Current feed type three-port converter

Abstract

The invention discloses a current feed type three-port converter, which is applied to a hybrid energy storage system consisting of a fuel cell and a power type energy storage device, and comprises a current feed module, a charging and discharging module, a transformer module and an active bridge module, and the current feed module comprises a filter inductor and a full-bridge unit. One end of the current feed module is connected with the fuel cell, the other end is connected with the power type energy storage device through the charging and discharging module, and the third end is connected with the load through the transformer module and the active bridge module in sequence. According to the three-port converter, charge and discharge current ripples are reduced, the service life of the fuel cell is prolonged, and the energy conversion efficiency of the fuel cell is improved. Besides, according to different load conditions, the three-port converter can work in a single-input and double-output mode, a double-input and single-output mode and a single-input and single-output mode, and efficient energy flow management among the three ports of the fuel cell, the power type energy storage device and the load is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of hybrid energy storage systems, and in particular relates to a current-fed three-port converter. Background Art

[0002] The hybrid energy storage system composed of fuel cells (such as proton exchange membrane fuel cells, alkaline fuel cells, phosphoric acid fuel cells, solid oxide fuel cells, molten carbonate fuel cells, etc.) and power-type energy storage devices (such as electrochemical capacitors, power-type lithium-ion batteries, sodium-ion batteries, etc.) can combine the advantages of both, improve the overall efficiency, power density and cycle life of the system, and is widely used in electrified transportation system vehicles (such as passenger cars, trucks, buses, ships, airplanes, etc.) and renewable energy systems (such as power grids, microgrids, etc.).

[0003] The three-port converter is a key component in the hybrid energy storage system, responsible for managing and optimizing the energy flow between the fuel cell, power storage device and the load. The existing three-port converter has deficiencies in efficiency, stability and safety due to the characteristics of its own circuit structure, especially in current ripple control and energy management, where there are problems such as large current ripple and low energy conversion efficiency. Therefore, how to reduce the current ripple of the three-port converter and improve the energy conversion efficiency of the three-port converter has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a current-fed three-port converter for a hybrid energy storage system, wherein the hybrid energy storage system can be applied to an electrified transportation system vehicle and a renewable energy system, wherein the electrified transportation system vehicle includes one or more of a passenger car, a truck, a bus, a ship, and an airplane, wherein the renewable energy system includes one or more of a power grid and a microgrid, wherein the hybrid energy storage system includes at least a power storage device and a fuel cell, wherein the power storage device includes one or more of an electrochemical capacitor, a power lithium-ion battery, and a sodium-ion battery, wherein the fuel cell includes one or more of a proton exchange membrane fuel cell, an alkaline fuel cell, a phosphoric acid fuel cell, a solid oxide fuel cell, and a molten carbonate fuel cell. The three-port converter adopts a partially isolated design and has the characteristics of low charge and discharge current ripple, thereby solving the technical problems of large current ripple and low energy conversion efficiency of the three-port converter in the prior art.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions:

[0006] The present invention provides a current-fed three-port converter, which is applied to a hybrid energy storage system composed of a fuel cell and a power-type energy storage device, and includes a current-fed module, a charge-discharge module, a transformer module and an active bridge module;

[0007] The current feeding module includes a filter inductor and a full-bridge unit, wherein the first end of the filter inductor is connected to the positive electrode of the fuel cell, the first input end of the full-bridge unit is connected to the second end of the filter inductor, and the second input end is connected to the negative electrode of the fuel cell;

[0008] The first end of the charging and discharging module is connected to the second end of the filter inductor, the second end is connected to the negative electrode of the fuel cell, the third end is connected to the negative electrode of the power type energy storage device, and the fourth end is connected to the positive electrode of the power type energy storage device;

[0009] The first input end of the transformer module is connected to the first output end of the full-bridge unit, and the second input end is connected to the second output end of the full-bridge unit;

[0010] The first input end of the active bridge module is connected to the first output end of the transformer module, the second input end is connected to the second output end of the transformer module, and the output end is connected to a load.

[0011] In one embodiment of the present invention, the charging and discharging module includes a first control switch, an energy storage inductor and a second control switch;

[0012] The first end of the first control switch is connected to the second end of the filter inductor as the first end of the charge and discharge module;

[0013] The first end of the energy storage inductor and the second end of the first control switch are connected to the negative electrode of the power type energy storage device as the third end of the charge and discharge module;

[0014] The first end of the second control switch is connected to the positive electrode of the power type energy storage device as the fourth end of the charge and discharge module, and the second end and the second end of the energy storage inductor are connected to the negative electrode of the fuel cell as the second end of the charge and discharge module.

[0015] In one embodiment of the present invention, the full-bridge unit includes a first bridge arm and a second bridge arm;

[0016] The first end of the first bridge arm and the first end of the second bridge arm are connected to the second end of the filter inductor as the first input end of the full-bridge unit;

[0017] The second end of the first bridge arm and the second end of the second bridge arm are connected to the negative electrode of the fuel cell as the second input end of the full-bridge unit;

[0018] The midpoint of the first bridge arm is connected to the first input end of the transformer module as the first output end of the full-bridge unit;

[0019] The midpoint of the second bridge arm is connected to the second input end of the transformer module as the second output end of the full-bridge unit.

[0020] In one embodiment of the present invention, the first bridge arm includes a first switch tube and a second switch tube, and the second bridge arm includes a third switch tube and a fourth switch tube;

[0021] The first end of the first switch tube is connected to the second end of the filter inductor as the first end of the first bridge arm;

[0022] The first end of the second switch tube and the second end of the first switch tube are connected to the first input end of the transformer module as the midpoint of the first bridge arm, and the second end is connected to the negative electrode of the fuel cell as the second end of the first bridge arm;

[0023] The first end of the third switch tube is connected to the second end of the filter inductor as the first end of the second bridge arm;

[0024] The first end of the fourth switch tube and the second end of the third switch tube are connected to the second input end of the transformer module as the midpoint of the second bridge arm, and the second ends are connected to the negative electrode of the fuel cell as the second ends of the second bridge arm.

[0025] In one embodiment of the present invention, the duty cycle of the switch tube control signal is greater than 0.5, and the upper and lower switch tube control signals of the same bridge arm overlap and have a phase difference of 180°.

[0026] In one embodiment of the present invention, the transformer module includes a transformer leakage inductance, a primary winding and a secondary winding;

[0027] The first end of the transformer leakage inductance is connected to the first output end of the full-bridge unit as the first input end of the transformer module;

[0028] The same-name end of the primary winding is connected to the second end of the transformer leakage inductance, and the opposite-name end is connected to the second output end of the full-bridge unit as the second input end of the transformer module;

[0029] The same-name end of the secondary winding is connected to the first input end of the active bridge module as the first output end of the transformer module, and the opposite-name end is connected to the second input end of the active bridge module as the second output end of the transformer module.

[0030] In one embodiment of the present invention, the active bridge module includes a third bridge arm and a fourth bridge arm;

[0031] The midpoint of the third bridge arm is connected to the first output end of the transformer module as the first input end of the active bridge module;

[0032] The midpoint of the fourth bridge arm is connected to the second output end of the transformer module as the second input end of the active bridge module;

[0033] The first end of the third bridge arm and the first end of the fourth bridge arm are connected to the positive electrode of the load as the first output end of the active bridge module;

[0034] The second end of the third bridge arm and the second end of the fourth bridge arm are connected to the negative electrode of the load as the second output end of the active bridge module.

[0035] In one embodiment of the present invention, the third bridge arm includes a fifth switch tube and a sixth switch tube, and the fourth bridge arm includes a seventh switch tube and an eighth switch tube;

[0036] The first end of the fifth switch tube is connected to the positive electrode of the load as the first end of the third bridge arm;

[0037] The first end of the sixth switch tube and the second end of the fifth switch tube are connected to the first output end of the transformer module as the midpoint of the third bridge arm, and the second ends are connected to the negative electrode of the load as the second ends of the third bridge arm;

[0038] The first end of the seventh switch tube is connected to the positive electrode of the load as the first end of the fourth bridge arm;

[0039] The first end of the eighth switch tube and the second end of the seventh switch tube are connected to the second output end of the transformer module as the midpoint of the fourth bridge arm, and the second ends are connected to the negative electrode of the load as the second ends of the fourth bridge arm.

[0040] In one embodiment of the present invention, the duty cycle of the switch tube control signal is less than 0.5, and the upper and lower switch tube control signals of the same bridge arm are provided with dead time and the phase difference is 180°.

[0041] In one embodiment of the present invention, the operating modes of the three-port converter include a single-input dual-output mode, a dual-input single-output mode and a single-input single-output mode.

[0042] As described above, the present invention provides a current-fed three-port converter, which is applied to a hybrid energy storage system composed of a fuel cell and a power-type energy storage device, including a current feeding module, a charging and discharging module, a transformer module and an active bridge module, wherein the current feeding module includes a filter inductor and a full-bridge unit, wherein the first end of the filter inductor is connected to the positive electrode of the fuel cell, the first input end of the full-bridge unit is connected to the second end of the filter inductor, and the second input end is connected to the negative electrode of the fuel cell, the first end of the charge and discharge module is connected to the second end of the filter inductor, the second end is connected to the negative electrode of the fuel cell, the third end is connected to the negative electrode of the power-type energy storage device, and the fourth end is connected to the positive electrode of the power-type energy storage device, the first input end of the transformer module is connected to the first output end of the full-bridge unit, the second input end is connected to the second output end of the full-bridge unit, the first input end of the active bridge module is connected to the first output end of the transformer module, the second input end is connected to the second output end of the transformer module, and the output end is connected to the load. The current-fed three-port converter of the present invention reduces the charge and discharge current ripple, and improves the service life and energy conversion efficiency of the fuel cell. In addition, according to different load conditions, the current-fed three-port converter can operate in three modes, namely, single-input dual-output, dual-input single-output, and single-input single-output, to achieve efficient energy flow management between three ports, namely, fuel cell, power storage device, and load. At the same time, the current-fed three-port converter adopts a partially isolated design, which improves the energy conversion efficiency of the system while ensuring the safety of the system. In addition, the secondary side of the transformer uses a dual active bridge for rectification, and cooperates with phase shift control to achieve clamping of the primary side voltage of the transformer, reduce the voltage stress of the primary side switch tube of the transformer, thereby reducing the circuit cost, and can select a switch tube with lower on-resistance to improve the energy conversion efficiency of the system. In addition, the dead time is introduced into the bridge arm on the secondary side of the transformer, and the short-time charging and discharging characteristics of the parasitic capacitance of the switch tube are utilized to achieve zero voltage opening of all switch tubes on the secondary side of the transformer, thereby improving the energy conversion efficiency of the system. Of course, any product implementing the present invention does not necessarily need to achieve all the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0044] Figure 1 A schematic diagram of the structure of a current-fed three-port converter provided by an exemplary embodiment of the present application.

[0045] Figure 2A schematic diagram of an equivalent circuit of a current-fed three-port converter provided by an exemplary embodiment of the present application.

[0046] Figure 3 A schematic diagram of key waveforms of a current-fed three-port converter provided by an exemplary embodiment of the present application operating in a single-input dual-output mode.

[0047] Figure 4a A circuit diagram of mode 1 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode.

[0048] Figure 4b A circuit diagram of mode 2 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode is shown.

[0049] Figure 4c A circuit diagram of mode 3 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode.

[0050] Figure 4d A circuit diagram of mode 4 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode.

[0051] Figure 4e A circuit diagram of mode 5 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode.

[0052] Figure 4f A circuit diagram of mode 6 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a single-input dual-output mode.

[0053] Figure 5 A schematic diagram of key waveforms of a current-fed three-port converter provided by an exemplary embodiment of the present application operating in a dual-input single-output mode.

[0054] Figure 6a A circuit diagram of mode 1 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0055] Figure 6b A circuit diagram of mode 2 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0056] Figure 6c A circuit diagram of Mode 3 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0057] Figure 6d A circuit diagram of mode 4 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0058] Figure 6e A circuit diagram of mode 5 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0059] Figure 6f A circuit diagram of mode 6 of a current-fed three-port converter provided by an exemplary embodiment of the present application working in a dual-input single-output mode.

[0060] The reference numerals are as follows:

[0061] 100 Fuel Cell

[0062] 200 Current Feed Module

[0063] 201 Full Bridge Unit

[0064] 300 Charge and discharge module

[0065] 400 Transformer Module

[0066] 500 Active Bridge Module

[0067] 600 Load

[0068] 700 Power Energy Storage Devices DETAILED DESCRIPTION

[0069] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0070] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0071] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, structures and devices known to the public are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0072] In order to solve the technical problems of large current ripple and low energy conversion efficiency of three-port converters in the prior art, the present invention provides a current-fed three-port converter, which is applied to a hybrid energy storage system composed of a fuel cell and a power-type energy storage device. The hybrid energy storage system is applied to electrified transportation system vehicles and renewable energy systems. The electrified transportation system vehicles include one or more of passenger cars, trucks, buses, ships, and airplanes. The renewable energy system includes one or more of power grids and microgrids. The fuel cell includes one or more of proton exchange membrane fuel cells, alkaline fuel cells, phosphoric acid fuel cells, solid oxide fuel cells, and molten carbonate fuel cells. The power-type energy storage device includes one or more of electrochemical capacitors, power lithium-ion batteries, and sodium-ion batteries.

[0073] In an exemplary embodiment of the present application, see Figure 1 As shown, the current-fed three-port converter includes a fuel cell 100, a current-feed module 200, a charge-discharge module 300, a transformer module 400, an active bridge module 500, a load 600 and a power storage device 700, wherein the current-feed module 200 further includes a filter inductor L FC and a full-bridge unit 201. The current-fed three-port converter can improve the system energy efficiency and reliability while meeting the hybrid energy storage system's demand for efficient energy management.

[0074] For details, please continue to refer to Figure 1 As shown, the filter inductor L FC The first end of the full-bridge unit 201 is connected to the positive electrode of the fuel cell 100, and the first input end of the full-bridge unit 201 is connected to the filter inductor L FC The second input end is connected to the negative electrode of the fuel cell 100, and the first end of the charging and discharging module 300 is connected to the filter inductor L FCThe second end is connected to the negative electrode of the fuel cell 100, the third end is connected to the negative electrode of the power type energy storage device 700, and the fourth end is connected to the positive electrode of the power type energy storage device 700. The first input end of the transformer module 400 is connected to the first output end of the full-bridge unit 201, and the second input end is connected to the second output end of the full-bridge unit 201. The first input end of the active bridge module 500 is connected to the first output end of the transformer module 400, the second input end is connected to the second output end of the transformer module 400, and the output end is connected to the load 600.

[0075] It should be noted that, in this embodiment, the power type energy storage device 700 can be a supercapacitor, and the fuel cell 100 can be a fuel cell with a rated output voltage between 20V and 40V. Of course, in other embodiments, fuel cells with different rated output voltages can also be selected according to actual application requirements. It is worth noting that a protection diode is also connected in series to the positive output end of the fuel cell 100, and the unidirectional conductivity of the diode is used to avoid the current reverse flow and damage to the fuel cell 100 when the system is shut down or a fault occurs. In addition, an output voltage stabilizing capacitor is also provided before the load end to stabilize the output voltage of the load end and reduce output noise.

[0076] See also Figure 1 and Figure 2 As shown, in an exemplary embodiment of the present application, the charging and discharging module 300 includes a first control switch S SC1 , energy storage inductor L SC and the second control switch S SC2 The first control switch S SC1 The first end of the charge and discharge module 300 is connected to the filter inductor L FC The second end of the energy storage inductor L SC The first end and the first control switch S SC1 The second end of the second control switch S is connected to the negative electrode of the power type energy storage device 700 as the third end of the charge and discharge module 300. SC2 The first end of the charging and discharging module 300 is connected to the positive electrode of the power type energy storage device 700, and the second end and the energy storage inductor L SC The second end of the charging and discharging module 300 is connected to the negative electrode of the fuel cell 100 as the second end of the charging and discharging module 300.

[0077] Please continue reading Figure 1 and Figure 2 As shown, in an exemplary embodiment of the present application, the full-bridge unit 201 includes a first bridge arm and a second bridge arm, and the first end of the first bridge arm and the first end of the second bridge arm serve as the first input end of the full-bridge unit 201 and the filter inductor LFC The second end of the first bridge arm and the second end of the second bridge arm are connected to the negative electrode of the fuel cell 100 as the second input end of the full-bridge unit 201, the midpoint of the first bridge arm is connected to the first input end of the transformer module 400 as the first output end of the full-bridge unit 201, and the midpoint of the second bridge arm is connected to the second input end of the transformer module 400 as the second output end of the full-bridge unit 201.

[0078] In an exemplary embodiment of the present application, the first bridge arm includes a first switch tube S1 and a second switch tube S2, the second bridge arm includes a third switch tube S3 and a fourth switch tube S4, and the first end of the first switch tube S1 is connected to the filter inductor L as the first end of the first bridge arm. FC The first end of the second switch tube S2 and the second end of the first switch tube S1 are connected to the first input end of the transformer module 400 as the midpoint of the first bridge arm, and the second end is connected to the negative electrode of the fuel cell 100 as the second end of the first bridge arm. The first end of the third switch tube S3 is connected to the filter inductor L as the first end of the second bridge arm. FC The second end of the fourth switch tube S4 and the second end of the third switch tube S3 are connected to the second input end of the transformer module 400 as the midpoint of the second bridge arm, and the second ends are connected to the negative electrode of the fuel cell 100 as the second ends of the second bridge arm.

[0079] It should be noted that the full-bridge unit 201 is an H-bridge circuit structure for converting direct current into alternating current. The types of the switch tubes S1-S4 include MOSFET and IGBT. In this embodiment, the switch tubes S1-S4 are N-type MOSFET. It is worth noting that the switch tubes S1-S4 have parasitic body diodes and parasitic capacitances.

[0080] In an exemplary embodiment of the present application, the duty cycle of the control signal of the switch tubes S1 to S4 is greater than 0.5, and the control signals of the upper and lower switch tubes of the same bridge arm overlap and the phase difference is 180°. It should be noted that in this embodiment, the control signal refers to the control signal of the gate terminal of the N-type MOSFET, a high level controls the switch tube to be turned on, and a low level controls the switch tube to be turned off.

[0081] Please continue reading Figure 1 and Figure 2 As shown, the transformer module 400 includes a transformer leakage inductance L lk , primary winding and secondary winding, the transformer leakage inductance L lkThe first end of the transformer module 400 is connected to the first output end of the full-bridge unit 201 as the first input end of the transformer module 400, and the same-name end of the primary winding is connected to the transformer leakage inductance L lk The second end of the secondary winding is connected, the opposite end is connected to the second output end of the full-bridge unit 201 as the second input end of the transformer module 400, the same end of the secondary winding is connected to the first input end of the active bridge module 500 as the first output end of the transformer module 400, and the opposite end is connected to the second input end of the active bridge module 500 as the second output end of the transformer module 400.

[0082] It should be noted that in this embodiment, the turns ratio of the primary winding to the secondary winding of the transformer is set to 1:2. Of course, in other embodiments, the turns ratio of the primary winding to the secondary winding of the transformer can be adaptively set according to actual application requirements. lk It refers to the induced electromotive force caused by the magnetic coupling relationship between the transformer and the surrounding space, in which part of the magnetic flux passes through the magnetic circuit but is not recovered by the other part.

[0083] Please continue reading Figure 1 and Figure 2 As shown, the active bridge module 500 includes a third bridge arm and a fourth bridge arm, the midpoint of the third bridge arm is connected to the first output end of the transformer module 400 as the first input end of the active bridge module 500, the midpoint of the fourth bridge arm is connected to the second output end of the transformer module 400 as the second input end of the active bridge module 500, the first end of the third bridge arm and the first end of the fourth bridge arm are connected to the positive pole of the load 600 as the first output end of the active bridge module 500, and the second end of the third bridge arm and the second end of the fourth bridge arm are connected to the negative pole of the load 600 as the second output end of the active bridge module 500.

[0084] In an exemplary embodiment of the present application, the third bridge arm includes a fifth switch tube S5 and a sixth switch tube S6, and the fourth bridge arm includes a seventh switch tube S7 and an eighth switch tube S8. The first end of the fifth switch tube S5 is connected to the positive electrode of the load 600 as the first end of the third bridge arm, the first end of the sixth switch tube S6 and the second end of the fifth switch tube S5 are connected to the first output end of the transformer module 400 as the midpoint of the third bridge arm, and the second ends are connected to the negative electrode of the load 600 as the second end of the third bridge arm. The first end of the seventh switch tube S7 is connected to the positive electrode of the load 600 as the first end of the fourth bridge arm, the first end of the eighth switch tube S8 and the second end of the seventh switch tube S7 are connected to the second output end of the transformer module as the midpoint of the fourth bridge arm, and the second ends are connected to the negative electrode of the load 600 as the second end of the fourth bridge arm.

[0085] It should be noted that the active bridge module 500 is an H-bridge circuit structure for converting AC power into DC power. The types of the switch tubes S5-S8 include MOSFET and IGBT. In this embodiment, the switch tubes S5-S8 are N-type MOSFET. It is worth noting that the switch tubes S5-S8 have parasitic body diodes and parasitic capacitances.

[0086] In an exemplary embodiment of the present application, the duty cycle of the control signal of the switch tubes S5 to S8 is less than 0.5, and the control signals of the upper and lower switch tubes of the same bridge arm are provided with a dead time and a phase difference of 180°.

[0087] In an exemplary embodiment of the present application, the operating modes of the three-port converter include a single-input dual-output mode, a dual-input single-output mode and a single-input single-output mode.

[0088] The working principle of the current-fed three-port converter will be analyzed in detail below.

[0089] It should be noted that, according to different load conditions, the current-fed three-port converter can operate in three modes, namely, single-input dual-output, dual-input single-output, and single-input single-output, to achieve efficient energy flow management between three ports, namely, fuel cell, power energy storage device, and load. The current-fed three-port converter adopts a partially isolated design. In this embodiment, the fuel cell and power energy storage device are electrically isolated from the load by a transformer, which improves the energy conversion efficiency of the system while ensuring system safety.

[0090] See also Figure 2 As shown, V FC is the fuel cell terminal voltage, L FC is the filter inductor, L SC is the energy storage inductor, V SCis the voltage across the power energy storage device, S1~S4 are the switches on the primary side of the transformer, S5~S8 are the switches on the secondary side of the transformer, C1~C8 are the parasitic capacitances of each switch, L lk is the transformer leakage inductance, Co is the output voltage stabilizing capacitor, Vo is the output voltage, the transformer turns ratio is 1:n, V AB is the transformer primary voltage, V CD is the transformer secondary voltage, xTs represents the filter inductance L FC The proportion of charging time in a half cycle in the entire cycle. In addition, the current-fed three-port converter includes four degrees of freedom, namely the duty cycle d1 of the switch tube on the primary side of the transformer, the duty cycle d2 of the switch tube on the secondary side of the transformer, the primary-secondary side phase shift angle α, and the secondary-side bridge-to-bridge phase shift angle β. The current-fed three-port converter mainly controls the flow of power through the primary-secondary side phase shift angle α and the secondary-side bridge-to-bridge phase shift angle β, and controls the current peak value during light load through the secondary-side bridge-to-bridge phase shift angle β. The duty cycle d1 of the switch tube on the primary side of the transformer of the current-fed three-port converter is greater than 0.5, and the control signals of the upper and lower switches of the same bridge arm overlap, with a phase difference of 180°. The duty cycle d2 of the switch tube on the secondary side of the transformer is slightly less than 0.5, and the phase difference between the upper and lower switches of the same bridge arm is 180°, leaving a certain margin of dead time. It is worth noting that the relationship between the duty cycle and the phase shift angle is d1=α+β+d2. At the same time, to ensure the power flows in the forward direction, α+β<0.5 must be satisfied.

[0091] It should be noted that when the current-fed three-port converter operates in the single-input dual-output mode, the first control switch S SC1 There is a switching behavior, the second control switch S SC2 When the current-fed three-port converter operates in the dual-input single-output mode, the second control switch S SC2 There is a switching behavior, the first control switch S SC1 When the current-fed three-port converter operates in the single-input single-output mode, the first control switch S SC1 and the second control switch S SC2 The default is off.

[0092] In addition, before conducting a detailed principle analysis, the following assumptions need to be made:

[0093] Filter inductor L FC And energy storage inductor L SC is large enough so that the corresponding current I FC and I SC is a constant value. In this embodiment, the filter inductor L FC And energy storage inductor L SCThe inductance value is required to be greater than or equal to 1mH; the transformer coupling coefficient is close to 1; all components are ideal devices; L lk The total transformer leakage inductance, or a series inductor including the transformer leakage inductance; the parasitic capacitance of the switch tube charges in a very short time and can be ignored. The output voltage stabilizing capacitor Co is large enough to keep the output voltage Vo constant.

[0094] The current-fed three-port converter operates in steady state, and each working cycle T S It can be divided into two symmetrical half-cycles. In these two half-cycles, the symmetrical switch tubes have the same working state. The working state of the half-cycle can be divided into six sub-modes, namely mode 1 [t0~t1], mode 2 [t1~t2], mode 3 [t2~t3], mode 4 [t3~t4], mode 5 [t4~t5], and mode 6 [t5~t6]. The following will combine the attached Figure 3 ~Attached Figure 6f To analyze the specific working process of each sub-mode.

[0095] Mode 1 [t0~t1]: Single-input dual-output mode, please refer to Figure 3 and Figure 4a For dual-input and single-output mode, please refer to Figure 5 and Figure 6a The switch tubes S1 to S4 are turned on, the sixth switch tube S6 and the seventh switch tube S7 are turned on, the fifth switch tube S5 and the eighth switch tube S8 are turned off, and the fuel cell port voltage V FC Applied to the filter inductor L FC The two ends of the filter inductor L FC The current increases, the transformer leakage inductance L lk The voltage across the two ends is Vo / n. At t0, the transformer leakage current is zero and rises linearly. In the single-input dual-output mode, the first control switch S SC1 At this moment, the energy storage inductor current I SC To charge the power type energy storage device. In the dual-input single-output mode, the second control switch S SC2 At this moment, the energy storage inductor current I SC In the single-input single-output mode, the first control switch S SC1 and the second control switch S SC2 All are turned off. During this process, the transformer leakage current is:

[0096]

[0097] Mode 2 [t1~t2]: Single-input dual-output mode, please refer to Figure 3 and Figure 4b For dual-input and single-output mode, please refer to Figure 5 and Figure 6bAs shown. The switching state of each switch tube is the same as mode 1. At t1, the transformer leakage inductance current is equal to I FC -I SC The current continues to rise, and the transformer leakage inductance current reaches its peak at time t2:

[0098]

[0099] Mode 3 [t2~t3]: Single-input dual-output mode, please refer to Figure 3 and Figure 4c For dual-input and single-output mode, please refer to Figure 5 and Figure 6c At time t2, the sixth switch tube S6 is turned off, due to the transformer leakage inductance L lk The existence of the transformer current will not change suddenly, the parasitic capacitor C6 of the sixth switch tube S6 starts to charge, and the current flows through the body diode D5 of the fifth switch tube S5 and the seventh switch tube S7. During this time, the fifth switch tube S5 can be turned on at zero voltage. CD =0, so through the transformer leakage inductance L lk The current remains unchanged.

[0100] Mode 4 [t3~t4]: Single-input dual-output mode, please refer to Figure 3 and Figure 4d For dual-input and single-output mode, please refer to Figure 5 and Figure 6d At time t3, the seventh switch tube S7 is turned off, and its parasitic capacitor C7 is charged. During this time, the eighth switch tube S8 is turned on to achieve zero voltage switching. The primary side voltage V AB =0, so the transformer leakage inductance L lk The voltage across the two ends is -Vo / n, through the transformer leakage inductance L lk The current starts to decrease. In the single-input dual-output mode, the first control switch S SC1 At this moment, the energy storage inductor current I SC In the dual-input single-output mode, the second control switch tube S SC2 At this moment, the energy storage inductor I SC Linear decrease. In single-input single-output mode, the first control switch S SC1 and the second control switch S SC2 All are turned off. During this process, the transformer leakage current is:

[0101]

[0102] Mode 5 [t4~t5]: Single-input dual-output mode, please refer to Figure 3 and Figure 4e For dual-input and single-output mode, please refer to Figure 5 and Figure 6e As shown. At t4, the transformer primary side voltage V AB =Vo / n, transformer leakage inductance L lk The voltage across the two ends is 0, and the leakage inductance L of the transformer lk The current remains unchanged, and the energy is transferred from the primary side to the secondary side. At this time, the transformer leakage current is I FC -I SC of current.

[0103] Mode 6 [t5~t6]: Single-input dual-output mode, please refer to Figure 3 and Figure 4f For dual-input and single-output mode, please refer to Figure 5 and Figure 6f At t5, the first switch tube S2 and the third switch tube S3 are turned on, and the corresponding parasitic capacitors C2 and C3 are discharged, and the primary side voltage V AB =0, transformer secondary side voltage V CD =Vo. In the single-input dual-output mode, the first control switch S SC1 At this moment, the energy storage inductor current I SC To charge the power storage device. In the dual-input single-output mode, the second control switch tube S SC2 At this moment, the energy storage inductor current I SC In the single-input single-output mode, the first control switch S SC1 and the second control switch S SC2 All turned off.

[0104] In summary, the current-fed three-port converter reduces the charge and discharge current ripple, and improves the service life and energy conversion efficiency of the fuel cell. In addition, according to different load conditions, the current-fed three-port converter can operate in three modes: single-input dual-output, dual-input single-output, and single-input single-output, realizing efficient energy flow management between three ports such as fuel cells, power storage devices, and loads. The current-fed three-port converter adopts a partially isolated design, which improves the energy conversion efficiency of the system while ensuring system safety. The secondary side of the transformer uses a dual active bridge for rectification, and cooperates with phase shift control to achieve the clamping of the primary side voltage of the transformer, reduce the voltage stress of the primary side switch tube of the transformer, thereby reducing the circuit cost, and can select a switch tube with lower on-resistance to improve the energy conversion efficiency of the system. In addition, the dead time is introduced into the bridge arm on the secondary side of the transformer, and the short-time charging and discharging characteristics of the parasitic capacitance of the switch tube are utilized to achieve zero voltage opening of all switches on the secondary side of the transformer, thereby improving the energy conversion efficiency of the system.

[0105] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A current-fed three-port converter, applied to a hybrid energy storage system consisting of a fuel cell and a power type energy storage device, characterized in that: It includes a current feeding module, a charging and discharging module, a transformer module and an active bridge module; The current feeding module includes a filter inductor and a full-bridge unit, wherein the first end of the filter inductor is connected to the positive electrode of the fuel cell, the first input end of the full-bridge unit is connected to the second end of the filter inductor, and the second input end is connected to the negative electrode of the fuel cell; The first end of the charging and discharging module is connected to the second end of the filter inductor, the second end is connected to the negative electrode of the fuel cell, the third end is connected to the negative electrode of the power type energy storage device, and the fourth end is connected to the positive electrode of the power type energy storage device; The first input end of the transformer module is connected to the first output end of the full-bridge unit, and the second input end is connected to the second output end of the full-bridge unit; The first input end of the active bridge module is connected to the first output end of the transformer module, the second input end is connected to the second output end of the transformer module, and the output end is connected to a load.

2. The current-fed three-port converter according to claim 1, characterized in that: The charging and discharging module includes a first control switch, an energy storage inductor and a second control switch; The first end of the first control switch is connected to the second end of the filter inductor as the first end of the charge and discharge module; The first end of the energy storage inductor and the second end of the first control switch are connected to the negative electrode of the power type energy storage device as the third end of the charge and discharge module; The first end of the second control switch is connected to the positive electrode of the power type energy storage device as the fourth end of the charge and discharge module, and the second end and the second end of the energy storage inductor are connected to the negative electrode of the fuel cell as the second end of the charge and discharge module.

3. The current-fed three-port converter according to claim 1, characterized in that: The full-bridge unit comprises a first bridge arm and a second bridge arm; The first end of the first bridge arm and the first end of the second bridge arm are connected to the second end of the filter inductor as the first input end of the full-bridge unit; The second end of the first bridge arm and the second end of the second bridge arm are connected to the negative electrode of the fuel cell as the second input end of the full-bridge unit; The midpoint of the first bridge arm is connected to the first input end of the transformer module as the first output end of the full-bridge unit; The midpoint of the second bridge arm is connected to the second input end of the transformer module as the second output end of the full-bridge unit.

4. The current-fed three-port converter according to claim 3, characterized in that: The first bridge arm includes a first switch tube and a second switch tube, and the second bridge arm includes a third switch tube and a fourth switch tube; The first end of the first switch tube is connected to the second end of the filter inductor as the first end of the first bridge arm; The first end of the second switch tube and the second end of the first switch tube are connected to the first input end of the transformer module as the midpoint of the first bridge arm, and the second end is connected to the negative electrode of the fuel cell as the second end of the first bridge arm; The first end of the third switch tube is connected to the second end of the filter inductor as the first end of the second bridge arm; The first end of the fourth switch tube and the second end of the third switch tube are connected to the second input end of the transformer module as the midpoint of the second bridge arm, and the second ends are connected to the negative electrode of the fuel cell as the second ends of the second bridge arm.

5. The current-fed three-port converter according to claim 4, characterized in that: The duty cycle of the switch tube control signal is greater than 0.5, and the upper and lower switch tube control signals of the same bridge arm overlap and have a phase difference of 180°.

6. The current-fed three-port converter according to claim 1, characterized in that: The transformer module includes a transformer leakage inductance, a primary winding and a secondary winding; The first end of the transformer leakage inductance is connected to the first output end of the full-bridge unit as the first input end of the transformer module; The same-name end of the primary winding is connected to the second end of the transformer leakage inductance, and the opposite-name end is connected to the second output end of the full-bridge unit as the second input end of the transformer module; The same-name end of the secondary winding is connected to the first input end of the active bridge module as the first output end of the transformer module, and the opposite-name end is connected to the second input end of the active bridge module as the second output end of the transformer module.

7. The current-fed three-port converter according to claim 1, characterized in that: The active bridge module includes a third bridge arm and a fourth bridge arm; The midpoint of the third bridge arm is connected to the first output end of the transformer module as the first input end of the active bridge module; The midpoint of the fourth bridge arm is connected to the second output end of the transformer module as the second input end of the active bridge module; The first end of the third bridge arm and the first end of the fourth bridge arm are connected to the positive electrode of the load as the first output end of the active bridge module; The second end of the third bridge arm and the second end of the fourth bridge arm are connected to the negative electrode of the load as the second output end of the active bridge module.

8. The current-fed three-port converter according to claim 7, characterized in that: The third bridge arm includes a fifth switch tube and a sixth switch tube, and the fourth bridge arm includes a seventh switch tube and an eighth switch tube; The first end of the fifth switch tube is connected to the positive electrode of the load as the first end of the third bridge arm; The first end of the sixth switch tube and the second end of the fifth switch tube are connected to the first output end of the transformer module as the midpoint of the third bridge arm, and the second ends are connected to the negative electrode of the load as the second ends of the third bridge arm; The first end of the seventh switch tube is connected to the positive electrode of the load as the first end of the fourth bridge arm; The first end of the eighth switch tube and the second end of the seventh switch tube are connected to the second output end of the transformer module as the midpoint of the fourth bridge arm, and the second ends are connected to the negative electrode of the load as the second ends of the fourth bridge arm.

9. The current-fed three-port converter according to claim 8, characterized in that: The duty cycle of the switch tube control signal is less than 0.5, and the upper and lower switch tube control signals of the same bridge arm are provided with a dead time and a phase difference of 180°.

10. The current-fed three-port converter according to claim 1, characterized in that: The working modes of the three-port converter include a single-input dual-output mode, a dual-input single-output mode and a single-input single-output mode.

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