Phase modulation pressurized water level measurement and control system for pumped storage power station

Abstract

The invention provides a pumped storage power station phase modulation pressurized water level measurement and control system which comprises a gas storage tank, a main pressure gas valve, a gulp valve, a draft tube liquid level switch, a draft tube exhaust valve and a matched pipeline, and further comprises a draft tube inlet pressure sensor and a lower reservoir water level sensor, and the draft tube water level h is calculated according to the real-time pressure P and the lower reservoir real-time water level H; and then phase modulation and pressurized water cooperative control is carried out by combining a draft tube liquid level switch signal. The continuous draft tube water level is calculated by fusing the draft tube pressure and the data of the lower reservoir water level sensor in real time based on the incidence relation of the draft tube water level, the runner chamber pressure and the lower reservoir water level. The calculation result can be used as a supplement of an original liquid level switch, cooperative control is achieved, the accuracy of a measured value can be checked, and the result is preferentially used as a control basis. Therefore, the control reliability is improved, working condition conversion failure caused by signal faults of the liquid level switch is avoided, and the conversion success rate and the operation safety of a power station are improved.

Description

Technical Field

[0001] This invention belongs to the field of pumped storage unit operation control, specifically relating to a pumped storage power station phase-regulating pressurized water level measurement and control system. Background Technology

[0002] Pumped storage power stations, as a primary regulating resource in the power system, provide active power regulation services through a two-way operation mode of generation and pumping. In addition, pumped storage power stations also provide reactive power regulation services through phase-shifting operation. When the units are in phase-shifting operation, it is generally to improve the power coefficient of the power system and maintain its voltage level, consuming active power to deliver reactive power to the system to compensate for the inductive and capacitive currents of transmission lines and asynchronous motors.

[0003] To reduce energy consumption and vibration during phase-shifting operation, a phase-shifting pressurized water system is typically configured to inject compressed air into the turbine runner chamber, lowering the water level below the runner. This allows the runner to rotate in the air, significantly reducing resistance during phase-shifting operation, minimizing active power loss, and reducing vibration. The phase-shifting pressurized water control process is divided into the air-charging and pressurizing process during phase-shifting startup and the air-venting and water-returning process during the transition from pumping to pumping. The hardware involved includes a pressurized water air storage tank, main pressure valve, air-replenishing valve, tailrace pipe level switch, volute, top cover, and tailrace pipe air-replenishing valve. The level switch is located in the tailrace cone chamber and is generally categorized as follows: high pressurized water level (SWX1), pressurized water level (SWX2), pressurized water air-replenishing (SWX3, trigger air-replenishment), and pressurized water completion (SWX4, stop air-replenishment). After the air-pressurization command is initiated, the main air valve and the make-up air valve open. Water is pressurized to SWX2, then the main air valve closes. The make-up air valve remains open until SWX4 is reached, then closes. When the water level rises to SWX3, the make-up air valve opens again, and water is pressurized to SWX4 before closing. If, after a certain delay, the air-pressurization command is issued and SWX1 and SWX3 signals are still received, or if SWX4 signal is not received, the pressurization fails, and the unit startup is locked.

[0004] Therefore, the level switch reflecting the tailrace water level is crucial for the unit's operating condition transition process. To ensure the unit can switch from stationary to pumping phase adjustment and from pumping phase adjustment to pumping power, the level switch must accurately and reliably reflect the water level in the runner chamber. Currently, most pumped storage power stations use magnetic float level gauges. During operation, gas often enters, causing the float position to not correspond to the actual water level, or the float may malfunction or fail to operate due to environmental factors (vibration, magnetic fields, etc.), ultimately leading to the unit's operating condition transition failure and causing unnecessary economic losses to the power station. Summary of the Invention

[0005] The main objective of this invention is to provide a pumped storage power station phase-regulating pressurized water level measurement and control system to address the aforementioned problems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A pumped storage power station phase-adjusting pressurized water level measurement and control system includes an air storage tank, a main air valve, a make-up air valve, a tailrace pipe level switch, a tailrace pipe vent valve, and supporting pipelines. It also includes a tailrace pipe inlet pressure sensor and a lower reservoir water level sensor. The tailrace pipe inlet pressure sensor is used to measure the real-time compressed air pressure P in the runner chamber, and the lower reservoir water level sensor is used to measure the real-time water level H in the lower reservoir. The tailrace pipe water level h is calculated based on the real-time pressure P and the real-time water level H in the lower reservoir. Then, the phase-adjusting pressurized water level coordinated control is carried out by combining the calculated water level h and the tailrace pipe level switch signal.

[0008] The phase-adjusting pressure water coordinated control uses the calculated tailwater pipe water level h and the tailwater pipe liquid level switch signal as two inputs. The control action is started when one of the inputs meets the action conditions.

[0009] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0010] As a preferred technical solution of the present invention: the tailrace pipe inlet pressure sensor is a tailrace pipe inlet pressure sensor or a tailrace pipe inlet pressure pulsation sensor configured in the pumped storage unit status monitoring system. The pressure pulsation sensor obtains the pressure P by extracting the low-frequency component in the output signal of the pressure pulsation sensor. The low-frequency component can be extracted using a conventional low-pass filter, and the filter cutoff frequency is lower than the main frequency of various pressure pulsations in the tailrace pipe.

[0011] As a preferred technical solution of the present invention: the formula for calculating the tailrace water level h is:

[0012] h = HP / ρg

[0013] In the formula, H is the real-time water level in the lower reservoir, P is the real-time pressure of compressed air in the turbine chamber, ρ is the density of water, and g is the acceleration due to gravity.

[0014] As a preferred technical solution of the present invention: the tailwater pipe level switch includes a high water pressure position SWX1, a water pressure position SWX2, a water pressure and air replenishment position SWX3, and a water pressure completion position SWX4.

[0015] As a preferred embodiment of the present invention, the pressure sensor at the inlet of the tailwater pipe is installed at an elevation higher than SWX1.

[0016] As a preferred technical solution of the present invention: the phase-adjusting pressurized water coordinated control is based on the calculated tailwater pipe water level h, and the initial aeration pressurized water control process is as follows:

[0017] After the power station issues the phase-adjusting pressurization order, it opens the main air pressure valve and the air supply valve.

[0018] If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed.

[0019] If the tailwater level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then the main air valve and the air supply valve will be closed simultaneously.

[0020] The air-pressure water control process is as follows:

[0021] If the tailwater level h rises continuously from below SWX4 to above SWX3, and the tailwater level switch reports a signal of SWX3, then the air supply valve will be opened.

[0022] If the tailwater level switch does not report the SWX3 signal, and the tailwater level h continues to rise and exceeds SWX2, then the main air valve and the air supply valve will be opened simultaneously.

[0023] If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed.

[0024] If the level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then both the main pressure valve and the make-up air valve will be closed simultaneously.

[0025] This invention provides a pumped storage power station phase-controlled pressurized water level measurement and control system, which has the following beneficial effects: Based on the correlation between the tailrace water level, turbine chamber pressure, and lower reservoir water level, this invention comprehensively utilizes the real-time measurements from the tailrace inlet pressure sensor and the lower reservoir water level sensor equipped in the power station's unit condition monitoring system to calculate the tailrace water level. This serves as a supplement to the tailrace water level switch in the phase-controlled pressurized water system, achieving coordinated control of the phase-controlled pressurized water system. Furthermore, considering the continuous change characteristics of the calculated water level as an analog quantity, it can be used to verify the accuracy of the measured value itself. Therefore, it can be prioritized as the tailrace water level data source within the control strategy, ensuring the accuracy of the water level data used for control and the reliability of the control. This avoids the problem of operating condition conversion failure caused by signal faults encountered in traditional systems that rely solely on the tailrace water level switch, effectively improving the efficiency of operating condition conversion and ensuring the safe and stable operation of the power station. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the pumped storage power station phase-adjusting pressurized water level measurement and control system provided by the present invention.

[0027] Figure 2This is a flowchart of the initial air-pressurization water control process of the system of the present invention.

[0028] Figure 3 This is a flowchart of the air replenishment and water pressure control system of the present invention.

[0029] In the diagram: 1-Rotator; 2-Vortex; 3-Tailpipe; 4-Air tank; 5-Main air valve; 6-Make-up air valve; 7-Tailpipe level switch; 8-Tailpipe vent valve; 9-Tailpipe inlet pressure sensor; 10-Lower tank; 11-Lower tank level sensor. Detailed Implementation

[0030] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, a phase-regulating pressurized water level measurement and control system for a pumped storage power station is disclosed. The phase-regulating pressurized water system of a pumped storage power station includes an air storage tank 4, a main air valve 5, a make-up air valve 6, a tailrace pipe level switch 7, a tailrace pipe exhaust valve 8, and supporting pipelines. It also includes a tailrace pipe inlet pressure sensor 9 and a lower reservoir water level sensor 11. The tailrace pipe inlet pressure sensor 9 is used to measure the real-time compressed air pressure P in the turbine runner chamber, and the lower reservoir water level sensor 11 is used to measure the real-time water level H in the lower reservoir 10.

[0032] The tailrace pipe level switch 7 includes four positions: high pressurized water level (SWX1), pressurized water level (SWX2), pressurized water and air replenishment (SWX3), and pressurized water completion (SWX4). SWX1 corresponds to an elevation of 103.85 meters and is used to trigger process interlocking. SWX2 corresponds to an elevation of 103.45 meters and is used to trigger pressurized water initiation, controlling the opening of the main air valve and the air replenishment valve. SWX3 corresponds to an elevation of 103.05 meters and is used to trigger pressurized water and air replenishment, controlling the opening of the air replenishment valve. SWX4 corresponds to an elevation of 102.8 meters and is used to trigger the cessation of air replenishment, controlling the closing of the air replenishment valve. All four level switch signals and reset statuses are sent to the power plant's computer monitoring system.

[0033] The phase regulation mode of a pumped storage power station is generally automatic. When the unit switches from a stable shutdown state to pumping phase regulation, the computer monitoring system issues a phase regulation command, automatically initiating the phase regulation and pressurization process. The level switch on the tailrace pipe level switch 7 controls the opening and closing of the main pressure valve 5 and the make-up air valve 6. When the unit switches from phase regulation pressurization to pumping, it automatically performs phase regulation return water until the splashing power is sufficient. After receiving the phase regulation pressurization command, the phase regulation PLC simultaneously issues commands to open the main pressure valve 5 and the make-up air valve 6, and close the tailrace pipe vent valve 8. When the runner chamber water level is lower than SWX3, the main pressure valve 5 is closed; when the runner chamber water level is lower than SWX4, the make-up air valve 6 is closed. At this point, pressurization is completed, and the runner chamber idles in the air. After the initial water pressure is completed, due to air leakage in the main shaft seal, guide vanes, and other parts, the water level in the runner chamber will slowly rise after the main pressure valve 5 and the make-up air valve 6 are closed. When the water level in the runner chamber rises above SWX3, the make-up air valve 6 opens; if it continues to rise to SWX2, the main pressure valve 5 opens. As the make-up air increases, the water level in the runner chamber begins to drop again. When it falls below SWX3, the main pressure valve 5 closes; when it falls below SWX4, the make-up air valve 6 closes. That is, the water level in the runner chamber is always controlled between SWX3 and SWX4. After receiving the phase adjustment return water command, the phase adjustment PLC simultaneously commands to close the main pressure valve 5 and the make-up air valve 6, and open the tailrace pipe vent valve 8. After the unit meets the splash power requirement or the PLC retracts the water command for 70 seconds, the tailrace pipe vent valve 8 is closed.

[0034] The tailrace pipe inlet pressure sensor 9 is the same sensor used in the unit condition monitoring system. This sensor is installed below the runner 1, at the inlet of the tailrace pipe 3, at an elevation of 105.2 meters, higher than the elevation of SWX1, and also higher than the outlet elevations of the tailrace pipe's air supply and exhaust pipes. The sensor has a measurement accuracy of 0.1 kPa. The sensor signal is connected to the unit condition monitoring system and then sent to the computer monitoring system. The data sampling interval is no more than 1 second. The volute 2 is also equipped with an exhaust valve and piping for switching between operating conditions such as exhaust water return and power generation.

[0035] The lower reservoir water level sensor 11 is an existing sensor in the power station. The signal has been connected to the computer monitoring system. The data sampling interval is no more than 1 second. The water level variation range of the lower reservoir is 172~193 meters. The measurement range of the lower reservoir water level sensor 11 is 150~200 meters, and the measurement accuracy is 0.01 meters.

[0036] When the phase-adjusting pressurized water system performs the aeration pressurization process, the water level in the tailrace pipe gradually decreases. At this time, the gas pressure P in the turbine chamber and the gas-water interface pressure are the same. The gas-water interface pressure is directly related to the water level in the lower reservoir, and the following relationship exists:

[0037] P=ρg(Hh)

[0038] In the formula, ρ is the density of water, g is the acceleration due to gravity, H is the water level in the lower reservoir, and h is the water level in the tailrace pipe. Therefore, the water level in the tailrace pipe can be calculated as:

[0039] h = HP / ρg.

[0040] Since the pressure sensor 9 at the tailrace inlet and the water level sensor 11 at the lower reservoir both measure continuous analog values, the tailrace water level h calculated using the above formula is also a continuously changing analog value. During the air-pressurization process of the phase-adjusting pressurization system, the tailrace water level h continuously decreases; during the exhaust and return process, it continuously rises. Considering these data variation characteristics, the calculated tailrace water level h is more reliable than the four switching signals from the tailrace level switch 7. Therefore, although conventionally the calculated tailrace water level h and the tailrace level switch signal can be used as two inputs, the control action is initiated when one input meets the operating conditions. This includes activating the main pressure valve and the make-up air valve when one input is higher than SWX2, closing the main pressure valve when one input is lower than SWX3, and closing the make-up air valve when one input is lower than SWX4. Subsequently, if the water level rises and one input is higher than SWX3, the make-up air valve is activated until one input is lower than SWX4, at which point the make-up air valve is closed. However, considering that the calculated tailrace water level h is more reliable than the four switching signals of the tailrace water level switch 7, the phase-changing pressurization control of the pumped storage power station in this embodiment will use the tailrace water level h as the reference data, and the four switching signals of the tailrace water level switch 7 as a supplement. Before the phase-changing start, it is determined that the guide vanes and ball valves are in the fully closed state. After the labyrinth ring cooling water is turned on, the air-pressurization is started. The initial air-pressurization control process is as follows: Figure 2 As shown, the process includes:

[0041] After the power station issues the phase-adjusting pressurization order, it opens the main air pressure valve and the air supply valve.

[0042] If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed.

[0043] If the tailwater level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then the main air valve and the air supply valve will be closed simultaneously.

[0044] After the initial air and water pressurization is completed, due to air leakage in the main shaft seal, guide vanes, etc., the water level in the tailrace pipe will rise slowly, requiring intermittent air and water replenishment operations. The air and water replenishment control process is as follows: Figure 3 As shown, the process includes the following:

[0045] If the tailwater level h rises continuously from below SWX4 to above SWX3, and the tailwater level switch reports a signal of SWX3, then the air supply valve will be opened.

[0046] If the tailwater level switch does not report the SWX3 signal, and the tailwater level h continues to rise and exceeds SWX2, then the main air valve and the air supply valve will be opened simultaneously.

[0047] If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed.

[0048] If the level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then both the main pressure valve and the make-up air valve will be closed simultaneously.

[0049] During the phase adjustment operation, depending on the air leakage of the main shaft seal, guide vanes, etc., multiple rounds of air replenishment and water pressure operation may be required. The above control process needs to be repeated many times.

[0050] In another embodiment, since the power plant unit condition monitoring system is only equipped with a pressure pulsation sensor at the tailrace inlet, the pressure P data is obtained by extracting the low-frequency component from the output signal of the pressure pulsation sensor. A Balvor low-pass filter is used, with a filter cutoff frequency of 0.2 Hz, which is lower than the dominant frequency of various pressure pulsations in the tailrace. Of course, since there is no pressure pulsation in the runner chamber during the air-pressurization process, the use of a low-pass filter in this embodiment has no impact on the results.

[0051] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A pumped storage power station phase-regulating pressurized water level measurement and control system, comprising an air storage tank, a main pressurization valve, a make-up air valve, a tailrace pipe level switch, a tailrace pipe vent valve, and supporting pipelines, characterized in that: It also includes a tailrace pipe inlet pressure sensor and a lower reservoir water level sensor. The tailrace pipe inlet pressure sensor is used to measure the real-time compressed air pressure P in the impeller chamber. The lower reservoir water level sensor is used to measure the real-time water level H in the lower reservoir. The tailrace pipe water level h is calculated based on the real-time pressure P and the real-time water level H in the lower reservoir. Then, the phase-adjusting pressure water coordinated control is carried out by combining the calculated water level h and the tailrace pipe liquid level switch signal. The phase-adjusting pressure water coordinated control uses the calculated tailwater pipe water level h and the tailwater pipe liquid level switch signal as two inputs. The control action is started when one of the inputs meets the action conditions.

2. The pumped storage power station phase-adjusting pressurized water level measurement and control system according to claim 1, characterized in that: The tailrace pipe inlet pressure sensor is either a tailrace pipe inlet pressure sensor or a tailrace pipe inlet pressure pulsation sensor configured in the pumped storage unit status monitoring system.

3. The pumped storage power station phase-regulating pressurized water level measurement and control system according to claim 1, characterized in that: The formula for calculating the tailrace water level h is: h = HP / ρg In the formula, H is the real-time water level in the lower reservoir, P is the real-time pressure of compressed air in the turbine chamber, ρ is the density of water, and g is the acceleration due to gravity.

4. The pumped storage power station phase-regulating pressurized water level measurement and control system according to claim 1, characterized in that: The tailwater pipe level switch includes a high water pressure position SWX1, a water pressure position SWX2, a water pressure and air replenishment position SWX3, and a water pressure completion position SWX4.

5. The pumped storage power station phase-regulating pressurized water level measurement and control system according to claim 1 or 4, characterized in that: The pressure sensor at the tailrace pipe inlet is installed at an elevation higher than SWX1.

6. The pumped storage power station phase-regulating pressurized water level measurement and control system according to claim 1, characterized in that: The phase-adjusting pressurized water coordinated control is based on the calculated tailrace water level h. The initial aeration pressurized water control process is as follows: After the power station issues the phase-adjusting pressurization order, it opens the main air pressure valve and the air supply valve. If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed. If the tailwater level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then the main air valve and the air supply valve will be closed simultaneously. The air-pressure water control process is as follows: If the tailwater level h rises continuously from below SWX4 to above SWX3, and the tailwater level switch reports a signal of SWX3, then the air supply valve will be opened. If the tailwater level switch does not report the SWX3 signal, and the tailwater level h continues to rise and exceeds SWX2, then the main air valve and the air replenishment valve will be opened simultaneously. If the tailwater level h drops below SWX3 and the tailwater level switch SWX3 resets, then the main air valve will be closed. If the level switch SWX3 fails to reset and the tailwater level h continues to drop below SWX4, then both the main air valve and the air supply valve will be closed simultaneously.

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