Carbon dioxide energy storage system charge-discharge switching control method and system

Abstract

The application relates to a carbon dioxide energy storage system charging and discharging switching control method and system. The method comprises the following steps: obtaining a mode switching request and a current operation mode, determining a current in-service branch and a target branch; obtaining pressure data, temperature data and phase state data of the target branch inlet; performing unloading control on the current in-service branch, and gradually pressurizing the target branch inlet through a transition buffer branch; adjusting the phase state of the carbon dioxide working medium through a phase state adjusting branch, and pre-matching the hot end through a thermal management branch; starting the compressor or expander corresponding to the target branch and gradually opening the target branch main channel, completing flow transfer and power transfer; and recovering residual carbon dioxide working medium and completing mode switching after the target branch is stably operated. The application can improve the stability, safety and operation efficiency of the charging and discharging switching process.

Description

Technical Field

[0001] This application relates to the field of energy storage system control technology, and in particular to a method and system for controlling the charging and discharging switching of a carbon dioxide energy storage system. Background Technology

[0002] Carbon dioxide energy storage systems typically utilize the state changes of carbon dioxide working fluid under different pressure and temperature conditions to achieve energy storage during charging and energy release during discharging. During charging, the carbon dioxide working fluid is usually compressed and energy is stored via a compression branch; during discharging, the carbon dioxide working fluid expands and performs work to output energy via an expansion branch. Because the carbon dioxide working fluid is highly sensitive to pressure and temperature changes, problems such as unstable branch pressure connections, fluctuations in the inlet working fluid state, and thermal mismatch of the equipment can easily occur when switching between charging and discharging modes.

[0003] In existing technologies, the charge / discharge switching control of carbon dioxide energy storage systems mostly adopts a combination of valve switching and equipment start / stop. Typically, the target branch is directly connected after the current operating branch is terminated, or the target branch is put into operation after simply meeting the pressure conditions. Although this type of scheme can achieve basic mode switching, it does not adequately consider the gradual pressure build-up, working fluid phase adjustment, and hot-end pre-matching during the switching process. This can easily lead to large fluctuations in the inlet pressure of the target branch, deviations in working fluid temperature from requirements, liquid entrainment, or phase instability, thereby affecting the smooth start-up and operation of the compressor or expander.

[0004] In addition, existing solutions typically lack coordinated control over the handover process between currently in-service branches and target branches, which can easily lead to flow fluctuations, power surges, and equipment shocks during the switching process, which is detrimental to stable system operation and equipment lifespan. At the same time, there is a lack of effective recovery control for residual carbon dioxide working fluid in out-of-service branches, which can easily cause working fluid retention and energy loss. Summary of the Invention

[0005] To at least partially overcome the problems of poor switching stability, insufficient control of working fluid status, and large equipment impact during the charging and discharging switching process of carbon dioxide energy storage systems in related technologies, this application provides a charging and discharging switching control method and system for carbon dioxide energy storage systems.

[0006] The proposed solution is as follows:

[0007] According to a first aspect of the embodiments of this application, a method for controlling the charge-discharge switching of a carbon dioxide energy storage system is provided, comprising: Obtain the mode switching request and the current operating mode, and determine the currently active branch and the target branch based on the mode switching request and the current operating mode; Acquire pressure, temperature, and phase data at the inlet of the target branch; Unloading control is performed on the currently in-service branch, while keeping the main channel of the target branch closed; Open the transition buffer branch and gradually build up pressure at the entrance of the target branch until the pressure data reaches the preset pressure range. The phase regulation branch is activated, and the carbon dioxide working fluid entering the target branch is subjected to at least two of the following treatments based on the phase data and temperature data: separation, interception, heating, cooling, and reflux mixing, until the phase data meets the access requirements of the compressor or expander corresponding to the target branch. The thermal management branch is activated, and the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch are pre-matched according to the temperature data until the temperature data reaches the preset temperature range. Start the compressor or expander corresponding to the target branch and open the main channel of the target branch step by step to complete the flow and power transfer between the current in-service branch and the target branch during the continuous unloading process of the current in-service branch; After determining that the target branch is operating stably, the main channel of the currently in-service branch is closed, and the residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container to complete the switch between charging mode and discharging mode.

[0008] Preferably, determining the currently active branch and the target branch based on the mode switching request and the current operating mode includes: If the current operating mode is charging mode, the currently active branch is determined to be a compression branch and the target branch is an expansion branch. If the current operating mode is discharge mode, the currently in-service branch is determined to be an expansion branch and the target branch is a compression branch; When the target branch is a compression branch, the corresponding device is a compressor; When the target branch is an expansion branch, the corresponding equipment is an expander.

[0009] Preferably, the transition buffer branch is activated to gradually build up pressure at the inlet of the target branch until the pressure data reaches a preset pressure range, including: With the main channel of the target branch closed, the pre-charge valve is opened to allow the carbon dioxide working medium in the corresponding storage unit to enter the transition buffer container. The throttle valve opening is adjusted according to the pressure data to control the working fluid flow rate from the transition buffer container to the target branch inlet; When the pressure data reaches the lower limit of the preset pressure range, the target branch inlet connecting valve is opened to connect the transition buffer container with the target branch inlet. When the pressure data exceeds the upper limit of the preset pressure range, the reflux valve is opened to guide part of the carbon dioxide working fluid back to the corresponding storage unit or the transition buffer container, so that the pressure data is maintained within the preset pressure range.

[0010] Preferably, when the target branch is an expansion branch, the carbon dioxide working fluid entering the target branch is processed according to the phase state data, including: When the phase data indicates that the carbon dioxide working fluid entering the expansion branch has liquid phase entrainment, the carbon dioxide working fluid is subjected to gas-liquid separation and droplet interception treatment. When the phase state data indicates that the temperature of the carbon dioxide working fluid entering the expansion branch is lower than the preset lower limit, the carbon dioxide working fluid is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working fluid entering the expansion branch, as indicated by the phase data, exceeds a preset range, the carbon dioxide working fluid is subjected to reflux mixing treatment. After the phase data meets the expander access requirements, the carbon dioxide working fluid is introduced into the expansion branch.

[0011] Preferably, when the target branch is a compression branch, the carbon dioxide working fluid entering the target branch is processed according to the phase state data, including: When the phase data indicates that the carbon dioxide working fluid entering the compression branch has liquid phase entrainment, the carbon dioxide working fluid is subjected to gas-liquid separation and droplet interception treatment. When the phase state data indicates that the temperature of the carbon dioxide working fluid entering the compression branch is lower than a preset lower limit, the carbon dioxide working fluid is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working fluid entering the compression branch, as indicated by the phase data, exceeds a preset range, the carbon dioxide working fluid is subjected to reflux mixing treatment. After the phase data meets the compressor access requirements, the carbon dioxide working fluid is introduced into the compression branch.

[0012] Preferably, based on the temperature data, a pre-matching process is performed on the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander at the hot end, including: When the temperature data is lower than the lower limit of the preset temperature range, the heat storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to preheat the target branch. When the temperature data is higher than the upper limit of the preset temperature range, the cold storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to pre-cool the target branch. The system continuously acquires temperature data after preheating or precooling treatment, and once the processed temperature data enters a preset temperature range, it controls the thermal management branch to enter a temperature maintenance state until the compressor or expander corresponding to the target branch starts.

[0013] Preferably, the compressor or expander corresponding to the target branch is started, and the main channel of the target branch is opened step by step, including: After the pressure data reaches the preset pressure range, the phase state data meets the access requirements of the compressor or expander corresponding to the target branch, and the temperature data reaches the preset temperature range, the compressor or expander corresponding to the target branch is started, so that the target branch enters the no-load connection state. After the target branch enters the no-load takeover state, the main channel of the target branch is opened step by step to increase the flow rate of carbon dioxide working fluid in the target branch. During the process of gradually opening the main channel of the target branch, unloading control is continuously performed on the currently in-service branch to reduce the carbon dioxide working fluid flow and power output in the currently in-service branch. Once the carbon dioxide working fluid flow rate and power output in the target branch reach the preset connection conditions, it is determined that the target branch has completed the flow and power handover to the currently in-service branch.

[0014] Preferably, after determining that the target branch is operating stably, the main channel of the currently in-service branch is shut down, and the residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container, including: Obtain the operating pressure data, operating temperature data, and operating flow rate data of the target branch; When the operating pressure data, the operating temperature data, and the operating flow rate data continuously meet the corresponding stable range, the target branch is determined to be operating stably. After determining that the target branch is operating stably, close the main channel of the currently in-service branch and open the residual working fluid recovery channel; The residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container through the residual working fluid recovery channel. After the residual carbon dioxide working fluid in the currently in-service branch is introduced, the residual working fluid recovery path is closed.

[0015] Preferably, unloading control is performed on the currently in-service branch, including: Obtain the current operating flow rate and power output data of the in-service branch circuit; Based on the operating flow rate data and power output data, the opening degree of the main channel valve of the currently in-service branch is gradually reduced, and the opening degree of the return valve is gradually increased, so as to reduce the carbon dioxide working fluid flow rate in the currently in-service branch. While reducing the flow rate of carbon dioxide working fluid in the currently in-service branch, the load output of the corresponding compressor or expander in the currently in-service branch is reduced simultaneously. After the operating flow data and power output data reach the preset unloading conditions, the currently in-service branch is kept in a low-load waiting-to-be-switched-out state.

[0016] According to a second aspect of the embodiments of this application, a charge-discharge switching control system for a carbon dioxide energy storage system is provided, comprising: Processor and memory; The processor and memory are connected via a communication bus: The processor is used to call and execute the program stored in the memory; The memory is used to store a program, which is at least used to execute a charge / discharge switching control method for a carbon dioxide energy storage system as described in any of the above claims.

[0017] The technical solution provided in this application may include the following beneficial effects: Upon receiving a mode switching request, this application first determines the currently in-service branch and the target branch. While performing unloading control on the currently in-service branch, it gradually builds up pressure at the entrance of the target branch through a transition buffer branch. This allows the target branch to gradually build up the required entrance pressure before the main channel is opened, effectively reducing pressure surges and impacts caused by direct branch switching during the charging and discharging process, and improving the stability and controllability of the switching process.

[0018] By using the phase regulation branch, based on the phase and temperature data at the inlet of the target branch, the carbon dioxide working fluid entering the target branch is subjected to at least two of the following treatments: separation, interception, heating, cooling, and reflux mixing. This ensures that the carbon dioxide working fluid entering the target branch meets the corresponding access requirements before being fed into the compressor or expander, thereby reducing the adverse effects of liquid entrainment, phase fluctuations, and temperature mismatch on equipment operation, and improving the stability and safety of the target branch during operation.

[0019] By performing thermal end pre-matching treatment on the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch through the thermal management branch, the target branch can reach the preset temperature range before formal connection. This can effectively reduce thermal shock and temperature difference disturbance during the switching process, improve the heat exchange connection effect, and enhance the reliability of equipment operation.

[0020] During the continuous unloading process of the currently in-service branch, the compressor or expander corresponding to the target branch is started, and the main channel of the target branch is opened step by step to realize the flow and power transfer between the currently in-service branch and the target branch. This can avoid the problems of flow jump and power change in traditional switching methods and improve the continuity and smoothness of the charging and discharging switching process.

[0021] After determining that the target branch is operating stably, this application introduces the residual carbon dioxide working fluid in the currently in-service branch into the corresponding storage unit or transition buffer container, which can reduce working fluid retention and energy loss, and improve working fluid utilization and overall system operating efficiency.

[0022] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0024] Figure 1 This is a schematic flowchart of a charge / discharge switching control method for a carbon dioxide energy storage system provided in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a charge / discharge switching control system for a carbon dioxide energy storage system provided in one embodiment of this application. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0026] Example 1 Figure 1 This is a flowchart illustrating a charge / discharge switching control method for a carbon dioxide energy storage system according to an embodiment of this application. (Refer to...) Figure 1 A method for controlling the charging and discharging switching of a carbon dioxide energy storage system, comprising: S11. Obtain the mode switching request and the current operating mode, and determine the currently active branch and the target branch based on the mode switching request and the current operating mode; S12. Obtain pressure data, temperature data, and phase state data at the inlet of the target branch; S13. Implement unloading control on the currently in-service branch road and keep the main channel of the target branch road closed; S14. Open the transition buffer branch and gradually build up pressure at the entrance of the target branch until the pressure data reaches the preset pressure range. S15. Open the phase adjustment branch and perform at least two of the following treatments on the carbon dioxide working fluid entering the target branch: separation, interception, heating, cooling and reflux mixing, based on the phase data and temperature data, until the phase data meets the access requirements of the compressor or expander corresponding to the target branch. S16. Start the thermal management branch and perform thermal end pre-matching processing on the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch according to the temperature data until the temperature data reaches the preset temperature range. S17. Start the compressor or expander corresponding to the target branch and open the main channel of the target branch step by step to complete the flow and power transfer between the current in-service branch and the target branch during the continuous unloading process of the current in-service branch. S18. After determining that the target branch is operating stably, close the main channel of the currently in-service branch and introduce the residual carbon dioxide working medium in the currently in-service branch into the corresponding storage unit or transition buffer container to complete the switching between charging mode and discharging mode.

[0027] For ease of understanding, the following explains some key terms in this embodiment: A mode switching request is an instruction issued by the system operator or automated control system, requiring the carbon dioxide energy storage system to switch from its current operating mode to another operating mode. This request is the initiating signal that triggers the mode switching process.

[0028] The current operating mode refers to the operating state of the carbon dioxide energy storage system before receiving a mode switching request, such as charging mode or discharging mode. This mode determines the type of branch currently in operation.

[0029] Currently in operation branches refer to those in the carbon dioxide energy storage system that are performing energy conversion or storage operations at the time the mode switch request is issued, such as compression or expansion branches. These branches need to be safely unloaded and taken out of operation.

[0030] The target branch refers to the branch that the CO2 energy storage system needs to switch to and put into operation after a mode switching request is issued, such as an expansion branch or a compression branch. This branch needs to undergo a series of pre-processing steps to start up smoothly.

[0031] Pressure, temperature, and phase state data are key parameters used to characterize the physical state of carbon dioxide working fluid at the inlet of the target branch. These data are acquired in real time via sensors and serve as the basis for gradual pressure build-up, phase state adjustment, and hot-end pre-matching.

[0032] Unloading control refers to the gradual reduction of the load and working fluid flow of currently in-service branch circuits to ensure that the branch circuit is safely and smoothly decommissioned and to avoid system impact.

[0033] A transition buffer branch is an auxiliary circuit used to regulate the pressure at the inlet of the target branch before it is put into operation. This branch achieves a gradual change in the inlet pressure of the target branch by introducing or discharging carbon dioxide as the working medium.

[0034] Gradual pressure build-up refers to the process of gradually increasing or decreasing the pressure at the inlet of the target branch from its current state by controlling the flow rate of the working fluid until it reaches the preset pressure range required for the normal operation of the target branch.

[0035] A phase adjustment branch is an auxiliary circuit used to adjust the phase state of carbon dioxide working fluid entering the target branch. This branch can perform gas-liquid separation, droplet trapping, heating, cooling, or reflux mixing of the working fluid to meet the stringent requirements of the target equipment for the working fluid phase state.

[0036] A thermal management branch is an auxiliary circuit used to pre-treat the temperature of key components (such as inlet pipe sections, associated heat exchangers, compressors, or expanders) in a target branch. This branch introduces a heat source or cold source to bring the temperature of these components to a preset temperature range that matches the target working fluid.

[0037] Flow rate handover and power handover refer to the coordinated process during mode switching where the working fluid flow rate and power output of the currently operating branch gradually decrease, while the working fluid flow rate and power output of the target branch gradually increase. This process ensures a smooth transition of the system's total flow rate and total power.

[0038] The following will describe in detail the charge / discharge switching control method of the carbon dioxide energy storage system of this application, with reference to specific embodiments.

[0039] First, the system acquires mode switching requests and the current operating mode, and determines the currently active branches and target branches based on this information. Mode switching requests can be manually entered by operators through a human-machine interface, or automatically triggered by the system according to a preset scheduling strategy. The current operating mode is identified by reading the system's current operating status parameters; for example, if the system is storing energy, it is identified as charging mode; if it is releasing energy, it is identified as discharging mode. Based on this information, the system uses internal logic or consults a preset mapping table to determine the currently operating branches and the branches about to be put into operation.

[0040] Secondly, it is crucial to acquire pressure, temperature, and phase data at the inlet of the target branch. The state of the working fluid at its inlet is critical before the target branch is put into operation. Pressure data can be monitored in real time using pressure sensors installed in the inlet pipe section of the target branch. Temperature data is acquired using temperature sensors. Phase data can be initially determined by consulting a carbon dioxide phase diagram in conjunction with pressure and temperature data, or by using density sensors, ultrasonic sensors, or other equipment to identify whether the working fluid contains liquid phase entrainment or is in a critical state.

[0041] Next, unloading control is implemented on the currently operating branch while keeping the main channel of the target branch closed. Unloading control of the currently operating branch can be achieved by gradually reducing the opening of its main channel valve, thereby gradually reducing the flow rate of carbon dioxide working fluid through that branch. Simultaneously, the load setpoint of the compressor or expander in the currently operating branch can be gradually reduced, causing its power output to decrease gradually. During this process, the main channel valve of the target branch is kept completely closed to ensure that no working fluid enters the target branch before pretreatment is completed.

[0042] Subsequently, the transition buffer branch is activated to gradually build up pressure at the inlet of the target branch until the pressure data reaches the preset pressure range. The transition buffer branch is activated by opening the corresponding valves, allowing a small amount of carbon dioxide working fluid to be slowly introduced from a high-pressure source (e.g., a storage tank) into the inlet section of the target branch. By controlling the flow rate of the introduced working fluid, the pressure at the inlet of the target branch is gradually increased or decreased. The control system continuously monitors the pressure data, and the gradual pressure build-up process stops when the pressure data enters the preset pressure range required for the normal operation of the target branch.

[0043] Furthermore, the phase regulation branch is activated, and based on phase and temperature data, the carbon dioxide working fluid entering the target branch undergoes at least two of the following treatments: separation, retention, heating, cooling, and reflux mixing, until the phase data meets the access requirements of the compressor or expander corresponding to the target branch. The phase regulation branch is activated to perform targeted treatment on the carbon dioxide working fluid entering the target branch based on real-time acquired phase and temperature data. For example, if the phase data indicates the presence of a liquid phase in the working fluid, a gas-liquid separator can be activated for separation. If the temperature data deviates from the temperature range required by the target equipment, a heater or cooler can be activated for temperature regulation. Reflux mixing can return a portion of the working fluid to the mixing point to mix with the newly entering working fluid, thus smoothing out phase fluctuations. These treatments aim to ensure that the phase parameters of the working fluid meet the stringent operating conditions of the target compressor or expander.

[0044] Based on this, the thermal management branch is activated. According to temperature data, pre-matching processing is performed on the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch until the temperature data reaches the preset temperature range. The thermal management branch is activated, and based on the temperature data at the inlet of the target branch, it determines whether preheating or precooling of key components of the target branch is necessary. For example, if the temperature is too low, hot fluid can flow through the inlet pipe section, associated heat exchanger, and jacket of the corresponding compressor or expander of the target branch to raise its temperature. If the temperature is too high, cold fluid can flow through these components for cooling. The temperature of these components is continuously monitored until it reaches the preset temperature range matching the target working fluid, thereby preventing equipment from being impacted by excessive temperature differences.

[0045] Subsequently, the compressor or expander corresponding to the target branch is started, and the main channel of the target branch is opened step by step to complete the flow and power transfer between the current and target branches during the continuous unloading process of the currently operating branch. After the pressure, phase state, and temperature at the inlet of the target branch meet the preset requirements, the compressor or expander corresponding to the target branch is started, putting it into no-load or low-load operation. Immediately afterwards, the main channel valve of the target branch is opened manually or automatically step by step, allowing the carbon dioxide working fluid flow rate to gradually increase. Throughout this process, the currently operating branch will continuously perform unloading operations, and its working fluid flow rate and power output will gradually decrease. By precisely coordinating the valve opening and equipment load of the two branches, a smooth transition of the total working fluid flow rate and total power of the system is achieved, ensuring the continuity and stability of the switching process.

[0046] Finally, after determining that the target branch is operating stably, the main channel of the currently operating branch is closed, and the remaining carbon dioxide working fluid in the currently operating branch is introduced into the corresponding storage unit or transition buffer container, completing the switch between charging and discharging modes. The determination of stable operation of the target branch can be confirmed by continuously monitoring its operating pressure, operating temperature, and operating flow data, and confirming that these data remain within the normal fluctuation range for a continuous period. Once the target branch is determined to be operating stably, the main channel valve of the currently operating branch will be completely closed. Subsequently, a residual working fluid recovery channel is opened, introducing the remaining carbon dioxide working fluid in the currently operating branch into the corresponding storage unit or transition buffer container through this channel, thereby effectively recovering the working fluid and reducing losses. After the recovery of the residual working fluid is completed, the entire switching process between charging and discharging modes is finished.

[0047] The carbon dioxide energy storage system charge / discharge switching control method provided in this embodiment reduces pressure shock caused by direct branch switching and improves switching smoothness by performing unloading control on the currently in-service branch and gradually building up pressure at the inlet of the target branch during mode switching. By adjusting the phase state of the carbon dioxide working fluid based on the phase and temperature data at the target branch inlet, the adverse effects of liquid entrainment, phase fluctuations, and temperature mismatch on compressor or expander operation can be reduced. Pre-matching the inlet pipe section, associated heat exchanger, and corresponding equipment of the target branch reduces thermal shock and improves heat exchange connection. Gradually opening the main channel of the target branch during the continuous unloading of the currently in-service branch enables flow and power transfer, improving the continuity and stability of the charge / discharge switching process. Furthermore, recovering residual carbon dioxide working fluid in the currently in-service branch reduces working fluid retention and energy loss, improving the overall system operating efficiency.

[0048] It should be noted that, based on the mode switching request and the current operating mode, the currently active branch and the target branch are determined, including: If the current operating mode is charging mode, the currently active branch is determined to be a compression branch and the target branch is an expansion branch. If the current operating mode is discharge mode, the currently in-service branch is determined to be an expansion branch and the target branch is a compression branch; When the target branch is a compression branch, the corresponding device is a compressor; When the target branch is an expansion branch, the corresponding equipment is an expander.

[0049] Specifically, during the operation of a carbon dioxide energy storage system, the control system continuously monitors the system's current operating mode. When a mode switching request is received, the system first determines the current operating mode. For example, if the system is currently in charging mode and receives a request to switch to discharging mode, the system logically determines that the currently operating physical path is the compression branch, while the physical path about to be put into operation to achieve the discharging function is the expansion branch. Conversely, if the system is currently in discharging mode and receives a request to switch to charging mode, the system determines that the currently active branch is the expansion branch, and the target branch is the compression branch. This explicit mapping relationship between modes and branches is usually implemented through a preset system configuration table or state machine logic, ensuring that the system can accurately identify and prepare the corresponding physical path in different switching directions.

[0050] Furthermore, this application clarifies the association between the target branch and specific core equipment. When the system determines that the target branch is a compression branch, its corresponding core equipment is identified as a compressor. The compressor is the key power equipment in the compression branch, responsible for compressing the carbon dioxide working fluid, increasing its pressure and temperature, thereby achieving energy storage. In system design, a compression branch typically includes one or more compressors, as well as related pipelines, valves, heat exchangers, and other auxiliary equipment. When the target branch is determined to be a compression branch, the control system identifies and prepares to start the compressor in that branch. Similarly, when the system determines that the target branch is an expansion branch, its corresponding core equipment is identified as an expander. The expander is the core power equipment in the expansion branch, responsible for expanding the high-pressure carbon dioxide working fluid to release energy and output electrical energy. An expansion branch typically includes one or more expanders, as well as related pipelines, valves, heat exchangers, and other auxiliary equipment. When the target branch is determined to be an expansion branch, the control system identifies and prepares to start the expander in that branch. This clear equipment association provides clear instructions for subsequent equipment preparation and startup.

[0051] It should be noted that activating the transition buffer branch allows for gradual pressure build-up at the target branch inlet until the pressure data reaches the preset pressure range, including: With the main channel of the target branch closed, the pre-charge valve is opened to allow the carbon dioxide working medium in the corresponding storage unit to enter the transition buffer container. Adjust the throttle valve opening based on pressure data to control the working fluid flow rate from the transition buffer container to the target branch inlet; When the pressure data reaches the lower limit of the preset pressure range, open the target branch inlet connecting valve to connect the transition buffer container with the target branch inlet. When the pressure data exceeds the upper limit of the preset pressure range, the reflux valve is opened to guide part of the carbon dioxide working fluid back to the corresponding storage unit or transition buffer container so that the pressure data is maintained within the preset pressure range.

[0052] Specifically, with the main channel of the target branch closed, the pre-charge valve is opened, allowing the carbon dioxide working fluid from the corresponding storage unit to enter the transition buffer container. This pre-charge valve is typically a solenoid valve, pneumatic valve, or electric valve, and its function is to control the initial flow of high-pressure carbon dioxide working fluid from the storage unit (e.g., a high-pressure storage tank or accumulator) to the transition buffer container. By keeping the main channel of the target branch closed, the core equipment in the target branch (such as a compressor or expander) can be effectively isolated from the initial high-pressure impact, ensuring the safety of the pre-charge process. The transition buffer container, as an intermediate buffer, can absorb the initial pressure fluctuations, providing a stable source of working fluid for subsequent fine-tuning of pressure.

[0053] Subsequently, the opening of the throttle valve is adjusted based on the pressure data to control the flow rate of the working fluid from the transition buffer container to the inlet of the target branch. The throttle valve can be a ball valve, a gate valve, or a regulating valve, and its opening is dynamically adjusted by the control system based on the pressure data monitored in real time at the inlet of the target branch. By precisely controlling the opening of the throttle valve, a gradual increase in the carbon dioxide working fluid flow rate can be achieved, thereby allowing the pressure at the inlet of the target branch to rise steadily at a controlled rate. This feedback control mechanism can effectively prevent sudden pressure rises and protect pipelines and equipment from excessive stress.

[0054] Furthermore, when the pressure data reaches the lower limit of the preset pressure range, the target branch inlet connecting valve is opened to connect the transition buffer container with the target branch inlet. The target branch inlet connecting valve is typically a fast-response on / off valve, such as a ball valve or butterfly valve. When the pressure at the target branch inlet has approached the lower limit of the target pressure range through adjustment by the throttle valve, opening this connecting valve establishes a direct path between the transition buffer container and the target branch inlet, accelerating the pressure balancing process. At this point, because the pressure difference has significantly decreased, opening the connecting valve will not cause a severe pressure shock.

[0055] Furthermore, when the pressure data exceeds the upper limit of the preset pressure range, the reflux valve is opened to guide a portion of the carbon dioxide working fluid back to the corresponding storage unit or transition buffer container, thereby maintaining the pressure data within the preset pressure range. The reflux valve can be a bypass valve or a pressure relief valve, used to return excess carbon dioxide working fluid to the storage unit or transition buffer container when the target branch inlet pressure is too high, forming a closed-loop pressure regulation circuit. This active pressure relief mechanism ensures that the pressure at the target branch inlet is always maintained within the preset safe operating range, preventing overpressure from damaging the equipment and creating a stable pressure environment for subsequent equipment startup.

[0056] It should be noted that when the target branch is an expansion branch, the carbon dioxide working fluid entering the target branch is processed based on phase state data, including: When phase data characterizes the presence of liquid entrainment in the carbon dioxide working fluid entering the expansion branch, gas-liquid separation and droplet interception are performed on the carbon dioxide working fluid. When the temperature of the carbon dioxide working medium entering the expansion branch, as characterized by phase state data, is lower than the preset lower limit, the carbon dioxide working medium is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working medium entering the expansion branch exceeds the preset range as characterized by phase data, the carbon dioxide working medium is subjected to reflux mixing treatment. After the phase data meets the expander access requirements, carbon dioxide working fluid is introduced into the expansion branch.

[0057] Specifically, when the phase data indicates that the carbon dioxide working fluid entering the expansion branch contains liquid entrainment, gas-liquid separation and droplet trapping treatment are required. Liquid entrainment refers to the phenomenon of gaseous carbon dioxide mixed with liquid carbon dioxide droplets. Expanders typically have strict requirements on the phase of the entering working fluid; liquid entrainment can lead to increased corrosion and wear of expander blades, and even water hammer effects, seriously affecting equipment lifespan and operational safety. Gas-liquid separation is usually achieved by installing a gas-liquid separator, which uses principles such as gravity, centrifugal force, or inertial impaction to separate droplets from the gas flow. Droplet trapping treatment, based on gas-liquid separation, further captures tiny droplets by installing devices such as demisters or liquid traps, ensuring that the working fluid entering the expander is a pure gaseous state.

[0058] When the phase state data indicates that the temperature of the carbon dioxide working fluid entering the expansion branch is lower than the preset lower limit, the carbon dioxide working fluid needs to be heated. Expanders typically require preheating before operation to avoid cold shock from the low-temperature working fluid, which could affect material properties and operating efficiency. When the phase state data indicates that the temperature of the carbon dioxide working fluid is lower than the preset lower limit of the expander's entry requirements, it needs to be heated. Heating can be achieved by installing a preheater or heat exchanger, utilizing an external heat source (such as electric heating, steam heating, or heat exchange with a high-temperature medium) to raise the temperature of the carbon dioxide working fluid to the temperature range required for safe operation of the expander.

[0059] When the phase fluctuations of the carbon dioxide working fluid entering the expansion branch, as indicated by the phase data, exceed a preset range, the carbon dioxide working fluid needs to be refluxed and mixed. Phase fluctuations refer to significant changes in parameters such as pressure, temperature, or density of the carbon dioxide working fluid within a short period, leading to phase instability. Severe phase fluctuations can cause unstable expansionr operation, reduced efficiency, and even trigger a protective shutdown. Reflux mixing involves refluxing a portion of the treated or stabilized carbon dioxide working fluid back into the working fluid to be treated for mixing. This mixing process helps to smooth out phase fluctuations and stabilize the parameters. For example, a portion of the stabilized working fluid at the expander outlet or in the storage tank can be refluxed back to the expander inlet to mix with the fluctuating working fluid, thereby achieving phase stabilization.

[0060] After the above processes are completed, and the phase data meets the expander's access requirements, the carbon dioxide working fluid is introduced into the expansion branch. This is the ultimate goal and execution condition of the aforementioned processes. Only when the phase data of the carbon dioxide working fluid (including pressure, temperature, liquid content, etc.) fully meets the various technical indicators for safe operation and efficient work specified by the expander manufacturer after the above processes can it be allowed to enter the expansion branch. This step, by controlling the opening of valves or actuators, delivers the qualified working fluid, after phase adjustment, into the expander, ensuring the safe start-up and stable operation of the expander.

[0061] It should be noted that when the target branch is a compression branch, the carbon dioxide working fluid entering the target branch is processed based on phase state data, including: When phase state data characterizes the presence of liquid entrainment in the carbon dioxide working fluid entering the compression branch, gas-liquid separation and droplet interception are performed on the carbon dioxide working fluid. When the temperature of the carbon dioxide working fluid entering the compression branch, as indicated by phase state data, is lower than the preset lower limit, the carbon dioxide working fluid is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working fluid entering the compression branch exceeds the preset range as characterized by phase data, the carbon dioxide working fluid is subjected to reflux mixing treatment. After the phase data meets the compressor access requirements, carbon dioxide working fluid is introduced into the compression branch.

[0062] When phase data indicates the presence of liquid entrainment in the carbon dioxide working fluid, meaning that liquid carbon dioxide droplets are mixed in with the gas, gas-liquid separation and droplet trapping are required. This process aims to separate the liquid carbon dioxide from the gaseous carbon dioxide to prevent it from entering the compressor. Liquid carbon dioxide entering the compressor can cause "liquid slugging," severely damaging compressor blades or internal structures and reducing compression efficiency. Specifically, gas-liquid separation devices can employ cyclone separators, wire mesh demisters, baffle plate separators, or coalescing separators. Cyclone separators use high-speed rotation to generate centrifugal force, causing denser droplets to be thrown towards the wall and flow down it; wire mesh demisters use wire mesh to capture droplets, causing them to coalesce and grow larger before separation under gravity; baffle plate separators change the airflow direction, causing droplets to impact the baffle plates and separate. Droplet trapping further ensures that tiny droplets are effectively removed to meet the compressor's stringent requirements for intake air dryness.

[0063] When phase data indicates that the temperature of the carbon dioxide working fluid is below the preset lower limit, the carbon dioxide working fluid needs to be heated. The purpose of this treatment is to ensure that the carbon dioxide working fluid entering the compressor is in a superheated state, preventing condensation and droplet formation due to temperature rise during compression. Compressors typically require superheated steam intake to ensure safe, stable operation and optimal efficiency. Specifically, heating can be achieved by using a preheater, which can be an electric heater or a heat exchanger utilizing other heat sources within the system (such as waste heat recovery or heat transfer fluid provided by thermal management branches). By precisely controlling the heating power or heat transfer fluid flow rate of the preheater, the temperature of the carbon dioxide working fluid is stably raised above the preset lower limit and maintained within the compressor's allowable intake temperature range.

[0064] When phase data indicates that the phase fluctuation of the carbon dioxide working fluid exceeds a preset range, reflux mixing is required. Phase fluctuations may manifest as rapid or significant changes in parameters such as pressure, temperature, or dryness, posing challenges to the stable operation of the compressor and potentially leading to surge or a sharp drop in efficiency. Specifically, reflux mixing typically involves mixing a portion of the treated or stabilized carbon dioxide working fluid (e.g., bypassed from a buffer container or compressor outlet) with the carbon dioxide working fluid to be introduced into the compressor. By adjusting the reflux flow rate and mixing ratio, phase fluctuations in the inlet working fluid can be effectively mitigated, stabilizing its parameters and providing the compressor with more uniform and controllable intake conditions.

[0065] After the aforementioned gas-liquid separation, droplet trapping, heating, and reflux mixing processes are completed, and the phase data is monitored and confirmed to meet the compressor's access requirements, the carbon dioxide working fluid can be introduced into the compression branch. Compressor access requirements typically include specific parameters such as pressure, temperature, dryness (no liquid entrainment), and phase stability. Specifically, the introduction process is achieved by opening or adjusting the valves on the main channel of the target branch, ensuring that the carbon dioxide working fluid can smoothly and safely enter the compressor to begin compression. This step is crucial to ensuring the compressor starts and operates under optimal conditions, avoiding equipment damage or operational interruptions due to unsuitable working fluid.

[0066] It should be noted that, based on temperature data, pre-matching processing is performed on the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander at the hot end, including: When the temperature data is lower than the lower limit of the preset temperature range, the heat storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to preheat the target branch. When the temperature data is higher than the upper limit of the preset temperature range, the cold storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to pre-cool the target branch. It continuously acquires temperature data after preheating or precooling treatment, and after the processed temperature data enters the preset temperature range, it controls the thermal management branch to enter the temperature maintenance state until the compressor or expander corresponding to the target branch starts.

[0067] This process involves pre-matching the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch based on the temperature data. The aim is to ensure that the temperatures of the key components (including the inlet pipe section, associated heat exchanger, and the core compressor or expander) of the target branch reach or approach their design operating temperature range before startup. This temperature pre-matching effectively avoids problems such as thermal stress, material fatigue, and seal failure caused by excessively high or low temperatures, thereby extending equipment lifespan and laying the foundation for stable operation. This process typically involves real-time monitoring by temperature sensors and precise adjustment of the control system.

[0068] When the temperature data falls below the lower limit of the preset temperature range, the system activates a preheating mechanism. Specifically, the control system instructs the heat storage medium (e.g., high-temperature water, heat transfer oil, or steam) to flow through specific pipelines and valves, passing through the inlet pipe section of the target branch, associated heat exchangers, and internal or external heat exchange channels of the compressor or expander. The heat storage medium transfers heat to these components, gradually increasing their temperature until the preset temperature range is reached. This process aims to eliminate the risks associated with low-temperature startup, such as excessively high lubricating oil viscosity and increased metal brittleness.

[0069] Conversely, when the temperature data exceeds the upper limit of the preset temperature range, the system will activate the pre-cooling mechanism. At this time, the control system will instruct the cold storage medium (e.g., cooling water, refrigerant, or cryogenic brine) to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the compressor or expander, carrying away excess heat and gradually lowering the component temperature. This process aims to avoid problems such as equipment overheating, uneven material expansion, and accelerated aging of seals that may occur during high-temperature startup, ensuring that the equipment starts under suitable temperature conditions.

[0070] After completing the initial preheating or precooling process and bringing the target branch temperature into the preset range, the system does not immediately stop thermal management. Instead, it continuously monitors temperature data and puts the thermal management branch into a temperature maintenance mode. In this mode, the thermal management system precisely stabilizes the temperature of the target branch within the preset range by fine-tuning the flow rate, temperature, or circulation path of the heat or cold storage medium based on real-time temperature fluctuations. This continuous temperature maintenance ensures that the equipment temperature does not deviate from the ideal range again during the waiting period before the compressor or expander actually starts, thus providing continuous temperature assurance for the smooth start-up and efficient operation of the equipment.

[0071] It should be noted that starting the compressor or expander corresponding to the target branch and sequentially opening the main channel of the target branch includes: Once the pressure data reaches the preset pressure range, the phase data meets the access requirements of the compressor or expander corresponding to the target branch, and the temperature data reaches the preset temperature range, start the compressor or expander corresponding to the target branch to put the target branch into the no-load connection state. After the target branch enters the no-load takeover state, the main channel of the target branch is opened step by step to increase the flow rate of carbon dioxide working fluid in the target branch. During the process of gradually opening the main channel of the target branch, unloading control is continuously performed on the currently in-service branch to reduce the carbon dioxide working fluid flow and power output in the currently in-service branch. Once the carbon dioxide working fluid flow rate and power output in the target branch reach the preset connection conditions, it is determined that the target branch has completed the flow and power handover to the currently in-service branch.

[0072] Specifically, after the pressure data reaches a preset pressure range, the phase state data meets the access requirements of the compressor or expander corresponding to the target branch, and the temperature data reaches a preset temperature range, the compressor or expander corresponding to the target branch is started, putting the target branch into an unloaded connection state. This step aims to ensure that the carbon dioxide working fluid at the inlet of the target branch fully meets the operating conditions before its core equipment (compressor or expander) is started. Pressure data, phase state data, and temperature data are key parameters for measuring the working fluid state. The preset pressure range, access requirements, and preset temperature range are determined based on the design characteristics and safe operation requirements of the compressor or expander. For example, for a compressor, the inlet working fluid may be required to be gaseous and the temperature not lower than a certain value to avoid liquid slugging; for an expander, the inlet working fluid may be required to be supercritical or gaseous and the temperature within a specific range to optimize efficiency. Only after these conditions are met is the compressor or expander corresponding to the target branch started, putting it into an unloaded connection state. The no-load take-off state refers to the equipment being started and running, but not yet fully carrying the working fluid flow or power output. For example, most of the working fluid is bypassed through a bypass valve, or the equipment is running at the lowest speed to preheat or precool and prepare for subsequent flow introduction.

[0073] Based on this, after the target branch enters the no-load take-off state, the main channel of the target branch is opened step by step to increase the flow rate of carbon dioxide working fluid in the target branch. This step describes the process of gradually introducing carbon dioxide working fluid flow into the target branch after the equipment is ready for no-load operation. "Step-by-step opening" of the main channel means increasing its opening in small steps and gradually by controlling the valves on the main channel (e.g., flow regulating valves), rather than opening them completely all at once. This gradual flow introduction strategy can effectively avoid system pressure shocks, sudden increases in equipment load, or vibrations caused by a sudden increase in working fluid flow, thereby protecting the equipment and maintaining system stability. The increase in flow can be dynamically adjusted according to a preset ramp curve or based on real-time monitoring of the system response.

[0074] Simultaneously, during the gradual opening of the target branch's main channel, unloading control is continuously applied to the currently operating branch to reduce the carbon dioxide working fluid flow and power output. This step emphasizes the coordination and synchronization between the flow introduction of the target branch and the flow cut-off of the currently operating branch. As the main channel of the target branch gradually opens and its working fluid flow and power output gradually increase, the currently operating branch synchronously and continuously performs unloading control. Unloading control can be achieved by gradually closing the main channel valve of the currently operating branch, gradually opening its return valve or bypass valve, and reducing the speed or load of the compressor or expander corresponding to the currently operating branch. This coordination mechanism ensures that the total working fluid flow and power output of the system remain relatively stable during the switching process, avoiding system imbalance caused by sudden increases or decreases in load on a single branch.

[0075] Finally, once the CO2 working fluid flow rate and power output in the target branch reach the preset takeover conditions, the system determines that the target branch has completed the flow and power handover to the currently operating branch. This step defines clear criteria for the completion of the flow and power handover. The preset takeover conditions are determined based on the system design and operating strategy, and typically include the working fluid flow rate in the target branch reaching a certain proportion (e.g., more than 90% of the total system flow rate), or its power output reaching a preset value, while the flow rate and power output of the currently operating branch have decreased to preset low load or standby levels. When these conditions are met, the system controller can determine that the flow and power handover has been successfully completed, providing a basis for the subsequent complete shutdown of the currently operating branch and working fluid recovery operations. This ensures the integrity and controllability of the switchover process.

[0076] It should be noted that after determining that the target branch is operating stably, the main channel of the currently in-service branch is shut down, and the residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container, including: Acquire the operating pressure, operating temperature, and operating flow data of the target branch; When the operating pressure data, operating temperature data, and operating flow data continuously meet the corresponding stable range, the target branch is determined to be operating stably. After determining that the target branch is operating stably, close the main channel of the currently in-service branch and open the residual working fluid recovery channel; The residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container through the residual working fluid recovery channel. After the residual carbon dioxide working fluid in the currently in-service branch is introduced, the residual working fluid recovery path is closed.

[0077] Specifically, the method involves acquiring operating pressure, operating temperature, and operating flow data for the target branch. These data are core parameters characterizing the operating status of a carbon dioxide energy storage system. This data can be acquired in real time by installing high-precision, fast-responding pressure sensors, temperature sensors, and flow meters at key locations in the target branch, such as the inlet, outlet, compressor, or expander, ensuring data real-time performance and accuracy, and providing a reliable basis for subsequent stable operation assessments.

[0078] Subsequently, when the operating pressure data, operating temperature data, and operating flow rate data continuously meet their corresponding stable ranges, the target branch is determined to be operating stably. The stable range refers to the allowable fluctuation range of operating pressure, operating temperature, and operating flow rate that the system should maintain under normal, safe, and efficient operating conditions. These ranges are typically preset based on system design parameters, equipment operating characteristics, and safety specifications. Continuous compliance means that these key parameters remain within their respective stable ranges over a period of time, rather than being met instantaneously. This can be achieved by setting a time window and continuously monitoring the data within that window; if all data points are within the stable range, the continuity requirement is considered met. This judgment mechanism effectively avoids misjudgments caused by instantaneous disturbances or sensor errors, ensuring that the target branch truly enters a stable operating state.

[0079] After confirming the target branch is operating stably, the main channel of the currently operating branch is closed, and the residual working fluid recovery pathway is opened. Closing the main channel of the currently operating branch is typically achieved by operating the valves on the main channel, for example, by completely closing the main channel valves to disconnect the branch from the system's main circulation. Opening the residual working fluid recovery pathway refers to opening a channel specifically for draining the remaining carbon dioxide working fluid from the currently operating branch. This pathway typically includes valves, piping, and interfaces connecting to storage units or transition buffer containers. This step aims to prepare for the safe and efficient handling of residual working fluid in the currently operating branch, preventing working fluid retention or disorderly discharge.

[0080] Next, the residual carbon dioxide working fluid in the currently operating branch is introduced into the corresponding storage unit or transition buffer container via the residual working fluid recovery pathway. The introduction of the residual carbon dioxide working fluid can be achieved in several ways. For example, the working fluid can be pushed into the storage unit or transition buffer container using the pressure differential within the system; or, if necessary, a small pump or compressor can be activated to assist in the recovery. The storage unit can be a dedicated tank for storing carbon dioxide, while the transition buffer container may be a temporary container used for buffering or preliminary treatment during the working fluid recovery process. This process aims to maximize the recovery of valuable working fluid, reduce waste, and prevent direct emission of working fluid into the environment, meeting both environmental and economic efficiency requirements.

[0081] Finally, after the residual carbon dioxide working fluid has been introduced into the currently operating branch, the residual working fluid recovery path is closed. Closing the recovery path after the residual working fluid introduction is to isolate the currently operating branch and prevent the entry of external media or leakage of internal residual working fluid. This is typically achieved by closing the valves on the recovery path. After this step is completed, the currently operating branch is completely isolated, marking the end of this phase of the system switchover process and providing a safety guarantee for subsequent system operation or maintenance.

[0082] It should be noted that the unloading control for currently in-service branch lines includes: Obtain the current operating flow rate and power output data of the in-service branch circuit; Based on the operating flow rate data and power output data, the opening degree of the main channel valve of the currently in-service branch is gradually reduced, and the opening degree of the return valve is gradually increased to reduce the carbon dioxide working fluid flow rate in the currently in-service branch. While reducing the flow rate of carbon dioxide working fluid in the currently in-service branch, the load output of the corresponding compressor or expander in the currently in-service branch is reduced simultaneously. Once the operating flow data and power output data reach the preset unloading conditions, the currently in-service branch is kept in a low-load, ready-to-be-switched-out state.

[0083] Specifically, this method first acquires the operating flow rate and power output data of the currently operating branch. This step aims to monitor the operating status of the currently operating branch in real time. Operating flow rate data can be obtained through flow meters installed on the branch pipeline, such as vortex flow meters and differential pressure flow meters, to accurately measure the mass flow rate or volumetric flow rate of the carbon dioxide working fluid flowing through the branch. Power output data is obtained by monitoring the electrical power sensors of the compressor or expander corresponding to the currently operating branch or by calculating its mechanical power, reflecting the energy output or consumption of the currently operating branch. This real-time data forms the basis for precise unloading control, ensuring that the control strategy can be dynamically adjusted according to actual operating conditions.

[0084] Subsequently, based on the operating flow rate and power output data, the opening of the main channel valve of the currently operating branch is gradually reduced, while the opening of the return valve is gradually increased to reduce the carbon dioxide working fluid flow rate in the currently operating branch. This step describes the specific method of controlling the working fluid flow rate by adjusting the valve opening. "Gradually reducing" and "gradually increasing" mean that the valve opening adjustment is not completed all at once, but rather in multiple stages to avoid drastic fluctuations in system parameters. The main channel valve is usually located on the main flow path of the currently operating branch; reducing its opening directly limits the total amount of working fluid entering or leaving the branch. The return valve is usually connected between the branch inlet or outlet and the storage unit or transition buffer container; increasing its opening diverts some of the working fluid from the main channel, preventing it from participating in the energy conversion process of the current branch, thereby effectively reducing the effective working fluid flow rate within the branch. This coordinated adjustment method enables stable and precise control of the working fluid flow rate.

[0085] During the reduction of the carbon dioxide working fluid flow rate in the currently operating branch, the load output of the corresponding compressor or expander in the currently operating branch is simultaneously reduced. This step emphasizes the synchronicity between working fluid flow control and main unit load output control. When the working fluid flow rate decreases, if the load output of the compressor or expander is not adjusted accordingly, it may cause the equipment to deviate from its optimal operating point, or even trigger instability phenomena such as surge or overspeed. Synchronous load reduction can be achieved in various ways. For example, for compressors, its compression work can be reduced by adjusting its speed (variable frequency control), changing the guide vane opening, or the unloading valve opening; for expanders, its expansion work can be reduced by adjusting its speed or the inlet guide vane opening. This synchronous control ensures stable operation of the equipment during the unloading process and avoids unnecessary energy loss.

[0086] Finally, after the operating flow rate and power output data reach the preset unloading conditions, the currently in-service branch remains in a low-load, ready-to-switch-out state. The "preset unloading conditions" refer to the flow rate and power thresholds determined during system design, indicating that the currently in-service branch has completed most of its unloading task. For example, when both the operating flow rate and power output data are below a certain safety threshold, the preset unloading conditions are considered met. Upon reaching this condition, the currently in-service branch enters a "low-load, ready-to-switch-out state," meaning that although the branch is still running, its working fluid flow rate and power output have dropped to extremely low levels, having a negligible impact on the entire system. At this point, the branch is ready to be completely shut down or switched over at any time. This state setting provides sufficient buffer time for the startup and flow handover of subsequent target branches and ensures the smoothness of the switching process.

[0087] Example 2 A charge / discharge switching control system for a carbon dioxide energy storage system, referring to Figure 2 ,include: Processor and memory; The processor and memory are connected via a communication bus: The processor is used to call and execute programs stored in memory. A memory is used to store a program, which is used to execute at least one of the carbon dioxide energy storage system charge / discharge switching control methods in the above embodiments.

[0088] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0089] It should be noted that in the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this application, unless otherwise stated, "a plurality of" means at least two.

[0090] Any process or method described in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the function involved, as will be understood by those skilled in the art to which embodiments of this application pertain.

[0091] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0092] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0093] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0094] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0095] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0096] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for controlling the charging and discharging switching of a carbon dioxide energy storage system, characterized in that, include: Obtain the mode switching request and the current operating mode, and determine the currently active branch and the target branch based on the mode switching request and the current operating mode; Acquire pressure, temperature, and phase data at the inlet of the target branch; Unloading control is performed on the currently in-service branch, while keeping the main channel of the target branch closed; Open the transition buffer branch and gradually build up pressure at the entrance of the target branch until the pressure data reaches the preset pressure range. The phase regulation branch is activated, and the carbon dioxide working fluid entering the target branch is subjected to at least two of the following treatments based on the phase data and temperature data: separation, interception, heating, cooling, and reflux mixing, until the phase data meets the access requirements of the compressor or expander corresponding to the target branch. The thermal management branch is activated, and the inlet pipe section, associated heat exchanger, and corresponding compressor or expander of the target branch are pre-matched according to the temperature data until the temperature data reaches the preset temperature range. Start the compressor or expander corresponding to the target branch and open the main channel of the target branch step by step to complete the flow and power transfer between the current in-service branch and the target branch during the continuous unloading process of the current in-service branch; After determining that the target branch is operating stably, the main channel of the currently in-service branch is closed, and the residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container to complete the switching between charging mode and discharging mode. Based on the mode switching request and the current operating mode, the currently active branch and the target branch are determined, including: If the current operating mode is charging mode, the currently active branch is determined to be a compression branch and the target branch is an expansion branch. If the current operating mode is discharge mode, the currently in-service branch is determined to be an expansion branch and the target branch is a compression branch. When the target branch is a compression branch, the corresponding device is a compressor; When the target branch is an expansion branch, the corresponding equipment is an expander; When the target branch is an expansion branch, the carbon dioxide working fluid entering the target branch is processed according to the phase state data, including: When the phase data indicates that the carbon dioxide working fluid entering the expansion branch has liquid phase entrainment, the carbon dioxide working fluid is subjected to gas-liquid separation and droplet interception treatment. When the phase state data indicates that the temperature of the carbon dioxide working fluid entering the expansion branch is lower than the preset lower limit, the carbon dioxide working fluid is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working fluid entering the expansion branch, as indicated by the phase data, exceeds a preset range, the carbon dioxide working fluid is subjected to reflux mixing treatment. After the phase data meets the expander access requirements, the carbon dioxide working fluid is introduced into the expansion branch; When the target branch is a compression branch, the carbon dioxide working fluid entering the target branch is processed according to the phase state data, including: When the phase data indicates that the carbon dioxide working fluid entering the compression branch has liquid phase entrainment, the carbon dioxide working fluid is subjected to gas-liquid separation and droplet interception treatment. When the phase state data indicates that the temperature of the carbon dioxide working fluid entering the compression branch is lower than a preset lower limit, the carbon dioxide working fluid is subjected to heating treatment. When the phase fluctuation of the carbon dioxide working fluid entering the compression branch, as indicated by the phase data, exceeds a preset range, the carbon dioxide working fluid is subjected to reflux mixing treatment. After the phase data meets the compressor access requirements, the carbon dioxide working fluid is introduced into the compression branch.

2. The method according to claim 1, characterized in that, Activate the transition buffer branch and gradually build up pressure at the inlet of the target branch until the pressure data reaches a preset pressure range, including: With the main channel of the target branch closed, the pre-charge valve is opened to allow the carbon dioxide working medium in the corresponding storage unit to enter the transition buffer container. The throttle valve opening is adjusted according to the pressure data to control the working fluid flow rate from the transition buffer container to the target branch inlet; When the pressure data reaches the lower limit of the preset pressure range, the target branch inlet connecting valve is opened to connect the transition buffer container with the target branch inlet. When the pressure data exceeds the upper limit of the preset pressure range, the reflux valve is opened to guide part of the carbon dioxide working fluid back to the corresponding storage unit or the transition buffer container, so that the pressure data is maintained within the preset pressure range.

3. The method according to claim 1, characterized in that, Based on the temperature data, pre-matching processing is performed on the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander at the hot end, including: When the temperature data is lower than the lower limit of the preset temperature range, the heat storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to preheat the target branch. When the temperature data is higher than the upper limit of the preset temperature range, the cold storage medium is controlled to flow through the inlet pipe section of the target branch, the associated heat exchanger, and the corresponding compressor or expander to pre-cool the target branch. The system continuously acquires temperature data after preheating or precooling treatment, and once the processed temperature data enters a preset temperature range, it controls the thermal management branch to enter a temperature maintenance state until the compressor or expander corresponding to the target branch starts.

4. The method according to claim 1, characterized in that, Start the compressor or expander corresponding to the target branch, and sequentially open the main channel of the target branch, including: After the pressure data reaches the preset pressure range, the phase data meets the access requirements of the compressor or expander corresponding to the target branch, and the temperature data reaches the preset temperature range, the compressor or expander corresponding to the target branch is started, so that the target branch enters the no-load connection state. After the target branch enters the no-load takeover state, the main channel of the target branch is opened step by step to increase the flow rate of carbon dioxide working fluid in the target branch. During the process of gradually opening the main channel of the target branch, unloading control is continuously performed on the currently in-service branch to reduce the carbon dioxide working fluid flow and power output in the currently in-service branch. Once the carbon dioxide working fluid flow rate and power output in the target branch reach the preset connection conditions, it is determined that the target branch has completed the flow and power handover to the currently in-service branch.

5. The method according to claim 1, characterized in that, After determining that the target branch is operating stably, the main channel of the currently in-service branch is shut down, and the residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container, including: Obtain the operating pressure data, operating temperature data, and operating flow rate data of the target branch; When the operating pressure data, the operating temperature data, and the operating flow rate data continuously meet the corresponding stable range, the target branch is determined to be operating stably. After determining that the target branch is operating stably, close the main channel of the currently in-service branch and open the residual working fluid recovery channel; The residual carbon dioxide working fluid in the currently in-service branch is introduced into the corresponding storage unit or transition buffer container through the residual working fluid recovery channel. After the residual carbon dioxide working fluid in the currently in-service branch is introduced, the residual working fluid recovery path is closed.

6. The method according to claim 1, characterized in that, Implement offloading control on currently in-service branch lines, including: Obtain the current operating flow rate and power output data of the in-service branch circuit; Based on the operating flow rate data and power output data, the opening degree of the main channel valve of the currently in-service branch is gradually reduced, and the opening degree of the return valve is gradually increased, so as to reduce the carbon dioxide working fluid flow rate in the currently in-service branch. While reducing the flow rate of carbon dioxide working fluid in the currently in-service branch, the load output of the corresponding compressor or expander in the currently in-service branch is reduced simultaneously. After the operating flow data and power output data reach the preset unloading conditions, the currently in-service branch is kept in a low-load waiting-to-be-switched-out state.

7. A charge / discharge switching control system for a carbon dioxide energy storage system, characterized in that, include: Processor and memory; The processor and memory are connected via a communication bus: The processor is used to call and execute the program stored in the memory; The memory is used to store a program, which is at least used to execute the charge / discharge switching control method for a carbon dioxide energy storage system according to any one of claims 1-6.

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