A multi-duty cycle modulation strategy and system based on dual active bridge converters

Abstract

This invention discloses a multi-duty cycle modulation strategy based on a dual active bridge converter. The dual active bridge converter includes a primary-side H-bridge and a secondary-side H-bridge connected by an inductor L and a high-frequency transformer. The primary-side H-bridge includes a switching transistor Q. 11 Q 12 Q 13 Q 14 The secondary H-bridge includes Q 21 Q 22 Q 23 Q 24 The input of the primary-side H-bridge is connected to the energy storage device, and the output of the secondary-side H-bridge is connected to the DC bus of the energy storage system. The modulation strategy is to control D1 and the primary-side H-bridge switch Q. 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal D2 and the secondary H-bridge switch Q 21 Trigger signal and switching transistor Q 24 The internal phase shift angle ratio D3 of the trigger signal reduces the effective value of the current under the same transmission power, expands the zero-voltage switching range of the switching transistors in the dual active bridge converter, improves the efficiency of the dual active bridge converter, and realizes the optimized operation of the dual active bridge converter controller.

Description

Technical Field

[0001] This invention belongs to the field of DC / DC converter control and modulation technology for DC energy storage systems, and specifically relates to a multi-duty cycle modulation strategy and system based on a dual active bridge converter. Background Technology

[0002] With the development of renewable energy and its power generation technology, DC distributed energy generation systems have attracted attention due to their advantages such as high operational reliability and strong ability to connect different distributed energy sources. The DC converter in a DC distributed generation system is the interface circuit connecting different DC voltage buses and renewable energy sources; its performance is closely related to the economy, reliability, and stability of the DC distributed energy generation system.

[0003] Therefore, DC-DC converter technology has become a hot research topic in the industry, and the most commonly used non-resonant DC-DC converter is the dual active bridge converter. The dual active bridge converter can achieve flexible control of the transmitted power, maintaining a constant output voltage even when the input voltage is disturbed, and features high efficiency and high power density. In energy storage systems, the efficient operation of the dual active bridge converter can shorten charging time and reduce damage to battery life.

[0004] The basic control technology for current dual active bridge converters is phase-shift control, mainly including single-phase-shift control, extended-phase-shift control, dual-phase-shift control, and triple-phase-shift control. The main problem with these dual active bridge control technologies is that the fixed duty cycle of the trigger pulse increases the modulation difficulty in the soft-switching region, limiting the operating range and efficiency of the dual active bridge. Asymmetric duty cycle modulation, proposed to address the difficulty in adjusting the soft-switching range of phase-shift control, reduces the current stress on the switching transistors and optimizes the soft-switching range; however, this modulation strategy has only two degrees of freedom, limiting control flexibility.

[0005] Chinese invention patent with publication number CN111049392A discloses a dual active bridge extended phase-shift minimum return power control method based on coordinate transformation. It improves the extended phase-shift control and proposes a dual active bridge extended phase-shift minimum return power control method based on coordinate transformation, which can achieve the goal of reducing return power. However, this patent cannot optimize the return power to 0 across the entire power level and does not optimize the control of the soft-switching region.

[0006] Chinese invention patent CN114825968A discloses a hybrid control method combining asymmetric duty cycle and inward phase shift. Using the inward phase shift of the primary bridge and the duty cycle of the secondary bridge as control variables, it aims to reduce switching current stress and improve the efficiency of a dual active bridge converter by optimizing the return power. However, since the relationship between return power, switching current stress, and soft-switching range is strongly coupled and nonlinear, it is difficult for the two control variables to simultaneously optimize these three factors at different power levels. Therefore, a better modulation strategy is needed to control the dual active bridge converter. Summary of the Invention

[0007] To address the problems existing in the prior art, the purpose of this invention is to provide a multi-duty cycle modulation strategy and system based on a dual active bridge converter, which improves control flexibility, reduces the effective value of current under the same transmission power, expands the soft-switching operating range of the switching transistors of the dual active bridge converter, and improves the efficiency of the dual active bridge converter.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A multi-duty-cycle modulation strategy based on a dual active bridge converter, comprising a primary-side H-bridge and a secondary-side H-bridge connected by an inductor L and a high-frequency transformer, wherein the primary-side H-bridge includes a switching transistor Q. 11 Q 12 Q 13 Q 14 The secondary H-bridge includes Q 21 Q 22 Q 23 Q 24 The midpoint of the primary-side H-bridge arm is connected to the primary side of the high-frequency transformer via inductor L, while the midpoint of the secondary-side H-bridge arm is directly connected to the high-frequency transformer. The input of the primary-side H-bridge is connected to the energy storage device, and the output of the secondary-side H-bridge is connected to the DC bus of the energy storage system. The modulation strategy involves controlling the switching transistor Q in the primary-side H-bridge. 11 Trigger signal and Q 13 The duty cycle D1 of the trigger signal, and the primary-side H-bridge switch Q 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal D2 and the secondary H-bridge switch Q 21 Trigger signal and switching transistor Q 24 The internal phase shift angle ratio D3 of the trigger signal reduces the effective value of the current under the same transmission power, expands the zero-voltage switching range of the switching transistors in the dual active bridge converter, improves the efficiency of the dual active bridge converter, and realizes the optimized operation of the dual active bridge converter controller.

[0010] Furthermore, the switching transistor Q in the primary H-bridge... 11 and Q 13 The duty cycle D1 of the trigger signal is equal; the switching transistor Q in the primary H-bridge is also equal. 12 The trigger signal and the switching transistor Q 14 The duty cycle of the trigger signal is (1-D1); the switching transistor Q in the primary H-bridge... 11 The trigger signal and the switching transistor Q in the secondary H-bridge 21 The trigger signal phase shift angle ratio D2, and the switching transistor Q in the primary H-bridge. 12 The trigger signal and the switching transistor Q in the secondary H-bridge 22 The phase shift angle ratios of the trigger signals D2 and Q are all equal; the secondary-side H-bridge switch Q 21 The trigger signal and the switching transistor Q 24 The internal phase shift angle ratio of the trigger signal D3 to the switching transistor Q 22 The trigger signal and the switching transistor Q 23 The phase shift angle of the trigger signal is equal to that of D3.

[0011] Furthermore, the modulation strategy includes the following steps:

[0012] Step 1: Calculate the voltage matching ratio k based on the measured input voltage V1 and output voltage V2;

[0013] Step 2, based on the measured output voltage V2 and the given output voltage V... 2ref After the difference is calculated, the primary side H-bridge switch Q is obtained through a proportional-integral controller. 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal is D2;

[0014] Step 3: Determine the current operating mode and its power setpoint P. ref and operational boundary constraints;

[0015] Step 4, based on the calculated transmission power P and power setpoint P ref Calculate the per-unit value P of the transmission power. * ;

[0016] Step 5: Based on the voltage matching ratio k and the external phase shift angle ratio D2, the optimal operating state (D1) is obtained using the fmincon function in MATLAB. （opt） D2 （opt） D3 （opt） );

[0017] Step 6, based on the optimal operating state (D1) （opt） D2 （opt） D3 （opt） ), to obtain the switching transistor Q11 Q 12 Q 13 Q 14 Q 21 Q 22 Q 23 Q 24 The trigger signal.

[0018] Furthermore, the dual active bridge converter includes a forward boost mode and a reverse boost mode. In the forward boost mode, the duty cycle D1 of the primary H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary and secondary H-bridges, and the inner phase shift angle ratio D3 of the secondary H-bridge should satisfy the following boundary constraints:

[0019] (1)

[0020] In the multi-duty-cycle modulation strategy of reverse boost mode, the duty cycle D1 of the primary H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary and secondary H-bridges, and the inner phase shift angle ratio D3 of the secondary H-bridge should satisfy the following boundary constraints:

[0021] (2).

[0022] Furthermore, in the forward boost mode, all switching transistors Q... 11 Q 12 Q 13 Q 14 Q 21 Q 22 Q 23 Q 24 Both can achieve zero-voltage switching.

[0023] Furthermore, the maximum transmission power of the dual active bridge converter in both forward boost and reverse boost operating modes... Where n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0024] Furthermore, based on the volt-second principle of inductance and the steady-state current in the forward boost mode, the expression for the transmission power in the forward boost mode is obtained as follows:

[0025] (3)

[0026] In the formula, n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0027] Furthermore, based on the volt-second principle of inductance and the steady-state current in reverse boost mode, the power transfer expression for reverse boost mode is obtained as follows:

[0028] (4)

[0029] In the formula, n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0030] Furthermore, the fmincon function in MATLAB is as follows:

[0031]

[0032] in, To optimize the objective, To influence the relevant variables that affect the solution objective, For the non-equilibrium constraints of the objective to be optimized, Equality constraints are set for the objective to be optimized.

[0033] The optimization objective is the effective value of the current, and its expression is:

[0034]

[0035] Voltage matching ratio , is a given value, duty cycle The quantity to be solved;

[0036] At each switching instant, the switching current of the dual active bridge converter is subject to constraints:

[0037]

[0038] This constraint is the inequality constraint for the optimization of the fmincon function.

[0039]

[0040] This constraint is an equality constraint for the fmincon function optimization.

[0041] This invention also provides a system applying a multi-duty-cycle modulation strategy based on a dual active bridge converter, the system comprising:

[0042] The sensor module is used to collect the input voltage V1, output voltage V2, and transmission power P in real time.

[0043] The data processing module is used to compare the output voltage V2 with the output voltage setpoint V. 2ref The difference is calculated, and the deviation value is subjected to PI control to obtain the external phase shift angle ratio D2 between the primary-side H-bridge and the secondary-side H-bridge. Based on the multi-duty cycle modulation strategy of the dual active bridge converter, the optimal operating state (D1) is calculated. （opt） D2 （opt） D3 （opt） The trigger signals of all switches in the dual active bridge converter are calculated from the optimal operating state.

[0044] The switching transistor driver module is used to convert trigger signals into drive signals to control the on / off state of the switching transistors in the dual active bridge converter.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] This invention provides a multi-duty cycle modulation strategy based on a dual active bridge converter. Compared with asymmetric duty cycle modulation and traditional phase-shift control, which only have one or two control variables and are difficult to simultaneously consider optimization objectives closely related to converter efficiency, such as switching current stress and soft-switching range, the modulation strategy provided by this invention has three control variables, thereby improving control flexibility and enabling synchronous optimization of switching current stress and soft-switching range at different power levels, thus improving the efficiency of the dual active bridge converter.

[0047] The present invention provides a multi-duty cycle modulation strategy based on a dual active bridge converter. Compared with asymmetric duty cycle modulation and traditional phase shift control, it expands the ZVS region, reduces the effective value of current under the same transmission power, expands the soft switching operating range of the switching transistors of the dual active bridge converter, and effectively improves the efficiency of the dual active bridge converter.

[0048] The modulation strategy provided by this invention involves numerous control variables, and a complex nonlinear coupling relationship exists between the switching transistor current stress and the soft-switching range. This complex nonlinear relationship between the multiple control variables and the optimization objective is a major obstacle to optimizing the converter's operating state. The modulation strategy optimization algorithm provided by this invention, implemented using the `fmincon` function in MATLAB, offers advantages over traditional optimization methods in terms of low operational complexity and fast optimization speed. Attached Figure Description

[0049] The present invention will now be described in further detail with reference to the accompanying drawings.

[0050] Figure 1 This is a schematic diagram of the dual active bridge converter topology of the present invention;

[0051] Figure 2This is a waveform diagram illustrating the multi-duty-cycle modulation strategy based on a dual active bridge converter of the present invention in both forward boost and reverse boost modes. Figure 2 (a) is the waveform in the positive boost mode. Figure 2 (b) is the waveform of the reverse boost mode;

[0052] Figure 3 A schematic diagram illustrating the zero-voltage switching operation analysis of the multi-duty cycle modulation strategy based on a dual active bridge converter provided by this invention, operating in forward boost mode, within nine time segments of one switching cycle.

[0053] Figure 4 The flowchart shows the optimization of the multi-duty cycle modulation strategy based on dual active bridge converters provided by this invention using the fmincon function;

[0054] Figure 5 The control block diagram of the multi-duty cycle modulation strategy based on dual active bridge converters provided by the present invention;

[0055] Figure 6 A comparison of the effective current values ​​of the multi-duty cycle modulation strategy based on a dual active bridge converter provided by this invention with other modulation strategies;

[0056] Figure 7 A comparison diagram of the soft-switching range of the multi-duty cycle modulation strategy based on dual active bridge converter provided by the present invention with other modulation strategies;

[0057] Figure 8 The efficiency comparison diagram of a multi-duty cycle modulation strategy based on a dual active bridge converter provided by the present invention with other modulation strategies is shown. Detailed Implementation

[0058] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0059] To make the objectives, technical effects, and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention. Based on the embodiments disclosed in this invention, other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0060] The control strategy provided by this invention controls a dual active bridge converter, the topology of which is as follows: Figure 1 As shown, it includes a primary-side H-bridge, a secondary-side H-bridge, an inductor L for connecting the primary-side H-bridge and the secondary-side H-bridge, and a high-frequency transformer. Q 11 Q 12 Q13 and Q 14 Q represents the switching transistor of the primary H-bridge. 21 Q 22 Q 23 and Q 24 V1 represents the switching transistor of the secondary-side H-bridge; V2 is the input terminal of the primary-side H-bridge, equivalent to the connected energy storage device; V3 is the output terminal of the secondary-side H-bridge, equivalent to the DC bus of the connected energy storage system; the midpoint of the arm of the primary-side H-bridge is connected to the primary side of the high-frequency transformer through inductor L, and the midpoint of the arm of the secondary-side H-bridge is directly connected to the secondary side of the high-frequency transformer. Switching transistor types that can be used in a dual active bridge converter topology include MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor).

[0061] Switch Q in the primary H-bridge 11 and Q 13 The duty cycle D1 of the trigger signal is equal; the switching transistor Q in the primary H-bridge is also equal. 12 The trigger signal and the switching transistor Q 14 The duty cycle of the trigger signal is (1-D1); the switching transistor Q in the primary H-bridge... 11 The trigger signal and the switching transistor Q in the secondary H-bridge 21 The trigger signal phase shift angle ratio D2, and the switching transistor Q in the primary H-bridge. 12 The trigger signal and the switching transistor Q in the secondary H-bridge 22 The phase shift angle ratios of the trigger signals D2 and Q are all equal; the secondary-side H-bridge switch Q 21 The trigger signal and the switching transistor Q 24 The internal phase shift angle ratio of the trigger signal D3 to the switching transistor Q 22 The trigger signal and the switching transistor Q 23 The phase shift angle of the trigger signal is equal to that of D3.

[0062] The modulation strategy of this invention is to optimize the control of the switching transistor Q in the primary-side H-bridge. 11 Trigger signal and Q 13 The duty cycle D1 of the trigger signal, and the primary-side H-bridge switch Q 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal D2 and the secondary H-bridge switch Q 21 Trigger signal and switching transistor Q 24 The internal phase shift angle ratio D3 of the trigger signal reduces the effective value of the current under the same transmission power, expands the zero-voltage switching range of the switching transistors in the dual active bridge converter, improves the efficiency of the dual active bridge converter, and realizes the optimized operation of the dual active bridge converter controller.

[0063] Compared with existing technologies, the multi-duty-cycle modulation strategy based on dual active bridge converters provided by this invention has three control variables: the duty cycle D1 of the primary H-bridge, the external phase shift angle ratio D2 between the primary and secondary H-bridges, and the internal phase shift angle ratio D3 of the secondary H-bridge, making control more flexible; it expands the ZVS region and has better current performance under the same transmission power, achieving better efficiency improvement of the dual active bridge converter; and it is easy to implement the modulation strategy by using the fmincon function in MATLAB.

[0064] The dual active bridge converter includes forward boost mode and reverse boost mode. The different operating modes are defined according to the voltage matching ratio k and the converter's transmission power P, as follows:

[0065] Among them, voltage matching ratio ,in This refers to the turns ratio of a high-frequency transformer.

[0066] To achieve direct power transfer, the duty cycle D1 of the primary-side H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary-side and secondary-side H-bridges, and the inner phase shift angle ratio D3 of the secondary-side H-bridge in the multi-duty cycle modulation strategy of the forward boost mode must satisfy the following boundary constraints:

[0067] (1)

[0068] In the multi-duty-cycle modulation strategy of reverse boost mode, the duty cycle D1 of the primary H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary and secondary H-bridges, and the inner phase shift angle ratio D3 of the secondary H-bridge should satisfy the following boundary constraints:

[0069] (2).

[0070] Figure 2 This is a waveform diagram illustrating the multi-duty-cycle modulation strategy based on a dual active bridge converter according to an embodiment of the present invention in both forward boost and reverse boost modes. Figure 2 (a) is the waveform in the positive boost mode. Figure 2 (b) shows the waveform in reverse boost mode; the two figures respectively show the switching transistor Q. 11 Q 12 Q 13 Q 14 and Q 21 Q 22 Q 23 Q 24 The drive signal, V H1 The voltage signal generated by the primary-side H-bridge, V H2 This is the voltage signal generated by the secondary H-bridge. This is the inductor current signal. For the switching cycle, For Q 12 The rising edge of the drive signal pulse, For Q 21 The rising edge of the drive signal pulse, For Q 24 The rising edge of the drive signal pulse.

[0071] like Figure 2 As shown in (a), the multi-duty cycle modulation strategy based on a dual active bridge converter provided by the present invention, when operating in the forward boost mode, can divide one switching cycle into 9 time segments, namely: , , , , , , , , In the forward boost mode, all switching transistors can achieve zero-voltage switching. Figure 3 This is a schematic diagram illustrating the zero-voltage switching operation analysis of the multi-duty cycle modulation strategy based on a dual active bridge converter provided by the present invention, operating in the forward boost mode, within nine time segments of one switching cycle.

[0072] This invention provides a multi-duty cycle modulation strategy based on a dual active bridge converter, which, when operating in forward boost mode, reduces the inductor current. The expression is:

[0073]

[0074] Due to inductor current Based on the volt-second principle of inductors, we can obtain the expression for the transmission power P in the forward boost mode:

[0075] (3)

[0076] The maximum transmission power of the dual active bridge converter in forward boost mode Where n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0077] This invention provides a multi-duty cycle modulation strategy based on a dual active bridge converter, which, when operating in reverse boost mode, reduces the inductor current. The expression is:

[0078]

[0079] Based on the volt-second principle of inductance and the steady-state current in reverse boost mode, the expression for the transmission power in reverse boost mode is as follows:

[0080] (4)

[0081] In the formula, n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0082] Maximum transmission power of the dual active bridge converter in reverse boost mode Where n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

[0083] Figure 4 The flowchart illustrates the optimization process using the fmincon function in the multi-duty-cycle modulation strategy based on a dual active bridge converter provided by this invention. This invention provides a multi-duty-cycle modulation strategy based on a dual active bridge converter, with the effective current value as the optimization objective, and optimizes it using the fmincon function in MATLAB. The fmincon function in MATLAB is as follows:

[0084]

[0085] in, To optimize the objective, To influence the relevant variables that affect the solution objective, For the non-equilibrium constraints of the objective to be optimized, The equality constraints are for the objective to be optimized.

[0086] The expression for the effective value of current is:

[0087]

[0088] Voltage matching ratio , is a given value, duty cycle The quantity to be solved;

[0089] To achieve Zero-Switching-Voltage (ZVS) and improve the operating efficiency of the dual active bridge converter by reducing switching losses, the switching current of the dual active bridge converter is subject to constraints at each switching instant:

[0090]

[0091] This constraint is the inequality constraint for the fmincon function optimization.

[0092] In addition, there is an equality constraint that the transmission power should be equal to the transmission power level, that is:

[0093] .

[0094] This constraint is the equality constraint for the fmincon function optimization.

[0095] Figure 5 This is a control block diagram of the multi-duty cycle modulation strategy based on a dual active bridge converter provided by the present invention. The control strategy provided by the present invention includes the following steps:

[0096] Step 1: Calculate the voltage matching ratio k based on the measured input voltage V1 and output voltage V2;

[0097] Step 2, based on the measured output voltage V2 and the given output voltage V... 2ref After the difference is calculated, the primary side H-bridge switch Q is obtained through a proportional-integral controller. 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal is D2;

[0098] Step 3: Determine the current operating mode and its power setpoint P. ref and operational boundary constraints;

[0099] Step 4, based on the calculated transmission power P and power setpoint P ref Calculate the per-unit value P of the transmission power. * ;

[0100] Step 5: Based on the voltage matching ratio k and the external phase shift angle ratio D2, the optimal operating state (D1) is obtained using the fmincon function in MATLAB. （opt） D2 （opt） D3 （opt） );

[0101] Step 6, based on the optimal operating state (D1) （opt） D2 （opt） D3 （opt） ), to obtain the switching transistor Q 11 Q 12 Q 13 Q 14 Q 21 Q 22 Q 23 Q 24 The trigger signal enables the dual active bridge converter to operate in its optimal state.

[0102] This invention also proposes a control system based on a multi-duty-cycle modulation strategy using a dual active bridge converter, comprising:

[0103] The sensor module is used to collect the input voltage V1, output voltage V2, and transmission power P in real time.

[0104] The data processing module is used to compare the output voltage V2 with the output voltage setpoint V. 2ref The difference is calculated, and the deviation value is subjected to PI control to obtain the external phase shift angle ratio D2 between the primary-side H-bridge and the secondary-side H-bridge. Based on the multi-duty cycle modulation strategy of the dual active bridge converter, the optimal operating state (D1) is calculated. （opt） D2 （opt） D3 （opt） The trigger signals of all switches in the dual active bridge converter are calculated from the optimal operating state.

[0105] The switching transistor driver module is used to convert trigger signals into drive signals to control the on / off state of the switching transistors in the dual active bridge converter.

[0106] In this invention, the effective current values ​​and soft-switching ranges of the traditional single-phase-shift modulation (SPS), extended phase-shift modulation (EPS), globally optimal conditional three-phase-shift modulation (GOC-TPS), three-phase-shift modulation (TPS), multi-objective three-phase-shift modulation (multi-objective TPS) strategy, and the multi-duty-cycle modulation strategy provided by this invention are compared and analyzed under the same transmission power. The comparative analysis results are as follows: Figure 6 and Figure 7 As shown. Figure 6 The diagram shows a comparison of the effective current values ​​of the multi-duty cycle modulation strategy provided by this invention with other modulation strategies under different voltage matching ratios k. Figure 6 This indicates that the effective current value under the multi-duty cycle modulation strategy provided by this invention is slightly higher than that under the globally optimal three-phase-shift modulation only when k=3. Under other conditions, the effective current value under the multi-duty cycle modulation strategy provided by this invention is the lowest in the entire power range. Figure 7 The soft-switching region of the multi-duty cycle modulation strategy provided by the present invention compared with other modulation strategies is shown. Figure 7 This indicates that the multi-duty cycle modulation strategy provided by the present invention has the widest ZVS region, demonstrating that the multi-duty cycle modulation strategy of the present invention can expand the soft switching range, thereby effectively reducing the switching losses of the switching transistors in the dual active bridge converter and improving the efficiency of the dual active bridge converter.

[0107] In summary, the multi-duty cycle modulation strategy based on a dual active bridge converter in this embodiment of the invention, by increasing control variables and using the fmincon function in MATLAB to optimize the effective value of the current, achieves the optimization goal of reducing the effective value of the current while expanding the soft-switching region and improving the operating efficiency of the dual active bridge converter.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A multi-duty cycle modulation strategy based on a dual active bridge converter, characterized in that, The dual active bridge converter includes a primary-side H-bridge and a secondary-side H-bridge connected by an inductor L and a high-frequency transformer. The primary-side H-bridge includes a switching transistor Q. 11 Q 12 Q 13 Q 14 The secondary H-bridge includes Q 21 Q 22 Q 23 Q 24 The midpoint of the arm of the primary-side H-bridge is connected to the primary side of the high-frequency transformer via an inductor L. The midpoint of the arm of the secondary-side H-bridge is directly connected to the high-frequency transformer. The input terminal of the primary-side H-bridge is connected to the energy storage device, and the output terminal of the secondary-side H-bridge is connected to the DC bus of the energy storage system. The modulation strategy is to control the switching transistor Q in the primary-side H-bridge. 11 Trigger signal and Q 13 The duty cycle D1 of the trigger signal, and the primary-side H-bridge switch Q 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal D2 and the secondary H-bridge switch Q 21 Trigger signal and switching transistor Q 24 The internal phase shift angle ratio D3 of the trigger signal reduces the effective value of the current under the same transmission power, expands the zero-voltage switching range of the switching transistors in the dual active bridge converter, improves the efficiency of the dual active bridge converter, and realizes the optimized operation of the dual active bridge converter controller. The modulation strategy includes the following steps: Step 1: Calculate the voltage matching ratio k based on the measured input voltage V1 and output voltage V2; Step 2, based on the measured output voltage V2 and the given output voltage V... 2ref After the difference is calculated, the primary side H-bridge switch Q is obtained through a proportional-integral controller. 11 Trigger signal and secondary-side H-bridge switch Q 21 The external phase shift angle ratio of the trigger signal is D2; Step 3: Determine the current operating mode and its power setpoint P. ref and operational boundary constraints; Step 4, based on the calculated transmission power P and power setpoint P ref Calculate the per-unit value P of the transmission power. * ; Step 5: Based on the voltage matching ratio k and the external phase shift angle ratio D2, the optimal operating state (D1) is obtained using the fmincon function in MATLAB. （opt） D2 （opt） D3 （opt） ); Step 6, based on the optimal operating state (D1) （opt） D2 （opt） D3 （opt） ), to obtain the switching transistor Q 11 Q 12 Q 13 Q 14 Q 21 Q 22 Q 23 Q 24 The trigger signal; The dual active bridge converter includes a forward boost mode and a reverse boost mode. In the forward boost mode, the duty cycle D1 of the primary H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary and secondary H-bridges, and the inner phase shift angle ratio D3 of the secondary H-bridge must satisfy the following boundary constraints: (1) In the multi-duty-cycle modulation strategy of reverse boost mode, the duty cycle D1 of the primary H-bridge trigger signal, the outer phase shift angle ratio D2 between the primary and secondary H-bridges, and the inner phase shift angle ratio D3 of the secondary H-bridge should satisfy the following boundary constraints: (2)； In the aforementioned positive boost operating mode, all switching transistors Q 11 Q 12 Q 13 Q 14 Q 21 Q 22 Q 23 Q 24 Both can achieve zero-voltage switching.

2. The multi-duty cycle modulation strategy based on a dual active bridge converter according to claim 1, characterized in that, Switch Q in the primary H-bridge 11 and Q 13 The duty cycle D1 of the trigger signal is equal; the switching transistor Q in the primary H-bridge is also equal. 12 The trigger signal and the switching transistor Q 14 The duty cycle of the trigger signal is (1-D1); the switching transistor Q in the primary H-bridge... 11 The trigger signal and the switching transistor Q in the secondary H-bridge 21 The trigger signal phase shift angle ratio D2, and the switching transistor Q in the primary H-bridge. 12 The trigger signal and the switching transistor Q in the secondary H-bridge 22 The phase shift angle ratios of the trigger signals D2 and Q are all equal; the secondary-side H-bridge switch Q 21 The trigger signal and the switching transistor Q 24 The internal phase shift angle ratio of the trigger signal D3 to the switching transistor Q 22 The trigger signal and the switching transistor Q 23 The phase shift angle of the trigger signal is equal to that of D3.

3. The multi-duty cycle modulation strategy based on a dual active bridge converter according to claim 1, characterized in that, The maximum transmission power of the dual active bridge converter in forward boost mode and reverse boost mode Where n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

4. The multi-duty cycle modulation strategy based on a dual active bridge converter according to claim 1, characterized in that, Based on the volt-second principle of inductance and the steady-state current in forward boost mode, the expression for the transmission power in forward boost mode is as follows: (3) In the formula, n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

5. A multi-duty cycle modulation strategy based on a dual active bridge converter according to claim 1, characterized in that, Based on the volt-second principle of inductance and the steady-state current in reverse boost mode, the expression for the transmission power in reverse boost mode is as follows: (4) In the formula, n is the turns ratio of the high-frequency transformer. For switching frequency, Input voltage, Where L is the output voltage and L is the inductance value.

6. The multi-duty cycle modulation strategy based on a dual active bridge converter according to claim 1, characterized in that, In step 5, the fmincon function in MATLAB is: in, To optimize the objective, To influence the relevant variables that affect the solution objective, For the non-equilibrium constraints of the objective to be optimized, Equality constraints are set for the objective to be optimized. The optimization objective is the effective value of the current, and its expression is: Voltage matching ratio , is a given value, duty cycle The quantity to be solved; At each switching instant, the switching current of the dual active bridge converter is subject to constraints: This constraint is the inequality constraint for the optimization of the fmincon function. This constraint is an equality constraint for the fmincon function optimization.

7. A system applying the multi-duty-cycle modulation strategy based on a dual active bridge converter as described in claim 1, characterized in that, The system includes: The sensor module is used to collect the input voltage V1, output voltage V2, and transmission power P in real time. The data processing module is used to compare the output voltage V2 with the output voltage setpoint V. 2ref The difference is calculated, and the deviation value is subjected to PI control to obtain the external phase shift angle ratio D2 between the primary-side H-bridge and the secondary-side H-bridge. Based on the multi-duty cycle modulation strategy of the dual active bridge converter, the optimal operating state (D1) is calculated. （opt） D2 （opt） D3 （opt） The trigger signals of all switches in the dual active bridge converter are calculated from the optimal operating state. The switching transistor driver module is used to convert trigger signals into drive signals to control the on / off state of the switching transistors in the dual active bridge converter.

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