Driving control method of DAB converter and related equipment

Abstract

The invention discloses a driving control method of a DAB converter and related equipment, and relates to the technical field of power electronic converter control, and the method comprises the steps: calculating a voltage transformation ratio based on an input voltage and an output voltage through a current stress adjustment module, and calculating an output power based on the output voltage and an output current, substituting the voltage transformation ratio and the output power into a current stress adaptive minimization algorithm to solve an internal phase shift angle; meanwhile, through a PI controller, an external shift phase angle is adjusted based on a difference value between the instruction voltage and the output voltage; outputting the inner phase shift angle and the outer phase shift angle to a PWM modulation generator to generate a switching tube driving signal; the DAB converter is controlled by the driving signal to realize rated voltage output and current stress minimization, so that the efficiency and reliability of the converter are improved.

Description

Technical Field

[0001] The present application relates to the technical field of power electronic converter control, and in particular to a drive control method for a DAB converter and related equipment. Background Art

[0002] In the hybrid power system onboard electric vehicles, the dual-active full-bridge (DAB) DC / DC converter serves as the energy conversion core between supercapacitors and power batteries. Its drive control faces the following technical challenges: Under traditional single-phase-shift control, the inductor current stress fluctuates significantly with the voltage ratio and output power, resulting in increased switching losses and shortened component life. When the voltage ratio and power change dynamically over a wide range, the traditional PI control strategy has difficulty balancing stability and response speed, especially when the power flows in both directions. There is a lack of unified stress optimization logic. The soft switching range of traditional phase-shift control is limited by the voltage ratio. When the ratio deviates from 1, the phase difference of the switch tube drive signal cannot effectively match the resonant condition, resulting in a surge in switching losses. Existing dual-phase-shift control or complex model predictive control schemes have the disadvantages of large algorithm computational complexity and high hardware implementation cost. 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 minimizing current stress adaptively and improving converter efficiency and reliability when the voltage ratio and power change dynamically over a wide range.

[0004] The present application provides a drive control method for a DAB converter, which is applied to a drive control device including a DAB converter, a PI controller, a PWM modulation generator, and a current stress adjustment module. The method includes: sampling and obtaining the input voltage, output voltage, and output current of the DAB converter; calculating the voltage transformation ratio based on the input voltage and output voltage, and calculating the output power based on the output voltage and output current through the current stress adjustment module; substituting the voltage transformation ratio and output power into a current stress adaptive minimization algorithm to solve the inner phase shift angle; at the same time, adjusting the outer phase shift angle based on the difference between the command voltage and the output voltage through the PI controller; outputting the inner phase shift angle and the outer phase shift angle to the PWM modulation generator to generate a switch tube drive signal; and controlling the DAB converter through the drive signal to achieve rated voltage output and current stress minimization.

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

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

[0007] Furthermore, the present application also proposes that the execution of the current stress adaptive minimization algorithm includes: defining the current stress per-unit value based on the inductor current peak expression; deriving the mathematical relationship between the power per-unit value and the phase shift angle; first differentiating the current stress per-unit value to obtain the minimum solution of the external phase shift angle; and inversely deriving the internal phase shift angle by combining the power equations.

[0008] Furthermore, the present application also proposes that the reverse calculation of the internal phase shift angle by the simultaneous power equations includes: when the voltage transformation ratio is ≥1: if the power per unit value ∈ [0, 1 / 2], the first kind of square root expression is used to calculate the internal phase shift angle; if the power per unit value ∈ (1 / 2, 2 / 3], the second kind of square root expression is used to calculate the internal phase shift angle; when the voltage transformation ratio is _1, the linear expression is used to calculate the internal phase shift angle.

[0009] Furthermore, the present application also 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.

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

[0011] Furthermore, the present 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 regulation module; wherein the current stress regulation module calculates a voltage transformation 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 transformation ratio and output power into a current stress adaptive minimization algorithm to solve an inner phase shift angle; at the same time, the PI controller is used to adjust an 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 switch tube drive signal according to the inner phase shift angle and the outer phase shift angle, so as to control the DAB converter through the switch tube drive signal to achieve rated voltage output and current stress minimization.

[0012] Furthermore, the present application also proposes a computer program product, comprising a computer program, which implements the steps of the above method when executed by a processor.

[0013] Furthermore, the present 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, execute the steps of the above method.

[0014] From the above, it can be seen that the driving control method and related equipment of a DAB converter provided in this application realize the joint optimization control of the inner phase shift angle and the outer phase shift angle under dynamic working conditions through the synergistic effect of the current stress regulation module and the PI controller, and have the advantages of adaptively minimizing the current stress in a wide range of voltage ratios and dynamic power changes, and improving the efficiency and reliability of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation to the technical solution of the present invention.

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

[0017] The technical solutions of this application will be described clearly and completely below, in conjunction with the accompanying drawings. It should be understood that the described embodiments represent only some, and not all, embodiments of this application. The components of this application, generally described and illustrated in the drawings herein, may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of this application provided in the drawings is not intended to limit the scope of the claimed application, but rather merely represents selected embodiments of this application. All other embodiments derived 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 represent similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings. Furthermore, in the description of this application, the terms "first," "second," etc., are used solely to distinguish descriptions and are not to be construed as indicating or implying relative importance.

[0018] Currently, pure electric vehicles (BEVs) are a popular development direction for new energy vehicles, offering advantages such as zero pollution, high energy conversion efficiency, low noise, and easier implementation of intelligent systems. However, the development of BEVs remains constrained. The primary issue is range. Currently, the power density of power batteries cannot match that of traditional fuel-powered engines. Furthermore, the increasing number of onboard electrical devices and the increasing electronic control loads place a greater strain on the vehicle. Therefore, the design of BEV power systems often requires larger battery capacities to achieve both sufficient specific power and specific energy. This not only increases battery costs but also significantly increases the size of the power system, complicating overall vehicle layout. Furthermore, to leverage the advantages of the 800V high-voltage platform and enhance vehicle output power to meet the demands of road conditions such as acceleration and hill climbing, the 800V onboard power supply system must not only support frequent and significant power output fluctuations but also often require high-power fast charging. To this end, composite power sources, as an alternative to power batteries, provide new research ideas. Supercapacitors, with their advantages of high specific power, rapid charge and discharge, strong environmental adaptability, and long cycle life, naturally become the preferred material for composite power sources, forming a composite power source construction model that combines high-power-density supercapacitors with high-energy-density power batteries. However, supercapacitors are relatively expensive, and their low energy density makes them unable to drive vehicles alone. Therefore, it is necessary to rationally distribute energy between supercapacitors and power batteries to leverage their advantages of instantaneous high power output and flexible absorption of braking energy. At the same time, this reduces the impact of high current on the power battery, delays battery performance degradation, and improves endurance.

[0019] Currently, dual-active-bridge (DAB) DC / DC converters are an ideal intermediate isolation-stage DC converter for regulating energy distribution between supercapacitors and power batteries in hybrid power systems for pure electric vehicles (BEVs). These converters offer advantages such as high electrical isolation, bidirectional energy flow, easy soft switching, high power density, and flexible bidirectional power flow switching. However, the traditional control method for DAB DC chopper circuits is typically single-phase-shift control. This method is characterized by its simplicity and relies on only one degree of freedom for bidirectional voltage and power regulation. However, single-phase control introduces significant backflow, which reduces converter transmission efficiency. Furthermore, when the input and output voltages do not match, the converter's soft-switching operating range decreases, reducing transmission efficiency and increasing device current stress. Therefore, single-phase-shift control is not suitable for BEV hybrid power systems requiring a wide output voltage range and high transmission efficiency. In addition, the DAB DC chopper circuit can also adopt a dual-phase shift control method. However, the inner phase shift angle generated by the PI current inner loop is not targeted enough when used to control the converter inductor current, and it cannot flexibly adapt to multiple complex working conditions and application scenarios.

[0020] To address this issue, the inventors discovered that current stress fluctuations are directly correlated with the voltage transformation ratio and output power, while traditional single-phase-shift control cannot dynamically adjust the phase-shift angle to match operating conditions. By decomposing the phase-shift angle into an inner phase-shift angle and an outer phase-shift angle, a current stress optimization mechanism and a voltage closed-loop control mechanism were established, respectively, to simultaneously minimize current stress and stabilize output voltage. Furthermore, an adaptive algorithm was used to calculate the inner phase-shift angle in real time, combined with a PI controller to adjust the outer phase-shift angle, achieving optimized control while reducing computational complexity.

[0021] In view of this, the purpose of the present invention is to propose a method for adaptively minimizing current stress in a dual-active full-bridge DC / DC converter suitable for an on-board hybrid power supply of an electric vehicle. The method uses a current stress adaptive minimization algorithm to calculate the inner phase shift angle of the active full-bridges on both sides to replace the traditional PI current loop's control of the inductor current of the dual-active full-bridge DC / DC converter. At the same time, a single PI voltage loop is used to adjust the outer phase shift angle to control the stability of 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 of the converter's circuit components.

[0022] refer to Figure 1 , Figure 1The figure shows an application scenario in which this embodiment can operate and be operated. This application scenario is an electric vehicle on-board power supply system network based on a composite power supply according to an embodiment of the present invention. The power supply system includes a DAB converter, a PI controller, a PWM modulation generator (integrated in the relevant power conversion control unit), and a current stress regulation module (which can be implemented based on the system control circuit). The DAB converter connects the supercapacitor and the power battery to achieve bidirectional energy flow; the motor, rectifier / inverter, etc. serve as the system load. When executing the method of this application, the system sampling circuit first obtains the DAB converter 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 the inner phase shift angle, and simultaneously the PI controller adjusts the outer phase shift angle based on the difference between the command voltage and the output voltage. The PWM modulation generator receives the inner and outer phase shift angles, generates the switch tube drive signal, and ultimately controls the DAB converter to achieve the rated voltage output and minimize the current stress, ensuring stable and efficient operation of the on-board power supply system.

[0023] refer to Figure 2 , Figure 2 A schematic diagram of 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 including a DAB converter, a PI controller, a PWM modulation generator, and a current stress adjustment module, and the method includes: Step 201: sampling and obtaining the input voltage, output voltage, and output current of the DAB converter; Step 202: Calculate the voltage transformation ratio based on the input voltage and the output voltage, calculate the output power based on the output voltage and the output current, and substitute the voltage transformation ratio and the output power into the current stress adaptive minimization algorithm to solve the inner phase shift angle. Simultaneously, adjust the outer phase shift angle 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 a PWM modulation generator to generate a switch tube drive signal; Step 204 : Control the DAB converter through the driving signal to achieve rated voltage output and minimize current stress.

[0024] The adaptive current stress minimization algorithm establishes a mathematical model based on the inductor current peak expression and obtains the phase-shift angle solution corresponding to the current stress minimum through differentiation. Specifically, a piecewise function can be used to implement calculations under different voltage ratio conditions. The voltage ratio refers to the ratio of input voltage to output voltage, which can be calculated in real time by collecting data from a voltage sensor. Output power refers to the product of output voltage and output current, which can be achieved through a current sensor and a multiplier circuit. A 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 through a voltage divider circuit and then fed into the voltage ratio calculation unit of the current stress regulation module. The output current is converted into a voltage signal by a Hall effect sensor and then fed together with the output voltage signal into the power calculation unit. Based on the real-time calculated voltage ratio and output power, the current stress regulation module selects a corresponding mathematical expression to solve for the inner phase shift angle. Simultaneously, the difference between the sampled output voltage and the command voltage is processed by a PI controller to generate the outer phase shift angle. These two phase shift angle parameters are fed into a pulse width modulation generator, where a comparator generates a drive pulse sequence with a specific phase difference to control the on-off timing of the switches in the full-bridge circuit.

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

[0027] refer to Figure 3 , Figure 3A flow chart of a drive control method for a DAB converter provided by an embodiment of the present invention. This application can sample the input voltage, output voltage, and output current of a dual-active full-bridge DC / DC converter; take the difference between the command voltage and the output voltage as a control signal, and adjust the external phase shift angle through a PI controller to maintain the rated output voltage; simultaneously, calculate the converter's voltage transformation ratio and output power, and substitute them into a current stress adaptive minimization algorithm to obtain the internal phase shift angle; then, synchronously output the internal and external phase shift angles to a PWM modulation generator to generate drive signals for each switch. This invention differs from traditional single-phase and dual-phase shift control strategies. It uses a current stress adaptive minimization algorithm to calculate the internal phase shift angle of the active full bridges on both sides, replacing the traditional PI current loop's control of the dual-active full-bridge DC / DC converter's inductor current. It then uses a single PI voltage loop to adjust the external phase shift angle to control the converter's output voltage stability. Ultimately, the present invention can achieve a stable rated output voltage for the dual-active full-bridge DC / DC converter while minimizing current stress on circuit components.

[0028] It can be understood that the present application can execute two steps in parallel: on the one hand, the voltage transformation ratio and output power are calculated using the sampled electrical signal, and the current stress adaptive minimization algorithm is substituted to solve the inner phase shift angle that minimizes the inductor current stress; on the other hand, the difference between the command voltage and the output voltage is used as the adjustment signal, and the outer phase shift angle is obtained through PI voltage loop adjustment, and then the inner and outer phase shift angles are output to the PWM modulation generator to generate the switch tube control drive signal.

[0029] refer to Figure 4 , Figure 4 A schematic diagram of the drive control device in the DAB converter drive control method provided by an embodiment of the present invention. On the circuit side, the DAB converter consists of a primary and secondary full-bridge (H1, H2), an equivalent inductor Leq, and a high-frequency transformer (transformation ratio n1:n2). U1 and U2 represent the voltages on both sides, and R represents the load. On the control side, the current stress adaptive minimization algorithm module collects electrical signals from U1 and U2 and calculates the inner phase angle control variable D1. A PI controller adjusts the output outer phase angle control variable D2 based on the difference between the command voltage U2ref and the output voltage U2. Both signals are output to a PWM modulation generator, generating drive signals for the g1-g8 switches, which coordinately control the on-off timing and phase difference of the primary and secondary bridge arms. This diagram fully illustrates the "sampling - inner / outer phase angle calculation - PWM drive - converter control" process described in claim 1, as well as the collaborative relationship between the DAB topology, PI controller, and algorithm module described in claims 2 and 3, to achieve the control objectives of rated voltage output and current stress minimization.

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

[0031] The bidirectional DC / DC topology is a transformer-coupled architecture for bidirectional energy transmission between two full-bridge circuits. This architecture can be implemented using four complementary MOSFET bridge arms coupled with high-frequency transformer windings. Power flow in both the forward and reverse directions is achieved by adjusting the switching timing. A high-frequency isolation transformer is a magnetically coupled device operating at frequencies above 20kHz. It can be implemented using a nanocrystalline core coupled with Litz wire windings. It is used to achieve electrical isolation between the primary and secondary sides and match the input and output voltages. The internal phase shift angle refers to the phase difference between the drive signals of the upper and lower transistors in the same bridge arm. This can be achieved by inserting dead time when a digital signal processor generates complementary PWM waveforms. It is used to control the zero-voltage switching state of the same bridge arm. The external phase shift angle refers to the phase difference between the drive signals of the primary and secondary bridge arms. This can be achieved by comparing the phase offset of the PWM carrier signals of the two bridge arms and is used to adjust the direction and amount of power transfer. The DAB small-signal equivalent model is a linearized mathematical model based on the state-space averaging method. This model is implemented by deriving the equivalent transfer function between the output voltage and the phase shift angle. It serves as the basis for stability analysis of closed-loop control systems.

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

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

[0034] Among them, the DAB small-signal equivalent model refers to the dynamic mathematical model obtained after linearizing the dual-active full-bridge converter. It can be established by the state-space averaging method to describe the dynamic relationship between the output voltage and the phase shift angle. The equivalent transfer function refers to the frequency domain mathematical expression between the output voltage and the phase shift angle, which specifically includes the load resistance, output capacitance and transformer parameters, and is used to characterize the dynamic characteristics of the system. Type 1 function refers to the system type in which the equivalent open-loop equivalent transfer function has a single integral link at the origin. Specifically, the zero point of the PI controller is set to offset the pole formed by the output capacitance and the load resistance, so that the system has the ability to eliminate steady-state errors. The condition for a gain of 1 means that the open-loop gain amplitude of the system at the bandwidth frequency is equal to 1. It is determined by solving the amplitude-frequency characteristic equation of the equivalent transfer function to ensure system stability and dynamic response speed.

[0035] It is understandable that when establishing the DAB small-signal equivalent model, the switching state of the converter is 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 consumption characteristics of the load resistor, and can accurately reflect 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, where the zero position is set to coincide with the pole formed by the output capacitor and the load resistor, thereby eliminating the impact of the pole on the system stability. Finally, according to the system bandwidth requirements, the gain intersection frequency is selected on the amplitude-frequency characteristic curve of the equivalent open-loop equivalent transfer function, and the numerical relationship between the proportional coefficient and the integral coefficient is determined by solving the complex domain equation, so that the system has amplitude 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 characteristics of the equivalent open-loop transfer function at a specific frequency point to maintain a stable operating state during dynamic regulation. This can be achieved by introducing an amplitude-frequency characteristic constraint 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. This can be determined by setting the crossover frequency to a range of 1 / 10 to 1 / 5 of the switching frequency. It is understood that during the PI controller design process, a small-signal equivalent model including the output voltage, load resistance, and output capacitance is first established to derive the voltage loop equivalent open-loop transfer function. By setting the gain condition to 1 at the system bandwidth frequency, the open-loop gain amplitude is made equal to 1, making this frequency a crossover point in the amplitude-frequency characteristic curve, thereby ensuring a phase margin of at least 45°. During parameter calculation, the proportional and integral coefficients of the PI controller are substituted into the equivalent transfer function amplitude equation, and the solution is found to satisfy the amplitude constraint of 1, ultimately determining the controller parameter combination.

[0037] Specifically, this application uses a DAB circuit as a bidirectional DC / DC converter topology for an electric vehicle's onboard composite power supply. The DAB circuit's internal and external phase shift angles jointly control the on / off switching of the switch tube, and through the output voltage feedback loop, the external phase shift angle is adjusted to achieve output voltage stability. The design process for 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, is the converter output voltage, is the converter output load, is the output side capacitance of the converter, The output voltage feedback loop is regulated by a PI controller, and the equivalent transfer function of the PI controller is: ; Therefore, the PI controller can be regarded as an equivalent transfer function Added a pole , a zero point . Let the PI controller add zero Right now , then the equivalent open-loop transfer function is Converted to a type 1 function, it has relatively stable working performance. Then let the gain of the converter be 1 when it works within the system bandwidth: ; In the formula The system bandwidth of the converter.

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

[0039] The present application further proposes that the execution of the current stress adaptive minimization algorithm includes: defining the current stress per-unit value based on the inductor current peak expression; deriving the mathematical relationship between the power per-unit value and the phase shift angle; first differentiating the current stress per-unit value to obtain the minimum solution of the external phase shift angle; and inversely deriving the internal phase shift angle by combining the power equations.

[0040] The per-unit current stress value is a dimensionless parameter obtained by normalizing the inductor current peak value. This can be achieved by taking the ratio of the instantaneous maximum inductor current to the reference current, eliminating the impact of voltage ratio differences on current stress assessment. The per-unit power value is the normalized ratio of the output power to the reference power, and can be achieved by taking the ratio of the output power to the rated power. This is used to establish a quantitative relationship between power transmission and phase shift angle. The minimum solution for the external phase angle is the phase angle parameter obtained through mathematical derivation that brings the per-unit current stress value to a local minimum. This can be achieved by taking the first-order derivative of the per-unit current stress value expression and setting it to zero. This is used to determine the critical point for current stress optimization. The reverse calculation of the internal phase angle from the simultaneous power equations is a system of equations constructed by combining the mathematical relationship between the per-unit power value and the phase shift angle with the minimum solution. This can be achieved by solving algebraic equations or numerical iteration methods, determining the optimal internal phase angle while meeting power transmission requirements.

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

[0042] The present application further proposes that the internal phase shift angle is inversely calculated by using simultaneous power equations, including: when the voltage transformation ratio is ≥1: if the power per unit value ∈ [0, 1 / 2], the internal phase shift angle is calculated using the first-class square root expression; if the power per unit value ∈ (1 / 2, 2 / 3], the internal phase shift angle is calculated using the second-class square root expression; when the voltage transformation ratio is _1, the internal phase shift angle is calculated using a linear expression.

[0043] The voltage transformation ratio refers to the ratio of input voltage to output voltage. It can be calculated in real time by a digital processor after collecting data from a voltage sensor. It characterizes the voltage matching status of the DAB converter during operation. The power per unit (PUP) value refers to the normalized ratio of the actual output power to the reference power. Specifically, it can be calibrated using the product of the output current and the rated current as the reference power. It quantifies the power transfer level. The first-type square root expression is an analytical expression for the phase shift angle based on the quadratic function root formula. Specifically, it can be expressed as d1 = √(2P_n), which is suitable for approximate calculations in the low-power range. The second-type square root expression is an optimized analytical expression that introduces a correction term. Specifically, it can be expressed as d2 = √(4P_n-1), which is used for precise calculations in the medium- and high-power range. The linear expression is a simplified calculation model based on the Taylor expansion. Specifically, it can be expressed as d3 = 2P_n / (1+m), where m is the voltage transformation ratio. It is suitable for fast calculations in step-down conditions.

[0044] Specifically, under boost conditions where the voltage transformation ratio is greater than or equal to 1, the power per unit value is divided into two intervals. When the power per unit value is detected to be in the range of 0 to 0.5, the first type of square root expression is used to directly calculate the internal phase shift angle. This expression simplifies the calculation process by ignoring high-order terms. When the power per unit value is in the range of 0.5 to 0.67, the second type of square root expression is switched to for compensation calculation, and the calculation accuracy is improved by introducing a quadratic correction term. Under step-down conditions where the voltage transformation ratio is less than 1, a linear expression is used to replace the square root operation, and the computational complexity is reduced through linearization processing. The above-mentioned 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 collected voltage and power data.

[0045] refer to Figure 5 , Figure 5 The following is a detailed flow chart of the current stress adaptive minimization algorithm according to an embodiment of the present invention. In this embodiment, the inner phase shift angle calculation process for minimizing the current stress is as follows: sampling the converter input voltage, output voltage, and output current; calculating the converter voltage ratio. and per-unit transmission power ;judge Is it greater than or equal to 1? The range is or ; Finally, according to The specific value range of is used to determine the specific value of the inner phase shift angle to achieve bidirectional flow of energy. The specific execution process of the current stress adaptive minimization algorithm can be as follows: While ensuring the stability of the output voltage, the converter inductor current stress is minimized, and the derivation process of minimizing the inductor current stress is: According to the DAB circuit current stress model, taking the expression at the maximum inductor current as the reference value, the per-unit value of the current stress is: ; In formula (1), the voltage transformation ratio , is the transformer primary and secondary turns ratio, is the internal phase shift angle between the two bridge arms on the same side, is the outward shift phase angle between the two bridge arms on the same side.

[0046] Taking the rated output power as the reference value, the per-unit value of the converter output power is: ; From formula (2), we can deduce Depend on The expression represented by: ; Substituting formula (3) into formula (1), we can obtain: ; In order to obtain the external phase angle with the minimum current stress , solve equation (4) The minimum value of right The derivative is zero, so we get The expression is: ; Combining equations (3) and (5), we can obtain the combination of the minimum current stress value and the inward and outward shifts as shown in the following table (1): 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 structure, the proposed invention methods are applicable to bidirectional power flow application scenarios.

[0048] The present application further proposes to generate the phase difference of complementary drive pulses of the same-side bridge arm according to the inner phase shift angle through a PWM modulation generator, and to generate the phase difference of the primary and secondary bridge arm drive pulses according to the outer phase shift angle through a PWM modulation generator. Among them, the phase difference of the complementary drive pulses of the same-side bridge arm refers to the time difference between the drive signals of the upper and lower bridge arm switches in the full-bridge circuit on the same side. Specifically, it can be achieved by using a digital signal processor to perform time conversion on the phase shift angle and then generate a complementary PWM waveform. The phase difference is used to control the alternating conduction timing of the switch tubes on the same side of the bridge arm to avoid a direct short circuit. The phase difference of the primary and secondary bridge arm drive pulses refers to the timing offset of the drive signal between the primary full bridge and the secondary full bridge. Specifically, it can be achieved by generating a synchronous PWM signal after performing phase offset compensation on the phase shift angle through a programmable logic device. The phase difference is used to adjust the power transmission direction and the energy flow rate.

[0049] Specifically, in the hybrid power system of electric vehicles, when the supercapacitor and the power battery interact with each other, the PWM modulation generator first receives the internal phase shift angle calculated by the current stress regulation module. This internal 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 full-bridge circuit on the same side form a timing relationship of alternating conduction. At the same time, the external phase shift angle output by the PI controller is converted into the phase difference between the primary full-bridge and secondary full-bridge drive pulses. For example, by adjusting the starting time offset of the primary bridge arm PWM signal relative to the secondary 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, which ultimately control the DAB converter to achieve zero-voltage switching state.

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

[0051] The present application further proposes a drive control device for a dual-active full-bridge converter, comprising a dual-active full-bridge converter, a proportional-integral controller, a pulse width modulation generator, and a current stress regulation module; wherein the current stress regulation module calculates the voltage transformation ratio based on the input voltage and output voltage 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 transformation ratio and output power into the current stress adaptive minimization algorithm to solve the inner phase shift angle; at the same time, 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 a switch tube drive signal according to the inner phase shift angle and the outer phase shift angle, so as to control the dual-active full-bridge converter through the switch tube drive signal to achieve the rated voltage output and current stress minimization.

[0052] Among them, the current stress regulation module refers to a hardware circuit or embedded algorithm module that performs dynamic calculations by collecting 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 according to the real-time operating conditions to reduce the inductor current peak. The proportional-integral controller refers to 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 the output voltage stability and compensate for the phase deviation caused by load fluctuations. The pulse width modulation generator refers to a hardware logic circuit that generates a complementary drive pulse sequence. Specifically, it can be implemented using a field programmable gate array or a dedicated driver chip. Its function is to convert the 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 the parameters into the built-in current stress optimization algorithm module to solve 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 operation to eliminate steady-state errors. After receiving the inner and outer phase shift angle parameters, the pulse width modulation generator uses a carrier comparison method to generate a drive pulse sequence with a specific phase difference, where the inner phase shift angle controls the conduction overlap time of the upper and lower switches on the same side of the bridge arm, and 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 switch tubes of the dual-active full-bridge converter through an isolated drive circuit, ensuring that the inductor current stress is at the lowest level while achieving precise control of the output voltage.

[0054] The present application further proposes a computer program product, comprising a computer program, which, when executed by a processor, implements the following steps: sampling and obtaining the input voltage, output voltage, and output current of a dual-active full-bridge converter; calculating the voltage transformation ratio and output power through a current stress regulation module, and substituting them into a current stress adaptive minimization algorithm to solve the inner phase shift angle; adjusting the outer phase shift angle through a PI controller; outputting the inner and outer phase shift angles to a pulse width modulation generator to generate a switch tube drive signal, thereby controlling the converter to achieve rated voltage output and current stress minimization.

[0055] The term "computer program product" refers to a storage medium containing executable code, which can be implemented as a solid-state drive or flash memory chip, and is used to store program instructions corresponding to the control algorithm. Processor execution refers to running program code through a central processing unit or embedded controller, which can be implemented as a multi-core processor or digital signal processor, which is used to parse instructions and perform voltage sampling, phase shift angle calculation, and signal generation operations. The current stress adaptive minimization algorithm refers to a mathematical optimization method based on the relationship between the peak per-unit value of the inductor current and power. It can be implemented by solving the extreme points of the derivative and simultaneous equations, and is used to dynamically adjust the internal 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 converter's input and output voltage and current parameters. The voltage ratio calculation module uses the input-output voltage ratio as an optimization parameter, 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 into the built-in optimization algorithm module, which calculates the inner phase shift angle using the corresponding square root or linear expression based on the preset voltage ratio threshold. Simultaneously, the voltage closed-loop control module inputs the difference between the output voltage and the target value into a PI controller, which adjusts the outer phase shift angle to maintain system stability. The resulting phase shift angle parameters are converted into complementary pulse signals to precisely control the conduction timing of the switches in the full-bridge circuit.

[0057] In some specific embodiments, the computer program can be packaged as a dynamic link library (DLL) and integrated into the vehicle control unit, with execution scheduled by a real-time operating system. The derivative solution for the current stress optimization algorithm can be implemented using a table lookup method, with the calculated extreme points under different voltage ratios pre-stored in non-volatile memory. Pulse-width modulation signal generation can be achieved by configuring a timer capture and comparison unit, utilizing a hardware acceleration module to reduce processor load.

[0058] The present application further proposes an electronic device comprising one or more processors and a memory associated with the one or more processors, wherein the memory is used to store program instructions. When the program instructions are read and executed by the one or more processors, the program instructions execute the steps of the driving control method of the dual active full-bridge converter.

[0059] The processor is the hardware unit that executes calculations and control logic. Specifically, it can be implemented as a multi-core central processing unit or digital signal processor. It processes sampled data of input voltage, output voltage, and output current in real time, and executes the current stress adaptive minimization algorithm and proportional-integral control algorithm. Memory is the physical medium that stores executable code and operating data. Specifically, it can be implemented as flash memory or dynamic random access memory. It is used to store program instructions and algorithm parameters to ensure the continuous execution of 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. It calculates the inner phase-shift angle based on the voltage transformation ratio and output power, and simultaneously adjusts the outer phase-shift angle using a proportional-integral controller. Ultimately, these two phase-shift angles are input into a pulse-width modulation generator to generate the switch drive signal. During this process, the processor uses algorithm parameters and program instructions stored in memory to ensure the simultaneous execution of current stress optimization and voltage control, thereby maintaining stable operation of the dual-active full-bridge converter over a wide range of voltage transformation ratios and dynamic power variations.

[0061] The above describes the technical solution provided by this application in detail. Specific examples are used herein to illustrate the principles and implementation methods of this application. The description of the above embodiments is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the contents of this specification should not be understood as limiting this application.

Claims

1. A driving control method for a DAB converter, characterized in that: 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 comprises: Sampling and obtaining the input voltage, output voltage and output current of the DAB converter; The current stress adjustment module calculates a voltage transformation ratio based on the input voltage and the output voltage, calculates an output power based on the output voltage and the output current, and substitutes the voltage transformation ratio and the output power into a current stress adaptive minimization algorithm to solve an inner phase shift angle; and simultaneously, the PI controller adjusts an outer phase shift angle based on a difference between a command voltage and an output voltage; Outputting the inner phase shift angle and the outer phase shift angle to a PWM modulation generator to generate a switch tube driving signal; The DAB converter is controlled by the driving signal to achieve rated voltage output and minimize current stress.

2. The method according to claim 1, characterized in that 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 internal phase shift angle controls the on-off timing of the switch tube on the same side of the bridge arm, and the external phase shift angle controls the power transmission phase difference between the primary and secondary bridge arms. The PI controller adjusts the external phase shift angle through an output voltage feedback loop designed based on the DAB small-signal equivalent model.

3. The method according to claim 2, characterized in that The design steps of the PI controller include: Establish a DAB small signal equivalent model and derive the equivalent transfer function including output voltage, load and capacitance parameters; The PI controller is used to supplement the poles and zeros, and the zero point is set to s = −1 / (RC2) to convert the equivalent open-loop transfer function into a type 1 function; Based on the system bandwidth setting gain of 1, the proportional coefficient and integral coefficient of the PI controller are calculated.

4. The method according to claim 1, wherein The execution of the current stress adaptive minimization algorithm includes: The current stress per unit value is defined based on the inductor current peak expression; Derive the mathematical relationship between power per unit and phase shift angle; First, the derivative of the per-unit value of the current stress is taken to obtain the minimum solution of the external phase angle; The internal phase shift angle can be inversely calculated by using the simultaneous power equations.

5. The method according to claim 4, characterized in that The simultaneous power equations for inversely calculating the internal phase shift angle include: When the voltage transformation ratio is ≥1: if the power per unit value ∈ [0, 1 / 2], the first kind of square root expression is used to calculate the internal phase shift angle; if the power per unit value ∈ (1 / 2, 2 / 3], the second kind of square root expression is used to calculate the internal phase shift angle; When the voltage transformation ratio is less than 1, a linear expression is used to calculate the internal phase shift angle.

6. The method according to claim 3, characterized in 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.

7. The method according to claim 1, characterized in that Outputting the inner phase shift angle and the outer phase shift angle to a PWM modulation generator to generate a switch tube drive signal includes: The phase difference of the complementary driving pulses of the same-side bridge arm is generated according to the internal phase shift angle through the PWM modulation generator; The phase difference of the original and secondary bridge arm drive pulses is generated according to the external shift phase angle through the PWM modulation generator.

8. A drive control device for a DAB converter, characterized in that: include: DAB converter, PI controller, PWM modulation generator and current stress regulation module; among them, The current stress adjustment module calculates a voltage transformation ratio based on the input voltage and output voltage of the DAB converter, calculates an output power based on the output voltage and output current of the DAB converter, and substitutes the voltage transformation ratio and the output power into a current stress adaptive minimization algorithm to solve an inner phase shift angle; and the PI controller is used to adjust an outer phase shift angle based on a difference between a command voltage and an output voltage; The PWM modulation generator is used to generate a switch tube drive signal according to the inner phase shift angle and the outer phase shift angle, so as to control the DAB converter through the switch tube drive signal to achieve rated voltage output and minimize current stress.

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

10. An electronic device, characterized in that: 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, wherein the program instructions, when read and executed by the one or more processors, perform the steps of the method according to any one of claims 1 to 7.

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