A bidirectional dc-dc converter and a control method thereof

Abstract

The application relates to the technical field of direct-current power distribution, and particularly provides a bidirectional direct-current converter and a control method thereof, which comprises a first conversion module, an isolation transformer and a second conversion module; the alternating-current side of the first conversion module is connected with the alternating-current side of the second conversion module through the isolation transformer; the direct-current side of the first conversion module and the direct-current side of the second conversion module are input / output ports of the bidirectional direct-current converter, and the input / output ports are used for connecting direct-current electricity. The application provides a high-voltage and high-power bidirectional isolation type direct-current converter structure with self-balancing capability, so that voltage conversion and bidirectional energy transmission between different voltage grades in a direct-current power distribution network are realized, and the multi-voltage power distribution capability and the energy transmission capability of the direct-current power distribution network are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of direct current power distribution, in particular to a bidirectional direct current converter and a control method thereof. BACKGROUND

[0002] With the development of power electronic control technology and device manufacturing technology, direct current power grid has achieved technical and economic advantages in many fields. Bidirectional isolated direct current converter plays an important role in direct current microgrid, energy storage system, fuel cell, electric vehicle and many other fields. In recent years, due to its energy management, power flow control, high-frequency electrical isolation, control freedom and many other functions, bidirectional isolated direct current converter has become one of the frontiers and hot research directions in the field of power electronics technology.

[0003] Although bidirectional isolated direct current converter has achieved certain results in energy storage system, direct current microgrid, fuel cell, electric vehicle and many other fields, in high-power and high-gain occasions, the traditional isolated topologies generally have problems such as large switching stress, serious switching loss and poor electromagnetic performance. For example, Figure 1 A traditional medium and high voltage direct current converter structure is shown, which adopts a high-voltage side series connection mode to reduce the embedding voltage of a single module, and a parallel connection mode on the low-voltage side to output large current. This structure has the following defects:

[0004] (1) There are differences in parameters and control between series-parallel modules, which can cause uneven voltage distribution on the series side and uneven transmission current on the output side;

[0005] (2) The increase in the number of intermediate transformers causes the complexity of the circuit structure to increase;

[0006] (3) The parallel structure of multiple units can cause operation hazards when energy is transmitted in the reverse direction due to inconsistent actions between units. SUMMARY

[0007] In order to overcome the above defects, the present application provides a bidirectional direct current converter and a control method thereof.

[0008] In a first aspect, a bidirectional direct current converter is provided, which comprises a first conversion module, an isolation transformer and a second conversion module.

[0009] The AC side of the first conversion module is connected to the AC side of the second conversion module through the isolation transformer;

[0010] The DC side of the first conversion module and the DC side of the second conversion module are input / output ports of the bidirectional direct current converter, and the input / output ports are used to access direct current.

[0011] Preferably, the input / output port accesses a DC grid, a distributed power source, an energy storage or a DC load.

[0012] Preferably, the first conversion module and the second conversion module are used for mutual conversion between DC and AC.

[0013] Preferably, the first conversion module comprises a first three-phase full-bridge conversion module, a second three-phase full-bridge conversion module and a third three-phase full-bridge conversion module.

[0014] The DC positive input / output end of the first three-phase full-bridge conversion module and the DC negative input / output end of the third three-phase full-bridge conversion module constitute an input / output port of the bidirectional DC converter.

[0015] The DC negative input / output end of the first three-phase full-bridge conversion module is connected to the DC positive input / output end of the second three-phase full-bridge conversion module.

[0016] The DC negative input / output end of the second three-phase full-bridge conversion module is connected to the DC positive input / output end of the third three-phase full-bridge conversion module.

[0017] The AC a-phase of the first three-phase full-bridge conversion module, the AC b-phase of the second three-phase full-bridge conversion module and the AC c-phase of the third three-phase full-bridge conversion module are respectively connected to the high-voltage side a-phase AC port, the high-voltage side b-phase AC port and the high-voltage side c-phase AC port of the isolation transformer through the corresponding transmission inductors.

[0018] The AC b-phase of the first three-phase full-bridge conversion module is connected to the AC a-phase of the third three-phase full-bridge conversion module through the corresponding transmission inductors.

[0019] The AC c-phase of the first three-phase full-bridge conversion module is connected to the AC a-phase of the second three-phase full-bridge conversion module through the corresponding transmission inductors.

[0020] The AC c-phase of the second three-phase full-bridge conversion module is connected to the AC b-phase of the third three-phase full-bridge conversion module through the corresponding transmission inductors.

[0021] Further, the second conversion module comprises a fourth three-phase full-bridge conversion module, a fifth three-phase full-bridge conversion module and a sixth three-phase full-bridge conversion module.

[0022] The DC negative input / output end of the fourth three-phase full-bridge conversion module, the DC negative input / output end of the fifth three-phase full-bridge conversion module and the DC negative input / output end of the sixth three-phase full-bridge conversion module are connected to each other.

[0023] The direct current positive input / output end of the fourth three-phase full-bridge conversion module, the direct current positive input / output end of the fifth three-phase full-bridge conversion module and the direct current positive input / output end of the sixth three-phase full-bridge conversion module are connected to each other;

[0024] The connecting point at which the direct current negative input / output end of the fourth three-phase full-bridge conversion module, the direct current negative input / output end of the fifth three-phase full-bridge conversion module and the direct current negative input / output end of the sixth three-phase full-bridge conversion module are connected to each other and the connecting point at which the direct current positive input / output end of the fourth three-phase full-bridge conversion module, the direct current positive input / output end of the fifth three-phase full-bridge conversion module and the direct current positive input / output end of the sixth three-phase full-bridge conversion module are connected to each other constitute the input / output port of the bidirectional direct current converter;

[0025] The alternating current a phase of the fourth three-phase full-bridge conversion module, the alternating current b phase of the fifth three-phase full-bridge conversion module and the alternating current c phase of the sixth three-phase full-bridge conversion module are respectively connected to the low-voltage side a phase alternating current port, the low-voltage side b phase alternating current port and the low-voltage side c phase alternating current port of the isolation transformer through the transmission inductors connected thereto;

[0026] The alternating current b phase of the fourth three-phase full-bridge conversion module is connected to the transmission inductor connected to the alternating current a phase of the sixth three-phase full-bridge conversion module;

[0027] The alternating current c phase of the fourth three-phase full-bridge conversion module is connected to the transmission inductor connected to the alternating current a phase of the fifth three-phase full-bridge conversion module;

[0028] The alternating current c phase of the fifth three-phase full-bridge conversion module is connected to the transmission inductor connected to the alternating current b phase of the sixth three-phase full-bridge conversion module.

[0029] Further, the three-phase full-bridge conversion module comprises a first semiconductor switch, a second semiconductor switch, a third semiconductor switch, a fourth semiconductor switch, a fifth semiconductor switch and a sixth semiconductor switch;

[0030] The connecting point at which the emitter of the first semiconductor switch, the emitter of the third semiconductor switch and the emitter of the fifth semiconductor switch are connected to each other is the direct current positive input / output end of the three-phase full-bridge conversion module;

[0031] The connecting point at which the collector of the second semiconductor switch, the collector of the fourth semiconductor switch and the collector of the sixth semiconductor switch are connected to each other is the direct current negative input / output end of the three-phase full-bridge conversion module;

[0032] The connecting point at which the collector of the first semiconductor switch and the emitter of the second semiconductor switch are connected to each other is the alternating current a phase of the three-phase full-bridge conversion module.

[0033] The connection point of the collector of the third semiconductor switch and the emitter of the fourth semiconductor switch is the AC b phase of the three-phase full-bridge conversion module;

[0034] The connection point of the collector of the fifth semiconductor switch and the emitter of the sixth semiconductor switch is the AC c phase of the three-phase full-bridge conversion module.

[0035] In a second aspect, a control method based on the bidirectional DC converter is provided, and the method comprises:

[0036] According to the phase difference between the first conversion module and the second conversion module, a phase-shift control algorithm is used to control the phase AC current of the three-phase full-bridge conversion module in the first conversion module.

[0037] Further, according to the phase difference between the first conversion module and the second conversion module, a phase-shift control algorithm is used to control the phase AC current of the three-phase full-bridge conversion module in the first conversion module, which comprises:

[0038] When the phase difference between the first conversion module and the second conversion module belongs to (0, π / 3), the phase AC current of the three-phase full-bridge conversion module in the first conversion module in the first equal interval in a control cycle is determined according to the following formula:

[0039] i Lx0 = i (t0) + u (t-t0) / 3L Lx (t0)+(u in +nu out )(t-t0) / 3L x

[0040] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the second equal interval in a control cycle is determined according to the following formula:

[0041] i Lx1 = i (t1) + u (t-t1) / 3L Lx (t1)+(u in -nu out )(t-t1) / 3L x

[0042] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the third equal interval in a control cycle is determined according to the following formula:

[0043] i Lx2 = i (t2) + 2u (t-t2) / 3L Lx (t2)+2(u in -nu out )(t-t2) / 3L x

[0044] The phase current of the three-phase full-bridge conversion module in the first conversion module in the fourth equal interval of a control cycle is determined by the following formula:

[0045] i Lx3 =i Lx (t3)+2(u in -nu out )(t-t3) / 3L x

[0046] The phase current of the three-phase full-bridge conversion module in the first conversion module in the fifth equal interval of a control cycle is determined by the following formula:

[0047] i Lx4 =i Lx (t4)+(u in -2nu out )(t-t4) / 3L x

[0048] The phase current of the three-phase full-bridge conversion module in the first conversion module in the sixth equal interval of a control cycle is determined by the following formula:

[0049] i Lx5 =i Lx (t5)+(u in -nu out )(t-t5) / 3L x

[0050] When the phase difference between the first conversion module and the second conversion module belongs to (π / 3, 2π / 3), the phase current of the three-phase full-bridge conversion module in the first conversion module in the first equal interval of a control cycle is determined by the following formula:

[0051] i Lx0 =i Lx (t0)+(u in +2nu out )(t-t0) / 3L x

[0052] The phase current of the three-phase full-bridge conversion module in the first conversion module in the second equal interval of a control cycle is determined by the following formula:

[0053] i Lx1 =i Lx (t1)+(u in +nu out )(t-t1) / 3L x

[0054] The phase current of the three-phase full-bridge conversion module in the first conversion module in the third equal interval of a control cycle is determined by the following formula:

[0055] i Lx2 =i Lx (t2)+(2u in +nu out )(t-t2) / 3L x

[0056] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the fourth equal interval in a control period is determined by the following formula:

[0057] i Lx3 =i Lx (t3)+(2u in -nu out )(t-t3) / 3L x

[0058] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the fifth equal interval in a control period is determined by the following formula:

[0059] i Lx4 =i Lx (t4)+(u in -nu out )(t-t4) / 3L x

[0060] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the sixth equal interval in a control period is determined by the following formula:

[0061] i Lx5 =i Lx (t5)+(u in -2nu out )(t-t5) / 3L x

[0062] wherein y=0, 1, 2, 3, 4 or 5, and x=a, b or c, in the above formula, i Lxy is the x-phase AC current command value of the three-phase full-bridge conversion module in the first conversion module in the y+1 equal interval in a control period, i Lx (t y ) is the x-phase AC current value of the three-phase full-bridge conversion module in the first conversion module at the starting time t y of the y+1 equal interval in a control period, u in is the input voltage of the first conversion module, u out is the output voltage of the first conversion module, n is the turns ratio of the isolation transformer, t is the current time, and L x is the x-phase equivalent leakage inductance of the three-phase full-bridge conversion module in the first conversion module.

[0063] In a third aspect, a storage medium is provided, which includes a stored program, wherein the storage medium is caused to perform the control method of the bidirectional DC converter when the program is run.

[0064] In a fourth aspect, a processor is provided, which is used to run a program, wherein the processor is caused to perform the control method of the bidirectional DC converter when the program is run.

[0065] The one or more technical solutions of the present application have at least one or more of the following beneficial effects:

[0066] The present application relates to the technical field of DC power distribution, and specifically provides a bidirectional DC converter and a control method thereof, which comprises a first conversion module, an isolation transformer and a second conversion module; an AC side of the first conversion module is connected to an AC side of the second conversion module through the isolation transformer; a DC side of the first conversion module and a DC side of the second conversion module are input / output ports of the bidirectional DC converter, and the input / output ports are used to access DC power. The present application improves the traditional double-active full-bridge structure and provides a high-voltage and high-power bidirectional isolation type DC converter structure with self-balancing capability, which can greatly reduce the fault isolation response time, uses an additional switching device to realize fault isolation, does not need mechanical equipment to act, and has fast response speed. Meanwhile, when the fault is isolated, all switching devices are turned off with zero current. Further, voltage conversion and bidirectional energy transmission between different voltage levels in a DC power distribution network are realized, and the multi-voltage power distribution capability and energy transmission capability of the DC power distribution network are improved. BRIEF DESCRIPTION OF DRAWINGS

[0067] Figure 1 is a traditional medium and high voltage DC converter structure block diagram;

[0068] Figure 2 is a main structure block diagram of the bidirectional DC converter of the present application;

[0069] Figure 3 is a specific structure block diagram of the bidirectional DC converter in the specific embodiment of the present application;

[0070] Figure 4 is an equivalent topology diagram of the conversion module of the bidirectional DC converter in the specific embodiment of the present application;

[0071] Figure 5 is an equivalent topology diagram of the three-phase full-bridge conversion module of the bidirectional DC converter in the specific embodiment of the present application;

[0072] Figure 6 is an equivalent topology diagram of the isolation transformer of the bidirectional DC converter in the specific embodiment of the present application. DETAILED DESCRIPTION

[0073] The specific embodiments of the present application will be further described in details below with reference to the drawings.

[0074] To make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0075] Referring to the drawings Figure 2 , Figure 2 is the main structure diagram of the bidirectional DC converter of the present application. As Figure 2 shown, the bidirectional DC converter of the present application mainly comprises a first conversion module, an isolation transformer and a second conversion module;

[0076] The AC side of the first conversion module is connected to the AC side of the second conversion module through the isolation transformer;

[0077] The DC side of the first conversion module and the DC side of the second conversion module are input / output ports of the bidirectional DC converter, and the input / output ports are used for connecting DC power.

[0078] In an embodiment, the input / output ports are connected to a DC power grid, a distributed power source, energy storage or a DC load.

[0079] In an embodiment, the first conversion module and the second conversion module are used for mutual conversion between DC power and AC power.

[0080] Specifically, the first conversion module comprises a first three-phase full-bridge conversion module, a second three-phase full-bridge conversion module and a third three-phase full-bridge conversion module;

[0081] The DC positive input / output end of the first three-phase full-bridge conversion module and the DC negative input / output end of the third three-phase full-bridge conversion module constitute the input / output ports of the bidirectional DC converter;

[0082] The DC negative input / output end of the first three-phase full-bridge conversion module is connected to the DC positive input / output end of the second three-phase full-bridge conversion module;

[0083] The DC negative input / output end of the second three-phase full-bridge conversion module is connected to the DC positive input / output end of the third three-phase full-bridge conversion module;

[0084] The AC a phase of the first three-phase full-bridge conversion module, the AC b phase of the second three-phase full-bridge conversion module and the AC c phase of the third three-phase full-bridge conversion module are connected to the high-voltage side a phase AC port, the high-voltage side b phase AC port and the high-voltage side c phase AC port of the isolation transformer through the transmission inductors connected thereto respectively;

[0085] The AC b phase of the first three-phase full-bridge conversion module is connected to the transmission inductor connected to the AC a phase of the third three-phase full-bridge conversion module;

[0086] The AC c phase of the first three-phase full-bridge conversion module is connected to the transmission inductor connected to the AC a phase of the second three-phase full-bridge conversion module;

[0087] The AC c phase of the second three-phase full-bridge conversion module is connected to the transmission inductor connected to the AC b phase of the third three-phase full-bridge conversion module.

[0088] The second conversion module comprises a fourth three-phase full-bridge conversion module, a fifth three-phase full-bridge conversion module and a sixth three-phase full-bridge conversion module;

[0089] The DC negative input / output terminals of the fourth three-phase full-bridge conversion module, the fifth three-phase full-bridge conversion module and the sixth three-phase full-bridge conversion module are connected to each other;

[0090] The DC positive input / output terminals of the fourth three-phase full-bridge conversion module, the fifth three-phase full-bridge conversion module and the sixth three-phase full-bridge conversion module are connected to each other;

[0091] The connection points at which the DC negative input / output terminals of the fourth three-phase full-bridge conversion module, the fifth three-phase full-bridge conversion module and the sixth three-phase full-bridge conversion module are connected to each other and the connection points at which the DC positive input / output terminals of the fourth three-phase full-bridge conversion module, the fifth three-phase full-bridge conversion module and the sixth three-phase full-bridge conversion module are connected to each other constitute the input / output port of the bidirectional DC converter;

[0092] The AC a phase of the fourth three-phase full-bridge conversion module, the AC b phase of the fifth three-phase full-bridge conversion module and the AC c phase of the sixth three-phase full-bridge conversion module are connected to the low-voltage side a phase AC port, the low-voltage side b phase AC port and the low-voltage side c phase AC port of the isolation transformer through the transmission inductors connected thereto respectively;

[0093] The AC phase b of the fourth three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC phase a of the sixth three-phase full-bridge converter module through its corresponding transmission inductor.

[0094] The AC c phase of the fourth three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC a phase of the fifth three-phase full-bridge converter module through its corresponding transmission inductor.

[0095] The AC c phase of the fifth three-phase full-bridge converter module is connected to the AC b phase of the sixth three-phase full-bridge converter module via its corresponding transmission inductor.

[0096] Furthermore, the three-phase full-bridge converter module includes: a first semiconductor switch, a second semiconductor switch, a third semiconductor switch, a fourth semiconductor switch, a fifth semiconductor switch, and a sixth semiconductor switch;

[0097] The connection point where the emitters of the first semiconductor switch, the third semiconductor switch, and the fifth semiconductor switch are connected is the DC positive input / output terminal of the three-phase full-bridge converter module;

[0098] The connection point where the collectors of the second semiconductor switch, the fourth semiconductor switch, and the sixth semiconductor switch are connected is the DC negative input / output terminal of the three-phase full-bridge converter module;

[0099] The connection point where the collector of the first semiconductor switch and the emitter of the second semiconductor switch are connected is the AC phase a of the three-phase full-bridge converter module;

[0100] The connection point where the collector of the third semiconductor switch and the emitter of the fourth semiconductor switch are connected is the AC phase b of the three-phase full-bridge converter module.

[0101] The connection point where the collector of the fifth semiconductor switch and the emitter of the sixth semiconductor switch are connected is the AC phase c of the three-phase full-bridge converter module.

[0102] In one specific implementation, such as Figure 3 As shown, the bidirectional DC-DC converter provided by this invention may include a DC interface, a conversion circuit, and an AC port. The DC port is used for inputting / outputting DC power; the conversion circuit is used for mutual conversion between DC and AC power. In conversion module A, as shown... Figure 4As shown, it is composed of three three-phase full-bridge conversion modules A1, A2 and A3 in series, the positive input / output end a1 of the conversion module A1 is connected to the first connection terminal T1, the negative input / output end b1 is connected to the positive input / output end a2 of the conversion module A2, the negative input end b2 of the conversion module A2 is connected to the positive input / output end a3 of the conversion module A3, and the negative input / output end b3 of the conversion module A3 is connected to the second connection terminal T2. Meanwhile, each three-phase full-bridge conversion module is composed of six semiconductor switches S1-S6, as shown. Figure 5 As shown. In the conversion module A1, the emitter of the first semiconductor switch S1 and the emitters of the third semiconductor switch S3 and the fifth semiconductor switch S5 are connected to the first connection terminal positive input / output end T1 / a1, the collector of the second semiconductor switch S2 and the collectors of the fourth semiconductor switch S4 and the sixth semiconductor switch S6 are connected to the negative input / output end b1, the collector of the first semiconductor switch S1 and the emitter of the second semiconductor switch S2 are connected to the first common connection point P1, the collector of the third semiconductor switch S3 and the emitter of the fourth semiconductor switch S4 are connected to the second common connection point P2, the collector of the fifth semiconductor switch S5 and the emitter of the sixth semiconductor switch S6 are connected to the third common connection point P3, the first common connection point P1 of the conversion module A1, the second common connection point P2 of the conversion module A2 and the third common connection point P3 of the conversion module A3 are connected to the transmission inductance, and then connected to the AC port of the high-frequency transformer, while the second common connection point P2 of the conversion module A1 and the first common connection point P1 of the conversion module A2 are connected through the transmission inductance, the third common connection point P3 of the conversion module A1 and the first common connection point P1 of the conversion module A3 are connected through the transmission inductance, and the third common connection point P3 of the conversion module A2 and the second common connection point P2 of the conversion module A3 are connected through the transmission inductance; the conversion module B is basically the same as the conversion module A, but the three three-phase full-bridge conversion modules B1, B2 and B3 in the conversion module B are connected in parallel, that is, the positive input / output port c1 of the conversion module B1, the positive input / output port c2 of the conversion module B2 and the positive input / output port c3 of the conversion module B3 are all connected to the third connection terminal T3, and the negative input / output port d1 of the conversion module B1, the negative input / output port d2 of the conversion module B2 and the negative input / output port d3 of the conversion module B3 are all connected to the fourth connection terminal T4; the AC port is used for inputting / outputting AC power.

[0103] For the isolation transformer, as shown Figure 6As shown, it includes a transformer and an alternating current port. The transformer is used to convert alternating current output by the conversion module into another alternating current; the alternating current port is used to input / output alternating current. The high-voltage high-power self-balancing bidirectional direct current converter isolation transformer provided by the present application adopts a star connection / angle connection mode, which has great advantages for switch device current stress.

[0104] Further, based on the above-mentioned bidirectional direct current converter, the present application further provides a control method based on the bidirectional direct current converter, the method comprising:

[0105] According to the phase difference between the first conversion module and the second conversion module, a phase-shift control algorithm is used to control the phase alternating current of the three-phase full-bridge conversion module in the first conversion module.

[0106] In one embodiment, according to the phase difference between the first conversion module and the second conversion module, a phase-shift control algorithm is used to control the phase alternating current of the three-phase full-bridge conversion module in the first conversion module, comprising:

[0107] When the phase difference between the first conversion module and the second conversion module belongs to (0, π / 3), the phase alternating current of the three-phase full-bridge conversion module in the first conversion module in the first equal interval in a control cycle is determined according to the following formula:

[0108] i Lx0 =i Lx (t0)+(u in +nu out )(t-t0) / 3L x

[0109] The phase alternating current of the three-phase full-bridge conversion module in the first conversion module in the second equal interval in a control cycle is determined according to the following formula:

[0110] i Lx1 =i Lx (t1)+(u in -nu out )(t-t1) / 3L x

[0111] The phase alternating current of the three-phase full-bridge conversion module in the first conversion module in the third equal interval in a control cycle is determined according to the following formula:

[0112] i Lx2 =i Lx (t2)+2(u in -nu out )(t-t2) / 3L x

[0113] The phase current of the three-phase full-bridge conversion module in the first conversion module in the fourth equal interval of a control cycle is determined by the following formula:

[0114] i Lx3 =i Lx (t3)+2(u in -nu out )(t-t3) / 3L x

[0115] The phase current of the three-phase full-bridge conversion module in the first conversion module in the fifth equal interval of a control cycle is determined by the following formula:

[0116] i Lx4 =i Lx (t4)+(u in -2nu out )(t-t4) / 3L x

[0117] The phase current of the three-phase full-bridge conversion module in the first conversion module in the sixth equal interval of a control cycle is determined by the following formula:

[0118] i Lx5 =i Lx (t5)+(u in -nu out )(t-t5) / 3L x

[0119] When the phase difference between the first conversion module and the second conversion module belongs to (π / 3, 2π / 3), the phase current of the three-phase full-bridge conversion module in the first conversion module in the first equal interval of a control cycle is determined by the following formula:

[0120] i Lx0 =i Lx (t0)+(u in +2nu out )(t-t0) / 3L x

[0121] The phase current of the three-phase full-bridge conversion module in the first conversion module in the second equal interval of a control cycle is determined by the following formula:

[0122] i Lx1 =i Lx (t1)+(u in +nu out )(t-t1) / 3L x

[0123] The phase current of the three-phase full-bridge conversion module in the first conversion module in the third equal interval of a control cycle is determined by the following formula:

[0124] i Lx2 =i Lx (t2)+(2u in +nu out )(t-t2) / 3L x

[0125] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the fourth equal interval in a control period is determined by the following formula:

[0126] i Lx3 =i Lx (t3)+(2u in -nu out )(t-t3) / 3L x

[0127] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the fifth equal interval in a control period is determined by the following formula:

[0128] i Lx4 =i Lx (t4)+(u in -nu out )(t-t4) / 3L x

[0129] The phase AC current of the three-phase full-bridge conversion module in the first conversion module in the sixth equal interval in a control period is determined by the following formula:

[0130] i Lx5 =i Lx (t5)+(u in -2nu out )(t-t5) / 3L x

[0131] wherein y=0, 1, 2, 3, 4 or 5, and x=a, b or c, in the above formula, i Lxy is the x-phase AC current command value of the three-phase full-bridge conversion module in the first conversion module in the y+1 equal interval in a control period, i Lx (t y ) is the x-phase AC current value of the three-phase full-bridge conversion module in the first conversion module at the start time t y of the y+1 equal interval in a control period, u in is the input voltage of the first conversion module, u out is the output voltage of the first conversion module, n is the ratio of the isolation transformer, t is the current time, and L x is the x-phase equivalent leakage inductance of the three-phase full-bridge conversion module in the first conversion module.

[0132] Further, the present application provides a storage medium including a stored program, wherein the device where the storage medium is located performs the control method of the bidirectional DC / DC converter when the program is run.

[0133] Further, the present application provides a processor for running a program, wherein the control method of the bidirectional DC / DC converter is performed when the program is run.

[0134] Those skilled in the art will understand that embodiments of the present application can be provided as methods, systems, or computer program products. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0135] The present application is described in reference to the flowcharts and / or block diagrams of the methods, apparatus (systems) and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, a special purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions, which are executed via the processor of the computer or other programmable data processing apparatus, generate a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the function specified in the flowchart block or blocks.

[0136] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer readable memory produce a manufacture including an instruction means, which implements the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the function specified in the flowchart block or blocks.

[0137] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus, so that a series of operational steps are performed on the computer or other programmable data processing apparatus to produce a computer implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a means for implementing the functions specified in the flowcharts and / or block diagrams. Figure 1 one or more flows and / or blocks Figure 1 means for carrying out the function specified in the flowchart block or blocks.

[0138] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the specific embodiments of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and any modification or equivalent replacement should be covered within the protection scope of the claims of the present application.

Claims

1. A bidirectional DC-DC converter, characterized in that, The bidirectional DC-DC converter includes: a first conversion module, an isolation transformer, and a second conversion module; The AC side of the first conversion module is connected to the AC side of the second conversion module via an isolation transformer; The DC side of the first conversion module and the DC side of the second conversion module are the input / output ports of the bidirectional DC-DC converter, and the input / output ports are used to connect DC power. The first conversion module includes: a first three-phase full-bridge conversion module, a second three-phase full-bridge conversion module, and a third three-phase full-bridge conversion module; The positive DC input / output terminal of the first three-phase full-bridge converter module and the negative DC input / output terminal of the third three-phase full-bridge converter module constitute the input / output port of the bidirectional DC converter; The DC negative input / output terminal of the first three-phase full-bridge converter module is connected to the DC positive input / output terminal of the second three-phase full-bridge converter module; The DC negative input / output terminal of the second three-phase full-bridge converter module is connected to the DC positive input / output terminal of the third three-phase full-bridge converter module; The AC phase a of the first three-phase full-bridge converter, the AC phase b of the second three-phase full-bridge converter, and the AC phase c of the third three-phase full-bridge converter are respectively connected to the AC port a, AC port b, and AC port c of the high-voltage side of the isolation transformer through their respective transmission inductors. The AC phase b of the first three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC phase a of the second three-phase full-bridge converter module through its corresponding transmission inductor. The AC c phase of the first three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC a phase of the third three-phase full-bridge converter module through its corresponding transmission inductor. The AC c phase of the second three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC b phase of the third three-phase full-bridge converter module through its corresponding transmission inductor. The second conversion module includes: a fourth three-phase full-bridge conversion module, a fifth three-phase full-bridge conversion module, and a sixth three-phase full-bridge conversion module; The DC negative input / output terminals of the fourth three-phase full-bridge converter module, the fifth three-phase full-bridge converter module, and the sixth three-phase full-bridge converter module are interconnected. The DC positive input / output terminals of the fourth three-phase full-bridge converter module, the fifth three-phase full-bridge converter module, and the sixth three-phase full-bridge converter module are interconnected. The connection point where the DC negative input / output terminals of the fourth three-phase full-bridge converter module, the DC negative input / output terminals of the fifth three-phase full-bridge converter module, and the DC negative input / output terminals of the sixth three-phase full-bridge converter module are interconnected, and the connection point where the DC positive input / output terminals of the fourth three-phase full-bridge converter module, the DC positive input / output terminals of the fifth three-phase full-bridge converter module, and the DC positive input / output terminals of the sixth three-phase full-bridge converter module are interconnected, constitute the input / output port of the bidirectional DC-DC converter; The AC phase a of the fourth three-phase full-bridge converter module, the AC phase b of the fifth three-phase full-bridge converter module, and the AC phase c of the sixth three-phase full-bridge converter module are respectively connected to the low-voltage side AC port a, the low-voltage side AC port b, and the low-voltage side AC port c of the isolation transformer through their respective transmission inductors. The AC phase b of the fourth three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC phase a of the fifth three-phase full-bridge converter module through its corresponding transmission inductor. The AC c phase of the fourth three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC a phase of the sixth three-phase full-bridge converter module through its corresponding transmission inductor. The AC c phase of the fifth three-phase full-bridge converter module is connected to the corresponding transmission inductor of the AC b phase of the sixth three-phase full-bridge converter module through its corresponding transmission inductor. The three-phase full-bridge converter module includes: a first semiconductor switch, a second semiconductor switch, a third semiconductor switch, a fourth semiconductor switch, a fifth semiconductor switch, and a sixth semiconductor switch; The connection point where the emitters of the first semiconductor switch, the third semiconductor switch, and the fifth semiconductor switch are connected is the DC positive input / output terminal of the three-phase full-bridge converter module; The connection point where the collectors of the second semiconductor switch, the fourth semiconductor switch, and the sixth semiconductor switch are connected is the DC negative input / output terminal of the three-phase full-bridge converter module; The connection point where the collector of the first semiconductor switch and the emitter of the second semiconductor switch are connected is the AC phase a of the three-phase full-bridge converter module; The connection point where the collector of the third semiconductor switch and the emitter of the fourth semiconductor switch are connected is the AC phase b of the three-phase full-bridge converter module. The connection point where the collector of the fifth semiconductor switch and the emitter of the sixth semiconductor switch are connected is the AC phase c of the three-phase full-bridge converter module.

2. The bidirectional DC-DC converter as described in claim 1, characterized in that, The input / output ports are connected to a DC power grid, distributed power source, energy storage, or DC load.

3. The bidirectional DC-DC converter as described in claim 1, characterized in that, Both the first conversion module and the second conversion module are used for mutual conversion between direct current and alternating current.

4. A control method based on the bidirectional DC-DC converter according to any one of claims 1-3, characterized in that, The method includes: Based on the phase difference between the first conversion module and the second conversion module, a phase-shifting control algorithm is used to control the AC current of each phase of the three-phase full-bridge conversion module in the first conversion module.

5. The method as described in claim 4, characterized in that, The step of controlling the AC current of each phase of the three-phase full-bridge converter in the first converter module using a phase-shift control algorithm based on the phase difference between the first converter module and the second converter module includes: When the phase difference between the first conversion module and the second conversion module is (0, π / 3), the AC current of each phase of the three-phase full-bridge conversion module in the first conversion module within the first equal time interval of a control cycle is determined by the following formula: i Lx0 =i Lx (t0)+(u in +nu out )(t-t0) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the second equally divided time period within a control cycle is determined by the following formula: i Lx1 =i Lx (t1)+(u in -no out )(t-t1) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the third equally divided time period within a control cycle is determined by the following formula: i Lx2 =i Lx (t2)+2(u in -nu out )(t-t2) / 3L x The AC current of each phase of the three-phase full-bridge converter in the first converter module during the fourth equally divided time period within a control cycle is determined by the following formula: to Lx3 =i Lx (t3)+2(u in -of out )(t-t3) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the fifth equally divided time period within a control cycle is determined by the following formula: i Lx4 =i Lx (t4)+(u in -2nu out )(t-t4) / 3L x The AC current of each phase of the three-phase full-bridge converter in the first converter module during the 6th equal time period within a control cycle is determined by the following formula: i Lx5 =i Lx (t5)+(u in -nu out )(t-t5) / 3L x When the phase difference between the first conversion module and the second conversion module is (π / 3, 2π / 3), the AC current of each phase of the three-phase full-bridge conversion module in the first conversion module within the first equal time period of a control cycle is determined by the following formula: i Lx0 =i Lx (t0)+(u in +2nu out )(t-t0) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the second equally divided time period within a control cycle is determined by the following formula: i Lx1 =i Lx (t1)+(u in +no out )(t-t1) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the third equally divided time period within a control cycle is determined by the following formula: i Lx2 =i Lx (t2)+(2u in +nu out )(t-t2) / 3L x The AC current of each phase of the three-phase full-bridge converter in the first converter module during the fourth equally divided time period within a control cycle is determined by the following formula: to Lx3 =i Lx (t3)+(2u in -of out )(t-t3) / 3L x The AC current of each phase of the three-phase full-bridge converter module in the first converter module during the fifth equally divided time period within a control cycle is determined by the following formula: i Lx4 =i Lx (t4)+(u in -nu out )(t-t4) / 3L x The AC current of each phase of the three-phase full-bridge converter in the first converter module during the 6th equal time period within a control cycle is determined by the following formula: i Lx5 =i Lx (t5)+(u in -2 no out )(t-t5) / 3L x Let y = 0, 1, 2, 3, 4 or 5, and x = a, b or c, then in the above formula, i Lxy Let i be the x-phase AC current command value of the three-phase full-bridge converter module in the first converter module during the (y+1)th equally divided time period within a control cycle. Lx (t y () represents the starting time t of the (y+1)th equally divided time interval within a control cycle. y The x-phase AC current value of the three-phase full-bridge converter module in the first converter module, u in u is the input voltage of the first conversion module. out Let n be the output voltage of the first conversion module, n be the turns ratio of the isolation transformer, t be the current time, and L be the voltage level. x The x-phase equivalent leakage inductance is the three-phase full-bridge converter module in the first converter module.

6. A storage medium, characterized in that, The storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the storage medium to perform the method described in any one of claims 4 to 5.

7. A processor, characterized in that, The processor is used to run a program, wherein the program executes the method according to any one of claims 4 to 5 when it runs.

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