Protection strategy for preventing over-temperature of pre-charging resistor

Abstract

The invention discloses a protection strategy for preventing over-temperature of a pre-charging resistor, and belongs to the technical field of new energy automobile batteries. The real resistance * capacitance value of the whole vehicle is calculated through the pre-charging proportion collected in the same sampling time interval, and the situation that the judgment accuracy is reduced due to the individual difference of the capacitance and the resistance is avoided; collected data of the environment temperature of the whole vehicle serves as the basic temperature of the pre-charging battery before power-on, and a resistance * capacitance allowable threshold value is calculated through temperature correction; if the standing time of the whole vehicle does not meet the set time requirement, the last data value is selected for calculation; whether the pre-charging resistor is over-temperature or not is judged by judging whether the actual value of the resistor meets the theoretical threshold requirement or not, so that over-temperature protection of the pre-charging resistor is realized, and the pre-charging resistor is prevented from being burnt down.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle batteries, and specifically refers to a protection strategy for preventing a pre-charging resistor from overheating. Background Art

[0002] During the continuous power-on and power-off operations of the new energy vehicle battery system, the pre-charging resistor will work continuously in a short period of time, causing the temperature to be too high and burn out. To avoid the burning of the pre-charging resistor, a temperature sensor can be added to the pre-charging resistor for temperature detection, but this method will increase the cost; Chinese patent 201510671774.1 discloses a pre-charging control method and system for electric vehicles, which uses voltage difference and combines a relationship comparison table of pre-charging resistor temperature increase values ​​corresponding to different voltage differences to determine the pre-charging resistor temperature increase value, but does not consider the influence of the actual voltage sampling tolerance. At the same time, there is a deviation in the experimental data through experimental data fitting, and the actual situation of the pre-charging resistor cannot be accurately determined. Summary of the Invention

[0003] The purpose of the present invention is to provide a protection strategy for preventing pre-charging resistors from overheating, which can reduce costs, accurately judge the actual situation of the pre-charging resistors, and effectively prevent the pre-charging resistors from being burned due to excessive temperatures.

[0004] To achieve the above object, the present invention provides a protection strategy for preventing the pre-charge resistor from overheating, comprising the following steps:

[0005] S1. Close the pre-charge relay;

[0006] S2. Close the main negative relay;

[0007] S3. The pre-charge ratio K1 collected for the first time;

[0008] S4. The pre-charge ratio K2 collected for the second time;

[0009] S5. The pre-charge ratio K3 collected for the third time;

[0010] S6. Calculate the sampling accuracy xK and RC value;

[0011] S7. Collect ambient temperature T;

[0012] S8. Determine whether the vehicle's rest time is greater than or equal to the required time;

[0013] S9. If the following conditions are met: the pre-charge resistor is considered to have a temperature equal to the ambient temperature, and the threshold RC1 is calculated.

[0014] S10. If not satisfied: then take the resistance × capacitance value RC' that meets the requirements of the last vehicle rest time and calculate the threshold RC1' at this time;

[0015] S11. Determine whether RC meets the threshold requirement;

[0016] If not, the pre-charge resistor overtemperature fault is reported, the main negative relay is disconnected, the pre-charge relay is disconnected, and the process ends;

[0017] S13. If it is satisfied, determine whether the pre-charge ratio meets the requirements. If it is satisfied, close the main positive relay and disconnect the pre-charge relay. The process ends and the power is successfully turned on. If the pre-charge ratio does not meet the requirements within the specified time, the pre-charge fails and the process ends.

[0018] As a further solution of the present invention: in step S3, the sampling time interval t of each acquisition is the same.

[0019] As a further solution of the present invention: in step S6, the sampling accuracy xK and the RC value are calculated by the sampling time interval t and the pre-charge ratios K1, K2, and K3 collected in steps S3 to S5, and the formula is as follows:

[0020]

[0021] Among them, formulas (2) and (4) are derived from formulas (1) and (3), and formula (5) is derived from formulas (2) and (4). RC is calculated by (5), where RC [Ω·μF] is the actual value of the product of resistance and capacitance; xK [%] is the sampling accuracy of the pre-charge ratio; K1 [%] is the pre-charge ratio collected for the first time; K2 [%] is the pre-charge ratio collected for the second time; K3 [%] is the pre-charge ratio collected for the third time; and t [ms] is the sampling time interval.

[0022] As a further solution of the present invention: in step S9, the calculation formula of the threshold RC1 is as follows:

[0023] RC1=RC×(1+(T R -T)×a×10 -6 )……(6)

[0024] Where: RC1[Ω·μF]: resistance-capacitance product judgment threshold, RC[Ω·μF]: actual value of resistance-capacitance product, T R [℃]: Pre-charge resistor temperature threshold, T[℃]: Ambient temperature, a[ppm / ℃]: Pre-charge resistor temperature coefficient.

[0025] As a further solution of the present invention: in step S10, the calculation formula of the threshold RC1′ is as follows:

[0026] RC1'=RC'×(1+(T R -T)×a×10 -6 )……(7)

[0027] Wherein, RC1′[Ω·μF]: resistance-capacitance product judgment threshold, RC′[Ω·μF]: actual value of the last capacitance-resistance product that satisfies the vehicle’s static time, T R [℃]: Pre-charge resistor temperature threshold, T[℃]: Ambient temperature, a[ppm / ℃]: Pre-charge resistor temperature coefficient.

[0028] Compared with the prior art, the present invention does not require the addition of additional temperature sensors, thus reducing costs; the actual resistance × capacitance value of the entire vehicle is calculated through the pre-charge ratio collected within the same sampling time interval, and the influence of the voltage collection accuracy can be eliminated, thereby accurately judging the actual situation of the pre-charge resistance and avoiding the reduction in judgment accuracy due to individual differences in capacitance and resistance; in the judgment of the initial temperature, if the standing time meets the requirements, the ambient temperature will be used; if the requirements are not met, the last calculated result will be used as a benchmark to further accurately judge the actual situation of the pre-charge resistance and effectively prevent the pre-charge resistance from being burned due to excessive temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention is a flow chart of a protection strategy for preventing a pre-charge resistor from overheating. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings.

[0031] A protection strategy for preventing pre-charge resistors from overheating includes the following steps: calculating the actual resistance × capacitance value of the entire vehicle using pre-charge ratios collected within the same sampling time interval to avoid reduction in judgment accuracy due to individual differences in capacitance and resistance; using collected data on the entire vehicle's ambient temperature as the base temperature of the pre-charged battery before power-on, and calculating an allowable resistance × capacitance threshold through temperature correction; if the entire vehicle's rest time does not meet a set time requirement, using the last data value for calculation to avoid inaccurate judgment due to inconsistency between the resistor temperature and the ambient temperature during operation; and determining whether the pre-charge resistor is overheated by determining whether the actual resistance value meets a theoretical threshold requirement, thereby implementing overtemperature protection for the pre-charge resistor and preventing it from burning out.

[0032] The specific steps include:

[0033] S1. Close the pre-charge relay;

[0034] S2. Close the main negative relay;

[0035] S3. The pre-charge ratio K1 collected for the first time;

[0036] S4. The pre-charge ratio K2 collected for the second time;

[0037] S5. The pre-charge ratio K3 collected for the third time;

[0038] S6. Calculate the sampling accuracy xK. The sampling time interval t is used to collect the precharge ratios K1, K2, and K3. The resistance R, capacitance C, and sampling time interval t are determined by the product itself. Therefore, the values ​​of the three parameters R, C, and t are consistent for the first, second, and third times. Therefore, formulas (1) and (3) are used to derive formulas (2) and (4). Formulas (2) and (4) are used to derive formula (5), and RC is calculated through (5).

[0039]

[0040] Where, RC[Ω·μF]: actual value of capacitance-resistance product; xK[%]: precharge ratio sampling accuracy; K1[%]: precharge ratio acquired for the first time; K2[%]: precharge ratio acquired for the second time; K3[%]: precharge ratio acquired for the third time; t[ms]: sampling interval;

[0041] S7. Collect ambient temperature T;

[0042] S8. Determine whether the vehicle's rest time is greater than or equal to the required time (used to determine whether the pre-charge resistor temperature is equal to the ambient temperature at this time);

[0043] S9. If the following is satisfied, it is assumed that the temperature of the pre-charge resistor is equal to the ambient temperature. The threshold RC1 at this time is calculated as shown in formula (6):

[0044] RC1=RC×(1+(T R -T)×a×10 -6 )……(6)

[0045] Where: RC1[Ω·μF]: capacitance-resistance product judgment threshold, RC[Ω·μF]: capacitance-resistance product actual value, T R [℃]: pre-charge resistance temperature threshold, T[℃]: ambient temperature, a[ppm / ℃]: pre-charge resistance temperature coefficient;

[0046] S10. If not satisfied: then take the resistance × capacitance value RC′ that met the requirement during the last vehicle rest time and calculate the threshold RC1′ at this time, see formula (7):

[0047] RC1'=RC'×(1+(T R -T)×a×10 -6 )……(7)

[0048] Wherein: RC1′[Ω·μF]: capacitance-resistance product judgment threshold; RC′[Ω·μF]: actual capacitance-resistance product value of the last time the vehicle satisfies the vehicle rest time; TR[℃]: pre-charge resistor temperature threshold; T[℃]: ambient temperature; a[ppm / ℃]: pre-charge resistor temperature coefficient;

[0049] Note: When continuous pre-charging or other working conditions cause the pre-charging resistor temperature to rise, the vehicle's rest time does not meet the requirements. Therefore, the threshold value calculation will be performed based on the condition that the vehicle's rest time previously met the requirements (the calculation is performed under the condition that the pre-charging resistor is at the same temperature as the ambient temperature).

[0050] S11. Determine whether RC meets the threshold requirement;

[0051] If not, the pre-charge resistor overtemperature fault is reported, the main negative relay is disconnected, the pre-charge relay is disconnected, and the process ends;

[0052] S13. If it is satisfied, determine whether the pre-charge ratio meets the requirements. If it is satisfied, close the main positive relay and disconnect the pre-charge relay. The process ends and the power is successfully turned on. If the pre-charge ratio does not meet the requirements within the specified time, the pre-charge fails and the process ends.

[0053] Example:

[0054] The system parameter settings are shown in the following table:

[0055]

[0056]

[0057] 1. The vehicle's static time meets the requirements

[0058] S1. Close the pre-charge relay;

[0059] S2. Close the main negative relay;

[0060] S3. The precharge ratio collected during the first 10ms is 4.93%;

[0061] S4. The precharge ratio collected at the second 20ms is 9.61%;

[0062] S5. The precharge ratio collected at the third 30ms is 14.07%;

[0063] S6. Calculate RC = 0.2 using formula (5);

[0064] S7. If the resting time is satisfied;

[0065] S8. Calculated by formula (6), RC1 = 0.2235;

[0066] S9. At this time, RC<RC1, and it is determined that the pre-charge resistor is not over-temperature.

[0067] 2. The standing time does not meet the requirements (continuous pre-charging condition)

[0068] S1. The first pre-charge can meet the requirements. See the example of the vehicle's static time meeting the requirements.

[0069] S2. After multiple pre-charges in a short period of time, assuming the pre-charge resistor temperature reaches 275°C, power is turned on. At 275°C, the actual resistance of the pre-charge resistor is 112.5Ω.

[0070] S3. The precharge ratio collected during the first 10ms is 4.42%;

[0071] S4. The precharge ratio collected at the second 20ms is 8.65%;

[0072] S5. The precharge ratio collected at the third 30ms is 12.69%;

[0073] S6. Calculated by formula (5), RC = 0.2235;

[0074] If the rest time is not satisfied, use the resistance that satisfied the rest time last time × the capacitance RC′, where RC′ = 0.2 (see the example of vehicle rest time meeting the requirement).

[0075] S8. Calculate RC1′=0.2235 using Formula 7;

[0076] S9. At this time, RC is not less than RC1′, and the pre-charge resistor overtemperature fault is reported.

[0077] The data acquisition process in the above embodiment is performed through a high-voltage sampling board, which transmits the acquired data to the BMS main board, which is then controlled by the BMS main board.

Claims

1. A protection strategy for preventing pre-charge resistor from overheating, characterized in that: The following steps are involved: S1. Close the pre-charge relay; S2. Close the main negative relay; S3. The pre-charge ratio K1 collected for the first time; S4. The pre-charge ratio K2 collected for the second time; S5. The pre-charge ratio K3 collected for the third time; S6. Calculate the sampling accuracy xK and RC value; S7. Collect ambient temperature T; S8. Determine whether the vehicle's rest time is greater than or equal to the required time; S9. If the following conditions are met: the pre-charge resistor is considered to have a temperature equal to the ambient temperature, and the threshold RC1 is calculated. S10. If not satisfied: then take the resistance × capacitance value RC' that meets the requirements of the last vehicle rest time and calculate the threshold RC1' at this time; S11. Determine whether RC meets the threshold requirement; If not, the pre-charge resistor overtemperature fault is reported, the main negative relay is disconnected, the pre-charge relay is disconnected, and the process ends; S13. If it is satisfied, determine whether the pre-charge ratio meets the requirements. If it is satisfied, close the main positive relay and disconnect the pre-charge relay. The process ends and the power is successfully turned on. If the pre-charge ratio does not meet the requirements within the specified time, the pre-charge fails and the process ends.

2. A protection strategy for preventing pre-charge resistor from overheating according to claim 1, characterized in that: Step S3 refers to S6, where the sampling time interval t for each acquisition is the same.

3. A protection strategy for preventing pre-charge resistor from overheating according to claim 2, characterized in that: In step S6, the sampling accuracy xK and the RC value are calculated using the sampling time interval t and the pre-charge ratios K1, K2, and K3 collected in steps S3 to S5. The formula is as follows: Among them, formulas (2) and (4) are derived from formulas (1) and (3), and formula (5) is derived from formulas (2) and (4). RC is calculated by (5), where RC [Ω·μF] is the actual value of the product of resistance and capacitance; xK [%] is the sampling accuracy of the pre-charge ratio; K1 [%] is the pre-charge ratio collected for the first time; K2 [%] is the pre-charge ratio collected for the second time; K3 [%] is the pre-charge ratio collected for the third time; and t [ms] is the sampling time interval.

4. A protection strategy for preventing pre-charge resistor from overheating according to claim 2, characterized in that: In step S9, the calculation formula of the threshold RC1 is as follows: RC1=RC×(1+(T R -T)×a×10 -6 )……(6) Where: RC1[Ω·μF]: resistance-capacitance product judgment threshold, RC[Ω·μF]: actual value of resistance-capacitance product, T R [℃]: Pre-charge resistor temperature threshold, T[℃]: Ambient temperature, a[ppm / ℃]: Pre-charge resistor temperature coefficient.

5. A protection strategy for preventing pre-charge resistor from overheating according to claim 2, characterized in that: In step S10, the threshold RC1′ is calculated as follows: RC1'=RC'×(1+(T R -T)×a×10 -6 )……(7) Wherein: RC1′[Ω·μF]: resistance-capacitance product judgment threshold; RC′[Ω·μF]: actual value of the last capacitance-resistance product that meets the vehicle's rest time; TR[℃]: pre-charge resistor temperature threshold; T[℃]: ambient temperature; a[ppm / ℃]: pre-charge resistor temperature coefficient.

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