CN101769811A - Measuring method for main steam pressure of steam turbine and measuring device therefor - Google Patents

Abstract

The invention provides a measuring method for main steam pressure of a steam turbine and a measuring device therefor. The method comprises the following steps of adding disturbance into a rotating speed reference signal of a steam turbine control system; obtaining the variation value of adjustment valve opening of the steam turbine in a certain period of time according to the disturbance; obtaining the variation value of the main steam pressure of the steam turbine in a certain time period according to the disturbance; fitting the parameters of the pressure loss variation of a main steam pipeline and a superheater of the steam turbine and the parameters of the volume effect of a steam drum and the superheater according to the opening variation value of an adjustment valve of the steam turbine and the variation value of the main steam pressure, so as to obtain the parameter value of the pressure loss variation and the parameter value of the volume effect; and obtaining the variation value of the main steam pressure of the steam turbine under any change of the adjustment valve of the steam turbine through utilizing the parameter value of the pressure loss variation and the parameter value of the volume effect and measuring the relationship between the variation value of the main steam pressure and the opening variation value of the adjustment valve. With the application of the invention, the parameter fitting is simple, and the measuring effect is good.

Description

Method and device for measuring main steam pressure of steam turbine

Technical Field

The invention relates to the technical field of stability research of a power system, in particular to a method and a device for measuring main steam pressure of a steam turbine in a steam turbine regulating system.

Background

In the research of the stability of the power system, the influence of main steam pressure change is not considered by a plurality of turbines for judging whether the power system is stable and the classical models of a turbine regulating system, namely the main steam pressure is not changed when the turbine regulating valve is supposed to be changed. In fact, the main steam pressure is very sensitive to the change of the regulating valve of the steam turbine, and when the regulating valve is opened greatly, the main steam pressure can be quickly reduced. Because the change of the main steam pressure directly affects the power of a unit, particularly the change of the power of a high-pressure cylinder, and the power response speed of the high-pressure cylinder is very high and is the most main contribution element of primary frequency modulation, in the process of judging the stability of a power grid by utilizing various classical models, a large error is usually brought by assuming that the main steam pressure is constant.

For example, when the opening of the steam turbine is increased, the steam inlet amount of the steam turbine is increased, the main steam pressure begins to be reduced, at the moment, although the fuel instruction is increased due to automatic control of the boiler, the supply of the steam drum is difficult to increase in a short time due to the delay link and the inertia of fuel release, the balance of the main steam pressure is broken, the main steam pressure is continuously reduced, and only after a long time, the effect of fuel increase gradually appears, and the main steam pressure can be recovered to a normal state.

To further illustrate the effect of main steam pressure changes on the power system stability study, the following description is provided with reference to the examples shown in fig. 1A-1C and fig. 2A-2B.

Referring to fig. 1A-1C, this example is performed on a simplified 3-machine 7-node power system. And cutting off part of the load of the No. 1 machine in the 10 th second of the dynamic process, and respectively recording the active power of the No. 2 generator under the two conditions of assuming constant main steam pressure and considering main steam pressure change, wherein the graph 1A is a graph of the organic power of the No. 2 generator, the graph 1B is a graph of system frequency, and the graph 1C is a graph of the change of the main steam pressure of the No. 2 generator. After the 1# machine cuts off partial load, the system frequency is reduced, the 2# machine speed regulator acts, and the active power output of the generator begins to increase. The active power is respectively increased by 5.4% and 6.1% under the condition of considering and not considering the change of the main steam pressure, and the amplification of the latter is increased by 12.9% compared with the former. The maximum reduction of the main steam pressure in the dynamic process is more than 1.5 percent.

Referring to fig. 2A-2B, in this example, measurement and analysis similar to the above example are performed on the north China power grid by applying a classical model without considering the pressure change of the main steam, and a 25r/min step disturbance is applied to the speed reference end of a certain electromechanical group of the north China power grid at the 10 th second of the analysis period, that is, the speed reference is suddenly strengthened to 3025r/min from the original 3000 r/min. Fig. 2A is a comparison of the active power output of the unit in consideration of whether the main steam pressure changes or not, and fig. 2B is a change of the main steam pressure in the dynamic process. It can be seen from the figure that, assuming that the main steam pressure is constant, the active power of the unit is increased by 6.8% at most in the dynamic process of 60 seconds, while the active power is increased by only 5.3% in the case of considering the main steam pressure change, and the amplitude of the main steam pressure is increased by 28% compared with the amplitude of the main steam pressure change.

The two examples and other extensive tests show that, in the process of researching the dynamic stability of the power system, the change of the main steam pressure often has a great influence on the analysis result, and the magnitude of the influence on the output of the unit generally exceeds 10%, and sometimes even reaches 30%.

To solve this problem, some models considering the change of the main steam pressure appear in the prior art, so as to apply the models together with other models to judge the stability of the power system. However, most of the models are complex and have many parameters, and the parameters are difficult to obtain according to the field actual measurement curve, so that the application is inconvenient.

Therefore, in the stability research of the power system, various models which do not consider the pressure change of the main steam are used for judging the stability of the power system, so that the result is inaccurate and the effect is poor; or a complex main steam pressure change model and other models are used together to judge the stability of the power system, so that system resources and calculation time are wasted, and the application is inconvenient.

Disclosure of Invention

The invention mainly aims to provide a method and a device for measuring main steam pressure of a steam turbine, which are used for solving the problems in the existing process of judging the stability of a power system.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a method of measuring main steam pressure of a steam turbine, the method comprising: adding disturbance to a rotating speed reference signal of a steam turbine control system; obtaining a change value of the opening degree of the regulating valve of the steam turbine within a period of time according to the disturbance; obtaining a main steam pressure change value of the steam turbine in the time period according to the disturbance; fitting parameters of pressure loss changes of a main steam pipeline and a superheater of the steam turbine and parameters of volume effects of a steam pocket and the superheater by using the main steam pressure change value and the valve opening change value to obtain a parameter value of the pressure loss changes and a parameter value of the volume effects; and measuring the main steam pressure change value of the steam turbine under any steam turbine regulating valve change by using the pressure loss change parameter value, the volume effect parameter value and the relation between the main steam pressure change value and the regulating valve opening change value.

A steam turbine main steam pressure measurement apparatus, the apparatus comprising: interference deviceThe dynamic generation unit is used for adding disturbance to a rotating speed reference signal of the steam turbine control system; the regulating valve opening change acquiring unit is used for acquiring a regulating valve opening change value of the steam turbine within a period of time according to the disturbance; the main steam pressure change obtaining unit is used for obtaining a main steam pressure change value of the steam turbine in the time period according to the disturbance; the fitting unit is used for fitting the pressure loss change parameters of the main steam pipeline and the superheater of the steam turbine and the volume effect parameters of the steam pocket and the superheater by using the main steam pressure change value and the opening change value of the regulating valve to obtain the pressure loss change parameter values and the volume effect parameter values; the measuring unit is used for measuring and obtaining a main steam pressure change value of the steam turbine under the condition of any steam turbine regulating valve change by utilizing the parameter value of the pressure loss change, the parameter value of the volume effect and the relation between the main steam pressure change value and the regulating valve opening change value; wherein the relationship between the main steam pressure change value and the opening change value of the regulating valve is

Wherein p is_T(s) is the main steam pressure variation value, mu_T(s) is a valve opening degree change value, and s is a complex parameter variable;

is an inertia link describing the pressure loss variation of the main steam pipeline and the superheater, and the parameters comprise K₁And T_pipeIn which K is₁Is the proportionality coefficient of the inertial element, T_pipeA time constant reflecting the pressure loss change of the main steam pipeline and the superheater;

is an inertial link describing the volume effect of the steam drum and the superheater, and the parameters comprise K₂And T_scIn which K is₂Is the proportionality coefficient of the inertial element, T_scIs a time constant reflecting the volume effect of the drum and superheater.

By the method and the device for measuring the main steam pressure of the steam turbine, in the process of judging the stability of the power system, the main steam pressure change is considered, so that a more accurate stability result of the power system is obtained, and a simple calculation formula is used, so that the calculation time is reduced, and the system resources are saved.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1A is a schematic diagram illustrating the change of the organic power of a 2# generator during an embodiment of determining the stability of a power system according to the prior art;

FIG. 1B is a schematic diagram illustrating the frequency variation of the system in the embodiment shown in FIG. 1A;

FIG. 1C is a schematic diagram of the pressure variation of the main steam of the 2# generator in the embodiment shown in FIG. 1A;

FIG. 2A is a schematic diagram illustrating comparison of active power of a unit in consideration of whether the main steam pressure changes in another embodiment process for determining the stability of an electric power system in the prior art;

FIG. 2B is a schematic diagram of the change in main steam pressure during a dynamic process;

FIG. 3 is a schematic flow diagram of a main steam pressure generation process;

FIG. 4 is a block diagram of a vapor pressure regulation system;

FIG. 5 is a block diagram of main steam pressure disturbance to the steam turbine inlet valve;

FIG. 6 is a block diagram of a main steam pressure change transfer function for a short period of time;

FIG. 7 is a block diagram of the main steam pressure change transfer function over a long period of time;

FIG. 8 is a simplified block diagram of the transfer function of main steam pressure change;

FIG. 9 is a flow chart of a method for measuring main steam pressure according to an embodiment of the present invention;

FIG. 10A is a schematic diagram of a main steam pressure variation curve measured using a complex transfer function and a model thereof in the prior art for a steam turbine governor disturbance 1;

FIG. 10B is a schematic representation of the main steam pressure profile measured using a simple relationship of an embodiment of the present invention for a steam turbine governor disturbance 1;

FIG. 11A is a schematic diagram of a main steam pressure variation curve measured using a prior art complex transfer function and model thereof under a turbine governor disturbance 2;

FIG. 11B is a schematic representation of the main steam pressure profile measured using a simple relationship of an embodiment of the present invention in the case of a turbine damper disturbance 2;

FIG. 12A is a schematic diagram of a main steam pressure curve measured using a complex transfer function and a model thereof in a low frequency accident simulated in an operation environment of a power system integrated stability program;

FIG. 12B is a schematic diagram of a main steam pressure curve measured using a simple relationship of an embodiment of the present invention in a simulated primary low frequency event in the operating environment of a power system integrated stability program;

FIG. 13A is a schematic view of a variation curve of the opening degree of the throttle valve under the condition of the upward step disturbance with reference to the rotation speed measured on site;

FIG. 13B is a schematic diagram illustrating a comparison between an actual measurement curve and a simulation curve of a change in a main steam pressure under an upward step disturbance condition of a reference rotation speed measured on site;

FIG. 14A is a schematic view of a variation curve of the opening degree of the throttle valve under the condition of the reference downward step disturbance of the rotation speed measured on site;

FIG. 14B is a schematic diagram illustrating a comparison between an actual measurement curve and a simulation curve of a change in a main steam pressure under a reference stepped-down disturbance condition of a rotation speed measured on site;

fig. 15 is a block diagram of the main steam pressure measuring device according to the embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are described in further detail below with reference to the embodiments and the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.

The first embodiment is as follows:

the embodiment of the invention provides a method for measuring main steam pressure of a steam turbine, which is described in detail below by combining the accompanying drawings.

In order to facilitate understanding of the method for measuring the main steam pressure of the steam turbine of the present invention, the generation process of the main steam pressure and the dynamic characteristics of each component will be described below.

Fig. 3 is a schematic diagram of a main steam pressure generation process, referring to fig. 3, fuel and corresponding air supply amount enter a hearth, heat generated by fuel combustion is absorbed by evaporation heating surfaces arranged around the hearth to generate steam, steam flow is heated by a heater to form superheated steam, and the superheated steam is sent to a steam turbine to do work through a steam pipeline. In FIG. 3,. mu._BAdjusting the opening degree of the mechanism for the fuel quantity; b is the fuel quantity; v is the air output; q_BThe heat of the hearth; p is a radical of_dIs the drum pressure; d_TThe steam amount for the steam turbine; p is a radical of_TIs the main steam pressure R_grIs superheater flow resistance; r_TIs the flow resistance of the steam turbine; p is a radical of_CBack pressure of the steam turbine; mu.s_TIs the opening degree of the steam inlet valve of the steam turbine.

As can be seen from fig. 3, the steam pressure adjusting system is composed of four parts, namely a boiler combustion part (hearth), an evaporation part (evaporation zone), a steam output part (superheater), a steam turbine and the like. The dynamic characteristics of each component of the steam pressure regulating system can be approximately derived by applying an analysis method according to the structure and physical characteristics of the system, and the dynamic characteristics of each component are briefly analyzed below.

A boiler combustion part:

the combustion part of the boiler refers to the opening degree mu of the slave fuel regulating mechanism_BChange to cause furnace heat Q_BThis portion is changed. Heat of furnace chamber Q_BRefers to the heat generated in unit time when the furnace fuel is completely combusted. Its relationship to fuel quantity can be expressed as:

$Q_B=B{Q}_d^y---\left(1\right)$

wherein, B is the fuel quantity,

is the application base lower heating value of the fuel.

The dynamic behavior of the combustion section of a boiler can be described by the transfer function of equation (2) according to its operating conditions:

<math><mrow><msub><mi>G</mi><mi>r</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow><mo>=</mo><mfrac><mrow><msub><mi>Q</mi><mi>B</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow><mrow><msub><mi>&mu;</mi><mi>B</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></mfrac><mo>=</mo><msub><mi>K</mi><mi>B</mi></msub><msubsup><mi>Q</mi><mi>d</mi><mi>y</mi></msubsup><msup><mi>e</mi><mrow><mo>-</mo><msub><mi>&tau;</mi><mi>B</mi></msub><mi>s</mi></mrow></msup><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow></math>

wherein, K_BThe transfer coefficient of the fuel regulating mechanism; tau is_BFor actual fuel heat Q from the fuel regulating mechanism action to the furnace_BThe time delay experienced by the change occurs.

And (3) evaporation part:

heat Q generated by combustion of fuel_BPart of the heat loss is removed, and the rest is absorbed by the furnace water in the water-cooled wall, so that the furnace water is evaporated into steam quantity D_Q。Q_BAnd D_QThe static relationship between can be established in an energy balance relationship:

D_Q(h_s-h_w)＝ηQ_B (3)

<math><mrow><msub><mi>D</mi><mi>Q</mi></msub><mo>=</mo><mfrac><mi>&eta;</mi><mrow><msub><mi>h</mi><mi>s</mi></msub><mo>-</mo><msub><mi>h</mi><mi>w</mi></msub></mrow></mfrac><msub><mi>Q</mi><mi>B</mi></msub><mo>=</mo><msub><mi>K</mi><mi>Q</mi></msub><msub><mi>Q</mi><mi>B</mi></msub><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>4</mn><mo>)</mo></mrow></mrow></math>

wherein eta is boiler efficiency h_sIs the enthalpy of saturated steam, h_wFor the enthalpy of feed water, K_QIs the transfer coefficient.

Amount of steam D generated due to heat of combustion of fuel_QThe steam output D of the boiler is not necessarily the same, so D can be used_QReferred to as hypothetical steam flow. The steam output D of the boiler is changed along with the load change of the steam turbine when D_QWhen D is greater than D, the excessive steam quantity can be stored in the boiler, and the change of boiler energy storage can cause the pressure p of the steam drum_dI.e.:

<math><mrow><msub><mi>p</mi><mi>d</mi></msub><mo>=</mo><mfrac><mn>1</mn><msub><mi>C</mi><mi>K</mi></msub></mfrac><mo>&Integral;</mo><mrow><mo>(</mo><msub><mi>D</mi><mi>Q</mi></msub><mo>-</mo><mi>D</mi><mo>)</mo></mrow><mi>dt</mi><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>5</mn><mo>)</mo></mrow></mrow></math>

wherein, C_KIs the heat storage coefficient of the boiler, C_KWhich refers to the amount of steam that the boiler needs to store (or release) for each unit of pressure change in the drum pressure. If at drum pressure p_dAs an output signal of the evaporation section of the boiler, the transfer function of this section can be expressed as:

$G_z\left(s\right)=\frac{p_d\left(s\right)}{D_Q\left(s\right)-D\left(s\right)}=\frac{1}{C_{K^s}}---\left(6\right)$

a steam output part:

the steam output part comprises a superheater and a main steam pipeline:

when the steam output device which takes the superheater as the steam pressure object is viewed, the superheater can be regarded as a resistant pipeline without considering the heat transfer relation, and the superheater can be regarded as a proportional link with the transfer function as follows:

$G_g\left(s\right)=\frac{D\left(s\right)}{p_d\left(s\right)-p_T\left(s\right)}=\frac{1}{R_{\mathrm{gr}}}---\left(7\right)$

wherein R is_grFor superheater tube resistance, D for boiler output steam flow, p_dIs drum pressure, p_TIs the main steam pressure.

For the main steam pipeline, the inflow of the main steam pipeline is the output steam flow D of the boiler, and the outflow is the gas consumption D of the steam turbine_TThe main steam pressure reflects D and D_TThe material balance index of the relationship between the two. Since the steam pipeline is a container with a small capacity coefficient, the steam pipeline can be regarded as a transfer function with integral characteristics as follows:

$G_K\left(s\right)=\frac{p_T\left(s\right)}{D\left(s\right)-D_T\left(s\right)}=\frac{1}{C_{m^s}}---\left(8\right)$

wherein, C_mIs the capacity factor of the steam pipeline.

A steam turbine:

steam admission D of a steam turbine_TAcceptor vapor pressure p_TBack pressure p of steam turbine_cAnd regulating the steamOpening degree mu of door (called adjusting door for short)_TGenerally, the back pressure is rarely changed, and the throttle characteristic of the steam turbine is assumed to be linear, so the steam inlet amount of the steam turbine can be expressed by the following formula:

<math><mrow><msub><mi>D</mi><mi>T</mi></msub><mo>=</mo><mfrac><mn>1</mn><msub><mi>R</mi><mi>T</mi></msub></mfrac><msub><mi>p</mi><mi>T</mi></msub><mo>+</mo><msub><mi>K</mi><mi>T</mi></msub><mi>&mu;T</mi><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>9</mn><mo>)</mo></mrow></mrow></math>

wherein R is_TAs flow resistance of the steam turbine, K_TIs the transmission coefficient of the turbine governor, mu_TThe opening degree of a throttle of the steam turbine.

As can be seen from the above-mentioned main steam pressure production flow and the above-mentioned analysis of the dynamic characteristics of the components of the steam pressure regulating system, the block diagram of the components of the steam pressure regulating system can be represented as shown in fig. 4.

The opening degree μ of the slave fuel adjusting mechanism_BChange to cause furnace heat Q_BThe time delay of the change process is relatively long, generally more than several minutes, while the time requirement of the current production department for stable measurement of the power system is generally 2000 cycles (40 seconds), and in the time period range, the heat released by the fuel, namely the furnace heat Q, can be considered_BIs constant, i.e. the main steam pressure of the turbine is only dependent on the throttle opening, and when only the turbine throttle opening is disturbed, the block diagram of fig. 4 can be represented as fig. 5, from which fig. 5 the throttle opening μ can be determined_TThe transfer function of the change of the main steam pressure under disturbance is as follows:

<math><mrow><mfrac><mrow><msub><mi>p</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow><mrow><msub><mi>&mu;</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></mfrac><mo>=</mo><mfrac><mrow><mo>-</mo><msub><mi>K</mi><mi>T</mi></msub><mrow><mo>(</mo><msub><mi>C</mi><mi>K</mi></msub><msub><mi>R</mi><mi>T</mi></msub><msub><mi>R</mi><mi>gr</mi></msub><mi>s</mi><mo>+</mo><msub><mi>R</mi><mi>T</mi></msub><mo>)</mo></mrow></mrow><mrow><msub><mi>R</mi><mi>T</mi></msub><msub><mi>R</mi><mi>gr</mi></msub><msub><mi>C</mi><mi>K</mi></msub><msub><mi>C</mi><mi>m</mi></msub><msup><mi>s</mi><mn>2</mn></msup><mo>+</mo><msub><mi>C</mi><mi>m</mi></msub><msub><mi>R</mi><mi>T</mi></msub><mi>s</mi><mo>+</mo><msub><mi>C</mi><mi>K</mi></msub><msub><mi>R</mi><mi>T</mi></msub><mi>s</mi><mo>+</mo><msub><mi>C</mi><mi>k</mi></msub><msub><mi>R</mi><mi>gr</mi></msub><mi>s</mi><mo>+</mo><mn>1</mn></mrow></mfrac><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>10</mn><mo>)</mo></mrow></mrow></math>

the formula (10) is a main steam pressure change model deduced according to theoretical analysis, the physical meaning of the model is clear, but the problem is that how to determine the values of the parameters is difficult. The field test cannot fit so many parameters because there are too few points. Therefore, it is necessary to simplify the model and reduce the number of parameters, so that the values of the parameters can be obtained by a mathematical fitting method by using a measurement curve of a field test.

In the process of implementing the invention, the inventor discovers that the capacity coefficient C of the steam pipeline of the actual steam turbine is caused by_mSpecific heat storage coefficient C of boiler_KThe size of the turbine is much smaller, and the latter is generally dozens of times or even hundreds of times of the former, so that the turbine can be used in a short time (the time period and C) after the opening degree of the regulating valve of the turbine is disturbed_mSimilarly), the integration element in fig. 5 can be omitted

The output of the link is considered to be constant over this period, in which case the change in the main steam pressure is to μ_TFIG. 5 can be simplified to the transfer function of FIG. 6The number is as follows:

<math><mrow><mfrac><mrow><msub><mi>p</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow><mrow><msub><mi>&mu;</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></mfrac><mo>=</mo><mo>-</mo><mfrac><mrow><msub><mi>K</mi><mi>T</mi></msub><mrow><msub><mi>R</mi><mi>gr</mi></msub><msub><mi>R</mi><mi>T</mi></msub></mrow></mrow><mrow><msub><mi>R</mi><mi>gr</mi></msub><mo>+</mo><msub><mi>R</mi><mi>T</mi></msub><msub><mrow><mo>+</mo><mi>R</mi></mrow><mi>gr</mi></msub><msub><mi>R</mi><mi>T</mi></msub><msub><mi>C</mi><mi>m</mi></msub><mi>s</mi></mrow></mfrac><mo>=</mo><mo>-</mo><mo>-</mo><mfrac><msub><mi>K</mi><mn>1</mn></msub><mrow><mn>1</mn><mo>+</mo><msub><mi>T</mi><mrow><mi>pip</mi><msup><mi>e</mi><mi>s</mi></msup></mrow></msub></mrow></mfrac><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>11</mn><mo>)</mo></mrow></mrow></math>

wherein,

equation (11) is a first order inertial element.

After a longer time after the port disturbance (this time period is associated with C)_KSimilar) due to C_mIs very small, so in FIG. 5

And

the inertia element can be approximated by a proportionality coefficient R_TIn this case, the change in the main steam pressure versus μ_TTransfer under disturbanceThe functional block diagram of fig. 5 can be simplified as shown in fig. 7. From FIG. 7, the transfer function is:

<math><mrow><mfrac><mrow><msub><mi>p</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow><mrow><msub><mi>&mu;</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></mfrac><mo>=</mo><mo>-</mo><mo>[</mo><mfrac><mrow><msub><mi>K</mi><mi>T</mi></msub><msub><mi>R</mi><mi>T</mi></msub><msub><mi>R</mi><mi>gr</mi></msub></mrow><mrow><msub><mi>R</mi><mi>T</mi></msub><mo>+</mo><msub><mi>R</mi><mi>gr</mi></msub></mrow></mfrac><mo>+</mo><mfrac><msub><mi>R</mi><mi>T</mi></msub><mrow><msub><mi>R</mi><mi>T</mi></msub><mo>+</mo><msub><mi>R</mi><mi>gr</mi></msub></mrow></mfrac><mo>&CenterDot;</mo><mfrac><mrow><msub><mi>K</mi><mi>T</mi></msub><msub><mi>R</mi><mi>T</mi></msub></mrow><mrow><mn>1</mn><mo>+</mo><msub><mi>C</mi><mi>K</mi></msub><mrow><mo>(</mo><msub><mi>R</mi><mi>T</mi></msub><mo>+</mo><msub><mi>R</mi><mi>gr</mi></msub><mo>)</mo></mrow><mi>s</mi></mrow></mfrac><mo>]</mo></mrow></math>

$=-[{\mathrm{<figure-callout\; id="1"\; label="K"\; filenames="H2009100760973E0000012.png,H2009100760973E0000022.png"\; state="\{\{state\}\}">K</figure-callout>}}_1+\frac{K_2}{1+T_{\mathrm{sc}}s}]---\left(12\right)$

wherein:T_sc＝(R_T+R_gr)C_K。

from the combinations (11) and (12), it can be found that the main steam pressure changes to mu in the whole period_TTransfer under disturbanceThe function can be approximated by equation (13), and fig. 8 is a model of the change in main steam pressure corresponding to the transfer function.

<math><mrow><mfrac><mrow><msub><mi>p</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow><mrow><msub><mi>&mu;</mi><mi>T</mi></msub><mrow><mo>(</mo><mi>s</mi><mo>)</mo></mrow></mrow></mfrac><mo>=</mo><mo>-</mo><mo>[</mo><mfrac><msub><mi>K</mi><mn>1</mn></msub><mrow><mn>1</mn><mo>+</mo><msub><mi>T</mi><mi>pipe</mi></msub><mi>s</mi></mrow></mfrac><mo>+</mo><mfrac><msub><mi>K</mi><mn>2</mn></msub><mrow><mn>1</mn><mo>+</mo><msub><mi>T</mi><mi>sc</mi></msub><mi>s</mi></mrow></mfrac><mo>]</mo><mo>-</mo><mo>-</mo><mo>-</mo><mrow><mo>(</mo><mn>13</mn><mo>)</mo></mrow></mrow></math>

By adopting the transfer function of the formula (13), a change curve mu of the opening degree of the throttle valve obtained by a field turbine disturbance test is obtained_T(s) and main steam pressure curve p_T(s) determining the parameters K of the two inertial links₁、T_pipe、K₂、T_scThe main steam pressure change under any throttle opening change can be measured, a reference basis is provided for stability judgment of the power system, and compared with the prior main steam pressure change transfer function, the main steam pressure change transfer function has the following advantages:

1. the simplified transfer function comprises two parallel inertia links, the structure of the simplified transfer function is simplified, and nonlinear links are eliminated.

2. The physical meaning of the parameters is clear. Inertia link with small time constant

Inertia link reflecting pressure loss change of main steam pipeline and superheater and having larger time constant

The volume effect of the steam pocket and the volume effect of the superheater are reflected, and when the regulating valve changes, the pressure change in front of the speed regulating valve is the superposition of the two effects.

3. The parameter K can be easily obtained according to a curve obtained by field experiment data₁、T_pipe、K₂、T_scAnd a basis is provided for further measuring the main steam pressure change under the condition of any throttle opening change.

The method for measuring the main steam pressure of the steam turbine in the embodiment of the invention utilizes the simplified main steam pressure transfer function, measures the change of the opening degree of the regulating valve and the change of the main steam pressure within a period of time by applying step disturbance to the rotating speed reference end of the steam turbine control system, and determines the parameter K according to the change curve of the opening degree of the regulating valve and the change curve of the main steam pressure obtained by the experimental data measured on site₁、T_pipe、K₂、T_scFurthermore, the simplified transfer function is utilized to measure the main steam pressure variation of any throttle opening variation, and the method for measuring the main steam pressure of the steam turbine according to the embodiment of the present invention is described in detail below with reference to fig. 9.

Referring to fig. 9, the method for measuring the main steam pressure of the steam turbine according to the embodiment of the present invention mainly includes:

901: adding disturbance to a rotating speed reference signal of a turbine control system.

In this embodiment, the disturbance may be a rotation speed reference upward step disturbance or a rotation speed reference downward step disturbance, and the purpose is to determine four parameters of two inertia links of the transfer function (13) by using a throttle opening variation curve and a main steam pressure variation curve obtained through measurement in the disturbance test, so as to further measure main steam pressure variation under any throttle opening variation in a real environment, and avoid a trouble caused by measurement of the main steam pressure each time in a stability judgment process of a power system.

902: and obtaining the opening change value of the steam turbine regulating valve within a period of time according to the disturbance.

In this embodiment, the change in the opening degree of the damper is measured by an in-situ measuring device in the presence of the disturbance, and the method has been implemented in the art and is not described herein again.

903: and obtaining the main steam pressure change value of the steam turbine in the time period according to the disturbance.

In the present embodiment, the main steam pressure variation is generated due to the variation of the opening degree of the damper in the presence of the disturbance and is measured by an on-site measuring device, and the method is implemented in the field for a long time and is not described herein again.

904: according to the relation between the main steam pressure change value and the valve opening change value, fitting the pressure loss change parameters of the main steam pipeline and the superheater of the steam turbine and the volume effect parameters of the steam pocket and the superheater by using the main steam pressure change value to obtain the pressure loss change parameter values and the volume effect parameter values.

In this embodiment, the relationship between the main steam pressure variation value and the throttle opening variation value is

Wherein p is_T(s) is the main steam pressure variation value, mu_T(s) is a valve opening degree change value, and s is a complex parameter variable;

is an inertia link describing the pressure loss variation of the main steam pipeline and the superheater, and the parameters comprise K1 and T_pipeIn which K is₁Is the proportionality coefficient of the inertial element, T_pipeA time constant reflecting the pressure loss change of the main steam pipeline and the superheater;

is an inertial link describing the volume effect of the steam drum and the superheater, and the parameters comprise K₂And T_scIn which K is₂Is the proportionality coefficient of the inertial element, T_scIs a time constant reflecting the volume effect of the drum and superheater.

905: and measuring the main steam pressure change value of the steam turbine under any steam turbine regulating valve change by using the pressure loss change parameter value, the volume effect parameter value and the relation between the main steam pressure change value and the regulating valve opening change value.

In the present embodiment, the parameter K of the pressure loss variation is determined₁And T_pipeAnd the parameter K of the volume effect₂And T_scReady to use

And measuring the main steam pressure change under any throttle opening change in the actual power system operation environment, and providing a reference basis for the stable operation of the power system.

According to the embodiment, due to the fact that the simple relational expression between the main steam pressure change and the throttle opening change is used, only four parameters in the relational expression can be easily determined according to field test data, simple operation steps are provided for further measuring the main steam pressure change under any throttle opening change, compared with the traditional complex transfer function and model thereof, the flow is simplified, system resources are saved, and the measuring effect is good.

In order to demonstrate the above-described effects achieved by the embodiments of the present invention, the following description will be made of a measurement method of the embodiments of the present invention by way of an example in a test.

Example one

Fig. 10A and 10B are schematic diagrams of main steam pressure changes in the case of turbine damper disturbance 1, fig. 11A and 11B are schematic diagrams of main steam pressure changes in the case of turbine damper disturbance 2, where fig. 10A and 11A are main steam pressure change curves measured by using a conventional complex transfer function and a model thereof, and fig. 10B and 11B are main steam pressure change curves measured by using a simple relationship according to an embodiment of the present invention. Fig. 12A and 12B are schematic diagrams of main steam pressure change in a primary low-frequency accident simulated in a comprehensive and stable operating environment of a power system, where fig. 12A is a main steam pressure change curve measured by using a conventional complex transfer function and a model thereof, and fig. 12B is a main steam pressure change curve measured by using a simple relationship according to an embodiment of the present invention.

Example two

Please refer to fig. 13A-13B and fig. 14A-14B.

Firstly, the relationship between the change of the main steam pressure and the change of the opening degree of the throttle in the embodiment of the invention is compared by utilizing the experimental data of the opening degree of the high-pressure throttle and the main steam pressure in the rotating speed reference upward step disturbance process

Four parameters K of₁、T_pipe、K₂、T_scThe identification is performed. Fig. 13A is a curve showing a change in the opening degree of the throttle valve measured on site, and fig. 13B is a curve showing a change in the main steam pressure measured on site. Within 5 seconds after disturbance, the main steam pressure is reduced rapidly, which is mainly the first inertia link on the right side of the middle mark in the relationship

So that the inertia element can be fitted with this curveTwo parameters K of₁、T_pipe. The specific fitting method is as follows (same below): firstly, selecting a plurality of points (more than 10 points) on the curve, then taking logarithms at two ends of the function, changing the exponential function into a linear relation, and finally calculating parameter values by using a common polynomial fitting method, wherein the results are as follows:

K₁＝0.32，T_pipe＝2.5 (14)

the main steam pressure curve after 5 seconds after disturbance becomes gradually gentle, which is mainly the second inertia link on the right side of the medium number in the relationshipSo that this curve can be used to fit the inertial element

Two parameters K of₂、T_scThe results are as follows:

K₂＝0.9，T_sc＝60 (15)

the main steam pressure change under any throttle change can be measured by using the result of the fitting parameters, the main steam pressure change curve and the throttle opening change curve, and a comparison between the main steam pressure change curve measured by using the method of the embodiment of the invention and the actually measured main steam pressure change curve is shown in fig. 13B.

In order to verify the effectiveness of the measuring method of the embodiment of the invention, a change curve of the main steam pressure under the change of the opening degree of the throttle is measured by utilizing a curve of the opening degree of the high-pressure throttle measured in the process of the step disturbance with the rotating speed reference downward as shown in fig. 14A, and a result as shown in fig. 14B is obtained.

Example two:

the embodiment of the invention also provides a main steam pressure measuring device of a steam turbine, and the main steam pressure measuring device of the steam turbine is described below with reference to the accompanying drawings.

Fig. 15 is a block diagram of the main steam pressure measuring device according to the embodiment of the present invention, and referring to fig. 15, the main steam pressure measuring device according to the embodiment of the present invention mainly includes:

the disturbance generating unit 151 is used for adding disturbance to a rotating speed reference signal of the steam turbine control system;

the valve opening change acquiring unit 152 is used for acquiring a valve opening change value of the steam turbine within a period of time according to the disturbance;

a main steam pressure change obtaining unit 153, configured to obtain a main steam pressure change value of the steam turbine in the time period according to the disturbance;

a fitting unit 154, configured to fit, according to a relationship between the main steam pressure change value and the valve opening change value, a pressure loss change parameter of a main steam pipeline and a superheater of the turbine and a volume effect parameter of a steam drum and a superheater of the turbine by using the main steam pressure change value, so as to obtain a pressure loss change parameter value and a volume effect parameter value;

the measuring unit 155 is used for measuring and obtaining a main steam pressure change value of the steam turbine under any steam turbine regulating valve change by using the parameter value of the pressure loss change, the parameter value of the volume effect and the relation between the main steam pressure change value and the regulating valve opening change value;

wherein the relationship between the main steam pressure change value and the opening change value of the regulating valve is

Wherein p is_T(s) is the main steam pressure variation value, mu_T(s) is a valve opening degree change value, and s is a complex parameter variable;

is an inertia link describing the pressure loss variation of the main steam pipeline and the superheater, and the parameters comprise K₁And T_pipeIn which K is₁Is the proportionality coefficient of the inertial element, T_pipeTo reflect the main steamingTime constants of pressure loss changes of the steam pipeline and the superheater;

is an inertial link describing the volume effect of the steam drum and the superheater, and the parameters comprise K₂And T_scIn which K is₂Is the proportionality coefficient of the inertial element, T_scIs a time constant reflecting the volume effect of the drum and superheater.

The main steam pressure measuring device of this embodiment corresponds to the main steam pressure measuring method of the first embodiment, and the working processes of the components have already been clearly described in the first embodiment, and are not described herein again.

By utilizing the measuring device of the embodiment, a simple relational expression between the main steam pressure change and the throttle opening change is used, only four parameters in the relational expression are easily determined according to field test data, simple operation steps are provided for further measuring the main steam pressure change under any throttle opening change, and compared with the traditional complex transfer function and model thereof, the measuring device simplifies the flow, saves the system resources and has good measuring effect.

In summary, in view of the fact that the influence of the main steam pressure on the active power output of the generator set is large in the dynamic process, it is necessary to consider the main steam pressure change in the power system stability judgment process, and by the main steam pressure measurement method and the main steam pressure measurement device of the embodiment of the invention, the following beneficial effects are achieved for the stability judgment of the power system:

1. the time interval concerned by the stability of the actual power system is generally within 50 seconds, the fuel change can be ignored in the process, the main steam pressure measuring method and the main steam pressure measuring device only consider the influence of the throttle change, and the relation between the single-input single-output main steam pressure change consisting of two parallel inertia links and the throttle opening change is utilized.

2. The parameters in the relation between the main steam pressure change and the opening change of the regulating valve are identified by utilizing a group of main steam pressure curves obtained by a dynamic disturbance experiment of the steam turbine, another group of dynamic disturbance experiments are simulated by utilizing the parameters, and the reasonability of the main steam pressure measuring method and the main steam pressure measuring device and the accuracy of fitting parameters are verified by comparing the measured value and the measured value of the main steam pressure.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (3)

1. A method of measuring main steam pressure of a steam turbine, the method comprising:

adding disturbance to a rotating speed reference signal of a steam turbine control system;

obtaining a change value of the opening degree of a steam turbine regulating valve within a period of time according to the disturbance;

obtaining a main steam pressure change value of the steam turbine in the time period according to the disturbance;

fitting a pressure loss change parameter of a main steam pipeline and a superheater of the steam turbine and a volume effect parameter of a steam pocket and the superheater by using the main steam pressure change value according to the relation between the main steam pressure change value and the opening change value of the regulating valve to obtain a pressure loss change parameter value and a volume effect parameter value;

and measuring the main steam pressure change value of the steam turbine under any steam turbine regulating valve change by using the pressure loss change parameter value, the volume effect parameter value and the relation between the main steam pressure change value and the regulating valve opening change value.

2. The method according to claim 1, wherein the relationship between the change value of the main steam pressure and the change value of the throttle opening is:

wherein p is_T(s) is the main steam pressure variation value, mu_T(s) is a valve opening degree change value, and s is a complex parameter variable;

is an inertia link describing the pressure loss variation of the main steam pipeline and the superheater, and the parameters comprise K₁And T_pipeIn which K is₁Is the proportionality coefficient of the inertial element, T_pipeA time constant reflecting the pressure loss change of the main steam pipeline and the superheater;

is an inertial link describing the volume effect of the steam drum and the superheater, and the parameters comprise K₂And T_scIn which K is₂Is the proportionality coefficient of the inertial element, T_scIs a time constant reflecting the volume effect of the drum and superheater.

3. A steam turbine main steam pressure measurement apparatus, the apparatus comprising:

the disturbance generating unit is used for adding disturbance to a rotating speed reference signal of the steam turbine control system;

the regulating valve opening change acquiring unit is used for acquiring a regulating valve opening change value of the steam turbine within a period of time according to the disturbance;

the main steam pressure change obtaining unit is used for obtaining a main steam pressure change value of the steam turbine in the time period according to the disturbance;

the fitting unit is used for fitting the pressure loss change parameters of the main steam pipeline and the superheater of the steam turbine and the volume effect parameters of the steam pocket and the superheater by using the main steam pressure change values according to the relation between the main steam pressure change values and the opening change values of the regulating valve, so as to obtain the pressure loss change parameter values and the volume effect parameter values;

the measuring unit is used for measuring and obtaining a main steam pressure change value of the steam turbine under the condition of any steam turbine regulating valve change by utilizing the parameter value of the pressure loss change, the parameter value of the volume effect and the relation between the main steam pressure change value and the regulating valve opening change value;

wherein the relationship between the main steam pressure change value and the opening change value of the regulating valve is

Wherein p is_T(s) is the main steam pressure variation value, mu_T(s) is a valve opening degree change value, and s is a complex parameter variable;

is an inertia link describing the pressure loss variation of the main steam pipeline and the superheater, and the parameters comprise K₁And T_pipeIn which K is₁Is the proportionality coefficient of the inertial element, T_pipeA time constant reflecting the pressure loss change of the main steam pipeline and the superheater;

is an inertial link describing the volume effect of the steam drum and the superheater, and the parameters comprise K₂And T_scIn which K is₂Is the proportionality coefficient of the inertial element, T_scIs a time constant reflecting the volume effect of the drum and superheater.

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