1. The energy recovery control method for the pure electric vehicle is characterized by comprising the following steps:

presetting a plurality of single voltage thresholds, and forming corresponding voltage subsection intervals according to the cut-off voltage of the battery single and the single voltage thresholds;

setting a corresponding regulation target power value and a power regulation gradient value for each voltage subsection interval;

acquiring a current SOC value, a current battery monomer temperature and a current battery monomer maximum voltage in real time, and acquiring the power required by a current vehicle-mounted accessory through a bus;

according to the current SOC value and the current battery monomer temperature, obtaining a pre-calibrated allowable energy recovery power corresponding to the current battery working condition by looking up a table;

calculating theoretical energy recovery maximum power by combining the allowed energy recovery power and the power required by the current vehicle-mounted accessory;

and when the current SOC value is larger than or equal to a preset SOC threshold value, based on the current battery monomer highest voltage, the regulation target power value and the power regulation gradient value, regulating the theoretical energy recovery maximum power and outputting a corresponding power value to execute energy recovery.

2. The energy recovery control method for the pure electric vehicle according to claim 1, wherein the adjusting the theoretical energy recovery maximum power and outputting a corresponding power value to perform energy recovery based on the current cell maximum voltage, the regulation target power value, and the power regulation gradient value comprises:

determining a corresponding target voltage subsection interval according to the current battery monomer highest voltage;

comparing the theoretical energy recovery maximum power with a regulation target power value corresponding to a target voltage subsection interval;

and according to the comparison result, reducing or increasing the theoretical energy recovery maximum power by utilizing the power regulation gradient value corresponding to the target voltage subsection interval.

3. The energy recovery control method for the pure electric vehicle according to claim 2, wherein the determining of the corresponding target voltage segment interval according to the current battery cell highest voltage comprises:

comparing the current cell maximum voltage to the cell voltage threshold.

4. The energy recovery control method for the pure electric vehicle according to claim 3, wherein if the current cell highest voltage is less than or equal to the minimum cell voltage threshold, the obtained theoretical energy recovery maximum power is used as output power required by a motor for energy recovery.

5. The energy recovery control method for the pure electric vehicle according to claim 2, wherein the reducing or increasing the theoretical energy recovery maximum power by using the power regulation gradient value corresponding to the target voltage segment interval according to the comparison result comprises:

if the theoretical energy recovery maximum power is larger than the corresponding regulation target power value, monitoring whether the single voltage change rate is larger than 0;

if so, gradually reducing the theoretical energy recovery maximum power to a regulation target power value according to the corresponding power regulation gradient value;

and if the theoretical energy recovery maximum power is smaller than the corresponding regulation target power value, gradually increasing the theoretical energy recovery maximum power to the regulation target power value according to the corresponding power regulation gradient value.

6. The pure electric vehicle energy recovery control method according to claim 5, wherein the step-by-step reduction of the theoretical energy recovery maximum power to a regulation target power value comprises:

in the process of reducing regulation, the change rate of the monomer voltage is continuously monitored;

if the change rate of the cell voltage is monitored to be less than or equal to 0 in the process of reducing regulation, the current power obtained by current regulation is used as the output power for executing energy recovery.

7. A pure electric vehicle energy recovery control method according to any one of claims 1-6, characterized in that when the current SOC value is smaller than a preset SOC threshold value, the obtained theoretical energy recovery maximum power is used as output power required by a motor for energy recovery.

8. A pure electric vehicle energy recovery control method according to any one of claims 1-6, wherein the step of combining the allowable energy recovery power and the current vehicle-mounted accessory required power to obtain the theoretical energy recovery maximum power comprises the following steps:

and fusing the allowable energy recovery power and the power required by the current vehicle-mounted accessory, and calculating the theoretical energy recovery maximum power by combining the energy conversion efficiency of the motor.

Background

The pure electric automobile can realize speed reduction and kinetic energy recovery through the motor when a driver needs to reduce speed. However, when the SOC of the power battery is high and the temperature is low, the allowable charging power is limited by the battery characteristics, or even charging is not allowed, so that many pure electric vehicles limit or even prohibit energy recovery of the motor under such a working condition.

The whole vehicle is used as an electricity utilization system, a plurality of high-voltage accessories and low-voltage accessories consume electricity, a part of recovered electricity can be directly consumed by the high-voltage accessories and the low-voltage accessories, and the other part of the recovered electricity can be charged into the battery; moreover, the allowable energy recovery power value of the battery is generally obtained by calibrating the battery rack, and because the protection of the upper limit of the cell voltage and the consistency of the battery cell are considered, and the service life is shortened and the internal resistance is increased, the calibration value is generally in a conservative bias, otherwise, the cell voltage exceeds the threshold value under partial working conditions, and the health of the battery is influenced.

Currently, a rack calibration mode is generally adopted for managing energy recovery power, the recovery capacity of batteries with different SOCs or different voltages and different temperatures is calibrated, then the recovery power allowed by the current battery is obtained by looking up a table, and the power is used as the capacity value of the motor for recovering the power.

As can be seen from the above analysis, the above method does not consider that the whole vehicle is used as a system, and the high-voltage and low-voltage accessories of the system have certain working power during the running process of the whole vehicle, and consume part of electric energy, that is, the motor can actually recover part of electric quantity to supply the accessories for working, and does not affect the energy recovery of the battery; and, if energy recovery is performed according to the original calibration power, the voltage of the battery cell may exceed the protection upper limit of the voltage of the battery cell, and the energy recovery may be forcibly exited.

Disclosure of Invention

In view of the above, the present invention is directed to provide an energy recovery control method for a pure electric vehicle, so as to solve the problem of poor energy recovery efficiency caused by the above reasons.

The technical scheme adopted by the invention is as follows:

a pure electric vehicle energy recovery control method comprises the following steps:

presetting a plurality of single voltage thresholds, and forming corresponding voltage subsection intervals according to the cut-off voltage of the battery single and the single voltage thresholds;

setting a corresponding regulation target power value and a power regulation gradient value for each voltage subsection interval;

acquiring a current SOC value, a current battery monomer temperature and a current battery monomer maximum voltage in real time, and acquiring the power required by a current vehicle-mounted accessory through a bus;

according to the current SOC value and the current battery monomer temperature, obtaining a pre-calibrated allowable energy recovery power corresponding to the current battery working condition by looking up a table;

calculating theoretical energy recovery maximum power by combining the allowed energy recovery power and the power required by the current vehicle-mounted accessory;

and when the current SOC value is larger than or equal to a preset SOC threshold value, based on the current battery monomer highest voltage, the regulation target power value and the power regulation gradient value, regulating the theoretical energy recovery maximum power and outputting a corresponding power value to execute energy recovery.

In at least one possible implementation manner, the adjusting the theoretical energy recovery maximum power and outputting a corresponding power value to perform energy recovery based on the current cell maximum voltage, the regulation target power value, and the power regulation gradient value includes:

determining a corresponding target voltage subsection interval according to the current battery monomer highest voltage;

comparing the theoretical energy recovery maximum power with a regulation target power value corresponding to a target voltage subsection interval;

and according to the comparison result, reducing or increasing the theoretical energy recovery maximum power by utilizing the power regulation gradient value corresponding to the target voltage subsection interval.

In at least one possible implementation manner, the determining, according to the current highest voltage of the battery cell, a corresponding target voltage segment interval includes:

comparing the current cell maximum voltage to the cell voltage threshold.

In at least one possible implementation manner, if the current cell highest voltage is smaller than or equal to the minimum cell voltage threshold, the obtained theoretical energy recovery maximum power is used as the output power required by the motor for energy recovery.

In at least one possible implementation manner, the reducing or increasing the theoretical energy recovery maximum power by using a power regulation gradient value corresponding to a target voltage segment interval according to the comparison result includes:

if the theoretical energy recovery maximum power is larger than the corresponding regulation target power value, monitoring whether the single voltage change rate is larger than 0;

if so, gradually reducing the theoretical energy recovery maximum power to a regulation target power value according to the corresponding power regulation gradient value;

and if the theoretical energy recovery maximum power is smaller than the corresponding regulation target power value, gradually increasing the theoretical energy recovery maximum power to the regulation target power value according to the corresponding power regulation gradient value.

In at least one possible implementation manner, the gradually reducing the theoretical energy recovery maximum power to a regulation target power value includes:

in the process of reducing regulation, the change rate of the monomer voltage is continuously monitored;

if the change rate of the cell voltage is monitored to be less than or equal to 0 in the process of reducing regulation, the current power obtained by current regulation is used as the output power for executing energy recovery.

In at least one possible implementation manner, when the current SOC value is smaller than a preset SOC threshold, the obtained theoretical energy recovery maximum power is used as the output power required by the motor for energy recovery.

In at least one possible implementation manner, the calculating the theoretical energy recovery maximum power by combining the allowable energy recovery power and the current required power of the vehicle-mounted accessory comprises:

and fusing the allowable energy recovery power and the power required by the current vehicle-mounted accessory, and calculating the theoretical energy recovery maximum power by combining the energy conversion efficiency of the motor.

The design concept of the invention is that the allowable energy recovery calibration power is obtained according to the current battery electric quantity and the battery temperature, the consumed power under the accessory is obtained according to the information of the vehicle-mounted accessory, and the theoretical required power value is obtained by combining the allowable energy recovery calibration power and the consumed power under the accessory. When the electric quantity is higher, the larger or smaller theoretical energy recovery power is adjusted through the preset regulation and control interval and the maximum value of the single voltage, and the situation that the energy recovery is interrupted due to the fact that the single voltage is too high due to the fact that the calibration power is too large is prevented, so that the battery is ensured to be in a sustainable energy recovery mode close to the limit of the capacity, and the increase of the energy recovery contribution rate under the working condition of the electric quantity is facilitated. The invention considers the power consumption of the accessories of the whole vehicle system, and based on the theoretical power, the theoretical power is accurately adjusted in a hierarchical mode under the working condition of higher electric quantity, so that the energy recovery efficiency is improved, and the energy recovery function of the motor is fully exerted. The method is suitable for controlling the energy recovery power and the torque of different types of pure electric vehicles, and particularly can continuously recover energy in a range close to the limit of the battery capacity by adjusting and controlling the power and the torque when the voltage of a single body is close to the cut-off voltage.

Drawings

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described with reference to the accompanying drawings, in which:

fig. 1 is a flowchart of a pure electric vehicle energy recovery control method provided by an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention.

The invention provides an embodiment of a pure electric vehicle energy recovery control method, which specifically comprises the following steps as shown in fig. 1:

step S1, presetting a plurality of single voltage thresholds, and forming corresponding voltage subsection intervals according to the cut-off voltage of the battery single and the single voltage thresholds;

step S2, setting corresponding regulation target power value and power regulation gradient value for each voltage subsection interval;

step S3, acquiring the current SOC value, the current battery monomer temperature and the current battery monomer maximum voltage in real time, and acquiring the power required by the current vehicle-mounted accessory through a bus;

step S4, according to the current SOC value and the current battery single temperature, obtaining the allowed energy recovery power corresponding to the current battery working condition calibrated in advance by looking up a table;

step S5, calculating theoretical energy recovery maximum power by combining the allowed energy recovery power and the power required by the current vehicle-mounted accessory;

and step S6, when the current SOC value is greater than or equal to a preset SOC threshold value, based on the current battery monomer maximum voltage, the regulation target power value and the power regulation gradient value, regulating the theoretical energy recovery maximum power and outputting a corresponding power value to execute energy recovery.

Further, the adjusting the theoretical energy recovery maximum power and outputting a corresponding power value to perform energy recovery based on the current cell maximum voltage, the regulation target power value, and the power regulation gradient value includes:

determining a corresponding target voltage subsection interval according to the current battery monomer highest voltage;

comparing the theoretical energy recovery maximum power with a regulation target power value corresponding to a target voltage subsection interval;

and according to the comparison result, reducing or increasing the theoretical energy recovery maximum power by utilizing the power regulation gradient value corresponding to the target voltage subsection interval.

Further, the determining a corresponding target voltage segment interval according to the current battery cell highest voltage includes:

comparing the current cell maximum voltage to the cell voltage threshold.

Further, if the highest voltage of the current battery cell is smaller than or equal to the minimum cell voltage threshold, the obtained theoretical energy recovery maximum power is used as the output power required by the motor for energy recovery.

Further, the reducing or increasing the theoretical energy recovery maximum power by using the power regulation gradient value corresponding to the target voltage segment interval according to the comparison result includes:

if the theoretical energy recovery maximum power is larger than the corresponding regulation target power value, monitoring whether the single voltage change rate is larger than 0;

if so, gradually reducing the theoretical energy recovery maximum power to a regulation target power value according to the corresponding power regulation gradient value;

and if the theoretical energy recovery maximum power is smaller than the corresponding regulation target power value, gradually increasing the theoretical energy recovery maximum power to the regulation target power value according to the corresponding power regulation gradient value.

Further, the step-wise decreasing the theoretical energy recovery maximum power to a regulation target power value comprises:

in the process of reducing regulation, the change rate of the monomer voltage is continuously monitored;

if the change rate of the cell voltage is monitored to be less than or equal to 0 in the process of reducing regulation, the current power obtained by current regulation is used as the output power for executing energy recovery.

Further, when the current SOC value is smaller than a preset SOC threshold value, the obtained theoretical energy recovery maximum power is used as output power required by the motor for energy recovery.

Further, the calculating a theoretical maximum energy recovery power by combining the allowable energy recovery power and the current power required by the vehicle-mounted accessory comprises:

and fusing the allowable energy recovery power and the power required by the current vehicle-mounted accessory, and calculating the theoretical energy recovery maximum power by combining the energy conversion efficiency of the motor.

To facilitate an understanding of the above embodiments and their preferred versions, a detailed description is provided herein as follows:

firstly, the current battery SOC, the current battery cell temperature, the current battery current, the current battery cell maximum voltage and other data can be obtained in real time, and the battery allowable energy recovery power value P10 (power P10 for short) under the corresponding current working condition, which is calibrated in advance by the rack, is obtained by mainly using the current battery SOC and the current battery cell temperature therein through table lookup. Meanwhile, the current working power P20 (power P20, that is, the power that the accessory may consume) of the high-voltage accessory and the low-voltage accessory CAN be obtained through the data (for example, the operating states of the accessories such as the compressor and the fan and the working parameters thereof) related to the current working state of the entire vehicle on the CAN bus.

According to the formula P ═ P10+ P20)/E, wherein E is the efficiency of the motor in energy recovery, the theoretical energy recovery maximum power P (referred to as theoretical power P for short) output to the motor is solved. In other embodiments, the maximum energy recovery torque T of the motor may also be calculated according to the theoretical maximum energy recovery power P and the current motor speed n by using the formula P ═ Tn/9550, where P and T may be used as initial maximum energy recovery values executed by the current motor.

Then, on the premise of presetting a certain SOC threshold (e.g. 80%), it can be determined that if the SOC is not high, energy recovery is performed according to the theoretical power P, and at this time, the cell voltage generally does not exceed the cell voltage upper limit Vmax (taking a certain ternary lithium battery as an example, the cell voltage upper limit Vmax may be 4200mV, that is, a cut-off voltage), and then the theoretical power P is the maximum energy recovery power value required by the motor; on the other hand, when the SOC is determined to be high based on the SOC threshold value, if energy recovery is performed according to the theoretical power P due to problems such as battery consistency, the cell voltage value may exceed the cutoff voltage Vmax, and in order to ensure battery safety, energy recovery is forcibly interrupted, thereby causing problems such as waste of part of energy and sudden loss of deceleration.

Therefore, under the specific working condition (the current SOC exceeds the SOC threshold), the theoretical power P obtained by the calculation can be adjusted according to the current cell maximum voltage and the cell voltage change rate (which can correspond to the cell maximum voltage), so as to ensure that the energy recovery is within the battery capacity range.

Considering that the voltage rise of the battery cell and the energy recovery power of the battery do not have a linear relationship in the energy recovery process, namely, the higher the voltage of the battery cell is, the smaller the voltage rise is when the same power is increased. Therefore, segmented control can be performed according to different battery cell voltages in advance, and the segmented number and the segmented voltage interval can be adjusted according to the requirement of control precision. For example, a plurality of cell voltage thresholds V may be set based on the cell voltage (for example, five cell voltage thresholds V1 to V5 may be set in order from big to small, where V1 is closest to the upper limit Vmax of the cell voltage), at least five segment voltage intervals (which may be referred to as a first to fifth segment voltage interval or a regulation interval) of [ Vmax, V1], [ V1, V2], [ V2, V3], [ V3, V4], [ V4, V5] may be obtained, and meanwhile, regulation target power values P1 to P5 may be set corresponding to the respective intervals, for example, P1 to P5 may be set to 1Kw to 5Kw, respectively.

In actual operation, whether a certain regulation and control interval is entered or not can be judged through the current highest voltage of the battery cell, specifically, when the SOC is greater than a set SOC threshold (as described above, this is a starting condition of power regulation and control, and of course, in other embodiments, the relation between the maximum voltage of the battery cell and the minimum cell voltage threshold V can also be considered to judge whether the battery cell enters the regulation and control interval or not), whether the current highest voltage of the battery cell is greater than a first cell voltage threshold V1 or not can be judged, and if so, it is judged that the battery cell voltage enters the first regulation and control interval; next, whether the maximum theoretical energy recovery power is greater than the regulation target power value corresponding to the current interval is examined (i.e., in this example, whether the theoretical power P is greater than the target power P1 is determined), and if so, it is indicated that the current output power may be too large, which may cause the cell voltage to exceed the cutoff voltage Vmax and interrupt energy recovery.

At this time, the calculated theoretical power P may be adjusted according to the section in which the cell voltage is located and the cell voltage change rate KV, that is, on the premise that P is greater than P1, it is determined whether the cell voltage change rate KV is greater than 0, if so, it is determined that there is a risk of exceeding the cutoff voltage, and the power adjustment gradient K value needs to be set in advance according to each voltage segment section (in different voltage segment sections, the power adjustment gradient K may be different, and the K is larger as approaching the upper limit Vmax of the cell voltage, and is smaller, otherwise, for example, corresponding to the first to fifth voltage segment sections, K1 ═ 0.05kw/ms, K2 ═ 0.04kw/ms, K3 ═ 0.03kw/ms, K4 ═ 0.02kw/ms, and K5 ═ 0.01kw/ms may be respectively taken to gradually reduce the power P, and the adjustment target is P1.

In the regulation and control process, if KV is less than or equal to 0, it indicates that the current energy recovery power can balance or decrease the cell voltage, and there is no risk of exceeding the cut-off voltage any more, and there is no need to continuously reduce the energy recovery power, at this time, the regulated and controlled current power is the maximum recovery power that the cell can bear under the current working condition, and the current power can be taken as the maximum energy recovery power output to the motor.

In the following, if the maximum voltage of the current battery cell is greater than the first regulation threshold V1 (entering the first regulation interval), under this condition, when it is determined that the theoretical energy recovery maximum power is smaller than the battery allowable energy recovery power threshold corresponding to the current SOC (i.e., the theoretical power P is smaller than the target power P1), the theoretical power P may be increased step by step directly according to the gradient k1 preset in the corresponding current voltage segment interval, and the regulation target is also P1. When the power P is equal to the target power P1, the energy recovery control is performed at P1.

In combination with a specific example, assuming that the current maximum energy recovery power P10 calibrated by the battery rack obtained after table lookup is 15KW, the power consumption P20 of the vehicle accessory provided by the bus data is 3KW, the motor efficiency E is 0.9, and the maximum theoretical power P of energy recovery is 20 KW.

The voltage of the battery monomer drops in the pure electric vehicle driving process, and the voltage of the battery monomer rises along with the increase of energy recovery power when the pure electric vehicle enters the energy recovery process:

if the voltage V of the single body is less than or equal to V5, the current output power can meet the energy recovery allowable power of the battery safety and the power consumption of accessories, and 20KW is directly output as the maximum value of the energy recovery power of the motor.

If the cell voltage V is larger than V5, the current 20KW power is larger, and if the current cell voltage is in an interval [ V4, V5], the cell voltage change rate KV is larger than 0, and meanwhile, the 20KW is larger than the target power P5, P is reduced towards P5 according to the gradient K5; if the voltage change rate KV is monitored to be less than or equal to 0 when the voltage is reduced to 18KW, energy can be recycled according to the current 18 KW.

And thirdly, if the voltage of the single body continues to rise in the reducing process and reaches an interval [ V3, V4], adjusting the power according to the gradient K4, monitoring that the voltage change rate KV is less than or equal to 0 when the voltage is reduced to 10KW, and recovering the energy according to the current 10 KW.

If the voltage of the single body begins to drop, for example, entering the interval [ V3, V4] from the interval [ V2, V3], if the current power is smaller than the target power of the current interval, increasing the current energy recovery output power according to the gradient of the interval.

In summary, the design concept of the present invention is to obtain the allowable energy recovery calibration power according to the current battery power and the battery temperature, obtain the power consumption under the accessory according to the information of the vehicle-mounted accessory, and combine the two to obtain the theoretical required power value. When the electric quantity is higher, the larger or smaller theoretical energy recovery power is adjusted through the preset regulation and control interval and the maximum value of the single voltage, and the situation that the energy recovery is interrupted due to the fact that the single voltage is too high due to the fact that the calibration power is too large is prevented, so that the battery is ensured to be in a sustainable energy recovery mode close to the limit of the capacity, and the increase of the energy recovery contribution rate under the working condition of the electric quantity is facilitated. The invention considers the power consumption of the accessories of the whole vehicle system, and based on the theoretical power, the theoretical power is accurately adjusted in a hierarchical mode under the working condition of higher electric quantity, so that the energy recovery efficiency is improved, and the energy recovery function of the motor is fully exerted. The method is suitable for controlling the energy recovery power and the torque of different types of pure electric vehicles, and particularly can continuously recover energy in a range close to the limit of the battery capacity by adjusting and controlling the power and the torque when the voltage of a single body is close to the cut-off voltage.

In the embodiments of the present invention, "at least one" means one or more, "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, and means that there may be three relationships, for example, a and/or B, and may mean that a exists alone, a and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c may 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.

The structure, features and effects of the present invention have been described in detail with reference to the embodiments shown in the drawings, but the above embodiments are merely preferred embodiments of the present invention, and it should be understood that technical features related to the above embodiments and preferred modes thereof can be reasonably combined and configured into various equivalent schemes by those skilled in the art without departing from and changing the design idea and technical effects of the present invention; therefore, the invention is not limited to the embodiments shown in the drawings, and all the modifications and equivalent embodiments that can be made according to the idea of the invention are within the scope of the invention as long as they are not beyond the spirit of the description and the drawings.