Flywheel energy storage power grid frequency modulation method and system based on adaptive state management

Abstract

The invention provides a flywheel energy storage power grid frequency modulation method and system based on adaptive state management. The method comprises the following steps: acquiring a frequency deviation and an automatic power generation control instruction of a power grid in real time, and calculating an original frequency modulation power demand based on the frequency deviation and the automatic power generation control instruction; acquiring the flywheel rotating speed in real time, and calculating the charge state of a flywheel energy storage unit based on the flywheel rotating speed; calculating a capability weight coefficient according to the state of charge and the direction of the original frequency modulation power demand, the direction of the original frequency modulation power demand comprising a charging instruction and a discharging instruction; calculating to obtain a final power instruction based on the capability weight coefficient and the original frequency modulation power demand; and sending the final power instruction to a flywheel energy storage unit to enable the flywheel energy storage unit to execute corresponding charging and discharging operations. According to the invention, the frequency modulation strategy can be dynamically adjusted by combining the real-time demand of the power grid and the flywheel charge state, and continuous, stable and safe frequency modulation control is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power system automation and control technology, in particular, to a flywheel energy storage grid frequency modulation method and system based on adaptive state management. BACKGROUND Flywheel energy storage has become a research hotspot in the field of grid frequency modulation in recent years due to its fast power response speed, long cycle life (up to 100,000 times or more), and strong environmental adaptability. Currently, research at home and abroad is mostly focused on the cooperative control of flywheel arrays or the response strategy of single machines based on simple threshold values, but there is still a lack of effective solutions for the capacity limitation and state management of individual flywheels in continuous frequency modulation.

[0002] For example, Chinese invention patent CN108631241A (publication date: October 09, 2018) proposes a "flywheel energy storage participates in grid primary frequency modulation control method and system", the core idea of which is to collect grid frequency deviation and automatic generation control (AGC) instructions, calculate the total frequency modulation power demand of the flywheel array, and distribute it to each flywheel unit according to the capacity proportion. This solution relies on the capacity superposition of multiple flywheels to make up for the deficiency of single machines, but does not involve state management of individual flywheels when they are running independently; when some flywheels exit operation, it is easy to cause a sharp drop in overall frequency modulation capacity.

[0003] US patent US9870652B2 (publication date: January 16, 2018) proposes a "grid secondary frequency modulation control strategy based on flywheel energy storage", which controls the charging and discharging of flywheels by setting a fixed dead zone threshold: when the flywheel speed (corresponding to the state of charge SoC) is below 20% or above 80%, it is forced to exit frequency modulation; when it is in the interval of 20% to 80%, it responds to the frequency modulation instruction at 100%. Although this solution considers the operating boundaries of single machines, the fixed dead zone design is likely to cause interruption of frequency modulation response, and does not consider the relationship between "frequency modulation instruction direction and state of charge (SoC) recovery", resulting in waste of frequency modulation efficiency.

[0004] European patent EP3258456A1 (publication date: December 20, 2017) discloses a "two-quadrant frequency modulation control method for flywheel energy storage system", which directly controls the charging or discharging of flywheels according to the positive or negative sign of the grid frequency deviation, and the adjustment logic only relies on grid demand without considering the SoC change of the flywheel itself. This method is likely to cause the flywheel to quickly reach the speed limit in actual application, thereby exiting operation at a critical stage of frequency modulation, resulting in over-regulation and failure risk.

[0005] As can be seen, the existing technology has the following problems in the application of single flywheel frequency modulation: Lack of state coupling control: mostly only rely on grid frequency modulation demand, ignore the SoC of the flywheel itself, resulting in the flywheel being forced to execute instructions when the SoC is close to the limit, and overcharging or overdischarging is prone to occur.

[0006] Discontinuous power output: when using a fixed dead zone strategy, the flywheel directly exits frequency modulation once it enters the dead zone, and the power response appears a step mutation, which may cause secondary disturbance to the grid frequency.

[0007] Waste of frequency modulation efficiency: unable to take advantage of the positive effect of "charging and discharging direction on SoC recovery", for example, charging at low SoC helps to restore capacity, but existing technologies still cut the response uniformly, resulting in that the available frequency modulation capacity is not fully utilized.

[0008] Therefore, how to make a single flywheel participate in grid frequency modulation under the condition of limited capacity and dynamically adjust the response capability according to its own state has become a technical problem to be solved. The present application is aimed at the above problems, and proposes a flywheel energy storage grid frequency modulation method and system based on adaptive state management. SUMMARY

[0009] The present application aims to overcome the defects of existing single flywheel energy storage systems in participating in grid frequency modulation, such as response rigidity, easy overcharging and overdischarging, and poor frequency modulation continuity, and provides a flywheel energy storage grid frequency modulation method and system based on adaptive state management, so that a single flywheel energy storage system can dynamically adjust the frequency modulation strategy according to the grid demand and its real-time state of charge, and realize the unity of frequency modulation efficiency maximization and operation safety.

[0010] In a first aspect, the present application provides a flywheel energy storage grid frequency modulation method based on adaptive state management, which comprises: real-time acquisition of the frequency deviation and automatic generation control instruction of the grid, and calculation of the original frequency modulation power demand based on the frequency deviation and the automatic generation control instruction; real-time acquisition of the flywheel speed, and calculation of the state of charge of the flywheel energy storage unit based on the flywheel speed; calculation of the ability weight coefficient according to the direction of the state of charge and the original frequency modulation power demand, wherein the direction of the original frequency modulation power demand includes charging instruction and discharging instruction; calculation of the final power instruction based on the ability weight coefficient and the original frequency modulation power demand; sending the final power instruction to the flywheel energy storage unit to make it execute corresponding charging and discharging operation.

[0011] In a second aspect, the present application further provides a flywheel energy storage grid frequency modulation system based on adaptive state management, which comprises: a core controller configured to execute the flywheel energy storage grid frequency modulation method based on adaptive state management; a flywheel energy storage unit configured to receive the final power instruction sent by the core controller and perform corresponding charging and discharging operations according to the final power instruction.

[0012] Compared with the prior art, the present application has the following advantages: First, by introducing the capability weight coefficient, the grid demand is dynamically coupled with the state of charge of the flywheel to avoid overcharging and overdischarging. Second, the linear decay method is used to control the output, so that the power is smoothly reduced when it approaches the limit, preventing power step disturbance to the grid. Third, actions that are beneficial to capacity recovery are preferentially performed in the low SoC or high SoC interval, so that the flywheel quickly returns to the high-efficiency working area and prolongs the duration of frequency modulation. Fourth, the capability decay area and multiple protection mechanisms are set to enhance the safety and reliability of system operation. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0014] Figure 1 is a flowchart of the flywheel energy storage grid frequency modulation method based on adaptive state management provided by the embodiments of the present application; Figure 2a and 2b is a block diagram of the flywheel energy storage grid frequency modulation system based on adaptive state management provided by the embodiments of the present application. DETAILED DESCRIPTION

[0015] The technical solutions of the present application will be further described in detail below with the help of drawings and embodiments. SUMMARY As described above, the present application provides a flywheel energy storage grid frequency modulation method and system based on adaptive state management, which can dynamically adjust the frequency modulation strategy in combination with the real-time demand of the grid and the state of charge of the flywheel, and realize continuous, stable and safe frequency modulation control.

[0017] Exemplary method Figure 1 is a flowchart of the flywheel energy storage grid frequency modulation method based on adaptive state management provided by the embodiments of the present application, which includes the following steps: S1: Real-time acquisition of frequency deviation (Δf) and automatic generation control instruction of power grid, and calculation of original frequency modulation power demand (P_demand) based on the frequency deviation and the automatic generation control instruction (P_AGC).

[0018] High-frequency noise is removed by a digital filter to ensure that the measurement error of Δf is less than or equal to ±0.01 Hz, providing reliable input for subsequent power calculation. The sampling and calculation refresh period of Δf and P_AGC is 10 ms to meet the real-time requirements of power grid frequency modulation and ensure the real-time response of frequency modulation, thereby effectively suppressing the frequency disturbance of power grid.

[0019] The essence of automatic generation control (AGC) is that the power grid dispatching center automatically sends power adjustment instructions to grid-connected power generation / energy storage devices by real-time monitoring of the difference between the power generation and power consumption load of the entire power grid (i.e., "power imbalance"), to ensure that the power grid frequency is stable within the standard range (50 Hz ± 0.2 Hz in China). For example, when the power consumption load suddenly increases, causing the frequency to drop, AGC will instruct the flywheel to quickly release electrical energy (discharge) to make up for the power gap and raise the frequency; conversely, it will instruct the flywheel to charge and absorb excess electrical energy.

[0020] The flywheel energy storage unit of the present application does not work independently, but participates in power grid frequency modulation as an AGC execution terminal: AGC first calculates the frequency modulation power demand required to maintain frequency stability (e.g., 200 kW of power is needed); this automatic generation control instruction is transmitted to the adaptive frequency modulation strategy module of the core controller, which dynamically adjusts the response strategy in combination with the current state of charge (SoC) of the flywheel energy storage unit (e.g., preferentially charging according to the automatic generation control instruction at low SoC, and preferentially discharging according to the automatic generation control instruction at high SoC), to avoid the flywheel being unable to respond to the automatic generation control instruction due to overcharging and overdischarging, and to solve the defect that the flywheel cannot follow the AGC instruction in time in the prior art (such as fixed dead zone control).

[0021] Specifically, the frequency deviation Δf and the automatic generation control instruction P_AGC of the power grid are acquired in real time, and the original frequency modulation power demand P_demand is calculated based on the frequency deviation and the automatic generation control instruction according to the following formula: P_demand = -K×Δf + P_AGC, where K is the frequency response coefficient. The value range of K is 50-100 kW / Hz, which can be dynamically configured according to the operating conditions of the power grid.

[0022] For example, when Δf = -0.1 Hz (frequency deviation is low) and P_AGC = 100 kW, P_demand = -50×(-0.1) + 100 = 105 kW, indicating that 105 kW of discharge is required.

[0023] S2: acquiring a flywheel rotating speed in real time, and calculating a state of charge of the flywheel energy storage unit based on the flywheel rotating speed.

[0024] The state of charge (SoC) of the flywheel energy storage unit is a core index for measuring the current energy storage capacity of the flywheel energy storage unit.

[0025] wherein ω is the flywheel rotating speed acquired in real time. A laser speed sensor is used for rotating speed detection, and the measurement accuracy is ±1 RPM, and the sampling frequency is 500 Hz.

[0026] ω_min is the lowest safe rotating speed allowed by the flywheel rotor (corresponding to the “fully discharged” state, SoC=0%).

[0027] ω_max is the highest safe rotating speed allowed by the flywheel rotor (corresponding to the “fully charged” state, SoC=100%).

[0028] This index essentially reflects the proportion of the kinetic energy currently stored by the flywheel to the maximum storable kinetic energy. For example, when SoC=50%, it means that the kinetic energy currently stored by the flywheel is half of its maximum energy storage capacity; when SoC approaches 0% or 100%, it indicates that the flywheel is about to reach the rotating speed limit, and the adaptive state management strategy in the present application needs to be adjusted to adjust the frequency response to avoid overcharging and overdischarging.

[0029] Preferably, ω_min=5000 RPM (SoC=0%), ω_max=15000 RPM (SoC=100%), and the SoC calculation refresh period is 10 ms.

[0030] In addition, the present application also synchronously detects auxiliary parameters such as motor temperature and alternating current side current, and provides these parameters to the protection module as trigger signals.

[0031] S3: calculating a capability weight coefficient according to the state of charge and the direction of the original frequency modulation power demand, wherein the direction of the original frequency modulation power demand includes a charging instruction and a discharging instruction.

[0032] The capability weight coefficient K_capability has a value range of 0-1, and is used to reflect the frequency modulation capability of the flywheel under different states of charge.

[0033] Specifically, the interval of the state of charge is divided into a high-efficiency working zone, a capability attenuation zone and a safety protection zone.

[0034] High-efficiency working zone: when the state of charge is in a first preset range (such as 30%-70%), the capability weight coefficient is set to 1.

[0035] The first preset range can be flexibly set according to the design parameters of the flywheel energy storage unit, for example, can be determined in combination with the minimum safe rotational speed (ω_min) of the flywheel rotor, the maximum safe rotational speed (ω_max), the capacity design margin and the expected frequency modulation working condition. Generally, the range should make the flywheel rotational speed away from the limit working condition, so as to have sufficient charging margin and discharging capacity at the same time, so that the flywheel energy storage unit can respond to the automatic generation control instruction of the power grid without attenuation, avoid the risk of discharging interruption caused by too low SoC, or the overcharging risk caused by too high SoC, so as to ensure longer duration of frequency modulation, more stable power output, and improve the effective utilization rate of single flywheel in power grid frequency modulation.

[0036] Capacity attenuation zone: when the state of charge is lower than the lower limit of the first preset range (such as SoC < 30%): If the original frequency modulation power demand is a discharge instruction, the capacity weight coefficient is attenuated from 1 to 0 as SoC decreases, preferably, the attenuation mode of the capacity weight coefficient is linear attenuation, for example, during the process of SoC decreasing from 30% to 10%, when SoC = 20%, the capacity weight coefficient is about 0.5, if P_demand = 300kW, the actual execution power is 150kW.

[0037] The linear function form is simple, the calculation amount is small, and it is convenient for real-time control system to quickly realize, at the same time, it can provide a smooth and predictable power regulation process when SoC gradually approaches the lower limit or the upper limit, avoiding secondary disturbance to the grid frequency caused by step mutation of power instruction. Compared with complex attenuation modes such as exponential or segmented function, linear attenuation is more stable, has lower implementation cost, and is easy to realize through table lookup or simple operation in hardware controller, so as to balance real-time performance, stability and engineering implementability.

[0038] If the original frequency modulation power demand is a charging instruction, the capacity weight coefficient is kept as 1 to preferentially execute the charging action and accelerate the capacity recovery.

[0039] When the state of charge is higher than the upper limit of the first preset range (such as SoC > 70%): If the original frequency modulation power demand is a charging instruction, the capacity weight coefficient is attenuated from 1 to 0 as SoC increases, for example, during the process of SoC increasing from 70% to 90%, when SoC = 80%, the capacity weight coefficient is about 0.5, if P_demand = -200kW, the actual execution power is -100kW; If the original frequency modulation power demand is a discharge instruction, the capacity weight coefficient is kept as 1 to preferentially release energy and return to the high-efficiency working zone.

[0040] The setting of the capacity decay zone realizes the transformation from mindless response to intelligent response. When the SoC is close to its limit, the flywheel power output decreases smoothly, avoiding the power step change caused by traditional fixed dead zone control, which is more grid-friendly; at the same time, it prioritizes actions that are conducive to its own capacity recovery (prioritizing charging when the SoC is low and prioritizing discharging when the SoC is high), so that the flywheel energy storage unit returns to the efficient operating area more quickly, thereby providing a longer and more efficient frequency regulation service as a whole.

[0041] Safety Protection Zone: When the state of charge is not greater than the first safety threshold (e.g., 10%) or not less than the second safety threshold (e.g., 90%), the capability weighting coefficient is set to 0, the flywheel energy storage unit suspends frequency modulation response and enters a protection state until the SoC recovers to the safe range before resuming operation. For example, when SoC = 8%, regardless of the received instruction, K_capability = 0, and the flywheel energy storage unit enters hibernation standby until it recovers through slow self-charging or other methods.

[0042] The purpose of setting up a safety protection zone is to prevent the flywheel energy storage unit from compromising its long-term stability and safety due to excessively low or high state of charge. When the state of charge is too low or too high, the frequency regulation response is suspended and the system enters a protection state, which helps to ensure the system's safety, reliability, and long-term operating capability. This avoids the risks that may arise from demanding excessive power under extreme state of charge conditions and ensures that the system can continue to operate efficiently after returning to a safe range.

[0043] In summary, flywheel energy storage units are divided into a high-efficiency operating zone, a capacity degradation zone, and a safety protection zone based on their state of charge (SoC) to achieve both proactive response to grid frequency regulation and self-protection. The high-efficiency operating zone typically occurs when the SoC is within a first preset range (e.g., 30%–70%), the flywheel operates at its optimal speed, has sufficient charge / discharge margin, and a capacity weighting coefficient K_capability = 1, enabling 100% response to grid frequency regulation demands and achieving rapid and stable power regulation. The capacity degradation zone occurs when the SoC is below the lower limit or above the upper limit of the high-efficiency zone. The flywheel limits its response power by linearly decaying the capacity weighting coefficient. In low-SoC discharge scenarios, the degradation zone reduces output power to prevent over-discharge from causing excessively low flywheel speed or capacity depletion. In high-SoC charging scenarios, the degradation zone reduces charging response to avoid overcharging that could lead to excessive speed or mechanical stress. The capacity degradation zone smooths power output, extends flywheel life, and maintains some frequency regulation capability, ensuring grid frequency regulation continuity. The safety protection zone is when the SoC approaches its limit (such as below 10% or above 90%). The flywheel pauses frequency modulation response and enters protection mode. It slowly charges itself or uses external auxiliary charging to pull the SoC back to the safe range before it re-engages in frequency modulation, thus ensuring the long-term safety and reliability of the system.

[0044] It should be noted that the setting of the safety protection area is not a necessary implementation condition. In some application scenarios, if the flywheel energy storage unit has higher mechanical strength or adopts more advanced heat management and redundancy protection means, the safety protection area can not be set, and the frequency control can be completed directly through the linear attenuation mechanism of the capacity weight coefficient. Therefore, the safety protection area is a preferred implementation manner, not a necessary limitation.

[0045] As an optional embodiment, a flywheel with a rated power of 500 kW and a speed operating range of 5000-15000 RPM (corresponding to SoC 0%-100%) has the following operation process: when SoC=50%, the capacity weight coefficient K_capability=1. When a charge instruction of-300 kW or a discharge instruction of +400 kW is received, it can be executed at 100%, realizing fast support for the grid frequency.

[0046] When SoC=20% (lower than 30% entering the discharge attenuation area), if a discharge instruction of +300 kW is received, since further discharge will continue to lower the SoC, the system will linearly reduce K_capability to 0.5 (example value), and the actual execution power is +150 kW, thereby ensuring a certain frequency regulation capacity while avoiding excessive discharge of the flywheel; if a charge instruction of-200 kW is received at this time, since charging helps to restore capacity, K_capability remains 1, and the system executes the charging operation at full capacity.

[0047] When SoC=8% (lower than the threshold of 10%), regardless of the instruction received, the system sets K_capability to 0, and the flywheel enters a dormant state, and only through slow self-charging or external auxiliary charging, the SoC is pulled back to the safety area before participating in frequency regulation again.

[0048] Through the above mechanism, the present application enables a single flywheel to provide efficient frequency regulation support while having self-protection functions, thereby significantly improving its commercial value and application feasibility as an independent frequency regulation unit.

[0049] In summary, by introducing the capacity weight coefficient (K_capability), the grid frequency regulation demand is dynamically coupled with the state of charge of the flywheel energy storage unit, avoiding overcharging or overdischarging caused by blind response, while ensuring the continuity and safety of frequency regulation, at least having the following advantages: First, when the SoC approaches the lowest or highest safety threshold, K_capability will automatically attenuate the response strength, ensuring that the flywheel does not exceed the speed limit, and protecting the mechanical safety and life; Second, even in low SoC or high SoC boundary operating conditions, the flywheel can still output part of the frequency regulation capacity, avoiding sudden changes in grid frequency; Third, the final output power matches the flywheel available capacity, avoiding "false capacity" or "inadequate", improving the consistency of command execution; Fourth, reduce deep discharge or overcharge, reduce mechanical parts and motor / bearing fatigue, reduce maintenance cost; Fifth, K_capability changes with SoC in real time, and the flywheel can dynamically adjust the response strategy like an intelligent frequency modulation unit, better adapting to the power grid working condition; Sixth, when multiple flywheels work together, the capacity weight coefficient can be used as a basis for distribution, so that flywheels in good condition contribute more and flywheels in poor condition contribute less, improving the reliability of overall group frequency modulation.

[0050] In summary, the application not only couples the original frequency modulation power demand with the available capacity of the flywheel, but also realizes safe, reliable and efficient dynamic adaptive frequency modulation response.

[0051] S4: based on the capacity weight coefficient and the original frequency modulation power demand, the final power instruction is calculated.

[0052] Specifically, based on the capacity weight coefficient K_capability and the original frequency modulation power demand P_demand, the final power instruction P_ref is calculated according to the following formula: P_ref = K_capability × P_demand.

[0053] Step S4 serves as a bridge connecting the power grid demand and the actual capacity of the flywheel, which avoids "mindless response" of the flywheel when the SoC is too low or too high, so as to avoid frequency modulation interruption or equipment damage caused by over-discharge / over-charge.

[0054] S5: send the final power instruction to the flywheel energy storage unit to make it perform corresponding charge / discharge operation.

[0055] After receiving P_ref, the switching mode (rectification / inversion) is switched, the switching sequence of IGBT is adjusted, and the current / voltage is accurately matched through closed-loop feedback control, so as to ensure that the actual output power is consistent with P_ref, and the response time is ≤10ms.

[0056] Exemplary system Correspondingly, the application also provides a flywheel energy storage grid frequency modulation system based on adaptive state management. The application can be used in an integrated control system of a single flywheel participating in grid frequency modulation design. The system dynamically adjusts the corresponding strategy through real-time sensing of grid demand and its own state. The core is to solve the contradiction between capacity limitation and frequency modulation efficiency in traditional single flywheel frequency modulation. The system takes a single flywheel energy storage unit as an execution subject, takes a core controller as a decision center, and is supplemented by a protection module to ensure safety, forming a closed-loop control system of "sensing-decision-execution-protection". Each part realizes data interaction through a high-speed communication bus, and the response delay control is within 50 ms, meeting the real-time requirements of grid frequency modulation.

[0057] Figure 2 is a block diagram of a flywheel energy storage grid frequency modulation system based on adaptive state management provided by the application, as shown in Figure 2a and 2b The system 100 provided by the embodiment includes: The core controller 101 is an intelligent decision core for executing the flywheel energy storage grid frequency modulation method based on adaptive state management.

[0058] The flywheel energy storage unit 102 is a hardware basis and is a physical carrier for energy storage and conversion. It is used to receive the final power instruction sent by the core controller 101 and execute the corresponding charge and discharge operation according to the final power instruction.

[0059] The flywheel energy storage unit 102 includes: The flywheel rotor is used for energy storage and conversion through rotation. The material is high-strength carbon fiber composite material, and the rated speed range is 5000-15000 RPM; The motor / generator integrated machine is used to drive the flywheel rotor and has the functions of motor (when charging the grid, the motor drives the flywheel to accelerate) and generator (when discharging the flywheel, the motor generates power to feedback to the grid). Preferably, it is a permanent magnet synchronous motor, and the power density is ≥2kW / kg; The power converter is used to receive the final power instruction sent by the core controller 101, convert the power instruction of the core controller 101 into actual current output, control the motor / generator integrated machine to drive the flywheel rotor to execute the corresponding charge and discharge operation, support bidirectional charge and discharge, and its rated power is 500kW, the response time is ≤10ms, and it supports four-quadrant operation, i.e., bidirectional charge and discharge; The vacuum cover is used to provide a high-vacuum operating environment for the flywheel rotor, and the vacuum degree is maintained below 1Pa to reduce wind resistance loss; The bearing system is used to support the flywheel rotor and provide low-friction rotation conditions. Preferably, magnetic levitation bearings are used, and the friction torque is ≤0.5N·m, which ensures stable operation of the flywheel rotor in a low-loss state.

[0060] The core controller 101 comprises: A power grid state monitoring module 103 is configured to acquire a frequency deviation of a power grid and an automatic power generation control instruction (P_AGC) in real time. High-frequency noise is removed through a digital filter, so that the measurement error of Δf is less than or equal to ±0.01 Hz, and a reliable input is provided for subsequent power calculation.

[0061] A flywheel state monitoring module 104 is configured to acquire a flywheel rotating speed in real time and calculate a state of charge. A laser speed sensor (measurement accuracy is ±1 RPM, sampling frequency is 500 Hz) is used to monitor the flywheel rotating speed (ω) in real time, and the state of charge (SoC) is calculated through a formula , wherein ω_min=5000 RPM (SoC=0%) and ω_max=15000 RPM (SoC=100%), and the SoC calculation refresh period is 10 ms. At the same time, auxiliary parameters such as motor temperature and AC output current are detected synchronously, and a trigger signal is provided for a protection module.

[0062] An adaptive frequency modulation strategy module 105 comprises: A frequency modulation demand calculation unit 106 is configured to calculate an original frequency modulation power demand based on the frequency deviation and the automatic power generation control instruction, to generate an original power demand P_demand by comprehensively considering the frequency deviation and the automatic power generation control instruction, and to calculate the original power demand P_demand according to a formula P_demand=-K×Δf+P_AGC (K is a frequency response coefficient, and the value is 50-100 kW / Hz, which can be dynamically configured according to a power grid requirement).

[0063] An adaptive weight calculation unit 107 is configured to calculate a capability weight coefficient based on the state of charge and the direction of the original frequency modulation power demand.

[0064] The adaptive weight calculation unit 107 calculates K_capability (continuous change between 0 and 1) in real time according to the SoC and the direction (charging / discharging) of P_demand.

[0065] For example, in an efficient working zone (30%≥SoC≤70%): K_capability=1, at this time, the flywheel is in an optimal rotating speed interval, the charging / discharging margin is sufficient, and the flywheel can respond to the power grid frequency modulation demand by 100%.

[0066] In a capability attenuation zone (SoC<30% or SoC>70%): SoC=30%→10% (discharging scenario, P_demand>0): K_capability linearly decreases from 1 to 0 (for example, when SoC=20%, K_capability=0.5).

[0067] SoC=30%→10% (charging scenario, P_demand<0): K capability remains 1 (priority to restore capacity).

[0068] SoC=70%→90% (charging scenario, P_demand<0): K capability linearly decreases from 1 to 0.

[0069] SoC=70%→90% (discharging scenario, P_demand>0): K capability remains 1.

[0070] Safety protection zone (SoC≤10% or SoC≥90%): K capability=0, suspend frequency regulation.

[0071] The power command correction unit 108 is configured to calculate a final power command based on the capability weight coefficient and the original frequency regulation power demand.

[0072] The power command correction unit 108 multiplies the original P demand by K capability to generate a final actual power command (P ref) sent to the power converter, and the calculation formula is P ref = K capability × P demand. The power command correction unit is a key bridge connecting the grid frequency regulation demand and the actual capability of the flywheel, and the core function is to avoid overcharging and overdischarging, equipment damage or frequency regulation interruption caused by forcibly responding to the grid demand when the flywheel is in a limited state (such as low / high SoC). The original frequency regulation demand (P demand) of the grid is generated based on the frequency deviation and the automatic power generation control command, and the current SoC (state of charge) of the flywheel is not considered. If the command is directly executed, it is easy to cause the flywheel to exceed the safe operating range. If the power command is not corrected, the flywheel will quickly consume the capacity due to “mindless response”, causing the flywheel to exit in the critical stage of grid frequency regulation, thereby reducing the frequency regulation reliability. If the uncorrected P demand is directly sent, the actual output will deviate from the command due to the mismatch between the execution capability of the flywheel and the command, or a power step will be generated due to sudden exit, thereby interfering with the grid frequency.

[0073] The system 100 can further include a protection module 109, which is a safety barrier for: Hard limit protection: when the flywheel speed is higher than a preset maximum speed threshold or lower than a minimum speed threshold, the connection between the flywheel energy storage unit 102 and the grid is cut off to avoid mechanical damage, wherein the hard limit protection threshold is ω max × 1.05 (15750 RPM) or ω min × 0.95 (4750 RPM); Soft limit protection: when the motor temperature exceeds the preset temperature threshold or the inverter current exceeds the preset current threshold, the capability weight coefficient is set to be not higher than 0.5, and the power output is reduced to alleviate the abnormal state. Preferably, the temperature threshold is 90°C, and the current threshold is 1.5 times the rated value; and / or Communication redundancy: a dual communication design is adopted, and when the communication between the core controller 101 and the power converter of the flywheel energy storage unit 102 is interrupted for not less than a preset time threshold, the capability weight coefficient is set to 0. Preferably, the communication interruption threshold is 100 ms, and the system will automatically switch to a local emergency mode (maintaining the current speed) to prevent out-of-control.

[0074] In summary, the protection module 109 realizes all-round protection of the flywheel energy storage unit 102 through multiple layers of safety strategies: not only preventing speed or temperature overrun from causing equipment damage, but also automatically adjusting the power output or switching to a safe mode in abnormal working conditions to ensure that the system remains controllable and stable in operation under extreme conditions, while ensuring the continuity and reliability of the frequency modulation function.

[0075] The grid state monitoring module 103 and the flywheel state monitoring module 104 synchronously collect data every 10 ms to update Δf, P_AGC and SoC. Based on real-time data, P_demand is generated to reflect the current power regulation demand of the grid. K_capability is calculated according to the direction of SoC and P_demand to dynamically adjust the response strength. The power converter converts P_ref into actual charging and discharging operations to realize energy interaction between the flywheel and the grid. The protection module monitors throughout to trigger the protection mechanism in abnormal conditions to ensure system safety. Steps S1-S5 are executed in a loop to realize dynamic adaptive control.

[0076] The power converter converts the final power command P_ref into actual charging and discharging operations through its internal controller and power module, and realizes it by adjusting voltage, current or frequency, and cooperating with closed-loop feedback regulation. The specific process is as follows: First step: after the controller of the power converter receives P_ref, it first judges the charging and discharging mode according to its positive and negative signs. P_ref>0 represents a discharging command, requiring the flywheel to convert kinetic energy into electrical energy and feed it into the grid; P_ref<0 is a charging command, which needs to obtain electrical energy from the grid to increase the flywheel speed. Second step: according to the charging and discharging mode, the controller switches the topology of the power module to realize "rectification" or "inversion" function to complete the bidirectional flow of energy. Third step: the controller converts the power demand of P_ref into switching timing control signals for IGBT, and realizes precise power matching by adjusting voltage, current or frequency. Fourth step: to avoid deviation between actual power and P_ref, the converter dynamically corrects through real-time feedback + PID regulation.

[0077] It is to be noted that, although the operation of the flywheel energy storage grid frequency regulation method based on adaptive state management of the present application is described in a particular order in the drawings, this is not required or implied in any way as to the order of the operations or that all illustrated operations be performed to achieve desirable results. Additionally or alternatively, certain steps can be omitted, combined into a single step, and / or broken into multiple steps.

[0078] Furthermore, although several means, units, or modules of the flywheel energy storage grid frequency regulation system based on adaptive state management are mentioned in the foregoing detailed description, this division is merely exemplary and not mandatory. Indeed, according to an implementation of the present application, the features and functionalities of two or more modules described above can be embodied in one module. Conversely, the features and functionalities of one module described above can be further divided into several modules.

[0079] While the spirit and principles of the present application have been described with reference to several specific implementations, it is to be understood that the present application is not limited to the specific implementations disclosed and that the division into aspects does not imply that features from these aspects cannot be combined to benefit. The division into aspects is merely for ease of presentation. The present application is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A flywheel energy storage grid frequency regulation method based on adaptive state management, characterized in that, The method comprises: real-time acquisition of frequency deviation and automatic generation control instruction of the power grid, and calculation of original frequency modulation power demand based on the frequency deviation and the automatic generation control instruction; real-time acquisition of flywheel speed, and calculation of state of charge of the flywheel energy storage unit based on the flywheel speed; calculation of capability weight coefficient according to the state of charge and direction of the original frequency modulation power demand, wherein the direction of the original frequency modulation power demand comprises charging instruction and discharging instruction; calculation of final power instruction based on the capability weight coefficient and the original frequency modulation power demand; sending of the final power instruction to the flywheel energy storage unit to enable the flywheel energy storage unit to perform corresponding charging and discharging operation.

2. The adaptive state management based flywheel energy storage grid frequency regulation method of claim 1, wherein, The step of calculating the capability weight coefficient according to the state of charge and the direction of the original frequency modulation power demand specifically comprises: when the state of charge is in a first preset range, setting the capability weight coefficient as 1; when the state of charge is lower than the lower limit of the first preset range: if the original frequency modulation power demand is the discharging instruction, then making the capability weight coefficient decay from 1 to 0; if the original frequency modulation power demand is the charging instruction, then keeping the capability weight coefficient as 1; when the state of charge is higher than the upper limit of the first preset range: if the original frequency modulation power demand is the charging instruction, then making the capability weight coefficient decay from 1 to 0; if the original frequency modulation power demand is the discharging instruction, then keeping the capability weight coefficient as 1.

3. The adaptive state management based flywheel energy storage grid frequency regulation method of claim 2, wherein, The decay mode of the capability weight coefficient is linear decay.

4. The adaptive state management based flywheel energy storage grid frequency regulation method of claim 1, wherein, The step of calculating the capability weight coefficient according to the state of charge and the direction of the original frequency modulation power demand specifically comprises: when the state of charge is not greater than a first safety threshold or not less than a second safety threshold, setting the capability weight coefficient as 0.

5. The adaptive state management based flywheel energy storage grid frequency regulation method according to any one of claims 1-4, wherein, The step of real-time acquisition of frequency deviation and automatic generation control instruction of the power grid, and calculation of original frequency modulation power demand based on the frequency deviation and the automatic generation control instruction specifically comprises: real-time acquisition of frequency deviation Δf and automatic generation control instruction P_AGC of the power grid, and calculation of original frequency modulation power demand P_demand based on the frequency deviation and the automatic generation control instruction according to the following formula: P_demand = -K × Δf + P_AGC, wherein K is a frequency response coefficient.

6. The adaptive state management based flywheel energy storage grid frequency regulation method according to any one of claims 1-4, wherein, The step of calculating the final power instruction based on the capability weight coefficient and the original frequency modulation power demand specifically comprises: calculation of the final power instruction P_ref based on the capability weight coefficient K_capability and the original frequency modulation power demand P_demand according to the following formula: P_ref = K_capability × P_demand.

7. A flywheel energy storage grid frequency regulation system based on adaptive state management, characterized in that, The system comprises: a core controller configured to perform the method according to any one of claims 1-6; a flywheel energy storage unit configured to receive the final power instruction sent by the core controller, and perform corresponding charging and discharging operation according to the final power instruction.

8. The adaptive state management based flywheel energy storage grid frequency modulation system of claim 7, wherein, The core controller comprises: a power grid state monitoring module configured to real-time acquisition of frequency deviation and automatic generation control instruction of the power grid. a flywheel state monitoring module configured to acquire flywheel rotating speed and calculate state of charge (SOC) in real time; a frequency modulation demand calculation unit configured to calculate original frequency modulation power demand based on the frequency deviation and automatic generation control (AGC) instruction; an adaptive weight calculation unit configured to calculate capability weight coefficient based on the SOC and direction of the original frequency modulation power demand; a power instruction correction unit configured to calculate final power instruction based on the capability weight coefficient and the original frequency modulation power demand.

9. The adaptive state management based flywheel energy storage grid frequency modulation system of claim 7, wherein, The system further comprises a protection module configured to: cut off the connection between the flywheel energy storage unit and the power grid when the flywheel rotating speed is higher than a preset maximum rotating speed threshold or lower than a minimum rotating speed threshold; set the capability weight coefficient not higher than 0.5 when detecting that the motor temperature exceeds a preset temperature threshold or the inverter current exceeds a preset current threshold; and / or set the capability weight coefficient to 0 when the communication between the core controller and the flywheel energy storage unit is interrupted for not less than a preset time threshold.

10. The adaptive state management based flywheel energy storage grid frequency modulation system of claim 7, wherein, The flywheel energy storage unit comprises: a flywheel rotor configured to store and convert energy through rotation; a motor / generator integrated machine configured to drive the flywheel rotor; a power inverter configured to receive the final power instruction sent by the core controller to control the motor / generator integrated machine to drive the flywheel rotor to perform corresponding charging and discharging operations, supporting bidirectional charging and discharging; a vacuum cover configured to provide a high-vacuum operating environment for the flywheel rotor; a bearing system configured to support the flywheel rotor and provide low-friction rotating conditions.

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