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CN-115315892-B - AC/DC converter stage for a converter system with an input series configuration having improved common mode performance

CN115315892BCN 115315892 BCN115315892 BCN 115315892BCN-115315892-B

Abstract

The invention relates to an AC/DC converter stage (1) for a converter system (3) with an input series configuration. The AC/DC converter stage (1) comprises two input terminals (IN 1, IN 2) for inputting an AC input voltage (Vin) to the AC/DC converter stage (1), at least one first branch (CB 1) having at least two switches (S1, S2), the at least two switches (S1, S2) being electrically connected IN series at a first connection point (N1), wherein a first input terminal (IN 1) of the two input terminals (IN 1, IN 2) is electrically connected to the first connection point (N1) of the first branch (CB 1). The AC/DC converter stage (1) further comprises at least one first accumulator (C1) for providing a DC output voltage, the first accumulator (C1) being electrically connected IN parallel to the first branch (CB 1), at least one controllable bi-directional switch (BS 0) being electrically connected between the two input terminals (IN 1, IN 2). The AC/DC converter stage has improved common mode performance.

Inventors

  • Pinivan tiwanka Bandara viekong

Assignees

  • 华为数字能源技术有限公司
  • 华为数字能源技术有限公司

Dates

Publication Date
20260421
Application Date
20200317
Priority Date
20200317

Claims (20)

  1. 1. An AC/DC converter stage (1) for a converter system (3) having an input series configuration, characterized in that, The converter system (3) comprises at least two conversion units connected in series at an input of the converter system (3), at least one of the at least two conversion units comprising the AC/DC converter stage (1); the AC/DC converter stage (1) comprises: -two input terminals (IN 1, IN 2) for inputting an AC input voltage (Vin) to the AC/DC converter stage (1); -at least one first branch (CB 1) having at least two switches (S1, S2), the at least two switches (S1, S2) being electrically connected IN series at a first connection point (N1), wherein a first input terminal (IN 1) of the two input terminals (IN 1, IN 2) is electrically connected to the first connection point (N1) of the first branch (CB 1); -at least one first accumulator (C1) for providing a DC output voltage, said first accumulator (C1) being electrically connected in parallel to said first branch (CB 1); At least one controllable bidirectional switch (BS 0) is electrically connected between the two input terminals (IN 1, IN 2).
  2. 2. An AC/DC converter stage (1) according to claim 1, characterized in that, The at least one controllable bi-directional switch (BS 0) is arranged to realize a zero state of the AC/DC converter stage (1) by providing a low impedance current path between the two input terminals (IN 1, IN 2) IN its on-state.
  3. 3. An AC/DC converter stage (1) according to claim 1, characterized in that, The AC/DC converter stage (1) is a bipolar boost converter comprising a second accumulator (L1); One of the two input terminals (IN 1, IN 2) is electrically connected to the at least one controllable bidirectional switch (BS 0) via the second accumulator (L1).
  4. 4. An AC/DC converter stage (1) according to claim 3, characterized in that, The at least one controllable bidirectional switch (BS 0) is used for realizing a zero state of the AC/DC converter stage (1) by providing a current path between the two input terminals (IN 1, IN 2) via the second accumulator (L1) IN its conducting state.
  5. 5. An AC/DC converter stage (1) according to claim 3, characterized in that, The first one (IN 1) of the two input terminals (IN 1, IN 2) is electrically connected to the first connection point (N1) of the first branch (CB 1) via the second accumulator (L1).
  6. 6. An AC/DC converter stage (1) according to any of claims 1-5, characterized in that, The AC/DC converter stage (1) further comprises a second branch (CB 2) having at least two switches (S3, S4), the at least two switches (S3, S4) being electrically connected in series at a second connection point (N2), wherein the second branch (CB 2) is electrically connected in parallel to the first branch (CB 1) and the first accumulator (C1); wherein a second input terminal (IN 2) of the two input terminals (IN 1, IN 2) is electrically connected to the second connection point (N2) of the second branch (CB 2).
  7. 7. An AC/DC converter stage (1) according to any of claims 1-5, characterized in that, The first accumulator (C1) comprises at least two first accumulator elements (C1 a, C1 b), which are electrically connected in series at a third connection point (N3).
  8. 8. An AC/DC converter stage (1) according to claim 7, characterized in that, IN case the AC/DC converter stage (1) comprises only the first branch (CB 1), a second one (IN 2) of the two input terminals (IN 1, IN 2) is electrically connected to the third connection point (N3).
  9. 9. An AC/DC converter stage (1) according to claim 7, characterized in that, In case the AC/DC converter stage (1) comprises the first leg (CB 1) and a second leg (CB 2): -at the first branch (CB 1) comprising more than two switches electrically connected in series, the third connection point (N3) being electrically connected via a switch (S15; S16) to at least one connection point (N11; N12) between two switches (S11, S12; S13, S14) of the first branch (CB 1) different from the first connection point (N1); The second branch (CB 2) comprises more than two switches electrically connected in series, the third connection point (N3) being electrically connected via a switch (S25; S26) to at least one connection point (N21; N22) between two switches (S21, S22; S23, S24) of the second branch (CB 2) different from the second connection point (N2).
  10. 10. An AC/DC converter stage (1) according to any of claims 1-5, characterized in that, Any one of the at least two switches comprises at least one of: at least one uncontrollable unidirectional semiconductor switch; At least one controllable semiconductor switch comprising an insulated gate bipolar transistor (Insulated Gate Bipolar transistor, IGBT).
  11. 11. An AC/DC converter stage (1) according to any of claims 1-5, characterized in that, The at least one controllable bi-directional switch (BS 0) comprises at least one controllable semiconductor switch.
  12. 12. An AC/DC converter stage (1) according to any of claims 1-5, characterized in that, The AC/DC converter stage (1) comprises two controllable bidirectional switches (BS 1, BS 2), which controllable bidirectional switches (BS 1, BS 2) are electrically connected IN series at a fourth connection point (N4) and are adapted to provide a current path between the two input terminals (IN 1, IN 2) IN their on-state.
  13. 13. An AC/DC converter stage (1) according to claim 12, characterized in that, In case the AC/DC converter stage (1) comprises the first branch (CB 1) and a second branch (CB 2), and in case the first accumulator (C1) comprises the at least two first accumulator elements (C1 a, C1 b) electrically connected in series at a third connection point (N3): The third connection point (N3) and the fourth connection point (N4) are electrically connected to each other.
  14. 14. An AC/DC converter stage (1) according to claim 12, characterized in that, In case the AC/DC converter stage (1) comprises only the first branch (CB 1): each switch (S1, S2) of the first branch (CB 1) comprises: Two uncontrollable unidirectional semiconductor switches (S1 a, S1b; S2a, S2 b) electrically connected in series at a fifth connection point (N51; N52), or Two controllable semiconductor switches (S1 a, S1b; S2a, S2 b), which are electrically connected in series at a fifth connection point (N51; N52), or In case the AC/DC converter stage (1) comprises the first leg (CB 1) and a second leg (CB 2): each switch (S1, S2, S3, S4) of the first branch (CB 1) and the second branch (CB 2) comprises: Two uncontrollable unidirectional semiconductor switches (S1 a, S1b; S2a, S2b; S3a, S3b; S4a, S4 b), which are electrically connected in series at a fifth connection point (N51; N52; N53; N54), or Two controllable semiconductor switches (S1 a, S1b; S2a, S2b; S3a, S3b; S4a, S4 b), which are electrically connected in series at a fifth connection point (N51; N52; N53; N54).
  15. 15. An AC/DC converter stage (1) according to claim 14, characterized in that, In the case that the first accumulator (C1) comprises the at least two first accumulator elements (C1 a, C1 b) electrically connected in series at a third connection point (N3): Each switch (S1; S2; S3; S4) comprises a slow recovery diode (D1 b; D2a; D3b; D4 a) and a fast recovery diode (D1 a; D2b; D3a; D4 b), the one slow recovery diode (D1 b; D2a; D3b; D4 a) and the one fast recovery diode (D1 a; D2b; D3a; D4 b) being electrically connected in series at the fifth connection point (N51; N52; N53; N54), wherein for each switch (S1; S2; S3; S4) a low current diode (D1 c; D2c; D3c; D4 c) for providing a recovered charge is electrically connected between the fifth connection point (N51; N52; N53; N54) and the third connection point (N3), or Each switch (S1; S2; S3; S4) comprises two controllable semiconductor switches (Q1 a, Q1b; Q2a, Q2b; Q3a, Q3b; Q4a, Q4 b), which are electrically connected in series at the fifth connection point (N51; N52; N53; N54), wherein for each switch (S1; S2; S3; S4) a low current diode (D1 c; D2c; D3c; D4 c) with equal voltage drop at the two controllable semiconductor switches (Q1 a, Q1b; Q2a, Q2b; Q3a, Q3b; Q4a, Q4 b) is electrically connected in series between the fifth connection point (N51; N52; N53; N54) and the third connection point (N3).
  16. 16. A converter system (3) with an input series configuration, characterized by comprising: at least two converter units (2 a, 2 b) electrically connected in series at an input of the converter system (3); Wherein at least one of the at least two converter units (2 a, 2 b) comprises an AC/DC converter stage (1) according to any one of claims 1 to 15 as a first converter stage.
  17. 17. The converter system (3) according to claim 16, characterized in that, One (2 a) of the at least two converter units (2 a, 2 b) comprises an AC/DC converter stage (1 a) with a second accumulator (L1), the other (2 b) of the at least two converter units (2 a, 2 b) comprises an AC/DC converter stage (1 b) without a second accumulator, or Each of the at least two converter units (2 a, 2 b) comprises an AC/DC converter stage (1) according to any one of claims 1 to 15 as a first converter stage.
  18. 18. The converter system (3) according to claim 16 or 17, characterized in that, At least one (2 a) of the at least two converter units (2 a, 2 b) comprises an electrically isolated DC/DC converter stage (4) as a second converter stage; a corresponding AC/DC converter stage (1) is arranged to provide a DC input voltage to the isolated DC/DC converter stage (4).
  19. 19. The converter system (3) according to claim 16 or 17, characterized in that, At least one of the at least two converter units (2 a, 2 b) is enclosed in a housing.
  20. 20. The converter system (3) according to claim 16 or 17, characterized in that, The converter system (3) comprises at least one phase unit (5 a, 5b, 5 c) for an AC input voltage; Each phase unit (5 a, 5b, 5 c) comprises the at least two converter units (2, 2a, 2 b), the at least two converter units (2, 2a, 2 b) being electrically connected in series at the input of the converter system (3).

Description

AC/DC converter stage for a converter system with an input series configuration having improved common mode performance Technical Field The invention relates to an AC/DC converter stage for a converter system comprising an input series arrangement, wherein the AC/DC converter stage has an improved common mode performance. The invention also relates to a converter system having an input series configuration comprising at least one such AC/DC converter stage. In particular, the converter system comprises at least two converter cells which are electrically connected in series at an input of the converter system, wherein at least one of the at least two converter cells comprises such an AC/DC converter stage as a first converter stage. The AC/DC converter stage may comprise a half-bridge structure or a full-bridge structure. Background For example, in a short-path converter system, a power conversion system is used to convert medium voltage AC (e.g., an AC voltage above 1000 volts, an AC frequency of 50Hz or 60Hz (depending on the region)) to a lower voltage, particularly a lower DC voltage, to provide a plurality of electrical loads. Examples of such electrical loads include data center applications and Electric Vehicle (EV) charging stations, among others. In the case of solar photovoltaics (solar photovoltaics, PV), DC power generated by a PV panel is converted to medium voltage AC using such a converter system. For converting an AC input voltage into a DC output voltage, in particular a lower DC voltage, a converter system with an input series configuration may be used, which comprises at least two converter cells, which are electrically connected in series at their input. Such a converter unit may comprise an AC/DC converter stage as a first converter stage and may further comprise an electrically isolated DC/DC converter stage as a second converter stage, wherein the isolated DC/DC converter provides electrical isolation between the AC input voltage and the DC output voltage. Disclosure of Invention Embodiments of the present invention are also based on the following considerations made by the inventors: In a converter system with a series input structure, each of the converter cells electrically connected in series at the input of the converter system may be enclosed in a housing (shell) which is kept at ground potential to ensure safety. The high power density requirements force these packaged converter cells to be very closely arranged in the converter system. In particular, for insulation purposes a solid insulating material is provided between the encapsulated converter units and thus between the high potential of the converter units and the ground potential of the housing. Since the housing may be made of metal, providing the solid insulating material may create parasitic capacitances between elements of the converter unit, in particular between the AC/DC converter stage and the electrically isolated DC/DC converter stage, and the metal housing being kept at ground potential. When an AC input voltage is supplied to the converter system with a series input structure, the converter system generates a high common mode voltage on the input side and on the grid side, respectively. These high common mode voltages generate high common mode currents and leakage currents, respectively, through the parasitic capacitances. These common mode currents may create several problems in the converter system, in particular the AC/DC converter stage, such as problems due to noise, electromagnetic compatibility (electromagnetic compatibility, EMC), in particular electromagnetic interference (electromagnetic interference, EMI), related problems, and additional power losses due to the common mode currents. In case the AC/DC converter stage comprises IGBTs, there may be a gate driver fire due to EMI/EMC caused by noise, ground potential offset and the common mode current. The above-described problems with common mode voltages in AC/DC converter stages are exemplarily described in connection with fig. 1 (a) and (b). Fig. 1 (a) and (b) show examples of AC/DC converter stages comprising full bridge structures in different switching states. The AC/DC converter stage shown in fig. 1 comprises four switches in the form of Insulated Gate Bipolar Transistors (IGBTs) (Q01, Q02, Q03, Q04) which are electrically connected to form a full bridge structure. In other words, the two IGBTs (Q01, Q02) are electrically connected in series at a first connection point N01, wherein a first input terminal a of the two input terminals (A, B) is connected to the first connection point N01 via an inductor L1. The two IGBTs (Q03, Q04) are electrically connected in series at a second connection point N02, wherein a second input terminal B of the two input terminals (A, B) is connected to the second connection point N02 via an inductor L1. The series connection of the two IGBTs (Q03, Q04) is electrically connected in parallel to the series connection