阅读说明：本技术 一种电动车制动能量回收方法 (Electric vehicle braking energy recovery method ) 是由 陈清付 胡维超 周乐栓 简瑞谦 宁德胜 于 2020-11-06 设计创作，主要内容包括：本发明公开了一种电动车制动能量回收方法。它包括以下步骤：S11、获取电动车的行驶参数以及设备参数；S12、根据刹车时间计算出电机制动转矩指令,令电机制动转矩指令T_(eb)~(**)随刹车时间计数值呈线性增长,并向电机额定制动转矩T_e逼近；S13、根据电机转速和电池最大充电功率计算出目标制动转矩指令；S14、根据电池SOC值、电池的温度计算出当前制动转矩指令。其优点在于：提高了驾驶员的驾驶体验；提高了能量回收效率；防止了长时间大电流充电对电池造成伤害,保证了电池的使用寿命。(The invention discloses a method for recovering braking energy of an electric vehicle. It comprises the following steps: s11, acquiring the driving parameters and the equipment parameters of the electric vehicle; s12, calculating a motor braking torque command according to the braking time, and commanding the motor braking torque command T eb ** The count value is increased linearly along with the braking time and is increased to the rated braking torque T of the motor e Approaching; s13, calculating a target braking torque instruction according to the motor rotating speed and the maximum charging power of the battery; and S14, calculating the current braking torque command according to the SOC value of the battery and the temperature of the battery. The advantages are that: the driving experience of the driver is improved; the energy recovery efficiency is improved; the damage to the battery caused by long-time heavy current charging is prevented, and the service life of the battery is ensured.)

1. The method for recovering the braking energy of the electric vehicle is characterized by comprising the following steps of:

s11, acquiring the driving parameters and the equipment parameters of the electric vehicle;

s12, calculating a motor braking torque command according to the braking time, and commanding the motor braking torque command T_eb ^**The count value is increased linearly along with the braking time and is increased to the rated braking torque T of the motor_eApproaching;

s13, calculating a target braking torque instruction according to the motor rotating speed and the maximum charging power of the battery;

and S14, calculating the current braking torque command according to the SOC value of the battery and the temperature of the battery.

2. The electric vehicle braking energy recovery method of claim 1, wherein: in step S11, the driving parameters and the device parameters include a braking signal, a motor speed n, a current battery SOC value, a battery temperature, and a maximum charging power P of the battery_{chg_max}。

3. According to claim 2The method for recovering the braking energy of the electric vehicle is characterized by comprising the following steps: the calculation formula of the motor rotating speed n is as follows:the SOC value and the temperature of the battery are determined by sampling of a controller, and the actual residual electric quantity and the working state of the battery are reflected; maximum charging power P of the battery_{chg_max}For nominal voltage U of battery_dcX maximum charging current of battery I_dc。

4. The electric vehicle braking energy recovery method of claim 2, wherein: in step S12, the brake signal is a brake handle signal or a brake button signal.

5. The electric vehicle braking energy recovery method of claim 1, wherein: in step S12, the motor braking torque command T is issued_eb ^**The count value is increased linearly along with the braking time and is increased to the rated braking torque T of the motor_eApproximation, namely:

6. the electric vehicle braking energy recovery method of claim 1, wherein: the specific flow method of step S13 is as follows:

s131, presetting motor parameters: first speed threshold n₁A second rotational speed threshold n₂And a third rotational speed threshold n₃Wherein n is₁<n₂<n₃<n_max，n_maxThe value is the highest rotating speed value of the motor;

s132, judging whether the motor rotating speed n is less than a first rotating speed threshold value n₁If not, executing step S133; if the target braking torque is less than the threshold value, the motor does not carry out feedback braking, and the target braking torque command T is carried out at the moment_eb ^*Is 0;

s133, judging whether the motor rotating speed n is less than a second rotating speed threshold value n₂If not, go to step S134; if the target braking torque is less than the threshold value, the motor feedback braking is started, and the target braking torque command T_eb ^*Increases as the motor speed n increases;

s134, judging and judging whether the motor rotating speed n is less than a third rotating speed threshold value n₃If less than the threshold, the target braking torque command T_eb ^*For motor braking torque command T_eb ^**At the moment, the output torque of the motor is constant; otherwise target brake torque command T_eb ^*The output power of the motor is constant at the moment when the rotating speed n of the motor is increased and reduced;

s135, according to the maximum charging power P of the battery_{chg_max}Calculating a target braking torque command T_eb ^*During regenerative braking, the actual regenerative power P supplied by the motor to the battery_{reg_chg}At maximum charging power P of the battery_{chg_max}Inner, motor actual feedback power P_{reg_chg}Comprises the following steps:

during regenerative braking, target braking torque command T is applied_eb ^*Limiting the amplitude, and obtaining the target braking torque command T after limiting_eb ^*Comprises the following steps:

7. the electric vehicle braking energy recovery method of claim 6, wherein: in step S133, the target braking torque command T_eb ^*

Calculated from the following equation:

8. the electric vehicle braking energy recovery method of claim 6, wherein: in step S134, the target braking torque command T_eb ^*Calculated from the following equation:

9. the electric vehicle braking energy recovery method of claim 2, wherein: the flow operation method of step S14 is as follows:

s141, looking up a table according to the SOC value and the temperature T of the battery, and if a battery influence factor k is obtained_soc；

S142, according to the obtained battery influence factor k_socFor target braking torque instruction T_eb ^*Correcting to obtain the current braking torque command T_eb；

And S143, controlling the motor to transit from the current torque to the target torque according to the current braking torque command.

Technical Field

The invention relates to an energy recovery technology in feedback braking of an electric vehicle controller, in particular to an electric vehicle braking energy recovery method, and belongs to the technical field of motor vector control.

Background

The two-wheeled electric vehicle is a little choice for people to go out green rapidly due to the advantages of zero emission, flexibility and small size, but the low energy density of the battery and the low driving range also become bottlenecks which hinder the development of the two-wheeled electric vehicle. The energy recovery technology can store part of braking energy in the form of electric energy through the conversion device in the braking process of the electric vehicle and reuse the energy in the driving process, so that the utilization rate of the energy and the driving range of the vehicle are improved.

At present, the application of an energy recovery technology in the field of two-wheeled electric vehicles is seriously insufficient, and the existing two-wheeled electric vehicle energy recovery strategy mainly enables a motor to work in a power generation state by a driver operating a brake handle switch or when a vehicle is in a free sliding state, so that energy is recovered to an energy storage device. However, research shows that the energy recovery mode of the strategy does not consider the motor characteristics and the battery state, and has the defects of low energy recovery efficiency, short service life of a power battery and the like.

Disclosure of Invention

The invention aims to provide an electric vehicle braking energy recovery method which can greatly improve the energy recovery efficiency and prolong the service life of a power battery.

In order to solve the technical problem, the method for recovering the braking energy of the electric vehicle comprises the following steps:

s11, acquiring the driving parameters and the equipment parameters of the electric vehicle;

s12, calculating a motor braking torque command according to the braking time, and commanding the motor braking torque command T_eb ^**The count value is increased linearly along with the braking time and is increased to the rated braking torque T of the motor_eApproaching;

s13, calculating a target braking torque instruction according to the motor rotating speed and the maximum charging power of the battery;

and S14, calculating the current braking torque command according to the SOC value of the battery and the temperature of the battery.

In step S11, the driving parameters and the device parameters include a braking signal, a motor speed n, and a current powerBattery SOC value, battery temperature and battery maximum charging power P_{chg_max}。

The calculation formula of the motor rotating speed n is as follows:

the SOC value and the temperature of the battery are determined by sampling of a controller, and the actual residual electric quantity and the working state of the battery are reflected; maximum charging power P of the battery_{chg_max}For nominal voltage U of battery_dcX maximum charging current of battery I_dc。

In step S12, the brake signal is a brake handle signal or a brake button signal.

In step S12, the motor braking torque command T is issued_eb ^**The count value is linearly increased along with the braking time and is changed to the rated braking torque T of the motor_eApproximation, namely:

the specific flow method of step S13 is as follows:

s131, presetting motor parameters: first speed threshold n₁A second rotational speed threshold n₂And a third rotational speed threshold n₃Wherein n is₁<n₂<n₃<n_max，n_maxThe value is the highest rotating speed value of the motor;

s132, judging whether the motor rotating speed n is less than a first rotating speed threshold value n₁If not, executing step S133; if the target braking torque is less than the threshold value, the motor does not carry out feedback braking, and the target braking torque command T is carried out at the moment_eb ^*Is 0;

s133, judging whether the motor rotating speed n is less than a second rotating speed threshold value n₂If not, go to step S134; if the target braking torque is less than the threshold value, starting to perform motor feedback braking, and obtaining a target braking torque command T_eb ^*Increases as the motor speed n increases;

s134, judging and judging whether the motor rotating speed n is less than a third rotating speed threshold value n₃If less than the threshold, the target braking torque command T_eb ^*For motor braking torque command T_eb ^**At the moment, the output torque of the motor is constant; otherwise target brake torque command T_eb ^*The output power of the motor is constant at the moment when the rotating speed n of the motor is increased and reduced;

s135, according to the maximum charging power P of the battery_{chg_max}Calculating a target braking torque command T_eb ^*During regenerative braking, the actual regenerative power P supplied by the motor to the battery_{reg_chg}At maximum charging power P of the battery_{chg_max}Inner, motor actual feedback power P_{reg_chg}Comprises the following steps:

during regenerative braking, target braking torque command T is applied_eb ^*Limiting amplitude, target brake torque command T after limiting amplitude_eb ^*Comprises the following steps:

in step S133, the target braking torque command T_eb ^*

Calculated from the following equation:

in step S134, the target braking torque command T_eb ^*Calculated from the following equation:

the flow operation method of step S14 is as follows:

s141, looking up a table according to the SOC value and the temperature T of the battery, and if a battery influence factor k is obtained_soc；

S142, according to the obtained battery influence factor k_socFor target braking torque instruction T_eb ^*Correcting to obtain the current braking torque command T_eb；

And S143, controlling the motor to transit from the current torque to the target torque according to the current braking torque command.

The invention has the advantages that:

(1) the braking torque change is controlled according to the braking time, so that the vehicle can not generate obvious braking impact and pause and frustration in the energy recovery process, and the driving experience of a driver is improved;

(2) by combining the characteristics of the motor and adjusting the braking strength of the motor according to the rotating speed of the motor, the regenerative braking capacity of the motor can be exerted to the maximum extent in a reasonable range, and the energy recovery efficiency is improved;

(3) the state of the battery equipment is monitored in real time, a battery influence factor ksoc is introduced to correct the motor braking strength, the battery is prevented from being damaged by long-time large-current charging, and the service life of the battery is guaranteed.

(4) The battery factors are considered in the whole recovery system, so that the service life of the battery is ensured, the charging and discharging efficiency of the energy storage system under different temperatures and SOC is also considered, and the efficiency is maximized.

Drawings

FIG. 1 is a flow chart of a first embodiment of the present invention;

FIG. 2 is a flowchart of step S13 according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a relationship between a motor rotation speed and a target braking torque according to an embodiment of the present invention;

FIG. 4 is a flowchart of step S14 according to an embodiment of the present invention;

FIG. 5 shows a battery SOC value, a battery temperature T and a battery influence factor k according to an embodiment of the present invention_socA three-dimensional relationship diagram;

FIG. 6 is a flowchart of a second embodiment of the present invention;

FIG. 7 is a block diagram of an electric vehicle braking energy recovery system of the present invention;

fig. 8 is a comparison graph of driving range in the present invention.

Detailed Description

The method for recovering braking energy of an electric vehicle according to the present invention will be described in detail with reference to the accompanying drawings and the following detailed description, wherein in the embodiment of the present invention, an energy recovery enabling flag is uniformly designated as F₁The rotation speed of the motor is n, and the first rotation speed threshold value is n₁The second rotation speed threshold is n₂The third rotation speed threshold is n₃The maximum rotation speed value of the motor is n_maxRated braking torque of motor T_eMotor braking torque command T_eb ^**Target brake torque command T_eb ^*Current brake torque command T_ebThe battery temperature is T, and the maximum charging power of the battery is P_{chg_max}。

The first embodiment is as follows:

referring to fig. 1, the method for recovering braking energy of an electric vehicle of the embodiment specifically includes the following steps:

step S11: and acquiring a brake key signal, the rotating speed of the motor, the current SOC (state of charge) and temperature of the battery and the maximum charging power of the battery.

Specifically, the electric vehicle running parameters are obtained through sampling: the method comprises the steps of obtaining equipment parameters including a brake key signal, a motor rotating speed n, a current SOC value of a battery and the like: including the temperature of the battery, the maximum charging power P of the battery_{chg_max}The brake key signal is determined by detecting the level state of the key through the controller; if the motor speed is measured by a motor Hall sensor, the sampling frequency is 62.5us, and the calculation formula of the motor speed n is as follows:

wherein, SixHallTimeSum is six Hall commutation time counting values, p is the pole pair number of the motor and is obtained by actual motor parameters;

the SOC value and the battery temperature of the battery can be determined by sampling of the controller, and the actual residual electric quantity and the working state of the battery are reflected; maximum charging power P of battery_{chg_max}Can be described as the nominal voltage U of the battery_dcX maximum charging current of battery I_dcAnd is determined by the characteristics of the power battery.

Specifically, whether the brake key is pressed down or not is judged, and if the brake key is pressed down, the energy recovery enabling mark F is set₁Entering an electronic braking (energy recovery) mode, executing the operation of step S12, otherwise clearing the energy recovery enabling mark F₁。

Step S12: and calculating a motor braking torque command according to the braking time and gradually approaching the rated torque of the motor.

Specifically, in order to comply with usual braking habits, the motor braking torque command T is made such that the vehicle does not generate significant braking shock and jerk during the energy recovery process_eb ^**The value increases linearly with the braking time and reaches the rated braking torque T of the motor_eGradual approximation, namely:

wherein, T_eb ^**For motor braking torque command, K_tFor the change step of the command (to be calibrated according to the control time), T_eThe rated braking torque of the motor corresponds to the electronic braking force in the program. Step S13: and calculating a target braking torque command according to the motor rotating speed and the maximum charging power of the battery, wherein a specific flow chart is shown in fig. 2.

Calculating a target braking torque command T according to the motor speed n_eb ^*Specifically, the permanent magnet synchronous motor has a similar characteristic curve when being driven during braking, so that the braking strength of the motor must be determined according to the power consumption to enable the motor to recover the kinetic energy of the vehicle in a reasonable range and prevent a driver from feeling discomfort caused by energy recoveryThe engine speed is regulated, namely constant torque is output below the basic speed, constant power is output above the basic speed, the output torque is reduced along with the increase of the rotation speed, and a relationship diagram of the motor rotation speed and the target braking torque is shown in a figure 3.

In S131, a first rotation speed threshold n needs to be preset₁A second rotational speed threshold n₂And a third speed threshold n₃Wherein n is₁<n₂<n₃<n_max，n_maxThe rotating speed threshold value is the highest rotating speed value of the motor and needs to be calibrated according to actual parameters of the motor.

In S132, it is determined whether or not the motor rotation speed n is less than a first rotation speed threshold n₁If not, executing step S133; if the value is less than the threshold value, the feedback braking energy does not exceed the copper loss and the iron loss of the motor and the loss of the inverter when the motor brakes at low speed, so the feedback braking of the motor is not basically adopted at low speed, and the target braking torque instruction T is used at the moment_eb ^*Is 0.

In S133, it is determined whether or not the motor rotation speed n is less than the second rotation speed threshold n₂If not, executing step S134; if the target braking torque is less than the threshold value, the motor feedback braking is started, and the target braking torque instruction T_eb ^*The target braking torque command T increases as the motor rotation speed n increases_eb ^*Can be calculated from the following formula:

wherein, T_eb ^*A target braking torque command, n is the rotation speed of the motor, n₁Is the first rotational speed threshold, n₂Is a second rotational speed threshold, T_eb ^**Is a motor braking torque command.

In S134, it is judged whether or not the motor rotation speed n is less than the third rotation speed threshold n₃If less than the threshold, the target braking torque command T_eb ^*For motor braking torque command T_eb ^**When the output torque of the motor is constant; otherwise target brake torque command T_eb ^*The target braking torque instruction T is reduced along with the increase of the motor rotating speed n, the output power of the motor is constant at the moment_eb ^*Can be calculated by the following formula:

wherein, T_eb ^*A target braking torque command, n is the rotation speed of the motor, n₃Is a third rotational speed threshold, T_eb ^**Is a motor braking torque command.

In S135, according to the maximum charging power P of the battery_{chg_max}Calculating a target braking torque command T_eb ^*In particular, due to the limited actual charging capacity of the battery, the actual regenerative power P supplied by the electric machine to the accumulator during regenerative braking_{reg_chg}Should be at the maximum charging power P of the battery_{chg_max}And (c) in the following. After a part of electric energy is lost by considering factors such as motor stator and rotor resistance, copper loss, heat loss and the like, the actual feedback power P of the motor_{reg_chg}Comprises the following steps:

wherein, T_eb ^*And n is the rotating speed of the motor, and eta (0.7-0.9) is the motor feedback braking power generation efficiency of the motor after the loss of the motor is considered.

Therefore, during regenerative braking, a target braking torque command T is required_eb ^*Limiting amplitude, target braking torque instruction T after limiting amplitude_eb ^*Comprises the following steps:

wherein, T_eb ^*To the eyesA standard braking torque command, n is the rotating speed of the motor, eta is the motor feedback braking power generation efficiency after the loss of the motor is considered, and P_{chg_max}The maximum charging power for the battery.

Step S14: a specific flowchart of calculating the target braking torque command from the battery SOC value and the battery temperature is shown in fig. 4.

Specifically, in the process of regenerative braking of the electric vehicle, in consideration of the safety of the energy storage system, when the SOC value of the storage battery is small, the braking force of the motor can be appropriately increased, and more braking energy can be recovered, and when the SOC value of the storage battery is high (generally, the SOC is taken as the design)>0.9) indicating battery capacity and near saturation, and mechanical braking alone is used without regenerative braking to avoid over-charging the battery and resulting in a shorter life. Generally, the working temperature of the storage battery has a safe interval, and when the temperature of the storage battery is too high or too low, the energy storage system can be protected, and charging and discharging cannot be carried out, so that when the temperature of the storage battery is detected to be outside the safe interval, the braking force of the motor is reduced to protect the storage battery. To fulfill these requirements, the battery impact factor k needs to be introduced_socFor target braking torque instruction T_eb ^*And (6) correcting. Battery SOC value, battery temperature T and battery influence factor k_socThe three-dimensional relationship diagram is shown in fig. 5.

In S141, look-up table is performed according to SOC value and temperature T of battery, such as table 1 (data in table 1 is not unique according to battery characteristics) to obtain battery influence factor k_soc. Particularly, when the battery SOC value and the battery temperature T are between two threshold values, linearization processing can be carried out to obtain the current battery influence factor k_socFor example, when the battery SOC value is 0.56 and the battery temperature T is 13 deg.C, the current battery influence factor k_socIs 0.902.

TABLE 1 Battery Effect factor k_socRelation table

In S142, the rootAccording to the obtained battery influence factor k_socFor target braking torque instruction T_eb ^*Correcting to obtain the current braking torque command T_eb，T_ebThe current brake torque command may be calculated by the following equation:

wherein, T_eb ^*For the target braking torque command, k_socAs a battery influencing factor, T_ebIs the current brake torque command.

In S143, the motor is controlled to transit from the current torque to the target torque according to the current braking torque command, specifically, the current braking torque command T obtained in S142_ebAnd controlling the motor to smoothly transit from the current actual torque to the target torque so that the motor finishes energy recovery work.

Example two:

referring to fig. 6, the method for recovering braking energy of an electric vehicle of the present embodiment includes the following steps.

Step S21: and acquiring a brake handle signal, the rotating speed of the motor, the current SOC (state of charge) and temperature of the battery and the maximum charging power of the battery.

Specifically, the driving parameters and the equipment parameters of the electric vehicle are acquired through sampling, wherein the brake lever signals are determined through detecting the level state of the brake lever by a controller; the rest of the parameters are described in detail above, and therefore are not described herein.

Specifically, whether a brake handle signal is triggered or not is judged, and if the brake handle signal is triggered, an energy recovery enabling mark F is set₁Entering an electronic braking (energy recovery) mode, executing the operation of step S22, otherwise clearing the energy recovery enabling mark F₁。

Step S22: the braking torque command of the motor is calculated according to the braking time and gradually approaches to the rated torque of the motor, please refer to the first embodiment, which has been described in detail above, and therefore, the detailed description is omitted here.

Step S23: the target braking torque command is calculated according to the motor speed and the maximum charging power of the battery, please refer to the first embodiment, which has been described in detail above, and therefore will not be described herein.

Step S24: referring to the first embodiment, the target braking torque command is calculated according to the battery SOC value and the battery temperature, which is described in detail above, and therefore will not be described herein.

In addition, the electric vehicle braking energy recovery method of the present invention may adopt an electric vehicle braking energy recovery system as shown in fig. 7, and as can be seen from fig. 7, the system includes:

the obtaining module 11 is configured to obtain a driving parameter of the electric vehicle: the method comprises the steps of obtaining the equipment parameters of the electric vehicle by a braking signal (a key signal or a brake handle signal), the rotating speed n of a motor, the SOC value of a current battery and the like: including the temperature of the battery, the maximum charging power P of the battery_{chg_max}And the like.

And the judging module 12 is used for judging whether to enter an electronic braking (energy recovery) mode according to the driving parameters and the equipment parameters.

A calculation module 13 for calculating a motor braking torque command T according to the driving parameters and the device parameters_eb ^**Target brake torque command T_eb ^*Current brake torque command T_eb。

And the control module 14 is used for controlling the motor to smoothly transit from the current actual torque to the target braking torque, and the braking torque is not suddenly changed.

The working principle is as follows:

the method comprises the steps of obtaining driving parameters and equipment parameters of the electric vehicle, including a braking signal, the rotating speed n of a motor, the current SOC value of a battery, the temperature of the battery and the maximum charging power P of the battery_{chg_max}Etc.; calculating a motor braking torque instruction T according to the braking time_eb ^**(ii) a Speed n of the electric machine and maximum charging power P of the battery_{chg_max}Calculating a motor braking torque command target braking torque command T_eb ^*(ii) a Calculating the current braking torque instruction T according to the SOC value and the temperature T of the battery_eb(ii) a From the current braking torque command T_ebControlling the motor to rotate from the current actual torque to the target torqueAnd (6) transition.

In addition, according to GB/T24157 'indication test method of driving range and residual electricity of electric motorcycle and electric moped', a working condition method in a driving range test is used for testing, and as can be seen through chart comparison, the energy recovery method provided by the invention enables the driving range to reach 108.85%, the battery performance is greatly improved, and verification shows that when braking feedback energy is carried out, the energy recovery is carried out maximally in the motor capacity range by combining the actual external characteristic (power generation capacity) of the motor for control, the recovered energy is improved, and the effect is obvious.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make modifications, changes, additions or substitutions within the spirit and scope of the present invention.