阅读说明：本技术 一种确定动力电池实时放电电流允许值的方法 (Method for determining real-time discharge current allowable value of power battery ) 是由 刘新 程尧 周建兵 汪斌 於家华 徐远 王建平 郑凯 黄棕 肖聪 李燕 肖恩 于 2021-09-23 设计创作，主要内容包括：一种确定动力电池实时放电电流允许值的方法,包括以下步骤：S1、电池管理系统BMS上电后,放电电流允许值为30s峰值电流；S2、当车辆实际电流大于动力电池当前允许的持续放电电流值,且持续30s时,放电电流允许值按照30A/s的变化速率降低,直至降到当前电芯温度和当前荷电状态下的持续放电电流值；若放电电流允许值的变化量低于5A,则直接跳变；S3、当车速下降,整车实际电流小于0.7倍动力电池当前允许的持续放电电流值,且持续2s时,放电电流允许值由持续放电电流值直接跳变到30s峰值电流；S4、循环步骤S2和S3,直至电池管理系统BMS下电。本设计不仅解决了电池放电过流问题,而且控制策略简单。(A method for determining a real-time discharge current allowable value of a power battery comprises the following steps: s1, after the battery management system BMS is electrified, the allowable value of the discharging current is 30S peak current; s2, when the actual current of the vehicle is larger than the current allowable continuous discharge current value of the power battery and lasts for 30S, reducing the allowable discharge current value according to the change rate of 30A/S until the current cell temperature and the continuous discharge current value in the current state of charge are reduced; if the variation of the discharge current allowable value is lower than 5A, directly jumping; s3, when the vehicle speed is reduced, the actual current of the whole vehicle is less than 0.7 time of the current allowed continuous discharge current value of the power battery, and the current allowed continuous discharge current value is directly jumped from the continuous discharge current value to the peak current of 30S when the current allowed continuous discharge current value lasts for 2S; s4, and loops through steps S2 and S3 until the battery management system BMS is powered down. The design not only solves the problem of over-current of battery discharge, but also has simple control strategy.)

1. A method for determining a real-time discharge current allowable value of a power battery is characterized by comprising the following steps:

s1, after the battery management system BMS is powered on, the discharging current allowable value sent by the battery management system BMS is 30S peak current;

s2, when the actual current of the vehicle is larger than the current allowed continuous discharging current value of the power battery and the duration time reaches the set time T1, the discharging current allowed value sent by the battery management system BMS is smoothly transited to the current cell temperature and the continuous discharging current value in the current state of charge from the peak current of 30S;

s3, when the vehicle speed is reduced, the actual current of the whole vehicle is smaller than the current allowed continuous discharging current value of the power battery, and the duration time reaches the set time T2, directly jumping the allowed discharging current value sent by the battery management system BMS from the continuous discharging current value to the peak current of 30S;

s4, and loops through steps S2 and S3 until the battery management system BMS is powered down.

2. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: in step S2, the set time T1 is 30S.

3. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: in step S2, the discharge current allowable value is decreased at a rate of 30A/S until the current cell temperature and the continuous discharge current value in the current state of charge are decreased.

4. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 3, wherein: in step S2, if the variation of the discharge current allowable value is lower than 5A, the discharge current allowable value directly jumps to the current cell temperature and the continuous discharge current value in the current state of charge.

5. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: in step S3, the fact that the actual current of the whole vehicle is smaller than the currently allowed continuous discharge current value of the power battery means that: the actual current of the whole vehicle is less than 0.7 time of the current allowed continuous discharge current value of the power battery.

6. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: in step S3, the set time T2 is 2S.

7. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: and the 30s peak current is obtained by inquiring a 30s peak current matrix table of the power battery according to the current cell temperature and the current charge state.

8. The method for determining the real-time discharge current allowable value of the power battery as claimed in claim 1, wherein: and the continuous discharge current value is obtained by inquiring a continuous discharge current matrix table of the power battery according to the current cell temperature and the current charge state.

Technical Field

The invention relates to the technical field of new energy automobiles, in particular to a method for determining a real-time discharge current allowable value of a power battery, which is mainly suitable for solving the problems of battery discharge overcurrent and complicated control strategy.

Background

In recent years, the power battery of the electric automobile also has been increased in a blowout mode along with the vigorous development of domestic new energy automobiles. The safety performance of a power battery, which is one of the most core parts of an electric automobile, is directly related to the safety of the whole automobile. If the actual discharge current of the power battery exceeds the allowable value for a long time, not only can the overcurrent alarm be frequently sent to bring poorer user experience, but also the battery can be damaged to cause battery safety accidents, and in fact, a large number of battery discharge overcurrent-caused battery failure accidents also exist. The power battery is used as an energy carrier, the magnitude of discharge current cannot be adjusted, the discharge current is determined by the load of the whole vehicle, such as the working conditions of a motor, an air conditioner compressor and other components, and the allowable discharge current of the battery is continuously changed according to the temperature and the current state of charge (SOC) based on the chemical characteristics of the battery. A power distribution unit of a Vehicle Control Unit (VCU) calculates required power based on real-time vehicle speed, electric door pedal opening, real-time current and the like, and finally the output power of the whole vehicle is reduced after comparing the required power with the allowable discharge power of a battery. The allowable discharge power of the battery is calculated by multiplying the allowable discharge current by the present voltage.

In order to avoid overcurrent of a power battery, a battery management system (BMS for short) needs to be designed to reasonably determine the limit value of the allowed discharge current of the BMS in real time, and a Vehicle Control Unit (VCU) accurately responds to the allowed discharge current value sent by the BMS. The allowable discharge current of the power battery is divided into two indexes of continuous discharge current and 30s peak current, and is sent to the VCU in the form of CAN messages. If two indexes are sent by two CAN message signals at the same time, the VCU cannot directly process the indexes and needs special processing in strategy; if only one signal is used for directly sending the continuous discharge current, after the VCU accurately responds, the power of the whole vehicle is limited to a certain extent, the peak power of a driving system cannot be exerted, and the starting is slow and the climbing is difficult.

The existing treatment methods include the following two methods: one method is to only send one index of 30s peak current, and simultaneously ensure that the rated power sum of all load parts of the whole vehicle is smaller than the continuous discharge power of the battery during electric model selection, so that not only can the driving system be ensured to exert the peak power, but also the actual current can be ensured not to exceed the continuous current of the power battery under the ordinary condition, but a certain risk still exists, if a driver drives violently or overloads for a long time, the actual current of the whole vehicle can be controlled below the peak current, but can be larger than the continuous current for a long time, and the battery is damaged. The other method is that the required current and the maximum allowable continuous current are respectively integrated and compared, when the required current is larger than the maximum allowable continuous current, calculation is started, and if the required current is smaller than the maximum allowable continuous current within 5s, the integral is cleared by 0; if the required current is still larger than the maximum allowable continuous current after 5s, calculating current integral for comparison; if the required current integral is larger than the maximum allowable continuous current integral, limiting the peak current of the battery system to be the maximum allowable continuous current; the method has complex calculation, slow response and certain difficulty in implementation.

Disclosure of Invention

The invention aims to overcome the defects and problems of battery discharge overcurrent and complicated control strategy in the prior art, and provides a method for determining the real-time discharge current allowable value of a power battery, which can effectively prevent the battery discharge overcurrent and has a simple control strategy.

In order to achieve the above purpose, the technical solution of the invention is as follows: a method for determining a real-time discharge current allowable value of a power battery comprises the following steps:

s1, after the battery management system BMS is powered on, the discharging current allowable value sent by the battery management system BMS is 30S peak current;

s2, when the actual current of the vehicle is larger than the current allowed continuous discharging current value of the power battery and the duration time reaches the set time T1, the discharging current allowed value sent by the battery management system BMS is smoothly transited to the current cell temperature and the continuous discharging current value in the current state of charge from the peak current of 30S;

s3, when the vehicle speed is reduced, the actual current of the whole vehicle is smaller than the current allowed continuous discharging current value of the power battery, and the duration time reaches the set time T2, directly jumping the allowed discharging current value sent by the battery management system BMS from the continuous discharging current value to the peak current of 30S;

s4, and loops through steps S2 and S3 until the battery management system BMS is powered down.

In step S2, the set time T1 is 30S.

In step S2, the discharge current allowable value is decreased at a rate of 30A/S until the current cell temperature and the continuous discharge current value in the current state of charge are decreased.

In step S2, if the variation of the discharge current allowable value is lower than 5A, the discharge current allowable value directly jumps to the current cell temperature and the continuous discharge current value in the current state of charge.

In step S3, the fact that the actual current of the whole vehicle is smaller than the currently allowed continuous discharge current value of the power battery means that: the actual current of the whole vehicle is less than 0.7 time of the current allowed continuous discharge current value of the power battery.

In step S3, the set time T2 is 2S.

And the 30s peak current is obtained by inquiring a 30s peak current matrix table of the power battery according to the current cell temperature and the current charge state.

And the continuous discharge current value is obtained by inquiring a continuous discharge current matrix table of the power battery according to the current cell temperature and the current charge state.

Compared with the prior art, the invention has the beneficial effects that:

1. in the method for determining the real-time discharging current allowable value of the power battery, after a Battery Management System (BMS) is electrified, the discharging current allowable value is 30s peak current; when the actual current of the vehicle is larger than the currently allowed continuous discharge current value of the power battery and the duration time reaches the set time T1, smoothly transitioning the discharge current allowed value from the peak current of 30s to the current cell temperature and the continuous discharge current value in the current state of charge; when the vehicle speed is reduced, the actual current of the whole vehicle is smaller than the current allowed continuous discharge current value of the power battery, and the duration time reaches the set time T2, the allowed discharge current value directly jumps to the peak current of 30s from the continuous discharge current value; the design adopts a signal to alternately send the 30s peak current and the continuous discharge current value, so that the potential risk of discharge overcurrent caused by the fact that the battery management system BMS only sends the 30s peak current is avoided while the power performance of the whole vehicle is ensured; meanwhile, the same CAN message signal is adopted to send the real-time discharging current allowable value of the power battery, and the whole vehicle controller is convenient to implement data processing and control strategies. Therefore, the invention not only can effectively prevent the battery from discharging and overflowing, but also simplifies the control strategy.

2. In the method for determining the real-time discharging current allowable value of the power battery, the discharging current allowable value is reduced according to the change rate of 30A/s until the discharging current allowable value is reduced to the continuous discharging current value under the current electric core temperature and the current charge state, steady step decrease and direct jump are not adopted, and the purpose is to prevent the driving force of a driving system from changing too fast to bring bad user experience due to sudden vehicle speed reduction. Therefore, the invention improves the user experience.

Drawings

FIG. 1 is a flow chart of the present invention.

Fig. 2 is a 30s peak current matrix table for a certain power cell.

Fig. 3 is a continuous discharge current matrix table of a certain power battery.

In fig. 1:representing the actual current of the vehicle;and the current value of the continuous discharge current currently allowed by the power battery is shown.

Detailed Description

The present invention will be described in further detail with reference to the following description and embodiments in conjunction with the accompanying drawings.

Referring to fig. 1 to 3, a method for determining a real-time discharge current allowable value of a power battery includes the following steps:

s1, after the battery management system BMS is powered on, the discharging current allowable value sent by the battery management system BMS is 30S peak current;

s2, when the actual current of the vehicle is larger than the current allowed continuous discharging current value of the power battery and the duration time reaches the set time T1, the discharging current allowed value sent by the battery management system BMS is smoothly transited to the current cell temperature and the continuous discharging current value in the current state of charge from the peak current of 30S;

s3, when the vehicle speed is reduced, the actual current of the whole vehicle is smaller than the current allowed continuous discharging current value of the power battery, and the duration time reaches the set time T2, directly jumping the allowed discharging current value sent by the battery management system BMS from the continuous discharging current value to the peak current of 30S;

s4, and loops through steps S2 and S3 until the battery management system BMS is powered down.

In step S2, the set time T1 is 30S.

In step S2, the discharge current allowable value is decreased at a rate of 30A/S until the current cell temperature and the continuous discharge current value in the current state of charge are decreased.

In step S2, if the variation of the discharge current allowable value is lower than 5A, the discharge current allowable value directly jumps to the current cell temperature and the continuous discharge current value in the current state of charge.

In step S3, the fact that the actual current of the whole vehicle is smaller than the currently allowed continuous discharge current value of the power battery means that: the actual current of the whole vehicle is less than 0.7 time of the current allowed continuous discharge current value of the power battery.

In step S3, the set time T2 is 2S.

And the 30s peak current is obtained by inquiring a 30s peak current matrix table of the power battery according to the current cell temperature and the current charge state.

And the continuous discharge current value is obtained by inquiring a continuous discharge current matrix table of the power battery according to the current cell temperature and the current charge state.

The principle of the invention is illustrated as follows:

the design aims at ensuring the power performance of the whole vehicle and avoiding the potential risk of discharging and overcurrent when the BMS only sends 30s peak current. In order to realize the purpose, a method for determining the real-time discharge current allowable value of the power battery is provided by combining the change of the actual current and the characteristics of the battery. The BMS sends the real-time discharging current allowable value of the power battery by using the same CAN message signal, and the real-time discharging current allowable value is alternately sent by 30s peak current and continuous discharging current according to a specific rule, so that the rule change is realized, the conventional method is broken, and the problem of battery discharging overcurrent is effectively prevented; meanwhile, the control strategy is simplified, the data processing is simple, the response is fast, the discharge current is limited more quickly, and the data processing and control strategy of the whole vehicle controller are convenient to realize.

In addition, the continuous discharging current value directly jumps to the peak current value of 30s instead of steadily rising, because the current required current of the whole vehicle is smaller than the continuous discharging current value and is even smaller than the peak current value of 30s, and the jumping of the vehicle speed cannot be influenced. After one cycle is finished, the discharge current allowable value sent by the BMS returns to the default 30s peak current again, and the discharge current allowable value is lowered to the continuous discharge current value only when the change condition is satisfied again.

Example (b):

referring to fig. 1, a method for determining a real-time discharge current allowable value of a power battery includes the following steps:

s1, after the battery management system BMS is powered on, the discharging current allowable value sent by the battery management system BMS is 30S peak current;

s2, when the actual current of the vehicle is larger than the current allowable continuous discharge current value of the power battery and the duration time reaches a set time T1 (the set time T1 is 30S), smoothly transitioning the allowable discharge current value sent by the battery management system BMS from the peak current of 30S to the current cell temperature and the continuous discharge current value in the current state of charge;

the allowable value of the discharge current is reduced according to the change rate of 30A/s until the allowable value of the discharge current is reduced to the continuous discharge current value at the current cell temperature and the current charge state;

if the variation of the discharging current allowable value is lower than 5A, directly jumping the discharging current allowable value to the continuous discharging current value at the current cell temperature and the current charge state;

s3, when the vehicle speed is reduced, the actual current of the whole vehicle is less than 0.7 time of the current allowed continuous discharging current value of the power battery, and the duration time reaches the set time T2 (the set time T2 is 2S), directly jumping the discharging current allowed value sent by the battery management system BMS from the continuous discharging current value to the peak current of 30S;

s4, and loops through steps S2 and S3 until the battery management system BMS is powered down.

The 30s peak current is obtained by querying a 30s peak current matrix table of the power battery according to the current cell temperature and the current state of charge, as shown in fig. 2.

The continuous discharge current value is obtained by querying a continuous discharge current matrix table of the power battery according to the current cell temperature and the current state of charge, as shown in fig. 3.