A dc / dc converter and a control method and apparatus therefor

Abstract

The present application relates to a kind of DC / DC converter and its control method and device, belong to direct current distribution control technical field.The converter is constituted by high-voltage side ANPC type three-level half bridge circuit, transmission inductance, isolation transformer and low-voltage side full-bridge circuit, high-voltage side ANPC type three-level half bridge circuit and low-voltage side full-bridge circuit are connected by transmission inductor and transformer.The converter is realized voltage grade conversion and power flow by controlling three-level alternating voltage zero level duty cycle and the phase shift of the center line of two alternating voltages, to solve the problem that soft switching cannot be realized under small power condition, simultaneously solve the problem of poor economy of two-level dual active bridge DC / DC converter.Its control method is mainly composed of two proportional integral controller links, a demarcation point calculation link and a control logic link.The corresponding relationship of each link according to input and output is connected, and the actual control quantity of the converter is finally obtained by a series of mathematical calculations and logical judgments.

Description

Technical Field

[0001] This invention relates to a DC / DC converter and its control method and apparatus, belonging to the field of DC power distribution control technology. Background Technology

[0002] DC distribution networks offer advantages such as large power supply capacity, long power supply radius, high operating efficiency, and minimal power quality issues, making them suitable for a wide range of applications. However, DC distribution networks suffer from voltage level mismatches with renewable energy sources or DC loads, failing to meet the direct connection requirements of these loads. This necessitates the use of DC / DC converters as interface devices to convert voltage levels and provide the necessary voltage for renewable energy sources or DC loads to connect to the grid.

[0003] Currently, the most commonly used DC / DC converter topology in the DC distribution network field is the "phase-shifting dual active bridge topology," with circuit connections as follows: Figure 1 As shown, the AC port voltage change during the operation of this phase-shifted dual active bridge topology converter is as follows: Figure 2 As shown, its control is simple and it can achieve maximum transmission power. However, it has the problem of not being able to achieve soft switching under low power conditions. Moreover, with the continuous expansion of the DC distribution network, the maximum voltage across the full-bridge side switching transistors of the DC / DC converter, which are directly connected to the DC grid, is also constantly increasing. This requires the selection of switching transistors with high voltage resistance and relatively high price, resulting in poor economic efficiency of the DC / DC converter. Summary of the Invention

[0004] The purpose of this invention is to provide a DC / DC converter and its control method and apparatus to solve the problem that the DC / DC converter cannot achieve soft switching under low power transmission conditions in the prior art, and at the same time solve the problem of poor economic efficiency of the DC / DC converter.

[0005] To achieve the above objectives, the beneficial effects of the technical solutions and corresponding solutions provided by this invention include:

[0006] This invention provides a DC / DC converter control method. The DC / DC converter includes an ANPC-type half-bridge circuit, an isolation transformer, a full-bridge circuit, and an energy storage capacitor. The AC side of the ANPC-type half-bridge circuit is connected to the AC side of the full-bridge circuit through the isolation transformer. The energy storage capacitor is connected in parallel with the DC side of the full-bridge circuit. The DC / DC converter control method includes using the obtained actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β The DC / DC converter is controlled; and the initial value calculation, boundary point calculation, and control logic are used to obtain the D... α and D β;

[0007] The initial value calculation stage is used to calculate the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The difference Err2, the enable signal of the controller used in the initial value calculation stage, and the initial values ​​of the controller parameters are used to calculate D. α initial values ​​and D β The initial value; the boundary point calculation step is used based on the DC port voltage sampling value U of the half-bridge circuit. dc1 U dc2 The turns ratio n between the full-bridge and half-bridge windings of the isolation transformer, combined with the set minimum duty cycle value D at zero voltage level. α_min The critical value D of the zero-level voltage duty cycle is calculated using the hysteresis width h. α_edg Compared to the critical value D of the phase shift angle shift β_edg and output D α_min D α_edg D β_edg h; the control logic element is used to determine the order based on D. α initial value, D β initial value, D α_min D a_edg D β_edg And h calculates the enable signal and controller parameters of the controller used in the initial value calculation stage of the next cycle, as well as D. α and D β .

[0008] The beneficial effects of the above technical solution are as follows: The DC / DC converter of the present invention no longer uses the phase-shifted dual active bridge topology. Instead, it modifies the two-level full-bridge circuit on the DC grid side into an ANPC-type three-level half-bridge circuit based on the phase-shifted dual active bridge topology. The switching transistors are driven according to a certain timing sequence, generating a three-level AC square wave with an adjustable zero-level duration at the AC terminal of the half-bridge circuit. By controlling the three-level AC voltage, the zero-level duty cycle and the phase shift ratio of the two AC voltage center lines are controlled to realize voltage level conversion and power flow. This achieves soft-switching characteristics of the switching transistors across the entire power range, reduces switching transistor losses during operation, and improves the converter performance indicators.

[0009] As a further improvement to the method, the initial value calculation step includes a first proportional-integral controller, the controller parameters of which are the integral coefficients of the first proportional-integral controller; the first proportional-integral controller is used to adjust and control -Err2 by combining the enable signal PI_alpha_En and the initial value of the integral coefficient PI_alpha_Init of the first proportional-integral controller to obtain D. α initial value D α_PIWhen PI_alpha_En changes from 0 to 1, the integral coefficient in the first proportional-integral controller is assigned a value according to PI_alpha_Init.

[0010] The beneficial effects of the above scheme are as follows: the initial value calculation stage uses a proportional-integral controller, which has simple control logic but high control accuracy. It can calculate the accurate initial value of the zero-level duty cycle of the AC port voltage of the half-bridge circuit based on the difference between the target value of the DC port voltage of the full-bridge circuit and the sampled value of the DC port voltage of the full-bridge circuit, combined with the enable signal of the first proportional-integral controller and the initial value of the parameters of the first proportional-integral controller, and use it as the input value of the control logic stage.

[0011] As a further improvement to the scheme, a second proportional-integral (PI) controller is also included. The controller parameters of the second PI controller are its integral coefficients. The second PI controller is used to adjust and control Err2 in conjunction with the enable signal PI_beta_En and the initial value of the integral coefficient PI_beta_Init of the second PI controller to obtain D. β initial value D β_PI When PI_beta_En changes from 0 to 1, the integral coefficient in the second proportional-integral controller is assigned a value according to PI_beta_Init.

[0012] The beneficial effects of the above scheme are as follows: The second proportional-integral controller uses a second proportional-integral controller, which has simple control logic but high control accuracy. It can calculate the accurate value of the half-bridge circuit AC port voltage compared with the center line shift of the full-bridge circuit AC port voltage based on the difference between the target value of the full-bridge circuit DC port voltage and the sampled value of the full-bridge circuit DC port voltage, combined with the enable signal of the second proportional-integral controller and the initial value of the parameters of the second proportional-integral controller, and use it as the input value of the control logic.

[0013] As a further improvement to the method, the calculation process of the boundary point calculation step includes:

[0014] A. Calculation Then calculate

[0015] B. Determine D α_edg Greater than or equal to D α_min Is it true? If so, let D α_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. α_edg =D α_min ;

[0016] C. Determine D β_edg If the condition is greater than or equal to 0, then let D be true. β_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =0.

[0017] The advantages of the above scheme are: the internal operation process of the boundary point calculation is sequential, meaning that execution is repeated after completion, resulting in a relatively simple and accurate calculation logic. Regarding the collected data U... dc1 U dc2 After calculation with n, Da_min, and h through the boundary point calculation stage, the accurate critical value D of the voltage zero level duty cycle is obtained. α_edg Compared to the critical value D of the phase shift angle shift β_edg As the input value of the control logic, it continues to output Da_min and h as part of the input values ​​of the next round of boundary point calculation.

[0018] As a further improvement to the method, PI_alpha_En, PI_alpha_Init, PI_beta_En, and PI_beta_En output by the control logic loop serve as the enable signal and controller parameters of the controller used in the initial value calculation loop of the next cycle calculation process; the specific implementation process includes:

[0019] a. Let PI_alpha_En=0, PI_beta_En=0, PI_alpha_Init=D α_edg PI_beta_Init = 0, then proceed to step b;

[0020] b. Determine D β_PI Greater than (D) β_edg If +h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_edg D α =D α_edg D β =D β_PI And continue with step b;

[0021] c. Determine D α_PI Greater than D α_edg And check if the set time is met. If yes, proceed to step b; otherwise, continue to check step D. α_PI Less than D α_min And check if the set time is met. If yes, execute step d; otherwise, set PI_alpha_En = 1, PI_beta_En = 0, and PI_beta_Init = D. β_edg D α =D α_PI D β =D β_edg And continue with step c;

[0022] d. Determine Dβ_PI Less than (D) β_edg If -h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_min D α =D α_min D β =D β_PI And continue with step d.

[0023] The beneficial effects of the above scheme are as follows: the control logic unit serves as the main calculation unit of this converter control method. The output values ​​of the proportional-integral controller unit and the boundary point calculation unit are used as input values ​​for this unit to perform logical calculations, thereby obtaining the parameters for controlling the converter's transformation, namely, the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β Furthermore, the input quantities for the proportional-integral control loop to continue operating simultaneously are the signal and controller parameters, ensuring that the overall cycle can continue indefinitely.

[0024] The present invention provides a DC / DC converter control device, comprising a memory and a processor, wherein the processor is used to execute computer program instructions stored in the memory to implement a DC / DC converter control method.

[0025] The present invention provides a DC / DC converter, comprising an ANPC type half-bridge circuit, an isolation transformer, a full-bridge circuit, and an energy storage capacitor. The AC side of the ANPC type half-bridge circuit is connected to the AC side of the full-bridge circuit through the isolation transformer. The energy storage capacitor is connected in parallel with the DC side of the full-bridge circuit. The converter also includes a memory and a processor. The processor is used to execute computer program instructions stored in the memory to implement the following control method.

[0026] Using the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β The DC / DC converter is controlled; and the initial value calculation, boundary point calculation, and control logic are used to obtain the D... α and D β ;

[0027] The initial value calculation stage is used to calculate the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The difference Err2, the controller enable signal, and the initial values ​​of the controller parameters are used to calculate D. α initial values ​​and Dβ The initial value; the boundary point calculation step is used based on the DC port voltage sampling value U of the half-bridge circuit. dc1 U dc2 The turns ratio n between the full-bridge and half-bridge windings of the isolation transformer, combined with the set minimum duty cycle value D at zero voltage level. α_min The critical value D of the duty cycle for zero voltage level is obtained by calculating the hysteresis width h. α_edg Compared to the critical value D of the phase shift angle shift β_edg , and input D α_min D α_edg D β_edg h; the control logic element is used to determine the order based on D. α initial value, D β initial value, D α_min D α_edg D β_edg The calculation of h yields the enable signal and controller parameters of the controller used in the initial value calculation stage of the next cycle, as well as D. α and D β .

[0028] The beneficial effects of the above technical solution are as follows: The DC / DC converter of the present invention no longer uses the phase-shifted dual active bridge topology. Instead, it modifies the two-level full-bridge circuit on the DC grid side into an ANPC-type three-level half-bridge circuit based on the phase-shifted dual active bridge topology. The switching transistors are driven according to a certain timing sequence, generating a three-level AC square wave with an adjustable zero-level duration at the AC terminal of the half-bridge circuit. By controlling the three-level AC voltage, the zero-level duty cycle and the phase shift ratio of the two AC voltage center lines are controlled to realize voltage level conversion and power flow. This achieves soft-switching characteristics of the switching transistors across the entire power range, reduces switching transistor losses during operation, and improves the converter performance indicators.

[0029] As a further improvement to the method, the initial value calculation stage includes a first proportional-integral controller and a second proportional-integral controller. This stage is used to adjust and control -Err2 and Err2 by combining the enable signal and the initial value of the integral coefficient of the integral controller to obtain D. α initial value D α_PI and D β initial value D β_PI When the enable signal changes from 0 to 1, the integral coefficient in the proportional-integral controller is assigned the initial value of the integral coefficient of the integral controller.

[0030] The beneficial effects of the above scheme are as follows: The initial value calculation stage uses a proportional-integral controller, which has simple control logic but high control accuracy. It can calculate the accurate initial value of the zero-level duty cycle of the AC port voltage of the half-bridge circuit and the initial value of the center line shift of the AC port voltage of the half-bridge circuit compared with that of the full-bridge circuit based on the difference between the target value of the DC port voltage of the full-bridge circuit and the sampled value of the DC port voltage of the full-bridge circuit, combined with the enable signal of the proportional-integral controller and the initial value of the proportional-integral controller parameters. These values ​​are used as input values ​​for the control logic stage.

[0031] As a further improvement to the method, the calculation process of the boundary point calculation step includes:

[0032] A. Calculation Then calculate

[0033] B. Determine D α_edg Greater than or equal to D α_min Is it true? If so, let D α_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. α_edg =D α_min ;

[0034] C. Determine D β_edg If the condition is greater than or equal to 0, then let D be true. β_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =0. The beneficial effects of the above scheme are: the internal operation process of the boundary point calculation is a sequential operation, that is, it continues to be executed after completion, and the calculation logic is relatively simple and accurate. For the collected data U dc1 U dc2 After calculation with n, Da_min, and h through the boundary point calculation stage, the accurate critical value D of the voltage zero level duty cycle is obtained. α_edg Compared to the critical value D of the phase shift angle shift β_edg As the input value of the control logic, it continues to output Da_min and h as part of the input values ​​of the next round of boundary point calculation.

[0035] As a further improvement to the method, the proportional-integral controller enable signals PI_alpha_En and PI_beta_En, and the integral controller coefficients PI_alpha_Init and PI_beta_En output by the control logic loop are used as the enable signals and controller parameters of the controller in the initial value calculation loop of the next cycle calculation process; the specific implementation process includes:

[0036] a. Let PI_alpha_En=0, PI_beta_En=0, PI_alpha_Init=D α_edg PI_beta_Init = 0, then proceed to step b;

[0037] b. Determine D β_PI Greater than (D) β_edg If +h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_edg D α =D α_edg D β =D β_PI And continue with step b;

[0038] c. Determine D α_PI Greater than D α_edg And check if the set time is met. If yes, proceed to step b; otherwise, continue to check step D. α_PI Less than D α_min And check if the set time is met. If yes, execute step d; otherwise, set PI_alpha_En = 1, PI_beta_En = 0, and PI_beta_Init = D. β_edg D α =D α_PI D β =D β_edg And continue with step c;

[0039] d. Determine D β_PI Less than (D) β_edg If -h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_min D α =D α_min D β =D β_PI And continue with step d.

[0040] The beneficial effects of the above scheme are as follows: the control logic unit serves as the main calculation unit of this converter control method. The output values ​​of the proportional-integral controller unit and the boundary point calculation unit are used as input values ​​for this unit to perform logical calculations, thereby obtaining the parameters for controlling the converter's transformation, namely, the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β Furthermore, the input quantities for the proportional-integral control loop to continue operating simultaneously are the signal and controller parameters, ensuring that the overall cycle can continue indefinitely. Attached Figure Description

[0041] Figure 1 This is a topology diagram of a dual active bridge phase-shifting DC / DC converter in the prior art;

[0042] Figure 2 This is a schematic diagram of the AC voltage during operation of a current dual active bridge phase-shifting DC / DC converter.

[0043] Figure 3 This is a schematic diagram of the DC / DC converter topology of the present invention;

[0044] Figure 4 This is a schematic diagram of the AC voltage during operation of the DC / DC converter of the present invention;

[0045] Figure 5 This is a schematic diagram of the control method logic of the present invention;

[0046] Figure 6 This is a schematic diagram of the logic of the boundary point calculation process in this invention;

[0047] Figure 7 This is a schematic diagram of the logic state of the logic control link of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0049] The purpose of this invention is to provide a DC / DC converter, a DC / DC converter control method, and a DC / DC converter control device, which enable the converter to achieve soft-switching characteristics of the switching transistors across the entire power range while performing voltage level conversion functions, thereby reducing the losses of the switching transistors during operation and improving the converter's performance indicators.

[0050] DC / DC converter examples:

[0051] The circuit topology of the DC / DC converter in this embodiment is as follows: Figure 3 As shown. A schematic diagram of the AC voltage during converter operation is shown below. Figure 4 As shown. This topology is in Figure 1The improvement is based on the existing design, specifically replacing the two-level full-bridge circuit on the DC grid side with an ANPC-type three-level half-bridge circuit to achieve voltage level conversion and power flow. The primary side of the transformer is connected to the AC side of the ANPC three-level half-bridge circuit via a transmission inductor L, while the secondary side is connected to the AC side of the full-bridge circuit. The ANPC three-level half-bridge circuit structure includes two capacitors C1 and C2 and six switching transistors (T11-T16), each with a diode (D11-D16) connected in reverse parallel. Switches T11, T12, T13, and T14 are connected in series between the positive and negative terminals of the DC bus. One end of T15 is connected to the junction of T11 and T12, and one end of T16 is connected to the junction of T13 and T14. The other ends of T15 and T16 are connected in parallel to the midpoint of capacitors C1 and C2. This ANPC three-level half-bridge circuit structure ensures that the switching transistors on the DC grid side only need to withstand half of the DC grid voltage, significantly reducing the voltage stress on the switching transistors.

[0052] Meanwhile, the switching transistors T11-T16 are driven according to a certain timing sequence, which can generate a three-level AC square wave with an adjustable zero-level duration at the AC terminal (U1) of the half-bridge circuit. By controlling the three-level AC voltage, the zero-level duty cycle (the proportion of the zero-level duration in the total AC voltage cycle time) and the phase shift ratio of the two AC voltage center lines are controlled, thus realizing voltage level conversion and power flow.

[0053] The control strategy adopted by this DC / DC converter is as follows: based on the calculated actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β This invention relates to a DC / DC converter control method, and its logic diagram is shown below. Figure 5 As shown, it comprises three stages: initial value calculation (including the first and second proportional-integral controller stages), breakpoint calculation, and control logic. These stages are interconnected based on the correspondence between input and output quantities. The details of each stage are described below:

[0054] 1) First proportional-integral controller stage: The first proportional-integral controller inputs the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The error amount Err1, combined with the enable signal PI_alpha_En of the first proportional-integral controller and the initial value of the first proportional-integral controller parameter PI_alpha_Init, is used to adjust and control the error amount Err1 to obtain the initial value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α_PI , which serves as the input to the control logic.

[0055] Specifically:

[0056] Error amount Err1 = -(U dc2_ref -U dc2 When the enable signal PI_alpha_En = 1, the first proportional-integral controller performs its function normally. When the enable signal PI_alpha_En changes from 1 to 0, the proportional term output of the first proportional-integral controller is zero (i.e., the proportional coefficient in the proportional-integral controller is set to 0), the integral term is frozen and continues to output the value before the enable signal changes. When the enable signal PI_alpha_En changes from 0 to 1, the integral term (i.e., the integral coefficient in the proportional-integral controller) in the first proportional-integral controller is assigned a value according to the initial value PI_alpha_Init of the first proportional-integral controller parameter.

[0057] 2) Second proportional-integral controller stage: The second proportional-integral controller inputs the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The error Err2, combined with the enable signal PI_beta_En of the second proportional-integral controller and the initial value PI_beta_Init of the second proportional-integral controller parameters, is used to adjust Err2 to obtain the initial value D of the phase angle shift of the center line of the half-bridge circuit AC port voltage compared with that of the full-bridge circuit AC port voltage. β_PI This serves as the input to the control logic. Specifically:

[0058] Error amount Err2 = U dc2_ref -U dc2 For the enable signal PI_beta_En, when PI_beta_En = 1, the second proportional-integral controller performs its function normally. When PI_beta_En changes from 1 to 0, the output of the proportional term (i.e., the proportional coefficient in the proportional-integral controller is set to 0) in the second proportional-integral controller is zero, and the integral term is frozen and continues to output the value before the enable signal changes. When PI_beta_En changes from 0 to 1, the integral term (i.e., the integral coefficient in the proportional-integral controller) in the second proportional-integral controller is assigned a value according to the initial value of the second proportional-integral controller parameter PI_beta_Init.

[0059] 3) Boundary Point Calculation Stage: This control stage is executed sequentially and continuously loops. Specifically, the boundary point calculation stage is based on the DC port voltage sampling value U of the half-bridge circuit. dc1 The DC port sampling value U of the full-bridge circuit dc2 The turns ratio n between the full-bridge and half-bridge windings of the isolation transformer, combined with the set minimum duty cycle value D at zero voltage level. α_minThe critical value D of the zero-level voltage duty cycle is calculated using the hysteresis width h. α_edg Compared to the critical value D of the phase shift angle shift β_edg And output D α_min D α_edg D β_edg h serves as the input quantity for the control logic.

[0060] like Figure 6 As shown, this step is implemented as follows:

[0061] A. Manually set up D α_min After setting h, proceed to step B;

[0062] B. Calculation After the calculation is complete, proceed to step C;

[0063] C. Calculation After the calculation is complete, proceed to step D;

[0064] D. Determine D α_edg Greater than or equal to D α_min Is it true? If so, then let If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. α_edg =D α_min After the judgment is completed, proceed to step E;

[0065] E. Determine D β_edg If the condition is greater than or equal to 0, then let... If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =0, after the judgment is completed, continue to execute step A;

[0066] 4) Logic Control Stage: The various implementation processes in this stage operate independently; the next operation will only proceed after a specific step is completed. Specifically, this is achieved by controlling the initial duty cycle value D at zero input voltage level. α_PI Minimum value D α_min and critical value D α_edg The phase shift angle is compared to the initial value D. α_PI and critical value D β_edg The enable signals (PI_alpha_En, PI_beta_En) and controller parameters (PI_alpha_Init, PI_beta_Init) of the controller used in the initial value calculation stage of the next cycle are calculated, as well as the D of the controller variable. α and D β .

[0067] like Figure 7 As shown, the specific implementation process of the control logic is as follows:

[0068] a. Let PI_alpha_En=0, PI_beta_En=0, PI_alpha_Init=D α_edg PI_beta_Init = 0, then proceed to step b;

[0069] b. Determine D β_Init Greater than (D) β_edg If +h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_edg D α =D α_edg D β =D β_Init And continue with step b;

[0070] c. Determine D α_Init Greater than D α_edg And check if the set time is met. If yes, proceed to step b; otherwise, continue to check step D. α_Init Less than D α_min And check if the set time is met. If yes, execute step d; otherwise, set PI_alpha_En = 1, PI_beta_En = 0, and PI_beta_Init = D. β_edg D α =D α_Init D β =D β_edg And continue with step c;

[0071] d. Determine D β_Init Less than (D) β_edg If -h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_min D α =D α_min D β =D β_Init And continue with step d.

[0072] This invention, without increasing the additional cost of the DC / DC converter, transforms the two-level full-bridge circuit on the DC grid side of the phase-shifted dual active bridge topology into an ANPC-type three-level half-bridge circuit. This allows the DC grid-side switching transistors to withstand only half of the DC grid voltage, significantly reducing the voltage stress on the switching transistors. Simultaneously, the AC terminal (U1) of the half-bridge circuit generates a three-level AC square wave with an adjustable zero-level duration. The zero-level duty cycle D is controlled by controlling the three-level AC voltage. α (The proportion of the zero-level duration to the total AC voltage cycle time) and the phase shift ratio of the two AC voltage center lines to Dβ This enables voltage level conversion and power flow.

[0073] Example of DC / DC converter control method:

[0074] This embodiment is aimed at... Figure 3 The DC / DC converter shown is in Figure 1 The improvement made on the basis is in the phase-shifting dual active bridge topology ( Figure 1 The two-level full-bridge circuit on the DC grid side was modified into an ANPC-type three-level half-bridge circuit. The control method employed involves calculating the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit using three stages: initial value calculation, boundary point calculation, and control logic. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β Through D α D β The DC / DC converter is controlled. The specific calculation process has been described in detail in the embodiments of the DC / DC converter control method, and will not be repeated in this embodiment.

[0075] Example of a DC / DC converter control device:

[0076] The DC / DC converter control device includes a memory and a processor, which interact with each other via an internal bus. The processor executes computer program instructions stored in the memory to implement a DC / DC converter control method according to the present invention. The specific details of this method have been described in detail in the embodiments of the DC / DC converter control method, and will not be repeated here. The memory can be selected from semiconductor memory, magnetic surface memory, read-only memory, sequential memory, etc., and the processor can be selected from Intel processors, MD processors, IBM processors, MediaTek processors, etc.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any modifications or changes made to the present invention by those skilled in the art after reading this application and referring to the above embodiments are within the scope of protection claimed in this patent application.

Claims

1. A DC / DC converter control method, wherein the DC / DC converter includes an ANPC-type half-bridge circuit, an isolation transformer, a full-bridge circuit, and an energy storage capacitor, wherein the AC side of the ANPC-type half-bridge circuit is connected to the AC side of the full-bridge circuit through the isolation transformer, and the energy storage capacitor is connected in parallel with the DC side of the full-bridge circuit, characterized in that, The DC / DC converter control method includes utilizing the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit. α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β The DC / DC converter is controlled; and the initial value calculation, boundary point calculation, and control logic are used to obtain the D... α and D β ; The initial value calculation stage is used to calculate the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The difference Err2, the enable signal of the controller used in the initial value calculation stage, and the initial values ​​of the controller parameters are used to calculate D. α initial values ​​and D β The initial value; the boundary point calculation step is used based on the DC port voltage sampling value U of the half-bridge circuit. dc1 U dc2 The turns ratio n between the full-bridge and half-bridge windings of the isolation transformer, combined with the set minimum duty cycle value D at zero voltage level. α_min The critical value D of the zero-level voltage duty cycle is calculated using the hysteresis width h. α_edg Compared to the critical value D of the phase shift angle shift β_edg and output D α_min D α_edg D β_edg h; the control logic element is used to determine the order based on D. α initial value, D β initial value, D α_min D α_edg D β_edg And h calculates the enable signal and controller parameters of the controller used in the initial value calculation stage of the next cycle, as well as D. α and D β .

2. The DC / DC converter control method according to claim 1, characterized in that, The initial value calculation stage includes a first proportional-integral (PI) controller, whose controller parameters are the integral coefficients. The first PI controller is used to adjust -Err2 by combining the enable signal PI_alpha_En and the initial value of the integral coefficient PI_alpha_Init to obtain D. α initial value D α_PI When PI_alpha_En changes from 0 to 1, the integral coefficient in the first proportional-integral controller is assigned a value according to PI_alpha_Init.

3. The DC / DC converter control method according to claim 2, characterized in that, It also includes a second proportional-integral (PI) controller, whose controller parameters are the integral coefficients of the second PI controller; the second PI controller is used to adjust Err2 by combining the enable signal PI_beta_En and the initial value of the integral coefficient PI_beta_Init of the second PI controller to obtain D. β initial value D β_PI When PI_beta_En changes from 0 to 1, the integral coefficient in the second proportional-integral controller is assigned a value according to PI_beta_Init.

4. The DC / DC converter control method according to any one of claims 1-3, characterized in that, The calculation process for the boundary point calculation step includes: A. Calculation Then calculate B. Determine D α_edg Greater than or equal to D α_min Is it true? If so, let D α_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =D α_min ; C. Determine D β_edg If the condition is greater than or equal to 0, then let D be true. β_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =0.

5. The DC / DC converter control method according to claim 3, characterized in that, The PI_alpha_En, PI_alpha_Init, PI_beta_En, and PI_beta_En output by the control logic loop serve as the enable signal and controller parameters for the initial value calculation loop in the next loop calculation process; the specific implementation process includes: a. Let PI_alpha_En=0, PI_beta_En=0, PI_alpha_Init=D α_edg PI_beta_Init = 0, then proceed to step b; b. Determine D β_PI Greater than (D) β_edg If +h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_edg D α =D α_edg D β =D β_PI And continue with step b; c. Determine D α_PI Greater than D α_edg And check if the set time is met. If yes, proceed to step b; otherwise, continue to check step D. α_PI Less than D α_min And check if the set time is met. If yes, execute step d; otherwise, set PI_alpha_En = 1, PI_beta_En = 0, and PI_beta_Init = D. β_edg D α =D α_PI D β =D β_edg And continue with step c; d. Determine D β_PI Less than (D) β_edg If -h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_min D α =D α_min D β =D β_PI And continue with step d.

6. A DC / DC converter control device, characterized in that, It includes a memory and a processor, the processor being configured to execute computer program instructions stored in the memory to implement the DC / DC converter control method as described in any one of claims 1-5.

7. A DC / DC converter, comprising an ANPC-type half-bridge circuit, an isolation transformer, a full-bridge circuit, and an energy storage capacitor, wherein the AC side of the ANPC-type half-bridge circuit is connected to the AC side of the full-bridge circuit via the isolation transformer, and the energy storage capacitor is connected in parallel with the DC side of the full-bridge circuit, characterized in that, It also includes a memory and a processor, the processor being used to execute computer program instructions stored in the memory to implement the following control method: Using the actual value D of the zero-level duty cycle of the AC port voltage of the half-bridge circuit α The actual value D is compared with the AC port voltage of the half-bridge circuit and the AC port voltage of the full-bridge circuit. β The DC / DC converter is controlled; and the initial value calculation, boundary point calculation, and control logic are used to obtain the D... α and D β ; The initial value calculation stage is used to calculate the target value U of the DC port voltage of the full-bridge circuit. dc2_ref The DC port voltage sampling value U of the full-bridge circuit dc2 The difference Err2, the controller enable signal, and the initial values ​​of the controller parameters are used to calculate D. α initial values ​​and D β The initial value; the boundary point calculation step is used based on the DC port voltage sampling value U of the half-bridge circuit. dc1 U dc2 The turns ratio n between the full-bridge and half-bridge windings of the isolation transformer, combined with the set minimum duty cycle value D at zero voltage level. α_min The critical value D of the duty cycle for zero voltage level is obtained by calculating the hysteresis width h. α_edg Compared to the critical value D of the phase shift angle shift β_edg , and input D α_min D α_edg D β_edg h; the control logic element is used to determine the order based on D. α initial value, D β initial value, D α_min D α_edg D β_edg The calculation of h yields the enable signal and controller parameters of the controller used in the initial value calculation stage of the next cycle, as well as D. α and D β .

8. The DC / DC converter according to claim 7, characterized in that, The initial value calculation stage includes a first proportional-integral controller and a second proportional-integral controller. This stage combines the enable signal and the initial value of the integral coefficient of the integral controller to adjust and control -Err2 and Err2 to obtain D. α initial value D α_PI and D β initial value D β_PI When the enable signal changes from 0 to 1, the integral coefficient in the proportional-integral controller is assigned the initial value of the integral coefficient of the integral controller.

9. The DC / DC converter according to any one of claims 7-8, characterized in that, The calculation process for the boundary point calculation step includes: A. Calculation Then calculate B. Determine D α_edg Greater than or equal to D α_min Is it true? If so, let D α_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =D α_min ; C. Determine D β_edg If the condition is greater than or equal to 0, then let D be true. β_edg If it remains unchanged, then let D remain unchanged; otherwise, let D remain unchanged. β_edg =0.

10. The DC / DC converter according to claim 8, characterized in that, The first proportional-integral controller enable signal PI_alpha_En, the first proportional-integral controller integral coefficient initial value PI_alpha_Init, the second proportional-integral controller enable signal PI_beta_En, and the second proportional-integral controller integral coefficient initial value PI_beta_En output by the control logic loop serve as the controller enable signal and controller parameters used in the initial value calculation loop of the next cycle calculation process; the specific implementation process includes: a. Let PI_alpha_En=0, PI_beta_En=0, PI_alpha_Init=D α_edg PI_beta_Init = 0, then proceed to step b; b. Determine D β_PI Greater than (D) β_edg If +h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_edg D α =D α_edg D β =D β_PI And continue with step b; c. Determine D α_PI Greater than D α_edg And check if the set time is met. If yes, proceed to step b; otherwise, continue to check step D. α_PI Less than D α_min And check if the set time is met. If yes, execute step d; otherwise, set PI_alpha_En = 1, PI_beta_En = 0, and PI_beta_Init = D. β_edg D α =D α_PI D β =D β_edg And continue with step c; d. Determine D β_PI Less than (D) β_edg If -h) is true, proceed to step c; otherwise, set PI_alpha_En = 0, PI_beta_En = 1, and PI_alpha_Init = D. α_min D α =D α_min D β =D β_PI And continue with step d.

Images