Bidirectional dc / dc power converter based on boost topology and control method

Abstract

The application belongs to the technical field of power electronic conversion, and discloses a bidirectional DC / DC power converter based on a Boost topology and a control method, which is suitable for bidirectional conversion of direct-current electric energy in energy storage, new energy vehicles and the like. The converter comprises an inductance current sampling module, a PI control operation module, a PWM driving module, a mode switching control module and a current buffer sub-module to form a closed-loop control system, and bidirectional energy transmission is realized by optimizing a topology circuit, and transient current impact is inhibited by matching a buffer module. The control method comprises modeling and presetting, parameter setting, construction of a switching and buffer mechanism, working condition verification and closed-loop optimization, voltage stability control and smooth charging and discharging switching are realized through simulation parameter mapping. The application has the advantages of simple structure, high control precision, wide adaptability, high design efficiency and reliable operation, effectively reduces device loss and improves overall system performance.

Description

Technical Field

[0001] This invention belongs to the field of power electronic conversion technology, and relates to a bidirectional DC / DC power converter and control method based on Boost topology, which is applicable to scenarios requiring bidirectional DC power conversion such as energy storage systems, new energy vehicles, and hybrid aircraft. Background Technology

[0002] Against the backdrop of rapid development in renewable energy and power electronics technology, DC / DC converters, as core devices for power conversion, are widely used in new energy vehicles, distributed generation, energy storage systems, and other fields. However, traditional DC / DC converters suffer from the following problems in practical applications: The dynamic response speed is slow, and the output voltage stability is poor when faced with sudden load changes or input voltage fluctuations; the steady-state performance is insufficient, and the output voltage ripple is large, which affects the life of electrical equipment; most converters only support unidirectional energy transmission and cannot meet the requirements of bidirectional charging and discharging switching; the control strategy is complex, the parameter tuning is difficult, and the adaptability is limited.

[0003] Existing DC / DC conversion technologies suffer from significant limitations at the topology level. Traditional Buck topologies can only perform buck conversion, while Boost topologies can only perform boost conversion, offering limited functionality and failing to adapt to scenarios with wide voltage fluctuations. Although Buck-Boost topologies support buck-boost switching, they exhibit low conversion efficiency, slow dynamic response, and large current ripple under high-power or wide-range voltage conversion conditions, making it difficult to meet the stringent requirements for high-efficiency energy conversion in scenarios such as new energy power generation and energy storage systems. At the control strategy level, mainstream control schemes still face technical bottlenecks. While sliding mode variable structure control possesses strong robustness against system parameter perturbations and external disturbances, its inherent "chattering" problem in its first-order control law can easily lead to high-frequency oscillations in the system output voltage, affecting control accuracy and device lifespan. Fuzzy control relies on expert experience rules for design and lacks precise mathematical model support, resulting in insufficient robustness under complex nonlinear conditions and difficulty in achieving precise closed-loop regulation. Traditional PID control, based on linearized model design, is significantly less adaptable and has insufficient anti-interference capability for highly nonlinear systems like DC / DC converters when faced with sudden load changes or large input voltage fluctuations, easily leading to problems such as large overshoot and long settling time, failing to guarantee stable system operation. Furthermore, with the rapid development of new energy vehicles, energy storage power stations, and industrial flexible power supply, DC / DC conversion systems face combined requirements for bidirectional energy transfer, high reliability, and high power density. Existing unidirectional conversion topologies and conventional control strategies are unable to simultaneously achieve efficient conversion, stable performance, and bidirectional energy dispatch capabilities. Therefore, there is an urgent need to develop a new type of DC / DC converter control system that deeply integrates topology and control algorithm to break through existing technical bottlenecks and meet the application requirements of high-performance power electronic conversion systems. Summary of the Invention

[0004] This invention aims to address the problems of poor parameter adaptability, large fluctuations during charge / discharge switching, and weak integration between simulation and actual control in existing Boost-type DC / DC converters. It provides a bidirectional DC / DC power converter and control method based on Boost topology. Using Matlab / Simulink, through modular design and simulation optimization, it achieves stable voltage control, smooth charge / discharge switching, and efficient anti-interference, thus improving system performance. Compared with traditional DC / DC converters, it has advantages such as bidirectional energy transfer, high-performance control, parameter optimization, and simple structure. This invention solves the problems of traditional converter topologies having limited functionality, bottlenecked control strategies, large fluctuations during charge / discharge switching, and weak integration between simulation and actual control.

[0005] To achieve the above objectives, the specific technical solution of the present invention is as follows: A bidirectional DC / DC power converter based on Boost topology is disclosed. The converter's physical architecture includes an energy storage inductor, a first switching element, a second switching element, a first diode, and a second diode. The energy storage inductor, the first switching element, and the first diode constitute a Boost topology circuit, with a branch consisting of a second switching element and a second diode connected in series in parallel across the series branch formed by the energy storage inductor and the first diode. The first switching element is controlled to conduct in charging mode, enabling the energy stored in the energy storage inductor to be boosted through the first diode for output. The second switching element is controlled to conduct in discharging mode, forming a feedback circuit with the second diode to achieve bidirectional energy flow. The converter also includes the following functional modules operating in concert: an inductor current sampling module, a PI control calculation module, a PWM drive module, a mode switching control module, and a current buffer submodule. The connection relationships between these modules are as follows: The output of the inductor current sampling module is connected to the input of the PI control operation module to provide feedback signals; the output of the PI control operation module is connected to the PWM drive module, and the output signal of the PWM drive module acts on the switching transistors in the topology circuit; the mode switching control module is logically connected to the PWM drive module, and realizes bidirectional energy flow by controlling the triggering sequence of different switching transistors; the current buffer submodule is physically connected in series in the second switching element and the second diode circuit to smooth out current fluctuations during switching.

[0006] The collaborative logic between the aforementioned modules embodies the bidirectional conversion characteristics based on the Boost topology: In charging mode, the mode switching control module instructs the first switching element to act as the master switch for pulse width modulation, utilizing the energy storage inductor characteristics to achieve boost conversion; in discharging mode, the mode switching control module adjusts the drive logic, instructing the second switching element to act as the master switch, utilizing the current buffer submodule to achieve reverse energy outflow. The parameters of the PI control operation module match the dynamic characteristics of the small-signal model of the Boost topology, ensuring closed-loop stability during bidirectional switching. This design, which changes the master-slave drive relationship of the switching transistors through the logic layer, enables the converter to maintain the high boost ratio advantage of the Boost topology while possessing controlled bidirectional energy flow capability.

[0007] The specific structure and implementation logic of each of the above functional modules are as follows: The inductor current sampling module consists of a current transformer (or Hall effect current sensor) and a signal conditioning submodule. Its implementation logic is as follows: the current transformer senses the magnetic field changes in the energy storage inductor of the main circuit in real time and converts them into a linear voltage signal; the signal conditioning submodule consists of a bandpass filter circuit and a level matching circuit. The bandpass filter circuit removes high-frequency switching noise and low-frequency fundamental interference from the linear voltage signal, while the level matching circuit scales the signal to a voltage range recognizable by the controller, thus providing high-precision real-time current feedback for closed-loop control.

[0008] The PI control calculation module consists of a proportional-integral (PI) arithmetic unit and an output limiting submodule. Its specific function and logic are as follows: The PI arithmetic unit receives the deviation between the target reference current and the sampled current, performs linear calculations using preset proportional and integral coefficients, and generates a preliminary duty cycle control signal. The preset proportional and integral coefficients are tuned based on a small-signal mathematical model established using the Boost topology state-space averaging method, i.e., establishing the transfer function from the duty cycle to the inductor current. The control law was tuned through frequency domain analysis, ensuring its compatibility with the nonlinear characteristics of the Boost topology. The limiting submodule uses logical judgment to restrict the duty cycle of the output to a reasonable range of 0 to 1. Its function is to prevent saturation of the controller due to integral accumulation and to avoid the drive signal exceeding the physical tolerance limit of the power switch.

[0009] The PWM drive module consists of a duty cycle modulator, a logic dead-time submodule, and a power amplifier drive circuit. These three components work sequentially according to signal flow, forming a complete link from control commands to the power switching transistor drive. The duty cycle modulator, as the first stage of the link, receives the voltage-type duty cycle control signal output from the PI control module, compares it with a high-frequency triangular carrier wave, and generates two initial complementary PWM pulse signals corresponding to the first and second switching elements. The logic dead-time submodule, as an intermediate stage, receives the complementary PWM pulse signals output from the duty cycle modulator and, based on the switching characteristics of the two switching elements in the main circuit, inserts a microsecond-level dead-time between the two drive signals to prevent momentary shoot-through short circuits during charging / discharging mode switching or complementary conduction. The power amplifier drive circuit, as the final stage of the link, receives the corrected PWM pulse signal after the dead-time is added, amplifies it to improve the signal's driving capability, and ultimately generates a strong current drive signal capable of driving the gate of the switching transistor, controlling the first and second switching elements to complete reliable switching operations.

[0010] The mode switching control module consists of a status monitoring interface, a logic judgment submodule, and a signal distribution submodule. Its functional logic is as follows: the status monitoring interface reads the battery's state of charge (SOC) in real time; the logic judgment submodule compares the battery's SOC with a preset threshold and outputs a charging or discharging status command; the signal distribution submodule changes the path direction of the PWM pulse signal according to the output status command, driving the first switching element to operate in charging mode and the second switching element to operate in discharging mode, thereby achieving automatic scheduling of energy flow.

[0011] Current buffer submodule: Composed of an inductor, its function is to buffer current. The specific implementation logic of this module is to utilize the physical characteristic that inductor current cannot change abruptly, and at the moment the mode switching logic takes effect, smoothly adjust the duty cycle increment of the PWM to offset the surge current generated by the voltage step. Its function is to reduce transient electrical stress during mode switching, ensuring electromagnetic compatibility and device lifespan in bidirectional operation.

[0012] The control method for the bidirectional DC / DC power converter based on the Boost topology described above includes the following steps: Step 1: For the Boost topology, based on the inductor current and output capacitor voltage As state variables, a mathematical model of the system in continuous conduction mode is established. The specific modeling process is as follows: First, the conduction state of the first switching element during one switching cycle is described. The linear state-space equation of the state, where For the switching cycle, To determine the duty cycle, the state-space averaging method is then used to calculate the duty cycle. A weighted average of the two sets of equations is performed to obtain a nonlinear average model that includes DC quantities and AC small-signal perturbations. A small-signal perturbation is introduced near the steady-state operating point and linearized, while ignoring second-order and higher-order terms, to derive the duty cycle perturbation. to inductor current disturbance Small signal transfer function .

[0013] Step 2: Small-signal transfer function from duty cycle to inductor current constructed in Step 1 Design a proportional-integral (PI) control law for the inner loop of the current circuit. The time-domain expression of the control law is: ,in, This is the voltage-type duty cycle control signal output by the PI control arithmetic module. The proportional gain of the PI controller. The integral coefficient of the PI controller; The deviation between the reference current and the sampled current, s The domain transfer function is expressed as The initial values ​​of the control parameters are calculated using frequency domain analysis, and the open-loop transfer function of the system is constructed. ,in, Let be the system open-loop transfer function for the inner current loop. For PI controller s Complex frequency domain (complex frequency domain) transfer function; setting the switching frequency of the converter to be... To ensure the stability of the control loop, the crossover frequency of the inner current loop is set to the switching frequency. The value is 1 / 10 to 1 / 5, and the target phase margin is set to 45° to 60°. Based on this, the following calculations are performed. and The initial value is introduced into the simulation model. and Initial values ​​were obtained, and parameters were optimized and adjusted through multiple iterations. The step response waveform and tracking performance of the current loop were monitored in real time using an oscilloscope to finally determine the optimal combination of PI parameters.

[0014] Step 3: Construction of bidirectional switching logic and buffer mechanism. In the simulation model, a logic judgment submodule and a current buffer submodule are set up. Automatic charging / discharging switching logic is built by setting the battery SOC threshold. The physical characteristics of the buffer inductor are used to smooth out sudden current changes during switching, completing the construction of a complete closed-loop control logic.

[0015] Step 4: Typical Operating Condition Simulation and Performance Verification. Perform full-condition simulation tests, and use a Scope oscilloscope to acquire waveforms of inductor current, output voltage, output current, and SOC changes; verify whether the current tracking is accurate, whether the voltage is stable within the preset range, and whether there are fluctuations exceeding the preset range during the switching process when switching charging and discharging modes.

[0016] Step 5: Closed-loop optimization and control scheme finalization. To address dynamic deviations or fluctuations observed during simulation verification, the current buffer parameters and PI controller parameters are fine-tuned in reverse, and the closed-loop response bandwidth of the inner current loop is adjusted until all dynamic and steady-state indicators of the system meet the design requirements. This ultimately results in a control scheme that can be mapped to a bidirectional DC / DC power converter based on a Boost topology.

[0017] The beneficial effects of this invention are as follows: (1) High control precision: Through simulation mapping and anti-interference and buffer design, voltage stability and current accurate tracking are ensured, and system stability is improved.

[0018] (2) Wide adaptability: Reserved parameter fine-tuning interface, supports SOC threshold switching, and adapts to the bidirectional power flow requirements of energy storage system.

[0019] (3) Excellent design efficiency: The simulation platform simplifies the debugging process, shortens the cycle, reduces costs, and facilitates iterative upgrades.

[0020] (4) Reliable operation: By limiting and buffering design, the risk of failure is avoided, the device loss is reduced, and the service life is extended. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the topology circuit of a bidirectional DC / DC power converter based on Boost topology.

[0022] Figure 2 This is the simulation circuit diagram.

[0023] Figure 3 This is a waveform diagram of the inductor current.

[0024] Figure 4 This is a waveform diagram of the output voltage.

[0025] Figure 5 The output current waveform is shown.

[0026] Figure 6 This is a waveform diagram of the battery's SOC (State of Charge). Detailed Implementation

[0027] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0028] This invention provides a bidirectional DC / DC power converter based on Boost topology, whose system architecture consists of an execution layer (topology circuit) and a control layer (functional modules). This converter overcomes the technical limitation of traditional Boost topologies, which can only boost voltage in one direction, and achieves bidirectional energy conversion and stable control through optimized device layout.

[0029] The converter's topology is the hardware foundation for realizing bidirectional energy flow, and its structure is as follows: Figure 1 As shown.

[0030] Interface configuration: Both the bus side and the battery side are equipped with DC+ (positive) and DC- (negative) interfaces to meet the bidirectional power interaction between the energy storage system and the load.

[0031] Energy storage element: Inductor L is connected in series in the main power circuit between the DC+ on the bus side and the DC+ on the battery side. As the core energy storage element of the Boost topology, the parameters of this inductor are calculated based on the voltage transformation ratio, switching frequency, and preset current ripple rate of the converter under rated operating conditions.

[0032] Switching and freewheeling layout: The topology includes switching transistors Q1 (first switching element) and Q2 (second switching element), as well as diodes D1 (first diode) and D2 (second diode). In charging mode, forward energy transfer is achieved using Q1 and D1; in discharging mode, energy return is achieved through the on / off control of Q2 and the reverse cutoff characteristic of D2.

[0033] Filtering component: Capacitor C1 is connected in parallel to the bus side interface to perform the output filtering function. The output voltage ripple is reduced by the appropriate capacitance design to ensure the safety of electrical equipment.

[0034] The control layer precisely adjusts the operating state of the topology circuit through signal links. For example... Figure 2 As shown, the closed-loop control model built on the Matlab / Simulink platform fully embodies the modules described in the invention: Inductor current sampling module: Real-time acquisition of inductor current signal of inductor L branch, and filtering and level matching through the supporting signal conditioning submodule, providing high-precision real-time current feedback for closed-loop control and ensuring control accuracy.

[0035] PI control calculation module: It consists of a proportional-integral arithmetic unit and an output limiting submodule. It receives the deviation signal between the reference current and the sampled current, performs calculations based on the proportional coefficient and integral coefficient tuned by the Boost topology small-signal model, and limits the output duty cycle to the range of 0 to 1 through the limiting submodule to avoid controller saturation and device overstress.

[0036] The PWM drive module consists of a duty cycle modulator, a logic dead-time submodule, and a power amplifier drive circuit that work together in a serial manner according to the signal flow direction. It receives the voltage-type duty cycle control signal output by the PI control operation module, generates a complementary PWM signal with dead time, and amplifies it to drive Q1 and Q2 to achieve reliable switching and prevent the switching elements from being shot-through and short-circuited.

[0037] Mode switching control module: The Relay unit monitors the battery state of charge (SOC) signal in real time, compares it with a preset threshold, and automatically determines the charging and discharging state. It then switches the PWM trigger logic, with the charging mode driving the Q1 action and the discharging mode driving the Q2 action, thereby realizing automatic scheduling of energy flow.

[0038] Current buffer submodule: Connected in series in the Q2 and D2 circuits, it is composed of inductors. Utilizing the physical characteristic that the inductor current cannot change abruptly, and in conjunction with the smooth adjustment of the PWM duty cycle, it suppresses the surge current during the switching of charging and discharging modes, reduces transient electrical stress, and ensures the electromagnetic compatibility of the system and the lifespan of the components.

[0039] This embodiment uses Matlab / Simulink to perform full-condition performance testing on the converter. The specific steps and results are as follows: Step 1: Modeling and initialization, building a complete simulation model including Boost topology, battery load and control module ( Figure 2 ( ), matching the actual hardware parameters.

[0040] Step 2: Control tuning. A small-signal mathematical model is established based on the state-space averaging method. The transfer function from the duty cycle to the inductor current is derived. The initial parameters of the PI controller are tuned through frequency domain analysis. The optimal proportional coefficient and integral coefficient are determined through iterative optimization. The current tracking performance is verified using a Scope oscilloscope to eliminate steady-state error.

[0041] Step 3: Switch logic construction, set up logic judgment submodule and current buffer submodule, and improve the automatic charging and discharging switching logic.

[0042] Step 4: Typical waveform verification. Based on... Figure 3 The inductor current waveform shows that the current can respond quickly and accurately track the preset reference value. According to... Figure 4 Output voltage and Figure 5 The output current shows that the system fluctuates little during mode switching and the voltage remains stable within the preset range, demonstrating the high efficiency of the control strategy. Figure 6 The results demonstrated that the battery SOC changes smoothly during the charging and discharging process, verifying the reliability of the mode switching logic.

[0043] Step 5: Closed-loop optimization. For dynamic deviations or fluctuations that occur in the simulation, fine-tune the current buffer parameters and PI controller parameters in reverse to optimize the closed-loop response bandwidth of the inner current loop until the dynamic and steady-state indicators of the system meet the design requirements.

[0044] In summary, this invention successfully achieves efficient bidirectional DC power conversion through the optimization of the traditional Boost topology and the deep integration of closed-loop control algorithms. Simulation results show that the system exhibits extremely high dynamic response speed and steady-state tracking accuracy in terms of control performance. The inductor current can quickly respond to preset reference commands with minimal tracking error, ensuring precise control of power conversion. Regarding mode switching stability, through the synergistic effect of the Relay logic unit and the current buffer mechanism, the output voltage fluctuation is small and quickly recovers to steady state during the switching between charging and discharging modes, effectively eliminating the risks of current surges and voltage drops during the switching process. In terms of system reliability, the use of PWM drive and limiting protection logic effectively avoids the risk of short circuits in the switching transistors and significantly reduces output ripple, thereby extending the lifespan of the energy storage battery and power devices. This invention uses mathematical models for parameter tuning, possessing strong parameter adaptability and ease of engineering implementation. This invention provides an efficient, stable, and reliable technical solution for scenarios requiring high-frequency bidirectional energy dispatch, such as new energy vehicles, distributed energy storage, and hybrid aircraft.

Claims

1. A bidirectional DC / DC power converter based on Boost topology, characterized in that, The converter physically comprises an energy storage inductor, a first switching element, a second switching element, a first diode, and a second diode. The energy storage inductor, the first switching element, and the first diode form a Boost topology circuit, with a branch consisting of the second switching element and the second diode connected in parallel across the series branch formed by the energy storage inductor and the first diode. The first switching element is controlled to conduct in charging mode, enabling the energy stored in the energy storage inductor to be boosted and output via the first diode. The second switching element is controlled to conduct in discharging mode, forming a feedback circuit with the second diode to achieve bidirectional energy flow. The converter also includes the following functional modules operating in tandem: an inductor current sampling module, a PI control calculation module, a PWM drive module, a mode switching control module, and a current buffer submodule. The connection relationships between these modules are as follows: The output of the inductor current sampling module is connected to the input of the PI control operation module to provide feedback signals; the output of the PI control operation module is connected to the PWM drive module, and the output signal of the PWM drive module acts on the switching transistors in the topology circuit; the mode switching control module is logically connected to the PWM drive module, and realizes bidirectional energy flow by controlling the triggering sequence of different switching transistors; the current buffer submodule is physically connected in series in the second switching element and the second diode circuit to smooth out current fluctuations during switching.

2. The bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, In charging mode, the mode switching control module instructs the first switching element to act as the main control switch to perform pulse width modulation and utilize the characteristics of the energy storage inductor to achieve boost conversion; in discharging mode, the mode switching control module adjusts the drive logic and instructs the second switching element to act as the main control switch and utilizes the current buffer submodule to achieve reverse energy outflow.

3. A bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, The aforementioned inductor current sampling module consists of a current transformer and a signal conditioning submodule. The current transformer senses the magnetic field changes in the energy storage inductor of the main circuit in real time and converts them into a linear voltage signal. The signal conditioning submodule consists of a bandpass filter circuit and a level matching circuit. The bandpass filter circuit is used to remove high-frequency switching noise and low-frequency fundamental interference from the linear voltage signal, while the level matching circuit scales the signal to a voltage range that the controller can recognize, thereby providing real-time current feedback for closed-loop control.

4. A bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, The PI control calculation module consists of a proportional-integral arithmetic unit and an output limiting submodule. The proportional-integral (PI) arithmetic unit receives the deviation between the target reference current and the sampled current, performs linear calculations using preset proportional and integral coefficients, and generates a preliminary duty cycle control signal. The preset proportional and integral coefficients are tuned based on a small-signal mathematical model established using the Boost topology state-space averaging method, that is, establishing a transfer function from duty cycle to inductor current. The control law is tuned through frequency domain analysis, ensuring its compatibility with the nonlinear characteristics of the Boost topology. The limiting submodule limits the duty cycle of the operation output to a reasonable range of 0 to 1 through logical judgment. Its function is to prevent the controller from saturating due to integral accumulation and to avoid the drive signal from exceeding the physical tolerance limit of the power switch.

5. A bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, The PWM drive module consists of a duty cycle modulator, a logic dead zone submodule, and a power amplifier drive circuit. The three components work together in series according to the signal flow direction to form a complete link from the control command to the power switch drive. The duty cycle modulator, as the first stage of the link, receives the voltage-type duty cycle control signal output by the PI control operation module, compares it with the high-frequency triangular carrier wave, and generates two initial complementary PWM pulse signals corresponding to the first and second switching elements. The logic dead zone submodule, as an intermediate stage, receives the complementary PWM pulse signal output by the duty cycle modulator. Based on the switching characteristics of the two switching elements in the main circuit, it inserts a microsecond-level dead time between the two drive signals to avoid instantaneous shoot-through short circuits in the switching elements during charging / discharging mode switching or complementary conduction. As the final stage of the link, the power amplifier drive circuit receives the corrected PWM pulse signal after the dead time is added, amplifies the current of the signal to improve the driving capability of the signal, and finally generates a strong current drive signal that can drive the gate of the switching transistor, controlling the first and second switching elements to complete reliable switching operations.

6. A bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, The mode switching control module consists of a state monitoring interface, a logic judgment submodule, and a signal distribution submodule. The state monitoring interface reads the battery's state of charge in real time. The logic judgment submodule compares the battery's state of charge with a preset threshold and outputs a charging or discharging state command. The signal distribution submodule changes the path direction of the PWM pulse signal according to the output state command, driving the first switching element to operate in charging mode and the second switching element to operate in discharging mode, thereby realizing automatic scheduling of energy flow.

7. A bidirectional DC / DC power converter based on Boost topology according to claim 1, characterized in that, The current buffer submodule consists of an inductor element, and its function is to buffer the current.

8. A control method for a bidirectional DC / DC power converter based on a Boost topology as described in any one of claims 1-7, characterized in that, The steps are as follows: Step 1: For the Boost topology, based on inductor current and output capacitor voltage As state variables, a mathematical model of the system in continuous conduction mode is established; the specific modeling process is as follows: First, the conduction state of the first switching element in one switching cycle is listed. The linear state-space equations, where For the switching cycle, To determine the duty cycle, the state-space averaging method is then used to calculate the duty cycle. We apply a weighted average to the two sets of equations to obtain a nonlinear average model that includes DC quantities and AC small-signal perturbations. We then introduce a small-signal perturbation near the steady-state operating point and linearize it, ignoring second-order and higher-order terms, to derive the duty cycle perturbation. to inductor current disturbance Small signal transfer function ; Step 2: Small-signal transfer function from duty cycle to inductor current constructed in Step 1 Design a proportional-integral (PI) control law for the inner loop of the current circuit; the time-domain expression of the control law is as follows: :,in, This is the voltage-type duty cycle control signal output by the PI control arithmetic module. The proportional gain of the PI controller. The integral coefficient of the PI controller; The deviation between the reference current and the sampled current, s The domain transfer function is expressed as The initial values ​​of the control parameters are calculated using frequency domain analysis, and the open-loop transfer function of the system is constructed. ,in, Let be the system open-loop transfer function for the inner current loop. For PI controller s Domain transfer function; set the switching frequency of the converter to... To ensure the stability of the control loop, the crossover frequency of the inner current loop is set to the switching frequency. The value is 1 / 10 to 1 / 5, and the target phase margin is set to 45° to 60°. The calculation yields... and The initial value; the calculated value is introduced into the simulation model. and Initial values ​​were obtained, and parameters were optimized and adjusted through multiple iterations. The step response waveform and tracking performance of the current loop were monitored in real time using an oscilloscope to finally determine the optimal combination of PI parameters. Step 3: Constructing bidirectional switching logic and buffering mechanism; Set up logic judgment submodule and current buffering submodule in simulation model, and build automatic charging and discharging switching logic by setting the battery's state of charge (SOC) threshold; Utilize the physical characteristics of buffer inductor to smooth the sudden current change during switching, and complete the construction of complete closed-loop control logic. Step 4: Typical operating condition simulation and performance verification; Perform full-condition simulation test, and use a Scope oscilloscope to collect the waveforms of inductor current, output voltage, output current and SOC changes; Verify whether the current tracking is accurate, whether the voltage is stable within the preset range, and whether there are fluctuations exceeding the preset range during the switching process when switching charging and discharging modes. Step 5: Closed-loop optimization and control scheme finalization; For dynamic deviations or fluctuations that occur during simulation verification, the current buffer parameters and PI controller parameters are fine-tuned in reverse, and the closed-loop response bandwidth of the inner current loop is adjusted until all dynamic and steady-state indicators of the system meet the design requirements, and finally a control scheme that can be mapped to a bidirectional DC / DC power converter based on Boost topology is formed.

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