Full-load adjustable state reconfiguration type steam turbine set, design method and operation method of full-load adjustable state reconfiguration type steam turbine set

Abstract

The invention provides a full-load adjustable state reconstruction type steam turbine set, a design method and an operation method thereof. The full-load adjustable state reconstruction type steam turbine set comprises a first low-pressure cylinder and a second low-pressure cylinder which are arranged in series, and a steam exhaust port of the first low-pressure cylinder communicates with a steam inlet of the second low-pressure cylinder; the dynamic rotating speed adjusting system is configured to adjust the rotating speed of the second low-pressure cylinder in real time according to the unit operation state, so that the rotating speed of the second low-pressure cylinder is independent of the rated rotating speed of the first low-pressure cylinder; the load matching mechanism is connected with the output end of the second low-pressure cylinder and used for transmitting mechanical work under the variable rotating speed. By dynamically adjusting the rotating speed of the second low-pressure cylinder, the blade linear speed tracks the change of the steam flow speed in real time, the stability of the speed ratio is reconstructed, under the low-load working condition, the rotating speed is synchronously reduced when the steam flow speed is reduced, and the speed ratio is forced to return to a design efficient area; a sectional rotating speed control strategy is adopted, steady-state operation is maintained in a rotating speed interval, the dynamic process duration is shortened by discretization rotating speed switching, and the alternating stress cycle number is restrained.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power generation steam turbine units, and in particular relates to a full-load adjustable state reconfigurable steam turbine unit, a design method and an operating method thereof. Background Art

[0002] In traditional thermal power generation systems, condensing steam turbines typically employ a coaxial series low-pressure cylinder configuration, where multiple low-pressure cylinders are rigidly connected to the same rotor and operate synchronously at a constant speed (e.g., 3000 rpm, 3600 rpm, or 1500 rpm). This structural design is based on the inherent requirement of grid frequency synchronization, but it has fundamental technical limitations: 1. Failure of thermodynamic matching When the unit load decreases, the steam mass flow rate of each stage of the steam turbine decays linearly, the pressure of the conventional stage group decreases linearly, causing the specific volume to rise synchronously, and the steam volume flow rate of each stage does not change much. Combined with the fact that the flow area of ​​each stage of the steam turbine is constant, the overall steam flow rate at the nozzle outlet of each stage does not change much, and the efficiency within the unit does not change significantly. However, the pressure of the low-pressure last stage of the steam turbine is limited by the back pressure of the unit and cannot decrease linearly with the decrease in the load of the unit. This causes a significant drop in the volume flow rate of the last stage of the low-pressure cylinder of the steam turbine under low-load conditions, a significant drop in the steam flow rate, a serious deviation in the velocity triangle of the low-pressure stage group of the steam turbine, severe blasting, a significant drop in unit efficiency, and a serious threat to the safety of the last-stage blades. 2. Secondary flow destruction in wet steam zone The final stage of the low-pressure cylinder is in the wet steam zone for a long time. Under the constraint of a constant speed, the steam flow rate decreases at low flow rates, but the centrifugal field strength remains unchanged. Liquid water droplets cannot be effectively accelerated by the steam flow, resulting in an increase in the relative velocity of the water droplets. The high-speed rotating blades hit the water droplets with extremely high kinetic energy, causing blade fatigue and easy damage. Therefore, the fundamental contradiction of the existing technology is that the energy conversion process of the steam turbine requires dynamic speed ratio adjustment, but the rigid rotor structure forces the speed to be constant. This contradiction is sharply amplified under deep peak-shaving conditions. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the purpose of the present invention is to provide a full-load adjustable state reconstructible steam turbine unit, a design method and an operating method thereof. By breaking through the rigid constraints of the speed, the operating state of the last stage of the low-pressure cylinder can be dynamically reconstructed with the load, thereby solving the defects of traditional steam turbine units such as constant speed and inability to dynamically adjust the speed ratio.

[0004] In order to solve the above problems, the technical solutions adopted by the present invention are as follows: In a first aspect, the present invention provides a fully load adjustable state reconfigurable steam turbine unit, comprising: a first low-pressure cylinder and a second low-pressure cylinder arranged in series, wherein a steam exhaust port of the first low-pressure cylinder is in communication with a steam inlet port of the second low-pressure cylinder; a dynamic speed regulation system configured to adjust the speed of the second low-pressure cylinder in real time according to the operating status of the unit, so that the speed of the second low-pressure cylinder is independent of the rated speed of the first low-pressure cylinder; The load matching mechanism is connected to the output end of the second low-pressure cylinder and is used to transmit mechanical work at a variable speed.

[0005] In some embodiments, the dynamic speed regulation system includes a speed regulation device, and the second low-pressure cylinder is coaxially connected to the constant speed rotation device of the first low-pressure cylinder through the speed regulation device to form a mechanical coupling.

[0006] In some embodiments, the load matching mechanism is a variable speed generator, and the variable speed generator is independently connected to the output end of the second low-pressure cylinder.

[0007] In some embodiments, the load matching mechanism is an auxiliary equipment group, the output end of the second low-pressure cylinder directly drives the auxiliary equipment, and the auxiliary equipment group includes at least one water pump or fan.

[0008] In some embodiments, the second low-pressure cylinder is composed of one sub-cylinder or multiple parallel sub-cylinders.

[0009] In some embodiments, the second low-pressure cylinder is composed of a single pressure stage or multiple pressure stages.

[0010] In the second aspect, the present invention provides a design method for a full-load adjustable state-reconstructable steam turbine unit as mentioned above, wherein the steam inlet design pressure of the second low-pressure cylinder is not higher than 100 times the condenser pressure and not lower than 3 times the condenser pressure.

[0011] In a third aspect, the present invention provides a method for operating a fully load adjustable state reconfigurable steam turbine unit, which is applied to the steam turbine unit as described above, comprising: Real-time acquisition of the steam flow parameters of the second low-pressure cylinder or the total load rate parameters of the unit; The rotational speed of the second low-pressure cylinder is dynamically adjusted according to the parameters so that the steam volume flow rate at the moving blade inlet and the rotational speed maintain a preset mapping relationship.

[0012] In some embodiments, the steam flow parameter is the real-time steam volume flow rate at the second low-pressure cylinder steam inlet.

[0013] In some embodiments, the steam flow parameter is a real-time steam volume flow rate at an inlet of the last stage moving blade of the second low-pressure cylinder.

[0014] In some embodiments, the preset mapping relationship is:n L2 = n 0· yes ; in, n L2 is the current set speed of the second low-pressure cylinder, n 0 is the speed of the unit under rated load, yes In order to calculate the ratio of the inlet volume flow rate of the second low-pressure cylinder at different pressure levels of the moving blades under the current load rate to the full load condition, the ratio is calculated as e 1… e n , taking the average value as yes .

[0015] In some embodiments, the speed range is divided into: based on the unit operating load range, the maximum speed of the second low-pressure cylinder is determined n H and minimum speed n L ; Set up segmented speed: in the interval [ n L , n H ] set up several speed sections, and select a representative speed in each speed section; Interval steady-state operation: When the calculated target speed falls into a certain speed range, the representative speed of the speed range is maintained until the range is switched.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects: By dynamically adjusting the speed of the second low-pressure cylinder, the blade linear velocity tracks the changes in steam flow rate in real time, reconstructing the stability of the speed ratio. Under low-load conditions, the speed is reduced synchronously with the decrease in steam flow rate, forcing the speed ratio u / c to return to the designed high-efficiency zone, significantly suppressing boundary layer separation. Slowing down the speed simultaneously reduces the centrifugal field strength and the relative velocity of the water droplets, reconstructing the dynamic balance of the two-phase flow, so that the kinetic energy of the water droplet impact is controlled below the material fatigue threshold, improving operational reliability; A segmented speed control strategy is adopted to maintain steady-state operation within the speed range. Discrete speed switching reduces the duration of the dynamic process and suppresses the number of alternating stress cycles. The mechanical subsystem achieves reconstruction of thermal-mechanical balance in the constant speed section, thereby extending the service life of the equipment.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention is further described with reference to the accompanying drawings. However, the embodiments in the accompanying drawings do not constitute any limitation to the present invention. A person skilled in the art can obtain other drawings based on the following drawings without inventive effort.

[0019] Figure 1 The present invention is a schematic diagram of a framework of a fully load adjustable state reconfigurable steam turbine unit under an implementation mode. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0022] In the description of the present invention, when a specific device is described as being located between a first device and a second device, an intervening device may or may not be present between the specific device and the first device or the second device. When a specific device is described as being connected to another device, the specific device may be directly connected to the other device without an intervening device, or may be directly connected to the other device but with an intervening device.

[0023] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0024] Reference Figure 1 This embodiment provides a fully load adjustable state reconfigurable steam turbine unit, comprising: A first low-pressure cylinder 10 and a second low-pressure cylinder 20 are arranged in series, wherein the exhaust port of the first low-pressure cylinder 10 is connected to the steam inlet of the second low-pressure cylinder 20; A dynamic speed adjustment system is configured to adjust the speed of the second low-pressure cylinder 20 in real time according to the operating status of the unit, so that the speed of the second low-pressure cylinder 20 is independent of the rated speed of the first low-pressure cylinder 10; The load matching mechanism 40 is connected to the output end of the second low-pressure cylinder 20 and is used to transmit mechanical work at a variable speed.

[0025] It should be noted that the first low-pressure cylinder 10 and the second low-pressure cylinder 20 are in a series relationship in the steam circuit, and the exhaust port of the first low-pressure cylinder 10 is connected to the steam inlet of the second low-pressure cylinder 20; in terms of the rotational connection relationship, although the first low-pressure cylinder 10 and the second low-pressure cylinder 20 are coaxially arranged, the dynamic speed adjustment system can independently adjust the speed of the second low-pressure cylinder 20, so that the speed of the second low-pressure cylinder 20 is different from the speed of the first low-pressure cylinder 10, and the load matching mechanism 40 is used to transmit mechanical work under variable speed.

[0026] In traditional coaxial turbines, multiple low-pressure cylinders share a common rotor, whose rotational speeds are strictly locked to the grid frequency. This means that the rotational speeds of the multiple low-pressure cylinders are consistent, leading to speed mismatches among the rear-end low-pressure cylinders in the series steam circuit. Therefore, this embodiment decouples the second low-pressure cylinder 20 from the rigid rotor system, forming an independent thermodynamic system. The exhaust steam from the first low-pressure cylinder 10, completing the basic expansion process, is directly introduced into the steam inlet chamber of the second low-pressure cylinder 20, enabling a step-by-step transfer of steam energy. The structural separation achieved by the dynamic speed regulation system creates an important degree of freedom: the speed of the second low-pressure cylinder 20 is no longer constrained by the synchronous speed of the first cylinder, but can be dynamically adjusted based on the steam state. This maintains the dynamic matching relationship between steam flow and blades under varying operating conditions. Under low-load conditions, the expansion process of the final-stage rotor blades remains within the optimal speed ratio range, avoiding entropy surges under off-design conditions and improving isentropic efficiency at full load.

[0027] As an embodiment, the dynamic speed regulation system includes a speed regulation device 30 , and the second low-pressure cylinder 20 is coaxially connected to the constant speed rotation device of the first low-pressure cylinder 10 through the speed regulation device 30 to form a mechanical coupling.

[0028] When the second low-pressure cylinder 20 needs to inherit the rotational energy of the first low-pressure cylinder 10 through the mechanical shaft system, how to achieve the speed difference becomes a technical breakthrough. This embodiment uses the speed regulating device 30 to achieve coaxial mechanical coupling between the first low-pressure cylinder 10 and the second low-pressure cylinder 20.

[0029] Preferably, the sun gear in the speed regulating device 30 is fixedly connected to the constant-speed output shaft of the first low-pressure cylinder 10, and the planetary carrier is rigidly connected to the rotor of the second low-pressure cylinder 20. The rotational phase of the ring gear is precisely controlled by a hydraulic servo system, so that the speed of the planetary carrier is continuously adjusted according to the steam flow signal. This design creatively embeds a speed conversion node in the energy transfer path—maintaining the efficient transmission of mechanical power (efficiency loss is less than 2%) while giving the second low-pressure cylinder 20 the ability to steplessly adjust the rated speed within a range of 30% to 100%. This "rigid and flexible" transmission method avoids the high slip losses of traditional hydraulic couplings while overcoming the torque limitation of electromagnetic clutches at megawatt power levels.

[0030] Specifically, the constant-speed rotation output by the first low-pressure cylinder 10 drives the sun gear, while the shaft of the second low-pressure cylinder 20 connects to the planetary carrier to form the main output end. The ring gear forms the adjustable end through a hydraulic actuator. This unique configuration eliminates the need for a simple transfer of the input speed, but rather the coupling of the three kinematic relationships. When the hydraulic system pushes the ring gear to micro-motor, a differential effect occurs in the planetary gear set, allowing the planetary carrier's speed to continuously change. Its ingenuity lies in the fact that the meshing path of the gears that transmit the main power always maintains direct contact, avoiding slip losses caused by the high power flowing through the oil medium in the hydraulic transmission device. The driving force required for regulation only needs to overcome the inertia of the ring gear, making the control energy consumption only a very small proportion of the total power.

[0031] When the unit is operating under stable conditions, the hydraulic system fully locks the ring gear, achieving peak system efficiency. When the load fluctuates, precisely controlled hydraulic pulses drive the ring gear for precise positioning, resulting in smooth and steady movement. This allows for flexible dynamic adjustment while limiting energy losses to the thermal dissipation level of mechanical friction.

[0032] Preferably, the load matching mechanism 40 is a variable-speed generator independently connected to the output of the second low-pressure cylinder 20. The output shaft of the second low-pressure cylinder 20 is directly connected to the generator rotor, and the stator winding output is connected to a full-power inverter. When the unit load decreases, causing the speed of the second low-pressure cylinder 20 to decrease, the inverter automatically increases the inverter frequency to maintain a stable output frequency of 50 Hz. The actual speed of the generator rotor is converted into an independent control variable and is no longer forcibly synchronized with the grid frequency.

[0033] Preferably, the load matching mechanism 40 is an auxiliary equipment group, and the output end of the second low-pressure cylinder 20 directly drives the auxiliary equipment, and the auxiliary equipment group includes at least one water pump or fan. Since the parasitic power consumption of a large number of auxiliary equipment in a thermal power generation system can reach 5% to 8% of the unit output, the traditional solution relies on the main generator to supply power through the power grid to form a secondary conversion. This embodiment constructs a direct energy transfer chain: the output end of the second low-pressure cylinder 20 is connected to the water pump or fan impeller through an elastic coupling, omitting the power conversion link. When the unit load decreases, the reduction in steam flow triggers a synchronous decrease in speed. At this time, the auxiliary torque demand curve is automatically matched with the drive torque, which not only saves conversion losses, but also significantly improves the system inertia response capability.

[0034] As an embodiment, the second low-pressure cylinder 20 is composed of one sub-cylinder or multiple parallel sub-cylinders. The second low-pressure cylinder 20 is composed of a single pressure stage or multiple pressure stages.

[0035] To address the flow matching challenges under wide load conditions, this implementation incorporates a modular cylinder design. Two identical second low-pressure cylinders (20) are arranged horizontally in parallel, with a dynamic steam distribution valve group installed on the steam inlet manifold. When the unit is operating at a high load of 70% or above, both cylinders operate simultaneously to ensure adequate flow area. When the load drops below 40%, the control system automatically isolates one cylinder, allowing the remaining cylinder to maintain efficient operation at an optimized speed. Each second low-pressure cylinder (20) is connected to a corresponding load matching mechanism (40) to achieve output isolation.

[0036] As an embodiment, the design steam inlet pressure of the second low-pressure cylinder 20 is not higher than 100 times the condenser pressure and not lower than 3 times the condenser pressure.

[0037] The design domain of the steam pressure at the inlet of the second low-pressure cylinder (20) is crucial for balancing structural safety and thermal efficiency. This embodiment establishes a pressure design criterion based on material fatigue limits: a lower limit on the inlet steam pressure ensures sufficient steam kinetic energy to maintain rotation of the last-stage blades at low loads, preventing flutter caused by boundary layer separation; an upper limit on the pressure prevents the combined effects of steam bending stress and centrifugal stress from exceeding the allowable blade root stress at high loads. Therefore, the inlet steam pressure of the second low-pressure cylinder (20) must be controlled between 3 and 100 times the condenser pressure.

[0038] Furthermore, because the speed of the first low-pressure cylinder (10) is independently controlled, the erosion problem in the wet steam zone shows a significant worsening trend under low-load, variable-speed operating conditions. This risk stems from the shift in fluid dynamics during the variable-speed regulation process. When the speed of the second low-pressure cylinder (20) drops below 40% of the design value, the simultaneous decrease in steam velocity causes a fundamental change in the relative motion trajectory of the droplets. This dramatic increase in the Stokes number means that larger droplets can traverse streamlines and impact the leading edge of the moving blades, carrying more than three times the kinetic energy of the impact compared to high-load conditions.

[0039] Therefore, an aerodynamic cyclone separation system is optionally integrated into the final stator ring of the second low-pressure cylinder. Its core technology lies in reconstructing the energy balance of water droplet motion trajectories. The system's actuator is an array of ultrasonic atomizing nozzles arranged circumferentially along the stator blade root. When the speed sensor detects that the rotor speed has fallen below a safety threshold, the control system immediately activates the charged polarization device. The atomizing nozzle sprays a negatively charged water mist with a diameter of less than 5 microns. These charged particles form a dynamic capture net within the steam flow. Large, positively charged droplets are forced to adsorb and aggregate under the Coulomb force. The mass of the droplets increases after particle collision and aggregation, allowing them to effectively settle in the weakened centrifugal field. Simultaneously, low-pressure suction channels on the stator blade back arc are activated, utilizing the negative pressure vortex formed by the pressure differential across the stator blade to continuously guide the aggregated droplets away from the main flow area. The essence of this coordinated control mechanism is to transform the problem of insufficient centrifugal field into a combined effect of electric field and pressure differential forces.

[0040] In terms of control methods, the control system collects real-time steam humidity and speed signals at the final-stage rotor blade inlet, dynamically optimizing atomization intensity and charge density through an improved coupling algorithm. The specific control logic is dynamically adjusted based on the Stokes number: the pulse frequency of the atomizing nozzle is automatically increased in the critical speed range, ensuring that the droplet diameter precisely matches the safety threshold at the current speed. This implementation significantly reduces the blade erosion rate compared to the original operating conditions and maintains stable protection even under transient conditions with frequent speed fluctuations.

[0041] In a second aspect, this embodiment provides a fully load adjustable state reconfigurable steam turbine unit operation method, which is applied to the steam turbine unit as in the above embodiment, comprising: Real-time acquisition of the steam flow parameter of the second low-pressure cylinder 20 or the total load rate parameter of the unit; The rotational speed of the second low-pressure cylinder 20 is dynamically adjusted according to the parameters so that the steam volume flow rate at the moving blade inlet and the rotational speed maintain a preset mapping relationship.

[0042] Preferably, the steam flow parameter is the real-time steam volume flow at the steam inlet of the second low-pressure cylinder 20 .

[0043] Preferably, the steam flow parameter is the real-time steam volume flow at the inlet of the last-stage moving blades of the second low-pressure cylinder 20 .

[0044] It should be noted that the core of this operating method is to establish a dynamic balance between steam flow and mechanical speed. The control system continuously monitors the real-time steam volume flow rate at the steam inlet of the second low-pressure cylinder 20 or the last-stage moving blades, converts it into a speed setting value, and maintains a constant residence time of steam through the moving blade grid. When the flow rate decreases and the steam flow rate decreases, the speed is reduced proportionally to extend the contact time between the steam and the blades, ensuring that the moving blades maintain the optimal angle of attack under any operating conditions. This method replaces the traditional indirect control mode that relies on steam pressure or temperature parameters, and directly locks the key variable with the highest energy conversion efficiency of the turbine.

[0045] As an implementation method, the preset mapping relationship is: n L2 = n 0· yes ; in, n L2 is the current set speed of the second low-pressure cylinder 20, n 0 is the speed of the unit under rated load, yes In order to calculate the ratio of the volume flow rate of the second low-pressure cylinder 20 at different pressure levels to the full-load working condition in real time, the ratio is calculated as e 1… e n , taking the average value as yes .

[0046] Since the flow conditions of the blades at each stage in the long blade low-pressure cylinder are significantly different, single signal control is likely to lead to local efficiency loss. Therefore, in this embodiment, an array of embedded pressure sensors is deployed at the leading edge of each stage of the blades to obtain the steam attack angle at different radial positions in real time. e 1… e n Perform weighted fusion, where the final level weight is as high as 60%, to form a comprehensive traffic ratio yes This design focuses on suppressing the backflow phenomenon of the last stage blades at low load, while avoiding excessive adjustment to interfere with the flow field of the previous stages. According to the preset mapping relationship set in this embodiment n L2 = n 0· yes , achieving overall optimization of the aerodynamic characteristics of the entire process.

[0047] As an implementation method, the speed range is divided into: based on the unit operating load range, the maximum speed of the second low-pressure cylinder 20 is determined n H and minimum speed n L ; Set up segmented speed: in the interval [ nL , n H ] set up several speed sections, and select a representative speed in each speed section; Interval steady-state operation: When the calculated target speed falls into a certain speed range, the representative speed of the speed range is maintained until the range is switched.

[0048] It should be noted that although continuous speed regulation is theoretically optimal, it will cause accelerated fatigue of the shaft system due to alternating stress. This embodiment adopts the "interval locking" strategy: the allowable speed range of the second low-pressure cylinder 20 is divided into three steady-state sections (low speed / medium speed / high speed). When the target speed calculated based on the flow rate falls into a certain section, no matter how slightly the flow rate fluctuates, the actual speed maintains the center value of the section. For example, when the target speed fluctuates within 1480~1520rpm, the actual speed is fixed at 1500rpm. This is equivalent to setting a speed dead zone in the control system, which significantly reduces the number of oscillations of the mechanical system during the transition process. At the same time, a ±3% load change threshold is set to avoid energy loss caused by frequent cross-zone switching. Although this discrete control slightly sacrifices instantaneous efficiency, it greatly improves the service life and operational stability of the mechanical system.

[0049] In summary, compared with the prior art, the above embodiment has at least the following technical advantages: By dynamically adjusting the speed of the second low-pressure cylinder, the blade linear velocity tracks the changes in steam flow rate in real time, reconstructing the stability of the speed ratio. Under low-load conditions, the speed is reduced synchronously with the decrease in steam flow rate, forcing the speed ratio u / c to return to the designed high-efficiency zone, significantly suppressing boundary layer separation. Slowing down the speed simultaneously reduces the centrifugal field strength and the relative velocity of the water droplets, reconstructing the dynamic balance of the two-phase flow, so that the kinetic energy of the water droplet impact is controlled below the material fatigue threshold, improving operational reliability; A segmented speed control strategy is adopted to maintain steady-state operation within the speed range. Discrete speed switching reduces the duration of the dynamic process and suppresses the number of alternating stress cycles. The mechanical subsystem achieves reconstruction of thermal-mechanical balance in the constant speed section, thereby extending the service life of the equipment.

[0050] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A fully load adjustable state reconfigurable steam turbine unit, characterized in that: include: a first low-pressure cylinder and a second low-pressure cylinder arranged in series, wherein a steam exhaust port of the first low-pressure cylinder is in communication with a steam inlet port of the second low-pressure cylinder; a dynamic speed regulation system configured to adjust the speed of the second low-pressure cylinder in real time according to the operating status of the unit, so that the speed of the second low-pressure cylinder is independent of the rated speed of the first low-pressure cylinder; The load matching mechanism is connected to the output end of the second low-pressure cylinder and is used to transmit mechanical work at a variable speed.

2. The steam turbine unit according to claim 1, wherein: The dynamic speed regulation system includes a speed regulation device, and the second low-pressure cylinder is coaxially connected to the constant speed rotation device of the first low-pressure cylinder through the speed regulation device to form a mechanical coupling.

3. The steam turbine unit according to claim 1, wherein: The load matching mechanism is a variable speed generator, and the variable speed generator is independently connected to the output end of the second low-pressure cylinder.

4. The steam turbine unit according to claim 1, wherein: The load matching mechanism is an auxiliary equipment group, and the output end of the second low-pressure cylinder directly drives the auxiliary equipment. The auxiliary equipment group includes at least one water pump or fan.

5. The steam turbine unit according to claim 1, wherein: The second low-pressure cylinder is composed of one sub-cylinder body or a plurality of parallel sub-cylinder bodies.

6. The steam turbine unit according to claim 1, wherein: The second low-pressure cylinder is composed of a single pressure stage or a plurality of pressure stages.

7. A design method for a fully load adjustable state reconfigurable steam turbine unit according to any one of claims 1 to 6, characterized in that: The design steam inlet pressure of the second low-pressure cylinder shall not be higher than 100 times the condenser pressure and not lower than 3 times the condenser pressure.

8. A method for operating a fully load adjustable state reconfigurable steam turbine unit, applied to the steam turbine unit according to any one of claims 1 to 6, characterized in that: include: Real-time acquisition of the steam flow parameters of the second low-pressure cylinder or the total load rate parameters of the unit; The rotational speed of the second low-pressure cylinder is dynamically adjusted according to the parameters so that the steam volume flow rate at the moving blade inlet and the rotational speed maintain a preset mapping relationship.

9. The operating method according to claim 8, characterized in that: The steam flow parameter is the real-time steam volume flow rate at the steam inlet of the second low-pressure cylinder.

10. The operating method according to claim 8, characterized in that: The steam flow parameter is the real-time steam volume flow at the inlet of the last-stage moving blade of the second low-pressure cylinder.

11. The operating method according to claim 8, characterized in that: The preset mapping relationship is: n L2 = n 0· ē ; in, n L2 is the current set speed of the second low-pressure cylinder, n 0 is the speed of the unit under rated load, ē In order to calculate the ratio of the inlet volume flow rate of the second low-pressure cylinder at different pressure levels of the moving blades under the current load rate to the full load condition, the ratio is calculated as e 1… e n , taking the average value as ē .

12. The operating method according to claim 8, characterized in that: Divide the speed range: Determine the maximum speed of the second low-pressure cylinder based on the unit's operating load range n H and minimum speed n L ; Set up segmented speed: in the interval [ n L , n H ] set up several speed sections, and select a representative speed in each speed section; Interval steady-state operation: When the calculated target speed falls into a certain speed range, the representative speed of the speed range is maintained until the range is switched.

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