Method for stability analysis and operation strategy optimization of hydroelectric generating set after tail water extension excavation

Abstract

The invention discloses a stability analysis and operation strategy optimization method for a hydroelectric generating set after tail water excavation. The method comprises the following steps: constructing a non-linear hydropower station diversion power generation system; establishing a nonlinear mathematical model of a nonlinear hydropower station water diversion and power generation system; the nonlinear mathematical model is converted into a high-order state equation form, and state equations of unit rotating speed relative deviation, guide vane opening relative deviation, water head relative deviation, surge chamber intermediate variables and tailrace tunnel flow are obtained; constructing a relational expression between the water level descending height of the tail water channel and the related parameters of the hydropower station; and respectively substituting the given basic parameters of the hydropower station and the related parameters of the hydropower station into the state equation, changing the speed regulator parameters in the state equation, drawing a dynamic response map, and selecting the optimal speed regulator parameters. The dynamic response process of the water diversion and power generation system of the hydropower station is analyzed according to the different water level descending heights of the tail water channel, and the optimal operation strategy corresponding to the different water level descending heights of the tail water channel is defined.

Description

Technical Field

[0001] The invention relates to the technical field of stable operation of hydropower stations, and in particular to a method for analyzing the stability of a hydropower unit after tailwater excavation and optimizing its operation strategy. Background Art

[0002] The comprehensive development and utilization of hydropower energy is related to the sustainable development of the national economy and society. Under the long-term development strategy of carbon peak and carbon neutrality, it undertakes a large amount of power consumption tasks. In order to effectively utilize the hydropower resources of the river section, the implementation of the tailwater excavation project can achieve the effect of improving the stability of the power generation system and the power generation efficiency. However, the environment where the turbine is located is affected by many factors, accompanied by strong nonlinear characteristics. At the same time, the setting of the tailwater tunnel must meet the requirements of ensuring the stable operation of the calculation and hydropower station. Therefore, it is particularly important to carry out stability analysis of the water diversion power generation system of the hydropower station after tailwater excavation and study the operation strategy.

[0003] Some of the research contents in the existing technology include: stability research of the speed control system of a hydropower station with a surge chamber under the action of nonlinear characteristics; Hopf bifurcation and dynamic simulation of the turbine control system of a hydropower station with a variable-roof tailwater tunnel; stability research of the turbine control system of a hydropower station with a variable-roof tailwater tunnel based on Hopf bifurcation; stability research of the turbine control system with an inclined-roof tailwater tunnel under load disturbance; influence of the tailwater full flow transition process on the transient parameters of the water transmission and power generation system and the regulation quality of the unit.

[0004] However, the research in the prior art has the following problems: the turbine with a downstream surge chamber and a variable-height tailwater tunnel system only considers a linear model, and does not involve the impact of tailwater excavation on the stability of the hydropower unit. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation, which not only considers the nonlinear model of the turbine, but also takes into account the influence of different water level drop heights of the tailwater channel after tailwater excavation on the stability of the hydropower unit, providing a scientific reference for the operation strategy after the potential development of the hydropower station.

[0006] To achieve the above object, the present invention proposes a method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation, which is particularly characterized in that it comprises the following steps:

[0007] S1) constructing a nonlinear hydropower station water diversion and power generation system, including a pressure pipe subsystem, a turbine subsystem, a generator subsystem, a downstream surge chamber subsystem, and a tailwater channel subsystem arranged in sequence from an upstream reservoir to a downstream reservoir;

[0008] The tailrace subsystem includes a tailrace tunnel subsystem with variable top height and an open channel subsystem;

[0009] S2) establishing a nonlinear mathematical model of a nonlinear hydropower station water diversion and power generation system, wherein the nonlinear mathematical model includes a pressure pipe model, a turbine nonlinear model, a turbine governor model, a generator model, a downstream surge chamber model, and a tailwater tunnel model with a variable top height;

[0010] S3) converting the nonlinear mathematical model into a high-order state equation form, taking the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the flow rate of the tailwater tunnel as state variables, and taking the resistance torque of the turbine as the external load disturbance, respectively obtaining the state equations of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the flow rate of the tailwater tunnel;

[0011] S4) determining the hydropower station related parameters related to the tailrace water level drop height, constructing the relationship between the tailrace water level drop height and the hydropower station related parameters; clarifying the tailrace water level drop height before and after the tailrace excavation, and calculating the change results of the related parameters of each hydropower station under different tailrace water level drop heights;

[0012] The relevant parameters of the hydropower station include: the working head of the unit, the water depth at the open and full flow interface, the water flow velocity at the open and full flow interface, the open channel wave velocity of the open flow section, the length of the pipeline from the downstream surge chamber to the tailwater channel, and the inertia time constant of the water flow in the pressure pipeline, the time constant of the downstream surge chamber, and the inertia time constant of the water flow in the tailwater tunnel;

[0013] S5) determining basic parameters of the hydropower station that are independent of the tailrace water level drop height, substituting the given basic parameters of the hydropower station and the hydropower station related parameters corresponding to different tailrace water level drop heights into the state equation in step S3), changing the governor parameters in the state equation, and drawing the dynamic response spectrum of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the head, and the tailrace tunnel flow at different tailrace water level drop heights, analyzing the system stability and regulation quality from the dynamic response spectrum, selecting the optimal governor parameters at different tailrace water level drop heights, thereby clarifying the optimal operation strategy corresponding to different tailrace water level drop heights;

[0014] The speed regulator parameters include different combinations of speed regulator proportional gain parameters and speed regulator integral parameters.

[0015] Furthermore, in S2), the pressure pipeline model is expressed as

[0016]

[0017] The nonlinear model of the turbine is expressed as

[0018]

[0019]

[0020] The turbine governor model is expressed as

[0021]

[0022] The generator model is expressed as

[0023]

[0024] The downstream surge tank model is expressed as

[0025]

[0026] The tailwater tunnel model with variable top height is expressed as

[0027]

[0028] In the formula,

[0029] dq t / dt is the differential form of the relative value of the pressure pipeline flow deviation,

[0030] q t is the relative value of pressure pipeline flow deviation,

[0031] T wt is the inertia time constant of water flow in the pressure pipe,

[0032] h is the relative deviation of water head,

[0033] z F is the intermediate variable of the surge chamber,

[0034] h t is the pipe head loss,

[0035] H 0 is the working water head of the unit,

[0036] dz F / dt is the differential form of the intermediate variable of the surge chamber,

[0037] T F is the time constant of the downstream surge chamber,

[0038] q y is the tailwater tunnel flow,

[0039] h y is the head loss in the tailrace tunnel,

[0040] λ is the tailwater tunnel section coefficient,

[0041] Q y0 is the initial tailwater tunnel flow,

[0042] c is the open channel wave velocity in the open flow section,

[0043] B is the width of the tailwater tunnel,

[0044] V x is the water velocity at the clear full flow interface,

[0045] g is the acceleration due to gravity,

[0046] α is the slope angle of the tailwater tunnel top,

[0047] tanα is the slope of the tailwater tunnel,

[0048] T wy is the inertia time constant of the tailrace tunnel flow,

[0049] m t is the relative value of turbine torque deviation,

[0050] e h0 、e x0 、e y0 are the turbine torque transfer coefficients,

[0051] x is the relative deviation of the unit speed,

[0052] y is the relative deviation of the guide vane opening,

[0053] e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients,

[0054] T a is the unit inertia time constant,

[0055] dx / dt is the differential form of the relative deviation of the unit speed,

[0056] m g is the turbine resistance torque,

[0057] e g is the load self-regulation coefficient,

[0058] dy / dt is the differential form of the relative deviation of the guide vane opening,

[0059] K p is the proportional gain of the speed regulator,

[0060] K i is the speed regulator integral gain.

[0061] Furthermore, in S3), the state equations of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the flow rate of the tailwater tunnel are respectively

[0062]

[0063] In the formula,

[0064] A simple expression method for the differential form of the relative deviation of the unit speed is: is a simple expression method of the differential form of the relative deviation of the guide vane opening, A simple expression method for the differential form of the relative deviation of the water head is: A simple expression method for the differential form of the intermediate variable of the surge chamber, is a simple expression method of the differential form of the tailwater tunnel flow, x is the relative deviation of the unit speed,

[0065] y is the relative deviation of the guide vane opening,

[0066] h is the relative deviation of water head,

[0067] z F is the intermediate variable of the surge chamber,

[0068] q y is the tailwater tunnel flow,

[0069] h y is the head loss in the tailrace tunnel,

[0070] e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients,

[0071] e h0 、e x0 、e y0 are the turbine torque transfer coefficients,

[0072] T a is the unit inertia time constant,

[0073] T wy is the inertia time constant of the tailrace tunnel flow,

[0074] T wt is the inertia time constant of water flow in the pressure pipe,

[0075] T F is the time constant of the downstream surge chamber,

[0076] m g is the turbine resistance torque,

[0077] e g is the load self-regulation coefficient,

[0078] h t is the pipe head loss,

[0079] H 0 is the working water head of the unit,

[0080] Q y0 is the initial tailwater tunnel flow,

[0081] c is the open channel wave velocity in the open flow section,

[0082] B is the width of the tailwater tunnel,

[0083] α is the slope angle of the tailwater tunnel top,

[0084] tanα is the slope of the tailwater tunnel,

[0085] λ is the tailwater tunnel section coefficient,

[0086] V x is the water velocity at the clear full flow interface,

[0087] K p is the proportional gain of the speed regulator,

[0088] K i is the speed regulator integral gain.

[0089] Furthermore, in S4), the relationship between the drop in the tailwater channel water level and the unit working head is:

[0090] H 0 =H 0 +z T

[0091] The relationship between the drop in the tailwater channel water level and the water depth at the open and full flow interface is:

[0092] H x =H x -z T ;

[0093] The relationship between the drop in tailrace water level and the length of the downstream surge tank to the tailrace pipe is:

[0094] L y =L y -z T / tanα;

[0095] Due to H 0 and H x changes, the water velocity at the full flow interface is related to H x The relationship between

[0096] V x =Q y0 / (BH x );

[0097] The relationship between the open channel wave velocity and H x The relationship between

[0098]

[0099] Inertia time constant of water flow in pressure pipe and H 0 The relationship between

[0100] T wt =L t V t / (gH 0 );

[0101] Downstream surge chamber time and H 0 The relationship between

[0102] T F =FH 0 / Q y0 ;

[0103] Inertia time constant of tailrace tunnel flow and H 0 The relationship between

[0104] T wy =L y V y / (gH 0 );

[0105] In the formula,

[0106] z T is the height of the tailwater channel water level drop,

[0107] H 0 is the working water head of the unit,

[0108] H x is the water depth at the interface of full flow,

[0109] V x is the water velocity at the clear full flow interface,

[0110] Q y0 is the initial tailwater tunnel flow,

[0111] B is the width of the tailwater tunnel,

[0112] c is the open channel wave velocity in the open flow section,

[0113] g is the acceleration due to gravity,

[0114] L y is the length of the pipeline from the downstream surge tank to the tailwater channel,

[0115] α is the slope angle of the tailwater tunnel top,

[0116] tanα is the slope of the tailwater tunnel,

[0117] T wt is the inertia time constant of water flow in the pressure pipe,

[0118] L t is the length of the pressure pipe,

[0119] V t is the pressure pipe flow rate,

[0120] T F is the time constant of the downstream surge chamber,

[0121] F is the area of ​​the downstream surge chamber,

[0122] T wy is the inertia time constant of the tailrace tunnel flow,

[0123] L y is the length of the pipeline from the downstream surge tank to the tailrace,

[0124] V y is the tailwater flow rate.

[0125] Furthermore, in S5), the basic parameters of the hydropower station include the initial tailwater tunnel flow Q y0 , Pipeline head loss h t , tailwater tunnel head loss h y , Pressure pipe length L t , Pressure pipe flow rate V t , tailwater velocity V y , downstream surge chamber area F, tailwater tunnel width B, tailwater tunnel slope tanα, tailwater tunnel top slope angle α, tailwater tunnel section coefficient λ, gravity acceleration g, unit inertia time constant T a , Load self-regulation coefficient e g , Turbine resistance moment m g , turbine flow transfer coefficient e qh0 、e qx0 、e qy0 , turbine torque transfer coefficient e h0 、e x0 、e y0 .

[0126] Furthermore, in S5), based on the Hopf bifurcation theory and the ODE45 function, the nonlinear hydropower station water diversion and power generation system is numerically simulated at different governor parameter state points to obtain the dynamic response spectrum of the system at different governor parameter state points.

[0127] Furthermore, in S5), the flow rate of the water tunnel at the beginning and the end, the governor parameter includes at least three groups of governor proportional gain parameters K with different value combinations. p and the speed regulator integral parameter K i .

[0128] The advantages of the present invention are:

[0129] 1. Compared with the prior art, the nonlinear mathematical model of the nonlinear hydropower station water diversion and power generation system established in the present invention includes a nonlinear model of a turbine, a downstream surge chamber model and a tailwater tunnel model with a variable top height, which fully considers the nonlinear characteristics of the turbine and the complex situation of the hydropower station system, analyzes the stability of the unit based on the Hopf bifurcation theory and the ODE45 function, and provides reliable guidance for the tailwater excavation project of the power station;

[0130] 2. The present invention fully considers the influence of tailwater excavation on the parameters of the water diversion and power generation system of the hydropower station, analyzes the dynamic response process of the water diversion and power generation system of the hydropower station with different tailwater excavation depths, selects the optimal governor parameters under different water level drop heights of the tailwater channel, and thus clarifies the optimal operation strategy corresponding to different water level drop heights of the tailwater channel;

[0131] The method for analyzing the stability of the hydropower unit and optimizing the operation strategy after tailwater excavation of the present invention fully considers the impact of tailwater excavation on the parameters of the water diversion and power generation system of the hydropower station, and analyzes the dynamic response process of the water diversion and power generation system of the hydropower station to different water level drop heights of the tailwater channel, and clarifies the optimal operation strategy corresponding to different water level drop heights of the tailwater channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0132] Figure 1 It is a structural schematic diagram of the water diversion and power generation system of the nonlinear hydropower station in the present invention;

[0133] Figure 2a to 2d The dynamic response spectrum of the unit under different sets of governor parameters when the tailwater channel water level drops by 1m in the embodiment;

[0134] Figure 3a~3d The dynamic response spectrum of the unit under different groups of governor parameters when the tailwater channel water level drops by 2m in the embodiment;

[0135] Figures 4a to 4d The dynamic response spectrum of the unit under different sets of governor parameters when the tailwater channel water level drops by 3m in the embodiment;

[0136] Figures 5a to 5d The dynamic response spectrum of the unit under different groups of governor parameters when the tailwater channel water level drops by 4m in the embodiment;

[0137] Figure 6a~6dIt is the dynamic response spectrum of the unit under different groups of governor parameters when the tailwater channel water level drops by 5m in the embodiment. DETAILED DESCRIPTION

[0138] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0139] The present invention provides a method for analyzing the stability of a hydropower unit after tailwater excavation and optimizing its operation strategy, comprising the following steps:

[0140] S1) constructing a nonlinear hydropower station water diversion and power generation system, including a pressure pipe subsystem, a turbine subsystem, a generator subsystem, a downstream surge chamber subsystem, and a tailwater channel subsystem arranged in sequence from an upstream reservoir to a downstream reservoir; the tailwater channel subsystem includes a tailwater tunnel subsystem with a variable top height and an open channel subsystem, such as Figure 1 shown.

[0141] S2) establishing a nonlinear mathematical model of a nonlinear hydropower station water diversion and power generation system, wherein the nonlinear mathematical model includes a pressure pipe model, a turbine nonlinear model, a turbine governor model, a generator model, a downstream surge chamber model, and a tailwater tunnel model with a variable top height.

[0142] Specifically, the pressure pipe model is expressed as

[0143]

[0144] The nonlinear model of the turbine is expressed as

[0145]

[0146]

[0147] The turbine governor model is expressed as

[0148]

[0149] The generator model is expressed as

[0150]

[0151] The downstream surge tank model is expressed as

[0152]

[0153] The tailwater tunnel model with variable top height is expressed as

[0154]

[0155] In the formula,

[0156] dq t / dt is the differential form of the relative value of the pressure pipeline flow deviation, q t is the relative value of pressure pipeline flow deviation,

[0157] T wt is the inertia time constant of water flow in the pressure pipe, unit is s,

[0158] h is the relative deviation of water head,

[0159] z F is the intermediate variable of the surge chamber,

[0160] h t is the pipe head loss, in m,

[0161] H 0 is the unit working head, in m,

[0162] dz F / dt is the differential form of the intermediate variable of the surge chamber,

[0163] T F is the time constant of the downstream surge chamber, in seconds,

[0164] q y is the tailwater tunnel flow, unit: m 3 / s,

[0165] h y is the tailwater tunnel head loss, unit is m,

[0166] λ is the tailwater tunnel section coefficient,

[0167] Q y0 is the initial tailwater tunnel flow, unit: m 3 / s,

[0168] c is the wave velocity in the open channel of the open flow section, in m / s,

[0169] B is the width of the tailwater tunnel, in m.

[0170] V x is the water velocity at the clear and full flow interface, in m / s, and g is the gravitational acceleration, in m / s 2 , α is the slope angle of the tailwater tunnel top, unit is rad, tanα is the slope of the tailwater tunnel,

[0171] T wy is the inertia time constant of the tailwater tunnel flow, unit is s,

[0172] m t is the relative value of turbine torque deviation,

[0173] e h0 、e x0 、ey0 are the turbine torque transfer coefficients,

[0174] x is the relative deviation of the unit speed,

[0175] y is the relative deviation of the guide vane opening,

[0176] e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients,

[0177] T a is the inertia time constant of the unit, in s,

[0178] dx / dt is the differential form of the relative deviation of the unit speed,

[0179] m g is the turbine resistance torque, in N·m,

[0180] e g is the load self-regulation coefficient, unit is s,

[0181] dy / dt is the differential form of the relative deviation of the guide vane opening,

[0182] K p is the proportional gain of the speed regulator,

[0183] K i is the speed regulator integral gain, unit: s -1 .

[0184] Compared with the prior art, the nonlinear mathematical model of the nonlinear hydropower station water diversion and power generation system established in the present invention includes a nonlinear model of the turbine, a downstream surge chamber model and a tailwater tunnel model with a variable top height, which fully considers the nonlinear characteristics of the turbine and the complex situation of the hydropower station system.

[0185] S3) The nonlinear mathematical model is converted into a high-order state equation form, and the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the tailwater tunnel flow are taken as state variables, and the turbine resistance torque is taken as the external load disturbance, and the state equations of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the tailwater tunnel flow are obtained respectively.

[0186] Specifically, the state equations for the relative deviation of unit speed, relative deviation of guide vane opening, relative deviation of water head, intermediate variables of surge chamber, and flow rate of tailwater tunnel are:

[0187]

[0188] In the formula,

[0189] A simple expression method for the differential form of the relative deviation of the unit speed is: is a simple expression method of the differential form of the relative deviation of the guide vane opening, A simple expression method for the differential form of the relative deviation of the water head is: A simple expression method for the differential form of the intermediate variable of the surge chamber, is a simple expression method of the differential form of the tailwater tunnel flow, x is the relative deviation of the unit speed,

[0190] y is the relative deviation of the guide vane opening,

[0191] h is the relative deviation of water head,

[0192] z F is the intermediate variable of the surge chamber,

[0193] q y is the tailwater tunnel flow, unit: m 3 / s,

[0194] h y is the tailwater tunnel head loss, unit is m,

[0195] e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients,

[0196] e h0 、e x0 、e y0 are the turbine torque transfer coefficients,

[0197] T a is the inertia time constant of the unit, in s,

[0198] T wy is the inertia time constant of the tailwater tunnel flow, unit is s,

[0199] T wt is the inertia time constant of water flow in the pressure pipe, unit is s,

[0200] T F is the time constant of the downstream surge chamber, in seconds,

[0201] m g is the turbine resistance torque, in N·m,

[0202] e g is the load self-regulation coefficient, unit is s,

[0203] h t is the pipe head loss, in m,

[0204] H0 is the unit working head, in m,

[0205] Q y0 is the initial tailwater tunnel flow, unit: m 3 / s,

[0206] c is the wave velocity in the open channel of the open flow section, in m / s,

[0207] B is the width of the tailwater tunnel, in m.

[0208] α is the slope angle of the tailwater tunnel top, in rad,

[0209] tanα is the slope of the tailwater tunnel,

[0210] λ is the tailwater tunnel section coefficient,

[0211] V x is the water velocity at the clear full flow interface, in m / s,

[0212] K p is the proportional gain of the speed regulator,

[0213] K i is the speed regulator integral gain, unit: s -1 .

[0214] S4) Determine the hydropower station related parameters related to the tailrace water level drop height, construct the relationship between the tailrace water level drop height and the hydropower station related parameters; clarify the tailrace water level drop height before and after the tailrace excavation, and calculate the change results of the relevant parameters of each hydropower station under different tailrace water level drop heights.

[0215] The relevant parameters of the hydropower station include: the working head of the unit, the water depth at the open and full flow interface, the water flow velocity at the open and full flow interface, the open channel wave velocity of the open flow section, the length of the pipeline from the downstream surge chamber to the tailwater channel, and the inertia time constant of the water flow in the pressure pipeline, the time constant of the downstream surge chamber, and the inertia time constant of the water flow in the tailwater tunnel.

[0216] S4), the relationship between the drop in the tailwater channel water level and the unit working head is:

[0217] H 0 =H 0 +z T

[0218] The relationship between the drop in the tailwater channel water level and the water depth at the open and full flow interface is:

[0219] H x =H x -z T ;

[0220] The relationship between the drop in tailrace water level and the length of the downstream surge tank to the tailrace pipe is:

[0221] L y =L y -z T / tanα;

[0222] Due to H 0 and H x changes, the water velocity at the full flow interface is related to H x The relationship between

[0223] V x =Q y0 / (BH x );

[0224] The relationship between the open channel wave velocity and H x The relationship between

[0225]

[0226] Inertia time constant of water flow in pressure pipe and H 0 The relationship between

[0227] T wt =L t V t / (gH 0 );

[0228] Downstream surge chamber time and H 0 The relationship between

[0229] T F =FH 0 / Q y0 ;

[0230] Inertia time constant of tailrace tunnel flow and H 0 The relationship between

[0231] T wy =L y V y / (gH 0 );

[0232] In the formula,

[0233] z T is the height of the tailwater channel water level drop,

[0234] H 0 is the working water head of the unit,

[0235] H x is the water depth at the interface of full flow,

[0236] Vx is the water velocity at the clear full flow interface,

[0237] Q y0 is the initial tailwater tunnel flow,

[0238] B is the width of the tailwater tunnel,

[0239] c is the open channel wave velocity in the open flow section,

[0240] g is the acceleration due to gravity,

[0241] L y is the length of the pipeline from the downstream surge tank to the tailwater channel,

[0242] α is the slope angle of the tailwater tunnel top,

[0243] tanα is the slope of the tailwater tunnel,

[0244] T wt is the inertia time constant of water flow in the pressure pipe,

[0245] L t is the length of the pressure pipe,

[0246] V t is the pressure pipe flow rate,

[0247] T F is the time constant of the downstream surge chamber,

[0248] F is the area of ​​the downstream surge chamber,

[0249] T wy is the inertia time constant of the tailrace tunnel flow,

[0250] L y is the length of the pipeline from the downstream surge tank to the tailrace,

[0251] V y is the tailwater flow rate.

[0252] In this embodiment, the given values ​​of the relevant parameters of the hydropower station are as follows: 0 = 80m, water depth at the interface of clear full flow H x =18.3m, water velocity V at the interface of bright and full flow x =3.9457m / s, open channel wave velocity c in open flow section = 13.3986m / s, length of downstream surge chamber to tailwater channel L y =550m, and the inertia time constant of the pressure pipe water flow T wt =3.45s, downstream surge chamber time constant T F =47.43s, tailwater tunnel flow inertia time constant T wy =2.1s.

[0253] S5) determining basic parameters of the hydropower station that are independent of the tailrace water level drop height, substituting the given basic parameters of the hydropower station and the hydropower station related parameters corresponding to different tailrace water level drop heights into the state equation in step S3), changing the governor parameters in the state equation, and drawing the dynamic response spectrum of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the head, and the tailrace tunnel flow at different tailrace water level drop heights, analyzing the system stability and regulation quality from the dynamic response spectrum, selecting the optimal governor parameters at different tailrace water level drop heights, thereby clarifying the optimal operation strategy corresponding to different tailrace water level drop heights;

[0254] The speed regulator parameters include different combinations of speed regulator proportional gain parameters and speed regulator integral parameters.

[0255] Specifically, the basic parameters of the hydropower station include the initial tailwater tunnel flow Q y0 , Pipeline head loss h t , tailwater tunnel head loss h y , Pressure pipe length L t , Pressure pipe flow rate V t , tailwater velocity V y , downstream surge chamber area F, tailwater tunnel width B, tailwater tunnel slope tanα, tailwater tunnel top slope angle α, tailwater tunnel section coefficient λ, gravity acceleration g, unit inertia time constant T a , Load self-regulation coefficient e g , Turbine resistance moment m g , turbine flow transfer coefficient e qh0 、e qx0 、e qy0 , turbine torque transfer coefficient e h0 、e x0 、e y0 .

[0256] In this embodiment, the given basic parameter values ​​of the hydropower station are as follows: initial tailwater tunnel flow Q y0 =506m 3 / s, pipeline head loss h t =1.46m, tailwater tunnel head loss h y =1.12m, pressure pipe length L t =774m, pressure pipeline flow rate V t =3.5m / s, tailwater velocity V y =3.0m / s, downstream surge chamber area F = 300m 2, tailwater tunnel width B = 7.19m, tailwater tunnel slope tanα = 0.06, tailwater tunnel section coefficient λ = 3, gravity acceleration g = 9.81m / s 2 , Unit inertia time constant T a =9.52s, load self-regulation coefficient e g =0, turbine resistance moment m g =-0.1, turbine flow transfer coefficient e qh0 =0.5, e qx0 =0, e qy0 =1.0, turbine torque transfer coefficient e h0 =1.5, e x0 =-1.0, e y0 =1.0.

[0257] Preferably, based on the Hopf bifurcation theory and the ODE45 function, a numerical simulation is performed on the water diversion and power generation system of a nonlinear hydropower station at different governor parameter state points to obtain a dynamic response spectrum of the system at different governor parameter state points.

[0258] Specifically, the flow rate of the water tunnel at the beginning and the end, the governor parameters include at least three groups of governor proportional gain parameters K with different value combinations. p and the speed regulator integral parameter K i .

[0259] When the tailrace water level drops to height z T =1m, the speed governor parameters are changed to obtain the dynamic response spectrum of the unit under three sets of speed governor parameters. The three sets of speed governor parameters are shown in Table 1.

[0260] Table 1 Governor parameters when the tailwater channel water level drops by 1m

[0261]

[0262] Get the relative deviation of the speed x, the relative deviation of the guide vane opening y, the relative deviation of the water head h, and the flow q of the unit y The dynamic response spectrum is as follows Figure 2a to 2d As shown. Figure 2a to 2d It can be seen that under the above three groups of speed regulator parameters, the first group of units has the fastest and most stable dynamic response and the best regulation quality. Therefore, it can be selected that when the water level in the tailwater channel drops by 1m, the first group is the best operating strategy.

[0263] Similarly, the tailrace water level drops by T =2m, the speed governor parameters are changed to obtain the dynamic response spectrum of the unit under the three speed governors. The three speed governor parameters are shown in Table 2.

[0264] Table 2 Governor parameters when the tailwater channel water level drops by 2m

[0265]

[0266] Get the relative deviation of the speed x, the relative deviation of the guide vane opening y, the relative deviation of the water head h, and the flow q of the unit y The dynamic response spectrum of Figure 3a~3d As shown. Figure 3a~3d It can be seen that under the above three groups of speed regulator parameters, the first group of units has the fastest and most stable dynamic response and the best regulation quality. Therefore, it can be selected that when the water level in the tailwater channel drops by 2m, the first group is the best operating strategy.

[0267] In the established nonlinear hydropower station water diversion and power generation system model, the tailwater channel water level drop height is changed to 3m, that is, z T =3m, change the speed governor parameters, and the three sets of speed governor parameters are shown in Table 3. Analyze the speed relative deviation x, guide vane opening relative deviation y, head relative deviation h, flow rate q of the unit under the three sets of speed governor parameters. y The dynamic response spectrum of Figures 4a to 4d shown.

[0268] Table 3 Governor parameters when the tailwater channel water level drops by 3m

[0269]

[0270] from Figures 4a to 4d It can be seen that under the above three groups of speed regulator parameters, the third group of units has the fastest and most stable dynamic response and the best regulation quality. Therefore, it can be selected that when the water level in the tailwater channel drops by 3m, the third group is the best operating strategy.

[0271] Further, continue to follow the above steps, the tailwater channel water level drops to height z T =4m, three sets of governor parameters are selected as shown in Table 4, speed relative deviation x, guide vane opening relative deviation y, head relative deviation h, flow rate q y The dynamic response spectrum of Figures 5a to 5d shown.

[0272] Table 4 Governor parameters when the tailwater channel water level drops by 4m

[0273]

[0274] from Figures 5a to 5d It can be seen that under the above three groups of speed regulator parameters, the third group of units has the fastest and most stable dynamic response and the best regulation quality. Therefore, it can be selected that when the water level in the tailwater channel drops by 4m, the third group is the best operating strategy.

[0275] Finally, similarly, the tailrace water level drops by T=5m, the three sets of governor parameters are shown in Table 5, speed relative deviation x, guide vane opening relative deviation y, head relative deviation h, flow rate q y The dynamic response spectrum of Figure 6a~6d shown.

[0276] Table 5 Governor parameters when the tailwater channel water level drops by 5m

[0277]

[0278] from Figure 6a~6d It can be seen that from the dynamic response comparison diagram of the unit under the three groups of speed governor parameters, the first group is the best operating strategy.

[0279] The method for analyzing the stability of the hydropower unit and optimizing the operation strategy after tailwater excavation of the present invention fully considers the impact of tailwater excavation on the parameters of the water diversion and power generation system of the hydropower station, and analyzes the dynamic response process of the water diversion and power generation system of the hydropower station to different water level drop heights of the tailwater channel, and clarifies the optimal operation strategy corresponding to different water level drop heights of the tailwater channel.

[0280] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation, characterized in that: The steps include: S1) constructing a nonlinear hydropower station water diversion and power generation system, including a pressure pipe subsystem, a turbine subsystem, a generator subsystem, a downstream surge chamber subsystem, and a tailwater channel subsystem arranged in sequence from an upstream reservoir to a downstream reservoir; The tailrace subsystem includes a tailrace tunnel subsystem with variable top height and an open channel subsystem; S2) establishing a nonlinear mathematical model of a nonlinear hydropower station water diversion and power generation system, wherein the nonlinear mathematical model includes a pressure pipe model, a turbine nonlinear model, a turbine governor model, a generator model, a downstream surge chamber model, and a tailwater tunnel model with a variable top height; S3) converting the nonlinear mathematical model into a high-order state equation form, taking the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the flow rate of the tailwater tunnel as state variables, and taking the resistance torque of the turbine as the external load disturbance, respectively obtaining the state equations of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the water head, the intermediate variable of the surge chamber, and the flow rate of the tailwater tunnel; S4) determining the hydropower station related parameters related to the tailrace water level drop height, constructing the relationship between the tailrace water level drop height and the hydropower station related parameters; clarifying the tailrace water level drop height before and after the tailrace excavation, and calculating the change results of the related parameters of each hydropower station under different tailrace water level drop heights; The relevant parameters of the hydropower station include: the working head of the unit, the water depth at the open and full flow interface, the water flow velocity at the open and full flow interface, the open channel wave velocity of the open flow section, the length of the pipeline from the downstream surge chamber to the tailwater channel, and the inertia time constant of the water flow in the pressure pipeline, the time constant of the downstream surge chamber, and the inertia time constant of the water flow in the tailwater tunnel; S5) determining basic parameters of the hydropower station that are independent of the tailrace water level drop height, substituting the given basic parameters of the hydropower station and the hydropower station related parameters corresponding to different tailrace water level drop heights into the state equation in step S3), changing the governor parameters in the state equation, and drawing the dynamic response spectrum of the relative deviation of the unit speed, the relative deviation of the guide vane opening, the relative deviation of the head, and the tailrace tunnel flow at different tailrace water level drop heights, analyzing the system stability and regulation quality from the dynamic response spectrum, selecting the optimal governor parameters at different tailrace water level drop heights, thereby clarifying the optimal operation strategy corresponding to different tailrace water level drop heights; The speed regulator parameters include different combinations of speed regulator proportional gain parameters and speed regulator integral parameters.

2. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 1 is characterized in that: S2), the pressure pipe model is expressed as The nonlinear model of the turbine is expressed as The turbine governor model is expressed as The generator model is expressed as The downstream surge tank model is expressed as The tailwater tunnel model with variable top height is expressed as In the formula, dq t / dt is the differential form of the relative value of the pressure pipeline flow deviation, q t is the relative value of pressure pipeline flow deviation, T wt is the inertia time constant of water flow in the pressure pipe, h is the relative deviation of water head, z F is the intermediate variable of the surge chamber, h t is the pipe head loss, H0 is the working water head of the unit, dz F / dt is the differential form of the intermediate variable of the surge chamber, T F is the time constant of the downstream surge chamber, q y is the tailwater tunnel flow, h y is the head loss in the tailrace tunnel, λ is the tailwater tunnel section coefficient, Q y0 is the initial tailwater tunnel flow, c is the open channel wave velocity in the open flow section, B is the width of the tailwater tunnel, V x is the water velocity at the clear full flow interface, g is the acceleration due to gravity, α is the slope angle of the tailwater tunnel top, tanα is the slope of the tailwater tunnel, T wy is the inertia time constant of the tailrace tunnel flow, m t is the relative value of turbine torque deviation, e h0 、e x0 、e y0 are the turbine torque transfer coefficients, x is the relative deviation of the unit speed, y is the relative deviation of the guide vane opening, e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients, T a is the unit inertia time constant, dx / dt is the differential form of the relative deviation of the unit speed, m g is the turbine resistance torque, e g is the load self-regulation coefficient, dy / dt is the differential form of the relative deviation of the guide vane opening, K p is the proportional gain of the speed regulator, K i is the speed regulator integral gain.

3. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 2 is characterized in that: In S3), the state equations of the relative deviation of unit speed, relative deviation of guide vane opening, relative deviation of water head, intermediate variable of surge chamber, and flow rate of tailwater tunnel are respectively In the formula, A simple expression method for the differential form of the relative deviation of the unit speed is: is a simple expression method of the differential form of the relative deviation of the guide vane opening, A simple expression method for the differential form of the relative deviation of the water head is: A simple expression method for the differential form of the intermediate variable of the surge chamber, is a simple expression method for the differential form of the tailrace tunnel flow, x is the relative deviation of the unit speed, y is the relative deviation of the guide vane opening, h is the relative deviation of water head, z F is the intermediate variable of the surge chamber, q y is the tailwater tunnel flow, h y is the head loss in the tailrace tunnel, e qh0 、e qx0 、e qy0 are the turbine flow transfer coefficients, e h0 、e x0 、e y0 are the turbine torque transfer coefficients, T a is the unit inertia time constant, T wy is the inertia time constant of the tailrace tunnel flow, T wt is the inertia time constant of water flow in the pressure pipe, T F is the time constant of the downstream surge chamber, m g is the turbine resistance torque, e g is the load self-regulation coefficient, h t is the pipe head loss, H0 is the working water head of the unit, Q y0 is the initial tailwater tunnel flow, c is the open channel wave velocity in the open flow section, B is the width of the tailwater tunnel, α is the slope angle of the tailwater tunnel top, tanα is the slope of the tailwater tunnel, λ is the tailwater tunnel section coefficient, V x is the water velocity at the clear full flow interface, K p is the proportional gain of the speed regulator, K i is the speed regulator integral gain.

4. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 3 is characterized by: S4), the relationship between the drop in the tailwater channel water level and the unit working head is: H0=H0+z T The relationship between the drop in the tailwater channel water level and the water depth at the open and full flow interface is: H x =H x -z T ; The relationship between the drop in tailrace water level and the length of the downstream surge tank to the tailrace pipe is: L y =L y -z T / tanα; Since H0 and H x changes, the water velocity at the full flow interface is related to H x The relationship between V x =Q y0 / (BH x ); The relationship between the open channel wave velocity and H x The relationship between The relationship between the inertia time constant of water flow in a pressure pipe and H0 is: T wt =L t V t / (gH0); The relationship between the downstream surge chamber time and H0 is: T F =FH0 / Q y0 ; The relationship between the inertial time constant of the tailwater tunnel flow and H0 is: T wy =L y V y / (gH0); In the formula, z T is the height of the tailwater channel water level drop, H0 is the working water head of the unit, H x is the water depth at the interface of full flow, V x is the water velocity at the clear full flow interface, Q y0 is the initial tailwater tunnel flow, B is the width of the tailwater tunnel, c is the open channel wave velocity in the open flow section, g is the acceleration due to gravity, L y is the length of the pipeline from the downstream surge tank to the tailwater channel, α is the slope angle of the tailwater tunnel top, tanα is the slope of the tailwater tunnel, T wt is the inertia time constant of water flow in the pressure pipe, L t is the length of the pressure pipe, V t is the pressure pipe flow rate, T F is the time constant of the downstream surge chamber, F is the area of ​​the downstream surge chamber, T wy is the inertia time constant of the tailrace tunnel flow, L y is the length of the pipeline from the downstream surge tank to the tailrace, V y is the tailwater flow rate.

5. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 4 is characterized in that: S5), the basic parameters of the hydropower station include the initial tailwater tunnel flow Q y0 , Pipeline head loss h t , tailwater tunnel head loss h y , Pressure pipe length L t , Pressure pipe flow rate V t , tailwater velocity V y , downstream surge chamber area F, tailwater tunnel width B, tailwater tunnel slope tanα, tailwater tunnel top slope angle α, tailwater tunnel section coefficient λ, gravity acceleration g, unit inertia time constant T a , Load self-regulation coefficient e g , Turbine resistance moment m g , turbine flow transfer coefficient e qh0 、e qx0 、e qy0 , turbine torque transfer coefficient e h0 、e x0 、e y0 .

6. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 1 is characterized in that: In S5), based on the Hopf bifurcation theory and ODE45 function, the nonlinear hydropower station water diversion and power generation system is numerically simulated at different governor parameter state points, and the dynamic response spectrum of the system at different governor parameter state points is obtained.

7. The method for stability analysis and operation strategy optimization of a hydropower unit after tailwater excavation according to claim 6 is characterized by: S5), the flow rate of the water tunnel at the beginning and the end, the governor parameters include at least three groups of governor proportional gain parameters K with different numerical combinations p and the speed regulator integral parameter K i .

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