Abstract: A non-linear load in the form of an arc furnace with an upstream furnace transformer is supplied with electric power from a power supply device with a plurality of converter units. The converter units have a plurality of main modules with inputs connected to a respective phase of a three-phase grid. The converter units have a common star point between the main modules and the primary side of the furnace transformer. Each main module has a series circuit with a coupling inductance and a plurality of submodules. The submodules have a bridge circuit with four self-commutated semiconductor switches and a bridge path with a storage capacitor between input and output. The semiconductor switches of the submodules can each be switched independently of the semiconductor switches of the other submodules of the same main module and of the other main modules.

Abstract: A power factor correction device for an AC voltage supply system includes a transformer which is interconnected, on the secondary side, to form a star point circuit and which has a secondary-side connection for each phase. A module series circuit with at least two switching modules, which are connected in series and each of which has at least four switches and a capacitor, is respectively connected between each of the secondary-side connections of the transformer and the star point of the star circuit. There is provided a transformer which is a high-leakage-reactance transformer.

Abstract: A power factor correction device for an AC voltage supply system includes a transformer which is interconnected, on the secondary side, to form a star point circuit and which has a secondary-side connection for each phase. A module series circuit with at least two switching modules, which are connected in series and each of which has at least four switches and a capacitor, is respectively connected between each of the secondary-side connections of the transformer and the star point of the star circuit. There is provided a transformer which is a high-leakage-reactance transformer.

Abstract: A rectifier arrangement includes at least one input alternating voltage terminal to which an alternating current can be supplied, at least two output direct voltage terminals at which direct current can be tapped and at least one series circuit with at least two sub-modules connected in series. Each sub-module of the series circuit includes at least one converter module, an inverter module and a transformer module. Each sub-module of the series circuit additionally includes a rectifier module. The outputs of the rectifier modules are connected in parallel and form the output direct voltage terminals of the rectifier arrangement.

Abstract: A non-linear load in the form of an arc furnace with an upstream furnace transformer is supplied with electric power from a power supply device with a plurality of converter units. The converter units have a plurality of main modules with inputs connected to a respective phase of a three-phase grid. The converter units have a common star point between the main modules and the primary side of the furnace transformer. Each main module has a series circuit with a coupling inductance and a plurality of submodules. The submodules have a bridge circuit with four self-commutated semiconductor switches and a bridge path with a storage capacitor between input and output. The semiconductor switches of the submodules can each be switched independently of the semiconductor switches of the other submodules of the same main module and of the other main modules.

Abstract: A method for controlling a plurality of multi-level converters, which are closed in parallel at alternating-voltage connections thereof and which each have a series arrangement of two-pole sub-modules. Each of the sub-modules has at least two controllable electronic switches and an energy storage device, wherein the controllable electronic switches are connected in series forming a series arrangement and the series arrangement is connected in parallel with the energy storage device. In the method, a stepped voltage curve is produced at the particular alternating-voltage connection of the multi-level converters. The voltage curve of a second multi-level converter is offset in time in relation to the voltage curve of a first multi-level converter. A converter assembly includes a device for the time delay of the alternating-voltage curve of at least one multi-level converter in relation to the alternating-voltage curve of a further multi-level converter.

Abstract: In a power supply system for a three-phase arc furnace (1), comprising at least one furnace transformer (4), the furnace transformer (4) is connected on the secondary side to the three-phase arc furnace (1). On the primary side, the furnace transformer (4) is connected to a three-phase supply mains (3) through an indirect converter (5). The indirect converter (5) comprises at least one rectifier (6) on the mains side, at least one inverter (7) on the transformer side, and an intermediate circuit (8) between the rectifier (6) and the inverter (7). Each phase of the three-phase supply mains (3) is connected to the intermediate circuit (8) through two converter elements (11) of the rectifier (6) in each case. Each primary-side phase of the furnace transformer (4) is connected to the intermediate circuit (8) through two converter elements (2) of the inverter (7) in each case.

Abstract: An energy storage arrangement for an electric load which exchanges electrical power with an energy supply network, has two connections in the form of a load to the parallel circuit and for the energy supply network, a converter which is switched between the connections, is voltage-impressed and contains an energy store. The energy store is designed to store an energy amount which exceeds that necessary for the regular operation of the converter by a multiple. An arc furnace which is fed as a load from an energy supply network contains such an energy storage arrangement.

Abstract: A multilevel converter has a plurality of converter strands, which are connected to the phases of a three-phase-network in a star or delta connection. From phase voltage values and phase current values, an active component characteristic of the overall active current and two asymmetrical components characteristic of a distribution of the overall flowing active and reactive currents are determined. The active and the two asymmetrical components are each filtered and multiplied with the phase voltage values and the two filtered asymmetrical components. The multiplied values are then weighed and added to the phase current values. From the asymmetrical components and the phase voltage values, a zero current is determined and added to the phase current values such that it symmetrizes a potential asymmetrical active current flow that would occur without the zero current. From the modified phase current values, a control state for the converter strands is determined.

Abstract: A multilevel converter has a plurality of converter strands, which are connected to the phases of a three-phase-network in a star or delta connection. From phase voltage values and phase current values, an active component characteristic of the overall active current and two asymmetrical components characteristic of a distribution of the overall flowing active and reactive currents are determined. The active and the two asymmetrical components are each filtered and multiplied with the phase voltage values and the two filtered asymmetrical components. The multiplied values are then weighed and added to the phase current values. From the asymmetrical components and the phase voltage values, a zero current is determined and added to the phase current values such that it symmetrizes a potential asymmetrical active current flow that would occur without the zero current. From the modified phase current values, a control state for the converter strands is determined.

Abstract: In a power supply system for a three-phase arc furnace (1), comprising at least one furnace transformer (4), the furnace transformer (4) is connected on the secondary side to the three-phase arc furnace (1). On the primary side, the furnace transformer (4) is connected to a three-phase supply mains (3) through an indirect converter (5). The indirect converter (5) comprises at least one rectifier (6) on the mains side, at least one inverter (7) on the transformer side, and an intermediate circuit (8) between the rectifier (6) and the inverter (7). Each phase of the three-phase supply mains (3) is connected to the intermediate circuit (8) through two converter elements (11) of the rectifier (6) in each case. Each primary-side phase of the furnace transformer (4) is connected to the intermediate circuit (8) through two converter elements (12) of the inverter (7) in each case.

Abstract: A static VAR compensator has several parallel compensation components (K1–K3). To connect the static VAR compensator to an operating voltage (U) the compensation components (K1–K3) are first successively connected to the operating voltage (U) by a control unit (CU) via a series resistor (R). The compensation components (K1–K3) are only connected to the operating voltage (U) without series resistance once the aforementioned connection has been completed.