Furnace power supply device, system for power supply of furnace, furnace, use of furnace power supply device, and method for operating furnace power supply device

Abstract

The invention relates to a furnace power supply device (100) for supplying an electric arc furnace, an electroreduction furnace or a submerged arc resistance furnace with electrical energy,-wherein the furnace power supply device (100) is connectable to a three-phase electrical network (110),-wherein the furnace power supply device (100) is connectable to at least one electrode (120),-wherein the furnace power supply device (100) comprises:-at least one AC / DC converter circuit (130), -at least one rectifier circuit (150) connectable to a three-phase electrical network (110) and configured to rectify an alternating current of at least one phase of the three-phase electrical network (110),-at least one DC / DC converter circuit (150) configured to process a voltage level higher than or equal to 500 VDC.

Description

Technical Field

[0001] The present invention relates to a furnace power supply, a system for powering a furnace, a furnace, uses of the furnace power supply and a method of operating the furnace power supply. Background Art

[0002] Metal, especially steel, is usually melted and heated in a melting cell using an electric arc. These electrically operated melting cells, specifically electric arc furnaces, electric reduction furnaces, or submerged arc resistance furnaces, operate with direct current (DC), alternating current (AC), or multiphase AC. Typically, at least one electrode is used for this purpose, which extends through the furnace roof into the furnace vessel, while further electrodes are provided corresponding to the first electrode or are arranged in the bottom of the melting vessel.

[0003] Electric arc furnaces, electric reduction furnaces or submerged arc resistance furnaces represent highly non-linear loads, which means that their operation may lead to undesirable grid distortions, in particular flicker, high harmonic currents etc. on the power supply network. Summary of the Invention

[0004] The present invention is based on the object of providing an improvement over the prior art.

[0005] (A1) According to a first aspect of the present invention, this object is achieved by a furnace power supply device for supplying electric energy to an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace. - wherein the furnace power supply device is connectable to a three-phase power grid, preferably to a medium voltage three-phase power grid; - wherein the furnace power supply is connectable to at least one electrode of the electric arc furnace, the electric reduction furnace or the submerged arc resistance furnace, -Wherein, the furnace power supply device includes: - at least one AC / DC converter circuit connectable to the three-phase grid and configured to rectify the alternating current of at least one phase of the three-phase grid, wherein the three-phase grid has a voltage level higher than or equal to 1000 VAC, and - at least one DC / DC converter circuit configured to handle voltage levels higher than or equal to 500 VDC, wherein the DC / DC converter circuit is connected to the DC side of the AC / DC converter circuit.

[0006] First of all, it should be explicitly pointed out that in the context of this patent application, indefinite articles and numbers (such as "one", "two", etc.) should generally be understood as "at least" information, that is, "at least one...", "at least two...", etc., unless it is clearly obvious from the corresponding context, or it is obvious or technically mandatory for a person skilled in the art to express only "exactly one...", "exactly two...", etc.

[0007] In the context of this patent application, the terms "particularly" and / or "in particular" should always be understood to mean that the terms introduce optional, preferred features. The expression should not be understood as "i.e.".

[0008] It is proposed herein to use a fully bidirectional furnace power supply device to control the amount of total harmonic distortion (THD), and in particular to reduce the amount of THD. This can significantly reduce grid interference and at the same time improve the efficiency of the use of energy provided by the grid, thereby improving the power factor of the provided energy because THD can be minimized or prevented.

[0009] Specifically, it is proposed to control the power factor, and in particular, improve the power factor, of a fully bidirectional furnace power supply, preferably using an active front end. This can reduce the need for external power compensators, such as static VAR compensators (SVCs) or static synchronous compensators (STATCOMs), as the furnace power supply can regulate the reactive power instantaneously introduced into the grid, in particular by supplying and / or absorbing reactive power. This significantly reduces the required installation area and cost of an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace at a given plant site.

[0010] Total harmonic distortion (THD) can be defined as the ratio of the root mean square (RMS) amplitude of the set of higher harmonic frequencies to the RMS amplitude of the first harmonic or fundamental frequency. It can be calculated using the following formula:

[0011] in: THD Y = total harmonic distortion of signal Y; Y h = the amplitude of the hth harmonic; and Y 1, RMS = RMS value of the amplitude of the fundamental frequency.

[0012] During operation of an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace, the electrical load on the three-phase grid can be asymmetrical, causing harmonic distortion in the three-phase grid. The total harmonic distortion of the three-phase grid can be influenced by using a fully bidirectional furnace power supply that allows instantaneous energy flow from the three-phase grid to the load and vice versa. In particular, the use of fully bidirectional converter components, specifically active front ends, can minimize total harmonic distortion.

[0013] Instantaneous apparent power (P ist ) can be calculated from the instantaneous voltage (V ist ) and instantaneous current (I ist ) is defined by the product of: P ist = V ist I ist

[0014] in: P ist = Instantaneous apparent power V ist = instantaneous voltage I ist = instantaneous current The portion of instantaneous apparent power that results in a net transfer of energy in one direction is called instantaneous "real power." The portion of instantaneous power that results in no net transfer of energy due to stored energy in the AC system, but rather oscillates between the source and the load during each cycle, is called instantaneous "reactive power." The ratio of real power to apparent power is called "power factor." The higher the power factor for a given electrical energy transfer, the higher the net energy transfer for a given apparent power transfer, and therefore the greater the efficiency of the net energy transfer.

[0015] An “electric arc furnace” is a furnace that uses electrical energy provided and / or processed by a “furnace power supply” to generate an electric arc to melt metal ingots in the electric arc furnace, the metal ingots being specifically scrap metal and / or a mixture of scrap metals and / or direct reduced iron (DRI) and / or hot briquetted iron (HBI) and / or hot metal and / or flux material. The electric arc furnace may be a ladle furnace.

[0016] An electric arc forms between the charge material and the electrodes. The charge in the electric arc furnace is heated by the current passing through it and by the radiant energy emitted by the arc. The arc temperature can reach approximately 3,000°C or higher.

[0017] An “electric reduction furnace” is a furnace that uses electrical energy provided and / or processed by a furnace power supply to generate an electric arc to melt metal pieces, specifically scrap metal and / or scrap metal mixtures of ferroalloys, such as, but not limited to, ferro-nickel (FeNi), ferro-manganese (FeMn), ferro-aluminum (FeAl), ferro-tungsten (FeW), ferro-chromium (FeCr), ferro-titanium (FeTi), ferro-magnesium (FeMg), etc., in an electric reduction furnace.

[0018] A "submerged arc resistance furnace" is a furnace that uses electrical energy, supplied and / or processed by the furnace power supply, to generate an arc between electrodes and the charge material, or to heat the charge material by resistance heating (Joule effect). The charge material is typically non-ferrous metals, ores and materials, reducing agents, but can also be ferroalloys, waste recycling, slag, and slag cleaning.

[0019] The electric arc furnace, electric reduction furnace, or submerged arc resistance furnace may have a charge capacity greater than or equal to 1 ton, preferably greater than or equal to 20 tons, and particularly preferably greater than or equal to 50 tons. Further advantageously, the electric arc furnace or submerged arc resistance furnace may have a charge capacity greater than or equal to 100 tons, preferably greater than or equal to 200 tons, and particularly preferably greater than or equal to 400 tons.

[0020] The furnace power supply can be connected to an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace, specifically to electrodes of the electric arc furnace, electric reduction furnace, or submerged arc resistance furnace, via busbars or tubular busbars, cables, or other suitable power transmission media (e.g., copper, aluminum, etc.). The busbars or tubular busbars can be cooled by air, gas, water, or another suitable cooling medium other than water or gas. The furnace power supply can preferably include less than one furnace transformer. In other words, the furnace power supply can be directly connected to at least one electrode of the electric arc furnace, electric reduction furnace, or submerged arc resistance furnace.

[0021] A "three-phase grid" is a multiphase system used for power generation, transmission, and distribution. A three-phase grid provides alternating current (AC), specifically, three AC currents, each of which is +120 degrees out of phase with one of the other two AC currents and -120 degrees out of phase with the corresponding other AC current.

[0022] The three-phase power grid can be a high-voltage three-phase power grid, a medium-voltage three-phase power grid, or a low-voltage three-phase power grid.

[0023] The high voltage may be greater than or equal to 36 kV, preferably greater than or equal to 60 kV, and in particular preferably greater than or equal to 100 kV. Further advantageously, the high voltage may be greater than or equal to 150 kV, preferably greater than or equal to 200 kV, and in particular preferably greater than or equal to 300 kV. Further advantageously, the high voltage may be greater than or equal to 400 kV, preferably greater than or equal to 700 kV, and in particular preferably greater than or equal to 1100 kV.

[0024] The medium voltage may be less than or equal to 36 kV. Further advantageously, the medium voltage may be less than or equal to 30 kV, preferably less than or equal to 20 kV, and in particular preferably less than or equal to 15 kV.

[0025] The medium voltage may be greater than or equal to 1 kV, preferably greater than or equal to 2 kV, and in particular preferably greater than or equal to 10 kV. Further advantageously, the medium voltage may be greater than or equal to 15 kV, preferably greater than or equal to 20 kV, and in particular preferably greater than or equal to 30 kV.

[0026] The low voltage may be greater than or equal to 50 V, preferably greater than or equal to 60 V, and particularly preferably greater than or equal to 100 V. Further advantageously, the low voltage may be greater than or equal to 120 V, preferably greater than or equal to 220 V, and particularly preferably greater than or equal to 240 V.

[0027] The low voltage may be less than or equal to 1.000 V, and in particular preferably less than or equal to 900 V. Further advantageously, the medium voltage may be less than or equal to 600 V, preferably less than or equal to 240 V, and in particular preferably less than or equal to 220 V.

[0028] Preferably, the voltage levels may be defined according to IEC 60038.

[0029] An "electrode" is an electrical conductor that is used to contact a portion of an electric circuit, specifically an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace, specifically a non-metallic portion of the circuit. In the case of an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace, the non-metallic portion of the circuit may correspond to the atmosphere in the electric arc furnace, the electric reduction furnace, or the submerged arc resistance furnace.

[0030] The electrodes can be made of high-density graphite and / or tungsten. The electrodes can be designed to transfer electrical energy, thereby forming an arc between the tip and the charge material. The electrodes can be pre-baked electrodes or self-baked electrodes (Soederberg electrodes) and / or extruded / composite electrodes, which are combinations of Soederberg electrodes with pre-baked electrodes as cores and / or hollow electrode systems, which allow for the filling of fine powders (pre-baked, self-baked) via the central hole. The choice of electrode type can thus depend on: the size of the electrode, the material / metallurgy of the production, and economic aspects (such as operating costs).

[0031] Electrodes for an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace may be located at the top of the furnace. Preferably, the electrodes located at the top are connected to a height adjustment member, thereby enabling the distance between the electrodes and a specific scrap material and / or a specific molten metal in the furnace to be varied. This variation can be controlled and / or adjusted by an electrode adjuster.

[0032] The second electrode may be disposed in a furnace vessel of an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace, or may be a component of an inner wall of the furnace vessel.

[0033] The second electrode may also be arranged on the top of the electric arc furnace, electric reduction furnace or submerged arc resistance furnace, and is preferably also connected to the height adjustment member.

[0034] The electric arc furnace, electric reduction furnace or submerged arc resistance furnace may also have three electrodes, four electrodes or more electrodes. Each electrode may be connected to a height adjustment member.

[0035] An electric arc furnace, electric reduction furnace or submerged arc resistance furnace can be operated with the aid of direct current (DC) or with the aid of alternating current (AC).

[0036] In an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace operated by direct current, the electrodes may be referred to as anodes and cathodes. The cathode may be located at the top of the furnace. The anode may be divided into several segments. The anode, preferably the bottom electrode, comprises a metal and / or conductive material at the bottom of the furnace, and the arc is formed from the top between the charge material and the cathode, preferably made of graphite, carbon, or tungsten.

[0037] An electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace operated by means of alternating current may be supplied by single-phase power or multi-phase power, in particular, three-phase power.

[0038] An AC / DC converter circuit is an electrical device that converts alternating current (AC) into direct current (DC).

[0039] The AC / DC converter circuit may provide a DC voltage level on the DC side of the AC / DC converter circuit that is greater than or equal to a root mean square (RMS) value of the AC voltage level on the AC side of the AC / DC converter circuit, preferably greater than or equal to the square root of two times the root mean square value of the AC voltage level on the AC side of the AC / DC converter circuit.

[0040] The AC / DC converter circuit may provide a DC voltage level at the DC side of the AC / DC converter circuit that is greater than or equal to 0.1 times the root mean square value of the AC voltage level at the AC side of the AC / DC converter circuit, preferably greater than or equal to 0.2 times the root mean square value, and in particular preferably greater than or equal to 0.5 times the root mean square value.

[0041] The AC / DC converter circuit may provide a DC voltage level on the DC side of the AC / DC converter circuit that is greater than or equal to 1.0 times the root mean square value of the AC voltage level on the AC side of the AC / DC converter circuit, preferably greater than or equal to 1.5 times the root mean square value, specifically preferably greater than or equal to 2 times the root mean square value, and particularly preferably greater than or equal to 3 times the root mean square value.

[0042] The AC / DC converter circuit may include at least one AC / DC converter unit. An "AC / DC converter unit" is an electrical device that converts alternating current into direct current.

[0043] The AC / DC converter unit may be an integrated component.The AC / DC converter unit may comprise at least one circuit board.

[0044] The AC / DC converter circuit may include a plurality of AC / DC converter units connected in parallel with each other. In this way, the upper current limit of the AC / DC converter circuit can be increased.

[0045] The AC / DC converter circuit may include a plurality of AC / DC converter units connected in series with each other. In this way, the upper voltage limit of the AC / DC converter circuit can be increased.

[0046] The AC / DC converter circuit may comprise an AC / DC housing. An AC / DC housing is a housing in the context of the present invention.

[0047] In the context of the present invention, a "housing" is designed to protect designated components inside from external influences, in particular from mechanical and / or electrical influences. In addition, the housing can be provided with an electrical ground connection so that the housing can increase the safety of people in the vicinity of the electrical components enclosed by the housing in a designated manner.

[0048] The housing may include a bottom portion, a top portion, and at least one side portion. The bottom portion, the top portion, and the at least one side portion may at least partially define a volume of the housing. The bottom portion, the top portion, and the at least one side portion may be connected to each other to form an integrated component.

[0049] The AC / DC housing may be configured to accommodate at least one AC / DC converter unit, preferably a plurality of AC / DC converter units, in the housing volume.

[0050] The AC / DC converter circuit may be an integrated component.The AC / DC converter circuit may include at least one circuit board.

[0051] In the context of the present invention, two parts forming an "integrated component" are interconnected by means of at least one mechanical connection. In other words, when the integrated component is moved from one spatial position to another, the two parts forming the integrated component change their spatial position relative to each other within the scope of their mechanical connection.

[0052] In a preferred embodiment of the invention, the mechanical connection of the integrated component is fixed. In other words, the relative position of the two parts forming the integrated component, wherein the mechanical connection between the two parts is fixed, is constant during changes in the spatial position of the integrated component.

[0053] The AC / DC converter unit may comprise a unit housing. The unit housing may be a housing in the context of the present invention.

[0054] Multiple AC / DC converter units connected in parallel and / or in series can be arranged within the housing volume of the AC / DC housing. This allows the AC / DC converter circuit to be formed as an integrated component. This makes it easier to replace the AC / DC converter circuit for maintenance or repair. Furthermore, individual AC / DC converter units can be easily replaced from the AC / DC converter circuit for maintenance or repair, thereby increasing the modularity of the AC / DC converter circuit.

[0055] The AC / DC converter circuit and / or the AC / DC converter unit may comprise at least one capacitor and / or at least one inductor to store electrical energy.In this way, a separation may be produced between the three-phase grid and the at least one pole.

[0056] The AC / DC converter circuit and / or AC / DC converter unit may include at least one half H-bridge circuit. An H-bridge circuit is an electronic circuit that converts direct current (DC) to alternating current (AC). A half H-bridge circuit includes two switching elements. A full H-bridge circuit includes four switching elements.

[0057] The upper voltage limit of the half H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0058] The AC / DC converter circuit and / or the AC / DC converter unit may include at least one full H-bridge circuit. The upper voltage limit of the full H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0059] The AC / DC converter circuit and / or the AC / DC converter unit may include a plurality of full H-bridge circuits and / or half H-bridge circuits connected in series. In this way, the upper voltage limit of the AC / DC converter circuit and / or the AC / DC converter unit may be increased.

[0060] The AC / DC converter circuit and / or the AC / DC converter unit may include multiple full H-bridge circuits and / or half H-bridge circuits connected in parallel. In this way, the upper current limit of the AC / DC converter circuit and / or the AC / DC converter unit can be increased.

[0061] The upper current limit of the AC / DC converter circuit and / or the AC / DC converter unit may be greater than or equal to 750 A, preferably greater than or equal to 1500 A, preferably greater than or equal to 2000 A, specifically preferably greater than or equal to 2500 A, and particularly preferably greater than or equal to 3000 A.

[0062] The AC / DC converter circuit may comprise exactly one AC / DC converter unit.

[0063] The AC / DC converter circuit may be configured to rectify alternating current of at least one phase of a three-phase power grid, wherein the three-phase power grid is a high voltage three-phase power grid, a medium voltage three-phase power grid, or a low voltage three-phase power grid.

[0064] The AC / DC converter circuit may be configured to rectify the alternating current of all phases of the three-phase grid.

[0065] The AC / DC converter circuit may be indirectly connected to the three-phase power grid. In other words, additional components may be interposed between the AC / DC converter circuit and the three-phase power grid. The additional components may include, but are not limited to, one or more transformers, one or more capacitors, one or more inductors, and the like.

[0066] The AC / DC converter circuit may be directly connectable to the three-phase grid. In other words, less than one component may be interposed between the AC / DC converter circuit and the three-phase grid, except for one or more power cables for transmitting electrical energy.

[0067] The AC / DC converter circuit and / or the AC / DC converter unit may have a switching frequency higher than or equal to 1 kHz, preferably higher than or equal to 2 kHz, and in particular preferably higher than or equal to 5 kHz. Advantageously, the AC / DC converter circuit and / or the AC / DC converter unit may have a switching frequency higher than or equal to 10 kHz, preferably higher than or equal to 15 kHz, and in particular preferably higher than or equal to 20 kHz.

[0068] In this way, instantaneous power factor correction can be achieved, thereby improving the power factor. This type of power factor correction can also be called dynamic power factor correction (DPFC).

[0069] The AC / DC converter circuit and / or the AC / DC converter unit may provide six-pulse modulation and / or any multiple of six-pulse modulation, i.e. twelve-pulse modulation or eighteen-pulse modulation, etc. In this way, THD may be significantly reduced since harmonics above the fundamental are significantly reduced.

[0070] A “DC / DC converter circuit” is an electrical device that converts direct current having a first voltage level into direct current having a second voltage level.

[0071] In the context of the present invention, a "first voltage level" is the voltage level of the current entering the DC / DC converter circuit in the direction of power delivery of the current. The current entering the DC / DC converter circuit can deliver power from the three-phase grid and / or another DC power source to the load, or vice versa.

[0072] In the context of the present invention, the "second voltage level" is the voltage level of the current leaving the DC / DC converter circuit in the direction of electrical energy transfer of the current. The current leaving the DC / DC converter circuit can transfer electrical energy from the three-phase grid and / or another DC power source to the load, or from the load to the three-phase grid and / or another DC power source.

[0073] The first voltage level may be higher or lower than the second voltage level. Alternatively, the first voltage level may be equal to the second voltage level.

[0074] The DC / DC converter circuit can be configured to provide a constant second voltage level. The constant second voltage level can vary from the nominal second voltage level by less than or equal to 80%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 5%. The voltage variation can be measured as the average voltage value of a given number of predetermined time intervals, which must be within a specified range around the nominal voltage level. For example, for a 20% deviation of the second voltage level from the specified nominal voltage level, 95% of the 1-minute average of the measured voltage values ​​at each hourly interval must be within the 20% deviation limit from the nominal voltage level. The time interval can vary. The required average voltage value of the given number can vary. Alternatively or additionally, the voltage variation can be measured according to one of the measurement principles of DIN EN 50160, DIN EN 61000-2-2, or DIN EN 61000-2-4, or any other standard suitable for the application area.

[0075] The DC / DC converter circuit may include at least one DC / DC converter unit. A "DC / DC converter unit" is an electrical device that converts direct current having a first voltage level into direct current having a second voltage level.

[0076] The DC / DC converter unit may include a unit housing. The DC / DC converter unit may be an integrated component. The DC / DC converter unit may include a circuit board.

[0077] The DC / DC converter circuit may comprise a DC / DC housing. A DC / DC housing is a housing in the context of the present invention. A DC / DC housing may be configured to accommodate at least one DC / DC converter unit in a housing volume.

[0078] The DC / DC converter circuit may be an integrated component. The DC / DC converter circuit may include a circuit board.

[0079] The DC / DC converter circuit may include a plurality of DC / DC converter units connected in parallel with each other. In this way, the upper current limit of the DC / DC converter circuit can be increased.

[0080] The DC / DC converter circuit may include a plurality of DC / DC converter units connected in series with each other. In this way, the upper voltage limit of the DC / DC converter circuit can be increased.

[0081] Multiple DC / DC converter units connected in parallel and / or in series can be arranged within the housing volume of the DC / DC housing of the DC / DC converter circuit. This allows the DC / DC converter circuit to be formed into an integrated component that can be easily replaced for maintenance or repair. Furthermore, individual DC / DC converter units can be easily replaced from the DC / DC converter circuit for maintenance or repair, thereby increasing the modularity of the DC / DC converter circuit.

[0082] The DC / DC converter circuit and / or the DC / DC converter unit may include at least one capacitor and / or at least one inductor to store electrical energy and smooth the current and / or voltage having the second voltage level. Smoothing the current reduces higher harmonics of the current.

[0083] The DC / DC converter circuit and / or the DC / DC converter unit may include at least one half H-bridge circuit. The upper voltage limit of the half H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0084] The DC / DC converter circuit and / or the DC / DC converter unit may include at least one full H-bridge circuit. The upper voltage limit of the full H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0085] The DC / DC converter circuit and / or the DC / DC converter unit may include a plurality of full H-bridge circuits and / or half H-bridge circuits connected in series with each other. In this way, the upper voltage limit of the DC / DC converter unit can be increased.

[0086] The DC / DC converter circuit and / or the DC / DC converter unit may include a plurality of full H-bridge circuits and / or half H-bridge circuits connected in parallel with each other. In this way, the upper current limit of the DC / DC converter unit can be increased.

[0087] The DC / DC converter circuit may comprise exactly one DC / DC converter unit.

[0088] The DC / DC converter circuit can be configured to process a voltage level greater than or equal to 300 VDC, preferably greater than or equal to 500 VDC, and particularly preferably greater than or equal to 800 VDC. In a preferred embodiment, the DC / DC converter circuit can be configured to process a voltage level greater than or equal to 1000 VDC, preferably greater than or equal to 1500 VDC, and particularly preferably greater than or equal to 2000 VDC. (A2) According to a preferred embodiment, the furnace power supply includes less than one transformer, preferably less than one step-down transformer, arranged between the three-phase grid and at least one electrode.

[0089] Omitting the transformer, preferably a step-down transformer, can further improve system efficiency and reduce overall cost. The presence of current harmonics in the transformer can lead to larger eddy currents in the transformer's magnetic core. Eddy current losses generally reduce transformer efficiency.

[0090] The furnace power supply may comprise less than one transformer, preferably less than one step-down transformer, arranged between the three-phase electrical network and the at least one AC / DC converter circuit.

[0091] The furnace power supply may include less than one transformer disposed between the at least one AC / DC converter circuit and the at least one electrode.

[0092] The furnace power supply may include less than one transformer arranged between the at least one DC / DC converter circuit and the at least one electrode.

[0093] The furnace power supply may include less than one transformer arranged between the at least one DC / AC converter circuit and the at least one electrode.

[0094] (A3) According to a preferred embodiment, the AC / DC converter circuit comprises at least one bidirectional AC / DC converter unit, preferably an active front end circuit.

[0095] A "bidirectional" AC / DC converter unit allows electrical energy to flow in essentially two directions, meaning that electrical energy can flow from a three-phase grid and / or other DC power source to a load, and from a load to a three-phase grid and / or other DC power source. In this way, the power factor of the furnace power supply can be increased because the AC / DC converter can instantaneously supply or compensate for reactive power.

[0096] The “active front end circuit” comprises controllable semiconductor elements, preferably insulated gate bipolar transistors (IGBTs).

[0097] The AC / DC converter circuit may comprise exactly one AC / DC converter unit, preferably an active front end circuit, wherein the AC / DC converter circuit and the AC / DC converter unit form an integrated component.

[0098] (A4) According to a preferred embodiment, at least one DC / DC converter circuit includes at least one bidirectional DC / DC converter unit.

[0099] A “bidirectional” DC / DC converter unit allows electrical energy to flow in essentially both directions, meaning that electrical energy can flow from a three-phase grid and / or other DC power sources to a load and from a load to a three-phase grid and / or other DC power sources.

[0100] (A5) According to a preferred embodiment, at least one DC / DC converter circuit comprises at least one electrically isolated DC / DC converter unit.

[0101] Galvanic isolation prevents electrical conduction between two circuits that are intended to exchange power or signals. The two circuits can be separated by a non-conductive coupling element. With galvanic isolation, the electrical potentials are separated, and the circuits are then potential-free. This prevents the propagation of ground faults.

[0102] Electrical isolation can be achieved by various means, such as magnetic flux and / or optical means, preferably light.

[0103] Transformers can be used for galvanic isolation.

[0104] When the furnace power supply is connected to an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace, at least one DC / DC converter circuit including at least one electrically isolated DC / DC converter unit can provide electrical isolation between the AC / DC converter circuit and at least one electrode. In this manner, the propagation of ground faults can be prevented, in particular without the use of an additional transformer within and / or connected to the furnace power supply.

[0105] (A6) According to a preferred embodiment, at least one DC / DC converter circuit comprises at least one switch-mode DC / DC converter unit.

[0106] A "switching DC / DC converter unit" converts one DC voltage level to another, which may be higher or lower, by temporarily storing energy and then releasing it at a different voltage level. In this way, the efficiency of the power conversion can be improved, in particular compared to a non-switching DC / DC converter unit.

[0107] The DC / DC converter circuit and / or the DC / DC converter unit can have a switching frequency higher than or equal to 1 kHz, preferably higher than or equal to 2 kHz, and in particular preferably higher than or equal to 5 kHz. Advantageously, the DC / DC converter circuit and / or the DC / DC converter unit can have a switching frequency higher than or equal to 10 kHz, preferably higher than or equal to 15 kHz, and in particular preferably higher than or equal to 20 kHz. In this way, the power factor can be improved instantaneously.

[0108] (A7) According to a preferred embodiment, at least one first snubber circuit using direct current is inserted between the AC / DC converter circuit and the DC / DC converter circuit, thereby connecting the AC / DC converter circuit and the DC / DC converter circuit, wherein the first snubber circuit is configured to store energy and create a separation between the three-phase grid and at least one pole.

[0109] The “first buffer circuit” is a circuit that transmits and / or stores electric energy.

[0110] The first snubber circuit can create a decoupling between the three-phase power grid and at least one electrode. This decoupling can be achieved by electrically isolating the electrical energy stored in the first snubber circuit. The electrical energy stored in the first snubber circuit can absorb fluctuations in power supply and / or demand, particularly transient fluctuations. For example, if the power demand of an electrical load directly or indirectly connected to the first snubber circuit decreases, the first snubber circuit can store excess power, preferably from the three-phase power grid connected to the first snubber circuit. If, for example, the power supply decreases, preferably from the three-phase power grid connected to the first snubber circuit, the first snubber circuit can supply the electrical load directly or indirectly connected to the first snubber circuit with energy from the stored energy in the first snubber circuit. In other words, the first snubber circuit can create a decoupling between the three-phase power grid and at least one electrode. In this way, the impact, particularly the negative impact, of fluctuations in the power supply from the three-phase power grid on at least one electrode can be reduced.

[0111] The first snubber circuit may include at least one capacitor configured to store energy. The first snubber circuit may include multiple capacitors connected in parallel and / or in series with one another. In this manner, improved isolation between the three-phase grid and the at least one electrode may be achieved.

[0112] The first snubber circuit may include at least one inductor configured to store energy. The first snubber circuit may include multiple inductors connected in parallel and / or in series with one another. In this manner, improved isolation between the three-phase grid and the at least one electrode may be achieved.

[0113] The first snubber circuit may include at least one battery configured to store energy. The first snubber circuit may include multiple batteries connected in parallel and / or in series. In this manner, improved isolation between the three-phase grid and the at least one electrode may be achieved.

[0114] The first snubber circuit may create a separation between the AC / DC converter circuit and the DC / DC converter circuit.

[0115] The first buffer circuit can have a voltage level greater than or equal to 1 kV, preferably greater than or equal to 10 kV, specifically greater than or equal to 100 kV, and particularly greater than or equal to 150 kV. Advantageously, the first buffer circuit can have a voltage level greater than or equal to 300 kV, preferably greater than or equal to 500 kV, specifically greater than or equal to 900 kV, and particularly greater than or equal to 1500 kV. The first buffer circuit can also be referred to as an HV DC link. In this manner, the first buffer circuit can provide increased power to at least one electrode.

[0116] The first snubber circuit voltage level may be dependent on an AC voltage level of the AC voltage at the alternating current side of the AC / DC converter circuit.The first snubber circuit voltage level may preferably be adjusted by an electronic control unit.

[0117] (A8) According to a preferred embodiment, at least one DC power source, preferably a regenerative DC power source, is connectable to the first buffer circuit.

[0118] A "DC power supply" is an electrical device that provides direct current (DC).

[0119] The DC power source may be a regenerative DC power source such as a wind turbine and / or a wind turbine power plant and / or a solar power plant and / or a geothermal power plant and / or a wave power plant. The DC power source may be a battery.

[0120] The DC power source may be another type of power plant that at least indirectly provides DC power, such as a nuclear power plant, a coal-fired power plant, a gas-fired power plant, and / or an oil-fired power plant.

[0121] The DC power source can be at least indirectly connectable to the first buffer circuit and / or the plurality of first buffer circuits. In this way, a stable energy supply can be provided for the furnace power supply device even in the event of disturbances and / or faults in the three-phase power grid.

[0122] Alternatively or additionally, the DC power source can be at least indirectly connectable to the second buffer circuit and / or the plurality of second buffer circuits. In this way, a stable energy supply can be provided to the furnace power supply even in the event of disturbances and / or faults in the three-phase grid and / or in the DC power source connected to the at least one first buffer circuit.

[0123] The DC power supply can directly or indirectly provide a voltage level that is substantially the same as the voltage level of the first buffer circuit. In this way, power can be supplied to the first buffer circuit with less interference.

[0124] The DC power source may be indirectly connected to the first buffer circuit and / or the second buffer circuit via one or more DC / DC converter circuits, the one or more DC / DC converter circuits being configured to provide a first voltage level and / or a second voltage level that matches the voltage level of the DC power source and / or the first buffer circuit and / or the second buffer circuit, depending on the direction of power delivery. In other words, when power flows from the DC power source to the first buffer circuit and / or the second buffer circuit, the DC / DC converter circuit may process the first voltage level, which is substantially the same voltage level provided by the DC power source, and provide a second voltage level that is substantially the same voltage level as the first buffer circuit and / or the second buffer circuit. When power flows from the first buffer circuit and / or the second buffer circuit to the DC power source, the DC / DC converter circuit may process the first voltage level, which is substantially the same voltage level provided by the first buffer circuit and / or the second buffer circuit, and provide a second voltage level that is substantially the voltage level of the DC power source.

[0125] At least one AC / DC converter circuit can be connected to a plurality of three-phase power grids. In this way, a stable energy supply can be provided for the furnace power supply device even in the event of a disturbance and / or a fault in one of the three-phase power grids.

[0126] (A9) According to a preferred embodiment, the furnace power supply comprises a plurality of AC / DC converter circuits connected in parallel with each other, wherein the AC / DC converter circuits are connected to a common first buffer circuit, preferably to a plurality of first buffer circuits.

[0127] A plurality of first buffer circuits may be connected in parallel to one another.

[0128] The multiple AC / DC converter circuits and the multiple first buffer circuits can be identical. In other words, the number of AC / DC converter circuits and the number of first buffer circuits can be the same. Each first buffer circuit can be inserted between one AC / DC converter circuit and one DC / DC converter circuit, thereby establishing a one-to-one connection between exactly one AC / DC converter circuit and exactly one DC / DC converter circuit. A one-to-one connection means that one AC / DC converter circuit is connected to exactly one DC / DC converter circuit, and one DC / DC converter circuit is connected to exactly one AC / DC converter circuit. In this way, even if one AC / DC converter circuit or one DC / DC converter circuit is shut down or malfunctions, energy can be supplied at the desired current level, voltage level, and / or frequency.

[0129] According to some embodiments of the present invention, a "common first buffer circuit" connects more than one AC / DC converter circuit with one or more DC / DC converter circuits.

[0130] According to some embodiments of the present invention, a common first buffer circuit connects one AC / DC converter circuit with more than one DC / DC converter circuit.

[0131] The common first snubber circuit can transfer electrical energy between a plurality of AC / DC converters and / or a plurality of DC / DC converters and thus allow a large amount of energy to be transferred while achieving a constant current level and keeping installation costs low.

[0132] Preferably, the common first snubber circuit can have a voltage level higher than or equal to 1 kV, preferably higher than or equal to 36 kV, and particularly preferably higher than or equal to 100 kV. Advantageously, the common first snubber circuit can have a voltage level higher than or equal to 300 kV, preferably higher than or equal to 500 kV, particularly preferably higher than or equal to 900 kV, and particularly preferably higher than or equal to 1500 kV.

[0133] (A10) According to a preferred embodiment, at least one second snubber circuit using direct current is inserted between the DC / DC converter circuit and the at least one electrode, thereby at least indirectly connecting the DC / DC converter circuit and the at least one electrode, wherein the second snubber circuit is configured to store energy and create a separation between the three-phase grid and the at least one electrode.

[0134] The "second buffer circuit" is a circuit that transmits and / or stores electrical energy.

[0135] The second buffer circuit can provide a decoupling between the DC / DC converter circuit and at least one electrode. This decoupling can be achieved by electrically isolating the electrical energy stored in the second buffer circuit. The electrical energy stored in the second buffer circuit can absorb fluctuations in electrical energy supply and / or demand, particularly transient fluctuations. In other words, the second buffer circuit can provide electrical decoupling between the DC / DC converter circuit and at least one electrode. In this way, the impact, particularly the negative impact, of fluctuations in the electrical energy supply from the DC / DC converter circuit on the at least one electrode can be reduced.

[0136] The second snubber circuit may include at least one capacitor configured to store energy. The second snubber circuit may include multiple capacitors connected in parallel and / or in series. In this manner, improved isolation between the three-phase grid and the at least one electrode may be achieved.

[0137] The second snubber circuit may include at least one inductor configured to store energy. The second snubber circuit may include multiple inductors connected in parallel and / or in series with one another. In this manner, improved isolation between the three-phase grid and the at least one electrode may be achieved.

[0138] The second snubber circuit can include at least one battery connected in series and / or in parallel to the second snubber circuit and configured to store energy. The second snubber circuit can include multiple batteries connected in parallel and / or in series to each other and / or to the second snubber circuit. In this manner, improved isolation between the three-phase grid and at least one electrode can be achieved.

[0139] The second buffer circuit can have a voltage level of less than or equal to 1500 kV, preferably less than or equal to 900 kV, specifically less than or equal to 500 kV, and particularly less than or equal to 300 kV. Advantageously, the second buffer circuit can have a voltage level of less than or equal to 150 kV, preferably less than or equal to 100 kV, specifically less than or equal to 10 kV, and particularly less than or equal to 1 kV. The second buffer circuit can also be referred to as a DC link. In this way, the second buffer circuit can provide increased power to at least one electrode.

[0140] The second buffer circuit voltage level may be dependent on the DC voltage level of the first buffer circuit.The second buffer circuit voltage level may be lower than the first buffer circuit voltage level.

[0141] The second buffer circuit voltage level may preferably be adjusted by the electronic control unit.

[0142] (A11) According to a preferred embodiment, the furnace power supply comprises an electronic control unit, wherein the electronic control unit is connectable to the AC / DC converter circuit and is configured to regulate the active power flow of the furnace power supply.

[0143] An "electronic control unit" is any electronic system which is adapted to receive signals and / or store signals and / or process signals and / or control or regulate the furnace power supply in dependence on at least one signal.

[0144] The furnace power supply may include one or more sensors to provide information about harmonic distortion and / or flicker and / or the ratio of active power flow to reactive power flow in the grid. An electronic control unit may be operably connected to one or more of these sensors and capable of receiving sensor signals, processing them, and using them to control or regulate the furnace power supply.

[0145] The electronic control unit may include a memory element configured to store sensor signals received by the plurality of sensors from the furnace power supply.

[0146] The electronic control unit may comprise a housing.The electronic control unit may be an integrated component.

[0147] The electronic control unit may be connectable to a DC / DC converter circuit, in particular to a plurality of DC / DC converter circuits.

[0148] The electronic control unit may be configured to control or regulate the AC / DC converter circuit, in particular to reduce or prevent harmonic distortion and / or flicker in the power grid, in particular to mitigate flicker.

[0149] The electronic control unit may be configured to control or regulate the AC / DC converter circuit, in particular to optimize the ratio of active power flow to reactive power flow in the grid.

[0150] The electronic control unit may be configured to control or regulate the DC / DC converter circuit, in particular to reduce or prevent harmonic distortion and / or flicker in the power grid, in particular to mitigate flicker.

[0151] The electronic control unit may be configured to control or regulate the DC / DC converter circuit, in particular to achieve a constant second voltage level.

[0152] The electronic control unit may be adapted to control the current loop and / or the voltage loop and / or the impedance loop and / or the active power loop and / or the active power with hysteresis loop of the furnace power supply.

[0153] The electronic control unit may be connectable to a DC / AC converter circuit, in particular to a plurality of DC / AC converter circuits.

[0154] The electronic control unit may be connectable to a DC chopper circuit, in particular to a plurality of DC chopper circuits.

[0155] The electronic control unit may be configured to control or regulate the DC chopper circuit and / or the DC / AC converter circuit, in particular to reduce or prevent harmonic distortion and / or flicker in the grid, in particular to mitigate flicker, in particular preferably by applying a pulse width modulation strategy algorithm.

[0156] The electronic control unit may be connectable to a DC power supply. The electronic control unit may be configured to control or regulate the DC power supply, specifically to optimize the power transferred from the DC power supply to the at least one first buffer circuit and / or the power transferred from the at least one first buffer circuit to the DC power supply, specifically to improve the efficiency of the power converter.

[0157] The furnace power supply may include an electrode regulator, preferably a plurality of electrode regulators. The furnace power supply may include one electrode regulator per electrode. The furnace power supply may be connectable to an electrode regulator, preferably a plurality of electrode regulators, and in particular preferably one electrode regulator per electrode.

[0158] The "electrode adjuster" may be configured to control and / or adjust the position of the electrode. The electrode may be automatically raised and lowered by a height adjustment member, which may use an electric winch crane, a hydraulic cylinder, a pneumatic cylinder, or the like.

[0159] The electrode regulators can pursue different goals individually or in combination, specifically, maintaining a nearly constant voltage and / or constant current and / or power input during melting of the charge, even though the scrap may move under the electrodes as it melts. The arc length can increase with increasing voltage supplied to the electric arc furnace, electric reduction furnace, or submerged arc resistance furnace.

[0160] The electrode adjuster can be operably connected to one or more electronic control units and can receive signals from the one or more electronic control units, process them, and use them to control or adjust the height adjustment members of one or more electrodes of an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace.

[0161] The electronic control unit may be connectable to the electronic coordination and regulation unit, wherein the electronic control unit is operatively connected to at least one AC / DC converter circuit and / or at least one DC / DC converter circuit and / or at least one DC / AC converter circuit and / or at least one DC chopper circuit and is adapted to regulate the active power flow of the furnace power supply.

[0162] An “electronic coordination and regulation unit” is any electronic system adapted to communicate with one or more electronic control units. Preferably, the electronic coordination and regulation unit is adapted to communicate with one or more electrode regulators, in particular with the aim of reducing harmonic distortion and / or reducing flicker, in particular mitigating flicker, and / or improving the power factor.

[0163] The electronic coordination and regulation unit may comprise a housing. The electronic coordination and regulation unit may be an integrated component. The electronic coordination and regulation may comprise a storage element configured to store a plurality of set point values.

[0164] The electronic coordination and regulation unit can be configured to take over the superordinate control or regulation of the connected electronic control units and electrode regulators of one or more furnace power supply devices.

[0165] The electronic coordination and regulation unit can be arranged to take over the superordinate control or regulation of the connected partial regulators in the system of the furnace power supply, in particular one or more connected electronic control units and / or one or more electrode regulators.

[0166] The electronic coordination and regulation unit may be operatively connected to the electronic control unit and / or the electrode regulator, preferably to each electronic control unit and / or each electrode regulator.

[0167] The electronic coordination and regulation unit can control or regulate the voltage set point and / or the current set point of one or several furnace power supply devices.

[0168] The electronic coordination and regulation unit can control or regulate the active power set point and / or the reactive power set point of one or several furnace power supply devices.

[0169] The electronic coordination and regulation unit can control or regulate the frequency set point of one or several furnace power supplies. In particular, the electronic coordination and regulation unit can control multiple frequency set points for one or several furnace power supplies, preferably different frequency set points for different melting stages during operation of an electric arc furnace, electric reduction furnace, or submerged arc resistance furnace.

[0170] The electronic coordination and regulation unit can control or regulate the impedance or resistance set point of one or several furnace power supply devices.

[0171] The electronic coordination and regulation unit can control or regulate the electrode height set point of one or several electrodes of one or several electric arc furnaces, electric reduction furnaces or submerged arc resistance furnaces.

[0172] (A12) According to a preferred embodiment, the furnace power supply comprises at least one DC / AC converter circuit configured to supply electrical energy to at least one electrode, wherein the at least one DC / DC converter circuit is connected to the at least one DC / AC converter circuit.

[0173] A "DC / AC converter circuit" is an electrical device that converts direct current into alternating current.

[0174] The DC / AC converter circuit may include a DC / AC housing. The DC / AC converter circuit may be an integrated component. The DC / AC converter circuit may include a circuit board.

[0175] The DC / AC converter circuit may include at least one DC / AC converter unit. A "DC / AC converter unit" is an electrical device that converts direct current into alternating current.

[0176] The DC / AC converter unit may include a unit housing. The DC / AC converter unit may be an integrated component. The DC / AC converter unit may include a circuit board.

[0177] The DC / AC housing may be configured to accommodate at least one DC / AC converter unit, preferably a plurality of DC / AC converter units, in the housing volume.

[0178] The DC / AC converter circuit may include a plurality of DC / AC converter units connected in parallel with each other. In this way, the upper current limit of the DC / AC converter circuit can be increased.

[0179] The DC / AC converter circuit may include a plurality of DC / AC converter units connected in series with each other. In this way, the upper voltage limit of the DC / AC converter circuit can be increased.

[0180] Multiple DC / AC converter units connected in parallel and / or in series can be arranged within the housing volume of the DC / AC housing. This allows the DC / AC converter circuit to be formed as an integrated component. This makes it easier to replace the DC / AC converter circuit for maintenance or repair. Furthermore, individual DC / AC converter units can be easily replaced from the DC / AC converter circuit for maintenance or repair, resulting in increased modularity of the DC / AC converter circuit.

[0181] The DC / AC converter circuit may comprise two or more DC / AC converter units connected in parallel and / or in series with one another, preferably four or more DC / AC converter units, particularly preferably 10 or more DC / AC converter units. Advantageously, the DC / AC converter circuit may comprise 20 or more DC / AC converter units connected in parallel and / or in series with one another, preferably 30 or more DC / AC converter units, and particularly preferably 40 or more DC / AC converter units.

[0182] The DC / AC converter circuit and / or the DC / AC converter unit may comprise at least one capacitor and / or at least one inductor to store electrical energy. In this way, a separation may be produced between the three-phase grid and the at least one pole.

[0183] The DC / AC converter circuit and / or the DC / AC converter unit may include at least one half H-bridge circuit. The upper voltage limit of the half H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0184] The DC / AC converter circuit and / or the DC / AC converter unit may include at least one full H-bridge circuit. The upper voltage limit of the full H-bridge circuit may be greater than or equal to 0.5 kV, preferably greater than or equal to 1.0 kV, and particularly preferably greater than or equal to 1.5 kV.

[0185] The DC / AC converter circuit and / or the DC / AC converter unit may include a plurality of full H-bridge circuits and / or half H-bridge circuits connected in series. In this way, the upper voltage limit of the DC / AC converter circuit and / or the DC / AC converter unit may be increased.

[0186] The DC / AC converter circuit and / or the DC / AC converter unit may include a plurality of full H-bridge circuits and / or half H-bridge circuits connected in parallel with each other. In this way, the upper current limit of the DC / AC converter circuit and / or the DC / AC converter unit may be increased.

[0187] The upper current limit of the DC / AC converter circuit and / or the DC / AC converter unit may be greater than or equal to 750 A, preferably greater than or equal to 1500 A, preferably greater than or equal to 2000 A, specifically preferably greater than or equal to 2500 A, and particularly preferably greater than or equal to 3000 A.

[0188] The DC / AC converter circuit may comprise exactly one DC / AC converter unit.

[0189] The DC / AC converter circuit and / or the DC / AC converter unit can have a switching frequency greater than or equal to 1 kHz, preferably greater than or equal to 2 kHz, and in particular preferably greater than or equal to 5 kHz. Advantageously, the DC / AC converter circuit and / or the DC / AC converter unit can have a switching frequency greater than or equal to 10 kHz, preferably greater than or equal to 15 kHz, and in particular preferably greater than or equal to 20 kHz. In this way, instantaneous power factor correction can be achieved, thereby improving the power factor. This type of power factor correction can also be referred to as dynamic power factor correction (DPFC).

[0190] The DC / AC converter circuit may be indirectly connected to one or more electrodes. In other words, additional components may be interposed between the DC / AC converter circuit and the one or more electrodes. Additional components may include, but are not limited to, one or more transformers, one or more capacitors, one or more inductors, etc.

[0191] The DC / AC converter circuit may be directly connectable to the one or more electrodes. In other words, less than one component may be interposed between the DC / AC converter circuit and the one or more electrodes, other than one or more power cables for delivering electrical energy.

[0192] The DC / AC converter circuit may be connectable to at least one electrode, preferably to a plurality of electrodes, and configured to supply electrical energy to the electrode / electrodes.

[0193] The DC / AC converter circuit may be connectable to exactly one electrode and configured to supply electrical energy to that electrode.

[0194] The furnace power supply may include a plurality of DC / AC converter circuits connected in parallel with each other, wherein each DC / AC converter circuit is configured to supply electrical energy to one or more electrodes.

[0195] The furnace power supply device may include a plurality of DC / AC converter circuits connected in parallel, wherein the DC / AC converter circuits connected in parallel may be connectable to the same electrode and configured to supply electrical energy to the same electrode. In this manner, even if one DC / AC converter circuit is shut down or malfunctions, energy can still be supplied at a desired current level, voltage level, and / or frequency.

[0196] (A13) According to a preferred embodiment, the furnace power supply comprises at least one DC chopper circuit configured to supply electrical energy to at least one electrode, wherein at least one DC / DC converter circuit is connected to the at least one DC chopper circuit.

[0197] A "DC chopper circuit" is an electrical device that directly converts direct current with a fixed voltage into direct current with a variable voltage.

[0198] Because the switching elements in the DC chopper circuit and / or DC chopper unit are fully switched on or off, their losses are low and the DC chopper circuit and / or DC chopper unit can provide high efficiency, with a switching speed greater than or equal to 1 kHz, preferably greater than or equal to 2 kHz, and particularly preferably greater than or equal to 5 kHz. Advantageously, the DC chopper circuit and / or DC chopper unit can have a switching frequency greater than or equal to 10 kHz, preferably greater than or equal to 15 kHz, and particularly preferably greater than or equal to 20 kHz. In this way, the arc can be advantageously stabilized while protecting the furnace power supply from possible drift.

[0199] The DC chopping circuit may include a DC chopping housing, an integrated component, or a circuit board.

[0200] The DC chopper circuit may include at least one DC chopper unit. A "DC chopper unit" is an electrical device that directly converts direct current with a fixed voltage into direct current with a variable voltage.

[0201] The DC chopping unit may include a unit housing, an integrated component, or a circuit board.

[0202] The DC chopper housing may be configured to accommodate at least one DC chopper unit, preferably a plurality of DC chopper units, in the housing volume.

[0203] The DC chopping circuit may include a plurality of DC chopping units connected in parallel with each other. In this way, the upper current limit of the DC chopping circuit can be increased.

[0204] The DC chopping circuit may include a plurality of DC chopping units connected in series with each other. In this way, the upper voltage limit of the DC chopping circuit can be increased.

[0205] A plurality of DC chopper units connected in parallel and / or in series can be arranged within the housing volume of the DC chopper housing. This allows the DC chopper circuit to be formed into an integrated component that can be easily replaced for maintenance or repair. Furthermore, individual DC chopper units can be easily replaced from the DC chopper circuit for maintenance or repair, thereby increasing the modularity of the DC chopper circuit.

[0206] The DC chopping circuit and / or the DC chopping unit may comprise at least one capacitor and / or at least one inductor to store electrical energy.In this way, a separation may be produced between the three-phase grid and the at least one electrode.

[0207] The upper current limit of the DC chopping circuit and / or the DC chopping unit may be greater than or equal to 750 A, preferably greater than or equal to 1500 A, preferably greater than or equal to 2000 A, specifically preferably greater than or equal to 2500 A, and particularly preferably greater than or equal to 3000 A.

[0208] The DC chopping circuit may include exactly one DC chopping unit.

[0209] The DC chopping circuit may be indirectly connected to one or more electrodes. In other words, additional components may be interposed between the DC chopping circuit and the one or more electrodes. The additional components may include, but are not limited to, one or more capacitors, one or more inductors, and the like.

[0210] The DC chopping circuit may be directly connectable to the one or more electrodes. In other words, less than one component may be interposed between the DC chopping circuit and the one or more electrodes, other than one or more power cables for transmitting electrical energy.

[0211] The DC chopper circuit may be connectable to at least one electrode, preferably to a plurality of electrodes, and configured to supply electrical energy to the electrode / electrodes.

[0212] The DC chopper circuit may be connectable to exactly one electrode and configured to supply electrical energy to that electrode.

[0213] The furnace power supply may include a plurality of DC chopper circuits connected in parallel with each other, wherein each DC chopper circuit is configured to supply electrical energy to one or more electrodes.

[0214] The furnace power supply device may include a plurality of DC chopper circuits connected in parallel, wherein the DC chopper circuits connected in parallel may be connectable to the same electrode and configured to supply power to the same electrode. In this manner, even if one DC chopper circuit is shut down or malfunctions, power can still be supplied at a desired current level and / or voltage level.

[0215] The AC / DC converter unit and / or the DC / DC converter unit and / or the DC / AC converter unit and / or the DC chopper unit may comprise at least one semiconductor element, preferably a plurality of semiconductor elements, comprising silicon carbide.

[0216] "Semiconductor elements" include materials with electrical conductivity values ​​that fall between conductors (such as metallic copper) and insulators (such as glass). Semiconductor elements can be used for amplification, switching, and energy conversion.

[0217] The semiconductor element may be a diode, a thyristor (such as a silicon-controlled rectifier (SCR)), a gate turn-off thyristor (GTO), an integrated gate-commutated thyristor (IGCT), a metal-oxide-semiconductor controlled thyristor (MCT), a transistor (such as a bipolar junction transistor (BJT), a metal-oxide-semiconductor field-effect transistor (MOSFET), an injection-enhanced gate transistor (IEGT), or an insulated gate bipolar transistor (IGBT)), or other suitable semiconductor element. The semiconductor element may comprise silicon and / or carbon, preferably silicon carbide (SiC).

[0218] A second snubber circuit using direct current can be inserted between the DC / DC converter circuit and the DC / AC converter circuit, or between the DC / DC converter circuit and the DC chopper circuit. The second snubber circuit is configured to store energy and create a separation between the three-phase grid and the poles.

[0219] The second snubber circuit can provide decoupling between the DC / DC converter circuit and the DC / AC converter circuit or DC chopper circuit. This decoupling can be achieved by electrically isolating the electrical energy stored in the second snubber circuit. The electrical energy stored in the second snubber circuit can absorb fluctuations in power supply and / or demand, particularly transient fluctuations. In other words, the second snubber circuit can provide electrical decoupling between the DC / DC converter circuit connected to the second snubber circuit and the DC / AC converter circuit or DC chopper circuit. In this way, the effects, particularly negative effects, of power supply fluctuations on the DC / AC converter circuit or DC chopper circuit can be reduced.

[0220] The second snubber circuit may create a separation between the DC / DC converter circuit and the DC / AC converter circuit or between the DC / DC converter circuit and the DC chopper circuit.

[0221] The furnace power supply may include a common second snubber circuit. The common second snubber circuit may connect a DC / DC converter circuit with more than one DC / AC converter circuit or more than one DC chopper circuit. Alternatively, the common second snubber circuit may connect more than one DC / DC converter circuit with one DC / AC converter circuit or one DC chopper circuit. The common second snubber circuit may transfer electrical energy between multiple DC / DC converters and / or multiple DC / AC converters and / or multiple DC chopper circuits, thereby transferring a large amount of energy while achieving a constant current level and keeping installation costs low.

[0222] The furnace power supply may include a plurality of second snubber circuits connected in parallel to each other.

[0223] Multiple DC / DC converter circuits, multiple second buffer circuits, and multiple DC / AC converter circuits or DC chopper circuits can be identical. In other words, the number of DC / DC converter circuits, the number of second buffer circuits, and the number of DC / AC converter circuits or DC chopper circuits can be identical. Each second buffer circuit can be inserted between one DC / DC converter circuit and one DC / AC converter circuit, or between one DC / DC converter circuit and one DC chopper circuit, thereby establishing a one-to-one connection between exactly one DC / DC converter circuit and exactly one DC / AC converter circuit, or a one-to-one connection between exactly one DC / DC converter circuit and one DC chopper circuit, thereby forming a power submodule. In this way, even if one DC / DC converter circuit, one DC / AC converter circuit, or one DC chopper circuit is shut down or malfunctions, energy can be supplied at the desired current level, voltage level, and / or frequency.

[0224] The power submodule may include a housing. The power submodule may be an integrated component.

[0225] The furnace power supply may include a plurality of power submodules connected in parallel to one another. Each power submodule may be capable of being connected to exactly one individual electrode, thereby generating an independent power supply for that electrode. In other words, there is a one-to-one assignment between one power submodule and one electrode.

[0226] According to a preferred embodiment of the furnace power supply, the AC / DC converter circuit, the first snubber circuit, the DC / DC converter circuit, the second snubber circuit and the DC / AC converter circuit or the DC chopper circuit may form a power module.

[0227] The power module may include a housing. The power module may be an integrated component.

[0228] Preferably, the furnace power supply comprises a plurality of power modules connected in parallel. Each power module can be connected to exactly one electrode, thereby generating an independent power supply for each of the electrodes. In other words, there is a one-to-one assignment between one power module and one electrode. This way, electrical disturbances in one electrode do not affect the others.

[0229] (A14) According to a second aspect of the invention, the object is achieved by a system for supplying electrical energy to at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace, - wherein the system is connectable to at least one three-phase electrical network; - wherein the system is connectable to at least one electrode of at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace; It is characterized by the following features: - the system comprises a plurality of furnace power supplies according to the first aspect of the invention, and - wherein the plurality of furnace power supply devices are connected in parallel with each other.

[0230] It will be appreciated that the advantages of the furnace power supply according to the first aspect of the invention, as described above, directly transfer to a system comprising the furnace power supply according to the first aspect of the invention.

[0231] The system may comprise an electrode adjuster, preferably operatively connected to each electronic control unit and / or each height adjustment member.

[0232] The system may comprise an electronic coordination and regulation unit operatively connected to the electronic control unit and / or the electrode regulators, preferably operatively connected to each electronic control unit and / or each electrode regulator.

[0233] (A15) According to a third aspect of the invention, the object is achieved by an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace, characterized in that the electric arc furnace, the electric reduction furnace or the submerged arc resistance furnace comprises a furnace power supply device according to the first aspect of the invention and / or a system according to the second aspect of the invention.

[0234] An electric arc furnace, electric reduction furnace, or submerged arc resistance furnace may include multiple furnace power supplies according to the first aspect of the present invention and / or multiple systems according to the second aspect of the present invention. Each furnace power supply according to the first aspect of the present invention and / or each system according to the second aspect of the present invention can be connected to exactly one electrode and is configured to supply multiphase electrical energy to that electrode. In this manner, a stable energy supply can be provided to the electric arc furnace, electric reduction furnace, or submerged arc resistance furnace, even in the event of a disturbance and / or failure in one of the furnace power supplies and / or systems.

[0235] It should be understood that, as described above, the advantages of the furnace power supply device according to the first aspect of the invention and / or the system for supplying electrical energy to one or more electrodes of an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace according to the second aspect of the invention are directly transferred to an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace including such a system according to the second aspect of the invention.

[0236] It should be noted that the subject matter of the third aspect may be advantageously combined with the subject matter of the preceding aspects of the invention, either individually or cumulatively, in any combination.

[0237] Alternatively, an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace may include a plurality of furnace power supplies according to the first aspect of the present invention and / or a plurality of systems according to the second aspect of the present invention. Each furnace power supply according to the first aspect of the present invention and / or each system according to the second aspect of the present invention is connectable to a plurality of electrodes and is configured to supply multi-phase electrical energy to the plurality of electrodes.

[0238] (A16) According to a fourth aspect of the invention, this object is achieved by the use of the furnace power supply device according to the first aspect of the invention to supply electrical energy to at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace.

[0239] (A17) According to a fifth aspect of the invention, the task is solved by a method for operating an electric arc furnace or an electric reduction furnace or a submerged arc resistance furnace, in particular an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace, according to the third aspect of the invention, wherein the ratio of the active power flow to the reactive power flow is controlled and / or adjusted by influencing the control quantity of the AC / DC converter circuit and / or the DC / DC converter circuit and / or the DC / AC converter circuit and / or the DC chopper circuit, in particular the reactive power flow is minimized by influencing the control quantity of the AC / DC converter circuit and / or the DC / AC converter circuit.

[0240] It will be appreciated that the advantages of the electric arc furnace, electric reduction furnace or submerged arc resistance furnace according to the third aspect of the invention as described above directly transfer to the method for operating the electric arc furnace, electric reduction furnace or submerged arc resistance furnace according to the third aspect of the invention.

[0241] It should be noted that the subject matter of the fifth aspect may be advantageously combined with the subject matter of the preceding aspects of the invention, either individually or cumulatively, in any combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0242] Further advantages, details and features of the invention are explained in the following description of embodiments, whereby: Figure 1 : shows a schematic diagram of a first embodiment of a furnace power supply device; Figure 2 : shows a schematic diagram of a second embodiment of a furnace power supply device; Figure 3 : shows a schematic diagram of a third embodiment of a furnace power supply device; Figure 4 : shows a schematic diagram of a fourth embodiment of a furnace power supply device; Figure 5 : shows a schematic diagram of a fifth embodiment of a furnace power supply device; Figure 6 : shows a schematic diagram of a sixth embodiment of a furnace power supply device; Figure 7 : A schematic diagram showing a first embodiment of a system for supplying electric energy to an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace; Figure 8 : A schematic diagram showing a second embodiment of a system for supplying electric energy to an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace; DETAILED DESCRIPTION

[0243] In the following description, the same reference numerals respectively describe the same elements and the same features, so that the description of one element with reference to one figure is also valid for the other figures, so that repetition of corresponding features is omitted.

[0244] Figure 1 The furnace power supply device 100 in the embodiment includes an AC / DC converter circuit 130 and a DC / DC converter circuit 150 connected to a DC side of the AC / DC converter circuit 130 .

[0245] The furnace power supply 100 can be connected to a three-phase power grid 110 and to an electrode 120 .

[0246] The AC / DC converter circuit 130 is configured to rectify the alternating current of at least one phase of the three-phase power grid 110 .

[0247] Figure 2 The furnace power supply 100 in further includes a DC / AC converter circuit 170. The furnace power supply is intended for use in an AC powered electric arc furnace or electric reduction furnace or submerged arc resistance furnace (not shown).

[0248] The furnace power supply 100 further includes a first snubber circuit 140 using direct current, which is interposed between the AC / DC converter circuit 130 and the DC / DC converter circuit 150, thereby connecting the AC / DC converter circuit 130 to the DC / DC converter circuit 150. The first snubber circuit 140 may be configured to store energy and generate a separation between the three-phase grid 110 and the electrode 120.

[0249] The furnace power supply 100 further comprises an electronic control unit 200 connected to the AC / DC converter circuit 130. The electronic control unit 200 is configured to regulate the active power flow of the furnace power supply 100.

[0250] The electronic control unit 200 is connected to the DC / DC converter circuit 150 and is configured to control or regulate the DC / DC converter circuit 150 .

[0251] The electronic control unit 200 is connected to the DC / AC converter circuit 170 and is configured to control or regulate the DC / AC converter circuit 170 .

[0252] The furnace power supply 100 is also connectable to a DC power source 300 . The DC power source 300 is connected to the first buffer circuit 140 .

[0253] The electronic control unit 200 is connected to the DC power source 300 and is configured to control and / or regulate the DC power source 300 .

[0254] The furnace power supply 100 further includes a second buffer circuit 160 using direct current interposed between the DC / DC converter circuit 150 and the DC / AC converter circuit 170 . The second buffer circuit 160 is configured to store energy and create a separation between the three-phase grid 110 and the electrode 120 .

[0255] Figure 2 An alternative embodiment (not shown) of the embodiment of the furnace power supply 100 in includes a DC chopper circuit 180 instead of the DC / AC converter circuit 170. The furnace power supply is intended for use in a DC-powered electric arc furnace or electric reduction furnace or submerged arc resistance furnace (not shown).

[0256] according to Figure 2 All other features of the embodiment of the furnace power supply of apply to this alternative embodiment of the furnace power supply.

[0257] Figure 3 The furnace power supply device 100 in FIG. 1 includes three DC / DC converter circuits 150 connected in parallel to each other. The DC / DC converter circuits 150 are connected to the DC side of the same AC / DC converter circuit 130 via a common first buffer circuit 140 .

[0258] The furnace power supply 100 also includes three DC / AC converter circuits 170 .

[0259] A DC / AC converter circuit 170 can be connected to the same electrode 120 .

[0260] The electronic control unit 200 is connected to each of the DC / DC converter circuits 150. The electronic control unit 200 is configured to individually control or regulate each DC / DC converter circuit 150, thereby allowing each DC / DC converter circuit 150 to be controlled or regulated independently.

[0261] The electronic control unit 200 is connected to each of the DC / AC converter circuits 170. The electronic control unit 200 is configured to individually control or regulate each DC / AC converter circuit 170, thereby allowing each DC / AC converter circuit 170 to be controlled or regulated independently.

[0262] The furnace power supply 100 also includes three second buffer circuits 160 using direct current. Each second buffer circuit 160 is inserted between a DC / DC converter circuit 150 and a DC / AC converter circuit 170, thereby forming three electrically isolated power submodules 510. Each power submodule 510 includes a DC / DC converter circuit 150, a DC / AC converter circuit 170, and a second buffer circuit 160 inserted between the DC / DC converter circuit 150 and the DC / AC converter circuit 170.

[0263] Figure 3 An alternative embodiment (not shown) of the embodiment of the furnace power supply 100 in includes three DC chopper circuits 180 instead of the three DC / AC converter circuits 170. The furnace power supply is intended for use in a DC-powered electric arc furnace, electric reduction furnace, or submerged arc resistance furnace (not shown).

[0264] The alternative embodiment of the furnace power supply 100 further includes three DC / DC converter circuits 150 connected in parallel to each other. The DC / DC converter circuits 150 are connected to the DC side of the same AC / DC converter circuit 130 via a common first buffer circuit 140 .

[0265] A DC chopping circuit 180 can be connected to the same electrode 120 .

[0266] The electronic control unit 200 is connected to each of the DC / DC converter circuits 150. The electronic control unit 200 is configured to individually control or regulate each DC / DC converter circuit 150, thereby allowing each DC / DC converter circuit 150 to be controlled or regulated independently.

[0267] The electronic control unit 200 is connected to each of the DC chopping circuits 180. The electronic control unit 200 is configured to individually control or regulate each of the DC chopping circuits 180, thereby allowing each of the DC chopping circuits 180 to be controlled or regulated independently.

[0268] An alternative embodiment of the furnace power supply 100 further includes three second buffer circuits 160 using direct current. Each second buffer circuit 160 is inserted between a DC / DC converter circuit 150 and a DC chopper circuit 180, thereby forming three electrically isolated power submodules 510. Each power submodule 510 includes a DC / DC converter circuit 150, a DC chopper circuit 180, and a second buffer circuit 160 inserted between the DC / DC converter circuit 150 and the DC chopper circuit 180.

[0269] Figure 4The furnace power supply 100 in FIG. 5 can be connected to three electrodes 120. Each power submodule 510 can be connected to exactly one individual electrode 120, thereby generating an independent power supply for each of the electrodes 120. In other words, there is a one-to-one assignment between one power submodule 510 and one electrode 120.

[0270] Figure 4 An alternative embodiment (not shown) of the furnace power supply 100 in FIG. 1 can be connected to three electrodes 120. Each power submodule 510 includes a DC chopper circuit 180 instead of a DC / AC converter circuit 170. Each power submodule 510 can be connected to exactly one individual electrode 120, thereby generating an independent power supply for each of the electrodes 120. In other words, there is a one-to-one assignment between one power submodule 510 and one electrode 120.

[0271] Figure 5 The furnace power supply 100 in FIG. 1 includes three AC / DC converter circuits 130 connected in parallel to each other. The AC / DC converter circuits 130 are connectable to a three-phase power grid 110 .

[0272] The AC / DC converter circuit 130 is connected to the DC / DC converter circuit 150 via a common first buffer circuit 140 .

[0273] The electronic control unit 200 is connected to each of the AC / DC converter circuits 130. The electronic control unit 200 is configured to individually control or regulate each of the AC / DC converter circuits 130, thereby allowing each AC / DC converter circuit 130 to be independently controlled or regulated. In this way, the active power flow of the furnace power supply 100 can be better regulated.

[0274] exist Figure 5 In an alternative embodiment (not shown) of the embodiment of the furnace power supply 100 , the power sub-modules 510 each include a DC chopper circuit 180 instead of a DC / AC converter circuit 170 .

[0275] An alternative embodiment of the furnace power supply 100 includes three AC / DC converter circuits 130 connected in parallel with each other. The AC / DC converter circuits 130 are connectable to a three-phase grid 110.

[0276] The AC / DC converter circuit 130 is connected to the DC / DC converter circuit 150 via a common first buffer circuit 140 .

[0277] The electronic control unit 200 is connected to each of the AC / DC converter circuits 130. The electronic control unit 200 is configured to individually control or regulate each of the AC / DC converter circuits 130, thereby allowing each AC / DC converter circuit 130 to be independently controlled or regulated. In this way, the active power flow of the furnace power supply 100 can be better regulated.

[0278] Figure 6 The furnace power supply device 100 includes three first buffer circuits 140. Each first buffer circuit 140 is inserted between one AC / DC converter circuit 130 and one DC / DC converter circuit 150, thereby establishing a one-to-one connection between exactly one AC / DC converter circuit 130 and exactly one DC / DC converter circuit 150.

[0279] The AC / DC converter circuit 130, the first buffer circuit 140, the DC / DC converter circuit 150, the second buffer circuit 160, and the DC / AC converter circuit 170 form a power module 500. The first buffer circuit 140 is interposed between the AC / DC converter circuit 130 and the DC / DC converter circuit 150. The second buffer circuit 160 is interposed between the DC / DC converter circuit 150 and the DC / AC converter circuit 170. Therefore, the furnace power supply device 100 includes three power modules 500.

[0280] Each power module 500 can be connected to exactly one individual electrode 120, thereby generating an independent power supply for each of the electrodes 120. In other words, there is a one-to-one assignment between one power module 500 and one electrode 120.

[0281] Figure 6 An alternative embodiment (not shown) of the furnace power supply 100 includes three first buffer circuits 140. Each first buffer circuit 140 is inserted between one AC / DC converter circuit 130 and one DC / DC converter circuit 150, thereby establishing a one-to-one connection between exactly one AC / DC converter circuit 130 and exactly one DC / DC converter circuit 150.

[0282] The AC / DC converter circuit 130, the first buffer circuit 140, the DC / DC converter circuit 150, the second buffer circuit 160, and the DC chopper circuit 180 form a power module 500. The first buffer circuit 140 is interposed between the AC / DC converter circuit 130 and the DC / DC converter circuit 150. The second buffer circuit 160 is interposed between the DC / DC converter circuit 150 and the DC chopper circuit 180. Therefore, the furnace power supply device 100 includes three power modules 500.

[0283] Each power module 500 can be connected to exactly one individual electrode 120, thereby generating an independent power supply for each of the electrodes 120. In other words, there is a one-to-one assignment between one power module 500 and one electrode 120.

[0284] Figure 7 A power supply system (not labeled) for electrodes 120 of an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace includes two or more furnace power supply devices 100 connected in parallel to each other.

[0285] The system further comprises an electronic coordination and regulation unit 400. The electronic coordination and regulation unit 400 is connected to the furnace power supply 100.

[0286] The system also includes an electrode adjuster 410 connectable to an electrode height adjustment member (not shown).

[0287] The electronic coordination and regulation unit 400 is configured to communicate with the electronic control unit 200 of the furnace power supply 100 and with the electrode regulator 410 .

[0288] Figure 8 A power supply system (not labeled) for a plurality of electrodes 120 of an electric arc furnace, an electric reduction furnace, or a submerged arc resistance furnace includes a plurality of electrode adjusters 410. Preferably, one electrode adjuster 410 can be connected to only one height adjustment member (not shown), wherein each electrode 120 includes one height adjustment member.

[0289] The plurality of power supply devices 100 corresponds to the plurality of electrodes 120. In other words, one power supply device 100 can be connected to only one electrode 120, resulting in a one-to-one assignment between one furnace power supply device 100 and one electrode 120.

[0290] Reference Signs List

[0291] 100 Furnace power supply device

[0292] 110 three-phase power grid

[0293] 120 electrodes

[0294] 130 AC / DC Converter Circuit

[0295] 140 First buffer circuit

[0296] 150 DC / DC converter circuit

[0297] 160 Second buffer circuit

[0298] 170 DC / AC Converter Circuit

[0299] 180 DC chopper circuit

[0300] 200 Electronic Control Unit

[0301] 300 DC power supply

[0302] 400 Electronic coordination and regulation unit

[0303] 410 Electrode Regulator

[0304] 500 Power Module

[0305] 510 power submodule

Claims

1. A furnace power supply device (100) for supplying electric energy to an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace, - wherein the furnace power supply device (100) is connectable to a three-phase power grid (110), preferably to a medium voltage three-phase power grid (110); - wherein the furnace power supply device (100) is connectable to at least one electrode (120) of the electric arc furnace, the electric reduction furnace or the submerged arc resistance furnace, - wherein the furnace power supply device (100) comprises: - at least one AC / DC converter circuit (130) connectable to the three-phase grid (110) and configured to rectify the alternating current of at least one phase of the three-phase grid (110), wherein the three-phase grid (110) has a voltage level higher than or equal to 1000 VAC, and - at least one DC / DC converter circuit (150) configured to handle voltage levels higher than or equal to 500 VDC, wherein the DC / DC converter circuit (150) is connected to the DC side of the AC / DC converter circuit (130).

2. The furnace power supply device (100) according to claim 1, characterized in that: The power supply device (100) comprises less than one transformer, preferably less than one step-down transformer, arranged between the three-phase power grid (110) and at least one electrode (120).

3. The furnace power supply device (100) according to claim 1 or claim 2, characterized in that: The AC / DC converter circuit (130) comprises at least one bidirectional AC / DC converter unit, preferably an active front end circuit.

4. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one DC / DC converter circuit (150) includes at least one bidirectional DC / DC converter unit.

5. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one DC / DC converter circuit (150) includes at least one electrically isolated DC / DC converter unit.

6. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one DC / DC converter circuit (150) includes at least one switching DC / DC converter unit.

7. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one first buffer circuit (140) using direct current is inserted between the AC / DC converter circuit (130) and the DC / DC converter circuit (150), thereby connecting the AC / DC converter circuit (130) and the DC / DC converter circuit (150), wherein the first buffer circuit (140) is configured to store energy and generate a separation between the three-phase grid (110) and the at least one electrode (120).

8. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one DC power source (300), preferably a regenerative DC power source (300), is connectable to the first buffer circuit (140).

9. The furnace power supply (100) according to one of the preceding claims, characterized in that The furnace power supply (100) comprises a plurality of AC / DC converter circuits (130) connected in parallel with each other, wherein the AC / DC converter circuit (130) is connected to a common first buffer circuit (140), preferably to a plurality of first buffer circuits (140).

10. The furnace power supply (100) according to one of the preceding claims, characterized in that At least one second buffer circuit 160 using direct current is inserted between the DC / DC converter circuit (150) and the at least one electrode (120), thereby at least indirectly connecting the DC / DC converter circuit (150) and the at least one electrode (120), wherein the second buffer circuit (160) is configured to store energy and to generate a separation between the three-phase grid (110) and the at least one electrode (120).

11. The furnace power supply (100) according to one of the preceding claims, characterized in that The furnace power supply (100) comprises an electronic control unit (200), wherein the electronic control unit (200) is connectable to the AC / DC converter circuit (130) and is configured to regulate the active power flow of the furnace power supply (100).

12. The furnace power supply (100) according to one of the preceding claims, characterized in that The furnace power supply (100) comprises at least one DC / AC converter circuit (170) configured to supply electrical energy to at least one electrode (120), wherein at least one DC / DC converter circuit (150) is connected to the at least one DC / AC converter circuit (170).

13. The furnace power supply device (100) according to one of claims 1 to 11, characterized in that The furnace power supply (100) includes at least one DC chopper circuit (180) configured to supply electrical energy to at least one electrode (120), wherein at least one DC / DC converter circuit (150) is connected to the at least one DC chopper circuit (180).

14. System for supplying electrical energy to at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace, - wherein the system is connectable to at least one three-phase electrical network (110); - wherein the system is connectable to at least one electrode (120) of at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace; It is characterized by It has the following characteristics: - the system comprises a plurality of furnace power supply devices (100) according to one of the preceding claims, and - wherein the plurality of furnace power supply devices (100) are connected in parallel with each other.

15. An electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace, characterized in that The electric arc furnace, the electric reduction furnace or the submerged arc resistance furnace comprises a furnace power supply device (100) according to one of claims 1 to 13 and / or a system according to claim 14.

16. Use of a furnace power supply (100) according to one of claims 1 to 13 for supplying electrical energy to at least one electric arc furnace and / or electric reduction furnace and / or submerged arc resistance furnace.

17. Method for operating an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace, in particular an electric arc furnace, an electric reduction furnace or a submerged arc resistance furnace according to claim 15, characterized in that The ratio of the active power flow to the reactive power flow is controlled and / or adjusted by influencing the control amount of the AC / DC converter circuit (130) and / or the DC / DC converter circuit (150) and / or the DC / AC converter circuit (170) and / or the DC chopper circuit (180), specifically minimizing the reactive power flow by influencing the control amount of the AC / DC converter circuit (130) and / or the DC / AC converter circuit (170).

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