Compressed air-super capacitor hybrid energy storage system for improving wind power utilization rate

Abstract

The invention belongs to the technical field of wind power generation and energy storage, and discloses a compressed air-super capacitor hybrid energy storage system for improving the wind power utilization rate. Based on the characteristic that compressed air energy storage with hour-level response cannot stabilize high-frequency wind power, a super capacitor with second-level response is coupled on the basis of a compressed air energy storage system. Compressed air energy storage gives play to the advantages of large energy storage capacity and hour-level response, undertakes main storage tasks and stabilizes low-frequency high-amplitude wind power. And the super capacitor stabilizes the fluctuation of high frequency and low amplitude according to the characteristics of small energy storage capacity and second-level response. Through complementarity of the two in capacity and response time, full-band coverage of wind power is realized, and the utilization rate of the wind power is improved. The super capacitor integrates the stored small-capacity electric energy into a large-capacity system of the CAES, and the impact risk caused by independent grid connection is reduced.

Description

Technical Field

[0001] This invention belongs to the field of wind power generation and energy storage technology, and relates to a compressed air-supercapacitor hybrid energy storage system for improving wind power utilization. Background Technology

[0002] Wind power, as a cornerstone of global energy transition, boasts significant advantages such as low cost, high reliability, and mature technology. Based on this, large-scale development of wind energy has become an inevitable trend. However, power spectral density analysis reveals that wind power fluctuations contain components of different frequencies and amplitudes. Specifically, low-frequency fluctuations (0.001–0.01 Hz) exhibit high amplitude characteristics, while high-frequency fluctuations (0.01–1 Hz) show low amplitude fluctuations. This characteristic significantly increases the difficulty of directly connecting wind power to the grid. Against this backdrop, wind curtailment measures must be implemented to ensure stable grid operation, but this results in substantial energy waste. To mitigate the volatility of wind power and improve its utilization rate, the application of energy storage systems has become an important research direction.

[0003] Among numerous energy storage technologies, compressed air energy storage (CAES) stands out as the most promising wind power grid-connected technology due to its advantages such as pollution-free medium, long service life (over 15 years), and high efficiency (70-80%). Its working principle involves compressing air using surplus wind power, generating electricity through air expansion when power supply is insufficient. This system features large capacity and hourly response, effectively mitigating low-frequency, high-amplitude wind power fluctuations. However, it struggles to handle high-frequency, low-amplitude components, leading to energy waste in these areas. This necessitates a complementary energy storage technology with a fast response time to fill the functional gaps in CAES systems.

[0004] Supercapacitors operate based on the double-layer energy storage principle, with energy storage and release processes relying on physical adsorption and involving almost no chemical reactions. The high reversibility of this process gives them a response speed in the order of seconds, making them highly advantageous in handling high-frequency wind power components. Furthermore, supercapacitors also possess a long cycle life (10... 6 ~10 7 Supercapacitors offer advantages such as high energy density and high energy efficiency (95%). However, limited by low energy density and high cost, the energy storage capacity of supercapacitors is much smaller than that of compressed air energy storage systems, making them unable to handle high-amplitude wind power fluctuations and restricting their large-scale application. Therefore, supercapacitors and compressed air energy storage systems are highly complementary in terms of energy storage capacity and response time, and can be coupled and integrated to achieve full-frequency coverage of wind power, further improving the constant power delivered to the grid.

[0005] Based on the above background technology and the differences in energy storage characteristics between compressed air energy storage and supercapacitors, this invention proposes a compressed air-supercapacitor hybrid energy storage system for improving wind power utilization. The compressed air energy storage system smooths out low-frequency, high-amplitude wind power, while the supercapacitor absorbs high-frequency, low-amplitude components, thus improving wind power utilization while maintaining the advantages of each. Summary of the Invention

[0006] The purpose of this invention is to provide a compressed air-supercapacitor hybrid energy storage system for improving wind power utilization. Compressed air energy storage leverages its large capacity and hourly response time to perform the primary storage task, smoothing out low-frequency, high-amplitude wind power fluctuations. Supercapacitors, with their small capacity and second-level response time, smooth out high-frequency, low-amplitude fluctuations. This hybrid energy storage system can effectively smooth out full-frequency fluctuations in wind power, improving wind power utilization. Furthermore, the small-capacity energy stored in the supercapacitors is integrated into the large-capacity CAES system, reducing the impact of separate grid connection on the power grid.

[0007] The technical solution of the present invention:

[0008] A compressed air-supercapacitor hybrid energy storage system for improving wind power utilization is described below:

[0009] First, the total wind power output E-1 from the wind farm is decomposed into high-frequency low-amplitude wind power E-2 and the first low-frequency high-amplitude wind power E-3 after passing through bandpass filter 1.

[0010] Among them, the high-frequency low-amplitude wind power is converted into DC power by AC / DC converter 2, and then the charging mode of the supercapacitor is opened by the first switch S-1 closing control; when the electrical energy stored in the supercapacitor reaches the first constant power electrical energy E-4, the discharging mode is opened, and the power is converted into AC power by DC / AC converter 3, and then the power is delivered to the CAES system by the second switch S-2 closing control.

[0011] The first low-frequency high-amplitude wind power E-3 is split into two streams. The second low-frequency high-amplitude wind power E-5 is connected to the grid after its parameters are adjusted by the first AC / AC converter 4. The third low-frequency high-amplitude wind power E-6 is connected to the grid after its parameters are adjusted by the second AC / AC converter 5 and then controlled by the closing of the third switch S-3 to start the charging mode of the CAES system, converting electrical energy into the internal energy of compressed air. The total electrical energy E-7 stored in the CAES system is equal to the sum of the third low-frequency high-amplitude wind power E-6 and the electrical energy E-4 of the first constant power. When the energy monitoring and control system 7 monitors that the electrical energy E-5 of the second low-frequency high-amplitude wind power is less than the electrical energy E-9 of the second constant power, the CAES system starts the discharge mode and outputs supplementary electrical energy E-8 to convert the internal energy of compressed air into electrical energy. After the relevant parameters are adjusted by the third AC / AC converter 6 and the grid connection standard is met, the fourth switch S-4 is closed. The electrical energy E-9 of the second constant power is equal to the sum of the electrical energy E-5 of the second low-frequency high-amplitude wind power and the supplementary electrical energy E-8.

[0012] The beneficial effects of this invention are as follows: Based on the process flow of this invention, a supercapacitor with a second-level response is coupled around a compressed air energy storage system with an hourly response, which can improve the utilization rate of wind power through full-band coverage; the small-capacity electrical energy stored by the supercapacitor can be integrated into the large capacity of the CAES system, reducing the impact risk brought by separate grid connection; and the constant power connected to the grid can be improved, enhancing the stability of grid operation. Attached Figure Description

[0013] Figure 1 This is a flowchart illustrating the technological principles of a compressed air-supercapacitor hybrid energy storage system coupled with a wind farm for grid connection.

[0014] Explanation of symbols and numbers in the diagram: 1, bandpass filter; 2, AC / DC converter; 3, DC / AC converter; 4, first AC / AC converter; 5, second AC / AC converter; 6, third AC / AC converter; 7, energy monitoring and control system; S-1, first switch; S-2, second switch; S-3, third switch; S-4, fourth switch; E-1, total wind power; E-2, high-frequency low-amplitude wind power; E-3, first low-frequency high-amplitude wind power; E-4, first constant power electrical energy; E-5, second low-frequency high-amplitude wind power; E-6, third low-frequency high-amplitude wind power; E-7, total electrical energy stored in the CAES system; E-8, supplementary electrical energy; E-9, first constant power electrical energy.

[0015] Figure 2 It is a typical daily wind power curve and its decomposed wind power.

[0016] Figure 3 It is a comparison of the specific electrical energy situation between the power grid and the CAES system. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0018] Example

[0019] The example establishes a wind farm-energy storage-grid coupling system based on the most fluctuating wind power data from a local wind farm, employing supplementary... Figure 1 The process is shown below. A typical daily wind power curve and its decomposed wind power of a wind farm are shown below. Figure 2 As shown, the total wind power accumulated was 478.00 MWh. After being separated by a bandpass filter, it yielded low-frequency high-amplitude wind power and high-frequency low-amplitude wind power, which were 387.18 MWh and 90.82 MWh, respectively.

[0020] The generated high-frequency wind power is fed to the supercapacitor after its parameters are adjusted by an AC / DC converter. When the power of the high-frequency wind power is less than the rated power (4 MW) of the supercapacitor, the supercapacitor enters charging mode. After storing 5.50 MWh of energy, it enters discharging mode, and after its parameters are adjusted by the DC / AC converter, it supplies power to the CAES system at a constant power (3.4 MW). Simulations show that the supercapacitor stores a total of 64.34 MWh of energy in one day, providing a total of 61.12 MWh to the CAES system.

[0021] The generated low-frequency wind power must first meet the grid's constant power demand, with any excess stored in the CAES system. If the wind farm's output cannot meet the grid's demand, the CAES system will discharge to supplement it. The constant power of this hybrid energy storage system coupled with the wind farm connected to the grid is 12.77 MW. When the wind farm's low-frequency wind power output exceeds 12.77 MW, the CAES system activates charging mode; otherwise, it activates discharging mode. During this process, the CAES system absorbs a total of 77.63 MWh of low-frequency wind power from the wind farm, the supercapacitor provides 61.12 MWh, and the stored energy totals 138.75 MWh. The total energy generated during the discharge process is 83.57 MWh. In addition, the total low-frequency wind power directly connected to the grid by the wind farm is 222.91 MWh. In summary, the total electrical energy output from the hybrid energy storage system coupled with the wind farm to the grid is equal to the sum of the low-frequency wind power directly connected to the wind farm and the supplementary electrical energy from the CAES system, totaling 306.48 MWh. The total electrical energy generated by the wind farm is 478.00 MWh. Therefore, the utilization efficiency of wind power is 64.12%. The energy storage capacity of the CAES system is 65.00 MWh.

[0022] Taking the annual wind power data of this wind farm as an example, the estimated construction investment for a 65.00 MWh compressed air energy storage device is 47.3148 million yuan, and the construction investment for a 5.50 MWh supercapacitor is 5.9265 million yuan, bringing the total investment for the hybrid energy storage system to 53.2413 million yuan. The CAES system in the hybrid energy storage system inputs approximately 28,109.57 MWh / year into the grid. Based on a wind power grid-connected price of 0.52 yuan / kWh, the annual revenue is 14.617 million yuan. The operating costs of the CAES system and the supercapacitor are 5.0821 million yuan / year and 0.6676 million yuan / year, respectively, totaling 5.7497 million yuan / year. Therefore, the profit of the hybrid energy storage system is 8.8673 million yuan / year, with an investment payback period of approximately 6 years.

[0023] When both the first switch S-1 and the second switch S-2 are open, only the CAES system is operational. This system can only smooth low-frequency wind power and cannot recover high-frequency wind power. The constant power of the CAES system coupled to the wind farm and connected to the grid is 10.65 MW. When the low-frequency wind power output from the wind farm exceeds 10.65 MW, the CAES system activates charging mode; otherwise, it activates discharging mode. During this process, the CAES system absorbs a total of 99.44 MWh of low-frequency, high-amplitude energy from the wind farm and generates a total of 54.50 MWh of energy during the discharge process. In addition, the total low-frequency wind power directly connected to the grid from the wind farm is 201.10 MWh. In summary, the CAES system outputs 255.60 MWh of energy to the grid coupled with the wind farm, while the total energy generated by the wind farm is 478.00 MWh. Therefore, the wind power utilization efficiency is 53.50%. The energy storage capacity of the CAES system is 58.00 MWh.

[0024] Taking the annual wind power data of this wind farm as an example, the estimated construction investment for a 58.00 MWh compressed air energy storage (CAES) device is 40.7341 million yuan; the electricity input to the grid by the CAES system is approximately 18331.59 MWh / year, and based on a wind power grid-connected electricity price of 0.52 yuan / kWh, the annual revenue is 9.5324 million yuan; the operating cost of the CAES system is 4.3815 million yuan / year. Therefore, the profit of the CAES system is 5.1509 million yuan / year, and the investment payback period is approximately 8 years.

[0025] Based on the above analysis, compared with the integration of wind farms into the grid using a CAES system, the wind power utilization rate of a hybrid energy storage system integrated into the grid is increased by 10.62%. Combined with... Figure 3 It can be seen that the amount of electricity directly connected to the grid increased by 11.38%, and the amount of electricity provided to the grid by the CAES system increased by 53.34%. In addition, the profit of the hybrid energy storage system increased by RMB 3.6857 million per year, and the investment payback period was shortened by 2 years.

Claims

1. A compressed air-ultra-capacitor hybrid energy storage system for improving the utilization of wind power, characterized in that, Specific as follows: First, the total wind power (E-1) output by the wind farm is decomposed into high-frequency low-amplitude wind power (E-2) and first low-frequency high-amplitude wind power (E-3) after passing through a band-pass filter (1); Among them, the high-frequency low-amplitude wind power is converted into direct current by an AC / DC converter (2), and then the first switch (S-1) is closed to control the super capacitor to start the charging mode; when the stored energy of the super capacitor reaches the first constant power energy (E-4), the discharge mode is started, which is converted into alternating current by a DC / AC converter (3), and then the second switch (S-2) is closed to control the delivery to the CAES system; The first low-frequency high-amplitude wind power (E-3) is divided into two streams, among which the second low-frequency high-amplitude wind power (E-5) is adjusted by the first AC / AC converter (4) after adjusting the relevant parameters and is integrated into the power grid; the third low-frequency high-amplitude wind power (E-6) is adjusted by the second AC / AC converter (5) after adjusting the relevant parameters, and then the third switch (S-3) is closed to control the CAES system to start the charging mode, and the energy is converted into the internal energy of compressed air; the total energy (E-7) stored in the CAES system is equal to the sum of the third low-frequency high-amplitude wind power (E-6) and the first constant power energy (E-4); when the energy monitoring and control system (7) monitors that the second low-frequency high-amplitude wind power (E-5) is less than the second constant power energy (E-9), the CAES system starts the discharge mode, outputs the supplementary energy (E-8), converts the internal energy of compressed air into electrical energy, adjusts the relevant parameters by the third AC / AC converter (6), and reaches the grid-connected standard, then the fourth switch (S-4) is closed; the second constant power energy (E-9) is equal to the sum of the second low-frequency high-amplitude wind power (E-5) and the supplementary energy (E-8).

2. The compressed air-ultracap hybrid energy storage system of claim 1, wherein, The internal energy of compressed air is stored at a pressure of 5 MPa to 10 MPa, and after expansion in the discharge mode, the pressure range is 0.1 MPa to 1 MPa, which can stabilize and suppress low-frequency high-amplitude wind power fluctuations of 0.001 to 0.01 Hz.

3. The compressed air-ultracap hybrid energy storage system of claim 1, wherein, The super capacitor recovers high-frequency low-amplitude wind power of 0.01 to 1 Hz.

4. The compressed air-ultracap hybrid energy storage system of claim 1, wherein, The energy output by the super capacitor is provided to the internal energy of compressed air in a constant power mode.

Images