Compressed air energy storage frequency modulation system

Abstract

The invention provides a compressed air energy storage frequency modulation system. The compressed air energy storage frequency modulation system comprises an air storage tank; the generator is electrically connected with the power grid; the inlet end of the expansion adjusting pipeline is communicated with the gas storage tank, the outlet end of the expansion adjusting pipeline is provided with an exhaust port, the expansion adjusting pipeline comprises at least one expansion branch, the expansion branch is provided with an expansion machine, the expansion machine is connected with the power generator, and when gas in the gas storage tank passes through the expansion machine, the expansion machine is connected with the power generator. The expansion machine is driven to work to control the power generation rate of the generator; the gas supply inlet end of the gas supply pipeline is communicated with the gas storage tank, and the gas supply outlet end of the gas supply pipeline is communicated with the gas inlet of at least one expansion machine, so that gas passing through the gas supply pipeline drives the expansion machine to do work to control the power generation rate of the generator. The problems that in the prior art, a compressed air energy storage system is insufficient in response and low in speed during frequency adjustment are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air energy storage system design, and in particular to a compressed air energy storage frequency modulation system. Background Art

[0002] With the rapid development of renewable energy, the supply and demand fluctuations of the power grid have intensified. Compressed air energy storage system (CAES) has attracted attention for its large-scale energy storage and peak load regulation capabilities. CAES system compresses air to store energy when power demand is low, and releases air to drive expanders to drive generators to generate electricity when power demand is high.

[0003] Energy storage systems are an important part of power systems, mainly used to store excess electrical energy and release it when needed. In power grids, the energy storage and release phases of energy storage systems are usually carried out separately. In the energy storage phase, when the power supply in the grid exceeds the demand, the energy storage system will store the excess electrical energy; and in the release phase, when the power demand in the grid exceeds the supply, the energy storage system will release the stored electrical energy to meet the needs of the grid.

[0004] In the power system, frequency stability is one of the key indicators for the stable operation of the system. The frequency of the power grid needs to be maintained within a certain range. For example, in China, the standard frequency of the power grid is 50Hz, and the allowable deviation range is usually ±0.2Hz. In order to maintain frequency stability, power grid operators will implement frequency regulation services, including primary frequency regulation, secondary frequency regulation, and tertiary frequency regulation. As a flexible regulation resource, the energy storage system can respond to the frequency regulation needs of the power grid by storing and releasing energy.

[0005] When a traditional CAES system performs a frequency regulation, the rate of regulation depends on the regulation characteristics of the unit itself. In some extreme working conditions, such as when the grid load gap is large, especially when the unit needs to be adjusted upward with a large ramp rate, the traditional regulation method has problems of insufficient response or slow rate and cannot fully support the grid frequency needs. Summary of the invention

[0006] The main purpose of the present invention is to provide a compressed air energy storage frequency modulation system to solve the problems of insufficient response and slow rate in frequency regulation of the compressed air energy storage system in the prior art.

[0007] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a compressed air energy storage and frequency modulation system is provided, comprising: a gas storage tank; a generator, the generator being electrically connected to a power grid; an expansion regulating pipeline, the inlet end of the expansion regulating pipeline being connected to the gas storage tank, the outlet end of the expansion regulating pipeline being provided with an exhaust port, the expansion regulating pipeline comprising at least one expansion branch, the expansion branch being provided with an expander, the expander being connected to the generator, wherein when the gas in the gas storage tank passes through the expander, the expander is driven to do work to control the power generation rate of the generator; an air supply pipeline, the air supply inlet end of the air supply pipeline being connected to the gas storage tank, the air supply outlet end of the air supply pipeline being connected to the gas inlet of at least one expander, so that the gas passing through the air supply pipeline drives the expander to do work to control the power generation rate of the generator.

[0008] Furthermore, the expansion regulating pipeline includes a plurality of expansion branches connected in series in sequence, and each expansion branch is provided with an expansion machine. The compressed air energy storage and frequency modulation system also includes an expansion heat exchange pipeline, and the expansion heat exchange pipeline includes: a first heat exchange branch, there are multiple first heat exchange branches, and the multiple first heat exchange branches are arranged in parallel, one end of each first heat exchange branch is connected to the heat storage tank, and the other end of the first heat exchange branch is connected to the cold storage tank, each first heat exchange branch is provided with a first heat exchanger, and the multiple first heat exchangers are respectively arranged corresponding to the multiple expansion machines, and the first heat exchanger is used to heat the airflow before the airflow enters the corresponding expansion machine.

[0009] Furthermore, the expansion branch includes at least a first-level expansion branch, a second-level expansion branch, and a third-level expansion branch. The inlet end of the first-level expansion branch is connected to the gas storage tank, the inlet end of the second-level expansion branch is connected to the outlet end of the first-level expansion branch, the inlet end of the third-level expansion branch is connected to the outlet end of the second-level expansion branch, the outlet end of the third-level expansion branch is provided with an exhaust port, and the first-level expansion branch, the second-level expansion branch, and the third-level expansion branch are all provided with an expander.

[0010] Furthermore, the air supply pipeline includes: a first air supply pipeline, the inlet end of the first air supply pipeline is connected to the air storage tank, and the outlet end of the first air supply pipeline is connected to the inlet of the expander of the secondary expansion branch; a second air supply pipeline, the inlet end of the second air supply pipeline is connected to the air storage tank, and the outlet end of the second air supply pipeline is connected to the inlet of the expander of the tertiary expansion branch.

[0011] Furthermore, the air supply pipeline includes: an air supply mother pipe, the air supply mother pipe is connected to the air storage tank, the inlet end of the first air supply pipeline is connected to the air supply mother pipe, and the inlet end of the second air supply pipeline is connected to the air supply mother pipe.

[0012] Furthermore, the air supply pipeline includes an air supply heat exchange pipeline, which includes: a second heat exchange branch, there are two second heat exchange branches, one end of each second heat exchange branch is connected to the heat storage tank, and the other end of the second heat exchange branch is connected to the cold storage tank, each second heat exchange branch is provided with a second heat exchanger, one second heat exchanger is arranged on the first air supply pipeline, so that the second heat exchanger heats the airflow flowing through the first air supply pipeline to the expansion machine corresponding to the first air supply pipeline, and the other second heat exchanger is arranged on the second air supply pipeline, so that the second heat exchanger heats the airflow flowing through the second air supply pipeline to the expansion machine corresponding to the second air supply pipeline.

[0013] Furthermore, each second heat exchange branch is provided with a heat exchange regulating valve.

[0014] Furthermore, each expansion branch is provided with an air release valve.

[0015] Furthermore, each expansion branch is provided with an inlet regulating valve and an outlet regulating valve at both ends of the expander.

[0016] Furthermore, each expander is connected to the rotor of the generator via a coupling.

[0017] By applying the technical solution of the present invention, an air supply pipeline is set to supply air to the expander, and the air supply pipeline and the expansion branch are controlled in a coordinated manner, so that the compressed air energy storage system can quickly respond and effectively control the speed under the condition of rapid response to primary frequency modulation, thereby improving the output of the unit and ensuring the climbing rate of the unit, thereby solving the technical problems of insufficient response or slow rate of traditional regulation methods and the inability to fully support the frequency requirements of the power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A structural schematic diagram of an embodiment of a compressed air energy storage frequency modulation system according to the present invention is shown.

[0020] The above drawings include the following reference numerals:

[0021] 1. Gas storage tank; 12. Heat exchange main valve; 13. High-pressure main gas valve; 14. Rush regulating valve; 15. Power regulating valve; 16. Inlet regulating valve; 17. Outlet regulating valve; 2. Heat storage tank; 23. Air release valve; 26. Heat exchange valve; 3. Cold storage tank; 30. Heat pump; 31. Generator; 32. Air supply main pipe; 33. First air supply pipeline; 34. Air intake branch regulating valve; 35. Second air supply pipeline; 37. Main pipe flow regulating valve; 38. Heat exchange regulating valve; 4. Expander; 40. Second heat exchanger; 8. First heat exchanger. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] Now, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. However, these exemplary embodiments may be implemented in a variety of different forms and should not be construed as being limited to the embodiments described herein. It should be understood that these embodiments are provided to make the disclosure of the present application thorough and complete, and to fully convey the concepts of these exemplary embodiments to those of ordinary skill in the art. In the accompanying drawings, for the sake of clarity, the thickness of the layers and regions may be enlarged, and the same reference numerals are used to represent the same devices, and thus their descriptions will be omitted.

[0026] In order to maintain frequency stability, grid operators will implement frequency regulation services, including primary frequency regulation, secondary frequency regulation and tertiary frequency regulation. As a flexible regulation resource, the compressed air energy storage system can respond to the frequency regulation needs of the grid by storing and releasing energy.

[0027] Primary frequency regulation, secondary frequency regulation and tertiary frequency regulation are different levels of automatic frequency regulation services implemented in the power system to maintain the stability of the power grid frequency. The main differences between them are response time, regulation range and control mechanism. The following is a detailed explanation of these three concepts:

[0028] 1. Primary frequency regulation: Primary frequency regulation is a fast-response frequency regulation that is usually completed within a few seconds. This is to cope with instantaneous frequency fluctuations in the power grid, such as frequency changes caused by sudden increases or decreases in load. Primary frequency regulation mainly automatically increases or decreases the power generation through the speed regulator of the generator to offset the frequency change. It works on a pre-set power-frequency control curve and can provide small but fast power adjustments. Primary frequency regulation is an automatic control based on the frequency deviation of the power grid and does not require direct instructions from the dispatch center. When the frequency drops, the generator automatically increases the output; when the frequency rises, it automatically reduces the output.

[0029] 2. Secondary frequency regulation: Response time: The response time of secondary frequency regulation is slower than that of primary frequency regulation, usually between tens of seconds and minutes. This is because it involves a wider range of power generation resources and load management. Regulation range: The goal of secondary frequency regulation is to restore the grid frequency to its reference value (such as 50Hz) and eliminate the frequency deviation left by primary frequency regulation. It is achieved by adjusting the output power of multiple generator sets through instructions from the dispatching center. Control mechanism: Secondary frequency regulation is implemented through the automatic generation control (AGC) system of the power dispatching center, which comprehensively considers the supply and demand of the power grid and the available capacity of the generator sets to allocate frequency regulation tasks in the most optimized way.

[0030] 3. Three-way frequency regulation: Response time: The response time of three-way frequency regulation is the slowest, which may take several minutes to several hours, or even longer. Regulation scope: Three-way frequency regulation mainly deals with long-term supply and demand imbalance problems. It may involve the adjustment of power generation plans, the dispatch of spare capacity, and cross-regional power transmission. Control mechanism: Three-way frequency regulation is controlled by the long-term dispatch and market mechanism of the power dispatch center. It may involve transactions and economic dispatch in the power market to ensure the long-term stability and economy of the power grid.

[0031] Frequency changes in power systems have different characteristics and time scales. The stability of the grid frequency needs to be adjusted in different time frames to adapt to various supply and demand changes from instantaneous to long-term. The hierarchical frequency regulation system can handle these changes more finely, ensuring the stability of the grid frequency while also considering economy and efficient use of resources. Primary frequency regulation focuses on rapid response, secondary frequency regulation focuses on medium-time scale frequency recovery, and tertiary frequency regulation focuses on long-term supply and demand balance. The three complement each other and jointly maintain the safe and stable operation of the power grid.

[0032] In view of the shortcomings of the prior art, the present invention provides a method and system for controlling the speed of compressed air energy storage power generation with rapid response and primary frequency modulation to stabilize the speed. The method achieves the purpose of stabilizing the system by controlling the air intake and inlet temperature of the expander to control the speed.

[0033] In order to improve the reliability of the CAES system and the stability of the power grid, it is necessary to develop a technology that can quickly respond and effectively control the speed in the case of a rapid primary frequency regulation. This technology solves the problem that when the unit is adjusted upward, the climbing rate is large and it cannot fully support the needs of the power grid frequency.

[0034] Combination Figure 1 As shown, according to a specific embodiment of the present application, a compressed air energy storage and frequency modulation system is provided, including: a gas storage tank 1; a generator 31, the generator 31 is electrically connected to the power grid; an expansion regulating pipeline, the inlet end of the expansion regulating pipeline is connected to the gas storage tank 1, and the outlet end of the expansion regulating pipeline is provided with an exhaust port, the expansion regulating pipeline includes at least one expansion branch, and the expansion branch is provided with an expander 4, the expander 4 is connected to the generator 31, wherein, when the gas in the gas storage tank 1 passes through the expander 4, the expander 4 is driven to do work to control the power generation rate of the generator 31; an air supply pipeline, the air supply inlet end of the air supply pipeline is connected to the gas storage tank 1, and the air supply outlet end of the air supply pipeline is connected to the gas inlet of at least one expander 4, so that the gas passing through the air supply pipeline drives the expander 4 to do work to control the power generation rate of the generator 31.

[0035] By applying the technical solution of the present invention, an air supply pipeline is set to supply air to the expander, and the air supply pipeline and the expansion branch are controlled in a coordinated manner, so that the compressed air energy storage system can quickly respond and effectively control the speed under the condition of rapid response to primary frequency modulation, thereby improving the output of the unit and ensuring the climbing rate of the unit, thereby solving the technical problems of insufficient response or slow rate of traditional regulation methods and the inability to fully support the frequency requirements of the power grid.

[0036] Through this design, the system can quickly respond to changes in grid frequency and provide stable and efficient frequency regulation services, which is suitable for power frequency regulation scenarios. This design effectively improves the system's response speed to frequency fluctuations. In practical applications, the system can significantly reduce the fluctuation range of grid frequency and improve the overall stability and security of the grid.

[0037] When the temperature of the expander inlet air increases, the density of the air decreases, and the work (energy) generated by expansion is related to the density and pressure of the air. Higher temperature means that the air has a larger volume at the same pressure, so it provides more energy when expanding, thereby increasing the speed of the expander.

[0038] In a frequency modulation, the system needs to respond to frequency changes in a short time and quickly adjust power output. If the grid frequency drops, it means that more power is needed to support the grid. At this time, the temperature of the expander inlet air can be quickly increased to increase the expander speed and increase power output, and vice versa.

[0039] To achieve this control mechanism, it is usually necessary to set up heating equipment (such as heat exchangers) and cooling equipment (such as coolers) in the system. When the speed needs to be increased, the heating equipment will increase the temperature of the expander inlet air; when the speed needs to be reduced, the cooling equipment will reduce the air temperature.

[0040] In order to effectively achieve the above temperature control, the system needs to integrate temperature, pressure and flow sensors, as well as an intelligent control system. The control system will automatically adjust the power of the heating and cooling equipment according to the real-time frequency deviation and expander speed to achieve the required speed stability.

[0041] In the scheme of the present invention, by adding intake branches of secondary and tertiary expanders in the compressed air energy storage power generation system and setting a temperature control system in these branches, the inlet temperature of these expanders can be quickly adjusted when the grid frequency demand changes, thereby directly affecting the output and speed of the expanders, and ultimately achieving rapid response and support for the system frequency, while ensuring the stability of the speed, avoiding the problems of insufficient response or complex structure of traditional CAES systems in frequency regulation.

[0042] In short, by controlling the expander inlet temperature, the work capacity of the expander can be changed, and then the speed and power output can be adjusted to meet the rapid changes in the primary frequency regulation of the power grid and ensure the stable operation of the power system.

[0043] Furthermore, the expansion regulating pipeline includes a plurality of expansion branches connected in series in sequence, and each expansion branch is provided with an expander 4. The compressed air energy storage and frequency modulation system also includes an expansion heat exchange pipeline, and the expansion heat exchange pipeline includes: a first heat exchange branch, there are multiple first heat exchange branches, and the multiple first heat exchange branches are arranged in parallel, one end of each first heat exchange branch is connected to the heat storage tank 2, and the other end of the first heat exchange branch is connected to the cold storage tank 3, and each first heat exchange branch is provided with a first heat exchanger 8, and the multiple first heat exchangers 8 are respectively arranged corresponding to the multiple expanders 4, and the first heat exchanger 8 is used to heat the airflow before the airflow enters the corresponding expander 4.

[0044] Figure 1 A total of four expansion branches are shown in the figure, forming a four-stage expansion branch, wherein, along the direction from the upstream end to the downstream end of the expansion regulating pipeline, there are a primary expansion branch, a secondary expansion branch, a tertiary expansion branch, and a quaternary expansion branch. The expander on the primary expansion branch is a primary expander. The expander on the secondary expansion branch is a secondary expander. The expander on the tertiary expansion branch is a tertiary expander. The expander on the quaternary expansion branch is a quaternary expander.

[0045] This multi-stage expansion and heat exchange design improves energy conversion efficiency and enhances system flexibility, making it suitable for scenarios that require efficient energy conversion and rapid response. The combined use of multi-stage expansion and heat exchange not only significantly improves the efficiency of energy conversion, but also provides a higher level of frequency regulation services, meeting the strict requirements of the power system for frequency regulation performance.

[0046] In a compressed air energy storage (CAES) system, the design of the expander stages and the way they are connected can vary from system to system, but typically, multi-stage expanders are configured in series to achieve efficient energy conversion and higher system performance.

[0047] When compressed air is released from the gas tank, it first expands and works through an expander in a high-temperature and high-pressure state. Since the compressed air cools significantly during the expansion process, in a multi-stage expander system, after passing through the first-stage expander, the air is directed to one or more heat exchangers to be reheated to a higher temperature before entering the next-stage expander to continue expanding and working. This cascade expander design can maximize energy recovery and improve the power output efficiency of the entire system.

[0048] Therefore, in the technical solution of the present invention, the secondary expander and the tertiary expander are connected in series, that is, the compressed air first expands through the secondary expander, and then enters the tertiary expander for further expansion after being heated. Each stage of the expander is equipped with its own air intake regulating valve and temperature control device to accurately control the expansion process of each stage, so as to achieve the purpose of quickly responding to the primary frequency modulation and stabilizing the speed. In this way, the entire system can adjust the power output more flexibly to adapt to the rapidly changing needs of the power grid.

[0049] Furthermore, the expansion branch includes at least a first-level expansion branch, a second-level expansion branch, and a third-level expansion branch. The inlet end of the first-level expansion branch is connected to the gas storage tank 1, the inlet end of the second-level expansion branch is connected to the outlet end of the first-level expansion branch, the inlet end of the third-level expansion branch is connected to the outlet end of the second-level expansion branch, and the outlet end of the third-level expansion branch is provided with an exhaust port. The first-level expansion branch, the second-level expansion branch, and the third-level expansion branch are all provided with an expander 4.

[0050] The multi-stage expansion design enables the system to maintain high energy conversion efficiency under different pressure and temperature conditions. The application of multi-stage expansion technology enables the system to maintain a stable and efficient operating state. This design is crucial to improving the adaptability and reliability of the power system, especially when the compression energy storage system is frequency modulated, it can quickly respond to frequency changes and maintain the stability of the power system.

[0051] Furthermore, the air supply pipeline includes: a first air supply pipeline 33, the inlet end of the first air supply pipeline 33 is connected to the air storage tank 1, and the outlet end of the first air supply pipeline 33 is connected to the inlet of the expander 4 of the secondary expansion branch; a second air supply pipeline 35, the inlet end of the second air supply pipeline 35 is connected to the air storage tank 1, and the outlet end of the second air supply pipeline 35 is connected to the inlet of the expander 4 of the tertiary expansion branch. In this embodiment, by adding two separate air supply pipelines at the outlet of the air storage tank, which are respectively connected to the secondary expander and the tertiary expander, when the energy storage generator system is running and the upward adjustment of the climbing rate is insufficient, the operating parameters of the two air supply pipelines can be adjusted to adjust the air intake of the secondary expander and the tertiary expander, improve the unit output, and ensure the unit climbing rate.

[0052] By setting up different levels of gas supply pipelines, the system can flexibly adjust the gas supply volume according to actual needs, improve the frequency regulation response speed and accuracy, and is suitable for scenarios with rapidly changing frequency requirements in the power system. The design of gas supply pipelines at different levels enables the system to accurately control the frequency regulation power and quickly respond to small fluctuations in the grid frequency. This fine control capability is crucial for fast frequency regulation services in the power market and can significantly improve the frequency stability and dispatch flexibility of the power system.

[0053] Furthermore, the air supply pipeline includes: an air supply mother pipe 32 , the air supply mother pipe 32 is connected to the gas storage tank 1 , the inlet end of the first air supply pipeline 33 is connected to the air supply mother pipe 32 , and the inlet end of the second air supply pipeline 35 is connected to the air supply mother pipe 32 .

[0054] The design of the gas supply mother pipe simplifies the system structure and improves the gas supply efficiency, so that the system can provide frequency regulation services more quickly and stably when facing grid frequency fluctuations. It is suitable for scenarios such as power market frequency regulation services and grid frequency stability control. The introduction of the gas supply mother pipe 32 not only simplifies the complexity of the system, but also improves the efficiency and stability of the gas supply process. This design enables the system to respond to the frequency regulation needs in the power market more efficiently, especially when the grid frequency changes suddenly, it can quickly provide the required frequency regulation power, prevent continuous fluctuations in the system frequency, and ensure the normal operation of the power system.

[0055] Further, the air supply pipeline includes an air supply heat exchange pipeline, and the air supply heat exchange pipeline includes: a second heat exchange branch, two second heat exchange branches, one end of each second heat exchange branch is connected to the heat storage tank 2, and the other end of the second heat exchange branch is connected to the cold storage tank 3, and each second heat exchange branch is provided with a second heat exchanger 40, one second heat exchanger 40 is provided on the first air supply pipeline 33, so that the second heat exchanger 40 heats the airflow flowing through the first air supply pipeline 33 to the expander 4 corresponding to the first air supply pipeline 33, and another second heat exchanger 40 is provided on the second air supply pipeline 35, so that the second heat exchanger 40 heats the airflow flowing through the second air supply pipeline 35 to the expander 4 corresponding to the second air supply pipeline 35. That is to say, a temperature adjustment system is provided for the first air supply pipeline 33 and the second air supply pipeline 35, and the system can automatically adjust the inlet temperature of the expander according to the real-time speed of the expander and the set speed value.

[0056] In the primary frequency response control of the compressed air energy storage (CAES) system, the design of the first air supply pipeline 33 and the second air supply pipeline is intended to improve the response speed and regulation accuracy of the system, especially when it is necessary to quickly increase or decrease the power generation to support the stability of the grid frequency. The specific functions are as follows:

[0057] First air supply pipeline 33: When the grid frequency drops or a load gap occurs, additional compressed air can be quickly introduced through the first air supply pipeline 33 to increase the output of the secondary expander. This allows the system to provide more electricity in a short period of time to make up for the power demand of the grid. The first air supply pipeline 33 is usually equipped with a heat exchange regulating valve and an intake branch regulating valve, which can accurately adjust the air flow and temperature entering the secondary expander. Fine flow and temperature control allows the system to respond more accurately to changes in grid frequency and avoid over-regulation or under-response.

[0058] Second air supply pipeline: In some cases, the regulation of the secondary expander alone may not be enough to meet the primary frequency regulation needs of the power grid. At this time, the role of the second air supply pipeline is particularly important. It further adjusts the system's power generation power by increasing or decreasing the intake volume of the tertiary expander to more comprehensively support the power grid frequency. Similar to the secondary expander, the second air supply pipeline is also equipped with a heat exchange regulating valve and an intake branch regulating valve. These devices allow the system to remain stable under a wider range of operating conditions, especially when a longer duration of frequency regulation is required, the participation of the tertiary expander can provide more continuous power regulation capabilities. By finely controlling the intake volume of expanders at different stages, the system can more effectively utilize the stored compressed air and avoid wasting energy during the regulation process. At the same time, adjusting the intake volume of expanders at different stages can also optimize the energy conversion efficiency of the entire system, ensuring that the system can operate in the best state under various operating conditions.

[0059] Figure 1 Also shown are the heat exchange main valve 12, the high-pressure main gas valve 13, the impulse regulating valve 14, the power regulating valve 15, the heat exchange valve 26, the heat pump 30, the intake branch regulating valve 34, and the mother pipe flow regulating valve 37.

[0060] During the charging phase of a compressed air energy storage system, when electricity demand is low, air is compressed by a compressor and stored in an underground air storage chamber or other type of air storage facility. This compression process generates a lot of heat, which would be a waste of energy if it were directly discharged into the environment. Therefore, thermal storage tanks are designed to store the heat generated during this compression process.

[0061] When the system enters the power generation phase and needs to release high-pressure air from the gas storage facility to drive the expander to generate electricity, the heat in the heat storage tank will be recovered and used to reheat the released compressed air. In this way, when the heated air expands and works in the expander, it can generate more power, thereby increasing the efficiency and output power of the system's power generation. This recovery and utilization of heat energy is an important way for the CAES system to improve energy efficiency and economy.

[0062] In contrast to thermal storage tanks, cold storage tanks store cold energy during the system charging phase. When the high-pressure air is cooled during the compression process, the cold energy generated is captured and stored in the cold storage tank. During the power generation phase, the released high-pressure air may need to be pre-cooled by the cold energy in the cold storage tank before it expands and performs work in the expander. Although this step may not be common in some CAES system designs, in specific working environments, such as in high-temperature areas or when special working conditions need to be handled, pre-cooling the air can improve the operating efficiency of the expander and reduce energy losses, thereby improving the energy utilization of the system overall.

[0063] The heat storage tank and cold storage tank store and recover the heat and cold energy generated during the inflation and deflation stages of the compressed air energy storage system, enabling the system to more effectively utilize this energy during the power generation stage, thereby improving the energy conversion efficiency and economy of the entire system.

[0064] In the compressed air energy storage (CAES) system, the functions of various valves and equipment are very critical. The following describes in detail the functions of the expander, heat exchange main valve, high-pressure main gas valve, impulse control valve and power control valve:

[0065] The expander is the core component of the CAES system. In power generation mode, it converts the high-pressure air from the gas tank into mechanical energy by reducing the pressure and expanding the volume, and then drives the generator to generate electricity through the coupling. During the expansion process, the temperature and pressure of the air decrease, the volume increases, and the internal energy of the air is converted into mechanical energy, and then converted into electrical energy.

[0066] The heat exchange valve controls the fluid passage between the compressed air and the heat exchange medium. Its function is to adjust the connection between the air and the heat exchange device, thereby achieving control of the air temperature. During the inflation phase, the heat exchange valve may be used to store the heat energy generated during the compression process in the heat storage tank; during the deflation phase, it may be used to reintroduce the heat energy in the heat storage tank into the air flow before the expander to improve the efficiency of the expander and the overall power generation of the system.

[0067] The high-pressure main air valve is a key valve that controls the main air passage between the air storage tank and the expander. Its main function is to control the flow and pressure of compressed air entering the expander, ensuring that the system can operate safely and stably during both the inflation and deflation stages. When the system is started or stopped, the opening and closing of the high-pressure main air valve controls the on-off of the airflow, thereby controlling the operating status of the system.

[0068] The surge control valve is mainly used to control the initial air flow entering the expander when starting the expander or generator. In the early stage of CAES system startup, a certain amount of airflow is required to start the expander, but the airflow should not be too large to avoid overspeed or other safety problems. The surge control valve can accurately control this initial airflow to ensure a safe and smooth system startup.

[0069] The function of the power control valve is to regulate the flow of compressed air from the air tank to the expander, thereby controlling the power output of the entire system. By adjusting the opening of the power control valve, the amount of air entering the expander can be changed, which means that the system can adjust its power generation to meet the real-time needs of the power grid. In situations such as primary frequency modulation, the rapid response of the power control valve is crucial for the system to be able to quickly adjust the power output.

[0070] The coordinated work of these devices and valves ensures that the CAES system can convert energy efficiently and stably, and can quickly adapt to fluctuations in grid demand and effectively provide power support under different operating modes, such as frequency modulation and peak regulation.

[0071] like Figure 1 As shown, the second and third stage expanders are provided with intake branch main pipes after the high-pressure main gas valve 13, intake branch regulating valves are installed at the inlets of the second and third stage expanders, and the pipelines are provided with flow metering devices for adjusting the intake flow of the second and third stage expanders.

[0072] By installing a heat exchanger on the air supply pipeline, the system can adjust the temperature of the air flow as needed, further improving the energy conversion efficiency and frequency modulation performance, which is particularly suitable for frequency modulation scenarios that require precise temperature control. Installing a heat exchanger on the air supply pipeline enables the system to accurately control the air flow temperature. This temperature regulation capability is of great significance for improving energy conversion efficiency and frequency modulation performance. Especially in the power market, advanced frequency modulation services have higher requirements for system response speed and accuracy. By accurately controlling the air flow temperature, the system can adapt to these needs more flexibly and provide high-quality frequency modulation services, thereby obtaining higher economic benefits in the power market.

[0073] Furthermore, each second heat exchange branch is provided with a heat exchange regulating valve 38. The setting of the heat exchange regulating valve enables the system to accurately control the heating degree of the airflow, enhances the adaptability and flexibility of the system, and is suitable for the frequency regulation requirements of different seasons and times in the power system. By setting the heat exchange regulating valve 38 on the heat exchange branch, the system can adjust the heating degree of the airflow according to different seasons and time changes. This dynamic heat load management capability is crucial for the stable operation of the power system. By accurately controlling the heating degree, the system can effectively respond to these changes and ensure that the best frequency regulation service can be provided under various working conditions.

[0074] Furthermore, each expansion branch is provided with a relief valve 23. The provision of the relief valve 23 not only improves the safety of the system, but also ensures the rapid response capability of the system in an emergency. This design is particularly important for emergency frequency response and load shedding in the power market, and can effectively avoid safety accidents caused by system overpressure. At the same time, in the process of rapid pressure release, it can also maintain the basic stability of the system and ensure that the supply and demand balance of the power market is not seriously affected.

[0075] Furthermore, each expansion branch is provided with an inlet regulating valve 16 and an outlet regulating valve 17 at both ends of the expander 4 .

[0076] Furthermore, each expander 4 is connected to the rotor of the generator 31 through a coupling. The introduction of the coupling greatly improves the stability and efficiency of the system during the energy conversion process. This design can significantly reduce the loss of energy during the transmission process and improve the overall frequency regulation service quality and economic benefits. Especially in the power market, fast frequency regulation services have higher requirements on the efficiency of energy conversion. The efficient energy transmission capacity of the coupling can quickly provide the required frequency regulation power in an emergency, ensure the frequency stability of the power system, and reduce operating costs.

[0077] In an optional embodiment, if Figure 1 As shown, the compressed air energy storage frequency modulation system includes a 4-stage expansion unit, a generator, a power grid, a high-pressure main gas valve, an expander inlet regulating valve, an expander outlet regulating valve, a power regulating valve, a surge regulating valve, an expansion generator unit bearing, a speed measuring device, a heat exchange valve, a gas storage tank, an expander outlet exhaust valve, and a plate heat exchanger. The speed measuring device is used to measure the speed of the generator, and the electric energy generated by the generator is connected to the power grid through a grid-connected switch. Between the gas storage tank 1 and the expander 4, first through the high-pressure main gas valve 13, and then through the power regulating valve 15 and the surge regulating valve 14, the two are connected in parallel.

[0078] An air supply main pipe 32 is arranged behind the high-pressure main air valve 13, and an air intake branch regulating valve 34 is installed at the inlet of the second-stage expander and the inlet of the third-stage expander. The pipeline is provided with a flow metering device for correspondingly adjusting the air intake flow supplemented by the second-stage expander and the third-stage expander.

[0079] The compressed air energy storage frequency modulation system includes a control system: according to the feedback flow signal and the predetermined speed value, the target flow and temperature that need to be adjusted are calculated, and the signal is output to the temperature and flow regulation system.

[0080] The compressed air energy storage frequency modulation system includes a temperature regulating actuator: according to the output signal of the control system, the actuator (branch regulating valve, expander intake branch regulating valve, temperature control) controls the intake flow and temperature of the secondary expander and the tertiary expander to ensure the climbing rate of the unit.

[0081] In an optional embodiment, the present application also provides a fast-response primary frequency modulation stabilization control method for a compressed air energy storage power generation system, comprising the following steps:

[0082] Step 1: The compressed air energy storage generator set operates normally. Due to the large frequency demand of the power grid, the compressed air energy storage unit needs to increase the climbing rate to quickly reach full load.

[0083] Step 2: The main pipe flow regulating valve 37 and the two heat exchange regulating valves 38 are opened. According to the unit power and real-time speed, the air intake branch regulating valve 34 and another air intake branch regulating valve 34 are opened to adjust the air intake volume of the second-stage expander and the third-stage expander in real time, and adjust the real-time power and unit speed.

[0084] Step 3: The system frequency decreases, a load gap appears, and the unit speed begins to decrease; when the speed drops to n s1 r / min, the frequency modulation speed regulation system responds and works quickly, 2990r / min≤n s1 <2994r / min; open the air intake branch regulating valve 34, use the heat exchange regulating valve 38 to adjust the branch air intake temperature of the secondary expander, adjust the air intake branch regulating valve 34 and the mother pipe flow regulating valve 37 to increase the output of the secondary expander, and ensure that the unit speed is restored to 3000r / min;

[0085] Step 4: According to the operation of step 3, if the speed does not rise significantly at this time, or the speed of the unit continues to drop to n s2 r / min, 2988r / min≤n s2 <2990r / min, open another air intake branch regulating valve 34, use the heat exchange regulating valve 38 to cooperate with the secondary expander branch intake temperature to adjust the output of the secondary expander and the tertiary expander through the air intake branch regulating valve 34, another air intake branch regulating valve 34, and the main pipe flow regulating valve 37 to ensure that the speed is quickly restored to 3000r / min;

[0086] Step 5: When a load gap occurs in the system, the unit output has not yet reached full load. While increasing the generator output, adjust the air intake branch regulating valve 34, another air intake branch regulating valve 34, and the main pipe flow regulating valve 37 to maintain the unit speed at 3000r / min. Adjust the unit climbing rate according to the load gap, cooperate with the generator to quickly adjust the input flow of compressed air, and increase the expander output to quickly reach full load, so as to respond to the system load gap demand.

[0087] Step 6: When the system frequency and load have met the requirements, the compressed air generator set needs to reduce its output. At this time, close the air intake branch regulating valve 34, another air intake branch regulating valve 34, and the main pipe flow regulating valve 37. After closing the air intake branch main pipe and branch pipe regulating valve, the compressed air will return to the main pipe and flow out, which may still cause the speed to exceed the rated speed. At this time, the air relief valve 23 is gradually opened according to the speed, and the inlet regulating valve 16 is adjusted to reduce the unit output. At the same time, the power regulating valve 15 is adjusted to control the compressed air flow entering the main line, and gradually match the unit output until the load gradually stabilizes;

[0088] Step 7: Close the air relief valve 23 and the unit returns to normal working mode.

[0089] A system and method for rapid response of a compressed air energy storage power generation system to primary frequency modulation speed control, an expander generator set, which may include compressed air generator sets, carbon dioxide generator sets and other units that drive generators through rotating machinery to generate active power.

[0090] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0091] By adding a branch air intake system, the present invention can respond quickly when the grid frequency decreases and there is a compliance gap, increase the unit climbing rate, and improve the system response rate. Through the technical solution of the present invention, the CAES system can operate more stably when facing grid fluctuations, which plays an important role in promoting the commercial application of compressed air energy storage technology.

[0092] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0093] In addition to the above, it should be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this specification refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of the present invention.

[0094] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A compressed air energy storage frequency modulation system, characterized in that: include: Gas tank (1); A generator (31), the generator (31) being electrically connected to a power grid; an expansion regulating pipeline, wherein the inlet end of the expansion regulating pipeline is in communication with the gas storage tank (1), the outlet end of the expansion regulating pipeline is provided with an exhaust port, the expansion regulating pipeline comprises at least one expansion branch, the expansion branch is provided with an expander (4), the expander (4) is connected to the generator (31), wherein when the gas in the gas storage tank (1) passes through the expander (4), the expander (4) is driven to perform work to control the power generation rate of the generator (31); An air supply pipeline, wherein the air supply inlet end of the air supply pipeline is connected to the air storage tank (1), and the air supply outlet end of the air supply pipeline is connected to the gas inlet of at least one of the expanders (4), so that the gas passing through the air supply pipeline drives the expander (4) to perform work to control the power generation rate of the generator (31).

2. The compressed air energy storage frequency modulation system according to claim 1 is characterized in that: The expansion regulating pipeline comprises a plurality of expansion branches connected in series, each of which is provided with the expander (4). The compressed air energy storage and frequency modulation system further comprises an expansion heat exchange pipeline, which comprises: A first heat exchange branch, wherein there are a plurality of first heat exchange branches, the plurality of first heat exchange branches are arranged in parallel, one end of each of the first heat exchange branches is connected to the heat storage tank (2), and the other end of the first heat exchange branch is connected to the cold storage tank (3), each of the first heat exchange branches is provided with a first heat exchanger (8), the plurality of first heat exchangers (8) are respectively arranged corresponding to the plurality of expanders (4), and the first heat exchanger (8) is used to heat the airflow before the airflow enters the corresponding expander (4).

3. The compressed air energy storage frequency modulation system according to claim 1, characterized in that: The expansion branch at least comprises a primary expansion branch, a secondary expansion branch and a tertiary expansion branch. The inlet end of the primary expansion branch is connected to the gas storage tank (1), the inlet end of the secondary expansion branch is connected to the outlet end of the primary expansion branch, the inlet end of the tertiary expansion branch is connected to the outlet end of the secondary expansion branch, the outlet end of the tertiary expansion branch is provided with the exhaust port, and the primary expansion branch, the secondary expansion branch and the tertiary expansion branch are all provided with an expander (4).

4. The compressed air energy storage frequency modulation system according to claim 3 is characterized in that: The air supply pipeline comprises: a first air supply pipeline (33), wherein an inlet end of the first air supply pipeline (33) is connected to the air storage tank (1), and an outlet end of the first air supply pipeline (33) is connected to an inlet of the expander (4) of the secondary expansion branch; A second air supply pipeline (35), wherein the inlet end of the second air supply pipeline (35) is connected to the air storage tank (1), and the outlet end of the second air supply pipeline (35) is connected to the inlet of the expander (4) of the third-stage expansion branch.

5. The compressed air energy storage frequency modulation system according to claim 4 is characterized in that: The air supply pipeline comprises: An air supply main pipe (32), the air supply main pipe (32) is connected to the air storage tank (1), the inlet end of the first air supply pipeline (33) is connected to the air supply main pipe (32), and the inlet end of the second air supply pipeline (35) is connected to the air supply main pipe (32).

6. The compressed air energy storage frequency modulation system according to claim 4, characterized in that: The air supply pipeline includes an air supply heat exchange pipeline, and the air supply heat exchange pipeline includes: A second heat exchange branch, wherein the number of the second heat exchange branches is two, one end of each of the second heat exchange branches is connected to the heat storage tank (2), and the other end of the second heat exchange branch is connected to the cold storage tank (3), and each of the second heat exchange branches is provided with a second heat exchanger (40), one of the second heat exchangers (40) is provided on the first air supply pipeline (33), so that the second heat exchanger (40) heats the airflow flowing through the first air supply pipeline (33) to the expander (4) corresponding to the first air supply pipeline (33), and the other of the second heat exchangers (40) is provided on the second air supply pipeline (35), so that the second heat exchanger (40) heats the airflow flowing through the second air supply pipeline (35) to the expander (4) corresponding to the second air supply pipeline (35).

7. The compressed air energy storage frequency modulation system according to claim 6, characterized in that: Each of the second heat exchange branches is provided with a heat exchange regulating valve (38).

8. The compressed air energy storage frequency modulation system according to claim 1, characterized in that: Each expansion branch is provided with an air release valve (23).

9. The compressed air energy storage frequency modulation system according to claim 1, characterized in that: Each expansion branch is provided with an inlet regulating valve (16) and an outlet regulating valve (17) at both ends of the expander (4).

10. The compressed air energy storage frequency modulation system according to claim 1, characterized in that: Each of the expanders (4) is connected to the rotor of the generator (31) via a coupling.

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