CN110347201B - One-way accurate control condensate auxiliary frequency modulation control method and system - Google Patents
One-way accurate control condensate auxiliary frequency modulation control method and system Download PDFInfo
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Abstract
The invention discloses a condensate auxiliary frequency modulation control method with unidirectional precise control, which comprises the following processes: acquiring unit operation parameters; calculating the working capacity limit of the current unit in the throttling, frequency-modulating and direction-increasing direction and the flow of condensate water needing to be changed according to the unit operation parameters; judging whether to trigger a frequency modulation function according to the working capacity limit of the current unit in the throttling frequency modulation increasing direction, if so, carrying out the next step, otherwise, not needing to be adjusted; calculating the override amount of the deaerator regulating valve according to the flow rate of the condensed water needing to be changed, the current unit load and the flow characteristic of the deaerator valve; and under the water level adjusting mode of the deaerator water level adjusting valve, controlling the deaerator water level adjusting valve to be corresponding in opening degree according to the override. The invention can rapidly improve the capability of the turbine with small throttling loss to do work upwards to respond to the primary frequency modulation of the power grid under the condition of ensuring the existing operation parameters and working conditions.
Description
Technical Field
The invention belongs to the technical field of coal-fired thermal power generating unit control, and particularly relates to a condensate auxiliary frequency modulation control method and system with unidirectional precise control.
Background
With the development of society, the economic requirement on the power generation of the thermal power generating unit is higher and higher. In order to improve the power generation coal consumption of a coal-fired generating set, the through-flow transformation of a steam turbine is a widely applied technology. Meanwhile, various newly-built units also reduce the throttling loss of the steam turbine under the normal operation working condition as one of important means for improving the power generation economy of the steam turbine.
The existing primary frequency modulation auxiliary control methods are various and have the characteristics. The type and working condition of the applicable unit and the effect generated by the primary frequency modulation of the unit are all different. The throttle frequency modulation of the steam turbine is most widely applied. In the normal operation process, if the unit throttling is increased, the power generation economy of the whole unit is adversely affected. The existing control method for auxiliary power regulation of bidirectional condensed water is a method for rapidly reducing and raising the load of a unit by rapidly increasing and reducing the flow of the condensed water to a deaerator. When the method is matched with the practical application condition of the set condensed water system, the adjustment amplitude and the response speed are relatively small; meanwhile, the control optimization strategy has great deviation of the auxiliary power adjusting capacity in the positive and the secondary directions in different load sections. The control method of the bidirectional condensed water auxiliary power regulation requires that the flow rate of the condensed water to the deaerator can be rapidly and greatly increased or rapidly and greatly reduced. Therefore, the unit power can be rapidly reduced and increased. However, in order to save the service power, the existing condensate system of each generator set basically works in the working state that the water regulating door of the deaerator is fully opened and the condensate pump regulates the water level according to the frequency. If a reduction in power is required at this time, a rapid increase in the flow of condensed water to the deaerator is required. The water feeding adjusting door of the deaerator is in a full open state. The increase of the condensed water quantity can only be achieved by increasing the frequency of a frequency converter of the condensed water pump; but each frequency converter cannot increase and decrease its frequency quickly due to its internal structure. This limits the rate at which such control strategies can quickly assist in load shedding. Meanwhile, in order to save purchasing cost and operation economy, the rated output of each condensate pump is basically close to the normal water flow from the condensate to the deaerator under the full-load working condition. The magnitude of the rapid load reduction by increasing the condensed water during the high load phase is therefore also small, especially near full load, and is substantially negligible.
In addition, in order to quickly reduce the load by the aid of the condensed water, the condensed water is required to be quickly added to the deaerator, the balance of the water inlet and outlet of the deaerator can be damaged, the water level of the deaerator is quickly increased, and the deaerator is dangerous to trip due to the fact that the water level of the deaerator is too high. In order to ensure the safe operation of the unit, the water level of the deaerator needs to be set to be relatively lower during normal operation. The water level of a certain deaerator is ensured not to reach a dangerous value due to the auxiliary frequency modulation of the condensed water. After the deaerator water level reduced in normal operation, when the supplementary frequency modulation of condensate water needs to increase the load through reducing the condensate water flow, the flow that reduces just needs the water yield of deposit to supplement in the deaerator, because the deaerator water level normal operating in-process just reduced, under the circumstances of guaranteeing unit operation safety, the time and the range of the flow that the deaerator water-feeding permission reduced all fall and reduce. Therefore, if the frequency is modulated in a bi-directional auxiliary manner, the deaerator water level is in a relatively safe position, i.e., a relatively neutral position. The volume of the deaerator determines that the amplitude and the response time of the bidirectional auxiliary frequency modulation action of the condensed water cannot be too large.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a condensate auxiliary frequency modulation control method and system with unidirectional precise control, which can rapidly improve the capability of a steam turbine with small throttling loss to do work upwards to respond to primary frequency modulation of a power grid under the condition of ensuring the existing operating parameters and working conditions.
In order to solve the problems of the prior art, the invention discloses a condensate auxiliary frequency modulation control method with unidirectional precise control, which comprises the following steps:
acquiring unit operation parameters, wherein the unit operation parameters comprise steam pressure, steam temperature and steam turbine flow;
calculating the primary frequency modulation demand, the working capacity limit of the current throttling frequency modulation increasing direction of the unit and the flow of condensate water needing to be changed according to the unit operation parameters;
judging whether a condensed water auxiliary frequency modulation function is triggered or not according to the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the primary frequency modulation demand, if so, carrying out the next step, otherwise, no adjustment is needed;
calculating the override amount of a water supply regulating valve on the deaerator according to the flow of the condensed water needing to be changed, the current unit load and the design flow from the condensed water to the deaerator under the rated load;
and under the mode that the deaerator water feeding regulating valve regulates the deaerator water level, locking the deaerator water level regulating system to perform main PID regulation, controlling the deaerator water level regulating system to regulate the valve to a corresponding opening degree according to the override, and finally controlling the flow of condensed water to reach a set value through the deaerator water level regulating system auxiliary PID closed-loop regulation.
Further, the air conditioner is provided with a fan,
the specific process of calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction according to the unit operation parameters comprises the following steps:
calculating the primary frequency modulation demand and the load variation caused by the flow variation of each 1% of the steam turbine at the rated steam temperature according to the unit operation parameters;
calculating the maximum value and the pressure correction coefficient of the throttling frequency modulation of the current unit according to the primary frequency modulation demand, the steam temperature changing by 1 ℃ and the load variation caused by the flow change by 1%;
and calculating the working capacity limit of the unit in the throttling frequency modulation increasing direction under any working condition according to the maximum value of the current unit throttling frequency modulation and the pressure correction coefficient.
Further, the air conditioner is provided with a fan,
the calculation formula of the primary frequency modulation demand is as follows:
ΔW1＝Wf/S；
wherein, WfWorking pressure P and rated steam temperature T corresponding to current unit loadeIncreasing the actual power increment after the flow of the lower steam turbine is increased by S%;
the calculation formula of the load variation caused by the steam temperature of every 1 ℃ reduction and the flow variation of every 1% is as follows:
ΔW2＝[Wf－(Wf－Wt)/ΔT]·ΔW1/Wf；
wherein, Δ T ═ Te-Tt，TtTo produce a power variation WtSteam temperature of (T)eAt rated steam temperature, WtAnd when the temperature deviation is delta T ℃ under the same pressure P, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%.
Further, the air conditioner is provided with a fan,
the calculation formula of the maximum value of the throttling frequency modulation under the steam pressure P of the current unit is as follows:
ΔWmax＝(100-TF)·ΔW2·[Wf-(Wf－Wt)·(Te-T)/ΔT]·Wf；
wherein, TeIs the rated steam temperature, which is a known value, T is the current steam temperature, TFFor frequency-modulated front flow of turbines, WtUnder the same pressure P, when the deviation of the temperature of the steam turbine and the rated steam is delta T ℃, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%;
the calculation formula of the pressure correction coefficient is as follows:
Kp＝[Wf-(Wf-Wf2)·(P-Px)/ΔP]/Wf；
wherein, Δ P ═ P-PeP is the resulting power change WfSteam pressure of PeTo produce a power variation Wf2Steam pressure of PxAt an arbitrary pressure, Wf2Under the working condition of deviation delta P, the actual power change value of the unit is increased by S% after the rated steam temperature and the steam turbine flow are increased.
Further, the air conditioner is provided with a fan,
under any working condition, the working capacity limit of the throttling, frequency modulation and direction increasing of the unit is calculated according to the formula:
ΔWmax2＝ΔWmax·Kp；
wherein, Δ WmaxSteam pressure P, steam temperature T and steam turbine flow TFMaximum value of throttling frequency modulation, K, of unitpIs a pressure correction factor.
Further, the air conditioner is provided with a fan,
the calculation formula of the condensate flow needing to be changed is as follows:
Fn＝η·(ΔW1－ΔWmax2)；
wherein, FnThe condensate flow is the condensate flow needing to be changed, eta is a condensate flow change coefficient, and the value of eta is the ratio of the reduction of the condensate flow of the unit to the generated unit load increment; Δ W1Δ W being the primary frequency modulation demandmax2Working capacity limit for throttling, frequency modulation and direction increase of current unit。
Further, the air conditioner is provided with a fan,
the condition of judging whether the frequency modulation function is triggered or not according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit is as follows:
if Δ W is satisfied1－ΔWmax2If the frequency is greater than 0, triggering an auxiliary frequency modulation function, otherwise not triggering the frequency modulation function;
wherein, Δ W1Δ W being the primary frequency modulation demandmax2The working capacity limit of the throttling, frequency modulation and direction increasing of the unit under the current working condition is obtained.
Further, the air conditioner is provided with a fan,
the formula for calculating the amount of override is:
Q＝[1-We/W·(Fn/Yn)]·100；
Wethe actual load of the unit before the auxiliary frequency modulation of the condensed water, W is the rated load of the unit, YnThe flow rate is designed for the condensed water to the deaerator under the rated load.
Further, the air conditioner is provided with a fan,
the method also comprises the following steps:
judging whether the deviation of the water level of the deaerator needs to be eliminated or not according to the deaerator water level after the frequency of the power grid is recovered and a preset water level, if so, switching the water level regulation of the deaerator into a frequency conversion regulation mode of a condensate pump, adding a positive offset to the frequency of a frequency converter of the condensate pump so as to quickly recover the water level of the deaerator until the deviation of the actual water level of the deaerator and the set water level value is within a set range, then recovering the frequency offset of the frequency converter of the condensate pump to be 0, finally, locking and releasing the output of a main PID (proportion integration differentiation) of the water level regulation of.
The invention also discloses a condensate auxiliary frequency modulation control system with unidirectional precise control, which comprises:
the acquisition module is used for acquiring unit operation parameters;
the first calculation module is used for calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the flow of condensate water needing to be changed according to the unit operation parameters;
the judging module is used for judging whether a condensed water auxiliary frequency modulation function is triggered or not according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit and the primary frequency modulation requirement of the unit, if so, the next step is carried out, and otherwise, the adjustment is not needed;
the second calculation module is used for calculating the override amount of the water feeding regulating valve of the deaerator according to the flow of the condensed water needing to be changed, the current unit load and the design flow from the condensed water under the rated load to the deaerator;
and the adjusting module is used for locking the main PID adjustment of the deaerator water level adjusting system under the deaerator water feeding adjusting valve adjusting deaerator water level mode, then controlling the deaerator water level adjusting system to adjust the valve to a corresponding opening degree according to the override, and finally controlling the flow of condensed water to reach a set value through the auxiliary PID closed-loop adjustment of the deaerator water level adjusting system.
The invention has the following beneficial effects:
1. the invention can quickly improve the capability of the turbine with small throttling loss to do work upwards to respond to the primary frequency modulation of the power grid in a short time under the condition of ensuring the existing operation parameters and working conditions.
2. After the frequency of the power grid is recovered, the water levels of the deaerator and the condenser are quickly and stably recovered by controlling the method of opening the deaerator water level regulating valve and improving the frequency of the condensed water pump frequency converter. The normal operation of the unit is ensured, and meanwhile, preparation is made for the next auxiliary frequency modulation of the condensed water.
3. The invention can unidirectionally reduce the flow of condensed water to the deaerator, and can increase the water storage capacity of the deaerator in the normal operation process by setting the water level of the deaerator at a higher safe water level, thereby ensuring the normal operation of boiler water supply by utilizing the water storage capacity of the deaerator to the maximum extent. The auxiliary frequency modulation of the condensed water can maintain the increased load amount as large as possible and for a long time until the coordination system acts by increasing the load amount of coal or the frequency of the power grid returns to normal.
Drawings
FIG. 1 is a diagram of the primary frequency modulation characteristic of the present invention;
FIG. 2 is a system diagram of the auxiliary frequency modulation process of the present invention;
FIG. 3 is a schematic diagram of a system for switching the deaerator water level regulation back to the condensate pump frequency conversion regulation loop after the grid frequency is restored in the present invention;
fig. 4 is a flow chart in the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
As shown in fig. 1 to 4, a condensate auxiliary frequency modulation control method with unidirectional precise control comprises the following processes:
and acquiring unit operation parameters, wherein the unit operation parameters comprise steam pressure, steam temperature and steam turbine flow.
And calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the flow of the condensate water needing to be changed according to the unit operation parameters. In particular, the amount of the solvent to be used,
the specific process of calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction according to the unit operation parameters comprises the following steps:
calculating load variation caused by the primary frequency modulation demand and the turbine flow variation of every 1% under the rated steam temperature according to the unit operation parameters, wherein the calculation formulas are respectively as follows:
ΔW1＝Wf/S；
wherein, WfThe pressure P and the rated steam temperature T corresponding to the rated load of the current uniteAnd (4) increasing the actual power increment after the flow of the lower turbine is increased by S%, wherein S is preferably 5 in the specific implementation process.
ΔW2＝[Wf－(Wf－Wt)/ΔT]·ΔW1/Wf；
Wherein, Δ T ═ Te-Tt，TtTo produce a power variation WtSteam temperature of (T)eAt rated steam temperature, WtWhen the deviation of the temperature of the steam turbine and the rated steam is delta T ℃ under the same pressure P, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%, and the delta T is preferably 10 ℃ in the specific implementation process.
Calculating the maximum value and the pressure correction coefficient of the throttling frequency modulation of the current unit according to the primary frequency modulation demand and the load variation caused by the steam temperature reduction of 1 ℃ and the flow variation of 1 percent, wherein the calculation formulas are respectively as follows:
ΔWmax＝(100-TF)·ΔW2·[Wf-(Wf－Wt)]·(Te-T)/ΔT]·Wf；
wherein, Δ WmaxFor the maximum value of the throttling frequency modulation of the current unit, TeIs the nominal steam temperature, which is a known value, in the specific implementation, TePreferably 605 deg.C, T being the steam temperature, TFFor frequency-modulated front flow of turbines, WtWhen the deviation of the pressure P and the rated steam temperature is delta T ℃, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%.
Kp＝[Wf-(Wf-Wf2)·(P-Px)/ΔP]/Wf；
Wherein, KpFor pressure correction factor, Δ P ═ P-PeIn MPa, P is the power change WfSteam pressure of PeTo produce a power variation Wf2Is a known quantity, PxAt an arbitrary pressure, Wf2Under the working condition of deviation delta P, the actual power change value of the unit is increased by S% after the rated steam temperature and the steam turbine flow are increased.
Calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction according to the maximum value of the unit throttling frequency modulation under the current pressure and the pressure correction coefficient, wherein the calculation formula is as follows:
ΔWmax2＝ΔWmax·Kp；
wherein, Δ Wmax2Working capacity limit, delta W, for machine set throttling, frequency modulation and direction increase under any working conditionmaxIs the maximum value of the throttling frequency modulation of the unit under the current pressure P, KpIs a pressure correction factor.
The formula for calculating the flow of the condensate needing to be changed according to the unit operation parameters is as follows:
Fn＝η·(ΔW1－ΔWmax2)；
wherein, FnAnd eta is a condensate flow change coefficient which is the ratio of the reduction of the condensate flow of the unit to the generated unit load increment.
The throttling frequency modulation direction-increasing working capacity limit delta W under the current working condition parameters of the unit can be calculated in real time through the modelmax2The value of (c). As shown in fig. 1, when the grid frequency fluctuates (lower than 49.9333Hz) and a grid-related unit is required to increase the load by primary frequency modulation, the corresponding primary frequency modulation demand is calculated through a frequency difference load conversion loop preset in the DCS system, the calculation method calculates according to the current grid frequency and the rated load of the unit, and the corresponding relationship is shown in fig. 1. The national standard requires that when the frequency of a power grid fluctuates by 0.183Hz, the primary frequency modulation demand of a unit corresponds to 6% Pe (rated load). The dead zone of + -0.0333 Hz, among others, is linear. 2rpm for 0.0333Hz and 11rpm for 0.183 Hz.
And judging whether to trigger an auxiliary frequency modulation function according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit, if so, carrying out the next step, and otherwise, not needing to be adjusted.
The judgment condition whether the frequency modulation function is triggered is as follows:
if Δ W is satisfied1－ΔWmax2If the frequency is more than 0, the throttling frequency modulation of the unit under the current working condition cannot meet the requirement of primary frequency modulation of the power grid, and auxiliary frequency modulation is required, otherwise, the throttling frequency modulation of the current unit can meet the requirement of primary frequency modulation of the full-scale unit, and the auxiliary frequency modulation is not performed.
And calculating the override amount of the deaerator regulating valve according to the flow characteristics of the condensate flow, the current unit load and the water supply regulating valve on the deaerator, which need to be changed. The formula for calculating the amount of override is:
Q＝[1-We/W·(Fn/Yn)]·100；
wherein, WeThe actual load of the unit before the auxiliary frequency modulation of the condensed water, W is the rated load of the unit, YnThe flow rate is designed for the condensate to the deaerator at rated load, which is a unit specific known quantity.
When the control of the valve operation is performed, a valve override instruction needs to be determined according to the override amount, the instruction is obtained by converting the override amount Q through a deaerator water supply valve flow characteristic function, the flow characteristic function is provided by a deaerator water supply valve manufacturer or obtained through a field valve flow characteristic test, and the flow characteristic function belongs to a known function or a function which can be easily obtained by a person skilled in the art, so that the derivation process is not repeated.
Under the mode that the deaerator water feeding regulating valve adjusts the deaerator water level, the deaerator regulating valve is controlled to be corresponding in opening degree according to the override instruction, and then the condensate flow is accurately controlled to be a certain amount through PID closed-loop adjustment, so that the purpose of accurate adjustment is achieved. Meanwhile, the existing throttling frequency modulation capability of the unit can be fully utilized, the fluctuation range of the flow of condensed water is reduced as much as possible, and the water level of the deaerator, the water level of the condenser, the water level regulation of each low-pressure heater and the pressure disturbance of a condensed water system caused by the auxiliary frequency modulation of the condensed water are reduced.
In the aspect of recovering and adjusting the deaerator water level control, when the control mode is the condensed water auxiliary action, the output of a main PID controlled by deaerator water level adjustment is firstly locked, so that the output is not changed in the whole process of the condensed water auxiliary frequency modulation.
When the frequency of the power grid returns to normal, the condensate flow is increased for the deaerator in a mode of adding positive offset to the condensate pump frequency converter through the water feeding throttle of the fully-opened deaerator. Specifically, whether the deviation of the water level of the deaerator needs to be eliminated is judged according to the deaerator water level after the power grid frequency is restored and a preset water level, if so, the deaerator water level is adjusted and switched to a condensate pump frequency conversion adjusting mode, the frequency of a condensate pump frequency converter is added with a positive offset of 5Hz, and the deaerator water level is restored quickly; when the water level of the deaerator is recovered to be close to a set value (the absolute value of the difference value between the actual water level and the set water level is within +/-30 mm), the frequency offset of the condensed water frequency converter is recovered to be 0, then the output lock of the deaerator water level regulation main PID is released, and the frequency conversion water level control of the condensed water pump is recovered.
Compared with the traditional combined regulation mode of regulating the water level of the deaerator in a cascade mode by PID (proportion integration differentiation), the combined regulation mode of reducing the water level deviation regulation by adding the open loop and the bias and then converting the water level deviation regulation into the closed loop regulation reduces the excessive water level reduction of the deaerator caused by the auxiliary frequency modulation of the condensed water and the time for recovering the water level regulation process, and simultaneously avoids the risk of high protection action of the deaerator caused by the excessive overshoot and the risk of oscillation of the water level regulation; meanwhile, the deaerator has short water regulation recovery time and safe and reliable control.
Based on the same inventive concept, the invention also discloses a condensate auxiliary frequency modulation control system with unidirectional precise control, which comprises:
the acquisition module is used for acquiring unit operation parameters before and after the change of the power grid frequency;
the first calculation module is used for calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the flow of condensate water needing to be changed according to the unit operation parameters;
the judging module is used for judging whether a condensed water auxiliary frequency modulation function is triggered or not according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit and the primary frequency modulation requirement of the unit, if so, the next step is carried out, and otherwise, the adjustment is not needed;
the second calculation module is used for calculating the override amount of the water feeding regulating valve of the deaerator according to the flow of the condensed water needing to be changed, the current unit load and the design flow from the condensed water under the rated load to the deaerator;
and the adjusting module is used for locking the main PID adjustment of the deaerator water level adjusting system under the deaerator water feeding adjusting valve adjusting deaerator water level mode, then controlling the deaerator water level adjusting system to adjust the valve to a corresponding opening degree according to the override, and finally controlling the flow of condensed water to reach a set value through the auxiliary PID closed-loop adjustment of the deaerator water level adjusting system.
The specific control process is as follows:
now, taking a certain 1000MW unit as an example, the invention can improve the output power of the unit for increasing the load of the primary frequency modulation. In the embodiment, the rated steam temperature of the unit is 605 ℃, the water inlet flow of the deaerator at the full load stage of the unit is 2050t/h, and the water inlet flow of the deaerator at the load point with the rated load of about 50% is 1100t/h, which can be obtained from a thermodynamic equilibrium diagram of the unit. The data for a given test are as follows. The unit is in a pressure control mode, water supply and coal supply instructions are unchanged, the unit is stable for 10 minutes, the actual load of the unit is 531.2MW at present, the flow of the deaerator with the current condensed water value is determined to be 1104t/h under the stable working condition of the unit, and the opening instruction of a main water supply regulating valve of the deaerator is changed. The command is reduced from 25% to 15%, after 15s, the condensate flow is reduced to 523t/h, and the unit load is increased to 539.2 MW. The actual load of the unit rises by 8 MW. The condensate flow rate was reduced 1104-523 by 581 t/h. And by analogy, if the condensed water regulating valve is completely closed at the moment, the flow of the condensed water to the deaerator is reduced to 0. The unit load increment is (1102/581) × 8 ═ 15.17 MW. The test load required for a 1000MW primary frequency modulation test is 0.1083Hz for 30 MW; the normal AGC adjusting range of the unit is 55% Pe-100% Pe. That is to say, at the lowest load point of AGC control of unit operation, the condensate auxiliary frequency modulation can provide about half primary frequency modulation demand output at maximum. And the throttling frequency modulation function of the machine set per se is added. The method is completely hopeful to meet the requirement of primary frequency modulation examination. Along with the increase of the load of the unit, the flow from the condensed water to the deaerator in the normal operation process is correspondingly increased. The range of reducing the flow of the condensed water to the deaerator by closing the deaerator water level regulating door can be increased, and the capacity of auxiliary frequency modulation of the condensed water is correspondingly increased. When the load is full, the flow of the condensed water from the condensed water to the deaerator in normal operation is more than 2000t/h, if the flow is the condensed water from the full-closed deaerator regulating gate, the load of the unit is increased by (2000/581) × 8 which is more than 27.5MW, and the auxiliary frequency modulation capability is larger.
The primary frequency modulation assessment of each unit by the power grid is carried out every month, and if the test is unqualified, the assessment is carried out in tens of thousands to one hundred thousand every time according to the difference of factors such as unit capacity and the like. In order to consider the power generation economy of a plurality of units, the advantages and disadvantages of primary frequency modulation examination and the power generation economy of the units are balanced, and the low-throttling operation mode is usually maintained. The primary frequency modulation of the unit is almost assessed every month. After the wide popularization and application of this patent, can improve this type of unit primary control response ability greatly. The power generation economy of the unit is improved, the anti-interference capability of the whole power grid is improved, and the method has great economic and social values.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (3)
1. A one-way accurate control condensed water auxiliary frequency modulation control method is characterized in that: the method comprises the following steps:
acquiring unit operation parameters, wherein the unit operation parameters comprise steam pressure, steam temperature and steam turbine flow;
calculating the primary frequency modulation demand, the working capacity limit of the current throttling frequency modulation increasing direction of the unit and the flow of condensate water needing to be changed according to the unit operation parameters;
judging whether a condensed water auxiliary frequency modulation function is triggered or not according to the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the primary frequency modulation demand, if so, carrying out the next step, otherwise, no adjustment is needed;
calculating the override amount of a water supply regulating valve on the deaerator according to the flow of the condensed water needing to be changed, the current unit load and the design flow from the condensed water to the deaerator under the rated load;
under the mode that the deaerator water feeding regulating valve regulates the deaerator water level, locking the deaerator water level regulating system to perform main PID regulation, then controlling the deaerator regulating valve to reach a corresponding opening degree according to the override, and finally controlling the flow of condensed water to reach a set value through the deaerator water level regulating system auxiliary PID closed-loop regulation;
the specific process of calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction according to the unit operation parameters comprises the following steps:
calculating the primary frequency modulation demand and the load variation caused by the flow variation of each 1% of the steam turbine at the rated steam temperature according to the unit operation parameters;
calculating the maximum value and the pressure correction coefficient of the throttling frequency modulation of the current unit according to the primary frequency modulation demand, the steam temperature changing by 1 ℃ and the load variation caused by the flow change by 1%;
calculating the working capacity limit of the unit in the throttling frequency modulation increasing direction under any working condition according to the maximum value of the current unit throttling frequency modulation and the pressure correction coefficient;
the calculation formula of the primary frequency modulation demand is as follows:
ΔW1＝Wf/S；
wherein, WfWorking pressure P and rated steam temperature T corresponding to current unit loadeIncreasing the actual power increment after the flow of the lower steam turbine is increased by S%;
the calculation formula of the load change amount caused by the steam temperature of 1 ℃ per reduction and the flow change of 1% is as follows:
ΔW2＝[Wf－(Wf－Wt)/ΔT]·ΔW1/Wf；
wherein, Δ T ═ Te-Tt，TtTo produce a power variation WtSteam temperature of (T)eAt rated steam temperature, WtUnder the same pressure P and when the temperature deviation is delta T ℃, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%;
the calculation formula of the maximum value of the throttling frequency modulation under the steam pressure P of the current unit is as follows:
ΔWmax＝(100-TF)·ΔW2·[Wf-(Wf－Wt)·(Te-T)/ΔT]·Wf；
wherein, TeIs the rated steam temperature, which is a known value, T is the current steam temperature, TFFor frequency-modulated front flow of turbines, WtUnder the same pressure P, when the deviation of the temperature of the steam turbine and the rated steam is delta T ℃, the actual power change value of the unit is obtained after the flow of the steam turbine is increased by S%;
the calculation formula of the pressure correction coefficient is as follows:
Kp＝[Wf-(Wf-Wf2)·(P-Px)/ΔP]/Wf；
wherein, Δ P ═ P-PeP is the resulting power change WfSteam pressure of PeTo produce a power variation Wf2Steam pressure of PxAt an arbitrary pressure, Wf2Rated steam temperature and in the case of deviation Δ PIncreasing the actual power change value of the unit after the flow of the steam turbine is increased by S%;
under any working condition, the working capacity limit of the throttling, frequency modulation and direction increasing of the unit is calculated by the following formula:
ΔWmax2＝ΔWmax·Kp；
wherein, Δ WmaxSteam pressure P, steam temperature T and steam turbine flow TFMaximum value of throttling frequency modulation, K, of unitpIs a pressure correction factor;
the calculation formula of the condensate flow needing to be changed is as follows:
Fn＝η·(ΔW1－ΔWmax2)；
wherein, FnThe condensate flow is the condensate flow needing to be changed, eta is a condensate flow change coefficient, and the value of eta is the ratio of the reduction of the condensate flow of the unit to the generated unit load increment; Δ W1Δ W being the primary frequency modulation demandmax2The working capacity limit of the current machine set in the throttling, frequency modulation and direction increasing direction is set;
the condition for judging whether the frequency modulation function is triggered or not according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit is as follows:
if Δ W is satisfied1－ΔWmax2If the frequency is greater than 0, triggering an auxiliary frequency modulation function, otherwise not triggering the frequency modulation function;
wherein, Δ W1Δ W being the primary frequency modulation demandmax2The working capacity limit of the throttling, frequency modulation and direction increasing of the unit under the current working condition is obtained;
the calculation formula of the override amount is as follows:
Q＝[1-We/W·(Fn/Yn)]·100；
Wethe actual load of the unit before the auxiliary frequency modulation of the condensed water, W is the rated load of the unit, YnThe flow rate from the condensed water to the deaerator is designed for the rated load of the unit.
2. The method for controlling the auxiliary frequency modulation of the condensed water with the unidirectional precise control as claimed in claim 1, wherein: the method also comprises the following steps:
judging whether the deviation of the water level of the deaerator needs to be eliminated or not according to the deaerator water level after the frequency of the power grid is recovered and a preset water level, if so, switching the water level regulation of the deaerator into a frequency conversion regulation mode of a condensate pump, adding a positive offset to the frequency of a frequency converter of the condensate pump so as to quickly recover the water level of the deaerator until the deviation of the actual water level of the deaerator and the set water level value is within a set range, then recovering the frequency offset of the frequency converter of the condensate pump to be 0, finally, locking and releasing the output of a main PID (proportion integration differentiation) of the water level regulation of.
3. A condensate assisted frequency modulation control system using the condensate assisted frequency modulation control method of claim 1, characterized in that: the method comprises the following steps:
the acquisition module is used for acquiring unit operation parameters;
the first calculation module is used for calculating the working capacity limit of the current unit in the throttling frequency modulation increasing direction and the flow of condensate water needing to be changed according to the unit operation parameters;
the judging module is used for judging whether a condensed water auxiliary frequency modulation function is triggered or not according to the working capacity limit of the current throttling frequency modulation increasing direction of the unit and the primary frequency modulation requirement of the unit, if so, the next step is carried out, and otherwise, the adjustment is not needed;
the second calculation module is used for calculating the override amount of the water feeding regulating valve of the deaerator according to the flow of the condensed water needing to be changed, the current unit load and the design flow from the condensed water under the rated load to the deaerator;
and the adjusting module is used for locking the main PID adjustment of the deaerator water level adjusting system under the deaerator water feeding adjusting valve adjusting deaerator water level mode, then controlling the deaerator water level adjusting system to adjust the valve to a corresponding opening degree according to the override, and finally controlling the flow of condensed water to reach a set value through the auxiliary PID closed-loop adjustment of the deaerator water level adjusting system.
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| CN113819070B (en) * | 2020-10-30 | 2024-07-12 | 湖北华电江陵发电有限公司 | Variable-frequency optimization energy-saving method and system for condensate pump of steam turbine unit |
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| CN112653159B (en) * | 2020-12-16 | 2023-08-15 | 润电能源科学技术有限公司 | Condensate water throttling auxiliary frequency modulation control method, device, equipment and storage medium |
| CN113031663B (en) * | 2021-02-26 | 2023-07-07 | 中广核工程有限公司 | Deaerator liquid level control method, deaerator liquid level control device and deaerator liquid level control equipment for nuclear power unit |
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