CN111398828A - 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 capacity and the remaining driving mileage of an electric vehicle, which comprises the steps of detecting the current battery current and the current battery voltage of a power battery of the electric vehicle in real time, estimating the current open-circuit voltage of the power battery by using a current battery current, the current battery voltage and an open-circuit voltage model, determining the current remaining 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 remaining capacity, estimating the remaining driving mileage by using the method for estimating the remaining driving mileage, estimating the remaining capacity at the current driving distance n × L, determining the average value of the change amount of the remaining capacity of the battery at the n-th driving distance L, estimating the remaining driving mileage based on the average value of the change amount of the remaining capacity and the remaining capacity, and improving the accuracy of estimating the remaining capacity and the remaining driving mileage by using the method for estimating the remaining.
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 the content of the first and second substances,u0(t) and U0(t-1) are the present and last cycle open circuit voltages, respectively, U1(t) and U1(t-1) are the present and last cycle equivalent capacitor voltages, respectively, Ib (t) and Ubus (t) are the present and present battery currents, 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 × L is adopted, wherein n is a natural number, and L is 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）。
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 the current open circuit voltage and the last cycle open circuit voltage respectively, U1(t) and U1(t-1) are the current equivalent capacitor voltage and the last cycle equivalent capacitor voltage respectively, A11、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 at two ends of the energy storage capacitor C0, in an off-line state, the battery is controlled to work under different residual capacities, and the corresponding output current, output voltage, and open-circuit voltage are measured when the residual capacities are different, so as to form a plurality of sets of off-line data.
The method comprises the steps of identifying parameters of each component, discretizing the identified parameters by MAT L AB software to estimate coefficients in an open-circuit voltage model, wherein the discretization is carried out on the identified parameters by MAT L AB software to well avoid the influence of extreme values in data on the model effect, so that the method has good robustness on abnormal data and can improve the estimation accuracy.
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.
And 21, estimating the remaining electric quantity at the current driving distance n × L, and recording the remaining electric quantity as SOC (n).
The set interval range can be determined according to actual conditions and estimation accuracy requirements, for example, L is 1Km, 2Km and the like.
When estimating the remaining driving range, it is first necessary to estimate the remaining capacity at the current driving distance n × L. the estimation of the remaining capacity is implemented by the method described in the embodiment of fig. 1 and the preferred embodiment thereof.
And step 22, determining the average value of the change amount of the battery residual capacity when the vehicle runs at the nth L, and recording the average value as SOCdeltmean (n).
The prior art has various determining methods for obtaining the average value of the change amount of the remaining battery power within a certain mileage interval, for example, determining the total power consumption of the electric vehicle within a certain mileage interval according to power integration, calculating the power consumption of each power consumption device of the electric vehicle except for the motor within the mileage interval, and further calculating the power consumption of the motor within the mileage interval, wherein 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 within 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 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）。
the remaining battery capacity is obtained by estimating the remaining battery capacity L according to the above formula after obtaining the remaining battery capacity at different driving distances, wherein SOCdelt (n-1) is the change amount of the battery remaining capacity at the nth L driving distance and the nth L driving distance, SOCdelt (1) is the change amount of the battery remaining capacity at the 1 st L driving distance, SOC (n), SOC (n-1), SOC (n-2) and SOC (1) are the remaining capacity at the n L driving distance, n-1) L, n-2) L and L driving distance, respectively, SOC (0) is the remaining capacity at the start of the electric vehicle, SOC (0) is the remaining capacity recorded at the last stop of the electric vehicle, SOC (n), SOC (n-1), SOC (n-2), … … and SOC (1) at different driving distances, and the remaining capacity SOC (L) is obtained by estimating the above formula after obtaining the remaining capacity at different driving distances.
Based on the amount of change in the remaining amount of battery at each time of running L, the average value of the amount of change in the remaining amount of battery SOCdeltmean (n-1) at the time of running n-1 st L is estimated by extrapolation:
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 device comprises a battery, a controller and a controller, wherein the battery is a battery residual capacity, SOCdeltmean (n-2), SOCdeltmean (n-3) and SOCdeltmean (1) are respectively an average value of changes of battery residual capacity when the vehicle runs for the n-2 th L, the n-3 th L and the 1 st L th, SOCdelt (0) = SOCdeltmean (0) is an average value of changes of battery residual capacity recorded when the vehicle is shut down last time, and SOCdelt (n-2) is a change of battery residual capacity when the vehicle 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 driving of the nth L according to the average value SOCdeltmean (n-1) of the change amount of the battery residual capacity during the driving of the nth L and the change amount SOCdellet (n) of the battery residual capacity during the driving of the nth L:
SOCdeltmean（n）= [SOCdeltmean（n-1）*n+ SOCdelt(n)*1]/（n+1）。
in calculating the average value of the change amount of the remaining amount of the battery when each L is driven, the average value of the change amount of the remaining amount of the battery when the mileage interval L is driven is adjusted with the change amount as an adjustment amount to reduce the estimation error of the average value of the change amount of the remaining amount as much as possible and improve the estimation accuracy.
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) when the driving distance is (n-1) × L to obtain a remaining driving mileage reduction amount 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.
If the remaining driving range reduction amount S is not greater than the set upper limit value, the estimated remaining driving range Srem (n) is displayed in real time, if S is greater than the set upper limit value, the difference between the estimated remaining driving range Srem (n-1) and the set upper limit value of the electric vehicle when the driving distance is (n-1) × L is displayed in real time as the current remaining driving range, for example, if the set upper limit value is 2Km, the estimated remaining driving range Srem (n-1) =55Km of the electric vehicle when the driving distance is (n-1) = L, and the estimated current remaining driving range Srem (n) =48Km, the remaining driving range reduction amount S is greater than the set upper limit value 2 Km., a sudden large reduction amount change occurs because there is an instantaneous large amount of power consumption, such as an upward slope, and an instantaneous large amount of power consumption at the moment when the remaining power is present, and the estimated remaining driving range is not more than the set upper limit value, and the estimated remaining driving range is not displayed as an actual driving range, and the estimated remaining driving range is not displayed in real time.
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 (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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