Energy storage system suitable for wide voltage range and control method

Abstract

The invention discloses an energy storage system suitable for a wide voltage range and a control method, and is suitable for AC-DC conversion in the field of battery energy storage. The method comprises the following specific implementation steps: firstly, analyzing the problem that the leakage inductance current peak value of secondary side extension phase shift modulation is relatively large in a wide voltage range, and then providing dual-mode modulation considering voltage gain; on the basis, soft switching conditions of a boost mode and a buck mode are analyzed, and an expression of a phase shift ratio and a switching frequency is deduced by constraining a leakage inductance current value at the switching-on moment of a specific switching tube. According to the control method, the converter can keep good electric energy quality in a wide voltage range, full-range soft switching is achieved, and the peak value of leakage inductance current is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the field of battery energy storage AC-DC, and more specifically, to an energy storage system and a control method adaptable to a wide voltage range. Background Art

[0002] In various energy storage systems such as on-vehicle chargers, battery energy storage, and DC power distribution systems, high-frequency isolated AC-DC converters, as key interfaces between the AC power grid and DC voltage, are widely used therein.

[0003] High-frequency isolated AC-DC converters can be classified into two-stage and single-stage types according to their structures. The two-stage structure consists of a power factor correction (PFC) circuit and a high-frequency isolated DC-DC circuit. The PFC circuit converts the AC voltage into a relatively constant DC bus voltage. To achieve voltage stabilization, it usually relies on large-capacity electrolytic capacitors, which will reduce the power density of the converter. In contrast, the single-stage AC-DC converter eliminates the intermediate large-capacity voltage-stabilizing electrolytic capacitor and can achieve single-stage conversion of the transmitted power. The single-stage dual active bridge (DAB) AC-DC converter is evolved from the dual active bridge DC-DC converter and has advantages such as a bidirectional wide voltage conversion range, high efficiency, long life, and high power density. In recent years, the single-stage DAB type AC-DC converter has received extensive attention.

[0004] The research focus of the single-stage DAB type AC-DC converter is on the control and optimization of DAB. The DAB converter usually adopts phase-shift modulation strategies including single-phase-shift modulation, extended phase-shift modulation, and triple-phase-shift modulation. For single-phase-shift modulation, due to being limited by only one phase-shift degree of freedom, when the input and output voltages do not match, the peak value of the leakage inductance current will increase significantly, and at the same time, a large amount of reverse power will occur. For extended phase-shift modulation and triple-phase-shift modulation, although they can optimize the DAB converter to varying degrees by increasing the phase-shift degree of freedom based on single-phase-shift modulation, it is still difficult to achieve soft switching in the full load range.

[0005] The mainstream research focuses on extended phase-shift modulation on the secondary side. These studies set the DC side voltage to a single fixed value, and the voltage gain K (K = nV dc / |v ac|) is always greater than 1. However, in applications such as battery energy storage and on-vehicle chargers, the output terminal of the AC-DC converter is usually connected to a battery with a very wide voltage range. Therefore, the single-stage DAB-type AC-DC converter needs to adapt to a very wide voltage gain range. In this case, there may be two situations for the single-stage DAB-type AC-DC converter, namely K>1 and K<1. Some studies have shown that when K<1, if the secondary-side extended phase-shift modulation is still used, although the switching tubes can achieve ZVS turn-on, at a certain transmission power, this modulation strategy will cause an increase in the reflux power and the peak value of the leakage inductance current, thus increasing the losses of the single-stage DAB-type AC-DC converter and significantly reducing the efficiency. Summary of the Invention

[0006] The object of the present invention is to address the problems of limited soft-switching range and large peak value of leakage inductance current of the single-stage DAB-type AC-DC converter in the energy storage system within a wide voltage range, and to propose an energy storage system and control method suitable for a wide voltage range. Through the designed extended phase-shift variable-frequency modulation strategy considering the voltage gain, all switching tubes can achieve full-range zero-voltage turn-on in both the boost mode and the buck mode, and to a certain extent, reduce the peak value of the leakage inductance current.

[0007] To solve the above technical problems, in a first aspect, the present application provides an extended phase-shift variable-frequency modulation method considering voltage gain for a single-stage DAB-type AC-DC converter. The single-stage DAB-type AC-DC converter includes a primary H-bridge composed of switching tubes S 1 , S 2 , S 3 , S 4 and a secondary H-bridge composed of switching tubes S 5 , S 6 , S 7 , S 8 . The method includes the following steps:

[0008] It is defined that when the voltage gain K of the single-stage DAB-type AC-DC converter is greater than 1, it is the boost mode; when the voltage gain K changes from greater than 1 to less than 1, it is the buck mode;

[0009] When the single-stage DAB-type AC-DC converter is in the boost mode, first simultaneously turn on the switching tubes S 1 , S 2 , S 3 , S 4 , then simultaneously turn on the switching tubes S 5 , S 6 , S 7 , S 8 , and when turning on the switching tubes S 1 , S 2 , S3 、At time t of S 4 , the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of -I 0 . At time t of turning on switches S ZVS1 , S 5 , S 6 , S 7 , S 8 , the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of I 1 ; ZVS2

[0010] When the single-stage DAB-type AC-DC converter is in the buck mode, first turn on switches S 1 , S 2 , S 3 , S 4 simultaneously, and then turn on switches S 5 , S 6 , S 7 , S 8 simultaneously. And at time t of turning on switches S 1 , S 2 , S 3 , S 4 , the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of -I 0 . At time t of turning on switches S ZVS3 , S 5 , S 6 , S 7 , S 8 , the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of I 1 . ZVS4

[0011] Based on the above, in the boost mode, by adjusting the phase shift ratio D 2 , D 3 and the switching frequency f s of the single-stage DAB-type AC-DC converter, the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of -I ZVS1 , and the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value of I ZVS2 ;

[0012] Among them, D 2 represents the external phase shift ratio between S 4 and S 5 , and D 3 represents the internal phase shift ratio between S 6 and S 8 ; The phase shift ratio D 2 , D​​3 and the switching frequency f s The expression is:

[0013]

[0014] where A, B, C, A 0 , B 0 , C 0 are:

[0015]

[0016]

[0017] In the buck mode, by adjusting the phase shift ratio D 1 , D 2 and the switching frequency f s , the leakage inductance current of the single-stage DAB type AC-DC converter is constrained to a constant value -I ZVS3 , and the leakage inductance current of the single-stage DAB type AC-DC converter is constrained to a constant value I ZVS4 ; where D 1 represents the internal phase shift ratio between S 2 and S 4 , D 2 represents the external phase shift ratio between S 4 and S 5 ; the phase shift ratios D 1 , D 2 and the switching frequency f s The expression is:

[0018]

[0019] where E, F, G, E 0 , F 0 , G 0 are:

[0020]

[0021] In the formula, v ac is the AC voltage, L k represents the leakage inductance referred to the primary side of the high-frequency transformer, V dc is the DC voltage output after conversion by the single-stage DAB type AC-DC converter, n is the turns ratio of the high-frequency transformer, I ac is the AC current amplitude, ω is the grid angular frequency, and t is the time.

[0022] Based on the above, it is characterized in that: the constant values I ZVS1 , I ZVS2 , I ZVS3, I ZVS4 Set to I ZVS1 = I ZVS2 = I ZVS3 = I ZVS4 = I ZVS , I ZVS is a constant value.

[0023] Based on the above, the constant value I ZVS is set to be much larger than the minimum currents I s,ac and I s,dc required for the charging and discharging processes of the junction capacitances of the primary and secondary side switching transistors, and the maximum value of

[0024] In a second aspect, the present application provides a single-stage DAB type AC-DC converter. When performing extended phase-shift modulation, the extended phase-shift variable-frequency modulation method considering voltage gain for the single-stage DAB type AC-DC converter described above is adopted.

[0025] In a third aspect, the present application provides an energy storage system adapted to a wide voltage range, including an AC power grid, an AC-DC converter, and a DC voltage system. The DC voltage system is connected to the AC power grid through the AC-DC converter, and the AC-DC converter adopts the single-stage DAB type AC-DC converter described above.

[0026] In a fourth aspect, the present application provides an energy storage control method adapted to a wide voltage range for an energy storage system. The energy storage system includes an AC power grid, an AC-DC converter, and a DC voltage system. The DC voltage system is connected to the AC power grid through the AC-DC converter. When performing extended phase-shift modulation on the AC-DC converter, the extended phase-shift variable-frequency modulation method considering voltage gain for the single-stage DAB type AC-DC converter described above is adopted.

[0027] In order to solve the problems of limited soft-switching range and large peak value of leakage inductance current of the single-stage DAB type AC-DC converter in the energy storage system, the present invention first analyzes the problem of large peak value of leakage inductance current existing in the extended phase-shift modulation on the secondary side in a wide voltage range, and proposes a dual-mode modulation method considering voltage gain, that is, a boost mode (in this mode, the internal phase-shift is the extended phase-shift modulation on the secondary side) and a buck mode (in this mode, the internal phase-shift is switched from the secondary side to the primary side to form the extended phase-shift modulation on the primary side). On this basis, the soft-switching conditions of the boost and buck modes are analyzed, and by constraining the value of the leakage inductance current at the turn-on moment of a specific switching transistor, the expressions of the phase-shift ratio and the switching frequency are derived. Then, by modulating the phase-shift ratio and the switching frequency, the soft-switching of the converter in a wide voltage range can be realized, the peak value of the leakage inductance current can be effectively reduced, and at the same time, good power quality can be maintained. Description of the Drawings

[0028] Figure 1 : It is a single-stage DAB-type AC-DC converter topology.

[0029] Figure 2 : It is a working waveform diagram in boost mode.

[0030] Figure 3 : It is a working waveform diagram in buck mode.

[0031] Figure 4 : It is the waveforms of the leakage inductance current and the primary and secondary bridge arm currents in boost mode.

[0032] Figure 5 : It is V dc = 200V, the curve of the external phase shift ratio compared with D 2 and the switching frequency f s of.

[0033] Figure 6 : It is the switching frequency under different DC voltages and different constant current values.

[0034] Figure 7 : It is the curve of the phase shift ratio of the converter under different DC voltages.

[0035] Figure 8 : It is a comparison diagram of the peak values of the leakage inductance current. Among them, (a) is the peak value of the leakage inductance current when the internal phase shift does not switch with K = 1, and (b) is the peak value of the leakage inductance current when the internal phase shift switches with K = 1.

[0036] Figure 9 is a diagram of various energy storage systems. Specific implementation manners

[0037] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present application.

[0038] The terms "including" and "having" in the specification and claims of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system including a series of steps or units is not limited to the listed steps or units, but may include steps or units not listed.

[0039] To facilitate the understanding of the technical solutions provided by the present application, the technical terms involved in the embodiments of the present application will be explained below.

[0040] Soft switching: By switching the control device under specific conditions, it tries to avoid turning on or off under non-zero voltage or current conditions, thus significantly reducing losses.

[0041] ZVS (Zero Voltage Switching) is a soft switching technology commonly used in power electronic circuits, especially in applications such as DC-DC converters and inverters. Its main purpose is to reduce switching losses, improve circuit efficiency, and reduce electromagnetic interference (EMI) by switching the switching device (such as MOSFET or IGBT) when it is in the zero voltage state.

[0042] Single-stage dual active bridge (DAB) AC-DC converter Figure 1 shows the topology of a single-stage dual active bridge type AC-DC converter. This AC-DC converter consists of a full-bridge rectifier circuit and a DAB converter. Among them, the full-bridge rectifier circuit is composed of 4 power frequency switching tubes Q 1 -Q 4 which is used to rectify the AC voltage v ac to v rec , that is, v rec =|v ac |. The output terminal of the rectifier circuit is a small-capacity filter capacitor C rec . The switching tubes S 1 -S 4 constitute the primary H-bridge of the DAB converter, and S 5 -S 8 constitute the secondary H-bridge. The primary and secondary H-bridges are connected through the intermediate high-frequency transformer T. The turns ratio of the high-frequency transformer is n:1. L k represents the leakage inductance referred to the primary side of the transformer. The DAB converter converts the rectified voltage into a stable DC voltage, and by controlling the turn-on sequence of the primary and secondary switching tubes of the DAB, it can realize the control of the DAB input current i 1 .

[0043] Next, in combination with the accompanying drawings, through some embodiments and their application scenarios, a energy storage system and control method adaptable to a wide voltage range provided by the embodiments of the present application will be described in detail.

[0044] In the first aspect, an extended phase-shifted frequency modulation method considering voltage gain for a single-stage DAB type AC-DC converter provided by the embodiments of the present application includes the following steps:

[0045] Step 1: Sample the parameters of v ac , i ac , and V dc of the single-stage DAB type AC-DC converter;

[0046] Step 2: Calculate the voltage gain \(K = nV\) dc / |v ac |;

[0047] When the voltage gain \(K\) of the single-stage DAB-type AC-DC converter is greater than 1, it is in the boost mode; when the voltage gain \(K\) changes from greater than 1 to less than 1, it is in the buck mode;

[0048] Step 3: When the voltage gain \(K\) is greater than 1, that is, when the single-stage DAB-type AC-DC converter is in the boost mode, first turn on the switching tubes \(S\) 1 、\(S\) 2 、\(S\) 3 、\(S\) 4 , then turn on the switching tubes \(S\) 5 、\(S\) 6 、\(S\) 7 、\(S\) 8 , and at the moment \(t\) 1 、\(S\) 2 、\(S\) 3 、\(S\) 4 when turning on the switching tubes \(S\) 0 , constrain the leakage inductance current of the single-stage DAB-type AC-DC converter to a constant value of \(-I\) ZVS1 , and at the moment \(t\) 5 、\(S\) 6 、\(S\) 7 、\(S\) 8 when turning on the switching tubes \(S\) 1 , constrain the leakage inductance current of the single-stage DAB-type AC-DC converter to a constant value of \(I\) ZVS2 ;

[0049] When the voltage gain \(K\) is less than 1, that is, when the single-stage DAB-type AC-DC converter is in the buck mode, first turn on the switching tubes \(S\) 1 、\(S\) 2 、\(S\) 3 、\(S\) 4 , then turn on the switching tubes \(S\) 5 、\(S\) 6 、\(S\) 7 、\(S\) 8 , and at the moment \(t\) 1 、\(S\) 2 、\(S\) 3 、\(S\) 4 when turning on the switching tubes \(S\) 0 , constrain the leakage inductance current of the single-stage DAB-type AC-DC converter to a constant value of \(-I\) ZVS3 , and at the moment \(t\) 5 、\(S\) 6 、\(S\) 7 、\(S\) 8 when turning on the switching tubes \(S\) 1At a moment, the leakage inductance current of the single-stage DAB-type AC-DC converter is constrained to a constant value I ZVS4 .

[0050] The following is the design process of the method in this embodiment:

[0051] Figure 2 The extended phase-shift modulation working waveform is shown. By analyzing the switch characteristics of the extended phase-shift modulation, the expression of the leakage inductance current at the turn-on moment of each switch tube is:

[0052]

[0053] The average value of the input current of the DAB converter is

[0054]

[0055] In applications such as battery energy storage and on-board chargers, the output terminal of the AC-DC converter is usually connected to a battery with a very wide voltage range. For example, an on-board charger needs to adapt to a DC voltage of 200 - 450V. In this wide voltage range, the voltage gain K (nV dc / |v ac |) may have two situations, namely K>1 and K<1. When K>1, the magnitudes of the DAB port voltage v p , nv s are consistent with the working waveform in Figure 2 . Therefore, at this time, the extended phase-shift modulation shown in Figure 2 can be used. When K<1, if the extended phase-shift modulation with inner phase-shift on the secondary side in Figure 2 is still used, during the time period from t 2 to t 3 , the voltages on both sides of the DAB, v p >nv s , will cause the leakage inductance current waveform to show an upward trend during this time period. Even if the switch ZVS turn-on can be achieved, however, at a certain transmission power, it will also cause the peak value of the leakage inductance current to increase, resulting in an increase in the loss of the AC-DC converter and a significant reduction in efficiency. To reduce the peak value of the leakage inductance current when K<1, it is proposed to switch the inner phase-shift in this mode from the secondary side to the primary side to form the primary-side extended phase-shift modulation, as shown in Figure 3 , which is defined as the buck mode.

[0056] Based on the above analysis, combined with the working waveforms of the boost and buck modes, it is proposed that within the entire boost mode cycle, the leakage inductance current value corresponding to the t 0 moment is set to a constant value -I ZVS1 , and the leakage inductance current value corresponding to the t 1 moment is set to a constant value I ZVS2 . According to the leakage inductance current expression, t2 The leakage inductance current value at the moment is naturally greater than I ZVS2 . If the constant current I ZVS1 and I ZVS2 are respectively set to values greater than I s,ac and I s,dc , it can ensure that all switching tubes in this mode meet the conditions for achieving ZVS turn-on, as Figure 4 shown; similarly, in the buck mode, the leakage inductance current value at time t 0 is set to a constant value -I ZVS3 , and the leakage inductance current value at time t 1 is set to a constant value I ZVS4 . If the constant current I ZVS3 and I ZVS4 are respectively set to values greater than I s,ac and I s,dc , it can also ensure that all switching tubes in this mode meet the conditions for achieving zero-voltage turn-on.

[0057] To achieve AC-side PFC, it is necessary to ensure that the average value of the input current of the DAB converter is equal to the absolute value of the AC current. From this, the following system of equations can be obtained:

[0058]

[0059] Combined with the leakage inductance current expression, the duty ratio D 2 , D 3 and the switching frequency f s expression

[0060]

[0061] where A, B, C, A 0 , B 0 , C 0 are

[0062]

[0063] The constraint equations in the buck mode are

[0064]

[0065] Combined with the leakage inductance current expression in the buck mode, the duty ratio D 1 , D 2 and the switching frequency f s expression

[0066]

[0067] where E, F, G, E 0 , F0 , G 0 is

[0068]

[0069]

[0070] In the above formula, D 2 represents the outward shift between S 4 and S 5 . Compared with the inward shift between S 3 and S 6 and S 8 , v ac is the AC voltage, L k represents the leakage inductance referred to the primary side of the high-frequency transformer, V dc is the DC voltage output after conversion by the single-stage DAB-type AC-DC converter, n is the turns ratio of the high-frequency transformer, f s is the switching frequency, I ac is the amplitude of the AC current, ω is the grid angular frequency, and t is time.

[0071] Figure 5 It can be seen from the expressions of the phase shift ratio and the switching frequency that the phase shift ratio and the switching frequency will be affected by the constant current value. As shown, when the constant current values are not equal, at the moment of switching between the boost and buck modes, the magnitudes of D 2 and f s both change suddenly. To avoid the possible transient oscillation of the AC-DC converter during mode switching, the constant current value can be set to I ZVS1 = I ZVS2 = I ZVS3 = I ZVS4 = I ZVS to ensure that the phase shift ratio and the switching frequency remain continuous at the moment of mode switching.

[0072] Figure 6 shows the switching frequency curves under different DC voltages and different constant current values I ZVS . A smaller constant current value will result in too high a switching frequency under light load, which will increase the difficulty of designing magnetic components and is not conducive to the selection of switching devices. Constrained by the switching frequency, the constant current value needs to be set much higher than the level required to achieve soft switching. However, too high a constant current value will increase the turn-off loss of the switching transistor. It is known that the maximum values of the minimum currents I s,ac and I s,dc required for the charging and discharging processes of the junction capacitors of the primary and secondary side switching transistors are 0.622 A and 0.4272 A respectively.

[0073] Taking everything into consideration, select I ZVS= 3A, and this constant current value is much higher than the current value required to achieve ZVS turn-on of the primary and secondary side switching transistors. Figure 7 shows the phase shift ratios of the AC-DC converter when the DC voltage is 200V and 450V respectively at I ZVS = 3A. Figure 7 It shows that the magnitudes of the phase shift ratios D 1 , D 2 and D 3 can meet the requirements of theoretical analysis and full-range soft switching.

[0074] Figure 8 is a comparison chart of the peak value of the leakage inductance current. Observing (a), it can be seen that when v p > nv s , the inner phase shift is still on the secondary side, indicating that the inner phase shift does not switch at the moment when the voltage gain is 1. Within half of the power frequency cycle, the leakage inductance current reaches the maximum value at about 0.005s, and the peak value of the leakage inductance current at this time is 9.61A. Observing (b), when v p > nv s , the inner phase shift switches to the primary side. Similarly, under the condition that the transmission power is 500W, the peak value of the leakage inductance current at this time is 8.70A.

[0075] Through comparison, it can be concluded that the dual-mode extended phase shift frequency modulation method considering voltage gain proposed in this embodiment can effectively reduce the peak value of the leakage inductance current under a certain transmission power.

[0076] In the second aspect, the embodiment of the present invention also provides a single-stage DAB type AC-DC converter, and when performing extended phase shift modulation, it adopts the extended phase shift frequency modulation method considering voltage gain for the single-stage DAB type AC-DC converter.

[0077] It should be noted that the device embodiment is similar to the method embodiment, so the description is relatively simple. For related parts, please refer to the method embodiment.

[0078] In the third aspect, the embodiment of the present invention also provides an energy storage system adapted to a wide voltage range, as Figure 9 shown, including an AC power grid, an AC-DC converter, and a DC voltage system. The DC voltage system is connected to the AC power grid through the AC-DC converter, and the AC-DC converter adopts the single-stage DAB type AC-DC converter.

[0079] Specifically, the DC voltage system is an electric vehicle charging system, a battery energy storage system, a photovoltaic system, a wind power system, or a household appliance energy storage system.

[0080] Fourthly, an embodiment of the present invention further provides a energy storage control method adaptable to a wide voltage range, which is used for an energy storage system. The energy storage system includes an AC power grid, an AC-DC converter, and a DC voltage system. The DC voltage system is connected to the AC power grid through the AC-DC converter. It is characterized in that when performing extended phase-shifted modulation on the AC-DC converter, the extended phase-shifted variable-frequency modulation method considering voltage gain for a single-stage DAB-type AC-DC converter is adopted.

[0081] Specifically, the DC voltage system is an electric vehicle charging system, a battery energy storage system, a photovoltaic system, a wind power system, or a household appliance energy storage system.

[0082] The above has introduced in detail the methods, systems, etc. provided in this application. Specific examples are used in this article to elaborate on the principles and implementation manners of this application. The description of the above embodiments is only used to help understand the method and its core idea of this application; at the same time, for those of ordinary skill in the art, according to the idea of this application, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to this application.

Claims

1. An extended phase-shift frequency conversion modulation method for a single-stage DAB type AC-DC converter taking into account voltage gain, wherein the single-stage DAB type AC-DC converter comprises a primary H-bridge composed of switch tubes S1, S2, S3, and S4 and a secondary H-bridge composed of switch tubes S5, S6, S7, and S8; characterized in that: The method comprises the following steps: It is defined that when the voltage gain K of a single-stage DAB type AC-DC converter is greater than 1, it is in boost mode; when the voltage gain K changes from greater than 1 to less than 1, it is in buck mode; When the single-stage DAB type AC-DC converter is in the boost mode, the switches S1, S2, S3, and S4 are turned on at the same time, and then the switches S5, S6, S7, and S8 are turned on at the same time. At the time t0 when the switches S1, S2, S3, and S4 are turned on, the leakage inductance current of the single-stage DAB type AC-DC converter is constrained to a constant value -I ZVS1 At the time t1 when the switches S5, S6, S7, and S8 are turned on, the leakage current of the single-stage DAB type AC-DC converter is constrained to a constant value I ZVS2 ; When the single-stage DAB type AC-DC converter is in the buck mode, the switch tubes S1, S2, S3, and S4 are turned on at the same time, and then the switch tubes S5, S6, S7, and S8 are turned on at the same time. At the time t0 when the switch tubes S1, S2, S3, and S4 are turned on, the leakage inductance current of the single-stage DAB type AC-DC converter is constrained to a constant value -I ZVS3 At the time t1 when the switches S5, S6, S7, and S8 are turned on, the leakage current of the single-stage DAB type AC-DC converter is constrained to a constant value I ZVS4 .

2. The extended phase-shift frequency conversion modulation method taking into account voltage gain for a single-stage DAB type AC-DC converter according to claim 1, characterized in that: In boost mode, the shift phase of the single-stage DAB AC-DC converter is adjusted by adjusting D2, D3 and the switching frequency f s , so that the leakage current of the single-stage DAB type AC-DC converter is constrained to a constant value -I ZVS1 , and constrain the leakage inductance current of the single-stage DAB type AC-DC converter to a constant value I ZVS2 ; Among them, D2 represents the outward shift ratio between S4 and S5, and D3 represents the inward shift ratio between S6 and S8; the shift ratios D2, D3 and the switching frequency f s The expression is: Among them, A, B, C, A0, B0, C0 are: In buck mode, the shift phase of the single-stage DAB AC-DC converter is adjusted by adjusting D1, D2 and the switching frequency f s , so that the leakage current of the single-stage DAB type AC-DC converter is constrained to a constant value -I ZVS3 , and constrain the leakage inductance current of the single-stage DAB type AC-DC converter to a constant value I ZVS4 ; Where D1 represents the internal shift ratio between S2 and S4, and D2 represents the external shift ratio between S4 and S5; the shift ratios D1, D2 and the switching frequency f s The expression is: Among them, E, F, G, E0, F0, G0 are: In the formula, v ac is the AC voltage, L k Represents the leakage inductance converted to the primary side of the high-frequency transformer, V dc is the DC voltage output by the single-stage DAB type AC-DC converter after conversion, n is the transformation ratio of the high-frequency transformer, I ac is the AC current amplitude, ω is the grid angular frequency, and t is the time.

3. The extended phase-shift frequency conversion modulation method taking into account voltage gain for a single-stage DAB type AC-DC converter according to claim 1 or 2, characterized in that: Masatsune Sadahi I ZVS1 , I ZVS2 , I ZVS3 , I ZVS4 Configuration I ZVS1 =I ZVS2 =I ZVS3 =I ZVS4 =I ZVS , I ZVS It's fixed.

4. The extended phase-shift frequency conversion modulation method taking into account voltage gain for a single-stage DAB type AC-DC converter according to claim 3, characterized in that: Constant value I ZVS It is set to be much larger than the minimum current I required by the junction capacitance of the primary and secondary side switches during the charging and discharging process. s,ac and I s,dc The maximum value of .

5. A single-stage DAB type AC-DC converter, characterized in that: When performing extended phase-shift modulation, the extended phase-shift frequency conversion modulation method taking into account voltage gain for a single-stage DAB type AC-DC converter as described in any one of claims 1 to 4 is adopted.

6. An energy storage system adaptable to a wide voltage range, comprising an AC power grid, an AC-DC converter and a DC voltage system, wherein the DC voltage system is connected to the AC power grid through the AC-DC converter, and characterized in that: The AC-DC converter adopts the single-stage DAB type AC-DC converter as claimed in claim 5.

7. The energy storage system adapted to a wide voltage range according to claim 6, characterized in that: The DC voltage system is an electric vehicle charging system, a battery energy storage system, a photovoltaic system, a wind power system or a household appliance energy storage system.

8. An energy storage control method adapted to a wide voltage range, used in an energy storage system, the energy storage system comprising an AC power grid, an AC-DC converter and a DC voltage system, the DC voltage system being connected to the AC power grid via the AC-DC converter, characterized in that: When the AC-DC converter is subjected to extended phase-shift modulation, the extended phase-shift frequency conversion modulation method taking into account voltage gain for a single-stage DAB type AC-DC converter as described in any one of claims 1 to 4 is adopted.

9. The energy storage control method adapted to a wide voltage range according to claim 8, characterized in that: The DC voltage system is an electric vehicle charging system, a battery energy storage system, a photovoltaic system, a wind power system or a household appliance energy storage system.

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