Electric arc furnace smelting device based on dual-mode flexible power supply

Abstract

The invention relates to an electric arc furnace smelting device based on a dual-mode flexible power supply, and belongs to the field of metallurgical equipment. The device comprises a dual-mode flexible power supply and a dual-mode electric arc furnace, the dual-mode flexible power supply comprises a rectification unit, a dual-mode current transformation unit and an impedance matching unit, and the rectification unit is connected to a front-end power grid and converts high-voltage alternating current of the front-end power grid into low-voltage direct current; the dual-mode converter unit converts the input direct current into direct current or alternating current in a target mode, and an impedance matching unit is arranged between the dual-mode converter unit and the dual-mode electric arc furnace to adjust a power factor; the dual-mode electric arc furnace comprises a plurality of electrodes and an electric furnace body, the electrodes are divided into furnace top electrodes and furnace bottom electrodes, and the direct-current or alternating-current working mode of the dual-mode electric arc furnace is adjusted according to the on-off conditions of the electrodes at the corresponding positions. High-voltage alternating current can be flexibly converted into low-voltage alternating current or low-voltage direct current, the working mode of the electric arc furnace is correspondingly adjusted, and the adaptability and flexibility of the electric arc furnace smelting device are improved.

Description

Technical Field

[0001] The invention belongs to the field of metallurgical equipment and relates to an arc furnace smelting device based on a dual-mode flexible power supply Background Art

[0002] Compared with the traditional long-process steelmaking, the short-process steelmaking has many advantages such as flexibility, environmental protection and energy saving, which is in line with the national dual-carbon strategy. The electric arc furnace has become an indispensable and important device in the short-process steelmaking due to its high thermal efficiency and convenient control.

[0003] Electric arc furnaces can be divided into AC arc furnaces and DC arc furnaces according to the type of power supply. Traditional AC arc furnaces use transformers to step down the voltage and then directly supply power, while traditional DC arc furnaces use diodes or thyristors to convert the current and then directly supply power. Regardless of the power supply method, there are problems such as low power factor and large grid-side harmonics.

[0004] The number of electrodes in an AC arc furnace is generally 3, and they are located at the top of the furnace body and arranged in a triangle. It has the characteristics of a wide hot zone, but because the electrodes are located at the top of the furnace body, the molten pool in the furnace starts to form from the top during smelting, resulting in uneven and insufficient melting of the charge, which has an adverse effect on the production of large charges and special steels that require uniform composition. The number of electrodes in a DC arc furnace is generally 2, and they are located at the top and bottom of the furnace body and arranged symmetrically. It has the characteristics of sufficient melting of the charge and strong stirring force, but because it uses a through-type power supply, when using charges with poor conductivity for production, the problem of arcing will occur.

[0005] In summary, there is currently a lack of an electric arc furnace design that can combine the advantages of both AC and DC arc furnaces while overcoming their limitations. This lack not only limits the further optimization and development of mini-process steelmaking technology, but also hinders its potential in achieving a more efficient, environmentally friendly and flexible steel production process. Summary of the invention

[0006] In view of this, an object of the present invention is to provide an electric arc furnace smelting device based on a dual-mode flexible power supply.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] An arc furnace smelting device based on a dual-mode flexible power supply, the arc furnace smelting device includes a dual-mode flexible power supply and a dual-mode arc furnace, the dual-mode flexible power supply converts high-voltage alternating current of a front-end power grid into low-voltage alternating current or low-voltage direct current and inputs it into the dual-mode arc furnace of the corresponding mode.

[0009] The dual-mode flexible power supply includes a rectifier unit, a dual-mode converter unit, and an impedance matching unit. The rectifier unit is connected to the front-end power grid to convert the high-voltage AC power of the front-end power grid into low-voltage DC power. The dual-mode converter unit then converts the input DC power into DC or AC power of the target mode, and an impedance matching unit is set between the dual-mode converter unit and the dual-mode arc furnace to adjust the power factor.

[0010] The dual-mode electric arc furnace includes a plurality of electrodes and an electric furnace body, wherein the electrodes are divided into furnace top electrodes and furnace bottom electrodes, and the DC or AC working mode of the dual-mode electric arc furnace is adjusted according to the on-off status of the electrodes at the corresponding positions.

[0011] Furthermore, the rectifier unit includes a phase-shifting transformer and a three-phase rectifier bridge, the input end of the phase-shifting transformer is connected to the front-end power grid, the output end is connected to the three-phase rectifier bridge, and the output end of the three-phase rectifier bridge is connected to the dual-mode converter unit; wherein, the phase-shifting transformer is a multi-winding phase-shifting transformer, and the number of windings is determined according to the grid-side harmonic target value and corresponds to the number of three-phase rectifier bridges; the three-phase rectifier bridge is an uncontrolled rectifier bridge, and diodes are used as power devices.

[0012] Furthermore, the dual-mode conversion unit includes a supporting capacitor and an H-bridge composed of power devices, wherein the supporting capacitor is connected between the positive and negative poles of the DC bus output by the rectifier unit, the input end of the H-bridge is connected to the DC bus, and the output end is connected to the impedance matching unit; the supporting capacitor and the H-bridge constitute a modular power unit, and the number of power units is adjusted according to power requirements.

[0013] Furthermore, when the dual-mode converter unit aims to output direct current, it controls the H-bridge circuit to output the chopper circuit; when the dual-mode converter unit aims to output alternating current, it controls the H-bridge circuit to convert the input direct current into alternating current for output.

[0014] Furthermore, the impedance matching unit includes an output inductor and an isolating switch, wherein the input end of the inductor is connected to the output end of the H-bridge, the output end is connected to the input end of the isolating switch, and the output end of the isolating switch is connected to the electrode end of the arc furnace; the value of the inductor is determined according to the required power factor.

[0015] Furthermore, the electrodes of the dual-mode electric arc furnace are connected to an impedance matching unit, and direct current or alternating current generates an arc between the electrodes of the dual-mode electric arc furnace, thereby melting the raw materials in the electric furnace body.

[0016] Furthermore, in the DC working mode, all the top electrodes and bottom electrodes of the dual-mode electric arc furnace are in a connected state; in the AC working mode, all the top electrodes of the dual-mode electric arc furnace are in a connected state, and all the bottom electrodes are in a disconnected state.

[0017] Furthermore, the number of the furnace top electrode and the furnace bottom electrode of the dual-mode electric arc furnace is set to at least one.

[0018] The beneficial effects of the present invention are:

[0019] The present invention first provides a dual-mode flexible power supply, which can flexibly convert the high-voltage AC power of the front-end power grid into low-voltage AC power or low-voltage DC power, meet the power supply requirements under different working modes, and improve the adaptability and flexibility of the arc furnace smelting device. Through the coordinated work of the rectifier unit, the dual-mode converter unit and the impedance matching unit, efficient conversion and precise control of the power supply are achieved, the smelting effect of the arc furnace is optimized, and the energy utilization rate is improved. The arc furnace can switch between DC or AC working modes, adapting to the needs of different smelting processes and broadening the application range of the arc furnace.

[0020] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0022] Figure 1 It is a structural schematic diagram of an electric arc furnace smelting device based on a dual-mode flexible power supply;

[0023] Figure 2 This is a working principle diagram of the dual-mode smelting device in the DC mode according to an embodiment of the present invention;

[0024] Figure 3 It is a working principle diagram of the dual-mode smelting device in the AC mode in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0026] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0027] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0028] See also Figure 1 to Figure 3 , which is an electric arc furnace smelting device based on a dual-mode flexible power supply.

[0029] like Figure 1 The present invention provides an electric arc furnace smelting device based on a dual-mode flexible power supply, which at least includes a dual-mode flexible power supply and a dual-mode electric arc furnace, wherein the dual-mode flexible power supply converts the high-voltage alternating current of the front-end power grid into low-voltage alternating current or low-voltage direct current and inputs it into the dual-mode electric arc furnace of the corresponding mode; wherein the dual-mode flexible power supply includes a rectifier unit, a dual-mode conversion unit, and an impedance matching unit.

[0030] The rectifier unit mainly includes a phase-shifting transformer and a three-phase rectifier bridge, wherein the input end of the phase-shifting transformer is connected to the front-end power grid, the output end is connected to the three-phase rectifier bridge, and the output end of the three-phase rectifier bridge is connected to the dual-mode converter unit. This unit can convert AC high voltage into AC low voltage, and then convert it into DC voltage. The phase-shifting transformer is a multi-winding phase-shifting transformer, and the number of windings corresponds to the number of three-phase rectifier bridges. The specific number can be determined by the grid-side harmonic target value. The three-phase rectifier bridge is an uncontrolled rectifier bridge, and diodes are used as power devices.

[0031] The dual-mode converter unit mainly includes a supporting capacitor and an H-bridge composed of power devices, wherein the supporting capacitor is connected between the positive and negative poles of the DC bus, the input end of the H-bridge is connected to the DC bus, and the output end is connected to the impedance matching unit. This unit can stabilize the DC bus voltage and convert the input DC power as needed. The supporting capacitor and the H-bridge constitute a modular power unit, and the number of power units can be adjusted according to the required power. The dual-mode converter link can output DC or AC power through the control program as needed.

[0032] The impedance matching unit mainly includes an output reactor and an isolating switch, wherein the input end of the reactor is connected to the output end of the H-bridge, the output end is connected to the input end of the isolating switch, and the output end of the isolating switch is connected to the electrode end of the arc furnace. This unit configures the reactor according to the dual-mode converter unit, which plays a role in improving the power factor and ensuring the safety of the device. The reactor in the impedance matching link can be freely connected as needed.

[0033] The dual-mode electric arc furnace mainly includes electrodes and an electric furnace body, wherein the electrodes are connected to an impedance matching unit. This device uses an arc generated between electrodes to melt raw materials. The electrodes are divided into furnace top electrodes and furnace bottom electrodes, and the number of furnace top electrodes and furnace bottom electrodes is not less than 1.

[0034] Example 1

[0035] Figure 2 The schematic diagram of the structure of an arc furnace smelting device based on a dual-mode flexible power supply in the DC mode in this embodiment is shown in FIG. The device mainly includes a rectifier unit, a dual-mode converter unit, an impedance matching unit and a dual-mode arc furnace.

[0036] The rectifier unit mainly includes a phase-shifting transformer and a three-phase rectifier bridge, wherein the input end of the transformer is connected to the front-end power grid, the output end is connected to the three-phase rectifier bridge, and the output end of the three-phase rectifier bridge is connected to the dual-mode converter unit. The phase-shifting transformer adopts a multi-winding phase-shifting transformer with two sets of windings, and the two windings have different phase shift angles, forming a 12-pulse rectification, which can reduce the harmonic content on the grid side. The three-phase rectifier bridge uses diodes as power devices to form a three-phase uncontrolled rectification. This unit can convert AC high voltage into AC low voltage, and then convert it into DC voltage.

[0037] The dual-mode converter unit mainly includes a support capacitor and an H-bridge composed of power devices, wherein the support capacitor is connected between the positive and negative poles of the DC bus, the input end of the H-bridge is connected to the DC bus, and the output end is connected to the impedance matching unit. The support capacitor and the H-bridge together constitute a power unit module, and multiple power unit modules are connected together in parallel, thereby increasing the output power of the device. In this embodiment, the device operates in a DC mode, in which the H-bridge circuit is controlled to a chopper circuit through program control, and finally the required DC power is output. This unit can stabilize the DC bus voltage and can output the input DC power as adjustable DC power through chopping.

[0038] The impedance matching unit mainly includes an output reactor and an isolating switch, wherein the input end of the reactor is connected to the output end of the H-bridge, the output end is connected to the input end of the isolating switch, and the output end of the isolating switch is connected to the electrode end of the arc furnace. In this embodiment, the device operates in a DC mode, and the output reactor is configured with parameters required for the DC mode. This unit configures the reactor according to the dual-mode converter unit, which plays a role in improving the power factor and ensuring the safety of the device.

[0039] The dual-mode electric arc furnace mainly includes electrodes and an electric furnace body, wherein the electrodes are connected to an impedance matching unit. In this embodiment, the device operates in a DC mode, and all electrodes are in use. The top electrode and the bottom electrode of the dual-mode electric arc furnace in the DC mode are configured as one on the top and one on the bottom, so that an arc is generated between the electrodes to play the role of melting raw materials.

[0040] Example 2

[0041] Figure 3 The schematic diagram of an embodiment of an arc furnace smelting device based on a dual-mode flexible power supply in AC mode in this embodiment. The device mainly includes a rectifier unit, a dual-mode converter unit, an impedance matching unit and a dual-mode arc furnace.

[0042] The rectifier unit mainly includes a phase-shifting transformer and a three-phase rectifier bridge, wherein the input end of the transformer is connected to the front-end power grid, the output end is connected to the three-phase rectifier bridge, and the output end of the three-phase rectifier bridge is connected to the dual-mode converter unit. The phase-shifting transformer adopts a multi-winding phase-shifting transformer with four sets of windings, and the four windings have different phase shift angles, forming a 24-pulse rectification, which can reduce the harmonic content on the grid side. The three-phase rectifier bridge uses diodes as power devices to form a three-phase uncontrolled rectification. This unit can convert AC high voltage into AC low voltage, and then convert it into DC voltage.

[0043] The dual-mode converter unit mainly includes a supporting capacitor and an H-bridge composed of power devices, wherein the supporting capacitor is connected between the positive and negative poles of the DC bus, the input end of the H-bridge is connected to the DC bus, and the output end is connected to the impedance matching unit. The supporting capacitor and the H-bridge together constitute a power unit module, and multiple power unit modules are connected together in parallel, thereby increasing the output power of the device. In this embodiment, the device operates in an AC mode, in which the H-bridge circuit outputs AC power through program control. This unit can stabilize the DC bus voltage and can output the input DC power as adjustable AC power through the H-bridge circuit.

[0044] The impedance matching unit mainly includes an output reactor and an isolating switch, wherein the input end of the reactor is connected to the output end of the H-bridge, the output end is connected to the input end of the isolating switch, and the output end of the isolating switch is connected to the electrode end of the arc furnace. In this embodiment, the device works in AC mode, and the output reactor is configured with the parameters required for the AC mode. This unit configures the reactor according to the dual-mode converter unit, which plays a role in improving the power factor and ensuring the safety of the device.

[0045] The dual-mode electric arc furnace mainly includes electrodes and an electric furnace body, wherein the electrodes are connected to an impedance matching unit. In this embodiment, the dual-mode electric arc furnace in the DC mode has three electrodes on the top and one electrode on the bottom but is not used. When the dual-mode electric arc furnace works in the AC mode, all the electrodes on the top are in use and the electrodes on the bottom are disconnected. This device uses the arc generated between the electrodes to melt the raw materials.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. An arc furnace smelting device based on a dual-mode flexible power supply, characterized in that: The electric arc furnace smelting device includes a dual-mode flexible power supply and a dual-mode electric arc furnace. The dual-mode flexible power supply converts the high-voltage alternating current of the front-end power grid into low-voltage alternating current or low-voltage direct current and inputs it into the dual-mode electric arc furnace of the corresponding mode, wherein: The dual-mode flexible power supply includes a rectifier unit, a dual-mode converter unit, and an impedance matching unit. The rectifier unit is connected to the front-end power grid to convert the high-voltage AC power of the front-end power grid into low-voltage DC power. The dual-mode converter unit then converts the input DC power into DC power or AC power of the target mode, and an impedance matching unit is set between the dual-mode converter unit and the dual-mode arc furnace to adjust the power factor. The dual-mode electric arc furnace includes a plurality of electrodes and an electric furnace body, wherein the electrodes are divided into furnace top electrodes and furnace bottom electrodes, and the DC or AC working mode of the dual-mode electric arc furnace is adjusted according to the on-off status of the electrodes at the corresponding positions.

2. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 1 is characterized in that: The rectifier unit includes a phase-shifting transformer and a three-phase rectifier bridge. The input end of the phase-shifting transformer is connected to the front-end power grid, and the output end is connected to the three-phase rectifier bridge. The output end of the three-phase rectifier bridge is connected to the dual-mode converter unit. The phase-shifting transformer is a multi-winding phase-shifting transformer, and the number of windings is determined according to the grid-side harmonic target value and corresponds to the number of three-phase rectifier bridges. The three-phase rectifier bridge is an uncontrolled rectifier bridge, and diodes are used as power devices.

3. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 1 is characterized in that: The dual-mode converter unit includes a supporting capacitor and an H-bridge composed of power devices, wherein the supporting capacitor is connected between the positive and negative poles of the DC bus output by the rectifier unit, the input end of the H-bridge is connected to the DC bus, and the output end is connected to the impedance matching unit; the supporting capacitor and the H-bridge constitute a modular power unit, and the number of power units is adjusted according to power requirements.

4. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 3 is characterized in that: When the dual-mode converter unit aims to output direct current, the H-bridge circuit is controlled to output a chopper circuit; when the dual-mode converter unit aims to output alternating current, the H-bridge circuit is controlled to convert the input direct current into alternating current for output.

5. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 1 is characterized in that: The impedance matching unit includes an output reactor and an isolating switch, wherein the reactor input end is connected to the H-bridge output end, the output end is connected to the isolating switch input end, and the isolating switch output end is connected to the electrode end of the arc furnace; the value of the reactor is determined according to the required power factor.

6. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 1 is characterized in that: The electrodes of the dual-mode electric arc furnace are connected to an impedance matching unit, and direct current or alternating current generates an arc between the electrodes of the dual-mode electric arc furnace, thereby melting the raw materials in the electric furnace body.

7. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 6 is characterized in that: In the DC working mode, all the top electrodes and bottom electrodes of the dual-mode electric arc furnace are in a connected state; in the AC working mode, all the top electrodes of the dual-mode electric arc furnace are in a connected state, and all the bottom electrodes are in a disconnected state.

8. The arc furnace smelting device based on a dual-mode flexible power supply according to claim 7 is characterized in that: The number of the furnace top electrode and the furnace bottom electrode of the dual-mode electric arc furnace is set to at least one.

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