Three-phase single-stage bidirectional AC / DC multi-level converter topology and control method thereof

Abstract

The invention provides a three-phase single-stage bidirectional AC / DC multi-level converter topology and a control method thereof, and relates to the technical field of power electronic conversion. The voltage stress borne by all primary side switch tubes of the three-phase single-stage bidirectional AC / DC multilevel converter topology is half of the bus voltage, so that the voltage stress requirement of the switch tubes is reduced, and the cost and loss of the switch tubes are reduced; all switching devices can realize zero-voltage switching in a wide range, so that the efficiency of the converter is greatly improved; the multi-level structure is realized, the number of switching tubes in a power path of the converter in a single mode is greatly reduced, the complexity of the control method is effectively reduced, the loss source is reduced, and the potential of further reducing the loss is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronic conversion, and in particular to a three-phase single-stage bidirectional AC / DC multi-level converter topology and a control method thereof. Background Art

[0002] In the construction of new power systems, distributed power sources dominated by renewable energy are exhibiting significant DC characteristics. Photovoltaic power generation units and battery energy storage systems are essentially DC sources and require an inverter before they can be connected to the AC grid. While rotating units such as wind turbines and diesel generators directly generate AC power, their output frequency differs from that of the grid and still requires two-stage AC-DC-AC power conversion for grid connection. When connecting to such distributed power sources, existing AC grid architectures generally suffer from prominent issues such as numerous power conversion stages, low system efficiency, and high investment in power electronics equipment. Especially in scenarios where multiple energy sources operate in tandem, energy losses caused by multiple AC-DC conversions can reach over 35% of the total system loss.

[0003] To address these technical bottlenecks, the AC / DC hybrid microgrid architecture offers unique advantages. By operating the AC and DC buses in tandem, this architecture reduces the repeated AC / DC and DC / AC conversion steps. Theoretical calculations indicate that overall system efficiency can be improved by 8-12 percentage points. The key to achieving efficient energy exchange between the AC and DC subgrids lies in the development of a three-phase AC / DC bidirectional converter with high reliability and modular scalability. Existing research focuses on three core areas: the application of soft-switching technology, high-frequency magnetic coupling isolation schemes, and the construction of single-stage power topologies. Resonant soft-switching technology can reduce switching losses by 40%-60%. High-frequency isolation devices such as planar transformers can increase power density to 3-5 times that of traditional power-frequency transformers. Single-stage topologies significantly reduce equipment size and cost by eliminating intermediate energy storage. The current technical challenge lies in achieving zero-voltage switching characteristics, smooth bidirectional power flow, and fast dynamic response in the three-phase system under high-frequency operating conditions. This places high demands on optimized magnetic component design and multi-modal control strategies. Summary of the Invention

[0004] The object of the present invention is to provide a three-phase single-stage bidirectional AC / DC multilevel converter topology and its control method, which are used to solve the problems of the existing three-phase single-stage bidirectional AC / DC converter, such as the long single-mode power path, large loss, and large voltage stress of the switch tube. The present invention can reduce the voltage stress, cost and loss of the switch tube, reduce the number of switch tubes in the power path under a single mode, and reduce the loss.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a three-phase single-stage bidirectional AC / DC multilevel converter topology, comprising a three-phase AC source, a three-phase transformer, a three-phase AC bridge arm, a three-phase DC bridge arm, a three-phase common bridge arm, a three-phase flying capacitor, a bus capacitor, a three-phase power inductor, a three-phase DC blocking capacitor, a secondary three-phase bridge arm, and an output capacitor; The three-phase AC source is connected to the three-phase AC bridge arm; the three-phase AC bridge arm, the three-phase DC bridge arm, and the three-phase flying capacitor are connected in parallel to the three-phase common bridge arm; the three-phase common bridge arm is connected to the bus capacitor; the three-phase DC bridge arm is connected to the three-phase transformer via the three-phase power inductor and the three-phase DC blocking capacitor; the three-phase transformer is connected to the secondary three-phase bridge arm; and the secondary three-phase bridge arm is connected to the output capacitor.

[0006] According to a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the three-phase AC bridge arm includes an A-phase AC bridge arm Q 2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B and C-phase AC bridge arm Q 2C , Q 3C ; The three-phase DC bridge arm includes the A-phase DC bridge arm Q 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BD and C-phase DC bridge arm Q 2CD , Q 3CD ; The three-phase common bridge arm includes the A-phase common bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C ; The three-phase flying capacitor includes the A-phase flying capacitor C a , B phase flying capacitor C b and C phase flying capacitor C c ; The bus capacitance includes the upper bus capacitance C bus1 and the lower bus capacitor C bus2 ; The three-phase power inductor includes the A-phase power inductor L ra , B phase power inductor L rb and C-phase power inductor L rc ; The three-phase DC isolation capacitor includes the A-phase DC isolation capacitor C ra , B phase separation capacitor C rb and C is separated by a DC capacitor C rc The secondary three-phase bridge arm includes the secondary A phase AC bridge arm Q s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4and the secondary side C phase AC bridge arm Q s5 , Q s6 ; The output capacitor includes the upper output capacitor C o1 and the lower output capacitor C o2 . According to a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the A phase, B phase and C phase of the three-phase AC source are respectively connected through the AC inductor L a , L b , L c With the three-phase AC bridge arm Q 2A , Q 3A , Q 2B , Q 3B , Q 2C , Q 3C The midpoints are connected; Phase A AC bridge arm Q 2A The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3A The source of the A phase shares the bridge arm Q 4A The drain of the B phase AC bridge arm is connected; 2B The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3B The source of the B phase shares the Q 4B The drain of the C phase AC bridge arm is connected; 2C The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3C The source of the C phase shares the Q 4C The drain of is connected; Phase A DC bridge arm Q 2AD The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3AD The source of the A phase shares the bridge arm Q 4A The drain of the B phase DC bridge arm is connected; 2BD The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3BD The source of the B phase shares the Q 4B The drain of the C phase DC bridge arm is connected; 2CD The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3CD The source of the C phase shares the Q 4C The drain of is connected; Phase A shares the bridge arm Q 1AThe drain of phase B and the Q 1B The drain of the C phase common bridge arm Q 1C The drain and upper bus capacitor C bus1 The positive pole of the A phase is connected; the Q 4A The source of the B phase shared bridge arm Q 4B The source of the C phase common bridge arm Q 4C The source and lower bus capacitor C bus2 The negative pole is connected.

[0007] According to a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the flying capacitor C of phase A a The positive pole of the A phase shares the bridge arm Q 1A The source of phase A is connected to the flying capacitor C a The negative pole of the bridge arm Q is shared with the A phase 4A The drain of phase B is connected; the flying capacitor C B The positive pole of the bridge arm Q is shared with the B phase 1B The source of the B phase is connected to the flying capacitor C b The negative pole of the bridge arm Q is shared with the B phase 4B The drain of the C phase is connected; the C phase flying capacitor C c The positive electrode of the bridge arm is shared with the C phase Q 1C The source of the C phase is connected to the flying capacitor C c The negative pole of the bridge arm is shared with the C phase Q 4C The drain is connected.

[0008] According to a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the A-phase power inductor L ra The first end of the A phase DC bridge arm Q 2AD , Q 3AD The midpoint of the B phase power inductor L rb The first end of the B phase DC bridge arm Q 2BD , Q 3BD The midpoint of the C phase power inductor L rc The first end of the C phase DC bridge arm Q 2CD , Q 3CD The midpoint of the phase A power inductor L ra The second end is separated from A by a DC capacitor C ra The first end of the B phase power inductor L rb The second end is separated from phase B by a DC capacitor C rb The first end of the C phase power inductor L rc The second end of C is separated from the capacitor C rc The first end is connected.

[0009] According to a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the three-phase transformer includes an A-phase transformer, a B-phase transformer and a C-phase transformer; the A-phase DC isolation capacitor C ra The second end of the capacitor C is connected to the first end of the primary side of the A-phase transformer, and the second end of the primary side of the A-phase transformer is grounded; rb The second end of the C phase is connected to the first end of the primary side of the B phase transformer, and the second end of the primary side of the B phase transformer is grounded; the C phase DC isolation capacitor C rc The second end of is connected to the first end of the primary side of the C-phase transformer, and the second end of the primary side of the C-phase transformer is grounded.

[0010] According to a three-phase single-stage bidirectional AC / DC multilevel converter topology provided by the present invention, the secondary side A phase AC bridge arm Q s1 , Q s2 The midpoint is connected to the first end of the secondary side of the A-phase transformer; the secondary side B-phase AC bridge arm Q s3 , Q s4 The midpoint is connected to the first end of the secondary side of the B-phase transformer; the secondary side C-phase AC bridge arm Q s5 , Q s6 The midpoint is connected to the first end of the secondary side of the C phase transformer; the second end of the secondary side of the A phase transformer, the second end of the secondary side of the B phase transformer, the second end of the secondary side of the C phase transformer, and the upper output capacitor C o1 The negative terminal of the output capacitor C o2 The positive electrode is connected; Secondary side A phase AC bridge arm Q s1 The drain of the secondary side B phase AC bridge arm Q s3 The drain of the secondary side C phase AC bridge arm Q s5 The drain and output capacitor C o1 The positive pole of the secondary side A phase AC bridge arm is connected; s2 The source of the secondary side B phase AC bridge arm Q s4 The source of the secondary side C phase AC bridge arm Q s6 The source and the lower output capacitor C o2 The negative pole is connected.

[0011] In a second aspect, the present invention provides a control method for the three-phase single-stage bidirectional AC / DC multilevel converter topology of the first aspect, comprising: The voltage of the three-phase AC source is collected, and the abc coordinate system is converted into the αβ coordinate system through Clarke transformation to obtain the voltage reference angle; The current of the three-phase AC source is collected, and the abc coordinate system is converted to the dq coordinate system through Park transformation. Combined with the voltage reference angle, the current value in the dq coordinate system is obtained; Based on the busbar capacitor voltage, d-axis current component and q-axis current component, determine the A-phase AC bridge arm Q2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B , C-phase AC bridge arm Q 2C , Q 3C , Phase A shares the bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C The duty cycle is adjusted to realize the control of bus capacitor voltage and three-phase input current.

[0012] According to a control method for a three-phase single-stage bidirectional AC / DC multilevel converter topology provided by the present invention, the flying capacitor C of phase A is a , B phase flying capacitor C b , C phase flying capacitor C c The voltage of phase A DC bridge arm Q is collected to obtain 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BD and C-phase DC bridge arm Q 2CD , Q 3CD The duty cycle and the phase difference between the three-phase DC bridge arm and the three-phase common bridge arm are used to control the three-phase flying capacitor voltage.

[0013] According to a control method for a three-phase single-stage bidirectional AC / DC multi-level converter topology provided by the present invention, the output capacitor C o1 and the lower output capacitor C o2 The voltage of the secondary side A phase AC bridge arm Q is collected to obtain s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4 and the secondary side C phase AC bridge arm Q s5 , Q s6 The duty cycle and the phase difference between the secondary three-phase bridge arm and the three-phase common bridge arm are used to control the transmission power.

[0014] The three-phase single-stage bidirectional AC / DC multilevel converter topology and control method proposed in the present invention have at least the following technical effects compared with the prior art: 1. The voltage stress borne by all primary-side switching tubes is half of the bus voltage, which reduces the voltage stress requirement of the switching tubes and reduces the cost and loss of the switching tubes.

[0015] 2. All switching devices can achieve zero-voltage turn-on in a wide range, greatly improving the efficiency of the converter.

[0016] 3. While realizing a multi-level structure, the number of switches in the power path of the converter in a single mode is greatly reduced, which effectively reduces the complexity of the control method and reduces the source of loss, providing the potential for further loss reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] In the attached figure: Figure 1 A circuit diagram of a three-phase single-stage bidirectional AC / DC multilevel converter topology according to the present invention; Figure 2 The main working waveform diagram of the three-phase single-stage bidirectional AC / DC multilevel converter topology of the present invention; Figures 3 to 10 They are equivalent circuit diagrams of each working sub-mode of the three-phase single-stage bidirectional AC / DC multi-level converter topology of the present invention. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0020] The following will describe some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0021] See also Figure 1 The embodiment of the present invention provides a three-phase single-stage bidirectional AC / DC multilevel converter topology, including a three-phase AC source, a three-phase transformer, a three-phase AC bridge arm, a three-phase DC bridge arm, a three-phase common bridge arm, a three-phase flying capacitor, a bus capacitor, a three-phase power inductor, a three-phase DC blocking capacitor, a secondary three-phase bridge arm, and an output capacitor; The three-phase AC source is connected to the three-phase AC bridge arm; the three-phase AC bridge arm, the three-phase DC bridge arm, and the three-phase flying capacitor are connected in parallel to the three-phase common bridge arm; the three-phase common bridge arm is connected to the bus capacitor; the three-phase DC bridge arm is connected to the three-phase transformer via the three-phase power inductor and the three-phase DC blocking capacitor; the three-phase transformer is connected to the secondary three-phase bridge arm; and the secondary three-phase bridge arm is connected to the output capacitor.

[0022] Specifically, the three-phase AC bridge arm includes the A-phase AC bridge arm Q 2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B and C-phase AC bridge arm Q 2C , Q 3C ; Three-phase DC bridge arm, including phase A DC bridge arm Q 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BD and C-phase DC bridge arm Q 2CD , Q 3CD ; Three-phase common bridge arm, including phase A common bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C ; Three-phase flying capacitors, including phase A flying capacitor C a , B phase flying capacitor C b and C phase flying capacitor C c ; Bus capacitance, including upper bus capacitance C bus1 and the lower bus capacitor C bus2 ; Three-phase power inductor, including A-phase power inductor L ra , B phase power inductor L rb and C-phase power inductor L rc ; Three-phase DC isolation capacitors, including A phase DC isolation capacitor C ra , B phase separation capacitor C rb and C is separated by a DC capacitor C rc ; Secondary three-phase bridge arm, including the secondary A phase AC bridge arm Q s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4 and the secondary side C phase AC bridge arm Q s5 , Q s6 ; Output capacitance, including upper output capacitance C o1 and the lower output capacitor C o2 .

[0023] Among them, the A phase, B phase, and C phase of the three-phase AC source pass through the AC inductor L a , L b , L c With the three-phase AC bridge arm Q 2A , Q 3A , Q 2B , Q 3B , Q 2C , Q 3CConnect the midpoints.

[0024] Phase A AC bridge arm Q 2A The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3A The source of the A phase shares the bridge arm Q 4A The drain of the B phase AC bridge arm is connected; 2B The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3B The source of the B phase shares the Q 4B The drain of the C phase AC bridge arm is connected; 2C The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3C The source of the C phase shares the Q 4C The drain of is connected; Phase A DC bridge arm Q 2AD The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3AD The source of the A phase shares the bridge arm Q 4A The drain of the B phase DC bridge arm is connected; 2BD The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3BD The source of the B phase shares the Q 4B The drain of the C phase DC bridge arm is connected; 2CD The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3CD The source of the C phase shares the Q 4C The drain of is connected; Phase A shares the bridge arm Q 1A The drain of phase B and the Q 1B The drain of the C phase common bridge arm Q 1C The drain and upper bus capacitor C bus1 The positive pole of the A phase is connected; the Q 4A The source of the B phase shared bridge arm Q 4B The source of the C phase common bridge arm Q 4C The source and lower bus capacitor C bus2 The negative pole is connected.

[0025] Phase A flying capacitor C a The positive pole of the A phase shares the bridge arm Q 1A The source of phase A is connected to the flying capacitor C aThe negative pole of the bridge arm Q is shared with the A phase 4A The drain of phase B is connected; the flying capacitor C B The positive pole of the bridge arm Q is shared with the B phase 1B The source of the B phase is connected to the flying capacitor C b The negative pole of the bridge arm Q is shared with the B phase 4B The drain of the C phase is connected; the C phase flying capacitor C c The positive electrode of the bridge arm is shared with the C phase Q 1C The source of the C phase is connected to the flying capacitor C c The negative pole of the bridge arm is shared with the C phase Q 4C The drain is connected.

[0026] A phase power inductor L ra The first end of the A phase DC bridge arm Q 2AD , Q 3AD The midpoint of the B phase power inductor L rb The first end of the B phase DC bridge arm Q 2BD , Q 3BD The midpoint of the C phase power inductor L rc The first end of the C phase DC bridge arm Q 2CD , Q 3CD The midpoint of the phase A power inductor L ra The second end is separated from A by a DC capacitor C ra The first end of the B phase power inductor L rb The second end is separated from phase B by a DC capacitor C rb The first end of the C phase power inductor L rc The second end of C is separated from the capacitor C rc The first end is connected.

[0027] The three-phase transformer includes A-phase transformer, B-phase transformer and C-phase transformer; A-phase DC isolation capacitor C ra The second end of the capacitor C is connected to the first end of the primary side of the A-phase transformer, and the second end of the primary side of the A-phase transformer is grounded; rb The second end of the C phase is connected to the first end of the primary side of the B phase transformer, and the second end of the primary side of the B phase transformer is grounded; the C phase DC isolation capacitor C rc The second end of is connected to the first end of the primary side of the C-phase transformer, and the second end of the primary side of the C-phase transformer is grounded.

[0028] Secondary side A phase AC bridge arm Q s1 , Q s2 The midpoint is connected to the first end of the secondary side of the A-phase transformer; the secondary side B-phase AC bridge arm Q s3 , Q s4 The midpoint is connected to the first end of the secondary side of the B-phase transformer; the secondary side C-phase AC bridge arm Q s5 , Qs6 The midpoint is connected to the first end of the secondary side of the C phase transformer; the second end of the secondary side of the A phase transformer, the second end of the secondary side of the B phase transformer, the second end of the secondary side of the C phase transformer, and the upper output capacitor C o1 The negative terminal of the output capacitor C o2 The positive electrode is connected; Secondary side A phase AC bridge arm Q s1 The drain of the secondary side B phase AC bridge arm Q s3 The drain of the secondary side C phase AC bridge arm Q s5 The drain and output capacitor C o1 The positive pole of the secondary side A phase AC bridge arm is connected; s2 The source of the secondary side B phase AC bridge arm Q s4 The source of the secondary side C phase AC bridge arm Q s6 The source and the lower output capacitor C o2 The negative pole is connected.

[0029] Another embodiment of the present invention provides a control method for the three-phase single-stage bidirectional AC / DC multilevel converter topology of the aforementioned embodiment, comprising: The voltage of the three-phase AC source is collected, and the abc coordinate system is converted into the αβ coordinate system through Clarke transformation to obtain the voltage reference angle; The current of the three-phase AC source is collected, and the abc coordinate system is converted to the dq coordinate system through Park transformation. Combined with the voltage reference angle, the current value in the dq coordinate system is obtained; Based on the busbar capacitor voltage, d-axis current component and q-axis current component, determine the A-phase AC bridge arm Q 2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B , C-phase AC bridge arm Q 2C , Q 3C , Phase A shares the bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C The duty cycle is adjusted to realize the control of bus capacitor voltage and three-phase input current.

[0030] Specifically, for the flying capacitor C of phase A a , B phase flying capacitor C b , C phase flying capacitor C c The voltage of phase A DC bridge arm Q is collected to obtain 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BDand C-phase DC bridge arm Q 2CD , Q 3CD The duty cycle and the phase difference between the three-phase DC bridge arm and the three-phase common bridge arm are used to control the three-phase flying capacitor voltage.

[0031] For the output capacitor C o1 and the lower output capacitor C o2 The voltage of the secondary side A phase AC bridge arm Q is collected to obtain s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4 and the secondary side C phase AC bridge arm Q s5 , Q s6 The duty cycle and the phase difference between the secondary three-phase bridge arm and the three-phase common bridge arm are used to control the transmission power.

[0032] Figure 2 The main working waveform diagram of the three-phase single-stage bidirectional AC / DC multilevel converter topology is shown in Figure 2. Figure 2 Only the A phase is shown in FIG, where G represents the drive signal of the corresponding switch tube, for example, G 1A Indicates the switch tube Q 1A The driving signal, V La is the AC inductor voltage, I La is the AC inductor current, V Lra is the A-phase power inductor voltage, I Lra is the power inductor current of phase A. Taking phase A as an example, according to Figure 2 The three-phase single-stage bidirectional AC / DC multilevel converter can be switched in a single switching cycle (mainly based on the A-phase power inductor voltage V Lra The voltage V of each sub-mode is Lra Different) is divided into eight working sub-modes. Figures 3 to 10 In the diagram, the black line indicates that the circuit is in the on state, and the red line indicates that the circuit is in the off state.

[0033] Working sub-mode 1 t 0, t 1]: Phase A shares the bridge arm Q 4A exist t 0, the AC inductor current I La For the A phase common bridge arm Q 1A The drain-source capacitance of the A-phase common bridge arm is discharged to 0V, and after the dead time ends, the Q 1A Zero voltage turn-on, at this time the AC inductor L a For upper bus capacitor C bus1 Charging the flying capacitor C of phase A a Discharge, upper bus capacitor C bus1 and the lower output capacitor Co2 For phase A power inductor L ra Charging, the equivalent circuit diagram is as follows Figure 3 shown.

[0034] Working sub-mode 2 t 1, t 2]: Q in the secondary side A phase AC bridge arm s2 exist t 1 is turned off at the moment, and the secondary current in the dead zone affects the Q s1 The drain-source capacitor is discharged to 0V, and the dead time ends. s1 Zero voltage turn-on, at this time the AC inductor L a For upper bus capacitor C bus1 Charging the flying capacitor C of phase A a Charging, upper bus capacitor C bus1 For phase A power inductor L ra and the upper output capacitor C o1 Charging, the equivalent circuit diagram is as follows Figure 4 shown.

[0035] Working sub-mode three t 2, t 3]: Q in the A-phase DC bridge arm 2AD exist t 2 is turned off at the moment, and the power inductor current I Lra For the A-phase DC bridge arm Q 3AD The drain-source capacitance of the A-phase DC bridge arm is discharged to 0V, and the dead time ends. 3AD Zero voltage turn-on, at this time the AC inductor L a For upper bus capacitor C bus1 Charging the flying capacitor C of phase A a Discharge, upper bus capacitor C bus1 and A-phase power inductor L ra For phase A flying capacitor C a and the upper output capacitor C o1 Charging, the equivalent circuit diagram is as follows Figure 5 shown.

[0036] Working sub-mode four[ t 3, t 4]: Phase A shares the bridge arm Q 1A exist t 3 is turned off at the moment, and the power inductor current I Lra For the A phase common bridge arm Q 4A The drain-source capacitance of the A-phase common bridge arm is discharged to 0V, and after the dead time ends, the Q 1A Zero voltage is turned on, at this time the lower bus capacitor C bus2 AC inductance L aCharging, A phase power inductor L ra To the lower bus capacitor C bus2 and the lower output capacitor C o2 Charging, the equivalent circuit diagram is as follows Figure 6 shown.

[0037] Working sub-mode five[ t 4, t 5]: Q in the secondary side A phase AC bridge arm s1 exist t 4 is turned off at all times. During the dead time, the secondary current affects the Q in the secondary A phase AC bridge arm. s2 The drain-source capacitor is discharged to 0V, and the dead time ends. s1 Zero voltage is turned on, at this time the lower bus capacitor C bus2 AC inductance L a Charging, A phase power inductor L ra and the lower output capacitor C o2 To the lower bus capacitor C bus2 Charging, the equivalent circuit diagram is as follows Figure 7 shown.

[0038] Working sub-mode six t 5, t 6]: Q in the A-phase AC bridge arm 3A exist t 5 is turned off at the moment, and the AC inductor current I La For the A phase AC bridge arm Q 2A The drain-source capacitance of the A-phase AC bridge arm is discharged to 0V, and the dead time ends. 2A Zero voltage turn-on, at this time the AC inductor L a and the lower bus capacitor C bus2 For phase A flying capacitor C a Charging, A phase power inductor L ra and the lower output capacitor C o2 To the lower bus capacitor C bus2 Charging, the equivalent circuit diagram is as follows Figure 8 shown.

[0039] Working sub-mode seven[ t 6, t 7]: Q in the A-phase DC bridge arm 3AD exist t 6 is turned off at the moment, and the power inductor current I Lra For the A-phase DC bridge arm Q 2AD The drain-source capacitance of the A-phase DC bridge arm is discharged to 0V, and the dead time ends. 2AD Zero voltage turn-on, at this time the AC inductor L a and the lower bus capacitor C bus2 For phase A flying capacitor Ca Charging, lower bus capacitor C bus1 For phase A power inductor L ra 、A phase flying capacitor C a and the lower output capacitor C o2 Charging, the equivalent circuit diagram is as follows Figure 9 shown.

[0040] Working sub-mode eight[ t 7, t 8]: Q in the A-phase AC bridge arm 2A exist t 8 is turned off at all times, and the AC inductor current I La For the A phase AC bridge arm Q 3A The drain-source capacitance of the A-phase AC bridge arm is discharged to 0V, and the dead time ends. 3A Zero voltage is turned on, at this time the lower bus capacitor C bus2 AC inductance L a Charging, lower bus capacitor C bus1 For phase A power inductor L ra 、A phase flying capacitor C a and the lower output capacitor C o2 Charging, the equivalent circuit diagram is as follows Figure 10 shown.

[0041] The above analysis demonstrates that the proposed three-phase, single-stage, bidirectional, AC / DC, multilevel converter topology achieves zero-voltage turn-on operation for all switches, significantly reducing switching losses and enabling high-frequency operation. This reduces size and increases power density, while ensuring high efficiency. Power transmission between each port is single-stage, resulting in high efficiency. Under the proposed control method, the proposed three-phase, single-stage, bidirectional, AC / DC, multilevel converter topology enables flexible control of power flow at each port.

[0042] In summary, the present invention provides a three-phase single-stage bidirectional AC / DC multilevel converter topology and a control method thereof. The voltage stress borne by all primary-side switching tubes of the three-phase single-stage bidirectional AC / DC multilevel converter topology is half of the bus voltage, which reduces the voltage stress requirement of the switching tubes, reduces the cost and loss of the switching tubes; all switching devices can achieve zero-voltage switching within a wide range, greatly improving the efficiency of the converter; while realizing a multi-level structure, the number of switching tubes in the power path of the converter in a single mode is greatly reduced, effectively reducing the complexity of the control method, and reducing the source of loss, providing the potential for further reducing losses.

[0043] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the embodiments disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and variations can be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A three-phase single-stage bidirectional AC / DC multilevel converter topology, characterized in that: Including three-phase AC source, three-phase transformer, three-phase AC bridge arm, three-phase DC bridge arm, three-phase common bridge arm, three-phase flying capacitor, bus capacitor, three-phase power inductor, three-phase DC blocking capacitor, secondary three-phase bridge arm and output capacitor; The three-phase AC source is connected to the three-phase AC bridge arm; the three-phase AC bridge arm, the three-phase DC bridge arm, and the three-phase flying capacitor are connected in parallel to the three-phase common bridge arm; the three-phase common bridge arm is connected to the bus capacitor; the three-phase DC bridge arm is connected to the three-phase transformer via the three-phase power inductor and the three-phase DC blocking capacitor; the three-phase transformer is connected to the secondary three-phase bridge arm; and the secondary three-phase bridge arm is connected to the output capacitor.

2. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 1, characterized in that: The three-phase AC bridge arm includes an A-phase AC bridge arm Q 2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B and C-phase AC bridge arm Q 2C , Q 3C ; The three-phase DC bridge arm includes the A-phase DC bridge arm Q 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BD and C-phase DC bridge arm Q 2CD , Q 3CD ; The three-phase common bridge arm includes the A-phase common bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C ; The three-phase flying capacitor includes the A-phase flying capacitor C a , B phase flying capacitor C b and C phase flying capacitor C c ; The bus capacitance includes the upper bus capacitance C bus1 and the lower bus capacitor C bus2 ; The three-phase power inductor includes the A-phase power inductor L ra , B phase power inductor L rb and C-phase power inductor L rc ; The three-phase DC isolation capacitor includes the A-phase DC isolation capacitor C ra , B phase separation capacitor C rb and C is separated by a DC capacitor C rc The secondary three-phase bridge arm includes the secondary A phase AC bridge arm Q s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4 and the secondary side C phase AC bridge arm Q s5 , Q s6 ; The output capacitor includes the upper output capacitor C o1 and the lower output capacitor C o2 .

3. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that: Phase A, phase B, and phase C of the three-phase AC source are connected through AC inductors L a , L b , L c With the three-phase AC bridge arm Q 2A , Q 3A , Q 2B , Q 3B , Q 2C , Q 3C The midpoints are connected; Phase A AC bridge arm Q 2A The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3A The source of the A phase shares the bridge arm Q 4A The drain of the B phase AC bridge arm is connected; 2B The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3B The source of the B phase shares the Q 4B The drain of the C phase AC bridge arm is connected; 2C The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3C The source of the C phase shares the Q 4C The drain of is connected; The A phase DC bridge arm Q 2AD The drain of the A phase shares the Q 1A The source of the A phase AC bridge arm is connected, and Q 3AD The source of the A phase shares the bridge arm Q 4A The drain of the B phase DC bridge arm is connected; Q 2BD The drain of the B phase shares the Q 1B The source of the B phase AC bridge arm is connected, and Q 3BD The source of the B phase shares the Q 4B The drain of the C phase DC bridge arm is connected; 2CD The drain of the C phase shares the Q 1C The source of the C phase AC bridge arm is connected. 3CD The source of the C phase shares the Q 4C The drain of is connected; The A phase shares the bridge arm Q 1A The drain of phase B and the Q 1B The drain of the C phase common bridge arm Q 1C The drain and upper bus capacitor C bus1 The positive electrode of the A phase is connected; the Q in the common bridge arm 4A The source of the B phase shared bridge arm Q 4B The source of the C phase common bridge arm Q 4C The source and lower bus capacitor C bus2 The negative pole is connected.

4. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that: The A phase flying capacitor C a The positive pole of the A phase shares the bridge arm Q 1A The source of phase A is connected to the flying capacitor C a The negative pole of the bridge arm Q is shared with the A phase 4A The drain of the B phase is connected; the B phase flying capacitor C B The positive pole of the bridge arm Q is shared with the B phase 1B The source of the B phase is connected to the flying capacitor C b The negative pole of the bridge arm Q is shared with the B phase 4B The C phase flying capacitor C c The positive electrode of the bridge arm is shared with the C phase Q 1C The source of the C phase is connected to the flying capacitor C c The negative pole of the bridge arm is shared with the C phase Q 4C The drain is connected.

5. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that: The A phase power inductor L ra The first end of the A phase DC bridge arm Q 2AD , Q 3AD The midpoint of the B phase power inductor L rb The first end of the B phase DC bridge arm Q 2BD , Q 3BD The midpoint of the C phase power inductor L rc The first end of the C phase DC bridge arm Q 2CD , Q 3CD The midpoint of the A phase power inductor L ra The second end is separated from A by a DC capacitor C ra The first end of the B phase power inductor L rb The second end is separated from phase B by a DC capacitor C rb The first end of the C phase power inductor L rc The second end of C is separated from the capacitor C rc The first end is connected.

6. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that: The three-phase transformer includes an A-phase transformer, a B-phase transformer and a C-phase transformer; the A-phase DC isolation capacitor C ra The second end of the B-phase DC-isolating capacitor C is connected to the first end of the primary side of the A-phase transformer, and the second end of the primary side of the A-phase transformer is grounded; rb The second end of the C phase is connected to the first end of the primary side of the B phase transformer, and the second end of the primary side of the B phase transformer is grounded; the C phase DC isolation capacitor C rc The second end of is connected to the first end of the primary side of the C-phase transformer, and the second end of the primary side of the C-phase transformer is grounded.

7. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that: The secondary side A phase AC bridge arm Q s1 , Q s2 The midpoint is connected to the first end of the secondary side of the A-phase transformer; the secondary side B-phase AC bridge arm Q s3 , Q s4 The midpoint of is connected to the first end of the secondary side of the B phase transformer; the secondary side C phase AC bridge arm Q s5 , Q s6 The midpoint of is connected to the first end of the secondary side of the C phase transformer; the second end of the secondary side of the A phase transformer, the second end of the secondary side of the B phase transformer, the second end of the secondary side of the C phase transformer, the upper output capacitor C o1 The negative terminal of the output capacitor C o2 The positive electrode is connected; The secondary side A phase AC bridge arm Q s1 The drain of the secondary side B phase AC bridge arm Q s3 The drain of the secondary side C phase AC bridge arm Q s5 The drain and output capacitor C o1 The positive electrode of the secondary side A phase AC bridge arm Q s2 The source of the secondary side B phase AC bridge arm Q s4 The source of the secondary side C phase AC bridge arm Q s6 The source and the lower output capacitor C o2 The negative pole is connected.

8. A control method for a three-phase single-stage bidirectional AC / DC multilevel converter topology according to any one of claims 1 to 7, characterized in that: include: The voltage of the three-phase AC source is collected, and the abc coordinate system is converted into the αβ coordinate system by Clarke transformation to obtain a voltage reference angle; The current of the three-phase AC source is collected, and the abc coordinate system is converted into a dq coordinate system by Park transformation, and the current value in the dq coordinate system is obtained by combining the voltage reference angle; Based on the bus capacitor voltage, d-axis current component and q-axis current component, the A-phase AC bridge arm Q is determined. 2A , Q 3A , B-phase AC bridge arm Q 2B , Q 3B , C-phase AC bridge arm Q 2C , Q 3C , Phase A shares the bridge arm Q 1A , Q 4A , B phase shares the bridge arm Q 1B , Q 4B Shares bridge arm Q with phase C 1C , Q 4C The duty cycle is adjusted to realize the control of bus capacitor voltage and three-phase input current.

9. The control method of a three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 8, characterized in that: The flying capacitor C of phase A a , B phase flying capacitor C b , C phase flying capacitor C c The voltage of the A-phase DC bridge arm Q is collected to obtain 2AD , Q 3AD , B-phase DC bridge arm Q 2BD , Q 3BD and C-phase DC bridge arm Q 2CD , Q 3CD The duty cycle of the three-phase flying capacitor and the phase difference between the three-phase DC bridge arm and the three-phase common bridge arm are used to control the three-phase flying capacitor voltage.

10. The control method of a three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 8, characterized in that: The upper output capacitor C o1 and the lower output capacitor C o2 The voltage of the secondary side A phase AC bridge arm Q is collected to obtain s1 , Q s2 , secondary side B phase AC bridge arm Q s3 , Q s4 and the secondary side C phase AC bridge arm Q s5 , Q s6 The duty cycle and the phase difference between the secondary three-phase bridge arm and the three-phase common bridge arm are used to control the transmission power.

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