Bi-directional medium voltage to low voltage converter topology
A bi-directional medium voltage converter topology includes an n-pulse line-interphase-transformer, LIT; a plurality of bi-directional medium voltage, MV converters connected to the LIT on an AC side thereof and connected in parallel on a DC side thereof; a bi-directional multi-stage DC/DC converter connected to the plurality of bi-directional MV converters; and a bi-directional low voltage, LV, DC/DC converter; wherein the multi-stage DC/DC converter and the LV DC/DC converter are connected to each other galvanically insulated.
1 . A bi-directional medium voltage converter topology, comprising:
a multi-pulse line-interphase-transformer (LIT) connected to a three-phase grid;
a plurality of bi-directional medium voltage (MV) converters connected to the multi-pulse LIT on an alternating current (AC) side and connected in parallel on a direct current (DC) side; and
a medium-voltage to low-voltage (MV-to-LV) DC-to-DC (DC/DC) converter with an AC interface, wherein the MV-to-LV DC/DC converter comprises:
a bi-directional multi-stage converter connected to the plurality of bi-directional MV converters; and
a bi-directional low voltage (LV) converter;
wherein the bi-directional multi-stage converter and the bi-directional LV converter are connected to each other but galvanically insulated via one or more medium frequency transformers (MFTs);
wherein the bi-directional multi-stage converter comprises a plurality of switch cells connected in series;
wherein an upper cell of the plurality of switch cells is connected to a first end of a primary transformer coil of one of the one or more MFTs, and a second end of the primary transformer coil of the one of the one or more MFTs is connected to a lower cell of the plurality of switch cells; and
wherein secondary transformer coils of the one or more MFTs are connected in parallel when there is more than one MFT of the one or more MFTs.
2 . The bi-directional medium voltage converter topology according to claim 1 , wherein each converter of the plurality of bi-directional MV converters comprises active switches, and wherein the active switches are a combination of:
an insulated-gate bipolar transistors (IGBT) and a diode;
an IGBT and a thyristor; or
an IGBT and an anti-parallel transistor.
3 . The bi-directional medium voltage converter topology according to claim 1 , wherein each converter of the plurality of bi-directional MV converters comprises active switches, and wherein at least one of the active switches comprises a metal-insulator-semiconductor field-effect transistor (MOSFET).
4 . The bi-directional medium voltage converter topology according to claim 1 , wherein each converter of the plurality of bi-directional MV converters is operated at a low frequency.
5 . The bi-directional medium voltage converter topology according to claim 1 , wherein pulse number of the multi-pulse LIT comprises 12, 18, 24, 36 or 48.
6 . The bi-directional medium voltage converter topology according to claim 1 , wherein each of the plurality of switch cells comprises a combination of a transistor and one of an antiparallel diode, a thyristor or a further transistor; and wherein the bi-directional multi-stage converter further comprises capacitors that are arranged in parallel to one or more of the plurality of switch cells.
7 . The bi-directional medium voltage converter topology according to claim 1 , wherein the upper cell is connected via a capacitor or via an inductor to the first end of the primary transformer coil of the one of the one or more MFTs.
8 . The bi-directional medium voltage converter topology according to claim 1 , wherein the bi-directional medium voltage converter topology is configured to simulate a pulse LIT concurrently with the operation of the multi-pulse LIT and to use results of the simulation for generating control signals for switches of the plurality of bi-directional MV converters.
9 . A bi-directional medium voltage converter topology, comprising:
a multi-pulse line-interphase-transformer (LIT) connected to a three-phase grid;
a plurality of bi-directional medium voltage (MV) converters connected to the multi-pulse LIT on an alternating current (AC) side and connected in parallel on a direct current (DC) side; and
a medium-voltage to low-voltage (MV-to-LV) DC-to-DC (DC/DC) converter with an AC interface, wherein the MV-to-LV DC/DC converter comprises:
a bi-directional multi-stage converter connected to the plurality of bi-directional MV converters; and
a bi-directional low voltage (LV) converter;
wherein the bi-directional multi-stage converter and the bi-directional LV converter are connected to each other but galvanically insulated via one or more medium frequency transformers (MFTs);
wherein the bi-directional multi-stage converter comprises a plurality of switch cells connected in series;
wherein each of the plurality of switch cells is connected to a corresponding first end of a primary transformer coil of a corresponding MFT of the one or more MFTs, and a lower side of each switch cell of the plurality of switch cells is connected to a corresponding second end of the primary transformer coil of the corresponding MFT of the one or more MFTs; and
wherein secondary transformer coils of the one or more MFTs are connected in parallel when there is more than one MFT of the one or more MFTs.