SOC calibration method for fuel cell vehicle

Abstract

The invention discloses a fuel cell automobile SOC calibration method. The method comprises the following steps that (1) a driver inputs an SOC calibration request through a central control screen; (2) after the vehicle is powered on, the vehicle control unit receives the request and judges whether the vehicle meets the condition of entering a parking charging mode or not; (3) the vehicle control unit adjusts and sets the target power of the fuel cell engine controller in real time according to the allowable charging power sent by the battery management system; (4) the battery management system adjusts allowable charging power in real time according to the state of the fuel cell, charges at the tail end with low power, and performs SOC full charge calibration on the fuel cell; (5) when the fuel cell reaches a full charge condition, the battery management system calibrates the SOC to 100% and sends the calibrated SOC value to the instrument for display; and the battery management system sends a charging stopping signal to the vehicle control unit, and the vehicle control unit controls the fuel cell engine controller to enter the standby mode and exit the parking charging mode.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy vehicles, and in particular to a SOC calibration method for a fuel cell vehicle. Background Art

[0002] As a clean energy vehicle, fuel cell vehicles offer significant advantages in energy conservation and emission reduction. However, due to their inherent characteristics, fuel cell engines cannot promptly respond to changes in vehicle power demand, particularly in scenarios requiring instantaneous high power output, such as starting and accelerating. Therefore, a power battery system is often required to work in conjunction with the engine. Power batteries not only provide additional high power support during starting and acceleration to maintain vehicle performance, but also recover energy during braking, reducing vehicle energy consumption and improving overall energy efficiency.

[0003] However, in actual use, some fuel cell vehicle users are accustomed to replenishing energy only through hydrogen refueling, and do not use external charging equipment to fully charge the power battery for a long time. This usage pattern will cause a large deviation between the SOC (State of Charge) of the power battery and the actual remaining capacity of the battery. This deviation will make the SOC of the power battery unable to accurately reflect the true remaining capacity of the battery, thereby affecting the energy management strategy and power allocation decision of the entire vehicle, and ultimately may cause the power battery to be unable to meet the power requirements of the entire vehicle, and even affect the normal operation of the vehicle. Therefore, for the SOC calibration problem of the power battery of fuel cell vehicles, an effective solution is urgently needed to eliminate the deviation between SOC and actual capacity, ensure that the power battery can accurately feedback the remaining capacity, and thus protect the power performance and operating efficiency of the entire vehicle. Summary of the Invention

[0004] The purpose of the present invention is to address the problem of a large deviation between the SOC (State of Charge) of a power battery and the actual remaining capacity of the battery in the prior art, and to propose a fuel cell vehicle SOC calibration method, comprising the following steps:

[0005] (1) The driver inputs the SOC calibration request through the central control screen;

[0006] (2) After the vehicle is powered on and ready, the vehicle controller receives the request and determines whether the vehicle meets the conditions for entering the parking charging mode; if so, it sends a mode switching command to the fuel cell engine controller and the battery management system;

[0007] (3) The vehicle controller adjusts the target power of the fuel cell engine controller in real time according to the allowed charging power sent by the battery management system;

[0008] (4) The battery management system adjusts the allowed charging power in real time according to the status of the fuel cell, charges at a low power at the end, and calibrates the fuel cell's SOC to full charge;

[0009] (5) When the fuel cell reaches the full charge condition, the battery management system calibrates the SOC to 100% and sends the calibrated SOC value to the instrument display; the battery management system sends a stop charging signal to the vehicle controller, and the vehicle controller controls the fuel cell engine controller to enter the standby mode and exit the parking charging mode.

[0010] Preferably, the condition of the parking charging mode is that the vehicle is in neutral and the speed is less than 5 km and the parking signal is valid.

[0011] Preferably, the allowed charging power is sent by controlling the fuel cell management system according to a battery charging MAP table.

[0012] Preferably, the target power range of the fuel cell engine controller is ±5% of the charging power allowed by the fuel cell management system.

[0013] Preferably, the SOC full charge calibration method includes the following steps:

[0014] (a) Enter the charging process; (b) Confirm whether the battery voltage is greater than 3.5V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 1C to 0.75C; (d) Confirm again whether the battery voltage is greater than 3.525V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.75C to 0.5C; (e) Confirm again whether the battery voltage is greater than 3.55V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.5C to 0.2C; (f) Confirm again whether the battery voltage is greater than 3.7V. After confirmation, the SOC is corrected to 100% and a stop charging command is sent to the vehicle controller.

[0015] Preferably, when the vehicle controller detects that one of the following conditions is met, it exits the parking power generation mode and sends a standby command to the fuel cell engine controller: (A) vehicle speed > 10 km / h; (B) the parking signal is invalid; (C) the battery management system stops charging command; (D) the vehicle gear is not in neutral.

[0016] The present invention has the following beneficial effects: It provides a method for periodically fully charging and calibrating the power battery's SOC without requiring an external off-board charger. This method is more suitable for fuel cell vehicle applications, as it eliminates the need for regular visits to charging stations to calibrate the power battery's SOC. It also provides a safe and reliable method for calibrating the power battery's SOC while the vehicle is parked, avoiding deviations in SOC calibration caused by the battery's charging / discharging process while the vehicle is in motion. The method also prevents damage to the power battery from braking feedback during driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For those skilled in the art, other relevant drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 The structural principle of the fuel cell vehicle of the present invention;

[0019] Figure 2 This is a logic block diagram of the SOC calibration of a fuel cell vehicle according to the present invention;

[0020] Figure 3 This is a diagram of the SOC calibration strategy for the charging terminal of the battery management system of the present invention;

[0021] Figure 4 This is a logic block diagram of the parking charging mode of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by the first technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by the first technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] Example

[0024] The following are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the following embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention.

[0025] Refer to the instruction manual Figure 1 The fuel cell engine controller (FCU) controls the fuel cell management system (BMS) to operate according to the target power set by the vehicle control unit (VCU) and provides feedback on the fuel cell engine's operating status. It also samples the fuel cell engine's total output voltage and current, the stack voltage and current, performs real-time hydrogen storage pressure detection, short-circuit monitoring, fault diagnosis (including temperature, voltage, current, and communication), and fuel cell management system safety management (including overcurrent, overheating, voltage difference, and temperature difference protection). The fuel cell management system (BMS) is responsible for battery charge / discharge management, real-time monitoring of battery physical parameters, battery state of charge (SOC) estimation, online diagnosis and early warning, and balancing management. The vehicle control unit (VCU) is responsible for overall vehicle energy management, real-time monitoring of the vehicle's physical parameters, and is the vehicle's control center, managing and monitoring the operation of each vehicle subsystem; it also provides online diagnosis and early warning for the vehicle control system. The central control screen is used for vehicle human-machine interaction. The driver uses the central control screen to set vehicle parameters, input operational requirements, and receive feedback on vehicle status.

[0026] Reference Manual Figure 2 A fuel cell vehicle SOC calibration method comprises the following steps:

[0027] (1) The driver inputs the SOC calibration request through the central control screen;

[0028] (2) After the vehicle is powered on and ready, the vehicle controller receives the request and determines whether the vehicle meets the conditions for entering the parking charging mode; if so, it sends a mode switching command to the fuel cell engine controller and the battery management system;

[0029] (3) The vehicle controller adjusts the target power of the fuel cell engine controller in real time according to the allowed charging power sent by the battery management system;

[0030] (4) The battery management system adjusts the allowed charging power in real time according to the status of the fuel cell, charges at a low power at the end, and calibrates the fuel cell's SOC to full charge;

[0031] (5) When the fuel cell reaches the full charge condition, the battery management system calibrates the SOC to 100% and sends the calibrated SOC value to the instrument display; the battery management system sends a stop charging signal to the vehicle controller, and the vehicle controller controls the fuel cell engine controller to enter the standby mode and exit the parking charging mode.

[0032] When the vehicle's power performance declines, or the vehicle has been parked for a long time, and the vehicle has not been fully charged with an external charger for a long time, the SOC displayed on the vehicle instrument panel is seriously inconsistent with the actual remaining power of the vehicle's power battery. The driver starts the power-on calibration of the power battery SOC by operating the vehicle's central control screen. After the vehicle is powered on and ready, the vehicle controller (VCU) receives the request from the central control screen and checks whether the vehicle is in neutral, whether the speed is less than 5km, and whether the parking signal is valid. Then it enters the parking charging mode, sends a mode command, and the fuel cell engine controller (FCU) starts to enter the standby mode. The allowed charging power is the target power range of the fuel cell engine controller sent by the fuel cell management system (BMS) according to the battery charging MAP table, which is the allowed charging power of the fuel cell management system (BMS) ±5%.

[0033] After the fuel cell management system (BMS) receives the parking charging mode command from the vehicle controller (VCU), the battery power MAP table switches from the driving MAP table to the charging MAP table, sends the allowed charging power to the vehicle controller (VCU), and configures the terminal SOC calibration strategy according to the DC charging mode. The supplementary battery power MAP table and charging MAP table are shown in the following table:

[0034] Table 1 Battery charging MAP table (kW)

[0035]

[0036] Table 2 Battery driving discharge MAP table (kW)

[0037]

[0038] Reference Manual Figure 2 The vehicle controller (VCU) adjusts the target power of the fuel cell engine controller (FCU) in real time based on the allowed charging power sent by the fuel cell management system (BMS). The fuel cell management system (BMS) adjusts the allowed charging power in real time based on the battery status, charges at a low power at the end, and calibrates the power battery's SOC. After completing the SOC calibration, a stop charging command is sent to the vehicle controller (VCU). In the laboratory, charging / discharging equipment and a battery cell OCV meter are used; based on the OCV meter, the SOC is fully calibrated at the charging end. The battery cell OCV meter is shown in the following table:

[0039] Table 3 OCV table of battery cells tested in the laboratory

[0040] SOC 0％ 5％ 10％ 20％ 30％ 40％ 50％ 60％ 70％ 80％ 90％ 95％ 100％ Cell voltage (V) 2.721 3.263 3.325 3.373 3.399 3.405 3.414 3.426 3.439 3.485 3.483 3.525 3.652

[0041] Reference Manual Figure 3, the SOC full charge calibration method includes the following steps:

[0042] (a) Enter the charging process; (b) Confirm whether the battery voltage is greater than 3.5V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 1C to 0.75C; (d) Confirm again whether the battery voltage is greater than 3.525V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.75C to 0.5C; (e) Confirm again whether the battery voltage is greater than 3.55V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.5C to 0.2C; (f) Confirm again whether the battery voltage is greater than 3.7V. After confirmation, the SOC is corrected to 100% and a stop charging command is sent to the vehicle controller.

[0043] Reference Manual Figure 4 When the vehicle controller detects that one of the following conditions is met, it exits the parking power generation mode and sends a standby command to the fuel cell engine controller: (A) vehicle speed > 10 km / h; (B) the parking signal is invalid; (C) the battery management system stops charging command; (D) the vehicle gear is not in neutral.

[0044] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A fuel cell vehicle SOC calibration method, characterized in that: The steps include: (1) The driver inputs the SOC calibration request through the central control screen; (2) After the vehicle is powered on and ready, the vehicle controller receives the request and determines whether the vehicle meets the conditions for entering the parking charging mode; If satisfied, a mode switching command is sent to the fuel cell engine controller and the battery management system; (3) The vehicle controller adjusts the target power of the fuel cell engine controller in real time according to the allowed charging power sent by the battery management system; (4) The battery management system adjusts the allowed charging power in real time according to the status of the fuel cell, charges at a low power at the end, and calibrates the fuel cell's SOC to full charge; (5) When the fuel cell reaches the full charge condition, the battery management system calibrates the SOC to 100% and sends the calibrated SOC value to the instrument display; the battery management system sends a stop charging signal to the vehicle controller, and the vehicle controller controls the fuel cell engine controller to enter the standby mode and exit the parking charging mode.

2. The fuel cell vehicle SOC calibration method according to claim 1, characterized in that: The conditions for the parking charging mode are that the vehicle is in neutral, the vehicle speed is less than 5 km, and the parking signal is valid.

3. The fuel cell vehicle SOC calibration method according to claim 1, characterized in that: The allowed charging power is sent by controlling the fuel cell management system according to the battery charging MAP table.

4. The fuel cell vehicle SOC calibration method according to claim 1, characterized in that: The target power range of the fuel cell engine controller is ±5% of the BMS allowed charging power.

5. The fuel cell vehicle SOC calibration method according to claim 1, characterized in that: The SOC full charge calibration method comprises the following steps: (a) Enter the charging process; (b) Confirm whether the battery voltage is greater than 3.5V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 1C to 0.75C; (d) Confirm again whether the battery voltage is greater than 3.525V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.75C to 0.5C; (e) Confirm again whether the battery voltage is greater than 3.55V. After confirmation, the allowable charging current sent to the vehicle controller is reduced from 0.5C to 0.2C; (f) Confirm again whether the battery voltage is greater than 3.7V. After confirmation, the SOC is corrected to 100% and a stop charging command is sent to the vehicle controller.

6. The fuel cell vehicle SOC calibration method according to claim 1, characterized in that: When the vehicle controller detects that one of the following conditions is met, it exits the parking power generation mode and sends a standby command to the fuel cell engine controller: (A) vehicle speed > 10 km / h; (B) the parking signal is invalid; (C) the battery management system stops charging; (D) the vehicle gear is not in neutral.

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