A stepwise pre-discharge scheduling method, system and device for a cascade hydropower station group

Abstract

A cascade hydropower station group grading pre-discharge scheduling method, system and device belong to the technical field of reservoir flood control scheduling. First, the possible inflow formed by backwater, landing rain and forecast rainfall is considered. Second, the flood control highest water level based on the conventional scheduling mode and the power generation flow of each hydropower station in the cascade hydropower station group are comprehensively considered to determine the pre-discharge timing. Finally, the grading pre-discharge amount is determined by considering the rechargeable water amount and reducing the abandoned water, and is adjusted according to the safety flow and other information. The cascade hydropower station group grading pre-discharge scheduling system comprises a possible inflow determination module, a pre-discharge timing determination module and a pre-discharge amount determination module, and is realized by a cascade hydropower station group grading pre-discharge scheduling device. The pre-discharge scheme prepared by the present application can reduce the flood control highest water level of the power station by pre-discharge, improve the flood control capacity, and also can utilize the pre-discharge water amount to generate power in advance; when the forecast is wrong, the power station still has enough inflow to recharge the reservoir water level, and ensures the power generation water head.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of reservoir flood control scheduling, and relates to a cascade pre-discharge scheduling method, system and device for cascade hydropower stations, in particular to a cascade pre-discharge scheduling method, system and device for cascade hydropower stations considering rainfall prediction and its uncertainty. BACKGROUND

[0002] Under the influence of global climate change, flood disasters tend to be more frequent and severe, seriously affecting people's normal production and life and endangering life and property safety. Reservoirs are important flood control and disaster mitigation engineering measures in a river basin. Frequent floods pose a challenge to reservoir scheduling. At the same time, as the operating life of water conservancy facilities increases, there are often weak river embankments and reduced river flood carrying capacity in the river basin, and the overall flood control standard of the river basin needs to be improved by relying on reservoir flood control scheduling. It is particularly important to develop a scientific and reasonable reservoir scheduling strategy to fully utilize the flood storage, flood detention, peak reduction and peak shifting functions of reservoir flood control capacity to improve the flood control and disaster mitigation benefits of the river basin.

[0003] Reservoir scheduling often uses measured water levels or inflow flow rates as the judgment index, but the water level and flow rate indicators appear late in the scheduling process, and conventional scheduling results in a lag in the start of flood control measures, limiting the improvement of the flood control function of reservoirs. Forecast scheduling methods that take into account rainfall or flood prediction information can extend the prediction period and make decisions in advance based on the predicted inflow, further improving the flood control and disaster mitigation function of reservoirs. Pre-discharge scheduling is one of the important ways of forecast scheduling. Existing research has mostly input forecast information as accurate information, but forecast information inevitably has uncertainty, which may lead to control risks. If the forecast is too large, the discharge will be too large, resulting in a decrease in the water level of the reservoir, and if there is a false alarm and no future flood, the pre-discharge water volume may not be able to be stored, affecting the beneficial use of the reservoir. Therefore, how to consider the uncertainty of the forecast and develop a reasonable control decision is the key to forecast scheduling. For hydropower stations, pre-discharge not only improves the flood control capacity but also allows for early power generation. Existing research has taken into account power generation factors, and increasing the pre-discharge of power generation flow can generate power in advance and reduce water abandonment. However, there are extensive cascade developments of power stations in China, and the power generation flow in the cascade is not the same. How to consider the power generation flow of cascade power stations is a difficulty in the pre-discharge of cascade power stations. Most existing research only considers the pre-discharge of a single power station, limiting the improvement of flood control and beneficial use. Most related technologies, such as Chinese invention patent CN119761839A, disclose a lake pre-discharge timing determination method and system based on short-term rainfall prediction, which directly inputs rainfall prediction data into a prediction model to calculate the total inflow into the lake and determine the pre-discharge method, without considering the uncertainty of rainfall prediction; Chinese invention patent CN105373847A discloses a pre-discharge decision-making method for a hydropower station reservoir based on CFS prediction, which considers the full-load flow of a single power station and increases the power generation flow during pre-discharge to reduce water abandonment. However, this method cannot further reduce the cascade water abandonment when applied to cascade power stations.

[0004] The application designs a hierarchical pre-discharge scheduling method, system and device for cascade hydropower stations considering forecast uncertainty: possible inflow is determined considering forecast uncertainty, pre-discharge timing is identified according to future inflow and full-load flow of the cascade hydropower stations, hierarchical pre-discharge flow is determined according to rechargeable water quantity, full-load flow and safe discharge quantity information of the cascade hydropower stations, and a pre-discharge scheme is formulated. The pre-discharge can reduce the highest water level for flood regulation of the power station and improve the flood control capacity, and the pre-discharge water quantity can be used for power generation in advance to improve the power generation benefit. When the forecast is wrong, the power station still has sufficient inflow to recharge the reservoir water level and ensure the power generation head. SUMMARY

[0005] In view of the deficiencies of the prior art, the application provides a hierarchical pre-discharge scheduling method, system and device for cascade hydropower stations, which can reduce the highest water level for flood regulation of the power station and improve the flood control capacity, and can also use the pre-discharge water quantity for power generation in advance and ensure the power generation head.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] In a first aspect, the application provides a hierarchical pre-discharge scheduling method for cascade hydropower stations, which is a hierarchical pre-discharge scheduling method for cascade hydropower stations considering forecast uncertainty. First, possible inflow formed by backwater, landed rain and forecast rainfall is considered. Second, the pre-discharge timing is determined by comprehensively considering the highest water level for flood regulation based on the conventional scheduling mode and the power generation flow of each hydropower station in the cascade hydropower stations. Finally, the hierarchical pre-discharge quantity is determined considering the rechargeable water quantity and the reduction of abandoned water, and is adjusted according to the safety flow and other information. The method includes the following steps:

[0008] Step 1: Determine the possible inflow under consideration of forecast uncertainty, i.e., determine the possible inflow formed by backwater, landed rain and forecast rainfall, i.e., the possible inflow includes possible net rainfall and possible backwater quantity; wherein the possible net rainfall refers to the base flow and the inflow formed by this rainfall, and the this rainfall includes landed rain and forecast rainfall; the possible backwater quantity refers to the backwater surplus of the last flood.

[0009] The calculation formula of the possible inflow is:

[0010] (1)

[0011] In the formula: is the current time; is the possible net rainfall, mm; A is the area of the basin, km 2 ; 3 ; ​For the possible incoming water, 10,000 m 3 .

[0012] The calculation steps of each part of the possible incoming water are:

[0013] Step 1.1, determine the rainfall forecast error distribution;

[0014] Select a rainfall forecast product that is widely used in the basin and has good effect, according to historical statistical information, classify according to rainfall standard, determine the forecast error distribution under different forecast levels (such as moderate rain, heavy rain, etc.), usually use P-III distribution.

[0015] Step 1.2, determine the net rainfall forecast error distribution;

[0016] Select a hydrological model that is widely used in the basin and has good effect, determine the net rainfall forecast error distribution of the selected hydrological model according to the net rainfall forecast results of the hydrological model on historical floods, usually use normal distribution or maximum entropy distribution.

[0017] Step 1.3, calculate the possible net rainfall;

[0018] According to the fallen rain and forecast rainfall of the current rainfall, the possible incoming water is calculated. Among them, the forecast rainfall considering the uncertainty of the forecast is determined according to the forecast error distribution determined in step 1.1, and the rainfall that will occur with a certain probability is the possible rainfall, and the value range of the certain probability is (0, 100%], and the recommended value range is [50, 100%]; The uncertainty from rainfall to net rainfall is also determined according to the net rainfall forecast error distribution to determine the net rainfall that will occur with a certain probability, and the value range of the certain probability is (0, 100%], and the recommended value range is [50, 100%]. The calculation formula of the possible net rainfall is as follows:

[0019] (2)

[0020] (3)

[0021] In the formula: is the current time; is the possible rainfall of the forecast level at time t, mm; is the actual rainfall anti-cumulative distribution function of the forecast level; is the confidence probability of rainfall forecast uncertainty; is the rainfall level at time t; is the possible net rainfall at time t, mm; ​​​​​The cumulative rainfall at any given time, in mm; The predicted net rainfall (in mm) is obtained by inputting the actual rainfall and the forecast rainfall into the hydrological model. This is the inverse cumulative distribution function of net rainfall forecast error; This represents the confidence probability of the uncertainty in the net rainfall forecast.

[0022] Step 1.4, calculate the possible water receding volume;

[0023] Based on existing watershed recession curves or hydrological models, determine the current potential recession volume. .

[0024] (4)

[0025] In the formula: This represents the projected discharge capacity at the end of the current forecast period, in 10,000 m³. 3 ; The representative of the predicted water receding process is obtained through watershed water receding curves or hydrological forecasting models; To account for the forecast lead time for landing rainfall and flood forecasts (which can be taken as the watershed confluence time), h; The storage time for the hydropower station is in hours (h).

[0026] Step 2, determine the timing of pre-release;

[0027] Based on the possible inflow determined in step 1, the predicted inflow process of the hydropower station is obtained by the hydrological model or by scaling a typical flood based on the possible net rainfall. This process is then input into the cascade hydropower station group scheduling model to obtain the scheduling process according to the conventional scheduling method. Pre-discharge will begin when one of the following two conditions is met during the process.

[0028] Condition 1: Water wastage occurs during the conventional dispatching scheme;

[0029] When a cascade hydropower station group is operated using the conventional scheduling method, if any hydropower station experiences water wastage, i.e., the outflow is greater than the full generating flow, the station will begin pre-discharge. The criterion for condition 1 is shown in formula (5):

[0030] (5)

[0031] In the formula: For the future; for Power plant outflow at any given time, m 3 / s; This refers to the number of power stations within the cascade. To consider the first The power station generates a full-capacity outflow of m 3 / s.

[0032] Condition 2: The highest flood regulating water level exceeds the set water level in the conventional scheduling mode;

[0033] If the highest flood regulating water level exceeds the set water level in the conventional scheduling mode of the cascade hydropower station group, the power station starts to pre-discharge. The set highest water level is the flood control high water level or the farmland compensation water level or the resettlement water level or other flood control characteristic water level. The discrimination formula is shown in formula (6):

[0034] (6)

[0035] In the formula, is the current time; is the water level at the time, m; is the set highest water level, m.

[0036] Step 3: Determine the pre-discharge amount in stages;

[0037] After determining that the hydropower station needs to pre-discharge according to step 2, the pre-discharge amount is further determined according to the rechargeable water amount, the full discharge flow of the power station, and the safety discharge amount. The determination of the pre-discharge amount is related to the water level. When the water level is small, it is mainly considered whether the water can be recharged after pre-discharge. When the water level is large, it is mainly considered whether there will be water abandonment. Therefore, first, the rechargeable water amount under the current water and rainfall condition is determined, then the water abandonment condition is determined, and the pre-discharge amount is determined in stages, as follows:

[0038] Step 3.1: Calculate the effective pre-discharge time according to formula (7):

[0039] (7)

[0040] In the formula, is the effective pre-discharge time considering flood rainfall forecast information, h; is the forecast prediction period, h; is the sum of information transmission and decision-making and operation time, h.

[0041] Step 3.2: Calculate the current rechargeable water amount;

[0042] After the power station pre-discharges for the effective pre-discharge time , if the actual water is smaller than the forecast water, the power station needs to reduce the discharge, and at the end of the flood forecast prediction period, the actual water is stored in the power station as much as possible to raise the water level as much as possible to ensure the power generation water head. Accordingly, the rechargeable water amount is calculated as shown in formula (8), including: the amount of water that the power station has pre-discharged before the time , which requires only the minimum flow to discharge water , the possible water in the prediction period ​The remaining part is stored in the hydropower station.

[0043] (8)

[0044] wherein, represents the rechargeable water volume calculated at the moment, million m 3 ; represents the possible incoming water at the moment; represents the minimum water outflow meeting the power generation or water supply requirement, m 3 / s; represents the water volume that has been pre-discharged before the moment, million m 3 ;

[0045] wherein:

[0046] (9)

[0047] wherein: represents the minimum flow meeting the power generation or water supply requirement, m 3 / s; represents the hydropower station recharge time.

[0048] Step 3.3, hierarchical determination of pre-discharge volume;

[0049] The determination of the pre-discharge volume is related to the incoming water level: when the incoming water volume is small, in order to avoid emptying the reservoir capacity and causing empty report and unable to recharge, pre-discharge is performed according to the rechargeable water volume; when the incoming water volume is large, the discharge flow is gradually increased according to the full-load flow of the hydropower station group to reduce water abandonment, and if the incoming water continues to increase, the discharge is further increased according to the possible incoming water to improve the flood control capacity. The incoming water level is determined according to the relationship between the rechargeable water volume and the water volume that can be pre-discharged according to the minimum full-load flow, and the formula is:

[0050] (10)

[0051] When formula (10) is not established, go to step 3.3.1; when formula (10) is established, go to step 3.3.2.

[0052] Step 3.3.1, pre-discharge according to the rechargeable water volume;

[0053] When formula (10) is established, the existence of prediction uncertainty may lead to that no flood occurs after pre-discharge, and the pre-discharged water volume cannot be recharged due to the too small predicted incoming water, thereby reducing the power generation head and affecting the power generation benefit. At this time, the pre-discharge volume is calculated according to the rechargeable water volume to ensure that even if the prediction is wrong, the incoming water volume is sufficient to ensure that the reservoir water level is recharged to the water level before pre-discharge. The schematic diagram of pre-discharge according to the rechargeable water volume is shown in FIG. 2.Figure 2 The details are as follows:

[0054] From the perspective of generating benefits, the hydropower head at the end of the forecast period must ensure that the recharge water level is higher than the water level at the start of the pre-release. That is, the pre-discharge volume Less than the rechargeable water volume From the perspective of flood control safety, The bigger the better. Taking into account both flood control and overall benefits, equal Even if the forecast is wrong, the water level can still be fully replenished to the level at the start of the pre-discharge. The required pre-discharge volume is calculated according to formula (11):

[0055] (11)

[0056] In the formula: for The required pre-discharge volume at any given time, in 10,000 m³ 3 .

[0057] The power station needs to release the required pre-release volume of water within the effective pre-release time. Based on this, the pre-release flow rate is calculated according to formula (12):

[0058] (12)

[0059] In the formula: for Pre-release flow rate at any time, m 3 / s. This is the effective pre-release time.

[0060] Step 3.3.2: Pre-release water based on the full-capacity flow of the cascade hydropower station group;

[0061] When formula (10) is not valid, the pre-discharge flow rate is determined based on the full-capacity flow rate of the hydropower station.

[0062] Step 3.3.2.1: Sort the full-capacity flow of the hydropower station in ascending order.

[0063] Step 3.3.2.2: Determine whether the water level at the hydropower station might exceed the set maximum water level;

[0064] When the hydroelectric power station Based on the full discharge flow, determine whether the highest water level is likely to exceed the set maximum water level. The predicted inflow process for hydropower stations (which can be obtained from hydrological models or by scaling typical floods based on predicted net rainfall) is as follows: Outflow is Hydropower station full flow The maximum reservoir capacity occupied by the power station is calculated according to formulas (13) and (14). and the highest flood control water level :

[0065] (13)

[0066] (14)

[0067] In the formula: To determine the maximum reservoir capacity that may be occupied during flood control, 10,000 m³ 3 ; For the power station at the current moment The warehouse capacity is 10,000 m³. 3 ; The highest possible water level for the hydropower station is in meters (m). This refers to the reservoir capacity-water level relationship of a hydropower station.

[0068] Determine whether the current water level of the power station may exceed the set maximum water level, that is, determine whether formula (15) is valid.

[0069] (15)

[0070] Step 3.3.2.3: When formula (15) is not valid, the power station pre-releases water at full power generation to reduce water wastage. The pre-discharge flow rate at any given time is determined according to formula (16).

[0071] (16)

[0072] Step 3.3.2.4: When formula (15) holds true, the hydropower station needs to pre-discharge an additional amount of water on top of the pre-discharge based on the full-capacity flow. The amount of water requiring additional pre-discharge... This is equivalent to releasing the excess reservoir capacity, and the calculation and update are based on the additional pre-released water volume. The value of the pre-leakage flow at any given time , , The calculations are shown in formulas (17) and (18) respectively:

[0073] (17)

[0074] (18)

[0075] In the formula: To accommodate the need for further pre-discharge of water beyond full capacity, 10,000 m³ 3 ; The relationship between water level and reservoir capacity at a hydropower station; This is the set maximum water level.

[0076] Step 3.3.2.5, when there is a larger full-flow discharge, judging whether the larger full-flow discharge is exceeded, i.e., judging whether formula (19) is established.

[0077] (19)

[0078] When formula (19) is established, take i.e. , repeat steps 3.3.2.2-3.3.2.5. When formula (19) is not established, step 3.4 is performed.

[0079] Step 3.4, according to the safety discharge and the set minimum water level limit pre-discharge flow;

[0080] The pre-discharge should not threaten the safety of flood control, according to the safety discharge of the hydropower station or the guaranteed flow limit of the downstream river channel When formula (20) is established, The pre-discharge flow at the moment According to formula (21), the value is taken:

[0081] (20)

[0082] (21)

[0083] In the formula: is the safety discharge of the hydropower station or the guaranteed flow of the downstream river channel, m 3 / s. is a coefficient, the value range is: .

[0084] The pre-discharge water level is not lower than the set minimum water level (usually set as the dead water level). When formula (22) is established, The pre-discharge flow at the moment According to formula (23), the value is taken:

[0085] (22)

[0086] (23)

[0087] In the formula: is the set minimum water level, m.

[0088] In a second aspect, the application provides a hierarchical pre-discharge scheduling system for a cascade hydropower station group, which is applied to the hierarchical pre-discharge scheduling method of the cascade hydropower station group. The hierarchical pre-discharge scheduling system for the cascade hydropower station group comprises:

[0089] A possible inflow determination module for determining possible inflow.​

[0090] A pre-discharge timing determination module is configured to determine the pre-discharge timing of the power station; the pre-discharge timing determination module comprises two sub-modules: sub-module 1 is configured to determine whether water abandonment is possible when the power station is scheduled according to the conventional schedule; and sub-module 2 is configured to determine whether the water level is likely to exceed the set water level when the power station is scheduled according to the conventional schedule.

[0091] A pre-discharge amount determination module is configured to determine the pre-discharge amount of the power station; the pre-discharge amount determination module comprises four sub-modules: sub-module 1 is configured to calculate the rechargeable water amount, sub-module 2 is configured to calculate the effective pre-discharge time, sub-module 3 is configured to determine the pre-discharge amount in stages, and sub-module 4 is configured to limit the pre-discharge flow rate according to the safety discharge amount and the set minimum water level.

[0092] In a third aspect, the application provides a cascade pre-discharge scheduling device for cascade hydropower stations, which is an execution device and comprises a memory and a processor, the memory is used to store a computer program, the processor is coupled with the memory, and the computer program is run to execute the cascade pre-discharge scheduling method for cascade hydropower stations.

[0093] The application has the following beneficial effects:

[0094] The application determines the possible inflow on the basis of considering the prediction uncertainty, identifies the pre-discharge timing according to the future inflow of the cascade hydropower stations and the full-load flow rate, determines the staged pre-discharge flow rate according to the rechargeable water amount, the full-load flow rate of the cascade hydropower stations and the safety discharge amount information, and formulates the pre-discharge scheme. The application can not only reduce the highest water level of the power station for flood regulation and improve the flood control capacity, but also can use the pre-discharge water amount to generate electricity in advance and improve the power generation benefit; when the prediction is wrong, the power station still has enough inflow to recharge the reservoir water level and ensure the power generation water head. BRIEF DESCRIPTION OF DRAWINGS

[0095] Figure 1 It is a flow chart of the cascade pre-discharge scheduling method for cascade hydropower stations considering the prediction uncertainty.

[0096] Figure 2 It is a method schematic diagram of pre-discharge according to the rechargeable water amount.

[0097] Figure 3 It is a process diagram of the Huanren hydropower station regulating the 20240722 flood flow.

[0098] Figure 4 It is a process diagram of the Huanren hydropower station regulating the 20240722 flood water level. DETAILED DESCRIPTION

[0099] The application will be further described below in combination with specific embodiments.

[0100] The application takes the regulation of 20240722 flood of the cascade hydropower station group in Hunjiang basin as an example, and the pre-discharge scheduling method is applied to Huanren power station in the cascade. The specific implementation is described in detail in combination with the technical scheme and the drawings. The water conservancy and hydropower projects built from top to bottom in the main stream of Hunjiang River include Huanren, Huilongshan and Taipingsha hydropower stations. Among them, the first leading Huanren hydropower station has an incomplete annual regulation performance, and Huilongshan and Taipingsha are day regulation hydropower stations for regulating runoff in the cascade interval. The cascade hydropower station group of Huanren, Huilongshan and Taipingsha is located in the middle and lower reaches of Hunjiang River. The total reservoir capacity of the cascade hydropower stations is 37.65×10 8 m 3 , and the total installed capacity of the power stations is 482.5MW.

[0101] A cascade hydropower station group hierarchical pre-discharge scheduling method considering forecast uncertainty is shown in Figure 1 , and the embodiment specifically includes the following steps:

[0102] Step 1, determine the possible inflow considering the forecast uncertainty;

[0103] Step 1.1, determine the rainfall forecast error distribution;

[0104] In this embodiment, the ECMWF model 0-24h rainfall forecast information with good application effect in Huanren basin is selected, and the archive resolution is 0.5°×0.5°, which is updated every 12h. According to the national standard of “Rainfall Grading” (GB / T 28592-2012), the historical rainfall is classified, and the forecast error distribution under different forecast levels is determined. Taking heavy rain level as an example, the heavy rain level distribution is as follows.

[0105] Table 1, ECMWF model 0-24h heavy rain forecast P-III distribution

[0106]

[0107] The actual rainfall under the forecast level has obvious statistical rules, which obeys P-III distribution.

[0108] Step 1.2, determine the net rainfall forecast error distribution;

[0109] The Xin'anjiang model which is widely used in the basin and has good effect is selected, and the net rainfall forecast error distribution of the selected hydrological model is determined according to the net rainfall forecast results of the model on the historical flood. The maximum entropy distribution is adopted, and the corresponding error value under the cumulative probability is calculated.

[0110] Table 2, rainfall forecast relative error distribution in Huanren basin

[0111]

[0112] The following is an example of the initial time of the 11th period, i.e. July 24, 8:00, to illustrate the implementation of steps 1.3-3.4. The current time is July 24, 8:00.

[0113] Step 1.3, calculate the possible net rainfall;

[0114] According to the fallen rain of the current rainfall and the forecast rainfall, the rainfall that will occur with a probability of 90% is taken as the possible rainfall, and the current rainfall forecast level is heavy rainfall level, and 9.9mm of rainfall will occur with a probability of 90%, . Time cumulative fallen rain 67.5mm, the fallen rain and the forecast rain are input into the hydrological model to obtain the predicted net rainfall 75.5mm. According to the net rainfall forecast error distribution, the possible net rainfall is calculated with a prediction uncertainty confidence probability of 90%.

[0115] Step 1.4, calculate the possible recession water amount;

[0116] In this embodiment, the comprehensive recession curve of Huanren Hydropower Station in the Huanren Hydropower Station Flood Forecast Scheme is selected, and according to the Research on Key Issues of Dynamic Control of Huanren Reservoir Flood Limit Level, the recession forecast scheme has a verification accuracy of Class A and can be applied in actual flood regulation.

[0117] The forecast lead time of Huanren Basin is ; the flood duration of Huanren Basin is generally about 7 days, of which 3 days of flood volume accounts for more than 70% of the field flood volume, and according to the history of the basin flood, the time of the hydropower station back storage is . Combined with the recession curve of the basin, the current possible recession water amount is calculated.

[0118] On the basis of steps 1.1-1.4, the current possible inflow is calculated as 63763.88 million m 3 .

[0119] Step 2, determine the pre-discharge timing;

[0120] For condition 1, the full discharge flow of Huanren Hydropower Station downstream Hui Longshan Hydropower Station (330m 3 / s) is less than the full discharge flow of Huanren Hydropower Station (500m 3 / s), and as the discharge increases, the first water will be abandoned. In the history of typical floods, the average flow of Huan- Hui basin before the flood rises is 50m 3 / s, and when Huanren Hydropower Station discharges 330-50=280m 3 / s, it can avoid the water abandonment of Hui Longshan Hydropower Station, so = 280 m 3 / s, the full discharge flow of Huanren power station = 500 m 3 / s. For condition 2, , the compensation water level of Huanren power station, i.e. = 303 m.

[0121] According to the current inflow determined in step 1, the inflow process of the power station is obtained by the hydrological model, and the scheduling process is obtained by inputting the cascade hydropower station group scheduling model according to the conventional scheduling mode. The process meets condition one, and the hydropower station continues to pre-discharge at the current time.

[0122] Step 3, determine the pre-discharge flow in stages;

[0123] Step 3.1, calculate the effective pre-discharge time;

[0124] The cascade hydropower station group water regime forecasting system of the basin is stable, the gate opening and closing time is relatively short, and the information transmission and decision operation time is taken as the effective prediction period

[0125] Step 3.2, calculate the current rechargeable water amount;

[0126] Take the corresponding flow of 53 m 3 / s according to the guaranteed power at the flood limit water level of Huanren hydropower station, calculate = 1373.76 million m 3 . The water amount pre-discharged before the time 2635.20 = million m 3 . Calculate the current rechargeable water amount = 59754.92 million m 3 .

[0127] Step 3.3, determine the pre-discharge amount in stages;

[0128] According to the rechargeable water amount judgment formula (10), it is established, so it is turned to step 3.3.2, and the full discharge flow of the cascade hydropower station group is pre-discharged according to the full discharge flow;

[0129] First, step 3.3.2.1 is performed, and the power stations are sorted in ascending order according to the full discharge flow , .

[0130] When , , proceed to step 3.3.2.2, get the inflow process of the hydropower station from the hydrological model, get the highest water level of flood control from the hydropower station scheduling model =304.94m, formula (15) is established, proceed to step 3.3.2.4. At this time, the hydropower station needs to additionally discharge water on the basis of pre-discharge according to full-load flow, and the calculation is , . Proceed to step 3.3.2.5, , formula (19) is established, take , , repeat steps 3.3.2.2-3.3.2.5.

[0131] When , , proceed to step 3.3.2.2, get the inflow process of the hydropower station from the hydrological model, get the highest water level of flood control from the hydropower station scheduling model , formula (15) is established, proceed to step 3.3.2.4. At this time, the hydropower station needs to additionally discharge water on the basis of pre-discharge according to full-load flow, and the calculation is , . Proceed to step 3.3.2.5, there is no larger full-load flow, proceed to step 3.4.

[0132] Step 3.4, according to the safety discharge and the set minimum water level limit pre-discharge flow;

[0133] Pre-discharge should not threaten flood control safety, according to the safety discharge of the hydropower station or the downstream river channel guarantee flow limit . The maximum outflow of Huanren Reservoir is 2850m 3 / s during the rising stage of Huanhui section, take , m 3 / s, take 0.49, at this time formula (20) is established, the pre-discharge flow at the moment . The pre-discharge water level is not lower than the set minimum water level , which is set as the dead water level 290m, formula (22) is not established. Therefore, finally, the pre-discharge flow at the current moment is .

[0134] For the entire flood control process: Huanren Hydropower Station adjusts from the flood limit water level 300m to adjust this flood process. On July 23, 8:00, the cumulative rainfall in Huanren Basin reached 17.9mm, and the future 0-24h heavy rain forecast was received, which may reach 22.2mm of net rainfall, meeting condition 1, and the station starts pre-discharge. At 8:00 on July 23, the station first pre-discharges according to the rechargeable water amount (as shown in Figure 2 ) which may cause water abandonment in Huilong, and discharge according to the full load of Huilong 280m3 / s pre-discharge, increasing outflow for power generation in advance. At 8:00 AM on the 24th, the cumulative rainfall reached 46.1mm. Simultaneously, a moderate rain forecast for the next 0-24 hours was received, with a potential net rainfall of 38.6mm. The power station's full-capacity discharge at Huilong may exceed the farmland compensation water level, necessitating the release of excess water. Considering full-capacity operation at Huanren, the pre-discharge is limited to 500m³. 3 / s, Huanren Hydropower Station reached full capacity ahead of schedule. At 20:00 on the 24th, the cumulative rainfall reached 56.6mm. A heavy rain forecast for the next 0-24 hours was received, with a potential net rainfall of 53.2mm. Even with Huanren Hydropower Station operating at full capacity, the discharge flow may still exceed the farmland compensation water level, requiring further discharge to remove the excess water. Based on the river's safe discharge limit, the pre-discharge flow rate is 1400 m³ / s. 3 / s. At 20:00 on the 26th, the power station pre-released water to 298.94 m, at which time the inflow to the power station exceeded 1400 m³ / s. 3 / s, the pre-discharge ends and the flood control phase begins.

[0135] Table 3. Results of flood control operations at Huanren Hydropower Station, 20240722.

[0136]

[0137] The process of Huanren Hydropower Station regulating the flood flow during the 20240722nd flood is as follows: Figure 3 As shown, the Huanren Hydropower Station regulated the flood level 20,240,722 times as follows: Figure 4 As shown, through pre-discharge scheduling, the highest flood control water level of Huanren Hydropower Station was 305.13m, which was 0.89m lower than the conventional scheduling level of 306.02m; the total power generation reached 65.54 million kWh, which was 6.77 million kWh higher than the conventional scheduling level; and the total water wastage was 1.96 billion m3, which was 55 million m3 lower than the conventional scheduling level.

[0138] Table 4. Results of Flood Control Operations by the Cascade Hydropower Station Group on July 22, 2024

[0139]

[0140] When the Huanren Hydropower Station adopted the pre-release scheduling mode, the power generation of the cascade hydropower station group was 144.72 million kWh, an increase of 10.06 million kWh compared with the conventional scheduling; the total water release was 7.352 billion m³. 3 This reduces the amount of data collected by 101 million m compared to conventional scheduling. 3 Pre-release scheduling can free up reservoir capacity in advance, lower the maximum flood control water level, reduce inundation losses, and at the same time, generate electricity in advance by utilizing the pre-release flow during the pre-release phase to reduce water wastage. Lowering the water level during the flood control phase allows the units to remain in operation for a longer period of time, which can effectively increase the power generation of the unit itself and the cascade, and reduce water wastage.

[0141] The above embodiments only express the implementation ways of the present application, and cannot be understood as the limitation to the scope of the present application patent. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A stepped water power station group step-by-step pre-discharge scheduling method, characterized in that, The step 1 comprises the following steps. Step 1, determining possible inflow under the consideration of forecast uncertainty, i.e., determining possible inflow formed by backwater, landed rain and forecast rainfall; the possible inflow comprises possible net rainfall and possible backwater; wherein, the possible net rainfall refers to base flow and inflow formed by this rainfall, and the this rainfall comprises landed rain and forecast rainfall; the possible backwater refers to backwater surplus of the last flood; Step 2, comprehensively considering the flood regulation highest water level based on the conventional regulation mode and the power generation flow of each power station in the cascade hydropower station group, to determine the pre-discharge time; According to the possible inflow determined in step 1, the forecast inflow process of the power station is obtained by the hydrological model, which is input into the cascade hydropower station group regulation model to obtain the regulation process under the conventional regulation mode, and the pre-discharge is started when the conditions are met in the process; Step 3, considering the rechargeable water amount and reducing the water abandonment to determine the grading pre-discharge amount, and adjusting it according to the safety flow; After determining that the power station needs to be pre-discharged according to step 2, the pre-discharge amount is further determined according to the rechargeable water amount, the full-load flow of the power station and the safety discharge amount; the determination of the pre-discharge amount is related to the inflow level, when the inflow is small, whether the pre-discharge can be recharged is considered, and when the inflow is large, whether there will be water abandonment is considered; specifically: Firstly, the rechargeable water amount under the current water and rainfall condition is determined, then the water abandonment condition is judged, and the pre-discharge amount is determined in stages: Step 3.1, calculating the effective pre-discharge time according to formula (7): （7）； In the formula: h is the effective pre-discharge time considering the flood rainfall forecast information; h is the forecast period; h is the sum of information transmission and decision-making and operation time; Step 3.2, calculating the current rechargeable water amount; The power station reduces the discharge if the actual inflow is less than the predicted inflow, and stores the actual inflow into the power station at the end of the flood prediction period to raise the water level and ensure the power generation water head The amount of water that can be stored is calculated according to the actual inflow As shown in equation (8), and the possible inflow in the prediction period is calculated The remaining part is stored in the power station （8）； wherein, represents the amount of water that can be recharged at the time point, 104 m 3 ; represents the amount of water that can be recharged at the time point; represents the minimum amount of water that satisfies the power generation or water supply requirement, 104 m 3 ; represents the amount of water that has been pre-released by the power plant before the time point, 104 m 3 ; Wherein: （9）； In the formula: represents the minimum flow rate that meets the power generation or water supply requirements, m 3 / s; represents the water and electricity storage time of the power station; Step 3.3, determining the pre-discharge amount in stages; The determination of the pre-discharge amount is related to the incoming water amount: when the incoming water amount is small, the pre-discharge is determined according to the rechargeable water amount; when the incoming water amount is large, the discharge amount is increased step by step according to the full-load discharge flow of the hydropower station group, the water abandonment is reduced, and if the incoming water continues to increase, the discharge is further increased according to the possible incoming water; the incoming water amount is determined according to the rechargeable water amount and the relationship between the pre-discharge water amount and the minimum full-load pre-discharge water amount, and the formula is: （10）； When formula (10) is not established, go to step 3.3.1; when formula (10) is established, go to step 3.3.2; Step 3.3.1, pre-discharge according to the rechargeable water amount; When formula (10) is not established, the pre-discharge amount is calculated according to the rechargeable water amount, to ensure that even if the forecast fails, the inflow amount can ensure that the reservoir water level is recharged to the water level before pre-discharge; Step 3.3.2, pre-discharge according to the full-load flow of the cascade hydropower station group; When formula (10) is established, the pre-discharge flow is determined according to the full-load flow of the power station.

2. The step-by-step pre-discharge scheduling method for a cascade hydropower station group according to claim 1, characterized in that, In step 1, the calculation formula of the possible inflow is: （1）； In the formula: is the current time; is the possible inflow under the forecast uncertainty, million m 3 ; is the possible net rainfall, mm; A is the watershed area, km 2 ; is the possible outflow, million m 3 .

3. The step-by-step pre-discharge scheduling method for a cascade hydropower station group according to claim 2, characterized in that, The calculation steps of each part of the possible inflow are as follows: Step 1.1, determining the rainfall forecast error distribution; Selecting a rainfall forecast product, according to historical statistical information, classifying according to rainfall standards, and determining the forecast error distribution under different forecast levels; Step 1.2, determining the net rainfall forecast error distribution; According to the net rainfall forecast results of historical floods by the hydrological model, the net rainfall forecast error distribution of the selected hydrological model is determined; Step 1.3, calculating the possible net rainfall; The possible incoming water is calculated from the fallen rain of the current rainfall and the predicted rainfall; wherein the predicted rainfall amount considering the prediction uncertainty is determined according to the prediction error distribution determined in step 1.1, and the rainfall amount that will occur with a certain probability is the possible rainfall amount, and the certain probability is in the range of (0, 100%]; the uncertainty in the process from rainfall to net rain is also determined according to the net rain prediction error distribution to determine the net rain amount that will occur with a certain probability, and the certain probability is in the range of (0, 100%]; and the calculation formula of the possible net rain amount is: （2）； （3）； wherein: is the current time; is the forecasted rainfall at the current time; is the possible rainfall at the forecasted magnitude at the current time, mm; is the forecasted rainfall at the current time; is the actual rainfall inverse cumulative distribution function at the current time; is the confidence probability of the rainfall forecast uncertainty at the current time; is the forecasted rainfall at the current time; is the rainfall magnitude at the current time; is the forecasted rainfall at the current time; is the possible net rainfall at the current time, mm; is the forecasted rainfall at the current time; is the cumulative precipitation at the current time, mm; is the forecasted net rainfall by inputting the precipitation and the forecasted rainfall into the hydrological model, mm; is the net rainfall forecast error inverse cumulative distribution function; is the confidence probability of the net rainfall forecast uncertainty. Step 1.4, calculating the possible backwater amount; According to the existing watershed recession curve or hydrological model, the current possible recession amount is determined ; （4）； In the formula: is the residual discharge at the end of the current forecast period, 10 4 m 3 ; represents the forecasted discharge process, which is obtained through the basin discharge curve or hydrological model; is the forecast period considering the forecast of rainfall and flood, ; is the reservoir recharge time of the hydropower station.

4. The step-by-step pre-discharge scheduling method for a cascade hydropower station group according to claim 3, characterized in that, In step 2, the conditions met in the process refer to one of the following two conditions, i.e., starting pre-discharge; the two conditions are as follows: Condition 1: there is water abandonment under the conventional regulation scheme; When the cascade hydropower station group is regulated by the conventional regulation mode, if there is water abandonment in any power station, i.e., the time outflow is greater than the full-load flow, the power station starts pre-discharge; the condition 1 is judged as shown in formula (5): （5） In the formula: is the future time; is the power plant dispatch outflow at time m 3 / s; is the number of power plants in the cascade; is the outflow considering full-load of the first power plant, m 3 / s; Condition 2: the highest flood regulating water level exceeds the set water level in the conventional scheduling mode; In the conventional scheduling mode, if the highest flood regulating water level exceeds the set highest water level, the power station starts pre-discharge, and the set highest water level is the high flood control water level or the farmland compensation water level or the resettlement water level; the judgment formula is shown in formula (6): （6）； In the formula, is the current time; is the power station is the water level at the time, m; is the set maximum water level, m.

5. The step-by-step pre-discharge scheduling method for a cascade hydropower station group according to claim 1, characterized in that, In step 3.3.1, the pre-discharge amount is calculated according to the rechargeable water amount, and the specific process is as follows: Considering the comprehensive flood control and benefit, the forecast error can still be completely recharged to the water level at the beginning of pre-discharge, and the water amount to be pre-discharged is calculated according to formula (11): （11）； In the formula: is water discharge amount at the time, 10,000 m 3 ; The power station needs to discharge the pre-discharge water volume within the effective pre-discharge time According to formula (12), the pre-discharge flow is calculated （12）； wherein: is the pre-discharge flow rate at the moment, m 3 / s; denotes the effective pre-discharge time.

6. The step-by-step pre-discharge scheduling method for a cascade hydropower station group according to claim 1, characterized in that, In step 3.3.2, the pre-discharge flow is determined according to the full-load flow of the hydropower station, and the specific process is as follows: Step 3.3.2.1, the full-load flow of the hydropower station is sorted in ascending order; Step 3.3.2.2, it is judged whether the water level of the hydropower station can exceed the set highest water level; When the hydropower station According to the full discharge, it is judged whether the highest water level is likely to exceed the set highest water level , the hydropower station forecast inflow process is , the outflow is The full discharge of the hydropower station , the occupied maximum reservoir capacity of the power station is calculated according to formula (13), formula (14) And the highest flood control water level : （13）； （14）； wherein: is the maximum reservoir capacity that can be occupied during the flood regulation process, million m 3 ; is the reservoir capacity at the current time of the power station, million m 3 ; is the maximum water level that can be reached by the hydropower station, m; is the reservoir capacity-water level relationship of the hydropower station; It is judged whether the current water level of the hydropower station can exceed the set highest water level, that is, whether formula (15) is established; （15）； Step 3.3.2.

3. When formula (15) is not established, the power station pre-releases according to the full-load discharge flow of the hydropower station to reduce the abandoned water, and the pre-release flow at the time is valued according to formula (16). Step 3.3.2.

3. When formula (15) is not established, the power station pre-releases according to the full-load discharge flow of the hydropower station to reduce the abandoned water, and the pre-release flow （16）； Step 3.3.2.4, when formula (15) is established, the hydropower station needs to additionally discharge water on the basis of pre-discharging according to the full discharge flow; the water quantity that needs to be additionally discharged equals the storage capacity corresponding to the excess part that is additionally discharged, and the value of the pre-discharge flow at the moment is calculated and updated according to the water quantity that is additionally discharged , , , The calculation is shown in formula (17) and formula (18) respectively: （17）； （18）； In the formula: is the water volume that needs to be further pre-released on the full release basis, 104m3 3 ; is the reservoir capacity corresponding to the set maximum water level, 104m3 3 ; Z high is the set maximum water level; Step 3.3.2.5, when there is a larger full-flow rate, determine whether the larger full-flow rate is exceeded, i.e., whether equation (19) is true; （19）； When formula (19) is established, take , i.e. , repeat steps 3.3.2.2~3.3.2.5; when formula (19) is not established, perform step 3.4; Step 3.4, limiting the pre-discharge flow according to the safety discharge amount and the set lowest water level; The pre-discharge should not threaten the flood control safety, and is limited according to the safe discharge of the hydropower station or the guaranteed discharge of the downstream river ; when formula (20) is established, The pre-discharge flow at the moment According to the value of formula (21): （20）； （21）； In the formula: is the safe discharge flow of the hydropower station or the guaranteed flow of the downstream river channel, m 3 / s; is a coefficient, and the value range is ; The pre-discharge water level is not lower than the set minimum water level ; when formula (22) is established, The pre-discharge flow at the moment According to formula (23): （22）； （23）； In the formula: m is the set maximum water level.

7. A cascade pre-discharge scheduling system for a cascade hydropower station group, characterized in that, The cascade hydropower station group hierarchical pre-discharge scheduling system comprises: A possible inflow determination module for determining possible inflow; A pre-discharge timing determination module for determining the pre-discharge timing of the power station; the pre-discharge timing determination module comprises two sub-modules: sub-module 1 is used to judge whether the power station can produce waste water in the conventional scheduling mode; and sub-module 2 is used to judge whether the water level of the power station can exceed the set water level in the conventional scheduling mode; A pre-discharge amount determination module for determining the pre-discharge amount of the power station; the pre-discharge amount determination module comprises four sub-modules: sub-module 1 is used to calculate the rechargeable water amount, sub-module 2 is used to calculate the effective pre-discharge time, sub-module 3 is used to determine the pre-discharge amount hierarchically, and sub-module 4 is used to limit the pre-discharge flow according to the safety discharge amount and the set lowest water level.

8. A cascade pre-discharge scheduling device for a cascade hydropower station group, characterized in that, The cascade hydropower station group hierarchical pre-discharge scheduling method of any one of claims 1-6 is implemented by the cascade hydropower station group hierarchical pre-discharge scheduling device, and the cascade hydropower station group hierarchical pre-discharge scheduling device is specifically an execution equipment comprising a memory and a processor, the memory is used to store a computer program, the processor is coupled with the memory, and the computer program is run to execute the cascade hydropower station group hierarchical pre-discharge scheduling method.

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