Three-phase vehicle-mounted charger hierarchical control method and system based on battery state

Abstract

The invention discloses a three-phase vehicle-mounted charger hierarchical control method and system based on a battery state, and the method comprises the steps: obtaining the battery state data of a vehicle-mounted power battery, the battery state data at least comprising a battery voltage and a battery charge state; determining a charging mode according to the battery voltage and / or the battery charge state; when the charging mode is a first charging mode, controlling the PFC converter to operate in a constant voltage output mode, and executing voltage following control on the bidirectional DC-DC converter based on the battery voltage; and when the charging mode is a second charging mode, executing voltage following control on the PFC converter based on the battery voltage, and controlling the bidirectional DC-DC converter to operate in a constant-frequency or constant-phase output mode at the same time. By setting hierarchical control strategies under different working conditions, the output voltage of the PFC converter is adaptively adjusted, the voltage regulation transformation ratio under different working conditions is optimized, the overall circuit structure is improved, and the charging efficiency of the vehicle-mounted charger within the full working condition range is improved.

Description

Technical Field

[0001] This invention relates to the field of on-board charging control technology, and in particular to a hierarchical control method and system for a three-phase on-board charger based on battery status. Background Technology

[0002] With the increasing popularity of electric vehicles, the on-board charger (OBC), as a key component connecting the AC power grid and the vehicle's power battery, is of paramount importance in terms of performance and efficiency. Currently, mainstream high-power on-board chargers typically employ a two-stage structure consisting of a front-end power factor correction (PFC) stage and a rear-end DC-DC converter (such as an LLC resonant converter or a dual active full-bridge DAB converter).

[0003] During charging, the voltage of the power battery changes with the state of charge (SOC). Existing charging control strategies typically maintain the bus voltage of the front-end PFC output at a constant level (e.g., at 400V or 800V), and then adjust the output voltage through the subsequent DC-DC converter to make the output voltage follow the changes in battery voltage.

[0004] Existing charging control methods suffer from the following problems: The turns ratio of the downstream DC-DC converter needs to accommodate the entire battery charging range. When the battery voltage is high, the voltage conversion ratio required by the downstream DC-DC converter is relatively small. To maintain a bus voltage higher than the rectified grid voltage, the upstream PFC needs to continuously perform boost operations, resulting in unnecessary switching and conduction losses and low energy conversion efficiency. When the battery voltage is low, the voltage conversion ratio required by the downstream DC-DC converter is large, necessitating large-volume voltage regulation components (such as transformers) with high turns ratios, leading to a large footprint and high cost for the on-board charger. Summary of the Invention

[0005] This invention provides a hierarchical control method and system for a three-phase on-board charger based on battery status. By setting hierarchical control strategies under different operating conditions, the output voltage of the PFC converter is adaptively adjusted to solve the problems of low energy conversion efficiency and large voltage regulation ratio in existing charging control methods.

[0006] According to one aspect of the present invention, a hierarchical control method for a three-phase on-board charger based on battery state is provided. The three-phase on-board charger includes a PFC converter and a bidirectional DC-DC converter. The primary side of the bidirectional DC-DC converter is connected to the PFC converter, and the secondary side of the bidirectional DC-DC converter is connected to an on-board power battery. The method includes: acquiring battery state data of the on-board power battery; wherein the battery state data includes at least battery voltage and battery state of charge; determining a charging mode based on the battery voltage and / or the battery state of charge; when the charging mode is a first charging mode, controlling the PFC converter to operate in a constant voltage output mode, and simultaneously performing voltage following control on the bidirectional DC-DC converter based on the battery voltage; when the charging mode is a second charging mode, performing voltage following control on the PFC converter based on the battery voltage, and simultaneously controlling the bidirectional DC-DC converter to operate in a constant frequency or constant phase output mode; the battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

[0007] Optionally, determining the charging mode based on the battery voltage and / or the battery state of charge includes: determining the charging mode as the first charging mode when the battery voltage is less than a preset voltage threshold and / or the battery state of charge is less than a preset state of charge threshold; and determining the charging mode as the second charging mode when the battery voltage is greater than or equal to the preset voltage threshold and / or the battery state of charge is greater than or equal to the preset state of charge threshold.

[0008] Optionally, the preset voltage threshold is greater than or equal to 15%*V. bat-max And less than or equal to 25%*V bat-max Any value of V; wherein, the V bat-max The maximum voltage value of the battery voltage is indicated; the preset state of charge threshold is any value greater than or equal to 15% and less than or equal to 25%.

[0009] Optionally, when the charging mode is the first charging mode, controlling the PFC converter to operate in a constant voltage output mode, and simultaneously performing voltage following control on the bidirectional DC-DC converter based on the battery voltage, includes: acquiring a first target voltage in the constant voltage output mode; wherein the first target voltage is a constant value; adjusting the duty cycle of the drive signals of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the first target voltage; adjusting the switching frequency of the primary-side switch of the bidirectional DC-DC converter, and / or adjusting the phase of the primary / secondary side of the bidirectional DC-DC converter so that the output voltage of the bidirectional DC-DC converter follows the battery voltage.

[0010] Optionally, the first target voltage is greater than or equal to 0.8V. bat And less than or equal to 1.0*V bat Any value of V; where V bat This indicates the rated voltage of the vehicle-mounted power battery.

[0011] Optionally, when the charging mode is the second charging mode, performing voltage following control on the PFC converter based on the battery voltage, and simultaneously controlling the bidirectional DC-DC converter to operate in a constant frequency or constant phase output mode, includes: determining a second target voltage based on the battery voltage; wherein the second target voltage follows the fluctuation of the battery voltage; adjusting the duty cycle of the drive signals of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the second target voltage; controlling the primary-side switch of the bidirectional DC-DC converter to turn on or off based on a preset switching frequency; and adjusting the phase of the secondary-side switch of the bidirectional DC-DC converter based on a multi-phase shift control strategy so that the phase difference between the primary and secondary sides remains constant.

[0012] Optionally, the gain of the bidirectional DC-DC converter satisfies: greater than or equal to 1:1.1, and less than or equal to 1.

[0013] Optionally, the bidirectional DC-DC converter adopts a resonant dual active bridge topology.

[0014] Optionally, the PFC converter adopts a three-phase totem-pole bridgeless PFC topology.

[0015] According to another aspect of the present invention, a hierarchical control system for a three-phase on-board charger based on battery state is provided for executing the aforementioned hierarchical control method for a three-phase on-board charger based on battery state. The three-phase on-board charger includes a PFC converter and a bidirectional DC-DC converter. The primary side of the bidirectional DC-DC converter is connected to the PFC converter, and the secondary side of the bidirectional DC-DC converter is connected to an on-board power battery. The system includes: a data acquisition module for acquiring battery state data of the on-board power battery; wherein the battery state data includes at least battery voltage and battery state of charge; and a hierarchical decision module for determining the charging method based on the battery voltage and / or the battery state of charge. The charging mode; the drive control module is configured to control the PFC converter to operate in constant voltage output mode when the charging mode is the first charging mode, and simultaneously perform voltage follower control on the bidirectional DC-DC converter based on the battery voltage; the drive control module is further configured to perform voltage follower control on the PFC converter based on the battery voltage when the charging mode is the second charging mode, and simultaneously control the bidirectional DC-DC converter to operate in constant frequency or constant phase output mode; the battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

[0016] Compared with the prior art, the technical solution of the present invention has the following advantages: Firstly, global efficiency optimization: When the charging voltage required for charging the vehicle power battery is high (i.e., the second charging mode), the output voltage of the PFC converter is controlled to follow the fluctuation of the battery voltage, and the bidirectional DC-DC converter is made to work at the optimal constant frequency / constant phase point, which greatly reduces the switching loss and conduction loss of the PFC stage. At the same time, the subsequent converter also works in the high efficiency region, thereby significantly improving the overall efficiency of the entire charging system. Secondly, it has high charging reliability: when the charging voltage required for charging the vehicle power battery is low (i.e., the first charging mode), the PFC converter is switched back to the constant voltage output mode of the bus voltage to avoid the bus voltage from continuously maintaining a high voltage value, thus ensuring the reliability and stability of the charging process. At the same time, the transformation ratio of the voltage regulation module is reduced, the circuit structure of the charging system is optimized, and the footprint and production cost are reduced. Third, it reduces stress and losses: In both charging modes, the bus voltage is controlled at a level slightly higher than the battery voltage, rather than a fixed high voltage. This reduces the overall voltage stress on the charging system, which helps to reduce switching losses and EMI, and improves the reliability of the charging system.

[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart of a hierarchical control method for a three-phase on-board charger based on battery state, provided as an embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the topology of a three-phase on-board charger provided in an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of a three-phase on-board charger hierarchical control system based on battery status, provided as an embodiment of the present invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0024] Figure 1The flowchart illustrates a hierarchical control method for a three-phase on-board charger based on battery status, as provided in this embodiment of the invention. The control method provided in this embodiment is applicable to application scenarios of three-phase, high-power on-board chargers.

[0025] Figure 2 This is a schematic diagram of the topology of a three-phase on-board charger provided in an embodiment of the present invention. See also... Figure 2 As shown, the three-phase on-board charger of the present invention includes a PFC converter and a bidirectional DC-DC converter. The primary side of the bidirectional DC-DC converter is connected to the PFC converter, and the secondary side of the bidirectional DC-DC converter is connected to the on-board power battery. The input side of the PFC converter is connected to the AC power grid via a filter circuit, and the output side of the PFC converter is connected to the primary side of the bidirectional DC-DC converter. The phase relationship between the input voltage and input current is adjusted by a combination of power switching transistors (such as MOSFETs) and freewheeling diodes, synchronizing the input current waveform with the input voltage waveform, reducing harmonic pollution and improving system efficiency. The output voltage of the PFC converter is the bus voltage, denoted as V-BUS; the output voltage of the secondary side of the bidirectional DC-DC converter is the charging voltage of the on-board power battery, denoted as V-out.

[0026] In some optional embodiments, the PFC converter of the present invention employs a three-phase totem-pole bridgeless PFC topology. See details below. Figure 2 As shown, the PFC converter of the present invention is provided with a high-frequency arm and a low-frequency arm. The high-frequency arm includes a first power switch Q1, a second power switch Q2, a third power switch Q3, a fourth power switch Q4, a fifth power switch Q5 and a sixth power switch Q6, and the low-frequency arm includes a seventh power switch Q7 and an eighth power switch Q8.

[0027] In some optional embodiments, the bidirectional DC-DC converter of the present invention employs a resonant dual active bridge topology. See, for details. Figure 2As shown, the resonant dual active bridge topology includes a resonant circuit and a dual active bridge (DAB) circuit. The resonant circuit includes a first inductor L1, a first capacitor C1, a transformer T1, a second inductor L2, and a second capacitor C2, forming a CLLLC resonant circuit structure. In this embodiment, the operating state of the resonant circuit can be adjusted by adjusting the operating frequency. The dual active bridge circuit includes a primary-side H-bridge and a secondary-side H-bridge. The primary-side H-bridge includes a ninth power switch Q9, a tenth power switch Q10, an eleventh power switch Q11, and a twelfth power switch Q12. The secondary-side H-bridge includes a thirteenth power switch Q13, a fourteenth power switch Q14, a fifteenth power switch Q15, and a sixteenth power switch Q16. In this embodiment, a multi-phase-shift control strategy can be used to adjust the operating state of the dual active bridge circuit.

[0028] See Figure 1 and Figure 2 As shown, the three-phase on-board charger hierarchical control method based on battery state of the present invention includes the following steps: S1: Obtain battery status data of the vehicle's power battery; Battery state data can be understood as parameters characterizing the energy storage state of a battery. In this embodiment, battery state data includes at least battery voltage and battery state of charge (SOC). SOC is a parameter that measures the ratio of a battery's remaining usable capacity to its fully charged capacity.

[0029] S2: Determine the charging mode based on the battery voltage and / or battery state of charge; The charging mode can be understood as a charging control strategy that adjusts the operating state of the PFC converter and the bidirectional DC-DC converter.

[0030] In this embodiment, determining the charging mode based on battery voltage and / or battery state of charge (SOC) means identifying the charging voltage required for charging the vehicle's power battery based on the battery voltage and / or SOC, and automatically switching the charging mode according to the required charging voltage. Specifically, when the required charging voltage for the vehicle's power battery is low (e.g., the battery voltage is lower than the voltage setting value or the remaining battery charge is lower than the SOC setting value), the charging mode is set to the first charging mode; when the required charging voltage for the vehicle's power battery is high (e.g., the battery voltage is higher than the voltage setting value or the remaining battery charge is higher than the SOC setting value), the charging mode is set to the second charging mode.

[0031] S3: When the charging mode is the first charging mode, control the PFC converter to operate in constant voltage output mode, and at the same time perform voltage follower control on the bidirectional DC-DC converter based on the battery voltage.

[0032] S4: When the charging mode is the second charging mode, the PFC converter is subjected to voltage follower control based on the battery voltage, and the bidirectional DC-DC converter is controlled to operate in constant frequency or constant phase output mode.

[0033] In this embodiment, the battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

[0034] Specifically, in the first charging mode, the charging voltage required for charging the vehicle power battery is relatively low. At this time, the control objective of the charger is to keep the bus voltage V-BUS output by the PFC converter stable, and at the same time, by adjusting the switching frequency of the resonant circuit or the phase of the DAB, make the output voltage V-out of the bidirectional DC-DC converter follow the battery voltage of the vehicle power battery.

[0035] In the second charging mode, the charging voltage required for the vehicle power battery is higher. At this time, the control objective of the charger is to control the bus voltage V-BUS output by the PFC converter to follow the fluctuation of the battery voltage, while controlling the resonant circuit to maintain a constant frequency or the DAB to maintain a constant phase.

[0036] Therefore, the technical solution of this invention switches to the second charging mode when the charging voltage required for charging the vehicle power battery is high. This controls the output voltage of the PFC converter to fluctuate with the battery voltage and allows the bidirectional DC-DC converter to operate at the optimal constant frequency / constant phase point, greatly reducing the switching and conduction losses of the PFC stage. At the same time, the subsequent converter also operates in the high-efficiency region, thereby significantly improving the overall efficiency of the entire charging system. When the charging voltage required for charging the vehicle power battery is low, the system switches to the first charging mode, switching the PFC converter back to the constant voltage output mode of the bus voltage. This avoids the bus voltage from continuously maintaining a high voltage value, ensuring the reliability and stability of the charging process. At the same time, it reduces the transformation ratio of the voltage regulation module, optimizes the circuit structure of the charging system, and reduces the footprint and production cost. By setting a graded control strategy under different operating conditions, the output voltage of the PFC converter is adaptively adjusted, which can optimize the voltage regulation ratio under different operating conditions, improve the overall circuit structure, and improve the charging efficiency of the vehicle charger across the entire operating range.

[0037] In some optional embodiments, determining the charging mode based on the battery voltage and / or the battery state of charge includes: determining the charging mode as a first charging mode when the battery voltage is less than a preset voltage threshold and / or the battery state of charge is less than a preset state of charge threshold; and determining the charging mode as a second charging mode when the battery voltage is greater than or equal to the preset voltage threshold and / or the battery state of charge is greater than or equal to the preset state of charge threshold.

[0038] Among them, the preset voltage threshold and the preset state of charge threshold can be understood as the critical thresholds for classifying the charging voltage required for charging the vehicle power battery.

[0039] Preferably, the preset voltage threshold is any value greater than or equal to 15%*Vbat-max and less than or equal to 25%*Vbat-max; where Vbat-max represents the maximum voltage value of the battery; the preset state of charge threshold is any value greater than or equal to 15% and less than or equal to 25%.

[0040] For example, taking a single parameter preset state of charge threshold as the classification standard, and setting the preset state of charge threshold to 20%, when the detected battery state of charge is less than 20%, the current charging mode of the on-board charger is determined as the first charging mode; when the detected battery state of charge is greater than or equal to 20%, the current charging mode of the on-board charger is determined as the second charging mode.

[0041] Therefore, by setting the voltage threshold and SOC threshold appropriately, a smooth and seamless switching between the two operating modes can be achieved, avoiding impact on the AC grid side and the vehicle's power battery.

[0042] In some optional embodiments, when the charging mode is the first charging mode, the PFC converter is controlled to operate in a constant voltage output mode, and voltage following control is performed on the bidirectional DC-DC converter based on the battery voltage, including: acquiring a first target voltage in the constant voltage output mode; wherein the first target voltage is a constant value; adjusting the duty cycle of the drive signals of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the first target voltage; adjusting the switching frequency of the primary-side switch of the bidirectional DC-DC converter, and / or adjusting the phase of the primary / secondary side of the bidirectional DC-DC converter so that the output voltage of the bidirectional DC-DC converter follows the battery voltage.

[0043] Optionally, the first target voltage is greater than or equal to 0.8V. bat And less than or equal to 1.0*V bat Any value of V; where V bat This indicates the rated voltage of the vehicle's power battery.

[0044] Preferably, the first target voltage is any value greater than or equal to 680V and less than or equal to 750V.

[0045] For example, taking a single parameter preset state of charge threshold as the grading standard, and setting the preset state of charge threshold to 20%, see [example missing]. Figure 2 As shown, the resonant dual active bridge topology includes a resonant circuit and a dual active bridge circuit (DAB). When the SOC is detected to be below 20%, it is determined that the charging voltage required for the current on-board power battery is low. The output voltage V-BUS of the PFC converter is controlled by adjusting the duty cycle of the switching transistors Q1 to Q6 to maintain the output voltage V-BUS of the PFC converter at the first target voltage (e.g., 750V). At the same time, the switching frequency of the primary-side switching transistors Q9 to Q12 of the DAB is adjusted, and / or the switching time of the secondary-side switching transistors Q13 to Q16 of the DAB is adjusted to change the phase difference between the primary and secondary sides to control the output voltage V-out, so that the output voltage V-out follows the battery voltage.

[0046] Therefore, the technical solution of the present invention, in application scenarios where the charging voltage required for vehicle power battery charging is relatively low, avoids maintaining a high voltage value on the bus voltage by switching the PFC converter back to the constant voltage output mode of the bus voltage, thus ensuring the reliability and stability of the charging process. At the same time, it reduces the transformation ratio of the voltage regulation module, optimizes the circuit structure of the charging system, and reduces the footprint and production cost.

[0047] In some optional embodiments, when the charging mode is the second charging mode, voltage follower control is performed on the PFC converter based on the battery voltage, and the bidirectional DC-DC converter is controlled to operate in a constant frequency or constant phase output mode, including: determining a second target voltage based on the battery voltage; wherein the second target voltage follows the fluctuation of the battery voltage; adjusting the duty cycle of the drive signals of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the second target voltage; controlling the primary-side switch of the bidirectional DC-DC converter to turn on or off based on a preset switching frequency; and adjusting the phase of the secondary-side switch of the bidirectional DC-DC converter based on a multi-phase shift control strategy so that the phase difference between the primary and secondary sides remains constant.

[0048] Preferably, the gain of the bidirectional DC-DC converter of the present invention satisfies: greater than or equal to 1:1.1, and less than or equal to 1.

[0049] Optionally, the preset switching frequency can be set to any value greater than or equal to 10KHz and less than or equal to 1MHz.

[0050] For example, taking a single parameter preset state of charge threshold as the grading standard, and setting the preset state of charge threshold to 20%, see [example missing]. Figure 2 As shown, the resonant dual active bridge topology includes a resonant circuit and a dual active bridge circuit (DAB). When the SOC is detected to be greater than or equal to 20%, it is determined that the charging voltage required for the current vehicle power battery is too high. At this time, by adjusting the duty cycle of PFC switches Q1 to Q6, the output voltage V-BUS of the PFC converter is controlled to follow the fluctuation of the battery voltage. The DAB controls the primary-side switches Q9 to Q12 to maintain a constant switching frequency, and then adjusts the phase of the secondary-side switches of the bidirectional DC-DC converter through a multi-phase shift control strategy, so that the secondary-side H-bridge and the primary-side H-bridge maintain a constant phase difference (phase shift angle). During constant phase charging, the phase shift angle remains a fixed value, and the output power is proportional to the phase shift angle. By controlling the phase difference between the fundamental frequency of the primary-side H-bridge output voltage and the fundamental frequency of the secondary-side H-bridge output voltage, the charging power flowing from the primary side to the secondary side is adjusted, keeping the gain between 1:1.1 and 1:1, thus charging the vehicle power battery.

[0051] Therefore, the technical solution of the present invention, in application scenarios where the charging voltage required for vehicle power battery charging is high, controls the output voltage of the PFC converter to follow the fluctuation of the battery voltage, and allows the bidirectional DC-DC converter to operate at the optimal constant frequency or constant phase point, which greatly reduces the switching loss and conduction loss of the PFC stage. At the same time, the subsequent converter also operates in the high-efficiency region, thereby significantly improving the overall efficiency of the entire charging system.

[0052] Based on any of the above embodiments, the present invention also provides a three-phase on-board charger hierarchical control system based on battery state. Figure 3 This is a schematic diagram of a three-phase on-board charger hierarchical control system based on battery state, provided as an embodiment of the present invention. See also... Figure 3As shown, the three-phase on-board charger hierarchical control system based on battery state includes: a data acquisition module 101, used to acquire battery state data of the on-board power battery; wherein, the battery state data includes at least battery voltage and battery state of charge; a hierarchical decision module 102, used to determine the charging mode based on battery voltage and / or battery state of charge; a drive control module 103, used to control the PFC converter to operate in constant voltage output mode when the charging mode is the first charging mode, and simultaneously perform voltage following control on the bidirectional DC-DC converter based on the battery voltage; the drive control module 103 is also used to perform voltage following control on the PFC converter based on the battery voltage when the charging mode is the second charging mode, and simultaneously control the bidirectional DC-DC converter to operate in constant frequency or constant phase output mode; the battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

[0053] Therefore, the three-phase on-board charger hierarchical control system based on battery status provided in this embodiment of the invention is used to execute the three-phase on-board charger hierarchical control method based on battery status provided in any of the above embodiments, and has the corresponding functional modules and beneficial effects of the execution method. The same parts will not be described again.

[0054] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0055] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A hierarchical control method for a three-phase on-board charger based on battery state, characterized in that, The three-phase on-board charger includes a PFC converter and a bidirectional DC-DC converter. The primary side of the bidirectional DC-DC converter is connected to the PFC converter, and the secondary side of the bidirectional DC-DC converter is connected to the on-board power battery. The method includes: Obtain the battery status data of the vehicle power battery; wherein the battery status data includes at least the battery voltage and the battery state of charge; The charging mode is determined based on the battery voltage and / or the battery state of charge. When the charging mode is the first charging mode, the PFC converter is controlled to operate in constant voltage output mode, and voltage follower control is performed on the bidirectional DC-DC converter based on the battery voltage. When the charging mode is the second charging mode, voltage follower control is performed on the PFC converter based on the battery voltage, and the bidirectional DC-DC converter is controlled to operate in constant frequency or constant phase output mode. The battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

2. The hierarchical control method for a three-phase on-board charger based on battery state according to claim 1, characterized in that, The step of determining the charging mode based on the battery voltage and / or the battery state of charge includes: When the battery voltage is less than a preset voltage threshold and / or the battery state of charge is less than a preset state of charge threshold, the charging mode is determined to be the first charging mode. When the battery voltage is greater than or equal to the preset voltage threshold, and / or the battery state of charge is greater than or equal to the preset state of charge threshold, the charging mode is determined to be the second charging mode.

3. The hierarchical control method for a three-phase on-board charger based on battery state according to claim 2, characterized in that, The preset voltage threshold is greater than or equal to 15%*V. bat-max And less than or equal to 25%*V bat-max Any value of V; wherein, the V bat-max This indicates the maximum voltage value of the battery. The preset state of charge threshold is any value greater than or equal to 15% and less than or equal to 25%.

4. The hierarchical control method for a three-phase on-board charger based on battery state according to claim 1, characterized in that, When the charging mode is the first charging mode, the PFC converter is controlled to operate in a constant voltage output mode, and voltage follower control is performed on the bidirectional DC-DC converter based on the battery voltage, including: Obtain the first target voltage under the constant voltage output mode; wherein, the first target voltage is a constant value; Adjust the duty cycle of the drive signal of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the first target voltage; Adjust the switching frequency of the primary-side switch of the bidirectional DC-DC converter, and / or adjust the phase of the primary / secondary side of the bidirectional DC-DC converter so that the output voltage of the bidirectional DC-DC converter follows the battery voltage.

5. The hierarchical control method for a three-phase on-board charger based on battery state according to claim 4, characterized in that, The first target voltage is greater than or equal to 0.8V. bat And less than 1.0*V bat Any value; Among them, V bat This indicates the rated voltage of the vehicle-mounted power battery.

6. The hierarchical control method for a three-phase on-board charger based on battery state according to claim 1, characterized in that, When the charging mode is the second charging mode, voltage follower control is performed on the PFC converter based on the battery voltage, and the bidirectional DC-DC converter is controlled to operate in constant frequency or constant phase output mode, including: A second target voltage is determined based on the battery voltage; wherein the second target voltage fluctuates with the battery voltage. Adjust the duty cycle of the drive signal of each switch in the PFC converter so that the output voltage of the PFC converter is equal to the second target voltage; The primary-side switching transistor of the bidirectional DC-DC converter is turned on or off based on a preset switching frequency. The phase of the secondary-side switch of the bidirectional DC-DC converter is adjusted based on a multi-phase-shift control strategy to keep the phase difference between the primary and secondary sides constant.

7. The hierarchical control method for a three-phase on-board charger based on battery state as described in claim 6, characterized in that, The gain of the bidirectional DC-DC converter satisfies the following condition: greater than or equal to 1:1.1, and less than or equal to 1.

8. The hierarchical control method for a three-phase on-board charger based on battery state according to any one of claims 1-7, characterized in that, The bidirectional DC-DC converter adopts a resonant dual active bridge topology.

9. The hierarchical control method for a three-phase on-board charger based on battery state according to any one of claims 1-7, characterized in that, The PFC converter adopts a three-phase totem pole bridgeless PFC topology.

10. A hierarchical control system for a three-phase on-board charger based on battery state, characterized in that, A method for hierarchical control of a three-phase on-board charger based on battery state, as described in any one of claims 1-9, wherein the three-phase on-board charger includes a PFC converter and a bidirectional DC-DC converter, the primary side of the bidirectional DC-DC converter is connected to the PFC converter, and the secondary side of the bidirectional DC-DC converter is connected to an on-board power battery, the system comprising: The data acquisition module is used to acquire the battery status data of the vehicle power battery; wherein, the battery status data includes at least the battery voltage and the battery state of charge; A hierarchical decision module is used to determine the charging mode based on the battery voltage and / or the battery state of charge. The drive control module is used to control the PFC converter to operate in constant voltage output mode when the charging mode is the first charging mode, and at the same time perform voltage following control on the bidirectional DC-DC converter based on the battery voltage. The drive control module is also used to perform voltage following control on the PFC converter based on the battery voltage when the charging mode is the second charging mode, and at the same time control the bidirectional DC-DC converter to operate in constant frequency or constant phase output mode. The battery voltage value in the first charging mode is less than the battery voltage value in the second charging mode; and / or, the remaining battery capacity in the first charging mode is less than the remaining battery capacity in the second charging mode.

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