A satellite lithium-ion battery pack capacity degradation assessment method and system

Abstract

The present invention proposes a method and system for evaluating the capacity decay of a satellite lithium-ion battery pack. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of shelving, the pressure difference change law of the battery pack self-discharge is obtained. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of supplementary charging, the actual charging capacity law of the battery pack supplementary charging is obtained. The capacity decay of the battery pack is partially characterized by the pressure difference change rate of the battery pack self-discharge. The method of the present invention further improves the reliability of the battery pack on-orbit operation.

Description

Technical Field

[0001] The invention relates to a method and system for evaluating the capacity decay of a satellite lithium-ion storage battery pack, which are suitable for evaluating the actual charging capacity decay of a satellite lithium-ion storage battery pack during supplementary charging during a long light period. Background Art

[0002] Lithium-ion battery packs are energy storage devices on satellites. Before satellite launch, during the active flight phase, during the transfer orbit and synchronous orbit Earth shadow, or when the output power of solar cells is insufficient, the power required by the satellite is output by the lithium-ion battery pack. Affected by factors such as increased internal resistance, the lithium-ion battery pack self-discharges during long-photoperiod shelving. When the voltage drops to the same range, the discharge time of the lithium-ion battery pack gradually decreases over time. That is, during the long-photoperiod supplementary charging period, the actual charging capacity of the lithium-ion battery pack gradually decreases over time. Lithium-ion battery packs have a capacity decay phenomenon.

[0003] With the widespread application and rapid growth of lithium-ion battery packs in space projects, evaluating the on-orbit performance of lithium-ion battery packs and gaining a deeper understanding of the changing trends in the on-orbit performance of lithium-ion battery packs are of great significance for improving the product development of subsequent projects and enhancing the on-orbit reliability of products. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a method for evaluating the capacity degradation of a satellite lithium-ion battery pack, to evaluate the capacity degradation of a satellite lithium-ion battery pack, and to improve the on-orbit working reliability of the on-board lithium-ion battery pack.

[0005] The technical solution of the present invention is:

[0006] A method for evaluating the capacity degradation of a satellite lithium-ion battery pack, comprising:

[0007] Each working cycle of the lithium-ion battery pack during the long light period includes a rest stage and a supplementary charging stage. During the long light period, for the rest stage and supplementary charging stage of each working cycle, the discharge time, discharge start voltage, discharge cut-off voltage, and charging time are obtained through satellite telemetry; during the long light period, the voltage change of the battery pack during the rest stage is statistically analyzed to obtain the battery pack voltage difference ΔUdi and the voltage difference change rate ΔUdpti of the i-th discharge cycle interval Δtdi;

[0008] The capacity change of the battery pack during the supplementary charging stage is counted to obtain the charging capacity Cci of the battery pack at the i-th supplementary charging cycle interval Δtci;

[0009] Calculate the self-discharge current Isdi of the battery pack in the i-th supplementary charging stage and the shelving stage;

[0010] Calculate the self-discharge capacity Csdi of the battery pack in the i-th supplementary charging stage;

[0011] Calculate the actual charging capacity Cri of the battery pack in the i-th supplementary charging stage;

[0012] According to the battery group voltage difference change rate ΔUdpti in the i-th storage period and the actual charging capacity Cri of the battery group in the i-th supplementary charging period, a capacity decay model of the battery group in the long-light period storage period and supplementary charging period is established;

[0013] Through the capacity degradation model of the battery pack, the voltage difference change rate ΔUdpt_i+1 and the actual charging capacity Cr_i+1 in the i+1th shelving stage and the supplementary charging stage are predicted, thereby realizing the capacity degradation assessment of the satellite lithium-ion battery pack.

[0014] Furthermore, the i-th discharge cycle interval is calculated as follows:

[0015] Δtdi=td2i-td1i

[0016] Wherein, td2i represents the discharge end time of the i-th discharge cycle, td1i represents the discharge start time of the i-th discharge cycle, i=1, 2...;

[0017] The battery pack voltage difference is calculated as follows:

[0018] ΔUdi=U1i-U2i

[0019] Where, U1i represents the discharge start voltage of the i-th discharge cycle, and U2i represents the discharge cut-off voltage of the i-th discharge cycle;

[0020] The pressure difference change rate is calculated as follows:

[0021] ΔUdpti=ΔUdi / Δtdi.

[0022] Furthermore, the calculation method of the battery pack charging capacity is as follows:

[0023] Cci=Ici×Δtci

[0024] Where, Ici represents the charging current of the i-th supplementary charging stage; Δtci represents the interval of the i-th supplementary charging stage;

[0025] Δtci=tc2i-tci

[0026] Wherein, tc2i represents the charging end time of the i-th supplementary charging stage, and tc1i represents the charging start time of the i-th supplementary charging stage.

[0027] Furthermore, the self-discharge current of the battery pack is calculated as follows:

[0028] Isdi=Cci / Δtsd

[0029] Where, Cci represents the charging capacity of the battery pack during the i-th supplementary charging stage; Δtsd represents the self-discharge time during the i-th supplementary charging stage;

[0030] Δtsd=Δtdi+Δtci.

[0031] Furthermore, the self-discharge capacity of the battery pack is calculated as follows:

[0032] Csdi=Isdi×Δtci.

[0033] Furthermore, the actual charging capacity of the battery pack is calculated as follows:

[0034] Cri=Cci-Csdi.

[0035] Furthermore, the capacity decay model of the battery pack during the long-photoperiod storage and supplementary charging stages refers to: using the battery pack pressure difference change rate ΔUdpti to characterize the actual charging capacity Cri of the battery pack in the same working cycle, and there is a one-to-one correspondence between the battery pack pressure difference change rate ΔUdpti and the actual charging capacity Cri of the battery pack.

[0036] Furthermore, the present invention also proposes a satellite lithium-ion battery capacity degradation assessment system, comprising:

[0037] Module 1: Each working cycle of the lithium-ion battery pack during the long light period includes a rest stage and a supplementary charging stage. During the long light period, for each working cycle of the rest stage and the supplementary charging stage, the discharge time, discharge start voltage, discharge end voltage, and charging time are obtained through satellite telemetry; during the long light period, the voltage change of the battery pack during the rest stage is counted to obtain the battery pack voltage difference ΔUdi and the voltage difference change rate ΔUdpti of the i-th discharge cycle interval Δtdi;

[0038] The second module: statistics the capacity change of the battery pack during the supplementary charging stage, and obtains the charging capacity Cci of the battery pack at the i-th supplementary charging cycle interval Δtci;

[0039] Self-discharge current calculation module: calculates the self-discharge current Isdi of the battery pack in the i-th supplementary charging and shelving stage;

[0040] Self-discharge capacity calculation module: calculates the self-discharge capacity Csdi of the battery pack in the i-th supplementary charging stage;

[0041] Actual charging capacity calculation module: calculates the actual charging capacity Cri of the battery pack in the i-th supplementary charging stage;

[0042] Capacity decay model establishment module: according to the battery group voltage difference change rate ΔUdpti in the i-th storage period and the actual charging capacity Cri of the battery group in the i-th supplementary charging period, the capacity decay model of the battery group in the long-light period storage period and supplementary charging period is established;

[0043] Capacity degradation assessment module: Through the capacity degradation model of the battery pack, the voltage difference change rate ΔUdpt_i+1 and the actual charging capacity Cr_i+1 in the i+1th shelving and supplementary charging stage are predicted, thereby realizing the capacity degradation assessment of the satellite lithium-ion battery pack.

[0044] The beneficial effects of the present invention compared with the prior art are:

[0045] (1) The evaluation method of the present invention is applied for the first time in a domestic high-orbit satellite equipped with a lithium-ion battery pack. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of shelving, the pressure difference change law of the battery pack self-discharge is obtained. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of supplementary charging, the actual charging capacity law of the battery pack supplementary charging is obtained. The pressure difference change rate of the battery pack self-discharge is used to partially characterize the capacity decay of the battery pack, further improving the reliability of the battery pack on orbit.

[0046] (2) Aiming at the capacity degradation phenomenon of lithium-ion battery packs, the present invention proposes a method for evaluating the capacity degradation of satellite lithium-ion battery packs. By analyzing lithium-ion telemetry data, the capacity degradation of lithium-ion battery packs is quantitatively calculated and qualitatively evaluated, and the actual charging capacity during the long-light period supplementary charging in the middle and late stages of on-orbit and at the end of life is predicted. The evaluation method can be applied to multiple projects, and the relevant research results can be extended to the on-orbit performance evaluation of lithium-ion battery packs of high-orbit satellites. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a flow chart of the method of the present invention;

[0048] Figure 2 Schematic diagram of the capacity decay model of a battery pack during long-photoperiod supplementary charging and a shelf period according to an embodiment of the present invention. DETAILED DESCRIPTION

[0049] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0050] The evaluation method of the present invention is applied for the first time in a domestic high-orbit satellite equipped with a lithium-ion battery pack. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of shelving, the pressure difference change law of the battery pack self-discharge is obtained. By analyzing the telemetry data of the lithium-ion battery pack during the long-light period of supplementary charging, the actual charging capacity law of the battery pack supplementary charging is obtained. The pressure difference change rate of the battery pack self-discharge partially characterizes the capacity decay of the battery pack, thereby designing an evaluation method for the capacity decay of the satellite lithium-ion battery pack, further improving the reliability of the battery pack on orbit.

[0051] like Figure 1 As shown, the present invention proposes a method for evaluating the capacity degradation of a satellite lithium-ion battery pack, comprising the following steps:

[0052] 1) Each working cycle of the lithium-ion battery pack during the long light period includes a rest stage and a supplementary charging stage (also called a rest period and a supplementary charging period). During the rest and supplementary charging period of the long light period (referring to the entire long light period), the telemetry data such as discharge time, discharge start voltage, discharge end voltage, and charging time are obtained through satellite telemetry; during the long light period, the voltage change of the battery pack during the rest mode is statistically analyzed to obtain the battery pack voltage difference ΔUdi and the voltage difference change rate ΔUdpti of the i-th discharge cycle (rest period) interval Δtdi. i = 1, 2...

[0053] Δtdi=td2i-td1i

[0054] Wherein, td2i represents the discharge end time of the i-th discharge cycle, and td1i represents the discharge start time of the i-th discharge cycle;

[0055] ΔUdi=U1i-U2i

[0056] Where, U1i represents the discharge start voltage of the i-th discharge cycle, and U2i represents the discharge cut-off voltage of the i-th discharge cycle;

[0057] ΔUdpti=ΔUdi / Δtdi Formula (1)

[0058] 2) The capacity change of the battery pack during the supplementary charging period is counted to obtain the charging capacity Cci of the battery pack during the i-th supplementary charging cycle interval Δtci. i=1, 2, . . .

[0059] Cci=Ici×Δtci formula (2)

[0060] Where, Ici represents the charging current of the i-th supplementary charging cycle; Δtci represents the interval between the i-th supplementary charging cycles;

[0061] Δtci=tc2i-tci

[0062] Wherein, tc2i represents the charging end time of the i-th supplementary charging cycle, and tc1i represents the charging start time of the i-th supplementary charging cycle.

[0063] 3) Calculate the self-discharge current Isdi of the storage battery pack in the i-th supplementary charging and storage cycle. i=1, 2, ...

[0064] Isdi=Cci / Δtsd Formula (3)

[0065] Where, Cci represents the battery pack charging capacity during the i-th supplementary charging cycle interval; Δtsd represents the self-discharge time during the i-th supplementary charging mode cycle;

[0066] Δtsd=Δtdi+Δtci.

[0067] 4) Calculate the self-discharge capacity Csdi of the battery pack in the i-th supplementary charging cycle. i = 1, 2, ...

[0068] Csdi=Isdi×Δtci formula (4)

[0069] 5) Calculate the actual charging capacity Cri of the battery pack in the i-th supplementary charging cycle. i = 1, 2, ...

[0070] Cri=Cci-Csdi Formula (5)

[0071] 6) According to the battery group voltage difference change rate ΔUdpti in the i-th shelf cycle and the actual charging capacity Cri of the battery group in the i-th supplementary charging cycle, a capacity decay model of the battery group in the long-light period supplementary charging and shelf cycle is established.

[0072] The capacity degradation model of the battery pack during long-photoperiod storage and supplementary charging cycles is as follows: the battery pack pressure difference change rate ΔUdpti is used to characterize the actual charging capacity Cri of the battery pack in the same working cycle; in the same figure, there is a one-to-one correspondence between the battery pack pressure difference change rate ΔUdpti and the actual charging capacity Cri of the battery pack.

[0073] The voltage difference change rate ΔUdpt_i+1 and the actual charging capacity Cr_i+1 of the i+1th shelving and supplementary charging cycle are predicted through the capacity decay model of the battery pack, where i=1, 2, . . .

[0074] This enables the capacity degradation assessment of satellite lithium-ion battery packs.

[0075] Example:

[0076] Parts of the present invention that are not described in detail belong to common knowledge among those skilled in the art.

[0077] 1) Take the battery capacity degradation phenomenon of a satellite in orbit as an example. The battery pressure difference change rate ΔUdpt of the first 10 discharge cycles obtained through satellite telemetry is:

[0078] [300.57 306.08 306.35 307.50 307.72 309.85 311.18 311.25 311.98313.38]mV / day;

[0079] 2) The battery pack charging capacity Cci during the first 10 supplementary charging cycles Δtci is

[0080] [34.70 34.10 34.02 33.92 33.76 33.56 33.45 33.37 33.21 33.15]Ah;

[0081] 3) The self-discharge current Isdi of the battery pack during the first 10 cycles of the supplementary charging mode and the standby mode is

[0082] [0.1197 0.1198 0.1196 0.1197 0.1196 0.1194 0.1195 0.1192 0.11890.1192]A;

[0083] 4) The self-discharge capacity Csdi of the battery pack in the first 10 supplementary charging mode cycles is

[0084] [3.54 3.45 3.44 3.43 3.41 3.39 3.38 3.36 3.34 3.34]Ah;

[0085] 5) The actual charging capacity Cri of the battery pack in the first 10 supplementary charging mode cycles is

[0086] [31.17 30.64 30.58 30.48 30.35 30.18 30.07 30.00 29.87 29.81]Ah;

[0087] 6) Based on the voltage difference change rate of the battery pack in the first 10 idle mode cycles and the actual charging capacity of the supplementary charging mode cycle, a capacity decay model of the battery pack in the long-light period supplementary charging mode and the idle mode cycle is established. The voltage difference change rate corresponds to the actual charging capacity curve one by one. The capacity decay model of the battery pack in the long-light period supplementary charging and the idle mode cycle is as follows Figure 2 shown.

[0088] It can be seen that the trend curve of the pressure difference change rate is, ΔUdptn=1.1777n+302.11, n represents the nth cycle;

[0089] The actual charging capacity trend curve is, Cin = -0.1329n + 31.044, n represents the nth cycle;

[0090] Through the capacity decay model of the battery pack, the voltage difference change rate and actual charging capacity of the n+1th standby mode and supplementary charging mode cycle are predicted, ΔUdpt_n+1=315.06mV / day is close to the measured data 313.61, and ΔCr_n+1=29.58Ah is close to the measured data 29.79.

Claims

1. A method for evaluating the capacity degradation of a satellite lithium-ion battery pack, characterized in that include: Each working cycle of the lithium-ion battery pack during the long light period includes a rest stage and a supplementary charging stage. During the long light period, for the rest stage and supplementary charging stage of each working cycle, the discharge time, discharge start voltage, discharge cut-off voltage, and charging time are obtained through satellite telemetry; during the long light period, the voltage change of the battery pack during the rest stage is statistically analyzed to obtain the battery pack voltage difference ΔUdi and the voltage difference change rate ΔUdpti of the i-th discharge cycle interval Δtdi; The capacity change of the battery pack during the supplementary charging stage is counted to obtain the charging capacity Cci of the battery pack at the i-th supplementary charging cycle interval Δtci; Calculate the self-discharge current Isdi of the battery pack in the i-th supplementary charging stage and the shelving stage; Calculate the self-discharge capacity Csdi of the battery pack in the i-th supplementary charging stage; Calculate the actual charging capacity Cri of the battery pack in the i-th supplementary charging stage; According to the battery group voltage difference change rate ΔUdpti in the i-th storage period and the actual charging capacity Cri of the battery group in the i-th supplementary charging period, a capacity decay model of the battery group in the long-light period storage period and supplementary charging period is established; The capacity decay model of the battery pack during the long-light period storage and supplementary charging stage refers to: using the battery pack pressure difference change rate ΔUdpti to characterize the actual charging capacity Cri of the battery pack in the same working cycle, and there is a one-to-one correspondence between the battery pack pressure difference change rate ΔUdpti and the actual charging capacity Cri of the battery pack; Through the capacity degradation model of the battery pack, the voltage difference change rate ΔUdpt_i+1 and the actual charging capacity Cr_i+1 in the i+1th shelving stage and the supplementary charging stage are predicted, thereby realizing the capacity degradation assessment of the satellite lithium-ion battery pack.

2. The method for evaluating the capacity degradation of a satellite lithium-ion battery pack according to claim 1, characterized in that: The calculation method of the i-th discharge cycle interval is as follows: Δtdi=td2i-td1i Wherein, td2i represents the discharge end time of the i-th discharge cycle, td1i represents the discharge start time of the i-th discharge cycle, i=1, 2...; The battery pack voltage difference is calculated as follows: ΔUdi=U1i-U2i Where, U1i represents the discharge start voltage of the i-th discharge cycle, and U2i represents the discharge cut-off voltage of the i-th discharge cycle; The pressure difference change rate is calculated as follows: ΔUdpti=ΔUdi / Δtdi.

3. The method for evaluating the capacity degradation of a satellite lithium-ion battery pack according to claim 2, characterized in that: The battery pack charging capacity is calculated as follows: Cci=Ici×Δtci Where, Ici represents the charging current of the i-th supplementary charging stage; Δtci represents the interval of the i-th supplementary charging stage; Δtci=tc2i-tci Wherein, tc2i represents the charging end time of the i-th supplementary charging stage, and tc1i represents the charging start time of the i-th supplementary charging stage.

4. The method for evaluating the capacity degradation of a satellite lithium-ion battery pack according to claim 3, characterized in that: The self-discharge current of the battery pack is calculated as follows: Isdi=Cci / Δtsd Where, Cci represents the charging capacity of the battery pack during the i-th supplementary charging stage; Δtsd represents the self-discharge time during the i-th supplementary charging stage; Δtsd=Δtdi+Δtci.

5. The method for evaluating the capacity degradation of a satellite lithium-ion battery pack according to claim 4, characterized in that: The self-discharge capacity of the battery pack is calculated as follows: Csdi=Isdi×Δtci.

6. The method for evaluating the capacity degradation of a satellite lithium-ion battery pack according to claim 5, characterized in that: The actual charging capacity of the battery pack is calculated as follows: Cri=Cci-Csdi.

7. A satellite lithium-ion battery capacity degradation assessment system, characterized in that include: Module 1: Each working cycle of the lithium-ion battery pack during the long light period includes a rest stage and a supplementary charging stage. During the long light period, for each working cycle of the rest stage and the supplementary charging stage, the discharge time, discharge start voltage, discharge end voltage, and charging time are obtained through satellite telemetry; during the long light period, the voltage change of the battery pack during the rest stage is counted to obtain the battery pack voltage difference ΔUdi and the voltage difference change rate ΔUdpti of the i-th discharge cycle interval Δtdi; The second module: statistics the capacity change of the battery pack during the supplementary charging stage, and obtains the charging capacity Cci of the battery pack at the i-th supplementary charging cycle interval Δtci; Self-discharge current calculation module: calculates the self-discharge current Isdi of the battery pack in the i-th supplementary charging and shelving stage; Self-discharge capacity calculation module: calculates the self-discharge capacity Csdi of the battery pack in the i-th supplementary charging stage; Actual charging capacity calculation module: calculates the actual charging capacity Cri of the battery pack in the i-th supplementary charging stage; Capacity decay model establishment module: according to the battery group voltage difference change rate ΔUdpti in the i-th storage period and the actual charging capacity Cri of the battery group in the i-th supplementary charging period, the capacity decay model of the battery group in the long-light period storage period and supplementary charging period is established; Capacity degradation assessment module: Through the capacity degradation model of the battery pack, the voltage difference change rate ΔUdpt_i+1 and the actual charging capacity Cr_i+1 in the i+1th shelving and supplementary charging stage are predicted, thereby realizing the capacity degradation assessment of the satellite lithium-ion battery pack.

8. The satellite lithium-ion battery capacity degradation assessment system according to claim 7, characterized in that: The calculation method of the i-th discharge cycle interval is as follows: Δtdi=td2i-td1i Wherein, td2i represents the discharge end time of the i-th discharge cycle, td1i represents the discharge start time of the i-th discharge cycle, i=1, 2...; The battery pack voltage difference is calculated as follows: ΔUdi=U1i-U2i Where, U1i represents the discharge start voltage of the i-th discharge cycle, and U2i represents the discharge cut-off voltage of the i-th discharge cycle; The pressure difference change rate is calculated as follows: ΔUdpti=ΔUdi / Δtdi The battery pack charging capacity is calculated as follows: Cci=Ici×Δtci Where, Ici represents the charging current of the i-th supplementary charging stage; Δtci represents the interval of the i-th supplementary charging stage; Δtci=tc2i-tci Wherein, tc2i represents the charging end time of the i-th supplementary charging stage, and tc1i represents the charging start time of the i-th supplementary charging stage; The self-discharge current of the battery pack is calculated as follows: Isdi=Cci / Δtsd Where, Cci represents the battery pack charging capacity during the i-th supplementary charging stage; Δtsd represents the self-discharge time during the i-th supplementary charging mode stage; Δtsd=Δtdi+Δtci.

9. A satellite lithium-ion battery capacity degradation assessment system according to claim 8, characterized in that: The self-discharge capacity of the battery pack is calculated as follows: Csdi=Isdi×Δtci The actual charging capacity of the battery pack is calculated as follows: Cri=Cci-Csdi.

Images