A dynamic testing method and device for a pump-turbine s-characteristic curve

Abstract

This invention discloses a dynamic testing method and apparatus for the S-characteristic curve of a water pump turbine. The method includes starting and connecting the water pump turbine unit to the grid on an open-type transient process test bench, collecting S-characteristic curve data, maintaining the grid-connected state of the water pump turbine unit, adjusting and maintaining a constant opening of the movable guide vanes, shutting down the circulating water pump, collecting data at high frequency through sensors, observing the real-time monitoring data waveform, stopping the water pump turbine unit after multiple cycles, closing the movable guide vanes, and plotting the S-characteristic curve of the water pump turbine based on the collected data. This invention provides a dynamic testing method and apparatus for the S-characteristic curve of a water pump turbine, suitable for open-type transient process test platforms, enabling continuous and complete measurement of the S-characteristic curve of the water pump turbine, and obtaining a high-accuracy S-characteristic curve.

Description

Technical Field

[0001] This invention belongs to the technical field of pumped storage power station model testing, specifically relating to a dynamic testing method and device for the S-characteristic curve of a water pump turbine. Background Technology

[0002] Pumped storage is currently the energy storage method with the most conditions for large-scale development, the most mature technology, the best economics, and the most environmentally friendly features. It will be the main force for regulating power sources in future power systems dominated by new energy sources. Vigorously developing pumped storage is key to achieving the "dual carbon" goal. Pumped storage power stations have both energy storage and power generation functions. They can operate in power generation mode when electricity demand is high and in pumping mode when electricity demand is low, resulting in significant economic benefits. Pumped storage power stations can also quickly complete the switching of operating conditions to balance the impact of intermittent energy sources such as wind power and solar power on the power grid, playing a supporting role in grid stability. The pump-turbine is the core component of a pumped storage power station, and its S-characteristic curve is an important data for the design of pumped storage power stations and a key boundary condition affecting the calculation accuracy of the transient process of pumped storage power stations.

[0003] like Figure 2 As shown, the S-characteristic curve of the water pump turbine appears in the first and fourth quadrants of the flow characteristic curve, typically n. ED ~Q ED Planar two-dimensional curve representation, n ED Q ED These represent unit rotational speed and unit flow rate, respectively.

[0004] Model experiments are currently the most common method for obtaining the S-characteristic curve of a pump-turbine. On a closed test rig, the S-characteristic curve can be measured using two static experimental methods: one is to change the head while keeping the pump-turbine unit's speed constant, and the other is to gradually change the pump-turbine unit's speed while maintaining a constant head. The limitations of static measurement methods are twofold: firstly, the measurement results are discrete; secondly, in the braking and reverse pumping regions of the pump-turbine's S-characteristic curve, the pump-turbine exhibits static instability, leading to jumps in the operating point and inaccurate measurement results. On a transient process test rig, the pump-turbine's S-characteristic curve can be dynamically measured through emergency load shedding tests. This method has stringent requirements regarding the unit's rotational inertia, piping system length, and operating head in the experimental setup, and the range of the measured S-characteristic curve is limited.

[0005] Therefore, the existing technology lacks a method for continuously and completely measuring the S-characteristic curve of a pump-turbine, which directly limits the effectiveness of S-characteristic curve measurement and the accuracy of using S-characteristic curve to simulate the transient process of a pumped storage power station. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dynamic testing method and apparatus for the S-characteristic curve of a water pump turbine. This method can continuously and completely measure the S-characteristic curve of a water pump turbine on an open transient process test bench. Since the water pump turbine unit is in grid-connected state, the opening degree of the movable guide vanes is constant, and the sensor collects data at a high frequency, it can ensure a large quantity of measurements, continuous data, and high data accuracy.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0008] A dynamic testing method for the S-characteristic curve of a water pump turbine includes the following steps:

[0009] Step 1: Based on the open-type transient process test bench, conduct the start-up and grid connection of the pump-turbine unit;

[0010] Step 2: Collect S-characteristic curve data of water pump turbine. Keep the water pump turbine unit in grid-connected state, adjust the opening of the movable guide vane and keep it constant, shut down the circulating water pump, collect data at high frequency through the sensor, observe the real-time monitoring data waveform, and after multiple change cycles, the water pump turbine unit stops and the movable guide vane is closed.

[0011] Step 3: Based on the collected data, plot the S-characteristic curve of the water pump turbine.

[0012] Furthermore, the open-type transition process test bench includes a circulating water pump, an upstream water tank, a downstream water tank, and a pump-turbine unit. The circulating water pump is connected to the upstream water tank via an upstream water supply pipe to fill the upstream water tank, and the circulating water pump is connected to the downstream water tank via a downstream water supply pipe to fill the downstream water tank. An upstream overflow pipe is connected to one side of the upstream water tank, and an upstream main pipe is connected to the other side. The height of the upstream main pipe is lower than the height of the upstream overflow pipe. The upstream main pipe is connected to the inlet of the pump-turbine unit. A downstream drain pipe is provided at the bottom of the downstream water tank, and a downstream main pipe is provided on the side. The downstream main pipe is connected to the outlet of the pump-turbine unit. A speed governor is provided on the pump-turbine unit, and the speed governor is used to adjust the opening of the movable guide vanes.

[0013] Furthermore, the upstream water tank and the downstream water tank are provided with vertical chutes, and the chutes are provided with overflow weirs. The height of the overflow weirs can be adjusted by moving the overflow weirs up and down on the chutes to adapt to the testing of the S-characteristic curves of the water pump turbine under different water heads.

[0014] Furthermore, step 1 specifically includes:

[0015] Step 1.1: Based on the open-type transient process test bench, start the circulating water pump to supply water to the upstream and downstream water tanks, fill the upstream and downstream water tanks to overflow state, and form a constant water head;

[0016] Step 1.2: Start the pump-turbine unit in turbine mode and connect it to the grid after it has stabilized.

[0017] Step 1.3: Adjust the opening of the movable guide vanes of the water pump turbine unit through the speed governor to keep the opening of the movable guide vanes of the water pump turbine unit constant.

[0018] Further, in step 1.1, the circulating water pump is started, and the circulating water pump fills the upstream water tank with water through the upstream water supply pipe until water can continuously flow out from the upstream overflow pipe, so that the upstream water tank is in an overflow state. The circulating water pump fills the downstream water tank with water through the downstream water supply pipe, so that the downstream water tank is in an overflow state.

[0019] Furthermore, in step 2, the sensors measure the water pump turbine flow rate Q, head H, torque T, and rotational speed n. The sensors include an electromagnetic flowmeter for measuring the water pump turbine flow rate Q, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n.

[0020] Furthermore, the electromagnetic flowmeter, the pressure sensor, the mechanical torque sensor, and the frequency sensor all measure frequencies above 1000Hz.

[0021] Furthermore, step 3 specifically includes:

[0022] Step 3.1: Based on the collected flow rate Q, head H, torque T, and rotational speed n, convert them into unit rotational speed n. ED Unit flow rate Q ED Unit torque T ED The formula is as follows:

[0023]

[0024] Where D2 is the outlet diameter of the water pump turbine, in meters (m); g is the acceleration due to gravity, in meters per second (m / s²). 2 ρ is the density of water;

[0025] Step 3.2: Based on the unit rotational speed n obtained above... ED Unit flow rate Q ED Unit torque T ED Plot the S-characteristic curve of the movable guide vane at a certain opening.

[0026] Furthermore, in step 2, after the circulating water pump is shut down, the upstream and downstream water tanks are no longer replenished. The water in the upstream water tank is first discharged from the upstream overflow pipe through the overflow, and then transported to the downstream through the upstream main pipe and the pump-turbine unit. The upstream water level continuously decreases, and the head of the pump-turbine unit continuously decreases. When the head of the pump-turbine unit decreases to a significantly low level, the flow rate reverses, and the water level in the upstream main pipe begins to rise instead. When a critical water level is reached, the head of the pump-turbine unit begins to decrease. Finally, a continuous reciprocating motion is formed in the upstream and downstream main pipes. After several cycles, the pump-turbine unit stops and the movable guide vanes are closed.

[0027] A dynamic testing device for the S-characteristic curve of a water pump turbine includes:

[0028] An open-type transient process test bench is used to perform dynamic testing experiments on the S-characteristic curve of a water pump turbine.

[0029] Sensors include an electromagnetic flowmeter for measuring the flow rate Q of a water pump turbine, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n.

[0030] The memory is used to store the data acquired by the sensor;

[0031] The processor is used to calculate and obtain the S-characteristic curve of the water pump turbine;

[0032] The display is used to show the waveforms of sensor monitoring data and the S-characteristic curves of the water pump and turbine.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. The dynamic testing method and device for the S-characteristic curve of a water pump turbine provided by the present invention are based on model tests, rather than mathematical derivation or numerical simulation, and have been verified by actual tests, and have high reliability.

[0035] 2. The present invention provides a dynamic testing method and apparatus for the S-characteristic curve of a water pump turbine, which can measure the S-characteristic curve of the water pump turbine completely and continuously. The S-characteristic curve obtained by the existing testing methods is local or discrete, providing a more accurate dynamic testing method for drawing the S-characteristic curve of the water pump turbine.

[0036] 3. The present invention provides a dynamic testing method and device for the S-characteristic curve of a water pump turbine, which requires a short testing time, a small amount of data, and a simple and convenient data processing process. Compared with traditional measurement methods, the experimental cycle is greatly shortened. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the dynamic testing method for the S-characteristic curve according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of the S-characteristic curve of an embodiment of the present invention.

[0039] Figure 3(a) is a schematic diagram of the stable operation of the pump turbine on the open-type transition process test bench in an embodiment of the present invention.

[0040] Figure 3(b) is a schematic diagram of the open-type transition process test bench shutting down the circulating water pump in an embodiment of the present invention.

[0041] Figure 3(c) is a schematic diagram of the sudden increase in upstream pressure after a gradual decrease in pressure on the open-type transition process test bench in an embodiment of the present invention.

[0042] Figure 3(d) is a schematic diagram of the continuous reciprocating oscillation of water flow in the upstream and downstream pipes of the open transition process test bench in an embodiment of the present invention.

[0043] Figure 4(a) shows the head measurement waveform obtained in an embodiment of the present invention.

[0044] Figure 4(b) shows the rotational speed measurement waveform obtained in an embodiment of the present invention.

[0045] Figure 4(c) shows the flow measurement waveform obtained in an embodiment of the present invention.

[0046] Figure 4(d) shows the torque measurement waveform obtained in an embodiment of the present invention.

[0047] Figure 5(a) shows the dynamic measurement of n in an embodiment of the present invention. ed ~Q ed S-characteristic curve of water pump turbine.

[0048] Figure 5(b) shows the dynamic measurement of n in an embodiment of the present invention. ed ~T ed S-characteristic curve of water pump turbine.

[0049] The components include: 1. Circulating water pump; 2. Upstream water supply pipe; 3. Downstream water supply pipe; 4. Upstream water tank; 5. Downstream water tank; 6. Water pump turbine unit; 7. Upstream overflow pipe; 8. Upstream main pipe; 9. Downstream main pipe; 10. Downstream drainage pipe. Detailed Implementation

[0050] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0051] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0052] This invention provides a dynamic testing method for the S-characteristic curve of a water pump turbine, such as... Figure 1 As shown, it includes the following steps:

[0053] Step 1: Based on the open-type transient process test bench, start-up and grid connection of pump-turbine unit 6 were carried out;

[0054] Step 2: Collect S-characteristic curve data of water pump turbine. Keep water pump turbine unit 6 in grid-connected state, adjust the opening of movable guide vane and keep it constant, shut down circulating water pump 1, collect data at high frequency through sensor, observe the real-time monitoring data waveform, and after multiple change cycles, water pump turbine unit 6 stops and movable guide vane is closed.

[0055] Step 3: Based on the collected data, plot the S-characteristic curve of the water pump turbine.

[0056] The static measurement method requires the unit to operate at a given single operating point each time. Therefore, it is necessary to perform multiple separate measurements under different operating conditions and then plot the discrete operating points as S-characteristic curves. In addition, each measurement requires restarting the unit for testing, resulting in a high error rate.

[0057] This invention is applicable to open-type transient process test benches. This method can continuously and completely measure the S-characteristic curve of a water pump turbine on an open-type transient process test bench. Since the water pump turbine unit 6 is in grid-connected state, the opening degree of the movable guide vanes is constant, and the sensor collects data at a high frequency, which can ensure a large number of measurements, continuous data, and high data accuracy.

[0058] In this invention, such as Figures 3(a)-3(d)As shown, the open-type transition process test bench includes a circulating water pump 1, an upstream water tank 4, a downstream water tank 5, and a pump-turbine unit 6. The circulating water pump 1 is connected to the upstream water tank 4 through the upstream water supply pipe 2 to fill the upstream water tank 4 with water. The circulating water pump 1 is connected to the downstream water tank 5 through the downstream water supply pipe 3 to fill the downstream water tank 5 with water. The upstream water tank 4 is connected to an upstream overflow pipe 7 on one side and an upstream main pipe 8 on the other side. The height of the upstream main pipe 8 is lower than the height of the upstream overflow pipe 7. The upstream main pipe 8 is connected to the inlet of the pump-turbine unit 6. The downstream water tank 5 is provided with a downstream drain pipe 10 at the bottom and a downstream main pipe 9 on the side. The downstream main pipe 9 is connected to the outlet of the pump-turbine unit 6. The pump-turbine unit 6 is provided with a speed regulator, which is used to adjust the opening of the movable guide vanes.

[0059] In this invention, based on an open-type transition process test rig, step 1 specifically includes:

[0060] Step 1.1: Based on the open-type transient process test bench, start the circulating water pump 1 to supply water to the upstream water tank 4 and the downstream water tank 5, fill the upstream water tank 4 and the downstream water tank 5 with water to the overflow state, and form a constant water head;

[0061] Step 1.2: Start the water pump turbine unit 6 in turbine mode and connect it to the grid after it runs stably;

[0062] Step 1.3: Adjust the opening of the movable guide vanes of the water pump turbine unit 6 by using the speed governor to keep the movable guide vanes of the water pump turbine unit 6 constant.

[0063] Specifically, in step 1.1, as shown in Figure 3(a), the circulating water pump 1 is started. The circulating water pump 1 fills the upstream water tank 4 with water through the upstream water supply pipe 2 until water can continuously flow out from the upstream overflow pipe 7, so that the upstream water tank 4 is in an overflow state. The circulating water pump 1 fills the downstream water tank 5 with water through the downstream water supply pipe 3, so that the downstream water tank 5 is in an overflow state. The water pump turbine unit 6 is started and connected to the grid in power generation mode.

[0064] In this invention, in step 2, the sensor measures the flow rate Q, head H, torque T, and rotational speed n of the water pump turbine unit 6. By operating the sensor at high frequency, the flow rate Q, head H, torque T, and rotational speed n of the water pump turbine unit 6 are dynamically, continuously, and completely measured.

[0065] Specifically, the sensors include an electromagnetic flowmeter for measuring the flow rate Q of the water pump turbine unit 6, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n.

[0066] The electromagnetic flowmeter is installed on the pipe at the inlet of the volute. Two pressure sensors are installed at the inlet of the volute and the inlet of the tailrace pipe, respectively. The head H is obtained by the difference between the two pressure sensors. The mechanical torque sensor is installed on the connecting shaft between the pump turbine and the generator / motor. The frequency sensor is installed on the outer edge of the generator / motor flywheel.

[0067] In this invention, in order to enable the sensor to measure at a high frequency and ensure the dynamic and continuous movement of the water pump turbine unit 6, and to obtain a large amount of accurate data, the electromagnetic flowmeter, pressure sensor, mechanical torque sensor and frequency sensor all measure at frequencies above 1000Hz.

[0068] In this invention, in step 2, the real-time monitoring data waveform is observed through a display.

[0069] In this invention, such as Figures 3(b)-3(d) As shown, in step 2, after the circulating water pump 1 is shut down, the upstream water tank 4 and the downstream water tank 5 are no longer replenished with water, maintaining the pump-turbine unit 6 in a grid-connected state. The opening of the movable guide vane is adjusted and kept constant. Data is collected at high frequency by sensors, and the real-time monitoring data waveform is observed. The water in the upstream water tank 4 is first discharged from the upstream overflow pipe 7 through the overflow, and then transported to the downstream through the upstream main pipe 8 via the pump-turbine unit 6. The upstream water level continuously decreases, and the head of the pump-turbine unit 6 continuously decreases. When the head of the pump-turbine unit 6 decreases to a significantly low level, the flow reverses, and the water level in the upstream main pipe 8 begins to rise instead. When a critical water level is reached, the head of the pump-turbine unit 6 begins to decrease. Finally, a continuous reciprocating motion is formed in the upstream main pipe 8 and the downstream main pipe 9. After several cycles of change, the pump-turbine unit 6 stops, and the movable guide vane closes.

[0070] In this invention, step 3 specifically includes:

[0071] Step 3.1: Based on the collected flow rate Q, head H, torque T, and rotational speed n, convert them into unit rotational speed n. ED Unit flow rate Q ED Unit torque T ED The formula is as follows:

[0072]

[0073] Where D2 is the outlet diameter of the water pump turbine, in meters (m); g is the acceleration due to gravity, in meters per second (m / s²). 2 ρ is the density of water.

[0074] Step 3.2: Based on the unit rotational speed n obtained above... ED Unit flow rate Q ED Unit torque T EDPlot the S-characteristic curve of the movable guide vane at a certain opening.

[0075] In this invention, specifically in step 3.2, the unit rotational speed n ED Using the X-axis as the axis and the unit flow rate Q ED Plot a two-dimensional curve along the Y-axis, or plot the curve in units of rotational speed n. ED With the X-axis as the axis and the unit torque T as the axis, ED Create a 2D curve graph along the Y-axis. This can be done using any commonly used graphing software such as Microsoft Excel or Origin.

[0076] This invention also provides a dynamic testing device for the S-characteristic curve of a water pump turbine, used to implement the dynamic testing method for the S-characteristic curve of a water pump turbine as described above, such as... Figures 3(a)-3(d) As shown, it includes:

[0077] An open-type transient process test bench is used to perform dynamic testing experiments on the S-characteristic curve of a water pump turbine.

[0078] The sensors include an electromagnetic flowmeter for measuring the flow rate Q of the water pump turbine unit 6, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n.

[0079] The memory is used to store the data acquired by the sensor;

[0080] The processor is used to calculate and obtain the S-characteristic curve of the water pump turbine.

[0081] The display is used to show the waveforms of sensor monitoring data and the S-characteristic curves of the water pump and turbine.

[0082] Specifically, the open-type transition process test bench includes a circulating water pump 1, an upstream water tank 4, a downstream water tank 5, and a pump-turbine unit 6. The circulating water pump 1 is connected to the upstream water tank 4 through the upstream water supply pipe 2 to fill the upstream water tank 4 with water. The circulating water pump 1 is connected to the downstream water tank 5 through the downstream water supply pipe 3 to fill the downstream water tank 5 with water. The upstream water tank 4 is connected to an upstream overflow pipe 7 on one side and an upstream main pipe 8 on the other side. The height of the upstream main pipe 8 is lower than the height of the upstream overflow pipe 7. The upstream main pipe 8 is connected to the inlet of the pump-turbine unit 6. The bottom of the downstream water tank 5 is equipped with a downstream drain pipe 10 for drainage, and the side is equipped with a downstream main pipe 9. The downstream main pipe 9 is connected to the outlet of the pump-turbine unit 6. The pump-turbine unit 6 is equipped with a speed regulator, which is used to adjust the opening of the movable guide vanes.

[0083] In addition, the upstream water tank 4 and the downstream water tank 5 are equipped with vertical chutes, and overflow weirs are provided on the chutes. The height of the overflow weirs can be adjusted by moving the overflow weirs up and down on the chutes to adapt to the testing of the S-characteristic curves of the water pump turbines under different water heads.

[0084] In one embodiment of the present invention, Figures 4(a)-4(d) The changes in the unit's mechanical and flow parameters after shutting down circulating water pump 1 are shown. Observations show that the head H of the pump-turbine continuously decreases under gravity. Between t = 10s and t = 50s, the flow rate Q and torque T of the pump-turbine gradually decrease to 0. Subsequently, the flow rate Q reverses direction and reaches a minimum at t = 62.5s. From t = 62.5s to t = 82.5s, the unit is in reverse pumping mode, pumping water from downstream to upstream, causing the head H to rise. From t = 82.5s to t = 96.5s, the flow rate Q and torque T rapidly increase to positive extreme values. Between t = 62.5s and t = 96.5s, the unit's flow rate Q and head H undergo a cycle. Throughout the entire process, because the pump-turbine unit 6 remains connected to the grid, the rotational speed n remains basically stable at the rated speed.

[0085] Figure 5(a) shows the dynamic measurement of n in an embodiment of the present invention. ed ~Q ed The S-characteristic curve of the water pump turbine, Figure 5(b) shows the dynamically measured n in an embodiment of the present invention. ed ~T ed The S-characteristic curves of the pump-turbine, Figures 5(a) and 5(b), show the change process of the dimensionless unit parameter based on the flow parameter over time. These are the S-characteristic curve results of an embodiment of the present invention, demonstrating that the measurement results of the dynamic testing method for the S-characteristic curve of the pump-turbine provided by the present invention have continuity and completeness.

[0086] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A dynamic testing method for the S-characteristic curve of a water pump turbine, characterized in that, Includes the following steps: Step 1: Based on the open-type transient process test bench, start-up and grid connection of the pump-turbine unit are performed. In Step 1, the open-type transient process test bench includes a circulating water pump, an upstream water tank, a downstream water tank, and a pump-turbine unit. The circulating water pump is connected to the upstream water tank through an upstream water supply pipe to fill the upstream water tank. The circulating water pump is connected to the downstream water tank through a downstream water supply pipe to fill the downstream water tank. An upstream overflow pipe is connected to one side of the upstream water tank, and an upstream main pipe is connected to the other side. The height of the upstream main pipe is lower than the height of the upstream overflow pipe. The upstream main pipe is connected to the inlet of the pump-turbine unit. The downstream water tank has a downstream drain pipe at the bottom and a downstream main pipe on the side. The downstream main pipe is connected to the outlet of the pump-turbine unit. The pump-turbine unit is equipped with a speed governor, which is used to adjust the opening of the movable guide vanes. Step 2: Data acquisition of the S-characteristic curve of the pump-turbine unit. Maintaining the pump-turbine unit in grid-connected status, adjusting and maintaining a constant opening of the movable guide vanes, shutting down the circulating water pump, and collecting data at high frequency through sensors to observe the real-time monitoring data waveform. After several cycles, the pump-turbine unit stops, and the movable guide vanes close. In Step 2, after shutting down the circulating water pump, the upstream and downstream water tanks are no longer replenished. The water in the upstream water tank is first discharged from the upstream overflow pipe, and then transported downstream through the upstream main pipeline via the pump-turbine unit. The upstream water level continuously decreases, and the head of the pump-turbine unit continuously decreases. When the head of the pump-turbine unit decreases to a significantly low level, the flow rate reverses, and the upstream main pipe water level begins to rise. When a critical water level is reached, the head of the pump-turbine unit begins to decrease. Finally, a continuous reciprocating motion is formed in the upstream and downstream main pipes. After several cycles, the pump-turbine unit stops, and the movable guide vanes close. Step 3: Based on the collected data, plot the S-characteristic curve of the water pump turbine.

2. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 1, characterized in that: The upstream and downstream water tanks are equipped with vertical chutes, and overflow weirs are provided on the chutes. The height of the overflow weirs can be adjusted by moving the overflow weirs up and down on the chutes to adapt to the testing of the S-characteristic curves of the water pump turbine under different water heads.

3. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 1, characterized in that, Step 1 specifically includes: Step 1.1: Based on the open-type transient process test bench, start the circulating water pump to supply water to the upstream and downstream water tanks, fill the upstream and downstream water tanks to overflow state, and form a constant water head; Step 1.2: Start the pump-turbine unit in turbine mode and connect it to the grid after it has stabilized. Step 1.3: Adjust the opening of the movable guide vanes of the water pump turbine unit through the speed governor to keep the opening of the movable guide vanes of the water pump turbine unit constant.

4. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 3, characterized in that: In step 1.1, the circulating water pump is started, and the circulating water pump fills the upstream water tank with water through the upstream water supply pipe until water can continuously flow out from the upstream overflow pipe, so that the upstream water tank is in an overflow state. The circulating water pump fills the downstream water tank with water through the downstream water supply pipe, so that the downstream water tank is in an overflow state.

5. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 1, characterized in that: In step 2, the sensors measure the water pump turbine flow rate Q, head H, torque T, and rotational speed n. The sensors include an electromagnetic flowmeter for measuring the water pump turbine flow rate Q, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n.

6. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 5, characterized in that: The electromagnetic flowmeter, the pressure sensor, the mechanical torque sensor, and the frequency sensor all measure frequencies above 1000Hz.

7. The dynamic testing method for the S-characteristic curve of a water pump turbine according to claim 5, characterized in that, Step 3 specifically includes: Step 3.1: Based on the collected flow rate Q, head H, torque T, and rotational speed n, convert them into unit rotational speed. Unit flow Unit torque The formula is as follows: in, The outlet diameter of the water pump turbine is in meters. This is the acceleration due to gravity, in units of 1. , The density of water; Step 3.2: Based on the unit rotational speed obtained above Unit flow Unit torque Plot the S-characteristic curve.

8. A dynamic testing device for the S-characteristic curve of a water pump turbine, used to implement the dynamic testing method for the S-characteristic curve of a water pump turbine according to any one of claims 1-7, characterized in that, include: An open-type transient process test bench is used to perform dynamic testing experiments on the S-characteristic curve of a water pump turbine. Sensors include an electromagnetic flowmeter for measuring the flow rate Q of a water pump turbine, a pressure sensor for measuring the head H, a mechanical torque sensor for measuring the torque T, and a frequency sensor for measuring the rotational speed n. The memory is used to store the data acquired by the sensor; The processor is used to calculate and obtain the S-characteristic curve of the water pump turbine; The display is used to show the waveforms of sensor monitoring data and the S-characteristic curves of the water pump and turbine.

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