A multi-level inverter topology is disclosed. A power converter circuit converts a DC source at its input to provide an alternating current (AC) at its output. The power converter circuit may have a controller operably attached to multiple series connections of switches. The controller may control one or more of the multiple series connections of switches to convert a DC input to provide multi-level AC voltages with DC offset across two terminals of the power converter circuit. The multi-level AC voltages with DC offset may then be converted by use of a plurality of series connections of switches to provide a single-phase AC voltage at a first output terminal with respect to at least one of a neutral potential, an earth potential, or a terminal of the power converter circuit.

An electrical converter (203) having an active diode-clamped multilevel topology is shown. Each clamping diode is connected in antiparallel with a switch (S5A, S5B). The converter comprises polyphase supply phases (A, B, C) each of which are connected via a respective phase leg (401, 402, 403) to dc rails (301, 302) and a dc-link capacitor. The dc-link capacitor includes a plurality of series-connected capacitors (404, 405). A controller is configured to, in response to an event signal, for each phase leg, activate a combination of switches therein to form a pair of parallel conduction paths to a midpoint (406) between two capacitors in the dc-link capacitor, thereby connecting each phase to the same node.

An electrical converter (203) having an active diode-clamped multilevel topology is shown. Each clamping diode is connected in antiparallel with a switch (S5A, S5B). The converter comprises polyphase supply phases (A, B, C) each of which are connected via a respective phase leg (401, 402, 403) to dc rails (301, 302) and a dc-link capacitor. The dc-link capacitor includes a plurality of series-connected capacitors (404, 405). A controller is configured to, in response to an event signal, for each phase leg, activate a combination of switches therein to form a pair of parallel conduction paths to a midpoint (406) between two capacitors in the dc-link capacitor, thereby connecting each phase to the same node.

A direct current smelting electric furnace includes a rectifying control circuit, a rectifying power supply device, a short network device, a multi-load layout device including multiple electrodes, and an electric furnace body. The rectifying power supply device includes at least two double-circuit direct current power supply packs. Four output terminals of each double-circuit direct current power supply pack are connected to three electrodes in the multi-load layout device by the short network device to constitute two current circuits by an electric furnace weld pool load. Each electrode in the multi-load layout device is connected to homo-polar output terminals of a three-phase negative semi-cycle rectifying output circuit and a three-phase positive semi-cycle rectifying output circuit, separately. The rectifying power supply device-includes multiple output current circuits. The number of output current circuits of the rectifying power supply device is the same as the number of electrodes in the multi-load layout device.

A controller (5) of an uninterruptible power supply apparatus includes: first to sixth comparator circuits (22a to 22f) respectively provided corresponding to first to sixth IGBTs (Q1 to Q6) and outputting, based on a comparison result of the magnitude of three-phase AC voltages, signals (A1 to A6) indicating that a corresponding IGBT is to be turned on; and a control unit (23) that, when a voltage between terminals (VD1 or VD2) of a first or second capacitor (C11 or C12) is higher than a target voltage (VDT), turns on and off each of the first to sixth IGBTs based on signals output from the first to sixth comparator circuits to decrease the voltage between terminals of the first or second capacitor.

Transformer assembly including a first transformer stage having a plurality of first-stage transformer cells; and a second transformer stage. An input of the second transformer stage is connected to an output of the first transformer stage. A lightning impulse breakdown voltage of a transformer cell of the second stage is at least double of a lightning impulse breakdown voltage of transformer cells of the first stage.

In a power converter, a first single-phase AC conversion unit, which is connected to a first line of a first phase and a second line of a second phase of a first three-phase AC, a second single-phase AC conversion unit, which is connected to the second line of the second phase and a third line of a third phase of the first three-phase AC, and a third single-phase AC conversion unit, which is connected to the third line of the third phase and the first line of the first phase of the first three-phase AC, form a delta-connected load for an AC power supply system. At least the first single-phase AC conversion unit, the second single-phase AC conversion unit, and the third single-phase AC conversion unit form a first set in which respective output terminals are connected in series to one another, and the first set, and a second set and a third set, which are different from the first set, form each phase of a star connected power supply. A reactive power control unit controls a reactive power of a converter of each single-phase AC conversion unit based on a reactive power command value generated based on an acquired value related to an active power.

A voltage converter is designed to convert an alternating input voltage into a direct output voltage. The voltage converter includes a first sub-converter having a first switch half-bridge, which is coupled to a first pole of the input voltage by a first main coil, and a second sub-converter having a second switch half-bridge, which is coupled to the first pole of the input voltage by a second main coil. In addition, the voltage converter includes a diode half-bridge, which is jointly used by the first sub-converter and the second sub-converter. The voltage converter has a first return coil and a second return coil, which couple a center point of the diode half-bridge to a second pole of the input voltage. The first and second main coils and the first and second return coils form a coupled choke, the coupled choke having a choke core. The choke core has at least one outer leg, which is surrounded by windings of the first and/or second main coil and/or of the first and/or second return coil, and at least one center leg, which is not surrounded by windings of the main coils or of the return coils. The outer leg and the center leg have materials with different permeabilities.

A method includes detecting a determined operating condition of a first power converter that is one of a plurality of first power converters in a power generating unit, and the power generating unit is one of a plurality of power generating units. The method further includes responding to detection of the determined operating condition by: controlling, via at least one remaining first power converter of the plurality of first power converters, a load current flowing through a power bus coupled to the plurality of power generating units, and altering one or more droop characteristics corresponding to one or more second power converters disposed in other power generating units based at least in part on the controlled load current flowing through the power bus, wherein the one or more second power converters disposed in other power generating units are coupled to the power bus.

A method includes detecting a determined operating condition of a first power converter that is one of a plurality of first power converters in a power generating unit, and the power generating unit is one of a plurality of power generating units. The method further includes responding to detection of the determined operating condition by: controlling, via at least one remaining first power converter of the plurality of first power converters, a load current flowing through a power bus coupled to the plurality of power generating units, and altering one or more droop characteristics corresponding to one or more second power converters disposed in other power generating units based at least in part on the controlled load current flowing through the power bus, wherein the one or more second power converters disposed in other power generating units are coupled to the power bus.