A current-sharing control strategy for dual-active full-bridge converter based on phase-shifted voltage disturbance

Abstract

The application discloses a current-sharing control strategy for a dual-active full-bridge converter based on phase-shift ratio disturbance, and belongs to the technical field of power electronic cascades. The dual-active full-bridge converter is composed of two or more dual-active full-bridge converter sub-modules in parallel, and has a multi-phase input; the current-sharing control strategy implements a fixed phase-shift ratio disturbance on each phase module in the dual-active full-bridge converter in sequence, estimates the parameter mismatching degree of each module according to the variation of the voltage closed loop of the parallel system after each disturbance, and calculates the compensation phase-shift ratio of each sub-module of the parallel system to meet the current sharing, so that the system current sharing is realized. The application realizes the automatic current sharing of the dual-active full-bridge converter, and balances the power distribution of each sub-module; can be used in new energy power generation, electric vehicles, aerospace and other high-power parallel switching power supply occasions, and has the advantages of simple realization logic, easy expansion of a multi-phase system, low cost, high reliability and the like.

Description

Technical Field

[0001] This invention belongs to the field of power electronics cascade technology, and particularly relates to a current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance. Background Technology

[0002] In recent years, converters in power electronic systems have been developing towards higher power, integration, lower cost, higher power density, and higher efficiency. Dual active full-bridge converters possess numerous advantages, including bidirectional power transmission, electrical isolation, high step-up / step-down ratio, and ease of soft-switching control. They can also be combined in parallel to achieve multiple modular solutions, and have become one of the core topologies for high-power parallel switching power supplies in applications such as new energy power generation, electric vehicles, aerospace, uninterruptible power supplies, DC power distribution systems, and energy storage systems.

[0003] Modular parallel schemes can effectively improve power capacity, reduce power transistor stress, and enhance system redundancy. However, in actual circuits, parameters such as series inductance of each submodule cannot be guaranteed to be completely consistent, leading to current imbalance among submodules and causing serious problems such as excessive current stress in some modules. Existing solutions mostly use active devices such as current sensors to collect the current of each module and achieve system current sharing by adjusting the phase shift angle of each module. Therefore, a large number of current sensors and sampling conditioning circuits are required, which not only increases the cost and size of the system but also reduces the system reliability. To solve the above problems, Chinese invention patent (application number: CN202210370109.9) proposes a multiphase input parallel output parallel dual active full-bridge converter and current sharing control method. Its core idea is to achieve current sharing of the parallel system by perturbing the switching frequency and estimating the parameter mismatch of each module. It should be noted that the switching frequency disturbance estimation algorithm proposed in this patent can only realize the disturbance between two-phase modules. When extended to multi-phase modules, its disturbance estimation logic is to first disturb the first and second phase modules, then disturb the first and third phase modules, and so on, disturbing the first and m phase modules.

[0004] Multiphase parallel systems are coupled systems, meaning that when two phase modules are disturbed, other modules can only be shut down or latched. The disturbance estimation logic is complex, making this method difficult to apply in practice. The paper "A Simple Sensorless Current Sharing Control for Input-Parallel Output-Parallel Dual Active Bridge Converters" published in IEEE Transactions on Power Electronics, Volume 69, Issue 11, 2022, proposes a sensorless current sharing method based on duty cycle disturbances. However, this parameter estimation algorithm can only achieve disturbance and parameter estimation between two phase modules. When extended to multiphase modules, the disturbance estimation logic can only proceed by first disturbing phases 1 and 2, then phases 1 and 3, and so on, disturbing phases 1 and m. Furthermore, when two phase modules are disturbed, all other modules can only be shut down or latched, making this method equally difficult to apply in practice.

[0005] To address the aforementioned issues, this invention proposes a current sharing control strategy for dual active full-bridge converters based on phase shift perturbation. This control strategy differs from existing two-phase module perturbation estimation algorithms. It sequentially applies perturbations to phases 1 through m. When one phase module is perturbed, other phase modules do not need to be shut down or latched. The proposed perturbation algorithm has simpler logic and better reflects actual operating conditions. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects existing in the above-mentioned background technology. This invention proposes a current sharing control strategy for dual active full-bridge converters based on phase shift perturbation. Unlike the existing two-phase module perturbation estimation algorithm, the perturbation logic of this patent is as follows: perturbation is applied to the first to m phase modules in sequence. When perturbing one phase module, other phase modules do not need to be shut down or latched. The proposed perturbation algorithm has simple logic execution and is more in line with actual operating conditions. After implementing m perturbations, the parameter mismatch degree of each module is estimated, thereby realizing the current sharing of the parallel system.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance includes the following steps:

[0009] Step S1: Analyze the current sharing conditions of the dual active full-bridge converter based on the phase shift compensation method;

[0010] Step S2: The dual active full-bridge converter adopts voltage closed-loop control, applying ΔD sequentially to the first phase and then the i-th phase module. pCompared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached. i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i where i = 1, 2, ..., m;

[0011] Step S3: Based on L calculated in step S2 i Calculate L i The value of / L1;

[0012] Step S4: Calculate the compensation phase shift angle ΔD i .

[0013] Furthermore, the dual active full-bridge converter is composed of two or more dual active full-bridge converter sub-modules connected in parallel;

[0014] The dual active full-bridge converter submodule P1 includes a first switching circuit S. 11 First series inductor L1, first isolation transformer T1, second switching circuit S 12 and the DC port side capacitor C of the converter 11 C 12 ;

[0015] The first series inductor L1 and the primary winding of the first isolation transformer T1 are connected in series, and the first switching circuit S 11 The second switching circuit S has an input port 1-1 and an output port 1-2. 12 It has input ports 1-3 and output ports 1-4.

[0016] Furthermore, the specific method of step S1 is as follows:

[0017] Based on the power transfer expression of the dual active full-bridge converter, derive the output current equations for each submodule:

[0018]

[0019] Among them: I oi P is the output current of the i-th submodule; i f is the transmission power of the i-th submodule; si n is the switching frequency of the i-th submodule; i L is the turns ratio of the i-th submodule; i It is the sum of the leakage inductance and auxiliary inductance of the transformer in the i-th submodule; D 2i V is the outward phase shift angle of the i-th submodule; in V is the input voltage of the i-th submodule; oIt is the output voltage of the i-th submodule;

[0020] For a dual active full-bridge converter, as shown in equation (1), there are two controllable variables in the output current expression of each submodule, including: D 2i and f si When the circuit parameters of each submodule are mismatched, based on the common phase-shifting control of the parallel system, D 21 =D 22 =…=D 2m Adjust the phase shift angle D of each submodule 2i To achieve current sharing in a parallel system; when achieving current sharing, the phase shift angles of each submodule have the following relationship:

[0021]

[0022] Among them, D 21 It is the phase shift angle of the first submodule; ΔD1~ΔD m-1 Based on the phase shift angle of the first submodule, the phase shift angle compensation values ​​for the second to m-th submodules are used to achieve current sharing among all submodules. For a dual active full-bridge converter, the input and output voltages of each submodule are equal. When the system achieves current sharing, the output current of each submodule must satisfy the following:

[0023] I o1 =I o2 =…=I om (3)

[0024] Substituting equation (2) into equation (1) and combining it with equation (3), we obtain:

[0025]

[0026] According to equation (4), L i / L1 calculates the switching frequency compensation values ​​ΔD1~ΔD for each submodule. m-1 Then, the phase shift angle of each sub-module is adjusted by equation (2) to achieve system current sharing.

[0027] Furthermore, the specific method for step S2 is as follows:

[0028] Firstly, the multi-phase parallel system employs voltage closed-loop control, and the voltage closed-loop output generates a common phase shift angle D. M To simultaneously control m sub-modules, the outward shift phase angle relationship of the m sub-modules is D. 21 =D 22 =…=D 2m=D; Then, a phase shift disturbance of ΔDp is applied to the output of the first submodule. Under the disturbance of ΔDp, when the system reaches a new steady state, the common outward phase shift angle D generated by the output voltage closed loop of the parallel system will be adjusted to Dp1. The phase shift angle of the voltage closed loop before and after the disturbance has the following relationship:

[0029] D p1 =D-Δd1 (5)

[0030] In equation (5), Δd1 represents the outward phase angle offset of the parallel system before and after the disturbance. This value is observed and stored by the digital control system when the system reaches steady state after the disturbance. The duty cycle of each phase module after the disturbance is expressed as:

[0031]

[0032] Substituting equation (6) into equation (1), the output current of each module after the disturbance is expressed as:

[0033]

[0034] The total output current can be obtained by summing the output currents of each phase module in the parallel system:

[0035]

[0036] From equation (1), the expression for the total output current of the parallel system before the disturbance is:

[0037]

[0038] Since the total output current of the parallel system remains unchanged before and after the disturbance, we have:

[0039] I o =I o ′ (10)

[0040] By combining (7) and (10), the expression for L1 can be derived as follows:

[0041]

[0042] Based on the above estimation steps: apply ΔD sequentially to the 2nd to mth phase modules. P Compared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached. i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i Where i = 2, 3, ..., m; after m disturbances, the equivalent series inductance L of each module is... i Represented as:

[0043]

[0044] Furthermore, the specific method of step S3 is as follows:

[0045] L is calculated by dividing the 2nd to mth terms in equation (12) by the 1st term in turn. i The expression for / L1 is

[0046]

[0047] Furthermore, the specific method for step S4 is as follows:

[0048] Get L i After / L1, the shift ratio compensation values ​​ΔD1~ΔD for each submodule to satisfy the output current sharing can be obtained from formula (4). m Furthermore, by adjusting the phase shift angle of each sub-module according to formula (2), the current sharing of the system can be achieved.

[0049] Furthermore, the current sharing control strategy can be applied to extended phase-shift modulation, dual phase-shift modulation, and triple phase-shift modulation strategies.

[0050] Compared with the prior art, the present invention, employing the above technical solution, has the following beneficial effects:

[0051] (1) The current sharing control strategy described in this invention realizes automatic current sharing of the dual active full-bridge converter, so that the power of each sub-module is evenly distributed, thereby avoiding the problem of excessive current stress in some modules.

[0052] (2) When the current sharing control strategy of the present invention disturbs a certain phase module, other phase modules do not need to be shut down or latched. The proposed disturbance algorithm has simple logic execution and is more in line with actual operating conditions.

[0053] (3) The current sharing control strategy described in this invention can be applied to extended phase-shift modulation, dual phase-shift modulation and triple phase-shift modulation strategies, and has strong scalability.

[0054] (4) The current sharing control strategy described in this invention has the advantages of simple implementation logic, easy expansion of multiphase systems, low cost, and high reliability. Attached Figure Description

[0055] Figure 1 This is a flowchart of the current sharing control strategy for a dual active full-bridge converter according to an embodiment of the present invention.

[0056] Figure 2 This is a flowchart of the perturbation algorithm for a dual active full-bridge converter according to an embodiment of the present invention;

[0057] Figure 3This is a diagram showing the phase shift angle change during the disturbance process of a dual active full-bridge converter according to Embodiment 1 of the present invention.

[0058] Figure 4 This invention relates to a dual active full-bridge converter;

[0059] Figure 5 When the method of this invention is not used, the inductor current i of the three-phase input parallel output parallel dual active full-bridge converter is... L1 i L2 i L3 Simulated waveforms;

[0060] Figure 6 When using the method of this invention, during the disturbance estimation stage, after sequentially applying a shift ratio disturbance of 0.05 to each module, the inductor current i of each module is... L1 i L2 i L3 Simulated waveforms;

[0061] Figure 7 When using the method of this invention, in the disturbance estimation stage, after applying a phase shift disturbance of 0.05 to each module in sequence, the simulated waveforms of the phase shift change Δd1~Δd3 of the parallel system voltage closed loop after each disturbance are obtained.

[0062] Figure 8 When using the method of this invention, the inductor current i of the three-phase input parallel output parallel dual active full-bridge converter is... L1 i L2 i L3 Simulated waveforms;

[0063] V in the attached diagram p V s It is the DC-side port voltage of a multi-phase input parallel output parallel dual active full-bridge converter, i in the attached figure. L1 i L2 i L3 The figure shows the inductor current of each submodule of a three-phase input-parallel output dual active full-bridge converter, with v in the attached diagram. h1 v h2 This refers to the AC voltage on the primary and secondary sides of the isolation transformer. Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] A current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance, such as... Figure 1 As shown, it includes the following steps:

[0066] Step S1: Analyze the current sharing conditions of the dual active full-bridge converter based on the phase shift compensation method;

[0067] Step S2: The dual active full-bridge converter adopts voltage closed-loop control, applying ΔD sequentially to the first phase and then the i-th phase module. p Compared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached. i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i where i = 1, 2, ..., m;

[0068] Step S3: Based on L calculated in step S2 i Calculate L i The value of / L1;

[0069] Step S4: Calculate the compensation phase shift angle ΔD i .

[0070] Furthermore, the dual active full-bridge converter, as shown below... Figure 4 As shown, it consists of two or more dual active full-bridge converter submodules connected in parallel;

[0071] The dual active full-bridge converter submodule P1 includes a first switching circuit S. 11 First series inductor L1, first isolation transformer T1, second switching circuit S 12 and the DC port side capacitor C of the converter 11 C 12 ;

[0072] The first series inductor L1 and the primary winding of the first isolation transformer T1 are connected in series, and the first switching circuit S 11 The second switching circuit S has an input port 1-1 and an output port 1-2. 12 It has input ports 1-3 and output ports 1-4.

[0073] Furthermore, the specific method of step S1 is as follows:

[0074] Based on the power transfer expression of the dual active full-bridge converter, derive the output current equations for each submodule:

[0075]

[0076] Among them: I oiP is the output current of the i-th submodule; i f is the transmission power of the i-th submodule; si n is the switching frequency of the i-th submodule; i L is the turns ratio of the i-th submodule; i It is the sum of the leakage inductance and auxiliary inductance of the transformer in the i-th submodule; D 2i V is the outward phase shift angle of the i-th submodule; in V is the input voltage of the i-th submodule; o It is the output voltage of the i-th submodule;

[0077] For a dual active full-bridge converter, as shown in equation (1), there are two controllable variables in the output current expression of each submodule, including: D 2i and f si When the circuit parameters of each submodule are mismatched, based on the common phase-shifting control of the parallel system, D 21 =D 22 =…=D 2m Adjust the phase shift angle D of each submodule 2i To achieve current sharing in a parallel system; when achieving current sharing, the phase shift angles of each submodule have the following relationship:

[0078]

[0079] Among them, D 21 It is the phase shift angle of the first submodule; ΔD1~ΔD m-1 Based on the phase shift angle of the first submodule, the phase shift angle compensation values ​​for the second to m-th submodules are used to achieve current sharing among all submodules. For a dual active full-bridge converter, the input and output voltages of each submodule are equal. When the system achieves current sharing, the output current of each submodule must satisfy the following:

[0080] I o1 =I o2 =…=I om (3)

[0081] Substituting equation (2) into equation (1) and combining it with equation (3), we obtain:

[0082]

[0083] According to equation (4), L i The value of / L1 is used to calculate the switching frequency compensation values ​​ΔD1~ΔD for each submodule. m-1 Then, the phase shift angle of each submodule is adjusted using equation (2) to achieve current sharing in the system; therefore, it is necessary to estimate L. i The value of / L1.

[0084] Furthermore, the specific method for step S2 is as follows:

[0085] Firstly, the multi-phase parallel system employs voltage closed-loop control, and the voltage closed-loop output generates a common phase shift angle D. M To simultaneously control m sub-modules, the outward shift phase angle relationship of the m sub-modules is D. 21 =D 22 =…=D 2m =D; Then, a phase shift disturbance of ΔDp is applied to the output of the first submodule. Under the disturbance of ΔDp, when the system reaches a new steady state, the common outward phase shift angle D generated by the output voltage closed loop of the parallel system will be adjusted to Dp1. The phase shift angle of the voltage closed loop before and after the disturbance has the following relationship:

[0086] D p1 =D-Δd1 (5)

[0087] In equation (5), Δd1 represents the outward phase angle offset of the parallel system before and after the disturbance. This value is observed and stored by the digital control system when the system reaches steady state after the disturbance. The duty cycle of each phase module after the disturbance is expressed as:

[0088]

[0089] Substituting equation (6) into equation (1), the output current of each module after the disturbance is expressed as:

[0090]

[0091] The total output current can be obtained by summing the output currents of each phase module in the parallel system:

[0092]

[0093] From equation (1), the expression for the total output current of the parallel system before the disturbance is:

[0094]

[0095] Since the total output current of the parallel system remains unchanged before and after the disturbance, we have:

[0096] I o =I o ′ (10)

[0097] By combining (7) and (10), the expression for L1 can be derived as follows:

[0098]

[0099] Based on the above estimation steps: apply ΔD sequentially to the 2nd to mth phase modules. P Compared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached.i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i Where i = 2, 3, ..., m; after m disturbances, the equivalent series inductance L of each module is... i Represented as:

[0100]

[0101] Furthermore, the specific method of step S3 is as follows:

[0102] L is calculated by dividing the 2nd to mth terms in equation (12) by the 1st term in turn. i The expression for / L1 is

[0103]

[0104] Furthermore, the specific method for step S4 is as follows:

[0105] Get L i After / L1, the shift ratio compensation values ​​ΔD1~ΔD for each submodule to satisfy the output current sharing can be obtained from formula (4). m Furthermore, by adjusting the phase shift angle of each sub-module according to formula (2), the current sharing of the system can be achieved.

[0106] Furthermore, the current sharing control strategy can be applied to extended phase-shift modulation, dual phase-shift modulation, and triple phase-shift modulation strategies.

[0107] Table 1 shows the circuit parameters of the three-phase input parallel output parallel dual active full-bridge converter;

[0108] Table 1 Circuit parameters of the three-phase parallel module

[0109]

[0110] Depend on Figure 5 As can be seen, without the present invention, the inductor current i of the three-phase input parallel output parallel dual active full-bridge converter is... L1 i L2 i L3 The simulated waveforms of the inductor current show huge differences, namely 4.3A, 3.59A and 3.078A, which are extremely unbalanced.

[0111] Depend on Figure 6 As can be seen, when using the method of the present invention, after applying a phase shift disturbance of 0.05 to each module in the disturbance estimation stage, the inductor current i of each module will be affected by the phase shift disturbance. L1 i L2 i L3Dynamic changes;

[0112] Depend on Figure 7 It can be seen that when using the method of the present invention, after applying a phase shift disturbance of 0.05 to each module in sequence during the disturbance estimation stage, the output of the parallel system voltage loop changes after each disturbance. After observing the values ​​of Δd1 to Δd3, according to formula (2) of the claim, L2 / L1=Δd1 / Δd2≈1.2, L3 / L1=Δd1 / Δd3=1.4 can be estimated. This matches the circuit parameter mismatch of each phase module in Table 1, indicating that the proposed parameter estimation algorithm can accurately estimate L. i The value of / L1;

[0113] Depend on Figure 8 As can be seen, after adopting this invention, the inductor current i in the three-phase input parallel output parallel circuit is reduced. L1 i L2 i L3 The simulated waveforms of the inductor current show very little difference, with values ​​of 3.636A, 3.676A, and 3.701A respectively, indicating a very balanced performance.

[0114] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance, characterized in that, The current sharing control strategy includes the following steps: Step S1: Analyze the current sharing conditions of the dual active full-bridge converter based on the phase shift compensation method; Step S2: The dual active full-bridge converter adopts voltage closed-loop control, applying ΔD sequentially to the first phase and then the i-th phase module. p Compared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached. i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i where i = 1, 2, ..., m; Step S3: Based on L calculated in step S2 i Calculate L i The value of / L1; Step S4: Calculate the compensation phase shift angle ΔD i .

2. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The dual active full-bridge converter is composed of two or more dual active full-bridge converter sub-modules connected in parallel; The dual active full-bridge converter submodule P1 includes a first switching circuit S. 11 First series inductor L1, first isolation transformer T1, second switching circuit S 12 and the DC port side capacitor C of the converter 11 C 12 ; The first series inductor L1 and the primary winding of the first isolation transformer T1 are connected in series, and the first switching circuit S 11 The second switching circuit S has an input port 1-1 and an output port 1-2. 12 It has input ports 1-3 and output ports 1-4.

3. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The specific method for step S1 is as follows: Based on the power transfer expression of the dual active full-bridge converter, derive the output current equations for each submodule: Among them: I oi P is the output current of the i-th submodule; i f is the transmission power of the i-th submodule; si n is the switching frequency of the i-th submodule; i L is the turns ratio of the i-th submodule; i It is the sum of the leakage inductance and auxiliary inductance of the transformer in the i-th submodule; D 2i V is the outward phase shift angle of the i-th submodule; in V is the input voltage of the i-th submodule; o It is the output voltage of the i-th submodule; For a dual active full-bridge converter, as shown in equation (1), there are two controllable variables in the output current expression of each submodule, including: D 2i and f si When the circuit parameters of each submodule are mismatched, based on the common phase-shifting control of the parallel system, D 21 =D 22 =…=D 2m Adjust the phase shift angle D of each submodule 2i To achieve current sharing in a parallel system; when achieving current sharing, the phase shift angles of each submodule have the following relationship: Among them, D 21 It is the phase shift angle of the first submodule; ΔD1~ΔD m-1 Based on the phase shift angle of the first submodule, the phase shift angle compensation values ​​for the second to m-th submodules are used to achieve current sharing among all submodules. For a dual active full-bridge converter, the input and output voltages of each submodule are equal. When the system achieves current sharing, the output current of each submodule must satisfy the following: I o1 =I o2 =…=I om (3) Substituting equation (2) into equation (1) and combining it with equation (3), we obtain: According to equation (4), L i / L1 calculates the switching frequency compensation values ​​ΔD1~ΔD for each submodule. m-1 Then, the phase shift angle of each sub-module is adjusted by equation (2) to achieve system current sharing.

4. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The specific method for step S2 is as follows: Firstly, the multi-phase parallel system employs voltage closed-loop control, and the voltage closed-loop output generates a common phase shift angle D. M To simultaneously control m sub-modules, the outward shift phase angle relationship of the m sub-modules is D. 21 =D 22 =....=D 2m =D; Then, a phase shift disturbance of ΔDp is applied to the output of the first submodule. Under the disturbance of ΔDp, when the system reaches a new steady state, the common outward phase shift angle D generated by the output voltage closed loop of the parallel system will be adjusted to Dp1. The phase shift angle of the voltage closed loop before and after the disturbance has the following relationship: D p1 =D-Δd1 (5) In equation (5), Δd1 represents the outward phase angle offset of the parallel system before and after the disturbance. This value is observed and stored by the digital control system when the system reaches steady state after the disturbance. The duty cycle of each phase module after the disturbance is expressed as: Substituting equation (6) into equation (1), the output current of each module after the disturbance is expressed as: The total output current is obtained by summing the output currents of each phase module in the parallel system: From equation (1), the expression for the total output current of the parallel system before the disturbance is: Since the total output current of the parallel system remains unchanged before and after the disturbance, we have: I o =I o ′ (10) Combining (7) and (10), the expression for L1 can be derived as follows: Based on the above estimation steps: apply ΔD sequentially to the 2nd to mth phase modules. P Compared to a fixed displacement disturbance, the change in the closed-loop output of the storage voltage ΔD when the system reaches steady state after each disturbance is reached. i Where i = 2, 3, ..., m; then, based on the principle that the total output current of the multiphase parallel system remains unchanged before and after the disturbance, the equivalent series inductance L of each module is derived and calculated. i Where i = 2, 3, ..., m; after m disturbances, the equivalent series inductance L of each module is... i Represented as:

5. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The specific method for step S3 is as follows: L is calculated by dividing the 2nd to mth terms in equation (12) by the 1st term in turn. i The expression for / L1 is 6. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The specific method for step S4 is as follows: Get L i After / L1, the shift ratio compensation values ​​ΔD1~ΔD for each submodule to satisfy the output current sharing can be obtained from formula (4). m Furthermore, by adjusting the phase shift angle of each sub-module according to formula (2), the current sharing of the system can be achieved.

7. The current sharing control strategy for a dual active full-bridge converter based on phase shift disturbance according to claim 1, characterized in that, The current sharing control strategy can be applied to extended phase-shift modulation, dual phase-shift modulation, and triple phase-shift modulation strategies.

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