Control method, device and equipment of dual active bridge inverter and storage medium

Abstract

The application discloses a kind of dual active bridge inverter control method, device, equipment and storage medium.Therein method includes: obtaining target transmission power parameter;Based on target transmission power parameter, determine target operating mode;Based on zero-voltage switching model, determine first phase shift control quantity;Based on target operating mode and target transmission power parameter, determine second phase shift control quantity and switching frequency control quantity;Wherein, when target operating mode is first mode, with the minimum reactive power of dual active bridge inverter as the first constraint condition to determine second phase shift control quantity, with actual transmission power matching expected transmission power as the second constraint condition to determine switching frequency control quantity;Based on first phase shift control quantity, second phase shift control quantity and switching frequency control quantity, generate drive signal control dual active bridge inverter.The application can realize zero-voltage switching in full operating frequency cycle, reduce hard switching loss, reduce reactive power under light load working condition, improve light load efficiency.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion control technology, specifically to a control method, device, equipment, and storage medium for a dual active bridge inverter. Background Technology

[0002] With the rapid development of renewable energy and energy storage technologies, energy storage inverter systems are placing increasingly higher demands on the efficiency, stability, and dynamic performance of single-phase off-grid inverters. In energy storage inverter systems, the inverter acts as the bridge between the battery bank and the user load, and its performance directly determines the reliability of the entire system. In the topology of single-phase off-grid inverters, traditional two-stage DC-AC converters typically consist of an isolated DC-DC converter and a DC-AC converter; while single-stage DC-AC converters are gaining widespread attention due to their simple structure, small size, and high conversion efficiency. In practical applications, the interaction between the two conversion stages in a two-stage converter can easily cause system stability problems and generate additional cascading losses, leading to a decrease in overall system efficiency.

[0003] Among existing single-stage topologies, microinverters based on dual-active-bridge (DAB) architectures have attracted significant attention due to their substantial advantages, including electrical isolation, high power density, high step-up ratio, and single-stage operation. DAB-type microinverters are generally classified into resonant and non-resonant types. Compared to resonant types, non-resonant DABs exhibit stronger robustness to parameter variations and lower manufacturing costs; however, their zero-voltage switching (ZVS) range under light load conditions is narrower, and their circulating current power is higher, making it difficult to achieve overall efficiency across the entire load range. Therefore, achieving ZVS and reducing circulating current power across the entire load range is a key issue in improving the efficiency of DAB-type single-phase off-grid inverters.

[0004] In existing DAB-type microinverter modulation methods, dual phase shift (DPS) and triple phase shift (TPS) modulation strategies are commonly used to optimize reactive power, ZVS conditions, and maximum current stress. In addition to phase shift modulation, switching frequency modulation is also used as an additional degree of control freedom to improve current stress and expand the ZVS range. However, the modulation methods proposed in the literature still have the following problems: (1) The ZVS model in the existing modulation methods is mostly idealized and does not consider the actual influence of the output parasitic capacitance (Coss) of the power switch and the excitation inductance (Lm) of the high-frequency transformer on the ZVS boundary. This results in some bridge arm hard switching phenomena during actual operation, especially near mode switching, which causes switching oscillation and efficiency loss; (2) The existing modulation methods based on mode switching rely on real-time condition judgment, which has a complex calculation process and long controller execution time, making it difficult to implement in low-cost digital controllers; (3) In the dual closed-loop control of the traditional DAB micro-inverter, the output of the outer loop voltage controller is coupled with the inner loop current controller, which makes the control loop bandwidth design difficult and easily generates third harmonic distortion, affecting the output waveform quality and total harmonic distortion (THD); (4) Under non-unity power factor load and off-grid operation conditions, since the power flow direction needs to be reversed in each power frequency cycle, waveform distortion is easy to occur near zero crossing, which further affects the off-grid operation quality.

[0005] In summary, existing DAB-type single-phase off-grid inverters still have significant room for improvement in terms of light-load efficiency, ZVS range, controller implementation complexity, and off-grid load adaptability. Therefore, there is an urgent need for a modulation and control method that comprehensively considers the parasitic capacitance of power switches and the magnetizing inductance of the transformer, achieves ZVS across the entire power range, and possesses low controller execution complexity and good off-grid load adaptability. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects existing in the prior art and provide a control method, device, equipment and storage medium for a dual active bridge inverter.

[0007] The first aspect of this invention provides a control method for a dual active bridge inverter, comprising: Obtain the target transmission power parameter that characterizes the expected transmission power; Based on the target transmission power parameters, the target operating mode is determined; Based on a preset zero-voltage switching model, a first phase shift control quantity is determined; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state. Based on the target operating mode and the target transmission power parameter, a second phase shift control quantity and a switching frequency control quantity are determined; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. Based on the first phase shift control quantity, the second phase shift control quantity, and the switching frequency control quantity, a drive signal is generated to control the dual active bridge inverter.

[0008] Furthermore, based on the target transmission power parameter, determining the target operating mode includes: obtaining a mode determination boundary value determined by the first phase shift control quantity; when the target transmission power parameter is less than or equal to the mode determination boundary value, determining the target operating mode as a first mode; when the target transmission power parameter is greater than the mode determination boundary value, determining the target operating mode as a second mode; wherein, when the target operating mode is the second mode, the switching frequency control quantity is set to a preset fixed frequency; Furthermore, based on a preset zero-voltage switching model, the first phase shift control quantity is determined, including: obtaining the leakage inductance energy storage parameter characterizing the energy storage state of the isolation component, and the parasitic capacitance energy storage parameter characterizing the energy storage state of the power switching device; under the energy balance critical condition that the leakage inductance energy storage parameter is greater than or equal to the parasitic capacitance energy storage parameter, the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary are calculated; the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary are weighted using preset bias weighting coefficients to obtain the first phase shift control quantity; Furthermore, the second phase shift control quantity is determined with the minimization of reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. This includes: constructing a functional relationship model of reactive power with respect to the second phase shift control quantity in the first mode; solving the extreme value conditions corresponding to the functional relationship model to obtain the second phase shift control quantity corresponding to the minimum reactive power; and calculating the switching frequency control quantity based on the steady-state equality constraint condition in the transmission power model that the actual output power equals the expected transmission power, combined with the second phase shift control quantity. Furthermore, obtaining the target transmission power parameter characterizing the expected transmission power includes: obtaining a reference output voltage and a reference output current; determining the target transmission power parameter based on the reference output voltage and the reference output current; when determining the second phase shift control quantity, the method further includes: calculating a product parameter of the reference output voltage and the reference output current; when the product parameter is greater than zero, determining that the system is in a forward power transmission state, and calling a first analytical logic matching the forward power transmission state to calculate the second phase shift control quantity; when the product parameter is less than zero, determining that the system is in a reverse power transmission state, and calling a second analytical logic matching the reverse power transmission state to calculate the second phase shift control quantity; Furthermore, after determining the switching frequency control quantity, the method further includes: filtering and smoothing the switching frequency control quantity using a preset low-pass filter to obtain a smoothed frequency parameter; when the smoothed frequency parameter is within a preset switching frequency range, using the smoothed frequency parameter as the final output switching frequency control quantity; when the smoothed frequency parameter exceeds the preset switching frequency range, limiting the final output switching frequency control quantity to a preset boundary frequency value. Further, obtaining the reference output voltage and reference output current includes: obtaining a preset reference voltage value as the reference output voltage; obtaining the actual output voltage of the dual active bridge inverter, and inputting the deviation parameter between the reference voltage value and the actual output voltage into the proportional-integral resonant controller to obtain an initial current reference value; obtaining the actual output current of the dual active bridge inverter, and performing low-frequency filtering on the actual output current using a feedforward compensator to obtain a feedforward compensation reference value; and superimposing the initial current reference value and the feedforward compensation reference value to synthesize the reference output current.

[0009] A second aspect of the present invention provides a control device for a dual active bridge inverter, comprising: The parameter acquisition module is used to acquire target transmission power parameters that characterize the expected transmission power. The mode determination module is used to determine the target operating mode based on the target transmission power parameter; The internal phase shift calculation module is used to determine the first phase shift control quantity based on a preset zero-voltage switching model; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state. The frequency modulation and calculation module is used to determine the second phase shift control quantity and the switching frequency control quantity based on the target operating mode and the target transmission power parameter; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. The drive module is used to generate a drive signal to control the dual active bridge inverter based on the first phase shift control quantity, the second phase shift control quantity, and the switching frequency control quantity.

[0010] A third aspect of the present invention provides an electronic device including a memory and a processor, wherein the memory stores a computer program that, when executed by the processor, implements the method described in the first aspect.

[0011] A fourth aspect of the present invention provides a computer-readable storage medium having program instructions stored thereon, which, when executed, implement the method described in the first aspect.

[0012] The advantages and beneficial effects of this invention are as follows: by obtaining the target transmission power parameter characterizing the expected transmission power, the target operating mode is determined based on the parameter, and the first phase shift control quantity is determined by a zero-voltage switching model that simultaneously considers the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component. Based on the target operating mode and the target transmission power parameter, the second phase shift control quantity is determined under the constraint of minimizing reactive power in the first mode, and the switching frequency control quantity is determined under the constraint of power matching. Finally, a drive signal is generated to control the dual active bridge inverter, thereby realizing zero-voltage switching throughout the entire power frequency cycle, reducing hard switching losses, and reducing reactive power under light load conditions, thus improving light load efficiency. Attached Figure Description

[0013] Figure 1 This is a flowchart of the control method for the dual active bridge inverter of the present invention; Figure 2 This is a schematic diagram of a dual active bridge single-phase off-grid micro inverter topology used in the method of this invention. Figure 3 This is a schematic diagram of the basic operating waveforms and drive signals of the dual active bridge inverter in this invention; Figure 4 This is a schematic diagram of the working waveforms of the inverter in the first and second modes of the present invention; Figure 5 This is an overall block diagram of the control strategy of the present invention; Figure 6 This is an experimental waveform diagram of the inverter prototype in this invention under a 110W resistive load; Figure 7 The graph shows the test results of the efficiency and total harmonic distortion rate of the method of the present invention under different loads; Figure 8 These are test waveforms of the method of the present invention under startup and load shedding conditions; Figure 9 This is a comparison chart of the execution time and efficiency of three control strategies; Figure 10 This is a schematic diagram of the control device structure of the dual active bridge inverter of the present invention. Detailed Implementation

[0014] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0015] This invention addresses the problems of low efficiency under light load, narrow ZVS range, severe controller coupling, and poor adaptability to off-grid loads in existing DAB-type single-phase off-grid inverters. It proposes a control method for a dual active bridge single-phase off-grid inverter based on a novel frequency modulation strategy. This method mainly includes: (1) comprehensively considering the parasitic capacitance of the power switch output. and high frequency transformer magnetizing inductance (1) The full-frequency cycle ZVS model; (2) The mode switching, phase shift and frequency hybrid modulation strategy based on the ZVS model; (3) The dual-loop control structure with an outer loop PIR controller and an inner loop current controller based on prediction and completely decoupled from the modulation strategy; (4) The power direction judgment logic based on the reference output voltage and reference output current sign to realize the load adaptive operation under off-grid conditions.

[0016] For example, Figure 2 This illustration shows the dual active bridge single-phase off-grid micro inverter topology used in the control method of this embodiment of the invention. The topology consists of a primary-side full bridge composed of four power switches S1 to S4, and a secondary-side half-bridge composed of four bidirectional switches S5-1, S5-2, S6-1, and S6-2. A large-capacity input capacitor is connected in parallel on the DC input side. Used to smooth DC bus voltage The high-frequency transformer has a turns ratio of 1:n, and its secondary leakage inductance is... The excitation inductance is Secondary capacitor and Each bears half of the output voltage This also helps achieve volt-second balance on the secondary side. The output is achieved through a filter inductor. Connect the load to filter out high-frequency switching ripple. When the reference output voltage is positive, S5-2 and S6-2 are turned on, and the topology is equivalent to a primary full-bridge plus a secondary half-bridge; when the reference output voltage is negative, S5-1 and S6-1 are turned on, and the topology is equivalent to a primary full-bridge plus a reverse secondary half-bridge, thereby realizing AC output.

[0017] The basic waveforms and drive signals during inverter operation are as follows: Figure 3 As shown. The phase shifts of primary-side switches S1 and S3 determine the primary-side bridge output voltage. The duty cycle; and the phase shift between S1 and the secondary side S5-1 determines the primary side voltage. With secondary voltage The phase difference between them. Defined in this invention. The duty cycle of zero voltage in the primary bridge output voltage. This represents the phase difference between the midpoint of the primary-side forward voltage and the midpoint of the secondary-side voltage. Because the secondary side of the high-frequency transformer uses a half-bridge structure, and the system design always ensures... Greater than The DAB always operates in buck mode, and two key modes can be selected from the traditional 12 operating modes to optimize ZVS range and return current power. Its operating waveform is as follows: Figure 4 As shown. The normalized expressions for transmission power corresponding to Mode A and Mode B are: Where M is the normalized transmission power, defined as , , .in For switching frequency, For reference output voltage, Used as reference output current. When Select mode A if necessary; otherwise switch to mode B to achieve the optimal trade-off between ZVS region and return power.

[0018] like Figure 1 As shown, the control method of the dual active bridge inverter of the present invention includes the following steps: S101. Obtain the target transmission power parameter that characterizes the expected transmission power.

[0019] In practice, the controller obtains the reference output voltage. and reference output current This controller can be, for example, a digital signal processor. Reference output voltage. and reference output current product This characterizes the expected output power of the inverter within the current power frequency cycle, i.e., the reference output power. For ease of subsequent mode determination and modulation calculation, [the following is used]... Normalization is performed to obtain the normalized transmission power M, which can be used as the target transmission power parameter. It should be noted that the normalization calculation is a preprocessing method to facilitate the solution; directly comparing the absolute power value is also an equivalent substitution. The target transmission power parameter can encompass all equivalent engineering parameters characterizing energy flow.

[0020] S102. Determine the target operating mode based on the target transmission power parameter.

[0021] In practice, the controller adjusts the internal phase shift angle between the primary-side full-bridge switches to change the duty cycle of the zero-voltage output voltage in the primary-side bridge. Due to internal phase shift and duty cycle There is a definite numerical correspondence; the first phase shift control quantity can be used as a parameter in the mathematical model construction of the control algorithm. It participates in algebraic operations. Similarly, the controller changes the phase difference by adjusting the external phase shift between the primary and secondary sides. The second phase shift control quantity is represented as a parameter in the algorithm model. It participates in algebraic operations. Based on the above relationship, the controller monitors the normalized transmission power M, which is the target transmission power parameter, in real time, and determines the transmission power based on M and the relationship between M and... The target operating mode is determined by comparing the determined mode determination boundary values. The mode determination boundary value is... Considering the discrete execution timing of digital control systems, when performing this step for mode determination in the current control cycle, the current cycle's... The calculation is not yet complete. Therefore, in the actual operation of the controller, the first phase shift control quantity used in this step can be the calculation result of the previous control cycle, a preset initial value, or a result determined through real-time calculation. When, the controller determines the target operating mode as the first mode, i.e., mode A; when At this time, the controller determines the target operating mode as the second mode, i.e., mode B, in order to achieve the optimal trade-off between the ZVS region and the return power.

[0022] S103. Based on the preset zero-voltage switching model, determine the first phase shift control quantity; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state.

[0023] When determining the first phase shift control value, the output parasitic capacitance of the power switch was also taken into account. Magnetizing inductance of high-frequency transformer Specifically, With drain-source voltage Changes can be made through the device datasheet. - The excitation current is obtained by fitting the curve. The excitation current is given by analytical expressions at each switching moment. Included in leakage inductance current In this context, the condition for ZVS to be satisfied at any given switching moment is: the energy stored in the leakage inductance must be greater than [a certain value]. Stored energy, i.e. Based on this, the ZVS boundaries of each switch on the primary and secondary sides can be derived. Taking mode A as an example, its primary-side ZVS boundary... The following relationship must be satisfied: ,in, This is the analytical expression for the inductor current at the primary-side commutation moment in Mode A. Similarly, the ZVS boundary value of the secondary side in Mode A can be obtained. Mode B original edge ZVS boundary and the secondary edge ZVS boundary of pattern B The corresponding algebraic relationship can be obtained in real time in a practical digital controller by solving the above algebraic relationship. During the solution process, the controller establishes an energy balance critical constraint to ensure that the charge in the parasitic capacitance is completely removed. Based on this physical constraint, the first phase shift control quantity that enables zero-voltage switching on the primary and secondary sides is calculated. This feature helps to suppress hard switching oscillations of the inverter near the mode switching dead zone and reduce the heat loss of the switching transistors.

[0024] S104. Based on the target operating mode and the target transmission power parameter, determine the second phase shift control quantity and the switching frequency control quantity; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition.

[0025] When the target operating mode is the first mode, i.e., mode A, corresponding to light load conditions, this invention proposes a frequency modulation strategy to address the problem of high reactive power and low overall efficiency of DAB inverters under light load conditions. This strategy constructs control logic with minimizing reactive power as the first physical constraint. Under operating mode A, this strategy internally constructs a reactive power control variable related to the second phase shift, i.e., the external phase shift, within the microcontroller. The functional relationship model, through reactive power Regarding the external phase shift Find the partial derivative ( ), to obtain the solution that minimizes reactive power. The parsing expression is: To maintain Based on the steady-state equality constraint in the transmission power model that the actual output power equals the expected transmission power, combined with the already solved... To obtain the switching frequency The parsing expression: This ultimately yields a frequency modulation law that is easy to implement in a digital controller: in | / ( ( ) represents the voltage gain. The construction and extremum solution of the above functional relationship is the process by which the controller, based on the physical system operating parameters, determines the control quantity corresponding to the lowest hardware energy consumption operating state. In other implementations, gradient approximation algorithms, hill-climbing algorithms, or fixed offline data packets are used to look up the corresponding control quantity in a table, achieving the same effect as the above implementation.

[0026] When the target operating mode is the second mode, i.e., mode B, due to the large inductor current, the inverter directly adopts a fixed frequency mode to avoid additional switching losses, and the switching frequency is fixed at a preset value. The second phase shift control quantity D2 is determined based on the normalized expression of the transmission power corresponding to mode B.

[0027] S105. Based on the first phase shift control quantity, the second phase shift control quantity, and the switching frequency control quantity, a drive signal is generated to control the dual active bridge inverter.

[0028] The controller converts the calculated control parameters into register configuration instructions for the internal hardware. The aforementioned phase shift control and frequency control quantities are directly sent to the high-resolution phase shift module. By generating physical levels on the logic pins, the on and off cycles of each power switch in the primary-side full-bridge and secondary-side half-bridge are precisely changed to execute the physical power conversion drive.

[0029] This invention achieves zero-voltage switching across the entire power frequency cycle by acquiring a target transmission power parameter that characterizes the expected transmission power, determining a target operating mode based on this parameter, and determining a first phase shift control quantity using a zero-voltage switching model that simultaneously considers the parasitic capacitance parameters of the power switching devices and the excitation inductance parameters of the isolation components. Based on the target operating mode and the target transmission power parameter, a second phase shift control quantity is determined under the first mode with reactive power minimization as a constraint, and a switching frequency control quantity is determined with power matching as a constraint. Finally, a drive signal is generated to control the dual active bridge inverter, thereby achieving zero-voltage switching across the entire power frequency cycle, reducing hard switching losses, and simultaneously reducing reactive power under light load conditions, thus improving light load efficiency.

[0030] To achieve an optimal trade-off between zero-voltage switching region and return current power, a preferred embodiment of the present invention involves determining a target operating mode based on the target transmission power parameter, including: obtaining a mode determination boundary value determined by the first phase shift control quantity; determining the target operating mode as a first mode when the target transmission power parameter is less than or equal to the mode determination boundary value; and determining the target operating mode as a second mode when the target transmission power parameter is greater than the mode determination boundary value; wherein, when the target operating mode is the second mode, the switching frequency control quantity is set to a preset fixed frequency.

[0031] The boundary value for this mode determination is determined by an expression containing the first phase shift control value. Determined. When the target transmission power parameter M is less than or equal to When the target operating mode is determined to be the first mode, i.e., mode A, which corresponds to light load conditions, frequency conversion modulation is used to reduce reactive power and improve light load efficiency; otherwise, it switches to the second mode, i.e., mode B, which corresponds to heavy load conditions, i.e., when M>D1(1-2D1), indicating the reference power. The maximum power limit that can be transmitted in mode A has been exceeded. , When operating in Mode B, due to the larger inductor current, the inverter directly adopts a fixed frequency mode to avoid additional switching losses. In Mode B, the switching frequency is fixed at a preset value, which can be within a preset range. (For example, from 10kHz to 40kHz) Select according to the actual application requirements.

[0032] To satisfy the zero-voltage switching condition during the determination of the first phase shift control quantity, a preferred embodiment of the present invention is to determine the first phase shift control quantity based on a preset zero-voltage switching model, including: obtaining the leakage inductance energy storage parameter characterizing the energy storage state of the isolation component, and the parasitic capacitance energy storage parameter characterizing the energy storage state of the power switching device; under the energy balance critical condition that the leakage inductance energy storage parameter is greater than or equal to the parasitic capacitance energy storage parameter, calculating the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary; and using a preset bias weighting coefficient to perform a weighted calculation on the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary to obtain the first phase shift control quantity.

[0033] In this embodiment, parasitic capacitance energy storage parameters This reflects the impact of parasitic capacitance of power switching devices on ZVS, leakage inductance energy storage parameters. In the middle, leakage inductance current Includes magnetizing inductor The generated excitation current component This allows the calculation of the ZVS boundary to reflect the influence of the magnetizing inductance of the isolation component on the ZVS critical state. This is achieved when the energy stored in the leakage inductance is greater than or equal to the energy stored in the parasitic capacitance. Under the critical condition of energy balance, the ZVS boundaries of each primary and secondary switch are derived separately, and the ZVS boundaries of the primary and secondary sides under mode A and mode B are synthesized in a normalized form. , , , Based on the aforementioned ZVS boundary, this embodiment of the invention proposes to control the boundary using a parameter α (0 ≤ α ≤ 1). The offset relative to the ZVS boundary is used to perform a weighted calculation based on a preset offset weight coefficient α to achieve a trade-off optimization between ZVS range and return power. The formula is expressed as: Where x is either A or B. Once D1 is determined, it is determined according to the current transmission direction and operating mode, based on the corresponding analytical expression. make Taking into account both reactive power optimization and ZVS range preservation, this embodiment sets α to 0.75.

[0034] To address the issue of high reactive power and low overall efficiency in DAB-type inverters under light load conditions, a preferred embodiment of this invention involves determining the second phase shift control quantity using minimizing the reactive power of the dual active bridge inverter as the first constraint, and determining the switching frequency control quantity using matching the expected transmission power with the actual transmission power as the second constraint. This includes: constructing a functional relationship model of reactive power with respect to the second phase shift control quantity under the first mode; solving for the extreme value conditions corresponding to the functional relationship model to obtain the second phase shift control quantity corresponding to the minimum reactive power; and calculating the switching frequency control quantity based on the steady-state equation constraint in the transmission power model that the actual output power equals the expected transmission power, combined with the second phase shift control quantity.

[0035] In the first mode, by controlling reactive power Regarding the partial derivative of the external phase shift D2, i.e. The analytical expression for D2 that minimizes reactive power is obtained as follows: Then, in order to maintain The analytical expression for the switching frequency can be obtained from the transmission equation. The extreme value equation is transformed into digital controller parameters, ultimately yielding a frequency modulation law that is easily implemented in a digital controller. .

[0036] To achieve stable operation of loads with different power factors under off-grid conditions and optimize waveform distortion near zero crossover, a preferred embodiment of the present invention involves obtaining a target transmission power parameter characterizing the expected transmission power, including: obtaining a reference output voltage and a reference output current; determining the target transmission power parameter based on the reference output voltage and the reference output current; and, when determining the second phase shift control quantity, the method further includes: calculating a product parameter of the reference output voltage and the reference output current; when the product parameter is greater than zero, determining that the system is in a forward power transmission state, and calling a first analytical logic matching the forward power transmission state to calculate the second phase shift control quantity; when the product parameter is less than zero, determining that the system is in a reverse power transmission state, and calling a second analytical logic matching the reverse power transmission state to calculate the second phase shift control quantity.

[0037] The system design is based on the reference output voltage. With reference output current Power direction determination logic of the symbol: when At 0, the power direction is forward transmission; when At 0, the power direction is reverse transmission. Based on the transmission direction, calculate using the corresponding analytical formula. Among them, forward transmission and reverse transmission correspond to The analytical expression can be derived from the normalized power transmission expressions corresponding to Mode A and Mode B, combined with the energy transmission direction, and will not be elaborated here. In this way, the DAB inverter can adaptively switch the power direction in each power frequency cycle, thereby adapting to mixed load conditions such as resistive loads, inductive loads, and non-unit power factor loads, and avoiding obvious current spikes or waveform distortions near zero crossover.

[0038] To prevent sudden changes in the switching frequency, a preferred embodiment of the present invention further includes, after determining the switching frequency control quantity, the method further comprising: filtering and smoothing the switching frequency control quantity using a preset low-pass filter to obtain a smoothed frequency parameter; when the smoothed frequency parameter is within a preset switching frequency range, using the smoothed frequency parameter as the final output switching frequency control quantity; and when the smoothed frequency parameter exceeds the preset switching frequency range, limiting the final output switching frequency control quantity to a preset boundary frequency value.

[0039] In practical implementation, the actual controller is used for... Apply a first-order low-pass filter. When Exceeding the preset range (For example, from 10kHz to 40kHz) the frequency switches to a fixed frequency. This fixed frequency is a specific implementation of the preset boundary frequency value, and its value can be the same as the fixed frequency value used in mode B, or it can be set according to the needs of the actual application scenario. If this filtering and limiting control is not performed, the ultra-low frequency pulses caused by digital sampling noise will cause the high-frequency transformer to become biased and fall into deep magnetic saturation, while the ultra-high frequency pulses will cause thermal runaway of the power switch, which may damage the device.

[0040] To address the problems in traditional control structures where coupling between the outer-loop voltage controller and the inner-loop current controller leads to difficulties in control loop bandwidth design and susceptibility to third harmonic distortion, a preferred embodiment of this invention involves obtaining a reference output voltage and a reference output current, including: obtaining a preset reference voltage value as the reference output voltage; obtaining the actual output voltage of the dual active bridge inverter and inputting the deviation parameter between the reference voltage value and the actual output voltage into a proportional-integral resonant controller to obtain an initial current reference value; obtaining the actual output current of the dual active bridge inverter and performing low-frequency filtering on the actual output current using a feedforward compensator to obtain a feedforward compensation reference value; and superimposing the initial current reference value and the feedforward compensation reference value to synthesize the reference output current.

[0041] Combination Figure 5 The outer loop voltage controller uses a proportional-integral-resonant (PIR) controller, whose transfer function is: The resonant frequency Corresponding to the fundamental frequency, it can effectively suppress fundamental frequency error and third harmonic components. Simultaneously, the actual output current passes through a feedforward compensator in the form of a first-order low-pass filter. Feedforward to the current reference to improve dynamic performance. Current reference at the outer loop output. As input to the modulation strategy, it is obtained through ZVS boundary, frequency modulation law, and power direction judgment logic. , and Then, the drive signals for each power switch are output through a high-resolution phase-shift function. Since the modulation strategy directly calculates the control variables based on the power reference, the outer-loop voltage controller is decoupled from the inner-loop current loop, and the current loop bandwidth is reduced by the control delay introduced by the digital controller. This is determined by the fact that the phase margin is difficult to guarantee in traditional dual-loop control, and the total harmonic distortion of the output is significantly reduced.

[0042] To verify the effectiveness of the control method of the present invention, the following is combined with... Figures 6 to 9Further experimental verification was conducted. This invention constructed a 300W DAB-type single-phase off-grid micro-inverter prototype. The primary-side power switch used was IPP034N08N5, and the secondary-side power switch used was C3M0045065D. The controller employed a TI TMS320F28377S digital signal processor (DSP) with high-resolution phase-shift pulse-width modulation (HRPWM) enabled. The system sampling and control frequency was fixed at 10kHz to ensure the discretization accuracy of the proportional-integral-resonant controller. Key system parameters included: DC bus voltage. =30 to 60V, output voltage amplitude =170 to 240V, output frequency 50Hz, transformer ratio n=3, switching frequency range 10kHz to 40kHz, secondary leakage inductance =135μH, magnetizing inductance =1.98mH, output filter inductance =220μH, secondary filter capacitor and 10μF each, input capacitor =2.2mF, rated output power =300W.

[0043] Combination Figure 6 It can be seen that, Figure 6 The measured output voltage of this prototype under a 110W resistive load. Output current and secondary inductor current Waveform. The power analyzer measured the system efficiency at this operating point to be 97.952% and THD to be 2.617%, verifying the high efficiency and low harmonic characteristics of the method proposed in this invention under light load conditions.

[0044] Combination Figure 7 It can be seen that, Figure 7 The efficiency and THD test results of the control method of the present invention under different load conditions (including mixed resistive and inductive loads) are shown. It can be seen that the THD is consistently below 3% in the medium to heavy load range, and the highest efficiency is achieved in the light to medium load range, verifying the good performance of the present invention across the entire load range.

[0045] In addition, the method of the present invention was also subjected to dynamic testing, and the results are as follows: Figure 8 As shown in the test results, the invention maintains good dynamic characteristics during startup and load switching, further verifying its engineering application and practical value.

[0046] Figure 9The execution time and efficiency of three modulation strategies under different operating power were compared. These three strategies are: the phase shift and frequency modulation-based strategy disclosed in reference [1], the mode switching modulation strategy disclosed in reference [2], and the control method proposed in the embodiments of this invention. Figure 9 It can be seen that although the method proposed in this invention has a slightly longer execution time due to the introduction of the ZVS model and frequency modulation law, it is far less than the 100μs control cycle of 10kHz. Even when migrated to a low-cost 100MHz MCU (such as TMS320F280049), it can still meet the real-time requirements. At the same time, the efficiency of this method under light load is significantly better than the scheme in reference [1], and under heavy load it is comparable to the scheme in reference [2], with an overall peak efficiency of 97.952%. The above comparison results fully verify that this invention can ensure excellent efficiency while taking into account the complexity of controller implementation, and achieve a good engineering trade-off effect.

[0047] In summary, the control method of the dual active bridge inverter of the present invention has the following technical effects: (1) By controlling the parasitic capacitance of the power switch tube output, and high frequency transformer magnetizing inductance Simultaneously, the ZVS model was incorporated, realizing ZVS near mode switching and throughout the entire power frequency cycle, significantly reducing hard switching losses; (2) By introducing a new frequency modulation law, reactive power and peak maximum inductor current were significantly reduced under light load conditions, improving light load efficiency; (3) By decoupling the outer loop PIR controller and the inner loop predictive current control, the controller design was simplified and the output THD was reduced; (4) By using power direction judgment logic based on reference voltage and reference current signs, adaptive operation of resistive, inductive and non-unity power factor loads under off-grid conditions was realized, and the waveform quality near zero crossover was optimized. Experimental results show that the method proposed in this invention achieved a peak efficiency of 97.952% and a THD of less than 3% on a 300W prototype, verifying its effectiveness and practicality in DAB-type single-phase off-grid inverters.

[0048] The present invention also provides a control device for a dual active bridge inverter, such as... Figure 10 As shown, it includes: The parameter acquisition module 401 is used to acquire the target transmission power parameter that characterizes the expected transmission power. The mode determination module 402 is used to determine the target operating mode based on the target transmission power parameter; The internal phase shift calculation module 403 is used to determine the first phase shift control quantity based on a preset zero-voltage switching model; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state. The frequency modulation and calculation module 404 is used to determine the second phase shift control quantity and the switching frequency control quantity based on the target operating mode and the target transmission power parameter; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. The drive module 405 is used to generate a drive signal to control the dual active bridge inverter based on the first phase shift control quantity, the second phase shift control quantity and the switching frequency control quantity.

[0049] In one embodiment, when determining a target operating mode based on the target transmission power parameter, the mode determination module 402 is specifically configured to: obtain a mode determination boundary value determined by the first phase shift control quantity; determine the target operating mode as a first mode when the target transmission power parameter is less than or equal to the mode determination boundary value; and determine the target operating mode as a second mode when the target transmission power parameter is greater than the mode determination boundary value; wherein, when the target operating mode is the second mode, the switching frequency control quantity is set to a preset fixed frequency.

[0050] In one embodiment, when the internal phase shift calculation module 403 determines the first phase shift control quantity based on a preset zero-voltage switching model, it is specifically used to: obtain the leakage inductance energy storage parameter characterizing the energy storage state of the isolation component, and the parasitic capacitance energy storage parameter characterizing the energy storage state of the power switching device; under the energy balance critical condition that the leakage inductance energy storage parameter is greater than or equal to the parasitic capacitance energy storage parameter, calculate the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary; and use a preset bias weighting coefficient to perform a weighted calculation on the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary to obtain the first phase shift control quantity.

[0051] In one implementation, when the frequency modulation and calculation module 404 determines the second phase shift control quantity with the minimum reactive power of the dual active bridge inverter as the first constraint and the switching frequency control quantity with the actual transmission power matching the expected transmission power as the second constraint, it is specifically used to: construct a functional relationship model of reactive power with respect to the second phase shift control quantity in the first mode; solve the extreme value conditions corresponding to the functional relationship model to obtain the second phase shift control quantity corresponding to the minimum reactive power; and calculate the switching frequency control quantity based on the steady-state equation constraint condition in the transmission power model that the actual output power is equal to the expected transmission power, combined with the second phase shift control quantity.

[0052] In one implementation, when acquiring the target transmission power parameter, the parameter acquisition module 401 is specifically used to: acquire a reference output voltage and a reference output current; and determine the target transmission power parameter based on the reference output voltage and the reference output current. When determining the second phase shift control quantity, the frequency modulation and calculation module 404 is further used to: calculate the product parameter of the reference output voltage and the reference output current; when the product parameter is greater than zero, determine that the system is in a forward power transmission state, and call a first analytical logic matching the forward power transmission state to calculate the second phase shift control quantity; when the product parameter is less than zero, determine that the system is in a reverse power transmission state, and call a second analytical logic matching the reverse power transmission state to calculate the second phase shift control quantity.

[0053] In one embodiment, the frequency modulation and calculation module 404 is further configured to: after determining the switching frequency control quantity, use a preset low-pass filter to filter and smooth the switching frequency control quantity to obtain a smoothed frequency parameter; when the smoothed frequency parameter is within a preset switching frequency range, use the smoothed frequency parameter as the final output switching frequency control quantity; when the smoothed frequency parameter exceeds the preset switching frequency range, limit the final output switching frequency control quantity to a preset boundary frequency value.

[0054] In one embodiment, when acquiring the reference output voltage and reference output current, the parameter acquisition module 401 is specifically used for: acquiring a preset reference voltage value as the reference output voltage; acquiring the actual output voltage of the dual active bridge inverter, and inputting the deviation parameter between the reference voltage value and the actual output voltage to the proportional-integral resonant controller to obtain an initial current reference value; acquiring the actual output current of the dual active bridge inverter, and performing low-frequency filtering on the actual output current using a feedforward compensator to obtain a feedforward compensation reference value; and superimposing the initial current reference value and the feedforward compensation reference value to synthesize the reference output current.

[0055] Figure 10 The control device of the dual active bridge inverter in the illustrated embodiment can be used to execute the technical solution of the above method embodiment. Its implementation principle and technical effect are similar, and will not be described again here.

[0056] This invention also provides an electronic device. This electronic device can execute the processing flow provided in the control method embodiments for a dual active bridge inverter. The electronic device can be a controller as described in the above embodiments or a dual active bridge inverter configured with the controller. The electronic device includes: a memory, a processor, a computer program, and a communication interface; wherein the computer program is stored in the memory and configured to be executed by the processor using the control method for a dual active bridge inverter as described above.

[0057] In addition, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon, the computer program being executed by a processor to implement the control method for the dual active bridge inverter described in the above embodiments.

[0058] References: [1]O. Kwon, K. -S. Kim and B. -H. Kwon, "Highly Efficient Single-Stage DAB Microinverter Using a Novel Modulation Strategy to MinimizeReactive Power," IEEE J. Emerg. Sel. Topics in Power Electron., vol. 10, no.1, pp. 544-552, Feb. 2022. [2]Q. Yang, J. Yang and R. Li, "Analysis of Grid Current Distortionand Waveform Improvement Methods of Dual-Active-Bridge Micro inverter," IEEETrans. Power Electron., vol. 38, no. 4, pp. 4345-4359, April 2023. It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A control method for a dual active bridge inverter, characterized in that, include: Obtain the target transmission power parameter that characterizes the expected transmission power; Based on the target transmission power parameters, the target operating mode is determined; Based on a preset zero-voltage switching model, a first phase shift control quantity is determined; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state. Based on the target operating mode and the target transmission power parameter, a second phase shift control quantity and a switching frequency control quantity are determined; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. Based on the first phase shift control quantity, the second phase shift control quantity, and the switching frequency control quantity, a drive signal is generated to control the dual active bridge inverter.

2. The method according to claim 1, characterized in that, Based on the target transmission power parameters, the target operating mode is determined, including: Obtain the mode determination boundary value determined by the first phase shift control quantity; When the target transmission power parameter is less than or equal to the mode determination boundary value, the target operating mode is determined to be the first mode; When the target transmission power parameter is greater than the mode determination boundary value, the target operating mode is determined to be the second mode; Specifically, when the target operating mode is the second mode, the switching frequency control quantity is set to a preset fixed frequency.

3. The method according to claim 1, characterized in that, Based on a preset zero-voltage switching model, the first phase shift control quantity is determined, including: Obtain leakage inductance energy storage parameters characterizing the energy storage state of the isolation component, and parasitic capacitance energy storage parameters characterizing the energy storage state of the power switching device; Under the critical condition that the energy balance of the leakage inductance energy storage parameter is greater than or equal to the parasitic capacitance energy storage parameter, the primary-side zero-voltage switching boundary and the secondary-side zero-voltage switching boundary are calculated. The first phase shift control quantity is obtained by weighting the primary-side zero-voltage switch boundary and the secondary-side zero-voltage switch boundary using a preset bias weighting coefficient.

4. The method according to claim 1, characterized in that, The second phase shift control quantity is determined with minimizing the reactive power of the dual active bridge inverter as the first constraint, and the switching frequency control quantity is determined with matching the actual transmission power to the expected transmission power as the second constraint, including: Construct a functional relationship model of reactive power with respect to the second phase shift control quantity in the first mode; Solve the extreme conditions corresponding to the functional relationship model to obtain the second phase shift control quantity corresponding to the minimum reactive power; Based on the steady-state equation constraint in the transmission power model that the actual output power equals the expected transmission power, and combined with the second phase shift control quantity, the switching frequency control quantity is calculated.

5. The method according to claim 1, characterized in that, Obtain the target transmission power parameters characterizing the expected transmission power, including: Obtain the reference output voltage and reference output current; The target transmission power parameter is determined based on the reference output voltage and the reference output current; In determining the second phase shift control value, the method further includes: Calculate the product parameter of the reference output voltage and the reference output current; When the product parameter is greater than zero, it is determined that the system is in a forward power transmission state, and the first analytical logic matching the forward power transmission state is invoked to calculate the second phase shift control quantity. When the product parameter is less than zero, it is determined that the system is in a reverse power transmission state, and the second analytical logic matching the reverse power transmission state is invoked to calculate the second phase shift control quantity.

6. The method according to claim 1, characterized in that, After determining the switching frequency control value, the method further includes: The switching frequency control quantity is filtered and smoothed using a preset low-pass filter to obtain a smoothed frequency parameter. When the smoothed frequency parameter is within the preset switching frequency range, the smoothed frequency parameter is used as the final output switching frequency control quantity. When the smoothed frequency parameter exceeds the preset switching frequency range, the final output switching frequency control quantity is limited to the preset boundary frequency value.

7. The method according to claim 5, characterized in that, Obtain the reference output voltage and reference output current, including: Obtain a preset reference voltage value as the reference output voltage; The actual output voltage of the dual active bridge inverter is obtained, and the deviation parameter between the reference voltage value and the actual output voltage is input to the proportional-integral resonant controller to obtain the initial current reference value. The actual output current of the dual active bridge inverter is obtained, and the actual output current is subjected to low-frequency filtering using a feedforward compensator to obtain the feedforward compensation reference value. The initial current reference value is superimposed with the feedforward compensation reference value to synthesize the reference output current.

8. A control device for a dual active bridge inverter, characterized in that, include: The parameter acquisition module is used to acquire target transmission power parameters that characterize the expected transmission power. The mode determination module is used to determine the target operating mode based on the target transmission power parameter; The internal phase shift calculation module is used to determine the first phase shift control quantity based on a preset zero-voltage switching model; wherein, the zero-voltage switching model characterizes the influence of the parasitic capacitance parameter of the power switching device and the excitation inductance parameter of the isolation component on the zero-voltage switching critical state. The frequency modulation and calculation module is used to determine the second phase shift control quantity and the switching frequency control quantity based on the target operating mode and the target transmission power parameter; wherein, when the target operating mode is the first mode, the second phase shift control quantity is determined with the minimization of the reactive power of the dual active bridge inverter as the first constraint condition, and the switching frequency control quantity is determined with the actual transmission power matching the expected transmission power as the second constraint condition. The drive module is used to generate a drive signal to control the dual active bridge inverter based on the first phase shift control quantity, the second phase shift control quantity, and the switching frequency control quantity.

9. An electronic device, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program that, when executed by the processor, implements the method as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, It stores program instructions that, when executed, implement the method as described in any one of claims 1-7.

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