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.

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.