A V2G bidirectional DC-DC conversion circuit and converter

Abstract

The present invention proposes a V2G bidirectional DC-DC conversion circuit and converter, which relates to the technical field of power electronics. The proposed V2G bidirectional DC-DC conversion circuit can work in multiple modes, including boost charging mode, buck charging mode, V2G boost feedback grid mode and V2G buck feedback grid mode, and in different working modes, the energy flow direction is different, which can realize bidirectional transmission of energy; it can adapt to different input and output voltage levels, broadening the working range of traditional converters; in the voltage conversion link, multiple converters can be connected in series to adapt to different voltage requirements at both ends of the grid side and the electric vehicle side. This conversion circuit and converter can directly connect multiple new energy power generation with energy storage or electric vehicles, realize bidirectional energy flow control, and fully meet V2G needs.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and more specifically, to a V2G bidirectional DC-DC conversion circuit and a converter. Background Art

[0002] At present, against the backdrop of severe energy and environmental problems, people are beginning to seek ways to solve the energy crisis and air pollution and achieve a low-carbon economy and green sustainable development. Electric vehicles powered by electricity are gradually emerging in this context.

[0003] The popularity of electric vehicles has also brought new technical requirements, especially V2G (Vehicle-to-Grid) technology, which not only regards electric vehicles as means of transportation, but also as mobile energy storage units to participate in the energy management of the power grid. Most electric vehicles have a much longer parking time than the time they are in use, so the energy stored in the power battery of electric vehicles can be reasonably utilized. In the implementation of V2G technology, the bidirectional DC-DC converter is the core component connecting the electric vehicle and the power grid, which can reasonably control the input and output of power quality, and thus reasonably optimize the operation of the power grid. When the electric vehicle is charging, the smart charger starts the charging mode, and the charging of the power battery of the electric vehicle is DC charging. At this time, the bidirectional DC-DC converter will be in the working mode, matching the voltage of the DC energy storage unit with the voltage output by the bidirectional converter AC-DC. When the electric vehicle is parked, it can be discharged, and the smart charger starts the discharge mode. The discharge process of the power battery of the electric vehicle is exactly the opposite of the charging process.

[0004] According to the different circuit structures, bidirectional converters include CLLC bidirectional resonant converters, SC converters, etc. Among them, CLLC bidirectional resonant converters are realized by using multiple capacitors and inductors. When the electric energy flows in both directions, the conversion from electric energy to magnetic energy to electric energy is realized because of the participation of inductors, and there are many links in the middle. In applications with relatively high input and output voltages, the power density of bidirectional converters is usually limited by the bulky magnetic components. The volume can be reduced by increasing the switching frequency, but the loss caused by switching will also cause the conversion efficiency of the bidirectional converter to decrease. The structure of the SC converter does not contain inductors and transformers, but only consists of a capacitor network and a switch tube. With its advantages of high efficiency, small size and light weight, it has shown a wide range of application prospects in many fields. However, there are still many problems with the SC converter, such as challenges in startup, protection, MOS tube gate drive, etc., which are limited to low-power applications. The current application direction is basically unidirectional energy transmission, which cannot meet the needs of V2G and has a narrow working range. Summary of the invention

[0005] In order to solve the problem of narrow working range of current bidirectional DC-DC converters, the present invention proposes a V2G bidirectional DC-DC conversion circuit and converter, which are mainly composed of capacitors, with less inductance components, light mass and volume, but have rich working modes, broadened working range, can adapt to different input and output voltage levels, and also meet V2G requirements.

[0006] In order to achieve the above technical effects, the technical solution of the present invention is as follows:

[0007] A V2G bidirectional DC-DC conversion circuit, the circuit comprising: an input DC port switch module, a switch capacitor module and an output DC port module;

[0008] The first end of the input DC port switch module is connected to the first end of the switch capacitor module, the second end of the input DC port switch module is connected to the second end of the switch capacitor module, and the third end of the switch capacitor module and the third end of the input DC port switch module are both connected to the output DC port module;

[0009] The input DC port switch module and the switch capacitor module are both provided with a plurality of power switch tubes, the gates of the plurality of power switch tubes are all connected to control signals, and the control signals control the power switch tubes to be turned on and off, so that the circuit operates in a boost charging mode, a buck charging mode, a V2G boost feedback grid mode and a V2G buck feedback grid mode, wherein the energy flow direction in the circuit in the boost charging mode and the buck charging mode is opposite to the energy flow direction in the circuit in the V2G boost feedback grid mode and the V2G buck feedback grid mode.

[0010] According to the above technical means, the V2G bidirectional DC-DC conversion circuit has a rich working mode, broadened the working range, and can adapt to different input and output voltage levels. In different working modes, the energy flow direction is different, and bidirectional energy transmission can be realized. It can directly connect multiple new energy power generation, energy storage or electric vehicles, and the ports are directly interconnected, fully meeting V2G needs.

[0011] Preferably, the input DC port switch module includes power switch tubes S1 and S2, the source of the power switch tube S1 is connected to the drain of the power switch tube S2; the switch capacitor module includes: a filter inductor L4, a power switch tube S7, a power switch tube S8, a power switch tube S9, a power switch tube S 10 , power switch tube S 11 , capacitor C1, capacitor C4 and capacitor C5; the output DC port module includes a filter inductor L7 and a capacitor C8;

[0012] The source of the power switch tube S1 is connected to the drain of the power switch tube S2, the drain of the power switch tube S1 is connected to the drain of the power switch tube S7, the source of the power switch tube S1 and the drain of the power switch tube S2 are both connected to one end of the filter inductor L4, and the other end of the filter inductor L4 is respectively connected to one end of the capacitor C1, one end of the capacitor C5 and the power switch tube S 11 The other end of capacitor C1 is connected to the source of power switch tube S7 and the source of power switch tube S8 respectively. The drain of power switch tube S8 and the source of power switch tube S9 are both connected to one end of capacitor C4. The other end of capacitor C4 is connected to the source of power switch tube S2. The drain of power switch tube S9 is connected to the other end of capacitor C5 and the source of power switch tube S 10 The drain of the power switch tube S 10 The source of the power switch tube S 11 The drain of the power switch S2 is connected to one end of the filter inductor L7, the other end of the filter inductor L7 is connected to one end of the capacitor C8, and the other end of the capacitor C8 is connected to the source of the power switch tube S2.

[0013] According to the above technical means, the bidirectional DC-DC conversion circuit is mainly composed of capacitors, with less inductance components, light mass and volume, which can reduce the cost of the converter.

[0014] Preferably, the grid charges the electric vehicle, the electric energy is transferred from the AC side to the DC side, and the power switch tube S 10 The power switch tube S8, power switch tube S9, power switch tube S 11 Turn off, the anti-parallel diodes of the power switch tube S8 and the power switch tube S9 work;

[0015] When the power switch tube S1 is turned off and the power switch tube S2 is turned on, the input DC port voltage U AB Charge capacitor C1 until the input DC port voltage U AB The voltage across capacitor C1 Equal to, satisfy:

[0016]

[0017] If the voltage of capacitor C5 is lower than the voltage of capacitor C4, capacitor C4 charges capacitor C5 until the voltage of capacitor C5 reaches The voltage of capacitor C4 equal, and the output DC port voltage U CD The voltage of capacitor C5 is equal to that of capacitor C5, satisfying:

[0018]

[0019] When the power switch tube S1 is turned on and the power switch tube S2 is turned off, the input DC port is connected in series with the capacitor C1 to charge the capacitor C4, and the input DC port is connected in series with the capacitor C5 to charge the output DC port, satisfying:

[0020]

[0021]

[0022] Under the premise that the power switch tube S1 and the power switch tube S2 are turned on alternately, the voltage of capacitor C4 Maintained at 2U AB ; When the power switch tube S1 is turned off and the power switch tube S2 is turned on, the output DC port voltage U CD Maintained at 2U AB When the power switch tube S1 is turned on and the power switch tube S2 is turned off, the output DC port voltage U CD Maintained at 3U AB ; The circuit operates in boost charging mode.

[0023] Preferably, the grid charges the electric vehicle, the electric energy is transferred from the AC side to the DC side, and the power switch tube S 10 When the power switch tube S1 is turned off, the power switch tube S8 and the power switch tube S9 are turned on. 11 When the power switch tube S2 is turned on, the power switch tube S7 is turned on and off alternately, and the input DC port voltage, capacitor C1, capacitor C4, and capacitor C5 form the first-level Buck step-down. The voltage of capacitor C4 With the input DC port voltage U AB The relationship satisfies: Power switch tube S 10 , filter inductor L4, capacitor C8 form the second stage Buck step-down, The circuit operates in a step-down charging mode.

[0024] According to the above technical means, through two-stage Buck step-down, the step-down charging of electric vehicles can be realized with high efficiency, meeting the charging needs of low-speed passenger cars.

[0025] Preferably, the electric vehicle is used as an energy storage unit to feed back to the power grid, the electric energy is transferred from the DC side to the AC side, and the power switch tube S7 and the power switch tube S9 are turned on;

[0026] When the power switch tube S1 is turned off and the power switch tube S2 is turned on, if the voltage of capacitor C4 With the output DC port voltage U CD Relationship satisfaction: U C4 ≤U CD , then the power switch tube S 10The output DC port voltage U CD Charge capacitors C4 and C5, so that the voltage of capacitor C5 With the output DC port voltage U CD satisfy:

[0027] U C5 ≥U CD

[0028] Then the power switch tube S 10 Turn off the power switch S 11 Conducting, output DC port voltage U CD Connected in series with capacitor C5 to charge capacitors C1 and C4, the voltage of capacitor C1 The voltage of capacitor C4 Output DC port voltage U CD and the voltage of capacitor C5 Satisfy between:

[0029]

[0030]

[0031] When the power switch tube S1 is turned off and the power switch tube S2 is turned off, the output DC port voltage U CD It is connected in series with capacitor C1 to charge the input DC port, capacitor C1 charges capacitor C5, and after boosting again, the electric energy is fed to the input DC port. The circuit works in V2G boost feedback grid mode.

[0032] Preferably, the electric vehicle is used as an energy storage unit to feed back to the grid, and the electric energy is transferred from the DC side to the AC side. The power switch tube S1 and the power switch tube S 11 Always off, power switch tube S2, power switch tube S7 and power switch tube S 10 Always on, input DC port voltage U AB Less than the output DC port voltage U CD When the power switch tube S9 is turned on and the power switch tube S8 is turned off, the filter inductor L7 and the power switch tube S 10 , power switch tube S9, capacitor C4 and capacitor C5 together form the first stage Buck buck; when the power switch tube S9 is turned on and the power switch tube S8 is turned on, the power switch tube S8, capacitor C1 and power switch tube S7 together form the second stage Buck buck; the circuit operates in the V2G buck feedback grid mode.

[0033] Preferably, the power switch tube is a MOSFET tube.

[0034] Preferably, the V2G bidirectional DC-DC conversion circuit is a switched capacitor conversion circuit.

[0035] The present application also proposes a V2G bidirectional DC-DC converter, which includes at least one V2G bidirectional DC-DC conversion circuit.

[0036] Preferably, the converter is composed of at least two of the V2G bidirectional DC-DC conversion circuits connected in series.

[0037] According to the above technical means, the V2G bidirectional DC-DC converter can adapt to the different voltage requirements on the grid side and the electric vehicle side in the voltage conversion link by connecting multiple stages in series, enriching the applicable range of the converter's working voltage and effectively reducing the complexity of the circuit system; moreover, when the V2G bidirectional DC-DC converter is reversely operated, it can make energy flow from the right side to the left side, realizing the V2G function, so that the port can adapt to different input and output voltage levels.

[0038] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0039] The present invention proposes a V2G bidirectional DC-DC conversion circuit and a converter. The working modes of the proposed V2G bidirectional DC-DC conversion circuit include a boost charging mode, a buck charging mode, a V2G boost feedback grid mode and a V2G buck feedback grid mode. There are many working modes, and in different working modes, the energy flow direction is different, and bidirectional energy transmission can be achieved; it can adapt to different input and output voltage levels, broaden the working range of traditional converters, and can adapt to different voltage requirements at both ends of the grid side and the electric vehicle side in the voltage conversion link through the property of being able to connect multiple stages in series. Multiple new energy power generation, energy storage or electric vehicles can be directly connected, and the ports are directly interconnected, fully meeting the V2G requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A circuit structure diagram showing a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention;

[0041] Figure 2 A schematic diagram showing the boost charging direction when the V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention works in a boost charging mode, the power switch tube S1 is turned off, and the power switch tube S2 is turned on;

[0042] Figure 3 A schematic diagram showing the boost charging direction when the V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention works in a boost charging mode, the power switch tube S1 is turned on, and the power switch tube S2 is turned off;

[0043] Figure 4A schematic diagram showing simulation results of a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention operating in a boost charging mode;

[0044] Figure 5 A schematic diagram showing the buck charging direction of the V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention when the power switch tube S7 is turned on and the circuit operates in the buck charging mode;

[0045] Figure 6 A schematic diagram showing the buck charging direction of the V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention working in a buck charging mode when the power switch tube S7 is turned off;

[0046] Figure 7 A schematic diagram showing simulation results of a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention operating in a buck charging mode;

[0047] Figure 8 A modal schematic diagram showing a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention working in a V2G boost feedback grid mode, with the power switch tube S1 turned off and the power switch tube S2 turned on;

[0048] Fig. 9 Another mode schematic diagram showing the V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention working in the V2G boost feedback grid mode, when the power switch tube S1 is turned off and the power switch tube S2 is turned on;

[0049] Fig.10 A modal schematic diagram showing a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention working in a V2G boost feedback grid mode, when the power switch tube S1 is turned off and the power switch tube S2 is turned off;

[0050] Fig.11 A schematic diagram showing simulation results of a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention operating in a V2G boost feedback grid mode;

[0051] Fig.12 A modal schematic diagram showing a V2G bidirectional DC-DC conversion circuit proposed in an embodiment of the present invention working in a V2G buck feedback grid mode;

[0052] Fig.13 A schematic diagram showing simulation results of a V2G bidirectional DC-DC conversion circuit according to an embodiment of the present invention operating in a V2G buck feedback grid mode. DETAILED DESCRIPTION

[0053] The drawings are for illustrative purposes only and should not be construed as limiting the present patent;

[0054] In order to better illustrate the present embodiment, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the actual size;

[0055] It is understandable to those skilled in the art that descriptions of certain well-known contents in the drawings may be omitted.

[0056] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0057] The positional relationships described in the drawings are only for illustrative purposes and should not be construed as limiting the present patent;

[0058] Example 1

[0059] like Figure 1 As shown, this embodiment proposes a V2G bidirectional DC-DC conversion circuit, see Figure 1 , including: an input DC port switch module 1, a switch capacitor module 2 and an output DC port module 3;

[0060] The first end of the input DC port switch module 1 is connected to the first end of the switch capacitor module 2, the second end of the input DC port switch module 1 is connected to the second end of the switch capacitor module 2, and the third end of the switch capacitor module 2 and the third end of the input DC port switch module 1 are both connected to the output DC port module 3;

[0061] A plurality of power switch tubes are provided in the input DC port switch module 1 and the switch capacitor module 2, and the gate of each power switch tube is connected to a control signal. In the present embodiment, the control signal may be issued by an external controller, that is, the gate of each power switch tube is connected to the controller, and the control signal controls the power switch tube to be turned on and off, so that the circuit operates in a boost charging mode, a buck charging mode, a V2G boost feedback grid mode and a V2G buck feedback grid mode, wherein the energy flow direction in the circuit in the boost charging mode and the buck charging mode is opposite to the energy flow direction in the circuit in the V2G boost feedback grid mode and the V2G buck feedback grid mode.

[0062] The V2G bidirectional DC-DC conversion circuit proposed in this embodiment has a variety of working modes, including boost charging mode, buck charging mode, V2G boost feedback grid mode and V2G buck feedback grid mode. Compared with the traditional switched capacitor converter, it has a wider working range and can adapt to different input and output voltage levels. In different working modes, the energy flow direction is different, and bidirectional energy transmission can be achieved. In the specific implementation market, multiple new energy power generation, energy storage or electric vehicles can be directly connected, and the ports are directly interconnected, which fully meets the V2G needs.

[0063] In this embodiment, if Figure 1As shown, the input DC port switch module 1 includes power switch tubes S1 and S2, and the source of the power switch tube S1 is connected to the drain of the power switch tube S2; the switch capacitor module 2 includes: a filter inductor L4, a power switch tube S7, a power switch tube S8, a power switch tube S9, a power switch tube S 10 , power switch tube S 11 , capacitor C1, capacitor C4 and capacitor C5; the output DC port module 3 includes a filter inductor L7 and a capacitor C8;

[0064] The source of the power switch tube S1 is connected to the drain of the power switch tube S2, the drain of the power switch tube S1 is connected to the drain of the power switch tube S7, the source of the power switch tube S1 and the drain of the power switch tube S2 are both connected to one end of the filter inductor L4, and the other end of the filter inductor L4 is respectively connected to one end of the capacitor C1, one end of the capacitor C5 and the power switch tube S 11 The other end of capacitor C1 is connected to the source of power switch tube S7 and the source of power switch tube S8 respectively. The drain of power switch tube S8 and the source of power switch tube S9 are both connected to one end of capacitor C4. The other end of capacitor C4 is connected to the source of power switch tube S2. The drain of power switch tube S9 is connected to the other end of capacitor C5 and the source of power switch tube S 10 The drain of the power switch tube S 10 The source of the power switch tube S 11 The drain of the power switch S2 is connected to one end of the filter inductor L7, the other end of the filter inductor L7 is connected to one end of the capacitor C8, and the other end of the capacitor C8 is connected to the source of the power switch tube S2.

[0065] Depend on Figure 1 It can be seen from the circuit shown that the bidirectional DC-DC conversion circuit proposed in this embodiment is mainly composed of capacitors with less inductance components. Compared with the traditional CLLC converter, it is light in mass and volume, thereby reducing the cost of the converter.

[0066] Example 2

[0067] In combination with the structure of the bidirectional DC-DC conversion circuit proposed in Example 1, the boost charging mode, buck charging mode, V2G boost feedback grid mode and V2G buck feedback grid mode of the circuit operation are described in turn.

[0068] Among them, the component parameters in the circuit satisfy: L4=0.1mH, L7=0.6mH, C1=C8=1000uF, C4=C5=500uF.

[0069] (1) Buck charging mode

[0070] In this mode, considering the grid charging the electric vehicle, the electric energy is transferred from the AC side to the DC side, and the power switch tube S10 The power switch tube S8 and the power switch tube S9 are turned on, and the anti-parallel diodes of the power switch tubes S8 and S9 work;

[0071] See also Figure 2 From left to right, in the direction of the first arrow, when the power switch tube S1 is turned off and the power switch tube S2 is turned on, the input DC port voltage U AB (here refers to the voltage after three-phase rectification) to charge capacitor C1 until the input DC port voltage U AB The voltage across capacitor C1 Equal to, satisfy:

[0072]

[0073] See also Figure 2 In the direction of the other arrows shown, if the voltage of capacitor C5 is lower than the voltage of capacitor C4, capacitor C4 charges capacitor C5 until the voltage of capacitor C5 reaches The voltage of capacitor C4 equal, and the output DC port voltage U CD The voltage of capacitor C5 is equal to that of capacitor C5, satisfying:

[0074]

[0075] like Figure 3 As shown, when the power switch tube S1 is turned on and the power switch tube S2 is turned off, refer to the direction of the arrow, the input DC port is connected in series with the capacitor C1 to charge the capacitor C4, and the input DC port is connected in series with the capacitor C5 to charge the output DC port, satisfying:

[0076]

[0077]

[0078] Under the premise that the power switch tube S1 and the power switch tube S2 are turned on alternately, the voltage of capacitor C4 Maintained at 2U AB ; When the power switch tube S1 is turned off and the power switch tube S2 is turned on, the output DC port voltage U CD Maintained at 2U AB When the power switch tube S1 is turned on and the power switch tube S2 is turned off, the output DC port voltage U CD Maintain at 3U AB .

[0079] In this embodiment, the power switch tubes S1, S2 and S7 are turned on alternately, and the power switch tubes S8, S9 and S1 are turned on alternately. 11 Turn off, the power switch tube S 10The switch frequency is 5.7kHz, 400V DC is input on the left, and 1200V DC is output on the right. Both voltage and current are positive, energy is transferred from left to right, and boost charging is achieved. The simulation results can be seen in the figure Figure 4 , the simulation voltage shown is the DC voltage at the output end on the right side of the circuit, which realizes the boost charging function from 400V to 1200V in a relatively short time. Under the premise that the power switch tube S1 and the power switch tube S2 are alternately turned on, the charging voltage remains basically constant as time increases.

[0080] (2) Buck charging mode

[0081] In this embodiment, the power grid charges the electric vehicle, and the electric energy is transferred from the AC side to the DC side. 10 When the power switch tube S1 is turned off, the power switch tube S8 and the power switch tube S9 are turned on. 11 When the power switch tube S2 is turned on, the power switch tube S7 is turned on and off alternately, and the input DC port voltage, capacitor C1, capacitor C4, and capacitor C5 form the first-level Buck step-down. The voltage of capacitor C4 With the input DC port voltage U AB The relationship satisfies: Power switch tube S 10 , filter inductor L4, capacitor C8 form the second stage Buck step-down,

[0082] Figure 5 The charging direction modal diagram when the power switch tube S7 is turned on is shown. Figure 6 The charging direction mode diagram shows the charging direction when the power switch tube S7 is turned off. The arrow direction indicates the charging direction. The power switch tube S7 is turned on and off alternately, and the power switch tubes S1 and S7 are kept on. 11 Turn off, the power switch tube S 10 When the power switch tube S8, power switch tube S9 and power switch tube S2 are turned on, the switching frequency is selected to be 17kHz, 400V DC is input on the left side, and 100V DC is output on the right side. Both the voltage and current are positive, the energy is transferred from left to right, and the step-down charging is achieved. The simulation result can be seen in Figure 7 The simulation voltage shown is the DC voltage at the output end on the right side of the circuit. Through two-stage Buck step-down, the 400V grid-side input voltage is converted into a 100V low-voltage output in a relatively short time, which can efficiently realize the step-down charging of electric vehicles and meet the charging needs of low-speed passenger vehicles.

[0083] (3) V2G boost feedback grid mode

[0084] In this mode, electric vehicles are used as energy storage units to feed back to the grid, and electric energy is transferred from the DC side to the AC side, and the power switch tubes S7 and S9 are turned on;

[0085] When the power switch tube S1 is turned off and the power switch tube S2 is turned on, if the voltage of capacitor C4 With the output DC port voltage U CD Relationship satisfaction: U C4 ≤U CD , then the power switch tube S 10 Turn-on, at this time, see Figure 8 The charging direction shown is determined by the output DC port voltage U CD Charge capacitors C4 and C5, so that the voltage of capacitor C5 With the output DC port voltage U CD satisfy:

[0086] U C5 ≥U CD

[0087] Then the power switch tube S 10 Turn off the power switch S 11 Turn-on, at this time, see Fig. 9 The charging direction shown, the output DC port voltage U CD Connected in series with capacitor C5 to charge capacitors C1 and C4, the voltage of capacitor C1 The voltage of capacitor C4 Output DC port voltage U CD and the voltage of capacitor C5 Satisfy between:

[0088]

[0089]

[0090] When the power switch tube S1 is turned off, the power switch tube S2 is turned off, see Fig.10 The charging direction shown, the output DC port voltage U CD It is connected in series with capacitor C1 to charge the input DC port, capacitor C1 charges capacitor C5, and after boosting again, the electric energy is fed to the input DC port. The circuit works in V2G boost feedback grid mode.

[0091] Keep the power switch tube S1 off all the time, ensure that the power switch tubes S7 and S9 are always on, and alternately turn on and off the power switch tube S2. When the power switch tube S1 is off and the power switch tube S2 is on, if U C4 ≤U CD , then the power switch tube S 10 , by U CDCharge capacitors C4 and C5. C5 ≥U CD When the power switch tube S is turned off 10 , turn on the power switch tube S 11 , U CD Connected in series with capacitor C5, capacitor C1 and capacitor C4 are charged. 100V DC is input to the right side of the circuit, and 400V DC is output on the left side. The voltage is positive and the current is negative. Energy is transferred from right to left, achieving V2G boost charging. The simulation results in this mode can be seen in the figure. Fig.11 The simulation voltage shown is the DC voltage at the output end on the left side of the circuit, which realizes the V2G boost charging function from 400V to 1200V in a relatively short time.

[0092] (4) V2G voltage reduction feedback grid mode

[0093] In this mode, electric vehicles are used as energy storage units to feed back to the grid, and the electric energy is transferred from the DC side to the AC side. Fig.12 As shown, the power switch tube S1 and the power switch tube S 11 Always off, power switch tube S2, power switch tube S7 and power switch tube S 10 Always on, input DC port voltage U AB Less than the output DC port voltage U CD When the power switch tube S9 is turned on and the power switch tube S8 is turned off, the filter inductor L7 and the power switch tube S 10 , power switch tube S9, capacitor C4 and capacitor C5 together form the first stage Buck buck; when the power switch tube S9 is turned on and the power switch tube S8 is turned on, the power switch tube S8, capacitor C1 and power switch tube S7 together form the second stage Buck buck. The charging direction in this mode can be seen in Fig.12 The simulation results can be found in Fig.13 , the simulation voltage shown is the DC voltage at the output end on the left side of the circuit, and the V2G step-down charging function from 400V to 100V is realized in a relatively short time. In actual implementation, 400V DC is input on the right side and 100V DC is output on the left side. A 4:1 step-down is achieved. The voltage is positive and the current is negative, so the energy is transferred from right to left, realizing V2G step-down charging.

[0094] In this embodiment, the power switch tube is a MOSFET tube, and the V2G bidirectional DC-DC conversion circuit is a switched capacitor conversion circuit.

[0095] Example 3

[0096] This embodiment further proposes a V2G bidirectional DC-DC converter, which includes at least one V2G bidirectional DC-DC conversion circuit. In specific implementation, in order to adapt to different voltage requirements at the grid side and the electric vehicle side, the converter can be composed of at least two V2G bidirectional DC-DC conversion circuits connected in series in sequence. In the voltage conversion link, the application range of the converter working voltage is enriched by the property of being able to be connected in series at multiple levels, and the complexity of the circuit system is effectively reduced; moreover, when the V2G bidirectional DC-DC converter is reversely operated, it can make energy flow from the right side to the left side, realizing the V2G function, so that the port can adapt to different input and output voltage levels.

[0097] The embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A V2G bidirectional DC-DC conversion circuit, characterized in that: The circuit comprises: an input DC port switch module, a switch capacitor module and an output DC port module; The first end of the input DC port switch module is connected to the first end of the switch capacitor module, the second end of the input DC port switch module is connected to the second end of the switch capacitor module, and the third end of the switch capacitor module and the third end of the input DC port switch module are both connected to the output DC port module; The input DC port switch module and the switch capacitor module are both provided with a plurality of power switch tubes, the gates of the plurality of power switch tubes are all connected to control signals, and the control signals control the power switch tubes to be turned on and off, so that the circuit operates in a boost charging mode, a buck charging mode, a V2G boost feedback grid mode and a V2G buck feedback grid mode, wherein the energy flow direction in the circuit in the boost charging mode and the buck charging mode is opposite to the energy flow direction in the circuit in the V2G boost feedback grid mode and the V2G buck feedback grid mode; The input DC port switch module includes power switch tubes S1 and S2, the source of the power switch tube S1 is connected to the drain of the power switch tube S2; the switch capacitor module includes: a filter inductor L4, a power switch tube S7, a power switch tube S8, a power switch tube S9, a power switch tube S 10 , power switch tube S 11 , capacitor C1, capacitor C4 and capacitor C5; the output DC port module includes a filter inductor L7 and a capacitor C8; The source of the power switch tube S1 is connected to the drain of the power switch tube S2, the drain of the power switch tube S1 is connected to the drain of the power switch tube S7, the source of the power switch tube S1 and the drain of the power switch tube S2 are both connected to one end of the filter inductor L4, and the other end of the filter inductor L4 is respectively connected to one end of the capacitor C1, one end of the capacitor C5 and the power switch tube S 11 The other end of capacitor C1 is connected to the source of power switch tube S7 and the source of power switch tube S8 respectively. The drain of power switch tube S8 and the source of power switch tube S9 are both connected to one end of capacitor C4. The other end of capacitor C4 is connected to the source of power switch tube S2. The drain of power switch tube S9 is connected to the other end of capacitor C5 and the source of power switch tube S 10 The drain of the power switch tube S 10 The source of the power switch tube S 11 The drain of the power switch S2 is connected to one end of the filter inductor L7, the other end of the filter inductor L7 is connected to one end of the capacitor C8, and the other end of the capacitor C8 is connected to the source of the power switch tube S2.

2. The V2G bidirectional DC-DC conversion circuit according to claim 1, characterized in that: The grid charges the electric vehicle, and the electric energy is transferred from the AC side to the DC side. The power switch tube S 10 The power switch tube S8, power switch tube S9, power switch tube S 11 Turn off, the anti-parallel diodes of the power switch tube S8 and the power switch tube S9 work; When the power switch tube S1 is turned off and the power switch tube S2 is turned on, the input DC port voltage Charge capacitor C1 until the input DC port voltage reaches The voltage across capacitor C1 Equal to, satisfy: If the voltage of capacitor C5 is lower than the voltage of capacitor C4, capacitor C4 charges capacitor C5 until the voltage of capacitor C5 reaches The voltage of capacitor C4 equal, and the output DC port voltage The voltage of capacitor C5 is equal to that of capacitor C5, satisfying: When the power switch tube S1 is turned on and the power switch tube S2 is turned off, the input DC port is connected in series with the capacitor C1 to charge the capacitor C4, and the input DC port is connected in series with the capacitor C5 to charge the output DC port, satisfying: Under the premise that the power switch tube S1 and the power switch tube S2 are turned on alternately, the voltage of capacitor C4 Maintain at 2 ; When the power switch tube S1 is turned off and the power switch tube S2 is turned on, the output DC port voltage Maintain at 2 When the power switch tube S1 is turned on and the power switch tube S2 is turned off, the output DC port voltage Maintain at 3 ; The circuit operates in boost charging mode.

3. The V2G bidirectional DC-DC conversion circuit according to claim 1, characterized in that: The grid charges the electric vehicle, and the electric energy is transferred from the AC side to the DC side. The power switch tube S 10 When the power switch tube S1 is turned off, the power switch tube S8 and the power switch tube S9 are turned on. 11 When the power switch tube S2 is turned on, the power switch tube S7 is turned on and off alternately, and the input DC port voltage, capacitor C1, capacitor C4, and capacitor C5 form the first-level Buck step-down. The voltage of capacitor C4 With input DC port voltage The relationship satisfies: ; Power switch tube S 10 , filter inductor L4, capacitor C8 form the second stage Buck step-down, ; The circuit operates in a buck charging mode.

4. The V2G bidirectional DC-DC conversion circuit according to claim 1, characterized in that: Using electric vehicles as energy storage units to feed back to the grid, electric energy is transferred from the DC side to the AC side, and the power switch tubes S7 and S9 are turned on; When the power switch tube S1 is turned off and the power switch tube S2 is turned on, if the voltage of capacitor C4 and output DC port voltage The relationship satisfies: , then the power switch tube S 10 conduction, by the output DC port voltage Charge capacitors C4 and C5, so that the voltage of capacitor C5 and output DC port voltage satisfy: Then the power switch tube S 10 Turn off the power switch S 11 Conducting, output DC port voltage Connected in series with capacitor C5 to charge capacitors C1 and C4, the voltage of capacitor C1 , the voltage of capacitor C4 , Output DC port voltage and the voltage of capacitor C5 Satisfy between: When the power switch tube S1 is turned off and the power switch tube S2 is turned off, the output DC port voltage It is connected in series with capacitor C1 to charge the input DC port, capacitor C1 charges capacitor C5, and after boosting again, the electric energy is fed to the input DC port. The circuit works in V2G boost feedback grid mode.

5. The V2G bidirectional DC-DC conversion circuit according to claim 1, characterized in that: Using electric vehicles as energy storage units to feed back to the grid, the electric energy is transferred from the DC side to the AC side, and the power switch tube S1 and the power switch tube S 11 Always off, power switch tube S2, power switch tube S7 and power switch tube S 10 Always on, Output DC port voltage When the power switch tube S9 is turned on and the power switch tube S8 is turned off, the filter inductor L7 and the power switch tube S 10 , power switch tube S9, capacitor C4 and capacitor C5 together form the first stage Buck buck; when the power switch tube S9 is turned on and the power switch tube S8 is turned on, the power switch tube S8, capacitor C1 and power switch tube S7 together form the second stage Buck buck; the circuit operates in the V2G buck feedback grid mode.

6. The V2G bidirectional DC-DC conversion circuit according to any one of claims 1 to 5, characterized in that: The power switch tube is a MOSFET tube.

7. The V2G bidirectional DC-DC conversion circuit according to any one of claims 1 to 5, characterized in that: The V2G bidirectional DC-DC conversion circuit is a switched capacitor conversion circuit.

8. A V2G bidirectional DC-DC converter, characterized in that: The converter comprises at least one V2G bidirectional DC-DC conversion circuit as described in any one of claims 1 to 5.

9. The V2G bidirectional DC-DC converter according to claim 8, characterized in that: The converter is composed of at least two V2G bidirectional DC-DC conversion circuits connected in series.

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