Phase-shift control method and system for a bidirectional DC / DC converter

Abstract

The present invention discloses a phase-shift control method and system for a bidirectional DC / DC converter based on an optimal fundamental wave. The phase-shift control method includes: obtaining the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side of the bidirectional DC / DC converter; obtaining the external phase-shift angle β'; obtaining the phase-shift angle α1dz converted from the dead-time on the primary side and the phase-shift angle α2dz converted from the dead-time on the secondary side of the bidirectional DC / DC converter; correcting the external phase-shift angle β' according to the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side to obtain the corrected external phase-shift angle β; calculating one or more of the reference offset phase angle D1 on the primary side, the lagging leg offset phase angle D2 on the primary side, the leading and lagging leg offset phase angle D3 on the secondary side, and the lagging leg offset phase angle D4 on the secondary side of the bidirectional DC / DC converter according to α1, α2, α1dz, α2dz, and β. The present invention can solve the problems of large reactive power, too high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss, and low efficiency when the system outputs under light load.

Description

Technical Field

[0001] The present invention relates to a phase-shift control method and system for a bidirectional DC / DC converter, specifically a three-phase-shift optimal fundamental wave strategy for an isolated bidirectional DC / DC converter. Background Art

[0002] With the gradual improvement of the degree of electrical automation of distribution equipment such as new energy DC microgrid systems, hybrid electric vehicle systems, and energy-saving elevator systems, as well as the continuous development and innovation of production technologies, bidirectional DC / DC converters have been increasingly widely used. At the same time, new application fields put more comprehensive requirements on bidirectional DC / DC converters, such as: small volume, light weight, high reliability, high frequency, and low loss, etc. These requirements are important indicators for putting the bidirectional converter into practical applications. The wide range of application fields promotes the development of bidirectional DC / DC converters; at the same time, developing a bidirectional DC / DC converter with excellent performance is of great significance for expanding the application scope of bidirectional DC / DC converters.

[0003] In recent years, the research on the control methods of double-active full-bridge bidirectional DC / DC converters has mainly focused on the analysis of the power characteristics of the system and the tube current stress under different control methods. For example, the traditional single-phase-shift control method can only control the phase-shift angle variable between the primary side and the secondary side bridges. This method is simple and easy to implement closed-loop regulation, but it cannot adjust the comprehensive power characteristics of the system, such as reactive power, tube current stress, etc., resulting in large reactive power when the system outputs at light load, too high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss, low efficiency, etc.

[0004] Correspondingly, in order to solve the above drawbacks, different multivariable control methods have been proposed one after another. Among them, the double-phase-shift modulation method not only generates a phase shift between the primary side and the secondary side bridges, but also generates a phase shift within the primary side bridge or the secondary side bridge. By finding the optimal combination of the two phase-shift angles, the reactive power and current stress of the system can be greatly reduced while ensuring a certain output power, thereby greatly improving the system efficiency.

[0005] Some scholars have proposed a triple-phase-shift control method. This control method not only generates a phase shift between the primary side and the secondary side bridges, but also generates phase-shift angles within the primary side bridge and the secondary side bridge. The control operation of the system is divided into multiple different stages, and it is analyzed through relevant algorithms that the system can maintain high efficiency and high stability under this control method. Currently, the control strategies for double-active full-bridge bidirectional DC / DC converters are all aimed at reducing reactive power and loss to improve the working efficiency of the converter. In addition to analyzing the working principles of the converter under several control methods, corresponding mathematical models of the system are established, relevant expressions are derived, and a steady-state mathematical model is given to compare the power characteristics of the converter under different control methods.

[0006] However, in the phase-shift control method of the dual-active full-bridge bidirectional DC / DC converter, the optimal characteristics of the phase-shift control method in the modulation process are not considered. Through theoretical derivation, it can be found that different modulation methods have an impact on various aspects of the system, such as reactive power, loss reduction, and current stress. Adopting an optimal control modulation strategy will play a key role in significantly improving the comprehensive performance of the system. At the same time, for different control methods, such as common single-phase-shift control methods, dual-phase-shift control methods, or triple-phase-shift control methods and related combined methods, it is particularly important to have a unified optimal fundamental wave strategy to implement various control algorithms. Summary of the Invention

[0007] In view of this, the present invention provides a phase-shift control method and system for a bidirectional DC / DC converter based on the optimal fundamental wave.

[0008] According to the first aspect of the present invention, a phase-shift control method for a bidirectional DC / DC converter is provided, including:

[0009] Step A: Obtain the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side of the bidirectional DC / DC converter;

[0010] Step B: Obtain the external phase-shift angle β of the bidirectional DC / DC converter ’ ;

[0011] Step C: Obtain the phase-shift angle α converted from the dead-time on the primary side and the phase-shift angle α converted from the dead-time on the secondary side of the bidirectional DC / DC converter 1dz and the phase-shift angle α converted from the dead-time on the secondary side 2dz ;

[0012] Step D: Correct the external phase-shift angle β according to the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side ’ to obtain the corrected external phase-shift angle β;

[0013] Step E: Calculate one or more of the primary-side reference offset phase angle D1, the primary-side lagging leg offset phase angle D2, the secondary-side leading leg offset phase angle D3, and the secondary-side lagging leg offset phase angle D4 of the bidirectional DC / DC converter according to the internal phase-shift angle α1 on the primary side, the internal phase-shift angle α2 on the secondary side, the phase-shift angle α converted from the dead-time on the primary side 1dz , the phase-shift angle α converted from the dead-time on the secondary side 2dz and the corrected external phase-shift angle β.

[0014] According to a specific and preferred embodiment, the specific content of step A is as follows:

[0015] Step A1: Obtain the modulation ratio coefficient m of the DC / DC converter based on the voltages on the primary side and secondary side of the bidirectional DC / DC converter;

[0016] Step A2: Determine whether m is greater than 1. When the result is no, set the primary side internal phase shift angle and the secondary side internal phase shift angle according to the primary side internal phase shift angle adjustment of the bidirectional DC / DC converter; when the result is yes, set the primary side internal phase shift angle and the secondary side internal phase shift angle according to the secondary side internal phase shift angle adjustment of the bidirectional DC / DC converter;

[0017] Step A3: Determine whether m belongs to [1 - δ, 1 + δ], where δ represents the allowable cross - modulation error range; if the result is yes, execute the following Step A4; if the result is no, use the primary side internal phase shift angle and the secondary side internal phase shift angle in Step A2;

[0018] Step A4: Calculate the active power P of the bidirectional DC / DC converter dc ; Determine whether |P dc | ≥ P o holds, where P o represents the set threshold of the allowable cross - active power. If it holds, execute the following Step A5; if it does not hold, execute the following Step A6;

[0019] Step A5: Calculate the active current i, and determine whether |i| ≥ i o holds, where i o represents the set threshold of the allowable cross - active current. If it holds, use the primary side internal phase shift angle and the secondary side internal phase shift angle in Step A2; if it does not hold, execute the following Step A6;

[0020] Step A6: Update the primary side internal phase shift angle and the secondary side internal phase shift angle to the set values respectively.

[0021] More preferably, in Step A1, m is calculated by the formula m = N ps V dc2 / V dc1 where V dc1 is the primary side voltage of the bidirectional DC / DC converter, V dc2 is the secondary side voltage of the bidirectional DC / DC converter, and N ps is the voltage ratio coefficient between the primary side and secondary side of the bidirectional DC / DC converter.

[0022] More preferably, in Step B, when the result is no, the primary side internal phase shift angle α1 = π(1 - m), and the secondary side internal phase shift angle α2 = 0; when the result is yes, the primary side internal phase shift angle α1 = 0, and the secondary side internal phase shift angle α2 = π(1 - 1 / m).

[0023] Preferably, in the step B, the external phase shift angle β is obtained through a control loop according to the voltage information and current information of the primary side and the secondary side of the bidirectional DC / DC converter. ’ Specifically, the voltage information and current information of the primary side and the secondary side of the bidirectional DC / DC converter are combined with a control loop to obtain the system external phase shift angle β. ’ The control loop is one of a voltage loop, a current loop, a combination of a voltage loop and a current loop, and a power loop.

[0024] Preferably, in the step C, according to the dead time of the secondary side and the primary side of the dual active full-bridge bidirectional DC / DC converter, the converted phase shift angle α of the dead time of the secondary side of the dual active full-bridge bidirectional DC / DC converter is obtained. 2dz And the converted phase shift angle α of the dead time of the primary side. 1dz .

[0025] Preferably, in the step D, the corrected external phase shift angle β is obtained by correcting through the fundamental wave optimal principle. The corrected external phase shift angle β is obtained according to the following formula.

[0026]

[0027] More preferably, in the step D, the external phase shift angle in the optimal fundamental wave mode adopts a midpoint symmetry method, and the system fundamental wave optimal principle can also be determined by combining the internal phase shift angle and the dead time.

[0028] Preferably, in the step E, one or more of the primary side reference offset phase angle D1, the primary side lagging leg offset phase angle D2, the secondary side leading leg offset phase angle D3, and the secondary side lagging leg offset phase angle D4 of the bidirectional DC / DC converter are calculated according to the following formula.

[0029] D1 = 0

[0030] D2 = (α1 + α 1dz ) / 2

[0031] D3 = β + α 1dz / 2 + α 2dz / 2

[0032] D4 = β + α 1dz / 2 + α 2dz .

[0033] Preferably, the bidirectional DC / DC converter is controlled through a PWM register according to the calculation result of the step E.

[0034] Preferably, in the step E, in the single-phase shift mode of the bidirectional DC / DC converter, the primary side internal phase shift angle α1 = 0 and the secondary side internal phase shift angle α2 = 0.

[0035] Preferably, in step E, in the dual-phase-shift mode of the bidirectional DC / DC converter, the internal phase-shift angle α1 of the primary side is 0 and the internal phase-shift angle α2 of the secondary side ≠ 0, or the internal phase-shift angle α1 of the primary side ≠ 0 and the internal phase-shift angle α2 of the secondary side is 0.

[0036] Preferably, in step E, in the triple-phase-shift mode of the bidirectional DC / DC converter, the internal phase-shift angle α1 of the primary side ≠ 0 and the internal phase-shift angle α2 of the secondary side ≠ 0.

[0037] According to the second aspect of the present invention, there is provided a phase-shift control system for a bidirectional DC / DC converter, including a control unit which is equipped with the phase-shift control method as described above.

[0038] Preferably, the phase-shift control system further includes a signal acquisition unit which is used to acquire the current information of the bidirectional DC / DC converter.

[0039] Preferably, the control unit is a DSP chip, and the phase-shift control system further includes a voltage conversion unit for converting the acquired voltage.

[0040] The present invention adopts the above scheme and has the following advantages compared with the prior art:

[0041] The phase-shift control method and system of the bidirectional DC / DC converter of the present invention consider the optimal characteristics of the phase-shift control method in the modulation process finally, adopt the optimal control modulation strategy, so that the comprehensive performance of the system is improved, and the problems of large reactive power, high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss and low efficiency when the system outputs under light load can be well solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0043] Figure 1 It is a hardware circuit diagram of a bidirectional DC / DC converter;

[0044] Figure 2 It is a schematic diagram of the optimal fundamental wave of the bidirectional DC / DC converter;

[0045] Figure 3 It is a flowchart of a phase-shift control method according to an embodiment of the present invention;

[0046] Figure 4 It is for Figure 3 The flowchart of step S12 in Detailed implementation manners

[0047] The following elaborates on the preferred embodiments of the present invention in conjunction with the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted here that the description of these embodiments is for helping to understand the present invention, but does not constitute a limitation to the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] According to an embodiment of the present invention, a phase-shift control method for a bidirectional DC / DC converter based on the optimal fundamental wave is provided, which is an optimal fundamental wave strategy for a three-phase-shift isolation type DC / DC converter. Specifically: by detecting the current information of the bidirectional DC / DC converter with a dual-active full-bridge; by detecting the voltage information of the bidirectional DC / DC converter with a dual-active full-bridge, the voltage information is mainly divided into secondary-side voltage information and primary-side voltage information, obtaining the internal phase-shift angle and the external phase-shift angle in the system, and combining the system phase-shift control amount with the dead-time compensation algorithms on the secondary side and the primary side of the bidirectional DC / DC converter with a dual-active full-bridge. For the obtained phase-shift angles, the optimal fundamental wave method is used to adjust each phase-shift angle, which is realized through a hardware circuit, so as to achieve the phase-shift control result of the optimal fundamental wave of the bidirectional DC / DC converter with a dual-active full-bridge.

[0049] Combined with Figure 2 and Figure 3 as shown, the flow of the phase-shift control method for the bidirectional DC / DC converter is as follows.

[0050] Step S10: Start.

[0051] Step S11: Collect the voltage and current information of the bidirectional DC / DC converter. The current information is the primary-side current information of the bidirectional DC / DC converter with a dual-active full-bridge, or the secondary-side current information, or the two current information of the primary side and the secondary side; the voltage information is the secondary-side voltage information and the primary-side voltage information.

[0052] Step S12: Obtain the internal phase-shift angle α1 on the primary side and the internal phase-shift angle α2 on the secondary side of the bidirectional DC / DC converter.

[0053] Step S13: Obtain the external phase-shift angle β of the bidirectional DC / DC converter ’ ;

[0054] According to the primary-side and secondary-side voltage information and current information of the bidirectional DC / DC converter with a dual-active full-bridge collected in step S11, the external phase-shift angle β of the system is obtained by combining the control loop ’, the control loop is a voltage loop, a current loop, a voltage loop and a current loop, or a power loop. The phase shift angle between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter is obtained through the control loop, and this phase shift angle is denoted as the external phase shift angle β of the system.

[0055] Step S14. Correct the external phase shift angle β ’ to obtain the corrected external phase shift angle β;

[0056] Through the fundamental wave optimization principle, the external phase shift angle β in the optimal fundamental wave mode of the system is corrected. Specifically, the corrected external phase shift angle β is obtained according to the following formula

[0057]

[0058] The external phase shift angle in the optimal fundamental wave mode adopts the midpoint symmetry method, and the fundamental wave optimization principle of the system can also be determined by combining the internal phase shift angle and the dead time.

[0059] Step S15. Obtain the dead time and control period of the primary and secondary sides of the bidirectional DC / DC converter;

[0060] T 1dz is the dead time of the primary side of the dual-active full-bridge bidirectional DC / DC converter, and T1 is the control period of the primary side of the dual-active full-bridge bidirectional DC / DC converter; T 2dz is the dead time of the secondary side of the dual-active full-bridge bidirectional DC / DC converter, and T2 is the control period of the secondary side of the dual-active full-bridge bidirectional DC / DC converter. The dead times of the secondary side and the primary side are mainly configured to prevent direct conduction of the upper and lower bridge arms on the secondary side and the primary side of the dual-active full-bridge bidirectional DC / DC converter, and this dead time is determined by indicators such as turn-on time and turn-off time.

[0061] Step S16. Obtain the phase shift angle α converted from the dead time of the primary side of the bidirectional DC / DC converter 1dz and the phase shift angle α converted from the dead time of the secondary side 2dz ;

[0062] The phase shift angle is obtained by converting the dead times of the primary and secondary sides, and the phase shift angle α converted from the dead time of the secondary side of the dual-active full-bridge bidirectional DC / DC converter 2dz and the phase shift angle α converted from the dead time of the primary side 1dz are obtained, where α 1dz = T 1dz / T1 * 2π,; α 2dz = T 2dz / T2 * 2π.

[0063] Step S17. According to the internal phase shift angle α1 of the primary side, the internal phase shift angle α2 of the secondary side, and the phase shift angle α converted from the dead time of the primary side 1dz, Dead-time conversion phase-shift angle α on the secondary side 2dz And calculate the primary-side reference offset phase angle D1, primary-side lagging leg offset phase angle D2, secondary-side leading leg offset phase angle D3, and secondary-side lagging leg offset phase angle D4 of the bidirectional DC / DC converter based on the corrected external phase-shift angle β. Specifically: D1 = 0, D2 = (α1 + α 1dz ) / 2, With Taking the primary side as the reference, then, D1 represents the primary-side reference offset phase angle of the dual-active full-bridge bidirectional DC / DC converter, D2 represents the primary-side lagging leg offset phase angle of the dual-active full-bridge bidirectional DC / DC converter, D3 represents the secondary-side leading leg offset phase angle of the dual-active full-bridge bidirectional DC / DC converter, and D4 represents the secondary-side lagging leg offset phase angle of the dual-active full-bridge bidirectional DC / DC converter.

[0064] Apply the obtained D1, D2, D3, and D4 through the PWM register and the hardware circuit to implement the optimal fundamental wave phase-shifting method of the dual-active full-bridge bidirectional DC / DC converter.

[0065] Refer to Figure 4 As shown, the specific implementation of the above step S12 is as follows.

[0066] S102. Calculate the system modulation ratio coefficient m of the bidirectional DC / DC converter after conversion.

[0067] m = N ps V dc2 / V dc1 ; where V dc1 is the primary-side voltage of the dual-active full-bridge bidirectional DC / DC converter; V dc2 is the secondary-side voltage of the dual-active full-bridge bidirectional DC / DC converter; N ps is the voltage ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, and this value can be obtained offline.

[0068] The N ps of the dual-active full-bridge bidirectional DC / DC converter is the voltage ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, which is mainly determined by the turns ratio of the isolation transformer, and this value can be modified offline.

[0069] S103. Judge whether m > 1?

[0070] When m ≤ 1, the inner phase - shift angle of the primary side of the dual - active - bridge bidirectional DC / DC converter is adjusted. The specific inner phase - shift angle is: the inner phase - shift angle of the primary side α1 = π(1 - m), and the inner phase - shift angle of the secondary side α2 = 0; when m > 1, the inner phase - shift angle of the secondary side of the dual - active - bridge bidirectional DC / DC converter is adjusted. The specific inner phase - shift angle is: the inner phase - shift angle of the primary side α1 = 0, and the inner phase - shift angle of the secondary side α2 = π(1 - 1 / m).

[0071] S104. Summarize the inner phase - shift angle.

[0072] If m ≤ 1, then set the inner phase - shift angle as: the inner phase - shift angle of the primary side α1 = π(1 - m), and the inner phase - shift angle of the secondary side α2 = 0.

[0073] If m > 1, then set the inner phase - shift angle as: the inner phase - shift angle of the primary side α1 = 0, and the inner phase - shift angle of the secondary side α2 = π(1 - 1 / m).

[0074] S105. Further determine whether m ∈ [1 - δ, 1 + δ]?

[0075] δ represents the allowable error range of the modulation index. Specifically, in this embodiment, δ = 1%.

[0076] If the judgment result is yes, that is, m ∈ [1 - δ, 1 + δ], then enter S106; otherwise, directly enter S111.

[0077] S106. Calculate the active power P of the dual - active - bridge bidirectional DC / DC converter dc , and the sign of this value represents the direction of the active power.

[0078] S107. Judge whether |P dc | ≥ P o holds.

[0079] P o represents the allowable threshold of the active power for crossing. In this embodiment, P o = 200W.

[0080] If the above formula holds, then enter S108; otherwise, directly enter S111.

[0081] S108. Calculate the active current i of the dual - active - bridge bidirectional DC / DC converter, and the sign of this value represents the direction of the active current.

[0082] S109. Judge whether |i| ≥ i o holds.

[0083] i o represents the allowable threshold of the active current for crossing. In this embodiment, the threshold of the secondary - side current is selected as i o = 1.8A.

[0084] If the above formula does not hold, then enter S110; if the above formula holds, then directly enter S111.

[0085] S110. Update the internal phase shift angle.

[0086] Adjust the internal phase shift angle on the primary side α1 = set value 1 and the internal phase shift angle on the secondary side α2 = set value 2 when the internal phase shift crosses and switches.

[0087] The set value 1 or the set value 2 is the allowed crossing final state value, or 0, or a value between the two, or a value specified by the user.

[0088] S111. Summarize the internal phase shift angle.

[0089] If the internal phase shift angle is not updated as in S110, then the internal phase shift angle α1 on the primary side and the internal phase shift angle α2 on the secondary side set in step S104 are adopted. Specifically: the internal phase shift angle α1 on the primary side = π(1 - m), and the internal phase shift angle α2 on the secondary side = 0; or, the internal phase shift angle α1 on the primary side = 0, and the internal phase shift angle α2 on the secondary side = π(1 - 1 / m).

[0090] If the internal phase shift angle is updated as in S110, then the internal phase shift angle updated in S110 is adopted. Specifically: the internal phase shift angle α1 on the primary side = set value 1, and the internal phase shift angle α2 on the secondary side = set value 2.

[0091] This embodiment also provides a phase shift control system for a dual-active full-bridge bidirectional DC / DC converter, including: a signal acquisition unit and a control unit. Among them, the signal acquisition unit is used to acquire the current information of the dual-active full-bridge bidirectional DC / DC converter; the control unit is equipped with the above phase shift control method.

[0092] The control unit, according to the voltage information and current information of the dual-active full-bridge DC-DC converter collected, combines loop control, and finally combines the external phase shift angle of the system, the internal phase shift on the primary side and the internal phase shift on the secondary side, the phase shift angle converted from the dead time on the primary side and the phase shift angle converted from the dead time on the secondary side, which is realized through a hardware circuit, so as to achieve the optimal fundamental wave phase shift control result of the dual-active full-bridge DC-DC converter.

[0093] The above control unit may adopt a DSP (Digital Signal Processor) chip. During implementation, the current information of the dual-active full-bridge bidirectional DC / DC converter is AC-DC. The signal acquisition unit uses a current sensor to detect the current. Since the control unit uses a DSP chip, the on-chip A / D converter is unipolar and can only receive voltage signals of 0 to 3.0V. Therefore, the control system also includes a voltage conversion unit to convert the collected voltage so that it can be connected to the DSP. The optimal fundamental phase-shift control algorithm of the dual-active full-bridge bidirectional DC-DC converter is implemented in the DSP and combined with the above control algorithm to control the output of the dual-active full-bridge bidirectional DC-DC converter, realizing the optimal dual-phase-shift control of the dual-active full-bridge bidirectional DC-DC converter.

[0094] Adopting the above phase-shift control method of the dual-active full-bridge bidirectional DC / DC converter, on the dual-active full-bridge bidirectional DC / DC converter circuit, problems such as a large amount of reactive power existing during light-load output of the system, too high effective value and peak value of the alternating current flowing through the leakage inductance of the transformer, large system loss and low efficiency can be well solved.

[0095] The above embodiments are only for illustrating the technical concept and features of the present invention and are a preferred embodiment. The purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A phase-shift control method for a bidirectional DC / DC converter, characterized in that Including: Step A: Obtain the primary-side internal phase-shift angle α1 and the secondary-side internal phase-shift angle α2 of the bidirectional DC / DC converter; Step B, obtain the external phase-shift angle β of the bidirectional DC / DC converter ’ ; Step C: Obtain the phase shift angle α for the dead time conversion on the primary side of the bidirectional DC / DC converter 1dz and the phase shift angle α for the dead time conversion on the secondary side 2dz ; where α 1dz = T 1dz / T1 * 2π, α 2dz = T 2dz / T2 * 2π, T 1dz is the dead time on the primary side of the bidirectional DC / DC converter, and T1 is the control period on the primary side of the bidirectional DC / DC converter; T 2dz is the dead time on the secondary side of the bidirectional DC / DC converter, and T2 is the control period on the secondary side of the bidirectional DC / DC converter; Step D: Modify the external phase shift angle β according to the internal phase shift angle α1 of the primary side and the internal phase shift angle α2 of the secondary side ’ to obtain the modified external phase shift angle β; Step E: Calculate the reference phase shift angle D1 of the primary side, the lagging leg phase shift angle D2 of the primary side, the leading arm phase shift angle D3 of the secondary side, and the lagging leg phase shift angle D4 of the secondary side of the bidirectional DC / DC converter according to the inner phase shift angle α1 of the primary side, the inner phase shift angle α2 of the secondary side, the phase shift angle α converted from the dead time of the primary side, the phase shift angle α converted from the dead time of the secondary side, and the corrected outer phase shift angle β, where D1 = 0, D2 = (α1 + α 1dz ) / 2, D3 = β + α 2dz / 2 + α 1dz / 2, D4 = β + α 1dz / 2 + α 2dz / 2, D4 = β + α 1dz / 2 + α 2dz ; The specific steps of Step A are as follows: Step A1: Obtain the modulation ratio coefficient m of the DC / DC converter based on the voltages of the primary side and the secondary side of the bidirectional DC / DC converter; m is calculated by the formula m = N ps V dc2 / V dc1 where V dc1 is the voltage of the primary side of the bidirectional DC / DC converter, V dc2 is the voltage of the secondary side of the bidirectional DC / DC converter, and N ps is the voltage ratio coefficient between the primary side and the secondary side of the bidirectional DC / DC converter; Step A2: Determine whether m is greater than 1. When the result is no, set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the primary-side internal phase-shift angle adjustment of the bidirectional DC / DC converter. The primary-side internal phase-shift angle α1 = π(1 - m), and the secondary-side internal phase-shift angle α2 = 0; when the result is yes, set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the secondary-side internal phase-shift angle adjustment of the bidirectional DC / DC converter. The primary-side internal phase-shift angle α1 = 0, and the secondary-side internal phase-shift angle α2 = π(1 - 1 / m); Step A3: Determine whether m belongs to [1 - δ, 1 + δ], where δ represents the allowable cross-modulation error range; if the result is yes, then execute the following Step A4; if the result is no, then use the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle of Step A2 and execute Step E; Step A4: Calculate the active power P of the bidirectional DC / DC converter dc ; Determine whether |P dc | ≥ P o holds. P o represents the set threshold of the allowable crossing active power. If it holds, execute the following step A5; if not, execute the following step A6; Step A5: Calculate the active current i and determine whether |i|≥i o holds, where i o represents the set threshold value of the allowable cross - active current. If it holds, use the original - side internal phase - shift angle and the secondary - side internal phase - shift angle of Step A2; if it does not hold, execute the following Step A6; Step A6: Update the primary-side internal phase-shift angle to the set value 1 and update the secondary-side internal phase-shift angle to the set value 2. The set value 1 or the set value 2 is the allowable cross-through final state value, or 0, or a value between 0 and the allowable cross-through final state value, or a user-specified value.

2. The phase shift control method according to claim 1, characterized in that In the said step B, an external phase shift angle β is obtained through a control loop according to the voltage information and current information on the primary side and secondary side of the bidirectional DC / DC converter. ’ .

3. The phase shift control method according to claim 1, wherein In Step D, the corrected external phase-shift angle β is obtained by correction according to the following formula:

4. The phase shift control method according to claim 1, wherein Control the bidirectional DC / DC converter through the PWM register based on the calculation result of Step E.

5. A phase-shifting control system for a bidirectional DC / DC converter, characterized in that, Including a control unit, which is equipped with the phase-shift control method described in any one of claims 1 to 3.

6. The phase-shifting control system according to claim 5, wherein The phase-shift control system further includes a signal acquisition unit, which is used to acquire the current information of the bidirectional DC / DC converter.

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