CN111398828A - Estimation method of remaining power and remaining mileage of electric vehicles - Google Patents

Abstract

The invention discloses a method for estimating the remaining power and remaining mileage of an electric vehicle. The remaining power estimation method includes: detecting the current battery current and current battery voltage of the electric vehicle power battery in real time, and estimating the current open circuit voltage of the power battery by using the current battery current, the current battery voltage and the open circuit voltage model; The current open-circuit voltage and the known corresponding relationship between the open-circuit voltage and the remaining power, determine the current remaining power corresponding to the current open-circuit voltage. The remaining mileage estimation method includes: estimating the remaining power when the current driving distance is n*L; determining the average value of the change of the remaining power of the battery when the nth L is traveled; estimating the remaining power based on the remaining power and the average value of the change of the remaining power. driven distance. By applying the present invention, the accuracy of remaining power estimation and remaining mileage estimation can be improved.

Description

Estimation method of remaining power and remaining mileage of electric vehicles

technical field

The invention belongs to the technical field of electric vehicles, and in particular relates to a method for estimating the remaining power and remaining mileage of electric vehicles.

Background technique

New energy vehicles represented by electric vehicles are generally considered to be one of the most effective ways to solve the current energy and pollution problems, and have attracted widespread attention at home and abroad. It is generally believed that an electric vehicle refers to a vehicle that is powered by an on-board power supply and driven by a motor, and meets the requirements of road traffic and safety regulations. Compared with traditional fuel vehicles, electric vehicles have the characteristics of high performance, low energy consumption and low pollution, as well as comprehensive advantages in technology, economy and environment, and their prospects are widely optimistic.

No matter what form of electric vehicle, the battery is an integral part of its powertrain. The accurate and real-time monitoring of the remaining battery power is related to the stable and reliable operation of the power system, and is one of the key issues in practical applications. With the deep discharge of electric vehicle power batteries and battery aging, the remaining mileage will be affected. Therefore, estimating the remaining mileage of electric vehicles has important guiding value for electric vehicle users to plan optimal energy-saving routes and find charging facilities. And it is of great significance to promote the use and promotion of electric vehicles.

The remaining power of an electric vehicle refers to the state of charge (State of Charge, referred to as SOC) of the battery. The popular explanation is the state of the remaining charge in the electric vehicle power battery. Accurate estimation of the remaining power is the key and difficult point of EMF (battery management system). EMF is based on the battery SOC to manage the energy balance of the battery. Many functions on electric vehicles depend on the SOC estimation results. Therefore, the accurate estimation of the SOC of the power battery is of great significance and function. The SOC is estimated by physical quantities such as voltage, current, and temperature. However, the accuracy of the SOC estimation is affected by many factors, such as the influence of the low sensor accuracy and the influence of electromagnetic interference. , the effect of uncertainty of past and future operating conditions, the effect of temperature on accuracy, etc. These factors are unavoidable, but they do exist, so the SOC of the battery is affected by various factors, so it is difficult to estimate the real remaining battery power in real time and accurately. It can only be determined by various measures and methods. Approach the true value of the remaining battery charge.

There are many methods for estimating the remaining power in the prior art, such as the charge accumulation method, the open-circuit voltage method, the combination of the open-circuit voltage method and the ampere-hour measurement method, and so on. The value is not accurate enough. For example, charge accumulation method, this method has the problem of accumulation error, the longer the running time, the greater the error. Regarding the open-circuit voltage method, it cannot be used when the battery is working, and this method can only be used after the battery has stopped working and has been stationary for a period of time, and the limitations are relatively large. The combination of these two methods is now widely used by many people, and has many advantages, which can complement the shortcomings of the two methods, but this combination method still cannot solve the shortcomings of the open circuit voltage method, and this method cannot remove the electromagnetic interference. The estimation of the remaining mileage of an electric vehicle is closely related to the remaining power. If the estimation of the remaining power is inaccurate, it is difficult to accurately estimate the remaining mileage, which affects the performance of the electric vehicle.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for estimating the remaining power and remaining mileage of an electric vehicle, so as to improve the accuracy of the estimation.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical scheme to realize:

A method for estimating the remaining power of an electric vehicle, comprising:

The current battery current and current battery voltage of the electric vehicle power battery are detected in real time, and the current open circuit voltage of the power battery is estimated by using the current battery current, the current battery voltage and the open circuit voltage model; the open circuit voltage model is:

U0(t)=A ₁₁ *U0(t-1)+A ₁₂ *U1(t-1)+B ₁₁ *Ib(t)+B ₁₂ *Ubus(t),

U1(t)=A ₂₁ *U0(t-1)+A ₂₂ *U1(t-1)+B ₂₁ *Ib(t)+B ₂₂ *Ubus(t);

Among them, U0(t) and U0(t-1) are the current open-circuit voltage and the last cycle open-circuit voltage, respectively, and U1(t) and U1(t-1) are the current equivalent capacitance voltage and the last cycle equivalent capacitance, respectively voltage, Ib(t) and Ubus(t) are the current battery current and the current battery voltage, respectively, A ₁₁ , A ₁₂ , B ₁₁ , B ₁₁ , A ₂₁ , A ₂₂ , B ₂₁ , and B ₂₂ are all coefficient;

According to the estimated current open-circuit voltage and the known correspondence between the open-circuit voltage and the remaining power, determine the current remaining power corresponding to the current open-circuit voltage;

The coefficients A ₁₁ , A ₁₂ , B ₁₁ , B ₁₁ , A ₂₁ , A ₂₂ , B ₂₁ , B ₂₂ determine the coefficient values in the following manner:

Establish the equivalent circuit model of the electric vehicle power battery;

Obtain the corresponding output current, output voltage and open-circuit voltage of the power battery when the remaining power is known, form offline data, and use the offline data to identify the parameters of the components in the equivalent circuit model, and determine the component identification parameter;

The component identification parameters are discretized, and the coefficients A ₁₁ , A ₁₂ , B ₁₁ , B ₁₁ , A ₂₁ , A ₂₂ , B ₂₁ , and B ₂₂ in the open-circuit voltage model are estimated.

A method for estimating the remaining mileage of an electric vehicle, comprising:

The above method is used to estimate the remaining power SOC(n) when the current driving distance is n*L; n is a natural number, and L is the set interval mileage;

Determine the average SOCdeltmean(n) of the change in the remaining battery power when driving the nth L;

Estimate the remaining electric vehicle mileage Srem(n) according to the following formula:

Srem(n)=SOC(n)/SOCdeltmean(n).

Compared with the prior art, the advantages and positive effects of the present invention are: the method for estimating the remaining power of an electric vehicle provided by the present invention establishes an equivalent capacitor voltage calculation formula that is related to battery current and battery voltage and includes a recursive relationship and The open-circuit voltage model of the open-circuit voltage calculation formula completes the identification of the coefficients in the open-circuit voltage model in an offline manner. During the use of the battery, based on the open-circuit voltage model, only the real-time battery current, real-time battery voltage and easily determined initial open-circuit voltage are needed. The real-time estimation of the open-circuit voltage can be realized, and then the estimation of the real-time remaining power can be completed according to the estimated real-time open-circuit voltage; this method is used to estimate the remaining power, regardless of whether the battery is in a static state or a working state; Even if the initial value is inaccurate, it can be quickly corrected in the recursion process, so that the final estimated value is always near the true value, with high accuracy; based on the high-accuracy estimation of the remaining battery power, it can also improve the battery-based Remaining charge estimates the accuracy of the remaining battery range.

Other features and advantages of the present invention will become more apparent after reading the detailed description of the present invention in conjunction with the accompanying drawings.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a flowchart of an embodiment of a method for estimating the remaining power of an electric vehicle based on the present invention;

2 is an equivalent circuit model of an embodiment of an electric vehicle power battery;

FIG. 3 is a flow chart of an embodiment of a method for estimating the remaining driving range of an electric vehicle based on the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Please refer to FIG. 1 , which shows a flow chart of an embodiment of a method for estimating the remaining power of an electric vehicle based on the present invention. Specifically, in order to improve the estimation of the remaining power of the electric vehicle, this embodiment adopts the following method to realize the online real-time estimation of the remaining power of the electric vehicle.

Step 11: Detect the current battery current and current battery voltage of the electric vehicle power battery in real time, and use the current battery current, current battery voltage and open circuit voltage model to estimate the current open circuit voltage of the power battery.

where the open circuit voltage model is a known model that satisfies:

U0(t)=A ₁₁ *U0(t-1)+A ₁₂ *U1(t-1)+B ₁₁ *Ib(t)+B ₁₂ *Ubus(t),

U1(t)=A ₂₁ *U0(t-1)+A ₂₂ *U1(t-1)+B ₂₁ *Ib(t)+B ₂₂ *Ubus(t);

Among them, U0(t) and U0(t-1) are the current open-circuit voltage and the last cycle open-circuit voltage, respectively, and U1(t) and U1(t-1) are the current equivalent capacitance voltage and the last cycle equivalent capacitance, respectively Voltage, A ₁₁ , A ₁₂ , B ₁₁ , B ₁₁ , A ₂₁ , A ₂₂ , B ₂₁ , B ₂₂ are all coefficients whose values have been determined. Ib(t) and Ubus(t) are the current battery current and the current battery voltage respectively, which can be directly measured and read easily, for example, obtained through the CAN bus of the battery control system.

For the open circuit voltage model, it is also necessary to determine the initial open circuit voltage U0_init and the initial equivalent capacitance voltage U1_init at the beginning of the cycle. For the initial open-circuit voltage U0_init, the default is the open-circuit voltage value saved when the electric vehicle was shut down last time; if the open-circuit voltage is calculated for the first time after the battery is fully charged, the initial open-circuit voltage is the open-circuit voltage value when the battery is fully charged, and this value can be known of. For the initial equivalent capacitor voltage U1_init, the default is 0. Therefore, for the above-mentioned open circuit voltage model whose coefficients and initial values have been determined, after obtaining the current battery current data Ib(t) and the current battery voltage data Ubus(t), based on the recursive relationship of the open circuit voltage model, cyclic calculation, namely The current open circuit voltage U0(t) can be determined. This process can also be performed in real time during battery use, so online real-time estimation of the open circuit voltage can be achieved.

The coefficients A ₁₁ , A ₁₂ , B ₁₁ , B ₁₁ , A ₂₁ , A ₂₂ , B ₂₁ , and B ₂₂ in the open-circuit voltage model are identified by an offline method. Specifically, each coefficient value is determined in the following manner:

First, the equivalent circuit model of the electric vehicle power battery is established.

The equivalent circuit model may use the RC equivalent circuit model in the prior art. As a preferred embodiment, this embodiment uses the second-order RC equivalent circuit model shown in FIG. 2 , which has a simple structure and high accuracy.

Then, obtain the output current, output voltage and open-circuit voltage corresponding to the power battery when the remaining power is known, form offline data, use the offline data to identify the components in the equivalent circuit model, and determine the component identification parameters .

In the equivalent circuit model shown in Figure 2, the output current is Ib, the output voltage is Ubus, and the open-circuit voltage is the voltage across the energy storage capacitor C0. In the offline state, control the battery to work under different remaining power levels, measure the corresponding output current, output voltage and open-circuit voltage at different remaining power levels to form corresponding sets of offline data. Then, use offline data to identify the parameters of the components in the equivalent circuit model. Specifically, identify the energy storage capacitor C0, ohmic internal resistance R0, polarization internal resistance R1 and polarization capacitor C1 in the equivalent circuit model. . In some preferred embodiments, when using offline data to identify the parameters of the components in the equivalent circuit model, the least squares algorithm can be used to identify the parameters with the help of the polyfit function with least squares meaning in MATLAB software, and determine the parameters. Device identification parameters.

Finally, the parameters of the identified components are discretized, and the coefficients in the open-circuit voltage model are estimated. For example, the identified parameters are discretized using MATLAB software to estimate the coefficients in the model. Through discretization processing, the influence of extreme values in the data on the model effect can be well avoided, and it has good robustness to abnormal data and can improve the estimation accuracy.

In a preferred embodiment, each coefficient value in the open-circuit voltage model is fitted as follows:

A11=0.996; A12=-0.004; _B11 =0.0001; B12=0.004; _A21 = _-0.0048 ; _A22 = _0.9926 ; _B21 =0.0001; _B22 = _0.0048 .

Step 12: Determine the current remaining power corresponding to the current open-circuit voltage according to the estimated current open-circuit voltage and the known correspondence between the open-circuit voltage and the remaining power.

The correspondence between the open-circuit voltage and the remaining capacity is known and pre-stored, and is obtained when the battery is in a quiescent state.

In some embodiments, the corresponding relationship between the open circuit voltage and the remaining power is determined using the following process:

The remaining power of the battery in the fully charged state is determined as the maximum value 1, and in the static state of the battery, the corresponding open circuit voltage of the battery in the fully charged state is measured and recorded.

Control the battery to discharge at a constant current at the set rate and continue for a set time, so that the remaining power of the battery is reduced by a known set value, calculate and record the remaining power of the battery at this time, measure and record the remaining power of the battery at this time. Corresponding battery open circuit voltage. For example, control the battery to discharge at a constant current rate of 1C for 3 minutes, and the remaining power of the battery will decrease by 5%. This process is repeated until the battery is completely discharged and the remaining charge is 0. Thus, a plurality of remaining powers and a plurality of battery open-circuit voltages corresponding to one-to-one are obtained.

All the remaining power and the one-to-one corresponding battery open-circuit voltage are stored as a two-dimensional table, which constitutes the corresponding relationship between the open-circuit voltage and the remaining power.

A specific example of the correspondence between the open circuit voltage and the remaining power is shown in the table below. In the table, OCV represents the open circuit voltage value in V; SOC represents the remaining power, 1.0000 means the remaining power is 100% of the full power, and 0.95 means the remaining power It is 95% of the full power, and the meaning of the rest of the SOC values is analogous.

When the corresponding relationship between the open-circuit voltage and the remaining power is the two-dimensional table determined in the above manner, the corresponding current remaining power is determined according to the current open-circuit voltage estimated in real time in step 11, specifically:

Find the battery open circuit voltage that is equal to or similar to the current open circuit voltage from the two-dimensional table, and determine the remaining power corresponding to the equal or similar battery open circuit voltage in the table as the current remaining power. For example, the current open-circuit voltage value is 6.416V. In the above-mentioned two-dimensional table, a voltage similar to this voltage value is 6.4193V, and the remaining power corresponding to the similar voltage value is 0.8. From this, it is determined that the current remaining power of the battery is 80% of the full power.

The form of a table is used as the corresponding relationship between the open circuit voltage and the remaining power, which is convenient to find and fast to determine the remaining power. Of course, in order to improve the accuracy of the corresponding relationship, it is required that there is as much data in the table as possible, and the remaining power interval is as small as possible.

In some other embodiments, the corresponding relationship between the open circuit voltage and the remaining power is determined by the following process:

The remaining power of the battery in the fully charged state is determined as the maximum value 1, and in the static state of the battery, the corresponding open circuit voltage of the battery in the fully charged state is measured and recorded.

Control the battery to discharge at a constant current at the set rate and continue for a set time, so that the remaining power of the battery is reduced by a known set value, calculate and record the remaining power of the battery at this time, measure and record the remaining power of the battery at this time. Corresponding battery open-circuit voltage; perform this process cyclically until the battery is completely discharged, and the remaining power is 0, and multiple remaining powers and one-to-one corresponding multiple battery open-circuit voltages are obtained.

Curve fitting is performed according to all the remaining power and the one-to-one corresponding battery open-circuit voltage to obtain a functional relationship between the remaining power and the battery open-circuit voltage, and the functional relationship is determined as the corresponding relationship between the open-circuit voltage and the remaining power. Generally, the functional relationship between the remaining power and the open-circuit voltage of the battery is set to a 7th-order functional relationship, which can not only ensure the accuracy, but also maintain a reasonable operation speed.

Different from some of the above embodiments, the corresponding relationship between the open-circuit voltage and the remaining battery power is represented in a two-dimensional table form, in these embodiments, a plurality of remaining battery powers and corresponding battery open-circuit voltages are obtained to form a plurality of data pairs, based on Curve fitting is performed on multiple data pairs to obtain the functional relationship between the remaining power and the open-circuit voltage of the battery, and the corresponding relationship between the open-circuit voltage and the remaining power is represented by the functional relationship.

When the corresponding relationship is a functional relationship, the corresponding current remaining power is determined according to the current open-circuit voltage estimated in real time in step 11. Specifically, the remaining power corresponding to the current open-circuit voltage is calculated according to the functional relationship, and the calculated value is determined as the current remaining power.

Using the methods for estimating the remaining power of electric vehicles in the above embodiments, establish an open-circuit voltage model related to the battery current and battery voltage, including the equivalent capacitor voltage calculation formula and the open-circuit voltage calculation formula with a recursive relationship, and complete the open-circuit in an offline manner. Identification of the coefficients in the voltage model. In the process of battery use, based on the open-circuit voltage model, the real-time estimation of the open-circuit voltage can be realized only according to the real-time battery current, the real-time battery voltage and the easily determined initial open-circuit voltage, and then the real-time remaining capacity can be calculated according to the estimated real-time open-circuit voltage. estimate. This method is used to estimate the remaining power, regardless of whether the battery is in a resting state or a working state. Moreover, using this method does not depend on the initial value, even if the initial value is inaccurate, it can be quickly corrected in the recursive process, so that the final estimated value is always near the true value, and the accuracy is high.

After estimating the remaining power of the electric vehicle based on the above embodiment, the remaining mileage of the electric vehicle may be further estimated based on the remaining power.

Fig. 3 shows a flowchart of an embodiment of the method for estimating the remaining mileage of an electric vehicle based on the present invention. Specifically, after estimating the remaining power of the electric vehicle based on the embodiment of Fig. 1 and its preferred embodiment, the remaining power is estimated based on the remaining power. An example of mileage.

As shown in FIG. 3 , this embodiment adopts the following method to realize the estimation of the remaining driving range of the electric vehicle.

Step 21: Estimate the remaining power when the current driving distance is n*L, and denote it as SOC(n).

Among them, n is a natural number, and L is the set interval mileage. The set interval mileage can be determined according to the actual situation and estimation accuracy requirements, for example, L is taken as 1Km, 2Km, etc. In this embodiment, for convenience of description, L=1Km is taken as an example for description. Then, when L=1Km, the current driving distance of the electric vehicle is n*L, which can be expressed as the current driving distance of the electric vehicle is nKm. In addition, the current travel distance is calculated from the time when the electric vehicle starts to travel.

When estimating the remaining mileage, it is first necessary to estimate the remaining power at the current driving distance n*L. The estimation of the remaining power is realized by the method described in the embodiment of FIG. 1 and its preferred embodiment.

Step 22: Determine the average value of the change in the remaining battery power when the nth L is driven, and record it as SOCdeltmean(n).

The average value of the amount of change in the remaining battery power refers to the average value of the amount of change in the nth L. For example, when L is 1Km, it refers to the average value of the amount of change in the remaining battery power when the nth 1Km is traveled. In the prior art, there are various determination methods for obtaining the average value of the change in the remaining battery power within a certain mileage interval. The power consumption of each power-consuming device in the mileage interval is calculated, and then the power consumption of the motor in the mileage interval is calculated; the power consumption of the motor is divided by the mileage interval to obtain the change in the remaining battery power in the mileage interval. average value.

In some preferred embodiments, the recursive method is used to estimate the average value of the amount of change in the remaining battery power, and the specific implementation process is as follows:

Determine the amount of change in the remaining battery charge for each L of driving:

SOCdelt(n)=SOC(n)-SOC(n-1)

SOCdelt(n-1)=SOC(n-1)-SOC(n-2)

SOCdelt(1)=SOC(1)-SOC(0).

Among them, SOCdelt(n) and SOCdelt(n-1) are the changes of the remaining battery power when driving the nth L and the n-1th L respectively, and SOCdelt(1) is the remaining battery power when driving the first L The amount of change; SOC(n), SOC(n-1), SOC(n-2), SOC(1) are the driving distance of n*L, (n-1)*L, (n-2)* The remaining power at L and L, SOC (0) is the remaining power when the electric vehicle is turned on. The remaining power SOC (0) of the electric vehicle when it is turned on is the remaining power recorded when it was last turned off. The remaining power SOC(n), SOC(n-1), SOC(n-2), . After obtaining the remaining power at different driving distances, according to the above recursive formula, the change amount of the remaining battery power during each L driving can be obtained.

Based on the amount of change in the remaining battery power when driving each L, the recursive method is used to estimate the average SOCdeltmean(n-1) of the change in the remaining battery power when the n-1th L is driven:

SOCdeltmean(n-1)=[SOCdeltmean(n-2)*(n-1)+ SOCdelt(n-1)*1]/(n)

SOCdeltmean(n-2)=[SOCdeltmean(n-3)*(n-2)+SOCdelt(n-2)*1]/(n-1)

SOCdeltmean(1)=SOCdeltmean(0)*0+SOCdelt(0)*1]/(1).

Among them, SOCdeltmean(n-2), SOCdeltmean(n-3), and SOCdeltmean(1) are the changes in the remaining battery power when driving the n-2 th L, the n-3 th L, and the 1st L, respectively. Average value, SOCdelt(0)=SOCdeltmean(0) is the average value of the change in the remaining battery power recorded when the electric vehicle was powered off last time, SOCdelt(n-2) is the change in the remaining battery power when the n-2th L is driven quantity.

Then, according to the average SOCdeltmean(n-1) of the change amount of the remaining battery power when driving the n-1th L, and the change amount of the remaining battery power SOCdelt(n) when driving the nth L, determine the remaining battery power when driving the nth L. The average value of the change in electricity SOCdeltmean(n):

SOCdeltmean(n) = [SOCdeltmean(n-1)*n+ SOCdelt(n)*1]/(n+1).

When calculating the average value of the change amount of the remaining battery power when driving each L, the change amount of the remaining battery power when the mileage interval L is traveled is considered, and the change amount is used as the adjustment amount to adjust the average value of the change amount so as to be as far as possible. Reduce the estimation error of the average value of the remaining power change, and improve the estimation accuracy.

Step 23: Estimating the remaining mileage Srem(n) according to the remaining power and the average value of the change of the remaining power.

Specifically, the calculation method of the remaining mileage Srem(n) is:

Srem(n)=SOC(n)/SOCdeltmean(n).

In the process of estimating the remaining mileage of the electric vehicle in this embodiment, the remaining power SOC(n) is estimated by the method of the embodiment of FIG. 1 and its preferred embodiment, and the estimation accuracy is high. Therefore, the remaining mileage estimated based on the remaining power estimated with high accuracy has high accuracy, and can provide the driver with an accurate and reliable remaining mileage, which is convenient for guiding the driving process according to the remaining mileage.

In some other preferred embodiments, after estimating the remaining mileage Srem(n) of the electric vehicle, the following process is further included:

The difference between the estimated remaining mileage Srem(n) of the electric vehicle when the estimated driving distance is n*L and the estimated remaining mileage Srem(n-1) of the electric vehicle when the driving distance is (n-1)*L is obtained. Remaining mileage reduction S: S=Srem(n-1)-Srem(n).

Compare S with the set upper limit value. The set upper limit value is a known mileage value and is preset, for example, the set upper limit value is 2Km.

If the remaining mileage reduction S is not greater than the set upper limit value, the estimated remaining mileage Srem(n) is displayed in real time. If S is greater than the set upper limit, the difference between the estimated remaining electric vehicle mileage Srem(n-1) when the driving distance is (n-1)*L and the set upper limit will be displayed in real time as the current remaining mileage . For example, when the upper limit is set to 2Km and the driving distance is (n-1)*L, the estimated remaining electric vehicle mileage Srem(n-1)=55Km, and the estimated current remaining mileage Srem(n)=48Km , then the remaining mileage reduction S=Srem(n-1)-Srem(n)=55-48=7 (Km). The mileage reduction amount S is greater than the set upper limit value of 2Km. Generally, the sudden large change in the mileage reduction is caused by the instantaneous large power consumption, such as going uphill, and it is precisely at the moment when the instantaneous large power consumption is estimated that the remaining power is estimated, and then the remaining mileage is estimated, but the actual The remaining mileage does not change significantly. In this case, the estimated remaining mileage estimated by the instantaneous large power consumption is not accurate. If the estimated remaining mileage is directly displayed, it is easy to cause misjudgment and greater pressure on drivers who do not understand the output performance of the battery. Drive normally. Therefore, in this embodiment, an appropriate upper limit value is set according to the actual situation, and the change of the remaining mileage is limited, which can not only provide the driver with a reasonable and accurate estimation of the remaining mileage, but also avoid unnecessary causes for the driver. pressure and enhance the driving experience.

In some other preferred embodiments, in order to reduce the system workload caused by the estimated remaining range of the electric vehicle, some restrictions can also be made when estimating the open circuit voltage of the power battery, for example, if the estimated open circuit voltage is the same as the last estimated value If the change is smaller than the set value, it is determined that the battery has no power consumption, or the power consumption is very small, which can be ignored. In this case, the remaining power and remaining mileage are no longer estimated, and the remaining mileage remains unchanged.

The above embodiments are only used to illustrate the technical solutions of the present invention, but not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art can still The recorded technical solutions are modified, or some technical features thereof are equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions claimed in the present invention.

Claims (9)

1. A method for estimating the remaining capacity of an electric vehicle is characterized by comprising the following steps:

detecting the current battery current and the current battery voltage of an electric automobile power battery in real time, and estimating the current open-circuit voltage of the power battery by using the current battery current, the current battery voltage and an open-circuit voltage model; the open circuit voltage model is:

U0(t)=A₁₁*U0(t-1)+A₁₂*U1(t-1)+B₁₁*Ib(t)+B₁₂*Ubus(t)，

U1(t)=A₂₁*U0(t-1)+A₂₂*U1(t-1)+B₂₁*Ib(t)+B₂₂*Ubus(t)；

wherein U0(t) and U0(t-1) are the present open circuit voltage and the last cycle open circuit voltage, respectively, U1(t) and U1(t-1) are the present equivalent capacitor voltage and the last cycle equivalent capacitor voltage, respectively, Ib (t) and Ubus (t) are the present battery current and the present battery voltage, respectively, A₁₁、A₁₂、B₁₁、B₁₁、A₂₁、A₂₂、B₂₁、B₂₂Are all coefficients;

determining the current residual capacity corresponding to the current open-circuit voltage according to the estimated current open-circuit voltage and the known corresponding relation between the open-circuit voltage and the residual capacity;

coefficient A₁₁、A₁₂、B₁₁、B₁₁、A₂₁、A₂₂、B₂₁、B₂₂Determining the coefficient values by:

establishing an equivalent circuit model of the power battery of the electric automobile;

obtaining output current, output voltage and open-circuit voltage corresponding to a plurality of known residual capacities of the power battery to form offline data, and performing parameter identification on components in the equivalent circuit model by using the offline data to determine component identification parameters;

discretizing the component identification parameters to estimate the coefficient A in the open-circuit voltage model₁₁、A₁₂、B₁₁、B₁₁、A₂₁、A₂₂、B₂₁、B₂₂。

2. The method for estimating the remaining capacity of the electric vehicle according to claim 1, wherein the equivalent circuit model is a second-order RC equivalent circuit model.

3. The method for estimating remaining capacity of an electric vehicle according to claim 1, wherein the correspondence relationship between the open circuit voltage and the remaining capacity is determined by the following procedure:

determining the residual electric quantity of the battery in a full-charge state as a maximum value 1, and measuring and recording the corresponding battery open-circuit voltage in the full-charge state in the static state of the battery;

controlling the battery to discharge at a constant current according to a set multiplying power and continue for a set time so that the residual capacity of the battery is reduced by a known set value, calculating and recording the residual capacity of the battery at the moment, and measuring and recording the open-circuit voltage of the battery corresponding to the residual capacity of the battery at the moment; circularly executing the process until the battery is completely discharged, the residual electric quantity is 0, and a plurality of residual electric quantities and a plurality of battery open-circuit voltages which correspond to one another one by one are obtained;

all the remaining electric quantities and the battery open-circuit voltages in one-to-one correspondence are stored as a two-dimensional table, and a correspondence relationship between the open-circuit voltages and the remaining electric quantities is formed.

4. The method for estimating remaining power of an electric vehicle according to claim 3, wherein determining the current remaining power corresponding to the current open-circuit voltage according to the estimated current open-circuit voltage and a known correspondence between the open-circuit voltage and the remaining power specifically comprises:

and searching the battery open-circuit voltage which is equal to or similar to the current open-circuit voltage from the two-dimensional table, and determining the residual electric quantity corresponding to the equal or similar battery open-circuit voltage in the table as the current residual electric quantity.

5. The method for estimating remaining capacity of an electric vehicle according to claim 1, wherein the correspondence relationship between the open circuit voltage and the remaining capacity is determined by the following procedure:

determining the residual electric quantity of the battery in a full-charge state as a maximum value 1, and measuring and recording the corresponding battery open-circuit voltage in the full-charge state in the static state of the battery;

controlling the battery to discharge at a constant current according to a set multiplying power and continue for a set time so that the residual capacity of the battery is reduced by a known set value, calculating and recording the residual capacity of the battery at the moment, and measuring and recording the open-circuit voltage of the battery corresponding to the residual capacity of the battery at the moment; circularly executing the process until the battery is completely discharged, the residual electric quantity is 0, and a plurality of residual electric quantities and a plurality of battery open-circuit voltages which correspond to one another one by one are obtained;

and performing curve fitting according to all the residual electric quantity and the battery open-circuit voltages in one-to-one correspondence to obtain a functional relation between the residual electric quantity and the battery open-circuit voltage, and determining the functional relation as the corresponding relation between the open-circuit voltage and the residual electric quantity.

6. The method for estimating remaining power of an electric vehicle according to claim 5, wherein determining the current remaining power corresponding to the current open-circuit voltage according to the estimated current open-circuit voltage and a known correspondence between the open-circuit voltage and the remaining power specifically comprises:

and calculating the residual capacity corresponding to the current open-circuit voltage according to the functional relation, and determining the calculated value as the current residual capacity.

7. A method for estimating remaining driving mileage of an electric vehicle, the method comprising:

estimating the remaining capacity SOC (n) of the current driving distance n x L by using the method of any one of the above claims 1 to 6, wherein n is a natural number, L is a set interval mileage;

determining an average value socdeltmean (n) of the amount of change in the remaining battery power at the time of the nth L run;

estimating the remaining driving mileage Srem (n) of the electric automobile according to the following formula:

Srem（n）=SOC（n）/ SOCdeltmean（n）。

8. the method for estimating the remaining driving range of the electric vehicle according to claim 7, wherein an average value socdeltmean (n) of the change amount of the remaining battery capacity at the nth L driving time is determined, specifically:

the amount of change in the remaining amount of battery at the time of running of each L is determined:

SOCdelt（n）=SOC（n）-SOC（n-1）

SOCdelt（n-1）=SOC（n-1）-SOC（n-2）

.......

SOCdelt（1）=SOC（1）-SOC（0）；

wherein, SOCdelt (n) and SOCdelt (n-1) are respectively the change quantity of the battery residual capacity when the electric automobile runs for the nth L and the nth L, SOCdelt (1) is the change quantity of the battery residual capacity when the electric automobile runs for the 1 st L, SOC (n), SOC (n-1), SOC (n-2) and SOC (1) are respectively the residual capacity when the running distance is n L, (n-1) L, (n-2) L and L, and SOC (0) is the residual capacity when the electric automobile is started;

estimating the average value SOCdeltmean (n-1) of the change amount of the remaining battery capacity when driving the (n-1) th L by a recursion method:

SOCdeltmean（n-1）=[SOCdeltmean（n-2）*(n-1)+ SOCdelt(n-1)*1]/（n）

SOCdeltmean（n-2）=[SOCdeltmean（n-3）*(n-2)+ SOCdelt(n-2)*1]/（n-1）

......

SOCdeltmean（1）=SOCdeltmean（0）*0+SOCdelt(0)*1]/（1）;

wherein, SOCdeltmean (n-2), SOCdeltmean (n-3), and SOCdeltmean (1) are average values of the change amounts of the remaining battery power when the electric vehicle runs for the n-2 th time of L, runs for the n-3 th time of L, and runs for the 1 st time of L, respectively, SOCdelt (0) = SOCdeltmean (0) is the average value of the change amounts of the remaining battery power recorded when the electric vehicle is last shut down, and SOCdelt (n-2) is the change amount of the remaining battery power when the electric vehicle runs for the n-2 th time of L;

determining an average value SOCdeltmean (n) of the change amount of the battery remaining capacity when the vehicle is traveling the nth L, based on the average value SOCdeltmean (n-1) of the change amount of the battery remaining capacity when the vehicle is traveling the nth L and the change amount socdelt (n) of the battery remaining capacity when the vehicle is traveling the nth L:

SOCdeltmean（n）= [SOCdeltmean（n-1）*n+ SOCdelt(n)*1]/（n+1）。

9. the method for estimating remaining mileage of an electric vehicle according to claim 7 or 8, further comprising:

the estimated remaining driving mileage Srem (n) of the electric automobile is differed from the estimated remaining driving mileage Srem (n-1) when the driving distance is (n-1) L, and a remaining driving mileage reduction amount S is obtained, wherein S = Srem (n-1) -Srem (n);

comparing S with a set upper limit value;

if the S is not greater than the set upper limit value, displaying the Srem (n) in real time; and if the S is larger than the set upper limit value, displaying the difference between the Srem (n-1) and the set upper limit value as the current remaining driving mileage in real time.

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