Bidirectional high-efficiency power conversion device and regulation method

Abstract

This invention belongs to the field of bidirectional energy transfer and control technology in AC / DC microgrids and V2G. To address the problem of poor stability in existing AC / DC network control strategies, it proposes a bidirectional high-efficiency power conversion device and control method. Based on the load dispatch signal from the AC distribution network side and the real-time operating status information from the DC side, the current energy transmission direction is determined. Within each spatial sector, the primary-side switching cycle of the transformer is divided into multiple vector intervals, and the vector interval of the current secondary-side voltage is determined. Based on the energy transmission direction, and according to the effective vector interval of the secondary-side voltage, the high and low levels in different effective vector intervals are used as references for phase shifting. Based on the symmetry of the transformer leakage inductance current, the high and low levels when the secondary-side voltage is in the zero vector interval are determined, achieving phase shift control. This invention effectively prevents transformer magnetization, suppresses even-order harmonic injection into the grid, and ensures the high-reliability operation of the AC / DC interconnection system.

Description

Technical Field

[0001] This invention belongs to the field of AC / DC microgrids and V2G bidirectional energy transfer and control technology, and particularly relates to a bidirectional high-efficiency power conversion device and control method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the development of vehicle-to-grid (V2G) interaction and AC / DC microgrid technologies, efficient bidirectional energy transfer between the AC distribution network and the DC side (such as power batteries) has become crucial. As a core hub connecting AC and DC networks, the control strategy of bidirectional power conversion devices (such as high-frequency chain matrix converters) is key to achieving bidirectional energy transmission. Meanwhile, wide-range and highly reliable operation are important goals pursued by bidirectional power conversion devices. The high-frequency chain matrix converter is a single-stage isolated power conversion topology with advantages such as high power density and energy conversion efficiency.

[0004] The current mainstream control strategy is space vector pulse width modulation (SVM) combined with single-phase shift modulation. Its basic principle is to shift the secondary voltage of the high-frequency transformer relative to the primary voltage by a fixed phase angle to achieve bidirectional energy transfer. However, in the single-phase shift modulation strategy, the phase shift angle is uncertain relative to the magnitudes of the zero and effective vectors in SVM, leading to a complex system model that makes it difficult to analyze the current stress at the transformer leakage inductance and the system's soft-switching characteristics. Furthermore, the power transfer patterns at the transformer leakage inductance can be as many as five different types within a single cycle, which is detrimental to the design of key parameters such as transformer turns ratio and leakage inductance. In the actual operation of bidirectional AC / DC network interconnection (such as V2G scenarios), the uncertainties in the above model and the complex leakage inductance current transfer patterns not only limit the efficiency and power quality of energy transfer between the AC and DC sides but also adversely affect the stable dispatching of the external AC distribution network and the reliable operation of DC-side energy storage batteries. Summary of the Invention

[0005] To overcome the shortcomings of the existing technologies in high-power interaction scenarios of AC / DC networks, this invention provides a bidirectional high-efficiency power conversion device and control method. Through the optimization of the underlying control strategy, bidirectional energy transmission and smooth dynamic switching between the AC distribution network and the DC side are realized. This not only ensures stable energy interaction over a wide range between AC and DC networks, but also effectively suppresses transformer bias and narrow pulses, ensuring the power quality and safe and reliable operation of the AC / DC interconnected system.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for controlling a bidirectional high-efficiency power conversion device, applied to an AC / DC power transmission network, comprising the following steps: Based on the load dispatch signals on the AC distribution network side and the real-time operating status information on the DC side, the current energy transmission direction between the AC and DC networks is determined. Within each spatial sector, the primary-side switching cycle of the transformer is divided into multiple vector intervals, and the vector interval in which the current secondary-side voltage of the transformer is located is determined. Based on the energy transmission direction, and according to the effective vector range of the transformer secondary voltage, the high and low levels in different effective vector ranges are used as a reference for phase shifting; Based on the symmetry of the transformer leakage inductance current, the high and low levels of the transformer secondary voltage when it is in the zero vector range are determined, thereby achieving phase shift control.

[0007] A second aspect of the present invention provides a bidirectional high-efficiency power conversion device for use in AC / DC power transmission networks, comprising: The energy transmission direction module is used to determine the current energy transmission direction between AC and DC networks based on the load dispatching signals on the AC distribution network side and the real-time operating status information on the DC side. The determination module is used to divide the primary-side switching cycle of the transformer into multiple vector intervals within each spatial sector and determine the vector interval in which the current secondary-side voltage of the transformer is located. The first control module is used to perform phase shifting based on the energy transmission direction and the effective vector range of the transformer secondary voltage, using the high and low levels in different effective vector ranges as a reference. The second control module is used to determine the high and low levels of the transformer secondary side voltage when it is in the zero vector range based on the energy transmission direction and the symmetry of the transformer leakage inductance current, thereby realizing phase shift control.

[0008] The above one or more technical solutions have the following beneficial effects: This invention, under the premise of clearly defining the energy transmission direction of the AC / DC network, uses the high and low levels corresponding to the transformer secondary voltage in different effective vector intervals as phase-shifting references for regulation; and determines the high and low levels when the transformer secondary voltage is in the zero vector interval based on the energy transmission direction and the symmetry of the transformer leakage inductance current. This invention's scheme rationally shifts the transformer secondary voltage, enabling bidirectional converters to achieve smooth bidirectional, wide-range energy transmission in AC / DC interconnected networks. By fully considering the symmetry of the transformer leakage inductance current, this invention effectively prevents transformer bias, thereby suppressing the increase of reactive power and the injection of even-order harmonics into the AC distribution network, ensuring the efficient and stable operation of the large-scale AC / DC interconnected system. Furthermore, this regulation scheme effectively suppresses the generation of narrow pulses, fundamentally avoiding the risk of failure of underlying hardware due to extreme electrical stress, ensuring the long-term, highly reliable operation of the bidirectional power conversion system.

[0009] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0010] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0011] Figure 1 This is a topology diagram of a high-frequency chain matrix converter; Figure 2 This is a schematic diagram of the spatial vector pulse width modulation strategy in Embodiment 1 of the present invention; Figure 3 This is a waveform diagram of the primary side voltage of the high-frequency transformer in the first sector of Embodiment 1 of the present invention; Figure 4 This is a wide-range, high-reliability phase-shift control strategy under rectified conditions in Embodiment 1 of the present invention; Figure 5 This is a wide-range, high-reliability phase-shift control strategy in the inverter state of Embodiment 1 of the present invention; Figure 6 This is the narrow pulse suppression strategy under rectified state in Embodiment 1 of the present invention; Figure 7 This refers to the narrow pulse suppression strategy in the inverter state in Embodiment 1 of the present invention; Figure 8 The waveforms of the primary and secondary sides of the transformer under rectification state in Embodiment 1 of the present invention are shown. Figure 9 The waveforms of the primary and secondary sides of the transformer in the inverter state are shown in Embodiment 1 of the present invention. Figure 10 This is the AC / DC side waveform during energy transmission direction switching in Embodiment 1 of the present invention; Figure 11 This is the voltage and current waveform at the transformer during narrow pulse suppression in the rectified state according to Embodiment 1 of the present invention; Figure 12 This is the voltage and current waveform at the transformer during narrow pulse suppression in the inverter state in Embodiment 1 of the present invention. Detailed Implementation

[0012] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0013] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0014] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0015] Example 1 This embodiment discloses a control method for a bidirectional high-efficiency power conversion device, applied to AC / DC power transmission networks such as V2G systems, specifically including the following steps: It acquires load dispatch signals from the AC distribution network side and real-time operating status information from the DC side, and determines the current energy transmission direction between the AC and DC networks accordingly. Within each spatial sector, the primary-side switching cycle of the transformer is divided into multiple vector intervals, and the vector interval in which the current secondary-side voltage of the transformer is located is determined. Based on the energy transmission direction, and according to the effective vector range of the transformer secondary voltage, the high and low levels in different effective vector ranges are used as a reference for phase shifting; Based on the direction of energy transmission and the symmetry of the transformer leakage inductance current, the high and low levels of the transformer secondary voltage when it is in the zero vector range are determined, thereby achieving phase shift control and realizing stable energy transmission between AC and DC power transmission networks.

[0016] The specific implementation process of this embodiment is as follows: First, the topology of the high-frequency chain matrix converter is described in the context of a bidirectional interactive AC / DC network system; then, taking the first sector in the space vector pulse width modulation strategy as an example, wide-range phase shift modulation strategies corresponding to the rectification state and the inverter state are designed respectively; finally, a narrow pulse suppression strategy is designed to ensure the safe and reliable operation of the system network.

[0017] like Figure 1 As shown, the AC input of the high-frequency chain matrix converter is connected to the AC distribution network, and its DC output is connected to the energy storage battery (or V2G DC network). It consists of an AC-side filter, a three-phase to single-phase matrix converter unit, a high-frequency transformer, a full-bridge converter, and a DC-side filter. u x and i x (x=a,b,c) represent the AC side voltage and current of the system, respectively. R x Represents the equivalent impedance of the line. L x and C x These are the AC side filter inductor and capacitor, respectively. v x and i xtThese represent the voltage and current at the three-phase to single-phase matrix converter unit, which consists of six bidirectional switches. These switches, through regulation, generate alternating positive and negative voltages and currents on the primary side of the high-frequency transformer. The high-frequency transformer isolates the AC and DC sides of the entire system. The side connected to the three-phase to single-phase matrix converter unit is the primary side, and the side connected to the full-bridge converter is the secondary side. By controlling the switching state of the full-bridge converter, phase shifting of the transformer's secondary voltage is achieved, enabling bidirectional, wide-range energy transfer. L o and C o These are the DC-side filter inductor and capacitor, respectively. u o and i o These represent the DC side voltage and current, respectively.

[0018] The working principle of high-frequency transformers for energy transmission is as follows: when the voltage phase of the primary side of the high-frequency transformer leads the voltage phase of the secondary side, energy is transmitted in the positive direction (rectification state); when the voltage phase of the primary side of the high-frequency transformer lags behind the voltage phase of the secondary side, energy is transmitted in the negative direction (inverter state).

[0019] The bidirectional energy transfer in the high-frequency chain matrix converter is accomplished by the cooperation of a three-phase to single-phase matrix converter unit and a full-bridge converter. A space vector pulse width modulation (SVM) strategy is selected for the three-phase to single-phase matrix converter unit. The spatial sector division and the resulting voltage waveform of this strategy are as follows: Figure 2 and Figure 3 As shown.

[0020] Table 1. Vector Table for Sector Selection

[0021] The transformer secondary voltage generated by the full-bridge converter differs under rectifier and inverter conditions. Therefore, the wide-range phase-shift control strategy is divided into two modes: (i) According to the received external load dispatch signal, when the system determines that the current energy transmission direction is from the AC side to the DC side (i.e., rectification state), the system enters the following phase shift control logic: According to the different vectors, one switching cycle of the primary side of the high-frequency transformer is divided into eight intervals. The high level of the secondary side voltage of the transformer in the second effective vector interval (2) and the third effective vector interval (3) and the low level of the secondary side voltage in the sixth effective vector interval (6) and the seventh effective vector interval (7) are used as the reference for phase shifting. The specific phase shifting method is as follows: The secondary side voltage of the transformer corresponding to the second effective vector interval (2) and the seventh effective vector interval (7) is regarded as a set of rectangular waves that are high first and then low. The rectangular waves are shifted backward. ,in, This represents the total duration of action of the initial effective vector and its opposite effective vector within a single cycle; the duration of action of the two vectors is the same. The phase shift ratio is used. The secondary side voltages corresponding to the third effective vector interval (3) and the sixth effective vector interval (6) are regarded as a set of rectangular waves that are first high and then low. The rectangular waves are shifted backward. .in, This represents the total duration of the effective vector at the end of the sector and its opposite effective vector within a single cycle, with both vectors having the same duration. Then, considering both forward energy transfer and the symmetry of the transformer leakage inductance current, the transformer secondary side is set to a low level in the first zero vector interval (1) and the eighth zero vector interval (8), and a high level in the fourth zero vector interval (4) and the fifth zero vector interval (5). The specific wide-range phase-shift control strategy for achieving forward energy transfer is as follows: Figure 4 As shown. The transmission power corresponding to this control strategy is: (1) in, f The operating frequency of the switching transistor. n For transformer turns ratio, L This is the transformer inductance value. V o Battery voltage, V m This refers to the three-phase voltage amplitude. m The modulation ratio, This represents the phase shift ratio.

[0022] (ii) According to the received external load dispatch signal, when the system determines that the current energy transmission direction is from the DC side to the AC side (i.e., the inverter state), the system enters the following phase shift control logic: Divide one switching cycle of the primary side of the high-frequency transformer into eight intervals, and take the secondary side voltage at the second effective vector interval (2) and the third effective vector interval (3) as high level and the secondary side voltage at the sixth effective vector interval (6) and the seventh effective vector interval (7) as low level as the reference for phase shifting. The specific phase shifting method is as follows: regard the secondary side voltage corresponding to the second effective vector interval (2) and the seventh effective vector interval (7) as a set of rectangular waves that are first high and then low, and move the rectangular waves forward. ,in, This represents the total duration of action of the initial effective vector and its opposite effective vector within a single cycle; the duration of action of the two vectors is the same. The phase shift ratio is used. The secondary side voltages corresponding to the third effective vector interval (3) and the sixth effective vector interval (6) are considered as a set of rectangular waves that are first high and then low. This rectangular wave is shifted forward. ,in, This represents the total duration of the effective vector at the end of the sector and its opposite effective vector within a single cycle, with both vectors having the same duration. Then, considering both negative energy transfer and the symmetry of the transformer leakage inductance current, the transformer secondary side is set to a high level in the first zero vector interval (1) and the eighth zero vector interval (8), and a low level in the fourth zero vector interval (4) and the fifth zero vector interval (5). The specific implementation strategy for wide-range phase-shift control of negative energy transfer is as follows: Figure 5 As shown. The transmission power corresponding to this control strategy is: (2) in, f The operating frequency of the switching transistor. n For transformer turns ratio, L This is the transformer inductance value. V o Battery voltage, V m This refers to the three-phase voltage amplitude. m The modulation ratio.

[0023] When the commutation time of the switching transistor exceeds the drive signal width of the full-bridge converter, a narrow pulse occurs, which can cause the switching transistor to shoot-through and lead to system burnout. Therefore, to ensure the safe and reliable operation of the system, narrow pulses must be suppressed.

[0024] In this embodiment, the narrow pulse suppression strategy is as follows: First, the critical duty cycle is calculated, assuming that the width at the full-bridge converter is less than the critical time of the narrow pulse. t The driving signal is a narrow pulse, when the phase shift ratio is The switching frequency is f At that time, the critical duty cycle corresponding to the effective vector is calculated to be: Then, the duty cycle corresponding to the effective vector is detected to determine the secondary side voltage; finally, narrow pulse suppression is achieved.

[0025] Taking the first sector as an example, the effective vector i ab and i ba The corresponding duty cycle is ,in, This represents the total duty cycle of the sector's initial effective vector and its opposite effective vector within a single cycle; the two vectors have the same duty cycle. i ac and i ca The corresponding duty cycle is ,in, This represents the total duty cycle of the sector termination effective vector and its opposite effective vector within a single cycle; the two vectors have the same duty cycle. When detected... and In either case, the voltage corresponding to the secondary side and the effective vector interval is not phase-shifted, while the voltage corresponding to the zero vector interval is kept consistent with the phase-shifted state.

[0026] Specifically, such as Figure 6 and Figure 7 As shown, during forward energy transfer, when the effective vector duty cycle is detected to be less than the critical duty cycle, the secondary voltage corresponding to the effective vector interval does not undergo phase shifting, and the secondary voltage corresponding to the zero vector interval is consistent with the phase shifting. Specifically, when the effective vector duty cycle is detected to be less than the critical duty cycle, the secondary voltage is high at the fourth zero vector interval (4), the fifth zero vector interval (5), the sixth effective vector interval (6), and the seventh effective vector interval (7), and low at the first zero vector interval (1), the second effective vector interval (2), the third effective vector interval (3), and the eighth zero vector interval (8).

[0027] During negative energy transfer, when the effective vector duty cycle is detected to be less than the critical duty cycle, the secondary voltage corresponding to the effective vector interval is not phase-shifted, and the secondary voltage corresponding to the zero vector interval is consistent with the phase-shifted voltage. Specifically, when the effective vector duty cycle is detected to be less than the critical duty cycle, the secondary voltage is low at the fourth zero vector interval (4), the fifth zero vector interval (5), the sixth effective vector interval (6), and the seventh effective vector interval (7), and high at the first zero vector interval (1), the second effective vector interval (2), the third effective vector interval (3), and the eighth zero vector interval (8).

[0028] To achieve bidirectional wide-range energy transfer, this embodiment designs the transformer secondary voltage according to the energy transfer direction. During positive energy transfer, the effective vector interval corresponds to a secondary voltage phase that lags behind the primary voltage phase, while the zero vector interval ensures both positive energy transfer and symmetrical leakage inductance current. During negative energy transfer, the effective vector interval corresponds to a secondary voltage phase that leads the primary voltage phase, while the zero vector interval ensures both negative energy transfer and symmetrical leakage inductance current.

[0029] This embodiment calculates the critical duty cycle based on the narrow pulse critical time, phase shift ratio, and switching frequency. When the duty cycle of the effective vector on the primary side of the transformer is detected to be less than the critical duty cycle, the voltage on the secondary side of the transformer corresponding to the effective vector interval is not phase-shifted. Combined with the arrangement of the secondary side voltage corresponding to the zero vector interval, the narrow pulse is effectively suppressed, ensuring high-reliability operation of the system.

[0030] This embodiment provides a wide-range, high-reliability control strategy for a bidirectional power conversion device, which reduces the complexity of the system model and facilitates the selection of parameters such as switching frequency of the switching transistor, transformer turns ratio, and leakage inductance, laying the foundation for the engineering application of high-frequency chain matrix converters.

[0031] This embodiment of the scheme reasonably shifts the phase of the transformer secondary side voltage, enabling the system to transmit energy bidirectionally over a wide range.

[0032] This embodiment of the solution can make the leakage inductance current of the transformer symmetrical, effectively prevent the transformer from becoming biased, thereby suppressing the increase of reactive power and the generation of even harmonics, and ensuring the efficient and stable operation of the system.

[0033] This embodiment suppresses narrow pulses, effectively preventing the switching transistor from shooting through and ensuring high-reliability operation of the system.

[0034] To verify the effectiveness of the proposed control strategy in this embodiment, a simulation model was built in the MATLAB / Simulink environment. The model parameters are shown in Table 2. Simulation results show that the proposed wide-range, high-reliability control strategy can achieve bidirectional wide-range energy transfer and ensure high-reliability operation of the system.

[0035] Table 2 Partial Simulation Parameters

[0036] like Figure 8 As shown, at the effective vector, the primary voltage phase of the transformer leads the secondary voltage phase, energy is transferred from the AC side to the DC side, and the leakage inductance current is symmetrical. Figure 9 As shown, at the effective vector, the primary voltage phase of the transformer lags behind the secondary voltage phase, energy is transferred from the DC side to the AC side, and the leakage inductance current is symmetrical. Simulation results show that the novel wide-range, high-reliability control strategy can achieve stable bidirectional energy transfer in the high-frequency chain matrix converter.

[0037] Control the DC side current to 20A and -40A and its dynamic switching, and the AC side waveform and DC side waveform are as follows: Figure 10 As shown in Table 2, the converter's power transmission range is [-13106W, 13106W] under the parameters shown in Table 2, as can be seen from formulas (1) and (2). This verifies that the proposed control strategy can achieve bidirectional wide-range energy transmission and smooth dynamic switching.

[0038] like Figure 11 and 12 As shown, with a switching frequency of 20kHz, a phase shift ratio of 50% at the full-bridge converter, and a narrow pulse critical time of 1μs, when the detection... d x ≤0.08 and d y When any one of the values ​​is ≤0.08, the voltage corresponding to the effective vector interval on the secondary side is not phase-shifted, and the voltage corresponding to the zero vector interval remains consistent with the phase-shifted state, thereby suppressing narrow pulses, preventing the switching transistor from shooting through, and ensuring high-reliability operation of the system.

[0039] Example 2 The purpose of this embodiment is to provide a bidirectional high-efficiency power conversion device for use in AC / DC power transmission networks, including: The energy transmission direction module is used to determine the current energy transmission direction between AC and DC networks based on the load dispatching signals on the AC distribution network side and the real-time operating status information on the DC side. The determination module is used to divide the primary-side switching cycle of the transformer into multiple vector intervals within each spatial sector and determine the vector interval in which the current secondary-side voltage of the transformer is located. The first control module is used to perform phase shifting based on the energy transmission direction and the effective vector range of the transformer secondary voltage, using the high and low levels in different effective vector ranges as a reference. The second control module is used to determine the high and low levels of the transformer secondary side voltage when it is in the zero vector range based on the energy transmission direction and the symmetry of the transformer leakage inductance current, thereby realizing phase shift control.

[0040] Those skilled in the art will understand that the modules or steps of the present invention described above can be implemented using general-purpose computer devices. Optionally, they can be implemented using computer-executable program code, thereby allowing them to be stored in a storage device for execution by a computer device, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. The present invention is not limited to any particular combination of hardware and software.

[0041] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A control method for a bidirectional high-efficiency power conversion device, applied to AC / DC power transmission networks, characterized in that, include: Based on the load dispatch signals on the AC distribution network side and the real-time operating status information on the DC side, the current energy transmission direction between the AC and DC networks is determined. Within each spatial sector, the primary-side switching cycle of the transformer is divided into multiple vector intervals, and the vector interval in which the current secondary-side voltage of the transformer is located is determined. Based on the energy transmission direction, and according to the effective vector range of the transformer secondary voltage, the high and low levels in different effective vector ranges are used as a reference for phase shifting; Based on the symmetry of the transformer leakage inductance current, the high and low levels of the transformer secondary voltage when it is in the zero vector range are determined, thereby achieving phase shift control.

2. The control method for a bidirectional high-efficiency power conversion device as described in claim 1, characterized in that, When the current energy transmission direction is determined to be charging from the AC side to the DC side, the transformer secondary voltage will be high in the second and third effective vector intervals, and low in the sixth and seventh effective vector intervals; the transformer secondary voltage will be low in the first and eighth zero vector intervals, and high in the fourth and fifth zero vector intervals.

3. The control method for a bidirectional high-efficiency power conversion device as described in claim 1, characterized in that, When the current energy transmission direction is determined to be discharge from the DC side to the AC side, the transformer secondary voltage will be high in the second and third effective vector intervals and low in the sixth and seventh effective vector intervals; the transformer secondary voltage will be high in the first and eighth zero vector intervals and low in the fourth and fifth zero vector intervals.

4. The control method for a bidirectional high-efficiency power conversion device as described in claim 2, characterized in that, If the current energy transfer direction is from AC side to DC side charging, the specific phase shifting method is as follows: The transformer secondary voltages corresponding to the second and seventh effective vector intervals are taken as a first rectangular wave that is high at the beginning and low at the end. The first rectangular wave is then shifted backward. , For phase shift ratio, This represents the total duration of action of the sector's initial effective vector and its opposite effective vector within a single cycle; The transformer secondary voltages corresponding to the third and sixth effective vector intervals are taken as a set of second rectangular waves that are first high and then low, and the second rectangular waves are shifted backward. , For phase shift ratio, This represents the total duration of action of the sector's terminating effective vector and its opposite effective vector within a single cycle.

5. The control method for a bidirectional high-efficiency power conversion device as described in claim 3, characterized in that, If the current energy transfer direction is from DC to AC discharge, the specific phase shifting method is as follows: The secondary side voltages corresponding to the second and seventh effective vector intervals are considered as a set of third rectangular waves that are first high and then low. These third rectangular waves are then shifted forward. , For phase shift ratio, This represents the total duration of action of the sector's initial effective vector and its opposite effective vector within a single cycle; The secondary side voltages corresponding to the third and sixth effective vector intervals are considered as a set of fourth rectangular waves that are first high and then low. These fourth rectangular waves are then shifted forward. , For phase shift ratio, This represents the total duration of action of the sector's terminating effective vector and its opposite effective vector within a single cycle.

6. The control method for a bidirectional high-efficiency power conversion device as described in claim 1, characterized in that, It also includes narrow pulse suppression modulation, specifically: Calculate the critical duty cycle; When the duty cycle of the effective vector is less than the critical duty cycle, no phase shift is performed when the voltage on the secondary side of the transformer is within the effective vector range; The voltage on the secondary side of the transformer corresponding to the zero vector interval is the same as that during phase shift.

7. The control method for a bidirectional high-efficiency power conversion device as described in claim 6, characterized in that, The critical duty cycle is calculated based on the narrow pulse critical time, phase shift ratio, and switching frequency. Specifically, the secondary side turn-on time of the transformer is less than the critical duty cycle. t The driving signal is used as a narrow pulse; the time... t With switching frequency f The product of the phase shift ratio and the phase shift ratio The ratio of the effective vectors is used as the critical duty cycle.

8. The control method for a bidirectional high-efficiency power conversion device as described in claim 6 or 7, characterized in that, When the duty cycle of the effective vector is less than the critical duty cycle, no phase shift is performed when the transformer secondary voltage is in the effective vector range. The transformer secondary voltage corresponding to the zero vector range is the same as during phase shifting. Specifically: If the current energy transmission direction is charging from the AC side to the DC side, when the duty cycle of the effective vector is less than the critical duty cycle, the transformer secondary voltage will be at a high level in the fourth zero vector interval, the fifth zero vector interval, the sixth effective vector interval, and the seventh effective vector interval. The voltage on the secondary side of the transformer is set to a low level in the first zero vector interval, the second effective vector interval, the third effective vector interval, and the eighth zero vector interval.

9. A control method for a bidirectional high-efficiency power conversion device as described in claim 6 or 7, characterized in that, When the duty cycle of the effective vector is less than the critical duty cycle, no phase shift is performed when the transformer secondary voltage is in the effective vector range. The transformer secondary voltage corresponding to the zero vector range is the same as during phase shifting. Specifically: If the current energy transmission direction is from DC side to AC side discharge, when the duty cycle of the effective vector is less than the critical duty cycle, the transformer secondary voltage will be at a low level in the fourth zero vector interval, the fifth zero vector interval, the sixth effective vector interval, and the seventh effective vector interval. The secondary voltage of the transformer is set to a high level in the first zero vector interval, the second effective vector interval, the third effective vector interval, and the eighth zero vector interval.

10. A bidirectional high-efficiency power conversion device, applied to AC / DC power transmission networks, characterized in that, include: The energy transmission direction module is used to determine the current energy transmission direction between AC and DC networks based on the load dispatching signals on the AC distribution network side and the real-time operating status information on the DC side. The determination module is used to divide the primary-side switching cycle of the transformer into multiple vector intervals within each spatial sector and determine the vector interval in which the current secondary-side voltage of the transformer is located. The first control module is used to perform phase shifting based on the energy transmission direction and the effective vector range of the transformer secondary voltage, using the high and low levels in different effective vector ranges as a reference. The second control module is used to determine the high and low levels of the transformer secondary side voltage when it is in the zero vector range based on the energy transmission direction and the symmetry of the transformer leakage inductance current, thereby realizing phase shift control.

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