Control method and device of energy storage system and energy storage system

Abstract

This application relates to the field of energy storage, providing a control method, apparatus, and energy storage system. The control method includes: acquiring the state of charge (SOC), state of energy (SOC), and individual cell voltages and remaining discharge times of multiple cells in the battery pack of the energy storage system; determining a target protection operation from multiple protection operations based on the SOC, SOC, individual cell voltages, and remaining discharge times, wherein the multiple protection operations include at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation; and executing the target protection operation. This solves the problem that related technologies often rely solely on voltage or SOC as a single criterion for energy storage system control, resulting in poor control reliability.

Description

Technical Field

[0001] This application relates to the field of energy storage, and in particular to a control method, device and energy storage system for an energy storage system. Background Technology

[0002] Existing over-discharge protection controls in energy storage systems suffer from six major drawbacks: a single criterion dimension, rigid protection methods, fixed threshold parameters, lack of predictive capabilities, neglect of individual cell differences, and susceptibility to instability at critical points. Specifically, many technologies rely solely on voltage or SOC (State of Charge) as the sole criterion, leading to insufficient protection reliability in areas with flat voltage plates in lithium iron phosphate batteries or when there are accumulated errors in SOC estimation. The common "one-size-fits-all" approach of hard-cutting upon reaching the threshold fails to provide sufficient response time for the upper-level energy management system, easily causing instantaneous power loss and hindering the supply of critical loads. Protection thresholds do not consider temperature changes and battery aging-related characteristic alterations, resulting in excessive over-discharge depth at low temperatures or accelerated battery life degradation at high temperatures. Protection mechanisms are all passive responses, lacking proactive prevention capabilities based on remaining discharge time. Monitoring only the total voltage leads to a "weakest link" effect, failing to identify localized over-discharge risks caused by individual cell inconsistencies. Furthermore, fixed thresholds lack hysteresis mechanisms, easily causing frequent protection jumps during critical point fluctuations, shortening circuit breaker lifespan. Summary of the Invention

[0003] This application provides a control method, device, and energy storage system for an energy storage system, which at least solves the problem that related technologies mostly rely on voltage or SOC as a single criterion for energy storage system control, resulting in poor control reliability.

[0004] According to some embodiments of this application, one aspect of this application provides a control method for an energy storage system, comprising: acquiring the state of charge (SOC), state of energy (SGE), individual cell voltages and remaining discharge time of multiple cells in the battery pack of the energy storage system; determining a target protection operation from multiple protection operations based on the SOC, SGE, individual cell voltages and remaining discharge time, wherein the multiple protection operations include at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation, wherein the first-level protection operation is to limit the charging and discharging power of the energy storage system to a preset proportion of the rated power and disconnect all unnecessary loads; the second-level protection operation is to control the energy storage inverter of the energy storage system to stop working to control the energy storage system to enter a standby state and disconnect all non-critical loads; the third-level protection operation is to disconnect the DC isolation circuit breaker of the energy storage system to make the energy storage system power down while retaining the wake-up circuit of the energy storage system to work; the non-critical loads include at least all the unnecessary loads; the preset proportion is less than 1; and executing the target protection operation.

[0005] In some embodiments, based on the state of charge, the state of energy, the individual cell voltage, and the remaining discharge time, one of the following is performed: a first-level protection operation, a second-level protection operation, and a third-level protection operation, including: calculating the difference between the state of charge and the state of energy to obtain a state difference value; if the absolute value of the state difference value is greater than a preset percentage, based on the minimum value between the state of charge and the state of energy, the individual cell voltage, and the remaining discharge time, one of the following is performed: a first-level protection operation, a second-level protection operation, and the third-level protection operation; if the absolute value of the state difference value is less than or equal to the preset percentage, based on the state of charge, the individual cell voltage, and the remaining discharge time, one of the following is performed: a first-level protection operation, a second-level protection operation, and the third-level protection operation.

[0006] In some embodiments, based on the state of charge, the individual cell voltage, and the remaining discharge time, one of the following is performed: a first-level protection operation, a second-level protection operation, and a third-level protection operation, including: determining a preset condition to be satisfied based on the magnitude of the state of charge of the energy storage system in the current operating state, the value of the individual cell voltage in the off-grid state and the grid-connected discharge state, and the magnitude of the remaining discharge time; and performing one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation based on the satisfied preset condition;

[0007] The preset conditions corresponding to the protection operation are set with different threshold values ​​to determine whether the preset conditions are met; the current working state is one of the following: off-grid state, grid-connected discharge state, grid-connected charging state.

[0008] In some embodiments, obtaining the remaining discharge time of the energy storage system includes: determining the initial remaining discharge time according to the following formula: RDT = (SOC_current - SOC_shutdown) × E_rated × SOH_f / P_current / 60, where RDT is the initial remaining discharge time, SOC_current is the estimated state of charge at the current moment, SOC_shutdown is the corrected protection shutdown state of charge threshold, E_rated is the rated energy, SOH_f is the health state decay factor, P_current is the current discharge power, and SOC_shutdown is obtained by at least temperature correction; smoothing the initial remaining discharge time and the previously smoothed remaining discharge time using an exponentially weighted moving average algorithm to obtain the remaining discharge time, where the previously smoothed remaining discharge time is the remaining discharge time obtained by the exponentially weighted moving average algorithm after the previous smoothing process.

[0009] In some embodiments, the exponentially weighted moving average algorithm is used to smooth the initial remaining discharge time and the remaining discharge time after the previous smoothing step to obtain the remaining discharge time, including: determining the remaining discharge time of the current step based on the initial remaining discharge time, the remaining discharge time after the previous smoothing step, and a smoothing factor.

[0010] In some embodiments, after performing one of the following: the first-level protection operation, the second-level protection operation, and the third-level protection operation, the method further includes: acquiring the state of charge and remaining discharge time of the energy storage system again to obtain the current state of charge and the current remaining discharge time; determining whether to release the restriction of the first-level protection operation or the restriction of the second-level protection operation based on the current state of charge and the current remaining discharge time; acquiring the individual cell voltage of the energy storage system again to obtain the current individual cell voltage, and determining whether to release the restriction of the third-level protection operation based on the magnitude of the current individual cell voltage, wherein a preset time window is set before the transition between the first-level protection operation, the second-level protection operation, and the third-level protection operation, and in the case of executing multiple protection operations, the protection operation with the highest priority is used as the power limitation constraint.

[0011] In some embodiments, after obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: determining an individual cell voltage threshold based on a voltage threshold at a base room temperature, the current room temperature, and a voltage temperature coefficient; and determining a state of charge threshold based on the state of charge at a base room temperature, the current room temperature, and the state of charge temperature coefficient.

[0012] In some embodiments, after obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: determining the difference between the maximum and minimum values ​​of each individual cell voltage as an individual cell voltage difference; and if the individual cell voltage difference is greater than or equal to a voltage difference threshold, adjusting the charging and discharging power of the energy storage system to at least 50% of the rated power.

[0013] According to some embodiments of this application, another aspect of this application provides a control device for an energy storage system. The device is applied to any of the control methods for the energy storage system described above, and includes: an acquisition unit for acquiring the state of charge (SOC), state of energy (SOE), individual cell voltages, and remaining discharge time of multiple cells in the battery pack of the energy storage system; and a first processing unit for determining a target protection operation from a multi-level protection operation based on the SOC, SOE, individual cell voltages, and remaining discharge time, wherein the multi-level protection operation includes at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation. The operation includes three levels: the first level protection operation is to limit the charging and discharging power of the energy storage system to a preset ratio of the rated power and disconnect all unnecessary loads; the second level protection operation is to control the energy storage converter of the energy storage system to stop working so that the energy storage system enters a standby state and disconnects all non-critical loads; the third level protection operation is to disconnect the DC isolation circuit breaker of the energy storage system so that the energy storage system loses power, while retaining the operation of the wake-up circuit of the energy storage system. The non-critical loads include at least all the unnecessary loads, and the preset ratio is less than 1; the second processing unit is used to execute the target protection operation.

[0014] According to some embodiments of this application, another aspect of this application provides an energy storage system, which is controlled using any of the control methods for the energy storage system described above.

[0015] The technical solution provided in this application has at least the following advantages: It introduces SOE as an auxiliary criterion and addresses the problem of cumulative error in SOC estimation by introducing voltage and SOE. It collects and independently judges the voltage of each cell in real time. When an individual cell reaches the protection threshold first due to consistency differences, protection can be triggered even if the total voltage is normal, preventing local over-discharge and improving the safety and reliability at the cell level. Based on real-time operating conditions, it calculates the remaining discharge time, predicts risks in advance before the battery is truly over-discharged, and triggers warnings or power reduction. This avoids the potential response lag or insufficient protection window when relying solely on instantaneous voltage or SOC threshold triggering. Thus, it solves the problem that many related technologies rely solely on voltage or SOC as a single criterion for energy storage system control, resulting in poor control reliability. Attached Figure Description

[0016] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the drawings in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic flowchart illustrating a control method for an energy storage system provided in an embodiment of this application;

[0018] Figure 2 This is a structural block diagram of a control device for an energy storage system provided in an embodiment of this application. Detailed Implementation

[0019] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0020] This application provides a control method for an energy storage system, such as... Figure 1 As shown, the method includes:

[0021] Step S101: Obtain the state of charge, state of energy, and individual cell voltage and remaining discharge time of multiple cells in the battery pack of the energy storage system.

[0022] Step S102: Based on the above-mentioned state of charge, energy state, individual cell voltage, and remaining discharge time, determine the target protection operation from the multi-level protection operations. The multi-level protection operation includes at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation. The first-level protection operation is to limit the charging and discharging power of the energy storage system to a preset ratio of the rated power and disconnect all unnecessary loads. The second-level protection operation is to control the energy storage converter of the energy storage system to stop working so that the energy storage system enters a standby state and disconnects all non-critical loads. The third-level protection operation is to disconnect the DC isolation circuit breaker of the energy storage system so that the energy storage system loses power while retaining the operation of the wake-up circuit of the energy storage system. The non-critical loads include at least all of the above-mentioned unnecessary loads, and the preset ratio is less than 1.

[0023] The priority levels, from lowest to highest, are: Level 1 protection operation, Level 2 protection operation, and Level 3 protection operation.

[0024] If multiple protection operations are triggered, the highest-level protection operation is selected as the final decision scheme for power limiting. For example, if the first-level protection operation, the second-level protection operation, and the third-level protection operation are triggered simultaneously, the third-level protection operation is selected as the final decision scheme for power limiting.

[0025] The specific judgment requirements for the three levels of protection operations are shown in Table 1, Table 2, and Table 3.

[0026] Table 1

[0027]

[0028] Table 2

[0029]

[0030] Table 3

[0031]

[0032] Step S103: Perform the target protection operation described above.

[0033] The system introduces State of Energy (SOE) as an auxiliary criterion and addresses the issue of cumulative errors in SOC estimation by incorporating voltage and SOE. It collects and independently judges the voltage of each individual cell in real time. When an individual cell reaches the protection threshold first due to inconsistency differences, protection can be triggered even if the total voltage is normal, preventing local over-discharge and improving the safety and reliability at the cell level. Based on real-time operating conditions, the remaining discharge time is calculated, and risks are predicted in advance before the battery is actually over-discharged, triggering warnings or power reduction. This avoids the response lag or insufficient protection window that may exist when relying solely on instantaneous voltage or SOC threshold triggering. Thus, it solves the problem that many related technologies rely solely on voltage or SOC as a single criterion for energy storage system control, resulting in poor control reliability.

[0034] SOC criterion: An extended Kalman filter (EKF) is used to fuse ampere-hour integral and open circuit voltage (OCV) correction information, achieving an estimation accuracy better than 3%. The SOC protection threshold is corrected in real time by the SOH (state of health) degradation factor: SOC_threshold_effective = SOC_threshold_nominal × (100 / SOH_current). When SOH decays to 80%, the nominal SOC threshold of 20% is effectively corrected to 25% of SOC (i.e., early triggering of protection), because the actual usable capacity has decreased by 20%.

[0035] SOC_threshold_effective is the effective SOC protection threshold after SOH correction; SOC_threshold_nominal is the nominal SOC protection threshold when the battery health status is 100%; SOH_current is the current battery health status percentage; 100 / SOH_current is the correction coefficient (the coefficient is 1 when SOH=100%, and the threshold remains unchanged; when SOH decreases, the coefficient is greater than 1, and the threshold is raised to trigger protection earlier).

[0036] Voltage composite criteria: Total voltage criterion: The total voltage of the battery pack is compared with the total voltage threshold after being filtered by a 5-second moving average, filtering out high-frequency noise and instantaneous load fluctuations. Individual cell voltage criterion: The voltage of each individual cell is independently compared with the individual cell threshold; triggering any single cell triggers an action (OR logic), effectively preventing the "weakest link" effect. Individual cell voltage difference criterion: When the maximum value Max(V_cell) - the minimum value Min(V_cell) ≥ ΔV_max (recommended value 300mV), the power is reduced and a voltage difference abnormality alarm is issued. Dynamic compensation for load voltage drop: V_threshold_compensated = V_threshold + I × R_internal, where R_internal is the battery's internal resistance as identified online by the BMS (Battery Management System). This compensation effectively prevents false triggering of protection due to internal resistance voltage drop during high-current discharge.

[0037] In some embodiments, based on the state of charge, the state of energy, the individual cell voltage, and the remaining discharge time, one of the following is performed: a first-level protection operation, a second-level protection operation, or a third-level protection operation, including: calculating the difference between the state of charge and the state of energy to obtain a state difference value; if the absolute value of the state difference is greater than a preset percentage, based on the minimum value between the state of charge and the state of energy, the individual cell voltage, and the remaining discharge time, one of the following is performed: the first-level protection operation, the second-level protection operation, or the third-level protection operation; if the absolute value of the state difference is less than or equal to the preset percentage, based on the state of charge, the individual cell voltage, and the remaining discharge time, one of the following is performed: the first-level protection operation, the second-level protection operation, or the third-level protection operation.

[0038] SOE Auxiliary Criterion: Specifically addressing the inherent characteristic of lithium iron phosphate batteries where the voltage plateau is extremely flat (OCV change is only about 0.1V) within the 20%~80% SOC range, SOE (State of Energy) is introduced as an auxiliary criterion. When the deviation between SOC and SOE exceeds 10% (confirmed for 60 seconds), the more conservative value (smaller value) is used as the protection trigger, ensuring a safety margin.

[0039] For battery systems with extremely flat voltage platforms, such as lithium iron phosphate (LFP), voltage changes are minimal when the State of Charge (SOC) varies within the middle range (e.g., 20%-80%). This results in low sensitivity and susceptibility to misjudgments when relying solely on voltage or SOC for judgment. By calculating the difference between SOC and SOE (energy integral, reflecting energy consumption more sensitively than voltage), and using SOE as an auxiliary criterion, a conservative (smaller) value is adopted as the trigger when the deviation between the two is large. This effectively fills the judgment gap of single-dimensional criteria during the voltage plateau period and prevents protection leakage caused by SOC estimation drift or a flat voltage plateau. This mechanism does not adopt the most conservative strategy in all cases but rather adaptively adjusts based on the state difference. When SOC and SOE are consistent (small difference), it indicates that the SOC estimation is accurate or the battery state is stable, and judgment can be made normally based on SOC, avoiding wasting usable battery capacity due to excessive conservatism. When the deviation between the two is large (large difference), it indicates estimation uncertainty or abnormal battery consistency / aging, and the system automatically switches to the more conservative SOE or minimum SOC value for judgment. This logic ensures absolute safety under abnormal operating conditions (preferring proactive protection) while avoiding over-protection under normal operating conditions, thus extending the actual usable depth of discharge of the battery. As the battery ages, SOC estimation errors may accumulate, and the consistency between individual cells deteriorates. The deviation between SOC and SOE often sensitively reflects this inconsistency in internal state or abnormal capacity decay caused by aging. By introducing this difference judgment, the system can identify the risk of the "weakest link" effect caused by individual cell differences or aging earlier, ensuring timely intervention when the battery condition deteriorates, preventing thermal runaway caused by over-discharge of individual cells, thereby improving the system's safety throughout its entire life cycle.

[0040] In some embodiments, based on the aforementioned state of charge, the aforementioned individual cell voltage, and the aforementioned remaining discharge time, one of the following is executed: the aforementioned first-level protection operation, the aforementioned second-level protection operation, and the aforementioned third-level protection operation, including: determining a preset condition to be satisfied based on the magnitude of the aforementioned state of charge of the energy storage system in the current operating state, the values ​​of the aforementioned individual cell voltage in the off-grid state and the grid-connected discharge state, and the magnitude of the aforementioned remaining discharge time; and executing one of the following based on the satisfied preset condition: the aforementioned first-level protection operation, the aforementioned second-level protection operation, and the aforementioned third-level protection operation; wherein, the preset condition corresponding to the protection operation is set with different threshold values ​​to determine whether the aforementioned preset condition is satisfied; the aforementioned current operating state is one of the following: off-grid state, grid-connected discharge state, and grid-connected charging state.

[0041] RDT: Remaining Discharge Time.

[0042] This application embodiment sets differentiated SOC and single-cell voltage thresholds for three different scenarios: off-grid, grid-connected discharge, and grid-connected charging (for example, the SOC protection point is more conservative during grid-connected charging and more flexible during off-grid discharge), and introduces Remaining Discharge Time (RDT) as a dynamic auxiliary criterion. This multi-dimensional conditional judgment logic can dynamically adjust the protection sensitivity according to the actual pressure the battery is under and the system operating mode, preventing protection failure due to changes in operating conditions and avoiding over-protection when the safety margin is sufficient, thereby extending the battery life. Through a three-level progressive protection architecture, the continuous power supply capability of critical loads is ensured, improving system availability. Traditional protection often directly cuts off the power supply when triggered, causing the system to lose power instantly. In this application embodiment, when the first and second level protections are triggered, the system only limits the power or cuts off non-critical loads, retaining the power supply to critical loads such as communication, security, and fire protection, and reserving a time window for upper-level EMS to perform load scheduling or maintenance intervention. This design transforms protection from passive hard disconnection to active soft intervention, reducing the impact of protection actions on user services, especially in off-grid or grid fluctuation scenarios, effectively extending the backup power supply time of critical equipment. Existing solutions mostly rely on the total battery pack voltage for judgment, easily overlooking the risk of local over-discharge of individual cells. In the embodiments of this application, the individual cell voltage is independently incorporated into the protection criteria and given the highest priority. Once the voltage of any individual cell reaches the safety threshold, a high-level protection is immediately triggered without waiting for the cumulative deterioration of the total voltage or SOC. At the same time, by combining multiple verifications of SOC, voltage, SOE, and RDT, the limitations of a single criterion (such as the flat voltage platform of lithium iron phosphate batteries and the cumulative error of SOC estimation) under specific operating conditions are effectively overcome, significantly reducing the probability of protection malfunctions and leaks, and ensuring that each cell in the battery cluster is within the safe operating range.

[0043] In some embodiments, obtaining the remaining discharge time of the energy storage system includes: determining the initial remaining discharge time according to the following formula: RDT = (SOC_current - SOC_shutdown) × E_rated × SOH_f / P_current / 60, where RDT is the initial remaining discharge time, SOC_current is the estimated state of charge at the current moment, SOC_shutdown is the corrected protection shutdown state of charge threshold (i.e., the three-level protection SOC threshold corrected by temperature and SOH), E_rated is the rated energy, SOH_f is the health state decay factor, P_current is the current discharge power, and SOC_shutdown is obtained by at least temperature correction; smoothing the initial remaining discharge time and the previous smoothed remaining discharge time using an exponentially weighted moving average algorithm to obtain the remaining discharge time, where the previous smoothed remaining discharge time is the remaining discharge time obtained by the exponentially weighted moving average algorithm after the previous smoothing process.

[0044] The SOH correction is reflected in two places in the formula, and these two corrections have different functions and do not constitute duplicate corrections. One correction adjusts the total energy, and the other adjusts the SOC scale. The first one is SOH_f (health status decay factor), which is the energy scaling. This is the ×SOH_f term in the main body of the formula. SOH_f = SOH / 100, and its function is to convert the rated energy into the current actual usable energy: E_actual = E_rated × SOH_f. For example, when SOH = 80%, the actual usable energy is only 80% of the rated value. If SOH_f is not multiplied, RDT will be overestimated by 1 / SOH, that is, the reduced energy is calculated as full energy for the range. It is reflected in the multiplication factor of RDT = (SOC_current - SOC_shutdown) × E_rated × SOH_f / P_current / 60.

[0045] The second point: SOH correction for SOC_shutdown, threshold anchoring. SOC_shutdown is the SOC threshold for Level 3 protection after correction for temperature and SOH, i.e., the threshold raised according to K_SOH=100 / SOH. For example, if the nominal Level 3 shutdown threshold is 10%, it is corrected to 10%×100 / 80=12.5% ​​when SOH=80%. This is reflected in the minuend of the numerator term (SOC_current-SOC_shutdown) in the formula.

[0046] SOH_f = SOH / 100, P_current is the current discharge power (W). Consider the Peukert (Peukert's Law / Peukert Effect) correction (optional, to improve accuracy at high discharge rates):

[0047] RDT=RDT_base×(P_nom / P_current) (k-1) ;

[0048] Where k is the Peukert coefficient, k≈1.02 for lithium iron phosphate batteries and k≈1.03~1.05 for ternary lithium batteries. EWMA smoothing: RDT_smooth(k) = 0.3×RDT_raw(k) + 0.7×RDT_smooth(k-1), with an equivalent time window of about 6 seconds (1Hz sampling rate).

[0049] RDT_base is the base remaining discharge time (the value before correction), which is the initial remaining discharge time calculated by the aforementioned formula RDT=(SOC_current-SOC_shutdown)×E_rated×SOH_f / P_current / 60, in minutes; P_nom is the rated discharge power, and P_current is the current discharge power.

[0050] By calculating the Residual Voltage Displacement (RDT), the system can predict the safe remaining time of the battery under current operating conditions in advance, rather than only cutting off power when the voltage or State of Charge (SOC) reaches a hard threshold. This allows the Energy Management System (EMS) and the load side to execute orderly load grading or power switching strategies in advance based on the remaining time window (e.g., 30 minutes, 15 minutes, etc.), avoiding business interruptions or critical equipment failures caused by sudden power outages, and greatly improving the continuity of power supply and system availability. Existing single criteria (such as looking only at voltage or SOC) are easily affected by instantaneous load fluctuations, sensor noise, or estimation errors, leading to false or missed triggering of protection actions. Introducing the EWMA algorithm to smooth the RDT (e.g., λ=0.3) can effectively filter out the drastic fluctuations in RDT caused by instantaneous power jumps, preventing frequent oscillations (i.e., jitter) in the protection state near the critical point, thereby extending the electrical life of actuators such as DC circuit breakers and contactors, and maintaining the stability of the control system.

[0051] EWMA: Exponentially Weighted Moving Average.

[0052] The relationship between RDT intervals and automatic actions is shown in Table 4.

[0053] Table 4

[0054]

[0055] RDT Trend Assisted Monitoring: If d(RDT) / dt < -1.5 (i.e., a decrease of more than 1.5 minutes per minute) and RDT < 20 minutes, the alert level is directly raised to orange emergency level without waiting for RDT to drop to 15 minutes. This mechanism can respond quickly in high-power mutation scenarios, compensating for the response lag caused by EWMA smoothing.

[0056] Hysteresis anti-jitter control mechanism: To prevent the protection from frequently triggering / recovering at the critical point, this application introduces a dual anti-jitter mechanism of hysteresis control and delayed confirmation in each level of protection, as shown in Table 5.

[0057] Table 5

[0058]

[0059] Where k_n is the noise standard deviation multiple. k_n = the multiple of the hysteresis bandwidth ΔV_hyst relative to the voltage noise standard deviation σ, and the formula is ΔV_hyst = k_n × σ.

[0060] Optimization Basis: The determination of hysteresis bandwidth follows the "minimum cost principle," with the objective function J(Δ) = α × P_oscillation(Δ) + β × Risk_under_protection(Δ) taking its minimum value. Here, P_oscillation (frequent switching cost) is inversely proportional to bandwidth Δ, while Risk_under_protection (protection hysteresis risk) is directly proportional to bandwidth Δ. An equal-weighted equilibrium point of α = β = 1 is chosen, and the recommended value is determined based on measured SOC and voltage noise levels.

[0061] Specifically, the first step is to measure the noise level σ: Data is continuously collected under typical steady-state conditions: SOC: Sampling at 1Hz for at least 24 hours (corresponding to the terminology for daily SOC fluctuation standard deviation in Table 5), obtaining a daily fluctuation sequence of the estimated SOC value; Voltage: Voltage (or lowest voltage) sequences for each individual cell are recorded simultaneously. The sequences are then detrended (slow true drift is removed, such as by using high-pass filtering or subtracting the moving average), and the remaining portion is considered as measurement / estimation noise. Its standard deviation is calculated: σ_SOC≈3~5%, σ_V≈25mV. These two measured values ​​are the input combined with the measured noise level.

[0062] Step 2: Express the two cost terms as a function of bandwidth Δ: P_oscillation(Δ) (frequent switching cost): a false switch occurs when random noise exceeds the bandwidth (or exceeds the trigger threshold + bandwidth and then falls back). The larger the bandwidth, the harder it is to exceed, hence it is inversely proportional to Δ. Quantization can be achieved using an analytical approximation under the Gaussian assumption (switching probability ≈ 2·Φ(-Δ / 2σ) correlation form), or by using a simulated feedback of measured noise sequences to count the number of protection actions / recoveries within a day.

[0063] Risk_under_protection(Δ) (Protection lag risk): When the actual state deteriorates, protection is only triggered after the gap of Δ is exceeded. The lag time ≈ Δ / (state change rate). The additional depth of protection during this period is the risk, and therefore it is proportional to Δ. The change rate is estimated by dSOC / dt and dV / dt under typical operating conditions.

[0064] Step 3: Normalize and solve for the optimal: The two cost terms have different dimensions (number vs. risk). First, normalize them to the same scale (e.g., divide by their respective values ​​under minimum bandwidth), and then substitute them into: J(Δ)=α·P_oscillation(Δ)+β·Risk_under_protection(Δ), and take α=β=1.

[0065] Let dJ / dΔ = 0 (or directly scan the Δ grid to find the minimum J) to obtain the optimal bandwidth Δ. Taking the approximation P = A / Δ and Risk = B·Δ as an example, Δ = √(A / B).

[0066] Step 4: Convert to k·σ form and round down: convert Δ Expressed as a multiple of the noise standard deviation: k = Δ / σ.

[0067] Voltage: Δ ≈100mV, σ=25mV→k=4; SOC: Δ ≈5%, σ is taken as the upper limit of the interval 5% (or the upper edge of σ=3~5%), k=1.0. Then rounded to an easy-to-use engineering setting: 0.10V / cell, 5%.

[0068] Step 5: Re-verification: Use the measured noise sequence for re-implementation and simulation to verify whether the number of false / missed operations and switching times within 24 hours under the selected bandwidth meets the standards; if not, fine-tune k and recalculate until balanced. Corresponding values ​​in Table 5: σ_V = 25mV, k = 4 → 4 × 25mV = 100mV = 0.10V / cell; σ_SOC = 3~5%, k = 1.0 (take the upper limit → 5%).

[0069] In some embodiments, the exponentially weighted moving average algorithm is used to smooth the initial remaining discharge time and the remaining discharge time after the previous smoothing step to obtain the remaining discharge time, including: determining the remaining discharge time of the current step based on the initial remaining discharge time, the remaining discharge time after the previous smoothing step, and the smoothing factor.

[0070] The exponentially weighted moving average (EWMA) algorithm is used to smooth the initial remaining discharge time, which can effectively filter out drastic jumps in RDT caused by instantaneous load fluctuations, current sampling noise, or power step changes, ensuring the continuity and stability of the prediction curve. At the same time, by assigning higher weights to recent data, the EWMA algorithm smooths noise while retaining the system's rapid response capability to changes in operating conditions, avoiding the serious lag effect caused by traditional long-period moving averages. Thus, while ensuring the reliability of the prediction results, the system can more quickly capture the true trend of the remaining discharge time, providing solid data support for the accurate triggering of graded protection criteria and preventing protection maloperation or failure to operate due to data fluctuations.

[0071] In some embodiments, after performing one of the following: the first-level protection operation, the second-level protection operation, and the third-level protection operation, the method further includes: acquiring the state of charge and remaining discharge time of the energy storage system again to obtain the current state of charge and the current remaining discharge time; determining whether to release the restriction of the first-level protection operation or the restriction of the second-level protection operation based on the current state of charge and the current remaining discharge time; acquiring the individual cell voltage of the energy storage system again to obtain the current individual cell voltage, and determining whether to release the restriction of the third-level protection operation based on the magnitude of the current individual cell voltage, wherein a preset time window is set before the transition between the first-level protection operation, the second-level protection operation, and the third-level protection operation, and in the case of executing multiple protection operations, the protection operation with the highest priority is used as the power limitation constraint.

[0072] This application monitors the current SOC and RDT in real time. Once the battery state recovers to a safe threshold (e.g., AC power is restored, battery resting voltage rebounds, or charging begins), it automatically and quickly releases the power limit or shutdown state. Especially for the first and second levels of protection (reversible protection), this real-time state-based release logic ensures that the system can immediately resume full power or normal standby operation after the crisis is resolved, minimizing usable energy loss and downtime caused by protection actions, and improving the energy utilization rate and response speed of the energy storage system. For the third level of hardware isolation (irreversible protection), this application specifies that the limitation is released by detecting the resting voltage rebound state of individual cells, which aligns with the voltage characteristics of lithium batteries (the voltage rebounds after discharge due to polarization elimination). Monitoring the change in this physical parameter to determine whether the recovery condition is met is more scientific and safer than simply relying on time delays. It prevents the risk of secondary over-discharge caused by premature recovery when the battery is still in a dangerous state, and avoids excessive conservatism caused by excessively long time settings, achieving a balance between safety and economy.

[0073] In some embodiments, after obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: determining an individual cell voltage threshold based on a voltage threshold at a base room temperature, the current room temperature, and a voltage temperature coefficient; and determining a state of charge threshold based on the state of charge at a base room temperature, the current room temperature, and the state of charge temperature coefficient.

[0074] Temperature correction for voltage threshold (linear approximation): V_cutoff(T) = V_cutoff(25℃) × [1 + α_V × (T - 25℃)];

[0075] Where α_V is the voltage temperature coefficient, V_cutoff(25℃) is the voltage threshold at 25℃, and V_cutoff(T) is the voltage threshold at temperature T. Recommended α_V values ​​for different battery types: LFP (Lithium Iron Phosphate (LiFePO4)) batteries: 0.0025~0.0035 / ℃; NMC (Lithium Nickel Cobalt Manganese Oxide (LiNiMnCoO2)) / NCA (Lithium Nickel Cobalt Aluminum Oxide (LiNiCoAlO2)) batteries: 0.0030~0.0040 / ℃; LTO (Lithium Titanate Oxide (Li4Ti5O4)) batteries: 0.0030~0.0040 / ℃. 12 (Lithium titanate) batteries 0.0015~0.0025 / ℃.

[0076] Temperature correction for SOC threshold: SOC_cutoff(T) = SOC_cutoff(25℃) + β_SOC × (T - 25℃);

[0077] Wherein, β_SOC is the SOC temperature compensation coefficient, with a recommended value of 0.15~0.25% / ℃. T is taken as the lowest single-cell temperature value in the battery pack (the most unfavorable principle).

[0078] At low temperatures, the electrolyte ionic conductivity decreases (≈1% / ℃), and the charge transfer impedance increases (activation energy Ea≈30kJ / mol, following the Arrhenius equation), leading to reduced usable capacity and increased internal resistance. While capacity can be recovered at high temperatures, side reactions accelerate, and lifetime decay speeds up, necessitating simultaneous limitation of charge and discharge power. The essence of temperature compensation is to maintain a consistent effective depth of discharge, rather than keeping the nominal protection threshold unchanged.

[0079] By introducing voltage temperature coefficient and SOC temperature coefficient, the protection threshold is dynamically adjusted (or adjusted upwards, depending on the specific coefficient definition and the conservatism of the protection logic; usually, lower temperatures require a more conservative approach, i.e., earlier triggering) based on the current room temperature. This ensures that the protection action remains consistent with the actual battery safety boundary under extreme temperatures, thereby protecting battery life and safety in harsh environments.

[0080] In some embodiments, after obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: determining the difference between the maximum and minimum values ​​of each individual cell voltage as an individual cell voltage difference; and adjusting the charging and discharging power of the energy storage system to at least 50% of the rated power when the individual cell voltage difference is greater than or equal to a voltage difference threshold.

[0081] During battery pack operation, due to individual differences, inconsistent internal resistance, or uneven heat dissipation, the voltage of individual cells often reaches a dangerous threshold before the total voltage. If only the total voltage is monitored, the high voltage of other normal cells may mask the low voltage of abnormal cells, causing some cells to remain in an over-discharge state for a long time, resulting in irreversible chemical damage or even thermal runaway. This application calculates the voltage difference between individual cells in real time, which can identify risks in advance when the total voltage is still within the normal range but individual cells show serious inconsistencies, thereby implementing precise protection at the individual cell level and extending the overall lifespan of the battery pack. When the voltage difference is detected to exceed the threshold, the solution does not directly trigger shutdown or hardware isolation, but takes a flexible intervention measure to limit the charging and discharging power to 50% of the rated power. This strategy effectively reduces the further damage of high current to battery consistency, slows down the widening trend of voltage difference, and provides sufficient time for the battery management system (BMS) to perform active balancing or for maintenance personnel to intervene.

[0082] SOH Adaptive Degradation Compensation: As the battery ages through cycles, the SOH gradually decreases, and the proportion of actual usable energy corresponding to the same nominal SOC decreases. This application introduces an SOH degradation factor to adaptively correct the protection threshold throughout its lifespan, i.e., an online SOH estimation method (weighted fusion of three methods) as shown in Table 6.

[0083] Table 6

[0084]

[0085] SOH_A represents the health status estimated by the cumulative throughput method; I represents the charge / discharge current; Δt represents the sampling time step; C_nom represents the rated capacity; N_cycle_life represents the nominal cycle life; and 2×C_nom×N_cycle_life represents the total throughput over the entire lifespan.

[0086] SOH_B represents the health status estimated by the internal resistance growth method; R_current represents the current internal resistance; R_initial represents the initial internal resistance; and R_EOL represents the end-of-life internal resistance.

[0087] SOH_C represents the health status estimated by the capacity decay method, i.e., the capacity retention rate; C_actual represents the actual available capacity; and C_nom represents the rated capacity.

[0088] Dynamic weight fusion formula:

[0089] w_i=(1 / σ_i²) / Σ_j(1 / σ_j²);

[0090] SOH_fused=w_A×SOH_A+w_B×SOH_B+w_C×SOH_C;

[0091] Protection threshold correction factor:

[0092] K_SOH=100 / SOH_fused;

[0093] SOC_threshold_effective=SOC_threshold_nominal×K_SOH;

[0094] Upper limit of correction range: K_SOH≤1.50 (corresponding to SOH not lower than 67%). When SOH is lower than 67%, it is recommended to force maintenance and replace the battery, and no longer try to compensate for excessive aging by adjusting the threshold.

[0095] Where w_i is the fusion weight of the i-th method (i takes values ​​A, B, and C), and the sum of the three is 1 (guaranteed by normalization of the denominator Σ_j). represents the proportion of this method in the fusion result. σ_i is the standard deviation (estimation uncertainty) of the estimation result of the i-th method, serving as the accuracy label for each method: SOH_B is greatly affected by operating conditions, so σ_B is usually the largest; SOH_C is the most accurate after full-charge-discharge calibration, so σ_C is the smallest; SOH_A has long-term smoothness, so σ_A is in the middle. σ_i is obtained from the historical estimation error statistics of each method, not calculated by a formula, and is an input parameter. 1 / σ_i² is the accuracy weight (reciprocal of variance). The smaller the variance, the higher the accuracy, and the larger the weight. When each method is independent and unbiased, weighting by 1 / σ² minimizes the variance of the fusion result. Σ_j(1 / σ_j²) is the sum of the accuracy weights of the three methods (j iterates through A, B, and C), used as the normalization denominator to ensure Σw_i=1.

[0096] Wherein, SOH_fused—the final estimated SOH value (%) after fusion, that is, the SOH used at the current moment, and also the estimation accuracy better than 3% (the quantity referred to). w_A, w_B, and w_C are the three obtained weights. SOH_A, SOH_B, and SOH_C are the estimated values ​​of the three methods in Table 6: SOH_A has long-term smoothness (slow tracking, strong noise resistance); SOH_B has good real-time performance (fast tracking, high noise); SOH_C is the most direct but is only updated 1-2 times per month. The three are weighted and complementary: A and B support real-time performance under normal circumstances, and C corrects long-term drift after calibration.

[0097] K_SOH is the protection threshold correction factor; SOH_fused is the fused SOH of the formula; SOC_threshold_effective is the corrected effective SOC protection threshold; SOC_threshold_nominal is the nominal SOC protection threshold.

[0098] The load grading offloading strategy is shown in Table 7.

[0099] Table 7

[0100]

[0101] Effect of extending critical load power supply: Taking an initial SOC of 25% and a total power of 30kW (of which the critical load is 3kW) as an example, the tiered offloading strategy can extend the continuous power supply time of the critical load from about 30 minutes in the one-size-fits-all solution to about 75 minutes, an extension of about 150%.

[0102] For the AC / DC power switching of the control system power board, this invention proposes an intelligent switching strategy based on battery status and AC quality, as shown in Table 8.

[0103] Table 8

[0104]

[0105] Switching constraints: AC power quality verification: Voltage amplitude deviation ≤ ±10% of rated value, frequency deviation ≤ ±0.5Hz of rated value, THD (Total Harmonic Distortion) ≤ 5%. If unqualified, DC power supply will be maintained and an alarm will be triggered. Switching method: Make-Before-Break soft switching; the time window for simultaneous closing of both relays is ≤ 20ms to ensure uninterrupted control power supply. Switching dead zone protection: If the target side voltage does not establish a stable output within 15ms, the switching will be automatically canceled and the system will revert to the original power supply side.

[0106] This application also provides a control device for an energy storage system, which is applied to any of the control methods for the aforementioned energy storage system, such as... Figure 2 As shown, the device includes: an acquisition unit 21, used to acquire the state of charge (SOC), state of energy (SEE), and individual cell voltages and remaining discharge times of multiple cells in the battery pack of the energy storage system; a first processing unit 22, used to determine a target protection operation from a multi-level protection operation based on the SOC, SEE, individual cell voltages, and remaining discharge time, wherein the multi-level protection operation includes at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation, wherein the first-level protection operation is to limit the charging and discharging power of the energy storage system to a preset ratio of the rated power and cut off all unnecessary loads; the second-level protection operation is to control the energy storage inverter of the energy storage system to stop working to control the energy storage system to enter a standby state and cut off all non-critical loads; the third-level protection operation is to disconnect the DC isolation circuit breaker of the energy storage system to make the energy storage system power down while retaining the operation of the wake-up circuit of the energy storage system; the non-critical loads include at least all of the aforementioned non-essential loads; and the preset ratio is less than 1; and a second processing unit 23, used to execute the target protection operation.

[0107] In some embodiments, the first processing unit includes: a first processing module for calculating the difference between the state of charge and the state of energy to obtain a state difference value; a second processing module for performing one of the following based on the minimum value of the state of charge and the state of energy, the individual cell voltage, and the remaining discharge time when the absolute value of the state difference is greater than a preset percentage: the first-level protection operation, the second-level protection operation, and the third-level protection operation; and a third processing module for performing one of the following based on the state of charge, the individual cell voltage, and the remaining discharge time when the absolute value of the state difference is less than or equal to the preset percentage: the first-level protection operation, the second-level protection operation, and the third-level protection operation.

[0108] The preset percentage can be 10%.

[0109] In some embodiments, the third processing module includes: a fourth processing module for determining preset conditions to be met based on the magnitude of the state of charge of the energy storage system in the current operating state, the values ​​of the individual cell voltage in the off-grid state and the grid-connected discharge state, and the magnitude of the remaining discharge time; and a fifth processing module for performing one of the following based on the preset conditions: the first-level protection operation, the second-level protection operation, or the third-level protection operation.

[0110] The preset conditions corresponding to the protection operation are set with different threshold values ​​to determine whether the above preset conditions are met; the above current working state is one of the following: off-grid state, grid-connected discharge state, grid-connected charging state.

[0111] In some embodiments, the acquisition unit includes: a determining module for determining the initial remaining discharge time according to the following formula: RDT = (SOC_current - SOC_shutdown) × E_rated × SOH_f / P_current / 60, where RDT is the initial remaining discharge time, SOC_current is the estimated state of charge at the current moment, SOC_shutdown is the corrected protection shutdown state of charge threshold, E_rated is the rated energy, SOH_f is the health state decay factor, P_current is the current discharge power, and SOC_shutdown is obtained by at least temperature correction; a sixth processing module for smoothing the initial remaining discharge time and the previously smoothed remaining discharge time using an exponentially weighted moving average algorithm to obtain the remaining discharge time, wherein the previously smoothed remaining discharge time is the remaining discharge time obtained by the exponentially weighted moving average algorithm after the previous smoothing process.

[0112] In some embodiments, the sixth processing module includes: a determining submodule for determining the remaining discharge time of the current step based on the initial remaining discharge time, the remaining discharge time after smoothing in the previous step, and the smoothing factor.

[0113] In some embodiments, the device further includes: a fourth processing unit configured to, after performing one of the following: the first-level protection operation, the second-level protection operation, and the third-level protection operation, again acquire the state of charge and remaining discharge time of the energy storage system to obtain the current state of charge and the current remaining discharge time, respectively; a first determining unit configured to, based on the current state of charge and the current remaining discharge time, determine whether to release the restriction of the first-level protection operation or the restriction of the second-level protection operation; and a second determining unit configured to, again acquire the individual cell voltage of the energy storage system to obtain the current individual cell voltage, and, based on the magnitude of the current individual cell voltage, determine whether to release the restriction of the third-level protection operation, wherein a preset time window is provided before the transition between the first-level protection operation, the second-level protection operation, and the third-level protection operation, and in the case of performing multiple protection operations, the protection operation with the highest priority is used as the power limitation constraint.

[0114] In some embodiments, the device further includes: a third determining unit configured to determine a single-cell voltage threshold based on a voltage threshold at a base room temperature, the current room temperature, and a voltage temperature coefficient after acquiring the single-cell voltage of multiple cells in the battery pack of the energy storage system; and a fourth determining unit configured to determine a state-of-charge threshold based on the state of charge at a base room temperature, the current room temperature, and the state-of-charge temperature coefficient.

[0115] In some embodiments, the device further includes: a fifth determining unit configured to determine, after acquiring the individual cell voltages of multiple cells in the battery pack of the energy storage system, the difference between the maximum and minimum values ​​of each individual cell voltage as an individual cell voltage difference; and an adjusting unit configured to adjust the charging and discharging power of the energy storage system to at least 50% of the rated power when the individual cell voltage difference is greater than or equal to a voltage difference threshold.

[0116] According to some embodiments of this application, another aspect of this application provides an energy storage system, which is controlled using any of the above-described energy storage system control methods.

[0117] The system consists of seven functional modules:

[0118] Data acquisition module: Real-time acquisition of parameters such as total battery pack voltage (accuracy ±0.1%), individual cell voltage (16-bit ADC (Analog-to-Digital Converter), accuracy ±1mV), charge / discharge current (Hall Effect Sensor, accuracy ±0.5%), individual cell temperature (NTC (Negative Temperature Coefficient) thermistor, accuracy ±0.5℃), and insulation resistance (IMD (Insulation Monitoring Device), accuracy ±5%).

[0119] State estimation module: Based on the collected data, it uses extended Kalman filter to estimate SOC online (accuracy better than 3%), and uses weighted fusion of cumulative throughput method, internal resistance growth method and capacity decay method to estimate SOH (accuracy better than 3%), and simultaneously estimates SOE (State of Energy) and battery internal resistance.

[0120] Multi-dimensional criterion generation module: Integrates information from three dimensions: SOC, voltage (total voltage + individual cell voltage + maximum voltage difference), and SOE. Through temperature compensation, SOH degradation compensation, and load voltage drop compensation, it performs real-time adaptive correction of the protection threshold and outputs the effective value of SOC (SOC_eff), the compensated voltage value (V_comp), and the effective value of SOE (SOE_eff).

[0121] RDT prediction module: Based on the current SOC, discharge power, rated energy and SOH factor, it calculates the remaining discharge time RDT in real time and uses an exponentially weighted moving average (EWMA, λ=0.3) for smoothing to reduce the impact of instantaneous power fluctuations.

[0122] The graded protection decision module, based on multi-dimensional composite criteria and RDT prediction results, determines the appropriate action to be taken according to a three-level progressive protection architecture: Level 1 early warning, Level 2 protection shutdown, or Level 3 hardware isolation. This module incorporates hysteresis control logic and a delay confirmation mechanism.

[0123] Execution module: Based on the decision results, it controls the PCS power output (0~100%Pmax), load switch (K1~K3 graded disconnection), DC circuit breaker (closing / opening), power supply switching relay (AC-DC switching) and low-power wake-up circuit.

[0124] Historical learning module: Records snapshots of operating conditions for each protection trigger (60 seconds before and after), forming a protection event dataset; statistically analyzes the trigger frequency of abnormal units; automatically analyzes the root causes of malfunction events and fine-tunes protection parameters (adjustment range not exceeding ±10% of the original threshold).

[0125] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0126] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0127] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0128] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0129] In the description of the embodiments of this application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0130] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0131] In the accompanying drawings corresponding to the embodiments of this application, the thickness and area of ​​the layers are enlarged for better understanding and ease of description. When describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be a third component between the two components. Conversely, when describing a component on the surface of another component, or when another component is formed or disposed on the surface of a component, it indicates that there is no third component between the two components. Furthermore, when describing a component as being "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0132] In the description of the embodiments of this application, when a component "includes" another component, other components are not excluded unless otherwise stated, and other components may be further included. Furthermore, when a component such as a layer, film, region, or plate is referred to as being "on / located" on another component, it can be "directly on" the other component (i.e., located on the surface of the other component with no other components between them), or another component may be present therein. Moreover, when a component such as a layer, film, region, or plate is "directly located" on another component, or when a component such as a layer, film, region, or plate is located on the surface of another component, it indicates that no other components are located therein.

[0133] The terminology used in the description of the various embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various embodiments and the appended claims, the term "part" is also intended to include the plural form unless the context clearly indicates otherwise. Components include layers, films, regions, or plates, etc.

[0134] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.

Claims

1. A control method for an energy storage system, characterized in that, include: The state of charge, state of energy, individual cell voltages and remaining discharge time of multiple cells in the battery pack of the energy storage system are obtained. Based on the state of charge, the state of energy, the individual cell voltage, and the remaining discharge time, a target protection operation is determined from a multi-level protection operation. The multi-level protection operation includes at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation. The first-level protection operation limits the charging and discharging power of the energy storage system to a preset percentage of the rated power and disconnects all unnecessary loads. The second-level protection operation controls the energy storage system's energy storage converter to stop working, thereby controlling the energy storage system to enter a standby state and disconnecting all non-critical loads. The third-level protection operation disconnects the DC isolation circuit breaker of the energy storage system, causing the energy storage system to lose power while retaining the energy storage system's wake-up circuit. The non-critical loads include at least all of the unnecessary loads, and the preset percentage is less than 1. Perform the target protection operation.

2. The control method for the energy storage system according to claim 1, characterized in that, Based on the state of charge, the state of energy, the individual cell voltage, and the remaining discharge time, perform one of the following: a first-level protection operation, a second-level protection operation, or a third-level protection operation, including: The state difference is obtained by calculating the difference between the state of charge and the state of energy. If the absolute value of the state difference is greater than a preset percentage, one of the following is executed based on the minimum value of the state of charge and the state of energy, the individual cell voltage, and the remaining discharge time: the first-level protection operation, the second-level protection operation, and the third-level protection operation. If the absolute value of the state difference is less than or equal to the preset percentage, one of the following operations is performed based on the state of charge, the individual cell voltage, and the remaining discharge time: the first-level protection operation, the second-level protection operation, or the third-level protection operation.

3. The control method for the energy storage system according to claim 2, characterized in that, Based on the state of charge, the individual cell voltage, and the remaining discharge time, perform one of the following: a first-level protection operation, a second-level protection operation, or a third-level protection operation, including: Based on the magnitude of the state of charge of the energy storage system in its current operating state, the values ​​of the individual cell voltage in the off-grid state and the grid-connected discharge state, and the magnitude of the remaining discharge time, the preset conditions to be satisfied are determined. Based on the preset conditions met, perform one of the following: the first level protection operation, the second level protection operation, or the third level protection operation; The preset conditions corresponding to the protection operation are set with different threshold values ​​to determine whether the preset conditions are met; the current working state is one of the following: off-grid state, grid-connected discharge state, grid-connected charging state.

4. The control method for the energy storage system according to claim 1, characterized in that, Obtaining the remaining discharge time of the energy storage system includes: The initial remaining discharge time is determined using the following formula: RDT = (SOC_current - SOC_shutdown) × E_rated × SOH_f / P_current / 60, where RDT is the initial remaining discharge time, SOC_current is the estimated state of charge at the current moment, SOC_shutdown is the corrected protection shutdown state of charge threshold, E_rated is the rated energy, SOH_f is the health state attenuation factor, P_current is the current discharge power, and SOC_shutdown is obtained with at least temperature correction. The initial remaining discharge time and the remaining discharge time after the previous smoothing step are smoothed using an exponentially weighted moving average algorithm to obtain the remaining discharge time. The remaining discharge time after the previous smoothing step is the remaining discharge time after the previous smoothing step obtained using the exponentially weighted moving average algorithm.

5. The control method for the energy storage system according to claim 4, characterized in that, The initial remaining discharge time and the remaining discharge time after the previous smoothing step are smoothed using an exponentially weighted moving average algorithm to obtain the remaining discharge time, including: The remaining discharge time for the current step is determined based on the initial remaining discharge time, the remaining discharge time after smoothing in the previous step, and the smoothing factor.

6. The control method for the energy storage system according to claim 1, characterized in that, After performing one of the following: the first-level protection operation, the second-level protection operation, or the third-level protection operation, the method further includes: The state of charge and remaining discharge time of the energy storage system are obtained again to obtain the current state of charge and the current remaining discharge time. Based on the current state of charge and the current remaining discharge time, determine whether to lift the restrictions of the first-level protection operation or the second-level protection operation; The individual cell voltage of the energy storage system is acquired again to obtain the current individual cell voltage. Based on the magnitude of the current individual cell voltage, it is determined whether to release the restriction of the third-level protection operation. A preset time window is set before the transition between the first-level protection operation, the second-level protection operation, and the third-level protection operation. In the case of executing multiple protection operations, the protection operation with the highest priority is used as the power limitation constraint.

7. The control method for the energy storage system according to claim 1, characterized in that, After obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: The individual unit voltage threshold is determined based on the voltage threshold at the baseline room temperature, the current room temperature, and the voltage temperature coefficient. The state of charge threshold is determined based on the state of charge at the baseline room temperature, the current room temperature, and the state of charge temperature coefficient.

8. The control method for the energy storage system according to claim 1, characterized in that, After obtaining the individual cell voltages of multiple cells in the battery pack of the energy storage system, the method further includes: The difference between the maximum and minimum values ​​of the individual cell voltages is defined as the individual cell voltage difference. If the voltage difference between the individual cells is greater than or equal to the voltage difference threshold, the charging and discharging power of the energy storage system shall be adjusted to at least 50% of the rated power.

9. A control device for an energy storage system, said device being applied to the control method of the energy storage system according to any one of claims 1 to 8, characterized in that, include: The acquisition unit is used to acquire the state of charge, state of energy, individual cell voltage and remaining discharge time of multiple cells in the battery pack of the energy storage system. The first processing unit is configured to determine a target protection operation from a multi-level protection operation based on the state of charge, the state of energy, the individual cell voltage, and the remaining discharge time. The multi-level protection operation includes at least one of the following: a first-level protection operation, a second-level protection operation, and a third-level protection operation. The first-level protection operation limits the charging and discharging power of the energy storage system to a preset percentage of its rated power and disconnects all unnecessary loads. The second-level protection operation controls the energy storage system's energy storage converter to stop operating, thereby controlling the energy storage system to enter a standby state and disconnecting all non-critical loads. The third-level protection operation disconnects the DC isolation circuit breaker of the energy storage system, causing the energy storage system to lose power while retaining the operation of the energy storage system's wake-up circuit. The non-critical loads include at least all of the unnecessary loads, and the preset percentage is less than 1. The second processing unit is used to perform the target protection operation.

10. An energy storage system, characterized in that, The energy storage system is controlled using the control method described in any one of claims 1 to 8.

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