US-20260128670-A1 - AUXILIARY SUPPLY FOR MEDIUM-VOLTAGE DC/DC CONVERTERS UTILIZING AN AUXILIARY TRANSFORMER INTEGRATED IN THE CONVERTER SYSTEM

US20260128670A1US 20260128670 A1US20260128670 A1US 20260128670A1US-20260128670-A1

Abstract

A converter for transferring power from a medium voltage (MV) side to a low voltage (LV) side is described. The converter comprises a MV unit at the MV side; a LV unit at the LV side; a first transformer cell configured to generate a LV AC voltage at a LV AC terminal from a MV AC voltage at a MV AC terminal; a second transformer cell configured to generate an auxiliary AC supply voltage at one or more supply terminals of the second transformer cell from the MV AC voltage at the MV AC terminal, an auxiliary power circuitry configured to provide auxiliary power to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage at the one or more supply terminals.

Inventors

Daniel Christen
Daniel Rothmund
Milos Stojadinovic
Francisco Canales
Sami Pettersson

Assignees

ABB SCHWEIZ AG

Dates

Publication Date: 20260507
Application Date: 20251105
Priority Date: 20241107

Claims (20)

1 . A converter for transferring power from a medium voltage (MV) side to a low voltage (LV) side, the converter comprising: a MV unit at the MV side, wherein the MV unit comprises a direct current (DC)/alternating current (AC) cell having a MV AC terminal, and the DC/AC cell is configured to generate a MV AC voltage at the MV AC terminal from a MV DC voltage; a LV unit at the LV side, wherein the LV unit comprises an AC/DC cell having a LV AC terminal, and the AC/DC cell is configured to generate a LV DC voltage from a LV AC voltage at the LV AC terminal; a first transformer cell comprising a first transformer, wherein the first transformer cell is electrically connected to the MV AC terminal and the LV AC terminal, and configured to generate the LV AC voltage at the LV AC terminal from the MV AC voltage at the MV AC terminal; a second transformer cell comprising a first resonant tank circuitry and a second transformer, wherein the second transformer cell is electrically connected to the MV AC terminal, and configured to generate an auxiliary AC supply voltage at one or more supply terminals of the second transformer cell from the MV AC voltage at the MV AC terminal; and an auxiliary power circuitry coupled to the one or more supply terminals of the second transformer cell, wherein the auxiliary power circuitry is configured to provide auxiliary power to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage at the one or more supply terminals
2 . The converter according to claim 1 , wherein the second transformer cell is connected in parallel to the first transformer cell, and the second transformer of the second transformer cell is connected in parallel to the first transformer of the first transformer cell.
3 . The converter according to claim 1 , wherein: the auxiliary power circuitry comprises a rectifier circuitry coupled to the one or more supply terminals of the second transformer, and the rectifier circuitry is configured to generate an auxiliary DC supply voltage (V aux ) based at least in part on the auxiliary AC supply voltage to provide DC power to the one or more components.
4 . The converter according to claim 3 , the auxiliary power circuitry comprising: one or more DC-DC converters coupled to the rectifier circuitry, wherein the one or more DC-DC converters are configured to generate one or more auxiliary DC voltages that provide auxiliary DC power to the one or more components of the MV unit.
5 . The converter according to claim 1 , wherein the first resonant tank circuitry of the second transformer cell comprises at least one of the following: a leakage inductance of the second transformer, a separate inductance electrically coupled to the second transformer, a separate capacitor electrically coupled to the second transformer, and a separate resonant circuit configuration electrically coupled to the second transformer.
6 . The converter according to claim 1 , wherein the second transformer of the second transformer cell is a multi-winding transformer, the multi-winding transformer comprising: a primary winding having a primary winding terminal electrically coupled to the MV AC terminal; a first secondary winding electrically coupled to a first supply terminal of the second transformer cell, wherein the second transformer cell is configured to generate a first auxiliary AC supply voltage at the first supply terminal from the MV AC voltage at the MV AC terminal; and a second secondary winding electrically coupled to a second supply terminal of the second transformer cell, wherein the second transformer is configured to generate a second auxiliary AC supply voltage at the second supply terminal from the MV AC voltage at the MV AC terminal, wherein the auxiliary power circuitry is configured to provide power to the one or more components of the MV unit based at least in part on the first auxiliary AC supply voltage and the second auxiliary AC supply voltage.
7 . The converter according to claim 6 , wherein: the second transformer of the second transformer cell comprises three or more secondary windings, and each of the three or more secondary windings is electrically coupled to a respective supply terminal of the second transformer for generating a respective auxiliary AC supply voltage, and the auxiliary power circuitry is configured to provide power to the one or more components of the MV unit based at least in part on the respective auxiliary AC supply voltages at the respective supply terminals.
8 . The converter according to claim 1 , further comprising a third transformer cell that comprises a second resonant tank circuitry and a third transformer, wherein: the third transformer cell is electrically connected to a supply terminal of the one or more supply terminals of the second transformer cell and the third transformer cell is configured to generate a third transformer auxiliary AC supply voltage, from the auxiliary AC supply voltage at the supply terminal of the one or more supply terminals of the second transformer cell, at one or more third transformer cell supply terminals of the third transformer cell, and the auxiliary power circuitry is configured to provide power to the one or more components of the MV unit based at least in part on the third transformer auxiliary AC supply voltage.
9 . The converter according to claim 6 , further comprising a third transformer cell that comprises a second resonant tank circuitry and a third transformer wherein: the third transformer cell is electrically connected to a supply terminal of the one or more supply terminals of the second transformer cell, and the third transformer is a multi-winding transformer comprising: a third-transformer primary winding having a third-transformer primary winding terminal electrically coupled to the first supply terminal of the second transformer cell; a third-transformer first-secondary winding having a third-transformer first-secondary winding terminal electrically coupled to a first third-transformer-cell supply terminal, wherein the third transformer cell is configured to generate a fourth auxiliary AC supply voltage at the first third-transformer supply terminal from the first auxiliary AC voltage at the first supply terminal of the second transformer cell; and a third-transformer second-secondary winding having a third-transformer second-secondary winding terminal coupled to a second third transformer supply terminal, wherein the third transformer cell is configured to generate a fifth auxiliary AC supply voltage at the second third-transformer supply terminal from the first auxiliary AC voltage at the first supply terminal of the second transformer cell, wherein the auxiliary power circuitry is configured to provide power to the one or more components of the MV unit based at least in part on the fourth auxiliary AC supply voltage and the fifth auxiliary AC supply voltage.
10 . The converter according to claim 1 , wherein the second transformer cell is configured to provide an auxiliary resonant frequency such that at a predetermined load, a voltage gain provided by the second transformer cell deviates from a unity voltage gain by no more than 20%.
11 . The converter according to claim 1 , the LV unit further comprising: a control circuitry coupled to the at least one AC/DC cell of the LV unit, wherein the control circuitry is configured to apply a start-up voltage at the LV AC terminal of the AC/DC cell, and wherein: the first transformer cell is further configured to generate a transformed start-up voltage at the MV AC terminal from the start-up voltage at the LV AC terminal, and the second transformer cell is further configured to generate the auxiliary AC supply voltage at a supply terminal of the one or more supply terminals of the second transformer cell from the transformed start-up voltage at the MV AC terminal.
12 . The converter according to claim 1 , wherein: the first transformer cell is configured to withstand a first basic insulation level to galvanically insulate the MV side from the LV side of the converter, and the second transformer cell is configured to withstand lesser insulation than the first transformer cell.
13 . The converter according to claim 1 , wherein: the at least one DC/AC cell is configured to generate a MV AC voltage from a MV DC voltage, and an absolute value of the MV DC voltage is in the range of 1 kV to 52 kV, and the second transformer cell and the auxiliary power circuitry are configured to provide as auxiliary DC power an auxiliary DC voltage to the one or more components having an absolute value in the range of 6 V to 200 V.
14 . A method for operating a converter configured to transfer power from a medium voltage (MV) side to a low voltage (LV) side, comprising: generating, by a direct current (DC)/alternating current (AC) cell of a MV unit at the MV side, a MV AC voltage from a MV DC voltage at a MV AC terminal of the DC/AC cell; generating, by at least one AC/DC cell of a LV unit at the LV side, a DC voltage from a LV AC voltage at a LV AC terminal of the AC/DC cell; generating, by a first transformer cell, the LV AC voltage at the LV AC terminal from the MV AC voltage at the MV AC terminal, wherein the first transformer cell comprises a first transformer, and the first transformer cell is electrically connected to the MV AC terminal and the LV AC terminal; generating, by a second transformer cell, an auxiliary AC supply voltage at one or more supply terminals of the second transformer cell from the MV AC voltage at the MV AC terminal, wherein the second transformer cell comprises a first resonant tank circuitry and a second transformer, and the second transformer cell is electrically connected to the MV AC terminal; and providing, by an auxiliary power circuitry, auxiliary power to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage at the one or more supply terminals.
15 . The method according to claim 14 , further comprising: applying, by a control circuitry coupled to the AC/DC cell of the LV unit, a start-up voltage at the LV AC terminal of the AC/DC cell; generating, by the first transformer cell, a transformed start-up voltage at the MV AC terminal from the start-up voltage at the LV AC terminal; and generating, by the second transformer cell, the auxiliary AC supply voltage at one or more supply terminals of the second transformer from the transformed voltage signal at the MV AC terminal.
16 . The method according to claim 14 , wherein the second transformer cell is connected in parallel to the first transformer cell, and the second transformer of the second transformer cell is connected in parallel to the first transformer of the first transformer cell.
17 . The method according to claim 14 , wherein the auxiliary power circuitry comprises a rectifier circuitry coupled to the one or more supply terminals of the second transformer, and the method further comprises: generating, by the rectifier circuitry, an auxiliary DC supply voltage (V aux ) based at least in part on the auxiliary AC supply voltage to provide DC power to the one or more components.
18 . The method according to claim 14 , wherein the first resonant tank circuitry of the second transformer cell comprises at least one of the following: a leakage inductance of the second transformer, a separate inductance electrically coupled to the second transformer, a separate capacitor electrically coupled to the second transformer, and a separate resonant circuit configuration electrically coupled to the second transformer.
19 . The method according to claim 14 , wherein the second transformer of the second transformer cell is a multi-winding transformer, the multi-winding transformer comprising: a primary winding having a primary winding terminal electrically coupled to the MV AC terminal; a first secondary winding electrically coupled to a first supply terminal of the second transformer cell; and a second secondary winding electrically coupled to a second supply terminal of the second transformer cell, and wherein the method further comprises: generating, by the second transformer cell, a first auxiliary AC supply voltage at the first supply terminal from the MV AC voltage at the MV AC terminal; generating, by the second transformer, a second auxiliary AC supply voltage at the second supply terminal from the MV AC voltage at the MV AC terminal; and providing, by the auxiliary power circuitry, power to the one or more components of the MV unit based at least in part on the first auxiliary AC supply voltage and the second auxiliary AC supply voltage.
20 . The method according to claim 14 , further comprising: generating, by a third transformer cell, from the auxiliary AC supply voltage at the supply terminal of the one or more supply terminals of the second transformer cell, a third transformer auxiliary AC supply voltage at one or more third transformer cell supply terminals of the third transformer cell, wherein the third transformer cell comprises a second resonant tank circuitry and a third transformer, and the third transformer cell is electrically connected to a supply terminal of the one or more supply terminals of the second transformer cell; and providing, by the auxiliary power circuitry, power to the one or more components of the MV unit based at least in part on the third transformer auxiliary AC supply voltage.

Description

CROSS REFERENCE TO RELATED APPLICATIONS The present application claims priority to European Patent Application No. 24211492.4 filed on Nov. 7, 2024, and titled “AUXILIARY SUPPLY FOR MEDIUM-VOLTAGE DC/DC CONVERTERS UTILIZING AN AUXILIARY TRANSFORMER INTEGRATED IN THE CONVERTER SYSTEM”, which is hereby incorporated by reference in its entirety. TECHNICAL FIELD The present disclosure relates to a converter for transferring power from a medium voltage side to a low voltage side, and a method for operating a converter for transferring power from a medium voltage side to a low voltage side. BACKGROUND Isolated DC/DC converters that employ medium-frequency transformers (MFTs) may require auxiliary power on both sides of the MFT's insulation barrier to operate control circuitry, power electronic switches, and for example fans for cooling. For example, in DC/DC converters that are part of a Solid-State Transformer (SST), the insulation requirements between the medium-voltage (MV) side and the low-voltage (LV) side of the SST can be derived from the MV-side grid voltage via standards such as the IEC 62477-2 and may require Basic Insulation Levels (BIL). For instance, the BIL of a 15 kV grid voltage corresponds to the range of 95 kV. To fulfill this standard, any possible path between the MV-side and the LV-side must guarantee the required insulation voltage or BIL. According to the conventional technology, auxiliary power may be provided to the MV-side auxiliary circuits directly from the MV-side DC-link which circumvents the BIL requirements. On the other hand, it may require a relatively complex and expensive auxiliary converter given the fact that the MV-side DC-link voltages can be in the range of 2 kV to 10 kV or even higher. A further option may be to employ an external isolated DC/DC converter that is supplied from the LV-side. Since it feeds power from the LV to the MV side, it may be required to provide the same insulation voltage as the MFT which can make it large and expensive although it might only be rated for a comparably low power. Thus, there is a need for an improved converter, particularly a converter suitable for use with medium voltages. BRIEF DESCRIPTION A first aspect relates to a converter for transferring power from a medium voltage (MV) side to a low voltage (LV) side. The converter may comprise: a MV unit at the MV side comprising a DC/AC cell having a MV AC terminal, the DC/AC cell configured to generate a MV AC voltage at the MV AC terminal from a MV DC voltage; a LV unit at the LV side comprising an AC/DC cell having a LV AC terminal, the AC/DC cell configured for generating a LV DC voltage from a LV AC voltage at the LV AC terminal. The converter may further comprise a first transformer cell comprising a first transformer, the first transformer cell being electrically connected to the MV AC terminal and the LV AC terminal, the first transformer cell configured to generate the LV AC voltage at the LV AC terminal from the MV AC voltage at the MV AC terminal. The converter may further comprise a second transformer cell comprising a first resonant tank circuitry and a second transformer, the second transformer cell being electrically connected to the MV AC terminal, the second transformer cell configured to generate an auxiliary AC supply voltage at one or more supply terminals of the second transformer cell from the MV AC voltage at the MV AC terminal. The converter may further comprise an auxiliary power circuitry coupled to the one or more supply terminals of the second transformer cell, the auxiliary power circuitry configured to provide auxiliary power to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage at the one or more supply terminals. The DC/AC cell at the MV side may comprise an electrical circuit which may transfer the MV DC voltage to a MV AC voltage. For example, the DC/AC cell may comprise one or more electrical components which cause an according DC to AC voltage transfer. For example, the DC/AC cell at the MV side may comprise an according DC/AC inverter. The MV AC terminal of the DC/AC cell may be regarded as an output terminal of the DC/AC cell where the MV AC voltage can be provided. The DC/AC cell at the MV side may further comprise a MV DC terminal which may function as an input terminal of the DC/AC cell where the MV DC voltage can be provided. The AC/DC cell at the LV side may comprise an electrical circuit which may transfer the LV AC voltage to an LV DC voltage. For example, the AC/DC cell may comprise one or more electrical components which cause an according AC to DC voltage transfer. For example, the AC/DC cell at the LV side may comprise an according AC/DC inverter. The LV AC terminal of the AC/DC cell may be regarded as an input terminal of the AC/DC cell where the LV AC voltage can be provided. The AC/DC cell at the LV side may further comprise a LV DC terminal which may function as an output terminal of the AC/DC