Dynamic power reduction control method for electric vehicle in low-voltage mode

Abstract

The invention discloses a dynamic power reduction control method for an electric vehicle in a low-voltage mode. The dynamic power reduction control method comprises the following steps: setting a corresponding table of fault levels of over-low single voltage faults at different temperatures and the lowest single voltage Vmin; the lowest single voltage Vmin of the current electric vehicle in the low-voltage mode is obtained, and the fault level of the fault with the too low single voltage is determined according to the corresponding table; in the normal driving mode, if the fault level is lower than 4, the minimum single voltage Vmin is controlled to be above 1700 mV by limiting power. According to the invention, the use convenience and safety of the vehicle can be improved.

Description

Technical Field

[0001] This invention relates to the technical field of power control for electric vehicles, and more specifically, to a dynamic power reduction control method for electric vehicles in low-voltage mode. Background Technology

[0002] Currently, in new energy commercial vehicles, for low cell voltage faults, the fault level is generally determined and handled based on the Vmin value at different temperatures, using a four-level fault system: Level 1, Level 2, Level 3, and Extreme Fault. Corresponding discharge power limits are applied when different fault levels are triggered. Due to the influence of individual battery temperature, the power reduction after a fault is triggered may cause the battery to directly reach Level 3 or 4 before even triggering Level 2. Once a Level 4 fault is reached, the battery is at its extreme fault level, and even if the vehicle is towed to a charging station, it cannot be charged. Manual fault clearing is required before normal charging can resume, causing significant inconvenience to customers. Therefore, how to limit discharge power when a fault occurs at the discharge end to improve vehicle usability and safety is of great importance. Summary of the Invention

[0003] This invention provides a dynamic power reduction control method for electric vehicles in low-voltage mode, which solves the problem of inconvenience caused by existing power control in low-voltage mode of electric vehicles, and can improve the convenience and safety of vehicle use.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A dynamic power reduction control method for electric vehicles in low-voltage mode includes:

[0006] Set up a table showing the correspondence between the fault level of a single-cell voltage low fault and the minimum single-cell voltage Vmin at different temperatures;

[0007] Obtain the lowest single-cell voltage Vmin in the current low-voltage mode of the electric vehicle, and determine the fault level of the low single-cell voltage fault according to the corresponding table.

[0008] In normal driving mode, if the fault level is lower than level 4, the minimum single-cell voltage Vmin is controlled above 1700mV by limiting power.

[0009] Preferred options also include:

[0010] The charging and discharging limits of the vehicle are set according to the fault level. No charging and discharging limits are imposed when the fault level is 1. The charging and discharging limits are set at 75% when the fault level is 2, at 50% when the fault level is 3, and at 0% when the fault level is 4.

[0011] Preferred options also include:

[0012] The duration of individual cell voltage between different voltage values ​​was calibrated on a test bench at different temperatures (0.5C, 0.3C, 0.1C, and 2.0C).

[0013] Obtain the required power of the whole vehicle, and calculate the vehicle power reduction rate based on the duration corresponding to different calibrated voltage values, the required power of the whole vehicle, and the fault level;

[0014] The vehicle power is controlled based on the calculated vehicle power reduction rate.

[0015] Preferably, the calculation of the vehicle power reduction rate includes:

[0016] The time required for the vehicle's power demand to decrease to 0KW under different fault levels was calculated using linear interpolation.

[0017] Calculate the vehicle power reduction rate based on the required time.

[0018] Preferably, the calculation of the vehicle power reduction rate further includes:

[0019] The average power demand of the vehicle in the first 5 seconds is used to determine the power demand of the vehicle in the next 1 second. Every 5 seconds, the rate of reduction is calculated in real time based on the current power demand.

[0020] Preferably, the step of calculating the vehicle power reduction rate based on the required time includes:

[0021] The vehicle power reduction rate is calculated using the formula: Vehicle power demand rate = Vehicle power demand / Required time corresponding to the voltage change range.

[0022] Preferably, when the individual cell voltage is too low and the fault level is 1, 2, or 3, the lowest individual cell voltage Vmin is controlled above 1900mV by reducing the power.

[0023] Preferably, the table showing the correspondence between the fault level of a low-voltage individual cell at different temperatures and the lowest individual cell voltage Vmin includes:

[0024] When the single-unit voltage is too low (Level 1 fault): Vmin≤2500mV (Tmin>25℃), Vmin≤2100mV (-10℃<Tmin≤25℃);

[0025] When a single-unit voltage is too low (Level 2 fault): Vmin≤2000mV (Tmin>25℃), Vmin≤1900mV (-10℃<Tmin≤25℃);

[0026] When a single-unit voltage is too low (Level 3 fault): Vmin≤1900mV (Tmin>25℃), Vmin≤1800mV (-10℃<Tmin≤25℃);

[0027] When the body voltage is low at level 4: Vmin≤1700mV (Tmin>25℃), Vmin≤1700mV (-10℃<Tmin≤25℃).

[0028] This invention provides a dynamic power reduction control method for electric vehicles in low-voltage mode. At the end of discharge, without prematurely limiting power, it rapidly limits the low-voltage fault of individual cells to the corresponding level based on multiple factors such as Vmin, the current power demand of the vehicle, and fault diagnosis time. In normal driving mode, the lowest individual cell voltage is controlled at ≥1700mV to facilitate timely charging. This solves the problem of inconvenience caused by existing power control methods in low-voltage mode for electric vehicles, improving the convenience and safety of vehicle use. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0030] Figure 1 This is a schematic diagram of a dynamic power reduction control method for electric vehicles in low-voltage mode provided by the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the embodiments of the present invention, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and implementation methods.

[0032] To address the inconvenience caused by power control in existing electric vehicles under low voltage mode, this invention provides a dynamic power reduction control method for electric vehicles under low voltage mode, which solves the problem of inconvenience caused by power control in existing electric vehicles under low voltage mode and can improve the convenience and safety of vehicle use.

[0033] like Figure 1 As shown, a dynamic power reduction control method for an electric vehicle in low-voltage mode includes:

[0034] S1: Set the table of fault levels for low cell voltage at different temperatures and their correspondence with the lowest cell voltage Vmin.

[0035] S2: Obtain the lowest single-cell voltage Vmin in the current low-voltage mode of the electric vehicle, and determine the fault level of the low single-cell voltage fault according to the corresponding table.

[0036] S3: In normal driving mode, if the fault level is lower than level 4, the minimum single-cell voltage Vmin is controlled above 1700mV by limiting power.

[0037] Furthermore, the table mapping the fault level of a low-voltage individual cell at different temperatures to the minimum individual cell voltage Vmin includes:

[0038] When the single-unit voltage is too low (Level 1 fault): Vmin≤2500mV (Tmin>25℃), Vmin≤2100mV (-10℃<Tmin≤25℃);

[0039] When a single-unit voltage is too low (Level 2 fault): Vmin≤2000mV (Tmin>25℃), Vmin≤1900mV (-10℃<Tmin≤25℃);

[0040] When a single-unit voltage is too low (Level 3 fault): Vmin≤1900mV (Tmin>25℃), Vmin≤1800mV (-10℃<Tmin≤25℃);

[0041] When the body voltage is low at level 4: Vmin≤1700mV (Tmin>25℃), Vmin≤1700mV (-10℃<Tmin≤25℃).

[0042] In practical applications, the corresponding table is shown in Table 1:

[0043]

[0044] The method also includes setting charging and discharging limits for the vehicle according to the fault level: no charging and discharging limits are imposed when the fault level is 1; the charging and discharging limits are set at 75% when the fault level is 2; the charging and discharging limits are set at 50% when the fault level is 3; and the charging and discharging limits are set at 0% when the fault level is 4.

[0045] The method also includes:

[0046] The duration of individual cell voltage between different voltage values ​​was calibrated on a test bench at different temperatures (0.5C, 0.3C, 0.1C, and 2.0C).

[0047] Obtain the required power of the vehicle and calculate the vehicle power reduction rate based on the duration corresponding to different calibrated voltage values, the required power of the vehicle, and the fault level.

[0048] The vehicle power is controlled based on the calculated vehicle power reduction rate.

[0049] In practical applications, the duration of different voltage values ​​at 0.5C, 0.3C, and 0.1C rates under different temperatures was calibrated on a test bench, as shown in Table 2. This means the vehicle's power demand needs to be limited to 0 kWh within the 2.000-1.900V time range, thus controlling the battery pack's Vmin voltage to ≥1900mV. This allows for control of individual cell voltages below level 3, at which point charging current is limited to half, but charging is still possible. The vehicle's power demand can be converted to the corresponding vehicle discharge power, i.e., 100kW corresponds to a 2.0C discharge rate.

[0050]

[0051] Furthermore, the calculation of the vehicle's power reduction rate includes:

[0052] The time required for the vehicle's power demand to decrease to 0KW under different fault levels was calculated using linear interpolation.

[0053] Calculate the vehicle power reduction rate based on the required time.

[0054] In practical applications, the vehicle's required power, fault level, power reduction rate, and required time are shown in Table 3:

[0055]

[0056] Furthermore, the step of calculating the vehicle power reduction rate based on the required time includes:

[0057] The vehicle power reduction rate is calculated using the formula: Vehicle power demand rate = Vehicle power demand / Required time corresponding to the voltage change range.

[0058] In one embodiment, the current power demand is 50kW, and the single-cell voltage is detected online as Vmin=2.200V. Then, it is reduced to 2.000V. Because 2.500-2.000V can support 30s of 50kW discharge, then from 2.200V to 2.000V, according to linear interpolation, it can only support 12s of 50kW discharge.

[0059] 2.5 - 2.0 = 0.5V;

[0060] 2.2 - 2.0 = 0.2V;

[0061] 0.5V / 30s = 0.2V / (Xs);

[0062] X=12s, that is, from 2.200V to 2.000V. According to linear interpolation, a 50kW discharge can only support 12s.

[0063] If a 50kW discharge can support a voltage drop from 2.200V to 1.900V for 5 seconds, then a total of 17 seconds (12+5=17) can be supported from 2.200V to 1.900V. That is, to reduce the vehicle's required power from 50kW to 0kW within 17 seconds, the rate of reduction is: 50 / 17 = 2.94kW / s.

[0064] Furthermore, the calculation of the vehicle's power reduction rate also includes:

[0065] The average power demand of the vehicle in the first 5 seconds is used to determine the power demand of the vehicle in the next 1 second. Every 5 seconds, the rate of reduction is calculated in real time based on the current power demand.

[0066] In one embodiment, if a vehicle currently requires 50kW of power, as calculated above, after a 5s reduction in power demand, the current power demand becomes 100kW, and Vmin decreases from 2.500V to 2.200V. The time required for Vmin to decrease from 2.200V to 2.000V is:

[0067] 2.5 - 2.0 = 0.5V;

[0068] 2.2 - 2.0 = 0.2V;

[0069] 0.5V / 10s = 0.2V / (Xs);

[0070] X=4s, that is, from 2.200V to 2.000V. According to linear interpolation, a 100kW discharge only supports 1s.

[0071] If a discharge of 100kW can support 2 seconds from 2.000V to 1.900V, then a discharge of 2.200V to 1.900V can support a total of 6 seconds (2+4=6).

[0072] If the required power of the vehicle is reduced from 100kW to 0kW within 6 seconds, then the rate of reduction is: 100 / 6 = 16.6kW / s.

[0073] Furthermore, when the individual cell voltage is low at levels 1, 2, or 3, the lowest individual cell voltage Vmin is controlled above 1900mV by reducing the power. At level -3 (lowest individual cell voltage), although the charging current is limited to half, charging is still possible.

[0074] As can be seen, this invention provides a dynamic power reduction control method for electric vehicles in low-voltage mode. At the end of discharge, without prematurely limiting power, it needs to quickly limit the low-voltage fault of individual cells to the corresponding level based on multiple factors such as Vmin, the current power demand of the entire vehicle, and the fault diagnosis time. In normal driving mode, the lowest individual cell voltage is controlled at ≥1700mV to facilitate timely charging. This solves the problem of inconvenience caused by existing power control in low-voltage mode of electric vehicles, improving the convenience and safety of vehicle use.

[0075] The structure, features, and effects of the present invention have been described in detail above with reference to the embodiments shown in the figures. The above description is only a preferred embodiment of the present invention, but the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent changes, shall be within the protection scope of the present invention as long as they do not exceed the spirit covered by the specification and figures.

Claims

1. A method for dynamic power reduction control in low voltage mode of an electric vehicle, characterized in that, The method comprises: setting a corresponding table of fault levels of the cell voltage too low fault at different temperatures and the minimum cell voltage Vmin; obtaining the minimum cell voltage Vmin in the low voltage mode of the electric vehicle, and determining the fault level of the cell voltage too low fault according to the corresponding table; in the normal driving mode, if the fault level is lower than level 4, the minimum cell voltage Vmin is controlled above 1700mV by limiting the power.

2. The method for dynamic power reduction control in low voltage mode of an electric vehicle as claimed in claim 1 wherein, Further comprising: setting the charging limit and discharging limit of the vehicle according to the fault level, when the fault level is at level 1, no charging and discharging limit is set, when the fault level is at level 2, the charging limit and discharging limit are set at 75%, when the fault level is at level 3, the charging limit and discharging limit are set at 50%, and when the fault level is at level 4, the charging limit and discharging limit are set at 0%.

3. The method of claim 2, wherein, Further comprising: labeling the time that the cell voltage continuously stays between different voltage values at 0.5C, 0.3C, 0.1C and 2.0C rate under different temperatures on the test bench; obtaining the demand power of the whole vehicle, and calculating the power reduction rate of the vehicle according to the demand power of the whole vehicle, the fault level and the time that the voltage continuously stays between the labeled different voltage values; controlling the power of the vehicle according to the calculated power reduction rate of the vehicle.

4. The method of claim 3, wherein, The calculation of the power reduction rate of the vehicle comprises: calculating the time required for the demand power of the whole vehicle to reduce to 0KW under different fault levels by linear interpolation method; calculating the power reduction rate of the vehicle according to the required time.

5. The method of claim 4, wherein, The calculation of the power reduction rate of the vehicle further comprises: taking the average value of the demand power of the whole vehicle in the previous 5s as the demand power of the whole vehicle in the next 1s, and after driving for 5s, calculating the reduction rate in real time according to the current demand power.

6. The method of claim 5, wherein, The calculation of the power reduction rate of the vehicle according to the required time comprises: calculating the power reduction rate of the vehicle according to the formula: power reduction rate of the vehicle = demand power of the whole vehicle / voltage variation interval corresponding required time.

7. The method of claim 6, wherein, When the cell voltage too low fault is at level 1, 2 or 3, the minimum cell voltage Vmin is controlled above 1900mV by reducing the power.

8. The method of claim 7, wherein, The corresponding table of fault levels of the cell voltage too low fault at different temperatures and the minimum cell voltage Vmin comprises: when the cell voltage too low fault is at level 1: Vmin≤2500mV (Tmin>25℃), Vmin≤2100mV (-10℃<Tmin≤25℃); when the cell voltage too low fault is at level 2: Vmin≤2000mV (Tmin>25℃), Vmin≤1900mV (-10℃<Tmin≤25℃); when the cell voltage too low fault is at level 3: Vmin≤1900mV (Tmin>25℃), Vmin≤1800mV (-10℃<Tmin≤25℃); when the cell voltage too low fault is at level 4: Vmin≤1700mV (Tmin>25℃), Vmin≤1700mV (-10℃<Tmin≤25℃).

Images