Instantaneous current control method and controller for three-phase dual active bridge converter

Abstract

The present invention discloses a transient current control method and controller for a three-phase dual active bridge converter, which belongs to the technical field of DC-DC converters. The method comprises: when the power transmission instruction changes and the absolute value of the change is greater than the mutation threshold, applying an intermediate duty cycle of D in the transient process. r The unit pulse of , makes the inductor current reach a stable state within 1 / 3 of the switching cycle. r The solution is to make the sum of the transient response of the inductor current before and after the power transfer command changes and the unit pulse response applied during the transient process equal to 0 at 1 / 3 of the switching cycle after the transient process begins. By solving this, the unique intermediate duty cycle D can be obtained. r This method can quickly suppress the instantaneous current oscillation of the three-phase DAB converter, giving the converter good dynamic regulation capabilities. It also effectively suppresses the inductor current impact when the power command suddenly changes, preventing the device from generating overcurrent risks and improving the reliability of the converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of DC-DC converters, and more particularly, relates to an instantaneous current control method and a controller for a three-phase dual active bridge converter. Background Art

[0002] Dual active bridge (DAB) DC converters offer advantages such as electrical isolation, bidirectional energy flow, and easy soft switching. They are widely used in DC distribution networks, energy storage systems, and electric vehicles. As a key device for voltage conversion and energy transfer, three-phase dual active bridge converters offer higher power density and improved performance, making them a preferred choice for building high-efficiency, high-power-density DC transformers. On the one hand, three-phase DABs utilize a three-phase transformer in the AC link. By superimposing the number of phases, they reduce voltage ripple on the DC side, minimizing the size of the converter's passive components and further increasing the converter's power density. On the other hand, the RMS output current, current stress, and harmonic content of each phase arm of the three-phase DAB are lower, effectively reducing losses in the inductor, transformer, and switching transistors, thereby improving the converter's operating efficiency.

[0003] Existing research on three-phase DAB converters primarily focuses on optimizing efficiency under steady-state conditions, specifically by expanding the soft-switching range of the switches and reducing the current stress on the switching devices to improve converter efficiency. While three-phase DAB converters offer excellent steady-state performance, sudden changes in operating conditions can cause transient oscillations in the inductor current that persist for multiple switching cycles. These oscillate significantly, resulting in high transient currents and excessive power losses, which can trigger protective shutdowns and even permanent damage to circuit components. In practical engineering applications, mitigating these transient oscillations often requires significantly reducing the regulation speed, even leaving the converter uncontrolled. This makes rapid regulation of DAB converters difficult. Therefore, addressing these transient oscillations is crucial for practical engineering applications.

[0004] During the control of single-phase DAB, the transient oscillations of the inductor current manifest as a DC bias phenomenon. Existing literature has yielded some research results on suppressing current oscillations in single-phase DAB. A method using symmetrical phase-shift control and an intermediate phase-shift angle has been proposed, which can completely eliminate transients within a single switching cycle. Because the three-phase circuit is coupled through the three-phase neutral point, the transient oscillations in three-phase DAB are more severe than those in single-phase DAB. Existing literature uses coordinate transformation to represent the spatial trajectory of the state variables and, by adding an intermediate phase-shift angle, obtains the optimal control trajectory during transients. However, specific expressions for solving the phase-shift ratio are not provided, and the analysis of transient characteristics during sudden changes in power commands is not addressed. In summary, rapidly suppressing transient current oscillations in three-phase DAB converters and improving their dynamic performance are of great research significance. Summary of the Invention

[0005] In view of the defects of the prior art and the need for improvement, the present invention provides an instantaneous current control method and controller for a three-phase dual active bridge converter, which aims to quickly suppress the instantaneous current oscillation of the three-phase DAB converter, thereby improving the dynamic performance of the three-phase DAB converter.

[0006] To achieve the above object, according to one aspect of the present invention, a method for instantaneous current control of a three-phase dual active bridge converter is provided, the method comprising: when the power transmission instruction controlling the three-phase dual active bridge converter changes and the absolute value of the change is greater than a mutation threshold, solving the problem of i xtra +i Lpul =0 intermediate duty cycle D r ; Among them, i xtra ΔI0 is the transient response current generated on the x-phase inductor of the three-phase dual active bridge converter, x is any phase among the three phases abc, ΔI0 is the difference between the inductor current in the steady state before the power transmission instruction changes and the inductor current in the steady state after the change, i Lpul The duty cycle is D in the transient process after the power transmission instruction changes. r The inductor current response generated by the unit pulse of the power transmission instruction is as follows: within the switching cycle after the absolute value of the change in the power transmission instruction is greater than the mutation threshold, the control d is equal to D in the first 1 / 3 switching cycle. r , in other switching cycles, d is controlled to be equal to D1, where d is the shift ratio between the primary side x-phase bridge arm and the secondary side x-phase bridge arm in the three-phase dual active bridge converter, and D1 is the shift ratio between the primary and secondary side bridge arms corresponding to the changed power transfer instruction.

[0007] Furthermore, ΔI0 is obtained by using the frequency domain method to establish the inductor terminal voltage model of the x-phase inductor in the transient process after the power transmission instruction changes; using the first-order equivalent RL circuit model of the x-phase, ΔI0 under the inductor terminal voltage model is calculated according to the current superposition theorem.

[0008] Furthermore, ΔI0 is:

[0009] ΔI0=i A,1 (D,t)-i A,1 (D1,t)

[0010]

[0011] Where D is the original secondary bridge arm displacement corresponding to the power transmission instruction before the change, t is the time, i A,1 (D,t) is the inductor current in steady state before the power transmission command changes, i A,1(D1,t) is the inductor current in steady state after the power transfer command changes, V1 is the input voltage of the three-phase dual active bridge converter, M is the voltage conversion ratio of the three-phase dual active bridge converter, R t is the equivalent series parasitic resistance of each phase, w represents the radian per unit period, and L is the transmission inductance.

[0012] Furthermore, i xtra for:

[0013] i xtra =ΔI0e -t / τ

[0014] Where t is time, τ is the time constant, τ = L / R t , L is the transmission inductance, R t is the equivalent series parasitic resistance of each phase.

[0015] Furthermore, i Lpul for:

[0016]

[0017] Where n is the turns ratio of the transformer in the three-phase dual active bridge converter, V2 is the output voltage of the three-phase dual active bridge converter, R t is the equivalent series parasitic resistance of each phase, T hs is the half switching period of the three-phase dual active bridge converter, t is the time, τ is the time constant, τ=L / R t , L is the transmission inductance.

[0018] Furthermore, the solution is to let i xtra +i Lpul =0 intermediate duty cycle D r Specifically include: using offline method to solve the problem of i xtra +i Lpul =0 intermediate duty cycle D r .

[0019] Furthermore, when the power transmission instruction changes and the absolute value of the change is not greater than the mutation threshold, the method further includes: controlling d to be equal to D1 within a switching cycle after the absolute value of the change of the power transmission instruction is not greater than the mutation threshold.

[0020] According to another aspect of the present invention, an instantaneous current controller for a three-phase dual active bridge converter is provided, wherein the controller is configured to execute the instantaneous current control method for a three-phase dual active bridge converter as described above.

[0021] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects: a method for instantaneous current control of a three-phase dual active bridge converter is provided, and when the power transmission instruction suddenly changes, an intermediate duty cycle D is introduced. r In order to eliminate the transient DC component, the shift phase of the primary and secondary bridge arms is controlled to be equal to D in the first 1 / 3 switching cycle after the power transmission instruction suddenly changes. r , in the subsequent switching cycles, d is controlled to be equal to the original secondary bridge arm shift phase D1 corresponding to the power transfer instruction after the mutation; from the perspective of speed, this method can make the inductor current reach a stable state within 1 / 3 of the switching cycle, greatly shortening the transient process, while accelerating the power regulation speed, so that the converter has good dynamic regulation capability; from the perspective of reliability, this method effectively suppresses the inductor current impact caused by the sudden change of the power instruction, so that the device avoids the risk of overcurrent, ensures the safety of the device, and improves the reliability of the converter; from the perspective of efficiency optimization, this method realizes the smooth transition of the inductor current when the power instruction suddenly changes, avoids the current oscillation that lasts for multiple switching cycles, and improves the performance and efficiency of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flow chart of an instantaneous current control method for a three-phase dual active bridge converter provided by an embodiment of the present invention;

[0023] Figure 2 A schematic structural diagram of a three-phase dual active bridge converter provided in an embodiment of the present invention;

[0024] Figure 3 An equivalent circuit diagram of a three-phase dual active bridge converter provided by an embodiment of the present invention;

[0025] Figure 4 is the inductor terminal voltage v under the fundamental wave analysis method LA1 Schematic diagram of the harmonic content of ;

[0026] Figure 5 is the equivalent first-order RL circuit model of phase A;

[0027] Figure 6 This is a control waveform diagram of the instantaneous current control method when the power command suddenly increases;

[0028] Figure 7 This is the circuit schematic diagram of the instantaneous current control method;

[0029] Figure 8 This is the response waveform of the three-phase inductor current when the power command suddenly increases;

[0030] Figure 9 This is a waveform diagram of the inductor current when the power command suddenly increases after adopting the method of the embodiment of the present invention;

[0031] Figure 10 This is the response waveform of the three-phase inductor current when the power command suddenly decreases;

[0032] Figure 11 This is a waveform diagram of the inductor current when the power command suddenly decreases after adopting the method of the embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0034] In the present invention, the terms "first", "second", etc. (if any) in the present invention and the drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0035] Example 1

[0036] A transient current control method for a three-phase dual active bridge converter, see Figure 1 , combined with Figure 2-Figure 11 , the instantaneous current control method for the three-phase dual active bridge converter in this embodiment is described in detail, and the method includes operations S1 to S2.

[0037] The structure of the main circuit unit of the three-phase dual active bridge converter is as follows Figure 2 The main circuit unit includes input voltage V1, output voltage V2, primary three-phase bridge arm (A1, B1, C1), secondary three-phase bridge arm (A2, B2, C2), three-phase auxiliary inductor (L A , L B , L C ), a three-phase YY connected high-frequency isolation transformer T with a turns ratio of n:1. The primary three-phase bridge arm contains six switching tubes Q 11 -Q 16 , switch tube Q 11 -Q 16 An anti-parallel diode D is provided accordingly 11 -D 16 The secondary three-phase bridge arm contains six switching tubes Q 21 -Q 26 , switch tube Q 21 -Q 26 An anti-parallel diode D is provided accordingly 21 -D 26The drive signals of the corresponding switching tubes A1 / B1 / C1 and A2 / B2 / C2 are 120° out of phase. The input voltage V1 and the parallel stabilizing capacitor C1 are connected between the positive and negative poles of the input DC bus; the output voltage V2 and the parallel stabilizing capacitor C2 are connected between the positive and negative poles of the output DC bus. The switching period of the three-phase DAB converter is T s , half switching period T hs =T s / 2, switching frequency f s =1 / T s , voltage conversion ratio M=nV2 / V1. Assume that the equivalent series parasitic resistances in phases A, B, and C are equal, that is, r A =r B =r C =R t .i A 、i B 、i C The current flowing through the auxiliary inductor L is A , L B , L C The positive direction of the current is as follows: Figure 2 Indicated by the arrow in the middle. d is the phase shift ratio between the primary and secondary three-phase bridge arms under single-phase shift control. Specifically, when the primary three-phase bridge arm is connected to the input voltage and the secondary three-phase bridge arm is connected to the load, the phase shift ratio d between the primary and secondary bridge arms is positive, and power is transferred from the primary to the secondary. When the primary three-phase bridge arm is connected to the load and the secondary three-phase bridge arm is connected to the input voltage, the phase shift ratio d between the primary and secondary bridge arms is negative, and power is transferred from the secondary to the primary.

[0038] Under single-phase-shift control, the driving signal for all switches is a square wave with a duty cycle of 50%. According to the calculation formula for the piecewise linear inductor current, the transmission power P of the three-phase DAB converter in steady-state operation can be obtained as:

[0039]

[0040] When d = 1 / 3, the maximum transmission power of the three-phase DAB converter is P max :

[0041]

[0042] From formula (1), we can see that under single phase shift control, when the external parameters are determined, the transmission power P is only determined by the phase shift d. When the transmission power instruction suddenly changes, that is, the phase shift changes from d k-1 Mutation to d k Since the inductor current cannot change suddenly immediately, the transmission power of the three-phase DAB converter cannot be directly converted from P(d k-1 ) mutated to P(d kInstead, the converter exhibits an oscillatory decay trend, typically requiring hundreds of switching cycles to reach a stable state. This results in slow power regulation and poor converter dynamic performance. Furthermore, the larger the shift phase mutation range, the greater the inductor current surge, significantly increasing the risk of device overcurrent and hindering safe and reliable converter operation.

[0043] Operation S1: When the power transmission instruction controlling the three-phase dual active bridge converter changes and the absolute value of the change is greater than the mutation threshold, solve the problem of setting i xtra +i Lpul =0 intermediate duty cycle D r ; Among them, i xtra is the transient response current ΔI0 generated on the x-phase inductor of the three-phase dual active bridge converter, x is any phase among the three phases abc, ΔI0 is the difference between the inductor current in the steady state before the power transfer command changes and the inductor current in the steady state after the change, i Lpul The duty cycle is D in the transient process after the power transmission instruction changes. r The inductor current response generated by the unit pulse.

[0044] In order to achieve effective control of the output voltage and transmission power of the three-phase DAB converter, the embodiment of the present invention adopts a direct power model to construct a closed-loop control system, where the controller output is the normalized transmission power p:

[0045]

[0046] Figure 3 The equivalent circuit diagram of the three-phase DAB converter is shown, where the neutral points of the three-phase high-frequency transformer YY connection are marked as m1 and m2, and the primary potential of the three auxiliary inductors is v Li1 , the secondary side potential is nv Li2 , the voltage across the inductor is v Li , i=A, B, C. Under single-phase shift modulation, the voltage difference between the midpoint of the three-phase high-frequency isolation transformer and the midpoint of the DC bus is a six-pulse waveform in one switching cycle, which is consistent with the voltage waveform in the steady state, indicating that the inductor current overshoot and DC offset in the transient process will not affect the midpoint potential. Therefore, Figure 3 The three-phase DAB equivalent circuit is decomposed into three equivalent circuits: A, B, and C. Since the equivalent circuit structure of each phase is the same, the following analysis will take the equivalent circuit diagram of phase A as an example.

[0047] Figure 4 The inductor terminal voltage v is shown in the fundamental wave analysis method. LA1 Schematic diagram of harmonic content. Inductor terminal voltage v LA1 The Fourier series expansion of (t) is:

[0048]

[0049] Wherein, d1 is the internal shift phase ratio between the primary bridge arms of the three-phase DAB converter. Figure 4 Figure 2 shows the amplitude variations of the 1st, 5th, and 7th harmonics as the internal shift ratio d1 changes. It can be seen that as the harmonic order n increases, the voltage amplitude of that harmonic decreases. Furthermore, the larger the internal shift ratio d1, the greater the gap between each harmonic content and the fundamental. This embodiment of the present invention uses a single-phase shift control method with an internal shift ratio d1 = 1. This results in a high fundamental content, making the frequency domain method a preferred choice for establishing a transient process model.

[0050] Figure 5 The first-order equivalent RL circuit model of phase A is shown, where v LA1,1 is the fundamental component of the primary side inductor voltage, v LA2,1 is the fundamental component of the secondary side inductor voltage. According to the superposition theorem, the inductor current i in steady state can be obtained. A,1 for:

[0051]

[0052] In the embodiment of the present invention, it is assumed that the moment when the power transmission instruction suddenly changes is t k =0, before the power transmission instruction suddenly changes, i.e. t k <0 is called the initial steady state. At this time, the external shift d=D, and the inductor current expression is as shown in formula (6). After the power command suddenly changes, that is, t k The target stable state when t > 0 is called the final steady state, at this time d = D1, and the inductor current expression is as shown in formula (7). k = 0, the difference between the initial steady-state and final steady-state inductor currents is ΔI0, which can be expressed as formula (8).

[0053]

[0054] ΔI0=i A,1 (D,t)-i A,1 (D1,t) (8)

[0055] Where D is the original secondary bridge arm displacement corresponding to the power transmission instruction before the change, t is the time, i A,1 (D,t) is the inductor current in steady state before the power transmission command changes, i A,1 (D1,t) is the inductor current in steady state after the power transfer command changes, V1 is the input voltage of the three-phase dual active bridge converter, M is the voltage conversion ratio of the three-phase dual active bridge converter, R t is the equivalent series parasitic resistance of each phase, w represents the radian per unit period, and L is the transmission inductance.

[0056] In summary, the method for obtaining ΔI0 is as follows: establish the inductor terminal voltage model of the x-phase inductor under the transient process after the change of the power transmission instruction by using the frequency domain method; use the first-order equivalent RL circuit model of the x-phase, and calculate ΔI0 under the inductor terminal voltage model according to the current superposition theorem.

[0057] In the first-order RL circuit, the inductor current i A The full response during the transient process can be divided into two parts, namely the steady-state response i Aste and the transient response i Atra , and the specific expression is shown in Equation (9). It can be seen that when the power instruction suddenly changes, the phase shift ratio changes from D in the initial steady state to D1 in the final steady state, but the inductor current cannot change suddenly, that is, ΔI0≠0. Therefore, the transient response i Atra caused by ΔI0 is also not equal to 0, resulting in a decaying oscillation process of the inductor current.

[0058] i A = i Aste + i Atra = i A,1 (D1, t)+ΔI0e -tτ (9)

[0059] Similarly, i xtra is i xtra =ΔI0e -t / τ , τ = L / R t .

[0060] The above analysis results show that: the transient component is the main reason for the decaying oscillation. Therefore, to suppress the oscillation, it is necessary to control the transient component. If the converter is to directly enter the steady state without experiencing the transient process at the moment of the power instruction mutation, ΔI0 needs to be zero. However, since the inductor current i A cannot change suddenly, this condition cannot be satisfied. On the other hand, the method of rapidly decaying the transient component by increasing R t will bring additional losses and is not advisable. Therefore, an effective method for controlling the transient component is to control the voltage v LA across the inductor, shorten the duration of the transient component, and reduce the peak value of the oscillation. [[ID=

[46] ]

[0061] The instantaneous current control method proposed in the embodiment of the present invention aims to make the transient component decay to zero within 1 / 3 of the switching period after the transient process occurs.

[0062] When the power transmission instruction suddenly increases, the principle of the instantaneous current control method is as Figure 6 shown, where D < D1; t0 = 0 is the occurrence time of the transient process; t^1 = DT hs ; t2 = D r T hs ; t3 = D1Ths Expected t k =1 / 3T s is the end time of the transient process; v p for Figure 2 The potential of point a1 on the central edge relative to the midpoint of the input voltage; v s for Figure 2 The potential of point a2 on the secondary side relative to the midpoint of the output voltage. To achieve this goal, take the voltage v s The middle shift at the rising edge is compared to D r As the control phase shift angle, by choosing the appropriate D r So that the transient component at t k The decay is zero.

[0063] See Figure 7 According to the superposition theorem, the voltage source after transient control can be regarded as the original voltage source v s A pulse voltage source P1 is superimposed on D r The action time and magnitude of the control unit pulse P1 are such that the direction of the inductor current of phase A is opposite to the assumed positive direction. The inductor current response i generated by the applied voltage source pulse is Lpul for:

[0064]

[0065] Where n is the turns ratio of the transformer in the three-phase dual active bridge converter, V2 is the output voltage of the three-phase dual active bridge converter, T hs is the half switching period of the three-phase dual active bridge converter.

[0066] It can be seen from equations (9) and (10) that the transient component generated when the transmission power changes suddenly is consistent with the attenuation function of the applied impulse response and is only affected by the system parameters L and R. t If t k At the moment, the sum of the two amplitudes is 0, that is, i Atra (t k )+i Lpul (t k )=0, then the transient component of the inductor current and the applied pulse response cancel each other out, leaving only the steady-state component in the system, and the system directly enters the steady-state process without the influence of current overshoot and long-period transient oscillation.

[0067] Preferably, in this embodiment, solve i xtra +i Lpul =0 intermediate duty cycle D r Specifically include: using offline method to solve the problem of i xtra +i Lpul =0 intermediate duty cycle D r .

[0068] Operation S2: After the absolute value of the change in the power transfer command exceeds the mutation threshold, control d to be equal to D in the first 1 / 3 of the switching cycle. r , in other switching cycles, d is controlled to be equal to D1, where d is the shift ratio between the primary side x-phase bridge arm and the secondary side x-phase bridge arm in the three-phase dual active bridge converter, and D1 is the shift ratio between the primary and secondary side bridge arms corresponding to the changed power transfer instruction.

[0069] In this embodiment, using Figure 2 The transient control unit in D r The calculation makes the converter reach steady state within 1 / 3 of the switching cycle; the driving signal modulation unit is used to control the on-off state of each switch tube.

[0070] According to an embodiment of the present invention, when the power transfer instruction changes and the absolute value of the change is not greater than the mutation threshold (it is considered that D=D1), the method also includes: within the switching cycle after the absolute value of the change in the power transfer instruction is not greater than the mutation threshold, controlling d to be equal to D1.

[0071] This method is simulated in MATLAB / Simulink with the following parameters: V1 = 400 V, V2 = 400 V, f s =40kHz, n=1, auxiliary inductor L=62.5uH, R t =0.1Ω, D=0.1, D1=0.4. When the phase shift angle suddenly changes from 0.1 to 0.4, the intermediate phase shift angle of transient control is calculated to be D r =0.242. Figure 8 、 Figure 10 The three-phase inductor current response waveforms are shown in Figure 1, respectively, when the power command suddenly increases and decreases. It can be seen that when the power command changes suddenly, the inductor current will experience severe overcurrent shock and long-term oscillation, and its stabilization time exceeds 100 switching cycles. Figure 9 、 Figure 11 The figures below show the inductor current waveforms when the power command suddenly increases and decreases after the proposed instantaneous current control method is adopted. It can be seen that the instantaneous current control method not only eliminates transient oscillations, but also prevents inductor current overshoot. At the same time, it reduces the transient transition time to 1 / 3 of the switching cycle, achieving smooth and fast switching between power levels.

[0072] Example 2

[0073] A transient current controller for a three-phase dual active bridge converter is provided. The controller is used to execute the transient current control method for the three-phase dual active bridge converter. The related technical solutions are the same as those in the first embodiment and will not be described in detail here.

[0074] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for controlling instantaneous current of a three-phase dual active bridge converter, characterized in that: include: When the power transmission instruction controlling the three-phase dual active bridge converter changes and the absolute value of the change is greater than the mutation threshold, solve the problem of i xtra +i Lpul =0 intermediate duty cycle D r ; Among them, i xtra ΔI0 is the transient response current generated on the x-phase inductor of the three-phase dual active bridge converter, x is any phase among the three phases abc, ΔI0 is the difference between the inductor current in the steady state before the power transmission instruction changes and the inductor current in the steady state after the change, i Lpul The duty cycle is D in the transient process after the power transmission instruction changes. r The inductor current response generated by the unit pulse; In the switching cycle after the absolute value of the change in the power transfer instruction is greater than the mutation threshold, control d to be equal to D in the first 1 / 3 of the switching cycle r , in other switching cycles, d is controlled to be equal to D1, where d is the shift ratio between the primary side x-phase bridge arm and the secondary side x-phase bridge arm in the three-phase dual active bridge converter, and D1 is the shift ratio between the primary and secondary side bridge arms corresponding to the changed power transfer instruction.

2. The instantaneous current control method for a three-phase dual active bridge converter according to claim 1, wherein: The method to obtain ΔI0 is: The frequency domain method is used to establish the inductor terminal voltage model of the x-phase inductor in the transient process after the power transmission command changes; The first-order equivalent RL circuit model of the x-phase is used to calculate ΔI0 under the inductor terminal voltage model according to the current superposition theorem.

3. The instantaneous current control method for a three-phase dual active bridge converter according to claim 2, wherein: ΔI0 is: ΔI0=i A,1 (D,t)-i A,1 (D1,t) Where D is the original secondary bridge arm displacement corresponding to the power transmission instruction before the change, t is the time, i A,1 (D,t) is the inductor current in steady state before the power transmission command changes, i A,1 (D1,t) is the inductor current in steady state after the power transfer command changes, V1 is the input voltage of the three-phase dual active bridge converter, M is the voltage conversion ratio of the three-phase dual active bridge converter, R t is the equivalent series parasitic resistance of each phase, w represents the radian per unit period, and L is the transmission inductance.

4. The instantaneous current control method for a three-phase dual active bridge converter according to claim 1, wherein: i xtra for: i xtra =ΔI0e -t / τ Where t is time, τ is the time constant, τ = L / R t , L is the transmission inductance, R t is the equivalent series parasitic resistance of each phase.

5. The instantaneous current control method for a three-phase dual active bridge converter according to any one of claims 1 to 4, characterized in that: i Lpul for: Where n is the turns ratio of the transformer in the three-phase dual active bridge converter, V2 is the output voltage of the three-phase dual active bridge converter, R t is the equivalent series parasitic resistance of each phase, T hs is the half switching period of the three-phase dual active bridge converter, t is the time, τ is the time constant, τ=L / R t , L is the transmission inductance.

6. The instantaneous current control method for a three-phase dual active bridge converter according to claim 1, wherein: The solution is to let i xtra +i Lpul =0 intermediate duty cycle D r Specifically include: using offline method to solve the problem of i xtra +i Lpul =0 intermediate duty cycle D r .

7. The instantaneous current control method for a three-phase dual active bridge converter according to claim 1, wherein: When the power transmission instruction changes and the absolute value of the change is not greater than the mutation threshold, the method further includes: controlling d to be equal to D1 within a switching cycle after the absolute value of the change of the power transmission instruction is not greater than the mutation threshold.

8. An instantaneous current controller for a three-phase dual active bridge converter, characterized in that: The controller is configured to execute the instantaneous current control method for a three-phase dual active bridge converter according to any one of claims 1 to 7.

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