SOC charging and discharging method based on lithium ion battery and super capacitor hybrid energy storage system

Abstract

The invention discloses an SOC (State of Charge) charging and discharging method based on a lithium ion battery and super capacitor hybrid energy storage system, which is used for partitioning charging and discharging state-of-charge curves of a lithium ion battery and a super capacitor into an over-charging region, a normal region and an over-discharging region. Comprising the following steps: adding an overcharge correction area between an overcharge area and a normal area of a charge state curve of the lithium ion battery and the super capacitor; and adding an over-discharge correction area between an over-discharge area and a normal area of the charge state curve of the lithium ion battery and the super capacitor. The main technical scheme has the advantages that the transition states of the lithium ion battery and the super capacitor in the charging and discharging process are controlled, sudden change of voltage and current of the system is effectively reduced, the service life of the energy storage device is prolonged, and when the load change is large, different partitions are set for the lithium ion battery and the super capacitor respectively, so that the energy storage efficiency is improved. The super capacitor can quickly respond to the transient power requirement, and the lithium ion battery bears a low-frequency load, so that the charging and discharging process is more stable, and the cycle frequency of the battery is reduced.

Description

Technical Field

[0001] The present invention relates to the field of charge and discharge control, and in particular to a SOC charge and discharge method based on a hybrid energy storage system of a lithium-ion battery and a supercapacitor. Background Art

[0002] The commonly used hybrid energy storage system is the lithium-ion battery-supercapacitor hybrid energy storage system. In this system, lithium-ion batteries and supercapacitors play different roles. Lithium-ion batteries are energy-type storage devices with the characteristics of high energy density, low power density, and slow response. Their charge and discharge SOC changes are relatively smooth; supercapacitors are power-type energy storage devices with the characteristics of high power density, low energy density, and fast response. Their charge and discharge SOC changes have greater fluctuations than lithium-ion batteries, and they are prone to reaching overcharge and over-discharge thresholds during continuous charging and discharging.

[0003] Due to the limited capacity of lithium-ion batteries and supercapacitors, it is inevitable that the remaining capacity will be insufficient to meet the current power demand during the charging and discharging process. If lithium-ion batteries and supercapacitors continue to work according to the current charging and discharging instructions, overcharging and over-discharging will occur, causing irreversible damage to the energy storage device.

[0004] The traditional overcharge and overdischarge protection of energy storage system divides SOC (state of charge) into three areas: overcharge area, overdischarge area and normal working area. Fig.10 In the charging state, when the SOC rises to the overcharge threshold (SOCmax), charging is stopped; in the discharging state, when the SOC drops to the over-discharge threshold (SOCmin), discharging is stopped. This method takes into account the constraints of the state of charge on the charging and discharging behavior, and to a certain extent avoids overcharging and over-discharging of the energy storage system. It has certain effectiveness, but because it does not consider the characteristics of different types of energy storage systems, and does not consider the differences in the discharge of lithium-ion batteries and supercapacitors, some energy storage systems are prone to overcharge and over-discharge thresholds, which will cause frequent action of protection instructions. At the same time, the sudden change of the state of the boundary between the overcharge and over-discharge thresholds and the normal working area will also cause sudden changes in the system voltage and current, which will have a certain impact on the reliability of the energy storage device and the stability of the system. Therefore, this method has certain limitations. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to solve the problem in the prior art that the sudden change of the state of the boundary point between the overcharge and over-discharge thresholds and the normal working area will also cause a sudden change in the system voltage and current, which will have a certain impact on the reliability of the energy storage device and the system stability. Therefore, this method has certain limitations. In addition, the SOC partitioning does not take into account the differences between lithium-ion batteries and supercapacitors during discharge. Further, a SOC charging and discharging method based on a hybrid energy storage system of lithium-ion batteries and supercapacitors is provided. In order to control the transition state of lithium-ion batteries and supercapacitors during the charging and discharging process by introducing an over-discharge correction zone and an overcharge correction zone, the sudden change of system voltage and current is effectively reduced, and the service life of the energy storage device is extended. When the load changes greatly, different partitions are set for lithium-ion batteries and supercapacitors respectively, and the supercapacitor can respond quickly to transient power demands, while the lithium-ion battery bears the low-frequency load, so that the charging and discharging process is smoother and the battery cycle frequency is reduced.

[0006] Technical solution:

[0007] The present application proposes a SOC charging and discharging method based on a hybrid energy storage system of a lithium-ion battery and a supercapacitor, which is used to partition the state of charge curves of the lithium-ion battery and the supercapacitor into an overcharge zone, a normal zone, and an over-discharge zone, including:

[0008] Add an overcharge correction zone between the overcharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors;

[0009] Add an over-discharge correction zone between the over-discharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors;

[0010] Construct different correction zone ranges for the overcharge correction zone and over-discharge correction zone on the state of charge curves of lithium-ion batteries and supercapacitors respectively;

[0011] Correct the state of charge curves of the overcharge correction area and over-discharge correction area of ​​lithium-ion batteries and supercapacitors.

[0012] Beneficial effects: Introducing overcharge correction zone and over-discharge correction zone: In the SOC curves of lithium-ion batteries and supercapacitors, an overcharge correction zone is added between the overcharge zone and the normal zone, and an over-discharge correction zone is added between the over-discharge zone and the normal zone, respectively. This can avoid drastic power fluctuations when the SOC is close to the limit state, and effectively reduce the impact on the energy storage unit;

[0013] According to the characteristics of lithium-ion batteries and supercapacitors, different SOC ranges are defined in the overcharge correction area and the over-discharge correction area. Lithium-ion batteries are energy storage devices and are suitable for working in a smoother transition area, while supercapacitors are power storage devices and are more suitable for rapid charge and discharge correction in a tighter range.

[0014] In the overcharge correction zone and over-discharge correction zone, specific charge and discharge protection strategies are applied to lithium-ion batteries and supercapacitors respectively. For example, in the overcharge correction zone of lithium-ion batteries, the charging current is gradually reduced to prevent the thermal effect caused by overcharging; in the over-discharge correction zone of supercapacitors, the discharge rate is gradually reduced to protect its transient power output capability.

[0015] Preferably, the ranges of different areas of the state of charge of the lithium-ion battery are allocated as follows:

[0016] 0 to 20% of the state of charge is the over-discharge zone;

[0017] 20% to 40% of the state of charge is the over-discharge correction zone;

[0018] 40% to 60% of the state of charge is the normal range;

[0019] 60% to 80% of the state of charge is the overcharge correction zone;

[0020] 80% to 100% state of charge is the overcharge zone;

[0021] Among them, 20% is the over-discharge threshold, 40% is the over-discharge correction threshold, 60% is the over-charge correction threshold, and 80% is the over-charge threshold. Beneficial effects: By adding the over-discharge correction zone and the over-charge correction zone, the charge and discharge current can be gradually reduced before entering the limit SOC interval (over-discharge zone and over-charge zone), avoiding the sudden stop of the battery when reaching the limit threshold, reducing the system instability caused by power fluctuations, and limiting the SOC variation range of the lithium-ion battery during the charge and discharge process. The battery is always in the best working state and avoids entering the limit area, thereby reducing the impact of deep charge and discharge on the battery and extending the battery life.

[0022] Preferably, the ranges of different areas of the state of charge of the supercapacitor are allocated as follows:

[0023] 0 to 15% of the state of charge is the over-discharge zone;

[0024] 15% to 30% of the state of charge is the over-discharge correction zone;

[0025] 30% to 70% of the state of charge is the normal range;

[0026] 70% to 95% of the state of charge is the overcharge correction zone;

[0027] 95% to 100% state of charge is the overcharge zone;

[0028] Among them, 15% is the over-discharge threshold, 30% is the over-discharge correction threshold, 70% is the over-charge correction threshold, and 95% is the over-charge threshold. Beneficial effects: By dividing the over-discharge area and the over-charge area into smaller ranges and setting the over-discharge and over-charge correction areas, it is helpful to gradually reduce the charge and discharge rate when approaching the limit SOC, avoid supercapacitor loss caused by excessive charging and discharging, and extend its service life. Under the adjustment of the over-discharge correction area and the over-charge correction area, the supercapacitor can flexibly manage power output to ensure that it provides efficient energy release within a wider SOC range, while reducing the stress on the system caused by frequent charging and discharging conversions.

[0029] Preferably, the state of charge curve of the lithium-ion battery overcharge correction zone is corrected by the following formula:

[0030] P′1=k bat1 P1;

[0031] Among them, P'1 is the correction charging power of the lithium-ion battery overcharge correction area, k bat1 It is the power correction coefficient of lithium-ion battery under charging state, and P1 is the charging power reference value of lithium-ion battery.

[0032] Preferably, the k bat1 The calculation formula is as follows:

[0033]

[0034] Among them, SOC max1 is the overcharge threshold of lithium-ion battery, SOC high1 is the overcharge correction threshold of lithium-ion batteries, SOCt is the current state of charge of the device, and the beneficial effect is: when charging close to the overcharge threshold SOC max1 The charging power reference value P1 is gradually corrected to a lower charging power P'1, which effectively slows down the temperature rise during the charging process, avoids the high temperature problem of lithium-ion batteries caused by rapid charging, and improves the safety of the battery. When the lithium-ion battery gradually reduces the charging rate in the overcharge correction zone, it can prevent the sudden change of charging current from causing voltage fluctuations, thereby improving the stability of the entire energy storage system when it is close to the limit charging state and ensuring the reliability of the system.

[0035] Preferably, the state of charge curve of the lithium-ion battery over-discharge correction zone is corrected by the following formula:

[0036] P′2=k bat2 P2;

[0037] Where P'2 is the corrected discharge power in the over-discharge correction zone of the lithium-ion battery, k bat2 is the power correction coefficient of the lithium-ion battery in the discharge state, and P2 is the discharge power reference value of the lithium-ion battery.

[0038] Preferably, the k bat2 The calculation formula is as follows:

[0039]

[0040] Among them, SOC min1 is the over-discharge threshold of lithium-ion batteries, SOC low1 is the over-discharge correction threshold of lithium-ion batteries, SOC t The current state of charge of the device is beneficial. When the SOC is close to the over-discharge threshold SOC min1 When the correction factor k bat2 The discharge power reference value P2 is gradually reduced to a lower discharge power P'2, thereby avoiding battery damage caused by deep discharge and helping to extend the battery life.

[0041] Preferably, the state of charge curve of the supercapacitor overcharge correction zone is corrected by the following formula:

[0042] P′3=k sc1 P3;

[0043] Where P'3 is the corrected charging power in the supercapacitor overcharge correction zone, k sc1 is the power correction coefficient of the supercapacitor under charging state, and P3 is the charging power reference value of the supercapacitor.

[0044] Preferably, the k sc1 The calculation formula is as follows:

[0045]

[0046] Among them, SOC max2 is the supercapacitor overcharge threshold, SOC t The current state of charge of the device, beneficial effect: when the SOC is close to the overcharge threshold SOC of the supercapacitor max2 When the correction factor k sc1 It will gradually decrease, adjusting the charging power reference value P3 to a smaller modified charging power P'3, reducing the thermal effect caused by excessive current during charging and ensuring the safety of the supercapacitor.

[0047] Preferably, the correction of the state of charge curve of the supercapacitor over-discharge correction zone includes the following formula:

[0048] P′4=k sc2 P4;

[0049] Where P'4 is the corrected discharge power in the supercapacitor over-discharge correction zone, k bat2is the power correction coefficient of the supercapacitor in the discharge state, and P4 is the discharge power reference value of the supercapacitor.

[0050] Preferably, the k bat2 The calculation formula is as follows:

[0051]

[0052] Among them, SOC min2 is the supercapacitor over-discharge threshold, SOC t The current state of charge of the device, beneficial effect: when the SOC of the supercapacitor is close to the over-discharge threshold SOC min When the correction factor k bat2 Gradually reduce and automatically adjust the discharge power P'4 to a lower level to avoid damage to the life of the supercapacitor caused by deep discharge, which helps to extend the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a schematic diagram of the charge and discharge state of charge (SOC) region of the present invention;

[0054] Figure 2 It is a schematic diagram of the charge and discharge state of charge (SOC) region of the lithium-ion battery of the present invention;

[0055] Figure 3 It is a schematic diagram of the charge and discharge state of charge (SOC) region of the supercapacitor of the present invention;

[0056] Figure 4 It is a schematic diagram of the power factor curve of the charge state of the supercapacitor of the present invention;

[0057] Figure 5 It is a schematic diagram of the power factor curve of the charge state of the supercapacitor of the present invention when discharging;

[0058] Figure 6 The supercapacitor power correction factor-SOC curve of the present invention;

[0059] Figure 7 A schematic diagram of a power factor curve of a lithium-ion battery of the present invention when it is charged;

[0060] Figure 8 It is a schematic diagram of a power factor curve of a lithium-ion battery of the present invention when it is discharged;

[0061] Fig. 9 The power correction factor-SOC curve of the lithium-ion battery of the present invention;

[0062] Fig.10 Schematic diagram of the state of charge (SOC) zoning of traditional energy storage systems. DETAILED DESCRIPTION

[0063] In order to make the technical solution of the present invention clearer, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0065] In view of the problems existing in the existing technology, such as Figure 1 As shown, an embodiment of the present invention provides a SOC charging and discharging method based on a hybrid energy storage system of a lithium-ion battery and a supercapacitor, which is used to partition the state of charge curves of the lithium-ion battery and the supercapacitor charging and discharging into an overcharge zone, a normal zone and an over-discharge zone, including:

[0066] Add an overcharge correction zone between the overcharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors;

[0067] Add an over-discharge correction zone between the over-discharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors;

[0068] Construct different correction zone ranges for the overcharge correction zone and over-discharge correction zone on the state of charge curves of lithium-ion batteries and supercapacitors respectively;

[0069] Correct the state of charge curves of the overcharge correction area and over-discharge correction area of ​​lithium-ion batteries and supercapacitors.

[0070] Specifically, an over-discharge correction zone is added between the over-discharge zone and the normal working zone to play a transition role, and an over-charge correction zone is added between the over-charge zone and the normal working zone to play a transition role. The significance of introducing the over-charge and over-discharge correction zones is that different charge and discharge protection strategies can be adopted in the transition zone to correct the charge and discharge power according to the characteristics of different energy storage systems, thereby further optimizing the charge and discharge management of the energy storage system, and achieving the purpose of protecting the energy storage device, improving the efficient charge and discharge rate, and stabilizing the hybrid energy storage system.

[0071] Over-discharge zone: When the SOC of the energy storage system is lower than this range, it indicates that the system is close to a deep discharge state. To prevent performance degradation caused by deep discharge, the system will enter protection mode and stop discharging.

[0072] Over-discharge correction zone: When the SOC is in this range, the system will reduce the discharge rate according to the discharge protection strategy to protect the energy storage system from over-discharge damage;

[0073] Normal working range: Within this range, the SOC is in a healthy state, and the system can freely implement charge and discharge instructions according to demand, and ensure that it does not approach the limit state;

[0074] Overcharge correction zone: When the SOC enters this zone, it indicates that the energy storage system is close to an overcharge state. At this time, the charging current will be reduced according to the charging protection strategy to avoid overcharging and protect the energy storage system to extend its life;

[0075] Overcharge zone: When the SOC value approaches or reaches this range, the system will stop charging to prevent safety issues such as thermal runaway of the energy storage system caused by overcharging;

[0076] Lithium-ion batteries have a higher energy density and are suitable for long-term storage and slow release of energy, but have a lower power density and a slow response speed. Supercapacitors have a higher power density and are suitable for short-term high-power output, but have a lower energy density. These characteristics determine that in energy storage systems, different charging and discharging areas need to be distinguished to give full play to the advantages of both.

[0077] By adopting the improved SOC partition control strategy, the SOC of the energy storage system can be monitored in real time and the charging and discharging strategy can be dynamically adjusted, which can not only meet the system's power demand but also ensure the safety and long-term performance of the energy storage system.

[0078] As a further preferred embodiment, Figure 2 , the range of different areas of charge state of lithium-ion batteries is allocated as follows:

[0079] 0 to 20% of the state of charge is the over-discharge zone;

[0080] 20% to 40% of the state of charge is the over-discharge correction zone;

[0081] 40% to 60% of the state of charge is the normal range;

[0082] 60% to 80% of the state of charge is the overcharge correction zone;

[0083] 80% to 100% state of charge is the overcharge zone;

[0084] Among them, 20% is the over-discharge threshold, 40% is the over-discharge correction threshold, 60% is the over-charge correction threshold, and 80% is the over-charge threshold.

[0085] Specifically, lithium-ion batteries are energy storage devices with the characteristics of high energy density, low power density, and slow response. Their charge and discharge SOC changes are relatively smooth, and their SOC charge and discharge working range is usually 20% to 80%. When the SOC is between 40% and 60%, it can show a relatively balanced charge and discharge characteristic, which is the normal working range. Based on this feature, the charge and discharge SOC range of lithium-ion batteries is improved;

[0086] Over-discharge zone (0-20% SOC): When the SOC is lower than 20%, the battery is in the over-discharge zone. At this time, the battery is in a deep discharge state. In order to protect the battery from damage caused by over-discharge, further discharge is usually stopped to avoid affecting the battery capacity and life.

[0087] Over-discharge correction zone (20-40% SOC): The over-discharge correction zone is between 20% and 40%. When the SOC is within this range, the system will gradually reduce the discharge rate to ensure that the battery does not quickly enter the over-discharge zone and reduce the damage to the battery caused by deep discharge.

[0088] Normal zone (40-60% SOC): This range is the ideal working zone for lithium-ion batteries. The SOC is between 40% and 60%. The battery can work in this range to ensure high charging and discharging efficiency, optimal battery performance, and free adjustment of power demand.

[0089] Overcharge correction zone (60-80% SOC): The overcharge correction zone is between 60% and 80%. When the SOC approaches the upper limit, the system will gradually reduce the charging power to prevent the battery from entering an overcharge state, reducing the thermal effect caused by overcharging and shortening the battery life;

[0090] Overcharge zone (80-100% SOC): When the SOC exceeds 80%, the battery enters the overcharge zone. At this time, the system will stop charging to prevent safety hazards caused by battery overcharging, such as temperature increase and possible thermal runaway.

[0091] As a further preferred embodiment, Figure 3 , the range of different areas of the supercapacitor's state of charge is allocated as follows:

[0092] 0 to 15% of the state of charge is the over-discharge zone;

[0093] 15% to 30% of the state of charge is the over-discharge correction zone;

[0094] 30% to 70% of the state of charge is the normal range;

[0095] 70% to 95% of the state of charge is the overcharge correction zone;

[0096] 95% to 100% state of charge is the overcharge zone;

[0097] Among them, 15% is the over-discharge threshold, 30% is the over-discharge correction threshold, 70% is the over-charge correction threshold, and 95% is the over-charge threshold.

[0098] Specifically: Supercapacitors are power-type energy storage devices with the characteristics of high power density, low energy density, and fast response. Compared with lithium-ion batteries, their charge and discharge SOC changes have greater fluctuations and are prone to overcharge and overdischarge thresholds during continuous charge and discharge. Therefore, according to their characteristics, the supercapacitor charge and discharge SOC intervals are improved and divided;

[0099] Over-discharge zone (0-15% SOC): When the SOC is lower than 15%, the supercapacitor is in the over-discharge zone. At this time, in order to protect the supercapacitor, the system usually stops further discharge to avoid damage to its capacity and life caused by excessive discharge;

[0100] Over-discharge correction zone (15-30% SOC): The over-discharge correction zone is between 15% and 30%. When the SOC is within this range, the system will gradually reduce the discharge power to prevent the supercapacitor from entering a deep discharge state, protect its service life and maintain sufficient power response capability;

[0101] Normal area (30-70% SOC): When the SOC is between 30% and 70%, the supercapacitor is in the normal working area, which is the best working range of the supercapacitor. It can provide efficient and fast charge and discharge response and is suitable for frequent power fluctuation requirements.

[0102] Overcharge correction area (70-95% SOC): The overcharge correction area is between 70% and 95%. When the SOC approaches the upper limit, the system gradually reduces the charging power to prevent entering the overcharge area, ensuring that the supercapacitor does not generate temperature rise or other damage due to overcharging;

[0103] Overcharge zone (95-100% SOC): When the SOC exceeds 95%, the supercapacitor enters the overcharge zone. To avoid safety hazards and thermal runaway, the system will stop charging to ensure that the supercapacitor remains within a safe charging range.

[0104] As a further preferred embodiment, Figure 7 , the charge state curve of the lithium-ion battery overcharge correction zone is corrected by the following formula:

[0105] P′1=k bat1 P1;

[0106] Among them, P'1 is the correction charging power of the lithium-ion battery overcharge correction area, k bat1 It is the power correction coefficient of lithium-ion battery under charging state, and P1 is the charging power reference value of lithium-ion battery.

[0107] As a further preferred embodiment, the k bat1 The calculation formula is as follows:

[0108]

[0109] Among them, SOC max1 is the overcharge threshold of lithium-ion battery, SOC high1 is the overcharge correction threshold of lithium-ion batteries, SOC t The current state of charge of the device.

[0110] Specifically, for lithium-ion batteries, in the overcharge and over-discharge correction zone, it is hoped that the power change will be nonlinear and continuous with an S-shaped curve. The closer to the SOC threshold, the smaller the power change will be, so as to reduce the temperature rise. Therefore, the power correction coefficient selected for the overcharge correction zone of lithium-ion batteries is detailed in the above formula. The charging power is corrected in the range of 0-100% as follows:

[0111]

[0112] In the formula, when in the normal charging working range (i.e. 0 to 60%), k bat1 When it is 1, in the overcharge area (i.e., greater than 80%), k bat1 When the charging correction area (i.e. 60%-80%) is 0, k bat1 Coefficient calculation correction curve;

[0113] exist Figure 7 In the figure, the short dashed line is the power coefficient-SOC curve without setting the overcharge correction zone (power jump occurs), the long dashed line is the power coefficient-SOC curve after setting the overcharge correction zone and using the existing linear power correction coefficient, and the solid line is the power coefficient-SOC curve after the improved power correction coefficient used in this article. It can be seen that compared with the overcharge correction zone and the one without setting the overcharge correction zone, the curve has better continuity in the part close to the normal working area, ensuring a smooth transition from the normal working area to the over-discharge correction zone; relative to the existing linear power correction coefficient correction, the closer to the normal working area, the smaller the absolute value of the slope of the curve becomes, so that the supercapacitor has a larger high-power absorption range.

[0114] As a further preferred embodiment, Figure 8 , the charge state curve of the lithium-ion battery over-discharge correction zone is corrected by the following formula:

[0115] P′2=k bat2 P2;

[0116] Where P'2 is the corrected discharge power in the over-discharge correction zone of the lithium-ion battery, k bat2 is the power correction coefficient of the lithium-ion battery in the discharge state, and P2 is the discharge power reference value of the lithium-ion battery.

[0117] As a further preferred embodiment, the k bat2 The calculation formula is as follows:

[0118]

[0119] Among them, SOC min1 is the over-discharge threshold of lithium-ion batteries, SOC low1 is the over-discharge correction threshold of lithium-ion batteries, SOC t The current state of charge of the device;

[0120] Specifically, the over-discharge correction zone uses the following power correction coefficient and the discharge protection strategy based on SOC under the corresponding discharge state. See the above formula for details. The power correction coefficient-SOC curve under the corresponding discharge state corresponds to the curve as follows: Figure 8 , the corrected charging power in the range of 0-100% is as follows:

[0121]

[0122] In the formula, when in the normal discharge working area (i.e. greater than 40%), k bat2 It is 1 in the over-discharge area (i.e. 0-20%), and it is 0, and the above correction coefficient is used in the discharge correction area (20%-40%);

[0123] exist Figure 8 In the figure, the short dashed line is the power coefficient-SOC curve without setting the over-discharge correction zone (power jump occurs), the long dashed line is the power coefficient-SOC curve after setting the over-discharge correction zone and adopting the linear power correction coefficient, and the solid line is the power coefficient-SOC curve after adopting the improved SOC power correction coefficient based on this article. It can be seen that the solid line in the over-discharge correction zone has better continuity and is differentiable than the dashed line, and its derivative is also continuous (the curve is smooth and has no jump). The closer to the two ends, the smaller the absolute value of the slope (the smoother the change), avoiding the drastic temperature rise of the battery due to power jump near the threshold.

[0124] As a further preferred embodiment, in combination with 9, a power coefficient-SOC curve after applying the improved power correction coefficient of the present invention under the charging and discharging state of a lithium-ion battery.

[0125] As a further preferred embodiment, Figure 4 , the charge state curve of the supercapacitor overcharge correction zone is corrected by the following formula:

[0126] P′3=k sc1 P3;

[0127] Where P'3 is the corrected charging power in the supercapacitor overcharge correction zone, k sc1is the power correction coefficient of the supercapacitor under charging state, and P3 is the charging power reference value of the supercapacitor.

[0128] As a further preferred embodiment, the k sc1 The calculation formula is as follows:

[0129]

[0130] Among them, SOC max2 is the supercapacitor overcharge threshold, SOC t The current state of charge of the device.

[0131] Specifically, the charging protection strategy based on SOC under the corresponding charging state of the supercapacitor can be expressed as the above formula, and the charging power is corrected in the range of 0-100% as follows:

[0132]

[0133] When in the normal charging range (i.e. 0 to 70%), it is 1, in the overcharge range (i.e. greater than 95%), it is 0, and in the charge correction range (70%-90%), k is used. sc1 ;

[0134] Combination Figure 4 In the figure, the short dashed line is the power coefficient-SOC curve without setting the overcharge correction zone (power jump occurs), the long dashed line is the power coefficient-SOC curve after setting the overcharge correction zone and using the conventional linear power correction coefficient, and the solid line is the power coefficient-SOC curve after the improved power correction coefficient used in this article. It can be seen that the solid line in the overcharge correction zone has better continuity than the short dashed line in the part close to the normal working area, ensuring a smooth transition from the normal working area to the over-discharge correction area; relative to the long dashed line, the closer to the normal working area, the smaller the absolute value of the slope of the curve becomes, which makes the supercapacitor have a larger high-power absorption range.

[0135] As a further preferred embodiment, Figure 5 , the charge state curve of the supercapacitor over-discharge correction zone is corrected by the following formula:

[0136] P′4=k sc2 P4;

[0137] Where P'4 is the corrected discharge power in the supercapacitor over-discharge correction zone, k bat2 is the power correction coefficient of the supercapacitor in the discharge state, and P4 is the discharge power reference value of the supercapacitor.

[0138] As a further preferred embodiment, the k bat2 The calculation formula is as follows:

[0139]

[0140] Among them, SOC min2 is the supercapacitor over-discharge threshold, SOC t The current state of charge of the device.

[0141] Specifically, the over-discharge correction zone uses the following power correction coefficient and the discharge protection strategy based on SOC under the corresponding discharge state. See the above formula for details. The charging power is corrected within the range of 0-100% as follows;

[0142]

[0143] When in the normal discharge working area (i.e. greater than 30%), it is 1, in the over discharge area (i.e. 0 to 15%), it is 0, and in the charge correction area (70%-90%), k is used. sc2 .

[0144] The above is only a specific implementation of the embodiment of the present invention, but the protection scope of the embodiment of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiment of the present invention should be included in the protection scope of the embodiment of the present invention. Therefore, the protection scope of the embodiment of the present invention should be based on the protection scope of the claims.

Claims

1. A SOC charging and discharging method based on a hybrid energy storage system of a lithium-ion battery and a supercapacitor, which is used to partition the state of charge curves of the lithium-ion battery and the supercapacitor into an overcharge zone, a normal zone and an over-discharge zone, and is characterized in that: include: Add an overcharge correction zone between the overcharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors; Add an over-discharge correction zone between the over-discharge zone and the normal zone of the state of charge curve of lithium-ion batteries and supercapacitors; Construct different correction zone ranges for the overcharge correction zone and over-discharge correction zone on the state of charge curves of lithium-ion batteries and supercapacitors respectively; Correct the state of charge curves of the overcharge correction area and over-discharge correction area of ​​lithium-ion batteries and supercapacitors.

2. The method according to claim 1, characterized in that The range of different areas of charge state of lithium-ion batteries is allocated as follows: 0 to 20% of the state of charge is the over-discharge zone; 20% to 40% of the state of charge is the over-discharge correction zone; 40% to 60% of the state of charge is the normal range; 60% to 80% of the state of charge is the overcharge correction zone; 80% to 100% state of charge is the overcharge zone; Among them, 20% is the over-discharge threshold, 40% is the over-discharge correction threshold, 60% is the over-charge correction threshold, and 80% is the over-charge threshold.

3. The method according to claim 1, characterized in that The range of different areas of the supercapacitor's state of charge is allocated as follows: 0 to 15% of the state of charge is the over-discharge zone; 15% to 30% of the state of charge is the over-discharge correction zone; 30% to 70% of the state of charge is the normal range; 70% to 95% of the state of charge is the overcharge correction zone; 95% to 100% state of charge is the overcharge zone; Among them, 15% is the over-discharge threshold, 30% is the over-discharge correction threshold, 70% is the over-charge correction threshold, and 95% is the over-charge threshold.

4. The method according to claim 1, characterized in that: Correction of the state of charge curve in the overcharge correction zone of lithium-ion batteries includes the following formula: P′1=k bat1 P1; Among them, P'1 is the correction charging power of the lithium-ion battery overcharge correction area, k bat1 It is the power correction coefficient of lithium-ion battery under charging state, and P1 is the charging power reference value of lithium-ion battery.

5. The method according to claim 4, characterized in that The k bat1 The calculation formula is as follows: Among them, SOC max1 is the overcharge threshold of lithium-ion batteries, SOC high1 is the overcharge correction threshold of lithium-ion batteries, SOC t The current state of charge of the device.

6. The method according to claim 1, characterized in that Correction of the state of charge curve in the over-discharge correction zone of lithium-ion batteries includes the following formula: P′2=k bat2 P2; Among them, P'2 is the corrected discharge power in the over-discharge correction zone of the lithium-ion battery, k bat2 is the power correction coefficient of the lithium-ion battery in the discharge state, and P2 is the discharge power reference value of the lithium-ion battery.

7. The method according to claim 6, characterized in that The k bat2 The calculation formula is as follows: Among them, SOC min1 is the over-discharge threshold of lithium-ion batteries, SOC low1 is the over-discharge correction threshold of lithium-ion batteries, SOC t The current state of charge of the device.

8. The method according to claim 1, characterized in that Correction of the state of charge curve in the supercapacitor overcharge correction zone includes the following formula: P′3=k sc1 P3; Where P'3 is the corrected charging power in the supercapacitor overcharge correction zone, k sc1 is the power correction coefficient of the supercapacitor under charging state, and P3 is the charging power reference value of the supercapacitor.

9. The method according to claim 8, characterized in that The k sc1 The calculation formula is as follows: Among them, SOC max2 is the supercapacitor overcharge threshold, SOC t The current state of charge of the device.

10. The method according to claim 1, characterized in that Correction of the state of charge curve of the supercapacitor over-discharge correction zone includes the following formula: P′4=k sc2 P4; Where P'4 is the corrected discharge power in the supercapacitor over-discharge correction zone, k bat2 is the power correction coefficient of the supercapacitor in the discharge state, and P4 is the discharge power reference value of the supercapacitor.

11. The method according to claim 10, characterized in that The k bat2 The calculation formula is as follows: Among them, SOC min2 is the supercapacitor over-discharge threshold, SOC t The current state of charge of the device.

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