Power grid frequency modulation method based on flywheel energy storage and electrochemical energy storage

Abstract

The invention discloses a power grid frequency modulation method based on flywheel energy storage and electrochemical energy storage. The method comprises the following steps: S1, receiving an AGC instruction issued by an AGC dispatching center; s2, preferentially responding to the frequency modulation demand through flywheel energy storage, and adjusting the rotating speed of the flywheel in real time based on the instantaneous power output capability and the residual electric quantity of the flywheel so as to compensate for the high-frequency small-amplitude power deviation; s3, when the flywheel energy storage power or energy is insufficient, battery energy storage supplements response, the charge and discharge depth of the battery is limited according to the charge state of the battery, and the service life is prolonged; and S4, combining the actual ramp rate of the thermal power generating unit, dynamically distributing the output of the energy storage system, and forming a thermal power-hybrid energy storage combined frequency modulation model. The frequency modulation performance index is improved; through instantaneous response of flywheel energy storage and continuous support of a battery, the Kp value is improved from 3.7 to more than 4.2 by combining a frequency modulation system; and the service life of the battery is prolonged, and the replacement cost and the comprehensive cost are reduced by limiting the charge-discharge depth (the SOC range is 20%-90%) of the lithium battery and reducing the high-frequency charge-discharge times of the lithium battery.

Description

Technical Field

[0001] The present invention belongs to the field of energy technology, and in particular relates to a power grid frequency modulation method based on flywheel energy storage and electrochemical energy storage. Background Art

[0002] As the proportion of renewable energy generation connected to the grid increases, grid frequency fluctuations intensify. Traditional thermal power generation units face challenges with frequency regulation, including slow response, significant equipment wear, and low regulation accuracy. Existing energy storage frequency regulation technologies struggle to balance instantaneous power support with sustained energy output with a single energy storage system. For example, while lithium batteries offer high capacity, they have a limited charge and discharge cycle (approximately 5,000 cycles), and deep discharge accelerates lifespan degradation. Flywheel energy storage, while offering fast response (milliseconds) and long life (10 million cycles), suffers from low energy density. Supercapacitors, while offering fast response, are expensive and lack sufficient energy density.

[0003] Chinese invention patent CN112737129A discloses an electrochemical and flywheel hybrid energy storage system, including an electrochemical energy storage device, a battery management system, a flywheel energy storage device, a flywheel control system, an energy storage energy management system, an energy storage auxiliary frequency regulation control device group, a bidirectional converter group and a transformer group. A device for combining a power plant unit with an electrochemical and flywheel hybrid energy storage system, including a power plant unit and the above-mentioned electrochemical and flywheel hybrid energy storage system. By combining the power plant unit with the electrochemical and flywheel hybrid energy storage system, when the power grid needs to increase / decrease load frequency regulation, the electrochemical energy storage device and the flywheel energy storage device are preferentially controlled to perform corresponding actions, which has the advantages of fast regulation speed, short response time and high regulation accuracy. In addition, the existing frequency regulation control strategy does not fully combine the complementary characteristics of flywheels and lithium batteries, resulting in limited system efficiency and economy.

[0004] Therefore, the present invention provides a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage to solve the problems raised by the above background technology. Summary of the Invention

[0005] In response to the problems raised by the above background technology, the purpose of the present invention is to provide a grid frequency regulation method based on flywheel energy storage and electrochemical energy storage, which complements the millisecond-level response of flywheel energy storage with the continuous output of lithium batteries, thereby improving the frequency regulation performance and extending the life of the equipment.

[0006] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows: A method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage comprises the following steps: S1: Receives AGC instructions issued by the AGC dispatch center; S2: The flywheel energy storage system prioritizes frequency modulation requirements. Based on its instantaneous power output capability and remaining capacity, the flywheel speed is adjusted in real time to compensate for small power deviations at high frequencies. S3: When the flywheel energy storage power or energy is insufficient, the battery energy storage responds by supplementing and limiting the charge and discharge depth according to the battery's state of charge to extend its service life; S4: Combined with the actual ramp rate of thermal power units, the output of the energy storage system is dynamically allocated to form a joint frequency regulation model of thermal power and hybrid energy storage.

[0007] It is further defined that the thermal power unit is used to respond to grid dispatch instructions and output base power, the flywheel energy storage is used to provide instantaneous high-power response to compensate for insufficient climbing rate of the thermal power unit; and the battery energy storage is used to provide continuous power support to supplement the energy gap of the flywheel energy storage.

[0008] It is further defined that the AGC instruction in S1 is decomposed into a thermal power unit frequency regulation instruction, a flywheel energy storage frequency regulation instruction and a battery energy storage frequency regulation instruction by the AGC dispatch center.

[0009] It is further defined that it also includes a hybrid energy storage control system, which receives the AGC instructions issued by the AGC dispatch center in S1, and then the hybrid energy storage control system distributes the hybrid energy storage frequency regulation instructions to the flywheel energy storage system and the battery energy storage system, and also sends the thermal power unit frequency regulation instructions to the thermal power unit.

[0010] It is further defined that the AGC instructions in S1 are decomposed by an AGC instruction allocation strategy, and the AGC instruction allocation strategy includes the following steps: S10: The AGC dispatch center generates a slope-limited generator set instruction based on the AGC instruction and the actual climbing capability of the thermal power unit; S11: The energy storage system command is obtained by subtracting the generator command from the AGC command; S12: The flywheel responds to the energy storage instruction first, and generates a flywheel instruction in combination with the flywheel power and capacity limit; S13: Subtract the flywheel response curve from the hybrid energy storage control system command to obtain the battery command.

[0011] It is further defined that the flywheel energy storage adopts a permanent magnet synchronous motor, magnetic levitation bearing and integrated flywheel rotor design, with a speed range of 10,000-30,000 rpm, a power density ≥1MW / 40MJ, and an overall conversion efficiency ≥85%.

[0012] It is further defined that the battery energy storage uses lithium iron phosphate batteries, the charge and discharge rate is 1C-2C, and the battery's state of charge operating range is 20%~90%.

[0013] Further defined, including a control strategy, the control strategy comprising the steps of: S20: A frequency-dividing control strategy is adopted to allocate the high-frequency component of the grid frequency fluctuation to the flywheel energy storage and the low-frequency component to the battery energy storage; S21: Introduce a variable proportion control algorithm to dynamically adjust the output ratio of the flywheel and the lithium battery according to the amplitude and change frequency of the AGC instruction.

[0014] It is further defined that the high-frequency component of the grid frequency fluctuation is 0.1-2 Hz, and the low-frequency component is <0.1 Hz.

[0015] It is further defined that the capacity configuration of the hybrid energy storage control system is a flywheel energy storage power of 2-3MW / 80-120MJ, a lithium battery energy storage capacity of 4-6MWh, and a system comprehensive performance index Kp≥4.0.

[0016] Beneficial effects of the present invention: 1. Improve frequency regulation performance: Through the instantaneous response of flywheel energy storage and the continuous support of lithium batteries, the combined frequency regulation system can increase the Kp value from 3.7 to over 4.2; 2. Extending battery life: Flywheel energy storage takes on high-frequency, small-amplitude frequency modulation tasks. By limiting the depth of charge and discharge of lithium batteries (SOC range 20%-90%) and reducing the number of high-frequency charge and discharge cycles, the battery replacement cycle is extended from 3 years to 5 years, reducing replacement costs. 3. Reduced overall costs: The static payback period of the hybrid energy storage system is shortened to 3.9 years (4MW lithium battery + 2MW flywheel solution), which increases the return on investment by 30% compared to a single lithium battery solution. 4. Enhanced system reliability: The mechanical characteristics of flywheel energy storage avoid the risk of chemical explosion. Combined with the continuous power supply capability of lithium batteries, it ensures a safe and stable frequency modulation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention can be further illustrated by the non-limiting examples given in the accompanying drawings; Figure 1 This is a graph showing the operation data of a thermal power unit according to an embodiment of a method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 2 This is a graph showing the operation data of a thermal power unit according to an embodiment of a method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 3 This is a graph showing the operation data of a thermal power unit according to an embodiment of a method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 4 This is a graph showing the operation data of a thermal power unit according to an embodiment of a method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 5 This is a graph showing the operation data of a thermal power unit according to an embodiment of a method for power grid frequency regulation based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 6 This is an AGC instruction data diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 7 A 10-minute segment diagram of the AGC instructions of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 8 A 10-minute segment diagram of the AGC instructions of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 9 This is a thermal power unit output curve diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 10 This is an energy storage output curve diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 11 This is an AGC instruction allocation diagram for an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 12 This is an energy storage output characteristic diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 13 This is a performance indicator diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 14 This is an AGC instruction allocation diagram for an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 15 This is an energy storage output characteristic diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 16 This is a performance indicator diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 17 This is an overall system module diagram of an embodiment of a grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to the present invention; Figure 18 This is a diagram of the energy storage frequency regulation control strategy for an embodiment of a grid frequency regulation method based on flywheel energy storage and electrochemical energy storage according to the present invention. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the present invention, the technical solutions of the present invention are further described below in conjunction with the accompanying drawings and embodiments. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0019] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0020] In addition, the descriptions of "first", "second", etc. in the present invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0021] A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage of the present invention comprises the following steps: S1: Receives AGC instructions issued by the AGC dispatch center; S2: The flywheel energy storage system prioritizes frequency modulation requirements. Based on its instantaneous power output capability and remaining capacity, the flywheel speed is adjusted in real time to compensate for small power deviations at high frequencies. S3: When the flywheel energy storage power or energy is insufficient, the battery energy storage responds by supplementing and limiting its charge and discharge depth according to the battery's state of charge (SOC) to extend its service life; S4: Combined with the actual ramp rate of thermal power units (2.5%Pn / min), the output of the energy storage system is dynamically allocated to form a joint frequency regulation model of thermal power and hybrid energy storage.

[0022] In the actual application of this embodiment, the thermal power unit is used to respond to the grid dispatch instruction and output the base power, the flywheel energy storage is used to provide instantaneous high-power response to compensate for the insufficient climbing rate of the thermal power unit; the battery energy storage is used to provide continuous power support to supplement the energy gap of the flywheel energy storage.

[0023] In practical applications of this embodiment, the AGC instruction in S1 is decomposed into a thermal power unit frequency regulation instruction, a flywheel energy storage frequency regulation instruction, and a battery energy storage frequency regulation instruction by the AGC dispatch center.

[0024] In practical applications of this embodiment, a hybrid energy storage control system is also included. The hybrid energy storage control system receives the AGC instructions issued by the AGC dispatch center in S1, and then distributes the hybrid energy storage frequency regulation instructions to the flywheel energy storage system and the battery energy storage system, and also sends the frequency regulation instructions of the thermal power unit to the thermal power unit.

[0025] In the practical application of this embodiment, the AGC instruction in S1 is decomposed by an AGC instruction allocation strategy, and the AGC instruction allocation strategy includes the following steps: S10: The AGC dispatch center generates a slope-limited generator set instruction based on the AGC instruction and the actual climbing capability of the thermal power unit; S11: The energy storage system command is obtained by subtracting the generator command from the AGC command; S12: The flywheel responds to the energy storage instruction first, and generates a flywheel instruction in combination with the flywheel power and capacity limit; S13: Subtract the flywheel response curve from the hybrid energy storage control system command to obtain the battery command.

[0026] In the practical application of this embodiment, the flywheel energy storage adopts a permanent magnet synchronous motor, a magnetic levitation bearing and an integrated flywheel rotor design, with a speed range of 10,000-30,000 rpm, a power density ≥1MW / 40MJ, and a comprehensive conversion efficiency ≥85%.

[0027] In the practical application of this embodiment, the battery energy storage adopts a lithium iron phosphate battery, the charge and discharge rate is 1C-2C, and the battery's state of charge operating range is 20%~90%.

[0028] In practical applications of this embodiment, a control strategy is also included, and the control strategy includes the following steps: S20: A frequency-dividing control strategy is adopted to allocate the high-frequency component of the grid frequency fluctuation to the flywheel energy storage and the low-frequency component to the battery energy storage; S21: Introduce a variable proportion control algorithm to dynamically adjust the output ratio of the flywheel and the lithium battery according to the amplitude and change frequency of the AGC instruction.

[0029] In practical applications of this embodiment, the high-frequency component of the grid frequency fluctuation is 0.1-2 Hz, and the low-frequency component is <0.1 Hz.

[0030] In the actual application of this embodiment, the capacity configuration of the hybrid energy storage control system is a flywheel energy storage power of 2-3MW / 80-120MJ, a lithium battery energy storage capacity of 4-6MWh, and a system comprehensive performance index Kp≥4.0.

[0031] like Figure 1-Figure 5 As shown, Figure 1-Figure 5 This is the daily operating data of Laicheng Power Plant. The blue curve in the figure is the AGC instruction, the purple curve is the output curve of the thermal power unit, and the green curve is collectively referred to as the machine storage output curve (flywheel energy storage and battery energy storage).

[0032] from Figure 1-Figure 5 It can be seen from the AGC command curve that most of the AGC commands of thermal power units vary in the range of 4-8MW, with very few commands exceeding 8MW. In addition, the commands change about 2-4 times every 2 minutes, which basically conforms to the rule of updating the commands every 30s-60s.

[0033] from Figure 2 From the thermal power unit curve, we can see that the power of the thermal power unit is 190MW at 13:47:30 and 218MW at 13:51:00. The ramp rate is (218-190) / 3.5min=8MW / min, 8MW / min / 300MW=2.6%Pn / min. Figure 1-Figure 5 The data climbing rate is 2.5%Pn / min. Since the current maximum limit of the climbing rate of thermal power units is 3%Pn / min, the thermal power units of Laicheng Power Plant climb faster.

[0034] In addition, from Figure 1 13:39:00 to 13:42:00, Figure 2 From 13:47:30 to 13:51:00, it can be seen that the generator storage output curve is almost parallel to the thermal power unit climbing curve, and the slope is close, indicating that the generator storage output value is relatively fixed. From the figure, it can be seen that the difference between the generator storage output curve and the thermal power unit curve basically varies between 2.5-4MW, and Figure 1 and Figure 2 There are many monotonic and unidirectional adjustment cycles. Figure 3 and Figure 4 The AGC instructions are being adjusted back and forth, and only the thermal power units have over-adjustment and under-adjustment phenomena.

[0035] According to the above existing data, the characteristics of AGC instructions are analyzed: 1. The command amplitude variation range is basically between 4-8MW.

[0036] 2. The AGC command change cycle is 30s-60s.

[0037] 3. The rated power of a single unit is 300MW, and the output of thermal power units is basically above 150MW, which is more than 50% depth.

[0038] Based on the above characteristics, random numbers are generated to fit the command values that are closer to the actual operating characteristics of the site, and AGC commands are randomly generated for one day, such as Figure 6-Figure 8 As shown, the instruction range varies between 175MW and 255MW, and it is updated every 30-60s. The change amount is 4-8MW. The instruction change trend has been covered. Figure 1-Figure 5 The working conditions such as same direction increase, same direction decrease, and back and forth change are representative and can reflect the overall characteristics of the scheduling AGC instructions.

[0039] like Figure 9-10 As shown: AGC Command Allocation Strategy: Plant-level AGC commands include the base operating values for the thermal power units. Therefore, these commands need to be broken down to derive power commands for the thermal power units, batteries, and flywheels. Considering that flywheels have a longer lifespan and smaller capacity than batteries, the top-level control strategy follows the basic principle: maximize ramping for the generator units (thermal power units), maximize flywheel power, and provide a backup battery.

[0040] The power command allocation steps are briefly described as follows: 1. Based on the AGC instructions, taking into account the actual climbing ability of the thermal power unit, generate the generator unit instructions with slope limit; 2. Subtract the generator set command from the AGC command to obtain the energy storage system command; 3. The flywheel responds to the energy storage instruction first, taking into account the flywheel power and capacity limitations, and generates the flywheel instruction; 4. Subtract the flywheel response curve from the energy storage system command to obtain the battery command.

[0041] refer to Figure 1-Figure 5 The AGC data of Laicheng Power Plant shows a thermal power unit ramp rate of 2.5% / min. Power is distributed according to the fitted AGC command curve, first to the thermal power units and hybrid energy storage equipment, and then redistributed to the hybrid energy storage equipment.

[0042] As the best configuration solution for this embodiment, select: Based on typical instructions, the operating characteristics and performance indicator Kp under different capacity configurations are analyzed, respectively equipped with 2MW / 2MWh battery + 2MW / 80MJ flywheel and 6MW / 6MWh battery + 3MW / 120MJ flywheel. When the energy storage device is not put into use, the unit has a high climbing rate, and the performance indicator Kp is around 3.7. This is not elaborated here.

[0043] When 2MW / 2MWh electricity + 2MW / 80MJ flywheel is put into use, the performance index Kp is about 3.95. When 6MW / 6MWh + 3MW / 120MJ flywheel is put into use, the performance index Kp is about 4.2. After the energy storage device is put into use, the performance index is greatly improved. The following analyzes the operating characteristics after the energy storage device is put into use.

[0044] One of the solutions: 2MW / 2MWh battery energy storage + 2MW / 80MJ flywheel energy storage like Figure 11 It can be seen from the AGC instruction and unit output curve that when only the thermal power unit output is not put into the machine storage device, most thermal power units in the regulation cycle cannot track the changes in the AGC instruction well. It can be seen from the AGC instruction and machine storage power curve in the figure that the effect is improved after the energy storage device is put into use.

[0045] like Figure 12 As shown in the figure, the allocation principle of the hybrid energy storage device is that the flywheel energy storage responds first and then the battery energy storage responds. In addition, because the total capacity of the 2MW / 2MWh battery + 2MW / 80MJ flywheel is relatively small, the actual energy storage cannot fully respond to the energy storage system's command requirements.

[0046] like Figure 13 As shown in the figure, the effective performance index Kp value after the energy storage device is put into use is around 3.95.

[0047] As another configuration scheme of this embodiment: Another option: 6MW / 6MWh battery energy storage + 3MW / 120MJ flywheel energy storage like Figure 14 It can be seen from the AGC command and unit output curve that only the thermal power unit output has not been put into the energy storage device. In most regulation cycles, the thermal power units cannot track the changes in the AGC command well. It can be seen from the AGC command and unit storage power curve in the figure that the effect is significantly improved after the energy storage device is put into use.

[0048] from Figure 15 As shown in the figure, the allocation principle of the hybrid energy storage device is to respond to the flywheel energy storage first and then the battery energy storage. Because the total capacity of the 6MW / 6MWh battery + 3MW / 120MJ flywheel meets the AGC instruction change requirements of the 300MW unit, the actual energy storage output can better track the energy storage system instruction changes.

[0049] Depend on Figure 16 As shown in the figure, the effective performance index Kp value after the energy storage device is put into use is around 4.2, and the improvement effect is obvious.

[0050] The economic analysis of the flywheel energy storage + lithium battery energy storage combined frequency regulation system is as follows: The economic analysis mainly considers the system investment cost, maintenance cost, and revenue, establishes a profit model with different capacity ratios, and performs optimization solutions.

[0051] 1. Cost Analysis Battery energy storage unit 1MW / 1MWh, unit cost The unit is RMB / MW. If m battery units are configured, the battery investment cost is for: (1) The unit cost of a flywheel energy storage unit of 1MW / 40MJ is , unit: yuan / MW; if n flywheel units are configured, the battery investment cost is for: (2) The investment cost of the power transformation and distribution system is recorded as 8% of the energy storage cost; the secondary control system and manufacturing cost is recorded as 6% of the energy storage cost; Operation and maintenance costs are recorded as 10% of the energy storage cost; 2. Battery life and operating life The service life of lithium-ion batteries is closely related to the depth of charge and discharge. Ascend to the end of the charging mission , then perform the discharge task from Descend to Depth of one charge-discharge cycle The calculation formula for energy storage charge and discharge depth is: (3) Where, The rated capacity of lithium battery energy storage; It is the energy storage discharge power of lithium battery.

[0052] According to the experimental data of charge and discharge depth and maximum charge and discharge times, the relationship function between energy storage charge and discharge depth and maximum charge and discharge times is fitted as follows: (4) Where, is the first charge and discharge depth; is the rated charge and discharge depth, here it is taken as 0.9; The maximum number of charge and discharge times at the rated charge and discharge depth is 5500.

[0053] Definition of equivalent charge and discharge coefficient For the depth of charge and discharge When charging and discharging once is equivalent to the number of charge and discharge times under full charge and discharge, the value range is (0,1), and the expression is: (5) Where, The maximum number of charge and discharge times at the depth of charge and discharge; It is the maximum charge and discharge times under full charge and discharge conditions.

[0054] The rain flow counting method is used to count the depth of charge and discharge in one day, and the equivalent number of charge and discharge times per day is obtained as follows: (6) Battery operating life: (7) During the 20-year life cycle, the number of battery replacements is 20 / Tlife, and the replacement cost is for: (8) The battery replacement process cannot respond to AGC instructions and the loss cost is ; 3. Total cost In summary, the total cost for: (9) 4) Benefit Analysis Refer to the "Shandong Electricity Spot Market Trading Rules (Trial) 2022 Trial Version V1.0" and "Appendix 1 of Shandong Electricity Grid Connection Operation Management Implementation Rules of Shandong Jianneng Market

[2023] No. 53" to calculate the benefits of auxiliary frequency regulation.

[0055] The expenses related to the frequency regulation market are divided into frequency regulation auxiliary service fees and shared expenses, and are settled by balancing income and expenditure and settling accounts daily and monthly.

[0056] The winning power generation units and independent ancillary service providers can obtain corresponding frequency regulation ancillary service fees by providing frequency regulation services in the frequency regulation market. The frequency regulation ancillary service fees of power generation units and independent ancillary service providers are calculated on a daily basis and settled on a monthly basis. The daily fee calculation formula for AGC services of power generation units and independent ancillary service providers is as follows: (10) in: CAGC is the daily charge for AGC services provided by power generation units or independent ancillary service providers.

[0057] D is the sum of the daily adjustments of power generation units or independent auxiliary service providers, that is (11) Where Dj is the jth regulation depth of the generation unit or independent ancillary service provider, and n is the number of daily regulation times. When a generation unit or independent ancillary service provider performs foldback regulation, 0.5% of its rated capacity is added to the regulation depth.

[0058] Kpd is the regulation performance indicator of the power generation unit or independent ancillary service provider on the day.

[0059] YAGC is the AGC ancillary service clearing price for power generation units or independent ancillary service providers on the operating day.

[0060] When calculating the energy storage AGC-assisted frequency regulation benefit, the AGC frequency regulation benefit of the unit itself needs to be removed.

[0061] 5) Profit model Record full life cycle profitability (Unit: 10,000 yuan): (12) Life cycle investment payback period (13) Multi-objective function, considering the profitability of the entire life cycle , battery replacement times, investment payback period and other multi-dimensional factors.

[0062] Constraints: 1) The battery cycle is no more than 5500 times; 2) Battery SOC value range (14) 3) Flywheel SOC value range (15) By establishing a mathematical model for optimization and solution, the energy storage capacity configuration plan can be obtained.

[0063] The comprehensive chart data analysis is as follows: (1) Taking Laicheng Power Plant as an example, the actual operating unit ramp rate is 2.5%. The existing energy storage battery has a life of approximately 3 years and needs to be replaced about 6 times.

[0064] (2) The flywheel is calculated based on 1MW / 40MJ. The "battery + flywheel" combination scheme is configured based on the goals of short investment recovery period and high total revenue: Solution ①: 4MW / 4MWh battery + 2MW / 80MJ flywheel solution, with a Kp performance index of 4.14, four battery replacements, and a static payback period of 3.9 years; Solution ②: 5MW / 5MWh battery + 2MW / 80MJ flywheel solution, with a Kp performance index of 4.14, four battery replacements, and a static payback period of 4.5 years; Solution ③: 5MW / 5MWh battery + 3MW / 120MJ flywheel solution, with a Kp performance index of 4.11, three battery replacements, and a static payback period of 4.2 years; Solution ④: 6MW / 6MWh battery + 2MW / 80MJ flywheel solution, with a Kp performance index of 4.12, four battery replacements, and a static payback period of 5.2 years; Solution ⑤: 6MW / 6MWh battery + 3MW / 120MJ flywheel solution, with a Kp performance index of 4.12, three battery replacements, and a static payback period of 4.7 years.

[0065] Taking into account the 20-year equipment operation and maintenance life cycle and the capacity of the thermal power units, the limited space in the frequency regulation plant area, and the current electrical main connection status of the AB section ring network busbars, we recommend Solution ① 4MW / 4MWh battery + 2MW / 80MJ and Solution ④ 6MW / 6MWh battery + 2MW / 80MJ flywheel combination solutions for the owner to choose.

[0066] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage, characterized in that: The steps include: S1: Receives AGC instructions issued by the AGC dispatch center; S2: The flywheel energy storage system prioritizes frequency modulation requirements. Based on its instantaneous power output capability and remaining capacity, the flywheel speed is adjusted in real time to compensate for small power deviations at high frequencies. S3: When the flywheel energy storage power or energy is insufficient, the battery energy storage responds by supplementing and limiting the charge and discharge depth according to the battery's state of charge to extend its service life; S4: Combined with the actual ramp rate of thermal power units, the output of the energy storage system is dynamically allocated to form a joint frequency regulation model of thermal power and hybrid energy storage.

2. A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: The thermal power unit is used to respond to grid dispatch instructions and output base power, the flywheel energy storage is used to provide instantaneous high-power response to compensate for the insufficient climbing rate of the thermal power unit; the battery energy storage is used to provide continuous power support to supplement the energy gap of the flywheel energy storage.

3. The grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: The AGC command in S1 is decomposed into a thermal power unit frequency regulation command, a flywheel energy storage frequency regulation command and a battery energy storage frequency regulation command by the AGC dispatch center.

4. A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 3, characterized in that: It also includes a hybrid energy storage control system, which receives the AGC instructions issued by the AGC dispatch center in S1, and then distributes the hybrid energy storage frequency regulation instructions to the flywheel energy storage system and the battery energy storage system, and also sends the frequency regulation instructions of the thermal power unit to the thermal power unit.

5. A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: The AGC instructions in S1 are decomposed by an AGC instruction allocation strategy, which includes the following steps: S10: The AGC dispatch center generates a slope-limited generator set instruction based on the AGC instruction and the actual climbing capability of the thermal power unit; S11: The energy storage system command is obtained by subtracting the generator command from the AGC command; S12: The flywheel responds to the energy storage instruction first, and generates a flywheel instruction in combination with the flywheel power and capacity limit; S13: Subtract the flywheel response curve from the hybrid energy storage control system command to obtain the battery command.

6. The grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: The flywheel energy storage adopts a permanent magnet synchronous motor, magnetic levitation bearing and integrated flywheel rotor design, with a speed range of 10,000-30,000 rpm, a power density of ≥1MW / 40MJ, and a comprehensive conversion efficiency of ≥85%.

7. The method for power grid frequency modulation based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: The battery energy storage adopts lithium iron phosphate battery, the charge and discharge rate is 1C-2C, and the battery state of charge working range is 20%~90%.

8. A grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 1, characterized in that: Also included is a control strategy comprising the steps of: S20: A frequency-dividing control strategy is adopted to allocate the high-frequency component of the grid frequency fluctuation to the flywheel energy storage and the low-frequency component to the battery energy storage; S21: Introduce a variable proportion control algorithm to dynamically adjust the output ratio of the flywheel and the lithium battery according to the amplitude and change frequency of the AGC instruction.

9. The method for power grid frequency modulation based on flywheel energy storage and electrochemical energy storage according to claim 7, characterized in that: The high-frequency component of the grid frequency fluctuation is 0.1-2 Hz, and the low-frequency component is <0.1 Hz.

10. The grid frequency modulation method based on flywheel energy storage and electrochemical energy storage according to claim 3, characterized in that: The hybrid energy storage control system has a capacity configuration of flywheel energy storage power 2-3MW / 80-120MJ, lithium battery energy storage capacity 4-6MWh, and a system comprehensive performance index Kp≥4.0.

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