An autotransformer for converting three-phase AC power to nine-phase AC power. The autotransformer includes three coils each having serial connected windings and non-serial connected windings. The combination of the serial and non-serial windings are interconnected to form a polygon for a total of six windings per phase, in an arrangement which reduces the power rating of an autotransformer suitable for 18-pulse AC to DC power converters. There are a plurality of direct outputs that are equal in magnitude and are out of phase with respect to the voltages at the input. The input is offset from the nine outputs to create the required phase magnitudes for DC power converters.

For power conversion, a power conversion system includes a plurality of power converters and a phase shifting transformer. The phase shifting transformer includes 3-phase primary windings, a core and a plurality of m secondary winding groups. Each of the secondary winding groups includes n secondary windings in electromagnetic communication with a corresponding primary winding and feeding the plurality of power converters. Phase angle sets of the secondary winding groups are all different with a non-zero secondary winding phase shift between any two secondary winding groups.

A power conversion system includes a first converter effectively connected in series to a second converter. Each converter has a plurality of output levels. A phase-shifted transformer is coupled to the converters. The phase-shifted transformer has a delta-wound winding and an open star winding. The first converter is coupled to the open star winding and the second converter is coupled to the delta winding. The open star winding is configured for direct connection to either of a load or the open star winding of a second phase-shifted transformer, having a delta winding connected to a third converter. One or more DC voltage sources are each connected to the first and second converters by a respective DC link capacitor. Each DC voltage source is connected to a common power grid by an isolated multiphase transformer winding.

A power conversion system includes a first converter effectively connected in series to a second converter. Each converter has a plurality of output levels. A phase-shifted transformer is coupled to the converters. The phase-shifted transformer has a delta-wound winding and an open star winding. The first converter is coupled to the open star winding and the second converter is coupled to the delta winding. The open star winding is configured for direct connection to either of a load or the open star winding of a second phase-shifted transformer, having a delta winding connected to a third converter. One or more DC voltage sources are each connected to the first and second converters by a respective DC link capacitor. Each DC voltage source is connected to a common power grid by an isolated multiphase transformer winding.

An arrangement for connecting a railway power supply for a railway track to a three-phase supply network. The arrangement has a three-phase AC transformer and a balancing device for a uniform electric load of the three phases of the three-phase supply network. The three-phase AC transformer is configured for connecting to the three-phase supply network on the primary side and is connected to the balancing device on the secondary side. The three-phase AC transformer is configured for connecting to a railway power supply which has an autotransformer system with two contact lines and two conductors that are carried along the railway track in an insulated manner.

An arrangement for connecting a railway power supply for a railway track to a three-phase supply network. The arrangement has a three-phase AC transformer and a balancing device for a uniform electric load of the three phases of the three-phase supply network. The three-phase AC transformer is configured for connecting to the three-phase supply network on the primary side and is connected to the balancing device on the secondary side. The three-phase AC transformer is configured for connecting to a railway power supply which has an autotransformer system with two contact lines and two conductors that are carried along the railway track in an insulated manner.

A quad-T transformer in some embodiments includes a first split winding, a second split winding, and two orthogonal closed-loop windings coupled between the first split winding and the second split winding. Wires can be wound around magnetic cores. A first of the two orthogonal closed-loop windings is coupled to a first portion of each of the first split winding and the second split winding. A second of the two orthogonal closed-loop windings is coupled to a second portion of each of the first split winding and the second split winding. A bi-directional single-phase/three-phase converter includes the quad-T transformer and a Scott-T transformer with an output connected to a three-phase connection. The Scott-T transformer also has a 90-degree input connected to the quad-T transformer and a zero-degree input connected to a single-phase connection.

A quad-T transformer in some embodiments includes a first split winding, a second split winding, and two orthogonal closed-loop windings coupled between the first split winding and the second split winding. Wires can be wound around magnetic cores. A first of the two orthogonal closed-loop windings is coupled to a first portion of each of the first split winding and the second split winding. A second of the two orthogonal closed-loop windings is coupled to a second portion of each of the first split winding and the second split winding. A bi-directional single-phase/three-phase converter includes the quad-T transformer and a Scott-T transformer with an output connected to a three-phase connection. The Scott-T transformer also has a 90-degree input connected to the quad-T transformer and a zero-degree input connected to a single-phase connection.

The present disclosure provides a DC power supply system and its control method. The system includes: a first power supply circuit and a second power supply circuit, at least one of the first power supply circuit and the second power supply circuit including a phase shifting transformer, wherein the first power supply circuit includes a number N of first AC/DC conversion circuits, and the second power supply circuit includes a number N of second AC/DC conversion circuits, where N is an integer greater than or equal to 2; an output side of each of the N first AC/DC conversion circuits is electrically connected in parallel with an output side of a corresponding second AC/DC conversion circuit of the N second AC/DC conversion circuits through a DC busbar to form N sets of redundant backup circuits.

Multiphase lighting fixtures having one or more light emitting diode (LED) light sources are provided. In one example implementation, a light fixture includes one or more light sources, such as LED light sources. The light fixture includes a power conversion circuit. The power conversion circuit can be configured to receive a multiphase input power comprising three or more alternating current (AC) phases. The power conversion circuit can be further configured to convert the multiphase input power to rectified output for powering the one or more light sources. In some example implementations, the DC rectified output can have a voltage ripple of less than about 7%, such as less than about 3%.