Power optimization method for flywheel energy storage system with multi-mode control combined with acceleration factor

Abstract

The embodiment of the application relates to the technical field of flywheel energy storage system control, in particular to a multi-mode control flywheel energy storage system power optimization method combined with an acceleration factor, the method comprising the following steps: after receiving a power instruction, judging whether the state of charge of all units is consistent according to the absolute value of the state of charge difference between any two flywheel units; if consistent, dividing the total power among the units; if not consistent, dynamically allocating power according to the state of charge difference, and introducing an acceleration factor to make the state of charge converge to be consistent; if no power instruction is received and the state of charge of the units is not consistent, adjusting the power output to make the state of charge tend to be consistent. Through dynamic switching, dynamic power correction with an acceleration factor and gradual state of charge adjustment, the three modes are realized, and efficient, stable and safe operation and rapid state of charge balancing of the flywheel energy storage array under different working conditions are realized.

Description

Technical Field

[0001] This application relates to the field of flywheel energy storage system control technology, and in particular to a power optimization method for multi-mode control flywheel energy storage systems incorporating acceleration factors. Background Technology

[0002] Flywheel energy storage has been widely used in electrified railways, new energy power generation, and microgrids due to its advantages such as long life cycle, fast charging and discharging speed, and high power density. However, the capacity of a single flywheel unit is limited and cannot meet the needs of large-scale energy storage. Therefore, multiple flywheel units are often connected in parallel to form a flywheel energy storage array.

[0003] In flywheel energy storage arrays, traditional power distribution strategies mainly include equal power distribution, equal torque distribution, and equal time distribution. Equal power distribution evenly distributes the total power to each unit, which is simple to calculate but ignores the differences in the state of charge between flywheel units, easily leading to overcharging or over-discharging of some units. Equal torque distribution sets the output torque of each unit to be the same, but it can easily cause uneven power distribution when the load fluctuates significantly. Equal time distribution evenly distributes power over time, but fails to consider the specific power requirements of each unit, making it difficult to fully utilize the energy storage capacity.

[0004] In summary, existing power allocation strategies have the following shortcomings: they cannot effectively cope with differences in state of charge, lack the ability to adapt to dynamic load changes, have unbalanced power allocation, have a slow state of charge balancing speed, and fail to fully consider overcharge and over-discharge protection issues. Summary of the Invention

[0005] To address these issues, this invention provides a power optimization method for a multi-mode control flywheel energy storage system that incorporates an acceleration factor. This method overcomes the problems in existing technologies, such as the inability to effectively address differences in the state of charge of flywheel units, lack of adaptability to dynamic load changes, uneven power distribution, and slow state of charge balancing.

[0006] To achieve the above objectives, this invention provides a power optimization method for a multi-mode control flywheel energy storage system incorporating an acceleration factor. It includes: Obtain the current rotational speed, upper speed limit, and lower speed limit of each flywheel unit in the flywheel energy storage array. Based on the squared difference between the current rotational speed of each flywheel unit and its upper and lower speed limits, calculate the state of charge of each flywheel unit. Calculate the absolute value of the difference in state of charge between any two flywheel units, and determine whether the state of charge of all flywheel units is consistent based on the absolute value; In response to the consistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, the output power command of each flywheel unit is determined based on the power command received by the flywheel energy storage array and the number of flywheel units; If the flywheel energy storage array does not receive a power command, the output power command of each flywheel unit will be set to zero; In response to the inconsistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, it calculates a power allocation coefficient related to the direction of the power command based on the difference in the state of charge of each flywheel unit, introduces an acceleration factor to correct the power allocation coefficient, determines the output power of each flywheel unit based on the corrected power allocation coefficient, and performs power adjustment and power limiting on the allocated output power. If the flywheel energy storage array does not receive a power command, the power output of each flywheel unit is adjusted so that the state of charge of all flywheel units in the flywheel energy storage array tends to be consistent.

[0007] Further, determining whether the state of charge of all flywheel units in the flywheel energy storage array is consistent includes: The absolute value of the calculated difference in state of charge between any two flywheel units is compared with a preset allowable deviation threshold. If all the absolute values ​​are less than or equal to the allowable deviation threshold, then all flywheel units are determined to have the same state of charge. If any of the absolute values ​​is greater than the allowable deviation threshold, then the charge state of all flywheel units is determined to be inconsistent.

[0008] Furthermore, the output power command for each flywheel unit is determined, including: Determine the number of flywheel units currently participating in power distribution in the flywheel energy storage array; The power command value received by the flywheel energy storage array is divided by the number of flywheel units to obtain a quotient value, which is then used as the output power command for each flywheel unit.

[0009] Furthermore, based on the differences in the state of charge of each flywheel unit, a power allocation coefficient related to the power command direction is calculated, including: When the power command is a discharge command, the power allocation coefficient of any flywheel unit is equal to the state of charge of that flywheel unit divided by the sum of the states of charge of all flywheel units. When the power command is a charging command, the power allocation coefficient of any flywheel unit is equal to the state of charge supplement value of that flywheel unit divided by the sum of the state of charge supplement values ​​of all flywheel units, and the state of charge supplement value is equal to a minus the state of charge. The output power of each flywheel unit is determined according to the power distribution coefficient.

[0010] Furthermore, an acceleration factor is introduced to correct the power allocation coefficient, including: The acceleration factor for each flywheel unit is determined based on the average state of charge influence factor, speed influence factor, and inverter current influence factor. The power distribution coefficient is corrected using the acceleration factor, and the output power of each flywheel unit is determined based on the corrected power distribution coefficient.

[0011] Furthermore, the method for determining the average state of charge influence factor is as follows: Calculate the average state of charge of the flywheel energy storage array; Using one as a baseline, add a first constant multiplied by the difference between the current flywheel unit's state of charge and the average state of charge to obtain the average state of charge influence factor.

[0012] Furthermore, the method for determining the speed influence factor is related to the direction of the power command: When the power command is a discharge command, the speed influence factor is equal to one plus a second constant multiplied by the real-time speed of the flywheel unit; When the power command is a charging command, the speed influence factor is equal to one minus the second constant multiplied by the real-time speed of the flywheel unit.

[0013] Furthermore, the inverter current influence factor is determined as follows: Using one as a baseline, add a third constant multiplied by the inverter current of the flywheel unit to obtain the inverter current influence factor.

[0014] Furthermore, the method of dynamically adjusting the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power regulation mechanism: The power regulation coefficient is calculated based on the state of charge of each flywheel unit; The power adjustment coefficient is multiplied by the allocated power to perform a secondary power adjustment; When the state of charge of the flywheel unit exceeds or falls below the preset upper limit of the state of charge, the output power of the flywheel unit is set to zero.

[0015] Furthermore, the calculation method of the power regulation coefficient is related to the direction of the power command: When the power command is a discharge command, the power adjustment coefficient is calculated as follows: ; When the power command is a charging command, the power adjustment coefficient is calculated as follows: ; Where, β i The power regulation coefficient is K, which is a constant, and the state of charge (SOC) is... i For flywheel unit i, SOCdL With SOC dH These are the lower and upper limits of the adjustment range during discharge, respectively, and the SOC. cL With SOC cH These are the lower and upper limits of the adjustment range during charging, respectively.

[0016] Furthermore, the method of dynamically adjusting the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power limiting mechanism: The power allocated to each flywheel unit is compared with its rated power; If the allocated power is greater than the rated power, then the output power command of the flywheel unit is set to its rated power.

[0017] Furthermore, the power limiting mechanism also includes power redistribution: Calculate the total power limited by the flywheel unit whose output power commands are all restricted to rated power; The remaining power to be allocated is obtained by subtracting the total power from the received power command; Among the remaining flywheel units whose output power command has not reached the rated power, the power distribution coefficient is recalculated and the acceleration factor is reintroduced for correction in order to complete the power redistribution.

[0018] Furthermore, adjusting the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array tend to be consistent includes: Calculate the power release factor for each flywheel unit, which increases as the difference in state of charge between flywheel units increases; The output power of each flywheel unit is determined based on the power release coefficient and the rated power of each flywheel unit. Reduce the output power of flywheel units whose state of charge is greater than the minimum state of charge of the array, so that their state of charge tends to the minimum state of charge.

[0019] Furthermore, the power release coefficient is calculated as follows: Calculate the difference between the current state of charge of the flywheel unit and the lowest state of charge in the array, divide it by the lowest state of charge, and obtain the first term; The second term is obtained by averaging the differences in the state of charge between the current flywheel unit and all other flywheel units in the array. Add the first term to the second term, and then multiply by the preset adjustment factor to obtain the power release coefficient.

[0020] Furthermore, adjusting the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array tend to be consistent also includes: When the state of charge of any flywheel unit in the flywheel array falls below the preset minimum allowable value, the state of charge of other flywheel units is limited to decrease further, so that their state of charge drops to a preset protection value.

[0021] Furthermore, the state of charge is calculated based on the current rotational speed of the flywheel unit and its upper and lower speed limits: ; Among them, SOC i Let ω be the charge state of flywheel unit i. i ω represents the current rotational speed of flywheel unit i. i,max and ω i,min These are the upper and lower speed limits of flywheel unit i, respectively.

[0022] Compared with existing technologies, the advantages of this invention lie in its ability to accurately identify the state of charge (SOC) distribution of the flywheel array by calculating the absolute value of the SOC difference between any two flywheel units and comparing it with a threshold. This allows the system to quickly enter an equal-power distribution mode to improve response speed when SOCs are consistent, and to promptly switch to a dynamic power correction mode or a gradual SOC adjustment mode to accelerate SOC convergence when SOCs are inconsistent. This mode-switching mechanism based on a quantized threshold ensures a smooth transition of the flywheel energy storage array under different operating conditions, avoids system oscillations caused by mode misjudgment or frequent switching, and improves system stability and reliability.

[0023] Furthermore, this invention, by ensuring equal power distribution under the premise of consistent state of charge, ensures that each flywheel unit participates in power release equally, avoiding some units from bearing excessive power burden while others remain idle, thereby maximizing the overall energy utilization efficiency of the flywheel energy storage array. Simultaneously, since the output power of each unit is equal, the rate of change of the state of charge of each flywheel unit is also consistent, which helps maintain the state of charge balance of the flywheel array and prevents new differences in state of charge caused by uneven distribution.

[0024] Furthermore, this invention achieves differentiated power allocation under discharge and charging conditions. Under a discharge command, the power allocation coefficient is directly proportional to the state of charge (SOC) of the flywheel unit; the flywheel unit with a higher SOC undertakes more discharge power, thereby fully utilizing the energy output capacity of high-energy-storage units. Under a charging command, the power allocation coefficient is inversely proportional to the SOC of the flywheel unit; the flywheel unit with a lower SOC undertakes more charging power, thereby prioritizing the replenishment of energy reserves in low-energy-storage units. This ensures that the SOC of each unit in the flywheel array gradually becomes consistent during charging and discharging, effectively avoiding the risk of overcharging or over-discharging some units.

[0025] Furthermore, this invention achieves long-term load balancing among flywheel units through a rotation scheduling mechanism. Rotation scheduling is triggered when the state of charge is consistent, without interfering with the original power allocation logic based on state of charge. By prioritizing the operation of units with shorter cumulative operating time, rotation scheduling effectively prevents some units from prematurely aging due to long-term operation. Simultaneously, rotation scheduling considers dynamic adjustments when power commands change, maximizing the utilization of rotation opportunities while ensuring the response to total power commands.

[0026] Furthermore, this invention introduces an acceleration factor to further improve the convergence speed of the flywheel array's state of charge (SOC) in the dynamic power correction mode. This acceleration factor comprehensively considers three key factors: the average SOC of the flywheel array, the real-time rotational speed of the flywheel units, and the inverter current. The average SOC factor ensures that flywheel units with an SOC above the average receive a larger power allocation coefficient, while those with an SOC below the average receive a smaller power allocation coefficient, thereby accelerating the discharge of high-SOC units or inhibiting their charging. The rotational speed factor ensures that high-speed flywheels bear more power and low-speed flywheels bear less power during discharge, and vice versa during charging. This aligns with the physical characteristics of flywheel energy storage systems and avoids unreasonable energy distribution caused by a single factor. The inverter current factor dynamically adjusts the power allocation based on the actual charge and discharge rates; a higher current means a faster energy exchange rate, resulting in a greater power allocation, and vice versa. The acceleration factor, obtained by multiplying these three factors, comprehensively and dynamically reflects the overall state of the flywheel units, allowing for refined correction of the power allocation coefficient. Compared with traditional strategies that rely solely on the proportion of state of charge (SOC), this invention significantly shortens the convergence time of the SOC of the flywheel array by introducing an acceleration factor. At the same time, it avoids drastic power fluctuations caused by excessive pursuit of convergence speed. Under the premise of ensuring system stability, it achieves rapid SOC equilibrium and further improves the overall operating efficiency and dynamic response capability of the flywheel energy storage system.

[0027] Furthermore, this invention achieves flexible adjustment of control bias by selecting and switching multiple sets of preset parameters. Compared to schemes that continuously adjust parameters in real time, it avoids the complexity and instability of parameter adjustment. The parameter group switching logic is simple, clear, and easy to implement in engineering. The smooth transition mechanism between parameter groups avoids power jumps caused by sudden parameter changes. The strategy of selecting parameter groups according to priority ensures that the system can prioritize safe operation when safety is threatened. It enables the flywheel energy storage system to automatically select the optimal control bias according to different operating states, achieving the best power distribution effect under different operating conditions.

[0028] Furthermore, this invention introduces a power regulation coefficient based on the logistic function to perform secondary adjustment of power allocation, effectively preventing overcharging and over-discharging of the flywheel unit. This power regulation mechanism dynamically adjusts the actual power allocated to the flywheel unit based on its current state of charge: in discharge mode, when the flywheel unit's state of charge approaches the lower limit of the discharge regulation range, the power regulation coefficient smoothly decreases as the state of charge decreases, thereby gradually limiting the discharge power and avoiding over-discharge; in charging mode, when the flywheel unit's state of charge approaches the upper limit of the charging regulation range, the power regulation coefficient smoothly decreases as the state of charge increases, thereby gradually limiting the charging power and avoiding overcharging. Through the smoothing characteristics of the logistic function, the power regulation coefficient changes continuously as the state of charge approaches the boundary, avoiding power oscillations caused by abrupt changes.

[0029] Furthermore, this invention achieves passive state-of-charge (SOC) balancing by employing a progressive SOC adjustment mode when the flywheel energy storage array receives no power command and the SOCs of its units are inconsistent. This mode dynamically adjusts the output power of each flywheel unit by calculating a power release coefficient. This coefficient comprehensively considers the difference between the current flywheel unit and the array's lowest SOC, as well as the average difference between the unit's SOC and all other units. These two factors are superimposed and multiplied by an adjustment factor, resulting in flywheel units with larger SOC differences receiving larger power release coefficients, thereby releasing more power to accelerate SOC convergence. Attached Figure Description

[0030] Figure 1 This is a control flowchart of the power optimization method for a multi-mode control flywheel energy storage system combined with acceleration factors according to an embodiment of this application; Figure 2 This is a schematic diagram showing the relationship between the power regulation coefficient and the state of charge in the discharge mode of an embodiment of this application; Figure 3 This is a schematic diagram showing the relationship between the power regulation coefficient and the state of charge in the charging mode of an embodiment of this application. Detailed Implementation

[0031] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0032] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0033] like Figure 1 As shown, the technical solution provided in this application includes the following steps: Obtain the current rotational speed, upper speed limit, and lower speed limit of each flywheel unit in the flywheel energy storage array. Based on the squared difference between the current rotational speed of each flywheel unit and its upper and lower speed limits, calculate the state of charge of each flywheel unit. Calculate the absolute value of the difference in state of charge between any two flywheel units, and determine whether the state of charge of all flywheel units is consistent based on the absolute value; In response to the consistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, the output power command of each flywheel unit is determined based on the power command received by the flywheel energy storage array and the number of flywheel units; If the flywheel energy storage array does not receive a power command, the output power command of each flywheel unit will be set to zero; In response to the inconsistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, it calculates a power allocation coefficient related to the direction of the power command based on the difference in the state of charge of each flywheel unit, introduces an acceleration factor to correct the power allocation coefficient, determines the output power of each flywheel unit based on the corrected power allocation coefficient, and performs power adjustment and power limiting on the allocated output power. If the flywheel energy storage array does not receive a power command, the power output of each flywheel unit is adjusted so that the state of charge of all flywheel units in the flywheel energy storage array tends to be consistent.

[0034] Specifically, determining whether the state of charge of all flywheel units in the flywheel energy storage array is consistent includes: The absolute value of the calculated difference in state of charge between any two flywheel units is compared with a preset allowable deviation threshold. If all the absolute values ​​are less than or equal to the allowable deviation threshold, then all flywheel units are determined to have the same state of charge. If any of the absolute values ​​is greater than the allowable deviation threshold, then the charge state of all flywheel units is determined to be inconsistent.

[0035] In this embodiment of the invention, the allowable deviation threshold is determined based on the rated capacity of the flywheel energy storage system, the number of flywheel units, and the safe operating range of the state of charge (SOC). Specifically, it is set at 1% to 5% of the length of the safe operating range of the SOC of the flywheel units. Furthermore, the proportional coefficient can be dynamically adjusted according to the real-time operating conditions of the flywheel energy storage system: when the system is under conditions of drastic load fluctuations, a smaller proportional coefficient (e.g., 1%) is used to improve the sensitivity of mode switching, enabling the system to quickly respond to changes in SOC and switch to a suitable power distribution mode in a timely manner; when the system is under steady-state operation, a larger proportional coefficient (e.g., 5%) is used to avoid frequent mode switching caused by minor disturbances, thereby reducing the computational burden on the control system and system oscillations caused by mode switching.

[0036] To achieve the aforementioned adaptive adjustment, the system monitors the following operating parameters in real time: the frequency and amplitude of power command changes, the rate of change of the flywheel array's state of charge, and the fluctuation rate of the load current. When the power command change frequency exceeds a preset frequency threshold or the load current fluctuation rate exceeds a preset fluctuation rate threshold, the system is determined to be in dynamic operation, and the proportional gain is automatically switched to a smaller value. When all the above parameters are below their corresponding thresholds and the duration exceeds a preset stabilization time threshold, the system is determined to be in steady-state operation, and the proportional gain is automatically switched to a larger value. The proportional gain switching adopts a hysteresis comparison method, that is, the threshold for switching from dynamic operation to steady-state operation is lower than the threshold for switching from steady-state operation to dynamic operation, to avoid frequent jumps in the proportional gain near the critical point.

[0037] Define the SOC difference between each pair of flywheel units i and j as: ; Among them, SOC i With SOC j The SOC values ​​of flywheel units i and j are ΔSOC, respectively. ij This represents the SOC difference between flywheel unit i and flywheel unit j.

[0038] This invention calculates the absolute value of the state of charge (SOC) difference between any two flywheel units and compares it to a threshold value. This allows the system to accurately identify the SOC distribution of the flywheel array. When the SOCs are consistent, the system quickly enters an equal-power distribution mode to improve response speed. When the SOCs are inconsistent, it promptly switches to a dynamic power correction mode or a gradual SOC adjustment mode to accelerate SOC convergence. This mode-switching mechanism based on a quantized threshold ensures a smooth transition of the flywheel energy storage array under different operating conditions, avoiding system oscillations caused by mode misjudgment or frequent switching, and improving system stability and reliability.

[0039] In this embodiment of the invention, to prevent frequent mode switching (i.e., "mode jitter") caused by fluctuations in the state of charge near a threshold boundary in multi-mode switching control, a mode switching anti-jitter and hysteresis control mechanism based on operating state characteristics is introduced. This mechanism ensures the stability and reliability of mode switching by setting an anti-jitter timer and a hysteresis comparator. The function of the anti-jitter timer is: when the system detects a change in the judgment result of the state of charge consistency (from consistent to inconsistent, or from inconsistent to consistent), it does not immediately execute a mode switch, but instead starts the anti-jitter timer. Only after the judgment result remains unchanged for a duration exceeding a preset anti-jitter time threshold is the actual mode switch executed. If the judgment result returns to its original state within the anti-jitter time, the switching operation is canceled. The anti-jitter time threshold can be adaptively adjusted according to the system operating conditions: a shorter time is used under dynamic operating conditions to ensure response speed, and a longer time is used under steady-state operating conditions to ensure stability.

[0040] The hysteresis comparator functions by setting two different thresholds for consistency judgment: a switch-out threshold and a switch-back threshold. When the system is currently in equal power distribution mode, a larger switch-out threshold is used; that is, switching to dynamic power correction mode only occurs when the state of charge difference exceeds this larger threshold. When the system is currently in dynamic power correction mode, a smaller switch-back threshold is used; that is, switching back to equal power distribution mode only occurs when the state of charge difference falls below this smaller threshold. This hysteresis comparison method creates an insensitive range around the threshold, making mode switching directionally dependent and effectively avoiding repeated switching caused by small fluctuations in the state of charge around a single threshold. The anti-jitter timer works in conjunction with the hysteresis comparator: first, the hysteresis comparator filters out small fluctuations around the threshold, and then the anti-jitter timer confirms the persistence of the judgment result. Together, they suppress mode jitter to the greatest extent possible.

[0041] In addition, the system adaptively adjusts the anti-jitter time threshold and hysteresis width based on the current operating conditions. When the system is detected to be in a dynamic operating condition with drastic load fluctuations and rapid changes in state of charge, the anti-jitter time is shortened and the hysteresis width is reduced to improve the sensitivity and response speed of mode switching; when the system is in a steady-state operating condition, the anti-jitter time is extended and the hysteresis width is increased to enhance the stability of mode switching.

[0042] Specifically, determining the output power command for each flywheel unit includes: Determine the number of flywheel units currently participating in power distribution in the flywheel energy storage array; The power command value received by the flywheel energy storage array is divided by the number of flywheel units to obtain a quotient value, which is then used as the output power command for each flywheel unit.

[0043] In this embodiment of the invention, the equal power allocation mode refers to the mode that is automatically entered when there is a power command and all flywheel units in the system have the same SOC. In this mode, the system follows the equal power allocation principle, that is, the power allocation of each flywheel unit will be completely equal, and no weight adjustment will be made according to the load of the flywheel unit or other factors.

[0044] In this mode, the power output of each flywheel unit is evenly distributed, with each flywheel unit bearing the same power output. This simple and efficient control strategy ensures that each flywheel unit participates in power release equally when the system's SOC is consistent, thereby maximizing system efficiency and preventing some flywheel units from bearing excessive power while others remain idle. The output power Pi* of each flywheel unit is shown below: .

[0045] This invention ensures that each flywheel unit participates in power release equally under the premise of consistent state of charge, avoiding some units from bearing excessive power burden while others remain idle, thereby maximizing the overall energy utilization efficiency of the flywheel energy storage array. Simultaneously, since the output power of each unit is equal, the rate of change of the state of charge of each flywheel unit is also consistent, which helps maintain the state of charge balance of the flywheel array and prevents new differences in state of charge caused by uneven distribution.

[0046] Specifically, the power allocation coefficient related to the power command direction is calculated based on the differences in the state of charge of each flywheel unit, including: When the power command is a discharge command, the power allocation coefficient of any flywheel unit is equal to the state of charge of that flywheel unit divided by the sum of the states of charge of all flywheel units. When the power command is a charging command, the power allocation coefficient of any flywheel unit is equal to the state of charge supplement value of that flywheel unit divided by the sum of the state of charge supplement values ​​of all flywheel units, and the state of charge supplement value is equal to a minus the state of charge. The output power of each flywheel unit is determined according to the power distribution coefficient.

[0047] In this embodiment of the invention, the power allocation coefficient α i The power allocation ratio of flywheel unit i is determined based on its SOC (State of Charge) value. Calculate the power allocation factor for flywheel unit i: ; Where, α i Let SOC be the power distribution factor for flywheel unit i. i Let d be the state of charge of flywheel unit i, d be the number of flywheel units participating in power distribution, and P be the state of charge of flywheel unit i. d Total power to be allocated (P)d >0 indicates a discharge command, P d <0 indicates a charging command.

[0048] This invention achieves differentiated power allocation under discharge and charging conditions. Under a discharge command, the power allocation coefficient is directly proportional to the state of charge (SOC) of the flywheel unit; the flywheel unit with a higher SOC undertakes more discharge power, thus fully utilizing the energy output capacity of high-energy-storage units. Under a charging command, the power allocation coefficient is inversely proportional to the SOC of the flywheel unit; the flywheel unit with a lower SOC undertakes more charging power, thus prioritizing the replenishment of energy reserves in low-energy-storage units. This ensures that the SOC of each unit in the flywheel array gradually becomes consistent during charging and discharging, effectively avoiding the risk of overcharging or over-discharging some units.

[0049] In this embodiment of the invention, in the dynamic power correction mode, the system not only calculates the power allocation coefficient based on the current state of charge (SOC), but also introduces a predictive pre-adjustment mechanism based on the SOC change trend. This mechanism monitors the rate of change of the SOC of each flywheel unit, predicts the direction of SOC evolution over a future period, and performs compensatory adjustments in advance during power allocation to avoid power allocation lag caused by response delay.

[0050] Specifically, the system calculates the rate of change of the state of charge (SOC) of each flywheel unit in real time, i.e., the increase or decrease in SOC per unit time. When there are multiple flywheel units in the flywheel array and their SOC change rates differ significantly, the system recalculates the power distribution factor based on the predicted future SOC values, rather than relying solely on the current SOC values. The prediction duration can be adaptively adjusted according to system operating conditions: a longer prediction duration is used to respond earlier when the system is in a dynamic operating condition with drastic load changes; a shorter prediction duration or disabling the pre-conditioning mechanism is used when the system is in a steady-state operating condition.

[0051] The specific implementation of pre-regulation is as follows: For a discharge command, if the state of charge (SOC) of a certain flywheel unit decreases significantly faster than that of other units, the system predicts that the SOC of that unit will be lower than that of other units in the short term. Therefore, in the current power allocation, the output power of that unit is appropriately reduced, and some power is transferred to units with a slower SOC decrease. For a charging command, if the SOC of a certain flywheel unit increases significantly faster than that of other units, the system predicts that the SOC of that unit will be higher than that of other units in the short term. Therefore, in the current power allocation, the charging power of that unit is appropriately reduced, and some power is transferred to units with a slower SOC increase.

[0052] In addition, the system incorporates a rate-of-charge smoothing mechanism to filter the measured values ​​of the rate of change of state of charge, avoiding pre-regulation malfunctions caused by measurement noise. The strength of the pre-regulation increases as the difference in the rate of change of state of charge increases and decreases as the difference decreases, achieving smooth and adaptive pre-regulation control.

[0053] In this embodiment of the invention, after power allocation is completed in the dynamic power correction mode, a flywheel unit rotation scheduling mechanism is added. This mechanism, without changing the original power allocation principle based on state of charge, serves as a supplementary scheduling step after power allocation is completed, and is used to achieve long-term load balancing among flywheel units.

[0054] The trigger condition for the rotation scheduling mechanism is that the maximum difference between the states of charge of all flywheel units in the flywheel energy storage array is less than the preset rotation trigger threshold. When this trigger condition is met, it indicates that the states of charge of each flywheel unit have become consistent, and rotation scheduling can be carried out without affecting the rationality of power allocation.

[0055] The specific execution method of the rotation scheduling is as follows: The system records the cumulative running time (or cumulative output energy) of each flywheel unit within a preset time window, and sorts the flywheel units in descending order of cumulative running time. Based on the current total power command and the number of flywheel units, the system calculates the minimum number of flywheel units required to operate simultaneously, N_min = ceil(P_total / P_rated), where P_total is the total power command, P_rated is the rated power of a single flywheel unit, and ceil is the rounding function. The system selects the units responsible for power output from the N_min flywheel units with the minimum cumulative running time, and sets the remaining flywheel units to a rotation state (output power command set to zero). Flywheel units in the rotation state do not participate in power output, but their state of charge remains unchanged. They can participate in power distribution normally after the rotation ends. The switching cycle of the rotation scheduling can be preset according to the system operating characteristics, for example, rotating every 30 minutes. If the system power command changes during the rotation cycle, resulting in a change in the required number of operating units, the rotation scheduling is re-executed. During the rotation scheduling process, priority is given to maintaining the status of currently running units, and adjustments are only made to newly added units that need to be run or stopped, in order to reduce the number of unit start-ups and shutdowns.

[0056] This invention achieves long-term load balancing among flywheel units through a rotation scheduling mechanism. Rotation scheduling is triggered when the state of charge (SOC) is consistent, without interfering with the original SOC-based power allocation logic. By prioritizing units with shorter cumulative operating time, rotation scheduling effectively prevents some units from prematurely aging due to long-term operation. Simultaneously, rotation scheduling considers dynamic adjustments when power commands change, maximizing the utilization of rotation opportunities while ensuring the overall power command response. Rotation scheduling is only an optional supplementary mechanism after power allocation has been completed in equal power allocation mode or dynamic power correction mode, and when the SOC is consistent.

[0057] Specifically, an acceleration factor is introduced to correct the power allocation coefficient, including: The acceleration factor for each flywheel unit is determined based on the average state of charge influence factor, speed influence factor, and inverter current influence factor. The power distribution coefficient is corrected using the acceleration factor, and the output power of each flywheel unit is determined based on the corrected power distribution coefficient.

[0058] Specifically, the method for determining the average state of charge influence factor is as follows: Calculate the average state of charge of the flywheel energy storage array; Using one as a baseline, add a first constant multiplied by the difference between the current flywheel unit's state of charge and the average state of charge to obtain the average state of charge influence factor.

[0059] Specifically, the method for determining the speed influence factor is related to the direction of the power command: When the power command is a discharge command, the speed influence factor is equal to one plus a second constant multiplied by the real-time speed of the flywheel unit; When the power command is a charging command, the speed influence factor is equal to one minus the second constant multiplied by the real-time speed of the flywheel unit.

[0060] Specifically, the inverter current influence factor is determined as follows: Using one as a baseline, add a third constant multiplied by the inverter current of the flywheel unit to obtain the inverter current influence factor.

[0061] In this embodiment of the invention, to accelerate the uniform convergence speed of the State of Charge (SOC) of each flywheel unit, an acceleration factor is introduced in the dynamic power regulation mode to speed up the uniform convergence speed of the SOC. The acceleration factor mainly considers three factors: the average SOC of the flywheel array, the speed of the flywheel unit, and the inverter current.

[0062] First, calculate the average SOC of the flywheel array. avg ;

[0063] Where δ is the average SOC influence factor of the flywheel array, and a is a constant used to adjust the magnitude of the influence factor of δ.

[0064] When SOC is larger than the average SOC, SOC i -SOC avg When the SOC is greater than 0, the coefficient δ will be greater than 1, leading to an increase in the coefficient. This indicates that a flywheel with a high SOC will allocate more power, consistent with the working principle of flywheel energy storage systems in practice. When the flywheel's SOC is high, it can provide more energy to accelerate the system's operation. When the SOC is lower than the average SOC, the SOC... i -SOC avg If the value is greater than 0, the coefficient δ will be less than 1, resulting in a decrease in the coefficient. The flywheel with a low SOC provides less power, thus avoiding excessive power allocation to the flywheel with a low SOC.

[0065] The second part explains the effect of rotational speed on power distribution: ; Where ε is the rotational speed influence factor, and b is a constant used to adjust the magnitude of the influence factor of ε.

[0066] In discharge mode, when the rotational speed is high, ω i A larger ω results in a larger coefficient, meaning a higher-speed flywheel will distribute more power. This reflects that during flywheel acceleration, a higher speed means the flywheel can release more energy for the system to use. When the speed is lower, ω... i The flywheel has a smaller coefficient, meaning it provides less power at lower speeds, resulting in relatively less power output during discharge. In charging mode, when the speed is higher, ω... i A larger value results in a smaller coefficient, meaning a high-speed flywheel will distribute less power. When the speed is low, ω... i The smaller the value, the larger the coefficient, meaning that the flywheel at low speeds will distribute more power.

[0067] The third part discusses the impact of inverter current on power distribution: ; Where μ is the inverter current influence factor, and c is a constant used to adjust the magnitude of the influence factor of μ, I i This represents the inverter current of flywheel unit i.

[0068] A higher inverter current means a faster flywheel charging and discharging rate, indicating a larger power distribution across the flywheel. Therefore, the current magnitude directly reflects the flywheel's charging or discharging rate. In charging mode, a lower current results in a slower flywheel charging and discharging rate, meaning less power is released. Low current means a slower energy exchange rate, necessitating a reduction in power distribution.

[0069] Ultimately, combining these three formulas yields the acceleration factor. i: .

[0070] This invention introduces an acceleration factor to further improve the convergence speed of the flywheel array's state of charge (SOC) in a dynamic power correction mode. This acceleration factor comprehensively considers three key factors: the average SOC of the flywheel array, the real-time rotational speed of the flywheel units, and the inverter current. Specifically, the average SOC factor ensures that flywheel units with an SOC above the average receive a larger power allocation coefficient, while those with an SOC below the average receive a smaller power allocation coefficient, thereby accelerating the discharge of high-SOC units or inhibiting their charging. The rotational speed factor ensures that high-speed flywheels bear more power and low-speed flywheels bear less power during discharge, and vice versa during charging, which aligns with the physical characteristics of flywheel energy storage systems and avoids unreasonable energy distribution caused by a single factor. The inverter current factor dynamically adjusts the power allocation according to the actual charge and discharge rates; a higher current means a faster energy exchange rate, resulting in more power allocation, and vice versa. The acceleration factor, obtained by multiplying these three factors, comprehensively and dynamically reflects the overall state of the flywheel units, allowing for refined correction of the power allocation coefficient. Compared with traditional strategies that rely solely on the proportion of state of charge (SOC), this invention significantly shortens the convergence time of the SOC of the flywheel array by introducing an acceleration factor. At the same time, it avoids drastic power fluctuations caused by excessive pursuit of convergence speed. Under the premise of ensuring system stability, it achieves rapid SOC equilibrium and further improves the overall operating efficiency and dynamic response capability of the flywheel energy storage system.

[0071] In this embodiment of the invention, multiple sets of acceleration factor parameter combinations are preset, each set corresponding to a different control bias: Balance Priority Group: Parameter a has a larger value, while b and c have smaller values. This set of parameters strengthens the adjustment effect of the average state of charge (SPC) factor on power distribution, suitable for scenarios where flywheel array SPC differences are large and rapid balancing is required. Response Priority Group: Parameters b and c have larger values, while a has a smaller value. This set of parameters strengthens the adjustment effect of the speed influence factor and inverter current influence factor on power distribution, suitable for scenarios where power commands change frequently and rapid dynamic response is required. Safety Priority Group: Parameter a has a larger value, and a boundary weight factor is added to the SPC factor, enabling flywheel units with SPCs close to the safety boundary to receive stronger adjustment. This set of parameters is suitable for scenarios where SPCs are close to the safe operating boundary and safety needs to be prioritized.

[0072] The system automatically selects the matching parameter group based on the current operating status. The selection logic is as follows: when the maximum difference in the state of charge of the flywheel array is greater than the first difference threshold (e.g., 0.15), the equalization priority group is selected; when the maximum difference in the state of charge of the flywheel array is less than or equal to the first difference threshold, but the power command change frequency is greater than the frequency threshold (e.g., 5 times per minute) or the power change rate is greater than the change rate threshold (e.g., 100kW / s), the response priority group is selected; when the state of charge of any flywheel unit is lower than the safety lower limit threshold (e.g., 0.25) or higher than the safety upper limit threshold (e.g., 0.75), the safety priority group is selected; when multiple conditions are met simultaneously, the selection is based on the priority order of safety priority > equalization priority > response priority. The parameter group switching adopts a smooth transition method: the current acceleration factor value is maintained at the moment of switching, and then linear interpolation is performed within a preset transition time (e.g., 100 milliseconds) to transition to the acceleration factor corresponding to the new parameter group, avoiding power jumps caused by parameter abrupt changes.

[0073] This invention achieves flexible adjustment of control bias by selecting and switching multiple sets of preset parameters. Compared to schemes that adjust parameters continuously in real time, it avoids the complexity and instability of parameter adjustment. The parameter group switching logic is simple, clear, and easy to implement in engineering. The smooth transition mechanism between parameter groups avoids power jumps caused by sudden parameter changes. The strategy of selecting parameter groups according to priority ensures that the system can prioritize safe operation when safety is threatened. It enables the flywheel energy storage system to automatically select the optimal control bias according to different operating states, achieving the best power distribution effect under different operating conditions.

[0074] Specifically, the dynamic adjustment of the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power regulation mechanism: The power regulation coefficient is calculated based on the state of charge of each flywheel unit; The power adjustment coefficient is multiplied by the allocated power to perform a secondary power adjustment; When the state of charge of the flywheel unit exceeds or falls below the preset upper limit of the state of charge, the output power of the flywheel unit is set to zero.

[0075] Specifically, the calculation method of the power regulation coefficient is related to the direction of the power command: When the power command is a discharge command, the power adjustment coefficient is calculated as follows: ; In this embodiment of the invention, K is a constant, which affects the shape of the Logistic curve. A larger value of K makes the Logistic function curve steeper, meaning that the power adjustment coefficient β... i When the SOC value is close to its upper or lower limit, it changes rapidly, allowing the system to respond more quickly to changes in SOC; conversely, a smaller K value makes the curve flatter, slowing down the power regulation response. In practical applications, by adjusting the value of K, the flexibility of the power allocation strategy can be precisely controlled to adapt to the operating requirements under different load and environmental conditions. dL With SOC dH These represent the lower and upper limits of the adjustment range during discharge, respectively. When the SOC value of the flywheel unit is within the adjustment range, the power regulation coefficient βi will smoothly adjust as the SOC value changes. Specifically, during discharge, the power regulation coefficient βi will adjust as the SOC approaches the lower limit of the adjustment range. dL And it keeps decreasing. K=40, SOC dL =0.2, SOC dH When β = 0.4, the adjustment coefficient β i The relationship with the flywheel unit SOC is as follows: Figure 2 As shown.

[0076] When the power command is a charging command, the power adjustment coefficient is calculated as follows: ; In the formula, SOC cL With SOC cH These represent the lower and upper limits of the adjustment range during charging, respectively. When the SOC value of the flywheel unit is within the adjustment range, the power regulation coefficient β... i It will adjust smoothly as the SOC value changes. Specifically, the power regulation coefficient β during charging... i The adjustment range will be adjusted as the SOC approaches the upper limit. dL And it keeps decreasing. K=40, SOC cL =0.6, SOC cH When βi = 0.8, the relationship between the adjustment coefficient βi and the SOC of the flywheel unit is as follows: Figure 3 As shown.

[0077] In this embodiment of the invention, to prevent overcharging or over-discharging of the flywheel units in the flywheel energy storage array, a power regulation coefficient β is introduced. i This is used for secondary adjustment of power distribution under different State of Charge (SOC) states. The charge and discharge state of a flywheel unit is typically affected by its SOC value. When the SOC value is too high or too low, the charge and discharge state of the flywheel unit may enter unreasonable extremes, thereby damaging the performance of the flywheel unit or shortening its lifespan. To avoid this situation, the power regulation coefficient β... i The power allocation of each flywheel unit can be dynamically adjusted based on its State of Charge (SOC), ensuring that each flywheel unit remains within a reasonable charge / discharge range. The upper and lower limits of the flywheel unit's SOC are set to 0.8 and 0.2, respectively. This means that when the flywheel unit's SOC is close to 0.8, the flywheel should reduce charging; and when the SOC is close to 0.2, the flywheel should reduce discharging and avoid over-discharging. To achieve this control, the power regulation coefficient βi is calculated based on the flywheel unit's SOC and smoothly adjusted using a Logistic function.

[0078] This invention introduces a power regulation coefficient based on the logistic function to perform secondary adjustment of power allocation, effectively preventing overcharging and over-discharging of the flywheel unit. This power regulation mechanism dynamically adjusts the actual power allocated to the flywheel unit based on its current state of charge: in discharge mode, when the flywheel unit's state of charge approaches the lower limit of the discharge regulation range, the power regulation coefficient smoothly decreases as the state of charge decreases, thereby gradually limiting the discharge power and avoiding over-discharge; in charging mode, when the flywheel unit's state of charge approaches the upper limit of the charging regulation range, the power regulation coefficient smoothly decreases as the state of charge increases, thereby gradually limiting the charging power and avoiding overcharging. Through the smoothing characteristics of the logistic function, the power regulation coefficient changes continuously as the state of charge approaches the boundary, avoiding power oscillations caused by abrupt changes.

[0079] As an alternative implementation, to reduce the computational complexity of the logistic function in embedded controllers, this invention provides a piecewise linear approximation as a replacement for the logistic function. The piecewise linear approximation divides the adjustment range into several continuous intervals, and within each interval, it approximates the logistic function with a linear function, replacing complex exponential operations with simple multiplication and addition operations.

[0080] Taking the discharge mode as an example, let the lower limit of the discharge adjustment range be SOC_dL and the upper limit be SOC_dH. Divide the adjustment range into several equally divided intervals. The calculation formula for the piecewise linearization approximation is: ; Among them, SOCmid1 SOC mid2 The intervals are defined by points k1 and k2, and the slopes and intercepts b1 and b2 of each linear interval are determined by fitting the logistic function curve. The number of segments can be selected according to the accuracy requirements; more segments result in higher accuracy but also greater computational burden. In practical applications, dividing the adjustment range into 3 to 5 linear intervals is usually sufficient to meet engineering accuracy requirements. Taking the charging mode as an example, a similar piecewise linearization approximation formula is used, with the adjustment range from SOC_cL to SOC_cH. The power regulation coefficient decreases as the state of charge increases. To achieve the piecewise linearization approximation, the system pre-stores the boundary point parameters and corresponding slopes and intercepts for each linear interval. During real-time calculation, the current state of charge is first determined to belong to the corresponding interval, and then a multiplication and an addition operation are performed to obtain the power regulation coefficient.

[0081] Specifically, the dynamic adjustment of the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power limiting mechanism: The power allocated to each flywheel unit is compared with its rated power; If the allocated power is greater than the rated power, then the output power command of the flywheel unit is set to its rated power.

[0082] Specifically, the power limiting mechanism also includes power redistribution: Calculate the total power limited by the flywheel unit whose output power commands are all restricted to rated power; The remaining power to be allocated is obtained by subtracting the total power from the received power command; Among the remaining flywheel units whose output power command has not reached the rated power, the power distribution coefficient is recalculated and the acceleration factor is reintroduced for correction in order to complete the power redistribution.

[0083] In this embodiment of the invention, the power allocated to flywheel unit i is: ; As can be seen, when the SOC value of a flywheel unit is within the set adjustment range, its charging and discharging power is limited by the power adjustment coefficient. This adjustment mechanism ensures that the flywheel unit always remains within a reasonable energy distribution range during charging and discharging, avoiding energy waste or system instability caused by excessive power output. When the SOC value of the flywheel unit exceeds the preset upper or lower limit, the system will set its charging and discharging power to 0, thereby effectively avoiding overcharging or over-discharging and protecting the flywheel unit from damage caused by overcharging and discharging.

[0084] To prevent flywheel units from overloading due to excessive charging and discharging, the power allocated to each flywheel unit must be limited. The purpose of limiting is to ensure that the power output of the flywheel unit does not exceed its rated power, thereby preventing damage or efficiency reduction due to excessive load. In actual operation, the power output of the flywheel unit should always be kept within its safe operating range. Especially during system operation, when the load fluctuates significantly, the power output of the flywheel unit may temporarily exceed its maximum load capacity; therefore, power limiting is crucial.

[0085] To prevent overload of the flywheel unit, its allocated power needs to be limited. That is, if the allocated power of the flywheel unit exceeds the rated power, its power command is set to the rated power. After limiting, the power command value P of flywheel unit i is... i_ref for: ; In the formula, P rated This refers to the rated power of each flywheel unit.

[0086] It is important to note that if some flywheel units are allocated power exceeding their rated power and then reverted to their rated power, the entire flywheel array's output power will fail to meet the power command requirements. Therefore, the system must readjust the power allocation to ensure that the total power command is met while avoiding flywheel unit overload. To achieve this, the system first calculates the total power limit for the flywheel units that have reached their rated power and subtracts this limit from the system's total power command. Then, starting from the power allocation coefficient calculation, the system redistributes power among the flywheel units whose allocated power has not reached their rated power.

[0087] The total power command for this flywheel unit is: ; In the formula, m is the number of flywheel units whose distributed power exceeds the rated power, and P dold This represents the total power allocated in the previous operation. For example, assuming a flywheel array contains 10 flywheel units, the power allocated to flywheel number 1 using the proposed power allocation method is calculated to be 1.05P. rated The power allocated to flywheel units 2 through 9 is all less than P. rated Then set the output power command of flywheel unit 1 to P. rated For the remaining power P all , ref-Prated Starting with the calculation of the power distribution factor, the power is redistributed among the nine flywheel units, from number 2 to number 9.

[0088] Specifically, adjusting the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array tend to be consistent includes: Calculate the power release factor for each flywheel unit, which increases as the difference in state of charge between flywheel units increases; The output power of each flywheel unit is determined based on the power release coefficient and the rated power of each flywheel unit. Reduce the output power of flywheel units whose state of charge is greater than the minimum state of charge of the array, so that their state of charge tends to the minimum state of charge.

[0089] Specifically, the power release coefficient is calculated as follows: Calculate the difference between the current state of charge of the flywheel unit and the lowest state of charge in the array, divide it by the lowest state of charge, and obtain the first term; The second term is obtained by averaging the differences in the state of charge between the current flywheel unit and all other flywheel units in the array. Add the first term to the second term, and then multiply by the preset adjustment factor to obtain the power release coefficient.

[0090] Specifically, adjusting the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array more consistent further includes: When the state of charge of any flywheel unit in the flywheel array falls below the preset minimum allowable value, the state of charge of other flywheel units is limited to decrease further, so that their state of charge drops to a preset protection value.

[0091] In this embodiment of the invention, the power release coefficient It will increase as the difference in SOC increases, thereby accelerating SOC convergence.

[0092] ; Where Y is an adjustment factor used to regulate the influence of SOC difference on power release. min(SOC1, SOC2, ..., SOC2) d ) represents the minimum SOC value among all flywheel units.

[0093] The formula is mainly divided into two parts: the difference between the current flywheel unit's SOC and the minimum flywheel SOC, and the sum of the SOC differences among flywheel units. The first part measures the relative energy state of each flywheel unit by calculating the difference in SOC between the current flywheel unit and the minimum flywheel unit in the array. Flywheel units with higher SOC will release more power to accelerate SOC convergence. The second part considers the SOC differences among flywheel units, dynamically adjusting the power release rate by summing the SOC differences of all flywheel units. When the SOC difference is large, the power release coefficient increases, accelerating the discharge of high-SOC flywheel units; when the SOC difference is small, the power release coefficient decreases, keeping the power output stable and avoiding over-discharge. Thus, through the synergistic effect of these two parts, the formula ensures that the system maintains stable power release while accelerating SOC balancing, avoiding over-discharge or over-charging issues.

[0094] To ensure the flywheel energy storage system doesn't fail to meet subsequent power commands due to excessively low State of Charge (SOC), a minimum SOC limit (e.g., 0.3) is set. When the SOC of any flywheel unit in the flywheel array falls below 0.3, the system automatically limits the SOC drop of other flywheel units, ensuring their SOC drops to a minimum of 0.35. In this way, the system maintains sufficient energy reserves in the gradual SOC adjustment mode, avoiding over-discharge and ensuring a normal response to power commands. To prevent excessive power output from flywheel units during SOC decline in the gradual SOC adjustment mode, which could cause bus voltage fluctuations or other adverse effects, the power output, in addition to considering the SOC difference, also needs to be considered as a percentage of the flywheel unit's rated power. Specifically, the power output calculation relies not only on the power release coefficient ψi but also considers the rated power of each flywheel unit, ensuring smooth power release and controlling the released power within a safe range.

[0095]

[0096] in, This is the output power command for flywheel unit i, where B% is the percentage of the flywheel unit's rated power, and Prated is the rated power of the flywheel unit. The process of gradually reducing the SOC ends when the SOC of the flywheel units becomes consistent.

[0097] This invention achieves passive state-of-charge (SOC) balancing in a flywheel energy storage array when there are no power commands and the SOCs of the individual units are inconsistent. This mode dynamically adjusts the output power of each flywheel unit by calculating a power release coefficient. This coefficient considers both the difference between the current flywheel unit and the array's lowest SOC, as well as the average difference between the unit's SOC and all other units. These two factors are summed and multiplied by an adjustment factor, resulting in flywheel units with larger SOC differences receiving larger power release coefficients, thus releasing more power to accelerate SOC convergence.

[0098] Specifically, the state of charge is calculated based on the current rotational speed of the flywheel unit, as well as its upper and lower speed limits: ; Among them, SOC i Let ω be the charge state of flywheel unit i. i ω represents the current rotational speed of flywheel unit i. i,max and ω i,min These are the upper and lower speed limits of flywheel unit i, respectively.

[0099] The above embodiments are merely illustrative examples and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.

Claims

1. A power optimization method for a multi-mode control flywheel energy storage system incorporating acceleration factors, characterized in that, include: Obtain the current rotational speed, upper speed limit, and lower speed limit of each flywheel unit in the flywheel energy storage array. Based on the squared difference between the current rotational speed of each flywheel unit and its upper and lower speed limits, calculate the state of charge of each flywheel unit. Calculate the absolute value of the difference in state of charge between any two flywheel units, and determine whether the state of charge of all flywheel units is consistent based on the absolute value; In response to the consistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, the output power command of each flywheel unit is determined based on the power command received by the flywheel energy storage array and the number of flywheel units; If the flywheel energy storage array does not receive a power command, the output power command of each flywheel unit will be set to zero; In response to the inconsistent state of charge of all flywheel units, if the flywheel energy storage array receives a power command, it calculates a power allocation coefficient related to the direction of the power command based on the difference in the state of charge of each flywheel unit, introduces an acceleration factor to correct the power allocation coefficient, determines the output power of each flywheel unit based on the corrected power allocation coefficient, and performs power adjustment and power limiting on the allocated output power. If the flywheel energy storage array does not receive a power command, the power output of each flywheel unit is adjusted so that the state of charge of all flywheel units in the flywheel energy storage array tends to be consistent.

2. The method according to claim 1, characterized in that, Determining whether the state of charge of all flywheel units in the flywheel energy storage array is consistent includes: The absolute value of the calculated difference in state of charge between any two flywheel units is compared with a preset allowable deviation threshold. If all the absolute values ​​are less than or equal to the allowable deviation threshold, then all flywheel units are determined to have the same state of charge. If any of the absolute values ​​is greater than the allowable deviation threshold, then the charge state of all flywheel units is determined to be inconsistent.

3. The method according to claim 1, characterized in that, Determine the output power command for each flywheel unit, including: Determine the number of flywheel units currently participating in power distribution in the flywheel energy storage array; The power command value received by the flywheel energy storage array is divided by the number of flywheel units to obtain a quotient value, which is then used as the output power command for each flywheel unit.

4. The method according to claim 1, characterized in that, The power allocation coefficient related to the power command direction is calculated based on the differences in the state of charge of each flywheel unit, including: When the power command is a discharge command, the power allocation coefficient of any flywheel unit is equal to the state of charge of that flywheel unit divided by the sum of the states of charge of all flywheel units. When the power command is a charging command, the power allocation coefficient of any flywheel unit is equal to the state of charge supplement value of that flywheel unit divided by the sum of the state of charge supplement values ​​of all flywheel units, and the state of charge supplement value is equal to a minus the state of charge. The output power of each flywheel unit is determined according to the power distribution coefficient.

5. The method according to claim 1, characterized in that, The power allocation coefficient is corrected by introducing an acceleration factor, including: The acceleration factor for each flywheel unit is determined based on the average state of charge influence factor, speed influence factor, and inverter current influence factor. The power distribution coefficient is corrected using the acceleration factor, and the output power of each flywheel unit is determined based on the corrected power distribution coefficient.

6. The method according to claim 5, characterized in that, The method for determining the average state of charge influence factor is as follows: Calculate the average state of charge of the flywheel energy storage array; Using one as a baseline, add a first constant multiplied by the difference between the current flywheel unit's state of charge and the average state of charge to obtain the average state of charge influence factor.

7. The method according to claim 5, characterized in that, The method for determining the speed influence factor is related to the direction of the power command: When the power command is a discharge command, the speed influence factor is equal to one plus a second constant multiplied by the real-time speed of the flywheel unit; When the power command is a charging command, the speed influence factor is equal to one minus the second constant multiplied by the real-time speed of the flywheel unit.

8. The method according to claim 5, characterized in that, The inverter current influence factor is determined as follows: Using one as a baseline, add a third constant multiplied by the inverter current of the flywheel unit to obtain the inverter current influence factor.

9. The method according to claim 1, characterized in that, The method of dynamically adjusting the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power regulation mechanism: The power regulation coefficient is calculated based on the state of charge of each flywheel unit; The power adjustment coefficient is multiplied by the allocated power to perform a secondary power adjustment; When the state of charge of the flywheel unit exceeds or falls below the preset upper limit of the state of charge, the output power of the flywheel unit is set to zero.

10. The method according to claim 9, characterized in that, The calculation method of the power regulation coefficient is related to the direction of the power command: When the power command is a discharge command, the power adjustment coefficient is calculated as follows: ； When the power command is a charging command, the power adjustment coefficient is calculated as follows: ； Where, β i The power regulation coefficient is K, which is a constant, and the state of charge (SOC) is... i For flywheel unit i, SOC dL With SOC dH These are the lower and upper limits of the adjustment range during discharge, respectively, and the SOC. cL With SOC cH These are the lower and upper limits of the adjustment range during charging, respectively.

11. The method according to claim 1, characterized in that, The method of dynamically adjusting the output power of each flywheel unit based on the difference in the state of charge of each flywheel unit also includes a power limiting mechanism: The power allocated to each flywheel unit is compared with its rated power; If the allocated power is greater than the rated power, then the output power command of the flywheel unit is set to its rated power.

12. The method according to claim 11, characterized in that, The power limiting mechanism also includes power redistribution: Calculate the total power limited by the flywheel unit whose output power commands are all restricted to rated power; The remaining power to be allocated is obtained by subtracting the total power from the received power command; Among the remaining flywheel units whose output power command has not reached the rated power, the power distribution coefficient is recalculated and the acceleration factor is reintroduced for correction in order to complete the power redistribution.

13. The method according to claim 1, characterized in that, Adjusting the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array tend to be consistent includes: Calculate the power release factor for each flywheel unit, which increases as the difference in state of charge between flywheel units increases; The output power of each flywheel unit is determined based on the power release coefficient and the rated power of each flywheel unit. Reduce the output power of flywheel units whose state of charge is greater than the minimum state of charge of the array, so that their state of charge tends to the minimum state of charge.

14. The method according to claim 13, characterized in that, The power release coefficient is calculated as follows: Calculate the difference between the current state of charge of the flywheel unit and the lowest state of charge in the array, divide it by the lowest state of charge, and obtain the first term; The second term is obtained by calculating the average of the differences in the state of charge between the current flywheel unit and all other flywheel units in the array. Add the first term to the second term, and then multiply by the preset adjustment factor to obtain the power release coefficient.

15. The method according to claim 1, characterized in that, The adjustment of the power output of each flywheel unit to make the state of charge of all flywheel units in the flywheel energy storage array tend to be consistent also includes: When the state of charge of any flywheel unit in the flywheel array falls below the preset minimum allowable value, the state of charge of other flywheel units is limited to continue to decrease, so that their state of charge drops to a minimum of the preset protection value.

16. The method according to claim 1, characterized in that, The state of charge is calculated based on the current rotational speed of the flywheel unit and its upper and lower speed limits: ； Among them, SOC i Let ω be the charge state of flywheel unit i. i ω represents the current rotational speed of flywheel unit i. i,max and ω i,min These are the upper and lower speed limits of flywheel unit i, respectively.

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