A water turbine generator water-machine coupling control method

Abstract

This invention discloses a hydro-turbine-electric coupling control method for hydropower units in the field of hydropower station energy dispatching technology. It includes analyzing the interaction mechanism of physical quantities among the hydraulic system, turbine, and electrical system in a hydro-solar combined power generation system. Based on this analysis, it constructs an elastic water hammer model, a turbine model, a regulating system model based on a PI-type governor and a hydraulic servo system, and a generator model. It then uses coupling variables such as head, flow rate, unit speed, and electromagnetic power to establish a complete hydro-turbine-electric coupling time-domain simulation model. Finally, it incorporates actual power station operating data and verifies the model's accuracy by comparing the measured data with the simulation results. This invention can fully reflect the dynamic coupling relationship between multiple hydro-turbine-electric subsystems, improving the model's response accuracy and stability under frequency disturbances and load changes.

Description

Technical Field

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

[0002] In combined hydropower and solar power systems, hydropower units typically undertake the main regulation tasks of grid frequency control and power balance. However, due to factors such as solar radiation intensity and meteorological conditions, the output of photovoltaic power plants exhibits significant randomness and fluctuations, leading to continuous changes in grid frequency and load levels. In such systems, fluctuations in photovoltaic output will couple to the hydropower units through the grid, causing dynamic changes in turbine influent flow, unit speed, and generator electromagnetic power, thus placing higher demands on the stable operation and regulation performance of the units.

[0003] In existing technologies, the modeling and control of hydropower units often employs a method of independently modeling the hydraulic system, turbine, speed control system, and generator. While this can reflect the static or local dynamic characteristics of each subsystem to some extent, it generally fails to adequately consider the coupling relationship between the hydraulic, turbine, and electrical systems. For example, in hydraulic system modeling, some methods use rigid water hammer models or simplified models, neglecting the influence of the elastic effect of the water intake pipe on the dynamics of the water flow, resulting in insufficient model accuracy under rapid adjustment or large disturbance conditions. In turbine modeling, approximations are often based on a single operating condition, making it difficult to accurately describe the nonlinear characteristics under the multivariate coupling of head, speed, and guide vane opening. Regarding the speed control system, most methods focus on control strategy design, lacking a unified framework for collaborative modeling with the hydraulic and electrical systems. In generator modeling, some methods oversimplify the electromagnetic transient process, making it difficult to accurately reflect the dynamic characteristics during power exchange.

[0004] Furthermore, when constructing the overall model, the subsystems are often simply connected in series or superimposed, lacking a unified coupling modeling method based on physical mechanisms. This makes it difficult for the model to truly reflect the dynamic interaction between key variables such as head, flow rate, rotational speed, and electromagnetic power, thus limiting the reliability and applicability of the model in engineering applications. Summary of the Invention

[0005] This invention provides a hydroelectric coupling control method for hydropower units, which solves the problem that existing models for hydropower units generally do not adequately consider the coupling relationship between the hydraulic system, turbine, speed control system and generator, resulting in the model failing to accurately reflect the dynamic interaction characteristics between head, flow rate, unit speed and electromagnetic power.

[0006] A hydroelectric coupling control method for a hydropower unit is provided, comprising the following steps:

[0007] The mechanism of physical quantity interaction in the hydro-solar combined power generation system was analyzed, and an elastic water hammer model to describe the hydraulic dynamic characteristics and a turbine model to describe the turbine operating characteristics were constructed.

[0008] Based on the turbine model, a governor model for the regulating system is established. A combination of a PI-type governor and a hydraulic servo system is used to obtain the dynamic response relationship between the frequency deviation and the guide vane opening adjustment, so as to perform closed-loop regulation of the turbine's operating status.

[0009] Under the action of the regulation system, a generator model is established to obtain the dynamic mapping relationship between the prime mover input power and the electromagnetic output power;

[0010] Based on the elastic water hammer model, turbine model, system governor model and generator model, a time-domain simulation model of water turbine-electric coupling is formed by combining the coupling variables.

[0011] After the hydro-turbine-electric coupling time-domain simulation model was constructed, actual power plant operation data was introduced to compare with the simulation results in order to verify the accuracy of the hydro-turbine-electric coupling time-domain simulation model.

[0012] Furthermore, the elastic water hammer model is discretized using the method of characteristics, and the governing equations are:

[0013] ;

[0014] ;

[0015] Where H is the pipe head; x is the pipe axial coordinate; a is the water hammer wave velocity; g is the gravitational acceleration; Q is the flow rate; A is the pipe cross-sectional area; λ is the friction coefficient; D is the pipe diameter; α is the pipe inclination angle; and t is time.

[0016] Furthermore, the elastic water hammer model is simplified using a variable-parameter second-order model, with the transfer function being:

[0017] ;

[0018] Where Δh is the pipe head deviation; Δq is the pipe flow rate deviation; The inertial time constant of the water flow; α is the elastic water hammer time constant; α is the elastic correction coefficient; s is the Laplace operator.

[0019] Furthermore, the torque characteristic and flow characteristic equations of the turbine model are as follows:

[0020] ;

[0021] ;

[0022] Where M is the turbine output torque; Q is the turbine flow rate; y is the guide vane opening; n is the unit speed; and H is the turbine working head.

[0023] Furthermore, the turbine model is linearized for small fluctuations near each operating point, and the dynamic characteristics are represented by the transfer coefficient. The linearized equation is:

[0024] ;

[0025] Where Δq is the flow rate deviation; Δm is the torque deviation; Δy is the guide vane opening deviation; Δω is the unit speed deviation; and Δh is the working head deviation. This is the transmission coefficient of turbine torque to guide vane opening. This is the torque transfer coefficient of the water turbine to its rotational speed; This is the transmission coefficient of turbine torque to water head; The transfer coefficient of turbine flow rate to guide vane opening; This is the transfer coefficient of the turbine's flow rate to its rotational speed; This is the transfer coefficient of the turbine flow rate to the water head.

[0026] Furthermore, the transfer function of the regulating system combining the PI-type speed controller and the hydraulic servo system is:

[0027] ;

[0028] Where Gr(s) is the governor transfer function; Δy is the guide vane opening adjustment; and Δω is the speed deviation. This refers to the proportional gain of the PI controller. The integral coefficient of the PI controller; This is the adjustment coefficient; is the time constant of the hydraulic servo system; s is the Laplace operator.

[0029] Furthermore, the generator model is described by the following system of equations:

[0030] ;

[0031] in, Electromagnetic power; This refers to the active power transmitted from the hydropower unit to the power grid. For copper loss; Reactive power; ω is the moment of inertia; ω is the rotor speed. This refers to the power of the prime mover; This is the excitation winding potential; This refers to the generator-side voltage. The d-axis reactance; δ is the q-axis reactance; δ is the power angle; This refers to the excitation regulation ratio coefficient; φ is the stator current; φ is the power factor angle; 0 represents the initial steady-state value.

[0032] Furthermore, the accuracy verification includes: designing multi-frequency disturbance conditions to perform frequency modulation simulation verification on the model, wherein the frequency disturbance conditions include at least a positive first disturbance condition, a negative first disturbance condition, a positive second disturbance condition, and a positive third disturbance condition.

[0033] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0034] 1. This invention systematically analyzes the coupling relationship between head, flow rate, unit speed, guide vane opening and electromagnetic power in the initial stage of modeling, so that the established model can reflect the dynamic correlation between the various subsystems of water turbine and electrical system from the mechanism level. This effectively overcomes the problem of insufficient integrity caused by the independent modeling of each subsystem in the prior art, thereby significantly improving the integrity and consistency of the model.

[0035] 2. This invention introduces an elastic water hammer model into the hydraulic subsystem and combines it with the nonlinear characteristics of the turbine and its linearized transfer coefficient model, enabling the model to simultaneously take into account the nonlinear response characteristics under a wide range of operating conditions and the dynamic analysis accuracy under small disturbance conditions, thereby improving the response accuracy under frequency fluctuation and load change conditions.

[0036] 3. This invention constructs a regulation model that includes a PI-type governor and a hydraulic servo system, and forms a closed-loop control relationship with the turbine model. This enables the guide vane opening adjustment to respond promptly to the unit speed deviation, improving the system's dynamic adjustment capability to grid frequency disturbances and enhancing the stability of unit operation. Furthermore, by coupling the models of each subsystem, a complete hydro-turbine coupled time-domain simulation model is formed. Actual power plant operating data is introduced for comparison and verification, making the model not only highly accurate in theory but also possessing good engineering applicability and reliability. This provides a reliable basis for optimizing the frequency regulation control strategy and improving the operation mode of hydro-generator units. Attached Figure Description

[0037] Figure 1 The figure shown is a model diagram of the turbine system transfer coefficient of the hydroelectric coupling control method for hydroelectric generators provided in an embodiment of the present invention.

[0038] Figure 2 The figure shown is a graph showing the relationship between M11 and y and n11 of the impulse turbine in the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention.

[0039] Figure 3 The figure shown is a graph showing the relationship between Q, y, and n11 of the impulse turbine in the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention.

[0040] Figure 4 The figure shown is a speed governor model diagram of the hydroelectric coupling control method for hydropower units provided in an embodiment of the present invention;

[0041] Figure 5 The figure shown is an exciter model diagram of the hydroelectric coupling control method for hydropower units provided in an embodiment of the present invention;

[0042] Figure 6 The figure shown is a monthly distribution box plot of the photovoltaic treatment of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention;

[0043] Figure 7 The diagram shows a flowchart of the hydroelectric coupling control method for a hydropower unit provided in an embodiment of the present invention.

[0044] Figure 8 The figure shown is a comparison of power changes of the hydroelectric generator set provided in the embodiment of the present invention under a disturbance of +0.1Hz.

[0045] Figure 9 The figure shown is a comparison of the opening degree changes of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention under a disturbance of +0.1Hz;

[0046] Figure 10 The figure shown is a comparison of power changes of the hydroelectric generator set provided in the embodiment of the present invention under a disturbance of -0.1Hz.

[0047] Figure 11 The figure shown is a comparison of the opening degree changes of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention under a disturbance of -0.1Hz;

[0048] Figure 12 The figure shown is a comparison of power changes of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention under a disturbance of +0.15Hz;

[0049] Figure 13 The figure shown is a comparison of the opening degree changes of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention under a disturbance of +0.15Hz;

[0050] Figure 14 The figure shown is a comparison of power changes of the hydroelectric generator set provided in the embodiment of the present invention under a disturbance of +0.2Hz.

[0051] Figure 15The figure shown is a comparison of the opening degree changes of the hydroelectric coupling control method of the hydropower unit provided in the embodiment of the present invention under a disturbance of +0.2Hz. Detailed Implementation

[0052] 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.

[0053] 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.

[0054] In one specific implementation, such as Figure 7 As shown, a hydroelectric coupling control method for a hydropower unit is provided, comprising the following steps:

[0055] The mechanism of physical quantity interaction in the hydro-solar combined power generation system was analyzed, and an elastic water hammer model to describe the hydraulic dynamic characteristics and a turbine model to describe the turbine operating characteristics were constructed.

[0056] Based on the turbine model, a governor model for the regulating system is established. A combination of a PI-type governor and a hydraulic servo system is used to obtain the dynamic response relationship between the frequency deviation and the guide vane opening adjustment, so as to perform closed-loop regulation of the turbine's operating status.

[0057] Under the action of the regulation system, a generator model is established to obtain the dynamic mapping relationship between the prime mover input power and the electromagnetic output power;

[0058] Based on the elastic water hammer model, turbine model, system governor model and generator model, a time-domain simulation model of water turbine-electric coupling is formed by combining the coupling variables.

[0059] After the hydro-turbine-electric coupling time-domain simulation model was constructed, actual power plant operation data was introduced to compare with the simulation results in order to verify the accuracy of the hydro-turbine-electric coupling time-domain simulation model.

[0060] In the hydraulic subsystem, considering the water hammer effect caused by the long water intake pipe, an elastic water hammer model is used to describe the dynamic characteristics of the water flow, and the governing equations are discretized using the method of characteristics. The governing equations are as follows:

[0061] ;

[0062] ;

[0063] Where H is the pipe head; x is the pipe axial coordinate; a is the water hammer wave velocity; g is the gravitational acceleration; Q is the flow rate; A is the pipe cross-sectional area; λ is the friction coefficient; D is the pipe diameter; α is the pipe inclination angle; and t is time.

[0064] To reduce computational complexity while maintaining accuracy, a second-order approximation is applied to the above model. A variable-parameter second-order transfer function is used to describe the dynamic characteristics of the water diversion system. The transfer function is:

[0065] ;

[0066] Where Δh is the pipe head deviation; Δq is the pipe flow rate deviation; The inertial time constant of the water flow; α is the elastic water hammer time constant; α is the elastic correction coefficient; s is the Laplace operator.

[0067] In the turbine subsystem, to reflect the influence of head, speed, and guide vane opening on the unit's operating state, a turbine torque and flow characteristic model is established, with the following expression:

[0068] ;

[0069] ;

[0070] Where M is the turbine output torque; Q is the turbine flow rate; y is the guide vane opening; n is the unit speed; and H is the turbine working head.

[0071] like Figure 1 and Figure 2 As shown, when performing small disturbance analysis near the unit's operating point, the above nonlinear relationship is linearized, and the linearized equation is:

[0072] ;

[0073] Where Δq is the flow rate deviation; Δm is the torque deviation; Δy is the guide vane opening deviation; Δω is the unit speed deviation; and Δh is the working head deviation. This is the transmission coefficient of turbine torque to guide vane opening. This is the torque transfer coefficient of the water turbine to its rotational speed; This is the transmission coefficient of turbine torque to water head; The transfer coefficient of turbine flow rate to guide vane opening; This is the transfer coefficient of the turbine's flow rate to its rotational speed; This is the transfer coefficient of the turbine flow rate to the water head.

[0074] like Figure 3 and Figure 4 As shown, in the modeling of impulse turbines, the deflector is usually considered to have only two states: fully closed and fully closed, to simulate the rapid start-up and cut-off of water supply of the impulse turbine. In this impulse turbine model, the deflector's action is ignored and it is assumed that all six nozzles operate simultaneously. A nonlinear turbine model is also used to improve the simulation accuracy.

[0075] like Figure 5 As shown, the regulating system employs a combination of a PI-type speed governor and a hydraulic servo system to achieve closed-loop regulation of the unit's speed deviation.

[0076] ;

[0077] Where Gr(s) is the governor transfer function; Δy is the guide vane opening adjustment; and Δω is the speed deviation. This refers to the proportional gain of the PI controller. The integral coefficient of the PI controller; This is the adjustment coefficient; is the time constant of the hydraulic servo system; s is the Laplace operator.

[0078] In the generator subsystem, a mathematical model is established based on the operating mechanism of the synchronous generator:

[0079] ;

[0080] in, Electromagnetic power; This refers to the active power transmitted from the hydropower unit to the power grid. For copper loss; Reactive power; ω is the moment of inertia; ω is the rotor speed. This refers to the power of the prime mover; This is the excitation winding potential; This refers to the generator-side voltage. The d-axis reactance; δ is the q-axis reactance; δ is the power angle; This is the excitation regulation ratio coefficient; φ is the stator current; φ is the power factor angle; 0 represents the initial steady-state value.

[0081] Specifically, all the above quantities are per-unit values. For the excitation part, the modeling is as follows: Figure 6 As shown.

[0082] The accuracy verification includes: designing multi-frequency disturbance conditions to perform frequency modulation simulation verification on the model, wherein the frequency disturbance conditions include at least a positive first disturbance condition, a negative first disturbance condition, a positive second disturbance condition, and a positive third disturbance condition.

[0083] Specifically, based on actual power plant data, the accuracy was verified by comparing measured data with simulation results.

[0084] Collect key operating data from actual power plants; under the same initial conditions, in this embodiment, select photovoltaic power, initial head, and initial load as input simulation models, and output corresponding time-series curves.

[0085] To verify the correctness and accuracy of the established coupling model, a specific simulation analysis was first conducted on the core frequency regulation function of the impulse turbine unit—primary frequency regulation—and the simulation results were quantitatively compared with field measured data. Based on common frequency fluctuation scenarios in actual power grid operation, four typical frequency disturbance conditions were designed: +0.1Hz (positive first disturbance condition), -0.1Hz (negative first disturbance condition), +0.15Hz (positive second disturbance condition), and +0.2Hz (positive third disturbance condition). For the first three frequency fluctuation conditions, the disturbance signal duration was set to 60 seconds, allowing the system to recover to the rated frequency after reaching a stable state. However, for the +0.2Hz large positive disturbance condition, to observe the unit's regulation capability and recovery characteristics under extreme frequency deviations, the disturbance signal duration was extended to 80 seconds to fully capture the entire process from disturbance occurrence, regulation action, to steady-state recovery.

[0086] During the simulation, all control parameters were strictly set according to the unit operating parameters in the field test report to ensure that the simulation conditions were highly consistent with the actual operating environment. The specific parameter configurations are as follows: droop coefficient ep = 4% (used to set the proportional relationship between the unit frequency change and the active power adjustment, which directly affects the frequency regulation sensitivity), PID controller proportional coefficient Kp = 5 (determines the strength of the regulation action and affects the response speed), integral coefficient Ki = 4 (eliminates static error and ensures steady-state accuracy), derivative coefficient Kd = 1 (suppresses overshoot and improves system stability), and frequency dead zone Ef = 0.05Hz (avoids frequent operation of the regulation mechanism due to small frequency fluctuations and reduces equipment wear).

[0087] Based on the above parameter configuration, this paper focuses on a comparative analysis of two core operating indicators of the impulse turbine: active power and nozzle opening. Active power is the core indicator of the unit's power transmission to the grid, and its dynamic response directly reflects the unit's frequency regulation capability. Nozzle opening is a key parameter for the impulse turbine to regulate the flow rate; its change directly determines the hydraulic system's effect on the unit's power regulation. The synergistic matching relationship between the two is an important basis for evaluating the accuracy of the model simulation. A detailed comparison between the simulation results and the field measured data is as follows: Figures 8-15 As shown in the figure, not only are the dynamic response curves of the unit's active power under different frequency disturbance conditions presented, but the real-time adjustment process of the nozzle opening is also displayed simultaneously, providing intuitive and reliable data support for subsequent quantitative evaluation of model accuracy and optimization of the unit's primary frequency regulation control strategy.

[0088] 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.

[0089] 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 hydroelectric coupling control method for a hydropower unit, characterized in that, Includes the following steps: The mechanism of physical quantity interaction in the hydro-solar combined power generation system was analyzed, and an elastic water hammer model to describe the hydraulic dynamic characteristics and a turbine model to describe the turbine operating characteristics were constructed. Based on the turbine model, a governor model for the regulating system is established. A combination of a PI-type governor and a hydraulic servo system is used to obtain the dynamic response relationship between the frequency deviation and the guide vane opening adjustment, so as to perform closed-loop regulation of the turbine's operating status. Under the action of the regulation system, a generator model is established to obtain the dynamic mapping relationship between the prime mover input power and the electromagnetic output power; Based on the elastic water hammer model, turbine model, system governor model and generator model, a time-domain simulation model of water turbine-electric coupling is formed by combining the coupling variables. After the hydro-turbine-electric coupling time-domain simulation model was constructed, actual power plant operation data was introduced to compare with the simulation results in order to verify the accuracy of the hydro-turbine-electric coupling time-domain simulation model.

2. The hydroelectric coupling control method for a hydropower unit according to claim 1, characterized in that, The elastic water hammer model is discretized using the method of characteristics, and the governing equations are: ； ； Where H is the pipe head; x is the pipe axial coordinate; a is the water hammer wave velocity; g is the gravitational acceleration; Q is the flow rate; A is the pipe cross-sectional area; λ is the friction coefficient; D is the pipe diameter; α is the pipe inclination angle; and t is time.

3. The hydroelectric coupling control method for a hydropower unit according to claim 2, characterized in that, The elastic water hammer model is simplified using a variable-parameter second-order model, and the transfer function is: ； Where Δh is the pipe head deviation; Δq is the pipe flow rate deviation; The inertial time constant of the water flow; α is the elastic water hammer time constant; α is the elastic correction coefficient; s is the Laplace operator.

4. The hydroelectric coupling control method for a hydropower unit according to claim 1, characterized in that, The torque and flow characteristics equations of the turbine model are as follows: ； ； Where M is the turbine output torque; Q is the turbine flow rate; y is the guide vane opening; n is the unit speed; and H is the turbine working head.

5. The hydroelectric coupling control method for a hydropower unit according to claim 4, characterized in that, The turbine model is linearized for small fluctuations near each operating point, and the dynamic characteristics are represented by the transfer coefficient. The linearization equation is as follows: ； Where Δq is the flow rate deviation; Δm is the torque deviation; Δy is the guide vane opening deviation; Δω is the unit speed deviation; and Δh is the working head deviation. This is the transmission coefficient of turbine torque to guide vane opening. This is the torque transfer coefficient of the water turbine to its rotational speed; This is the transmission coefficient of turbine torque to water head; The transfer coefficient of turbine flow rate to guide vane opening; This is the transfer coefficient of the turbine's flow rate to its rotational speed; This is the transfer coefficient of the turbine flow rate to the water head.

6. The hydroelectric coupling control method for a hydropower unit according to claim 1, characterized in that, The transfer function of the regulating system combining the PI-type speed governor and the hydraulic servo system is: ； Where Gr(s) is the governor transfer function; Δy is the guide vane opening adjustment; and Δω is the speed deviation. This refers to the proportional gain of the PI controller. The integral coefficient of the PI controller; This is the adjustment coefficient; is the time constant of the hydraulic servo system; s is the Laplace operator.

7. The hydroelectric coupling control method for a hydropower unit according to claim 1, characterized in that, The generator model is described by the following system of equations: ； in, Electromagnetic power; This refers to the active power transmitted from the hydropower unit to the power grid. For copper loss; Reactive power; ω is the moment of inertia; ω is the rotor speed. This refers to the power of the prime mover; This is the excitation winding potential; This refers to the generator-side voltage. The d-axis reactance; δ is the q-axis reactance; δ is the power angle; This refers to the excitation regulation ratio coefficient; φ is the stator current; φ is the power factor angle; 0 represents the initial steady-state value.

8. The hydroelectric coupling control method for a hydropower unit according to claim 1, characterized in that, The accuracy verification includes: designing multi-frequency disturbance conditions to perform frequency modulation simulation verification on the model, wherein the frequency disturbance conditions include at least a positive first disturbance condition, a negative first disturbance condition, a positive second disturbance condition, and a positive third disturbance condition.

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