CN117930021A - SOC correction method of energy storage battery - Google Patents

Abstract

The invention belongs to the technical field of energy storage batteries, and particularly relates to an SOC correction method of an energy storage battery. Determining whether to check the SOC-OCV table according to whether the standing time reaches a set threshold value to obtain a SOC true value; calculating a difference value delta SOC between the SOC real value and the SOC display value, taking the difference value as an initial value of the corrected SOC display value, and adding or subtracting a corrected compensation value to the SOC display value at each sampling time of the next charge and discharge; to prevent overcorrection, the correction cutoff time is calculated using ampere-hour integration. The invention can improve the SOC estimation precision of the energy storage battery, eliminate the accumulated error of the ampere-hour integration method and reduce the endurance anxiety of the user.

Description

SOC correction method of energy storage battery

Technical Field

The invention belongs to the technical field of energy storage batteries, and particularly relates to an SOC correction method of an energy storage battery.

Background

SOC (State-of-Charge) reflects the residual quantity of a Battery, is a key parameter for measuring the discharge capacity of the Battery, the balanced control of the Battery and the cut-off condition of Charge and discharge, and cannot be directly measured, and can only be estimated by collecting parameters such as voltage, current and temperature through a BMS (Battery Management System).

SOC estimation is one of the most important tasks in a battery management system because accurate estimation of other states, such as SOH (State-of-Health), SOE (State-of-Energy), SOP (State-of-Power), etc., are all relatively dependent on accurate SOC. Currently, a single algorithm cannot meet the accuracy requirement of SOC estimation, so a series of corrective measures need to be added to improve the accuracy.

The main current SOC estimation strategy is to use an ampere-hour integration method as a core and add various correction algorithms to improve the estimation precision of the ampere-hour integration method, and the ampere-hour integration method has the advantages of being simple in principle, capable of calculating the SOC in real time and the like, and is widely applied to a battery management system, but because the accurate initial SOC is not easy to acquire, the current sensor has measurement noise, and the accumulated error is larger and larger, so that SOC correction measures are required to be added to eliminate the influence of the accumulated error.

Disclosure of Invention

In order to overcome the problems in the prior art, the invention provides an SOC correction method of an energy storage battery.

The technical scheme for solving the technical problems is as follows:

The invention provides an SOC correction method of an energy storage battery, which comprises the following steps:

Calculating the battery standing time, and judging whether the battery standing time exceeds a preset limit value;

If the standing time exceeds a preset limit value, acquiring a current terminal voltage value, and checking a preset SOC-OCV table according to the current terminal voltage value to obtain an SOC true value;

Acquiring an SOC display value, calculating a difference value between the SOC real value and the SOC display value, and taking the difference value as an initial value of the corrected SOC display value;

based on the initial value of the corrected SOC display value, correcting the SOC display value by adopting a corrected compensation value;

calculating an accumulated correction compensation value, calculating the ratio of the accumulated correction compensation value to the battery capacity, and calculating the difference value between the accumulated correction compensation value and the absolute value of the initial value of the correction SOC; if the difference is less than or equal to zero, the correction is considered to be the correction cut-off time at the moment, and the correction is ended.

Further, the calculating the battery rest time includes: collecting current, and judging whether the battery reaches a standing state according to the collected current, wherein the standing state is that the current is more than-0.1A and less than 0.1A; if the static state is reached, calculating the static time.

Further, before calculating the battery rest time, the method further comprises: an SOC-OCV table of the battery in a stationary state is previously established, and includes a charge SOC-OCV table and a discharge SOC-OCV table, which are obtained by experiments, respectively.

Further, looking up the SOC-OCV table according to the current terminal voltage value to obtain the SOC real value, including:

Selecting different SOC-OCV table data according to the value of the current, and if the value of the current is greater than zero, using the charged SOC-OCV table data as the input of a difference method; otherwise, using the discharging SOC-OCV table data as the input of a difference method; a table look-up is performed using a difference method to obtain a current SOC real value.

Further, using a difference method to look up a table to obtain a current SOC real value includes:

Acquiring terminal voltage, traversing the OCV in the SOC-OCV table, and comparing whether the input terminal voltage is smaller than or equal to the current traversed OCV;

if yes, the current SOC real value is:

Where Volt_in is the voltage; table_in () is a calibrated OCV value; table_In (i-1) is the OCV value at the i-1 traversal time, and Table_In (i) is the OCV value at the i traversal time;

if not, traversing the next OCV in the SOC-OCV table;

if the above condition is still not satisfied after traversing all OCVs in the SOC-OCV table, the SOC true value=1.

Further, based on the initial value of the correction SOC, a correction compensation value is calculated:

Wherein, SOC (t) is the current t moment SOC, SOC _t0 is the initial value of the corrected SOC, deltaK is the correction coefficient, I (t) is the t moment current, and C _n is the battery capacity;

The corrected compensation value Δc _n is as follows:

ΔC_n＝ΔK×I(t)。

compared with the prior art, the invention has the following technical effects:

In the invention, whether to check the SOC-OCV table to obtain the SOC real value is determined according to whether the standing time reaches a set threshold value; calculating a difference value delta SOC between the SOC real value and the SOC display value, taking the difference value as an initial value of the corrected SOC display value, and adding or subtracting a corrected compensation value to the SOC display value at each sampling time of the next charge and discharge; to prevent overcorrection, the correction cutoff time is calculated using ampere-hour integration. The invention can improve the SOC estimation precision of the energy storage battery, eliminate the accumulated error of the ampere-hour integration method and reduce the endurance anxiety of the user.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions and advantages of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are only some embodiments of the invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic flow chart of a method for correcting SOC of an energy storage battery according to the present invention;

fig. 2 is a flow chart of the correction method of the present invention.

Detailed Description

In order to further describe the technical means and effects adopted by the present invention to achieve the preset purpose, the following detailed description is given below of the specific implementation, structure, features and effects of the technical solution according to the present invention with reference to the accompanying drawings and preferred embodiments. The particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

In one embodiment of the present invention, there is provided an SOC correction method for an energy storage battery, including the steps of:

S100: calculating the battery standing time, and judging whether the battery standing time exceeds a preset limit value; if the standing time exceeds the preset limit value, acquiring a current terminal voltage value, and checking an SOC-OCV table according to the current terminal voltage value to obtain an SOC true value.

It should be noted that, in this embodiment, a lithium iron phosphate battery is used, and the open circuit voltage curve is very gentle in some areas during the plateau period of the lithium iron phosphate battery, which is called as a voltage plateau. In these areas, the battery can maintain a relatively stable open circuit voltage as the battery discharges, and a wide range of SOC variations correspond to small voltage variations, and there is a large error in using the open circuit voltage to look up a table, so that to avoid the large error, the table is disabled when in the plateau phase.

The SOC-OCV curve of the lithium iron phosphate battery in the platform stage is gentle, very small voltage change can cause very large SOC fluctuation, the estimation accuracy of an open circuit voltage method can be interfered, the SOC-OCV curve in the platform stage can be optimized, one OCV is obtained at intervals of 5% of SOC, and other intervals are 10%. End correction is initiated when operating in the plateau phase.

The step S100 specifically comprises the following substeps:

S110, pre-establishing an SOC-OCV table of the battery in a static state, wherein the SOC-OCV table comprises a charging SOC-OCV table and a discharging SOC-OCV table, and the SOC-OCV table represents the relation between the SOC and the OCV. The charge SOC-OCV table and the discharge SOC-OCV table may be obtained through a charge-discharge experiment, and this part is implemented by using the prior art, which is not repeated herein.

S121, collecting current, and judging whether the battery reaches a standing state according to the collected current, wherein the standing state is that the current is more than-0.1A and less than 0.1A;

S122, if the battery reaches a standing state, calculating standing time; judging whether the standing time of the battery exceeds a preset limit value or not;

start_time is the start time of the battery to reach a stationary state; gcount is the count variable of the controller, which is a value that is always increased; if the battery reaches a rest state, firstly making the start_time=0, when the current is larger than-0.1A and smaller than 0.1A, detecting whether the start_time is zero, if the start_time=0, making the value of the start_time equal to the counter value at the moment, then calculating the rest time through a time_diff function, and as long as the current still keeps a state larger than-0.1A and smaller than 0.1A, the start_time is unchanged or equal to the counter value just entering the rest, and when the current is larger than 0.1A or smaller than-0.1A, the start_time=0.

S123, selecting different SOC-OCV table data according to the value of the current;

If the current value is greater than zero, acquiring SOC-OCV table data by using a charging experiment as input of a difference method; otherwise, the SOC-OCV table data is obtained by using a discharge experiment and is used as the input of a difference method.

S124, acquiring the current terminal voltage, and performing table lookup by using a difference method to obtain the current SOC true value:

Acquiring terminal voltage, traversing the OCV in the SOC-OCV table, and comparing whether the input terminal voltage is smaller than or equal to the current traversed OCV;

if yes, the current SOC real value is:

Where Volt_in is the voltage; table_in () is a calibrated OCV value; table_In (i-1) is the OCV value at the i-1 traversal time, and Table_In (i) is the OCV value at the i traversal time;

if not, traversing the next OCV in the SOC-OCV table;

if the above condition is still not satisfied after traversing all OCVs in the SOC-OCV table, the SOC true value=1.

S200: when the sufficient standing condition is met, acquiring an SOC display value, calculating a difference value between the SOC real value and the current SOC display value, and taking the difference value as an initial value of the corrected SOC display value; and adding or subtracting a correction compensation value to or from the SOC display value at each sampling time of the next charge and discharge.

Setting 1 hour as a standing threshold, standing the battery for 1 hour to meet the condition of sufficient standing, and judging whether the standing time is longer than 1 hour; if yes, calculating the current SOC to be corrected as follows:

Δsoc=soc display value-SOC real value

In the equation, Δsoc is the SOC currently required to be corrected.

Adding or subtracting a correction compensation value to or from the SOC display value at each sampling time of the next charge and discharge, including:

In the formula, SOC (t) is a current time SOC display value, SOC _t0 is an initial value of a corrected SOC display value, deltaK is a correction coefficient, I (t) is current, and C _n is battery capacity.

The correction compensation value Δcn is:

ΔCn＝ΔK×I(t)

when discharging, the following steps are carried out: if delta SOC is less than 0, subtracting the correction compensation value at the next discharging moment; if delta SOC is more than 0, adding a correction compensation value at the next discharging time;

When in charging: if delta SOC is less than 0, adding a correction compensation value at the next discharging moment; if Δsoc >0, the correction compensation value is subtracted at the next discharge time.

S300: in order to prevent over repair, calculating a correction cutoff time by utilizing ampere-hour integration;

Calculating an accumulated correction amount SOC_Cal, and judging:

If yes, the moment is considered as the correction cut-off moment, and the correction is ended;

let Δk=0 at this time, i.e., Δcn=0.

The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention.

Claims (6)

1. The SOC correction method of the energy storage battery is characterized by comprising the following steps of:

Calculating the battery standing time, and judging whether the battery standing time exceeds a preset limit value; if the standing time exceeds a preset limit value, acquiring a current terminal voltage value, and checking a preset SOC-OCV table according to the current terminal voltage value to obtain an SOC true value;

Acquiring an SOC display value, calculating a difference value between the SOC real value and the SOC display value, and taking the difference value as an initial value of the corrected SOC display value; based on the initial value of the corrected SOC display value, correcting the SOC display value by adopting a corrected compensation value;

calculating the ratio of the accumulated correction compensation value to the battery capacity, and calculating the difference value between the accumulated correction compensation value and the absolute value of the initial value of the correction SOC; if the difference is less than or equal to zero, the correction is considered to be the correction cut-off time at the moment, and the correction is ended.

2. The SOC correction method of an energy storage battery of claim 1, wherein the calculating the battery rest time includes: collecting current, and judging whether the battery reaches a standing state according to the collected current, wherein the standing state is that the current is more than-0.1A and less than 0.1A; if the static state is reached, calculating the static time.

3. The SOC correction method of an energy storage battery as defined in claim 1, further comprising, before calculating the battery rest time: an SOC-OCV table of the battery in a stationary state is established in advance, the SOC-OCV table including a charge SOC-OCV table and a discharge SOC-OCV table.

4. The SOC correction method of claim 3, wherein the SOC real value is obtained by looking up the SOC-OCV table according to the current terminal voltage value, comprising:

Selecting different SOC-OCV table data according to the value of the current, and if the value of the current is greater than zero, using the charged SOC-OCV table data as the input of a difference method; otherwise, using the discharging SOC-OCV table data as the input of a difference method; a table look-up is performed using a difference method to obtain a current SOC real value.

5. The SOC-OCV correction method of claim 4, wherein the step of looking up a table using a difference method to obtain the current SOC real value comprises:

Acquiring terminal voltage, traversing the OCV in the SOC-OCV table, and comparing whether the input terminal voltage is smaller than or equal to the current traversed OCV;

if yes, the current SOC real value is:

Where Volt_in is the voltage; table_in () is a calibrated OCV value; table_In (i-1) is the OCV value at the i-1 traversal time, and Table_In (i) is the OCV value at the i traversal time;

if not, traversing the next OCV in the SOC-OCV table;

if the above condition is still not satisfied after traversing all OCVs in the SOC-OCV table, the SOC true value=1.

6. The SOC correction method of claim 5, wherein the correction compensation value is calculated based on an initial value of the corrected SOC:

Wherein, SOC (t) is the current t moment SOC, SOC _t0 is the initial value of the corrected SOC, deltaK is the correction coefficient, I (t) is the t moment current, and C _n is the battery capacity;

Wherein, the corrected compensation value Δc _n is:

ΔC_n＝ΔK×I(t)。