A control method for a prop-folding axial-flow unit

Abstract

The application provides a control method of an axial flow variable pitch unit and relates to the field of automatic control. The axial flow variable pitch unit suitable for the control method comprises a control unit, an excitation system, a speed regulation system, a water pressurizing system, a draft tube and guide vanes, wherein the water pressurizing system comprises a water pressurizing main valve and a supplementary air valve. When the unit is in a power generation working condition, the active power thereof is reduced to a preset value, the loss of excitation protection, the loss of step protection and the reverse power protection are sequentially exited, the speed regulation system enters a phase modulation mode, the guide vanes are fully closed, the water pressurizing system is used for water pressurizing, and the water pressurizing main valve and the supplementary air valve are sequentially opened. When the water level is reduced to a preset minimum water level, the water pressurizing main valve is closed, the water level is controlled through the supplementary air valve, the excitation system enters the phase modulation mode, the active power is absorbed and the reactive power is emitted, and the unit operates in a phase modulation working condition. The control method adds the phase modulation working condition operation mode to the axial flow variable pitch unit, so that the axial flow variable pitch unit can absorb a small amount of active power from a system and provide reactive power to the system.

Description

Technical Field

[0001] This invention relates to the field of automation control, and in particular to a control method for an axial-flow propeller unit. Background Technology

[0002] Existing axial-flow propeller turbine units have power generation, idling, and no-load operation modes, and the unit control only has operation mode switching modes of power generation-no-load-idling-stop and stop-idling-no-load-power generation. In other words, in the current technology, axial-flow propeller turbine units do not have a phase-shifting operation mode, and there is no control method to switch the unit from power generation mode to phase-shifting mode.

[0003] Therefore, existing axial-flow propeller turbine units lack the advantages of phase-shifting operation. Specifically, when the generator is not driven by a prime mover, it cannot absorb a small amount of active power from the system or provide reactive power to the system, nor does it possess the ability to stabilize and regulate voltage while maintaining unit operation. Furthermore, it cannot quickly switch to generating mode; it can only slowly start from a shutdown state and switch to generating mode, failing to meet system load demands in a timely manner. Moreover, current control technologies applicable to pumped-storage turbine units are not suitable for axial-flow propeller turbine units. Summary of the Invention

[0004] To address the problems existing in the prior art, the purpose of this invention is to provide a control method for switching operating conditions of an axial-flow propeller turbine unit. This method adds a phase-shifting operating mode to the axial-flow propeller turbine unit and provides a control method for switching between generation and phase-shifting operating modes. Due to the addition of the phase-shifting operating mode, this method allows the axial-flow propeller turbine unit to absorb a small amount of active power from the system and provide reactive power to the system. The generator phase shifting can ensure the stable operation of the power grid and meet the phase and voltage requirements of the power grid. Furthermore, this operating mode allows for rapid switching of generation modes to better meet system load demands.

[0005] To achieve the above objectives, the present invention provides a control method for an axial-flow propeller turbine unit, comprising:

[0006] The axial-flow propeller turbine unit includes a control unit, an excitation system, a draft tube, and guide vanes. It is characterized by further including a speed control system and a pressurization system. The control unit is individually connected to the excitation system, speed control system, pressurization system, and guide vanes. The pressurization system includes a main pressurization valve and an air supply valve.

[0007] This includes the steps of switching from power generation mode to phase modulation mode, specifically:

[0008] Reduce active power until it drops to a preset percentage of the rated power; continue reducing the unit's active power. If the active power reaches the preset value after a delay of t1, continue; otherwise, the unit returns to generating mode.

[0009] The excitation system sequentially deactivates the loss-of-excitation protection, loss-of-step protection, and reverse power protection.

[0010] To put the speed control system into phase adjustment mode: close all guide vanes. After a delay of t2, if the guide vanes are still in the fully closed state, the speed control system will enter phase adjustment mode; otherwise, the control unit will sequentially activate the excitation system's loss of excitation protection, loss of synchronism protection, and reverse power protection, and the unit will return to the power generation mode.

[0011] To put the pressurized water system into phase-adjustment mode: Start the pressurized water system, open the main pressurized water valve and the air supply valve in sequence to pressurize water. After a delay of t3, if the tailrace water level drops below the rotor speed, the pressurized water system enters phase-adjustment mode. When the tailrace water level drops to the preset minimum water level, close the main pressurized water valve and control the water level through the air supply valve to keep the tailrace water level below the rotor speed. Otherwise, if the pressurization fails, the pressurized water system exits, the speed control system opens the guide vanes, and sequentially engages the loss of excitation protection, loss of synchronism protection, and reverse power protection. The unit then returns to power generation mode.

[0012] The excitation system is put into phase-shifting mode: the excitation system absorbs active power and generates reactive power;

[0013] The unit was switched to phase-shifting operation.

[0014] The steps for an axial-flow propeller turbine unit to switch from phase-shifting operation to power generation operation are as follows:

[0015] Close the gas supply valve;

[0016] The pressurized water system stops operating. After a delay of t4, if the tailrace water level reaches the power generation water level, it will continue; otherwise, the unit will return to the phase adjustment mode.

[0017] The speed control system exits phase modulation mode and switches to frequency control mode; the excitation system exits phase modulation mode and switches to no-load mode.

[0018] The excitation system is sequentially equipped with loss of excitation protection, loss of synchronism protection, and reverse power protection.

[0019] The speed control system exits the phase modulation mode, opens the guide vanes, and if the guide vanes are not fully closed after a delay of t5, it continues; otherwise, the unit returns to the phase modulation mode.

[0020] If both active and reactive power reach the preset values ​​after a delay of t6, the process continues; otherwise, the unit returns to phase adjustment mode.

[0021] The speed control system enters the power generation mode, and the unit is in power generation operation.

[0022] Optionally, the control unit can be any control system or component capable of controlling the excitation system, speed regulation system, and pressurized water system to achieve corresponding functions, such as: unit coordinated control system (CCS), sequential control system (SCS), and distributed control system (DCS). As a preferred embodiment, the local control unit currently used in axial-flow propeller turbine units is well adapted to the axial-flow propeller turbine units involved in the method provided by this invention.

[0023] Alternatively, there are several methods to determine the water level, such as using a level gauge for real-time monitoring or using a float level switch.

[0024] Optionally, the process control unit in the local control unit determines the guide vane switch status by acquiring guide vane data collected by the data acquisition and processing unit.

[0025] Optionally, the process control unit in the local control unit determines whether the active power and reactive power have reached preset values ​​by acquiring power data collected by the data acquisition and processing unit.

[0026] Preferably, after each of the above judgments, if it is impossible to continue, the system returns to the operating condition before the conversion and continues to operate.

[0027] Optionally, the process control unit in the local control unit determines whether the active power has reached a preset value by acquiring power data collected by the data acquisition and processing unit.

[0028] Optionally, the process control unit in the local control unit determines the guide vane switch status by acquiring guide vane data collected by the data acquisition and processing unit.

[0029] Optionally, a level gauge can be used for real-time monitoring, or a float level switch can be used to determine the water level in the tailrace pipe. As a specific monitoring method or device, both the level gauge and the float level switch are connected to the data acquisition and processing unit of the local control unit. The data acquisition and processing unit transmits the specific data and judgment results to the process control unit as a trigger condition to enable the local control unit to start the next step of the process.

[0030] As described above, this technical solution adds a new operating mode compared to traditional axial-flow propeller turbine units: phase-shifting mode. Furthermore, this technical solution provides a detailed control method for switching between phase-shifting and generation modes of the axial-flow propeller turbine unit. Due to the addition of the phase-shifting mode, this method allows the axial-flow propeller turbine unit to absorb a small amount of active power from the system and provide reactive power to the system. It also ensures the stable operation of the power grid and meets the phase and voltage requirements of the grid through generator phase shifting. In addition, this mode enables the axial-flow propeller turbine unit to quickly switch to generation mode to better meet system load demands. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process of switching from power generation mode to phase modulation mode in one embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the process of switching from phase modulation mode to electrical mode in one embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the circuit structure of one embodiment of the present invention. Detailed Implementation

[0034] To address the technical problems existing in the prior art, this invention provides a control method for switching between power generation mode and phase-shifting mode of an axial-flow propeller turbine unit. It should be noted that in the prior art, axial-flow propeller turbine units do not have a phase-shifting mode; therefore, this control method is based on creating a phase-shifting mode for the axial-flow propeller turbine unit. As is well known, phase-shifting mode, as an operating mode of a generator unit, can ensure the stable operation of the power grid by adjusting the generator phase, meeting the phase and voltage requirements of the power grid, and enabling rapid switching of power generation modes to better meet system load demands.

[0035] Specifically, the control method of the present invention is based on the existing axial propeller mechanism and mainly uses the local control unit for process control to realize the mutual conversion between the two working conditions. It does not involve changes to the existing equipment, nor does it require the addition of new equipment.

[0036] Example 1

[0037] The following embodiment provides a control method for switching an axial-flow propeller turbine unit from power generation mode to phase-shifting mode, the process of which is as follows: Figure 1 As shown:

[0038] The circuit structure diagram of this embodiment is shown below. Figure 3 As shown.

[0039] When it is necessary to switch the unit to phase-shifting operation, the local control unit first determines whether the unit is in power generation mode. If so, the process continues; otherwise, the process exits and returns to the starting point. The unit's operating status can be further determined based on the power information displayed by the information display unit in the local control unit.

[0040] Based on the above judgment, if the unit is in power generation mode, the staff will operate the host computer to gradually reduce the active power through the local control unit until the active power drops below the preset ratio of the rated power.

[0041] When the active power drops below the preset ratio of the rated power, the host computer sends a power generation switching signal s, and the local control unit receives and responds to the signal s, further adjusting the active power to the preset value.

[0042] The local control unit starts timing upon receiving signal s. After time interval t1, it judges the power status of the unit. If the active power of the unit reaches the preset value, the process continues; if it does not reach the preset value, it issues an alarm, exits the process, and returns to the starting point.

[0043] Furthermore, the local control unit sequentially deactivates the loss-of-excitation protection, out-of-step protection, and reverse power protection, and controls the speed control system to fully close the guide vanes, initiating a new timing cycle for a new round of delay judgment. After time interval t2, the opening and closing status of the guide vanes is determined. If the guide vanes are fully closed, the process continues; if the guide vanes are not fully closed, the local control unit sequentially activates the loss-of-excitation protection, out-of-step protection, and reverse power protection for the excitation system, ensuring the unit continues to operate in power generation mode.

[0044] Based on the judgment result that "the guide vanes are fully closed," the local control unit starts the pressurized water system, sequentially opening the main pressurized water valve and the air supply valve to pressurize water and start a new timing. After time interval t3, the tailrace water level is judged. If the water level is below the rotor, the process continues; if the water level is above the rotor, it indicates that the pressurization has failed. The local control system controls the pressurized water system to shut down, controls the speed control system to open the guide vanes, and sequentially controls the activation of loss of excitation protection, loss of synchronism protection, and reverse power protection, so that the unit continues to generate electricity.

[0045] When the water level drops to the preset minimum water level, the main pressure valve is closed, and the water level is controlled by the air supply valve to keep the tailwater pipe water level below the rotation level.

[0046] The local control unit controls the excitation system to absorb active power and generate reactive power, at which point the unit enters phase-shifting mode, and the process ends. At this time, the speed control system, the water pumping system, and the excitation system are all in phase-shifting mode.

[0047] Example 2

[0048] The following embodiment provides a control method for switching an axial-flow propeller turbine unit from phasing mode to power generation mode, and the process is as follows: Figure 2 As shown:

[0049] The circuit structure diagram of this embodiment is shown below. Figure 3 As shown.

[0050] Once it is confirmed that the unit is in phase-shifting operation, the host computer sends a phase-shifting forwarding telegram s' to the local unit. The local control unit receives and responds to the telegram s', sequentially controlling the closure of the main pressurized water valve and the air supply valve. After the air supply valve is closed, the local control unit controls the pressurized water system to exit operation and performs a delayed judgment on the tailrace water level. If the water level reaches the power generation level, the process continues.

[0051] Here, the tailrace water level is determined using a float level switch: when the water level rises, the float rises accordingly and reaches a preset vertical position, triggering the data acquisition and processing unit in the ground control unit to report the current water level to the process control unit. Alternatively, a level gauge can be used for real-time water level monitoring.

[0052] During this process, the local control unit exits the control water pressurization system and starts timing. After time interval t4, if the water level reaches the power generation level, the process continues; if it does not reach the level, an alarm is issued, the process exits, and returns to the starting point.

[0053] Specifically, when the water level reaches the power generation level after a preset time interval t4, the local control unit controls the speed regulation system to exit phase modulation mode and switch to frequency control mode; and controls the excitation system to exit phase modulation mode and switch to no-load mode. It is important to note that there is no explicit sequential relationship between the timing of the local control unit's control of the two systems exiting phase modulation mode. After the speed regulation system and excitation system exit phase modulation mode, the local control unit controls the excitation system to sequentially activate loss-of-excitation protection, loss-of-synchronization protection, and reverse power protection.

[0054] If the local control unit determines that the tailrace water level has reached the power generation water level, it starts a new timer and, after a time interval t5, determines the opening and closing status of the guide vanes: if the guide vanes are not fully closed, the process continues; if the guide vanes are fully closed, an alarm is issued, the process exits, and returns to the starting point. Here, the determination of the guide vane opening and closing status relies on the data acquisition device originally installed on the axial-flow propeller turbine unit. Specifically, this device belongs to the data acquisition and processing unit within the local control unit. The data acquisition and processing unit feeds back the acquired and processed results to the process control unit as the trigger condition for the local control unit to control other modules to proceed to the next step.

[0055] Based on the feedback from the data acquisition and processing unit to the process control unit that "the guide vanes are not fully closed," the local control unit initiates the third timing. Specifically, after a time interval t6, the unit's power status is assessed. If both the unit's active and reactive power reach preset values, the process continues; otherwise, an alarm is issued, the process exits, and the unit returns to the starting point. Here, the power status assessment still relies on the existing devices and functions of the axial-flow propeller turbine unit.

[0056] The "issuing an alarm" step in the above three judgment processes can employ any alarm method that serves a warning purpose, such as: ring alarm, broadcast alarm, flashing alarm, vibration alarm, etc. The alarm device that issues the alarm is integrated into the information display unit of the local control unit.

[0057] Based on the premise that "both active power and reactive power have reached the preset values" as determined by the unit power assessment, the local control unit controls the speed regulation system to enter the power generation mode, the unit is in power generation condition, and the process ends.

[0058] The methods and devices used in Examples 1 and 2 for determining unit power, guide vane switch status, tailrace water level, and issuing alarms are the same. Specifically, the methods and devices used in the same unit are completely identical. The only difference is that the judgment criteria will be adjusted accordingly based on the different operating conditions and switching directions.

[0059] As can be seen, this technical solution adds a new operating mode compared to traditional axial-flow propeller turbines: phase-shifting mode. Furthermore, this solution provides a detailed control method for switching between phase-shifting and generation modes of the axial-flow propeller turbine. Due to the addition of the phase-shifting mode, this method allows the axial-flow propeller turbine to absorb a small amount of active power from the system and provide reactive power to the system. It also ensures the stable operation of the power grid and meets the phase and voltage requirements of the grid through generator phase shifting. In addition, this mode allows the axial-flow propeller turbine to quickly switch to generation mode to better meet system load demands.

[0060] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for an axial-flow propeller turbine unit, the axial-flow propeller turbine unit comprising a control unit, an excitation system, a draft tube, and guide vanes, characterized in that, It also includes a speed control system and a water pressure system; the control unit is connected separately to the excitation system, the speed control system, the water pressure system and the guide vane; the water pressure system includes a main water pressure valve and an air supply valve; This includes the steps of switching from power generation mode to phase modulation mode, specifically: Reduce active power until it drops to a preset percentage of the rated power; continue reducing the unit's active power. If the active power reaches the preset value after a delay of t1, continue; otherwise, the unit returns to generating mode. The excitation system sequentially deactivates the loss-of-excitation protection, loss-of-step protection, and reverse power protection. To put the speed control system into phase adjustment mode: close all guide vanes. After a delay of t2, if the guide vanes are still in the fully closed state, the speed control system will enter phase adjustment mode; otherwise, the control unit will sequentially activate the excitation system's loss of excitation protection, loss of synchronism protection, and reverse power protection, and the unit will return to the power generation mode. To put the pressurized water system into phase-adjustment mode: Start the pressurized water system, open the main pressurized water valve and the air supply valve in sequence to pressurize water. After a delay of t3, if the tailrace water level drops below the rotor speed, the pressurized water system enters phase-adjustment mode. When the tailrace water level drops to the preset minimum water level, close the main pressurized water valve and control the water level through the air supply valve to keep the tailrace water level below the rotor speed. Otherwise, if the pressurization fails, the pressurized water system exits, the speed control system opens the guide vanes, and sequentially engages the loss of excitation protection, loss of synchronism protection, and reverse power protection. The unit then returns to power generation mode. The excitation system is put into phase-shifting mode: the excitation system absorbs active power and generates reactive power; The unit was switched to phase-shifting operation.

2. The control method for an axial-flow propeller turbine unit as described in claim 1, characterized in that, It also includes the step of switching from phase-shifting operation to power generation operation, specifically: Close the gas supply valve; The pressurized water system stops operating. After a delay of t4, if the tailrace water level reaches the power generation water level, it will continue; otherwise, the unit will return to the phase adjustment mode. The speed control system exits phase modulation mode and switches to frequency control mode; the excitation system exits phase modulation mode and switches to no-load mode. The excitation system is sequentially equipped with loss of excitation protection, loss of synchronism protection, and reverse power protection. The speed control system exits the phase modulation mode, opens the guide vanes, and if the guide vanes are not fully closed after a delay of t5, it continues; otherwise, the unit returns to the phase modulation mode. If both active and reactive power reach the preset values ​​after a delay of t6, the process continues; otherwise, the unit returns to phase adjustment mode. The speed control system enters the power generation mode, and the unit is in power generation operation.

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