CN110753410B - Transformer oil auxiliary heating device based on electromagnetic induction and control method thereof - Google Patents
Transformer oil auxiliary heating device based on electromagnetic induction and control method thereof Download PDFInfo
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- CN110753410B CN110753410B CN201911046241.9A CN201911046241A CN110753410B CN 110753410 B CN110753410 B CN 110753410B CN 201911046241 A CN201911046241 A CN 201911046241A CN 110753410 B CN110753410 B CN 110753410B
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 194
- 238000000034 method Methods 0.000 title claims abstract description 28
- 230000005674 electromagnetic induction Effects 0.000 title claims abstract description 23
- 239000003990 capacitor Substances 0.000 claims abstract description 17
- 238000011896 sensitive detection Methods 0.000 claims description 53
- 230000010363 phase shift Effects 0.000 claims description 16
- 239000010410 layer Substances 0.000 claims description 11
- 239000013307 optical fiber Substances 0.000 claims description 11
- 238000002955 isolation Methods 0.000 claims description 6
- 238000013459 approach Methods 0.000 claims description 5
- 239000011491 glass wool Substances 0.000 claims description 5
- 238000004321 preservation Methods 0.000 claims description 5
- 238000004804 winding Methods 0.000 claims description 5
- 229910001018 Cast iron Inorganic materials 0.000 claims description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 230000001105 regulatory effect Effects 0.000 claims description 4
- 239000002356 single layer Substances 0.000 claims description 4
- 230000001276 controlling effect Effects 0.000 claims description 2
- 230000000694 effects Effects 0.000 abstract description 4
- 230000007613 environmental effect Effects 0.000 abstract description 2
- 229910052802 copper Inorganic materials 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011810 insulating material Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
Classifications
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B6/00—Heating by electric, magnetic or electromagnetic fields
- H05B6/02—Induction heating
- H05B6/06—Control, e.g. of temperature, of power
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/08—Cooling; Ventilating
- H01F27/10—Liquid cooling
- H01F27/12—Oil cooling
- H01F27/14—Expansion chambers; Oil conservators; Gas cushions; Arrangements for purifying, drying, or filling
-
- 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
- H05B6/10—Induction heating apparatus, other than furnaces, for specific applications
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- Engineering & Computer Science (AREA)
- Electromagnetism (AREA)
- Power Engineering (AREA)
- General Physics & Mathematics (AREA)
- Automation & Control Theory (AREA)
- General Induction Heating (AREA)
Abstract
The invention relates to an electromagnetic induction-based transformer oil auxiliary heating device and a control method thereof. The device comprises a heating unit and a control unit for controlling the operation of the heating unit, and is characterized in that: the heating unit comprises a heating oil pipe (3), an insulating layer (2) is covered outside the heating oil pipe (3), an electromagnetic coil (1) is wound outside the insulating layer (2), the electromagnetic coil (1) and a resonant capacitor (4) are connected in series to serve as an equivalent load, and a temperature sensor is respectively arranged at an oil inlet and an oil outlet of the heating oil pipe (3); the control unit comprises a controller connected with all the temperature sensors and also comprises a 380V power frequency alternating current power supply. The device developed by the invention has the advantages of high heating efficiency, high heating rate, uniform heating effect and accurate temperature control; the transformer can effectively adapt to various environmental temperature conditions, ensure the quality of oil products to the greatest extent and ensure the reliable and stable operation of the transformer.
Description
Technical Field
The invention relates to an electromagnetic induction-based transformer oil auxiliary heating device and a control method thereof.
Background
When an alternating current or a converter transformer in an electric power system is newly installed or overhauled, insulating oil is required to be filtered, and the oil is heated to promote evaporation of moisture and precipitation of gas in the oil, remove the moisture and impurities in the oil, improve the electric strength of the oil and protect paper insulation in the oil.
The heating temperature of the transformer oil is generally 55-60 ℃, and the common transformer oil auxiliary heating scheme in the current power system is mainly divided into three types, namely a resistance internal heating type, a resistance external heating type and a short circuit heating method. The resistance internal heating type is a method of directly heating by using resistance wires in an oil-filled heating tank or pipeline. The method has the advantages that the heat source is in direct contact with the transformer oil, and the heating efficiency is high. However, the heat source is a point heat source or a linear heat source, and the situation of excessively high local temperature rise can occur. Therefore, the heating effect of the method is uneven, accurate temperature control is difficult to carry out, and local overheating of transformer oil can occur. The resistance external heating type is a method that a heat source is not in direct contact with transformer oil, an intermediate medium is heated through a resistance wire, and then the intermediate medium transfers heat to the transformer oil through a pipe wall to realize heating. The method can realize uniform heating, but the heat source is not in direct contact with the oil, so that the heating efficiency is low. The short-circuit heating method is a method for short-circuiting the low-voltage side of the transformer, applying power frequency or low-frequency alternating current to the other side, and heating the transformer oil through winding heating. The method has no perfect temperature and power control system and has high risk of short-circuit operation.
In summary, a transformer oil auxiliary heating device is needed to improve the oil filtering working efficiency and ensure the oil quality, which has important significance for the development of the electric equipment of the electric power system to the green and saving.
Disclosure of Invention
The invention aims to provide an electromagnetic induction-based transformer oil auxiliary heating device which is high in heating efficiency, high in heating rate, uniform in heating effect and accurate in temperature control.
The second object of the present invention is to provide a control method of the above device.
The utility model provides a transformer oil auxiliary heating device based on electromagnetic induction, includes heating element and the control unit that controls this heating element work, its characterized in that: the heating unit comprises a heating oil pipe, a heat preservation layer is covered outside the heating oil pipe, an electromagnetic coil is wound outside the heat preservation layer, the electromagnetic coil and a resonance capacitor are connected in series to serve as equivalent loads, and a temperature sensor is respectively arranged at an oil inlet and an oil outlet of the heating oil pipe; the control unit comprises a controller connected with all the temperature sensors and also comprises a 380V power frequency alternating current power supply, wherein the 380V power frequency alternating current power supply is connected with the equivalent load through a three-phase bridge type uncontrollable rectifying circuit and a single-phase full-bridge inverter circuit in sequence, so that the 380V power frequency alternating current is rectified and then inverted to obtain high-frequency alternating current square wave voltage, and the high-frequency alternating current square wave voltage is fed into the equivalent load; the controller is also connected with a voltage sensor and a current sensor respectively, the voltage sensor is connected in parallel with two ends of the resonant capacitor, and the current sensor is connected in series with the electromagnetic coil; the controller is connected with the single-phase full-bridge inverter circuit through the isolation circuit so as to output PWM wave signals to control the single-phase full-bridge inverter circuit to work, and the controller also comprises a phase sensitive detection circuit which is respectively connected with the current sensor and the controller, so that the resonant frequency can be automatically tracked, and the frequency of the high-frequency alternating current output by the single-phase full-bridge inverter circuit can be regulated through the controller so as to enable the resonant capacitor and the electromagnetic coil to work in a resonant state.
The output ends of the voltage sensor and the current sensor are respectively connected with the signal acquisition end of the protection circuit, and the protection signal output end of the protection circuit is connected with the controller.
The controller is connected with the industrial personal computer through the optical fiber receiver and the optical fiber, so that an expected temperature value of transformer oil sent by the industrial personal computer is obtained, and the actual temperature value of the transformer oil and a voltage and current value signal of the electromagnetic coil are sent to the industrial personal computer by the controller.
Wherein the heating oil pipe is made of cast iron material, and the heat insulation layer is made of glass wool.
The heating oil pipe is formed by connecting four sections of oil pipes in series, each section of oil pipe is 1m long, the outer diameter is 0.06m, the inner diameter is 0.0568m, the length of the oil pipe wrapped by the electromagnetic coil is 0.8m, the electromagnetic coil is formed by tightly winding copper wires with the diameter of 2.5mm in a single layer, and each section of heating oil pipe electromagnetic coil is 320 turns.
Wherein the equivalent inductance of the electromagnetic coil of the heating oil pipe is 2mH, and the resonance capacitance connected in series with the electromagnetic coil is 2uF, so that an equivalent load with the inherent resonance frequency of 2.5kHz is obtained.
Two bridge arms of the single-phase full-bridge inverter circuit respectively generate square wave voltages with opposite polarities and 90-degree phase difference and 50% duty ratio.
Wherein the controller adopts a DSP controller.
The control method of the transformer oil auxiliary heating device based on electromagnetic induction is characterized by comprising the following steps of:
(1) The controller receives a transformer oil heating expected temperature value t H given by the industrial personal computer;
(2) The temperature sensors arranged at the oil inlet and the oil outlet of the heating oil pipe convey the measured actual temperature value t L to the controller, and the controller determines the magnitude of the phase shift angle delta through proportion adjustment according to the difference value delta t between the expected temperature value t H and the actual temperature value t L of the transformer oil;
(3) When the actual temperature value t L and the expected temperature value t H of the transformer oil differ greatly, the phase shift angle delta is adjusted to be zero, and heating is carried out at the maximum output power; when the actual temperature value t L of the transformer oil continuously approaches the expected temperature value t H, the phase shift angle delta is adjusted to be gradually increased, and the output power is gradually reduced, so that the temperature of the transformer oil is prevented from exceeding the upper limit temperature value.
The control method of the transformer oil auxiliary heating device based on electromagnetic induction is characterized by comprising the following steps of:
(1) When the heating device works in a resonance state, the output power of the phase sensitive detection circuit reaches the maximum; when the working frequency of the heating device is smaller than the resonant frequency, the output power of the phase sensitive detection circuit is increased along with the increase of the working frequency; when the working frequency of the heating device is larger than the resonant frequency, the output power of the phase sensitive detection circuit is reduced along with the increase of the working frequency;
(2) Compared with the nth output power P n of the phase sensitive detection circuit, the controller judges whether the (n+1) th output power P n+1 of the phase sensitive detection circuit is reduced, if P n-Pn+1＞Pmin, the heating device is judged to be deviated from the resonance point to work; otherwise, judging that the heating device works near the resonance point;
(3) If the heating device works at a position deviated from the resonance point, the working frequency of the device is increased by a fixed step length delta f=100 Hz, and compared with the n+1th output power P n+1 of the phase sensitive detection circuit, the controller judges whether the n+2th output power P n+2 of the phase sensitive detection circuit is increased, if P n+2-Pn+1＞Pmin, the working frequency of the device is still increased by the fixed step length delta f=100 Hz until the working frequency of the phase sensitive detection circuit is P n+3-Pn+2＜Pmin, and at the moment, the working frequency of the heating device is the corresponding frequency in the n+2th comparison; otherwise, the working frequency of the device is reduced by a fixed step length delta f= -100Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit is reached, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison;
(4) The operation was continued for 1 minute at the frequency determined at the time of the n+2th comparison, and the next cycle was performed until the heating was completed.
The device developed by the invention has the advantages of high heating efficiency, high heating rate, uniform heating effect and accurate temperature control; the transformer can effectively adapt to various environmental temperature conditions, ensure the quality of oil products to the greatest extent and ensure the reliable and stable operation of the transformer. The device of the invention utilizes the electromagnetic induction principle to lead the heating oil pipe to generate induction current, and the pipe wall heats to realize the purpose of uniformly heating the oil product. Because the pipe wall is in direct contact with the transformer oil, the thermal resistance is very low, and the heating efficiency is high. In addition, the electromagnetic coil wound on the surface of the heating oil pipe does not generate heat, and is manufactured by adopting an insulating material and a high-temperature cable, so that the problem that the service life of the resistance wire is shortened due to oxidation at a high temperature is solved. The invention designs a heating pipeline of the electromagnetic induction auxiliary heating device, and determines the maximum heating power under different flow rates and inlet oil temperatures. In particular, as the electric parameters of the electromagnetic coil are changed due to the change of temperature, the auxiliary heating device can work away from the resonance point.
Drawings
FIG. 1 is an overall block diagram of a transformer oil auxiliary heating apparatus;
FIG. 2 is a schematic view of a section of heating oil pipe 3;
FIG. 3 is a graph of transformer oil maximum temperature as a function of inlet flow rate, wherein inlet temperature: heating power at 0 ℃): 15000W/m 2;
FIG. 4 is a schematic diagram of a phase sensitive detector circuit;
Fig. 5 is a flow chart of the phase sensitive detection auto-tracking resonance point.
Detailed Description
The invention provides an electromagnetic induction-based transformer oil auxiliary heating device, which comprises a heating unit and a control unit for controlling the heating unit to work, wherein the heating unit comprises a heating oil pipe 3, an insulating layer 2 is covered outside the heating oil pipe 3, an electromagnetic coil 1 is wound outside the insulating layer 2, the electromagnetic coil 1 and a resonance capacitor 4 are connected in series to serve as equivalent loads, and a temperature sensor is respectively arranged at an oil inlet and an oil outlet of the heating oil pipe 3; the control unit comprises a controller connected with all the temperature sensors and also comprises a 380V power frequency alternating current power supply, wherein the 380V power frequency alternating current power supply is connected with the equivalent load through a three-phase bridge type uncontrollable rectifying circuit and a single-phase full-bridge inverter circuit in sequence, so that the 380V power frequency alternating current is rectified and then inverted to obtain high-frequency alternating current square wave voltage, and the high-frequency alternating current square wave voltage is fed into the equivalent load; the controller is also connected with a voltage sensor and a current sensor respectively, the voltage sensor is connected in parallel with two ends of the resonant capacitor 4, and the current sensor is connected in series with the electromagnetic coil 1; the controller is connected with the single-phase full-bridge inverter circuit through the isolation circuit so as to output PWM wave signals to control the single-phase full-bridge inverter circuit to work, and the controller further comprises a phase sensitive detection circuit which is respectively connected with the current sensor and the controller, so that the resonant frequency can be automatically tracked, and the frequency of high-frequency alternating current output by the single-phase full-bridge inverter circuit can be regulated through the controller so that the resonant capacitor 4 and the electromagnetic coil 1 work in a resonant state.
The output ends of the voltage sensor and the current sensor are respectively connected with the signal acquisition end of the protection circuit, and the protection signal output end of the protection circuit is connected with the controller. The controller is connected with the industrial personal computer through the optical fiber receiver and the optical fiber, so that the expected temperature value of the transformer oil sent by the industrial personal computer is obtained, and the actual temperature value of the transformer oil and the voltage and current value signal of the electromagnetic coil 1 are sent to the industrial personal computer by the controller. The heating oil pipe 3 is made of cast iron, and the heat preservation layer 2 is made of glass wool. The heating oil pipe 3 is formed by connecting four sections of oil pipes in series, each section of oil pipe is 1m long, the outer diameter is 0.06m, the inner diameter is 0.0568m, the length of the oil pipe wrapped by the electromagnetic coil 1 is 0.8m, the electromagnetic coil 1 is formed by tightly winding copper wires with the diameter of 2.5mm in a single layer, and each section of heating oil pipe 3 is 320 turns of the electromagnetic coil 1. The equivalent inductance of the electromagnetic coil 1 of the heating oil pipe 3 is 2mH, and the resonance capacitance 4 connected in series with the electromagnetic coil 1 is 2uF, so that an equivalent load with a natural resonance frequency of 2.5kHz is obtained.
In addition, two bridge arms of the single-phase full-bridge inverter circuit respectively generate square wave voltages with opposite polarities and 90-degree phase difference and 50% duty ratio. The controller adopts a DSP controller.
A transformer oil auxiliary heating device control method based on electromagnetic induction comprises the following steps:
(1) The controller receives a transformer oil heating expected temperature value t H given by the industrial personal computer;
(2) The temperature sensors arranged at the oil inlet and the oil outlet of the heating oil pipe 3 convey the measured actual temperature value t L to a controller, and the controller determines the magnitude of the phase shift angle delta through proportion adjustment according to the difference value delta t between the expected temperature value t H and the actual temperature value t L of transformer oil;
(3) When the actual temperature value t L and the expected temperature value t H of the transformer oil differ greatly, the phase shift angle delta is adjusted to be zero, and heating is carried out at the maximum output power; when the actual temperature value t L of the transformer oil continuously approaches the expected temperature value t H, the phase shift angle delta is adjusted to be gradually increased, and the output power is gradually reduced, so that the temperature of the transformer oil is prevented from exceeding the upper limit temperature value.
A transformer oil auxiliary heating device control method based on electromagnetic induction comprises the following steps:
(1) When the heating device works in a resonance state, the output power of the phase sensitive detection circuit reaches the maximum; when the working frequency of the heating device is smaller than the resonant frequency, the output power of the phase sensitive detection circuit is increased along with the increase of the working frequency; when the working frequency of the heating device is larger than the resonant frequency, the output power of the phase sensitive detection circuit is reduced along with the increase of the working frequency;
(2) Compared with the nth output power P n of the phase sensitive detection circuit, the controller judges whether the (n+1) th output power P n+1 of the phase sensitive detection circuit is reduced, if P n-Pn+1＞Pmin, the heating device is judged to be deviated from the resonance point to work; otherwise, judging that the heating device works near the resonance point;
(3) If the heating device works at a position deviated from the resonance point, the working frequency of the device is increased by a fixed step length delta f=100 Hz, and compared with the n+1th output power P n+1 of the phase sensitive detection circuit, the controller judges whether the n+2th output power P n+2 of the phase sensitive detection circuit is increased, if P n+2-Pn+1＞Pmin, the working frequency of the device is still increased by the fixed step length delta f=100 Hz until the working frequency of the phase sensitive detection circuit is P n+3-Pn+2＜Pmin, and at the moment, the working frequency of the heating device is the corresponding frequency in the n+2th comparison; otherwise, the working frequency of the device is reduced by a fixed step length delta f= -100Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit is reached, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison;
(4) The operation was continued for 1 minute at the frequency determined at the time of the n+2th comparison, and the next cycle was performed until the heating was completed.
Example 1:
an auxiliary heating device for transformer oil based on electromagnetic induction comprises the following invention points:
The transformer oil auxiliary heating device based on electromagnetic induction mainly comprises the following parts:
① The device comprises a DSP controller, a ② main circuit, a ③ isolation circuit, a ④ resonant capacitor 4, a ⑤ heating oil pipe 3, a ⑥ temperature sensor, a ⑦ phase sensitive detection circuit, a ⑧ current sensor, a ⑨ voltage sensor and a ⑩ optical fiber interface; inventive point 1 comprises the following steps:
In a ② main circuit, a three-phase bridge type uncontrollable rectifying circuit rectifies 380V power frequency alternating current, a single-phase full-bridge inverter circuit is adopted to invert direct current into high-frequency alternating current square wave voltage, a ④ resonant capacitor 4 and an electromagnetic coil 1 wound on the surface of a ⑤ heating oil pipe 3 are connected in series to serve as an equivalent load, and the high-frequency alternating current square wave voltage generated by the single-phase full-bridge inverter circuit is led into the equivalent load;
Step (2), a PWM wave control signal generated by a ① DSP controller drives a single-phase full-bridge inverter circuit to work after passing through a ③ isolation circuit, and a ② main circuit outputs high-frequency alternating current with the same frequency as the natural resonant frequency of an equivalent load under the action of the ① DSP controller, so that a ④ resonant capacitor 4 and an electromagnetic coil 1 work in a resonant state, and the output power of an auxiliary heating device reaches the maximum;
Step (3), adopting ⑥ temperature sensors to monitor temperature t L at the oil inlet and the oil outlet of the ⑤ heating oil pipe 3 in real time, changing a phase shift angle delta according to deviation deltat of expected temperature value t H and actual value t L of transformer oil, and adjusting output power of an auxiliary heating device;
step (4), connecting ⑨ voltage sensors in parallel at two ends of the ④ resonant capacitor 4, connecting ⑧ current sensors in series in a loop of the electromagnetic coil 1, transmitting the acquired voltage and current values to a ① DSP controller through a measuring circuit, and if the voltage and current values exceed a set upper limit value, adopting overvoltage and overcurrent protection measures by the ① DSP controller to adjust the output power of the auxiliary heating device to zero;
And (5) receiving an expected temperature value t H of the transformer oil sent by the industrial personal computer through a ⑩ optical fiber receiver by the ① DSP controller, and transmitting signals such as an actual temperature value t L and a voltage current value of the transformer oil to the industrial personal computer through a ⑩ optical fiber transmitter.
2. The ⑤ heating oil pipe 3 is respectively an oil pipe, a heat insulation layer 2 and an electromagnetic coil 1 from inside to outside; the ② main circuit adopts a single-phase full-bridge inverter circuit, and adjusts the output power of the auxiliary heating device in a phase-shifting mode according to temperature values measured by ⑥ temperature sensors arranged at the oil inlet and the oil outlet of the ⑤ heating oil pipe 3; the method comprises the following steps:
Step (1), ⑤ heating the oil pipe 3 by adopting cast iron material, wherein the low resistivity of the iron can form larger induced vortex so as to provide higher heating power;
the material of the heat preservation layer 2 of the ⑤ heating oil pipe 3 is glass wool, and the highest temperature which can be born by the glass wool is 350 ℃;
Step (3), each section of ⑤ heating oil pipe 3 is 1m long, the outer diameter is 0.06m, the inner diameter is 0.0568m, the length of the heating oil pipe is 0.8m, which is wrapped by the electromagnetic coil 1, the electromagnetic coil 1 is formed by tightly winding copper wires with the diameter of 2.5mm in a single layer, each section of heating oil pipe 3 is about 320 turns of the electromagnetic coil 1, and the heating pipelines of each group of heating devices are formed by connecting 4 sections of oil pipes in series;
Step (4), the equivalent inductance of each group of heating pipeline electromagnetic coils 1 is about 2mH, and the electromagnetic coils 1 and ④ resonant capacitors 4 of 2uF are connected in series to obtain an equivalent load with the inherent resonant frequency of 2.5 kHz;
Step (5), two bridge arms of a single-phase full-bridge inverter circuit in a ② main circuit respectively generate square wave voltages with opposite polarities and 90-degree phase difference and 50% duty ratio, and the output power of the auxiliary heating device is regulated by adopting a phase shifting mode;
Step (6), receiving a desired transformer oil heating temperature value t H from an industrial personal computer through a ⑩ optical fiber interface by a ① DSP controller, transmitting a measured actual temperature value t L to the ① DSP controller by ⑥ temperature sensors arranged at an oil inlet and an oil outlet of a ⑤ heating oil pipe 3, and determining the magnitude of a phase shift angle delta through proportional adjustment by the ① DSP controller according to a difference delta t between the desired transformer oil temperature value t H and the actual transformer oil temperature value t L; when the actual temperature value t L and the expected temperature value t H of the transformer oil are greatly different, the phase shift angle delta is zero, and heating is carried out at the maximum output power; when the actual temperature value t L of the transformer oil continuously approaches the expected temperature value t H, the phase shift angle delta is gradually increased, the output power is gradually reduced, and the transformer oil temperature is prevented from exceeding the upper limit temperature value.
3. The heating object of the invention is KI45X transformer oil, which is limited by an expected temperature value t H of the transformer oil, and the average power output by a main circuit in the whole heating process ② is determined according to the flow rate of ⑤ for heating the transformer oil at the oil inlet of the oil pipe 3; the method comprises the following steps:
Step (1), when the flow rate of transformer oil at the oil inlet of ⑤ heating oil pipe 3 is set to be 1.34m/s, the average power output by ② main circuit is set to be 11500W/m 2 in the process of heating from 0 ℃ to 60 ℃;
Step (2), when the flow rate of transformer oil at the oil inlet of the ⑤ heating oil pipe (3) is set to be 0.67m/s (5.5 t/h), the average power output by a ② main circuit is set to be 800W/m 2 in the process of heating from 0 ℃ to 60 ℃;
And (3) when the output power of the ② main circuit is set to 15000W/m 2,⑤ and the flow rate of the transformer oil at the oil inlet of the heating oil pipe 3 is not more than 1.4m/s, otherwise, the highest temperature of the transformer oil is lower than the critical temperature (85 ℃).
4. The ⑦ phase sensitive detection circuit is adopted to automatically track the resonant frequency, so that the auxiliary heating device always works near the resonant point, and the maximum power output is always achieved in the heating process; the method comprises the following steps:
Step (1), only when the heating device works in a resonance state, the output power of the phase sensitive detection circuit reaches the maximum; when the working frequency of the heating device is smaller than the resonant frequency, the output power of the phase sensitive detection circuit is increased along with the increase of the working frequency; when the working frequency of the heating device is larger than the resonant frequency, the output power of the phase sensitive detection circuit is reduced along with the increase of the working frequency;
Step (2), comparing with the nth output power P n of the phase sensitive detection circuit, the DSP controller judges whether the (n+1) th output power P n+1 of the phase sensitive detection circuit is reduced, if P n-Pn+1＞Pmin, the heating device is judged to be deviated from the resonance point to work; otherwise, judging that the heating device works near the resonance point;
Step (3), if the heating device works at a position deviated from the resonance point, the working frequency of the device is increased by a fixed step length delta f=100 Hz, compared with the output power P n+1 of the phase sensitive detection circuit for the n+1th time, the DSP controller judges whether the output power P n+2 of the phase sensitive detection circuit for the n+2th time is increased, if P n+2-Pn+1＞Pmin, the working frequency of the device is still increased by the fixed step length delta f=100 Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th time of comparison; otherwise, the working frequency of the device is reduced by a fixed step length delta f= -100Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit is reached, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison;
and (4) continuously working for 1 minute at the frequency determined in the n+2th comparison, and performing the next cycle until the heating is finished.
Example 2:
1. The 380V power frequency alternating current is fed into a ② main circuit, the ② main circuit rectifies the 380V power frequency alternating current by adopting a three-phase bridge type uncontrollable rectification circuit, and the direct current is inverted into high-frequency alternating current by adopting a single-phase full-bridge inverter circuit.
2. The 4 sections of heating oil pipes 3 are connected in series to form a group of pipelines, and the electromagnetic coil 1 wound on the surface of the ⑤ heating oil pipes 3 is connected in series with the ④ resonant capacitor 4 of 2uF to form an equivalent load with the inherent resonant frequency of about 2.5 kHz.
3. When the power-on is started, the ① DSP controller outputs a PWM wave control signal with the frequency of 2.5kHz, and the PWM wave control signal passes through the ③ isolation circuit and then drives the single-phase full-bridge inverter circuit to work.
4. When the transformer oil auxiliary heating device works in a resonance state, the voltage at two ends of the load is a square wave of 2.5kHz, the current flowing through the load is close to a sine wave, the frequency is also 2.5kHz, the voltage and the current are in the same phase, and the heating device works in the resonance state.
5. The ⑨ voltage sensors are connected in parallel to two ends of the ④ resonant capacitor 4, the ⑧ current sensors are connected in series in a load loop, the collected voltage and current values are transmitted to the ① DSP controller, and if the voltage and current values exceed a set upper limit value, the ① DSP controller takes protective measures to adjust the output power of the auxiliary heating device to zero.
6. When the flow rate of the transformer oil at the oil inlet of ⑤ heating oil pipe 3 is set to be 1.34m/s, the average power output by a ② main circuit is set to be 11500W/m 2 in the process of heating from 0 ℃ to 60 ℃; when the flow rate of the transformer oil at the oil inlet of ⑤ heating oil pipe 3 is set to be 0.67m/s (5.5 t/h), the average power output by a ② main circuit is set to be 800W/m 2 in the process of heating from 0 ℃ to 60 ℃; when the output power of the ② main circuit is set to 15000W/m 2,⑤ and the flow rate of the transformer oil at the oil inlet of the heating oil pipe 3 is not more than 1.4m/s, otherwise, the highest temperature of the transformer oil is lower than the critical temperature (85 ℃).
7. When the engine is started to heat, the ① DSP controller receives a transformer oil heating expected temperature value t H given by an industrial personal computer through a ⑩ optical fiber interface, ⑥ temperature sensors arranged at an oil inlet and an oil outlet of the ⑤ heating oil pipe 3 convey a measured actual temperature value t L to the ① DSP controller, and the ① DSP controller determines the magnitude of a phase shift angle delta through proportion adjustment according to a difference delta t between the transformer oil expected temperature value t H and the actual temperature value t L; when the actual temperature value t L and the expected temperature value t H of the transformer oil are greatly different, the phase shift angle delta is zero, and heating is carried out at the maximum output power; when the actual temperature value t L of the transformer oil continuously approaches the expected temperature value t H, the phase shift angle delta is gradually increased, the output power is gradually reduced, and the transformer oil temperature is prevented from exceeding the upper limit temperature value.
8. The relation that the per unit value P of the output power of the phase sensitive detection circuit/P.U. changes along with the working frequency f/kHz is as follows: only when the heating device works in a resonance state, the output power of the phase sensitive detection circuit reaches the maximum; when the working frequency of the heating device is smaller than the resonant frequency, the output power of the phase sensitive detection circuit is increased along with the increase of the working frequency; when the operating frequency of the heating device is greater than the resonant frequency, the output power of the phase sensitive detection circuit decreases with increasing operating frequency.
9. Adopting ⑦ phase sensitive detection circuit to automatically track resonant frequency, comparing with the nth output power P n of the phase sensitive detection circuit, the DSP controller judging whether the (n+1) th output power P n+1 of the phase sensitive detection circuit is reduced, if P n-Pn+1＞Pmin, judging that the heating device is deviated from the resonant point to work; on the contrary, it is determined that the heating device is operated in the vicinity of the resonance point.
10. If the heating device works at a position deviated from the resonance point, the working frequency of the device is increased by a fixed step length delta f=100 Hz, compared with the n+1th output power P n+1 of the phase sensitive detection circuit, the DSP controller judges whether the n+2th output power P n+2 of the phase sensitive detection circuit is increased, if P n+2-Pn+1＞Pmin, the working frequency of the device is still increased by the fixed step length delta f=100 Hz until the working frequency of the phase sensitive detection circuit is up to the output power P n+3-Pn+2＜Pmin, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison; otherwise, the working frequency of the device is reduced by a fixed step length delta f= -100Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit is reached, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison;
11. the procedure was continued for 1 minute at the frequency determined at the n+2th comparison and the next cycle was performed until the heating was completed.
Claims (8)
1. The utility model provides a transformer oil auxiliary heating device based on electromagnetic induction, includes heating element and the control unit of controlling this heating element work, its characterized in that: the heating unit comprises a heating oil pipe (3), an insulating layer (2) is covered outside the heating oil pipe (3), an electromagnetic coil (1) is wound outside the insulating layer (2), the electromagnetic coil (1) and a resonant capacitor (4) are connected in series to serve as an equivalent load, and a temperature sensor is respectively arranged at an oil inlet and an oil outlet of the heating oil pipe (3); the control unit comprises a controller connected with all the temperature sensors and also comprises a 380V power frequency alternating current power supply, wherein the 380V power frequency alternating current power supply is connected with the equivalent load through a three-phase bridge type uncontrollable rectifying circuit and a single-phase full-bridge inverter circuit in sequence, so that the 380V power frequency alternating current is rectified and then inverted to obtain high-frequency alternating current square wave voltage, and the high-frequency alternating current square wave voltage is fed into the equivalent load; the controller is also connected with a voltage sensor and a current sensor respectively, the voltage sensor is connected in parallel with two ends of the resonant capacitor (4) and the current sensor is connected in series with the electromagnetic coil (1); the controller is connected with the single-phase full-bridge inverter circuit through the isolation circuit so as to output PWM wave signals to control the single-phase full-bridge inverter circuit to work, and the controller further comprises a phase sensitive detection circuit which is respectively connected with the current sensor and the controller, so that the resonant frequency can be automatically tracked, and the frequency of high-frequency alternating current output by the single-phase full-bridge inverter circuit can be regulated through the controller so that the resonant capacitor (4) and the electromagnetic coil (1) work in a resonant state;
the output ends of the voltage sensor and the current sensor are respectively connected with the signal acquisition end of the protection circuit, and the protection signal output end of the protection circuit is connected with the controller;
The controller is connected with the industrial personal computer through the optical fiber receiver and the optical fiber, so that an expected temperature value of transformer oil sent by the industrial personal computer is obtained, and the actual temperature value of the transformer oil and a voltage and current value signal of the electromagnetic coil (1) are sent to the industrial personal computer by the controller.
2. The electromagnetic induction-based transformer oil auxiliary heating device according to claim 1, wherein: wherein the heating oil pipe (3) is made of cast iron material, and the heat preservation layer (2) is made of glass wool.
3. The electromagnetic induction-based transformer oil auxiliary heating device according to claim 1, wherein: the heating oil pipe (3) is formed by connecting four sections of oil pipes in series, each section of oil pipe is 1m long, the outer diameter is 0.06m, the inner diameter is 0.0568m, the length of the oil pipe wrapped by the electromagnetic coil (1) is 0.8m, the electromagnetic coil (1) is formed by tightly winding a copper wire with the diameter of 2.5mm in a single layer, and each section of heating oil pipe (3) is 320 turns.
4. The electromagnetic induction-based transformer oil auxiliary heating device according to claim 3, wherein: wherein the equivalent inductance of the electromagnetic coil (1) of the heating oil pipe (3) is 2mH, and the resonance capacitance (4) connected in series with the electromagnetic coil (1) is 2uF, so that an equivalent load with the inherent resonance frequency of 2.5kHz is obtained.
5. The electromagnetic induction-based transformer oil auxiliary heating device according to claim 1, wherein: two bridge arms of the single-phase full-bridge inverter circuit respectively generate square wave voltages with opposite polarities and 90-degree phase difference and 50% duty ratio.
6. The electromagnetic induction-based transformer oil auxiliary heating device according to claim 1, wherein: wherein the controller adopts a DSP controller.
7. A control method of an electromagnetic induction based transformer oil auxiliary heating apparatus according to any one of claims 1-6, characterized by comprising the steps of:
(1) The controller receives a transformer oil heating expected temperature value t H given by the industrial personal computer;
(2) The temperature sensors arranged at the oil inlet and the oil outlet of the heating oil pipe (3) convey the measured actual temperature value t L to the controller, and the controller determines the magnitude of the phase shift angle delta through proportion adjustment according to the difference delta t between the expected temperature value t H and the actual temperature value t L of the transformer oil;
(3) When the actual temperature value t L and the expected temperature value t H of the transformer oil differ greatly, the phase shift angle delta is adjusted to be zero, and heating is carried out at the maximum output power; when the actual temperature value t L of the transformer oil continuously approaches the expected temperature value t H, the phase shift angle delta is adjusted to be gradually increased, and the output power is gradually reduced, so that the temperature of the transformer oil is prevented from exceeding the upper limit temperature value.
8. A control method of an electromagnetic induction based transformer oil auxiliary heating apparatus according to any one of claims 1-6, characterized by comprising the steps of:
(1) When the heating device works in a resonance state, the output power of the phase sensitive detection circuit reaches the maximum; when the working frequency of the heating device is smaller than the resonant frequency, the output power of the phase sensitive detection circuit is increased along with the increase of the working frequency; when the working frequency of the heating device is larger than the resonant frequency, the output power of the phase sensitive detection circuit is reduced along with the increase of the working frequency;
(2) Compared with the nth output power P n of the phase sensitive detection circuit, the controller judges whether the (n+1) th output power P n+1 of the phase sensitive detection circuit is reduced, if P n-Pn+1＞Pmin, the heating device is judged to be deviated from the resonance point to work; otherwise, judging that the heating device works near the resonance point;
(3) If the heating device works at a position deviated from the resonance point, the working frequency of the device is increased by a fixed step length delta f=100 Hz, and compared with the n+1th output power P n+1 of the phase sensitive detection circuit, the controller judges whether the n+2th output power P n+2 of the phase sensitive detection circuit is increased, if P n+2-Pn+1＞Pmin, the working frequency of the device is still increased by the fixed step length delta f=100 Hz until the working frequency of the phase sensitive detection circuit is P n+3-Pn+2＜Pmin, and at the moment, the working frequency of the heating device is the corresponding frequency in the n+2th comparison; otherwise, the working frequency of the device is reduced by a fixed step length delta f= -100Hz until the output power P n+3-Pn+2＜Pmin of the phase sensitive detection circuit is reached, and at the moment, the working frequency of the heating device is the frequency corresponding to the n+2th comparison;
(4) The operation was continued for 1 minute at the frequency determined at the time of the n+2th comparison, and the next cycle was performed until the heating was completed.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN206152472U (en) * | 2016-09-29 | 2017-05-10 | 国家电网公司 | Transformer oil electromagnetic induction auxiliary heating device |
| CN207977206U (en) * | 2018-03-30 | 2018-10-16 | 安徽华环电气设备有限公司 | A kind of transformer heating system |
| CN110139412A (en) * | 2019-06-20 | 2019-08-16 | 胜利油田金色河口石化工程有限公司 | Electromagnetic induction heater |
| CN211209965U (en) * | 2019-10-30 | 2020-08-07 | 国网宁夏电力有限公司检修公司 | Transformer oil auxiliary heating device based on electromagnetic induction |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN206152472U (en) * | 2016-09-29 | 2017-05-10 | 国家电网公司 | Transformer oil electromagnetic induction auxiliary heating device |
| CN207977206U (en) * | 2018-03-30 | 2018-10-16 | 安徽华环电气设备有限公司 | A kind of transformer heating system |
| CN110139412A (en) * | 2019-06-20 | 2019-08-16 | 胜利油田金色河口石化工程有限公司 | Electromagnetic induction heater |
| CN211209965U (en) * | 2019-10-30 | 2020-08-07 | 国网宁夏电力有限公司检修公司 | Transformer oil auxiliary heating device based on electromagnetic induction |
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