An expansion generator set system and method for black start of compressed air energy storage power stations

Abstract

This invention discloses an expander generator system and method for black start of compressed air energy storage power stations. It mainly consists of an air expander, a generator, a starting valve, a hydraulic regulating valve, an anti-wear hydraulic oil pump, an anti-wear hydraulic oil tank, a gearbox, and various pipelines. The air expander can either directly drive the generator and the anti-wear hydraulic oil pump, or it can output mechanical power to the generator and the anti-wear hydraulic oil pump after speed change via the gearbox. The rotor supports of the expander, generator, and oil pump all use rolling bearings, eliminating the need for a lubrication station or reducing related power consumption. During the initial start-up process, the starting valve is fully open, ensuring that the expander generator's speed can reach 90%. Precise and rapid response control of the speed and power required for subsequent grid connection requires the use of a hydraulic regulating valve connected in parallel. This invention can meet the black start requirements of 100MW and larger power-level compressed air energy storage power stations, and the overall structure is simple, highly reliable, and easy to maintain.

Description

Technical Field

[0001] This invention relates to the field of compressed air energy storage, specifically to black start power supply and expander control for compressed air energy storage (CAES) power plants. More specifically, it is an expander generator system and method for the black start process of a compressed air energy storage power plant, which provides fast, reliable, low-consumption and precisely controlled power supply for the entire process from static to power generation of the compressed air energy storage power plant. Background Technology

[0002] Energy storage systems can significantly improve the operational efficiency, economy, and security of power grids, and have seen widespread development in recent years. To further enhance the efficiency of Compressed Air Energy Storage (CAES) systems and their role in peak shaving for the power grid, energy storage power stations with power ratings of 100MW and above have been put into operation. The black-start capability of such energy storage power stations after a complete grid outage—that is, the ability to autonomously restore power to critical auxiliary equipment and control systems and gradually drive the main unit to start and connect to the grid without external power support—is an important indicator of their reliability and self-recovery capability as critical power infrastructure. The power consumption during the black-start phase of a CAES power station is characterized by high power density, strong impact, long duration, and stringent requirements for frequency and voltage quality and dynamic response.

[0003] In engineering practice, the black start process of high-power compressed air energy storage power stations requires a large amount of power from auxiliary equipment or subsystems, such as lubricating oil pumps, anti-wear hydraulic oil pumps, high-pressure jacking oil pumps, heat exchange working fluid pumps, cooling water circulating pumps, instrument air compressors, cooling towers, distributed control systems (DCS), and electric regulating valves. If the power (in the hundreds of kilowatts) and electricity consumption (maintaining operation for at least 10 minutes until the main power generation system is connected to the grid) of these auxiliary equipment or subsystems were all handled by an uninterruptible power supply (UPS), it would be extremely costly. Therefore, it is necessary to consider how to solve the black start requirements of medium-to-high power compressed air energy storage power stations in a low-cost and highly reliable manner.

[0004] Meanwhile, CAES power plant black start sequences typically require the power supply side to have rapid ramp-up capability from zero to rated capacity, coordinate the sequence and timing of multi-level load input, and provide sufficient short-circuit capacity and voltage support in islanded grid conditions to ensure the reliable execution of high-voltage power distribution equipment, local soft starters / frequency converters, protection settings, and interlocking logic. Existing technologies generally suffer from shortcomings in the complete chain of rapid speed-up—meticulous control—power ramp-up—long-term stability, such as response lag, insufficient control precision, low energy efficiency, or high dependence on external support conditions.

[0005] For existing related technologies, such as the grid black start system disclosed in Chinese invention patent CN114614503A, the thermal power high-voltage direct-connected energy storage black start system disclosed in CN114825452A, and the liquid compressed air energy storage peak-shaving system and method for supplying black start power disclosed in CN112049698A, these patents only provide the system flow of black start, focusing more on electrical coupling and switching, relying on complex valve groups, cryogenic units or high-voltage converters, and do not have a systematic valve control and speed / power closed loop for the rapid start-up of air expander units, the stability of isolated grid frequency and the friendliness of auxiliary equipment under large impacts. Moreover, they are highly dependent on backup batteries or power electronic devices and have limited field adaptability. The energy storage system and method for black start disclosed in CN111244984A uses manual control for the air generator set, lacks automatic valve control and protection logic, cannot meet the speed and power control accuracy required by plant power or grid, has insufficient dynamic response and redundancy for sudden loads, and has limited engineering applicability.

[0006] In summary, existing CAES power plant black start power supply technology still has significant shortcomings. Therefore, how to reduce dependence on UPS power supply, achieve low-cost and high-reliability power supply, and at the same time ensure that the power plant can start up and connect to the grid quickly and accurately is an urgent technical problem to be solved. Summary of the Invention

[0007] (I) Purpose of the Invention

[0008] To address the aforementioned deficiencies and shortcomings of existing technologies, this invention aims to provide an expander generator system and method for black start of compressed air energy storage power stations. By constructing a dedicated expander generator set using compressed air as a primary energy source, establishing a valve control strategy that integrates rapid start-up with precise stability control, creating self-supplied hydraulic and control energy on the generator side, and optimizing shaft system and lubrication adaptation as well as thermal management under low-temperature conditions, this invention achieves rapid start-up under conditions without external power supply, friendly power supply to high-power inductive auxiliary equipment, frequency and voltage stability and high-quality grid connection under islanded grid conditions. This significantly reduces dependence on large-capacity UPS and external gas turbines / diesel engines, improving the reliability, efficiency, and engineering adaptability of black start.

[0009] (II) Technical Solution

[0010] To achieve the objective of this invention and solve its technical problems, the present invention adopts the following technical solution:

[0011] The first objective of this invention is to provide an expander generator system for black start of a compressed air energy storage power station. This system utilizes stored high-pressure compressed air as a power source during the black start process to provide stable and reliable power to the power station's auxiliary equipment and subsystems, meeting the precise control requirements of speed and power during startup while reducing reliance on uninterruptible power supplies. The system is characterized by comprising at least an expander subsystem, an intake regulation subsystem, a power generation and transmission subsystem, and a hydraulic oil supply and control subsystem, wherein:

[0012] The expander subsystem includes at least one air expander, whose exhaust pipeline is connected to the atmosphere and whose intake pipeline is connected to the high-pressure air storage device of the compressed air energy storage power station to receive high-pressure compressed air. The expander rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start.

[0013] The intake regulation subsystem is located between the high-pressure air storage device and the air expander intake port, and includes at least a start valve located on the expander intake pipeline and a hydraulic regulating valve arranged in parallel with it. The start valve is configured to supply air quickly with a large opening during the black start acceleration phase, so that the unit accelerates from a standstill to the target speed range. The hydraulic regulating valve is hydraulically driven and continuously and adjustablely controls the intake flow rate and intake pressure difference when the unit enters the steady state phase, so as to maintain the stability of the generator speed and active power output.

[0014] The power generation and transmission subsystem includes at least one generator connected to the air expander for converting the mechanical energy of the expander into electrical energy and supplying power to the plant load during the black start phase of the power plant. The generator rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start.

[0015] The hydraulic oil supply and control subsystem includes an anti-wear hydraulic oil pump and an anti-wear hydraulic oil tank. The anti-wear hydraulic oil pump is connected to the air expander, and the pump rotor adopts a rolling support structure to establish valve-controlled drive capability without external power under black start conditions. Its inlet is connected to the anti-wear hydraulic oil tank through a pipeline, and its outlet is connected to the hydraulic regulating valve in the intake regulating subsystem through a pipeline. It is used to output hydraulic oil flow and pressure that meet the control requirements of the hydraulic regulating valve after the unit speed reaches the set speed, so as to realize precise regulation of power generation and grid connection control.

[0016] The second objective of this invention is to provide a black-start control method for a compressed air energy storage power station. Based on the aforementioned expander generator system for black-starting a compressed air energy storage power station, this invention enables the rapid restoration of the power station's auxiliary power supply in the event of a grid power outage or a complete power station shutdown, achieving an autonomous start-up process from a static to a generating state. The method includes at least the following steps:

[0017] S100. Start-up preparation and self-test: After receiving the black start command, the small UPS provides the minimum control power to confirm that the pressure of the high-pressure gas storage device meets the preset threshold, and checks that each rolling support structure, inlet and outlet pipeline, hydraulic oil pipeline, valve position status of the start valve and hydraulic regulating valve, level and temperature of the anti-wear hydraulic oil tank, and communication status of the DCS control system are in normal and usable condition.

[0018] S200. Rapid start-up phase (start valve main control): Open the start valve to the preset maximum opening, so that the compressed air in the high-pressure air storage device enters the air expander in a large flow through the start valve, which drives the expander impeller to rotate rapidly and drives the generator and anti-wear hydraulic oil pump connected to it to accelerate synchronously. The control unit limits the opening change rate of the start valve according to the target speed climb curve over time, and suppresses speed overshoot and aerodynamic instability.

[0019] S300. Hydraulic Establishment and Valve Control Preparation: As the speed of the expander generator increases, the anti-wear hydraulic oil pump outputs pressurized oil, which establishes stable oil pressure and oil temperature through the hydraulic oil pipeline and supplies oil to the hydraulic regulating valve. When the hydraulic oil pressure and flow rate reach the minimum driving condition of the hydraulic regulating valve, the hydraulic regulating valve is switched to the actuated state, enabling it to regulate the intake flow of the air expander. The hydraulic oil supply and control subsystem enters the normal working state.

[0020] S400. Seamless switching and steady-state takeover (hydraulic valve master control): When the speed of the expansion generator set reaches the preset speed threshold (e.g., 80-95% of the rated speed) and the generator terminal voltage has been established, the opening of the starting valve is gradually reduced according to the set slope, while the opening of the hydraulic regulating valve is increased to realize the transition zone of parallel control of the two valves; after the switching is completed, the hydraulic regulating valve dynamically controls the intake flow and pressure difference in a single valve closed loop according to the changes in the plant power load to maintain the stability of power output;

[0021] S500. Plant power supply and power plant start-up phase: After the expansion generator set is running stably, in the state of being disconnected from the plant bus, according to the power plant black start procedure, its output power is supplied to the auxiliary equipment of the power plant through the plant power distribution system, and the various subsystems of the power plant are gradually started. When the main system of the power plant has the start-up conditions, the power plant enters the normal power generation state through the main system start-up procedure, completing the entire process of transition from black start to normal operation.

[0022] S600. Expansion Generator Set Shutdown and System Switching Phase: When the main power plant system starts generating electricity normally and the auxiliary power can be supplied by the main power system, the opening of the hydraulic regulating valve is gradually reduced to reduce the output power of the expansion generator set, and the auxiliary power supply is smoothly switched. Finally, the hydraulic regulating valve is closed to shut down the expansion generator set, the entire black start control process ends, and the power plant returns to normal operation.

[0023] (III) Technical Effects

[0024] Compared with the prior art, the expander generator system and method for black start of compressed air energy storage power stations of the present invention have the following beneficial and significant technical effects:

[0025] (1) The expansion generator set of the present invention has no other power requirements except for the DCS system control and the high power electrical cabinet which are handled by the UPS power supply. It does not need to be equipped with other auxiliary equipment, so it is suitable as a black start device for compressed air energy storage power stations.

[0026] (2) The expansion generator set of the present invention has a simple structure, is reliable, has high control precision, starts and stops quickly, is easy to maintain, and has multiple options for power generation and structural form. It is suitable for the black start requirements of compressed air energy storage power stations with power levels of 100MW and above.

[0027] (3) The expansion generator set of the present invention can reduce the capacity and cost of UPS by more than 80%, because the total power of various auxiliary machines such as oil pumps, working fluid reheat pumps, cooling water pumps, instrument air compressors, cooling fans, and electric regulating valves in medium and large compressed air energy storage power stations is large, and it is necessary to maintain the entire black start process until the power station starts to output power. Attached Figure Description

[0028] Figure 1 The diagram shown is a schematic diagram of a single-shaft expansion generator system provided in an embodiment of the present invention;

[0029] Figure 2 The figure shown is a schematic diagram of an expansion generator set system with a high-speed shaft single-end coupling connected by a variable speed gearbox, provided in an embodiment of the present invention.

[0030] Figure 3 The figure shown is a schematic diagram of an expansion generator system with a high-speed shaft suspended at both ends with a variable speed gearbox provided in an embodiment of the present invention.

[0031] Figure 4 The diagram shows the black start control method of a compressed air energy storage power station.

[0032] Explanation of reference numerals in the attached drawings: 1-Air expander, 2-Generator, 3-Anti-wear hydraulic oil pump, 4-Anti-wear hydraulic oil tank, 5-Hydraulic regulating valve, 6-Starting valve, 7-Speed ​​gearbox, 8-Lubricating oil pump. Detailed Implementation

[0033] This invention aims to provide an expander generator system and method for black start of a compressed air energy storage power station. It utilizes stored high-pressure compressed air as a power source during the black start process of the power station, providing stable and reliable power to auxiliary equipment and subsystems, meeting the precise control requirements of speed and power during power station startup, and reducing reliance on uninterruptible power supplies (UPS). To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings. The described embodiments are some, but not all, embodiments of this invention, and are exemplary, intended to explain the invention, and should not be construed as limiting the invention.

[0034] Example 1: Expander Generator System

[0035] like Figures 1-3 As shown in the embodiment of the present invention, the expander generator system for black start of a compressed air energy storage power station mainly includes an expander subsystem, an intake regulation subsystem, a power generation and transmission subsystem, and a hydraulic oil supply and control subsystem. The expander subsystem includes at least an air expander 1, whose exhaust pipeline is connected to the atmosphere, and whose intake pipeline is connected to the high-pressure air storage device of the compressed air energy storage power station to receive high-pressure compressed air. The expander rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start. The intake regulation subsystem is located between the high-pressure air storage device and the air inlet of the air expander 1, and includes at least a starting valve 6 located on the expander intake pipeline and a hydraulic regulating valve 5 arranged in parallel with it. The starting valve 6 is configured to supply air quickly with a large opening during the black start acceleration phase, accelerating the unit from a standstill to the target speed range. The hydraulic regulating valve 5 is hydraulically driven and regulates the intake flow rate and intake pressure when the unit enters the steady-state phase. The differential continuously adjustable control maintains the stability of generator 2 speed and active power output. The power generation and transmission subsystem includes at least generator 2, which is driven by air expander 1, to convert mechanical energy of expansion into electrical energy and supply power to the plant's auxiliary load during the black start phase. The generator rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start. The hydraulic oil supply and control subsystem includes anti-wear hydraulic oil pump 3 and anti-wear hydraulic oil tank 4. The anti-wear hydraulic oil pump 3 is driven by air expander 1, and the pump rotor adopts a rolling support structure so that it can establish valve-controlled drive capability without external power under black start conditions. Its inlet is connected to anti-wear hydraulic oil tank 4 through a pipeline, and its outlet is connected to hydraulic regulating valve 5 in the intake regulating subsystem through a pipeline. It is used to output hydraulic oil flow and pressure that meet the control requirements of hydraulic regulating valve after the unit speed reaches the set speed, so as to realize precise regulation of power generation and grid connection control.

[0036] In a preferred embodiment of the present invention, such as Figure 1As shown, the transmission connection between the power generation and transmission subsystems in the expander generator set system can be a single-shaft structure, that is, the rotors of the air expander 1, generator 2, and anti-wear hydraulic oil pump 3 are set on the same main shaft, or the transmission connection of the three is achieved through rigid or flexible couplings, so that the three rotate at the same speed. This speed is designed to be the synchronous speed of the power grid or an integer multiple thereof, such as 1500 RPM or 3000 RPM. This allows the generator to be directly driven to generate electricity at the 50 Hz power frequency, thereby simplifying the mechanical structure, reducing transmission losses, and improving the compactness and reliability of the system.

[0037] In a preferred embodiment of the present invention, such as Figure 2 As shown, the transmission connection between the power generation and transmission subsystems in the expander generator set system can also be a structure with a variable speed gearbox, i.e., a variable speed gearbox 7 between the air expander 1 and the generator 2. The rotor of the air expander 1 is driven to the power input end of the variable speed gearbox 7, and the generator 2 and the anti-wear hydraulic oil pump 4 are driven to the output shaft of the variable speed gearbox 7. The speed of the expander 1 is different from that of the generator 2 and the anti-wear hydraulic oil pump 3 (i.e., the EH oil pump). The air expander 1 rotates at a first speed and drives the generator 2 and the anti-wear hydraulic oil pump 3 at a second speed different from the first speed after being changed by the variable speed gearbox 7. This is used to realize the deceleration transmission when the expander 1 adopts a high-speed operation mode, so as to ensure that the generator 2 operates at the standard industrial speed. Thus, while optimizing the aerodynamic design of the expander and allowing it to operate at the optimal efficiency point, the generator 2 can operate at the standard speed of 1500RPM or 3000RPM to achieve 50Hz power frequency power generation.

[0038] In a preferred embodiment of the present invention, for the transmission connection method of the power generation and transmission subsystem with a variable speed gearbox, the rotor of the expander 1 can be supported independently (e.g., Figure 2 As shown), it is connected to gearbox 7 via a coupling, or impellers can be suspended on both sides of the high-speed gear shaft of gearbox 7 (such as...). Figure 3 As shown, the impellers on both sides have identical geometry to counteract axial thrust and reduce mechanical losses. Furthermore, the transmission gearbox 7 preferably includes an oil injection lubrication and cooling circuit. This circuit is connected to the output shaft or intermediate shaft of the transmission gearbox 7 via a lubrication pump 8. This pump provides forced lubrication for gear meshing after the unit reaches a predetermined speed, and allows for short-term oil-free operation of the gears before the unit reaches a preset speed threshold during the initial black start phase.

[0039] Furthermore, such as Figure 2As shown, when the rotor of the air expander 1 adopts a single-shaft end power output structure and is supported by an independent bearing system, its power output end is connected to the power input end of the gearbox 7 through a rigid or flexible coupling. The transmission ratio of the gearbox 7 is determined according to the matching relationship between the optimal operating speed of the expander and the rated speed of the generator, ensuring that the air expander 1 operates in the high-efficiency range while the generator can generate electricity stably at the standard speed of 1500RPM or 3000RPM.

[0040] Furthermore, such as Figure 3 As shown, when the air expander 1 adopts an impeller-opposed structure, impellers with identical geometry are suspended at both ends of the high-speed input shaft of the variable speed gearbox 7. The axial thrust generated by the two symmetrically arranged impellers cancels each other out, eliminating or significantly reducing the net axial thrust acting on the expander rotor, so as to maintain axial force balance and reduce the thrust bearing load under all working conditions.

[0041] It should be noted that, Figures 1 to 3 In the diagram, the inlet arrow of air expander 1 represents high-pressure air intake, and the outlet arrow represents atmospheric pressure air exhaust. The inlet arrow of anti-wear hydraulic oil pump 3 represents oil suction from the oil tank, and the outlet arrow represents oil supply to the hydraulic valve. All rotors of the expander generator set are supported by rolling bearings (the triangular positions in the diagram), meaning that pressurized lubricating oil does not need to be supplied to the bearings during startup, avoiding the need for a lubrication station and the associated power consumption associated with sliding bearings. In addition to the support bearings, the expander rotor should also be equipped with a rolling thrust bearing (or a combined support-thrust bearing) to prevent axial movement of the rotor. Even if the expander is designed with a pneumatic blade-opposed structure, a small amount of thrust will still be generated due to manufacturing errors. All rolling support structures do not require an external high-pressure oil jacking device or a lubrication station to supply pressurized lubricating oil before black start and throughout the entire startup process.

[0042] Preferably, once the air expander 1 in the expander generator set reaches a preset speed (e.g., 90% of rated speed), it can provide sufficient driving force for the anti-wear hydraulic oil pump 3, enabling the anti-wear hydraulic oil pump 3 to pump out the control oil pressure and flow rate required by the hydraulic regulating valve. For structures with a variable gearbox, the gear meshing requires oil injection lubrication, therefore a lubricating oil pump should be provided. Before starting to the preset speed, the gear meshing is in a short-term oil-free lubrication state, which is acceptable for black-start expander generator sets, which are rarely used. The lubricating oil pump draws lubricating oil from the lubricating oil tank (not shown in the figure), mainly responsible for supplying lubricating oil to the gear meshing, and can also provide appropriate lubrication for the rolling bearings.

[0043] Preferably, when the starting valve 6 is fully open, the speed of the expander generator set can reach 90%. Precise and rapid response control of the speed and power required for subsequent grid connection necessitates the use of a hydraulic regulating valve 5 connected in parallel. The expander generator set requires no other auxiliary equipment or preheating, therefore the entire startup process takes no more than 5 minutes, allowing for rapid restoration of power supply to the plant. Furthermore, the air expander 1 can be a single-stage impeller with a high-speed structure (requiring a gearbox to drive the generator and shaft oil pump) or a multi-stage impeller with a low-speed structure (not requiring a gearbox). The impeller can be radial, axial, or mixed-flow type, determined by a combination of aerodynamic and structural design considerations. The aerodynamic design of the air expander can employ an opposed impeller structure to counteract axial thrust; if a non-opposed structure is used, rolling thrust bearings must be employed.

[0044] It should be noted that the starting valve 6 can be manually, electrically, or pneumatically operated. Electrically and pneumatically operated valves consume little power, avoiding the need for on-site personnel. Pneumatically operated valves directly utilize the high-pressure air from the compressed air energy storage power station's air storage device. The starting valve 6 should be designed so that its maximum air supply when fully open allows the unit to reach up to 90% of its rated speed. Afterward, the hydraulically operated valve should be engaged to meet the precise grid connection and power generation control requirements of the expander generator set. Once the air expander 1 drives the generator 2 to begin normal power generation, the hydraulically operated regulating valve 5 controls the power generation to meet the plant power requirements during the black start process of the compressed air energy storage system. Because the black start process of medium-to-high power level compressed air energy storage power stations requires significant power consumption, the expander generator set of this invention is suitable for the black start requirements of 100MW and larger power level compressed air energy storage power stations.

[0045] Example 2: Black Start Control Method

[0046] Based on Embodiment 1 above, Embodiment 2 further provides a black-start control method for a compressed air energy storage power station. Based on the aforementioned expander generator system for black-starting a compressed air energy storage power station, this invention enables rapid restoration of the power station's auxiliary power supply in the event of a grid power outage or a complete power station shutdown, achieving an autonomous start-up process from a static to a generating state. Figure 4 As shown, the black-start control method mainly includes the following steps during implementation:

[0047] S100. Startup Preparation and Self-Check:

[0048] Upon receiving the black start command, the small UPS provides the minimum control power to confirm that the pressure of the high-pressure gas storage device meets the preset threshold. It also checks that the rolling support structure, inlet and outlet pipelines, hydraulic oil pipelines, valve position status of the start valve and hydraulic regulating valve, level and temperature of the anti-wear hydraulic oil tank, and communication status of the DCS control system are all in normal and usable condition.

[0049] As a preferred option, the minimum control power supply is only supplied to the control unit, valve position feedback, and critical measurement circuits; self-checks are performed on the pressure, temperature, and valve interlock status of the high-pressure gas storage device to confirm that the gas storage pressure is not lower than the black start set threshold and that the safety valve and vent valve are in the permissible position; leak and continuity checks are performed on the intake and exhaust pipelines and hydraulic oil pipelines, and the integrity and range of the speed, vibration, oil pressure, and electrical parameter detection channels are verified; if any self-check fails, the control unit locks the start command and generates a diagnostic code until the defect is resolved.

[0050] S200. Rapid start-up phase (start valve main control):

[0051] Open the start valve to the preset maximum opening degree, so that the compressed air in the high-pressure air storage device enters the air expander in a large flow rate through the start valve, which drives the expander impeller to rotate rapidly and drives the generator and anti-wear hydraulic oil pump connected to it to accelerate synchronously. The control unit limits the opening change rate of the start valve according to the target speed rise curve over time, and suppresses speed overshoot and aerodynamic instability.

[0052] As a preferred approach, a segmented speed control strategy is adopted, dividing the acceleration process from standstill to the target speed into three stages: initial acceleration, medium-speed transition, and high-speed approach. In the initial acceleration stage, a large starting valve opening is used to achieve rapid start-up. In the medium-speed transition stage, the starting valve opening is adjusted appropriately based on speed feedback to avoid speed overshoot. In the high-speed approach stage, a small-amplitude opening adjustment is used to achieve a smooth approach to the target speed. Throughout the acceleration process, key operating parameters such as expander intake and exhaust pressure, temperature, speed, and vibration are monitored in real time. If any parameter exceeds the safe range, the starting valve opening is immediately reduced or an emergency shutdown procedure is executed to ensure the safety and controllability of the rapid start-up process.

[0053] S300. Hydraulic Establishment and Valve Control Preparation:

[0054] As the speed of the expander generator increases, the anti-wear hydraulic oil pump outputs pressurized oil, which establishes a stable oil pressure and temperature through the hydraulic oil pipeline and supplies oil to the hydraulic regulating valve. When the hydraulic oil pressure and flow rate reach the minimum driving condition of the hydraulic regulating valve, the hydraulic regulating valve is switched to the actuated state, enabling it to regulate the intake flow of the air expander. The hydraulic oil supply and control subsystem then enters normal working condition.

[0055] Preferably, the outlet pressure of the anti-wear hydraulic oil pump is monitored in real time by a pressure sensor installed on the hydraulic oil line. When the oil pressure reaches 110% of the minimum working pressure of the hydraulic regulating valve and the pressure fluctuation is less than the set range, the hydraulic system is confirmed to be successfully established. At the same time, the hydraulic oil temperature is monitored by a temperature sensor to ensure that it is within a suitable working temperature range. The functional test of the hydraulic regulating valve is performed, including small-amplitude opening and closing actions to verify its response performance. The hydraulic oil line is checked for leaks and the oil tank level is confirmed to be maintained within a safe range. After the above verification is completed, the hydraulic regulating valve enters the standby state to prepare to take over the intake flow control task.

[0056] In addition, after the oil pressure and flow rate established by the anti-wear hydraulic oil pump reach the minimum driving conditions of the hydraulic regulating valve, the valve stroke zero-point calibration and dead zone compensation are performed to complete the loading of the opening-flow relationship curve; the oil temperature is stabilized and the pipeline air resistance is cleared through the bypass and return oil branch, and the oil temperature is raised to the allowable range for a short time if necessary; before the valve control preparation is completed, the control unit keeps the starting valve as the only effective air supply path to avoid the superimposed control in the uncalibrated state from causing disturbance to the speed.

[0057] S400. Seamless switching and steady-state control (hydraulic valve master control):

[0058] When the speed of the expansion generator set reaches the preset speed threshold (e.g., 80-95% of the rated speed) and the generator terminal voltage has been established, the opening of the starting valve is gradually reduced according to the set slope, while the opening of the hydraulic regulating valve is increased to realize the transition zone of parallel control of the two valves; after the switching is completed, the hydraulic regulating valve dynamically controls the intake flow and pressure difference in a single valve closed loop according to the changes in the plant power load to maintain the stability of power output.

[0059] As a preferred approach, a two-valve parallel, non-disruptive switching strategy is adopted. The control unit uses a linear or piecewise linear weighting function to reverse-couple the opening of the starting valve and the hydraulic regulating valve, so that the equivalent opening of the air supply remains continuously differentiable within the switching window. When the spindle speed and generator terminal voltage enter the target bandwidth and stabilize to the set dwell time, the starting valve is frozen at a small opening or closed, and only the hydraulic regulating valve implements closed-loop stability control. If the hydraulic oil pressure drops below the threshold or the valve feedback is abnormal, the control returns to the starting valve and the power output is limited. In addition, this step further includes the generator grid connection preparation process. After the hydraulic regulating valve is connected to the control unit, the power quality of the generator output is detected. When all power quality indicators meet the plant power supply standard requirements, the grid connection procedure between the generator and the plant bus is started. The grid connection process adopts a synchronous parallel method to ensure the matching of voltage, frequency and phase. After successful grid connection, the generator active power output is adjusted according to the plant load demand. At the same time, necessary protection devices, including overload protection, short circuit protection, frequency protection, etc., are configured to ensure the safe operation of the generator. The generator's operating status is continuously monitored throughout the grid connection and operation process, and the control parameters are adjusted as needed.

[0060] S500. Power Supply and Power Plant Start-up Phase:

[0061] After the expansion generator set is running stably, it is disconnected from the plant bus. According to the black start procedure of the power station, the electrical energy it outputs is supplied to the auxiliary equipment of the power station through the plant power distribution system, and the various subsystems of the power station are started gradually. When the main system of the power station meets the start-up conditions, the power station enters the normal power generation state through the main start-up procedure, completing the entire process of transition from black start to normal operation.

[0062] As a preferred option, the plant's power loads are supplied in a predetermined sequence and in stages from small to large capacity. For each inductive motor load, a limited slope switching or soft start / frequency conversion method is used to reduce inrush current. The control unit uses spindle speed / frequency as the main control variable and active power as the secondary control variable. It uses a dead-zone-proportional-integral composite algorithm to adjust the opening of the hydraulic regulating valve. If necessary, the target frequency is temporarily lowered or the power ramp-up gradient is limited to absorb the dynamic of sudden load increases. When the frequency deviation exceeds the limit, the subsequent load supply is suspended until stability is restored.

[0063] S600. Expansion Generator Set Decommissioning and System Switching Phase:

[0064] When the main power plant system starts generating electricity normally and the auxiliary power can be supplied by the main power system, the opening of the hydraulic regulating valve is gradually reduced to reduce the output power of the expansion generator set, so as to complete the smooth switching of the auxiliary power supply. Finally, the hydraulic regulating valve is closed to shut down the expansion generator set, and the entire black start control process ends, and the power plant returns to normal operation.

[0065] As a preferred approach, the shutdown and system switching of the expansion generator set adopt a gradual power transfer strategy. After the main power system of the power station starts generating electricity, the load distribution is first verified to confirm that the main power system has the ability to bear all the plant auxiliary power load. Then, according to the preset power reduction curve, the output power of the expansion generator set is gradually reduced while the proportion of the main power system is increased. During the power transfer process, the stability of the plant auxiliary bus voltage and frequency is continuously monitored. When the power of the expansion generator set drops to less than 10% of the rated power, the disconnection operation is performed. After disconnection, it continues to run for a period of time for standby. Finally, the expansion generator set is smoothly shut down by gradually closing the hydraulic regulating valve. After shutdown, the system reset procedure is executed to prepare for the next black start. The entire switching process ensures the continuity and reliability of the plant auxiliary power supply.

[0066] During the execution of this control method, the judgment conditions for each stage of transition are based on real-time monitored parameters such as speed, pressure, temperature, and power. The reliability and safety of the black start process are ensured through preset control logic and safety protection strategies. The entire control method does not rely on a large-capacity UPS power supply, which significantly reduces the cost and complexity of the black start system.

[0067] The objectives of this invention have been fully and effectively achieved through the above embodiments. Those skilled in the art will understand that this invention includes, but is not limited to, the contents described in the accompanying drawings and the specific embodiments described above. Although the invention has been described with reference to what is currently considered the most practical and preferred embodiments, it should be understood that the invention is not limited to the disclosed embodiments, and any modifications that do not depart from the functional and structural principles of the invention will be included within the scope of the claims.

Claims

1. An expander generator system for black start in a compressed air energy storage power station, characterized in that, It includes at least the expander subsystem, the intake regulation subsystem, the power generation and transmission subsystem, and the hydraulic oil supply and control subsystem, wherein: The expander subsystem includes at least one air expander, whose exhaust pipeline is connected to the atmosphere and whose intake pipeline is connected to the high-pressure air storage device of the power station to receive high-pressure compressed air. The air expander rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start. The intake regulation subsystem includes at least a start valve located on the air expander intake pipeline and a hydraulic regulating valve arranged in parallel therewith. The start valve is configured to supply air quickly with a large opening during the black start acceleration phase, so that the unit can accelerate from a standstill to the target speed range. The hydraulic regulating valve is hydraulically driven and continuously and adjustablely controls the intake flow rate and intake pressure difference when the unit enters the steady state phase. The power generation and transmission subsystem includes at least one generator connected to the air expander for converting the mechanical energy of the air expander into electrical energy and supplying power to the plant load during the black start phase of the power station. The generator rotor adopts a rolling support structure and does not require pre-lubrication by an external lubrication station before black start. The hydraulic oil supply and control subsystem includes an anti-wear hydraulic oil pump and an anti-wear hydraulic oil tank. The anti-wear hydraulic oil pump is connected to the air expander via a drive, and the rotor of the anti-wear hydraulic oil pump adopts a rolling support structure so that it can establish valve-controlled drive capability without external power under black start conditions. Its inlet is connected to the anti-wear hydraulic oil tank through a pipeline, and its outlet is connected to the hydraulic regulating valve in the intake regulating subsystem through a pipeline. It is used to output hydraulic oil flow and pressure that meet the control requirements of the hydraulic regulating valve after the unit speed reaches the set speed, so as to realize precise regulation of power generation and grid connection control.

2. The expander generator system for black start of a compressed air energy storage power station according to claim 1, characterized in that, The transmission connection in the power generation and transmission subsystem is a single-shaft direct connection structure. The rotors of the air expander, generator, and anti-wear hydraulic oil pump are mounted on the same main shaft, or the transmission connection of the three is achieved through rigid or flexible couplings, so that the three rotate synchronously. The speed is designed to be the synchronous speed of the power grid or an integer multiple thereof, driving the generator to output 50Hz power frequency AC.

3. The expander generator set system for black start of a compressed air energy storage power station according to claim 1, characterized in that, The power generation and transmission subsystem also includes a speed change gearbox located between the air expander and the generator. The rotor of the air expander is driven to the power input end of the speed change gearbox, and the generator and the anti-wear hydraulic oil pump are driven to the output shaft of the speed change gearbox. The air expander rotates at a first speed and drives the generator and the anti-wear hydraulic oil pump at a second speed different from the first speed after being changed by the speed change gearbox. When the air expander adopts a high-speed operation mode, it realizes deceleration transmission.

4. The expander generator set system for black start of a compressed air energy storage power station according to claim 3, characterized in that, The transmission gearbox is equipped with an oil injection lubrication and cooling circuit. The oil injection lubrication and cooling circuit is equipped with at least one lubricating oil pump that is connected to the output shaft or intermediate shaft of the transmission gearbox. This pump is used to provide forced lubrication for gear meshing after the unit reaches the set speed, and to allow the gear meshing to operate without oil lubrication for a short period of time before the black start unit reaches the set speed threshold.

5. The expander generator set system for black start of a compressed air energy storage power station according to claim 3, characterized in that, The air expander rotor adopts a single-shaft power output structure and is supported by an independent bearing system. Its power output end is connected to the power input end of the gearbox via a rigid or flexible coupling. The transmission ratio of the gearbox is determined based on the matching relationship between the optimal operating speed of the air expander and the rated speed of the generator.

6. The expander generator set system for black start of a compressed air energy storage power station according to claim 3, characterized in that, The air expander adopts an impeller-opposed structure, with impellers of identical geometry suspended at both ends of the high-speed input shaft of the variable speed gearbox. The axial thrust generated by the two symmetrically arranged impellers cancels each other out, maintaining axial force balance and reducing the load on the thrust bearing.

7. The expander generator system for black start of a compressed air energy storage power station according to claim 1, characterized in that, The rolling support structures of the rotors of the air expander, generator, and anti-wear hydraulic pump are all configured with rolling bearings. Each rolling support structure includes at least a radial rolling bearing for bearing radial loads, and a rolling thrust bearing or a combined support and thrust bearing located at the axial positioning end to bear axial loads and limit axial movement. All rolling support structures do not require an external high-pressure oil jacking device or a lubrication station to supply pressurized lubricating oil before black start and throughout the entire start-up process.

8. The expander generator system for black start of a compressed air energy storage power station according to claim 1, characterized in that, The air expander operates in either a normal temperature high-pressure intake mode or a medium-high temperature high-pressure intake mode. In the normal temperature high-pressure intake mode, the air expander directly receives normal temperature high-pressure air from the high-pressure air storage device and discharges low-temperature normal-pressure air, without the need for preheating the intake air. In the medium-high temperature high-pressure intake mode, a heat exchanger, a heat pump, and related pipelines for intake air reheating are further configured. The heat pump is only driven to heat the high-pressure intake air after the black start unit starts generating electricity, thereby increasing the intake air temperature and enhancing the work capacity of the air expander.

9. The expander generator system for black start of a compressed air energy storage power station according to claim 1, characterized in that, The air expander is configured as either a single-stage impeller high-speed structure or a multi-stage impeller low-speed structure. The single-stage impeller high-speed structure requires a gearbox to reduce the high speed before driving the generator and anti-wear hydraulic pump. The multi-stage impeller low-speed structure does not require a gearbox and directly drives the generator and anti-wear hydraulic pump. The impeller type of the air expander can be centripetal, axial, or mixed-flow, determined by a combination of aerodynamic and structural design.

10. A black-start control method for a compressed air energy storage power station, based on the expander generator set system for black-starting a compressed air energy storage power station as described in any one of claims 1 to 9, characterized in that, It should include at least the following steps: S100. Upon receiving the black start command, the small UPS provides the minimum control power to confirm that the pressure of the high-pressure gas storage device meets the preset threshold, and checks that the rolling support structure, inlet and outlet pipelines, hydraulic oil pipelines, valve position status of the start valve and hydraulic regulating valve, level and temperature of the anti-wear hydraulic oil tank, and communication status of the DCS control system are all in normal and usable condition. S200. Open the start valve to the preset maximum opening degree, so that the compressed air in the high-pressure air storage device enters the air expander in a large flow rate through the start valve, which drives the air expander impeller to rotate rapidly and drives the generator and anti-wear hydraulic oil pump connected to it to accelerate synchronously. The control unit limits the opening change rate of the start valve according to the target climb curve of the speed over time. S300. As the speed of the expansion generator set increases, the anti-wear hydraulic oil pump outputs pressurized oil, which establishes a stable oil pressure and oil temperature through the hydraulic oil pipeline and supplies oil to the hydraulic regulating valve. When the hydraulic oil pressure and flow rate reach the minimum driving condition of the hydraulic regulating valve, the hydraulic regulating valve is switched to the actuated state. S400. When the speed of the expansion generator set reaches the set speed threshold, the opening of the starting valve is gradually reduced, while the opening of the hydraulic regulating valve is increased. After the switching is completed, the hydraulic regulating valve dynamically controls the intake flow and pressure difference in a single-valve closed loop according to the changes in the plant power load. After the S500 expansion generator set is running stably, according to the black start procedure, the output electrical energy is supplied to the auxiliary equipment of the power station through the plant power distribution system. When the main system of the power station meets the start-up conditions, the power station enters the normal power generation state through the main start-up procedure. S600. When the main power plant system starts generating electricity normally, gradually reduce the opening of the hydraulic regulating valve to reduce the output power of the expansion generator set and complete the smooth switching of the plant power supply.

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