Power supply device for electric furnaces

Abstract

A power supply device (10) used in an electric furnace (11), It is configured to convert electrical energy supplied from a three-phase power grid (13) and to supply at least one pair of single-phase AC currents and voltages having a desired intensity and frequency as output, and comprises at least one base power module (20, 120, 220) having at least two submodules (21, 21A~21F), Each of the at least two submodules (21, 21A to 21F) comprises a power supply device (10) including a device (27), a DC intermediate circuit (28), and at least one inverter device (29).

Description

Technical Field

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[0001] The present invention relates to a power supply device for an electric furnace used for steelmaking applications for producing iron, or for other fields for processing metallic or vitreous materials, or other materials similar or equivalent thereto. In particular, this power supply device is applicable to an electric furnace operating with alternating current and alternating voltage.

Background Art

[0002] As is known, an electric furnace used for melting metals in steelmaking applications requires an efficient power supply system for supplying high power.

[0003] It is also known that the melting process generally consists of a plurality of steps, usually including a boring step of the metal material, a melting step of the material, and a refining step.

[0004] Since the power and electrical energy required by the electric furnace in the melting process may vary greatly for each step, it is necessary to appropriately adjust the amount of electrical energy supplied at any time.

[0005] In particular, the power consumed by the electric furnace in the boring step and melting step of the metal material is generally greater than the power required in the refining step, and depending on the type of material charged into the furnace, the power consumption may vary greatly even within the same step.

[0006] A power supply device for an electric arc furnace is generally known to be connected to a three-phase power grid and to convert its voltage and current into a voltage and current suitable for driving the electrodes of the electric arc furnace.

[0007] Known devices include a rectifier device for converting alternating current supplied from the power grid into direct current, and one or more inverter devices for converting the direct current back into alternating current to supply power to the electrodes.

[0008] Subsequently, the amount of power supplied to the electrodes is adjusted by giving appropriate commands to the inverter device.

[0009] Generally, these inverter devices consist of one or more switches that are switched on and off at high frequencies. Therefore, when it is necessary to dynamically change the amount of energy supplied to an electric furnace, or when there are multiple inverter devices, voltage fluctuations can occur, which can affect the circuit in a reverse flow and cause problems in the power grid.

[0010] In fact, these inverter devices modulate the current, generating harmonics that can be harmful when they enter the power grid.

[0011] Known types of devices are described, for example, in U.S. Patent No. 1,1346605 and U.S. Patent No. 1,1382191.

[0012] Therefore, there is a need to improve power supply devices for AC or DC user devices that can overcome at least one drawback of the conventional technology.

[0013] One object of the present invention is to provide a power supply device and method for an electric arc furnace that can effectively control the operation and power of the electric furnace as required.

[0014] Another object of the present invention is to provide and implement an apparatus that can adjust the characteristics of the voltage and current supplied to an electric furnace, particularly an arc furnace, and ensure the stability of the electric arc at each step of the melting process.

[0015] Another objective of the present invention is to complete a balanced power supply device that minimizes the impact (disruption) on the power grid.

[0016] Another objective of the present invention is to complete a power supply device that prevents the generation of current harmonics that could be harmful if they flow into the power grid.

[0017] Another objective of the present invention is to complete a power supply device having a modular structure, thereby enabling flexible adaptation to the requirements of the plant where it is installed and the characteristics of the electric furnace to which it is applied.

[0018] Another objective of the present invention is to perfect a method for supplying power to an electric furnace, thereby enabling the supply of the necessary and desired amount of power as needed, while simultaneously preventing disruptions to the power grid.

[0019] The applicant invented, tested, and embodied the present invention in order to overcome the shortcomings of the prior art and to achieve these and other objectives and advantages. [Overview of the project]

[0020] The present invention is defined and its features are described in the independent claims. Dependent claims describe other features of the invention and variations of the main inventive concept.

[0021] In accordance with the above objectives, a power supply device is provided that is suitable for supplying power to electric furnaces used in steelmaking applications or other fields that process metallic or glassy materials or other similar or equivalent materials.

[0022] The device includes at least one base power module that is connected to the three-phase power grid and three-phase power lines when in use. The base power module is configured to convert electrical energy supplied from the power grid and output at least one pair of single-phase alternating current and voltage having a desired intensity and frequency.

[0023] Preferably, the power supply unit comprises multiple base modules, which are connected in parallel to each other between the three-phase network and the load to be powered.

[0024] The load to be supplied with power is, for example, an arc electric furnace, a submerged arc electric furnace, a pot furnace, or an electric furnace similar or equivalent thereto, in which electrodes are arranged penetrating the upper arch of the furnace, and is connected to a power line during use.

[0025] According to some embodiments, the base power module or each base power module includes at least two sub-modules, and each sub-module is suitable for supplying single-phase voltage and current.

[0026] In particular, the base power module or each base power module includes a number of sub-modules corresponding to the number of connections (i.e., number of phases) supplied at the output. According to the present invention, each sub-module includes a rectifying device configured to convert three-phase alternating current and voltage into direct current and voltage, a direct current intermediate circuit (DC link) configured to store electrical energy, and at least one inverter device connected to the intermediate circuit and configured to convert direct current and voltage to generate alternating current and voltage suitable for supplying different phases of the power line. The rectifying device, the intermediate circuit, and the inverter device are arranged continuously with each other.

[0027] In particular, at least one base module includes, for each phase supplied by the base power module at the output, a direct current intermediate circuit (DC link) and at least one inverter device connected to each DC link. Therefore, the number of DC links is the same as the number of phases.

[0028] For example, if the output phases are two, there are a total of two DC links; if the output phases are three, there are also three DC links; in the case of six phases, there are six DC links.

[0029] According to the present invention, all the intermediate circuits of the sub-modules are short-circuited with each other.

[0030] In other words, the DC intermediate circuits of all submodules belonging to the same base module are all at the same potential, which allows a set of harmonics to cancel each other out and obtain a common average value, thereby reducing the magnitude of disturbances in one or more submodules.

[0031] Furthermore, even if a failure occurs in the DC intermediate circuit of a submodule, other submodules can compensate for the failed submodule and supply energy to the inverter device connected to the failed DC intermediate circuit.

[0032] Therefore, this solution, through the redundancy of the rectifier devices and the short-circuit connections between each intermediate circuit, makes it possible to supply all desired output phase connections under any circumstances, even in the event of a power drop.

[0033] On the one hand, this configuration makes it possible to store energy, at least temporarily, and at the same time, by providing separation between the power grid and the load to which power should be supplied, it is possible to prevent disturbances and unwanted harmonic effects from the load side to the power grid side. On the other hand, it is also possible to absorb imbalances between at least two phases.

[0034] According to one aspect of the present invention, each submodule includes two or more, for example, two to eight inverter devices, all of which are connected in parallel to the same DC intermediate circuit and supply the same single output phase.

[0035] Preferably, each submodule contains 4 to 6 inverter devices.

[0036] In one embodiment of the present invention, the apparatus comprises at least one three-phase transformer device for each base module, the three-phase transformer device configured to convert electrical energy supplied from the power grid into electrical energy having voltage and current values ​​suitable for driving submodules.

[0037] Preferably, the transformer device may be physically separated from each submodule, located at a certain distance, installed in a different building, and connected to the corresponding submodule via appropriate cables.

[0038] In one embodiment of the present invention, the transformer device comprises a single transformer primary side having three-phase inputs connected to each phase of the power grid during use, and a plurality of transformer secondary sides connected to the respective three-phase outputs corresponding to each submodule. In this configuration, the single transformer primary side is coupled to all of the transformer secondary sides. This configuration makes it possible to reduce the impact on the grid side, i.e., the harmonic components and reactive power exchanged within the grid by the combination of the transformer secondary sides and the rectifier device.

[0039] According to some embodiments, the rectifier device comprises multiple rectifier circuits, particularly one rectifier circuit for each input phase, all of which are connected to the same DC intermediate circuit.

[0040] According to some embodiments, the phases on the secondary side of each transformer in the same base power module are out of phase with respect to each other, thereby achieving a balance of current and / or voltage within each base power module.

[0041] According to possible embodiments, in the case of two transformer secondary sides, each can have a positive and a negative phase angle with respect to a common reference.

[0042] In other embodiments, in the case of three transformer secondary sides, two of them may each be phase-shifted by a phase angle in one direction or the other relative to the third transformer, and similarly, the same applies to the case of four or more transformer secondary sides.

[0043] According to another aspect of the present invention, the apparatus comprises a plurality of base modules connected in parallel to one another between a power grid and a power line, each base module receiving three three-phase connections as inputs and supplying two, three, four, six or more single-phase voltage and current connections as outputs.

[0044] If the device comprises two or more base modules connected in parallel, the intermediate circuits of each submodule of each base power module are short-circuited only with other intermediate circuits within the same base power module, and not with intermediate circuits of other base power modules.

[0045] The number of base modules can be increased as needed. For example, the number of base power modules may be 2 to 60, such as 12, 24, 30, 36, 48, or an intermediate number (even or odd).

[0046] This modular configuration allows the power supply to be adapted to the plant's requirements, both during the design phase and in use. Specifically, during the design phase, the total number of base modules can be defined according to the required scale and productivity, and during use, the power supplied can be optimally adjusted as needed by, for example, activating only some of the base modules as required.

[0047] Generally, when two or more base power modules are present, the phase connections of each transformer device can be partially or completely different in order to balance and equalize the voltage and current not only within each base power module but also across all base power modules.

[0048] According to another aspect of the present invention, a method for supplying power to an electric furnace is: - A step of supplying a three-phase AC current and voltage having a predetermined frequency to at least one base module using a three-phase power grid, wherein the at least one base module includes two or more submodules, each of which is configured to receive a three-phase voltage and current at its input and to supply its respective single-phase AC voltage and current having a desired intensity and frequency at its output. - The step of energizing one or more electrodes of an electric furnace using single-phase AC voltage and current, It is equipped with.

[0049] According to one aspect of the power supply method of the present invention, Each of the aforementioned submodules includes: Rectification involves rectifying the respective phase voltages and currents to obtain a common DC voltage and current for the three phases, Temporary energy storage, A separation that separates the power grid and the electrodes via a DC intermediate circuit, An inversion method is used to reverse the DC voltage and current using at least one inverter device to obtain the respective single-phase AC voltage and current, A system is in place.

[0050] According to another aspect of the present invention, the method is configured to short-circuit all of the intermediate circuits of the at least one base power supply module and keep them at the same potential.

[0051] In this way, the inverter devices of each submodule belonging to the same base module operate with a common DC voltage and current. This common DC voltage and current can be considered to be the average value of the voltage and current supplied by the corresponding rectifier device in each submodule.

[0052] In one embodiment of the present invention, the method specifies supplying three-phase alternating current and voltage to a plurality of base modules connected in parallel to each other between a power grid and the power lines of the electrodes, and controlling and commanding at least the inverter devices of one or more of the plurality of base modules depending on a specific step of the melting process carried out in an electric furnace and / or the material to be melted, and changing one or more parameters of the current and voltage supplied to the electrodes as needed.

[0053] These and other aspects, features and advantages of the present invention will become apparent from the following description of some embodiments with reference to the accompanying drawings, which are provided as limited examples. [Brief explanation of the drawing]

[0054] [Figure 1] Figure 1 is a circuit diagram showing a first embodiment of a power supply device according to the present invention, comprising a base module having two submodules, and applied to an electric arc furnace. [Figure 2] Figure 2 is a circuit diagram showing a second embodiment of the power supply device according to the present invention, which comprises a base module having three submodules and is applied to an electric arc furnace. [Figure 3] Figure 3 is a circuit diagram showing a simplified circuit of the two submodules. [Figure 4] Figure 4 shows circuit diagrams of power supply devices according to several modifications, each comprising two base modules, each having three submodules, and is applied to electric arc furnaces. [Figure 5] Figure 5 shows a circuit diagram of a power supply device relating to another modification, in which each base module has six submodules and is applied to a submerged arc furnace. [Modes for carrying out the invention]

[0055] To facilitate understanding, the same reference numerals are used for identical common elements in the drawings whenever possible. Furthermore, elements and features of one embodiment are understood to be interchangeable or incorporated into other embodiments as appropriate without further explanation.

[0056] Herein, possible embodiments of the present invention will be described in detail. One or more examples are shown in the accompanying drawings as non-limiting examples. The expressions and terms used herein are also used for the purpose of illustrating non-limiting examples.

[0057] The embodiments described below with reference to the attached drawings relate to an electrical energy supply device 10 for an electric furnace 11, and more particularly for an AC electric furnace.

[0058] The electric furnace 11 is, for example, an electric arc furnace (EAF) or a submerged arc furnace (SAF), and is of a type that can be used in a steelmaking plant 15 to melt scrap and other metallic materials by an electric arc ignited by two or more electrodes 16A, 16B, 16C, 16D, 16E, 16F (collectively referred to as "16").

[0059] These electrodes 16 are generally inserted into the furnace vessel of the core from the top of the furnace and are usually movable toward or away from the material to be melted.

[0060] The power supply unit 10 includes an electrical energy supply means 12 capable of supplying electrical energy having predetermined voltage, current, and frequency values.

[0061] According to some embodiments, the electrical energy supply means 12 includes a three-phase power grid 13 configured to supply alternating current power. In Figure 1, the letters R, S, and T indicate three phases.

[0062] The power supply unit 10 is connected to the power grid 13 and the electric furnace 11 via appropriate input and output connection means.

[0063] Input and output connection means generally consist of connecting wires, connectors, and the like.

[0064] The device 10 includes at least one base power module 20, 120, 220 that is connected between the power grid 13 and the electric furnace 11 when in use. This module is configured to convert the power supplied from the power grid 13 and to output at least one pair of single-phase alternating current and voltage having a desired intensity and frequency.

[0065] Each phase supplied from the submodule can be connected to the electrodes 16 of the electric furnace 11 via the power line 32 as needed.

[0066] In particular, when two electrodes, 16A and 16B, are provided, each of the two phases can be connected to one of the electrodes 16A and 16B (see Figure 1).

[0067] If three electrodes 16 are provided, the power line 32 can be of the three-phase type, and each phase R, S, and T can be connected to the respective electrodes 16A, 16B, 16C, 16D, 16E, and 16F (see Figures 2, 4, and 5).

[0068] When there are few or many electrodes 16, it is possible to connect only some of the three phases R, S, and T, or to connect two or more phases to two or more electrodes 16.

[0069] The currents and voltages of phases R, S, and T supplied to electrode 16 can be varied according to the melting and / or refining process of the metal material in furnace 11.

[0070] For example, the current supplied to electrode 16 is on the order of tens of kA, and for an electric furnace 11 with a capacity of approximately 100 tons, it may be 40kA to 70kA. The power supplied to electrode 16 is on the order of tens of MW, and for example, it may be 35MW to 80MW.

[0071] In one embodiment of the present invention, the base modules 20, 120, and 220 include at least two submodules 21, each submodule capable of receiving three-phase power as input and supplying single-phase AC current and voltage as output. This output can be supplied, for example, to any of phases R, S, and T of a three-phase power line 32, or to any of the direct electrodes 16.

[0072] As an example, Figure 1 shows a first embodiment of a device 10 in which the base module 20 includes only two submodules 21, which are indicated by the letters A and B for ease of identification.

[0073] As will be explained below, the number of submodules 21 can be more than 2, for example, 3, 4, 6, or more.

[0074] Each submodule 21 includes a rectifier device 27 configured to convert DC current and voltage, a DC intermediate circuit 28 (DC link) common to all phases, and at least one inverter device 29 connected to the intermediate circuit 28 and configured to convert DC voltage and current to AC voltage and current, and these are arranged in series with respect to each other.

[0075] According to the present invention, all intermediate circuits 28 of the base power module 20 are short-circuited to each other.

[0076] In other words, each intermediate circuit 28 belonging to the same base power module 20 is provided with its respective electrical connection 22, 23 having substantially zero impedance or, in any case, negligible impedance, and as a result, the intermediate circuits 28 of all submodules 21 are at substantially the same potential.

[0077] In this way, the inverter devices 29 connected to each intermediate circuit 28 operate with the same DC voltage and current values, which are approximately equal to the average values ​​of the voltage and current of each submodule 21.

[0078] As shown in the attached drawing, the short-circuit connections 22 and 23 exist only between the intermediate circuits 28 of submodules 21 belonging to the same base power module 20. However, connections 22 and 23 do not exist between the intermediate circuits 28 of submodules 21 belonging to different base power modules 20.

[0079] According to some embodiments, the device 10 may include one or more inductors 17 connected downstream of the inverter device 29 for each submodule 21.

[0080] According to several embodiments, for example, as described with reference to Figure 3, each rectifier device 27 may include corresponding rectifier circuits 27R, 27S, and 27T for each phase.

[0081] The rectifier device 27 can be configured as a diode bridge or a thyristor bridge, and may include devices selected from diodes, silicon-controlled rectifiers (SCRs), gate-turn-off (GTO) thyristors, integrated gate-commuted thyristors (IGCTs), metal-oxide-semiconductor-controlled (MCTs), bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), silicon carbide (SiC) devices, and the like.

[0082] According to several embodiments, each submodule 21 is provided with its own DC intermediate circuit 28. One side of the intermediate circuit 28 is connected to a rectifier device, i.e., each rectifier circuit 27R, 27S, 27T, and the other side is connected to one or more inverter devices 29.

[0083] The intermediate circuit 28 may include one or more capacitors 35, such as a capacitor bank, which are suitable for storing energy and creating isolation between the rectifier device 27 and one or more inverter devices 29 (and thus between the power grid 13 and the electrodes 16 (i.e., power lines 32)).

[0084] According to some embodiments, the inverter device 29 may include one or more switches 36, which are selected from, for example, thyristors or transistors, such as gate turn-off (GTO) thyristors, integrated gate-commuted thyristors (IGCTs), metal-oxide-semiconductor controlled (MCT) thyristors, bipolar junction transistors (BJTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and insulated gate bipolar transistors (IGBTs). Typically, each switch 36 may also be connected to a corresponding diode (not shown).

[0085] According to some embodiments, each submodule 21 includes a plurality of inverter devices 29, which are connected in parallel to an intermediate circuit 28 and all supply the same output phase, for example, one of phases R, S, or T of the power line 32.

[0086] For example, M inverter devices 29 can be provided, and the number of M may be 2 to 8, preferably 4 to 6.

[0087] The operation of the inverter device 29, and consequently the switch, is controlled by the control unit 40 to obtain a current with a desired strength and frequency. The control unit 40 is shown as an example in Figure 3, but can be applied to all embodiments described herein.

[0088] The control unit 40 is configured to manage and command the inverter device 29 according to specific steps of the melting process carried out in the electric furnace 11, and can change one or more parameters of the current and voltage supplied to the electrode 16, such as intensity and / or frequency.

[0089] In possible embodiments of the present invention, the control unit 40 may include, or be connected to, an adjustment device 18 configured to adjust the power supply frequency of the voltage and current supplied to the electrode 16, thereby allowing the reactance value in the power supply circuit of the electrode 16 to be changed as needed.

[0090] For example, the adjustment device 18 may include a hysteresis modulator or a PWM (pulse width modulation) modulator.

[0091] The device 10 includes at least one three-phase transformer device 24, which is associated with at least one base power module 20, and the three-phase transformer device 24 is configured to convert power supplied from the power grid into power having voltage and current values ​​suitable for driving the submodule 21.

[0092] In particular, the device 10 is equipped with one transformer device 24 for each base module 20.

[0093] The transformer device 24 includes at least one transformer primary side 25 with three-phase inputs that connect to each phase of the power grid 13 when in use, and a plurality of transformer secondary sides 26, each of which is connected to a corresponding submodule 21 via a corresponding three-phase output.

[0094] The number of transformer secondary side 26 is equal to the number of phases supplied by the output, i.e., the number of submodules 21.

[0095] According to some embodiments, preferably, the transformer device 24 is physically separated from each submodule 21 and positioned at a certain distance. Alternatively, it may be installed in different buildings or different plant sites and connected to each submodule 21 using appropriate cables.

[0096] For example, the apparatus 10 includes a regulating unit G1 having at least submodules 20, 120, and 220, and optionally an inductor 17 located near the furnace 11, and also includes a transformer unit G2 including a transformer device 24, the transformer unit G2 being separated from the regulating unit G1 and located at a distance of several tens of meters or more.

[0097] As a possible variation, depending on the available space, the two units G1 and G2 can be installed within the same building.

[0098] In Figures 1, 2, and 4, the transformer secondary side 26 is exemplified by the letters R, S, and T, respectively, depending on the phase supplied by the associated submodule 21.

[0099] In one embodiment of the present invention, the transformer device 24 comprises a single transformer primary side 25 coupled to all of the transformer secondary sides 26.

[0100] According to some embodiments, the phases R, S, and T of the primary side 25 and secondary side 26 of the transformer can be connected in a star connection or a delta connection.

[0101] According to a preferred embodiment, the phases R, S, and T of the primary side 25 and secondary side 26 of the transformer are connected in a delta connection.

[0102] According to one aspect of the present invention, the phases of the secondary sides 26 of each transformer belonging to the same base power supply modules 20, 120, and 220 are connected with a phase difference from each other, so that a balance of current and / or voltage can be obtained within each base power supply module 20.

[0103] According to one embodiment of the present invention, the phases of the secondary sides 26 of each transformer belonging to the same base power supply modules 20, 120, and 220 are connected with a phase difference from each other, so that a balance of current and / or voltage can be obtained within each base power supply module 20.

[0104] In the example shown in Figure 1, each base module 20 has a transformer device 24 comprising one transformer primary side 25 and two transformer secondary sides 26 indicated by the letters R and S.

[0105] In this case, the phases of the two transformer secondary sides 26 are connected in a delta configuration and can have positive and negative phase angles α, respectively, that are symmetrical with respect to a common reference.

[0106] For example, the phase angle α can be between 15° and 25°.

[0107] Figure 2 shows a second embodiment of the device 10 having a base module 120, where each submodule 21 comprises a rectifier device 27, a DC intermediate circuit 28, and five inverter devices 29. In this case, the base module 120 is configured to supply different three-phase R, S, and T currents and voltages as outputs. The three intermediate circuits 28 are all connected to each other by short-circuit connections 22 and 23.

[0108] In the example shown in Figure 2, the transformer secondary side 26S has a phase angle of 0, while the remaining transformer secondary sides 26R and 26T are out of phase by positive and negative phase angles α, respectively.

[0109] Figure 5 shows another embodiment of the apparatus 10. For example, it is connected to a submerged arc (SAF) electric furnace 11 and has six electrodes 16A to 16F in this example, but the number may vary.

[0110] The device 10 in this embodiment has one or more base modules 220, each having six submodules 21, and the intermediate circuits 28 of these submodules are connected to each other by short-circuit connections 22, 23. In this example, there are five inverter devices 29, but as mentioned above, this number may be fewer or more.

[0111] In this case, the six submodules 21 of the base module 220 are connected in pairs to each phase R, S, and T of the power line 32, and each electrode 16 is connected to one of these phases R, S, and T. In this example, each phase R, S, and T is connected to two different electrodes 16.

[0112] In this embodiment, the primary side 25 of the transformer is connected to six secondary sides 26 of the transformer.

[0113] According to several embodiments, each phase of the transformer secondary side 26 can be configured to be phase-shifted, as shown in the example in Figure 3. It is also possible to set different phase angles. For example, the transformer secondary sides 26A and 26C can be configured to be phase-shifted by a first phase angle α1 relative to the transformer secondary side 26B, and the transformer secondary sides 26D and 26F can be configured to be phase-shifted by a second phase angle α2, which is different from the first phase angle α1, relative to the transformer secondary side 26E.

[0114] However, it is clear that other connection combinations and combinations of phase angles for each phase are also possible.

[0115] According to one aspect of the invention, the apparatus 10 may include N base modules 20, 120, 220 connected in parallel to each other between the power grid 13 and the electric furnace 11. The number N of base modules can be selected according to requirements and parameters such as the power required for the furnace 11, the required productivity, and the total number of electrodes 16 to which power should be supplied.

[0116] The number N of base modules can be variable, for example, between 2 and 60, and may be, for example, 3, 4, 5, 6, 8, 10, 12, 18, 24, 36, 48, or any other intermediate number (even or odd).

[0117] Preferably, the number N of the base modules 20, 120, and 220 is set such that the total number of all submodules 21 is a multiple of 3, thereby enabling the equal supply of three phases R, S, and T to the power lines 32.

[0118] As an example, Figure 4 shows a device 10 having two or more base modules 120 according to the embodiment of Figure 2, indicated by the letters A and B, respectively. These are connected to the power grid 13 on one hand and to a load 11 on the other, in this case connected via power lines 32.

[0119] This multi-module configuration can also be achieved by replacing the base module 120 in the embodiment of Figure 2 with the base module 20 or 220 in the embodiment of Figure 1 or Figure 5.

[0120] According to some embodiments, in the case of a device 10 comprising multiple base modules 20, 120, 220, it may be specified that all transformer devices 24 have substantially the same configuration.

[0121] In possible modifications, if there are multiple base modules 20, 120, 220, the connections of each phase R, S, T of the primary side 25 and / or secondary side 26 of the transformer in at least one transformer device 24 may be of a different type than those of at least one other transformer device 24.

[0122] "Different types of connections" refers to a case where the phases R, S, and T of the primary side 25 or secondary side 26 of at least one transformer device 24 are connected in a star connection, and the phases R, S, and T of another transformer device are connected in a delta connection, as well as a case where both are of the same type of connection (e.g., delta connection) but there is a certain phase difference between the respective phases R, S, and T.

[0123] According to another embodiment, if multiple base modules 20, 120, 220 are provided, the connections between the input phases and output phases R, S, T of each transformer 24 can all be different from each other, or they can be repeated in a desired order.

[0124] It is preferable that different configurations of phase connections of the transformer 24 within one base module 20, 120, 220, or different configurations of phase connections between multiple base modules 20, 120, 220, be selected so as a whole they differ from each other, at least in terms of connection type and phase angle between phases. This is to achieve a balance of current and voltage not only within a single base module 20 but also in the entire device 10.

[0125] Some embodiments described herein also relate to a plant 15 that includes a power supply unit 10 according to the present invention and an electric furnace 11 having two or more electrodes 16 connected to each of the phases R, S, and T of a power line 32, respectively.

[0126] According to other embodiments, a method is also provided for supplying power to an electric furnace 11 having two or more electrodes 16, the method being - A step of supplying a three-phase AC current and voltage having a predetermined frequency to at least one base module 20, 120, 220 using a three-phase power grid 13, wherein the at least one base module 20, 120, 220 includes at least two submodules 21, each of which is configured to receive a three-phase voltage and current at its input and to supply a single-phase AC voltage and current having a desired intensity and frequency at its output, and - A step of supplying power to electrodes 16, 16A~16F of the electric furnace 11 by the single-phase AC voltage and current, It is equipped with.

[0127] According to one aspect of the present invention, Each of the aforementioned submodules 21, 22, and 23 includes: Rectification involves rectifying the respective phase voltages and currents R, S, and T to obtain a common DC voltage and current for the three phases R, S, and T. Temporary energy storage, A separation is provided between the power grid 13 and the electrodes 16, 16A~16F via a DC intermediate circuit 28, An inversion system is used to reverse the DC voltage and current using at least one inverter device 29 to obtain the respective single-phase AC voltage and current. A system is in place, All of the DC intermediate circuits 28 of at least one of the base power modules 20, 120, and 220 are short-circuited to each other and kept at the same potential.

[0128] The voltage and current of each single phase supplied by the base module 20 are suitable for supplying the different phases (R, S, T) of the power line 32, respectively.

[0129] In some embodiments, the method according to the present invention provides control over the operation of at least an inverter device 29 in relation to the type of electric furnace 11 to be powered, or the characteristics of the melting process carried out therein, such as the type of material to be melted, the power required, the number of electrodes 16 used, or different process steps.

[0130] According to some embodiments, this method provides a method for adjusting the inverter device 29 by PWM adjustment or hysteresis adjustment.

[0131] According to other embodiments, if there are multiple base modules 20, 120, 220, the method according to the present invention can also determine the voltage and current characteristics to be supplied to the electrodes 16 as needed, based on the requirements of the plant 15, the characteristics of the electric furnace 11, or the characteristics of the material to be melted, and activate only the base modules 20, 120, 220 that are necessary and sufficient to supply the predetermined voltage and current.

[0132] It is clear that the power supply unit 10 described herein may be modified and / or have components added without departing from the scope and spirit defined by the claims of the present invention.

[0133] In the following claims, the reference numerals in parentheses are for readability purposes only and should not be construed as elements that limit the scope of protection defined by each individual claim.

Claims

1. A power supply device (10) for an electric furnace (11) used in steelmaking or in the field of processing metal or glassy materials, It is configured to convert electrical energy supplied from a three-phase power grid (13) and to supply at least one pair of single-phase AC currents and voltages having a desired intensity and frequency as output, and comprises at least one base power module (20, 120, 220) having at least two submodules (21, 21A to 21F), Each of the at least two submodules (21, 21A to 21F) is, A rectifier device (27) configured to convert three-phase alternating current and voltage into direct current and voltage, A DC intermediate circuit, or DC link (28), configured to store electrical energy, Connected to the intermediate circuit (28), at least one inverter device (29) configured to convert the DC current and voltage into single-phase AC current and voltage, Equipped with, The rectifier device (27), the intermediate circuit (28), and the inverter device (29) are arranged in a continuous manner with respect to each other. A power supply device (10) characterized in that all of the intermediate circuits (28) of at least one base power supply module (20, 120, 220) are short-circuited to each other by short-circuit connections (22, 23).

2. The system comprises a plurality of base power modules (20, 120, 220) connected in parallel between the power grid (13) and the electric furnace (11). The apparatus (10) according to feature 1.

3. Each of the intermediate circuits (28) of the base power modules (20, 120, 220) is short-circuited only with other intermediate circuits (28) within the same base power module (20, 120, 220) by the short-circuit connections (22, 23), and is not connected to intermediate circuits (28) belonging to different base power modules (20, 120, 220). The apparatus (10) according to feature 2.

4. Each of the aforementioned submodules (21, 21A to 21F) is connected in parallel to the same DC intermediate circuit (28) and comprises a plurality of inverter devices (29) that contribute to supplying a common single-phase AC voltage and current. The apparatus (10) according to any one of claims 1 to 3.

5. The system includes at least one transformer device (24) associated with the at least one base power module (20, 120, 220) and configured to convert the electrical energy supplied from the power grid (13) into electrical energy having voltage and current values ​​suitable for driving the submodules (21, 21A to 21F). The apparatus (10) according to any one of claims 1 to 4.

6. The transformer device (24) comprises at least one transformer primary side (25) and a number of transformer secondary sides (26) corresponding to the number of phases to be supplied to the output and the number of submodules (21, 21A to 21F) of the at least one base power supply module (20, 120, 220). The apparatus (10) according to feature 5.

7. A single transformer primary side (25) is provided, which has three-phase inputs that are connected to the phases (R, S, T) of the power grid (13) when in use. The single primary side (25) of the transformer is coupled to all of the secondary sides (26) of the transformer, and each of the secondary sides (26) of the transformer is connected to one of the submodules (21, 21A to 21F). The phases of at least two transformer secondary sides (26) in the at least one base power supply module (20, 120, 220) are out of phase with respect to each other. The apparatus (10) according to feature 6.

8. The system comprises a plurality of transformer devices (24), each connected between the power grid (13) and one of the plurality of base modules (20, 120, 220). The apparatus (10) according to claims 2 and 5.

9. The base power modules (20, 120, 220) or each base power module (20, 120, 220) comprises two to eight submodules (21, 21A to 21F) and a corresponding number of intermediate circuits (28) that are short-circuited to each other. The apparatus (10) according to any one of claims 1 to 8.

10. The electric furnace (11) includes a control unit (40) configured to manage and command at least the inverter device (29) in relation to a specific step of the melting process, and to change one or more parameters of the current and voltage supplied to one or more electrodes (16, 16A to 16F) as needed. The apparatus (10) according to any one of claims 1 to 9.

11. A plant (15) for melting metal materials, A power supply device (10) according to any one of claims 1 to 10, connected between the power grid (13) and the power line (32), An electric furnace (11) equipped with two or more electrodes (16, 16A to 16F), Equipped with, Each of the electrodes (16, 16A to 16F) is connected to a phase (R, S, T) of the power line (32). A plant characterized by the following (15).

12. A method for supplying power to an electric furnace (11) used in steelmaking or in the field of processing metal or glassy materials, which is equipped with two or more electrodes (16, 16A to 16F), - A step of supplying a three-phase AC current and voltage having a predetermined frequency to at least one base module (20, 120, 220) using a three-phase power grid (13), wherein the at least one base module (20, 120, 220) includes two or more submodules (21, 21A to 21F), and each of the two or more submodules (21, 21A to 21F) is configured to receive a three-phase voltage and current at its input and to supply a respective single-phase AC voltage and current having a desired intensity and frequency at its output. - A step of supplying power to each electrode (16, 16A to 16F) of the electric furnace (11) by the single-phase AC voltage and current, Equipped with, Each of the aforementioned submodules (21, 21A to 21F) includes: Rectification involves rectifying the respective phase voltages and currents (R, S, T) to obtain a common DC voltage and current for the three phases (R, S, T), Temporary energy storage, A separation is provided between the power grid (13) and the electrodes (16, 16A to 16F) via a DC intermediate circuit (28), An inversion system is used to reverse the DC voltage and current using at least one inverter device (29) to obtain the respective single-phase AC voltage and current, A system is in place, All of the intermediate circuits (28) of the at least one base power supply module (20, 120, 220) are short-circuited to each other by short-circuit connections (22, 23) and are configured to maintain them at the same potential. A method characterized by the following:

13. The three-phase alternating current and voltage are supplied to a plurality of base modules (20, 120, 220) connected in parallel to each other between the power grid (13) and the power lines (32) of the electrodes (16, 16A to 16F). In relation to a specific step of the melting process carried out in the electric furnace (11) and / or the material being melted, one or more inverter devices (29) of the plurality of base modules (20, 120, 220) are controlled and commanded, and one or more parameters of the current and voltage supplied to the electrodes (16, 16A to 16F) are changed as needed. The power supply method according to feature 12.

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