CN111216595B - SOC calibration method of severe hybrid electric vehicle based on lithium battery equivalent circuit model - Google Patents

SOC calibration method of severe hybrid electric vehicle based on lithium battery equivalent circuit model Download PDF

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CN111216595B
CN111216595B CN202010003996.7A CN202010003996A CN111216595B CN 111216595 B CN111216595 B CN 111216595B CN 202010003996 A CN202010003996 A CN 202010003996A CN 111216595 B CN111216595 B CN 111216595B
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lithium battery
polarization
battery
internal resistance
voltage
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CN111216595A (en
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康义
王翰超
王云
尹坤
孙艳
刘欢
沈永柏
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Ligao Shandong New Energy Technology Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/12—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries responding to state of charge [SoC]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/24—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/367—Software therefor, e.g. for battery testing using modelling or look-up tables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
    • G01R31/382—Arrangements for monitoring battery or accumulator variables, e.g. SoC
    • G01R31/3842—Arrangements for monitoring battery or accumulator variables, e.g. SoC combining voltage and current measurements
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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Abstract

The invention discloses a SOC calibration method of a severe hybrid electric vehicle based on a lithium battery equivalent circuit model, which comprises the steps of simplifying and dispersing the equivalent circuit model of a lithium battery, analyzing to obtain the corresponding relation between the terminal voltage of the lithium battery and the current, the equivalent current after filtering and the battery cell parameter of the lithium battery, and calculating the terminal voltage when the residual electric quantity of the lithium battery is a boundary value by utilizing the corresponding relation; collecting the voltage of a single body in the lithium battery pack in real time; and comparing the terminal voltage when the residual electric quantity of the battery is a boundary value with the real-time acquired monomer voltage in the lithium battery pack so as to calibrate the S0C value of the residual electric quantity of the battery. The method solves the problem of large error caused by the fact that the SOC of the battery residual capacity of the hybrid electric vehicle cannot be calibrated for a long time.

Description

SOC calibration method of severe hybrid electric vehicle based on lithium battery equivalent circuit model
Technical Field
The invention relates to the technical field of battery management of new energy automobiles, in particular to a SOC calibration method of a severe hybrid electric vehicle based on a lithium battery equivalent circuit model.
Background
A Battery Management System (BMS), which is one of the core components of an electric vehicle, has been the focus of electric vehicle development. Compared with the traditional fuel vehicle, the hybrid electric vehicle is more environment-friendly, and the problems of insufficient endurance mileage and long charging time of the pure electric vehicle are solved. At present, hybrid electric vehicles such as hydrogen fuel vehicles, plug-in hybrid electric vehicles, extended range hybrid electric vehicles and the like use lithium batteries as media to store and distribute energy so as to achieve the effects of saving energy and reducing oil consumption, so that the hybrid electric vehicles have very high precision requirements on the battery residual capacity SOC of the lithium batteries. Compared with a pure electric vehicle, the heavy hybrid electric vehicle has the characteristics of small battery capacity and long working time, which causes the condition that the error of the traditional ampere-hour integration algorithm is large under the hybrid working condition and the static open-circuit voltage method cannot be triggered under the hybrid working condition. Because the battery residual capacity SOC is the most important basis of the whole vehicle control strategy, the accuracy of SOC calculation directly influences the whole vehicle energy consumption, the service life of a lithium battery and the driving experience.
At present, an ampere-hour integral method, a static open-circuit voltage method and a Kalman filtering algorithm are commonly used in a battery management system BMS to correct the battery residual capacity SOC of a current lithium battery.
The ampere-hour integration method is to integrate the current in the charging and discharging process and then divide the current by the total capacity to obtain the SOC value corresponding to the battery. However, this method has some disadvantages: (1) The accuracy of the ampere-hour integration algorithm depends on the precision of the current sensor, and after the current sensor works for a long time under the hybrid working condition, the current sensor has system errors, so that the SOC value has larger deviation. (2) Because the lithium battery has a self-discharge phenomenon, the ampere-hour integration algorithm does not consider the situation, and the long-time pure ampere-hour integration algorithm inevitably causes the situation that the SOC value is falsely high. (3) The accuracy of the ampere-hour integral algorithm is closely related to the total capacity of the battery, and the small-capacity characteristic of the battery of the hybrid electric vehicle can easily cause larger deviation.
The open circuit voltage method is a method in which a current SOC value is determined from a correspondence table between an open circuit voltage of a battery and an OCV-SOC relationship after the charge and discharge of the battery are completed and the voltage characteristics are stabilized, and an effective SOC value can be obtained by a voltage calibration method. However, this method also has some disadvantages: (1) Due to the characteristic of long-time operation under the hybrid working condition, the probability of performing OCV calibration by fully standing is relatively low. (2) Aiming at the condition that the lithium iron phosphate battery has a plateau period, the voltage change amplitude in the interval of 30% to 90% is very small, the voltage acquisition precision of the current BMS is generally 5mv, and a scheme for calibrating by using OCV (open control voltage) has a very large error.
The Kalman filtering algorithm is to estimate the SOC value through the change of the voltage and the current of the battery by combining the equivalent circuit model of the lithium battery with least square estimation. However, this method also has some disadvantages: (1) the dependence on the parameters of lithium batteries is very severe. (2) A situation in which the calculation diverges when there is a difference between the parameter and the actual battery characteristic occurs. And (3) the implementation process is complex.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention provides the SOC calibration method of the heavy hybrid electric vehicle based on the lithium battery equivalent circuit model, and solves the problem of large error caused by long-term incapability of calibrating the residual battery SOC of the hybrid electric vehicle.
In order to achieve the purpose, the invention adopts the following technical scheme that:
the SOC calibration method of the severe hybrid electric vehicle based on the lithium battery equivalent circuit model comprises the following steps: internal power supply, internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a First polarization internal resistance R p1 And a first polarization capacitor C p1 A first resistance-capacitance circuit of the lithium battery is formed by connecting in parallel, and a second polarization internal resistance R p2 And a second polarization capacitor C p2 A second resistance-capacitance circuit connected in parallel to form a lithium battery; internal resistance R 0 The first resistance-capacitance circuit and the second resistance-capacitance circuit are sequentially connected in series on the anode of the power supply; the terminal voltages at two ends of the internal power supply are the static open-circuit voltage V of the lithium battery OCV (ii) a The terminal voltage of two ends of the whole lithium battery is V; the terminal voltage at two ends of the first resistance-capacitance circuit is V p1 (ii) a The voltage at the two ends of the second resistance-capacitance circuit is V p2 (ii) a The terminal voltage at two ends of the lithium battery is V; the current of the lithium battery is i;
the method comprises the following steps:
s1, analyzing and obtaining the terminal voltage V of the lithium battery and the current i and the internal resistance R of the lithium battery according to the equivalent circuit model of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relation between the two; namely, the value of the terminal voltage V of the lithium battery can be determined according to the current i and the internal resistance R of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV Calculation was performed with V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) F is a corresponding relation function;
s2, determining a boundary value of the battery residual capacity of the hybrid electric vehicle for power switching, wherein the boundary value of the battery residual capacity of the pure electric power system entering the fuel power system is SOC1, and the boundary value of the battery residual capacity of the fuel power system entering the pure electric power system is SOC2;
s3, testing to obtain the static open-circuit voltage V when the residual capacity of the battery of the lithium battery is SOC1 at different temperatures OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second diode capacitor C p2 (ii) a Under different temperatures, testing to obtain the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC2 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
S4, collecting the current temperature and current of the lithium battery pack in real time in the running process of the hybrid electric vehicle, and collecting the monomer voltage of each monomer lithium battery in the lithium battery pack in real time to obtain the highest monomer voltage V in the lithium battery pack max And the lowest cell voltage V min (ii) a The single voltage of the single lithium battery is the terminal voltage V at two ends of the single lithium battery;
s5, obtaining the current temperature of the lithium battery pack acquired in real time according to the test result of the step S3 and the current temperature of the lithium battery pack acquired in real time in the step S4Static open-circuit voltage V at the current temperature when the battery residual capacity of the lithium battery is SOC1 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a Obtaining a static open-circuit voltage V when the battery residual capacity of the lithium battery is SOC2 at the current temperature OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
S6, according to the current of the lithium battery pack collected in real time in the step S4, and according to the static open-circuit voltage V obtained in the step S5 when the battery residual capacity of the lithium battery at the current temperature is SOC1 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) Calculating the end voltage V1 when the battery residual capacity of the lithium battery is SOC 1;
according to the current of the lithium battery pack collected in real time in the step S4 and the static open-circuit voltage V when the battery residual capacity of the lithium battery at the current temperature is SOC2, which is obtained in the step S5 OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 Second polarizationCapacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) Calculating a terminal voltage V2 when the battery residual capacity of the lithium battery is SOC2;
s7, if the lithium battery is in the discharging process, judging the lowest monomer voltage V acquired in real time in the step S4 every 1 second min Whether the voltage is smaller than the terminal voltage V1 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 1;
if the lowest cell voltage V min If the SOC value of the battery residual electricity quantity of the current lithium battery is smaller than V1 in the continuous n seconds, calibrating the SOC value of the battery residual electricity quantity of the current lithium battery towards the boundary value SOC1 direction, wherein the calibration step length is Y;
s8, if the lithium battery is in the charging process, judging the highest monomer voltage V acquired in real time in the step S4 every 1 second max Whether the voltage is larger than the terminal voltage V2 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 2;
if the highest cell voltage V max If the SOC value of the battery residual electricity quantity of the current lithium battery is larger than V2 in continuous n seconds, calibrating the SOC value of the battery residual electricity quantity of the current lithium battery towards the direction of a boundary value SOC2, wherein the calibration step length is Y;
and S9, smoothing the corrected residual battery SOC.
In step S1, the terminal voltage V of the lithium battery and the current i and the internal resistance R of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) The method specifically comprises the following steps:
V(k)＝V OCV -R P1 ·i f1 (k)-R P2 ·i f2 (k)-i(k)·R 0 ；
wherein k represents the kth sampling instant; v (k) represents the terminal voltage at two ends of the lithium battery at the kth sampling moment; i (k) represents the current of the lithium battery at the kth sampling moment;
i f1 (k) The current after the first-order lag filtering of the first resistance-capacitance circuit at the kth sampling time is obtained;
Figure BDA0002354546150000041
Figure BDA0002354546150000042
a 1 coefficients representing first order lag filtering of the first rc circuit; Δ t represents a sampling period; v p1 (k-1) represents the terminal voltage at two ends of the first resistance-capacitance circuit under the k-1 sampling period; i (k-1) represents the current of the lithium battery at the k-1 th sampling moment;
i f2 (k) The current after the first-order lag filtering of the second resistance-capacitance circuit at the kth sampling time is obtained;
Figure BDA0002354546150000051
Figure BDA0002354546150000052
a 2 coefficients representing a first order lag filter of the second rc circuit; v p2 And (k-1) represents the terminal voltage at two ends of the second resistance-capacitance circuit under the k-1 sampling period.
In step S3, the static open-circuit voltage V of the lithium battery OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 The test method (2) is as follows:
charging the lithium battery to 100%, standing for two hours, then discharging 5% in sequence at a current of 0.33C, and standing for two hours when 5% of the discharge is finished;
when the residual capacity of the lithium battery is dischargedWhen the battery is in SOC1 state, after standing for two hours, measuring the terminal voltage V of the two ends of the lithium battery, and taking the terminal voltage V of the two ends of the lithium battery measured after standing for two hours as the static open-circuit voltage V when the battery residual capacity of the lithium battery is in SOC1 state OCV And measuring the internal resistance R of the lithium battery obtained at the moment 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Internal resistance R when the remaining battery capacity of the lithium battery is SOC1 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
When discharging till the residual electric quantity of the lithium battery is SOC2, standing for two hours, measuring the terminal voltages V at the two ends of the lithium battery, and taking the terminal voltages V at the two ends of the lithium battery measured after standing for two hours as the static open-circuit voltage V when the residual electric quantity of the lithium battery is SOC2 OCV (ii) a And measuring the internal resistance R of the lithium battery obtained at the moment 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Internal resistance R when the remaining battery capacity of the lithium battery is SOC2 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
According to the mode, the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC1 is measured and obtained at different temperatures respectively OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And measuring the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC2 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second diode capacitor C p2 。
In step S7 and step S8, 30 < n < 60.
In step S7 and step S8, 0 < Y < 10%.
Step S7, in the discharging process of the lithium battery, calibrating the SOC value of the battery residual capacity of the current lithium battery towards the boundary value SOC1 direction, namely reducing the SOC value of the battery residual capacity of the current lithium battery; in step S8, in the charging process of the lithium battery, the SOC value of the remaining battery capacity of the current lithium battery is calibrated toward the boundary value SOC2, that is, the SOC value of the remaining battery capacity of the current lithium battery is increased.
The invention has the advantages that:
(1) The method avoids the risk of overcharging of the hybrid electric vehicle under the condition of virtual low SOC and the risk of overdischarging and leaning of the hybrid electric vehicle under the condition of virtual high SOC, and the SOC value is calibrated by the highest single voltage in the charging process and the SOC value is calibrated by the lowest single voltage in the discharging process, thereby solving the problem of inaccurate calculation of the SOC value caused by the consistency difference of the lithium battery pack.
(2) The method solves the problem that the OCV calibration algorithm is limited by the driving working condition, has wider application scenes, is not limited by the driving working condition, can calibrate in real time when meeting the conditions in the running process, and can be applied to pure electric vehicles, hybrid electric vehicles and even shallow-charging and shallow-discharging mine cars without standing.
(3) The invention simplifies the circuit model algorithm, converts the calculation of the terminal voltage of the lithium battery from the complex discrete state matrix operation of the equivalent circuit into the simple equation operation between the current and the filtered equivalent current and the battery cell parameter, reduces the program calculation amount and complexity and avoids the risk of occurrence of a sick matrix.
(4) The terminal voltage algorithm of the lithium battery solves the problems of large calculation amount and more required parameters of a Kalman filtering algorithm, reduces the measurement amount of the parameters of the battery core, and only needs to measure the static open-circuit voltage V of the SOC1 and the SOC2 of the residual electric quantity of the lithium battery at different temperatures OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second diode capacitor C p2 。
Drawings
Fig. 1 is an equivalent circuit diagram of a lithium battery.
Fig. 2 is a flowchart of the SOC calibration method for a heavy hybrid electric vehicle based on the lithium battery equivalent circuit model.
Fig. 3 is a schematic diagram illustrating the calibration of the SOC value of the battery during the discharging process of the lithium battery.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The battery residual capacity SOC of the lithium battery has a close relation with the battery voltage, and the more the battery residual capacity SOC is, the higher the battery voltage is; in the discharging process, the battery voltage is lower and lower along with the reduction of the battery residual capacity of the lithium battery, and in the charging process, the battery voltage is higher and higher along with the increase of the battery residual capacity SOC of the lithium battery. Because the lithium battery has the characteristics, a stable corresponding relation exists between the static open-circuit voltage of the lithium battery and the residual battery capacity SOC, and the accurate residual battery capacity SOC can be obtained by measuring the static open-circuit voltage of the lithium battery.
The equivalent circuit model of the lithium battery is shown in fig. 1:
in FIG. 1, V OCV Is the static open circuit voltage of the lithium battery; r 0 Is the internal resistance of the lithium battery; r p1 、R p2 The polarization internal resistance of the lithium battery is obtained; c p1 、C p2 All are polarization capacitors of lithium batteries; r p1 And C p1 A first resistance-capacitance circuit of the lithium battery is formed in parallel; r p2 And C p2 The second resistance-capacitance circuit of the lithium battery is formed in parallel; v is the terminal voltage of two ends of the lithium battery; v p1 Is the terminal voltage at two ends of the first resistance-capacitance circuit; v p2 Is the terminal voltage across the second rc circuit.
In the invention, for unified formula calculation, the following rules are specified: the discharge current is positive and the charge current is negative.
According to the equivalent circuit model of the lithium battery shown in fig. 1, the following formula is obtained:
Figure BDA0002354546150000071
Figure BDA0002354546150000072
V t ＝V OCV -V P1 -V P2 -iR 0 ； (3)
wherein t represents time t, namely the time from the initial time, namely time 0 to the current time; v p1 (0) Representing terminal voltages at two ends of the first resistance-capacitance circuit at the initial moment; v p1 (t) represents the terminal voltage at both ends of the first resistance-capacitance circuit at time t; v p2 (0) Representing terminal voltages at two ends of the second resistance-capacitance circuit at the initial moment; v p2 (t) represents the terminal voltage at both ends of the second resistance-capacitance circuit at time t; i (t) represents the current at time t; and V (t) is the terminal voltage of two ends of the lithium battery at the moment t.
Discretizing the above formulas (1), (2) and (3) to obtain the following formula:
Figure BDA0002354546150000081
Figure BDA0002354546150000082
V(k)＝V OCV -V P1 -V P2 -i(k)·R 0 ； (6)
where Δ t represents the sampling period in the discrete process; k represents the kth sampling instant; k-1 denotes the k-1 sample periodA period; v p1 (k-1) represents the terminal voltage at two ends of the first resistance-capacitance circuit under the k-1 sampling period; v p1 (k) Representing terminal voltages at two ends of the first resistance-capacitance circuit at the kth sampling time; v p2 (k-1) represents the terminal voltage at two ends of the second resistance-capacitance circuit under the k-1 sampling period; v p2 (k) The terminal voltage at two ends of the second resistance-capacitance circuit at the kth sampling time is shown; i (k-1) represents the current at the k-1 sampling instant; i (k) represents the current at the kth sampling instant; and V (k) represents the terminal voltage of two ends of the lithium battery at the kth sampling moment.
Suppose that:
Figure BDA0002354546150000083
V p1 (k) And V p2 (k) Is 0;
R p1 and R p2 The value is a fixed value in a short time and does not have mutation;
then, according to the above equations (4) and (5), the following equation is obtained:
Figure BDA0002354546150000084
Figure BDA0002354546150000085
from the above equations (7) and (8), it can be seen that, for the RC circuit, the terminal voltage V at both ends of the first RC circuit p1 Equal to its corresponding internal polarization resistance R p1 Multiplying by the current after first-order lag filtering; terminal voltage V at two ends of second resistance-capacitance circuit p2 Equal to its corresponding polarization internal resistance R p2 Multiplied by the first order lag filtered current.
Currents after first-order lag filtering of the first resistance-capacitance circuit and the second resistance-capacitance circuit in the above equations (7) and (8) are respectively equivalent to i f1 (k) And i f2 (k) (ii) a Then, according to the above equations (7), (8), (6), the following equation is obtained:
V p1 (k)＝R P1 ·i f1 (k)； (9)
V p2 (k)＝R P2 ·i f2 (k)； (10)
V(k)＝V OCV -R P1 ·i f1 (k)-R P2 ·i f2 (k)-i(k)·R 0 ； (11)
based on the analysis, the invention obtains the cell parameter of the lithium battery, namely V through experimental test oc 、R 0 、 R p1 、R p2 、C p1 、C p2 And then, according to the formulas (9), (10) and (11), the corresponding relation between the terminal voltage V and the current at the two ends of the lithium battery can be obtained.
Based on the SOC calculation mode, the invention also provides a weight hybrid electric vehicle SOC calibration method based on the lithium battery equivalent circuit model, which is shown in FIG. 2 and comprises the following steps:
s1, analyzing and obtaining the terminal voltage V of the lithium battery and the current i and the internal resistance R of the lithium battery according to the equivalent circuit model of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relation between the two; namely:
V(k)＝V OCV -R P1 ·i f1 (k)-R P2 ·i f2 (k)-i(k)·R 0 ；
wherein k represents the kth sampling instant; v (k) represents the terminal voltage at two ends of the lithium battery at the kth sampling moment; i (k) represents the current of the lithium battery at the kth sampling moment;
i f1 (k) The current after the first-order lag filtering of the first resistance-capacitance circuit at the kth sampling time is obtained;
Figure BDA0002354546150000091
Figure BDA0002354546150000092
a 1 coefficients representing first order lag filtering of the first rc circuit; Δ t represents a sampling period; v p1 (k-1) represents the terminal voltage at two ends of the first resistance-capacitance circuit under the k-1 sampling period; i (k-1) represents the current of the lithium battery at the k-1 th sampling moment;
i f2 (k) The current after the first-order lag filtering of the second resistance-capacitance circuit at the kth sampling time is obtained;
Figure BDA0002354546150000093
Figure BDA0002354546150000094
a 2 coefficients representing first order lag filtering of the second rc circuit; v p1 (k-1) represents V p2 And (k-1) represents the terminal voltage at two ends of the second resistance-capacitance circuit under the k-1 sampling period.
S2, determining a boundary value of the battery residual capacity of the hybrid electric vehicle for power switching, wherein the boundary value of the battery residual capacity of the pure electric power system entering the fuel power system is SOC1, and the boundary value of the battery residual capacity of the fuel power system entering the pure electric power system is SOC2; SOC2> SOC1.
S3, testing to obtain the cell parameter when the residual battery capacity of the lithium battery is SCO1 and the cell parameter when the residual battery capacity of the lithium battery is SOC2 at different temperatures;
the cell parameters include: static open circuit voltage V OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
The method for testing the cell parameters comprises the following steps:
charging the lithium battery to 100%, standing for two hours, and then sequentially discharging 5% at a current of 0.33C, wherein each 5% discharge needs to be kept standing for two hours; c represents rated capacity of 1 hour, and the unit is Ah;
when discharging till the residual electric quantity of the lithium battery is SOC1, standing for two hours, measuring terminal voltages V at two ends of the lithium battery, and taking the terminal voltages V at two ends of the lithium battery measured after standing for two hours as the static open-circuit voltage V when the residual electric quantity of the lithium battery is SOC1 OCV ；
When discharging till the residual electric quantity of the lithium battery is SOC2, standing for two hours, measuring terminal voltages V at two ends of the lithium battery, and taking the terminal voltages V at two ends of the lithium battery measured after standing for two hours as static open-circuit voltages V when the residual electric quantity of the lithium battery is SOC2 OCV (ii) a Meanwhile, the internal resistance R of the lithium battery when the residual battery capacity is SCO1 can be obtained by adopting HPPC test and parameter identification algorithm 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 。
According to the mode, the static open-circuit voltage V when the battery residual capacity of the lithium battery is SOC1 is measured and obtained at different temperatures respectively OCV And measuring the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC2 OCV (ii) a Meanwhile, the internal resistance R of the lithium battery when the residual battery capacity is SCO2 can be obtained by adopting HPPC test and parameter identification algorithm 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 。
S4, collecting the current temperature and current of the lithium battery pack in real time in the running process of the hybrid electric vehicle, and collecting the monomer voltage of each monomer lithium battery in the lithium battery pack in real time to obtain the highest monomer voltage V in the lithium battery pack max And the lowest cell voltage V min (ii) a The cell voltage of the single lithium battery is the terminal voltage V at the two ends of the single lithium battery.
S5, according to the test result of the step S3 and the current temperature of the lithium battery pack acquired in real time according to the step S4Obtaining the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC1 at the current temperature OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a Obtaining a static open-circuit voltage V when the battery residual capacity of the lithium battery is SOC2 at the current temperature OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 。
S6, according to the current of the lithium battery pack collected in real time in the step S4, and according to the static open-circuit voltage V obtained in the step S5 when the battery residual capacity of the lithium battery at the current temperature is SOC1 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second diode capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And the static open-circuit voltage V of the lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) And calculating the end voltage V1 when the battery residual capacity of the lithium battery is SOC1.
According to the current of the lithium battery pack collected in real time in the step S4 and the static open-circuit voltage V when the battery residual capacity of the lithium battery at the current temperature is SOC2, which is obtained in the step S5 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 The first stepTwo polarization capacitance C p2 And the static open-circuit voltage V of the lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) And calculating the terminal voltage V2 when the battery residual capacity of the lithium battery is SOC 2.
S7, if the lithium battery is in the discharging process, judging the lowest monomer voltage V acquired in real time in the step S4 every 1 second min Whether the voltage is smaller than the terminal voltage V1 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 1;
if the lowest cell voltage V min If the SOC value of the battery residual electricity quantity of the current lithium battery is smaller than V1 in the continuous n seconds, calibrating the SOC value of the battery residual electricity quantity of the current lithium battery towards the boundary value SOC1 direction, wherein the calibration step length is Y;
in the discharging process of the lithium battery, the SOC value of the battery residual capacity of the lithium battery is definitely not lowered to the boundary value SOC1, and if the SOC value of the battery residual capacity of the lithium battery is lowered to the boundary value SOC1, the lithium battery enters a fuel oil power system, namely the lithium battery is not in a discharging state. In the discharging process of the lithium battery, the SOC value of the current battery residual capacity of the lithium battery is calibrated towards the boundary value SOC1 direction, and actually, the SOC value of the current battery residual capacity of the lithium battery is reduced.
S8, if the lithium battery is in the charging process, judging the highest monomer voltage V acquired in real time in the step S4 every 1 second max Whether the voltage is larger than the terminal voltage V2 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 2;
if the highest cell voltage V max If the SOC value is larger than V2 in the continuous n seconds, the SOC value of the battery residual electricity quantity of the current lithium battery is calibrated towards the boundary value SOC2 direction, and the calibration step length is Y;
during the charging process of the lithium battery, the SOC value of the battery residual capacity of the lithium battery is definitely not higher than the boundary value SOC2, and if the SOC value of the battery residual capacity of the lithium battery is higher than the boundary value SOC2, the lithium battery enters an electric power system, namely the lithium battery is not in a charging state. In the charging process of the lithium battery, the SOC value of the battery residual capacity of the current lithium battery is calibrated towards the boundary value SOC2 direction, and actually, the SOC value of the battery residual capacity of the current lithium battery is increased.
In the invention, n is more than 30 and less than 60; y is more than 0 and less than 10 percent.
And S9, smoothing the corrected residual battery SOC to prevent the SOC value from jumping.
In this embodiment, fig. 3 shows a calibration of the SOC value of the current remaining battery capacity of the lithium battery during the discharging process of the lithium battery. In fig. 3, the reference voltage corresponding to the SCO1 is the calculated terminal voltage V1 when the remaining battery capacity of the lithium battery is SCO 1; when the lowest cell voltage V min When the SOC value is less than the reference voltage corresponding to SCO1 within continuous 60 seconds, triggering calibration, and calibrating the SOC value of the battery residual capacity of the current lithium battery towards a boundary value SOC1 direction, namely reducing the SOC value of the battery residual capacity, wherein the calibration step length is not more than 10%; and smoothing the corrected residual battery SOC.
The invention is not to be considered as limited to the specific embodiments shown and described, but is to be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

Claims (6)

1. The SOC calibration method of the severe hybrid electric vehicle based on the lithium battery equivalent circuit model comprises the following steps: internal power supply, internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a First polarization internal resistance R p1 And a first polarization capacitor C p1 A first resistance-capacitance circuit of the lithium battery is formed by connecting in parallel, and a second polarization internal resistance R p2 And a second polarization capacitor C p2 A second resistance-capacitance circuit of the lithium battery is formed in parallel; internal resistance R 0 The first resistance-capacitance circuit and the second resistance-capacitance circuit are sequentially connected in series on the positive electrode of the power supply; the terminal voltages at two ends of the internal power supply are the static open-circuit voltage V of the lithium battery OCV (ii) a The terminal voltage at two ends of the whole lithium battery is V; the terminal voltage at two ends of the first resistance-capacitance circuit is V p1 (ii) a The terminal voltage at both ends of the second resistance-capacitance circuit is V p2 (ii) a The terminal voltage at two ends of the lithium battery is V; the current of the lithium battery is i;
the method is characterized by comprising the following steps:
s1, analyzing and obtaining the terminal voltage V of the lithium battery and the current i and the internal resistance R of the lithium battery according to the equivalent circuit model of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relation between the two; that is, the terminal voltage V of the lithium battery can be determined according to the current i and the internal resistance R of the lithium battery 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Static open circuit voltage V of lithium battery OCV Calculation was performed with V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) F is a corresponding relation function;
s2, determining a boundary value of the battery residual capacity of the hybrid electric vehicle for power switching, wherein the boundary value of the battery residual capacity of the pure electric power system entering the fuel power system is SOC1, and the boundary value of the battery residual capacity of the fuel power system entering the pure electric power system is SOC2;
s3, testing to obtain the static open-circuit voltage V when the residual capacity of the battery of the lithium battery is SOC1 at different temperatures OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a Under different temperatures, testing to obtain the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC2 OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
S4, collecting the current temperature and current of the lithium battery pack in real time and collecting each monomer in the lithium battery pack in real time in the running process of the hybrid electric vehicleObtaining the highest cell voltage V in the lithium battery pack by using the cell voltage of the lithium battery max And the lowest cell voltage V min (ii) a The single voltage of the single lithium battery is the terminal voltage V at two ends of the single lithium battery;
s5, obtaining the static open-circuit voltage V when the battery residual capacity of the lithium battery is SOC1 at the current temperature according to the test result of the step S3 and the current temperature of the lithium battery pack collected in real time in the step S4 OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 (ii) a Obtaining a static open-circuit voltage V when the battery residual capacity of the lithium battery is SOC2 at the current temperature OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
S6, according to the current of the lithium battery pack collected in real time in the step S4, and according to the static open-circuit voltage V obtained in the step S5 when the battery residual capacity of the lithium battery at the current temperature is SOC1 OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second diode capacitor C p2 Static open circuit voltage V of lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) Calculating a terminal voltage V1 when the battery residual capacity of the lithium battery is SOC 1;
according to the current of the lithium battery pack acquired in real time in the step S4 and the static open-circuit voltage V when the battery residual capacity of the lithium battery at the current temperature is SOC2, which is acquired in the step S5 OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And according to the terminal voltage V at the two ends of the lithium battery obtained by analysis in the step S1 and the current i and the internal resistance R in the equivalent circuit of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And the static open-circuit voltage V of the lithium battery OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) Calculating a terminal voltage V2 when the battery residual capacity of the lithium battery is SOC2;
s7, if the lithium battery is in the discharging process, judging the lowest monomer voltage V acquired in real time in the step S4 every 1 second min Whether the voltage is smaller than the terminal voltage V1 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 1;
if the lowest cell voltage V min If the SOC value is smaller than V1 in the continuous n seconds, calibrating the SOC value of the battery residual capacity of the current lithium battery towards the boundary value SOC1 direction, wherein the calibration step length is Y;
s8, if the lithium battery is in the charging process, judging the highest monomer voltage V acquired in real time in the step S4 every 1 second max Whether the voltage is larger than the terminal voltage V2 when the battery residual capacity of the lithium battery calculated in the step S6 is SCO 2;
if the highest cell voltage V max If the SOC value is larger than V2 in the continuous n seconds, the SOC value of the battery residual capacity of the current lithium battery is calibrated towards the boundary value SOC2 direction, and the calibration step length is Y;
and S9, smoothing the calibrated SOC.
2. The SOC calibration method for the severe hybrid electric vehicle based on the lithium battery equivalent circuit model as claimed in claim 1, wherein in step S1, the terminal voltage V of the lithium battery and the current i and the internal resistance R of the lithium battery 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second diode capacitor C p2 Lithium batteryStatic open circuit voltage V of pool OCV The corresponding relationship between V = f (i, V) OCV ,R 0 ,R p1 ,R p2 ,C p1 ,C p2 ) The method comprises the following specific steps:
V(k)＝V OCV -R P1 ·i f1 (k)-R P2 ·i f2 (k)-i(k)·R 0 ；
wherein k represents the kth sampling instant; v (k) represents the terminal voltage of two ends of the lithium battery at the kth sampling moment; i (k) represents the current of the lithium battery at the kth sampling moment;
i f1 (k) The current after the first-order lag filtering of the first resistance-capacitance circuit at the kth sampling time is obtained;
Figure FDA0002354546140000031
Figure FDA0002354546140000032
a 1 coefficients representing first order lag filtering of the first rc circuit; Δ t represents a sampling period; v p1 (k-1) represents the terminal voltage at two ends of the first resistance-capacitance circuit under the k-1 sampling period; i (k-1) represents the current of the lithium battery at the k-1 sampling moment;
i f2 (k) The current after the first-order lag filtering of the second resistance-capacitance circuit at the kth sampling time is obtained;
Figure FDA0002354546140000033
Figure FDA0002354546140000034
a 2 coefficients representing first order lag filtering of the second rc circuit; v p2 And (k-1) represents the terminal voltage at two ends of the second resistance-capacitance circuit under the k-1 sampling period.
3. The SOC calibration method for the heavy hybrid electric vehicle based on the lithium battery equivalent circuit model as claimed in claim 1, wherein in step S3, the static open-circuit voltage V of the lithium battery OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 The test method (2) is as follows:
charging the lithium battery to 100%, standing for two hours, and then sequentially discharging 5% at a current of 0.33C, wherein each 5% discharge needs to be kept standing for two hours;
when discharging till the residual electric quantity of the lithium battery is SOC1, standing for two hours, measuring terminal voltages V at two ends of the lithium battery, and taking the terminal voltages V at two ends of the lithium battery measured after standing for two hours as the static open-circuit voltage V when the residual electric quantity of the lithium battery is SOC1 OCV And measuring the internal resistance R of the lithium battery obtained at the moment 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Internal resistance R when the remaining battery capacity of the lithium battery is SOC1 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
When discharging till the residual electric quantity of the lithium battery is SOC2, standing for two hours, measuring terminal voltages V at two ends of the lithium battery, and taking the terminal voltages V at two ends of the lithium battery measured after standing for two hours as static open-circuit voltages V when the residual electric quantity of the lithium battery is SOC2 OCV (ii) a And measuring the internal resistance R of the lithium battery obtained at the moment 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 Internal resistance R when the battery residual capacity of the lithium battery is SOC2 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 ；
According to the mode, the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC1 is measured and obtained at different temperatures respectively OCV Internal resistance R 0 First polarization internal resistance R p1 A second polarization resistor R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 And measuring the static open-circuit voltage V when the residual battery capacity of the lithium battery is SOC2 OCV Internal resistance R 0 First polarization internal resistance R p1 The second diode resistance R p2 A first polarization capacitor C p1 A second polarization capacitor C p2 。
4. The SOC calibration method for the heavy hybrid electric vehicle based on the lithium battery equivalent circuit model is characterized in that in the steps S7 and S8, 30 < n < 60.
5. The SOC calibration method for the severe hybrid electric vehicle based on the lithium battery equivalent circuit model as claimed in claim 1, wherein in step S7 and step S8, 0 < Y < 10%.
6. The SOC calibration method for the heavy hybrid electric vehicle based on the lithium battery equivalent circuit model is characterized in that, in the step S7, during the discharging process of the lithium battery, the SOC value of the battery residual capacity of the current lithium battery is calibrated towards the boundary value SOC1 direction, namely the SOC value of the battery residual capacity of the current lithium battery is adjusted to be low; in step S8, in the charging process of the lithium battery, the SOC value of the remaining battery capacity of the current lithium battery is calibrated toward the boundary value SOC2, that is, the SOC value of the remaining battery capacity of the current lithium battery is increased.
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