A high-integration single-stage bidirectional isolated resonant SEPIC AC-DC converter

Abstract

The application belongs to the technical field of AC-DC converters, and particularly relates to a high-integration single-stage bidirectional isolated resonant SEPIC AC-DC converter. The application comprises an AC input port, a DC output port, a primary-side bidirectional switch bridge arm, a resonant network module, an isolation transformer and a secondary-side active bridge arm. The first inductor and the third capacitor constitute a SEPIC energy storage network, the second inductor and the first and second capacitors constitute a resonant commutation network, and the transformer realizes electrical isolation between the primary and secondary sides. By coordinating the conduction states of the primary and secondary bridge arms, bidirectional power transmission between the AC side and the DC side is realized. The application combines the bridgeless SEPIC structure and the isolated resonant conversion structure, cancels the large DC bus capacitor, reduces the number of power devices, improves the power density, realizes zero-voltage or zero-current soft switching of the switch tube in the full load range by using the resonant network, greatly reduces the switching loss and electromagnetic interference, and has high efficiency and high reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of AC-DC converters, and particularly relates to a high-integration single-stage bidirectional isolated resonant SEPIC AC-DC converter. BACKGROUND

[0002] With the in-depth development of more-electric and all-electric aircraft technology, the aviation power supply system puts forward strict requirements on power conversion devices, such as high efficiency, high power density, high reliability and bidirectional energy flow capability. In the aviation hybrid power supply, energy storage system and electric propulsion system, flexible and efficient energy exchange needs to be realized between the AC bus, DC bus and energy storage device, so that the bidirectional isolated AC-DC converter has become a key interface equipment of such systems.

[0003] At present, most of the existing bidirectional isolated AC-DC converters adopt a two-stage structure composed of a front-stage power factor correction (PFC) circuit and a rear-stage isolated DC-DC converter. Although this kind of topology can realize input current shaping, electrical isolation and bidirectional power transmission, its inherent defects are very prominent: first, an independent DC bus and a large-capacity energy storage capacitor must be set, which leads to a large number of system devices, complex control, significant increase in volume and weight, and seriously restricts the improvement of power density, making it difficult to meet the core demand of lightweight for aviation applications. Secondly, the energy passes through two-stage conversion, which produces additional loss and reduces the overall conversion efficiency of the system. To overcome the above shortcomings, researchers have proposed a variety of single-stage bidirectional AC-DC converter topologies. However, the existing single-stage schemes generally have poor input current quality, limited soft switching range of power devices, high voltage stress or complex control strategy, etc. In addition, the traditional hard-switching converter generates huge switching loss and electromagnetic interference when operating at high frequency, hindering the development of the converter towards high frequency and miniaturization. Figure 22 Patent CN120185434A discloses a bidirectional single-stage AC / DC circuit based on SEPIC, which can realize isolated bidirectional energy transmission, but uses the traditional PWM working mode and does not fully utilize the resonant soft switching technology, resulting in large switching loss and device stress when operating at high frequency.

[0004] Patent CN121098131A discloses a bidirectional single-stage AC-DC converter based on Swiss rectifier and Sigma-LLC resonant network, which has soft switching characteristics, but the topology structure is complex, the number of devices is large, and the control implementation is difficult.

[0005]

[0006] ​Therefore, how to fundamentally reduce the number of power devices and passive components while ensuring bidirectional energy transmission and electrical isolation, and at the same time achieving soft switching and high power factor operation in a wide load range, is a technical problem to be solved in the field of current aviation power supply and high-efficiency power electronic conversion. SUMMARY

[0007] The application is to solve the problems of the prior art, such as many power devices and passive energy storage elements, complex circuit topology, large size and weight of the converter, narrow soft switching load range of the single-stage converter, and low power factor. A high-integration single-stage bidirectional isolated resonant SEPIC AC-DC converter is proposed, which is characterized by comprising: an AC input port for connecting an AC power supply V ac ;

[0008] a DC output port for connecting a DC power supply V dc ;

[0009] a primary bridge arm module, one end of which is electrically connected to the AC input port, and the other end of which is electrically connected to one end of a resonant network module;

[0010] the other end of the resonant network module is electrically connected to one end of a transformer module;

[0011] the other end of the transformer module is electrically connected to a secondary rectifier module;

[0012] the secondary rectifier module is electrically connected to the DC output port; the primary bridge arm module is a primary bidirectional switching bridge arm; the secondary rectifier module is a secondary active bridge arm; the resonant network module includes a resonant inductor unit and a resonant capacitor unit; the transformer module is used to realize electrical isolation between the AC side and the DC side; the primary bridge arm module and the secondary rectifier module realize bidirectional energy transmission between the AC side and the DC side by coordinating the conduction state.

[0013] According to the above-mentioned high-integration single-stage bidirectional isolated resonant SEPIC AC-DC converter, the primary bridge arm module 100 comprises: a first switch tube S1 and a second switch tube S2;

[0014] The first switch tube S1 and the second switch tube S2 are connected in series on the same branch, forming a primary bidirectional switching bridge arm; the source of the first switch tube S1 is connected to the drain of the second switch tube S2;

[0015] One end of the second switch tube S2 is connected to the negative electrode of the AC power supply V ac , the drain of the first switch tube S1 is connected with a first inductor L, and the positive electrode of the AC power supply V ac is connected to the other end of the first inductor L;

[0016] The series connection point of the first switch tube S1 and the second switch tube S2 is the primary side bridge arm midpoint.

[0017] According to the high-integration single-stage bidirectional isolation resonant SEPIC AC-DC converter, the resonant network module 200 comprises a second inductor L r , a first capacitor C r1 and a second capacitor C r2 .

[0018] The second inductor L r is electrically connected with one end of the first inductor L as a resonant inductor.

[0019] The first capacitor C r1 and the second capacitor C r2 are resonant capacitors; the first capacitor C r1 is connected in parallel between the drain and the source of the first switch tube S1; and the second capacitor C r2 is connected in parallel between the drain and the source of the second switch tube S2.

[0020] According to the high-integration single-stage bidirectional isolation resonant SEPIC AC-DC converter, the transformer module 300 is a first isolation transformer T;

[0021] The first isolation transformer T comprises a primary side winding n p of the first isolation transformer and a secondary side winding n s of the first isolation transformer.

[0022] One end of the primary side winding n p of the first isolation transformer is electrically connected with the second inductor L r .

[0023] The primary side winding n p of the first isolation transformer is connected in parallel with the second inductor L r at both ends of the branch where the first switch tube S1 and the second switch tube S2 are located.

[0024] According to the high-integration single-stage bidirectional isolation resonant SEPIC AC-DC converter, the secondary side rectification module 400 comprises a third switch tube S3, a fourth switch tube S4, a fourth capacitor C dc1 and a fifth capacitor C dc2 .

[0025] The third switch tube S3 and the fourth switch tube S4 are connected in series to form one bridge arm of the secondary side active bridge arm.

[0026] The fourth capacitor Cdc1 With the fifth capacitor C dc2 They are connected in series to form another arm of the secondary active bridge arm;

[0027] The fourth capacitor C dc1 and the fifth capacitor C dc2 As an output capacitor.

[0028] According to the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter described above, the third switch S3, the fourth switch S4, and the fourth capacitor C... dc1 and the fifth capacitor C dc2 Forming a bridge structure;

[0029] The positive and negative ends of the bridge structure are respectively connected to the DC power supply V. dc The positive and negative electrodes;

[0030] The series connection point of the third switch S3 and the fourth switch S4 is the midpoint of one arm of the secondary active bridge arm.

[0031] The fourth capacitor C dc1 With the fifth capacitor C dc2 The series connection point is the midpoint of the other arm of the secondary active bridge arm.

[0032] According to the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter described above, the secondary winding n of the first isolation transformer... s One end is connected to the series connection point of the third switch S3 and the fourth switch S4, and the other end is connected to the fourth capacitor C. dc1 With the fifth capacitor C dc2 The series connection point.

[0033] According to the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter described above, the first inductor L and the second inductor L r A third capacitor C is connected between them; one end of the third capacitor C is connected to the second inductor L. r One end of the third capacitor C is electrically connected; the other end of the third capacitor C is connected to one end of the first inductor L and the first capacitor C, respectively. r1 One end of the capacitor is electrically connected; the third capacitor C serves as an energy storage capacitor.

[0034] The first inductor L and the third capacitor C constitute a SEPIC power transfer network; the second inductor L r As a resonant inductor, it is related to the first capacitor C. r1 and the second capacitor C r2 Together with the resonant capacitors, they form a resonant converter network.

[0035] According to the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter described above, the first isolation transformer T further includes a first isolation transformer magnetizing inductor L. m The first isolation transformer leakage inductance L p The first isolation transformer magnetizing inductance L m The primary winding n of the first isolation transformer p Parallel connection; leakage inductance L of the first isolation transformer p One end is connected to the second inductor L r One end is electrically connected; the leakage inductance L of the first isolation transformer p The other end is connected to the magnetizing inductance L of the first isolation transformer. m One end, the primary winding n of the first isolation transformer p One end is electrically connected.

[0036] According to the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter described above, in the rectification operation mode, the converter realizes the conversion of AC power to DC power, and the energy flows from the AC power supply Vac side to the DC power supply Vdc side.

[0037] In inverter operation mode, the converter realizes the conversion of DC power to AC power, and the energy flows from the DC power supply Vdc side to the AC power supply Vac side.

[0038] The beneficial effects of this invention are as follows:

[0039] 1. Significantly improved power density and integration. Compared with existing two-stage bidirectional AC-DC converters, this invention deeply integrates the bridgeless SEPIC structure and the isolated resonant converter structure through component reuse, eliminating the large intermediate bus capacitor. Comparative analysis shows that the number of power devices and passive energy storage components is reduced, the circuit topology is more compact, and the size and weight of the converter are effectively reduced: the number of power switching devices is reduced from 12 to 4, a reduction of approximately 66.7%; the total number of main power devices and energy storage components is reduced from 17 to 12, a reduction of approximately 29.4%. This particularly meets the urgent needs of multi-electric aircraft for lightweight and highly integrated airborne equipment.

[0040] 2. Achieve soft-switching operation over a wide load range. Addressing the issue of narrow soft-switching range in existing single-stage converters, the first capacitor C of this invention... r1 Second capacitor C r2 A resonant commutation network is formed with the second inductor Lr. By creating parallel or series resonant cavities during switching transients, the bus voltage resonance returns to zero or the current resonance crosses zero, thereby ensuring soft switching of the topology across the entire load range. Theoretical analysis and waveform verification show that this invention significantly suppresses switching stress and voltage spikes.

[0041] 3. Significantly reduced switching losses and electromagnetic interference. Based on the aforementioned soft-switching characteristics across the entire load range, this invention fundamentally overcomes the high-frequency bottleneck of traditional hard-switching converters. The switching transistor completes state switching under zero voltage or zero current conditions, resulting in lower switching losses compared to hard-switching solutions. Simultaneously, by eliminating high-frequency oscillations in di / dt and dv / dt, electromagnetic interference emissions are significantly reduced. This not only simplifies the filtering circuit but also improves the electromagnetic compatibility of the converter in aviation power systems, enhancing reliability.

[0042] 4. Achieving high-quality input current and single-stage bidirectional power transfer. The SEPIC-type energy storage network composed of the first inductor L and the third capacitor C of this invention can achieve continuous shaping of the input current without the need for an additional PFC stage. Theoretical analysis and experimental waveforms consistently show that the input current iL has good sinusoidal characteristics and low harmonic content. Simultaneously, by coordinating the control of the primary-side bridge arm and the secondary-side active bridge, the rectification and inversion operating modes can be seamlessly switched using only a single-stage energy conversion channel, simplifying the control strategy and reducing conduction losses by 20%.

[0043] 5. Improved conversion efficiency and energy transfer smoothness. Due to the integration of the resonant network and the SEPIC network, the high-frequency isolation transformer in this invention achieves more continuous and smoother energy transfer throughout the entire switching cycle. In rectification mode, the third switch S3, the fourth switch S4, and the fourth capacitor C... dc1 Fifth capacitor C dc2 To ensure synchronous rectifier operation, diode rectification voltage drop losses are eliminated; in inverter mode, the secondary bridge achieves ZVS commutation. Compared with existing two-stage topologies, this invention eliminates the intermediate DC bus energy storage stage, avoids the cumulative losses of multi-stage conversion, and effectively optimizes the overall operating efficiency of the converter. Attached Figure Description

[0044] Figure 1 This is a simplified circuit diagram of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0045] Figure 2 This is a schematic diagram of the circuit structure of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0046] Figure 3 This is a schematic diagram of the operating waveform of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter in rectification mode according to the present invention.

[0047] Figure 4 This is a schematic diagram of the working waveform of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter in inverter mode according to the present invention.

[0048] Figure 5 This is an equivalent circuit diagram of the switching mode I in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0049] Figure 6 This is an equivalent circuit diagram of the switching mode II in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0050] Figure 7 This is an equivalent circuit diagram of the switching mode III in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0051] Figure 8 This is an equivalent circuit diagram of the switching mode IV in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0052] Figure 9 This is an equivalent circuit diagram of the switching mode V in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0053] Figure 10 This is an equivalent circuit diagram of the switching mode VI in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0054] Figure 11 This is an equivalent circuit diagram of the switching mode VII in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0055] Figure 12 This is an equivalent circuit diagram of the switching mode VIII in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0056] Figure 13 This is an equivalent circuit diagram of the switching mode IX in the rectification mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0057] Figure 14 This is an equivalent circuit diagram of the switching mode I in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0058] Figure 15 This is an equivalent circuit diagram of the switching mode II in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0059] Figure 16 This is an equivalent circuit diagram of the switching mode III in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0060] Figure 17 This is an equivalent circuit diagram of the switching mode IV in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0061] Figure 18 This is an equivalent circuit diagram of the switching mode V in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0062] Figure 19 This is an equivalent circuit diagram of the switching mode VI in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0063] Figure 20 This is an equivalent circuit diagram of the switching mode VII in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0064] Figure 21 This is an equivalent circuit diagram of the switching mode VIII in the inverter mode of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to the present invention.

[0065] Figure 22 The circuit diagram shows the existing AC-DC converter with an independent DC bus and a large-capacity energy storage capacitor. Detailed Implementation

[0066] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0067] like Figures 1 to 2 As shown: This embodiment of a highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter includes: a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, and a first capacitor C. r1 Second capacitor C r2 Third capacitor C, fourth capacitor C dc1 Fifth capacitor C dc2 First inductor L, second inductor L r AC power supply V acDC power supply V dc and the first isolation transformer T; the first isolation transformer T includes the primary winding n of the first isolation transformer. p The secondary winding n of the first isolation transformer s .

[0068] The first switch S1 and the second switch S2 are connected in series, and one end of the branch containing them is connected to the AC power supply V. ac The negative terminal is connected to one end of the first inductor L, and the AC power supply V is connected to the other end. ac The positive terminal is connected to the other end of the first inductor L.

[0069] First capacitor C r1 Second capacitor C r2 The source and drain of the first switch S1 and the source and drain of the second switch S2 are connected in parallel respectively.

[0070] The first isolation transformer T includes the primary winding n of the first isolation transformer. p The secondary winding n of the first isolation transformer s The primary winding n of the first isolation transformer p One end is connected to the second inductor L r Connected in series, the other end is connected to AC power supply V. ac Negative terminal, second inductor L r The other end is connected in series with the third capacitor C, and the primary winding n of the first isolation transformer p With the third capacitor C and the second inductor L r The branch is connected in parallel to both ends of the branch containing the first switch S1 and the second switch S2;

[0071] The secondary winding n of the first isolation transformer s One end is connected to the connection point of the third switch S3 and the fourth switch S4, and the other end is connected to the fourth capacitor C. dc1 Fifth capacitor C dc2 The connection points are connected;

[0072] The third switch S3, the fourth switch S4, and the fourth capacitor C dc1 Fifth capacitor C dc2 It forms a bridge structure and is connected in parallel in the forward direction to the DC power supply V. dc The positive and negative terminals, the third switch S3 and the fourth switch S4 are on the same bridge arm, and the fourth capacitor C dc1 Fifth capacitor C dc2 On the other bridge arm.

[0073] In one specific embodiment of the present invention, the first switch S1 and the second switch S2 constitute a primary-side bidirectional switch bridge arm;

[0074] The third switch S3 and the fourth switch S4 form the secondary active bridge arm; the first inductor L serves as the input inductor, the third capacitor C serves as the energy storage capacitor, and the second inductor L... r As a resonant inductor, the first capacitor C r1 Second capacitor C r2 As a resonant capacitor, the first isolation transformer T, and the fourth capacitor C dc1 Fifth capacitor C dc2 Together with the output capacitor, they constitute a single-stage bidirectional isolated resonant SEPIC converter;

[0075] In this system, the first inductor L serves as the input inductor, the third capacitor C serves as the energy storage capacitor, forming the SEPIC energy transmission network. The first isolation transformer T provides electrical isolation between the AC and DC sides. The second inductor L... r As a resonant inductor L r With the first capacitor C r1 Second capacitor C r2 It serves as a resonant capacitor to form a resonant converter network.

[0076] By coordinating the conduction states of the primary-side bidirectional switching bridge arm and the secondary-side active bridge arm, bidirectional energy transfer between the AC and DC sides is achieved. In rectification mode, the converter converts AC power to DC power; in inverter mode, it converts DC power to AC power.

[0077] Figure 2 The specific circuit structure of the converter proposed in this invention is given. To simplify the analysis, the following assumptions are made: (a) all devices are ideal devices; (b) the parasitic devices of the first switch S1 and the second switch S2 are considered only as body diodes and junction capacitances; (c) the magnetizing inductance of the first isolation transformer T is L. m Leakage inductance is L p (d) Due to the leakage inductance L of the first isolation transformer T p Much smaller than the resonant inductance L r Furthermore, since both are connected in series in the same branch, for ease of analysis, they are combined and equivalent to L. r (e) Capacitor C is equivalent to a constant voltage source.

[0078] The following is based on Figure 2 Circuit structure diagram, combined with Figures 5 to 13 The specific working principle of this invention will be described.

[0079] Depend on Figure 3 It can be seen that the entire converter has 9 switching modes in one switching cycle in rectification mode: [t0~t1], [t1~t4], [t4~t5], [t5~t6], [t6~t7], [t7~t8], [t8~t9 ... 10 ]、[t 10~t 11 ]、[t 11 ~t 12 The working conditions of each switching mode under rectification mode are analyzed in detail.

[0080] Figures 5 to 13 The main physical quantity in it is: T s It is the switching cycle, V GS1 V GS2 V GS3 V GS4 These represent the gate and source voltages of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 when they are in the ON state, respectively. m L is the magnetizing inductance of the first isolation transformer T. p L is the leakage inductance of the first isolation transformer T, n is the turns ratio of the primary and secondary windings of the first isolation transformer, and L is the leakage inductance of the first isolation transformer T. r It is the second inductor, i L i represents the current flowing through the first inductor L. r Represents the flow through the second inductor L r The resonant current, i Lm This represents the current flowing through the magnetizing inductance of the first isolation transformer T. The fourth capacitor C... dc1 and the fifth capacitor C dc2 Equivalent to a constant voltage source of 0.5V dc V MN V is the voltage across the bridge arm containing the first switch S1 and the second switch S2. DS1 V DS2 With V DS3 V DS4 These are the drain and source voltages of the first switching transistor S1 and the drain and source voltages of the second switching transistor S2, respectively. DS3 and i DS4 These are the currents flowing through the third switch S3 and the fourth switch S4, respectively.

[0081] Depend on Figure 4 It can be seen that in inverter mode, there are 8 switching modes in one switching cycle: [t0~t2], [t2~t3], [t3~t4], [t4~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t6], [t7~t8], [t8~t9], [t9~t6], [t7~t8], [t9~t9], [t8~t9], [t8~t9], [t9 ... 10 The following section provides a detailed analysis of the operation of each switching mode.

[0082] like Figure 5As shown: Switching Mode I [t0~t1]: At time t0, the voltage across the first switch S1 drops to zero, and its body diode is forward biased and turns on. Simultaneously, since the branch containing the secondary switch, i.e., the third switch S3, is on, the primary voltage of the first isolation transformer T is clamped at nV. dc / 2. At this time, the second inductor L in the resonant circuit r , with the second capacitor C r2 This forms a parallel resonant network.

[0083] like Figure 6 As shown: Switching Mode II [t1~t4]: When i DS3 After the voltage drops to zero at time t1, turning off the third switch S3 achieves zero-current turn-off. Subsequently, the secondary branch switches, the fourth switch S4 turns on, and the primary voltage of the first isolation transformer T is re-clamped to -nV. dc / 2. At times t2 and t3, the fourth switch S4 and the first switch S1 are turned on successively. Both achieve zero-voltage turn-on due to the prior conduction of the body diode. The resonant network remains the second inductor L. r With the second capacitor C r2 The topology is in parallel, but the polarity of the primary-side equivalent clamping voltage of the first isolation transformer T is reversed.

[0084] like Figure 7 As shown: Switching mode III [t4~t5]: At time t4, the resonant capacitor, i.e., the second capacitor C r2 The current drops to zero, and its voltage reaches the peak of the resonant period. Afterward, the second capacitor C... r2 Energy begins to be released into the resonant network, resulting in C r2 The voltage at both ends gradually decreases.

[0085] like Figure 8 As shown: Switching Mode IV [t5~t6]: When the bus voltage VMN drops to zero at time t5, the anti-parallel diode of the second switch S2 turns on, and then a drive signal is applied to the second switch S2, achieving zero-voltage turn-on. During this stage, the bus voltage VMN is zero because the first switch S1 and the second switch S2 are grounded. Due to the energy storage capacitor (i.e., the third capacitor C) and the second inductor L... r The resulting series resonant frequency is much lower than the system's switching frequency fs, and the resonant current i r Approximately linear inverse growth.

[0086] like Figure 9 As shown: Switching mode V [t6~t7]: At time t6, the first switch S1 is turned off, and at this time the resonant capacitor, i.e., the first capacitor C, is... r1The circuit is connected and operation begins. The fourth switch S4 remains on, and the primary voltage of the first isolation transformer T is still clamped by the secondary side and maintained at -nV. dc / 2. By the second inductor L r With the first capacitor C r1 The resulting parallel resonant network causes the bus voltage VMN to rise resonantly, while the resonant current i r andi DS4 It then gradually decreases.

[0087] like Figure 10 As shown: Switching mode VI [t7~t8]: At time t7, i DS4 The voltage is reduced to zero, and the fourth switch S4 is turned off to achieve ZCS (zero-current turn-off). Since the primary voltage of the first isolation transformer T has not yet risen to the clamping voltage, the transformer exhibits magnetizing inductance L. m The characteristics of the resonant circuit. The resonant circuit consists of a resonant inductor, i.e., the second inductor L. r With L m After being connected in series, it participates in resonance, and the resonant current continues to converge, causing the primary-side voltage of the first isolation transformer T to rise further in resonance.

[0088] like Figure 11 As shown: Switching mode VII [t8~t9]: When the primary voltage of the first isolation transformer T rises to nV at time t8. dc At time t2, the first isolation transformer T is clamped by the secondary side voltage, and the body diode of the third switch S3 conducts. Subsequently, at time t9, the third switch S3 is turned on to ensure zero-voltage start-up. The resonant circuit returns to the state of the second inductor L. r With the first capacitor C r1 in parallel.

[0089] like Figure 12 As shown: Switching mode VIII [t9~t 10 ]: In t 10 At time , the first capacitor C r1 The branch current crosses zero, and the first capacitor C r1 The voltage rises to its highest point. Then the first capacitor C... r1 Upon entering the discharge mode, the bus voltage VMN begins to decrease.

[0090] like Figure 13 As shown: Switching mode IX [t] 10 ~t 11 ]: In t 11 The second switch S2 is always turned off, and the resonant capacitor, i.e., the second capacitor C, is... r2 Participating in resonance. At this time, the third switch S3 remains on, and the primary voltage of the first isolation transformer T continues to be clamped at nV. dc / 2. At this time, the resonant capacitance is the first capacitance C. r1With the second capacitor C r2 In a series structure, the resonant capacitance is halved. The resonant current continues to decay, and the second capacitor C... r2 The voltage across the terminals increases from zero, while the first capacitor C... r1 The voltage is discharged to zero, thus completing the commutation of the entire cycle and entering the next switching cycle.

[0091] by Figure 2 Circuit structure diagram, combined with Figures 14 to 21 The specific working principle of this invention will be described.

[0092] Depend on Figure 4 It can be seen that in inverter mode, there are 8 switching modes in one switching cycle: [t0~t2], [t2~t3], [t3~t4], [t4~t6], [t6~t7], [t7~t8], [t8~t9], [t9~t6], [t7~t8], [t8~t9], [t9~t6], [t7~t8], [t9~t9], [t8~t9], [t8~t9], [t9 ... 10 The following section provides a detailed analysis of the operation of each switching mode.

[0093] like Figure 14 As shown: Switching Mode I [t0~t2]: When the power transistor, i.e., the fourth switch S4, is turned off at time t0, the junction capacitance of the third switch S3 begins to release charge, causing its drain-source voltage V to... DS3 The voltage drops linearly to zero. Subsequently, the body diode of the third switch S3 is forward biased and turns on, clamping the primary voltage of the first isolation transformer T to nV. dc / 2. During this process, drive signals are provided to the first switch S1 and the second switch S2 successively. Since the diodes of both have already undergone commutation before turn-on, both can achieve zero-voltage turn-on (ZVS). During this stage, the energy storage capacitor, i.e., the third capacitor C, and the resonant inductor, i.e., the second inductor L... r The resonant frequency of the series circuit is much lower than the system operating frequency, and the primary loop current i s The voltage increases approximately linearly from negative to positive. At this time, the secondary voltage of the first isolation transformer T is V. dc / 2, secondary current i r2 It starts to decrease monotonically from a positive value.

[0094] like Figure 15 As shown: Switching mode II [t2~t3]: At time t2, the resonant current i r It decreases to zero, and then a phase reversal occurs, starting to show a reverse growth trend.

[0095] like Figure 16 As shown: Switching mode III [t3~t4]: Up to time t3, the secondary current i of the first isolation transformer T r2 The circuit crosses zero. At this point, the freewheeling process of the third switch S3 ends, and the secondary current i of the first isolation transformer T... r2It continues to increase within the reverse interval.

[0096] like Figure 17 As shown: Switching mode IV [t4~t6]: At time t4, the third switch S3 is turned off, causing the parasitic capacitance of the fourth switch S4 to begin discharging. When the voltage V across the fourth switch S4... DS4 After the voltage drops to zero, its body diode conducts, and the primary voltage of the first isolation transformer T is clamped to -nV. dc / 2. After the drive signal is applied at time t5, the fourth switch S4 achieves zero-voltage turn-on (ZVS). During this stage, the primary current i of the first isolation transformer T... s As the voltage decreases from the positive side, the secondary voltage becomes -V. dc / 2, secondary current i r2 It started to rise from the negative direction.

[0097] like Figure 18 As shown: Switching mode V [t6~t7]: At time t6, the power transistor, i.e., the first switching transistor S1, is turned off, and the resonant capacitor, i.e., the first capacitor C, is turned off. r1 Connect to the resonant circuit. Although the primary side of the first isolation transformer T is still clamped at -nV. dc / 2, but the second inductor L r With the first capacitor C r1 A parallel resonant network has been formed, causing the bus voltage VMN to rise in a resonant manner, and the primary current i of the first isolation transformer T... s Continuous decay.

[0098] like Figure 19 As shown: Switching mode VI [t7~t8]: At time t7, the primary current i of the first isolation transformer T s Reduced to zero, at this point the resonant capacitance, i.e., the first capacitance C, is... r1 The stored energy reaches its peak, and the terminal voltage rises to its highest point. Subsequently, the first capacitor C... r1 When reverse discharge occurs through the resonant cavity, its voltage begins to decrease resonantly. At this time, the resonant circuit is the second inductor L. r With the first capacitor C r1 in parallel.

[0099] like Figure 20 As shown: Switching mode VII [t8~t9]: Up to time t8, the secondary current i of the first isolation transformer T r2 When the current is reduced to zero, the freewheeling phase of the fourth switch S4 ends, and thereafter i r2 It has begun its upward climb.

[0100] like Figure 21 As shown: Switching mode VIII [t9~t 10 [: First capacitor C at time t9] r1The voltage resonance drops back to zero. The secondary current i of the first isolation transformer T. r2 Maintaining the growth trend, the body diode of the first switching transistor S1 automatically turns on due to the voltage returning to zero. Until t 10 When the fourth switch S4 is turned off, the converter completes one cycle of commutation and re-enters the mode I stage of the next cycle.

[0101] In summary, the highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter proposed in this invention achieves single-stage bidirectional energy transfer between the AC and DC sides by organically integrating the SEPIC network with the isolated resonant converter network. Utilizing the energy exchange process between the resonant inductor and resonant capacitor, the power switching devices can achieve full-range soft switching, thereby effectively reducing switching losses and improving system conversion efficiency. Simultaneously, the converter has a continuous input current, eliminating the need for a separate DC bus and additional power factor correction stage, reducing the number of power devices and energy transfer links, and increasing system power density. This converter also features good electrical isolation performance, low electromagnetic interference, high input current quality, strong bidirectional operation capability, and simple structure, making it suitable for applications such as multi-electric aircraft, power electronic converters, and aviation power systems.

[0102] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter, characterized in that, include: AC input port, used to connect AC power supply V ac ; The DC output port is used to connect a DC power supply V. dc ; The original side bridge arm module (100) has one end electrically connected to the AC input port and the other end electrically connected to one end of the resonant network module (200); The other end of the resonant network module (200) is electrically connected to one end of the transformer module (300); The other end of the transformer module (300) is electrically connected to the secondary rectifier module (400); The secondary-side rectifier module (400) is electrically connected to the DC output port; the primary-side bridge arm module (100) is a primary-side bidirectional switching bridge arm; the secondary-side rectifier module (400) is a secondary-side active bridge arm; the resonant network module (200) includes a resonant inductor unit and a resonant capacitor unit; the transformer module (300) is used to realize electrical isolation between the AC side and the DC side; the primary-side bridge arm module (100) and the secondary-side rectifier module (400) coordinate to control the conduction state to realize bidirectional energy transmission between the AC side and the DC side.

2. The highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 1, characterized in that, The primary side bridge arm module (100) includes: a first switch S1 and a second switch S2; The first switch S1 and the second switch S2 are connected in series on the same branch to form a primary-side bidirectional switch bridge arm; the source of the first switch S1 is connected to the drain of the second switch S2. One end of the second switching transistor S2 is connected to the AC power supply V. ac The negative terminal of the first switching transistor S1 is connected to the drain of the first inductor L, and the AC power supply V is connected to the negative terminal of the first switching transistor S1. ac The positive terminal is connected to the other end of the first inductor L; The connection point of the first switch S1 and the second switch S2 in series is the midpoint of the primary side bridge arm.

3. The highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 2, characterized in that, The resonant network module (200) includes: a second inductor L r First capacitor C r1 Second capacitor C r2 ; The second inductor L r As a resonant inductor, it is electrically connected to one end of the first inductor L; The first capacitor C r1 and the second capacitor C r2 As a resonant capacitor; the first capacitor C r1 The second capacitor C is connected in parallel between the drain and source of the first switching transistor S1; r2 It is connected in parallel between the drain and source of the second switch S2.

4. The highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 3, characterized in that, The transformer module (300) is the first isolation transformer T; The first isolation transformer T includes the primary winding n of the first isolation transformer. p and the secondary winding n of the first isolation transformer s ; The primary winding n of the first isolation transformer p One end is connected to the second inductor L r Electrically connected; The primary winding n of the first isolation transformer p With the second inductor L r The branch in question is connected in parallel to both ends of the branch containing the first switch S1 and the second switch S2.

5. The highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 4, characterized in that, The secondary-side rectifier module (400) includes: a third switch S3, a fourth switch S4, and a fourth capacitor C. dc1 and the fifth capacitor C dc2 ; The third switch S3 and the fourth switch S4 are connected in series to form one arm of the secondary active bridge arm. The fourth capacitor C dc1 With the fifth capacitor C dc2 They are connected in series to form another arm of the secondary active bridge arm; The fourth capacitor C dc1 and the fifth capacitor C dc2 As an output capacitor.

6. The highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 5, characterized in that, The third switch S3, the fourth switch S4, and the fourth capacitor C dc1 and the fifth capacitor C dc2 Forming a bridge structure; The positive and negative ends of the bridge structure are respectively connected to the DC power supply V. dc The positive and negative electrodes; The series connection point of the third switch S3 and the fourth switch S4 is the midpoint of one arm of the secondary active bridge arm. The fourth capacitor C dc1 With the fifth capacitor C dc2 The series connection point is the midpoint of the other arm of the secondary active bridge arm.

7. A highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 6, characterized in that, The secondary winding n of the first isolation transformer s One end is connected to the series connection point of the third switch S3 and the fourth switch S4, and the other end is connected to the fourth capacitor C. dc1 With the fifth capacitor C dc2 The series connection point.

8. A highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 7, characterized in that, The first inductor L and the second inductor L r A third capacitor C is connected between them; one end of the third capacitor C is connected to the second inductor L. r One end of the third capacitor C is electrically connected; the other end of the third capacitor C is connected to one end of the first inductor L and the first capacitor C, respectively. r1 One end of the capacitor is electrically connected; the third capacitor C serves as an energy storage capacitor. The first inductor L and the third capacitor C constitute a SEPIC power transfer network; the second inductor L r As a resonant inductor, it is related to the first capacitor C. r1 and the second capacitor C r2 Together with the resonant capacitors, they form a resonant converter network.

9. A highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 8, characterized in that, The first isolation transformer T also includes the first isolation transformer magnetizing inductor L. m The first isolation transformer leakage inductance L p The first isolation transformer magnetizing inductance L m The primary winding n of the first isolation transformer p in parallel; The first isolation transformer leakage inductance L p One end is connected to the second inductor L r One end is electrically connected; the leakage inductance L of the first isolation transformer p The other end is connected to the magnetizing inductance L of the first isolation transformer. m One end, the primary winding n of the first isolation transformer p One end is electrically connected.

10. A highly integrated single-stage bidirectional isolated resonant SEPIC AC-DC converter according to claim 9, characterized in that, In rectifier operation mode, the converter realizes the conversion of AC power to DC power, and the energy flows from the AC power supply Vac side to the DC power supply Vdc side. In inverter operation mode, the converter realizes the conversion of DC power to AC power, and the energy flows from the DC power supply Vdc side to the AC power supply Vac side.

Images