CN111398828B - Method for estimating remaining electric quantity and remaining driving mileage of electric automobile - Google Patents
Method for estimating remaining electric quantity and remaining driving mileage of electric automobile Download PDFInfo
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Abstract
The invention discloses a method for estimating the remaining electric quantity and the remaining driving mileage of an electric automobile. The remaining capacity estimation method includes: 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; and 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. The remaining mileage estimation method includes: estimating the residual capacity when the current driving distance n x L; determining an average value of the amount of change in the remaining battery capacity when the vehicle travels the nth L; the remaining driving range is estimated based on the remaining capacity and the average value of the amount of change in the remaining capacity. By applying the method and the device, the accuracy of the residual electric quantity estimation and the residual travel mileage estimation can be improved.
Description
Technical Field
The invention belongs to the technical field of electric automobiles, and particularly relates to a method for estimating the remaining electric quantity and the remaining driving mileage of an electric automobile.
Background
New energy vehicles, represented by electric vehicles, are widely regarded as one of the most effective ways to solve the current problems of energy and pollution, and attract extensive attention at home and abroad. Generally, an electric vehicle is a vehicle which uses a vehicle-mounted power supply as power and drives wheels by a motor, and meets various requirements of road traffic and safety regulations. Compared with the traditional fuel oil automobile, the electric automobile has the characteristics of high performance, low energy consumption and low pollution, and has comprehensive advantages in the aspects of technology, economy, environment and the like, and the prospect is widely seen.
In any form of electric vehicle, the battery is an indispensable part of the power system. Accurate and real-time monitoring of the residual battery capacity is related to stable and reliable operation of a power system, and is one of key problems of practical application. The residual driving mileage can be influenced along with the deep discharge of the power battery of the electric automobile and the aging of the power battery, so that the estimation of the residual driving mileage of the electric automobile has important guiding values for planning an optimal energy-saving route, searching for charging facilities and the like of an electric automobile user, and has very important significance for promoting the use and popularization of the electric automobile.
The remaining electric quantity of the electric vehicle refers to a State of Charge (SOC) of the battery, and a popular explanation is a State of remaining Charge in a power battery of the electric vehicle. Accurate estimation of the remaining capacity is a key and difficult point of EMF (battery management system), which is based on the SOC of the battery and performs energy balance management on the battery, and many functions on the electric vehicle depend on the estimation result of the SOC. Therefore, the SOC of the power battery has important significance and effect, the SOC is estimated through physical quantities such as voltage, current and temperature, but the accuracy of the SOC estimation is influenced by many factors, such as low accuracy of a sensor, electromagnetic interference, uncertain influence of past and future operation conditions, influence of temperature on accuracy and the like. These factors are unavoidable, but exist actually, so the SOC of the battery is influenced by various factors, so that it is difficult to accurately estimate the true remaining capacity of the battery in real time, and the true value of the remaining capacity of the battery can only be approximated by various measures and methods.
In the prior art, there are many methods for estimating the remaining capacity, such as a charge accumulation method, an open-circuit voltage method, a method combining the open-circuit voltage method and an ampere-hour meter method, and so on, and there are many factors that are not considered when these methods are applied, so that the accuracy of the estimated value is not sufficient. For example, the charge integration method has a problem of an integration error, and the error is larger as the operation time is longer. With respect to the open circuit voltage method, the method cannot be used when the battery is in operation, and cannot be used until the battery stops operating and is stationary for a certain period of time, which has a relatively large limitation. The combination of the two methods is now used by many people in large quantities, has many advantages, and can complement the disadvantages of the two methods, but the combination method still cannot solve the disadvantages of the open-circuit voltage method, and the method cannot remove the electromagnetic interference. The estimation of the remaining driving mileage of the electric vehicle is closely related to the remaining power, and if the estimation of the remaining power is not accurate, the remaining driving mileage is difficult to accurately estimate, which affects the use performance of the electric vehicle.
Disclosure of Invention
The invention aims to provide a method for estimating the remaining electric quantity and the remaining driving mileage of an electric automobile, so as to improve the accuracy of estimation.
In order to realize the purpose of the invention, the invention is realized by adopting the following technical scheme:
a method for estimating the residual capacity of an electric automobile comprises 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。
A method for estimating remaining driving mileage of an electric vehicle comprises the following steps:
estimating the residual electric quantity SOC (n) when the current driving distance n x L is obtained by adopting the method; n is a natural number, and L is a set interval mileage;
determining an average value SOCdeltmean (n) of the change amount of the remaining battery capacity when the vehicle travels the nth L;
estimating the remaining driving mileage Srem (n) of the electric automobile according to the following formula:
Srem（n）=SOC（n）/ SOCdeltmean（n）。
compared with the prior art, the invention has the advantages and positive effects that: the method for estimating the residual electric quantity of the electric automobile comprises the steps of establishing an open-circuit voltage model which is related to battery current and battery voltage and comprises an equivalent capacitance voltage calculation formula and an open-circuit voltage calculation formula in a recursion relation, and identifying coefficients in the open-circuit voltage model in an off-line mode; the method is adopted to estimate the residual electric quantity, and the method is applicable to the situation whether the battery is in a static state or a working state; moreover, the method does not depend on the initial value, and can carry out quick correction in the recursion process even if the initial value is inaccurate, so that the final estimated value is always near the true value, and the accuracy is high; the accuracy of estimating the remaining mileage of the battery based on the remaining amount of the battery can also be improved based on the highly accurate estimation of the remaining amount of the battery.
Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flowchart illustrating an electric vehicle remaining capacity estimation method according to an embodiment of the present invention;
FIG. 2 is an equivalent circuit model of one embodiment of an electric vehicle power cell;
FIG. 3 is a flowchart of an embodiment of a method for estimating remaining driving range of an electric vehicle according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings and examples.
Referring to fig. 1, a flowchart of an embodiment of a method for estimating remaining capacity of an electric vehicle according to the present invention is shown. Specifically, to improve estimation of the remaining capacity of the electric vehicle, the embodiment adopts the following method to realize online real-time estimation of the remaining capacity of the electric vehicle.
Step 11: the current battery current and the current battery voltage of the power battery of the electric automobile 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.
Wherein the open circuit voltage model is a known model satisfying:
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 respectivelyFor the present and last cycle open circuit voltages, U1(t) and U1(t-1) are the present and last cycle equivalent capacitor voltages, A, respectively11、A12、B11、B11、A21、A22、B21、B22Are all coefficients whose values have been determined. Ib (t) and ubus (t), respectively, are the current battery current and the current battery voltage, which CAN be measured directly and conveniently read, for example, via a CAN bus of a battery control system.
For the open circuit voltage model, an initial open circuit voltage U0_ init and an initial equivalent capacitor voltage U1_ init at the beginning of a cycle also need to be determined. The initial open-circuit voltage U0_ init is defaulted to be the open-circuit voltage value saved when the electric automobile is shut down last time; if the open circuit voltage is calculated for the first startup after the battery is fully charged, the initial open circuit voltage is the open circuit voltage value in the fully charged state of the battery, and the value can be known. For the initial equivalent capacitor voltage U1_ init, 0 is defaulted. Therefore, for the open circuit voltage model with the determined coefficients and initial values, after the current battery current data ib (t) and the current battery voltage data ubus (t) are obtained, the current open circuit voltage U0(t) can be determined by loop calculation based on the recursion relationship of the open circuit voltage model. The process can be carried out in real time in the using process of the battery, so that the on-line real-time estimation of the open-circuit voltage can be realized.
For coefficient A in the open circuit voltage model11、A12、B11、B11、A21、A22、B21、B22And identifying in an off-line mode. Specifically, each coefficient value is determined by:
firstly, an equivalent circuit model of the power battery of the electric automobile is established.
The equivalent circuit model can adopt an RC equivalent circuit model in the prior art, and as a preferred implementation, the embodiment adopts a second-order RC equivalent circuit model as shown in fig. 2, and the model has a simple structure and high accuracy.
And then, obtaining output current, output voltage and open-circuit voltage corresponding to the power battery when the residual capacity is known, forming off-line data, performing parameter identification on the components in the equivalent circuit model by using the off-line data, and determining component identification parameters.
In the equivalent circuit model shown in fig. 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. And in an off-line state, controlling the battery to work under different residual capacities, and measuring the corresponding output current, output voltage and open-circuit voltage when the different residual capacities are measured to form corresponding multiple groups of off-line data. And then, performing parameter identification on the components in the equivalent circuit model by using offline data, specifically, identifying the energy storage capacitor C0, the ohmic internal resistance R0, the polarization internal resistance R1 and the polarization capacitor C1 in the equivalent circuit model. In some preferred embodiments, when the off-line data is used for performing parameter identification on the component in the equivalent circuit model, the least square algorithm can be used for performing parameter identification by means of the polyfit function with the least square meaning in the MATLAB software, so as to determine the component identification parameters.
And finally, discretizing the identified parameters of each component, and estimating coefficients in the open-circuit voltage model. 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 data on the model effect can be well avoided, the abnormal data is well robust, and the estimation accuracy can be improved.
In a preferred embodiment, the values of the coefficients fitted to the open circuit voltage model are 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: and 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.
The correspondence relationship of the open-circuit voltage and the remaining capacity is known and stored in advance, and is obtained in a state where the battery is stationary.
In some embodiments, the correspondence relationship between the open-circuit voltage and the remaining capacity is determined by the following process:
the residual electric quantity of the battery in the full-charge state is determined as the maximum value 1, and the corresponding battery open-circuit voltage in the full-charge state is measured and recorded in the battery static state.
And 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. For example, the battery is controlled to discharge for 3min at a constant current of 1C rate, and the residual capacity of the battery is reduced by 5%. This process is cyclically executed until the battery is completely discharged and the remaining capacity is 0. Thus, a plurality of residual capacities and a plurality of battery open-circuit voltages in one-to-one correspondence 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.
A table of a correspondence relationship between the open circuit voltage and the remaining capacity of a specific example is shown below, in which OCV represents an open circuit voltage value in units of V; SOC represents the remaining capacity, 1.0000 represents the remaining capacity as 100% of full capacity, 0.95 represents the remaining capacity as 95% of full capacity, and so on for the remaining SOC values.
When the corresponding relationship between the open-circuit voltage and the remaining power is the two-dimensional table determined in the above manner, the current remaining power is determined according to the current open-circuit voltage estimated in real time in step 11, which specifically includes:
and searching the battery open-circuit voltage which is equal to or close to the current open-circuit voltage from the two-dimensional table, and determining the residual electric quantity corresponding to the equal or close battery open-circuit voltage in the table as the current residual electric quantity. For example, the current open circuit voltage value is 6.416V, the voltage close to the current open circuit voltage value is 6.4193V in the two-dimensional table, and the remaining capacity corresponding to the close voltage value is 0.8. Thus, it is determined that the current remaining capacity of the battery is 80% of the full capacity.
The form of the table is used as the corresponding relation between the open-circuit voltage and the residual capacity, so that the searching is convenient, and the residual capacity determining speed is high. Of course, in order to improve the accuracy of the corresponding relationship, it is required that the data in the table is as much 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 capacity is determined by the following process:
the residual electric quantity of the battery in the full-charge state is determined as the maximum value 1, and the corresponding battery open-circuit voltage in the full-charge state is measured and recorded in the battery static state.
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; the process is executed in a circulating mode until the battery is completely discharged, the residual capacity is 0, and a plurality of residual capacities and a plurality of battery open-circuit voltages corresponding to one another 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. Generally, the functional relationship between the remaining capacity and the open-circuit voltage of the battery is set to be a 7-order functional relationship, so that the accuracy can be ensured, and the reasonable operation speed can be kept.
In some embodiments, a plurality of remaining power levels and corresponding battery open-circuit voltages are obtained, a plurality of data pairs are formed, curve fitting is performed based on the plurality of data pairs, a functional relationship between the remaining power levels and the battery open-circuit voltages is obtained, and the corresponding relationship between the open-circuit voltages and the remaining power levels is represented by the functional relationship.
When the corresponding relationship is a functional relationship, determining the corresponding current remaining capacity according to the current open-circuit voltage estimated in step 11 in real time, specifically: 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.
By adopting the method for estimating the remaining capacity of the electric vehicle in each embodiment, an open-circuit voltage model which is related to the battery current and the battery voltage and comprises an equivalent capacitance voltage calculation formula and an open-circuit voltage calculation formula in a recursion relationship is established, and the identification of the coefficient in the open-circuit voltage model is completed in an off-line mode. In the using process of the battery, 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 initial open-circuit voltage which is easy to determine, and then the real-time estimation of the residual capacity is completed according to the estimated real-time open-circuit voltage. The method is adopted to estimate the residual electric quantity, and is suitable for the battery in a static state or a working state. Moreover, the method is independent of the initial value, and can quickly correct in the recursion process even if the initial value is inaccurate, so that the final estimated value is always near the true value, and the accuracy is high.
After the remaining electric quantity of the electric vehicle is estimated based on the above embodiments, the remaining driving range of the electric vehicle can be further estimated based on the remaining electric quantity.
Fig. 3 is a flowchart illustrating an embodiment of a method for estimating remaining driving range of an electric vehicle according to the present invention, and more particularly, an embodiment of estimating remaining driving range of an electric vehicle based on remaining capacity after estimating remaining capacity of the electric vehicle based on the embodiment of fig. 1 and the preferred embodiment thereof.
As shown in fig. 3, the embodiment adopts the following method to realize the estimation of the remaining driving range of the electric vehicle.
Step 21: and estimating the remaining electric quantity when the current driving distance n is L, and recording the remaining electric quantity as SOC (n).
Wherein n is a natural number, and L is a set interval mileage. The set interval mileage can be determined according to actual conditions and estimation accuracy requirements, for example, L is 1Km, 2Km, and the like. In this embodiment, for convenience of description, L =1Km is described as an example. When L =1Km, the current driving distance of the electric vehicle is n × L, which may be represented as nKm. The current travel distance is calculated from when the electric vehicle starts traveling.
When estimating the remaining driving range, the remaining power at the current driving distance n × L needs to be estimated first. The estimation of the remaining capacity is performed by the method described in the embodiment of fig. 1 and the preferred embodiment thereof.
Step 22: the average value of the amount of change in the remaining battery power when the vehicle travels the nth L is determined and recorded as socdeltmean (n).
The average value of the remaining power change amount is an average value of the change amount when the vehicle travels the nth L, for example, when L is 1Km, the average value of the change amount of the remaining power of the battery when the vehicle travels the nth 1 Km. In the prior art, there are various determining methods for obtaining an average value of the change amount of the remaining battery capacity in a certain mileage interval, for example, determining the total power consumption of the electric vehicle in the certain mileage interval according to the power integral, calculating the power consumption of each power consumption device of the electric vehicle except for the motor in the mileage interval, and further calculating the power consumption of the motor in the mileage interval; the power consumption of the motor is divided by the mileage interval to obtain the average value of the change amount of the remaining battery power in the mileage interval.
In some preferred embodiments, the average value of the change amount of the remaining battery capacity is estimated by a recursive method, which is implemented as follows:
the amount of change in the remaining amount of battery while traveling 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 of the battery residual capacity when driving the nth L and the driving the nth-1L, and SOCdelt (1) is the change of the battery residual capacity when driving the 1 st L; SOC (n), SOC (n-1), SOC (n-2), SOC (1) are the remaining electric energy when the driving distance is n × L, (n-1) × L, (n-2) × L, L, respectively, and SOC (0) is the remaining electric energy when the electric vehicle is started. The remaining capacity SOC (0) of the electric vehicle when the electric vehicle is started is the remaining capacity recorded when the electric vehicle is shut down last time. The residual electric quantity SOC (n), SOC (n-1), SOC (n-2), … … and SOC (1) at different driving distances are obtained by estimation by adopting the method described in the embodiment of FIG. 1 and the preferred embodiment thereof. After the remaining capacity at different travel distances is obtained, the amount of change in the remaining capacity of the battery at each L of travel can be obtained according to the above recursion formula.
Estimating a change amount average value SOCdeltmean (n-1) of the battery remaining capacity while traveling n-1 th L by a recursive method based on the change amount of the battery remaining capacity while traveling each L:
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）。
the controller comprises a controller, a controller and a controller, wherein SOCdeltmean (n-2), SOCdeltmean (n-3) and SOCdeltmean (1) are respectively the average value of the change amount of the remaining battery capacity when the controller runs for the (n-2) th L, the (n-3) th L and the 1 st L, SOCdelt (0) = SOCdeltmean (0) is the average value of the change amount of the remaining battery capacity recorded when the electric automobile is shut down last time, and SOCdelt (n-2) is the change amount of the remaining battery capacity when the controller runs for the (n-2) th L.
And determining the average value SOCdeltmean (n) of the change amount of the battery residual capacity during the nth L according to the average value SOCdeltmean (n-1) of the change amount of the battery residual capacity during the nth L and the change amount SOCdelt (n) of the battery residual capacity during the nth L:
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 each L is driven, the average value of the change amount of the remaining battery power when the L is driven is considered, and the change amount is used as the adjustment amount to adjust the average value of the change amount, so that the estimation error of the average value of the change amount of the remaining battery power is reduced as much as possible, and the estimation accuracy is improved.
Step 23: the remaining mileage srem (n) is estimated from the average value of the remaining amount of electricity and the amount of change in the remaining amount of electricity.
Specifically, the method for calculating the remaining driving range srem (n) is as follows:
Srem（n）=SOC（n）/ SOCdeltmean（n）。
in the process of estimating the remaining driving range of the electric vehicle in the embodiment, the remaining power soc (n) is estimated by using the method in the embodiment of fig. 1 and the preferred embodiment thereof, and the estimation accuracy is high. Therefore, the estimated remaining driving mileage based on the high-accuracy estimated remaining power is high in accuracy, accurate and reliable remaining driving mileage can be provided for a driver, and the driving process can be guided according to the remaining driving mileage.
In other some preferred embodiments, after estimating the remaining driving range srem (n) of the electric vehicle, the following process is further included:
and (3) subtracting the estimated remaining driving mileage Srem (n) of the electric automobile when the driving distance is n L from the estimated remaining driving mileage Srem (n-1) of the electric automobile when the driving distance is (n-1) L to obtain a remaining driving mileage reduction amount S: s = Srem (n-1) -Srem (n).
S is compared with a set upper limit value. The upper limit is a known mileage value and is set in advance, for example, to 2 Km.
And if the remaining driving mileage reduction amount S is not larger than the set upper limit value, displaying the estimated remaining driving mileage Srem (n) in real time. And if S is larger than the set upper limit value, displaying the difference between the estimated remaining driving mileage Srem (n-1) of the electric automobile and the set upper limit value as the current remaining driving mileage in real time when the driving distance is (n-1) × L. For example, if the upper limit value is set to 2Km and the driving distance is (n-1) × L, the estimated remaining driving range Srem (n-1) =55Km, and the estimated current remaining driving range Srem (n) =48Km, the remaining driving range reduction amount S = Srem (n-1) -Srem (n) =55-48=7 (Km). The mileage decrement S is larger than the set upper limit value of 2 Km. Generally, a sudden large change in the mileage reduction amount occurs because there is an instantaneous large power consumption, such as an uphill slope, and it is precisely at the moment when there is an instantaneous large power consumption that the remaining power is estimated and the remaining mileage is estimated, but the actual remaining mileage does not change greatly. In this case, the estimated remaining driving range for the instantaneous large power consumption is not accurate, and if the estimated remaining driving range is directly displayed, erroneous judgment and large stress are easily caused to a driver who cannot know the output performance of the battery, and normal driving is affected. Therefore, the embodiment sets a proper set upper limit value according to the actual situation, limits the change of the remaining driving mileage, can provide reasonable and accurate remaining mileage estimation for the driver, can avoid causing unnecessary stress to the driver, and improves the driving experience.
In other preferred embodiments, in order to reduce the system workload of the electric vehicle due to estimating the remaining mileage, some restrictions may be made on estimating the open-circuit voltage of the power battery, for example, if the estimated open-circuit voltage is changed by a smaller amount than the set value compared with the last estimated value, it is determined that there is no or little power consumption in the battery, and the power consumption may be ignored. In this case, the remaining capacity and the remaining mileage are not estimated any more, and the remaining mileage is kept unchanged.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (7)
1. A method for estimating remaining driving mileage of an electric vehicle, the method comprising:
estimating the residual electric quantity SOC (n) when the current driving distance n x L; n is a natural number, and L is a set interval mileage;
determining an average value SOCdeltmean (n) of the change amount of the remaining battery capacity when the vehicle travels the nth L;
estimating the remaining driving mileage Srem (n) of the electric automobile according to the following formula:
Srem（n）=SOC（n）/ SOCdeltmean（n）；
determining an average value SOCdeltmean (n) of the change amount of the battery remaining capacity when the vehicle travels the nth L, specifically:
the amount of change in the remaining amount of battery while traveling 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）；
the system comprises a battery, a plurality of electric vehicles, a plurality of control modules and a plurality of control modules, wherein SOCdelt (n) and SOCdelt (n-1) are respectively the change quantity of the battery residual capacity when the electric vehicles run for the nth L and the nth-1L, SOCdelt (1) is the change quantity of the battery residual capacity when the electric vehicles run for the 1 st L, SOC (n), SOC (n-1), SOC (n-2) and SOC (1) are respectively the residual capacity when the electric vehicles run for the distance of n L, (n-1) L and (n-2) L, L, and SOC (0) is the residual capacity when the electric vehicles are started;
estimating the average value SOCdeltmean (n-1) of the change amount of the battery remaining 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）;
the method comprises the following steps that SOCdeltmean (n-2), SOCdeltmean (n-3) and SOCdeltmean (1) are average values of change amounts of the residual electric quantity of a battery when driving for the (n-2) th L, the (n-3) th L and the 1 st L respectively, SOCdelt (0) = SOCdeltmean (0) is the average value of the change amounts of the residual electric quantity of the battery recorded when the electric automobile is shut down last time, and SOCdelt (n-2) is the change amount of the residual electric quantity of the battery when driving for the (n-2) th L;
determining an average value SOCdeltmean (n) of the change amount of the battery remaining capacity during the nth L from the average value SOCdeltmean (n-1) of the change amount of the battery remaining capacity during the nth L and the change amount SOCdelt (n) of the battery remaining capacity during the nth L:
SOCdeltmean（n）= [SOCdeltmean（n-1）*n+ SOCdelt(n)*1]/（n+1）；
estimating the current remaining power specifically includes:
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 remaining mileage of an electric vehicle according to claim 1, further comprising:
and (3) subtracting the estimated remaining driving mileage Srem (n) of the electric automobile from the estimated remaining driving mileage Srem (n-1) of the electric automobile when the driving distance is (n-1) × L to obtain a remaining driving mileage reduction amount S: 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.
3. The method for estimating the remaining driving range of the electric vehicle according to claim 1, wherein the equivalent circuit model is a second-order RC equivalent circuit model.
4. The method for estimating the remaining driving range of the electric vehicle according to claim 1, wherein the correspondence relationship between the open circuit voltage and the remaining capacity is determined by using:
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.
5. The method for estimating remaining driving range of an electric vehicle according to claim 4, wherein determining the current remaining capacity 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 capacity 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.
6. The method for estimating the remaining driving range of the electric vehicle according to claim 1, wherein the correspondence relationship between the open circuit voltage and the remaining capacity is determined by using:
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.
7. The method for estimating remaining driving range of an electric vehicle according to claim 6, wherein determining the current remaining capacity 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 capacity 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.
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| CN102621497A (en) * | 2012-03-22 | 2012-08-01 | 青岛理工大学 | Method and device for monitoring residual electric quantity of storage battery |
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