Temperature control system and method of lithium ion battery energy storage system

Abstract

The invention relates to a temperature control technology of an energy storage system, and discloses a temperature control system and method of a lithium ion battery energy storage system, which can realize accurate temperature control, reduce the power consumption of temperature control and reliably guarantee high-efficiency and long-life operation of the lithium ion battery energy storage system. The temperature control system comprises a battery management system, a heat management system and a battery temperature sampling unit, the battery temperature sampling unit is used for sampling the temperature of each battery cell in the energy storage system in real time; the battery management system is used for generating a temperature control strategy according to a preset temperature feature point in combination with the current temperature data of the battery cell and the current working state of the energy storage system, and issuing the temperature control strategy to the thermal management system; the temperature characteristic point is preset according to characteristic data of a battery cell used in the energy storage system; and the heat management system is used for controlling the temperature of the energy storage system by executing a temperature control strategy. The method is suitable for the energy storage system.

Description

Technical Field

[0001] The present invention relates to a temperature control technology for an energy storage system, and in particular to a temperature control system and method for a lithium-ion battery energy storage system. Background Art

[0002] With the transformation of energy structure and the development of green energy, the demand for energy storage is also increasing. Lithium-ion battery energy storage system has the advantages of high energy density, long life, green environmental protection, and high safety, and is widely used in the field of energy storage. When the lithium-ion battery energy storage system is working, the lithium-ion battery needs to work at a suitable temperature to charge and discharge at the rated power. If it cannot work at a suitable temperature, the service life of the lithium-ion battery energy storage system will be rapidly reduced, the aging of the battery cell will be accelerated, and even the lithium-ion battery will be short-circuited due to lithium deposition, which poses a safety risk.

[0003] In order to ensure the normal operation of lithium-ion battery energy storage systems, they are usually equipped with temperature control systems to control the temperature of the energy storage system within a reasonable range. However, improper temperature control methods may lead to increased power consumption of temperature control and may also cause inaccurate temperature control, thus affecting the working efficiency of the energy storage system. Summary of the invention

[0004] The technical problem to be solved by the present invention is to propose a temperature control system and method for a lithium-ion battery energy storage system, which can reduce the power consumption of temperature control while achieving precise temperature control, and reliably ensure the high-efficiency and long-life operation of the lithium-ion battery energy storage system.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] On the one hand, the present invention provides a temperature control system for a lithium-ion battery energy storage system, comprising: a battery management system, a thermal management system and a battery temperature sampling unit;

[0007] The battery temperature sampling unit is used to sample the temperature of each battery cell in the energy storage system in real time;

[0008] The battery management system is used to generate a temperature control strategy based on preset temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, and send it to the thermal management system; the temperature characteristic points are preset based on the characteristic data of the battery cell used in the energy storage system;

[0009] The thermal management system is used to control the temperature of the energy storage system by executing a temperature control strategy;

[0010] The thermal management system comprises a cooling device, a heating device, a heat exchange device and a circulation device connected by pipelines; the pipelines are filled with coolant;

[0011] The cooling device is used to cool the coolant;

[0012] The heating device is used to heat the coolant;

[0013] The heat exchange device is used to achieve heat exchange between the battery core and the coolant;

[0014] The circulation device is used to realize the circulation flow of the coolant between various devices in the thermal management system.

[0015] Furthermore, the temperature control system also includes an ambient temperature sampling unit for sampling the current ambient temperature of the energy storage system; the battery management system is also used to correct the preset temperature characteristic points according to the current ambient temperature of the energy storage system, and use the corrected temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, to generate a temperature control strategy and send it to the thermal management system.

[0016] On the other hand, based on the above temperature control system, the present invention also provides a temperature control method for a lithium-ion battery energy storage system, comprising the following steps:

[0017] S1, the battery temperature sampling unit samples the temperature of each battery cell in the energy storage system in real time;

[0018] S2. The battery management system generates a temperature control strategy based on preset temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, and sends it to the thermal management system; the temperature characteristic points are preset based on the characteristic data of the battery cell used in the energy storage system;

[0019] S3. The thermal management system controls the temperature of the energy storage system by executing a temperature control strategy.

[0020] Further, in step S2, the preset temperature characteristic points include: a first target temperature, a second target temperature, a first heating temperature, and a second heating temperature;

[0021] The first target temperature is the median value of the ideal temperature range of the battery cells used in the energy storage system;

[0022] The second target temperature is the maximum operating temperature of the battery cell under the condition of ensuring the service life;

[0023] The first heating temperature is the lowest temperature point corresponding to the battery cell charging power being greater than 20% of the rated charging power;

[0024] The second heating temperature is the lowest temperature point corresponding to the battery cell charging power being equal to the battery cell rated power;

[0025] And the following is satisfied: first heating temperature<second heating temperature<first target temperature<second target temperature.

[0026] Furthermore, in step S2, the current temperature data of the battery cell includes: the lowest temperature of the battery cell, the highest temperature of the battery cell, the average temperature of the battery cell and the temperature difference of the battery cell; the lowest temperature of the battery cell refers to the minimum value of the current sampled temperatures of all the battery cell cells; the highest temperature of the battery cell refers to the maximum value of the current sampled temperatures of all the battery cell cells; the average temperature of the battery cell refers to the average value of the current sampled temperatures of all the battery cell cells; the temperature difference of the battery cell refers to the difference between the highest temperature of the battery cell and the lowest temperature of the battery cell.

[0027] Furthermore, in step S2, a temperature control strategy is generated in combination with the current temperature data of the battery cell and the current working state of the energy storage system, including:

[0028] S21, judging the current working state of the energy storage system, if it is in the standby state, proceeding to step S22, if it is in the running state, proceeding to step S23; the running state is the charging or discharging state, and the standby state is the non-charging and discharging state;

[0029] S22, when the energy storage system is in standby mode, determine whether the current average temperature of the battery cell is in the ideal temperature range of the battery cell. If so, determine whether to enable the thermal management system according to the current battery cell temperature difference; otherwise, enable the thermal management system: if the current average temperature of the battery cell is lower than the ideal temperature range of the battery cell, determine whether to start the heating device and the circulation device for heating according to the lowest temperature of the battery cell, and determine whether to continue the circulation according to the current battery cell temperature difference after the heating is completed; if the current average temperature of the battery cell is higher than the ideal temperature range of the battery cell, start the cooling device and the circulation device for cooling, and determine whether to continue the circulation according to the current battery cell temperature difference after the cooling is completed;

[0030] S23. When the energy storage system is in operation, determine whether the following conditions are met: the current minimum temperature of the battery cell ≥ the second heating temperature, and the current maximum temperature of the battery cell ≤ the second target temperature; if so, determine whether to enable the thermal management system based on the current battery cell temperature difference; otherwise, enable the thermal management system: if the current minimum temperature of the battery cell is lower than the second heating temperature, start the heating device and the circulation device for heating, and after the heating is completed, determine whether to continue the circulation based on the current battery cell temperature difference; if the current maximum temperature of the battery cell is higher than the second target temperature, start the cooling device and the circulation device for cooling, and after the cooling is completed, determine whether to continue the circulation based on the current battery cell temperature difference.

[0031] Furthermore, in steps S22 and S23, judging whether to enable the thermal management system according to the current battery cell temperature difference includes:

[0032] If the current battery cell temperature difference is greater than 3°C, the circulation device in the thermal management system is enabled, otherwise, the thermal management system is not enabled, that is, the thermal management system is in a static state;

[0033] The determining whether to continue the cycle according to the current battery cell temperature difference includes:

[0034] If the current battery cell temperature difference is greater than 3°C, the circulation continues; otherwise, the circulation device is turned off.

[0035] Furthermore, step S22 further includes:

[0036] When the energy storage system is in standby mode and the cycle stops, the cycle will be started again when the current battery cell temperature difference is greater than 4°C.

[0037] Furthermore, in step S22, judging whether to start the heating device and the circulation device for heating according to the lowest temperature of the battery cell monomer includes:

[0038] If the lowest temperature of the battery cell is lower than the first heating temperature, the outlet water temperature of the heating device is set to the second heating temperature + 2°C, the heating device and the circulation device are started for heating, and when the lowest temperature of the battery cell is higher than the second heating temperature, the heating device is turned off to stop heating.

[0039] Furthermore, in step S22, if the current average temperature of the battery cell is higher than the ideal temperature range of the battery cell, the cooling device and the circulation device are started to perform refrigeration, including:

[0040] If the current average temperature of the battery cells is higher than the ideal temperature range of the battery cells, the cooling device and the circulation device are started to perform cooling until the current average temperature of the battery cells reaches the first target temperature, and then the cooling device is turned off to stop cooling.

[0041] Furthermore, in step S23, if the current lowest temperature of the battery cell is lower than the second heating temperature, the heating device and the circulation device are started to heat, including:

[0042] If the current lowest temperature of the battery cell is lower than the second heating temperature, the outlet water temperature of the heating device is set to the second heating temperature + 2°C, and the heating device and the circulation device are turned on for heating until the lowest temperature of the battery cell is higher than the second heating temperature, and then the heating device is turned off to stop heating.

[0043] Furthermore, in step S23, if the current maximum temperature of the battery cell monomer is greater than the second target temperature, the cooling device and the circulation device are started to perform refrigeration, including:

[0044] If the current maximum temperature of the battery cell is greater than the second target temperature, the cooling device and the circulation device are started to perform cooling according to the step-by-step cooling power control;

[0045] The step-type cooling power is:

[0046] If the current maximum temperature of the battery cell exceeds the second target temperature by more than 5°C, the rated cooling power is output until the current maximum temperature of the battery cell drops to the second target temperature + 5°C. Thereafter, the cooling power is reduced by 20% for every 1°C drop in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device is turned off and the cooling is stopped.

[0047] If the current maximum temperature of the battery cell - the second target temperature is less than 5°C, then taking 20% ​​of the rated cooling power as the base, the cooling power will be increased by 20% for every 1°C the current maximum temperature of the battery cell exceeds the second target temperature, and the current cooling power will be calculated in this way. Thereafter, the cooling power will be reduced by 20% for every 1°C decrease in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device will be turned off and cooling will be stopped.

[0048] Furthermore, step S1 also includes: the ambient temperature sampling unit samples the current ambient temperature of the energy storage system;

[0049] In step S2, the temperature characteristic point is preset according to the characteristic data of the battery cell used in the energy storage system, and is corrected according to the current ambient temperature of the energy storage system and the current working state of the energy storage system. The correction method includes:

[0050] If the energy storage system is currently in standby mode, then:

[0051] When the current ambient temperature is ≥ the first target temperature, the corrected first target temperature = the first target temperature - the first temperature deviation coefficient; when the current ambient temperature is < the first target temperature, the corrected first target temperature = the first target temperature + the first temperature deviation coefficient;

[0052] Wherein, the first temperature deviation coefficient = |(current ambient temperature - first target temperature)| / 5;

[0053] If the energy storage system is currently in operation, then:

[0054] When the current ambient temperature is ≥ the second target temperature, the corrected second target temperature = the second target temperature - the second temperature deviation coefficient; wherein, the second temperature deviation coefficient = |(current ambient temperature - the second target temperature)| / 5.

[0055] The beneficial effects of the present invention are:

[0056] (1) The present invention presets different temperature characteristic points based on the characteristics of different types of battery cells, and then generates corresponding temperature control strategies based on these temperature characteristic points in combination with the current temperature data of the battery cells and the current working state of the energy storage system, and sends them to the thermal management system, so as to finely adjust the output of the thermal management system, realize precise control of the battery cell temperature, reduce the power consumption of temperature control, improve the overall efficiency of the energy storage system, and extend the service life of the energy storage system.

[0057] (2) When generating the temperature control strategy, the temperature characteristic points are corrected by further considering the ambient temperature data, so that the temperature control of the battery cell can approach the control target more quickly under the influence of environmental factors, thereby improving the efficiency and accuracy of temperature control and reducing the power consumption of temperature control.

[0058] (3) The solution of the present invention can adapt to the needs of different working conditions and can match the battery cells and thermal management systems of different manufacturers. It has universal applicability and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 It is a structural block diagram of a temperature control system of a lithium-ion battery energy storage system in an embodiment of the present invention;

[0060] Figure 2 is a flow chart of a lithium-ion battery energy storage method in an embodiment of the present invention;

[0061] Figure 3 Schematic diagram of the temperature control strategy of the energy storage system in the standby state in an embodiment of the present invention;

[0062] Figure 4 Schematic diagram of the temperature control strategy of the energy storage system in the operating state in an embodiment of the present invention;

[0063] Figure 5 is a flow chart of a method for correcting target temperature in an embodiment of the present invention;

[0064] Markings in the figure: 100 is a thermal management system, 101 is a heat exchange device, 102 is a cooling device, 103 is a heating device, 104 is a circulation device, 105 is a pipeline, 200 is a battery management system, 300 is an ambient temperature sampling unit, 400 is a battery temperature sampling unit, and 500 is a battery cell. DETAILED DESCRIPTION

[0065] The present invention aims to provide a temperature control system and method for a lithium-ion battery energy storage system, which can reduce the power consumption of temperature control while achieving precise temperature control, and reliably ensure the high-efficiency and long-life operation of the lithium-ion battery energy storage system. The core idea is: based on the characteristic data of the battery cells used in the energy storage system, different temperature characteristic points are obtained to calibrate the temperature control targets of the battery cells under different working conditions of the energy storage system. The battery management system generates corresponding control strategies by acquiring the real-time temperature data of the battery cells and the ambient temperature data, combining the actual working state of the energy storage system and these temperature characteristic points, and sends them to the thermal management system, so as to finely adjust the output of the thermal management system and achieve precise control of the battery cell temperature, thereby reducing the power consumption of temperature control, improving the overall efficiency of the energy storage system, and extending the service life of the energy storage system.

[0066] The scheme of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0067] Example

[0068] See also Figure 1 The temperature control system of the lithium-ion battery energy storage system provided in this embodiment includes: a thermal management system 100, a battery management system 200, an ambient temperature sampling unit 300 and a battery temperature sampling unit 400; the specific functions of each part are:

[0069] The ambient temperature sampling unit 300 is used to sample the current ambient temperature of the energy storage system;

[0070] The battery temperature sampling unit 400 is used to sample the temperature of each battery cell 500 in the energy storage system in real time;

[0071] The battery management system 200 is used to generate a temperature control strategy based on preset temperature characteristic points, combined with the current temperature data of the battery cell 500 and the current working state of the energy storage system, and send it to the thermal management system 100; the temperature characteristic points are preset based on the characteristic data of the battery cell 500 used in the energy storage system;

[0072] The thermal management system 100 is used to control the temperature of the energy storage system by executing a temperature control strategy;

[0073] The thermal management system 100 includes a heat exchange device 101, a cooling device 102, a heating device 103 and a circulation device 104 connected by a pipeline 105; the pipeline 105 is filled with a coolant;

[0074] A cooling device 102, used for cooling the coolant;

[0075] A heating device 103, used to heat the coolant;

[0076] The heat exchange device 101 is used to realize heat exchange between the battery cell 500 and the coolant;

[0077] The circulation device 104 is used to realize the circulation flow of the coolant between various devices in the thermal management system 100 .

[0078] In the above system, in order to achieve heat exchange, when the cooling device 102 is started, the circulation device 104 will be started at the same time, and when the heating device 103 is started, the circulation device 104 will also be started at the same time; in addition, the circulation device 104 can also be started separately.

[0079] Based on the above temperature control system, the temperature control method of the lithium-ion battery energy storage system provided in this embodiment can be found in Figure 2 , which includes the following implementation process:

[0080] S1. Cell temperature and ambient temperature sampling

[0081] In this step, the current ambient temperature of the energy storage system is sampled in real time by the ambient temperature sampling unit 300; the temperature of each battery cell 500 in the energy storage system is sampled in real time by the battery temperature sampling unit 400; these sampled temperature data are transmitted to the battery management system 200 for analysis and processing as the basic data for the temperature control strategy.

[0082] S2. Generation and distribution of temperature control strategies

[0083] In this step, the battery management system 200 generates a temperature control strategy based on the preset temperature feature points, combined with the current temperature data of the battery cell 500, the current ambient temperature data of the energy storage system and the current working state of the energy storage system, and sends it to the thermal management system 100.

[0084] The temperature characteristic points are preset according to the characteristic data of the battery cells used in the energy storage system. In an exemplary embodiment, the temperature characteristic points include a first target temperature, a second target temperature, a first heating temperature, and a second heating temperature.

[0085] The first target temperature is the median value of the ideal temperature range of the battery cells used in the energy storage system;

[0086] The second target temperature is the maximum operating temperature of the battery cell under the condition of ensuring the service life;

[0087] The first heating temperature is the lowest temperature point corresponding to the battery cell charging power being greater than 20% of the rated charging power;

[0088] The second heating temperature is the lowest temperature point corresponding to the battery cell charging power being equal to the battery cell rated power;

[0089] And the following is satisfied: first heating temperature<second heating temperature<first target temperature<second target temperature.

[0090] It can be understood that for a specific model of battery cell, different charging and discharging powers correspond to different battery cell temperature conditions. Under more suitable temperature conditions, the battery cell can be charged and discharged at rated power. Accordingly, this embodiment sets the first heating temperature and the second heating temperature to meet the corresponding lowest temperature point under the battery cell charging power conditions, wherein the first heating temperature is used as a judgment condition for turning on the heating device in the standby state (non-charging and discharging state) of the energy storage system. In order to maintain the battery cell temperature of the energy storage system in the standby state within a suitable range, so as to facilitate the switching to the operating state to provide support to the power grid with a certain charging and discharging power, this embodiment sets the first heating temperature to the lowest temperature point corresponding to the battery cell charging power being greater than 20% of the rated charging power. Taking a certain model of battery cell as an example, its rated charging power is 0.5P. According to its performance parameters, the corresponding charging temperatures at 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 45℃, 50℃, 55℃ and 60℃ are 0.04P, 0.12P, 0.16P, 0.16P, 0.35P, 0.5P, 0.5P, 0.5P, 0.5P and 0 respectively; then the charging powers at 5℃, 10℃, 15℃, 20℃, 25℃, 45℃, 50℃ and 55℃ all meet the requirement of being greater than 20% of the rated charging power (i.e. 0.5P*20%=0.1P), and the minimum value of these temperature values, i.e. 5℃, is taken as the first heating temperature.

[0091] The second heating temperature is used as a judgment condition for turning on the heating device when the energy storage system is in operation (charging or discharging state). It is set to the lowest temperature point corresponding to the battery cell charging power being equal to the battery cell rated power, so that the battery cell can be charged and discharged at the rated power. According to the performance parameters of the battery cells of the above-mentioned models, the charging power is the rated charging power at 25°C, 45°C, 50°C and 55°C, and 25°C is taken as the second heating temperature.

[0092] The first target temperature is used as a control target for the battery cell temperature in the standby state of the energy storage system. That is, through temperature control, the temperature of each battery cell is made close to this suitable temperature value, thereby extending the overall life of the energy storage system. It also allows the energy storage system to quickly operate at rated power consumption when switched to the operating state, thereby improving the efficiency of the energy storage system. For this reason, this embodiment sets the first target temperature to the median value of the ideal temperature range of the battery cells used in the energy storage system.

[0093] The second target temperature is the control target of the battery cell temperature when the energy storage system is in operation, that is, through temperature control, the temperature of each battery cell is made close to this value. It can be understood that, under normal circumstances, the higher the temperature of the battery cell, the higher the activity, and the charging and discharging energy efficiency will also be improved accordingly. However, too high a temperature will affect the life of the battery cell and also bring safety hazards. For this reason, this embodiment sets the second target temperature to the highest operating temperature of the battery cell under the condition of ensuring the service life.

[0094] The specific values ​​of the above-mentioned temperature characteristic points may vary according to the type of battery cell, but the corresponding data can be obtained from the battery cell specification sheet, and this embodiment does not limit the specific values.

[0095] The "current temperature data of the battery cell" described in this step is obtained by analyzing the data of real-time sampling of the temperature of each battery cell 500 in the energy storage system by the battery temperature sampling unit 400 by the battery management system 200. In an exemplary scheme, it includes: the lowest temperature of the battery cell, the highest temperature of the battery cell, the average temperature of the battery cell and the temperature difference of the battery cell; the lowest temperature of the battery cell refers to the minimum value of the current sampling temperatures of all battery cell cells; the highest temperature of the battery cell refers to the maximum value of the current sampling temperatures of all battery cell cells; the average temperature of the battery cell refers to the average value of the current sampling temperatures of all battery cell cells; the temperature difference of the battery cell refers to the difference between the highest temperature of the battery cell and the lowest temperature of the battery cell.

[0096] The temperature control strategy is divided into the temperature control strategy of the energy storage system in the standby state and the temperature control strategy of the energy storage system in the operating state. The standby state and the operating state of the energy storage system can be determined by the method of detecting the current, or the specific working state information can be given by the system preset operating strategy. For the current detection method, for example: the energy storage system is initially in the standby state when it is powered on. When it is detected that the system has current for 1 minute, it switches to the operating state; after detecting that the system has no current for 1 minute, it switches to the standby state.

[0097] The temperature control strategies of the energy storage system in standby and operating states are described in detail below:

[0098] 1. Temperature control strategy of energy storage system in standby state. For the process diagram, see Figure 3 , which includes:

[0099] a. Determine whether the current average temperature of the battery cell is within the ideal temperature range of the battery cell;

[0100] In this step, the average temperature of the battery cell reflects the overall temperature of the battery. If it is in the ideal temperature range of the battery cell, there is no need for heating or cooling. It is only necessary to consider whether to start the cycle to balance the temperature difference between the battery cells and proceed to step b. If it is not in the ideal temperature range of the battery cell, it is necessary to enable the thermal management system to intervene in heating or cooling; proceed to step c.

[0101] b. Determine whether to enable the thermal management system based on the current battery cell temperature difference;

[0102] In this step, the temperature difference of the current battery cell is the difference between the highest temperature of the battery cell and the lowest temperature of the battery cell, which reflects the difference in temperature distribution of different battery cells. A better situation is that this difference is small, that is, the temperature difference of each battery cell is not large, then there is no need to start the thermal management system, that is, all devices in the thermal management system are not started, and the thermal management system is in a "static state". In an exemplary scheme, the threshold of this difference is set to 3°C. If the current battery cell temperature difference is greater than 3°C, the circulation device in the thermal management system is enabled to reduce the temperature difference of the battery cell. If the current battery cell temperature difference is less than or equal to 3°C, the thermal management system is not enabled, that is, the thermal management system is in a static state.

[0103] c. Refrigeration scheduling or heating scheduling judgment;

[0104] In this step, there are two cases where the average temperature of the battery cell is not within the ideal temperature range of the battery cell. One is that the average temperature of the battery cell is higher than the ideal temperature range of the battery cell; the other is that the average temperature of the battery cell is lower than the ideal temperature range of the battery cell. For the first case, proceed to step d, and for the second case, proceed to step e.

[0105] d. Carry out refrigeration scheduling;

[0106] In this step, if the current average temperature of the battery cell is higher than the ideal temperature range of the battery cell, the cooling device and the circulation device are started to perform cooling until the current average temperature of the battery cell reaches the first target temperature, then the cooling device is turned off and cooling is stopped; thereby reducing the temperature of the battery cell to near the first target temperature.

[0107] After the refrigeration is completed, it is determined whether to continue the circulation based on the current battery cell temperature difference. For example, when the current battery cell temperature difference is greater than 3°C, the circulation continues to reduce the temperature difference of the battery cells so that the temperature distribution of each battery cell tends to be uniform. Of course, when the battery cell temperature difference is less than or equal to 3°C, there is no need to continue the circulation and the circulation device is turned off. At this time, the thermal management system is in a static state.

[0108] It should be noted that in the standby state of the energy storage system, when the cycle is closed, the cycle will be restarted only when the temperature difference of the battery cell is greater than 4°C. This is because the different layout positions of different battery cells will cause some battery cells to be affected by the ambient temperature, resulting in a large difference in the temperature difference of each cell. Therefore, the temperature difference threshold for restarting the cycle will be set larger to reduce the influence of interference factors and reduce the cycle power consumption.

[0109] e. Carry out heating scheduling;

[0110] In this step, if the current average temperature of the battery cell is lower than the ideal temperature range of the battery cell, it is determined whether to start the heating device and the circulation device for heating according to the lowest temperature of the battery cell. If the lowest temperature of the battery cell is lower than the first heating temperature, it means that the temperature of the battery cell is lower than the minimum temperature value that can satisfy the energy storage system to provide a certain operating power when it switches to the operating state, and it needs to be heated. In an exemplary scheme, the water outlet temperature of the heating device is set to the second heating temperature + 2°C, and the heating device and the circulation device are started for heating. When the lowest temperature of the battery cell is heated to be greater than the second heating temperature, the heating device is turned off to stop heating.

[0111] The purpose of setting the outlet water temperature of the heating device 2°C higher than the second heating temperature is to take into account the heat loss in the heat exchange process, so that the overall temperature of the battery cell can quickly approach the second heating temperature, that is, the temperature value that can meet the requirement of the energy storage system to quickly operate at the rated operating power when it switches to the operating state.

[0112] After the heating is finished, the current temperature difference of the battery cells is also used to determine whether to continue the cycle. For example, when the current temperature difference of the battery cells is greater than 3°C, the cycle will continue to be run to reduce the temperature difference of the battery cells and make the temperature distribution of each battery cell uniform. Of course, when the temperature difference of the battery cells is less than or equal to 3°C, the cycle does not need to be continued and the circulation device is turned off. At this time, the thermal management system is in a static state. Similarly, when the cycle is closed, the cycle will be turned on again when the temperature difference of the battery cells is greater than 4°C.

[0113] The above is a temperature control strategy for the energy storage system in standby state. Based on this strategy, the battery cells in the energy storage system can be maintained at a suitable temperature when the energy storage system is not working, which can extend the life of the battery cells and enable the energy storage system to be quickly put into operation when the state is switched to the operating state.

[0114] 2. Temperature control strategy of energy storage system under operation state. For the process diagram, see Figure 4 , which includes:

[0115] a. Determine whether the temperature of the battery cell is within the temperature range suitable for operation;

[0116] In this step, the temperature range suitable for operation is defined as between the second heating temperature and the second target temperature, because the battery cell in this temperature range has good activity, can give full play to its energy efficiency, and will not affect the service life.

[0117] Therefore, this step is to determine whether the following conditions are met: the current lowest temperature of the battery cell is ≥ the second heating temperature, and the current highest temperature of the battery cell is ≤ the second target temperature.

[0118] If this condition is met, there is no need to perform cooling or heating. It is only necessary to consider whether the temperature distribution of each battery cell is balanced through circulation, and then proceed to step b; if this condition is not met, it is necessary to activate the thermal management system to intervene in heating or cooling; then proceed to step c.

[0119] b. Determine whether to enable the thermal management system based on the current battery cell temperature difference;

[0120] In this step, the temperature difference of the current battery cell is the difference between the highest temperature of the battery cell and the lowest temperature of the battery cell, which reflects the difference in temperature distribution of different battery cells. A better situation is that this difference is small, that is, the temperature difference of each battery cell is not large, then there is no need to start the thermal management system, that is, all devices in the thermal management system are not started, and the thermal management system is in a "static state". In an exemplary scheme, the threshold of this difference is set to 3°C. If the current battery cell temperature difference is greater than 3°C, the circulation device in the thermal management system is enabled to reduce the temperature difference of the battery cell. If the current battery cell temperature difference is less than or equal to 3°C, the thermal management system is not enabled, that is, the thermal management system is in a static state.

[0121] c. Refrigeration scheduling or heating scheduling judgment;

[0122] In this step, there are two situations when the temperature of the battery cell is not in a temperature range suitable for operation. One is that the current minimum temperature of the battery cell is lower than the second heating temperature; the other is that the current maximum temperature of the battery cell is higher than the second target temperature. For the first situation, go to step d, and for the second situation, go to step e.

[0123] d. Carry out heating scheduling;

[0124] In this step, if the current minimum temperature of the battery cell is lower than the second heating temperature, the battery cell cannot be put into operation at the rated power, thereby affecting the efficiency of the energy storage system. Therefore, the battery cell temperature needs to be increased. In an exemplary solution, the outlet water temperature of the heating device is set to the second heating temperature + 2°C, and the heating device and the circulation device are turned on for heating until the minimum temperature of the battery cell is higher than the second heating temperature, and then the heating device is turned off to stop heating.

[0125] The water outlet temperature of the heating device is set 2°C higher than the second heating temperature to take into account the heat loss during the heat exchange process, so that the temperature of the battery cell can be quickly raised to the second heating temperature, thereby exerting energy efficiency at rated power.

[0126] After the heating is completed, whether to continue the circulation is determined based on the current battery cell temperature difference. If circulation is not required, the circulation device is turned off and the thermal management system is in a static state.

[0127] e. Carry out refrigeration scheduling;

[0128] In this step, if the current maximum temperature of the battery cell is greater than the second target temperature, the life of the battery cell will be affected, so the battery cell temperature needs to be lowered. In an exemplary solution, cooling is performed by starting the cooling device and the circulation device according to the step-by-step cooling power control;

[0129] The step-type cooling power is:

[0130] If the current maximum temperature of the battery cell exceeds the second target temperature by more than 5°C, the rated cooling power is output until the current maximum temperature of the battery cell drops to the second target temperature + 5°C. Thereafter, the cooling power is reduced by 20% for every 1°C drop in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device is turned off and the cooling is stopped.

[0131] If the current maximum temperature of the battery cell - the second target temperature is less than 5°C, then taking 20% ​​of the rated cooling power as the base, the cooling power will be increased by 20% for every 1°C the current maximum temperature of the battery cell exceeds the second target temperature, and the current cooling power will be calculated in this way. Thereafter, the cooling power will be reduced by 20% for every 1°C decrease in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device will be turned off and cooling will be stopped.

[0132] This step-by-step control method allows the refrigeration process to better match other temperature influencing factors, dynamically control the refrigeration power to reduce refrigeration power consumption, and ultimately reduce the battery cell temperature to a level that allows it to work efficiently without affecting its service life.

[0133] After the cooling is completed, whether to continue the circulation is determined based on the current battery cell temperature difference. If circulation is not required, the circulation device is turned off and the thermal management system is in a static state.

[0134] The above is the temperature control strategy when the energy storage system is in operation. Based on this strategy, the battery cells in the energy storage system can be maintained in an appropriate temperature range when working, which can fully exert their performance without affecting the service life of the battery cells.

[0135] In addition, this embodiment also takes into account the influence of environmental factors. When generating the temperature control strategy, the temperature characteristic points are corrected by further considering the ambient temperature data, so that the temperature control of the battery cell can approach the control target more quickly under the influence of environmental factors, thereby improving the efficiency and accuracy of temperature control while reducing the power consumption of temperature control.

[0136] In an exemplary embodiment, the method for correcting the temperature characteristic point is as follows: Figure 5 , which includes:

[0137] If the energy storage system is currently in standby mode, then:

[0138] When the current ambient temperature is ≥ the first target temperature, the corrected first target temperature = the first target temperature - the first temperature deviation coefficient; when the current ambient temperature is < the first target temperature, the corrected first target temperature = the first target temperature + the first temperature deviation coefficient;

[0139] Wherein, the first temperature deviation coefficient = |(current ambient temperature - first target temperature)| / 5;

[0140] If the energy storage system is currently in operation, then:

[0141] When the current ambient temperature is ≥ the second target temperature, the corrected second target temperature = the second target temperature - the second temperature deviation coefficient; wherein, the second temperature deviation coefficient = |(current ambient temperature - the second target temperature)| / 5.

[0142] When the energy storage system switches from the running state to the standby state, because the running state will make the battery cell temperature approach the second target temperature, which will be greater than the first target temperature, cooling will be performed at this time to reduce the battery cell temperature; according to the above correction method, if the ambient temperature is greater than or equal to the first target temperature, it means that the ambient temperature is relatively high. Correcting the first target temperature to a lower level can allow the battery cell to maintain a suitable temperature range for a longer time, avoiding frequent start and stop of the thermal management system; conversely, if the ambient temperature is lower than the first target temperature, it means that the ambient temperature is relatively low. Correcting the first target temperature to a higher level can use the ambient temperature to gradually cool down the battery cell, thereby reducing the power consumption of temperature control. Through this process, the battery cell can also be maintained in a suitable temperature range for a longer time, avoiding frequent start and stop of the thermal management system.

[0143] When the energy storage system switches from standby mode to operating mode, the temperature control target of the operating mode is to maintain the second target temperature through cooling by the thermal management system when the temperature of the battery cell meets the second heating temperature and the temperature rise of the battery cell during operation approaches the second target temperature; according to the above correction method, if the ambient temperature is greater than or equal to the second target temperature, it means that the ambient temperature is relatively high, and usually when selecting a thermal management system, the cooling capacity under certain ambient temperature conditions will be matched. When the ambient temperature is higher than the matched ambient temperature, there may be insufficient cooling capacity. Therefore, the second target temperature is corrected to a lower level and the cooling is started relatively early, which can prevent the battery cell temperature from exceeding expectations due to excessively high ambient temperature; conversely, if the ambient temperature is lower than the second target temperature, it means that the ambient temperature is relatively low, and the battery cell temperature rise rate can be reduced. When the maximum temperature of the battery cell exceeds the second target temperature, normal cooling is performed to ensure the service life of the battery cell. Therefore, when the ambient temperature is lower than the second target temperature, the second target temperature is not corrected.

[0144] In addition, considering that the time of each state of the energy storage system is within a certain range, the probability of a sudden temperature change within this time range is small. At the same time, in order to avoid multiple corrections that will increase the logical complexity of the program, the target temperature can be corrected once in each state of the energy storage system, that is, once in the standby state, once after switching to the running state, once after switching to the standby state next time, once after switching to the running state next time... and so on.

[0145] S3. Execute temperature control strategy

[0146] In this step, after the thermal management system 100 receives the temperature control strategy sent by the battery management system 200, it executes the corresponding temperature control strategy to achieve temperature control of the energy storage system.

[0147] Finally, it should be noted that the above embodiments are only preferred implementations and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, several modifications, equivalent replacements, improvements, etc. can be made without departing from the scope of the present invention and the scope of protection of the claims, and all of these should be included in the protection scope of the present invention.

Claims

1. A temperature control system for a lithium-ion battery energy storage system, characterized in that: include: Battery management system, thermal management system and battery temperature sampling unit; The battery temperature sampling unit is used to sample the temperature of each battery cell in the energy storage system in real time; The battery management system is used to generate a temperature control strategy based on preset temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, and send it to the thermal management system; The temperature characteristic points are preset according to characteristic data of the battery cells used in the energy storage system; The thermal management system is used to control the temperature of the energy storage system by executing a temperature control strategy; The thermal management system comprises a cooling device, a heating device, a heat exchange device and a circulation device connected by pipelines; the pipelines are filled with coolant; The cooling device is used to cool the coolant; The heating device is used to heat the coolant; The heat exchange device is used to achieve heat exchange between the battery core and the coolant; The circulation device is used to realize the circulation flow of the coolant between various devices in the thermal management system.

2. A temperature control system for a lithium-ion battery energy storage system as claimed in claim 1, characterized in that: The temperature control system also includes an ambient temperature sampling unit for sampling the current ambient temperature of the energy storage system; the battery management system is also used to correct the preset temperature characteristic points according to the current ambient temperature of the energy storage system, and use the corrected temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, to generate a temperature control strategy and send it to the thermal management system.

3. A temperature control method for a lithium-ion battery energy storage system, applied to the temperature control system of the lithium-ion battery energy storage system as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: S1, the battery temperature sampling unit samples the temperature of each battery cell in the energy storage system in real time; S2. The battery management system generates a temperature control strategy based on preset temperature characteristic points, combined with the current temperature data of the battery cell and the current working state of the energy storage system, and sends it to the thermal management system; the temperature characteristic points are preset based on the characteristic data of the battery cell used in the energy storage system; S3. The thermal management system controls the temperature of the energy storage system by executing a temperature control strategy.

4. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 3, characterized in that: In step S2, the preset temperature characteristic points include: a first target temperature, a second target temperature, a first heating temperature, and a second heating temperature; The first target temperature is the median value of the ideal temperature range of the battery cells used in the energy storage system; The second target temperature is the maximum operating temperature of the battery cell under the condition of ensuring the service life; The first heating temperature is the lowest temperature point corresponding to the battery cell charging power being greater than 20% of the rated charging power; The second heating temperature is the lowest temperature point corresponding to the battery cell charging power being equal to the battery cell rated power; And the following is satisfied: first heating temperature<second heating temperature<first target temperature<second target temperature.

5. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 4, characterized in that: In step S2, the current temperature data of the battery cell includes: the lowest temperature of the battery cell, the highest temperature of the battery cell, the average temperature of the battery cell and the temperature difference of the battery cell; the lowest temperature of the battery cell refers to the minimum value of the current sampling temperatures of all the battery cell cells; the highest temperature of the battery cell refers to the maximum value of the current sampling temperatures of all the battery cell cells; the average temperature of the battery cell refers to the average value of the current sampling temperatures of all the battery cell cells; the temperature difference of the battery cell refers to the difference between the highest temperature of the battery cell and the lowest temperature of the battery cell.

6. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 5, characterized in that: In step S2, a temperature control strategy is generated based on the current temperature data of the battery cell and the current working state of the energy storage system, including: S21, judging the current working state of the energy storage system, if it is in the standby state, proceeding to step S22, if it is in the running state, proceeding to step S23; the running state is the charging or discharging state, and the standby state is the non-charging and discharging state; S22, when the energy storage system is in standby mode, determine whether the current average temperature of the battery cell is in the ideal temperature range of the battery cell. If so, determine whether to enable the thermal management system according to the current battery cell temperature difference; otherwise, enable the thermal management system: if the current average temperature of the battery cell is lower than the ideal temperature range of the battery cell, determine whether to start the heating device and the circulation device for heating according to the lowest temperature of the battery cell, and determine whether to continue the circulation according to the current battery cell temperature difference after the heating is completed; if the current average temperature of the battery cell is higher than the ideal temperature range of the battery cell, start the cooling device and the circulation device for cooling, and determine whether to continue the circulation according to the current battery cell temperature difference after the cooling is completed; S23. When the energy storage system is in operation, determine whether the following conditions are met: the current minimum temperature of the battery cell ≥ the second heating temperature, and the current maximum temperature of the battery cell ≤ the second target temperature; if so, determine whether to enable the thermal management system based on the current battery cell temperature difference; otherwise, enable the thermal management system: if the current minimum temperature of the battery cell is lower than the second heating temperature, start the heating device and the circulation device for heating, and after the heating is completed, determine whether to continue the circulation based on the current battery cell temperature difference; if the current maximum temperature of the battery cell is higher than the second target temperature, start the cooling device and the circulation device for cooling, and after the cooling is completed, determine whether to continue the circulation based on the current battery cell temperature difference.

7. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 6, characterized in that: In steps S22 and S23, judging whether to enable the thermal management system according to the current battery cell temperature difference includes: If the current battery cell temperature difference is greater than 3°C, the circulation device in the thermal management system is enabled, otherwise, the thermal management system is not enabled, that is, the thermal management system is in a static state; The determining whether to continue the cycle according to the current battery cell temperature difference includes: If the current battery cell temperature difference is greater than 3°C, the circulation continues; otherwise, the circulation device is turned off.

8. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 7, characterized in that: Step S22 also includes: When the energy storage system is in standby mode and the cycle stops, the cycle will be started again when the current battery cell temperature difference is greater than 4°C.

9. A temperature control method for a lithium-ion battery energy storage system as claimed in claim 6, characterized in that: In step S22, judging whether to start the heating device and the circulation device for heating according to the lowest temperature of the battery cell monomer includes: If the lowest temperature of the battery cell is lower than the first heating temperature, the outlet water temperature of the heating device is set to the second heating temperature + 2°C, the heating device and the circulation device are started for heating, and when the lowest temperature of the battery cell is higher than the second heating temperature, the heating device is turned off to stop heating.

10. A temperature control method for a lithium-ion battery energy storage system according to claim 6, characterized in that: In step S22, if the current average temperature of the battery cell is higher than the ideal temperature range of the battery cell, the cooling device and the circulation device are started to perform refrigeration, including: If the current average temperature of the battery cells is higher than the ideal temperature range of the battery cells, the cooling device and the circulation device are started to perform cooling until the current average temperature of the battery cells reaches the first target temperature, and then the cooling device is turned off to stop cooling.

11. A temperature control method for a lithium-ion battery energy storage system according to claim 6, characterized in that: In step S23, if the current lowest temperature of the battery cell is lower than the second heating temperature, the heating device and the circulation device are started to heat, including: If the current lowest temperature of the battery cell is lower than the second heating temperature, the outlet water temperature of the heating device is set to the second heating temperature + 2°C, and the heating device and the circulation device are turned on for heating until the lowest temperature of the battery cell is higher than the second heating temperature, and then the heating device is turned off to stop heating.

12. A temperature control method for a lithium-ion battery energy storage system according to claim 6, characterized in that: In step S23, if the current maximum temperature of the battery cell is greater than the second target temperature, the cooling device and the circulation device are started to perform refrigeration, including: If the current maximum temperature of the battery cell is greater than the second target temperature, the cooling device and the circulation device are started to perform cooling according to the step-by-step cooling power control; The step-type cooling power is: If the current maximum temperature of the battery cell exceeds the second target temperature by more than 5°C, the rated cooling power is output until the current maximum temperature of the battery cell drops to the second target temperature + 5°C. Thereafter, the cooling power is reduced by 20% for every 1°C drop in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device is turned off and the cooling is stopped. If the current maximum temperature of the battery cell - the second target temperature is less than 5°C, then taking 20% ​​of the rated cooling power as the base, the cooling power will be increased by 20% for every 1°C the current maximum temperature of the battery cell exceeds the second target temperature, and the current cooling power will be calculated in this way. Thereafter, the cooling power will be reduced by 20% for every 1°C decrease in the maximum temperature of the battery cell. When the maximum temperature of the battery cell is lower than the second target temperature, the cooling device will be turned off and cooling will be stopped.

13. A temperature control method for a lithium-ion battery energy storage system according to any one of claims 4 to 12, characterized in that: Step S1 also includes: the ambient temperature sampling unit samples the current ambient temperature of the energy storage system; In step S2, the temperature characteristic point is preset according to the characteristic data of the battery cell used in the energy storage system, and is corrected according to the current ambient temperature of the energy storage system and the current working state of the energy storage system. The correction method includes: If the energy storage system is currently in standby mode, then: When the current ambient temperature is ≥ the first target temperature, the corrected first target temperature = the first target temperature - the first temperature deviation coefficient; when the current ambient temperature is < the first target temperature, the corrected first target temperature = the first target temperature + the first temperature deviation coefficient; Wherein, the first temperature deviation coefficient = |(current ambient temperature - first target temperature)| / 5; If the energy storage system is currently in operation, then: When the current ambient temperature is ≥ the second target temperature, the corrected second target temperature = the second target temperature - the second temperature deviation coefficient; wherein, the second temperature deviation coefficient = |(current ambient temperature - the second target temperature)| / 5.

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