A method for calculating the blocking condition of pumped storage power station units based on built power stations

Abstract

The application provides a calculation method for blocked condition of pumped storage power station unit based on built power station, and relates to the technical field of water conservancy and hydropower engineering. The application analyzes the influence of rated water head, continuous full-load hours and operation water level of built power station on the blocked condition of pumped storage unit, and calculates the blocked condition and loss of pumped storage power station unit according to basic water energy parameters. According to the formula provided by the application, the application can provide reference for site selection of pumped storage power station using built reservoir in the future, so as to facilitate the selection of upper reservoir site in a suitable range and avoid the influence of the selection of rated water head in power station design due to the occurrence of the blocked condition of unit. In addition, the application can calculate the loss of blocked condition in advance when designing the pumped storage power station using built reservoir in the future, although the blocked condition of unit occurs in the actual situation, so as to facilitate comparison and analysis, and select suitable reservoir site and rated water head and other water energy parameters.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering technology, specifically a method for calculating the obstruction conditions of pumped storage power station units based on existing power stations. Background Technology

[0002] Pumped storage power stations are crucial for addressing the randomness, volatility, and uncertainty of new energy output and ensuring the safe and stable operation of the power grid. However, conventional pumped storage power station site resources are limited, restricting development scale. Pumped storage power stations utilizing existing reservoir power stations have significant advantages such as short construction period, rapid commissioning, and strong regulation capacity, and are also moderately economical. They are of great practical significance for addressing power and peak-shaving capacity gaps.

[0003] Ensuring stable operation of the generating units is a crucial consideration in the design of pumped storage power stations. Besides the inherent characteristics of the units themselves, the selection of rated head, continuous full-load hours, and operating water level during the planning and design phase are all important parameters affecting unit operation. The selection of these parameters impacts the power station's engineering investment and power generation efficiency. For example, a higher rated head allows for greater energy storage for the same volume of water. This is particularly important for pumped storage power stations built using existing hydropower stations. The operation of a pumped storage power station must take into account the impact of water level fluctuations in the existing hydropower station. If the water level fluctuations in the existing hydropower station are significant, the operation of the pumped storage power station may experience prolonged periods of obstruction within the large fluctuation range. Therefore, pumped storage power stations built on existing power stations need to consider the effects of rated head, continuous full-load hours, and operating water level in advance to minimize the occurrence of power output obstruction while ensuring the safe and stable operation of the units.

[0004] Currently, obstruction calculations for pumped-storage units typically involve stratified energy storage analysis under predetermined reservoir conditions and specific head parameters. This means analyzing obstruction scenarios with all parameters fixed and selecting parameters such as rated head based on the obstruction situation. However, during the planning and design process, previous calculation methods cannot analyze obstruction scenarios for pumped-storage units when specific parameters are uncertain. Therefore, they cannot guide pumped-storage unit site selection and design in the initial planning stages. If obstruction is severe, calculations can only be performed after selecting parameters within the feasible range of the actual construction area.

[0005] A search revealed that current literature lacks formulas for calculating the obstruction conditions and obstruction losses of pumped storage units based on rated head, continuous full-load operating hours, and operating water level of existing power stations. Summary of the Invention

[0006] To address the current lack of formulas for calculating the obstruction conditions and losses of pumped storage units based on the absence of rated head, continuous full-load operating hours, and operating water level of existing power stations, this invention proposes a method for calculating the obstruction conditions of pumped storage power station units based on existing power stations.

[0007] The present invention achieves its objective by employing the following technical solution:

[0008] A method for calculating the obstruction situation of pumped storage power station units based on existing power stations analyzes the impact of rated head, continuous full-load hours, and operating water level of existing power stations on the obstruction situation of pumped storage units. Based on basic hydroelectric parameters, the obstruction situation and obstruction losses of pumped storage power station units can be calculated. The method includes the following steps:

[0009] Step 1: Obtain design water level, operational data, and reservoir capacity curve data for existing power stations. Obtain design data for pumped storage power stations.

[0010] Step 2: Determine the K value of the unit corresponding to different water heads and the ratio of the maximum head to the minimum head of the pump-turbine.

[0011] Step 3: Analyze the relationship between factors affecting the stable operation of the unit and the obstruction situation of the pumped storage unit.

[0012] Step 4: Calculate the maximum and minimum normal water level and dead water level of the upper reservoir.

[0013] Step 5: Calculation of feasible indicators for unit obstruction.

[0014] Step 6: If the unit is obstructed, calculate the unit's power loss.

[0015] The next step is to include the design water level of the existing power station, which includes the normal storage water level and the dead water level; the operation data, which includes the operating water level data; and the design data of the pumped storage power station, which includes the maximum and minimum head loss during power generation and the maximum pumping head increase.

[0016] The next step, step two, is to determine the K-value of the unit corresponding to different heads and the ratio of the maximum head to the minimum head of the pump-turbine:

[0017] The maximum head and minimum head ratio of the pump-turbine are based on reference values ​​from the U.S. Bureau of Reclamation manual, the "Design Code for Pumped Storage Power Stations" (NB / T 10072), and domestic and international practical engineering experience. The limits for the maximum head and minimum head ratio of the pump-turbine are shown in Table 1.

[0018] Table 1 - Limits for the Ratio of Maximum Head to Minimum Head of Pump-Turbine

[0019] Hpmax range (m) 100 150 200 250 300 350 400 450 Limit 1.4 1.35 1.33 1.3 1.28 1.25 1.22 1.2 Hpmax range (m) 500 550 600 650 700 750 800 Limit 1.18 1.16 1.15 1.14 1.12 1.1 1.05

[0020] The further step, step three, involves analyzing the relationship between factors affecting the stable operation of the unit and the obstruction situation of the pumped-storage unit:

[0021] Among the hydropower parameters, the factors that affect the stable operation of the unit are usually the ratio of the turbine's maximum head to its minimum head, the head characteristic coefficient, the rated head, and the number of consecutive full-load hours.

[0022] (1) Maximum head and minimum head ratio of the turbine

[0023] For pumped storage power stations, the head and head of the pump turbine should not be too large due to the limitations of the pump operating conditions. The head variation has little impact on the operation of the turbine, but in the pump operating conditions, the guide vane adjustment effect is small and the high efficiency range is narrow. Excessive head variation will lead to a sharp decrease in efficiency, strong vibration, instability and failure to pump water [7]. The formula for calculating the maximum head and minimum head of the turbine is as follows:

[0024]

[0025] In the formula: H p,max H t,min These represent the maximum pumping head and minimum head for power generation of a pumped storage power station, respectively; Z up,n Z up,d These are the normal water level and dead water level of the upper reservoir, respectively; Z low,n Z low,d These are the normal water level and dead water level of the lower reservoir, respectively; f p,max f t,max These are the maximum head loss under pumping conditions and the maximum head loss under power generation conditions, respectively.

[0026] (2) Head characteristic coefficient

[0027] The selection of the rated head needs to consider the stability of the unit's operation. A lower rated head can better meet the system's peak-shaving needs for the power plant, but it will affect the safe and stable operation of the unit. Based on past engineering experience, the rated head H of the power plant unit has been analyzed. r The relationship between the hydroelectric head characteristic coefficient K and the power station head is expressed by the following formula:

[0028]

[0029] In the formula: H r The rated head of the unit; H t,max The maximum head under power generation conditions; f t,min This represents the minimum head loss under power generation conditions. K is the head characteristic coefficient. When K>0.5, it indicates that the rated head is higher than the arithmetic mean head. When K<0.5, it indicates that the rated head is lower than the arithmetic mean head. A higher K value is beneficial to the safe and stable operation of the unit.

[0030] (3) Rated head

[0031] Even when the unit operates without obstruction, the impact of the rated head must be considered. A higher rated head ensures the safe and stable operation of the unit, but an excessively high rated head can restrict the unit's power generation capacity. Therefore, the following formula is proposed for an unobstructed pumped-storage unit:

[0032]

[0033] In the formula: F r For the installed capacity of the power plant; H t The head during the power generation period of the pumped storage power station; F t For the current power generation output of the pumped storage power station, when H t ≥H r At that time, the power output equals the installed capacity, when H t <H r When the power output is lower than the installed capacity, it indicates that the unit's operation is obstructed.

[0034] (4) Continuous full-load hours

[0035] For the design of pumped storage power stations, equation (2) has already proposed the scenario where the unit operates without obstruction. However, it is still necessary to analyze the time during which the unit operates without obstruction based on this equation, in order to comprehensively analyze the obstruction scenario and power generation efficiency. Therefore, the formula for the continuous full-load hours of a pumped storage power station is proposed as follows:

[0036]

[0037] In the formula: T m T x These represent the design full-capacity operating hours and calculated full-capacity operating hours of the pumped storage power station, respectively; △H represents the water level fluctuation; Z up,n The normal water level H of the upper reservoir p f is the actual operating water level of the lower reservoir at frequency p; t This is for head loss during power generation.

[0038] The next step, step four, involves calculating the maximum and minimum normal water levels and dead water levels in the upper reservoir:

[0039] The minimum dead water level and maximum normal water level of the upper reservoir can be derived from the formulas for the maximum head and minimum head ratio of the turbine and the head characteristic coefficient:

[0040] Z up,d ≥Z low,n +f t,max +[K*(f p,max +f t,min )+H r ] / (1-K+K*Rh)

[0041] Z up,n ≤Z low,d +[Rh*(H r +K*f t,max )+(K-1)*f p,max ] / (1-K+K*Rh)

[0042] The maximum dead water level and minimum normal water level of the upper reservoir can be derived from the formulas for the head characteristic coefficient and the number of consecutive full-load hours:

[0043] Z up,d ≤[K*(Z up,n,max -Z low,d -f t,min )-(1-K)(Z low,n +f t,max )-H r ] / (K-1)

[0044]

[0045] The next step, step five, is to calculate the feasibility indicators for unit disruption:

[0046] In practice, the calculated water level must satisfy the actual relationships, namely, the maximum normal storage level of the upper reservoir must be greater than the minimum normal storage level of the upper reservoir, the maximum dead water level of the upper reservoir must be greater than the minimum dead water level of the upper reservoir, and the maximum normal storage level of the upper reservoir must be greater than the minimum dead water level of the upper reservoir, in order to indicate that the project actually exists. If these conditions are not met, it indicates that the pumping and storage is obstructed; if they are met, it indicates that the pumping and storage operation is not obstructed. Therefore, a feasibility index f1 is defined, with the following formula:

[0047] f1=min(Z up,n,max -Z up,n,min Z up,low,max -Z up,low,min Z up,n,max -Z low,n,min )

[0048] When f1 < 0, it indicates that a solution does not exist and the unit cannot operate at full capacity. To facilitate the representation of feasible parameter segments, the feasible indices are normalized, and 0 is included in the normalization range.

[0049] In the next step, if the unit is obstructed, calculate the unit's power loss:

[0050] In actual operation, the fluctuation range of the upper reservoir during the entire power generation process of a pumped storage power station is the difference between the normal water level and the dead water level. The water level change process is relatively uniform, so the average water level can be used to calculate the average output. The power loss function f2 is defined as follows:

[0051]

[0052] When the unit is unobstructed, the calculated average output is the installed capacity of the power station. When the feasible index f1 < 0, the unit is obstructed and the average output is lower than the installed capacity of the power station.

[0053] Beneficial effects

[0054] Compared with existing technologies, this invention, through its analysis in step three of the relationship between the turbine's maximum head and minimum head ratio, head characteristic coefficient, rated head, and continuous full-load hours on unit operation, can derive the boundary conditions for the maximum and minimum normal water levels and dead water levels of the upper reservoir in step four. The calculation formulas for the maximum and minimum normal water levels and dead water levels of the upper reservoir in step four, and the proposed feasible indicators in step five, enable this invention to provide a reference for future site selection of pumped storage power stations utilizing existing reservoirs. This facilitates the selection of upper reservoir sites within a suitable range and avoids the impact of unit obstruction on the selection of rated head in power station design. Furthermore, the unit power loss function in step six of this invention allows for the calculation of obstruction losses in advance during the design of future pumped storage power stations utilizing existing reservoirs, even in the event of actual unit obstruction. This facilitates comparative analysis and the selection of appropriate reservoir sites and rated head, among other hydropower parameters. Attached Figure Description

[0055] Appendix Figure 1 A graph showing the relationship between feasible indicators and rated head;

[0056] Appendix Figure 2 A graph showing the relationship between feasible indicators and the number of consecutive full-load hours;

[0057] Appendix Figure 3 A graph showing the relationship between feasible indicators and rated head;

[0058] Appendix Figure 4 This is a diagram showing the relationship between the rated head and the operating water level of the lower reservoir.

[0059] Appendix Figure 5 This is a graph showing the relationship between power loss and operating water level. Detailed Implementation

[0060] To further understand the content, features, and effects of this invention, the following embodiments are provided for further explanation, but they should not be construed as limiting the invention.

[0061] Example: Taking a pumped storage power station as an example, this pumped storage power station has an installed capacity of 1400MW, daily regulation capability, and a continuous full-load operation time of 6 hours. Its upper reservoir has a normal water level of 1116m, a dead water level of 1104m, and a regulating capacity of 575m³. 3The lower reservoir is an existing hydroelectric power station. The normal water level of the lower reservoir is 475m, the dead water level is 425m, the water level fluctuation is 50m, and the installed capacity of the power station is 1020MW. The maximum and minimum head losses for power generation are set at 10.1m and 0.1m, respectively. The maximum pumping head increase is 5.3m. The pumped storage power station has a head operating range of 618.84m to 690.88m, an arithmetic mean head of 654.86m, and a rated power generation flow of 253m3 / s. The project's tasks include system peak shaving, valley filling, energy storage, frequency regulation, phase regulation, and emergency backup.

[0062] The calculation method for the obstruction situation of pumped storage power station units based on existing power stations will be applied to this pumped storage power station. The specific implementation steps are as follows:

[0063] Step 1: Obtain design water level, operational data, and reservoir capacity curve data for existing power stations. Obtain design data for pumped storage power stations.

[0064] Step 2: Determine the K value and pumping ratio of the unit corresponding to different heads: The maximum head and minimum head of the pump turbine are based on the reference values ​​in the U.S. Bureau of Reclamation manual, the "Design Code for Pumped Storage Power Stations" (NB / T 10072), and domestic and foreign practical engineering experience. The limit values ​​of the ratio of maximum head to minimum head of the pump turbine are shown in Table 1.

[0065] Step 3: Analyze the relationship between factors affecting the stable operation of the unit and the obstruction of the pumped storage unit. Among the hydropower parameters, the factors affecting the stable operation of the pumped storage power station unit are usually the ratio of the maximum head to the minimum head of the turbine, the head characteristic coefficient, the rated head, and the number of consecutive full-load hours.

[0066] Step 4: Calculate the maximum and minimum normal water level and dead water level of the upper reservoir.

[0067] Minimum dead water level and maximum normal water level of the upper reservoir:

[0068] Z up,d ≥Z low,n +f t,max +[K*(f p,max +f t,min )+H r ] / (1-K+K*Rh)

[0069] Z up,n ≤Z low,d +[Rh*(H r +K*f t,max )+(K-1)*f p,max ] / (1-K+K*Rh)

[0070] Maximum dead water level and minimum normal water level of the upper reservoir:

[0071] Z up,d≤[K*(Z up,n,max -Z low,d -f t,min )-(1-K)(Z low,n +f t,max )-H r ] / (K

[0072] -1)

[0073]

[0074] The following explains the different rated heads:

[0075] The pumped storage power station assumes that the rated head increases gradually from 150m to 750m in 50m intervals, the maximum continuous full-load hours are 6.3h, the continuous full-load hours are 3h, the lower reservoir operating water level is taken as the average water level of 450m, and the results of the maximum and minimum normal water level and dead water level of the upper reservoir when the computer group is not obstructed are shown in Table 2.

[0076] Table 2 - Maximum and minimum normal water level and dead water level in the upper reservoir when the unit is operating without obstruction.

[0077]

[0078] Step 5: Calculation of feasible indicators for unit obstruction.

[0079] Specifically, it includes:

[0080] The calculated water level must satisfy the actual relationships, namely, the maximum normal water level of the upper reservoir must be greater than the minimum normal water level of the upper reservoir, the maximum dead water level of the upper reservoir must be greater than the minimum dead water level of the upper reservoir, and the maximum normal water level of the upper reservoir must be greater than the minimum dead water level of the upper reservoir for the project to be considered to actually exist. If these conditions are not met, it indicates that the pumping and storage is obstructed; if they are met, it indicates that the pumping and storage operation is not obstructed. Therefore, a feasibility index f1 is defined, with the following formula:

[0081] f1=min(Z up,n,max -Z up,n,min Z up,low,max -Z up,low,min Z up,n,max -Z low,n,min )

[0082] When f1 < 0, it indicates that a solution does not exist and the unit cannot operate at full capacity. To facilitate the representation of feasible parameter segments, the feasible indices are normalized, and 0 is included in the normalization range.

[0083] The following explanation uses different rated heads from step four as examples:

[0084] Based on the calculation results of the maximum and minimum normal water levels and dead water levels in step four, feasible indicators are calculated and normalized. The feasible indicators and standards are then normalized. Table 3 shows the results of the feasible indicators and whether the unit is obstructed. A diagram showing the relationship between rated head and unit obstruction is also provided. Figure 1 The results show that only when the reservoir's operating water level is 450m and the pumping head is between 300m and 650m can the unit achieve a continuous full-load utilization of 3 hours without obstruction. This calculation method can also analyze feasible indicators for different continuous full-load operation hours and different reservoir operating water levels. The relationship between continuous full-load operation hours and unit obstruction, and the relationship between the actual operating water level of the existing reservoir and unit obstruction, are shown in the following figures: Figure 2 and Figure 3 The obstruction time can also be analyzed based on the actual operation of the lower reservoir. The unobstructed time diagram for different rated head conditions is shown below. Figure 4 .

[0085] Table 3 - Calculation Results of Feasibility Indicators

[0086]

[0087]

[0088] Step 6: If the unit is obstructed, calculate the unit's power loss.

[0089] Specifically, this includes: calculating average power output using average water level, and defining the power loss function f2, as shown in the following formula:

[0090]

[0091] When the unit is unobstructed, the calculated average output is the installed capacity of the power station. When the feasible index f1 < 0, the unit is obstructed and the average output is lower than the installed capacity of the power station.

[0092] The following is an example of the result from step five:

[0093] Based on the feasibility index calculation results from step five, when the operating water level is 450m, the continuous full-load utilization hours are 3 hours, and there is obstruction at the 700m rated head, the rated head is set to 700m, and the continuous full-load utilization hours are set to 3 hours. The power loss calculation results for different lower reservoir operation are shown in Table 4. The diagram showing the power loss due to obstruction at the lower reservoir operating water level is shown below. Figure 5The results show that when the reservoir's operating water level is at the dead water level of 425m, the pumped-storage units can operate continuously at full capacity for 3 hours without obstruction. However, as the reservoir's operating water level gradually increases to 450m, the units begin to experience obstruction, unable to maintain continuous full capacity operation for 3 hours. The average power output is 1396.6MW, with a power loss of 0.25%. When the reservoir's operating water level gradually increases to the normal storage level of 475m, the obstruction becomes increasingly severe, with an average output of 1347.7MW and a power loss of 3.74%.

[0094] Table 4 - Calculation of Power Loss at Different Lower Reservoir Operating Water Levels

[0095]

[0096]

[0097] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for calculating the obstruction conditions of pumped storage power station units based on existing power stations, characterized in that: Includes the following steps: Step 1: Obtain the design water level, operation data, reservoir capacity curve data of the existing power stations, and the design data of the pumped storage power stations; Step 2: Determine the K value of the unit corresponding to different water heads and the ratio of the maximum head to the minimum head of the pump-turbine; Step 3: Analyze the relationship between factors affecting the stable operation of the unit and the obstruction situation of the pumped-storage unit; Step 4: Calculate the maximum and minimum normal water level and dead water level of the upper reservoir; Step 5: Calculation of feasible indicators for unit obstruction; Step Six: If the unit is obstructed, calculate the unit's power loss; Step three involves analyzing the relationship between factors affecting the stable operation of the unit and the obstruction situation of the pumped-storage unit. The method is as follows: Among the hydropower parameters, the factors affecting the stable operation of the unit are the ratio of the turbine's maximum head to its minimum head, the head characteristic coefficient, the rated head, and the number of consecutive full-load operating hours. The calculation formulas for each factor are as follows: (1) The formula for calculating the ratio of the maximum head to the minimum head of the turbine is as follows: ； In the formula: H p,max H t,min These represent the maximum pumping head and minimum head for power generation of a pumped storage power station, respectively; Z up,n Z up,d These are the normal water level and dead water level of the upper reservoir, respectively; Z low,n Z low,d These are the normal water level and dead water level of the lower reservoir, respectively; f p,max f t,max These are the maximum head loss under pumping conditions and the maximum head loss under power generation conditions, respectively. (2) The characteristic coefficient of the water head is calculated using the following formula: ； In the formula: H r The rated head of the unit; H t,max The maximum head under power generation conditions; f t,min The minimum head loss under power generation conditions; K is the head characteristic coefficient, when K>0.5 it indicates that the rated head is higher than the arithmetic mean head, when K<0.5 it indicates that the rated head is lower than the arithmetic mean head; (3) For the rated head, the following formula is proposed for the pumped storage unit without obstruction: ； In the formula: F r For the installed capacity of the power plant; H t The head during the power generation period of the pumped storage power station; F t This represents the power output of the pumped storage power station during the current period; when H t ≥H r At that time, the power output equals the installed capacity, when H t <H r When the power generation output is lower than the installed capacity, it indicates that the unit's operation is hindered. (4) The number of consecutive full-load hours is calculated using the following formula: ； In the formula: T m T x These represent the design full-capacity operating hours and calculated full-capacity operating hours of the pumped storage power station, respectively; △H represents the water level fluctuation; Z up,n The normal water level H of the upper reservoir p f is the actual operating water level of the lower reservoir at frequency p; t For head loss during power generation; Step four, the calculation of the maximum and minimum normal water levels and dead water levels in the upper reservoir, is performed as follows: The minimum dead water level and maximum normal water level of the upper reservoir can be derived from the formulas for calculating the maximum head and minimum head ratio of the turbine and the formula for calculating the head characteristic coefficient. ； ； The maximum dead water level and minimum normal water level of the upper reservoir are derived from the formulas for calculating the head characteristic coefficient and the number of consecutive full-load hours: ； ； Step five involves calculating the feasibility indicators for unit obstruction: Define feasible metrics The formula is as follows: ； when When the value is less than 0, it indicates that a solution does not exist and the unit cannot generate full power. In step six, if the unit is obstructed, calculate the unit's power loss: Define the power loss function The formula is as follows: ； When the generating units are unobstructed, the calculated average output is the installed capacity of the power station. (This is based on feasible indicators.) When the value is less than 0, the unit is experiencing obstruction, and the average output is lower than the installed capacity of the power station.

2. The method for calculating the obstruction situation of pumped storage power station units based on existing power stations according to claim 1, characterized in that: In step one, the design water level of the existing power station includes the normal storage water level and the dead water level; the operation data includes the operating water level data; and the design data of the pumped storage power station includes the maximum and minimum head loss during power generation and the increase in the maximum pumping head.

3. The method for calculating the obstruction situation of pumped storage power station units based on existing power stations according to claim 2, characterized in that: Step two involves determining the K-value of the unit corresponding to different heads and the ratio of maximum head to minimum head of the pump-turbine. The ratio of maximum head to minimum head of the pump-turbine is determined by combining reference values ​​from the U.S. Bureau of Reclamation manual, the "Design Code for Pumped Storage Power Stations" NB / T 10072, and domestic and international practical engineering experience. The limits for the maximum head to minimum head ratio of the pump-turbine are as follows: when Hpmax ranges from 100 to 800 m, the corresponding limits are 1.4, 1.35, 1.33, 1.3, 1.28, 1.25, 1.22, 1.2, 1.18, 1.16, 1.15, 1.14, 1.12, 1.1, and 1.05, respectively.

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