Hydraulic short-circuit mode system operating state calculation method considering pipeline characteristics

Abstract

The application discloses a kind of hydraulic short circuit mode system operating state calculation methods considering pipeline characteristics, first ignore water head loss in hydraulic short circuit mode, give initial preset working water head;Second, the initial preset working water head is substituted into unit characteristic curve, the preset working water head corresponding flow is solved, and the water head loss is calculated by water head loss formula again;Subsequently, the working water head is corrected using water head loss;Finally, the above-mentioned preset working water head flow is repeated, and the corresponding water head is obtained by flow, until the water head difference of adjacent two iterations is less than preset convergence criterion, and iteration is ended.The application effectively solves the problem that the pump-turbine operating parameters change under the pipeline characteristics of hydraulic short circuit mode and are difficult to calculate directly, and provides key technical support for the rapid response and flexible adjustment of unit.

Description

Technical Field

[0001] This invention belongs to the field of pumped storage power station operation and control technology, and particularly relates to a method for calculating the operating status of a hydraulic short-circuit mode system that takes into account pipeline characteristics. Background Technology

[0002] Pumped storage power stations are an important means of peak shaving, frequency regulation, and emergency backup for power grids, and their operational flexibility and regulation range are receiving increasing attention. In recent years, to further expand the power regulation range and operating condition adaptability of pumped storage power stations, the "hydraulic short-circuit" operation mode has been proposed. In this mode, two units in a single-pipe dual-unit system share a main hydraulic pipeline, with one unit generating electricity while the other pumps water. The purpose of this mode is to increase the power regulation range of the single-pipe dual-unit system.

[0003] However, under hydraulic short-circuit mode, the flow path of the pipeline system is complex, and the hydraulic characteristics are highly coupled with the unit's operating state, making traditional operating state calculation methods difficult to apply. Especially when two units are operating together, parameters such as unit flow rate, power, and head influence each other, and changes in pipeline characteristics significantly impact unit performance and economy. Therefore, there is an urgent need for a calculation method that can accurately reflect the coupling relationship between pipeline characteristics and unit operating parameters under hydraulic short-circuit mode, providing technical support for optimized system control and flexible operation. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating the operating status of a hydraulic short-circuit system that takes into account pipeline characteristics, thereby solving the problem in the prior art where the system operating status parameters are difficult to calculate accurately due to the complex coupling between pipeline characteristics and unit operating parameters in the hydraulic short-circuit operation mode of a single pipe and two units.

[0005] The technical solution adopted in this invention is a method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics. The specific steps are as follows: Step 1: Define the hydraulic short-circuit mode. The hydraulic short-circuit mode is a dual-unit system with the first unit operating in turbine mode and output power being positive; the second unit operating in pump mode and input power being negative. Step 2: Obtain the target operating parameters of the dual-pipe system, including at least the water level difference between the upstream and downstream reservoirs. H、 Total power dispatched by the power grid P 总 Define the running state parameters to be solved iteratively, including the number of iterations n and the main flow rate. Q Water turbine flow rate q 1. Water pump flow rate q 2. Turbine guide vane opening α1, pump guide vane opening α2, main pipe head loss h0. Head loss in the first branch pipe h 1 、 Head loss in the second branch pipe h 2 、 Effective head of the main body H 0. Effective head of turbine branch pipe H 1. Effective head of the water pump branch pipe H 2; Step 3: Initialize iteration parameters, define system constraints, and set the initial head loss of the main pipe and branch pipes to 0, and the initial effective head... H 0 (0) = H 1 (0) = H 2 (0) = H Input parameters H and P 总 Set the convergence accuracy threshold ε and the initial number of iterations n=0; Step 4, in the n In this iteration, the effective working head on the pump side will be... H 2 (n) Substituting the constant-speed pump's coordination curve, the pump flow rate can be obtained by solving the problem. q 2 (n) Water pump input power P 2 (n) and the guide vane opening α2 of the water pump (n) Calculate the turbine output power based on the total power dispatched by the power grid and the input power of the water pumps. P 1 (n) = P 总 - P 2 (n) and the effective working head on the turbine side H 1 (n) With the output power of the water turbine P 1 (n) Substituting the turbine characteristic curve, the turbine flow rate can be obtained. q 1 (n) And the turbine guide vane opening α1 (n) ; Step 5, calculate head loss and correct working head: based on main pipeline flow rate. Q (n) = q 1 (n) + q 2 (n) , will manage traffic Q (n) Substituting the values ​​into the head loss formula, we can obtain the head loss of the main pipeline. h 0 (n) The effective head of the main pipe is adjusted according to the flow direction of the main pipe. H 0 (n+1) If the flow direction in the main pipeline is consistent with the preset positive direction of the first unit, then H 0 (n+1) = H 0 (n) - h 0 (n) If the flow direction in the main pipeline is consistent with the preset positive direction of the second unit, then... H 0 (n+1) = H 0 (n) + h 0 (n) ; Synchronous correction of the effective working head on the turbine side H 1 (n+1) = H 1 (n) - h 1 (n) Effective working head on the pump side H 2 (n+1) = H 2 (n) + h 2 (n) ; Step 6, Iterative Convergence Judgment: Calculate the effective working head difference between two adjacent iterations. If | H 0 (n+1) - H 0 (n) If |>ε, then let n=n+1, and repeat steps 4-5; if | H 0 (n+1) - H 0 (n) If |≤ε, the iteration terminates, and the system operating status parameters are output.

[0006] Furthermore, in step 5, the head loss includes the main pipe head loss and the branch pipe head loss, wherein: the formula for the main pipe head loss is... h 0 = K1 × Q 2 The formula for head loss in the branch pipe is: h i =K2× q i 2 , i= 1, 2; K1 is the main pipe loss coefficient, and K2 is the branch pipe loss coefficient.

[0007] Furthermore, the sign rule for the effective head correction in step 5 is as follows: when the flow direction of the main pipeline is consistent with the positive direction of the first unit, the working head is reduced by the head loss; when the flow direction of the main pipeline is opposite to the positive direction of the first unit, the working head is increased by the head loss.

[0008] Furthermore, the output power of the turbine operating condition described in step 1 P 1 represents positive, indicating the water pump input power. P 2 is negative, and the total power coupling relationship satisfies P 总 = P 1+ P 2.

[0009] Furthermore, the setting of zero initial pipeline loss in step 4 means that the hydraulic loss of the main pipe and branch pipes is negligible in the initial state, and the initial effective head is equal to the difference in water level between the upstream and downstream reservoirs.

[0010] Furthermore, the constant-speed pump coupling curve expresses the relationship between operating head, opening degree, flow rate, and power; the turbine characteristic curve includes two sub-curves, which respectively express the relationship between operating head, opening degree, and power, and the relationship between operating head, opening degree, and flow rate.

[0011] Furthermore, the system operating status parameters in step 6 include at least: the effective working head of the main pipe obtained from the final iteration. H 0 (n+1) Effective working head on the turbine side H 1 (n+1) Effective working head on the pump side H 2 (n+1) , Managerial flow Q (n+1) Water turbine flow rate q 1 (n+1) Water pump flow rate q 2 (n+1) α1 of the turbine guide vane (n+1) α2 of water pump guide vane opening (n+1) Water turbine output power P 1 (n+1) Water pump input power P 2 (n+1) Head loss in main pipeline h 0 (n+1) Head loss in the first branch pipe h 1 (n+1) and head loss in the second branch pipe h 2 (n+1) .

[0012] Furthermore, the method is applied to a single-pipe dual-unit system of a constant-speed pumped storage unit.

[0013] The beneficial effects of this invention are as follows: This invention provides a method for calculating the operating status of a hydraulic short-circuit mode system considering pipeline characteristics. First, it obtains the upstream and downstream water level difference, the system's target total power, the relationship between pump operating head and opening, flow rate and power, and the relationship between turbine operating head and opening and flow rate and power. Second, it uses an iterative method to calculate pipeline characteristics and obtain the corresponding pump-turbine operating parameters. Furthermore, taking all operating points of a single-pipe dual-unit pumped storage power station as targets, and considering the operating range constraints of the pump-turbine, it finally obtains the pipeline loss situation and pump-turbine operating parameters for all operating points. This invention effectively solves the problem that the changes in pump-turbine operating parameters caused by pipeline characteristics under hydraulic short-circuit mode make direct calculation difficult, providing key technical support for the unit's rapid response and flexible adjustment. Attached Figure Description

[0014] Figure 1 This is a flowchart of the system operation state calculation method for hydraulic short-circuit mode considering pipeline characteristics according to the present invention; Figure 2 This is a diagram illustrating the iterative process of Embodiment 1 of the present invention. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] The present invention provides a method for calculating the operating state of a hydraulic short-circuit mode system that considers pipeline characteristics, such as... Figure 1 As shown, the specific operation steps are as follows: Step 1: In the hydraulic short-circuit mode, one of the first generating units operates in turbine mode, while the other second generating unit operates in pump mode. The output power of the turbine mode is positive, and the input power of the pump mode is negative. Step 2: Obtain the target operating parameters of the single-pipe dual-machine system, including the water level difference between the upstream and downstream reservoirs. H、 Total power dispatched by the power grid P 总 Number of iterations n, main flow rate Q Flow rate of the first unit q 1. Flow rate of the second unit q 2. Guide vane opening α1 of the first unit, guide vane opening α2 of the second unit, and head loss in the main pipe. h0. Head loss in the branch pipe of the first unit h 1 、 Head loss in the second unit's branch pipe h 2 、 Effective head of the main body H 0. Effective head of the first unit's branch pipe H 1. Effective head of the second unit's branch pipe H 2; The specific formula for head loss is as follows: h =K1× Q 2 +K2× q 2 Where K1 is the main pipe loss coefficient and K2 is the branch pipe loss coefficient, determined by the pipe material, diameter, and length; based on this formula, the formula for the main pipe head loss in the hydraulic short-circuit mode is as follows: h 0 = K1 × Q 2 Formula for head loss in branch pipes: h i =K2× q i 2 , i= 1, 2; Step 3: Define system constraints, setting the initial head loss of the main pipe and branch pipes to 0, and the initial effective head... H 0 (0) = H 1 (0) = H 2 (0) = H Input parameters H and P 总 Set the convergence accuracy threshold ε and the initial number of iterations n=0; Step 4: H 2 (n) Substitute the constant-speed water pump coordination curve and solve. q 2 (n) and P 2 (n) and α2 (n) ;according to P 1 (n) = P 总 - P 2 (n) ,Will H 1 (n) and P 1 (n)Substitute the turbine characteristic curves and solve. q 1 (n) and α1 (n) ; Step 5: Head Loss Calculation and Correction: Based on Q (n) = q 1 (n) + q 2 (n) Calculate the main flow Q (n) ,Will Q (n) Substitute into the head loss formula to solve. h 0 (n) The effective head of the main pipe is adjusted according to the flow direction of the main pipe. H 0 (n+1) If the flow direction in the main pipeline is the same as that of the first unit, then H 0 (n+1) = H 0 (n) - h 0 (n) If the flow direction in the main pipeline is the same as that of the second unit, then... H 0 (n +1) = H 0 (n) + h 0 (n) Synchronous correction H 1 (n+1) = H 1 (n) - h 1 (n) , H 2 (n+1) = H 2 (n) + h 2 (n) ; The effective head correction rule for the main pipeline is as follows: when the flow direction of the main pipeline is consistent with the positive direction of the first unit, the working head is reduced by the head loss; when the flow direction of the main pipeline is opposite to the positive direction of the first unit, the working head is increased by the head loss. Step 6: Iterative convergence judgment: If | H 0 (n+1) - H 0 (n) |>ε, n=n+1, repeat steps 4-5; if | H 0 (n+1) - H 0(n) If |≤ε, the iteration terminates, and the system operating state parameters are output, including H 0 (n+1) , H 1 (n+1) , H 2 (n+1) , Q (n+1) , q 1 (n+1) , q 2 (n+1) α1 (n+1) α2 (n+1) , P 1 (n+1) , P 2 (n+1) , h 0 (n+1) , h 1 (n+1) , h 2 (n+1) .

[0017] Managerial flow Q (n) The main pipe flow rate must equal the sum of the flow rates of the two branch pipes, i.e. Q (n) = q 1 (n) + q 2 (n) ; The constant-speed pump coupling curve expresses the relationship between operating head, opening degree, flow rate, and power; the turbine characteristic curve contains two graphs, which respectively express the relationship between operating head, opening degree, and power, and the relationship between operating head, opening degree, and flow rate.

[0018] Example 1 Embodiment 1 of the present invention provides a method for calculating the operating status of a hydraulic short-circuit mode system in which two constant-speed generator units operate together. This embodiment of the present invention sets the upstream and downstream water level difference. H =430m, target total power of a dual-machine system P 总 =80MW, the pump-turbine characteristics are illustrated in the following steps, taking a power station as an example: Step 1: Obtain the operating characteristic curves of the water pump and turbine to obtain the relationship between operating head, opening degree, flow rate, and power. Based on the multiple requirements of the power station's response speed and accuracy, comprehensively set the convergence accuracy threshold ε=10. -4 m, initial loop count n=0; Step 2: Set the initial supervisor's loss along the path Δ h 0 (0)Friction loss along the turbine branch pipe Δ h 1 (0) Water pump branch pipe loss Δ h 2 (0) All are 0m, with the positive direction being from upstream to downstream; Step 3: Based on the relationship between the pump's operating head, pump opening, flow rate, and power, obtain the pump flow rate from the pump characteristic curve. q 2 (0) =66.55m 3 / s and power P 2 (0) =299.91MW; based on the total system power P 总 = P 1+ P 2. Calculate the turbine power. P 1 (0) =219.91MW; Based on the relationship between the turbine's operating head, turbine opening, flow rate, and power, the turbine opening and its corresponding flow rate are calculated. q 1 (0) =56.93m 3 / s; Step 4: Calculate the actual pipeline loss value Δ under the current flow rate using the head loss calculation formula. h 0 (1) =K1× Q ² = 0.022m; Δ h 1 (1) =K2× q 1² = 1.522m; Δ h 2 (1) =K2× q 2² = 2.080m.

[0019] Step 5: According to | H 0 (1) - H 0 (0) |>ε, so the iteration continues, n=n+1, and steps 3 to 4 are repeated until | H 0 (1) - H 0 (0) When |≤ε, the iteration ends. At this point, the iteration process of the main working head is as follows: Figure 2 As shown, with a water level difference of 430m upstream and downstream, three iterations can reduce the head error calculated in two iterations to less than 10. -4 m. At this time Δ h 0 = 0.02008m, Δ h 1 = 1.52213m, Δ h 2 = 2.04870m, H0 = 430.02008m H 1 = 428.49795m H 2 = 432.06879m Q= -9.11780m 2 / s、 q 1 = 56.93330 m² / s q 2 = -66.05100m 2 / s、 P 1 = 219.03131MW P 2 = -299.03131MW. The iterative process of the main working head at this time is as follows: Figure 2 As shown: In the 0th iteration, the initial main pipe loss is set to 0, and the main pipe working head is 430m; after the first iteration, the main pipe working head is 430.02235m; after the second iteration, the main pipe working head is 430.02006m; after the third iteration, the main pipe working head is 430.02008m. With each iteration, the main pipe working head initially deviates from the initial value, then falls back, and then rises slightly again. The overall slight fluctuations gradually converge and approach the final precise value.

[0020] Example 2 Embodiment 2 of the present invention provides a method for calculating the operating status of a hydraulic short-circuit mode system in which two constant-speed generator units operate together. This embodiment of the present invention sets the upstream and downstream water level difference. H =430m, target total power of a dual-machine system P 总 =120MW, the pump-turbine characteristics are illustrated in the following steps, taking a power station as an example: Step 1: Obtain the operating characteristic curves of the water pump and turbine to obtain the relationship between operating head, opening degree, flow rate, and power. Based on the multiple requirements of the power station's response speed and accuracy, comprehensively set the convergence accuracy threshold ε=10. -4 m, initial loop count n=0; Step 2: Set the initial supervisor's loss along the path Δ h 0 (0) Friction loss along the turbine branch pipe Δ h 1 (0) Water pump branch pipe loss Δ h 2 (0) All are 0m, with the positive direction being from upstream to downstream; Step 3: Based on the relationship between the pump's operating head, pump opening, flow rate, and power, obtain the pump flow rate from the pump characteristic curve. q 2 (0) =66.55m 3 / s and power P 2 (0) =299.91MW; based on the total system powerP 总 = P 1+ P 2. Calculate the output power of the water turbine. P 1 (0) =179.91MW; Based on the relationship between the turbine's operating head, turbine opening, flow rate, and power, the turbine opening and its corresponding flow rate are calculated. q 1 (0) =47.59m 3 / s; Step 4: Calculate the actual pipeline loss value Δ under the current flow rate using the head loss calculation formula. h 0 (1) =K1× Q ² = 0.08676m; Δ h 1 (1) =K2× q 1² = 1.06375m; Δ h 2 (1) =K2× q 2² = 2.07963m.

[0021] Step 5: According to | H 0 (1) - H 0 (0) |>ε, so the iteration continues, n=n+1, and steps 3 to 4 are repeated until | H 0 (1) - H 0 (0) If |≤ε, the iteration ends; With a water level difference of 430m upstream and downstream, three iterations can reduce the head error calculated in two iterations to less than 10. - 4 m. At this time Δ h 0 = 0.08291m, Δ h 1 = 1.05999m, Δ h 2 = 2.04778m, H 0 = 430.08291m H 1 = 429.02291m H 2 = 432.13069m Q= -18.52553m 2 / s、 q 1 = 47.51070 m² / s q 2 = -66.03613m 2 / s、 P 1 = 179.00462MW P 2 = -299.00462MW.

[0022] Example 3 The present invention provides a method for calculating the operating state of a hydraulic short-circuit mode system that considers pipeline characteristics. In the hydraulic short-circuit mode, head loss is first ignored, and an initial preset operating head is given. Next, the initial preset operating head is substituted into the unit characteristic curve to solve for the flow rate corresponding to the preset operating head, and then the head loss is calculated using the head loss formula. Subsequently, the operating head is corrected using the head loss. Finally, the process of calculating the flow rate from the preset operating head and then calculating the corresponding head from the flow rate is repeated until the head difference between two adjacent iterations is less than a preset convergence criterion, at which point the iteration ends.

[0023] The above description is only 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 protection scope of the present invention.

Claims

1. A method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics, characterized in that, Includes the following steps: Step 1: Define the hydraulic short-circuit mode. The hydraulic short-circuit mode is a dual-unit system with the first unit operating in turbine mode and output power being positive; the second unit operating in pump mode and input power being negative. Step 2: Obtain the target operating parameters of the dual-pipe system, including at least the water level difference between the upstream and downstream reservoirs. H、 Total power dispatched by the power grid P 总 Define the running state parameters to be solved iteratively, including the number of iterations n and the main flow rate. Q Water turbine flow rate q 1. Water pump flow rate q 2. Turbine guide vane opening α1, pump guide vane opening α2, main pipe head loss h 0. Head loss in turbine branch pipes h 1 、 Water pump branch pipe head loss h 2 、 Effective head of the main body H 0. Effective head of turbine branch pipe H 1. Effective head of the water pump branch pipe H 2; Step 3: Initialize iteration parameters, define system constraints, and set the initial head loss of the main pipe and branch pipes to 0, and the initial effective head... H 0 (0) = H 1 (0) = H 2 (0) = H Input parameters H and P 总 Set the convergence accuracy threshold ε and the initial iteration count n=0; Step 4, in the n In this iteration, the effective working head on the pump side will be... H 2 (n) Substituting the constant-speed pump's coordination curve, the pump flow rate can be obtained by solving the problem. q 2 (n) Water pump input power P 2 (n) and the guide vane opening α2 of the water pump (n) Calculate the turbine output power based on the total power dispatched by the power grid and the input power of the water pumps. P 1 (n) = P 总 - P 2 (n) and the effective working head on the turbine side H 1 (n) With the output power of the water turbine P 1 (n) Substituting the turbine characteristic curve, the turbine flow rate can be obtained. q 1 (n) And the turbine guide vane opening α1 (n) ; Step 5, calculate head loss and correct working head: based on main pipeline flow rate. Q (n) = q 1 (n) + q 2 (n) , will manage traffic Q (n) Substituting the values ​​into the head loss formula, we can obtain the head loss of the main pipeline. h 0 (n) The effective head of the main pipe is adjusted according to the flow direction of the main pipe. H 0 (n+1) ; Synchronous correction of effective working head on turbine side H 1 (n+1) Effective working head on the pump side H 2 (n+1) ; If the flow direction in the main pipeline is consistent with the preset positive direction of the first unit, then H 0 (n+1) = H - h 0 (n) ; If the flow direction in the main pipeline is consistent with the preset positive direction of the second unit, then... H 0 (n+1) = H + h 0 (n) ; Synchronous correction of effective working head on turbine side H 1 (n+1) = H 0 (n) - h 1 (n) Effective working head on the pump side H 2 (n+1) = H 0 (n) + h 2 (n) ; in ，H (n) It is an effective head. h 1 (n) It is the head loss in the turbine branch pipe. h 2 (n) It is the head loss in the pump branch pipe; Step 6, Iterative Convergence Judgment: Calculate the effective working head difference between two adjacent iterations. If | H 0 (n+1) - H 0 (n) If |>ε, then let n=n+1, and repeat steps 4-5; if | H 0 (n+1) - H 0 (n) If |≤ε, the iteration terminates, and the system operating status parameters are output.

2. The method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics according to claim 1, characterized in that, In step 5, the head loss includes the main pipe head loss and the branch pipe head loss, wherein: the formula for the main pipe head loss is... h 0 = K1 × Q 2 The formula for head loss in the branch pipe is: h i =K2× q i 2 , i= 1, 2; K1 is the main pipe loss coefficient, and K2 is the branch pipe loss coefficient.

3. The method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics according to claim 1, characterized in that, The output power of the turbine in step 1 P 1 represents positive, indicating the water pump input power. P 2 is negative, and the total power coupling relationship satisfies P 总 = P 1+ P 2.

4. The method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics according to claim 1, characterized in that, The setting of zero initial pipeline loss in step 3 means that the hydraulic loss of the main pipe and branch pipes is negligible in the initial state, and the initial effective head is equal to the difference in water level between the upstream and downstream reservoirs.

5. The method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics according to claim 1, characterized in that, The constant-speed pump coupling curve expresses the relationship between operating head, opening degree, flow rate, and power; the turbine characteristic curve contains two sub-curves, which respectively express the relationship between operating head, opening degree, and power, and the relationship between operating head, opening degree, and flow rate.

6. The method for calculating the operating state of a system considering pipeline characteristics under hydraulic short-circuit mode according to claim 1, characterized in that, The system operating status parameters in step 6 include at least the effective working head of the main pipe obtained from the final iteration. H 0 (n+1) Effective working head on the turbine side H 1 (n+1) Effective working head on the pump side H 2 (n+1) , Manager of traffic Q (n+1) Water turbine flow rate q 1 (n+1) Water pump flow rate q 2 (n+1) α1 of the turbine guide vane opening (n+1) α2 of water pump guide vane opening (n+1) Water turbine output power P 1 (n+1) Water pump input power P 2 (n+1) Head loss in main pipeline h 0 (n+1) Head loss in turbine branch pipes h 1 (n+1) and head loss in the pump branch pipe h 2 (n+1) .

7. The method for calculating the operating state of a hydraulic short-circuit mode system considering pipeline characteristics according to claim 1, characterized in that, The method is applied to a single-pipe dual-unit system of a constant-speed pumped storage unit.

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