A single-stage three-port ac / dc converter, control method and system

Abstract

The application belongs to the technical field of power electronic conversion, and discloses a single-stage three-port AC / DC converter, a control method and a system. The converter comprises a high-voltage direct-current power supply HV, a low-voltage end LV, a first capacitor C01, a second capacitor C02, a third capacitor Cdc, a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a fourth switch tube Q4, a fifth switch tube Q5, a sixth switch tube Q6, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first inductor L1 and a second inductor L2, and a third inductor Lf. The application integrates a vehicle-mounted charger and a low-voltage DC-DC converter into a single topology, realizes three-port energy interaction through an AC input port, a high-voltage battery port and a low-voltage battery port, does not need additional AC relays or switching components, reduces the number of semiconductor devices, and improves the system integration and power density.

Description

Technical Field

[0001] This invention belongs to the field of power electronic conversion technology, specifically relating to a single-stage three-port AC / DC converter, control method, and system. Background Technology

[0002] Traditional solutions employ a separate design for the OBC (On-Board Charger) and LDC (Low Voltage DC-DC Converter), requiring separate configurations of core components such as power switches, magnetic components, and filter capacitors for each device. This results in redundant components and low integration of the overall system, increasing manufacturing costs and the size and weight of the equipment, contradicting the lightweight and miniaturized design requirements of light electric vehicles. More importantly, traditional converters (especially two-stage topologies) generally rely on large-capacity electrolytic capacitors as energy storage components in the intermediate DC link. However, electrolytic capacitors suffer from short lifespans and poor reliability due to inherent characteristics such as electrolyte evaporation and high-temperature failure, becoming a core bottleneck restricting the long-term stable operation of the vehicle's energy system. This also limits the high-frequency design and power density improvement of the converter.

[0003] Chinese Patent Publication No. CN114221535A, entitled "A Vehicle Charger, DC-DC Converter, and Control Method," includes: an input terminal of a high-voltage DC-DC converter connected to the output terminal of a power factor correction circuit; an input terminal of a low-voltage DC-DC converter connected to the output terminal of the high-voltage DC-DC converter or the output terminal of the power factor correction circuit; and an output terminal of the low-voltage DC-DC converter connected to a low-voltage battery. The low-voltage DC-DC converter includes a main power transistor and a controllable switching transistor. When the low-voltage DC-DC converter starts, the controller uses a current loop soft-start to generate a drive signal for the main power transistor, gradually increasing the current flowing through the inductor. The current setpoint of the current loop depends on the current reference value output by the voltage loop and the output result of the soft-start function. After the low-voltage DC-DC converter starts, the voltage loop and current loop are cascaded to generate the drive signal for the main power transistor. The voltage loop outputs a current reference value to the input terminal of the current loop, reducing the inrush current to the main power transistor during LVDC startup. This patent application cannot simultaneously integrate OBC and LDC functions, resulting in a large overall system weight and size. Summary of the Invention

[0004] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide a single-stage three-port AC / DC converter, control method and system. The single-stage multi-port converter of this invention can realize the functions of OBC and LDC in one integrated manner, without the need for additional switching components, and can avoid the defects of electrolytic capacitors. It solves the problems of many components, low reliability and complex mode switching in traditional solutions, and achieves high integration, high power density and efficient and stable energy conversion.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a single-stage three-port AC / DC converter, comprising: a high-voltage DC power supply HV, a low-voltage terminal LV, a first capacitor C01, a second capacitor C02, a third capacitor Cdc, a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first node a, a second node b, a third node c, a fourth node d, a first inductor L1, a second inductor L2, and a third inductor Lf; The positive terminal of the high-voltage DC power supply HV is connected to the first terminal of the first capacitor C01, the drain of the sixth switch Q6, and the drain of the fifth switch Q5; the negative terminal of the high-voltage DC power supply HV is connected to the second terminal of the first capacitor C01, the anode of the fourth diode D4, the anode of the third diode D3, the second terminal of the second capacitor C02, and the negative terminal of the low-voltage terminal LV; the source of the sixth switch Q6 is connected to the fourth node d, and the source of the fifth switch Q5 is connected to the third node c; the fourth node d is connected to the second terminal of the second inductor L2 and the cathode of the fourth diode D4; the third node c is connected to the second terminal of the first inductor L1 and the cathode of the third diode D3; the first terminal of the first inductor L1 is connected to the first terminal of the secondary winding of the transformer, and the second terminal of the secondary winding of the transformer is connected to the first terminal of the second inductor L2; the secondary winding of the transformer is connected to the positive terminal of the low-voltage terminal LV and the first terminal of the second capacitor C02; The first terminal of the third capacitor Cdc is connected to the cathode of the first diode D1, the drain of the first switching transistor Q1, and the drain of the third switching transistor Q3; the second terminal of the third capacitor Cdc is connected to the anode of the second diode D2, the source of the second switching transistor Q2, and the source of the fourth switching transistor Q4; the cathode of the second diode D2 is connected to the anode of the first diode D1 and the first terminal of the third inductor Lf, and the second terminal of the third inductor Lf is connected to the primary winding of the transformer; the first terminal of the primary winding of the transformer is connected to the first node a, and the second terminal of the primary winding of the transformer is connected to the second node b; the first node a is connected to the source of the first switching transistor Q1 and the drain of the second switching transistor Q2; the second node b is connected to the drain of the fourth switching transistor Q4 and the source of the third switching transistor Q3.

[0006] Optionally, both the first capacitor C01 and the second capacitor C02 are thin-film capacitors.

[0007] Optionally, a voltmeter or ammeter is connected to the first terminal of the third inductor Lf.

[0008] Optionally, the low-voltage LV port is electrically connected to onboard auxiliary equipment and a low-voltage battery.

[0009] Secondly, the present invention provides a control method for a single-stage three-port AC / DC converter, comprising the following steps: Detects whether the AC port is connected to the power grid. When the power grid voltage is detected, it switches to charging mode; otherwise, it switches to LDC independent mode. In charging mode, the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 are switched diagonally with a fixed duty cycle to form an interleaved boost structure; the fifth switch Q5 and the sixth switch Q6 are controlled by 180° phase shift to adjust the phase of the transformer secondary voltage so that the grid voltage and current are in phase, and at the same time adjust the charging power of the high-voltage battery. In LDC independent mode, control the second switching transistor. and the fourth switching transistor When turned on, the circuit is automatically reconfigured into an interleaved buck converter with coupled inductors, and the low-voltage output voltage is controlled by adjusting the duty cycle.

[0010] Optionally, an AC voltage sensor can be used to detect whether the AC port is connected to the power grid.

[0011] Optionally, the formula for adjusting the charging power of the high-voltage battery is:

[0012] Where VCdc is the voltage across the third capacitor Cdc. This is the grid voltage. The angular frequency of the power grid. This is the high-voltage port voltage. The switching angular frequency, The transformer turns ratio This is the equivalent inductance value of the coupled inductor in charging mode.

[0013] Optionally, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 switch diagonally with a fixed duty cycle of 50%.

[0014] Optionally, when adjusting the phase of the secondary voltage of the transformer, the instantaneous phase shift angle is controlled to be half the phase shift ratio multiplied by the sampling period.

[0015] Thirdly, the present invention provides a control system for the control method of the aforementioned single-stage three-port AC / DC converter, comprising: A low-pass filter (LPF) is used to filter the actual low-voltage side voltage V. LV Perform filtering processing; A subtractor is used to convert the low-side voltage setpoint V. * LV and the actual low-voltage side voltage V after being filtered by the low-pass filter LPF LV make a mistake; A PI controller is used to input the difference obtained from the subtractor and output the Buck duty cycle instruction D. buck ; A comparator is used to convert the duty cycle instruction D... buck Compared with the carrier signal, a drive signal is generated to drive the fifth switch Q5 and a complementary drive signal to drive the sixth switch Q6.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention integrates the functions of an on-board charger and a low-voltage DC-DC converter into a single topology, achieving three-port energy exchange through a single AC input port, a high-voltage battery port, and a low-voltage battery port. It eliminates the need for additional AC relays or switching components, reducing the number of semiconductor devices and removing the intermediate DC-DC link of traditional two-stage converters, thus improving system integration and power density. Through single-stage topology integration, reduced electrolytic capacitor count, and dynamic adjustment of the coupled inductor, the system size and weight are reduced, meeting the stringent requirements of lightweight and miniaturized vehicles.

[0017] Furthermore, this invention uses a thin-film capacitor instead of a traditional large-capacity electrolytic capacitor, avoiding the problems of short lifespan and low reliability caused by electrolyte evaporation and high-temperature failure of electrolytic capacitors. This improves the overall reliability and environmental adaptability of the converter, which is beneficial to the long-term stable operation of the vehicle's energy system.

[0018] Furthermore, this invention utilizes the magnetic coupling characteristics of coupled inductors. In charging mode, the current directions of the inductor branches are opposite, resulting in a small equivalent inductance value, making it suitable for dual active bridge (DAB) operation. In LDC independent mode, the current directions are the same, resulting in a large equivalent inductance value, making it suitable for interleaved buck converter requirements. This achieves relay-free adaptive mode switching, avoiding switching delays and fault risks.

[0019] Furthermore, in charging mode, this invention, based on the DAB converter principle, employs a dual-variable modulation strategy of phase shift angle and duty cycle to ensure that the grid voltage and current are in phase, achieving power factor correction (PFC). Simultaneously, it precisely adjusts the charging power of the high-voltage battery to ensure charging efficiency and grid-side power quality. In LDC independent mode, the circuit is automatically reconfigured into an interleaved buck converter with coupled inductors. By adjusting the duty cycle, it stabilizes the low-voltage output voltage, significantly reducing current ripple at the low-voltage port and providing high-quality DC power to vehicle auxiliary equipment (lights, central control system) and the low-voltage battery.

[0020] Furthermore, the control system of the present invention is configured with a dual-mode control strategy: the charging mode adopts a dual-loop PI and Smith-Predictor to overcome the time delay problem, and the LDC independent mode adopts a simple PI control; the AC voltage sensor automatically detects the grid connection status to achieve seamless mode switching without manual operation, ensuring stable operation of the system under different operating conditions. Attached Figure Description

[0021] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely schematic to aid in understanding the invention and do not specifically limit the shapes and proportions of the components. In the drawings: Figure 1 This is a topology diagram of a single-stage three-port AC / DC converter according to an embodiment of the present invention; Figure 2 This is the equivalent circuit of the LDC stand-alone mode in an embodiment of the present invention; Figure 3 This is a magnetic analysis diagram of an embodiment of the present invention; wherein Figure 3 (a) is a magnetic analysis diagram of the charging mode. Figure 3 (b) is the magnetic analysis diagram of LDC standalone mode; Figure 4 This is a schematic diagram of the control system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the control method flow according to an embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0023] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0024] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0025] When an element is referred to as being "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments. The use of the term "horizontal" does not imply that the component is required to be absolutely horizontal, but rather that it may be slightly tilted. "Horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it may be slightly tilted.

[0026] It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be understood that the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof.

[0027] Unless otherwise defined, 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. The terminology used herein in the specification of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] The present invention will now be described in detail with reference to the accompanying drawings.

[0029] The core of the energy system of a light electric vehicle consists of a high-voltage (HV) battery, a low-voltage (LV) battery, an on-board charger (OBC), a low-voltage DC-DC converter (LDC), and a traction inverter (TC). The OBC is responsible for converting AC power from the grid into high-voltage DC power to charge the HV battery, while the LDC converts the high-voltage DC power from the HV battery into low-voltage DC power to power on-board auxiliary equipment (such as headlights and central control systems) and the LV battery. Together, they ensure the vehicle's range and operational stability.

[0030] However, existing energy conversion systems for light electric vehicles still face many technical challenges.

[0031] To address the drawbacks of discrete architectures, the industry has gradually explored multi-port integrated converter solutions, mainly categorized into two-stage and single-stage types. Two-stage multi-port converters require cascading a power factor correction (PFC) stage and a DC-DC stage to achieve energy conversion. While this meets basic power supply requirements, the electrolytic capacitors in the intermediate DC link remain unreplaced, and additional power losses occur during the two-stage conversion process, making it difficult to balance efficiency and reliability. Single-stage multi-port converters, while simplifying the topology and reducing energy conversion stages, still have shortcomings: some topologies rely on multi-winding transformers and numerous power switches, leading to complex control logic and significant engineering challenges; other solutions require additional AC relays to switch operating modes, increasing system complexity and potentially introducing switching delays and fault risks, making them unsuitable for the stringent reliability and integration requirements of light electric vehicles.

[0032] The present invention discloses a single-stage three-port AC / DC converter, comprising: a high-voltage DC power supply HV, a low-voltage terminal LV, a first capacitor C01, a second capacitor C02, a third capacitor Cdc, a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first node a, a second node b, a third node c, a fourth node d, a first inductor L1, a second inductor L2, and a third inductor Lf.

[0033] The positive terminal of the high-voltage DC power supply HV is connected to the first terminal of the first capacitor C01, the drain of the sixth switch Q6, and the drain of the fifth switch Q5; the negative terminal of the high-voltage DC power supply HV is connected to the second terminal of the first capacitor C01, the anode of the fourth diode D4, the anode of the third diode D3, the second terminal of the second capacitor C02, and the negative terminal of the low-voltage terminal LV; the source of the sixth switch Q6 is connected to the fourth node d, and the source of the fifth switch Q5 is connected to the third node c; the fourth node d is connected to the second terminal of the second inductor L2 and the cathode of the fourth diode D4; the third node c is connected to the second terminal of the first inductor L1 and the cathode of the third diode D3; the first terminal of the first inductor L1 is connected to the first terminal of the secondary winding of the transformer, and the second terminal of the secondary winding of the transformer is connected to the first terminal of the second inductor L2; the secondary winding of the transformer is connected to the positive terminal of the low-voltage terminal LV and the first terminal of the second capacitor C02.

[0034] The first terminal of the third capacitor Cdc is connected to the cathode of the first diode D1, the drain of the first switching transistor Q1, and the drain of the third switching transistor Q3; the second terminal of the third capacitor Cdc is connected to the anode of the second diode D2, the source of the second switching transistor Q2, and the source of the fourth switching transistor Q4; the cathode of the second diode D2 is connected to the anode of the first diode D1 and the first terminal of the third inductor Lf, and the second terminal of the third inductor Lf is connected to the primary winding of the transformer; the first terminal of the primary winding of the transformer is connected to the first node a, and the second terminal of the primary winding of the transformer is connected to the second node b; the first node a is connected to the source of the first switching transistor Q1 and the drain of the second switching transistor Q2; the second node b is connected to the drain of the fourth switching transistor Q4 and the source of the third switching transistor Q3.

[0035] The control method for a single-stage three-port AC / DC converter includes the following steps: Detects whether the AC port is connected to the power grid. When the power grid voltage is detected, it switches to charging mode; otherwise, it switches to LDC independent mode. In charging mode, the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 are switched diagonally with a fixed duty cycle to form an interleaved boost structure; the fifth switch Q5 and the sixth switch Q6 are controlled by 180° phase shift to adjust the phase of the transformer secondary voltage so that the grid voltage and current are in phase, and at the same time adjust the charging power of the high-voltage battery. In LDC independent mode, control the second switching transistor. and the fourth switching transistor When turned on, the circuit is automatically reconfigured into an interleaved buck converter with coupled inductors, and the low-voltage output voltage is controlled by adjusting the duty cycle.

[0036] A control system for the control method of a single-stage three-port AC / DC converter according to the present invention includes: A low-pass filter (LPF) is used to filter the actual low-voltage side voltage V. LV Perform filtering processing; A subtractor is used to convert the low-side voltage setpoint V. * LV and the actual low-voltage side voltage V after being filtered by the low-pass filter LPF LV make a mistake; A PI controller is used to input the difference obtained from the subtractor and output the Buck duty cycle instruction D. buck ; A comparator is used to convert the duty cycle instruction D... buck Compared with the carrier signal, a drive signal is generated to drive the fifth switch Q5 and a complementary drive signal to drive the sixth switch Q6.

[0037] This invention integrates the functions of an on-board charger and a low-voltage DC-DC converter into a single topology, achieving three-port energy exchange through a single AC input port, a high-voltage battery port, and a low-voltage battery port. It eliminates the need for additional AC relays or switching components, reducing the number of semiconductor devices and removing the intermediate DC-DC link of traditional two-stage converters, significantly improving system integration and power density. Through single-stage topology integration, reduced electrolytic capacitor count, and dynamic adjustment of the coupled inductor, the system size and weight are reduced, meeting the stringent requirements of lightweight and miniaturized vehicles.

[0038] Example 1 The present invention discloses a single-stage three-port AC / DC converter, comprising: a high-voltage DC power supply HV, a low-voltage terminal LV, a first capacitor C01, a second capacitor C02, a third capacitor Cdc, a first switch Q1, a second switch Q2, a third switch Q3, a fourth switch Q4, a fifth switch Q5, a sixth switch Q6, a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first node a, a second node b, a third node c, a fourth node d, a first inductor L1, a second inductor L2, and a third inductor Lf.

[0039] The positive terminal of the high-voltage DC power supply HV is connected to the first terminal of the first capacitor C01, the drain of the sixth switch Q6, and the drain of the fifth switch Q5; the negative terminal of the high-voltage DC power supply HV is connected to the second terminal of the first capacitor C01, the anode of the fourth diode D4, the anode of the third diode D3, the second terminal of the second capacitor C02, and the negative terminal of the low-voltage terminal LV; the source of the sixth switch Q6 is connected to the fourth node d, and the source of the fifth switch Q5 is connected to the third node c; the fourth node d is connected to the second terminal of the second inductor L2 and the cathode of the fourth diode D4; the third node c is connected to the second terminal of the first inductor L1 and the cathode of the third diode D3; the first terminal of the first inductor L1 is connected to the first terminal of the secondary winding of the transformer, and the second terminal of the secondary winding of the transformer is connected to the first terminal of the second inductor L2; the secondary winding of the transformer is connected to the positive terminal of the low-voltage terminal LV and the first terminal of the second capacitor C02.

[0040] The first terminal of the third capacitor Cdc is connected to the cathode of the first diode D1, the drain of the first switching transistor Q1, and the drain of the third switching transistor Q3; the second terminal of the third capacitor Cdc is connected to the anode of the second diode D2, the source of the second switching transistor Q2, and the source of the fourth switching transistor Q4; the cathode of the second diode D2 is connected to the anode of the first diode D1 and the first terminal of the third inductor Lf, and the second terminal of the third inductor Lf is connected to the primary winding of the transformer; the first terminal of the primary winding of the transformer is connected to the first node a, and the second terminal of the primary winding of the transformer is connected to the second node b; the first node a is connected to the source of the first switching transistor Q1 and the drain of the second switching transistor Q2; the second node b is connected to the drain of the fourth switching transistor Q4 and the source of the third switching transistor Q3.

[0041] This invention constructs a three-port topology including an AC port, a high-voltage DC (HV) port, and a low-voltage DC (LV) port. It integrates two branches of an interleaved buck converter with the secondary branch of a single-stage converter, forming an integrated topology. This topology requires no additional AC relays or components, achieving both AC-DC charging and DC-DC buck conversion functions through natural branch integration. It reduces the number of semiconductor devices and eliminates the intermediate DC link of traditional two-stage converters, simplifying the system structure.

[0042] The AC port is used to connect to the power grid, the HV port is used to connect to the high-voltage battery, and the LV port is used to connect to the low-voltage battery or vehicle auxiliary load.

[0043] Optionally, both the first capacitor C01 and the second capacitor C02 are film capacitors. Using film capacitors as DC-side energy storage elements replaces the large-capacity electrolytic capacitors in traditional two-stage converters, avoiding the inherent defects of short lifespan and high-temperature failure of electrolytic capacitors, thus improving system reliability and power density. A coupling inductor is configured, with its two windings wound on the same iron core, utilizing the magnetic field coupling effect to dynamically adjust the equivalent inductance value.

[0044] Thin-film capacitors are used as DC-side energy storage elements to replace the large-capacity electrolytic capacitors in traditional two-stage converters, avoiding the problems of low reliability and limited power density caused by electrolytic capacitors. A coupled inductor structure is configured, with its windings wound on the same iron core. Utilizing the magnetic field coupling effect, the equivalent inductance value is adjusted by changing the current direction under different modes, specifically satisfying the following relationship: In charging mode, the inductor voltage satisfies: This forms a small inductance adapter for the DAB converter to operate.

[0045] In LDC independent mode, the inductor voltage satisfies: A large inductance is formed to meet the requirements of the interleaved buck converter. Among them, V L1 The voltage across the first inductor L1, , These are the inductance values ​​of the two windings of the coupled inductor. Mutual inductance value, This represents the inductor current.

[0046] The charging mode adopts a bridgeless push-pull AC / DC structure, operating based on the principle of a dual active bridge (DAB) converter. On the primary side, the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 switch diagonally with a fixed duty cycle, forming two interleaved boost converters that generate a voltage across the DC capacitor that satisfies:

[0047] The fifth switch on the secondary side Sixth switch tube Using 180° phase shift control, the transformer secondary voltage Vcd satisfies:

[0048] Design phase shifting Duty cycle The dual-variable modulation strategy adjusts two variables to ensure that the grid voltage and current are in phase, thereby achieving power factor correction. Simultaneously, it regulates the high-voltage battery charging power using the following formula:

[0049] Where VCdc is the voltage across the third capacitor Cdc. This is the grid voltage. The angular frequency of the power grid. This is the high-voltage port voltage. The switching angular frequency, The transformer turns ratio This is the equivalent inductance value of the coupled inductor in charging mode.

[0050] In LDC stand-alone mode, the second switch on the first-stage side is controlled. and the fourth switching transistor When the circuit is turned on, the primary side is short-circuited, the impedance of the secondary side of the transformer becomes zero, and the circuit automatically converts into an interleaved buck converter with coupled inductors. This is achieved by adjusting the duty cycle. Control the low-voltage output voltage to meet the following requirements:

[0051] The high-voltage DC input at the HV power port is converted into low-voltage DC to adapt to the auxiliary system, thereby achieving stable power supply for low-voltage batteries or passive loads; whereby... This is the output voltage of the low-voltage port.

[0052] The charging mode is configured with a dual-loop PI controller. The outer loop uses the HV port voltage as the control target and generates a high-voltage battery current reference value through PI regulation. The inner loop uses a Smith-Predictor PI controller to overcome the time delay problem caused by approximate modeling by controlling the phase shift angle. Adjusting the output power and power flow direction, the phase shift angle satisfies:

[0053] The LDC stand-alone mode configuration uses a simple PI controller, with the LV port voltage as the control target, and adjusts the duty cycle. Stable output voltage. An automatic mode selection mechanism is designed, which detects whether the AC port is connected to the power grid via an AC voltage sensor and automatically switches to the corresponding operating mode, achieving seamless connection; wherein... The sampling period.

[0054] Example 2 like Figure 3 As shown, in charging mode, the currents in the inductor branches are in opposite directions, and the magnetic fluxes in the iron core cancel each other out, so the equivalent inductance satisfies... This allows for the adaptation of the small inductance to the operation of the DAB converter; In LDC independent mode, the inductor branch currents are in the same direction, the core magnetic flux is superimposed, and the equivalent inductance satisfies... This forms a large inductance to meet the requirements of the interleaved buck converter.

[0055] The modulation strategy for the charging mode is designed based on the principle of dual active bridge (DAB) converters, and adopts a bridgeless push-pull AC / DC structure. The specific parameter configuration is shown in Table 1 below: Table 1

[0056] The primary-side switches (Q1, Q2, Q3, and Q4) switch diagonally at a high switching frequency and a 50% duty cycle, forming two interleaved boost converters to generate a voltage across the DC capacitor that satisfies... ; The voltage on the primary side of the transformer meets the requirements. ; The fifth switch Q5 and the sixth switch Q6 on the secondary side are controlled by a 180-degree phase shift, and the voltage on the secondary side of the transformer meets the following requirements: ; Using phase shift angle Duty cycle A bivariate modulation strategy adjusts two variables to ensure the grid voltage and current are in phase, thereby achieving power factor correction. Adjust the charging power of the high-voltage battery to ensure charging efficiency and power quality of the grid.

[0057] In LDC stand-alone mode, the second switch on the first-stage side is controlled. and the fourth switching transistor When the circuit is turned on, the primary side is short-circuited, the impedance of the secondary side of the transformer becomes zero, and the circuit automatically converts into an interleaved buck converter with a coupled inductor. The specific parameter configuration is shown in Table 2 below: Table 2

[0058] By adjusting the duty cycle Control the low-voltage output voltage to meet the requirements. .

[0059] The high-voltage DC input at the HV port is converted into the low-voltage DC required by the LV port to power onboard auxiliary equipment (such as headlights and central control systems) and low-voltage batteries, significantly reducing the current ripple at the low-voltage port.

[0060] The charging mode control is configured with a dual-loop PI controller.

[0061] The outer loop uses the HV port voltage as the control target, and generates a high-voltage battery current reference value through PI regulation based on the deviation between the voltage reference value and the actual value. The inner loop uses a PI Smith-Predictor to overcome the time delay problem caused by approximate modeling by controlling the phase shift angle. Adjusting output power and power flow direction, the phase shift angle satisfies... .

[0062] Two triangular charge carriers on the first stage side , With a 180-degree phase shift and alternation, the modulation signal is fixed at 50%, corresponding to the branch gate drive signal; the secondary side uses triangular carriers... Moving forward Time generation By modulating the signal Compared with the triangular carrier wave, a fifth switching transistor is generated. Sixth switch tube PWM drive pulse.

[0063] LDC stand-alone mode control uses a simple PI controller, with the LV port voltage as the control target, and adjusts the duty cycle according to the voltage deviation. It stabilizes the output voltage, ensuring the stability of power supply to low-voltage loads.

[0064] Automatic mode switching detects whether the AC port is connected to the power grid using an AC voltage sensor: when the grid voltage is detected, it automatically switches to charging mode; when the grid voltage is not detected, it switches to LDC independent mode, achieving seamless connection between the two modes without manual operation.

[0065] Unless otherwise specified, the equipment components involved in the above embodiments are all conventional equipment components, and the structural settings, working methods or control methods involved are all conventional settings, working methods or control methods in the art unless otherwise specified.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A single-stage three-port AC / DC converter, characterized in that, include: High voltage DC power supply HV, low voltage terminal LV, first capacitor C01, second capacitor C02, third capacitor Cdc, first switch Q1, second switch Q2, third switch Q3, fourth switch Q4, fifth switch Q5, sixth switch Q6, first diode D1, second diode D2, third diode D3, fourth diode D4, first node a, second node b, third node c, fourth node d, first inductor L1, second inductor L2, third inductor Lf; The positive terminal of the high-voltage DC power supply HV is connected to the first terminal of the first capacitor C01, the drain of the sixth switch Q6, and the drain of the fifth switch Q5; the negative terminal of the high-voltage DC power supply HV is connected to the second terminal of the first capacitor C01, the anode of the fourth diode D4, the anode of the third diode D3, the second terminal of the second capacitor C02, and the negative terminal of the low-voltage terminal LV; the source of the sixth switch Q6 is connected to the fourth node d, and the source of the fifth switch Q5 is connected to the third node c; the fourth node d is connected to the second terminal of the second inductor L2 and the cathode of the fourth diode D4; the third node c is connected to the second terminal of the first inductor L1 and the cathode of the third diode D3; the first terminal of the first inductor L1 is connected to the first terminal of the secondary winding of the transformer, and the second terminal of the secondary winding of the transformer is connected to the first terminal of the second inductor L2; the secondary winding of the transformer is connected to the positive terminal of the low-voltage terminal LV and the first terminal of the second capacitor C02; The first terminal of the third capacitor Cdc is connected to the cathode of the first diode D1, the drain of the first switching transistor Q1, and the drain of the third switching transistor Q3; the second terminal of the third capacitor Cdc is connected to the anode of the second diode D2, the source of the second switching transistor Q2, and the source of the fourth switching transistor Q4; the cathode of the second diode D2 is connected to the anode of the first diode D1 and the first terminal of the third inductor Lf, and the second terminal of the third inductor Lf is connected to the primary winding of the transformer; the first terminal of the primary winding of the transformer is connected to the first node a, and the second terminal of the primary winding of the transformer is connected to the second node b; the first node a is connected to the source of the first switching transistor Q1 and the drain of the second switching transistor Q2; the second node b is connected to the drain of the fourth switching transistor Q4 and the source of the third switching transistor Q3.

2. The single-stage three-port AC / DC converter according to claim 1, characterized in that, Both the first capacitor C01 and the second capacitor C02 are thin-film capacitors.

3. A single-stage three-port AC / DC converter according to claim 1, characterized in that, A voltmeter and ammeter are connected to the first terminal of the third inductor Lf.

4. A single-stage three-port AC / DC converter according to claim 1, characterized in that, The low-voltage (LV) port is electrically connected to onboard auxiliary equipment and a low-voltage battery.

5. A control method for a single-stage three-port AC / DC converter as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Detects whether the AC port is connected to the power grid. When the power grid voltage is detected, it switches to charging mode; otherwise, it switches to LDC independent mode. In charging mode, the first switch Q1, the second switch Q2, the third switch Q3 and the fourth switch Q4 are switched diagonally with a fixed duty cycle to form an interleaved boost structure; the fifth switch Q5 and the sixth switch Q6 are controlled by 180° phase shift to adjust the phase of the transformer secondary voltage so that the grid voltage and current are in phase, and at the same time adjust the charging power of the high-voltage battery. In LDC independent mode, control the second switching transistor. and the fourth switching transistor When turned on, the circuit is automatically reconfigured into an interleaved buck converter with coupled inductors, and the low-voltage output voltage is controlled by adjusting the duty cycle.

6. The control method for a single-stage three-port AC / DC converter according to claim 5, characterized in that, An AC voltage sensor is used to detect whether the AC port is connected to the power grid.

7. The control method for a single-stage three-port AC / DC converter according to claim 5, characterized in that, The formula for adjusting the charging power of a high-voltage battery is: Where VCdc is the voltage across the third capacitor Cdc. This is the grid voltage. The angular frequency of the power grid. This is the high-voltage port voltage. The switching angular frequency, The transformer turns ratio This is the equivalent inductance value of the coupled inductor in charging mode.

8. The control method for a single-stage three-port AC / DC converter according to claim 5, characterized in that, The first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4 switch diagonally with a fixed duty cycle of 50%.

9. The control method for a single-stage three-port AC / DC converter according to claim 5, characterized in that, When adjusting the phase of the secondary voltage of the transformer, the instantaneous phase shift angle is controlled by multiplying the phase shift by half the sampling period.

10. A control system for a control method of a single-stage three-port AC / DC converter according to any one of claims 5 to 9, characterized in that, include: A low-pass filter (LPF) is used to filter the actual low-voltage side voltage V. LV Perform filtering processing; A subtractor is used to convert the low-side voltage setpoint V. * LV and the actual low-voltage side voltage V after being filtered by the low-pass filter LPF LV make a mistake; A PI controller is used to input the difference obtained from the subtractor and output the Buck duty cycle instruction D. buck ; A comparator is used to convert the duty cycle instruction D... buck Compared with the carrier signal, a drive signal is generated to drive the fifth switch Q5 and a complementary drive signal to drive the sixth switch Q6.

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