A dynamic coordinated control method for a hydroelectric generating set

Abstract

The application discloses a kind of water power station energy scheduling technical field's water-turbine-generator unit dynamic coordination control method, by obtaining unit operating state parameters and water delivery system state parameters, and control nozzle needle valve is slowly closed, simultaneously control deflector collaborative action, make deflector opening gradually reduce and carry out deflection to jet flow;In the deflector action process, real-time monitoring pressure parameter and flow rate parameter on jet flow path, and analyze pressure pulsation and flow characteristic change, the closing speed of deflector and action law are dynamically regulated;After deflector opening reduces to preset threshold, make jet flow completely deviate from runner bucket, to realize unit smoothly enters phase-modulation operating state;The application can effectively reduce unit torque fluctuation, weaken water hammer pressure and pressure pulsation, improve the stability and security of phase-modulation starting process.

Description

Technical Field

[0001] This invention relates to a dynamic coordinated control method for hydropower units, belonging to the field of hydropower station energy dispatching technology. Background Technology

[0002] As a crucial energy conversion device in hydropower stations, water turbines are widely used in high-head, low-flow conditions, achieving energy conversion through high-speed jet impact on the runner buckets. During power system operation, to meet grid regulation requirements, water turbine units need to switch between generation mode and phase-regulating mode. The phase-regulating start-up process is a critical stage in the transition of the unit from generation operation to synchronous no-load operation.

[0003] During the phase-adjustment start-up process, the unit typically controls the opening of the nozzle needle valve to gradually close the jet, while simultaneously deflecting the water flow with the rapid action of the deflector, thereby gradually separating the jet from the water bucket and achieving the transition from hydraulic drive to motor drive operation.

[0004] However, during this transition process, the coupling effect between nozzle flow rate changes and deflector operation causes significant changes in the jet flow state, leading to complex hydraulic transient phenomena. Specifically, as the deflector gradually intervenes and deflects the jet, the position, angle, and intensity of the jet impact on the water bucket become unstable, easily causing severe fluctuations in the water bucket torque and impeller torque, and even negative torque phenomena. This results in increased unit vibration and affects operational stability. Simultaneously, the deflector operation also causes rapid changes in flow rate, creating water hammer pressure in the water supply system, which propagates along the pipeline, impacting upstream pipelines and the unit structure, posing certain safety hazards.

[0005] In existing technologies, the control of the phase-shifting start-up process mainly focuses on the action control of a single component, and the nozzle needle valve or deflector is controlled according to preset rules, lacking systematic regulation of both. At the same time, there is a lack of real-time feedback and adjustment mechanisms for the pressure pulsation, flow structure changes and the impact on the unit torque generated during the jet deflection process, making it difficult to simultaneously suppress torque fluctuations and control water hammer effects during the deflector operation process. Summary of the Invention

[0006] This invention provides a dynamic coordinated control method for hydropower units, which solves the problems of large oscillations or even negative torque in the water bucket torque and impeller torque during the deflection process of the existing deflector intervention, as well as the water hammer pressure induced by the rapid action of the deflector and the change in nozzle flow rate in the water conveyance system, causing pressure pulsation to propagate along the flow channel.

[0007] A dynamic coordinated control method for hydropower units includes the following steps:

[0008] Acquire unit operating status parameters and water transmission system status parameters;

[0009] Based on the unit's operating status parameters, the nozzle needle valve is controlled to continuously close from the no-load opening to zero opening, while the deflector is controlled to perform coordinated action, so that the deflector opening gradually decreases and the jet is deflected.

[0010] During the deflector operation, the pressure and velocity parameters on the jet path are monitored in real time. The pressure parameters are used to analyze the water hammer pressure change and the energy distribution on the water bucket surface. The velocity parameters are used to analyze the flow state characteristics during the jet deflection process.

[0011] Based on the water hammer pressure change, the energy distribution law, the flow state characteristics, and the unit torque change, the closing speed of the deflector and the switching sequence of the opening degree at each stage are adjusted;

[0012] After the deflector opening is reduced to the preset threshold, the jet completely deviates from the turbine water bucket, and the unit enters the phase adjustment operation state.

[0013] Furthermore, the real-time monitoring of pressure and velocity parameters along the jet path, and the analysis of water hammer pressure changes and energy distribution patterns on the water bucket surface based on the pressure parameters, includes:

[0014] Using total pressure coefficient Characterizing the energy distribution on the front and back of the water bucket:

[0015] ;

[0016] in, ρ is the dimensionless total pressure coefficient, Tp is the pressure value at the position to be analyzed on the front or back of the water bucket, Pref is the reference pressure, H is the unit operating head before the deflector is closed, ρ is the density of water, and g is the acceleration due to gravity.

[0017] Furthermore, the real-time monitoring of pressure and velocity parameters along the jet path includes the real-time monitoring of velocity parameters along the jet path, which comprises:

[0018] The influence of deflector action on the jet velocity field is characterized by the velocity coefficient Cv.

[0019] ;

[0020] in, is a dimensionless velocity coefficient; v is the instantaneous flow velocity at each measuring point along the jet path. The average jet velocity at the nozzle exit section;

[0021] When the monitoring point is If a sudden drop occurs, it is determined that the deflector has begun to interfere with the jet, and the closing speed of the deflector is adjusted.

[0022] Furthermore, the step of gradually reducing the deflector opening includes three sequentially performed stages:

[0023] In the first stage, the deflector opening is greater than 50%, and the deflector has not yet contacted the jet. It closes continuously at a uniform speed, and the nozzle needle valve closes synchronously from the no-load opening to the zero opening direction. At this time, the deflector action does not cause the jet to deflect, and the unit torque is affected by the nozzle opening.

[0024] In the second stage, the deflector opening is 20% to 50%: the deflector contacts the jet and produces a deflection effect, increasing the closing speed and passing through this range, so as to shorten the duration of the jet impacting the back of the water bucket and reduce the negative fluctuation amplitude of the impeller torque;

[0025] In the third stage, when the deflector opening is less than 20%, the deflector has completely deflected the water jet away from the water bucket, and the surface of the water bucket is no longer impacted by the water flow. The unit then enters a phase-adjusting operation state of idling in the air.

[0026] Furthermore, the first stage also includes power regulation:

[0027] The control unit adjusts the nozzle from the working opening to the no-load opening to complete the transition from power generation mode to phase modulation start-up, creating the initial boundary conditions for the first-stage deflector;

[0028] In the power regulation and subsequent first, second and third stages, the unit speed is always maintained at synchronous speed.

[0029] Furthermore, as the deflector opening gradually decreases, four fixed pressure pulsation measuring points, Q1, Q2, Q3, and Q4, are set along the initial central axis of the jet before the deflector actuates:

[0030] Q1 is installed on the initial jet center axis near the runner side to monitor the amplitude of water hammer pressure propagating upstream to the unit side;

[0031] Q2 is positioned at the center of the initial jet axis to capture the initial change in water hammer pressure when the deflector comes into contact with the jet;

[0032] Q3 is positioned on the central axis of the initial jet near the deflector side to monitor the change in flow velocity in this region after the deflector deflects the refracted flow.

[0033] Q4 is installed downstream of the jet path behind the deflector to assess the water hammer effect of the deflector's operation on the downstream water conveyance system.

[0034] Furthermore, in the step of obtaining the state parameters of the water conveyance system, a 1D-3D coupled simulation method is used to predict the pressure response of the water conveyance system under different deflector closure schemes. The turbine is simulated using a three-dimensional CFD method, and the water conveyance system is simulated using a one-dimensional characteristic line method. The two are coupled at the coupling interface through a partially overlapping coupling method, where C⁺ and C⁻ represent the forward and reverse characteristics in the pipeline, respectively.

[0035] ;

[0036] This represents the computational flow rate at the coupling interface. The calculated head at the coupling interface, Let be the pipeline characteristic constant, where A is the cross-sectional area of ​​the pipe, a is the water hammer wave velocity, and g is the acceleration due to gravity. and These are the positive and negative characteristic line coefficients, respectively.

[0037] Furthermore, adjusting the closing speed of the deflector includes:

[0038] When the water bucket torque or impeller torque is detected to have a negative fluctuation and the fluctuation amplitude exceeds the preset threshold, the deflector closing speed is increased to shorten the time the deflector is in the 20% to 50% opening range and reduce the duration of the jet impact on the back of the water bucket.

[0039] When the water hammer pressure at the Q2 measuring point is detected to exceed the preset upper limit threshold in real time, the deflector closing speed is reduced.

[0040] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0041] 1. This invention obtains the unit's operating status parameters and the water supply system's status parameters, and on this basis controls the nozzle needle valve to close slowly and the deflector to cooperate in action, thereby achieving orderly control of the jet deflection process and avoiding the flow abrupt change problem caused by independent control of a single component.

[0042] 2. This invention monitors the pressure and velocity parameters along the jet path in real time during the deflector's operation and analyzes the pressure pulsation and flow characteristics, enabling the control process to reflect the actual flow field changes. This provides an accurate basis for subsequent adjustments and improves the pertinence and dynamic response capability of the control strategy. Attached Figure Description

[0043] Figure 1 The diagram shown is a structural diagram of the nozzle and deflector closure scheme of a dynamic coordinated control method for hydropower units provided in an embodiment of the present invention.

[0044] Figure 2The diagram shown is a schematic diagram of a one-dimensional and three-dimensional coupling method for a dynamic coordinated control method for hydropower units provided in an embodiment of the present invention.

[0045] Figure 3 The figure shown is a comparison of 1D-3D and 1D simulation calculation results of a dynamic coordinated control method for hydropower units provided in an embodiment of the present invention.

[0046] Figure 4 The diagram shown illustrates the deflector-nozzle coordinated closure pattern of different schemes of a dynamic coordinated control method for hydropower units provided in this embodiment of the invention.

[0047] Figure 5 The diagram shown is a flowchart of a dynamic coordination control method for hydropower units provided in an embodiment of the present invention. Detailed Implementation

[0048] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0049] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0050] In one specific implementation, such as Figure 5 As shown, a dynamic coordinated control method for hydropower units is provided, including the following steps:

[0051] Acquire unit operating status parameters and water transmission system status parameters;

[0052] Based on the unit's operating status parameters, the nozzle needle valve is controlled to slowly close from the no-load opening to zero opening, while the deflector is controlled to perform coordinated action, so that the deflector opening gradually decreases and the jet is deflected.

[0053] During the deflector operation, the pressure and velocity parameters on the jet path are monitored in real time. The pressure parameters are used to analyze the water hammer pressure change and the energy distribution law on the water bucket surface. The velocity parameters are used to analyze the flow state characteristics during the jet deflection process.

[0054] Based on the water hammer pressure change, the energy distribution law, the flow state characteristics, and the unit torque change, the closing speed of the deflector and the switching sequence of the opening degree at each stage are adjusted;

[0055] After the deflector opening is reduced to the preset threshold, the jet completely deviates from the turbine water bucket, and the unit enters the phase adjustment operation state.

[0056] In the step of analyzing the energy distribution law on the surface of the water bucket based on pressure parameters, the total pressure coefficient is used. Characterizing the energy distribution on the front and back of the water bucket:

[0057] ;

[0058] in, Tp is a dimensionless total pressure coefficient used to characterize the energy distribution level of the water bucket surface relative to the reference state; Tp is the pressure value at the analyzed location on the front or back of the water bucket, in Pa. ref For reference pressure, standard atmospheric pressure is used, with the unit being Pa. H is the unit's operating head before the deflector is closed, ρ is the density of water, and g is the acceleration due to gravity.

[0059] When the back of the water bucket A positive value appears that is greater than the value of the front in the same position. When this occurs, it indicates that the back of the water bucket is impacted by the jet and generates a reverse drag torque, thereby triggering the above-mentioned adjustment steps to increase the deflector closing speed and shorten the duration of this unfavorable energy distribution state.

[0060] In the step of real-time monitoring of flow velocity parameters along the jet path, a velocity coefficient is used. Quantitative characterization of the effect of deflector action on the jet velocity field:

[0061] ;

[0062] in, is a dimensionless velocity coefficient; v is the instantaneous flow velocity at each measuring point along the jet path. The average flow velocity at the nozzle outlet.

[0063] When the monitoring point is When a sudden drop occurs, it is determined that the deflector has begun to interfere with the jet, triggering an adjustment step to adjust the deflector closing speed in order to control the water hammer pressure amplitude within the allowable range.

[0064] The step of gradually reducing the deflector opening includes three sequential stages:

[0065] In the first stage, the deflector opening is greater than 50%: the deflector has not yet contacted the jet and is continuously closed at a uniform or slow speed, while the nozzle needle valve closes synchronously from the no-load opening to the zero opening direction; in this stage, the deflector action does not cause the jet to deflect, and the unit torque is mainly controlled by the nozzle opening.

[0066] In the second stage, the deflector opening is between 20% and 50%: the deflector contacts the jet and produces a deflection effect. A quick closing strategy is adopted to pass through this range in order to shorten the duration of the jet impacting the back of the water bucket and reduce the negative fluctuation amplitude of the impeller torque.

[0067] In the third stage, when the deflector opening is less than 20%, the deflector has completely deflected the water jet away from the water bucket, and the surface of the water bucket is no longer impacted by the water flow. The unit then enters a phase-adjusting operation state of idling in the air.

[0068] Before the first stage begins, there is also a power regulation stage: the control unit adjusts the nozzle from the working opening to the no-load opening to complete the transition from power generation mode to phase-shifting start-up, creating the initial boundary conditions for the deflector-nozzle coordinated closure in the first stage; in the power regulation stage and the subsequent first, second and third stages, the unit speed is always maintained at the synchronous speed.

[0069] As the deflector opening gradually decreases, four fixed pressure pulsation measuring points, Q1, Q2, Q3, and Q4, are set along the initial central axis of the jet before the deflector operates. The positions of each measuring point do not change with the deflector operation throughout the entire process.

[0070] Q1 is positioned on the central axis of the initial jet near the runner side to monitor the amplitude of water hammer pressure propagating upstream to the unit side; Q2 is positioned at the center of the central axis of the initial jet to capture the initial change in water hammer pressure when the deflector contacts the jet; Q3 is positioned on the central axis of the initial jet near the deflector side to monitor the change in flow velocity in this region after the deflector deflects the flow; Q4 is positioned downstream of the jet path behind the deflector to assess the impact of the deflector's operation on the water hammer of the downstream water conveyance system.

[0071] Q1, Q2, and Q3 are arranged along a fixed initial jet axis. The jet trajectory deviation caused by the deflector action is reflected in the change of the velocity coefficient Cv at each measuring point, without the need for dynamic adjustment of the measuring point position. When the pressure parameters at Q2 and Q1 undergo synchronous abrupt change, it is determined that the water hammer pressure has spread upstream, thereby triggering the adjustment step.

[0072] In the step of obtaining the state parameters of the water conveyance system, a 1D-3D coupled simulation method is used to predict the pressure response of the water conveyance system under different deflector closure schemes. The turbine is simulated using a three-dimensional CFD method, and the water conveyance system is simulated using a one-dimensional characteristic line method. The two are coupled at the coupling interface through a partially overlapping coupling method, where C⁺ and C⁻ represent the forward and reverse characteristics in the pipeline, respectively.

[0073] ;

[0074] This represents the computational flow rate at the coupling interface. The calculated head at the coupling interface, Let be the pipeline characteristic constant, where A is the cross-sectional area of ​​the pipe, a is the water hammer wave velocity, and g is the acceleration due to gravity. and These are positive and negative characteristic line coefficients, determined by the flow rate and head of the upstream and downstream nodes at the previous moment, reflecting the influence of the upstream and downstream boundary states on the hydraulic parameters of the coupling interface. By comparing the peak water hammer pressure at Q2 with the unit torque fluctuation amplitude under different deflector closing times T using the coupling simulation method, the closing time T that minimizes torque fluctuation under the premise that the water hammer pressure does not exceed the design allowable value of the water conveyance system is selected as the quantitative basis for the adjustment steps.

[0075] The step of adjusting the closing speed of the deflector includes:

[0076] When the water bucket torque or impeller torque is detected to have a negative fluctuation and the fluctuation amplitude exceeds the preset threshold, the deflector closing speed is increased to shorten the time the deflector is in the 20% to 50% opening range and reduce the duration of the jet impact on the back of the water bucket.

[0077] When the water hammer pressure at the Q2 measuring point is detected to exceed the preset upper limit threshold in real time, the deflector closing speed is reduced to ensure that the transient pressure of the water conveyance system does not exceed the design allowable value.

[0078] The adjustment range of the above-mentioned shutdown speed is constrained by the safety boundary value of the shutdown time T determined by the coupled simulation method.

[0079] In this embodiment, the process of switching the turbine from power generation mode to phase adjustment mode is divided into two stages. The first stage is the power regulation stage, in which the nozzle is adjusted from the working opening to the no-load opening, and the unit speed remains constant at the synchronous speed in this state. The second stage is the phase adjustment entry stage, in which the nozzle needle valve is slowly closed from the no-load opening to the zero opening, and at the same time the deflector quickly deflects the jet, and the unit transitions from the power generation state to the phase adjustment no-load state.

[0080] like Figure 4 As shown, the deflector control method provided in this embodiment optimizes the control of the second stage, namely the deflector-nozzle coordinated closing process.

[0081] During the transition between phasing start-up and shutdown of the turbine, the slow opening and closing of the nozzle needle valve combined with the rapid action of the deflector helps the turbine quickly switch between power generation mode and phasing mode; for example Figure 1 As shown, the relative opening s of the nozzle needle valve n With absolute distance S n The relationship between them is:

[0082] ;

[0083] Where D0 is the diameter of the cross section where the jet is located.

[0084] In this embodiment, the needle valve and the deflector are configured to move simultaneously; under this condition, the needle valve moves in a certain direction. Figure 1 The deflector moves in the direction indicated by the middle arrow, gradually decreasing from the unloaded opening to 0. The deflector rotates in the opposite direction of the arrow in (b), with y gradually decreasing from 100% to 0%.

[0085] For the turbine phase-changing stop condition, this embodiment only considers the movement of the needle valve; under this condition, the needle valve with different numbers of nozzles moves in the direction indicated by the arrow in (a) and gradually opens from 0 to the no-load opening degree.

[0086] It should be noted that in CFD numerical simulation, the motion of the nozzle needle valve and deflector falls under the category of boundary motion and deformation problems, and a dynamic mesh is used to simulate their motion. This embodiment, based on the motion characteristics of the structural hexahedral mesh, employs a layered algorithm to control the mesh deformation of the nozzle and deflector. A control method based on the mesh height ratio is used to adjust mesh merging and splitting. After debugging, a splitting factor of 0.4 and a collapse factor of 0.2 were determined to effectively control the quality of mesh splitting and merging.

[0087] This invention employs a 1D-3D coupled numerical simulation method to predict and evaluate the deflector control process. The turbine section is simulated using a three-dimensional CFD method, with the VOF two-phase flow model capturing the water-air interface and the SSTk-ω turbulence model selected; the time step is chosen to be 5.0 × 10⁻⁶. 4 s, corresponding to a rotation of 1.125° per step at a rated speed of 375 rpm, ensuring that at least 15 time steps are required for adjacent water buckets to reach their current position, and controlling all residuals within 10. -4 The following methods are used: The momentum equation and turbulence term discretization employs a second-order upwind scheme; the pressure term uses the PRESTO scheme; the time discretization uses a first-order implicit scheme; and the pressure-velocity coupling uses the PISO algorithm. The water conveyance system is simulated using the one-dimensional characteristic line method, where C⁺ and C⁻ represent the forward and reverse characteristics in the pipe, respectively. The characteristic equations for C⁺ and C⁻ are established based on the pipe water hammer theory.

[0088] ;

[0089] in, This represents the computational flow rate at the coupling interface at the current moment. The calculated head at the coupling interface at the current moment; Let be the pipe characteristic constant, expressed as: =gA / a, where g is the acceleration due to gravity, A is the cross-sectional area of ​​the pipe, and a is the water hammer wave velocity inside the pipe; The coefficients of the positive characteristic lines are calculated as follows: Cn is the negative characteristic coefficient, calculated as follows: ; This represents the flow rate at upstream node A at the previous moment. This represents the flow rate at downstream node B at the previous moment. The water head at upstream node A at the previous moment; Δt is the water head at downstream node B at the previous moment; f is the friction coefficient along the pipeline; and D is the pipeline diameter.

[0090] like Figure 2 and Figure 3 As shown, a partially overlapping coupling method is used between 1D and 3D, and the static pressure in the CFD domain at each time step is obtained through a user-defined function in Fluent. and traffic Substituting these values ​​as input parameters into the C⁺ and C⁻ equations of the MOC, the static pressure at the next time step is obtained. and traffic Then apply static pressure The 3D boundary conditions are updated to the CFD computational domain, achieving time-step progressive coupling between the two domains. Verification was performed by comparing the opening / closing process of six nozzles from a relative opening of 0 to 1.0 using the 1D-3D coupling method and the pure 1DMOC method. The nozzle outlet head and the pressure chamber water level change curves showed good agreement, proving the effectiveness of the coupling method.

[0091] During the second stage of phase-shifting startup, the needle valve is slowly closed from its no-load opening (approximately 3% of its rated opening) to 0, i.e., s. n The deflector opening percentage decreased linearly from 3% to 0%, and the deflector opening percentage decreased synchronously from 100% to 0%.

[0092] Furthermore, the deflector control process is implemented in three stages.

[0093] Phase 1: Initial Closure Stage with Deflector Opening Greater Than 50%: Before the deflector contacts the jet ejected from the nozzle, it closes from 100% to 50% at a uniform speed according to the preset closure curve or according to a specified pattern. Simultaneously, the needle valve closes linearly from the no-load opening to zero opening. The unit speed is maintained at the synchronous speed (375 rpm) by the speed governor, with an allowable deviation of no more than ±0.5%. The water bucket torque and impeller torque are monitored. This stage is mainly controlled by the nozzle opening and remains relatively stable without significant fluctuations. The verification index for this stage is the total pressure coefficient. Maintaining the velocity coefficient C at measuring points Q1 to Q3 within a reasonable range under normal power generation conditions. vIt remained basically around 1.0, with no mutations.

[0094] The second stage: the mid-closing phase when the deflector opening is between 20% and 50%, is the critical control stage for the entire phase-shifting start-up transition process. When the deflector opening drops below 50%, the deflector begins to contact the jet and deflects it, causing drastic and irregular changes in the angle, position, and force of the jet impacting the water bucket. The water bucket torque fluctuates significantly between positive and negative torques. A rapid closing strategy is employed in this stage, meaning that the deflector opening is closed within the 20%–50% range using the shortest possible closing time T. Based on simulation comparison studies, a rapid shutdown scheme with a total shutdown time T not exceeding 2.0s is recommended to achieve the following control objectives: shorten the duration of back impact on the water bucket, minimizing the duration of the jet impact on the back of the water bucket and reducing the accumulation of reverse resistance torque; reduce the amplitude of runner torque fluctuation, lowering the frequency of back impact on the water bucket, significantly reducing the number and amplitude of negative fluctuations in runner torque, and weakening unit vibration; control the influence of water bucket notch outflow, as the deflector deflects the refracted flow, causing the jet center to shift from the tangent position of the water bucket nodal circle to near the water bucket notch, resulting in notch outflow. Rapid shutdown can compress the duration of this unfavorable flow state to the shortest possible time, reducing the interference impact of notch outflow on the back of the subsequent water bucket.

[0095] Phase 3: Late Closure Stage (Deflector Opening Less Than 20%): The deflector has completely deflected the water jet away from the water bucket, and the surface of the water bucket is no longer impacted by the water flow; the deflector continues to close from 20% to 0% according to the rapid closing strategy, completing all deflection actions; the unit runs in an air-cooled state under the drive of the motor, maintaining synchronous speed, and the torque curve tends to be stable; once it is confirmed that the water bucket torque and the impeller torque have stabilized within a small fluctuation range close to zero, and the unit vibration is significantly reduced, it can be determined that the phase-adjustment start-up is successful, and the unit officially enters the phase-adjustment operation mode.

[0096] To comprehensively capture the generation, propagation, and attenuation patterns of pressure pulsations during deflector operation, four pressure pulsation monitoring points, Q1 to Q4, were set up along the jet path of the unit. The specific locations and functions of each monitoring point are shown in Table 1.

[0097] Q1 In front of the deflector, near the wheel side Monitor the amplitude of water hammer pressure transmitted to the unit side; detect sudden increases in turbine bucket torque. Q2 In front of the deflector, in the center position <![CDATA[The initial location where water hammer pressure is generated; C T and C v synchronous fluctuation is a direct signal of the deflector interfering with the jet flow]]> Q3 In front of the deflector, near the deflector side <![CDATA[Monitoring the flow velocity change in the area after the deflector deflects the jet; C v drops to a low level first]]> Q4 Behind the deflector, downstream of the jet path Assess the impact of deflector operation on downstream nozzles and the water delivery system; due to the physical obstruction of the deflector, the water hammer pressure decreases significantly.

[0098] Table 1. Layout and Functional Description of Pressure Pulsation Measurement Points

[0099] In this embodiment, a 10% drop from the original measuring point is considered a sudden drop;

[0100] The typical response pattern of each measuring point during the middle stage of deflector closure is as follows: C at measuring point Q2 T Sudden increase and C vThe sudden drop occurred simultaneously, and its amplitude was greater than that of Q1. This is because Q2 is closer to the deflector and directly bears the impact of the jet deflection; the C at the measuring point of Q1 T Sudden increase and C v A sudden drop followed, slightly later than Q2, indicating that the water hammer pressure was propagating from Q2 upstream to Q1. No drastic fluctuations in the total pressure coefficient were observed at measuring point Q3 because the deflector action shifted the jet away from Q3, resulting in very little water flowing through that point. At measuring point Q4, the CT (transformer pressure) continued to rise, while Cv (volume) rapidly decreased, a normal hydraulic response to the deflector obstructing the downstream flow. The water hammer pressure first occurred at Q2, then propagated upstream (towards Q1) and downstream (towards Q3 and Q4), but the attenuation rates differed significantly between the two directions: upstream, without deflector obstruction, attenuation was slow, and the water hammer pressure at Q2 could be smoothly transmitted to Q1 and further act on the impeller, causing a sudden increase in both the bucket torque and impeller torque; downstream, the water hammer pressure was significantly weakened by the physical obstruction of the deflector, and the water hammer pressure at Q4 had rapidly and significantly attenuated, having minimal impact on the downstream nozzles and water delivery system. By employing continuous wavelet transform to perform time-frequency analysis on the pressure time-domain signals at each measuring point, the frequency distribution characteristics and energy distribution characteristics of non-stationary signals such as water hammer pressure at different time nodes can be accurately captured, which can be used to quantitatively evaluate the differences in water hammer intensity among different deflector closure schemes.

[0101] This embodiment compares three total deflector closing time schemes of 1.5s, 2.0s, and 2.5s.

[0102] The peak-to-peak value of the water bucket torque ΔMb and the peak-to-peak value of the impeller torque ΔMr of each scheme within the deflector opening range of 20% to 50% are extracted as core evaluation indicators. As the closing time T increases, both ΔMb and ΔMr increase significantly, and the frequency of a single water bucket entering negative torque increases. Therefore, under the premise of satisfying the water hammer pressure constraint, a smaller T value should be selected first.

[0103] Comparing the back of the water bucket under different schemes The distribution area and duration of the back impact effect are as follows: the shorter the closing time, the shorter the duration of the positive CT on the back of the water bucket, the weaker the back impact effect, and the higher the energy transfer efficiency of the unit.

[0104] The shorter the shut-off time, the greater the rate of change in water flow caused by the deflector action, and the higher the amplitude of the resulting water hammer pressure. It is necessary to ensure that the maximum CT at the Q2 measuring point does not exceed the maximum transient head ratio allowed by the unit design in order to ensure the structural safety of the water transmission system.

[0105] Based on the above three evaluation indicators, this embodiment adopts a deflector fast-closing scheme with a total shut-off time T ≤ 2.0s. In specific engineering implementation, precise calibration can be performed through 1D-3D coupled simulation according to the actual unit head and water conveyance system parameters to ensure that the water hammer pressure amplitude is within an acceptable range, while minimizing unit torque fluctuations and the duration of water bucket back impact.

[0106] The complete implementation process of the deflector control method described in this invention in the second stage of turbine phasing start-up is as follows:

[0107] S1, Initial state confirmation: Confirm that the unit speed has been maintained at synchronous speed, the nozzle needle valve is at no-load opening (about 3% of rated opening), the deflector is at 100% opening (fully open), and the second stage of phase adjustment start-up is ready for start-up.

[0108] S2, coordinated shutdown start, simultaneously issuing deflector shutdown command and needle valve shutdown command, the deflector starts to close from 100% according to the fast closing scheme (T≤2.0s), the needle valve synchronously and linearly closes from no-load opening to zero opening, the two coordinate actions;

[0109] S3, turn off initial monitoring (y is greater than 50%), continue to monitor the CT and Cv values ​​of Q1 to Q4 measuring points, confirm that each parameter is within the normal range and there is no abnormal fluctuation, and the deflector continues to be turned off according to the instruction;

[0110] S4, close the mid-term rapid passage (y is 20% to 50%), the deflector passes through the 20% to 50% opening range at the fastest allowed speed, while closely monitoring the CT surge at Q2 and Q1. If the CT exceeds the warning threshold, record the peak water hammer pressure for subsequent optimization, and confirm that the time of positive CT on the back of the water bucket is as short as possible.

[0111] S5, close the later confirmation (y less than 20%), continue to close the deflector to 0%, confirm that the water bucket torque and runner torque have become stable, CT and Cv fluctuations have subsided, and the unit is in phase-adjusting idling state;

[0112] S6, Phase Shift Operation Confirmation: After the unit has been running continuously and stably for no less than 30 seconds, if the speed is confirmed to be maintained at the synchronous speed and the torque fluctuation is within the allowable range, then the phase shift start is determined to be successful and the unit officially enters the phase shift operation mode.

[0113] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0114] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A dynamic coordinated control method for hydropower units, characterized in that, Includes the following steps: Acquire unit operating status parameters and water transmission system status parameters; Based on the unit's operating status parameters, the nozzle needle valve is controlled to continuously close from the no-load opening to zero opening, while the deflector is controlled to perform coordinated action, so that the deflector opening gradually decreases and the jet is deflected. During the deflector operation, pressure and velocity parameters along the jet path are acquired in real time. The pressure parameters are used to analyze the water hammer pressure changes and energy distribution patterns on the water bucket surface, and the velocity parameters are used to analyze the flow state characteristics during the jet deflection process. The closing speed of the deflector is adjusted based on the changes in water hammer pressure, energy distribution, flow characteristics, and unit torque. After the deflector opening is reduced to the preset threshold, the jet completely deviates from the turbine water bucket, and the unit enters the phase adjustment operation state.

2. The dynamic coordinated control method for hydropower units according to claim 1, characterized in that, The analysis of water hammer pressure changes and energy distribution patterns on the surface of the water bucket based on the aforementioned pressure parameters includes: Using total pressure coefficient Characterizing the energy distribution on the front and back of the water bucket: ； in, It is a dimensionless total pressure coefficient. This represents the pressure value at the location to be analyzed, either on the front or back of the water bucket. For reference pressure, H is the unit operating head before the deflector is closed, ρ is the density of water, and g is the acceleration due to gravity.

3. The dynamic coordinated control method for hydropower units according to claim 1, characterized in that, The velocity parameters along the jet path include the velocity coefficient Cv, which is used to quantitatively characterize the influence of the deflector action on the jet velocity field. The formula is as follows: ； in, is a dimensionless velocity coefficient; v is the instantaneous flow velocity at each measuring point along the jet path. The average jet velocity is located at the nozzle exit section.

4. The dynamic coordinated control method for hydropower units according to claim 3, characterized in that, When the monitoring point is If a sudden drop occurs, it is determined that the deflector has begun to interfere with the jet, and the closing speed of the deflector is adjusted.

5. The dynamic coordinated control method for hydropower units according to claim 1, characterized in that, The coordinated operation of the control deflector includes: In the first stage when the deflector opening is greater than 50%, it closes continuously at a uniform speed, and the nozzle needle valve closes synchronously from the no-load opening to the zero opening direction. In the second stage, when the deflector opening is 20%–50%, the closing speed is increased. In the third stage, when the deflector opening is less than 20%, the control unit switches to phase adjustment operation.

6. The dynamic coordinated control method for hydropower units according to claim 5, characterized in that, The first stage also includes power regulation: The control unit adjusts the nozzle from the working opening to the no-load opening to complete the transition from power generation mode to phase modulation start-up, creating the initial boundary conditions for the first stage deflector; In the first, second, and third stages, the unit speed is always maintained at synchronous speed.

7. The dynamic coordinated control method for hydropower units according to claim 5, characterized in that, As the deflector opening gradually decreases, four fixed pressure pulsation measuring points, Q1, Q2, Q3, and Q4, are set along the initial central axis of the jet before the deflector operates: Q1 is installed on the initial jet center axis near the runner side to monitor the amplitude of water hammer pressure propagating upstream to the unit side; Q2 is positioned at the center of the initial jet axis to capture the initial change in water hammer pressure when the deflector comes into contact with the jet; Q3 is positioned on the central axis of the initial jet near the deflector side to monitor the change in flow velocity in this region after the deflector deflects the refracted flow. Q4 is installed downstream of the jet path behind the deflector to assess the water hammer effect of the deflector's operation on the downstream water conveyance system.

8. The dynamic coordinated control method for hydropower units according to claim 1, characterized in that, Obtaining the state parameters of the water conveyance system includes: predicting the pressure response of the water conveyance system under different deflector closure schemes using a 1D-3D coupled simulation method; simulating the turbine using a three-dimensional CFD method; and simulating the water conveyance system using a one-dimensional characteristic line method. Data exchange between the two is achieved at the coupling interface through a partially overlapping coupling method, where C⁺ and C⁻ represent the forward and reverse characteristics in the pipeline, respectively. ； This represents the computational flow rate at the coupling interface. The calculated head at the coupling interface, Let be the pipeline characteristic constant, where A is the cross-sectional area of ​​the pipe, a is the water hammer wave velocity, and g is the acceleration due to gravity. and These are the positive and negative characteristic line coefficients, respectively.

9. The dynamic coordinated control method for hydropower units according to claim 1, characterized in that, Adjusting the closing speed of the deflector includes: When the water bucket torque or impeller torque is detected to have a negative fluctuation and the fluctuation amplitude exceeds the preset threshold, the deflector closing speed is increased to shorten the time the deflector is in the 20% to 50% opening range and reduce the duration of the jet impact on the back of the water bucket. When the water hammer pressure at the Q2 measuring point is detected to exceed the preset upper limit threshold in real time, the deflector closing speed is reduced.

10. A deflector control system during the phase-adjustment start-up process of a water turbine, characterized in that, The dynamic coordination control method for hydropower units as described in any one of claims 1-9 is adopted.

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