Electric arc furnace based on optical fiber synchronous carrier and control method

Abstract

The invention provides an electric arc furnace based on optical fiber synchronous carrier waves and a control method, and relates to the technical field of electric arc furnaces. Each power supply module comprises a plurality of power supply modules which are connected in parallel; a slow synchronization optical fiber and a fast synchronization optical fiber are connected between the integrated controller and each power supply module in each power supply module; the centralized controller transmits a square wave signal of a first frequency to each power supply module in each power supply module through a slow synchronization optical fiber, and is used for realizing staggered triggering of each power supply module through rising edge triggering of the square wave signal; the centralized controller transmits a square wave signal of a second frequency to each power supply module in each power supply module through a fast synchronization optical fiber so as to realize synchronization among the power supply modules in the power supply module; the second frequency is greater than the first frequency. The smelting efficiency and the power supply stability of the electric arc furnace can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electric arc furnaces, and in particular to an electric arc furnace based on optical fiber synchronous carrier and a control method thereof. Background Art

[0002] In the industrial application of electric arc furnaces, traditional electric arc furnaces are usually designed with a single power supply module, that is, one power supply module is used to power the electric arc furnace. However, the design of a single power supply module has some limitations and shortcomings. First, the smelting efficiency of a single-module electric arc furnace is limited and cannot meet the needs of large-scale industrial production. Secondly, since a single-module electric arc furnace needs to operate independently, it will take up a lot of space and resources. In addition, due to the large size and poor fault tolerance of a single module, if a fault occurs, the electric arc furnace needs to be shut down for maintenance, and the stability also has certain limitations. Summary of the invention

[0003] In order to address the deficiencies in the prior art, the purpose of the present invention is to provide an electric arc furnace and a control method based on an optical fiber synchronous carrier, which adopts multiple power supply modules to realize the power supply of the electric arc furnace, and utilizes optical fiber transmission technology to realize the synchronous control and signal transmission of each power supply module, thereby improving the melting efficiency and power supply stability of the electric arc furnace.

[0004] In order to achieve the above-mentioned purpose, according to some embodiments, the first aspect of the present invention provides an electric arc furnace based on optical fiber synchronous carrier, comprising multiple power supply modules and a centralized controller connected to each power supply module; each power supply module comprises multiple parallel power supply modules; slow synchronization optical fiber and fast synchronization optical fiber are connected between the centralized controller and each power supply module in each power supply module; the centralized controller transmits a square wave signal of a first frequency to each power supply module in each power supply module through the slow synchronization optical fiber, so as to realize the staggered triggering of each power supply module through the rising edge triggering of the square wave signal; the centralized controller transmits a square wave signal of a second frequency to each power supply module in each power supply module through the fast synchronization optical fiber, so as to realize the synchronization between each power supply module in the power supply module; the second frequency is greater than the first frequency.

[0005] A second aspect of the present invention, based on the electric arc furnace provided in the first aspect, further provides an electric arc furnace control method, comprising:

[0006] Obtain arc furnace smelting requirements;

[0007] Match the preset melting parameters according to the arc furnace melting requirements;

[0008] According to the frequency parameters in the smelting parameters, the power supply modules are synchronized through the slow synchronization optical fiber; at the same time, during the operation of the arc furnace, the fast synchronization optical fiber is used to ensure the synchronization of the power supply modules at any time;

[0009] The voltage and current parameters in the smelting parameters are sent to each power supply module in the form of a carrier through a fast synchronous optical fiber, and each power supply module is independently controlled according to the received voltage and current parameters.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] The present invention provides an arc furnace and control method based on optical fiber synchronous carrier wave, which adopts multiple power supply modules to realize power supply of the arc furnace, can realize module power superposition as needed, thereby improving overall power and production capacity, and can also improve the emergency response and fault tolerance of the arc furnace. When emergency start is required, even if a module fails, other modules can also ensure the normal power supply of the arc furnace. In order to ensure the synchronous operation of multiple modules and modules in the module, and avoid the problem of uneven power distribution or phase shift, optical fiber is used as a transmission medium, and the staggered control of each power supply module is realized through slow synchronous optical fiber, so as to ensure the coordinated work between modules and ensure the efficient operation of the system; the staggered control between each power supply module in the same power supply module is realized through fast synchronous optical fiber, and the staggered trigger control of each module is realized, so as to ensure the precise synchronization between each module, and improve the response speed of the system, and the fast synchronous optical fiber also undertakes the data transmission function, and transmits the given current and other information of each module through the signal duty cycle simulation serial port function, so as to realize the constant current control between modules and the voltage balancing control of the module, and improve the stability and reliability of power supply.

[0012] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 This is a schematic diagram of the overall structure of the electric arc furnace;

[0015] Figure 2 Schematic diagram of the module that supplies power to the electric arc furnace;

[0016] Figure 3 A schematic diagram showing the connection relationship between the centralized controller and the power supply module;

[0017] Figure 4 Schematic diagram of carrying data information through duty cycle. DETAILED DESCRIPTION

[0018] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0019] like Figure 1-Figure 4 As shown, an embodiment of the present invention first provides an electric arc furnace based on optical fiber synchronous carrier, comprising multiple power supply modules and a centralized controller connected to each power supply module; each power supply module comprises multiple parallel power supply modules; a slow synchronization optical fiber and a fast synchronization optical fiber are connected between the centralized controller and each power supply module in each power supply module; the centralized controller transmits a square wave signal (slow synchronization signal) of a first frequency to each power supply module in each power supply module through the slow synchronization optical fiber, for realizing staggered triggering of each power supply module through the rising edge triggering of the square wave signal; the centralized controller transmits a square wave signal (fast synchronization signal) of a second frequency to each power supply module in each power supply module through the fast synchronization optical fiber, for realizing synchronization between each power supply module in the power supply module; the second frequency is greater than the first frequency.

[0020] In view of the defects of using a single power supply module for power supply, an embodiment of the present invention proposes to design multiple power supply modules to power the arc furnace, and each power supply module includes multiple parallel power supply modules. The advantage of multiple modules working in parallel is that by working in parallel, their power can be superimposed, thereby improving the overall power and production capacity. In addition, the emergency response and fault tolerance of the system can be improved. When emergency startup is required, even if a module / module fails, other modules / modules can continue to work. Multiple modules working in parallel can also realize distributed control and management, which is conducive to the collaborative work between modules and improves the flexibility and adaptability of the system.

[0021] However, multi-module parallel technology needs to solve the difficult problems of synchronous control and constant voltage and current sharing control: multi-module parallel operation requires precise synchronous control algorithms and high-speed communication networks to ensure synchronous operation between modules to avoid problems such as uneven power distribution or phase shift; it is also necessary to implement constant voltage and current sharing control between modules to make the voltage and current between modules evenly distributed to ensure the stable operation of the entire system. Traditional arc furnace control technology usually uses hardware control and analog signal transmission, but this method has problems such as low control accuracy, poor anti-interference ability, and difficulty in achieving system phase synchronization. It is not suitable for scenarios where multiple modules work in parallel, and it is difficult to achieve same-frequency and same-phase control between multiple modules.

[0022] In order to solve the above problems, this embodiment uses optical fiber as a transmission medium to connect the power supply modules and power supply modules of multiple arc furnaces together to achieve parallel operation; and uses an optical fiber signal centralized controller to achieve current sharing control between modules and constant voltage control of the entire power supply module. Specifically, each module is equipped with an optical fiber interface, and the modules are connected into a whole through optical fiber. The optical fiber transmits synchronization signals and carrier signals, where the carrier signal includes the given current of each module. At the same time, through the same frequency and phase technology, the optical fiber signal centralized controller is used to keep the operating frequency and phase between the power supply modules of each arc furnace consistent.

[0023] The focus of arc furnace modularization technology is to achieve synchronous control and signal transmission of arc furnace based on optical fiber transmission technology. Based on optical fiber transmission, phase synchronization information is transmitted through optical fiber: synchronization signal and carrier signal, and the optical fiber signal centralized controller is used to achieve current sharing control between multiple modules and constant voltage control of the entire module group, effectively solving the problem of same-frequency and same-phase control between multiple modules, while improving the stability and reliability of the system.

[0024] Secondly, in the modular technology of electric arc furnaces, optical fibers are used to transmit synchronous control signals, such as the frequency and duty cycle of optical fiber signals. Through optical fiber transmission technology, fast and reliable information exchange between modules is achieved, thereby improving the response speed and accuracy of the entire system, improving the automation level and production efficiency of the electric arc furnace system, which is of great significance to industrial production.

[0025] The phase information between optical fiber transmission modules is used, and the synchronization signal is transmitted by slow synchronous optical fiber to realize the synchronous control of the power supply module. Three power supply modules are set up in the arc furnace corresponding to the three-phase electricity, and the three groups of power supply modules work in coordination through three square wave signals with a phase difference of 120°.

[0026] Use fast synchronization optical fiber to achieve synchronization and staggered triggering of modules within the module: Each module within each group of modules must maintain the same frequency and phase to ensure efficient operation of the entire system. Use fast synchronization optical fiber to achieve synchronous control and staggered triggering between modules within the module. The synchronization signal frequency of the fast synchronization optical fiber is the same as the carrier frequency. This design can improve the response speed of the system and ensure accurate synchronization between modules.

[0027] Interleaved trigger synchronous monitoring: Interleaved trigger synchronous monitoring is achieved through the rising edge of the fast synchronous fiber optic signal. At the same time, the duty cycle of the fast synchronous fiber optic signal is used to realize the UART (universal asynchronous receiver / transmitter) analog serial port function to issue control instructions, which can effectively improve the reliability and accuracy of data transmission.

[0028] The fiber optic signal centralized controller is an important component for realizing the function. The centralized controller is responsible for realizing the generation and distribution of slow synchronous fiber and fast synchronous fiber synchronization signals, thereby realizing the current sharing control between modules and the constant voltage control of the whole group of modules. Through centralized control, the working status of each module can be effectively coordinated to improve the stability of the whole system.

[0029] Fiber optic signal abnormality monitoring: The voltage of each module in the module is sampled through the fault bus to determine whether there is a fault in the power supply module, avoid further expansion of the module fault, and ensure the safe and stable operation of the system; at the same time, the slow synchronous fiber and fast synchronous fiber signals are monitored and sampled. When the frequency and duty cycle of the fiber optic signal exceed the set range, it is considered that the synchronous fiber has failed and triggers abnormal monitoring to avoid system malfunctions caused by fiber optic transmission path problems, reduce the system's operating failure rate, and increase operational stability.

[0030] like Figure 1 As shown, the centralized controller is used as the control module of the system to send the synchronization signal to the power supply module. The centralized controller is connected to an external synchronization signal generation module to generate a slow synchronization signal for realizing synchronization control between power supply modules and a fast synchronization signal for realizing data transmission and interleaved triggering between modules in the module. The centralized controller also has an optical fiber relay module for realizing signal conversion and expansion, thereby meeting the multi-module and multi-module control of the arc furnace. The arc furnace power supply module circuit is shown in FIG. Figure 2 As shown, in this embodiment, the number of power supply modules is 3, and there is a stable phase difference (120°) between the three power supply modules. Each power supply module in the module maintains the same frequency and phase. A, X, B, Y, C, and Z in the figure correspond to the output interfaces of the three modules respectively. Each module includes multiple power supply modules. Taking the power supply module 1-1 in the power supply module 1 as an example, the power supply module 1-1 is a power electronic converter composed of four bridge arms, and each bridge arm is respectively provided with a controlled switching device (for example, a power transistor can be used), which can realize the arc required by the inverter output arc furnace. Considering the uneven current caused by the inconsistency of the inverter bridge drive inside the module, both output ends are connected to the current sharing inductor. The design of the multi-module parallel structure is to meet the requirements of the large output current of the arc furnace. The power of a single module is not enough, so each module is connected in parallel with multiple modules to provide the required power.

[0031] Figure 3 It is a schematic diagram of the connection relationship between the centralized controller and the power supply module. Taking the power supply module 1 as an example, the centralized controller and each power supply module in the power supply module 1 are connected through a fast synchronization optical fiber and a slow synchronization optical fiber, so as to realize the sending of slow synchronization signals and fast synchronization signals.

[0032] The slow synchronization signal is generated by a slow synchronization fiber optic transmission module (not shown in the figure). The slow synchronization fiber optic transmission module transmits three square wave signals with a phase difference of 120° at a frequency of 5Hz and a cycle of 200ms each. The rising edge of the square wave signal of the slow synchronization fiber optic is used to transmit the phase synchronization information (i.e., the instantaneous moment when the low level of the square wave signal is converted to the high level). The three square wave signals are received by the slow synchronization fiber optic relay module in the centralized controller, which converts the fiber optic signal into an electrical signal and further expands it to a maximum of 48 fiber optic signals to ensure the effective transmission of the signal and meet the synchronization requirements of the system.

[0033] When the main control board in each controlled power supply module detects the rising edge of the square wave signal, the slow synchronization optical fiber transmission module uses the PWM (pulse width modulation) principle to generate a square wave signal with a phase difference of 120° for a synchronization calibration reset. After the rising edge is detected, the waveform is reset so that the modules that need to be synchronized regenerate the waveform at the same time, achieving the effect of synchronization calibration and ensuring that the output modules in the same output module are in the same phase.

[0034] Three groups of inverter output modules receive the above square wave signals, and the output phase difference is 120°; and the N parallel power supply modules in each group of inverter output modules are synchronized. Simply put, power supply module 1 is synchronized according to the slow synchronization signal of the first phase, and the N parallel power supply modules in power supply module 1 are all synchronized according to the slow signal of the first phase; power supply module 2 is synchronized according to the slow synchronization signal of the second phase, and the slow synchronization signal of the second phase lags 120° behind the slow synchronization signal of the first phase, and the N parallel power supply modules in power supply module 2 are all synchronized according to the slow signal of the second phase; power supply module 3 is synchronized according to the slow synchronization signal of the third phase, and the slow synchronization signal of the third phase lags 120 degrees behind the slow synchronization signal of the second phase, and is 120 degrees ahead of the slow synchronization signal of the first phase, thereby realizing phase interleaving control to ensure that the phase difference between each module remains stable.

[0035] The fast synchronization signal is generated by the fast synchronization fiber optic transmitter module (not shown in the figure), which can generate selectable pulse signals with a frequency of 2.5kHz and a phase difference of 180°, 120° and 90°, and the frequency is the same as the carrier frequency of the main control board. These pulse signals are used for the pulse interleaving control of the carrier frequency signal of the main control board, which can achieve higher frequency control than slow synchronization.

[0036] The fiber optic signal centralized controller receives the fast synchronization signal and slow synchronization signal from the fast synchronization fiber optic transmission module and the slow synchronization fiber optic transmission module, and uses the fiber optic analog UART serial communication protocol to transmit current setting, power limit and other signals. In this way, the instructions are sent to each power supply module to ensure the current sharing control between each power supply module and the constant voltage control of the entire group of modules. The duty cycle of the fast synchronization signal is used to realize the asynchronous serial communication UART (Universal Asynchronous Receiver / Transmitter) analog serial port function. According to the above synchronization principle, a synchronous action is performed according to the instruction after receiving the rising edge. It can be seen that the duty cycle does not affect the synchronous action. The transmitter uses pulse width modulation (PWM) to adjust the duty cycle of the signal for data transmission. When the pulse width of the square wave signal collected by the receiving end within a cycle is less than 40%, it can be set to 1; when the collected pulse width is greater than 80%, it can be set to 0, that is, it can carry data information without affecting the synchronization signal, realizing asynchronous serial communication. The schematic diagram of duty cycle carrying data information is shown in Figure 4 shown.

[0037] The frequency of the fast synchronization signal is set to 2.5kHz, that is, a rising edge is generated every 400 microseconds (1 / 2500 seconds). A synchronization time time1 is preset, and the CPU in each power supply module is synchronized according to time1. Time1 is preferably an integer multiple of the fast synchronization signal period (400 microseconds). Whenever the CPU timer receives a set number of rising edges, it means that time1 has been reached. At this time, the synchronization action is triggered and the timer is cleared, which realizes the synchronization of multiple power supply modules, thereby ensuring that even if there is a deviation in the crystal oscillator corresponding to the CPU of each power supply module, each module can achieve synchronization at a common time point.

[0038] Furthermore, to achieve interleaved control, that is, to allow different power supply modules to perform the same operation but with a certain phase difference (time difference), the fast synchronization signal is configured as a multi-channel signal with different phase differences, thereby achieving interleaved control of different power supply modules.

[0039] In some embodiments, a fault monitoring and protection system is further designed. A fault bus is correspondingly set for each group of power supply modules, and the fault buses between the power supply modules are connected in series, and the fault bus is also connected to the centralized controller. The fault bus signal is a high-level signal during normal operation. When a group of power supply modules detects a fatal fault (for example, the IGBT module is damaged or the bus voltage is too high), the high-level signal of the fault bus will be converted to a low-level signal. When other power modules receive a low-level signal from the fault bus, the module stops working immediately to achieve overall protection of the system. At the same time, the centralized controller synchronously receives the fault signal and executes the corresponding alarm and / or fault response strategy. This design effectively avoids the further expansion of the power supply module and the power supply module fault under the multi-module power supply state, ensuring the safe and stable operation of the system.

[0040] Some embodiments further provide an arc furnace control method, comprising:

[0041] Obtain arc furnace smelting requirements;

[0042] Match the preset melting parameters according to the arc furnace melting requirements;

[0043] According to the frequency parameters in the smelting parameters, the power supply modules are synchronized through the slow synchronization optical fiber; at the same time, during the operation of the arc furnace, the fast synchronization optical fiber is used to ensure the synchronization of the power supply modules at any time;

[0044] The voltage and current parameters in the smelting parameters are sent to each power supply module in the form of a carrier through a fast synchronous optical fiber, and each power supply module is independently controlled according to the received voltage and current parameters.

[0045] Specifically, voltage and current requirements are sent to the centralized controller according to process requirements. The centralized controller sends the voltage and current requirement information to each power supply module in the form of a carrier through fast synchronous optical fiber. Each power supply module decodes the pulses and independently adjusts the closed loop according to the voltage and current it receives to control the output.

[0046] The scheme provided in this embodiment can also realize the variable frequency control of the electric arc furnace. Based on the working characteristics of the electric arc furnace, ultra-low frequency can be used to ensure the uniformity of electrode roasting during electrode roasting. Under normal smelting conditions, the frequency can be dynamically variable during the smelting process. For example, if you want to concentrate the heat just after the furnace is out of the furnace, low-frequency operation is adopted. If you want to expand the molten pool in the late stage of smelting close to the furnace discharge stage, high-frequency smelting is adopted. According to the process conditions, the curve of current frequency and time is formulated to realize intelligent control. Therefore, the frequency demand can be sent to the centralized controller according to the needs of the process, and the frequency information is synchronized with each module through a slow synchronization signal. For current demand, multiple operation modes such as electrode roasting, frozen furnace start-up and hot furnace start-up can be preset, corresponding to different current rising curves, respectively, to realize the intelligent and precise control mode of current. According to different products (calcium carbide, silicon manganese, ferrosilicon, etc.) and processes (slag smelting, slag-free smelting, etc.), the original data and algorithms in the accumulated database are used to ensure that the system runs in the best working condition. The key parameters in the smelting process, such as electrode position, electrode current, output power, operating frequency, electrode impedance and electrode voltage, are taken as control targets to achieve optimal control, thus omitting the process of users repeatedly exploring parameters to adapt to new power sources.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An electric arc furnace based on optical fiber synchronous carrier, characterized in that: It comprises a plurality of power supply modules and a centralized controller connected to each power supply module; each power supply module comprises a plurality of power supply modules connected in parallel; a slow synchronization optical fiber and a fast synchronization optical fiber are connected between the centralized controller and each power supply module in each power supply module; the centralized controller transmits a square wave signal of a first frequency to each power supply module in each power supply module through the slow synchronization optical fiber, so as to realize the staggered triggering of each power supply module through the rising edge triggering of the square wave signal; the centralized controller transmits a square wave signal of a second frequency to each power supply module in each power supply module through the fast synchronization optical fiber, so as to realize the synchronization between each power supply module in the power supply module; the second frequency is greater than the first frequency.

2. An electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: The centralized controller also realizes asynchronous serial communication by controlling the duty cycle of the square wave signal of the second frequency.

3. An electric arc furnace based on optical fiber synchronous carrier according to claim 2, characterized in that: When the pulse width of the square wave signal received by the receiving end within one cycle is less than the first set value, the value transmitted by the square wave signal is set to 1; when the pulse width of the square wave signal received by the receiving end within one cycle is greater than the second set value, the value transmitted by the square wave signal is set to 0.

4. The electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: The centralized controller transmits multiple square wave signals of the first frequency to each power supply module in each power supply module group through a slow synchronous optical fiber. There is a set phase difference between each signal, and the number of signals is the same as the number of power supply modules.

5. The electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: The power supply module is a power electronic converter consisting of four bridge arms, each of which is provided with a controlled switch device for inverting and outputting the arc required by the arc furnace.

6. An electric arc furnace based on optical fiber synchronous carrier according to claim 5, characterized in that: Both output ends of each power supply module are connected with current sharing inductors.

7. An electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: The centralized controller is connected to the slow synchronous optical fiber transmitting module, and is used for converting the square wave signal of the first frequency generated by the slow synchronous optical fiber transmitting module and sending it to each power supply module.

8. The electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: The centralized controller is connected to the fast-synchronous optical fiber transmitting module and is used to change the duty cycle of the square wave signal of the second frequency generated by the fast-synchronous optical fiber transmitting module to implement the sending of instructions to each power supply module.

9. An electric arc furnace based on optical fiber synchronous carrier according to claim 1, characterized in that: It also includes a fault bus. Each group of power supply modules has a corresponding fault bus. The fault buses between the power supply modules are connected in series and connected to the centralized controller for feeding back fault signals of the power supply modules.

10. An arc furnace control method, characterized in that: include: Obtain arc furnace smelting requirements; Match the preset melting parameters according to the arc furnace melting requirements; According to the frequency parameters in the melting parameters, each power supply module is synchronized through the slow synchronization optical fiber; At the same time, during the operation of the arc furnace, the fast synchronization optical fiber is used to ensure the synchronization of each power supply module at any time; The voltage and current parameters in the smelting parameters are sent to each power supply module in the form of a carrier through a fast synchronous optical fiber, and each power supply module is independently controlled according to the received voltage and current parameters.

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