Steam Turbine Control Switching Method and System

Abstract

This application discloses a method and system for switching turbine control valves, belonging to the field of power system control technology. The method includes: acquiring unit operating information, including unit status information and unit power generation information; detecting the grid connection status of the unit based on the unit operating information and grid connection status criteria; if it is determined that the unit is not connected to the grid, driving the speed control device to control the turbine control valves; if it is determined that the unit is connected to the grid, switching the turbine control valves to the grid-coordinated control system. This method helps to achieve seamless switching of turbine control valves before and after grid connection.

Description

Technical Field

[0001] This application relates to the field of power system control technology, and in particular to a method and system for controlling and switching the control valve of a steam turbine. Background Technology

[0002] Isolated or weakly connected grids refer to local power grids with weak electrical connections to the main power grid, or even completely disconnected from it. These systems typically exist in remote areas with a high proportion of renewable energy connected to the grid, island power grids, independently operated industrial self-owned power plants, and fault-prone power grids operating independently. In engineering practice, isolated or weakly connected grids often suffer from weak communication infrastructure, leading to significant latency, packet loss, or link interruptions. Because system inertia and short-circuit capacity change in real time, accurately sensing the system status and updating control parameters within a very short time (milliseconds) remains a major challenge limiting control accuracy. Summary of the Invention

[0003] This invention provides a method and system for switching turbine control valves, aiming to achieve seamless switching of turbine control valves before and after grid connection.

[0004] To achieve the above objectives, in a first aspect, a method for controlling and switching turbine control valves is provided, comprising: Acquire unit operation information, which includes unit status information and unit power generation information; Based on the unit operation information and grid connection status criteria, the grid connection status of the unit is detected; When it is determined that the unit is not connected to the grid, the drive speed control device controls the turbine regulating valve; Once the unit is connected to the grid, the turbine control valve is switched to the grid-coordinated control system.

[0005] In some embodiments, the machine-network coordination control system includes a control backend, a machine-network coordination decision station communicatively connected to the control backend, a plurality of machine-network coordination execution stations located on the unit side and communicatively connected to the machine-network coordination decision station, and a load-side execution station located on the load side and communicatively connected to the machine-network coordination decision station, wherein the plurality of machine-network coordination execution stations are respectively set for each unit; Each of the aforementioned generator-grid coordination execution stations is used to collect the generator generation information of each unit and send it to the generator-grid coordination decision station. The load-side execution station is used to collect power consumption information of the load circuit and send it to the machine-network coordination decision station; The grid-machine coordination decision station is used to determine the second comprehensive valve position command for controlling the turbine control valve based on the total power generation of all grid units and the total power consumption of the grid, and sends the second comprehensive valve position command to the grid-machine coordination execution station; wherein, the total power generation of all grid units is calculated based on the grid topology and the power generation information of each unit; the total power consumption of the grid is calculated based on the power consumption information of the load circuit and the switching power of the tie line.

[0006] In some embodiments, the unit status information includes the generator output circuit breaker status, and the unit power generation information includes generator electrical quantities; The generator output circuit breaker status includes a closed state and an open state; The generator electrical quantities include at least one of the generator active power and the generator excitation current.

[0007] In some embodiments, the grid connection status criterion includes the generator outlet circuit breaker status criterion and electrical quantity criterion; The generator output circuit breaker status criterion includes whether the generator output circuit breaker is in a closed state. The electrical quantity criteria include: The generator's active power is greater than a preset active power threshold; and / or The generator excitation current is greater than the preset excitation current threshold.

[0008] In some embodiments, the preset active power threshold is a preset percentage of the unit's rated power; The preset excitation current threshold is the no-load excitation current, or an excitation current threshold set according to the no-load excitation current.

[0009] In some embodiments, detecting the grid connection status of the unit based on the unit operating information and grid connection status criteria includes: The unit is confirmed to be connected to the grid if the unit's operating information meets the following conditions: The generator output circuit breaker is in the closed state; In addition, the active power of the generator is greater than a preset active power threshold; In addition, the generator excitation current is greater than a preset excitation current threshold.

[0010] In some embodiments, when it is determined that the unit is not connected to the grid, the turbine control switching method further includes: The speed control device is driven to generate a first comprehensive valve position command based on the target speed of the steam turbine; The machine-network coordination execution station is driven to track and execute the first integrated valve position command to adjust the opening of the turbine control valve and make the turbine speed reach the target speed.

[0011] In some embodiments, after determining that the unit is connected to the grid, the turbine control switching method further includes: The generator-grid coordination execution station is driven to execute the second integrated valve position command to adjust the opening of the turbine control valve and make the power generation of the entire grid units consistent with the power consumption of the entire grid. The speed control device is driven to track the second integrated valve position command.

[0012] In some embodiments, the method by which the machine-network coordination decision station determines the second integrated valve position command includes: Calculate the power deviation between the total power generation of the entire grid and the total power consumption of the entire grid; Based on the power deviation and the power generation information of each unit, the second integrated valve position command corresponding to each unit is determined.

[0013] In some embodiments, when the load changes abruptly, a feedforward compensation amount is superimposed on the second integrated valve position command. The feedforward compensation amount is determined based on the load change amount, which includes the load change magnitude and the load change rate.

[0014] In some embodiments, the turbine control switching method further includes: When the machine-network coordination execution station and the machine-network coordination decision station are communicating normally, the machine-network coordination execution station is driven to perform a primary frequency modulation, and the machine-network coordination decision station is driven to perform a secondary frequency modulation.

[0015] In some embodiments, the turbine control switching method further includes: In the event of a communication failure between the machine-network coordination execution station and the machine-network coordination decision station, the machine-network coordination execution station is driven to perform primary and secondary frequency modulation.

[0016] Secondly, a turbine regulating valve control switching system is also proposed, the turbine regulating valve control switching system comprising: The acquisition module is used to acquire unit operating information, which includes unit status information and unit power generation information; The detection module is used to detect the grid connection status of the unit based on the unit's operating information and grid connection status criteria. The switching control module is used to drive the speed control device to control the turbine control valve when it is determined that the unit is not connected to the grid; and to switch the grid-coordinated control system to control the turbine control valve when it is determined that the unit is connected to the grid.

[0017] The turbine control switching method of this application acquires unit operating information and detects the unit's grid connection status by combining grid connection status criteria. When the unit is not connected to the grid, the turbine control valve is controlled by the speed control device. After the unit is connected to the grid, the control is switched to the turbine-grid coordinated control system. This allows the turbine control valve target to switch according to the changes in the unit's operating stage, which helps to achieve seamless switching of turbine control valve before and after grid connection, and improves the stability, anti-interference and rapid response capability of turbine-grid coordinated control in isolated or weakly connected systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the architecture of a machine-network coordinated control system according to an exemplary embodiment of this application; Figure 2 This is a flowchart illustrating a turbine control switching method according to an exemplary embodiment of this application. Figure 3 This is a schematic diagram illustrating the logic of turbine control switching according to an exemplary embodiment of this application; Figure 4 This is an interactive schematic diagram of a machine-network coordinated control system according to an exemplary embodiment of this application; Figure 5 This is a schematic diagram of a turbine control switching system according to an exemplary embodiment of this application.

[0020] Explanation of icon numbers: 10. Speed ​​control device; 21. Machine-network coordination decision station; 22. Machine-network coordination execution station; 23. Load-side execution station; 24. Control background; 201. Acquisition module; 202. Detection module; 203. Switching control module.

[0021] The realization of the objectives, functional features and advantages of the embodiments of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0023] Furthermore, descriptions involving "first," "second," etc., in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0024] Isolated or weakly connected grids refer to local power grids with weak electrical connections to the main power grid, or even completely disconnected from it. They are typically found in remote areas with large-scale integration of renewable energy sources, island power grids, independently operated industrial self-owned power plants, and fault-prone power grids. As power system construction continues, power grid configurations are becoming increasingly complex, and isolated and weakly connected grid operation modes have become one of the normal operating conditions for power systems. Isolated grid systems lack strong support from the main power grid, resulting in insufficient system inertia and susceptibility to severe fluctuations in source-load matching control. They exhibit typical characteristics of complex operating conditions and poor disturbance rejection capabilities.

[0025] The generator-grid coordinated control system is a core system that enables coordinated regulation of active and reactive power of generator sets, ensuring grid frequency stability, voltage qualification, and dynamic balance between source and load. It is widely used in thermal power, hydropower, distributed energy, and energy storage combined generation scenarios.

[0026] As described in the background section, in engineering practice, in isolated or weak network scenarios, there is often a problem of weak communication measures, which leads to the risk of large delays, packet loss or link interruption. Since the system inertia and short-circuit capacity change in real time, how to accurately perceive the system status and update the control parameters in a very short time (millisecond level) remains a pain point that restricts the control accuracy.

[0027] Meanwhile, before the unit is connected to the grid, the main purpose is to control the turbine speed. After the unit is connected to the grid, the control objective is to maintain the balance of power generation and consumption and the stability of the grid frequency. In isolated grid or weak grid operation scenarios, the control of the turbine control valve needs to be switched according to the fundamental change in control objective and control logic to ensure the stable operation of the system.

[0028] The judgment criteria for grid connection of generating units usually only use the closing status of the grid connection switch. For isolated or weak grid systems, there are multiple operating conditions such as operation connected to the large grid and operation in isolation. Using only the closing status of the switch as the criterion has the problem of insufficient adaptability to changes in operating mode and cannot perceive the real electrical quantity status.

[0029] Furthermore, given the current situation where existing machine-network coordinated control systems employ centralized or decentralized control, centralized control will lose its coordination function when the central control station fails, while distributed control lacks centralized control over the entire network and has limited adjustment capacity.

[0030] Based on this, this application proposes a turbine control valve switching method applicable to scenarios such as isolated grids, weak grids, local grid connection, self-owned power plant connection, and multi-unit joint operation. This method can automatically switch the control authority of the turbine control valve according to the unit's grid connection status, ensuring that the turbine control valve is controlled by the speed control device before unit startup and grid connection, and by the generator-grid coordination control system after grid connection. This balances the speed control requirements during startup and the load and frequency coordination control requirements after grid connection, aiming to solve the problems of turbine control valve switching, insufficient adaptability of grid connection criteria, slow communication response, and risks associated with both centralized and decentralized control in isolated or weak grid scenarios. Furthermore, it enables rapid coordinated control of multiple units under long-term or short-term isolated grid operation conditions, and coordinated control of distributed control systems (DCS) for multiple boilers, improving the overall regulation characteristics of the power plant, achieving rapid and unified output, and ensuring the safe and stable operation of the system.

[0031] Please refer to Figure 1 , Figure 1 A schematic diagram of the architecture of a turbine-grid coordinated control system according to an exemplary embodiment of this application is shown. In this exemplary embodiment, the turbine control valve switching system may include a speed control device 10 and a turbine-grid coordinated control system. The turbine-grid coordinated control system may include a turbine-grid coordinated decision station 21, a turbine-grid coordinated execution station 22, a load-side execution station 23, and a control backend 24. The turbine-grid coordinated decision station 21, the turbine-grid coordinated execution station 22, the load-side execution station 23, and the control backend 24 can be connected via a high-speed redundant bus.

[0032] In one optional implementation, the grid-machine coordinated control system can be divided into a coordination control layer, a unit control layer, and a field equipment execution layer according to the control hierarchy. The coordination control layer may include a control backend 24 and a grid-machine coordinated decision station 21. The control backend 24 can be used for human-machine interaction, historical data storage, information display, real-time alarms, parameter configuration, and operational status monitoring. The grid-machine coordinated decision station 21 is used to collect or receive grid-wide power information, including unit generation information, load-side power consumption information, and inter-domain tie-line exchange power, as well as to obtain grid topology information, and perform active power allocation, reactive power allocation, real-time secondary frequency regulation, real-time secondary voltage regulation, source-load balance calculation, and control command generation based on the above information.

[0033] The unit control layer may include a grid-machine coordination execution station 22 corresponding to each unit, and a load-side execution station 23. Each unit may be configured with one grid-machine coordination execution station 22. The grid-machine coordination execution station 22 is used to collect information such as unit status, turbine valve status, unit power generation information, DCS status, excitation system status, and speed control device 10 during the operation of each unit, and upload it to the grid-machine coordination decision station 21. Among them, the unit status information includes the generator outlet circuit breaker status, and the unit power generation information includes the generator electrical quantities. At the same time, the grid-machine coordination execution station 22 is also used to receive unit control commands (i.e., second integrated valve position commands) issued by the grid-machine coordination decision station 21, and output control commands to the field equipment execution layer of the corresponding unit to control the turbine valve opening, so that the power generation of the entire grid units and the power consumption of the entire grid are consistent. The load-side execution station 23 is used to collect power consumption information of the load circuit and send the power consumption information of the load side to the machine-network coordination decision station 21 or the machine-network coordination execution station 22; the load-side execution station 23 is also used to receive load control commands issued by the machine-network coordination decision station 21 and output corresponding control signals to the load-side PLC (programmable controller).

[0034] The coordinated control layer's machine-network coordination decision station 21 and control backend 24, and the unit control layer's machine-network coordination execution station 22 and load-side execution station 23 are connected via a star network structure. Each unit is equipped with a machine-network coordination execution station 22, which connects downwards to the unit's DCS, excitation system, and speed control device 10 at the field equipment execution layer of each unit for information exchange. The load-side execution station 23 connects downwards to the load-side PLC.

[0035] The field equipment execution layer may include the unit DCS, the unit excitation system, the speed control device 10, and the load-side PLC. Specifically, the speed control device 10 generates a first integrated valve position command based on the turbine's target speed when the unit is not connected to the grid, to control the turbine control valve opening and thus the turbine speed; the excitation system regulates generator excitation; the DCS controls the boiler, turbine, and other auxiliary equipment; and the turbine control valve regulates the steam flow entering the turbine, thereby adjusting the turbine speed or unit output.

[0036] Through the above system architecture, rapid coordination of unit output and load-side power consumption can be achieved in scenarios such as unit startup, grid connection, islanded operation, weak network operation, load surges, and communication anomalies.

[0037] The following describes the turbine control switching method provided in the embodiments of this application. Please refer to... Figure 2This application provides a method for switching control of a steam turbine regulating valve. This method can be executed by a steam turbine regulating valve control switching system, which includes a turbine-grid coordination control system. Therefore, it can also be executed by a controller, server, control station, or related control module located within the turbine-grid coordination control system. The steam turbine regulating valve control switching method includes the following steps: S100: Obtain unit operation information.

[0038] In one embodiment, the unit operation information may include unit status information and unit power generation information. Specifically, the unit status information may include the status of the generator output circuit breaker; the unit power generation information may specifically include the generator electrical quantities. Further, the generator output circuit breaker status includes a closed state and an open state. The generator electrical quantities may include at least one of generator active power and generator excitation current.

[0039] In one embodiment, to improve the accuracy of grid connection status determination, the unit operating information includes at least the generator output circuit breaker status, generator active power, and generator excitation current. The generator output circuit breaker status can be provided by circuit breaker auxiliary contacts, protection and control devices, DCS, or electrical monitoring systems; the generator active power can be provided by power acquisition devices, generator protection devices, control devices, or electricity metering devices; and the generator excitation current can be provided by the excitation system or related current measuring devices.

[0040] S200 detects the grid connection status of the unit based on unit operation information and grid connection status criteria.

[0041] The grid connection status criterion is used to determine whether the generating unit has been connected to the power grid. Unlike a single criterion that relies solely on the closing status of the generator output circuit breaker, this application embodiment uses a comprehensive criterion that combines the circuit breaker status and electrical quantities to reduce the risk of false grid connection, signal misjudgment, or incorrect identification of operating mode.

[0042] In one embodiment, the grid connection status criterion includes a generator output circuit breaker status criterion and an electrical quantity criterion. The generator output circuit breaker status criterion includes the generator output circuit breaker being in a closed state. The electrical quantity criterion includes the generator active power being greater than a preset active power threshold, and / or the generator excitation current being greater than a preset excitation current threshold.

[0043] In a preferred embodiment, grid connection of the unit is determined when the unit's operating information meets the following conditions: The generator output circuit breaker is in the closed state. In addition, the generator's active power is greater than the preset active power threshold; In addition, the generator excitation current is greater than the preset excitation current threshold.

[0044] Furthermore, the preset active power threshold can be a preset percentage of the unit's rated power. Understandably, the preset percentage can be 1%, or a suitable value between the power measurement error and the initial load of the unit after grid connection. Since the unit needs to immediately carry the initial load after grid connection to prevent reverse power protection from tripping, the initial load is typically 3-5% of the rated power. However, the active power threshold should not be set too close to the initial load to prevent the grid-machine coordination station from intervening too late, causing load and speed fluctuations. At the same time, it should not be set too low, not less than the high-precision power measurement error (0.2-0.65%), to avoid invalidating the criterion.

[0045] The preset excitation current threshold can be the no-load excitation current or an excitation current threshold set based on the no-load excitation current. For example, the preset excitation current threshold can be the no-load excitation current, a preset multiple of the no-load excitation current, or a value obtained by adding a safety margin to the no-load excitation current.

[0046] By combining the above criteria, a dual criterion of switch position and electrical quantity can be formed. The closed state of the generator output circuit breaker reflects the electrical connection status between the unit and the grid, the generator active power reflects whether the unit outputs effective power to the grid, and the excitation current reflects the generator's excitation and electromagnetic state. Combining these three factors allows for a more reliable identification of whether the unit is truly connected to the grid.

[0047] S300: When it is determined that the unit is not connected to the grid, drive the speed control device to control the turbine regulating valve.

[0048] When the unit is not connected to the grid, it has not yet output effective electrical power to the grid. The main objective of turbine control valve is to control the turbine speed, enabling the turbine to complete the processes of starting, accelerating, maintaining speed, and adjusting speed before synchronization at the target speed. Therefore, when it is determined that the unit is not connected to the grid, the turbine control valve is controlled by the speed control device 10.

[0049] Specifically, the speed control device 10 can generate a first integrated valve position command based on the target turbine speed. This first integrated valve position command is used to adjust the opening of the turbine control valves so that the turbine speed reaches the target speed. Understandably, each turbine control valve executes this first integrated valve position command, controlling the steam flow through the valves to rotate the turbine rotor and overcome resistance to reach the target speed.

[0050] In one embodiment, the turbine-grid coordination execution station 22 tracks and executes the first integrated valve position command. That is, the speed control device 10 calculates the first integrated valve position command, and the turbine-grid coordination execution station 22 outputs this command to the servo mechanism of the turbine control valve, causing the turbine control valve to operate according to the command. By having the turbine-grid coordination execution station 22 track and execute the first integrated valve position command output by the speed control device 10, the station can maintain real-time tracking of the turbine control valve command and actual valve position before grid connection, providing a basis for control authority switching after grid connection and reducing sudden valve position changes during switching.

[0051] Specifically, please refer to Figure 3 During the turbine startup and initial run-up process, the unit is not connected to the grid and has no effective output to the grid. It cannot perform primary or secondary frequency regulation and is not in a coordinated control state. At this time, the turbine speed is controlled by the speed control system of the speed control device 10. The controller of the speed control device 10 outputs a first comprehensive valve position command. The turbine-grid coordination execution station 22 tracks and executes the first comprehensive valve position command calculated by the speed control device 10. This first comprehensive valve position command is output from the servo card of the turbine-grid coordination execution station 22. At this time, the opening of the turbine control valve is actually adjusted by receiving the first comprehensive valve position command output by the controller of the speed control device 10. The opening of the turbine valve is measured by an LVDT (Linear Variable Differential Transformer, used to measure the turbine control valve opening) and returned to the servo card of the turbine-grid coordination execution station 22, then to the controller of the turbine-grid coordination execution station 22. Finally, it is sent to the controller of the speed control device 10 through the AO (Analog Output) module under the turbine-grid coordination execution station 22 and the AI ​​(Analog Input) module under the controller of the speed control device 10. The AO module is responsible for outputting 4-20mA / 0-20mA or other types of analog signals, while the AI ​​module is responsible for receiving 4-20mA / 0-20mA or other types of analog signals.

[0052] S400. When the unit is connected to the grid, switch the turbine control valves of the grid-coordinated control system.

[0053] Once the grid connection status criterion confirms that the unit has been connected to the grid, the unit begins to output electrical power to the grid. The control objective changes from simple speed control to adjusting the unit's output based on load demand, frequency deviation, unit operating constraints, and overall grid load balance requirements. Therefore, when grid connection is confirmed, the turbine control valve authority switches from the speed control device 10 to the turbine-grid coordination control system, which transmits redundant commands internally.

[0054] Specifically, the grid coordination decision station 21 first determines the grid topology and calculates the total grid generation based on the generation information sent by the grid coordination execution station 22 corresponding to each unit. Simultaneously, it calculates the total grid power consumption based on the load circuit power consumption information sent by the load-side execution station 23 and the collected tie-line switching power. Then, it calculates the power deviation between the total grid generation and the total grid power consumption, and determines the second integrated valve position command corresponding to each unit based on the power deviation and the generation information of each unit. Understandably, the second integrated valve position command corresponding to each unit is determined based on the unit generation information (i.e., the unit's output capacity) and conditions such as whether the current load is close to the upper or lower limits. Therefore, in this case, the second integrated valve position commands corresponding to each unit may be the same or different.

[0055] Furthermore, the second integrated valve position command can be output by the grid-machine coordination execution station 22 to the servo mechanism of the turbine control valve to adjust the opening of the turbine control valve so that the power generation of the entire grid units and the power consumption of the entire grid are consistent.

[0056] After the unit is confirmed to be connected to the grid, the speed control device 10 can track the second integrated valve position command. That is, the grid-machine coordination execution station 22, acting as the main control device, calculates or outputs the second integrated valve position command. The speed control device 10 no longer controls the turbine control valve, but instead tracks the second integrated valve position command output by the grid-machine coordination execution station 22 in real time. Therefore, in the event of subsequent disconnection, changes in grid connection status, exit of the coordination system, or other situations requiring a switchback to the speed control device 10, the speed control device 10 can smoothly take over control based on the tracked valve position status, avoiding abrupt control changes.

[0057] Specifically, please continue to refer to Figure 3 When the unit is connected to the grid, the unit is connected to the network or isolated to the grid. When the unit starts generating electricity, it needs to accept the control of the grid coordination system. At this time, the control authority is switched to the grid coordination system. The grid coordination system calculates the second comprehensive valve position command of the turbine valve and sends the command to the servo card and turbine control valve through the controller of the grid coordination execution station 22. At the same time, the command is sent to the controller of the speed control device 10 for it to track.

[0058] Through the above control logic, the speed control device 10 and the turbine-grid coordinated control system both track the comprehensive valve position command output by the other when not controlling the turbine control valve, thereby achieving seamless switching of control authority and improving the stability of turbine control valve control.

[0059] In one embodiment, when the load changes abruptly, a feedforward compensation amount can be superimposed on the second integrated valve position command. This feedforward compensation amount can be determined based on the load change, which may include the load change amplitude and the load change rate.

[0060] Specifically, when a sudden load change is detected, the grid-machine coordinated control system can superimpose feedforward control on top of conventional feedback control. For example, when the load-side actuator 23 detects a large-capacity load being added, it can send the load increase as a feedforward compensation to the grid-machine coordinated decision station 21 or the grid-machine coordinated actuator 22. The grid-machine coordinated control system can then increase the unit output or adjust the turbine valve opening in advance based on the feedforward compensation. Conversely, when a large-capacity load is detected being cut off, it can reduce the unit output or decrease the turbine valve opening in advance. By superimposing feedforward, the system response speed can be improved and the frequency fluctuation amplitude reduced.

[0061] In isolated or weakly interconnected grid scenarios, if the unit's regulation capacity is insufficient to completely offset load changes, the grid coordination decision station 21 can also issue load control commands to the load-side execution station 23. The load-side execution station 23 controls the load-side PLC to perform operations such as load switching, load limiting, load tiered shelving, or load restoration according to the load control commands, in order to maintain source-load balance and grid stability.

[0062] Furthermore, when communication between the grid coordination execution station 22 and the grid coordination decision station 21 is normal, the grid coordination execution station 22 is driven to perform primary frequency regulation, and the grid coordination decision station 21 is driven to perform secondary frequency regulation. When communication between the grid coordination execution station 22 and the grid coordination decision station 21 is abnormal, the grid coordination execution station 22 is driven to perform both primary and secondary frequency regulation; that is, in the event of communication abnormality, the grid coordination execution station 22 performs both primary and secondary frequency regulation functions. In one embodiment, the primary frequency regulation trigger condition can be that the deviation between the actual speed and the rated speed is greater than the dead zone. After crossing the dead zone, a load increase / decrease command calculated according to the speed deviation is output. If the speed is high, the regulating valve is adjusted to reduce the load; conversely, if the speed is low, the regulating valve is opened to increase the load, thus suppressing further changes in the grid frequency. Secondary frequency regulation is based on the deviation of comprehensive power (power generation and power consumption) (combined with the deviation of the power grid frequency and the deviation of the power exchanged by the inter-regional tie line). When the deviation exceeds the limit, a load change command is issued to the generating unit. The generating unit adjusts the opening of the unit's regulating valve according to the command. If the command increases, the regulating valve is opened larger, and vice versa. The load change of the generating unit makes the power generation and consumption of the power grid balanced, eliminates the deviation of the primary frequency regulation, and restores the power grid frequency to the rated value.

[0063] Specifically, there are generally two control architectures for mechatronics coordinated control systems: centralized and decentralized. A centralized mechatronics coordinated control system uses a single control station to integrate all primary and secondary frequency regulation functions. This station connects to multiple generating units and communicates with each unit's DCS, speed control device 10, excitation system, etc., offering a large adjustable capacity. However, when this control station fails, the functionality of the mechatronics coordinated control system is severely affected, rendering it inoperable. A decentralized mechatronics coordinated control system, on the other hand, does not have a single master station. The primary and secondary frequency regulation functions, originally centralized in a single controller, are distributed to local coordination controllers in each generating unit. Each mechatronics coordinated control node achieves information exchange and collaborative decision-making through network communication. Compared to a centralized coordinated control system, it has the advantage that the failure of a single node does not affect the operation of other equipment. However, its global optimality is inferior to that of a centralized mechatronics coordinated control system, its collaborative control logic is more complex, and its coordination efficiency is lower.

[0064] Based on this, the embodiments of this application adopt a centralized-decentralized control method. Under normal operating conditions, the communication signal quality between the grid coordination decision station 21 and the grid coordination execution station 22 is normal. The grid coordination decision station 21 mainly implements the secondary frequency regulation function. By collecting data such as the total grid power and the power generation / consumption imbalance, it performs rapid coordination control and accurately controls the load of each unit. When the load exceeds the adjustment range, it issues instructions to the load-side execution station 23 to adjust the load and maintain the stable operation of the isolated or weakly connected grid system. At this time, the grid coordination execution station 22 mainly implements the primary frequency regulation function. When the grid coordination decision station 21 fails, the communication signal quality between the grid coordination decision station 21 and the grid coordination execution station 22 is abnormal. At this time, the secondary frequency regulation function is implemented by the secondary frequency regulation logic built into the grid coordination execution station 22. The grid coordination execution station 22 simultaneously performs the primary frequency regulation and part of the secondary frequency regulation function. When the grid coordination execution station 22 fails, it still has the advantage that the failure of a single node does not affect the operation of other equipment.

[0065] Further, please refer to Figure 4 , Figure 4The communication methods between the machine-network coordinated control system and other systems are illustrated. In one embodiment, high-speed redundant bus communication is used internally within the machine-network coordinated control system. High-speed redundant communication with 10ms levels can be used between the machine-network coordinated decision station 21 and the machine-network coordinated execution station 22, between the machine-network coordinated decision station 21 and the load-side execution station 23, between the machine-network coordinated decision station 21 and the control backend 24, and between each control station and I / O module in the unit control layer. Understandably, each control station is interconnected to form a system, and each control station is equipped with a certain number of I / O modules, connecting only to the I / O modules equipped in that station. Redundant communication links reduce the impact of single communication link failures on the control system; the 10ms communication cycle improves the machine-network coordinated control system's ability to quickly detect frequency, power, load fluctuations, and equipment status changes.

[0066] In one embodiment, critical signals between the turbine-grid coordination control system and external systems are transmitted using hard-wired methods, while general signals are transmitted using communication methods to ensure transmission capacity. The signal interaction with each system covers signal acquisition and command issuance from each unit and the load side. External systems may include a DCS, excitation system, speed control device 10, servo mechanism of turbine control valves, protection and control devices, load-side PLC, and electrical monitoring system, etc. Furthermore, critical signals can be considered those related to the turbine-grid coordination control, while other signals are considered general signals. For example, critical signals between the turbine-grid coordination system and the DCS include: load commands, current power, unit load increase / decrease rate settings, and unit maximum / minimum load settings; general signals may be various parameters unrelated to the turbine-grid coordination control, such as temperature, liquid level, flow rate, pressure, and equipment on / off status. As another example, critical signals between the turbine-grid coordination system and the speed control device include: valve position commands and actual valve positions; general signals may be other status signals such as turbine temperature and pressure.

[0067] By combining hard-wiring of critical signals, communication transmission of general signals, and high-speed redundant buses within the system, the system can balance control real-time performance, communication reliability, and data capacity, thus meeting the requirements for rapid coordinated control in isolated or weakly networked scenarios.

[0068] Secondly, a turbine control switching system for regulating valves is also proposed; please refer to [reference needed]. Figure 5 The turbine control valve switching includes: The acquisition module 201 is used to acquire unit operation information, which includes unit status information and unit power generation information; Detection module 202 is used to detect the grid connection status of the unit based on unit operating information and grid connection status criteria; The switching control module 203 is used to drive the speed control device to control the turbine control valve when it is determined that the unit is not connected to the grid; and to switch the grid-coordinated control system to control the turbine control valve when it is determined that the unit is connected to the grid.

[0069] The above description is merely an optional embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made based on the inventive concept of this application and the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for controlling and switching the control valve of a steam turbine, characterized in that, include: Acquire unit operation information, which includes unit status information and unit power generation information; Based on the unit operation information and grid connection status criteria, the grid connection status of the unit is detected; When it is determined that the unit is not connected to the grid, the drive speed control device controls the turbine regulating valve; Once the unit is connected to the grid, the turbine control valve is switched to the grid-coordinated control system.

2. The turbine control switching method according to claim 1, characterized in that, The machine-network coordination control system includes a control backend, a machine-network coordination decision station communicatively connected to the control backend, multiple machine-network coordination execution stations located on the unit side and communicatively connected to the machine-network coordination decision station, and a load-side execution station located on the load side and communicatively connected to the machine-network coordination decision station. The multiple machine-network coordination execution stations are respectively set for each unit. Each of the aforementioned generator-grid coordination execution stations is used to collect the generator generation information of each unit and send it to the generator-grid coordination decision station. The load-side execution station is used to collect power consumption information of the load circuit and send it to the machine-network coordination decision station; The grid-machine coordination decision station is used to determine the second comprehensive valve position command for controlling the turbine control valve based on the total power generation of all grid units and the total power consumption of the grid, and sends the second comprehensive valve position command to the grid-machine coordination execution station; wherein, the total power generation of all grid units is calculated based on the grid topology and the power generation information of each unit; the total power consumption of the grid is calculated based on the power consumption information of the load circuit and the switching power of the tie line.

3. The turbine control switching method according to claim 1, characterized in that, The unit status information includes the status of the generator output circuit breaker, and the unit power generation information includes the generator electrical quantities; The generator output circuit breaker status includes a closed state and an open state; The generator electrical quantities include at least one of the generator active power and the generator excitation current.

4. The turbine control switching method according to claim 3, characterized in that, The grid connection status criteria include generator outlet circuit breaker status criteria and electrical quantity criteria; The generator output circuit breaker status criterion includes whether the generator output circuit breaker is in a closed state. The electrical quantity criteria include: The generator's active power is greater than a preset active power threshold; and / or The generator excitation current is greater than the preset excitation current threshold.

5. The turbine control switching method according to claim 4, characterized in that, The preset active power threshold is a preset percentage of the unit's rated power; The preset excitation current threshold is the no-load excitation current, or an excitation current threshold set according to the no-load excitation current.

6. The turbine control switching method according to claim 4, characterized in that, The process of detecting the grid connection status of the generating unit based on the unit's operating information and grid connection status criteria includes: The unit is confirmed to be connected to the grid if the unit's operating information meets the following conditions: The generator output circuit breaker is in the closed state. In addition, the active power of the generator is greater than a preset active power threshold; In addition, the generator excitation current is greater than a preset excitation current threshold.

7. The turbine control switching method according to claim 2, characterized in that, When it is determined that the unit is not connected to the grid, the turbine control switching method further includes: The speed control device is driven to generate a first comprehensive valve position command based on the target speed of the steam turbine; The machine-network coordination execution station is driven to track and execute the first integrated valve position command to adjust the opening of the turbine control valve and make the turbine speed reach the target speed.

8. The turbine control switching method according to claim 2, characterized in that, After confirming the unit's grid connection, the turbine control switching method further includes: The generator-grid coordination execution station is driven to execute the second integrated valve position command to adjust the opening of the turbine control valve and make the power generation of the entire grid units consistent with the power consumption of the entire grid. The speed control device is driven to track the second integrated valve position command.

9. The turbine control switching method according to claim 2, characterized in that, The method by which the machine-network coordination decision station determines the second integrated valve position command includes: Calculate the power deviation between the total power generation of the entire grid and the total power consumption of the entire grid; Based on the power deviation and the power generation information of each unit, the second integrated valve position command corresponding to each unit is determined.

10. The turbine control switching method according to claim 2, characterized in that, When the load changes abruptly, a feedforward compensation amount is superimposed on the second integrated valve position command. The feedforward compensation amount is determined based on the load change amount, which includes the load change amplitude and the load change rate.

11. The turbine control switching method according to claim 2, characterized in that, The turbine control switching method further includes: When the machine-network coordination execution station and the machine-network coordination decision station are communicating normally, the machine-network coordination execution station is driven to perform a primary frequency modulation, and the machine-network coordination decision station is driven to perform a secondary frequency modulation.

12. The turbine control switching method according to claim 2, characterized in that, The turbine control switching method further includes: In the event of a communication failure between the machine-network coordination execution station and the machine-network coordination decision station, the machine-network coordination execution station is driven to perform primary and secondary frequency modulation.

13. A steam turbine control valve switching system, characterized in that, The turbine control and switching system includes: The acquisition module is used to acquire unit operating information, which includes unit status information and unit power generation information; The detection module is used to detect the grid connection status of the unit based on the unit's operating information and grid connection status criteria. The switching control module is used to drive the speed control device to control the turbine control valve when it is determined that the unit is not connected to the grid; and to switch the grid-coordinated control system to control the turbine control valve when it is determined that the unit is connected to the grid.

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