A distributed energy storage system charging and discharging regulation method and system

Abstract

The application belongs to the technical field of energy storage regulation, and particularly relates to a distributed energy storage system charging and discharging regulation method and system, which comprises the following steps: collecting the terminal voltage and load current of each energy storage node at a high frequency, extracting the terminal voltage transient drop amplitude and current transient change amount at the current step, and obtaining the dynamic internal resistance by using polarization relaxation compensation correction; calculating the heat generation power according to the dynamic internal resistance and the current instruction, and calculating the heat dissipation power, and taking the ratio of the two as the thermal safety margin factor; when the thermal safety margin factor is lower than the threshold value, the current instruction is reduced according to the margin deviation; the reduced power is converted into the quota according to the voltage of the energy storage node, and the current instruction of the healthy energy storage node is increased by taking the thermal safety margin redundancy proportion of the healthy energy storage node as the weight, the thermal safety margin factor after distribution is estimated, if it is out of limit, it is truncated and iteratively redistributed until safe acceptance or alarm. The application can improve the thermal balance capability of the distributed energy storage system under the cold and warm temperature difference.

Description

Technical Field

[0001] This invention relates to the field of energy storage regulation technology, specifically to a method and system for regulating the charging and discharging of a distributed energy storage system. Background Technology

[0002] In distributed energy storage systems deployed in high-altitude and cold regions, the ventilation conditions and space dimensions of each energy storage node vary due to different installation locations, resulting in a gradient change in the heat exchange capacity of the energy storage node's outer shell surface along the spatial distribution.

[0003] After repeated charge-discharge cycles, the internal aging process of battery modules in a distributed energy storage system is not synchronized. There are significant differences in capacity decay and impedance growth among the energy storage nodes. These differences change the actual terminal voltage response and internal loss level of different energy storage nodes under the same current command.

[0004] However, current energy storage control systems mostly use the factory internal resistance or the average internal resistance of the entire station as a benchmark. After matching a fixed temperature protection threshold, they uniformly issue charging and discharging current commands to all energy storage nodes. This scheduling method, which is based on the average value, does not take into account the coupling effect of local temperature difference and aging degree differences on electrochemical impedance. As a result, the control loop lacks a judgment basis that can reflect the thermal tolerance boundary of each energy storage node, which leads to energy storage safety risks.

[0005] When operating under continuous high load, energy storage nodes with poor heat dissipation conditions may have their internal heat generation rate approach or even exceed the heat dissipation limit of their environment before other energy storage nodes, leading to heat accumulation inside the energy storage node.

[0006] Existing energy storage system charging and discharging control mechanisms typically only monitor whether the shell temperature or bus current exceeds the limit, without simultaneously comparing the heat generation power and heat dissipation power, making it difficult to detect early signs of thermal runaway before the temperature rises sharply.

[0007] Even if protection is triggered, the conventional handling falls into two categories: one is to directly withdraw the total dispatch power of the system, resulting in a power gap on the grid side; the other is to distribute the unexecuted power of the restricted energy storage nodes to the other energy storage nodes, forcing the energy storage nodes with insufficient heat dissipation reserves to take on additional loads.

[0008] Neither approach provides a means to transfer derated power based on the difference in actual heat dissipation margin of each energy storage node under the constraint of keeping the total dispatch power unchanged. The equal redistribution is particularly prone to ignoring the heat dissipation limit of the receiving energy storage node, causing the originally safe energy storage node to become a new risk point of exceeding the limit.

[0009] In summary, the key technical problem to be solved is how to establish a thermal safety judgment mechanism at the energy storage node level, based on the real-time ratio of heat generation to heat dissipation, while taking into account the differences in heat dissipation and impedance changes between energy storage nodes, and how to implement a smooth current reduction for energy storage nodes with a tendency to accumulate heat under the constraint of no reduction in total dispatch power, while transferring the reduced power to other energy storage nodes according to the acceptable margin. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides a method and system for regulating the charging and discharging of a distributed energy storage system, the technical solution of which is as follows:

[0011] In a first aspect, the present invention provides a method for regulating the charging and discharging of a distributed energy storage system, comprising:

[0012] The terminal voltage and load current of each energy storage node are collected synchronously. When a current step is detected, the transient drop amplitude of the terminal voltage and the transient change of the current are determined. The ratio of the drop amplitude to the change of current is corrected by polarization relaxation compensation to obtain the dynamic internal resistance of each energy storage node.

[0013] The heat generation power is calculated based on the dynamic internal resistance and the current command of the energy storage node. The heat dissipation power is calculated based on the convective heat transfer coefficient, the heat dissipation area of ​​the energy storage node, and the difference between the surface temperature of the energy storage node and the ambient temperature. The heat dissipation power is divided by the heat generation power to obtain the thermal safety margin factor.

[0014] When the thermal safety margin factor of any energy storage node is lower than the critical threshold, the margin deviation of the energy storage node is calculated, and the original current command is reduced according to the margin deviation using the attenuation mapping function to obtain the reduced current command.

[0015] The power reduction caused by the reduction in current command is converted into a power quota based on the energy storage node voltage. Energy storage nodes with a thermal safety margin factor greater than the critical threshold are identified as healthy energy storage nodes. The proportion of the thermal safety margin redundancy of each healthy energy storage node to the sum of the thermal safety margin redundancy of all healthy energy storage nodes is used as the non-orthogonal projection weight. The power quota is allocated to each healthy energy storage node according to this weight, and its current command is increased. The thermal safety margin factor of each healthy energy storage node after the increase in current command is estimated. If the estimated thermal safety margin factor of any healthy energy storage node is lower than the critical threshold, the power quota that causes secondary over-limit is truncated. The truncated part is returned to the weight allocation step as a new power to be allocated and iteratively executed until all power quotas are safely accepted or a system alarm is triggered and an overall derialization is requested, thus completing the charging and discharging regulation of the distributed energy storage system.

[0016] Preferably, obtaining the dynamic internal resistance of each energy storage node includes: monitoring the rate of change of the load current; determining a current step trigger when the rate of change of the current exceeds a preset step trigger threshold; and extracting a voltage and current data window containing the step transient process; performing denoising processing on the voltage and current data window; extracting the difference between the steady state before and after the step based on the denoised data; obtaining the transient voltage drop amplitude and the transient current change; and constructing a multi-exponential decay function with the terminal voltage and the load current as input variables. The exponential decay function is integrated from the start of the current step to the end of the polarization process to obtain the polarization relaxation accumulation time effect; the current ambient temperature change gradient and battery cycle aging data are obtained, and the preset benchmark compensation coefficient is adaptively tuned by looking up a table or linear correction to obtain the polarization compensation calibration coefficient; the ratio of the transient voltage drop amplitude to the transient current change is used as the transient impedance ratio, and the product of the polarization relaxation accumulation time effect and the polarization compensation calibration coefficient is added to the transient impedance ratio to obtain the dynamic internal resistance.

[0017] Preferably, obtaining the thermal safety margin factor includes: calculating the product of the dynamic internal resistance and the square of the energy storage node current command, and superimposing a minimum positive bias to obtain the transient heat generation power; taking the product of the convective heat transfer coefficient and the heat dissipation area of ​​the energy storage node as the total heat transfer thermal conductivity, and multiplying the total heat transfer thermal conductivity by the energy storage node-ambient temperature difference obtained by subtracting the ambient temperature from the surface temperature of the energy storage node to obtain the convective heat dissipation power; and using the convective heat dissipation power as the numerator and the transient heat generation power as the denominator to perform a division operation to output the thermal safety margin factor.

[0018] Preferably, obtaining the reduced current command includes: determining the margin deviation as the difference between the critical threshold and the thermal safety margin factor; obtaining the ratio of the current total dispatch power of the system to the rated total power of the system as a load correction factor; linearly superimposing a preset basic sensitivity coefficient and the load correction factor to generate an attenuation control sensitivity coefficient; inputting the product of the margin deviation and the attenuation control sensitivity coefficient as a negative exponential term into the exponential smoothing attenuation function; and performing continuous contraction correction on the original current command to output the reduced current command.

[0019] Preferably, the step of allocating the power quota to each healthy energy storage node and increasing its current command according to the weight includes: calculating the difference between the original current command and the reduced current command to obtain the current reduction amount, and multiplying the current reduction amount by the energy storage node voltage of the energy storage node that has been reduced to convert it into the power quota; screening energy storage nodes whose thermal safety margin factor is greater than the critical threshold to construct the healthy energy storage node set, and calculating the difference between the thermal safety margin factor of each energy storage node and the critical threshold to obtain the thermal safety margin redundancy; dividing the thermal safety margin redundancy of a single energy storage node by the sum of the thermal safety margin redundancy of all energy storage nodes in the healthy energy storage node set to obtain the non-orthogonal projection weight; allocating the power quota to the corresponding thermally redundant energy storage node according to the non-orthogonal projection weight, and converting it into an additional command current based on the energy storage node voltage of the corresponding energy storage node, and accumulating it into the original current command of the corresponding energy storage node.

[0020] Preferably, the step of returning the truncated portion as new power to be allocated to the weight allocation step for iterative execution includes: substituting the accumulated current command into the heat generation power calculation to re-derive the updated thermal safety margin factor for the corresponding energy storage node; when the updated thermal safety margin factor is less than the critical threshold, calculating the safe current limit of the corresponding energy storage node based on the critical threshold and the convective heat dissipation power of the corresponding energy storage node; truncating the power quota corresponding to the portion of the accumulated current command that exceeds the safe current limit to obtain the remaining unallocated power, and after removing the fully loaded energy storage node from the healthy energy storage node set, triggering the next round of iterative reallocation.

[0021] Preferably, triggering the system alarm and requesting an overall reduction includes: continuously monitoring the number of energy storage nodes in the healthy energy storage node set and the current iteration number during the iterative redistribution process; when the number of energy storage nodes in the healthy energy storage node set drops to zero or the current iteration number reaches a preset iteration limit, and the remaining unallocated power is still greater than zero, determining that it is impossible to safely accept all the power reductions; terminating the iterative redistribution and triggering the system reduction alarm, and outputting the required value for requesting an overall reduction to the scheduling system.

[0022] Preferably, the weight allocation step is executed iteratively, including: calculating the ratio of the current total dispatch power of the system to the rated total power of the system to generate dispatch status evaluation parameters; when the dispatch status evaluation parameters exceed a preset load threshold, establishing that the current system has entered a high load discharge dispatch interval, and triggering a traversal detection mechanism for the thermal safety margin factor of all energy storage nodes.

[0023] Secondly, the present invention provides a charging and discharging control system for a distributed energy storage system, which adopts the following technical solution:

[0024] A distributed energy storage system charge and discharge control system includes a processor and a memory, wherein the memory stores computer program instructions, and when the computer program instructions are executed by the processor, the distributed energy storage system charge and discharge control method described above is implemented.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. Construct a thermal safety margin factor to reflect the instantaneous surplus or deficit of heat dissipation capacity of each energy storage node relative to the heat generation level, so that the charge and discharge main control system can get rid of the limitation of the global average internal resistance model and accurately lock the specific energy storage node whose heat dissipation reserve is close to the critical point.

[0027] 2. The reduction in current command after compression deepens as the deviation increases. The entire change process is free of abrupt changes, avoiding transient disturbances to the energy storage converter and grid side caused by sudden current changes. The gradual reduction in current command directly reduces the heat generation power of the energy storage node, curbing the continuous temperature rise caused by insufficient heat dissipation.

[0028] 3. The power gap caused by derating at dangerous nodes is converted into a quota based on the terminal voltage. The quota is then allocated and converted into additional current based on the proportion of the thermal safety margin redundancy of each healthy node to the total redundancy of all healthy nodes. After allocation, the thermal safety margin factor is estimated. If a secondary over-limit occurs, the over-limit part is cut off and iterative redistribution is carried out until the system can safely take over or trigger a derating alarm. This ensures that the power reduction is directed to nodes with sufficient heat dissipation under the condition of total power conservation, replacing the amortized transfer, suppressing the chain thermal over-limit, and improving the system's thermal field balance capability under high-altitude and cold conditions. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the implementation of a charging and discharging control method for a distributed energy storage system according to an embodiment of the present invention. Detailed Implementation

[0030] S1: Calculation of dynamic internal resistance of energy storage nodes based on current step transient response and polarization relaxation compensation.

[0031] An independent dynamic internal resistance calculation process is established for each energy storage node. The terminal voltage and load current are collected synchronously at high frequency. The voltage transient response is captured at the moment a current step event is detected. Polarization relaxation compensation is introduced to correct the transient impedance. The resulting dynamic internal resistance is directly used as the input parameter for subsequent heat generation power calculation.

[0032] The data acquisition unit synchronously acquires the terminal voltage time series and load current time series of each energy storage node at a sampling rate of not less than 1kHz. In this embodiment, the sampling rate is set to 5kHz, which can be adjusted by the implementer according to the specific implementation scenario.

[0033] The terminal voltage sequence is denoted as The load current sequence is denoted as , where subscript This is the number of the energy storage node. At the sampling time, these two time series together constitute the raw data for transient identification.

[0034] Calculate the rate of change of current during continuous monitoring. The magnitude of this rate of change directly reflects the degree of instantaneous fluctuation in the load current, where Represents the integral symbol.

[0035] when When the absolute value exceeds the preset trigger threshold, a current step event is determined to have occurred. The preset trigger threshold is usually set to 20A / s. The implementer can adjust it according to the current change characteristics of the system. This threshold is a preset parameter, and its function is to calibrate a detection threshold for a sudden current change.

[0036] Once a current step is detected, a complete voltage and current data window covering the steady state before the step, the transient state after the step, and the steady state after the step is captured, based on the moment the step occurs.

[0037] The data window and Median filtering and Kalman filtering were applied successively to remove high-frequency measurement noise and electromagnetic interference from the extraction of step features. The specific implementation of these two filtering methods is a well-known technique and will not be elaborated here.

[0038] After denoising, the average value of the steady-state current before the step jump is taken. and the average value of the steady-state current after the step The difference between the two is the transient change in current. In the formula, This is the transient change in current, in amperes. This change directly reflects the amplitude of the current jump at the instant of the step and can be used as the denominator input for calculating the ohmic internal resistance component. This represents the average steady-state current after the step jump, in amperes. This represents the average steady-state current before the step jump, in amperes.

[0039] Correspondingly, the transient voltage drop amplitude is extracted from the denoised terminal voltage data. .

[0040] Specifically, at the instant of the step jump, the voltage drops sharply, and the average steady-state voltage before the step jump is... The lowest value of the voltage waveform within a very short time after the step jump Subtracting them gives the instantaneous drop magnitude. In the formula, The transient voltage drop amplitude, in volts, is used to calculate the ohmic part of the transient impedance in conjunction with the current change, after deducting the effect of the slow recovery of the polarization voltage. The average steady-state voltage before the step jump is expressed in volts. This represents the transient minimum value in the voltage waveform after a step jump, expressed in volts.

[0041] If we directly take the ratio As an internal resistance, the obtained value still includes the additional effect of electrochemical polarization on transient voltage, and the dynamic impedance component directly related to heat generation cannot be isolated separately.

[0042] Therefore, polarization relaxation compensation is introduced to correct this ratio, and a polarization compensation function is defined. This function uses a multi-exponential decay fitting form, with terminal voltage and load current as input variables, and outputs a dimensionless coefficient that decays over time to describe the decay process of polarization voltage after a step jump.

[0043] The specific parameters of the multi-exponential decay model are obtained by offline testing of the electrochemical impedance spectroscopy of the battery module and stored in the control unit as offline calibrated constants.

[0044] For functions From the start of the step When the polarization process is basically over Integrating, we obtain the cumulative time effect of polarization relaxation. In the formula, The cumulative time effect is expressed in seconds, and its magnitude incorporates the time contribution of each decay component during the polarization voltage recovery process after a step jump. This is the start time of the current step jump; This refers to the time point at which polarization relaxation essentially ends, as determined by the voltage recovery curve, i.e., the time point at which the voltage recovery rate drops below a preset threshold. It is a multi-exponential decay function, and the output is a dimensionless coefficient.

[0045] Based on this, the ohmic resistance component is added to the polarization relaxation compensation term to establish the formula for calculating the dynamic internal resistance:

[0046]

[0047] In the formula, For the first The dynamic internal resistance of an energy storage node, in ohms, takes into account the ohmic response during a step transition and compensates for the interference of the polarization relaxation process. It can more accurately reflect the impedance level of the energy storage node under the current temperature, state of charge and aging conditions, and can be directly used to calculate the heat generation power of the energy storage node.

[0048] The ohmic internal resistance component is based on the transient response, in ohms.

[0049] The polarization compensation calibration coefficient, in ohms per second, is tuned using the following adaptive formula: ;in, As the baseline value; For reference ambient temperature; This is the sliding average of the current ambient temperature over the most recent 10 control periods; This is a temperature correction factor; Here, is the aging correction factor, where These are all empirical values ​​and can be adjusted by the implementer according to the specific implementation scenario.

[0050] This represents the accumulated equivalent number of cycles for the energy storage nodes. For design cycle life, the above coefficients need to be calibrated by HPPC (Hybrid Pulse Power Characteristics) test before commissioning. If online calibration cannot be achieved, the factory default values ​​should be used and locked.

[0051] At the same time, if in a continuous time window If no valid current step event is detected within a second, the dynamic calculation for this cycle is abandoned, and a two-dimensional lookup table of internal resistance based on the current SOC and temperature is used instead. As The alternative values, generated from offline electrochemical impedance spectroscopy measurements, ensure that the algorithm still has usable internal resistance input under steady-state conditions. The values ​​are based on experience and can be adjusted by the implementer according to the specific implementation scenario.

[0052] The cumulative time effect of polarization relaxation is expressed in seconds.

[0053] This constitutes the polarization resistance correction term, with dimensions in ohms.

[0054] The resulting dynamic internal resistance After stripping away the polarization effect, the impedance component that is more closely related to the direct conversion of current into Joule heat when it passes through the electrodes and electrolyte is obtained, which enables subsequent heat generation calculations based on this internal resistance to more realistically match the instantaneous thermal state of the energy storage node.

[0055] S2: Determination of heat generation and heat dissipation power of energy storage nodes and acquisition of thermal safety margin factor.

[0056] The first obtained from S1 Dynamic internal resistance of each energy storage node During operation, the Joule heat generated by the energy storage node under the action of charging and discharging current will drive the internal temperature to rise, while the heat dissipation from the surface of the energy storage node to the surrounding environment will suppress the temperature rise.

[0057] In high-altitude and cold regions, the local ambient temperature, air velocity, and surface condition of different energy storage nodes vary due to their different installation locations. This results in significant differences in the net heat accumulation of different energy storage nodes at the same current level. Dynamic internal resistance alone cannot be used to directly determine whether a particular energy storage node is approaching the thermal runaway boundary.

[0058] The heat generation power and heat dissipation power of each energy storage node are calculated separately, and the ratio of heat dissipation power to heat generation power is taken as the thermal safety margin factor, which serves as a unified basis for comparing the real-time thermal risk levels of each energy storage node.

[0059] The control system sends to the first control cycle in each control cycle Each energy storage node issues a current command. Unit ampere.

[0060] The heat loss of the battery module during charging and discharging is mainly ohmic heat. Using the dynamic internal resistance obtained from S1, the heat generation power of this energy storage node is calculated according to Joule's law. In the formula, For the first The heat generation capacity of each energy storage node, in watts; The current command for this energy storage node during the current control cycle, in amperes; The dynamic internal resistance is expressed in ohms. To minimize the positive bias, an empirical value is used. W is a preset parameter that can be adjusted by the implementer according to the system current level. Its function is to prevent the heat generation power from becoming zero when the current command is zero, thereby avoiding the denominator from becoming zero in the subsequent ratio calculation. The power consumed as heat across the internal resistance of the energy storage node, directly corresponding to the current, is measured in watts.

[0061] Subsequently, a heat dissipation power calculation based on convection heat dissipation was established for the same energy storage node. In the cold outdoor environment, the heat dissipation of the energy storage node shell mainly relies on natural convection and forced air cooling, and the heat exchange process follows the cooling law.

[0062] Collection of the first Surface temperature of each energy storage node The unit is Kelvin, and the ambient temperature at the location of the energy storage node. The unit is Kelvin.

[0063] Heat dissipation area of ​​energy storage node The unit is square meters, determined by the geometry of the battery module.

[0064] convective heat transfer coefficient It is related to local wind speed, air thermophysical properties and surface geometry. The unit is watts per square meter of Kelvin. This coefficient can be estimated by combining real-time data collected by wind speed sensors with empirical formulas. In the absence of wind speed sensors, a conservative empirical value can be taken based on the season and base station ventilation design.

[0065] In this embodiment, and The product of these two values ​​is used as the total heat transfer thermal conductivity, which is directly used to calculate the heat dissipation power. In the formula, The heat dissipation power of the energy storage node, measured in watts; Total heat transfer thermal conductivity, measured in watts per Kelvin; The value represents the temperature difference between the surface of the energy storage node and the ambient temperature, expressed in Kelvin.

[0066] When the surface temperature of the energy storage node is higher than the ambient temperature, the temperature difference is positive, and the heat dissipation power is transferred from the energy storage node to the environment; under extremely cold conditions, the temperature difference increases significantly, the heat dissipation capacity is correspondingly enhanced, and the heat dissipation power increases accordingly.

[0067] After obtaining the heat generation and heat dissipation power of the same energy storage node, a thermal safety margin factor is defined. The ratio of heat dissipation power to heat generation power:

[0068]

[0069] In the formula, For unitless values, when When the value is greater than 1, the heat dissipation power exceeds the heat generation power, the temperature of the energy storage node tends to decrease, and the thermal state is within a safe range; when When the value is less than 1, the heat generation power exceeds the heat dissipation power, and net heat accumulation occurs inside the energy storage node, posing a risk of temperature rise.

[0070] when When the temperature approaches or falls below the critical threshold, it indicates that the current heat dissipation capacity of the energy storage node is insufficient to suppress heat generation, and the possibility of thermal runaway increases sharply.

[0071] In this way, the thermal safety level of each energy storage node is expressed by a uniform, unitless numerical value. This factor integrates the combined effects of spatial temperature difference, internal resistance variation, and local cooling condition differences on the thermal state of the energy storage node, providing a basis for identifying over-limit and subsequent proactive derating intervention.

[0072] S3: When the thermal safety margin factor of any energy storage node is lower than the critical threshold, its current command is reduced by an exponential decay function that is positively correlated with the margin deviation.

[0073] After the system enters the charge / discharge scheduling state, the control unit iterates through the thermal safety margin factors of all energy storage nodes in each control cycle. .

[0074] When the traversal process detects the first Energy storage nodes Less than the preset critical threshold When the temperature rises, it indicates that the heat dissipation power of the energy storage node is no longer able to balance its own heat generation power under the current environment, and the internal temperature is in a state of net heat accumulation. If the original current command is maintained, the temperature rise will be further aggravated and may develop into thermal runaway.

[0075] Critical threshold The empirical value of 1.2 is used. This value is dimensionless and is a preset parameter. It can also be adjusted by the implementer based on the thermal tolerance test data of the battery module and the system safety level.

[0076] Since sudden current cut-offs or step-like large current reductions can impact grid power balance and energy storage converters, this step uses an exponential smooth decay function to continuously reduce the current command of the energy storage node.

[0077] The exponential decay function has the characteristics of monotonically decreasing and continuous boundary within its domain. When the margin deviation increases, the decay amplitude automatically increases. The reduced current command decreases smoothly relative to the original command without any jumps.

[0078] First, calculate the current margin deviation of the energy storage node. That is, the difference between the critical threshold and the thermal safety margin factor. In the formula, For dimensionless margin deviation, when hour The larger the deviation, the higher the thermal risk of the energy storage node and the more serious the heat dissipation capacity gap.

[0079] by and attenuation control sensitivity coefficient As parameters, the original current command is applied through an exponential decay function. The current command is reduced to a smaller value. In the formula, The current command for the reduced energy storage node is expressed in amperes (A). This is the initial current command given by the control system during this control cycle, in amperes (A). The attenuation control sensitivity coefficient is dimensionless and determines the magnitude of current reduction under the same margin deviation. Dimensionless, exponential term The value of is in the interval (0,1), such that It must be less than And remain non-negative.

[0080] Attenuation control sensitivity coefficient The system dynamically and adaptively adjusts based on real-time operating conditions to match the sensitivity requirements for thermal risk suppression under different load levels.

[0081] In this embodiment, Calculation using a linear superposition method of base values ​​and load corrections In the formula, The basic sensitivity coefficient is taken as an empirical value of 2.0. It is dimensionless and belongs to the preset parameters. It can also be adjusted by the implementer according to the battery thermal time constant. This is the load correction factor, with an empirical value of 1.5. It is dimensionless and belongs to the preset parameters. This is the ratio of the system's current total dispatch power to the system's rated total power, and is dimensionless.

[0082] When the system is under high load Increase The increased current allows for a greater reduction in current under the same margin deviation, thus suppressing the rate of heat accumulation at dangerous energy storage nodes more quickly.

[0083] In one embodiment, taking a certain energy storage node as an example, if , ,but The system load ratio during this control cycle ,but The exponent term is approximately This means that the current command for the energy storage node is reduced to approximately 28.6% of the original command.

[0084] In one embodiment, if the margin deviation is small, for example , Under the same load, the exponential term is approximately The current command is retained at approximately 73.2%, and the reduction is positively correlated with the margin deviation.

[0085] For thermal safety margin factor Greater than or equal to The current command of the energy storage node remains unchanged in this step, that is... .

[0086] Therefore, this step, based on the relationship between the real-time thermal safety margin factor and the critical threshold of each energy storage node, completed the active derating of the critical energy storage nodes, and obtained the reduced current command for all energy storage nodes. .

[0087] S4: Power transfer and iterative truncation allocation based on thermal safety margin redundancy.

[0088] After the current is reduced by S3, the actual power carried by the dangerous energy storage node decreases. Under the constraint that the total dispatch power remains unchanged, the reduced power needs to be transferred to other energy storage nodes, otherwise a power gap will occur on the grid side.

[0089] However, the remaining heat dissipation capacity of each healthy energy storage node is not the same. If the power reduction is distributed evenly, energy storage nodes with insufficient heat dissipation reserves may be overloaded and exceed their limits.

[0090] This step first converts the current reduction of all dangerous energy storage nodes into power quotas and sums them up as the total amount to be allocated; then, it constructs non-orthogonal projection weights according to the thermal safety margin redundancy ratio of healthy energy storage nodes, allocates the power quotas to each healthy energy storage node, and then through iterative prediction and verification, cuts off and redistributes the power portion that causes secondary over-limits until all quotas are safely taken over or trigger a system alarm.

[0091] Satisfy the requirements within the current control cycle The energy storage nodes are classified into the set of hazardous energy storage nodes. .

[0092] For each energy storage node in the set to give its original current command Subtract reduced current command The current reduction amount is obtained. Unit ampere.

[0093] because Therefore If the value is greater than zero, the power deficit cannot be directly obtained from the current difference alone; it needs to be calculated in conjunction with the voltage at the energy storage node.

[0094] Read the terminal voltage of the hazardous energy storage node at the moment of reduction. The unit is volts, and this voltage is obtained from the data acquisition channel of S1.

[0095] Multiplying the current reduction by the terminal voltage yields the power reduction of the energy storage node. The unit is watt.

[0096] For all hazardous energy storage nodes Summing gives the total power to be allocated. The unit is watts, representing the total power that needs to be transferred within this control cycle.

[0097] At the same time, from all energy storage nodes, those with a thermal safety margin factor greater than [missing information] are selected. The energy storage nodes, as healthy energy storage nodes capable of handling additional power, constitute a collection. .

[0098] right Each energy storage node Its thermal safety margin factor minus A thermal safety margin redundancy is obtained. The redundancy value is unitless. The larger the redundancy value, the more sufficient the heat dissipation margin of the energy storage node is relative to the heat generation. It can withstand more additional loads without exceeding its limits and directly measures the current thermal buffer space of the energy storage node.

[0099] To tilt power allocation toward energy storage nodes with high redundancy, a non-orthogonal projection weight is constructed for each healthy energy storage node based on its redundancy percentage. :

[0100]

[0101] In the formula, Unitless, denominator is The sum of thermal safety margin redundancy of all healthy energy storage nodes.

[0102] The weight is determined based on the proportion of the actual heat dissipation margin of each energy storage node. The higher the redundancy, the greater the weight, and the more power quota will be allocated in the future. The weight of energy storage nodes with redundancy close to the threshold is correspondingly smaller to avoid them being pushed into exceeding the limit.

[0103] Weighted Distributed to each healthy energy storage node, energy storage node The additional power obtained is The unit is watt.

[0104] Since the sum of all weights is 1, all allocations are completed, and the additional power is then converted into additional current commands.

[0105] Read healthy energy storage nodes terminal voltage The unit is volts. Divide by Receive additional current command Unit ampere.

[0106] Combine it with energy storage nodes The original current commands are added together to obtain the pre-allocated current command. The unit is amperes, used for subsequent over-limit verification. For other energy storage nodes that are neither dangerous nor healthy, the current command remains unchanged.

[0107] After the initial allocation is completed, the data will not be directly distributed but will undergo iterative verification. The weight allocation is based on the thermal safety margin factor of each healthy energy storage node before it takes over. However, the additional power will increase the heat production power, causing the margin factor to decrease, and some energy storage nodes may fall below the threshold. Secondary overruns occur.

[0108] Therefore, for each healthy energy storage node ,use Replace the original current command and derive the estimated heat generation power by referring to the heat generation power calculation method in S2. The unit is watt, of which, The dynamic internal resistance obtained from S1, This is the smallest positive bias, and its value is the same as S2.

[0109] Heat dissipation power We will continue to use the current value of S2, since the heat dissipation conditions will remain basically unchanged in the short term.

[0110] The ratio of the two is used to obtain the estimated thermal safety margin factor. No unit.

[0111] like If the energy storage node remains safe after taking over, then it will be safe; if If the limit is exceeded, it is determined that a secondary limit has been exceeded, meaning that the power allocated to the energy storage node has exceeded its capacity.

[0112] For energy storage nodes that experience secondary over-limit events, calculate the maximum current they can safely withstand. In the formula, The unit is ampere. This formula starts from the definition of the thermal safety margin factor, and sets the margin factor equal to... Substituting the heat dissipation power and dynamic internal resistance, the inverse solution of the current yields the result, indicating that the energy storage node can continue to operate under the existing heat dissipation conditions without triggering the upper limit of the current limit.

[0113] Will Subtract the original current command If the difference is positive, take that value; otherwise, take zero, to obtain the additional current that the energy storage node can safely handle. Unit ampere.

[0114] Original allocated additional current Exceeding The portion exceeding the limit is the part that is multiplied by the terminal voltage. The over-limit power quota of the energy storage node is obtained. The unit is watts; if not exceeded, then The value is zero. The total over-limit power for this round is obtained by summing the over-limit power allowances of all healthy energy storage nodes. In the formula, For energy storage nodes exhibiting secondary over-limit behavior, the pre-allocated current command is truncated to the safety boundary, i.e., a mandatory command, measured in watts. .

[0115] Will As the new power to be allocated, return to the weight allocation step, and simultaneously from... The energy storage nodes that have reached their maximum safe current limit are removed, and the remaining energy storage nodes that still have positive redundancy form a new set. Recalculate redundancy and weights, perform allocation and verification again, and iterate the counter. Increment by 1, and continue iterating until the termination condition is met.

[0116] The first termination condition: after a certain round of allocation, the total over-limit power. The value is 0, meaning that the estimated value of all healthy energy storage nodes after receiving and allocating resources is 0. All are no less than All power reduction has been safely taken over, the iteration is over, and at this time the current command locked by each energy storage node after verification is sent to the energy storage converter as the final command.

[0117] The second termination condition is: during the iteration process, the set of healthy energy storage nodes becomes empty, or the number of iterations reaches zero. Reaching the preset limit However, there is still unallocated, over-limit power remaining. The value of 20 is a preset parameter that can be adjusted by the implementer according to the system scale. At this point, it is determined that the system does not have enough heat dissipation margin to bear all the load reduction, the iteration stops, an alarm is triggered in the upper-level system, and a request is made to the power grid dispatch to reduce the current total dispatch power as a whole to prevent healthy energy storage nodes from being forcibly overloaded and causing a chain of over-limits.

[0118] If the system triggers a derating alarm due to its inability to safely handle the load and has already sent a derating command to the dispatch system, it must actively recover after the thermal condition improves. When the system is in derating operation, the control unit continuously monitors the thermal safety margin factor of all online energy storage nodes; if the thermal safety margin factor of all nodes is detected for five consecutive control cycles... The total scheduling power is then gradually increased in increments of 5% per cycle until it returns to the requested scheduling value or the derating condition is triggered again. This involves 5 control cycles and a 5% increment. The values ​​are based on experience and can be adjusted by the implementer according to the specific implementation scenario.

[0119] This invention also discloses a distributed energy storage system charge and discharge control system, including a processor and a memory. The memory stores computer program instructions, and when the computer program instructions are executed by the processor, the distributed energy storage system charge and discharge control method of this invention is implemented.

[0120] The system also includes other components well known to those skilled in the art, such as communication buses and communication interfaces, the settings and functions of which are known in the art and will not be described in detail here.

[0121] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating the charging and discharging of a distributed energy storage system, characterized in that, include: The terminal voltage and load current of each energy storage node are collected synchronously. When a current step is detected, the transient drop amplitude of the terminal voltage and the transient change of the current are determined. The ratio of the drop amplitude to the change of current is corrected by polarization relaxation compensation to obtain the dynamic internal resistance of each energy storage node. The heat generation power is calculated based on the dynamic internal resistance and the current command of the energy storage node. The heat dissipation power is calculated based on the convective heat transfer coefficient, the heat dissipation area of ​​the energy storage node, and the difference between the surface temperature of the energy storage node and the ambient temperature. The heat dissipation power is divided by the heat generation power to obtain the thermal safety margin factor. When the thermal safety margin factor of any energy storage node is lower than the critical threshold, the margin deviation of the energy storage node is calculated, and the original current command is reduced according to the margin deviation using the attenuation mapping function to obtain the reduced current command. The power reduction caused by the reduction in current command is converted into a power quota based on the energy storage node voltage; Energy storage nodes with thermal safety margin factors greater than the critical threshold are identified as healthy energy storage nodes. The proportion of thermal safety margin redundancy of each healthy energy storage node to the sum of thermal safety margin redundancy of all healthy energy storage nodes is used as the non-orthogonal projection weight. The power quota is allocated to each healthy energy storage node according to this weight and its current command is increased. The thermal safety margin factor of each healthy energy storage node is estimated after the current command is increased. If the estimated thermal safety margin factor of any healthy energy storage node is lower than the critical threshold, the power quota that causes secondary over-limit is truncated. The truncated part is returned as the new power to be allocated to the weight allocation step for iterative execution until all power quotas are safely accepted or a system alarm is triggered and an overall dereasing is requested, thus completing the charging and discharging regulation of the distributed energy storage system.

2. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The process of obtaining the dynamic internal resistance of each energy storage node includes: Monitor the rate of change of the load current, and when the rate of change of the current exceeds a preset step trigger threshold, determine that a current step is triggered, and capture a voltage and current data window containing the step transient process. The voltage and current data window is denoised, and the difference between the steady state before and after the step is extracted based on the denoised data to obtain the transient voltage drop amplitude and the transient current change. A multi-exponential decay function with the terminal voltage and the load current as input variables is constructed. The multi-exponential decay function is integrated from the start of the current step to the end of the polarization process to obtain the polarization relaxation accumulation time effect. The current ambient temperature change gradient and battery cycle aging data are obtained. The preset benchmark compensation coefficient is adaptively tuned by looking up a table or linear correction to obtain the polarization compensation calibration coefficient. The ratio of the transient voltage drop to the transient current change is used as the transient impedance ratio, and the product of the polarization relaxation accumulation time effect and the polarization compensation calibration coefficient is added to the transient impedance ratio to obtain the dynamic internal resistance.

3. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The obtained thermal safety margin factor includes: The transient heat generation power is obtained by multiplying the dynamic internal resistance by the square of the energy storage node current command and superimposing the minimum positive bias. The total heat transfer conductivity is obtained by multiplying the convective heat transfer coefficient by the heat dissipation area of ​​the energy storage node, and the convective heat dissipation power is obtained by multiplying the total heat transfer conductivity by the energy storage node surface temperature minus the ambient temperature. The thermal safety margin factor is output by using the convective heat dissipation power as the numerator and the transient heat generation power as the denominator through division.

4. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The obtained reduced current command includes: The difference between the critical threshold and the thermal safety margin factor is determined as the margin deviation; The ratio of the current total dispatch power of the system to the rated total power of the system is obtained as the load correction factor. The preset basic sensitivity coefficient is linearly superimposed with the load correction factor to generate the attenuation control sensitivity coefficient. The product of the margin deviation and the attenuation control sensitivity coefficient is used as a negative exponential term and input into the exponential smooth attenuation function to perform continuous contraction correction on the original current command and output the reduced current command.

5. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The process of allocating the power quota to each healthy energy storage node according to the weight and increasing its current command includes: The difference between the original current command and the reduced current command is calculated to obtain the current reduction amount, and the current reduction amount is multiplied by the energy storage node voltage of the energy storage node that has been reduced to convert it into the power quota. The set of healthy energy storage nodes is constructed by selecting energy storage nodes whose thermal safety margin factor is greater than the critical threshold, and the thermal safety margin redundancy is obtained by calculating the difference between the thermal safety margin factor and the critical threshold of each energy storage node. The nonorthogonal projection weight is obtained by dividing the thermal safety margin redundancy of a single energy storage node by the sum of the thermal safety margin redundancy of all energy storage nodes in the set of healthy energy storage nodes. The power quota is allocated to the corresponding thermally redundant energy storage nodes according to the non-orthogonal projection weight, and the energy storage node voltage of the corresponding energy storage node is converted into an additional command current, which is then added to the original current command of the corresponding energy storage node.

6. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The step of returning the truncated portion as new power to be allocated in the weight allocation step is executed iteratively, including: Substitute the accumulated current command into the heat generation power calculation to obtain the updated thermal safety margin factor for the corresponding energy storage node. When the updated thermal safety margin factor is less than the critical threshold, the upper limit of the safe current of the corresponding energy storage node is calculated based on the critical threshold and the convective heat dissipation power of the corresponding energy storage node. The power quota corresponding to the portion of the accumulated current command that exceeds the safe current limit is truncated to obtain the remaining unallocated power. After removing the fully loaded energy storage nodes from the healthy energy storage node set, the next round of iterative reallocation is triggered.

7. The method for regulating the charging and discharging of a distributed energy storage system according to claim 6, characterized in that, The triggering of system alarms and requests for overall rate reduction includes: During the iterative redistribution process, the number of energy storage nodes in the healthy energy storage node set and the current iteration number are continuously monitored. When the number of energy storage nodes in the healthy energy storage node set drops to zero or the current iteration count reaches the preset iteration limit, and the remaining unallocated power is still greater than zero, it is determined that the safe transfer of all power reduction cannot be achieved. The iterative reallocation is terminated and the system de-rating alarm is triggered. The system then outputs the required value for overall de-rating to the scheduling system.

8. The method for regulating the charging and discharging of a distributed energy storage system according to claim 1, characterized in that, The weight allocation step is executed iteratively, including: The ratio of the current total scheduling power of the system to the rated total power of the system is used to generate scheduling status evaluation parameters; When the scheduling status evaluation parameter exceeds the preset load threshold, the current system is established to have entered the high load discharge scheduling interval, and a traversal detection mechanism for the thermal safety margin factor of all energy storage nodes is triggered.

9. A charging and discharging control system for a distributed energy storage system, characterized in that, include: A processor and a memory, wherein the memory stores computer program instructions that, when executed by the processor, implement a charging and discharging control method for a distributed energy storage system according to any one of claims 1-8.

Images