Direct current fast charging preheating control method for new energy vehicle

Abstract

The application discloses a direct current fast charging preheating control method for a new energy vehicle, and proposes a control logic of a PTC in a fast charging preheating process and an interaction timing of each related controller, so that the control of heating a battery pack before charging is realized. After detecting a charging start, high voltage on a power battery is first executed; if the battery monomer temperature is too low at this time, the power battery is then peeled off and the high voltage components of the whole vehicle are enabled, and then the fast charging preheating state is started in combination with the current power battery inlet and outlet water temperature; then the gear of the PTC is regulated according to the charging pile output voltage until the battery monomer temperature rises, and then the power battery is reconnected to the high voltage loop and the normal direct current fast charging control is executed. The high-quality and strong-compatibility fast charging preheating control mode proposed by the application realizes the battery fast charging function in an extremely low temperature environment through the coordination of the related controllers of the vehicle and the direct current charging pile system, and effectively protects the battery from being damaged in the low temperature fast charging working condition.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of new energy vehicles, and particularly relates to a direct current fast charging preheating control method for a new energy vehicle. BACKGROUND

[0002] Battery charging performance is limited in a low temperature environment, and current mainstream pure electric / mixed vehicle fast charging preheating control strategies are mostly battery high voltage relay attraction methods, and it is difficult to achieve zero current closed loop control for high voltage battery and fast charging pile current control, and current pouring into the battery pack phenomenon is easily generated frequently, resulting in vehicle overcurrent fault reporting, and therefore a new preheating control scheme based on fast charging is urgently needed in the industry. SUMMARY

[0003] In view of the above, the present application aims to provide a direct current fast charging preheating control method for a new energy vehicle to solve the aforementioned technical problems.

[0004] The technical solution adopted by the present application is as follows:

[0005] The present application provides a direct current fast charging preheating control method for a new energy vehicle, which comprises:

[0006] After detecting a charging program start signal, the direct current fast charging pile wakes up the vehicle;

[0007] After determining that the charging high voltage condition meets the preset condition by the awakened vehicle controller, the high voltage power-on request is sent to the battery management system, and after the high voltage power-on is completed, the high voltage loop between the direct current fast charging pile and the power battery is turned on by the battery management system;

[0008] If the battery management system detects that the current battery cell minimum temperature is lower than the preset lower temperature threshold, the power battery is peeled off from the high voltage loop and the preheating state is fed back;

[0009] The vehicle controller enables the high voltage components of the vehicle in the preheating state, and controls the PTC to enter the fast charging preheating state in combination with the temperature of the power battery inlet and outlet;

[0010] In the fast charging preheating state, the vehicle controller regulates the PTC according to the output voltage of the direct current fast charging pile sent by the battery management system: when the output voltage is less than or equal to the first preset voltage threshold, the PTC duty cycle is controlled to drop to the initial gear; and after the PTC duty cycle drops to the initial gear, if the output voltage is greater than or equal to the second preset voltage threshold and lasts for a first predetermined time, the PTC duty cycle is controlled to rise by one gear, and thereafter the PTC duty cycle is controlled to rise by one gear at a preset period;

[0011] Until the current lowest battery cell temperature is higher than the preset temperature recovery threshold, a preheating end state is entered, the power battery is reconnected to the high-voltage loop, and direct current fast charging control is performed.

[0012] In at least one possible implementation, the disconnection of the power battery from the high-voltage loop specifically includes:

[0013] When the lowest battery cell temperature is lower than the preset lower temperature threshold, a fast charging preheating lower high-voltage request is sent by the battery management system to the vehicle controller;

[0014] The vehicle controller disables the high-voltage components of the vehicle and waits until the first predetermined condition is met, and then sends a lower high-voltage request to the battery management system.

[0015] The high-voltage positive and negative relays are controlled to be disconnected by the battery management system.

[0016] In at least one possible implementation, the first predetermined condition includes that the current of the power battery is less than a preset current limit, or a preset timer reaches.

[0017] In at least one possible implementation, the reconnection of the power battery to the high-voltage loop includes:

[0018] When the lowest battery cell temperature is higher than the preset temperature recovery threshold, a preheating end state is sent to the vehicle controller, and the fast charging preheating lower high-voltage request is changed to a cancel lower high-voltage request.

[0019] When the vehicle controller receives the preheating end state or the fast charging preheating lower high-voltage request is changed to the cancel lower high-voltage request, the vehicle controller disables the high-voltage components of the vehicle and waits until the second predetermined condition is met, and then performs upper high-voltage control and enters a direct current charging control timing.

[0020] In at least one possible implementation, during the fast charging preheating state, if the output voltage is less than or equal to a third preset voltage threshold for a second predetermined time duration, or the output voltage is less than or equal to a fourth preset voltage threshold for a third predetermined time duration, the entire direct current fast charging process is directly triggered to end, where the third preset voltage threshold is greater than the fourth preset voltage threshold, and the second predetermined time duration is greater than the third predetermined time duration.

[0021] In at least one possible implementation, the charging upper high-voltage condition includes that the vehicle and the battery management system have no predetermined level of failure, the gear is in P, the motor speed is less than a preset speed, and the fast charging gun state is connected.

[0022] Compared with the prior art, the main design concept of the application is that the control logic of PTC in the fast charging preheating process and the interaction timing of each related controller are proposed by using the vehicle-mounted control device, the control of heating the battery pack before charging is realized, and the battery pack temperature is heated to the target temperature before charging. Specifically, after detecting the charging program start signal, the high voltage on the power battery is realized by the battery management system through the awakened vehicle controller; if the battery monomer temperature is too low, the power battery is peeled off and the vehicle high voltage components are enabled by the vehicle controller, and the fast charging preheating state is started in combination with the current power battery inlet and outlet temperature; then the PTC is regulated according to the charging pile output voltage until the battery monomer temperature rises, then the power battery is reconnected to the high voltage loop and the normal direct current fast charging control is performed. The high-quality and strong-compatibility fast charging preheating control mode proposed in the application realizes the battery fast charging function in the extreme low temperature environment by coordinating the VCU, BMS, MCU, GCU, PTC, OBC / DCDC and other vehicle related controllers and the direct current charging pile system, and effectively protects the battery from being damaged in the low temperature fast charging working condition. On the one hand, the power battery is in the peeled state from the high voltage loop in the fast charging preheating state, which avoids the risk of current pouring into the power battery, and can effectively improve the success of the direct current charging pile fast charging preheating; on the other hand, the application can be reliably covered in the case that the direct current charging pile does not support the constant voltage mode or the voltage output ability of some direct current charging piles on the market is weak at the initial charging stage. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described below in combination with the drawings, in which:

[0024] Figure 1 A schematic diagram of the direct current fast charging preheating control method for new energy vehicles provided by the embodiment of the present application. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below, and the examples of the embodiments are shown in the drawings, in which the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, but cannot be explained as a limitation of the present application.

[0026] The present application proposes an embodiment of a direct current fast charging preheating control method for new energy vehicles, specifically as shown in Figure 1 , which includes:

[0027] Step S1, after detecting the charging program start signal, the direct current fast charging pile wakes up the vehicle;

[0028] In actual operation, when the user inserts the gun and swipes the card, the DC charging pile outputs an A+ wake-up signal, which mainly wakes up the vehicle controller VCU; with the VCU being awakened, the VCU controls the wake-up relay to perform the closing action, thereby waking up the battery management system BMS, PTC, motor controller MCU, and air conditioner controller of the vehicle;

[0029] Step S2, after the awakened vehicle controller determines that the preset charging high-voltage condition is met, the vehicle controller sends a high-voltage power-on request to the battery management system, and after the high-voltage power-on is completed, the battery management system turns on the high-voltage loop between the DC fast charging pile and the power battery;

[0030] The VCU interacts with the BMS through the vehicle CAN to complete the charging high-voltage and the charging process control mentioned later. For the high-voltage part mentioned in this step, after the VCU is awakened, it is first determined whether the vehicle state meets the preset charging high-voltage condition. If it meets, the VCU sends a high-voltage power-on request to the BMS, wherein the charging high-voltage condition includes: the vehicle has no level 3 and above faults, the BMS has no level 3 and above faults, the gear is in P, the motor speed is less than 100 rpm, and the fast charging gun state is connected (the BMS detects that the CC2 is normal and sends a fast charging gun connected signal to the VCU).

[0031] Then, after receiving the high-voltage power-on request from the VCU, the BMS controls the high-voltage positive relay and the high-voltage negative relay to be attracted, so as to control the high-voltage loop between the power battery and the high-voltage distribution box of the vehicle to be connected, and feedback a high-voltage power-on completed signal to the VCU. After receiving the high-voltage power-on completed signal from the BMS, the VCU sends a charging permission instruction to the BMS. After receiving the charging permission instruction, the BMS controls the fast charging positive relay and the fast charging negative relay to be attracted, thereby turning on the high-voltage loop between the DC charging pile and the power battery.

[0032] Step S3, if the battery management system detects that the current lowest battery cell temperature is lower than the preset lower temperature threshold, the battery management system triggers the power battery to be peeled off from the high-voltage loop and feedbacks a preheating state.

[0033] For example, the BMS determines whether the current lowest battery cell temperature is less than -20℃. If it is less than -20℃, the BMS sends a high-voltage request for fast charging preheating to the VCU. After receiving the high-voltage request for fast charging preheating from the BMS, the VCU first disables the high-voltage components of the vehicle, and then sends a high-voltage request to the BMS when the current of the power battery is less than 5A or after 1.5s.

[0034] After the BMS receives the high-voltage request from the VCU, the high-voltage positive relay and the high-voltage negative relay are controlled to be disconnected, so as to disconnect the power battery from the high-voltage circuit, thereby ensuring that the power battery is not filled with current. At this time, the power battery enters a preheating state, waits for the PTC controller to control the PTC to perform battery heating related work, and sends the preheating state to the VCU.

[0035] In step S4, the vehicle controller enables the high-voltage components of the vehicle in the preheating state, and controls the PTC to enter a fast charging preheating state in combination with the current temperature of the power battery inlet and outlet.

[0036] In step S5, in the fast charging preheating state, the vehicle controller controls the PTC according to the output voltage of the DC fast charging pile sent by the battery management system: when the output voltage is less than or equal to a first preset voltage threshold, the PTC duty cycle is controlled to drop to the initial gear; and after the PTC duty cycle drops to the initial gear, if the output voltage recovers to be greater than or equal to a second preset voltage threshold and lasts for a first predetermined time, the PTC duty cycle is controlled to rise by one gear, and then the PTC duty cycle is controlled to rise by one gear at a preset period.

[0037] During the fast charging preheating state, the DC fast charging pile interacts with the BMS through the fast charging CAN to transmit pile-related information to the BMS, and the BMS sends charging-related instructions to the charging pile through the fast charging CAN; specifically, the DC charging pile sends the output voltage value of the DC charging pile to the BMS in real time, and the BMS forwards the signal to the VCU; the VCU changes the PTC control strategy according to the voltage value, specifically as follows: when the VCU judges that the output voltage of the DC charging pile is less than or equal to 235V, the PTC duty cycle is requested to drop to 1 gear; after the PTC duty cycle drops, if the output voltage of the DC charging pile recovers to be greater than or equal to 250V and lasts for 5 minutes, the PTC duty cycle is requested to rise to 2 gears, and then the PTC duty cycle is requested to rise by 1 gear every 15 seconds. Additionally, during the fast charging preheating state, if the BMS detects that the output voltage of the DC charging pile is less than or equal to a third preset voltage threshold of 225V and lasts for a second predetermined time of 30 seconds, or the output voltage of the DC charging pile is less than or equal to a fourth preset voltage threshold of 215V and lasts for a third predetermined time of 3 seconds, when one of the two conditions is met, the BMS sends a charging end request to the VCU, and the VCU directly controls the vehicle to end the entire DC fast charging process after receiving the charging end request from the BMS.

[0038] In step S6, until the lowest temperature of the current battery cell is detected to be higher than a preset temperature recovery threshold, the preheating end state is entered, the power battery is reconnected to the high-voltage circuit, and the DC fast charging control is performed.

[0039] That is to say, after entering the fast charging preheating state, if the BMS judges that the minimum temperature of the single battery is greater than -15 DEG C, the preheating end state is sent to the VCU, and the fast charging preheating high voltage request is changed to the cancel high voltage request; when the VCU receives the preheating end state of the BMS or the fast charging preheating high voltage request is changed to the cancel high voltage request, the vehicle high voltage component is first disabled, and after the PTC power is less than 1.5Kw, the high voltage process control (the power battery is reconnected to the electrical stripping) is performed, and then the normal direct current charging control timing is entered.

[0040] To sum up, the main design concept of the application is to use the vehicle control device, propose the control logic of the PTC in the fast charging preheating process and the interaction timing of the related controllers, realize the control of heating the battery pack before charging, and heat the battery pack temperature to the target temperature before charging. Specifically, after detecting the charging program start signal, the power battery is connected to the high voltage by the battery management system through the awakened vehicle controller; if the battery monomer temperature is too low, the power battery is stripped and the vehicle high voltage component is enabled by the vehicle controller, and the fast charging preheating state is entered in combination with the current power battery inlet and outlet temperature; then the PTC is regulated according to the charging pile output voltage until the battery monomer temperature rises, then the power battery is reconnected to the high voltage loop and the normal direct current fast charging control is performed. The high-quality and strong-compatibility fast charging preheating control mode proposed in the application realizes the battery fast charging function in the extreme low temperature environment by coordinating the VCU, BMS, MCU, GCU, PTC, OBC / DCDC and other vehicle related controllers and the direct current charging pile system, and effectively protects the battery from being damaged in the low temperature fast charging working condition.

[0041] In the embodiment of the application, if the expression of the position is mentioned, it is based on the relative concept of the embodiment, and "at least one" means one or more, and "multiple" means two or more. The "and / or" describes the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Wherein A and B can be singular or plural. The character " / " generally represents that the front and rear associated objects are in an "or" relationship. "At least one of the following" and similar expressions mean any combination of these items, including any combination of single or multiple items. For example, at least one of a, b and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, wherein a, b and c can be single or multiple.

[0042] The above detailed description of the embodiments shown in the drawings illustrates the structure, features and effects of the present application, but the above is only a preferred embodiment of the present application, and it should be noted that the technical features involved in the above embodiments and preferred modes can be reasonably combined and matched into various equivalent schemes by those skilled in the art without departing from or changing the design idea and technical effects of the present application; therefore, the present application is not limited to the implementation range shown in the drawings, and any changes or modifications made in accordance with the concept of the present application, or equivalent embodiments with equivalent changes, shall be within the scope of protection of the present application.

Claims

1. A DC fast charging preheating control method for new energy vehicles, characterized in that, include: The DC fast charging station wakes up the vehicle after detecting the charging program start signal; After the vehicle controller is awakened and determines that the preset high voltage charging conditions are met, it sends a high voltage power-on request to the battery management system. After the high voltage power-on is completed, the battery management system connects the high voltage circuit between the DC fast charging pile and the power battery. If the battery management system detects that the current minimum temperature of a single battery cell is lower than the preset lower limit threshold, it will disconnect the power battery from the high-voltage circuit and report a preheating status. The vehicle controller enables the high-voltage components of the vehicle in the preheating state and, in conjunction with the current temperature of the power battery inlet and outlet, controls the PTC to operate in order to enter the fast charging preheating state. During the fast charging preheating state, the vehicle controller adjusts the PTC according to the output voltage of the DC fast charging pile sent by the battery management system: when the output voltage is ≤ the first preset voltage threshold, the PTC duty cycle is controlled to drop to the initial level. Furthermore, after the PTC duty cycle drops to the initial level, if the output voltage is ≥ the second preset voltage threshold and continues for the first predetermined duration, the PTC duty cycle is controlled to increase by one level, and then the PTC duty cycle is controlled to increase level by level according to the preset cycle. Once the lowest temperature of the current battery cell is detected to be higher than the preset temperature rise threshold, the preheating process ends, the power battery is reconnected to the high-voltage circuit, and DC fast charging control is executed.

2. The DC fast charging preheating control method for new energy vehicles according to claim 1, characterized in that, The process of disconnecting the power battery from the high-voltage circuit specifically includes: When the minimum temperature of a single battery cell is lower than the preset lower limit threshold, the battery management system sends a fast charging preheating high voltage request to the vehicle controller. The vehicle controller disables the high-voltage components of the vehicle and waits for the first predetermined condition to be met before sending a request to reduce the high voltage to the battery management system. The high-voltage positive and negative relays are disconnected by the battery management system.

3. The DC fast charging preheating control method for new energy vehicles according to claim 2, characterized in that, The first predetermined condition includes: the current of the power battery is less than the preset current limit, or the preset time is reached.

4. The DC fast charging preheating control method for new energy vehicles according to claim 1, characterized in that, The process of reconnecting the power battery to the high-voltage circuit includes: When the minimum temperature of a single battery cell is higher than the preset temperature rise threshold, a preheating end status is sent to the vehicle controller, and the fast charging preheating high voltage request is changed to cancel the high voltage request. When the vehicle controller receives a preheating end status or a fast charging preheating high voltage request changes to a canceled high voltage request, it disables the high voltage components of the vehicle and waits for the second predetermined condition to be met before executing high voltage control and entering the DC charging control sequence.

5. The DC fast charging preheating control method for new energy vehicles according to claim 1, characterized in that, During the fast charging preheating process, if the output voltage is less than or equal to the third preset voltage threshold and continues for the second predetermined time, or if the output voltage is less than or equal to the fourth preset voltage threshold and continues for the third predetermined time, the entire DC fast charging process will be directly triggered to end. The third preset voltage threshold is greater than the fourth preset voltage threshold, and the second predetermined time is greater than the third predetermined time.

6. The DC fast charging preheating control method for new energy vehicles according to any one of claims 1 to 5, characterized in that, The conditions for charging at high voltage include: no predetermined level of fault in the vehicle and battery management system, the gear is in P gear, the motor speed is less than the preset speed, and the fast charging gun is connected.

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