Single-stage wide voltage isolation bidirectional AC / DC converter

Abstract

This invention discloses a single-stage wide-voltage isolation bidirectional AC / DC converter, belonging to the technical field of power generation, transformation, or distribution. The converter consists of an input inductor, a primary-side inverter bridge, a primary-side DC bus capacitor, a high-frequency transformer, a transmission inductor, a DC blocking capacitor, a secondary-side inverter bridge, a secondary-side DC bus capacitor, and an LC filter. The high-frequency transformer is a center-tapped isolation transformer on the primary side, forming a current-source type active clamp push-pull structure with the primary-side inverter bridge. The primary-side inverter bridge, high-frequency transformer, transmission inductor, output bridge arm, and DC blocking capacitor form the bridge arm of the dual active bridge multiplexed secondary-side inverter bridge. The LC filter is a low-pass filter composed of two inductors and 1-3 capacitors. This invention utilizes the high-frequency AC components contained in the output waveform of the secondary-side inverter bridge under SPWM control, isolates the low-frequency AC components through capacitors, and uses a dual active bridge for power transmission and control, enabling bidirectional power transmission.

Description

Technical Field

[0001] This invention relates to power electronics application technology, specifically disclosing a single-stage wide-voltage isolated bidirectional AC / DC converter, belonging to the technical field of power generation, transformation, or distribution. Background Technology

[0002] In the face of the global energy crisis, the search for efficient, sustainable, and clean new energy sources has become a key theme of international development. Clean energy power generation involves photovoltaics, energy storage batteries, and other equipment that output direct current (DC). To connect to the grid or supply power to AC appliances, DC-AC conversion is required. Among these, the AC-DC converter plays a crucial role in voltage conversion and power transmission, making its performance paramount. Small-sized, high-efficiency converters can significantly reduce losses and minimize space requirements.

[0003] Traditional converters often employ a two-stage topology with a cascaded boost and inverter. The first stage converts the DC input voltage to approximately 350V DC, while the second stage utilizes the boosted DC voltage and converts it to 220V AC. In applications requiring isolation, the boost stage commonly uses a push-pull circuit in conjunction with a high-frequency transformer. The inverter stage employs a common full-bridge inverter topology, using unipolar or bipolar SPWM modulation. Because the boost stage in this type of scheme can only operate unidirectionally, it can only transfer power from the DC side to the AC side. In traditional schemes, both stages are relatively mature solutions, operating and controlled independently, making them simple and easy to design. However, since each stage needs to handle all the transmitted power, the power undergoes two complete conversions, resulting in lower converter efficiency and a large number of components, making it difficult to reduce size. Furthermore, because the push-pull boost stage operates at approximately a constant turns ratio, this type of inverter lacks wide-voltage operating capability.

[0004] To address the problems inherent in two-stage inverter topologies, there has been extensive research on single-stage converter topologies. Among these, high-frequency link converter topologies are particularly popular. These topologies utilize bidirectional switching transistors connected in series to form a two-way switch, directly using the high-frequency AC voltage output from the high-frequency transformer for SPWM modulation; or they employ isolated Buck-boost topologies such as flyback converters to modulate a continuous sinusoidal half-wave, which is then expanded into a continuous sine wave using a low-frequency half-bridge. This approach eliminates the DC link between the boost stage and the inverter stage, removing the DC filter capacitor and significantly reducing size. However, the bidirectional switching structure requires a large number of switching devices, making its control and drive complex and resulting in high application costs. Since the voltage stress on the high-frequency transformer and devices is positively correlated with the input voltage, this type of converter often has weak wide-voltage operating capability and lacks bidirectional power conversion capability. Furthermore, this type of converter cannot control DC-side current ripple; in grid-connected photovoltaic applications, input-side current ripple will significantly reduce the effective output power of the photovoltaic panels.

[0005] Existing DC-side high-frequency full-bridge circuits with wide input voltage operating capability typically employ a structure of two-phase interleaved parallel boosters and a full-bridge multiplexed configuration. This structure exhibits current source input characteristics and exhibits relatively low high-frequency current ripple. When operating at 50% duty cycle, the high-frequency output of the full-bridge reaches its optimal operating point, but the losses of the boost inductor also reach their maximum value; a trade-off between the two is not possible. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the aforementioned background technology by providing a single-stage wide-voltage isolated bidirectional AC-DC converter. Through a current-source active clamping structure, the converter achieves stable operation under a wide input voltage range. Furthermore, by employing a topology of a secondary inverter bridge and dual active bridge multiplexed arms, it can perform bidirectional power transfer and power control in conjunction with the dual active bridges while maintaining normal inverter output. This solves the technical problems of numerous components and low efficiency in two-stage inverters, and the complex control, high voltage stress, and poor wide-voltage operating characteristics of single-stage inverters. The invention aims to achieve a miniaturized AC-DC converter and improve converter efficiency.

[0007] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0008] A single-stage wide-voltage isolation bidirectional AC / DC converter includes: an input inductor, a primary-side inverter bridge, a primary-side DC bus capacitor, a high-frequency transformer, a transmission inductor, a DC blocking capacitor, a secondary-side inverter bridge, a secondary-side DC bus capacitor, and an LC filter.

[0009] The input inductor, the primary inverter bridge, and the primary winding of the high-frequency transformer form an active clamp push-pull topology. One end of the input inductor is connected to the positive terminal of the DC port, and the other end of the input inductor is connected to the tap of the primary winding of the high-frequency transformer. The two ends of the primary winding of the high-frequency transformer are connected to the high-frequency port formed by the midpoint of the two arms of the primary inverter bridge. The primary DC bus capacitor is connected between the positive and negative terminals of the DC bus of the primary inverter bridge, and the negative terminal of the DC port is connected to the negative DC bus of the primary inverter bridge.

[0010] The primary-side inverter bridge, high-frequency transformer, transmission inductor, output bridge arm, and DC blocking capacitor constitute a dual active bridge. The branch formed by the secondary winding of the high-frequency transformer and the transmission inductor in series forms a loop with the output bridge arm through the DC blocking capacitor. The output bridge arm is realized by multiplexing any one of the bridge arms in the secondary-side inverter bridge. The DC blocking capacitor and the secondary-side DC bus capacitor are respectively connected between the positive and negative terminals of the DC bus of the secondary-side inverter bridge.

[0011] The two input terminals of the LC filter are connected to the midpoint of one arm of the secondary inverter bridge, and the output terminal of the LC filter is the AC port.

[0012] As a further optimization scheme for a single-stage wide-voltage isolation bidirectional AC / DC converter, when only one pole of a DC blocking capacitor is connected to the positive or negative pole of the DC bus of the secondary inverter bridge, one end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the midpoint of the first arm of the secondary inverter bridge, and the other end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the other pole of the DC blocking capacitor; when two DC blocking capacitors are connected in series between the positive and negative poles of the DC bus of the secondary inverter bridge, one end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the midpoint of the first arm of the secondary inverter bridge, and the other end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the connection point of the two DC blocking capacitors.

[0013] As a further optimization of the single-stage wide voltage isolation bidirectional AC / DC converter, the LC filter includes: a first filter inductor, a second filter inductor, and a filter capacitor. One end of the first filter inductor constitutes one input terminal of the LC filter, and one end of the second filter inductor constitutes the other input terminal of the LC filter. One terminal of the filter capacitor is connected to the other end of the first filter inductor, and the other terminal of the filter capacitor is connected to the other end of the second filter inductor. The two terminals of the filter capacitor constitute the output terminal of the LC filter.

[0014] As a further optimization of the single-stage wide voltage isolation bidirectional AC / DC converter, the primary-side inverter bridge and the secondary-side inverter bridge operate at the same frequency.

[0015] The control method of a single-stage wide voltage isolation bidirectional AC / DC converter adopts a driving mode of complementary upper and lower transistors and 180° phase shift of the two bridge arms to control the primary inverter bridge and perform bipolar modulation on the secondary inverter bridge.

[0016] As a further optimization of the control method for a single-stage wide-voltage isolation bidirectional AC / DC converter, the transmission power of the bidirectional AC / DC converter is adjusted by selecting control degrees of freedom including, but not limited to, internal phase shift on the secondary side, internal phase shift on the primary side, and external phase shift on both the primary and secondary sides.

[0017] As a further optimization of the control method for a single-stage wide-voltage isolation bidirectional AC / DC converter, the transmission power of the bidirectional AC / DC converter is adjusted by regulating the duty cycle of the primary-side inverter bridge.

[0018] As a further optimization of the control method for a single-stage wide voltage isolation bidirectional AC / DC converter, when performing bipolar modulation on the secondary inverter bridge, a control strategy with equal or unequal modulation depths is adopted for the two arms of the secondary inverter bridge.

[0019] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0020] (1) The DC-DC converter submitted in this invention uses a dual active bridge that reuses one arm of the secondary inverter bridge, retains the voltage and power regulation capability of the dual active bridge, and has a stronger wide voltage operating capability compared with the existing single-stage topology, and shortens the power transmission link and reduces the number of components.

[0021] (2) The DC converter submitted in this invention adopts a dual active bridge and full bridge inverter multiplexing structure. It realizes the functions of the converter topology that the prior art requires to be built through two-stage structure through a single-stage topology. Therefore, the design of DC bus capacitor can be retained, making the control of voltage and power more stable. The DC bus capacitor can withstand a certain current ripple, thereby reducing the input power fluctuation. The multiplexing structure realizes the voltage doubler rectification function of the secondary side of the high-frequency transformer, reduces the voltage stress of the transformer, and reduces the influence of the transformer parasitic capacitance.

[0022] (3) The DC-DC converter submitted in this invention constructs an active clamp push-pull topology with boost function through the tap structure of the primary winding of the high-frequency transformer, the input inductor, and the primary inverter bridge, which improves the wide voltage adaptability of the converter proposed in this invention. In low input voltage applications, the active clamp push-pull structure can effectively reduce the current stress of the primary winding of the transformer. In addition, the active clamp push-pull topology can, to a certain extent, make the voltage fluctuations generated by the two arms of the primary inverter bridge cancel each other out, and make the voltage fluctuation frequency on the input inductor twice the switching frequency, thereby reducing the requirements of the input inductor and reducing the input high-frequency ripple.

[0023] (4) The DC converter submitted in this invention can use mature SPWM inverter control strategy or PWM rectifier control strategy to control the secondary inverter bridge, which reduces the design difficulty. The control of the secondary inverter bridge and the power transmission control of the dual active bridge operate independently, and the power and voltage control can be more effective and accurate, which helps to reduce the complexity of control strategies such as DC bus voltage control and grid connection control.

[0024] (5) The DC converter submitted in this invention can also achieve independent control of the two arms of the secondary inverter bridge through the control strategy of unequal modulation depth, which improves the bus voltage utilization rate, reduces the current stress of the multiplexed arms, transformers and inductors, and lowers the selection requirements.

[0025] (6) The DC converter submitted in this invention, under the drive of the control strategy, fully utilizes the characteristics of the dual active bridges to realize the normal inverter output of the secondary inverter bridge while performing bidirectional power transmission and power control from the primary side to the secondary side or from the secondary side to the primary side, thus meeting the application requirements of bidirectional AC-DC. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a structural diagram of the single-stage wide voltage isolation bidirectional AC / DC converter proposed in this invention.

[0028] Figure 2 This is a circuit topology diagram of the single-stage wide voltage isolation bidirectional AC / DC converter proposed in this invention.

[0029] Figure 3 The diagram shows the working waveforms of the primary-side inverter bridge drive signal and the current source type active clamp push-pull circuit of the bidirectional AC / DC converter proposed in this invention.

[0030] Figure 4 The diagram shows the relevant operating waveforms of the dual active bridge circuit of the bidirectional AC / DC converter proposed in this invention.

[0031] Figure 5 The diagram shows the main operating waveforms of the bidirectional AC / DC converter proposed in this invention when the input is 30V and the output is 450W.

[0032] Figure 6 The diagram shows the main operating waveforms of the bidirectional AC / DC converter proposed in this invention when the input is 15V and the output is 225W.

[0033] Figure 7 The diagram shows the main operating waveforms of the bidirectional AC / DC converter proposed in this invention when the input is 45V and the output is 225W.

[0034] Explanation of the labels in the diagram: M1, primary-side inverter bridge; C in Bypass filter capacitor, L boost Input inductance, C DC_Pri Primary DC bus capacitor, Tr; High-frequency transformer, L t Transmission inductance, C b1 ~C b2 First and second DC blocking capacitors, M2, secondary inverter bridge, C DC_Sec Secondary DC capacitor, L f1 ~L f2 First and second filter inductors, C s_ac Filter capacitors, Q1 to Q8, and the first to eighth switching transistors. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In a specific embodiment, such as Figure 1 As shown, a single-stage isolated bidirectional AC / DC converter consists of an input inductor L boost Primary inverter bridge M1, primary DC bus capacitor C DC_Pri High-frequency transformer Tr, transmission inductance L t DC blocking capacitor, secondary inverter bridge M2, secondary DC capacitor C DC_Sec LC filter, DC port V in and communication port v AC Composition. Input inductance L boost The primary-side inverter bridge M1 and the primary winding of the high-frequency transformer Tr constitute an active clamp push-pull topology. The primary-side inverter bridge M1, the high-frequency transformer Tr, and the transmission inductor L... t Output bridge arm, DC blocking capacitor C b This forms a dual active bridge, where the output arm is implemented by multiplexing one arm of the secondary-side inverter bridge. An LC filter can be a structure of two filter inductors and one differential-mode filter capacitor, or it can be a structure of two inductors, one differential-mode filter capacitor, and two common-mode filter capacitors. Figure 1 The LC filter shown has a structure consisting of two filter inductors and one differential filter capacitor. The first filter inductor L... f1 One end forms an input terminal of the LC filter, and the second filter inductor L f2 One end forms the other input terminal of the LC filter, and the filter capacitor C s_ac One pole is connected to the first filter inductor L f1 At the other end, the filter capacitor C s_ac The other pole is connected to the second filter inductor L f2 At the other end, the filter capacitor C s_ac The two stages constitute the output terminal of the LC filter, which is the AC port.

[0037] like Figure 2 As shown, the primary-side inverter bridge M1 is a full-bridge structure, composed of the first to fourth switches Q1 to Q4. Switch Q1 and switch Q2 are connected in series to form the first arm of the primary-side inverter bridge, and switch Q3 and switch Q4 are connected in series to form the second arm. The midpoint of the first arm and the midpoint of the second arm constitute the high-frequency port. The primary-side DC bus capacitor C is connected between the positive and negative ports of the primary-side inverter bridge M1.DC_Pri The high-frequency port is connected to the primary winding of the high-frequency transformer Tr. The negative terminal of the negative port of the DC bus of the primary inverter bridge M1 is also the DC port V. in The negative terminal. The drive signal of the primary-side inverter bridge M1 is the same as the drive signal required for a conventional two-phase interleaved parallel Boost converter. The drive signals of the upper and lower transistors of the two half-bridges formed by Q1, Q2 and Q3, Q4 are complementary, and the phase difference between the drive signals of the two half-bridges is 180 degrees.

[0038] like Figure 2 As shown, the primary winding of the high-frequency transformer Tr has a center-tapped structure, and the secondary winding is a single winding. The center tap of the primary winding of the high-frequency transformer Tr is connected to the input inductor L. boost One end, input inductor L boost The other end is connected to the DC port V. in The positive terminal of the converter has a bypass filter capacitor C at its DC port. in Input inductance L boost The primary winding of the high-frequency transformer Tr and the primary inverter bridge M1 form a current-source type active clamp push-pull topology. The secondary winding of the high-frequency transformer Tr and the transmission inductor L... t The series branch formed by the connection forms a loop with the first arm of the secondary inverter bridge M2 via the DC blocking capacitor.

[0039] like Figure 2 As shown, the secondary-side inverter bridge M2 is a full-bridge structure, composed of the fifth to eighth switches Q5 to Q8. Switch Q5 and switch Q6 are connected in series to form the first arm of the secondary-side inverter bridge, and switch Q7 and switch Q8 are connected in series to form the second arm. The positive and negative terminals of the DC bus of the secondary-side inverter bridge M2 are connected to the secondary-side DC bus capacitor C. DC_Sec The positive and negative DC buses of the secondary inverter bridge constitute the secondary DC bus V. Bus_Sec The first arm of the secondary inverter bridge is connected to the secondary winding of the high-frequency transformer Tr, which is the transmission inductor L. t - While the DC blocking capacitor is connected in series with one input terminal of the LC filter, the first arm of the multiplexed secondary inverter bridge becomes the output arm of the dual active bridge. The second arm of the secondary inverter bridge is connected to the other input terminal of the LC filter, and the output terminal of the LC filter forms the AC port V. AC The drive signal for the secondary inverter bridge M2 is a bipolar SPWM modulated signal.

[0040] There can be one or two DC blocking capacitors. When there is one DC blocking capacitor, one terminal of the DC blocking capacitor is connected to the positive or negative terminal of the DC bus of the secondary inverter bridge, and the other terminal of the DC blocking capacitor is connected to the secondary winding of the high-frequency transformer Tr and the transmission inductor L. t One end of the series structure; when there are two DC blocking capacitors, the first DC blocking capacitor C b1Second DC blocking capacitor C b2 The DC blocking capacitor is connected in series, with its two ends connected to the positive and negative terminals of the secondary inverter bridge DC bus, respectively. The midpoint of the DC blocking capacitor series branch is connected to the secondary winding of the high-frequency transformer Tr and the transmission inductor L. t One end of the series structure.

[0041] During SPWM modulation, the output waveform of the secondary inverter bridge contains a large number of high-frequency AC components, specifically a superposition of a power frequency sine wave and high-frequency pulses with periodically varying equivalent amplitudes. The power frequency sine wave component, after LC filtering, serves as the AC output of the converter. The midpoint voltage of the first arm of the secondary inverter bridge, i.e., the multiplexed arm, is applied across the series branch of the high-frequency transformer secondary winding and the transmission inductor after passing through a DC blocking capacitor. The voltage across the series branch of the high-frequency transformer secondary winding and the transmission inductor is a high-frequency pulse voltage without low-frequency AC components. The dual active bridge utilizes this high-frequency pulse voltage to achieve power transfer. Because the SPWM waveform output from the full secondary bridge directly affects the AC port output voltage, the duty cycle of the secondary inverter bridge cannot be used to control the power transfer of the dual active bridge. Furthermore, since the equivalent amplitude of the high-frequency pulse fluctuates significantly within one cycle, calculations show that this fluctuation also has a significant impact on the power transfer characteristics of the dual active bridge. In addition to the secondary-side internal phase shift, it also has two control degrees of freedom: primary-side internal phase shift and primary-secondary-side external phase shift, which can be used for power regulation in dual active bridge topologies. Although the duty cycle of the secondary-side inverter bridge fluctuates significantly within a single cycle, the average duty cycle within each power frequency cycle remains relatively constant. The converter's transmission power can be controlled by adjusting the external phase shift angles of the primary and secondary sides; the transmission power can be adjusted by controlling the external phase shifts of the primary and secondary sides, and the secondary-side DC bus capacitor C can be controlled through a closed loop. DC_Sec The voltage at both ends is maintained at the set value.

[0042] When the current-source active clamp push-pull topology structure formed by the primary-side inverter bridge M1 is working normally, its principle is similar to that of the Boost circuit, and the main waveforms are as follows: Figure 3 As shown, where v AB The high-frequency port voltage of the primary-side inverter bridge, v CD i is the voltage between the midpoint of the multiplexed bridge arm of the secondary-side inverter bridge and one terminal of the DC blocking capacitor. s Let D be the secondary winding current of the high-frequency transformer. Since the primary tap voltage of the high-frequency transformer is the average voltage at the midpoint of the two arms of the primary inverter bridge, let the duty cycle of Q1 and Q3 be D. p According to L boost The volt-second balance can be used to calculate C. DC_Pri Voltage V at both ends boost =V in / D p The voltage waveform is a positive and negative pulse wave, with a peak value of V. boost The duty cycle expression is as follows:

[0043]

[0044] Current-source active clamp push-pull topologies can alter the primary bus voltage and converter power transfer characteristics by changing the duty cycle, and their voltage adaptability range is wider than conventional push-pull, half-bridge, and full-bridge topologies. As the primary inverter bridge approaches its maximum output duty cycle (50%), L... boost The smaller the voltage ripple at both ends, the more efficient L becomes when the primary-side inverter bridge approaches its maximum output duty cycle. boost The losses are also smaller. This structure significantly reduces the losses at the optimal operating point of the primary-side inverter bridge compared to a two-phase interleaved parallel Boost multiplexed full-bridge structure with similar functions and characteristics.

[0045] One arm of the secondary-side full-bridge is reused as the output arm of the dual active bridge, effectively creating a voltage doubler rectification on the secondary side of the high-frequency transformer. This halves the number of turns in the transformer secondary winding, effectively reducing the impact of parasitic capacitance in the transformer windings when using planar transformers. Because the secondary-side inverter bridge uses one half-bridge arm reused with the dual active bridge, and employs a control strategy with unequal modulation depths for the two arms, the current stress on the reused arms, transformer, and inductors can be reduced while ensuring bus voltage utilization, thus lowering selection requirements. Reducing the modulation depth of the arm reused with the dual active bridge allows for smaller changes in the power transfer characteristics of the dual active bridge within a single power frequency cycle, thereby reducing design requirements and device current stress. The relevant operating waveforms of the dual active bridge circuit of the bidirectional AC / DC converter proposed in this invention are as follows: Figure 4 As shown.

[0046] Conventional two-stage topologies often employ unidirectional converter topologies in their boost stages, limiting the bidirectional application of AC-DC converters. Dual active bridge topologies, however, possess bidirectional power transfer capabilities. When the secondary-side drive signal lags behind the primary-side drive signal, power is transferred in the forward direction; when the secondary-side drive signal leads the primary-side drive signal, power is transferred in the reverse direction. If the control mode of the secondary-side inverter bridge M2 is changed to a PWM rectifier, and the secondary-side inverter bridge is allowed to lead the primary-side inverter bridge, then the primary-side active clamp push-pull circuit operates in rectification mode, thus achieving reverse power transfer and meeting the application requirements of AC-DC converters.

[0047] To verify the feasibility of this converter, a circuit model was built in simulation software for verification. The simulation prototype adopted the topology described in this patent, with the following parameters: rated input voltage of 30V, supporting inputs from 15V to 45V; output voltage of 220V at 50Hz; rated power of 450W; and switching frequency of 200kHz. The transformer has a turns ratio of 1:3, a center tap on the primary winding, a transmission inductance of 30μH, and two 220nF DC blocking capacitors. In the simulation, the prototype could output a rated power of 450W at a rated input voltage of 30V, and 225W at input voltages of 15V and 45V. Under different input voltages and loads, the key voltage and current waveforms during stable operation of the converter are as follows: Figures 5-7 As shown, where v AC This indicates the AC port output voltage. The converter can operate normally under different input voltage and load conditions.

[0048] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A single-stage wide-voltage isolation bidirectional AC / DC converter, characterized in that, include: Input inductor, primary-side inverter bridge, primary-side DC bus capacitor, high-frequency transformer, transmission inductor, DC blocking capacitor, secondary-side inverter bridge, secondary-side DC bus capacitor, LC filter; The input inductor, the primary inverter bridge, and the primary winding of the high-frequency transformer form an active clamp push-pull topology. One end of the input inductor is connected to the positive terminal of the DC port, and the other end of the input inductor is connected to the tap of the primary winding of the high-frequency transformer. The two ends of the primary winding of the high-frequency transformer are connected to the high-frequency port formed by the midpoint of the two arms of the primary inverter bridge. The primary DC bus capacitor is connected between the positive and negative terminals of the DC bus of the primary inverter bridge, and the negative terminal of the DC port is connected to the negative DC bus of the primary inverter bridge. The primary-side inverter bridge, high-frequency transformer, transmission inductor, output bridge arm, and DC blocking capacitor constitute a dual active bridge. The branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor forms a loop with the output bridge arm through the DC blocking capacitor. The output bridge arm is realized by multiplexing any one of the bridge arms in the secondary-side inverter bridge. The DC blocking capacitor and the secondary-side DC bus capacitor are respectively connected between the positive and negative terminals of the DC bus of the secondary-side inverter bridge. The two input terminals of the LC filter are respectively connected to the midpoint of one arm of the secondary inverter bridge, and the output terminal of the LC filter is the AC port.

2. The single-stage wide-voltage isolation bidirectional AC / DC converter according to claim 1, characterized in that, When only one pole of the DC blocking capacitor is connected to the positive or negative pole of the DC bus of the secondary inverter bridge, one end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the midpoint of the first arm of the secondary inverter bridge, and the other end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the other pole of the DC blocking capacitor; when two DC blocking capacitors are connected in series between the positive and negative poles of the DC bus of the secondary inverter bridge, one end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the midpoint of the first arm of the secondary inverter bridge, and the other end of the branch formed by the series connection of the secondary winding of the high-frequency transformer and the transmission inductor is connected to the connection point of the two DC blocking capacitors.

3. The single-stage wide-voltage isolation bidirectional AC / DC converter according to claim 1, characterized in that, The LC filter includes: a first filter inductor, a second filter inductor, and a filter capacitor. One end of the first filter inductor forms one input terminal of the LC filter, and one end of the second filter inductor forms the other input terminal of the LC filter. One terminal of the filter capacitor is connected to the other end of the first filter inductor, and the other terminal of the filter capacitor is connected to the other end of the second filter inductor. The two terminals of the filter capacitor form the output terminal of the LC filter.

4. The single-stage wide-voltage isolation bidirectional AC / DC converter according to claim 1, characterized in that, The primary-side inverter bridge and the secondary-side inverter bridge operate at the same frequency.

5. The control method for the single-stage wide-voltage isolation bidirectional AC / DC converter according to any one of claims 1 to 4, characterized in that, The primary inverter bridge is controlled by a drive method that uses complementary upper and lower tubes and a 180° phase shift between the two bridge arms, and the secondary inverter bridge is subjected to bipolar modulation.

6. The control method for the single-stage wide voltage isolation bidirectional AC / DC converter according to claim 5, characterized in that, The transmission power of the bidirectional AC / DC converter can be adjusted by selecting control degrees of freedom that include internal phase shift on the secondary side, internal phase shift on the primary side, and external phase shift on both the primary and secondary sides.

7. The control method for the single-stage wide voltage isolation bidirectional AC / DC converter according to claim 5, characterized in that, The transmission power of the bidirectional AC / DC converter is adjusted by regulating the duty cycle of the primary-side inverter bridge.

8. The control method for the single-stage wide voltage isolation bidirectional AC / DC converter according to claim 5, characterized in that, When performing bipolar modulation on the secondary-side inverter bridge, a control strategy of equal or unequal modulation depths is adopted for the two arms of the secondary-side inverter bridge.

Images