Method for improving automatic power generation control quality of multi-fuel gas coal-fired unit

Abstract

The invention discloses a method for improving the automatic power generation control quality of a multi-fuel combustion coal-fired unit, and the method comprises the steps: 1, employing a self-adaptive strategy for PID parameters of a boiler main control regulator; secondly, an instruction of the boiler main control regulator is sent to a feedforward signal of each sub-control regulator to increase load dynamic feedforward; thirdly, the using number of the coal mills is adjusted according to the actual characteristics of the boiler; fourthly, BFG and COG fuel quantity feed-forward signals are added to act on a boiler air quantity control loop according to the combined working conditions of various different fuels of the boiler and the steady-state and variable-load working conditions of a unit, and corresponding oxygen quantity curves are set according to pure combustion coal and co-combustion coal gas; and fifthly, according to various different fuel combination working conditions of the boiler and unit steady-state and variable-load working conditions, parameter values of all the F (x) functions are set through a thermal state test. The invention solves the problems of large disturbance caused by multiple types of fuels and frequent switching of the type of unit and aggravated combustion hysteresis of the boiler due to environment-friendly transformation.

Description

Technical Field

[0001] The invention relates to an automatic control technology for a generator set in a thermal power plant, and more specifically to a method for improving the automatic power generation control quality of a mixed gas-fired coal-fired generator set. Background Art

[0002] With the continuous development of power technology, automation control technology has been widely used in the field of power station control. The installed capacity of thermal power plant generator sets is getting larger and larger, and the control requirements of unit operating parameters are constantly improving. There are also higher requirements for the frequency regulation and peak regulation capabilities of the units and the quality of automatic generation control (AGC for short).

[0003] The object of the thermal power unit coordination system is a multi-input and multi-output system with strong coupling. The pressure control object boiler has large delay, large inertia and time-varying characteristics, and responds slowly, while the load control object steam turbine responds quickly. The coupling between the two is very strong, forming a contradictory unity. The thermal power unit coordination control system is the main control system of the generator set. It coordinates the boiler and steam turbine as a whole, coordinates the work of the boiler control system and the steam turbine control system to eliminate the obvious differences in the dynamic response characteristics of the boiler and the steam turbine, so that the coordinated control quality of the unit can adapt to the needs of the grid load changes, maximize the frequency regulation and peak regulation capabilities of the unit, and also ensure the safe, stable and economical operation of the unit.

[0004] The three main equipment of a generator set are boiler, steam turbine and generator. The boiler burns and heats water to generate steam, which is sent to the steam turbine to rotate and drive the generator to generate electricity. From the actual response characteristics, the steam turbine generator responds very quickly, while the boiler responds slowly. Whether the output power of the generator set is consistent with the load demand reflects the balance between the energy supply and demand between the unit and the external power grid; and the main steam pressure reflects the balance between the energy medium "steam" between the boiler and the steam turbine generator inside the unit. Therefore, the stability of the two important parameters of the unit load and steam pressure represents the quality of the generator set coordinated control system, that is, the quality of the automatic power generation control of the generator set.

[0005] The coordinated control system of the generator set mainly includes the boiler master control system and the steam turbine master control system. These two master control systems control their respective sub-control systems. For example, the boiler master control system controls the fuel quantity, air volume, feed water, coal mill rotary separator, secondary air and peripheral air and other sub-control systems. Due to the strong coupling characteristics of the above-mentioned boiler and steam turbine control objects, especially for special types of units, the conventional PID regulator control and load feedforward strategy adopted by the boiler master control system of the coordinated control system is difficult to take into account the rapidity of load and the stability of pressure. For example, some coal-fired units in the self-provided power plants of some steel enterprises use a large amount of blast furnace gas (BFG) and coke oven gas (COG) which are by-products of steelmaking and ironmaking in order to reduce gas emission and environmental pollution and improve energy utilization. BFG has a very low calorific value and poor combustion stability. Coal-fired units that burn coal gas use fuel oil under low load conditions, and need to mix BFG and COG coal gas irregularly and in an irregular amount according to the requirements of the steelmaking process. The fuel types are complex (including coal, fuel oil, BFG blast furnace gas, COG coke oven gas) and are frequently switched on and off, which causes many dynamic disturbances to the system. These have seriously affected the quality of the coordinated control system of this type of unit and brought considerable difficulties to the setting of the coordinated control system. At the same time, this type of unit has implemented a boiler low-nitrogen burner transformation to meet the requirements of environmental protection indicators. Although the NOx emission concentration index in the exhaust flue gas has reached the environmental protection requirements after the transformation, it is difficult to comprehensively consider the overall boiler design and take into account the environmental emission indicators and the quality of the coordinated control system like a new unit, resulting in the deterioration of the quality of the coordinated control system of the unit, that is, the response performance and control accuracy of the unit to the automatic power generation control of the power grid have been greatly reduced. In order to adapt to the characteristics of mixed combustion of coal gas in boilers of this type of unit, improve the quality of the coordinated control system of the unit after the low-nitrogen burner modification, and meet the needs of the unit's automatic power generation control quality, advanced control optimization strategies must be adopted in a targeted manner.

[0006] The control object of the coordination system of thermal power units is a multi-input and multi-output system with strong coupling. The response characteristics of boilers and steam turbines vary greatly, especially for special types of units, such as coal-fired units that burn coal gas and have implemented low-nitrogen burner transformation. Unlike conventional single coal-fired thermal power units, they use fuel oil under low-load conditions and mix low-calorific value BFG and COG irregularly and quantitatively according to the requirements of steelmaking process and gas balance. The fuel types are complex and frequently switched, with many dynamic disturbances. After the boiler low-nitrogen burner transformation was implemented to ensure the NOx environmental emission indicators, some main combustion areas of the boiler lack oxygen, resulting in a decrease in the boiler combustion rate and the working fluid heat absorption, thereby increasing the lag of boiler combustion, and the regulation characteristics of the unit's main steam pressure change, resulting in a significant deterioration in the unit's coordination quality, and a significant decrease in the load response performance and control accuracy of the unit's automatic power generation control of the power grid. The actual operating characteristics of the boiler also have large differences in load increase and load reduction characteristics, and large differences in characteristics of different load sections.

[0007] The above-mentioned actual operating characteristics of coal-fired units that have mixed combustion of coal gas and implemented low-nitrogen burner transformation have seriously affected the quality of the coordinated control system of this type of unit, bringing considerable difficulties to the optimization and adjustment of the coordinated control system. This also determines that it is difficult to meet the technical indicators of the coordinated quality of this type of unit by only using conventional PID control and load feedforward strategies.

[0008] like Figure 1 As shown, Figure 1 Position A in the middle represents the strategy block diagram of proportional P. The parameters P, I, and D of the boiler master regulator are converted into parameter values ​​only according to the unit load command through the function F(x). Position B is the strategy block diagram of integral I, and position C is the strategy block diagram of differential D, which is the same as the strategy block diagram of proportional P, but with different specific parameters.

[0009] Continue to refer Figure 1 As shown, the strategy block diagram at position D represents the load feedforward from the boiler master control regulator command to each sub-control regulator, and mainly uses load command differentiation to speed up the boiler's response speed to the load. This technical solution is not able to take into account and improve the boiler response speed under various conditions for units with different actual response characteristics under load increase and decrease conditions and different load intervals, and does not play a role in improving the coordination quality. The strategy block diagrams at positions E, F, G, and H are the same as the strategy block diagram at position D, but with different specific parameters.

[0010] like Figure 2 As shown in the figure, the I position represents the boiler air volume, which is the boiler master control command output by the boiler master control PID regulator, and the command calculated by the air volume regulator. After the excess air rate calculated and output by the oxygen PI regulator is corrected, the final air volume command is generated to each blower. The oxygen volume setting of the oxygen PI regulator is only formed by the load command after conversion by the function F(x), without taking into account the different characteristics of the oxygen (air volume) required by different fuels, and without considering the impact of changes in gas fuel on the air volume in the furnace. Summary of the invention

[0011] In view of the defects existing in the prior art, the purpose of the present invention is to provide a method for improving the automatic power generation control quality of mixed gas and coal-fired units, so as to solve the problem that this type of unit has large disturbances due to the large variety of fuels and frequent switching, and the environmental protection transformation has aggravated the boiler combustion lag.

[0012] To achieve the above object, the present invention adopts the following technical solution:

[0013] A method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit:

[0014] Firstly, the PID parameters of the boiler master regulator adopt an adaptive strategy;

[0015] In the second aspect, the feedforward signal sent by the command of the boiler master control regulator to each sub-control regulator increases the load dynamic feedforward;

[0016] Thirdly, adjust the number of coal mills used according to the actual characteristics of the boiler;

[0017] Fourthly, for the combined working conditions of various fuels of the boiler, as well as the steady-state and variable load working conditions of the unit, the BFG and COG fuel quantity feedforward signals are added to the boiler air volume control loop, and the corresponding oxygen content curves are set according to the different working conditions of pure coal burning and mixed coal gas burning;

[0018] Fifthly, the parameter values ​​of the above-mentioned F(x) functions are adjusted and set through hot tests for the combined operating conditions of various fuels of the boiler, as well as the steady-state and variable load conditions of the unit.

[0019] Preferably, the PID parameters of the boiler master regulator adopt an adaptive strategy specifically including:

[0020] Different P, I and D parameter curves are adopted according to the load instructions of the generator set under the three operating conditions of fuel burning condition, variable load condition and stable load condition.

[0021] Preferably, the instruction of the boiler master control regulator to send a feedforward signal to each sub-control regulator to increase the load dynamic feedforward specifically includes:

[0022] On the basis of the load feedforward of the boiler main control regulator, the load dynamic feedforward of the fuel quantity, air volume, water supply, coal mill rotary separator, secondary air and peripheral damper is added to form a comprehensive load feedforward of each sub-control regulator.

[0023] Preferably, the BFG and COG fuel quantity feedforward signals are added to act on the boiler air volume control loop, and the corresponding oxygen content curves are set according to different working conditions of pure coal burning and mixed coal gas burning, specifically including:

[0024] When the unit is burning pure coal, the total amount of coal actually burned is calculated by the F(x) function to generate the corresponding amount of oxygen required;

[0025] Under the mixed-gas combustion condition, the unit calculates the required oxygen amount according to the actual coal consumption, BFG blast furnace gas, and COG coke oven gas through different F(x) functions, and then superimposes them to form the total oxygen amount required under the mixed-gas combustion condition.

[0026] When the unit is operating at low load and only burning fuel, the required oxygen amount is calculated by the F(x) function based on the actual fuel flow.

[0027] Preferably, the fifth aspect specifically includes:

[0028] Under the steady-state condition of the unit, the condition of increased load of the unit, the condition of reduced load of the unit, and the condition of low load and only fuel oil of the unit, and with different amounts of BFG blast furnace gas or COG coke oven gas added or cut, under the actual operating conditions of the above units, the actual dynamic response curves of the control loops involved are observed in real time, and the parameters are adjusted and optimized according to the dynamic changes and characteristics of the curves, so that the settings of various parameters can eventually adapt to the operating conditions of various units.

[0029] The present invention provides a method for improving the automatic power generation control quality of a coal-fired unit that burns a large amount of steelmaking and ironmaking byproducts BFG and COG. For special types of units, such as coal-fired units that burn a large amount of steelmaking and ironmaking byproducts BFG and COG, due to irregular and unquantified mixed burning of blast furnace gas and coke oven gas, complex fuel types and frequent switching, and many and frequent dynamic disturbances, the quality of the coordinated control system of this type of unit is seriously affected. The present invention adopts a boiler main control regulation loop to increase an adaptive strategy, optimizes the coal mill commissioning combination mode, increases the oxygen correction gain under pure coal burning and mixed coal gas burning conditions, and adopts different oxygen control curves, and the boiler main control instruction to each main sub-control loop adds a dynamic comprehensive automatic gain correction function, etc., and the method of setting parameters through hot test effectively improves the automatic power generation control quality of the unit, which can be extended to the same type of power generation units. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the PID parameter control principle of the existing boiler master regulator;

[0031] Figure 2 yes Figure 1 Schematic diagram of the control principle of the air volume regulator;

[0032] Figure 3 It is a schematic diagram of the PID parameter control principle of the boiler master regulator of the present invention;

[0033] Figure 4 yes Figure 3 Schematic diagram of the control principle of the air volume regulator;

[0034] Figures 1 to 4 In the figure, T represents T switching, x represents multiplier, + represents adder, - represents subtractor, R represents rate of change, Fx is F(x) function curve (linear curve or broken line curve), P represents proportion, I represents integration, and D represents differentiation. DETAILED DESCRIPTION

[0035] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0036] Combination Figure 3 and Figure 4As shown, the present invention provides a method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit:

[0037] First, since the unit uses many types of fuel, frequent switching, and complex operating conditions, and the boiler low-nitrogen burner modification was implemented to ensure NOx environmental emission indicators, the main combustion area inside the boiler is relatively short of oxygen, and the temperature of the main combustion area is reduced, resulting in a decrease in the responsiveness of the boiler combustion, increased boiler combustion lag, and changes in the unit's main steam pressure regulation characteristics, resulting in further deterioration of the unit's coordination quality. A fixed set of boiler master control regulator PID parameters or PID parameters that only change linearly with load are difficult to adapt to various dynamic operating conditions. Therefore, the PID parameters of the boiler master control regulator adopt an adaptive strategy. Different fuel combinations and different variable load conditions use different P, I, and D parameters. They are mainly aimed at different combinations of fuels such as fuel oil, coal, BFG blast furnace gas, and COG coke oven gas (such as fuel oil, pure coal burning, mixed gas burning, etc.). Different P, I, and D parameters are used in different typical operating conditions such as fuel oil (low load) conditions, variable load conditions (coal burning or mixed gas burning), and stable load conditions (coal burning or mixed gas burning). In this way, the controlled object is identified online, the performance of the current system is compared with the expected optimal performance, and the parameters of the regulator are automatically corrected to optimize the regulation. Different P, I, and D parameters are configured according to different working conditions and fuel combinations, that is, differentiated processing. These parameters are adjusted through hot tests and are not fixed values.

[0038] Secondly, the actual operation characteristics of the boiler have the problem that the characteristics of increasing and decreasing loads are greatly different, and the characteristics of different load sections are greatly different. Therefore, on the basis of the conventional load feedforward of the boiler master control regulator (i.e., differential processing is performed according to the load command to speed up the response speed), the load dynamic feedforward of the boiler master control command to each sub-control loop such as fuel quantity, air volume, water supply, coal mill rotary separator, secondary air and peripheral air is added. According to the different working conditions of increasing and decreasing loads and different load area segments, the boiler command feedforward signal of each sub-control regulator is processed differently, that is, the two working conditions of increasing and decreasing loads are distinguished, and different load interval segments are divided by the F(x) function. Different feedforward parameter curves are set for the boiler command feedforward signal of each sub-control regulator, forming a comprehensive load feedforward of each sub-control regulator, so that the control loop can automatically adjust the feedforward amount with the change of increasing and decreasing loads and the change of load deviation, and avoid overshoot while accelerating the rapidity of boiler response under variable load conditions.

[0039] Thirdly, according to the actual characteristics of the boiler, the number of coal mills in use is optimized and adjusted. After tracking the actual characteristics of the boiler, the more coal mills are put into use, the higher the NOx concentration in the boiler exhaust gas. Taking a coal-fired unit that burns coal gas as an example (installed capacity of 350MW, equipped with 5 coal mills), when the unit is under a load of 260MW and 4 coal mills are put into use at the same time, the NOx concentration in the exhaust gas is significantly higher than the NOx concentration when 3 coal mills are put into use at the same time. Therefore, under the premise that the fuel heat can meet the unit load, the number of coal mills in use in the pulverizing system is optimized to increase the coal amount of the coal mills that have been put into use and minimize the number of coal mills in use to avoid the increase of NOx concentration in the exhaust gas, thereby improving the boiler response lag to a certain extent, improving the main steam pressure quality, and improving the coordination control quality.

[0040] Fourthly, in view of the combined operating conditions of various fuels in the boiler, as well as the steady-state and variable load conditions of the unit, the BFG and COG fuel quantity feedforward signals are added to act on the boiler air volume control loop, and corresponding oxygen curves are set according to different operating conditions such as pure coal burning and mixed gas burning. Under the pure coal burning condition of the unit, the actual total amount of coal burned is calculated by the F(x) function to generate the corresponding required oxygen. Under the mixed gas burning condition of the unit, the actual amount of coal burned, the BFG blast furnace gas amount, and the COG coke oven gas amount are respectively calculated by different F(x) functions to generate the corresponding required oxygen and superimposed to form the required total oxygen under the mixed gas burning condition. When only fuel oil is burned under low load conditions of the unit, the corresponding required oxygen amount is calculated by the F(x) function according to the actual fuel oil flow rate. That is, by accurately setting the oxygen demand corresponding to different fuels, the purpose of reasonably adjusting the total air volume of the boiler, improving the response speed of the boiler, and improving the quality of coordinated control is achieved.

[0041] Fifthly, for the combined working conditions of various fuels of the boiler, as well as the steady-state and variable load working conditions of the unit, the parameters of the F(x) functions such as PID regulator, load feedforward, oxygen curve, BFG and COG feedforward are adjusted and optimized through hot tests. The specific methods of adjusting and optimizing parameters are mainly under different actual operating conditions of the unit, such as the steady-state working condition of the unit (distinguishing different steady-state load points), the load increase working condition of the unit (using different load change rates), the load reduction working condition of the unit (using different load change rates), and the unit Only fuel oil is used at low load, and different amounts of BFG blast furnace gas or COG coke oven gas are added or cut. Under the actual operating conditions of the above units, the actual dynamic response curve of the control loop involved is observed in real time. According to the dynamic changes and characteristics of the curve, each parameter is adjusted and optimized, and finally the setting of each parameter can adapt to the operating conditions of various units and is optimal, thereby ensuring that the unit can achieve the stability of the main steam pressure and load under all major conditions, improving the quality of the group coordination control system, and meeting the needs of the unit's automatic power generation control quality. Parameter adjustment and optimization do not require calculation, but are adjusted by observing and tracking the actual response characteristics under actual dynamic tests.

[0042] Example

[0043] This embodiment takes a coal-fired generator set in a self-provided power plant of a steel enterprise as an example, which uses fuel oil as the start-up and stable combustion fuel. The unit is a self-provided power plant generator set of the steel enterprise, with a designed installed capacity of 350MW, and is responsible for balancing the by-products BFG and COG gas of the steel enterprise. The boiler is a subcritical pressure, one-time intermediate reheating, multiple forced circulation boiler, and the combustion method is four-corner double tangential circle combustion. It can burn coal powder, BFG gas, COG gas, fuel oil and other fuels. The pulverizing system is a positive pressure direct blowing type, and is equipped with 5 medium-speed coal mills. Due to the mixed combustion of a large amount of coal gas, the exhaust gas flow generated after the boiler is burned is much larger than that of a conventional single coal-fired unit. The boiler furnace burner is equipped with nine layers, including five layers of coal powder burners, two layers of BFG burners, one layer of burners that can choose to burn fuel oil (light oil) or COG, and one layer of COG burners. A burner is arranged at each of the four corners of each layer of the boiler, and each burner is equipped with a fuel oil igniter. In order to ensure that the NOx environmental indicators of the unit's exhaust meet the standards, the boiler has been modified to use a low-nitrogen burner, that is, the conventional pulverized coal burner has been replaced with a low-nitrogen burner, and overburnt air has been added above the main burner.

[0044] Due to the large differences in the inherent characteristics of boilers and steam turbines, they have strong coupling characteristics; and the boiler operating conditions of the unit in this example are complex. Fuel oil is used when the unit is started, and fuel oil is added for stable combustion under low-load conditions. At the same time, BFG and COG gas are mixed and burned irregularly and in an irregular amount according to the requirements of the steelmaking process. The fuel types are complex and the switching is frequent, there are many dynamic disturbances, and the mixed combustion ratio varies greatly; in order to ensure the NOx environmental emission indicators of the unit's exhaust, the boiler low-nitrogen burner transformation was implemented. In order to reduce the generation of NOx, some of the main combustion areas of the boiler are lacking in oxygen, resulting in a decrease in the boiler combustion rate and a decrease in the heat absorption of the working fluid, further increasing the lag of the boiler combustion, resulting in a slower boiler response; the actual operating characteristics of the boiler unit in this example also have large differences in load increase and load reduction characteristics (specifically, during the load increase and reduction process, the main steam pressure fluctuates greatly, which is mainly manifested in the over-adjustment of fuel regulation at the initial stage of load change, and the over-adjustment phenomenon occurs after the pressure changes), the response characteristics of the boilers in different load areas are different, and the main steam pressure deviation increases in proportion to the increase in the average coal amount of the coal mill in use. These characteristics make it difficult for the boiler master control regulator to use the traditional PID parameters that change linearly only with the unit load, and the conventional load feedforward strategy to adapt to various complex operating conditions of the unit. To solve the above problems, the present invention specifically proposes a method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit, and the main technical solution is:

[0045] 1. The boiler master control regulator PID adopts a complex adaptive strategy:

[0046] In the actual operation of the boiler in this example, due to the influence of load changes, fuel changes or interference factors, there are too many internal and external disturbance factors of the controlled object, which leads to unstable adjustment of the main control parameters. The original P, I, and D parameters of the boiler main control PID regulator only change linearly with the random group load command (as shown in the attached figure). Figure 1 The strategy block diagram of the proportion P shown in A in the figure) cannot adapt well to this change. This embodiment adopts a complex adaptive strategy. For different fuel combinations, different fuel mixing ratios, and different load increase and decrease conditions of the boiler, different proportional P, integral I, and differential D parameters are used respectively to identify the controlled object online and automatically correct the parameters of the boiler master control regulator to optimize the regulation. Specifically, the P, I, and D parameters of the boiler master control PID regulator all adopt a complex adaptive strategy, and different P, I, and D parameter curves are used under three operating conditions: fuel oil (low load) condition, variable load condition (coal burning or mixed combustion of coal gas), and stable load condition (coal burning or mixed combustion of coal gas). For these three conditions, differentiated P, I, and D parameters are set according to the unit load instructions to optimize the regulation quality of the boiler master control to speed up the response of the boiler. The specific control strategy is shown in the attached Figure 3In the strategy block diagram of proportional P shown in A′, when the unit is in low-load fuel operating condition, the load command generates proportional P parameter value through F(x) function; when the unit is in variable load condition (including increasing and decreasing load, as well as coal burning, mixed burning of gas and other conditions), the load command generates proportional P parameter value through F(x) function; when the unit is in steady-state load condition (i.e. non-low-load fuel operating condition and variable load condition, including coal burning and mixed burning of gas under steady-state load condition), the load command generates proportional P parameter value through F(x) function, that is, for different load and fuel combination conditions, different proportional P parameter values ​​are generated through different F(x) functions to form differentiated P parameters.

[0047] 2. The feedforward signal from the boiler master control regulator to each sub-control regulator increases the load dynamic feedforward:

[0048] In this embodiment, the instructions of the main control regulator of the generator set boiler are synchronously sent to each sub-control regulator for control, mainly including the fuel regulator, air volume regulator, feed water regulator, coal mill rotary separator regulator, and secondary air / peripheral wind sub-control regulator.

[0049] The original load feedforward from the boiler master control regulator to each sub-control regulator mainly generates a feedforward signal based on the differential of the load command (such as the attached Figure 1 The technology is used to speed up the boiler's response to the load. However, for units with different actual response characteristics under load increase and decrease conditions and in different load intervals, it cannot take into account and improve the boiler's response speed under various operating conditions, and cannot improve the coordination quality.

[0050] In order to improve the response characteristics of the boiler under all operating conditions, with respect to the load feedforward originally adopted by the boiler master control regulator, this embodiment distinguishes between the two operating conditions of increasing and decreasing loads, and distinguishes different load intervals through the function of F(x), and performs differentiated processing on the boiler command feedforward signal of each sub-control regulator to accelerate the boiler response. In addition, on the basis of the load feedforward of the original boiler master control regulator, the load dynamic feedforward of the boiler master control command to each sub-control regulator, such as fuel quantity, air volume, water supply, coal mill rotary separator, secondary air and peripheral damper, is added to form a comprehensive load feedforward of each sub-control regulator, that is, the feedforward amount is automatically adjusted as the load deviation changes, so as to accelerate the rapidity of the boiler response under variable load conditions while avoiding overshoot.

[0051] As attached Figure 3The load feedforward strategy block diagram shown in D′ is for the feedforward signal added from the boiler master control command to the fuel regulator. Under the two different operating conditions of increasing and decreasing the load of the generator set, the load command (i.e. the load setting after being processed by the change rate R) is processed by the lead differential D (to speed up the boiler response) and then the load deviation dynamic feedforward (the larger the load deviation, the larger the correction coefficient and the faster the boiler response) is superimposed on the command from the boiler master control to each sub-control regulator as the comprehensive load feedforward.

[0052] The strategy block diagrams of E′, F′, G′, and H′ are the same as the strategy block diagram of D′ (with different specific parameters), which are the feedforward signals added from the boiler master control regulator to the air volume regulator, feed water regulator, coal mill rotary separator regulator, and secondary air / peripheral air regulator.

[0053] 3. In order to ensure the rigid environmental protection index and reduce the generation of NOx, the unit of this embodiment lacks oxygen in some main combustion areas of the boiler, resulting in a decrease in the boiler combustion rate, further increasing the hysteresis of the boiler combustion. According to the tracking of the actual characteristics of the boiler, the more coal mills are put into use, the higher the NOx concentration in the boiler exhaust gas. For example, when the unit is under a load of 260MW and 4 coal mills are put into use at the same time, the NOx concentration in the exhaust gas is obviously higher than the NOx concentration when 3 coal mills are put into use at the same time. Therefore, under the premise that the fuel heat can meet the unit load, the number of coal mills (a total of 5) in the pulverizing system is optimized to increase the coal volume of the coal mills that have been put into use and minimize the number of coal mills put into use to prevent the increase of NOx concentration in the exhaust gas. Through this measure, the hysteresis of boiler combustion is improved to a certain extent, the response of the boiler is accelerated, and the quality of coordinated control is improved.

[0054] 4. If Figure 4 In the strategy block diagram shown in I′, according to the actual characteristics of the boiler, the oxygen content in the flue gas has a significant impact on the NOx concentration. When the oxygen content increases and the air excess rate increases, the NOx concentration in the exhaust gas increases significantly. In order to reduce the NOx concentration in the exhaust gas and meet the environmental protection indicators, it is necessary to control and reduce the oxygen content. The oxygen content represents the air excess rate, that is, the boiler air volume. Low air volume will increase the lag of boiler combustion, that is, there is a contradiction between meeting environmental protection indicators and improving boiler response speed, which requires comprehensive consideration and balance. Therefore, reasonable adjustment and control of the total air volume is an important measure to improve the boiler combustion response speed under the premise of ensuring environmental protection indicators. This technology is aimed at the characteristics of the unit boiler burning BFG and COG gas. Different oxygen curves for the total air volume control of the boiler are used for oil, pure coal and mixed gas conditions, and the BFG and COG fuel quantity feedforward signal correction function is added to the air volume control loop, so as to achieve the purpose of reasonably adjusting the total air volume of the boiler, improving the boiler response speed, and improving the quality of coordinated control.

[0055] 5. According to the various fuel combination operating conditions of the unit, as well as the steady-state and load increase and decrease conditions of the unit, the parameter values ​​of the above F(x) functions are adjusted and set through hot tests.

[0056] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit, characterized in that: Firstly, the PID parameters of the boiler master regulator adopt an adaptive strategy; In the second aspect, the feedforward signal sent by the command of the boiler master control regulator to each sub-control regulator increases the load dynamic feedforward; Thirdly, adjust the number of coal mills used according to the actual characteristics of the boiler; Fourthly, for the combined working conditions of various fuels of the boiler, as well as the steady-state and variable load working conditions of the unit, the BFG and COG fuel quantity feedforward signals are added to the boiler air volume control loop, and the corresponding oxygen content curves are set according to the different working conditions of pure coal burning and mixed coal gas burning; Fifthly, for the combined operating conditions of various fuels of the boiler, as well as the steady-state and variable load conditions of the unit, the parameter values ​​of the PID regulator, load feedforward, oxygen content curve, BFG and COG feedforward F(x) functions are adjusted and set through hot tests.

2. The method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit according to claim 1, characterized in that: The PID parameters of the boiler master regulator adopt an adaptive strategy specifically including: Different P, I and D parameter curves are adopted according to the load instructions of the generator set under the three operating conditions of fuel burning condition, variable load condition and stable load condition.

3. The method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit according to claim 1, characterized in that: The instruction of the boiler master control regulator to send a feedforward signal to each sub-control regulator to increase the load dynamic feedforward specifically includes: On the basis of the load feedforward of the boiler main control regulator, the load dynamic feedforward of the fuel quantity, air volume, water supply, coal mill rotary separator, secondary air and peripheral damper is added to form a comprehensive load feedforward of each sub-control regulator.

4. The method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit according to claim 1, characterized in that: The method of increasing the BFG and COG fuel quantity feedforward signals to act on the boiler air volume control loop and setting corresponding oxygen quantity curves according to different working conditions of pure coal burning and mixed coal gas burning specifically includes: When the unit is burning pure coal, the total amount of coal actually burned is calculated by the F(x) function to generate the corresponding amount of oxygen required; Under the mixed-gas combustion condition, the unit calculates the required oxygen amount according to the actual coal consumption, BFG blast furnace gas, and COG coke oven gas through different F(x) functions, and then superimposes them to form the total oxygen amount required under the mixed-gas combustion condition. When the unit is operating at low load and only burning fuel, the required amount of oxygen is calculated based on the actual fuel flow through the F(x) function.

5. The method for improving the automatic power generation control quality of a mixed gas-fired coal-fired unit according to claim 1, characterized in that: The fifth aspect specifically includes: Under the steady-state condition of the unit, the condition of increased load of the unit, the condition of reduced load of the unit, and the condition of low load and only fuel oil of the unit, and with different amounts of BFG blast furnace gas or COG coke oven gas added or cut, under the actual operating conditions of the above units, the actual dynamic response curves of the control loops involved are observed in real time, and the parameters are adjusted and optimized according to the dynamic changes and characteristics of the curves, so that the settings of various parameters can eventually adapt to the operating conditions of various units.

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