CN106780103B - DC boiler, steam turbine and power grid coordination control method for primary frequency modulation analysis - Google Patents
DC boiler, steam turbine and power grid coordination control method for primary frequency modulation analysis Download PDFInfo
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Abstract
The invention discloses a coordinated control method for a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis, and relates to a coordinated control method for a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis. The invention aims to solve the problems that the prior art does not consider the characteristics of a boiler, brings great resistance to a high-capacity high-parameter thermal power generating unit participating in primary frequency modulation, and is not beneficial to safe and stable operation of a power system. The method comprises the following steps: firstly, the method comprises the following steps: analyzing the energy state of the once-through boiler to determine the energy state of the once-through boiler; II, secondly: analyzing the energy state of the power grid to determine the energy state of the power grid; thirdly, the method comprises the following steps: and determining a grid source energy coordination control strategy according to the energy state of the once-through boiler determined in the step one and the energy state of the power grid determined in the step two. On the premise of meeting the requirement of safe operation of a power grid, the invention ensures that the thermal power generating unit can fully participate in frequency modulation and can safely and efficiently operate. The invention is applied to the field of primary frequency modulation analysis.
Description
Technical Field
The invention relates to a coordinated control method for a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis.
Background
Because the supercritical and ultra-supercritical units are superior to the subcritical units in the aspects of economy, environmental protection, efficiency and capacity, the supercritical and ultra-supercritical units become the main development stream of future thermal power construction. The ultra-high temperature and ultra-high pressure characteristics of the supercritical and ultra-supercritical units lead to that a once-through boiler is required, and the once-through boiler has the problems of small heat storage, sensitivity to disturbance, serious coupling between the units and the boiler and the like. With the grid connection of intermittent energy sources such as wind power and the like, the frequency modulation requirement of a power system is increased, and the power of a supercritical unit and an ultra-supercritical unit is frequently changed, so that the main steam pressure of the once-through boiler is greatly fluctuated, and the running risk of the once-through boiler is increased.
From the perspective of power grid operation, a steam turbine set is directly interconnected with a power grid, so that the traditional power grid coordination is mainly a generator set, a boiler is less considered, and the safety and dynamic characteristics of the boiler are ignored. The traditional turbine-boiler coordination control means that when the external load changes, a power change instruction is simultaneously sent to a boiler and a steam turbine control system, and the opening of an adjusting valve and the boiler are synchronously adjusted and coordinately controlled. The core idea of the control is to improve the response speed of the unit to the load change of the power grid, and the boiler air pressure fluctuation caused by the large-capacity high-parameter unit when the load fluctuation is responded is not fully considered. Under the background that the direct-flow boiler is seriously coupled with the steam turbine and the direct-flow boiler has small heat storage, the safety problem of the direct-flow boiler needs to be paid attention again.
From the above analysis, if the characteristics of the boiler are not considered in the primary frequency modulation control, great resistance is brought to the high-capacity high-parameter thermal power generating unit to participate in the primary frequency modulation, and the safe and stable operation of the power system is not facilitated.
Disclosure of Invention
The invention provides a coordinated control method for a direct current boiler, a steam turbine and a power grid for primary frequency modulation analysis, and aims to solve the problems that the characteristics of the boiler are not considered in the prior art, great resistance is brought to a high-capacity high-parameter thermal power generating unit to participate in primary frequency modulation, and safe and stable operation of a power system is not facilitated.
A coordinated control method for a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis is realized according to the following steps:
the method comprises the following steps: analyzing the energy state of the once-through boiler to determine the energy state of the once-through boiler;
step two: analyzing the energy state of the power grid to determine the energy state of the power grid;
step three: and determining a grid source energy coordination control strategy according to the energy state of the once-through boiler determined in the step one and the energy state of the power grid determined in the step two.
The invention has the following effects:
in consideration of the characteristics of supercritical and ultra-supercritical units, the invention designs a new control method which comprises the following steps: the boiler, the steam turbine and the power grid are regarded as a control object, and the safety and stability problems of the boiler, the steam turbine and the power grid are comprehensively considered. On the premise of meeting the requirement of safe operation of a power grid, the thermal power generating unit can fully participate in frequency modulation and can safely and efficiently operate, and the win-win purpose of the power grid and a power supply is achieved.
According to the simulation result, the method of the invention has good influence on the frequency of the power grid under the states of balanced, slightly high, low and very low power grid energy, and the control method utilizes the dynamic energy of the boiler, so that the fluctuation range of the main steam pressure of the supercritical once-through boiler is greatly reduced.
(1) The service life of the once-through boiler can be prolonged by the coordinated control method of the once-through boiler, the steam turbine and the power grid. The direct flow boiler has the advantages that the energy utilization of the boiler is more reasonable due to the direct flow frequency modulation strategy, the pressure and temperature fluctuation of the boiler in the running process is reduced, and the service life loss of a water-cooled wall and a superheater of the direct flow boiler is reduced, so that the service life of the boiler is prolonged. By adopting a coordinated control method of a once-through boiler, a steam turbine and a power grid, the service life of the water-cooled wall is prolonged by 7.19%, and the service life of the superheater is prolonged by 3.85%.
(2) The coordinated control method of the once-through boiler, the steam turbine and the power grid increases the frequency modulation capability of the power system. On the basis of a power system frequency modulation model containing different types of units, the supercritical unit accounts for 20%, other various units account for 20%, and 1-day actual load is used as input: during the climbing period, CPS1 is lifted from 2.77 to 2.91; during a stationary period, CPS1 is lifted from 2.86 to 2.96; CPS1 is promoted from 2.78 to 2.86 as calculated for the day-wide data. The control performance is improved better. The SCPS1 of the supercritical unit is improved from 1.74 to 2.09, which is beneficial to unit assessment.
(3) The coordinated control method of the once-through boiler, the steam turbine and the power grid cannot generate great influence on the power flow. The line power flow variation is related to the variation of the injected power of the nodes at the first end and the last end, and is related to the topological structure of the nodes. And under the per unit value, the difference value of the injected power increment of the head node and the tail node is basically equivalent to the line power flow variation. When conservative estimation is carried out, when the direct current boiler, the steam turbine and the power grid coordinate control method is within 2% of the variable of the power, the line tide variation is within 2%.
Drawings
FIG. 1 is a schematic diagram of a modified power command method;
FIG. 2 is a plot of corrected primary modulation inequalities;
FIG. 3 is a graph of grid 1000s frequency data under variable load;
FIG. 4 is a diagram showing the effect of the coordination of the once-through boiler, the steam turbine and the power grid on the regulation of power and main steam pressure in the state of energy balance of the power grid;
FIG. 5 is a diagram showing the effect of coordinating the DC boiler, the steam turbine and the power grid on the adjustment of power and main steam pressure in the state of low power grid energy;
FIG. 6 is a diagram showing the effect of regulating power and main steam pressure by coordinating a once-through boiler, a steam turbine and a power grid under the condition of very low power grid energy.
Detailed Description
The first embodiment is as follows: a coordinated control method for a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis comprises the following steps:
the method comprises the following steps: analyzing the energy state of the once-through boiler to determine the energy state of the once-through boiler;
step two: analyzing the energy state of the power grid to determine the energy state of the power grid;
step three: and determining a grid source energy coordination control strategy according to the energy state of the once-through boiler determined in the step one and the energy state of the power grid determined in the step two.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the determining of the input variables and the output variables of the controller in the first step is specifically as follows:
the main steam pressure and the energy form a better linear relation, and the main steam pressure can be used for reflecting the dynamic energy of the boiler. In actual operation, the boiler energy at each moment can be known only by knowing the conversion coefficient between the two. The conversion coefficient is obtained at one time by installing a sensor at a relevant position in the debugging stage of the once-through boiler.
The energy state of the once-through boiler is defined according to the high and low main steam pressure of the once-through boiler, and is shown in the table 1. The upper limit of the primary frequency adjustment is typically 3.5% of the rated power, thus defining Δ PtMIs the main steam pressure difference which is suffered in the time corresponding to 3.5 percent of rated power.
TABLE 1 once-through boiler energy State
When-0.1 MPa is less than or equal to delta PtMWhen the pressure is less than or equal to 0.1MPa, the energy of the boiler is basically balanced, the energy state of the once-through boiler is defined as balance, and the delta PtMThe pressure difference of the main steam received by the once-through boiler within the time corresponding to 3.5 percent of rated power;
when Δ PtM<When the pressure is 0.1MPa, the energy of the boiler is low, and the energy state of the once-through boiler is defined as shortage;
when Δ PtM>When the pressure is 0.1MPa, the energy of the boiler is excessive, and the energy state of the once-through boiler is defined to be excessive.
Other steps and parameters are the same as those in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the step two of determining the energy state of the power grid specifically comprises the following steps:
the invention determines the energy state of the power grid according to the frequency of the power grid. By combining the actual grid data and analyzing the frequency from the aspect of minute-scale time scale and statistics, the grid frequency fluctuation has the following conclusions (as shown in table 2):
1) in more time (33.2%), Δ f falls in the range of [ -0.01,0.01], and the grid energy is defined as "balanced".
2) Within the excessive half time (51.5%), the delta f exceeds the balance range but does not exceed the frequency modulation dead zone, namely, falls within +/-0.01, 0.0333, and the power grid energy is defined to be slightly high or low at the moment. According to statistics, Δ f is the majority (84.7%) of the intervals [ -0.0333, +0.0333 ].
3) Some time (11.6%), Δ f exceeds the dead zone and falls within the interval [0.033,0.046], defining the grid energy state as "high" or "low" at this time. If the delta f exceeds the dead zone, the duration outside the dead zone is 1min-2min, and the unit is required to change the output force to recover the frequency. According to the statistical result, the time when the deltaf falls in the interval of-0.0466 and +0.0466 is the most (96.3%).
4) In a few times (3.5%), Δ f falls within the range of ± [0.0466,0.0699], defining the grid energy state as "very high" or "very low" at that time. At the moment, the energy imbalance of the power grid is serious, generally occurs under a small-amplitude variable load, and the unit is required to increase the adjustment force to recover the frequency of the power grid. According to the statistical result, the time of the delta f falling in the interval of [ -0.0699, +0.0699] is the most (99.8%).
5) And in a very small time (0.2%), the delta f falls within the range of +/-0.0699, 0.1, and the energy state of the power grid at the moment is defined as extremely low or extremely high. The load variation amplitude is large at this time.
TABLE 2 grid energy State
In the regional power grid CPS standard, the physical meaning of B is the power shortage corresponding to the frequency difference of 0.1Hz, in other words, the current power shortage of the power grid can be calculated according to the magnitude of the frequency difference. The partial power grid work frequency difference coefficient B is determined according to the following method: the highest load per 0.1Hz was estimated at 1.5% annually. The gate of each provincial network scheduling department has different values according to actual conditions, but the value is not less than 1% of the annual expected maximum load/0.1 Hz. Invention B1.5% PyM/0.1Hz, wherein PyMThe highest load (MW) is expected for the year. When no tie line power deviation is taken into account, the local power margin delta PsThe frequency modulation strength should be based on the system power margin (10B) Δ f. When the power headroom of the tie line is taken into account, the power headroom of the local area is delta Ps＝ACE。
According to the above analysis, the grid energy is divided into nine states, balanced, low, high, low, extremely low, and high, as shown.
Other steps and parameters are the same as those in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the specific process for determining the network source energy coordination control strategy in the third step is as follows:
the coordination control strategy is based on the following two methods:
(1) method for correcting power command
The principle of the modified power command method is shown in fig. 1. Outside the dotted line is a power frequency regulating turbine model which consists of a forward channel and two feedback channels of power and frequency. The forward channel comprises four links of PI integration, an actuating mechanism, steam volume and rotor inertia, and specific parameters are shown in Table 3.
Within the dotted line is a new control method, equivalent to the original power set point RtAdding a correction quantity, wherein the correction quantity is given by H(s), and the specific value of H(s) is determined by the energy level of the once-through boiler. PtIs the actual value of the main steam pressure, PtsThe rated value of the main steam pressure is the value of C which is different but constant according to different power grids and direct-current boiler states;
the turbine model parameters are shown in table 3.
(2) Method for correcting primary frequency modulation unequal rate
The method for correcting the given power can realize more power generation when the energy of the boiler is high and less power generation when the energy is low. However, in actual operation, the boiler energy is high and the power grid energy is high, at this time, the supercritical and ultra-supercritical units still need to reduce the load to meet the primary frequency modulation requirement of the power grid, but from the perspective of boiler safety, it is desirable to bear less primary frequency modulation task under this working condition, so that the boiler energy tends to be stable. The adjustment task is mostly undertaken by the units with lower main steam pressure in the system.
TABLE 3 steam turbine model parameters
By using the idea of dynamic primary frequency modulation for reference, the effect of weakening reverse regulation is achieved by changing the gain of the feedback loop, namely, the control channel of the primary frequency modulation is switched, so that the frequency modulation effect of the supercritical and ultra-supercritical units is weakened when the unit operates under the condition. As shown in fig. 2. Wherein the primary frequency-modulated control channel 1 is the original primary frequency-modulated control channel, i.e.
The primary control channel 2 is a channel designed to reduce the effect of the modulation, i.e. a channel designed to reduce the modulation effect
2＞1I.e. when the primary frequency modulation control channel 2 is put into use, the frequency modulation effect is weakened.
Adding a primary frequency modulation control channel, namely the original primary frequency modulation control channel is a primary frequency modulation control channel 1, and the primary frequency modulation unequal rate is1(ii) a The added primary frequency modulation control channel is a primary frequency modulation control channel 2, and the primary frequency modulation unequal rate is2(ii) a Wherein2＞1When the primary frequency modulation control channel 2 is input, the frequency modulation effect is weakened;
by combining the above power grid energy analysis and direct-current boiler energy analysis, the supercritical and ultra-supercritical units should use corresponding control strategies to keep the power grid frequency stable for the nine proposed energy states from the power grid side. From the power supply side, a straightforward control strategy is adopted as much as possible for three energy states of the once-through boiler provided by the table 1 to contribute to the grid frequency modulation, specifically, when the energy of the boiler is excessive, adjustment of a system delta f <0 time period is undertaken more, adjustment of delta f >0 time period is appropriately reduced, and otherwise, the same principle is adopted, so that the goal of network source win-win is achieved.
By combining the two methods, the control strategies of the supercritical and ultra-supercritical units under different power grid and direct current boiler energy states are as follows:
1) when the energy of the power grid is balanced: the power generation and the load of the supercritical and ultra-supercritical units are balanced without adjustment, but the energy of part of the units is excessive and the energy of part of the units is in short supply due to the fluctuation of the heat value of the fire coal of the once-through boiler, so that the energy of the units is recovered and the energy balance of the system is not influenced, the units with excessive energy are allowed to naturally release energy, the units with insufficient energy naturally accumulate energy, and the natural release and the natural accumulation are carried out: c is 0.5, a primary frequency modulation control channel 1 is put into the generator set (the primary frequency modulation control channel 1 does not act when the primary frequency modulation control channel does not exceed the frequency modulation dead zone), and the original generating capacity of the generator set is kept unchanged; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
2) when the grid frequency is slightly high: since the frequency modulation dead zone has not yet been exceeded, the unit must in principle not be adjusted. Because of energy shortage, the power generation of part of once-through boilers can be properly reduced, which is beneficial to frequency recovery and also enables the main steam pressure of the boilers to be recovered, and beneficial influence is generated on the service life of the boilers, the control strategy of the once-through boilers with energy shortage is accelerated accumulation, when the accelerated accumulation is C-1, a primary frequency modulation control channel 1 is put into use (the frequency modulation dead zone is not exceeded, the primary frequency modulation control channel 1 does not act); the accelerated release is also possible. Putting the units with surplus energy and the units with balanced energy into a primary frequency modulation control channel 1, wherein C is 0;
3) when the grid frequency is low slightly: the control strategy of the once-through boiler with excess energy is accelerated release, and during the accelerated release: c is 1, and a primary frequency modulation control channel 1 is input; the unit with energy shortage and the unit with energy balance are put into a primary frequency modulation control channel 1, and C is 0;
4) when the energy of the power grid is high: the frequency difference exceeds the frequency modulation dead zone, but the power excess of the power grid does not exceed 0.69 percent PyMAnd the primary frequency modulation of the unit is required to act to reduce the generated energy. Part of the direct current boiler is short of energy, can provide more negative energy for the power grid, can adjust frequency according to the boiler except for normal one-time frequencyThe generated energy is properly reduced by the main steam pressure of the furnace, the main steam pressure contributes to primary frequency modulation, the recovery of the main steam pressure is facilitated, the accelerated accumulation and the primary frequency modulation are defined, at the moment, C is 1, and a primary frequency modulation control channel 1 is put into the furnace. And also has partial energy balance of the once-through boiler, and the control strategy is defined as primary frequency modulation, at the moment: and a primary frequency modulation control channel 1 is input, and C is equal to 0. And part of the energy of the direct current boiler is excessive and conflicts with the energy of the power grid. Therefore, the power surplus of the power grid does not exceed 0.69 percent PyMAnd properly weakening the primary frequency modulation regulation effect can not bring negative effects on the frequency modulation of the power grid, and is beneficial to the recovery of the energy state of the boiler, and the control strategy is defined as properly weakening the primary frequency modulation, at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. half of the original regulating effect. The same reason that the energy of the power grid is lower.
The control strategies of the direct-flow boiler with energy shortage are accelerated accumulation and primary frequency modulation, at the moment, C is 1, and a primary frequency modulation control channel 1 is put into; the control strategy of the once-through boiler with excessive energy is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
5) when the energy of the power grid is low: the control strategies of the once-through boiler with the surplus energy are accelerated release and primary frequency modulation, wherein C is 1, and a primary frequency modulation control channel 1 is put into; the control strategy of the once-through boiler with energy shortage is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
6) when the power grid energy is very high: at the moment, the power of the power grid is seriously unbalanced, and the power excess does not exceed 1.05 percent PyM. The control strategy for the once-through boiler with energy shortage is fast accumulation and primary frequency modulation, at this time: c is 2, and a primary frequency modulation control channel 1 is input; the control strategy of the once-through boiler with excessive energy is that the primary frequency modulation is properly weakened, and at the moment: c is 0, and the mixture is added onceThe frequency modulation control channel 2 changes the unit primary frequency modulation unequal rate into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0; because the system is generally provided with a water turbine, a steam drum boiler type unit set and a pumped storage power station in a certain proportion, the response speed and the heat storage capacity of the unit set have better response to the variable load of the system, and a small part of supercritical and ultra-supercritical unit sets weaken primary frequency modulation and cannot generate adverse effect on the frequency modulation of the system. Principle of low power grid energy
7) When the power grid energy is very low: the control strategy of the once-through boiler with the surplus energy is quick release and primary frequency modulation, and at the moment: c is 2, and a primary frequency modulation control channel 1 is input; the control strategy of the once-through boiler with energy shortage is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
8) when the energy of the power grid is extremely high: at the moment, large disturbance occurs, and the primary task is to ensure the frequency stability of the power grid within a few minutes after the disturbance. All the units are put into primary frequency modulation, namely, the primary frequency modulation control channel 1 is put into. The control strategy of the once-through boiler with energy shortage is rapid accumulation and primary frequency modulation, namely C is 2, and the once-through frequency modulation control channel 1 is put into; putting the energy-balanced unit and the energy-excessive unit into a primary frequency modulation control channel 1, wherein C is 0;
9) when the energy of the power grid is extremely low: the control strategy of the once-through boiler with the surplus energy is quick release and primary frequency modulation, namely C is 2, and the once-through boiler is put into a primary frequency modulation control channel 1; and (3) putting the energy-balanced unit and the energy-deficient unit into a primary frequency modulation control channel 1, wherein C is 0.
The control strategy of the supercritical and ultra-supercritical unit set in each grid and source energy state is shown in table 4, and the specific operation is shown in table 5.
TABLE 4 Unit control strategy under each network and source energy state
TABLE 5 specific operation of the unit control strategy in each grid and source energy state
Other steps and parameters are the same as those in one of the first to third embodiments.
The first embodiment is as follows:
in order to verify the effectiveness of the proposed furnace-machine-grid coordination control method, the influence of the furnace-machine-grid coordination control method on the boiler and the power grid is verified relative to the original control method according to the 1000s frequency data of a certain power grid under large load change. Specifically, under the conditions of energy balance, slight height, low and very low of a power grid, the front main steam pressure and the rear main steam pressure are input and compared with the furnace-machine-grid coordination control. The rated main steam pressure is 24.2MPa, the reference value of the frequency difference is 50Hz,2＝21. The time period frequency is shown in fig. 3.
In order to explain the control function of the control method in different power grid energy states and unit energy states, the power grid states selected in this embodiment include: energy balance (80s-130s), slightly high grid energy (130s-160s), low grid energy (320s-360s) and very low grid energy (200s-240 s). The active power and the main steam pressure of the unit are compared under the furnace-machine-network coordination control method and the traditional primary frequency modulation control method respectively.
When the power grid energy is balanced. According to the control strategy, the supercritical thermal power generating unit with the surplus energy can naturally release energy, and the supercritical thermal power generating unit with the shortage energy can naturally accumulate energy. The unit naturally accumulates energy due to energy shortage, the pressure fluctuation of main steam is reduced by 0.1MPa, and the recovery effect is good; the generated energy is reduced by about 0.004p.u. compared with the original control mode, and is in an acceptable range. As shown by the curve 80s-130s in fig. 4. When the power of the power grid is slightly high. According to the control strategy, the unit with energy shortage accelerates the accumulated energy, and other units keep the original generating capacity. The energy of the unit is short, so the energy accumulation is accelerated, the main steam pressure is recovered better, the power generation is reduced by about 0.008p.u. compared with the original control mode, and the power generation is also in an acceptable range. As shown by the 130s-160s curve in fig. 4.
When the grid energy is low. According to the control strategy, the unit with excess energy can accelerate the release of energy except for normal one-time frequency modulation. The energy of the unit is excessive, so that the energy is released in an accelerated manner, the fluctuation of the main steam pressure is reduced by 0.1MPa, and the generated energy is increased by about 0.011p.u. As shown by the curve 320s-360s in fig. 5.
When the grid energy is low. According to the control strategy, the unit with the surplus energy can quickly release energy except for normal primary frequency modulation. The energy of the unit is excessive, so the unit can be released quickly, the pressure fluctuation of the main steam is reduced by 0.2MPa, and the generated energy is increased by about 0.020p.u. As shown by the 200s-240s curve in fig. 6.
By synthesizing the simulation results, the furnace-machine-network coordination control method has good influence on the frequency of the power grid in the states of balanced, slightly high, low and very low power grid energy, and the control method utilizes the dynamic energy of the boiler to greatly reduce the fluctuation range of the main steam pressure of the supercritical once-through boiler.
Claims (1)
1. A coordinated control method of a once-through boiler, a steam turbine and a power grid for primary frequency modulation analysis comprises the following steps:
the method comprises the following steps: analyzing the energy state of the once-through boiler to determine the energy state of the once-through boiler;
step two: analyzing the energy state of the power grid to determine the energy state of the power grid;
step three: determining a grid source energy coordination control strategy according to the energy state of the once-through boiler determined in the step one and the energy state of the power grid determined in the step two;
the determining of the input variables and the output variables of the controller in the first step is specifically as follows:
when-0.1 MPa is less than or equal to delta PtMWhen the pressure is less than or equal to 0.1MPa, the energy state of the once-through boiler is defined as balance, and the delta PtMMain steam pressure of the once-through boiler in the time corresponding to 3.5% of rated powerForce difference;
when Δ PtM<-0.1MPa, defining the once-through boiler energy status as shortage;
when Δ PtM>When the pressure is 0.1MPa, the energy state of the once-through boiler is defined to be surplus;
the step two of determining the energy state of the power grid specifically comprises the following steps:
when delta f is less than or equal to 0.01 and less than or equal to 0.01, the power grid energy is defined as balance, and the delta f is the difference value between the power grid frequency and the rated power grid frequency;
when-0.033 is less than or equal to Δ f < 0.01, the power grid energy is defined as a tiny low;
when the delta f is more than or equal to 0.01 and less than or equal to 0.033, the energy of the power grid is defined as height;
when the delta f is less than or equal to-0.046 and less than-0.033, the power grid energy is defined to be lower;
when the delta f is less than or equal to 0.033 and less than or equal to 0.046, the power grid energy is defined to be high;
when the delta f is less than or equal to-0.0699 and less than-0.046, the power grid energy is defined as very low;
when the delta f is less than or equal to 0.046 and less than or equal to 0.0699, the power grid energy is defined to be very high;
when the delta f is less than or equal to-0.1 and less than or equal to-0.0699, the power grid energy is defined as extremely low;
when delta f is more than or equal to 0.0699 and less than or equal to 0.1, the power grid energy is defined to be extremely high;
the method is characterized in that the specific process of determining the network source energy coordination control strategy in the third step is as follows:
the coordination control strategy is based on the following two methods:
(1) method for correcting power command
At given power value R of turbinetAdding a correction quantity given by H(s), PtIs the actual value of the main steam pressure, PtsIs the main steam pressure rating, C is a constant;
(2) method for correcting primary frequency modulation unequal rate
Adding a primary frequency modulation control switchThe channel, namely the original primary frequency modulation control channel is a primary frequency modulation control channel 1, and the primary frequency modulation unequal rate is1(ii) a The added primary frequency modulation control channel is a primary frequency modulation control channel 2, and the primary frequency modulation unequal rate is2(ii) a Wherein2＞1When the primary frequency modulation control channel 2 is input, the frequency modulation effect is weakened;
by combining the two methods, the control strategies of the supercritical and ultra-supercritical units under different power grid and direct current boiler energy states are as follows:
1) when the energy of the power grid is balanced: the power generation power and the load of the supercritical and ultra-supercritical units are balanced without adjustment, the units with excess energy are allowed to naturally release energy, the units with shortage of energy naturally accumulate energy, and during natural release and natural accumulation: c is 0.5, a primary frequency modulation control channel 1 is put into the power generating unit to keep the original power generating capacity of the power generating unit unchanged; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
2) when the grid frequency is slightly high: the control strategy of the once-through boiler with energy shortage is accelerated accumulation, and when the accumulation is accelerated: c is 1, and a primary frequency modulation control channel 1 is input; putting the units with surplus energy and the units with balanced energy into a primary frequency modulation control channel 1, wherein C is 0;
3) when the grid frequency is low slightly: the control strategy of the once-through boiler with excess energy is accelerated release, and during the accelerated release: c is 1, and a primary frequency modulation control channel 1 is input; the unit with energy shortage and the unit with energy balance are put into a primary frequency modulation control channel 1, and C is 0;
4) when the energy of the power grid is high: the control strategies of the direct-flow boiler with energy shortage are accelerated accumulation and primary frequency modulation, at the moment, C is 1, and a primary frequency modulation control channel 1 is put into; the control strategy of the once-through boiler with excessive energy is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
5) when the energy of the power grid is low: the control strategies of the once-through boiler with the surplus energy are accelerated release and primary frequency modulation, wherein C is 1, and a primary frequency modulation control channel 1 is put into; at the end of energy shortageThe control strategy for the flow boiler is such that the primary frequency modulation is properly attenuated, at which time: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
6) when the power grid energy is very high: the control strategy for the once-through boiler with energy shortage is fast accumulation and primary frequency modulation, at this time: c is 2, and a primary frequency modulation control channel 1 is input; the control strategy of the once-through boiler with excessive energy is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
7) when the power grid energy is very low: the control strategy of the once-through boiler with the surplus energy is quick release and primary frequency modulation, and at the moment: c is 2, and a primary frequency modulation control channel 1 is input; the control strategy of the once-through boiler with energy shortage is that the primary frequency modulation is properly weakened, and at the moment: c is equal to 0, a primary frequency modulation control channel 2 is put in, and the primary frequency modulation unequal rate of the unit is changed into2I.e. the regulation is weakened; the energy balance unit is put into a primary frequency modulation control channel 1, and C is 0;
8) when the energy of the power grid is extremely high: the control strategy of the once-through boiler with energy shortage is rapid accumulation and primary frequency modulation, namely C is 2, and the once-through frequency modulation control channel 1 is put into; putting the energy-balanced unit and the energy-excessive unit into a primary frequency modulation control channel 1, wherein C is 0;
9) when the energy of the power grid is extremely low: the control strategy of the once-through boiler with the surplus energy is quick release and primary frequency modulation, namely C is 2, and the once-through boiler is put into a primary frequency modulation control channel 1; and (3) putting the energy-balanced unit and the energy-deficient unit into a primary frequency modulation control channel 1, wherein C is 0.
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