controller 1 can only output two states, a high level and a zero level. The PWM5 signal is electrically isolated by the fifth optocoupler 801 and then connected to the voltage comparator 802 to output a signal PWM5_ F with high level and negative level as a reference signal of the analog multiplier 803. At this time, the frequency and phase of the PWM5_ F are both the same as the output voltage of the single-phase full-bridge inverter 201, and are square wave voltages with alternating positive and negative. The current signal i _ F + output by the second inverter 403 is used as an input signal of the analog multiplier 803. When the PWM5_ F is positive in amplitude, the output signal of the analog multiplier 803 is in phase with i _ F +; when the PWM5_ F is negative in magnitude, the output signal of the analog multiplier 803 is in opposite phase to i _ F +. The output signal passes through the filter 804 to obtain a stable dc power Analog signal power _ Analog. The direct current power Analog signal power _ Analog is converted into a Digital signal power _ Digital by the Analog-to-Digital converter 5 and is transmitted to the DSP controller 1. When the transformer oil auxiliary heating device works in a resonance state, the output signal of the Analog multiplier 803 is an steamed bread wave, and the direct current power Analog quantity signal power _ Analog reaches a maximum value; when the working frequency of the transformer oil auxiliary heating device is smaller than the load natural resonant frequency, the direct current power _ Analog signal is increased along with the increase of the working frequency of the transformer oil auxiliary heating device; when the working frequency of the transformer oil auxiliary heating device is greater than the load natural resonant frequency, the direct current power Analog signal power _ Analog is reduced along with the increase of the working frequency of the transformer oil auxiliary heating device, and therefore the purpose of tracking the maximum power is achieved.

Preferably, as shown in fig. 10, the operating circuit of the transformer oil auxiliary heating apparatus further includes: a communication circuit 9. The communication circuit 9 includes: a fiber optic transceiver 901 and an industrial personal computer 902. The input end and the output end of the optical fiber transceiver 901 are electrically connected with the DSP controller 1. Specifically, the DSP controller 1 may provide a signal transmitting pin SCI _ TXD and a signal receiving pin SCI _ RXD. The input end and the output end of the optical fiber transceiver 901 are both connected with the industrial personal computer 902 through optical fiber communication.

In the operation process of the transformer oil auxiliary heating device, the DSP controller 1 is interrupted by a timer, the operation parameters of the transformer oil auxiliary heating device are continuously transmitted to the industrial personal computer 902 through the optical fiber transceiver 901 to be displayed, and the instruction from the industrial personal computer 902 is received through the optical fiber transceiver 901. The DSP controller 1 and the industrial personal computer 902 adopt an RS-232 communication protocol.

The entire heating process can be automatically controlled and supervised by the communication circuit 9.

To sum up, the working circuit of the transformer oil auxiliary heating device provided by the embodiment of the utility model has the advantages of simple circuit, safety and reliability, and can measure the voltage and current of the power heating circuit in real time and the temperature of the transformer oil at multiple positions; according to the working characteristics of the heating device, the working circuit is divided into a weak current control circuit and a strong current power circuit, so that the weak current control part and the strong current power part are effectively and electrically isolated, and the reliability of the auxiliary heating device can be effectively improved; the resonance point of the auxiliary heating device is automatically tracked by adopting the maximum power tracking circuit, so that the auxiliary heating device always works near the resonance point in the heating process, the output power reaches the maximum, the energy conversion efficiency is high, and the heating efficiency can be obviously improved.

The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. An operating circuit of a transformer oil auxiliary heating apparatus, the transformer oil auxiliary heating apparatus comprising: heating oil pipe, its characterized in that, the working circuit includes: the device comprises a DSP controller, a power heating circuit, a voltage measuring circuit, a current measuring circuit and an analog-to-digital converter;

the power heating circuit includes: the electromagnetic coil is wound on the surface of the heating oil pipe, the resonant capacitor and the electromagnetic coil are connected in series to form an equivalent load, the input end of the single-phase full-bridge inverter is electrically connected with the output end of the DSP controller, and the output end of the single-phase full-bridge inverter is connected to two ends of the equivalent load in parallel;

the voltage measurement circuit includes: the input end of the voltage sensor is connected with two ends of the resonance capacitor in parallel, the output end of the voltage sensor is electrically connected with one end of the first resistor, the other end of the first resistor is grounded, the input ends of the first inverter and the first phase inverter are connected with two ends of the first resistor in parallel, the output ends of the first inverter and the first phase inverter are electrically connected with the input end of the first rectification filter, the output end of the first rectification filter is electrically connected with the input end of the first differential amplifier, and the output end of the first differential amplifier is electrically connected with the input end of the analog-to-digital converter;

the current measurement circuit includes: the input end of the current sensor is connected with two ends of the electromagnetic coil in parallel, the output end of the current sensor is electrically connected with one end of the second resistor, the other end of the second resistor is grounded, the input ends of the second inverter and the second phase inverter are connected with two ends of the second resistor in parallel, the output ends of the second inverter and the second phase inverter are electrically connected with the input end of the second rectifier filter, the output end of the second rectifier filter is electrically connected with the input end of the second differential amplifier, and the output end of the second differential amplifier is electrically connected with the input end of the analog-to-digital converter;

and the output end of the analog-to-digital converter is electrically connected with the input end of the DSP controller.

2. The operating circuit of a transformer oil auxiliary heating apparatus according to claim 1, further comprising: an isolation drive circuit, the isolation drive circuit comprising: the output end of the DSP controller is electrically connected with the four input ends of the single-phase full-bridge inverter through the four first optocouplers respectively.

3. The operating circuit of a transformer oil auxiliary heating apparatus according to claim 1, further comprising: a temperature measurement circuit, the temperature measurement circuit comprising: the system comprises a plurality of thermocouples, a plurality of temperature converters, a second optical coupler, three third optical couplers, a fourth optical coupler, a decoder and a data selector;

the thermocouples are arranged at the points to be measured of the heating oil pipe, the output end of each thermocouple is electrically connected with the input end of each temperature converter, the output end of each temperature converter is respectively electrically connected with the input end of the data selector, the input end of the second optocoupler is electrically connected with the output end of the data selector, the output end of the second optocoupler is electrically connected with the input end of the DSP controller, the input end of each third optocoupler is electrically connected with the output end of the DSP controller, the output end of each third optocoupler is electrically connected with the input end of the decoder and the input end of the data selector, the input end of the fourth optical coupler is electrically connected with the output end of the DSP controller, the output end of the fourth optical coupler is electrically connected with the input end of each temperature converter, and the output end of the decoder is electrically connected with the input end of each temperature converter.

4. The operating circuit of a transformer oil auxiliary heating apparatus according to claim 1, further comprising: a maximum power tracking circuit, the maximum power tracking circuit comprising: a fifth optical coupler, a voltage comparator, an analog multiplier and a filter;

the input end of the fifth optical coupler is electrically connected with the output end of the DSP controller, the output end of the fifth optical coupler is electrically connected with the input end of the voltage comparator, the output end of the voltage comparator and the output end of the second in-phase device are electrically connected with the input end of the analog multiplier, the output end of the analog multiplier is electrically connected with the input end of the filter, and the output end of the filter is electrically connected with the input end of the analog-to-digital converter.

5. The operating circuit of a transformer oil auxiliary heating apparatus according to claim 1, further comprising: a communication circuit, the communication circuit comprising: the input end and the output end of the optical fiber transceiver are electrically connected with the DSP controller, and the input end and the output end of the optical fiber transceiver are connected with the industrial personal computer through optical fiber communication.