CN114156938A - Method for evaluating safety of thermoelectric generator set in wind-light-fire coupling system - Google Patents

Method for evaluating safety of thermoelectric generator set in wind-light-fire coupling system Download PDF

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CN114156938A
CN114156938A CN202111394871.2A CN202111394871A CN114156938A CN 114156938 A CN114156938 A CN 114156938A CN 202111394871 A CN202111394871 A CN 202111394871A CN 114156938 A CN114156938 A CN 114156938A
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rotor
generating unit
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鲁录义
陈识危
周桂平
吕旭明
王顺江
王磊
赵苑竹
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Huazhong University of Science and Technology
State Grid Liaoning Electric Power Co Ltd
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Abstract

The invention belongs to the field of wind, light and fire coupling related technologies, and discloses a method for evaluating safety of a fire-electricity generating set in a wind, light and fire coupling system, which comprises the following steps: constructing a wind turbine generator power model and a photovoltaic generator power model; coupling a wind turbine generator power model, a photovoltaic generator power model and a thermal power generator model to obtain a power tracking system model, and obtaining thermal power generator power according to the power tracking system model; obtaining the temperature variation relation of different radiuses of each shaft section of a steam turbine rotor in the thermal power unit along with time according to the power of the thermal power unit, and further obtaining the fatigue loss of the thermal power unit rotor; obtaining harmonic waves of the wind turbine generator and the photovoltaic generator, and superposing the harmonic waves to act on a shaft system of the thermal power generating unit, so that the impact of the harmonic waves on the shaft system of the thermal power generating unit can be obtained; and carrying out safety assessment on the thermal power generating unit based on fatigue loss and harmonic waves. The method can accurately evaluate the safety of the thermal power generating unit in the wind-solar-thermal coupling system, and has very important guiding significance for the application of the thermal power generating unit.

Description

Method for evaluating safety of thermoelectric generator set in wind-light-fire coupling system
Technical Field
The invention belongs to the field of wind, light and fire coupling related technologies, and particularly relates to a method for evaluating safety of a fire-electricity generating set in a wind, light and fire coupling system.
Background
The electric energy plays a very important role in industrial and agricultural production and people's life, along with the rapid development of economy, the demand of each industry to the electric energy increases gradually, and in order to guarantee the stability of energy supply and reduce the destruction of traditional fossil power to the environment, the development and the utilization of renewable energy have become the important research direction in the energy field now.
Among renewable energy sources, wind energy and solar energy are clean energy sources which are the most abundant in resources in China and mature in power generation technology, however, the problem of wind abandoning and light abandoning in remote areas far away from a load center is very serious, and in order to solve the problem of wind abandoning and light abandoning, new energy sources need to be transported to the load center for a long distance. Because wind energy and solar energy have the characteristics of large fluctuation and strong randomness, the mode of thermal power, wind power and photovoltaic coupling is adopted to adapt to peak regulation change caused by the fluctuation of wind energy and solar energy. However, in order to ensure the stability of the power grid during the coupling of wind power, thermal power and photovoltaic power, the thermal power generating unit needs to be used as a peak regulation power source to complete a peak regulation task to perform frequent variable load operation, which affects the safety of the thermal power generating unit. Therefore, how to evaluate the safety of the thermoelectric generator in the wind power, photoelectric and thermal power coupling system has very important significance for the research of large-scale new energy consumption and delivery modes in China.
Disclosure of Invention
Aiming at the defects or improvement requirements of the prior art, the invention provides the method for evaluating the safety of the thermal power unit in the wind, light and fire coupling system.
To achieve the above object, according to one aspect of the present invention, there is provided a method for evaluating safety of a fire-electric generating set in a wind-solar-fire coupling system, the method including: s1: building a wind turbine generator power model based on wind speed and building a photovoltaic generator power model based on environmental parameters; s2: coupling the wind turbine generator power model, the photovoltaic generator power model and the thermal power generator model to obtain a power tracking system model, and obtaining thermal power generator power according to the power tracking system model; s3: obtaining the time-varying relation of the temperature of each shaft section of the steam turbine rotor in the thermal power generating unit at different radiuses based on the one-dimensional unsteady state heat conduction principle of the hollow cylinder without the internal heat source according to the power of the thermal power generating unit; s4: obtaining thermal stress of the steam turbine rotor according to the time-dependent change relationship of the temperature of each shaft section of the steam turbine rotor at different radiuses and a one-dimensional unstable heat conduction equation, and further obtaining fatigue loss of the thermal power unit rotor; s5: respectively carrying out Fourier transform on output voltage waveforms of the inversion devices of the generator of the wind turbine generator and the photovoltaic generator set to obtain harmonic waves of the wind turbine generator set and the photovoltaic generator set; s6: superposing the harmonic waves of the wind turbine generator and the photoelectric generator on a shaft system of the thermal power generating unit, so that the impact of the harmonic waves on the shaft system of the thermal power generating unit can be obtained; s7: and carrying out safety evaluation on the thermal power generating unit based on the impact of the fatigue loss and the harmonic waves of the thermal power generating unit rotor on a thermal power generating unit shafting.
Preferably, step S6 further includes performing equivalent processing on a shafting of the thermal power generating unit, specifically: each shaft section of a plurality of section shafting of the thermal power generating unit is equivalent to a concentrated mass block, and the mass blocks are equivalent to spring connection without mass.
Preferably, the shafting equation of the thermal power generating unit is as follows:
Figure BDA0003369909920000021
wherein, Delta deltaiIs the angular displacement of the rotor on the i-th shaft, Δ ωiThe angular speed increment of the rotor on the ith section of shaft; delta TeiIncrement of electromagnetic torque for the i-th section of the shaft, HiIs the inertia constant of the rotor on the i-th section shaft, DiiIs the self-damping coefficient of the rotor on the i-th section shaft, Ki，i+1，Ki，i-1Expressed as the spring constant between each adjacent lumped mass.
Preferably, the wind turbine generator set power model P in step S1WComprises the following steps:
Figure BDA0003369909920000031
wherein C is the wind energy conversion efficiency coefficient of the blade, rho is the air density, A is the circular area formed by airflow when the fan blade of the wind motor rotates, and v is the wind speed.
Preferably, the photovoltaic power module power model PVComprises the following steps:
PV＝ηVSI[1-0.005(t0+25)]
wherein eta isVFor photovoltaic cell conversion efficiency, S is the photovoltaic array area, I is the solar radiation intensity, t0Is the temperature.
Preferably, the power tracking system model l (t) is:
L(t)＝PW(t)+PV(t)+PT(t)
Figure BDA0003369909920000032
wherein, PW(t) wind turbine power, P, at time tV(t) photovoltaic power generation power, P, at time tT(t) is the thermal power unit power to be solved at the moment t, L (t) is the preset output power of the load changing along with the time at the moment t, Pi(t-1) is the active power of the shaft of the thermal power generating unit at the ith section in the t-1 th period, Pi(t) is the active power of the shaft of the thermal power generating unit at the ith period,
Figure BDA0003369909920000033
the maximum descending power of the thermal power generating unit at the ith section of shaft system at a single moment is obtained;
Figure BDA0003369909920000034
and the maximum rising power of the thermal power generating unit at the ith section of the shaft system at a single moment is obtained.
Preferably, in step S3, the relationship between the temperature T at different radii of each shaft section of the turbine rotor and the time τ is:
Figure BDA0003369909920000035
wherein η ═ F (P)T，Tq) Eta is the temperature rise of the steam, PTFor power of thermal power generating units, TqIs the temperature of the steam, T0Is an initial value of the rotor, R0Is the external diameter of the rotor, a is the thermal diffusivity, r is the radius of any point of the rotor, B is the coefficient of unit node displacement array, beta is the coefficient of linear expansion of the rotor material, n is the number of nodes of the temperature value to be obtained, J0For the initial value of the variation calculation in the cell, F0The initial value of the equivalent nodal force of the concentrated force.
Preferably, the thermal stress σ of the turbine rotor in step S4thThe expression of (a) is:
Figure BDA0003369909920000041
wherein E is the elastic modulus of the rotor material, upsilon is the Poisson ratio of the rotor material, c is the specific heat of the rotor material, and ρ0Is the density of the rotor material, lambda is the heat conductivity coefficient of the rotor, R is the thickness of the rotor, and R is Rb-R0，RbIs the rotor inner diameter, f is the form factor, ηgIs the g-th steam temperature rise, etag-1Is the g-1 th steam temperature rise rate, K is a time correction factor, taugTime of change of g-th steam temperature rise, τg-1The time of the g-1 steam temperature rise change is shown.
Preferably, the electromagnetic torque increment delta T caused by the impact of the harmonic waves on a thermal power generating unit shaftingeComprises the following steps:
Figure BDA0003369909920000042
wherein, ω is0For disturbance frequency of harmonic after superposition of harmonic of wind turbine and harmonic of photovoltaic generator, EG0For terminal voltage, U, of thermal power generating unitsA0Is an initial value delta of the bus voltage at the grid-connected part of the wind power generating unit and the thermal power generating unit0Is an initial value, X, of a voltage phase angle of a machine end of a thermal power generating unitGFor the circuit impedance of the thermal power generating unit, delta is the variation value of the voltage phase angle of the terminal of the thermal power generating unit, kpIs a coefficient, kqAs a function of the number of the coefficients,
Figure BDA0003369909920000043
XWis the total circuit impedance of the wind power optical-mechanical unit, EW0For fan-side and photovoltaic-side voltages, θ0And the wind power optical-mechanical unit is a generator terminal voltage initial phase angle of grid connection.
Preferably, step S4 obtains the fatigue loss of the thermal power unit rotor by performing finite element analysis on the thermal stress of the rotor of the steam turbine.
Generally, compared with the prior art, the method for evaluating the safety of the thermoelectric generator set in the wind, light and fire coupling system has the following beneficial effects:
1. according to the method, the fatigue loss of the rotor of the thermal power unit in the wind-solar-fire coupling system and the impact influence of the harmonic waves of the wind power unit and the thermal power unit on the rotor rotating shaft can be known through thermal stress analysis, so that the safety evaluation of the whole shafting of the thermal power unit can be realized, and the evaluation is more comprehensive;
2. the coupling power of the thermal power generating unit is obtained by constructing a wind turbine generator power model and a photovoltaic generator power model, and then the temperature field of the rotor and the thermal stress of the rotor are reversely deduced according to the power, so that the method is simple and easy to implement;
3. in the shafting analysis process of the thermal power generating unit, the shafting is divided by adopting a spring equivalent mode to respectively calculate the influence of harmonic waves on each section of shaft, the calculation is more accurate, the harmonic wave impact of each shaft end can be obtained, and therefore accurate and efficient guidance is provided for subsequent safety evaluation.
Drawings
FIG. 1 is a step diagram of a method for evaluating the safety of a thermoelectric generator set in a wind-solar-electric coupling system;
FIG. 2 is a flow chart of a method for evaluating safety of a thermoelectric generator set in the wind-solar-electric coupling system.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Referring to fig. 1 and 2, the invention provides a method for evaluating safety of a thermoelectric generator set in a wind, light and fire coupling system, which specifically includes the following steps S1-S7.
S1: and constructing a wind turbine generator power model based on wind speed and constructing a photovoltaic generator power model based on environmental parameters.
In the field of wind energy prediction, the wind speed and the wind power have a very close relationship, and a wind turbine generator power model PWComprises the following steps:
Figure BDA0003369909920000061
wherein C is the wind energy conversion efficiency coefficient of the blade, rho is the air density, A is the circular area formed by airflow when the fan blade of the wind motor rotates, and v is the wind speed.
The output power of the photovoltaic power station is influenced by various factors, such as solar irradiation intensity, wind speed, relative humidity, temperature, weather and the like, and the power model P of the photovoltaic unitVComprises the following steps:
PV＝ηVSI[1-0.005(t0+25)]
wherein eta isVFor photovoltaic cell conversion efficiency, S is the photovoltaic array area, I is the solar radiation intensity, t0Is the temperature.
S2: and coupling the wind turbine generator power model, the photovoltaic generator power model and the thermal power generator model to obtain a power tracking system model, and obtaining the thermal power generator power according to the power tracking system model.
If the process of the external output of the wind-solar electric coupling system meets the energy balance principle and the ramp rate constraint of the thermal power generating unit, the power tracking system model L (t) is as follows:
L(t)＝PW(t)+PV(t)+PT(t)
Figure BDA0003369909920000062
wherein, PW(t) wind turbine power, P, at time tV(t) photovoltaic power generation power, P, at time tT(t) is the thermal power unit power to be solved at the moment t, L (t) is the preset output power of the load changing along with the time at the moment t, Pi(t-1) is the active power of the shaft of the thermal power generating unit at the ith section in the t-1 th period, Pi(t) is the active power of the shaft of the thermal power generating unit at the ith period,
Figure BDA0003369909920000063
the maximum descending power of the thermal power generating unit at the ith section of shaft system at a single moment is obtained;
Figure BDA0003369909920000064
and the maximum rising power of the thermal power generating unit at the ith section of the shaft system at a single moment is obtained.
S3: and obtaining the time-varying relation of the temperature of each shaft section of the steam turbine rotor in the thermal power unit at different radiuses based on the one-dimensional unsteady state heat conduction principle of the hollow cylinder without the internal heat source according to the power of the thermal power unit.
When the initial temperature of the rotor is in a uniform state and is consistent with the initial steam temperature, if the steam temperature linearly changes along with time, the change relationship of the temperature T at different radiuses of each shaft section of the rotor of the steam turbine along with the time tau is as follows:
Figure BDA0003369909920000071
wherein η ═ F (P)T，Tq) Eta is the temperature rise of the steam, PTFor power of thermal power generating units, TqIs the temperature of the steam, T0Is an initial value of the rotor, R0Is the external diameter of the rotor, a is the thermal diffusivity, r is the radius of any point of the rotor, B is the coefficient of unit node displacement array, beta is the coefficient of linear expansion of the rotor material, n is the number of nodes of the temperature value to be obtained, J0For the initial value of the variation calculation in the cell, F0The initial value of the equivalent nodal force of the concentrated force.
S4: and obtaining the thermal stress of the steam turbine rotor according to the time-dependent change relationship of the temperature of each shaft section of the steam turbine rotor at different radiuses and a one-dimensional unstable heat conduction equation, and further obtaining the fatigue loss of the thermal power unit rotor.
Thermal stress sigma of a steam turbine rotorthThe expression of (a) is:
Figure BDA0003369909920000072
wherein E is the elastic modulus of the rotor material, upsilon is the Poisson ratio of the rotor material, c is the specific heat of the rotor material, and ρ0Is the density of the rotor material, lambda is the heat conductivity coefficient of the rotor, R is the thickness of the rotor, and R is Rb-R0，RbIs the rotor inner diameter, f is the form factor, ηgIs the g th steam temperature rise rate，ηg-1Is the g-1 th steam temperature rise rate, K is a time correction factor, taugTime of change of g-th steam temperature rise, τg-1The time of the g-1 steam temperature rise change is shown.
The fatigue loss of the thermal power unit rotor can be obtained by carrying out finite element analysis on the thermal stress of the rotor of the steam turbine.
S5: and performing Fourier transform on output voltage waveforms of the inversion devices of the generator of the wind turbine generator and the photovoltaic generator respectively to obtain harmonic waves of the wind turbine generator and the photovoltaic generator.
For a wind power grid-connected system, because a high-power current transformation state is adopted, power electronic devices in a current transformation device are the most important harmonic sources in the wind power device. Here, a constant-speed and constant-frequency wind turbine is taken as an example. Modern wind power generators all adopt doubly-fed asynchronous generators, and at present, the wind power generators are mainly analyzed from stator windings and rotor windings. The high-order harmonic generated by the rotor side alternating current excitation system is a main harmonic source when the wind power system is in grid-connected operation, and the output voltage U waveform of the high-order harmonic source is obtained by Fourier analysis:
Figure BDA0003369909920000081
wherein, UkFor the maximum value of each harmonic voltage, it can be seen that the harmonic number is 6n ± 1(n is 1, 2, 3 …), when k is 6n +1, each positive-sequence harmonic voltage component is represented, and when k is 6n-1, each negative-sequence harmonic voltage component is represented, and a pulse-type change is generated by adding a dc-side voltage, and the change will bring integral multiple harmonics of fundamental frequency to the whole system through an inverter.
Harmonic waves generated by an inverter in a photovoltaic power generation system are a main harmonic wave source in a power grid, an asynchronous modulation mode is used for the control of the existing inverter, synchronous modulation can be seen as a special condition of the asynchronous modulation, and therefore the problem of harmonic wave generation can be analyzed in the asynchronous modulation mode. According to the harmonic characteristic analysis, a Fourier basis expansion of a half bridge can be firstly obtained, and then a voltage Fourier series harmonic expansion is obtained by using a harmonic superposition principle, so that the characteristics of specific harmonics of the Fourier series expansion in an asynchronous modulation mode are as follows:
(1) when n is 1, 3, 5 … …, k is 3(2m-1), and when n is 1, 2, 3
Figure BDA0003369909920000082
(2) When n is 2, 4, 6 … …, k is 6m +1, m is 0, 1, 2, 3.; k 6m-1, m 0, 1, 2, 3
Figure BDA0003369909920000091
Wherein u isabAs a fundamental component of line voltage, ud/2Is a half-voltage several-wave component of the DC capacitor, JkIs Bessel number, omega0For angular frequency, omega, of the signal wavesIs the carrier angular frequency and phi is the initial phase angle.
S6: and superposing the harmonic waves of the wind turbine generator and the photoelectric generator on a thermal power unit shaft system, so as to obtain the impact of the harmonic waves on the thermal power unit shaft system.
The method also comprises the following steps of carrying out equivalent treatment on a shaft system of the thermal power generating unit, specifically:
each shaft section of a plurality of section shafting of the thermal power generating unit is equivalent to a concentrated mass block, and the mass blocks are equivalent to spring connection without mass.
After equivalence, the shafting equation of the thermal power generating unit is as follows:
Figure BDA0003369909920000092
wherein, Delta deltaiIs the angular displacement of the rotor on the i-th shaft, Δ ωiThe angular speed increment of the rotor on the ith section of shaft; delta TeiIncrement of electromagnetic torque for the i-th section of the shaft, HiIs the inertia constant of the rotor on the i-th section shaft, DiiIs the self-damping coefficient of the rotor on the i-th section shaft, Ki，i+1，Ki，i-1Expressed as the elastic coefficient between each adjacent lumped mass, the maximum value of i is the number of axial segments.
Electromagnetic torque increment delta T caused by impact of harmonic waves on thermal power generating unit shaftingeComprises the following steps:
Figure BDA0003369909920000093
wherein, ω is0For disturbance frequency of harmonic after superposition of harmonic of wind turbine and harmonic of photovoltaic generator, EG0For terminal voltage, U, of thermal power generating unitsA0Is an initial value delta of the bus voltage at the grid-connected part of the wind power generating unit and the thermal power generating unit0Is an initial value, X, of a voltage phase angle of a machine end of a thermal power generating unitGFor the circuit impedance of the thermal power generating unit, delta is the variation value of the voltage phase angle of the terminal of the thermal power generating unit, kpIs a coefficient, kqAs a function of the number of the coefficients,
Figure BDA0003369909920000101
XWis the total circuit impedance of the wind power optical-mechanical unit, EW0For fan-side and photovoltaic-side voltages, θ0And the wind power optical-mechanical unit is a generator terminal voltage initial phase angle of grid connection.
S7: and carrying out safety evaluation on the thermal power generating unit based on the impact of the fatigue loss and the harmonic waves of the thermal power generating unit rotor on a thermal power generating unit shafting.
Therefore, managers can comprehensively evaluate the safety of the thermal power generating unit by analyzing the thermal stress dangerous part and the harmonic wave impact dangerous section. Thermal stress fatigue analysis mainly aims at a rotor at the inner position of a high and medium pressure cylinder, and harmonic impact analysis mainly aims at a coupler position outside the cylinder.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A method for evaluating safety of a thermoelectric generator set in a wind, light and fire coupling system is characterized by comprising the following steps:
s1: building a wind turbine generator power model based on wind speed and building a photovoltaic generator power model based on environmental parameters;
s2: coupling the wind turbine generator power model, the photovoltaic generator power model and the thermal power generator model to obtain a power tracking system model, and obtaining thermal power generator power according to the power tracking system model;
s3: obtaining the time-varying relation of the temperature of each shaft section of the steam turbine rotor in the thermal power generating unit at different radiuses based on the one-dimensional unsteady state heat conduction principle of the hollow cylinder without the internal heat source according to the power of the thermal power generating unit;
s4: obtaining thermal stress of the steam turbine rotor according to the time-dependent change relationship of the temperature of each shaft section of the steam turbine rotor at different radiuses and a one-dimensional unstable heat conduction equation, and further obtaining fatigue loss of the thermal power unit rotor;
s5: respectively carrying out Fourier transform on output voltage waveforms of the inversion devices of the generator of the wind turbine generator and the photovoltaic generator set to obtain harmonic waves of the wind turbine generator set and the photovoltaic generator set;
s6: superposing the harmonic waves of the wind turbine generator and the photoelectric generator on a shaft system of the thermal power generating unit, so that the impact of the harmonic waves on the shaft system of the thermal power generating unit can be obtained;
s7: and carrying out safety evaluation on the thermal power generating unit based on the impact of the fatigue loss and the harmonic waves of the thermal power generating unit rotor on a thermal power generating unit shafting.
2. The method according to claim 1, wherein the step S6 further includes performing equivalent processing on a shafting of the thermal power generating unit, specifically:
each shaft section of a plurality of section shafting of the thermal power generating unit is equivalent to a concentrated mass block, and the mass blocks are equivalent to spring connection without mass.
3. The method according to claim 2, wherein the thermal power generating unit shafting equation is as follows:
Figure FDA0003369909910000021
wherein, Delta deltaiIs the angular displacement of the rotor on the i-th shaft, Δ ωiThe angular speed increment of the rotor on the ith section of shaft; delta TeiIncrement of electromagnetic torque for the i-th section of the shaft, HiIs the inertia constant of the rotor on the i-th section shaft, DiiIs the self-damping coefficient of the rotor on the i-th section shaft, Ki，i+1，Ki，i-1Expressed as the spring constant between each adjacent lumped mass.
4. The method of claim 1, wherein the wind turbine generator set power model P in step S1WComprises the following steps:
Figure FDA0003369909910000022
wherein C is the wind energy conversion efficiency coefficient of the blade, rho is the air density, A is the circular area formed by airflow when the fan blade of the wind motor rotates, and v is the wind speed.
5. Method according to claim 1, characterized in that the photovoltaic power model PVComprises the following steps:
PV＝ηVSI[1-0.005(t0+25)]
wherein eta isVFor photovoltaic cell conversion efficiency, S is the photovoltaic array area, I is the solar radiation intensity, t0Is the temperature.
6. The method of claim 1, wherein the power tracking system model L (t) is:
L(t)＝PW(t)+PV(t)+PT(t)
Figure FDA0003369909910000023
wherein, PW(t) wind turbine power, P, at time tV(t) photovoltaic power generation power, P, at time tT(t) is the thermal power unit power to be solved at the moment t, L (t) is the preset output power of the load changing along with the time at the moment t, Pi(t-1) is the active power of the shaft of the thermal power generating unit at the ith section in the t-1 th period, Pi(t) is the active power of the shaft of the thermal power generating unit at the ith period,
Figure FDA0003369909910000031
the maximum descending power of the thermal power generating unit at the ith section of shaft system at a single moment is obtained;
Figure FDA0003369909910000032
and the maximum rising power of the thermal power generating unit at the ith section of the shaft system at a single moment is obtained.
7. The method according to claim 1 or 6, wherein in step S3, the temperature T at different radii of each shaft section of the turbine rotor varies with time τ in accordance with the relationship:
Figure FDA0003369909910000033
wherein η ═ F (P)T，Tq) Eta is the temperature rise of the steam, PTFor power of thermal power generating units, TqIs the temperature of the steam, T0Is an initial value of the rotor, R0Is the external diameter of the rotor, a is the thermal diffusivity, r is the radius of any point of the rotor, B is the coefficient of unit node displacement array, beta is the coefficient of linear expansion of the rotor material, n is the number of nodes of the temperature value to be obtained, J0For the initial value of the variation calculation in the cell, F0The initial value of the equivalent nodal force of the concentrated force.
8. Method according to claim 7, characterized in that the thermal stress σ of the turbine rotor in step S4thThe expression of (a) is:
Figure FDA0003369909910000034
wherein E is the elastic modulus of the rotor material, upsilon is the Poisson ratio of the rotor material, c is the specific heat of the rotor material, and ρ0Is the density of the rotor material, lambda is the heat conductivity coefficient of the rotor, R is the thickness of the rotor, and R is Rb-R0，RbIs the rotor inner diameter, f is the form factor, ηgIs the g-th steam temperature rise, etag-1Is the g-1 th steam temperature rise rate, K is a time correction factor, taugTime of change of g-th steam temperature rise, τg-1The time of the g-1 steam temperature rise change is shown.
9. The method of claim 1, wherein the electromagnetic torque delta Δ T caused by the impact of the harmonics on the thermal power unit shaftingeComprises the following steps:
Figure FDA0003369909910000035
wherein, ω is0For disturbance frequency of harmonic after superposition of harmonic of wind turbine and harmonic of photovoltaic generator, EG0For terminal voltage, U, of thermal power generating unitsA0Is an initial value delta of the bus voltage at the grid-connected part of the wind power generating unit and the thermal power generating unit0Is an initial value, X, of a voltage phase angle of a machine end of a thermal power generating unitGThe delta is the circuit impedance of the thermal power generating unit, and is the terminal voltage angle change value k of the thermal power generating unitpIs a coefficient, kqAs a function of the number of the coefficients,
Figure FDA0003369909910000041
XWis the total circuit impedance of the wind power optical-mechanical unit, EW0For fan-side and photovoltaic-side voltages, θ0And the wind power optical-mechanical unit is a generator terminal voltage initial phase angle of grid connection.
10. The method according to claim 1, wherein step S4 is performed by performing finite element analysis on thermal stress of a rotor of a steam turbine to obtain fatigue loss of the rotor of the thermal power generating unit.
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