Rapid load changing method for self-adaptive temperature regulation and control

Abstract

The invention discloses a quick load changing method for self-adaptive temperature regulation and control, which actively and controllably changes a steam temperature and pressure set value so as to improve the operation flexibility of a unit. According to the method, a boiler master control instruction is obtained through two parts, a feedback instruction is obtained through a load instruction, main steam temperature and main steam pressure, a main steam temperature set value is obtained according to the load instruction, then a main steam pressure set value is calculated through the load instruction and the main steam temperature set value, and finally the feedback instruction is obtained through PID calculation; the feed-forward instruction is obtained through a load instruction and a main steam temperature and pressure set value, a steady-state heat demand instruction corresponding to a target load is obtained through calculation in sequence, and the feed-forward instruction is obtained through load, main steam temperature and main steam pressure change compensation and summation; finally, the feedback instruction and the feedforward instruction are added and subjected to amplitude limiting to obtain a boiler master control instruction, a temperature and pressure control strategy of a variable temperature and pressure control target is built, decoupling of boiler heat storage and steam turbine quick response is achieved, and the operation flexibility of a coal-fired power generation unit is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of operation management of coal-fired power generation units, and in particular relates to a rapid load changing method with adaptive temperature control. Background Art

[0002] To support the integration of a high proportion of renewable energy into the grid, there is an urgent need to improve the operational flexibility of coal-fired power generation units with rapid load changes. With the transformation and upgrading of my country's energy system, coal-fired power generation units will need to undertake more peak load and frequency regulation tasks to support the integration of a high proportion of renewable energy into the grid. Therefore, there is an urgent need to improve the operational flexibility of coal-fired power generation units with rapid load changes.

[0003] The sliding temperature and pressure operation mode of coal-fired power generation units achieves higher operating efficiency and better boiler operation matching by actively and controllably changing the steam temperature and pressure set values, thereby comprehensively improving the economy, safety and flexibility of coal-fired power generation units to cope with the increasingly heavy peak-shaving and frequency regulation tasks. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies of the above-mentioned existing technologies, provide a rapid load change method with adaptive temperature control, construct a temperature and pressure control strategy with variable temperature and pressure control targets, and improve the flexibility of coal-fired power generation units.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A rapid load-changing method with adaptive temperature control is proposed. The boiler master control command is the core command signal of the coordinated control system of the coal-fired power generation unit. The rapid load-changing process is optimized by optimizing the generation of the boiler master control command. The acquisition of the boiler master control command consists of two parts: feedback command and feedforward command.

[0007] The acquisition of feedback instructions is mainly obtained from load instructions, main steam temperature and main steam pressure:

[0008] The first step is to obtain the main steam pressure set value, which is calculated through the load instruction, main steam temperature and main steam temperature set value. The sliding pressure curve is as follows:

[0009] F1(x)=P set-base +K st ×(F2(x)-T st )

[0010] Where: F1(x) is the main steam pressure setting value; P set-base is the basic sliding pressure curve; K st is the proportional coefficient; F2(x) is the main steam temperature setting value; T st is the main steam temperature;

[0011] Among them, the basic sliding pressure curve corresponding to the main steam pressure setting value adopts the "fixed-sliding-fixed" segmented fitting load instruction and the main steam pressure value of the corresponding design condition. The basic sliding pressure curve is as follows:

[0012] P set-base =A×fhd 2 +B×fhd+C

[0013] Where: A, B, C are constant coefficients obtained by fitting; fhd is the load command of the coal-fired generator set;

[0014] The sliding temperature curve corresponding to the main steam temperature set value is obtained by fitting the load instruction and the main steam temperature value of the corresponding design condition. The sliding temperature curve is as follows:

[0015] F2(x)=D×fhd+E

[0016] Where: D, E are constant coefficients obtained by fitting;

[0017] The second step is to obtain the feedback instruction, which is calculated by the main steam pressure and the main steam pressure set value. The calculation formula is as follows:

[0018] e p =F1(x)-P st

[0019] Δu p (t) = K p *(e p (t)-e p (t-1))+K i *e p (t)

[0020] +K d *(e p (t)-2*e p (t-1)+e p (t-2))

[0021] u p (t)=Δu p (t)+u p (t-1)

[0022] Where: e p is the main steam pressure deviation; P st is the main steam pressure; Δu p (t) is the main steam pressure feedback instruction increment at the current moment; K p is the proportional coefficient; e p (t) is the main steam pressure deviation at the current moment; e p (t-1) is the main steam pressure deviation at the previous moment; K iis the integral coefficient; K d is the differential coefficient; e p (t-2) is the main steam pressure deviation at the previous moment; u p (t) is the main steam pressure feedback instruction at the current moment; u p (t-1) is the main steam pressure feedback instruction at the previous moment;

[0023] The acquisition of feedforward instructions is mainly obtained from the load instruction, main steam temperature setting value and main steam pressure setting value:

[0024] The first step is to obtain the main steam temperature set value F2(x), as shown in the expression of F2(x) in the feedback instruction acquisition section;

[0025] The second step is to obtain the steady-state heat demand instruction corresponding to the target load. The calculation formula is as follows:

[0026] F3(x)=k1×fhd×g(F2(x))

[0027] Where: F3(x) is the steady-state heat demand instruction corresponding to the target load; k1 is the gain coefficient; g(F2(x)) is the correction coefficient,

[0028] F3(x) is an increasing function of the load instruction fhd of the coal-fired generator set, and F3(x) is a decreasing function of the main steam temperature set value F2(x);

[0029] The third step is to obtain load change compensation. The calculation formula is as follows:

[0030]

[0031] Where: F4(x) is the load change compensation; k2 is the gain coefficient;

[0032] The fourth step is to obtain the main steam temperature change compensation to reflect the heat storage change caused by the temperature change. The calculation formula is as follows:

[0033]

[0034] Where: F5(x) is the compensation for main steam temperature change; k3 is the gain coefficient;

[0035] The fifth step is to obtain the main steam pressure change compensation to reflect the heat storage change caused by the pressure change. The calculation formula is as follows:

[0036]

[0037] Where: F6(x) is the main steam pressure change compensation; k4 is the gain coefficient;

[0038] The sixth step is to obtain the feedforward instruction. The calculation formula is as follows:

[0039] u for =F3(x)+F4(x)+F5(x)+F6(x)

[0040] Where: u for is a feedforward instruction;

[0041] Finally, the boiler master control command is obtained by calculating the feedback command and the feedforward command, and the calculation formula is as follows:

[0042] DOB=u p +u for

[0043] Where: DOB is the boiler master control instruction.

[0044] Preferably, the basic sliding pressure curve is obtained in two steps:

[0045] The first step is to obtain the fitting curve of the lowest critical main steam pressure set value in the variable load process. At different variable load rates, and under the conditions that the main steam temperature and reheat steam temperature in the variable load process do not exceed the limit, and the maximum deviation of the main steam temperature or reheat steam temperature does not differ from the limit control deviation by more than 0.2°C, the lowest value that the 50% THA main steam pressure can reach is fitted. The fitting curve is as follows:

[0046]

[0047] Where: P set-lj is the critical main steam pressure setting value; A1 is the quadratic term coefficient; B1 is the linear term coefficient; C1 is the constant term;

[0048] The curve needs to be fitted according to the load increase and load decrease processes respectively;

[0049] The second step is to obtain the basic sliding pressure curve, and according to the initial value of the 100% THA main steam pressure setting value and the critical main steam pressure setting value, the sliding pressure curve is fitted according to the "fixed-sliding-fixed" method.

[0050] Under the premise of strictly constraining the temperature deviation between main steam and reheat steam, this scheme effectively ensures the safety and control accuracy of key temperature parameters in the variable load process through refined fitting of critical pressure.

[0051] Preferably, the sliding temperature curve is obtained by linear fitting, and the form is as follows:

[0052] F2(x)=D×fhd+E

[0053] The main steam temperature set value F2(x) is a decreasing function of the load instruction fhd. During the load reduction process, the main steam temperature set value increases to increase the boiler heat storage capacity. During the load increase process, the main steam temperature set value decreases to reduce the boiler heat storage capacity.

[0054] This solution uses the load changes of coal-fired power generation units to actively adjust the main steam temperature set value, actively regulate boiler heat storage, and improve the response speed and stability of coal-fired power generation units to load changes.

[0055] Preferably, the calculated boiler master control instruction satisfies the following relationship:

[0056] DOB min <DOB<DOB max

[0057] Where: DOB min DOB is the lower limit of the boiler master control instruction; max It is the upper limit of boiler master control instruction.

[0058] Compared with the prior art, the present invention has the following advantages:

[0059] (1) The method of the present invention adds compensation instructions such as main steam temperature and main steam pressure to eliminate response lag. Through feedforward and feedback composite control, the boiler main control instructions calculated when the load changes are more accurate;

[0060] (2) The method of the present invention actively and adaptively controls the set value of the main steam temperature and promptly and proactively adjusts the boiler heat storage, thereby achieving, to a certain extent, the decoupling of boiler heat storage and the rapid response of the steam turbine;

[0061] (3) The method of the present invention improves the flexibility of the coal-fired power generation unit by adding feedforward compensation such as load changes and real-time calculation of heat storage requirements, so that the boiler master control instructions are matched with energy requirements in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is a flow chart of the rapid load variation method for adaptive temperature control proposed by the present invention.

[0063] Figure 2 1 is a graph comparing the automatic generation control (AGC) performance indicators of the method of the present invention and the traditional method, where (a) is the comparison of the initial response time of the load, and (b) is the comparison of the ramp rate. DETAILED DESCRIPTION

[0064] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0065] The present invention proposes a method for rapid load variation with adaptive temperature control, and the specific implementation method is as follows: the boiler master control instruction is the core instruction signal of the coordinated control system of the coal-fired power generation unit, and the rapid load variation process optimization is achieved through the optimization generated by the boiler master control instruction.

[0066] like Figure 1 As shown, the acquisition of the boiler master control instruction includes two parts, namely the feedback instruction S01 and the feedforward instruction S02;

[0067] The acquisition of feedback instruction S01 is mainly obtained from the load instruction, main steam temperature and main steam pressure:

[0068] The first step is to obtain the main steam pressure set value, which is calculated through the load instruction, main steam temperature and main steam temperature set value. The sliding pressure curve is as follows:

[0069] F1(x)=P set-base +K p ×(F2(x)-T st )

[0070] Where: F1(x) is the main steam pressure setting value; P set-base is the basic sliding pressure curve; K p is the proportional coefficient; F2(x) is the main steam temperature setting value; T st is the main steam temperature;

[0071] Among them, the basic sliding pressure curve corresponding to the main steam pressure setting value adopts the "fixed-sliding-fixed" segmented fitting load instruction and the main steam pressure value of the corresponding design condition. The basic sliding pressure curve is as follows:

[0072] P set-base =A×fhd 2 +B×fhd+C

[0073] Where: A, B, C are constant coefficients obtained by fitting; fhd is the load command of the coal-fired generator set;

[0074] The sliding temperature curve corresponding to the main steam temperature set value is obtained by fitting the load instruction and the main steam temperature value of the corresponding design condition. The sliding temperature curve is as follows:

[0075] F2(x)=D×fhd+E

[0076] Where: D, E are constant coefficients obtained by fitting;

[0077] The second step is to obtain the feedback instruction, which is calculated by the main steam pressure and the main steam pressure set value. The calculation formula is as follows:

[0078] e p =F1(x)-Pst

[0079] Δu p (t) = K p *(e p (t)-e p (t-1))+K i *e p (t)

[0080] +K d *(e p (t)-2*e p (t-1)+e p (t-2))

[0081] u p (t)=Δu p (t)+u p (t-1)

[0082] Where: e p is the main steam pressure deviation; P st is the main steam pressure; Δu p (t) is the main steam pressure feedback instruction increment at the current moment; K p is the proportional coefficient; e p (t) is the main steam pressure deviation at the current moment; e p (t-1) is the main steam pressure deviation at the previous moment; K i is the integral coefficient; K d is the differential coefficient; e p (t-2) is the main steam pressure deviation at the previous moment; u p (t) is the main steam pressure feedback instruction at the current moment; u p (t-1) is the main steam pressure feedback instruction at the previous moment.

[0083] The acquisition of the feedforward instruction S02 is mainly obtained from the load instruction, the main steam temperature setting value and the main steam pressure setting value:

[0084] The first step is to obtain the main steam temperature set value F2(x), specifically the expression of F2(x) described in the feedback instruction S01 acquisition part;

[0085] The second step is to obtain the steady-state heat demand instruction corresponding to the target load. The calculation formula is as follows:

[0086] F3(x)=k1×fhd×g(F2(x))

[0087] Where: F3(x) is the steady-state heat demand instruction corresponding to the target load; k1 is the gain coefficient; g(F2(x)) is the correction coefficient,

[0088] F3(x) is an increasing function of the load instruction fhd of the coal-fired generator set, and F3(x) is a decreasing function of the main steam temperature set value F2(x);

[0089] The third step is to obtain load change compensation. The calculation formula is as follows:

[0090]

[0091] Where: F4(x) is the load change compensation; k2 is the gain coefficient;

[0092] The fourth step is to obtain the main steam temperature change compensation to reflect the heat storage change caused by the temperature change. The calculation formula is as follows:

[0093]

[0094] Where: F5(x) is the compensation for main steam temperature change; k3 is the gain coefficient;

[0095] The fifth step is to obtain the main steam pressure change compensation to reflect the heat storage change caused by the pressure change. The calculation formula is as follows:

[0096]

[0097] Where: F6(x) is the main steam pressure change compensation; k4 is the gain coefficient;

[0098] The sixth step is to obtain the feedforward instruction. The calculation formula is as follows:

[0099] u for =F3(x)+F4(x)+F5(x)+F6(x)

[0100] Where: u for is a feedforward instruction.

[0101] Finally, the boiler master control command is obtained by calculating the feedback command S01 and the feedforward command S02, and the calculation formula is as follows:

[0102] DOB=u p +u for

[0103] Where: DOB is the boiler master control instruction.

[0104] like Figure 2 The figure shows the comparison of the AGC performance indicators of coal-fired power generation units under the control of the present invention and the traditional method. Figure 2As can be seen in (a), compared with the traditional method, the initial load response time of the present invention (the time from the issuance of the instruction to the unit power change exceeding 1% of the rated load) is significantly reduced. This is mainly due to the advance adjustment of the feedforward compensation instructions such as the main steam temperature and main steam pressure, which improves the load transient response capability of the coal-fired power generation unit; at the same time, Figure 2 (b) Comparing the ramp rates of the method of the present invention with those of the traditional method, it can be seen that the ramp rate corresponding to the method of the present invention is higher. This is mainly due to the strategy of adaptively controlling the main steam temperature set value according to the load adopted by the method of the present invention. By actively controlling the boiler heat storage to improve the AGC ramp rate, ultimately, the rapid load change capability of the coal-fired power generation unit is improved.

Claims

1. A rapid load-changing method with adaptive temperature control, characterized by: The boiler master control command is the core command signal of the coordinated control system of the coal-fired power generation unit. The rapid load change process is optimized through the optimization of the boiler master control command generation. The acquisition of the boiler master control command consists of two parts: feedback command and feedforward command. The acquisition of feedback instructions is mainly obtained from load instructions, main steam temperature and main steam pressure: The first step is to obtain the main steam pressure set value, which is calculated through the load instruction, main steam temperature and main steam temperature set value. The sliding pressure curve is as follows: F1(x)=P set-base +K st ×(F2(x)-T st ) Where: F1(x) is the main steam pressure setting value; P set-base is the basic sliding pressure curve; K st is the proportional coefficient; F2(x) is the main steam temperature setting value; T st is the main steam temperature; Among them, the basic sliding pressure curve corresponding to the main steam pressure setting value adopts the "fixed-sliding-fixed" segmented fitting load instruction and the main steam pressure value of the corresponding design condition. The basic sliding pressure curve is as follows: P set-base =A×fhd 2 +B×fhd+C Where: A, B, C are constant coefficients obtained by fitting; fhd is the load command of the coal-fired generator set; The sliding temperature curve corresponding to the main steam temperature set value is obtained by fitting the load instruction and the main steam temperature value of the corresponding design condition. The sliding temperature curve is as follows: F2(x)=D×fhd+E Where: D, E are constant coefficients obtained by fitting; The second step is to obtain the feedback instruction, which is calculated by the main steam pressure and the main steam pressure set value. The calculation formula is as follows: e p =F1(x)-P st Δu p (t)=K p *(e p (these p (t-1))+K i *e p (t)+K d *(e p (t)-2*e p (t-1)+e p (t-2)) u p (t)=Δu p (t)+u p (t-1) Where: e p is the main steam pressure deviation; P st is the main steam pressure; Δu p (t) is the main steam pressure feedback instruction increment at the current moment; K p is the proportional coefficient; e p (t) is the main steam pressure deviation at the current moment; e p (t-1) is the main steam pressure deviation at the previous moment; K i is the integral coefficient; K d is the differential coefficient; e p (t-2) is the main steam pressure deviation at the previous moment; u p (t) is the main steam pressure feedback instruction at the current moment; u p (t-1) is the main steam pressure feedback instruction at the previous moment; The acquisition of feedforward instructions is mainly obtained from the load instruction, main steam temperature setting value and main steam pressure setting value: The first step is to obtain the main steam temperature set value F2(x), as shown in the expression of F2(x) in the feedback instruction acquisition section; The second step is to obtain the steady-state heat demand instruction corresponding to the target load. The calculation formula is as follows: F3(x)=k1×fhd×g(F2(x)) Where: F3(x) is the steady-state heat demand instruction corresponding to the target load; k1 is the gain coefficient; g(F2(x)) is the correction coefficient, F3(x) is an increasing function of the load instruction fhd of the coal-fired generator set, and F3(x) is a decreasing function of the main steam temperature set value F2(x); The third step is to obtain load change compensation. The calculation formula is as follows: Where: F4(x) is the load change compensation; k2 is the gain coefficient; The fourth step is to obtain the main steam temperature change compensation to reflect the heat storage change caused by the temperature change. The calculation formula is as follows: Where: F5(x) is the compensation for main steam temperature change; k3 is the gain coefficient; The fifth step is to obtain the main steam pressure change compensation to reflect the heat storage change caused by the pressure change. The calculation formula is as follows: Where: F6(x) is the main steam pressure change compensation; k4 is the gain coefficient; The sixth step is to obtain the feedforward instruction. The calculation formula is as follows: u for =F3(x)+F4(x)+F5(x)+F6(x) Where: u for is a feedforward instruction; Finally, the boiler master control command is obtained by calculating the feedback command and the feedforward command, and the calculation formula is as follows: DOB=u p +in for Where: DOB is the boiler master control instruction.

2. The method for rapid load variation with adaptive temperature control according to claim 1, characterized in that: The acquisition of the basic sliding pressure curve is divided into two steps: The first step is to obtain the fitting curve of the lowest critical main steam pressure set value in the variable load process. At different variable load rates, and under the conditions that the main steam temperature and reheat steam temperature in the variable load process do not exceed the limit, and the maximum deviation of the main steam temperature or reheat steam temperature does not differ from the limit control deviation by more than 0.2°C, the lowest value that the 50% THA main steam pressure can reach is fitted. The fitting curve is as follows: Where: P set-lj is the critical main steam pressure setting value; A1 is the quadratic term coefficient; B1 is the linear term coefficient; C1 is the constant term; The curve needs to be fitted according to the load increase and load decrease processes respectively; The second step is to obtain the basic sliding pressure curve and fit the sliding pressure curve according to the "fixed-sliding-fixed" method based on the initial value of the 100% THA main steam pressure setting value and the critical main steam pressure setting value.

3. The method for rapid load variation with adaptive temperature control according to claim 1, characterized in that: The sliding temperature curve is obtained through linear fitting and is in the following form: F2(x)=D×fhd+E The main steam temperature set value F2(x) is a decreasing function of the load instruction fhd. During the load reduction process, the main steam temperature set value increases to increase the boiler heat storage capacity. During the load increase process, the main steam temperature set value decreases to reduce the boiler heat storage capacity.

4. The method for rapid load variation with adaptive temperature control according to claim 1, characterized in that: The calculated boiler master control command satisfies the following relationship: DRUM min <DRUMS<DRUMS max Where: DOB min DOB is the lower limit of the boiler master control instruction; max It is the upper limit of boiler master control instruction.

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