Three-port converter suitable for fuel cell vehicle and control method of three-port converter

Abstract

The invention relates to a three-port converter suitable for a fuel cell vehicle and a control method of the three-port converter, and the topological structure of the three-port converter comprises a primary side interleaved Boost circuit and a secondary side phase-shifted full bridge; the input side and the output side of the primary side interleaved Boost circuit are respectively used for connecting a fuel cell stack and a storage battery of the fuel cell automobile; the secondary side phase-shifted full bridge is coupled with the primary side interleaved Boost circuit, and the output side of the secondary side phase-shifted full bridge is used for connecting a high-voltage bus or a load. According to the invention, the defects of large volume and high cost of two independent DC-DC converters are avoided. Three ports of the converter are respectively connected with a fuel cell stack, a storage battery and a high-voltage bus (load), and energy can flow among the three different ports, so that power distribution between the fuel cell and the storage battery can be decoupled and controlled. The method can be widely applied to the field of fuel cell automobile design.

Description

Technical Field

[0001] The invention relates to a three-port converter suitable for a fuel cell vehicle and a control method thereof, belonging to the field of fuel cell vehicle design. Background Art

[0002] According to the way the battery is connected to the high-voltage bus, the topology of fuel cell vehicles is generally divided into a unidirectional DC-DC structure and a bidirectional DC-DC structure. However, these two topologies have the following problems: like Figure 1 As shown in the figure, the unidirectional DC-DC structure is to connect the battery directly in parallel on both sides of the high-voltage bus, without the need for a separate DC-DC converter. The advantages of this structure are simple structure and low cost, but because the battery is directly connected to the high-voltage bus, the high-voltage bus voltage will vary over a large range with the remaining power of the battery, which will cause certain difficulties in motor design. In addition, since this structure has only one DC-DC converter, the power distribution of the battery and the fuel cell can only be indirectly controlled by adjusting the high-voltage bus voltage, and direct energy decoupling control cannot be achieved.

[0003] like Figure 2 As shown in the figure, the bidirectional DC-DC structure is equipped with a DC-DC converter for the fuel cell and the battery respectively, that is, the fuel cell and the battery are connected to the high-voltage bus through a DC-DC converter respectively. The advantage of this structure is that the voltage of the high-voltage bus is relatively constant, and it is convenient to decouple and control the power distribution of the fuel cell and the battery, but the disadvantage is that it is large in size and high in cost. Summary of the invention

[0004] In view of the problems of large bus voltage fluctuations and inability to decouple power control in the electrical systems of current commercial fuel cell vehicles, the purpose of the present invention is to provide a three-port converter suitable for fuel cell vehicles and a control method thereof, which reduces the size and cost of the converter while meeting the requirements of constant high-voltage bus voltage and decoupled power control.

[0005] To achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a three-port converter suitable for fuel cell vehicles, and the topology structure of the three-port converter includes a primary-side interleaved parallel Boost circuit and a secondary-side phase-shifted full-bridge; the input side and the output side of the primary-side interleaved parallel Boost circuit are respectively used to connect the fuel cell stack and the battery of the fuel cell vehicle; the secondary-side phase-shifted full-bridge is coupled to the primary-side interleaved parallel Boost circuit, and the output side of the secondary-side phase-shifted full-bridge is used to connect a high-voltage bus or a load.

[0006] Furthermore, the primary-side staggered parallel Boost circuit includes a first Boost branch and a second Boost branch connected in parallel, and the first Boost branch and the second Boost branch are 180° out of phase with each other.

[0007] Further, the first Boost branch includes a first coupled inductor, a first primary upper switch tube and a first primary lower switch tube, and the second Boost branch includes a second coupled inductor, a second primary upper switch tube and a second primary lower switch tube; One end of the first coupled inductor and the second coupled inductor are connected in parallel and serve as an input side to be connected to the positive electrode of the fuel cell stack in the fuel cell vehicle; The other end of the first coupled inductor is simultaneously connected to the source end of the first primary upper switch tube and the drain end of the first primary lower switch tube; The other end of the second coupled inductor is connected to the source end of the second primary upper switch tube and the drain end of the second primary lower switch tube at the same time; The drain end of the first primary switch tube and the drain end of the second primary switch tube are connected in parallel and connected to the positive electrode of the battery in the fuel cell vehicle as the output side; The source terminal of the first primary lower switch tube and the source terminal of the second primary lower switch tube are connected in parallel and are respectively connected to the negative electrode of the fuel cell stack of the fuel cell vehicle and the negative electrode of the battery; The primary sides of the first coupled inductor and the second coupled inductor are used as filter inductors of the first Boost branch and the second Boost branch respectively; After the secondary sides of the first coupled inductor and the second coupled inductor are connected in reverse series, the leakage inductance is converted to the secondary side phase-shifted full bridge.

[0008] Further, the secondary side phase-shift full bridge includes a third coupled inductor, a fourth coupled inductor and a phase-shift full bridge; The third coupled inductor and the fourth coupled inductor are connected in series, and both ends are respectively connected to the midpoint of the phase-shift full bridge, and the third coupled inductor is coupled to the secondary side of the first coupled inductor in the primary-side staggered parallel Boost circuit, and the fourth coupled inductor is coupled to the second coupled inductor in the primary-side staggered parallel Boost circuit; the phase-shift full bridge is used for phase shifting.

[0009] Further, the phase-shift full bridge comprises a first phase-shift branch, a second phase-shift branch and a capacitor branch connected in parallel; The first phase-shifting branch comprises a first secondary upper switch tube and a first secondary lower switch tube connected in series, and a connection point between the first secondary upper switch tube and the first secondary lower switch tube serves as one of the midpoints of the phase-shifting full bridge; The second phase-shifting branch comprises a second secondary upper switch tube and a second secondary lower switch tube connected in series, and the connection point between the second secondary upper switch tube and the second secondary lower switch tube serves as another midpoint of the phase-shifting full bridge; the two midpoints are respectively connected to the third coupled inductor and the fourth coupled inductor; The capacitor branch is connected with a capacitor, and both ends of the capacitor are connected to a high-voltage bus or a load.

[0010] Furthermore, the duty cycle of the first secondary upper switch tube and the first secondary lower switch tube is 0.5, and the on-time of both is 0.5T; the duty cycle of the second secondary upper switch tube and the second secondary lower switch tube is 0.5, and the on-time of both is 0.5T.

[0011] Furthermore, a phase-shift inductor is further provided in the secondary-side phase-shift full-bridge, and the phase-shift inductor is connected in series with the third coupling inductor and the fourth coupling inductor.

[0012] In a second aspect, the present invention provides a control method for a three-port converter suitable for a fuel cell vehicle, comprising the following steps: The input side and output side of the primary-side staggered parallel Boost circuit in the three-port converter are connected to the fuel cell stack and the battery of the fuel cell vehicle respectively; the output side of the secondary-side phase-shifted full bridge is connected to the high-voltage bus or the load; The voltage on the battery and the voltage on the load are collected, and based on the voltage collection results, the duty cycle of the primary-side interleaved parallel Boost circuit and the phase shift angle of the secondary-side phase-shifted full-bridge are controlled.

[0013] Furthermore, the voltage on the battery and the voltage on the load are collected, and based on the voltage collection results, the duty cycle of the primary-side interleaved parallel Boost circuit and the phase shift angle of the secondary-side phase-shifted full bridge are controlled, including: Collect the voltage on the battery and the voltage on the load; According to the voltage acquisition results, the duty cycle of the primary-side interleaved parallel Boost circuit is designed so that the battery voltage is maintained within the preset range; The phase shift angle of the secondary phase-shifted full-bridge is controlled so that the voltage outputted by the secondary phase-shifted full-bridge to the load meets the preset requirements.

[0014] Furthermore, the phase shift angle of the secondary phase-shifted full bridge is controlled so that the voltage outputted from the secondary phase-shifted full bridge to the load meets a preset requirement, including: Calculate the voltage on both sides of the secondary phase-shifted full bridge; Assume that the voltages on both sides are and ,but The voltage amplitude is expressed as:

[0015] in, Primary voltage The voltage amplitude is, N is the transformer ratio, is the input voltage of the primary-side interleaved parallel Boost circuit, is the duty cycle of the primary-side interleaved parallel Boost circuit; Voltage The voltage amplitude is equal to the output voltage of the phase-shifted full bridge:

[0016] in, is the output voltage of the phase-shifted full bridge, that is, the voltage on the load of the three-port converter; right and The phase shift angle of the voltage waveform is adjusted so that the voltage output from the secondary phase-shifted full-bridge to the load meets the preset requirements.

[0017] The present invention adopts the above technical solution, which has the following advantages: 1. The present invention has designed a new three-port converter, which avoids the disadvantages of large size and high cost of two independent DC-DC converters. The three ports of the converter are respectively connected to the fuel cell stack, the battery and the high-voltage bus (load), which can realize the flow of energy between the three different ports, thereby decoupling and controlling the power distribution between the fuel cell and the battery; 2. The present invention connects the fuel cell stack and the battery to the high-voltage bus respectively through a three-port converter, so that the battery is no longer directly connected in parallel to the high-voltage bus, and the bus voltage can also be controlled to a constant value, which is beneficial to the design of the motor.

[0018] The present invention can be widely applied to the field of fuel cell vehicle design. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings: Figure 1 The existing fuel cell vehicles adopt a unidirectional DC-DC topology structure; Figure 2 The existing fuel cell vehicles use a bidirectional DC-DC topology; Figure 3 The three-port converter topology structure applicable to a fuel cell vehicle provided by an embodiment of the present invention; Figure 4 It is an interleaved parallel Boost converter topology; Figure 5a and Figure 5b is a time domain waveform diagram of a three-port converter provided by an embodiment of the present invention, wherein: Figure 5a The duty cycle is greater than 0.5; Figure 5b The medium duty cycle is less than 0.5; Figure 6 is a control block diagram of a three-port converter provided by an embodiment of the present invention; The reference numerals in the figures are as follows: 1. High-voltage bus; 2. Unidirectional DC-DC; 3. Fuel cell; 4. Battery; 5. Load; 6. Bidirectional DC-DC; 7. Three-port converter; 8. Primary-side staggered parallel Boost circuit; 9. Secondary-side phase-shifted full-bridge; 10. First Boost branch; 11. Second Boost branch; 12. Phase-shifted full-bridge; 13. First phase-shifted branch; 14. Second phase-shifted branch; 15. Capacitor branch. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0021] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0022] In some embodiments of the present invention, a three-port converter suitable for fuel cell vehicles is proposed, and its topological structure includes: a three-port converter, wherein the three ports of the three-port converter are respectively connected to the fuel cell, the battery and the high-voltage bus (load), so that energy can flow between three different ports, thereby decoupling and controlling the power distribution between the fuel cell and the battery, avoiding the shortcomings of two independent DC-DC converters, which are large in size and high in cost. In addition, since the battery is no longer directly connected in parallel to the high-voltage bus, the bus voltage can also be controlled to a constant value, which is beneficial to the design of the motor. The new three-port converter suitable for fuel cell vehicles proposed by the present invention reduces the size and cost of the converter while satisfying the constant bus voltage and power decoupling control.

[0023] In other embodiments of the present invention, a control method for a three-port converter suitable for a fuel cell vehicle is provided.

[0024] Example 1 like Figure 3 , Figure 4 As shown, a three-port converter suitable for a fuel cell vehicle is provided in this embodiment. The topological structure of the three-port converter 7 includes: a primary-side interleaved parallel Boost circuit 8 and a secondary-side phase-shifted full bridge 9. The input side and the output side of the primary-side interleaved parallel Boost circuit 8 are respectively used to connect the fuel cell 3 and the battery 4 of the fuel cell vehicle; the input side of the secondary-side phase-shifted full bridge 9 is coupled with the primary-side interleaved parallel Boost circuit 8, and the output side of the secondary-side phase-shifted full bridge 9 is used to connect the high-voltage bus or the load 5.

[0025] Preferably, if Figure 4 As shown, the primary side staggered parallel Boost circuit 8 includes a first Boost branch 10 and a second Boost branch 11 connected in parallel, and the first Boost branch 10 and the second Boost branch 11 are 180° out of phase with each other, which can effectively reduce the current ripple size on the fuel cell side and increase the service life of the fuel cell stack.

[0026] Specifically, the first Boost branch 10 includes a first coupled inductor L1, a first primary upper switch tube S1 and a first primary lower switch tube S2, and the second Boost branch 11 includes a second coupled inductor L2, a second primary upper switch tube S3 and a second primary lower switch tube S4. Among them, one end of the first coupling inductor L1 and the second coupling inductor L2 are connected in parallel and connected to the positive electrode of the fuel cell 3 in the fuel cell vehicle as the input side; the other end of the first coupling inductor L1 is simultaneously connected to the source end of the first primary upper switch tube S1 and the drain end of the first primary lower switch tube S2; the other end of the second coupling inductor L2 is simultaneously connected to the source end of the second primary upper switch tube S3 and the drain end of the second primary lower switch tube S4; the drain end of the first primary upper switch tube S1 and the drain end of the second primary upper switch tube S3 are connected in parallel and connected to the positive electrode of the battery 4 in the fuel cell vehicle as the output side; the source end of the first primary lower switch tube S2 and the source end of the second primary lower switch tube S4 are connected in parallel and connected to the negative electrode of the fuel cell 3 and the negative electrode of the battery 4 of the fuel cell vehicle respectively. The primary sides of the first coupled inductor L1 and the second coupled inductor L2 are used as filter inductors of the first Boost branch 11 and the second Boost branch 12 respectively; after the secondary sides of the first coupled inductor L1 and the second coupled inductor L2 are connected in reverse series, the leakage inductance is converted to the secondary side phase-shifted full bridge 9.

[0027] Preferably, the secondary side phase-shift full bridge 9 includes a third coupling inductor L3, a fourth coupling inductor L4 and a phase-shift full bridge 12. The third coupling inductor L3 and the fourth coupling inductor L4 are connected in series, and both ends are connected to the midpoint of the phase-shift full bridge 14 respectively, and the third coupling inductor L3 is coupled to the secondary side of the first coupling inductor L1 in the primary side interleaved parallel Boost circuit 8, and the fourth coupling inductor L4 is coupled to the second coupling inductor L2 in the primary side interleaved parallel Boost circuit 8.

[0028] Preferably, the phase-shift full bridge 12 includes a first phase-shift branch 13, a second phase-shift branch 14 and a capacitor branch 15 connected in parallel, the first phase-shift branch 13 includes a first secondary side upper switch tube Q1 and a first secondary side lower switch tube Q2 connected in series, and the connection between the first secondary side upper switch tube Q1 and the first secondary side lower switch tube Q2 serves as one of the midpoints of the phase-shift full bridge 12; the second phase-shift branch 14 includes a second secondary side upper switch tube Q3 and a second secondary side lower switch tube Q4 connected in series, and the connection between the second secondary side upper switch tube Q1 and the second secondary side lower switch tube Q2 serves as another midpoint of the phase-shift full bridge 12, which is respectively connected to the third coupling inductor L3 and the fourth coupling inductor L4; a capacitor is connected to the capacitor branch 15, and both ends of the capacitor are connected to the high-voltage bus 1 or the load 5.

[0029] Among them, the duty cycle of the first secondary upper switch tube Q1 and the first secondary lower switch tube Q2 are both 0.5, and the conduction time of both is 0.5T; the duty cycle of the second secondary upper switch tube Q3 and the second secondary lower switch tube Q4 are both 0.5, and the conduction time of both is 0.5T.

[0030] Preferably, a phase-shift inductor L5 is further provided in the secondary phase-shift full bridge 9, and the phase-shift inductor L5 is connected in series with the third coupling inductor L3 and the fourth coupling inductor L4 to adjust the phase-shift angle of the secondary phase-shift full bridge. The phase-shift inductor L5 can be realized by using the leakage inductance of the first coupling inductor L1 and the second coupling inductor L2 or by connecting an additional inductor.

[0031] Example 2 Based on the three-port converter suitable for a fuel cell vehicle provided in the above embodiment 1, this embodiment provides a control method for a three-port converter suitable for a fuel cell vehicle, comprising the following steps: 1) The input side and output side of the primary-side staggered parallel Boost circuit 8 in the three-port converter 7 are connected to the fuel cell vehicle fuel cell 3 and the battery 4 respectively; the output side of the secondary-side phase-shifted full bridge 9 is connected to the high-voltage bus 1 or the load 5; 2) The voltage on the battery 4 and the voltage on the load 5 are collected, and based on the voltage collection results, the duty cycle of the primary-side interleaved parallel Boost circuit 8 and the phase shift angle of the secondary-side phase-shifted full bridge 9 are controlled.

[0032] Preferably, the above step 2) includes the following steps: 2.1) Collecting the voltage on the battery 3 and the voltage on the load 5; 2.2) According to the voltage acquisition result, the duty cycle of the primary-side staggered parallel Boost circuit 8 is designed so that the voltage of the battery 3 is maintained within a preset range; 2.3) The phase shift angle of the secondary phase-shifted full bridge 9 is controlled so that the voltage outputted from the secondary phase-shifted full bridge 9 to the load 5 meets the preset requirement.

[0033] Specifically, assuming that the switching period of the switch tube in the primary interleaved parallel Boost circuit 8 is T and the duty cycle is D, the conduction time of the first primary lower switch tube S2 and the second primary lower switch tube S4 is DT, and the conduction time of the first primary upper switch tube S1 and the second primary upper switch tube S3 is (1-D) T. By controlling the duty cycle D, the output voltage of the primary interleaved parallel Boost circuit 8, that is, the voltage of the battery 3, can be adjusted.

[0034] Assume that the voltages on both sides of the leakage inductance are and , then the voltage of load 5 can be and It is determined by the phase shift angle of the voltage waveform.

[0035] Primary voltage The voltage amplitude is determined by the output voltage of the primary interleaved parallel Boost circuit 8 and the transformer ratio, while the output voltage of the primary interleaved parallel Boost circuit 8 is determined by its input voltage and duty cycle. The voltage amplitude can be expressed as:

[0036] in, Primary voltage The voltage amplitude is, N is the transformer ratio, is the input voltage of the primary side interleaved parallel Boost circuit 8, is the duty cycle of the primary-side interleaved parallel Boost circuit.

[0037] Secondary voltage The voltage amplitude is equal to the output voltage of the phase-shifted full bridge:

[0038] in, is the output voltage of the phase-shifted full-bridge, that is, the voltage on the load of the three-port converter.

[0039] Example 3 like Figure 5a and Figure 5b As shown in FIG. 1 , it is a time domain waveform diagram of a three-port converter in an embodiment of the present invention. According to whether the duty cycle of the primary-side interleaved parallel Boost circuit in the three-port converter is greater than or less than 0.5, it can be divided into two categories: S 1- S 4 is the driving waveform of the primary switch tube. Q 1- Q 4 is the driving waveform of the secondary switch tube. The primary side adjusts the voltage on the battery by controlling the duty cycle, and the secondary side adjusts the output voltage on the load by controlling the phase shift angle.

[0040] like Figure 6 The control strategy of the three-port converter proposed by the present invention is shown in FIG. The control method requires two voltage sensors to respectively collect the voltage on the battery ( U CL ) and the voltage across the load ( U H ). By controlling the duty cycle of the primary side, the voltage on the battery is maintained within a reasonable range, and by controlling the phase shift angle, the output voltage is controlled.

[0041] The three-port converter proposed in the present invention avoids the disadvantages of large size and high cost of two independent DC-DC converters. The three ports of the converter are respectively connected to the fuel cell stack, the battery and the high-voltage bus (load), so that energy can flow between the three different ports, thereby decoupling and controlling the power distribution between the fuel cell and the battery. In addition, since the battery is no longer directly connected in parallel to the high-voltage bus, the bus voltage can also be controlled to a constant value, which is beneficial to the design of the motor.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A three-port converter suitable for a fuel cell vehicle, characterized in that: The topological structure of the three-port converter includes a primary-side interleaved parallel Boost circuit and a secondary-side phase-shifted full bridge; the input side and output side of the primary-side interleaved parallel Boost circuit are respectively used to connect to a fuel cell stack and a battery of a fuel cell vehicle; the secondary-side phase-shifted full bridge is coupled to the primary-side interleaved parallel Boost circuit, and the output side of the secondary-side phase-shifted full bridge is used to connect to a high-voltage bus or a load.

2. A three-port converter suitable for a fuel cell vehicle as claimed in claim 1, characterized in that: The primary-side staggered parallel Boost circuit includes a first Boost branch and a second Boost branch connected in parallel, and the first Boost branch and the second Boost branch are 180° out of phase with each other.

3. A three-port converter suitable for a fuel cell vehicle as claimed in claim 2, characterized in that: The first Boost branch includes a first coupled inductor, a first primary upper switch tube and a first primary lower switch tube, and the second Boost branch includes a second coupled inductor, a second primary upper switch tube and a second primary lower switch tube; One end of the first coupled inductor and the second coupled inductor are connected in parallel and serve as an input side to be connected to the positive electrode of the fuel cell stack in the fuel cell vehicle; The other end of the first coupled inductor is simultaneously connected to the source end of the first primary upper switch tube and the drain end of the first primary lower switch tube; The other end of the second coupled inductor is connected to the source end of the second primary upper switch tube and the drain end of the second primary lower switch tube at the same time; The drain end of the first primary switch tube and the drain end of the second primary switch tube are connected in parallel and connected to the positive electrode of the battery in the fuel cell vehicle as the output side; The source terminal of the first primary lower switch tube and the source terminal of the second primary lower switch tube are connected in parallel and are respectively connected to the negative electrode of the fuel cell stack of the fuel cell vehicle and the negative electrode of the battery; The primary sides of the first coupled inductor and the second coupled inductor are used as filter inductors of the first Boost branch and the second Boost branch respectively; After the secondary sides of the first coupled inductor and the second coupled inductor are connected in reverse series, the leakage inductance is converted to the secondary side phase-shifted full bridge.

4. A three-port converter suitable for a fuel cell vehicle as claimed in claim 3, characterized in that: The secondary side phase-shift full bridge comprises a third coupled inductor, a fourth coupled inductor and a phase-shift full bridge; The third coupled inductor and the fourth coupled inductor are connected in series, and both ends are respectively connected to the midpoint of the phase-shift full bridge, and the third coupled inductor is coupled to the secondary side of the first coupled inductor in the primary-side staggered parallel Boost circuit, and the fourth coupled inductor is coupled to the second coupled inductor in the primary-side staggered parallel Boost circuit; the phase-shift full bridge is used for phase shifting.

5. A three-port converter suitable for a fuel cell vehicle as claimed in claim 4, characterized in that: The phase-shift full bridge comprises a first phase-shift branch, a second phase-shift branch and a capacitor branch connected in parallel; The first phase-shifting branch comprises a first secondary upper switch tube and a first secondary lower switch tube connected in series, and a connection point between the first secondary upper switch tube and the first secondary lower switch tube serves as one of the midpoints of the phase-shifting full bridge; The second phase-shifting branch comprises a second secondary upper switch tube and a second secondary lower switch tube connected in series, and the connection point between the second secondary upper switch tube and the second secondary lower switch tube serves as another midpoint of the phase-shifting full bridge; the two midpoints are respectively connected to the third coupled inductor and the fourth coupled inductor; The capacitor branch is connected with a capacitor, and both ends of the capacitor are connected to a high-voltage bus or a load.

6. A three-port converter suitable for a fuel cell vehicle as claimed in claim 5, characterized in that: The duty cycle of the first secondary upper switch tube and the first secondary lower switch tube is 0.5, and the on-time of both is 0.5T; the duty cycle of the second secondary upper switch tube and the second secondary lower switch tube is 0.5, and the on-time of both is 0.5T.

7. A three-port converter suitable for a fuel cell vehicle as claimed in claim 4, characterized in that: A phase-shift inductor is also provided in the secondary phase-shift full bridge, and the phase-shift inductor is connected in series with the third coupling inductor and the fourth coupling inductor.

8. A control method for a three-port converter suitable for a fuel cell vehicle, characterized in that The following steps are involved: The input side and output side of the primary-side staggered parallel Boost circuit in the three-port converter are connected to the fuel cell stack and the battery of the fuel cell vehicle respectively; the output side of the secondary-side phase-shifted full bridge is connected to the high-voltage bus or the load; The voltage on the battery and the voltage on the load are collected, and based on the voltage collection results, the duty cycle of the primary-side interleaved parallel Boost circuit and the phase shift angle of the secondary-side phase-shifted full-bridge are controlled.

9. A control method for a three-port converter suitable for a fuel cell vehicle as claimed in claim 7, characterized in that: The voltage on the battery and the voltage on the load are collected, and based on the voltage collection results, the duty cycle of the primary-side staggered parallel Boost circuit and the phase shift angle of the secondary-side phase-shifted full bridge are controlled, including: Collect the voltage on the battery and the voltage on the load; According to the voltage acquisition results, the duty cycle of the primary-side interleaved parallel Boost circuit is designed so that the battery voltage is maintained within the preset range; The phase shift angle of the secondary phase-shifted full-bridge is controlled so that the voltage outputted by the secondary phase-shifted full-bridge to the load meets the preset requirements.

10. A control method for a three-port converter suitable for a fuel cell vehicle as claimed in claim 7, characterized in that: The controlling of the phase shift angle of the secondary phase-shifted full bridge so that the voltage outputted from the secondary phase-shifted full bridge to the load meets a preset requirement includes: Calculate the voltage on both sides of the secondary phase-shifted full bridge; Assume that the voltages on both sides are and ,but The voltage amplitude is expressed as: in, Primary voltage The voltage amplitude, N is the transformer ratio, is the input voltage of the primary-side interleaved parallel Boost circuit, is the duty cycle of the primary-side interleaved parallel Boost circuit; Voltage The voltage amplitude is equal to the output voltage of the phase-shifted full bridge: in, is the output voltage of the phase-shifted full bridge, that is, the voltage on the load of the three-port converter; right and The phase shift angle of the voltage waveform is adjusted so that the voltage output from the secondary phase-shifted full-bridge to the load meets the preset requirements.

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