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EP-4742525-A1 - AUXILIARY SUPPLY FOR MEDIUM-VOLTAGE DC/DC CONVERTERS UTILIZING AN AUXILIARY TRANSFORMER INTEGRATED IN THE CONVERTER SYSTEM

EP4742525A1EP 4742525 A1EP4742525 A1EP 4742525A1EP-4742525-A1

Abstract

The present disclosure relates to a converter (100) for transferring power from a medium voltage, MV, side to a low voltage, LV, side, comprising: a MV unit (20) at the MV side comprising a DC/AC cell (210) having a MV AC terminal (212), the DC/AC cell configured for generating an MV AC voltage (211) at the MV AC terminal (212) from a MV DC voltage; a LV unit (30) at the LV side comprising an AC/DC cell (310) having a LV AC terminal (312), the AC/DC cell configured for generating a LV DC voltage from a LV AC voltage (311) at the LV AC terminal; a first transformer cell (40) comprising a first transformer (401), the first transformer cell being electrically connected to the MV AC terminal (212) and the LV AC terminal (312), the first transformer cell configured to generate the LV AC voltage (311) at the LV AC terminal from the MV AC voltage (211) at the MV AC terminal; a second transformer cell (60) comprising a first resonant tank circuitry and a second transformer (603), the second transformer cell being electrically connected to the MV AC terminal (212), the second transformer cell configured to generate an auxiliary AC supply voltage (611) at one or more supply terminals (612, 621, 631) of the second transformer cell from the MV AC voltage (211) at the MV AC terminal (212), an auxiliary power circuitry (90) coupled to the one or more supply terminals (612, 621, 631) of the second transformer cell (60), the auxiliary power circuitry configured to provide auxiliary power (91) to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage (611) at the one or more supply terminals (612). Furthermore, the present disclosure relates to an according method for operating a converter.

Inventors

  • CHRISTEN, DANIEL
  • ROTHMUND, Daniel
  • Stojadinovic, Milos
  • CANALES, FRANCISCO
  • PETTERSSON, SAMI

Assignees

  • ABB SCHWEIZ AG

Dates

Publication Date
20260513
Application Date
20241107

Claims (15)

  1. A converter (100) for transferring power from a medium voltage, MV, side to a low voltage, LV, side, comprising: a MV unit (20) at the MV side comprising a DC/AC cell (210) having a MV AC terminal (212), the DC/AC cell configured for generating an MV AC voltage (211) at the MV AC terminal (212) from a MV DC voltage; a LV unit (30) at the LV side comprising an AC/DC cell (310) having a LV AC terminal (312), the AC/DC cell configured for generating a LV DC voltage from a LV AC voltage (311) at the LV AC terminal; a first transformer cell (40) comprising a first transformer (401), the first transformer cell being electrically connected to the MV AC terminal (212) and the LV AC terminal (312), the first transformer cell configured to generate the LV AC voltage (311) at the LV AC terminal from the MV AC voltage (211) at the MV AC terminal; a second transformer cell (60) comprising a first resonant tank circuitry and a second transformer (603), the second transformer cell being electrically connected to the MV AC terminal (212), the second transformer cell configured to generate an auxiliary AC supply voltage (611) at one or more supply terminals (612, 621, 631) of the second transformer cell from the MV AC voltage (211) at the MV AC terminal (212), an auxiliary power circuitry (90) coupled to the one or more supply terminals (612, 621, 631) of the second transformer cell (60), the auxiliary power circuitry configured to provide auxiliary power (91) to one or more components of the MV unit based at least in part on the auxiliary AC supply voltage (611) at the one or more supply terminals (612).
  2. The converter according to claim 1, wherein the second transformer cell (60) is connected in parallel to the first transformer cell (40), particularly wherein the second transformer (603) of the second transformer cell is connected in parallel to the first transformer (401) of the first transformer cell.
  3. The converter according to claim 1 or 2, wherein the auxiliary power circuitry (90) comprises a rectifier circuitry (613, 623, 633) coupled to the one or more supply terminals (621, 631, 612) of the second transformer (60), the rectifier circuitry 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 (90) comprising: one or more DC-DC converters (81, 82, 83) [preferably one or more HF DC-DC converters] coupled to the rectifier circuitry (613), the one or more DC-DC converters configured to generate one or more auxiliary DC voltages for providing auxiliary DC power to one or more components of the MV unit (20).
  5. The converter according to any of claims 1-4, 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, a separate LC-circuit configuration electrically coupled to the second transformer.
  6. The converter according to any of claims 1-5, wherein the second transformer (603) of the second transformer cell (60) is a multi-winding transformer comprising: a primary winding (61) having a primary winding terminal being electrically coupled to the MV AC terminal (212); a first secondary winding (62) electrically coupled to a first supply terminal (621) of the second transformer cell, the second transformer cell (60) configured to generate a first auxiliary AC supply voltage (622) at the first supply terminal (621) from the MV AC voltage (211) at the MV AC terminal (212); a second secondary winding (63) electrically coupled to a second supply terminal (631) of the second transformer cell, the second transformer (60) configured to generate a second auxiliary AC supply voltage (632) at the second supply terminal (631) from the MV AC voltage (211) at the MV AC terminal (212); the auxiliary power circuitry (90) being 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 (622) and the second auxiliary AC supply voltage (632).
  7. The converter according to claim 6, wherein the second transformer of the second transformer cell (60) comprises three or more secondary windings, each of the three or more secondary windings electrically coupled to a respective supply terminal of the second transformer for generating a respective auxiliary AC supply voltage; the auxiliary power circuitry (90) being configured to provide power to the one or more components of the MV unit (20) based at least in part on the respective auxiliary AC supply voltages at the respective supply terminals.
  8. The converter according to any of claims 1-7, further comprising a third transformer cell (70) comprising a second resonant tank circuitry and a third transformer (701), the third transformer cell electrically connected to a supply terminal (621) of the one or more supply terminals of the second transformer cell (60), the third transformer cell (70) configured to generate a third transformer auxiliary AC supply voltage (722) at one or more third transformer cell supply terminals (721, 731) of the third transformer cell (70) from the auxiliary AC supply voltage (621) at the supply terminal (621) of the one or more supply terminals of the second transformer cell (60); the auxiliary power circuitry (90) being configured to provide power to the one or more components of the MV unit (20) based at least in part on the third transformer auxiliary AC supply voltage (722).
  9. The converter according to claims 6 or 7, further comprising a third transformer cell (70) comprising a second resonant tank circuitry and a third transformer (701), the third transformer cell electrically connected to a supply terminal (621) of the one or more supply terminals of the second transformer cell (60), wherein the third transformer is a multi-winding transformer comprising: a third-transformer primary winding (71) having a third-transformer primary winding terminal (711) electrically coupled to the first supply terminal (621) of the second transformer cell (60); a third-transformer first-secondary winding (72) having a third-transformer first-secondary winding terminal electrically coupled to a first third-transformer-cell supply terminal (721), the third transformer cell configured to generate a fourth auxiliary AC supply voltage (722) at the first third-transformer supply terminal (721) from the first auxiliary AC voltage (642) at the first supply terminal (621) of the second transformer cell (60); a third-transformer second-secondary winding (73) having a third-transformer second-secondary winding terminal coupled to a second third transformer supply terminal (731), the third transformer cell configured to generate a fifth auxiliary AC supply voltage (732) at the second third-transformer supply terminal (731) from the first auxiliary AC voltage (642) at the first supply terminal (621) of the second transformer cell (60); the auxiliary power circuitry (90) being configured to provide power to the one or more components of the MV unit (20) based at least in part on the fourth auxiliary AC supply voltage and the fifth auxiliary AC supply voltage.
  10. The converter according to any of claims 1-9, wherein the second transformer cell is configured to provide an auxiliary resonant frequency such that at a predetermined load, particularly a maximum rated load, a voltage gain provided by the second transformer cell deviates from a unity voltage gain by no more than 20%, preferably 10 %, more preferably 5 %, more preferably 2 %.
  11. The converter according to any of claims 1-10, the LV unit further comprising: a control circuitry coupled to the at least one AC/DC cell (310) of the LV unit (30), the control circuitry configured to apply a start-up voltage at the LV AC terminal (312) of the AC/DC cell (310); the first transformer cell (40) being further configured to generate a transformed start-up voltage at the MV AC terminal (212) from the start-up voltage at the LV AC terminal (312); the second transformer cell (60) being further configured to generate the auxiliary AC supply voltage (611) at a supply terminal (612, 621, 631) 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 any of claims 1-11, the first transformer cell (40) configured to withstand a first basic insulation level to galvanically insulate the MV side from the LV side of the converter; the second transformer cell (60) configured for lesser insulation than the first transformer cell (40).
  13. The converter according to any of claims 1-12, with the at least one DC/AC cell (210) being configured to generate an MV AC voltage from a MV DC voltage, wherein an absolute value of the MV DC voltage is in the range of 1 kV to 52 kV; wherein the second transformer cell (60) and the auxiliary power circuitry (90) 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. Method for operating a converter for transferring power from a medium voltage, MV, side to a low voltage, LV, side, comprising: by a DC/AC cell (210) of a MV unit (20) at the MV side: generating an MV AC voltage from a MV DC voltage at a MV AC terminal (212) of the DC/AC cell; by at least one AC/DC cell (310) of a LV unit (30) at the LV side: generating a DC voltage from a LV AC voltage (311) at a LV AC terminal (312) of the AC/DC cell; by a first transformer cell (40), comprising a first transformer, the first transformer cell being electrically connected to the MV AC terminal (212) and the LV AC terminal (312): generating the LV AC voltage at the LV AC terminal (312) from the MV AC voltage at the MV AC terminal (212); by a second transformer cell (60) comprising a first resonant tank circuitry and a second transformer, the second transformer cell being electrically connected to the MV AC terminal (212): generating an auxiliary supply voltage (611) at one or more supply terminals (612) of the second transformer cell from the MV AC voltage at the MV AC terminal (212); by an auxiliary power circuitry (90): providing power to one or more components of the MV unit (20) based at least in part on the auxiliary supply voltage (611) at the one or more supply terminals (612).
  15. Method according to claim 14, further comprising: by a control circuitry coupled to the AC/DC cell (310) of the LV unit (30): applying a start-up voltage at the LV AC terminal (212) of the AC/DC cell; by the first transformer cell (40): generating a transformed start-up voltage at the MV AC terminal (212) from the start-up voltage at the LV AC terminal (212); by the second transformer cell (60): generating the auxiliary AC supply voltage at one or more supply terminals (612) of the second transformer from the transformed voltage signal at the MV AC terminal (212).

Description

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. Technical 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 e.g. 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 15kV grid voltage corresponds to the range of 95kV. 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. Summary of the invention 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 for generating an 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 an 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 cell where the LV DC voltage can be provided. In an example, the first transformer cell input terminal may be connected to the MV AC terminal of the DC/AC cell of the MV unit and the first transfer output terminal may be connected to the LV AC terminal of the AC/DC cell of the LV unit. A medium voltage, MV, as used herein, may refer to (absolute