High-power-density flywheel energy storage converter array and control method thereof

Abstract

The invention belongs to the technical field of electric power energy storage, and discloses a high-power-density flywheel energy storage converter array and a control method thereof.The high-power-density flywheel energy storage converter array comprises a hierarchical control framework and a modular unit design and communication and monitoring mechanism and further comprises the hierarchical control framework which is divided into a top layer, a middle layer and a bottom layer, the top layer receives a power grid dispatching instruction through a communication bus by a dispatching center to realize switching between a grid-connected mode and an island mode, and the grid-connected mode receives the power grid dispatching instruction and issues the power grid dispatching instruction to the middle layer controller. Through the arrangement of the modularized flywheel unit array, breakthrough improvement can be achieved for the problems of single power limitation and insufficient expansibility, the annular symmetrical layout design that the N flywheel units are connected in parallel is adopted, flywheel units of different power levels can be flexibly combined, the system power is expanded from 100 kW to 10 MW in a wide range, and the system reliability is improved. Compared with a traditional monomer design, deployment cost is reduced, electromagnetic interference is reduced through annular layout, and system reliability is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric energy storage, and in particular relates to a high-power-density flywheel energy storage converter array and a control method thereof. Background Art

[0002] Flywheel energy storage is a physical energy storage technology that uses a high-speed rotating flywheel to store and release energy. Its core principle is to store electrical energy in the form of kinetic energy. It has the characteristics of high power density, long cycle life, and environmental friendliness. As the proportion of renewable energy power generation (such as wind power and photovoltaic power) continues to increase, the power grid has an increasingly urgent need for frequency and peak regulation and power stability.

[0003] Currently, traditional single-unit flywheel energy storage systems face the following multiple technical bottlenecks in practical applications:

[0004] 1. Limited single-unit power and insufficient scalability: Traditional single-unit flywheels typically have low power, making it difficult to directly meet megawatt-level project requirements (e.g., grid frequency regulation requires power of more than 1MW). Single-unit designs lack modular scalability and cannot be flexibly adapted to different power levels through parallel connection, increasing the deployment cost of large-scale energy storage systems.

[0005] 2. Multi-array control strategy flaws: Uneven power distribution. When multiple flywheel arrays are connected in parallel, traditional droop control strategies result in uneven power distribution due to differences in impedance between units (such as line impedance and converter parameter deviations). This leads to a high risk of overloading some flywheels and a decrease in overall system efficiency.

[0006] 3. Inadequate torque-power coupling control: Existing vector control strategies fail to fully integrate the dynamic coupling characteristics of the flywheel's "speed-power-torque" relationship. In particular, they lack precise control of the motor's d-axis and q-axis currents, making it impossible to maintain constant torque at varying speeds. This limits power density and response speed.

[0007] 4. Poor adaptability to engineering application scenarios: Existing solutions are difficult to cover the wide power range of 100kW to 10MW. When a 1MW energy storage system is required, traditional solutions require customized high-power single flywheels, resulting in long design cycles, high costs, and low maintenance flexibility.

[0008] In response to the above problems, the present invention proposes a high power density flywheel energy storage converter array and a control method thereof to solve the problems of traditional single flywheel energy storage systems in practical applications. Summary of the Invention

[0009] To address the problems raised in the above background technology, the present invention provides a high-power-density flywheel energy storage and conversion device array, including a hierarchical control architecture, a modular unit design, and a communication and monitoring mechanism. The hierarchical control architecture further includes: the hierarchical control architecture is divided into a top layer, a middle layer, and a bottom layer. The top layer receives grid dispatch instructions from a dispatch center via a communication bus to implement switching between a grid-connected mode and an island mode. The grid-connected mode receives grid dispatch instructions and sends them to a middle layer controller. The island mode autonomously calculates system power requirements and performs power balancing and distribution within the island.

[0010] The middle layer includes a flywheel array controller, and the plurality of flywheel array controllers are used to execute an improved droop control strategy to achieve power balance and dynamic response among multiple arrays, and at least two groups of flywheel array controllers are used for execution;

[0011] The bottom layer includes a flywheel unit converter, wherein a plurality of flywheel unit converters are connected to a corresponding flywheel unit, and the flywheel unit converter adopts maximum torque current ratio vector control to regulate the motor torque and power through d / q axis current decoupling;

[0012] The modular unit includes a plurality of flywheel units, each of which includes a permanent magnet synchronous motor, a converter and a condition monitoring module. The plurality of flywheel units are connected in parallel via a DC bus to support expansion of N ≥ 2 units.

[0013] The communication and monitoring collects status signals such as SOC, Te, and speed through the status monitoring module in the multiple flywheel units at the bottom layer, and transmits them to the middle layer array controller in real time via the communication bus; the middle layer generates a reference power instruction and droop control correction amount based on the scheduling requirements and feedback signals, and sends them to the bottom layer for execution, forming a closed-loop control link of power allocation-execution-feedback.

[0014] Preferably, the middle-layer improved droop control strategy includes equal torque power distribution. In the arc island mode, based on the speed deviation and charge state difference of the multiple flywheel units, the array controller dynamically adjusts the unit reference power to ensure the torque balance of multiple arrays;

[0015] The tie line power compensation mechanism is introduced into the grid connection mode adaptation. According to the real-time power instruction of the power grid, the power distribution of each array is corrected by the array controller to improve the grid connection response accuracy.

[0016] Preferably, the underlying flywheel unit converter is based on the d / q axis mathematical model of the permanent magnet synchronous motor, and realizes independent regulation of torque and power through a current decoupling algorithm, thereby meeting the constant torque output characteristics within a wide speed range and improving the system power density.

[0017] Preferably, the top layer and the middle layer in the hierarchical control architecture are connected via an industrial-grade communication bus; the middle layer and the bottom layer interact via a DC bus and a signal bus to support real-time power command issuance and status feedback.

[0018] Preferably, the modular unit layout satisfies that the axes of adjacent flywheel rotors are arranged in a circular symmetrical manner, with a spacing D ≥ 1.5 m + D / 2, where D is the diameter of the flywheel rotor.

[0019] Preferably, the power distribution logic in the island mode is to modify the reference power by weighting, combining the rotation speed of each flywheel unit and the average state of the system, and the formula is: Among them, ωi is the unit speed, reflecting the current kinetic energy storage state of the flywheel, SOCi is the unit charge state, which is used to directly relate to the remaining energy of the flywheel, ωavg is the system average speed, which serves as a reference benchmark for speed balance, and SOCavg represents the system average charge state. Through weighted correction, the energy storage of each unit is balanced. When charging in the off-peak period, power is allocated to the unit with low SOC first to improve the overall discharge capacity.

[0020] Preferably, the tie line compensation in the grid-connected mode is to introduce a grid power deviation compensation term ΔP into the middle layer droop control. g rid), the correction formula is:

[0021] P ref_i is the baseline power initially allocated to the i-th flywheel unit in the middle layer, ensuring the power balance of multiple units based on the equal torque strategy;

[0022] P′ ref_i The corrected reference power is used to drive the underlying converter to track the grid power command;

[0023] ΔP grid It is the deviation between the grid dispatching command power and the actual system output power, reflecting the difference between the grid power demand and the system output;

[0024] k is the compensation coefficient, which is used to adjust the compensation intensity to match the grid response speed.

[0025] This solution also provides a control method for a high power density flywheel energy storage converter device, comprising the following steps:

[0026] S1: Top-level dispatch: The dispatch center receives grid instructions, grid connection mode, and calculates the total power demand in island mode, and then executes S2;

[0027] S2: Middle-level allocation: The array controller uses an equal torque strategy to decompose the total power demand into the reference power of each flywheel array, and corrects the power deviation between arrays through droop control, and then executes S3;

[0028] S3: Bottom-level execution: Each flywheel unit converter controls the motor d / q axis current in real time based on the MTPA algorithm to achieve dynamic tracking of torque and power, while also feeding back the charge state and electromagnetic torque to the middle level.

[0029] This solution also provides a method for ensuring the integrity of a high power density flywheel energy storage converter device, comprising the following steps:

[0030] S4: Initialization step: set the initial values ​​of the speed, torque and state of charge of each flywheel unit, and then execute S5;

[0031] S5: Closed-loop correction step: real-time monitoring of the speed difference Δω. If Δω exceeds the threshold, droop control correction is triggered, and then S6 is executed;

[0032] S6: Fault handling steps: When a unit fails, the middle-level controller automatically redistributes power to other units to maintain system operation.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention can achieve a breakthrough improvement on the problems of single-unit power limitation and insufficient scalability through the setting of a modular flywheel unit array. The ring-shaped symmetrical layout design with N flywheel units in parallel can flexibly combine flywheel units of different power levels, so that the system power can be expanded from 100kW to 10MW. Compared with the traditional single-unit design, the deployment cost is reduced. At the same time, the ring layout reduces electromagnetic interference and improves system reliability.

[0035] Furthermore, by improving the setting of the droop control strategy at the middle level, on the one hand, the equal torque power distribution algorithm and the interconnection line power compensation mechanism are used to solve the problem of uneven power distribution caused by impedance differences when multiple arrays are connected in parallel, so that the power distribution error of each flywheel unit is ≤5%, avoiding the risk of overload; on the other hand, by introducing the grid power deviation compensation item, the array power distribution is corrected in real time, and the grid response accuracy is improved by more than 40%. At the same time, in the island mode, the energy storage of each unit is dynamically balanced based on the speed and charge state, thereby improving the overall discharge capacity.

[0036] Furthermore, through the maximum torque-to-current ratio (MTPA) vector control setting of the underlying flywheel unit converter, on the one hand, current decoupling is achieved based on the mathematical model of the d / q axes of the permanent magnet synchronous motor, and the torque is kept constant over a wide speed range, thereby increasing the system power density by more than 35%; on the other hand, the closed-loop correction mechanism monitors the speed difference in real time to trigger droop control correction, combined with the automatic power redistribution function in the event of a fault, to ensure that the system can still maintain operation in the event of a fault, thereby improving system stability and dynamic response speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the hierarchical control architecture of the present invention;

[0038] Figure 2 is a power control flow chart of the present invention;

[0039] Figure 3 is a flow chart of the communication and monitoring link of the present invention;

[0040] Figure 4 is a flow chart of the hierarchical control method of the present invention;

[0041] Figure 5 Flowchart of the integrity assurance method of the present invention. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0043] like Figures 1 to 5 As shown, the present invention provides a high-power density flywheel energy storage converter array and a control method thereof, including a hierarchical control architecture, a modular unit design, and a communication and monitoring mechanism. The hierarchical control architecture further includes: the hierarchical control architecture is divided into a top layer, a middle layer, and a bottom layer. The top layer receives grid dispatch instructions from a dispatch center through a communication bus to implement switching between a grid-connected mode and an island mode. The grid-connected mode receives grid dispatch instructions and sends them to a middle layer controller. The island mode autonomously calculates system power requirements and performs power balance distribution within the island.

[0044] Specifically, the island mode of top-level scheduling: autonomously calculate the system power demand (load power + backup power), and adjust the charge and discharge power of the flywheel array (based on kinetic energy) ), realize power balance in island mode (such as voltage / frequency stability during black start of microgrid); grid-connected mode: receive grid dispatch instructions (P g ,Q g ), based on the traditional droop control, tie line power compensation is introduced to quickly respond to the grid power deviation (ΔP grid =P g -∑P i ), and improve the grid connection response accuracy.

[0045] like Figures 1 to 5As shown, the middle layer includes a flywheel array controller, and multiple flywheel array controllers are used to execute an improved droop control strategy to achieve power balance and dynamic response among multiple arrays. It includes at least two groups of flywheel array controllers. The middle layer improved droop control strategy includes equal torque power distribution. In the arc island mode, based on the speed deviation and charge state difference of multiple flywheel units, the unit reference power is adjusted by the array controller dynamically to ensure torque balance among multiple arrays.

[0046] A tie-line power compensation mechanism is introduced in the grid-connected mode adaptation. Based on the real-time power instructions of the power grid, the array controller corrects the power distribution of each array to improve the grid-connected response accuracy.

[0047] Specifically, in equal torque power distribution (island mode): based on the speed deviation of each flywheel unit (Δω=ω avg -ω i ) and state of charge difference (ΔSOC=SOC avg -SOC i ), dynamically adjust the unit reference power;

[0048] Speed ​​balance: When the speed of a unit is lower than the average speed of the system (such as ω i <ω avg ), through the positive Δω correction, increase the unit reference power (such as P ref,i+ =K ω Δω, K ω =0.5kW / (rad / s)), so that it charges first and increases the speed, thus suppressing the speed fluctuation of multiple units.

[0049] SOC balance: When the state of charge of a unit is lower than the system average (such as SOC i <SOC avg ), through the positive ΔSOC correction, increase the unit reference power (such as P ref,i+ =α SOC ΔSOC, α SOC =0.1kW / ), energy is allocated to it first during valley charging to reduce SOC dispersion.

[0050] Tie-line power compensation (grid-connected mode): Introducing grid power deviation ΔP grid =P g -∑P i , the reference power (P ref,i+ =P ref,i +k·ΔP grid / N), quickly respond to grid instructions (such as ΔP grid = +200kW, adjust power output within 150ms) to improve grid-connected response accuracy.

[0051] like Figures 1 to 5 As shown, the bottom layer includes a flywheel unit converter. Multiple flywheel unit converters are connected to one flywheel unit. The flywheel unit converter adopts maximum torque current ratio vector control and regulates the motor torque and power through d / q axis current decoupling. The bottom layer flywheel unit converter is based on the d / q axis mathematical model of the permanent magnet synchronous motor. It realizes independent regulation of torque and power through current decoupling algorithm, meets the constant torque output characteristics in a wide speed range, and improves the system power density.

[0052] Specifically, the principle of vector control: Torque calculation uses the formula T e =1.5pψ f i q (where p is the number of motor pole pairs, ψ f is the permanent magnet flux, i q The torque is calculated based on the q-axis current, which directly relates the motor torque to the q-axis current to ensure the accuracy of torque control.

[0053] MTPA optimization: Optimizing the d-axis current i through algorithms d , so that the maximum torque can be generated per unit current (such as i d according to- Calculate, where L d is the d-axis inductor), and cooperates with a three-level converter (flywheel unit converter) to track power commands within 150ms, achieving efficient power output and improving motor efficiency and power density.

[0054] Wide-speed constant torque output: Torque fluctuation is maintained at ≤2% within a wide speed range of 5000-15000 rpm, ensuring stable power output from the flywheel unit at different speeds. Combined with the three-level converter, it achieves fast power tracking (responding to power command changes within 150ms), improving system responsiveness.

[0055] Improved power density: Through the combination of MTPA control and three-level topology, the system power density reaches ≥60kW / m 3 , meeting the application requirements of high power density flywheel energy storage devices (such as grid frequency regulation and industrial energy storage scenarios).

[0056] like Figures 1 to 5 As shown, the modular unit includes multiple flywheel units, each flywheel unit includes a permanent magnet synchronous motor, a converter and a condition monitoring module. Multiple flywheel units are connected in parallel through a DC bus to support the expansion of N ≥ 2 units. The modular unit layout satisfies the requirement that the axes of adjacent flywheel rotors are arranged in a circular symmetrical manner with a spacing of D ≥ 1.5 m + D / 2, where D is the diameter of the flywheel rotor.

[0057] Specifically, a single flywheel unit contains a 100kW permanent magnet synchronous motor and an 800V three-level converter (switching frequency 10kHz). Ten units are connected in parallel to form a 1MW system via 100mm×10mm copper busbars. When arranged in a ring, the angle between adjacent axes is 36°, and the spacing is d=1.5m+D / 2 (D=1.2m).

[0058] like Figures 1 to 5 As shown in the figure, communication and monitoring collects status signals such as SOC, Te, and speed in multiple flywheel units at the bottom layer through the status monitoring module, and transmits them to the middle layer array controller in real time via the communication bus; the middle layer generates reference power instructions and droop control corrections based on scheduling requirements and feedback signals, and sends them to the bottom layer for execution, forming a closed-loop control link of power allocation-execution-feedback.

[0059] Specifically, the underlying condition monitoring module uses a high sampling rate of 100kHz to collect the flywheel unit's state of charge (SOC), electromagnetic torque (Te), and speed in real time. The SOC is calculated using the flywheel kinetic energy formula, accurately reflecting the energy storage state. The speed is obtained using a high-precision encoder to ensure accurate monitoring. The electromagnetic torque is calculated based on the permanent magnet synchronous motor's d / q axis current model, providing real-time torque feedback. These signals are uploaded to the mid-level array controller via the CANopen bus, with communication latency strictly controlled to ≤100μs to ensure timely data transmission.

[0060] The middle-level array controller receives top-level dispatch commands (such as Pg in grid-connected mode and Ptotal in island mode), combines them with bottom-level feedback status signals, and applies an improved droop control strategy (equal torque distribution and tie-line compensation) to generate each unit's reference power command (Prefi) and droop correction factors (such as correction terms for speed deviation Δω and state of charge deviation ΔSOC). These commands are then sent to the bottom level via the SPI bus, ensuring low latency and high reliability.

[0061] After receiving the middle-level instructions, the bottom-level converter adopts the maximum torque-to-current ratio (MTPA) vector control algorithm to decouple the d / q-axis current, adjust the motor torque and power in real time, and accurately track the reference power. At the same time, the bottom level feeds back the updated status (SOC, speed, Te) to the middle level, forming a "scheduling-allocation-execution-feedback" closed loop. Through this mechanism, the system dynamically adjusts power distribution to ensure the balance of speed and charge state among multiple units, thereby improving overall stability and response speed.

[0062] like Figures 1 to 5 As shown in the figure, the top layer and the middle layer in the hierarchical control architecture are connected through an industrial-grade communication bus; the middle layer and the bottom layer interact through the DC bus and the signal bus to support real-time power command issuance and status feedback.

[0063] Specifically, the top and middle layers use the industrial-grade EtherCAT bus (100μs delay) to quickly transmit power commands, and the middle and bottom layers transmit energy through an 800V DC bus, jointly building a low-latency closed-loop control system to support the system's 200ms response to ±10% power steps and multi-unit balancing with an SOC discreteness of ≤3%, thereby improving the grid's frequency regulation and island operation stability.

[0064] This solution also provides a hierarchical control method for a high power density flywheel energy storage converter device, comprising the following steps:

[0065] S1: The top layer receives grid instructions when connected to the grid and calculates load power when isolated. It implements mode switching through kinetic energy balance and then executes S2.

[0066] S2: Middle-level allocation: The array controller adopts an equal torque strategy, uses the speed and state of charge deviation to correct the power distribution, introduces grid power deviation compensation when connecting to the grid, ensures the torque balance of multiple units, decomposes the total power demand into the reference power of each flywheel array, and corrects the power deviation between arrays through droop control, and then executes S3;

[0067] S3: Bottom-layer execution: The flywheel unit converters, based on the MTPA algorithm, perform real-time control of the motor's d / q-axis currents to achieve dynamic tracking of torque and power, while also feeding back states such as the state of charge and electromagnetic torque to the middle layer. The bottom layer decouples the d / q-axis currents based on the MTPA algorithm to achieve constant torque over a wide speed range, and provides real-time feedback on the state to form a closed loop. The three work together to solve the problems of uneven power and slow response of traditional flywheels through the "dispatching-allocation-execution-feedback" mechanism, supporting scenarios such as grid frequency regulation and industrial energy storage. This embodies the innovative integration of equal torque control and MTPA vector control, meeting the dynamic control needs of high-power-density flywheel arrays.

[0068] like Figures 1 to 5 As shown in the figure, the power distribution logic in island mode is to combine the speed of each flywheel unit and the average state of the system, and modify the reference power by weighting. The formula is: Among them, ωi is the unit speed, reflecting the current kinetic energy storage state of the flywheel, SOCi is the unit charge state, which is used to directly relate to the remaining energy of the flywheel, ωavg is the system average speed, which serves as a reference benchmark for speed balance, and SOCavg represents the system average charge state. Through weighted correction, the energy storage of each unit is balanced. When charging in the off-peak period, power is allocated to the unit with low SOC first to improve the overall discharge capacity.

[0069] Specifically, the engineering implementation of the weighted correction formula is:

[0070]

[0071] in:

[0072] The compensation coefficient Kω is set to 0.5kW / (rad / s) and αSOC is set to 0.1kW / %, which are determined through multi-unit parallel experiments to balance the control effects of speed and state of charge and avoid system fluctuations;

[0073] State quantity calculation: System average rotation speed ωavg: The arithmetic average of the rotation speeds of each unit, collected and calculated by a high-precision encoder to ensure the accuracy of the speed balance reference;

[0074] Unit state of charge (SOCi): Calculates the remaining energy percentage based on the flywheel's moment of inertia and rated speed, directly related to the energy storage status;

[0075] System average state of charge (SOCavg): The arithmetic average of the state of charge of each unit, which serves as the benchmark for energy storage balance

[0076] Example verification: When N = 10, Ptotal = 1000kW, the speed of a unit is 14000rpm (the system average is 15000rpm), and SOCi = 40% (the system average is 50%), then:

[0077]

[0078] The energy storage and speed are increased in a short period of time, and the torque imbalance of multiple units is significantly reduced, verifying the optimization effect of the formula on power distribution and energy storage balance.

[0079] like Figures 1 to 5 As shown, the tie line compensation in the grid-connected mode is: the grid power deviation compensation term ΔP is introduced into the middle layer droop control g rid), the correction formula is:

[0080] P ref_i is the baseline power initially allocated to the i-th flywheel unit in the middle layer, ensuring the power balance of multiple units based on the equal torque strategy;

[0081] P′ ref_i The corrected reference power is used to drive the underlying converter to track the grid power command;

[0082] ΔP grid It is the deviation between the grid dispatching command power and the actual output power of the system, reflecting the difference between the grid power demand and the system output;

[0083] k is the compensation coefficient, which is used to adjust the compensation intensity to match the grid response speed.

[0084] Specifically, the engineering implementation of tie line compensation includes deviation calculation:

[0085] Among them, P g is the grid dispatching command power (e.g. 1.2MW), ∑P i The sum of the actual output power of N flywheel units is collected in real time by a high-precision power transmitter;

[0086] Compensation coefficient adjustment: k = 0.8 (default value), determined by the power grid frequency regulation experiment, when k = 0.8, the system has a grid = +200kW response time is 200ms, overshoot ≤ 5%;

[0087] Adaptive regulation mechanism: When the grid frequency fluctuates > 0.5Hz, k is automatically increased to 1.0 to speed up the response; Modified execution process: The middle-level DSP (TMS320F28379D) calculates ΔP every 10ms grid ;

[0088] When |ΔP grid |>10%P total When the compensation correction is triggered: P′ ref,i =P ref,i +0.8·ΔP grid / N The bottom converter receives P ref,i After ', the power output is adjusted within 150ms through MTPA control;

[0089] When P g =1200kW, system initial output ∑P i =1000kW, ΔP grid =200kW, corrected single unit P ref,i ′=120+0.8×200 / 10=136kW, bottom power tracking error ≤1.5%.

[0090] This solution also provides a method for ensuring the integrity of a high power density flywheel energy storage converter device, comprising the following steps:

[0091] S4: Initialization step: Set the speed, torque and SOC initial values ​​of each flywheel unit. This step is the starting point of the entire system operation and provides basic data for subsequent power distribution and control. The initial speed value determines the initial kinetic energy state of the flywheel, affecting its energy storage and release capabilities; the initial torque value is used to determine the force conditions when the motor starts to ensure smooth motor startup; the initial SOC value reflects the initial charge state of the flywheel unit, which is related to the unit's proportion in the entire system energy storage and the formulation of subsequent charging and discharging strategies. By reasonably setting these initial values, the system can be in the optimal state at startup, ensuring the coordinated operation of each unit, and then execute S5;

[0092] S5: Closed-loop correction step, real-time monitoring of the speed difference Δω. If Δω exceeds the threshold, droop control correction is triggered. During system operation, the actual speed of each flywheel unit may differ due to load changes, environmental factors, etc. Δω reflects the deviation between the unit speed and the expected speed or average speed. When Δω exceeds the set threshold, it means that the speed difference between the units is too large, which may lead to problems such as torque imbalance and unreasonable power distribution. At this time, droop control correction is triggered. By adjusting the reference power allocated to each unit at the middle level, the faster speed unit appropriately reduces the power output, and the slower speed unit increases the power input, so that the speed of each unit tends to be balanced, ensuring stable system operation, improving the accuracy of power distribution and the overall system efficiency, and then executing S6;

[0093] S6: Fault handling steps. When a unit fails, the middle-level controller automatically redistributes power to other units to maintain system operation. In actual operation, the flywheel unit may fail due to hardware failure (such as converter damage, motor winding short circuit) or software failure (such as control algorithm error). At this time, the middle-level controller, as the "brain" of the system, can monitor the status of each unit in real time. Once a unit failure is detected, it will respond quickly and isolate the faulty unit from the power distribution system. Then, based on the parameters of the remaining normal units (such as speed, SOC, torque, etc.), according to the equal torque strategy or other optimization algorithms, recalculate and distribute power to the normal units, ensuring that the system can still maintain operation in a reduced capacity when some units fail, thereby improving the reliability and fault tolerance of the system and reducing the system downtime and economic losses caused by unit failures.

[0094] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0095] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A high power density flywheel energy storage and conversion device array, including a hierarchical control architecture, a modular unit design, and a communication and monitoring mechanism, characterized in that: The hierarchical control architecture further includes: the hierarchical control architecture is divided into a top layer, a middle layer, and a bottom layer, wherein the top layer receives grid dispatch instructions from a dispatch center via a communication bus to implement switching between a grid-connected mode and an island mode, the grid-connected mode receives grid dispatch instructions and sends them to a middle layer controller, and the island mode autonomously calculates system power requirements and performs power balancing and distribution within the island; The middle layer includes a flywheel array controller, and the plurality of flywheel array controllers are used to execute an improved droop control strategy to achieve power balance and dynamic response among multiple arrays, and at least two groups of flywheel array controllers are used for execution; The bottom layer includes a flywheel unit converter, wherein a plurality of flywheel unit converters are connected to a corresponding flywheel unit, and the flywheel unit converter adopts maximum torque current ratio vector control to regulate the motor torque and power through d / q axis current decoupling; The modular unit includes a plurality of flywheel units, each of which includes a permanent magnet synchronous motor, a converter and a condition monitoring module. The plurality of flywheel units are connected in parallel via a DC bus to support expansion of N ≥ 2 units. The communication and monitoring collects status signals such as SOC, Te, and speed through the status monitoring module in the multiple flywheel units at the bottom layer, and transmits them to the middle layer array controller in real time via the communication bus; the middle layer generates a reference power instruction and droop control correction amount based on the scheduling requirements and feedback signals, and sends them to the bottom layer for execution, forming a closed-loop control link of power allocation-execution-feedback.

2. A high power density flywheel energy storage and conversion device array according to claim 1, characterized in that: The improved mid-layer droop control strategy includes equal torque power distribution. In the arc island mode, based on the speed deviation and charge state difference of the multiple flywheel units, the array controller dynamically adjusts the unit reference power to ensure multi-array torque balance; The tie line power compensation mechanism is introduced into the grid connection mode adaptation. According to the real-time power instruction of the power grid, the power distribution of each array is corrected by the array controller to improve the grid connection response accuracy.

3. The high power density flywheel energy storage and conversion device array according to claim 2, characterized in that: The underlying flywheel unit converter is based on the d / q axis mathematical model of the permanent magnet synchronous motor, and realizes independent regulation of torque and power through a current decoupling algorithm, thereby meeting the constant torque output characteristics within a wide speed range and improving the system power density.

4. The high power density flywheel energy storage and conversion device array according to claim 3, characterized in that: The top layer and the middle layer in the hierarchical control architecture are connected via an industrial-grade communication bus; the middle layer and the bottom layer interact via a DC bus and a signal bus to support real-time power command issuance and status feedback.

5. The control method of a high power density flywheel energy storage converter device according to claim 4, characterized in that: The modular unit layout satisfies that adjacent flywheel rotor axes are arranged in a circular symmetrical manner, with a spacing D ≥ 1.5 m + D / 2, where D is the diameter of the flywheel rotor.

6. A high power density flywheel energy storage converter array and control method thereof according to claims 1-5, characterized in that: The hierarchical control approach includes the following steps: S1: Top-level dispatch: The dispatch center receives grid instructions, grid connection mode, and calculates the total power demand in island mode, and then executes S2; S2: Middle-level allocation: The array controller uses an equal torque strategy to decompose the total power demand into the reference power of each flywheel array, and corrects the power deviation between arrays through droop control, and then executes S3; S3: Bottom-level execution: Each flywheel unit converter controls the motor d / q axis current in real time based on the MTPA algorithm to achieve dynamic tracking of torque and power, while also feeding back the charge state and electromagnetic torque to the middle level.

7. The high power density flywheel energy storage and conversion device array according to claim 6, characterized in that: The power distribution logic in the island mode is to modify the reference power by weighting, combining the speed of each flywheel unit and the average state of the system. The formula is: Among them, ωi is the unit speed, reflecting the current kinetic energy storage state of the flywheel, SOCi is the unit charge state, which is used to directly relate to the remaining energy of the flywheel, ωavg is the system average speed, which serves as a reference benchmark for speed balance, and SOCavg represents the system average charge state. Through weighted correction, the energy storage of each unit is balanced. When charging in the off-peak period, power is allocated to the unit with low SOC first to improve the overall discharge capacity.

8. The high power density flywheel energy storage and conversion device array and control method thereof according to claim 7, characterized in that: The tie line compensation in the grid-connected mode is to introduce the grid power deviation compensation term ΔP into the middle layer droop control. g rid), the correction formula is: P ref_i is the baseline power initially allocated to the i-th flywheel unit in the middle layer, ensuring the power balance of multiple units based on the equal torque strategy; P′ ref_i The corrected reference power is used to drive the underlying converter to track the grid power command; ΔP grid It is the deviation between the grid dispatching command power and the actual output power of the system, reflecting the difference between the grid power demand and the system output; k is the compensation coefficient, which is used to adjust the compensation intensity to match the grid response speed.

9. The method for ensuring the integrity of a high power density flywheel energy storage and conversion device according to claim 6, characterized in that: The following steps are involved: S4: Initialization step: set the initial values ​​of the speed, torque and state of charge of each flywheel unit, and then execute S5; S5: Closed-loop correction step: real-time monitoring of the speed difference Δω. If Δω exceeds the threshold, droop control correction is triggered, and then S6 is executed; S6: Fault handling steps: When a unit fails, the middle-level controller automatically redistributes power to other units to maintain system operation.

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