CN214891078U - Automatic fuel quantity control system of thermal power generating unit - Google Patents
Automatic fuel quantity control system of thermal power generating unit Download PDFInfo
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- CN214891078U CN214891078U CN202121255007.XU CN202121255007U CN214891078U CN 214891078 U CN214891078 U CN 214891078U CN 202121255007 U CN202121255007 U CN 202121255007U CN 214891078 U CN214891078 U CN 214891078U
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Abstract
The utility model discloses a thermal power unit fuel volume automatic control system, this system boiler furnace, the boiler heating surface pipeline of setting in boiler furnace, the feeder through giving coal pipe and boiler furnace entry linkage, through the steam turbine of steam pipe and boiler furnace exit linkage, the generator with steam turbine coaxial coupling, set up fuel flow table and steam pressure gauge on giving coal pipe and the steam pipe respectively, the output of generator sets up the electric power table, still include thermal power unit fuel volume control module, its input is connected fuel flow meter, steam pressure table and electric power table, the input that the output is connected the feeder is used for controlling the fuel volume that gets into the boiler; the utility model discloses can realize that fuel quantity control ignites the full-process automatic control of thermal power generating unit generator load operation from the boiler to can effectively avoid the overshoot phenomenon, maintain boiler steam pressure stable, reducible thermal power generating unit excess temperature superpressure risk guarantees thermal power generating unit safe operation.
Description
Technical Field
The utility model belongs to the automatic control field of thermal power factory relates to the automatic control of thermal power unit boiler fuel volume. In particular to an automatic fuel quantity control system of a thermal power generating unit, which can control the fuel quantity from the ignition of a boiler to the load operation of a generator of the thermal power generating unit based on the steam pressure state.
Background
A boiler of a thermal power plant is an energy conversion apparatus. The fuel and air entering the boiler are mixed in the boiler hearth and then combusted, and water in the pipeline of the heating surface of the boiler is heated to generate steam with certain heat energy. The boiler comprises a boiler and a furnace. The original meaning of the boiler refers to a water container heated on fire, and the water container refers to a pipeline of a heating surface of a boiler. The furnace refers to a place for burning fuel, and is particularly referred to as a boiler hearth. After water enters the boiler, absorbed heat is transferred to water in a pipeline on the heating surface of the boiler, so that the water is heated into steam with certain temperature and pressure. In the boiler combustion equipment part, fuel is combusted to continuously release heat, high-temperature flue gas generated by combustion transfers the heat to a boiler heating surface through heat propagation, the temperature of the high-temperature flue gas is gradually reduced, and the high-temperature flue gas is finally discharged from a chimney. Steam generated in the boiler enters a steam turbine to convert heat energy into mechanical energy, and the mechanical energy is converted into electric energy through a generator connected with the steam turbine.
The amount of fuel entering the boiler is an important regulating object for the control of the thermal power plant. In the ignition stage of the boiler, the initial fuel entering the hearth is ignited by the ignition device, and the fuel quantity is slowly increased. The heat is continuously released along with the combustion of the fuel, and the water of the heating surface pipeline of the heating boiler is heated to generate steam. Along with the increase of the fuel quantity entering the hearth, the steam generated by the boiler heating surface pipeline is also increased continuously, and the steam pressure of the boiler heating surface outlet pipeline is also increased continuously. This stage is called the boiler ramp up stage.
And after the pressure of steam at the outlet of the pipeline of the heating surface of the boiler reaches the impulse pressure of the steam turbine, ending the temperature and pressure raising stage of the boiler, and entering the impulse stage of the steam turbine. At the moment, steam enters the steam turbine to drive the rotating speed of the steam turbine to be continuously increased until the rotating speed of the steam turbine reaches 3000 rpm. And then, the generator is connected to the grid for power generation, and in order to ensure that the steam quantity generated by the boiler can meet the required power requirement of the generator, the steam quantity generated by controlling the fuel quantity is required to maintain proper steam pressure according to the power change of the generator.
The quantity of fuel of the thermal power generating unit is generally controlled by taking steam pressure as a controlled object. Since the steam pressure of the boiler slowly rises after ignition of the boiler and is difficult to accurately control, before the grid connection of the thermal power generating unit, the fuel quantity is usually manually controlled by an operator or designed to be open-loop control for increasing the fuel quantity at a certain rate. When the quality of fuel quantity changes, the heat generated by burning the same fuel quantity is different, which can cause the evaporation quantity of steam generated by a boiler to be unstable, thereby causing the fluctuation of steam pressure.
And the fuel input amount of the operators is automatically controlled after the unit is connected to the power grid. PID control with steam pressure as the regulated quantity is usually used to keep the steam pressure in a certain relation with the load of the generator. However, as the fuel is combusted in the boiler to heat water to generate steam, the control pressure reaches the required pressure with great delay, and the conventional control often has the phenomenon of pressure overshoot to cause the fluctuation of the steam pressure.
Fluctuations in the steam pressure of thermal power generating units lead to frequent manual intervention of the fuel quantity by operating personnel. Because the working capacities of the steam with different pressures are different, the fluctuation of the steam pressure can cause the fluctuation of the generator power of the unit. The excessive fluctuation of the steam pressure can also increase the over-temperature and over-pressure risk of the thermal power generating unit and influence the safe operation of the thermal power generating unit.
Disclosure of Invention
In view of the problem that prior art exists above, the utility model provides a system based on steam pressure state control thermal power unit fuel volume can realize that fuel volume control ignites to thermal power unit generator load operation overall process automatic control from the boiler to the overshoot phenomenon that conventional PID control often appears can be effectively avoided, boiler steam pressure stability is maintained. The thermal power unit can be used for reducing the over-temperature and over-pressure risks due to the stable control of the steam pressure of the thermal power unit, and ensuring the safe operation of the thermal power unit.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
an automatic fuel quantity control system of a thermal power generating unit comprises a boiler hearth 2, a boiler heating surface pipeline 3 arranged in the boiler hearth 2, a coal feeder 1 connected with an inlet of the boiler hearth 2 through a coal feeding pipeline, a steam turbine 4 connected with an outlet of the boiler hearth 2 through a steam pipeline, a generator 5 coaxially connected with the steam turbine 4, a fuel flow meter 6 arranged on the coal feeding pipeline, a steam pressure gauge 7 arranged on the steam pipeline, and an electric power meter 8 arranged at an output end of the generator 5, and a thermal power generating unit fuel quantity control module 9, wherein an input end of the thermal power generating unit fuel quantity control module 9 is connected with the fuel flow meter 6, the steam pressure gauge 7 and the electric power meter 8, and an output end of the thermal power generating unit fuel quantity control module 9 is connected with an input end of the coal feeder 1 and used for controlling the quantity of fuel entering a boiler, so as to maintain the stability of steam pressure; wherein, the coal feeder 1 sends fuel into a boiler, the fuel is burned in a hearth 2 of the boiler, a heating surface pipeline 3 of the boiler generates steam with certain heat energy, the steam enters a steam turbine 4 to convert the heat energy into mechanical energy, and the mechanical energy is converted into electric energy through a generator 5 connected with the steam turbine;
the flow meter 6 is used for measuring fuel quantity FF entering the boiler, the pressure meter 7 is used for measuring steam pressure PS output by the boiler, and the electric power meter 8 is used for measuring unit power PW output by the generator.
The thermal power unit fuel quantity control module 9 can receive a unit load instruction LD output by the unit load control module 10, compare the unit power PW with the unit load instruction LD, generate a feedforward fuel control feedforward, compensate disturbance of steam flow change to steam pressure when the unit load instruction changes, and realize quick self-adaptive adjustment of the thermal power unit fuel quantity.
The thermal power unit fuel quantity control module 9 judges the operation stage of the thermal power unit according to the unit power PW output by the generator measured by the power meter 8 and the steam pressure PS output by the boiler measured by the steam pressure gauge 7, and calculates a steam pressure target value and a steam pressure change rate target value of the current operation stage of the unit, thereby realizing automatic control of the ignition, temperature and pressure rise stage of the boiler, the steam turbine running stage and the loaded operation stage of the generator of the unit.
The control method of the automatic fuel quantity control system of the thermal power generating unit comprises the following steps of:
step 1: the thermal power unit fuel quantity control module 9 obtains a steam pressure target value PSt according to the unit operation state, for a certain thermal power unit, the steam pressure target value and the current unit power PW have a fixed functional relationship, and the steam pressure target value PSt corresponding to the current unit power is obtained through the current unit power PW; the steam pressure target value corresponding to the current unit power PW of 0MW is called the unit steam engine impulse pressure PSto; the thermal power generating unit fuel quantity control module 10 calculates a steam pressure value change rate DPS according to a steam pressure value PS measured by a steam pressure gauge 7;
step 2: the thermal power generating unit fuel quantity control module 9 compares the steam pressure value PS with the unit steam turbine impulse pressure PSto, and judges that the unit is in a temperature and pressure increasing stage when the steam pressure value PS subtracts the unit steam turbine impulse pressure PSto to obtain a difference value of-0.02 MPa before the unit is not connected to the grid; when the unit is in a temperature rise and pressure rise stage, the fuel quantity control module 9 of the thermal power generating unit controls the fuel quantity of the boiler, and maintains the steam pressure change rate DPS equal to a steam pressure change rate target value DPSt which is a function of a difference value delta PS between a steam pressure value PS and a unit steam turbine impulse rotation pressure PSto; when the steam pressure change rate DPS is smaller than the steam pressure change rate target value DPSt, slowly increasing the unit fuel quantity control instruction AO; when the steam pressure change rate DPS is larger than the steam pressure change rate target value DPSt, slowly reducing the unit fuel quantity control instruction AO; the rate dO at which the fuel amount control command AO increases or decreases is a function of the difference between the vapor pressure change rate DPS and a preset vapor pressure change rate target value DPSt;
and step 3: the thermal power generating unit fuel quantity control module 9 compares the steam pressure value PS with the unit steam turbine running pressure PSto, and when the difference value Δ PS (Δ PS — PSto) between the steam pressure value PS and the unit steam turbine running pressure PSto is greater than-0.02 MPa, and the unit is not connected to the grid, that is, the unit power PW is 0, it is determined that the unit is in the steam turbine running stage; at the moment, the target value DPSt of the steam pressure change rate is equal to 0 MPa/min; at the moment, the fuel quantity control module 9 of the thermal power generating unit controls the fuel quantity entering the boiler, and the steam pressure change rate DPS is maintained to be equal to 0MPa/min, namely the steam pressure is controlled to be maintained near the impulse pressure of the steam turbine; in the stage, when the steam pressure value change rate DPS is less than 0 and the Delta PS is less than-0.02, slowly increasing the unit fuel quantity control command AO; when the steam pressure value change rate DPS is greater than 0 and Delta PS is greater than 0.02, slowly reducing the unit fuel quantity command, wherein the increasing or decreasing rate dO of the fuel quantity control command AO is a function of the steam pressure value change rate DPS;
and 4, step 4: when the thermal power unit fuel quantity control module 9 judges that the power PW of the unit is greater than 0, the unit is judged to be in a generator loading stage; when the generator is in a load stage, obtaining a steam pressure target value PSt corresponding to the current set power PW from the current set power PW; the steam pressure change rate target value DPSt is a function of the difference Δ PS between the steam pressure value PS and the pressure target value PSt. When the steam pressure change rate DPS is smaller than the steam pressure change rate target value DPSt, slowly increasing the unit fuel quantity instruction; when the steam pressure change rate DPS is greater than the steam pressure change rate parameter DPSt, the unit fuel quantity command is slowly decreased. The rate of increase or decrease dO commanded by the fuel quantity control command AO is a function of the steam pressure value change rate DPS and the steam pressure value change rate target value DPSt difference Δ DPS.
According to the control method of the automatic fuel quantity control system of the thermal power generating unit, when the thermal power generating unit is in a temperature rise and pressure rise stage, a receiver unit operator 'pressure rise keeping' instruction suspends temperature rise and pressure rise; when the steam temperature reaches 190 ℃, the solubility of iron ions on the heating surface of the boiler is highest, and a unit operator needs to test the steam quality and wait for the qualified steam quality to meet the requirements of the steam turbine; when the temperature and the pressure are temporarily increased, the fuel quantity automatic control system maintains the current steam pressure, the steam temperature is favorably maintained at 190 ℃, and the hot cleaning time is effectively shortened.
The control method of the automatic fuel quantity control system of the thermal power generating unit can realize that the fuel quantity control obtains the target values of steam pressure and steam pressure change rate of different operation stages of the thermal power generating unit from the automatic control of the whole process of the ignition temperature rise and pressure rise stage, the steam turbine impulse stage and the loaded operation stage of the generator set generator, when the steam pressure is close to the target value of the steam pressure, the steam pressure change rate is controlled to be close to 0, the over-regulation phenomenon which often occurs in the conventional PID control can be effectively avoided, the stability of the steam pressure of the boiler is maintained, the over-temperature and over-pressure risks of the thermal power generating unit are reduced, and the safe operation of the thermal power generating unit is ensured.
Compared with the prior art, the utility model discloses possess following advantage:
1. the conventional control system and method cannot realize the automatic control of the whole process of the fuel of the thermal power generating unit, and particularly needs manual operation of an operator in the ignition and temperature rise stage of the boiler. The utility model discloses a system and method can judge thermal power generating unit's operation stage automatically, realize that boiler ignition intensification step-up stage, steam turbine rush to stage, unit generator load operation stage and other different stage overall process automatic control.
2. Since the steam pressure of the boiler slowly rises after ignition of the boiler and is difficult to accurately control, before the grid connection of the thermal power generating unit, the fuel quantity is usually manually controlled by an operator or designed to be open-loop control for increasing the fuel quantity at a certain rate. When the quality of fuel quantity changes, the heat generated by burning the same fuel quantity is different, which can cause the evaporation quantity of steam generated by a boiler to be unstable, thereby causing the fluctuation of steam pressure. The utility model discloses a system and method can realize that automatic control steam pressure rises to dash and changes pressure with reasonable boost speed in the boiler intensification boost stage, and control steam pressure is keeping dashing and changes pressure when being close to dashing and change pressure.
3. The utility model discloses a steam pressure target value and steam pressure change rate target value of the different operation stages of thermal power generating unit are reachd automatically to system and method, and control steam pressure change rate also is close to 0 when steam pressure is close to the steam pressure target value. Compared with a conventional PID control strategy, the method can effectively avoid the problems of deaerator valve fluctuation, system overshoot and the like in the adjusting stage, and the overall stability of the control system is enhanced.
4. When the unit is in a temperature rise and pressure rise stage, a unit operator needs to test the steam quality and wait for the qualified steam quality to meet the requirements of the steam turbine. The steam temperature reaches the solubility of boiler heating surface iron ion when 190 ℃ is the highest, the utility model discloses a system and method when the unit is in the intensification stage of stepping up, receiver group operation personnel instruction pause intensification step up, maintain current steam pressure, be favorable to steam temperature to maintain boiler heating surface temperature at 190 ℃, can effectively shorten hot cleaning time.
5. The utility model discloses a system and method pass through unit load instruction and unit power deviation feedforward when unit load instruction changes, and the disturbance that steam flow changes and cause steam pressure when can compensate unit load instruction changes realizes the quick self-adaptation of thermal power unit fuel volume and adjusts.
Drawings
Fig. 1 is a schematic structural diagram of the present invention.
Fig. 2 is a control schematic diagram of the method of the present invention.
Description of reference numerals:
the system comprises a coal feeder 1, a boiler hearth 2, a boiler heating surface pipeline 3, a steam turbine 4, a generator 5, a fuel flow meter 6, a steam pressure meter 7, an electric power meter 8, a thermal power unit fuel quantity control module 9 and a thermal power unit load control module 10.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, an automatic fuel quantity control system for a thermal power generating unit comprises a boiler furnace 2, a boiler heating surface pipeline 3 arranged in the boiler furnace 2, a coal feeder 1 connected with an inlet of the boiler furnace 2 through a coal feeding pipeline, a steam turbine 4 connected with an outlet of the boiler furnace 2 through a steam pipeline, a generator 5 coaxially connected with the steam turbine 4, a fuel flow meter 6 arranged on the coal feeding pipeline, a steam pressure gauge 7 arranged on the steam pipeline, and a power meter 8 arranged at an output end of the generator 5, and further comprises a fuel quantity control module 9 for the thermal power generating unit, wherein an input end of the fuel quantity control module 9 for the thermal power generating unit is connected with the fuel flow meter 6, the steam pressure gauge 7 and the power meter 8, and an output end of the fuel quantity control module is connected with an input end of the coal feeder 1 and is used for controlling the fuel quantity entering the boiler and maintaining the stability of steam pressure; the coal feeder 1 feeds fuel into the boiler, which is burned in the boiler furnace 2. The boiler heating surface pipeline 3 generates steam with certain heat energy, the steam enters a steam turbine 4 to convert the heat energy into mechanical energy, and the mechanical energy is converted into electric energy through a generator 5 connected with the steam turbine.
The flow meter 6 is used for measuring fuel quantity FF (unit t/h) entering the boiler, the pressure meter 7 is used for measuring steam pressure PS (unit MPa) output by the boiler, and the electric power meter 8 is used for measuring unit power PW (unit MW) output by the generator. The thermal power unit fuel quantity control module 9 generates a thermal power unit fuel quantity control instruction AO (unit t/h). The flow meter (6), the pressure meter (7) and the electric power meter (8) are connected with the input end of the thermal power unit fuel quantity control module (9). The output end of the thermal power unit fuel quantity control module 9 is connected to the input end of the coal feeder 8 and used for controlling the quantity of fuel entering the boiler and maintaining the stability of the steam pressure PS.
The thermal power generating unit fuel quantity control module 9 receives a unit load instruction LD output by the unit load control module 10. The system compares the power PW of the unit with the load instruction LD of the unit to generate feed-forward fuel control feed-forward, compensates disturbance of steam flow change to steam pressure when the load instruction of the unit changes, and achieves quick self-adaptive adjustment of the fuel quantity of the thermal power unit.
The control method of the automatic fuel quantity control system of the thermal power generating unit comprises the following steps of:
step 1: the thermal power generating unit fuel quantity control module 9 obtains a steam pressure target value PSt according to the unit operation state. For a certain thermal power generating unit, the target value of the steam pressure value and the current power PW of the unit have a fixed functional relationship, and the target value PSt (unit MPa) of the pressure corresponding to the current power of the unit can be obtained from the current power PW of the unit. In particular, the pressure target PSto corresponding to the unit power PW of 0MW is referred to as the unit steam turbine kick pressure. For a certain thermal power generating unit, PSto is a fixed parameter.
The thermal power generating unit fuel quantity control module 9 calculates a steam pressure value PS (unit MPa) measured by the pressure gauge 7 to obtain a steam pressure value change rate DPS (unit MPa/min).
Step 2: the thermal power unit fuel amount control module 9 compares the steam pressure value PS with the unit steam turbine impulse pressure PSto (in MPa). And when the unit is not connected to the grid, namely the power PW of the unit is 0, and the difference value of the steam pressure value PS minus the impulse pressure PSto of the unit and the steam turbine is less than-0.02 MPa, judging that the unit is in a temperature rise and pressure rise stage. When the unit is in a temperature rise and pressure rise stage, the fuel quantity control module 9 of the thermal power unit controls the fuel quantity of the boiler, and maintains the steam pressure change rate DPS equal to the steam pressure change rate target value DPSt. The target value DPSt of the steam pressure change rate is a function of a difference Δ PS between the steam pressure value PS and the turbine boost pressure PSto of the unit (Δ PS — PSto), for example, 0.05 MPa/min. When the steam pressure change rate DPS is smaller than the steam pressure change rate target value DPSt, slowly increasing the unit fuel quantity instruction; when the steam pressure change rate DPS is greater than the steam pressure change rate target value DPSt, the unit fuel amount control command is slowly decreased. The rate dO (in t/h) at which the fuel quantity control command AO (in t/h) increases or decreases is a function of the difference between the steam pressure change rate DPS and a preset steam pressure change rate target value DPSt.
When the thermal power generating unit fuel quantity control module 9 is in a temperature rise and pressure rise stage, the temperature rise and pressure rise can be suspended by a receiver unit operation personnel 'pressure rise keeping' instruction. When the unit is in a temperature and pressure rise stage and temperature and pressure rise are suspended, the fuel quantity control module 9 of the thermal power unit controls the fuel quantity of the boiler to maintain the steam pressure value change rate DPS to be 0MPa/min, namely, the steam pressure is controlled to maintain the current value. When the unit is in a temperature rise and pressure rise stage, a unit operator needs to test the steam quality and wait for the qualified steam quality to meet the requirements of the steam turbine. When the steam temperature reaches 190 ℃, the solubility of iron ions on the heating surface of the boiler is the highest, and at the moment, the temperature rise and the pressure rise are suspended, so that the current steam pressure is maintained, the steam temperature is favorably maintained at 190 ℃, and the hot cleaning time can be effectively shortened. When the unit is in a temperature and pressure rise stage and temperature and pressure rise are suspended, when the steam pressure change rate DPS is less than 0, the fuel quantity of the unit is slowly increased; and when the steam pressure value change rate DPS is greater than 0, slowly reducing the unit fuel quantity. After the steam quality test of the unit operator confirms that the steam quality is qualified, the unit operator automatically recovers to continue the temperature rise and pressure rise stage, the fuel quantity control module 9 of the thermal power unit controls the fuel quantity of the boiler, and the steam pressure change rate DPS is maintained to be equal to the steam pressure change rate target value DPSt.
And step 3: the thermal power unit fuel amount control module 9 compares the steam pressure value PS with the unit steam turbine kick pressure PSto. And when the difference value delta PS (delta PS is PS-PSto) between the steam pressure value PS and the steam turbine running pressure PSto of the unit is larger than-0.02 MPa and the unit is not connected to the grid (the unit power PW is 0), judging that the unit is in a steam turbine running stage, and at the moment, the target value DPSt of the steam pressure change rate is equal to 0 MPa/min. At the moment, the fuel quantity control module 9 of the thermal power generating unit controls the fuel quantity entering the boiler, and the steam pressure change rate DPS is maintained to be equal to 0MPa/min, namely the steam pressure is controlled to be maintained near the impulse pressure of the steam turbine. In the stage, when the steam pressure value change rate DPS is less than 0 and the delta PS is less than-0.02, slowly increasing the unit fuel quantity control instruction; and when the steam pressure value change rate DPS is greater than 0 and the delta PS is greater than 0.02, slowly reducing the unit fuel quantity command. The rate dO at which the fuel amount control command AO increases or decreases is a function of the vapor pressure value change rate DPS.
And 4, step 4: and when the thermal power unit fuel quantity control module 9 judges that the unit power PW is greater than 0, the unit is judged to be in a generator load stage. For a certain thermal power generating unit, a fixed function relationship exists between the steam pressure target value and the current power PW of the unit, and the steam pressure target value PSt (unit MPa) corresponding to the current power PW of the unit can be obtained from the current power PW of the unit. The target steam pressure rate DPSt is a function of the difference Δ PS between the steam pressure value PS and the target pressure value PSt during the generator load phase (Δ PS — PSt). When the steam pressure change rate DPS is smaller than the steam pressure change rate target value DPSt, slowly increasing the unit fuel quantity instruction; when the steam pressure change rate DPS is greater than the steam pressure change rate parameter DPSt, the unit fuel quantity command is slowly decreased. The rate dO at which the fuel quantity control command AO commands an increase or decrease is a function of the difference Δ DPS (DPS ═ DPS-DPSt) between the steam pressure value change rate DPS and the steam pressure value change rate target value DPSt.
The method comprises the steps that a unit load instruction signal LD (unit MW) can be received, and when a unit load instruction is increased, if the current unit power is smaller than the unit load instruction after speed limitation, a fuel quantity control instruction AO instruction is rapidly increased through an open-loop feedforward action; when the unit load instruction is reduced, if the current unit power is larger than the unit load instruction after speed limitation, the fuel quantity control instruction AO instruction is rapidly reduced through an open-loop feedforward action. When the power of the unit deviates from the load instruction of the unit after speed limitation, the fuel quantity is matched with the load instruction through the open-loop feedforward action.
The embodiment of the invention provides a control method of an automatic fuel quantity control system of a thermal power generating unit, which specifically comprises the following steps:
1. and obtaining a furnace outlet steam pressure target value PSt (steam pressure) in unit MPa according to the power PW (unit MW) of the unit measured by the power meter (8). Namely, the steam pressure target value PSt is a functional relation of the unit power PW, and PSt is F1(PW). A typical functional relationship between PSt and PW is shown in the following table.
TABLE 1
| PW(MW) | PSt(MPa) |
| 0 | 9.7 |
| 300 | 9.7 |
| 500 | 14.5 |
| 900 | 25 |
| 950 | 25 |
| 1050 | 25.2 |
2. The steam pressure value PS (unit MPa) measured by the pressure gauge 7 is used for calculating the steam pressure value change rate DPS, unit MPa/min.
4. The steam pressure change rate target value DPSt is obtained by the difference value delta PS (delta PS is PS-PSt) between the steam pressure value PS and the pressure target value PSt, and the unit is MPa/min. That is, the target value DPSt of the change rate of the steam pressure is a function of the pressure difference Δ PS, where DPSt is F2(. DELTA.PS). The steam pressure change rate target value DPSt is a typical function of the pressure difference Δ PS as shown in the following table:
TABLE 2
| △PS | DTws(MPa/min) |
| <-2 | -0.2*A |
| -2～-0.02 | -0.2△PS*A |
| -0.02～0.02 | 0 |
| 0.02～1 | -0.2△PS*A |
| >2 | -0.2*A |
When unit power PW<At 30% rated load, a is constant and a is 1 in table two. As can be seen from Table 1, the power PW of the unit>At 30% of the rated load, the steam pressure target PSt is fixed. Power PW of machine set>At 30% of rated load, the steam pressure target value PSt is greatly changed along with the increase of the power PW of the unit. In order to ensure the power PW of the machine set>At 30% rated load, the steam pressure is consistent with the target value of the steam pressure, and the power PW of the unit is>At 30% rated load, the target value DPSt of the steam pressure change rate is increased by multiplying the target value DPSt by a coefficient A as shown in the table II, wherein A is a function of the power PW of the unit, and A is F3(PW). As shown in the following table:
TABLE 3
| PW(MW) | A |
| <300 | 1 |
| 300 | 1 |
| 500 | 5 |
| 1050 | 10.5 |
5. Obtaining the difference delta DPs (DPSt-DPSt) between the actual steam pressure change rate DPS and the steam pressure change rate target value DPStRate of change of unit fuel quantity command dO. Namely, the change rate dO of the fuel quantity command of the thermal power generating unit is a functional relation of a pressure change rate difference delta DPS, and dO is F4(. DELTA.DPS). A typical functional relationship between dO and Δ DPS is shown in the following table.
TABLE 4
| △DPS | dO(t/h/s) |
| <-2 | 1 |
| -2～-0.005 | -0.5*△DPS |
| -0.005～0.005 | 0 |
| 0.005～2 | -0.5*△DPS |
| >2 | -1 |
6. Based on the above table, when the delta DPS is-0.005, the current fuel quantity command AO of the thermal power generating unit is kept unchanged; slowly increasing the thermal power unit fuel amount command AO at a rate of dO (t/h/s) when Δ DTw > 0.02; when the delta DTw < -0.02, the thermal power unit fuel quantity command AO is slowly increased at a rate of dO (t/h/s).
The utility model relates to a thermal power unit fuel quantity automatic control's system and method, acceptable unit load command signal LD (unit MW), unit load command signal LD warpThe corrected overload change rate results in the speed-limited load command signal LD2 (in MW). And obtaining a feedforward FF (F) of the fuel quantity instruction of the thermal power unit according to the difference delta MW (PW-LD 2) between the power PW of the unit and the load instruction signal LD2 after speed limiting5(. DELTA.MW). Typical functions of FF and Δ MW are shown in the following table.
TABLE 5
| △MW | FF(t/h/s) |
| <-40 | 10 |
| -50～-5 | -0.25*△MW |
| -5～5 | 0 |
| 5～40 | -0.25*△MW |
| >40 | -10 |
The utility model provides a pair of realize thermal power unit fuel quantity automatic control's system through control steam pressure change rate based on unit load, steam pressure state. When the steam pressure PS deviates from the steam pressure target value PSt, it is possible to achieve that the steam pressure PS reaches the steam pressure target value PSt at the set pressure change rate DPS by adjusting the fuel amount. When the steam pressure PS coincides with the steam pressure target PSt, the fuel quantity is adjusted to maintain the current steam pressure. When the unit load instruction changes, the fuel quantity is quickly changed to match the unit load through the open-loop feed-forward action. The automatic control of the whole process from boiler ignition to the on-load operation of the generator of the thermal power generating unit can be realized, the overshoot phenomenon frequently occurring in the conventional PID control can be effectively avoided, and the stable steam pressure of the boiler is maintained. The thermal power unit can be used for reducing the over-temperature and over-pressure risks due to the stable control of the steam pressure of the thermal power unit, and ensuring the safe operation of the thermal power unit.
Claims (1)
1. The automatic fuel quantity control system of the thermal power generating unit is characterized by comprising a boiler hearth (2), a boiler heating surface pipeline (3) arranged in the boiler hearth (2), a coal feeder (1) connected with an inlet of the boiler hearth (2) through a coal feeding pipeline, a steam turbine (4) connected with an outlet of the boiler hearth (2) through a steam pipeline, a generator (5) coaxially connected with the steam turbine (4), a fuel flow meter (6) is arranged on the coal feeding pipeline, a steam pressure meter (7) is arranged on the steam pipeline, an electric power meter (8) is arranged at the output end of the generator (5), a fuel quantity control module (9) of the thermal power generating unit is further included, the input end of the fuel quantity control module (9) of the thermal power generating unit is connected with the fuel flow meter (6), the steam pressure meter (7) and the electric power meter (8), and the output end is connected with the input end of the coal feeder (1) and used for controlling the fuel quantity entering the boiler, the steam pressure is maintained stable.
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| CN202121255007.XU CN214891078U (en) | 2021-06-04 | 2021-06-04 | Automatic fuel quantity control system of thermal power generating unit |
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| CN202121255007.XU CN214891078U (en) | 2021-06-04 | 2021-06-04 | Automatic fuel quantity control system of thermal power generating unit |
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