Three-phase single-stage electric energy conversion device and control method

Abstract

The invention discloses a three-phase single-stage electric energy conversion device and a control method, and belongs to the field of alternating-current and direct-current electric energy conversion. The three-phase single-stage electric energy conversion device comprises an alternating-current / direct-current conversion circuit and a direct-current / direct-current conversion circuit; the input end of the alternating current / direct current conversion circuit is connected with three-phase alternating current, the output end of the alternating current / direct current conversion circuit is connected with the input end of the direct current / direct current conversion circuit, and the output end of the direct current / direct current conversion circuit is connected with a load. Soft switching of the high-frequency switch is realized, so that switching loss is reduced, higher conversion efficiency is obtained, and meanwhile, three-phase input current control and output voltage control are completed by adjusting the switching frequency of the LLC resonant cavity according to the wide gain characteristic of LLC.

Description

Technical Field

[0001] The present invention relates to the field of AC / DC power conversion, and particularly to a three-phase single-stage power conversion device and a control method therefor. Background Art

[0002] With the explosive growth of distributed energy storage, microgrids, and vehicle-to-grid (V2G) applications, isolated AC / DC conversion devices, as key power electronic devices for converting grid AC power into DC power, have received extensive attention.

[0003] Currently, isolated AC / DC conversion devices generally adopt a two-stage structure. The front stage uses a three-phase PFC converter structure to complete the three-phase current control task, cope with various grid distortion problems, and ensure the power quality of the grid. The rear stage uses an isolated DC / DC structure to achieve electrical isolation between the power supply side and the load side, and achieve stable output voltage under different load conditions. However, due to two-stage power conversion, this structure has disadvantages such as low conversion efficiency and high cost. In addition, the two-stage structure also requires a large-volume bus capacitor to buffer the energy of the front and rear stage converters, which will reduce the reliability of the converter and limit the optimization of its power density.

[0004] Single-stage AC / DC conversion devices can improve the overall efficiency and power density of the converter by reducing the energy conversion level and removing the intermediate DC bus capacitor, which better meets the design requirements of current AC / DC power supply equipment. Structures such as those using a phase-shifted control-based dual-active bridge structure and a matrix conversion structure composed of bidirectional switches with complex conduction timings can also achieve single-stage AC / DC energy conversion through complex control strategies, but they cannot ensure that all switching tubes achieve soft switching under full load conditions. Summary of the Invention

[0005] The present invention aims to provide a three-phase single-stage power conversion device and a control method therefor.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A three-phase single-stage power conversion device includes an AC / DC conversion circuit and a DC / DC conversion circuit. The input end of the AC / DC conversion circuit is connected to three-phase alternating current, the output end of the AC / DC conversion circuit is connected to the input end of the DC / DC conversion circuit, and the output end of the DC / DC conversion circuit is connected to a load.

[0008] Further, the DC / DC conversion circuit includes a capacitor unit, a switch unit, a multi-cavity resonance conversion unit, a rectification unit, a secondary side output unit, and a resonance conversion unit; the capacitor unit is connected to the AC / DC conversion circuit and the switch unit, the input terminals of the switch unit are respectively connected to a first terminal, a second terminal, and a third terminal, the switch unit is connected to the input terminal of the multi-cavity resonance conversion unit, the output terminal of the multi-cavity resonance conversion unit is connected to the input terminal of the rectification unit, the output terminal of the rectification unit is connected to the input terminal of the secondary side output unit, and the output terminal of the secondary side output unit is connected to a load; the input terminal of the resonance conversion unit is connected to the output terminal of the switch unit, and the output terminal of the resonance conversion unit is connected to the output terminal of the rectification unit.

[0009] Further, the multi-cavity resonance conversion unit includes a plurality of arms and a plurality of resonance conversion modules, the rectification unit includes a plurality of rectification modules, the output terminal of the resonance conversion unit is connected in parallel to the output terminal of any one of the rectification modules, the two ends of each arm are connected in parallel to the output terminal of the AC / DC conversion circuit, the first terminal of the input terminal of each resonance conversion module is connected to the midpoint of an arm of one of the arms, the second terminals of the input terminals of each resonance conversion module are connected together, the output terminal of each resonance conversion module is connected to the input terminal of one of the rectification modules, and the output terminals of the plurality of rectification modules obtain an output voltage through the secondary side output unit.

[0010] Further, the secondary side output unit connects the output terminals of the plurality of rectification modules in series or in parallel and then connects to a load.

[0011] Further, the resonance conversion unit is an isolated DC / DC conversion circuit.

[0012] Further, the resonance conversion unit includes a resonance module and a rectification module, the resonance module includes a first inductor, a first capacitor, and a first transformer, the first inductor, the primary winding of the first transformer, and the first capacitor are connected in series, and the two ends after series connection are the input terminals of the resonance conversion unit, the secondary winding of the first transformer is connected to the input terminal of the rectification module, and the output terminal of the rectification module is connected to the rectification module of the multi-cavity resonance conversion unit.

[0013] In a specific embodiment, the switch unit includes a ninth switch, a tenth switch, an eleventh switch, and a twelfth switch, the first end of the ninth switch is connected to the first terminal, the second end of the ninth switch is connected to the first end of the tenth switch, the second end of the tenth switch and the first end of the eleventh switch are connected to the second terminal, the second end of the eleventh switch is connected to the first end of the twelfth switch, and the second end of the twelfth switch is connected to the third terminal.

[0014] In a specific embodiment, the switching unit includes a thirteenth switch, a fourteenth switch, a fifteenth switch, a sixteenth switch, a first bidirectional switch, and a second bidirectional switch. The first ends of the first bidirectional switch and the second bidirectional switch are connected to the second terminal. The first end of the thirteenth switch is connected to the first terminal, and the second end of the thirteenth switch is connected to the second end of the first bidirectional switch. The first end of the fourteenth switch is connected to the first terminal, and the second end of the fourteenth switch is connected to the second end of the second bidirectional switch. The first end of the fifteenth switch is connected to the second end of the first bidirectional switch, and the second end of the fifteenth switch is connected to the third terminal. The first end of the sixteenth switch is connected to the second end of the second bidirectional switch, and the second end of the sixteenth switch is connected to the third terminal.

[0015] In a specific embodiment, the switching unit includes a seventeenth switch, an eighteenth switch, a nineteenth switch, a twentieth switch, a twenty-first switch, a twenty-second switch, a twenty-third switch, a twenty-fourth switch, a twenty-fifth switch, and a twenty-sixth switch. The first ends of the nineteenth switch, the twentieth switch, the twenty-first switch, and the twenty-second switch are connected to the second terminal. The first end of the seventeenth switch is connected to the first terminal, and the second end of the seventeenth switch is connected to the second end of the nineteenth switch through the twenty-third switch, the second end of the twentieth switch through the twenty-fourth switch, the second end of the twenty-first switch through the twenty-fifth switch, and the second end of the twenty-second switch through the twenty-sixth switch. The second end of the seventeenth switch is connected to the third terminal through the eighteenth switch.

[0016] In a specific embodiment, the switching unit includes a twenty-seventh switch, a twenty-eighth switch, a twenty-ninth switch, a thirtieth switch, a third bidirectional switch, and a fourth bidirectional switch. The first ends of the third bidirectional switch and the fourth bidirectional switch are connected to the second terminal. The second end of the third bidirectional switch is connected to the first end of the twenty-ninth switch, and the second end of the fourth bidirectional switch is connected to the first end of the thirtieth switch. The second end of the twenty-ninth switch is connected to the first terminal through the twenty-seventh switch, and the second end of the thirtieth switch is connected to the third terminal through the twenty-eighth switch.

[0017] In a specific embodiment, the switching unit includes a thirty - first switch, a thirty - second switch, a thirty - third switch, a thirty - fourth switch, a thirty - fifth switch, a thirty - sixth switch, a thirty - seventh switch, and a thirty - eighth switch. The first end of the thirty - first switch is connected to the first terminal, the second end of the thirty - first switch is connected to the first end of the thirty - second switch, the second end of the thirty - second switch is connected to the first end of the thirty - third switch, the second end of the thirty - third switch is connected to the first end of the thirty - fourth switch, the second end of the thirty - fourth switch is connected to the third terminal, the second terminal is connected to the connection mid - point between the thirty - second switch and the thirty - third switch, the first end of the thirty - fifth switch is connected to the first end of the thirty - second switch, the second end of the thirty - fifth switch is connected to the first end of the thirty - seventh switch, the second end of the thirty - seventh switch is connected to the first end of the thirty - fourth switch, the first end of the thirty - sixth switch is connected to the first end of the thirty - second switch, the second end of the thirty - sixth switch is connected to the first end of the thirty - eighth switch, and the second end of the thirty - eighth switch is connected to the first end of the thirty - fourth switch.

[0018] A control method for a three - phase single - stage power conversion device, which is applied to the above - mentioned three - phase single - stage power conversion device, includes the following steps:

[0019] Step S1, sampling three - phase alternating current, three - phase input current, and output current;

[0020] Step S2, determining the driving logic of the bidirectional switches S ay , bidirectional switch S by , bidirectional switch S cy and determining the three phases of P, Y, and N;

[0021] Step S3, determining the driving logic of the switches in the switching unit;

[0022] Step S4, determining the driving logic of the switches in the multi - cavity resonant conversion unit.

[0023] In a specific embodiment, when u P >u N , in the positive half - cycle of each switching period, the ninth switch and the eleventh switch are closed, and the tenth switch and the twelfth switch are open; in the negative half - cycle of each switching period, the tenth switch and the eleventh switch are closed, and the ninth switch and the twelfth switch are open;

[0024] When u P <u N , in the positive half - cycle of each switching period, the tenth switch and the twelfth switch are closed, and the ninth switch and the eleventh switch are open; in the negative half - cycle of each switching period, the tenth switch and the eleventh switch are closed, and the ninth switch and the twelfth switch are open.

[0025] In a specific embodiment, when u P > u N , in the positive half - cycle of each switching period, the thirteenth switch and the second bidirectional switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the first bidirectional switch and the fourteenth switch are closed, and the rest of the switches are open;

[0026] When u P < u N , in the positive half - cycle of each switching period, the first bidirectional switch and the sixteenth switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the second bidirectional switch and the fifteenth switch are closed, and the rest of the switches are open.

[0027] In a specific embodiment, when u P > u N , in the positive half - cycle of each switching period, the seventeenth switch, the twenty - second switch, and the twenty - third switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the seventeenth switch, the twenty - first switch, and the twenty - fourth switch are closed, and the rest of the switches are open;

[0028] When u P < u N , in the positive half - cycle of each switching period, the eighteenth switch, the nineteenth switch, and the twenty - sixth switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the eighteenth switch, the twentieth switch, and the twenty - fifth switch are closed, and the rest of the switches are open.

[0029] In a specific embodiment, when u P > u N , in the positive half - cycle of each switching period, the twenty - seventh switch and the twenty - ninth switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the third bidirectional switch is closed, and the rest of the switches are open;

[0030] When u P < u N , in the positive half - cycle of each switching period, the third bidirectional switch, the fourth bidirectional switch, the thirtieth switch, and the twenty - eighth switch are closed, and the rest of the switches are open; in the negative half - cycle of each switching period, the second bidirectional switch is closed, and the rest of the switches are open.

[0031] In a specific embodiment, when u P > u NWhen, the thirty - first switch and the thirty - third switch are closed, and the thirty - second switch and the thirty - fourth switch are open. In the positive half - cycle of each switching period, the thirty - sixth switch and the thirty - seventh switch are closed, and the thirty - fifth switch and the thirty - eighth switch are open; in the negative half - cycle of each switching period, the thirty - fifth switch and the thirty - eighth switch are closed, and the thirty - sixth switch and the thirty - seventh switch are open.

[0032] When u P <u N When, the thirty - second switch and the thirty - fourth switch are closed, and the thirty - first switch and the thirty - third switch are open. In the positive half - cycle of each switching period, the thirty - sixth switch and the thirty - seventh switch are closed, and the thirty - fifth switch and the thirty - eighth switch are open; in the negative half - cycle of each switching period, the thirty - fifth switch and the thirty - eighth switch are closed, and the thirty - sixth switch and the thirty - seventh switch are open.

[0033] Beneficial effects: The present invention adds a resonant conversion circuit to the Swiss - type AC / DC conversion process. By means of the LLC resonant cavity, soft - switching of high - frequency switches is achieved to reduce switching losses and obtain higher conversion efficiency. At the same time, by utilizing the wide - gain characteristic of LLC, the three - phase input current control and output voltage control are completed by adjusting the switching frequency of the LLC resonant cavity. Meanwhile, a multi - cavity parallel structure is adopted, which can effectively reduce the peak value of the resonant cavity current. Without the need for a bus capacitor, only a single - stage structure is required to complete the energy conversion, and a higher power density can be obtained.

[0034] To make the above - mentioned features and advantages of the invention more obvious and understandable, specific embodiments are hereinafter given and described in detail in conjunction with the accompanying drawings as follows. Brief Description of the Drawings

[0035] Figure 1 It is a structural block diagram of a three - phase single - stage power conversion device of the present invention.

[0036] Figure 2 It is a circuit schematic diagram of the first specific embodiment of a three - phase single - stage power conversion device of the present invention.

[0037] Figure 3 It is a circuit schematic diagram of the second specific embodiment of a three - phase single - stage power conversion device of the present invention.

[0038] Figure 4 It is a circuit schematic diagram of the third specific embodiment of a three - phase single - stage power conversion device of the present invention.

[0039] Figure 5 It is a circuit schematic diagram of the fourth specific embodiment of a three - phase single - stage power conversion device of the present invention.

[0040] Figure 6 It is a circuit schematic diagram of the fifth specific embodiment of a three - phase single - stage power conversion device of the present invention.

[0041] Figure 7 This is the circuit schematic diagram of the sixth specific embodiment of the three-phase single-stage power conversion device of the present invention.

[0042] Figure 8 This is the control circuit block diagram of the three-phase single-stage power conversion device of the present invention.

[0043] Figure 9 This is the voltage and current waveform diagram in the upper resonance region.

[0044] Figure 10 This is the voltage and current waveform diagram in the lower resonance region.

[0045] Figure 11 This is the switch drive and voltage and current waveform diagram in the multi-cavity resonance conversion unit.

[0046] Figure 12 This is the voltage and current waveform diagram of the multi-cavity resonance conversion unit when the operating frequency is greater than the resonance frequency.

[0047] Figure 13 This is the voltage and current waveform diagram of the multi-cavity resonance conversion unit when the operating frequency is less than the resonance frequency.

[0048] Figure 14 This is the voltage waveform diagram in the AC / DC conversion circuit.

[0049] Figure 15 This is the circuit schematic diagram of the seventh specific embodiment of the three-phase single-stage power conversion device of the present invention.

[0050] In the drawings, like reference numerals refer to the same elements of the drawings. Detailed Embodiments

[0051] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the drawings of the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0052] As Figure 1 shown is the structural block diagram of the three-phase single-stage power conversion device of the present invention. The three-phase single-stage power conversion device includes an AC / DC conversion circuit 11 and a DC / DC conversion circuit 12. The input end of the AC / DC conversion circuit 11 is connected to three-phase alternating current u A 、u B 、u C, the output terminal of the AC / DC conversion circuit 11 is connected to the input terminal of the DC / DC conversion circuit 12, and the output terminal of the DC / DC conversion circuit 12 is connected to the load.

[0053] More specifically, the AC / DC conversion circuit 11 converts three-phase alternating current u A , u B , u C into three-phase voltages of P, Y, and N, and the DC / DC conversion circuit 12 converts the three-phase voltages of P, Y, and N into direct current to the load.

[0054] As Figure 2 shown is the first specific embodiment of the present invention.

[0055] In this specific embodiment, the AC / DC conversion circuit 21 is a Swiss rectifier circuit.

[0056] The output terminals of the AC / DC conversion circuit 21 are the first terminal P, the second terminal Y, and the third terminal N. The first terminal P, the second terminal Y, and the third terminal N respectively output voltages u P , voltage u Y , voltage u N .

[0057] More specifically, the AC / DC conversion circuit 21 specifically includes diodes D au , diode D bu , diode D cu , diode D ad , diode D bd , diode D cd , bidirectional switches S ay , bidirectional switches S by , bidirectional switches S cy . The anode of diode D au is connected to the cathode of diode D ad . The anode of diode D bu is connected to the cathode of diode D bd . The anode of diode D cu is connected to the cathode of diode D cd . The cathodes of diodes D au , D bu , and D cu are connected together to be the first terminal P. The anodes of diodes D ad , D bd , and D cd are connected together to be the third terminal N. The alternating current u A is connected to diode D au and diode D adThe series midpoint, alternating current u B Connect diode D bu With diode D bd The series midpoint, alternating current u C Connect diode D cu With diode D cd The series midpoint, diode D au With diode D ad Connect the series midpoint of diode D to the bidirectional switch S ay The first end of, diode D bu With diode D bd Connect the series midpoint of diode D to the bidirectional switch S by The first end of, diode D cu With diode D cd Connect the series midpoint of diode D to the bidirectional switch S cy The first end of, bidirectional switch S ay The second end of, bidirectional switch S by The second end of, bidirectional switch S cy The second ends are connected together to form the second terminal Y.

[0058] Optionally, the bidirectional switch S ay The bidirectional switch S by The bidirectional switch S cy Includes two switches connected in reverse series.

[0059] Furthermore, the DC / DC conversion circuit 22 includes a capacitor unit 221, a switch unit 222, a multi-cavity resonance conversion unit 223, a rectification unit 224, a secondary output unit 225 and a resonance conversion unit 226; the capacitor unit 221 is connected to the AC / DC conversion circuit 11 and the switch unit 222, the input ends of the switch unit 222 are respectively connected to the first terminal P, the second terminal Y, the third terminal N, the switch unit 222 is connected to the input end of the multi-cavity resonance conversion unit 223, the output end of the multi-cavity resonance conversion unit 223 is connected to the input end of the rectification unit 224, the output end of the rectification unit 224 is connected to the input end of the secondary output unit 225, and the output end of the secondary output unit 225 is connected to the load; the input end of the resonance conversion unit 226 is connected to the output end of the switch unit 222, and the output end of the resonance conversion unit 226 is connected to the output end of the rectification unit 224.

[0060] Optionally, the resonance conversion unit 226 is an isolated DC / DC conversion circuit, including but not limited to Sigma-LLC circuit, DAB circuit, etc.

[0061] In this application, the circuit is a three-phase three-wire system. Therefore, the sum of the currents is 0. By controlling two line voltages and two phase currents simultaneously, the voltage and current of the entire circuit can be controlled. Among them, the resonant conversion unit 226 controls the larger part of the PY / YN line voltage and the Y current, handling about 22% of the total power; the multi-cavity resonant conversion unit 223 controls the smaller phase of the PN voltage and the P / N current, handling the remaining power. Thus, through a physical method, decoupling of the Y current and the smaller phase of the P / N current is achieved, that is, decoupling from the topology. Therefore, there is no correlation between the two sets of frequency controls, no coupling exists, and it is more convenient in modulation.

[0062] More specifically, the capacitor unit 221 includes capacitor C PY , capacitor C PN , capacitor C NY . The first end of capacitor C PY is connected to the first terminal P, and the second end of capacitor C PY is connected to the second terminal Y; the first end of capacitor C PN is connected to the first terminal P, and the second end of capacitor C PY is connected to the third terminal N; the first end of capacitor C NY is connected to the third terminal N, and the second end of capacitor C PY is connected to the second terminal Y; capacitor C PY , capacitor C PN , capacitor C NY form a low-pass filter for regulating the voltage and current at the first terminal P, the second terminal Y, and the third terminal N, making the system output more stable.

[0063] More specifically, the switch unit 222 includes switch S 9 , switch S 10 , switch S 11 , switch S 12 . The first end of switch S 9 is connected to the first terminal P, the second end of switch S 9 is connected to the first end of switch S 10 , the second end of switch S 10 and the first end of switch S 11 are connected to the second terminal Y, the second end of switch S 11 is connected to the first end of switch S 12 , and the second end of switch S 12 is connected to the third terminal N.

[0064] Further, the multi - cavity resonance conversion unit 223 includes a plurality of arms and a plurality of resonance conversion modules, the rectification unit 224 includes a plurality of rectification and filtering modules, the output end of the resonance conversion unit 226 is connected in parallel to the output end of any of the rectification and filtering modules, both ends of each arm are connected in parallel between the first terminal P and the third terminal N, the first terminal of the input end of each resonance conversion module is connected to the mid - point of an arm of each arm, the second terminals of the input ends of each resonance conversion module are connected together, the output end of each resonance conversion module is connected to the input end of a rectification and filtering module respectively, and the output voltages of the plurality of rectification and filtering modules obtain the output voltage U through the secondary - side output unit 225. dc . Among them, the number of arms is equal to the number of resonance conversion modules. Figure 2 Figure 0000737 shows that the multi - cavity resonance conversion unit 223 includes four arms and four resonance conversion modules. The multi - cavity resonance conversion unit 223 may also include other numbers of arms and resonance conversion modules, and the present invention is not limited thereto.

[0065] Optionally, the resonance - cavity parameters of each resonance conversion module are equal.

[0066] More specifically, the multi - cavity resonance conversion unit 223 includes arm P a - N a , arm P b - N b , arm P c - N c , arm P d - N d . The arm P a - N a includes switches S 1 , S 2 . The switches S 1 , S 2 are connected in series in the same direction; the arm P b - N b includes switches S 3 , S 4 . The switches S 3 , S 4 are connected in series in the same direction; the arm P c - N c includes switches S 5 , S 6 . The switches S 5 , S 6 are connected in series in the same direction; the arm P d - N d includes switches S 7 , S 8 . The switches S 7 , S8 Connected in series in the same direction.

[0067] More specifically, the multi - cavity resonance conversion unit 223 further includes a first resonance conversion module, a second resonance conversion module, a third resonance conversion module, and a fourth resonance conversion module; a first terminal of the input end of the first resonance conversion module is connected to the arm mid - point a of the bridge arm P a -N a A first terminal of the input end of the second resonance conversion module is connected to the arm mid - point b of the bridge arm P b -N b A first terminal of the input end of the third resonance conversion module is connected to the arm mid - point c of the bridge arm P c -N c A first terminal of the input end of the fourth resonance conversion module is connected to the arm mid - point d of the bridge arm P d -N d The second terminals of the input ends of the first resonance conversion module, the second resonance conversion module, the third resonance conversion module, and the fourth resonance conversion module are connected to the common point O.

[0068] The rectification unit 224 includes a first rectification module, a second rectification module, a third rectification module, and a fourth rectification module. The input end of the first rectification module is connected to the output end of the first resonance conversion module, the input end of the second rectification module is connected to the output end of the second resonance conversion module, the input end of the third rectification module is connected to the output end of the third resonance conversion module, and the input end of the fourth rectification module is connected to the output end of the fourth resonance conversion module.

[0069] Optionally, the secondary - side output unit 225 connects the output ends of the first rectification and filtering module, the second rectification and filtering module, the third rectification and filtering module, and the fourth rectification and filtering module in series or in parallel and then connects to the load R o .

[0070] More specifically, the first resonance conversion module includes an inductor L ra , an inductor L ma , a capacitor C ra , a transformer T a , the arm mid - point a of the bridge arm P a -N a , the inductor L ra , the primary winding of the transformer T a , the capacitor C ra , the common point O are connected in sequence. The inductor L ma is in parallel with the primary winding of the transformer T a , and the transformer T aThe secondary winding is connected in parallel with the input end of the first rectifying and filtering module.

[0071] Optionally, the first rectifying and filtering module includes diode D 1a , diode D 2b , diode D 3c , diode D 4d . The diode D 1a , the diode D 2b , the diode D 3c , the diode D 4d form a full-bridge rectification topology.

[0072] The second resonant conversion module, the third resonant conversion module, the fourth resonant conversion module and the first resonant conversion module have the same topological structure; the second rectifying and filtering module, the third rectifying and filtering module, the fourth rectifying and filtering module and the first rectifying and filtering module have the same topological structure, which will not be elaborated here one by one.

[0073] Furthermore, in this specific embodiment, the resonant conversion unit 226 includes a resonant module and a rectifying module. The resonant module includes inductor L re , capacitor C re , transformer T e . The inductor L re , the primary winding of the transformer T e , and the capacitor C re are connected in series. The two ends after series connection are the input end of the resonant conversion unit 226, which is connected to the switching unit 222. The secondary winding of the transformer T e is connected to the input end of the rectifying module, and the output end of the rectifying module is connected in parallel with the output end of the first rectifying module.

[0074] In this specific embodiment, the first terminal of the input end of the resonant conversion unit 226 is connected to the connection midpoint between the switch S 9 and the switch S 10 , and the second terminal of the input end of the resonant conversion unit 226 is connected to the connection midpoint between the switch S 11 and the switch S 12 .

[0075] Optionally, the rectifying unit includes diode D 1e , diode D 2e , diode D 3e , diode D 4e . The diode D 1e , the diode D 2e , the diode D 3e , the diode D 4eForm a full - bridge rectifier topology.

[0076] As Figure 3 shown in the second specific embodiment of the present invention. In this specific embodiment, the switching unit 322 is a full - bridge topology, specifically including switches S 13 , switch S 14 , switch S 15 , switch S 16 , bidirectional switch S dy , bidirectional switch S ey . The first end of the bidirectional switch S dy and the first end of the bidirectional switch S ey are connected to the second terminal Y. The first end of the switch S 13 is connected to the first terminal P. The second end of the switch S 13 is connected to the second end of the bidirectional switch S dy . The first end of the switch S 14 is connected to the first terminal P. The second end of the switch S 14 is connected to the second end of the bidirectional switch S ey . The first end of the switch S 15 is connected to the second end of the bidirectional switch S dy . The second end of the switch S 15 is connected to the third terminal N. The first end of the switch S 16 is connected to the second end of the bidirectional switch S ey . The second end of the switch S 16 is connected to the third terminal N.

[0077] In this specific embodiment, the first terminal of the input end of the resonant conversion unit 326 is connected to the connection mid - point between the switch S 13 and the bidirectional switch S dy . The second terminal of the input end of the resonant conversion unit 326 is connected to the connection mid - point between the bidirectional switch S ey and the switch S 14 .

[0078] Other parts of this specific embodiment are the same as the circuit topology of the specific embodiment in Figure 2 and will not be elaborated here.

[0079] As Figure 4 shown in the third specific embodiment of the present invention. In this specific embodiment, the switching unit 422 is a full - bridge topology including low - frequency switches, specifically including switches S 17 , switch S 18 , switch S 19 , switch S 20 , switch S 21 , switch S22 、 Switch S 23 、 Switch S 24 、 Switch S 25 、 Switch S 26 , the switch S 19 、 the switch S 20 、 the switch S 21 、 the switch S 22 's first end is connected to the second terminal Y, the switch S 17 's first end is connected to the first terminal P, the switch S 17 's second end passes through the switch S 23 and is connected to the switch S 19 's second end, the switch S 17 's second end passes through the switch S 24 and is connected to the switch S 20 's second end, the switch S 17 's second end passes through the switch S 25 and is connected to the switch S 21 's second end, the switch S 17 's second end passes through the switch S 26 and is connected to the switch S 22 's second end, the switch S 17 's second end passes through the switch S 18 and is connected to the third terminal N.

[0080] In this specific embodiment, the first terminal of the input end of the resonant conversion unit 426 is connected to the connection midpoint between the switch S 21 and the switch S 25 , and the connection midpoint between the switch S 19 and the switch S 23 , the second terminal of the input end of the resonant conversion unit 426 is connected to the connection midpoint between the switch S 22 and the switch S 26 , and the connection midpoint between the switch S 20 and the switch S 24 .

[0081] Other parts of this specific embodiment are the same as the circuit topology of the specific embodiment in Figure 2 , and will not be elaborated here.

[0082] As Figure 5 shown is the fourth specific embodiment of the present invention. The switch unit 522 is a half-bridge topology including low-frequency tubes, specifically including switch S 27 、 Switch S 28 、 Switch S 29 、 Switch S 30 、 Bidirectional switch Sfy and a two-way switch S gy , the two-way switch S fy and a two-way switch S gy has its first end connected to the second terminal Y, and the second end of the two-way switch S fy is connected to the first end of the switch S 29 , and the second end of the two-way switch S gy is connected to the first end of the switch S 30 , and the second end of the switch S 29 is connected to the first terminal P through the switch S 27 , and the second end of the switch S 30 is connected to the third terminal N through the switch S 28 .

[0083] In this specific embodiment, the second terminal of the input end of the resonant conversion unit 526 is connected to the second terminal Y, and the first terminal of the input end of the resonant conversion unit 526 is connected to the connection midpoint between the two-way switch S gy and the switch S 30 and the connection midpoint between the two-way switch S fy and the switch S 29 .

[0084] Other parts of this specific embodiment are the same as the circuit topology of the specific embodiment in Figure 2 and will not be elaborated here.

[0085] As Figure 6 shown in the fifth specific embodiment of the present invention, the switch unit 622 includes switches S 31 , switches S 32 , switches S 33 , switches S 34 , switches S 35 , switches S 36 , switches S 37 , switches S 38 , the first end of the switch S 31 is connected to the first terminal P, the second end of the switch S 31 is connected to the first end of the switch S 32 , the second end of the switch S 32 is connected to the first end of the switch S 33 , the second end of the switch S 33 is connected to the first end of the switch S 34 , the second end of the switch S 34 is connected to the third terminal N, the second terminal Y is connected to the connection midpoint between the switch S 32 and the switch S 33 , and the first end of the switch S 35 is connected to the switch S32 The first end of 35 The second end of is connected to switch S 37 The first end of 37 The second end of is connected to switch S 34 The first end of 36 The first end of is connected to switch S 32 The first end of 36 The second end of is connected to switch S 38 The first end of 38 The second end of is connected to switch S 34 The first end.

[0086] Among them, switch S 31 , switch S 32 , switch S 33 , switch S 34 are low-frequency switches, and switch S 35 , switch S 36 , switch S 37 , switch S 38 are high-frequency switches.

[0087] In this specific embodiment, the capacitor unit 621 includes capacitor C PN1 and capacitor C PN2 . The first end of capacitor C PN1 is connected to the second end of switch S 31 . The second end of capacitor C PN1 is connected to the first end of switch S 34 . The first end of capacitor C PN2 is connected to the first terminal P, and the second end of capacitor C PN2 is connected to the third terminal N.

[0088] In this specific embodiment, the first terminal of the input end of the resonant conversion unit 626 is connected to the connection midpoint of the switch S 36 and the switch S 38 . The second terminal of the input end of the resonant conversion unit 626 is connected to the connection midpoint of the switch S 35 and the switch S 37 .

[0089] Figure 6 The topology in improves the utilization rate of high-frequency switches, that is, all high-frequency switches will be utilized in each cycle, and there will be no situation where some switches are not utilized due to different working regions. At the same time, the use of filter capacitors is reduced. In the first to fourth specific embodiments, filter capacitors are required between the PN / YN / PY voltages, and now only two places need to add filter capacitors.

[0090] In the first to fourth specific embodiments, since the voltages corresponding to the rectification of the AC / DC conversion circuit are directly connected to different working areas, filtering is required for both when calling the PY / YN voltages before inputting them to the high-frequency components. In this specific embodiment, only filtering before input is needed. Therefore, only a filter capacitor needs to be added in front of the high-frequency switch to filter out the high-frequency components. Since the PN voltage is constantly processed in the four-chamber part, filtering the PN voltage is sufficient.

[0091] As Figure 7 shown in the sixth specific embodiment of the present invention, the switches S 32 and S 33 in the fifth specific embodiment are replaced with diodes D 1 and D 2 . The switch unit 722 includes switches S 31 , D 1 , D 2 , S 34 , S 35 , S 36 , S 37 , S 38 , S 31 . The first end of switch S 31 is connected to the first terminal P. The second end of switch S 1 is connected to the cathode of diode D 1 . The anode of diode D 2 is connected to the cathode of diode D 2 . The anode of diode D 34 is connected to the first end of switch S 34 . The second end of switch S 1 is connected to the third terminal N. The second terminal Y is connected to the connection midpoint of diode D 2 and D 35 . The first end of switch S 1 is connected to the cathode of diode D 35 . The second end of switch S 37 is connected to the first end of switch S 37 . The second end of switch S 34 is connected to the first end of switch S 36 . The first end of switch S 1 is connected to the cathode of diode D 36 . The second end of switch S 38 is connected to the first end of switch S 38 . The second end of switch S 34 is connected to the first end of switch S

[0092] In this specific embodiment, two switches that select the Y port in the low-frequency switch are replaced with diodes, reducing costs and losses. Taking the selection of the P / Y port as an example, when the P transistor is turned on, since the voltage always has u P >u Y , at this time, the diode is turned off under negative voltage and does not need to be turned off by program control. When the P transistor is turned off, since the inductor current cannot change suddenly, according to Kirchhoff's current (KCL) equation, it can be obtained that the current direction of the Y transistor is always upward and there is no reverse current. The diode can be naturally turned on as long as the diode direction is the same as the current direction and no control for turning on is required. The selection of the Y and N phases is the same, and one switching transistor can be replaced with a body diode. Among them, the P transistor is switch S 31 , the N transistor is switch S 32 , and the Y transistor is diode D 1 or diode D 2 according to different working states.

[0093] As Figure 15 shown, this is the seventh specific embodiment of the present invention. In this specific embodiment, the secondary rectification is integrated and then connected to a voltage multiplier circuit, which can realize the functions of high-frequency rectification and voltage multiplication and expand the output range.

[0094] The present invention also provides a control method for a three-phase single-stage power conversion device. The following description is based on the first specific embodiment. Refer to Figure 8 shown, and specifically includes the following steps:

[0095] Step S1, sample three-phase alternating current u A , u B , u C , three-phase input currents i A , i B , i C , and output current i o .

[0096] Step S2, determine the driving logic of the bidirectional switches S ay , S by , S cy in the AC / DC conversion circuit and determine the P, Y, and N phases.

[0097] More specifically, the bidirectional switches S ay , S by , S cy are switched on at low frequency when the two-phase voltages intersect. Please refer to Figure 14 , the bidirectional switches S ay , S by , S cyAmong them, the switch corresponding to the phase with the larger absolute value of the voltage amplitude in the two intersecting phases is turned off, and at the same time, the switch corresponding to the phase with the smaller amplitude is turned on. In this way, the phase with the larger amplitude in the positive voltage passes through the diode D at the upper end au or diode D bu or diode D cu and is connected to the first terminal P. The phase with the larger amplitude in the negative voltage passes through the diode D at the lower end ad or diode D bd or diode D cd and is connected to the third terminal N. The remaining phase is connected to the second terminal Y through the conducting bidirectional switch S ay or bidirectional switch S by or bidirectional switch S cy Among them, the voltage u P is the phase with the larger amplitude in the positive voltage of the three-phase alternating current, the voltage u N is the phase with the larger amplitude in the negative voltage of the three-phase alternating current, and the voltage u Y is the remaining phase of the three-phase alternating current.

[0098] Furthermore, through the voltage u P and the voltage u Y and the voltage u N three positive line voltages u PY and line voltage u YN and line voltage u PN can be obtained. Whether the input voltage is normal power supply or there are problems such as distortion or three-phase imbalance, the line voltage u PN is always the largest one, and the line voltage u PY and the line voltage u YN alternate.

[0099] Step S3, determine the drive logic of the switches in the switch unit.

[0100] More specifically, the output current i o is compared with the output current reference value i ref and modulated to output the maximum current value I max . The modulation can be PI modulation; the absolute values of the N-phase currents i N are taken to obtain the absolute values of the N-phase currents |i N |, and the absolute values of the N-phase phases sinθ N are taken to obtain the absolute values of the N-phase phases |sinθ N |; the absolute values of the P-phase currents i P are taken to obtain the absolute values of the P-phase currents |i P |, and the absolute values of the P-phase phases sinθ P are taken to obtain the absolute values of the P-phase phases |sinθ P|; For the Y-phase current i Y Take the absolute value to obtain the absolute value of the Y-phase current |i Y |, for the Y-phase phase sinθ Y Take the absolute value to obtain the absolute value of the Y-phase phase |sinθ Y |; Multiply the absolute value of the Y-phase phase |sinθ Y | by the peak value I of the input current max To obtain the reference value I of the Y-phase current Yref ; Multiply the absolute value of the N-phase phase |sinθ N | by the peak value I of the input current max To obtain the reference value I of the N-phase current Nref ; Multiply the absolute value of the P-phase phase |sinθ P | by the peak value I of the input current max To obtain the reference value I of the P-phase current pref .

[0101] Compare the reference value I of the Y-phase current Yref with the absolute value of the Y-phase current |i Y |, and after PI regulation, obtain the frequency f of the voltage u applied to the input resonator Y ; When u Y > u P >, compare the reference value I of the N-phase current N with the absolute value of the N-phase current |i Nref |, and after PI regulation, obtain the frequency f of the voltage u applied to the input resonator N ; When u N < u N P N < u N P Pref P P |, and after PI regulation, obtain the frequency f of the voltage u applied to the input resonator P ; According to the frequency f P or the frequency f N or the frequency f P and the frequency f Y Perform frequency control to determine the drive logic of the switches in the switch unit.

[0102] More specifically, in the first specific embodiment, the drive logic of the switches includes:

[0103] When u P > u N >, in the positive half-cycle of each switching period, switch S 9 and switch S 11 are closed, switch S 10 and switch S 12 are open, and at this time the input voltage U PYTo the resonance conversion unit; in the negative half-cycle of each switching period, switch S 10 and switch S 11 are closed, and switch S 9 and switch S 12 are opened, and at this time, zero level is input to the resonance conversion unit. Figure 9 Shows the voltage and current waveforms in the upper resonance region, where i Lr_sigma is the resonance current of the resonance conversion unit, and i Lm_sigma is the exciting current of the resonance conversion unit.

[0104] When u P <u N In the positive half-cycle of each switching period, switch S 10 and switch S 12 are closed, and switch S 9 and switch S 11 are opened, and at this time, the input voltage U YN is input to the resonance conversion unit; in the negative half-cycle of each switching period, switch S 10 and switch S 11 are closed, and switch S 9 and switch S 12 are opened, and at this time, zero level is input to the resonance conversion unit. Figure 10 Shows the voltage and current waveforms in the lower resonance region, where i Lr_sigma is the resonance current of the resonance conversion unit, and i Lm_sigma is the exciting current of the resonance conversion unit.

[0105] More specifically, in the second specific embodiment, the driving logic of the switches includes:

[0106] When u P >u N In the positive half-cycle of each switching period, switch S 13 , bidirectional switch S ey are closed, and the remaining switches are opened, and at this time, the input voltage U PY is input to the resonance conversion unit; in the negative half-cycle of each switching period, bidirectional switch S dy , switch S 14 are closed, and the remaining switches are opened, and at this time, the input voltage -U PY is input to the resonance conversion unit.

[0107] When u P <u N In the positive half-cycle of each switching period, bidirectional switch S dy , switch S 16 are closed, and the remaining switches are opened, and at this time, the input voltage U YN is input to the resonance conversion unit; in the negative half-cycle of each switching period, bidirectional switch Sey and switch S 15 is closed, and the rest of the switches are open. At this time, the input voltage is -U YN to the resonance conversion unit.

[0108] More specifically, in the third specific embodiment, the driving logic of the switches includes:

[0109] When u P > u N during the positive half cycle of each switching period, switches S 17 , switch S 22 , switch S 23 are closed, and the rest of the switches are open. At this time, the input voltage is U PY to the resonance conversion unit; during the negative half cycle of each switching period, switches S 17 , switch S 21 , switch S 24 are closed, and the rest of the switches are open. At this time, the input voltage is -U PY to the resonance conversion unit.

[0110] When u P < u N during the positive half cycle of each switching period, switches S 18 , switch S 19 , switch S 26 are closed, and the rest of the switches are open. At this time, the input voltage is U YN to the resonance conversion unit; during the negative half cycle of each switching period, switches S 18 , switch S 20 , switch S 25 are closed, and the rest of the switches are open. At this time, the input voltage is -U YN to the resonance conversion unit.

[0111] More specifically, in the fourth specific embodiment, the driving logic of the switches includes:

[0112] When u P > u N during the positive half cycle of each switching period, switches S 27 , switch S 29 are closed, and the rest of the switches are open. At this time, the input voltage is U PY to the resonance conversion unit; during the negative half cycle of each switching period, the bidirectional switch S fy is closed, and the rest of the switches are open. At this time, the input zero level is to the resonance conversion unit.

[0113] When u P < u N during the positive half cycle of each switching period, the bidirectional switch S fy , the bidirectional switch S gy , switch S30 、 Switch S 28 is closed, and the rest of the switches are open. At this time, the input voltage U YN is applied to the resonant conversion unit; in the negative half-cycle of each switching period, the bidirectional switch S gy is closed, and the rest of the switches are open. At this time, the input zero level is applied to the resonant conversion unit.

[0114] More specifically, in the fifth specific embodiment, the driving logic of the switches includes:

[0115] When u P > u N , switches S 31 and S 33 are closed, and switches S 32 and S 34 are open. In the positive half-cycle of each switching period, switches S 36 and S 37 are closed, and switches S 35 and S 38 are open. At this time, the input voltage U PY is applied to the resonant conversion unit; in the negative half-cycle of each switching period, switches S 35 and S 38 are closed, and switches S 36 and S 37 are open. At this time, the input voltage -U PY is applied to the resonant conversion unit.

[0116] When u P < u N , switches S 32 and S 34 are closed, and switches S 31 and S 33 are open. In the positive half-cycle of each switching period, switches S 36 and S 37 are closed, and switches S 35 and S 38 are open. At this time, the input voltage U YN is applied to the resonant conversion unit; in the negative half-cycle of each switching period, switches S 35 and S 38 are closed, and switches S 36 and S 37 are open. At this time, the input voltage -U YN is applied to the resonant conversion unit.

[0117] More specifically, in the sixth specific embodiment, the driving logic of the switches includes:

[0118] When u P > u N , switch S31 Closed, switch S 34 Open, diode D 2 Conducting, diode D 1 Turned off, during the positive half - cycle of each switching period, switch S 36 and switch S 37 Closed, switch S 35 and switch S 38 Open, at this time the input voltage U PY to the resonant conversion unit; during the negative half - cycle of each switching period, switch S 35 and switch S 38 Closed, switch S 36 and switch S 37 Open, at this time the input voltage - U PY to the resonant conversion unit.

[0119] When u P < u N , switch S 34 Closed, switch S 31 Open, during the positive half - cycle of each switching period, switch S 36 and switch S 37 Closed, switch S 35 and switch S 38 Open, diode D 1 Conducting, diode D 2 Turned off, at this time the input voltage U YN to the resonant conversion unit; during the negative half - cycle of each switching period, switch S 35 and switch S 38 Closed, switch S 36 and switch S 37 Open, diode D 1 Turned off, diode D 2 Turned off, at this time the input voltage - U YN to the resonant conversion unit.

[0120] Furthermore, by adjusting two frequency loops, the transmitted energy per period is adjusted, thereby controlling the current so that the converter current waveform is a part of a sine wave.

[0121] Within each switching period, the positive and negative half - cycle waveforms of the input voltage of each cavity are symmetric and there is no DC bias.

[0122] Step S4, determining the driving logic of the switches in the multi - cavity resonant conversion unit.

[0123] Such as Figure 11As shown, taking four bridge arms and four resonant conversion modules as an example, the two switches of each bridge arm are complementarily turned on; the switching frequencies and duty cycles of the switches of each bridge arm are the same, and the switching logics of each bridge arm are mutually different by 90°; the input voltage waveforms of each resonant conversion module are the same, and the phases are mutually different by 90°; the resonant current waveforms of each resonant conversion module are the same, and the phases are mutually different by 90°, satisfying the equivalent relationship i Lra +i Lrb +i Lrc +i Lrd =0, where i Lra is the resonant current of the resonant cavity of the first resonant conversion module, i Lrb is the resonant current of the resonant cavity of the second resonant conversion module, i Lrc is the resonant current of the resonant cavity of the third resonant conversion module, i Lrd is the resonant current of the resonant cavity of the fourth resonant conversion module. Among them, u a0 -u d0 refers to the voltage of each cavity to the ground, and 0 refers to the ground voltage; U Pa0 and U Na0 refer to the voltage applied to port a to the ground as P or N voltage; each cavity of the four-cavity part applies P voltage for half a cycle and N voltage for half a cycle, and they are mutually staggered by 90°.

[0124] Figure 12 Figure 13 is the voltage and current waveform diagram of the multi-cavity resonant conversion unit when the operating frequency is greater than the resonant frequency. At this time, the resonant capacitors and resonant inductors of each resonant conversion module participate in resonance; is the voltage and current waveform diagram of the multi-cavity resonant conversion unit when the operating frequency is less than the resonant frequency. At this time, the resonant capacitors, resonant inductors, and exciting inductors of each resonant conversion module participate in resonance.

[0125] Among them, the resonant current of each resonant conversion module will be divided into two parts, flowing into the first terminal P and the third terminal N of the AC / DC conversion circuit respectively. The two currents are defined as part of the three-phase current and are given to the three-phase input port.

[0126] More specifically, according to the driving logics of the switches in the steps S2 to S4, the voltages and currents at the first terminal, the second terminal, and the third terminal are adjusted, so as to realize the adjustment of the output voltage and output current of the three-phase single-stage power conversion device.

[0127] The beneficial effects of the present invention are:

[0128] The present invention adds a resonant conversion unit to the Swiss-type AC / DC conversion process, realizes soft switching of high-frequency switching tubes by means of an LLC resonant cavity to reduce switching losses and obtain higher conversion efficiency. At the same time, by utilizing the wide gain characteristic of the LLC, the three-phase input current control and output voltage control are completed by adjusting the switching frequency of the LLC resonant cavity. Meanwhile, a multi-cavity parallel structure is adopted, which can effectively reduce the peak value of the resonant cavity current. Without the need for a bus capacitor, only a single-stage structure is required to complete the energy conversion, and a higher power density can be obtained.

[0129] Although the present invention has been disclosed above by way of examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field to which the present invention pertains may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to that defined by the appended patent application scope.

Claims

1. A three-phase single-stage electric energy conversion device, characterized in that: It includes an AC / DC conversion circuit and a DC / DC conversion circuit; the input end of the AC / DC conversion circuit is connected to three-phase AC power, the output end of the AC / DC conversion circuit is connected to the input end of the DC / DC conversion circuit, and the output end of the DC / DC conversion circuit is connected to a load; The DC / DC conversion circuit comprises a capacitor unit, a switch unit, a multi-cavity resonant conversion unit, a rectifier unit, a secondary output unit and a resonant conversion unit; the capacitor unit is connected to the AC / DC conversion circuit and the switch unit, the input end of the switch unit is respectively connected to a first terminal, a second terminal and a third terminal, the switch unit is connected to the input end of the multi-cavity resonant conversion unit, the output end of the multi-cavity resonant conversion unit is connected to the input end of the rectifier unit, the output end of the rectifier unit is connected to the input end of the secondary output unit, and the output end of the secondary output unit is connected to a load; the input end of the resonant conversion unit is connected to the output end of the switch unit, and the output end of the resonant conversion unit is connected to the output end of the rectifier unit.

2. A three-phase single-stage electric energy conversion device as claimed in claim 1, characterized in that: The multi-cavity resonant conversion unit includes multiple bridge arms and multiple resonant conversion modules, the rectifier unit includes multiple rectifier modules, the output end of the resonant conversion unit is connected in parallel to the output end of any of the rectifier modules, the two ends of each bridge arm are connected in parallel to the output end of the AC / DC conversion circuit, the first terminal of the input end of each of the resonant conversion modules is connected to the midpoint of a bridge arm, the second terminal of the input end of each of the resonant conversion modules is connected together, the output end of each of the resonant conversion modules is connected to the input end of one of the rectifier modules, and the output ends of the multiple rectifier modules obtain output voltages through the secondary output unit.

3. A three-phase single-stage electric energy conversion device as claimed in claim 2, characterized in that: The secondary output unit connects the output ends of the plurality of rectifier modules in series or in parallel and then connects them to a load.

4. A three-phase single-stage electric energy conversion device as claimed in claim 1, characterized in that: The resonant conversion unit is an isolated DC / DC conversion circuit.

5. A three-phase single-stage electric energy conversion device as claimed in claim 4, characterized in that: The resonant conversion unit includes a resonant module and a rectifier module. The resonant module includes a first inductor, a first capacitor, and a first transformer. The first inductor, the primary winding of the first transformer, and the first capacitor are connected in series. The two ends of the series connection are the input ends of the resonant conversion unit. The secondary winding of the first transformer is connected to the input end of the rectifier module. The output end of the rectifier module is connected to the rectifier module of the multi-cavity resonant conversion unit.

6. The three-phase single-stage electric energy conversion device according to claim 1, characterized in that: The switch unit includes a ninth switch, a tenth switch, an eleventh switch, and a twelfth switch, wherein a first end of the ninth switch is connected to the first terminal, a second end of the ninth switch is connected to a first end of the tenth switch, a second end of the tenth switch and a first end of the eleventh switch are connected to the second terminal, a second end of the eleventh switch is connected to a first end of the twelfth switch, and a second end of the twelfth switch is connected to the third terminal.

7. The three-phase single-stage electric energy conversion device according to claim 1, characterized in that: The switch unit includes a thirteenth switch, a fourteenth switch, a fifteenth switch, a sixteenth switch, a first bidirectional switch, and a second bidirectional switch, wherein a first end of the first bidirectional switch and a first end of the second bidirectional switch are connected to the second terminal, a first end of the thirteenth switch is connected to the first terminal, a second end of the thirteenth switch is connected to the second end of the first bidirectional switch, a first end of the fourteenth switch is connected to the first terminal, a second end of the fourteenth switch is connected to the second end of the second bidirectional switch, a first end of the fifteenth switch is connected to the second end of the first bidirectional switch, a second end of the fifteenth switch is connected to the third terminal, a first end of the sixteenth switch is connected to the second end of the second bidirectional switch, and a second end of the sixteenth switch is connected to the third terminal.

8. The three-phase single-stage electric energy conversion device according to claim 1, characterized in that: The switch unit includes a seventeenth switch, an eighteenth switch, a nineteenth switch, a twentieth switch, a twenty-first switch, a twenty-second switch, a twenty-third switch, a twenty-fourth switch, a twenty-fifth switch, and a twenty-sixth switch. The first ends of the nineteenth switch, the twenty-th switch, the twenty-first switch, and the twenty-second switch are connected to the second terminal. The first end of the seventeenth switch is connected to the first terminal. The second end of the seventeenth switch is connected to the second end of the nineteenth switch via the twenty-third switch. The second end of the seventeenth switch is connected to the second end of the 20th switch via the twenty-fourth switch. The second end of the seventeenth switch is connected to the second end of the 21st switch via the twenty-fifth switch. The second end of the seventeenth switch is connected to the second end of the 22nd switch via the twenty-sixth switch. The second end of the seventeenth switch is connected to the third terminal via the eighteenth switch.

9. The three-phase single-stage electric energy conversion device according to claim 1, characterized in that: The switch unit includes a twenty-seventh switch, a twenty-eighth switch, a twenty-ninth switch, a thirtieth switch, a third bidirectional switch, and a fourth bidirectional switch, wherein the first ends of the third bidirectional switch and the fourth bidirectional switch are connected to the second terminal, the second end of the third bidirectional switch is connected to the first end of the twenty-ninth switch, the second end of the fourth bidirectional switch is connected to the first end of the thirtieth switch, the second end of the twenty-ninth switch is connected to the first terminal via the twenty-seventh switch, and the second end of the thirtieth switch is connected to the third terminal via the twenty-eighth switch.

10. The three-phase single-stage electric energy conversion device according to claim 1, characterized in that: The switch unit includes a thirty-first switch, a thirty-second switch, a thirty-third switch, a thirty-fourth switch, a thirty-fifth switch, a thirty-sixth switch, a thirty-seventh switch, and a thirty-eighth switch, wherein a first end of the thirty-first switch is connected to a first terminal, a second end of the thirty-first switch is connected to a first end of the thirty-second switch, a second end of the thirty-second switch is connected to a first end of the thirty-third switch, a second end of the thirty-third switch is connected to a first end of the thirty-fourth switch, a second end of the thirty-fourth switch is connected to a third terminal, and a second terminal is connected to a connection midpoint between the thirty-second switch and the thirty-third switch, a first end of the thirty-fifth switch is connected to a first end of the thirty-second switch, a second end of the thirty-fifth switch is connected to a first end of the thirty-seventh switch, a second end of the thirty-seventh switch is connected to a first end of the thirty-fourth switch, a first end of the thirty-sixth switch is connected to a first end of the thirty-second switch, a second end of the thirty-sixth switch is connected to a first end of the thirty-eighth switch, and a second end of the thirty-eighth switch is connected to a first end of the thirty-fourth switch.

11. A control method for a three-phase single-stage electric energy conversion device, applied to the three-phase single-stage electric energy conversion device according to any one of claims 1 to 10, characterized in that: The steps include: Step S1, sampling three-phase alternating current, three-phase input current, and output current; Step S2, determining the bidirectional switch S in the AC / DC conversion circuit ay , Bidirectional switch S by , Bidirectional switch S cy The driving logic and determine the three phases P, Y and N; Step S3, determining the driving logic of the switch in the switch unit; Step S4, determining the driving logic of the switches in the multi-cavity resonant conversion unit.

12. The control method of the three-phase single-stage electric energy conversion device according to claim 11, characterized in that: When u P >u N When , in the positive half cycle of each switching cycle, the ninth switch and the eleventh switch are closed, and the tenth switch and the twelfth switch are opened; In the negative half cycle of each switching cycle, the tenth switch and the eleventh switch are closed, and the ninth switch and the twelfth switch are opened; When u P N When , in the positive half cycle of each switching cycle, the tenth switch and the twelfth switch are closed, and the ninth switch and the eleventh switch are opened;​ In the negative half cycle of each switching cycle, the tenth switch and the eleventh switch are closed, and the ninth switch and the twelfth switch are opened.

13. The control method of the three-phase single-stage electric energy conversion device according to claim 11, characterized in that: When u P >u N When, in the positive half cycle of each switching cycle, the thirteenth switch and the second bidirectional switch are closed, and the other switches are opened; in the negative half cycle of each switching cycle, the first bidirectional switch and the fourteenth switch are closed, and the other switches are opened; When u P N When , in the positive half cycle of each switching cycle, the first bidirectional switch and the sixteenth switch are closed, and the remaining switches are opened;​ In the negative half cycle of each switching cycle, the second bidirectional switch and the fifteenth switch are closed, and the remaining switches are opened.

14. The control method of the three-phase single-stage electric energy conversion device according to claim 11, characterized in that: When u P >u N When , in the positive half cycle of each switching cycle, the seventeenth switch, the twenty-second switch, and the twenty-third switch are closed, and the remaining switches are opened; in the negative half cycle of each switching cycle, the seventeenth switch, the twenty-first switch, and the twenty-fourth switch are closed, and the remaining switches are opened; When u P N In the positive half cycle of each switching cycle, the eighteenth switch, the nineteenth switch, and the twenty-sixth switch are closed, and the remaining switches are opened; in the negative half cycle of each switching cycle, the eighteenth switch, the twentieth switch, and the twenty-fifth switch are closed, and the remaining switches are opened.​ 15. The control method of the three-phase single-stage electric energy conversion device according to claim 11, characterized in that: When u P >u N When , in the positive half cycle of each switching cycle, the twenty-seventh switch and the twenty-ninth switch are closed, and the other switches are opened; in the negative half cycle of each switching cycle, the third bidirectional switch is closed, and the other switches are opened; When u P N In the positive half cycle of each switching cycle, the third bidirectional switch, the fourth bidirectional switch, the 30th switch, and the 28th switch are closed, and the remaining switches are opened; in the negative half cycle of each switching cycle, the second bidirectional switch is closed, and the remaining switches are opened.​ 16. The control method of the three-phase single-stage electric energy conversion device according to claim 11, characterized in that: When u P >u N When the 31st switch and the 33rd switch are closed, the 32nd switch and the 34th switch are opened; in the positive half cycle of each switching cycle, the 36th switch and the 37th switch are closed, and the 35th switch and the 38th switch are opened; in the negative half cycle of each switching cycle, the 35th switch and the 38th switch are closed, and the 36th switch and the 37th switch are opened; When u P N When , the 32nd switch and the 34th switch are closed, the 31st switch and the 33rd switch are opened, and in the positive half cycle of each switching cycle, the 36th switch and the 37th switch are closed, and the 35th switch and the 38th switch are opened;​ In the negative half cycle of each switching period, the thirty-fifth switch and the thirty-eighth switch are closed, and the thirty-sixth switch and the thirty-seventh switch are opened.

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