Flywheel energy storage frequency modulation system and frequency modulation method

Abstract

The invention relates to the technical field of electric energy storage, and particularly discloses a flywheel energy storage frequency modulation system and a frequency modulation method.According to the real-time rotating speed, power upper and lower limits and residual energy of each flywheel energy storage unit, the output weight is calculated and iteratively distributed, a preliminary power instruction is generated, and saturation amplitude limiting and vacancy redistribution are executed; and outputting a final power instruction to execute control. When the power of the flywheel energy storage units is saturated or the flywheel energy storage units are in fault off-network, the fault flywheel energy storage units are automatically removed, the vacancy of the flywheel energy storage units is smoothly distributed to the rest flywheel energy storage units again, the output weight of the flywheel energy storage units is recovered by soft start when the fault flywheel energy storage units are recovered, the array output is ensured to be continuous and stable, and the energy consumption of each flywheel energy storage unit is more balanced. And the extreme condition that one flywheel energy storage unit is over-discharged while the other flywheel energy storage unit is almost immovable is avoided, so that overload tripping is avoided, and the service life of equipment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of electric energy storage, and more specifically, to a flywheel energy storage frequency modulation system and a frequency modulation method. Background Art

[0002] Traditional thermal power units and pumped hydropower storage are limited by their own mechanical inertia and startup response time, making it difficult to meet the millisecond-level fast frequency compensation requirements. Flywheel energy storage systems, with their advantages such as high response speed, long cycle life and pollution-free, have gradually become an important supplementary means of primary and secondary frequency regulation of power grids. The existing literature 1 (Zuo Xinglong. Technical research on flywheel energy storage participating in power system frequency regulation services and inertial response [D]. North China Electric Power University (Beijing), 2024) provides the following: Figure 2 The structural composition of the flywheel energy storage system shown.

[0003] In engineering applications, the energy capacity and rated power of a single flywheel unit are limited and cannot independently support the short-term high-power frequency regulation needs of large-scale power grids. Existing literature 2 (Yang Weipeng. Research on primary frequency regulation of nuclear power units assisted by flywheel energy storage arrays [D]. North China Electric Power University (Beijing), 2023. DOI: 10.27140 / d.cnki.ghbbu.2023.001632.) provides the following: Figure 3 The array coordination control strategy flow chart shown requires connecting multiple flywheel units in parallel to form an array, and outputting them to the outside through centralized or distributed control to form accumulative power and energy capacity. In the existing technology, a proportional allocation method based on frequency difference or an improved proportional allocation strategy is often used to allocate power to each unit in the array. When certain units are limited due to local failure or overload protection, the available power received by the array suddenly drops, and when the line is restored, there will be a "reconnection mutation", which will bring a secondary impact to the downstream bus. A technical solution is now provided. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a flywheel energy storage frequency regulation system and a frequency regulation method, which are used to output the final power instruction execution control by executing saturation limiting and shortage redistribution, and are used to solve the problem that when a local fault or overload protection is limited in advance, the available power received by the flywheel energy storage unit array suddenly drops and there will be a "reconnection mutation" when it is restored to the line, which brings a secondary impact to the downstream bus. The system makes the energy consumption of each flywheel energy storage unit more balanced, thereby avoiding the risk of unit overload tripping and extending the life of the equipment, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions: A flywheel energy storage frequency modulation system includes several flywheel energy storage units, a central controller, an adaptive coordination control unit, and a fault limiting and processing unit; the adaptive coordination control unit is used to calculate and iteratively allocate the output weights according to the real-time rotational speeds, upper and lower power limits, and remaining energies of each flywheel energy storage unit, generate a preliminary power command, perform saturation limiting and deficit reallocation, and output a final power command for execution control; the adaptive coordination control unit includes a data acquisition unit, an energy storage unit state acquisition module, an energy storage unit weight allocation module, a power command allocation and adjustment module, and a local execution control module; the data acquisition unit is used to monitor the power grid frequency in real time, compare the power grid with the preset nominal frequency to obtain the frequency deviation, and calculate the total required power based on the frequency deviation and the primary frequency modulation coefficient; the energy storage unit state acquisition module is used to measure the first state parameters of each flywheel energy storage unit in real time; the first state parameters include the real-time rotational speed, upper power limit, lower power limit, and real-time energy; the energy storage unit weight allocation module is used to calculate its output weight in frequency modulation according to the first state parameters of each flywheel energy storage unit and the current energy storage; the power command allocation and adjustment module is used to allocate the power commands of each flywheel energy storage unit according to the output weights , perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unmet power deficit. If exceeds its power limit, its power is limited to the allowable range, that is, when , then , or when , then ; otherwise, then , where is the actual power output of the i-th flywheel energy storage unit.

[0006] The formula for performing saturation judgment and adjustment on each flywheel energy storage unit is expressed as: ; In the formula: is other cases; As a further solution of the present invention, record the unmet power deficit , and reallocate the power deficit according to the weights of the remaining unsaturated flywheel energy storage units, and iterate until the power outputs of all flywheel energy storage units are within their respective allowable ranges.

[0007] As a further solution of the present invention, the output weight in frequency modulation is obtained through a weight determination model: for the discharging case, take the ratio of the current available energy of each flywheel energy storage unit as the output weight: , for the charging case, use the ratio of the remaining capacity as the output weight: , is the maximum energy capacity of the i-th flywheel energy storage unit.

[0008] The formula for the weight determination model is as follows: ; In the formula: is the output weight, is the current energy storage of the i-th flywheel energy storage unit, is the number of flywheel energy storage units, is the maximum energy capacity of the i-th flywheel energy storage unit, is the total demand power.

[0009] As a further solution of the present invention, the power command allocation and adjustment module records the unmet power deficit, reallocates the power deficit according to the weights of the remaining unsaturated flywheel energy storage units, and iterates until the power outputs of all flywheel energy storage units are within their respective allowable ranges.

[0010] As a further solution of the present invention, the fault limiting and processing unit is used to automatically remove the faulty flywheel energy storage unit and re-smoothly allocate its deficit to the remaining flywheel energy storage units when the flywheel energy storage unit is power saturated or fails to disconnect from the grid, and adopts soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable array output.

[0011] As a further solution of the present invention, the fault limiting and processing unit includes a power overload reallocation module, a fault removal and isolation module, and a faulty unit reconnecting module; the power overload reallocation module is used to automatically trigger power reallocation when the flywheel energy storage unit fails to meet the command due to reaching the power limit; The fault removal and isolation module is used to make a fault removal and isolation reaction by the central controller when there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault; The faulty unit reconnecting module is used to adopt soft start measures when the faulty flywheel energy storage unit is repaired and reconnected to operation.

[0012] As a further solution of the present invention, in the fault removal and isolation module, the central controller will make a fault removal and isolation reaction, specifically: first, judge the fault status of the flywheel energy storage unit through communication and monitoring, and remove it from the control allocation calculation within one control cycle, that is, make the weight of the faulty unit , no longer allocate power commands to the faulty flywheel energy storage unit, regard the power output of the faulty flywheel energy storage unit as 0, and reallocate the original power demand among the remaining flywheel energy storage units.

[0013] A flywheel energy storage frequency modulation method for implementing the above flywheel energy storage frequency modulation system includes the following steps: Step 1: Calculate and iteratively allocate the output weight according to the real-time speed, upper and lower power limits, and remaining energy of each flywheel energy storage unit, generate a preliminary power command, perform saturation limiting and deficit reallocation, and output the final power command for execution control; Step 2: When the power of the flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, automatically remove the faulty flywheel energy storage unit, re-smoothly allocate its deficit to the remaining flywheel energy storage units, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable output of the array.

[0014] As a further solution of the present invention, in Step 1, the specific steps for performing saturation limiting and deficit reallocation are as follows: Step 11: Real-time monitor the grid frequency, compare the grid with the preset nominal frequency to obtain the frequency deviation, and calculate the total required power based on the frequency deviation and the primary frequency modulation coefficient; Step 12: Real-time measure the first state parameter of each flywheel energy storage unit; Step 13: Calculate its output weight in frequency modulation according to the first state parameter of each flywheel energy storage unit and the current energy storage; Step 14: Allocate the power commands of each flywheel energy storage unit according to the output weight, perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unsatisfied power deficit; Step 15: The local execution control module outputs the power of each flywheel energy storage unit finally obtained and sends it to the central controller of the corresponding flywheel energy storage unit.

[0015] As a further solution of the present invention, in Step 2, when the power of the flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, automatically remove the faulty flywheel energy storage unit, re-smoothly allocate its deficit to the remaining flywheel energy storage units, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers. The specific steps are as follows: Step 21: When the flywheel energy storage unit fails to meet the command due to reaching the power limit, power reallocation will be automatically triggered; Step 22: When there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault, the central controller will make a fault removal and isolation reaction; Step 23: When the faulty flywheel energy storage unit is repaired and reconnected to operation, soft start measures will be adopted when the flywheel energy storage unit is reconnected.

[0016] Technical effects and advantages of a flywheel energy storage frequency modulation system and a frequency modulation method according to the present invention: According to the real-time rotational speeds, power upper and lower limits, and remaining energies of each flywheel energy storage unit, the present invention calculates and iteratively distributes output weights to generate a preliminary power command, performs saturation limiting and deficit redistribution, and outputs a final power command for execution control, avoiding the phenomena of "not bearing when there is surplus" and "being vulnerable to collapse when being weak" under fixed ratio distribution, and maximizing the overall frequency modulation capacity; when the power of a flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, the faulty flywheel energy storage unit is automatically removed, and its deficit is redistributed smoothly to the remaining flywheel energy storage units. When the faulty flywheel energy storage unit recovers, its output weight is restored by soft start, ensuring continuous and stable output of the array, making the energy consumption of each flywheel energy storage unit more balanced, avoiding extreme situations where one flywheel energy storage unit is over-discharged while another hardly moves, thereby avoiding the risk of unit overload tripping and extending the equipment life. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a comparison diagram of the power responses of each flywheel energy storage unit in a flywheel array under collaborative control provided by the present invention; Figure 2 It is the structural composition of an existing flywheel energy storage system provided by the present invention; Figure 3 It is a coordination control strategy diagram of an existing flywheel energy storage unit array provided by the present invention; Figure 4 It is a diagram showing the changes in the output power of each flywheel energy storage unit and the total output over time under traditional control provided by the present invention; Figure 5 It is an operating state interface of a flywheel energy storage unit provided by the present invention; Figure 6 It is a schematic structural diagram of a flywheel energy storage frequency modulation system provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The following will clearly and completely describe the technical solutions in the present invention with reference to the accompanying drawings in the present invention. Obviously, the described technical solutions are only a part of the present invention, rather than all of it. Based on the technical solutions in the present invention, all other technical solutions obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0019] Example 1. Figure 6 It shows a schematic structural diagram of a flywheel energy storage frequency modulation system provided by the present invention. As Figure 6As shown in the figure, a flywheel energy storage frequency modulation system in this embodiment includes a plurality of flywheel energy storage units, a central controller, an adaptive coordination control unit, and a fault limiting and processing unit; the plurality of flywheel energy storage units and the central controller are respectively connected to the adaptive coordination control unit, and the plurality of flywheel energy storage units and the central controller are connected to the fault limiting and processing unit.

[0020] The flywheel energy storage unit is used for energy storage through a flywheel; The central controller is used for issuing control commands; The adaptive coordination control unit is used for calculating and iteratively allocating output weights according to the real-time rotational speed, power upper and lower limits, and remaining energy of each flywheel energy storage unit, generating a preliminary power command, performing saturation limiting and deficit redistribution, and outputting a final power command to execute control; The fault limiting and processing unit is used for automatically removing a faulty flywheel energy storage unit when the power of the flywheel energy storage unit is saturated or the unit is fault-disconnected from the grid, redistributing its deficit smoothly to the remaining flywheel energy storage units, and using soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable output of the array.

[0021] Specifically, the adaptive coordination control unit includes a data acquisition unit, an energy storage unit state acquisition module, an energy storage unit weight distribution module, a power command distribution and adjustment module, and a local execution control module; the energy storage unit state acquisition module is connected to the energy storage unit weight distribution module, the data acquisition unit and the energy storage unit weight distribution module are respectively connected to the power command distribution and adjustment module, and the power command distribution and adjustment module is connected to the local execution control module.

[0022] The data acquisition unit is used for real-time monitoring of the grid frequency , comparing the grid with a preset nominal frequency to obtain a frequency deviation , and calculating the total required power based on the frequency deviation and the primary frequency modulation coefficient . .

[0023] It should be noted that if at this time, it means discharging; if at this time, it means charging.

[0024] The energy storage unit state acquisition module is used for real-time measurement of the first state parameters of each flywheel energy storage unit; the first state parameters include the real-time rotational speed , the power upper limit , the power lower limit , and the real-time energy , where is the moment of inertia of the i-th flywheel rotor.

[0025] The energy storage unit weight distribution module is used to calculate its output weight in frequency modulation according to the first state parameters of each flywheel energy storage unit and the current energy storage , and .

[0026] The power command distribution and adjustment module is used to distribute the power commands of each flywheel energy storage unit according to the output weight , perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unmet power deficit.

[0027] The local execution control module is used to output the power of each flywheel energy storage unit finally obtained and send it to the central controller of the corresponding flywheel energy storage unit. The central controller adopts a double-loop structure: the outer loop generates a torque command according to the power command, and the inner loop is a speed control to track the target speed.

[0028] When the power output is , the central controller commands the motor to generate electricity and applies an electromagnetic torque to decelerate the flywheel; when charging, it drives the motor to accelerate the flywheel to store energy.

[0029] It should be noted that the output weight in frequency modulation The setting rule is as follows: If , the flywheel energy storage unit with a higher SOC should be given a larger output weight and give priority to output; the output weight of the flywheel energy storage unit with a lower SOC is reduced to avoid over-discharge. Ideally, the SOC of each unit tends to be consistent after discharge.

[0030] If , the flywheel energy storage unit with a lower SOC should have a larger output weight and bear more charging power; the output weight of the flywheel energy storage unit with a higher SOC is reduced to avoid overcharging.

[0031] Specifically, the output weight in frequency modulation is obtained through the weight determination model: for the discharge case, take the ratio of the current available energy of each flywheel energy storage unit as the output weight: , for the charging case, use the ratio of the remaining capacity as the output weight: , is the maximum energy capacity of the i-th flywheel energy storage unit.

[0032] The formula of the weight determination model is: ; In the formula: is the output weight, is the current energy storage of the i-th flywheel energy storage unit, is the number of flywheel energy storage units, is the maximum energy capacity of the i-th flywheel energy storage unit, is the total required power.

[0033] Specifically, saturation judgment and adjustment are performed on each flywheel energy storage unit, specifically: if exceeds its power limit, its power limit is set to the allowable range, that is, when then or when then ; otherwise, wherein, is the actual power output of the i-th flywheel energy storage unit.

[0034] The formula for saturation judgment and adjustment of each flywheel energy storage unit is expressed as: ; In the formula: is other situations.

[0035] Record the unmet power deficit and redistribute the power deficit according to the weights of the remaining unsaturated flywheel energy storage units, and iterate until the power outputs of all flywheel energy storage units are within their respective allowable ranges.

[0036] Specifically, the fault limit processing unit includes a power overload redistribution module, a fault removal and isolation module, and a fault unit reconnecting module.

[0037] The power overload redistribution module is used to automatically trigger power redistribution when a flywheel energy storage unit fails to meet the command due to reaching the power limit.

[0038] It should be noted that if all flywheel energy storage units are fully output, at this time the array has done its best and cannot completely eliminate the frequency difference, and the remaining frequency deviation needs to be restored by secondary frequency modulation.

[0039] The fault removal and isolation module is used to make a fault removal and isolation reaction by the central controller when there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault.

[0040] The fault unit reconnecting module is used to adopt soft start measures when the faulty flywheel energy storage unit is repaired and reconnected to operation.

[0041] Specifically, automatically trigger power redistribution, specifically: when it is detected that the output power of flywheel energy storage unit i exceeds the preset power range When it reaches its output limit, its output limit value will be output, and the resulting power gap will be redistributed by the central controller according to the weights of the remaining flywheel energy storage units. The adjustment is carried out through multiple rounds of iteration, and finally the power gap is absorbed among other unsaturated flywheel energy storage units. Thus, when a flywheel energy storage unit reaches its capacity limit, the system will promptly increase the output of other flywheel energy storage units to make up for it, preventing the total output from suddenly interrupting.

[0042] Specifically, the central controller will make a fault removal and isolation response, specifically: First, judge the fault status of the flywheel energy storage unit through communication and monitoring (such as detecting that the unit no longer feeds back power, the current is zero, etc.), and remove it from the control allocation calculation within one control cycle (on the order of dozens of milliseconds), that is, set the weight of the faulty unit , and no longer allocate power commands to the faulty flywheel energy storage unit. At the same time, immediately regard the power output of the faulty flywheel energy storage unit as 0, and redistribute the power demand originally belonging to it among the remaining flywheel energy storage units. The redistribution process is similar to the overload redistribution process, except that the faulty flywheel energy storage unit is equivalent to "permanently saturated at 0 output". If the remaining flywheel energy storage units have sufficient redundancy (for example, they were not fully loaded before), then their output will be gradually increased within several control cycles to partially or completely make up for the power missing from the faulty flywheel energy storage unit.

[0043] It should be noted that to avoid suddenly increasing the response of the remaining units and causing new pressure, a smoothing coefficient can be introduced in the redistribution process, so that the power commands of other units linearly reach the new value within several cycles, rather than jumping in one step, forming an emergency support control: adjacent units top up at a controlled rate to weaken the impact of the faulty flywheel energy storage unit on the total output. If the capacity of the faulty flywheel energy storage unit accounts for a relatively large proportion, and the remaining flywheel energy storage units cannot fully fill the gap even when outputting at full capacity, then the total output will inevitably decrease, and the corresponding frequency may experience a secondary drop. However, this control still outputs the maximum power as much as possible, reduces the frequency deviation, and waits for the frequency modulation reserve or conventional units to intervene to restore the frequency.

[0044] Specifically, the faulty unit reconnecting module is used to adopt soft start measures when the faulty flywheel energy storage unit is repaired and put back into operation. Specifically: That is, gradually increase the weight of the flywheel energy storage unit, slowly transitioning from 0 to the output weight calculated according to the normal rules. At the moment of reconnection, regard the new flywheel energy storage unit as having a low SOC value and a limited power upper limit, so that its initial allocated power is very small, and set a time constant , multiplied by a gain factor to make its output weight exponentially approach the actual value.

[0045] For example, it reaches about 63% after 1 second and 95% after 3 seconds after reclosing. In this way, the output of the new flywheel energy storage unit gradually climbs from 0, and the output of the remaining flywheel energy storage units decreases slowly accordingly, realizing a smooth transition. During this process, the total output may deviate slightly from the ideal value (because the new unit does not immediately fully undertake its part), but since the frequency regulation demand is usually supported by the remaining flywheel energy storage units during the fault, the frequency state is close to stable at this time, and slightly delaying the intervention of the new flywheel energy storage unit will not cause serious impacts. Instead, its gradual connection can be used to restore the frequency to the ideal level.

[0046] It should be noted that before reclosing, the flywheel speed of the flywheel energy storage unit needs to be pre-controlled to a level commensurate with the current average SOC of the array. For example, during the fault, the flywheel may be in an idle state (not feeding power), and its speed and SOC remain unchanged or increase. To prevent a large power reallocation impact due to too large a difference in SOC during reclosing, a short period of time can be used before reclosing to let the unit run following the system frequency with a small power, narrowing the SOC gap with other flywheel energy storage units. Then, it is connected to the grid and outputs power according to the above soft start process, similar to the alignment of frequency and phase before a synchronous generator is connected to the grid, except that the flywheel adjusts its speed or SOC.

[0047] Figure 5 This is the operation status interface of the flywheel energy storage unit provided by the present invention; the unit number is named according to the unique identifier of each flywheel energy storage unit in the array, which is convenient for positioning and management; the rotational speed is the rotational speed of the flywheel rotor measured in real time; the power corresponds to the actual charge / discharge power output of the unit in this period; the status: "Normal operation": indicates that the unit is operating within the rated range and can continue to participate in frequency regulation; "Fault": the unit has been disconnected from the grid or triggered protection, and needs to be removed by the fault removal and isolation module and trigger the reallocation logic.

[0048] Perform saturation judgment on the preliminary instructions of each unit, strictly limit them within the preset power range, and avoid any unit triggering protection tripping due to overload. Iteratively allocate the deficit power generated after saturation among the unsaturated units according to the weight, ensuring that the total power of the array can meet the frequency regulation demand as much as possible, and preventing output interruption or significant decline. The faulty unit is removed within milliseconds, and its original instructions are immediately allocated to the healthy units, avoiding a single-point fault having a major impact on the overall frequency regulation ability. The compensation for the remaining units adopts a linear or smooth coefficient, avoiding a sudden increase in load at one time and reducing the sudden current / torque impact on the unit itself and the bus. After the faulty unit recovers, it first accesses with a minimum weight, and then gradually climbs the output according to an exponential gain, ensuring that the total power does not jump and avoiding secondary fluctuations in frequency or bus voltage. Before reclosing, it first runs following with a small power to make the SOC of the unit approach the array average value, further alleviating the energy mutation during reclosing.

[0049] Embodiment 2. A flywheel energy storage frequency modulation method for implementing the above-mentioned flywheel energy storage frequency modulation system, comprising the following steps: Step 1: Calculate and iteratively allocate the output weight according to the real-time rotation speed, power upper and lower limits, and remaining energy of each flywheel energy storage unit, generate a preliminary power command, perform saturation limiting and deficit reallocation, and output the final power command for execution control.

[0050] Step 2: When the power of the flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, automatically remove the faulty flywheel energy storage unit, re-smoothly allocate its deficit to the remaining flywheel energy storage units, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable output of the array.

[0051] Specifically, in Step 1, the specific steps of performing saturation limiting and deficit reallocation are as follows: Step 11: Real-time monitor the grid frequency, compare the grid with the preset nominal frequency to obtain the frequency deviation, and calculate the total required power based on the frequency deviation and the primary frequency modulation coefficient.

[0052] Step 12: Real-time measure the first state parameter of each flywheel energy storage unit.

[0053] Step 13: Calculate its output weight in frequency modulation according to the first state parameter of each flywheel energy storage unit and the current energy storage.

[0054] Step 14: Allocate the power command of each flywheel energy storage unit according to the output weight, perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unmet power deficit.

[0055] Step 15: The local execution control module outputs the final power output of each flywheel energy storage unit and sends it to the central controller of the corresponding flywheel energy storage unit.

[0056] Specifically, in Step 2, when the power of the flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, automatically remove the faulty flywheel energy storage unit, re-smoothly allocate its deficit to the remaining flywheel energy storage units, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers. The specific steps are as follows: Step 21: When the flywheel energy storage unit fails to meet the command due to reaching the power limit, power reallocation will be automatically triggered.

[0057] Step 22: When there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault, the central controller will make a fault excision and isolation reaction.

[0058] Step 23: When the faulty flywheel energy storage unit is repaired and reconnected to operation, soft start measures are adopted when the flywheel energy storage unit is reconnected.

[0059] Example 3. At the beginning of the existing system, the SOC of the three flywheels are different: No. 1 is 70%, No. 2 is 50%, and No. 3 is 90%. At t=2s, the load suddenly increases, causing the frequency to drop. The array needs to output 1.2pu power to support the frequency. Among them, the No. 2 flywheel energy storage unit exits due to overload failure at t=5s, and after 5 seconds, it automatically reconnects to participate in frequency regulation at t=10s. Figure 4 The output power of each flywheel energy storage unit (P1, P2, P3) and the total output ( ) over time, Figure 1 A comparison diagram of the power responses of each flywheel energy storage unit in the flywheel array under coordinated control.

[0060] from Figure 4 As can be seen, using traditional control, during the period t < 5s, the three flywheel energy storage units share the load equally, each outputting approximately 0.4 pu of power. The flywheel energy storage unit SOC is not taken into account. Therefore, even though flywheel unit 2 initially has a SOC of only 50%, it is still required to output the same power as the other flywheel energy storage units. As a result, within just 3 seconds, flywheel 2's speed drops to its safe lower limit, forcing it to trip (the 5s fault in the simulation corresponds to this situation). After the fault occurs (5-10s), the traditional control algorithm lacks a reallocation mechanism. Since flywheel 2 is no longer producing power, the total frequency difference cannot be fully compensated, resulting in a second drop in frequency. Driven by the widening frequency difference, the remaining flywheel units 1 and 3 attempt to increase their output to 0.6 pu, but are saturated at their respective maximum power levels of 0.5 pu. Therefore, for 5-10s, the total array output can only maintain approximately 1.0 pu (a decrease of approximately 16% from the required 1.2 pu), significantly reducing frequency support capability. Until flywheel storage unit 2 reconnects at t=10s, conventional control will instantly distribute 1.2 pu of power evenly across the three units, or 0.4 pu per unit. This means that the output of flywheel storage units 1 and 3 drops sharply from 0.5 to 0.4 pu, while the output of flywheel storage unit 2 jumps from 0 to 0.4 pu, causing the total array power to rise at 10s (from 1.0 pu to 1.2 pu). This "drop-and-replenish" power waveform is directly reflected in the frequency response, causing secondary frequency dips and surges, resulting in poor frequency regulation quality. Furthermore, the SOC of each flywheel storage unit varies throughout the process: flywheel storage units 1 and 3 experience a significant drop in SOC due to their continued high output, while flywheel storage unit 2, which drops midway, maintains a near-perfect SOC. This further widens the SOC difference after reconnection, hindering subsequent operation.

[0061] from Figure 1It can be seen that in the case of coordinated control: when t < 5s, each flywheel energy storage unit distributes power in unequal portions according to the initial SOC. The 3rd flywheel energy storage unit with the highest SOC outputs approximately 0.6 pu, taking on more of the frequency regulation power; the 2nd flywheel energy storage unit with a lower SOC outputs approximately 0.3 pu, with a reduced burden, and the 1st flywheel energy storage unit is between the two at approximately 0.3 pu. With such a distribution, the total output of the array is still 1.2 pu to meet the frequency regulation requirements, but the energy consumption rate of the 2nd flywheel energy storage unit is significantly reduced, and the decrease in SOC is much smaller than Figure 4 the situation. By 5s, the 2nd flywheel energy storage unit does not reach the lower limit SOC, and its fault tripping under this strategy is not due to its own exhaustion. At the moment the fault occurs, the controller detects that the 2nd unit is offline, immediately resets its weight to 0, and redistributes the originally 0.3 pu power belonging to it between the 1st and 3rd units. Since the 1st and 3rd units were not fully loaded previously and the 3rd unit still has capacity, after redistribution, the output of the 3rd flywheel energy storage unit increases to approximately 0.7 pu, and the 1st unit increases to 0.5 pu, and the two together continue to provide a total power of 1.2 pu exactly. It is not difficult to see that the total output power is hardly affected by the fault and remains at 1.2 pu. The black dashed line in the simulation curve is basically straight, without an obvious drop as in traditional control, meaning that the grid frequency will not experience a secondary decline at 5s, and the frequency regulation effect is maintained. During the next 5 - 10s, the 1st flywheel energy storage unit has reached its rated output of 0.5 pu, and the 3rd flywheel energy storage unit's 0.7 pu slightly exceeds the rated value. The two together support the frequency. In addition, the central controller continuously monitors the SOC and finds that the output of the 3rd flywheel energy storage unit is relatively high and its SOC drops rapidly, which may not be conducive to long-term balance. Therefore, during 7 - 10s, the weight of the 3rd unit is slightly reduced and the weight of the 1st unit is increased (from 0.5 to about 0.55 pu) to balance the energy output of the two, reflecting the adaptive adjustment ability of the strategy.

[0062] When the 2nd flywheel recovers at 10s, the coordinated control does not immediately restore its command to the original value of 0.3 pu, but gradually increases its weight according to the soft start strategy. From Figure 1 what can be observed, after 10s, the power of the 2nd flywheel climbs slowly from 0 and rises to 0.3 pu within about 2 seconds; at the same time, the outputs of the 1st and 3rd flywheels decrease smoothly, and finally tend to a new steady-state distribution: the 1st ≈ 0.3 pu, the 2nd ≈ 0.3 pu, the 3rd ≈ 0.6 pu (at this time, the 3rd SOC is still the highest, so it continues to take on a little more). During the entire reconnecting process, the total power remains stable near 1.2 pu, without the step jumps and fluctuations in the total output under traditional control. This smooth transition ensures the monotonic recovery of the frequency without secondary overshoot. At the same time, the SOCs of each flywheel gradually approach in the later stage of frequency regulation - the 1st is slightly higher, the 2nd has recovered somewhat, the 3rd has dropped a bit, and the gap between the three decreases, which is beneficial for the preparation of the next frequency regulation.

[0063] It can be clearly seen through the comparison of typical working conditions that the coordinated control strategy is significantly superior to the traditional control. The specific manifestations are as follows: the lowest point of the frequency is increased, and the frequency recovery is smoother; the output gap during unit failure is greatly reduced and quickly bridged; the sudden change in power distribution is avoided during reclosing. For the flywheel energy storage unit itself, the coordinated control makes the energy consumption of each flywheel energy storage unit more balanced, avoiding the extreme situation where one flywheel energy storage unit is over-discharged while another hardly moves, thus avoiding the risk of unit overload tripping and extending the equipment life.

[0064] In the embodiment of the present invention, by calculating and iteratively distributing the output weight according to the real-time speed, power upper and lower limits, and remaining energy of each flywheel energy storage unit, generating a preliminary power command, performing saturation limiting and deficit reallocation, and outputting the final power command for execution control, the phenomena of "not taking the surplus" and "being vulnerable to collapse when weak" under the fixed ratio distribution are avoided, and the overall frequency modulation capacity is maximally exerted; when the power of the flywheel energy storage unit is saturated or the unit fails and is disconnected from the grid, the faulty flywheel energy storage unit is automatically removed, and its deficit is smoothly redistributed to the remaining flywheel energy storage units. When the faulty flywheel energy storage unit recovers, its output weight is restored by soft start to ensure continuous and stable output of the array, making the energy consumption of each flywheel energy storage unit more balanced, avoiding the extreme situation where one flywheel energy storage unit is over-discharged while another hardly moves, thus avoiding the risk of unit overload tripping and extending the equipment life.

[0065] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claimed rights.

[0066] Finally: The above is only the preferred solution of the present invention and is not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flywheel energy storage frequency modulation system, comprising a plurality of flywheel energy storage units, a central controller, an adaptive coordination control unit, and a fault amplitude limiting processing unit; characterized in that, The adaptive coordination control unit is used to calculate and iteratively allocate the output weights according to the real-time speeds, upper and lower power limits, and remaining energies of each flywheel energy storage unit, generate a preliminary power command, perform saturation limiting and deficit reallocation, and output the final power command for execution control; the adaptive coordination control unit includes a data acquisition unit, an energy storage unit state acquisition module, an energy storage unit weight allocation module, a power command allocation and adjustment module, and a local execution control module; the data acquisition unit is used to monitor the grid frequency in real time, compare the grid with the preset nominal frequency to obtain the frequency deviation, and calculate the total required power based on the frequency deviation and the primary frequency modulation coefficient. The energy storage unit status acquisition module is used to measure the first status parameters of each flywheel energy storage unit in real time; the first status parameters include the real-time rotational speed, the upper power limit, the lower power limit, and the real-time energy; the energy storage unit weight distribution module is used to calculate its output weight in frequency modulation according to the first status parameters of each flywheel energy storage unit and the current energy storage; the power command distribution and adjustment module is used to distribute the power commands of each flywheel energy storage unit according to the output weight , perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unmet power deficit. If exceeds its power limit, its power limit is set to the allowable range, that is, when , then , or when , then ; otherwise, then , where is the actual power output of the i-th flywheel energy storage unit.

2. The flywheel energy storage frequency modulation system according to claim 1, wherein, Output weight in frequency modulation Obtained through the weight determination model: For the discharging case, take the ratio of the current available energy of each flywheel energy storage unit as the output weight: , and for the charging case, use the ratio of the remaining capacity as the output weight: , is the maximum energy capacity of the i-th flywheel energy storage unit.

3. The flywheel energy storage frequency modulation system according to claim 1, wherein The power command allocation and adjustment module records the unmet power deficit, redistributes the power deficit according to the weights of the remaining unsaturated flywheel energy storage units, and iterates until the power outputs of all flywheel energy storage units are within their respective allowable ranges.

4. A flywheel energy storage frequency modulation system according to claim 1, characterized in that, The fault limiting and handling unit is used to automatically remove the faulty flywheel energy storage unit, redistribute its deficit smoothly to the remaining flywheel energy storage units when the power of the flywheel energy storage unit is saturated or fails to disconnect from the grid, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable output of the array.

5. The flywheel energy storage frequency modulation system according to claim 4, characterized in that The fault limiting and handling unit includes a power overload reallocation module, a fault removal and isolation module, and a faulty unit reconnecting module; the power overload reallocation module is used to automatically trigger power reallocation when the flywheel energy storage unit fails to meet the command due to reaching the power limit. The fault removal and isolation module is used for the central controller to make a fault removal and isolation reaction when there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault. The faulty unit reconnecting module is used to adopt soft start measures when the faulty flywheel energy storage unit is repaired and reconnected to operation.

6. The flywheel energy storage frequency modulation system according to claim 5, wherein In the fault removal and isolation module, the central controller will make a fault removal and isolation response, specifically: First, it judges the fault status of the flywheel energy storage unit through communication and monitoring, and excludes it from the control allocation calculation within one control cycle, that is, sets the weight of the faulty unit , no longer allocates power commands to the faulty flywheel energy storage unit, regards the power output of the faulty flywheel energy storage unit as 0, and redistributes the power demand originally belonging to it among the remaining flywheel energy storage units.

7. A flywheel energy storage frequency modulation method for implementing a flywheel energy storage frequency modulation system according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1, calculate and iteratively allocate the output weights according to the real-time speeds, upper and lower power limits, and remaining energies of each flywheel energy storage unit, generate a preliminary power command, perform saturation limiting and deficit reallocation, and output the final power command for execution control; Step 2, when the power of the flywheel energy storage unit is saturated or fails to disconnect from the grid, automatically remove the faulty flywheel energy storage unit, redistribute its deficit smoothly to the remaining flywheel energy storage units, and use soft start to restore its output weight when the faulty flywheel energy storage unit recovers, ensuring continuous and stable output of the array.

8. A flywheel energy storage frequency modulation method according to claim 7, characterized in that In Step 1, the specific steps for performing saturation limiting and deficit reallocation are as follows: Step 11, monitor the grid frequency in real time, compare the grid with the preset nominal frequency to obtain the frequency deviation, and calculate the total required power based on the frequency deviation and the primary frequency modulation coefficient; Step 12, measure the first state parameter of each flywheel energy storage unit in real time; Step 13, calculate its output weight in frequency modulation according to the first state parameter of each flywheel energy storage unit and the current energy storage; Step 14, allocate the power commands of each flywheel energy storage unit according to the output weight, perform power saturation judgment and adjustment on each flywheel energy storage unit, and record the unmet power deficit. Step 15, the local execution control module outputs the power of each flywheel energy storage unit finally obtained and sends it to the central controller of the corresponding flywheel energy storage unit.

9. A flywheel energy storage frequency modulation method according to claim 7, characterized in that In step 2, when the flywheel energy storage unit is power saturated or fails to disconnect from the grid, the faulty flywheel energy storage unit is automatically removed, and its deficit is redistributed smoothly to the remaining flywheel energy storage units. When the faulty flywheel energy storage unit recovers, its output weight is restored by soft start. The specific steps are as follows: Step 21, when the flywheel energy storage unit cannot meet the instruction due to reaching the power limit, power redistribution will be automatically triggered; Step 22, when there is a flywheel energy storage unit that is forced to disconnect from operation due to a fault, the central controller will make a fault removal and isolation reaction; Step 23, when the faulty flywheel energy storage unit is repaired and put back into operation, soft start measures are adopted when the flywheel energy storage unit is reconnected.

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