A single-stage three-port vehicle-mounted charging and discharging circuit and method

Abstract

The present application discloses a single-stage three-port vehicle-mounted charging and discharging circuit and method, the circuit comprising: a transformer, a three-phase bridge circuit connected between an AC power source and a primary winding of the transformer, a first power conversion circuit connected between a first secondary winding of the transformer and a first battery, and a second power conversion circuit connected between a second secondary winding of the transformer and a second battery, so that the transformer directly couples the three-phase bridge circuit, the first power conversion circuit, and the second power conversion circuit. Thus, the transformer can convert the voltages corresponding to the primary winding, the first secondary winding, and the second secondary winding to each other, thereby realizing the transmission of electric energy between the AC power source, the first battery, and the second battery. Since the coupling between multiple circuits is completed using only one transformer, it not only reduces the volume of the entire circuit, but also reduces the power loss during the electrical transmission process, thereby improving work efficiency.

Description

Technical Field

[0001] The present application relates to the field of automobile technology, and in particular to a single-stage three-port vehicle-mounted charging and discharging circuit and method. Background Art

[0002] With the popularity of new energy vehicles, electricity consumption is also rising, and the demand for car charging is also increasing. The traditional on-board charger (OBC) technical solution usually uses a power factor correction (PFC) circuit in series with a single high-voltage DC transmission circuit to charge the high-voltage battery. The traditional technical solution requires a large number of circuit components to be built, not only requiring PFC inductors, bus electrolytic capacitors, OBC main transformers, DCDC main transformers and other components for electrical coupling.

[0003] Moreover, with the increase in charging demand, it is now necessary to charge the low-voltage battery in the vehicle, that is, multiple charging methods have been added. Since there are multiple charging methods and the working parameters of each power source are different, it is necessary to set up corresponding electrical coupling circuits and corresponding control circuits between each power source, which further increases the number of required circuits and components, resulting in the inability to miniaturize the on-board charger, low working efficiency, and high cost. Summary of the invention

[0004] The main purpose of this application is to provide a single-stage three-port vehicle-mounted charging and discharging circuit and method, aiming to solve the technical problem of how to reduce the size of the vehicle-mounted charger and improve the working efficiency of the vehicle-mounted charger.

[0005] To achieve the above objectives, the present application provides a single-stage three-port vehicle-mounted charging and discharging circuit. The single-stage three-port vehicle-mounted charging and discharging circuit includes:

[0006] A transformer, comprising a primary winding, a first secondary winding and a second secondary winding, for mutually converting a first winding voltage of the primary winding, a second winding voltage of the first secondary winding and a third winding voltage of the second secondary winding;

[0007] A three-phase bridge circuit, connected to an AC power source and the primary winding, respectively, for providing a voltage boost, converting the power frequency voltage into a high-frequency voltage through a switching action and transmitting it to the secondary side via the transformer;

[0008] a first power conversion circuit, the first power conversion circuit being connected between the first secondary winding and the first battery and configured to cooperate with the three-phase bridge circuit to perform a switching action so as to achieve power factor correction while performing power conversion;

[0009] The second power conversion circuit is connected between the second secondary winding and the second battery.

[0010] In one embodiment, the transformer is further used to convert the first winding voltage transmitted by the three-phase bridge circuit into the second winding voltage, and transmit the second winding voltage to the first power conversion circuit, so that the AC power supply charges the first battery;

[0011] The transformer is further used to convert the second winding voltage transmitted by the first power conversion circuit into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit to discharge the first battery.

[0012] In one embodiment, the transformer is further used to convert the first winding voltage transmitted by the three-phase bridge circuit into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit, so that the AC power supply charges the second battery;

[0013] The transformer is further used to convert the third winding voltage transmitted by the second power conversion circuit into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit to discharge the second battery.

[0014] In one embodiment, the transformer is further used to convert the second winding voltage transmitted by the first power conversion circuit into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit, so that the first battery charges the second battery;

[0015] The transformer is further used to convert the third winding voltage transmitted by the second power conversion circuit into the second winding voltage, and transmit the second winding voltage to the first power conversion circuit, so that the second battery charges the first battery.

[0016] In one embodiment, the second power conversion circuit includes: a rectifier circuit and a voltage stabilizing circuit;

[0017] The rectifier circuit is respectively connected to the second secondary winding and the voltage stabilizing circuit, and the voltage stabilizing circuit is also connected to the second battery;

[0018] The rectifier circuit is used to rectify the current transmitted by the second secondary winding;

[0019] The voltage stabilizing circuit is used to stabilize the rectified current to a preset voltage corresponding to the second battery.

[0020] In one embodiment, the voltage stabilizing circuit includes: a first switch tube, a first inductor and a first capacitor;

[0021] The first end of the first switch tube is respectively connected to the rectifier circuit and the first end of the first inductor, the second end of the first inductor is respectively connected to the first end of the first capacitor and the second battery, and the second end of the first capacitor is grounded.

[0022] In one embodiment, the rectifier circuit includes: a second switch tube, a third switch tube and a fourth switch tube;

[0023] The first end of the second switch tube is connected to the first end of the second secondary winding, the first end of the third switch tube is connected to the second end of the second secondary winding, and the first end of the fourth switch tube is connected to the middle end of the second secondary winding; the second end of the second switch tube and the second end of the third switch tube are grounded; the second end of the fourth switch tube is connected to the voltage stabilizing circuit;

[0024] Or, the rectifier circuit includes: a fifth switch tube, a sixth switch tube and a seventh switch tube;

[0025] The first end of the fifth switch tube is connected to the first end of the second secondary winding, the first end of the sixth switch tube is connected to the second end of the second secondary winding, the second end of the seventh switch tube is connected to the second end of the fifth switch tube and the second end of the sixth switch tube, and the first end of the seventh switch tube is grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit;

[0026] Or, the rectifier circuit includes: an eighth switch tube, a ninth switch tube, a tenth switch tube and an eleventh switch tube;

[0027] The first end of the eighth switch tube is connected to the first end of the ninth switch tube, the second end of the eighth switch tube is connected to the first end of the second secondary winding, the first end of the tenth switch tube is connected to the first end of the eleventh switch tube, the second end of the tenth switch tube is connected to the second end of the second secondary winding, the second end of the ninth switch tube and the second end of the eleventh switch tube are grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit.

[0028] In one embodiment, the three-phase bridge circuit includes: a twelfth switch tube to a seventeenth switch tube, a second capacitor, a second inductor and a third inductor;

[0029] The first end of the twelfth switch tube, the first end of the fourteenth switch tube, and the first end of the sixteenth switch tube are connected to the first end of the second capacitor, and the second end of the twelfth switch tube and the first end of the thirteenth switch tube are connected to the first end of the second inductor; the second end of the thirteenth switch tube, the second end of the fifteenth switch tube, and the second end of the seventeenth switch tube are connected to the second end of the second capacitor; the second end of the fourteenth switch tube and the first end of the fifteenth switch tube are connected to the first end of the third inductor; the second end of the sixteenth switch tube and the first end of the seventeenth switch tube are connected to the negative electrode of the AC power supply; the second end of the second inductor is connected to the first end of the primary winding, the second end of the third inductor is connected to the second end of the primary winding, and the midpoint of the primary winding is also connected to the positive electrode of the AC power supply.

[0030] In one embodiment, the first power conversion circuit includes: an eighteenth switch tube to a twenty-first switch tube, a third capacitor and a fourth capacitor;

[0031] The first end of the eighteenth switch tube, the first end of the twentieth switch tube and the first end of the fourth capacitor are connected to the positive electrode of the first battery, the second end of the eighteenth switch tube and the first end of the nineteenth switch tube are connected to the first end of the first secondary winding; the second end of the nineteenth switch tube, the second end of the twenty-first switch tube and the second end of the fourth capacitor are connected to the negative electrode of the first battery; the second end of the 20th switch tube and the first end of the twenty-first switch tube are connected to the second end of the third capacitor; the first end of the third capacitor is connected to the second end of the first secondary winding.

[0032] In addition, to achieve the above purpose, the present application also provides a single-stage three-port vehicle-mounted charging and discharging method, which is applied to the single-stage three-port vehicle-mounted charging and discharging circuit as described above, and the steps of the single-stage three-port vehicle-mounted charging and discharging method include:

[0033] Determine the current working mode;

[0034] Based on the working mode, the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit are controlled to cooperate with the transformer to convert the first winding voltage of the primary winding of the transformer, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding to each other, so as to realize the power transmission between the AC power supply, the first battery and the second battery.

[0035] An embodiment of the present application provides a single-stage three-port vehicle-mounted charging and discharging circuit and method, wherein the single-stage three-port vehicle-mounted charging and discharging circuit includes: a transformer, including a primary winding, a first secondary winding and a second secondary winding, for converting the first winding voltage of the primary winding, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding; a three-phase bridge circuit, respectively connected to an AC power supply and the primary winding, for providing a voltage boost, converting the industrial frequency voltage into a high-frequency voltage through a switching action and transmitting it to the secondary side through the transformer; a first power conversion circuit, wherein the first power conversion circuit is connected between the first secondary winding and the first battery, and is used to cooperate with the three-phase bridge circuit to perform a switching action to achieve power factor correction while performing power conversion; and a second power conversion circuit, connected between the second secondary winding and the second battery.

[0036] By connecting the three-phase bridge circuit connected to the AC power supply to the primary winding of the transformer, connecting the first power conversion circuit connected to the first battery to the first secondary winding of the same transformer, and connecting the second power conversion circuit connected to the second battery to the second secondary winding of the same transformer, the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit can be directly coupled through the same transformer. In this way, the transformer can mutually convert the first winding voltage of the primary winding, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding, thereby realizing the mutual transmission of electric energy between the AC power supply, the first battery and the second battery. Since the coupling between multiple circuits is completed by only one transformer, it not only reduces the volume of the entire circuit, but also reduces the power loss in the electrical transmission process, improves the working efficiency of the circuit and reduces the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 A structural connection diagram provided for the first embodiment of the single-stage three-port vehicle-mounted charging and discharging circuit of the present application;

[0040] Figure 2 A first circuit connection diagram provided for the second embodiment of the single-stage three-port vehicle-mounted charging and discharging circuit of the present application;

[0041] Figure 3 A second circuit connection diagram provided for the second embodiment of the single-stage three-port vehicle-mounted charging and discharging circuit of the present application;

[0042] Figure 4 A third circuit connection diagram provided for the second embodiment of the single-stage three-port vehicle-mounted charging and discharging circuit of the present application;

[0043] Figure 5 A flow chart of the single-stage three-port vehicle-mounted charging and discharging method according to the present application is provided.

[0044] The purpose, features and advantages of this application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0045] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application.

[0046] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0047] The main solution of the present application is: using a transformer, a three-phase bridge circuit connected between an AC power supply and a primary winding of the transformer, a first power conversion circuit connected between a first secondary winding of the transformer and a first battery, and a second power conversion circuit connected between a second secondary winding of the transformer and a second battery, so that the transformer directly couples the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit.

[0048] At present, with the popularization of new energy vehicles, electricity consumption is also rising continuously, and the demand for car charging is also increasing. The traditional on-board charger (OBC) technical solution usually uses a power factor correction (Power Factor Correction, PFC) circuit in series with a single high-voltage DC transmission circuit to charge the high-voltage battery. The traditional technical solution requires a large number of circuit components to be built, not only requiring PFC inductors, busbar electrolytic capacitors, OBC main transformers, DCDC main transformers and other devices for electrical coupling. Moreover, with the increase in charging demand, it is now necessary to charge the low-voltage battery in the whole vehicle, that is, a variety of charging methods have been added. Since there are multiple charging methods and the working parameters of each power supply are different, it is necessary to set up corresponding electrical coupling circuits and corresponding control circuits between each power supply, which further increases the number of required circuits and devices, resulting in the inability to miniaturize the on-board charger and the high cost. Therefore, how to reduce the size of the on-board charger and improve the working efficiency of the on-board charger is a problem that needs to be solved urgently.

[0049] The present application connects the three-phase bridge circuit connected to the AC power supply to the primary winding of the transformer, connects the first power conversion circuit connected to the first battery to the first secondary winding of the same transformer, and connects the second power conversion circuit connected to the second battery to the second secondary winding of the same transformer, so that the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit can be directly coupled through the same transformer. Thereby, the transformer can convert the first winding voltage of the primary winding, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding to each other, thereby realizing the power transmission between the AC power supply, the first battery and the second battery. Since the coupling between multiple circuits is completed by only one transformer, the volume of the entire circuit is also reduced.

[0050] Based on this, the present application proposes a single-stage three-port vehicle-mounted charging and discharging circuit of the first embodiment, please refer to Figure 1 , the single-stage three-port vehicle-mounted charging and discharging circuit comprises:

[0051] A transformer T, comprising a primary winding, a first secondary winding and a second secondary winding, for mutually converting a first winding voltage of the primary winding, a second winding voltage of the first secondary winding and a third winding voltage of the second secondary winding;

[0052] The three-phase bridge circuit 10 is connected to the AC power source U0 and the primary winding respectively, and is used to provide a voltage boost, and converts the power frequency voltage into a high-frequency voltage through a switching action and transmits it to the secondary side through the transformer;

[0053] a first power conversion circuit 20, which is connected between the first secondary winding and the first battery B1 and is used to cooperate with the three-phase bridge circuit 10 to perform switching actions, so as to achieve power factor correction while performing power conversion;

[0054] The second power conversion circuit 30 is connected between the second secondary winding and the second battery B2.

[0055] It should be noted that, in this embodiment, the AC power supply U0 is used to output or receive a preset AC power, the first battery B1 is used to output or receive a first DC power, and the second battery B2 is used to output or receive a second DC power. The three-phase bridge circuit 10, the first power conversion circuit 20, and the second power conversion circuit 30 can all transmit current in both directions, but since the power sources connected to the three circuits are different, the three-phase bridge circuit 10 is connected to the AC power supply U0, the first power conversion circuit 20 is connected to the first battery B1, and the second power conversion circuit 30 is connected to the second battery B2, so the electrical parameters of the input and output of each circuit are also different. Among them, the first DC power can be a high-voltage DC power, and the second DC power can be a low-voltage DC power.

[0056] It is worth noting that in this embodiment, the three-phase bridge circuit 10, the first power conversion circuit 20 and the second power conversion circuit 30 can cooperate with each other to adjust the phase of the voltage and current by controlling the switching timing of each internal switch tube, thereby providing a power factor correction function and realizing power conversion.

[0057] It is easy to understand that in this embodiment, the transformer T plays the role of coupling and voltage transformation, and the three-phase bridge circuit 10 is connected through the primary winding, the first power conversion circuit 20 is connected through the first secondary winding, and the second power conversion circuit 30 is connected through the second secondary winding, so as to electrically couple the three-phase bridge circuit 10, the first power conversion circuit 20, and the second power conversion circuit 30. In a specific implementation, the three-phase bridge circuit 10, the first power conversion circuit 20, and the second power conversion circuit 30 can be controlled to work in a corresponding working mode. In the corresponding working mode, the first winding voltage of the primary winding, the second winding voltage of the first secondary winding, and the third winding voltage of the second secondary winding are mutually converted, so as to realize mutual power transmission between the three-phase bridge circuit 10, the first power conversion circuit 20, and the second power conversion circuit 30. Since the power of the three-phase bridge circuit 10 comes from the AC power supply U0, the power of the first power conversion circuit 20 comes from the first battery B1, and the power of the second power conversion circuit 30 comes from the second battery B2, it can also be understood that power is transmitted between the AC power supply U0, the first battery B1 and the second battery B2.

[0058] Through the above circuit structure, only one transformer T is needed for coupling. Combined with the control of the working modes of the three-phase bridge circuit 10, the first power conversion circuit 20 and the second power conversion circuit 30, it is possible to transmit electric energy from the three-phase bridge circuit 10 to the first power conversion circuit 20 and / or the second power conversion circuit 30, or to transmit electric energy from the first power conversion circuit 20 to the three-phase bridge circuit 10 or the second power conversion circuit 30, or to transmit electric energy from the second power conversion circuit 30 to the three-phase bridge circuit 10 or the first power conversion circuit 20, that is, to freely control the charging or discharging of the AC power supply U0, the first battery B1 and the second battery B2. Compared with the bipolar topology formed by the PFC circuit and high-voltage DC transmission circuit commonly used in on-board chargers in the prior art, a large number of electronic devices such as PFC inductors, electrolytic capacitors, various switches on the OBC battery side, and various switches on the high-voltage side of the DCDC circuit can be removed. There is no need to add additional coupling circuits and control circuits corresponding to the coupling circuits between the circuits. A large number of circuit structures can be integrated to reduce the overall redundancy of the circuit and the power loss caused by the electrical transmission process, which is convenient for the miniaturization of the circuit, saves costs, and reduces the control complexity of the circuit operation. In addition, since the electrolytic capacitors are removed, while reducing the overall volume of the circuit, the product life can be extended and the product reliability can be improved.

[0059] An embodiment of the present application provides a single-stage three-port vehicle-mounted charging and discharging circuit, which includes: a transformer, including a primary winding, a first secondary winding and a second secondary winding, for converting the first winding voltage of the primary winding, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding; a three-phase bridge circuit, respectively connected to an AC power supply and the primary winding, for providing a voltage boost, converting the industrial frequency voltage into a high-frequency voltage through a switching action and transmitting it to the secondary side through the transformer; a first power conversion circuit, the first power conversion circuit is connected between the first secondary winding and the first battery, and is used to cooperate with the three-phase bridge circuit to perform switching actions to achieve power factor correction while performing power conversion; a second power conversion circuit, connected between the second secondary winding and the second battery. By connecting the three-phase bridge circuit connected to the AC power supply to the primary winding of the transformer, connecting the first power conversion circuit connected to the first battery to the first secondary winding of the same transformer, and connecting the second power conversion circuit connected to the second battery to the second secondary winding of the same transformer, the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit can be directly coupled through the same transformer. In this way, the transformer can mutually convert the first winding voltage of the primary winding, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding, thereby realizing the mutual transmission of electric energy between the AC power supply, the first battery and the second battery. Since the coupling between multiple circuits is completed by only one transformer, it not only reduces the volume of the entire circuit, but also reduces the power loss in the electrical transmission process, improves the working efficiency of the circuit and reduces the cost.

[0060] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above-mentioned embodiment 1 can refer to the above introduction, and will not be repeated later. Figures 2 to 4 , the transformer T is further used to convert the first winding voltage transmitted by the three-phase bridge circuit 10 into the second winding voltage, and transmit the second winding voltage to the first power conversion circuit 20, so as to enable the AC power supply U0 to charge the first battery B1;

[0061] The transformer T is further used to convert the second winding voltage transmitted by the first power conversion circuit 20 into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit 10 to discharge the first battery B1.

[0062] It should be noted that, in this embodiment, the three-phase bridge circuit 10 includes a plurality of switch tubes, and the switching action of each internal switch tube can be controlled to control the power transmission between the primary winding of the transformer T and the AC power supply U0. The first power conversion circuit 20 also includes a plurality of switch tubes, and the switching action of each internal switch tube can be controlled to control the bidirectional power transmission between the first secondary winding of the transformer T and the first battery B1.

[0063] In a specific implementation, in the first working mode, the power frequency voltage of the preset AC power output by the AC power source U0 can be converted into a high-frequency voltage (first winding voltage) through the three-phase bridge circuit 10, and the high-frequency voltage (first winding voltage) is transmitted to the secondary side after being transformed by the transformer T. The first power conversion circuit 20 rectifies the second winding voltage of the first secondary winding, then converts it into a first DC voltage, and transmits it to the first battery B1, so as to charge the first battery B1 through the AC power source U0.

[0064] In the second working mode, the first DC voltage output by the first battery B1 can be converted into a high-frequency voltage (second winding voltage) by the first power conversion circuit 20, and the high-frequency voltage (second winding voltage) is output to the primary side after being transformed by the transformer T. The three-phase bridge circuit 10 rectifies the first winding voltage of the primary winding, and then converts it into a preset AC power frequency voltage, and transmits it to the AC power supply U0, so as to charge the AC power supply U0 through the first battery B1, or it can be understood as the first battery B1 discharging.

[0065] Furthermore, in this embodiment, the transformer T is also used to convert the first winding voltage transmitted by the three-phase bridge circuit 10 into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit 30, so as to enable the AC power supply U0 to charge the second battery B2;

[0066] The transformer T is further used for converting the third winding voltage transmitted by the second power conversion circuit 30 into the first winding voltage, and transmitting the first winding voltage to the three-phase bridge circuit 10 to discharge the second battery B2.

[0067] It should be noted that, in the present embodiment, the second power conversion circuit 30 includes a push-pull circuit (rectifier circuit 31) and a voltage stabilizing circuit 32, and the push-pull circuit and the voltage stabilizing circuit 32 can be controlled to cooperate to control bidirectional power transmission between the second secondary winding of the transformer T and the second battery B2.

[0068] In a specific implementation, in the third working mode, the power frequency voltage of the preset AC power output by the AC power source U0 can be converted into a high-frequency voltage (first winding voltage) through the three-phase bridge circuit 10, and the high-frequency voltage (first winding voltage) is transmitted to the secondary side after being transformed by the transformer T. The second power conversion circuit 30 rectifies the third winding voltage of the second secondary winding, then converts it into a second DC voltage, and transmits it to the second battery B2, so as to charge the second battery B2 through the AC power source U0.

[0069] In the fourth working mode, the second DC voltage output by the second battery B2 can be converted into a high-frequency voltage (third winding voltage) by the second power conversion circuit 30, and the high-frequency voltage (third winding voltage) is output to the primary side after being transformed by the transformer T. The three-phase bridge circuit 10 rectifies the first winding voltage of the primary winding, and then converts it into a preset AC power frequency voltage, and transmits it to the AC power supply U0, so as to realize charging the AC power supply U0 through the second battery B2, or it can be understood as discharging the second battery B2.

[0070] Furthermore, in this embodiment, the transformer T is also used to convert the second winding voltage transmitted by the first power conversion circuit 20 into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit 30, so that the first battery B1 charges the second battery B2;

[0071] The transformer T is further used for converting the third winding voltage transmitted by the second power conversion circuit 30 into the second winding voltage, and transmitting the second winding voltage to the first power conversion circuit 20, so that the second battery B2 charges the first battery B1.

[0072] It should be noted that, in this embodiment, the first battery B1 and the second battery B2 can also directly perform bidirectional power transmission.

[0073] In a specific implementation, in the fifth working mode, the first DC voltage output by the first battery B1 can be converted into a high-frequency voltage (second winding voltage) by the first power conversion circuit 20, and the high-frequency voltage (second winding voltage) is output to the second secondary winding after being transformed by the transformer T. The second power conversion circuit 30 rectifies the third winding voltage of the second secondary winding, then converts it into a second DC voltage, and transmits it to the second battery B2, so as to realize charging the second battery B2 through the first battery B1.

[0074] In the sixth working mode, the second DC voltage output by the second battery B2 can be converted into a high-frequency voltage (third winding voltage) by the second power conversion circuit 30, and the high-frequency voltage (third winding voltage) is output to the first secondary winding after being transformed by the transformer T. The first power conversion circuit 20 rectifies the second winding voltage of the first secondary winding, then converts it into a first DC voltage, and transmits it to the first battery B1, so as to charge the first battery B1 through the second battery B2.

[0075] Furthermore, in this embodiment, the transformer T is also used to simultaneously convert the first winding voltage transmitted by the three-phase bridge circuit 10 into the second winding voltage and the third winding voltage, and transmit the second winding voltage to the first power conversion circuit 20, and simultaneously transmit the third winding voltage to the second power conversion circuit 30, so that the AC power source U0 can charge the first battery B1 and the second battery B2 at the same time;

[0076] The transformer T is also used to simultaneously convert the second winding voltage transmitted by the first power conversion circuit 20 and the third winding voltage transmitted by the second power conversion circuit 30 into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit 10 to achieve simultaneous discharge of the first battery B1 and the second battery B2.

[0077] It should be noted that, in this embodiment, the bidirectional transmission of electric energy between the AC power source U0 and the first battery B1 and the bidirectional transmission of electric energy between the AC power source U0 and the second battery B2 can be performed in one direction at the same time.

[0078] In a specific implementation, in the seventh working mode, the power frequency voltage of the preset AC power output by the AC power supply U0 can be converted into a high-frequency voltage (first winding voltage) through the three-phase bridge circuit 10, and the high-frequency voltage (first winding voltage) is transmitted to the secondary side after being transformed by the transformer T. The first power conversion circuit 20 rectifies the second winding voltage of the first secondary winding, then converts it into a first DC voltage, and transmits it to the first battery B1. At the same time, the second power conversion circuit 30 rectifies the third winding voltage of the second secondary winding, then converts it into a second DC voltage, and transmits it to the second battery B2, so as to realize charging the first battery B1 and the second battery B2 simultaneously through the AC power supply U0.

[0079] In the eighth working mode, the first DC voltage output by the first battery B1 can be converted into a high-frequency voltage (second winding voltage) by the first power conversion circuit 20, and the high-frequency voltage (second winding voltage) is output to the primary side after being transformed by the transformer T. At the same time, the second power conversion circuit 30 converts the second DC voltage output by the second battery B2 into a high-frequency voltage (third winding voltage), and the high-frequency voltage (third winding voltage) is output to the primary side after being transformed by the transformer T. On the primary side of the transformer T, the three-phase bridge circuit 10 rectifies the first winding voltage of the primary winding, and then converts it into a preset AC power frequency voltage, and transmits it to the AC power supply U0. It is realized that the AC power supply U0 is charged simultaneously by the first battery B1 and the second battery B2, or it is understood that the first battery B1 and the second battery B2 are discharged at the same time.

[0080] Further, in this embodiment, the second power conversion circuit 30 includes: a rectifier circuit 31 and a voltage stabilizing circuit 32;

[0081] The rectifier circuit 31 is respectively connected to the second secondary winding and the voltage stabilizing circuit 32, and the voltage stabilizing circuit 32 is also connected to the second battery B2;

[0082] The rectifier circuit 31 is used to rectify the current transmitted by the second secondary winding;

[0083] The voltage stabilizing circuit 32 is used to stabilize the rectified current to a preset voltage corresponding to the second battery B2.

[0084] It should be noted that the preset voltage can be understood as the second DC voltage that the second battery B2 should theoretically output. In this embodiment, the rectifier circuit 31 can be a push-pull circuit, so that it can realize the rectification function for different current transmission directions based on different working modes.

[0085] It is worth noting that in this embodiment, the voltage stabilizing circuit 32 and the rectifier circuit 31 can also cooperate to convert the second DC voltage output by the second battery B2 into an AC third winding voltage, which can be transmitted to the second secondary winding of the transformer T to release the electrical energy stored in the second battery B2.

[0086] Furthermore, in this embodiment, the voltage stabilizing circuit 32 includes: a first switch tube Q1, a first inductor L1 and a first capacitor C1;

[0087] The first end of the first switch tube Q1 is respectively connected to the rectifier circuit 31 and the first end of the first inductor L1, the second end of the first inductor L1 is respectively connected to the first end of the first capacitor C1 and the second battery B2, and the second end of the first capacitor C1 is grounded.

[0088] It is easy to understand that in this embodiment, the on-off state of the first switch tube Q1 can be controlled based on the corresponding working mode, so as to control the power transmission between the first inductor L1 and the first capacitor C1, so that the power stored in the first capacitor C1 remains relatively stable, thereby keeping the voltage across the first capacitor C1 relatively stable, and further achieving voltage stabilization of the voltage output or received by the second battery B2.

[0089] Furthermore, in this embodiment, the rectifier circuit 31 includes: a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4;

[0090] The first end of the second switch tube Q2 is connected to the first end of the second secondary winding, the first end of the third switch tube Q3 is connected to the second end of the second secondary winding, and the first end of the fourth switch tube Q4 is connected to the middle end of the second secondary winding; the second end of the second switch tube Q2 and the second end of the third switch tube Q3 are grounded; the second end of the fourth switch tube Q4 is connected to the voltage stabilizing circuit 32;

[0091] Or, the rectifier circuit 31 includes: a fifth switch tube Q5, a sixth switch tube Q6 and a seventh switch tube Q7;

[0092] The first end of the fifth switch tube Q5 is connected to the first end of the second secondary winding, the first end of the sixth switch tube Q6 is connected to the second end of the second secondary winding, the second end of the seventh switch tube Q7 is connected to the second end of the fifth switch tube Q5 and the second end of the sixth switch tube Q6, and the first end of the seventh switch tube Q7 is grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit 32;

[0093] Or, the rectifier circuit 31 includes: an eighth switch tube Q8, a ninth switch tube Q9, a tenth switch tube Q10 and an eleventh switch tube Q11;

[0094] The first end of the eighth switch tube Q8 is connected to the first end of the ninth switch tube Q9, the second end of the eighth switch tube Q8 is connected to the first end of the second secondary winding, the first end of the tenth switch tube Q10 is connected to the first end of the eleventh switch tube Q11, the second end of the tenth switch tube Q10 is connected to the second end of the second secondary winding, the second end of the ninth switch tube Q9 and the second end of the eleventh switch tube Q11 are grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit 32.

[0095] It should be noted that, in this embodiment, the rectifier circuit 31 can have three design structures. Figure 2 . Figure 2The rectifier circuit 31 shown in the figure is composed of three switch tubes to form a simple push-pull circuit. The second switch tube Q2 is arranged between the first end of the second secondary winding and the ground wire, and is used to control the voltage at the first end of the second secondary winding; the third switch tube Q3 is arranged between the second end of the second secondary winding and the ground wire, and is used to control the voltage at the second end of the second secondary winding; the fourth switch tube Q4 is arranged between the middle end of the second secondary winding and the voltage stabilizing circuit 32, and is used to control the on-off state of the power transmission channel between the voltage stabilizing circuit 32 and the second secondary winding. Among them, the second switch tube Q2 and the third switch tube Q3 form a push-pull circuit structure, which is mainly used to rectify the current transmitted by the transformer T, or convert the DC current transmitted by the voltage stabilizing circuit 32 into AC power and transmit it to the transformer T.

[0096] refer to Figure 3 , Figure 3 The rectifier circuit 31 shown in FIG. 3 is also composed of three switch tubes to form a push-pull circuit, wherein the fifth switch tube Q5 is arranged between the first end of the second secondary winding and the second end of the seventh switch tube Q7, the sixth switch tube Q6 is arranged between the second end of the second secondary winding and the first end of the seventh switch tube Q7, and the first end of the seventh switch tube Q7 is grounded; the middle end of the second secondary winding is directly connected to the voltage stabilizing circuit 32. Only when the seventh switch tube Q7 is turned on, the fifth switch tube Q5 and the sixth switch tube Q6 form a push-pull circuit structure and perform rectification. Since the seventh switch tube Q7 is reversely connected to the fifth switch tube Q5 and the sixth switch tube Q6, the body diode inside the seventh switch tube Q7 is opposite to the body diode of the fifth switch tube Q5 and the body diode of the sixth switch tube Q6.

[0097] refer to Figure 4 , Figure 4 The rectifier circuit 31 shown in FIG. Figure 3 A variation of the rectifier circuit 31 shown is a push-pull circuit formed by four switch tubes. Among them, the first end of the second secondary winding and the ground are controlled by two reverse series connected eighth switch tubes Q8 and ninth switch tubes Q9, and the second end of the second secondary winding and the ground are controlled by two reverse series connected tenth switch tubes Q10 and eleventh switch tubes Q11.

[0098] Further, in this embodiment, the three-phase bridge circuit 10 includes: a twelfth switch tube Q12 to a seventeenth switch tube Q17, a second capacitor C2, a second inductor L2 and a third inductor L3;

[0099] The first end of the twelfth switch tube Q12, the first end of the fourteenth switch tube Q14, and the first end of the sixteenth switch tube Q16 are connected to the first end of the second capacitor C2, the second end of the twelfth switch tube Q12 and the first end of the thirteenth switch tube Q13 are connected to the first end of the second inductor L2; the second end of the thirteenth switch tube Q13, the second end of the fifteenth switch tube Q15, and the second end of the seventeenth switch tube Q17 are connected to the second end of the second capacitor C2; the second end of the fourteenth switch tube Q14 and the first end of the fifteenth switch tube Q15 are connected to the first end of the third inductor L3; the second end of the sixteenth switch tube Q16 and the first end of the seventeenth switch tube Q17 are connected to the negative electrode of the AC power supply U0; ​​the second end of the second inductor L2 is connected to the first end of the primary winding, the second end of the third inductor L3 is connected to the second end of the primary winding, and the middle point of the primary winding is also connected to the positive electrode of the AC power supply U0.

[0100] It should be noted that, in the present embodiment, the three-phase bridge circuit 10 mainly includes six switch tubes, and the twelfth switch tube Q12 to the seventeenth switch tube Q17 are paired in pairs to form a three-phase bridge arm. Among them, the first phase bridge arm formed by the twelfth switch tube Q12 and the thirteenth switch tube Q13 and the second phase bridge arm formed by the fourteenth switch tube Q14 and the fifteenth switch tube Q15 are used to modulate the frequency of the alternating current and perform voltage conversion in combination with the transformer T, and the third phase bridge arm formed by the sixteenth switch tube Q16 and the seventeenth switch tube Q17 is used for rectification. The second inductor L2 and the third inductor L3 are both resonant inductors, which are used to form a resonant circuit through the three-phase bridge arm in each state and the second capacitor C2.

[0101] The second capacitor C2 can be understood as a DC blocking capacitor or a resonant capacitor. The second inductor L2 and the third inductor L3 can be discrete inductors on the primary side of the transformer T, discrete inductors in the resonant cavity of the first power conversion circuit 20 on the secondary side of the transformer T, or leakage inductors of the transformer T.

[0102] It is easy to understand that in this embodiment, in the fifth working mode and the sixth working mode, the three-phase bridge circuit 10 is not required to work. In addition, in other working modes where the three-phase bridge circuit 10 is required to work, the twelfth switch tube Q12 and the fifteenth switch tube Q15 in the three-phase bridge circuit 10 can be controlled to be switched on and off at the same time with a preset fixed frequency and a 50% duty cycle, and the switching timing of the corresponding thirteenth switch tube Q13 and the fourteenth switch tube Q14 is opposite and complementary to the switching timing of the twelfth switch tube Q12 and the fifteenth switch tube Q15, thereby converting the power frequency voltage and the high frequency voltage (first winding voltage) to each other. Among them, the sixteenth switch tube Q16 and the seventeenth switch tube Q17 can be power frequency tubes, which are used for rectification when the AC power supply U0 is used to charge the first battery B1 and / or the second battery B2, and they can be replaced by diodes.

[0103] Further, in this embodiment, the first power conversion circuit 20 includes: an eighteenth switch tube Q18 to a twenty-first switch tube Q21, a third capacitor C3 and a fourth capacitor C4;

[0104] The first end of the eighteenth switch tube Q18, the first end of the twentieth switch tube Q20 and the first end of the fourth capacitor C4 are connected to the positive electrode of the first battery B1, the second end of the eighteenth switch tube Q18 and the first end of the nineteenth switch tube Q19 are connected to the first end of the first secondary winding; the second end of the nineteenth switch tube Q19, the second end of the twenty-first switch tube Q21 and the second end of the fourth capacitor C4 are connected to the negative electrode of the first battery B1; the second end of the twentieth switch tube Q20 and the first end of the twenty-first switch tube Q21 are connected to the second end of the third capacitor C3; the first end of the third capacitor C3 is connected to the second end of the first secondary winding.

[0105] It should be noted that, in the present embodiment, the first power conversion circuit 20 mainly includes four switch tubes, wherein the eighteenth switch tube Q18 and the nineteenth switch tube Q19 constitute the first bridge arm of the first power conversion circuit 20, and the twentieth switch tube Q20 and the twenty-first switch tube Q21 constitute the second bridge arm of the first power conversion circuit 20. Through the above two bridge arms, the second winding voltage output by the first secondary winding of the transformer T can be rectified. In addition, the function of power factor correction can also be realized by controlling the switching timing of each switch tube in the three-phase bridge circuit 10 and the first power conversion circuit 20.

[0106] It is easy to understand that in this embodiment, the switching timing of each switch tube in the three-phase bridge circuit 10 and the first power conversion circuit 20 can be used to realize the function of charging the first battery B1 and the function of discharging the first battery B1, and the input power or output power in the corresponding state can also be changed.

[0107] In a specific implementation, the eighteenth switch tube Q18 and the twenty-first switch tube Q21 in the first power conversion circuit 20 can be controlled to be turned on and off at the same time with a preset fixed frequency and a 50% duty cycle, and the nineteenth switch tube Q19 and the twentieth switch tube Q20 can also be controlled to be turned on and off at the same time with a preset fixed frequency and a 50% duty cycle, but the switching timing is different from the former, so as to convert the first DC voltage and the high-frequency voltage (second winding voltage) to each other. Wherein, when it is necessary to charge the first battery B1, the switching timing of the eighteenth switch tube Q18 and the twenty-first switch tube Q21 needs to lag behind the switching timing of the twelfth switch tube Q12 and the fifteenth switch tube Q15 by a phase angle of α; when it is necessary to discharge the first battery B1, the switching timing of the eighteenth switch tube Q18 and the twenty-first switch tube Q21 needs to lead the switching timing of the twelfth switch tube Q12 and the fifteenth switch tube Q15 by a phase angle of β. The power factor modulation can be realized by changing the specific values ​​of the α phase angle and the β phase angle, and the input power or output power can be adjusted.

[0108] In addition, to achieve the above purpose, the embodiment of the present application also proposes a single-stage three-port vehicle-mounted charging and discharging method, which is applied to the single-stage three-port vehicle-mounted charging and discharging circuit as described above. The steps of the single-stage three-port vehicle-mounted charging and discharging method include:

[0109] Step S10, determining the current working mode;

[0110] Step S20, based on the working mode, controls the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit to cooperate with the transformer, and converts the first winding voltage of the primary winding of the transformer, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding to each other, so as to realize the power transmission between the AC power supply, the first battery and the second battery.

[0111] It should be noted that in this embodiment, the executing entity can be a controller of a single-stage three-port vehicle-mounted charging and discharging circuit, which can control the working mode of the single-stage three-port vehicle-mounted charging and discharging circuit, or can be understood as being able to control the working modes of the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit.

[0112] It is easy to understand that in this embodiment, the working mode of the current single-stage three-port vehicle-mounted charging and discharging circuit can be judged by the externally transmitted control instruction received by the current controller, and the direction of power transmission between the current AC power supply, the first battery and the second battery can be confirmed. After judging the current working mode, the switching action of each switch tube in the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit can be controlled based on the corresponding working mode. The winding voltages of the windings connected to the transformer of at least two circuits of the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit are mutually converted, that is, electrical coupling is performed through the transformer, so that the electric energy is transmitted from one circuit to another or two circuits, and then the electric energy is transmitted from any one of the AC power supply, the first battery and the second battery to another or two power supplies, so as to achieve the effect of charging and discharging any power supply.

[0113] The above-mentioned embodiment of the single-stage three-port vehicle-mounted charging and discharging method can be applied to all embodiments of the single-stage three-port vehicle-mounted charging and discharging circuit as described above. Since there is no coupling circuit in the single-stage three-port vehicle-mounted charging and discharging circuit that needs to be controlled to couple the circuits, but a transformer is used as a coupling device, only the working state of each circuit connected to each winding of the transformer can be controlled to achieve electrical coupling between various power supplies. Therefore, the single-stage three-port vehicle-mounted charging and discharging method proposed in this application can achieve electrical coupling between various power supplies without controlling the coupling circuit between various power supplies, realize mutual transmission of electric energy between various power supplies, or be understood as charging or discharging each power supply. It can be seen that by using this method to realize the mutual transmission of electric energy between various power supplies, there is no need to independently set up three independent coupling circuits for the three power supplies (for example, independently setting up a two-stage topology of a PFC circuit and a high-voltage DC transmission circuit between the AC power supply and the first battery), and there is no need to set up a corresponding control circuit for the coupling circuit. Therefore, it is possible to realize mutual charging and discharging between multiple power supplies to transmit electric energy while reducing the required circuit structure and saving the volume of the entire circuit, which can solve the technical problem of how to reduce the volume of the on-board charger and improve the working efficiency of the on-board charger. In addition, since the number of switching tubes that need to be controlled in the circuit is reduced, the control algorithm can be designed to be simpler, reducing the control complexity.

[0114] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent processing scope of the present application.

Claims

1. A single-stage three-port vehicle-mounted charging and discharging circuit, characterized in that: The single-stage three-port vehicle-mounted charging and discharging circuit comprises: A transformer, comprising a primary winding, a first secondary winding and a second secondary winding, for mutually converting a first winding voltage of the primary winding, a second winding voltage of the first secondary winding and a third winding voltage of the second secondary winding; A three-phase bridge circuit, connected to an AC power source and the primary winding, respectively, for providing a voltage boost, converting the power frequency voltage into a high-frequency voltage through a switching action and transmitting it to the secondary side via the transformer; a first power conversion circuit, the first power conversion circuit being connected between the first secondary winding and the first battery and configured to cooperate with the three-phase bridge circuit to perform a switching action so as to achieve power factor correction while performing power conversion; The second power conversion circuit is connected between the second secondary winding and the second battery.

2. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 1, characterized in that: The transformer is further used to convert the first winding voltage transmitted by the three-phase bridge circuit into the second winding voltage, and transmit the second winding voltage to the first power conversion circuit, so that the AC power supply charges the first battery; The transformer is further used to convert the second winding voltage transmitted by the first power conversion circuit into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit to discharge the first battery.

3. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 1, characterized in that: The transformer is further used to convert the first winding voltage transmitted by the three-phase bridge circuit into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit, so that the AC power supply charges the second battery; The transformer is further used to convert the third winding voltage transmitted by the second power conversion circuit into the first winding voltage, and transmit the first winding voltage to the three-phase bridge circuit to discharge the second battery.

4. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 1, characterized in that: The transformer is further used to convert the second winding voltage transmitted by the first power conversion circuit into the third winding voltage, and transmit the third winding voltage to the second power conversion circuit, so that the first battery charges the second battery; The transformer is further used to convert the third winding voltage transmitted by the second power conversion circuit into the second winding voltage, and transmit the second winding voltage to the first power conversion circuit, so that the second battery charges the first battery.

5. The single-stage three-port vehicle-mounted charging and discharging circuit according to any one of claims 1, characterized in that: The second power conversion circuit includes: a rectifier circuit and a voltage stabilizing circuit; The rectifier circuit is respectively connected to the second secondary winding and the voltage stabilizing circuit, and the voltage stabilizing circuit is also connected to the second battery; The rectifier circuit is used to rectify the current transmitted by the second secondary winding; The voltage stabilizing circuit is used to stabilize the rectified current to a preset voltage corresponding to the second battery.

6. The single-stage three-port vehicle-mounted charging and discharging circuit as claimed in claim 5, characterized in that: The voltage stabilizing circuit comprises: a first switch tube, a first inductor and a first capacitor; The first end of the first switch tube is respectively connected to the rectifier circuit and the first end of the first inductor, the second end of the first inductor is respectively connected to the first end of the first capacitor and the second battery, and the second end of the first capacitor is grounded.

7. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 5, characterized in that: The rectifier circuit includes: a second switch tube, a third switch tube and a fourth switch tube; The first end of the second switch tube is connected to the first end of the second secondary winding, the first end of the third switch tube is connected to the second end of the second secondary winding, and the first end of the fourth switch tube is connected to the middle end of the second secondary winding; the second end of the second switch tube and the second end of the third switch tube are grounded; the second end of the fourth switch tube is connected to the voltage stabilizing circuit; Or, the rectifier circuit includes: a fifth switch tube, a sixth switch tube and a seventh switch tube; The first end of the fifth switch tube is connected to the first end of the second secondary winding, the first end of the sixth switch tube is connected to the second end of the second secondary winding, the second end of the seventh switch tube is connected to the second end of the fifth switch tube and the second end of the sixth switch tube, and the first end of the seventh switch tube is grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit; Or, the rectifier circuit includes: an eighth switch tube, a ninth switch tube, a tenth switch tube and an eleventh switch tube; The first end of the eighth switch tube is connected to the first end of the ninth switch tube, the second end of the eighth switch tube is connected to the first end of the second secondary winding, the first end of the tenth switch tube is connected to the first end of the eleventh switch tube, the second end of the tenth switch tube is connected to the second end of the second secondary winding, the second end of the ninth switch tube and the second end of the eleventh switch tube are grounded; the middle end of the second secondary winding is connected to the voltage stabilizing circuit.

8. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 1, characterized in that: The three-phase bridge circuit includes: a twelfth switch tube to a seventeenth switch tube, a second capacitor, a second inductor and a third inductor; The first end of the twelfth switch tube, the first end of the fourteenth switch tube, and the first end of the sixteenth switch tube are connected to the first end of the second capacitor, and the second end of the twelfth switch tube and the first end of the thirteenth switch tube are connected to the first end of the second inductor; the second end of the thirteenth switch tube, the second end of the fifteenth switch tube, and the second end of the seventeenth switch tube are connected to the second end of the second capacitor; the second end of the fourteenth switch tube and the first end of the fifteenth switch tube are connected to the first end of the third inductor; the second end of the sixteenth switch tube and the first end of the seventeenth switch tube are connected to the negative electrode of the AC power supply; the second end of the second inductor is connected to the first end of the primary winding, the second end of the third inductor is connected to the second end of the primary winding, and the midpoint of the primary winding is also connected to the positive electrode of the AC power supply.

9. The single-stage three-port vehicle-mounted charging and discharging circuit according to claim 1, characterized in that: The first power conversion circuit includes: an eighteenth switch tube to a twenty-first switch tube, a third capacitor and a fourth capacitor; The first end of the eighteenth switch tube, the first end of the twentieth switch tube and the first end of the fourth capacitor are connected to the positive electrode of the first battery, the second end of the eighteenth switch tube and the first end of the nineteenth switch tube are connected to the first end of the first secondary winding; the second end of the nineteenth switch tube, the second end of the twenty-first switch tube and the second end of the fourth capacitor are connected to the negative electrode of the first battery; the second end of the 20th switch tube and the first end of the twenty-first switch tube are connected to the second end of the third capacitor; the first end of the third capacitor is connected to the second end of the first secondary winding.

10. A single-stage three-port vehicle-mounted charging and discharging method, characterized in that: Applied to the single-stage three-port vehicle-mounted charging and discharging circuit according to any one of claims 1 to 9, the steps of the single-stage three-port vehicle-mounted charging and discharging method include: Determine the current working mode; Based on the working mode, the three-phase bridge circuit, the first power conversion circuit and the second power conversion circuit are controlled to cooperate with the transformer to convert the first winding voltage of the primary winding of the transformer, the second winding voltage of the first secondary winding and the third winding voltage of the second secondary winding to each other, so as to realize the power transmission between the AC power supply, the first battery and the second battery.

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