CN205842637U - A kind of Directed Energy Balance Coordinated Control control system for large-size circulating fluidized bed unit - Google Patents

Abstract

The utility model discloses a direct energy balance coordination control system for a large-scale circulating fluidized bed unit, which includes a boiler main control controller, a fuel main control controller and a steam turbine main control controller; the boiler main control controller adopts a The steam drum heat signal of the second order differential and the dynamic and static feedforward signals; the dynamic and static feedforward signals include the static feedforward signal LSff of the unit load command to the boiler fuel, and the dynamic feedforward signal LDff of the unit load command to the boiler fuel , the dynamic feedforward signal PDff of the unit pressure to the boiler fuel, the dynamic feedforward VtDf of the bed temperature change rate to the boiler main control, and the dynamic and static feedforward of the primary air volume from the load command; the boiler main control controller adopts PID variable parameter control, fuel master controller adopts coal quality correction control loop. The utility model has the advantages of improving the coordinated control ability of the circulating fluidized bed unit, and solving the problems of large main steam pressure fluctuation and low load response rate of the unit under the coordinated control mode.

Description

A Direct Energy Balance Coordinated Control System for Large Circulating Fluidized Bed Units

technical field

The utility model relates to a direct energy balance coordinated control system for large-scale circulating fluidized bed units, which belongs to the field of coordinated control of circulating fluidized bed units.

Background technique

In recent years, circulating fluidized bed units have been widely used in the field of power generation due to their high efficiency and environmental protection. The control effect of the coordinated control system of the circulating fluidized bed unit is not ideal, the bed temperature and main steam pressure fluctuate greatly, and the variable load rate of the unit is difficult to meet the assessment indicators.

Utility model content

The technical problem to be solved by the utility model is to provide a direct energy balance coordination control system for a large circulating fluidized bed unit that is safe, stable, small in fluctuation and high in response rate.

The technical scheme that the utility model adopts for its technical problem is as follows:

A direct energy balance coordinated control system for a large circulating fluidized bed unit, which includes a boiler main control controller, a fuel main control controller and a steam turbine main control controller; the boiler main control controller adopts a second-order Differential steam drum heat signal and dynamic and static feed-forward signal. The heat signal of the second-order differential can more accurately represent the heat signal of the boiler drum than the heat signal of the first-order differential, which improves the adjustment quality of the main control controller of the boiler to a certain extent.

The dynamic and static feedforward signals include the static feedforward signal LSff of the unit load command to the boiler fuel, the dynamic feedforward signal LDff of the unit load command to the boiler fuel, the dynamic feedforward signal PDff of the unit pressure to the boiler fuel, and the bed temperature change rate to the dynamic feedforward VtDf of the boiler master control and the load command to the dynamic and static feedforward of the primary air volume; the boiler master controller adopts PID variable parameter control according to different load segments, and the fuel master controller adopts coal Quality calibration control loop.

Further, the steam drum heat signal with second-order differential is the adjusted quantity of the boiler main control controller in the direct energy balance coordinated control system, and the heat storage coefficient of the steam drum is obtained through the door switch test. The boiler drum heat signal based on the second order differential can accurately represent the stored heat of the drum under different working conditions, improve the accuracy of the fuel required by the unit, and accurately realize the supply and demand balance of electricity and coal.

Further, the static feedforward signal LSff of the unit load command to the boiler fuel is a boiler fuel load command generated at twice the unit variable load rate, and the load command required by the boiler master controller is passed through the load and coal The broken line function of the quantity increases or decreases the coal supply to the coal supply required by the target load in advance, which reduces the pure delay time of the circulating fluidized bed boiler to a certain extent and improves the response rate of the boiler.

Further, the dynamic feed-forward signal LDff of the unit load command to the boiler fuel is the differential of the actual unit load command minus the rate limit. The broken line function of the differential time determines the differential amount of the unit load command; the correction system of the load dynamic feedforward is determined through the variable load test, and the product of the differential amount of the load command and the differential correction coefficient is the dynamic feedforward of the load command.

Further, the dynamic feed-forward signal PDff of the unit pressure to the boiler fuel is the differential of the unit energy signal minus the rate limit and the differential of the main steam pressure set value minus the rate limit Sum.

Further, the differential of the unit energy signal after the unit energy signal minus the rate limit, and the differential of the main steam pressure set value after the rate limit is subtracted from the main steam pressure set value are all determined by the variable load test. The upper and lower limits of the differential, Derivative time and correction coefficient of dynamic feedforward.

Further, the dynamic feed-forward VtDf of the bed temperature change rate to the boiler main control is to correct the boiler main control instruction according to the bed temperature and the bed temperature change rate under the premise of satisfying the air-to-coal ratio.

Further, when the bed temperature is within a reasonable range, the rate of change of the bed temperature passes the fuel correction amount corresponding to the fuel quantity correction function, and at the same time according to the correction coefficient corresponding to the deviation value of the main steam pressure, the product of the two is the main control requirement of the boiler Corrected fuel volume; when the bed temperature exceeds the reasonable range, the boiler master control command will directly reduce the command by 2% to prevent the bed temperature from overheating.

Further, the dynamic and static feedforward of the primary air volume by the load command includes the static feedforward of the primary air volume corresponding to the primary wind load command produced at three times the variable load rate of the unit through the broken line function and the differential of the unit load command. As the dynamic feedforward of the primary air volume, the sum of the dynamic and static primary air volume commands is the primary air volume command. This method can make the primary air volume overshoot ahead of the unit load and coal supply, make full use of the heat storage capacity of the boiler, and speed up the response of the boiler. In the coordinated control mode, the actual value of the main steam pressure can quickly follow the given value of the main steam pressure.

The beneficial effects of the utility model are as follows: the utility model improves the ability of the coordinated control of the circulating fluidized bed unit, reduces the fluctuation of the main steam pressure, and solves the large fluctuation of the main steam pressure and the low load response rate of the unit in the coordinated control mode The technical problems of the unit ensure the safe and stable operation of the unit when the load is variable and the unit is in a steady state, and meet the unit's assessment indicators for AGC control.

The utility model overcomes the problems of large delay and large inertia of the circulating fluidized bed unit to a certain extent, improves the adjustment quality of the main steam pressure of the circulating fluidized bed unit under various working conditions, and optimizes the adjustment quality of the coordinated control system , improving the variable load rate of the unit.

Description of drawings

Fig. 1 is the realization block diagram of the boiler main control controller of the utility model.

Fig. 2 is a realization block diagram of the main fuel control controller of the utility model.

detailed description

Below in conjunction with Fig. 1 ~ Fig. 2 and embodiment the utility model is described further.

As shown in Figures 1 to 2, this embodiment includes a boiler main control controller, a fuel main control controller and a steam turbine main control controller; the boiler main control controller adopts the steam drum heat signal and Dynamic and static feedforward signals. The heat signal of the second-order differential can more accurately represent the heat signal of the boiler drum than the heat signal of the first-order differential, which improves the adjustment quality of the main control controller of the boiler to a certain extent.

The dynamic and static feedforward signals include the static feedforward signal LSff of the unit load command to the boiler fuel, the dynamic feedforward signal LDff of the unit load command to the boiler fuel, the dynamic feedforward signal PDff of the unit pressure to the boiler fuel, and the bed temperature change rate to the dynamic feedforward VtDf of the boiler main control and the load command to the dynamic and static feedforward of the primary air volume; the boiler main control controller adopts PID variable parameter control according to different load segments, and the fuel main control controller adopts coal Quality calibration control loop.

Further, the steam drum heat signal with second-order differential is the adjusted quantity of the boiler main control controller in the direct energy balance coordinated control system, and the heat storage coefficient of the steam drum is obtained through the door switch test. The boiler drum heat signal based on the second order differential can accurately represent the stored heat of the drum under different working conditions, improve the accuracy of the fuel required by the unit, and accurately realize the supply and demand balance of electricity and coal.

Further, the static feedforward signal LSff of the unit load command to the boiler fuel is a boiler fuel load command generated at twice the unit variable load rate, and the load command required by the boiler master controller is passed through the load and coal The broken line function of the quantity increases or decreases the coal supply to the coal supply required by the target load in advance, which reduces the pure delay time of the circulating fluidized bed boiler to a certain extent and improves the response rate of the boiler.

Further, the dynamic feed-forward signal LDff of the boiler unit load command to the boiler fuel is the differential of the actual unit load command minus the rate limit, which corresponds to The differential value of the load command of the unit is determined by the broken line function of different differential times; the correction system of the load dynamic feedforward is determined through the variable load test, and the product of the differential value of the load command and the differential correction coefficient is the dynamic feedforward of the load command.

Further, the dynamic feed-forward signal PDff of the unit pressure to the boiler fuel is the differential of the unit energy signal minus the rate limit and the differential of the main steam pressure set value minus the rate limit Sum.

Further, the differential of the unit energy signal after the unit energy signal minus the rate limit, and the differential of the main steam pressure set value after the rate limit is subtracted from the main steam pressure set value are all determined by the variable load test. The upper and lower limits of the differential, Derivative time and correction coefficient of dynamic feedforward.

Further, the dynamic feed-forward VtDf of the bed temperature change rate to the boiler main control is to correct the boiler main control instruction according to the bed temperature and the bed temperature change rate under the premise of satisfying the air-to-coal ratio.

Further, when the bed temperature is within a reasonable range, the rate of change of the bed temperature passes the fuel correction amount corresponding to the fuel quantity correction function, and at the same time according to the correction coefficient corresponding to the deviation value of the main steam pressure, the product of the two is the main control requirement of the boiler Corrected fuel volume; when the bed temperature exceeds the reasonable range, the boiler master control command will directly reduce the command by 2% to prevent the bed temperature from overheating.

Further, the dynamic and static feedforward of the primary air volume by the load command includes the static feedforward of the primary air volume corresponding to the primary wind load command produced at three times the variable load rate of the unit through the broken line function and the differential of the unit load command. As the dynamic feedforward of the primary air volume, the sum of the dynamic and static primary air volume commands is the primary air volume command. This method can make the primary air volume overshoot ahead of the unit load and coal supply, make full use of the heat storage capacity of the boiler, and speed up the response of the boiler. In the coordinated control mode, the actual value of the main steam pressure can quickly follow the given value of the main steam pressure.

This embodiment is a boiler system-based CCBF control system. This control method can respond quickly to load requirements and can maximize the AGC assessment index. It is different from the general CCBF method. The point is that it achieves the decoupling control of unit load and main steam pressure by satisfying the balance of heat signal and energy signal, that is, it resolves a multi-variable system with double input and double output into an inner loop with energy control as the inner loop. The load control is a dual-loop cascade control system with an outer loop.

The DEB coordinated control system is a coordinated control system that directly controls the input heat signal of the boiler with the energy demand signal of the steam turbine. The system can ensure the balance between the energy demand of the steam turbine and the heat input of the boiler under any working conditions. In order to overcome the problems of large delay and strong coupling of CFB boilers, a coordinated control strategy based on direct energy balance is proposed. DEB coordinated control uses the ratio of the pressure of the steam turbine governor stage (P1) to the pressure in front of the main steam valve of the steam turbine (Pt) multiplied by the set value of the pressure in front of the turbine (Ps) as the energy demand signal of the steam turbine for the boiler, namely (P1/Pt) ×Ps; the heat signal (P1+C*(dPd/dt)) of the boiler drum is used as the feedback signal of the fuel. Appropriate adjustments to the boiler heat signal can make the positive differential area of P1 and the negative differential area of dPd/dt basically equal under the disturbance of the boiler heat signal by the door opening, so that (P1+dPd/dt) is at the door opening It is basically unchanged under the disturbance, but only reflects the change of fuel. The direct energy balance system is to use the characteristics that P1*Ps/Pt only reflects the energy demand of the steam turbine on the boiler and (P1+dPd/dt) only reflects the characteristics of fuel changes, so as to realize the demand of the unit load for fuel and ensure that the turbine and boiler can always maintain Energy supply and demand balance. According to the characteristics of the circulating fluidized bed boiler, the utility model proposes a DEB coordinated control system based on the second-order differential of the heat signal.

Boiler main control controller optimization: The boiler main control generates the boiler main control instruction (LDC_B) according to the deviation between the steam turbine energy demand signal and the boiler input heat signal, and the boiler main control instruction realizes the balance between the steam turbine energy demand and the steam drum heat by changing the amount of fuel , to ensure the stability of the main steam pressure. In the static process, the main steam pressure is regulated by PID to stabilize the main steam pressure; in the dynamic process, the control quality mainly depends on various feedforward controls: static feedforward (LSff) of unit load command to boiler fuel, unit load command to boiler fuel Dynamic feed-forward (LDff) of pressure setting value to boiler fuel dynamic feed-forward (PDff), PID variable parameter control, etc.

All main parameters need to be determined through a large number of experiments during the debugging process. In the DEB coordinated control system, the heat storage coefficient of the steam drum has a great influence on the control quality of the system. If the heat storage coefficient is set too small, the heat storage capacity of the boiler drum will be underestimated, which will easily lead to over-regulation of the fuel quantity. If the heat storage coefficient is set larger than the actual heat storage capacity of the boiler, the main steam pressure will converge slowly, which will affect the adjustment quality of the main steam pressure. Therefore, in the debugging and tuning process of the direct energy balance coordinated control system, the heat storage coefficient must be accurately determined.

Optimization of the fuel master control loop: the task of the fuel quantity control system is to convert the boiler master control instructions into coal supply instructions. The fuel volume is determined according to the air-to-coal ratio limit. The fuel volume calculated by the boiler main control is compared with the fuel volume converted from the total air volume to determine the set value of the fuel main control, which not only ensures that the total air volume is not lower than the fuel volume, but also ensures that the total air volume is not lower than the fuel volume. Improved fuel control system response. In order to overcome the large delay characteristics of circulating fluidized bed boilers, the main fuel control regulator automatically adjusts the PID parameters according to the number of coal feeders (N_feeders) to speed up the response of fuel to load changes; to compensate for changes in coal calorific value , use the calorific value correction coefficient (CVC_c) to automatically adjust the PID parameters (BC_p, BC_i) of the fuel main control regulator: when the coal quality is good, the adjustment effect of the fuel main control PID regulator is automatically reduced, and the coal feeder command signal The change of the coal feeder will be correspondingly reduced; when the coal quality is poor, the adjustment function of the main fuel control PID regulator will be automatically enhanced, and the change of the command signal of the coal feeder will be correspondingly enhanced to speed up the response of the combustion control system.

The static load command feedforward of the boiler fuel is the boiler fuel load command generated at twice the variable load rate of the unit. The load command required by the boiler main control controller can advance the coal supply through the broken line function of the load and coal quantity. The amount of coal needed to increase or decrease to the target load reduces the pure delay time of the circulating fluidized bed boiler to a certain extent and improves the response rate of the boiler.

The dynamic load command feedforward of boiler fuel is the differential of the actual unit load command minus the rate limit, and the unit load command is determined by limiting the range of the upper and lower limits of the differential and the broken line function corresponding to different differential times with different load fluctuation ranges The differential amount of the load; the load dynamic feedforward correction system is determined through the variable load test, and the product of the differential amount of the load command and the differential correction coefficient is the dynamic feedforward of the load command.

The dynamic feed-forward of the unit pressure is the sum of the differential of the unit energy signal minus the rate limit and the differential of the main steam pressure setting minus the rate limit. Both of them can determine the upper and lower limit of differential, differential time and correction coefficient of dynamic feedforward through variable load test.

The dynamic feedforward of the bed temperature change rate Vt to the boiler master control is to correct the boiler master control instruction according to the bed temperature and the bed temperature change rate under the premise of satisfying the air-to-coal ratio. When the bed temperature is within a reasonable range, the product of the fuel correction amount corresponding to the bed temperature change rate and the fuel quantity correction function, and the correction coefficient corresponding to the deviation value of the main steam pressure is the fuel quantity that needs to be corrected by the boiler master control; When the bed temperature exceeds the reasonable range, the main control command of the boiler will directly change the command by 2% to prevent the bed temperature from overheating. (The main steam pressure correction coefficient is determined: when Vt>0.1, when the pressure deviation △P>-0.3, the pressure correction coefficient is 1, △P<-0.5 pressure correction coefficient is 0; when Vt<-0.1, when the pressure deviation △P >0.5, the pressure correction coefficient is 0, and △P<0.3 the pressure correction coefficient is 1.) Introduce the feedforward of the bed temperature change rate in the main controller of the boiler, and the bed temperature will change due to the change of the coal amount during the load change process , if there is no feed-forward effect, due to the lag of the main steam pressure, the main control over-adjustment of the boiler often occurs, resulting in too much coal and then excessive fluctuations in the main steam pressure. When the amount of change is large, the main control of the boiler is called back in time, so that the change of coal feed to the boiler is within the controllable range, and the stable control of the main steam pressure is realized, and then the stable control of the unit is realized.

The task of primary air volume control is to ensure the combustion and fluidization air of the boiler. The primary air volume and the secondary air volume form their respective air volume commands through the coal volume-primary air volume function and the coal volume-total air volume function. The total air volume command and the 30% minimum air volume are taken to form the final total air volume command. The primary air volume and the secondary air volume According to the ratio of 4:5 according to the boiler instructions. The boiler fuel command is obtained through the broken line function to obtain the theoretical value of the primary air volume, and then multiplied by the oxygen amount correction to obtain the set value of the primary air volume. The dynamic and static feedforward of the load command to the primary air volume is added in the primary air volume command loop, and the dynamic and static feedforward of the load command to the primary air volume is to correspond to the primary wind load command produced at three times the variable load rate of the unit through the broken line function The static feedforward of the primary air volume and the differential of the unit load command are used as the dynamic feedforward of the primary air volume, and the sum of the dynamic and static primary air volume commands is the primary air volume command. This method can make the primary air volume overshoot ahead of the unit load command and coal supply, make full use of the heat storage capacity of the boiler, and speed up the response of the boiler. In the coordinated control mode, the actual value of the main steam pressure can quickly follow the given value of the main steam pressure. Since the primary air load command is greater than the boiler fuel load command, the primary air always changes ahead of the coal supply when the load is raised and lowered, which can reduce the fluctuation of the bed temperature when the load changes to a certain extent, which not only improves the response rate of the unit, but also improves boiler stability.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present utility model, and are not intended to limit it; although the utility model has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention .

Claims (9)

1. A direct energy balance coordinated control system for large-scale circulating fluidized bed units, characterized in that: it includes a boiler master controller, a fuel master controller and a steam turbine master controller; the boiler master controller The controller adopts the steam drum heat signal with second-order differential and the dynamic and static feedforward signals; the dynamic and static feedforward signals include the static feedforward signal LSff of the unit load command to the boiler fuel, and the dynamic response of the unit load command to the boiler fuel. The feedforward signal LDff, the dynamic feedforward signal PDff of the unit pressure to the boiler fuel, the dynamic feedforward VtDf of the bed temperature change rate to the boiler main control, and the dynamic and static feedforward of the primary air volume to the load command; the boiler main control control The device adopts PID variable parameter control according to different load segments, and the main fuel control controller adopts a coal quality correction control loop. 2. A direct energy balance coordinated control system for large circulating fluidized bed units according to claim 1, characterized in that: said drum heat signal with second order differential is said direct energy balance coordinated control The adjusted volume of the main control controller of the boiler in the system is obtained through the door switch test to obtain the heat storage coefficient of the steam drum. 3. A kind of direct energy balance coordinated control system that is used for large circulating fluidized bed unit according to claim 1, it is characterized in that: the static feedforward signal LSff of described unit load order to boiler fuel is twice The boiler fuel load command generated by the variable load rate of the unit, the load command required by the boiler main control controller increases or decreases the coal supply to the coal supply required by the target load in advance through the broken line function of load and coal quantity. 4. A kind of direct energy balance coordinated control system for large-scale circulating fluidized bed unit according to claim 1, it is characterized in that: the dynamic feed-forward signal LDff of said unit load command to boiler fuel is the actual unit load command The differential of the actual unit load command after subtracting the rate limit, the differential value of the unit load command is determined by limiting the range of the upper and lower limits of the differential and the broken line function corresponding to different differential times for different load fluctuation ranges; the load dynamic feedforward is determined by the variable load test The correction system of the load command, the product of the differential value of the load command and the differential correction coefficient is the dynamic feedforward of the load command. 5. A kind of direct energy balance coordinated control system for large-scale circulating fluidized bed unit according to claim 1, it is characterized in that: the dynamic feed-forward signal PDff of described unit pressure to boiler fuel is the unit energy signal minus The sum of the differential of the unit energy signal after rate limiting and the differential of the main steam pressure set point after rate limiting minus the differential of the main steam pressure set point after rate limiting. 6. A kind of direct energy balance coordinated control system for large-scale circulating fluidized bed unit according to claim 5, characterized in that: the differential of the unit energy signal after the unit energy signal minus the rate limit, the main steam pressure The differential of the main steam pressure set value after the set value minus the rate limit is determined by the variable load test to determine the upper and lower limits of the differential, the differential time and the correction coefficient of the dynamic feedforward. 7. A kind of direct energy balance coordinated control system for large-scale circulating fluidized bed unit according to claim 1, it is characterized in that: the dynamic feed-forward VtDf of the bed temperature change rate to the main control of the boiler is to satisfy the wind Under the premise of coal ratio, the main control command of the boiler is corrected according to the bed temperature and the rate of change of the bed temperature. 8. A direct energy balance coordinated control system for a large circulating fluidized bed unit according to claim 7, characterized in that: when the bed temperature is within a reasonable range, the rate of change of the bed temperature is corrected by the amount of fuel The fuel correction amount corresponding to the function, and according to the correction coefficient corresponding to the deviation value of the main steam pressure, the product of the two is the fuel amount that the boiler master control needs to correct; The second instruction prevents the bed temperature from overheating. 9. A direct energy balance coordinated control system for large-scale circulating fluidized bed units according to claim 1, characterized in that: the dynamic and static feedforward of the primary air volume of the load command includes three times The primary air load command produced by the variable load rate of the unit passes the static feedforward of the primary air volume corresponding to the broken line function and the dynamic feedforward of the primary air volume with the differential of the unit load command as the primary air volume. The sum of the dynamic and static primary air volume commands is the primary air volume command.