Integrated protection method of flow battery energy storage system

Abstract

An integrated protection method for a flow battery energy storage system belongs to the technical field of flow battery systems, and comprises the following steps: S1, adopting a layered architecture design for a system architecture; s2, adopting a multi-stage protection mechanism through a safety and fault management scheme designed based on a system architecture design thought; S21, constructing a battery over-charge / over-discharge protection function; s22, constructing a thermal runaway early warning, and triggering a shutdown function; and S23, three-level safety protection is set between the PCS and the BMS. On the basis of BMS and PCS cooperative control, strategy optimization is implemented, the efficiency and safety of the integrated energy storage system can be remarkably improved, a control algorithm such as self-adaptive PID adjustment is improved, the charging and discharging process can be accurately balanced, and the overload or undervoltage risk is prevented. The collaborative design ensures seamless matching of the battery state and the power output, and provides reliable support for an overall energy storage scheme.

Description

Technical Field

[0001] This invention belongs to the field of flow battery system technology, and specifically relates to an integrated protection method for a flow battery energy storage system. Background Technology

[0002] With the continuous development of power systems, energy storage has become an important development direction for power systems, enabling efficient energy utilization and stable operation of the power system. Flow batteries, as an emerging energy storage method, have become the preferred technology for large-scale energy storage applications due to their advantages such as flexible and independent adjustment of battery power and energy according to application scenarios, low cost, long lifespan, and high safety. However, in practical applications, flow battery energy storage systems often face various faults, such as grid faults, power supply faults, load faults, communication faults, and fire faults; if these faults are not detected and handled in a timely manner, they may lead to system paralysis or even safety accidents. Existing solutions have the following problems: 1. Existing EMS (Energy Management System) and PCS (Power Conversion System) operation and protection schemes are mainly designed for lithium-ion batteries and do not adequately support the charge and discharge characteristics of flow batteries. 2. When the external power quality deteriorates, the protection at each level of EMS, PCS, and BMS (Battery Management System) cannot provide protection step by step, affecting the protection effect.

[0003] The existing technology CN120103149A discloses a monitoring and early warning system for lithium battery energy storage, but it still has some shortcomings. Its core drawbacks are concentrated in three aspects: limited applicability to a single battery type, insufficient protection coordination, and weak parameter monitoring specificity, as follows: 1. Limited applicability to certain battery types; cannot match the characteristics of flow batteries. Existing technologies are designed specifically for lithium batteries and do not take into account the unique needs of flow batteries. Their charging and discharging strategies and parameter monitoring dimensions (such as focusing only on general parameters such as voltage and current) are based on the characteristics of lithium batteries and cannot be adapted to the core characteristics of flow batteries, such as "independent adjustment of power and energy" and "dependence on electrolyte temperature / liquid pump speed". This results in a lack of targeted protection for flow batteries.

[0004] 2. Poor coordination among protection systems at all levels, lacking a tiered linkage mechanism. In existing technologies, although the modules (data acquisition, analysis, and control) of monitoring and early warning systems operate independently, they lack hierarchical collaborative protection logic among EMS, PCS, and BMS. When external power quality deteriorates (such as grid frequency fluctuations), the various levels of the system cannot achieve "step-by-step response and complementary protection," which can easily lead to problems such as untimely or over-protection, affecting system stability.

[0005] 3. Incomplete parameter monitoring dimensions, lacking key indicators for flow batteries. Current monitoring parameters focus on lithium batteries, such as voltage, current, temperature, and internal resistance, but do not cover core operating parameters of flow batteries, such as electrolyte temperature, pump speed, valve opening / closing status, and stack voltage. This lack of information can lead to the inability to detect unique flow battery faults (such as electrolyte leakage or pump failure) in a timely manner, posing safety hazards.

[0006] 4. Lacks the ability to handle offline modes and has weak adaptability to extreme scenarios. Existing technologies are designed only for conventional grid-connected operation scenarios of lithium batteries and do not consider extreme situations where energy storage systems are disconnected from the main grid. When a grid failure causes the system to go offline, it cannot quickly switch to "microgrid mode" to ensure power supply to critical loads and lacks protection and support capabilities in emergency scenarios. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes an integrated protection method for a flow battery energy storage system, comprising the following steps: S1. The system architecture adopts a layered architecture design; S2. The security and fault management scheme designed based on system architecture design principles adopts a multi-level protection mechanism: S21. Construct battery overcharge / over-discharge protection function; S22. Construct thermal runaway early warning and shutdown trigger functions; S23, PCS and BMS are equipped with three levels of security protection.

[0008] Furthermore, in step S1, the layered architecture design includes: Sensing layer: Real-time acquisition of battery voltage, temperature, SOC / SOH, and grid frequency data through BMS, PCS, electricity meters, and temperature control sensor devices.

[0009] Furthermore, in step S1, the layered architecture design also includes: Communication layer: Adopts a multi-protocol compatible architecture, supports RS485 and Ethernet communication, and enables efficient data interaction between devices.

[0010] Furthermore, in step S1, the layered architecture design also includes: Control layer: Based on edge computing and cloud collaboration, it executes charging and discharging strategies, fault diagnosis and emergency protection commands with a response time of ≤1 second to ensure system real-time performance.

[0011] Furthermore, in step S1, the layered architecture design also includes: Application layer: Provides a visual monitoring interface and supports energy scheduling, report generation, and remote operation and maintenance functions.

[0012] Furthermore, in step S21, the EMS formulates a suitable charging and discharging strategy for the flow battery based on peak and off-peak electricity prices, grid demand, and battery status in the BMS, and sends the charging and discharging power to the PCS; the BMS provides real-time battery data to the PCS and sends the maximum allowable charging and discharging current value; the PCS dynamically adjusts the charging and discharging control based on the power set by the EMS and the maximum allowable power of the battery, taking the smaller of the two.

[0013] Furthermore, in step S22, the EMS collects real-time and periodic data on all monitored operating parameters and statuses to determine if any abnormal data occurs, and issues timely alarms to remind maintenance personnel to investigate and handle the issues, thereby ensuring the safe and stable operation of the energy storage system.

[0014] Furthermore, in step S22, the information collected includes: total voltage, current, average temperature, state of charge (SOC), state of health (SOH), open circuit voltage (OCV), charge / discharge current and power limits, stack voltage, electrolyte temperature, pump speed, valve opening / closing, equipment faults and alarm information, historical charge / discharge capacity, and historical charge / discharge energy of each battery group in the BMS system.

[0015] Furthermore, in step S22, the information collected also includes: relevant parameters of the PCS: voltage / current / power of each branch on the DC side, active power, reactive power, voltage, current, power factor, frequency and temperature of each phase on the AC side, cabinet temperature, operating status, alarm and fault information, as well as daily charging amount, daily discharging amount, cumulative charging amount, and cumulative discharging amount are also within the monitoring range; at the same time, the voltage, current, active power, reactive power, and frequency information of each phase of the load will also be monitored in real time.

[0016] Furthermore, in step S23, the security protection between the BMS and PCS is implemented in accordance with industry group standards, specifically designed as a three-level protection system: The first level protects the system by controlling the actions of the PCS through the restriction commands uploaded from the BMS to the PCS. At the second level, the BMS instructs the PCS to perform protection actions via fault commands or dry contacts: Under normal communication conditions, when a battery fault occurs, the BMS will take protective action through the fault command PCS; when communication fails, the BMS will take protective action through the dry contact command PCS. The dry contact signal is normally closed by default. When the battery pack has a fault, the BMS will notify the PCS to take action by disconnecting the dry contact signal; when the fault disappears, the BMS should be able to restore the dry contact signal. The third level, when the first two levels of protection fail, is when the BMS shuts down the main battery circuit via command control.

[0017] The beneficial effects of this invention are as follows: Addressing the shortcomings of existing technology CN120103149A—limited applicability to certain battery types and inability to match the characteristics of flow batteries—this invention provides a solution: A charging and discharging strategy is designed specifically for flow batteries. The EMS (Electromagnetic System) formulates a dedicated strategy based on peak and off-peak electricity prices, grid demand, and the flow battery status (such as SOC / SOH and electrolyte temperature) fed back by the BMS (Battery Management System). The PCS (Power Control System) dynamically adjusts according to the EMS power command and the BMS's "maximum allowable charging and discharging current" to adapt to the power-energy regulation characteristics of the flow battery. The result is precise control of the flow battery charging and discharging process, preventing battery damage caused by strategy mismatch.

[0018] Addressing the shortcomings of existing technology CN120103149A—poor coordination among protection levels and lack of a hierarchical linkage mechanism—this invention provides a solution: constructing a three-tiered safety protection system: Level 1: The BMS controls the PCS via limiting commands (charging / discharging voltage / current); Level 2: When communication is normal, the BMS triggers the PCS with fault commands; when communication fails, it triggers with dry contact signals; Level 3: When the first two levels fail, the BMS directly shuts off the battery main circuit. The control layer is based on edge computing and cloud collaboration, with a response time ≤1 second, ensuring real-time hierarchical protection. The solution achieves hierarchical linkage protection across all levels of the system, avoiding protection failure issues when external power quality deteriorates. Addressing the shortcomings of existing technology CN120103149A—namely, incomplete parameter monitoring dimensions and lack of key indicators for flow batteries—this invention provides the following solution: The sensing layer adds specific monitoring parameters for flow batteries: electrolyte temperature, pump speed, valve opening / closing status, and stack voltage. The EMS collects these parameters from the BMS in real time, along with the DC-side branch power and AC-side frequency of the PCS, covering all operational dimensions of the flow battery. The solution effectively detects unique faults of flow batteries (such as pump failure and electrolyte overheating), eliminating potential safety hazards.

[0019] Addressing the shortcomings of existing technology CN120103149A—namely, the lack of off-grid mode capability and weak adaptability to extreme scenarios—this invention provides a solution: It designs an off-grid mode switching function. When the system disconnects from the main grid, the EMS sends a command to the PCS to switch to "microgrid mode." In off-grid mode, the energy storage system acts as a local grid power source, providing voltage / frequency control to ensure power supply to critical loads. The solution effectively addresses extreme scenarios such as grid failures, ensuring the orderly handling of power outages by personnel and equipment, and improving system adaptability.

[0020] In summary, the advantages of this invention are as follows: 1. Redundancy design improves the reliability of the energy storage monitoring system; 2. Independent network design improves system control speed and stability; 3. Highly efficient dispatching capabilities, simplified centralized control logic, facilitating rapid power response and peak shaving / frequency regulation at the grid level; 4. Based on the collaborative control of BMS and PCS, implementing strategy optimization can significantly improve the efficiency and safety of integrated energy storage systems. Improving control algorithms, such as adaptive PID control, can precisely balance the charging and discharging process, preventing overload or undervoltage risks. This collaborative design ensures seamless matching between battery state and power output, providing reliable support for the overall energy storage solution. Attached Figure Description

[0021] Figure 1 This is a diagram showing the communication architecture between the EMS, PCS, and BMS of the energy storage system of this invention. Figure 2 This is a communication topology diagram between the EMS, PCS, and BMS of the energy storage control system of this invention; Figure 3 This is a design diagram of the energy storage system architecture of the present invention. Detailed Implementation

[0022] To make the technical means and objectives of this invention easier to understand, the invention is further described below with reference to specific embodiments. An integrated protection method for a flow battery energy storage system includes the following steps: S1. The system architecture adopts a layered architecture design; S2. The security and fault management scheme designed based on system architecture design principles adopts a multi-level protection mechanism: S21. Construct battery overcharge / over-discharge protection function; S22. Construct thermal runaway early warning and shutdown trigger functions; S23, PCS and BMS are equipped with three levels of security protection.

[0023] In step S1, the core element of this solution lies in the efficient collaboration and deep integration of various key subsystems, including a compact physical layout and seamless functional integration, such as... Figures 1-2 As shown, the various subsystems, through their compact physical layout, provide data to each other, compare and coordinate with each other to ensure the safe operation of the flow battery system.

[0024] like Figure 3 As shown, the system architecture design adopts a layered architecture: 1. Sensing Layer: Real-time data collection of battery voltage, temperature, SOC / SOH, grid frequency, etc., through devices such as BMS, PCS, electricity meters, and temperature control sensors.

[0025] 2. Communication Layer: Adopts a multi-protocol compatible architecture (Modbus RTU / TCP, IEC 61850, IEC 104), supports RS485 and Ethernet communication, and enables efficient data interaction between devices.

[0026] 3. Control Layer: Based on edge computing and cloud collaboration, it executes charging and discharging strategies, fault diagnosis and emergency protection commands with a response time of ≤1 second to ensure system real-time performance.

[0027] 4. Application layer: Provides a visual monitoring interface and supports functions such as energy scheduling, report generation, and remote operation and maintenance.

[0028] In step S2, the safety and fault management scheme designed based on the above system architecture design idea adopts a multi-level protection mechanism: battery overcharge / over-discharge protection (BMS linked with PCS current limiting); thermal runaway warning, trigger shutdown and other functions, and three-level safety protection between PCS and BMS.

[0029] In step S21, the EMS formulates a suitable charging and discharging strategy for the flow battery based on factors such as peak and off-peak electricity prices, grid demand, and battery status in the BMS, and sends the charging and discharging power to the PCS; the BMS provides real-time battery data to the PCS and sends the maximum allowable charging and discharging current value; the PCS dynamically adjusts the charging and discharging control based on the power set by the EMS and the maximum allowable power of the battery, taking the smaller of the two.

[0030] In step S22, the EMS can collect real-time and timed data on all monitored operating parameters and statuses. Commonly used information such as the total voltage, current, average temperature, SOC (State of Charge), SOH (State of Health), OCV (Open Circuit Voltage), charge / discharge current and power limits, stack voltage, electrolyte temperature, pump speed, valve opening / closing, equipment faults and alarm information, historical charge / discharge capacity, and historical charge / discharge energy of each battery in the BMS system will be accurately collected. PCS-related parameters, such as voltage / current / power of each branch on the DC side, active power, reactive power, voltage, current, power factor, frequency and temperature of each phase on the AC side, cabinet temperature, operating status, alarms and fault information, as well as daily charging, daily discharging, cumulative charging, and cumulative discharging are also monitored. Simultaneously, the voltage, current, active power, reactive power, and frequency of each phase of the load are also monitored in real time. Once abnormal data appears, an alarm can be issued promptly to remind maintenance personnel to investigate and handle the issue, ensuring the safe and stable operation of the energy storage system.

[0031] In step S23, the security protection between the BMS and PCS is implemented in accordance with industry group standards, specifically designed as a three-level protection system: The first level protects the system by controlling the PCS's actions through the restriction commands (charging and discharging voltage and current, charging / discharging prohibition) uploaded from the BMS to the PCS. At the second level, the BMS instructs the PCS to perform protection actions via fault commands or dry contacts: Under normal communication conditions, when a battery fault occurs, the BMS initiates protection actions via the fault command PCS; when communication fails, the BMS initiates protection actions via the dry contact command PCS. The dry contact signal is normally closed by default. When a battery pack fault occurs, the BMS notifies the PCS to activate by disconnecting the dry contact signal; when the fault disappears, the BMS should be able to restore the dry contact signal.

[0032] Level 3: When the first two levels of protection fail, the BMS can shut down the main battery circuit via command.

[0033] EMS uses strategies (such as peak-valley price differences) to schedule PCS discharge during peak electricity price periods and optimizes discharge depth through BMS data to improve revenue.

[0034] When a flow storage system disconnects from the main grid for various reasons, the EMS (Energy Management System) can issue a command to the PCS (Power Generation System) to switch to off-grid mode based on the actual situation. Off-grid mode involves one or more generation systems connected in parallel to form a local "microgrid." The main characteristic of off-grid mode is that the local grid is disconnected from all major power grids, and the rated power of the energy storage system is approximately equal to the total power generated by the local grid. In this system, the energy storage system must be able to act as a grid power source, providing voltage and frequency control to the local grid. In some cases, the energy storage system also needs to switch between acting as a power source and synchronizing with the generation equipment. In this mode, the flow storage system can ensure uninterrupted power supply to important loads within the local area, ensuring that personnel and equipment can respond to power outages in an orderly manner, and gaining critical processing time.

[0035] During off-grid operation, the EMS dynamically adjusts the charging and discharging power output of the flow battery by monitoring the AC side frequency and voltage fluctuations of the PCS in real time. When the frequency deviates from the rated value (±0.5Hz) or the voltage fluctuation exceeds the set threshold (±5%), the system automatically triggers the secondary frequency / voltage regulation function: limiting the maximum charging and discharging current of the battery pack through the BMS, and coordinating the PCS inverter to adjust the reactive power output to ensure that the local grid frequency is stable within the range of 49.5-50.5Hz and the voltage fluctuation rate is controlled within ±3%. This control logic is implemented through the edge computing node of the control layer, with a response delay of ≤200ms, which is 3 times faster than the traditional solution. When the main grid restores power supply, the EMS adopts soft grid connection technology, and compares the voltage phase difference (≤5°), frequency difference (≤0.1Hz), and amplitude difference (≤3%) on both sides through a synchronous detection device to achieve a smooth switch of the PCS from off-grid mode to grid connection mode, avoiding the inrush current caused by asynchronous grid connection. The entire switching process is visualized through an application-layer interface, displaying key parameters such as voltage / frequency curves and power flow, and generating an operation report containing data such as switching time and maximum deviation value for operation and maintenance personnel to analyze and optimize.

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

Claims

1. An integrated protection method for a flow battery energy storage system, characterized in that, Includes the following steps: S1. The system architecture adopts a layered architecture design; S2. The security and fault management scheme designed based on system architecture design principles adopts a multi-level protection mechanism: S21. Construct battery overcharge / over-discharge protection function; S22. Construct thermal runaway early warning and shutdown trigger functions; S23, PCS and BMS are equipped with three levels of security protection.

2. The integrated protection method for a flow battery energy storage system as described in claim 1, characterized in that, In step S1, the layered architecture design includes: Sensing layer: Real-time acquisition of battery voltage, temperature, SOC / SOH, and grid frequency data through BMS, PCS, electricity meters, and temperature control sensor devices.

3. The integrated protection method for a flow battery energy storage system as described in claim 2, characterized in that, In step S1, the layered architecture design also includes: Communication layer: Adopts a multi-protocol compatible architecture, supports RS485 and Ethernet communication, and enables efficient data interaction between devices.

4. The integrated protection method for a flow battery energy storage system as described in claim 3, characterized in that, In step S1, the layered architecture design also includes: Control layer: Based on edge computing and cloud collaboration, it executes charging and discharging strategies, fault diagnosis and emergency protection commands with a response time of ≤1 second to ensure system real-time performance.

5. The integrated protection method for a flow battery energy storage system as described in claim 4, characterized in that, In step S1, the layered architecture design also includes: Application layer: Provides a visual monitoring interface and supports energy scheduling, report generation, and remote operation and maintenance functions.

6. The integrated protection method for a flow battery energy storage system as described in claim 1, characterized in that, In step S21, the EMS formulates a suitable charging and discharging strategy for the flow battery based on peak and off-peak electricity prices, grid demand, and battery status in the BMS, and sends the charging and discharging power to the PCS; the BMS provides real-time battery data to the PCS and sends the maximum allowable charging and discharging current value; the PCS dynamically adjusts the charging and discharging control based on the power set by the EMS and the maximum allowable power of the battery, taking the smaller of the two.

7. The integrated protection method for a flow battery energy storage system as described in claim 1, characterized in that, In step S22, the EMS collects real-time and periodic data on all monitored operating parameters and statuses to determine if any abnormal data occurs, and issues timely alarms to remind maintenance personnel to investigate and handle the issues, thereby ensuring the safe and stable operation of the energy storage system.

8. The integrated protection method for a flow battery energy storage system as described in claim 7, characterized in that, In step S22, the information collected includes: total voltage, current, average temperature, state of charge (SOC), state of health (SOH), open circuit voltage (OCV), charge / discharge current and power limits, stack voltage, electrolyte temperature, pump speed, valve opening / closing, equipment faults and alarm information, historical charge / discharge capacity, and historical charge / discharge energy of each battery group in the BMS system.

9. The integrated protection method for a flow battery energy storage system as described in claim 7, characterized in that, In step S22, the collected information also includes: relevant parameters of the PCS: voltage / current / power of each branch on the DC side, active power, reactive power, voltage, current, power factor, frequency and temperature of each phase on the AC side, cabinet temperature, operating status, alarm and fault information, as well as daily charging amount, daily discharging amount, cumulative charging amount, and cumulative discharging amount are also within the monitoring range; at the same time, the voltage, current, active power, reactive power, and frequency information of each phase of the load will also be monitored in real time.

10. The integrated protection method for a flow battery energy storage system as described in claim 1, characterized in that, In step S23, the security protection between the BMS and PCS is implemented in accordance with industry group standards, specifically designed as a three-level protection system: The first level protects the system by controlling the actions of the PCS through the restriction commands uploaded from the BMS to the PCS. At the second level, the BMS instructs the PCS to perform protection actions via fault commands or dry contacts: Under normal communication conditions, when a battery fault occurs, the BMS will take protective action through the fault command PCS; when communication fails, the BMS will take protective action through the dry contact command PCS. The dry contact signal is normally closed by default. When the battery pack has a fault, the BMS will notify the PCS to take action by disconnecting the dry contact signal; when the fault disappears, the BMS should be able to restore the dry contact signal. The third level, when the first two levels of protection fail, is when the BMS shuts down the main battery circuit via command control.

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