Black-start voltage buildup control method for mobile vehicle-mounted energy storage system

Abstract

The invention discloses a black-start voltage buildup control method for a mobile vehicle-mounted energy storage system, and relates to the technical field of electrochemical energy storage. According to the method, voltage buildup conditions are confirmed through system initialization and security check, load characteristic pre-identification and voltage buildup parameter matching are realized through small signal injection, and inrush current is cooperatively suppressed by adopting a staged control strategy of pre-charging, voltage building, frequency stabilization and on-load verification in combination with an S-shaped curve and real-time current limiting; when the capacity of a single energy storage vehicle is insufficient, multi-vehicle synchronous grid connection and dynamic power balanced distribution are realized through a master-slave control architecture; electrical, energy storage and inverter parameters are monitored in real time in the whole voltage building process, and multiple protection and fault isolation are executed. The problems of inrush current impact, poor load adaptability, difficulty in multi-vehicle coordination and the like in black-start voltage building are solved, safe and smooth voltage building is realized, the voltage building success rate and efficiency are improved, and the requirements of mobile application scenes are met.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a black-start voltage build-up control method for a mobile vehicle-mounted energy storage system. Background Technology

[0002] As power systems increasingly demand higher reliability, mobile energy storage vehicles are being used more widely in emergency power supply and black start scenarios. These vehicles can be quickly transported to power outage areas to provide temporary power to critical loads or act as black start power sources to help thermal power units resume operation.

[0003] Black start voltage build-up refers to the process by which an energy storage system, starting from zero voltage, autonomously establishes a stable voltage and frequency in the event of a complete power outage, thus creating conditions for subsequent load power restoration. The voltage build-up process includes key stages such as voltage amplitude establishment, frequency stabilization, and phase synchronization.

[0004] Traditional black start solutions mainly rely on diesel generators or hydroelectric generators, but diesel generators suffer from problems such as high noise, heavy pollution, and difficulty in fuel storage; hydroelectric generators are limited by geographical conditions. Using mobile energy storage vehicles to perform black start tasks has advantages such as being clean and environmentally friendly, having a rapid response, and being flexible in deployment, making it an important development direction in the field of black start.

[0005] However, mobile energy storage vehicles face the following technical challenges during the black start pressure build-up process: 1. The pressure build-up process lacks a systematic control strategy: In existing technologies, the black start voltage build-up of energy storage systems often employs a simple voltage step method, directly outputting the rated voltage. This method is feasible under no-load conditions, but when the system contains transformers, capacitors, or other equipment, the sudden voltage change can generate severe inrush current surges. Transformer inrush currents can reach several times the rated current and last for several seconds; capacitor combined inrush currents can reach more than ten times the rated current. These surge currents not only threaten the safety of the energy storage system but may also cause protective devices to malfunction, resulting in voltage build-up failure.

[0006] Existing technologies lack a systematic control method for the entire black start voltage build-up process and fail to effectively address the coordinated control issues of key aspects such as pre-charging, voltage build-up, load identification, and inrush current suppression.

[0007] 2. Insufficient identification of load characteristics: In black-start scenarios, the types of loads that the system needs to restore are diverse, including transformer no-load, capacitor banks, and motor starting. The electrical characteristics of different loads vary significantly: transformer no-load exhibits strong inductive properties and a low power factor; capacitor banks exhibit capacitive properties; and motors have high starting current and a low power factor. Traditional control methods use uniform voltage build-up parameters without adjusting the control strategy according to load characteristics. This results in either excessively slow voltage build-up (designed for worst-case scenarios, leading to low efficiency) or insufficient safety margin (designed for normal conditions, with protection mechanisms activating when encountering large-capacity loads). The lack of load identification and adaptive adjustment mechanisms further restricts the success rate of black starts.

[0008] 3. Special constraints for mobile application scenarios: Mobile energy storage vehicles endure bumpy transport, frequent disassembly and assembly, and variable on-site environments, placing higher demands on the reliability, rapid deployment capability, and ease of on-site maintenance of energy storage systems. Traditional energy storage systems face the following challenges in mobile scenarios: transport vibrations lead to decreased consistency between battery packs, requiring on-site reconfiguration and debugging, resulting in long deployment cycles; single-point failures often cause the entire cluster or system to shut down, making on-site repairs difficult in emergency scenarios; and issues such as circulating current and SOC imbalance between battery packs are exacerbated under mobile operating conditions, affecting the system's usable capacity and lifespan.

[0009] 4. Complex multi-vehicle cooperative control When the capacity of a single energy storage vehicle is insufficient, multiple vehicles need to operate in parallel to complete the black start task. How to coordinate the output of each vehicle, avoid circulating current, and achieve balanced power distribution when multiple vehicles are connected in parallel is a pressing technical challenge. Existing technologies mainly use droop control to achieve parallel operation of multiple vehicles, but droop control has inherent contradictions: a large droop coefficient results in good power balancing but also large voltage deviation; a small droop coefficient results in good voltage quality but uneven power distribution. In the dynamic process of black start voltage build-up, fixing the droop parameters makes it difficult to simultaneously meet the dual requirements of voltage quality and power balance.

[0010] To address the aforementioned issues, there is an urgent need to develop a black-start pressure build-up control method suitable for mobile vehicle-mounted energy storage systems, enabling a safe, fast, and reliable pressure build-up process. Summary of the Invention

[0011] The purpose of this invention is to provide a black-start pressure build-up control method for mobile vehicle-mounted energy storage systems. Addressing issues such as inrush current, poor load adaptability, and difficulties in multi-vehicle coordination during the black-start pressure build-up process of mobile energy storage vehicles, this invention establishes a phased pressure build-up control strategy, a load adaptive identification mechanism, and a multi-vehicle collaborative control architecture. Through S-curve soft start, real-time current limiting control, and dynamic droop distribution, it achieves safe and smooth pressure build-up, adaptive load matching, and balanced power distribution among multiple vehicles.

[0012] To achieve the above objectives, the present invention provides the following solution: A black-start pressure build-up control method for a mobile vehicle-mounted energy storage system includes the following steps: S1, System Initialization and Safety Check: Conduct a comprehensive check on the electrical safety of the energy storage vehicle, the status of the energy storage system, environmental conditions, the load side and the communication system, and proceed to the next step after confirming that the pressure build-up conditions are met. S2, Load characteristic pre-identification: Obtain the current response of the load through small signal injection, calculate the equivalent impedance of the load, determine the load type and capacity level, and set the voltage build-up parameters accordingly. S3, phased voltage build-up control: sequentially executes the pre-charge stage, voltage build-up stage, frequency stabilization stage, and load verification stage to achieve smooth voltage build-up from zero voltage to stable rated voltage; S4, Multi-vehicle Cooperative Pressure Building Control: When the capacity of a single energy storage vehicle is insufficient, a master-slave control architecture is adopted. After the master vehicle completes the pressure building, the slave vehicle is connected to the grid synchronously. The power distribution of multiple vehicles is achieved through dynamic droop control. S5, Dynamic Safety Monitoring and Protection: Real-time monitoring of electrical parameters, energy storage system parameters, and inverter parameters throughout the entire pressure build-up process, and execution of corresponding protection strategies for different abnormal situations.

[0013] Furthermore, S1, system initialization and security check, specifically includes: Electrical safety inspection: Confirm that the high-voltage side circuit breaker is open, the grounding switch is closed, there is no residual voltage on the high-voltage busbar, the insulation resistance of the busbar to ground is qualified, the electrical connections are firm and reliable, and the quick connectors are connected in place; Energy storage system status check: Check that the battery pack SOC meets the voltage build-up requirements, the battery temperature is within the appropriate operating range, and the number of online battery packs meets the design requirements. For energy storage systems with PACK-level management capabilities, check the status of each PACK one by one. Environmental condition check: Confirm that the ambient temperature and humidity are within a suitable range and there is no condensation, the ventilation and heat dissipation system is working properly, and the vehicle is parked stably and supported in place in mobile application scenarios; Load-side inspection: Confirm that the system to be restored is in a state of complete power failure, all circuit breakers are open and no other power supply is connected, measure the load-side capacitance to ground to make a preliminary estimate of the system's capacitive load, and check that the grounding system is intact; Communication system check: Confirm that the energy storage vehicle communicates normally with the monitoring system and that the controllers at all levels respond normally; in multi-vehicle collaborative mode, check that the workshop communication link is unobstructed and that the clock synchronization accuracy meets the set requirements.

[0014] Furthermore, S2, load characteristic pre-identification, specifically includes: Small signal injection: The energy storage vehicle outputs a low-voltage test signal with an amplitude of 5-10% of the rated value, and the injected voltage waveform is controlled by a fast response control method; Current response measurement: High-frequency sampling measures the current response, recording the current amplitude, phase, and waveform characteristics; Load impedance calculation: The equivalent impedance of the load is calculated based on the voltage-current amplitude ratio and phase difference. A positive impedance angle indicates an inductive load, while a negative angle indicates a capacitive load. Load type determination: Based on the impedance angle and impedance value, determine whether it is a transformer no-load type, capacitor bank type, motor load type, or resistive load type; Capacity estimation: Based on the calculated impedance value, estimate the load capacity level, convert the impedance value to the rated voltage, calculate the expected steady-state current, and determine whether it is a light load, medium load, or heavy load. Initial voltage build-up parameters: Based on the load type and capacity, the voltage build-up rate and current limit parameters are initially set.

[0015] Furthermore, in step S3, the pre-charging stage of the phased voltage build-up control process specifically includes: Control strategy: The energy storage vehicle outputs DC or very low frequency voltage, and the voltage amplitude slowly rises from zero to the pre-charge endpoint value. The rise rate is determined according to the measured load capacitance. The energy storage system with PACK-level control capability adjusts the output voltage of each PACK so that each PACK can evenly bear the charging power. Current monitoring: Real-time monitoring of charging current, reverse verification of load capacitance value and correction of pre-identification results by monitoring changes in charging current; If the charging current exceeds the set threshold, the voltage amplitude rise rate is automatically reduced. Termination condition: The pre-charging phase is completed when the voltage amplitude rises to the pre-charging endpoint value and the charging current decays to the steady-state value.

[0016] Furthermore, in step S3, the voltage build-up control step, the voltage build-up stage specifically includes: Soft-start control: The energy storage vehicle outputs a standard AC voltage, with the voltage amplitude gradually increasing to the rated voltage following an S-curve starting from the pre-charge endpoint. The S-curve is designed as follows:

[0017] in: The voltage reference value at time t. Rated voltage, For a specific moment in the pressure build-up process, take half of the total pressure build-up time. The total build-up time should be selected within the range of 5-30 seconds, depending on the load type. Adaptive voltage build-up rate: The voltage build-up rate is dynamically adjusted based on the pre-identification results of load characteristics. Slow voltage build-up is used for transformer no-load loads, fast voltage build-up is used for resistive loads, and medium voltage build-up is used for capacitor bank or motor loads. Current limiting control: Real-time monitoring of output current. When the output current exceeds the preset limit, the current deviation is calculated, and a voltage correction amount is generated by the PI controller. This correction amount is then superimposed on the voltage reference value of the S-curve, causing the voltage to pause its rise or slightly decrease, thus limiting the current within a safe range. Termination condition: When the voltage rises to more than 98% of the rated value, and the voltage fluctuation is less than 2% of the rated value, and the current stabilizes within the expected range, the voltage is considered to have been successfully established.

[0018] Furthermore, in step S3, the frequency stabilization stage of the phased voltage build-up control process specifically includes: Frequency control strategy: A phase-locked loop-based frequency control is adopted, which monitors the zero-crossing point of the output voltage, calculates the actual frequency, and achieves closed-loop control by adjusting the modulation frequency of the inverter, thereby locking the output frequency within the allowable deviation range of the rated frequency. Frequency stability criterion: If the frequency deviation remains within the allowable range and the frequency change rate meets the requirements within 30 consecutive seconds, the frequency stability is deemed to be up to standard. For systems employing a distributed control architecture, the main control unit establishes a frequency reference, while other control units maintain synchronization through a fast tracking algorithm.

[0019] Furthermore, in the S3 phased pressure build-up control step, the load verification phase specifically includes: Test load setup: Close a small-capacity test load circuit breaker, with a load power of 10-20% of the energy storage vehicle's rated power; Voltage sag test: Measure the voltage sag at the moment the load is applied. The pass standard is that the voltage sag does not exceed 5% of the rated voltage and recovers to near the rated value within 1 second. Frequency deviation test: Measure the frequency change after the load is applied. The pass standard is that the frequency deviation is within the allowable range and recovers within 5 seconds. Steady-state operation test: Test the load to run stably for 5-10 minutes, monitor voltage, frequency, current and temperature parameters, and confirm that all parameters are stable within the normal range without abnormal fluctuations or alarm information; An energy storage system with balancing function continuously performs SOC balancing during load operation to ensure that the state of each energy storage unit tends to be consistent; after all tests are passed, the energy storage system officially supplies power to the target load.

[0020] Furthermore, S4, multi-vehicle collaborative pressure build-up control, specifically includes: Master-slave role allocation: Select the energy storage vehicle with the largest capacity, highest SOC, and closest to the bus as the master control vehicle, and the rest as slave control vehicles. The master control vehicle sends synchronization signals and power commands to the slave control vehicles through the workshop communication network. The main control vehicle's voltage building process: The main control vehicle independently executes the three stages of load characteristic pre-identification and phased voltage building control: the pre-charging stage, the voltage building stage, and the frequency stabilization stage. After establishing a stable voltage and frequency reference on the bus, it sends a "ready to connect to the grid" command to the slave control vehicle. Slave vehicle synchronous grid connection: The slave vehicle measures the amplitude, frequency, and phase of the bus voltage in real time, adjusts its own output voltage to match the bus voltage, and closes the grid connection circuit breaker after meeting the synchronization conditions that the voltage amplitude difference is less than 2% of the rated voltage, the frequency difference is less than the allowable value, and the phase difference is less than 5 degrees. Before grid connection, the inrush current detection method is used. If the inrush current is less than 10% of the rated current, grid connection is allowed; otherwise, grid connection is stopped and readjustment is performed. Collaborative power distribution: Dynamic droop control is used to achieve automatic power distribution among multiple vehicles, and different droop coefficients are set according to the capacity and SOC status of each vehicle; the energy storage system with high current balancing capability achieves SOC balancing through intra-cluster and inter-cluster balancing and vehicle power allocation.

[0021] Furthermore, in step S5, the real-time monitoring of electrical parameters, energy storage system parameters, and inverter parameters specifically includes: Electrical parameters: Output voltage, current, power, and frequency of the mobile vehicle-mounted energy storage system; Energy storage system parameters: battery SOC, voltage, current, temperature; Inverter parameters: power device junction temperature, heat sink temperature, DC bus voltage.

[0022] Furthermore, in step S5, the dynamic security monitoring and protection step, corresponding protection strategies are implemented for different abnormal situations, specifically including: Overcurrent protection: When the output current exceeds 250% of the rated current and continues for more than a set time, the inverter output will be immediately blocked and the output circuit breaker will be disconnected. Undervoltage / overvoltage protection: When the output voltage is lower or higher than the set ratio of the rated value and continues for more than the set time, the voltage build-up process is paused and the fault diagnosis mode is entered; Frequency anomaly protection: When the frequency deviation or frequency change rate exceeds the limit, the load is immediately disconnected and the voltage is rebuilt; Temperature protection: When the battery temperature or the junction temperature of the power device exceeds the limit, the output power is reduced and heat dissipation is enhanced. If the battery temperature or the junction temperature of the power device continues to rise, the output is immediately shut off. SOC lower limit protection: When the SOC drops to the preset lower limit, an alarm is issued. If it continues to drop, the output power will be forcibly reduced or non-critical loads will be cut off. Unit-level fault isolation: When a fault is detected in an energy storage unit, the energy storage unit is automatically isolated, while the remaining energy storage units continue to work and power is redistributed. Communication interruption protection: In multi-vehicle collaborative mode, if the communication between the master and slave vehicles is interrupted for more than a set time, the slave vehicle will automatically switch to independent operation mode.

[0023] According to specific embodiments of the present invention, the black-start pressure build-up control method for mobile vehicle-mounted energy storage systems provides a solution to technical challenges faced by mobile energy storage vehicles during black-start pressure build-up, such as inrush current impact, poor load adaptability, and difficulties in multi-vehicle coordination, by establishing a phased pressure build-up control strategy, a load adaptive identification mechanism, and a multi-vehicle collaborative control architecture. The following technical effects are disclosed: (1) The surge impact is significantly suppressed, and the pressure build-up safety is significantly improved: By employing an S-shaped voltage rise curve combined with real-time current limiting control, the inrush current suppression effect is excellent. Compared with traditional linear voltage build-up, the peak inrush current is significantly reduced, far below the safety limit, avoiding malfunction of protection devices and equipment damage. The pre-charging stage allows for stable charging of capacitive components, further reducing the risk of inrush current during subsequent voltage build-up. For strongly inductive loads such as transformer no-load, the excitation inrush current suppression effect is outstanding.

[0024] (2) Enhanced load adaptability and high pressure build-up success rate: Automatic load type identification is achieved through small signal injection. For different loads such as transformers, capacitors, motors, and resistive loads, parameters such as voltage build-up rate and current limiting value are adaptively matched to solve the problems of slow voltage build-up or insufficient safety margin caused by the traditional "one-size-fits-all" approach. The phased voltage build-up process (pre-charging, voltage establishment, frequency stabilization, and load verification) ensures a smooth transition from zero voltage to rated voltage, and voltage build-up can be successful in a single attempt without retrying.

[0025] (3) Multi-vehicle coordination is efficient and precise, balancing power distribution and voltage quality: Under the master-slave control architecture, the inrush current of the slave vehicle synchronous grid connection is small, the synchronization accuracy is high, and the preparation time for multi-vehicle coordination is greatly shortened; the dynamic droop control adjusts the droop coefficient in real time according to the capacity and SOC of each vehicle, which not only achieves balanced power distribution, but also ensures that the voltage deviation is within the allowable range, avoiding the inherent contradiction of traditional fixed droop.

[0026] (4) Improved pressure build-up efficiency, making deployment and maintenance more convenient: The total pressure build-up time is short, significantly reducing the start-up time compared to traditional diesel generators. Energy consumption accounts for a low proportion of the total system capacity, making it economical and efficient. It is suitable for mobile scenarios, supports active isolation of PACK-level faults, and is plug-and-play. Single-point failures result in only a small loss of capacity, eliminating the need for reconfiguration and debugging. Fault recovery is fast, and system availability is significantly improved.

[0027] (5) The system operates stably, and the entire process is safe and controllable: Dynamic safety monitoring covers electrical parameters, energy storage system status, and inverter parameters. Multiple protection strategies (overcurrent, undervoltage / overvoltage, temperature, etc.) ensure no abnormal alarms during the entire voltage build-up process. Under load, voltage fluctuations are small, frequency deviation is controlled within a reasonable range, SOC balancing effect is significant, consistency of status of each unit is high, and equipment life is extended. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart of the black start pressure build-up control method for the mobile vehicle-mounted energy storage system of the present invention; Figure 2 This is a three-dimensional evolution surface diagram (3D diagram) of voltage-current-time during the voltage build-up process in an embodiment of the present invention. Figure 3 This is a schematic diagram of the load characteristic pre-identification principle in an embodiment of the present invention, wherein (a) is a small signal injection test waveform diagram, (b) is an impedance phasor diagram, (c) is a representation of the load type criterion, and (d) is a flowchart of the voltage build-up parameter mapping. Figure 4 This is a diagram of the three-level control architecture of a flexible energy storage system according to an embodiment of the present invention; Figure 5 The above is a comparison diagram of the S-type voltage build-up curve and inrush current suppression in an embodiment of the present invention. (a) is a comparison diagram of the voltage rise curves of the three voltage build-up methods, and (b) is a comparison diagram of the inrush current of the three voltage build-up methods (logarithmic coordinates clearly show the order of magnitude difference). Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] The purpose of this invention is to provide a black-start voltage build-up control method for a mobile vehicle-mounted energy storage system. This method can achieve a smooth voltage build-up process from zero voltage to rated voltage, effectively suppressing inrush current surges; adaptively adjust voltage build-up parameters according to load characteristics to improve adaptability to different load types; realize coordinated control of multiple energy storage vehicles to ensure balanced power distribution and voltage quality; and ensure high reliability and rapid deployment capability in mobile application scenarios.

[0032] This invention is applicable to various types of mobile vehicle-mounted energy storage systems. Preferably, systems employing flexible energy storage technology can better leverage the advantages of this invention. Flexible energy storage systems have the following characteristics: PACK-level independent control: Each battery pack can be independently controlled for charging and discharging, monitored for status, and isolated for faults; High-current equalization: High-current energy transfer (up to 140A or more) can be carried out within and between clusters, and the equalization speed is much faster than traditional passive equalization. Active fault isolation: Automatic isolation when a single PACK fails, without affecting the overall system operation; Plug and play: No precise matching is required between PACKs, enabling quick replacement and maintenance; However, the above characteristics are not necessary conditions for this invention. The pressure build-up control method of this invention (load identification, S-curve, multi-vehicle coordination) can also be applied to traditional energy storage systems.

[0033] The three major technological innovations of this invention: 1. Load Adaptive Recognition Mechanism Automatically identify load type (transformer, capacitor, motor, resistive) by injecting a small signal. Automatically match the pressure build-up parameters (rate, current limit, curve shape) according to the load type; It solves the problem of insufficient inrush suppression or slow pressure build-up caused by the traditional "one-size-fits-all" approach.

[0034] 2. S-curve combined with real-time current limiting control The S-shaped curve achieves a smooth voltage rise (slow at the beginning, fast in the middle, and slow at the end), avoiding sudden voltage changes. Real-time monitoring of output current; when the current exceeds the limit, the voltage rise is paused, forming a dynamic closed-loop control. The inrush suppression rate is >94%, which is far superior to linear pressure build-up and step pressure build-up.

[0035] 3. Multi-vehicle dynamic coordination strategy The main control vehicle builds up voltage, and the slave control vehicle quickly synchronizes and connects to the grid (inrush current <10% of rated value). Dynamic droop control: Adjusts the droop coefficient in real time based on capacity and SOC; It balances power balance and voltage quality, avoiding the contradictions of traditional fixed droop.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figures 1-5 As shown, the present invention provides a black-start pressure build-up control method for a mobile vehicle-mounted energy storage system, comprising the following steps: Step 1: System Initialization and Security Check After the energy storage vehicle arrives at the site, it first performs a system self-check and an environmental check to ensure that it is ready to build up pressure.

[0038] The safety inspection items include: Electrical safety inspection: Confirm that the high-voltage side circuit breaker is open, the grounding switch is closed, and there is no residual voltage on the high-voltage busbar. Measure the busbar insulation resistance to ground and ensure it is within acceptable limits. Check that electrical connections are secure and reliable, and that quick-connect couplings are properly engaged.

[0039] Energy storage system status check: Check that the battery pack's SOC meets the voltage build-up requirements and that the battery temperature is within the suitable operating range; check that the number of online battery packs meets design requirements. For energy storage systems with PACK-level management capabilities, check the status of each PACK individually.

[0040] Environmental condition check: Confirm that the ambient temperature and humidity are within a suitable range and there is no condensation; check that the ventilation and heat dissipation system is working properly; for mobile applications, check that the vehicle is parked stably and supported in place.

[0041] Load-side check: Confirm that the system to be restored is in a complete power outage state, all circuit breakers are open, and no other power supply is connected. Measure the load-side capacitance to ground to make a preliminary estimate of the system's capacitive load. Check that the grounding system is intact.

[0042] Communication system check: Confirm that the energy storage vehicle communicates normally with the monitoring system and that all levels of controllers respond normally. If it is a multi-vehicle collaborative mode, check that the workshop communication link is unobstructed and that the clock synchronization accuracy meets the requirements.

[0043] After all inspection items pass, record the initial parameters and prepare to enter the pressure build-up process. If any item fails to meet the requirements, the mobile vehicle-mounted energy storage system will refuse to start and issue an alarm. For mobile vehicle-mounted energy storage systems with fault isolation capabilities, faulty units can be automatically isolated without affecting the overall pressure build-up capacity.

[0044] Step 2: Load Characteristics Pre-identification Before formal pressure build-up, load characteristics are identified through small signal injection to provide a basis for subsequent pressure build-up parameter settings. For example... Figure 3 As shown, (a) is a small-signal injection waveform diagram: showing the time-domain waveforms of the injection voltage and current response; (b) is an impedance phasor diagram: a complex plane diagram showing the impedance vector and marking the boundary between the inductive and capacitive regions; (c) is a load type criterion table: listing the impedance characteristics of four load types; (d) is a voltage build-up parameter mapping diagram: showing the mapping relationship from load type to voltage build-up parameters.

[0045] The pre-identification process is as follows: (1) Small signal injection: The energy storage vehicle outputs a low-voltage test signal with a voltage amplitude of about 5-10% of the rated value, which excites the electrical characteristics of the load but does not trigger the equipment to operate. The system adopts fast response control to accurately control the injected voltage waveform.

[0046] (2) Current response measurement: High-frequency sampling is used to measure the current response and record the current amplitude, phase and waveform characteristics.

[0047] (3) Load impedance calculation: Calculate the equivalent load impedance based on the voltage-current amplitude ratio and phase difference. A positive impedance angle indicates an inductive load, and a negative angle indicates a capacitive load.

[0048] (4) Load type determination: Transformer no-load type: large impedance angle (>60°) and impedance value greater than the rated impedance of the energy storage system. It is characterized by strong inductive properties, light load, and risk of inrush current. Capacitor bank type: The impedance angle is negative, characterized by capacitive characteristics, large inrush current but rapid decay; Motor load type: medium impedance angle (30-60°) and impedance value is less than the rated impedance of the energy storage system. It is characterized by inductive properties, large starting current and long duration. Resistive load type: The impedance angle is close to zero degrees, characterized by stability and no risk of inrush current.

[0049] (5) Capacity estimation: Based on the measured impedance value, estimate the load capacity level. Convert the impedance value to the rated voltage, calculate the expected steady-state current, and determine whether it is a light load, medium load, or heavy load.

[0050] (6) Initial setting of voltage build-up parameters: Based on the load type and capacity, initially set parameters such as voltage build-up rate and current limit: Transformer no-load type: slow voltage build-up (20-30 seconds to reach rated voltage), strict current limiting (limited to 150% of rated current); Capacitor type: medium-speed voltage build-up (10-15 seconds), moderate current limiting (200% of rated current); Resistive load: Fast voltage build-up (5-8 seconds), relaxed current limit (250% of rated current).

[0051] Step 3: Phased pressure build-up control The voltage build-up process is divided into four stages executed sequentially: pre-charging stage, voltage build-up stage, frequency stabilization stage, and load verification stage.

[0052] like Figure 2As shown, a three-dimensional evolution surface diagram of voltage-current-time during the voltage build-up process is displayed. In this 3D surface diagram, the horizontal axis represents time (0-120 seconds), the vertical axis represents voltage (0-20kV phase voltage), and the horizontal axis represents current (0-50A). The color gradient reflects the power level, with blue representing the low-power region and red representing the high-power region. The S-shaped voltage build-up process and inrush current suppression effect are clearly demonstrated: at the moment of inrush current occurrence, the voltage rises halted, and the current rapidly decreased.

[0053] (1) Pre-charging stage Objective: To charge capacitive components such as capacitor banks and transformer distributed capacitance in the system to avoid excessive inrush current during subsequent voltage build-up.

[0054] Control strategy: The energy storage vehicle outputs DC or extremely low frequency voltage, with the voltage amplitude slowly increasing from zero to 30-50% of the rated value. (Rise rate...) According to the formula Determined; among them, This is the preset allowable charging current (usually 20%-30% of the rated current). This represents the measured load capacitance value. The rise rate is determined based on the measured load capacitance; the larger the capacitance, the slower the rise.

[0055] For systems with PACK-level control capabilities, the output voltage of each PACK can be precisely adjusted to achieve a smoother voltage rise curve. Each PACK distributes the charging power evenly, preventing overload of any single PACK.

[0056] Current monitoring: Real-time monitoring of charging current. Theoretically, charging current equals the product of capacitance and voltage change rate. By monitoring current changes, the load capacitance value can be verified, and pre-identification results can be corrected. If the current exceeds a set threshold, the voltage rise rate is automatically reduced.

[0057] Termination condition: The pre-charging phase is completed when the voltage rises to the target value and the charging current decays to the steady-state value.

[0058] (2) Voltage establishment stage Objective: To establish a stable rated voltage, which is the core stage of the voltage build-up process.

[0059] Soft-start control: The energy storage vehicle outputs a standard AC voltage, and the voltage amplitude starts from the pre-charge endpoint and gradually rises to the rated voltage according to a preset curve. The voltage rise curve adopts an S-shaped curve, which is slow at the beginning, accelerates in the middle, and decelerates at the end to ensure a smooth transition.

[0060] Core control formula: The S-curve of voltage reference value changing over time is designed as follows:

[0061] in: The voltage reference value (V) at time t; Rated voltage (V); The time point during the pressure buildup process is taken as half of the total pressure buildup time (s). The total build-up time (in seconds) is selected within the range of 5-30 seconds, depending on the load type.

[0062] The characteristics of this S-shaped curve are that the change is gradual at the beginning and end, and the middle section transitions rapidly, which meets the requirements of soft start and can effectively suppress voltage surges.

[0063] Adaptive voltage build-up rate: The voltage build-up rate is dynamically adjusted based on the load type identified in step 2. For transformer-type unloaded loads, a slow voltage build-up rate is used; for resistive loads, a fast voltage build-up rate is used; and for capacitor-type or motor-type loads, a medium rate is used.

[0064] During voltage build-up, the system continuously monitors the current response. If the current exceeds a preset limit, the voltage rise is immediately paused, maintaining the current voltage unchanged until the current decays before resuming. This mechanism effectively addresses inrush current surges.

[0065] Current limiting control: When the output current exceeds the limit, the controller corrects the voltage reference value, causing the voltage to pause its rise or slightly decrease, thus limiting the current within a safe range. Specifically, the current deviation is calculated, a voltage correction is generated by the PI controller, and then superimposed on the S-curve reference value.

[0066] Termination condition: When the voltage rises to more than 98% of the rated value, and the voltage fluctuation is less than 2% of the rated value, and the current stabilizes within the expected range, the voltage is considered to have been successfully established.

[0067] (3) Frequency stabilization phase Objective: To accurately and stably output the frequency, ensuring that frequency deviation and frequency fluctuation meet the requirements of the power system.

[0068] Frequency control strategy: A phase-locked loop (PLL) based frequency control is adopted to lock the output frequency near the rated frequency. The control algorithm monitors the zero-crossing point of the output voltage, accurately calculates the actual frequency, and achieves closed-loop control by adjusting the modulation frequency of the inverter.

[0069] Frequency stability criterion: If the frequency deviation remains within the allowable range for a continuous period of time (e.g., 30 seconds), and the frequency change rate meets the requirements, then the frequency is considered to be stable.

[0070] For systems employing a distributed control architecture, the frequency control of each control unit is independent yet coordinated. The master control unit is responsible for establishing a frequency reference, while other units maintain synchronization through a fast tracking algorithm.

[0071] (4) Load-bearing verification stage Objective: To verify the system's voltage build-up quality and load-carrying capacity through a small-capacity load test before officially supplying power to the load.

[0072] Test load application: Close a small-capacity test load circuit breaker, with the load power being about 10-20% of the rated power of the energy storage vehicle, and observe the system response.

[0073] Voltage sag test: Measures the voltage drop at the moment the load is applied. The pass / fail standard is that the voltage drop does not exceed 5% of the rated voltage and recovers to near the rated value within a short time (e.g., 1 second).

[0074] Frequency deviation test: Measures the frequency change after a load is applied. The passing standard is that the frequency deviation is within the allowable range and recovers quickly.

[0075] Steady-state operation test: The test load is run stably for a certain period of time (e.g., 5-10 minutes), and parameters such as voltage, frequency, current, and temperature are monitored. Confirm that all parameters are stable within the normal range, with no abnormal fluctuations or alarm messages. For systems with balancing functions, continuous SOC balancing is performed during load operation to ensure that the states of each unit tend to be consistent.

[0076] After all tests are passed, the pressure build-up process is successfully completed, and the system can officially supply power to the target load.

[0077] Step 4: Multi-vehicle collaborative pressure build-up control When the capacity of a single energy storage vehicle is insufficient to complete the black start task, multiple vehicles are connected in parallel to collaboratively build up pressure. This invention adopts a master-slave control architecture.

[0078] Master-servant role allocation: Among multiple energy storage vehicles, the one with the largest capacity, highest SOC, and closest to the bus is selected as the master control vehicle. The remaining energy storage vehicles serve as slave control vehicles. The master control vehicle sends synchronization signals and power commands to the slave control vehicles through the workshop communication network.

[0079] For systems with plug-and-play capabilities, slave vehicles do not require complex parameter configurations; they only need to receive synchronization signals to quickly connect to the network, significantly reducing the preparation time for multi-vehicle collaboration.

[0080] Main control vehicle pressure building process: The main control vehicle independently executes the entire voltage build-up process in steps 2 and 3. The main control vehicle first independently completes the three stages of pre-charging, voltage build-up, and frequency stabilization, establishing a stable voltage and frequency reference on the bus.

[0081] After the main control vehicle completes voltage build-up (voltage and frequency are stable), it sends a "prepare to connect to the grid" command to the slave control vehicle.

[0082] Vehicle-to-grid synchronization: After receiving the command, the slave vehicle initiates the synchronization and grid connection process. The slave vehicle measures the amplitude, frequency, and phase of the bus voltage in real time and adjusts its own output voltage to match the bus voltage.

[0083] Synchronization criteria: voltage amplitude difference less than 2% of rated voltage, frequency difference less than allowable value, and phase difference less than 5 degrees. After the synchronization criteria are met, close the grid connection circuit breaker of the slave vehicle to complete grid connection.

[0084] The grid connection adopts the "inrush current detection" method, which detects the expected inrush current just before the circuit breaker closes. If the inrush current is less than 10% of the rated current, it indicates good synchronization and grid connection is allowed; if the inrush current exceeds the threshold, it indicates poor synchronization, grid connection is stopped and readjusted.

[0085] Cooperative power allocation: Dynamic droop control is used to achieve automatic power distribution among multiple vehicles. The basic principle is to set different droop coefficients based on the capacity and SOC (State of Charge) of each vehicle. With capacity and state of charge The relationship is expressed by the following formula:

[0086] in, For the first The sag coefficient of the Taiwan energy storage vehicle The baseline coefficient set for the system, This is the vehicle's rated capacity. This represents the vehicle's current state of charge. The sensitivity factor is adjusted (its value typically ranges from 1 to 2). According to this formula, vehicles with larger capacity and higher SOC have a smaller calculated droop coefficient, thus bearing more load; vehicles with smaller capacity and lower SOC have a larger calculated droop coefficient, thus bearing less load.

[0087] The droop factor calculation takes into account both capacity and SOC factors. The capacity factor reflects the rated power of the energy storage vehicle; the SOC factor reflects the deviation between the current SOC and the target SOC. When the SOC is higher than the target value, more output is encouraged, and when the SOC is lower than the target value, output is restricted.

[0088] For systems with high current balancing capabilities, balancing technology plays a crucial role in multi-vehicle collaboration: it not only achieves energy redistribution within a single vehicle but also enables SOC balancing across the entire workshop through workshop power allocation. Due to the large balancing current and fast balancing speed, the SOC consistency during multi-vehicle collaborative operation is maintained at a higher level, avoiding power distribution imbalances caused by SOC differences.

[0089] By combining the aforementioned adaptive droop control with energy balancing technology, the system can achieve reasonable power distribution and rapid balancing of the state of charge (SOC) of each vehicle while ensuring voltage quality.

[0090] Step 5: Dynamic Security Monitoring and Protection Dynamic safety monitoring is implemented throughout the entire pressure building process, and protective measures are taken immediately if any abnormality is detected.

[0091] Real-time monitoring parameters include: Electrical parameters: Output voltage, current, power, and frequency of the mobile vehicle-mounted energy storage system, updated rapidly. Special attention is paid to the rate of current change to detect abnormal inrush current; frequency stability is monitored to detect oscillations.

[0092] Energy storage system parameters: battery SOC, voltage, current, and temperature, updated regularly. Monitoring includes the lower limit of SOC, the range of individual cell voltages, and the upper limit of temperature. For systems with PACK-level monitoring capabilities, the status of each PACK can be precisely monitored.

[0093] Inverter parameters: power device junction temperature, heat sink temperature, DC bus voltage, updated regularly. Junction temperature is monitored to ensure it does not exceed limits, and bus voltage fluctuations are within permissible ranges.

[0094] Protection strategy: Overcurrent protection: When the output current exceeds a certain multiple (e.g., 250%) of the rated current and continues for more than a set time, it is determined to be a serious overcurrent fault. The inverter output is immediately blocked, the output circuit breaker is disconnected, and the voltage build-up process is terminated. This protection prevents damage to the equipment from inrush current or short circuit.

[0095] Undervoltage / Overvoltage Protection: When the output voltage is lower or higher than the rated value by a certain percentage and continues for more than a set time, the voltage abnormality protection is triggered. The voltage build-up process is paused, and the system enters fault diagnosis mode.

[0096] Frequency anomaly protection: When the frequency deviation or rate of change exceeds the limit, frequency anomaly protection is triggered. This situation may be caused by control instability or sudden load changes, requiring immediate load disconnection and voltage re-establishment.

[0097] Temperature protection: When the battery temperature or the junction temperature of the power devices exceeds the limit, temperature protection is triggered. The system reduces output power and enhances heat dissipation. If the temperature continues to rise, the output is immediately shut down.

[0098] SOC lower limit protection: When the SOC drops to a preset lower limit, an alarm is issued, indicating insufficient remaining capacity. If it continues to drop, the output power is forcibly reduced or non-critical loads are disconnected.

[0099] Unit-level fault isolation: For systems with active fault isolation capabilities, when a fault is detected in a unit, that unit is automatically isolated, while the remaining units continue to operate. During the isolation process, the system automatically redistributes power to ensure a smooth output transition. Compared to traditional systems where a single point of failure leads to widespread outages, systems with fault isolation capabilities offer significantly improved reliability.

[0100] Communication interruption protection: In multi-vehicle collaborative mode, if the communication between the master and slave vehicles is interrupted for more than a set time, the slave vehicle will automatically switch to independent operation mode to maintain the current output and avoid loss of control.

[0101] After the protection action, the system records the time of the fault, the type of fault, and the parameters before the fault, providing data for fault analysis. For systems with plug-and-play characteristics, faulty units can be quickly replaced without the need for reconfiguration and debugging, significantly shortening fault recovery time.

[0102] Example 1: Single-vehicle voltage restoration to transformer no-load I. System Configuration A certain 35kV energy storage mobile vehicle adopts flexible energy storage technology, with a single vehicle rated capacity of 2MW / 4MWh.

[0103] System topology: Three-phase system, with 6 battery clusters connected in parallel per phase, each cluster containing 20 battery packs, for a total of 360 packs. Each pack is equipped with an independent power controller (FPC), each cluster with a cluster control board (FCC), and the system level with a stack control board (FSC). The output line voltage per vehicle is 35kV.

[0104] Battery configuration: Lithium iron phosphate battery, single pack capacity 11.11kWh, initial SOC 80%, temperature 25°C. The system has high current balancing capability (rated balancing current 150A) and can realize bidirectional energy transfer within and between clusters.

[0105] Control System: Employs a three-level control architecture (FPC-FCC-FSC), with millisecond-level control cycles, high-frequency sampling, and CAN bus communication. Specifically: Stack-level (FSC): Stack control board, responsible for system coordination, multi-vehicle communication, black-start voltage build-up control, and fault management; Cluster-level (FCC): Cluster control boards (6 in total), responsible for intra-cluster equalization, current control, and fault isolation; Module-level (FPC): PACK controllers (20 per cluster), responsible for power regulation and fast protection.

[0106] Onboard equipment: Containerized integrated design, equipped with quick electrical connectors, onboard shock absorption system, and liquid cooling system.

[0107] II. Task Scenarios Task: To restore power to a 35kV substation that has experienced a power outage, the first step is to charge a 10MVA main transformer under no-load conditions.

[0108] Load characteristics: The no-load power of a 10MVA transformer is approximately 60kW (no-load loss), the no-load current is approximately 10A (about 6% of the rated current of 165A), and the power factor is approximately 0.15 (strong inductive). The transformer is subject to inrush current risk, and the peak inrush current can reach 6-8 times the rated current.

[0109] III. Pressure Building Process Phase 0: Initialization and Pre-identification (approximately 25 seconds) Once the energy storage vehicle arrived at the site, the operators connected the vehicle-mounted quick connector to the 35kV busbar of the substation, a connection that took approximately 3 minutes.

[0110] Perform step 1, the security check: Electrical safety inspection: The high-voltage side circuit breaker is open, the grounding switch is closed, and the insulation resistance of the busbar to ground is 13,500 megohms, which is qualified; Energy storage system status check: total system SOC 80%, SOC range of each PACK 78%-82%, number of online PACKs 360, online rate 100%, battery temperature range 23-27°C; Environmental conditions check: Ambient temperature 18°C, humidity 62%, suitable for work; Load-side inspection: The 35kV busbar of the substation is completely de-energized, all feeder circuit breakers are open, and the busbar-to-ground capacitance is measured to be approximately 2.5μF. Communication system check: The vehicle monitoring system communicates normally with the backend, and all 360 FPCs, 18 FCCs, and 1 FSC are online; Inspection results: All items passed, and the system allows pressure build.

[0111] Perform step 2: Load pre-identification The output test voltage is 3.5kV (10% of the rated value), the frequency is 50Hz, and the duration is about 2 seconds. The measured three-phase combined current was 0.58A, with each cluster outputting in tandem and the current distribution being uniform. Calculate the load impedance: with an impedance angle of 87 degrees (strong inductive), the impedance value is approximately 10471 ohms; Load type determination: Transformer no-load type load; The system automatically calls the preset parameters: total pressure build-up time 30 seconds, current limit 150% of rated current (82.5A), and S-curve parameter settings; The operator confirms the pressure build-up parameters and issues the "Start Pressure Build-up" command.

[0112] Phase 1: Pre-charging (approximately 10 seconds) During the pre-charging phase, the system outputs DC voltage, which starts to rise from 0V.

[0113] The voltage increases linearly at a rate of approximately 800V per second. Each pack has a slightly different output depending on its own SOC state, and the equalization system adjusts in real time to maintain a balanced output across all packs.

[0114] After approximately 30 seconds, the voltage rose to approximately 1.6 kV, and a charging current of approximately 0.9 A was detected, which was in line with expectations. The current distribution across all clusters was uniform, with a deviation of less than 5%.

[0115] The voltage eventually rises to 8kV (phase voltage, approximately 40% of the rated value), and the charging current decreases to approximately 0.05A, which is less than the limit.

[0116] The system determines that pre-charging is complete, which takes approximately 10 seconds.

[0117] Phase 2: Voltage establishment (approximately 30 seconds) During the voltage build-up phase, the system switches from DC output to AC output at a frequency of 50Hz. The voltage amplitude rises from the pre-charge endpoint value to the rated value following an S-shaped curve.

[0118] The inverters of each FPC start up synchronously and output a standard sine wave.

[0119] After about 5 seconds, the voltage rose to 12kV phase voltage (about 60% of the rated value), and the measured current was about 4.3A, which was slightly higher than the expected steady-state value. The system automatically reduced the voltage rise rate by 20%.

[0120] The equalization system adjusts in real time: if the current of some clusters is slightly high, the output power allocation ratio of that cluster is increased to promote SOC equalization.

[0121] About 10 seconds later, the voltage rose to 15kV phase voltage (about 74% of the rated value), and the current suddenly increased to 17.5A, which the system identified as inrush current.

[0122] FSC immediately executes the inrush suppression algorithm: The voltage rise is halted, and the voltage reference value is locked at 15kV. Each FPC enters current limiting mode, limiting the output current to no more than 20A; Start the timer to monitor current decay; After a pause of about 2 seconds, the current decayed to 11.8A. The system determined that the inrush current was suppressed and allowed to continue increasing the voltage, but further reduced the rate of rise.

[0123] Continue the pressure build-up process: After about 15 seconds, the voltage rose to 16.5kV (about 82% of the rated value) and the current was 9.2A; After about 20 seconds, the voltage rose to 18.5kV (about 92% of the rated value), and the current stabilized at 8.5A; After about 25 seconds, the voltage rose to 19.8kV (about 98% of the rated value), and the current stabilized at 10.0A; After approximately 30 seconds, the voltage stabilized at 20.2kV (100% rated value), the current was 10.3A, and the voltage fluctuation was less than 1%. The FSC determination voltage establishment phase is complete.

[0124] like Figure 5 As shown, (a) is a comparison of voltage-time curves, illustrating the voltage rise characteristics of the three voltage build-up methods: Direct closing method (solid red line): instantaneous voltage step change; Linear rise mode (yellow dashed line): Voltage rises at a constant rate; S-curve method (thick green solid line, this invention): smooth voltage transition, slow at the beginning, fast in the middle, and slow at the end.

[0125] (b) is a comparison graph of current-time curves (logarithmic scale), showing the inrush size comparison of the three pressure build-up methods: Direct closing method: Peak value 1050A, marked "12.7 times over limit", located in the danger zone (red fill); Linear rise mode: peak value 320A, marked "3.9 times over limit", partially exceeding the safety limit line; S-curve method: Peak value 17.5A, marked "Not exceeded, safe", located in the safe area (green fill); Figure 5 Draw the current limit line (82.5A, gray dotted line) in the middle, and label the inrush current suppression effect in the text box.

[0126] Key effects: By adopting an S-shaped voltage build-up curve, the peak inrush current is only 17.5A. Compared with the direct closing method (inrush current can reach 1050A, which is 6.4 times the rated current) and the linear rise method (inrush current is about 320A), the inrush current suppression rate reaches 98.3% and 94.5% respectively. The current is always controlled below the safety limit (82.5A), avoiding the impact on the energy storage vehicle and transformer.

[0127] Phase 3: Frequency stabilizes (approximately 30 seconds) Once the frequency stabilizes, the FSC initiates a precision frequency control algorithm based on phase-locked loop (PLL) technology. Each FPC's inverter uses a unified clock source to ensure three-phase frequency synchronization.

[0128] Initial frequency measurement: The frequency was calculated to be 49.995Hz by detecting the zero-crossing point of the voltage, with a deviation of -0.005Hz.

[0129] After about 5 seconds, the FSC fine-tunes the PWM modulation frequency of each FPC by +0.005Hz.

[0130] After about 7 seconds, the frequency stabilized at 50.001Hz, with a deviation of +0.001Hz, which met the requirements.

[0131] Continuous monitoring for approximately 30 seconds, frequency range: 49.996Hz to 50.004Hz, average frequency 50.000Hz, maximum frequency change rate 0.03Hz / s.

[0132] Frequency stability test passed, each PACK operates smoothly, and the output power is stable at around 60kW.

[0133] Phase 4: Load testing (approximately 10 minutes) Prepare to put the test load into operation. The operator remotely closes the circuit breaker of the No. 1 lighting feeder, which carries a 200kW lighting load, approximately 10% of the rated power of the energy storage vehicle.

[0134] After the test load is applied: Voltage sag test: At the moment the load is applied, the phase voltage drops from 20.2kV to 19.9kV, a drop of about 1.5%, and recovers to 20.15kV after about 0.35 seconds; Frequency deviation test: The frequency dropped from 50.00Hz to 49.97Hz, a deviation of -0.03Hz, and recovered to 50.01Hz after about 1.8 seconds; Current change: increased from 10.3A to 15.8A (an increase of approximately 5.5A); The current in each cluster is automatically adjusted and evenly distributed. Equalization system response: After the load increases, the SOC of some PACKs drops slightly faster. The FCC automatically starts intra-cluster equalization, increasing the output of PACKs with high SOC and decreasing the output of PACKs with low SOC. The equalization current is about 5A.

[0135] The test load ran stably for about 10 minutes: Voltage: 20.18kV±0.05kV (fluctuation less than 0.25%); Frequency: 50.00Hz ± 0.005Hz; Current: 15.7A; Total output power: 260kW (200kW lighting load + 60kW transformer no-load loss). Temperature of each pack: 26-30°C, average 28°C; SOC of each pack: 77.8%-81.8%, standard deviation 0.8% (significant balancing effect); Cumulative running data: Cumulative discharge capacity: approximately 43.3 kWh; SOC decreased from 80% to 78.9%, a decrease of approximately 1.1%, which is in line with theoretical expectations. Zero failures, zero alarms, all 360 PACKs are working normally; Overall efficiency: approximately 97%; The operators confirmed that the pressure build-up was up to standard and the system was operating stably and reliably. The substation operator reported: the main transformer was behaving normally, with no abnormal vibrations, and all protection devices had not activated. The pressure build-up task was successfully completed.

[0136] IV. Effectiveness Evaluation Pressure build-up success rate: Pressure build-up is successful on the first attempt, with no protection actions and no need to retry. There are no PACK faults or alarms throughout the process.

[0137] Inrush suppression effect: The peak value of the inrush current decreased from the theoretical value of 1050A to 17.5A; Compared to the direct closing method, the suppression rate reaches 98.3%; Compared to the linear ascent method, the inhibition rate reached 94.5%; The peak current is far below the safety limit (82.5A), and the system has sufficient safety margin.

[0138] Pressure build-up time: Security check: approximately 15 seconds; Load pre-identification: approximately 10 seconds; Pre-charge: approximately 10 seconds; Voltage build-up: Approximately 30 seconds; Frequency stabilizes: approximately 30 seconds; Load verification: approximately 5 seconds; Total time: Approximately 100 seconds (1.7 minutes); Compared to starting a traditional diesel generator (which requires 10-15 minutes of preheating), the time is reduced by about 85%.

[0139] Energy consumption: The voltage build-up process consumes approximately 18 kWh of electricity, accounting for 0.45% of the total capacity, making it economical and efficient.

[0140] Technological advantages are reflected in: Balancing effect: The standard deviation of SOC of each PACK was 1.2% before pressure build-up, and decreased to 0.7% after steady-state operation; Fault tolerance capability: The system has the capability to automatically isolate single-pack faults, and a single point of failure will only result in a loss of 0.28% of capacity; Rapid deployment: No grouping is required between PACKs, it is plug and play, and it takes about 20 minutes from arrival to successful pressure build-up; Temperature management: Uniform temperature rise of each PACK, efficient liquid cooling system (power consumption only 8kW), IGBT junction temperature below 60°C; Comparative Example 1: Traditional Linear Pressure Buildup Method I. System Configuration and Task Scenarios The same energy storage vehicle and load conditions as in Example 1 were used: 35kV energy storage vehicle, 2MW / 4MWh, to build up voltage to the 10MVA main transformer under no-load conditions.

[0141] II. Traditional Linear Pressure Buildup Method The traditional linear voltage building method is adopted, that is, the voltage rises at a constant rate without load pre-identification and without using an S-curve.

[0142] Pressure build-up parameter settings: Total pressure build-up time: 30 seconds (same as in Example 1); Voltage rise method: linear and uniform rise, at a rate of approximately 0.67kV per second (phase voltage rises from 0 to 20kV). Current limit: 150% of rated current (82.5A); There is no pre-charging stage; it directly outputs AC voltage.

[0143] III. Pressure Building Process Initial phase (0-5 seconds): After the system completes initialization and safety checks, it starts building up voltage directly, outputting a 50Hz AC voltage that rises steadily from 0.

[0144] After about 5 seconds, the voltage rose to about 3.3kV (phase voltage) and the current was about 1.5A. The system operated smoothly.

[0145] The surge phase (approximately 15 seconds): At approximately 15 seconds, the voltage rises to approximately 10kV (phase voltage). At this point, the transformer core enters the nonlinear region, and the excitation current begins to increase rapidly.

[0146] At approximately 18 seconds, the voltage rose to approximately 12kV, and the current surged to approximately 65A.

[0147] After about 20 seconds, the voltage continued to rise to about 13.4kV, and the current surged to 320A! This far exceeded the safety limit (82.5A).

[0148] Protective actions: The system detected that the current exceeded the limit and lasted for more than 100ms, triggering overcurrent protection. The system immediately blocked the PWM output, disconnected the output circuit breaker, and terminated the voltage build-up process.

[0149] At this point, the peak inrush current reached 320A, which is about 3.9 times the rated current. Although this is lower than the direct closing method (inrush current can reach 1050A), it still exceeds the safety limit, resulting in the failure to build up voltage.

[0150] Fault diagnosis: The system recorded the following fault information: Overcurrent protection activated, peak current 320A, voltage at the time of the fault 13.4kV.

[0151] The operators analyzed the cause of the fault: the linear voltage build-up speed was too fast, and the inrush current was not effectively suppressed.

[0152] Rebuild pressure (reduce rate): The operator reduced the pressure build-up rate to 50% of the original rate, which extended the total pressure build-up time to 60 seconds.

[0153] The voltage build-up process restarts, and the voltage rises at a rate of approximately 0.33 kV per second.

[0154] Approximately 40 seconds later, the voltage rose to approximately 13.4 kV (the point of the previous fault), and the current rose to approximately 45 A. There was still inrush current, but it did not exceed the limit.

[0155] The voltage continued to build up, and after about 60 seconds, the voltage finally rose to 20.2kV, and the current stabilized at around 10.3A.

[0156] However, the total pressure build-up time is about 60 seconds (20 seconds for the first failure + 10 seconds for restart preparation + 60 seconds for the second pressure build-up = 90 seconds). With the time for fault diagnosis and parameter adjustment, the actual time takes more than 5 minutes.

[0157] IV. Comparative Analysis As shown in Table 1.

[0158] Table 1

[0159] in conclusion: Traditional linear voltage build-up methods are prone to generating large inrush currents when building up voltage to a transformer under no-load conditions. These inrush currents can exceed safety limits, leading to protection activation and voltage build-up failure. Manual intervention is required to reduce the voltage build-up rate and retry, resulting in long overall processing time and poor reliability.

[0160] The S-shaped pressure build-up curve combined with real-time flow limiting control used in this invention can effectively suppress inrush flow (suppression rate 94.5%), achieve successful pressure build-up on the first attempt, and shorten the total time by about 67%, significantly improving the success rate, safety and efficiency of black start pressure build-up.

[0161] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A black-start pressure build-up control method for a mobile vehicle-mounted energy storage system, characterized in that, Includes the following steps: S1, System Initialization and Safety Check: Conduct a comprehensive check on the electrical safety of the energy storage vehicle, the status of the energy storage system, environmental conditions, the load side and the communication system, and proceed to the next step after confirming that the pressure build-up conditions are met. S2, Load characteristic pre-identification: Obtain the current response of the load through small signal injection, calculate the equivalent impedance of the load, determine the load type and capacity level, and set the voltage build-up parameters accordingly. S3, phased voltage build-up control: sequentially executes the pre-charge stage, voltage build-up stage, frequency stabilization stage, and load verification stage to achieve smooth voltage build-up from zero voltage to stable rated voltage; S4, Multi-vehicle Cooperative Pressure Building Control: When the capacity of a single energy storage vehicle is insufficient, a master-slave control architecture is adopted. After the master vehicle completes the pressure building, the slave vehicle is connected to the grid synchronously. The power distribution of multiple vehicles is achieved through dynamic droop control. S5, Dynamic Safety Monitoring and Protection: Real-time monitoring of electrical parameters, energy storage system parameters, and inverter parameters throughout the entire pressure build-up process, and execution of corresponding protection strategies for different abnormal situations.

2. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, S1, system initialization and security check, specifically includes: Electrical safety inspection: Confirm that the high-voltage side circuit breaker is open, the grounding switch is closed, there is no residual voltage on the high-voltage busbar, the insulation resistance of the busbar to ground is qualified, the electrical connections are firm and reliable, and the quick connectors are connected in place; Energy storage system status check: Check that the battery pack SOC meets the voltage build-up requirements, the battery temperature is within the appropriate operating range, and the number of online battery packs meets the design requirements. For energy storage systems with PACK-level management capabilities, check the status of each PACK one by one. Environmental condition check: Confirm that the ambient temperature and humidity are within a suitable range and there is no condensation, the ventilation and heat dissipation system is working properly, and the vehicle is parked stably and supported in place in mobile application scenarios; Load-side inspection: Confirm that the system to be restored is in a state of complete power failure, all circuit breakers are open and no other power supply is connected, measure the load-side capacitance to ground to make a preliminary estimate of the system's capacitive load, and check that the grounding system is intact; Communication system check: Confirm that the energy storage vehicle communicates normally with the monitoring system and that the controllers at all levels respond normally; in multi-vehicle collaborative mode, check that the workshop communication link is unobstructed and that the clock synchronization accuracy meets the set requirements.

3. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, S2, load characteristic pre-identification, specifically includes: Small signal injection: The energy storage vehicle outputs a low-voltage test signal with an amplitude of 5-10% of the rated value, and the injected voltage waveform is controlled by a fast response control method; Current response measurement: High-frequency sampling measures the current response, recording the current amplitude, phase, and waveform characteristics; Load impedance calculation: The equivalent impedance of the load is calculated based on the voltage-current amplitude ratio and phase difference. A positive impedance angle indicates an inductive load, while a negative angle indicates a capacitive load. Load type determination: Based on the impedance angle and impedance value, determine whether it is a transformer no-load type, capacitor bank type, motor load type, or resistive load type; Capacity estimation: Based on the calculated impedance value, estimate the load capacity level, convert the impedance value to the rated voltage, calculate the expected steady-state current, and determine whether it is a light load, medium load, or heavy load. Initial voltage build-up parameters: Based on the load type and capacity, the voltage build-up rate and current limit parameters are initially set.

4. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, In step S3, the pre-charging stage of the phased voltage build-up control process specifically includes: Control strategy: The energy storage vehicle outputs DC or very low frequency voltage, and the voltage amplitude slowly rises from zero to the pre-charge endpoint value. The rise rate is determined according to the measured load capacitance. The energy storage system with PACK-level control capability adjusts the output voltage of each PACK so that each PACK can evenly bear the charging power. Current monitoring: Real-time monitoring of charging current, reverse verification of load capacitance value and correction of pre-identification results by monitoring changes in charging current; If the charging current exceeds the set threshold, the voltage amplitude rise rate is automatically reduced. Termination condition: The pre-charging phase is completed when the voltage amplitude rises to the pre-charging endpoint value and the charging current decays to the steady-state value.

5. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 4, characterized in that, In step S3, the voltage build-up control step, the voltage build-up stage specifically includes: Soft-start control: The energy storage vehicle outputs a standard AC voltage, with the voltage amplitude gradually increasing to the rated voltage following an S-curve starting from the pre-charge endpoint. The S-curve is designed as follows: in: The voltage reference value at time t. Rated voltage, For a specific moment in the pressure build-up process, take half of the total pressure build-up time. The total build-up time should be selected within the range of 5-30 seconds, depending on the load type. Adaptive voltage build-up rate: The voltage build-up rate is dynamically adjusted based on the pre-identification results of load characteristics. Slow voltage build-up is used for transformer no-load loads, fast voltage build-up is used for resistive loads, and medium voltage build-up is used for capacitor bank or motor loads. Current limiting control: Real-time monitoring of output current. When the output current exceeds the preset limit, the current deviation is calculated, and a voltage correction amount is generated by the PI controller. This correction amount is then superimposed on the voltage reference value of the S-curve, causing the voltage to pause its rise or slightly decrease, thus limiting the current within a safe range. Termination condition: When the voltage rises to more than 98% of the rated value, and the voltage fluctuation is less than 2% of the rated value, and the current stabilizes within the expected range, the voltage is considered to have been successfully established.

6. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 5, characterized in that, In step S3, the frequency stabilization phase of the phased voltage build-up control process specifically includes: Frequency control strategy: A phase-locked loop-based frequency control is adopted, which monitors the zero-crossing point of the output voltage, calculates the actual frequency, and achieves closed-loop control by adjusting the modulation frequency of the inverter, thereby locking the output frequency within the allowable deviation range of the rated frequency. Frequency stability criterion: If the frequency deviation remains within the allowable range and the frequency change rate meets the requirements within 30 consecutive seconds, the frequency stability is deemed to be up to standard. For systems employing a distributed control architecture, the main control unit establishes a frequency reference, while other control units maintain synchronization through a fast tracking algorithm.

7. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 6, characterized in that, In step S3, the phased pressure build-up control step, the load verification stage specifically includes: Test load setup: Close a small-capacity test load circuit breaker, with a load power of 10-20% of the energy storage vehicle's rated power; Voltage sag test: Measure the voltage sag at the moment the load is applied. The pass standard is that the voltage sag does not exceed 5% of the rated voltage and recovers to near the rated value within 1 second. Frequency deviation test: Measure the frequency change after the load is applied. The pass standard is that the frequency deviation is within the allowable range and recovers within 5 seconds. Steady-state operation test: Test the load to run stably for 5-10 minutes, monitor voltage, frequency, current and temperature parameters, and confirm that all parameters are stable within the normal range without abnormal fluctuations or alarm information; An energy storage system with balancing function continuously performs SOC balancing during load operation to ensure that the state of each energy storage unit tends to be consistent; after all tests are passed, the energy storage system officially supplies power to the target load.

8. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, The S4, multi-vehicle collaborative pressure build-up control, specifically includes: Master-slave role allocation: Select the energy storage vehicle with the largest capacity, highest SOC, and closest to the bus as the master control vehicle, and the rest as slave control vehicles. The master control vehicle sends synchronization signals and power commands to the slave control vehicles through the workshop communication network. The main control vehicle's voltage building process: The main control vehicle independently executes the three stages of load characteristic pre-identification and phased voltage building control: the pre-charging stage, the voltage building stage, and the frequency stabilization stage. After establishing a stable voltage and frequency reference on the bus, it sends a "ready to connect to the grid" command to the slave control vehicle. Slave vehicle synchronous grid connection: The slave vehicle measures the amplitude, frequency, and phase of the bus voltage in real time, adjusts its own output voltage to match the bus voltage, and closes the grid connection circuit breaker after meeting the synchronization conditions that the voltage amplitude difference is less than 2% of the rated voltage, the frequency difference is less than the allowable value, and the phase difference is less than 5 degrees. Before grid connection, the inrush current detection method is used. If the inrush current is less than 10% of the rated current, grid connection is allowed; otherwise, grid connection is stopped and readjustment is performed. Collaborative power distribution: Dynamic droop control is used to achieve automatic power distribution among multiple vehicles, and different droop coefficients are set according to the capacity and SOC status of each vehicle; the energy storage system with high current balancing capability achieves SOC balancing through intra-cluster and inter-cluster balancing and vehicle power allocation.

9. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, In step S5, the dynamic safety monitoring and protection step, the real-time monitoring of electrical parameters, energy storage system parameters, and inverter parameters specifically includes: Electrical parameters: Output voltage, current, power, and frequency of the mobile vehicle-mounted energy storage system; Energy storage system parameters: battery SOC, voltage, current, temperature; Inverter parameters: power device junction temperature, heat sink temperature, DC bus voltage.

10. The black-start pressure build-up control method for a mobile vehicle-mounted energy storage system according to claim 1, characterized in that, In step S5, the dynamic security monitoring and protection step, corresponding protection strategies are implemented for different abnormal situations, specifically including: Overcurrent protection: When the output current exceeds 250% of the rated current and continues for more than a set time, the inverter output will be immediately blocked and the output circuit breaker will be disconnected. Undervoltage / overvoltage protection: When the output voltage is lower or higher than the set ratio of the rated value and continues for more than the set time, the voltage build-up process is paused and the fault diagnosis mode is entered; Frequency anomaly protection: When the frequency deviation or frequency change rate exceeds the limit, the load is immediately disconnected and the voltage is rebuilt; Temperature protection: When the battery temperature or the junction temperature of the power device exceeds the limit, the output power is reduced and heat dissipation is enhanced. If the battery temperature or the junction temperature of the power device continues to rise, the output is immediately shut off. SOC lower limit protection: When the SOC drops to the preset lower limit, an alarm is issued. If it continues to drop, the output power will be forcibly reduced or non-critical loads will be cut off. Unit-level fault isolation: When a fault is detected in an energy storage unit, the energy storage unit is automatically isolated, while the remaining energy storage units continue to work and power is redistributed. Communication interruption protection: In multi-vehicle collaborative mode, if the communication between the master and slave vehicles is interrupted for more than a set time, the slave vehicle will automatically switch to independent operation mode.

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