Transient DC bias suppression method and system for converter, medium and equipment

Abstract

The invention relates to the technical field of converters, and provides a converter transient DC bias suppression method and system, a medium and equipment, and the method comprises the steps: in response to a current track switching instruction, switching an A-phase duty ratio and a B-phase duty ratio of a three-phase dual-active bridge converter to intermediate duty ratio parameters and switching a C-phase duty ratio to a target duty ratio in a half-switching period, the A-phase phase shift of the three-phase dual-active bridge converter is switched into the initial phase shift before switching, the B-phase phase shift is a middle initial phase shift correlation value, and the C-phase phase shift is switched into the C-phase shift after switching; wherein the initial phase shift before switching and the initial phase shift after switching are both related to the current duty ratio, and the intermediate initial phase shift and the intermediate duty ratio parameter are both related to the target duty ratio and the duty ratio before switching. Therefore, in the process of increasing the duty ratio, the current track can be stably and smoothly transited to a new steady state from an initial state, so that the generation of direct current bias is effectively inhibited.

Description

Technical Field

[0001] The present invention belongs to the technical field of converters, and in particular relates to a method, system, medium and equipment for suppressing transient direct current bias of a converter. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The three-phase dual active bridge (DAB3) converter topology was proposed in 1988 together with the single-phase dual active (DAB1) converter. It is a well-known topology for high-power DC (direct current)-DC conversion. Due to its many advantages such as bidirectional power flow, soft switching, high conversion ratio, electrical isolation, high power density, and convenient series and parallel connection, the DAB3 converter has received great attention in modern power electronics applications. Compared with DAB1, DAB3 has higher power transmission capability, smaller DC capacitance, and higher power density.

[0004] Single Phase Shift (SPS) control is the simplest control strategy for the DAB3 converter. Existing methods control the transformer current trajectory by introducing transient phase shift and implement current dynamic control to suppress DC bias. However, this method is only applicable to SPS control. When used to analyze duty cycle control, the total current trajectory will be very complicated and the switching process analysis will be difficult.

[0005] In order to improve the performance of the DAB3 converter, the duty cycle was proposed. On the basis of single phase shift control, pulse width control was added to transmit power through three control variables, greatly expanding the soft switching range. However, when the control variables change, the DAB3 converter will have volt-second imbalance, resulting in transient DC bias in the transformer winding voltage.

[0006] The prior art proposes a fast current control in duty cycle control, which suppresses transient DC bias in duty cycle control by simultaneously introducing transient duty cycle and transient phase shift. It can be used for duty cycle control. However, in fast current control, it calculates the transient duty cycle required in the transient process by analyzing the current trajectory of each stage, and its analysis method is very complicated. Moreover, in response to sudden conditions such as sudden increase in duty cycle, sudden decrease in duty cycle, and current reversal, current overshoot will occur, which will not only affect the life of the switch tube, but even cause damage to the switch tube in severe cases, thereby seriously affecting the operation of the converter. Summary of the invention

[0007] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method, system, medium and equipment for suppressing transient DC bias of a converter. Phase shift control is introduced on the basis of changing the duty cycle. The phase shift switching is closely related to the change of the duty cycle, and they work together to adjust the current trajectory, ensuring that in the process of increasing the duty cycle, the current trajectory can stably and smoothly transition from the initial state to a new steady state, thereby effectively suppressing the generation of DC bias.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a method for suppressing transient DC bias of a converter, comprising:

[0010] In response to the current trajectory switching instruction, within a half switching period, the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter are both intermediate duty cycle parameters, the C-phase duty cycle is switched to the target duty cycle, the A-phase phase shift of the three-phase dual active bridge converter is the initial phase shift before switching, the B-phase phase shift is the intermediate initial phase shift related value, and the C-phase phase shift is the C-phase shift after switching;

[0011] Among them, the initial phase shift before switching and the initial phase shift after switching are both related to the current duty cycle, and the intermediate initial phase shift and the intermediate duty cycle parameters are both related to the target duty cycle and the duty cycle before switching.

[0012] Furthermore, the intermediate duty cycle parameters include: Among them, the intermediate duty cycle parameter D c1△ For phase A duty cycle, intermediate duty cycle parameter D c2△ For the B phase duty cycle, D c(k-1) is the duty cycle before switching, D ck is the target duty cycle.

[0013] Furthermore, the initial phase shift before switching is: Among them, D c(k-1) is the duty cycle before switching.

[0014] Furthermore, the phase shifts of the A, B, and C phases of the three-phase dual active bridge converter before switching are

[0015] Furthermore, the intermediate initial phase shift correlation value is The initial phase shift in the middle is =(1-D ck -D c(k-1) ) / 3, where D c(k-1) is the duty cycle before switching, D ck is the target duty cycle.

[0016] Furthermore, after switching, the phase shifts of the three-phase A, B, and C of the three-phase dual active bridge converter are

[0017] Furthermore, the initial phase shift after switching is: Among them, D ck is the target duty cycle.

[0018] A second aspect of the present invention provides a converter transient DC bias suppression system, comprising:

[0019] A control module, which is configured to: in response to a current trajectory switching instruction, switch the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter to the intermediate duty cycle parameters within a half switching period, switch the C-phase duty cycle to the target duty cycle, switch the A-phase phase shift of the three-phase dual active bridge converter to the initial phase shift before switching, the B-phase phase shift to the intermediate initial phase shift related value, and the C-phase phase shift to the C-phase shift after switching;

[0020] Among them, the initial phase shift before switching and the initial phase shift after switching are both related to the current duty cycle, and the intermediate initial phase shift and the intermediate duty cycle parameters are both related to the target duty cycle and the duty cycle before switching.

[0021] A third aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the method for suppressing transient DC bias of a converter as described above.

[0022] A fourth aspect of the present invention provides a computer device, comprising a computer-readable storage medium, a processor, and a computer program stored on the computer-readable storage medium and executable on the processor, wherein when the processor executes the program, the steps in a method for suppressing transient DC bias of a converter as described above are implemented.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention introduces phase shift control on the basis of changing the duty cycle. The phase shift switching is closely related to the change of the duty cycle, and they work together to adjust the current trajectory, ensuring that in the process of increasing the duty cycle, the current trajectory can stably and smoothly transition from the initial state to a new steady state, thereby effectively suppressing the generation of DC bias.

[0025] The calculation formula of the intermediate duty cycle parameter of the present invention is derived based on the trajectory length analysis and the change law of the inductor current, which ensures that the current can transition as smoothly as possible during the switching process and reduces the impact and DC bias caused by sudden changes.

[0026] The present invention enables the DAB3 converter to reach any stable state within a half switching cycle, and the transient DC bias of the winding current is significantly suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 is a schematic diagram of a method for suppressing transient DC bias of a converter according to a first embodiment of the present invention;

[0029] Figure 2 is a topological diagram of a DAB3 converter according to a first embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of a sub-model of the first embodiment of the present invention;

[0031] Figure 4 is a schematic diagram of the switch state and its corresponding vector direction according to the first embodiment of the present invention;

[0032] Figure 5 is a schematic diagram of an equilateral triangle current trajectory of the first embodiment of the present invention;

[0033] Figure 6 is a schematic diagram of a hexagonal current trajectory of the first embodiment of the present invention;

[0034] Figure 7 1 is a schematic diagram of switching of an equilateral triangle current trajectory according to the first embodiment of the present invention;

[0035] Figure 8 Schematic diagram of switching between regular triangle and hexagonal current trajectories according to the first embodiment of the present invention;

[0036] Fig. 9 is a schematic diagram of hexagonal current trajectory switching according to the first embodiment of the present invention;

[0037] Fig.10 It is a structural diagram of a computer device according to a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0038] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0039] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0040] Embodiment 1

[0041] Focusing on three-phase dual active bridge (DAB3) converters, such as Figure 2 As shown, in order to solve the problem of transient DC bias occurring during the duty cycle control process, this embodiment provides a method for suppressing transient DC bias of a converter.

[0042] The present embodiment provides a method for suppressing transient DC bias of a converter. The core of the method is to reasonably regulate the current paths of the primary bridge arm and the secondary bridge arm to ensure that when the control variable changes, the current trajectory of each sub-model can achieve a smooth and unbiased transition, thereby effectively suppressing the transient DC bias and improving the performance and stability of the converter.

[0043] The present embodiment provides a method for suppressing transient DC bias of a converter. Based on the superposition theorem, the current trajectories of the primary and secondary sides are analyzed respectively. By controlling the current trajectories of the primary and secondary bridge arms respectively, DAB3 can be made to reach any stable state within a half switching cycle, and the transient DC bias of the winding current is significantly suppressed.

[0044] This embodiment provides a method for suppressing transient DC bias of a converter, comprising the following steps:

[0045] Step 1: Switch state definition and space vector representation.

[0046] like Figure 2 and Figure 3 As shown in the figure, the DAB3 converter can be divided into two sub-models by superposition theorem. Sub-model 1 corresponds to the current trajectory of the primary side (rectifier unit), and sub-model 2 corresponds to the current trajectory of the secondary side (inverter unit). The current trajectory analysis process of the two sub-models is exactly the same. p1 , Q p2 and Q p3 It is the upper tube of the primary bridge arm of the DAB3 converter, Q p4 , Q p5 and Q p6 It is the lower tube of the primary bridge arm of the DAB3 converter, Q s1 , Q s2 and Q s3 It is the upper tube of the secondary bridge arm of the DAB3 converter, Q s4 , Q s5 and Q s6 It is the lower tube of the secondary bridge arm of the DAB3 converter.

[0047] Under the PWM (pulse width modulation) control mechanism, each three-phase bridge arm of the DAB3 converter has 7 clear switching states, namely q = {1, 2, 3, 4, 5, 6, 7}, such as Figure 4As shown, 1, 2, 3, 4, 5, and 6 correspond to six different switch combinations (for example, 1 represents Q p1 =1,Q p2 =0,Q p3 =1), which represents 6 directions in the α-β coordinates, 7 of which points to the origin and has no direction.

[0048] Among them, the switch state of the primary bridge arm is determined by Q p1 , Q p2 and Q p3 The conduction and cut-off states of the three switch tubes are determined by the switch state of the secondary bridge arm. s1 , Q s2 and Q s3 The on and off states of the three switch tubes determine that the current trajectory of the original secondary side is exactly the same, and the duty cycle of the switch tubes is D c When the three-phase voltage is converted to the α-β coordinate system, the space vector corresponding to each switching state has a specific amplitude and direction.

[0049] Step 2: Correlation between duty cycle and current trajectory shape.

[0050] As the switch duty cycle D c With the change of , the switch state combination of the bridge arm will also change accordingly, which will directly affect the shape of the current trajectory.

[0051] When 0 <D c When <1 / 2, the current trajectory will present two typical shapes: regular triangle and hexagon, such as Figure 5 and Figure 6 As shown, specifically:

[0052] When 0 <D c <1 / 3, when the bridge arm switch state is q={1,3,5,7}, the current trajectory presents an equilateral triangle, such as Figure 5 As shown;

[0053] When 1 / 3 <D c <1 / 2, and when the bridge arm switch states are q={1,2,3,4,5,6}, the current trajectory is a hexagon, such as Figure 6 shown.

[0054] In particular, when D c When =1 / 2, the current trajectory is a regular hexagon, which is the typical current trajectory shape under traditional single-phase phase shift (SPS) control.

[0055] In order to accurately quantify the characteristics of these current trajectories of different shapes, the duration of each switching state of the bridge arm is carefully analyzed, and the length of each trajectory can be accurately calculated, such as Figure 5 and Figure 6As shown:

[0056] For a triangular trajectory, the trajectory length S can be calculated from the switching state time: S = D c ×T s ;

[0057] For the hexagonal trajectory, the long side S1 and the short side S2 also have their own precise calculation formulas: S 1 =(2 / 3-D c )×T s , S 2 =(D c -1 / 3)×T s .

[0058] Among them, T s The characteristic formula of the switching cycle and the trajectory side length provides a solid foundation for the subsequent accurate regulation of the current trajectory when the control variable changes; is the shift ratio between the original and secondary sides, It is the delayed conduction time of each tube on the secondary side relative to the primary side.

[0059] Step 3: Suppress the transient DC bias of the DAB3 converter.

[0060] (1) When dealing with the situation where the duty cycle increases, the duty cycle changes from one triangular current trajectory to another triangular current trajectory, such as Figure 7 As shown in the figure, the trajectory length of the switching process can be calculated through trajectory analysis. This transient trajectory is the initial trajectory D c1△ T s and target trajectory D c2△ T s Among them, the key intermediate duty cycle parameter in the switching process, namely D c1△ and D c2△ The calculation formula is derived based on the trajectory length analysis and the variation law of the inductor current, which ensures that the current can transition as smoothly as possible during the switching process, reducing the impact and DC bias caused by sudden changes:

[0061]

[0062]

[0063] Among them, D c(k-1) is the duty cycle before switching, D ck is the duty cycle after switching.

[0064] (2) Figure 8 and Fig. 9 As shown, in some specific duty cycle increase conditions (D ck>1 / 3), directly switching in the conventional duty cycle will result in switching spikes. This is because during the switching process, the duration of state 2 and state 4 is too long, causing the accumulation and change of current in these states to exceed the ideal range, resulting in a large current mutation, which manifests as a switching spike. In order to solve this problem, phase shift control is introduced on the basis of changing the duty cycle to determine the time T1 and T2 that need to be reduced in state 2 and state 4. By adjusting the phase shift signal, the current in these states can transition more smoothly, avoiding excessive accumulation and mutation of current.

[0065] In order to ensure that the switching frequency of the entire converter is not affected, an initial phase shift is set for the switch signal and the reference signal of each bridge arm. When the duty cycle D c As it increases, an intermediate initial phase shift is further introduced And through Figure 1 The switching signal diagram shown shows the precise coordination relationship between each phase shift signal and the switch tube action, where the horizontal axis of the coordinate, k is a positive integer, kT s is the kth switching cycle moment, (k-1)T S The same goes for the rest. In this process, the size of the phase shift and the timing of its introduction have been carefully designed. They work closely with the change in duty cycle and work together to adjust the current trajectory, ensuring that as the duty cycle increases, the current trajectory can stably and smoothly transition from the initial state to the new steady state, thereby effectively suppressing the generation of DC bias.

[0066] (3)Detailed operations.

[0067] In steady-state operation, the current duty ratios of the A, B, and C phases of the DAB3 converter are all D c(k-1) ; The phase shifts of A, B, and C are The displacement of the secondary bridge arm of the three phases A, B, and C relative to the primary bridge arm is D (k-1) ;D c(k-1) T s is the conduction time of the upper tubes of the three phases A, B, and C; D is the delayed conduction time of the three phases A, B, and C of the primary bridge arm relative to the reference switch signal; (k-1) T s It is the delayed conduction time of the secondary bridge arms A, B, and C relative to the primary bridge arms A, B, and C three-phase switching tubes.

[0068] In response to the current trajectory switching command, within the half switching cycle, the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter are switched to the intermediate duty cycle parameters, the C-phase duty cycle is switched to the target duty cycle, the A-phase phase shift of the three-phase dual active bridge converter is switched to the initial phase shift before switching, the B-phase phase shift is the intermediate initial phase shift related value, and the C-phase phase shift is the C-phase shift after switching. Specifically: at a certain moment, a current trajectory switching command is received, requiring the duty cycle to transition to the target duty cycle D ck (The three-phase duty cycle of the three-phase dual active bridge converter after switching), the shift ratio between the three-phase original and auxiliary bridge arms is D k At this time, the duty cycle of this switching cycle starts to switch from phase A to phase D c1△ , B phase is D c2△ , C phase is D ck ; The phase shift of phase A is The phase shift of phase B is The phase shift of phase C is The three-phase original secondary bridge arms are all switched to D k , so far all transition is completed; D c1△ T s is the conduction time of the upper tube of phase A, D c2△ T s is the conduction time of the upper tube of phase B, D ck T s is the conduction time of the upper tube of phase C; is the delayed on-time of the primary bridge arm A phase relative to the reference switch signal, is the delayed on-time of the primary bridge arm B phase relative to the reference switch signal, D is the delayed on-time of the primary bridge arm phase C relative to the reference switch signal; k T s It is the delayed conduction time of the secondary bridge arms A, B, and C relative to the primary bridge arms A, B, and C three-phase switching tubes.

[0069] In the next cycle, the duty ratios of the three-phase A, B, and C of the three-phase DAB converter are all D. ck ; The phase shifts of A, B, and C are D k D is the shift ratio between the original and auxiliary bridge arms of the three-phase after switching. ck T s is the conduction time of the upper tubes of the three phases A, B, and C; D is the delayed conduction time of the three phases A, B, and C of the primary bridge arm relative to the reference switch signal; k T s It is the delayed conduction time of the secondary bridge arms A, B, and C relative to the primary bridge arms A, B, and C three-phase switching tubes.

[0070] The present embodiment provides a method for suppressing transient DC bias of a converter, which effectively suppresses the DC bias of a DAB3 converter in a transient process by operating a switch signal and thereby controlling a current trajectory.

[0071] The present embodiment provides a method for suppressing transient DC bias of a converter, which enables the DAB3 converter to reach any stable state within a half switching cycle by controlling the current trajectories of the primary and secondary bridge arms respectively, and the transient DC bias of the winding current is significantly suppressed.

[0072] The present embodiment provides a method for suppressing transient DC bias of a converter, which compares different duty cycles, analyzes the current trajectory types, applies different control schemes to current trajectories of different shapes, and finally achieves a perfect transition of the transient current trajectory. The method can be simply implemented in an existing closed-loop controller, and can significantly shorten the transient process and suppress the transient DC bias.

[0073] Embodiment 2

[0074] This embodiment provides a converter transient DC bias suppression system, which specifically includes:

[0075] A control module, which is configured to: in response to a current trajectory switching instruction, switch the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter to the intermediate duty cycle parameters within a half switching period, switch the C-phase duty cycle to the target duty cycle, switch the A-phase phase shift of the three-phase dual active bridge converter to the initial phase shift before switching, the B-phase phase shift to the intermediate initial phase shift related value, and the C-phase phase shift to the C-phase shift after switching;

[0076] Among them, the initial phase shift before switching and the initial phase shift after switching are both related to the current duty cycle, and the intermediate initial phase shift and the intermediate duty cycle parameters are both related to the target duty cycle and the duty cycle before switching.

[0077] It should be noted here that each module in this embodiment corresponds to each step in Example 1 one by one, and the specific implementation process is the same, which will not be repeated here.

[0078] Embodiment 3

[0079] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the steps of the method for suppressing transient DC bias of a converter as described in the first embodiment above are implemented.

[0080] Embodiment 4

[0081] This embodiment provides a computer device, such as Fig.10As shown, it includes a computer-readable storage medium 1003, a processor 1001, a communication interface 1002, and a computer program stored on the computer-readable storage medium 1003 and executable on the processor 1001, wherein the processor 1001, the communication interface 1002, and the computer-readable storage medium 1003 can be connected via a bus or other means. The communication interface 1002 is used to receive and send data, and when the processor 1001 executes the program, the steps in the method for suppressing transient DC bias of a converter as described in the first embodiment are implemented.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for suppressing transient DC bias of a converter, characterized in that: include: In response to the current trajectory switching instruction, within a half switching period, the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter are both intermediate duty cycle parameters, the C-phase duty cycle is switched to the target duty cycle, the A-phase phase shift of the three-phase dual active bridge converter is the initial phase shift before switching, the B-phase phase shift is the intermediate initial phase shift related value, and the C-phase phase shift is the C-phase shift after switching; Among them, the initial phase shift before switching and the initial phase shift after switching are both related to the current duty cycle, and the intermediate initial phase shift and the intermediate duty cycle parameters are both related to the target duty cycle and the duty cycle before switching.

2. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: The intermediate duty cycle parameters include: Among them, the intermediate duty cycle parameter D c1△ For phase A duty cycle, intermediate duty cycle parameter D c2△ For the B phase duty cycle, D c(k-1) is the duty cycle before switching, D ck is the target duty cycle.

3. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: The initial phase shift before switching is: Among them, D c(k-1) is the duty cycle before switching.

4. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: Before switching, the phase shifts of the A, B, and C phases of the three-phase dual active bridge converter are 5. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: The intermediate initial phase shift correlation value is The initial phase shift in the middle is Among them, D c(k-1) is the duty cycle before switching, D ck is the target duty cycle.

6. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: After switching, the phase shifts of A, B, and C of the three-phase dual active bridge converter are 7. A method for suppressing transient DC bias of a converter according to claim 1, characterized in that: The initial phase shift after switching is: Among them, D ck is the target duty cycle.

8. A converter transient DC bias suppression system, characterized in that: include: A control module, which is configured to: in response to a current trajectory switching instruction, switch the A-phase duty cycle and the B-phase duty cycle of the three-phase dual active bridge converter to the intermediate duty cycle parameters within a half switching period, switch the C-phase duty cycle to the target duty cycle, switch the A-phase phase shift of the three-phase dual active bridge converter to the initial phase shift before switching, the B-phase phase shift to the intermediate initial phase shift related value, and the C-phase phase shift to the C-phase shift after switching; Among them, the initial phase shift before switching and the initial phase shift after switching are both related to the current duty cycle, and the intermediate initial phase shift and the intermediate duty cycle parameters are both related to the target duty cycle and the duty cycle before switching.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of a method for suppressing transient DC bias of a converter as described in any one of claims 1 to 8 are implemented.

10. A computer device comprising a computer-readable storage medium, a processor, and a computer program stored in the computer-readable storage medium and executable on the processor, characterized in that: When the processor executes the program, the steps in a method for suppressing transient DC bias of a converter as described in any one of claims 1-8 are implemented.

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