Direct current commutated power supply and control method for electric arc furnace, smelting furnace and melting separation furnace

Abstract

This invention relates to a DC commutation power supply and control method for electric arc furnaces, submerged arc furnaces, and melting furnaces, belonging to the field of metallurgical power technology, and is used to solve the problems of uneven electrode loss and uneven molten pool temperature distribution in multi-electrode systems. The power supply includes a phase-shifting transformer, a converter power module, and a converter controller. The primary side of the phase-shifting transformer is connected to the power grid, and the secondary side is connected to the input terminal of the converter power module. After AC-to-controllable DC conversion by the converter power module, the output controllable DC power is connected to the electrodes via a short grid. The secondary side of the phase-shifting transformer has one or more output terminals. The converter power module includes one or more sets of converter power components. When used in conjunction with the method described herein, the energy distribution uniformity of multi-electrode systems can be significantly improved, electrode consumption can be balanced, and the overall furnace service life can be extended. This can save smelting costs, and the controllable strong excitation polarity switching accelerates furnace charge melting, improving smelting stability and efficiency.

Description

Technical Field

[0001] This invention relates to the field of metallurgical power technology, and in particular to a DC commutation power supply and control method for electric arc furnaces, submerged arc furnaces and melting furnaces. Background Technology

[0002] With the increasing demands of modern industry for metallurgical production efficiency and product quality, traditional AC electric furnaces have gradually revealed various limitations during operation. In contrast, DC power supply technology is receiving increasing attention from the metallurgical industry due to its significant advantages in arc stability, energy efficiency control, and grid compatibility.

[0003] DC electric arc furnaces typically use direct current for power supply, featuring stable arc combustion, concentrated energy, high thermal efficiency, and low power consumption. Furthermore, due to smaller input current fluctuations, the impact on the power grid is significantly reduced, resulting in a higher grid-side power factor and contributing to improved overall grid stability. However, despite the advantages of DC electric arc furnaces over AC furnaces in several aspects, their long-term widespread application still faces a key technical bottleneck—the reliability and lifespan of the bottom electrode in conventional single-cathode DC furnaces with a bottom anode. As a critical component of the current loop, the bottom anode is exposed to high-temperature, highly corrosive smelting environments, making it prone to burn-out and corrosion. This necessitates frequent furnace shutdowns for maintenance or even replacement, severely impacting production continuity and economic efficiency. Moreover, under conditions of poor charge conductivity or uneven distribution of non-metallic materials within the furnace, difficulties in arc ignition and arc interruption often occur, requiring recharging or adjustments to the batching structure, further increasing operational complexity and production costs.

[0004] To adapt to large-capacity, high-power smelting scenarios, such as high-power electric arc furnaces, submerged arc furnaces, and melting furnaces, multi-electrode arrangements have gradually become the mainstream direction of technological development. This type of structure typically employs multiple top-mounted electrodes, serving as both cathodes and anodes, to enhance the uniformity of energy distribution within the furnace and the stability of the smelting process. However, multi-electrode once-through furnaces also face a series of unresolved problems in actual operation: due to the directional movement of charged particles in the DC arc, electrons move at high speed from the cathode to the anode, resulting in the anode experiencing higher energy impact and heat load, causing the positive electrode (anode) to be consumed significantly faster than the negative electrode (cathode). Simultaneously, this polarity effect also exacerbates the thermal and chemical erosion of the furnace lining in the positive electrode region, accelerating the wear and tear of refractory materials in this area, thus adversely affecting the overall furnace lining life and the stability of the furnace structure. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a DC commutation power supply and control method for electric arc furnaces, submerged arc furnaces and melting furnaces, so as to improve the energy distribution balance of multi-electrode systems, balance electrode consumption and extend the overall furnace service life, save smelting costs, controllable strong excitation switching polarity, accelerate furnace charge melting, improve smelting stability and efficiency, and shorten production time.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A DC commutation power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace includes: a phase-shifting transformer, a converter power supply module, and a converter controller;

[0008] The phase-shifting transformer has its primary side connected to the power grid and its secondary side connected to the input terminal of the converter power supply module. After the AC-to-controllable DC conversion of the converter power supply module, the output controllable DC power is connected to the electrode through a short grid.

[0009] The converter power module includes one or more sets of converter power components. The input terminal of each set of converter power components is connected to one secondary output terminal of the phase-shifting transformer. The output terminal of each set of converter power components is a set of positive and negative outputs with reversible polarity.

[0010] The secondary side of the phase-shifting transformer has one or more output windings. When there are multiple windings, they form multiple phase-shifting output terminals.

[0011] The output terminal of the power converter is connected to a corresponding set of dual electrodes, and when multiple electrodes are working, the number of electrodes is twice the number of power converter components.

[0012] The power converter assembly consists of two anti-parallel rectifier units and one output reactor.

[0013] Furthermore, the two rectifier units are a positive rectifier unit and a negative rectifier unit, and the rectifier units are composed of a three-phase bridge rectifier circuit or a three-phase half-wave rectifier circuit made of thyristors.

[0014] Furthermore, in the converter power assembly, the input terminals of the two rectifier units are both connected to the same secondary winding of the phase-shifting transformer.

[0015] Furthermore, in the power converter component, either the positive or negative output terminal of the two rectifier units is connected to the output reactance.

[0016] Furthermore, the phase-shifting transformer can integrate an on-load tap changer. The number and range of tap changer positions are set according to the number of output windings of the phase-shifting transformer, the single-stage adjustment percentage, the system voltage fluctuation requirements, and the reactive power compensation requirements, among other process conditions.

[0017] A control method for a DC commutated power supply of an electric arc furnace, a submerged arc furnace, and a melting furnace, wherein the converter controller is responsible for the commutation control and stable output current of the converter power supply module, and monitors the smelting operation stages, the operation stages including at least an arc initiation stage and a melting stage, the melting stage being further divided into a polarity fixing period and a polarity commutation period; including the following steps:

[0018] S1: Real-time acquisition of the voltage and current output of each group of electrode circuits, calculation of power value, and detection of the grid-side voltage phase synchronization signal.

[0019] S2: Based on the given current signal I set The initial sign is used to determine the polarity of the initial arc, and then to determine whether the rectifier unit enabled in each group of converter power components is the positive group or the negative group. The converter controller sets the ramp time for arc initiation to determine the arc initiation duration.

[0020] S3: Collect the current value and current setpoint I in each electrode circuit. set The difference is input into its current regulator, and the synchronization signal is taken as the phase reference of the trigger pulse. The output of the regulator is used as the adjustment amount of the thyristor trigger angle, and each group of converter power components is independently current controlled.

[0021] S4: When the polarity is fixed, the converter controller sets the DC commutation cycle, and the commutation cycle duration can be adjusted during the smelting process.

[0022] S5: During the polarity reversal period, when the loop current value |I| drops to the current polarity switching threshold I th At this time, the converter controller is set with an appropriate dead time, and the initial firing angle of the rectifier unit after commutation is set to [value missing]. At the same time, it quickly detects whether the thyristors of the currently operating rectifier unit are all turned off, and after waiting for the dead time, it triggers another set of rectifier units to achieve controllable strong excitation switching polarity without interruption of arc.

[0023] S6: When overcurrent and / or overpower occur in each group of electrode circuits, the trigger pulse is directly blocked and / or the trigger angle of the currently operating rectifier unit is quickly increased to a certain value, forcing it to switch from rectifier operation to inverter operation, thereby rapidly reducing the output current and power.

[0024] Among them, the given current signal I for each group of converter power components set The expression is:

[0025]

[0026] Among them, I N The rated output current value for each group of electrodes.

[0027] 1. Arc initiation stage t1~t2: t1 is the initial arc initiation time, t2 is the time when the current in each group of electrode circuits rises from zero to the rated current value, k1 is the arc initiation slope, and the positive or negative sign indicates the initial arc initiation polarity.

[0028] 2. Melting stage t>t2:

[0029] 1) Period of polarity fixation :I set The value is fixed, and the positive or negative sign indicates the working polarity;

[0030] 2) Polarity reversal period t3 and t6 are the times when the current begins to decrease from its rated value, and t4 and t7 are the times when the current decreases to the polarity switching threshold ±I. th At the specified times, t5 and t8 are the times when the current rises to the rated value, k2 is the polarity commutation slope, and the positive and negative signs indicate the commutation polarity. A positive sign indicates switching from positive to negative, and a negative sign indicates switching from negative to positive.

[0031] Furthermore, in S2, the initial sign of the given current signal for each group of converter power components is determined by the distribution of the furnace charge. When a new batch is produced, the initial sign of the given current signal is determined by the distribution of the furnace charge and the loss difference of each group of electrodes.

[0032] Furthermore, in S4, the DC commutation cycle of each group of power converter components is determined by the combined electrode loss and the temperature distribution of the material area. When the loss difference between the two electrodes in each group is large or the temperature difference in the material area below the electrodes is large, the commutation cycle duration is adjusted in time to balance the electrode loss and temperature distribution.

[0033] Furthermore, in S5, the current polarity switching threshold is a percentage of the rated output current of each group of electrodes. The polarity switching threshold and the initial firing angle of the rectifier unit after switching are both determined by the furnace type, furnace charge composition and smelting process.

[0034] Optionally, the arc initiation slope and polarity commutation slope of a given current signal are calculated according to the following formulas:

[0035]

[0036] Among them, arc initiation time and reversal duration It is a percentage value of the DC commutation cycle, I N I is the rated output current value for each group of electrodes. th This is the threshold for switching current polarity.

[0037] A method for extending the power of a DC commutated power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace includes the following:

[0038] (1) Determine the number, connection method and phase shift angle of the secondary winding of the phase-shifting transformer according to the power level required by the power system;

[0039] (2) Configure the number of converter power components and rectifier units according to the number of secondary windings of the phase-shifting transformer.

[0040] The beneficial effects of this invention are as follows:

[0041] (1) The method of the present invention provides a DC commutation power supply for electric arc furnace, electric arc furnace and melting furnace, which can flexibly configure the number of power components to match the furnace capacity and the required power level. When the phase-shifting transformer has multiple secondary windings, it can form a multi-pulse rectification with the power group, thereby improving the grid-side power factor and the furnace power.

[0042] (2) The method of the present invention provides a control method for DC commutation power supply of electric arc furnace, electric arc furnace and melting furnace. The algorithm is easy to implement, simple to operate and effective. It can be widely used in various DC furnace smelting occasions.

[0043] (3) The method of the present invention provides a DC switching power supply and control method for electric arc furnace, electric arc furnace and melting furnace, which can significantly improve the energy distribution balance of multi-electrode system, balance electrode consumption and extend the overall furnace service cycle, save smelting costs, and control the strong excitation switching polarity, accelerate furnace charge melting, improve smelting stability and efficiency, and shorten production time.

[0044] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0046] Figure 1 This is a schematic diagram of the DC commutation power supply connection for the dual-top electrode electric arc furnace in Example 1;

[0047] Figure 2 This is a schematic diagram of the DC commutation power supply connection for the four-top electrode melting furnace in Example 2;

[0048] Figure 3 This is a schematic diagram of the DC commutation power supply connection for the six-top electrode submerged arc furnace in Example 3;

[0049] Figure 4 (a) is a schematic diagram of the converter power component topology in this invention;

[0050] Figure 4 (b) is a schematic diagram of the rectifier unit topology in this invention;

[0051] Figure 5 This is a flowchart of the DC commutation power supply control method described in this invention;

[0052] Figure 6 This is a schematic diagram of the given current signal of the converter power component in this invention;

[0053] Reference numerals: Phase-shifting transformer 201, power converter module 210, power converter controller 220, first power converter component 211, second power converter component 212, third power converter component 213, first furnace top electrode E1, second furnace top electrode E2, third furnace top electrode E3, fourth furnace top electrode E4, fifth furnace top electrode E5, sixth furnace top electrode E6. Detailed Implementation

[0054] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed 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 are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0055] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0056] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0057] To facilitate understanding, the present invention provides three implementation examples, and the specific embodiments are described in detail below with reference to the accompanying drawings.

[0058] like Figures 1-3 As shown, the DC commutated power supply of the present invention includes a phase-shifting transformer 201, a converter power supply module 210, and a converter controller 220. The primary side of the phase-shifting transformer 201 is connected to the power grid, and the secondary side is connected to the input terminal of the converter power supply module 210. After AC-to-controllable DC conversion by the converter power supply module 210, the output controllable DC power is connected to the electrodes via a short network. The phase-shifting transformer 201 may integrate an on-load tap changer. The number and range of tap changers are set according to the number of output windings of the phase-shifting transformer, the percentage of adjustment per tap, system voltage fluctuation requirements, and reactive power compensation requirements, among other process conditions.

[0059] In Example 1, as Figure 1 As shown, the secondary side of the phase-shifting transformer 201 has a single output winding; the converter power module 210 includes a single set of converter power components 211, the input terminal of the converter power component 211 is connected to the single secondary side output terminal of the phase-shifting transformer 201, and the output terminal of the converter power component 211 is a set of positive and negative outputs with reversible polarity, connected to the first furnace top electrode E1 and the second furnace top electrode E2.

[0060] In Example 2, as Figure 2 As shown, the secondary side of the phase-shifting transformer 201 has two output windings, forming two phase-shifting output terminals; the power converter module 210 includes two sets of power converter components 211 and 212. The input terminal of the power converter component 211 is connected to the first secondary side output terminal of the phase-shifting transformer 201, and the input terminal of the power converter component 212 is connected to the second secondary side output terminal of the phase-shifting transformer 201. The output terminal of the power converter component 211 is a set of positive and negative outputs with reversible polarity, connected to the first furnace top electrode E1 and the second furnace top electrode E2. The output terminal of the power converter component 212 is a set of positive and negative outputs with reversible polarity, connected to the third furnace top electrode E3 and the fourth furnace top electrode E4.

[0061] In Example 3, as Figure 3As shown, the secondary side of the phase-shifting transformer 201 has three output windings, forming three phase-shifting output terminals; the power converter module 210 includes three sets of power converter components 211, 212, and 213. The input terminal of power converter component 211 is connected to the first secondary side output terminal of the phase-shifting transformer 201, the input terminal of power converter component 212 is connected to the second secondary side output terminal of the phase-shifting transformer 201, and the input terminal of power converter component 213 is connected to the third secondary side output terminal of the phase-shifting transformer 201. The output terminal of power converter component 211 is a set of positive and negative outputs with reversible polarity, connected to the first furnace top electrode E1 and the second furnace top electrode E2. The output terminal of power converter component 212 is a set of positive and negative outputs with reversible polarity, connected to the third furnace top electrode E3 and the fourth furnace top electrode E4. The output terminal of power converter component 213 is a set of positive and negative outputs with reversible polarity, connected to the fifth furnace top electrode E5 and the sixth furnace top electrode E6.

[0062] like Figure 4 As shown in (a), the power converter assembly consists of two anti-parallel rectifier units and one output reactor. Either the positive or negative output terminal of the two rectifier units can be connected to the output reactor. The two rectifier units are a positive rectifier unit and an anti-rectifier unit, respectively, and the input terminals of both rectifier units are connected to the same secondary output winding of the phase-shifting transformer. Figure 4 As shown in (b), the rectifier unit is a three-phase bridge rectifier circuit composed of thyristors, or it can be a three-phase half-wave rectifier circuit.

[0063] The flowchart of the DC commutation power supply control method provided in this invention is as follows: Figure 5 As shown, the converter controller is responsible for the commutation control and stable output current of the converter power module, and monitors the smelting operation stages. The operation stages include at least the arc initiation stage and the melting stage, which is further divided into a polarity fixing period and a polarity commutation period; specifically, it includes the following steps:

[0064] S1: Real-time acquisition of the voltage and current output of each group of electrode circuits, calculation of power value, and detection of the grid-side voltage phase synchronization signal.

[0065] S2: Based on the given current signal I set The initial sign is used to determine the polarity of the initial arc, and then to determine whether the rectifier unit enabled in each group of converter power components is the positive group or the negative group. The converter controller sets the ramp time for arc initiation to determine the arc initiation duration.

[0066] S3: Collect the current value and current setpoint I in each electrode circuit. set The difference is input into its current regulator, and the synchronization signal is taken as the phase reference of the trigger pulse. The output of the regulator is used as the adjustment amount of the thyristor trigger angle, and each group of converter power components is independently current controlled.

[0067] S4: When the polarity is fixed, the converter controller sets the DC commutation cycle, and the commutation cycle duration can be adjusted during the smelting process.

[0068] S5: During the polarity reversal period, when the loop current value |I| drops to the current polarity switching threshold I th At this time, the converter controller is set with an appropriate dead time, and the initial firing angle of the rectifier unit after commutation is set to [value missing]. At the same time, it quickly detects whether the thyristors of the currently operating rectifier unit are all turned off, and after waiting for the dead time, it triggers another set of rectifier units to achieve controllable strong excitation switching polarity without interruption of arc.

[0069] S6: When overcurrent or overpower occurs in each group of electrode circuits, the trigger pulse is directly blocked or the trigger angle of the currently operating rectifier unit is quickly increased to a certain value, forcing it to switch from rectifier operation to inverter operation, thereby rapidly reducing the output current and power.

[0070] The given current I for each group of converter power components set The expression is as follows. Figure 6 A schematic diagram of the given current when the arc is initiated in the positive direction is given.

[0071]

[0072] Among them, I N The rated output current value for each group of electrodes.

[0073] (1) Arc initiation stage t1~t2: t1 is the initial arc initiation time, t2 is the time when the current in each group of electrode circuits rises from zero to the rated current value, k1 is the arc initiation slope, and the positive or negative sign indicates the initial arc initiation polarity.

[0074] (2) Melting stage t>t2:

[0075] a. Period of polarity fixation :I set The value is fixed, and the positive or negative sign indicates the working polarity;

[0076] b. Polarity reversal period t3 and t6 are the times when the current begins to decrease from its rated value, and t4 and t7 are the times when the current decreases to the polarity switching threshold ±I. th At the specified times, t5 and t8 are the times when the current rises to the rated value, k2 is the polarity commutation slope, and the positive and negative signs indicate the commutation polarity. A positive sign indicates switching from positive to negative, and a negative sign indicates switching from negative to positive.

[0077] In S2, the initial sign of the given current signal for each group of converter power components is determined by the distribution of the furnace charge. When a new batch is produced, the loss difference between the two electrodes in each group must also be considered.

[0078] In S4, the DC commutation cycle of each group of power converter components is determined by a combination of electrode losses and material temperature distribution. When the loss difference between the two electrodes in each group and / or the temperature difference in the material area below the two electrodes reaches a certain value, the commutation cycle duration is adjusted in a timely manner to balance electrode losses and temperature distribution.

[0079] In S5, the current polarity switching threshold is a percentage of the rated output current of each group of electrodes. The polarity switching threshold and the initial firing angle of the rectifier unit after switching are determined by the furnace type, furnace charge composition and smelting process.

[0080] The arc initiation slope and polarity commutation slope of the given current signal are calculated according to the following formulas:

[0081]

[0082] Among them, arc initiation time and reversal duration It is a percentage value of the DC commutation cycle, I N I is the rated output current value for each group of electrodes. th This is the threshold for switching current polarity.

[0083] The power expansion method for DC commutated power supplies of electric arc furnaces, submerged arc furnaces, and melting furnaces in this invention includes the following:

[0084] (1) Determine the number, connection method and phase shift angle of the secondary winding of the phase-shifting transformer according to the power level required by the power system;

[0085] (2) Configure the number of converter power components and rectifier units according to the number of secondary windings of the phase-shifting transformer.

[0086] In summary, the present invention provides a DC commutation power supply and control method for electric arc furnaces, submerged arc furnaces, and melting furnaces, which can significantly improve the energy distribution balance of multi-electrode systems, balance electrode consumption, and extend the overall furnace service life. It can save smelting costs, and controllable strong excitation polarity switching can accelerate furnace charge melting, improve smelting stability and efficiency, and shorten production time. It can be widely applied to various DC furnace smelting applications with multi-electrode configurations.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A DC commutated power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace, characterized in that, include: Phase-shifting transformers, converter power supply modules, and converter controllers; The phase-shifting transformer has its primary side connected to the power grid, and its secondary side undergoes AC-to-controllable DC conversion by the converter power module. The output controllable DC power is connected to the electrodes through a short grid. The secondary side of the phase-shifting transformer has multiple output windings and multiple phase-shifting output terminals; The power converter module includes multiple sets of power converter components. The input terminal of each power converter component is connected to one secondary output terminal of the phase-shifting transformer. The output terminal of each power converter component is a set of positive and negative outputs with reversible polarity. The output terminal of the power converter component is connected to a corresponding set of dual electrodes. The number of electrodes is twice the number of power converter components. The power converter component is composed of two anti-parallel rectifier units and one output reactor. The converter controller is responsible for the commutation control and stable output current of the converter power module, and monitors the smelting working stage. The working stage includes at least the arc initiation stage and the melting stage, and the melting stage is further divided into the polarity fixed period and the polarity commutation period. Among them, the given current signal I for each group of converter power components set The expression is: Among them, I N The rated output current value for each group of electrodes; (1) Arc initiation stage t1~t2: t1 is the initial arc initiation time, t2 is the time when the current in each group of electrode circuits rises from zero to the rated current value, k1 is the arc initiation slope, and the positive or negative sign indicates the initial arc initiation polarity; (2) Melting stage t>t2: a. Period of polarity fixation :I set The value is fixed, and the positive or negative sign indicates the working polarity; b. Polarity reversal period t3 and t6 are the times when the current begins to decrease from its rated value, and t4 and t7 are the times when the current decreases to the polarity switching threshold ±I. th At the specified times, t5 and t8 are the times when the current rises to the rated value, k2 is the polarity commutation slope, and the positive and negative signs indicate the commutation polarity. A positive sign indicates switching from positive to negative, and a negative sign indicates switching from negative to positive.

2. The DC commutation power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace according to claim 1, characterized in that, The two rectifier units are a positive rectifier unit and a negative rectifier unit, and each rectifier unit is composed of a three-phase bridge rectifier circuit or a three-phase half-wave rectifier circuit made of thyristors.

3. The DC commutation power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace according to claim 1, characterized in that, The input terminals of the two rectifier units of the power converter are both connected to the same secondary winding of the phase-shifting transformer, and either the positive or negative output terminal of the two rectifier units of the power converter is connected to the output reactance.

4. The DC commutation power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace according to claim 1, characterized in that, The phase-shifting transformer has an integrated on-load tap changer. The number and / or range of tap changer positions are set according to the number of output windings of the phase-shifting transformer, the percentage of adjustment per tap, the system voltage fluctuation requirements, and the reactive power compensation requirements and process conditions.

5. A control method for a DC commutated power supply for an electric arc furnace, a submerged arc furnace, and a melting furnace as described in claim 1, characterized in that, Includes the following steps: S1: Real-time acquisition of the voltage and current output of each group of electrode circuits, calculation of power value, and detection of grid-side voltage phase synchronization signal; S2: Based on the current setting value I set The initial sign is used to determine the polarity of the initial arc, and then to determine whether the rectifier unit enabled in each group of converter power components is the positive group or the negative group. The arc duration is determined according to the ramp time set by the converter controller. S3: Collect the current value I and the current setpoint I in each electrode circuit. set The difference is input into its current regulator, and the synchronization signal is taken as the phase reference of the trigger pulse. The output of the regulator is used as the adjustment amount of the thyristor trigger angle, and each group of converter power components is independently current controlled. S4: During the period of fixed polarity, the converter controller sets the DC commutation cycle and adjusts the commutation cycle duration during the smelting process; S5: During the polarity reversal period, the loop current value |I| drops to the current polarity switching threshold I. th At that time, the converter controller is set with an appropriate dead time, and the initial firing angle of the rectifier unit after commutation is set to 0. At the same time, it quickly detects whether the thyristors of the currently working rectifier unit are all turned off, and after waiting for the dead time, it triggers another set of rectifier units to achieve controllable strong excitation switching polarity without interruption of arcing. S6: If overcurrent or overpower occurs in each electrode circuit, the trigger pulse will be blocked directly or the trigger angle of the currently operating rectifier unit will be increased to a specified value, forcibly switching the rectifier operation state to the inverter operation state, and rapidly reducing the output current and power.

6. The control method for the DC commutated power supply of the electric arc furnace, submerged arc furnace, and melting furnace according to claim 5, characterized in that, In S2, the initial sign of the given current signal for each group of converter power components is determined by the distribution of the furnace charge and / or the loss difference between the two electrodes in each group.

7. The control method for the DC commutated power supply of the electric arc furnace, submerged arc furnace, and melting furnace according to claim 5, characterized in that, In S4, the DC commutation cycle of each group of power converter components is determined by the electrode loss and / or the temperature distribution of the material area. When the loss difference between the two electrodes in each group and / or the temperature difference in the material area below the electrodes reaches a certain value, the commutation cycle duration is adjusted to balance the electrode loss and temperature distribution.

8. The control method for the DC commutated power supply of the electric arc furnace, submerged arc furnace, and melting furnace according to claim 5, characterized in that, In S5, the current polarity switching threshold I th The percentage of the rated output current for each group of electrodes, and the polarity switching threshold I. th The initial firing angle of the rectifier unit after switching is The determination is based on the furnace type, furnace charge composition, and smelting process.

9. The control method for the DC commutation power supply of the electric arc furnace, submerged arc furnace, and melting furnace according to claim 5, characterized in that, The arc initiation slope k1 and polarity commutation slope k2 of a given current signal are calculated using the following formulas: Among them, arc initiation time and reversal duration I is a percentage value of the DC commutation cycle. N I is the rated output current value for each group of electrodes. th This is the threshold for switching current polarity.

10. The control method for the DC commutated power supply of the electric arc furnace, submerged arc furnace, and melting furnace according to claim 5, characterized in that, To match the furnace type and smelting process conditions, the power of the converter components is extended, including: (1) Determine the number, connection method and phase shift angle of the secondary winding of the phase-shifting transformer according to the power level required by the power system; (2) Configure the number of converter power components and rectifier units according to the number of secondary windings of the phase-shifting transformer.

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