Optimal control method for load rejection water hammer pressure of pumped storage power station with constant-variable speed unit

Abstract

The application discloses a kind of optimal control methods of load rejection water hammer pressure of fixed-speed and variable-speed unit containing pumped storage power station.The application is first based on the full characteristic curve of pump-turbine, and the efficiency of variable-speed unit is optimized to determine the highest efficiency of variable-speed unit and the optimal speed corresponding thereto;Then, the transition process mathematical model of water delivery and power generation system of pumped storage power station containing fixed-speed and variable-speed unit is established, and by using different guide vane closing law for fixed-speed unit and variable-speed unit, the pareto frontier with the maximum pressure of spiral case and the minimum pressure of draft tube as optimization objective under different control schemes is calculated;Finally, the maximum pressure of spiral case and the minimum pressure of draft tube are normalized, and a multi-objective evaluation function of transient characteristics is established, and the optimal control scheme is selected from the pareto frontier.The method of the application can effectively improve the water hammer pressure extreme value caused by hydraulic interference between fixed-speed and variable-speed units, improve the operation stability and safety of power station, and has good engineering adaptability.

Description

Technical Field

[0001] This invention relates to the field of water conservancy and hydropower engineering, specifically to an optimized control method for the load shedding water hammer pressure of a pumped storage power station containing a constant-speed and variable-speed unit. Background Technology

[0002] With the rapid development of renewable energy and the increasing demand for regulation capacity in power systems, pumped storage power stations, as an important component of large-scale energy storage technology, play an irreplaceable role in grid peak shaving, frequency regulation, and emergency backup. However, traditional constant-speed pumped storage units suffer from narrow operating range, low weighted efficiency, and limited regulation capacity when facing complex operating conditions. In recent years, variable-speed pumped storage technology, with its flexible operating characteristics, higher energy conversion efficiency, and stronger adaptability to operating conditions, has become a key research and application area in the field of water conservancy and hydropower engineering due to its significant engineering value in improving grid stability, optimizing energy utilization efficiency, and promoting the consumption of renewable energy.

[0003] Although variable-speed turbines offer numerous advantages in terms of operational performance and regulation quality, the high cost of their electrical equipment limits their large-scale application in production practice. Therefore, to optimize investment costs while ensuring regulation performance, some pumped-storage power stations adopt a configuration of different turbines operating on the same pipe, forming a unit structure with conventional fixed-speed turbines as the main component and variable-speed turbines as a supplement. This configuration retains the lower cost advantage of fixed-speed turbines while enhancing the power station's regulation capability and operational efficiency under complex operating conditions by introducing variable-speed turbines, providing a feasible solution for balancing the economy and regulation performance of pumped-storage power stations.

[0004] Although numerous studies have explored the control optimization of load shedding transition processes in constant-speed pumped storage power stations and small-fluctuation transition processes in variable-speed units, research on the load shedding transition process in pumped storage power stations with a mixed arrangement of constant-speed and variable-speed units is relatively limited. Typically, the units in a constant-speed pumped storage power station operate symmetrically, meaning the operating parameters of the two units are identical. However, variable-speed units adjust their steady-state operating speed to maximize efficiency, resulting in differences in operating parameters such as speed, flow rate, and guide vane opening compared to constant-speed units. These differences make the hydraulic coupling between constant-speed and variable-speed units exceptionally complex, exacerbating water hammer pressure fluctuations during the unit transition process and threatening the operational safety of the pumped storage power station.

[0005] Therefore, there is an urgent need to invent an optimized control method for water hammer pressure in pumped storage power stations with constant-speed and variable-speed units under load shedding conditions, so as to provide a basis for the safe and stable operation of the power station. Summary of the Invention

[0006] An optimized control method for water hammer pressure in a pumped storage power station with constant-speed and variable-speed units under load shedding conditions, characterized by the following steps:

[0007] Step 1: Based on the full characteristic curve of the pump-turbine, optimize the efficiency of the variable speed unit to determine the highest efficiency and the corresponding optimal speed of the variable speed unit.

[0008] Step 2: Establish a mathematical model of the transient process of the pumped storage power station's water transmission and power generation system, which includes a constant-speed and variable-speed turbine unit. The mathematical model consists of a pressurized pipeline system and a pump-turbine unit system.

[0009] Step 3: Based on the numerical simulation model of the transient process in Step 2, by adopting different guide vane closing laws for constant speed units and variable speed units, calculate the Pareto front with the maximum pressure of the volute and the minimum pressure of the tailrace pipe as optimization objectives under different control schemes.

[0010] Step 4: Normalize the maximum pressure of the volute and the minimum pressure of the tailrace pipe to establish a comprehensive evaluation function for transient characteristics;

[0011] Step 5: Substitute the Pareto front scheme from Step 3 into the transient characteristic comprehensive evaluation function from Step 4, and determine the optimal control scheme by comparing the transient characteristic comprehensive evaluation function values ​​under different Pareto front schemes.

[0012] In step one, an improved Suter transform is used to process the full characteristic curve of the pump-turbine, and the data on the full characteristic curve is expressed by the following formula:

[0013]

[0014] WB=m1′(3) Where: x Z Let q1′ be the independent variable of the flow function and the torque function, and q1′ be the relative unit flow rate, where q1′ = Q. 11 / Q 11r Q 11 Q is the unit flow rate. 11r q is the rated unit flow rate; 1B ′ is the offset coefficient; n1′ is the relative unit rotational speed, n1′=N 11 / N 11r N 11 For unit rotational speed, N 11r The rated unit speed is m1′; the relative unit torque is m1′; WH is the flow rate function; WB is the torque function; m1′ = M 11 / M 11r M 11 M is the unit torque. 11r The rated unit torque; the subscript r indicates the rated value;

[0015] The expressions for the unit speed, unit flow rate, and unit torque of a water pump turbine are:

[0016]

[0017]

[0018] Where: n, D1, H T P, Q T These are the unit's rotational speed, impeller diameter, head, and output flow rate, respectively.

[0019] With the goal of maximizing unit efficiency, an efficiency optimization method based on the full characteristic curve is proposed. The specific steps are as follows:

[0020] (a) Input unit speed n is n min ;

[0021] (b) Assume the unit flow rate Q is Q assumed ;

[0022] (c) Based on the unit flow rate Q assumed The operating head H of the generating unit is obtained by considering the water levels of the upstream and downstream reservoirs and the head loss coefficient of the water transmission pipeline. T ;

[0023] (d) Based on the unit's operating head, flow rate, and rotational speed, calculate the unit's unit rotational speed N using equations (4) and (5). 11 and unit flow Q 11 ;

[0024] (e) x is calculated using equations (1) and (2). Z And WH, and then interpolate the flow function curve to obtain the opening τ;

[0025] (f) x obtained from step (e) Z And τ, interpolate the torque function curve to obtain WB, and then obtain the unit output according to equation (6);

[0026] (g) If the difference between the output and the target output is greater than the allowable error ε, then the reference flow rate Q is re-assumed based on the output deviation. assumed Then repeat step (b); if the difference between the output and the target output is less than ε, then end the loop calculation and proceed to step (h);

[0027] (h) Output the unit's speed, opening degree, efficiency, output, and flow rate;

[0028] (i) If the unit speed n <n max If n = n + Δ, then step (a) is repeated.

[0029] (j) By comparing the efficiency at different speeds, output the speed, opening degree, efficiency, output, and flow rate at the optimal efficiency.

[0030] In step two, the dynamic equation and continuity equation describing the pressurized pipeline of the elastic water body are as follows:

[0031]

[0032] In the formula: Q is the flow rate; A is the cross-sectional area of ​​the pipe; H is the piezometric head; x is the pipe coordinate; f is the friction coefficient; c is the water hammer wave velocity; and D is the pipe diameter.

[0033] The equation of motion for the water pump turbine rotor is:

[0034]

[0035] Where: m g The relative value of the generator's electromagnetic torque, m g =M g / M r M g M is the electromagnetic torque of the generator. r Rated shaft torque; n is the relative rotational speed; T a is the unit's inertial time constant; m is the relative value of the turbine shaft torque;

[0036] Equation (10) is the head balance equation for a water pump turbine, representing the head H. T With the volute manometer head H SC and tailrace pipe pressure gauge head H DT Relationship:

[0037]

[0038] In the formula: Q T For unit operating flow rate; A SC A is the cross-sectional area of ​​the volute; DT Let g be the cross-sectional area of ​​the tailrace pipe, and g be the acceleration due to gravity.

[0039] In step three, the maximum pressure of the spiral casing is a "lower is better" indicator, while the minimum pressure of the tailrace is a "higher is better" indicator. Taking a pumped storage power station with two constant-speed turbines and one variable-speed turbine as an example, the objective functions for the spiral casing and tailrace pressure are as follows:

[0040] MinF1=max{H Smax-1#FSU H Smax-2#FSU H Smax-VSU} (11)

[0041] MaxF2=min{H Dmin-1#FSU1 H Dmin-2#FSU HDmin-VSU In equation (12): H SMAX H represents the maximum pressure on the volute; Dmin This indicates the minimum pressure of the tailrace pipe; the subscripts 1#FSU, 2#FSU and VSU represent the 1# constant speed unit, the 2# constant speed unit and the variable speed unit, respectively; F1 indicates the maximum pressure of the spiral casing and F2 indicates the minimum pressure of the tailrace pipe.

[0042] Based on the mathematical model of the transient process in step two, the maximum pressure of the volute and the minimum pressure of the tailrace pipe of the unit under different control schemes are calculated. Then, by combining equations (11) and (12), the Pareto front scheme with the maximum pressure of the volute and the minimum pressure of the tailrace pipe as the optimization objectives is obtained.

[0043] In step four, the maximum pressure of the volute and the minimum pressure of the tailrace pipe are normalized using the maximum-minimum normalization method:

[0044]

[0045] The final comprehensive evaluation function for transient characteristics is as follows:

[0046] maxF object =w1F1′+w2F2′ (15)

[0047] In the formula: w1 and w2 are weighting coefficients, F1′ is the maximum pressure of the volute after normalization, and F2′ is the minimum pressure of the tailrace pipe after normalization; F 1-max and F 1-min These represent the maximum and minimum maximum volute pressures under different control schemes; F 2-max and F 2-min These represent the maximum and minimum tailrace pipe pressures under different control schemes; F object This represents the comprehensive evaluation function for transient characteristics.

[0048] In step five, the Pareto front scheme calculated in step three is substituted into equation (15) to obtain F. object Select the largest F object The corresponding control scheme is the optimal control scheme.

[0049] Beneficial Effects: This invention addresses the unfavorable hydraulic coupling effect between constant-speed and variable-speed turbine units under load shedding conditions. It provides an optimized control method for water hammer pressure in pumped-storage power stations with both constant-speed and variable-speed units under load shedding conditions. This method effectively reduces the extreme values ​​of water hammer pressure caused by hydraulic interference between constant-speed and variable-speed units, thereby improving the operational stability and safety of the power station. The method is simple to implement, has good engineering adaptability, and broad application prospects. Attached Figure Description

[0050] Figure 1This is a flowchart of the method of the present invention;

[0051] Figure 2 This is a schematic diagram of the water conveyance and power generation system layout of the pumped storage power station with constant-speed and variable-speed units as described in the embodiment.

[0052] Figure 3 This represents the Pareto front for the maximum pressure of the volute and the minimum pressure of the tailwater under different control schemes in this embodiment.

[0053] Figure 4 This example illustrates the fluctuation process of volute pressure and tailrace pressure under different typical control schemes. Figure 4 In the examples, (a) represents Scheme 1; (b) represents Scheme 20; and (c) represents Scheme 11. Detailed Implementation

[0054] The invention will now be further described with reference to the accompanying drawings.

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0056] This invention proposes an optimized control method for water hammer pressure in pumped storage power stations with constant-speed and variable-speed turbine units under load shedding conditions. The flowchart of this method is shown below. Figure 1 As shown, it mainly includes the following 5 steps.

[0057] Step 1: Based on the full characteristic curve of the pump-turbine, optimize the efficiency of the variable speed unit to determine the highest efficiency and the corresponding optimal speed of the variable speed unit.

[0058] Step 2: Establish a mathematical model of the transient process of the pumped storage power station water transmission and power generation system containing constant-speed and variable-speed units. The mathematical model consists of a pressurized pipeline system and a pump-turbine unit system.

[0059] Step 3: Based on the numerical simulation model of the transient process in Step 2, by adopting different guide vane closing laws for constant speed units and variable speed units, calculate the Pareto front with the maximum pressure of the volute and the minimum pressure of the tailrace pipe as optimization objectives under different control schemes.

[0060] Step 4: Normalize the maximum pressure of the volute and the minimum pressure of the tailrace pipe to construct a comprehensive evaluation function for transient characteristics;

[0061] Step 5: Substitute the Pareto front scheme from Step 3 into the transient characteristic comprehensive evaluation function from Step 4, and determine the optimal control scheme by comparing the transient characteristic comprehensive evaluation function values ​​under different Pareto front schemes.

[0062] In step 1, an improved Suter transform is used to process the full characteristic curve of the pump-turbine, and the data on the full characteristic curve are expressed by the following formula:

[0063]

[0064] WB=m1′ (3) where: is x Z Let q1′ be the independent variable of the flow function and the torque function, and q1′ be the relative unit flow rate, where q1′ = Q. 11 / Q 11r Q 11 Q is the unit flow rate. 11r q is the rated unit flow rate; 1B ′ is the offset coefficient; n1′ is the relative unit rotational speed, n1′=N 11 / N 11r N 11 For unit rotational speed, N 11r The rated unit speed is m1′; the relative unit torque is m1′; WH is the flow rate function; WB is the torque function; m1′ = M 11 / M 11r M 11 M is the unit torque. 11r The rated unit torque; the subscript r indicates the rated value;

[0065] The expressions for the unit speed, unit flow rate, and unit torque of a water pump turbine are:

[0066]

[0067]

[0068] Where: n, D1, H T P, Q T These are the unit's rotational speed, impeller diameter, head, and output flow rate, respectively.

[0069] With the goal of maximizing unit efficiency, an efficiency optimization method based on the full characteristic curve is proposed. The specific steps are as follows:

[0070] (a) Input unit speed n is n min ;

[0071] (b) Assume the unit flow rate Q is Q assumed ;

[0072] (c) Based on the unit flow rate Q assumed The operating head H of the generating unit is obtained by considering the water levels of the upstream and downstream reservoirs and the head loss coefficient of the water transmission pipeline. T ;

[0073] (d) Based on the unit's operating head, flow rate, and rotational speed, calculate the unit's unit rotational speed N using equations (4) and (5). 11 and unit flow Q 11 ;

[0074] (e) x is calculated using equations (1) and (2). Z And WH, and then interpolate the flow function curve to obtain the opening τ;

[0075] (f) x obtained from step (e) Z And τ, interpolate the torque function curve to obtain WB, and then obtain the unit output according to equation (6);

[0076] (g) If the difference between the output and the target output is greater than the allowable error ε, then the reference flow rate Q is re-assumed based on the output deviation. assumed Then repeat step (b); if the difference between the output and the target output is less than ε, then end the loop calculation and proceed to step (h);

[0077] (h) Output the unit's speed, opening degree, efficiency, output, and flow rate;

[0078] (i) If the unit speed n <n max If n = n + Δ, then step (a) is repeated.

[0079] (j) By comparing the efficiency at different speeds, output the speed, opening degree, efficiency, output, and flow rate at the optimal efficiency.

[0080] Specifically, the following uses a pumped-storage power station with constant-speed and variable-speed turbine units as an example to further illustrate this method. A schematic diagram of the power station layout is shown below. Figure 2 As shown, the rated speed is 500 r / min, and the variable speed operating range is 500 ± 8% r / min. The rated head is 665 m, and the rated output is 408.16 MW.

[0081] Based on the efficiency optimization method proposed above, the highest operating efficiency of the power station at rated head and rated output is 90.81%, and the corresponding optimal speed is 464.20 r / min.

[0082] In step 2, the dynamic equation and continuity equation describing the pressurized pipeline of the elastic water body are as follows:

[0083]

[0084]

[0085] In the formula: Q is the flow rate; A is the cross-sectional area of ​​the pipe; H is the piezometric head; x is the pipe coordinate; f is the friction coefficient; c is the water hammer wave velocity; and D is the pipe diameter.

[0086] The equation of motion for the water pump turbine rotor is:

[0087]

[0088] Where: m g The relative value of the generator's electromagnetic torque, m g =M g / M r M g M is the electromagnetic torque of the generator. r Rated shaft torque; n is the relative rotational speed; T a is the unit's inertial time constant; m is the relative value of the turbine shaft torque;

[0089] Equation (10) is the head balance equation for a water pump turbine, representing the head H. T With the volute manometer head H SC and tailrace pipe pressure gauge head H DT Relationship:

[0090]

[0091] In the formula: Q T For unit operating flow rate; A SC A is the cross-sectional area of ​​the volute; DT Let g be the cross-sectional area of ​​the tailrace pipe, and g be the acceleration due to gravity.

[0092] In step 3, the maximum pressure of the spiral casing is a "lower is better" indicator, while the minimum pressure of the tailrace is a "higher is better" indicator. Taking a pumped storage power station with two constant-speed turbines and one variable-speed turbine as an example, the objective functions for the spiral casing and tailrace pressure are as follows:

[0093] MinF1=max{H Smax-1#FSU H Smax-2#FSU H Smax-VSU} (11)

[0094] MaxF2=min{H Dmin-1#FSU1 H Dmin-2#FSU H Dmin-VSU In equation (12): H SMAX H represents the maximum pressure on the volute; Dmin The minimum pressure of the tailrace pipe is indicated by the subscripts 1#FSU, 2#FSU and VSU, which represent the 1# constant speed unit, the 2# constant speed unit and the variable speed unit, respectively. F1 represents the maximum pressure of the spiral casing and F2 represents the minimum pressure of the tailrace pipe.

[0095] Based on the transient process simulation model in step 2, the maximum pressure of the volute and the minimum pressure of the tailrace pipe under different control schemes are calculated. Then, by combining equations (11) and (12), the Pareto front with the maximum pressure of the volute and the minimum pressure of the tailrace pipe as the optimization objectives can be obtained.

[0096] Specifically, based on the actual operating conditions of the power station, the guide vane closing time T of the constant-speed unit was selected. F The guide vane closing time T of the variable speed unit is 20s-40s. V The Pareto front of the maximum pressure in the volute and the minimum pressure in the tailrace under different control schemes is calculated through numerical simulation within a range of 20-40 seconds and a step size of 1 second. Figure 3 As shown in Table 1.

[0097] Table 1. Pareto Fronts of Maximum Pressure in Volute and Minimum Pressure in Tailstream under Different Control Schemes

[0098]

[0099]

[0100] Depend on Figure 3 As shown in Table 1, numerical simulations of 441 control methods yielded 20 Pareto solutions. Theoretically, all of these solutions can be applied in practice. However, in real-world applications, power plant operators may struggle to accurately determine whether a particular solution is superior to others due to limited understanding of operational strategies when evaluating candidate solutions. Therefore, it is necessary to further construct a comprehensive evaluation function for transient characteristics to assist engineers in selecting the optimal control strategy.

[0101] In step 4, the maximum pressure of the volute and the minimum pressure of the tailrace pipe are normalized using the maximum-minimum normalization method:

[0102]

[0103] The final transient characteristic multi-objective function is as follows:

[0104] maxF object =w1F1′+w2F2′ (15)

[0105] Step four describes the use of a maximum-minimum normalization method to normalize the maximum pressure of the volute and the minimum pressure of the tailrace pipe:

[0106]

[0107] The final comprehensive evaluation function for transient characteristics is as follows:

[0108] maxF object =w1F1′+w2F2′ (15)

[0109] In the formula: w1 and w2 are weighting coefficients, which are taken as follows for this power station. and F1′ is the maximum pressure of the volute after normalization, and F2′ is the minimum pressure of the tailrace pipe after normalization; F 1-max and F 1-min These represent the maximum and minimum maximum volute pressures under different control schemes; F 2-max and F 2-min These represent the maximum and minimum tailrace pipe pressures under different control schemes; F object This represents the comprehensive evaluation function for transient characteristics.

[0110] In step 5, the Pareto front scheme calculated in step 3 is substituted into equation (15) to obtain F. object Select the largest F object The corresponding control scheme is the optimal control scheme.

[0111] Specifically, by substituting the Pareto front schemes calculated in step 3 into equation (15), the Pareto solution set can be sorted. Among all the Pareto front schemes, the objective function F of scheme 11 (i.e., the constant-speed unit uses a 40s guide vane closing time, and the variable-speed unit uses a 31s guide vane closing time) is the best. object The maximum value is achieved. Therefore, this control scheme is selected as the optimal control scheme for load shedding at this power station.

[0112] To further verify the effectiveness of the proposed optimized control method, three representative control schemes were selected for comparative analysis. Scheme 1 corresponds to the maximum minimum pressure in the tailrace pipe, and its control scheme is to shut down the constant-speed turbine unit within 36 seconds and the variable-speed turbine unit within 24 seconds; Scheme 20 corresponds to the minimum maximum pressure in the volute, and its control scheme is to shut down the guide vanes of both the constant-speed and variable-speed turbine units within 40 seconds; Scheme 11 is the optimized control strategy proposed in this invention. Figure 4 Table 2 shows the transient characteristics of the unit under three control schemes.

[0113] Table 2. Maximum pressure of the spiral casing and minimum pressure of the tailrace pipe under three typical control schemes.

[0114]

[0115] Depend on Figure 4As shown in Table 2, compared to Scheme 11, although Scheme 1 increases the minimum pressure of the tailrace tube by 3.28 m, it also increases the maximum pressure of the spiral casing by 9.42 m, indicating that its transient performance is slightly worse than that of Scheme 11. Furthermore, although Scheme 20 reduces the maximum pressure of the spiral casing by 1.24 m compared to Scheme 11, the minimum pressure of the tailrace tube decreases by 27.04 m. Due to the excessively low minimum pressure of the tailrace tube in Scheme 20, its transient characteristics are significantly worse than those of Scheme 11.

[0116] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optimized control method for load shedding water hammer pressure in a pumped-storage power station containing a constant-speed / variable-speed unit, characterized in that, Includes the following steps: Step 1: Based on the full characteristic curve of the pump-turbine, optimize the efficiency of the variable speed unit to determine the highest efficiency and the corresponding optimal speed of the variable speed unit. Step 2: Establish a mathematical model of the transient process of the pumped storage power station's water transmission and power generation system, which includes a constant-speed and variable-speed turbine unit. The mathematical model consists of a pressurized pipeline system and a pump-turbine unit system. Step 3: Based on the mathematical model of the transient process in Step 2, by adopting different guide vane closing laws for constant speed units and variable speed units, calculate the Pareto front scheme with the maximum pressure of the volute and the minimum pressure of the tailrace pipe as the optimization objectives under different control schemes. Step 4: Normalize the maximum pressure of the volute and the minimum pressure of the tailrace pipe to establish a comprehensive evaluation function for transient characteristics; Step 5: Substitute the Pareto front scheme from Step 3 into the transient characteristic comprehensive evaluation function from Step 4, and determine the optimal control scheme by comparing the transient characteristic comprehensive evaluation function values ​​under different Pareto front schemes. Step four involves normalizing the maximum pressure of the volute and the minimum pressure of the tailrace pipe. (13) (14) The final comprehensive evaluation function for transient characteristics is as follows: (15) In the formula: w1 and w2 are weighting coefficients. This represents the maximum pressure of the volute after normalization. F represents the minimum pressure in the tailrace pipe after normalization treatment. 1-max and F 1-min These represent the maximum and minimum maximum volute pressures under different control schemes; F 2-max and F 2-min These represent the maximum and minimum tailrace pipe pressures under different control schemes; F object This represents the comprehensive evaluation function for transient characteristics; In step five, the Pareto front scheme calculated in step three is substituted into equation (15) to obtain F. object Select the largest F object The corresponding control scheme is the optimal control scheme.

2. The optimized control method for load shedding water hammer pressure in pumped-storage power stations with constant-speed and variable-speed units as described in claim 1, characterized in that, The specific method of step one is to use the improved Suter transform to process the full characteristic curve of the pump-turbine, and express the data on the full characteristic curve of the pump-turbine using the following formula: (1) (2) (3) In the formula: Let be the independent variables of the flow function and the torque function. For relative unit flow, Q 11 Q is the unit flow rate. 11r Rated unit flow rate; This is the offset coefficient; Relative unit rotational speed, N 11 For unit rotational speed, N 11r Rated unit speed; For relative unit dynamic torque, For flow function, It is a torque function. ; M 11 M is the unit torque. 11r This is the rated unit torque; The subscript 'r' indicates the rated value; Unit speed of water pump turbine Unit flow and unit torque The expression is: (4) (5) (6) Where: n, D1, H T P, Q T These are the unit's rotational speed, impeller diameter, head, output, and flow rate, respectively. With the goal of maximizing unit efficiency, an efficiency optimization method based on the full characteristic curve is proposed. The specific steps are as follows: (a) Input unit speed n is n min ; (b) Assume the unit flow rate Q is Q assumed ; (c) Based on the unit flow rate Q assumed The operating head H of the generating unit is obtained by considering the water levels of the upstream and downstream reservoirs and the head loss coefficient of the water transmission pipeline. T ; (d) Based on the unit's operating head, flow rate, and rotational speed, calculate the unit's unit rotational speed using equations (4) and (5). and unit flow ; (e) Calculated using equations (1) and (2) And WH, and then interpolate the flow function curve to obtain the opening. ; (f) According to step (e) and Interpolation of the torque function curve yields Then, the unit output is obtained according to equation (6); (g) If the difference between the output and the target output is greater than the allowable error ε, then the reference flow rate Q is re-assumed based on the output deviation. assumed Then repeat step (b); if the difference between the output and the target output is less than ε, then end the loop calculation and proceed to step (h); (h) Output the unit's speed, opening degree, efficiency, output, and flow rate; (i) If the unit speed n < n max If n = n + Δ, then step (a) is repeated. (j) By comparing the efficiency at different speeds, output the speed, opening degree, efficiency, output, and flow rate at the optimal efficiency.

3. The optimized control method for load shedding water hammer pressure in pumped-storage power stations with constant-speed and variable-speed units as described in claim 2, characterized in that, The specific method for step two is as follows: The dynamic equations and continuity equations for a pressurized pipe describing an elastic water body are as follows: (7) (8) Where: Q is the flow rate; A is the pipe cross-sectional area; H is the piezometric head; x is the pipe coordinates; f is the friction coefficient; c is the water hammer wave velocity; D is the pipe diameter; The equation of motion for the water pump turbine rotor is: (9) Where: m g The relative value of the generator's electromagnetic torque, m g = M g / M r M g M is the electromagnetic torque of the generator. r Rated shaft torque; n is the relative rotational speed; T a is the unit's inertial time constant; m is the relative value of the turbine shaft torque; Equation (10) is the head balance equation for a water pump turbine, representing the head H. T With the volute manometer head H SC and tailrace pipe pressure gauge head H DT Relationship: (10) In the formula: Q T For unit operating flow rate; A SC A is the cross-sectional area of ​​the volute; DT Let g be the cross-sectional area of ​​the tailrace pipe, and g be the acceleration due to gravity.

4. The optimized control method for load shedding water hammer pressure in pumped-storage power stations with constant-speed and variable-speed units as described in claim 3, characterized in that, The specific method for step three is as follows: the maximum pressure of the volute is a "the smaller the better" indicator, and the minimum pressure of the tailrace pipe is a "the larger the better" indicator.

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