Direct current energy storage control system of distributed sodium ion battery

Abstract

The invention is suitable for the technical field of energy storage control, and provides a direct current energy storage control system of a distributed sodium ion battery, which comprises a distributed energy storage unit, a direct current bus network, an intelligent monitoring unit and an energy management unit, the distributed energy storage unit is connected with the direct current bus network; the intelligent monitoring unit is connected with the sodium ion battery module in the distributed energy storage unit, and transmits monitored data to the energy management unit through the CAN communication module; the energy management unit is connected with the non-isolated bidirectional DC converter in the distributed energy storage unit, performs fault analysis based on the received parameters, generates a duty ratio adjustment instruction, and dynamically adjusts the duty ratio of the non-isolated bidirectional DC converter according to the duty ratio adjustment instruction. And the bus voltage of the direct-current bus network is adaptively adjusted within the preset range. According to the method, the loss in the energy conversion process is reduced, and the energy utilization efficiency is improved by flexibly configuring the energy storage capacity in a direct-current load scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage control, in particular to a direct-current energy storage control system of distributed sodium ion batteries. BACKGROUND

[0002] Current energy storage technology has gradually become the key to balancing renewable energy generation fluctuations, improving grid flexibility and stability. Sodium ion battery energy storage technology is more abundant and widespread than lithium batteries, and has lower cost. Secondly, sodium ion batteries have higher safety and higher thermal runaway temperature, and are less likely to cause fire accidents and other safety incidents. In addition, sodium ion batteries have a longer cycle life and can meet the demand for frequent charging and discharging of energy storage systems.

[0003] In the prior art, most of the energy storage technology applications are mainly centralized energy storage systems. Such systems are deployed in a specific area by concentrating large-scale energy storage units and using a unified management system for regulation and control. However, the centralized architecture of energy storage does not match the characteristics of distributed energy. On the one hand, the time and space distribution characteristics of renewable energy lead to the dispersion of energy production and consumption nodes, and centralized long-distance energy transmission can easily lead to high line loss rate and difficulty in balancing power fluctuations. On the other hand, in direct current load scenarios such as electric vehicles and data centers, the two-way energy conversion link in the alternating coupling architecture of the centralized system will generate additional losses, further reducing system efficiency and increasing equipment costs.

[0004] In view of this, a direct-current energy storage control system of distributed sodium ion batteries is proposed. SUMMARY

[0005] The present application provides a direct-current energy storage control system of distributed sodium ion batteries, which solves the problem of additional losses in the two-way energy conversion link in the alternating coupling architecture of the centralized system, further reduces system efficiency and increases equipment costs.

[0006] The present application provides a direct-current energy storage control system of distributed sodium ion batteries, comprising:

[0007] a distributed energy storage unit, a direct-current bus network, an intelligent monitoring unit and an energy management unit;

[0008] The distributed energy storage unit comprises a sodium ion battery module and a non-isolated bidirectional direct-current converter. The input end of the non-isolated bidirectional direct-current converter is electrically connected to the first output end of the sodium ion battery module through a copper bar, and the output end of the non-isolated bidirectional direct-current converter is connected to the input interface of the direct-current bus network through a high-voltage cable.

[0009] The intelligent monitoring unit comprises a battery state sensor and a CAN (Controller Area Network) communication module; an input end of the battery state sensor is connected to a second output end of the sodium ion battery module; an input end of the CAN communication module is connected to an output end of the battery state sensor; an output end of the CAN communication module is connected to the energy management unit; and the CAN communication module is used to transmit parameters collected by the battery state sensor to the energy management unit.

[0010] The energy management unit is connected to the non-isolated bidirectional DC converter, generates a duty cycle adjustment instruction after fault analysis based on the received parameters, and dynamically adjusts the duty cycle of the non-isolated bidirectional DC converter according to the duty cycle adjustment instruction, so that the bus voltage of the DC bus network is adaptively adjusted within a preset range.

[0011] Further, the sodium ion battery module comprises a plurality of sodium ion battery sub-modules, each of which comprises a parallel group of battery cells and a voltage balancing circuit.

[0012] Further, the voltage balancing circuit comprises a master switch, an energy storage inductor, an energy storage capacitor and a balancing control element; the master switch is connected to the positive and negative poles of the sodium ion battery cell; the energy storage inductor and the energy storage capacitor are connected in parallel to form an energy storage module, and the energy storage module is coupled to the sodium ion battery cell through the master switch;

[0013] The balancing control element integrates a single cell voltage sensor for real-time detection of single cell voltage data of each battery cell in the sodium ion battery sub-module; based on the single cell voltage data, the voltage difference between adjacent battery cells is calculated, and when the voltage difference exceeds a preset threshold, a switching control signal is generated to drive the master switch to turn on or turn off, so that the energy storage inductor and the energy storage capacitor transfer the energy in the battery cell with higher voltage to the adjacent battery cell with lower voltage through the turn-on or turn-off of the master switch, to achieve voltage balancing of the battery cells.

[0014] Further, the non-isolated bidirectional DC converter comprises a power switching device and a filter inductor, and the filter inductor is connected in series between the power switching device and the DC bus network.

[0015] The control end of the power switching device is connected to the energy management unit through a PWM (Pulse Width Modulation) signal line, so that the energy management unit controls the bidirectional energy transmission between the sodium ion battery module and the DC bus network by adjusting the duty cycle of the power switching device.

[0016] Further, the direct current bus network comprises an input interface, an output interface and a bus voltage regulation module;

[0017] The input interface comprises an external direct current power supply interface for connecting a photovoltaic direct current output end or a wind power direct current output end.

[0018] The output interface is connected with a direct current load device and a backup interface.

[0019] The bus voltage regulation module integrates a voltage and current monitoring unit and a protection unit, the voltage and current monitoring unit collects bus voltage and current data of the direct current bus network in real time, and the protection unit triggers a fuse or a contactor to act based on data of the voltage and current monitoring unit to cut off an abnormal loop.

[0020] Further, the battery state sensor comprises a module voltage sensor, a module current sensor and a module temperature sensor, which respectively transmit detected module total voltage, module total current and module overall temperature parameters to the energy management unit through the CAN communication module.

[0021] Further, the energy management unit comprises a data acquisition module, a fault analysis module and a control strategy module.

[0022] The data acquisition module is connected with the CAN communication module and the equalization control element of the sodium ion battery sub-module, and is used for receiving module total voltage, module total current and module overall temperature parameters collected by the battery state sensor and cell voltage data detected by the equalization control element.

[0023] The fault analysis module is connected with the data acquisition module, and performs fault feature extraction and classification based on the module total voltage, module total current, module overall temperature parameters and cell voltage data.

[0024] The control strategy module is connected with the fault analysis module, generates a duty cycle regulation instruction according to a fault classification result, and sends the duty cycle regulation instruction to the power switching device of the non-isolated bidirectional direct current converter through a PWM signal line.

[0025] Further, the fault analysis module performs the following steps for fault analysis:

[0026] The module total voltage, module total current, module overall temperature parameters and cell voltage data are filtered and normalized.

[0027] High-frequency noise features in the module total current are extracted by fast Fourier transform, and the standard deviation of the cell voltage is calculated by a sliding window algorithm.

[0028] input the high-frequency noise features, the single-body voltage standard deviation and the module temperature parameters into a pre-trained fault classification model, and output a fault type and a severity level; the pre-trained fault classification model is a multi-classification model generated by a random forest algorithm based on high-frequency noise energy, single-body voltage standard deviation and module temperature parameters extracted from historical fault samples;

[0029] Based on the fault type and the severity level, a preset duty cycle adjustment strategy is matched to generate a corresponding duty cycle adjustment instruction.

[0030] Furthermore, the matching of the preset duty cycle adjustment strategy based on the fault type and the severity level to generate the corresponding duty cycle adjustment instruction comprises:

[0031] If the high-frequency noise energy exceeds the threshold value and the single-body voltage standard deviation suddenly increases, the arc fault is determined, and the control strategy module generates a duty cycle zero instruction and triggers a fuse to cut off the fault loop;

[0032] If the total voltage of the module exceeds the preset range, a step-down or step-up duty cycle instruction is generated to restore the bus voltage by adjusting the duty cycle of the non-isolated bidirectional DC converter;

[0033] If the overall temperature of the module exceeds the safety threshold, a power reduction duty cycle instruction is generated and the liquid cooling system is started to dissipate heat until the temperature returns to normal.

[0034] Furthermore, the dynamic adjustment of the duty cycle of the non-isolated bidirectional DC converter according to the duty cycle adjustment instruction to adaptively adjust the bus voltage of the DC bus network within the preset range comprises:

[0035] Real-time acquisition of bus voltage monitoring data of the DC bus network, calculation of the deviation value of the current bus voltage from the preset target voltage;

[0036] Based on the voltage deviation value, a duty cycle adjustment amount is generated by a proportional-integral control algorithm;

[0037] The duty cycle adjustment amount is converted into a PWM signal, which is sent to the power switching device of the non-isolated bidirectional DC converter through a PWM signal line to real-time adjust the conduction timing of the power switching device;

[0038] The filter inductor of the non-isolated bidirectional DC converter smooths the current ripple, and the bus voltage of the DC bus network is adaptively adjusted within the preset range.

[0039] From the above technical solutions, the present application has the following advantages:

[0040] The application generates a duty ratio adjustment instruction corresponding to the non-isolated bidirectional DC converter by analyzing the fault state of the sodium ion battery module in the distributed energy storage unit, and adjusts the duty ratio of the non-isolated bidirectional DC converter, so that the bus voltage of the DC bus network is adaptively adjusted within the preset range. The DC energy storage system of the application does not need to convert AC and DC, reduces the loss in the energy conversion process, and improves the overall efficiency of the system. In addition, in the DC load scene, the energy utilization efficiency is improved by flexibly configuring the energy storage capacity, thereby optimizing the operation of the power system. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A system architecture diagram of a distributed sodium ion battery DC energy storage control system in the application;

[0042] Figure 2 A partial structure diagram of a sodium ion battery module in the application;

[0043] Figure 3 A non-isolated bidirectional DC converter topology structure diagram in the application;

[0044] Figure 4 A structure diagram of a DC bus network in the application;

[0045] Figure 5 A system partial structure diagram of a distributed sodium ion battery DC energy storage control system in the application. DETAILED DESCRIPTION

[0046] The terms "first", "second", "third", "fourth" and the like in the specification of this application and in the above drawings, if any, are used to distinguish similar objects, and do not necessarily have to be used to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "correspond to" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0047] Embodiment one

[0048] Please refer to Figure 1The direct-current energy storage control system of the distributed sodium-ion battery provided in the embodiments of the present application comprises a distributed energy storage unit 1, a direct-current bus network 2, an intelligent monitoring unit 3 and an energy management unit 4; wherein the distributed energy storage unit 1 comprises a sodium-ion battery module 101 and a non-isolated bidirectional direct-current converter 102; the input end of the non-isolated bidirectional direct-current converter 102 is electrically connected to the first output end of the sodium-ion battery module 101 through a copper bar, and the output end of the non-isolated bidirectional direct-current converter 102 is connected to the input interface 201 of the direct-current bus network 2 through a high-voltage cable; the intelligent monitoring unit 3 comprises a battery state sensor 301 and a CAN communication module 302, the battery state sensor 301 is connected to the second output end of the sodium-ion battery module 101, and the input end of the CAN communication module 302 is connected to the output end of the battery state sensor 301; the output end of the CAN communication module 302 is connected to the energy management unit 4, and the CAN communication module 302 is used for transmitting the parameters collected by the battery state sensor 301 to the energy management unit 4; the energy management unit 4 is connected to the non-isolated bidirectional direct-current converter 102, the energy management unit 4 generates a duty ratio adjustment instruction after fault analysis based on the received parameters, and dynamically adjusts the duty ratio of the non-isolated bidirectional direct-current converter 102 according to the duty ratio adjustment instruction, so that the bus voltage of the direct-current bus network 2 is adaptively adjusted within a preset range.

[0049] Specifically, the sodium-ion battery module 101 is composed of sodium-ion battery cells, is responsible for the storage and release of electric energy, and has the characteristics of high energy density and long cycle life; the non-isolated bidirectional direct-current converter 102 adopts an H-bridge topology structure, controls the energy flow direction and power by adjusting the duty ratio, and realizes the bidirectional energy conversion between the low-voltage side of the battery (the output voltage of the sodium-ion battery module) and the high-voltage side of the direct-current bus; the direct-current bus network 2 uniformly distributes the electric energy from the energy storage unit and external energy sources, and reduces the line loss through high-voltage transmission; the battery state sensor 301 is embedded in the sodium-ion battery module to ensure the data acquisition accuracy; the CAN communication module 302 transmits the data collected by the battery state sensor to the energy management unit through the CAN bus, supports high-speed and low-delay communication; the energy management unit 4 is used for identifying arc faults, overvoltage / undervoltage, overtemperature and other abnormalities, dynamically controls the power switching devices of the non-isolated bidirectional direct-current converter, and at the same time combines the real-time feedback of the bus voltage to ensure that the voltage is stable within the preset range.

[0050] Embodiment two

[0051] Please refer to Figure 2 In the embodiment, the sodium-ion battery module 101 comprises a plurality of sodium-ion battery sub-modules, each of which contains a parallel group of battery cells and a voltage balancing circuit.

[0052] The voltage balancing circuit is arranged in each sodium ion battery sub-module, and includes a master switch, an energy storage inductor, an energy storage capacitor and a balancing control element; the master switch is connected to the positive and negative electrodes of the sodium ion battery cell; the energy storage inductor and the energy storage capacitor are connected in parallel to form an energy storage module, and the energy storage module is coupled with the sodium ion battery cell through the master switch;

[0053] The balancing control element integrates a single-cell voltage sensor for real-time detection of single-cell voltage data of each battery cell in the sodium ion battery sub-module; based on the single-cell voltage data, the voltage difference between adjacent battery cells is calculated, and when the voltage difference exceeds a preset threshold, a switch control signal is generated to drive the master switch to be turned on or turned off, so that the energy storage inductor and the energy storage capacitor transfer the energy in the battery cell with a higher voltage to the adjacent battery cell with a lower voltage through the on or off of the master switch, so as to balance the voltage of the battery cells.

[0054] Specifically, one sodium ion battery pack includes a plurality of sodium ion battery sub-modules, and the connection mode of the plurality of sodium ion battery sub-modules is not limited and can be a series connection mode; the sodium ion battery cells in the sub-modules are connected in parallel to form a stable voltage / current output, and when the plurality of sodium ion battery sub-modules are connected in series, the total voltage is the sum of the voltages of the sub-modules, thereby meeting the high-voltage requirement of the DC bus.

[0055] The preset threshold is set to 50 mV, and if the voltage difference exceeds 50 mV, it is determined that the voltage is unbalanced, and the balancing process is triggered; by driving the master switch, the energy storage module is coupled with the high-voltage battery cell, the energy storage inductor absorbs the energy and temporarily stores it in the capacitor; then the switch path is switched to release the energy to the low-voltage battery cell, and the dynamic energy transfer is completed.

[0056] Please refer to Figure 3 The non-isolated bidirectional DC converter 102 includes a power switching device and a filter inductor, and the filter inductor is connected in series between the power switching device and the DC bus network; the control end of the power switching device is connected to the energy management unit through a PWM signal line, so that the energy management unit controls the bidirectional energy transmission between the sodium ion battery module and the DC bus network by adjusting the duty cycle of the power switching device.

[0057] Specifically, the power switch device is a full-bridge topology composed of power switch tubes [Q1], [Q2], [Q3], and [Q4] as bidirectional energy transmission switching elements, wherein each switch tube is connected in anti-parallel with a freewheeling diode [D1] and [D2] for providing a current freewheeling path during the off period of the switch tube; a filter inductor [L] is connected in series between [Q1], [Q2], [Q3], [Q4] and the high-voltage side bus (750V) for smoothing current ripple and storing energy; the low-voltage side is connected to the full-bridge output end through the high-voltage side filter capacitor [C_H] and the filter inductor [L]; the high-voltage side filter capacitor is connected in parallel to the bus side for stabilizing the bus voltage and filtering out high-frequency noise; the control ends of [Q1], [Q2], [Q3],

[0058] [Q4] are connected to the energy management unit through the PWM signal line to receive duty cycle adjustment instructions. It should be noted that in the charging mode, if the voltage of a certain sub-module is unbalanced, the energy management unit can preferentially adjust the charging duty cycle of the corresponding sub-module to achieve local energy optimization distribution. In the discharging mode, energy is fed back to the low-voltage side through the cooperative switching action of [D1] and [D2] and [Q1], [Q2], [Q3], [Q4]. When a bus short circuit or overvoltage is detected, the energy management unit immediately sets the duty cycle to zero, turns off [Q1], [Q2], [Q3], [Q4], and at the same time activates the passive freewheeling function of the low-voltage side anti-parallel diode to maintain the fault current path, and cuts off the fault circuit through the fuse.

[0059] Please refer to Figure 4 , the DC bus network 2 includes an input interface, an output interface, and a bus voltage regulation module;

[0060] The input interface includes an external DC power supply interface, which is used to connect a photovoltaic DC output end or a wind power DC output end (i.e. Figure 4 photovoltaic or wind power in ); the output interface connects a DC load device and a backup interface (i.e. Figure 4 backup interface in ); the bus voltage regulation module integrates a voltage and current monitoring unit and a protection unit, which are connected to the DC bus (750V copper bus); the voltage and current monitoring unit collects real-time bus voltage and current data of the DC bus network, and the protection unit triggers the action of the fuse or contactor based on the data of the voltage and current monitoring unit to cut off the abnormal circuit.

[0061] Specifically, the input side of the DC bus network 2: the DC power supply of photovoltaic / wind power is connected to the 750V copper bus through the input interface, and after being monitored by the bus voltage regulation module, it provides renewable energy power for the system; the output side of the DC bus network 2: the bus power is distributed to charging piles, industrial loads and other equipment through the output interface, and the standby interface supports future expansion or emergency power supply. When the sodium-ion battery bidirectional DC converter is in the charging mode, the bus voltage may deviate due to external power fluctuations or load mutations. The voltage and current monitoring unit detects the deviation value in real time, and if it exceeds the preset range (such as ±5%), the energy management unit is triggered to adjust the duty cycle of the non-isolated bidirectional DC converter to compensate the bus voltage through charging and discharging; the protection unit synchronously monitors abnormal signals and immediately triggers the action of the fuse to ensure the safety of the system.

[0062] Further, the battery state sensor 301 includes a module voltage sensor 301a, a module current sensor 301b, and a module temperature sensor 301c. The module voltage sensor, the module current sensor, and the module temperature sensor respectively transmit the detected module total voltage, module total current, and module overall temperature parameters to the energy management unit through the CAN communication module.

[0063] Specifically, the module voltage sensor adopts a differential voltage sampling circuit, which is directly connected in parallel across the positive and negative electrodes of the sodium-ion battery module. The module total voltage is linearly converted into a low-voltage signal through a voltage dividing resistor network, and then quantitatively processed by an analog-to-digital converter to obtain a digital voltage value. The module current sensor is based on the Hall effect technology, and a magnetic ring is connected in series in the battery loop. The magnetic field change generated by the current-carrying conductor is sensed by a Hall element and outputted as a voltage signal proportional to the current. The module temperature sensor adopts a negative temperature coefficient thermistor (NTC) which is packaged in the battery module shell or close to the battery cell position. The resistance value decreases with the increase of temperature, which is converted into a voltage signal through a voltage dividing circuit and then quantified by an ADC. The module voltage, current, and temperature data are packaged into CAN messages at a preset period and sent to the energy management unit 4 through the CAN communication module. The energy management unit identifies module internal short circuit, poor contact and other faults by combining voltage, current mutation and temperature abnormalities.

[0064] Example Three

[0065] Please refer to Figure 5 The energy management unit 4 includes a data acquisition module 401, a fault analysis module 402, and a control strategy module 403.

[0066] The data acquisition module 401 is connected with the CAN communication module and the sodium-ion battery module 101, and is configured to receive the total module voltage collected by the module voltage sensor 301a, the total module current collected by the module current sensor 301b, the overall module temperature parameter collected by the module temperature sensor 301c, and the single cell voltage data detected by the balancing control element of the sodium-ion battery submodule in the sodium-ion battery module 101 through the CAN communication module; the fault analysis module 402 is connected with the data acquisition module 401, and is configured to perform fault feature extraction and classification based on the total module voltage, the total module current, the overall module temperature parameter and the single cell voltage data; and the control strategy module 403 is connected with the fault analysis module 402 and the non-isolated bidirectional DC converter 102 respectively, and is configured to generate a duty cycle adjustment instruction according to the fault classification result, and send the duty cycle adjustment instruction to the power switching device of the non-isolated bidirectional DC converter 102 through the PWM signal line.

[0067] Specifically, the data acquisition module 401 obtains the total module voltage, the total current and the overall temperature data through the CAN communication module, directly reads the single cell voltage data of the sodium-ion battery submodule in the sodium-ion battery module 101, and performs preliminary verification, time stamp alignment and buffering on the original data to ensure data integrity and time sequence consistency. The fault analysis module 402 extracts fault features from the data and classifies them. Here, a machine learning fault model is constructed, the input of the model is the module voltage, current, temperature and single cell voltage data set, the algorithm in the model combines signal processing and machine learning to identify abnormal patterns, and the model outputs the duty cycle of the non-isolated bidirectional DC converter.

[0068] Further, the fault analysis module performs the following steps for fault analysis:

[0069] 1. Filtering and normalizing the total module voltage, the total module current, the overall module temperature parameter and the single cell voltage data;

[0070] 2. Extracting high-frequency noise features in the total module current by fast Fourier transform, and calculating the standard deviation of the single cell voltage by a sliding window algorithm;

[0071] 3. Inputting the high-frequency noise features, the single cell voltage standard deviation and the module temperature parameter into a pre-trained fault classification model to output the fault type and severity level; the pre-trained fault classification model is a multi-classification model generated by training the high-frequency noise energy, the single cell voltage standard deviation and the module temperature parameter extracted from the historical fault samples by a random forest algorithm;

[0072] 4. Based on the fault type and severity level, matching the pre-set duty cycle adjustment strategy to generate the corresponding duty cycle adjustment instruction.

[0073] The filtering process is a low-pass filtering of the module total current signal to eliminate high-frequency noise interference, and a moving average filtering of the single cell voltage data to smooth random fluctuations. The normalization process is to scale the voltage, current, and temperature data to the [0, 1] interval to eliminate dimensional differences. High-frequency noise analysis is a fast Fourier transform (FFT) of the module total current signal to extract energy features above 10 kHz for arc fault detection. The sliding window algorithm is used to calculate the standard deviation of the single cell voltage within the window to identify cell imbalance problems. Input high-frequency noise energy, voltage standard deviation, and module temperature feature vectors, and train the data set based on the random forest algorithm to include historical fault samples such as arc, overvoltage, and overheating. The model outputs fault types including arc, voltage anomaly, temperature anomaly, and severity levels including mild, moderate, and severe.

[0074] Further, based on the fault type and severity level, the preset duty cycle adjustment strategy is matched to generate corresponding duty cycle adjustment instructions, including:

[0075] 1. If the high-frequency noise energy exceeds the threshold and the single cell voltage standard deviation increases sharply, it is determined as an arc fault, and the control strategy module generates a duty cycle zero instruction and triggers a fuse to cut off the fault loop;

[0076] 2. If the module total voltage exceeds the preset range, generate a step-down or step-up duty cycle instruction to restore the bus voltage by adjusting the duty cycle of the non-isolated bidirectional DC converter;

[0077] 3. If the overall temperature of the module exceeds the safety threshold, generate a power reduction duty cycle instruction and start the liquid cooling system to dissipate heat until the temperature returns to normal.

[0078] When the fault analysis module detects that the high-frequency noise energy exceeds the threshold value, for example, the energy in the frequency band above 10 kHz in the current signal exceeds 100 mW / Hz, and the single cell voltage standard deviation suddenly increases, such as the standard deviation rising from 5 mV to 50 mV within 1 second, it is determined as an arc fault, such as a discharge phenomenon caused by poor contact or short circuit. At this time, the control strategy module immediately generates a duty ratio zero command, turns off the power switch device (Q1-Q4) of the non-isolated bidirectional DC converter through the PWM signal line, stops energy transmission; at the same time, sends a fuse trigger signal to the protection unit to cut off the connection between the fault sub-module and the DC bus, preventing the spread of arc. If the module total voltage exceeds the preset range, such as the 750V bus voltage deviation exceeding ±5%, generate a duty ratio command according to the voltage direction: when the voltage is too high, reduce the discharge duty ratio of the bidirectional converter to reduce the energy injection into the bus; when the voltage is too low, increase the charging duty ratio to absorb energy from the battery to compensate the bus. If the overall temperature of the module exceeds the safety threshold (such as 60°C), the control strategy module generates a power reduction duty ratio command to limit the maximum power output of the bidirectional converter, and starts the liquid cooling system (S-shaped flow channel liquid cooling plate) to force cooling until the temperature returns to the safe range.

[0079] Further, according to the duty ratio adjustment command, the duty ratio of the non-isolated bidirectional DC converter is dynamically adjusted, so that the bus voltage of the DC bus network is adaptively adjusted within the preset range, including:

[0080] 1. Real-time acquisition of bus voltage monitoring data of DC bus network, calculation of deviation value of current bus voltage and preset target voltage;

[0081] The voltage and current monitoring unit real-time collects the voltage data of the DC bus network, such as the preset target value is 750V, and calculates the deviation value of the current bus voltage and the preset target value.

[0082] 2. Based on the voltage deviation value, generate the duty ratio adjustment amount by proportional integral control algorithm;

[0083] Based on the voltage deviation, the duty ratio adjustment amount is calculated by proportional integral algorithm, and the calculation formula is:

[0084] Duty ratio adjustment amount = K p ·ΔV+K i ·∫ΔV dt

[0085] Where: ΔV is the voltage deviation, K p is the proportional coefficient, which quickly responds to voltage fluctuations, K i is the integral coefficient, which eliminates steady-state error.

[0086] 3. The duty cycle adjustment amount is converted into a PWM signal, which is sent to the power switching device of the non-isolated bidirectional DC converter through the PWM signal line to adjust the conduction timing of the power switching device in real time;

[0087] The duty cycle adjustment amount is converted into a PWM waveform (such as a frequency of 20 kHz and a duty cycle of 0%-100%), which is sent to the power switching device (Q1-Q4) of the non-isolated bidirectional DC converter through the PWM signal line to dynamically adjust the conduction timing thereof. For example, if boosting is required, the discharge mode duty cycle is increased, and the Q1 / Q4 conduction time is extended; if bucking is required, the conduction time is shortened or switched to the charging mode.

[0088] 4. The filter inductor of the non-isolated bidirectional DC converter smoothes the current ripple to adaptively adjust the bus voltage of the DC bus network within a preset range.

[0089] The filter inductor in the converter suppresses current mutation through energy storage and release during switching; at the same time, it forms an LC filter network with the high-voltage side filter capacitor to further smooth the bus voltage ripple. The adjusted bus voltage is collected by the monitoring unit again to form a closed-loop feedback. Through continuous iteration of the PI algorithm, the bus voltage is finally stabilized within the preset range, achieving adaptive adjustment.

[0090] The above embodiments realize the safe operation of the distributed sodium-ion battery energy storage system through the energy management unit. The data acquisition module integrates the total voltage, total current, temperature, and single-cell voltage data of the battery module in real time to provide multi-dimensional input for fault analysis; the fault analysis module extracts fault modes such as arc characteristics, cell imbalance, and temperature abnormalities based on filtering, Fourier transform, and machine learning algorithms; the control strategy module dynamically generates hierarchical instructions to immediately cut off the circuit and shut down the converter for arc faults, adjust the duty cycle to achieve adaptive stabilization of the bus voltage for voltage deviation through the PI algorithm, and reduce the power and start liquid cooling for temperature overload. This effectively shortens the fault response time, reduces the risk of overcharging / overdischarging of the cells, significantly improves the system reliability, energy utilization rate, and battery cycle life, and is suitable for high-fluctuation renewable energy access scenarios.

[0091] It can be understood that those skilled in the art can combine various embodiments in the above embodiments to obtain technical solutions of various embodiments.

[0092] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A direct current energy storage control system of a distributed sodium-ion battery, characterized in that, The application relates to a distributed energy storage unit, a direct-current bus network, an intelligent monitoring unit and an energy management unit. The distributed energy storage unit comprises a sodium ion battery module and a non-isolated bidirectional direct-current converter; the input end of the non-isolated bidirectional direct-current converter is electrically connected with the first output end of the sodium ion battery module through a copper bar; and the output end of the non-isolated bidirectional direct-current converter is connected with the input interface of the direct-current bus network through a high-voltage cable. The intelligent monitoring unit comprises a battery state sensor and a CAN communication module; the input end of the battery state sensor is connected with the second output end of the sodium ion battery module; the input end of the CAN communication module is connected with the output end of the battery state sensor; and the output end of the CAN communication module is connected with the energy management unit. The CAN communication module is used for transmitting the parameters collected by the battery state sensor to the energy management unit. The energy management unit is connected with the non-isolated bidirectional direct-current converter; the energy management unit generates a duty ratio adjustment instruction after fault analysis based on the received parameters, and dynamically adjusts the duty ratio of the non-isolated bidirectional direct-current converter according to the duty ratio adjustment instruction, so that the bus voltage of the direct-current bus network is adaptively adjusted within a preset range. The sodium ion battery module comprises a plurality of sodium ion battery submodules, and each sodium ion battery submodule comprises a parallel group of battery cells and a voltage balancing circuit.

2. The distributed sodium-ion battery direct current energy storage control system of claim 1, wherein, The voltage balancing circuit comprises a master switch, an energy storage inductor, an energy storage capacitor and an equalization control element; the master switch is connected with the positive and negative poles of the sodium ion battery cell; the energy storage inductor and the energy storage capacitor are connected in parallel to form an energy storage module, and the energy storage module is coupled with the sodium ion battery cell through the master switch; 3. The distributed sodium-ion battery DC energy storage control system of claim 2, wherein, The equalization control element integrates a single-cell voltage sensor and is used for detecting single-cell voltage data of each battery cell in the sodium ion battery submodule in real time; the voltage difference between adjacent battery cells is calculated based on the single-cell voltage data; when the voltage difference exceeds a preset threshold, a switch control signal is generated to drive the master switch to be turned on or turned off, so that the energy storage inductor and the energy storage capacitor transfer the energy in the battery cell with a higher voltage to the adjacent battery cell with a lower voltage through the turn-on or turn-off of the master switch, thereby realizing the voltage balancing of the battery cells. The non-isolated bidirectional direct-current converter comprises a power switching device and a filter inductor, and the filter inductor is connected in series between the power switching device and the direct-current bus network; 4. The distributed sodium-ion battery direct current energy storage control system of claim 1, wherein, The control end of the power switching device is connected with the energy management unit through a PWM signal line, so that the energy management unit controls the bidirectional energy transmission between the sodium ion battery module and the direct-current bus network by adjusting the duty ratio of the power switching device. The direct-current bus network comprises an input interface, an output interface and a bus voltage adjustment module; 5. The distributed sodium-ion battery direct current energy storage control system of claim 1, wherein, The input interface comprises an external direct-current power supply interface, and the external direct-current power supply interface is used for connecting a photovoltaic direct-current output end or a wind power direct-current output end; The output interface is connected with a direct-current load device and a standby interface; ​ The bus voltage regulation module integrates a voltage and current monitoring unit and a protection unit, the voltage and current monitoring unit collects bus voltage and current data of the DC bus network in real time, and the protection unit triggers the action of a fuse or contactor based on the data of the voltage and current monitoring unit to cut off an abnormal circuit.

6. The distributed sodium-ion battery direct current energy storage control system of claim 1, wherein, The battery state sensor includes a module voltage sensor, a module current sensor, and a module temperature sensor, which respectively transmit detected module total voltage, module total current, and module overall temperature parameters to the energy management unit through the CAN communication module.

7. The distributed sodium-ion battery direct current energy storage control system of claim 3, wherein, The energy management unit includes a data acquisition module, a fault analysis module, and a control strategy module. The data acquisition module is connected to the CAN communication module and the equalization control element of the sodium-ion battery sub-module, and is used to receive the module total voltage, module total current, and module overall temperature parameters collected by the battery state sensor, and the single cell voltage data detected by the equalization control element. The fault analysis module is connected to the data acquisition module, and performs fault feature extraction and classification based on the module total voltage, module total current, module overall temperature parameters, and single cell voltage data. The control strategy module is connected to the fault analysis module, generates a duty cycle adjustment instruction according to the fault classification result, and sends the duty cycle adjustment instruction to the power switching device of the non-isolated bidirectional DC converter through the PWM signal line.

8. The distributed sodium-ion battery direct current energy storage control system of claim 7, wherein, The fault analysis module performs the following steps for fault analysis: Filtering and normalization processing is performed on the module total voltage, module total current, module overall temperature parameters, and single cell voltage data; High-frequency noise features in the module total current are extracted by fast Fourier transform, and the standard deviation of the single cell voltage is calculated by a sliding window algorithm; The high-frequency noise features, single cell voltage standard deviation, and module temperature parameters are input into a pre-trained fault classification model to output fault types and severity levels; the pre-trained fault classification model is a multi-classification model generated by random forest algorithm training based on high-frequency noise energy, single cell voltage standard deviation, and module temperature parameters extracted from historical fault samples; Based on the fault type and severity level, a preset duty cycle adjustment strategy is matched to generate a corresponding duty cycle adjustment instruction.

9. The distributed sodium-ion battery direct current energy storage control system of claim 8, wherein, The matching of the preset duty cycle adjustment strategy based on the fault type and severity level to generate the corresponding duty cycle adjustment instruction includes: If the detected high-frequency noise energy exceeds the threshold value and the single cell voltage standard deviation suddenly increases, it is determined as an arc fault, the control strategy module generates a duty cycle zero instruction and triggers a fuse to cut off the fault circuit; If the module total voltage exceeds the preset range, a duty cycle instruction for voltage reduction or voltage increase is generated to restore the bus voltage by adjusting the duty cycle of the non-isolated bidirectional DC converter; If the module overall temperature exceeds the safety threshold, a duty cycle instruction for power reduction is generated and the liquid cooling system is started to dissipate heat until the temperature returns to normal.

10. The distributed sodium-ion battery direct current energy storage control system of claim 1, wherein, The duty cycle of the non-isolated bidirectional DC converter is dynamically adjusted according to the duty cycle adjustment instruction, so that the bus voltage of the DC bus network is adaptively adjusted within a preset range, comprising: Real-time acquisition of bus voltage monitoring data of the DC bus network, calculation of the deviation value of the current bus voltage and the preset target voltage; Based on the voltage deviation value, a duty cycle adjustment amount is generated through a proportional integral control algorithm; The duty cycle adjustment amount is converted into a PWM signal, which is sent to the power switching device of the non-isolated bidirectional DC converter through a PWM signal line to real-time adjust the conduction timing of the power switching device; Through the filter inductor smooth current ripple of the non-isolated bidirectional DC converter, the bus voltage of the DC bus network is adaptively adjusted within the preset range.

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