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CN-121984317-A - Three-phase single-stage isolated AC-DC converter topology and control method

CN121984317ACN 121984317 ACN121984317 ACN 121984317ACN-121984317-A

Abstract

The invention discloses a topology of a three-phase single-stage isolated AC-DC converter and a control method thereof, which comprises a Swiss (SWISS) rectifier, a voltage selector and two double-active-bridge (DAB) converters, wherein the input voltage of the DAB converters is controlled by introducing the voltage selector, so that the fluctuation of the input voltage of the DAB converters can be effectively reduced, the input and output voltage matching of the DAB converters is facilitated, the system efficiency is improved, and the switch states of the SWISS rectifier and the voltage selector can be obtained through a phase-locked loop in the control method. The reference power required by the two DAB converters can be obtained by combining the phase angle of the power grid and the amplitude of the phase voltage. And phase-shifting angle variables of the two DAB converters are calculated, so that unit power factor operation of the three-phase system is realized. The topological structure and the control method of the invention are simple and visual, and the problem of large-range fluctuation of the input voltage of the DAB converter in the traditional three-phase single-stage isolated AC-DC topology is solved, thereby improving the efficiency of the converter.

Inventors

  • XU QIANMING
  • ZHOU GUANQING
  • GUO PENG
  • TANG CHENG
  • XU BAILONG
  • LIU JIAYUN
  • Ran Boyu

Assignees

  • 湖南大学

Dates

Publication Date
20260505
Application Date
20260206

Claims (9)

  1. 1. The topological structure of the three-phase single-stage isolated AC-DC converter is characterized by comprising a SWISS rectifier, wherein the SWISS rectifier is electrically connected with a voltage selector, and the voltage selector is electrically connected with an upper DAB converter (DAB 1) and a lower DAB converter (DAB 2); The SWISS rectifier comprises a first network side filter inductor (L f1 ), A second net side filter inductor (L f2 ) and a third net side filter inductor (L f3 ), wherein one end of the first net side filter inductor (L f1 ) is electrically connected with one end of an A-phase power grid power supply, the other end is electrically connected with the source electrode of a rectifier switching tube I (S 1 ), The drain electrode of the rectifier switching tube IV (S 4 ) and the drain electrode of the rectifier switching tube seven (S 7 ), the source electrode of the rectifier switching tube seven (S 7 ) is electrically connected with the source electrode of the rectifier switching tube ten (S 10 ), one end of the second network side filter inductor (L f2 ) is electrically connected with one end of the B-phase power grid power supply, the other end is electrically connected with the source electrode of the rectifier switching tube II (S 2 ), The drain electrode of the rectifier switching tube five (S 5 ) and the drain electrode of the rectifier switching tube eight (S 8 ), the source electrode of the rectifier switching tube eight (S 8 ) is electrically connected with the source electrode of the rectifier switching tube eleven (S 11 ), one end of the third network side filter inductor (L f3 ) is electrically connected with one end of the C-phase power grid power supply, the other end is electrically connected with the source electrode of the rectifier switching tube three (S 3 ), The drain electrode of the rectifier switching tube six (S 6 ) and the drain electrode of the rectifier switching tube nine (S 9 ), the source electrode of the rectifier switching tube nine (S 9 ) is electrically connected with the source electrode of the rectifier switching tube twelve (S 12 ), the drain electrode of the rectifier switching tube one (S 1 ) is electrically connected with the drain electrode of the rectifier switching tube two (S 2 ) and the drain electrode of the rectifier switching tube three (S 3 ), the source electrode of the rectifier switching tube four (S 4 ) is electrically connected with the source electrode of the rectifier switching tube five (S 5 ) and the source electrode of the rectifier switching tube six (S 6 ), and the drain electrode of the rectifier switching tube ten (S 10 ) is electrically connected with the drain electrode of the rectifier switching tube eleven (S 11 ) and the drain electrode of the rectifier switching tube twelve (S 12 ); The voltage selector comprises a first selector switch tube (S P1 ), a source electrode of the first selector switch tube (S P1 ) is electrically connected with a drain electrode of a second selector switch tube (S P2 ), a source electrode of the second selector switch tube (S P2 ) is electrically connected with a drain electrode of a third selector switch tube (S P3 ) and a drain electrode of a tenth rectifier switch tube (S 10 ), a source electrode of the third selector switch tube (S P3 ) is electrically connected with a drain electrode of a fourth selector switch tube (S P4 ), a drain electrode of the first selector switch tube (S P1 ) is electrically connected with a drain electrode of the first rectifier switch tube (S 1 ), a drain electrode of the second rectifier switch tube (S 2 ) and a drain electrode of the third rectifier switch tube (S 3 ), and a source electrode of the fourth selector switch tube (S P4 ) is electrically connected with a source electrode of the fourth rectifier switch tube (S 4 ), a source electrode of the fifth rectifier switch tube (S 5 ) and a source electrode of the sixth rectifier switch tube (S 6 ).
  2. 2. The topology of a three-phase single-stage isolated AC-DC converter of claim 1, wherein said upper DAB converter (DAB 1) comprises a first input filter capacitor (C in1 ), one end of said first input filter capacitor (C in1 ) being electrically connected to the drain of an upper converter switching tube one (S U1 ), The drain of the up-converter switching tube III (S U3 ) and the drain of the selector switching tube I (S P1 ), the other end of the first input filter capacitor (C in1 ) is electrically connected with the source of the up-converter switching tube II (S U2 ), The source of the up-converter switching tube IV (S U4 ) and the source of the selector switching tube IV (S P4 ), the source of the up-converter switching tube I (S U1 ) is electrically connected with the drain of the up-converter switching tube II (S U2 ) and one end of the auxiliary inductor (L k1 ), the other end of the auxiliary inductor (L k1 ) is electrically connected with the primary side inductor homonymous end of the first transformer (T1), the source of the up-converter switching tube III (S U3 ) is electrically connected with the drain of the up-converter switching tube IV (S U4 ) and the primary side inductor homonymous end of the first transformer (T1), the secondary side inductor homonymous end of the first transformer (T1) is electrically connected with the source of the up-converter switching tube seven (S U7 ) and the drain of the up-converter switching tube eight (S U8 ), the secondary side inductor homonymous end of the first transformer (T1) is electrically connected with the source of the up-converter switching tube six (S U5 ), and the output of the up-converter switching tube eight (S U7 ) is electrically connected with the drain of the up-converter switching tube seven (S3635) and the output of the up-converter switching tube eight (S4638).
  3. 3. The topology of a three-phase single-stage isolated AC-DC converter of claim 1, wherein said lower DAB converter (DAB 2) comprises a second input filter capacitor (C in2 ), one end of said second input filter capacitor (C in2 ) being electrically connected to the drain of a down-converter switching tube one (S D1 ), the drain electrode of the down-converter switching tube III (S D1 ) and the drain electrode of the selector switching tube II (S P2 ), the other end of the second input filter capacitor (C in2 ) is electrically connected with the source electrode of the down-converter switching tube II (S D2 ), The source of the down converter switch tube IV (S D4 ) and the drain of the selector switch tube IV (SP 4), the source of the down converter switch tube I (S D1 ) is electrically connected with the drain of the down converter switch tube II (S D2 ) and one end of the second auxiliary inductor (L k2 ), the other end of the second auxiliary inductor (L k2 ) is electrically connected with the primary inductor homonymous end of the second transformer (T2), the source of the down converter switch tube III (S D3 ) is electrically connected with the drain of the down converter switch tube IV (S D4 ) and the primary inductor heteronymous end of the second transformer (T2), the secondary inductor homonymous end of the second transformer (T2) is electrically connected with the source of the down converter switch tube V (S D5 ) and the drain of the down converter switch tube VI (S D6 ), the secondary inductor heteronymous end of the second transformer (T2) is electrically connected with the source of the down converter switch tube seven (S D7 ) and the drain of the down converter switch tube eight (S D8 ), and the secondary inductor homonymous end of the second transformer (T2) is electrically connected with the drain of the down converter switch tube V (S D5 ) and the down converter switch tube V (S D7 ), A drain electrode of an up-converter switching tube seven (S U7 ), The anode of the second output filter capacitor (C o2 ) and one end of the load (R o ), the source electrode of the down-converter switch tube six (S D6 ) is electrically connected with the source electrode of the down-converter switch tube eight (S D8 ), The source of the up-converter switching tube eight (S U8 ), the cathode of the second output filter capacitor (C o2 ) and the other end of the load (R o ).
  4. 4. The control method of the topological structure of the three-phase single-stage isolated AC-DC converter is characterized by comprising the following steps: step one, constructing a topological structure of the three-phase single-stage isolated AC-DC converter according to any one of claims 1 to 3; Step two, sampling voltages u a 、u b 、u c of A phase, B phase and C phase of a three-phase power supply, and obtaining a power grid phase angle theta through a phase-locked loop; Step three, according to the phase angle theta of the power grid and the control of the SWISS rectifier, the switching state of the SWISS rectifier is obtained; step four, obtaining the switching state of the voltage selector according to the phase angle theta of the power grid and the control of the voltage selector; Step five, sampling to obtain a sampling output voltage U dc , taking a voltage error between a given output voltage U dc_ref and a sampling output voltage U dc as input of a closed-loop controller to output three-phase total reference power P o_ref , and combining a grid phase angle theta and a phase voltage amplitude U d to obtain reference power of an upper DAB converter (DAB 1) and a lower DAB converter (DAB 2); Step six, according to the reference power of the upper DAB converter (DAB 1) and the lower DAB converter (DAB 2), and based on the modulation strategy of the DAB converter, obtaining each phase shift angle variable of the upper DAB converter (DAB 1) and the lower DAB converter (DAB 2), namely a primary side inner shift phase angle D p1 of the upper DAB converter, a secondary side inner shift phase angle D s1 of the upper DAB converter, an outer shift phase angle D f1 between the primary side and the secondary side of the upper DAB converter, a secondary side phase angle D p2 of the lower DAB converter, a secondary side inner shift phase angle D s2 of the lower DAB converter and an outer shift phase angle D f2 between the primary side and the secondary side of the lower DAB converter, and further controlling the switching tubes of the upper DAB converter (DAB 1) and the lower DAB2 to be in corresponding switching states.
  5. 5. The method for controlling a topology of a three-phase single-stage isolated AC-DC converter of claim 4, wherein in step three, a phase angle θ of a power grid is obtained through a phase-locked loop according to the sampled three-phase power grid voltage u a 、u b 、u c , and a switching state of a SWISS rectifier is obtained according to the phase angle θ as follows: When θ=0, rectifier switch one (S 1 ) is on, rectifier switch two (S 2 ) is off, rectifier switch three (S 3 ) is off, rectifier switch four (S 4 ) is off, rectifier switch five (S 5 ) is off, rectifier switch six (S 6 ) is on, rectifier switch seven (S 7 ) is off, rectifier switch eight (S 8 ) is on, rectifier switch nine (S 9 ) is off, rectifier switch ten (S 10 ) is off, rectifier switch eleven (S 11 ) is on, and rectifier switch twelve (S 12 ) is off; When θ=2pi/6, rectifier switch one (S 1 ) is turned off, rectifier switch two (S 2 ) is turned on, rectifier switch three (S 3 ) is turned off, rectifier switch four (S 4 ) is turned off, rectifier switch five (S 5 ) is turned off, rectifier switch six (S 6 ) is turned on, rectifier switch seven (S 7 ) is turned on, rectifier switch eight (S 8 ) is turned off, rectifier switch nine (S 9 ) is turned off, rectifier switch ten (S 10 ) is turned on, rectifier switch eleven (S 11 ) is turned off, and rectifier switch twelve (S 12 ) is turned off; when θ=4pi/6, rectifier switch tube one (S 1 ) is turned off, rectifier switch tube two (S 2 ) is turned on, rectifier switch tube three (S 3 ) is turned off, rectifier switch tube four (S 4 ) is turned on, rectifier switch tube five (S 5 ) is turned off, rectifier switch tube six (S 6 ) is turned off, rectifier switch tube seven (S 7 ) is turned off, rectifier switch tube eight (S 8 ) is turned off, rectifier switch tube nine (S 9 ) is turned on, rectifier switch tube ten (S 10 ) is turned off, rectifier switch tube eleven (S 11 ) is turned off, and rectifier switch tube twelve (S 12 ) is turned on; When θ=pi, rectifier switch one (S 1 ) is turned off, rectifier switch two (S 2 ) is turned off, rectifier switch three (S 3 ) is turned on, rectifier switch four (S 4 ) is turned on, rectifier switch five (S 5 ) is turned off, rectifier switch six (S 6 ) is turned off, rectifier switch seven (S 7 ) is turned off, rectifier switch eight (S 8 ) is turned on, rectifier switch nine (S 9 ) is turned off, rectifier switch ten (S 10 ) is turned off, rectifier switch eleven (S 11 ) is turned on, and rectifier switch twelve (S 12 ) is turned off; When θ=8pi/6, rectifier switch one (S 1 ) is turned off, rectifier switch two (S 2 ) is turned off, rectifier switch three (S 3 ) is turned on, rectifier switch four (S 4 ) is turned off, rectifier switch five (S 5 ) is turned on, rectifier switch six (S 6 ) is turned off, rectifier switch seven (S 7 ) is turned on, rectifier switch eight (S 8 ) is turned off, rectifier switch nine (S 9 ) is turned off, rectifier switch ten (S 10 ) is turned on, rectifier switch eleven (S 11 ) is turned off, rectifier switch twelve (S 12 ) is turned off, when θ=10pi/6, rectifier switch one (S 1 ) is turned on, rectifier switch two (S 2 ) is turned off, rectifier switch three (S 3 ) is turned off, rectifier switch four (S 4 ) is turned off, rectifier switch five (S 5 ) is turned on, rectifier switch six (S 6 ) is turned off, rectifier switch eleven (S3493) is turned off, rectifier switch eleven (S8232) is turned off, and rectifier switch eleven (S8232) is turned off.
  6. 6. The method according to claim 4, wherein in the fourth step, the phase angle θ of the power grid is obtained through a phase-locked loop according to the sampled three-phase power grid voltage u a 、u b 、u c . The switching state of the voltage selector is obtained according to the phase angle theta: When θ=pi/6, the first selector switch tube (S P1 ) is turned off, the third selector switch tube (S P3 ) is turned off, the second selector switch tube (S P2 ) is turned on, and the fourth selector switch tube (S P4 ) is turned on; When θ=3pi/6, the selector switch tube two (S P2 ) is turned off, the selector switch tube four (S P4 ) is turned off, the selector switch tube one (S P1 ) is turned on, and the selector switch tube three (S P3 ) is turned on; when θ=5pi/6, the first selector switch tube (S P1 ) is turned off, the third selector switch tube (S P3 ) is turned off, the second selector switch tube (S P2 ) is turned on, and the fourth selector switch tube (S P4 ) is turned on; when θ=7pi/6, the selector switch tube two (S P2 ) is turned off, the selector switch tube four (S P4 ) is turned off, the selector switch tube one (S P1 ) is turned on, and the selector switch tube three (S P3 ) is turned on; When θ=9pi/6, the first selector switch tube (S P1 ) is turned off, the third selector switch tube (S P3 ) is turned off, the second selector switch tube (S P2 ) is turned on, and the fourth selector switch tube (S P4 ) is turned on; When θ=11π/6, the second selector switch tube (S P2 ) is turned off, the fourth selector switch tube (S P4 ) is turned off, the first selector switch tube (S P1 ) is turned on, and the third selector switch tube (S P3 ) is turned on.
  7. 7. The method for controlling the topology of a three-phase single-stage isolated AC-DC converter of claim 4, wherein said step five comprises the specific steps of: 7.1 Sampling to obtain a sampled output voltage U dc , and taking a voltage error between a given output voltage U dc_ref and a sampled output voltage U dc as an input of a voltage closed-loop controller so as to output three-phase total reference power P o_ref ; 7.2 The sampled three-phase grid voltage is subjected to coordinate transformation to obtain the amplitude u d of the phase voltage, and the amplitude u d is shown as the following formula: 7.3 According to the phase angle theta and the phase voltage amplitude u d , the maximum phase voltage u max , the intermediate phase voltage u mid and the minimum phase voltage u min of the three-phase system are obtained as shown in the following formula: The input voltages of the upper DAB converter (DAB 1) and the lower DAB converter (DAB 2) are respectively the maximum line voltages according to the switching state of the voltage selector And the next largest line voltage The corresponding expression is as follows: 7.4 According to the three-phase total reference power P o_ref and the phase voltage amplitude u d , the reference amplitude I m_ref of the three-phase current under the unit power factor operation condition is obtained as shown in the following formula: further combining with the phase angle theta of the power grid, the three-phase instantaneous reference current is obtained as shown in the following formula: 、 And Instantaneous reference currents for phase a, phase B and phase C, respectively; 7.5 According to three-phase instantaneous reference current i a_ref 、i b_ref 、i c_ref , maximum line voltage And the next largest line voltage Obtaining the reference transmission power of the upper DAB converter (DAB 1) And reference transmission power of lower DAB converter (DAB 2) The following formula is shown: 。
  8. 8. The method for controlling the topology of a three-phase single-stage isolated AC-DC converter of claim 4, wherein said step six comprises the specific steps of: 8.1 According to the modulation strategy of the DAB converter, the upper DAB converter (DAB 1) has four typical working modes, and the phase shift angle calculation expression under different working modes is shown as follows: Wherein P n1 =p gh /P base1 is the per unit power of the upper DAB converter, P base1 =(n 1 u gh U dc T s )/(8L k1 ) is the reference power of the upper DAB converter, n 1 is the transformer turns ratio, T s is the switching period, T h is the half switching period, k 1= u gh /(n 1 U dc ) is the voltage conversion ratio of the upper DAB converter, P bound1 =2k 1 (1-k 1 ) is the modal boundary power when k 1 <1, and P bound2 =2(k 1 -1)/(k 1 ≡2) is the modal boundary power when k 1 is more than or equal to 1; 8.2 Substituting the reference power p gh of the upper DAB converter (DAB 1) into the phase shift angle calculation expression, thereby obtaining a phase shift angle variable D p1 、D s1 、D f1 of the upper DAB converter (DAB 1); The phase-shift angle variable D p2 、D s2 、D f2 of the lower DAB converter (DAB 2) is obtained by the same method; 8.3 According to the solved phase-shift angle variable D p1 、D s1 、D f1 、D p2 、D s2 、D f2 , the switch states of the switch tubes in the upper DAB converter (DAB 1) and the lower DAB converter (DAB 2) are obtained as shown in the following formula: Wherein, the The switching-on instant of the switching tube x is indicated, The switching-off times of the switching tubes x are indicated, x e SU1-SU8 and SD1-SD8.
  9. 9. The method of controlling the topology of a three-phase single-stage isolated AC-DC converter of claim 4, wherein said unity power factor operation is implemented based on the switching states of a SWISS rectifier, a voltage selector, and two DAB converters.

Description

Three-phase single-stage isolated AC-DC converter topology and control method Technical Field The invention relates to the field of power electronics, in particular to a topology and a control method of a three-phase single-stage isolated AC-DC converter. Background With the rapid development of fields such as data centers and electric automobiles, the demand for efficient high-performance three-phase isolated AC-DC topology is increasingly remarkable. The traditional topology scheme generally adopts a two-stage topology, a front-stage AC-DC converter realizes power factor correction, and a rear-stage DC-DC converter realizes electrical isolation and load voltage stabilization. Although the structure technology is mature, a large-capacity electrolytic capacitor is needed to be used on the middle direct-current bus to maintain voltage stability, and the power density and reliability of the system are reduced. Compared with the prior art, the single-stage topology can realize power factor correction and output voltage control by using only one-stage circuit, and does not need a large electrolytic capacitor in the middle, thereby being beneficial to improving the power density and the reliability of the system. In the three-phase single-stage isolated AC-DC topology, the three-phase single-stage isolated AC-DC topology based on the SWISS rectifier and the double DAB converter is flexible and simple to control, and all high-frequency power devices can realize soft switching, so that the high-efficiency operation of the system can be realized, and the three-phase single-stage isolated AC-DC topology is widely focused in the industry. However, in this topology, the input voltages of both sets of DAB converters are changed from zero to 1.5 times the peak value of the phase voltage, the fluctuation range of the input voltages is large, and the matching degree is low. The lower voltage matching increases the inductor current efficiency of the DAB converter, thereby reducing the efficiency of the system. Disclosure of Invention In order to reduce the input voltage fluctuation of the DAB converter and realize the unit power factor operation of the system, the invention discloses a topology and a control method of a three-phase single-stage isolated AC-DC converter. In order to achieve the above purpose, the technical scheme of the invention is as follows: the topological structure of the three-phase single-stage isolated AC-DC converter comprises a SWISS rectifier, wherein the SWISS rectifier is electrically connected with a voltage selector, and the voltage selector is electrically connected with an upper DAB converter DAB1 and a lower DAB converter DAB2; the SWISS rectifier comprises a first network side filter inductance L f1, A second net side filter inductance L f2 and a third net side filter inductance L f3, wherein one end of the first net side filter inductance L f1 is electrically connected with one end of the A phase power grid power supply, the other end is electrically connected with the source electrode of a rectifier switching tube S 1, The drain electrode of the rectifier switching tube IV S 4 and the drain electrode of the rectifier switching tube seven S 7, the source electrode of the rectifier switching tube seven S 7 is electrically connected with the source electrode of the rectifier switching tube ten S 10, one end of the second network side filter inductor L f2 is electrically connected with one end of a B-phase power grid power supply, and the other end is electrically connected with the source electrode of the rectifier switching tube II S 2, The drain electrode of the rectifier switching tube five S 5 and the drain electrode of the rectifier switching tube eight S 8, the source electrode of the rectifier switching tube eight S 8 is electrically connected with the source electrode of the rectifier switching tube eleven S 11, one end of the third net side filter inductor L f3 is electrically connected with one end of a C-phase power grid power supply, and the other end is electrically connected with the source electrode of the rectifier switching tube three S 3, The drain electrode of the rectifier switch tube six S 6 and the drain electrode of the rectifier switch tube nine S 9, the source electrode of the rectifier switch tube nine S 9 is electrically connected with the source electrode of the rectifier switch tube twelve S 12, the drain electrode of the rectifier switch tube one S 1 is electrically connected with the drain electrode of the rectifier switch tube two S 2 and the drain electrode of the rectifier switch tube three S 3, the source electrode of the rectifier switch tube four S 4 is electrically connected with the source electrode of the rectifier switch tube five S 5 and the source electrode of the rectifier switch tube six S 6, and the drain electrode of the rectifier switch tube ten S 10 is electrically connected with the drain electrode of the rectifier switch tube eleve