CN-122001220-A - Auxiliary power supply for medium voltage DC/DC converter employing auxiliary transformer integrated in converter system

CN122001220ACN 122001220 ACN122001220 ACN 122001220ACN-122001220-A

Abstract

The present disclosure relates to a converter for transferring power from a medium voltage side to a low voltage side, comprising a medium voltage unit located at the medium voltage side, comprising a DC/AC unit having a medium voltage alternating current terminal, a low voltage unit located at the low voltage side, configured to generate a low voltage direct current voltage from a low voltage alternating current voltage at the low voltage alternating current terminal, a first transformer unit configured to generate a low voltage alternating current voltage at the low voltage alternating current terminal from a medium voltage alternating current voltage at the medium voltage alternating current terminal, a second transformer unit configured to generate an auxiliary alternating current supply voltage at one or more supply terminals of the second transformer unit from the medium voltage alternating current voltage at the medium voltage alternating current terminal, and an auxiliary power supply circuit configured to provide an auxiliary power supply to one or more components of the medium voltage unit based at least in part on the auxiliary alternating current supply voltage at the one or more supply terminals. Furthermore, the disclosure relates to a corresponding method for operating a converter.

Inventors

D. Kristen
D. Rotmund
M. Stoyadinovic
F. Canales
S. PETERSON

Assignees

ABB瑞士股份有限公司

Dates

Publication Date: 20260508
Application Date: 20251031
Priority Date: 20241107

Claims (15)

1. A converter (100) for transferring power from a medium voltage side to a low voltage side, wherein the converter comprises: a medium voltage unit (20) at a medium voltage side, the medium voltage unit comprising a DC/AC unit (210) having a medium voltage AC terminal (212), the DC/AC unit being configured to generate a medium voltage AC voltage (211) from a medium voltage DC voltage at the medium voltage AC terminal (212); A low voltage unit (30) at the low voltage side, the low voltage unit comprising an AC/DC unit (310) having a low voltage AC terminal (312), the AC/DC unit being configured to generate a low voltage DC voltage from a low voltage AC voltage (311) at the low voltage AC terminal; A first transformer unit (40) comprising a first transformer (401) electrically connected to the medium voltage ac terminal (212) and the low voltage ac terminal (312), the first transformer unit being configured to generate a low voltage ac voltage (311) at the low voltage ac terminal from a medium voltage ac voltage (211) at the medium voltage ac terminal (212); A second transformer unit (60) comprising a first resonant cavity circuit and a second transformer (603), the second transformer unit being electrically connected to the medium voltage ac terminal (212), the second transformer unit being configured to generate an auxiliary ac supply voltage (611) from the medium voltage ac voltage (211) at the medium voltage ac terminal (212) at one or more supply terminals (612, 621, 631) of the second transformer unit; An auxiliary power circuit (90) coupled to the one or more power supply terminals (612, 621, 631) of the second transformer unit (60), the auxiliary power circuit configured to provide an auxiliary power supply (91) to one or more components of the medium voltage unit based at least in part on an auxiliary ac power supply voltage (611) at the one or more power supply terminals.
2. The converter according to claim 1, wherein the second transformer unit (60) is connected in parallel with the first transformer unit (40), in particular wherein the second transformer (603) of the second transformer unit is connected in parallel with the first transformer (401) of the first transformer unit.
3. The converter of claim 1 or2, wherein the auxiliary power circuit (90) comprises a rectifier circuit (613, 623, 633) coupled to the one or more supply terminals (621, 631, 612) of the second transformer unit (60), the rectifier circuit being 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. A converter according to claim 3, wherein the auxiliary power circuit (90) comprises one or more DC-DC converters (81, 82, 83), preferably one or more high frequency DC-DC converters, coupled to the rectifier circuit (613), the one or more DC-DC converters being configured to generate one or more auxiliary direct voltages for providing the auxiliary direct power to one or more components of the medium voltage unit (20).
5. The converter of any of claims 1-4, wherein the first resonant cavity circuit of the second transformer unit comprises at least one of 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 to 5, wherein the second transformer (603) of the second transformer unit (60) is a multi-winding transformer comprising: a primary winding (61) having a primary winding terminal electrically coupled to a medium voltage ac terminal (212); A first secondary winding (62) electrically coupled to a first supply terminal (621) of a second transformer unit, the second transformer unit (60) being configured to generate a first auxiliary ac supply voltage (622) at the first supply terminal (621) from a medium voltage ac voltage (211) at the medium voltage ac terminal (212); A second secondary winding (63) electrically coupled to a second supply terminal (631) of the second transformer unit, the second transformer unit (60) being configured to generate a second auxiliary ac supply voltage (632) at the second supply terminal (631) from the medium voltage ac voltage (211) at the medium voltage ac terminal (212), The auxiliary power circuit (90) is configured to power the one or more components of the medium voltage unit based at least in part on the first auxiliary ac power supply voltage (622) and the second auxiliary ac power supply voltage (632).
7. The converter according to claim 6, wherein the second transformer of the second transformer unit (60) comprises three or more secondary windings, each of the three or more secondary windings being electrically coupled to a respective supply terminal of the second transformer unit for generating a respective auxiliary ac supply voltage, The auxiliary power circuit (90) is configured to power the one or more components of the medium voltage unit (20) based at least in part on the respective auxiliary ac power supply voltage at each power supply terminal.
8. The converter according to any of claims 1 to 7, further comprising a third transformer unit (70) comprising a second resonant tank circuit and a third transformer (701), the third transformer unit being electrically connected to one of the one or more supply terminals (621) of the second transformer unit (60), the third transformer unit (70) being configured to generate a third transformer auxiliary ac supply voltage (722) at one or more third transformer unit supply terminals (721, 731) of the third transformer unit (70) from the auxiliary ac supply voltage (621) at the one of the one or more supply terminals (621) of the second transformer unit (60), The auxiliary power circuit (90) is configured to power the one or more components of the medium voltage unit (20) based at least in part on a third transformer auxiliary ac power supply voltage (722).
9. The converter of claim 6 or 7, further comprising a third transformer unit (70) comprising a second resonant cavity circuit and a third transformer (701), the third transformer unit being electrically connected to a supply terminal (621) of the one or more supply terminals of the second transformer unit (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 power supply terminal (621) of the second transformer unit (60); A third transformer first secondary winding (72) having a third transformer first secondary winding terminal electrically coupled to the first third transformer unit power supply terminal (721), the third transformer unit configured to generate a fourth auxiliary ac power supply voltage (722) at the first third transformer unit power supply terminal (721) from the first auxiliary ac voltage (642) at the first power supply terminal (621) of the second transformer unit (60); A third transformer second secondary winding (73) having a third transformer second secondary winding terminal coupled to a second third transformer unit supply terminal (731), the third transformer unit configured to generate a fifth auxiliary ac supply voltage (732) from the first auxiliary ac voltage (642) at the first supply terminal (621) of the second transformer unit (60) at the second third transformer unit supply terminal (731); the auxiliary power circuit (90) is configured to power the one or more components of the medium voltage 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 to 9, wherein the second transformer unit is configured to provide an auxiliary resonance frequency such that the voltage gain provided by the second transformer unit deviates from the unity voltage gain by no more than 20%, preferably no more than 10%, more preferably no more than 5%, more preferably no more than 2% at a predetermined load, in particular at a maximum rated load.
11. The converter of any one of claims 1 to 10, wherein the low voltage unit further comprises: A control circuit coupled to at least one of the AC/DC units (310) of the low voltage unit (30), the control circuit being configured to apply a start-up voltage at a low voltage alternating current terminal (312) of the AC/DC unit (310), The first transformer unit (40) is further configured to generate a converted starting voltage at the medium voltage ac terminal (212) from the starting voltage at the low voltage ac terminal (312), The second transformer unit (60) is further configured to assist an ac supply voltage (611) at one of the one or more supply terminals (612, 621, 631) of the second transformer unit from the converted starting voltage at the medium voltage ac terminal.
12. The converter according to any one of claims 1 to 11, wherein, The first transformer unit (40) is configured to withstand a first basic insulation level to electrically isolate a medium voltage side from a low voltage side of the converter; The second transformer unit (60) is configured to have a lower insulation level than the first transformer unit (40).
13. The converter according to any one of claims 1 to 12, wherein, At least one of the DC/AC units (210) is configured to generate a medium voltage alternating voltage from a medium voltage direct voltage, wherein the absolute value of the medium voltage direct voltage is in the range of 1 kV to 52 kV; Wherein the second transformer unit (60) and the auxiliary power circuit (90) are configured to provide the one or more components with an auxiliary direct voltage as an auxiliary direct power source, the auxiliary direct voltage having an absolute value in the range of 6V to 200V.
14. A method for operating a converter for transferring power from a medium voltage side to a low voltage side, the method comprising: Generating a medium voltage alternating voltage at a medium voltage alternating terminal (212) of the DC/AC unit from the medium voltage direct voltage by means of a DC/AC unit (210) of the medium voltage unit (20) located on the medium voltage side; generating a direct voltage from a low voltage alternating voltage (311) at a low voltage alternating terminal (312) of the AC/DC unit by at least one AC/DC unit (310) of the low voltage unit (30) located at the low voltage side; Generating a low voltage ac voltage (311) at the low voltage ac terminal (312) from a medium voltage ac voltage at the medium voltage ac terminal (212), by a first transformer unit (40) comprising a first transformer electrically connected to the medium voltage ac terminal (212) and the low voltage ac terminal (312); Generating an auxiliary supply voltage (611) at one or more supply terminals of the second transformer unit from the medium voltage ac voltage at the medium voltage ac terminal (212), by means of the second transformer unit (60) comprising the first resonant tank circuit and the second transformer, the second transformer unit being electrically connected to the medium voltage ac terminal (212); by means of an auxiliary power supply circuit (90), one or more components of the medium voltage unit (20) are supplied based at least partly on an auxiliary supply voltage (611) at the one or more supply terminals.
15. The method of claim 14, further comprising: applying a starting voltage at a low voltage alternating current terminal (212) of an AC/DC unit (30) by a control circuit of the AC/DC unit (310) coupled to the AC/DC unit; generating a converted starting voltage at the medium voltage ac terminal (212) from the starting voltage at the low voltage ac terminal (212) by means of a first transformer unit (40); An auxiliary ac supply voltage is generated at one or more supply terminals of the second transformer unit from said converted starting voltage at the medium voltage ac terminal (212) by the second transformer unit (60).

Description

Auxiliary power supply for medium voltage DC/DC converter employing auxiliary transformer integrated in converter system Technical Field The present disclosure relates to a converter for transferring electric power from a medium voltage side to a low voltage side, and a method for operating a converter for transferring electric power from a medium voltage side to a low voltage side. Background An isolated DC/DC converter employing an intermediate frequency transformer (MFT) may require auxiliary power to be provided on both sides of the MFT insulation barrier to operate the control circuitry, power electronic switches, and, for example, cooling fans. For example, in a DC/DC converter that is 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 may be derived from the medium side grid voltage in accordance with standards such as IEC 62477-2, and may need to meet Basic Insulation Levels (BIL). For example, BIL of 15kV grid voltage corresponds to a range of 95 kV. To meet this criterion, any possible path between the medium and low voltage sides must guarantee the required insulation voltage or BIL. According to the conventional technology, the auxiliary power supply can be directly supplied to the medium-voltage side auxiliary circuit from the medium-voltage side direct current link, which circumvents the BIL requirement. On the other hand, considering that the medium side dc link voltage can range from 2 kV to 10 kV or even higher, this may require the use of a relatively complex and expensive auxiliary converter. Another option is to use an external isolated DC/DC converter supplied from the low voltage side. Since it feeds power from the low voltage side to the medium voltage side, it may be necessary to provide the same insulation voltage as the MFT, which may result in a bulky and costly device, although its rated power may be relatively low. Accordingly, there is a need for an improved converter, in particular for medium voltage converters. Disclosure of 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 medium voltage unit on the medium voltage side comprising a DC/AC unit with a medium voltage AC terminal, the DC/AC unit being configured to generate a medium voltage AC voltage from a medium voltage DC voltage at the medium voltage AC terminal, and a low voltage unit on the low voltage side comprising an AC/DC unit with a low voltage AC terminal, the AC/DC unit being configured to generate a low voltage DC voltage from a low voltage AC voltage at the low voltage AC terminal. The converter may further include a first transformer unit including a first transformer electrically connected to the medium voltage ac terminal and the low voltage ac terminal, the first transformer unit configured to generate a low voltage ac voltage at the low voltage ac terminal from the medium voltage ac voltage at the medium voltage ac terminal. The converter may further include a second transformer unit including a first resonant cavity circuit and a second transformer, the second transformer unit electrically connected to the medium voltage ac terminal, the second transformer unit configured to generate an auxiliary ac supply voltage at one or more supply terminals of the second transformer unit from the medium voltage ac voltage at the medium voltage ac terminal. The converter may further include an auxiliary power circuit coupled to the one or more power supply terminals of the second transformer unit, the auxiliary power circuit configured to provide an auxiliary power to one or more components of the medium voltage unit based at least in part on an auxiliary ac power supply voltage at the one or more power supply terminals. The DC/AC unit located on the medium voltage side may comprise a circuit which may convert a medium voltage direct voltage into a medium voltage alternating voltage. For example, the DC/AC unit may include one or more electrical components that enable corresponding direct current to alternating current voltage conversion. For example, the DC/AC unit located on the medium voltage side may comprise a corresponding DC/AC inverter. The medium voltage alternating current terminal of the DC/AC unit may be regarded as an output terminal of the DC/AC unit, where a medium voltage alternating current voltage may be provided. The DC/AC unit located at the medium voltage side may further comprise a medium voltage direct current terminal, which may serve as an input terminal of the DC/AC unit, where a medium voltage direct current voltage may be provided. The AC/DC unit located at the low voltage side may include a circuit that may convert a low voltage AC voltage into a low voltage DC voltage. For example, the AC/DC unit may include one or more electrical components that perform a corresponding AC-to-DC voltage