Isolated three-port DC / DC converter

Abstract

The invention provides an isolation type three-port DC / DC converter which comprises a three-winding transformer, three inductors, three blocking capacitors, three voltage stabilizing capacitors, two full-bridge circuits and a full-bridge capacitor clamping three-level circuit. A primary winding of the transformer is connected with new energy ports such as a fuel cell / a photovoltaic module through a first power transmission inductor L1, a first blocking capacitor Cb1 and a first full-bridge circuit, and a first secondary winding of the transformer is connected with energy storage element ports such as a storage battery / a super capacitor through a second power transmission inductor L2, a second blocking capacitor Cb2 and a second full-bridge circuit. And a second secondary winding of the transformer is connected with the direct current bus port through a third power transmission inductor L3, a third blocking capacitor Cb3 and a full-bridge capacitor clamping three-level circuit. According to the invention, zero voltage switching (ZVS) of the converter can be ensured, the efficiency of the converter is improved, high-power-density integration is realized, and the size and the cost are reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy conversion, in particular to an isolated three-port DC / DC converter. BACKGROUND

[0002] With the development of hydrogen energy, photovoltaic and other new energy, fuel cells and photovoltaic cells have become a research hotspot in recent years. However, fuel cells have the disadvantages of slow dynamic response and difficulty in self-starting, and photovoltaic power generation has the disadvantage of volatility. Therefore, in a fuel cell and photovoltaic module and other new energy power generation system, a battery / super capacitor and other energy storage element system is often added to improve power supply quality. Generally, the voltage level of a fuel cell / photovoltaic module and other new energy power generation unit and a battery / super capacitor and other energy storage element unit is relatively low, and multiple DC converters are needed to be used to step up before being connected to a common DC bus. This will result in a complex structure, high cost and low power density of the multiple DC converter system, and coordination control between multiple converters is also needed. Using a DC converter with multiple ports to replace multiple independent DC / DC converters not only avoids using more power switching devices and reduces power loss, but also helps the system to be miniaturized, greatly reduces the cost of the system, and improves the efficiency of the system.

[0003] Three-port DC / DC converters can be divided into three types according to whether there is electrical isolation: non-isolated, partially isolated and fully isolated. Non-isolated converters have compact structure and high power density, but the boost effect brought by the duty cycle modulation of the switching tube is limited, and they are only suitable for working in the case where the input voltages of the ports are not much different, and the safety factor is low. Partially isolated converters have three ports that are not fully coupled together, and are suitable for applications where high and low voltage DC buses need to be electrically isolated in the system, but problems such as transformer winding voltage mismatch and low efficiency at light load may occur.

[0004] Compared with the above two types, fully isolated converters can achieve electrical isolation of all ports, have good port adaptability, low switching loss, flexible and diverse control methods, and switching power devices can easily achieve soft switching. However, fully isolated converters have problems such as high voltage stress of switching power devices. Therefore, it is necessary to further improve the topology of fully isolated three-port DC / DC converters to relieve the voltage stress of switching power devices while achieving efficient power transmission between the three ports. SUMMARY

[0005] In view of the problems existing in the prior art, the application provides an isolated three-port DC / DC converter, which can ensure the realization of zero-voltage switching (ZVS) characteristics, obtain wide voltage gain characteristics, reduce the voltage stress of a switching power device, reduce the loss of the converter and improve the efficiency.

[0006] The object of the application is achieved by the following technical solutions:

[0007] An isolated three-port DC / DC converter comprises a three-winding transformer, three inductors, three DC blocking capacitors, three voltage stabilizing capacitors, two full-bridge circuits and a full-bridge capacitor clamping three-level circuit.

[0008] The three inductors comprise a first power transmission inductor L1 which is the sum of a leakage inductance on a primary winding side of the three-winding transformer and an external inductance, a second power transmission inductor L2 which is the sum of a leakage inductance on a first secondary winding side of the three-winding transformer and an external inductance, and a third power transmission inductor L3 which is the sum of a leakage inductance on a second secondary winding side of the three-winding transformer and an external inductance. b1 The three DC blocking capacitors comprise a first DC blocking capacitor C b2 , a second DC blocking capacitor C b3 and a third DC blocking capacitor C a1 . The three voltage stabilizing capacitors comprise a first voltage stabilizing capacitor C1, a second voltage stabilizing capacitor C2 and a third voltage stabilizing capacitor C5.

[0009] The two full-bridge circuits comprise a first full-bridge circuit and a second full-bridge circuit, the first full-bridge circuit is connected to a new energy port such as a fuel cell / photovoltaic module, the second full-bridge circuit is connected to a storage element port such as a storage battery / super capacitor, and each of the first full-bridge circuit and the second full-bridge circuit comprises a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7 and an eighth switch tube S8.

[0010] The full-bridge capacitor clamping three-level circuit is connected to a DC bus port and comprises a ninth switch tube S a1 , a tenth switch tube S a2 , an eleventh switch tube S a3 , a twelfth switch tube S a4 , a thirteenth switch tube S b1 , a fourteenth switch tube S b2 , a fifteenth switch tube S b3 , a sixteenth switch tube S b4 , a first embedded capacitor C3 and a second embedded capacitor C4.

[0011] Further, the first full-bridge circuit comprises a first bridge arm branch formed by the first switch tube S1 and the second switch tube S2 in series, a second bridge arm branch formed by the third switch tube S3 and the fourth switch tube S4 in series, and the first bridge arm branch and the second bridge arm branch are connected in parallel.

[0012] The primary winding of the three-winding transformer, whose same name end is connected between the first switch tube S1 and the second switch tube S2, and whose different name end is connected between the third switch tube S3 and the fourth switch tube S4.

[0013] The first power transmission inductor L1 and the first direct-current blocking capacitor C b1 are connected in series, and the other end of the first power transmission inductor L1 is connected to the same name end of the primary winding of the three-winding transformer, and the other end of the first direct-current blocking capacitor C b1 is connected between the first switch tube S1 and the second switch tube S2.

[0014] Further, the second full-bridge circuit comprises: a third bridge arm branch formed by the fifth switch tube S5, the sixth switch tube S6 in series; a fourth bridge arm branch formed by the seventh switch tube S7, the eighth switch tube S8 in series; and the third bridge arm branch and the fourth bridge arm branch are connected in parallel.

[0015] The first secondary winding of the three-winding transformer, whose same name end is connected between the fifth switch tube S5 and the sixth switch tube S6, and whose different name end is connected between the seventh switch tube S7 and the eighth switch tube S8.

[0016] The second power transmission inductor L2 and the second direct-current blocking capacitor C b2 are connected in series, and the other end of the second power transmission inductor L2 is connected to the same name end of the first secondary winding of the three-winding transformer, and the other end of the second direct-current blocking capacitor C b2 is connected between the fifth switch tube S5 and the sixth switch tube S6.

[0017] Further, the full-bridge capacitor clamping three-level circuit comprises: a fifth bridge arm branch formed by the ninth switch tube S a1 , the tenth switch tube S a2 , the eleventh switch tube S a3 , the twelfth switch tube S a4 in series; a first capacitor branch formed by a first embedded capacitor C3; a sixth bridge arm branch formed by the thirteenth switch tube S b1 , the fourteenth switch tube S b2 , the fifteenth switch tube S b3 , the sixteenth switch tube S b4 in series; a second capacitor branch formed by a second embedded capacitor C4; the fifth bridge arm branch and the sixth bridge arm branch are connected in parallel; one end of the first capacitor branch is connected between the ninth switch tube S a1 and the tenth switch tube S a2 , and the other end is connected between the eleventh switch tube S a3 and the twelfth switch tube S a4 . One end of the second capacitor branch is connected between the thirteenth switch tube Sb1 between the fourteenth switch tube S b2 and the fifteenth switch tube S b3 between the sixteenth switch tube S b4 .

[0018] the second secondary winding of the three-winding transformer, the same name end of which is connected to the tenth switch tube S a2 and the eleventh switch tube S a3 , the different name end of which is connected to the fourteenth switch tube S b2 and the fifteenth switch tube S b3 .

[0019] The third power transmission inductor L3 is connected in series with the third DC blocking capacitor C b3 , the other end of the third power transmission inductor L3 being connected to the same name end of the second secondary winding of the three-winding transformer, and the other end of the third DC blocking capacitor C b3 being connected between the tenth switch tube S a2 and the eleventh switch tube S a3 .

[0020] Further, the isolation type three-port DC / DC converter comprises three ports, the new energy port of the fuel cell / photovoltaic module is connected in parallel with the first bridge arm branch, the energy storage element port of the storage battery / super capacitor is connected in parallel with the third bridge arm branch, and the DC bus port is connected in parallel with the sixth bridge arm branch.

[0021] Further, the isolation type three-port DC / DC converter comprises three voltage stabilizing capacitors, the first voltage stabilizing capacitor is connected in parallel across the new energy port of the fuel cell / photovoltaic module, the second voltage stabilizing capacitor is connected in parallel across the energy storage element port of the storage battery / super capacitor, and the third voltage stabilizing capacitor is connected in parallel across the DC bus port.

[0022] Further, the isolation type three-port DC / DC converter adopts PWM phase shift control to realize bidirectional power transmission of the new energy port of the fuel cell / photovoltaic module, the energy storage element port of the storage battery / super capacitor and the DC bus port.

[0023] Compared with the prior art, the isolation type three-port DC / DC converter topology of the present application has the following advantages:

[0024] (1) The isolation type three-port DC / DC converter topology with a three-winding structure reduces the number of power switch tubes and transformers, and improves the power density;

[0025] (2) The power flow between the new energy port of the fuel cell / photovoltaic module, the energy storage element port of the storage battery / super capacitor and the DC bus port is bidirectional;

[0026] (3) Adding the direct-current capacitor at the three ports can eliminate the direct-current voltage and interference voltage, and can inhibit the magnetic bias of the three-winding transformer to avoid the saturation of the transformer.

[0027] (4) Adding the full-bridge capacitor clamping three-level circuit at the direct-current bus port can reduce the voltage stress of the power switch tube, can be compatible with a wide range of fluctuation of the direct-current bus voltage, can reduce the cost and loss, and can improve the power transmission efficiency.

[0028] (5) The three-port DC / DC converter can realize the zero-voltage turn-on (ZVS) of the switch tube by phase-shifting control and the parasitic capacitance of the switch tube, and has the characteristics of low voltage stress of the switch tube, low loss, and high efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 A schematic diagram of an isolation type three-port DC / DC converter topology structure is provided for the embodiments of the present application.

[0031] Figure 2 A working waveform diagram of an isolation type three-port DC / DC converter under single phase-shifting control is provided for the embodiments of the present application.

[0032] Figure 3 A schematic diagram of main working modes of an isolation type three-port DC / DC converter under one switching cycle is provided for the embodiments of the present application.

[0033] Figure 4 A PWM phase-shifting generation logic circuit diagram of an isolation type three-port DC / DC converter is provided for the embodiments of the present application.

[0034] Figure 5 A PWM timing diagram of an isolation type three-port DC / DC converter is provided for the embodiments of the present application.

[0035] Figure 6 (a) A direct-current bus port voltage simulation waveform diagram of an isolation type three-port DC / DC converter under single phase-shifting control is provided for the embodiments of the present application.

[0036] Figure 6 (b) A full-bridge capacitor clamping three-level circuit switch tube voltage simulation waveform diagram of an isolation type three-port DC / DC converter under single phase-shifting control is provided for the embodiments of the present application.

[0037] Figure 7 An isolated three-port DC / DC converter provided by the embodiment of the present application is under single phase-shift control of switch tubes S1, S5 and S a1 The voltage waveform diagram between the drive signal and the drain-source of S1. DETAILED DESCRIPTION

[0038] Embodiments of the present application will be described in more detail by referring to the drawings. Although some embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms, and should not be interpreted as being limited to the embodiments set forth herein, but rather, the embodiments are provided to make the present application more thorough and complete. It should be understood that the drawings and embodiments of the present application are for exemplary purposes only, and are not intended to limit the scope of protection of the present application.

[0039] The embodiment provides an isolated three-port DC / DC converter as shown in the figure, comprising a three-winding transformer, three inductors, three DC blocking capacitors, three voltage stabilizing capacitors, two full-bridge circuits and a full-bridge capacitor clamping three-level circuit. Figure 1

[0040] The three inductors comprise a first power transmission inductor L1 which is the sum of the leakage inductance on the primary winding side of the three-winding transformer and the external inductance, a second power transmission inductor L2 which is the sum of the leakage inductance on the first secondary winding side of the three-winding transformer and the external inductance, and a third power transmission inductor L3 which is the sum of the leakage inductance on the second secondary winding side of the three-winding transformer and the external inductance. b1 b2 b3 The three DC blocking capacitors comprise a first DC blocking capacitor C a1 , a second DC blocking capacitor C a2 and a third DC blocking capacitor C a3 The voltage stabilizing capacitors comprise a first voltage stabilizing capacitor C1, a second voltage stabilizing capacitor C2 and a third voltage stabilizing capacitor C5.

[0041] The two full-bridge circuits comprise a first full-bridge circuit and a second full-bridge circuit, the first full-bridge circuit is connected to a new energy port such as a fuel cell / photovoltaic module, the second full-bridge circuit is connected to a storage element port such as a battery / super capacitor, and each comprises a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4 and a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7 and an eighth switch tube S8.

[0042] The full-bridge capacitor clamping three-level circuit is connected to a DC bus port and comprises a ninth switch tube S a1 , a tenth switch tube S a2 , an eleventh switch tube S a3 , a twelfth switch tube S a4 , a thirteenth switch tube S b1 , a fourteenth switch tube S b2the fifteenth switch tube S b3 the sixteenth switch tube S b4 and the first and second embedded capacitors C3 and C4.

[0043] Due to the high voltage on the DC bus side and the large fluctuation range, a full-bridge capacitor clamping three-level circuit is added on the DC bus side to reduce the switching tube voltage stress, reduce the loss and improve the efficiency. The voltage level of the new energy side such as fuel cell / photovoltaic module and the energy storage element side such as battery / super capacitor is low, so the three-level circuit does not need to be added. The winding of the new energy side such as fuel cell / photovoltaic module passes through the first power transmission inductor L1, the first DC blocking capacitor C b1 The first full-bridge circuit and the first voltage stabilizing capacitor C1 are connected with the new energy port of fuel cell / photovoltaic module, and the winding of the energy storage element side such as battery / super capacitor passes through the second power transmission inductor L2, the second DC blocking capacitor C b2 The second full-bridge circuit and the second voltage stabilizing capacitor C2 are connected with the energy storage element port of battery / super capacitor, and the winding of the DC bus side passes through the third power transmission inductor L3, the third DC blocking capacitor C b3 The full-bridge capacitor clamping three-level circuit and the third voltage stabilizing capacitor C5 are connected with the DC bus port.

[0044] The parameters in the application are defined as follows: the voltages of the three ports are respectively the new energy voltage V1 of fuel cell / photovoltaic module, the energy storage element voltage V2 of battery / super capacitor and the DC bus voltage V3, and the definitions are as follows: Figure 1 The arrow direction is the positive direction of voltage and current, and the inductor currents of the converter are respectively i L1 , i L2 , i L3 The voltages of the middle points of the two bridge arms of the three ports are respectively u1, u2 and u3, and the phase shift angles between the new energy port of fuel cell / photovoltaic module and the energy storage element port of battery / super capacitor and between the new energy port of fuel cell / photovoltaic module and the DC bus port are respectively φ 12 and φ 13 When the new energy port of fuel cell / photovoltaic module transmits power to the energy storage element port of battery / super capacitor and the DC bus port, φ 12 and φ 13 are positive, and vice versa. For the convenience of describing the operation principle of the application, only the case that the new energy port of fuel cell / photovoltaic module charges the energy storage element port of battery / super capacitor and the DC bus port is considered, that is, the case that φ 12 and φ 13 are positive.

[0045] It can be seen from Figure 2 that the isolated three-port DC / DC converter can be divided into 12 working modes under one period, Figure 3The main working mode diagram of the isolated three-port DC / DC converter provided by the embodiment of the present application in one switching cycle is shown in the figure, which comprises:

[0046] Mode 1 [t0-t1]: Before t0 moment: the new energy port of fuel cell / photovoltaic module: S2 and S3 are turned on, the inductor current flows out of the transformer i L1 <0, the power supply current flows out of V1, and the power is emitted; the energy storage element port of battery / super capacitor: S6 and S7 are turned on, the inductor current flows out of the transformer i L2 <0, the power supply current flows out of V2, and the power is emitted; the DC bus port: S b1 (S b2 ) and S a3 (S a4 ) are turned on, and the inductor current flows into the transformer i L3 <0, because S a1 (S a2 ) and S b3 (S b4 ) are turned off at this time, therefore i L3 only can naturally conduct through the anti-parallel diode of S b1 (S b2 ) and S a3 (S a4 ), the power supply current flows into V3, and the power is absorbed.

[0047] The working mode of the converter in the period of t0-t1 is shown in Figure 3 (a). The new energy port of fuel cell / photovoltaic module: at t0 moment, S1 and S4 are turned on, S2 and S3 are turned off, the inductor current i L1 charges the parasitic capacitance of the switching tube S2 and S3, the parasitic capacitance of the switching tube S1 and S4 is discharged, the voltage drops to zero, and the natural conduction freewheeling is realized through the anti-parallel diode of S1 and S4, therefore, the switching tube S1 and S4 realize zero voltage (ZVS) conduction, at this time, the power supply current flows into V1, and the power is absorbed by the new energy port of fuel cell / photovoltaic module; the switching tubes of the energy storage element port of battery / super capacitor and the DC bus port continue to maintain the switching state of the previous moment in this mode, and the inductor currents i L2 and i L3 have not passed zero point, and the direction has not changed, therefore the mode of the energy storage element port of battery / super capacitor and the DC bus port in the period of t0-t1 is consistent with that at t0 moment, that is, the energy storage element port of battery / super capacitor: S6 and S7 are turned on, the inductor current flows out of the transformer i L2 <0, the power supply current flows out of V2, and the power is emitted; the DC bus port: S b1 (S b2 ) and S a3 (S a4The inductor current flows into the transformer i L3 <0, the power supply current flows into V3, absorbing power. The port voltage in this mode is: u1 = V1, u2 = -V2, u3 = -V3.

[0048] Mode 2 [t1-t2]: the working mode of the converter in the t1-t2 period is as shown in Figure 3 (b). The new energy port such as fuel cell / photovoltaic module: at t1, the inductor current i L1 passes through zero, flows into the transformer from negative to positive, at this time i L1 > 0, the freewheeling stage of the anti-parallel diodes of S1 and S4 ends, the inductor current flows through S1 and S4, the power supply current flows out of V1, and the new energy port such as fuel cell / photovoltaic module outputs power; the energy storage element port such as battery / super capacitor and the DC bus port: the switch tube is in the conducting state and the inductor current i L2 , i L3 does not change in direction, so the working state of mode 1 is continued. The port voltage in this mode is: u1 = V1, u2 = -V2, u3 = -V3.

[0049] Mode 3 [t2-t3]: the working mode of the converter in the t2-t3 period is as shown in Figure 3 (c). The new energy port such as fuel cell / photovoltaic module and the DC bus port: the switch tube is in the conducting state and the inductor current i L1 , i L3 does not change in direction, so the working state of mode 2 is continued. The energy storage element port such as battery / super capacitor: at t2, S5 and S8 are turned on, S6 and S7 are turned off, the inductor current i L2 charges the parasitic capacitance of the switch tubes S6 and S7, the parasitic capacitance of the switch tubes S5 and S8 is discharged, the voltage drops to zero, the freewheeling of the anti-parallel diodes of S5 and S8 is naturally turned on, the switch tubes S5 and S8 achieve zero voltage (ZVS) conduction, at this time the power supply current flows into V2, and the energy storage element port such as battery / super capacitor absorbs power. The port voltage in this mode is: u1 = V1, u2 = V2, u3 = -V3.

[0050] Mode 4 [t3-t4]: the working mode of the converter in the t3-t4 period is as shown in Figure 3 (d). The new energy port such as fuel cell / photovoltaic module and the energy storage element port such as battery / super capacitor: the switch tube is in the conducting state and the inductor current i L1 , i L2 does not change in direction, so the working state of mode 3 is continued; the DC bus port: at t3, the inductor current i L3 passes through zero, flows out of the transformer from negative to positive, at this time i L3>0, S b1 (S b2 ) and S a3 (S a4 The freewheeling phase of the anti-parallel diode ends, and the inductor current i L3 Circulation S b1 (S b2 ) and S a3 (S a4 When the power supply current flows out of V3, the DC bus port outputs power. The port voltages in this mode are: u1 = V1, u2 = V2, u3 = -V3.

[0051] Mode 5 [t4-t5]: The operating mode of the converter during the time period t4-t5 is as follows Figure 3 As shown in (e). Fuel cell / photovoltaic module and other new energy source ports and DC bus ports: switch on-state and inductor current i L1 i L3 The direction of the current has not changed, so it continues to maintain the operating state of mode 4; for energy storage components such as batteries / supercapacitors: at time t4, the inductor current i L2 At the zero point, the current flows from negative to positive into the transformer; at this time, segment i... L2 >0, the freewheeling phase of the anti-parallel diodes in S5 and S8 ends, and the inductor current i L2 With S5 and S8 connected, inductor current flows out of V2, and power is emitted from the ports of energy storage components such as batteries / supercapacitors. In this mode, the port voltages are: u1 = V1, u2 = V2, u3 = -V3.

[0052] Mode 6 [t5-t6]: The operating mode of the converter during the t5-t6 time period is as follows Figure 3 As shown in (f). Ports for new energy sources such as fuel cells / photovoltaic modules and ports for energy storage components such as batteries / supercapacitors: switch conduction state and inductor current i L1 i L2 The direction has not changed, so it continues to maintain the operating state of mode 5; DC bus port: at time t5, S a1 (S a2 ) and S b3 (S b4 ) Open, S b1 (S b2 ) and S a3 (S a4 When switched off, the inductor current i L3 Give the switching transistor S b1 (S b2 ) and S a3 (S a4 The parasitic capacitance of the switch S is charged. a1 (S a2 ) and S b3 (Sb4 ) of the parasitic capacitance, the voltage drops to zero, and the power supply current flows through S a1 (S a2 ) and S b3 (S b4 ) of the anti-parallel diode naturally conducts to continue the current, and the switch S a1 (S a2 ) and S b3 (S b4 ) realizes zero voltage (ZVS) conduction, at this time, the power supply current flows into V3, and the DC bus port absorbs power. The port voltage under this mode is: u1=V1, u2=V2, and u3=V3.

[0053] Figure 4 A PWM phase shift generation logic circuit diagram of an isolated three-port DC / DC converter provided by an embodiment of the present application, Figure 5 A PWM timing diagram of an isolated three-port DC / DC converter provided by an embodiment of the present application, thereby generating the PWM signal of the isolated three-port DC / DC converter under single phase shift control proposed by the present application.

[0054] Up to now, the modes 1-6 are the positive half cycle of a switching period, and the modes 7-12 are the negative half cycle of a switching period, and the operation characteristics of each mode can be obtained by comparing the corresponding modes of the positive half cycle, which will not be described here.

[0055] Figure 6 (a) is a DC bus port voltage simulation waveform diagram of an isolated three-port DC / DC converter under single phase shift control provided by an embodiment of the present application, Figure 6 (b) is a switch voltage simulation waveform diagram of a full-bridge capacitor clamped three-level circuit of an isolated three-port DC / DC converter under single phase shift control provided by an embodiment of the present application, and as can be seen from the diagram, the switch voltage stress of the full-bridge capacitor clamped three-level circuit is half of the DC bus port voltage, which reduces power loss, reduces cost, and improves conversion efficiency. Figure 7 A voltage waveform diagram between the drive signal and the drain-source of the switch S1, S5 and S a1 of an isolated three-port DC / DC converter under single phase shift control provided by an embodiment of the present application, and as can be seen from the diagram, the isolated three-port DC / DC converter topology proposed by the present application can realize soft switching.

[0056] The above specific embodiments have described the technical solutions and beneficial effects of the present application in detail, and it should be understood that the above description is only the most preferred embodiment of the present application, and is not used to limit the present application, and any modification, supplement and equivalent replacement, etc. within the principle range of the present application should be included in the protection range of the present application.

Claims

1. An isolated three-port DC / DC converter, characterized by, The application relates to an isolated three-port DC / DC converter. The two full-bridge circuits comprise a first full-bridge circuit and a second full-bridge circuit, the first full-bridge circuit is connected with a new energy port of a fuel cell / photovoltaic module, the second full-bridge circuit is connected with a storage element port of a storage battery / super capacitor, and the first full-bridge circuit and the second full-bridge circuit respectively comprise a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7 and an eighth switch tube S8. The three inductances include a first power transmission inductance L1 which is a sum of a leakage inductance on a primary winding side of a three-winding transformer and an external inductance, a second power transmission inductance L2 which is a sum of a leakage inductance on a first secondary winding side of the three-winding transformer and the external inductance, and a third power transmission inductance L3 which is a sum of a leakage inductance on a second secondary winding side of the three-winding transformer and the external inductance, and the three direct-current blocking capacitors include a first direct-current blocking capacitor C b1 , a second direct-current blocking capacitor C b2 , and a third direct-current blocking capacitor C b3 , the voltage stabilizing capacitors include a first voltage stabilizing capacitor C1, a second voltage stabilizing capacitor C2, and a third voltage stabilizing capacitor C5. The first full-bridge circuit comprises a first bridge arm branch formed by the first switch tube S1 and the second switch tube S2 in series connection and a second bridge arm branch formed by the third switch tube S3 and the fourth switch tube S4 in series connection. The full-bridge capacitor clamping three-level circuit is connected with a direct current bus port, and comprises a ninth switch tube S a1 , a tenth switch tube S a2 , an eleventh switch tube S a3 , a twelfth switch tube S a4 , a thirteenth switch tube S b1 , a fourteenth switch tube S b2 , a fifteenth switch tube S b3 , a sixteenth switch tube S b4 and a first embedding capacitor C3 and a second embedding capacitor C4.

2. An isolated three-port DC / DC converter according to claim 1, characterized in that The primary winding of the three-winding transformer is connected between the first switch tube S1 and the second switch tube S2 at the same name end and connected between the third switch tube S3 and the fourth switch tube S4 at the opposite name end. The second full-bridge circuit comprises a third bridge arm branch formed by the fifth switch tube S5 and the sixth switch tube S6 in series connection and a fourth bridge arm branch formed by the seventh switch tube S7 and the eighth switch tube S8 in series connection. The other end of the first power transmission inductor L1 is connected to the same end of the primary winding of the three-winding transformer in series, and the other end of the first DC blocking capacitor C b1 is connected between the first switch tube S1 and the second switch tube S2. b1 is connected between the first switch tube S1 and the second switch tube S2.

3. The isolated three-port DC / DC converter of claim 1, wherein The first secondary winding of the three-winding transformer is connected between the fifth switch tube S5 and the sixth switch tube S6 at the same name end and connected between the seventh switch tube S7 and the eighth switch tube S8 at the opposite name end. The isolated three-port DC / DC converter comprises three ports, the new energy port of the fuel cell / photovoltaic module is connected with the first bridge arm branch in parallel connection, the storage element port of the storage battery / super capacitor is connected with the third bridge arm branch in parallel connection, and the DC bus port is connected with the sixth bridge arm branch in parallel connection. The second power transmission inductance L2 is connected to the same end of the first secondary winding of the three-winding transformer through the second DC blocking capacitor C b2 In series, the other end of the second power transmission inductance L2 is connected to the same end of the first secondary winding of the three-winding transformer, and the other end of the second DC blocking capacitor C b2 is connected between the fifth switch tube S5 and the sixth switch tube S6.

4. The isolated three-port DC / DC converter of claim 1, wherein The full-bridge capacitor clamping three-level circuit comprises: a fifth bridge arm branch formed by a ninth switch S a1 , a tenth switch S a2 , an eleventh switch S a3 , a twelfth switch S a4 in series; a first capacitor branch formed by a first embedding capacitor C3; a sixth bridge arm branch formed by a thirteenth switch S b1 , a fourteenth switch S b2 , a fifteenth switch S b3 , a sixteenth switch S b4 in series; a second capacitor branch formed by a second embedding capacitor C4; the fifth bridge arm branch and the sixth bridge arm branch are in parallel; one end of the first capacitor branch is connected between the ninth switch S a1 and the tenth switch S a2 , and the other end is connected between the eleventh switch S a3 and the twelfth switch S a4 . One end of the second capacitor branch is connected between the thirteenth switch S b1 and the fourteenth switch S b2 , and the other end is connected between the fifteenth switch S b3 and the sixteenth switch S b4 . a second secondary winding of the three-winding transformer, whose same-named end is connected to the tenth switch S a2 and whose differently named end is connected to the fourteenth switch S a3 and whose differently named end is connected to the fifteenth switch S b2 and whose differently named end is connected to the fifteenth switch S b3 . The other end of the third power transmission inductance L3 is connected to the same end of the second secondary winding of the three-winding transformer in series, and the other end of the third DC blocking capacitor C b3 is connected to the tenth switch tube S b3 , and the other end of the eleventh switch tube S a2 . a3 ​ 5. The isolated three-port DC / DC converter of claim 1, wherein The isolated three-port DC / DC converter comprises three voltage stabilizing capacitors, a first voltage stabilizing capacitor is connected across the new energy port of the fuel cell / photovoltaic module in parallel connection, a second voltage stabilizing capacitor is connected across the storage element port of the storage battery / super capacitor in parallel connection, and a third voltage stabilizing capacitor C5 is connected across the DC bus port in parallel connection.

6. The isolated three-port DC / DC converter of claim 1, wherein The PWM phase shift control is adopted to realize bidirectional power transmission of the new energy port of the fuel cell / photovoltaic module, the storage element port of the storage battery / super capacitor and the DC bus port.

7. The isolated three-port DC / DC converter of claim 1, wherein ​

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