阅读说明：本技术 一种三端口能量传输电路的控制方法及能量传输设备 (Control method of three-port energy transmission circuit and energy transmission equipment ) 是由 冯颖盈 姚顺 徐金柱 罗永亮 敖华 于 2021-07-27 设计创作，主要内容包括：本发明公开了一种三端口能量传输电路的控制方法及能量传输设备,其中三端口能量传输电路的控制方法包括步骤：三端口能量传输电路在不同的能量传输模式下都通过控制开关管的占空比进行能量传输,并在不同的能量传输模式下通过调节对应的开关管来控制输出电压的大小。本发明只通过调节开关管的占空比的方式使控制器至始至终都处于同一种工作状态,切换工作模式时控制器不需要重置初始化配置,所以不会发生中断的情况。因此本发明在行车模式切换到逆变模式的过程中,能保证向电动汽车的低压系统供电不中断的同时,还能输出交流电供车载电子设备使用。(The invention discloses a control method of a three-port energy transmission circuit and energy transmission equipment, wherein the control method of the three-port energy transmission circuit comprises the following steps: the three-port energy transmission circuit performs energy transmission by controlling the duty ratio of the switching tube in different energy transmission modes, and controls the magnitude of output voltage by adjusting the corresponding switching tube in different energy transmission modes. The controller is in the same working state from beginning to end only by adjusting the duty ratio of the switching tube, and the controller does not need to reset the initialization configuration when the working mode is switched, so that the interruption condition can not occur. Therefore, in the process of switching the driving mode to the inversion mode, the alternating current can be output to be used by vehicle-mounted electronic equipment while the power supply to the low-voltage system of the electric automobile is not interrupted.)

1. A method of controlling a three-port energy transfer circuit, comprising the steps of:

the three-port energy transmission circuit transmits energy by controlling the duty ratio of the switching tube in different energy transmission modes; and the output voltage is controlled by adjusting the corresponding switch tube under different energy transmission modes.

2. The method of claim 1, wherein the different energy transfer modes are modes corresponding to energy transfer from the high-voltage secondary circuit to the primary circuit and/or the low-voltage secondary circuit.

3. The method of claim 2, wherein the high voltage secondary circuit transmits energy to the low voltage secondary circuit in a drive mode; the high-voltage secondary side circuit transmits energy to the low-voltage secondary side circuit and the primary side circuit in an inversion mode.

4. The method of controlling a three-port energy transfer circuit of claim 3,

in the inversion mode, controlling all switching tubes of the high-voltage secondary side circuit to emit waves at a preset duty ratio; detecting the output voltage of a primary side circuit;

judging whether the output voltage of the primary side circuit exceeds a primary side voltage preset threshold range or not; if not, maintaining the duty ratios of all the switching tubes of the high-voltage secondary side circuit;

and if so, adjusting the duty ratio of the lower bridge arm of the primary side circuit and the duty ratios of all the switching tubes of the high-voltage secondary side circuit to maintain the output voltage of the primary side circuit within the range of the preset threshold value of the primary side voltage.

5. The method for controlling the three-port energy transmission circuit according to claim 4, wherein the step of adjusting the duty ratio of the lower bridge arm of the primary circuit and the duty ratios of all the switching tubes to maintain the output voltage of the primary circuit within the preset threshold range of the primary voltage comprises the steps of:

when the output voltage of the primary side circuit is lower than the minimum threshold voltage of the primary side voltage preset threshold range, increasing the duty ratio of a lower bridge arm of the primary side circuit;

judging whether the duty ratio of a lower bridge arm of the primary circuit is larger than a preset duty ratio threshold range of the lower bridge arm;

if yes, returning to the step of detecting the output voltage of the primary side circuit after increasing the duty ratios of all the switching tubes of the high-voltage secondary side circuit; if not, directly returning to the step of detecting the output voltage of the primary side circuit.

6. The method for controlling the three-port energy transmission circuit according to claim 4, wherein the step of adjusting the duty ratio of the lower arm of the primary circuit and the duty ratios of all the switching tubes to maintain the output voltage of the primary circuit within the preset threshold range of the primary voltage further comprises:

when the output voltage of the primary side circuit is higher than the maximum threshold voltage of the primary side voltage preset threshold range, reducing the duty ratio of a lower bridge arm of the primary side circuit;

judging whether the duty ratio of the lower bridge arm of the primary circuit is smaller than a preset duty ratio threshold range of the lower bridge arm;

if not, returning to the step of detecting the output voltage of the primary side circuit; if yes, judging whether the duty ratios of all the switching tubes of the high-voltage secondary side circuit are larger than a preset duty ratio or not;

if the duty ratios of all the switching tubes of the high-voltage secondary circuit are larger than the preset duty ratio, reducing the duty ratios of all the switching tubes of the high-voltage secondary circuit and then returning to the step of detecting the output voltage of the primary circuit; and if the duty ratios of all the switching tubes of the high-voltage secondary side circuit are smaller than the preset duty ratio, controlling the lower bridge arm of the primary side circuit to be cut off.

7. The method of controlling a three-port energy transfer circuit of claim 3,

when the inverter mode or the driving mode is adopted, all switching tubes of the high-voltage secondary side circuit are controlled to emit waves at a preset duty ratio;

detecting the output voltage of the low-voltage secondary side circuit;

judging whether the output voltage of the low-voltage secondary side circuit exceeds a secondary side voltage preset threshold range or not; if not, maintaining the duty ratios of all switching tubes and buck control switches of the high-voltage secondary side circuit; if so, adjusting the duty ratio of a buck control switch of the low-voltage secondary side circuit and the duty ratios of all switching tubes of the high-voltage secondary side circuit to maintain the output voltage of the low-voltage secondary side circuit within a secondary side voltage preset threshold range.

8. The method for controlling the three-port energy transmission circuit according to claim 7, wherein the step of adjusting the duty ratio of the buck control switch of the low-voltage secondary side circuit and the duty ratios of all the switching tubes of the high-voltage secondary side circuit to maintain the output voltage of the low-voltage secondary side circuit within the secondary side voltage preset threshold range comprises:

when the output voltage of the low-voltage secondary side circuit is lower than the minimum threshold voltage of a preset threshold range of the secondary side voltage, increasing the duty ratio of a buck control switch;

judging whether the duty ratio of the buck control switch is larger than the duty ratio threshold range of the preset buck control switch or not;

if yes, returning to the step of detecting the output voltage of the low-voltage secondary side circuit after increasing the duty ratios of all the switching tubes of the high-voltage secondary side circuit; if not, directly returning to the step of detecting the output voltage of the low-voltage secondary side circuit.

9. The method of claim 7, wherein the step of adjusting the duty cycle of the low-voltage secondary circuit and the duty cycles of all the switching tubes to maintain the output voltage of the low-voltage secondary circuit within a secondary voltage preset threshold further comprises:

when the output voltage of the low-voltage secondary side circuit is higher than the maximum threshold voltage of the secondary side voltage preset threshold range, the duty ratio of the buck control switch is reduced;

judging whether the duty ratio of the buck control switch is smaller than the minimum value of the duty ratio threshold range of the preset buck control switch;

if not, returning to the step of detecting the output voltage of the low-voltage secondary side circuit; if yes, judging whether the duty ratios of all the switching tubes of the high-voltage secondary side circuit are larger than a preset duty ratio or not;

if the duty ratios of all the switching tubes of the high-voltage secondary side circuit are larger than the preset duty ratio, reducing the duty ratios of all the switching tubes of the high-voltage secondary side circuit and then returning to the step of detecting the output voltage of the low-voltage secondary side circuit; and if the duty ratios of all the switching tubes of the high-voltage secondary side circuit are smaller than the preset duty ratio, controlling buck to control the switch to be cut off.

10. An energy transfer device comprising: a primary side circuit, a high voltage secondary side circuit, a low voltage secondary side circuit, and a transformer connecting the primary side circuit, the high voltage secondary side circuit, and the low voltage secondary side circuit, characterized in that the control method of the three-port energy transmission circuit according to any one of claims 1 to 9 is used for energy transmission and voltage regulation.

11. The energy transfer device of claim 10, wherein the primary circuit comprises: an inductor L1, a switching tube Q5-Q8 and a capacitor C2; two ends of the capacitor C2 are connected with the alternating current conversion module; the drain electrode of the switching tube Q5 is connected with the source electrode of the switching tube Q7 and then connected to the two ends of the capacitor; the drain of the switch tube Q6 is connected with the source of the switch tube Q8 and then connected with the two ends of the capacitor C2; after the inductor L1 and the second winding are connected in series, one end of the inductor L1 is connected between the switching tubes Q5 and Q7, and the other end of the inductor L1 is connected between the switching tubes Q6 and Q8; the switching tubes Q5 and Q6 are the lower bridge arm of the primary circuit.

12. The energy transfer device of claim 10, wherein the low voltage secondary side circuit comprises: a switching tube Q9 to a switching tube Q12, an inductor L3 and a capacitor C3; the source electrode of the switching tube Q9 is connected with the source electrode of the switching tube Q10 and then connected to the two ends of the third winding; the source of the switching tube Q11, the inductor L3 and the capacitor C3 are sequentially connected, the drain of the switching tube Q11 is connected to the middle of the third winding, and the other end of the capacitor C3 is connected between the switching tubes Q9 and Q10; the drain electrode of the switching tube Q12 is connected between the switching tube Q11 and the inductor L3, and the source electrode is connected between the switching tubes Q9 and Q10; two ends of the capacitor C3 are connected with the low-voltage system; the switching tube Q11 is a buck control switch.

Technical Field

The invention relates to the field of energy transmission, in particular to a control method of a three-port energy transmission circuit and energy transmission equipment.

Background

With the requirements of energy conservation and emission reduction and air pollution control, new energy automobiles are gradually popularized and applied in the market, wherein electric automobiles are more dominant force automobiles. The electric automobile is provided with a vehicle-mounted charger, and the power battery pack supplies power to a storage battery low-voltage network of the electric automobile (namely, a driving mode) through the vehicle-mounted charger. When a user uses the vehicle-mounted electronic equipment (namely, in an inversion mode), the vehicle-mounted charger needs to supply power to a low-voltage system of the electric automobile and also needs to provide alternating current output for the vehicle-mounted electronic equipment to use.

In the prior art, the output voltage of the low-voltage secondary side circuit is controlled by continuously adjusting the duty ratio of a switching tube in a driving mode; in an inversion mode, the duty ratio of the switching tube is fixed, and then the phase difference of the switching tube is adjusted to control the output voltage of the primary side circuit. These are two different control methods, so when the driving mode is switched to the inverter mode, the controller needs to reset the initialization configuration. Therefore, energy transmission interruption occurs, and a low-voltage system cannot work normally, so that automobile faults are caused, and the safe operation of the automobile is threatened.

Disclosure of Invention

The invention provides a control method of a three-port energy transmission circuit and energy transmission equipment, aiming at the problem of energy transmission interruption when a driving mode is switched to an inversion mode in the prior art.

The technical scheme of the invention is to provide a control method of a three-port energy transmission circuit and energy transmission equipment, wherein the control method of the three-port energy transmission circuit comprises the following steps:

the three-port energy transmission circuit transmits energy by controlling the duty ratio of the switching tube in different energy transmission modes; and the size of the output voltage is controlled by adjusting the corresponding switch tube under different energy transmission modes, which specifically comprises the following steps:

step S11: when the energy transmission mode is an inversion mode, controlling all switching tubes of the high-voltage secondary side circuit to emit waves at a preset duty ratio;

step S12: detecting the output voltage of the primary side circuit, and judging whether the output voltage of the primary side circuit exceeds the primary side voltage preset threshold range;

step S121: when the output voltage of the primary side circuit does not exceed the primary side voltage preset threshold range, the duty ratios of all the switching tubes of the high-voltage secondary side circuit are maintained, and then the step S12 is returned;

step S122: when the output voltage of the primary side circuit is lower than the minimum threshold voltage of the primary side voltage preset threshold range, increasing the duty ratio of a lower bridge arm of the primary side circuit, and then entering step S13;

step S123: when the output voltage of the primary side circuit is higher than the maximum threshold voltage of the primary side voltage preset threshold range, reducing the duty ratio of a lower bridge arm of the primary side circuit, and then entering step S14;

step S13: judging whether the duty ratio of a lower bridge arm of the primary circuit is larger than a preset duty ratio threshold range of the lower bridge arm;

step S131: when the duty ratio of the lower bridge arm of the primary side circuit is larger than the preset threshold range of the duty ratio of the lower bridge arm, increasing the duty ratios of all switching tubes of the high-voltage secondary side circuit, and then returning to the step S12; when the duty ratio of the lower bridge arm of the primary circuit does not exceed the preset threshold range of the duty ratio of the lower bridge arm, directly returning to the step S12;

step S14: judging whether the duty ratio of the lower bridge arm of the primary circuit is smaller than a preset duty ratio threshold range of the lower bridge arm; when the duty ratio of the lower bridge arm of the primary circuit is smaller than the preset threshold range of the duty ratio of the lower bridge arm, the method goes to step S15; when the duty ratio of the lower bridge arm of the primary circuit is not lower than the preset range of the duty ratio threshold of the lower bridge arm, directly returning to the step S12;

step S15: judging whether the duty ratios of all switching tubes of the high-voltage secondary side circuit are larger than a preset duty ratio or not;

step S151: when the duty ratios of all the switching tubes of the high-voltage secondary side circuit are larger than the preset duty ratio, reducing the duty ratios of all the switching tubes of the high-voltage secondary side circuit and returning to the step S12;

step S152: when the duty ratios of all the switching tubes of the high-voltage secondary side circuit are smaller than the preset duty ratio, controlling the lower bridge arm of the primary side circuit to be cut off, and then returning to the step S12;

step S21: when the energy transmission mode is an inversion mode or a driving mode, controlling all switching tubes of the high-voltage secondary side circuit to emit waves at a preset duty ratio;

step S22: detecting the output voltage of the low-voltage secondary side circuit, and judging whether the output voltage of the low-voltage secondary side circuit exceeds a secondary side voltage preset threshold range or not;

step S221: when the output voltage of the low-voltage secondary side circuit does not exceed the secondary side voltage preset threshold range, maintaining the duty ratios of all the switching tubes and the buck control switch of the high-voltage secondary side circuit, and then returning to the step S22;

step S222: when the output voltage of the low-voltage secondary side circuit is lower than the minimum threshold voltage of the preset threshold range of the secondary side voltage, increasing the duty ratio of the buck control switch, and then entering the step S23;

step S223: when the output voltage of the low-voltage secondary side circuit is higher than the maximum threshold voltage of the secondary side voltage preset threshold range, reducing the duty ratio of the buck control switch, and then entering the step S24;

step S23: judging whether the duty ratio of the buck control switch is larger than the duty ratio threshold range of the preset buck control switch or not;

step S231: when the duty ratio of the buck control switch is larger than the duty ratio threshold range of the preset buck control switch, increasing the duty ratios of all the switching tubes of the high-voltage secondary side circuit and returning to the step S22; when the duty ratio of the buck control switch does not exceed the preset duty ratio threshold range of the buck control switch, directly returning to the step S22;

step S24: judging whether the duty ratio of the buck control switch is smaller than the duty ratio threshold range of the preset buck control switch or not; when the duty ratio of the buck control switch is smaller than the preset duty ratio threshold range of the buck control switch, the step S25 is executed; when the duty ratio of the buck control switch is not less than the preset duty ratio threshold range of the buck control switch, directly returning to the step S22;

step S25: judging whether the duty ratios of all switching tubes of the high-voltage secondary side circuit are larger than a preset duty ratio or not;

step S251: when the duty ratios of all the switching tubes of the high-voltage secondary side circuit are larger than the preset duty ratio, reducing the duty ratios of all the switching tubes of the high-voltage secondary side circuit and returning to the step S22;

step S252: when the duty ratios of all the switching tubes of the high-voltage secondary side circuit are smaller than the preset duty ratio, controlling the buck to control the switch to be cut off, and then returning to the step S22;

the invention also provides energy transmission equipment, and the control method of the three-port energy transmission circuit is used for energy transmission and voltage regulation.

Compared with the prior art, the controller is in the same working state from beginning to end only by adjusting the duty ratio of the switching tube, and the controller does not need to reset the initialization configuration when the working mode is switched, so that the interruption condition cannot occur. Therefore, in the process of switching the driving mode to the inversion mode, the alternating current can be output to be used by vehicle-mounted electronic equipment while the power supply to the low-voltage system of the electric automobile is not interrupted.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is an overall block diagram of a three port energy transfer circuit of the present invention;

FIG. 2 is a circuit diagram of a three port energy transfer circuit of the present invention;

FIG. 3 is a flow chart of regulation of the output voltage of the primary side circuit of the present invention;

FIG. 4 is a flow chart of the regulation of the output voltage of the low voltage secondary side circuit according to the present invention;

FIG. 5 is a timing diagram of signals from the switch Q1 to the switch Q4 in the driving mode of the present invention

FIG. 6 is a timing diagram of the signals from the inverter mode switch Q1 to the switch Q6;

FIG. 7 is a waveform diagram illustrating operation of the three-port energy transfer circuit of FIG. 2 in an inverter mode;

fig. 8 is a current waveform diagram of the inductor L1 when the three-port energy transfer circuit shown in fig. 2 is in the inverter mode.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Thus, a feature indicated in this specification will serve to explain one of the features of one embodiment of the invention, and does not imply that every embodiment of the invention must have the stated feature. Further, it should be noted that this specification describes many features. Although some features may be combined to show a possible system design, these features may also be used in other combinations not explicitly described. Thus, the combinations illustrated are not intended to be limiting unless otherwise specified.

The invention provides a control method of a three-port energy transmission circuit, which can be used for various energy transmission devices. For the convenience of describing the principle and structure of the present invention in detail, the present invention is applied to charging an electric vehicle, and the principle and structure of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

In the prior art, the output voltage of the low-voltage secondary side circuit is controlled by continuously adjusting the duty ratio of a switching tube in a driving mode; in an inversion mode, the duty ratio of the switching tube is fixed, and then the phase difference of the switching tube is adjusted to control the output voltage of the primary side circuit. Therefore, the driving mode needs to control the duty ratio of the switching tube, and the inversion mode needs to fix the duty ratio to adjust the phase difference, which are two different control modes. It is necessary for the controller to reset the initialization configuration when the driving mode and the inverter mode are switched with each other. Therefore, a break may occur, which threatens the normal driving of the electric vehicle.

In view of the problems in the prior art, the present invention provides a control method for a three-port energy transmission circuit, comprising: the three-port energy transmission circuit performs energy transmission by controlling the duty ratio of the switching tube in different energy transmission modes, and controls the magnitude of output voltage by adjusting the corresponding switching tube in different energy transmission modes. The invention ensures that the controller is in the same working state from beginning to end by adjusting the duty ratio of the switching tube, and the controller does not need to reset the initialization configuration when the working mode is switched, thereby solving the problem that the power supply of the automobile is interrupted when the driving mode is switched to the inversion mode in the prior art.

As shown in fig. 1 and 2, the three-port energy transmission circuit according to the present invention includes: the high-voltage secondary side circuit comprises a primary side circuit connected with a vehicle-mounted load, a high-voltage secondary side circuit connected with a battery pack, a low-voltage secondary side circuit connected with a low-voltage system, a transformer and a controller for controlling the working state of switching tubes in the primary side circuit, the high-voltage secondary side circuit and the low-voltage secondary side circuit, wherein a first winding n1 of the transformer is connected with the high-voltage secondary side circuit, a second winding n2 of the transformer is connected with the primary side circuit, and a third winding n3 of the transformer is connected with the low-voltage secondary side circuit. And the three-port energy transmission circuit can work under the following three working modes: a charging mode, a driving mode and an inversion mode. Meanwhile, in this embodiment, the primary side circuit provides voltage input for the PFC circuit, so as shown in fig. 2, the output end of the primary side circuit is further connected to the PFC circuit module. In the charging mode, the PFC circuit is used for power factor correction; under the inversion mode, the PFC circuit is used for converting the voltage input by the primary side circuit into alternating current and outputting the alternating current.

In the charging mode, the electric automobile is connected with an alternating current power supply, and the power battery pack is charged through the vehicle-mounted charger. The energy is transmitted to the high-voltage secondary circuit through the PFC circuit module, the primary circuit and the transformer, and then the power battery pack of the electric automobile is charged.

When the electric automobile is in a driving mode, the primary side circuit has no voltage input, and a low-voltage system of the electric automobile is powered by the power battery pack. At the moment, the high-voltage secondary circuit transmits high-voltage direct current provided by the power battery pack to the transformer, and the transformer converts the high-voltage direct current into low-voltage direct current to be transmitted to the low-voltage secondary circuit so as to supply power to a low-voltage system.

When in the inversion mode, the flow direction of the energy is opposite to that of the charging mode, the primary side circuit has no voltage input, and the power battery pack provides an energy source. The high-voltage direct current provided by the power battery pack is converted into low-voltage direct current through the high-voltage secondary side circuit and the transformer to supply power for a low-voltage system. Meanwhile, the high-voltage direct current acquired from the power battery pack is converted by the high-voltage secondary circuit through the primary circuit, and the alternating current is output from the PFC circuit module, so that the alternating current in the vehicle is supplied for a user to select, great convenience is provided for the user, and vehicle experience is improved.

The working principle of the three-port energy transmission circuit is described below with reference to fig. 1, 2, 3, and 4.

The primary side circuit includes: an inductor L1, an inductor L2, switching tubes Q5-Q8 and a capacitor C2; two ends of the capacitor C2 are connected with the PFC circuit module; the drain electrode of the switching tube Q5 is connected with the source electrode of the switching tube Q7, and then the whole is connected with the two ends of the capacitor C2; the source electrode of a drain electrode switching tube Q8 of the switching tube Q6 is connected, and then the whole is connected to the two ends of a capacitor C2; after the inductor L1 and the second winding are connected in series, one end of the inductor L1 is connected between the switching tubes Q5 and Q7, and the other end of the inductor L1 is connected between the switching tubes Q6 and Q8; an inductor L2 is further connected in parallel to two ends of the second winding of the transformer, the inductor L2 is an excitation inductor of the transformer, and the switching tubes Q5 and Q6 are lower bridge arms of the primary circuit.

The high-voltage secondary side circuit comprises: a switching tube Q1-Q4 and a capacitor C1; the drain electrode of the switching tube Q2 is connected with the source electrode of the switching tube Q1, and then the whole is connected with the two ends of the battery pack; the drain electrode of the switching tube Q4 is connected with the source electrode of the switching tube Q3, and then the whole is connected with the two ends of the battery pack; the capacitor C1 is connected in series with the first winding of the transformer, and then one end of the whole is connected between the switching tubes Q1, Q2, and the other end of the whole is connected between the switching tubes Q4, Q5.

The low-voltage secondary side circuit comprises: the circuit comprises switching tubes Q9-Q12, an inductor L3 and a capacitor C3, wherein the switching tube Q11 is set as a buck control switch; the source electrode of the switching tube Q9 is connected with the source electrode of the switching tube Q10, and then the source electrode is integrally connected with two ends of a third winding of the transformer; the source of the switching tube Q11, the inductor L3 and the capacitor C3 are sequentially connected, the drain of the switching tube Q11 is connected to the middle of the third winding of the transformer, and the other end of the capacitor C3 is connected between the switching tubes Q9 and Q10; the drain electrode of the switching tube Q12 is connected between the switching tube Q11 and the inductor L3, and the source electrode is connected between the switching tubes Q9 and Q10; the two ends of the capacitor C3 are also connected with the low-voltage system.

Meanwhile, the switching tubes Q1-Q12 are MOS tubes, and the purpose is to reduce loss. The diodes D1-D12 can be body diodes of the switching tubes Q1-Q12, or can be diodes which are independently connected in parallel with the switching tubes Q1-Q12, and the purpose is to protect the switching tubes from voltage breakdown.

The control method of the three-port energy transmission circuit provided by the invention controls the total transmission energy by adjusting the duty ratio of the switching tubes Q1-Q4 in a driving mode and an inversion mode. When the load of the low-voltage secondary side circuit or the primary side circuit is increased, the output voltage VO1 or VO2 is reduced, the duty ratio of the switching tubes Q1 to Q4 is increased by the controller, so that the conduction time of the switching tubes Q1 to Q4 is prolonged in one period, the energy transmission time is prolonged, and the transmitted energy is increased. When the load of the low-voltage secondary circuit or the primary circuit is reduced, the output voltage VO1 or VO2 is increased, the duty ratio of the switching tubes Q1 to Q4 is adjusted by the controller, so that in one period, the conduction time of the switching tubes Q1 to Q4 is shortened, the energy transmission time is shortened, the transmitted energy is reduced, the energy accumulation speed is lower than the energy consumption speed, and the output voltage can be reduced to be in a normal range.

Meanwhile, the size of the VO1 is adjusted by controlling the switching tube Q11 and the switching tubes Q1-Q4 in the driving mode and the inversion mode. The size of the VO2 is adjusted by controlling the duty ratio of the switching tubes Q5-Q6 and the switching tubes Q1-Q4 in the inversion mode.

The following specific steps of analyzing the operating states and current flow directions of the components of the three-port energy transmission circuit in the driving mode and the inversion mode, and adjusting the magnitudes of VO1 and VO2 in detail with reference to fig. 2 to 4 and the embodiment:

in the driving mode, as shown in fig. 5, the switching tubes Q1 and Q4 are synchronously switched, the switching tubes Q2 and Q3 are synchronously switched, and the switching tubes Q1 and Q4 and the switching tubes Q2 and Q3 are alternately switched on and off; when the switching tubes Q1 and Q4 are conducted, the switching tubes Q9 and Q11 are conducted; then, the switching tubes Q1, Q4, Q9 and Q11 are turned off, and the switching tube Q12 is turned on. Similarly, when the switching tubes Q2 and Q3 are switched on, the switching tubes Q10 and Q11 are switched on; then, the switching tubes Q2, Q3, Q10 and Q11 are turned off, and the switching tube Q12 is turned on.

When the switching tubes Q1 and Q4 are turned on simultaneously, the switching tubes Q2 and Q3 are turned off simultaneously, and the switching tubes Q9 and Q11 are turned on simultaneously, the current flow in the high-voltage secondary side circuit is as follows: the switching tube Q1, the capacitor C1, the first winding n1 and the switching tube Q4; the current flow in the low-voltage secondary side circuit is as follows: the middle of the third winding n3 is the lower end of a switching tube Q11, an inductor L3, a capacitor C3, a switching tube Q9 and a third winding n 3. The inductor L3 stores energy during this process. Then, the switching tubes Q1, Q4, Q9, and Q11 are turned off, the switching tube Q12 is turned on, and the inductor L3 discharges. The current then flows through in sequence: the right end of the inductor L3, the capacitor C3, the switching tube 12 and the left end of the inductor L3.

When the switching tubes Q1 and Q4 are turned off at the same time, the switching tubes Q2 and Q3 are turned on at the same time, and the switching tubes Q10 and Q11 are turned on at the same time, the current flow in the high-voltage secondary side circuit is as follows: the switching tube Q3-the first winding n 1-the capacitor C1-the switching tube Q2; the current flow in the low-voltage secondary side circuit is as follows: the middle of the third winding n3, namely the switching tube Q11, the inductor L3, the capacitor C3, the switching tube Q10 and the upper end of the third winding n3, stores energy through the inductor L3 in the process. Then, the switching tubes Q2, Q3, Q10, and Q11 are turned off, the switching tube Q12 is turned on, and the inductor L3 discharges. The current then flows through in sequence: the right end of the inductor L3, the capacitor C3, the switching tube Q12 and the left end of the inductor L3.

As shown in fig. 4, the regulation process of VO1 is as follows: firstly, the switching tubes Q1-Q4 emit waves according to a preset duty ratio, then the size of the VO1 is detected, whether the VO1 is between a third threshold voltage and a fourth threshold voltage is judged, the preset duty ratio can be the minimum duty ratio of the switching tubes Q1-Q4 set by a system, the preset duty ratio adopted by the invention is 30%, and the preset duty ratio can also be set according to actual requirements, and is not limited herein. If yes, the duty ratios of the switching tube Q11 and the switching tubes Q1-Q4 are maintained; if not, the following two cases are specifically classified:

when VO1 is less than the third threshold voltage, the duty cycle of the switching tube Q11 is increased, and the duty cycle of the switching tube Q11 is ensured to be less than the third threshold duty cycle. When the duty ratio of the switching tube Q11 is increased to the third threshold duty ratio and the voltage of the VO1 is still smaller than the third threshold voltage, the duty ratios of the switching tubes Q1-Q4 are increased until the voltage of the VO1 is within the preset voltage range.

When VO1 is greater than the fourth threshold voltage, the duty cycle of transistor Q11 is reduced and the duty cycle of transistor Q11 is guaranteed to be greater than the fourth threshold duty cycle. When the duty cycle of the switching tube Q11 is reduced to the fourth threshold duty cycle and the VO1 is still greater than the fourth threshold voltage, it is determined whether the duty cycles of the switching tubes Q1-Q4 are greater than the preset duty cycle. If the duty ratio of the switching tubes Q1-Q4 is larger than the preset duty ratio, the duty ratio of the switching tubes Q1-Q4 is reduced until the voltage of VO1 is within the preset voltage range; and if the duty ratio of the switching tube Q1-Q4 is smaller than the preset duty ratio, controlling the switching tube Q11 to be cut off. When the switching tube Q11 is turned off, the voltage transmitted by the third winding n3 is chopped, and the switching tube Q11, the inductor L3, the capacitor C3 and the switching tube Q12 form a Buck circuit to reduce the size of VO 1.

Wherein the third threshold voltage is less than the fourth threshold voltage, and the third threshold duty cycle is greater than the fourth threshold duty cycle. In this embodiment, the third threshold voltage is 13.9V, the fourth threshold voltage is 14.1V, and the value can be adjusted according to the resistance of the low-voltage load in practical situations. The third threshold duty cycle is 60% and the fourth threshold duty cycle is 0. When the duty ratio of the switching tube Q11 reaches twice of that of the switching tubes Q1-Q4, the on-time of the switching tube Q11 is equal to that of the switching tube Q1-Q4, the energy transmission time is determined by the duty ratio of the switching tube Q1-Q4, and the duty ratio of the switching tube Q11 is adjusted upwards, so that the voltage regulation function cannot be achieved.

Under the inversion mode, the high-voltage secondary side circuit still transmits energy to the low-voltage secondary side circuit according to the working mode of the driving mode. Meanwhile, as shown in fig. 6, the switching tube Q5 and the switching tube Q6 of the primary side circuit are synchronously and alternately turned on and off; when the switching tube Q5 and the switching tube Q6 are conducted, the inductor L1 stores energy; when the switch tube Q5 and the switch tube Q6 are turned off, the inductor L1 releases energy. When the switching tubes Q1 and Q4 are conducted simultaneously, the energy transmitted to the second winding by the high-voltage secondary side circuit sequentially passes through: inductor L1-diode D7-capacitor C2-diode D6; when the switching tubes Q2 and Q3 are conducted simultaneously, the energy transmitted to the second winding by the high-voltage secondary side circuit sequentially passes through: diode D8-capacitor C2-diode D5-inductor L1. VO2 gradually rises in this process, but the rising speed is relatively slow and the transmission power is small.

Because the efficiency of energy transmission through the diode is low, the invention improves the efficiency of energy transmission and the size regulation of VO2 by controlling the duty cycles of the switching tubes Q5-Q6 and the switching tubes Q1-Q4. The specific steps can be as follows:

when the switching tubes Q1, Q4, Q5 and Q6 are switched on, current flows through the following switching tubes in sequence: the upper end of the second winding n2, the inductor L1, the switching tube Q5, the switching tube Q6 and the lower end of the second winding n2 are connected, and the inductor L1 stores energy rapidly in the process. Then the switching tubes Q1, Q4, Q5 and Q6 are switched off, the switching tube Q7 is switched on, and the inductor L1 discharges to quickly raise the voltage across the capacitor C2. At this time, the current flows through: the left end of the inductor L1, the switching tube Q7, the capacitor C2, the diode D6 and the right end of the inductor L1. When the switching tubes Q2, Q3, Q5 and Q6 are turned on simultaneously, current flows through the following components in sequence: the lower end of the second winding n 2-a switching tube Q6-a switching tube Q5-an inductor L1-the upper end of the second winding n 2. In the process, the inductor L1 stores energy rapidly, then the switching tubes Q2, Q3, Q5 and Q6 are disconnected, the switching tube Q8 is switched on, the inductor L1 discharges to supplement voltage to the capacitor C2, and at the moment, current flows through the following steps: the right end of the inductor L1, the switching tube Q8, the capacitor C2, the diode D5 and the left end of the inductor L1. Because the two ends of the capacitor C2 are connected with the PFC circuit module, the PFC circuit module provides the converted alternating current power to the vehicle-mounted electronic device for use.

As shown in fig. 3, the regulation process of VO2 is as follows: firstly, the switching tubes Q1-Q4 emit waves according to a preset duty ratio, then the controller detects the size of the VO2, whether the VO2 is between a first threshold voltage and a second threshold voltage is judged, the preset duty ratio can be the minimum duty ratio of the switching tubes Q1-Q4 set by a system, the preset duty ratio adopted by the invention is 30%, and the preset duty ratio can also be set according to actual requirements, and is not limited herein. If yes, maintaining the duty ratios of the switching tubes Q5-Q6 and the switching tubes Q1-Q4; if not, the following two cases are specifically classified:

when the VO2 is smaller than the first threshold voltage, the duty ratio of the switching tubes Q5-Q6 is increased, the duty ratio of the switching tubes Q5-Q6 is ensured to be smaller than the first threshold duty ratio, and when the duty ratio of the switching tubes Q5-Q6 is increased to the first threshold duty ratio and the VO2 is still smaller than the third threshold voltage, the duty ratio of the switching tubes Q1-Q4 is increased until the voltage of the VO1 is within a preset voltage range.

When the VO2 is greater than the second threshold voltage, the duty ratio of the switching tubes Q5-Q6 is reduced, the duty ratio of the switching tubes Q5-Q6 is ensured to be greater than the second threshold duty ratio, and when the duty ratio of the switching tubes Q5-Q6 is reduced to the second threshold duty ratio and the VO2 is still greater than the second threshold voltage, whether the duty ratio of the switching tubes Q1-Q4 is greater than the preset duty ratio is judged. If the duty ratio of the switching tubes Q1-Q4 is larger than the preset duty ratio, the duty ratio of the switching tubes Q1-Q4 is reduced until the voltage of VO2 is within the preset voltage range; if the duty ratio of the switching tubes Q1-Q4 is smaller than the preset duty ratio, the switching tubes Q5-Q6 are controlled to be cut off, at the moment, energy is transmitted through the diode D8, the capacitor C2, the diode D5 and the inductor L1, transmission efficiency is slow, the efficiency of vehicle-mounted load consumption is larger than the transmission efficiency, and the VO2 can be reduced quickly.

Wherein the first threshold voltage is less than the second threshold voltage, and the first threshold duty cycle is greater than the second threshold duty cycle. In this embodiment, the first threshold voltage is 350V, and the second threshold voltage is 400V. Since the voltage provided by the capacitor C2 to the ac conversion module does not need to be stable, but since the output of the ac conversion module is 220V ac, the voltage of C2 is about 310V, and the withstand voltage of C2 is 450V, the operating range of 350V to 400V is a comprehensive evaluation value in the embodiment of the present invention, and can be adjusted according to the actual situation. The first threshold duty cycle is 30% and the second threshold duty cycle is 0. The range of 0-30% is considered to be that the secondary side peak current is too high due to too large duty ratio of the switching tubes Q5-Q6.

Fig. 7 to 8 are specific simulation results of a control method of a three-port energy transmission circuit according to the present invention, specifically simulating a process of transmitting energy from a high-voltage secondary circuit to a primary circuit. The parameters involved in this simulation are: transformer turns ratio n 1: n2= 15: 14; inductance L1 is 30 uH; the input voltage of the high-voltage secondary side circuit is 380V; the working frequency of the switching tubes Q1, Q2, Q3 and Q4 is 80kHZ, and the duty ratio is 20%; the working frequency of the switching tube Q5 and Q6 is 160kHZ, and the duty ratio is 20%; the output voltage of the primary side circuit is 400V, and the output power is 1350W.

As can be seen from fig. 8: at the time of T1-T2, the switching tubes Q1 and Q4 are switched on, the switching tubes Q2 and Q3 are switched off, the switching tubes Q5 and Q6 are switched on, the current of the inductor L1 rises, and energy is stored in the inductor L1; at the time of T2-T3, the switching tubes Q1 and Q4 are turned off, the switching tubes Q2 and Q3 are turned off, the switching tubes Q5 and Q6 are turned off, the current of the inductor L1 drops, and energy is released to the capacitor C2 through the diode D7 or the switching tube Q7; at the time T3-T4, the inductor L1 stops releasing energy; at the time of T4-T5, the switching tubes Q2 and Q3 are switched on, the switching tubes Q1 and Q4 are switched off, the switching tubes Q5 and Q6 are switched on, the current of the inductor L1 rises reversely, and energy is stored in the inductor L1; at the time of T5-T6, the switching tubes Q2 and Q3 are turned off, the switching tubes Q1 and Q4 are turned off, the switching tubes Q5 and Q6 are turned off, the current of the inductor L1 drops, and energy is released to the capacitor C2 through the diode D8 or the switching tube Q8; at time T6-T7, inductor L1 stops discharging energy.

In the process of switching the driving mode to the inversion mode, the invention can ensure that the power supply to the low-voltage system of the electric automobile is not interrupted, and can output alternating current for the vehicle-mounted electronic equipment. Meanwhile, when the inverter is in an inverter mode, the primary side circuit plays a role of a DC-AC conversion circuit, and the inverter utilizes the primary side circuit as an input circuit when the DC-AC conversion circuit is used, so that the condition that one additional DC-AC input circuit is additionally added for AC output is avoided, and the cost is reduced.

The above is only a part or preferred embodiment of the present invention, and neither the text nor the drawings should limit the scope of the present invention, and all equivalent structural changes made by the present specification and the contents of the drawings or the related technical fields directly/indirectly using the present specification and the drawings are included in the scope of the present invention.