Wide-temperature-range sodium-lithium hybrid energy storage system and control method thereof

Abstract

The invention discloses a wide-temperature-range sodium-lithium hybrid energy storage system and a control method thereof. According to the system, the working temperature range of the energy storage system is effectively expanded through sodium-lithium hybrid energy storage; the sodium ion battery unit bears a low-temperature working condition, and the lithium ion battery unit bears a normal-temperature basic load, so that the low-temperature and power characteristics of a sodium battery and the high-energy density advantage of a lithium battery are exerted, and complementation of energy density and temperature adaptability is realized; and the independent bidirectional DC / DC converter is adopted for power coupling, so that the problem of voltage mismatching possibly caused by direct parallel connection is effectively avoided, and the reliability and the control precision of the system are improved. The system has intelligent environment perception and adaptive control capabilities, can adaptively adjust a working mode and a power distribution strategy according to environment conditions, and is high in intelligent degree. The modular design is adopted, system expansion and maintenance are facilitated, and the operation and maintenance cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, and in particular to a wide-temperature-range sodium-lithium hybrid energy storage system and its control method. Background Technology

[0002] The demand for reliable operation of energy storage systems in extreme environments is rapidly increasing. However, existing energy storage systems, which employ a single-battery technology approach, face significant technical challenges. First, lithium-ion battery energy storage systems typically operate in a temperature range of -20°C to 45°C, experiencing severe capacity degradation and a significant decline in charge-discharge performance at low temperatures. Second, while sodium-ion battery energy storage systems, as an emerging technology, exhibit excellent low-temperature characteristics and can maintain a considerable capacity retention rate at -30°C, their energy density is relatively limited, making it difficult to meet the demands of high-energy-density scenarios when used alone. Therefore, a single-battery technology approach struggles to simultaneously meet the dual requirements of low-temperature performance and high energy density, and existing energy storage systems lack effective multi-battery hybrid coordination mechanisms. In applications in frigid regions, to ensure system operation, energy storage systems typically require additional heating equipment to maintain normal battery function, increasing energy consumption and posing a risk of failure to start in extreme environments where external power is unavailable.

[0003] The above problems urgently need to be solved. Summary of the Invention

[0004] To address the related technical problems, this invention provides a wide-temperature-range sodium-lithium hybrid energy storage system and its control method to solve the problems mentioned in the background section above.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: In a first aspect, embodiments of the present invention provide a wide-temperature-range sodium-lithium hybrid energy storage system, the system comprising a sodium-ion battery unit, a lithium-ion battery unit, and a main controller; the main controller is configured to execute a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit, so that they operate in an optimal state.

[0006] As an optional implementation, the wide-temperature-range sodium-lithium hybrid energy storage system further includes a bidirectional DC / DC converter; the sodium-ion battery unit and the lithium-ion battery unit are respectively connected in parallel to the DC bus through independent bidirectional DC / DC converters to achieve voltage matching and independent power regulation for different battery platforms.

[0007] As an optional implementation, the main controller establishes a communication link with the sodium-ion battery unit and the lithium-ion battery unit to execute a differentiated power adjustment strategy based on the battery temperature characteristics, thereby realizing the linkage control of temperature and power between the sodium-ion battery unit and the lithium-ion battery unit.

[0008] As an optional implementation, the wide-temperature-range sodium-lithium hybrid energy storage system further includes an environmental sensing component; the environmental sensing component is used to monitor environmental data and output the monitoring data to the main controller.

[0009] As an optional implementation, the wide-temperature-range sodium-lithium hybrid energy storage system further includes a thermal management component; the thermal management component is used to heat or dissipate heat from the sodium-ion battery cells and the lithium-ion battery cells, so that the batteries operate at a preset temperature.

[0010] Secondly, embodiments of the present invention provide a wide-temperature-range sodium-lithium hybrid energy storage control method. This method executes a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit in the wide-temperature-range sodium-lithium hybrid energy storage system proposed in the first aspect above, so that the wide-temperature-range sodium-lithium hybrid energy storage system operates in an optimal state.

[0011] As an optional implementation, the differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery cells and lithium-ion battery cells in the wide-temperature-range sodium-lithium hybrid energy storage system includes: The system is configured with "Sodium Priority Mode," "Hybrid Equilibrium Mode," "Lithium Priority Mode," and "Heating Priority Mode." The main controller of the wide-temperature-range sodium-lithium hybrid energy storage system is based on, but is not limited to, ambient temperature Tenv and the battery temperature T of the lithium-ion battery cells. Li The battery temperature Tna of the sodium-ion battery cell, the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell, and the load power P. load The switching criteria are used to adaptively switch to the corresponding working mode.

[0012] As an optional implementation, after the main controller switches the wide-temperature-range sodium-lithium hybrid energy storage system to "hybrid equilibrium mode", it performs power distribution control based on the deviation ΔSOC between the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell. By monitoring the state of charge of the battery, it dynamically adjusts the power distribution strategy to adjust ΔSOC to a preset range.

[0013] As an optional implementation, the wide-temperature-range sodium-lithium hybrid energy storage control method is also equipped with a "fault bypass mode", which disconnects the faulty unit via a relay when any battery unit fails and becomes a faulty unit.

[0014] As an optional implementation, the wide-temperature-range sodium-lithium hybrid energy storage control method is also equipped with a "maintenance mode". After the main controller switches the wide-temperature-range sodium-lithium hybrid energy storage system to the "maintenance mode", it can control the charging and discharging status of each battery cell individually and support remote operation of the wide-temperature-range sodium-lithium hybrid energy storage system.

[0015] The beneficial effects of this embodiment are as follows: 1. The sodium-lithium hybrid energy storage effectively expands the operating temperature range of the energy storage system, enabling it to operate stably from -20℃ to 50℃ to a wide temperature range of -40℃ to 80℃, significantly improving the system's temperature adaptability. In the sodium-lithium hybrid energy storage system, the sodium-ion battery unit undertakes the low-temperature operating conditions, while the lithium-ion battery unit undertakes the basic load at room temperature, achieving a complementary performance of wide temperature adaptability and energy density, and fully leveraging the advantages of both battery technologies.

[0016] 2. An independent bidirectional DC / DC converter architecture is adopted. Sodium-ion battery units and lithium-ion battery units are connected in parallel to the DC bus through independent bidirectional DC / DC converters to achieve voltage matching and independent power regulation of different battery platforms. This effectively avoids voltage mismatch problems that may be caused by direct parallel connection and improves the reliability and control accuracy of the system.

[0017] 3. A complete system of six working modes has been established, including differentiated power adjustment strategies based on battery temperature characteristics (sodium priority mode, hybrid balance mode, lithium priority mode, heating priority mode) and system-level operation modes (fault bypass mode, maintenance mode), realizing the logical separation of normal operation control and fault handling and maintenance.

[0018] 4. This invention has intelligent environmental perception and adaptive control capabilities. The main controller can adaptively adjust the working mode and power distribution strategy according to environmental conditions based on switching criteria such as ambient temperature, battery temperature, SOC, and load power, and has a high level of intelligence.

[0019] 5. This invention adopts a modular design, which facilitates system expansion and maintenance, reducing operation and maintenance costs. This invention enables the system to fully utilize the low-temperature and power characteristics of sodium batteries and the high energy density advantages of lithium batteries within a wide temperature range, allowing for efficient, reliable, and intelligent operation across a wide temperature range, making it suitable for widespread application. Attached Figure Description

[0020] To more clearly illustrate and understand the technical solutions in the embodiments of the present invention, the accompanying drawings used in the background technology and embodiment descriptions of the present invention will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the content of the embodiments of the present invention and these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the principle architecture of the wide-temperature-range sodium-lithium hybrid energy storage system provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the safety protection and control strategy for the wide-temperature-range sodium-lithium hybrid energy storage system provided in Embodiment 2 of the present invention; Figure 3 This is a flowchart of the wide-temperature-range sodium-lithium hybrid energy storage control method provided in Embodiment 3 of the present invention. Detailed Implementation

[0022] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 Please refer to Figure 1 The above, Figure 1 This is a schematic diagram of the principle architecture of a wide-temperature-range sodium-lithium hybrid energy storage system provided in Embodiment 1 of the present invention. The schematic diagram includes the overall system architecture, main controller, environmental sensing components, and thermal management components.

[0024] As shown in the figure, this embodiment of the wide-temperature-range sodium-lithium hybrid energy storage system includes a sodium-ion battery unit, a lithium-ion battery unit, a main controller, an environmental sensing component, a thermal management component, and a bidirectional DC / DC converter. The system executes a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit to make them work in the optimal state.

[0025] For example, the sodium-ion battery unit and the lithium-ion battery unit are connected in parallel to the DC bus via independent bidirectional DC / DC converters to achieve voltage matching and independent power regulation for different battery platforms, avoiding voltage mismatch problems that may arise from direct parallel connection. In this embodiment, the sodium-ion battery unit is a sodium battery module composed of sodium-ion cells, or a battery cluster composed of multiple sodium battery modules connected in series; the lithium-ion battery unit is a lithium battery module composed of lithium-ion cells, or a battery cluster composed of multiple lithium battery modules connected in series; the selection range of lithium-ion cells includes lithium iron phosphate and lithium titanate. Each battery unit adopts a quick-connect connection method, supporting flexible system expansion. This structure effectively avoids the matching problems that may arise from direct parallel connection of different battery platform voltages, improving the reliability of the system.

[0026] For example, both the sodium-ion battery cell and the lithium-ion battery cell are equipped with dedicated battery management systems (BMS), referred to as Na-BMS and Li-BMS, respectively. The main controller establishes independent communication links with the Na-BMS and Li-BMS respectively through dual CAN bus interfaces to obtain battery status information and send control commands. The bidirectional DC / DC converter also receives power and mode commands from the main controller through the communication links.

[0027] For example, the main controller establishes independent communication links with the BMS of the sodium-ion battery unit and the BMS of the lithium-ion battery unit to execute differentiated power adjustment strategies based on battery temperature characteristics, thereby realizing the linkage control of temperature and power of the sodium-ion battery unit and the lithium-ion battery unit.

[0028] In this embodiment, the main controller is configured with dual CAN bus interfaces, establishing independent communication links with the BMS of the sodium-ion battery unit and the BMS of the lithium-ion battery unit, respectively. The bidirectional DC / DC converter receives power and mode commands through the communication links. The main controller maintains real-time interaction with each component at a period of 10-100ms, using key messages including but not limited to allowable charge / discharge power, SOC, SOH, voltage, current, temperature, and fault bits.

[0029] For example, the main controller is used to execute a differentiated power adjustment strategy based on the battery temperature characteristics, thereby achieving coordinated control of the temperature and power of the sodium-ion battery unit and the lithium-ion battery unit. The main controller adaptively switches between six operating modes based on parameters such as ambient temperature, battery temperature, SOC state, and load power, and employs a hysteresis anti-jitter mechanism to ensure switching stability.

[0030] For example, the wide-temperature-range sodium-lithium hybrid energy storage system further includes an environmental sensing component; the environmental sensing component is used to monitor environmental data and output the monitoring data to the main controller. In this embodiment, the environmental data monitored by the environmental sensing component includes, but is not limited to, temperature, humidity, and light parameters, providing strong environmental data support for the operation of the wide-temperature-range sodium-lithium hybrid energy storage system.

[0031] For example, the wide-temperature-range sodium-lithium hybrid energy storage system further includes a thermal management component; the thermal management component is used to heat or dissipate heat from the sodium-ion battery cells and lithium-ion battery cells, enabling the batteries to operate at a preset temperature. In practical applications, the thermal management component includes, but is not limited to, a PTC heater, a cooling fan, a liquid cooling pump, and a temperature sensor. In this embodiment, in low-temperature environments, the sodium-ion battery cell is activated first, which can power the heating device built into the lithium-ion battery cell to preheat the lithium battery. Furthermore, the preheating process can be coordinated with photovoltaic power generation to improve preheating efficiency.

[0032] Example 2 Please refer to Figure 2 The above, Figure 2 This diagram illustrates the safety protection and control strategy of the wide-temperature-range sodium-lithium hybrid energy storage system provided in Embodiment 2 of the present invention. The diagram showcases the multi-layered safety protection architecture, differentiated temperature-power linkage control strategy, and switching logic for six operating modes of the wide-temperature-range sodium-lithium hybrid energy storage system proposed in Embodiment 1. It includes three core parts: safety protection mechanism, temperature characteristics and power limitations, and an overview of the operating modes.

[0033] For example, the wide-temperature-range sodium-lithium hybrid energy storage system is also equipped with several hardwired DI / DO security links; the hardwired DI / DO security links are used as direct channels for critical faults such as emergency shutdown and hardware interlock, forming a multi-layer control and security network of "communication bus + hardwired connection".

[0034] In this embodiment, the main controller sets a period to maintain real-time interaction with the BMS of the sodium-ion battery unit, the BMS of the lithium-ion battery unit, and the bidirectional DC / DC converter through key messages. These key messages include, but are not limited to, allowable charge / discharge power, SOC, SOH, V / I / T, fault bits, etc.

[0035] In this embodiment, the wide-temperature-range sodium-lithium hybrid energy storage system employs a differentiated temperature response strategy, setting, but not limited to, the battery operating temperature range for the lithium-ion battery cells: 10-45℃ during charging and -10-45℃ during discharging; and the battery operating temperature range for the sodium-ion battery cells: -20-45℃. The wide-temperature-range sodium-lithium hybrid energy storage system implements differentiated power limiting based on the battery temperature characteristics.

[0036] In this embodiment, the main controller is configured with temperature-power linkage control; temperature control of the lithium-ion battery cell: T Li Do not charge when the temperature is below 10℃; T Li At 10-15℃, charging rate ≤0.2C; T Li Optimal operating temperature range: 15-35℃ (down to 0.5℃); T Li Derated operation when >45℃; T Li Shutdown protection occurs when the temperature exceeds 55℃. During discharge, T... Li When <-10°, C≤0.3C; T Li At -10–0°, C ≤ 0.5C.

[0037] In this embodiment, the temperature control of the sodium-ion battery cell is: T Na Available in the temperature range of -20 to 45°C. Na Control derating when the temperature is >55℃, T Na Cut-off is controlled when the temperature is >65℃, and dynamic derating can be performed according to the set R(T,SOC) table.

[0038] Specifically, in this embodiment, the wide-temperature-range sodium-lithium hybrid energy storage system executes a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery cells and the lithium-ion battery cells to ensure that the wide-temperature-range sodium-lithium hybrid energy storage system operates in an optimal state. This includes four differentiated power adjustment modes: "Sodium Priority Mode," "Hybrid Balancing Mode," "Lithium Priority Mode," and "Heating Priority Mode"; and two system-level operating modes: "Fault Bypass Mode" and "Maintenance Mode." The switching criteria of the main controller of the wide-temperature-range sodium-lithium hybrid energy storage system are based on the ambient temperature Tenv and the battery temperature T of the lithium-ion battery cells. li The battery temperature Tna of the sodium-ion battery cell, the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell, and the load power P. load The fault level is determined, and a hysteresis anti-jitter mechanism is adopted to ensure switching stability.

[0039] In this embodiment, the main controller of the wide-temperature-range sodium-lithium hybrid energy storage system maintains real-time interaction with the BMS (Na-BMS) of the sodium-ion battery unit, the BMS (Li-BMS) of the lithium-ion battery unit, and the bidirectional DC / DC converter through key messages at a period of 10-100ms. It adaptively switches between "sodium priority mode", "hybrid equalization mode", "lithium priority mode", "heating priority mode", "fault bypass mode", and "maintenance mode" according to specific operating conditions. The key messages include, but are not limited to, allowable charge / discharge power, SOC, SOH, V / I / T, and fault bit.

[0040] In this embodiment, the main controller is configured with temperature-power linkage control; temperature control of the lithium-ion battery cell: T li Do not charge when the temperature is below 10℃; T li At 10-15℃, charging rate ≤0.2C; T li Optimal operating temperature range: 15-35℃ (down to 0.5℃); T li Derated operation when >45℃; T li Shutdown protection at temperatures above 55°C. For example, a sodium-ion battery cell is linearly dated according to the R(T,SOC) table at -20–45°C, with a short-term 1.5C pulse (≤10s).

[0041] In this embodiment, when the ambient temperature is detected to be lower than a preset threshold, such as 0°C, the system switches to "sodium priority mode". When the ambient temperature is detected to be lower than the preset threshold, the sodium-ion battery unit is controlled to take on all the power of the system load.

[0042] In this embodiment, when switching to the "hybrid equalization mode" at a normal temperature (e.g., 10-35℃), the sodium-ion battery unit and the lithium-ion battery unit work together, distributing the load according to their respective SOC states and power characteristics. The sodium-ion battery unit bears the load with larger power fluctuations, while the lithium-ion battery unit bears the basic load, thereby achieving power complementarity and SOC balance. The magnitudes of the larger power fluctuations and the basic load are set according to the specific application scenario.

[0043] In this embodiment, under the "hybrid equalization mode," power allocation control is performed based on the deviation ΔSOC between the SOC of lithium-ion battery cells and sodium-ion battery cells. By monitoring the battery state of charge, the power allocation strategy is dynamically adjusted to bring ΔSOC within a preset range, ensuring the stable operation of the wide-temperature-range sodium-lithium hybrid energy storage system and improving battery lifespan. For example, in one application, if the deviation ΔSOC between the lithium-ion battery cell SOC and the sodium-ion battery cell SOC exceeds 5%, equalization scheduling is triggered. The goal is to reduce the difference to within 2%, and the equalization time for a single operation should not exceed 30 minutes.

[0044] In this embodiment, SOC estimation uses the ampere-hour integration method, supplemented by periodic calibration using the open-circuit voltage (OCV) curve that varies with temperature, and zero drift correction is performed simultaneously; SOH is calculated recursively using internal resistance R0 and capacity estimation.

[0045] In this embodiment, when the SOC of the sodium-ion battery cell is lower than a preset value (e.g., 20%), when switching to "lithium priority mode", the lithium-ion battery cell takes priority to bear the full power of the wide-temperature-range sodium-lithium hybrid energy storage system load, and the sodium-ion battery cell is in standby mode.

[0046] In this embodiment, when the ambient temperature is detected to be lower than a preset threshold, in the "heating priority mode," the sodium-ion battery unit provides power to the heating device built into the lithium-ion battery unit to preheat the lithium-ion battery to a suitable operating temperature range. During the preheating process, the wide-temperature-range sodium-lithium hybrid energy storage system monitors the temperature change of the lithium-ion battery. Once the temperature reaches the suitable operating range, the lithium-ion battery begins to participate in the system's operation.

[0047] It is worth mentioning that this heating function can work in conjunction with a photovoltaic power generation system. Under sunlight conditions, the photovoltaic power generation and sodium-ion battery work together to power the heating device, improving preheating efficiency.

[0048] In this embodiment, when any battery cell of the lithium-ion battery cell or the sodium-ion battery cell fails and becomes a faulty cell, in the "fault bypass mode", when any battery cell of the lithium-ion battery cell or the sodium-ion battery cell fails and becomes a faulty cell, the faulty cell is disconnected by a relay. At this time, the remaining healthy cells independently bear the load of the wide-temperature-range sodium-lithium hybrid energy storage system.

[0049] In this embodiment, the "maintenance mode" is used for the inspection and parameter calibration of the wide-temperature-range sodium-lithium hybrid energy storage system. In this mode, the charge and discharge states of each battery cell can be controlled independently, enabling capacity calibration, internal resistance testing, and equalization maintenance. In this embodiment, the "maintenance mode" supports remote operation, facilitating system diagnostics and parameter adjustments by maintenance personnel.

[0050] In this embodiment, the wide-temperature-range sodium-lithium hybrid energy storage system has two levels of fault thresholds; at the alarm level, the system is triggered to operate at reduced derating; at the trip level, the circuit is immediately cut off, and dual protection is provided by hardware links (e.g., fuses, hardware overvoltage / overcurrent / insulation protection). In this embodiment, typical protection thresholds include upper and lower voltage limits, temperature exceeding limits, insulation degradation, short circuit, reverse connection, overcurrent, and overpower.

[0051] It is worth mentioning that in the event of severe situations such as DC / DC failure, the wide-temperature-range sodium-lithium hybrid energy storage system can choose to degrade its operation and switch to single-battery-pack operation by bypassing the fault unit through a relay; if the BMS communication is lost, the system will enter a strict power-limiting mode; and in the event of multiple faults, the system will be triggered to enter a safe power-down process.

[0052] The wide-temperature-range sodium-lithium hybrid energy storage system proposed in this embodiment effectively extends the operating temperature range of the energy storage system, enabling it to operate stably in a wide temperature range from -40℃ to 80℃, significantly improving the operating temperature range. In the sodium-lithium hybrid energy storage system, the sodium-ion battery unit handles low-temperature conditions, while the lithium-ion battery unit handles the basic load at room temperature, achieving complementary performance. Their synergistic operation fully leverages the advantages of both battery technologies. A collaborative control mechanism is adopted for the wide-temperature-range sodium-lithium hybrid energy storage system. The sodium-ion battery unit and the lithium-ion battery unit are connected to the DC bus in parallel, and power coupling can be achieved using an independent bidirectional DC / DC converter, effectively avoiding voltage mismatch problems that may arise from direct parallel connection, thus improving system reliability and control accuracy. This invention adopts a modular design, facilitating system expansion and maintenance, and reducing operation and maintenance costs. The wide-temperature-range sodium-lithium hybrid energy storage system proposed in this embodiment fully utilizes the low-temperature and power characteristics of sodium batteries and the high energy density advantages of lithium batteries, enabling efficient, reliable, and intelligent operation over a wide temperature range.

[0053] Example 3 Please refer to Figure 3 The above, Figure 3 This is a flowchart of the wide-temperature-range sodium-lithium hybrid energy storage control method provided in Embodiment 3 of the present invention.

[0054] As shown in the figure, the wide-temperature-range sodium-lithium hybrid energy storage control method in this embodiment is applied to the wide-temperature-range sodium-lithium hybrid energy storage system proposed in either Embodiment 1 or Embodiment 2. Based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit in the wide-temperature-range sodium-lithium hybrid energy storage system, a differentiated power adjustment strategy is executed to make the wide-temperature-range sodium-lithium hybrid energy storage system work in the optimal state.

[0055] For example, the main controller acquires the ambient temperature T of the environmental sensing component in real time through a communication link at a preset period. env The battery temperature T reported by the BMS of the sodium-ion battery cell _Na and SOC _Na The battery temperature T reported by the BMS of the lithium-ion battery cell _Li and SOC _Li and load power P load System status parameters, etc.

[0056] For example, based on the acquired real-time data and according to preset switching criteria, the main controller selects the optimal operating mode. The operating modes that implement differentiated power adjustment strategies based on the battery temperature characteristics of sodium-ion battery units and lithium-ion battery units in the wide-temperature-range sodium-lithium hybrid energy storage system include: The system is configured with "Sodium Priority Mode", "Mixed Balance Mode", "Lithium Priority Mode" and "Heating Priority Mode". In addition, to ensure the safe and stable operation of wide-temperature-range sodium-lithium hybrid energy storage, this embodiment also includes "Fault Bypass Mode" and "Maintenance Mode" for the wide-temperature-range sodium-lithium hybrid energy storage control method.

[0057] In this embodiment, the switching criteria of the main controller of the wide-temperature-range sodium-lithium hybrid energy storage system are based on the ambient temperature Tenv and the battery temperature T of the lithium-ion battery cells. li The battery temperature Tna of the sodium-ion battery cell, the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell, and the load power P. load The fault level is determined, and hysteresis (±2°C, ±5% SOC, hold for 10s) is used for anti-shake.

[0058] In this embodiment, the main controller of the wide-temperature-range sodium-lithium hybrid energy storage system maintains real-time interaction with the BMS (Na-BMS) of the sodium-ion battery unit, the BMS (Li-BMS) of the lithium-ion battery unit, and the bidirectional DC / DC converter via a communication link at a preset period (10-100ms) to obtain the ambient temperature T of the environmental sensing component in real time. env The battery temperature T reported by the BMS of the sodium-ion battery cell Na and SOC Na The battery temperature T reported by the BMS of the lithium-ion battery cell Li and SOC Li and load power P load System status parameters, including but not limited to charge / discharge allowance, SOC, SOH, V / I / T, and fault bits.

[0059] For example, the main controller performs mode judgment and switching based on the acquired real-time data, and selects the optimal operating mode according to preset switching criteria. The differentiated power adjustment strategy implemented based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit in the wide-temperature-range sodium-lithium hybrid energy storage system includes four differentiated power adjustment modes and two system-level operating modes: 1) Differentiated power adjustment mode: "Sodium Priority Mode": When the ambient temperature is below a preset threshold, the sodium-ion battery cells take the lead in bearing all the power of the system load; "Hybrid Balance Mode": Under normal temperature conditions (10-35℃), the two types of batteries work together, and power distribution control is performed based on the SOC deviation ΔSOC; "Lithium Priority Mode": When the SOC of the sodium-ion battery cell is lower than the preset value, the lithium-ion battery cell takes priority to bear the system load, and the sodium-ion battery cell is in standby mode. "Heating Priority Mode": When the ambient temperature is detected to be lower than a preset threshold, the sodium-ion battery unit supplies power to the heating device of the lithium-ion battery unit.

[0060] 2) System-level operating mode: "Fault Bypass Mode": When any battery cell in the lithium-ion battery cell or sodium-ion battery cell fails and becomes a faulty cell, the faulty cell is disconnected via a relay, and the healthy cell independently assumes the load. "Maintenance Mode": Used for system maintenance and parameter calibration. This mode allows for individual control of the charging and discharging status of each battery cell, as well as capacity calibration, internal resistance testing, and equalization maintenance. This mode supports remote operation and individual control.

[0061] For example, the main controller is based on the ambient temperature T env The battery temperature T of a lithium-ion battery cell Li The battery temperature T of a sodium-ion battery cell Na Lithium-ion battery cell SOC and sodium-ion battery cell SOC, load power P load The system adapts to the corresponding working mode based on the switching criteria and employs a hysteresis anti-shake mechanism to ensure switching stability.

[0062] For example, the hysteresis anti-shake mechanism can be set as follows: temperature hysteresis 2°C, SOC hysteresis 5%, and hold time 10s.

[0063] For example, based on the selected operating mode, the main controller executes the corresponding power allocation strategy: In the "hybrid equalization mode," power allocation control is performed based on the deviation ΔSOC between the SOC of lithium-ion battery cells and sodium-ion battery cells. The power allocation strategy is dynamically adjusted by monitoring the battery state of charge. For example, equalization scheduling is triggered if ΔSOC exceeds 5%, with the goal of reducing the difference to within 2% and ensuring that a single equalization session does not exceed 30 minutes.

[0064] Meanwhile, the sodium-ion battery unit bears the load with large power fluctuations, while the lithium-ion battery unit bears the basic load, thereby achieving power complementarity and SOC balance; the magnitude of the large power fluctuations and the basic load are set according to the specific application scenario.

[0065] For example, the system continuously monitors the status of each component and executes temperature-power linkage control and multi-level protection strategies.

[0066] In this embodiment, a feasible SOC estimation is to use the ampere-hour integration method supplemented by the open-circuit voltage (OCV) curve that varies with temperature for periodic calibration, while performing zero drift correction; SOH (state of health) is calculated recursively through internal resistance R0 and capacity estimation.

[0067] In this embodiment, the wide-temperature-range sodium-lithium hybrid energy storage system has two levels of fault thresholds. The alarm level triggers derated operation; the trip level immediately disconnects the circuit, with double protection provided by hardware links (e.g., fuses, hardware overvoltage / overcurrent / insulation protection). Typical protection thresholds in this embodiment include upper and lower voltage limits, temperature exceeding limits, insulation degradation, short circuit, reverse connection, overcurrent, and overpower. It is worth noting that in severe situations such as DC / DC faults, the wide-temperature-range sodium-lithium hybrid energy storage system can choose to degrade operation and switch to single-battery-pack operation via relay bypass of the fault unit; if BMS communication fails, the system will enter a strict power-limiting mode; and in the event of multiple faults, the system will be triggered to enter a safe power-down procedure.

[0068] For example, in "heating priority mode," the system monitors the temperature change of the lithium-ion battery. Once the temperature reaches the suitable operating range, the lithium-ion battery begins to participate in the system's operation. This heating function can work in conjunction with a photovoltaic power generation system. Under sunlight conditions, both the photovoltaic power generation system and the sodium-ion battery jointly power the heating device, improving preheating efficiency.

[0069] The wide-temperature-range sodium-lithium hybrid energy storage control method proposed in this embodiment employs a collaborative control mechanism for the wide-temperature-range sodium-lithium hybrid energy storage system. This enables the system to adaptively adjust its operating mode and power distribution strategy according to environmental conditions, resulting in a high degree of intelligence. Through this proposed method, the wide-temperature-range sodium-lithium hybrid energy storage system fully leverages the low-temperature and power characteristics of sodium batteries and the high energy density of lithium batteries, achieving efficient, reliable, and intelligent operation across a wide temperature range.

[0070] It should be noted that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A wide-temperature-range sodium-lithium hybrid energy storage system, characterized in that, It includes a sodium-ion battery cell, a lithium-ion battery cell, and a main controller; the main controller is configured to execute a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery cell and the lithium-ion battery cell, so that they operate in an optimal state.

2. The wide-temperature-range sodium-lithium hybrid energy storage system according to claim 1, characterized in that, It also includes a bidirectional DC / DC converter; the sodium-ion battery unit and the lithium-ion battery unit are respectively connected in parallel to the DC bus through independent bidirectional DC / DC converters to achieve voltage matching and independent power regulation for different battery platforms.

3. The wide-temperature-range sodium-lithium hybrid energy storage system according to claim 1, characterized in that, The main controller establishes a communication link with the sodium-ion battery unit and the lithium-ion battery unit to execute a differentiated power adjustment strategy based on the battery temperature characteristics, thereby realizing the linkage control of temperature and power between the sodium-ion battery unit and the lithium-ion battery unit.

4. The wide-temperature-range sodium-lithium hybrid energy storage system according to claim 1, characterized in that, It also includes an environmental sensing component; the environmental sensing component is used to monitor environmental data and output the monitoring data to the main controller.

5. The wide-temperature-range sodium-lithium hybrid energy storage system according to any one of claims 1 to 4, characterized in that, It also includes a thermal management component; the thermal management component is used to heat or dissipate heat from the sodium-ion battery cells and the lithium-ion battery cells so that the batteries operate at a preset temperature.

6. A wide-temperature-range sodium-lithium hybrid energy storage control method, characterized in that, The method implements a differentiated power adjustment strategy based on the battery temperature characteristics of the sodium-ion battery unit and the lithium-ion battery unit in the wide-temperature-range sodium-lithium hybrid energy storage system according to claim 1, so that the wide-temperature-range sodium-lithium hybrid energy storage system operates in the optimal state.

7. The wide-temperature-range sodium-lithium hybrid energy storage control method according to claim 6, characterized in that, The differentiated power adjustment strategy implemented based on the battery temperature characteristics of sodium-ion and lithium-ion battery cells in the wide-temperature-range sodium-lithium hybrid energy storage system includes: The system is configured with "Sodium Priority Mode", "Hybrid Balance Mode", "Lithium Priority Mode", and "Heating Priority Mode". The main controller of the wide-temperature-range sodium-lithium hybrid energy storage system is based on, but is not limited to, ambient temperature Tenv and the battery temperature T of the lithium-ion battery cells. Li The battery temperature Tna of the sodium-ion battery cell, the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell, and the load power P. load The switching criteria are used to adaptively switch to the corresponding working mode.

8. The wide-temperature-range sodium-lithium hybrid energy storage control method according to claim 7, characterized in that, After the main controller switches the wide-temperature-range sodium-lithium hybrid energy storage system to "hybrid equilibrium mode", it performs power distribution control based on the deviation ΔSOC between the SOC of the lithium-ion battery cell and the SOC of the sodium-ion battery cell. By monitoring the state of charge of the battery, it dynamically adjusts the power distribution strategy to adjust ΔSOC to a preset range.

9. The wide-temperature-range sodium-lithium hybrid energy storage control method according to claim 6, characterized in that, The "fault bypass mode" is set so that when any battery cell fails and becomes a faulty cell, the faulty cell is disconnected via a relay.

10. The wide-temperature-range sodium-lithium hybrid energy storage control method according to any one of claims 6 to 9, characterized in that, When the "maintenance mode" is set, the main controller switches the wide-temperature-range sodium-lithium hybrid energy storage system to "maintenance mode," which allows for individual control of the charging and discharging status of each battery cell and supports remote operation of the wide-temperature-range sodium-lithium hybrid energy storage system.

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