A method and system for optimizing soft switching region of a DAB converter

Abstract

The application discloses a kind of DAB converter soft switch domain optimization control method and system, according to photovoltaic voltage reference value, real-time acquisition DAB converter primary side partial pressure capacitor voltage and secondary side output voltage, calculate soft switch region control quantity boundary value, zero voltage duty ratio and phase shift ratio;Combining hysteresis control method, determine the duty ratio instruction and phase shift ratio instruction of DAB converter;Voltage balancing method is used to correct the duty ratio instruction of DAB converter;Based on the duty ratio instruction and phase shift ratio instruction of the corrected DAB converter, using preset modulation method, the switch trigger signal of DAB converter is obtained.The application utilizes the adjustable ability of duty ratio, adopts optimization phase shift control strategy, compared with traditional single phase shift control strategy, significantly improve the soft switch operation ability of DAB half load, improve the operation efficiency in the whole working condition range of photovoltaic converter.

Description

Technical Field

[0001] This invention relates to the field of power electronics technology, specifically to a soft-switching domain optimization control method and system for a DAB converter. Background Technology

[0002] To address global climate change, the penetration rate of new energy power generation such as wind power and photovoltaics is increasing daily, and photovoltaic power generation is developing towards large-scale and grid-connected centralization. Dual active DC / DC converters (DABs) have enormous application potential in large-scale photovoltaic power generation due to their advantages such as bidirectional power flow, electrical isolation, and high operating efficiency. Improving the power density and reducing the cost of DABs, and optimizing their operating efficiency through soft switching are key. Traditional single-phase-shift control (SPS) is prone to soft-switching failure when there is voltage mismatch across the DAB, significantly increasing device switching losses, reducing conversion efficiency, and increasing the cost of the cooling system. While dual-phase-shift control (DPS) can extend the soft-switching operating range, it increases the complexity of the control algorithm. Summary of the Invention

[0003] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the traditional single-phase-shift control method in the prior art, which is prone to soft-switching failure and significantly increases the switching losses of the device when the voltages on both sides of the DAB are mismatched, and the shortcomings of the dual-phase-shift control method, which increases the complexity of the control algorithm. Thus, a soft-switching domain optimization control method and system for DAB converter is provided.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] In a first aspect, embodiments of the present invention provide a soft-switching domain optimization control method for a DAB converter. The primary side of the DAB converter is connected to a photovoltaic panel, and the secondary side of the DAB converter is connected to a grid-connected DC unit. The method includes: calculating the boundary values ​​of the soft-switching region control quantities, the zero-voltage duty cycle, and the shift ratio based on a photovoltaic voltage reference value, real-time acquisition of the voltage of the voltage divider capacitor on the primary side of the DAB converter, and the output voltage on the secondary side; determining the duty cycle command and shift ratio command of the DAB converter based on the boundary values ​​of the soft-switching region control quantities, the zero-voltage duty cycle, and the shift ratio, combined with a hysteresis control method; correcting the duty cycle command of the DAB converter using a voltage balancing method based on the real-time acquisition of the voltage divider capacitor voltage on the primary side of the DAB converter; and obtaining a switching trigger signal of the DAB converter based on the corrected duty cycle command and shift ratio command using a preset modulation method. The switching trigger signal is used to control the operating state of the DAB converter.

[0006] In one embodiment, the DAB converter consists of an ANPC converter, a high-frequency transformer, and an H-bridge converter. The ANPC converter and the H-bridge converter are connected through the high-frequency transformer. The process of calculating the boundary values ​​of the control quantity in the soft-switching region includes: acquiring the voltage of the voltage divider capacitor on the primary side and the output voltage on the secondary side of the DAB converter; calculating the voltage matching coefficient on both sides of the DAB based on the voltage divider capacitor voltage, the output voltage on the secondary side, and the turns ratio of the high-frequency transformer; and calculating the boundary values ​​of the control quantity in the soft-switching region based on the dead time of the internal components of the DAB converter, the switching frequency, and the voltage matching coefficient on both sides of the DAB. The boundary values ​​of the control quantity in the soft-switching region include: the upper boundary value of the shift ratio, the upper boundary value of the duty cycle, and the lower boundary value of the duty cycle.

[0007] In one embodiment, the process of calculating the zero-voltage duty cycle and the shift ratio includes: acquiring the voltages of the two voltage-dividing capacitors on the primary side of the DAB converter and the output voltage on the secondary side; calculating the photovoltaic voltage based on the voltages of the two voltage-dividing capacitors on the primary side of the DAB converter and the output voltage on the secondary side; obtaining the zero-voltage duty cycle by proportionally integrating the difference between the photovoltaic voltage reference value and the photovoltaic voltage; and obtaining the shift ratio by proportionally integrating the difference between the photovoltaic voltage reference value and the photovoltaic voltage after inverting the difference.

[0008] In one embodiment, the process of determining the duty cycle command and shift ratio command of the DAB converter based on the soft-switching region control boundary value, zero-voltage duty cycle, and shift ratio, combined with the hysteresis control method, includes: using the soft-switching region control boundary value to divide the DAB converter into two operating modes corresponding to different operating power; selecting the corresponding operating mode based on the shift ratio, the boundary minimum of the shift ratio, the soft-switching region control boundary value, and the hysteresis control parameters, thereby determining the duty cycle command and shift ratio command of the DAB converter.

[0009] In one embodiment, the process of selecting the corresponding operating mode to determine the duty cycle command and shift ratio command of the DAB converter includes: determining whether the shift ratio is within a preset range of the upper boundary value of the shift ratio based on the boundary minimum value of the shift ratio; when the shift ratio is not within the preset range of the upper boundary value of the shift ratio, comparing the shift ratio with the upper boundary value of the shift ratio, and determining the duty cycle command and shift ratio command of the DAB converter based on the comparison result; when the shift ratio is within the preset range of the upper boundary value of the shift ratio, determining the soft-switching duty cycle command and soft-switching shift ratio command of the DAB converter based on the hysteresis control parameters.

[0010] In one embodiment, the process of determining the duty cycle command and shift ratio command of the DAB converter based on the comparison result includes: when the shift ratio is greater than the upper boundary value of the shift ratio, the lower boundary value of the duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the shift ratio command of the DAB converter; when the shift ratio is less than the upper boundary value of the shift ratio, the upper boundary value of the duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the shift ratio command of the DAB converter; when the shift ratio is equal to the upper boundary value of the shift ratio, the zero voltage duty cycle is used as the duty cycle command of the DAB converter, and the upper boundary value of the shift ratio is used as the shift ratio command of the DAB converter.

[0011] In one embodiment, two hysteresis loops are set. The process of calculating the hysteresis loop control parameters includes: adding a minimum amount to the upper boundary value of the shift ratio and the boundary of the shift ratio as the first parameter of the upper hysteresis loop; adding the first parameter of the upper hysteresis loop and the hysteresis loop width as the second parameter of the upper hysteresis loop; adding a minimum amount to the difference between the upper boundary value of the shift ratio and the boundary of the shift ratio as the first parameter of the lower hysteresis loop; and adding the difference between the first parameter of the lower hysteresis loop and the hysteresis loop width as the second parameter of the lower hysteresis loop.

[0012] In one embodiment, the process of determining the duty cycle command and shift ratio command of the DAB converter based on the hysteresis control parameters includes: when the upper hysteresis is in a high position, using the lower boundary value of the duty cycle as the duty cycle command of the DAB converter and the shift ratio as the shift ratio command of the DAB converter; when the lower hysteresis is in a low position, using the upper boundary value of the duty cycle as the duty cycle command of the DAB converter and the shift ratio as the shift ratio command of the DAB converter; when the upper hysteresis is not in a high position and the lower hysteresis is not in a low position, using the zero voltage duty cycle as the duty cycle command of the DAB converter and the upper boundary value of the shift ratio as the shift ratio command of the DAB converter.

[0013] In one embodiment, the process of correcting the duty cycle command of the DAB converter by using a voltage balancing method based on the real-time acquisition of the voltage of the primary side voltage divider capacitors of the DAB converter includes: acquiring the voltage of the two voltage divider capacitors on the primary side of the DAB converter; obtaining the duty cycle fine-tuning amount by proportional and limiting the difference between the voltages of the two voltage divider capacitors; and correcting the duty cycle of the positive and negative levels of the ANPC converter using the duty cycle fine-tuning amount.

[0014] Secondly, embodiments of the present invention provide a soft-switching domain optimization control system for a DAB converter, comprising: a first calculation module, used to calculate the boundary values ​​of the soft-switching region control quantities, the zero-voltage duty cycle, and the shift ratio based on a photovoltaic voltage reference value, real-time acquisition of the primary-side voltage divider capacitor voltage and the secondary-side output voltage of the DAB converter; a second calculation module, used to determine the duty cycle command and shift ratio command of the DAB converter based on the boundary values ​​of the soft-switching region control quantities, the zero-voltage duty cycle, and the shift ratio, combined with a hysteresis control method; a correction module, used to correct the duty cycle command of the DAB converter based on the real-time acquisition of the primary-side voltage divider capacitor voltage of the DAB converter using a voltage balance method; and a modulation module, used to obtain a switching trigger signal of the DAB converter based on the corrected duty cycle command and shift ratio command of the DAB converter using a preset modulation method, wherein the switching trigger signal is used to control the operating state of the DAB converter.

[0015] Thirdly, embodiments of the present invention provide a computer device, including: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the DAB converter soft-switching domain optimization control method of the first aspect of the present invention.

[0016] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer instructions for causing a computer to execute the DAB converter soft-switching domain optimization control method of the first aspect of the present invention.

[0017] The technical solution of this invention has the following advantages:

[0018] The present invention provides a DAB converter soft-switching domain optimization control method and system. Based on the photovoltaic voltage reference value, real-time acquisition of the primary-side voltage divider capacitor voltage and secondary-side output voltage of the DAB converter, the boundary values ​​of the soft-switching region control quantities, the zero-voltage duty cycle, and the phase shift ratio are calculated. Based on the soft-switching region control quantity boundary values, the zero-voltage duty cycle, and the phase shift ratio, combined with a hysteresis control method, the duty cycle command and phase shift ratio command of the DAB converter are determined. Based on the real-time acquisition of the primary-side voltage divider capacitor voltage of the DAB converter, the duty cycle command of the DAB converter is corrected using a voltage balancing method. Based on the corrected duty cycle command and phase shift ratio command of the DAB converter, a preset modulation method is used to obtain the switching trigger signal of the DAB converter, which is used to control the operating state of the DAB converter. This invention utilizes the adjustable duty cycle capability and adopts an optimized phase shift control strategy, which, compared to the traditional single-phase shift control strategy, significantly improves the soft-switching operation capability of the DAB converter near half-load and enhances the operating efficiency of the photovoltaic converter across the entire operating range. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a DAB converter topology diagram provided in an embodiment of the present invention;

[0021] Figure 2 The AC voltage and current waveforms of the ANPC half-bridge DAB provided in the embodiments of the present invention;

[0022] Figure 3 This is a schematic diagram of the DAB soft-switching operation boundary provided in an embodiment of the present invention;

[0023] Figure 4 A flowchart illustrating a specific example of the optimization control method provided in this embodiment of the invention;

[0024] Figure 5 This is a block diagram of the DAB optimization control strategy provided in an embodiment of the present invention;

[0025] Figure 6 This is a flowchart of the DAB control mode switching provided in an embodiment of the present invention;

[0026] Figure 7 A composition diagram of a specific example of the optimization control system provided in an embodiment of the present invention;

[0027] Figure 8 This is a composition diagram of a specific example of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0031] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] With the increase in DC voltage of photovoltaic modules, photovoltaic converter units are increasingly adopting three-level topology. The three-level half-bridge can naturally output a voltage square wave with an adjustable duty cycle. The DAB with a three-level half-bridge in the front stage and an H-bridge in the back stage also has dual control degrees of freedom, which can optimize the operation of the DAB. Figure 1 The DAB circuit structure for photovoltaic applications uses an active neutral-point clamped three-level circuit (ANPC) on the primary side and an H-bridge circuit on the secondary side. The two sides are connected by a high-frequency transformer. The primary side is connected to the photovoltaic panel, and the secondary side is connected to the DC unit of the grid-connected device. L1 represents the commutation inductance, which includes the equivalent leakage inductance of the high-frequency transformer and the sum of the auxiliary inductance. U1 and U2 represent the ANPC and H-bridge square wave voltages on the photovoltaic side of the transformer, respectively.

[0034] Figure 2 The operating voltage and current waveforms of the DAB converter in this embodiment of the invention are shown below. Figure 2 It can be seen that controlling the duty cycle and shift ratio can adjust the average value of the inductor current, thereby controlling the DAB transmission power.

[0035] Figure 3For different voltage matching condition coefficients k, the DAB operates in the soft-switching power region, with U1 as the reference and U2 represented by k. The power is expressed as the maximum power P. n Using this as a reference, the power boundary values ​​for different k are obtained as follows:

[0036]

[0037] In the formula P min This represents the soft-switching power boundary value when k < 1. Below this value, soft switching will fail. edg This represents the power switching boundary between the two soft-switching modes when k>1. Considering a maximum photovoltaic voltage of 1500V and an output voltage of 1000V, photovoltaic systems can generally operate in a soft-switching state.

[0038] To achieve soft-switching operation across the entire photovoltaic operating range, this invention optimizes the duty cycle of the ANPC half-bridge and the phase shift angle of the voltage waveforms on both sides, enabling the DAB to achieve high-efficiency operation. The soft-switching domain optimization control method for the DAB converter provided in this invention includes, for example... Figure 4 As shown, it includes:

[0039] Step S11: Based on the photovoltaic voltage reference value, the real-time acquisition of the voltage divider capacitor voltage on the primary side of the DAB converter and the output voltage on the secondary side, calculate the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio.

[0040] Optionally, the DAB converter consists of an ANPC converter, a high-frequency transformer, and an H-bridge converter. The ANPC converter and the H-bridge converter are connected through the high-frequency transformer. The process of calculating the boundary values ​​of the control quantity in the soft-switching region includes:

[0041] (1) Collect the voltage of the primary side voltage divider capacitor and the secondary side output voltage of the DAB converter.

[0042] (2) Calculate the voltage matching coefficients on both sides of DAB based on the voltage of the voltage divider capacitor, the output voltage on the secondary side and the turns ratio of the high-frequency transformer.

[0043] Specifically, the voltage U of the voltage divider capacitor on the primary side of the DAB is collected. c1 and U c2 Output voltage U dc2 Calculated photovoltaic voltage U pv The sum of the voltage divider capacitors and the voltage matching coefficient k across DAB are expressed as follows:

[0044]

[0045] In the formula, n represents the turns ratio of the secondary side to the primary side of the high-frequency transformer.

[0046] (3) Based on the dead time of the internal devices of the DAB converter, the switching frequency and the voltage matching coefficient on both sides of the DAB, calculate the boundary values ​​of the control quantity in the soft switching region. The boundary values ​​of the control quantity in the soft switching region include: the upper boundary value of the shift ratio, the upper boundary value of the duty cycle and the lower boundary value of the duty cycle.

[0047] Specifically, the boundary values ​​of the control quantity in the soft-switching region are calculated based on the voltage matching coefficient k, and the dual control quantity is defined as follows:

[0048]

[0049] In the formula, D α D β These are the zero-voltage duty cycle and the shift ratio, respectively.

[0050] The boundary expression for the control quantity is:

[0051]

[0052] In the formula, t d f represents the device dead time. s D represents the switching frequency. αmin D is the lower boundary value of the duty cycle. αedg D is the upper boundary value of the duty cycle. βedg The shift is compared to the upper boundary value.

[0053] Optionally, the process of calculating the zero-voltage duty cycle and the shift phase includes:

[0054] (1) Collect the voltage of the two voltage divider capacitors on the primary side of the DAB converter and the output voltage on the secondary side.

[0055] (2) Calculate the photovoltaic voltage based on the voltage of the two voltage divider capacitors on the primary side of the DAB converter and the output voltage on the secondary side.

[0056] (3) By proportionally integrating the difference between the photovoltaic voltage reference value and the photovoltaic voltage, the zero voltage duty cycle D is obtained. α1 By inverting the difference between the photovoltaic reference value and the photovoltaic voltage and then performing proportional integration, the shift ratio D is obtained. β1 .

[0057] Specifically, Figure 5 This is a block diagram of the DAB optimized control strategy of the present invention, with the photovoltaic voltage reference value U. pvref With the actual value of photovoltaic voltage U pv The difference is used to obtain the error ΔU pv The input PI controller generates the control input, where PI controller I generates a zero-voltage duty cycle D. α1 The PI controller II generates a reverse shift compared to -D β1 .

[0058] Step S12: Based on the boundary values ​​of the soft-switching region control quantity, the zero-voltage duty cycle, and the shift ratio, and combined with the hysteresis control method, determine the duty cycle command and shift ratio command of the DAB converter.

[0059] Specifically, in this embodiment of the invention, to avoid displacement compared to D β1 At the upper boundary D of the shift ratio βedg When there are fluctuations in the vicinity, the calculated duty cycle command and shift ratio command of the DAB converter change frequently. Hysteresis is used to avoid the above situation.

[0060] Optionally, the process of determining the duty cycle command and shift ratio command of the DAB converter based on the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio, combined with the hysteresis control method, includes: (1) using the boundary value of the soft-switching region control quantity to divide the DAB converter into two operating modes corresponding to different operating powers; (2) selecting the corresponding operating mode based on the shift ratio, the boundary minimum of the shift ratio, the boundary value of the soft-switching region control quantity, and the hysteresis control parameters, so as to determine the duty cycle command and shift ratio command of the DAB converter.

[0061] Optionally, selecting the corresponding operating mode to determine the duty cycle command and shift ratio command of the DAB converter includes:

[0062] (1) Based on the minimum value added to the boundary of the shift ratio, determine whether the shift ratio is within the preset range of the upper boundary value of the shift ratio.

[0063] Specifically, by using zero voltage shift ratio D β1 The boundary of the shift ratio is supplemented with a minimum value Δ and the hysteresis width to determine the zero-voltage shift ratio D. β1 Is it at the boundary value D of the shift ratio? βdeg Nearby, where two hysteresis loops are set, the process of calculating the hysteresis control parameters includes:

[0064] ①The sum of the minimum value of the upper boundary value of the shift phase and the boundary value of the zero voltage shift phase is taken as the first parameter of the upper hysteresis; the sum of the first parameter of the upper hysteresis and the hysteresis width is taken as the second parameter of the upper hysteresis.

[0065] ②The difference between the minimum value of the upper boundary value of the shift phase and the boundary value of the zero voltage shift phase is taken as the first parameter of the lower hysteresis; the difference between the first parameter of the lower hysteresis and the hysteresis width is taken as the second parameter of the lower hysteresis.

[0066] Specifically, if the hysteresis width is set to h, then D β1 The expressions for the upper and lower hysteresis loops when crossing the boundary are:

[0067]

[0068] In the formula, Δ is to ensure Dβ It can operate at a minimum of its boundary values, where h′1 is the first parameter of the lower hysteresis loop, h1 is the second parameter of the lower hysteresis loop, h′2 is the first parameter of the upper hysteresis loop, and h2 is the second parameter of the upper hysteresis loop.

[0069] (2) When the shift ratio is not within the preset range of the upper boundary value of the shift ratio, compare the size of the shift ratio with the upper boundary value of the shift ratio, and determine the duty cycle command and shift ratio command of the DAB converter based on the comparison result.

[0070] Specifically, when the shift is compared to D β1 The shift ratio of the DAB converter is not at the upper boundary value D. βdeg When the location is nearby, the process of determining the duty cycle command and shift ratio command of the DAB converter includes:

[0071] ① When the shift ratio is greater than the upper boundary value of the shift ratio, the lower boundary value of the duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the shift ratio command of the DAB converter.

[0072] ② When the shift ratio is less than the upper boundary value of the shift ratio, the upper boundary value of the duty cycle is used as the duty cycle instruction of the DAB converter, and the shift ratio is used as the shift ratio instruction of the DAB converter.

[0073] ③ When the shift ratio is equal to the upper boundary value of the shift ratio, the zero voltage duty cycle is used as the duty cycle command of the DAB converter, and the upper boundary value of the shift ratio is used as the shift ratio command of the DAB converter.

[0074] Specifically, according to D β1 Select DAB operating mode based on the relationship between D and the size of the control boundary: If D β1 >D βedg Then take the shift ratio of the DAB converter to D βref =D β1 The duty cycle D of the DAB converter αref =D αmin If D β1 <D βedg Then take D. βref =D β1 D αref =D αedg If D β1 =D βedg Then take D. βref =D βedg D αref =D α1 To prevent ANPC from directly accessing the half-bridge, D αref Minimum amplitude at D αmin .

[0075] (3) When the shift ratio is within the preset range of the upper boundary value of the shift ratio, the soft switching duty cycle command and the soft switching shift ratio command of the DAB converter are determined according to the hysteresis control parameters.

[0076] Specifically, when the shift is compared to D β1 The boundary value D is shifted relative to the upper boundary value. βedg When the location is nearby, the process of determining the duty cycle command and shift ratio command of the DAB converter includes:

[0077] ① When the upper hysteresis loop is in the high position, the lower boundary value of the duty cycle is used as the duty cycle instruction of the DAB converter, and the shift ratio is used as the shift ratio instruction of the DAB converter.

[0078] ②When the current hysteresis is in the low position, the upper boundary value of the duty cycle is used as the duty cycle instruction of the DAB converter, and the shift ratio is used as the shift ratio instruction of the DAB converter.

[0079] ③ When the upper hysteresis is not in a high position and the lower hysteresis is not in a low position, the zero voltage duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the upper boundary value as the shift ratio command of the DAB converter.

[0080] Specifically, such as Figure 6 As shown, to prevent D β1 In D βedg When the near-terminal fluctuations occur, the mode frequently switches. Two hysteresis loops are introduced for mode switching. When the lower hysteresis loop H1 is at a low level, D αref =D αedg The shift ratio of the DAB converter compared to the instruction D βref =D β1 When the upper hysteresis loop H2 is at a high level, D αref =D αmin The shift ratio of the DAB converter compared to the instruction D βref =D β1 The remaining states will be D β1 Frozen in D βedg And D αref =D α1 .

[0081] Step S13: Based on the real-time acquisition of the voltage divider capacitor voltage on the primary side of the DAB converter, the duty cycle command of the DAB converter is corrected using a voltage balancing method.

[0082] Optionally, to prevent imbalance of the ANPC voltage divider capacitor, a voltage balancing strategy is added to the duty cycle, including:

[0083] ① Collect the voltage of the two voltage divider capacitors on the primary side of the DAB converter.

[0084] ②After proportional and limiting control of the voltage difference between the two voltage divider capacitors, the duty cycle fine-tuning amount is obtained.

[0085] ③ Use duty cycle fine-tuning to correct the duty cycle commands for the positive and negative levels of the ANPC converter.

[0086] Specifically, such as Figure 5 As shown, the voltage difference between the upper and lower voltage divider capacitors is processed by the P controller to obtain the duty cycle fine-tuning amount ΔD. The expression for the duty cycle of the upper and lower bridges is:

[0087]

[0088] In the formula, D αpref D αnref Corrected duty cycle of ANPC upper and lower bridge arm devices, k b This is the proportional coefficient of the P controller.

[0089] Step S14: Based on the corrected duty cycle command and shift ratio command of the DAB converter, the switch trigger signal of the DAB converter is obtained using a preset modulation method. The switch trigger signal is used to control the operating state of the DAB converter.

[0090] Specifically, such as Figure 5 As shown, D αpref D αnref and D βref All inputs are to the ANPC modulation module, and the secondary H-bridge modulation module outputs a constant 50% voltage square wave modulation signal as a reference.

[0091] It should be noted that the ANPC half-bridge DAB soft-switching region optimization control strategy provided in this embodiment of the invention is not limited to DAB modules used in the photovoltaic power generation field, but can also be used for DAB modules belonging to other converters such as DC transformers; the full-condition soft-switching region representation method includes, but is not limited to, topologies such as ANPC half-bridge DAB converters and two-sided H-bridge DAB converters.

[0092] Example 2

[0093] This invention provides a soft-switching domain optimization control system for a DAB converter, such as... Figure 7 As shown, it includes:

[0094] The first calculation module 1 is used to calculate the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio based on the photovoltaic voltage reference value, the real-time acquisition of the voltage of the primary side voltage divider capacitor and the secondary side output voltage of the DAB converter; this module executes the method described in step S11 of embodiment 1, which will not be repeated here.

[0095] The second calculation module 2 is used to determine the duty cycle command and shift ratio command of the DAB converter based on the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio, combined with the hysteresis control method. This module executes the method described in step S12 of embodiment 1, which will not be repeated here.

[0096] The correction module 3 is used to correct the duty cycle command of the DAB converter based on the real-time acquisition of the voltage divider capacitor voltage on the primary side of the DAB converter and using a voltage balancing method. This module executes the method described in step S13 of embodiment 1, which will not be repeated here.

[0097] Modulation module 4 is used to obtain the switch trigger signal of the DAB converter based on the corrected duty cycle command and shift ratio command of the DAB converter using a preset modulation method. The switch trigger signal is used to control the operating state of the DAB converter. This module executes the method described in step S1 of embodiment 14, which will not be repeated here.

[0098] Example 3

[0099] This invention provides a computer device, such as... Figure 8 As shown, the system includes: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, a memory 404, and at least one communication bus 402. The communication bus 402 is used to enable communication between these components. The communication interface 403 may include a display screen or a keyboard; optionally, the communication interface 403 may also include a standard wired interface or a wireless interface. The memory 404 may be high-speed RAM (Random Access Memory) or non-volatile memory, such as at least one disk storage device. Optionally, the memory 404 may also be at least one storage device located remotely from the processor 401. The processor 401 can execute the DAB converter soft-switching domain optimization control method of Embodiment 1. The memory 404 stores a set of program code, and the processor 401 calls the program code stored in the memory 404 to execute the DAB converter soft-switching domain optimization control method of Embodiment 1.

[0100] The communication bus 402 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The communication bus 402 can be divided into an address bus, a data bus, and a control bus, etc. For ease of representation, Figure 8 The symbol is represented by only one line, but this does not mean that there is only one bus or one type of bus.

[0101] The memory 404 may include volatile memory, such as random-access memory (RAM); the memory may also include non-volatile memory, such as flash memory, hard disk drive (HDD) or solid-state drive (SSD); the memory 404 may also include a combination of the above types of memory.

[0102] The processor 401 can be a central processing unit (CPU), a network processor (NP), or a combination of CPU and NP.

[0103] The processor 401 may further include a hardware chip. This hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0104] Optionally, the memory 404 is also used to store program instructions. The processor 401 can call the program instructions to implement the DAB converter soft-switching domain optimization control method as described in Embodiment 1 of this application.

[0105] This invention also provides a computer-readable storage medium storing computer-executable instructions that can execute the DAB converter soft-switching domain optimization control method of Embodiment 1. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk drive (HDD), or solid-state drive (SSD), etc.; the storage medium may also include combinations of the above types of memory.

[0106] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A soft-switching domain optimization control method for a DAB converter, wherein the primary side of the DAB converter is connected to a photovoltaic panel, and the secondary side of the DAB converter is connected to a grid-connected DC unit, characterized in that, include: Based on the photovoltaic voltage reference value, the real-time acquisition of the primary side voltage divider capacitor voltage and the secondary side output voltage of the DAB converter, the boundary value of the soft-switching region control quantity, the zero voltage duty cycle and the shift ratio are calculated. Based on the boundary values ​​of the soft-switching region control quantity, the zero-voltage duty cycle, and the shift ratio, combined with the hysteresis control method, the duty cycle command and the shift ratio command of the DAB converter are determined. Based on the real-time acquisition of the voltage of the primary side voltage divider capacitor of the DAB converter, the duty cycle command of the DAB converter is corrected using a voltage balancing method. Based on the corrected duty cycle command and shift ratio command of the DAB converter, a switch trigger signal of the DAB converter is obtained using a preset modulation method. The switch trigger signal is used to control the operating state of the DAB converter. The DAB converter consists of an ANPC converter, a high-frequency transformer, and an H-bridge converter. The ANPC converter and the H-bridge converter are connected through the high-frequency transformer. The process of calculating the boundary values ​​of the soft-switching region control quantity includes: acquiring the voltage of the primary side voltage divider capacitor and the secondary side output voltage of the DAB converter; calculating the voltage matching coefficient on both sides of the DAB based on the voltage of the voltage divider capacitor, the secondary side output voltage, and the turns ratio of the high-frequency transformer; and calculating the boundary values ​​of the soft-switching region control quantity based on the dead time of the internal components of the DAB converter, the switching frequency, and the voltage matching coefficient on both sides of the DAB. The boundary values ​​of the soft-switching region control quantity include: the upper boundary value of the shift ratio, the upper boundary value of the duty cycle, and the lower boundary value of the duty cycle. The lower boundary value of the duty cycle is calculated based on the device dead time and switching frequency, while the upper boundary values ​​of the duty cycle and shift ratio are calculated based on the voltage matching coefficients on both sides of the DAB. The expression for the voltage matching coefficient across DAB is as follows: In the formula, This represents the voltage matching coefficient across DAB, and n represents the turns ratio of the secondary side to the primary side of the high-frequency transformer. U c1 and U c2 Both represent the voltage of the primary side voltage divider capacitor of DAB. U dc2 Indicates the output voltage; The boundary expression for the control quantity is: In the formula, t d Indicates the device dead time. f s Indicates the switching frequency. D αmin This is the lower boundary value of the duty cycle. This is the upper boundary value of the duty cycle. The shift is compared to the upper boundary value.

2. The DAB converter soft-switching domain optimization control method according to claim 1, characterized in that, The process of calculating the zero-voltage duty cycle and the phase shift includes: The voltages of the two voltage divider capacitors on the primary side and the output voltage on the secondary side of the DAB converter are collected. The photovoltaic voltage is calculated based on the voltage of the two voltage divider capacitors on the primary side and the output voltage on the secondary side of the DAB converter. The zero-voltage duty cycle is obtained by proportionally integrating the difference between the photovoltaic voltage reference value and the photovoltaic voltage. The shift ratio is obtained by proportionally integrating the difference between the photovoltaic voltage reference value and the photovoltaic voltage after inverting it.

3. The DAB converter soft-switching domain optimization control method according to claim 1, characterized in that, The process of determining the duty cycle command and shift ratio command of the DAB converter based on the soft-switching region control boundary value, zero-voltage duty cycle, and shift ratio, combined with the hysteresis control method, includes: Using the boundary value of the soft-switching region control quantity, the DAB converter is divided into two operating modes corresponding to different operating power. Based on the shift ratio, the boundary minimum of the shift ratio, the boundary value of the soft-switching region control quantity, and the hysteresis control parameters, the corresponding operating mode is selected to determine the duty cycle command and shift ratio command of the DAB converter.

4. The DAB converter soft-switching domain optimization control method according to claim 3, characterized in that, The process of selecting the corresponding operating mode to determine the duty cycle instruction and shift ratio instruction of the DAB converter includes: Based on the minimum value added to the boundary of the shift ratio, determine whether the shift ratio is within the preset range of the upper boundary value of the shift ratio; When the shift ratio is not within the preset range of the upper boundary value of the shift ratio, the shift ratio is compared with the upper boundary value of the shift ratio, and based on the comparison result, the duty cycle command and shift ratio command of the DAB converter are determined. When the shift ratio is within the preset range of the upper boundary value of the shift ratio, the soft-switching duty cycle command and the soft-switching shift ratio command of the DAB converter are determined according to the hysteresis control parameters.

5. The DAB converter soft-switching domain optimization control method according to claim 4, characterized in that, Based on the comparison results, the process of determining the duty cycle command and shift ratio command of the DAB converter includes: When the shift ratio is greater than the upper boundary value of the shift ratio, the lower boundary value of the duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the shift ratio command of the DAB converter. When the shift ratio is less than the upper boundary value of the shift ratio, the upper boundary value of the duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the shift ratio command of the DAB converter. When the shift ratio is equal to the upper boundary value of the shift ratio, the zero voltage duty cycle is used as the duty cycle command of the DAB converter, and the upper boundary value of the shift ratio is used as the shift ratio command of the DAB converter.

6. The DAB converter soft-switching domain optimization control method according to claim 4, characterized in that, If two hysteresis loops are set, the process of calculating the hysteresis control parameters includes: The sum of the upper boundary value of the shift ratio and the boundary of the shift ratio plus a minimum amount is used as the first parameter of the upper hysteresis loop; the sum of the first parameter of the upper hysteresis loop and the hysteresis loop width is used as the second parameter of the upper hysteresis loop. The difference between the upper boundary value of the shift ratio and the boundary value of the shift ratio is added by a very small amount and used as the first parameter of the lower hysteresis loop; the difference between the first parameter of the lower hysteresis loop and the hysteresis loop width is used as the second parameter of the lower hysteresis loop.

7. The DAB converter soft-switching domain optimization control method according to claim 6, characterized in that, The process of determining the duty cycle command and shift ratio command of the DAB converter based on the hysteresis control parameters includes: When the upper hysteresis is in the high position, the lower boundary value of the duty cycle is used as the duty cycle instruction of the DAB converter, and the shift ratio is used as the shift ratio instruction of the DAB converter. When the current hysteresis is in the low position, the upper boundary value of the duty cycle is used as the duty cycle instruction of the DAB converter, and the shift ratio is used as the shift ratio instruction of the DAB converter. When the upper hysteresis loop is not in a high position and the lower hysteresis loop is not in a low position, the zero voltage duty cycle is used as the duty cycle command of the DAB converter, and the shift ratio is used as the upper boundary value as the shift ratio command of the DAB converter.

8. The DAB converter soft-switching domain optimization control method according to claim 1, characterized in that, The process of correcting the duty cycle command of the DAB converter based on the real-time acquisition of the primary side voltage divider capacitor voltage and using a voltage balancing method includes: The voltages of the two voltage-dividing capacitors on the primary side of the DAB converter are collected; The duty cycle fine-tuning amount is obtained by proportionally and limiting the voltage difference between the two voltage divider capacitors. The duty cycle fine-tuning amount is used to correct the duty cycle commands for the positive and negative levels of the ANPC converter.

9. A soft-switching domain optimization control system for a DAB converter, characterized in that, include: The first calculation module is used to calculate the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio based on the photovoltaic voltage reference value, the real-time acquisition of the voltage of the primary side voltage divider capacitor and the secondary side output voltage of the DAB converter; The second calculation module is used to determine the duty cycle command and shift ratio command of the DAB converter based on the boundary value of the soft-switching region control quantity, the zero-voltage duty cycle and the shift ratio, combined with the hysteresis control method. The correction module is used to correct the duty cycle command of the DAB converter based on the real-time acquisition of the voltage divider capacitor voltage on the primary side of the DAB converter and using a voltage balancing method. The modulation module is used to obtain the switch trigger signal of the DAB converter based on the corrected duty cycle command and shift ratio command of the DAB converter using a preset modulation method. The switch trigger signal is used to control the operating state of the DAB converter. The DAB converter consists of an ANPC converter, a high-frequency transformer, and an H-bridge converter. The ANPC converter and the H-bridge converter are connected through the high-frequency transformer. The process of calculating the boundary values ​​of the soft-switching region control quantity includes: acquiring the voltage of the primary side voltage divider capacitor and the secondary side output voltage of the DAB converter; calculating the voltage matching coefficient on both sides of the DAB based on the voltage of the voltage divider capacitor, the secondary side output voltage, and the turns ratio of the high-frequency transformer; and calculating the boundary values ​​of the soft-switching region control quantity based on the dead time of the internal components of the DAB converter, the switching frequency, and the voltage matching coefficient on both sides of the DAB. The boundary values ​​of the soft-switching region control quantity include: the upper boundary value of the shift ratio, the upper boundary value of the duty cycle, and the lower boundary value of the duty cycle. The lower boundary value of the duty cycle is calculated based on the device dead time and switching frequency, while the upper boundary values ​​of the duty cycle and shift ratio are calculated based on the voltage matching coefficients on both sides of the DAB. The expression for the voltage matching coefficient across DAB is as follows: In the formula, This represents the voltage matching coefficient across DAB, and n represents the turns ratio of the secondary side to the primary side of the high-frequency transformer. U c1 and U c2 Both represent the voltage of the primary side voltage divider capacitor of DAB. U dc2 Indicates the output voltage; The boundary expression for the control quantity is: In the formula, t d Indicates the device dead time. f s Indicates the switching frequency. D αmin This is the lower boundary value of the duty cycle. This is the upper boundary value of the duty cycle. The shift is compared to the upper boundary value.

10. A computer device, characterized in that, include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the DAB converter soft-switching domain optimization control method according to any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to execute the DAB converter soft-switching domain optimization control method according to any one of claims 1-8.

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