A control method for over-temperature and terminal derating of an energy storage integrated system

Abstract

The application discloses a control method for over-temperature and terminal derating of an energy storage integrated system, and specifically comprises the following steps: obtaining over-temperature derating power, obtaining discharging linear derating power P 放线性 , obtaining charging linear derating power P 充线性 , selecting the minimum power from the over-temperature derating power P 超温 , the linear derating power P 放线性 and the set power P 放电设定 and issuing the minimum power to an energy storage converter as operating power in a discharging process, selecting the minimum power from the over-temperature derating power P 超温 , the linear derating power P 充线性 and the set power P 充电设定 and issuing the minimum power to the energy storage converter as operating power in a charging process. The method has the beneficial effects that the over-temperature derating and terminal derating are set to ensure that a battery pack works safely within a set temperature, and the method of derating avoids frequent protection and alarm caused by over-temperature and over-voltage, and maximizes the income of a user.

Description

Technical Field

[0001] This invention relates to the technical field of derating control methods, specifically to a method for controlling overheating and end-point derating in an integrated energy storage system. Background Technology

[0002] Currently, battery packs in energy storage systems mainly use lithium iron phosphate batteries. Lithium batteries generate heat during charging and discharging, primarily due to the following reasons: 1. Chemical reaction: During discharge, the positive and negative electrode materials undergo a chemical reaction under the action of the electrolyte, generating a certain amount of heat; 2. Resistance heat: There is a certain resistance inside the battery, and the movement of charges generates a certain amount of heat; 3. Over-discharge: When the battery is over-discharged, it can cause uncontrolled internal reactions that release a large amount of heat, potentially leading to battery damage or explosion, or even a fire.

[0003] In practical applications, a higher charging and discharging power is desired to maximize efficiency. However, pursuing high power can introduce thermal runaway due to cell overheating, reducing battery pack lifespan and even causing other unpredictable safety issues such as fires. Therefore, when the cell temperature becomes too high, it is necessary to reduce the power or even shut down the system. Figure 1 As shown, the curve is relatively flat when the SOC is between 20% and 80%, while the voltage change is steeper when it is below 20% and above 80%. Due to its characteristics, the voltage changes rapidly at the end of charging and discharging. If the power is not derated at the end of charging and discharging, it will affect the service life of the battery pack and even its safety.

[0004] Therefore, there is an urgent need for a method that can control the power of the energy storage converter based on the temperature of the battery cell and the voltage of the battery cell at the end of charging and discharging, thereby achieving derating. Summary of the Invention

[0005] To address the aforementioned problems, and especially the shortcomings of existing technologies, this invention provides a method for controlling overheating and end-point derating in an integrated energy storage system, which can solve the above problems.

[0006] To achieve the above objectives, the present invention employs the following technical means:

[0007] A method for controlling overheating and end-point derating in an integrated energy storage system is described below:

[0008] Obtain over-temperature derating power:

[0009] The temperature of each cell is collected by the BMS system, and the highest and lowest temperatures of individual cells at the cluster level are statistically analyzed. The energy storage integration system uses the highest temperature of individual cells reported by the BMS system to classify the highest temperature of cells into four derating levels. Each level is set with a percentage derating. The derating level can be obtained by judging the over-temperature level of individual cells.

[0010] When overheating occurs, the power after overheating derating is P. 超温 =P 额定 *Class%, where P 超温 For overheating derating power, P 额定 The rated power is indicated by Class%, which is the derating percentage corresponding to the overheating class.

[0011] Obtain the linear derating power P of the discharge 放线性 :

[0012] V2 is set as the linear starting voltage at the end of discharge, V1 as the linear cutting-off voltage at the end of discharge, V0 as the discharge stop voltage, P1 as the linear starting power at the end of discharge, and P2 as the cutting-off power at the end of discharge. The linear discharge equation y = k1x + b1 is obtained from points (P1, V2) and (P2, V1), where k1 is the slope of the linear discharge and b1 is the bias of the linear discharge. The energy storage integrated system obtains the lowest voltage V of the single cell.

[0013] When the minimum voltage V of a single cell is greater than or equal to V2, P 放线性 =P1;

[0014] When the minimum voltage V of a single cell is greater than V1 and less than V2, linear derating is triggered. 放线性 =k1*V+b1;

[0015] When the minimum voltage V of a single unit is in the range of not greater than V1 and not less than V0, P 放线性 =P2;

[0016] Obtain the linear derating power P of the charging circuit 充线性 :

[0017] V3 is set as the linear starting voltage at the end of charging, V4 as the linear cutting off voltage at the end of charging, V5 as the voltage to stop charging, P3 as the linear starting power at the end of charging, and P4 as the linear cutting off power at the end of charging. The linear charging equation y = k2x + b2 is obtained from points (P3, V3) and (P4, V4), where k2 is the slope of the linear charging and b2 is the bias of the linear charging. The energy storage integrated system obtains the highest voltage V of the single cell.

[0018] When the highest voltage V of a single cell is less than or equal to V3, P 充线性 =P3;

[0019] When the highest voltage V of a single cell is greater than V3 and less than V4, linear derating is triggered. 充线性 =k2*V+b2;

[0020] When the highest voltage V of a single unit is in the range of not less than V4 and not greater than V5, P 充线性 =P4;

[0021] Select operating power:

[0022] During the discharge process, the energy storage integrated system experiences over-temperature derating of power P. 超温 Linear derating power P 放线性 There is also the power setting P issued by the user through the EMS policy. 放电设定 The minimum power is selected and sent to the energy storage converter as the operating power.

[0023] During charging, the energy storage integrated system experiences over-temperature derating of power P. 超温 Linear derating power P 充线性 There is also the power setting P issued by the user through the EMS policy. 充电设定 The minimum power is selected and sent to the energy storage converter as the operating power.

[0024] A further aspect of the present invention is that the temperatures corresponding to the four derating levels in the obtained over-temperature derating power are 38°C, 40°C, 42°C, and 44°C, respectively. The percentage derating corresponding to 38°C is 90%, the percentage derating corresponding to 40°C is 75%, the percentage derating corresponding to 42°C is 50%, and the percentage derating corresponding to 44°C is 0%.

[0025] The beneficial effects of this invention are:

[0026] This invention ensures the battery pack operates safely within a set temperature range by setting over-temperature derating and end-of-life derating. By derating, it avoids frequent protection and alarms caused by over-temperature or under-voltage, thus maximizing the user's benefits. Attached Figure Description

[0027] Figure 1 This is a graph showing the OCV-SOC of lithium iron phosphate according to the present invention;

[0028] Figure 2 This is a flowchart of the over-temperature level determination process for a single battery cell according to the present invention;

[0029] Figure 3 This is a schematic diagram of the linear charging and discharging at the end of the present invention;

[0030] Figure 4 This is a flowchart of the linear derating at the end of the charge and discharge cycle of the present invention;

[0031] Figure 5This is a flowchart of the power output from the charging and discharging terminal of the present invention to the energy storage converter. Detailed Implementation

[0032] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example

[0034] A method for controlling overheating and end-point derating in an integrated energy storage system, the specific method is as follows:

[0035] Obtain over-temperature derating power:

[0036] The temperature of each cell is collected by the BMS system, and the highest and lowest temperatures of individual cells at the cluster level are statistically analyzed. The energy storage integration system uses the highest temperature of individual cells reported by the BMS system to classify the highest temperature of cells into four derating levels. Each level is set with a percentage derating. The derating level can be obtained by judging the over-temperature level of individual cells.

[0037] The over-temperature derating parameters are composed of the following parameters:

[0038] Single cell derating temperature hysteresis 2℃ Level 4 derating temperature 44℃ Level 3 descent temperature 42℃ Secondary descent temperature 40℃ Level 1 descent temperature 38℃ Level 1 Overheating Deduction Percentage 90% of rated power Level 2 overheating reduction percentage 75% of rated power Level 3 overheating reduction percentage 50% of rated power Level 4 overheating reduction percentage 0%*Rated Power

[0039] Table 1 Over-temperature derating setting parameters

[0040] To explain the over-temperature derating process in detail, let's assume that the battery is being charged at the rated power of 100kW. Due to the high charging power, the battery cells accumulate heat, and the cell temperature continues to rise. When the highest detected cell temperature reaches 38℃, the first-level derating temperature is met. The charging power is then reduced to 100kW * first-level over-temperature derating percentage = 100kW * 90% = 90kW. If charging continues at the 90kW after the first-level derating, the temperature still rises to the second-level derating power. The power is then adjusted to 100kW * second-level over-temperature derating percentage = 100kW * 75% = 75kW, further reducing the charging power. This reduces the heat generated by the battery cell. However, due to environmental factors or blockage of the vents, the battery cell temperature may rise further, triggering Level 3 over-temperature derating or Level 4 derating shutdown. The method is similar to Level 1 and Level 2 derating and will not be described further. If the battery cell temperature decreases after reaching Level 2 over-temperature derating and drops to: Level 2 derating temperature - single cell derating temperature hysteresis = 40℃ - 2℃ = 38℃, then Level 2 over-temperature derating will be exited and Level 1 over-temperature derating will be returned. If the temperature continues to decrease to: Level 1 derating temperature - single cell derating temperature hysteresis = 38℃ - 2℃ = 36℃, then the rated power of 100kW charging will be restored.

[0041] The specific implementation process flow is as follows: Figure 2 As shown, the deduction level can be obtained through the above process. Class=0 means that the overheating level has not been reached, Class=1 means that the level of overheating has been reached, Class=2 means that the level of overheating has been reached, Class=4 means that the level of overheating has been reached, and Class=8 means that the level of overheating has been reached.

[0042] When overheating occurs, the power of the energy storage converter after overheating derating is P. 超温 =P 额定 *Class%, where P 超温 For overheating derating power, P 额定 The rated power is indicated by Class%, which is the derating percentage corresponding to the overheating class.

[0043] Obtaining linear derating power:

[0044] The energy storage system acquires the highest and lowest voltages of individual cells in the cluster-level battery pack. The BMS system collects the voltage of each cell and calculates the highest and lowest voltages of individual cells in the cluster, performing linear derating at the end of the charge and discharge cycle.

[0045] Obtain the linear derating power P of the discharge 放线性 :

[0046] like Figure 3 and Figure 4 As shown, V2 is set as the linear starting voltage at the end of discharge, V1 is the linear cutting off voltage at the end of discharge, V0 is the discharge stop voltage, P1 is the linear starting power at the end of discharge, and P2 is the cutting off power at the end of discharge. The linear discharge equation y = k1x + b1 is obtained from points (P1, V2) and (P2, V1), where k1 is the slope of the linear discharge and b1 is the bias of the linear discharge. The energy storage integrated system obtains the lowest voltage V of the single cell.

[0047] When the minimum voltage V of a single cell is greater than or equal to V2, P 放线性 =P1;

[0048] When the minimum voltage V of a single cell is greater than V1 and less than V2, linear derating is triggered. 放线性 =k1*V+b1;

[0049] When the minimum voltage V of a single unit is in the range of not greater than V1 and not less than V0, P 放线性 =P2;

[0050] Obtain the linear derating power P of the charging circuit 充线性 :

[0051] like Figure 3 and Figure 4As shown, V3 is set as the linear starting voltage at the end of charging, V4 as the linear cutting off voltage at the end of charging, V5 as the stopping voltage for charging, P3 as the linear starting power at the end of charging, and P4 as the linear cutting off power at the end of charging. The linear charging equation y = k2x + b2 is obtained from points (P3, V3) and (P4, V4), where k2 is the slope of the linear charging and b2 is the bias of the linear charging. The energy storage integrated system obtains the highest voltage V of the single cell.

[0052] When the highest voltage V of a single cell is less than or equal to V3, P 充线性 =P3;

[0053] When the highest voltage V of a single cell is greater than V3 and less than V4, linear derating is triggered. 充线性 =k2*V+b2;

[0054] When the highest voltage V of a single unit is in the range of not less than V4 and not greater than V5, P 充线性 =P4;

[0055] Select operating power:

[0056] like Figure 5 As shown, during the discharge process, the energy storage integrated system experiences a power derating of P due to over-temperature conditions. 超温 Linear derating power P 放线性 There is also the power setting P issued by the user through the EMS policy. 放电设定 The minimum power is selected and sent to the power storage converter (PCS) as the operating power.

[0057] like Figure 5 As shown, during the charging process, the energy storage integrated system experiences a power derating of P due to over-temperature conditions. 超温 Linear derating power P 充线性 There is also the power setting P issued by the user through the EMS policy. 充电设定 The minimum power is selected and sent to the energy storage converter (PCS) as the operating power.

[0058] The examples provided in this invention are not intended to limit the implementation. Those skilled in the art will recognize that various variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of this invention.

Claims

1. A method for controlling overheating and end-point derating in an integrated energy storage system, characterized in that, The specific method is as follows: Obtain over-temperature derating power: The temperature of each cell is collected by the BMS system, and the highest and lowest temperatures of individual cells at the cluster level are statistically analyzed. The energy storage integration system uses the highest temperature of individual cells reported by the BMS system to classify the highest temperature of cells into four derating levels. Each level is set with a percentage derating. The derating level can be obtained by judging the over-temperature level of individual cells. When overheating occurs, the power after overheating derating is P. 超温 =P 额定 *Class%, where P 超温 For overheating derating power, P 额定 The rated power is indicated by Class%, which is the derating percentage corresponding to the overheating class. Obtain the linear derating power P of the discharge 放线性 : V2 is set as the linear starting voltage at the end of discharge, V1 as the linear cutting-off voltage at the end of discharge, V0 as the discharge stop voltage, P1 as the linear starting power at the end of discharge, and P2 as the cutting-off power at the end of discharge. The linear discharge equation y = k1x + b1 is obtained from points (P1, V2) and (P2, V1), where k1 is the slope of the linear discharge and b1 is the bias of the linear discharge. The energy storage integrated system obtains the lowest voltage V of the single cell. When the minimum voltage V of a single cell is greater than or equal to V2, P 放线性 =P1; When the minimum voltage V of a single cell is greater than V1 and less than V2, linear derating is triggered. 放线性 =k1*V+b1; When the minimum voltage V of a single unit is in the range of not greater than V1 and not less than V0, P 放线性 =P2; Obtain the linear derating power P of the charging circuit 充线性 : V3 is set as the linear starting voltage at the end of charging, V4 as the linear cutting off voltage at the end of charging, V5 as the voltage to stop charging, P3 as the linear starting power at the end of charging, and P4 as the linear cutting off power at the end of charging. The linear charging equation y = k2x + b2 is obtained from points (P3, V3) and (P4, V4), where k2 is the slope of the linear charging and b2 is the bias of the linear charging. The energy storage integrated system obtains the highest voltage V of the single cell. When the highest voltage V of a single cell is less than or equal to V3, P 充线性 =P3; When the highest voltage V of a single cell is greater than V3 and less than V4, linear derating is triggered. 充线性 =k2*V+b2; When the highest voltage V of a single unit is in the range of not less than V4 and not greater than V5, P 充线性 =P4; Select operating power: During the discharge process, the energy storage integrated system experiences over-temperature derating of power P. 超温 Linear derating power P 放线性 There is also the power setting P issued by the user through the EMS policy. 放电设定 The minimum power is selected and sent to the energy storage converter as the operating power. During charging, the energy storage integrated system experiences over-temperature derating of power P. 超温 Linear derating power P 充线性 There is also the power setting P issued by the user through the EMS policy. 充电设定 The minimum power is selected and sent to the energy storage converter as the operating power.

2. The method for controlling overheating and end-point derating in an integrated energy storage system according to claim 1, characterized in that, The temperatures corresponding to the four derating levels in the obtained over-temperature derating power are 38℃, 40℃, 42℃, and 44℃, respectively. The percentage derating corresponding to 38℃ is 90%, the percentage derating corresponding to 40℃ is 75%, the percentage derating corresponding to 42℃ is 50%, and the percentage derating corresponding to 44℃ is 0%.

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