An isolated global soft-switching AC-DC-AC converter with primary and secondary side cooperative multiplexing and modulation method

Abstract

This invention discloses an isolated, fully soft-switching AC-DC-AC converter with primary and secondary side co-multiplexing and a modulation method. The converter includes a front-stage AC-DC converter, an intermediate-stage full-bridge LLC resonant converter, and a rear-stage DC-AC converter. This invention multiplexes the primary-side bridge arm of the full-bridge LLC resonant converter with the output bridge arm of the front-stage AC-DC converter, and the secondary-side bridge arm with the input bridge arm of the rear-stage DC-AC converter, forming an integrated AC-DC-AC converter structure, thereby reducing the number of components. Simultaneously, it employs PWM and phase-shift modulation strategies to control the inductor current of the four-transistor Buck-Boost circuit into a quadrilateral inductor current, thus achieving soft switching of all switching transistors. This topology is suitable for isolated AC conversion scenarios, enabling soft switching of switching devices, electrical isolation, wide-range voltage regulation, and effectively reducing the number of components. It also offers advantages such as high power density, high conversion efficiency, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter technology, specifically to an isolated global soft-switching AC-DC-AC converter and modulation method with primary and secondary side co-multiplexing. Background Technology

[0002] In daily life and industrial applications, electrical energy is typically obtained from the AC power grid. The load side often requires voltage transformation, electrical isolation, and AC power supply with adjustable output frequency or amplitude. Therefore, AC-AC converters are widely used in motor drives, power supply voltage regulators, uninterruptible power supply systems, and high-performance AC power supplies. In engineering, AC-AC conversion is usually achieved through a double-conversion structure of AC-DC cascaded DC-AC converters to obtain a stable DC bus and flexible, controllable AC output.

[0003] Existing cascaded AC-DC-AC converters typically consist of a front-stage rectifier PFC converter, an isolated DC-DC converter, and a rear-stage inverter, all connected in series. To meet electrical isolation and high efficiency requirements, the isolation stage often employs a full-bridge LLC resonant converter to achieve soft-switching operation. However, this multi-stage cascaded structure requires multiple independent bridge arms and power devices, resulting in multiple energy conversions and transfers. This leads to a large number of devices, complex control, large size, and low power density. Furthermore, when multiple stages of hard switching or some operating conditions lose their soft-switching characteristics, it can cause significant switching losses and electromagnetic interference, limiting system efficiency and high-frequency development.

[0004] Therefore, how to reuse and integrate the power units of the front and rear stages while ensuring the functions of input rectification and voltage regulation, electrical isolation and AC inverter output, reduce the number of power switching devices and energy conversion stages, and achieve soft switching operation over a wide operating range, thereby improving system efficiency and power density, has become a technical problem that urgently needs to be solved in the field of AC-AC converters.

[0005] Based on the aforementioned issues, there is an urgent need for an isolated soft-switching AC-DC-AC converter topology. This topology should, while fulfilling the functions of AC input rectification and voltage regulation, electrical isolation, and AC inverter output, reduce the number of power switching devices and simplify the power path structure through power arm multiplexing in both the front and rear stages. Furthermore, by combining modulation strategies and soft-switching technology, it should achieve high efficiency and high power density operation over a wide operating range. This converter should be able to achieve high power factor rectification and wide-range voltage regulation on the input side, while ensuring efficient energy transfer in the isolation stage and flexible controllability of the AC voltage and frequency on the output side. Simultaneously, bridge arm multiplexing can reduce the number of devices, further increasing the converter's power density. Using appropriate modulation strategies, all switches can achieve soft switching, improving efficiency. In addition, it should also consider the miniaturization and high-frequency characteristics of the isolated structure to meet the application requirements of high-power-density AC power supply systems.

[0006] The invention disclosed in CN120074256A is a bridge-arm multiplexed soft-switching AC-DC converter and its control circuit and method. This bridge-arm multiplexed soft-switching AC-DC converter multiplexes the primary-side switches of a full-bridge LLC resonant converter and the rear-arm switches of a bridgeless AC-DC converter, enabling power factor correction, soft switching of all switches, and a reduction in the number of components. This invention achieves full-range soft switching, electrical isolation, and wide-range voltage regulation, effectively reducing the number of components and achieving high power density, high conversion efficiency, and high reliability. However, this invention only achieves unidirectional energy conversion from AC input to DC output, and can only power DC loads. It cannot directly output AC voltage with adjustable amplitude and frequency, making it difficult to adapt to AC-AC conversion scenarios such as motor drives and uninterruptible power supply systems. To meet AC load requirements, additional independent inverters need to be cascaded, which not only adds 4-6 switching transistors and supporting drive circuits to the system, highlighting device redundancy, but also requires energy to undergo two independent AC-DC→DC-AC conversions, increasing conversion losses and electromagnetic interference. Furthermore, the original bridge arm multiplexing is limited to unidirectional multiplexing between the LLC primary side and the AC-DC rear bridge arm, failing to achieve full integration of the AC-DC-AC link. This results in a large system size and difficulty in further improving power density, failing to address the core requirements of integration, high efficiency, and high power density in the AC-AC conversion field. Summary of the Invention

[0007] The purpose of this invention is to provide an isolated, fully soft-switching AC-DC-AC converter with primary and secondary side co-multiplexing and a modulation method. The primary side arm of the full-bridge LLC resonant converter is multiplexed with the FSBB output arm of the preceding AC-DC converter, and the secondary side arm of the full-bridge LLC resonant converter is multiplexed with the FSBB input arm of the subsequent DC-AC converter, forming an integrated AC-DC-AC converter structure. Energy transfer and electrical isolation are achieved through an isolated LLC resonant network. This structure ensures the integrity of rectification, voltage regulation, isolation conversion, and inverter output functions while avoiding device redundancy and multiple energy conversions caused by series connection of multiple independent power units. Arm multiplexing reduces the number of power switches and increases power density. A suitable modulation strategy enables soft switching of all switches, reducing switching losses. This converter achieves integrated AC power supply with high power factor, high efficiency, electrical isolation, and high power density, and is suitable for isolated AC conversion scenarios.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention discloses an isolated global soft-switching AC-DC-AC converter with primary and secondary side co-multiplexing, the converter comprising a front-stage AC-DC converter, an intermediate-stage full-bridge LLC resonant converter and a rear-stage DC-AC converter;

[0010] The front-stage AC-DC converter uses two four-transistor Buck-Boost converters with differential inputs and parallel outputs to achieve AC input rectification and bus voltage regulation; the rear-stage DC-AC converter uses two four-transistor Buck-Boost converters with parallel inputs and differential outputs to achieve AC voltage output.

[0011] The primary arm of the intermediate-stage full-bridge LLC resonant converter is multiplexed with the output arm of the preceding AC-DC converter, and the secondary arm is multiplexed with the input arm of the subsequent DC-AC converter, forming an integrated AC-DC-AC converter structure. Energy transfer and electrical isolation between the input and output sides are achieved through an isolated LLC resonant network. PWM and phase-shift modulation strategies are employed, setting the duty cycle of all multiplexed arms to a fixed value. Pre-set cross-stage grouping synchronous on / off logic for the multiplexed arms enables the intermediate-stage LLC resonant converter to resonate. The primary-side multiplexed bridge arms and secondary-side multiplexed bridge arms of the converter are synchronously switched on and off in corresponding groups. Multiplexed bridge arms in different groups at the same level work in a complementary and cooperative manner. At the same time, by adjusting the duty cycle of the non-multiplexed bridge arms in the front-stage AC-DC converter and the rear-stage DC-AC converter, as well as the phase shift angle at the turn-on time of the non-multiplexed bridge arms and the corresponding multiplexed bridge arms, the inductor currents of the front-stage AC-DC converter and the rear-stage DC-AC converter are modulated into quadrilateral waveforms, providing current conditions for the soft switching of all switching transistors, thereby realizing full-domain soft switching of all switching transistors.

[0012] Furthermore, the front-end AC-DC converter includes: a first AC source v ac1 The first input capacitor C inA The second input capacitor C inB First DC bus capacitor C bus1 First inductor L a Second inductor L b The first switch Q of the non-multiplexed bridge arm in the front stage A1 The second switch Q of the non-multiplexed bridge arm in the front stage A2 The first switch transistor Q of the front-end multiplexing bridge arm A3 The second switch Q of the front-end multiplexing bridge arm A4 Its anti-parallel diode and junction capacitance, and the third switch Q of the non-multiplexed bridge arm in the front stage. B1 The fourth switch Q of the non-multiplexed bridge arm in the front stage B2 The third switch Q of the front-end multiplexing bridge arm B3 The fourth switch Q of the front-end multiplexing bridge arm B4Its anti-parallel diodes and junction capacitance;

[0013] Among them, the first exchange source v ac1 One end is connected to the first input capacitor C inA One end and the first switch Q of the previous non-multiplexed bridge arm A1 The drains are connected, and the first switching transistor Q of the non-multiplexed bridge arm in the preceding stage is connected. A1 The source and the second switch Q of the non-multiplexed bridge arm of the pre-amplifier A2 The drain and the first inductor L a One end is connected, the first inductor L a The other end is connected to the first switch Q of the preceding multiplexing bridge arm. A3 The source and the fourth switch Q A4 The drains are connected, and the first switching transistor Q of the front-end multiplexing bridge arm is connected. A3 The drain and the first DC bus capacitor C bus1 One end is connected to the first DC bus capacitor C. bus1 The other end is connected to the second switch Q of the preceding multiplexing bridge arm. A4 The source and the second switch Q of the non-multiplexed bridge arm of the pre-amplifier A2 The source and the first input capacitor C inA The other end is connected; the first AC source v ac1 The other end is connected to the second input capacitor C inB One end and the third switch Q of the previous non-multiplexed bridge arm B1 The drains are connected, and the third switch Q of the non-multiplexed bridge arm in the front stage is connected. B1 The source and the fourth switch Q of the non-multiplexed bridge arm of the pre-amplifier B2 The drain and the second inductor L b One end is connected, the second inductor L b The other end is connected to the third switch Q of the preceding multiplexing bridge arm. B3 The source and the fourth switch Q of the pre-amplifier multiplexed bridge arm B4 The drains are connected, and the third switch Q of the front-end multiplexing bridge arm is connected. B3 The drain and the first DC bus capacitor C bus1 One end is connected to the first DC bus capacitor C. bus1 The other end is connected to the fourth switch Q of the preceding multiplexing bridge arm. B4 The source and the fourth switch Q of the non-multiplexed bridge arm of the pre-amplifier B2 The source and second input capacitor C inB The other end is connected.

[0014] Furthermore, the subsequent DC-AC converter includes a second DC bus capacitor C. bus2 First output capacitor C outC Second output capacitor C outD Second source of communication v ac2Third inductor L c Fourth inductor L d The first switch Q of the subsequent multiplexing bridge arm C1 The second switch Q of the subsequent multiplexing bridge arm C2 The first switch transistor Q of the non-multiplexed bridge arm in the later stage C3 The second switch Q of the non-multiplexed bridge arm in the later stage C4 Its anti-parallel diode and junction capacitance, and the third switch Q of the subsequent multiplexed bridge arm. D1 The fourth switch Q of the subsequent multiplexing bridge arm D2 The third switch Q of the non-multiplexed bridge arm in the later stage D3 The fourth switch Q of the non-multiplexed bridge arm in the later stage D4 Its anti-parallel diodes and junction capacitance;

[0015] Among them, the second DC bus capacitor C bus2 One end is connected to the first switch Q of the subsequent multiplexing bridge arm. C1 The drains are connected, and the first switch Q of the subsequent multiplexing bridge arm is used. C1 The source and the second switch Q of the subsequent multiplexed bridge arm C2 The drain and the third inductor L c One end is connected, and the third inductor L c The other end is connected to the first switch Q of the subsequent non-multiplexed bridge arm. C3 The source and the second switch Q of the non-multiplexed bridge arm of the subsequent stage C4 The drains are connected, and the first switch Q of the subsequent non-multiplexed bridge arm is connected. C3 The drain of the first output capacitor C outC One end and the second AC source v ac2 One end is connected to the first output capacitor C. outC The other end is connected to the second switch Q of the subsequent non-multiplexed bridge arm. C4 The source is connected; the second DC bus capacitor C bus2 One end is connected to the third switch Q of the subsequent multiplexing bridge arm. D1 The drains are connected, and the third switch Q of the subsequent multiplexing bridge arm is used. D1 The source and the fourth switch Q of the subsequent multiplexed bridge arm D2 The drain and the fourth inductor L d One end is connected, the fourth inductor L d The other end is connected to the third switch Q of the subsequent non-multiplexed bridge arm. D3 The source and the fourth switch Q of the non-multiplexed bridge arm of the subsequent stage D4 The drains are connected, and the third switch Q of the subsequent non-multiplexed bridge arm is connected. D3 The drain of the second output capacitor C outD One end is connected to the second AC source v ac2 The other end is connected to the second output capacitor C. outDThe other end is connected to the fourth switch Q of the subsequent non-multiplexed bridge arm. D4 The source and the first output capacitor C outC The other end and the second DC bus capacitor C bus2 The other end and the second switch Q of the subsequent multiplexing bridge arm C2 The source and the fourth switch Q of the subsequent multiplexed bridge arm D2 The source poles are connected.

[0016] Furthermore, the intermediate-stage full-bridge LLC resonant converter includes a resonant inductor L. r Magnetizing inductance L m Resonant capacitor C r Transformer T r Its primary side bridge arm reuses the output bridge arm of the preceding AC-DC converter, and its secondary side bridge arm reuses the input bridge arm of the following DC-AC converter; the output bridge arm of the preceding AC-DC converter includes the first switch Q of the multiplexed bridge arm. A3 The second switch Q of the front-end multiplexing bridge arm A4 The third switch Q of the front-end multiplexing bridge arm B3 and the fourth switch Q of the multiplexed bridge arm B4 The input bridge arm of the subsequent DC-AC converter includes the first switch Q of the subsequent multiplexed bridge arm. C1 The second switch Q of the subsequent multiplexing bridge arm C2 The third switch Q of the subsequent multiplexing bridge arm D1 and the fourth switch Q of the subsequent multiplexing bridge arm D2 ;

[0017] Among them, the first switch Q of the front-stage multiplexing bridge arm A3 The source of the multiplexed bridge arm of the pre-amplifier is connected to the second switch Q. A4 Drain and resonant capacitor C r One end is connected to the resonant capacitor C. r The other end is connected to the resonant inductor L r One end is connected to the resonant inductor L. r The other end is connected to the magnetizing inductor L m One end and transformer T r One end of the primary side is connected, transformer T r The other end of the primary side is connected to the magnetizing inductor L m The other end and the third switch Q of the preceding multiplex bridge arm B3 The source, the fourth switch Q of the pre-amplifier multiplexed bridge arm B4 The drains are connected; transformer T r One end of the secondary side is connected to the first switch Q of the subsequent multiplexing bridge arm. C1 The source, the second switch Q of the post-stage multiplexing bridge arm C2 The drains are connected, and the transformer T rThe other end of the secondary side is connected to the third switch Q of the subsequent multiplexing bridge arm. D1 The source, the fourth switch Q of the multiplexed bridge arm D2 The drains are connected.

[0018] Furthermore, the duty cycle of all reused bridge arms is fixed at 50%.

[0019] Furthermore, the first switch Q of the front-end multiplexing bridge arm A3 The fourth switch Q of the front-end multiplexing bridge arm B4 The first switch transistor Q of the subsequent multiplexing bridge arm C1 and the third switch Q of the subsequent multiplexing bridge arm D2 Simultaneously switching on and off, the second switch Q of the preceding multiplex bridge arm... A4 and the third switch Q of the pre-stage multiplexed bridge arm B3 The second switch Q of the subsequent multiplexing bridge arm C2 and the third switch Q of the subsequent multiplexing bridge arm D1 Simultaneous on / off;

[0020] In the front-end AC-DC converter, by adjusting the first switch Q of the front-end non-multiplexed bridge arm... A1 Duty cycle D ya and the third switch Q of the non-multiplexed bridge arm in the preceding stage B1 Duty cycle D yb Adjust the first DC bus capacitor C connected between the drain of the multiplexed bridge arm and ground. bus1 The voltage and respectively connected to the first AC source v ac1 The first input capacitor C between the two terminals and ground inA Second input capacitor C inB The voltage is adjusted by regulating the first switch Q of the non-multiplexed bridge arm in the preceding stage. A1 With the first switch Q of the bridge arm of the pre-stage multiplexing bridge A3 Phase shift angle D at the activation time θa The third switch Q of the non-multiplexed bridge arm in the front stage B1 The third switch Q of the bridge arm of the multiplexed bridge is used in conjunction with the preceding stage. B3 Phase shift angle D at the activation time θb This causes the first inductor L in the preceding AC-DC converter, which is connected in series between the non-multiplexed bridge arm and the multiplexed bridge arm, to... a Second inductor L b The inductor current is modulated into a quadrilateral inductor current;

[0021] In the subsequent DC-AC converter, by adjusting the first switch Q of the subsequent non-multiplexed bridge arm... C3 Duty cycle D yc and the third switch Q of the subsequent non-multiplexed bridge arm D3 Duty cycle D yd Adjust the connections respectively to the second AC source vac2 The first output capacitor C between the two terminals and ground outC Second output capacitor C outD The voltage and the second AC source v ac2 The voltage is adjusted by regulating the first switch Q of the subsequent multiplexed bridge arm. C1 With the second switch Q of the subsequent multiplexed bridge arm C2 Phase shift angle D at the activation time θc The third switch Q of the subsequent multiplexing bridge arm D1 With the third switch Q of the subsequent non-multiplexed bridge arm D3 Phase shift angle D at the activation time θd This causes the third inductor L, which is connected in series between the multiplexed and non-multiplexed bridge arms in the subsequent DC-AC converter, to... c Fourth inductor L d The inductor current is modulated into a quadrilateral inductor current;

[0022] The quadrilateral inductor current is maintained as a non-zero current through the freewheeling phase, providing energy for the charging and discharging of the junction capacitance of the switching transistors, thereby achieving zero-voltage turn-on of all switching transistors.

[0023] Secondly, this invention also discloses a modulation method for an isolated, fully soft-switching AC-DC-AC converter with primary and secondary sides co-multiplexing. The modulation method employs a PWM and phase-shift fusion modulation strategy and includes the following steps:

[0024] S1, set the duty cycle of all multiplexed bridge arms to a fixed value, preset cross-level group synchronous on / off logic, let the first switch of the previous multiplexed bridge arm, the fourth switch of the previous multiplexed bridge arm, the first switch of the subsequent multiplexed bridge arm and the third switch of the subsequent multiplexed bridge arm be the first group, let the second switch of the previous multiplexed bridge arm, the third switch of the previous multiplexed bridge arm, the second switch of the subsequent multiplexed bridge arm and the third switch of the subsequent multiplexed bridge arm be the second group, the switches of each group are synchronously turned on and off, and the two groups are in a complementary and cooperative working state;

[0025] S2, for the front-end AC-DC converter, adjust the duty cycle D of the first switch transistor of the front-end non-multiplexed bridge arm. ya Duty cycle D of the third switch in the non-multiplexed bridge arm of the preceding stage yb Stabilize the first DC bus capacitor C bus1 First input capacitor C inA and the second input capacitor C inB The voltage; simultaneously adjust the phase shift angle D at the turn-on time of the first switch of the non-multiplexed bridge arm and the first switch of the multiplexed bridge arm. θa The phase shift angle D at the turn-on time of the third switch of the non-multiplexed bridge arm and the third switch of the multiplexed bridge arm. θb , the first inductor L a Second inductor Lb The current is modulated into a quadrilateral waveform;

[0026] S3, for the subsequent DC-AC converter, adjust the duty cycle D of the first switch transistor in the subsequent non-multiplexed bridge arm. yc The duty cycle D of the third switch in the subsequent non-multiplexed bridge arm yd Stabilize the first output capacitor C outC Second output capacitor C outD and the second source of exchange v ac2 The voltage; simultaneously adjust the phase shift angle D at the turn-on time of the first switch of the subsequent multiplexed bridge arm and the first switch of the subsequent non-multiplexed bridge arm. θc The phase shift angle D at the turn-on time of the third switch of the subsequent multiplexed bridge arm and the third switch of the subsequent non-multiplexed bridge arm. θd The currents of the third and fourth inductors are modulated into quadrilateral waveforms;

[0027] S4. The quadrilateral inductor current in steps S2 and S3 provides soft-switching current conditions for all switching transistors. Combined with the resonant characteristics of the intermediate LLC resonant network, global soft-switching of all switching transistors is achieved.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] First, the primary-secondary side co-multiplexed isolated full-domain soft-switching AC-DC-AC converter of the present invention integrates and innovates the circuit topology based on the front-stage AC-DC converter, the intermediate-stage full-bridge LLC resonant converter, and the rear-stage DC-AC converter. It multiplexes the primary-side bridge arm of the full-bridge LLC resonant converter with the FSBB output bridge arm of the front-stage AC-DC converter, and multiplexes the secondary-side bridge arm of the full-bridge LLC resonant converter with the FSBB input bridge arm of the rear-stage DC-AC converter, thus forming an integrated AC-DC-AC converter structure. Compared with traditional multi-stage cascaded AC-DC-AC converters, the present invention can achieve soft switching of all switching transistors while ensuring the integrity of rectification, isolation, and inversion functions. Furthermore, by multiplexing the bridge arms, it effectively reduces the number of components, achieving higher power density and efficiency.

[0030] Secondly, the isolated full-range soft-switching AC-DC-AC converter of the present invention, which utilizes primary and secondary side co-multiplexing, enables each power switch to operate in a soft-switching manner over a wide input voltage and load range by introducing an LLC resonant network and a reasonable modulation control strategy. This significantly reduces switching losses and improves system operating efficiency and reliability. At the same time, the high-frequency isolation characteristics of the LLC converter are used to achieve electrical isolation between the input and output sides, effectively protecting downstream electrical equipment and supporting wide-range voltage regulation and AC output control.

[0031] Third, the isolated global soft-switching AC-DC-AC converter with primary and secondary side co-multiplexing of the present invention has the advantages of fewer devices, high power density, high conversion efficiency, wide input and output voltage range and strong system reliability, and is suitable for high-performance isolated AC-AC energy conversion scenarios. Attached Figure Description

[0032] Figure 1 The circuit structure of the isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing is described in this invention.

[0033] Figure 2 The waveform diagram of the isolated global soft-switching AC-DC-AC converter at the power frequency cycle.

[0034] Figure 3 This is a waveform diagram of the isolated global soft-switching AC-DC-AC converter at the switching frequency. Detailed Implementation

[0035] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0036] This invention discloses an isolated global soft-switching AC-DC-AC converter with primary and secondary side co-multiplexing, the converter comprising a front-stage AC-DC converter, an intermediate-stage full-bridge LLC resonant converter, and a rear-stage DC-AC converter;

[0037] The front-stage AC-DC converter uses two four-transistor Buck-Boost converters with differential inputs and parallel outputs to achieve AC input rectification and bus voltage regulation; the rear-stage DC-AC converter uses two four-transistor Buck-Boost converters with parallel inputs and differential outputs to achieve AC voltage output.

[0038] The primary arm of the intermediate-stage full-bridge LLC resonant converter is co-multiplexed with the output arm of the preceding AC-DC converter (the same arm simultaneously performs the output regulation of the preceding AC-DC converter and the resonant drive function of the LLC primary side), and the secondary arm is co-multiplexed with the input arm of the subsequent DC-AC converter (i.e., the same arm simultaneously performs the resonant rectification of the LLC secondary side and the input regulation function of the subsequent DC-AC converter), forming an integrated AC-DC-AC converter structure. Energy transfer and electrical isolation are achieved between the input and output sides through an isolated LLC resonant network, and PWM and phase-shift modulation strategies are employed to set the occupancy of all multiplexed arms. With a fixed duty cycle, the primary-side multiplexed bridge arm and the secondary-side multiplexed bridge arm of the intermediate-stage LLC resonant converter are synchronously switched on and off by pre-set cross-stage grouping synchronous switching logic. The multiplexed bridge arms of different groups in the same level are in a complementary and cooperative working state. At the same time, by adjusting the duty cycle of the non-multiplexed bridge arms in the front-stage AC-DC converter and the rear-stage DC-AC converter, as well as the phase shift angle of the non-multiplexed bridge arm and the corresponding multiplexed bridge arm at the turn-on time, the inductor current of the front-stage AC-DC converter and the rear-stage DC-AC converter are modulated into quadrilateral waveforms, providing current conditions for the soft switching of all switching transistors, thereby realizing full-domain soft switching of all switching transistors.

[0039] The circuit structure of the isolated global soft-switching AC-DC-AC converter of the present invention is as follows: Figure 1 As shown, its topology includes: a front-stage AC-DC converter, a rear-stage DC-AC converter, and an intermediate-stage full-bridge LLC resonant converter.

[0040] The front-end AC-DC converter includes an AC source v ac1 Input capacitor C inA C inB DC bus capacitor C bus1 Inductor L a L b Switch Q A1 Q A2 Q A3 Q A4 and its anti-parallel diode D A1 D A2 D A3 D A4 junction capacitance C A1 C A2 C A3 C A4 Switch Q B1 Q B2 Q B3 Q B4 and its anti-parallel diode D B1 D B2 D B3 DB4 junction capacitance C B1 C B2 C B3 C B4 The subsequent DC-AC converter includes the DC bus capacitor C. bus2 Output capacitor C outC C outD Exchange source v ac2 Inductor L c L d Switch Q C1 Q C2 Q C3 Q C4 and its anti-parallel diode D C1 D C2 D C3 D C4 junction capacitance C C1 C C2 C C3 C c4 Switch Q D1 Q D2 Q D3 Q D4 and its anti-parallel diode D D1 D D2 D D3 D D4 junction capacitance C D1 C D2 C D3 C D4 The intermediate-stage full-bridge LLC resonant converter includes a resonant inductor L. r Magnetizing inductance L m Resonant capacitor C r Transformer T r Its primary side bridge arm is multiplexed from the output bridge arm Q of the AC-DC converter. A3 and Q A4 Q B3 and Q B4 Its secondary bridge arm multiplexes the input bridge arm Q of the DC-AC converter. C1 and Q C2 Q D1 and Q D2 .

[0041] Define the switching transistor Q A1 and Q A2 Q B1 and Q B2 Q C3 and Q C4 Q D3 and Q D4 For non-reusable bridge arms, Q A3 and QA4 Q B3 and Q B4 Q C1 and Q C2 Q D1 and Q D2 For reusing bridge arms. Reused bridge arm Q A3 Q A4 Q B3 Q B4 Q C1 Q C2 Q D1 Q D2 The duty cycle is fixed at 50%, and Q A3 Q B4 Q C1 and Q D2 Simultaneous on / off, Q A4 and Q B3 Q C2 and Q D1 Simultaneous on / off switching.

[0042] like Figure 1 As shown, in the front-end AC-DC converter, v ac1 One end and C inA one end and Q A1 The drains are connected, Q A1 source and Q A2 The drain and L a One end is connected, L a The other end and Q A3 source and Q A4 The drains are connected, Q A3 The drain and C bus1 One end is connected, C bus1 The other end and Q A4 source and Q A2 The source and C inA The other end is connected; v ac1 The other end and C inB one end and Q B1 The drains are connected, Q B1 source and Q B2 The drain and L b One end is connected, L b The other end and Q B3 source and Q B4 The drains are connected, Q B3 The drain and C bus1 One end is connected, C bus1 The other end and Q B4 source and Q B2 The source and C inB The other end is connected.

[0043] In the intermediate-stage full-bridge LLC resonant converter, the bridge arm Q is reused. A3 The source and Q A4 The drain and C r One end is connected, C r The other end and L r One end is connected, L r The other end and L m one end and T r Connect one end of the original edge, T r The other end of the original side is connected to L m The other end and the reused bridge arm Q B3 source and Q B4 The drains are connected; T r One end of the secondary side is connected to the multiplex bridge arm Q C1 source and Q C2 The drains are connected, Q C1 Drain and Q D1 The drain and C bus2 One end is connected, T r The other end of the secondary side connects to the multiplex bridge arm Q. D1 source and Q D2 The drains are connected, Q D2 source and Q D2 The source and C bus2 The other end is connected.

[0044] In the subsequent DC-AC converter, C bus2 One end and Q C1 The drains are connected, Q C1 source and Q C2 The drain and L c One end is connected, L c The other end and Q C3 source and Q C4 The drains are connected, Q C3 The drain and C outC one end and v ac2 One end is connected, C outC The other end and Q C4 The source is connected; C bus2 One end and Q D1 The drains are connected, Q D1 source and Q D2 The drain and L d One end is connected, L d The other end and Q D3 source and Q D4 The drains are connected, Q D3 The drain and C outD One end is connected to vac2 The other end is connected, C outD The other end and Q D4 source and Q C4 The source and C outC The other end and C bus2 The other end and Q C2 source and Q D2 The source poles are connected.

[0045] The modulation strategy of the isolated soft-switching AC-DC-AC converter of the present invention is PWM + phase-shift modulation.

[0046] For the front-end AC-DC converter, when the AC source v ac1 When the voltage is greater than 0, the input capacitor C inA The corresponding four-transistor Buck-Boost converter is in the forward operating state, Q A1 It should precede Q. A3 Off, Q A3 It should precede Q. A2 Off, Q A2 It should precede Q. A4 Off, Q A4 It should precede Q. A1 Turn off, switching transistor Q A1 Q A2 Complementary conduction, switching transistor Q A3 Q A4 The duty cycle is fixed at 50%; the input capacitor C inB The corresponding four-transistor Buck-Boost converter is in reverse operation, Q B3 It should precede Q. B1 Off, Q B1 It should precede Q. B4 Off, Q B4 It should precede Q. B2 Off, Q B2 It should precede Q. B3 Turn off; switching transistor Q B1 Q B2 Complementary conduction, switching transistor Q B3 Q B4 The duty cycle is fixed at 50%; by adjusting the switching transistor Q A1 Duty cycle D ya and switching transistor Q B1 Duty cycle D yb This adjusts the bus capacitance C. bus1 voltage and input capacitance C inA C inB The voltage is adjusted by regulating the switching transistor Q. A1 With the switching transistor Q A3 Phase shift angle D at the activation time θaSwitching transistor Q B1 With the switching transistor Q B3 Phase shift angle D at the activation time θb This causes the inductor L a L b The inductor current is modulated into a quadrilateral inductor current, thereby achieving soft switching for all switching transistors. When the AC source v ac1 When the voltage is less than 0, the input capacitor C inA The corresponding four-transistor Buck-Boost converter is in reverse operation, and the input capacitor C inB The corresponding four-tube Buck-Boost converter operates in the forward direction, with a similar modulation strategy.

[0047] For the subsequent DC-AC converter, when the AC source v ac2 When the voltage is greater than 0, the output capacitor C outC The corresponding four-transistor Buck-Boost converter is in the forward operating state, Q C1 It should precede Q. C3 Off, Q C3 It should precede Q. C2 Off, Q C2 It should precede Q. C4 Off, Q C4 It should precede Q. C1 Turn off, switching transistor Q C3 Q C4 Complementary conduction, switching transistor Q C1 Q C2 The duty cycle is fixed at 50%; the output capacitor C outD The corresponding four-transistor Buck-Boost converter is in reverse operation, Q D3 It should precede Q. D1 Off, Q D1 It should precede Q. D4 Off, Q D4 It should precede Q. D2 Off, Q D2 It should precede Q. D3 Turn off; switching transistor Q D3 Q D4 Complementary conduction, switching transistor Q D1 Q D2 The duty cycle is fixed at 50%; by adjusting the switching transistor Q C3 Duty cycle D yc and switching transistor Q D3 Duty cycle D yd This adjusts the output capacitor C. outC C outD voltage and AC source v ac2 The voltage is adjusted by regulating the switching transistor Q. C1 With the switching transistor QC2 Phase shift angle D at the activation time θc Switching transistor Q D1 With the switching transistor Q D3 Phase shift angle D at the activation time θd This causes the inductor L c L d The inductor current is modulated into a quadrilateral inductor current, thereby achieving soft switching for all switching transistors. When the AC source v ac2 When the voltage is less than 0, the output capacitor C outC The corresponding four-transistor Buck-Boost converter is in reverse operation, and the output capacitor C outD The corresponding four-tube Buck-Boost converter operates in the forward direction, with a similar modulation strategy.

[0048] For the intermediate-stage full-bridge LLC resonant converter, the primary-side bridge arm switch Q... A3 Q B4 Simultaneously on and off, the switching transistor Q... A4 Q B3 Simultaneously on and off, the switching transistor Q... A3 Q A4 The duty cycle is fixed at 50% with alternating switching, and the switching transistor Q... B3 Q B4 The duty cycle is fixed at 50% with alternating switching; the secondary bridge arm switch Q... C1 Q D2 Simultaneously on and off, the switching transistor Q... C2 Q D1 Simultaneously on and off, the switching transistor Q... C1 Q C2 The duty cycle is fixed at 50% with alternating switching, and the switching transistor Q... D1 Q D2 The duty cycle is fixed at 50% with alternating switching; among the four bridge arms on the primary and secondary sides, the switching transistor Q... A3 Q B4 Q C1 and Q D2 Simultaneous on / off, Q A4 and Q B3 Q C2 and Q D1 Simultaneous on / off switching. This is the overall modulation timing.

[0049] The isolated soft-switching AC-DC-AC converter of the present invention includes 22 switching modes. Figure 2 This is a waveform diagram of the isolated, fully soft-switching AC-DC-AC converter at the power frequency cycle T, visually demonstrating the input AC voltage / current (V) of the front-end stage. ac1 / i ac1 ), two input voltages of the front stage inA / v inBIntermediate DC bus voltage (V) bus1 / v bus2 ), the two output voltages of the later stage V outC / v outD The output AC voltage / current of the later stage (V) ac2 / i ac2 By observing the waveform coordination relationship, it can be seen that the input current and input voltage are approximately in phase, confirming the high power factor correction effect of the preceding AC-DC converter; the output AC voltage (V ac2 The waveform is sinusoidal, reflecting the inverter regulation capability of the subsequent DC-AC converter, and the bus voltage (V) bus1 / v bus2 It remains stable within the power frequency cycle with no obvious ripple, demonstrating the voltage stabilizing effect of the capacitor and the coordinated control accuracy of the front / back stage converter. Figure 3 This is a waveform diagram of the fully isolated soft-switching AC-DC-AC converter at the switching frequency, which intuitively shows the key timing nodes (t1, t2, t3, ..., t) in each switching cycle. 22 ...) drive signals for each switching transistor, inductor current (i La / i Lb / i Lc / i Ld ), voltage across the resonant capacitor (V Cr ), the current across the resonant inductor / magnetizing inductor (i Lr / i Lm The high-frequency dynamic waveform of the magnetizing inductor, between t4 and t6, shows the current i of the magnetizing inductor. Lm Amplitude I m With the current i of the resonant inductor Lr The inductor current exhibits a quadrilateral waveform, demonstrating the effectiveness of the phase-shift modulation strategy. At the on / off moments of the switching transistor drive signal, the corresponding inductor current is non-zero and the junction capacitance voltage transitions smoothly, intuitively reflecting the zero-voltage turn-on (ZVS) characteristics of all switching transistors. The LLC resonant network voltage / current exhibits a sinusoidal resonant waveform, reflecting the efficient energy transfer of the isolation stage.

[0050] The topology of this invention is applicable to isolated AC power supply and energy conversion scenarios. It can realize soft switching, electrical isolation, and wide-range voltage regulation of switching devices, and effectively reduce the number of devices. It has the advantages of high power density, high conversion efficiency and high reliability.

[0051] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0052] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A primary-secondary side co-multiplexed isolated global soft-switching AC-DC-AC converter, characterized in that, The converter includes a front-stage AC-DC converter, an intermediate-stage full-bridge LLC resonant converter, and a rear-stage DC-AC converter. The front-stage AC-DC converter uses two four-transistor Buck-Boost converters with differential inputs and parallel outputs to achieve AC input rectification and bus voltage regulation; the rear-stage DC-AC converter uses two four-transistor Buck-Boost converters with parallel inputs and differential outputs to achieve AC voltage output. The primary arm of the intermediate-stage full-bridge LLC resonant converter is multiplexed with the output arm of the preceding AC-DC converter, and the secondary arm is multiplexed with the input arm of the subsequent DC-AC converter, forming an integrated AC-DC-AC converter structure. Energy transfer and electrical isolation between the input and output sides are achieved through an isolated LLC resonant network. PWM and phase-shift modulation strategies are employed, setting the duty cycle of all multiplexed arms to a fixed value. Pre-set cross-stage grouping synchronous on / off logic for the multiplexed arms enables the intermediate-stage LLC resonant converter to resonate. The primary-side multiplexed bridge arms and secondary-side multiplexed bridge arms of the converter are synchronously switched on and off in corresponding groups. Multiplexed bridge arms in different groups at the same level work in a complementary and cooperative manner. At the same time, by adjusting the duty cycle of the non-multiplexed bridge arms in the front-stage AC-DC converter and the rear-stage DC-AC converter, as well as the phase shift angle at the turn-on time of the non-multiplexed bridge arms and the corresponding multiplexed bridge arms, the inductor currents of the front-stage AC-DC converter and the rear-stage DC-AC converter are modulated into quadrilateral waveforms, providing current conditions for the soft switching of all switching transistors, thereby realizing full-domain soft switching of all switching transistors.

2. The isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing according to claim 1, characterized in that, The preceding AC-DC converter includes: a first AC source v ac1 The first input capacitor C inA The second input capacitor C inB First DC bus capacitor C bus1 First inductor L a Second inductor L b The first switch Q of the non-multiplexed bridge arm in the front stage A1 The second switch Q of the non-multiplexed bridge arm in the front stage A2 The first switch transistor Q of the front-end multiplexing bridge arm A3 The second switch Q of the front-end multiplexing bridge arm A4 Its anti-parallel diode and junction capacitance, and the third switch Q of the front-end non-multiplexed bridge arm. B1 The fourth switch Q of the non-multiplexed bridge arm in the front stage B2 The third switch Q of the front-end multiplexing bridge arm B3 The fourth switch Q of the front-end multiplexing bridge arm B4 Its anti-parallel diode and junction capacitance; Among them, the first exchange source v ac1 One end is connected to the first input capacitor C inA One end and the first switch Q of the non-multiplexed bridge arm of the preceding stage A1 The drains are connected, and the first switching transistor Q of the non-multiplexed bridge arm in the preceding stage is connected. A1 The source and the second switch Q of the non-multiplexed bridge arm of the pre-amplifier A2 The drain and the first inductor L a One end is connected, the first inductor L a The other end is connected to the first switch Q of the preceding multiplexing bridge arm. A3 The source and the fourth switch Q A4 The drains are connected, and the first switching transistor Q of the front-end multiplexing bridge arm is connected. A3 The drain and the first DC bus capacitor C bus1 One end is connected to the first DC bus capacitor C. bus1 The other end is connected to the second switch Q of the preceding multiplexing bridge arm. A4 The source and the second switch Q of the non-multiplexed bridge arm of the pre-amplifier A2 The source and the first input capacitor C inA The other end is connected; the first AC source v ac1 The other end is connected to the second input capacitor C inB One end and the third switch Q of the previous non-multiplexed bridge arm B1 The drains are connected, and the third switch Q of the non-multiplexed bridge arm in the front stage is connected. B1 The source and the fourth switch Q of the non-multiplexed bridge arm of the pre-amplifier B2 The drain and the second inductor L b One end is connected, the second inductor L b The other end is connected to the third switch Q of the preceding multiplexing bridge arm. B3 The source and the fourth switch Q of the pre-amplifier multiplexed bridge arm B4 The drains are connected, and the third switch Q of the front-end multiplexing bridge arm is connected. B3 The drain and the first DC bus capacitor C bus1 One end is connected to the first DC bus capacitor C. bus1 The other end is connected to the fourth switch Q of the preceding multiplexing bridge arm. B4 The source and the fourth switch Q of the non-multiplexed bridge arm of the pre-amplifier B2 The source and second input capacitor C inB The other end is connected.

3. The isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing according to claim 1, characterized in that, The subsequent DC-AC converter includes a second DC bus capacitor C. bus2 First output capacitor C outC Second output capacitor C outD Second source of communication v ac2 Third inductor L c Fourth inductor L d The first switch Q of the subsequent multiplexing bridge arm C1 The second switch Q of the subsequent multiplexing bridge arm C2 The first switch transistor Q of the non-multiplexed bridge arm in the later stage C3 The second switch Q of the non-multiplexed bridge arm in the later stage C4 Its anti-parallel diode and junction capacitance, and the third switch Q of the subsequent multiplexed bridge arm. D1 The fourth switch Q of the subsequent multiplexing bridge arm D2 The third switch Q of the non-multiplexed bridge arm in the later stage D3 The fourth switch Q of the non-multiplexed bridge arm in the later stage D4 Its anti-parallel diode and junction capacitance; Among them, the second DC bus capacitor C bus2 One end is connected to the first switch Q of the subsequent multiplexing bridge arm. C1 The drains are connected, and the first switch Q of the subsequent multiplexing bridge arm is used. C1 The source and the second switch Q of the subsequent multiplexed bridge arm C2 The drain and the third inductor L c One end is connected, and the third inductor L c The other end is connected to the first switch Q of the subsequent non-multiplexed bridge arm. C3 The source and the second switch Q of the non-multiplexed bridge arm of the subsequent stage C4 The drains are connected, and the first switch Q of the subsequent non-multiplexed bridge arm is connected. C3 The drain of the first output capacitor C outC One end and the second AC source v ac2 One end is connected to the first output capacitor C. outC The other end is connected to the second switch Q of the subsequent non-multiplexed bridge arm. C4 The source is connected; the second DC bus capacitor C bus2 One end is connected to the third switch Q of the subsequent multiplexing bridge arm. D1 The drains are connected, and the third switch Q of the subsequent multiplexing bridge arm is used. D1 The source and the fourth switch Q of the subsequent multiplexed bridge arm D2 The drain and the fourth inductor L d One end is connected, the fourth inductor L d The other end is connected to the third switch Q of the subsequent non-multiplexed bridge arm. D3 The source and the fourth switch Q of the non-multiplexed bridge arm of the subsequent stage D4 The drains are connected, and the third switch Q of the subsequent non-multiplexed bridge arm is connected. D3 The drain of the second output capacitor C outD One end is connected to the second AC source v ac2 The other end is connected to the second output capacitor C. outD The other end is connected to the fourth switch Q of the subsequent non-multiplexed bridge arm. D4 The source and the first output capacitor C outC The other end and the second DC bus capacitor C bus2 The other end and the second switch Q of the subsequent multiplexing bridge arm C2 The source and the fourth switch Q of the subsequent multiplexed bridge arm D2 The source poles are connected.

4. The isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing according to claim 1, characterized in that, The intermediate-stage full-bridge LLC resonant converter includes a resonant inductor L r Magnetizing inductance L m Resonant capacitor C r Transformer T r Its primary side bridge arm reuses the output bridge arm of the preceding AC-DC converter, and its secondary side bridge arm reuses the input bridge arm of the following DC-AC converter; the output bridge arm of the preceding AC-DC converter includes the first switch Q of the multiplexed bridge arm. A3 The second switch Q of the front-end multiplexing bridge arm A4 The third switch Q of the front-end multiplexing bridge arm B3 and the fourth switch Q of the pre-stage multiplexed bridge arm B4 The input bridge arm of the subsequent DC-AC converter includes the first switch Q of the subsequent multiplexed bridge arm. C1 The second switch Q of the subsequent multiplexing bridge arm C2 The third switch Q of the subsequent multiplexing bridge arm D1 and the fourth switch Q of the subsequent multiplexing bridge arm D2 ; Among them, the first switch Q of the front-stage multiplexing bridge arm A3 The source of the multiplexed bridge arm of the pre-amplifier is connected to the second switch Q. A4 Drain and resonant capacitor C r One end is connected to the resonant capacitor C. r The other end is connected to the resonant inductor L r One end is connected to the resonant inductor L. r The other end is connected to the magnetizing inductor L m One end and transformer T r One end of the primary side is connected, transformer T r The other end of the primary side is connected to the magnetizing inductor L m The other end and the third switch Q of the preceding multiplex bridge arm B3 The source, the fourth switch Q of the pre-amplifier multiplexed bridge arm B4 The drains are connected; transformer T r One end of the secondary side is connected to the first switch Q of the subsequent multiplexing bridge arm. C1 The source, the second switch Q of the post-stage multiplexing bridge arm C2 The drains are connected, and the transformer T r The other end of the secondary side is connected to the third switch Q of the subsequent multiplexing bridge arm. D1 The source, the fourth switch Q of the multiplexed bridge arm D2 The drains are connected.

5. The isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing according to claim 1, characterized in that, The duty cycle of all reused bridge arms is fixed at 50%.

6. The isolated global soft-switching AC-DC-AC converter with primary and secondary side collaborative multiplexing according to claim 4, characterized in that, The first switching transistor Q of the front-stage multiplexing bridge arm A3 The fourth switch Q of the front-end multiplexing bridge arm B4 The first switch transistor Q of the subsequent multiplexing bridge arm C1 and the third switch Q of the subsequent multiplexing bridge arm D2 Simultaneously switching on and off, the second switch Q of the preceding multiplex bridge arm... A4 and the third switch Q of the multiplexed bridge arm B3 The second switch Q of the subsequent multiplexing bridge arm C2 and the third switch Q of the subsequent multiplexing bridge arm D1 Simultaneous on / off; In the front-end AC-DC converter, by adjusting the first switch Q of the front-end non-multiplexed bridge arm... A1 Duty cycle D ya and the third switch Q of the non-multiplexed bridge arm in the preceding stage B1 Duty cycle D yb Adjust the first DC bus capacitor C connected between the drain of the multiplexed bridge arm and ground. bus1 The voltage and respectively connected to the first AC source v ac1 The first input capacitor C between the two terminals and ground inA Second input capacitor C inB The voltage is adjusted by regulating the first switch Q of the non-multiplexed bridge arm in the preceding stage. A1 With the first switch Q of the bridge arm of the pre-stage multiplexing bridge A3 Phase shift angle D at the activation time θa The third switch Q of the non-multiplexed bridge arm in the front stage B1 The third switch Q of the bridge arm of the multiplexed bridge is used in conjunction with the preceding stage. B3 Phase shift angle D at the activation time θb This causes the first inductor L in the preceding AC-DC converter, which is connected in series between the non-multiplexed bridge arm and the multiplexed bridge arm, to... a Second inductor L b The inductor current is modulated into a quadrilateral inductor current; In the subsequent DC-AC converter, by adjusting the first switch Q of the subsequent non-multiplexed bridge arm... C3 Duty cycle D yc and the third switch Q of the subsequent non-multiplexed bridge arm D3 Duty cycle D yd Adjust the connections respectively to the second AC source v ac2 The first output capacitor C between the two terminals and ground outC Second output capacitor C outD The voltage and the second AC source v ac2 The voltage is adjusted by regulating the first switch Q of the subsequent multiplexed bridge arm. C1 With the first switch Q of the subsequent non-multiplexed bridge arm C3 Phase shift angle D at the activation time θc The third switch Q of the subsequent multiplexing bridge arm D1 With the third switch Q of the subsequent non-multiplexed bridge arm D3 Phase shift angle D at the activation time θd This causes the third inductor L, which is connected in series between the multiplexed and non-multiplexed bridge arms in the subsequent DC-AC converter, to... c Fourth inductor L d The inductor current is modulated into a quadrilateral inductor current; The quadrilateral inductor current is maintained as a non-zero current through the freewheeling phase, providing energy for the charging and discharging of the junction capacitance of the switching transistors, thereby achieving zero-voltage turn-on of all switching transistors.

7. A modulation method for an isolated global soft-switching AC-DC-AC converter based on the primary-secondary side collaborative multiplexing described in claim 6, characterized in that, The modulation method employs a PWM and phase-shift fusion modulation strategy, including the following steps: S1, set the duty cycle of all multiplexed bridge arms to a fixed value, preset cross-level group synchronous on / off logic, let the first switch of the previous multiplexed bridge arm, the fourth switch of the previous multiplexed bridge arm, the first switch of the subsequent multiplexed bridge arm and the third switch of the subsequent multiplexed bridge arm be the first group, let the second switch of the previous multiplexed bridge arm, the third switch of the previous multiplexed bridge arm, the second switch of the subsequent multiplexed bridge arm and the third switch of the subsequent multiplexed bridge arm be the second group, the switches of each group are synchronously turned on and off, and the two groups are in a complementary and cooperative working state; S2, for the front-end AC-DC converter, adjust the duty cycle D of the first switch transistor of the front-end non-multiplexed bridge arm. ya Duty cycle D of the third switch in the non-multiplexed bridge arm of the preceding stage yb Stabilize the first DC bus capacitor C bus1 First input capacitor C inA and the second input capacitor C inB The voltage; simultaneously adjust the phase shift angle D at the turn-on time of the first switch of the non-multiplexed bridge arm and the first switch of the multiplexed bridge arm. θa The phase shift angle D at the turn-on time of the third switch of the non-multiplexed bridge arm and the third switch of the multiplexed bridge arm. θb , the first inductor L a Second inductor L b The current is modulated into a quadrilateral waveform; S3, for the subsequent DC-AC converter, adjust the duty cycle D of the first switch transistor in the subsequent non-multiplexed bridge arm. yc The duty cycle D of the third switch in the subsequent non-multiplexed bridge arm yd Stabilize the first output capacitor C outC Second output capacitor C outD and the second source of exchange v ac2 The voltage; simultaneously adjust the phase shift angle D at the turn-on time of the first switch of the subsequent multiplexed bridge arm and the first switch of the subsequent non-multiplexed bridge arm. θc The phase shift angle D at the turn-on time of the third switch of the subsequent multiplexed bridge arm and the third switch of the subsequent non-multiplexed bridge arm. θd The currents of the third and fourth inductors are modulated into quadrilateral waveforms; S4. The quadrilateral inductor current in steps S2 and S3 provides soft-switching current conditions for all switching transistors. Combined with the resonant characteristics of the intermediate LLC resonant network, global soft-switching of all switching transistors is achieved.

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