Lithium iron phosphate battery backup power supply intelligent management system based on distribution network terminal

Abstract

The invention discloses a lithium iron phosphate battery backup power supply intelligent management system based on a distribution network terminal, and relates to the technical field of lithium iron phosphate battery backup power supply intelligent management, and the system comprises the steps: carrying out the sampling at a cabinet door slot, obtaining the equivalent resistance and equivalent capacitance of the slot, determining whether the frequency boundary is 5-30 MHz, and generating a risk sign; the risk duration and the load average power are counted in a unified time window, and the charge state minimum value and the theoretical charging current are calculated and issued in an amplitude limiting mode; the risk is to reduce the switch edge slope of the DC converter; and measuring a voltage effective value in the frequency band and performing constant-amplitude compensation on the under-voltage threshold to serve as a final criterion for switching and protection. According to the invention, false switching and false protection can be reduced, and the configuration accuracy and interference resistance of the lithium iron phosphate battery backup power supply are improved.

Description

Technical Field

[0001] This invention relates to the field of intelligent management technology for lithium iron phosphate battery backup power, and in particular to an intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal. Background Technology

[0002] In coastal areas prone to severe lightning strikes, distribution network terminals typically employ metal-enclosed cabinets to house protection, monitoring, control, and communication functions. These cabinets are constantly exposed to high humidity and salinity, experiencing condensation and drying cycles due to diurnal temperature variations. Salt spray residue and pitting easily accumulate at door seams and fastener areas, altering the electrical behavior of conduction and displacement paths at these gaps. When lightning strikes, switching operations, frequency converter operation, or external narrowband wireless services occur, electromagnetic disturbances in the 5 MHz to 30 MHz frequency band are more likely to penetrate along these gaps to the DC side and measurement links. Simultaneously, the switching edges of the distribution network terminal and its DC converter may also generate additional emissions in this frequency band. While lithium iron phosphate batteries are usually configured as backup power to ensure power continuity during abnormal periods, the combined effects of these environmental factors and interference cause the equivalent impedance of the cabinet gaps to change over time and with varying moisture and salt conditions. This leads to frequency drift in interception, resulting in a chain reaction of monitoring misjudgments and improper energy dispatching risks.

[0003] In existing technologies, lithium iron phosphate battery management largely relies on fixed thresholds and coulomb counts for backup time estimation. Undervoltage protection often uses fixed thresholds or simple hysteresis, and the switching edges of DC-DC converters are mostly preset with fixed parameters. These approaches fail to incorporate frequency boundary drift caused by environmental changes in the gap electrical state into the criteria, resulting in two main drawbacks: first, rapid interference causing a short-term drop in voltage readings can easily trigger false switching or false protection; second, the settings for backup energy and charging current do not consider the constraints of the interference duration and the average load power within the same time window, easily leading to insufficient energy replenishment or excessive charging stress. Therefore, there is an urgent need for an intelligent management system for lithium iron phosphate battery backup power for distribution network terminals. Summary of the Invention

[0004] The purpose of this invention is to solve the problem in the prior art that the electrical state of the cabinet gaps changes with wet salt and corrosion in scenarios such as coastal areas with strong lightning, resulting in a decrease in the ability to block interference from 5 MHz to 30 MHz, which leads to false switching, false protection and inaccurate backup energy configuration. The invention proposes an intelligent management system for lithium iron phosphate battery backup power based on the distribution network terminal.

[0005] To address the problems existing in the prior art, the present invention adopts the following technical solution: A smart management system for lithium iron phosphate battery backup power based on a distribution network terminal includes: The intercept frequency module is used to calculate the intercept frequency based on the set low frequency point less than one MHz and the target frequency point in the range of five MHz to thirty MHz. The risk assessment module is used to generate risk indicators based on the interception frequency; The minimum state of charge module is used to calculate the minimum state of charge within a preset time window based on risk indicators and system prior parameters. The charging current control module is used to calculate the theoretical charging current based on the minimum state of charge and generate charging current control commands based on the theoretical charging current and the system maximum charging current. The switching edge adjustment module is used to adjust the switching edge of the switching devices in the DC-DC converter according to the risk indicator; The threshold drive switching module is used to calculate the effective value ripple voltage of the DC bus in the range of 5 MHz to 30 MHz, set the compensated undervoltage protection threshold according to the risk flag, and control the backup power supply switching according to the compensated undervoltage protection threshold.

[0006] Preferably, the interception frequency is calculated based on a set low-frequency point less than one MHz and a target frequency point in the range of five MHz to thirty MHz, including: A measurement channel is set at the cabinet door seam, and a low frequency point less than one MHz and a target frequency point in the range of five MHz to thirty MHz are set. A test signal is applied to the measurement channel, and the voltage and current of the test signal at the measurement channel are acquired simultaneously. The impedance at the low-frequency point is calculated based on the voltage and current collected at the low-frequency point, and the real part of the impedance is used as the equivalent resistance at the cabinet door seam position. The impedance at the target frequency is calculated based on the voltage and current collected at the target frequency, and the equivalent capacitance at the cabinet door seam is calculated based on the imaginary part of the impedance at the target frequency. The interception frequency is determined based on the equivalent resistance and equivalent capacitance.

[0007] Preferably, generating a risk indicator based on the interception frequency includes: When the interception frequency is in the range of 5 MHz to 30 MHz, a risk flag with a value of 1 is generated. A risk flag with a value of zero is generated when the interception frequency is not within the range of 5 MHz to 30 MHz.

[0008] Preferably, based on risk indicators and prior system parameters, the minimum state of charge is calculated within a preset time window, including: The system's prerequisite parameters include: undervoltage alarm state of charge, battery nominal voltage, battery rated capacity, and system efficiency; The duration of risk is obtained by accumulating the time when the risk indicator is one within a preset time window; During the duration of the risk, the load power of the DC bus is periodically sampled, and the sampled values ​​are averaged over time to obtain the average load power. The minimum state of charge (SOC) is determined based on the average load power and the duration of the risk. The formula for calculating the minimum SOC is as follows: In the formula, This is the lowest value of the state of charge. The low voltage alarm indicates a charged state. The average power of the load. For the duration of the risk, This is the battery's nominal voltage. For the battery's rated capacity, For system efficiency.

[0009] Preferably, the theoretical charging current is calculated based on the minimum state of charge, and a charging current control command is generated based on the theoretical charging current and the system maximum charging current, including: Read the current state of charge of the lithium iron phosphate battery, the charging enable signal of the DC bus, and the maximum charging current of the system; When the current state of charge (SOC) of the lithium iron phosphate battery is lower than the minimum SOC value and the DC bus charging permission signal is enabled, the SOC difference is calculated. The formula for calculating the SOC difference is as follows: In the formula, Due to the difference in state of charge, This is the lowest value of the state of charge. The current state of charge; The theoretical charging current is calculated based on the state-of-charge difference, battery rated capacity, and risk duration. The formula for calculating the theoretical charging current is as follows: In the formula, The theoretical charging current, For the battery's rated capacity, Due to the difference in state of charge, Duration of risk; A charging current control command is generated based on the smaller value between the theoretical charging current and the maximum charging current.

[0010] Preferably, adjusting the switching edges of the switching devices in the DC-DC converter according to a risk indicator includes: Read the system's default rising edge slope and default falling edge slope; When the risk flag is one, the rising edge slope setting is set to half of the default rising edge slope, and the falling edge slope setting is set to half of the default falling edge slope. The rising edge slope setting value and the falling edge slope setting value are sent to the gate drive channel of the DC-DC converter to adjust the switching edge of the switching device in the DC-DC converter; When the risk flag is zero, the rising edge slope setting is restored to the default rising edge slope, the falling edge slope setting is restored to the default falling edge slope, and the restored setting is sent to the gate drive channel of the DC-DC converter for execution.

[0011] Preferably, the effective value ripple voltage of the DC bus in the range of 5 MHz to 30 MHz is calculated, and the compensated undervoltage protection threshold is set according to the risk indicator, including: Read the system's default undervoltage protection threshold; Configure a bandpass filter in the range of 5 MHz to 30 MHz on the DC bus voltage measurement channel; Within a preset measurement time window, the DC bus voltage is acquired through a bandpass filter, and the effective value ripple voltage within the range of 5 MHz to 30 MHz within the measurement time window is calculated. When the risk flag is one, the compensated undervoltage protection threshold is obtained by subtracting the effective value ripple voltage from the default undervoltage protection threshold. When the risk flag is zero, the compensated undervoltage protection threshold is set as the default undervoltage protection threshold.

[0012] Preferably, controlling the backup power supply switching based on the compensated undervoltage protection threshold includes: The compensated undervoltage protection threshold is used as the current undervoltage protection threshold, and the instantaneous voltage of the DC bus is continuously monitored. When the instantaneous voltage of the DC bus remains below the current undervoltage protection threshold for a preset duration, the drive switch switches to backup power supply mode.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention establishes a measurement channel at the cabinet door seam and simultaneously injects a small-amplitude test signal at a low-frequency point and a target frequency point between 5 MHz and 30 MHz. The equivalent resistance and equivalent capacitance are obtained respectively. The frequency boundary is determined by the time constant of the first-order resistive-capacitive network. Whether it falls within the key engineering frequency band of 5 MHz to 30 MHz is mapped as a risk indicator with a clear value. This forms a single criterion chain from on-site measurability to control triggering. It can transform environmental changes such as wet salt and corrosion into verifiable data sources, reduce misjudgments of voltage readings and state quantities, and provide a unified entry point for subsequent energy management and protection control.

[0014] 2. This invention obtains the duration of risk by accumulating the risk to one within a preset time window, and calculates the average load power within the same time window. Based on the energy conservation relationship, it calculates the minimum value of the state of charge, and then obtains the theoretical charging current using the coulomb measurement relationship. The smaller value between this current and the maximum charging current of the system is then issued as a charging current control command. This precisely aligns the time constraint with the power requirement, ensuring that the transition from the current state of charge to the target state of charge is completed with the minimum necessary current within the risk duration. This avoids both standby failure caused by insufficient energy replenishment and lifespan and safety hazards caused by excessive charging stress, thereby improving the accuracy and predictability of standby capacity configuration.

[0015] 3. This invention suppresses high-frequency components in the 5 MHz to 30 MHz band by simultaneously reducing the rise and fall slopes of the switching device to half of the default value when risks exist. At the same time, the voltage measurement link uses the effective voltage value of this frequency band to perform equal-amplitude compensation on the undervoltage protection threshold. The compensated threshold combined with timing conditions is used as the final criterion for backup switching and undervoltage protection. This reduces the interference of the switching process on measurement and power supply determination, and avoids false triggering by short-term rapid fluctuations during disturbance periods. It significantly reduces false switching and false protection events and ensures power supply continuity during abnormal periods. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a functional block diagram of an intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal, provided as an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0018] Example: This example provides an intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal. See [link to relevant documentation]. Figure 1 Specifically, including: The intercept frequency module is used to calculate the intercept frequency based on the set low frequency point less than one MHz and the target frequency point in the range of five MHz to thirty MHz. In embodiments of the present invention, calculating the interception frequency based on a set low-frequency point less than one MHz and a target frequency point in the range of five MHz to thirty MHz includes: A measurement channel is set at the cabinet door seam, and a low frequency point less than one MHz and a target frequency point in the range of five MHz to thirty MHz are set. Specifically, setting up a measurement channel at the cabinet door seam is to directly obtain electrical information related to shielding effectiveness along the most vulnerable leakage path of the metal enclosure. This is because gaps and openings in the shielding shell are major weak points under mid-to-high frequency conditions, while a complete, open-free metal shell can significantly improve electromagnetic suppression effectiveness. Once gaps and openings exist, their transmission of electromagnetic waves becomes more pronounced with increasing frequency. Using two separate frequency points for sampling is to accurately capture the main conductive electrical behavior of the metal enclosure in different frequency domains with minimal test quantity: low-frequency points below one MHz are used to obtain resistive information mainly based on the conduction path. This reflects the equivalent conductivity of the contact surface and conductive connection at low frequencies. Using the transfer impedance quantization method in the low-frequency band can effectively characterize the conductivity of the gap material and the connection part and serve as an effective parameter basis for shielding performance. The target frequency points in the range of 5 MHz to 30 MHz are used to observe the capacitance and gap radiation effects of gaps and openings in the higher frequency domain. This frequency band belongs to the core range of conventional conducted emission assessment of electronic equipment and overlaps with the energy range of transient electromagnetic disturbances caused by lightning and operation interruption that are of widespread concern in engineering. Therefore, it can directly reflect the suppression starting point and penetration risk of the gap in the key frequency band.

[0019] Specifically, a pair of sheet-like measuring electrodes are fixed to the metal flange surfaces on both sides of the distribution network terminal cabinet door seam. The relative positions of the two electrodes are aligned with the center line of the cabinet door seam, and the distance between the electrode edges and the cabinet door seam does not exceed 5mm. Electrical isolation between the electrodes and the flange surface is achieved through polytetrafluoroethylene insulating gaskets with a thickness of 0.1mm to 0.5mm. Conductive adhesive is used to bond and fix the electrodes to the flange surface to ensure contact stability. A double-shielded coaxial signal transmission line is connected to each measuring electrode. One end of the shielding layer of the transmission line is reliably grounded to the flange surface, and the other end is connected to the corresponding signal generation port and signal acquisition port of the management unit, thus forming the cabinet door. The measurement channel for the seam position; the management unit sets two test frequencies through its internal frequency configuration module, one of which is a low frequency, with a value range of 1kHz-500kHz, avoiding the 50Hz power frequency and its integer multiples of harmonic frequencies. 10kHz is preferred as the low frequency to balance measurement accuracy and anti-interference capability; the other is a target frequency, with a value range of 5MHz-30MHz. 5MHz, 15MHz, and 30MHz are preferred as the target frequency. The parameters of the two frequencies are stored in the memory of the management unit after being set to ensure stable recall when test signals are applied later.

[0020] A test signal is applied to the measurement channel, and the voltage and current of the test signal at the measurement channel are acquired simultaneously. The impedance at the low-frequency point is calculated based on the voltage and current collected at the low-frequency point, and the real part of the impedance is used as the equivalent resistance at the cabinet door seam position. The impedance at the target frequency is calculated based on the voltage and current collected at the target frequency, and the equivalent capacitance at the cabinet door seam is calculated based on the imaginary part of the impedance at the target frequency. The interception frequency is determined based on the equivalent resistance and equivalent capacitance. Specifically, applying a test signal to the measurement channel and simultaneously acquiring voltage and current is to obtain the complex impedance by the ratio of voltage to current according to the electrical engineering definition of impedance. This allows for the simultaneous acquisition of both the real and imaginary parts under the same measurement aperture, where the real part corresponds to resistance and the imaginary part corresponds to reactance. This approach enables the subsequent separation of the equivalent resistance related to the conduction path and the equivalent capacitance related to the displacement path from the same injection, ensuring a single and traceable parameter source and reducing disturbance to on-grid equipment. To improve identification accuracy, when determining impedance at low frequencies, the capacitive reactance of the capacitor increases significantly with decreasing frequency, and the gap channel exhibits predominantly resistive behavior. Therefore, using the real part of the impedance as the equivalent resistance of the gap is reasonable. When determining impedance at target frequencies between 5 MHz and 30 MHz, the capacitive reactance of the capacitor decreases with increasing frequency, and the displacement path of the gap channel dominates. Therefore, calculating the equivalent capacitance based on the imaginary part of the impedance more accurately reflects the dielectric state within this frequency band. The interception frequency is then determined using the equivalent resistance and equivalent capacitance. This represents the transition boundary of a first-order resistive-capacitive network, expressed as the product of the equivalent resistance and equivalent capacitance multiplied by twice pi and then the reciprocal. This boundary is commonly used to characterize the channel's ability to separate low and high frequencies, and is a common engineering standard for filtering and time-domain constants. The target frequency band of 5 MHz to 30 MHz is chosen because gaps and openings in the metal casing are more sensitive to coupling with external fields in this band. Gaps and holes significantly reduce shielding effectiveness. Electromagnetic compatibility conducted tests and engineering pre-compatibility measurements generally cover the 150 kHz to 30 MHz range. Therefore, obtaining the equivalent capacitance within this bandwidth and using it in conjunction with the equivalent resistance to determine the interception frequency not only matches the actual interference spectrum but also aligns with industry measurement standards, thus providing a measurable and calculable single input for subsequent risk assessment and threshold compensation.

[0021] Specifically, when a test signal is applied to the measurement channel, a small-amplitude test signal is generated by a sine wave signal source configured by the system. The signal amplitude is controlled within the range of 50mV to 100mV to avoid interference with the normal circuit of the distribution network terminal. This test signal is transmitted to the copper foil electrodes of the measurement channel through the previously constructed shielded twisted-pair cable. At the same time, a high-speed data acquisition module synchronized with the signal source is activated. The sampling rate of the high-speed data acquisition module is set to above 100MSps to meet the acquisition accuracy of the target frequency signal of 5 MHz to 30 MHz. One acquisition channel is connected between two copper foil electrodes to obtain the voltage signal of the test signal at both ends of the measurement channel. The other acquisition channel obtains the sampling voltage through a high-precision sampling resistor (resistance value selected from 10Ω to 100Ω and temperature coefficient less than 50ppm / ℃) connected in series in the measurement channel. The voltage signal across the resistor is converted into a current signal in the measurement channel according to Ohm's law, ensuring that the voltage and current signals are acquired synchronously and for a duration of no less than 10 signal cycles. When calculating the impedance at a low-frequency point based on the voltage and current acquired at that point, Fourier transforms are first performed on the acquired voltage and current data to extract the amplitude of the fundamental component with the same frequency as the low-frequency point. Then, the fundamental voltage amplitude is divided by the fundamental current amplitude to obtain the impedance amplitude at that frequency. At the same time, the real and imaginary parts of the impedance are calculated through the phase difference. Since the capacitive reactance of the equivalent capacitance of the cabinet door gap at the low-frequency point is much greater than the resistance of the equivalent resistance, the influence of the imaginary part on the impedance can be ignored. Therefore, the real part of the impedance at the low-frequency point is directly used as the equivalent resistance at the cabinet door gap. When calculating the impedance at the target frequency based on the voltage and current collected at that frequency, the same Fourier transform and amplitude / phase extraction methods as used for calculating the impedance at low frequencies are employed to obtain the real and imaginary parts of the impedance at the target frequency. Since the target frequency is in the range of 5 MHz to 30 MHz, the capacitive reactance of the equivalent capacitance of the cabinet door gap is significantly reduced, and the imaginary part becomes the main component affecting the impedance. Furthermore, this imaginary part is a capacitive reactance. Therefore, by using the relationship between capacitive reactance, frequency, and capacitance, the equivalent capacitance at the cabinet door gap is calculated using the frequency value of the target frequency and the absolute value of the imaginary part of the impedance. When determining the interception frequency based on the equivalent resistance and equivalent capacitance, the interception frequency is calculated by multiplying the product of the equivalent resistance and equivalent capacitance by twice pi and taking the reciprocal. This helps to accurately identify the leakage risk of the cabinet in the range of 5 MHz to 30 MHz.

[0022] The risk assessment module is used to generate risk indicators based on the interception frequency; In an embodiment of the present invention, generating a risk flag based on the interception frequency includes: When the interception frequency is in the range of 5 MHz to 30 MHz, a risk flag with a value of 1 is generated. When the interception frequency is not in the range of 5 MHz to 30 MHz, a risk flag with a value of zero is generated. The risk flag is set to one when the interception frequency is in the range of 5 MHz to 30 MHz. This is because, on the one hand, this frequency band is highly consistent with the common frequency band for conducted emissions and measurements in the field of electromagnetic compatibility, and belongs to the interference bandwidth that is subject to key restrictions and monitoring. On the other hand, transient processes such as lightning strikes and interruptions contain considerable energy in the range of kilohertz to tens of megahertz. Once the gaps and openings of the metal enclosure exhibit low shielding capability in this frequency band, interference can more easily penetrate to the DC side and measurement link. Therefore, it needs to be used as a risk state trigger condition. When the interception frequency is not in the above range, it indicates that the gap's suppression of this key frequency band is still in a relatively strong state, and the risk flag can be set to zero to avoid unnecessary relaxation of protection and control actions. The above interception frequency is derived from the boundary frequency determined by the equivalent resistance and equivalent capacitance of the gap. It is an engineering quantity describing the inflection point between low-frequency suppression and high-frequency leakage. When it falls into the key frequency band of electromagnetic compatibility and coincides with the main spectral range of transient interference, setting the risk flag to one can directly transform environmental and structural changes into deterministic trigger conditions for subsequent energy management and protection thresholds.

[0023] The minimum state of charge module is used to calculate the minimum state of charge within a preset time window based on risk indicators and system prior parameters. In embodiments of the present invention, the minimum state of charge is calculated within a preset time window based on risk indicators and prior system parameters, including: The system's prerequisite parameters include: undervoltage alarm state of charge, battery nominal voltage, battery rated capacity, and system efficiency; Specifically, the undervoltage alarm state of charge (SOC) refers to the warning threshold issued by the management unit when the SOC of a lithium iron phosphate battery drops to a certain value under normal discharge conditions. This threshold is used to provide early warning and prevent further discharge that could lead to undervoltage protection or deep discharge. The threshold is set by the project or manufacturer based on lifespan, safety, and availability requirements. The nominal battery voltage refers to the approximate average voltage of the lithium iron phosphate battery under typical operating conditions. It is used to identify the battery type and match the electrical equipment. In this system, it serves as the reference voltage for energy calculation and is involved in the derivation of key parameters such as the minimum SOC value. The rated battery capacity refers to the minimum amount of electricity that a lithium iron phosphate battery can discharge under specific discharge rates, temperatures, and termination voltage conditions. System efficiency refers to the ratio between the system's output performance or energy and the input energy within a specified time. It is used to evaluate the effectiveness of energy transfer from the battery to the DC bus and load side and is a necessary parameter when converting power and time into standby available energy and SOC budget.

[0024] The duration of risk is obtained by accumulating the time when the risk indicator is one within a preset time window; During the duration of the risk, the load power of the DC bus is periodically sampled, and the sampled values ​​are averaged over time to obtain the average load power. Specifically, the system management unit first configures a rolling time window. The duration of this time window can be flexibly set according to the typical risk exposure scenarios of the backup power supply of the distribution network terminal, for example, one hour. The management unit monitors the risk flag output by the risk judgment module in real time with millisecond-level time resolution. Whenever the risk flag value is one, a timer is started, and the time segments with the risk flag value of one are continuously accumulated within the rolling time window. The sum of the durations of these time segments is taken as the risk duration. While determining the risk duration, the management unit triggers a periodic sampling process of the DC bus load power: through the power sampling module installed on the DC bus, the voltage and current of the DC bus are synchronously collected according to a preset sampling period, for example, once every ten seconds. After each collection, the corresponding instantaneous load power value is calculated based on the instantaneous values ​​of voltage and current. During the risk duration, all collected instantaneous load power values ​​are continuously recorded. After the risk duration ends, the arithmetic mean of these instantaneous load power values ​​is calculated, and the average value is taken as the average load power.

[0025] The minimum state of charge (SOC) is determined based on the average load power and the duration of the risk. The formula for calculating the minimum SOC is as follows: In the formula, This is the lowest value of the state of charge. The low voltage alarm indicates a charged state. The average power of the load. For the duration of the risk, This is the battery's nominal voltage. For the battery's rated capacity, For system efficiency; Specifically, the minimum state of charge (SOC) value is determined based on the principle of energy conservation and the engineering definition of SOC. During the risk duration, the actual energy required by the load is equal to the product of the average load power and the risk duration. The effective energy that the battery can provide to the DC bus in the nominal operating range is equal to the product of the battery nominal voltage, the battery rated capacity, the system efficiency, and the releaseable SOC increment. To ensure the normal operation of the distribution network terminal during the risk duration, these two must be equal. Thus, the releaseable SOC increment is equal to the average load power multiplied by the risk duration and then divided by the product of the battery nominal voltage, the battery rated capacity, and the system efficiency. Considering that the undervoltage alarm SOC is used to protect the battery and provide early warning and serves as a baseline for discharge, the minimum SOC value should be added to the aforementioned SOC increment above this baseline, thus forming the calculation formula. This derivation maps time and power to energy demand and converts energy demand into SOC increment using nominal voltage, capacity, and efficiency. The dimensions are consistent and match the relatively stable nominal platform voltage of lithium iron phosphate batteries, facilitating charging control and backup capacity constraints with a single threshold.

[0026] The charging current control module is used to calculate the theoretical charging current based on the minimum state of charge and generate charging current control commands based on the theoretical charging current and the system maximum charging current. In an embodiment of the present invention, the theoretical charging current is calculated based on the minimum state of charge, and a charging current control command is generated based on the theoretical charging current and the system maximum charging current, including: Read the current state of charge of the lithium iron phosphate battery, the charging enable signal of the DC bus, and the maximum charging current of the system; Specifically, the current state of charge (SBC) refers to the management unit's estimate of the ratio of the remaining usable capacity of the lithium iron phosphate battery to its rated capacity at a given time. The DC bus charging enable signal is a single logic quantity generated by the management unit after determining the power supply conditions, safety conditions, and electrical interlock status; it indicates whether charging of the DC bus side is currently permitted. The system's maximum charging current refers to the upper limit of the charging current allowed to be sent to the DC-DC converter under the current environmental and hardware capability constraints.

[0027] When the current state of charge (SOC) of the lithium iron phosphate battery is lower than the minimum SOC value and the DC bus charging permission signal is enabled, the SOC difference is calculated. The formula for calculating the SOC difference is as follows: In the formula, Due to the difference in state of charge, This is the lowest value of the state of charge. The current state of charge; Specifically, after determining that the current state of charge (SOC) of the lithium iron phosphate battery is lower than the minimum SOC and the DC bus charging permission signal is enabled, the calculation is performed using the larger of the SOC difference being zero and the minimum SOC minus the current SOC. This is because the difference physically corresponds to the minimum release capacity ratio required to raise the battery from the current SOC to the minimum SOC. This ratio should be non-negative to avoid generating reverse or meaningless charging commands when the current SOC is not lower than the minimum SOC. By using the larger of the two cutoff strategies, small negative values ​​caused by measurement noise estimation bias and short-term fluctuations can be suppressed. This ensures that when the theoretical charging current is subsequently calculated based on the battery's rated capacity and the risk duration, only positive and minimally necessary constant current requests are generated, avoiding overcharging and oscillation control, and improving the predictability and feasibility of the charging control chain.

[0028] The theoretical charging current is calculated based on the state-of-charge difference, battery rated capacity, and risk duration. The formula for calculating the theoretical charging current is as follows: In the formula, The theoretical charging current, For the battery's rated capacity, Due to the difference in state of charge, Duration of risk; Specifically, the determination of the theoretical charging current is based on the common physical relationship between coulomb measurement and the constant current stage. The amount of charge required to reach the minimum state of charge is expressed as the battery's rated capacity multiplied by the state of charge difference. That is, the required charge is equal to the battery's rated capacity multiplied by the state of charge difference. Based on the fundamental law that charge equals current multiplied by time, in order to complete the above charge replenishment within the risk duration, the constant current should be equal to the required charge divided by the risk duration. Therefore, the theoretical charging current is equal to the battery's rated capacity multiplied by the state of charge difference divided by the risk duration. This calculation directly transforms the target state of charge improvement requirement into an equivalent constant current value within a limited time window, while ensuring that the precise transition from the current state of charge to the minimum state of charge is achieved with the minimum necessary current without exceeding the time constraint. This provides a clear benchmark for subsequent comparison with the maximum charging current and saturation constraints.

[0029] The charging current control command is generated based on the smaller value between the theoretical charging current and the maximum charging current. Specifically, the theoretical charging current is compared with the maximum charging current. When the theoretical charging current is less than or equal to the maximum charging current, the theoretical charging current is directly determined as the charging current value to be executed. When the theoretical charging current is greater than the maximum charging current, the maximum charging current is determined as the charging current value to be executed, thus ensuring that the charging current does not exceed the system's allowed safety limit. The management unit converts the determined charging current value to be executed into a control signal form that the DC-DC converter can recognize. For example, it converts the digital current value into a corresponding analog voltage signal through a digital-to-analog converter module, or generates a pulse width modulation signal containing current command information. Finally, the charging current control command is sent to the control interface of the DC-DC converter through a dedicated control bus, and a command verification mechanism is activated to monitor in real time whether the actual output current fed back by the DC-DC converter is consistent with the control command. If there is a deviation, dynamic correction is performed until the actual charging current stabilizes within the command set value range.

[0030] The switching edge adjustment module is used to adjust the switching edge of the switching devices in the DC-DC converter according to the risk indicator; In an embodiment of the present invention, adjusting the switching edge of the switching device in the DC-DC converter according to a risk flag includes: Read the system's default rising edge slope and default falling edge slope; Specifically, the default rising edge slope refers to the baseline switching speed of the system in a non-risk state. Specifically, it is the rate of voltage change of the switching node voltage of the DC-DC converter switching device from a low level to a high level, measured as the average slope of the range of 10% to 90%. This value is determined by the gate drive capability and the gate circuit device parameters, or by the factory configuration or calibration of the programmable gate driver. The default falling edge slope refers to the baseline turning-off speed of the system in a non-risk state. Specifically, it is the rate of voltage change of the switching node voltage of the DC-DC converter switching device from a high level to a low level, measured as the average slope of the range of 10% to 90%. This value is determined by the gate drive capability and the gate circuit device parameters, or by the factory configuration or calibration of the programmable gate driver.

[0031] When the risk flag is one, the rising edge slope setting is set to half of the default rising edge slope, and the falling edge slope setting is set to half of the default falling edge slope. The rising edge slope setting value and the falling edge slope setting value are sent to the gate drive channel of the DC-DC converter to adjust the switching edge of the switching device in the DC-DC converter; When the risk flag is zero, the rising edge slope setting value is restored to the default rising edge slope, the falling edge slope setting value is restored to the default falling edge slope, and the restored setting value is sent to the gate drive channel of the DC-DC converter for execution. Specifically, when the risk flag is 1, the rising edge slope setting and falling edge slope setting are set to half of the default rising edge slope and default falling edge slope, respectively, and this setting is sent to the gate drive channel of the DC-DC converter. This is a deterministic suppression measure based on the spectral characteristics of the pulse switching waveform and the electromagnetic emission mechanism of the power supply. The reduced voltage change rate directly lengthens the rise time and fall time, significantly attenuating the high-frequency harmonic amplitude in the range of 5 MHz to 30 MHz, thereby reducing the high-frequency interference energy of the switching node to the DC bus and measurement link. At the same time, the fixed ratio of half can provide a predictable emission reduction and an acceptable efficiency cost without introducing empirical weights, facilitating rapid execution within the control cycle and maintaining consistency between different models. When the risk flag is zero, the rising edge slope setting and falling edge slope setting are restored to the default rising edge slope and default falling edge slope and sent for execution. This avoids the additional switching losses and dynamic response caused by maintaining a low slope for a long time in a non-risk state. The system addresses the issue of slow response by enabling targeted suppression when risks exist. Once the risks are eliminated, it automatically returns to a baseline operating state characterized by high efficiency and rapid dynamics. Overall, it achieves a reproducible trade-off between edge control based on a single trigger quantity and energy efficiency. The gate drive channel of the DC-DC converter refers to the dedicated execution path within the DC-DC converter where the switching control quantity output from the management unit is transmitted and applied to the gate of the power switching device. It includes signal receiving and logic shaping sections, isolation and level conversion sections, gate charging and discharging current supply sections, and gate circuit elements and protection networks. It can convert the rising edge slope setting value and the falling edge slope setting value into the amplitude and timing of the gate charging current and the gate discharging current, thereby directly determining the voltage change rate and current change rate of the switching device. This channel also undertakes functions such as gate overvoltage and overcurrent protection, turn-off clamping, vibration damping and anti-misleading turn-on, and provides stable and repeatable rising edge and falling edge behavior to the power stage, so that the edge slope setting issued by the management unit is realized at the power device level.

[0032] The threshold drive switching module is used to calculate the effective value ripple voltage of the DC bus in the range of 5 MHz to 30 MHz, set the compensated undervoltage protection threshold according to the risk flag, and control the backup power supply switching according to the compensated undervoltage protection threshold. In an embodiment of the present invention, the effective value ripple voltage of the DC bus in the range of 5 MHz to 30 MHz is calculated, a compensated undervoltage protection threshold is set according to the risk indicator, and the backup power supply switching is controlled according to the compensated undervoltage protection threshold, including: Read the system's default undervoltage protection threshold; Specifically, the default undervoltage protection threshold refers to a voltage threshold value that is comprehensively adjusted and fixed by the management unit during the system design and commissioning phase based on the battery discharge termination voltage, the minimum operating voltage of the DC bus, the power level safety margin, and the load maintenance requirements. It is used to determine whether the DC bus is undervoltage during operation and serves as the baseline criterion for undervoltage protection action and backup power switching. The application location is the DC bus measurement aperture, and the value should be higher than the battery discharge termination voltage and lower than the nominal operating voltage platform to avoid deep discharge and premature disconnection from power supply.

[0033] Configure a bandpass filter in the range of 5 MHz to 30 MHz on the DC bus voltage measurement channel; Within a preset measurement time window, the DC bus voltage is acquired through a bandpass filter, and the effective value ripple voltage within the range of 5 MHz to 30 MHz within the measurement time window is calculated. Specifically, a bandpass filter with a range of 5 MHz to 30 MHz is configured on the DC bus voltage measurement channel, and the effective value ripple voltage is calculated only for the voltage components within this bandwidth within a preset measurement time window. This is to ensure that the measurement aperture is completely consistent with the frequency band used for risk assessment, thereby ensuring that the assessment and compensation are based on the same physical interval and are not affected by out-of-band components. The bandpass filter suppresses low-frequency steady-state fluctuations and fast components above 30 MHz, so that the obtained waveform specifically represents the fast disturbances within the target frequency band.

[0034] Specifically, when configuring a bandpass filter in the range of 5 MHz to 30 MHz on the DC bus voltage measurement channel, an active RC bandpass filter circuit is selected as the core filtering unit. The passband range of this filter circuit is strictly limited to 5 MHz to 30 MHz, and the ripple in the passband is controlled within ±0.5 dB to ensure the flatness of signal transmission. The stopband attenuation is set to no less than 40 dB per decade. This attenuation requirement must be met for both the low-frequency band below 5 MHz and the high-frequency band above 30 MHz to effectively suppress interference signals in non-target frequency bands. The bandpass filter is connected in series between the signal acquisition terminal and the data acquisition module of the DC bus voltage measurement channel. The input impedance of the filter is matched to 1 M ohm to adapt to the output impedance of the DC bus voltage sampling resistor, and the output impedance is matched to 50 ohms to adapt to the input impedance of the data acquisition module, so as to avoid waveform distortion caused by reflection due to impedance mismatch during signal transmission. When acquiring DC bus voltage and calculating RMS ripple voltage within a preset measurement time window, the management unit first sets the duration of the measurement time window. This duration is set to 100 milliseconds based on the periodic characteristics of the DC bus ripple, ensuring coverage of at least 5 ripple cycles to guarantee the representativeness of the sampled data. When the risk flag output by the risk assessment module is one, the management unit triggers the data acquisition module to start acquisition. The sampling rate of the data acquisition module is set to no less than 60 MHz to meet the Nyquist sampling theorem requirements for acquiring signals in the 5 MHz to 30 MHz frequency band. During the acquisition process, a bandpass filter is used to sample the DC bus voltage. The voltage signal is filtered in real time, retaining only the AC ripple signal in the range of 5 MHz to 30 MHz, while filtering out DC components and interference signals from other frequency bands. After acquisition, the management unit processes the filtered voltage sampling data. First, it further removes residual high-frequency noise through a digital filtering algorithm, and then calculates the instantaneous voltage value of all sampling points within the measurement time window. Each instantaneous voltage value is squared, and the sum of all squared values ​​is divided by the number of sampling points to obtain the average value. Finally, the square root of the average value is taken, and the result is the effective value ripple voltage in the range of 5 MHz to 30 MHz within the measurement time window.

[0035] When the risk flag is one, the compensated undervoltage protection threshold is obtained by subtracting the effective value ripple voltage from the default undervoltage protection threshold. When the risk flag is zero, the compensated undervoltage protection threshold is set to the default undervoltage protection threshold. The compensated undervoltage protection threshold is used as the current undervoltage protection threshold, and the instantaneous voltage of the DC bus is continuously monitored. When the instantaneous voltage of the DC bus remains below the current undervoltage protection threshold for a preset duration, the drive switch switches to backup power supply mode. Specifically, when the risk flag output by the risk assessment module is one, the management unit activates the undervoltage protection threshold compensation mechanism. This is achieved by subtracting the effective ripple voltage from the default undervoltage protection threshold; the result is the compensated undervoltage protection threshold, thus offsetting the interference of bus ripple on voltage monitoring during the risk period. When the risk flag is zero, the management unit determines that there is no significant ripple interference and directly sets the default undervoltage protection threshold as the compensated undervoltage protection threshold without additional adjustment. Subsequently, using the compensated undervoltage protection threshold as the current undervoltage protection threshold, the instantaneous voltage of the DC bus is continuously acquired through the DC bus voltage measurement channel. The acquisition frequency is set to once every millisecond to ensure real-time monitoring. After each acquisition, the instantaneous voltage is compared with the current undervoltage protection threshold. The system pre-sets an undervoltage action delay, which is set to 50 to 200 milliseconds based on the dynamic response characteristics of the distribution network terminal, to avoid misjudgments caused by instantaneous voltage fluctuations. When the instantaneous voltage of the DC bus is continuously monitored to be lower than the current undervoltage protection threshold, and the duration of this state reaches or exceeds the preset undervoltage action delay, the management unit immediately generates a backup switching execution command and sends it to the switcher's drive interface via the control bus. After receiving the command, the switcher quickly disconnects the main power supply circuit from the DC bus and simultaneously closes the backup power supply circuit from the DC bus, switching the system to the backup power supply mode powered by the lithium iron phosphate battery. The switcher then sends a switching completion signal back to the management unit to confirm the successful state switch.

[0036] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A smart management system for lithium iron phosphate battery backup power based on a distribution network terminal, characterized in that, include: The intercept frequency module is used to calculate the intercept frequency based on the set low frequency point less than one MHz and the target frequency point in the range of five MHz to thirty MHz. The risk assessment module is used to generate risk indicators based on the interception frequency; The minimum state of charge module is used to calculate the minimum state of charge within a preset time window based on risk indicators and system prior parameters. The charging current control module is used to calculate the theoretical charging current based on the minimum state of charge and generate charging current control commands based on the theoretical charging current and the system maximum charging current. The switching edge adjustment module is used to adjust the switching edge of the switching devices in the DC-DC converter according to the risk indicator; The threshold drive switching module is used to calculate the effective value ripple voltage of the DC bus in the range of 5 MHz to 30 MHz, set the compensated undervoltage protection threshold according to the risk flag, and control the backup power supply switching according to the compensated undervoltage protection threshold.

2. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, The interception frequency is calculated based on the set low-frequency points below one MHz and the target frequency points in the range of five MHz to thirty MHz, including: A measurement channel is set at the cabinet door seam, and a low frequency point less than one MHz and a target frequency point in the range of five MHz to thirty MHz are set. A test signal is applied to the measurement channel, and the voltage and current of the test signal at the measurement channel are acquired simultaneously. The impedance at the low-frequency point is calculated based on the voltage and current collected at the low-frequency point, and the real part of the impedance is used as the equivalent resistance at the cabinet door seam position. The impedance at the target frequency is calculated based on the voltage and current collected at the target frequency, and the equivalent capacitance at the cabinet door seam is calculated based on the imaginary part of the impedance at the target frequency. The interception frequency is determined based on the equivalent resistance and equivalent capacitance.

3. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, Risk indicators are generated based on interception frequency, including: When the interception frequency is in the range of 5 MHz to 30 MHz, a risk flag with a value of 1 is generated. A risk flag with a value of zero is generated when the interception frequency is not within the range of 5 MHz to 30 MHz.

4. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, Based on risk indicators and prior system parameters, the minimum state of charge is calculated within a preset time window, including: The system's prerequisite parameters include: undervoltage alarm state of charge, battery nominal voltage, battery rated capacity, and system efficiency; The duration of risk is obtained by accumulating the time when the risk indicator is one within a preset time window; During the duration of the risk, the load power of the DC bus is periodically sampled, and the sampled values ​​are averaged over time to obtain the average load power. The minimum state of charge (SOC) is determined based on the average load power and the duration of the risk. The formula for calculating the minimum SOC is as follows: In the formula, This is the lowest value of the state of charge. Undervoltage alarm, charging status. Average load power For the duration of the risk, This is the battery's nominal voltage. For the battery's rated capacity, For system efficiency.

5. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 4, characterized in that, The theoretical charging current is calculated based on the minimum state of charge. Charging current control commands are generated based on the theoretical charging current and the system's maximum charging current, including: Read the current state of charge of the lithium iron phosphate battery, the charging enable signal of the DC bus, and the maximum charging current of the system; When the current state of charge (SOC) of the lithium iron phosphate battery is lower than the minimum SOC value and the DC bus charging permission signal is enabled, the SOC difference is calculated. The formula for calculating the SOC difference is as follows: In the formula, Due to the difference in state of charge, This is the lowest value of the state of charge. The current state of charge; The theoretical charging current is calculated based on the state-of-charge difference, battery rated capacity, and risk duration. The formula for calculating the theoretical charging current is as follows: In the formula, The theoretical charging current, For the battery's rated capacity, Due to the difference in state of charge, Duration of risk; A charging current control command is generated based on the smaller value between the theoretical charging current and the maximum charging current.

6. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, Adjusting the switching edges of the switching devices in the DC-DC converter according to the risk indicators includes: Read the system's default rising edge slope and default falling edge slope; When the risk flag is one, the rising edge slope setting is set to half of the default rising edge slope, and the falling edge slope setting is set to half of the default falling edge slope. The rising edge slope setting value and the falling edge slope setting value are sent to the gate drive channel of the DC-DC converter to adjust the switching edge of the switching device in the DC-DC converter; When the risk flag is zero, the rising edge slope setting is restored to the default rising edge slope, the falling edge slope setting is restored to the default falling edge slope, and the restored setting is sent to the gate drive channel of the DC-DC converter for execution.

7. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, Calculate the effective ripple voltage of the DC bus in the range of 5 MHz to 30 MHz, and set the compensated undervoltage protection threshold according to the risk indicator, including: Read the system's default undervoltage protection threshold; Configure a bandpass filter in the range of 5 MHz to 30 MHz on the DC bus voltage measurement channel; Within a preset measurement time window, the DC bus voltage is acquired through a bandpass filter, and the effective value ripple voltage within the range of 5 MHz to 30 MHz within the measurement time window is calculated. When the risk flag is one, the compensated undervoltage protection threshold is obtained by subtracting the effective value ripple voltage from the default undervoltage protection threshold. When the risk flag is zero, the compensated undervoltage protection threshold is set as the default undervoltage protection threshold.

8. The intelligent management system for lithium iron phosphate battery backup power based on a distribution network terminal according to claim 1, characterized in that, The backup power supply switching is controlled based on the compensated undervoltage protection threshold, including: The compensated undervoltage protection threshold is used as the current undervoltage protection threshold, and the instantaneous voltage of the DC bus is continuously monitored. When the instantaneous voltage of the DC bus remains below the current undervoltage protection threshold for a preset duration, the drive switch switches to backup power supply mode.

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