Low head long tail water power station surge chamber water level fluctuation stability device

Abstract

The application provides a low-head long-tail hydropower station surge chamber fluctuation stability implementation method, including the following steps: S1. determining the adjustment basis, including the power grid state, the unit output condition and the unit guide vane opening; S2. calculating the power grid frequency modulation capacity ratio coefficient; S3. judging the surge chamber fluctuation stability condition; S4. outputting or adjusting, if S3 is judged to be stable, outputting the result and returning to S1, if S3 is judged to be unstable, starting the unit guide vane opening adjustment, reducing the guide vane opening to the predetermined guide vane opening value and returning to S1, and solving the technical problem of the fluctuation instability of the subatomic surge chamber in the prior art.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower technology, and in particular to a device for stabilizing water level fluctuations in the surge tank of a low-head, long-tail hydropower station. Background Technology

[0002] To ensure the stability of a hydropower station's water conveyance system, a surge tank is typically required. For low-head hydropower stations, due to their large flow rates, the Thomas critical section calculated using the Thomas formula for calculating the stability cross-section of the surge tank is often very large. However, in actual engineering projects, some hydropower stations may have a surge tank cross-sectional area smaller than the Thomas critical section due to topographical, geological, or investment constraints. When a hydropower station's surge tank does not meet the Thomas condition, it is called a "sub-Thoma surge tank." Under certain grid conditions, a sub-Thoma surge tank can meet the requirements for stable operation. The ratio k of the power plant's grid-connected generating capacity to the total capacity of all generating units participating in frequency regulation has a significant impact on the small-fluctuation stability analysis of the surge tank. According to the formula proposed by Stein et al., when the power output of the power plant accounts for 40% of the total frequency regulation capacity of the entire grid, the actual surge tank critical section is equal to 10% of the Thomas critical section. Therefore, it is necessary to propose a fluctuation stability device to ensure the small-fluctuation stability of the sub-Thoma surge tank of a low-head, long-tailed hydropower station under local grid conditions. Summary of the Invention

[0003] The purpose of this invention is to provide a method for achieving the fluctuation stability of the surge chamber in a low-head, long-tail hydropower station, so as to solve the technical problem of fluctuation instability in the Yatoma surge chamber in the prior art.

[0004] This invention provides a method for achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station, comprising the following steps: S1. Determining the adjustment basis, including grid status, unit output, and unit guide vane opening; S2. Calculating the grid frequency regulation ratio coefficient; S3. Judging the fluctuation stability of the surge tank; S4. Outputting or adjusting: if S3 determines that it is stable, the result is output and returned to S1; if S3 determines that it is unstable, the unit guide vane opening adjustment is initiated, reducing the guide vane opening to a predetermined value, and then returning to S1.

[0005] Furthermore, the frequency regulation ratio coefficient in S2 is the ratio of the grid-connected power generation capacity of this plant to the total actual capacity of all generator units participating in frequency regulation in the power grid.

[0006] Furthermore, the criteria for determining the stability of the pressure regulating chamber fluctuation in S3 are as follows: if the frequency regulation ratio coefficient is less than the predetermined frequency regulation ratio coefficient, it is determined to be stable; if more than one unit in the same hydraulic unit is not generating power, it is determined to be stable; if the guide vane opening of each unit in the same hydraulic unit is less than the predetermined value, it is determined to be stable; if any of the above conditions are met, it is determined to be stable.

[0007] Furthermore, the preset frequency modulation ratio coefficient is determined by numerical simulation analysis.

[0008] Furthermore, the predetermined value of the guide vane opening is determined by numerical simulation analysis.

[0009] Furthermore, the unit is a low-head mixed-flow unit.

[0010] A surge tank fluctuation stability device employing a method for achieving surge tank fluctuation stability in low-head, long-tail hydropower stations includes: a turbine output sensor connected to each turbine unit for monitoring turbine output; a power grid detector connected to the power grid for monitoring grid status; a turbine guide vane opening sensor located at each turbine guide vane for monitoring guide vane opening; and a control feedback terminal, comprising: a storage unit connected to the turbine output sensor, the power grid detector, and the turbine guide vane opening sensor for storing data on grid status, turbine output, and turbine guide vane opening; a calculation unit for calculating the frequency regulation ratio coefficient; and a control unit for determining the current surge tank stability.

[0011] Furthermore, the guide vane opening sensor is paired with each unit in the same hydraulic unit, and the unit output sensor is paired with each unit in the same hydraulic unit.

[0012] Furthermore, when the control feedback terminal determines that a certain unit is causing unstable fluctuations in the pressure regulating chamber, the control unit only changes the guide vane opening of that unit.

[0013] This invention provides a method for achieving fluctuation stability of the surge chamber in a low-head, long-tailed hydropower station. By combining real-time monitoring, the operating status of each unit in the same hydraulic unit is monitored and adjusted in real time. By reducing the unit output, the fluctuation stability of the surge chamber is achieved. This minimizes the adverse effects of turbine characteristics on the fluctuation stability of the surge chamber and fully utilizes the beneficial effects of the local power grid on the small fluctuation stability of the surge chamber. This significantly improves the small fluctuation stability of the surge chamber in a low-head, long-tailed hydropower station and solves the technical problem of fluctuation instability in the Yatoma surge chamber in the prior art. Attached Figure Description

[0014] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0015] Figure 1This embodiment provides a control feedback diagram for the method of achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station.

[0016] Figure 2 The turbine characteristic curves provided in this embodiment. Detailed Implementation

[0017] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] The surge tank fluctuation stability device for a low-head, long-tailed hydropower station provided in this embodiment includes a turbine output sensor, a turbine guide vane opening sensor, a power grid monitor, and a control feedback terminal. The surge tank level fluctuation sensor is located within the surge tank. The turbine output sensor is connected to each turbine unit. The turbine guide vane opening sensor is located at the guide vanes of each turbine unit. The power grid monitor is connected to the power grid. The control feedback terminal is connected via cables to a first pressure sensor, a second pressure sensor, the turbine output sensor, the turbine guide vane opening sensor, and the power grid monitor. The control feedback terminal includes a storage unit, a processing unit, and a control unit. The turbine output monitor, power grid monitor, and guide vane opening sensor transmit turbine output, power grid status, and guide vane opening data to the storage unit of the control feedback terminal via cables. The processing unit of the control feedback terminal automatically calculates the frequency regulation ratio parameter under the current power grid status and then transmits the data to the control unit to determine the current surge tank stability. For ease of control, the turbine guide vane opening sensors are paired and connected one-to-one with the turbine units of the same hydraulic unit. Each unit's output sensor is paired and connected to a specific hydraulic unit. When the control feedback terminal determines that a particular unit may cause instability in the pressure regulating chamber, the control unit only changes the guide vane opening of that unit.

[0019] This embodiment of the project comprises two hydraulic units, both with essentially the same water intake system. The water conveyance system consists of an intake, a water intake tunnel, a tailrace branch tunnel, a tailrace surge chamber, a long tailrace tunnel, and a tailrace outlet. The water intake tunnel is arranged in a single-unit, single-tunnel configuration, with a lining diameter of 7.7m. The tailrace branch tunnel has the same cross-sectional dimensions as the water intake tunnel, and there are also six such tunnels. The tailrace surge chamber connects to the tailrace branch tunnel. There are two tailrace surge chambers, shared by all three units. The tailrace tunnels, totaling two and approximately 8.6km in length, extend beyond the surge chambers. The tailrace surge chamber is massive, with a horizontal cross-section approaching 3000㎡, characteristic of the Yatoma cross-section. The unit parameters for this embodiment are shown in the table below.

[0020]

[0021]

[0022] The frequency regulation ratio coefficient k is the ratio of the plant's grid-connected generating capacity to the total actual capacity of all generating units participating in frequency regulation in the grid. The plant's maximum output in the grid is 51.8%. Numerical simulation analysis indicates that the predetermined value for the frequency regulation ratio coefficient k is 0.78, meaning that the actual operating frequency regulation ratio coefficient k cannot exceed 0.78. Numerical simulation analysis also indicates that the predetermined value for the unit's guide vane opening is 88%.

[0023] This embodiment provides a method for achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station, including the following steps:

[0024] S1. Determine the basis for adjustment.

[0025] The adjustment is based on factors including grid status, generator output, and guide vane opening. Specifically, the grid monitor tracks the grid status and transmits the data to the storage unit of the control feedback terminal. Generator output sensors monitor the output of generators within the same hydraulic unit and transmit the data to the storage unit of the control feedback terminal. Guide vane opening sensors upload the guide vane opening information to the storage unit of the control feedback terminal.

[0026] In this embodiment, 80% of the capacity of other power plants does not participate in frequency regulation. The initial operating rates of the three turbines in the same hydraulic unit are 0.97, 0.97, and 0.97. The initial output of the three turbines in the same hydraulic unit is 105.9MW, 105.9MW, and 105.9MW.

[0027] S2. Calculate the frequency modulation ratio coefficient.

[0028] The frequency modulation ratio coefficient under the current state is calculated by the computing unit of the control feedback terminal, and the data is simultaneously transmitted to the storage unit of the control feedback terminal for storage. In this embodiment, the frequency modulation ratio coefficient k = 0.874.

[0029] S3. Judgment.

[0030] If the frequency regulation ratio is less than a predetermined value, the system is considered stable. If more than one unit in the same hydraulic unit is not generating power, the system is considered stable. If the guide vane opening of all units in the same hydraulic unit is less than a predetermined value, the system is considered stable. The system is considered stable if any of the above conditions are met.

[0031] In this embodiment, if the frequency regulation ratio coefficient k = 0.874 > 0.78, or if all three turbines of the same hydraulic unit are started, or if the initial opening degree of all three turbines of the same hydraulic unit is greater than 88%, then it is determined to be unstable.

[0032] S4. Output or adjustment.

[0033] If the system is determined to be stable, output the result and return S1.

[0034] When the system is determined to be unstable, the unit's guide vane opening adjustment is initiated to reduce the guide vane opening to the predetermined guide vane opening, reducing the guide vane opening to 88%, and then returning to S1.

[0035] For low-head mixed-flow units, the δ value increases rapidly after the guide vane opening is greater than the optimal efficiency opening. Therefore, the measure to stabilize the fluctuation in the pressure chamber is to reduce the guide vane opening.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for achieving fluctuation stability in the surge tank of a low-head, long-tail hydropower station, characterized in that, Includes the following steps: S1. Determine the basis for regulation, including grid status, unit output, and unit guide vane opening; S2. Calculate the grid frequency regulation ratio coefficient, wherein the frequency regulation ratio coefficient in S2 is the ratio of the grid-connected generation capacity of this plant to the total actual capacity of all generating units participating in grid frequency regulation; S3. Determine the stability of the pressure regulating chamber fluctuations; S4. Output or adjustment, If S3 is determined to be stable, output the result and return S1. If S3 determines that the system is unstable, the unit's guide vane opening adjustment will be initiated, reducing the guide vane opening to the predetermined value, and then returning to S1. The basis for determining the stability of the pressure regulating chamber fluctuation in S3 is as follows: If the frequency modulation ratio is less than the preset frequency modulation ratio, it is considered stable. If more than one unit in the same hydraulic unit is not generating power, it is considered stable. If the guide vane opening of each unit in the same hydraulic unit is less than the predetermined value, it is considered stable. If any of the above conditions are met, the system is considered stable.

2. The method for achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station according to claim 1, characterized in that, The preset frequency modulation ratio coefficient is determined by numerical simulation analysis.

3. The method for achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station according to claim 1, characterized in that, The predetermined value of the guide vane opening was determined by numerical simulation analysis.

4. The method for achieving fluctuation stability in the surge tank of a low-head, long-tailed hydropower station according to claim 1, characterized in that, The unit is a low-head mixed-flow unit.

5. A surge chamber fluctuation stability device employing the method for achieving surge chamber fluctuation stability in a low-head, long-tail hydropower station as described in claim 1, characterized in that, include: The unit output sensor is connected to each turbine unit and is used to monitor the unit output. A power grid detector, connected to the power grid, is used to monitor the power grid's condition. The guide vane opening sensor is installed at the guide vane of each unit to monitor the guide vane opening. Control feedback terminal, the control feedback terminal includes: - A storage unit, connected to the unit output sensor, the power grid detector and the unit guide vane opening sensor, is used to store data on power grid status, unit output status and unit guide vane opening; -Arithmetic unit, used to calculate the frequency modulation ratio coefficient; - Control unit, used to determine the current stability of the pressure regulating chamber.

6. The stabilization device according to claim 5, characterized in that, The guide vane opening sensor is paired with and connected to each unit in the same hydraulic unit, and the unit output sensor is paired with and connected to each unit in the same hydraulic unit.

7. The stabilization device according to claim 5, characterized in that, When the control feedback terminal determines that a certain unit is causing unstable fluctuations in the pressure regulating chamber, the control unit only changes the guide vane opening of that unit.

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