A hybrid dual active bridge DC-DC converter, control method and control system

Abstract

This invention discloses a hybrid dual active bridge DC-DC converter, its control method, and a control system. The converter includes: an auxiliary half-bridge and a current-fed DAB converter; the auxiliary half-bridge includes a first half-bridge and an auxiliary inductor L1; the current-fed DAB converter includes a first full-bridge, a second full-bridge, and a high-frequency link; the high-frequency link includes an intermediate inductor L2 and a transformer T; the first half-bridge is connected to the input power supply, and a capacitor C1 is connected in parallel across its two ends; the second full-bridge serves as the output terminal; a supporting capacitor C is connected in parallel across the two ends of the first full-bridge. m The auxiliary inductor L1 connects the first and second half-bridges; the second half-bridge connects the intermediate inductor L2 and the corresponding terminals of the first winding n1 of transformer T in sequence, and the non-corresponding terminals of the first winding n1 of transformer T are connected to the third half-bridge; the second winding n2 of transformer T connects to the fourth and fifth half-bridges. This achieves zero-voltage conduction of all switching transistors under wide input voltage conditions, reduces return current power, and improves converter efficiency.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, and more specifically, relates to a hybrid dual active bridge DC-DC converter, a control method, and a control system. Background Technology

[0002] Entering the 21st century, energy issues have become a major challenge for social development, with traditional fossil fuels facing depletion and causing significant environmental pollution. Against this backdrop, the new energy industry has experienced rapid development. In fields such as UPS (Uninterruptible Power Supply), distributed energy storage, solar power generation, and electric vehicle charging, DC-DC converters are the core units for energy regulation. Solar power generation, wind power generation, hydropower generation, and fuel cell power supply all feature wide output voltage ranges. DC-DC converters for charging or discharging batteries require efficient power conversion of DC voltage over a wide voltage range.

[0003] DAB converters are suitable for bidirectional DC-DC applications due to their advantages such as bidirectional power flow, high power density, ability to operate in Buck and Boost modes, fewer passive components, simple control, the ability to use transformer leakage inductance for power transfer, and zero-voltage switching (ZVS). However, traditional DAB converters can only achieve ZVS and low return current power across the entire load range under voltage matching conditions. When faced with wide input voltage ranges, they can cause a sharp increase in return current power, loss of ZVS, and voltage polarity reversal, leading to reduced converter efficiency and thermal runaway. Summary of the Invention

[0004] In view of the shortcomings of related technologies, the present invention aims to provide a hybrid dual active bridge DC-DC converter, control method and control system, which aims to solve the problems of a sharp increase in return current power, loss of ZVS, reduced converter efficiency and thermal runaway when the input voltage is wide.

[0005] To achieve the above objectives, the present invention provides a hybrid dual active bridge DC-DC converter, comprising: an auxiliary half-bridge and a current-fed DAB converter;

[0006] The auxiliary half-bridge includes a first half-bridge and an auxiliary inductor L1; the two ends of the first half-bridge are connected to the input power supply as input terminals, and a capacitor C1 is connected in parallel across the two ends of the first half-bridge; the midpoint of the first half-bridge is connected to the first end of the auxiliary inductor L1.

[0007] The current-fed DAB converter includes a first full-bridge, a second full-bridge, and a high-frequency link; the two ends of the second full-bridge serve as output terminals, and an output filter capacitor C is connected in parallel. o ;

[0008] The first full bridge has parallel support capacitors C at both ends. m The second end of the auxiliary inductor L1 is connected to the midpoint of the second half-bridge of the first full bridge; the high-frequency link includes an intermediate inductor L2 and a transformer T, the midpoint of the second half-bridge of the first full bridge is also connected to the intermediate inductor L2 and then to the same-name end of the first winding n1 of the transformer T, and the midpoint of the third half-bridge of the first full bridge is connected to the non-same-name end of the first winding n1 of the transformer T.

[0009] The midpoint of the fourth half-bridge of the second full bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint of the fifth half-bridge of the second full bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T.

[0010] Optionally, the first half-bridge includes a first switch Q1 and a second switch Q2, with the source of the first switch Q1 and the drain of the second switch Q2 connected, the positive terminal of the input power supply connected to the drain of the first switch Q1, and the negative terminal connected to the source of the second switch Q2.

[0011] The first full-bridge includes a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6; the source of the third switch Q3 and the drain of the fourth switch Q4 are connected to form a second half-bridge, and the supporting capacitor C... m The two ends of the second half-bridge are connected in parallel. The midpoint of the bridge arm of the second half-bridge is connected to the second end of the auxiliary inductor L1. The midpoint of the bridge arm of the second half-bridge is also connected to the intermediate inductor L2 and then to the same-name terminal of the first winding n1 of the transformer T. The source of the fifth switch Q5 and the drain of the sixth switch Q6 are connected to form the third half-bridge. The midpoint of the bridge arm of the third half-bridge is connected to the non-same-name terminal of the first winding n1 of the transformer T.

[0012] The source of the second switch Q2, the source of the fourth switch Q4, and the source of the sixth switch Q6 are connected, and the drain of the third switch Q3 and the drain of the fifth switch Q5 are connected.

[0013] Optionally, the second full bridge includes a seventh switch Q7, an eighth switch Q8, a ninth switch Q9, and a tenth switch Q1. 10 ;

[0014] The source of the seventh switch Q7 and the drain of the eighth switch Q8 are connected to form a fourth half-bridge. The source of the ninth switch Q9 and the drain of the tenth switch Q8 are connected to form a fourth half-bridge. 10The drains of the fourth half-bridge are connected to form the fifth half-bridge; the midpoint of the bridge arm of the fourth half-bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint of the bridge arm of the fifth half-bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T; the drain of the seventh switch Q7 is connected to the drain of the ninth switch Q9, and the source of the eighth switch Q8 is connected to the source of the tenth switch Q9. 10 The source connection.

[0015] In a second aspect, the present invention also provides a control method for a hybrid dual active bridge DC-DC converter, applied to a hybrid dual active bridge DC-DC converter as described in any of the first aspects, comprising:

[0016] According to the input voltage V of the hybrid dual active bridge DC-DC converter in and target output power P o Determine whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM).

[0017] When the FRM is running, voltage matching control is used to fix the duty cycle d3 of the first full bridge to 0.5, and the gain of the converter is adjusted by adjusting the duty cycle d1 of the first switch Q1 in the auxiliary half bridge.

[0018] When SRM is running, extended gain control EG is used, and it is determined whether the current converter is in Buck or Boost state. The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge is fixed at d. min Or d max The gain of the converter is adjusted by adjusting the duty cycle d3 of the third switch Q3 of the first full bridge.

[0019] Optionally, the step is based on the input voltage V of the hybrid dual active bridge DC-DC converter. in and target output power P o Determining whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM) includes:

[0020] When the per-unit input voltage range is 0.625-2, the hybrid dual active bridge DC-DC converter operates in the first half-bridge regulation mode (FRM).

[0021] When the per-unit input voltage range exceeds 0.625-2, the hybrid dual active bridge DC-DC converter operates in the second half-bridge regulation mode (SRM).

[0022] Optionally, adjusting the converter gain by adjusting the duty cycle d1 of the first switch Q1 in the auxiliary half-bridge includes:

[0023] The capacitance C is adjusted by adjusting the duty cycle d1 of the first switching transistor Q1 in the auxiliary half-bridge. m Support voltage V at both ends m This makes the supporting voltage V m and output filter capacitor C o Output voltage V at both ends o Matching, that is, satisfying: V m / V o = n1 / n2, where n1 is the number of turns in the first winding and n2 is the number of turns in the second winding.

[0024] Optionally, adjusting the converter gain by adjusting the duty cycle d3 of the third switch Q3 of the first full bridge includes:

[0025] Based on the measured freewheeling current i of the auxiliary inductor L1 fw Determine and control the phase shift angle of the auxiliary half-bridge

[0026] According to the input voltage V in and target output power P o Determine the optimal operating points of the first and second full bridges by referring to the table. And based on the optimal operating point The parameters control the duty cycle d3 of the third switch Q3 of the first full bridge and the phase shift angle of the seventh switch Q7 of the second full bridge.

[0027] Thirdly, the present invention also provides a control system for a hybrid dual active bridge DC-DC converter, including a controller and a hybrid dual active bridge DC-DC converter as described in any of the first aspects, wherein the controller is used to execute the control method for the hybrid dual active bridge DC-DC converter as described in any of the second aspects;

[0028] The controller includes a mode selection module, a freewheeling current regulator (FIR), a lookup table module, a voltage calculation module, a parallel regulator (MVR), an output regulator (OVR), a modulation module, and a drive module.

[0029] The mode selection module is used to select the input voltage V of the hybrid dual active bridge DC-DC converter. in and target output power P o Determine whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM).

[0030] The freewheeling current regulator FIR is used to adjust the freewheeling current i of the measured auxiliary inductor L1. fw Determine and control the phase shift angle of the auxiliary half-bridge

[0031] The lookup table module is used to determine the input voltage V based on the input voltage V. in and target output power P o Determine the optimal operating points of the first and second full bridges by referring to the table.

[0032] The voltage calculation module is used to convert the duty cycle d3 of the optimal operating point into a reference support voltage V. m_ref ;

[0033] The parallel regulator MVR is used to adjust the reference support voltage V. m_ref and measured support voltage V m The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge and the target duty cycle d3 of the third switch Q3 in the first full-bridge are obtained.

[0034] The output regulator OVR is used to adjust the output voltage V based on the reference output voltage V. o_ref and measured output voltage V o Phase shift angle of the seventh switch Q7 in the second full-bridge generation

[0035] The modulation module is used to generate phase-shift modulation signals and pulse-width modulation signals based on the outputs of the freewheeling current regulator FIR, the parallel regulator MVR and the output regulator OVR.

[0036] The driving module is used to control the auxiliary half-bridge, the first full-bridge, and the second half-bridge according to the phase-shift modulation signal and pulse width modulation signal generated by the modulation module.

[0037] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0038] Beneficial effects:

[0039] 1. This invention introduces a half-bridge circuit into a current-feed DAB converter to form a new hybrid dual active bridge DC-DC converter. This hybrid dual active bridge DC-DC converter solves the problem that a single DAB converter can only achieve full-load range ZVS and low return current power under voltage matching conditions. By introducing a half-bridge circuit in front of the current-feed DAB converter, this hybrid dual active bridge DC-DC converter can cope with wide voltage input, ensure ZVS of all switches, reduce return current power, and improve the efficiency of the converter.

[0040] 2. The hybrid dual active bridge DC-DC converter provided by this invention can achieve zero-voltage turn-on of the switching transistors across the entire power range, solving the problem that DAB converters are difficult to achieve zero-voltage turn-on under light load and reducing the switching losses of the converter.

[0041] 3. The hybrid dual active bridge DC-DC converter provided by the present invention consists of an auxiliary half-bridge converter and a current-feed DAB converter. The auxiliary half-bridge converter solves the problems of traditional voltage-feed DAB converters being limited by the difficulty of ZVS implementation and the narrow input voltage range, thereby expanding the voltage gain.

[0042] 4. The control method for the hybrid dual active bridge DC-DC converter provided by this invention adopts a joint control strategy of pulse width modulation and phase shift modulation: the half-bridge circuit uses pulse width modulation and phase shift modulation, and the current-fed DAB converter part uses pulse width modulation and phase shift modulation. There is no coupling relationship between the degrees of freedom. The two variables, Q1 duty cycle d1 and Q3 and Q5 duty cycle d3, are used to adjust the voltage gain. The phase shift angle between Q1 and Q3... Used to adjust the freewheeling current i fw Phase shift angle between Q3 and Q7 Controlling power flow is simple and easy to implement, reducing the complexity of control.

[0043] 5. The input DC voltage source V in the control system of the hybrid dual active bridge DC-DC converter provided by this invention in and output DC voltage source V o Both can achieve bidirectional energy flow, and the output capacitor C o In situations where a UPS is required, a battery can be connected to ensure uninterrupted power supply to the entire DC microgrid system, improving power supply reliability. It has a wide range of applications in new energy scenarios, enabling energy regulation and efficient utilization. Attached Figure Description

[0044] Figure 1 This is a circuit diagram of a hybrid dual active bridge DC-DC converter provided in Embodiment 1 of the present invention;

[0045] Figure 2 The waveform diagram of the hybrid dual active bridge DC-DC converter provided by the present invention in the first half-bridge regulation mode (FRM) is shown.

[0046] Figure 3 The circuit diagram of the hybrid dual active bridge DC-DC converter provided by the present invention under the first half-bridge regulation mode FRM, wherein (a), (b), (c), (d), and (e) correspond to the circuit diagrams of stages I to V, respectively.

[0047] Figure 4 The waveform diagram of the hybrid dual active bridge DC-DC converter provided by the present invention operating in the second half-bridge regulation mode (SRM).

[0048] Figure 5The circuit diagram of the hybrid dual active bridge DC-DC converter provided by the present invention under the second half-bridge regulation mode SRM, wherein (a) and (b) correspond to the circuit diagrams of stage III and stage IV, respectively.

[0049] Figure 6 The hybrid dual active bridge DC-DC converter provided by this invention achieves four waveform diagrams of ZVS under the first half-bridge regulation mode (SRM), where (a) is the waveform diagram of trapezoidal wave-Buck in SRM-I mode, (b) is the waveform diagram of trapezoidal wave-Boost in SRM-II mode, (c) is the waveform diagram of triangular wave-Buck in SRM-III mode, and (d) is the waveform diagram of triangular wave-Boost in SRM-IV mode.

[0050] Figure 7 The hybrid dual active bridge DC-DC converter provided by this invention has a duty cycle d3 and a phase shift duty cycle under ZVS constraints. The diagram shows the relationship between the two voltages, where (a) is a diagram of the normalized input voltage Vin = 3 and (b) is a diagram of the normalized input voltage Vin = 5.

[0051] Figure 8 A three-dimensional graph showing the relationship between the transmission power, input voltage, and duty cycle of the hybrid dual active bridge DC-DC converter provided by this invention;

[0052] Figure 9 The auxiliary bridge arm operating waveforms in the hybrid dual active bridge DC-DC converter provided by the present invention are shown in (a) and (b) respectively.

[0053] Figure 10 The diagram shows the ZVS range of the hybrid dual active bridge DC-DC converter provided by the present invention under extended gain control, wherein (a) is the ZVS range diagram when running in FRM-Buck mode, (b) is the ZVS range diagram when running in FRM-Boost mode, (c) is the ZVS range diagram when running in SRM-Buck mode, and (d) is the ZVS range diagram when running in SRM-Boost mode.

[0054] Figure 11 A schematic diagram of the return power of the hybrid dual active bridge DC-DC converter provided by the present invention;

[0055] Figure 12 This is a schematic diagram showing the relationship between the return power and duty cycle of the hybrid dual active bridge DC-DC converter provided by the present invention, where (a) is the per-unit input voltage V. in When the return current power ratio is 3, the duty cycle is related to the return current power ratio. (b) is the per-unit input voltage V. inThe relationship between return power ratio and duty cycle when = 5;

[0056] Figure 13 The comparison diagram of extended gain control and voltage matching control of the hybrid dual active bridge DC-DC converter provided by the present invention is shown in (a) for the relationship between return power ratio and input voltage when the per-unit transmission power P = 0.4, and (b) for the relationship between return power ratio and input voltage when the per-unit transmission power P = 0.9.

[0057] Figure 14 The overall control block diagram of the hybrid dual active bridge DC-DC converter provided by the present invention. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be 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 illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0059] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0060] Example 1

[0061] Figure 1 The circuit diagram of a hybrid dual active bridge DC-DC converter provided in Embodiment 1 of the present invention is shown.

[0062] like Figure 1 As shown, a hybrid dual active bridge DC-DC converter includes: an auxiliary half-bridge and a current-fed DAB converter;

[0063] The auxiliary half-bridge includes a first half-bridge and an auxiliary inductor L1; the two ends of the first half-bridge are connected to the input power supply as input terminals, and a capacitor C1 is connected in parallel across the two ends of the first half-bridge; the midpoint of the first half-bridge is connected to the first terminal e of the auxiliary inductor L1.

[0064] The current-fed DAB converter includes a first full-bridge, a second full-bridge, and a high-frequency link; the two ends of the second full-bridge serve as output terminals, and an output filter capacitor C is connected in parallel. o ;

[0065] The first full bridge has parallel support capacitors C at both ends. mThe second end a of the auxiliary inductor L1 is connected to the midpoint of the second half-bridge of the first full bridge; the high-frequency link includes an intermediate inductor L2 and a transformer T, the midpoint of the second half-bridge of the first full bridge is also connected to the intermediate inductor L2 and then to the same-name end of the first winding n1 of the transformer T, and the midpoint b of the third half-bridge of the first full bridge is connected to the non-same-name end of the first winding n1 of the transformer T.

[0066] The midpoint c of the fourth half-bridge of the second full bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint d of the fifth half-bridge of the second full bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T.

[0067] Optionally, the first half-bridge includes a first switch Q1 and a second switch Q2, with the source of the first switch Q1 and the drain of the second switch Q2 connected, and the input power supply V in The positive terminal is connected to the drain of the first switch Q1, and the negative terminal is connected to the source of the second switch Q2.

[0068] The first full-bridge includes a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6; the source of the third switch Q3 and the drain of the fourth switch Q4 are connected to form a second half-bridge, and the supporting capacitor C... m The two ends of the second half-bridge are connected in parallel. The midpoint of the bridge arm of the second half-bridge is connected to the second end a of the auxiliary inductor L1. The midpoint of the bridge arm of the second half-bridge is also connected to the intermediate inductor L2 and then to the same-name terminal of the first winding n1 of the transformer T. The source of the fifth switch Q5 and the drain of the sixth switch Q6 are connected to form the third half-bridge. The midpoint b of the bridge arm of the third half-bridge is connected to the non-same-name terminal of the first winding n1 of the transformer T.

[0069] The source of the second switch Q2, the source of the fourth switch Q4, and the source of the sixth switch Q6 are connected, and the drain of the third switch Q3 and the drain of the fifth switch Q5 are connected.

[0070] Optionally, the second full bridge includes a seventh switch Q7, an eighth switch Q8, a ninth switch Q9, and a tenth switch Q1. 10 ;

[0071] The source of the seventh switch Q7 and the drain of the eighth switch Q8 are connected to form a fourth half-bridge. The source of the ninth switch Q9 and the drain of the tenth switch Q8 are connected to form a fourth half-bridge. 10The drains of the fourth half-bridge are connected to form the fifth half-bridge; the midpoint c of the bridge arm of the fourth half-bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint d of the bridge arm of the fifth half-bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T; the drain of the seventh switch Q7 is connected to the drain of the ninth switch Q9, and the source of the eighth switch Q8 is connected to the source of the tenth switch Q9. 10 The source connection.

[0072] In the half-bridge converter, the two switching transistors conduct complementaryly from top to bottom. Different control methods are employed when the converter operates at different voltages. The support voltage V is adjusted by regulating the duty cycle d1 of the first switching transistor Q1. m This makes V m / V o =n1 / n2, which can achieve zero-voltage turn-on of the switching transistors across the entire power range, solving the problem that DAB converters are difficult to achieve zero-voltage turn-on under light load, and reducing the switching losses of the converter.

[0073] This invention introduces an auxiliary half-bridge circuit into a current-feed DAB converter to construct a novel hybrid dual active bridge DC-DC converter. This hybrid dual active bridge DC-DC converter solves the problem that a single DAB converter can only achieve full-load range ZVS and low return current power under voltage matching conditions. By introducing an auxiliary half-bridge circuit on the front side of the current-feed DAB converter, this hybrid dual active bridge DC-DC converter can cope with wide voltage input, ensure ZVS of all switches, reduce return current power, and improve the converter efficiency.

[0074] Example 2

[0075] A control method for a hybrid dual active bridge DC-DC converter, applied to any of the hybrid dual active bridge DC-DC converters described in the above embodiments, includes:

[0076] According to the input voltage V of the hybrid dual active bridge DC-DC converter in and target output power P o Determine whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM).

[0077] When the FRM is running, voltage matching control is used to fix the duty cycle d3 of the first full bridge to 0.5, and the gain of the converter is adjusted by adjusting the duty cycle d1 of the first switch Q1 in the auxiliary half bridge.

[0078] When SRM is running, extended gain control EG is used, and it is determined whether the current converter is in Buck or Boost state. The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge is fixed at d. min Or dmax The gain of the converter is adjusted by adjusting the duty cycle d3 of the third switch Q3 of the first full bridge.

[0079] Optionally, the step is based on the input voltage V of the hybrid dual active bridge DC-DC converter. in and target output power P o Determining whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM) includes:

[0080] When the per-unit input voltage range is 0.625-2, the hybrid dual active bridge DC-DC converter operates in the first half-bridge regulation mode (FRM).

[0081] When the per-unit input voltage range exceeds 0.625-2, the hybrid dual active bridge DC-DC converter operates in the second half-bridge regulation mode (SRM).

[0082] When the per-unit input voltage range is 0.625-2, the first half-bridge regulation mode (FRM) is used. In the first half-bridge regulation mode (FRM), voltage matching control is adopted, and the duty cycle d1 of the first switching transistor Q1 in the auxiliary half-bridge is adjusted to adjust the supporting capacitor C. m Support voltage V at both ends m This makes V m / V o =n1 / n2, i.e., the supporting voltage V m and output filter capacitor C o Output voltage V at both ends o Matching; where n1 is the number of turns in the first winding and n2 is the number of turns in the second winding. At this time, all switching transistors can achieve ZVS.

[0083] like Figure 2 As shown, when operating in an FRM, there are 5 operating stages within half a switching cycle. Due to symmetry, the boost and buck processes of the converter are similar; this embodiment uses the boost mode as an example for analysis. To simplify the analysis, assume the transformer turns ratio: n1 / n2 = N = 1. The operational analysis of each stage is as follows:

[0084] Phase I [t0-t1]: such as Figure 3As shown in (a), before time t0, the current in the auxiliary inductor L1 is negative, and the current in the intermediate inductor L2 is positive. At time t0, the first switch Q1 of the auxiliary half-bridge is turned off, and the second switch Q2 is turned on; the fourth switch Q4 and the fifth switch Q5 of the first full-bridge are turned on as zero-voltage switches (ZVS), and the third switch Q3 and the sixth switch Q6 are turned off; the current in the auxiliary inductor L1 is approximately constant and freewheels through the second switch Q2 and the fourth switch Q4; correspondingly, the seventh switch Q7 and the tenth switch Q8 of the second full-bridge are also present. 10 When the circuit is turned on, the eighth switch Q8 and the ninth switch Q9 are turned off. Over time, the current in the intermediate inductor L2 decreases linearly. During this phase, the current in inductor L2 can be expressed as:

[0085]

[0086] Phase II [t1-t2]: such as Figure 3 As shown in (b), at time t1, the switching transistors in the auxiliary half-bridge and the first full-bridge are in the same state during stage I, and the current in the intermediate inductor L2 decreases linearly and then reverses. The seventh switch Q7 and the tenth switch Q... 10 The turn-off phase involves the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q10. 10 The dead time. The current in the secondary winding n2 freewheels through the body diodes of the eighth switch Q8 and the ninth switch Q9, providing the conditions for the zero-voltage switching (ZVS) of the eighth switch Q8 and the ninth switch Q9.

[0087] Phase III [t2-t3]: such as Figure 3 As shown in (c), at time t2, the switching states of the auxiliary half-bridge and the first full-bridge are in the same stage II. The eighth switch Q8 and the ninth switch Q9 are turned on with ZVS. The auxiliary inductor L1 remains approximately constant, and the voltage across the intermediate inductor L2 is 0. L2 Approximately constant. The primary winding n1 transfers power to the secondary winding n2 through the intermediate inductor L2.

[0088] Phase IV [t3-t4]: such as Figure 3 As shown in (d), at time t3, the switching transistors in the first and second full-bridges are in the same state (Level III). The second switch Q2 of the auxiliary half-bridge is turned off. This stage is the dead time of the first switch Q1 and the second switch Q2. The current of the auxiliary inductor L1 freewheels through the body diode of the first switch Q1, which provides the conditions for the first switch Q1 to achieve ZVS.

[0089] Stage V [t4-t5]: such as Figure 3As shown in (e), at time t4, the switching transistors in the first and second full-bridge are in the same state (III). The first switching transistor Q1 of the auxiliary half-bridge is turned on at ZVS. The auxiliary inductor L1 is subjected to voltage V. in Linear current, i L1 The voltage increases linearly. The voltage across the intermediate inductor L2 is 0, i L2 The current is approximately constant. During this stage, the current in the auxiliary inductor L1 is expressed as:

[0090] i L1 (t)=i L1 (t4)+V in (t-t4) / L1 (2)

[0091] like Figure 4 As shown, when operating under SRM, there are 8 operating stages within half a switching cycle. Due to symmetry, the boost and buck processes of the converter are similar. This embodiment assumes that the DAB converter operates in buck mode, and takes stages III and IV as examples for description. The operating states of the two stages are analyzed as follows:

[0092] Phase III [t2-t3]: Before time t2, such as Figure 5 As shown in (a), the first switch Q1 in the auxiliary bridge is turned off, and the second switch Q2 is turned on; the third switch Q3 in the second half-bridge is turned on, and the fourth switch Q4 is turned off. The current in the intermediate inductor L2 is positive. At time t2, the sixth switch Q6 in the third half-bridge is turned off, and the current freewheels through the body diode of the fifth switch. This stage is the dead time of the fifth switch Q5 and the sixth switch Q6. The current in the primary winding n1 freewheels through the body diode of the fifth switch Q5, providing the condition for the zero-voltage switching (ZVS) of the fifth switch Q5.

[0093] Phase IV [t3-t4]: At time t3, such as Figure 5 As shown in (b), the fifth switch Q5 is turned on at ZVS, the current in the auxiliary inductor L1 decreases linearly, and the current in the intermediate inductor L2 decreases with voltage -V o When the linear circuit is de-energized, the current i in the intermediate inductor... L2 It decreases linearly. The current in the intermediate inductor L2 is expressed as:

[0094] i L2 (t)=i L2 (t3)-V o (t-t3) / NL2 (3)

[0095] There are three main differences between the characteristics of SRM:

[0096] like Figure 4As shown, when operating in SRM mode, since the duty cycle of the first full-bridge switch connected to the primary winding n1 is not 0.5, the dead time of the fifth switch Q5 and the sixth switch Q6 is advanced, increasing the zero-level stage. During the zero-level stage, there is no power path between the primary winding n1 and the secondary winding n2, thus reducing the return power.

[0097] In the second half-bridge regulation mode (SRM), there are also issues with reduced maximum power transfer capability and more stringent ZVS conditions, requiring further optimization using extended gain control (EG). The optimization approach for EG is as follows: In SRM, there are two control variables related to power transfer: the duty cycle d3 of the third switch Q3 and the phase shift angle between the drive pulse of the seventh switch Q7 and the drive pulse of the third switch Q3. In the first full-bridge circuit, the duty cycle of the fifth switch Q5 is equal to the duty cycle d3 of the third switch Q3. Since the upper and lower switches in the half-bridge are complementary in conduction, the duty cycles of the fourth switch Q4 and the sixth switch Q6 are d4 = 1 - d3. In the second full-bridge circuit, the switches in the fourth and fifth half-bridges are complementary in conduction, Q7, Q8, Q9, and Q6. 10 The duty cycle of all switching transistors is 0.5. The drive pulse of the first switching transistor Q1 is the reference, and the drive pulse of the third switching transistor Q3 lags behind the phase of the drive pulse of the first switching transistor Q1 by [phase value missing]. That is, the phase shift angle of the third switch Q3 is The drive pulse of the fifth switch Q5 lags behind the drive pulse of the third switch Q3 by 180°, and the drive pulse of the seventh switch Q7 is phase-shifted by the drive pulse of the third switch Q3.

[0098] Extended gain control differs from voltage matching control. In voltage matching control, the duty cycle d3 of the third switch Q3 is only used to control the parallel voltage. Extended gain control, however, extends the gain range and load range of the ZVS by adjusting the duty cycle d3 of the third switch Q3. The optimal value within the ZVS range is determined with minimum return power as the optimization objective. Operating point. The modulation of the auxiliary bridge has also been improved to extend the ZVS range. The extended gain control is explained in detail in three parts below.

[0099] 1. Extended Gain Method

[0100] For a full-bridge circuit between the primary and secondary sides of a transformer, no power transfer occurs if the voltages on the primary and secondary sides do not overlap. Therefore, when there is a voltage mismatch, all switches can achieve four operating modes, such as... Figure 6As shown, (a) is a waveform diagram of trapezoidal wave-Buck in SRM-I mode, (b) is a waveform diagram of trapezoidal wave-Boost in SRM-II mode, (c) is a waveform diagram of triangular wave-Buck in SRM-III mode, and (d) is a waveform diagram of triangular wave-Boost in SRM-IV mode. SEM-I represents the trapezoidal inductor current waveform operating mode under buck conditions, SEM-II represents the trapezoidal inductor current waveform operating mode under boost conditions, SEM-III represents the triangular inductor current waveform operating mode under buck conditions, and SEM-IV represents the triangular inductor current waveform operating mode under boost conditions. The mode division is based on the waveform of the current in the intermediate inductor and the buck / boost conditions. Compared to the triangular wave, the trapezoidal current waveform implies a larger phase shift ratio and power. To determine whether the converter is in Buck or Boost mode, the duty cycle d1 of the first switch Q1 in the auxiliary half-bridge is fixed to d. min Or d max The gain of the converter is adjusted by regulating the duty cycle d3 of the third switch Q3 of the first full bridge.

[0101] The optimization process of EG is illustrated below using SRM-I as an example.

[0102] The current waveform of the intermediate inductor L2 in SRM-I is as follows: Figure 6 As shown, due to the symmetry of the waveform, the current condition for ZVS can be expressed as:

[0103]

[0104] Where k is the voltage conversion ratio of DAB, k = V o / NV m .

[0105] The classification constraints of SRM-I can be described as follows:

[0106]

[0107] The phase shift ratio can be obtained by using the ZVS current limiting condition of the switching transistor. The minimum value constraint is:

[0108]

[0109] The ZVS region can be obtained according to formulas (5) and (6), such as Figure 7 As shown, (a) is a schematic diagram of the per-unit input voltage Vin = 3, and (b) is a schematic diagram of the per-unit input voltage Vin = 5. When the converter is in Buck state, the duty cycle d of the first switch Q1 is taken. min The duty cycle d is 0.2. When the converter is in Boost mode, the duty cycle d of the first switch Q1 is taken.max It is 0.8. Among them, and These are the maximum constraint d3 / 2 and the minimum constraint d3-0.5 for the phase shift ratio. To ensure...

[0110] exist and Between them, the constraint of d3 can be expressed as:

[0111]

[0112] like Figure 7 As can be seen from the image, and This forms the edge of the ZVS region. Under voltage mismatch conditions, the expression for the transmitted power is as follows:

[0113]

[0114] For ease of explanation, the V in the text in "Normalization" refers to the normalized input voltage. Substituting equations (5) and (6) into equation (8), we obtain the maximum value P of the transmission power P corresponding to the duty cycle d3 of the third switch Q3. max and minimum value P min The expression, P max and P min like Figure 8 As shown, the maximum transmission power in the ZVS region is at d 3max The minimum transmission power is obtained at d. 3min or d 3max It can be obtained from there.

[0115] The optimization of the auxiliary half-bridge is based on the optimization results of the current-feed DAB. The auxiliary half-bridge most commonly uses quadrangular current control (QCC), such as... Figure 9 As shown in (a), I ZVS This is the minimum inductor current used to achieve ZVS. QCC controls the variable... The freewheeling current i of the auxiliary inductor L1 fw Closed-loop control is implemented. Therefore, the ZVS constraint of the first switch Q1 and the second switch Q2 is achieved through the inductor current i. L1 Achieved. The ZVS constraint of the third switch Q3 and the fourth switch Q4 is achieved through the current i of the auxiliary inductor. L1 and the current i of the intermediate inductor L2 It is achieved. However, QCC will lose ZVS of Q2 or Q3 under light load with a wide input voltage range.

[0116] To address this, a triangular current control (TCC) method for assisting half-bridges is proposed to extend the ZVS range, such as... Figure 9 As shown in (b). Because i L2 The TCC provides current for the zero-current freewheeling (ZVS) of the first switch Q1 and the third switch Q3, so they can achieve ZVS even when the current in L1 is 0 when Q1 and Q3 are on. The freewheeling current control method of the TCC is exactly the same as that of the QCC, except that the control command is changed from IZVS to 0. The TCC extends the ZVS range under light loads and completely eliminates the power loss of the switches and inductors caused by the freewheeling current through the increased zero-current freewheeling phase.

[0117] Because of the use of TCC, buck mode can achieve full-range ZVS. In boost mode (FRM-Boost and SRM-Boost), TCC will cause Q1 or Q2 to lose ZVS. Therefore, TCC is used to achieve ZCS under light load in boost mode. Under heavy load in boost mode, due to the small input voltage and small inductor current amplitude, the minimum freewheeling current increases and becomes positive, and the first switch Q1 and the fourth switch Q4 lose ZVS. Therefore, the ZVS range of boost mode is relatively narrow.

[0118] like Figure 10 As shown, this expands the ZVS range and working range. Figure 10 Figures (a) and (c) show that full-range ZVS is achievable for all switches when running on FRM-Buck and SRM-Buck. Therefore, SRM-Boost has a limited ZVS range, while FRM and SRM-Buck can achieve almost full-range ZVS.

[0119] 2. Optimization of return current power

[0120] Return power refers to the power flowing from the transformer to the input voltage source. Return power results in additional losses in the converter. Figure 11 The shaded area is shown. When the input voltage V in When the transmission power P is determined, d3 and It still has adjustable degrees of freedom, so the optimal operating point can be selected. This is to reduce return current power. The expression for return current power is:

[0121]

[0122] Considering that return power is related to transmission power, the return power ratio is defined as:

[0123]

[0124] For a given transmission power, The expression can be obtained from (8). Substituting into formula (10), we can obtain M. back Relationship with d3. Return power ratio M back The relationship with duty cycle d3 is as follows Figure 12 As shown, due to the complexity of the expression, it is not listed in this paper to obtain the minimum M. back The running status points are marked with corresponding points.

[0125] like Figure 12 As shown, M back It has a unique minimum value with respect to d3. However, M back The expression for d3 is quite complex, and the expression for its derivative is even more complex. Therefore, finding the optimal expression for d3 directly is not feasible; the optimal value of d3 is obtained using a lookup table. Compared with voltage matching control, the return power optimization effect of gain extension control is as follows: Figure 13 As shown in the figure, it can be seen that the proposed extended gain control method can significantly reduce the return power.

[0126] 3. Control Strategy

[0127] Optionally, the gain of the converter can be adjusted by regulating the duty cycle d3 of the third switch Q3 of the first full-bridge, including:

[0128] Based on the measured freewheeling current i fw Determine and control the phase shift angle of the auxiliary half-bridge

[0129] According to the input voltage V in and target output power P o Determine the optimal operating points of the first and second full bridges by referring to the table. And based on the optimal working point The parameters control the duty cycle d3 of the third switch Q3 of the first full-bridge and the phase shift angle of the seventh switch Q7 of the second full-bridge.

[0130] According to the input voltage V in and output power P o The operating mode is determined. Then it looks up the optimal operating point in a table. The voltage calculation section converts the duty cycle d3 of the optimal operating point into the support voltage V. m_ref The reference value is [reference value]. The control system contains three regulators: a freewheeling current regulator (FIR), a parallel regulator (MVR), and an output regulator (OVR). The FIR determines the command value through operating mode parameters, i [reference value]. fw This is the measured freewheeling current. They all employ the classic PI control algorithm, v FIR v MVR and v OVR These are the outputs of FIR, MVR, and OVR, respectively; v FIRPhase shift angle used to generate the auxiliary half-bridge v MVR1 and v MVR2 The duty cycles d1 and d3 of the auxiliary bridge and the first full bridge used to generate the primary-side circuit; v OVR The second full-bridge phase shift angle used to generate the secondary-side circuit. Best working point The value is converted to the regulator's setpoint, which can prevent overvoltage and bring better dynamic and steady-state performance.

[0131] The technical solution of this invention provides a control method for the hybrid dual active bridge DC-DC converter, including phase-shift modulation and pulse width modulation. Based on the input voltage range, this control method includes a first half-bridge adjustment mode and a second half-bridge adjustment mode. In the first half-bridge adjustment mode, voltage matching control (VM) can achieve zero-voltage switching (ZVS) for all switches. In the second half-bridge adjustment mode, extended gain control (EG) is used, with minimum return power as the optimization objective, which can extend the voltage gain and soft-switching range. The control method provided by this invention enables the hybrid dual active bridge DC-DC converter used in this embodiment to achieve zero-voltage turn-on of the switches across the entire power range, solving the problem of difficulty in achieving zero-voltage turn-on under light load in DAB converters and reducing the switching losses of the converter.

[0132] The control method for the hybrid dual active bridge DC-DC converter provided in this embodiment of the invention adopts a joint control strategy of pulse width modulation and phase shift modulation. The half-bridge circuit uses pulse width modulation and phase shift modulation, and the current-fed DAB converter section also uses pulse width modulation and phase shift modulation. There is no coupling relationship between the degrees of freedom. The duty cycle d1 of the first switch Q1 and the duty cycles d3 of the third switch Q3 and the fifth switch Q5 are used to adjust the voltage gain. The phase shift angle between the first switch Q1 and the third switch Q3... Used to adjust the freewheeling current i fw The phase shift angle between the third switch Q3 and the seventh switch Q7 Controlling power flow is simple and easy to implement, reducing the complexity of control.

[0133] The hybrid dual active bridge DC-DC converter provided in this embodiment of the invention solves the problems of traditional voltage-fed DAB converters being limited by the difficulty of ZVS implementation and the narrow input voltage range, thereby expanding the voltage gain.

[0134] Example 3

[0135] Figure 14 This is a schematic diagram of the control system of a hybrid dual active bridge DC-DC converter provided in Embodiment 3 of the present invention.

[0136] like Figure 14 As shown, a control system for a hybrid dual active bridge DC-DC converter includes a controller and a hybrid dual active bridge DC-DC converter as described in any of the above embodiments. The controller is used to execute the control method of the hybrid dual active bridge DC-DC converter as described in any of the above embodiments.

[0137] The controller includes a mode selection module, a freewheeling current regulator (FIR), a lookup table module, a voltage calculation module, a parallel regulator (MVR), an output regulator (OVR), a modulation module, and a drive module.

[0138] The mode selection module is used to select the input voltage V of the hybrid dual active bridge DC-DC converter. in and target output power P o Determine whether it operates in the first half-bridge regulation mode (FRM) or the second half-bridge regulation mode (SRM).

[0139] The freewheeling current regulator FIR is used to adjust the measured freewheeling current i. fw Determine and control the phase shift angle of the auxiliary half-bridge

[0140] The lookup table module is used to determine the input voltage V based on the input voltage V. in and target output power P o Determine the optimal operating points of the first and second full bridges by referring to the table.

[0141] The voltage calculation module is used to convert the duty cycle d3 of the optimal operating point into a reference support voltage V. m_ref ;

[0142] The parallel regulator MVR is used to adjust the reference support voltage V. m_ref and measured support voltage V m The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge and the target duty cycle d3 of the third switch Q3 in the first full-bridge are obtained.

[0143] The output regulator OVR is used to adjust the output voltage V based on the reference output voltage V. o_ref and measured output voltage V o Phase shift angle of the seventh switch Q7 in the second full-bridge generation

[0144] The modulation module is used to generate phase-shift modulation signals and pulse-width modulation signals based on the outputs of the freewheeling current regulator FIR, the parallel regulator MVR and the output regulator OVR.

[0145] The driving module is used to control the auxiliary half-bridge, the first full-bridge, and the second half-bridge according to the phase-shift modulation signal and pulse width modulation signal generated by the modulation module.

[0146] In the control system of the hybrid dual active bridge DC-DC converter provided in this embodiment of the invention, both the input DC voltage source Vin and the output DC voltage source Vo can realize bidirectional energy flow, and the output capacitor Co can be connected to a battery in the case of UPS, so as to ensure that the entire DC microgrid system can be powered without interruption, thereby improving the reliability of power supply. It has a wide range of applications in new energy scenarios, realizing energy regulation and efficient utilization.

[0147] The control system of the hybrid dual active bridge DC-DC converter provided in the embodiments of the present invention can execute the control method of the hybrid dual active bridge DC-DC converter provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method.

[0148] Those skilled in the art will readily understand 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 within the scope of protection of the present invention.

Claims

1. A hybrid dual active bridge DC-DC converter, characterized in that, include: Auxiliary half-bridge, current-fed DAB converter; The auxiliary half-bridge includes a first half-bridge and an auxiliary inductor L1; the two ends of the first half-bridge serve as input terminals and are connected to the input power supply, and a capacitor C1 is connected in parallel across the two ends of the first half-bridge; the midpoint of the first half-bridge is connected to the first end of the auxiliary inductor L1. The current-fed DAB converter includes a first full-bridge, a second full-bridge, and a high-frequency link; the two ends of the second full-bridge serve as output terminals, and an output filter capacitor C is connected in parallel. o ; The first full bridge has parallel support capacitors C at both ends. m The second end of the auxiliary inductor L1 is connected to the midpoint of the second half-bridge of the first full bridge; the high-frequency link includes an intermediate inductor L2 and a transformer T, the midpoint of the second half-bridge of the first full bridge is also connected to the intermediate inductor L2 and then to the same-name end of the first winding n1 of the transformer T, and the midpoint of the third half-bridge of the first full bridge is connected to the non-same-name end of the first winding n1 of the transformer T. The midpoint of the fourth half-bridge of the second full bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint of the fifth half-bridge of the second full bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T. The first half-bridge includes a first switch Q1 and a second switch Q2. The source of the first switch Q1 and the drain of the second switch Q2 are connected. The positive terminal of the input power supply is connected to the drain of the first switch Q1, and the negative terminal is connected to the source of the second switch Q2. The first full-bridge includes a third switch Q3, a fourth switch Q4, a fifth switch Q5, and a sixth switch Q6; the source of the third switch Q3 and the drain of the fourth switch Q4 are connected to form a second half-bridge, and the supporting capacitor C... m The two ends of the second half-bridge are connected in parallel. The midpoint of the bridge arm of the second half-bridge is connected to the second end of the auxiliary inductor L1. The midpoint of the bridge arm of the second half-bridge is also connected to the intermediate inductor L2 and then to the same-name terminal of the first winding n1 of the transformer T. The source of the fifth switch Q5 and the drain of the sixth switch Q6 are connected to form the third half-bridge. The midpoint of the bridge arm of the third half-bridge is connected to the non-same-name terminal of the first winding n1 of the transformer T. The source of the second switch Q2, the source of the fourth switch Q4, and the source of the sixth switch Q6 are connected, and the drain of the third switch Q3 and the drain of the fifth switch Q5 are connected.

2. The hybrid dual active bridge DC-DC converter of claim 1, wherein, The second full bridge includes the seventh switch Q7, the eighth switch Q8, the ninth switch Q9, and the tenth switch Q1. 10 ; The source of the seventh switch Q7 and the drain of the eighth switch Q8 are connected to form a fourth half-bridge. The source of the ninth switch Q9 and the drain of the tenth switch Q8 are connected to form a fourth half-bridge. 10 The drains of the fourth half-bridge are connected to form the fifth half-bridge; the midpoint of the bridge arm of the fourth half-bridge is connected to the same-name terminal of the second winding n2 of the transformer T, and the midpoint of the bridge arm of the fifth half-bridge is connected to the non-same-name terminal of the second winding n2 of the transformer T; the drain of the seventh switch Q7 is connected to the drain of the ninth switch Q9, and the source of the eighth switch Q8 is connected to the source of the tenth switch Q9. 10 The source connection.

3. A control method of a hybrid dual active bridge DC-DC converter, applied to the hybrid dual active bridge DC-DC converter according to any one of claims 1-2, characterized in that, include: According to the input voltage V of the hybrid dual active bridge DC-DC converter in and the target output power P o determining whether to operate in a first half-bridge regulation mode FRM or a second half-bridge regulation mode SRM; When the FRM is running, voltage matching control is used to fix the duty cycle d3 of the first full bridge to 0.5, and the gain of the converter is adjusted by adjusting the duty cycle d1 of the first switch Q1 in the auxiliary half bridge. When SRM is running, extended gain control EG is used, and it is determined whether the current converter is in Buck or Boost state. The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge is fixed at d. min Or d max The gain of the converter is adjusted by adjusting the duty cycle d3 of the third switch Q3 of the first full bridge.

4. The control method of a hybrid dual active bridge DC-DC converter according to claim 3, characterized in that, said input voltage V in and a target output power P o determining whether to operate in a first half-bridge regulation mode FRM or in a second half-bridge regulation mode SRM, comprises When the per-unit input voltage range is 0.625-2, the hybrid dual active bridge DC-DC converter operates in the first half-bridge regulation mode (FRM). When the per-unit input voltage range exceeds 0.625-2, the hybrid dual active bridge DC-DC converter operates in the second half-bridge regulation mode (SRM).

5. The control method of a hybrid dual active bridge DC-DC converter according to claim 3, characterized in that, The method of adjusting the converter gain by adjusting the duty cycle d1 of the first switch Q1 in the auxiliary half-bridge includes: The capacitance C is adjusted by adjusting the duty cycle d1 of the first switching transistor Q1 in the auxiliary half-bridge. m Support voltage V at both ends m This makes the supporting voltage V m and output filter capacitor C o Output voltage V at both ends o Matching, that is, satisfying: V m / V o =n1 / n2, where n1 is the number of turns in the first winding and n2 is the number of turns in the second winding.

6. The control method of a hybrid dual active bridge DC-DC converter according to claim 3, wherein, The method of adjusting the converter gain by adjusting the duty cycle d3 of the third switch Q3 of the first full bridge includes: The freewheeling current of the measured auxiliary inductance L1 i fw Determining and controlling the phase shift angle φ of the auxiliary half-bridge h ; According to the input voltage V in and target output power P o The optimal operating point d3-φ of the first full bridge and the second full bridge is determined by referring to the table, and the duty cycle d3 of the third switch Q3 of the first full bridge and the phase shift angle φ of the seventh switch Q7 of the second full bridge are controlled according to the parameters of the optimal operating point d3-φ.

7. A control system for a hybrid dual active bridge DC-DC converter, characterized in that, It includes a controller and a hybrid dual active bridge DC-DC converter as described in any one of claims 1-2, wherein the controller is used to execute the control method of any hybrid dual active bridge DC-DC converter as described in claims 3-6; The controller includes a mode selection module, a freewheeling current regulator (FIR), a lookup table module, a voltage calculation module, a parallel regulator (MVR), an output regulator (OVR), a modulation module, and a drive module. The mode selection module is configured to determine, according to an input voltage V in and a target output power P o whether to operate in a first half-bridge regulation mode FRM or a second half-bridge regulation mode SRM. The freewheeling current regulator FIR is used to adjust the freewheeling current based on the measured freewheeling current of the auxiliary inductor L1. i fw Determine and control the phase shift angle φ of the auxiliary half-bridge h ; The table lookup module is configured to determine, according to the input voltage V in and the target output power P o the optimal working point d3-φ of the first full bridge and the second full bridge through table lookup. The voltage calculation module is configured to convert the duty cycle d3 of the optimal working point into a reference support voltage V m_ref ; The parallel regulator MVR is used to adjust the reference support voltage V. m_ref and measured support voltage V m The duty cycle d1 of the first switch Q1 in the auxiliary half-bridge and the target duty cycle d3 of the third switch Q3 in the first full-bridge are obtained. The output regulator OVR is used to adjust the output voltage V based on the reference output voltage V. o_ref and measured output voltage V o Generate the phase shift angle φ of the seventh switch Q7 of the second full bridge; The modulation module is used to generate phase-shift modulation signals and pulse-width modulation signals based on the outputs of the freewheeling current regulator FIR, the parallel regulator MVR and the output regulator OVR. The driving module is used to control the auxiliary half-bridge, the first full-bridge, and the second half-bridge according to the phase-shift modulation signal and pulse width modulation signal generated by the modulation module.

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