A boost charging system for electric vehicles

Abstract

This invention proposes a boost charging system for electric vehicles, relating to the field of electric vehicle charging technology. The system includes a power battery, a DC charging port, a bus capacitor, and a boost charging device. The boost charging device includes an electric drive module and a boost accessory module, wherein the three-phase inverter bridge and electric drive winding in the electric drive module effectively form a boost inductor during the boost charging process. By constructing a multi-objective control model, output voltage, output current, input voltage, and input current are incorporated into the same control framework. Switching and continuous transitions between constant voltage input / constant voltage output mode, constant voltage input / constant current output mode, constant current input / constant voltage output mode, constant current input / constant current output mode, and constant current input / voltage stable mode are achieved by adjusting the control weight coefficients. This system can achieve multiple control modes without changing the power topology, adapting to the charging requirements of different DC charging piles, and exhibiting high stability during the charging process.

Description

Technical Field

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

[0002] With the rapid development of electric vehicles, DC charging technology has become an important means to improve vehicle charging efficiency. Currently, electric vehicles typically charge their batteries using DC charging stations. When the output voltage of the charging station is lower than the voltage required by the battery, boost charging technology is needed to meet the battery's charging demands.

[0003] Existing boost charging systems typically construct a boost power conversion path through the inverter bridge circuit and motor windings in the electric drive module, making the motor windings equivalent to boost inductors to achieve the boost conversion of the DC charging pile's output voltage. In terms of control methods, constant voltage or constant current control strategies are mostly adopted, switching between different control modes according to the charging stage or operating conditions. However, existing control methods typically construct independent control loops for output voltage or output current, lacking a unified coordination mechanism between different control objectives. This easily leads to coupling interference during the control process, affecting system stability. Secondly, during the switching between different charging modes, discrete switching methods are usually adopted. When switching from constant current charging to constant voltage charging or vice versa, sudden changes in voltage or current can easily occur, affecting the charging safety and stability of the power battery. In addition, existing boost charging control methods have limited adaptability to the output characteristics of DC charging piles. When the charging pile operates in different output modes (such as constant voltage output or constant current output) or the output capacity changes, existing control strategies are difficult to adjust in time, resulting in poor charging compatibility and even charging failure. Different control modes are usually designed or implemented independently, lacking a unified control framework, resulting in complex system structure, poor control strategy scalability, and difficulty in achieving multi-mode coordinated control under complex operating conditions.

[0004] Therefore, there is an urgent need for a new boost charging system and control method that can achieve coordinated adjustment of multiple control objectives under a unified control framework and can achieve continuous transition between different control modes, so as to improve the system's stability, adaptability and charging success rate. Summary of the Invention

[0005] In view of the problems in the background art, the present invention provides a boost charging system for electric vehicles, which solves the defects existing in the electric vehicle charging system in the prior art.

[0006] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A boost charging system for electric vehicles includes a power battery, a DC charging port, a bus capacitor, and a boost charging device. The boost charging device includes an electric drive module and a boost accessory module. The electric drive module is connected to the power battery through the bus capacitor, and the boost accessory module is connected to the DC charging port. The electric drive module includes a three-phase inverter bridge, A-phase, B-phase, and C-phase electric drive windings connected to the three-phase inverter bridge, and a controller. During the boost charging process, the A-phase, B-phase, and C-phase electric drive windings effectively form a boost inductor. The controller internally establishes a unified multi-objective control model to determine the reference value of the boost inductor current based on the power battery side voltage, power battery charging current, DC charging port input voltage, and DC charging port input current, according to the following relationship: ; in, This is a reference value for the boost inductor current; This refers to the voltage on the power battery side. The charging current for the power battery; Input voltage to the DC charging port; Input current to the DC charging port; This is the target voltage reference value for the power battery side; This is a reference value for the target charging current on the power battery side. The target reference value for the DC charging port input voltage; K1, K2, K3, and K4 are the target reference values ​​for the DC charging port input current; K1, K2, K3, and K4 are control weighting coefficients. The controller controls the boost inductor current by adjusting the duty cycle of the three-phase inverter bridge, and achieves any one of the following five modes by adjusting the control weighting coefficients K1, K2, K3, and K4, while keeping the boost power path structure unchanged: constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode, and constant current input voltage stabilization mode; and achieves continuous transition between different control modes. The control weight coefficients K1, K2, K3, and K4 are non-negative real numbers; in the steady-state operation of the five modes, two of the control weight coefficients are greater than zero, and the other two are equal to zero.

[0007] Preferably, when the control weight coefficients satisfy K1>0, K2=0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant current output mode. When the control weight coefficients satisfy K1>0, K2=0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant current output mode; When the control weight coefficients satisfy K1=0, K2=0, K3>0, K4>0, the controller enables the boost charging device to operate in the input constant current input voltage stable mode.

[0008] Preferably, the control weight coefficients K1, K2, K3, and K4 are dynamically adjusted based on at least one of the following parameters: state of charge (SOC) of the power battery, voltage deviation of the power battery side, charging current deviation of the power battery, input voltage deviation of the DC charging port, and input current deviation of the DC charging port.

[0009] Preferably, the control weighting coefficients K1, K2, K3, and K4 are continuously varying parameters to enable a continuous transition between the constant voltage input constant voltage output mode, the constant voltage input constant current output mode, the constant current input constant voltage output mode, the constant current input constant current output mode, and the constant current input voltage stabilization mode.

[0010] Preferably, the A-phase, B-phase, and C-phase electric drive windings are coordinated and controlled according to a preset phase relationship under synchronous control to suppress motor torque fluctuations during the boost charging process.

[0011] Preferably, the boost accessory module includes an input current detection unit and an input voltage detection unit. The controller periodically updates the unified multi-objective control model by collecting the power battery side voltage, power battery charging current, DC charging port input voltage, and DC charging port input current, so as to achieve stable charging of the power battery under different DC charging pile output conditions.

[0012] A boost charging control method, applied to the above-mentioned boost charging system, includes the following steps: S1: During the charging process, the DC charging port input voltage and the maximum allowable voltage of the power battery are collected. When the DC charging port input voltage is lower than the maximum allowable voltage of the power battery, the boost charging control process is started. Otherwise, the current charging state is maintained and the DC charging port input voltage is checked cyclically to determine whether the boost start condition is met. S2: After starting the boost charging control process, the target control mode of the boost charging device is determined according to the current status of the DC charging port and the charging condition of the power battery. This includes constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode, and constant current input voltage stabilization mode. S3: Based on the target control mode and the real-time collected power battery side voltage, power battery charging current, DC charging port input voltage and DC charging port input current, a unified multi-target control model is established inside the controller to calculate the reference value of the boost inductor current. S4: Based on the calculated reference value and real-time charging conditions, dynamically adjust the control weight coefficients K1, K2, K3, and K4 to continuously transition from the current value to the weight value corresponding to the target control mode, thereby achieving smooth switching between different control modes; S5: Based on the reference value and control weight coefficient, adjust the duty cycle of the three-phase inverter bridge to make the boost inductor current track the reference value and obtain a stable boost output; S6: Periodically determine the state of charge (SOC) of the power battery, the output status of the DC charging port, and the safety limit. When at least one charging termination condition is met, stop the boost charging control process and stop boost charging. The termination conditions include the power battery SOC reaching the set upper limit, or the DC charging port input voltage or DC charging port input current exceeding the safety limit.

[0013] The beneficial effects of this invention are as follows: (1) This invention constructs a unified multi-objective control model that includes output voltage, output current, input voltage and input current, couples multiple control objectives into the same control framework, and coordinates and adjusts them through control weight coefficients, thereby achieving coordinated control of multiple control objectives under the same boost power path. Compared with the existing independent control methods that construct voltage control and current control separately, this invention can avoid mutual interference between multiple control loops and improve the stability and consistency of the overall system control.

[0014] (2) This invention maps constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode and constant current input voltage stabilization mode to the same control model. By adjusting the control weight coefficient, the selection and continuous transition between different control modes can be achieved. Compared with the existing discrete mode switching method, it can effectively avoid voltage change and current impact, and improve the stability and safety of the power battery charging process.

[0015] (3) By introducing a balancing adjustment mechanism for control weight coefficients into the boost charging system, the system can achieve continuous and smooth switching between different control modes. The controller dynamically adjusts each weight coefficient according to the real-time changes in the state of charge, voltage, and current of the power battery, so that different target currents and voltages are coordinated and distributed during the charging process, thereby achieving a smooth transition in power output. This continuous adjustment method can effectively avoid voltage or current surges caused by traditional discrete mode switching, improve the stability and safety of power battery charging, and enhance the system's adaptability to different DC charging pile output characteristics and operating conditions, thereby improving charging efficiency and extending the service life of the power battery. Attached Figure Description

[0016] 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.

[0017] Figure 1 This is a schematic diagram of the structure of a boost charging system for electric vehicles provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the boost charging device provided in an embodiment of the present invention. Detailed Implementation

[0018] 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 following embodiments and technical features 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.

[0019] Please refer to Figure 1 as well as Figure 2 , Figure 1 This is a schematic diagram of the structure of a boost charging system for electric vehicles provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the boost charging device provided in an embodiment of the present invention.

[0020] See Figure 1In this embodiment of the invention, the boost charging system for an electric vehicle 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 external high-voltage bus capacitor 300 of the vehicle, 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 external power battery of the boost charging device is connected to the DC bus 300, and the other end is connected to the DC charging port 100. The system includes a boost accessory module 500 inside the DC charging device; an electric drive module 400 provides vehicle motor drive and boost power conversion control functions; the boost accessory module 500 provides boost circuit on / off, EMI filtering, and boost input current and voltage detection functions; a DC charging port 100 is used to connect to an external DC charging pile to provide high-voltage DC power to the vehicle; a 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 connected; and a vehicle high-voltage bus capacitor 300 is the sum of the X capacitors of each high-voltage assembly bus port on the vehicle high-voltage bus, which plays a role in stabilizing the bus voltage and reducing bus voltage ripple.

[0021] See Figure 2In this embodiment of the invention, the boost accessory module includes: an input current detection unit 12, 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 external DC charging port 100 of the boost charging device, and the other end is connected to the positive terminal of the input capacitor 32; the positive terminal of the input voltage detection unit 22 is connected to the positive terminal of the input capacitor 32, and the negative terminal of the input voltage detection unit 22 is connected to the negative terminal of the input capacitor 32; the positive terminal of the input capacitor 32 is connected to the positive terminal of the EMI filter circuit 80, the positive terminal of the input voltage detection unit 22, and the positive terminal of the external DC charging port 100 of the boost charging device, respectively, and the negative terminal of the input capacitor 32 is connected to the negative terminal of the EMI filter circuit 80, the negative terminal of the input voltage detection unit 22, and the negative terminal of the external DC charging port 100 of the boost charging device, respectively; one end of the output negative relay 93 is connected to the negative terminal of the EMI filter circuit 80, and the other end is connected to the internal drive module 400. The high-voltage DC negative terminal of the three-phase inverter bridge circuit 40 is connected to the three-phase inverter bridge circuit 40. One end of the output positive relay 92 is connected to the positive terminal of the EMI filter circuit 80, and the other end is connected to the common connection center point of the A-phase electric drive winding 61, B-phase electric drive winding 62 and C-phase electric drive winding 63 inside the electric drive module 400. The input current detection unit 12 is used to detect the input current of the DC charging port, and the input voltage detection unit 22 is used to detect the input voltage of the DC charging port. The input voltage of the DC charging port is the voltage signal collected from the output terminal of the DC charging pile. The input capacitor 32 is used for current buffering and to reduce voltage ripple. The EMI filter circuit 80 provides EMI filtering function for the boost charging device. The input positive relay 91, output positive relay 92 and output negative relay 93 are used to control the on and off of the boost circuit. When the vehicle recognizes that boost charging is needed, the input positive relay 91, output positive relay 92 and output negative relay 93 are closed. When the vehicle recognizes that boost charging is not needed, the input positive relay 91, output positive relay 92 and output negative relay 93 are turned off.

[0022] Furthermore, the electric drive module 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 external bus capacitor 300 of the boost charging device, and the other end is connected to the electric drive module. The positive terminal of the high-voltage bus capacitor 31 inside block 400 is connected to the positive terminal of the high-voltage bus capacitor 31, and the negative terminal of the high-voltage bus voltage detection unit 21 is connected to the negative terminal of the high-voltage bus capacitor 31. The positive terminal of the high-voltage bus capacitor 31 is connected to the positive terminal of the high-voltage bus current detection unit 11, the high-voltage bus voltage detection unit 21, and the high-voltage DC positive terminal of the three-phase inverter bridge circuit 40, respectively. The negative terminal of the high-voltage bus capacitor 31 is connected to the negative terminal of the high-voltage bus voltage detection unit 21 and the high-voltage DC positive terminal of the three-phase inverter bridge circuit 40, respectively. The DC negative terminal, the internal output negative relay 93 of the boost accessory module 500, and the negative terminal of the external bus capacitor 300 of the boost charging device are connected; the high-voltage DC positive terminal of the three-phase inverter bridge circuit 40 is connected to the positive terminal of the high-voltage bus capacitor 31, the high-voltage DC negative terminal of the three-phase inverter bridge circuit 40 is connected to the negative terminal of the high-voltage bus capacitor 31, the A-phase bridge arm output of the three-phase inverter bridge circuit 40 is connected to the A-phase current detection unit 51, the B-phase bridge arm output of the three-phase inverter bridge circuit 40 is connected to the B-phase current detection unit 52, and the C-phase... The phase bridge arm output is connected to the C-phase current detection unit 53; the electric drive controller MCU70 is connected to the high-voltage bus current detection unit 11, the high-voltage bus voltage detection unit 21, the A-phase current detection unit 51, the B-phase current detection unit 52 and the C-phase current detection unit 53, the boost accessory module input voltage detection unit 22, the boost accessory module input current detection unit 12, the boost accessory module input positive relay 91, the boost accessory module output positive relay 92 and the boost accessory module output negative relay 93 respectively.

[0023] The high-voltage bus current detection unit 11 is responsible for detecting the charging current of the power battery; the high-voltage bus voltage detection unit 21 is responsible for detecting the voltage on the power battery side; the high-voltage bus capacitor 31 is the high-voltage bus X capacitor inside the electric drive module, which plays a role in stabilizing the voltage and reducing voltage ripple; the electric drive three-phase inverter bridge circuit 40 is responsible for the switching operation of the electric drive module's inverter 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 provides functions such as vehicle motor drive control, vehicle CAN communication interaction, acquisition of voltage and current signals inside the boost charging device, drive of the high-voltage relay inside the boost charging device, and boost power conversion control drive.

[0024] In this embodiment of the invention, during the boost charging process, the three-phase drive windings are equivalent to a boost inductor under three-phase synchronous control, and the three-phase inverter bridge achieves boost power conversion through switch control. Under three-phase symmetrical and synchronous control conditions, the three-phase boost structure can be equivalent to a single-phase boost circuit. The boost inductor is the equivalent inductance of the parallel connection of the A-phase drive winding, B-phase drive winding, and C-phase drive winding, and its size is 1 / 3 of the size of the single-phase inductor; the current is the equivalent current of the three-phase parallel inductor, and its size is 3 times the current of the single-phase inductor.

[0025] In this embodiment, the controller constructs a unified multi-objective control model to describe the relationship between the boost inductor current reference value and multiple control objectives: ; in, This is a reference value for the boost inductor current; This refers to the voltage on the power battery side. The charging current for the power battery; Input voltage to the DC charging port; Input current to the DC charging port; This is the target voltage reference value for the power battery side; This is a reference value for the target charging current on the power battery side. The target reference value for the DC charging port input voltage; K1, K2, K3, and K4 are the target reference values ​​for the DC charging port input current; K1, K2, K3, and K4 are control weighting coefficients. The controller controls the boost inductor current by adjusting the duty cycle of the three-phase inverter bridge. By adjusting the control weighting coefficients K1, K2, K3, and K4, it achieves any one of five control modes while maintaining the boost power path structure unchanged, and provides a continuous transition between these modes: constant voltage input / constant voltage output mode, constant voltage input / constant current output mode, constant current input / constant voltage output mode, constant current input / constant current output mode, and constant current input voltage stabilization mode. The control weighting coefficients are non-negative real numbers. In the steady-state operation of the five control modes, two of the control weighting coefficients are greater than zero, and the other two are equal to zero. The control weighting coefficients change continuously during the transition between different control modes.

[0026] In this embodiment, by adjusting the control weighting coefficients K1, K2, K3, and K4, five control modes are achieved while maintaining the unchanged boost power path structure: constant voltage input / constant voltage output mode, constant voltage input / constant current output mode, constant current input / constant voltage output mode, constant current input / constant current output mode, and constant current input voltage stabilization mode. The constant current input voltage stabilization mode is used when the DC charging pile operates in constant current output mode. In this mode, the system jointly controls the input current and input voltage, where the input current is constrained by the constant current target, and the input voltage is simultaneously stabilized.

[0027] When the control weight coefficients satisfy K1>0, K2=0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant current output mode. When the control weight coefficients satisfy K1>0, K2=0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant current output mode; When the control weighting coefficients satisfy K1=0, K2=0, K3>0, and K4>0, the controller enables the boost charging device to operate in a constant current input voltage stable mode. When switching between different control modes, the controller does not use a discrete switching method, but rather continuously adjusts the control weighting coefficients to gradually transition from one mode's value to another, thus achieving a smooth transition between control modes. For example, during the transition from constant current output mode to constant voltage output mode, K2 can be gradually decreased and K1 increased to avoid sudden changes in output current or output voltage.

[0028] Furthermore, the control weighting coefficients K1, K2, K3, and K4 are dynamically adjusted based on at least one of the following parameters: state of charge (SOC) of the power battery, voltage deviation of the power battery side, charging current deviation of the power battery, input voltage deviation of the DC charging port, and input current deviation of the DC charging port.

[0029] Furthermore, the control weighting coefficient is a continuously varying parameter to enable a continuous transition between the constant voltage input constant voltage output mode, the constant voltage input constant current output mode, the constant current input constant voltage output mode, the constant current input constant current output mode, and the constant current input voltage stabilization mode.

[0030] Furthermore, the A-phase, B-phase, and C-phase electric drive windings are coordinated and controlled according to a preset phase relationship under synchronous control to suppress motor torque fluctuations during the boost charging process.

[0031] Furthermore, the boost accessory module includes an input current detection unit and an input voltage detection unit. The controller periodically updates the unified multi-objective control model by collecting the power battery side voltage, power battery charging current, DC charging port input voltage, and DC charging port input current, so as to achieve stable charging of the power battery under different DC charging pile output conditions.

[0032] In another embodiment, a boost charging control method is also provided, applied to a boost charging system, comprising the following steps: S1: During the charging process, the DC charging port input voltage and the maximum allowable voltage of the power battery are collected. When the DC charging port input voltage is lower than the maximum allowable voltage of the power battery, the boost charging control process is started. Otherwise, the current charging state is maintained and the DC charging port input voltage is checked cyclically to determine whether the boost start condition is met. S2: After starting the boost charging control process, the target control mode of the boost charging device is determined according to the current status of the DC charging port and the charging condition of the power battery. This includes constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode, and constant current input voltage stabilization mode. S3: Based on the target control mode and the real-time collected power battery side voltage, power battery charging current, DC charging port input voltage and DC charging port input current, a unified multi-target control model is established inside the controller to calculate the reference value of the boost inductor current. S4: Based on the calculated reference value and real-time charging conditions, dynamically adjust the control weight coefficients K1, K2, K3, and K4 to continuously transition from the current value to the weight value corresponding to the target control mode, thereby achieving smooth switching between different control modes; S5: Based on the reference value and control weight coefficient, adjust the duty cycle of the three-phase inverter bridge to make the boost inductor current track the reference value and obtain a stable boost output; S6: Periodically determine the state of charge (SOC) of the power battery, the output status of the DC charging port, and the safety limit. When at least one charging termination condition is met, stop the boost charging control process and stop boost charging. The termination conditions include the power battery SOC reaching the set upper limit, or the DC charging port input voltage or DC charging port input current exceeding the safety limit.

[0033] In another embodiment of the present invention, to achieve a smooth transition between different control modes, the controller continuously adjusts the control weight coefficients K1, K2, K3, and K4 to prevent sudden changes in output voltage or current during mode switching, thereby improving charging stability and safety. The specific implementation is as follows: the control weight coefficients change continuously over time, satisfying the following recursive relationship; K i (t+Δt)=K i (t)+α i (K i,target -K i (t)); i=1,2,3,4; Among them, K i (t) represents the real-time control weighting coefficient at time t; K i,target α represents the target weight value corresponding to the control mode. i The step size is used to control the adjustment speed and can be dynamically adjusted according to the vehicle's charging conditions, such as the state of charge (SOC) of the power battery, voltage deviation, and current deviation. Δt is the control cycle time interval, which is usually consistent with the controller's sampling period. Through this recursive relationship, the control weight coefficient smoothly transitions from its current value to the target value, thereby achieving continuous mode switching. By rationally designing the adjustment step size of the control weight coefficient, the system can achieve a smooth and controllable power transition during charging. A reasonable step size setting can avoid voltage and current abrupt changes caused by rapid weight changes, while ensuring that the system response speed meets the dynamic requirements of the charging conditions. Continuous and smooth switching between different control modes can make the steady-state transition of the boost inductor current and output voltage smoother, improve the charging stability and safety of the power battery, and reduce the impact of system oscillations and shocks on the charging device and power battery. In addition, the adjustment step size can be adaptively adjusted according to the power battery status and charging pile output conditions, thereby achieving optimal control and efficient charging under different operating conditions.

[0034] During the boost charging process, the controller smoothly transitions according to the logic implementation mode: it detects the current operating condition, acquires the bus voltage, charging current, DC charging port input voltage and input current of the power battery side; and selects the target control mode and determines the target weight K based on the output characteristics of the DC charging pile and the power battery requirements. i,target The control weight coefficients K1, K2, K3, and K4 are smoothly updated using the aforementioned recursive formula to achieve the transition from the current control mode to the target control mode. Simultaneously, the duty cycle of the three-phase inverter bridge is adjusted to ensure that the boost inductor current stably tracks the reference value. During the transition process, if input voltage or current deviation or SOC abnormality is detected, the step size can be dynamically adjusted to extend or shorten the transition time, achieving a safer and smoother switching.

[0035] Different step sizes can be set for different charging modes to adapt to the characteristics of constant voltage / constant current output conditions. For example, a smaller step size can be used in constant current output mode to avoid impact; the step size can be appropriately increased in constant voltage output mode to improve the transition response speed. In actual implementation, the weight can be continuously adjusted and updated synchronously with the controller duty cycle output to ensure a smooth and stable overall system response. Through the above continuous adjustment and smooth mode transition mechanism, the system can avoid voltage and current surges caused by traditional discrete mode switching; achieve coordinated control of multiple control objectives, taking into account the stability of power battery charging and the compatibility of charging pile output; improve the safety and stability of the charging process, reduce charging impact and equipment loss; and support joint adjustment of current and voltage in constant current input voltage stable mode to improve the adaptability to different DC charging pile conditions.

[0036] It is worth noting that this invention constructs a unified multi-objective control model that includes output voltage, output current, input voltage, and input current, coupling multiple control objectives within the same control framework. This is achieved through coordinated adjustment of control weight coefficients, enabling collaborative control of multiple control objectives within the same boost power path. Compared to existing independent control methods that separately construct voltage and current controls, this invention avoids mutual interference between multiple control loops, improving the overall stability and consistency of the system control. This invention maps constant voltage input / constant voltage output mode, constant voltage input / constant current output mode, constant current input / constant voltage output mode, constant current input / constant current output mode, and constant current input / voltage stability mode to the same control model. By adjusting the control weight coefficients, the selection and continuous transition between different control modes are achieved. Compared to existing methods that use discrete mode switching, this invention effectively avoids voltage surges and current spikes, improving the smoothness and safety of the power battery charging process. This invention introduces both input voltage control and input current control terms into the control model, enabling the boost charging system to adaptively adjust the control weight coefficients according to whether the DC charging pile is in a constant voltage or constant current output state. This allows for stable charging under different charging pile output characteristics and operating conditions, improving the compatibility of electric vehicles with different DC charging piles and increasing the charging success rate.

[0037] 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 system for electric vehicles, comprising a power battery, a DC charging port, a bus capacitor, and a boost charging device, characterized in that: The boost charging device includes an electric drive module and a boost accessory module. The electric drive module is connected to the power battery through the bus capacitor, and the boost accessory module is connected to the DC charging port. The electric drive module includes a three-phase inverter bridge, A-phase, B-phase and C-phase electric drive windings connected to the three-phase inverter bridge, and a controller. During the boost charging process, the A-phase, B-phase and C-phase electric drive windings effectively form a boost inductor. The controller internally establishes a unified multi-objective control model to determine the reference value of the boost inductor current based on the power battery side voltage, power battery charging current, DC charging port input voltage, and DC charging port input current, according to the following relationship: ； in, This is a reference value for the boost inductor current; This refers to the voltage on the power battery side. The charging current for the power battery; Input voltage to the DC charging port; Input current to the DC charging port; This is the target voltage reference value for the power battery side; This is a reference value for the target charging current on the power battery side. The target reference value for the DC charging port input voltage; K1, K2, K3, and K4 are the target reference values ​​for the DC charging port input current; K1, K2, K3, and K4 are control weighting coefficients. The controller controls the boost inductor current by adjusting the duty cycle of the three-phase inverter bridge, and achieves any one of the following five modes by adjusting the control weighting coefficients K1, K2, K3, and K4, while keeping the boost power path structure unchanged: constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode, and constant current input voltage stabilization mode; and achieves continuous transition between different control modes. The control weight coefficients K1, K2, K3, and K4 are non-negative real numbers; in the steady-state operation of the five modes, two of the control weight coefficients are greater than zero, and the other two are equal to zero.

2. The boost charging system according to claim 1, characterized in that, When the control weight coefficients satisfy K1>0, K2=0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3>0, K4=0, the controller enables the boost charging device to operate in constant voltage input and constant current output mode. When the control weight coefficients satisfy K1>0, K2=0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant voltage output mode. When the control weight coefficients satisfy K1=0, K2>0, K3=0, K4>0, the controller enables the boost charging device to operate in constant current input and constant current output mode; When the control weight coefficients satisfy K1=0, K2=0, K3>0, K4>0, the controller enables the boost charging device to operate in the input constant current input voltage stable mode.

3. The boost charging system according to claim 1, characterized in that, The control weight coefficients K1, K2, K3, and K4 are dynamically adjusted based on at least one of the following parameters: state of charge (SOC) of the power battery, voltage deviation of the power battery side, charging current deviation of the power battery, input voltage deviation of the DC charging port, and input current deviation of the DC charging port.

4. The boost charging system according to claim 1, characterized in that, The control weighting coefficients K1, K2, K3, and K4 are continuously varying parameters to enable a continuous transition between the constant voltage input constant voltage output mode, the constant voltage input constant current output mode, the constant current input constant voltage output mode, the constant current input constant current output mode, and the constant current input voltage stabilization mode.

5. The boost charging system according to claim 1, characterized in that, The A-phase, B-phase, and C-phase electric drive windings are coordinated and controlled according to a preset phase relationship under synchronous control to suppress motor torque fluctuations during the boost charging process.

6. The boost charging system according to claim 1, characterized in that, The boost accessory module includes an input current detection unit and an input voltage detection unit. The controller periodically updates the unified multi-objective control model by collecting the power battery side voltage, power battery charging current, DC charging port input voltage, and DC charging port input current, so as to achieve stable charging of the power battery under different DC charging pile output conditions.

7. A boost charging control method, applied to the boost charging system of claim 1, characterized in that, Includes the following steps: S1: During the charging process, the DC charging port input voltage and the maximum allowable voltage of the power battery are collected. When the DC charging port input voltage is lower than the maximum allowable voltage of the power battery, the boost charging control process is started. Otherwise, the current charging state is maintained and the DC charging port input voltage is checked cyclically to determine whether the boost start condition is met. S2: After starting the boost charging control process, the target control mode of the boost charging device is determined according to the current status of the DC charging port and the charging condition of the power battery. This includes constant voltage input constant voltage output mode, constant voltage input constant current output mode, constant current input constant voltage output mode, constant current input constant current output mode, and constant current input voltage stabilization mode. S3: Based on the target control mode and the real-time collected power battery side voltage, power battery charging current, DC charging port input voltage and DC charging port input current, a unified multi-target control model is established inside the controller to calculate the reference value of the boost inductor current. S4: Based on the calculated reference value and real-time charging conditions, dynamically adjust the control weight coefficients K1, K2, K3, and K4 to continuously transition from the current value to the weight value corresponding to the target control mode, thereby achieving smooth switching between different control modes; S5: Based on the reference value and control weight coefficient, adjust the duty cycle of the three-phase inverter bridge to make the boost inductor current track the reference value and obtain a stable boost output; S6: Periodically determine the state of charge (SOC) of the power battery, the output status of the DC charging port, and the safety limit. When at least one charging termination condition is met, stop the boost charging control process and stop boost charging. The termination conditions include the power battery SOC reaching the set upper limit, or the DC charging port input voltage or DC charging port input current exceeding the safety limit.

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