A boost charging control method for an electric vehicle

Abstract

This invention proposes a boost charging control method for electric vehicles, relating to the field of electric vehicle charging technology, and applied to a vehicle charging system including a power battery, a DC charging port, an electric drive module, and a boost accessory module. After the vehicle communicates with the DC charging pile, it selects either a boost charging mode or a non-boost charging mode based on a comparison between the rated output voltage of the charging pile and the maximum allowable charging voltage of the power battery. In boost charging mode, boost pre-charging and main boost charging are performed, and mode switching transition judgment, end charging, and charging termination control are executed when corresponding conditions are met. When the active discharge of the DC charging pile exceeds the timeout and the voltage at both ends of the DC charging port is higher than the safety threshold, the boost charging device is controlled to construct an active discharge circuit, improving the continuity, stability, compatibility, and interface safety of electric vehicle boost charging.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle charging technology, and more specifically, to a boost charging control method for electric vehicles. Background Technology

[0002] With the increasing popularity of electric vehicles and the continuous improvement of power battery operating voltage platforms, more and more electric vehicles are adopting high-voltage power battery systems. However, the output voltage levels of existing DC charging piles are not entirely uniform, and some DC charging piles still have relatively low rated output voltages. When the rated output voltage of a DC charging pile is lower than the maximum allowable charging voltage of the power battery, the DC charging pile cannot directly meet the charging needs of the high-voltage power battery, resulting in problems such as vehicle-charging pile voltage mismatch, decreased charging compatibility, and reduced charging efficiency.

[0003] Currently, boost charging for electric vehicle power batteries typically involves reusing motor windings and inverter bridges to boost the DC voltage output from the charging pile, thereby improving the compatibility of low-voltage DC charging piles with high-voltage power batteries. In addition, there are technical solutions that switch between different charging circuits to achieve boost charging, DC fast charging, or other charging methods. For example, CN119408428A discloses a charging control circuit and its control method, which, through the cooperation of a mode switching module, a high-voltage battery pack, and an integrated control module, achieves switching of charging circuits under different charging modes, thereby improving charging speed and expanding the applicability of charging scenarios.

[0004] However, while existing charging solutions have made some progress in circuit structure reuse, multi-mode loop switching, and boost charging implementation, they still have the following shortcomings: Insufficient consideration of phased control throughout the entire boost charging process. Especially in the process where DC charging piles and vehicles jointly complete boost charging, a unified and coordinated control mechanism is often lacking, leading to insufficient connection between different stages of the charging process. The pre-charging stage uses conventional continuous modulation, which is prone to problems such as insufficient voltage regulation accuracy at the DC charging port and large voltage fluctuations across the input capacitor, causing the DC charging pile to misjudge the vehicle's charging conditions, or even fail to properly conduct the charging pile's output circuit. Boost charging devices are prone to problems such as excessively strong control target coupling, unclear mode switching boundaries, and sudden changes in duty cycle leading to fluctuations in the power battery terminal voltage or charging current. Particularly when the system needs to switch between different charging control modes such as constant current, constant voltage, or constant power, the lack of mode switching transition control can easily cause jumps in the duty cycle of the main boost conduction pulse, resulting in charging disturbances and decreased system stability. When the power battery is close to full charge, there is often a lack of dedicated control for the final charging stage. If the modulation method used in the fast charging phase is still adopted, it can easily lead to increased fluctuations in the battery terminal voltage and charging current, which is not conducive to the smooth convergence and full charging of the battery, and will also increase the risk of overcharging and control instability at the end of the charging process. After charging is completed or the charging system stops due to a fault, the residual voltage at the interface is not adequately handled, and there is still a lack of a unified control mechanism that coordinates with the entire boost charging process.

[0005] Therefore, there is an urgent need to propose a boost charging control method for electric vehicles that can achieve coordinated control in various stages, including pre-charging, high-precision voltage regulation, main boost closed-loop regulation, mode switching transition, end-charge convergence, and end of charging, thereby improving the continuity, stability, compatibility, and safety of boost charging. Summary of the Invention

[0006] In view of the problems in the background art, the present invention provides a boost charging control method for electric vehicles, which solves the defects existing in the charging control of electric vehicles in the prior art.

[0007] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A boost charging control method for electric vehicles is applied to a vehicle charging system including a power battery, a DC charging port, an electric drive module, and a boost accessory module, wherein the electric drive module and the boost accessory module together constitute a boost charging device, comprising the following steps: S1: Obtain the rated output voltage of the DC charging pile, and start the boost charging mode or non-boost charging mode according to the comparison result between the rated output voltage and the maximum allowable charging voltage of the power battery. S2: In boost charging mode, a pre-charge target voltage is given, and the pre-charge pulse release interval is adjusted according to the voltage deviation between the input voltage of the boost accessory module and the pre-charge target voltage, so that the voltage across the input capacitor on the DC charging port side enters the neighborhood of the pre-charge target voltage. S3: After pre-charging is completed and the DC charging pile output circuit is turned on, control the boost charging device to work in the main boost mode and perform closed-loop adjustment of the duty cycle of the main boost conduction pulse; S4: During the charging phase of the main boost mode, the duty cycle of the main boost conduction pulse is restricted and adjusted according to whether the boost charging operation parameters enter the mode switching threshold neighborhood and continue to reach the preset confirmation time. S5: When the state of charge (SOC) of the power battery reaches a preset threshold or the terminal voltage of the power battery enters the target charging voltage neighborhood, the final charging stage is entered, and a one-way decreasing constraint is applied to the duty cycle of the main boost conduction pulse. S6: After detecting a charging completion signal or a charging fault shutdown signal, execute the charging end control based on the active discharge timeout judgment result and the voltage at both ends of the DC charging port.

[0008] Preferably, in step S1, the rated output voltage of the DC charging pile is obtained by CAN communication between the controller inside the electric drive module and the DC charging pile; when the rated output voltage is lower than the maximum allowable charging voltage of the power battery, the boost charging mode is started; when the rated output voltage is greater than or equal to the maximum allowable charging voltage of the power battery, the non-boost charging mode is started.

[0009] Preferably, in step S2, in boost charging mode, the controller inside the electric drive module provides the pre-charge target voltage, and the input voltage of the boost accessory module is the voltage across the input capacitor located on the DC charging port side; when the absolute value of the voltage deviation between the input voltage of the boost accessory module and the pre-charge target voltage is greater than the pre-charge deviation threshold, a pre-charge conduction pulse is released in each control cycle; when the absolute value of the voltage deviation is less than or equal to the pre-charge deviation threshold, the pre-charge conduction pulse is released intermittently in multiple consecutive control cycles according to the pre-charge pulse release interval coefficient, so as to reduce the equivalent duty cycle; the equivalent duty cycle is: , D p This refers to the equivalent duty cycle during the pre-charge phase. t on,p The conduction time of the precharge conduction pulse. T p For the pre-charge modulation reference period, N p This is the pre-charge pulse release interval coefficient. N pIt is a positive integer greater than or equal to 1, and the precharge pulse release interval coefficient increases as the absolute value of the voltage deviation between the input voltage of the boost accessory module and the precharge target voltage decreases.

[0010] Preferably, in step S3, the duty cycle of the main boost conduction pulse is adjusted in a closed loop according to at least one of the following: the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and a given target output voltage, target output current, or target output power.

[0011] Preferably, in step S4, when the state of charge (SOC) of the power battery has not reached a preset threshold and the battery terminal voltage has not entered the target charging voltage neighborhood, a mode switching transition judgment stage is entered. In the mode switching transition judgment stage, it is determined whether at least one of the following—the input voltage of the boost accessory module, the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and the SOC of the power battery—has entered the corresponding mode switching threshold neighborhood and has continued to reach a preset confirmation time. If the preset confirmation time has not been reached, the current main boost conduction pulse duty cycle is maintained. If the preset confirmation time is reached, the main boost conduction pulse duty cycle is gradually changed according to a preset slope limit.

[0012] Preferably, during the final charging phase of step S5, the duty cycle of the main boost conduction pulse satisfies a unidirectional decreasing constraint: D b(k+1) ≤D b(k) ; where D b(k) D represents the duty cycle of the main boost conduction pulse in the k-th control cycle. b(k+1) It represents the duty cycle of the main boost conduction pulse in the (k+1)th control cycle.

[0013] Preferably, in step S6, it is determined whether the DC charging pile has exceeded the active discharge timeout; when it is determined that the DC charging pile has exceeded the active discharge timeout and the voltage at both ends of the DC charging port is higher than the safety threshold, the active discharge circuit is started; when the voltage at both ends of the DC charging port is lower than or equal to the safety threshold, the charging process ends.

[0014] Preferably, after starting the active discharge circuit, the corresponding discharge pulse duty cycle is selected based on the voltage difference between the voltage across the DC charging port and the safety threshold; wherein, when the voltage difference is greater than the first discharge threshold, the first discharge pulse duty cycle D is selected. d1 When the voltage difference is less than or equal to the first discharge threshold and greater than the second discharge threshold, the duty cycle D of the second discharge pulse is selected. d2 When the voltage difference is less than or equal to the second discharge threshold, the duty cycle D of the third discharge pulse is selected. d3 And satisfy: D d1 >D d2>D d3 ≥0, the first discharge threshold is greater than the second discharge threshold.

[0015] Preferably, when the non-boost charging mode is activated, steps S2 to S6 are not executed, and the power battery is directly charged by the DC charging pile through the DC charging port.

[0016] The beneficial effects of this invention are as follows: (1) This invention achieves overall coordinated control of the entire process of electric vehicle boost charging by organically combining the boost pre-charging stage, the closed-loop duty cycle adjustment of the main boost stage, the smooth switching of different charging modes, the unidirectional decreasing constraint of the end charging stage, and the active discharge stage at the end of charging. The cooperation of each stage enables the power battery to smoothly transition from low-voltage input pre-charging and stabilization to the main boost closed-loop adjustment and then to the mode switching during the charging process, and finally converge smoothly at the end charging stage. At the same time, the active discharge control ensures the interface safety, thereby significantly improving the charging continuity, stability, compatibility and safety.

[0017] (2) By controlling the output interval of the pre-charge conduction pulse, the voltage across the input capacitor on the DC charging port side is precisely brought into the pre-charge target voltage neighborhood, ensuring the voltage stabilization accuracy of the first stage of boost charging and improving the compatibility of DC charging piles with vehicles and the charging success rate. When switching between different charging modes (constant current, constant voltage, constant power) during the main boost stage, a method of restoring the duty cycle with a preset slope is adopted to achieve a smooth transition between modes, avoid sudden changes, reduce charging disturbances, and enhance the voltage and current continuity at the power battery end.

[0018] (3) When the power battery is close to full charge, the duty cycle of the main boost conduction pulse adopts a unidirectional decreasing constraint, so that the battery smoothly transitions from the fast charging state to the convergent full charge state, improving the accuracy of the charging end, preventing overcharging, and extending the life of the power battery. After charging is completed or the charging fails and the machine stops, the vehicle-side active discharge circuit selects the discharge pulse duty cycle according to the DC charging port voltage in stages to effectively release the residual voltage, ensure interface safety, and coordinate with the control of the aforementioned stages to improve the overall charging safety. Attached Figure Description

[0019] To facilitate understanding of the invention, it will be described in more detail with reference to the specific embodiments shown in the accompanying drawings. These drawings depict only typical embodiments of the invention and should not be considered as limiting the scope of protection of the invention.

[0020] Figure 1 This is a schematic diagram of the electric vehicle charging system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the boost charging device provided in an embodiment of the present invention; Figure 3This is a schematic flowchart of the electric vehicle boost charging control method provided in an embodiment of the present invention. Detailed Implementation

[0021] Embodiments of the present invention are described below with reference to the accompanying drawings to enable those skilled in the art to better understand and implement the invention. However, the listed embodiments are not intended to limit the invention. Unless otherwise specified, the embodiments and technical features described below can be combined with each other, wherein identical components are denoted by the same reference numerals. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0022] Please refer to Figure 1 , Figure 2 as well as Figure 3 , Figure 1 This is a schematic diagram of the electric vehicle charging system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the boost charging device provided in an embodiment of the present invention; Figure 3 This is a schematic flowchart of the electric vehicle boost charging control method provided in an embodiment of the present invention.

[0023] See Figure 1 In this embodiment of the invention, the electric vehicle charging system includes a DC charging port 100, a power battery 200, a bus capacitor 300, an electric drive module 400, and a boost accessory module 500; wherein the electric drive module 400 and the boost accessory module 500 constitute a boost charging device; one end of the electric drive module 400 is connected to the bus capacitor 300, and the other end is connected to the boost accessory module 500; one end of the boost accessory module 500 is connected to the electric drive module 400, and the other end is connected to the DC charging port 100 and the power battery 200; one end of the power battery 200 is connected to the bus capacitor 300, and the other end is connected to the DC charging port 100 and the boost accessory module. Module 500; Electric drive module 400 provides vehicle motor drive and boost power conversion control functions; boost accessory module 500 provides boost circuit on / off, EMI filtering, and boost input current and voltage detection functions; DC charging port 100 is used to connect to an external DC charging pile to provide high-voltage DC power to the vehicle; Power battery 200 is used for high-voltage energy storage and vehicle charging / discharging control, providing power to the vehicle when no external DC charging device is available; Bus capacitor 300 is the sum of the X capacitors of each high-voltage assembly bus port on the vehicle's high-voltage bus, which plays a role in stabilizing the bus voltage and reducing bus voltage ripple.

[0024] See Figure 2In this embodiment of the invention, the boost accessory module 500 includes: an active discharge unit 12, an input current detection unit 20, an input voltage detection unit 22, an input capacitor 32, an EMI filter circuit 80, an input positive relay 91, an output positive relay 92, and an output negative relay 93; one end of the input positive relay 91 is connected to the positive terminal of the DC charging port 100, and the other end is connected to the positive terminal of the input capacitor 32; the active discharge unit 12 is used for releasing the energy of the boost accessory module capacitor, the input voltage detection unit 22 is used for detecting the input voltage of the boost accessory module, the input capacitor 32 is used for current buffering to reduce voltage ripple, the EMI filter circuit 80 provides EMI filtering for the boost charging device, and the input positive relay 91, the output positive relay 92, and the output negative relay 93 are used to control the on / off state of the boost circuit. When the vehicle recognizes the need for boost charging, the input positive relay 91, the output positive relay 92, and the output negative relay 93 are closed; when the vehicle recognizes the need for boost charging, the input positive relay 91, the output positive relay 92, and the output negative relay 93 are turned off.

[0025] Furthermore, the electric drive module 400 includes: an electric drive controller MCU 70, a high-voltage bus current detection unit 11, a high-voltage bus voltage detection unit 21, a high-voltage bus capacitor 31, a three-phase inverter bridge circuit 40, an A-phase electric drive winding 61, a B-phase electric drive winding 62, a C-phase electric drive winding 63, an A-phase current detection unit 51, a B-phase current detection unit 52, and a C-phase current detection unit 53; one end of the high-voltage bus current detection unit 11 is connected to the positive terminal of the bus capacitor 300, and the other end is connected to the positive terminal of the high-voltage bus capacitor 31.

[0026] The high-voltage bus current detection unit 11 is used to detect the current of the electric drive high-voltage bus; the high-voltage bus voltage detection unit 21 is used to detect the high-voltage bus voltage; the high-voltage bus capacitor 31 is the internal high-voltage bus X capacitor of the electric drive module, which plays a role in stabilizing the voltage and reducing voltage ripple; the three-phase inverter bridge circuit 40 is used for the switching operation of the electric drive module for inversion and boost charging; the A-phase current detection unit 51, the B-phase current detection unit 52 and the C-phase current detection unit 53 are used to detect the current of the A-phase electric drive winding 61, the B-phase electric drive winding 62 and the C-phase electric drive winding 63, respectively; the electric drive controller MCU 70 is used to provide functions such as vehicle motor drive control, vehicle CAN communication interaction, internal voltage and current signal acquisition of the boost charging device, active discharge control of the boost charging device, internal high-voltage relay drive of the boost charging device and boost power conversion control drive.

[0027] See Figure 3 In this embodiment of the invention, the boost charging control method for electric vehicles is applied to a vehicle charging system including a power battery, a DC charging port, an electric drive module, and a boost accessory module. The electric drive module and the boost accessory module together constitute a boost charging device, which includes the following steps: S1: Obtain the rated output voltage of the DC charging pile, and start the boost charging mode or non-boost charging mode based on the comparison result between the rated output voltage and the maximum allowable charging voltage of the power battery. In step S1, the controller inside the electric drive module communicates with the DC charging pile via CAN to obtain the rated output voltage of the DC charging pile; when the rated output voltage is lower than the maximum allowable charging voltage of the power battery, the boost charging mode is started; when the rated output voltage is greater than or equal to the maximum allowable charging voltage of the power battery, the non-boost charging mode is started.

[0028] S2: In boost charging mode, a pre-charge target voltage is given, and the pre-charge pulse release interval is adjusted according to the deviation between the input voltage of the boost accessory module and the pre-charge target voltage, so that the voltage across the input capacitor on the DC charging port side enters the neighborhood of the pre-charge target voltage. In step S2, in boost charging mode, the controller inside the electric drive module provides a pre-charge target voltage, and the input voltage of the boost accessory module is the voltage across the input capacitor located on the DC charging port side. When the absolute value of the voltage deviation between the input voltage of the boost accessory module and the pre-charge target voltage is greater than the pre-charge deviation threshold, a pre-charge conduction pulse is released in each control cycle. When the absolute value of the voltage deviation is less than or equal to the pre-charge deviation threshold, the pre-charge conduction pulse is released intermittently in multiple consecutive control cycles according to the pre-charge pulse release interval coefficient, so as to reduce the equivalent duty cycle. The equivalent duty cycle is: , D p This refers to the equivalent duty cycle during the pre-charge phase. t on,p The conduction time of the precharge conduction pulse. T p For the pre-charge modulation reference period, N p This is the pre-charge pulse release interval coefficient. N p It is a positive integer greater than or equal to 1, and the precharge pulse release interval coefficient increases as the absolute value of the voltage deviation between the input voltage of the boost accessory module and the precharge target voltage decreases.

[0029] S3: After pre-charging is completed and the DC charging pile output circuit is turned on, control the boost charging device to work in the main boost mode and perform closed-loop adjustment of the duty cycle of the main boost conduction pulse; In step S3, the duty cycle of the main boost conduction pulse is adjusted in a closed loop according to the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and at least one of the given target output voltage, target output current, or target output power.

[0030] S4: During the charging phase of the main boost mode, the duty cycle of the main boost conduction pulse is restricted and adjusted according to whether the boost charging operation parameters enter the mode switching threshold neighborhood and continue to reach the preset confirmation time. In step S4, when the state of charge (SOC) of the power battery does not reach the preset threshold and the battery terminal voltage does not enter the target charging voltage neighborhood, a mode switching transition judgment stage is entered. In the mode switching transition judgment stage, it is determined whether at least one of the following—the input voltage of the boost accessory module, the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and the SOC of the power battery—has entered the corresponding mode switching threshold neighborhood and has been continuously maintained for a preset confirmation time. If the preset confirmation time has not been continuously maintained, the current main boost conduction pulse duty cycle is maintained. If the preset confirmation time is continuously maintained, the main boost conduction pulse duty cycle is gradually changed according to a preset slope limit.

[0031] S5: When the state of charge (SOC) of the power battery reaches a preset threshold or the terminal voltage of the power battery enters the target charging voltage neighborhood, the final charging stage is entered, and a one-way decreasing constraint is applied to the duty cycle of the main boost conduction pulse. During the final charging phase of step S5, the duty cycle of the main boost conduction pulse satisfies a unidirectional decreasing constraint: D b(k+1) ≤D b(k) ; where D b(k) D represents the duty cycle of the main boost conduction pulse in the k-th control cycle. b(k+1) It represents the duty cycle of the main boost conduction pulse in the (k+1)th control cycle.

[0032] S6: After detecting a charging completion signal or a charging fault shutdown signal, execute the charging end control based on the active discharge timeout judgment result and the voltage at both ends of the DC charging port; In step S6, it is determined whether the DC charging pile has exceeded the active discharge timeout. When it is determined that the DC charging pile has exceeded the active discharge timeout and the voltage across the DC charging port is higher than the safety threshold, the active discharge circuit is activated. When the voltage across the DC charging port is lower than or equal to the safety threshold, the charging process ends. After activating the active discharge circuit, the corresponding discharge pulse duty cycle is selected based on the voltage difference between the voltage across the DC charging port and the safety threshold. Specifically, when the voltage difference is greater than the first discharge threshold, the first discharge pulse duty cycle D is selected. d1 When the voltage difference is less than or equal to the first discharge threshold and greater than the second discharge threshold, the duty cycle D of the second discharge pulse is selected. d2 When the voltage difference is less than or equal to the second discharge threshold, the duty cycle D of the third discharge pulse is selected. d3 And satisfy: D d1 >D d2 >D d3≥0, meaning the first discharge threshold is greater than the second discharge threshold. By selecting different discharge pulse duty cycles for different voltage ranges, it is possible to ensure the discharge speed while avoiding voltage fluctuations caused by excessively rapid discharge when the interface voltage approaches the safety threshold, thereby improving interface safety and system reliability after charging is completed.

[0033] Furthermore, during the main boost charging stage, the boost charging device operates in boost mode. The MCU (Microcontroller Unit) adjusts the duty cycle of the main boost conduction pulse in the three-phase inverter bridge circuit in a closed loop based on the detection results of the input current of the boost accessory module, the output voltage of the boost charging device, and the output current of the boost charging device. This achieves tracking control of at least one of the target output voltage, target output current, or target output power during the battery charging process. The main boost conduction pulse duty cycle refers to the PWM modulation duty cycle output by the MCU to the switching transistors of the three-phase inverter bridge circuit. Its variation is used to adjust the inductor energy storage of the boost power converter and the release of energy to the high-voltage bus.

[0034] Furthermore, when the DC charging pile operates in constant voltage output mode, the main boost charging stage preferably employs a closed-loop regulation method with output current deviation as the primary adjustment variable, ensuring that the output current of the boost charging device tracks the target output current given by the controller. When the DC charging pile operates in constant current output mode, the main boost charging stage preferably employs a closed-loop regulation method with output voltage deviation and / or DC charging port voltage deviation as the primary adjustment variables, ensuring that the output voltage of the boost charging device tracks the target output voltage given by the controller and suppressing input voltage fluctuations. Through these methods, the control objectives on the DC charging pile side and the power battery side are decoupled during the main boost charging stage, thereby reducing system control complexity and improving system stability.

[0035] Furthermore, in one embodiment, the main boost charging stage employs a control structure combining inner and outer loop control of the inductor current. The outer loop generates an inductor current reference value based on the error between the target output and the feedback output. The inner loop generates a PWM modulation control quantity based on the error between the inductor current reference value and the inductor current feedback value, which is then converted into the duty cycle of the main boost conduction pulse by a PWM modulator. Since the inner loop has a faster response speed than the outer loop, it can improve the system's dynamic response speed and disturbance rejection capability, while the outer loop is used to improve the output steady-state accuracy and system stability.

[0036] Furthermore, after charging is completed or the system malfunctions and stops, if the active discharge of the DC charging pile times out and the voltage across the DC charging port is still higher than the safety threshold, the vehicle enters the active discharge phase. During the active discharge phase, the boost charging device is controlled to construct an active discharge circuit on the DC charging port side, and different levels of discharge pulse duty cycles are selected based on the voltage difference between the voltage across the DC charging port and the safety threshold to achieve phased discharge of the residual voltage at the interface.

[0037] Furthermore, when the non-boost charging mode is activated, the vehicle charging system does not enter the boost charging mode branch. Therefore, the boost pre-charging, main boost, mode switching transition judgment, end charging, and charging end control process under the boost branch defined in steps S2 to S6 are not executed. Instead, the DC charging pile directly charges the power battery through the DC charging port. When the non-boost charging mode ends, the charging end process is completed according to the conventional shutdown and safety confirmation process between the DC charging pile and the vehicle charging system.

[0038] Further, during the charging phase of the main boost mode in step S3, the controller prioritizes requesting the DC charging pile to operate in the pile-side constant current output mode. When an overcurrent fault or undervoltage fault occurs during the charging start-up process of the pile-side constant current output mode, resulting in charging failure, the controller records the corresponding DC charging pile's device identification code and failure mode. Upon re-identifying the same device identification code, the controller requests the DC charging pile to operate in the pile-side constant voltage output mode. When charging fails in the pile-side constant voltage output mode, the controller records the corresponding DC charging pile's device identification code and failure mode. Upon re-identifying the same device identification code, the controller determines the pile-side output request mode based on the recorded failure mode. Specifically, after entering the mode switching transition judgment phase corresponding to step S4, when the input voltage V of the boost accessory module... i Boost accessory module input current i ch 1. Output voltage V of boost charging device o , Boost charging device output current i oWhen at least one of the State of Charge (SOC) of the power battery enters the mode switching threshold neighborhood and continues to do so for a preset confirmation time, the corresponding charging control mode switch is executed; when the output voltage of the boost charger enters the target output voltage neighborhood, after completing the transition control, the boost charger constant current output mode is switched to the boost charger constant voltage output mode; when the input voltage of the boost accessory module enters the preset voltage regulation range, after completing the transition control, the boost charger constant voltage output mode or the boost charger constant current output mode is switched to the boost charger constant power mode; when the output current of the boost charger enters the target output current neighborhood, after completing the transition control, the boost charger constant voltage output mode is switched to the boost charger constant current output mode; when the SOC of the power battery reaches the preset threshold or the power battery terminal voltage enters the target charging voltage neighborhood, the final charging stage corresponding to step S5 is entered. It should be noted that "entering the mode switching threshold neighborhood" refers to the state where the deviation of the corresponding physical quantity from its mode switching threshold falls within the preset range. In practical applications, the deviation range can be set according to different physical quantities, and can be in the form of absolute deviation or relative deviation. For example, the voltage deviation range is a certain percentage of the rated value; the current deviation range is a certain percentage of the target value; or it can be adaptively set according to the system stability requirements.

[0039] Furthermore, in another embodiment, the recovery slope of the duty cycle of the main boost conduction pulse satisfies: ;in, D b The duty cycle of the main boost conduction pulse. S b The duty cycle recovery slope is set to an upper limit. By constraining the rate of change of the main boost conduction pulse duty cycle, the disturbances to the charging voltage and current of the power battery during the charging mode switching phase can be effectively suppressed, improving the smoothness of the mode switching process and the stability of system control. The corresponding mode switching condition can be determined based on at least one of the following: input voltage, input current, output voltage, output current, and power battery state of charge (SOC) entering the neighborhood of the mode switching threshold. During the mode switching transition judgment phase in step S4, the main boost conduction pulse duty cycle is adjusted according to the preset slope only when the mode switching condition continues to reach the preset confirmation time; the slope of the main boost conduction pulse duty cycle satisfies: .

[0040] Further, in step S2, the buck pre-charge mode corresponds to the boost charging device operating in buck mode, where the power battery charges the input capacitor in the boost accessory module. The controller provides the pre-charge target voltage and controls the boost charging device to operate in buck pre-charge mode; based on the input voltage V of the boost accessory module... iThe voltage deviation between the voltage and the pre-charge target voltage is used to adjust the output interval of the pre-charge turn-on pulse, so that the voltage across the input capacitor located on the DC charging port side reaches the pre-charge target voltage; wherein, the input voltage V of the boost accessory module... i The voltage across the input capacitor; when the input voltage V of the boost accessory module... i When the pre-charge target voltage is reached, the pre-charge mode ends and the process proceeds to step S3.

[0041] Furthermore, during the boost charging process, when the boost charging device switches from one charging control mode to another, a mode switching transition judgment stage is set to avoid overshoot or oscillation of the charging voltage and charging current at the power battery terminal caused by sudden changes in the duty cycle of the main boost conduction pulse. During the mode switching transition judgment stage, the current duty cycle of the main boost conduction pulse remains unchanged until the corresponding mode switching condition is met; after the corresponding mode switching condition is met, the duty cycle of the main boost conduction pulse is not modified by abrupt change, but is gradually restored according to a preset slope, so that the duty cycle of the main boost conduction pulse smoothly transitions to the duty cycle trajectory corresponding to the switched control mode.

[0042] Furthermore, when the state of charge (SOC) of the power battery reaches a preset threshold or the battery terminal voltage enters the neighborhood of the target charging voltage, the boost charging device switches from the main boost charging stage to the final charging stage. During the final charging stage, to ensure the power battery transitions from a fast charging state to a stable, fully charged state, a unidirectional decreasing constraint is applied to the duty cycle of the main boost conduction pulse. That is, within a continuous control cycle, the duty cycle of the main boost conduction pulse remains constant or gradually decreases to limit the continued rapid input of energy to the power battery, reducing output oscillations and the risk of overcharging during the final stage.

[0043] Furthermore, in yet another embodiment, the duty cycle of the main boost conduction pulse during the final charging phase satisfies: D b(k+1) ≤D b(k) ; where D b(k) D represents the duty cycle of the main boost conduction pulse in the k-th control cycle. b(k+1) This represents the duty cycle of the main boost conduction pulse in the (k+1)th control cycle. Preferably, when the deviation of the power battery terminal voltage and / or the deviation of the boost charging device output current exceeds the preset allowable bandwidth, the unidirectional decreasing constraint is released so that the controller can increase the duty cycle adjustment freedom again, preventing the accumulation of control errors caused by excessive constraints. Through the above-mentioned end-charging mode, the power battery charging process can smoothly transition to the convergent fully charged state, improving the charging stability under high charge conditions.

[0044] It is worth noting that this invention achieves overall coordinated control of the entire electric vehicle boost charging process by organically combining the boost pre-charging stage, the closed-loop duty cycle adjustment of the main boost stage, the smooth switching of different charging modes, the unidirectional decreasing constraint of the end charging stage, and the active discharge stage at the end of charging. The cooperation of each stage ensures a smooth transition of the power battery from low-voltage input pre-charging stabilization to main boost closed-loop adjustment, and then to mode switching, ultimately converging smoothly at the end of the charging stage. Simultaneously, active discharge control ensures interface safety, thereby significantly improving charging continuity, stability, compatibility, and safety. By controlling the output interval of the pre-charging conduction pulse, the voltage across the input capacitor on the DC charging port side accurately reaches the pre-charging target voltage, ensuring the voltage stabilization accuracy of the initial boost charging stage and improving the compatibility of the DC charging pile with the vehicle and the charging success rate. When switching between different charging modes (constant current, constant voltage, constant power) during the main boost stage, a method of restoring the duty cycle with a preset slope is used to achieve a smooth mode transition, avoid abrupt changes, reduce charging disturbances, and enhance the voltage and current continuity at the power battery end. During the near-full charge phase of the power battery, the duty cycle of the main boost pulse adopts a unidirectional decreasing constraint, allowing the battery to smoothly transition from a fast charging state to a convergent fully charged state. This improves the accuracy of the charging end, prevents overcharging, and extends the battery life. After charging is complete or the battery stops due to a charging fault, the vehicle-side active discharge circuit selects the discharge pulse duty cycle according to the DC charging port voltage levels to effectively release residual voltage, ensuring interface safety. This, combined with the control of the aforementioned stages, enhances overall charging safety. Through the organic combination of the pre-charge stage, main boost stage, mode switching transition, and final charging stage, the synchronous optimization of fast charging and safety protection of the power battery is achieved. Duty cycle adjustment, mode switching, and final charging work together to significantly reduce charging losses, suppress voltage and current disturbances, and ensure the stability and reliability of the charging process. The various charging stages and mode switching steps cooperate to form a complete closed-loop regulation and control system, thereby achieving improved charging efficiency, suppression of current and voltage disturbances, and improved charging process stability while ensuring charging safety.

[0045] The embodiments in this invention are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. The embodiments described above are merely preferred embodiments of this invention. The terms "in one embodiment," "in another embodiment," "in yet another embodiment," or "in other embodiments" used in this specification can all refer to one or more of the same or different embodiments according to this disclosure. Ordinary variations and substitutions made by those skilled in the art within the scope of the technical solutions of this invention should be included within the protection scope of this invention.

Claims

1. A boost charging control method of an electric vehicle, applied to a vehicle charging system comprising a power battery, a direct current charging port, an electric drive module and a boost accessory module, the electric drive module and the boost accessory module jointly constituting a boost charging device, characterized in that, Includes the following steps: S1: Obtain the rated output voltage of the DC charging pile, and start the boost charging mode or non-boost charging mode according to the comparison result between the rated output voltage and the maximum allowable charging voltage of the power battery. S2: In boost charging mode, a pre-charge target voltage is given, and the pre-charge pulse release interval is adjusted according to the voltage deviation between the input voltage of the boost accessory module and the pre-charge target voltage, so that the voltage across the input capacitor on the DC charging port side enters the neighborhood of the pre-charge target voltage. S3: After pre-charging is completed and the DC charging pile output circuit is turned on, control the boost charging device to work in the main boost mode and perform closed-loop adjustment of the duty cycle of the main boost conduction pulse; S4: During the charging phase of the main boost mode, the duty cycle of the main boost conduction pulse is restricted and adjusted according to whether the boost charging operation parameters enter the mode switching threshold neighborhood and continue to reach the preset confirmation time. S5: When the state of charge (SOC) of the power battery reaches a preset threshold or the terminal voltage of the power battery enters the target charging voltage neighborhood, the final charging stage is entered, and a one-way decreasing constraint is applied to the duty cycle of the main boost conduction pulse. S6: After detecting a charging completion signal or a charging fault shutdown signal, execute the charging end control based on the active discharge timeout judgment result and the voltage at both ends of the DC charging port; In step S2, in boost charging mode, the controller inside the electric drive module provides the pre-charge target voltage, and the input voltage of the boost accessory module is the voltage across the input capacitor located on the DC charging port side; when the absolute value of the voltage deviation between the input voltage of the boost accessory module and the pre-charge target voltage is greater than the pre-charge deviation threshold, a pre-charge turn-on pulse is released in each control cycle; when the absolute value of the voltage deviation is less than or equal to the pre-charge deviation threshold, the pre-charge turn-on pulse is released intermittently in multiple consecutive control cycles according to the pre-charge pulse release interval coefficient, so as to reduce the equivalent duty cycle; the equivalent duty cycle is: , D p This refers to the equivalent duty cycle during the pre-charge phase. t on,p The on-time of the pre-charge turn-on pulse. T p For the pre-charge modulation reference period, N p This is the precharge pulse release interval coefficient. N p It is a positive integer greater than or equal to 1, and the precharge pulse release interval coefficient increases as the absolute value of the voltage deviation between the input voltage of the boost accessory module and the precharge target voltage decreases.

2. The boost charging control method for electric vehicles according to claim 1, characterized in that, In step S1, the controller inside the electric drive module communicates with the DC charging pile via CAN to obtain the rated output voltage of the DC charging pile; when the rated output voltage is lower than the maximum allowable charging voltage of the power battery, the boost charging mode is started; when the rated output voltage is greater than or equal to the maximum allowable charging voltage of the power battery, the non-boost charging mode is started.

3. The boost charging control method of an electric vehicle according to claim 1, characterized by, In step S3, the duty cycle of the main boost conduction pulse is adjusted in a closed loop according to the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and at least one of the given target output voltage, target output current, or target output power.

4. The boost charging control method of an electric vehicle according to claim 1, characterized by, In step S4, when the state of charge (SOC) of the power battery does not reach the preset threshold and the voltage of the power battery terminal does not enter the target charging voltage neighborhood, the mode switching transition judgment stage is entered; in the mode switching transition judgment stage, it is determined whether at least one of the input voltage of the boost accessory module, the input current of the boost accessory module, the output voltage of the boost charging device, the output current of the boost charging device, and the state of charge (SOC) of the power battery enters the corresponding mode switching threshold neighborhood and continues to reach the preset confirmation time. If the preset confirmation time is not reached, the current main boost conduction pulse duty cycle is maintained. If the preset confirmation time is reached continuously, the duty cycle of the main boost conduction pulse will be gradually changed according to the preset slope limit.

5. The boost charging control method of an electric vehicle according to claim 1, characterized by, At the end of the charging phase of step S5, the main boost on-pulse duty cycle satisfies the unidirectional decreasing constraint: D b(k+1) ≤ D b(k) ; Wherein, D b(k) is the main boost conduction pulse duty ratio of the kth control cycle, D b(k+1) is the main boost conduction pulse duty ratio of the k+1th control cycle.

6. The boost charging control method of an electric vehicle according to claim 1, characterized by, In step S6, it is determined whether the DC charging pile has exceeded the active discharge timeout; when it is determined that the DC charging pile has exceeded the active discharge timeout and the voltage at both ends of the DC charging port is higher than the safety threshold, the active discharge circuit is started; when the voltage at both ends of the DC charging port is lower than or equal to the safety threshold, the charging process ends.

7. The boost charging control method of an electric vehicle according to claim 6, characterized by, After activating the active discharge circuit, the corresponding discharge pulse duty cycle is selected based on the voltage difference between the voltage across the DC charging port and the safety threshold; wherein, when the voltage difference is greater than the first discharge threshold, the first discharge pulse duty cycle D is selected. d1 When the voltage difference is less than or equal to the first discharge threshold and greater than the second discharge threshold, the duty cycle D of the second discharge pulse is selected. d2 When the voltage difference is less than or equal to the second discharge threshold, the duty cycle D of the third discharge pulse is selected. d3 And satisfy: D d1 >D d2 >D d3 ≥0, the first discharge threshold is greater than the second discharge threshold.

8. The boost charging control method of an electric vehicle according to claim 1, characterized by, When the non-boost charging mode is started, steps S2 to S6 are not performed, and the power battery is directly charged by the direct current charging post through the direct current charging port.

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