An optimal scheduling method for reducing tailwater level during operation of a run-of-river power station

Abstract

This invention provides an optimized scheduling method for reducing the tailwater level of a run-of-river power station during operation. Using scheduling and operation data of the hydropower station, spillway facilities, sediment flushing facilities, and navigation structures as the basis for calculation, the tailwater level of the power station under various combined operation and spillway conditions of hydraulic facilities is simulated and calculated through a hydrodynamic mathematical model. The tailwater level of the power station is compared with the tailwater level of the power station under commonly used scheduling and operation conditions to obtain the power station hub scheduling and operation mode that can reduce the tailwater level of the power station and increase the power generation head.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, specifically to an optimized scheduling method for reducing the tailwater level of run-of-river power stations during operation. Background Technology

[0002] Run-of-river hydropower stations generate electricity using natural runoff. However, they cannot regulate the incoming flow. Run-of-river power stations have relatively low head; when the outflow increases, the downstream water level rises, causing a decrease in the generating head. When the generating head is lower than the rated head of the generating unit, the power output of the station is limited, and the power generation decreases.

[0003] Currently, domestic and international research mainly focuses on improving the generating head of run-of-river power plants through preliminary planning and engineering measures. However, it does not address existing power plants or those requiring renovation, and does not propose engineering measures to lower the tailrace water level. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide an optimized scheduling method for reducing the tailwater level during the operation of run-of-river power plants. This method reduces the tailwater level and increases the power generation head by optimizing the scheduling and operation mode of hydraulic facilities during the operation of existing hydropower hubs.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: an optimized scheduling method for reducing the tailwater level of a run-of-river hydropower station during operation, wherein the run-of-river hydropower station is a power station unit whose power output is limited by water head, comprising the following steps:

[0006] S1: Based on the inflow rate at different flow levels and the corresponding reservoir operating water level, the power generation flow rate when the power station reaches the expected output at different operating heads is derived by analyzing the hub operation data.

[0007] S2: If the inflow is greater than the power generation flow and water wastage is taken into account, considering the safety of the spillway, the operation of the sand flushing facility and the navigation safety restrictions, the discharge flow of the spillway, sand flushing facility and drift removal facility can be further obtained.

[0008] S3: Establish a hydrodynamic mathematical model with the discharge flow of the above-mentioned spillway facilities as the boundary condition, and simulate and calculate the tailwater level under the common scheduling and operation mode of the hub and the scheduling and operation mode of different combinations of hydraulic facilities under different inflow flows.

[0009] S4: Compared with the commonly used scheduling and operation mode of the hub, the study found a combined operation mode of hydraulic facilities that can effectively reduce the tailwater level and increase the power generation head.

[0010] Preferably, the hub operation data mentioned in S1 includes power generation dispatch operation data, water discharge hydraulic facility operation data, and sediment and drift removal facility operation data.

[0011] Preferably, the power generation dispatch and operation data specifically includes: the output limit line corresponding to the installed capacity, the relationship between the power station's comprehensive output coefficient and gross head, the relationship between tailrace water level and flow rate, the relationship between head loss and inflow, and the relationship between reservoir operating water level and inflow.

[0012] Preferably, the operational data of the water spillway hydraulic facilities specifically includes: the scheduling and operation procedures of the water spillway facilities of the water conservancy hub, the discharge capacity of the water spillway facilities, and the relationship between the position of the water jump head and the downstream water level and unit width flow rate.

[0013] Preferably, the operational data of the sediment discharge and drift removal facilities specifically includes: the discharge capacity of the sediment discharge and drift removal facilities at different operating water levels in the reservoir.

[0014] Preferably, the governing equations of the hydrodynamic model described in S3 are a two-dimensional planar shallow water equation set obtained by simplifying the Navier-Stokes equations, which includes the flow continuity equation and the flow momentum equation.

[0015] Furthermore, the total water depth of the two-dimensional water flow:

[0016] h=η+d

[0017] The continuity equation for flow in two-dimensional shallow water is:

[0018]

[0019] The water flow equation for two-dimensional shallow water is:

[0020]

[0021] In the formula: x, y, z are Cartesian coordinates; Let u and v be the velocity components in the x and y directions, integrated along the water depth direction and then divided by the water depth; t is time; h is water depth; η is water level; d is still water depth; g is gravitational acceleration; ρ is the density of water; ρ0 is the relative density of water; p a Atmospheric pressure; s xx s xy s yy These represent the radiation stress components; S is the source term; u s v s The velocity of the source water flow in the x and y directions is given by f; f is the Coriolis force coefficient. ω is the Earth's angular velocity. The latitude is T. ij The horizontal viscous stress term includes viscous forces. Turbulent stress and horizontal convection stress τ bx τ by τ represents the stress components of the bottom stress in the x and y directions.sx τ sy These are the stress components of wind stress in the x and y directions.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention avoids the approach of modifying existing power plants and taking engineering measures to lower the tailwater level. Instead, it directly lowers the tailwater level by optimizing the scheduling and operation of hydraulic facilities during the operation of existing hydropower hubs, thereby increasing the power generation head. This is a new method for improving the efficiency of existing power plants.

[0024] 2. This invention uses the scheduling and operation data of hydropower stations, spillway facilities, sediment flushing facilities, and navigation structures as the basis for calculation. It uses a hydrodynamic mathematical model to simulate and calculate the tailwater level of the power station under the combined operation and spillway conditions of various hydraulic facilities, providing a scientific basis for run-of-river power station hubs to reduce the tailwater level and increase the power generation head through scheduling and operation. Attached Figure Description

[0025] Figure 1 This is a panoramic view of the Gezhouba Dam water conservancy project according to an embodiment of the present invention.

[0026] Figure 2 This indicates the output limit line corresponding to the installed capacity in this embodiment of the invention;

[0027] Figure 3 This represents the comprehensive output coefficient curve of the Gezhouba Hydropower Station after capacity expansion and renovation according to an embodiment of the present invention.

[0028] Figure 4 This illustrates the relationship between the tailrace water level and flow rate of the Gezhouba Dam in an embodiment of the present invention.

[0029] Figure 5 This illustrates the relationship between the average head loss and the inflow rate in this embodiment of the invention.

[0030] Figure 6 This illustrates the relationship between reservoir water level and inflow rate in an embodiment of the present invention.

[0031] Figure 7 This diagram illustrates the jump-head position in an embodiment of the present invention (L represents the distance below the end of the gate pier).

[0032] Figure 8 This invention presents a hydraulic model illustrating the flood season operation mode of the Gezhouba hydraulic engineering facilities, representing an embodiment of the present invention.

[0033] Figure 9 In this embodiment of the invention, Q = 45000m 3 / s, working condition (1) downstream water level distribution map of Gezhouba Dam;

[0034] Figure 10 In this embodiment of the invention, Q = 45000m 3 / s, Working condition (2) Gezhouba downstream water level distribution map;

[0035] Figure 11 In this embodiment of the invention, Q = 45000m 3 / s, working condition (3) downstream water level distribution map of Gezhouba Dam. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] An optimized scheduling method for reducing the tailrace level of a run-of-river hydropower station during operation, wherein the power output of the station is limited by the head, includes the following steps:

[0038] S1: Based on the inflow rate at different flow levels and the corresponding reservoir operating water level, the power generation flow rate when the power station reaches the expected output at different operating heads is derived by analyzing the hub operation data.

[0039] S2: If the inflow is greater than the power generation flow and water wastage is taken into account, considering the safety of the spillway, the operation of the sand flushing facility and the navigation safety restrictions, the discharge flow of the spillway, sand flushing facility and drift removal facility can be further obtained.

[0040] S3: Establish a hydrodynamic mathematical model with the discharge flow of the above-mentioned spillway facilities as the boundary condition, and simulate and calculate the tailwater level under the common scheduling and operation mode of the hub and the scheduling and operation mode of different combinations of hydraulic facilities under different inflow flows.

[0041] S4: Compared with the commonly used scheduling and operation mode of the hub, the study found a combined operation mode of hydraulic facilities that can effectively reduce the tailwater level and increase the power generation head.

[0042] Preferably, the hub operation data mentioned in S1 includes power generation dispatch operation data, water discharge hydraulic facility operation data, and sediment and drift removal facility operation data.

[0043] Preferably, the power generation dispatch and operation data specifically includes: the output limit line corresponding to the installed capacity, the relationship between the power station's comprehensive output coefficient and gross head, the relationship between tailrace water level and flow rate, the relationship between head loss and inflow, and the relationship between reservoir operating water level and inflow.

[0044] Preferably, the operational data of the water spillway hydraulic facilities specifically includes: the scheduling and operation procedures of the water spillway facilities of the water conservancy hub, the discharge capacity of the water spillway facilities, and the relationship between the position of the water jump head and the downstream water level and unit width flow rate.

[0045] Preferably, the operational data of the sediment discharge and drift removal facilities specifically includes: the discharge capacity of the sediment discharge and drift removal facilities at different operating water levels in the reservoir.

[0046] Preferably, the governing equations of the hydrodynamic model described in S3 are a two-dimensional planar shallow water equation set obtained by simplifying the Navier-Stokes equations, which includes the flow continuity equation and the flow momentum equation. The governing equations of the hydrodynamic model in this invention do not consider vertical (i.e., z-direction in the Cartesian coordinate system) flow changes, but only consider planar (i.e., x and y-directions in the Cartesian coordinate system) flow changes.

[0047] Furthermore, the total water depth of the two-dimensional water flow:

[0048] h=η+d

[0049] The continuity equation for flow in two-dimensional shallow water is:

[0050]

[0051] The water flow equation for two-dimensional shallow water is:

[0052]

[0053] In the formula: x, y, z are Cartesian coordinates; Let u and v be the velocity components in the x and y directions, integrated along the water depth direction and then divided by the water depth; t is time; h is water depth; η is water level; d is still water depth; g is gravitational acceleration; ρ is the density of water; ρ0 is the relative density of water; p a Atmospheric pressure; s xx s xy s yy These represent the radiation stress components; S is the source term; u s v s The velocity of the source water flow in the x and y directions is given by f; f is the Coriolis force coefficient. ω is the Earth's angular velocity. The latitude is T. ij The horizontal viscous stress term includes viscous forces. Turbulent stress and horizontal convection stress τ bx τ by τ represents the stress components of the bottom stress in the x and y directions; sx τ sy These are the stress components of wind stress in the x and y directions.

[0054] The following uses an inflow rate of 45,000 m³. 3 This invention is explained using the optimization of the operation mode of the Gezhouba Dam hydraulic engineering facilities during the flood season as an example. A panoramic view of the Gezhouba Dam in this embodiment is shown below. Figure 1 This includes the following steps:

[0055] S1-1: Collecting hub operation data includes:

[0056] Power generation dispatch and operation data: Output limit line corresponding to installed capacity (see...) Figure 2 ), the relationship between the power plant's overall output coefficient and gross head (see Figure 3 ), Tailwater level-discharge relationship (see Figure 4 ), the relationship between head loss and inflow (see) Figure 5 ), the relationship between reservoir operating water level and inflow (see Figure 6 );

[0057] Operational data of the spillway hydraulic facilities: The scheduling and operation procedures of the Gezhouba Hydropower Project's spillway facilities are shown in Table 1; the spillway capacity is shown in Table 2; and the relationship between the location of the water jump head and the downstream water level and unit width flow rate is shown in (see...). Figure 7 );

[0058] Table 1. Operation and Scheduling Procedures for the Gezhouba Dam Water Conservancy Project's Spillway Facilities

[0059]

[0060] Table 2. Discharge Capacity of Gezhouba Dam (Unit: m) 3 / s

[0061]

[0062] Data on the operation of sediment and drift removal facilities: the discharge capacity of sediment and drift removal facilities at different operating water levels in the reservoir;

[0063] S1-2: Inflow rate reaches 45000 m³ 3 At a speed of / s, based on the fitting parameters from the power generation dispatch and operation data, the reservoir water level can be calculated to be 66.0m, the tailrace water level fitting value is 52.85m, the gross head is 13.15m, the average head loss is 0.38m, the net head is 12.77m (less than the rated head of 18.6m), and the comprehensive output coefficient is 8.38. According to the output limit line (the relationship between net head and the power station's expected output), the expected output limit for a single 170MW unit is 100MW, requiring a flow rate of 935m³ / s. 3 / s, the projected output of a single 150MW unit is limited to 89MW, requiring a flow rate of 830m³ / s. 3 / s, the total power generation flow of the unit is 17649m³ / s. 3 / s.

[0064] S2: Inflow rate is 45000 m³ 3 / s is greater than the total generating flow of the entire unit 17649m³ 3 / s, with all units running, the water discharge rate can be obtained by subtracting the power generation rate from the inflow rate. 27351m³ / s. 3 / s, the discharged water is released through hydraulic structures such as spillway, sediment flushing, and floatation discharge. Spillway and sediment flushing facilities are often multi-hole structures, and some spillway facilities may be arranged in zones. The safe discharge zone range of the spillway facility is calculated by relating the position of the hydraulic jump head to the downstream water level and the unit width flow rate. The range of the number of open orifices is calculated by dividing the discharge flow rate by the unit width flow rate. Different numbers of open orifices or zoned operation of the spillway facility will result in different tailrace water levels at the power station. The main river sediment flushing bottom orifice is opened intermittently for a discharge of 2400m. 3 / s, Dajiang Drift Hole 475m 3 / s, Dajiang Sand Dune 360m 3 / s, the Dajiang flushing gate is activated and the number of Erjiang spillway gates opened is controlled according to the position diagram of the water leap head so that the water leap head is within a safe range. Three operating modes can be listed: (1) The Dajiang flushing gate is not opened and the Erjiang spillway gate discharges 24116m of water. 3 / s, the Erjiang spillway can open 19 to 26 gates; (2) Considering the discharge of 7000m from the Dajiang sand flushing gate. 3 / s, Erjiang sluice gate discharges 17116m³ of water. 3 / s, the Erjiang spillway can open 13 to 19 gates; (3) Considering the discharge of 15,000m of the Dajiang sand flushing gate. 3 / s, 9116m³ of water was discharged from the Erjiang sluice gate. 3 / s, the Erjiang spillway can open 7 to 10 gates.

[0065] S3-1: The established hydrodynamic model is shown in [link / reference]. Figure 8 The hydrodynamic model uses a simplified Navier-Stokes equations system to obtain a two-dimensional planar shallow water equation system that does not consider vertical (i.e., z-direction in the Cartesian coordinate system) water flow changes, but only planar (i.e. y-direction in the Cartesian coordinate system) water flow changes. This system includes the water flow continuity equation and the water flow momentum equation.

[0066] Total water depth in two-dimensional water flow:

[0067] h=η+d

[0068] The continuity equation for the two-dimensional shallow water equation is:

[0069]

[0070] The momentum equation for two-dimensional shallow water equations is:

[0071]

[0072]

[0073] In the formula: x, y, z are Cartesian coordinates; Let u and v be the velocity components in the x and y directions, integrated along the water depth direction and then divided by the water depth; t is time; h is water depth; η is water level; d is still water depth; g is gravitational acceleration; ρ is the density of water; ρ0 is the relative density of water; p a Atmospheric pressure; s xx s xy s yy These represent the radiation stress components; S is the source term; u s v s The velocity of the source water flow in the x and y directions is given by f; f is the Coriolis force coefficient. ω is the Earth's angular velocity. The latitude is T. ij The horizontal viscous stress term includes viscous forces. Turbulent stress and horizontal convection stress τ bx τ by τ represents the stress components of the bottom stress in the x and y directions. sx τ sy These are the stress components of wind stress in the x and y directions.

[0074] The hydrodynamic model uses the finite volume method to divide the continuous computational domain into non-overlapping grid cells. The grid cells can be triangular, quadrilateral, or a hybrid of both. This type of grid is also called an unstructured grid. The computational domain is then discretized after the grid is divided.

[0075] For spatially discrete solutions, either first-order or second-order methods can be used. Second-order methods have higher accuracy but consume more computation time. For calculations of pure hydrodynamic mathematical models, first-order methods are sufficient to meet the accuracy requirements.

[0076] There are two main methods for solving two-dimensional shallow water equations: one is low-order solution and the other is high-order solution. For pure hydrodynamic models, the low-order solution method can achieve the required computational accuracy.

[0077] S3-2: Model Validation. Operational data of the Gezhouba Dam hydraulic facilities on April 7, 2018, May 30, 2019, and September 7, 2020 were used to validate the model. The river channel parameters used in the calculations were: 0.020 for excavated channels and slopes, 0.027 for river channel elevations below 65.0m, and 0.033 for riverbank elevations above 65.0m. The turbulent viscosity coefficient was calculated using the Smagorinsky formula, with the Smagorinsky coefficient set to 0.28.

[0078] Table 3 shows the calculated and measured values ​​of characteristic point locations of the Gezhouba Hydropower Project's hydraulic facilities during operation on April 7, 2018, May 30, 2019, and September 7, 2020. The table shows that the calculated and measured water level values ​​are basically consistent, with the difference being no greater than 0.02m for most of the time, meeting the relevant specifications. Therefore, this model can meet the requirements of engineering calculations.

[0079] Table 3 Comparison of Observation and Calculation Results for Gezhouba Hydraulic Facilities

[0080]

[0081] S4: The inflow rate was calculated to be 45,000 m³ / s using a hydrodynamic mathematical model. 3 When the Dajiang sluice gate is in operation and releasing water, the downstream tailwater level of the power station is seen. Figure 9 , Figure 10 , Figure 11 The tailwater level was compared with that of the corresponding flow level spillway facilities under common operating conditions in different sections and zones, as shown in Table 4. It was found that the tailwater level of the power station under operating condition (3) was 0.16m lower than that under common operating condition (1). The participation of the Dajiang spillway in water discharge can effectively increase the power generation head.

[0082]

[0083] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The embodiments and features described in these embodiments can be arbitrarily combined without conflict. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. An optimized scheduling method for reducing the tailrace level of a run-of-river power station during operation, wherein the run-of-river power station is a power station unit whose power output is limited by water head, characterized in that: Includes the following steps: S1: Based on the inflow rate at different flow levels and the corresponding reservoir operating water level, the power generation flow rate when the power station reaches the expected output at different operating heads is derived by analyzing the hub operation data. S2: If the inflow exceeds the power generation flow and water is wasted, under the premise that the total inflow and total power generation flow remain unchanged, the safety of the spillway, the operation of the flushing facility, and the navigation safety restrictions are comprehensively considered. The safe discharge range of each spillway is calculated by the relationship between the position of the water jump head of the spillway and the downstream water level and the unit width flow. Then, the water wasted flow is allocated to the spillway, flushing facility, and drift removal facility according to the unit width flow range. The safe discharge flow corresponding to each facility is determined. The number of openings / zone range is calculated by dividing the discharge flow of the spillway by the unit width flow. S3: Establish a hydrodynamic mathematical model with the discharge flow of the above-mentioned spillway facilities as the boundary condition, and simulate and calculate the tailwater level under the common scheduling and operation mode of the hub and the scheduling and operation mode of different combinations of hydraulic facilities under different inflow flows. S4: Compared with the commonly used scheduling and operation mode of the hub, the study found a combined operation mode of hydraulic facilities that can effectively reduce the tailwater level and increase the power generation head; The hub operation data mentioned in S1 includes power generation dispatch operation data, water spillway hydraulic facility operation data, and sediment and drift removal facility operation data; The governing equations of the hydrodynamic mathematical model described in S3 are a two-dimensional planar shallow water equation set obtained by simplifying the Navier-Stokes equations, which includes the flow continuity equation and the flow momentum equation.

2. The optimized scheduling method for reducing the tailrace level of a run-of-river hydropower station during operation, as described in claim 1, is characterized in that: The power generation dispatch and operation data specifically includes: the output limit line corresponding to the installed capacity, the relationship between the power station's comprehensive output coefficient and gross head, the relationship between tailrace water level and flow rate, the relationship between head loss and inflow, and the relationship between reservoir operating water level and inflow.

3. The optimized scheduling method for reducing the tailrace level of a run-of-river hydropower station during operation, as described in claim 1, is characterized in that: The specific operational data of the water spillway hydraulic facilities include: the scheduling and operation procedures of the water spillway facilities of the water conservancy hub, the discharge capacity of the water spillway facilities, and the relationship between the position of the water leap head and the downstream water level and unit width flow.

4. The optimized scheduling method for reducing the tailrace level of a run-of-river hydropower station during operation, as described in claim 1, is characterized in that: The specific operational data for the sediment and drift removal facilities include: the discharge capacity of the sediment and drift removal facilities at different operating water levels in the reservoir.

5. The optimized scheduling method for reducing the tailrace level of a run-of-river hydropower station during operation, as described in claim 1, is characterized in that: Total water depth in two-dimensional water flow: ； The continuity equation for flow in two-dimensional shallow water is: ； The water flow equation for two-dimensional shallow water is: ； ； ； ； ； ； In the formula: x, y, z are Cartesian coordinates; , The velocity components u and v in the x and y directions are integrated along the water depth direction and then divided by the water depth to obtain the flow velocity. h represents time; h represents water depth. For water level, Still water is deep; It is the acceleration due to gravity; The density of water; The relative density of water; Atmospheric pressure; , , These are the radiation stress components; For source terms; , For the source of the water flow , velocity in the direction; The Cobb force coefficient, , Earth's angular velocity, The latitude is the local latitude. The horizontal viscous stress term includes viscous forces. Turbulent stress and horizontal convection stress ; , These are the stress components of the bottom stress in the x and y directions; , These are the stress components of wind stress in the x and y directions.

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