Power conversion module, control method and power conversion system

Abstract

The invention relates to a power conversion module, a control method and a power conversion system, a bridging branch is arranged between a first power unit and a second power unit, the bridging branch comprises a resonant capacitor and a switch unit which are electrically connected, the resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or is connected in series with the resonant capacitor. By controlling the on-off of the bridging branch, the current opposite to the power grid is generated on the branch connecting the first bridge arm and the second bridge arm, so that the soft switching of the switching tube of the power conversion module is realized with a small number of auxiliary circuits, and the working efficiency of the system is favorably improved.

Description

Technical Field

[0001] The present application relates to the technical field of electronic circuits, and in particular to a power conversion module, a control method and a power conversion system. Background Art

[0002] SST (Solid-state-transformer), also known as power electronic transformer, generally refers to a device that directly converts medium-voltage or high-voltage grid voltage into low-voltage output through power electronic circuits and high-frequency isolation transformers. It has the significant advantages of small size and light weight, and has broad application prospects in energy storage, electric vehicles, data centers and other electricity-consuming fields.

[0003] Using SST power supply can improve system efficiency and power density. In traditional technology, the SST structure is usually composed of AC-DC stage and DC-DC stage, in which the front stage has power factor adjustment function and adopts continuous current control mode. In this working mode, the switching device is hard switching, resulting in large switching loss and low system operating frequency.

[0004] How to reduce switching losses and increase system operating frequency has become an urgent problem to be solved. Summary of the invention

[0005] Based on this, it is necessary to provide a power conversion module, a control method, and a power conversion system to address the problems in the above-mentioned background technology, so as to solve the problem that the switching device of SST in the prior art works in a hard switching state, resulting in large switching losses and low system operating frequency.

[0006] In a first aspect, the present application provides a power conversion module, comprising:

[0007] A first power unit, comprising a first bridge arm, a first capacitor unit, a first side and a second side, wherein the second side of the first power unit is connected to two ends of the first bridge arm, the first capacitor unit and the first bridge arm are connected in parallel, and the first capacitor unit has a positive end and a negative end;

[0008] A second power unit comprises a second bridge arm, a second capacitor unit, a first side and a second side, wherein the second side of the second power unit is connected to two ends of the second bridge arm, the second capacitor unit and the second bridge arm are connected in parallel, the second capacitor unit has a positive end and a negative end, and the midpoints of the second bridge arm and the first bridge arm are interconnected to realize the second power unit and the first side of the first power unit being connected in series;

[0009] a jumper branch connected between the second side of the first power unit and the second side of the second power unit, the jumper branch comprising a resonant capacitor and a switch unit electrically connected to each other, and

[0010] The resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or is connected in series with the resonant capacitor.

[0011] In one embodiment, the switch unit includes a first switch, the first switch and the resonant capacitor are connected in series, and the jumper branch is connected between the positive end of the first capacitor unit and the negative end of the second capacitor unit.

[0012] In one embodiment, the switch unit comprises:

[0013] A third bridge arm is connected in parallel with the first capacitor unit; and

[0014] The fourth bridge arm is connected in parallel with the second capacitor unit, and the resonant capacitor is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm.

[0015] In one embodiment, the first capacitor unit includes a first capacitor and a second capacitor connected in series;

[0016] The second capacitor unit comprises a third capacitor and a fourth capacitor connected in series;

[0017] The switch unit comprises:

[0018] A third bridge arm is connected in parallel with the first capacitor;

[0019] a fifth bridge arm connected in parallel with the second capacitor;

[0020] a fourth bridge arm connected in parallel with the third capacitor, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm; and

[0021] The sixth bridge arm is connected in parallel with the fourth capacitor.

[0022] In one embodiment, the first bridge arm comprises a second switch, a third switch, a fourth switch and a fifth switch connected in sequence, and the second bridge arm comprises a sixth switch, a seventh switch, an eighth switch and a ninth switch connected in sequence,

[0023] The power conversion module further includes a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a first main power capacitor, a second main power capacitor, a first transformer, a second transformer, a first rectifier circuit, and a second rectifier circuit.

[0024] wherein the first diode and the second diode are connected in series and connected in parallel to the first bridge arm; the common connection point of the first diode and the second diode and the midpoint of the first bridge arm are respectively connected to the first side of the first power unit; the cathode of the fifth diode is connected to the common connection point of the second switch and the third switch; the anode of the fifth diode is connected to the common connection point of the first capacitor and the second capacitor; the anode of the sixth diode is connected to the common connection point of the fourth switch and the fifth switch; the cathode of the sixth diode is connected to the common connection point of the first capacitor and the second capacitor; the first main power capacitor and the primary winding of the first transformer are connected in series and connected between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm; the first rectifier circuit is connected to the secondary winding of the first transformer;

[0025] The third diode and the fourth diode are connected in series and connected in parallel to the second bridge arm, the common connection point of the third diode and the fourth diode and the midpoint of the second bridge arm are respectively connected to the first side of the second power unit, the cathode of the seventh diode is connected to the common connection point of the sixth switch and the seventh switch, the anode of the seventh diode is connected to the common connection point of the third capacitor and the fourth capacitor, the anode of the eighth diode is connected to the common connection point of the eighth switch and the ninth switch, the cathode of the eighth diode is connected to the common connection point of the third capacitor and the fourth capacitor, the second main power capacitor and the primary winding of the second transformer are connected in series and connected between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm, and the second rectifier circuit is connected to the secondary winding of the second transformer.

[0026] In one embodiment, the positive end of the first capacitor unit and the midpoint of the first bridge arm are connected to the first side of the first power unit, and the negative end of the second capacitor unit and the midpoint of the second bridge arm are connected to the first side of the second power unit.

[0027] In one embodiment, the first power unit further includes a seventh bridge arm, the seventh bridge arm is connected in parallel with the first bridge arm, and the midpoint of the first bridge arm and the midpoint of the seventh bridge arm are connected to the first side of the first power unit, and

[0028] The second power unit further includes an eighth bridge arm, the eighth bridge arm is connected in parallel with the second bridge arm, and the midpoint of the second bridge arm and the midpoint of the eighth bridge arm are connected to the first side of the second power unit.

[0029] In one embodiment, it also includes a control unit, which controls the switch unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft turning on of the switch.

[0030] In a second aspect, the present application further provides a control method for the power conversion module described in the first aspect. The control method comprises:

[0031] Step S1: Control the switch unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft turning on of the switch.

[0032] In one embodiment, the first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm.

[0033] The switch unit comprises:

[0034] A third bridge arm is connected in parallel with the first capacitor unit; and

[0035] a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series,

[0036] When current flows into the first end point of the first side of the first power unit, the step S1 includes:

[0037] Step S11: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or

[0038] Step S12: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or

[0039] Step S13: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm; or

[0040] Step S14: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm.

[0041] When current flows out from the first end point of the first side of the first power unit, the step S1 includes:

[0042] Step S15: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or

[0043] Step S16: before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or

[0044] Step S17: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm; or

[0045] Step S18: Before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off. After the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm.

[0046] In one embodiment, in step S11, the upper switch of the third bridge arm is turned on T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on 2×T / 3 after the upper switch of the first bridge arm is switched from off to on, where T is the working period of the upper switch and the lower switch of the third bridge arm and the fourth bridge arm;

[0047] In step S12, the upper switch of the fourth bridge arm is turned on 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on T / 6 after the upper switch of the first bridge arm is switched from off to on;

[0048] In step S13, the upper switch of the third bridge arm is turned off 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the upper switch of the first bridge arm is switched from off to on;

[0049] In step S14, the upper switch of the fourth bridge arm is turned off T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the upper switch of the first bridge arm is switched from off to on;

[0050] In step S15, the upper switch of the third bridge arm is turned on 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on T / 6 after the lower switch of the first bridge arm is switched from off to on;

[0051] In step S16, the upper switch of the fourth bridge arm is turned on T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on 2×T / 3 after the lower switch of the first bridge arm is switched from off to on;

[0052] In step S17, the upper switch of the third bridge arm is turned off T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the lower switch of the first bridge arm is switched from off to on; and

[0053] In step S18, the upper switch of the fourth bridge arm is turned off 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the lower switch of the first bridge arm is switched from off to on.

[0054] In one embodiment, the first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm.

[0055] The switch unit comprises:

[0056] A third bridge arm is connected in parallel with the first capacitor unit; and

[0057] a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series,

[0058] When current flows into the first end point of the first side of the first power unit, the step S1 includes:

[0059] Step S101: Detecting whether the upper switch of the first bridge arm switches from off to on, if it is detected at a first moment that the upper switch of the first bridge arm switches from off to on, predicting the moment when the upper switch of the first bridge arm switches from off to on next time according to the first moment; or

[0060] Step S102: Detecting whether the upper switch of the first bridge arm switches from off to on, if it is detected at a first moment that the upper switch of the first bridge arm switches from off to on, predicting the next time when the upper switch of the first bridge arm switches from on to off according to the first moment;

[0061] When current flows out from the first end point of the first side of the first power unit, the step S1 includes:

[0062] Step S103: Detecting whether the lower switch of the first bridge arm switches from off to on, if it is detected at a first moment that the lower switch of the first bridge arm switches from off to on, predicting the next time the lower switch of the first bridge arm switches from off to on according to the first moment; or

[0063] Step S104: Detect whether the lower switch of the first bridge arm switches from off to on. If it is detected at the first moment that the lower switch of the first bridge arm switches from off to on, predict the moment when the lower switch of the first bridge arm switches from on to off next time based on the first moment.

[0064] In one embodiment, it also includes:

[0065] Step S2: Control the switch unit to reduce the voltage oscillation on the resonant capacitor after a switch in the first bridge arm and the second bridge arm is turned off.

[0066] In one embodiment, the first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm.

[0067] The switch unit comprises:

[0068] A third bridge arm is connected in parallel with the first capacitor unit; and

[0069] a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series,

[0070] When current flows into the first end point of the first side of the first power unit, the step S2 includes:

[0071] Step S201: Detect whether the upper switch of the first bridge arm switches from on to off, and if it is detected at a first moment that the upper switch of the first bridge arm switches from on to off, predict the moment when the upper switch of the first bridge arm switches from on to off next time according to the first moment; or

[0072] Step S202: Detecting whether the upper switch of the first bridge arm is switched from on to off, if it is detected at a first moment that the upper switch of the first bridge arm is switched from on to off, predicting the moment when the upper switch of the first bridge arm is switched from off to on next time according to the first moment;

[0073] When current flows out from the first end point of the first side of the first power unit, the step S2 includes:

[0074] Step S203: Detect whether the lower switch of the first bridge arm switches from on to off, and if it is detected at a first moment that the lower switch of the first bridge arm switches from on to off, predict the moment when the lower switch of the first bridge arm switches from on to off next time according to the first moment; or

[0075] Step S204: Detect whether the lower switch of the first bridge arm switches from on to off. If it is detected at the first moment that the lower switch of the first bridge arm switches from on to off, predict the moment when the lower switch of the first bridge arm switches from off to on next time based on the first moment.

[0076] In one embodiment, the first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm.

[0077] The switch unit comprises:

[0078] A third bridge arm is connected in parallel with the first capacitor unit; and

[0079] a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series,

[0080] When current flows into the first end point of the first side of the first power unit, the step S2 includes:

[0081] Step S21: before the upper switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or

[0082] Step S22: before the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0083] Step S23: after the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0084] Step S24: before the upper switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or

[0085] Step S25: before the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or

[0086] Step S26: after the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously;

[0087] When current flows out from the first end point of the first side of the first power unit, the step S2 includes:

[0088] Step S27: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or

[0089] Step S28: before the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0090] Step S29: after the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0091] Step S30: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or

[0092] Step S31: before the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or

[0093] Step S32: After the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously.

[0094] In one embodiment, in step S21, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-on time interval of the upper switch of the third bridge arm and the turn-off time interval of the upper switch of the first bridge arm is 2×T / 3;

[0095] In the step S22, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 3;

[0096] In the step S23, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 3 or 5×T / 6;

[0097] In the step S24, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0098] In the step S25, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0099] In the step S26, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0100] In the step S27, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6;

[0101] In the step S28, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6;

[0102] In the step S29, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6;

[0103] In the step S30, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is 2×T / 3;

[0104] In the step S31, the on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3;

[0105] In step S32, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3 or 5×T / 6.

[0106] In one embodiment, the first power unit further includes a seventh bridge arm, the seventh bridge arm is connected in parallel with the first bridge arm, and the midpoint of the first bridge arm and the midpoint of the seventh bridge arm are connected to the first side of the first power unit, and

[0107] The second power unit further includes an eighth bridge arm, the eighth bridge arm is connected in parallel with the second bridge arm, and the midpoint of the second bridge arm and the midpoint of the eighth bridge arm are connected to the first side of the second power unit.

[0108] In one embodiment, the positive end of the first capacitor unit and the midpoint of the first bridge arm are connected to the first side of the first power unit, and the negative end of the second capacitor unit and the midpoint of the second bridge arm are connected to the first side of the second power unit.

[0109] In a third aspect, the present application further provides a power conversion system, characterized in that it comprises N power conversion modules as described in any one of the first aspects, where N is an integer greater than or equal to 1.

[0110] In one embodiment, the first side of the first power unit and the first side of the second power unit are connected in series to form the first side of the power conversion module, and the first sides of N power conversion modules are connected in series, where N>=2.

[0111] In one embodiment, an AC / DC circuit is further included, and the first sides of N power conversion modules are connected in series to the DC side of the AC / DC circuit.

[0112] In one embodiment, an AC / DC circuit is further included, wherein the first side of the first power unit and the first side of the second power unit are connected in series to a DC side of the AC / DC circuit, and N=1.

[0113] The above power conversion module, control method, and power conversion system have at least the following advantages:

[0114] The present application sets a jumper branch between the first power unit and the second power unit, and the jumper branch includes an electrically connected resonant capacitor and a switch unit, wherein the resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or in series with the resonant capacitor. The present application controls the on-off of the jumper branch so that a current opposite to that of the power grid is generated on the branch connecting the first bridge arm and the second bridge arm, thereby realizing soft switching of the switch tube of the power conversion module with a small number of auxiliary circuits, which helps to improve the working efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0115] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0116] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0117] Figure 1 is a structural block diagram of a power conversion module in one embodiment;

[0118] Figure 2 is another structural block diagram of a power conversion module in one embodiment;

[0119] Figure 3 is a structural block diagram of a switch unit in one embodiment;

[0120] Figure 4 is another structural block diagram of a switch unit in one embodiment;

[0121] Figure 5 is a structural block diagram of a switch unit in another embodiment;

[0122] Figure 6 is another structural block diagram of a switch unit in another embodiment;

[0123] Figure 7 is a schematic structural diagram of a power conversion module in one embodiment;

[0124] Figure 8 is a schematic structural diagram of a power conversion module in another embodiment;

[0125] Fig. 9 is a schematic structural diagram of a power conversion module in another embodiment;

[0126] Fig.10is a schematic diagram of the structure of a first power unit and a second power unit in an embodiment;

[0127] Fig.11 is a schematic structural diagram of a first power unit and a second power unit in another embodiment;

[0128] Fig.12 is a schematic structural diagram of a power conversion module in another embodiment;

[0129] 13(a)-(d) are schematic diagrams of a front-stage working circuit in a steady state process in one embodiment;

[0130] Fig.14 A comparison diagram of the modes of the front and rear stages in an embodiment;

[0131] Fig.15 is a schematic diagram of a current loop during an opening process in an embodiment;

[0132] Fig.16 A schematic diagram of a simulation of a turn-on process of a switch S11 in an embodiment;

[0133] 17(a)-(c) are schematic diagrams showing simulations of the shutdown process in different switching sequences in another embodiment;

[0134] Fig.18 A schematic diagram of the state trajectory of the resonant circuit during the switching-on process of the switch S11 in one embodiment;

[0135] Fig.19 A schematic diagram of a simulation of a switch S11 turning off process in an embodiment;

[0136] Fig. 20 A schematic diagram of the state trajectory of the resonant circuit during the shutdown process of the switch S11 in one embodiment;

[0137] Fig.21 An example of the switching sequence and time interval of the subsequent stage in another embodiment;

[0138] Fig. 22 is a schematic structural diagram of a power conversion module in another embodiment;

[0139] Figure 23(a) shows Fig. 22 Simulation diagram of

[0140] FIG23( b ) is a partial enlarged view of the steady-state process in FIG23( a );

[0141] FIG23( c ) is a partial enlarged view of the opening process in FIG23( a );

[0142] FIG23( d ) is a partial enlarged view of the shut-down process in FIG23( a );

[0143] Fig.24 is a structural block diagram of a power conversion system in one embodiment;

[0144] Fig.25 is a structural block diagram of a power conversion system in another embodiment;

[0145] Fig.26 is a schematic structural diagram of a power conversion system in one embodiment;

[0146] Fig. 27 FIG. 4 is a schematic diagram of the structure of a power conversion system in another embodiment. DETAILED DESCRIPTION

[0147] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0148] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0149] In the case of using "including", "having", and "comprising" described herein, another component may be added unless an explicit limiting term such as "only", "consisting of", etc. is used. Unless mentioned otherwise, a term in the singular form may include a plural form and should not be understood as being one in number.

[0150] It should be understood that although the terms "first", "second", etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of the present application.

[0151] In this application, unless otherwise clearly specified and limited, the terms "connected", "connection" and the like should be understood in a broad sense, for example, it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0152] See also Figure 1 and Figure 2 In some embodiments, the present application provides a power conversion module, which specifically includes: a first power unit, a second power unit, a jumper branch and a resonant inductor.

[0153] The first power unit includes a first bridge arm, a first capacitor unit, a first side, and a second side. The first bridge arm and the first capacitor unit are connected in parallel, and the first capacitor unit has a positive end and a negative end. The first side of the first power unit is one of the input side and the output side of the first power unit, and the second side of the first power unit is the other of the input side and the output side of the first power unit. Exemplarily, Figure 1 and Figure 2 In the embodiment, the input side of the first power unit is taken as the first side and the output side is taken as the second side. Then, the first side of the first power unit includes a first endpoint and a second endpoint, wherein the first endpoint is connected to the endpoint of the first bridge arm connected to the power grid, and the second endpoint is connected to the midpoint of the first bridge arm; the second side of the first power unit is connected to the two ends of the first bridge arm. In some other embodiments, other input sources can be used instead of the power grid to supply power to the power conversion module.

[0154] The second power unit includes a second bridge arm, a second capacitor unit, a first side, and a second side. The second bridge arm and the second capacitor unit are connected in parallel, and the second capacitor unit has a positive end and a negative end. The first side of the second power unit is one of the input side and the output side of the second power unit, and the second side of the second power unit is the other of the input side and the output side of the second power unit. Exemplarily, Figure 1 and Figure 2 In the embodiment, the input side of the second power unit is taken as the first side and the output side is taken as the second side. Then, the first side of the second power unit also includes a first endpoint and a second endpoint, wherein the first endpoint is connected to the midpoint of the second bridge arm and the second endpoint is connected to the endpoint where the second bridge arm is connected to the power grid; the second side of the second power unit is connected to both ends of the second bridge arm.

[0155] Midpoints of the first bridge arm and the second bridge arm are interconnected to achieve series connection of the first side of the first power unit and the second power unit.

[0156] The jumper branch is connected between the second side of the first power unit and the second side of the second power unit, and the jumper branch includes a resonant capacitor and a switch unit which are electrically connected to each other.

[0157] The resonant inductor in this embodiment has two connection modes, such as Figure 1 As shown, the resonant inductor and the resonant capacitor are connected in series; or, as shown Figure 2 As shown, the resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm.

[0158] In the above embodiment, the first power unit, the second power unit, the resonant inductor and the jumper branch connected between the first power unit and the second power unit constitute a resonant circuit. By controlling the on and off of the switch unit, the resonant current can be injected into the jumper branch to generate a current opposite to the input current. At this time, the first bridge arm and the second bridge arm are opened or closed to achieve soft switching. In addition, the switch unit in the jumper branch can also be used as a subsequent circuit to output power to the load, realizing the reuse of the switching element, further reducing the switching devices and driving circuits required to realize the soft switching of the previous circuit, and saving costs. At the same time, the design of the resonant capacitor connecting between the two power units can use a small-capacity resonant capacitor, which also improves the power density.

[0159] See also Figure 3 and Figure 4 In a feasible embodiment, the switch unit includes: a first switch P11. In this case, the jumper branch includes the first switch P11 and the resonant capacitor Ct, and the jumper branch is connected between the positive end of the first capacitor unit and the negative end of the second capacitor unit. The resonant inductor has two different positions. Figure 3 As shown, the first switch P11, the resonant capacitor Ct and the resonant inductor Lt are connected in series. Figure 4 As shown, the resonant inductor Lt is connected between the midpoints of the first bridge arm and the second bridge arm. It should be noted that the first switch P11 in this embodiment is a transistor, and the transistor includes a reverse biased diode.

[0160] See also Figure 5 and Figure 6 In another feasible embodiment, the switch unit includes: a third bridge arm and a fourth bridge arm.

[0161] The third bridge arm is connected in parallel with the first capacitor unit.

[0162] The fourth bridge arm is connected in parallel with the second capacitor unit.

[0163] At this time, the bridging branch includes the third bridge arm, the fourth bridge arm and the resonant capacitor Ct. Figure 5 As shown, the resonant capacitor Ct and the resonant inductor Lt are connected in series and connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm. Figure 6 As shown, the resonant capacitor Ct is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm, and the resonant inductor Lt is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm.

[0164] In the above embodiment, the first power unit and the second power unit constitute the front-stage AC-DC circuit of the power conversion module, the switch unit constitutes the rear-stage DC-DC circuit, and the high-frequency bridge arm of the front stage, the switch unit of the rear stage, the resonant inductor and the resonant capacitor form a resonant circuit. By controlling the on and off of the switch unit, the power conversion module can inject the resonant current into the jumper branch after being connected to the power grid, so that a current opposite to the input current is generated on the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm, thereby realizing the soft switching of the front stage. In addition, the switch unit of the rear stage can be reused by the switch unit in the jumper branch, further reducing the switching devices and driving circuits required to realize the soft switching of the front stage, saving costs and improving the power density of the system.

[0165] See also Figure 7-Figure 11 In order to adapt to different types of converters, the switch unit of the present application can select different topological structures according to the needs. The switch units with different topological structures and the cross-connection branch formed by the resonant capacitor Ct can also realize the soft switching effect in the above embodiment by controlling the on and off of the switch unit. Furthermore, the topological structure of the first power unit and the second power unit can also be adjusted, and the soft switching effect can also be realized based on the same principle. The following is an example of the resonant inductor Lt connected between the midpoints of the first bridge arm and the second bridge arm.

[0166] See also Figure 7 Exemplarily, for a cascade half bridge converter (SHB), the first capacitor unit includes a first capacitor C11 and a second capacitor C12 connected in series, and the second capacitor unit includes a third capacitor C21 and a fourth capacitor C22 connected in series.

[0167] The switch unit includes: a third bridge arm, a fourth bridge arm, a fifth bridge arm and a sixth bridge arm.

[0168] The third bridge arm is connected in parallel with the first capacitor C11, and includes a switch P11 and a switch P12 connected in series.

[0169] The fourth bridge arm is connected in parallel with the third capacitor C21, and includes a switch P21 and a switch P22 connected in series.

[0170] The fifth bridge arm is connected in parallel with the second capacitor C12, and the fifth bridge arm includes a switch P13 and a switch P14 connected in series.

[0171] The sixth bridge arm is connected in parallel with the fourth capacitor C22, and the sixth bridge arm includes a switch P23 and a switch P24 connected in series.

[0172] The resonant capacitor Ct is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm.

[0173] See also Figure 8Further, the first bridge arm includes a second switch S11, a third switch S12, a fourth switch S13 and a fifth switch S14 connected in sequence, and the second bridge arm includes a sixth switch S21, a seventh switch S22, an eighth switch S23 and a ninth switch S24 connected in sequence.

[0174] The power conversion module also includes a first diode D11, a second diode D12, a third diode D21, a fourth diode D22, a fifth diode D13, a sixth diode D14, a seventh diode D23, an eighth diode D24, a first main power capacitor CT1, a second main power capacitor CT2, a first transformer T1, a second transformer T2, a first rectifier circuit and a second rectifier circuit.

[0175] Among them, the first diode D11 and the second diode D12 are connected in series and connected in parallel with the first bridge arm, the common connection point of the first diode D11 and the second diode D12 and the midpoint of the first bridge arm are respectively connected to the first side of the first power unit, the cathode of the fifth diode D13 is connected to the common connection point of the second switch S11 and the third switch S12, the anode of the fifth diode D13 is connected to the common connection point of the first capacitor C11 and the second capacitor C12, the anode of the sixth diode D14 is connected to the common connection point of the fourth switch S13 and the fifth switch S14, the cathode of the sixth diode D14 is connected to the common connection point of the first capacitor C11 and the second capacitor C12, the first main power capacitor CT1 and the primary winding of the first transformer T1 are connected in series and connected between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm, and the first rectifier circuit is connected to the secondary winding of the first transformer.

[0176] The third diode D21 and the fourth diode D22 are connected in series and connected in parallel to the second bridge arm. The common connection point of the third diode D21 and the fourth diode D22 and the midpoint of the second bridge arm are respectively connected to the first side of the second power unit. The cathode of the seventh diode D23 is connected to the common connection point of the sixth switch S21 and the seventh switch S22. The anode of the seventh diode D23 is connected to the common connection point of the third capacitor C21 and the fourth capacitor C22. The anode of the eighth diode D24 is connected to the common connection point of the eighth switch S23 and the ninth switch S24. The cathode of the eighth diode D24 is connected to the common connection point of the third capacitor C21 and the fourth capacitor C22. The second main power capacitor CT2 and the primary winding of the second transformer T2 are connected in series and connected between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm. The second rectifier circuit is connected to the secondary winding of the second transformer.

[0177] See also Fig. 9 , exemplarily, for the resonant converter, the first capacitor unit includes a first capacitor C11, and the second capacitor unit includes a third capacitor C21.

[0178] The switch unit includes: a third bridge arm, a fourth bridge arm, a fifth bridge arm and a sixth bridge arm.

[0179] The third bridge arm and the fifth bridge arm are connected in parallel with the first capacitor C11. The third bridge arm includes a switch P11 and a switch P12 connected in series, and the fifth bridge arm includes a switch P13 and a switch P14 connected in series.

[0180] The fourth bridge arm and the sixth bridge arm are connected in parallel with the third capacitor C21. The fourth bridge arm includes a switch P21 and a switch P22 connected in series, and the sixth bridge arm includes a switch P23 and a switch P24 connected in series.

[0181] The resonant capacitor Ct is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm, the first main power capacitor CT1 and the primary winding of the first transformer T1 are connected in series and then connected between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm, and the first rectifier circuit is connected to the secondary winding of the first transformer T1. The second main power capacitor CT2 and the primary winding of the second transformer T2 are connected in series and then connected between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm, and the second rectifier circuit is connected to the secondary winding of the second transformer T2.

[0182] See also Fig.10 In some embodiments, the first power unit and the second power unit are half-bridge structures. In this case, the positive end of the first capacitor unit and the midpoint of the first bridge arm are connected to the first side of the first power unit, and the negative end of the second capacitor unit and the midpoint of the second bridge arm are connected to the first side of the second power unit.

[0183] See also Fig.11 In some embodiments, the first power unit and the second power unit are full-bridge structures. In this case, the first power unit further includes a seventh bridge arm, the seventh bridge arm is connected in parallel with the first bridge arm, and the midpoint of the first bridge arm and the midpoint of the seventh bridge arm are connected to the first side of the first power unit. Fig.11 As shown, the switch S15 and the switch S16 are connected in series to form the seventh bridge arm.

[0184] The second power unit further includes an eighth bridge arm, the eighth bridge arm and the second bridge arm are connected in parallel, and the midpoint of the second bridge arm and the midpoint of the eighth bridge arm are connected to the first side of the second power unit. Fig.11 As shown, the switch S25 and the switch S26 are connected in series to form the eighth bridge arm.

[0185] It should be understood that the power conversion module in this embodiment also includes a control unit, which is used to control the switching unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft opening of the switch.

[0186] In some embodiments, the present application further provides a control method, which is applicable to the power conversion module provided in the above embodiments, and the control method includes:

[0187] Step S1: Control the switch unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft turning on of the switch.

[0188] See also Fig.12 , the following combination Fig.12 The structure of step S1 is described in detail.

[0189] like Fig.12 As shown, the second end point of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first end point of the first side of the second power unit is connected to the midpoint of the second bridge arm.

[0190] The third bridge arm of the switch unit is connected in parallel with the first capacitor unit, the fourth bridge arm is connected in parallel with the second capacitor unit, and the resonant capacitor is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm. The first bridge arm includes an upper switch S11 and a lower switch S12 connected in series, the second bridge arm includes an upper switch S21 and a lower switch S22 connected in series, the third bridge arm includes an upper switch P11 and a lower switch P12 connected in series, and the fourth bridge arm includes an upper switch P21 and a lower switch P22 connected in series.

[0191] When the current ig flows into the first terminal of the first side of the first power unit, step S1 includes:

[0192] Step S11: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or

[0193] Step S12: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or

[0194] Step S13: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm; or

[0195] Step S14: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm.

[0196] When the current flows out from the first terminal of the first side of the first power unit, step S1 includes:

[0197] Step S15: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or

[0198] Step S16: before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or

[0199] Step S17: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm; or

[0200] Step S18: Before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off. After the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm.

[0201] Specifically, in the process of injecting resonant current into the jumper branch to complete the previous stage ZVS commutation, the optimal switching sequence can effectively reduce the current and voltage oscillations of the resonant circuit during the soft switching process and improve the power density. Therefore, this application first analyzes the switching mode of the resonant circuit to obtain the optimal switching process. Fig.12 In the structure shown, the switch S11 and the switch S22 have the same mode, and the switch S12 and the switch S21 have the same mode. The following takes the input current ig>0 and the switch S11 as an example to illustrate the modal analysis and the switching process of the present invention:

[0202] Please refer to Figures 13(a)-(d) and Fig.14 , Figure 13(a)-(d) shows the schematic diagram of the front stage working circuit in the steady state process, Fig.14 The figure shows the comparison of the modes of the front and rear stages. Among them, the voltage Vdc is the port voltage of the resonant cavity, that is, the voltages across the capacitors C11 and C21 in Figures 13(a)-(d) are both Vdc; Vab is the voltage between the common connection point a of the switch P11 and the switch P12 and the common connection point b of the switch P21 and the switch P22 in Figures 13(a)-(d).

[0203] In the steady-state process, the input current in the front-stage circuit of Figure 13(a) flows through the diode D11, switch S11, switch S22 in sequence, and finally flows out from the diode D22. The input current in the front-stage circuit of Figure 13(b) flows through the diode D11, capacitor C11, switch S12, switch S22 in sequence, and finally flows out from the diode D22. The input current in the front-stage circuit of Figure 13(c) flows through the diode D11, switch S11, switch S21, capacitor C21 in sequence, and finally flows out from the diode D22. The input current in the front-stage circuit of Figure 13(d) flows through the diode D11, capacitor C11, switch S12, switch S21, capacitor C21 in sequence, and finally flows out from the diode D22.

[0204] It can be seen that during the commutation of the front-stage bridge arm switch, in the absence of resonant current, the grid-side current it>0 can make switches S12 and S21 naturally achieve ZVS opening, while switches S11 and S22 cannot naturally achieve ZVS opening. Similarly, the grid-side current it<0 can make switches S11 and S22 naturally achieve ZVS opening, while switches S12 and S21 cannot naturally achieve ZVS opening. When the front-stage switches are in different modes and the rear-stage switches work synchronously (P11 and P12 are turned on and off at the same time), the voltage Vab and the resonant capacitor voltage Vct will change, and the resonant capacitor voltage is only related to the state of the front-stage switch and has nothing to do with the state of the rear-stage switch. Therefore, according to the analysis results, the commutation of the front-stage bridge arm must complete the ZVS opening of switches S11 and S22 and the change of the state of the cross-connected resonant capacitor.

[0205] See also Fig.15 and Fig.16 , Fig.15 Schematic diagram of the current loop from time t1 to time t2 when the switching sequence of the front-end and rear-end modules is P11→S11→P21 during the opening process. Fig.16 It is a simulation diagram of the switch S11 turning on process. Fig.15 The dotted arrow in the figure indicates the flow path of the input current ig, which passes through the diode D11, switch S11, switch S22, and diode D22 in sequence. When the switch P11 is turned on at time t1, the voltage Vab changes, generating a resonant current iCt, which is superimposed on the input current to generate a reverse current it. At this time, the current direction is as follows: Fig.15The solid arrow in the figure indicates the direction, which passes through switch P11, resonant capacitor Ct, resonant inductor Lt, switch P22, switch S22, switch S12, capacitor C11 in sequence, and the value of the reverse current satisfies it=ig-iCt. Switch S11 is turned on at time t2, at which time the cascade side current it<0, the resonant current satisfies the ZVS condition of S11, and soft turning on can be achieved. Moreover, the voltage Vab changes, and the resonant current also changes accordingly. P21 is turned on at time t3, at which time the resonant capacitor voltage just changes from 0 to -Vdc, without unnecessary current and voltage oscillations. With the above scheme, during the simultaneous turning on of switches P11 and P21, by controlling the turning on sequence of switches P11 and P21, the previous switch S11 can be assisted to complete the soft switching process, and at this time the switching frequency of the subsequent stage is greater than the switching frequency of the previous stage.

[0206] Furthermore, in this embodiment, the ZVS turn-on process of the switch S11 can also be implemented when the switch P11 and the switch P21 are turned off, and the switching sequence of the switch P11 and the switch P21 can also be different.

[0207] In some embodiments, the Figure 1 to Figure 13(d) as well as Fig.15 An inductor is added in the circuit, and the inductor is connected in series with the first side of the first power unit and the first side of the second power unit and then connected to a power grid or other input source.

[0208] Please refer to FIG. 17 , which is a schematic diagram of the simulation of the shutdown process in different switching sequences. Figure 17(a) and 17(b) FIG17( a ) is the ZVS turn-on process of switch S11 when switch P11 and switch P21 are turned off, and the switching sequence in FIG17( a ) is P21→S11→P11, and the switching sequence in FIG17( b ) is P11→S11→P21; FIG17( c ) is the ZVS turn-on process of switch S11 when switch P11 and switch P21 are turned on, and the switching sequence is P21→S11→P11.

[0209] In the above embodiment, the voltage Vab can be changed by the asynchronous action of the switch P11 and the switch P12, generating a resonant current, which generates a reverse current after being superimposed on the input current, and can assist the front-stage switch S11 to complete the soft switching process. At the same time, the present application can also optimize the time to better achieve the ZVS opening of the front stage and prevent oscillation.

[0210] Optionally, in step S11, the upper switch of the third bridge arm is turned on T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on 2×T / 3 after the upper switch of the first bridge arm is switched from off to on, and T is the duty cycle of the upper switch and the lower switch of the third bridge arm and the fourth bridge arm.

[0211] In step S12, the upper switch of the fourth bridge arm is turned on 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on T / 6 after the upper switch of the first bridge arm is switched from off to on.

[0212] In step S13, the upper switch of the third bridge arm is turned off 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the upper switch of the first bridge arm is switched from off to on.

[0213] In step S14, the upper switch of the fourth bridge arm is turned off T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the upper switch of the first bridge arm is switched from off to on.

[0214] In step S15, the upper switch of the third bridge arm is turned on 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on T / 6 after the lower switch of the first bridge arm is switched from off to on.

[0215] In step S16, the upper switch of the fourth bridge arm is turned on T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on 2×T / 3 after the lower switch of the first bridge arm is switched from off to on.

[0216] In step S17, the upper switch of the third bridge arm is turned off T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the lower switch of the first bridge arm is switched from off to on.

[0217] In step S18, the upper switch of the fourth bridge arm is turned off 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the lower switch of the first bridge arm is switched from off to on.

[0218] Specifically, see Fig.18 , Fig.18 Schematic diagram of the state trajectory of the resonant circuit during the on-state process of the switch S11. According to the state trajectory, the on-state current of the switch S11 and the on-state time interval during the on-state process can be calculated. Fig.18 VctN in the figure is the normalized resonant capacitor voltage and satisfies

[0219] And Vct is the actual resonant capacitor voltage, Vdc is the capacitor voltage of C11 and C21. IctN is the normalized resonant inductor current, and satisfies

[0220] Among them, the turn-on current I on The expression is:

[0221]

[0222] Opening time interval T on The expression is:

[0223]

[0224] The resonant frequency f of the resonant circuit t and period T t The relationship is:

[0225]

[0226] Then Δt1 and Δt2 in Figure 17(a)-(c) are respectively:

[0227]

[0228] Among them, L t is the inductance of the resonant inductor, C t is the capacitance value of the resonant capacitor, T t is the duty cycle of switch S11.

[0229] Based on the above-mentioned opening time interval, the on and off of the third bridge arm and the fourth bridge arm are controlled, so that the voltage on the resonant capacitor can be stabilized, unnecessary current and voltage oscillations can be prevented, and the power conversion efficiency can be improved.

[0230] Optionally, the control method in the embodiment of the present application is also used to detect the action time of the previous stage switch. If the action of the previous stage switch is detected at time t1, the next action time t2 is predicted based on the above-mentioned opening time interval.

[0231] When current flows into the first terminal of the first side of the first power unit, step S1 further includes:

[0232] Step S101: Detect whether the upper switch of the first bridge arm switches from off to on. If it is detected at a first moment that the upper switch of the first bridge arm switches from off to on, predict the time when the upper switch of the first bridge arm switches from off to on next time according to the first moment; or

[0233] Step S102: Detect whether the upper switch of the first bridge arm switches from off to on. If it is detected at the first moment that the upper switch of the first bridge arm switches from off to on, predict the next time the upper switch of the first bridge arm switches from on to off based on the first moment.

[0234] When the current flows out from the first terminal of the first side of the first power unit, step S1 further includes:

[0235] Step S103: Detect whether the lower switch of the first bridge arm switches from off to on. If it is detected at the first moment that the lower switch of the first bridge arm switches from off to on, predict the time when the lower switch of the first bridge arm switches from off to on next time according to the first moment; or

[0236] Step S104: Detect whether the lower switch of the first bridge arm switches from off to on. If it is detected at the first moment that the lower switch of the first bridge arm switches from off to on, predict the next time the lower switch of the first bridge arm switches from on to off based on the first moment.

[0237] In the above embodiment, by detecting the action moment of the previous stage switch and predicting the next action moment, precise control of the on and off of the previous and next stage switches can be achieved, further improving the power conversion efficiency.

[0238] Optionally, the control method of the embodiment of the present application further comprises:

[0239] Step S2: Control the switch unit to reduce the voltage oscillation on the resonant capacitor after a switch in the first bridge arm and the second bridge arm is turned off.

[0240] See also Fig.19 , Fig.19 The simulation diagram of the switch S11 turn-off process. According to the above steady-state analysis, after the switch S11 is turned off, the voltage on the resonant capacitor will also change. Therefore, the turn-off process of the switch S11 also needs to be modally controlled to make the voltage on the resonant capacitor stable and prevent unnecessary current and voltage oscillations. The turn-off process is similar to the turn-on process. Fig.19 The shutdown sequence shown is P11→S11→P21: When switch P11 is turned off at time t1, the voltage across the resonant cavity changes, generating a resonant current iCt, which is superimposed on the input current. Soft-turning can also be achieved by turning off S11 and turning on S12 at time t2. When switch P21 is turned off at time t3, the resonant capacitor voltage changes from -Vdc to 0 without unnecessary oscillation.

[0241] See also Fig.12 , the following combination Fig.12 The structure of step S2 is described in detail.

[0242] When the current ig flows into the first terminal of the first side of the first power unit, step S2 includes:

[0243] Step S21: before the upper switch of the first bridge arm is turned off, one of the upper switches of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or

[0244] Step S22: before the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0245] Step S23: after the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0246] Step S24: before the upper switch of the first bridge arm is turned off, one of the upper switches of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or

[0247] Step S25: before the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or

[0248] Step S26: After the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously;

[0249] When the current flows out from the first terminal of the first side of the first power unit, step S2 includes:

[0250] Step S27: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or

[0251] Step S28: before the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0252] Step S29: after the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or

[0253] Step S30: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or

[0254] Step S31: before the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or

[0255] Step S32: After the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously.

[0256] Optionally, in step S21, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-on time interval of the upper switch of the third bridge arm and the turn-off time interval of the upper switch of the first bridge arm is 2×T / 3;

[0257] In step S22, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 3;

[0258] In step S23, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-on time interval of the upper switch of the third bridge arm and the turn-off time interval of the upper switch of the first bridge arm is T / 3 or 5×T / 6;

[0259] In step S24, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0260] In step S25, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0261] In step S26, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6;

[0262] In step S27, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6;

[0263] In step S28, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6;

[0264] In step S29, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-on time interval of the upper switch of the third bridge arm and the turn-off time interval of the upper switch of the first bridge arm is T / 6;

[0265] In step S30, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is 2×T / 3;

[0266] In step S31, the on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3;

[0267] In step S32, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3 or 5×T / 6.

[0268] Specifically, see Fig. 20 , Fig. 20 Schematic diagram of the state trajectory of the resonant circuit during the shutdown process of the switch S11. According to the state trajectory, the shutdown current of the switch S11 and the shutdown time interval during the shutdown process can be calculated.

[0269] The expression of the shutdown current is:

[0270]

[0271] The expression for the off time interval is:

[0272]

[0273] Based on the above-mentioned off time interval, the on and off of the third bridge arm and the fourth bridge arm are controlled, so that the voltage on the resonant capacitor can be stabilized, unnecessary current and voltage oscillations can be prevented, and the power conversion efficiency can be improved.

[0274] Optionally, before the power conversion module is controlled in real time to achieve the purpose of soft switching of the previous stage, the embodiment of the present application further selects a suitable switching time T according to the operating frequency of the previous and next stages. on ; Then, according to formula (2) and formula (6), calculate the resonant frequency of the cross-connected branch; finally, according to the known turn-on current I on The capacitance value of the resonant capacitor and the inductance value of the resonant inductor are determined by using formula (1) and formula (5).

[0275] Optionally, the control method in the embodiment of the present application is also used to detect the action time of the previous stage switch. If the action of the previous stage switch is detected at time t1, the next action time t2 is predicted based on the above-mentioned opening time interval.

[0276] When current flows into the first terminal of the first side of the first power unit, step S2 further includes:

[0277] Step S201: Detect whether the upper switch of the first bridge arm switches from on to off. If it is detected at the first moment that the upper switch of the first bridge arm switches from on to off, predict the next time the upper switch of the first bridge arm switches from on to off according to the first moment; or

[0278] Step S202: Detect whether the upper switch of the first bridge arm is switched from on to off. If it is detected at the first moment that the upper switch of the first bridge arm is switched from on to off, predict the moment when the upper switch of the first bridge arm is switched from off to on next time according to the first moment;

[0279] When the current flows out from the first terminal of the first side of the first power unit, step S2 further includes:

[0280] Step S203: Detect whether the lower switch of the first bridge arm switches from on to off. If it is detected at the first moment that the lower switch of the first bridge arm switches from on to off, predict the time when the lower switch of the first bridge arm switches from on to off next time according to the first moment; or

[0281] Step S204: Detect whether the lower switch of the first bridge arm switches from on to off. If it is detected at the first moment that the lower switch of the first bridge arm switches from on to off, predict the next time the lower switch of the first bridge arm switches from off to on based on the first moment.

[0282] In the above embodiment, by detecting the action moment of the previous stage switch and predicting the next action moment, precise control of the on and off of the previous and next stage switches can be achieved, further improving the power conversion efficiency.

[0283] See also Fig.21 It should be noted that, similar to the turn-on process, the turn-off process of S11 can also be realized in the turn-on and turn-off process of P11 and P21, and does not affect the ZVS turn-on of S12. Similarly, it can be extended to the case where the input current ig<0. For example, Fig.21 The switching sequence and time interval of switch S11 and switch S12 for realizing soft switching are given in FIG. According to the time shown in Table 21, ZVS and resonant capacitor mode conversion can be quickly realized. Since the resonance changes periodically, each action time difference can add an integer number of resonant cycles to the action time shown in the table, that is, n×Tt resonant cycles are added.

[0284] See also Fig. 22 and Figure 23(a)-(d), Fig. 22 The topology shown in Figure 23(a)-(d) is a two-stage topology. Fig. 22The simulation schematic diagram of the topological structure shown in , wherein FIG23(a) is an overall simulation schematic diagram of the steady-state process, the turn-on process and the turn-off process of the switch S11, FIG23(b) is a partial enlarged diagram of the steady-state process, FIG23(c) is a partial enlarged diagram of the turn-on process, and FIG23(d) is a partial enlarged diagram of the turn-off process. And Ilr1 and Ilr2 represent the current of the rear-stage resonant cavity, that is, the primary current of the transformer; Ilm1 and Ilm2 represent the current flowing through the transformer excitation inductance; Ils1 and Ils2 represent the current flowing through the secondary side of the transformer. According to FIG23(a)-(d), the steady-state process, the turn-on process and the turn-off process of the switch S11 are comprehensively analyzed. It can be seen that the switching process of the present invention is completed within half a cycle of the rear-stage switch, and has no effect on the input current and the ZVS of the rear-stage switch, and the resonant current only circulates between the front and rear stage circuits, has no effect on the input current, and has no effect on the system EMI. In addition, in this embodiment, the current on the cross-branch circuit changes greatly only during the switching time, the conduction loss increases less, the required capacitance is small, and the power density is improved.

[0285] The above control method is to set a jumper branch and a resonant inductor between the first power unit and the second power unit, wherein the jumper branch includes an electrically connected resonant capacitor and a switch unit, and the resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or in series with the resonant capacitor. The present application controls the on-off of the jumper branch so that a current opposite to that of the power grid is generated on the branch connecting the first bridge arm and the second bridge arm, thereby realizing soft switching of the switch tube of the power conversion module with a smaller number of auxiliary circuits, which helps to improve the working efficiency of the system.

[0286] See also Fig.24 In some embodiments, the present application further provides a power conversion system, comprising N power conversion modules as provided in the above embodiments, where N is an integer greater than or equal to 1. The structure of the power conversion module has been described in detail in the above embodiments, and will not be repeated here to save space.

[0287] Optionally, the first side of the first power unit and the first side of the second power unit are connected in series to form the first side of the power conversion module. When the number of power conversion modules satisfies N>=2, the first sides of N power conversion modules are connected in series and then connected to the power grid.

[0288] See also Fig.25 Optionally, the power conversion system of the embodiment of the present application further includes an AC / DC circuit. When the number of power conversion modules is multiple, the first sides of N power conversion modules are connected in series to the DC side of the AC / DC circuit, and the AC side of the AC / DC circuit is connected to the power grid.

[0289] See also Fig.26When the number of power conversion modules is one, the first side of the first power unit and the first side of the second power unit are connected in series to the DC side of the AC-DC circuit, and the AC side of the AC-DC circuit is connected to the power grid, N=1. Fig. 22 The AC-DC circuit in the embodiment uses a rectifier bridge. In this case, the front stage is composed of power frequency rectification and cascade Boost, and the flying capacitor between the primary bridge arms of the LLC in the rear stage assists resonance to achieve ZVS startup of the front stage Boost switch. This embodiment can flexibly select semiconductor devices according to the withstand voltage level and actual needs.

[0290] See also Fig. 27 In another feasible embodiment, the first side of the power conversion module can also be connected to a DC bus. In this case, the front stage is a cascaded DC-DC circuit. Based on the same principle, the soft switching of the front stage switch can also be achieved by controlling the on and off of the switch unit.

[0291] In the power conversion system, a jumper branch and a resonant inductor are arranged between the first power unit and the second power unit. The jumper branch includes an electrically connected resonant capacitor and a switch unit. The resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or in series with the resonant capacitor. The present application controls the on-off of the jumper branch so that a current opposite to that of the power grid is generated on the branch connecting the first bridge arm and the second bridge arm, thereby realizing soft switching of the switch tube of the power conversion module with a smaller number of auxiliary circuits, which helps to improve the working efficiency of the system.

[0292] Please note that the above embodiments are for illustrative purposes only and are not meant to limit the present invention.

[0293] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0294] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0295] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A power conversion module, characterized in that: Include: A first power unit, comprising a first bridge arm, a first capacitor unit, a first side and a second side, wherein the second side of the first power unit is connected to two ends of the first bridge arm, the first capacitor unit and the first bridge arm are connected in parallel, and the first capacitor unit has a positive end and a negative end; A second power unit comprises a second bridge arm, a second capacitor unit, a first side and a second side, wherein the second side of the second power unit is connected to two ends of the second bridge arm, the second capacitor unit and the second bridge arm are connected in parallel, the second capacitor unit has a positive end and a negative end, and the midpoints of the second bridge arm and the first bridge arm are interconnected to realize the second power unit and the first side of the first power unit being connected in series; a jumper branch connected between the second side of the first power unit and the second side of the second power unit, the jumper branch comprising a resonant capacitor and a switch unit electrically connected to each other; as well as The resonant inductor is connected between the midpoints of the first bridge arm and the second bridge arm or is connected in series with the resonant capacitor.

2. The power conversion module according to claim 1, characterized in that: The switch unit includes a first switch, the first switch and the resonant capacitor are connected in series, and the jumper branch is connected between the positive end of the first capacitor unit and the negative end of the second capacitor unit.

3. The power conversion module according to claim 1, characterized in that: The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor unit; and The fourth bridge arm is connected in parallel with the second capacitor unit, and the resonant capacitor is connected between the midpoint of the third bridge arm and the midpoint of the fourth bridge arm.

4. The power conversion module according to claim 1, characterized in that: The first capacitor unit includes a first capacitor and a second capacitor connected in series; The second capacitor unit comprises a third capacitor and a fourth capacitor connected in series; The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor; a fifth bridge arm connected in parallel with the second capacitor; a fourth bridge arm connected in parallel with the third capacitor, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm; and The sixth bridge arm is connected in parallel with the fourth capacitor.

5. The power conversion module according to claim 4, characterized in that: The first bridge arm comprises a second switch, a third switch, a fourth switch and a fifth switch connected in sequence, and the second bridge arm comprises a sixth switch, a seventh switch, an eighth switch and a ninth switch connected in sequence, The power conversion module further includes a first diode, a second diode, a third diode, a fourth diode, a fifth diode, a sixth diode, a seventh diode, an eighth diode, a first main power capacitor, a second main power capacitor, a first transformer, a second transformer, a first rectifier circuit, and a second rectifier circuit. wherein the first diode and the second diode are connected in series and connected in parallel to the first bridge arm; the common connection point of the first diode and the second diode and the midpoint of the first bridge arm are respectively connected to the first side of the first power unit; the cathode of the fifth diode is connected to the common connection point of the second switch and the third switch; the anode of the fifth diode is connected to the common connection point of the first capacitor and the second capacitor; the anode of the sixth diode is connected to the common connection point of the fourth switch and the fifth switch; the cathode of the sixth diode is connected to the common connection point of the first capacitor and the second capacitor; the first main power capacitor and the primary winding of the first transformer are connected in series and connected between the midpoint of the third bridge arm and the midpoint of the fifth bridge arm; the first rectifier circuit is connected to the secondary winding of the first transformer; The third diode and the fourth diode are connected in series and connected in parallel to the second bridge arm, the common connection point of the third diode and the fourth diode and the midpoint of the second bridge arm are respectively connected to the first side of the second power unit, the cathode of the seventh diode is connected to the common connection point of the sixth switch and the seventh switch, the anode of the seventh diode is connected to the common connection point of the third capacitor and the fourth capacitor, the anode of the eighth diode is connected to the common connection point of the eighth switch and the ninth switch, the cathode of the eighth diode is connected to the common connection point of the third capacitor and the fourth capacitor, the second main power capacitor and the primary winding of the second transformer are connected in series and connected between the midpoint of the fourth bridge arm and the midpoint of the sixth bridge arm, and the second rectifier circuit is connected to the secondary winding of the second transformer.

6. The power conversion module according to claim 1, characterized in that: The positive end of the first capacitor unit and the midpoint of the first bridge arm are connected to the first side of the first power unit, and the negative end of the second capacitor unit and the midpoint of the second bridge arm are connected to the first side of the second power unit.

7. The power conversion module according to claim 1, characterized in that: The first power unit further includes a seventh bridge arm, the seventh bridge arm is connected in parallel with the first bridge arm, a midpoint of the first bridge arm and a midpoint of the seventh bridge arm are connected to the first side of the first power unit, and The second power unit further includes an eighth bridge arm, the eighth bridge arm is connected in parallel with the second bridge arm, and the midpoint of the second bridge arm and the midpoint of the eighth bridge arm are connected to the first side of the second power unit.

8. The power conversion module according to any one of claims 1 to 7, characterized in that: It also includes a control unit, which controls the switch unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft turning on of the switch.

9. A control method for the power conversion module according to claim 1, comprising: Step S1: Control the switch unit so that before a switch in the first bridge arm and the second bridge arm is turned on, the current flowing through the branch connecting the midpoint of the first bridge arm and the midpoint of the second bridge arm is opposite to the current flowing through the first side of the first power unit, so as to achieve soft turning on of the switch.

10. The control method according to claim 9, characterized in that: The first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm, The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor unit; as well as a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series, When current flows into the first end point of the first side of the first power unit, the step S1 includes: Step S11: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or Step S12: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the upper switch of the first bridge arm; or Step S13: before the upper switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm; or Step S14: before the upper switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the upper switch of the first bridge arm. When current flows out from the first end point of the first side of the first power unit, the step S1 includes: Step S15: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or Step S16: before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned on, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned on to achieve soft turning on of the lower switch of the first bridge arm; or Step S17: before the lower switch of the first bridge arm is turned on, the upper switch of the third bridge arm is turned off, and after the lower switch of the first bridge arm is switched from off to on, the upper switch of the fourth bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm; or Step S18: Before the lower switch of the first bridge arm is turned on, the upper switch of the fourth bridge arm is turned off. After the lower switch of the first bridge arm is switched from off to on, the upper switch of the third bridge arm is turned off to achieve soft turning on of the lower switch of the first bridge arm.

11. The control method according to claim 10, characterized in that: In step S11, the upper switch of the third bridge arm is turned on T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on 2×T / 3 after the upper switch of the first bridge arm is switched from off to on, where T is the duty cycle of the upper switch and the lower switch of the third bridge arm and the fourth bridge arm; In step S12, the upper switch of the fourth bridge arm is turned on 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on T / 6 after the upper switch of the first bridge arm is switched from off to on; In step S13, the upper switch of the third bridge arm is turned off 2×T / 3 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the upper switch of the first bridge arm is switched from off to on; In step S14, the upper switch of the fourth bridge arm is turned off T / 6 before the upper switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the upper switch of the first bridge arm is switched from off to on; In step S15, the upper switch of the third bridge arm is turned on 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned on T / 6 after the lower switch of the first bridge arm is switched from off to on; In step S16, the upper switch of the fourth bridge arm is turned on T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the third bridge arm is turned on 2×T / 3 after the lower switch of the first bridge arm is switched from off to on; In step S17, the upper switch of the third bridge arm is turned off T / 6 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off 2×T / 3 after the lower switch of the first bridge arm is switched from off to on; as well as In step S18, the upper switch of the fourth bridge arm is turned off 2×T / 3 before the lower switch of the first bridge arm is turned on, and the upper switch of the fourth bridge arm is turned off T / 6 after the lower switch of the first bridge arm is switched from off to on.

12. The control method according to claim 9, characterized in that: The first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm, The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor unit; as well as a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series, When current flows into the first end point of the first side of the first power unit, the step S1 includes: Step S101: Detecting whether the upper switch of the first bridge arm switches from off to on, if it is detected at a first moment that the upper switch of the first bridge arm switches from off to on, predicting the moment when the upper switch of the first bridge arm switches from off to on next time according to the first moment; or Step S102: Detecting whether the upper switch of the first bridge arm switches from off to on, if it is detected at a first moment that the upper switch of the first bridge arm switches from off to on, predicting the next time when the upper switch of the first bridge arm switches from on to off according to the first moment; When current flows out from the first end point of the first side of the first power unit, the step S1 includes: Step S103: Detecting whether the lower switch of the first bridge arm switches from off to on, if it is detected at a first moment that the lower switch of the first bridge arm switches from off to on, predicting the next time the lower switch of the first bridge arm switches from off to on according to the first moment; or Step S104: Detect whether the lower switch of the first bridge arm switches from off to on. If it is detected at the first moment that the lower switch of the first bridge arm switches from off to on, predict the moment when the lower switch of the first bridge arm switches from on to off next time based on the first moment.

13. The control method according to claim 9, characterized in that: Also includes: Step S2: Control the switch unit to reduce the voltage oscillation on the resonant capacitor after a switch in the first bridge arm and the second bridge arm is turned off.

14. The control method according to claim 13, characterized in that: The first side of the first power unit and the first side of the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm, The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor unit; as well as a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series, When current flows into the first end point of the first side of the first power unit, the step S2 includes: Step S201: Detecting whether the upper switch of the first bridge arm is switched from on to off, if it is detected at a first moment that the upper switch of the first bridge arm is switched from on to off, predicting the moment when the upper switch of the first bridge arm is switched from on to off next time according to the first moment; or Step S202: Detecting whether the upper switch of the first bridge arm is switched from on to off, if it is detected at a first moment that the upper switch of the first bridge arm is switched from on to off, predicting the moment when the upper switch of the first bridge arm is switched from off to on next time according to the first moment; When current flows out from the first end point of the first side of the first power unit, the step S2 includes: Step S203: Detecting whether the lower switch of the first bridge arm switches from on to off, if it is detected at a first moment that the lower switch of the first bridge arm switches from on to off, predicting the moment when the lower switch of the first bridge arm switches from on to off next time according to the first moment; or Step S204: Detect whether the lower switch of the first bridge arm switches from on to off. If it is detected at the first moment that the lower switch of the first bridge arm switches from on to off, predict the moment when the lower switch of the first bridge arm switches from off to on next time based on the first moment.

15. The control method according to claim 13, characterized in that: The first side of the first power unit and the second power unit both include a first endpoint and a second endpoint, the second endpoint of the first side of the first power unit is connected to the midpoint of the first bridge arm, and the first endpoint of the first side of the second power unit is connected to the midpoint of the second bridge arm; The switch unit comprises: A third bridge arm is connected in parallel with the first capacitor unit; as well as a fourth bridge arm connected in parallel with the second capacitor unit, the resonant capacitor being connected between a midpoint of the third bridge arm and a midpoint of the fourth bridge arm, the first bridge arm, the second bridge arm, the third bridge arm and the fourth bridge arm all comprising an upper switch and a lower switch connected in series, When current flows into the first end point of the first side of the first power unit, the step S2 includes: Step S21: before the upper switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or Step S22: before the upper switch of the first bridge arm is turned off, asynchronously turning on the upper switch of the third bridge arm and the upper switch of the fourth bridge arm; or Step S23: after the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or Step S24: before the upper switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or Step S25: before the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or Step S26: after the upper switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; When current flows out from the first end point of the first side of the first power unit, the step S2 includes: Step S27: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned on; or Step S28: before the lower switch of the first bridge arm is turned off, asynchronously turning on the upper switch of the third bridge arm and the upper switch of the fourth bridge arm; or Step S29: after the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned on asynchronously; or Step S30: before the lower switch of the first bridge arm is turned off, one of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off, and after the upper switch of the first bridge arm is switched from on to off, the other of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is turned off; or Step S31: before the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously; or Step S32: After the lower switch of the first bridge arm is turned off, the upper switch of the third bridge arm and the upper switch of the fourth bridge arm are turned off asynchronously.

16. The control method according to claim 15, characterized in that: In the step S21, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-on time interval of the upper switch of the third bridge arm and the turn-off time interval of the upper switch of the first bridge arm is 2×T / 3; In the step S22, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 3; In the step S23, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 3 or 5×T / 6; In the step S24, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6; In the step S25, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6; In the step S26, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 6; In the step S27, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6; In the step S28, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6; In the step S29, the turn-on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the interval between the turn-on time of the upper switch of the third bridge arm and the turn-off time of the upper switch of the first bridge arm is T / 6; In the step S30, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is 2×T / 3; In the step S31, the on time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is 5×T / 6 or T / 6, and the off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3; In step S32, the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the fourth bridge arm is T / 3 or T / 6, and the turn-off time interval of the upper switch of the third bridge arm and the upper switch of the first bridge arm is T / 3 or 5×T / 6.

17. The control method according to claim 9, characterized in that: The first power unit further includes a seventh bridge arm, the seventh bridge arm is connected in parallel with the first bridge arm, a midpoint of the first bridge arm and a midpoint of the seventh bridge arm are connected to the first side of the first power unit, and The second power unit further includes an eighth bridge arm, the eighth bridge arm is connected in parallel with the second bridge arm, and the midpoint of the second bridge arm and the midpoint of the eighth bridge arm are connected to the first side of the second power unit.

18. The control method according to claim 9, characterized in that: The positive end of the first capacitor unit and the midpoint of the first bridge arm are connected to the first side of the first power unit, and the negative end of the second capacitor unit and the midpoint of the second bridge arm are connected to the first side of the second power unit.

19. A power conversion system, characterized in that: It comprises N power conversion modules as described in any one of claims 1 to 8, where N is an integer greater than or equal to 1.

20. The power conversion system according to claim 19, characterized in that: The first side of the first power unit and the first side of the second power unit are connected in series to form the first side of the power conversion module. The first sides of N power conversion modules are connected in series, where N>=2.

21. The power conversion system according to claim 20, characterized in that: It also includes an AC / DC circuit, wherein the first sides of N power conversion modules are connected in series to the DC side of the AC / DC circuit.

22. The power conversion system according to claim 19, characterized in that: It also includes an AC / DC circuit, wherein the first side of the first power unit and the first side of the second power unit are connected in series to a DC side of the AC / DC circuit, and N=1.

Images