Three-phase single-stage bidirectional ac-dc multilevel converter topology and control method thereof

Abstract

The application 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 multi-level converter topology is half of the bus voltage, the voltage stress demand of the switch tube is reduced, the cost and the loss of the switch tube are reduced, all switch devices can realize zero voltage turn-on in a wide range, the efficiency of the converter is greatly improved, the number of switch tubes in the power path of the converter in a single mode is greatly reduced while realizing the multi-level structure, the complexity of the control method is effectively reduced, the loss source is reduced, and the potential for further reducing the loss is provided.

Description

TECHNICAL FIELD

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

[0002] In the construction of new power systems, distributed power sources dominated by renewable energy sources exhibit significant DC characteristics. Photovoltaic power generation units, battery energy storage systems, and other DC sources need to be connected to the AC power grid through an inverter. While rotating machines such as wind turbines and diesel generators directly produce AC power, their output frequency differs from that of the power grid, and they still need to be connected to the grid through AC-DC-AC two-stage power conversion. The existing AC power grid architecture generally has the problems of multiple power conversion stages, low system efficiency, and high investment in power electronic equipment when connecting to such distributed power sources. In particular, in the multi-energy collaborative operation scenario, the energy loss caused by multiple AC / DC and DC / AC conversions can reach more than 35% of the total system loss.

[0003] To address the above technical bottlenecks, the AC-DC hybrid microgrid architecture has unique advantages. This architecture can reduce the AC / DC and DC / AC conversion stages through the coordinated operation of the AC bus and the DC bus. Theoretical calculations show that the overall system efficiency can be improved by 8-12 percentage points. The key to achieving efficient energy interaction between the AC and DC subnets is to develop a three-phase AC / DC bidirectional conversion device with high reliability and modular expansion capability. Existing research focuses on three core directions: soft switching technology application, high-frequency magnetic coupling isolation scheme, and single-stage power topology construction. The use of resonant soft switching technology can reduce switching losses by 40%-60%. The use of planar transformers and other high-frequency isolation devices can increase the power density to 3-5 times that of traditional power frequency transformers. The single-stage topology structure can significantly reduce the size and cost of the device by reducing the intermediate energy storage stage. The current technical difficulty lies in how to achieve zero-voltage switching characteristics, smooth switching of bidirectional power flow, and fast dynamic response capability in a high-frequency operating condition, which puts higher requirements on the optimization design of magnetic components and multi-modal control strategies. SUMMARY

[0004] The present application aims to provide a three-phase single-stage bidirectional AC-DC multi-level converter topology and a control method thereof, which can solve the problems of long power path, high loss, and high voltage stress of switching tubes in existing three-phase single-stage bidirectional AC-DC converters, reduce the voltage stress, cost, and loss of switching tubes, reduce the number of switching tubes in the power path under a single mode, and have low loss.

[0005] In order to achieve the above object, the first aspect of the present application provides a three-phase single-stage bidirectional AC-DC multi-level 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;

[0006] The three-phase AC source is connected with 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 and connected with the three-phase common bridge arm; the three-phase common bridge arm is connected with the bus capacitor; the three-phase DC bridge arm is connected with the three-phase transformer through the three-phase power inductor and the three-phase DC blocking capacitor; the three-phase transformer is connected with the secondary three-phase bridge arm; and the secondary three-phase bridge arm is connected with the output capacitor.

[0007] According to the three-phase single-stage bidirectional AC-DC multi-level converter topology provided by the present application, the three-phase AC bridge arm comprises A-phase AC bridge arms Q 2A , Q 3A , B-phase AC bridge arms Q 2B , Q 3B and C-phase AC bridge arms Q 2C , Q 3C ; the three-phase DC bridge arm comprises A-phase DC bridge arms Q 2AD , Q 3AD , B-phase DC bridge arms Q 2BD , Q 3BD and C-phase DC bridge arms Q 2CD , Q 3CD ; the three-phase common bridge arm comprises A-phase common bridge arms Q 1A , Q 4A , B-phase common bridge arms Q 1B , Q 4B and C-phase common bridge arms Q 1C , Q 4C ; the three-phase flying capacitor comprises A-phase flying capacitors C a , B-phase flying capacitors C b and C-phase flying capacitors C c ; the bus capacitor comprises upper bus capacitors C bus1 and lower bus capacitors C bus2 ; the three-phase power inductor comprises A-phase power inductors L ra , B-phase power inductors L rb and C-phase power inductors L rc ; the three-phase DC blocking capacitor comprises A-phase DC blocking capacitors C ra , B-phase DC blocking capacitors C rb and C-phase DC blocking capacitors C rc ; and the secondary three-phase bridge arm comprises secondary A-phase AC bridge arms Q s1 , Q s2 , secondary B-phase AC bridge arms Q s3 , Qs4 and the secondary side C phase AC bridge arm Q s5 , Q s6 ; the output capacitor includes an upper output capacitor C o1 and a lower output capacitor C o2 .

[0008] According to the application, a three-phase single-stage bidirectional AC-DC multi-level converter topology is provided, wherein the A phase, the B phase and the C phase of a three-phase AC source are respectively connected to the midpoints of the three-phase AC bridge arms Q a , L b , L c through AC inductors L 2A , Q 3A , Q 2B , Q 3B , Q 2C , Q 3C .

[0009] The drain electrode of Q 2A in the A phase AC bridge arm is connected to the source electrode of Q 1A in the A phase common bridge arm, and the source electrode of Q 3A in the A phase AC bridge arm is connected to the drain electrode of Q 4A in the A phase common bridge arm; the drain electrode of Q 2B in the B phase AC bridge arm is connected to the source electrode of Q 1B in the B phase common bridge arm, and the source electrode of Q 3B in the B phase AC bridge arm is connected to the drain electrode of Q 4B in the B phase common bridge arm; the drain electrode of Q 2C in the C phase AC bridge arm is connected to the source electrode of Q 1C in the C phase common bridge arm, and the source electrode of Q 3C in the C phase AC bridge arm is connected to the drain electrode of Q 4C in the C phase common bridge arm.

[0010] The drain electrode of Q 2AD in the A phase DC bridge arm is connected to the source electrode of Q 1A in the A phase common bridge arm, and the source electrode of Q 3AD in the A phase AC bridge arm is connected to the drain electrode of Q 4A in the A phase common bridge arm; the drain electrode of Q 2BD in the B phase DC bridge arm is connected to the source electrode of Q 1B in the B phase common bridge arm, and the source electrode of Q 3BD in the B phase AC bridge arm is connected to the drain electrode of Q 4B in the B phase common bridge arm; the drain electrode of Q 2CD in the C phase DC bridge arm is connected to the source electrode of Q 1C in the C phase common bridge arm, and the source electrode of Q 3CD in the C phase AC bridge arm is connected to the drain electrode of Q 4Cthe drain of Q

[0011] Q in the A-phase common bridge arm 1A the drain of Q 1B the drain of Q 1C the drain of Q in the A-phase common bridge arm is connected with the positive pole of the upper bus capacitor C bus1 the source of Q in the A-phase common bridge arm, the source of Q 4A the source of Q in the B-phase common bridge arm, the source of Q 4B the source of Q in the C-phase common bridge arm is connected with the negative pole of the lower bus capacitor C 4C the source of Q in the A-phase common bridge arm, the source of Q bus2 the source of Q in the B-phase common bridge arm, the source of Q a the source of Q in the C-phase common bridge arm is connected with the negative pole of the lower bus capacitor C 1A

[0012] According to the three-phase single-stage bidirectional AC-DC multi-level converter topology provided by the application, the positive pole of the A-phase flying capacitor C a is connected with the source of Q 4A in the A-phase common bridge arm, the negative pole of the A-phase flying capacitor C B is connected with the drain of Q 1B in the A-phase common bridge arm, the positive pole of the B-phase flying capacitor C b is connected with the source of Q 4B in the B-phase common bridge arm, the negative pole of the B-phase flying capacitor C c is connected with the drain of Q 1C in the B-phase common bridge arm, the positive pole of the C-phase flying capacitor C c is connected with the source of Q 4C in the C-phase common bridge arm.

[0013] According to the three-phase single-stage bidirectional AC-DC multi-level converter topology provided by the application, the first end of the A-phase power inductor L ra is connected with the midpoint of Q 2AD , Q 3AD in the A-phase DC bridge arm; the first end of the B-phase power inductor L rb is connected with the midpoint of Q 2BD , Q 3BD in the B-phase DC bridge arm; the first end of the C-phase power inductor L rc is connected with the midpoint of Q 2CD , Q 3CD in the C-phase DC bridge arm; the second end of the A-phase power inductor L ra is connected with the first end of the A-phase isolated capacitor C ra ; the second end of the B-phase power inductor L rb is connected with the first end of the B-phase isolated capacitor C rb ; the second end of the C-phase power inductor L rc is connected with the first end of the C-phase isolated capacitor C​rc The first end is connected.

[0014] According to the present invention, a three-phase single-stage bidirectional AC / DC multilevel converter topology is provided, wherein the three-phase transformer includes an A-phase transformer, a B-phase transformer, and a C-phase transformer; the A-phase DC blocking capacitor C... ra The second terminal is connected to the first terminal of the primary winding of phase A transformer, and the second terminal of the primary winding of phase A transformer is grounded; phase B DC blocking capacitor C rb The second terminal is connected to the first terminal of the primary side of the B-phase transformer, and the second terminal of the primary side of the B-phase transformer is grounded; the C-phase DC blocking capacitor C rc The second end 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.

[0015] According to the present invention, a three-phase single-stage bidirectional AC / DC multilevel converter topology is provided, wherein the secondary 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 terminal of the secondary side of the C-phase transformer; the second terminal of the secondary side of the A-phase transformer, the second terminal of the secondary side of the B-phase transformer, the second terminal of the secondary side of the C-phase transformer, and the upper output capacitor C o1 The negative terminal and the lower output capacitor C o2 The positive electrode is connected;

[0016] In the secondary side A phase AC bridge arm Q s1 Q in the drain and secondary side B-phase AC bridge arm s3 Q in the drain and secondary side C-phase AC bridge arm s5 The drain and the upper output capacitor C o1 The positive terminal is connected; Q is in the secondary side A phase AC bridge arm. s2 Q in the source and secondary side B phase AC bridge arm s4 Q in the source and secondary side C-phase AC bridge arm s6 The source and the lower output capacitor C o2 The negative terminal is connected.

[0017] In a second aspect, the present invention provides a control method for a three-phase single-stage bidirectional AC / DC multilevel converter topology, comprising:

[0018] The voltage of the three-phase AC source is acquired, and the abc coordinate system is transformed into the αβ coordinate system through Clark transformation to obtain the voltage reference angle;

[0019] The current of the three-phase alternating current source is collected, and the abc coordinate system is converted into the dq coordinate system through the Park transformation, and the current value in the dq coordinate system is obtained in combination with the voltage reference angle;

[0020] Based on the bus capacitance voltage, the d-axis current component and the q-axis current component, the duty cycles of the A-phase AC bridge arm Q 2A , Q 3A , the B-phase AC bridge arm Q 2B , Q 3B , the C-phase AC bridge arm Q 2C , Q 3C , the A-phase common bridge arm Q 1A , Q 4A , the B-phase common bridge arm Q 1B , Q 4B and the C-phase common bridge arm Q 1C , Q 4C are determined, so that the bus capacitance voltage and the three-phase input current are controlled.

[0021] According to the control method of the three-phase single-stage bidirectional AC-DC multi-level converter topology provided by the application, the voltages of the A-phase flying capacitor C a , the B-phase flying capacitor C b and the C-phase flying capacitor C c are collected, the duty cycles of the A-phase DC bridge arm Q 2AD , Q 3AD , the B-phase DC bridge arm Q 2BD , Q 3BD and the C-phase DC bridge arm Q 2CD , Q 3CD and the phase difference between the three-phase DC bridge arm and the three-phase common bridge arm are obtained, so that the three-phase flying capacitor voltage is controlled.

[0022] According to the control method of the three-phase single-stage bidirectional AC-DC multi-level converter topology provided by the application, the voltages of the upper output capacitor C o1 and the lower output capacitor C o2 are collected, the duty cycles of the secondary-side A-phase AC bridge arm Q s1 , Q s2 , the secondary-side B-phase AC bridge arm Q s3 , Q s4 and the secondary-side C-phase AC bridge arm Q s5 , Q s6 and the phase difference between the secondary-side three-phase bridge arm and the three-phase common bridge arm are obtained, so that the transmission power is controlled.

[0023] Compared with the prior art, the three-phase single-stage bidirectional AC-DC multi-level converter topology and the control method thereof provided by the application have at least the following technical effects:

[0024] 1. All the voltage stresses of the primary side switch tubes are half of the bus voltage, which reduces the voltage stress requirement of the switch tube, reduces the cost and loss of the switch tube.

[0025] 2. All the switching devices can realize zero voltage turn-on in a wide range, which greatly improves the efficiency of the converter.

[0026] 3. While realizing the multi-level structure, the number of switch tubes 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 loss source, and provides the potential for further reducing the loss. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] In the drawings:

[0029] Figure 1 It is a circuit structure diagram of the three-phase single-stage bidirectional AC-DC multi-level converter topology of the present application.

[0030] Figure 2 It is a main working waveform diagram of the three-phase single-stage bidirectional AC-DC multi-level converter topology of the present application.

[0031] Figures 3 to 10 It is an equivalent circuit diagram of each working sub-mode of the three-phase single-stage bidirectional AC-DC multi-level converter topology of the present application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application more clear, the technical scheme in the present application will be described clearly and completely in combination with the drawings in the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0033] The following will describe some embodiments of the present application in combination with the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Please refer to Figure 1The embodiment of the present application provides a three-phase single-stage bidirectional AC-DC multi-level converter topology, which comprises 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.

[0035] The three-phase AC source is connected with 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 and connected with the three-phase common bridge arm; the three-phase common bridge arm is connected with the bus capacitor; the three-phase DC bridge arm is connected with the three-phase transformer through the three-phase power inductor and the three-phase DC blocking capacitor; the three-phase transformer is connected with the secondary three-phase bridge arm; and the secondary three-phase bridge arm is connected with the output capacitor.

[0036] Specifically, the three-phase AC bridge arm comprises an A-phase AC bridge arm Q 2A , Q 3A , a B-phase AC bridge arm Q 2B , Q 3B and a C-phase AC bridge arm Q 2C , Q 3C ; the three-phase DC bridge arm comprises an A-phase DC bridge arm Q 2AD , Q 3AD , a B-phase DC bridge arm Q 2BD , Q 3BD and a C-phase DC bridge arm Q 2CD , Q 3CD ; the three-phase common bridge arm comprises an A-phase common bridge arm Q 1A , Q 4A , a B-phase common bridge arm Q 1B , Q 4B and a C-phase common bridge arm Q 1C , Q 4C ; the three-phase flying capacitor comprises an A-phase flying capacitor C a , a B-phase flying capacitor C b and a C-phase flying capacitor C c ; the bus capacitor comprises an upper bus capacitor C bus1 and a lower bus capacitor C bus2 ; the three-phase power inductor comprises an A-phase power inductor L ra , a B-phase power inductor L rb and a C-phase power inductor L rc ; the three-phase DC blocking capacitor comprises an A-phase DC blocking capacitor C ra , a B-phase DC blocking capacitor C rb and a C-phase DC blocking capacitor C rc ; and the secondary three-phase bridge arm comprises a secondary A-phase AC bridge arm Q s1 , Q s2 , a secondary B-phase AC bridge arm Q s3 , Q s4 and a secondary C-phase AC bridge arm Qs5 , Q s6 ; output capacitor, comprising upper output capacitor C o1 and lower output capacitor C o2 .

[0037] Wherein, A phase, B phase, C phase of three-phase AC source are connected through AC inductance L a , L b , L c and three-phase AC bridge arm Q 2A , Q 3A , Q 2B , Q 3B , Q 2C , Q 3C midpoint.

[0038] Drain of Q 2A in A phase AC bridge arm is connected with source of Q 1A in A phase common bridge arm, source of Q 3A in A phase AC bridge arm is connected with drain of Q 4A in A phase common bridge arm; drain of Q 2B in B phase AC bridge arm is connected with source of Q 1B in B phase common bridge arm, source of Q 3B in B phase AC bridge arm is connected with drain of Q 4B in B phase common bridge arm; drain of Q 2C in C phase AC bridge arm is connected with source of Q 1C in C phase common bridge arm, source of Q 3C in C phase AC bridge arm is connected with drain of Q 4C in C phase common bridge arm;

[0039] Drain of Q 2AD in A phase DC bridge arm is connected with source of Q 1A in A phase common bridge arm, source of Q 3AD in A phase AC bridge arm is connected with drain of Q 4A in A phase common bridge arm; drain of Q 2BD in B phase DC bridge arm is connected with source of Q 1B in B phase common bridge arm, source of Q 3BD in B phase AC bridge arm is connected with drain of Q 4B in B phase common bridge arm; drain of Q 2CD in C phase DC bridge arm is connected with source of Q 1C in C phase common bridge arm, source of Q 3CD in C phase AC bridge arm is connected with drain of Q 4C in C phase common bridge arm;

[0040] Q1A The drain and B phase share the bridge arm in Q 1B The drain and C phase share the bridge arm in Q 1C The drain and the upper bus capacitor C bus1 The positive terminals are connected; phase A shares the Q terminal in the bridge arm. 4A The source and B phase share the bridge arm Q 4B The source and C phase share the bridge arm in Q 4C The source and lower bus capacitance C bus2 The negative terminal is connected.

[0041] A-phase flying capacitor C a The positive electrode shares a bridge arm with phase A in phase Q. 1A The source phase is connected, and the flying capacitor C of phase A is connected. a The negative electrode shares a bridge arm with phase A in phase Q. 4A The drain of phase B is connected; the flying capacitor C of phase B is connected. B The positive electrode and phase B share the same bridge arm in Q. 1B The source phase is connected, and the flying capacitor C of phase B is connected. b The negative electrode shares a bridge arm with phase B, in which Q... 4B The drain phase is connected; the C-phase flying capacitor C c The positive electrode and the C phase share the bridge arm in Q. 1C The source phase is connected, and the C-phase flying capacitor C c The negative electrode shares a bridge arm with the C phase in the Q phase. 4C The drains are connected.

[0042] Phase A power inductor L ra The first end is connected to the A-phase DC bridge arm Q 2AD Q 3AD The midpoints of phases B and B are connected; the power inductor L is connected. rb The first end is connected to the B-phase DC bridge arm Q. 2BD Q 3BD The midpoints of the phases are connected; the C-phase power inductor L rc The first end is connected to the C-phase DC bridge arm Q 2CD Q 3CD The midpoints of phases are connected; the power inductor L of phase A is connected. ra The second terminal is separated from A by a direct capacitor C. ra The first phase is connected; the B-phase power inductor L rb The second terminal is separated from B by a direct capacitor C. rb The first terminal is connected; C-phase power inductor L rc The second terminal is separated from C by a direct capacitor C. rc The first end is connected.

[0043] The three-phase transformer includes phase A, phase B, and phase C; phase A has a DC blocking capacitor C. raThe second terminal is connected to the first terminal of the primary winding of phase A transformer, and the second terminal of the primary winding of phase A transformer is grounded; phase B DC blocking capacitor C rb The second terminal is connected to the first terminal of the primary side of the B-phase transformer, and the second terminal of the primary side of the B-phase transformer is grounded; the C-phase DC blocking capacitor C rc The second end 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.

[0044] Secondary 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 terminal of the secondary side of the C-phase transformer; the second terminal of the secondary side of the A-phase transformer, the second terminal of the secondary side of the B-phase transformer, the second terminal of the secondary side of the C-phase transformer, and the upper output capacitor C o1 The negative terminal and the lower output capacitor C o2 The positive electrode is connected;

[0045] In the secondary side A phase AC bridge arm Q s1 Q in the drain and secondary side B-phase AC bridge arm s3 Q in the drain and secondary side C-phase AC bridge arm s5 The drain and the upper output capacitor C o1 The positive terminal is connected; Q is in the secondary side A phase AC bridge arm. s2 Q in the source and secondary side B phase AC bridge arm s4 Q in the source and secondary side C-phase AC bridge arm s6 The source and the lower output capacitor C o2 The negative terminal is connected.

[0046] Another embodiment of the present invention provides a control method for the three-phase single-stage bidirectional AC / DC multilevel converter topology of the foregoing embodiments, comprising:

[0047] The voltage of the three-phase AC source is acquired, and the abc coordinate system is transformed into the αβ coordinate system through Clark transformation to obtain the voltage reference angle;

[0048] 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.

[0049] Based on the bus 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 Q3B , C-phase AC bridge arm Q 2C , Q 3C , A-phase common bridge arm Q 1A , Q 4A , B-phase common bridge arm Q 1B , Q 4B and C-phase common bridge arm Q 1C , Q 4C duty cycles, to achieve control of bus capacitor voltage and three-phase input current.

[0050] Specifically, the voltages of A-phase flying capacitor C a , B-phase flying capacitor C b , and C-phase flying capacitor C c are collected to obtain the duty cycles of 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 and the phase difference between three-phase DC bridge arms and three-phase common bridge arms, to achieve control of three-phase flying capacitor voltage.

[0051] The voltages of upper output capacitor C o1 and lower output capacitor C o2 are collected to obtain the duty cycles of secondary-side A-phase AC bridge arm Q s1 , Q s2 , secondary-side B-phase AC bridge arm Q s3 , Q s4 and secondary-side C-phase AC bridge arm Q s5 , Q s6 and the phase difference between secondary-side three-phase bridge arms and three-phase common bridge arms, to achieve control of transmission power.

[0052] Figure 2 is a main working waveform diagram of the three-phase single-stage bidirectional AC-DC multi-level converter topology, Figure 2 only shows the case of A-phase, wherein G represents the driving signal of the corresponding switch tube, for example, G 1A represents the driving signal of switch tube Q 1A , V La is the AC inductor voltage, I La is the AC inductor current, V Lra is the A-phase power inductor voltage, and I Lra is the A-phase power inductor current. Taking the A-phase as an example, according to Figure 2 the three-phase single-stage bidirectional AC-DC multi-level converter can be divided into a plurality of sub-modes in a single switching period (mainly according to the change of A-phase power inductor voltage V Lra , voltage V Lra(Different) are divided into eight working sub-modes. Figures 3 to 10 In the diagram, black lines indicate that the circuit is in a conducting state, while red lines indicate that the circuit is in a turning-off state.

[0053] Working sub-mode 1 [ t 0, t 1]: Q in the shared bridge arm of phase A 4A exist t When the circuit is turned off at time 0, the AC inductor current I during the dead time is... La Q in the shared bridge arm of phase A 1A The drain-source capacitor discharges to 0V, and after the dead time ends, Q in the shared bridge arm of phase A... 1A Zero voltage switching on, at which time the AC inductor L a upper bus capacitor C bus1 Charging, for phase A flying capacitor C a Discharge, upper bus capacitor C bus1 and the lower output capacitor C o2 For phase A power inductor L ra Charging, equivalent circuit diagram as follows Figure 3 As shown.

[0054] Working sub-mode 2 [ t 1, t 2]: Q in the secondary side A phase AC bridge arm s2 exist t At time 1, the secondary current is turned off, and during the dead time, the secondary current affects the Q in the secondary A-phase AC bridge arm. s1 The drain-source capacitor discharges to 0V, and the dead time ends in the Q phase of the secondary A-phase AC bridge arm. s1 Zero voltage switching on, at which time the AC inductor L a upper bus capacitor C bus1 Charging, for phase A flying capacitor C a Charging, upper bus capacitor C bus1 For phase A power inductor L ra and the output capacitor C o1 Charging, equivalent circuit diagram as follows Figure 4 As shown.

[0055] Working sub-mode three [ t 2, t 3]: Q in phase A DC bridge arm 2AD exist t At time 2, the power inductor current I during the dead time is turned off. Lra Q in phase A DC bridge arm 3AD When the drain-source capacitor discharges to 0V, the dead time ends and Q in the A-phase DC bridge arm... 3AD Zero voltage switching on, at which time the AC inductor L a upper bus capacitor C bus1 Charging, for phase A flying capacitor Ca Discharge, upper bus capacitor C bus1 and A-phase power inductor L ra For phase A flying capacitor C a and the output capacitor C o1 Charging, equivalent circuit diagram as follows Figure 5 As shown.

[0056] Working submodal four [ t 3, t 4]: Q in the shared bridge arm of phase A 1A exist t 3. Turn-off time, dead time power inductor current I Lra Q in the shared bridge arm of phase A 4A The drain-source capacitor discharges to 0V, and after the dead time ends, Q in the shared bridge arm of phase A... 1A Zero-voltage start-up, at this time the lower bus capacitor C bus2 For AC inductor L a Charging, A-phase power inductor L ra For the lower bus capacitor C bus2 and the lower output capacitor C o2 Charging, equivalent circuit diagram as follows Figure 6 As shown.

[0057] Working sub-mode five [ t 4, t 5]: Q in the secondary side A phase AC bridge arm s1 exist t At time 4, the secondary current is turned off, and during the dead time, the secondary current affects the Q in the secondary A-phase AC bridge arm. s2 The drain-source capacitor discharges to 0V, and the dead time ends in the Q phase of the secondary A-phase AC bridge arm. s1 Zero-voltage start-up, at this time the lower bus capacitor C bus2 For AC inductor L a Charging, A-phase power inductor L ra and the lower output capacitor C o2 For the lower bus capacitor C bus2 Charging, equivalent circuit diagram as follows Figure 7 As shown.

[0058] Working submodal six [ t 5, t 6]: Q in phase A AC bridge arm 3A exist t At time 5, the AC inductor current I during the dead time is turned off. La Q in phase A AC bridge arm 2A The drain-source capacitor discharges to 0V, the dead time ends, and Q in phase A AC bridge arm... 2A Zero voltage switching on, at which time the AC inductor L a and lower bus capacitor C bus2For phase A flying capacitor C a Charging, A-phase power inductor L ra and the lower output capacitor C o2 For the lower bus capacitor C bus2 Charging, equivalent circuit diagram as follows Figure 8 As shown.

[0059] Working sub-mode seven [ t 6, t 7]: Q in phase A DC bridge arm 3AD exist t The power inductor current I during the dead time is turned off at time 6. Lra Q in phase A DC bridge arm 2AD When the drain-source capacitor discharges to 0V, the dead time ends and Q in the A-phase DC bridge arm... 2AD Zero voltage switching on, at which time the AC inductor L a and lower bus capacitor C bus2 For phase A flying capacitor C a Charging, lower bus capacitor C bus1 For phase A power inductor L ra Phase A flying capacitor C a and the lower output capacitor C o2 Charging, equivalent circuit diagram as follows Figure 9 As shown.

[0060] Working submodal eight [ t 7, t 8]: Q in phase A AC bridge arm 2A exist t Turn-off at time 8, AC inductor current I during dead time La Q in phase A AC bridge arm 3A The drain-source capacitor discharges to 0V, the dead time ends, and Q in phase A AC bridge arm... 3A Zero-voltage start-up, at this time the lower bus capacitor C bus2 For AC inductor L a Charging, lower bus capacitor C bus1 For phase A power inductor L ra Phase A flying capacitor C a and the lower output capacitor C o2 Charging, equivalent circuit diagram as follows Figure 10 As shown.

[0061] From the above analysis, it can be seen that the three-phase single-stage bidirectional AC-DC multi-level converter topology proposed by the application can realize zero-voltage turn-on operation of all switch tubes, greatly reduces the switching loss, so that the converter can adapt to high-frequency operation, thereby reducing the volume and improving the power density, the power transmission between each port is single-stage power transmission, and the application has the characteristics of high efficiency. The three-phase single-stage bidirectional AC-DC multi-level converter topology proposed by the application can realize flexible control of the power flow of each port under the control method proposed.

[0062] In summary, the application provides a three-phase single-stage bidirectional AC-DC multi-level converter topology and a control method thereof, the voltage stress borne by all primary side switch tubes of the three-phase single-stage bidirectional AC-DC multi-level converter topology is half of the bus voltage, the voltage stress requirement of the switch tube is reduced, the cost and loss of the switch tube are reduced, all switch devices can realize zero-voltage turn-on in a wide range, the efficiency of the converter is greatly improved, the number of switch tubes in the power path of the converter in a single mode is greatly reduced while realizing the multi-level structure, the complexity of the control method is effectively reduced, the loss source is reduced, and the potential for further reducing the loss is provided.

[0063] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. The specification and examples given herein are intended as illustrative only and not intended to limit the scope of the present application. It is therefore intended that the application be limited only by the scope of the appended claims, including the full range of equivalents to which such claims are entitled.

Claims

1. A three-phase single-stage bidirectional AC / DC multilevel converter topology, characterized in that, It includes a three-phase AC power 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 power 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 and then connected 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 a three-phase power inductor and a three-phase DC blocking capacitor; the three-phase transformer is connected to the secondary three-phase bridge arm; 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 phase A 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 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 The three-phase shared bridge arm includes the A-phase shared bridge arm Q. 1A Q 4A Phase B shares bridge arm Q 1B Q 4B Shared bridge arm Q with phase C 1C Q 4C The three-phase flying capacitor includes the A-phase flying capacitor C. a Phase B flying capacitor C b and C phase flying capacitor C c Bus capacitors include the upper bus capacitor C. bus1 and lower bus capacitor C bus2 Three-phase power inductors include phase A power inductor L. ra B-phase power inductor L rb and C-phase power inductor L rc The three-phase DC blocking capacitor includes phase A DC blocking capacitor C. ra Phase B is separated by a DC capacitor C. rb The capacitor C is separated from C by a DC capacitor. 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 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, Phases A, B, and C of the three-phase AC source are respectively connected to 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 Connect the midpoints; In phase A AC bridge arm, Q 2A The drain of phase A shares a bridge arm with phase Q. 1A The source phase is connected, and the Q phase in the A phase AC bridge arm is connected. 3A The source electrode of phase A shares a bridge arm with Q. 4A The drain phase is connected; Q in the B-phase AC bridge arm 2B The drain of phase B shares a bridge arm with phase Q. 1B The source phase is connected, and the Q phase in the B phase AC bridge arm is connected. 3B The source electrode of the B phase shares a bridge arm with Q. 4B The drain phase is connected; Q in the C-phase AC bridge arm 2C The drain and C phase share the bridge arm in Q. 1C The source phase is connected, and the Q phase in the C phase AC bridge arm is connected. 3C The source electrode and the C phase share the bridge arm in Q 4C The drains are connected; Q in phase A DC bridge arm 2AD The drain of phase A shares a bridge arm with phase Q. 1A The source phase is connected, and the Q phase in the A phase AC bridge arm is connected. 3AD The source electrode of phase A shares a bridge arm with Q. 4A The drain terminals are connected; Q in the B-phase DC bridge arm 2BD The drain of phase B shares a bridge arm with phase Q. 1B The source phase is connected, and the Q phase in the B phase AC bridge arm is connected. 3BD The source electrode of the B phase shares a bridge arm with Q. 4B The drain terminals are connected; Q in the C-phase DC bridge arm 2CD The drain and C phase share the bridge arm in Q. 1C The source phase is connected, and the Q phase in the C phase AC bridge arm is connected. 3CD The source electrode and the C phase share the bridge arm in Q 4C The drains are connected; Q in the shared bridge arm of phase A 1A The drain and B phase share the bridge arm in Q 1B The drain and C phase share the bridge arm in Q 1C The drain and the upper bus capacitor C bus1 The positive electrode of phase A is connected; the Q in the common bridge arm of phase A is connected. 4A The source and B phase share the bridge arm Q 4B The source and C phase share the bridge arm in Q 4C The source and lower bus capacitance C bus2 The negative terminal is connected.

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

5. The three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 2, characterized in that, The power inductor L of phase A ra The first end is connected to the A-phase DC bridge arm Q 2AD Q 3AD The midpoints of the phases are connected; the B-phase power inductor L rb The first end is connected to the B-phase DC bridge arm Q. 2BD Q 3BD The midpoints of the C-phase power inductors are connected; rc The first end is connected to the C-phase DC bridge arm Q 2CD Q 3CD The midpoints of the phases are connected; the power inductor L of phase A is connected. ra The second terminal is separated from A by a direct capacitor C. ra The first terminal is connected; the B-phase power inductor L rb The second terminal is separated from B by a direct capacitor C. rb The first terminal is connected; the C-phase power inductor L rc The second terminal is separated from C by a direct 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 blocking capacitor C... ra The second terminal is connected to the first terminal of the primary side of phase A transformer, and the second terminal of the primary side of phase A transformer is grounded; the phase B DC blocking capacitor C rb The second terminal is connected to the first terminal of the primary side of the B-phase transformer, and the second terminal of the primary side of the B-phase transformer is grounded; the C-phase DC isolation capacitor C rc The second end 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 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 and the lower output capacitor C o2 The positive electrode is connected; Q in the secondary A phase AC bridge arm s1 Q in the drain and secondary side B-phase AC bridge arm s3 Q in the drain and secondary side C-phase AC bridge arm s5 The drain and the upper output capacitor C o1 The positive terminal is connected; Q in the secondary side A phase AC bridge arm s2 Q in the source and secondary side B phase AC bridge arm s4 Q in the source and secondary side C-phase AC bridge arm s6 The source and the lower output capacitor C o2 The negative terminal is connected.

8. A control method for a three-phase single-stage bidirectional AC / DC multilevel converter topology as described in any one of claims 2 to 7, characterized in that, include: The voltage of the three-phase AC source is acquired, 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 into 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 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 bridge arm Q 1A Q 4A Phase B shares bridge arm Q 1B Q 4B Shared bridge arm Q with phase C 1C Q 4C The duty cycle is adjusted to control the bus capacitor voltage and three-phase input current.

9. The control method for the three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 8, characterized in that, For the flying capacitor C of phase A a Phase B flying capacitor C b C-phase flying capacitor C c The voltage is collected to obtain the voltage of the DC bridge arm Q of phase A. 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 voltage of the three-phase flying capacitor.

10. The control method for the three-phase single-stage bidirectional AC / DC multilevel converter topology according to claim 8, characterized in that, For the upper output capacitor C o1 and the lower output capacitor C o2 The voltage is collected to obtain the Q of the secondary side A-phase AC bridge arm. s1 Q s2 Secondary side B phase AC bridge arm Q s3 Q s4 and 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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