A method for predicting peak discharge amplitude of hydropower station based on water level amplitude control

Abstract

The present invention discloses a method for predicting the peak-shaving discharge amplitude of a hydropower station based on water level amplitude control. The method comprises: using a one-dimensional Saint-Venant equation group to simulate the non-steady flow process in the river channel; solving the water level at each station and at each time along the downstream river channel of the hydropower station, and calculating the water level amplitude of each station along the downstream river channel of the hydropower station; establishing a functional relationship between the peak-shaving discharge amplitude of the hydropower station and the water level amplitude of the downstream navigable river section; substituting the water level amplitude of the downstream navigable river section required by shipping into the functional relationship, and obtaining the peak-shaving discharge amplitude of the hydropower station that meets the water level amplitude control requirements of the downstream navigable river section. The present invention establishes the correlation between the peak-shaving discharge amplitude of the hydropower station and the water level amplitude of the downstream navigable river section in advance through one-dimensional non-steady flow simulation calculation, and then directly converts the water level amplitude control requirements of the downstream navigable river section into the peak-shaving discharge amplitude of the hydropower station, providing clear constraints for the scheduling of the hydropower station, and achieving the goal of real-time and flexible scheduling of the hydropower station.

Description

Technical Field

[0001] The invention belongs to the technical field of peak load regulation of hydropower stations, and in particular relates to a method for predicting the peak load discharge amplitude of a hydropower station based on water level amplitude control. Background Art

[0002] Peak shaving of a hydropower station refers to starting a turbine unit to bear part of the power load of the power grid during the peak period of electricity consumption. Peak shaving of a hydropower station usually causes changes in the daily discharge flow process of the hydropower station, causing non-constant flow and water level fluctuations in the downstream river. Especially in the high mountain canyon river section, affected by the complex river conditions and huge installed capacity, the peak shaving of the hydropower station often causes the water level in the downstream river to rise and fall sharply, and the maximum hourly fluctuation of the water level can reach 8-9m. However, from the perspective of shipping safety, it is usually required that the hourly or daily fluctuation of the water level in the river downstream of the hydropower station should not be too large, so as not to cause danger to the navigation and berthing of ships. Based on the control demand of shipping on the fluctuation of the water level in the river downstream of the hydropower station (for example, the hourly fluctuation of the water level is required to be no more than 1.0m), the peak discharge amplitude of the hydropower station is predicted and limited, so as to reasonably formulate the peak shaving operation mode of the hydropower station, which is of great significance to the dispatching and operation of the hydropower station that undertakes the shipping task.

[0003] Determining the peak-shaving dispatching mode of a hydropower station is usually a process of seeking the optimal solution of the peak-shaving dispatching model of a hydropower station under the constraints of multiple objectives such as water inflow, power load, flood control, ecology, and shipping. Generally speaking, constraints (including water quantity constraints, output constraints, flow constraints, water level constraints, water level fluctuation constraints, etc.) are easy to obtain, so previous studies usually focus on the peak-shaving dispatching model of a hydropower station, and by improving the model and algorithm, reduce the randomness of the solution results, and improve the model stability and solution efficiency.

[0004] However, if the constraints are difficult to give accurately in special circumstances, it will directly affect the solution of the hydropower station peak-shaving scheduling model. For example, if the navigation water level amplitude requirements at a certain location or a certain interval of the river section downstream are known, but the water level amplitude below the dam or the peak-shaving discharge amplitude requirements of the hydropower station are unknown, the hydropower station peak-shaving scheduling model cannot be accurately solved. More typically, in the cascade channelized river section of the high mountain canyon, due to the limitations of navigable water flow conditions, navigation is not possible within a certain range below the dam, and navigation and trans-dam transportation are the main methods. The navigable range may even be extended or shortened with the change of the next cascade backwater range. At this time, because the change of the navigable range is in dynamic adjustment, the water level amplitude control requirements based on the shipping target are difficult to quickly and accurately convert into the constraints required by the hydropower station peak-shaving scheduling model (i.e., the water level amplitude below the dam or the peak-shaving discharge amplitude of the hydropower station), which is a major problem for the real-time scheduling of the hydropower station. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the above-mentioned background technology and provide a method for predicting the peak-shaving discharge amplitude of a hydropower station based on water level amplitude control. It can solve the problem that the navigation constraints are difficult to accurately give when solving the peak-shaving dispatching model of a hydropower station under special circumstances (such as cascade channelized river sections in high mountain canyons), and improve the accuracy of model solution; in addition, directly converting the water level amplitude control requirements into the peak-shaving discharge amplitude of the hydropower station is conducive to the real-time dispatching of the hydropower station and ensures the navigation safety of the downstream river section of the hydropower station.

[0006] The technical solution adopted by the present invention is: a method for predicting the peak discharge amplitude of a hydropower station based on water level amplitude control, comprising the following steps:

[0007] Step 1: Use the one-dimensional Saint-Venant equations to simulate the unsteady flow process in the river. The control equations include the continuity equation and the motion equation, which are as follows:

[0008]

[0009]

[0010] Where Q is the flow rate in the river, unit: m 3 / s; A is the flow area of ​​the river, unit: m 2 ;q l is the lateral single width inflow, unit: m 2 / s; t is time, unit: s; x is mileage, unit: m; z is water level, unit: m; n is Manning's roughness coefficient; R is hydraulic radius, unit: m; g is gravitational acceleration, unit: m / s 2 ;

[0011] Except for the water level z, the other parameters are known or can be expressed as a function of the water level z. According to the above equation, the water level at each station and at each time along the river downstream of the hydropower station can be obtained;

[0012] Step 2: According to the characteristics of power load in the power system and the characteristics of the power station units, formulate various possible downstream flow processes during the peak-shaving operation of the hydropower station, take the downstream flow process of the hydropower station (i.e., Q in the formula of step 1) and the flow area of ​​the river (i.e., A in the formula of step 1) as input conditions, input the equation group in step 1, solve the water level of each station along the downstream river of the hydropower station at each time, and calculate the water level variation of each station along the downstream river of the hydropower station according to the following formula:

[0013]

[0014] In the formula, i is the station number; n is the time number, t max is the maximum time number; represents the water level at the i-th station at the n-th hour; represents the water level at the i-th station at hour n+1; Δz i represents the water level variation at the i-th station;

[0015] Step 3: Count the water level variation Δz in a navigable river section downstream of the hydropower station max , where Δz max =max(Δz i ), i is the station number in the navigable river section, and then the peak discharge amplitude of the hydropower station ΔQ is calculated according to the downstream discharge process of the hydropower station, and the one-to-one corresponding scattered data of the water level variation in the navigable river section and the peak discharge amplitude of the hydropower station are fitted to obtain the functional correlation relationship Δz between the water level variation in the downstream navigable river section and the peak discharge amplitude of the hydropower station max =f(ΔQ), where Δz max is the water level fluctuation, unit: m / h, ΔQ is the peak discharge amplitude of the hydropower station, unit: m 3 / s / h;

[0016] Step 4: Substitute the water level fluctuation of the downstream navigable river section required by shipping into Δz max =f(ΔQ), and the peak discharge amplitude of the hydropower station that meets the water level fluctuation control requirements of the downstream navigable river section is obtained.

[0017] The peak flow regulation amplitude of the hydropower station in the present invention refers to the maximum hourly fluctuation amplitude of the flow, and the water level fluctuation amplitude refers to the maximum hourly fluctuation amplitude of the water level.

[0018] The Saint-Venant equations belong to the first-order quasi-linear hyperbolic partial differential equations, and generally, it is impossible to find their general analytical solutions. The present invention uses the implicit finite difference method to discretize the above control equations and solves them using the Newton-Raphson iterative method.

[0019] The functional correlation Δz between the water level fluctuation of the downstream navigable river section and the peak discharge amplitude of the hydropower station max =f(ΔQ), which is usually complex and multi-factorial. When the operating water level of the next cascade power station changes and the range of the navigable river section changes, the above correlation is different. In addition, the peak discharge amplitude of the hydropower station is positively correlated with the amplitude of the water level change in the downstream navigable river section, that is, the greater the peak discharge amplitude of the hydropower station, the greater the amplitude of the water level change in the downstream navigable river section.

[0020] In order to ensure the safety of navigation in the navigable river sections downstream of the hydropower station, it is usually required that the water level fluctuation should not be too large. For example, the navigable river sections downstream of the Three Gorges of the Yangtze River and the Gezhouba Water Conservancy Project are controlled to have a water level fluctuation of no more than 1.0m / h. In the high mountain canyon area where the water level rises and falls sharply and the characteristics of ships are different, the water level fluctuation control requirements can be appropriately relaxed through research. Generally speaking, the stricter the water level fluctuation control requirements and the smaller the control value, the smaller the peak discharge amplitude of the hydropower station, and the greater the restrictions on the peak regulation of the hydropower station.

[0021] The present invention solves the water level fluctuation amplitude of the downstream river channel during the peak flow regulation of the hydropower station by establishing a one-dimensional river channel non-steady flow mathematical model; clarifies the navigation range of the downstream river channel, and establishes the correlation between the peak flow regulation amplitude of the hydropower station and the water level fluctuation amplitude of the downstream navigable river section; clarifies the control requirements of navigation on the water level fluctuation amplitude, and deduces the peak flow regulation amplitude of the hydropower station that meets the water level fluctuation control requirements of the downstream navigable river section according to the established correlation, so as to provide a basis for the real-time dispatch of the hydropower station.

[0022] The present invention establishes in advance the correlation between the peak-shaving discharge amplitude of the hydropower station and the water level fluctuation amplitude of the downstream navigable river section through one-dimensional non-steady flow simulation calculation, and then directly converts the water level fluctuation control requirements of the downstream navigable river section into the peak-shaving discharge amplitude of the hydropower station, thereby providing clear constraints for the hydropower station scheduling and achieving the goal of real-time and flexible scheduling of the hydropower station. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is the logic diagram of the present invention;

[0024] Figure 2 Schematic diagram of the downstream section near the dam of Wudongde Hydropower Station according to an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of a typical peak-shaving discharge process of the Wudongde Hydropower Station according to an embodiment of the present invention;

[0026] Figure 4 Schematic diagram a of the distribution of water level amplitude along the process under different peak regulation and discharge processes in the embodiment of the present invention;

[0027] Figure 5 Schematic diagram b of the distribution of water level amplitude along the process under different peak regulation and discharge processes in the embodiment of the present invention;

[0028] Figure 6 Schematic diagram c of the distribution of water level amplitude along the process in different peak regulation and discharge processes according to the embodiment of the present invention;

[0029] Figure 7 d is a schematic diagram of the distribution of water level amplitude along the process in different peak regulation and discharge processes according to an embodiment of the present invention;

[0030] Figure 8 It is a schematic diagram of the correlation between the peak discharge amplitude of the Wudongde Hydropower Station and the water level variation amplitude of the downstream navigable river section (Sidouzhong-Baihetan river section) according to an embodiment of the present invention;

[0031] Fig. 9 It is a schematic diagram of the correlation between the peak discharge amplitude of the Wudongde Hydropower Station and the water level fluctuation amplitude of the downstream navigable river section (Lujia Village ~ Baihetan River Section) in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments to facilitate a clear understanding of the present invention, but they do not constitute a limitation on the present invention.

[0033] The present invention takes the Wudongde Hydropower Station on the Jinsha River as an example to explain in detail the method for predicting the peak-shaving discharge amplitude of a hydropower station based on water level amplitude control, which is also of guiding significance for the scheduling of other hydropower stations that undertake shipping tasks, especially for the peak-shaving scheduling operation of hydropower stations on cascade channelized rivers in high mountain canyons such as the Jinsha River and the Dadu River.

[0034] Wudongde Hydropower Station is the first of four cascade hydropower stations in the lower reaches of Jinsha River. The project development task is mainly power generation, while taking into account flood control, shipping and promoting local economic and social development. The total installed capacity of the power station is 10,200MW, and the average annual power generation is 38.91 billion kW·h. There are 12 generators in total. The opening and closing of a single generator will cause the flow to increase or decrease by 672.5m 3 / s or so. Baihetan Hydropower Station is the next stage of Wudongde Hydropower Station. The river section from Wudongde hub to Baihetan hub is 183km long, of which Wudongde dam site ~ Sidouzhong is the variable backwater area of ​​Baihetan Reservoir, with a total length of about 38.5km; Sidouzhong ~ Baihetan dam site is the perennial backwater area of ​​Baihetan Reservoir, with a total length of about 144.5km. The dead water level of Baihetan Reservoir is 765m, the flood control limit water level is 785m, and the normal water storage level is 825m. The downstream section near the dam of Wudongde Hydropower Station (i.e. the river section at the tail of Baihetan Reservoir), from Wudongde dam site to Pudu River estuary, is about 41km long and is the river section greatly affected by the peak regulation operation of Wudongde Hydropower Station (see Figure 1 This section of the river is narrow and winding, with steep banks and numerous shoals. In addition, the installed capacity of the Wudongde Hydropower Station is large, and the peak-shaving operation of the hydropower station causes the water level fluctuation in the downstream river channel to be much greater than that of ordinary mountain rivers, which greatly affects shipping safety. This is the key research section.

[0035] The prediction method of peak discharge amplitude of Wudongde Hydropower Station based on water level amplitude control is carried out in the following steps:

[0036] Step 1: Establish a one-dimensional river channel unsteady flow mathematical model:

[0037] A one-dimensional unsteady flow mathematical model of the river downstream of the Wudongde Hydropower Station is established, and the one-dimensional Saint-Venant equations are used to simulate the unsteady flow process in the river. The control equations include continuity equations and motion equations, which are as follows:

[0038]

[0039]

[0040] Where Q is the flow rate in the river, unit: m 3 / s; A is the flow area of ​​the river, unit: m 2 ;q l is the lateral single width inflow, unit: m 2 / s; t is time, unit: s; x is mileage, unit: m; z is water level, unit: m; n is Manning's roughness coefficient; R is hydraulic radius, unit: m; g is gravitational acceleration, unit: m / s 2 .

[0041] In order to reduce the impact of the lower boundary condition setting on the calculation results, the calculation area was appropriately extended on the basis of the key research section, and the 93km river section downstream of the Wudongde Hydropower Station was selected, during which 234 large river sections were arranged, with an average section spacing of 398m. The unsteady flow mathematical model was calibrated and verified using the measured water surface line of the downstream river in February 2009 and the latest measured water level process of the Wudongde hydrological station in February 2020. The mathematical model was verified to have high accuracy and can be used for the next step of research.

[0042] Step 2: Calculate the water level fluctuation of the downstream river during the peak discharge of the hydropower station:

[0043] Wudongde Hydropower Station mainly supplies electricity to Yunnan and Guangdong provinces. Guangdong Province has obvious seasonal characteristics of electricity consumption, with a daily load curve showing three peaks and three valleys in summer and two peaks and two valleys in winter. Yunnan Province has a large proportion of hydropower and there is a difference between flood and dry seasons. The daily load curve shows three peaks and three valleys in the flood season and two peaks and two valleys in the dry season. When solving the downstream river water level fluctuation caused by the peak flow regulation of the hydropower station, the load characteristics of the Yunnan and Guangdong power systems and the characteristics of the Wudongde Hydropower Station units are fully considered, and four typical peak flow regulation and discharge processes of the Wudongde Hydropower Station are initially proposed, such as Figure 2 shown.

[0044] The above four typical peak-shaving discharge processes of Wudongde Hydropower Station are input into the one-dimensional unsteady flow mathematical model of the downstream river of Wudongde Hydropower Station in step 1 to solve the water level variation of each station along the downstream river. The results are as follows: Figure 3 As shown. Figure 3 It can be seen from the data that the water level in the river downstream of the Wudongde Hydropower Station rises and falls sharply, with the maximum water level fluctuation reaching 9.0m / h; the greater the peak discharge amplitude of the Wudongde Hydropower Station, the greater the water level fluctuation in the downstream river generally; the river section downstream of the Wudongde Hydropower Station is affected by the water level support of the Baihetan Reservoir, and raising the water level of the Baihetan Reservoir is conducive to reducing the water level fluctuation.

[0045] Step 3: Establish the correlation between the peak discharge amplitude of the hydropower station and the water level fluctuation amplitude of the downstream navigable river section:

[0046] For the downstream river section of the Wudongde Hydropower Station, when the Baihetan Reservoir operates at a low water level, the river section exhibits the hydraulic characteristics of a natural river section, with many shoals, shallow water, rapid currents, and poor navigation conditions; when the Baihetan Reservoir operates at a high water level, the river section is submerged and becomes a reservoir area, and the navigation flow conditions are significantly improved. Therefore, the navigable range of the downstream river section of the Wudongde Hydropower Station changes with the change of the water level of the Baihetan Reservoir. In the analysis here, two navigable river sections are selected, namely the Siduzhong (38.5km from the Wudongde dam site) to Baihetan river section and the Lujiacun (18km from the Wudongde dam site) to Baihetan river section, and the peak discharge amplitude of the Wudongde Hydropower Station is established (the peak discharge amplitudes corresponding to the peak discharge processes ①-④ of the Wudongde Hydropower Station are 7393m 3 / s / h、5833m 3 / s / h、4430m 3 / s / h and 2776m 3 / s / h) and the correlation between the water level fluctuations in the above two navigable river sections.

[0047] Based on the water level fluctuation results of each station along the downstream river obtained in step 2, the maximum water level fluctuations in the navigable river sections (Sidouzhong-Baihetan section and Lujiacun-Baihetan section) corresponding to the four peak discharge amplitudes of the Wudongde Hydropower Station were calculated, as shown in Tables 1 and 2. y = μe βx The obtained scattered data were fitted with an exponential function relationship of the form (y is the water level fluctuation, x is the peak discharge amplitude of the hydropower station, μ and β are parameters to be determined, and e is a natural constant), and the correlation between the peak discharge amplitude of the Wudongde Hydropower Station and the water level fluctuation amplitude of the downstream navigable river section was obtained. Figure 4 Obviously, when the water level of Baihetan Reservoir and the scope of navigable river section are different, the above correlation will also be different.

[0048] Table 1 Statistical unit of maximum water level fluctuation in the river section from Sidouzhong to Baihetan: m / h

[0049]

[0050] Table 2 Statistical unit of maximum water level fluctuation in the Lujiacun-Baihetan section: m / h

[0051]

[0052]

[0053] Note: Before the backwater of Baihetan Reservoir reaches the Lujiacun section (i.e. when the water level of Baihetan is 800m or below), the maximum water level fluctuation of the Lujiacun-Baihetan section is not affected by the backwater of Baihetan Reservoir. Therefore, the maximum water level fluctuation of the Lujiacun-Baihetan section is the same under the three conditions of Baihetan water level of 765m, 785m and 800m in Table 2.

[0054] Step 4: Determine the peak discharge amplitude of the hydropower station that meets the water level amplitude control requirements of the downstream navigable river section:

[0055] In order to ensure the safety of navigation in the navigable river section downstream of the hydropower station, it is usually required that the water level fluctuation should not be too large. In ordinary mountain rivers, the water level fluctuation is generally required to be no more than 1.0m / h. In the high mountain canyon areas such as the Jinsha River and the Dadu River, the water level rises and falls sharply, and the characteristics of ships are different. The water level fluctuation control requirements can be appropriately relaxed through research. For the navigable river section downstream of the Wudongde Hydropower Station, "water level fluctuation does not exceed 1.0m / h" and "water level fluctuation does not exceed 1.5m / h" are used as control conditions to deduce the peak discharge amplitude of the hydropower station.

[0056] Specifically, the water level amplitude control requirements are substituted into the correlation formula established in step 3, and the peak flow discharge amplitude of the hydropower station that meets the water level amplitude control requirements of the navigable river section downstream of Wudongde can be deduced, as shown in Table 3. When solving the peak-shaving dispatching model and formulating the dispatching plan, the peak-shaving discharge amplitude in Table 3 can be selected as the navigation constraint condition to improve the accuracy of the model solution; when the Wudongde Hydropower Station is dispatched in real time, the peak-shaving discharge amplitude in Table 3 can also be used as a reference for discharge control, improve the level of real-time dispatching, and ensure shipping safety.

[0057] Table 3 Peak discharge amplitude of Wudongde Hydropower Station Unit: m 3 / s / h

[0058]

[0059]

[0060] Note: The “—” in Table 3 indicates that the calculated peak-shaving discharge amplitude has exceeded the peak-shaving capacity of the hydropower station itself, or that the water level fluctuation will not exceed the standard when the Wudongde Hydropower Station operates at its maximum peak-shaving capacity.

[0061] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A method for predicting the peak discharge amplitude of a hydropower station based on water level amplitude control, characterized in that: The following steps are involved: Step 1: Use the one-dimensional Saint-Venant equations to simulate the unsteady flow process in the river. The control equations include the continuity equation and the motion equation, which are as follows: Where Q is the flow rate in the river, unit: m 3 / s; A is the flow area of ​​the river, unit: m 2 ; q l is the lateral single width inflow, unit: m 2 / s; t is time, unit: s; x is the mileage, unit: m; z is the water level, unit: m; n is the Manning roughness coefficient; R is the hydraulic radius, unit: m; g is the gravitational acceleration, unit: m / s 2 ; Step 2: According to the characteristics of power load in the power system and the characteristics of the power station units, formulate various possible downstream flow processes during the peak-shaving operation of the hydropower station, take the downstream flow process of the hydropower station and the flow area of ​​the river as input conditions, input the equation group in step 1, solve the water level of each station along the downstream river of the hydropower station at each time, and calculate the water level amplitude of each station along the downstream river of the hydropower station according to the following formula: In the formula, i is the station number; n is the time number, t max is the maximum time number; represents the water level at the i-th station at the n-th hour; represents the water level at the i-th station at hour n+1; Δz i represents the water level variation at the i-th station; Step 3: Count the water level variation Δz in a navigable river section downstream of the hydropower station max , where Δz max =max(Δz i ), i is the station number in the navigable river section, and then the peak discharge amplitude of the hydropower station ΔQ is calculated according to the downstream discharge process of the hydropower station, and the one-to-one corresponding scattered data of the water level variation in the navigable river section and the peak discharge amplitude of the hydropower station are fitted to obtain the functional relationship Δz between the water level variation in the downstream navigable river section and the peak discharge amplitude of the hydropower station max =f(ΔQ), where Δz max is the water level fluctuation, unit: m / h, ΔQ is the peak discharge amplitude of the hydropower station, unit: m 3 / s / h; Step 4: Substitute the water level fluctuation of the downstream navigable river section required by shipping into Δz max =f(ΔQ), and the peak discharge amplitude of the hydropower station that meets the water level fluctuation control requirements of the downstream navigable river section is obtained.

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