Three-level dual active bridge converter inductor current root mean square control method and system

Abstract

The application provides a three-level dual active bridge converter inductance current effective value control method and system, and the method comprises the following steps: obtaining transmission power and inductance current of the three-level dual active bridge converter under full-half bridge mode based on dividing the full-half bridge mode of the three-level dual active bridge converter; solving inductance current effective value according to the inductance current, and obtaining an optimized control table based on numerical optimization of the effective value according to the transmission power; offsetting the optimized effective value under the half bridge mode with an empirical value, comparing the offset result with the optimized effective value under the full bridge mode, and determining an ideal mode switching boundary; obtaining an actual mode switching boundary according to the ideal mode switching boundary; and coordinating and controlling the converter based on the actual mode switching boundary and the optimized control table. The control method can greatly reduce the switching loss of the converter, realize inductance current impact-free connection between mode switching, and improve the overall operation efficiency under the premise of ensuring the safe operation of the converter.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter optimization technology, and in particular to a method and system for controlling the effective value of inductor current in a three-level dual active bridge converter. Background Technology

[0002] The three-level dual active bridge converter (3L-DABConverter), as a new type of DC-DC converter, not only inherits the advantages of traditional dual active bridge converters such as bidirectional energy flow, input-output isolation, high energy density, and compact structure, but also has the advantages of high controllability, strong adaptability to medium and high voltage and large capacity, and easy implementation of power devices ZVS (Zero Voltage Switching). It has received widespread attention in the past 20 years.

[0003] Three-level dual active bridge converters are generally controlled by phase-shift controllers. However, when there is a mismatch between input and output voltages or a light load, the overall efficiency of the converter decreases, and the current stress on the converter is high. When higher optimization is required, multiple control degrees of freedom are needed. Because different control dimensions influence each other, the control methods with higher control dimensions become more complex and it becomes increasingly difficult to optimize the effective value of the inductor current using traditional mathematical methods such as differentiation, Lagrange multiplier method, and Kuhn-Taku method. Without increasing the control degrees of freedom, changing the switching circuit structure, or altering the transformer structure, it is often difficult to significantly improve the converter's operating efficiency. Furthermore, the existing control of three-level dual active bridge converters operates on a complete three-level full bridge, making it impossible to control only a single three-level bridge arm to switch to half-bridge operation. It does not consider the coordination between both sides simultaneously switching to half-bridge and full-bridge operating modes, resulting in low converter operating efficiency and high switching power consumption. Summary of the Invention

[0004] The present invention aims to provide a method and system for controlling the effective value of inductor current in a three-level dual active bridge converter, so as to solve the above-mentioned technical problems, significantly reduce the switching losses of the converter, realize the inductor current surge connection between mode switching, and improve the overall operating efficiency while ensuring the safe operation of the converter.

[0005] To address the aforementioned technical problems, this invention provides a method for controlling the effective value of the inductor current in a three-level dual active bridge converter, comprising:

[0006] Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, the transmission power and inductor current of the three-level dual active bridge converter under the full- and half-bridge modes are obtained; the full- and half-bridge modes include the full-bridge mode and the half-bridge mode;

[0007] The effective value of the inductor current is calculated based on the inductor current, and the effective value is numerically optimized based on the transmission power to obtain an optimized control table.

[0008] The effective value optimized under half-bridge mode is biased by empirical values, and the bias result is compared with the effective value optimized under full-bridge mode to determine the ideal mode switching boundary;

[0009] Obtain the actual mode switching boundary based on the ideal mode switching boundary;

[0010] The converter is controlled in a coordinated manner based on the actual mode switching boundary and the optimized control table.

[0011] The control method proposed in the above scheme does not change the inherent characteristic of traditional three-level dual active bridge converter control in optimizing the effective value of current and inductance, that is, it does not increase the control difficulty or computational burden. Under the above premise, the above scheme switches the converter to different modes to cope with different operating conditions; and performs numerical optimization on the effective value of inductor current obtained under different modes; based on the optimization results, the optimized effective value under half-bridge mode with empirical bias is compared with the optimized effective value under full-bridge mode to determine the actual mode switching boundary; finally, the actual mode switching boundary and the optimized control table are used to complete the switching control of the three-level dual active bridge.

[0012] In the above scheme, the converter is controlled based on the actual mode switching boundary. The converter can generate the corresponding DC bias in the corresponding working mode to adapt to different input and output voltage ratios. This can significantly reduce the switching loss of the converter and realize inductor-free current surge connection between mode switching. Furthermore, the converter is controlled based on the optimized control table, which enables the converter to have good steady-state performance and improves the overall operating efficiency while ensuring the safe operation of the converter.

[0013] Furthermore, the full-half-bridge mode includes a full-bridge mode and a half-bridge mode, specifically:

[0014] Based on the relationship between the phase shift angles within the bridge and between the bridges, the full-bridge modal operating modes are determined to include a full-bridge modal first mode and a full-bridge modal second mode, and the half-bridge modal operating modes include a half-bridge modal first mode and a half-bridge modal second mode.

[0015] In the above scheme, by specifically dividing the different operating conditions of the converter, the specific parameters of each operating condition can be optimized to ensure that the optimization results are most targeted and improve the operating efficiency of the converter.

[0016] Furthermore, the method of obtaining the transmission power and inductor current of the three-level dual active bridge converter in the full-half-bridge mode based on the division of the three-level dual active bridge converter is specifically as follows:

[0017] Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, the transmission power and inductor current of the three-level dual active bridge converter are obtained based on the equivalent circuit model of the converter under the full- and half-bridge modes.

[0018] Furthermore, the step of solving for the effective value of the inductor current based on the inductor current, and then numerically optimizing the effective value based on the transmission power to obtain an optimized control table, specifically involves:

[0019] Determine the effective value of the inductor current based on the inductor current;

[0020] Using the effective value of the inductor current as the objective function and the transmission power as the constraint, a row-wise numerical traversal optimization of the effective value of the inductor current is performed across the entire power range to obtain a three-dimensional graph of the optimization results for the full- and half-bridge modes. An optimization control table is then established, including optimized effective values ​​for both the half-bridge and full-bridge modes. Specifically, the optimized effective values ​​for the half-bridge mode are empirically biased, and the bias result is compared with the optimized effective values ​​for the full-bridge mode to determine the ideal mode switching boundary.

[0021] The effective value optimized under the half-bridge mode is biased by an empirical value to obtain the corresponding three-dimensional graph after biasing.

[0022] The 3D plot corresponding to the biased mode is overlaid with the 3D plot corresponding to the effective value optimized under full-bridge mode, and the ideal mode switching boundary is determined by the bottom view.

[0023] Furthermore, the step of obtaining the actual mode switching boundary based on the ideal mode switching boundary specifically involves:

[0024] The ideal mode switching boundary is approximated by using piecewise straight lines, and the approximated piecewise straight lines are used as the actual mode switching boundary.

[0025] Furthermore, the coordinated control based on the actual mode switching boundary and the optimized control table specifically includes:

[0026] Based on the given control conditions and the actual mode switching boundary, the actual operating mode of the converter is determined and switched accordingly.

[0027] The converter is coordinated and controlled after the actual operating mode is switched using an optimized control table.

[0028] Furthermore, the coordinated control of the converter after switching the actual operating mode using the optimized control table specifically includes:

[0029] The in-bridge phase shift angle of the converter is determined based on the optimized control table;

[0030] The phase shift angle between bridges is adjusted by a PI controller to enable steady-state control of the converter.

[0031] Modulation is performed based on the phase shift angle within the bridge and the phase shift angle between the bridges to generate drive signals and achieve coordinated control of the converter.

[0032] In the above scheme, the phase shift angle within the bridge of the converter determined by the optimized control table directly acts on the converter, and the steady-state control requirements of the converter are achieved by adjusting the phase shift angle between the bridges through the PI controller, thus ensuring the robustness and dynamic response speed of the system.

[0033] This invention provides a control system for the effective value of inductor current in a three-level dual active bridge converter, used to implement a method for controlling the effective value of inductor current in a three-level dual active bridge converter. The system includes a converter parameter acquisition module, a numerical optimization module, an ideal mode switching boundary determination module, an actual mode switching boundary acquisition module, and a coordination control module; wherein:

[0034] The converter parameter acquisition module is used to acquire the transmission power and inductor current of the three-level dual active bridge converter in full-half-bridge mode based on the division of the full-half-bridge mode of the three-level dual active bridge converter; the full-half-bridge mode includes full-bridge mode and half-bridge mode;

[0035] The numerical optimization module is used to solve for the effective value of the inductor current based on the inductor current, and to perform numerical optimization on the effective value based on the transmission power to obtain an optimized control table.

[0036] The ideal mode switching boundary determination module is used to bias the effective value of the optimization under half-bridge mode with an empirical value and compare the bias result with the effective value of the optimization under full-bridge mode to determine the ideal mode switching boundary;

[0037] The actual mode switching boundary acquisition module is used to acquire the actual mode switching boundary based on the ideal mode switching boundary;

[0038] The coordination and cooperation control module is used to coordinate and cooperate the converter based on the actual mode switching boundary and the optimized control table.

[0039] The system provided by the above solution is simple to build and easy to implement. It can effectively implement the method of controlling the effective value of inductor current in a three-level dual active bridge converter. Based on the actual mode switching boundary, it controls the converter and can generate the corresponding DC bias in the corresponding operating mode to adapt to different input and output voltage ratios. This can significantly reduce the switching losses of the converter and achieve inductor current surge connection between mode switching. Furthermore, the control of the converter based on the optimized control table gives the converter good steady-state performance and improves the overall operating efficiency while ensuring the safe operation of the converter.

[0040] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the above-described method for controlling the effective value of the inductor current of a three-level dual active bridge converter is implemented. Attached Figure Description

[0041] Figure 1 This is a schematic flowchart of a method for controlling the effective value of inductor current in a three-level dual active bridge converter according to an embodiment of the present invention;

[0042] Figure 2 This is a circuit topology diagram of a three-level dual active bridge converter provided in an embodiment of the present invention;

[0043] Figure 3 This is a control framework diagram for the effective value of the inductor current of a three-level dual active bridge converter provided in an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the working waveforms of various operating modes of a converter provided in an embodiment of the present invention;

[0045] Figure 5 A three-dimensional schematic diagram of the optimized results of the effective value of the inductor current in various operating modes of the converter provided in an embodiment of the present invention;

[0046] Figure 6 This is a diagram of the operating regions for each mode provided in an embodiment of the present invention;

[0047] Figure 7 This is a schematic diagram of the controller controlling the converter according to an embodiment of the present invention;

[0048] Figure 8 This is a control system architecture diagram for the effective value of inductor current of a three-level dual active bridge converter provided in an embodiment of the present invention. Detailed Implementation

[0049] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] Please see Figure 1 This embodiment provides a method for controlling the effective value of the inductor current in a three-level dual active bridge converter, including:

[0051] S1: Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, obtain the transmission power and inductor current of the three-level dual active bridge converter in the full- and half-bridge modes; the full- and half-bridge modes include the full-bridge mode and the half-bridge mode;

[0052] S2: Solve for the effective value of the inductor current based on the inductor current, and perform numerical optimization on the effective value based on the transmission power to obtain the optimized control table;

[0053] S3: Apply empirical bias to the effective value of the optimization under half-bridge mode and compare the bias result with the effective value of the optimization under full-bridge mode to determine the ideal mode switching boundary;

[0054] S4: Obtain the actual mode switching boundary based on the ideal mode switching boundary;

[0055] S5: Coordinate and control the converter based on the actual mode switching boundary and the optimized control table.

[0056] The control method proposed in this embodiment does not change the inherent characteristic of traditional three-level dual active bridge converter control in optimizing the effective value of current and inductance, i.e., it does not increase the control difficulty or computational burden. Under the above premise, the above scheme switches the converter to different modes to cope with different operating conditions; and performs numerical optimization on the effective value of inductor current obtained under different modes; based on the optimization results, the optimized effective value under half-bridge mode with empirical bias is compared with the optimized effective value under full-bridge mode to determine the actual mode switching boundary; finally, the actual mode switching boundary and the optimized control table are used to complete the switching control of the three-level dual active bridge.

[0057] In this embodiment, the converter is controlled based on the actual mode switching boundary. The converter can generate a corresponding DC bias in the corresponding operating mode to adapt to different input and output voltage ratios. This can significantly reduce the switching loss of the converter and achieve inductor-free current surge connection between mode switching. Furthermore, the converter is controlled based on the optimized control table, which enables the converter to have good steady-state performance and improves the overall operating efficiency while ensuring the safe operation of the converter.

[0058] It should be noted that the three-level dual active bridge converter is a three-level dual active bridge converter based on DC blocking capacitors. Compared with the two-level full bridge, it still retains the control degree of freedom between the inner and outer transistors in the half-bridge working mode, and can further optimize the effective value of the inductor current. If it is a two-level half bridge, it cannot obtain the control degree of freedom to optimize the effective value of the inductor current.

[0059] Furthermore, the full-half-bridge mode includes a full-bridge mode and a half-bridge mode, specifically:

[0060] Based on the relationship between the phase shift angles within the bridge and between the bridges, the full-bridge modal operating modes are determined to include a full-bridge modal first mode and a full-bridge modal second mode, and the half-bridge modal operating modes include a half-bridge modal first mode and a half-bridge modal second mode.

[0061] In this embodiment, the division of full-bridge and half-bridge modes is as follows: by simultaneously disconnecting all the upper transistors and turning on all the lower transistors of one arm of the three-level bridge at the converter's input and output ports, the full bridge can be converted into a half-bridge operation. The converter's operating modes can be divided into two types: full-bridge / full-bridge and half-bridge / half-bridge. Both modes are controlled by a combination of inter-arm phase shifting and inter-bridge phase shifting. The inter-arm phase shift angle is the same as the intra-bridge phase shift angle. Inter-bridge phase shift angle Both working modes have two operating modes. For pattern A, This is Mode B. There are four operating modes: Full-bridge Mode I (Mode A), Full-bridge Mode 1; Full-bridge Mode I (Mode B), Full-bridge Mode 2; Half-bridge Mode II (Mode A), Half-bridge Mode 1; and Half-bridge Mode II (Mode B), Half-bridge Mode 2. Simultaneously... Must meet

[0062] In this embodiment, by specifically dividing the different operating conditions of the converter, the specific parameters of each subsequent operating condition can be optimized to ensure that the optimization results are most targeted and improve the operating efficiency of the converter.

[0063] Furthermore, the method of obtaining the transmission power and inductor current of the three-level dual active bridge converter in the full-half-bridge mode based on the division of the three-level dual active bridge converter is specifically as follows:

[0064] Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, the transmission power and inductor current of the three-level dual active bridge converter are obtained based on the equivalent circuit model of the converter under the full- and half-bridge modes.

[0065] In this embodiment, the transmission power and inductor current of the three-level dual active bridge converter are obtained based on the equivalent circuit model of the converter in different modes. Based on the effect of the DC blocking capacitor, it is assumed that the power unit output in half-bridge mode is a three-level circuit consisting of positive and negative half of the DC bus voltage and zero. In full-bridge mode, the DC blocking capacitor has no effect on the power unit output, and it is assumed that its output is a three-level circuit consisting of positive and negative DC bus voltages and zero.

[0066] Furthermore, the step of solving for the effective value of the inductor current based on the inductor current, and then numerically optimizing the effective value based on the transmission power to obtain an optimized control table, specifically involves:

[0067] Determine the effective value of the inductor current based on the inductor current;

[0068] Using the effective value of the inductor current as the objective function and the transmission power as the constraint, the effective value of the inductor current is optimized by row numerical traversal over the full power range. A three-dimensional graph of the optimization results for the full- and half-bridge modes is obtained, and an optimization control table is established that includes the optimized effective values ​​under the half-bridge mode and the optimized effective values ​​under the full-bridge mode.

[0069] It should be noted that the RMS value of the inductor current is obtained based on the inductor current obtained from the equivalent circuit model. The RMS values ​​of the inductor current in different modes... The expression is as follows:

[0070] Full-bridge modal mode A:

[0071]

[0072] Full-bridge modal mode B:

[0073]

[0074] Half-bridge mode A:

[0075]

[0076] Half-bridge mode B:

[0077]

[0078] In the above expressions, the parameter m represents the voltage transformation ratio of the converter under the corresponding operating mode.

[0079] It should be further noted that the optimized control table includes the control quantity under the optimal control of the converter. RMS value of inductor current between the controlled variable and the controlled variable Operating voltage ratio m and transmission power P * A one-to-one correspondence.

[0080] Furthermore, the step of empirically biasing the effective value optimized under the half-bridge mode and comparing the biased result with the effective value optimized under the full-bridge mode to determine the ideal mode switching boundary specifically involves:

[0081] The effective value optimized under the half-bridge mode is biased by an empirical value to obtain the corresponding three-dimensional graph after biasing.

[0082] The 3D plot corresponding to the biased mode is overlaid with the 3D plot corresponding to the effective value optimized under full-bridge mode, and the ideal mode switching boundary is determined by the bottom view.

[0083] In this embodiment, the result of empirically biasing the effective value optimized under the half-bridge mode can be represented as irms_offset*. By plotting the biased result and the effective value optimized under the full-bridge mode in three dimensions, the m and P values ​​of the half-bridge mode can be obtained. * 3D plot of irms_offset* and m, P of full-bridge mode * 3D plot of irms*. Then, plot the m and P values ​​of the full-bridge modes. * IRMS* 3D plot, m and P of half-bridge mode * The 3D graphs irms_offset* are overlapped, and the modal switching boundary is defined by the bottom view of the overlapped 3D graphs. The intersection line of the two 3D graphs in the bottom view is the ideal modal switching boundary.

[0084] Furthermore, the step of obtaining the actual mode switching boundary based on the ideal mode switching boundary specifically involves:

[0085] The ideal mode switching boundary is approximated by using piecewise straight lines, and the approximated piecewise straight lines are used as the actual mode switching boundary.

[0086] In this embodiment, the ideal mode switching boundary is approximated using piecewise straight lines. The mode switching boundary formed by the piecewise straight lines consists of four straight line segments, and the range of the mode boundary formed by these segments is as follows:

[0087] The boundary conditions for operating in Mode I (full-bridge mode) are:

[0088]

[0089] The boundary conditions for operating in Mode II (half-bridge mode) are:

[0090]

[0091] Furthermore, the coordinated control based on the actual mode switching boundary and the optimized control table specifically includes:

[0092] Based on the given control conditions and the actual mode switching boundary, the actual operating mode of the converter is determined and switched accordingly.

[0093] The converter is coordinated and controlled after the actual operating mode is switched using an optimized control table.

[0094] Furthermore, the coordinated control of the converter after switching the actual operating mode using the optimized control table specifically includes:

[0095] The in-bridge phase shift angle of the converter is determined based on the optimized control table;

[0096] The phase shift angle between bridges is adjusted by a PI controller to enable steady-state control of the converter.

[0097] Modulation is performed based on the phase shift angle within the bridge and the phase shift angle between the bridges to generate drive signals and achieve coordinated control of the converter.

[0098] In this embodiment, the bridge phase shift angle of the converter determined by the optimized control table directly acts on the converter, and the steady-state control requirements of the converter are achieved by adjusting the inter-bridge phase shift angle through the PI controller, thus ensuring the robustness and dynamic response speed of the system.

[0099] The control method provided in this embodiment determines the actual operating mode of the converter based on the actual mode switching boundary and switches accordingly, significantly reducing the switching losses of the converter. Then, by using the inductor current RMS value optimization control table to adjust the phase shift angle within the bridge, the effective value of the inductor current under the same power transmission is effectively reduced to the minimum, significantly reducing current stress. Finally, steady-state control is achieved by adjusting the inter-bridge phase shift angle through the PI controller. This partitioned mode switching control with inductor current RMS value optimization not only significantly reduces the switching losses of the converter, but also enables inductor current-free connection between mode switching, improving the overall operating efficiency while ensuring the safe operation of the converter.

[0100] Compared to existing three-level dual active bridge converter control strategies, this embodiment can switch the port operating mode to a half-bridge to generate DC bias on the DC blocking capacitor to adapt to different input and output voltage ratios, significantly reducing switching losses. Furthermore, in order to further optimize the RMS value of the inductor current across the entire power range, the RMS value of the inductor current is optimized for different operating modes of the converter using numerical methods. Based on the optimization results, the RMS value of the inductor current is optimized and controlled, resulting in good steady-state performance.

[0101] To further illustrate the technical solution of the present invention and highlight its technical effects, this embodiment provides a specific application example of the method for controlling the effective value of inductor current in a three-level dual active bridge converter.

[0102] This embodiment provides a topology for a three-level dual active bridge converter based on a DC blocking capacitor, as shown below. Figure 2As shown, the main circuit topology is divided into two parts: the input side and the output side. Both the input and output sides consist of a three-level full-bridge circuit composed of eight switches, which acts as a three-level pulse power supply to establish an energy transfer path between the DC buses on both sides. The operating mode of the input and output sides is determined by the actual operating conditions. When operating in half-bridge mode, the DC blocking capacitor reduces the output voltage of the pulse power supply on this side to half of the bus voltage through the bias voltage to adapt to different voltage ratios. Moreover, there is still control freedom even when operating in three-level half-bridge mode. By controlling the inner and outer transistors on the three-level half-bridge arms, the effective value of the inductor current of the converter after the combination of various input and output side modes can be further optimized, ultimately realizing a three-level dual active bridge converter inductor current effective value control method (DC Blocking Capacitors Based Current RMS Minimize Control, DCBCB-CRMSMC).

[0103] This embodiment transforms a three-level full-bridge converter into a three-level half-bridge by keeping the upper switch normally open and the lower switch normally closed in one arm of the three-level full-bridge on the input / output side during light-load operation. This is achieved using voltage bias provided by a DC blocking capacitor, reducing switching losses caused by half of the switching devices in the converter. The converter operates in two modes, each with two operating modes. Utilizing simultaneous operation of the primary and secondary sides in full-bridge or half-bridge mode improves the converter's efficiency over a wider voltage input / output range. This method optimizes the converter's efficiency using the RMS value of the inductor current. The transmitted power and RMS value of the inductor current in each mode are obtained through the circuit states under different modes. Using the RMS value of the inductor current in each mode as the objective function and the transmitted power as the constraint, numerical optimization is performed, and the optimization results are used for optimal control, establishing an optimized control table. The advantage of this embodiment is that better voltage adaptability can be achieved through mode switching, especially during light-load operation in half-bridge mode. This control algorithm can optimize the effective value of the inductor current, resulting in a smaller effective value of the inductor current and a smaller total switching loss under the same voltage ratio and transmission power, thus achieving better steady-state performance.

[0104] Please see Figure 3 , Figure 3 A framework diagram for controlling the effective value of the inductor current in a three-level dual active bridge converter is provided, which is a general diagram of the implementation of this invention, and specifically includes the following steps:

[0105] S1: Based on the division of the three-level dual active bridge converter into full- and half-bridge modes, the transmission power and inductor current of the three-level dual active bridge converter in full- and half-bridge modes are obtained, specifically:

[0106] S11: Divide the converter into different operating modes and operating conditions. Divide the operation of the converter in two modes and four conditions in total within the full power range. The control quantity range corresponding to different modes is shown in Table 1.

[0107] Table 1. Range of Modal Mode Control Quantities

[0108]

[0109] The control range shown in the table above represents the entire operating range under the corresponding modal mode, which is the natural operating range before optimization.

[0110] S12: Obtain the transmission power P* and inductor current i based on the equivalent circuit of different modes. L (t), by combining the equivalent circuit models of different modal modes and Figure 4 The waveform diagrams for each working mode in the diagram show the transmission power and inductor current for the corresponding mode, as shown in Table 2.

[0111] Table 2 shows the transmission power and inductor current for each mode.

[0112]

[0113] S2: Solve for the effective value of the inductor current based on the inductor current, and perform numerical optimization on the effective value based on the transmission power to obtain an optimized control table; specifically, the expressions for the effective value of the inductor current in each mode are as follows:

[0114] Full-bridge modal mode A:

[0115]

[0116] Full-bridge modal mode B:

[0117]

[0118] Half-bridge mode A:

[0119]

[0120] Half-bridge mode B:

[0121]

[0122] Next, the effective value of the inductor current is numerically optimized through a traversal process. The three-dimensional plots of the optimization results for the full-bridge mode and the half-bridge mode are shown below. Figure 5 As shown, an optimization control table is established based on the optimization results.

[0123] S3: The effective values ​​optimized under the half-bridge mode are empirically biased, and the bias results are compared with the effective values ​​optimized under the full-bridge mode to determine the ideal mode switching boundary; specifically:

[0124] An empirical bias is applied to the effective value optimized for half-bridge mode. The bias value is -0.1, meaning that irms_offset* is obtained by subtracting 0.1 from irms* in the half-bridge mode optimization result. The bias value is used to balance the effective current value and switching losses, and should be obtained based on actual operation. Different values ​​can be taken depending on the optimization requirements; this embodiment uses 0.1 as an example. The empirically biased result irms_offset* of half-bridge mode is compared with the full-bridge optimization result irms*. The corresponding 3D graphs are overlaid, and the ideal mode switching boundary is determined through the bottom view.

[0125] S4: Obtain the actual mode switching boundary based on the ideal mode switching boundary; specifically:

[0126] An approximation of the ideal mode switching boundary is achieved using piecewise straight lines, and these approximated piecewise straight lines are used as the actual mode switching boundary. The switching boundary consists of four straight lines, as shown in Table 3, corresponding to the modal operating regions. Figure 6 As shown.

[0127] Table 3 Modal Switching Boundary Table

[0128]

[0129] S5: Based on the actual mode switching boundary and optimized control table, the converter is coordinated and controlled. The controller control flow is as follows: Figure 7 As shown.

[0130] This embodiment controls the converter based on the actual mode switching boundary. It can generate the corresponding DC bias in the corresponding operating mode to adapt to different input and output voltage ratios, which can significantly reduce the switching loss of the converter and realize inductor-free current surge connection between mode switching. Furthermore, the converter is controlled based on the optimized control table, which enables the converter to have good steady-state performance and improves the overall operating efficiency while ensuring the safe operation of the converter.

[0131] Please see Figure 8 This embodiment provides a control system for the effective value of the inductor current of a three-level dual active bridge converter, used to implement a method for controlling the effective value of the inductor current of a three-level dual active bridge converter. It includes a converter parameter acquisition module, a numerical optimization module, an ideal mode switching boundary determination module, an actual mode switching boundary acquisition module, and a coordination control module; wherein:

[0132] The converter parameter acquisition module is used to acquire the transmission power and inductor current of the three-level dual active bridge converter in full-half-bridge mode based on the division of the full-half-bridge mode of the three-level dual active bridge converter; the full-half-bridge mode includes full-bridge mode and half-bridge mode;

[0133] The numerical optimization module is used to solve for the effective value of the inductor current based on the inductor current, and to perform numerical optimization on the effective value based on the transmission power to obtain an optimized control table.

[0134] The ideal mode switching boundary determination module is used to bias the effective value of the optimization under half-bridge mode with an empirical value and compare the bias result with the effective value of the optimization under full-bridge mode to determine the ideal mode switching boundary;

[0135] The actual mode switching boundary acquisition module is used to acquire the actual mode switching boundary based on the ideal mode switching boundary;

[0136] The coordination and cooperation control module is used to coordinate and cooperate the converter based on the actual mode switching boundary and the optimized control table.

[0137] The system provided in this embodiment is simple to build and easy to implement. It can retain the inherent characteristics of traditional three-level dual active bridge converter control in optimizing the effective value of inductor current. Without increasing the control dimension or affecting the computational burden, it can improve the control performance of the system, improve the problem of low efficiency under light load when the input and output voltages are mismatched, reduce the effective value of inductor current, reduce total switching losses, and improve the converter operating efficiency.

[0138] The present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the above-described method for controlling the effective value of the inductor current of a three-level dual active bridge converter is implemented.

[0139] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for controlling the effective value of inductor current in a three-level dual active bridge converter, characterized in that, include: Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, the transmission power and inductor current of the three-level dual active bridge converter under the full- and half-bridge modes are obtained; the full- and half-bridge modes include the full-bridge mode and the half-bridge mode; The effective value of the inductor current is calculated based on the inductor current, and the effective value is numerically optimized based on the transmission power to obtain an optimized control table. Specifically, the effective value of the inductor current is calculated based on the inductor current. Using the effective value of the inductor current as the objective function and the transmission power as the constraint, the effective value of the inductor current is traversed and optimized in a row-valued manner over the entire power range to obtain a three-dimensional graph of the optimization results for the full- and half-bridge modes. An optimization control table is then established that includes the optimized effective values ​​under the half-bridge mode and the optimized effective values ​​under the full-bridge mode. The effective values ​​optimized under half-bridge mode are empirically biased, and the biased results are compared with the effective values ​​optimized under full-bridge mode to determine the ideal mode switching boundary. Specifically, the effective values ​​optimized under half-bridge mode are empirically biased to obtain the corresponding three-dimensional plot after biasing; the corresponding three-dimensional plot after biasing is overlaid with the three-dimensional plot corresponding to the effective values ​​optimized under full-bridge mode, and the ideal mode switching boundary is determined by the bottom view. Obtain the actual mode switching boundary based on the ideal mode switching boundary; The converter is controlled in a coordinated manner based on the actual mode switching boundary and the optimized control table. Specifically, the actual operating mode of the converter is determined and switched according to the actual mode switching boundary with reference to the given control conditions. The converter is then controlled in a coordinated manner after the actual operating mode is switched using the optimized control table. Specifically, the in-bridge phase shift angle of the converter is determined based on the optimized control table. The inter-bridge phase shift angle is adjusted by the PI controller to enable steady-state control of the converter. The in-bridge and inter-bridge phase shift angles are modulated to generate a drive signal to achieve coordinated control of the converter.

2. The method for controlling the effective value of inductor current in a three-level dual active bridge converter according to claim 1, characterized in that, The full-half-bridge mode includes full-bridge mode and half-bridge mode, specifically: Based on the relationship between the phase shift angles within the bridge and between the bridges, the full-bridge modal operating modes are determined to include a full-bridge modal first mode and a full-bridge modal second mode, and the half-bridge modal operating modes include a half-bridge modal first mode and a half-bridge modal second mode.

3. The method for controlling the effective value of the inductor current in a three-level dual active bridge converter according to claim 1, characterized in that, The method for obtaining the transmission power and inductor current of the three-level dual active bridge converter under full-half-bridge modes based on the division of the three-level dual active bridge converter is as follows: Based on the division of the full- and half-bridge modes of the three-level dual active bridge converter, the transmission power and inductor current of the three-level dual active bridge converter are obtained based on the equivalent circuit model of the converter under the full- and half-bridge modes.

4. The method for controlling the effective value of the inductor current in a three-level dual active bridge converter according to any one of claims 1 to 3, characterized in that, The process of obtaining the actual mode switching boundary based on the ideal mode switching boundary specifically involves: The ideal mode switching boundary is approximated by using piecewise straight lines, and the approximated piecewise straight lines are used as the actual mode switching boundary.

5. A control system for the effective value of inductor current in a three-level dual active bridge converter, characterized in that, It includes a converter parameter acquisition module, a numerical optimization module, an ideal mode switching boundary determination module, an actual mode switching boundary acquisition module, and a coordination control module; among which: The converter parameter acquisition module is used to acquire the transmission power and inductor current of the three-level dual active bridge converter in full-half-bridge mode based on the division of the full-half-bridge mode of the three-level dual active bridge converter; the full-half-bridge mode includes full-bridge mode and half-bridge mode; The numerical optimization module is used to solve for the effective value of the inductor current based on the inductor current, and to perform numerical optimization on the effective value based on the transmission power to obtain an optimization control table. Specifically, the numerical optimization module is used to solve for the effective value of the inductor current based on the inductor current; with the effective value of the inductor current as the objective function and the transmission power as the constraint, the effective value of the inductor current is traversed and optimized in a row-wise numerical manner over the full power range to obtain a three-dimensional graph of the optimization results for the full-half-bridge mode, and to establish an optimization control table including the optimized effective value under the half-bridge mode and the optimized effective value under the full-bridge mode. The ideal mode switching boundary determination module is used to empirically bias the effective values ​​optimized under half-bridge mode and compare the biased result with the effective values ​​optimized under full-bridge mode to determine the ideal mode switching boundary. Specifically, the ideal mode switching boundary determination module is used to empirically bias the effective values ​​optimized under half-bridge mode to obtain the corresponding three-dimensional map after biasing; the corresponding three-dimensional map after biasing is overlaid with the three-dimensional map corresponding to the effective values ​​optimized under full-bridge mode, and the ideal mode switching boundary is determined by the bottom view. The actual mode switching boundary acquisition module is used to acquire the actual mode switching boundary based on the ideal mode switching boundary; The coordination and cooperation control module is used to perform coordinated and cooperation control of the converter based on the actual mode switching boundary and the optimized control table. Specifically, the coordination and cooperation control module is used to determine the actual operating mode of the converter and switch it according to the actual mode switching boundary with reference to the given control conditions; and to perform coordinated and cooperation control of the converter after switching the actual operating mode using the optimized control table. Specifically, the module determines the intra-bridge phase shift angle of the converter based on the optimized control table; adjusts the inter-bridge phase shift angle through the PI controller to enable the converter to achieve steady-state control; and modulates the intra-bridge phase shift angle and the inter-bridge phase shift angle to generate a drive signal to achieve coordinated and cooperation control of the converter.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method for controlling the effective value of the inductor current of a three-level dual active bridge converter as described in any one of claims 1 to 4.

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