A Cross-Over Switching Control Method and System for a Bidirectional DC / DC Converter

Abstract

The present invention discloses a cross-over switching control method and system for a bidirectional DC / DC converter, which improves the stability during the cross-over process. In this cross-over switching control method, A. Obtain the modulation ratio coefficient m of the DC / DC converter; B. Judge whether m is greater than 1. When the result is yes, set the internal phase-shift angle according to the internal phase-shift regulation on the primary side; when the result is no, set the internal phase-shift angle according to the internal phase-shift regulation on the secondary side; C. Judge whether m belongs to [1-δ, 1+δ]; if so, execute step D; otherwise, adopt the internal phase-shift angles on the primary side and the secondary side in step B; D. Calculate the active power Pdc of the bidirectional DC / DC converter; judge whether |Pdc|≥Po holds. If it holds, execute step E; otherwise, execute step F; E. Calculate the active current i, judge whether |i|≥io holds. If it holds, adopt the internal phase-shift angle in step B; otherwise, execute step F; F. Update the internal phase-shift angles to the set values respectively.

Description

Technical Field

[0001] The present invention relates to a cross-over switching control method and system for a bidirectional DC / DC converter. Background Art

[0002] A high-power density dual-active full-bridge bidirectional DC / DC converter can efficiently and flexibly control the bidirectional flow of electric energy, and will be widely applied in systems such as electric vehicles, aerospace power supply systems, and new energy and renewable energy power generation systems. The dual-active full-bridge bidirectional DC / DC converter plays an important role in the energy management of new energy and renewable energy power generation. In new energy and renewable energy power generation, due to the large power variation range brought by the instability of new energy, the dual-active full-bridge bidirectional DC / DC converter can optimize the performance of the new energy and renewable energy power generation system, and at the same time realize the feedback of surplus energy and improve the utilization efficiency of electric energy.

[0003] As Figure 1 shown, the main circuit of the dual-active full-bridge bidirectional DC / DC converter consists of a high-frequency transformer, an inductor (the sum of the externally connected inductor and the leakage inductance of the transformer), full-bridge circuits on both sides of the transformer, capacitors and power supplies. Among them, the high-frequency transformer plays the role of electrical isolation and voltage conversion, the inductor ensures the energy transmission of the converter, and the capacitors on both sides of the transformer play the role of filtering and voltage stabilization. There is a voltage-fed full-bridge conversion unit at both ends of the isolation transformer of the converter. The energy flow between the DC sources is controlled by changing the driving control phase angle difference between the conversion units in the converter. The converter performs step-up and step-down operations, has few filtering elements, and is a simple first-order stable system. In general, there are no large hysteresis delay passive components in the converter adopting this control type, and the dynamic response is relatively fast.

[0004] Currently, the control method of the dual-active full-bridge bidirectional DC / DC converter mainly adopts single-phase-shift control. By phase-shift control, a square-wave voltage with a certain phase-shift duty cycle is applied across the leakage inductance of the high-frequency transformer, and power transfer is achieved through the voltage difference. The magnitude and direction of power transmission are realized by adjusting the phase-shift angle between the primary and secondary bridges, and the control is simple and convenient.

[0005] The traditional single-phase-shift control method can only control the phase-shift angle variable between the primary and secondary 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 and tube current stress, resulting in large reactive power 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 losses and low efficiency, etc.

[0006] To address these drawbacks, various multivariable control methods have been proposed. Dual-phase-shift modulation, for example, not only shifts the phase angle between the primary and secondary bridges but also shifts the phase within the primary or secondary bridge itself. By finding the optimal combination of these two phase-shift angles, while maintaining a constant output power, the system's reactive power and current stress can be significantly reduced, significantly improving system efficiency.

[0007] The current dual phase-shift modulation method is mainly implemented by using the inter-bridge phase-shift angle variable and the phase shift generated within the primary bridge or the secondary bridge. In practice, the dual-active full-bridge bidirectional DC / DC converter selects different internal phase shift amounts according to m. For example, in a given case, when m≤1, the dual-active full-bridge bidirectional DC / DC converter performs the primary-side internal phase shift angle adjustment, and the specific internal phase shift angles are: primary-side internal phase shift angle α1=π(1-m), secondary-side internal phase shift angle α2=0; when m>1, the dual-active full-bridge bidirectional DC / DC converter performs the secondary-side internal phase shift angle adjustment, and the specific internal phase shift angles are: primary-side internal phase shift angle α1=0, secondary-side internal phase shift angle α2=π(1-1 / m);

[0008] However, in the dual active full-bridge bidirectional DC / DC converter, when crossing m=N ps V dc2 / V dc1 =1, N ps is the voltage ratio coefficient between the primary and secondary sides of the dual-active full-bridge bidirectional DC / DC converter. This value can be obtained offline and calculated as m=N ps V dc2 / V dc1 However, in actual operation, it is impossible to accurately calculate the converted system modulation ratio coefficient m of the dual-active full-bridge bidirectional DC / DC converter, which will cause the dual-active full-bridge bidirectional DC / DC converter's phase shift angle to oscillate. During the ride-through process, the internal phase shift angle of the primary side and the internal phase shift angle of the secondary side switch back and forth, resulting in reduced stability of the system controller and degradation of system performance. In actual practice, a method that can meet the requirements of internal phase ride-through switching is urgently needed to solve the system stability problem caused by oscillation during the ride-through process. Summary of the Invention

[0009] In order to solve the above technical problems, an object of the present invention is to provide a ride-through switching control method and system for a bidirectional DC / DC converter, which improves the stability during the ride-through process.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A ride-through switching control method for a bidirectional DC / DC converter, comprising:

[0012] Step A: 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;

[0013] Step B: Determine whether m is greater than 1. When the result is no, set the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side according to the inner phase-shift angle adjustment of the primary side of the bidirectional DC / DC converter; when the result is yes, set the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side according to the inner phase-shift angle adjustment of the secondary side of the bidirectional DC / DC converter;

[0014] Step C: 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 D; if the result is no, use the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side in Step B;

[0015] Step D: 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 E; if it does not hold, execute the following Step F;

[0016] Step E: 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 inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side in Step B; if it does not hold, execute the following Step F;

[0017] Step F: Update the inner phase-shift angle of the primary side and the inner phase-shift angle of the secondary side to the set values respectively;

[0018] Step G: Obtain the outer phase-shift angle based on the voltages and currents on the primary side and secondary side of the bidirectional DC / DC converter;

[0019] Step H: Calculate one or more of the primary-side reference offset phase angle, primary-side lagging leg offset phase angle, secondary-side leading leg offset phase angle, and secondary-side lagging leg offset phase angle of the bidirectional DC / DC converter according to the inner phase-shift angle of the primary side, the inner phase-shift angle of the secondary side, and the outer phase-shift angle.

[0020] Preferably, in Step A, m is calculated by the formula m = N ps V dc2 / V dc1 where V dc1 is the voltage on the primary side of the bidirectional DC / DC converter, V dc2 is the voltage on the secondary side of the bidirectional DC / DC converter, and N psis the voltage conversion ratio coefficient between the primary side and the secondary side of the bidirectional DC / DC converter.

[0021] Preferably, in step B, when the result is no, 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; when the result is yes, 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).

[0022] Preferably, in step C, δ = 1%.

[0023] Preferably, in step G, the external phase shift angle of the system is obtained through a control loop based on the voltage information and current information of the primary side and the secondary side of the bidirectional DC / DC converter.

[0024] More preferably, the control loop includes a voltage loop, a current loop, a power conversion, or a combination of a voltage loop and a current loop.

[0025] Preferably, in step H,

[0026] the reference offset phase angle D1 on the primary side = 0; and / or

[0027] the lagging leg offset phase angle D2 on the primary side = α1; and / or

[0028] the leading leg offset phase angle D3 on the secondary side = β + D2 = β + α1; and / or

[0029] the lagging leg offset phase angle D4 on the secondary side = D3 + α2 = β + α1 + α2 = β + α1 + α2;

[0030] In the above formula, α1, α2, and β respectively represent the internal phase shift angle on the primary side, the internal phase shift angle on the secondary side, and the external phase shift angle.

[0031] Preferably, the bidirectional DC / DC converter is controlled through a PWM register according to the calculation result of step H.

[0032] The present invention also adopts the following technical solution:

[0033] A cross-over switching control system for a bidirectional DC / DC converter includes a control unit, which is equipped with the cross-over switching control method as described above.

[0034] Preferably, the cross-over switching control system further includes a signal acquisition unit, which is used to acquire the current information of the bidirectional DC / DC converter.

[0035] Preferably, the control unit is a DSP chip, and the cross-over switching control system further includes a voltage conversion unit for converting the acquired voltage.

[0036] In the above technical solution, the bidirectional DC / DC converter is preferably a dual-active full-bridge bidirectional DC / DC converter. The external phase-shift angle β of the system is obtained by combining the voltage information and current information with the control loop. At the same time, m = N is calculated in real time ps V dc2 / V dc1 is calculated, 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 transformation ratio coefficient between the primary side and the secondary side of the dual-active full-bridge bidirectional DC / DC converter, and m is the reduced system modulation ratio coefficient of the dual-active full-bridge bidirectional DC / DC converter. By selecting different internal phase-shift amounts through m and combining the internal phase-shift crossing switching method, the internal phase-shift and the external phase-shift are combined to realize the dual-phase-shift control quantity, which is realized through the hardware circuit, so as to realize the internal phase-shift crossing switching control result of the dual-active full-bridge bidirectional DC / DC converter

[0037] The present invention adopts the above scheme and has the following advantages compared with the prior art

[0038] The crossing switching control method and system of the bidirectional DC / DC converter of the present invention can well solve the stability problems such as the reduction of the system controller stability and the degradation of the system performance caused by the back-and-forth switching of the internal phase-shift angle on the primary side and the internal phase-shift angle on the secondary side during the crossing process in the dual-active full-bridge bidirectional DC / DC converter circuit BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solution 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. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts

[0040] Figure 1 is the hardware circuit diagram of a bidirectional DC / DC converter

[0041] Figure 2 is the flowchart of a crossing switching control method according to an embodiment of the present invention

[0042] Figure 3 is the crossing switching schematic diagram according to an embodiment of the present invention DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] 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.

[0044] This embodiment provides a cross - over switching control method for a bidirectional DC / DC converter, specifically an inner - phase - shift cross - over switching selection strategy for an isolated dual - active - bridge bidirectional DC / DC converter, which is an active cross - over switching phase - shift control method. Refer to Figure 2 As shown, the specific implementation of this cross - over switching control method is as follows.

[0045] S100. Start.

[0046] S101. Collect the voltage and current information of the bidirectional DC / DC converter. The current information is the primary - side current information, or the secondary - side current information, or the two current information of the primary - side and secondary - side of the dual - active - bridge bidirectional DC / DC converter; the voltage information is the secondary - side voltage information and the primary - side voltage information.

[0047] S102. Calculate the system modulation ratio coefficient m after conversion of the bidirectional DC / DC converter.

[0048] m = N ps V dc2 / V dc1 ; where V dc1 is the primary - side voltage of the dual - active - bridge bidirectional DC / DC converter; V dc2 is the secondary - side voltage of the dual - active - bridge bidirectional DC / DC converter; N ps is the voltage ratio coefficient between the primary - side and secondary - side of the dual - active - bridge bidirectional DC / DC converter, and this value can be obtained offline.

[0049] The N ps of the dual - active - bridge bidirectional DC / DC converter is the voltage ratio coefficient between the primary - side and secondary - side of the dual - active - bridge bidirectional DC / DC converter, which is mainly determined by the turns ratio of the isolation transformer, and this value can be modified offline.

[0050] S103. Judge whether m > 1?

[0051] When m ≤ 1, the inner phase - shift regulation of the primary side of the dual - active - bridge bidirectional DC / DC converter is implemented. The specific inner phase - shift angles are: 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 regulation of the secondary side of the dual - active - bridge bidirectional DC / DC converter is implemented. The specific inner phase - shift angles are: 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).

[0052] S104. Summarize the inner phase - shift angles.

[0053] If m ≤ 1, then set the inner phase - shift angles 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.

[0054] If m > 1, then set the inner phase - shift angles 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).

[0055] S105. Further determine whether m ∈ [1 - δ, 1 + δ]?

[0056] δ represents the allowable modulation index error range. Specifically in this embodiment, δ = 1%.

[0057] If the judgment result is yes, that is, m ∈ [1 - δ, 1 + δ], then enter S106; otherwise, directly enter S111.

[0058] S106. Calculate the active power P of the dual - active - bridge bidirectional DC / DC converter dc , and this value indicates the direction of the active power by positive and negative.

[0059] S107. Judge whether |P dc | ≥ P o is established.

[0060] P o represents the allowable active - power setting threshold. In this embodiment, P o = 200W.

[0061] If the above formula holds, then enter S108; otherwise, directly enter S111.

[0062] S108. Calculate the active current i of the dual - active - bridge bidirectional DC / DC converter, and this value indicates the direction of the active current by positive and negative.

[0063] S109. Judge whether |i| ≥ i o is established.

[0064] i o represents the allowable active - current setting threshold. In this embodiment, it is selected as the secondary - side current setting threshold i o = 1.8A.

[0065] If the above equation does not hold, then enter S110; if the above equation holds, then directly enter S111.

[0066] S110. Update the internal phase shift angle.

[0067] 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 the switch.

[0068] The set value 1 or the set value 2 is the allowable crossing final state value, or 0, or a value between the two, or a value specified by the user.

[0069] S111. Aggregate the internal phase shift angle.

[0070] If the internal phase shift angle is not updated as in S110, then use the internal phase shift angle on the primary side α1 and the internal phase shift angle on the secondary side α2 set in step S104. Specifically: the internal phase shift angle on the primary side α1 = π(1 - m), the internal phase shift angle on the secondary side α2 = 0; or, the internal phase shift angle on the primary side α1 = 0, the internal phase shift angle on the secondary side α2 = π(1 - 1 / m).

[0071] If the internal phase shift angle is updated as in S110, then use the updated internal phase shift angle in S110. Specifically: the internal phase shift angle on the primary side α1 = set value 1, the internal phase shift angle on the secondary side α2 = set value 2.

[0072] S112. Calculate the external phase shift angle of the system.

[0073] According to the voltage information and current information of the primary side and secondary side of the dual-active full-bridge bidirectional DC / DC converter collected in step S101, combined with the control loop to obtain the external phase shift angle β of the system. The control loop is a voltage loop, or a current loop, or a voltage loop and a current loop, or a power loop. The phase shift angle of the primary side and secondary side of the dual-active full-bridge bidirectional DC / DC converter is controlled through the control loop, and this phase shift angle is denoted as the external phase shift angle β of the system. The dual-active full-bridge bidirectional DC / DC converter is implemented using classical control theory or modern control theory. The dual-active full-bridge bidirectional DC / DC converter is generally a closed-loop control system.

[0074] S113. Calculate one or more of the primary side reference offset phase angle, primary side lagging leg offset phase angle, secondary side leading leg offset phase angle, and secondary side lagging leg offset phase angle of the bidirectional DC / DC converter.

[0075] The original side internal phase shift angle α1 and the secondary side internal phase shift angle α2 obtained by summarizing according to S111, and the system external phase shift angle β obtained by S112 are combined to obtain all or part of D1 = 0, D2 = α1, D3 = β + D2 = β + α1, and D4 = D3 + α2 = β + α1 + α2 = β + α1 + α2. Specifically, it needs to be determined in combination with the PWM register and the hardware circuit. D1 represents the reference offset phase angle of the primary side of the dual active full-bridge bidirectional DC / DC converter, D2 represents the offset phase angle of the lagging leg on the primary side of the dual active full-bridge bidirectional DC / DC converter, D3 represents the leading arm offset phase angle of the secondary side of the dual active full-bridge bidirectional DC / DC converter, and D4 represents the lagging leg offset phase angle of the secondary side of the dual active full-bridge bidirectional DC / DC converter.

[0076] The obtained D1, D2, D3, and D4 are applied through the PWM register and the hardware circuit to implement the method of internal phase shift cross-over switching of the dual active full-bridge bidirectional DC / DC converter.

[0077] This embodiment also provides a cross-over switching 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-mentioned cross-over switching control method.

[0078] The control unit, according to the voltage information and current information of the dual active full-bridge bidirectional DC / DC converter collected, combines loop control, and finally combines the system external phase shift angle, the primary side internal phase shift, and the secondary side internal phase shift, and is implemented through the hardware circuit in combination with the internal phase shift cross-over switching method, so as to achieve the internal phase shift cross-over switching control result of the dual active full-bridge bidirectional DC / DC converter.

[0079] The above control unit can use a DSP (Digital Signal Processor) chip. During implementation, the current information of the dual active full-bridge bidirectional DC / DC converter is AC and DC, and 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 above-mentioned cross-over switching control method of the dual active full-bridge bidirectional DC / DC converter is implemented in the DSP to control the output of the dual active full-bridge bidirectional DC / DC converter and achieve the internal phase shift cross-over switching control of the dual active full-bridge bidirectional DC / DC converter.

[0080] Refer to Figure 3As shown, the above-mentioned dual-active full-bridge bidirectional DC / DC converter internal phase-shift ride-through switching method is adopted in the dual-active full-bridge bidirectional DC / DC converter circuit, which can effectively solve the stability problem of the system during the ride-through process, such as the reduced stability of the system controller and the degradation of system performance due to the back-and-forth switching of the internal phase-shift angle of the primary side and the internal phase-shift angle of the secondary side.

[0081] The above embodiment is intended only to illustrate the technical concepts and features of the present invention and is a preferred embodiment. Its purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. It is not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A cross-over switching control method for a bidirectional DC / DC converter, characterized in that, Including: Step A: Collect the voltage information of the secondary side and the primary side of the bidirectional DC / DC converter, and obtain the modulation ratio coefficient m of the DC / DC converter according to 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 B: Determine whether m is greater than 1. When the result is no, adjust and set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the internal phase-shift angle of the primary side 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, adjust and set the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle according to the internal phase-shift angle of the secondary side 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 C: Determine whether m belongs to [1 - δ, 1 + δ], where δ represents the allowable modulation degree error range. If the result is yes, execute the following Step D. If the result is no, use the primary-side internal phase-shift angle and the secondary-side internal phase-shift angle of Step B and execute the following Step H. Step D, 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 crossing active power. If it holds, execute the following step E; if not, execute the following step F; Step E: 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 B; if not, execute the following Step F; Step F: 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 crossing final state value, or 0, or a value between 0 and the allowable crossing final state value, or a user-specified value. Step G: Obtain the external phase-shift angle according to the voltages and currents of the primary side and the secondary side of the bidirectional DC / DC converter. Step H: Calculate the primary-side reference offset phase angle, the primary-side lagging bridge arm offset phase angle, the secondary-side leading arm offset phase angle, and the secondary-side lagging bridge arm offset phase angle of the bidirectional DC / DC converter according to the primary-side internal phase-shift angle, the secondary-side internal phase-shift angle, and the external phase-shift angle. Among them, the primary-side reference offset phase angle D1 = 0; the primary-side lagging bridge arm offset phase angle D2 = α1; the secondary-side leading arm offset phase angle D3 = β + α1; the secondary-side lagging bridge arm offset phase angle D4 = β + α1 + α2. In the above formula, β represents the external phase-shift angle.

2. The cross-switching control method according to claim 1, characterized in that In Step C, δ = 1%.

3. The cross-switching control method according to claim 1, wherein In Step G, obtain the system external phase-shift angle 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.

4. The cross-switching control method according to claim 1, wherein Control the bidirectional DC / DC converter through a PWM register according to the calculation result of Step H.

5. A cross-over switching control system for a bidirectional DC / DC converter, characterized in that, Including a control unit, which is equipped with the crossing switching control method described in any one of claims 1 to 4.

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

7. The cross-switching control system according to claim 5, wherein The control unit is a DSP chip, and the crossing switching control system further includes a voltage conversion unit for converting the acquired voltage.

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