High voltage DC/DC converter
View Patent ↗It is presented a high voltage DC/DC converter for converting between a first DC connection and a second DC connection. The high voltage DC/DC converter comprises: a first set of DC terminals; a second set of DC terminals); a multiphase transformer device comprising a plurality of primary windings and a corresponding plurality of secondary windings; a first converter arranged to convert DC to AC, comprising a plurality of phase legs serially connected between the first set of DC terminals, wherein each phase leg is connected to an AC connection of a respective primary winding; and a second converter arranged to convert AC from the secondary windings to DC on the second set of DC terminals.
1. A high voltage DC/DC converter for converting between a first DC side and a second DC side, the high voltage DC/DC converter comprising:
a first set of DC terminals;
a second set of DC terminals;
a multiphase transformer device comprising a plurality of primary windings and a corresponding plurality of secondary windings;
a first converter arranged to convert DC to AC, comprising a plurality of phase legs serially connected between the first set of DC terminals, wherein each phase leg:
comprises a plurality of converter cells;
is connected to an AC connection of a respective primary winding;
comprises a first AC connection terminal and a second AC connection terminal; and
comprises a phase branch comprising at least two converter cells, and having first and second branch end terminals;
a second converter arranged to convert AC from the secondary windings to DC on the second set of DC terminals; and
each phase leg of the first converter comprising a capacitor, wherein:
the capacitor is connected between the first branch end terminal and the first AC connection terminal, the capacitor forming a DC blocking capacitor;
the second AC connection terminal is connected to the second branch end terminal; and
the series connection of the phase legs between the first set of DC terminals is such that a first series connection point in a phase leg is located between the first branch end terminal and the DC blocking capacitor, while a second series connection point is located between the second branch end terminal and the second AC connection terminal, and the second series connection point of one of the phase legs is directly connected to the first series connection point of another one of the phase legs that is immediately after the one of the phase legs.
2. The high voltage DC/DC converter according to claim 1 , wherein the second converter comprises a plurality of bridge legs connected in parallel between the second set of DC terminals, wherein each bridge leg is connected to a respective AC connection terminal of the plurality of secondary windings.
3. The high voltage DC/DC converter according to claim 1 , wherein the second converter comprises a plurality of phase legs serially connected between the second set of DC terminals, wherein each phase leg is connected to an AC connection of a respective secondary winding.
4. The high voltage DC/DC converter according to claim 1 , wherein the second converter is controllable to provide a constant DC voltage.
5. The high voltage DC/DC converter according to claim 1 , wherein the first converter is controllable to provide a defined voltage and frequency to the primary windings.
6. The high voltage DC/DC converter according to claim 1 , wherein the DC/DC converter is reversible, allowing bidirectional power transfer.
7. The high voltage DC/DC converter according to claim 1 , wherein each phase branch of each phase leg of the first converter comprises a cascade of at least two series connected and independently switchable converter cells.
8. The high voltage DC/DC converter according to claim 7 , wherein the phase branch of each phase leg of the second converter comprises at least two parallel connected cascades of converter cells.
9. A high voltage DC/DC converter for converting between a first DC side and a second DC side, the high voltage DC/DC converter comprising:
a first set of DC terminals;
a second set of DC terminals;
a multiphase transformer device comprising a plurality of primary windings and a corresponding plurality of secondary windings;
a first converter arranged to convert DC to AC, comprising a plurality of phase legs serially connected between the first set of DC terminals, wherein each phase leg:
comprises a plurality of converter cells;
is connected to an AC connection of a respective primary winding;
comprises a first AC connection terminal and a second AC connection terminal; and
comprises a phase branch comprising at least two converter cells, and having first and second branch end terminals (E);
a second converter arranged to convert AC from the secondary windings to DC on the second set of DC terminals;
each phase leg of the first converter comprising a capacitor, wherein:
the capacitor is connected between the first branch end terminal and the first AC connection terminal, the capacitor forming a DC blocking capacitor;
the second AC connection terminal is connected to the second branch end terminal;
the series connection of the phase legs between the first set of DC terminals is such that a first series connection point in a phase leg is located between the first branch end terminal and the DC blocking capacitor, while a second series connection point is located between the second branch end terminal and the second AC connection terminal; and
each phase branch of each phase leg of the first converter comprises a cascade of at least two series connected and independently switchable converter cells; and
a control system configured to control the switching of the converter cells of the phase branch of a phase leg of the first converter to provide a voltage according to the following expression between the first and second series connections points of a phase leg: U k =U k DC +Û ν AC sin(ωt+Θ k )
where k indicates the k th phase leg, kε[1,P], P being the number of phases of the first converter; U k DC denotes a predetermined desired DC voltage between the first and second connection points, where
∑
k
=
1
P
U
k
DC
=
U
DC
,
U DC being the voltage between the DC connection terminals; Û ν AC is a desired peak AC voltage between the first and second connection points, t is time, ω is the desired angular frequency at the AC connection and Θ k is the desired phase angle.
10. The high voltage DC/DC converter according to claim 9 , wherein the predetermined desired DC voltage corresponds to
V
1
P
,
where V1 is the voltage between the DC connection terminals and P is the number of phases of the first converter.
11. The high voltage DC/DC converter according to claim 1 , wherein at least part of the converter cells conform to a half bridge structure.
12. The high voltage DC/DC converter according to claim 1 , wherein at least part of the converter cells conform to a full bridge structure.
13. The high voltage DC/DC converter according to claim 2 , wherein the second converter is controllable to provide a constant DC voltage.
14. The high voltage DC/DC converter according to claim 3 , wherein the second converter is controllable to provide a constant DC voltage.
15. The high voltage DC/DC converter according to claim 2 , wherein the first converter is controllable to provide a defined voltage and frequency to the primary windings.
16. The high voltage DC/DC converter according to claim 3 , wherein the first converter is controllable to provide a defined voltage and frequency to the primary windings.
17. The high voltage DC/DC converter according to claim 4 , wherein the first converter is controllable to provide a defined voltage and frequency to the primary windings.
18. The high voltage DC/DC converter according to claim 2 , wherein the DC/DC converter is reversible, allowing bidirectional power transfer.
19. The high voltage DC/DC converter according to claim 3 , wherein the DC/DC converter is reversible, allowing bidirectional power transfer.
20. The high voltage DC/DC converter according to claim 4 , wherein the DC/DC converter is reversible, allowing bidirectional power transfer.