TWI851364B - Outlier diagnosis method for series-connected cells - Google Patents

Outlier diagnosis method for series-connected cells Download PDF

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TWI851364B
TWI851364B TW112128668A TW112128668A TWI851364B TW I851364 B TWI851364 B TW I851364B TW 112128668 A TW112128668 A TW 112128668A TW 112128668 A TW112128668 A TW 112128668A TW I851364 B TWI851364 B TW I851364B
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voltage
discharge
score
outliers
outlier
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謝侑承
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儲盈科技股份有限公司
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Abstract

The invention discloses a method for diagnosing cell outliers among series-connected lithium battery, the average voltage changes at the initial stage of discharge Vx and the average voltage change at the end of charge Vy are detected and calculated for each cell, then an outlier index and z-score are calculated, and the z-score is used to find the cell outliers that need attention.

Description

串聯電芯離群診斷方法Series Cell Outlier Diagnosis Method

本發明係有關於一種串聯電芯離群診斷方法,特別是在串聯鋰電池中,自動分析並檢出離群電芯的方法。The present invention relates to a method for diagnosing outliers in series-connected cells, and in particular to a method for automatically analyzing and detecting outliers in series-connected lithium batteries.

先前技藝是靠人工判讀個別電芯的數據或是圖形,然後關注離群電芯。先前技藝無法自動化分析,需要耗費許多時間與人力。Previous technologies relied on manual interpretation of individual cell data or graphs, and then focused on outlier cells. Previous technologies could not automate analysis and required a lot of time and manpower.

本案首先構想自動化分析,只要輸入各種參數便可以自動分析,系統便會自動提供需要關注的離群電芯名單。The first idea of this case is to automate the analysis. Simply input various parameters and the system will automatically provide a list of outlier cells that need attention.

圖1 為本發明的流程圖 包含下述步驟: 步驟A 計算電芯的放電初期平均電壓變化Vx; 步驟B計算電芯的充電末期平均電壓變化Vy; 步驟C計算電芯的離群指標與z分數(z-score); 步驟D設定離群(z分數)之門檻值;以及 步驟E輸出超過門檻值之電芯名單。 後續圖2將說明放電初期平均電壓變化Vx的計算、圖3將說明充電末期平均電壓變化Vy的計算、以及圖4將說明各電芯離群指標x與z分數(z-score)的計算。FIG1 is a flow chart of the present invention, which includes the following steps: Step A calculates the average voltage change Vx at the initial stage of discharge of the battery cell; Step B calculates the average voltage change Vy at the end of charge of the battery cell; Step C calculates the outlier index and z-score of the battery cell; Step D sets the threshold value of the outlier (z-score); and Step E outputs the list of batteries that exceed the threshold value. FIG2 will explain the calculation of the average voltage change Vx at the initial stage of discharge, FIG3 will explain the calculation of the average voltage change Vy at the end of charge, and FIG4 will explain the calculation of the outlier index x and z-score of each battery cell.

本發明中的基準電壓值Vo是指: 放電開始的前一筆電流為0A的數據,也就是還未放電的最後一筆是計算放電初期平均電壓變化Vx的基準電壓值 Vo。一般為充飽電且尚未放電時的電壓值,可為浮充或靜置時的電壓值。The reference voltage value Vo in the present invention refers to: the data of the last current before the start of discharge is 0A, that is, the last current before discharge is the reference voltage value Vo for calculating the average voltage change Vx at the initial stage of discharge. Generally, it is the voltage value when fully charged and not yet discharged, which can be the voltage value when floating or static.

放電初期平均電壓變化Vx的計算:為放電開始後,陸續採樣電壓值n次,直到放電超過 5% 容量時為止,每筆數據都與基準電壓值Vo相比較,用基準電壓值Vo減去採樣電壓值Vi得到電壓差,然後相加每筆電壓差,再做平均,得到放電初期平均電壓變化Vx。Calculation of the average voltage change Vx at the initial stage of discharge: After the start of discharge, the voltage value is sampled n times continuously until the discharge exceeds 5% of the capacity. Each data is compared with the reference voltage value Vo, and the voltage difference is obtained by subtracting the sampled voltage value Vi from the reference voltage value Vo. Then, each voltage difference is added and averaged to obtain the average voltage change Vx at the initial stage of discharge.

放電初期平均電壓變化Vx計算公式:Vx = ;其中, Vo 為基準電壓值,Vi為採樣電壓、n為電壓採樣數。 浮充係指:充電機用固定電壓對已經充飽電的電池持續充電,保持其狀態 ,此時充電電流會微大於 0A。 The calculation formula of the average voltage change Vx at the initial stage of discharge is: Vx = ; Among them, Vo is the reference voltage value, Vi is the sampling voltage, and n is the number of voltage samples. Floating charge means: the charger continuously charges the fully charged battery with a fixed voltage to maintain its state. At this time, the charging current will be slightly greater than 0A.

靜置係指:沒有任何電流對電池充放電。Static means: there is no current charging or discharging the battery.

z 分數 (z-score)係指:統計學上用以計算某數值與平均的差距為多少個標準差的指標。篩選標準可以設定為z 分數 z > 3~6。例如:在160顆電芯串聯組成的系統中,可以使用 z > 6 作為篩選標準。為了方便說明,我們挑出其中的16顆電芯的數據,列如表一所示,說明本案精神,電芯顆數較少時,平均值與標準差都會有變化,因此,這裡使用 z > 3作為篩選標準,電芯1 的z > 3 ,視為離群而被篩選出,其餘電芯的z < 3,視為是與整體表現一致的電芯。The z-score is a statistical indicator used to calculate the number of standard deviations between a value and the average. The screening criteria can be set to z-score z > 3~6. For example, in a system consisting of 160 cells connected in series, z > 6 can be used as the screening criteria. For the sake of convenience, we have selected the data of 16 cells, as shown in Table 1, to illustrate the spirit of this case. When the number of cells is small, the mean and standard deviation will change. Therefore, z > 3 is used as the screening criteria here. Cell 1 has z > 3 and is considered an outlier and is screened out. The remaining cells have z < 3 and are considered to be cells that are consistent with the overall performance.

標準差計算公式:σ = ;其中, Standard deviation calculation formula: σ = ;in,

x為離群指標,x-bar 為x的平均值,Nc 為電芯數量;x is the outlier indicator, x-bar is the average value of x, and Nc is the number of cells;

單電芯之z 分數 (z-score) 的計算公式:z = ;其中, The calculation formula for the z-score of a single cell is: z = ;in,

x 為電芯離群指標,x-bar 為x的平均值,σ為標準差。x is the cell outlier indicator, x-bar is the mean value of x, and σ is the standard deviation.

表一:挑出16顆電芯的數據說明本案精神 電芯編號 放電初期 平均電壓變化 (Vx) 充電末期 平均電壓變化 (Vy) 離群指標 (x) (Vx+Vy)/2 z 分數 (z-score) 1 409.5444444 89.53846154 249.541453 3.724441209 2 363.1833333 6.230769231 184.7070513 0.276102884 3 347.3055556 5.307692308 176.3066239 -0.17068948 4 351.4888889 5.076923077 178.282906 -0.065577241 5 345.7055556 4.384615385 175.0450855 -0.237786751 6 332.2388889 4.230769231 168.2348291 -0.600002913 7 343.5166667 3.615384615 173.5660256 -0.316453301 8 341.2277778 2.923076923 172.0754274 -0.395733545 9 355.2777778 5 180.1388889 0.033136665 10 352.0277778 5.615384615 178.8215812 -0.036926797 11 361.9444444 5.461538462 183.7029915 0.222700093 12 339.6277778 5 172.3138889 -0.383050524 13 338.7444444 4.461538462 171.6029915 -0.420860928 14 324.9444444 5.230769231 165.0876068 -0.767393785 15 336.95 3.307692308 170.1288462 -0.499266089 16 342.4722222 2.923076923 172.6976496 -0.362639498 x 平均(x-bar) 179.5158654 標準差(σ) 18.80163592 Table 1: Data of 16 cells are selected to illustrate the spirit of this case Cell number Average voltage change at the initial stage of discharge (Vx) Average voltage change at the end of charging (Vy) Outlier index (x) (Vx+Vy)/2 z - score 1 409.5444444 89.53846154 249.541453 3.724441209 2 363.1833333 6.230769231 184.7070513 0.276102884 3 347.3055556 5.307692308 176.3066239 -0.17068948 4 351.4888889 5.076923077 178.282906 -0.065577241 5 345.7055556 4.384615385 175.0450855 -0.237786751 6 332.2388889 4.230769231 168.2348291 -0.600002913 7 343.5166667 3.615384615 173.5660256 -0.316453301 8 341.2277778 2.923076923 172.0754274 -0.395733545 9 355.2777778 5 180.1388889 0.033136665 10 352.0277778 5.615384615 178.8215812 -0.036926797 11 361.9444444 5.461538462 183.7029915 0.222700093 12 339.6277778 5 172.3138889 -0.383050524 13 338.7444444 4.461538462 171.6029915 -0.420860928 14 324.9444444 5.230769231 165.0876068 -0.767393785 15 336.95 3.307692308 170.1288462 -0.499266089 16 342.4722222 2.923076923 172.6976496 -0.362639498 x- average (x-bar) 179.5158654 Standard deviation (σ) 18.80163592

表一顯示電芯1的測試結果為:Table 1 shows the test results of battery 1:

放電初期平均電壓變化Vx = 409.54…;Average voltage change at the initial stage of discharge Vx = 409.54…;

充電末期平均電壓變化Vy = 89.53…;The average voltage change at the end of charging is Vy = 89.53…;

離群指標x= (409.54+89.53)/2 = 249.54…;Outlier index x = (409.54+89.53)/2 = 249.54…;

z = (249.54-179.51)/18.80=3.72…。z = (249.54-179.51)/18.80=3.72….

其他電芯的資料,表達方式類似,請參考表一,此不再贅述。上表中,離群指標平均值為179.51…,離群指標x的標準差為18.80…。假設使用 z 分數 z > 3作為異常標準時,電芯1 的z > 3 視為離群將被標示為異常,其餘電芯的z < 3,視為是正常品質的電芯。The data of other cells are expressed in a similar way. Please refer to Table 1. I will not elaborate on them here. In the above table, the average value of the outlier index is 179.51…, and the standard deviation of the outlier index x is 18.80…. Assuming that z score z > 3 is used as the abnormal standard, cell 1 with z > 3 is considered an outlier and will be marked as abnormal, and the rest of the cells with z < 3 are considered to be normal quality cells.

圖2為放電初期平均電壓變化Vx的計算Figure 2 shows the calculation of the average voltage change Vx at the initial stage of discharge.

步驟一:放電開始,放電開始為第一筆有放電電流的時候,以160顆電芯串聯時,我們設定串聯電芯的電流下限為 20A ,即是串聯電芯的放電電流大於 20A ,判斷為放電開始。但此電流下限可以依據使用此指標的人自由調整。Step 1: Discharge starts. Discharge starts when the first discharge current appears. When 160 cells are connected in series, we set the current lower limit of the series cells to 20A. That is, when the discharge current of the series cells is greater than 20A, it is judged that discharge has started. However, this current lower limit can be freely adjusted according to the person using this indicator.

步驟二:採樣多次,採樣當下計算電壓差 (Vo - Vi) ,即基準電壓值Vo減去採樣當下的電壓值Vi。Step 2: Sample multiple times and calculate the voltage difference (Vo - Vi) at the time of sampling, that is, the reference voltage value Vo minus the voltage value Vi at the time of sampling.

步驟三:電壓差加總,將前面所有採樣的電壓差加總 Step 3: Sum the voltage difference. Sum the voltage differences of all previous samples. .

步驟四:放電超過5%容量時停止。Step 4: Stop when discharge exceeds 5% capacity.

步驟五:計算放電初期平均電壓變化Vx,即是:電壓差加總除以電壓採樣數 Vx = Step 5: Calculate the average voltage change Vx at the initial stage of discharge, that is: the sum of the voltage differences divided by the number of voltage samples Vx = ;

其中: Vo為飽電狀態且放電電流為0A的最後一筆電壓值,Vi 為採樣電壓,n 為電壓採樣數。Where: Vo is the last voltage value when the discharge current is 0A in full charge state, Vi is the sampling voltage, and n is the number of voltage samples.

鋰鐵電池充電曲線進入平台區後電壓變化微小,因此,本案只使用放電前期的變化數據。前期的基準通常為標定容量的 5%,實際需視各廠牌電芯而定;將電壓差的總和除以 n 筆得出放電初期平均電壓變化Vx。The voltage change of lithium-iron battery charging curve is very small after entering the platform area. Therefore, this case only uses the change data in the early stage of discharge. The early benchmark is usually 5% of the rated capacity, which actually depends on the battery cell of each brand. The sum of the voltage difference is divided by n records to obtain the average voltage change Vx in the early stage of discharge.

圖3為充電末期平均電壓變化Vy的計算。Figure 3 shows the calculation of the average voltage change Vy at the end of charging.

步驟六:充電開始;Step 6: Charging starts;

步驟七:採樣多次,將電壓值存於佇列;Step 7: Sample multiple times and store the voltage values in a queue;

步驟八:佇列所代表資料超過10%充電容量時;以及Step 8: When the data represented by the queue exceeds 10% of the charging capacity; and

步驟九:計算充電末期平均電壓變化 Vy;即是將存於佇列中的每一筆電壓值分別與佇列第一筆的電壓值的差,加總除以採樣數。Step 9: Calculate the average voltage change Vy at the end of charging; that is, add up the difference between each voltage value in the queue and the first voltage value in the queue and divide it by the number of samples.

圖4為計算各電芯離群指標與z分數(z-score)Figure 4 shows the calculation of outlier index and z-score for each battery cell.

步驟十:計算各電芯離群指標與z分數(z-score);Step 10: Calculate the outlier index and z-score of each cell;

離群指標x的計算:x = (Vx*k1 + Vy*k2)/2;其中,k1、k2 係調整係數,可以視需要做調整。本案範例中採用k1=1、k2=1計算之。Calculation of outlier index x: x = (Vx*k1 + Vy*k2)/2; k1 and k2 are adjustment coefficients that can be adjusted as needed. In this case, k1=1 and k2=1 are used for calculation.

標準差計算公式為:       σ = ;其中, The formula for calculating standard deviation is: σ = ;in,

x為各電芯離群指標,x-bar 為平均值,Nc 為電芯數量x is the outlier index of each battery cell, x-bar is the average value, and Nc is the number of batteries

單電芯之z 分數 (z-score) 的計算公式:z = ;其中, The calculation formula for the z-score of a single cell is: z = ;in,

x 為電芯離群指標,x-bar 為x的平均值,σ為標準差;x is the cell outlier indicator, x-bar is the mean value of x, and σ is the standard deviation;

步驟十一:設定離群(z分數)之門檻值;Step 11: Set the outlier (z-score) threshold;

步驟十二:輸出超過門檻值之電芯名單。Step 12: Output the list of cells that exceed the threshold value.

前述描述所使用的參數,僅是作為範例說明,方便讀者明了本案的精神,並非用來限制本案的權利範圍。前述描述揭示了本發明之較佳實施例以及設計圖式,惟,較佳實施例以及設計圖式僅是舉例說明,並非用於限制本發明之權利範圍於此,凡是以均等之技藝手段實施本發明者、或是以下述之「申請專利範圍」所涵蓋之權利範圍而實施者,均不脫離本發明之精神而為申請人之權利範圍。The parameters used in the above description are only used as examples to help readers understand the spirit of the case, and are not used to limit the scope of rights of the case. The above description reveals the preferred embodiments and design diagrams of the present invention, but the preferred embodiments and design diagrams are only examples and are not used to limit the scope of rights of the present invention. Anyone who implements the present invention with equal technical means or implements it within the scope of rights covered by the following "patent application scope" shall not deviate from the spirit of the present invention and shall be the scope of rights of the applicant.

Vo:基準電壓值Vo: reference voltage value

Vi:採樣電壓Vi: sampling voltage

n:電壓採樣數n: Number of voltage samples

Nc:電芯數量Nc: Number of cells

z:z分數z:z score

σ:標準差σ: standard deviation

k1、k2:修正係數k1, k2: correction coefficient

x:離群指標x: outlier indicator

x-Bar:x的平均值x-Bar: the average value of x

圖1 為本發明的流程圖 圖2為放電初期平均電壓變化的計算 圖3為充電末期平均電壓變化的計算 圖4為計算各電芯離群指標與z分數(z-score)Figure 1 is a flow chart of the present invention. Figure 2 is the calculation of the average voltage change at the beginning of discharge. Figure 3 is the calculation of the average voltage change at the end of charge. Figure 4 is the calculation of the outlier index and z-score of each battery cell.

Claims (6)

一種串聯電芯離群診斷方法,包含下述步驟:步驟A計算放電初期平均電壓變化Vx;步驟B計算充電末期平均電壓變化Vy;步驟C計算各電芯離群指標x與z分數;步驟D設定離群(z分數)之門檻值;以及步驟E輸出超過門檻值之電芯名單;其中,所述離群指標x的計算,係指x=(Vx*k1+Vy*k2)/2;以及所述z分數的計算,係指:
Figure 112128668-A0305-02-0009-2
A method for diagnosing outliers in series cells comprises the following steps: step A calculates an average voltage change Vx at the initial stage of discharge; step B calculates an average voltage change Vy at the end of charge; step C calculates an outlier index x and a z score of each cell; step D sets a threshold value of an outlier (z score); and step E outputs a list of cells exceeding the threshold value; wherein the calculation of the outlier index x refers to x=(Vx*k1+Vy*k2)/2; and the calculation of the z score refers to:
Figure 112128668-A0305-02-0009-2
.
如請求項1所述之串聯電芯離群診斷方法,其中,所述之步驟A計算放電初期平均電壓變化Vx,更包含:步驟一:放電開始,設定串聯電芯放電電流大於事先指定的電流(安培)閥值時,判斷為放電開始;步驟二:採樣多次,採樣當下計算電壓差(Vo-Vi),即基準電壓值Vo減去採樣當下的電壓值Vi;步驟三:電壓差加總,將前面所有採樣的電壓差加總;步驟四:放電超過P1%容量時停止;以及步驟五:計算放電初期平均電壓變化Vx,即是:電壓差加總除以電壓採樣數;
Figure 112128668-A0305-02-0009-1
;其中,Vo為基準電壓值,Vi為採樣電壓、n為電壓採樣數。
The method for diagnosing outliers in series cells as described in claim 1, wherein the step A of calculating the average voltage change Vx at the initial stage of discharge further comprises: step 1: when discharge starts, when the discharge current of the series cells is set to be greater than a pre-specified current (ampere) threshold value, it is determined that discharge has started; step 2: sampling multiple times, calculating the voltage difference (Vo-Vi) at the time of sampling, that is, the reference voltage value Vo minus the voltage value Vi at the time of sampling; step 3: summing up the voltage difference, summing up the voltage differences of all previous samples; step 4: stopping when the discharge exceeds P1% capacity; and step 5: calculating the average voltage change Vx at the initial stage of discharge, that is: the sum of the voltage differences divided by the number of voltage samples;
Figure 112128668-A0305-02-0009-1
; Wherein, Vo is the reference voltage value, Vi is the sampling voltage, and n is the number of voltage samples.
如請求項2所述之串聯電芯離群診斷方法,其中,步驟四所述之P1%,係指3%~7%。 In the method for diagnosing outliers in series cells as described in claim 2, the P1% described in step 4 refers to 3%~7%. 如請求項1所述之串聯電芯離群診斷方法,其中,所述之步驟B計算充電末期平均電壓變化Vy,更包含:步驟六:充電開始;步驟七:採樣多次,將電壓值存於佇列;步驟八:佇列所代表資料超過P2%充電容量時;以及步驟九:計算充電末期平均電壓變化Vy,即是將存於佇列中的每一筆電壓值分別與佇列第一筆的電壓值的差,加總除以採樣數。 The method for diagnosing outliers in series cells as described in claim 1, wherein the step B of calculating the average voltage change Vy at the end of charging further includes: step 6: charging starts; step 7: sampling multiple times and storing the voltage values in a queue; step 8: when the data represented by the queue exceeds P2% of the charging capacity; and step 9: calculating the average voltage change Vy at the end of charging, that is, summing up the differences between each voltage value stored in the queue and the voltage value of the first value in the queue and dividing by the number of samples. 如請求項4所述之串聯電芯離群診斷方法,其中,步驟八所述之P2%,係指7%~13%。 In the method for diagnosing outliers in series cells as described in claim 4, the P2% described in step eight refers to 7%~13%. 如請求項1所述之串聯電芯離群診斷方法,其中,所述之步驟C計算各電芯離群指標x與z分數,更包含:步驟十:計算各電芯離群指標x與z分數;離群指標x的計算:x=(Vx*k1+Vy*k2)/2;其中,k1、k2係調整係數,可以視需要做調整;步驟十一:設定離群(z分數)之門檻值;以及步驟十二:輸出超過門檻值之電芯名單。 The method for diagnosing outliers in series cells as described in claim 1, wherein the step C of calculating the outlier index x and z score of each cell further comprises: step 10: calculating the outlier index x and z score of each cell; calculation of outlier index x: x=(Vx*k1+Vy*k2)/2; wherein k1 and k2 are adjustment coefficients and can be adjusted as needed; step 11: setting the threshold value of outliers (z score); and step 12: outputting a list of cells exceeding the threshold value.
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