A method for regulating and controlling the load change rate of a generator set

Abstract

The application discloses a kind of generator set load change rate adjustment control methods, including according to the rated load of generator set Load change rate index C1 is set;Establish the functional relationship between load change rate coefficient Y and machine front pressure differential value X;Machine front pressure differential value at t time is calculated;The load change state of generator set at t time is judged;According to the load change state of generator set determined and the machine front pressure differential value calculated, load change rate coefficient at t time is set;The load change rate coefficient set is multiplied with the load change rate index C1 set, obtains the dynamic load change rate C (t) of generator set at t time, its advantage is in real-time, the real-time load change state of generator set is combined with machine front pressure differential value to carry out dynamic adjustment to generator set, both can guarantee load response rate, also can effectively reduce machine front pressure fluctuation amplitude, effectively increase the coordination ability of boiler steam turbine, guarantee the safe and stable operation of unit.

Description

Technical fields:

[0001] This invention relates to the field of generator set regulation and control, and in particular to a generator set load change rate regulation and control method. Background technology:

[0002] To better meet users' electricity demand, power plants must have a strong ability to participate in grid peak shaving and frequency regulation. Currently, large thermal power plants mainly ensure their grid peak shaving and frequency regulation capabilities through coordinated control systems. The basic principle of the coordinated control system is to comprehensively control the boiler and steam turbine as a unit unit, so that the unit unit can respond to the grid load demand as quickly as possible.

[0003] Taking the furnace-following control system as an example, in the furnace-following control system, such as Figure 1 As shown, the unit load N E and machine front pressure p t It is the controlled variable of the system, the steam turbine regulating valve opening u. T and fuel quantity u B It is the system's control input. To meet the requirement of the unit's output power quickly tracking changes in AGC (Automatic Generation Control) commands, the feedback signal N of the main control unit is used. E With preset value N ESP After comparison, the data is sent to the power regulator, which then adjusts the turbine's steam control valve opening, u. T The boiler tracks load changes by altering the steam inlet flow rate; to stabilize the turbine inlet pressure, the boiler main control feedback signal p... t Compared with the preset value p tsp After comparison, the fuel is sent to the pressure regulator, which then adjusts the fuel quantity u. B The input is obtained by changing the fuel quantity u. B To adjust the valve opening u T The change in turbine inlet pressure is caused by variations in pressure. Under this coordinated control mode, in steady state, the turbine maintains load, and the boiler maintains pressure. In dynamic states, the turbine responds instantaneously to the load via feedforward, and the boiler responds to the turbine's demands based on energy and load commands fed forward. The boiler-turbine coordinated control system ensures the unit quickly tracks AGC command changes while fully utilizing boiler heat storage, but it is prone to causing changes in turbine inlet pressure (p). t The pressure fluctuates significantly. Therefore, effectively maintaining stable pressure at the machine entrance while meeting the AGC load response rate is a key challenge. Summary of the Invention:

[0004] The purpose of this invention is to provide a dynamic load change rate control strategy that effectively reduces pressure fluctuations in front of the machine while ensuring the AGC load response rate.

[0005] The application is implemented by the following technical scheme: a generator set load change rate adjusting control method, comprising the following steps:

[0006] S100: setting a load change rate index C1 according to a generator set rated load;

[0007] S200: establishing a function relation between a load change rate coefficient Y and a front pressure differential value X, and determining the load change rate coefficient Y of the generator set according to the front pressure differential value X;

[0008] S300: calculating the front pressure differential value X(t) at t moment;

[0009] S400: judging the load change state of the generator set at t moment;

[0010] S500: setting the load change rate coefficient Y(t) at t moment according to the generator set load change state determined in S400 and the front pressure differential value X(t) calculated in S300;

[0011] S600: multiplying the load change rate coefficient Y(t) set in S500 and the load change rate index C1 set in S100 to obtain the dynamic load change rate C(t) of the generator set at t moment, i.e. C(t)=Y(t)*C1;

[0012] S700: adjusting and controlling the generator set at t moment according to the dynamic load change rate C(t) calculated in S600.

[0013] Preferably, the load change rate coefficient Y in S200 comprises an ascending load change rate coefficient Y1 and a descending load change rate coefficient Y2.

[0014] Preferably, the judgment on the load change state of the generator set at t moment in S400 comprises the following steps:

[0015] S410: obtaining a preset load value NESP of the generator set and a real-time load value NE(t) of the generator set at t moment;

[0016] S420: calculating the difference SUM(t) between the preset load value NESP of the generator set and the load value NE(t) at t moment;

[0017] S430: judging the load change state of the generator set at t moment according to the SUM(t) calculated in S420,

[0018] when SUM(t)>1, it is judged that the generator set is in an ascending load state at t moment;

[0019] when SUM(t)<1, it is judged that the generator set is in a descending load state at t moment.

[0020] Preferably, the step S600 further comprises limiting the dynamic load change rate C(t) of the generator set at time t.

[0021] The present application has the advantages of high real-time performance, dynamic adjustment of the generator set based on the real-time load change state of the generator set and the differential value of the front pressure, which can ensure the load response rate and effectively reduce the fluctuation amplitude of the front pressure, effectively increase the coordination ability of the boiler and the steam turbine, and ensure the safe and stable operation of the generator set. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0023] Figure 1 It is a control schematic diagram of the furnace-following machine control system in the prior art.

[0024] Figure 2 It is a flow chart of the adjustment control method of the present application.

[0025] Figure 3 It is a trend chart of the change of various parameters in the load increase process of Example 1.

[0026] Figure 4 It is a trend chart of the change of various parameters in the load decrease process of Example 2.

[0027] Figure 5 It is a trend chart of the change of various parameters in the load increase process of Comparative Example 1.

[0028] Figure 6 It is a trend chart of the change of various parameters in the load decrease process of Comparative Example 2. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] The present application discloses a load change rate adjustment control method of a generator set, which can effectively reduce the fluctuation amplitude of the front pressure.

[0031] Generally, the change of the front pressure is mainly caused by the change of the boiler combustion amount uB and turbine governing valve opening degree u T The change causes; the boiler combustion exists larger inertia, therefore to the front of machine pressure influence exists certain hysteresis, the turbine governing valve opening degree change determines the steam quantity size entering the steam turbine directly, can respond to the front of machine pressure quickly. In response to the load increase demand, the turbine governing valve opens quickly, the initial boiler combustion reaction cannot satisfy the steam demand of the steam turbine, so that the front of machine pressure will show a downward trend, until the boiler combustion inertia time, the front of machine pressure change direction begins to reverse to the upward trend, vice versa. In the process, the change rate of turbine governing valve opening degree is directly affected by the change rate of power generation load, the faster the power generation load changes, the faster the turbine governing valve switching rate, the greater the influence on the front of machine pressure. As can be seen, theoretically at the beginning of variable load, the front of machine pressure is opposite to the load change direction, and after the boiler combustion inertia time, the front of machine pressure begins to gradually change with the load change direction.

[0032] The present application utilizes the above characteristics to develop the following adjustment strategy: set a smaller load change rate at the beginning of variable load, and set a larger load change rate when the front of machine pressure reverses. Theoretically, a variable can be judged by the differential element for its future change direction, so under this adjustment strategy, the load change rate is set according to the differential value of the front of machine pressure by utilizing the coupling relationship characteristics of the front of machine pressure and the load change rate. Specifically, as shown in Figure 2 The power generation unit load change rate adjustment control method of the present application includes the following steps:

[0033] S100: Set the load change rate index C1 according to the rated load of the power generation unit, usually, the value of the index needs to be greater than or equal to 1% of the rated load value of the unit, for example, for a 330MW unit, the set load change rate index C1 should be not less than 3.3MW / min; in actual production, the load change rate index C1 is set through the DCS control system.

[0034] S200: Establish a functional relationship between the load change rate coefficient Y and the differential value X of the front of machine pressure, and determine the load change rate coefficient Y of the power generation unit according to the differential value X of the front of machine pressure; in this step, the load change rate coefficient Y to be set includes the ascending load change rate coefficient Y1 and the descending load change rate coefficient Y2.

[0035] In the present application, two load change rate coefficients are calculated by using multi-point polyline functions. Among them, when calculating the ascending load change rate coefficient Y1, the set multi-point polyline function f1 is as shown in Table 1, and when calculating the descending load change rate coefficient Y2, the set multi-point polyline function f2 is as shown in Table 2.

[0036] Table 1 Multi-point polyline function f1 used when calculating the ascending load change rate coefficient Y1

[0037] X -100 -5 -2.5 -1 0 1 2.5 5 100 [Y1] 0.2 0.5 0.7 0.8 1 1.2 1.5 2 3

[0038] Table 2 Multi-point broken line function f2 used in calculating the load reduction rate coefficient Y2

[0039] X -100 -5 -2.5 -1 0 1 2.5 5 100 -100 [Y2] 3 2 1.5 1.2 1 0.8 0.7 0.5 0.2 3

[0040] After the load change rate index C1 and the load change rate coefficient Y are preset, the load change rate of the generator set is adjusted in real time, specifically, the following steps are executed:

[0041] S300: Calculate the differential value X(t) of the front pressure of the generator set at time t;

[0042] S400: Determine the load change state of the generator set at time t, that is, determine whether the generator set is in a load increasing state or a load decreasing state at time t, and the specific determination process includes the following steps:

[0043] S410: Obtain the preset load value NESP of the generator set and the real-time load value NE(t) of the generator set at time t;

[0044] S420: Calculate the difference SUM(t) between the preset load value NESP of the generator set and the load value NE(t) at time t;

[0045] S430: Determine the load change state of the generator set at time t according to SUM(t) calculated in S420,

[0046] When SUM(t) > 1, it is determined that the generator set is in a load increasing state at time t;

[0047] When SUM(t) < 1, it is determined that the generator set is in a load decreasing state at time t.

[0048] S500: According to the load change state of the generator set determined in S400 and the differential value X(t) of the front pressure calculated in S300, set the load change rate coefficient Y(t) at time t, when it is determined that the generator set is in a load increasing state, use the multi-point broken line function f1 to calculate the load change rate Y(t) at time t, and when it is determined that the generator set is in a load decreasing state, use the multi-point broken line function f2 to calculate the load change rate Y(t) at time t.

[0049] S600: Multiply the load change rate coefficient Y(t) set in S500 by the load change rate index C1 set in S100 to obtain the dynamic load change rate C(t) of the generator set at time t,

[0050] That is: C(t) = Y(t) * C1.

[0051] In this step, in order to avoid that the dynamic load change rate exceeds the unit performance, the dynamic load rate C(t) is limited according to the generator set performance, and for example, for a 330MW generator set, the maximum load change rate is 8MW / min, and then the maximum value of C(t) is limited to 8MW / min; in addition, the minimum value of the load change rate can also be limited according to the operation of the generator set.

[0052] S700: The generator set at the moment t is adjusted and controlled according to the dynamic load change rate C(t) calculated in S600.

[0053] Embodiment 1:

[0054] The load change rate adjustment and control method of the present application is used to increase the load of the unit, and as shown in Figure 3 The dynamic load change rate of the unit, the front pressure of the unit and the load change trend of the unit during the load increase process are shown in the figure.

[0055] Specifically, at 14:31:58 on September 23, 2020, the unit load starts to increase from 240MW, the load change rate index C1 is set to 3.5MW / min through the DCS control system, at 14:50:12, the load is increased to 310MW, and the load increase is completed. As can be seen from the figure, during the process, the front pressure of the unit shows a downward trend in the initial stage of load increase, and the dynamic load change rate takes a small value as a whole, and when the front pressure of the unit starts to show an upward trend, the dynamic load change rate takes a large value.

[0056] The whole load increase process takes 18 minutes and 24 seconds, and the actual increase rate is 3.81MW / min.

[0057] Embodiment 2:

[0058] The load change rate adjustment and control method of the present application is used to decrease the load of the unit, and as shown in Figure 4 The dynamic load change rate of the unit, the front pressure of the unit and the load change trend of the unit during the load decrease process are shown in the figure.

[0059] Specifically, at 11:26:10 on September 22, 2020, the unit load starts to decrease from 310MW, the load change rate index C1 is set to 3.5MW / min through the DCS control system, at 11:44:10, the load is decreased to 240MW, and as can be seen from the figure, Figure 4 As can be seen from the figure, the front pressure of the unit shows an upward trend in the initial stage of load decrease, and at this time, it is not suitable for rapid load decrease, and the load change rate is kept at the minimum value, and when the front pressure of the unit shows a downward trend after the complete release of the boiler heat storage and the weakening of the combustion, the rapid load decrease condition is met, and the load increase rate is increased according to the differential function output of the front pressure.

[0060] The whole load reduction process takes 18 minutes and 00 seconds, and the actual speed reduction rate is 3.89 MW / min.

[0061] Comparative Example 1

[0062] In this embodiment, the load change rate adjustment control method of the present application is not used to increase the load of the unit, and the dynamic load change rate, the front pressure of the unit and the load change trend of the unit during the load increase process are shown in FIG. 1. Figure 5

[0063] As shown in the figure, during the load increase stage, the load change rate index C1 set by the DCS control system is also 3.5 MW / min, but the actual speed increase rate is 3.3 MW / min, and the front pressure fluctuation is higher than that in Example 1.

[0064] Comparative Example 2

[0065] In this embodiment, the load change rate adjustment control method of the present application is not used to reduce the load of the unit, and the dynamic load change rate, the front pressure of the unit and the load change trend of the unit during the load reduction process are shown in FIG. 2. Figure 6

[0066] As shown in the figure, during the load reduction stage, the load change rate index C1 set by the DCS control system is also 3.5 MW / min, but the actual speed increase rate is 3.3 MW / min, and the front pressure fluctuation is higher than that in Example 2.

[0067] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.​​

Claims

1. A method for regulating and controlling the load change rate of a generator set, characterized in that, Includes the following steps: S100: Set the load change rate index C1 according to the rated load of the generator set; S200: Establish the functional relationship between the load change rate coefficient Y and the differential value of the inlet pressure X, and determine the load change rate coefficient Y of the generator set based on the differential value of the inlet pressure X; S300: Calculate the differential value of the pressure at the front of the machine at time t, X(t); S400: Determine the load change status of the generator set at time t; S5 00: Based on the generator set load change state determined by S400 and the differential value of the inlet pressure X(t) calculated by S300, set the load change rate coefficient Y(t) at time t; S600: Multiply the load change rate coefficient Y(t) set in S500 with the load change rate index C1 set in S100 to obtain the dynamic load change rate C(t) of the generator set at time t. Right now: C(t) = Y(t) * C1; S700: The generator set at time t is regulated and controlled based on the dynamic load change rate C(t) calculated by S600.

2. The generator set load change rate regulation and control method according to claim 1, characterized in that, The load change rate coefficient Y in step S200 includes the load increase change rate coefficient Y1 and the load decrease change rate coefficient Y2.

3. The generator set load change rate regulation and control method according to claim 1, characterized in that, Step S400, determining the load change status of the generator set at time t, specifically includes the following steps: S410: Obtain the preset load value NESP of the generator set and the real-time load value NE(t) of the generator set at time t; S420: Calculate the difference SUM(t) between the preset load value NESP of the generator set and the load value NE(t) at time t; S430: Determine the load change status of the generator unit at time t based on SUM(t) calculated from S420. When SUM(t)>1, it is determined that the generator set is in a load-increasing state at time t; When SUM(t) < 1, it is determined that the generator set is in a load reduction state at time t.

4. A generator set load change rate regulation and control method according to any one of claims 1-3, characterized in that, Step S600 also includes limiting the dynamic load change rate C(t) of the generator set at time t.

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