Voltage transformer
The invention relates to a voltage transformer for converting a primary-side alternating voltage at a first voltage level into a secondary-side alternating voltage at a second voltage level, the voltage transformer having a DC link in which a first direct voltage generated from the primary-side alternating voltage is converted into a second direct voltage by means of a DC-to-DC voltage converter, characterised in that an output circuit for providing a third direct voltage for the connection of at least one load is coupled to the DC link, in particular to the DC-to-DC voltage converter thereof.
1. A voltage transformer for converting a primary-side alternating voltage (MVAC) at a first voltage level into a secondary-side alternating voltage (LVAC) at a second voltage level, comprising:
a direct voltage intermediate circuit with a DC-DC voltage converter for converting a first DC voltage generated from a primary-side AC voltage into a second DC voltage,
a decoupling circuit for providing a third DC voltage for connecting at least one load couplable to the DC-DC voltage converter, wherein the DC-DC voltage converter has a plurality of DC-DC converter modules which are either connected directly in series on a primary side or are connected in series by AC-DC converter modules, wherein the DC-DC converter modules each have a transformer and have a primary-side converter cell and a secondary side converter cell, wherein the primary-side converter cell and the secondary side converter cell are coupled to one another by galvanically isolated windings of the transformer, and
a decoupling module coupled to a further winding of the transformer so that the decoupling module is inductively supplied with electrical energy by the transformer,
wherein the decoupling circuit for providing the third DC voltage is connected in series or in parallel respectively by a series connection or parallel connection of the transformer.
2. The voltage transformer as claimed in claim 1 , wherein a first voltage level of the first DC voltage is a voltage level of an AC medium voltage network and wherein a second voltage level of the second DC voltage is a voltage level of an AC low-voltage network.
3. The voltage transformer as claimed in claim 1 wherein the decoupling circuit is integrated into the DC-DC voltage converter in an electrical and/or magnetic manner.
4. The voltage transformer as claimed in claim 1 wherein the DC-DC voltage converter is constructed in a modular manner from a multiplicity of individual DC-DC voltage converter modules which are connected to one another in parallel on a secondary side.
5. The voltage transformer as claimed in claim 4 , wherein the DC-DC voltage converter modules are connected on the primary side either directly in series or via AC-DC converter modules in series.
6. The voltage transformer as claimed in claim 4 further comprising one or more decoupling modules added to some or all of the DC-DC voltage converter modules on the primary side, wherein the decoupling modules are connected to one another to form the decoupling circuit.
7. The voltage transformer as claimed in claim 6 , wherein the one or more decoupling modules are connected to one another in series to provide the third DC voltage.
8. The voltage transformer as claimed in claim 1 wherein the transformer has a magnetic core on which windings of the transformer are arranged.
9. The voltage transformer as claimed in claim 1 further comprising a charging station for charging electric vehicles coupled with the third DC voltage.
10. The voltage transformer as claimed in claim 9 , wherein the charging station is coupled with the third DC voltage by a DC-DC voltage converter.
11. A method for providing electrical energy for charging electric vehicles with direct current, comprising:
converting, using a voltage converter a primary-side AC voltage at a first voltage level into a secondary-side AC voltage at a second voltage level, wherein the voltage converter has an intermediate DC voltage circuit in which a first DC voltage generated from the primary-side AC voltage is converted into a second DC voltage by a DC-DC voltage converter, and
a third DC voltage decoupled from the intermediate DC voltage circuit by a decoupling circuit is fed into the electric vehicle for charging the electric vehicle,
wherein the third DC voltage is formed by series or parallel connection of decoupling modules, wherein each of the decoupling modules is supplied with electrical energy inductively by a transformer,
wherein the intermediate DC voltage circuit has a plurality of DC-DC converter modules which are either connected directly in series on the primary side or connected in series by AC-DC converter modules, wherein the DC-DC converter modules each have a transformer and have a primary-side converter cell and a secondary-side converter cell which are coupled to one another by galvanically isolated windings of the transformer,
wherein a decoupling module is coupled to a further winding of the transformer.
12. The method as claimed in claim 11 wherein the third DC voltage is decoupled from the DC-DC converter of the intermediate DC voltage circuit.
13. The voltage transformer as claimed in claim 1 wherein the decoupling circuit is coupled with the intermediate DC voltage circuit by the DC-DC converter of the intermediate DC voltage circuit.