A method of driving control of a DAB converter and related apparatus

Abstract

The application discloses a driving control method of a DAB converter and related equipment, and relates to the technical field of power electronic converter control. The method comprises the following steps: through a current stress adjustment module, calculating a voltage transformation ratio based on an input voltage and an output voltage, calculating output power based on the output voltage and an output current, and substituting the voltage transformation ratio and the output power into a current stress self-adaptive minimization algorithm to solve an inner moving phase angle; at the same time, through a PI controller, adjusting an outer moving phase angle based on the difference between an instruction voltage and the output voltage; outputting the inner moving phase angle and the outer moving phase angle to a PWM modulation generator to generate a switching tube driving signal; and controlling the DAB converter through the driving signal to realize rated voltage output and current stress minimization, so as to improve the efficiency and reliability of the converter.

Description

Technical Field

[0001] This application relates to the field of power electronic converter control technology, and more specifically, to a drive control method and related equipment for a DAB converter. Background Technology

[0002] In the on-board hybrid power system of electric vehicles, the dual active full-bridge (DAB) DC / DC converter, as the core of energy conversion between supercapacitors and power batteries, faces the following technical challenges in its drive control: Under traditional single phase-shift control, the inductor current stress fluctuates significantly with voltage ratio and output power, leading to increased switching losses and shortened component lifespan; when the voltage ratio and power change dynamically over a wide range, traditional PI control strategies struggle to balance stability and response speed, especially lacking unified stress optimization logic when power flows bidirectionally; the soft-switching range of traditional phase-shift control is limited by the voltage ratio, and when the ratio deviates from 1, the phase difference of the switching transistor drive signal cannot effectively match the resonance condition, resulting in a surge in switching losses, while existing dual phase-shift control or complex model predictive control schemes suffer from high computational complexity and high hardware implementation costs. Summary of the Invention

[0003] The purpose of this application is to provide a drive control method and related equipment for a DAB converter, which has the advantages of adaptively minimizing current stress and improving converter efficiency and reliability when the voltage ratio and power dynamics change over a wide range.

[0004] This application provides a drive control method for a DAB converter, applied to a drive control device comprising a DAB converter, a PI controller, a PWM modulation generator, and a current stress adjustment module. The method includes: sampling and acquiring the input voltage, output voltage, and output current of the DAB converter; calculating the voltage ratio based on the input voltage and output voltage, and calculating the output power based on the output voltage and output current using the current stress adjustment module; substituting the voltage ratio and output power into a current stress adaptive minimization algorithm to solve for the inner phase shift angle; simultaneously, adjusting the outer phase shift angle based on the difference between the command voltage and the output voltage using the PI controller; outputting the inner and outer phase shift angles to the PWM modulation generator to generate a switching transistor drive signal; and controlling the DAB converter through the drive signal to achieve rated voltage output and current stress minimization.

[0005] Furthermore, this application also proposes that the DAB converter adopts a bidirectional DC / DC topology, including a primary-side full-bridge circuit, a secondary-side full-bridge circuit, and a high-frequency isolation transformer connecting the two. The inner phase angle controls the on-off timing of the switching transistors on the same side of the bridge arm, and the outer phase angle controls the power transmission phase difference between the primary and secondary bridge arms. The PI controller adjusts the outer phase angle through the output voltage feedback loop designed based on the DAB small-signal equivalent model.

[0006] Furthermore, this application proposes that the design steps of the PI controller include: establishing a DAB small-signal equivalent model and deriving the equivalent transfer function containing output voltage, load and capacitance parameters; using the PI controller to supplement poles and zeros, setting the zero to s=−1 / (RC2) to convert the equivalent open-loop equivalent transfer function into a type 1 function; and calculating the proportional coefficient and integral coefficient of the PI controller based on the condition that the gain is set to 1 according to the system bandwidth.

[0007] Furthermore, this application also proposes that the execution of the current stress adaptive minimization algorithm includes: defining the per-unit value of current stress based on the inductor current peak expression; deriving the mathematical relationship between the per-unit power value and the phase shift angle; first obtaining the minimum solution of the outer phase shift angle by differentiating the per-unit value of current stress; and then deriving the inner phase shift angle by simultaneously solving the power equations.

[0008] Furthermore, this application also proposes that the method of inversely calculating the inner phase shift angle by solving the simultaneous power equations includes: when the voltage ratio is ≥1: if the power per unit value ∈ [0, 1 / 2], the inner phase shift angle is calculated using the first type of square root expression; if the power per unit value ∈ (1 / 2, 2 / 3], the inner phase shift angle is calculated using the second type of square root expression; when the voltage ratio is -1, the inner phase shift angle is calculated using a linear expression.

[0009] Furthermore, this application also proposes that the condition for the system bandwidth setting gain to be 1 is that the open-loop gain amplitude of the DAB converter at the system bandwidth frequency is equal to 1.

[0010] Furthermore, this application also proposes to output the inner phase shift angle and the outer phase shift angle to a PWM modulation generator to generate a switching transistor drive signal, including: generating the phase difference of complementary drive pulses of the same side bridge arm according to the inner phase shift angle through the PWM modulation generator; and generating the phase difference of primary and secondary side bridge arm drive pulses according to the outer phase shift angle through the PWM modulation generator.

[0011] Furthermore, this application also proposes a drive control device for a DAB converter, comprising: a DAB converter, a PI controller, a PWM modulation generator, and a current stress adjustment module; wherein, the current stress adjustment module calculates the voltage ratio based on the input voltage and output voltage of the DAB converter, calculates the output power based on the output voltage and output current of the DAB converter, and substitutes the voltage ratio and output power into a current stress adaptive minimization algorithm to solve for the inner phase shift angle; simultaneously, the PI controller is used to adjust the outer phase shift angle based on the difference between the command voltage and the output voltage; the PWM modulation generator is used to generate a switching transistor drive signal according to the inner and outer phase shift angles, so as to control the DAB converter to achieve rated voltage output and current stress minimization through the switching transistor drive signal.

[0012] Furthermore, this application also proposes a computer program product, including a computer program that, when executed by a processor, implements the steps of the above-described method.

[0013] Furthermore, this application also proposes an electronic device comprising: one or more processors; and a memory associated with the one or more processors, the memory being used to store program instructions, which, when read and executed by the one or more processors, perform the steps of the method described above.

[0014] As can be seen from the above, the drive control method and related equipment for a DAB converter provided in this application achieve joint optimization control of the inner phase shift angle and the outer phase shift angle under dynamic operating conditions through the synergistic effect of the current stress adjustment module and the PI controller. It has the advantages of adaptively minimizing current stress and improving converter efficiency and reliability when the voltage ratio and power change dynamically over a wide range. Attached Figure Description

[0015] The accompanying drawings are provided to further understand the technical solutions of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the technical solutions of the present invention, and do not constitute a limitation on the technical solutions of the present invention.

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram illustrating an application scenario in which the present invention can work and operate; Figure 2 A schematic diagram illustrating the steps of the drive control method for a DAB converter provided in an embodiment of the present invention; Figure 3 A flowchart illustrating the driving control method for a DAB converter provided in an embodiment of the present invention; Figure 4 A schematic diagram of the drive control device in the drive control method for the DAB converter provided in the embodiments of the present invention; Figure 5 This is a detailed flowchart illustrating the adaptive minimization algorithm for current stress according to an embodiment of the present invention. Figure 6 The inductor current waveform using single-phase-shift control is shown in an embodiment of the present invention. Figure 7 The inductor current waveform is controlled by the current stress adaptive minimization method in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application. It should be noted that similar reference numerals and letters in the following drawings indicate similar items; therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0018] Currently, pure electric vehicles (EVs) have become a popular direction for the development of new energy vehicles due to their advantages such as zero pollution, high energy conversion efficiency, low noise, and easier intelligentization. However, the development of EVs is still constrained. The most prominent issue is the driving range. Currently, the power density of power batteries cannot compare with that of traditional internal combustion engines. Furthermore, the increasing complexity of onboard electrical equipment and the heavier load on electronic control systems necessitate larger battery capacities in the design of EV power systems to ensure sufficient power-to-weight ratio and energy density. This not only increases battery costs but also significantly increases the size of the power system, complicating vehicle layout. In addition, to leverage the advantages of the 800V high-voltage platform and enhance vehicle output power to meet the demands of acceleration, hill climbing, and other road conditions, the 800V onboard power supply system must not only support frequent and significant power output changes but also often accommodate high-power fast charging requirements. Therefore, hybrid power sources offer a new research approach as an alternative to power batteries. Due to the advantages of supercapacitors, such as high specific power, rapid charging and discharging, strong environmental adaptability, and long cycle life, they naturally become the preferred material for hybrid power sources, leading to a hybrid power source construction model that combines high-power-density supercapacitors with high-energy-density power batteries. However, the high cost and low energy density of supercapacitors prevent them from driving vehicles independently. Therefore, it is essential to rationally allocate energy between the supercapacitor and the power battery, leveraging the advantages of supercapacitors' instantaneous high-power output and flexible absorption of braking energy. Simultaneously, it is crucial to reduce the high-current surge of the power battery, delay battery performance degradation, and improve driving range.

[0019] Currently, dual-active-bridge (DAB) DC / DC converters are the ideal intermediate isolation stage DC converter choice for regulating energy distribution between supercapacitors and power batteries in the on-board hybrid power supply layout of pure electric vehicles due to their advantages such as high electrical isolation safety, support for bidirectional energy flow, ease of soft switching, high power density, and flexible bidirectional power flow switching. However, the traditional control method for DAB DC chopper circuits is generally single-phase shift control. While single-phase shift control is simple, relying on only one degree of freedom for bidirectional voltage and power adjustment, it suffers from significant backflow power, leading to a decrease in converter transmission efficiency. Furthermore, when the input and output voltages are mismatched, the converter's soft-switching operating range shrinks, transmission efficiency decreases, and current stress on the devices increases. Therefore, the single-phase shift control method is not suitable for pure electric vehicle on-board hybrid power supply applications requiring a wide output voltage range and high transmission efficiency. In addition, the DAB DC chopper circuit can also adopt the dual phase-shift control method, but the inner phase-shift angle generated by the PI current inner loop has problems such as weak performance optimization and inability to flexibly adapt to various complex operating conditions when used to control the converter inductor current.

[0020] To address the aforementioned issues, the inventors discovered a direct correlation between current stress fluctuations and voltage transformation ratio and output power, while traditional single-phase-shift control cannot dynamically adjust the phase shift angle to match changing operating conditions. By decomposing the phase shift angle into an inner phase shift angle and an outer phase shift angle, and establishing a current stress optimization mechanism and a voltage closed-loop control mechanism respectively, both current stress minimization and output voltage stability can be achieved simultaneously. Furthermore, an adaptive algorithm is used to calculate the inner phase shift angle in real time, combined with a PI controller to adjust the outer phase shift angle, enabling optimized control while reducing computational complexity.

[0021] In view of this, the purpose of this invention is to propose an adaptive current stress minimization method for dual active full-bridge DC / DC converters suitable for on-board composite power supplies in electric vehicles. This method uses an adaptive current stress minimization algorithm to calculate the inner phase shift angle of the two active full-bridge converters, replacing the traditional PI current loop's control of the inductor current. Simultaneously, a single PI voltage loop adjusts the outer phase shift angle to stabilize the converter's output voltage. Under the simultaneous control of the inner and outer phase shift angles, the inductor current acquires a new operating mode, thereby minimizing the current stress on the converter circuit components.

[0022] refer to Figure 1 , Figure 1The illustration shows an application scenario in which this embodiment can work and operate. This application scenario is an electric vehicle on-board power supply system network based on a composite power supply according to this invention. The power supply system includes a DAB converter, a PI controller, a PWM modulation generator (integrated into a related power conversion control unit), and a current stress regulation module (which can be implemented using the system control circuit). The DAB converter connects the supercapacitor and the power battery, enabling bidirectional energy flow; the motor, rectifier / inverter, etc., are the system loads. When executing the method of this application, the system sampling circuit first obtains the DAB converter's input voltage (supercapacitor side voltage), output voltage (power battery side voltage), and output current (current between the DAB and the power battery). The current stress regulation module calculates the voltage ratio and output power based on the sampled electrical signals, substitutes them into the algorithm to solve for the inner phase shift angle, and simultaneously, the PI controller adjusts the outer phase shift angle according to the difference between the command voltage and the output voltage. The PWM modulation generator receives the inner and outer phase shift angles, generates a switching transistor drive signal, and finally controls the DAB converter to achieve rated voltage output and minimize current stress, ensuring stable and efficient operation of the on-board power supply system.

[0023] refer to Figure 2 , Figure 2 This is a schematic diagram illustrating the steps of a drive control method for a DAB converter provided in an embodiment of the present invention; in some embodiments, the drive control method for a DAB converter is applied to a drive control device comprising a DAB converter, a PI controller, a PWM modulation generator, and a current stress adjustment module, and the method includes: Step 201: Sample and acquire the input voltage, output voltage, and output current of the DAB converter; Step 202: The voltage ratio is calculated based on the input voltage and output voltage by the current stress adjustment module, and the output power is calculated based on the output voltage and output current. The voltage ratio and output power are substituted into the current stress adaptive minimization algorithm to solve for the inner phase shift angle. At the same time, the outer phase shift angle is adjusted based on the difference between the command voltage and the output voltage by the PI controller. Step 203: Output the inner phase shift angle and the outer phase shift angle to the PWM modulation generator to generate the switching transistor drive signal; Step 204: Control the DAB converter with a drive signal to achieve rated voltage output and minimize current stress.

[0024] The adaptive current stress minimization algorithm refers to establishing a mathematical model based on the peak inductor current expression, and obtaining the phase shift angle solution corresponding to the minimum current stress by differentiation. Specifically, it can be implemented using a piecewise function to calculate under different voltage ratio conditions. The voltage ratio refers to the ratio of the input voltage to the output voltage, which can be calculated in real time using data collected by a voltage sensor. Output power is the product of the output voltage and the output current, which can be implemented using a current sensor and a multiplier circuit. The pulse width modulation generator is a device that generates complementary drive pulses based on the phase shift angle, which can be implemented using a digital signal processor in conjunction with logic gate circuits.

[0025] Specifically, the input and output voltages are sampled by a voltage divider circuit and then input to the voltage ratio calculation unit of the current stress regulation module. The output current is converted into a voltage signal by a Hall sensor and input together with the output voltage signal to the power calculation unit. The current stress regulation module selects the corresponding mathematical expression to solve for the inner phase shift angle based on the real-time calculated voltage ratio and output power. Simultaneously, the difference between the sampled output voltage value and the command voltage is processed by a PI controller to generate the outer phase shift angle. These two phase shift angle parameters are input to a pulse width modulation generator, which then uses a comparator to generate a drive pulse sequence with a specific phase difference to control the on / off timing of the switching transistors in the full-bridge circuit.

[0026] Through the above technical solution, this application effectively solves the problem of current stress fluctuation under wide voltage ratio conditions, reducing switching losses while maintaining stable output voltage. By separating the control logic of inner and outer phase shift angles, it retains the stability advantages of traditional PI control and achieves dynamic optimization of current stress, avoiding the hardware resource consumption caused by complex algorithms.

[0027] refer to Figure 3 , Figure 3This is a flowchart illustrating the drive control method for a DAB converter provided in an embodiment of the present invention. This application samples the input voltage, output voltage, and output current of a dual active full-bridge DC / DC converter; takes the difference between the command voltage and the output voltage as an adjustment signal, and adjusts the outer phase shift angle through a PI controller to maintain the output voltage at its rated value; simultaneously, it calculates the converter's voltage ratio and output power, and substitutes them into a current stress adaptive minimization algorithm to obtain the inner phase shift angle; then, it synchronously outputs the inner and outer phase shift angles to a PWM modulation generator to generate drive signals for each switching transistor. This invention differs from traditional single-phase and dual-phase-shift control strategies by using a current stress adaptive minimization algorithm to calculate the inner phase shift angle of both active full-bridge components, replacing the traditional PI current loop's control of the inductor current in the dual active full-bridge DC / DC converter. It also uses a single PI voltage loop to adjust the outer phase shift angle to control the stability of the converter's output voltage. Ultimately, this invention can achieve stable output of the rated voltage from the dual active full-bridge DC / DC converter while minimizing the current stress on the circuit components.

[0028] Understandably, this application can perform two steps in parallel: on the one hand, it uses the sampled electrical signal to calculate the voltage ratio and output power, substitutes them into the current stress adaptive minimization algorithm, and solves for the inner phase shift angle that minimizes the inductor current stress; on the other hand, it uses the difference between the command voltage and the output voltage as the adjustment signal, adjusts it through the PI voltage loop to obtain the outer phase shift angle, and then outputs the inner and outer phase shift angles to the PWM modulation generator to generate the switching transistor control drive signal.

[0029] refer to Figure 4 , Figure 4 This diagram illustrates the drive control device in the drive control method for the DAB converter provided in this embodiment of the invention. On the circuit side, the DAB converter consists of a primary and secondary full-bridge (H1, H2), an equivalent inductance Leq, and a high-frequency transformer (turns ratio n1:n2). U1 and U2 are the voltages on both sides, and R is the load. On the control side, the current stress adaptive minimization algorithm module acquires electrical signals such as U1 and U2 and calculates the inner phase shift control quantity D1. The PI controller adjusts the output outer phase shift control quantity D2 based on the difference between the command voltage U2ref and the output voltage U2. Both are output to the PWM modulation generator to generate g1-g8 switching transistor drive signals, which collaboratively control the on / off timing and phase difference of the primary and secondary bridge arms. This diagram fully presents the process of "sampling-inner / outer phase shift calculation-PWM drive-control converter" in claim 1, as well as the collaborative relationship between the DAB topology, PI controller, and algorithm module in claims 2 and 3, achieving the control objective of minimizing rated voltage output and current stress.

[0030] like Figure 4As shown, this application further proposes a DAB converter with a bidirectional DC / DC topology, including a primary-side full-bridge circuit, a secondary-side full-bridge circuit, and a high-frequency isolation transformer connecting the two. The inner phase angle controls the on / off timing of the switching transistors on the same side of the bridge arm, and the outer phase angle controls the power transmission phase difference between the primary and secondary bridge arms. The PI controller adjusts the outer phase angle through the output voltage feedback loop designed based on the DAB small-signal equivalent model.

[0031] The bidirectional DC / DC topology refers to a bidirectional energy transfer architecture formed by two sets of full-bridge circuits coupled through a transformer. Specifically, it can be implemented using four sets of complementary driven MOSFET bridge arms with high-frequency transformer windings. Power flow can be directed in either direction by adjusting the switching timing. The high-frequency isolation transformer is a magnetic coupling device with an operating frequency higher than 20kHz. Specifically, it can be implemented using a nanocrystalline magnetic core with Litz wire windings, used to achieve electrical isolation between the primary and secondary sides and match the input and output voltages. The inner phase shift angle refers to the phase difference between the drive signals of the upper and lower transistors on the same bridge arm. Specifically, it can be achieved by inserting a dead time when generating complementary PWM waveforms using a digital signal processor, used to control the zero-voltage switching state of the same side bridge arm. The outer phase shift angle refers to the phase difference between the drive signals of the primary and secondary bridge arms. Specifically, it can be achieved by comparing the phase offset of the PWM carrier signals of the two bridge arms, used to adjust the direction and amount of power transmission. The DAB small-signal equivalent model is a linearized mathematical model based on the state-space averaging method. Specifically, it can be achieved by deriving the equivalent transfer function between the output voltage and the phase shift angle, used to construct the basis for stability analysis of the closed-loop control system.

[0032] Specifically, the primary-side full-bridge circuit consists of an H-bridge structure formed by four power switching transistors. The upper and lower bridge arms are alternately turned on by complementary drive signals. The secondary-side full-bridge circuit adopts the same structure to form a symmetrical topology. The primary winding of the high-frequency isolation transformer is connected to the output of the primary-side full-bridge, and the secondary winding is connected to the input of the secondary-side full-bridge. Bidirectional energy flow is achieved by adjusting the phase relationship between the primary and secondary drive signals. The inner phase shift angle, by adjusting the phase difference between the drive signals of the upper and lower transistors on the same side of the bridge arm, controls the switching transistors to complete state switching under zero-voltage conditions, reducing switching losses. The outer phase shift angle, by changing the phase offset of the primary and secondary bridge arm drive signals, adjusts the power transmission direction and power level. The PI controller, based on the equivalent transfer function established by the DAB small-signal equivalent model, dynamically adjusts the outer phase shift angle in the output voltage feedback loop, ensuring stable output voltage during sudden load changes.

[0033] This application further proposes the following design steps for a PI controller: establishing a DAB small-signal equivalent model and deriving the equivalent transfer function containing output voltage, load, and capacitance parameters; supplementing poles and zeros using a PI controller, setting the zero to s=−1 / (RC2) to convert the equivalent open-loop equivalent transfer function into a type 1 function; and calculating the proportional coefficient and integral coefficient of the PI controller based on the condition that the gain is 1 according to the system bandwidth.

[0034] The DAB small-signal equivalent model refers to the dynamic mathematical model obtained after linearizing the dual active full-bridge converter. Specifically, it can be established using the state-space averaging method and is used to describe the dynamic relationship between the output voltage and the phase shift angle. The equivalent transfer function is the frequency domain mathematical expression between the output voltage and the phase shift angle, specifically including the load resistance, output capacitance, and transformer parameters, used to characterize the system's dynamic characteristics. A type-1 function refers to a system type where the equivalent open-loop equivalent transfer function has a single integrator at the origin. This is achieved by setting the zero point of the PI controller to cancel the poles formed by the output capacitor and load resistance, enabling the system to eliminate steady-state errors. A gain of 1 means that the open-loop gain amplitude of the system at the bandwidth frequency is equal to 1, specifically determined by solving the amplitude-frequency characteristic equation of the equivalent transfer function, used to ensure system stability and dynamic response speed.

[0035] Understandably, when establishing the DAB small-signal equivalent model, the switching states of the converter are first linearized to derive the equivalent transfer function between the output voltage disturbance and the phase shift angle disturbance. This equivalent transfer function includes the capacitive reactance characteristics of the output capacitor and the energy dissipation characteristics of the load resistor, accurately reflecting the dynamic characteristics of the system. Subsequently, by introducing a PI controller, an integral pole and a differential zero are added to the equivalent transfer function. The zero is positioned to coincide with the pole formed by the output capacitor and the load resistor, thereby eliminating the influence of this pole on system stability. Finally, based on the system bandwidth requirements, the gain intersection frequency is selected on the amplitude-frequency response curve of the equivalent open-loop equivalent transfer function. The numerical relationship between the proportional coefficient and the integral coefficient is determined by solving the complex domain equation, ensuring that the system has gain margin and phase margin within the target bandwidth.

[0036] This application further proposes that the condition for setting the system bandwidth gain to 1 is that the open-loop gain amplitude of the DAB converter at the system bandwidth frequency is equal to 1. The gain condition refers to setting the amplitude characteristic of the equivalent open-loop transfer function at a specific frequency point to ensure the system maintains a stable operating state during dynamic adjustment. Specifically, this can be achieved by introducing amplitude-frequency characteristic constraints during the PI controller parameter calculation process. The system bandwidth frequency refers to the upper frequency limit at which the closed-loop control system can effectively track the input signal, which can be determined by setting the crossover frequency to be in the range of 1 / 10 to 1 / 5 of the switching frequency. It can be understood that in the PI controller design process, a small-signal equivalent model including output voltage, load resistance, and output capacitance is first established, and the equivalent open-loop transfer function of the voltage loop is derived. By setting the gain condition to ensure that the open-loop gain amplitude at the system bandwidth frequency is equal to 1, this frequency point becomes the crossover point of the amplitude-frequency characteristic curve, thereby ensuring a phase margin of more than 45°. During parameter calculation, the proportional coefficient and integral coefficient of the PI controller are substituted into the equivalent transfer function amplitude equation to solve for the constraint condition that the amplitude is 1, ultimately determining the controller parameter combination.

[0037] Specifically, this application uses a DAB circuit as the topology of a bidirectional DC / DC converter for an electric vehicle's on-board composite power supply. The inner and outer phase shift angles of the DAB circuit jointly control the switching on and off of the switching transistors, and the output voltage is stabilized by adjusting the outer phase shift angle through a feedback loop. The design process of the single PI voltage loop is as follows: According to the small-signal equivalent model of the DAB circuit, the equivalent transfer function of the DAB circuit is: ; in, For the converter output voltage, For the converter output load, For the output capacitor of the converter, This represents the outward phase shift angle between the primary and secondary bridge arms. The output voltage feedback loop uses a PI controller for regulation. The equivalent transfer function of the PI controller is: ; Therefore, the PI controller can be viewed as an equivalent transfer function. Added an extreme point A zero point To replenish the zero point of the PI controller. Right now Then the equivalent open-loop equivalent transfer function Converting it to a type 1 function results in more stable performance. Then, setting the gain of the converter to 1 when operating at the system bandwidth: ; In the formula The system bandwidth for the converter to operate on.

[0038] At this point, all control parameters of the PI controller have been obtained. and .

[0039] This application further proposes that the execution of the adaptive current stress minimization algorithm includes: defining the per-unit value of current stress based on the peak inductor current expression; deriving the mathematical relationship between the per-unit power value and the phase shift angle; first, differentiating the per-unit value of current stress to obtain the minimum solution of the outer phase shift angle; and then using the power equations to deduce the inner phase shift angle.

[0040] Among them, the per-unit current stress value refers to the dimensionless parameter after normalizing the peak value of the inductor current. Specifically, it can be achieved by the ratio of the instantaneous maximum value of the inductor current to the reference current, used to eliminate the influence of voltage ratio differences on current stress assessment. The per-unit power value refers to the normalized ratio of the output power to the reference power, specifically the ratio of the output power to the rated power, used to establish the quantitative relationship between power transmission and phase shift angle. The external phase shift angle minimum solution refers to the phase shift angle parameter obtained by mathematical differentiation that makes the per-unit current stress value reach a local minimum. Specifically, it can be achieved by performing a first derivative operation on the expression for the per-unit current stress value and setting it equal to zero, used to determine the critical point for current stress optimization. The simultaneous power equation back-derived internal phase shift angle refers to constructing a system of equations by combining the mathematical relationship between the per-unit power value and the phase shift angle with the minimum solution. Specifically, it can be achieved by solving algebraic equations or numerical iteration methods, used to determine the optimal internal phase shift angle under the premise of meeting power transmission requirements.

[0041] Specifically, during the operation of an electric vehicle hybrid power system, when the DAB converter faces a wide range of voltage ratios and dynamic power changes, the peak inductor current expression is first calculated based on the real-time acquired input and output voltages. Normalization is then used to eliminate the impact of voltage fluctuations on current stress. Subsequently, a mathematical model relating the per-unit power value to the phase shift angle is established, and the critical point of the outer phase shift angle that minimizes current stress is determined through differentiation. Finally, the power equation and the minimum solution are combined, and algebraic operations are used to derive the optimal inner phase shift angle solution that meets the current power transmission requirements. For example, in scenarios where the voltage ratio is greater than or equal to 1, the corresponding square root expression is selected for solving based on the range of the per-unit power value; when the voltage ratio is less than 1, a linear expression is used for rapid calculation.

[0042] This application further proposes a method for calculating the inner phase shift angle by combining the power equations, including: when the voltage ratio is ≥1: if the power per unit value ∈ [0, 1 / 2], the inner phase shift angle is calculated using the first type of square root expression; if the power per unit value ∈ (1 / 2, 2 / 3], the inner phase shift angle is calculated using the second type of square root expression; when the voltage ratio is -1, the inner phase shift angle is calculated using a linear expression.

[0043] The voltage transformation ratio refers to the ratio of the input voltage to the output voltage. It is specifically calculated in real-time by a digital processor after data is collected by a voltage sensor, and is used to characterize the voltage matching status of the DAB converter during operation. The per-unit power value is the normalized ratio of the actual output power to the reference power. It can be calibrated using the product of the output current and the rated current as the reference power, and is used to quantify the power transmission level. The first type of square root expression is an analytical expression for the phase shift angle based on the quadratic function root-finding formula, specifically expressed as d1=√(2P_n), suitable for approximate calculations in the low-power range. The second type of square root expression is an optimized analytical expression with a correction term, specifically expressed as d2=√(4P_n-1), used for accurate solutions in the medium-to-high power range. The linear expression is a simplified calculation model based on Taylor expansion, specifically expressed as d3=2P_n / (1+m), where m is the voltage transformation ratio, suitable for rapid calculations in buck operation.

[0044] Specifically, under boost operation with a voltage ratio greater than or equal to 1, the per-unit power value is divided into two ranges. When the detected per-unit power value is in the range of 0 to 0.5, the first type of square root expression is used to directly calculate the inner phase shift angle, which simplifies the calculation process by ignoring higher-order terms. When the per-unit power value is in the range of 0.5 to 0.67, the calculation is switched to the second type of square root expression for compensation, which improves the calculation accuracy by introducing a quadratic correction term. Under buck operation with a voltage ratio less than 1, a linear expression is used instead of the square root calculation, reducing the computational complexity through linearization. The above segmented calculation strategy is implemented through the logic judgment module of the digital signal processor, which automatically selects the corresponding algorithm based on the real-time acquired voltage and power data.

[0045] refer to Figure 5 , Figure 5 This is a detailed flowchart illustrating the adaptive current stress minimization algorithm according to an embodiment of the present invention. Specifically, in this embodiment, the process of calculating the inner phase shift angle to minimize current stress involves: sampling the input voltage, output voltage, and output current of the converter; and calculating the voltage turns ratio of the converter. and per-unit transmission power ;judge Is it greater than or equal to 1? Then check. The range is or Finally, based on The specific range of values ​​is determined to establish the specific value of the inner phase shift angle, thereby enabling bidirectional energy flow. The specific execution process of the current stress adaptive minimization algorithm can be as follows: While ensuring stable output voltage, the inductor current stress of the converter is minimized, and the derivation process for minimizing the inductor current stress is as follows: Based on the DAB circuit current stress model, and taking the expression for the moment of maximum inductor current as the reference value, the per-unit value of the current stress is: ; In equation (1), the voltage transformation ratio , The ratio of the number of turns on the primary and secondary sides of the transformer. The phase shift angle between the two arms of the bridge on the same side is the inward phase angle. It is the outward phase angle between the same side arms of the two bridges.

[0046] Based on the rated output power, the per-unit value of the converter output power is: ; From equation (2), we can derive that Depend on The expression represented is: ; Substituting equation (3) into equation (1), we get: ; To obtain the outer phase shift angle with minimum current stress Solve equation (4) The minimum value, i.e. right The derivative is zero, so we can solve for... The expression is: ; Combining equations (3) and (5), the combination of the minimum current stress and the inward and outward shifts is shown in Table (1) below: Table (1)

[0047] Based on the above process, the converter in this application can support bidirectional power flow, and due to the symmetry of the converter topology, the proposed methods are all applicable to bidirectional power flow operating scenarios.

[0048] This application further proposes generating the phase difference of complementary drive pulses for the same-side bridge arms using a PWM modulation generator based on the inner phase shift angle, and generating the phase difference of drive pulses for the primary and secondary-side bridge arms using a PWM modulation generator based on the outer phase shift angle. The phase difference of the complementary drive pulses for the same-side bridge arms refers to the time difference between the drive signals of the upper and lower bridge arm switches in the same full-bridge circuit. Specifically, this can be achieved by using a digital signal processor to perform time conversion on the phase shift angle and generate complementary PWM waveforms. This phase difference is used to control the alternating conduction timing of the switches on the same-side bridge arms to avoid shoot-through and short circuits. The phase difference of the drive pulses for the primary and secondary-side bridge arms refers to the timing offset of the drive signals between the primary and secondary full-bridge circuits. Specifically, this can be achieved by using a programmable logic device to compensate for the phase shift angle and generate synchronous PWM signals. This phase difference is used to adjust the power transmission direction and energy flow rate.

[0049] Specifically, in a hybrid power system for electric vehicles, when the supercapacitor interacts with the power battery, the PWM modulator first receives the inner phase shift angle calculated by the current stress regulation module. This inner phase shift angle is converted into the phase difference of the complementary drive pulses of the same-side bridge arm. For example, the angle value is mapped to the time interval between the rising and falling edges of the PWM waveform, so that the two complementary switches in the same-side full-bridge circuit form an alternating conduction timing relationship. At the same time, the outer phase shift angle output by the PI controller is converted into the phase difference between the primary-side and secondary-side full-bridge drive pulses. For example, by adjusting the start time offset of the primary-side bridge arm PWM signal relative to the secondary-side bridge arm signal, the phase matching of power transmission is controlled. The two phase difference parameters are integrated into the drive signal generation logic to form four PWM waveforms with precise timing relationships, ultimately controlling the DAB converter to achieve zero-voltage switching.

[0050] In some embodiments, before applying the method of this embodiment, simulation analysis can be performed using Matlab. In this simulation model, the converter input voltage is 400V, the output voltage is 1200V, the transformer turns ratio is 1:2, and the voltage transformation ratio is... The maximum output power is 40kW, the rated output power is 30kW, and the per-unit output power is... .like Figure 6 As shown, when using the traditional single-phase-shift control method, the peak inductor current, i.e., the current stress on the converter circuit components, is approximately 186A; while... Figure 7 As shown, when using the adaptive current stress minimization method, the peak inductor current is around 160A, and the current stress decreases significantly.

[0051] This application further proposes a drive control device for a dual active full-bridge converter, including a dual active full-bridge converter, a proportional-integral controller, a pulse width modulation generator, and a current stress regulation module. The current stress regulation module calculates the voltage ratio based on the input and output voltages of the dual active full-bridge converter, calculates the output power based on the output voltage and output current of the dual active full-bridge converter, and substitutes the voltage ratio and output power into an adaptive current stress minimization algorithm to solve for the inner phase shift angle. Simultaneously, the proportional-integral controller is used to adjust the outer phase shift angle based on the difference between the command voltage and the output voltage. The pulse width modulation generator is used to generate switching transistor drive signals based on the inner and outer phase shift angles, so as to control the dual active full-bridge converter to achieve rated voltage output and minimize current stress through the switching transistor drive signals.

[0052] The current stress regulation module refers to a hardware circuit or embedded algorithm module that dynamically calculates input and output voltage parameters in real time. Specifically, it can be implemented using a digital signal processor in conjunction with voltage and current sensors. Its function is to automatically optimize the phase shift angle based on real-time operating conditions to reduce the peak inductor current. The proportional-integral controller (PIC) is a closed-loop control unit based on error integral compensation. Specifically, it can be implemented using an operational amplifier circuit or a microcontroller. Its function is to maintain stable output voltage and compensate for phase deviations caused by load fluctuations. The pulse width modulation (PWM) generator is a hardware logic circuit that generates complementary drive pulse sequences. Specifically, it can be implemented using a field-programmable gate array (FPGA) or a dedicated driver chip. Its function is to convert phase shift angle parameters into precise switching timing signals to control the power transmission of the full-bridge circuit.

[0053] Specifically, the current stress regulation module obtains the current operating parameters through the voltage ratio calculation unit and the power calculation unit, respectively, and inputs these parameters into the built-in current stress optimization algorithm module to solve for the optimal inner phase shift angle. The proportional-integral controller continuously compares the deviation between the output voltage and the target value, and dynamically adjusts the outer phase shift angle through proportional-integral operations to eliminate steady-state errors. After receiving the inner and outer phase shift angle parameters, the pulse width modulation generator generates a drive pulse sequence with a specific phase difference using a carrier comparison method. The inner phase shift angle controls the conduction overlap time of the upper and lower switches on the same side of the bridge arm, while the outer phase shift angle controls the power transmission phase difference between the primary and secondary bridge arms. This drive pulse sequence is applied to the power switches of the dual active full-bridge converter through an isolated drive circuit, ensuring that the inductor current stress is kept at a minimum while achieving precise output voltage control.

[0054] This application further proposes a computer program product, including a computer program that, when executed by a processor, performs the following steps: sampling and acquiring the input voltage, output voltage, and output current of a dual active full-bridge converter; calculating the voltage ratio and output power through a current stress adjustment module, and substituting them into an adaptive current stress minimization algorithm to solve for the inner phase shift angle; adjusting the outer phase shift angle through a PI controller; and outputting the inner and outer phase shift angles to a pulse width modulation generator to generate a switching transistor drive signal, thereby controlling the converter to achieve rated voltage output and current stress minimization.

[0055] Among these, computer program products refer to storage media containing executable code, specifically solid-state drives (SSDs) or flash memory chips, used to store program instructions corresponding to control algorithms. Processor execution refers to running the program code through a central processing unit (CPU) or embedded controller, specifically using a multi-core processor or digital signal processor (DSP), used to parse instructions and perform voltage sampling, phase shift angle calculation, and signal generation operations. The current stress adaptive minimization algorithm is a mathematical optimization method based on the relationship between the peak per-unit value of inductor current and power. Specifically, it can be implemented by solving derivative extrema and simultaneous equations, used to dynamically adjust the inner phase shift angle to reduce switching device losses.

[0056] Specifically, when the computer program is loaded into the vehicle power management system, it first periodically collects the input and output voltage and current parameters of the converter. The voltage ratio calculation module uses the ratio of the input and output voltages as optimization parameters, and the output power calculation module generates a real-time power value based on the product of the output voltage and current. These two parameters are input to the built-in optimization algorithm module, which selects the corresponding square root or linear expression to calculate the inner phase shift angle based on a preset voltage ratio threshold. Simultaneously, the voltage closed-loop control module inputs the difference between the output voltage and the target value into the PI controller, which maintains system stability by adjusting the outer phase shift angle. The final generated phase shift angle parameter is converted into a complementary pulse signal to precisely control the conduction timing of the switching transistors in the full-bridge circuit.

[0057] In some specific implementations, the computer program can be packaged as a dynamic link library and integrated into the vehicle control unit, and executed through a real-time operating system. The derivative calculation process of the current stress optimization algorithm can be implemented using a lookup table method, with the extreme point calculation results under different voltage ratios pre-stored in non-volatile memory. The generation of the pulse width modulation signal can be achieved by configuring a timer capture and comparison unit, utilizing a hardware acceleration module to reduce the processor load.

[0058] This application further proposes an electronic device including one or more processors and a memory associated with the one or more processors, the memory being used to store program instructions, which, when read and executed by the one or more processors, perform the steps of a drive control method for a dual active full-bridge converter.

[0059] The processor refers to the hardware unit that executes computation and control logic. Specifically, it can be implemented using a multi-core central processing unit (CPU) or a digital signal processor (DSP). It is used to process sampled data of input voltage, output voltage, and output current in real time, and to execute current stress adaptive minimization algorithms and proportional-integral (PI) control algorithms. The memory refers to the physical medium that stores executable code and runtime data. Specifically, it can be implemented using flash memory or dynamic random access memory (DRAM). It is used to store program instructions and algorithm parameters, ensuring the continuous execution of the control logic.

[0060] Specifically, the electronic device uses a processor to collect the input voltage, output voltage, and output current of the dual active full-bridge converter in real time. Based on the voltage ratio and output power, it calculates the inner phase shift angle and adjusts the outer phase shift angle through a proportional-integral controller. Finally, the two phase shift angles are input to a pulse-width modulation generator to generate drive signals for the switching transistors. During this process, the algorithm parameters and program instructions stored in the memory are called by the processor to ensure the synchronous execution of current stress optimization and voltage control, thereby maintaining the stable operation of the dual active full-bridge converter under wide voltage ratio and dynamic power variation scenarios.

[0061] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A drive control method for a DAB converter, characterized in that, The method, applied to a drive control device comprising a DAB converter, a PI controller, a PWM modulation generator, and a current stress regulation module, includes: The input voltage, output voltage, and output current of the DAB converter are sampled and acquired. The voltage ratio is calculated based on the input voltage and the output voltage by the current stress adjustment module, and the output power is calculated based on the output voltage and the output current. The voltage ratio and the output power are then substituted into the current stress adaptive minimization algorithm to solve for the inner phase shift angle. At the same time, the outer phase shift angle is adjusted based on the difference between the command voltage and the output voltage by the PI controller. The inner phase shift angle and the outer phase shift angle are output to the PWM modulation generator to generate the switching transistor drive signal; The DAB converter is controlled by the drive signal to achieve rated voltage output and minimize current stress. The execution of the adaptive current stress minimization algorithm includes: The per-unit value of current stress is defined based on the expression for the peak value of inductor current; Derive the mathematical relationship between per-unit power and phase shift angle; First, differentiate the per-unit value of the current stress to obtain the solution for the minimum value of the outward phase angle; By simultaneously solving the power equations, the internal phase shift angle can be derived. Specifically, the per-unit value of current stress is obtained by using the ratio of the instantaneous maximum value of inductor current to the reference current, and the per-unit value of power is obtained by using the ratio of output power to rated power. The solution for the minimum external phase shift angle is the phase shift angle parameter that makes the per-unit value of current stress reach a local minimum, obtained by mathematical differentiation. The solution for the minimum external phase shift angle is obtained by performing a first derivative operation on the expression for the per-unit value of current stress and setting it equal to zero. The method of inversely deriving the internal phase shift angle by solving the simultaneous power equations combines the mathematical relationship between the per-unit power value and the phase shift angle with the minimum solution to construct a system of equations. The optimal internal phase shift angle is obtained by solving algebraic equations or numerical iteration methods. The DAB converter adopts a bidirectional DC / DC topology, including a primary full-bridge circuit, a secondary full-bridge circuit, and a high-frequency isolation transformer connecting the two. The inner phase angle controls the on / off timing of the switching transistors on the same side of the bridge arm, and the outer phase angle controls the power transmission phase difference between the primary and secondary bridge arms. The PI controller adjusts the outer phase angle through the output voltage feedback loop designed based on the DAB small-signal equivalent model.

2. The method according to claim 1, characterized in that, The design steps for the PI controller include: Establish a DAB small-signal equivalent model and derive the equivalent transfer function including output voltage, load and capacitance parameters; By using a PI controller to supplement poles and zeros, and setting the zero to s=−1 / (RC2), the equivalent open-loop equivalent transfer function is converted into a type 1 function; Calculate the proportional and integral coefficients of the PI controller based on the condition that the gain is set to 1 according to the system bandwidth.

3. The method of claim 1, wherein, The method of back-deriving the inner phase shift angle from the simultaneous power equations includes: When the voltage ratio is ≥1: if the per-unit power value ∈ [0, 1 / 2], the first type of square root expression is used to calculate the inner phase shift angle; if the per-unit power value ∈ (1 / 2, 2 / 3], the second type of square root expression is used to calculate the inner phase shift angle. When the voltage ratio is less than 1, the inner phase shift angle is calculated using a linear expression; Among them, the first type of square root expression is the phase shift angle analytical expression d1= based on the quadratic function root-finding formula. P_n is the per-unit power value, and the second type of square root expression is the optimized analytical expression d2= with the introduction of a correction term. The linear expression is a simplified calculation model based on Taylor expansion: d3=2P_n / (1+m), where m is the voltage transformation ratio.

4. The method according to claim 2, characterized in that, The condition for setting the system bandwidth gain to 1 is that the open-loop gain amplitude of the DAB converter at the system bandwidth frequency is equal to 1.

5. The method according to claim 1, characterized in that, The step of outputting the inner phase shift angle and the outer phase shift angle to the PWM modulation generator to generate the switching transistor drive signal includes: The phase difference of complementary drive pulses on the same side bridge arm is generated by the PWM modulation generator based on the inner phase shift angle; The phase difference of the primary and secondary bridge arm drive pulses is generated by the PWM modulation generator based on the external phase shift angle.

6. A drive control device for a DAB converter, characterized in that, include: The system comprises a DAB converter, a PI controller, a PWM modulation generator, and a current stress regulation module; among which... The current stress regulation module calculates the voltage ratio based on the input and output voltages of the DAB converter, calculates the output power based on the output voltage and output current of the DAB converter, and substitutes the voltage ratio and the output power into the current stress adaptive minimization algorithm to solve for the inner phase shift angle; at the same time, the PI controller is used to adjust the outer phase shift angle based on the difference between the command voltage and the output voltage. The PWM modulation generator is used to generate a switching transistor drive signal based on the inner phase shift angle and the outer phase shift angle, so as to control the DAB converter to achieve rated voltage output and minimize current stress through the switching transistor drive signal; The execution of the adaptive current stress minimization algorithm includes: The per-unit value of current stress is defined based on the expression for the peak value of inductor current; Derive the mathematical relationship between per-unit power and phase shift angle; First, differentiate the per-unit value of the current stress to obtain the solution for the minimum value of the outward phase shift angle; By simultaneously solving the power equations, the internal phase shift angle can be deduced. Specifically, the per-unit value of current stress is obtained by using the ratio of the instantaneous maximum value of inductor current to the reference current, and the per-unit value of power is obtained by using the ratio of output power to rated power. The solution for the minimum external phase shift angle is the phase shift angle parameter that makes the per-unit value of current stress reach a local minimum, obtained by mathematical differentiation. The solution for the minimum external phase shift angle is obtained by performing a first derivative operation on the expression for the per-unit value of current stress and setting it equal to zero. The method of inversely deriving the internal phase shift angle by solving the simultaneous power equations combines the mathematical relationship between the per-unit power value and the phase shift angle with the minimum solution to construct a system of equations. The optimal internal phase shift angle is obtained by solving algebraic equations or numerical iteration methods. The DAB converter adopts a bidirectional DC / DC topology, including a primary full-bridge circuit, a secondary full-bridge circuit, and a high-frequency isolation transformer connecting the two. The inner phase angle controls the on / off timing of the switching transistors on the same side of the bridge arm, and the outer phase angle controls the power transmission phase difference between the primary and secondary bridge arms. The PI controller adjusts the outer phase angle through the output voltage feedback loop designed based on the DAB small-signal equivalent model.

7. A computer program product, comprising a computer program, characterized in that, When executed by a processor, the computer program implements the steps of the method according to any one of claims 1 to 5.

8. An electronic device, comprising: include: One or more processors; as well as A memory associated with the one or more processors, the memory being used to store program instructions that, when read and executed by the one or more processors, perform the steps of the method according to any one of claims 1 to 5.

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