Buck-boost bidirectional DCDC converter control method and system, and storage medium

Abstract

The invention relates to the technical field of power management, in particular to a buck-boost bidirectional DCDC converter control method and system and a storage medium, and the method comprises the steps: obtaining a DC bus voltage and a battery voltage of a converter; the switching frequency, the dead time and the bus voltage of the converter are obtained, and hysteresis parameters are calculated based on the switching frequency, the dead time and the bus voltage; the correlation between the direct current bus voltage and the battery voltage is obtained based on the hysteresis parameter, the working modes needing to be operated of the converter are judged based on the correlation between the direct current bus voltage and the battery voltage, and the working modes comprise the BUCK mode, the BOOST mode and the upper tube direct connection mode; and adjusting the PWM waveform of the driving switch tube so as to control the operation of a corresponding working mode. The defects that a traditional control mode is large in switching loss, high in common-mode noise and low in specific working condition efficiency are effectively overcome, the conversion efficiency of the converter is remarkably improved, common-mode interference is reduced, and the electric energy conversion stability and reliability are enhanced.

Description

Technical Field

[0001] The present invention relates to the field of power management technology, and specifically relates to a control method, system and storage medium of step-up and buck-up bidirectional DCDC converter. Background Art

[0002] With the widespread application of new energy and energy storage systems such as photovoltaic and wind power generation, the output of photovoltaic and battery are all DC voltage, and the demand for DC conversion products is growing. DC microgrid system is a typical application scenario. Due to the uncertainty of energy flow in DC microgrid system and the large fluctuation range of DC voltage of photovoltaic and battery, DC converter needs to have the functions of bidirectional energy conversion and step-up and step-down conversion. At the same time, considering that the new energy power generation system and energy storage system have very high requirements for the conversion efficiency of the converter.

[0003] At present, the mainstream topology of DC converters uses four-switch BUCK-BOOST conversion. The four-switch BUCK-BOOST converter consists of four switch tubes, one energy storage inductor, and DC voltage output on both sides. The two ends can be connected to the DC bus and the battery, and can realize the battery charging and discharging working modes. The voltage at both ends does not need to be limited to the voltage range, and the voltage range can overlap, which is very suitable for application scenarios such as photovoltaic power generation and battery energy storage.

[0004] For the four-switch BUCK-BOOST, it has a very traditional and simple control method, that is, Q1 and Q3 work at the same time, Q2 and Q4 work at the same time, and the two groups of MOS are turned on alternately; although there is no control mode switching involved and it is easy to implement, the disadvantage is that the four switch tubes are always working, resulting in large switching losses, low conversion efficiency, and large common-mode noise. Summary of the invention

[0005] In view of the above shortcomings of the prior art, the present invention provides a control method, system and storage medium for step-up and buck-up bidirectional DCDC converter to solve the above technical problems.

[0006] In a first aspect, the present invention provides a buck-boost bidirectional DCDC converter control method, wherein the buck-boost bidirectional DCDC converter includes four switch tubes, namely, switch tube Q1, switch tube Q2, switch tube Q3 and switch tube Q4, and includes the following steps: S1, obtain the DC bus voltage and battery voltage of the converter; S2, obtain the switching frequency, dead time and bus voltage of the converter, and calculate the hysteresis parameters based on the switching frequency, dead time and bus voltage; S3, obtaining the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and judging the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage, the working modes including BUCK mode, BOOST mode and upper tube direct mode; S4, adjust the PWM waveform of the drive switch tube to control the operation of the corresponding working mode.

[0007] In an optional embodiment, in step S2, the calculation of the hysteresis parameter specifically includes: Take the inverse switching period of the switching frequency; Calculate the proportion of dead time during the switching period as the proportion of dead time; The hysteresis parameters are obtained based on the dead-band ratio multiplied by the bus voltage.

[0008] In an optional embodiment, step S3 specifically includes: To determine whether the battery voltage is greater than the sum of the DC bus voltage and the hysteresis parameters, if it is determined to be greater than, you need to run the BUCK mode; If it is determined to be not greater than, further determine whether the battery voltage is less than the difference between the DC bus voltage and the hysteresis parameter. If it is determined to be less than, it is necessary to run the BOOST mode; if it is determined to be not less than, it is necessary to run the upper tube direct mode.

[0009] In an optional embodiment, step S4 specifically includes: In BUCK mode, adjust the PWM waveform of the drive switch tube, turn on the switch tube Q1 and turn off the switch tube Q2, adjust the duty cycle through PI control, and turn on the switch tube Q3 and the switch tube Q4 alternately according to the duty cycle; In BOOST mode, the PWM waveform driving the switch tube is adjusted to turn on the switch tube Q4 and turn off the switch tube Q3. The duty cycle is adjusted through PI control, and the switch tubes Q1 and Q2 are turned on alternately according to the duty cycle. In the upper tube straight-through mode, adjust the PWM waveform of the drive switch tube to enable the switch tube Q1 and switch tube Q4 to be turned on, and the switch tube Q2 and switch tube Q3 are closed.

[0010] In an alternative embodiment, In BUCK mode, the on-time of the switch tube Q3 is the switching period multiplied by the duty cycle, and the on-time of the switch tube Q4 is, the switching period is minus the product of the switching period and duty cycle, and the duty cycle is calculated as:

[0011] In BOOST mode, the on-time of switching tube Q1 is the switching period multiplied by the duty cycle, and the on-time of switching tube Q2 is, the switching period is minus the product of switching period and duty cycle, and the duty cycle is calculated as:

[0012] in, is the converter DC bus voltage, is the converter battery voltage.

[0013] In an optional embodiment, the switch tube Q1 is connected in series with the switch tube Q2, and the switch tube Q3 is connected in series with the switch tube Q4. The converter also includes an inductor, one end of the inductor is connected to the connection between the switch tube Q1 and the switch tube Q2, and the other end of the inductor is connected to the connection between the switch tube Q3 and the switch tube Q4. In the upper tube direct-pass mode, the battery side and the DC bus side are directly connected through the inductor.

[0014] In an alternative embodiment, the switching frequency is calculated as: In BUCK mode, according to the inductor current ripple formula, it is obtained:

[0015] in, is the allowable inductor current ripple, is the inductor, is the switching frequency in BUCK mode; In BOOST mode, according to the inductor current ripple formula, it is obtained:

[0016] in, is the switching frequency in BUCK mode.

[0017] In an optional embodiment, obtain the switch tube opening time and turn-off time , the dead time is calculated as:

[0018] in, is the dead time, is the safety factor, and ; The switching period is obtained based on the switching frequency, the proportion of dead time to the switching period is calculated, and the dead time is adjusted according to the preset proportional interval.

[0019] In a second aspect, the present invention provides a buck-boost bidirectional DCDC converter control system. When the system is implemented, the buck-boost bidirectional DCDC converter control method is executed. The buck-boost bidirectional DCDC converter includes four switch tubes, namely, switch tube Q1, switch tube Q2, switch tube Q3 and switch tube Q4. The system includes: Voltage acquisition module to obtain the DC bus voltage and battery voltage of the converter; The hysteresis parameter calculation module obtains the switching frequency, dead time and bus voltage of the converter, and calculates the hysteresis parameters based on the switching frequency, dead time and bus voltage; A working mode acquisition module obtains the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and determines the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage. The working modes include BUCK mode, BOOST mode and upper tube direct mode. Control the operation module and adjust the PWM waveform of the drive switch tube to control the corresponding operating mode.

[0020] According to a third aspect, a computer storage medium is provided, wherein the computer-readable storage medium stores instructions, and when the instructions are executed on a computer, the computer executes the methods described in the above aspects.

[0021] The beneficial effect of the present invention is that the buck-boost bidirectional DCDC converter control method, system and storage medium provided by the present invention accurately obtain the DC bus voltage, battery voltage, switching frequency, dead time and calculate the hysteresis parameters, thereby accurately determining the converter working mode (BUCK, BOOST, upper tube direct mode), and then accurately controlling the operating mode by adjusting the PWM waveform of the driving switch tube, effectively solving the disadvantages of large switching loss, high common-mode noise and low efficiency under specific working conditions of the traditional control method, significantly improving the converter conversion efficiency, reducing common-mode interference, enhancing the stability and reliability of power conversion, optimizing system performance, effectively adapting to the stringent requirements of new energy power generation and energy storage systems for efficient and stable power conversion, and laying a solid foundation for the stable and efficient operation of the DC microgrid system.

[0022] In addition, the invention has a reliable design principle, a simple structure and a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention 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 work.

[0024] Figure 1 It is a schematic flowchart of the step-up step-up bidirectional DCDC converter control method according to one embodiment of the present invention.

[0025] Figure 2 It is a schematic diagram of the four-switch BUCK-BOOST circuit PWM waveform control circuit according to an embodiment of the present invention.

[0026] Figure 3It is a four-switch BUCK-BOOST circuit control method diagram according to an embodiment of the present invention.

[0027] Figure 4 It is a four-switch BUCK-BOOST circuit control flowchart according to an embodiment of the present invention.

[0028] Figure 5a It is a PWM waveform timing diagram in the BUCK mode of a four-switch BUCK-BOOST circuit according to an embodiment of the present invention.

[0029] Figure 5b It is a PWM waveform timing diagram in the BOOST mode of a four-switch BUCK-BOOST circuit according to an embodiment of the present invention.

[0030] Figure 5c It is a PWM waveform timing diagram in the four-switch BUCK-BOOST circuit in the direct-through mode of the four-switch BUCK-BOOST circuit according to an embodiment of the present invention.

[0031] Figure 6a FIG. 1 is an equivalent circuit diagram of a four-switch BUCK-BOOST circuit in BUCK mode according to an embodiment of the present invention.

[0032] Figure 6b It is an equivalent circuit diagram in the BOOST mode of a four-switch BUCK-BOOST circuit according to an embodiment of the present invention.

[0033] Figure 6c It is an equivalent circuit diagram in the four-switch BUCK-BOOST circuit upper tube through mode according to an embodiment of the present invention.

[0034] Figure 7 It is a schematic block diagram of a buck-boost bidirectional DCDC converter control system according to one embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0037] The step-up buck-booth DCDC converter control method provided by the embodiment of the present invention is performed by a computer device, and accordingly, the step-up buck-booth DCDC converter control system is operated in the computer device.

[0038] Figure 1 is a schematic flow chart of a method according to an embodiment of the present invention. Figure 1 The execution body may be a buck-boost bidirectional DCDC converter control system. Depending on different requirements, the order of steps in the flowchart can be changed, and some can be omitted.

[0039] The step-up and buck-up bidirectional DCDC converter includes four switching tubes, namely switching tube Q1, switching tube Q2, switching tube Q3 and switching tube Q4, such as Figure 1 As shown, the method includes: S1, obtain the DC bus voltage and battery voltage of the converter; Fully grasp the power status of the input (battery voltage terminal) and the output (DC bus voltage terminal) so that the converter can adapt to the working mode according to the voltage level.

[0040] S2, obtain the switching frequency, dead time and bus voltage of the converter, and calculate the hysteresis parameters based on the switching frequency, dead time and bus voltage; Reasonable switching frequency balances component size and switching loss, precise dead time prevents direct damage to the switch tube, and adaptive hysteresis parameters enhance the sensitivity and stability of mode switching, ensuring continuous and reliable conversion and transmission of electric energy, extending component life, improving the overall reliability and durability of the system, adapting to complex working conditions, and reducing the risk of power fluctuations and interruptions.

[0041] S3, obtaining the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and judging the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage, the working modes including BUCK mode, BOOST mode and upper tube direct mode; Automatically switch to BUCK (step-down), BOOST (step-up) or upper tube direct-through mode under different voltage scenarios to achieve precise step-down, step-up or low-loss direct conversion. Reduce switching loss, improve efficiency, reduce common-mode noise, enhance power quality and conversion efficiency, optimize system energy efficiency management, ensure the system operates stably, economically and efficiently under variable working conditions, and meet the needs of various load and energy scenarios.

[0042] S4, adjust the PWM waveform of the drive switch tube to control the operation of the corresponding working mode.

[0043] The on / off timing and duty cycle of the switch tube are flexibly modulated according to the mode requirements. In the BUCK mode, the voltage is steadily reduced, in the BOOST mode, the voltage is accurately increased, and in the upper tube pass-through mode, the voltage is directly connected with low loss. This ensures that the output voltage is accurate and stable, and the power transmission is efficient and continuous. It improves the system's dynamic response capability, optimizes the power quality, ensures stable load operation, enhances the system's adaptability to load and power fluctuations, and improves overall reliability and operating efficiency.

[0044] Optionally, as an embodiment of the invention, reference Figure 2 , it can be concluded that the buck-boost bidirectional DCDC converter control circuit specifically includes: DC bus output side load, DC bus output side filter capacitor, DC bus side switch tube Q1, DC bus side switch tube Q2, inductor, battery input side switch tube Q3, battery input side switch tube Q4, battery input side filter capacitor; The switch tube Q1 is connected in series with the switch tube Q2, the switch tube Q3 is connected in series with the switch tube Q4, one end of the inductor is connected to the connection point of the switch tube Q1 and the switch tube Q2, the other end of the inductor is connected to the connection point of the switch tube Q3 and the switch tube Q4, the DC bus output side load is connected in parallel to the two ends of the switch tube Q1 and the switch tube Q2 connected in series, the DC bus output side filter capacitor is connected in parallel to the two ends of the switch tube Q1 and the switch tube Q2 connected in series, and the battery input side filter capacitor is connected in parallel to the two ends of the switch tube Q3 and the switch tube Q4 connected in series; The four switch tubes are the core components of the circuit, which control the flow of current and the conversion of energy.

[0045] The inductor is an energy storage inductor that plays the role of storing and releasing energy in the circuit. During the process of the switch tube being turned on and off, the current in the inductor will gradually rise or fall, thereby realizing the voltage conversion; the size of the inductance value will affect the working characteristics of the circuit, such as the current ripple size, dynamic response speed, etc. A larger inductance value will reduce the current ripple, but may cause the dynamic response to slow down; conversely, a smaller inductance value will increase the current ripple, but the dynamic response will become faster. In actual design, it is necessary to select the appropriate inductance value according to the specific application requirements.

[0046] The battery input side filter capacitor is used to stabilize the input voltage and reduce the ripple of the input voltage. It can filter out high-frequency noise in the power supply and provide a relatively stable DC voltage source for the circuit.

[0047] The filter capacitor on the output side of the DC bus is used to stabilize the output voltage and reduce the ripple of the output voltage. It can store electricity and quickly release electricity when the load changes to maintain stability of the output voltage.

[0048] The four-switch BUCK-BOOST circuit is connected to a control circuit that generates a drive signal to control the on and off time of the four power switches. It usually includes a pulse width modulation (PWM) controller that monitors the output voltage through a feedback mechanism and adjusts the duty cycle of the PWM signal according to the difference with the reference voltage, thereby achieving precise control of the output voltage.

[0049] Optionally, as an embodiment of the present invention, in step S2, the calculation of the hysteresis parameter specifically includes: Take the inverse switching period of the switching frequency; In BUCK mode, according to the inductor current ripple formula, it is obtained:

[0050] in, is the allowable inductor current ripple, is the inductor, is the switching frequency in BUCK mode; In BOOST mode, according to the inductor current ripple formula, it is obtained:

[0051] in, is the switching frequency in BUCK mode.

[0052] Calculate the proportion of dead time during the switching period as the proportion of dead time; Get the switch on time and turn-off time , the dead time is calculated as:

[0053] in, is the dead time, is the safety factor, and ; The switching period is obtained based on the switching frequency, the proportion of dead time to the switching period is calculated, and the dead time is adjusted according to the preset proportional interval.

[0054] The hysteresis parameters are obtained based on the dead-band ratio multiplied by the bus voltage.

[0055] Optionally, as an embodiment of the invention, the converter parameter is the switching frequency =6kHz, dead time =2us, bus voltage =750V, the hysteresis parameter ΔV is calculated as follows: Switching cycle =1 / 6kHz=166.7us Dead zone ratio = / *100=1.2% Hysteresis parameter ΔV= *1.2%=9V Optionally, as an embodiment of the invention, reference Figure 2 and Figure 3 , step S3 specifically includes: To determine whether the battery voltage is greater than the sum of the DC bus voltage and the hysteresis parameters, if it is determined to be greater than, you need to run the BUCK mode; If it is determined to be not greater than, further determine whether the battery voltage is less than the difference between the DC bus voltage and the hysteresis parameter. If it is determined to be less than, it is necessary to run the BOOST mode; if it is determined to be not less than, it is necessary to run the upper tube direct mode.

[0056] Optionally, as an embodiment of the present invention, step S4 specifically includes: Reference Figure 5a and Figure 6a In BUCK mode, adjust the PWM waveform of the driving switch tube (Vgs1 is the waveform for controlling the switch tube Q1, Vgs2 is the waveform for controlling the switch tube Q2, Vgs3 is the waveform for controlling the switch tube Q3, and Vgs4 is the waveform for controlling the switch tube Q4), so that the switch tube Q1 is turned on (Vgs1 maintains a high level) and the switch tube Q2 is turned off (Vgs2 maintains a low level), and the duty cycle is adjusted through PI control, and the switch tubes Q3 and Q4 are turned on alternately according to the duty cycle; at this time, ; Reference Figure 5b and Figure 6b In BOOST mode, by adjusting the PWM waveform of the driving switch tube, the switch tube Q4 is turned on (Vgs4 maintains a high level) and the switch tube Q3 is turned off (Vgs3 maintains a low level). The duty cycle is adjusted through PI control, and the switch tubes Q1 and Q2 are turned on alternately according to the duty cycle. At this time ; Reference Figure 5c and Figure 6c In the upper tube direct mode, adjust the PWM waveform of the driving switch tube to turn on the switch tube Q1 and the switch tube Q4 (Vgs1 and Vgs4 maintain a high level), turn off the switch tube Q2 and the switch tube Q3 (Vgs2 and Vgs3 maintain a low level), and the battery side and the DC bus side are directly connected through the inductor. .

[0057] Optionally, as an embodiment of the present invention, the upper tube direct mode can also be replaced by a full shutdown mode. In the full shutdown mode, when the input voltage and the output voltage are close, all four switch tubes are turned off, and the input and output are disconnected, and no energy is exchanged.

[0058] Although the full shutdown mode can also reduce switching losses and common-mode noise, the circuit is blocked because the input and output are disconnected. When the load and power generation fluctuate greatly, or the voltage at both ends changes up and down alternately, the full shutdown mode will cause the voltage at both ends to fluctuate greatly, and even cause serious problems such as device damage. Therefore, it is better to use the upper tube direct mode.

[0059] In some embodiments, the buck-boost bidirectional DCDC converter control system may include a plurality of functional modules composed of computer program segments. The computer program of each program segment in the buck-boost bidirectional DCDC converter control system may be stored in a memory of a computer device and executed by at least one processor to execute (see Figure 1 Description) Functions of buck-boost bidirectional DCDC converter control.

[0060] In this embodiment, the buck-boost bidirectional DCDC converter control system can be divided into multiple functional modules according to the functions it performs, such as Figure 7 As shown. The functional modules of the system may include: a voltage acquisition module, a hysteresis parameter calculation module, a working mode acquisition module and a control operation module. The module referred to in the present invention refers to a series of computer program segments that can be executed by at least one processor and can complete fixed functions, which are stored in a memory. In this embodiment, the functions of each module will be described in detail in subsequent embodiments. The system includes: Voltage acquisition module to obtain the DC bus voltage and battery voltage of the converter; The hysteresis parameter calculation module obtains the switching frequency, dead time and bus voltage of the converter, and calculates the hysteresis parameters based on the switching frequency, dead time and bus voltage; A working mode acquisition module obtains the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and determines the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage. The working modes include BUCK mode, BOOST mode and upper tube direct mode. Control the operation module and adjust the PWM waveform of the drive switch tube to control the corresponding operating mode.

[0061] The voltage acquisition module accurately monitors the DC bus and battery voltage, laying the foundation for subsequent precise regulation; the hysteresis parameter calculation module calculates the adaptation parameters according to the switching frequency, dead time and bus voltage, optimizes the mode switching logic and stability, and reduces losses and increases efficiency; the working mode acquisition module uses hysteresis parameters to intelligently determine voltage correlation and accurately select working modes to improve the accuracy and efficiency of power conversion; the control operation module drives the switch tube by cleverly modulating the PWM waveform to stabilize the power conversion process and optimize the output characteristics in each mode. The system as a whole reduces energy consumption, strengthens stability, precise control, and improves energy efficiency, which effectively promotes the efficient and reliable operation of the converter in new energy and energy storage systems, meets the needs of diverse and complex working conditions, expands application prospects, and consolidates the foundation of system performance.

[0062] The present invention also provides a computer storage medium, wherein the computer storage medium may store a program, and when the program is executed, the program may include some or all of the steps in each embodiment provided by the present invention. The storage medium may be a magnetic disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM).

[0063] Those skilled in the art can clearly understand that the technology in the embodiments of the present invention can be implemented by means of software plus a necessary general hardware platform. Based on this understanding, the technical solution in the embodiments of the present invention, in essence or in other words, the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk, and other media that can store program codes, including several instructions for enabling a computer terminal (which can be a personal computer, a server, or a second terminal, a network terminal, etc.) to execute all or part of the steps of the methods described in each embodiment of the present invention.

[0064] In this specification, the same or similar parts between the various embodiments can be referred to each other. In particular, for the terminal embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description in the method embodiment.

[0065] In the several embodiments provided by the present invention, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic. For example, the division of the modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or modules, which can be electrical, mechanical or other forms.

[0066] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0067] In addition, each functional module in each embodiment of the present invention may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0068] Although the present invention has been described in detail with reference to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily think of changes or substitutions within the technical scope disclosed by the present invention, and these shall be within the scope of protection of the present invention.

Claims

1. A buck-boost bidirectional DCDC converter control method, characterized in that: The buck-boost bidirectional DCDC converter includes four switch tubes, namely switch tube Q1, switch tube Q2, switch tube Q3 and switch tube Q4. The following steps are involved: S1, obtaining the DC bus voltage and battery voltage of the converter; S2, obtaining the switching frequency, dead time and bus voltage of the converter, and calculating the hysteresis parameter based on the switching frequency, dead time and bus voltage; S3, obtaining the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and judging the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage, the working modes including BUCK mode, BOOST mode and upper tube direct mode; S4, adjusting the PWM waveform of the driving switch tube to control the corresponding operation mode.

2. The buck-boost bidirectional DCDC converter control method according to claim 1, characterized in that: In step S2, the calculation of the hysteresis parameter specifically includes: Take the inverse switching period of the switching frequency; Calculate the proportion of the dead time in the switching cycle as the dead time proportion; The hysteresis parameter is obtained by multiplying the dead zone ratio by the bus voltage.

3. The buck-boost bidirectional DCDC converter control method according to claim 1, characterized in that: Step S3 specifically includes: Determine whether the battery voltage is greater than the sum of the DC bus voltage and the hysteresis parameter. If it is greater, the BUCK mode needs to be run; If it is determined to be not greater than, further determine whether the battery voltage is less than the difference between the DC bus voltage and the hysteresis parameter. If it is determined to be less than, it is necessary to run the BOOST mode; if it is determined to be not less than, it is necessary to run the upper tube direct mode.

4. The buck-boost bidirectional DCDC converter control method according to claim 1, characterized in that: Step S4 specifically includes: In BUCK mode, the PWM waveform driving the switch tube is adjusted to turn on the switch tube Q1 and turn off the switch tube Q2. The duty cycle is adjusted through PI control, and the switch tubes Q3 and Q4 are turned on alternately according to the duty cycle. In BOOST mode, the PWM waveform driving the switch tube is adjusted to turn on the switch tube Q4 and turn off the switch tube Q3. The duty cycle is adjusted through PI control, and the switch tubes Q1 and Q2 are turned on alternately according to the duty cycle. In the upper tube direct-pass mode, the PWM waveform driving the switch tube is adjusted to turn on the switch tube Q1 and the switch tube Q4, and turn off the switch tube Q2 and the switch tube Q3.

5. The buck-boost bidirectional DCDC converter control method according to claim 4, characterized in that: In BUCK mode, the on-time of switch Q3 is the switching period multiplied by the duty cycle, and the on-time of switch Q4 is the switching period minus the product of the switching period and the duty cycle. The duty cycle is calculated as: In BOOST mode, the on-time of switch Q1 is the switching period multiplied by the duty cycle, and the on-time of switch Q2 is the switching period minus the product of the switching period and the duty cycle. The duty cycle is calculated as: in, is the converter DC bus voltage, is the converter battery voltage.

6. The buck-boost bidirectional DCDC converter control method according to claim 5, characterized in that: The switch tube Q1 is connected in series with the switch tube Q2, and the switch tube Q3 is connected in series with the switch tube Q4. The converter also includes an inductor, one end of the inductor is connected to the connection between the switch tube Q1 and the switch tube Q2, and the other end of the inductor is connected to the connection between the switch tube Q3 and the switch tube Q4. In the upper tube direct-pass mode, the battery side and the DC bus side are directly connected through the inductor.

7. The buck-boost bidirectional DCDC converter control method according to claim 6, characterized in that: The switching frequency is calculated as: In BUCK mode, according to the inductor current ripple formula: in, is the allowable inductor current ripple, is the inductor, is the switching frequency in BUCK mode; In BOOST mode, according to the inductor current ripple formula: in, is the switching frequency in BUCK mode.

8. The buck-boost bidirectional DCDC converter control method according to claim 6, characterized in that: Get the switch on time and turn-off time , the dead time is calculated as: in, is the dead time, is the safety factor, and ; The switching period is obtained based on the switching frequency, the ratio of the dead time to the switching period is calculated, and the dead time is adjusted according to a preset ratio interval.

9. A buck-boost bidirectional DCDC converter control system, characterized in that: When the system is implemented, the buck-boost bidirectional DCDC converter control method according to any one of claims 1 to 8 is executed, the buck-boost bidirectional DCDC converter includes four switch tubes, namely, switch tube Q1, switch tube Q2, switch tube Q3 and switch tube Q4, and the system includes: A voltage acquisition module, which acquires the DC bus voltage and battery voltage of the converter; A hysteresis parameter calculation module obtains the switching frequency, dead time and bus voltage of the converter, and calculates the hysteresis parameter based on the switching frequency, dead time and bus voltage; A working mode acquisition module obtains the correlation between the DC bus voltage and the battery voltage based on the hysteresis parameter, and determines the working mode that the converter needs to operate based on the correlation between the DC bus voltage and the battery voltage. The working modes include BUCK mode, BOOST mode and upper tube direct mode. The control operation module adjusts the PWM waveform of the driving switch tube to control the operation of the corresponding working mode.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes one or more program instructions, and the one or more program instructions are used by a processor to execute the buck-boost bidirectional DCDC converter control method according to any one of claims 1 to 8.

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