Method for controlling coal feed quantity of coal-fired power generating unit based on direct balance

Abstract

The invention discloses a coal-fired power generation unit coal feed quantity control method based on direct # imgabs0 # balance, which comprises the following steps: firstly, calculating # imgabs1 # flow carried by working media at an inlet and an outlet of a boiler system by using cleaned data, and further obtaining net output working media # imgabs2 # flow of the boiler system; and respectively calculating the storage # imgabs3 quantity of each device of the boiler system and the steam turbine system to obtain the total storage # imgabs4 change rate of the boiler system and the steam turbine system. And then, calculating the # imgabs5 demand of the steam turbine system and the # imgabs6 output of the boiler system, and controlling the coal feeding amount by using the deviation between the # imgabs7 demand of the steam turbine system and the # imgabs8 output of the boiler system to form a coal feeding amount control instruction. According to the method, the control effect of the key thermal parameters of the coal-fired power generation unit can be greatly improved, and the operation flexibility of the coal-fired power generation unit can be remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal power system control optimization, and specifically relates to a method based on direct Balanced coal feed control method for coal-fired power generation units. Background Art

[0002] The world's energy structure continues to develop and transform in the direction of clean, low-carbon, efficient and diversified development. However, due to the strong time-varying characteristics of renewable energy such as wind energy and solar energy, it is difficult to absorb renewable energy power generation, and the problems of wind and solar power abandonment are serious. Improving the operating flexibility of conventional coal-fired power generation units and providing absorption services for renewable energy power generation are important technical directions. Coal-fired power generation will shift from the main energy source to the basic energy source, and the load variation amplitude and load variation frequency of coal-fired power generation units will gradually increase. Therefore, the thermal power system will be in a transient condition with frequent load changes for a long time, and the requirements for its rapid load change capability are getting higher and higher. The control strategy based on direct energy balance is the core of the existing control system of coal-fired power generation units. The core idea is to maintain a balance between the energy required by the turbine system and the energy provided by the boiler system. However, the same energy flow may have different fluctuations with temperature parameters. The energy balance cannot directly represent the balance of the working capacity of the working fluid. This problem is particularly obvious when the load fluctuates rapidly, which often makes it difficult to balance the control effect of the unit power, main steam pressure and steam temperature, limiting the improvement of the unit's flexibility. How to directly control a parameter that directly and accurately represents the balance of the working capacity of the working fluid is an important part of the optimization of the coordinated control system of the boiler and the coal-fired power generation unit. Summary of the invention

[0003] In order to overcome the problems of the above-mentioned prior art, the purpose of the present invention is to provide a A balanced coal-fired power generation unit coal feed control method using direct The balance replaces the original direct energy balance to control the coal supply, and better maintains the working capacity balance between the boiler system and the turbine system. Output Signals and Steam Turbine Systems Demand signal, taking into account the requirements of the steam turbine system Flow and boiler system actually provide The deviation between the flows and the thermal system itself By controlling the chemical composition of the fuel input to the boiler system Flow, timely replenish the boiler system storage To achieve accurate Balance, and finally achieve the purpose of accurately regulating the coal feeding amount of a coal-fired power generation unit during rapid load changes. The present invention can greatly improve the control effects of the unit power, main steam pressure, main steam and reheat steam temperature during the rapid load change process of the coal-fired unit.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A coal feeding amount control method for a coal-fired power generation unit based on direct balance, the coal feeding amount control signal is calculated from the deviation between the output of the boiler system and the demand of the steam turbine system ;

[0006] The calculation formula for the coal feeding amount control instruction is:

[0007] m coal = f PID (EX t - EX b ) + m coal,ff

[0008] In the formula: m coal is the coal feeding amount control instruction, kg / s; f PID is a PID controller based on the deviation between the demand of the steam turbine and the output of the boiler system ; EX t is the demand of the steam turbine system ; EX b is the output of the boiler system ; m coal,ff is the feedforward instruction of the coal feeding amount of the boiler system, kg / s;

[0009] Among them, the output of the boiler system uses the net output working fluid flow of the boiler system and the total storage change rate of the boiler system for calculation:

[0010]

[0011] In the formula: is the net output working fluid flow of the boiler system, MW; is the total storage change rate of the boiler system, MW;

[0012] The demand of the steam turbine system uses the set value of the net output working fluid flow of the boiler system and the total storage change rate of the steam turbine system for calculation:

[0013]

[0014] In the formula: is the net output working fluid flow rate of the boiler system, MW; flow set value, MW; is the total storage change rate of the steam turbine system, MW. change rate, MW.

[0015] Regarding the net output working fluid flow rate of the boiler system flow The specific calculation method is as follows:

[0016] Subtract the total output working fluid flow rate of the boiler system flow from the total input working fluid flow to obtain the net output working fluid flow rate of the boiler system flow:

[0017]

[0018] In the formula: is the total output working fluid flow rate of the boiler system, MW; flow, MW; is the total input working fluid flow rate of the boiler system flow, MW;

[0019] Among them, the output working fluid flow rate of the boiler system flow includes m working fluid flow rates leaving the boiler system flow, and for each working fluid flow rate leaving the boiler system, the flow and the total output working fluid flow rate of the boiler system flow calculation formulas are as follows:

[0020]

[0021] In the formula: is the flow rate carried by the i-th working fluid flow rate leaving the boiler system, MW; m flow, MW; m out,i is the mass flow rate of the i-th working fluid leaving the boiler system, kg / s; h out,i is the enthalpy value of the i-th working fluid leaving the boiler system, kJ / kg; s out,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K); h 0 is the environmental reference enthalpy value, kJ / kg; s 0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K; where i = 1 to m;

[0022] The input working fluid flow rate of the boiler system flow includes m working fluid flow rates entering the boiler system flow, where each item of the working fluid entering the boiler system flow and the total input working fluid of the boiler system The calculation formula for the flow is as follows:

[0023]

[0024] In the formula: is the flow carried by the i-th working fluid flow entering the boiler system, MW; m in,i is the mass flow rate of the i-th working fluid entering the boiler system, kg / s; h in,i is the enthalpy value of the i-th working fluid entering the boiler system, kJ / kg; s in,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K); where i = 1 to m.

[0025] The specific determination methods for the mass flow rate of the working fluid entering the boiler system and the mass flow rate of the working fluid leaving the boiler system are as follows:

[0026] The mass flow rate of the working fluid entering the boiler system includes the feed water flow rate and the cold reheat steam flow rate, and the mass flow rate of the working fluid leaving the boiler system includes the main steam flow rate and the hot reheat steam flow rate, where the cold reheat steam flow rate is equal to the hot reheat steam flow rate; preferably, the working fluid flow rate collected and calculated by the coal-fired power generation unit itself is used, and for the working fluid flow rate that cannot be directly collected from the unit, the Flügel formula is used for calculation; where if the feed water flow rate cannot be obtained from the coal-fired power generation unit, the feed water flow rate is regarded as the same as the main steam flow rate;

[0027] Among them, the main steam flow rate is calculated using the regulating stage pressure, temperature, and the pressure of the high-pressure cylinder exhaust steam:

[0028]

[0029] m in,1 = m fw = m ls

[0030] In the formula: m out,1 and m in,1 are respectively the mass flow rates of the working fluid leaving and entering the boiler system for the first one, kg / s; m ls and m ls0 are respectively the real-time main steam flow rate and the main steam flow rate under the design condition, kg / s; p tj and p tj0 are respectively the real-time regulating stage pressure and the regulating stage pressure under the design condition; p ehp and p ehp0 are respectively the real-time high-pressure cylinder exhaust steam pressure and the high-pressure cylinder exhaust steam pressure under the design condition; T tj and Ttj0 are the real-time regulating stage pressure and the regulating stage temperature under design conditions, in °C; m fw is the feed water flow rate of the unit, in kg / s;

[0031] The reheated steam flow rate, that is, the mass flow rate of the working fluid entering and leaving the boiler system at the i-th, is calculated using the pressure, temperature of the working fluid leaving the boiler system at the i-th, and the second-stage extraction steam pressure after the working fluid returns to the steam turbine:

[0032]

[0033] In the formula: m out,i and m out,i0 are respectively the real-time mass flow rate and the mass flow rate under design conditions of the working fluid leaving the boiler system at the i-th, in kg / s; m in,i is the real-time mass flow rate of the working fluid entering the boiler system at the i-th, in kg / s; p out,i and p out,i0 are respectively the real-time pressure and the pressure under design conditions of the working fluid leaving the boiler system at the i-th; p out,i+2 and p out,(i+2)0 are respectively the real-time pressure and the pressure under design conditions of the second-stage extraction steam after the working fluid leaving the boiler system at the i-th enters the steam turbine; T out,i0 and T out,i are respectively the real-time pressure and the temperature under design conditions of the working fluid leaving the boiler system at the i-th, in °C, where i = 2 to m;

[0034] Through the above calculations, the mass flow rate m out,i of the working fluid leaving the boiler system and the mass flow rate m in,i of the working fluid entering the boiler system are all calculated.

[0035] Regarding the total storage change rate of the boiler system, the specific calculation method is as follows:

[0036] The total storage change rate calculation formula of the boiler system is:

[0037]

[0038] In the formula: E x,B is the total storage of the boiler system, in MJ;

[0039] Among them, the total storage of the boiler system is the sum of the working fluid storage and the metal storage inside the boiler system, and the specific calculation formula is:

[0040] E x,B= ΣE x-b,j = ∑(E x-wfb,j + E x-mb,j )

[0041] E x-wfb,j = ∑m wfb,j [u wfb,j - u 0 - T 0 (s wfb,j - s 0 )]

[0042]

[0043] Where: E x-b,j is the storage of the j-th equipment in the boiler system, x-wfb,j MJ; E is the working medium storage x-mb,j of the j-th equipment inside the boiler system, MJ; E wfb,j is the mass of the working medium stored in the j-th equipment inside the boiler system, kg; u wfb,j is the thermodynamic energy of the working medium stored in the j-th equipment inside the boiler system, kJ / kg; s wfb,j is the entropy value of the working medium stored in the j-th equipment inside the boiler system, kJ / (kg·K); c p,m is the specific heat capacity of the metal, kJ / (kg·K); m mb,j is the mass of the metal of the j-th equipment inside the boiler system, kg; T mb,j is the average temperature of the metal of the j-th equipment inside the boiler system, K; s 0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K; u 0 is the environmental reference thermodynamic energy, kJ / kg.

[0044] Regarding the specific method for calculating the mass of the working medium stored in the j-th equipment inside the boiler system and the storage of the working medium is as follows:

[0045] According to the structural parameters, determine the working medium volume V b,j and the metal mass m b,j of the H heat exchange equipment in the boiler system, j = 1 to H;

[0046] The storage of the working medium inside the equipment in the boiler system is mainly divided into two types. One is that the internal working medium is single-phase, and the other is that the internal working medium is two-phase. The mass calculation of the single-phase working medium inside the equipment adopts the following formula:

[0047] m wfbd,j = ρwfbd,j V b,j

[0048] Where: ρ wfbd,j is the average density of the internal working fluid of the j-th equipment in the boiler system, which is obtained by means of the temperature and pressure of the internal working fluid of the j-th equipment in the boiler system with the help of thermophysical functions. If there are no measuring points for the temperature and pressure of the working fluid inside the j-th equipment, the average value of the densities of the working fluid at the inlet and outlet of the j-th equipment is used, kg / m 3 ; V b,j is the volume inside the j-th equipment in the boiler system, m 3 ;

[0049] For the mass calculation of the two-phase working fluid inside the equipment, the relationship between the equipment liquid level and the working fluid volume is used, and the following formula is adopted to calculate the mass of the working fluid in different phases:

[0050] V wb,j = f (h-v)b,j (h wb,j )

[0051] V sb,j = V b,j - V wb,j

[0052] m wb,j = ρ wb,j V wb,j

[0053] m sb,j = ρ sb,j V sb,j

[0054] Where: V wb,j and V sb,j are the volumes of the liquid working fluid and the vapor working fluid inside the j-th equipment in the boiler system respectively, m 3 ; h wb,j is the internal liquid level of the j-th equipment in the boiler system, m; f (h - v) bj is the functional relationship between the internal liquid level of the j-th equipment in the boiler system and the volume of the liquid working fluid, which is related to the specific structure of the j-th equipment; m wb,j and m sb,j are the masses of the liquid working fluid and the vapor working fluid inside the j-th equipment in the boiler system respectively, kg; ρ wb,j and ρ sb,j are the densities of the liquid working fluid and the vapor working fluid inside the j-th equipment in the boiler system respectively, which can be obtained according to the temperature or pressure of the internal working fluid of the j-th equipment in the boiler system with the help of thermophysical functions, kg / m 3 ;

[0055] Therefore, the mass of the working fluid stored in the j-th device inside the boiler system is:

[0056] When the internal working fluid is single-phase, the calculation formula for the mass of the working fluid is m wfb,j = m wfbd,j , and at this time, the stored of the working fluid in each device inside the boiler system is calculated as:

[0057] E x-wfb,j = m wfbd,j [u wfbd,j - u 0 - T 0 (s wfbd,j - s 0 )]

[0058] Where: u wfbd,j is the internal energy of the single-phase working fluid in the j-th device of the boiler system, kJ / kg; s wfbd,j is the specific entropy of the single-phase working fluid in the j-th device of the boiler system, kJ / (kg·K);

[0059] When the internal working fluid is two-phase, the mass of the liquid working fluid m wfb,j = m wb,j , and the mass of the vapor working fluid m wfb,j = m sb,j . At this time, when calculating the stored of the working fluid in each device inside the boiler system, the stored of the liquid working fluid and the vapor working fluid need to be added together, that is

[0060] E x-wfb,j = m wb,j [u wb,j - u 0 - T 0 (s wb,j - s 0 )] + m sb,j [u sb,j - u 0 - T 0 (s sb,j - s 0 )]

[0061] Where: u wb,j and u sb,j are the internal energies of the liquid working fluid and the vapor working fluid in the j-th device of the boiler system, respectively, kJ / kg; s wb,j and s sb,j are the specific entropies of the liquid working fluid and the vapor working fluid in the j-th device of the boiler system, respectively, kJ / (kg·K).

[0062] Regarding the set value of the net output working fluid flow rate of the boiler system The specific calculation method is as follows:

[0063] When the coal-fired power generation unit operates in a steady state condition, the net output working fluid flow of the boiler system at this time is used as the set value of the net output working fluid flow of the boiler system in the control system, and the calculation formula is: is used as the set value of the net output working fluid flow of the boiler system in the control system, and the calculation formula is:

[0064]

[0065] In the formula: is the total output working fluid flow of the boiler system during the steady-state operation of the coal-fired power generation unit flow, MW; is the total input working fluid flow of the boiler system during the steady-state operation of the coal-fired power generation unit flow, MW;

[0066] The calculation formula for the total output working fluid flow of the boiler system during the steady-state operation of the coal-fired power generation unit is as follows:

[0067]

[0068] In the formula: is the flow carried by the i-th working fluid flow leaving the boiler system flow, MW; m out,i is the mass flow rate of the i-th working fluid leaving the boiler system, kg / s; h out,i is the enthalpy value of the i-th working fluid leaving the boiler system, kJ / kg; s out,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K); h 0 is the environmental reference enthalpy value, kJ / kg; s 0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K;

[0069] The calculation formula for the total input working fluid flow of the boiler system during the steady-state operation of the coal-fired power generation unit is as follows:

[0070]

[0071] In the formula: is the flow carried by the i-th working fluid flow entering the boiler system flow, MW; m in,i is the mass flow rate of the i-th working fluid entering the boiler system, kg / s; h in,i is the enthalpy value of the i-th working fluid entering the boiler system, kJ / kg; s in,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K);

[0072] The set values of the net output working medium flow rate of the boiler system under steady-state conditions of coal-fired power generation units corresponding to different unit loads are fitted with the unit loads to obtain a curve of the set values of the net output working medium flow rate of the boiler system corresponding to different unit loads: The set values of the net output working medium flow rate of the boiler system under steady-state conditions of coal-fired power generation units corresponding to different unit loads are fitted with the unit loads to obtain a curve of the set values of the net output working medium flow rate of the boiler system corresponding to different unit loads: Flow rate setting value curve:

[0073]

[0074] In the formula: LDC is the load command of the coal-fired power generation unit.

[0075] Regarding the total storage Rate of change The specific calculation method is as follows:

[0076] Total storage of the steam turbine system The calculation formula for the rate of change is:

[0077]

[0078] In the formula: E x,T Is the total storage of the steam turbine system , MJ;

[0079] Among them, the total storage of the steam turbine system Includes the working medium storage And metal storage The sum of them, and the specific calculation formula is:

[0080] E x,T = ∑E x-t,k = Σ(E x-wft,k + E x-mt,k )

[0081] E x-wft,k = Σm wft,k [u wft,k - u 0 - T 0 (s wft,k - s 0 )]

[0082]

[0083] In the formula: E x-t,k Is the storage of the kth stage regenerative heater inside the steam turbine system MJ; E x-wft,k Is the working medium storage of the kth stage regenerative heater inside the steam turbine system MJ; E x-mt,k Is the metal storage of the kth stage regenerative heater inside the steam turbine system MJ; m wft,k$m$ is the mass of the working fluid stored in the $k$-th regenerative heater inside the steam turbine system, kg; $u$ wft,k $u$ is the thermodynamic energy of the working fluid stored in the $k$-th regenerative heater inside the steam turbine system, kJ / kg; $s$ wft,k $s$ is the entropy value of the working fluid stored in the $k$-th regenerative heater inside the steam turbine system, kJ / (kg·K); $c$ p,m $c$ is the specific heat capacity of the metal, kJ / (kg·K); $m$ mt,k $m$ is the equivalent metal mass participating in heat transfer in the $k$-th regenerative heater of the steam turbine system, kg; $T$ mt,k $T$ is the average metal temperature of the $k$-th regenerative heater inside the steam turbine system. When there is no measurement data, the average temperature of the working fluid on the feed water side and the extraction steam side of the $k$-th regenerative heater inside the steam turbine system is used as a substitute, K; $s$ 0 $s$ is the environmental reference entropy value, kJ / (kg·K); $T$ 0 $T$ is the environmental reference temperature, K; $u$ 0 $u$ is the environmental reference thermodynamic energy, kJ / kg.

[0084] Regarding the specific method for calculating the mass of the working fluid stored in each regenerative heater of the steam turbine system and the storage of the working fluid is as follows:

[0085] Determine the volume $V$ of the working fluid in the $Z$ regenerative heaters of the steam turbine system t,k and the metal mass $m$ t,k , $k = 1$ to $Z$;

[0086] There are two types of working fluids inside the regenerative heater, namely the feed water side and the working fluid side. The calculation formula for the mass of the working fluid stored on the feed water side is:

[0087] $m$ fwt,k $=$ $\rho$ fwt,k $V$ t,k

[0088] In the formula: $m$ fwt,k is the mass of the working fluid stored on the feed water side inside the $k$-th regenerative heater of the steam turbine system, kg; $\rho$ fwt,k is the density of the working fluid stored on the feed water side inside the $k$-th regenerative heater of the steam turbine system. The average value of the densities of the working fluid at the inlet and outlet of the $k$-th regenerative heater of the steam turbine system is used, kg / m 3 ; $V$ fwt,k is the volume of the working fluid stored on the feed water side of the $k$-th regenerative heater of the steam turbine system, m 3 ;

[0089] Both the liquid working fluid and the vapor working fluid are contained in the extraction steam side of the regenerative heater. Therefore, it is necessary to calculate the mass of the liquid working fluid and the mass of the vapor working fluid separately by means of the internal water level information of each regenerative heater:

[0090] $V$dwt,k = f (h-v)tk (h wt,k )

[0091] V set,k = V t,k - V dwt,k

[0092] m dwt,k = ρ dwt,k V dwt,k

[0093] m set,k = ρ set,k V set,k

[0094] Where: V dwt,k and V set,k are the volumes of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater in the steam turbine system, m 3 ; h wt,k is the internal liquid level on the extraction side of the k-th regenerative heater in the steam turbine system, m; f (h-v)tk is the functional relationship between the internal liquid level and the volume of the liquid working medium on the extraction side of the k-th regenerative heater in the steam turbine system, and is related to the specific structure of the extraction side of the k-th regenerative heater; m dwt,k and m set,k are the masses of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater in the steam turbine system, kg; ρ dwt,k and ρ set,k are the average densities of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater in the steam turbine system, which can be obtained by means of a thermophysical property function according to the temperature or pressure of the internal working medium on the extraction side of the k-th regenerative heater in the steam turbine system, kg / m 3 ;

[0095] Therefore, the mass of the working medium stored in the k-th regenerative heater inside the steam turbine system is:

[0096] When calculating the internal working medium on the feed water side, the calculation formula for the mass of the working medium is m wft,k = m fwt,k ;

[0097] When calculating the internal working medium on the extraction side, the mass of the liquid working medium is m wft,k = m dwt,k , and the mass of the vapor working medium is m wft,k = m set,k , and at this time, when calculating the storage of the working medium in each device inside the steam turbine system the storage of the liquid working medium and the vapor working medium needs to be added , that is

[0098] Ex-wft,k = m fwt,k [u fwt,k - u 0 - T 0 (s fwt,k - s 0 ) + m dwt,k [u dwt,k - u 0 - T 0 (s dwt,k - s 0 )]

[0099] + m set,k [u set,k - u 0 - T 0 (s set,k - s 0 )]

[0100] where: u fwt,k , u dwt,k and u set,k are the thermodynamic energies of the working fluid on the feed - water side, the internal liquid working fluid and the vapor - phase working fluid on the extraction - steam side of the k - th feed - water heater in the steam turbine system, respectively, in kJ / kg; s fwt,k , s dwt,k and s set,k are the specific entropies of the working fluid on the feed - water side, the internal liquid working fluid and the vapor - phase working fluid on the extraction - steam side of the k - th feed - water heater in the boiler system and the steam turbine system, respectively, in kJ / (kg·K).

[0101] The feed - forward command m of the coal - feeding amount in the boiler system coal,ff uses the total storage change rate of the boiler system for feed - forward:

[0102]

[0103] where: η ex,B is the efficiency of the boiler system , in %; LHV is the lower calorific value of the actual coal burned in the boiler system, in kJ / kg.

[0104] The PID algorithm for calculating the coal - feeding amount control command of the boiler system adopts the incremental PID algorithm.

[0105] The beneficial effects of the present invention are as follows: The present invention proposes a coal - feeding amount control method for a coal - fired power generation unit based on direct balance, using direct The balance replaces the original direct energy balance. The direct energy balance controls the fuel quantity by maintaining the energy balance between the boiler system and the steam turbine system. In order to accommodate more renewable energy power generation, coal-fired power units will be in the process of rapid load change more frequently. The drastic fluctuations in parameters make it impossible for the energy balance to accurately reflect the balance between the work capacities of the working fluids. And the direct balance controls the balance between the boiler system and the steam turbine system. The flow input from the boiler to the steam turbine can directly and accurately reflect the work capacity of the working fluid under any operating condition. Therefore, compared with the direct energy balance, the direct balance can adjust the coal feeding quantity more accurately. Based on the direct balance, the coal feeding quantity control method constructs the demand signal of the steam turbine system and the output signal of the boiler system . Among them, the demand signal of the steam turbine system comprehensively considers the flow required by the steady-state steam turbine system and the change rate of the total storage of the steam turbine system. It not only represents the work capacity of the working fluid required by the coal-fired power unit at different loads, but also takes into account its own absorption and release of flow. The output signal of the boiler system comprehensively considers the flow provided by the boiler system to the steam turbine system in real time and the change rate of the total storage of the boiler system. It not only represents the work capacity of the working fluid actually provided by the boiler to the steam turbine during the operation process, but also the adjustment effect of the change of its own storage on the fuel input.

[0106] Adding the coal feeding quantity control method for coal-fired power generation units based on the direct balance can accurately control the input fuel quantity when the coal-fired power unit rapidly changes the load, directly and accurately represent the balance of the work capacities between the boiler and the turbine, and comprehensively improve the control effect of the key thermal parameters of the unit.

[0107] Advantages of the present invention

[0108] 1) The present invention provides a coal feeding quantity control method for coal-fired power generation units based on the direct balance. Its advantages are reflected in the calculation method of the coal feeding quantity of the coal-fired power unit: The present invention optimizes the core of the previous boiler-turbine coordinated control system, the direct energy balance, into the direct balance. It can more accurately reflect the balance of the work capacities between the boiler system and the steam turbine system when the unit rapidly changes the load and the parameters fluctuate drastically. By maintaining the The balance relationship of the flow is sought to meet the requirements of the unit's work capacity, and then the real-time fuel chemistry input to the unit is feedback-controlled. The flow. By matching the real-time net output of the boiler system in real time flow and the steam turbine system corresponding to each load demand, more direct and accurate control of the coal feeding amount is achieved.

[0109] 2) The present invention provides a method for controlling the coal feeding amount of a coal-fired power generation unit based on direct balance. When constructing the demand signal of the steam turbine system the total storage of the steam turbine system is added change rate, which reflects the influence of the throughput of the steam turbine system itself on the conversion of the work capacity of the working medium input during the transient operation of the unit. This makes the demand signal of the steam turbine system corresponding to different loads more accurate when the unit quickly changes load. When constructing the output signal of the boiler system the total storage of the boiler system is added change rate, which reflects the influence of the throughput of the boiler system itself on the conversion process of fuel chemistry to the output working medium during the transient operation of the unit. Through the regulation of the coal feeding amount chemistry flow, the net output of the working medium of the boiler system can be more accurately regulated flow, filling the change of its own storage

[0110] change. Description of the Drawings

[0110] Figure 1 It is the relative deviation change curve of the unit power of a 330MW subcritical coal-fired power generation unit during the process of rapid load increase from 50% to 75% using the method of the present invention and the original direct energy balance control method.

[0111] Figure 2 It is the relative deviation change curve of the main steam pressure of a 330MW subcritical coal-fired power generation unit during the process of rapid load increase from 50% to 75% using the method of the present invention and the original direct energy balance control method.

[0112] Figure 3 It is the change curve of the main steam temperature of a 330MW subcritical coal-fired power generation unit during the process of rapid load increase from 50% to 75% using the method of the present invention and the original direct energy balance control method.

[0113] Figure 4The reheat steam temperature change curves of a 330MW subcritical coal-fired power generation unit during the process of rapidly increasing the load from 50% to 75% by using the method of the present invention and the original direct energy balance control method. Detailed implementation manners

[0114] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the method of the present invention will be further described in detail below in combination with specific implementation cases. It should be understood that the specific implementation cases described herein are only used to explain the present invention and are not used to limit the present invention.

[0115] A coal feeding amount control method for a coal-fired power generation unit based on direct balance. First, calculate the flows carried by the working fluids at the inlet and outlet of the boiler system by using the cleaned data, and then obtain the net output working fluid flow of the boiler system; calculate the storage amounts of each device in the boiler system and the steam turbine system respectively, and obtain the total storage change rate of the boiler system and the steam turbine system. Then, calculate the demand of the steam turbine system and the output of the boiler system, and use the deviation between the demand of the steam turbine system and the output of the boiler system to control the coal feeding amount, and form a coal feeding amount control instruction. The present invention can greatly improve the control effect of the key thermal parameters of the coal-fired power generation unit and can significantly enhance the operation flexibility of the coal-fired power generation unit.

[0116] The coal feeding amount control signal of the present invention is calculated from the deviation between the output of the boiler system and the demand of the steam turbine system; the calculation formula of the coal feeding amount control instruction is:

[0117] m coal = f PID (EX t - EX b ) + m coal,ff

[0118] In the formula: m coal is the coal feeding amount control instruction, kg / s; f PID is a PID controller based on the deviation between the demand of the steam turbine and the output of the boiler system; EX t is the demand of the steam turbine system; EX b is the output of the boiler system; m coal,ff is the feedforward instruction of the coal feeding amount of the boiler system, kg / s;

[0119] Among them, the boiler system The output uses the net output working fluid of the boiler system Flow and the total storage of the boiler system The change rate is calculated as follows:

[0120]

[0121] In the formula: Is the net output working fluid of the boiler system Flow, MW; Is the total storage of the boiler system Change rate, MW;

[0122] The steam turbine system The demand uses the net output working fluid of the boiler system Flow set value and the total storage of the steam turbine system The change rate is calculated as follows:

[0123]

[0124] In the formula: Is the net output working fluid of the boiler system Flow set value, MW; Is the total storage of the steam turbine system Change rate, MW.

[0125] Preferably, regarding the net output working fluid of the boiler system Flow The specific calculation method is as follows:

[0126] Subtract the total output working fluid of the boiler system Flow from the total input working fluid Flow to obtain the net output working fluid of the boiler system Flow:

[0127]

[0128] In the formula: Is the total output working fluid of the boiler system Flow, MW; Is the total input working fluid of the boiler system Flow, MW;

[0129] Among them, the output working fluid of the boiler system Flow includes m working fluid flows leaving the boiler system Flow, and for each working fluid flow leaving the boiler system, the Flow and the total output working fluid of the boiler system The calculation formula of the flow is as follows:

[0130]

[0131] In the formula: is the flow carried by the i-th working fluid flow leaving the boiler system, MW; m out,i is the mass flow rate of the i-th working fluid leaving the boiler system, kg / s; h out,i is the enthalpy value of the i-th working fluid leaving the boiler system, kJ / kg; s out,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K); h 0 is the environmental reference enthalpy value, kJ / kg; s 0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K; where i = 1 to m;

[0132] The input working fluid flow of the boiler system includes m working fluid flows entering the boiler system, and for each working fluid flow entering the boiler system and the total input working fluid flow of the boiler system, the calculation formulas are as follows:

[0133]

[0134] In the formula: is the flow carried by the i-th working fluid flow entering the boiler system, MW; m in,i is the mass flow rate of the i-th working fluid entering the boiler system, kg / s; h in,i is the enthalpy value of the i-th working fluid entering the boiler system, kJ / kg; s in,i is the entropy value of the i-th working fluid leaving the boiler system, kJ / (kg·K); where i = 1 to m.

[0135] Preferably, the specific determination methods for the mass flow rate of the working fluid entering the boiler system and the mass flow rate of the working fluid leaving the boiler system are as follows:

[0136] The mass flow rate of the working fluid entering the boiler system includes the feed water flow rate and the cold reheat steam flow rate, and the mass flow rate of the working fluid leaving the boiler system includes the main steam flow rate and the hot reheat steam flow rate, where the cold reheat steam flow rate is equal to the hot reheat steam flow rate; preferably, the working fluid flow rate collected and calculated by the coal-fired power generation unit itself is adopted, and for the working fluid flow rate that cannot be directly collected from the unit, the Flügel formula is used for calculation; where if the feed water flow rate cannot be obtained from the coal-fired power generation unit, the feed water flow rate is regarded as the same as the main steam flow rate;

[0137] Among them, the main steam flow rate is calculated using the regulating stage pressure, temperature and the pressure of the high-pressure cylinder exhaust:

[0138]

[0139] m in,1 = m fw = m ls

[0140] where: m out,1 and m in,1 are the mass flow rates of the working fluid leaving and entering the boiler system for the first time, kg / s; m ls and m ls0 are the real-time main steam flow rate and the main steam flow rate under the design condition, kg / s; p tj and p tj0 are the real-time regulating stage pressure and the regulating stage pressure under the design condition; p ehp and p ehp0 are the real-time high-pressure cylinder exhaust pressure and the high-pressure cylinder exhaust pressure under the design condition; T tj and T tj0 are the real-time regulating stage pressure and the regulating stage temperature under the design condition, °C; m fw is the feed water flow rate of the unit, kg / s;

[0141] The reheated steam flow rate, i.e., the flow rate of the working fluid entering and leaving the boiler system for the i-th time, is calculated using the pressure and temperature of the working fluid leaving the boiler system for the i-th time and the second-stage extraction steam pressure after the working fluid returns to the steam turbine:

[0142]

[0143] where: m out,i and m out,i0 are the real-time mass flow rate and the mass flow rate under the design condition of the working fluid leaving the boiler system for the i-th time, kg / s; m in,i is the real-time mass flow rate of the working fluid entering the boiler system for the i-th time, kg / s; p out,i and p out,i0 are the real-time pressure and the pressure under the design condition of the working fluid leaving the boiler system for the i-th time; p out,i+2 and p out,(i+2)0 are the real-time pressure and the pressure under the design condition of the second-stage extraction steam after the working fluid leaving the boiler system for the i-th time enters the steam turbine; T out,i0 and T out,i are the real-time pressure and the temperature under the design condition of the working fluid leaving the boiler system for the i-th time, °C, where i = 2 to m;;

[0144] Through the above calculations, the mass flow rate m out,i of the working fluid leaving the boiler system and the mass flow rate m in,iAll calculations are obtained.

[0145] Preferably, regarding the total storage Change rate The specific calculation method is as follows:

[0146] Total storage of the boiler system The change rate calculation formula is:

[0147]

[0148] In the formula: E x,B Is the total storage of the boiler system MJ;

[0149] Among them, the total storage of the boiler system Is the sum of the working medium storage And metal storage Of each device inside the boiler system, and the specific calculation formula is:

[0150] E x,B = ∑E x-b,j = ∑(E x-wfb,j + E x-mb,j )

[0151] E x-wfb,j = ∑m wfb,j [u wfb,j - u 0 - T 0 (s wfb,j - s 0 )]

[0152]

[0153] In the formula: E x-b,j Is the storage of the j-th device in the boiler system MJ; E x-wfb,j Is the working medium storage of the j-th device inside the boiler system MJ; E x-mb,j Is the metal storage of the j-th device inside the boiler system MJ; m wfb,j Is the mass of the working medium stored inside the j-th device in the boiler system, kg; u wfb,j Is the thermodynamic energy of the working medium stored inside the j-th device in the boiler system, kJ / kg; s wfb,j Is the entropy value of the working medium stored inside the j-th device in the boiler system, kJ / (kg·K); c p,m Is the specific heat capacity of the metal, kJ / (kg·K); m mb,j Is the mass of the metal of the j-th device inside the boiler system, kg; T mb,j Is the average temperature of the metal of the j-th device inside the boiler system, K; s0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K; u 0 is the environmental reference thermodynamics energy, kJ / kg.

[0154] Preferably, the specific method for calculating the mass and the storage of the working medium in the j-th device inside the boiler system is as follows: The specific method is as follows:

[0155] According to the structural parameters, determine the working medium volume V and the metal mass m of the H heat exchange devices in the boiler system, j = 1~H; b,j and the metal mass m b,j , j = 1~H;

[0156] The storage of the working medium inside the devices in the boiler system is mainly divided into two types. One is that the working medium inside is single-phase, and the other is that the working medium inside is two-phase. The mass calculation of the single-phase working medium inside the device adopts the following formula:

[0157] m wfbd,j = ρ wfbd,j V b,j

[0158] In the formula: ρ wfbd,j is the average density of the working medium inside the j-th device in the boiler system, which is obtained by means of the temperature and pressure of the working medium inside the j-th device in the boiler system with the help of the thermophysical property function. If there are no measuring points for the temperature and pressure of the working medium inside the j-th device, the average value of the densities of the working medium at the inlet and outlet of the j-th device is adopted, kg / m 3 ; V b,j is the volume inside the j-th device in the boiler system, m 3 ;

[0159] For the mass calculation of the two-phase working medium inside the device, the relationship between the device liquid level and the working medium volume is used, and the following formula is adopted to calculate the mass of the working medium in different phases:

[0160] V wb,j = f (h-v)b,j (h wb,j )

[0161] V sb,j = V b,j - V wb,j

[0162] m wb,j = ρ wb,j V wb,j

[0163] m sb,j = ρ sb,j V sb,j

[0164] In the formula: Vwb,j and V sb,j are the volumes of the internal liquid working medium and vapor working medium of the j-th device in the boiler system, respectively, in m 3 ; h wb,j is the internal liquid level of the j-th device in the boiler system, in m; f (h-v)bj is the functional relationship between the internal liquid level and the volume of the liquid working medium of the j-th device in the boiler system, which is related to the specific structure of the j-th device; m wb,j and m sb,j are the masses of the internal liquid working medium and vapor working medium of the j-th device in the boiler system, respectively, in kg; ρ wb,j and ρ sb,j are the densities of the internal liquid working medium and vapor working medium of the j-th device in the boiler system, respectively, which can be obtained by means of thermophysical property functions based on the temperature or pressure of the internal working medium of the j-th device in the boiler system, in kg / m 3 ;

[0165] Therefore, the mass of the working medium stored in the j-th device inside the boiler system is:

[0166] When the internal working medium is single-phase, the calculation formula for the working medium mass is m wfb,j = m wfbd,j , and at this time, calculating the working medium storage in each device inside the boiler system is:

[0167] E x-wfb,j = m wfbd,j [u wfbd,j - u 0 - T 0 (s wfbd,j - s 0 )]

[0168] In the formula: u wfbd,j is the internal single-phase working medium's thermodynamic energy of the j-th device in the boiler system, in kJ / kg; s wfbd,j is the internal single-phase working medium's specific entropy of the j-th device in the boiler system, in kJ / (kg·K);

[0169] When the internal working medium is two-phase, the liquid working medium mass m wfb,j = m wb,j , the vapor working medium mass m wfb,j = m sb,j , and at this time, when calculating the working medium storage in each device inside the boiler system, the storage of the liquid working medium and vapor working medium needs to be added together, that is

[0170] E x-wfb,j = m wb,j [u wb,j - u 0 - T0 (s wb,j -s 0 )]+m sb,j [u sb,j -u 0 -T 0 (s sb,j -s 0 )]

[0171] Where: u wb,j and u sb,j are the internal thermodynamic energies of the liquid and vapor working fluids of the j-th device in the boiler system, respectively, in kJ / kg; s wb,j and s sb,j are the specific entropies of the liquid and vapor working fluids of the j-th device in the boiler system, respectively, in kJ / (kg·K).

[0172] Preferably, for the set value of the net output working fluid flow rate of the boiler system the specific calculation method is as follows:

[0173] When the coal-fired power generation unit operates in a steady state condition, take the net output working fluid flow rate of the boiler system at this time as the set value of the net output working fluid flow rate in the control system. The calculation formula is:

[0174]

[0175] Where: is the total output working fluid flow rate of the boiler system during the steady operation of the coal-fired power generation unit, in MW; is the total input working fluid flow rate of the boiler system during the steady operation of the coal-fired power generation unit, in MW;

[0176] The calculation formula for the total output working fluid flow rate of the boiler system during the steady operation of the coal-fired power generation unit is as follows:

[0177]

[0178] Where: is the flow rate carried by the i-th working fluid flow leaving the boiler system, in MW; m out,i is the mass flow rate of the i-th working fluid leaving the boiler system, in kg / s; h out,i is the enthalpy value of the i-th working fluid leaving the boiler system, in kJ / kg; s out,i is the entropy value of the i-th working fluid leaving the boiler system, in kJ / (kg·K); h 0 is the environmental reference enthalpy value, in kJ / kg; s 0is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K;

[0179] When the coal-fired power generation unit operates in a steady state, the total working medium flow entering the boiler system is calculated as follows:

[0180]

[0181] In the formula: is the flow carried by the i-th working medium flow entering the boiler system, MW; m in,i is the mass flow rate of the i-th working medium entering the boiler system, kg / s; h in,i is the enthalpy value of the i-th working medium entering the boiler system, kJ / kg; s in,i is the entropy value of the i-th working medium leaving the boiler system, kJ / (kg·K);

[0182] The set values of the net output working medium flow of the boiler system under steady-state conditions of the coal-fired power generation unit corresponding to different unit loads are fitted with the unit load to obtain the curve of the set values of the net output working medium flow of the boiler system corresponding to different unit loads:

[0183]

[0184] In the formula: LDC is the load command of the coal-fired power generation unit.

[0185] Preferably, the specific calculation method for the total storage change rate of the steam turbine system is as follows:

[0186] The total storage change rate of the steam turbine system is calculated as:

[0187]

[0188] In the formula: E x,T is the total storage of the steam turbine system, MJ;

[0189] Among them, the total storage of the steam turbine system includes the working medium storage and metal storage of each regenerative heater in the steam turbine system, and the sum is specifically calculated as:

[0190] E x,T = ∑E x-t,k = ∑(E x-wft,k + E x-mt,k )

[0191]

[0192] Where: E x-t,k is the storage of the k-th regenerative heater inside the steam turbine system MJ; E x-wft,k is the working fluid storage of the k-th regenerative heater inside the steam turbine system MJ; E x-mt,k is the metal storage of the k-th regenerative heater inside the steam turbine system MJ; m wft,k is the mass of the working fluid stored inside the k-th regenerative heater in the steam turbine system, kg; u wft,k is the thermodynamic energy of the working fluid stored inside the k-th regenerative heater in the steam turbine system, kJ / kg; s wft,k is the entropy value of the working fluid stored inside the k-th regenerative heater in the steam turbine system, kJ / (kg·K); c p,m is the specific heat capacity of the metal, kJ / (kg·K); m mt,k is the equivalent metal mass participating in heat transfer of the k-th regenerative heat exchanger in the steam turbine system, kg; T mt,k is the average metal temperature of the k-th regenerative heater in the steam turbine system. When there is no measurement data, the average temperature of the working fluid on the feed water side and the extraction steam side of the k-th regenerative heater in the steam turbine system is used as a substitute, K; s 0 is the environmental reference entropy value, kJ / (kg·K); T 0 is the environmental reference temperature, K; u 0 is the environmental reference thermodynamic energy, kJ / kg.

[0193] Preferably, the specific methods for calculating the mass of the working fluid stored in each regenerative heater of the steam turbine system and the working fluid storage are as follows:

[0194] Determine the volume V t,k of the working fluid and the metal mass m t,k of the Z regenerative heaters in the steam turbine system, k = 1 to Z;

[0195] There are two working fluids inside the regenerative heater, namely the feed water side and the working fluid side. The calculation formula for the mass of the working fluid stored on the feed water side is:

[0196] m fwt,k = ρ fwt,k V t,k

[0197] Where: m fwt,k is the mass of the working fluid stored on the feed water side inside the k-th regenerative heater of the steam turbine system, kg; ρ fwt,kis the density of the working medium stored on the feed water side inside the k-th regenerative heater of the steam turbine system. The average value of the densities of the working medium at the inlet and outlet of the k-th regenerative heater of the steam turbine system is used, kg / m 3 ; V fwt,k is the volume of the working medium stored on the feed water side of the k-th regenerative heater of the steam turbine system, m 3 ;

[0198] Both the liquid working medium and the vapor working medium are contained in the extraction side of the regenerative heater. Therefore, the mass of the liquid working medium and the mass of the vapor working medium need to be calculated separately by means of the internal water level information of each regenerative heater:

[0199] V dwt,k = f (h-v)tk (h wt,k )

[0200] V set,k = V t,k - V dwt,k

[0201] m dwt,k = ρ dwt,k V dwt,k

[0202] m set,k = ρ set,k V set,k

[0203] Where: V dwt,k and V set,k are the volumes of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater of the steam turbine system, respectively, m 3 ; h wt,k is the internal liquid level on the extraction side of the k-th regenerative heater of the steam turbine system, m; f (h-v ) tk is the functional relationship between the internal liquid level and the volume of the liquid working medium on the extraction side of the k-th regenerative heater of the steam turbine system, and is related to the specific structure of the extraction side of the k-th regenerative heater; m dwt,k and m set,k are the masses of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater of the steam turbine system, respectively, kg; ρ dwt,k and ρ set,k are the average densities of the internal liquid working medium and the vapor working medium on the extraction side of the k-th regenerative heater of the steam turbine system, respectively, and can be obtained by means of the thermophysical property function according to the temperature or pressure of the internal working medium on the extraction side of the k-th regenerative heater of the steam turbine system, kg / m 3 ;

[0204] Therefore, the mass of the working medium stored inside the k-th regenerative heater in the steam turbine system is:

[0205] When calculating the working fluid inside the feed water side, the formula for the mass of the working fluid is m wft,k = m fwt,k ;

[0206] When calculating the working fluid inside the extraction steam side, the mass of the liquid working fluid is m wft,k = m dwt,k , and the mass of the vaporous working fluid is m wft,k = m set,k . At this time, when calculating the storage of the working fluid in each device inside the steam turbine system , it is necessary to sum up the storage of the liquid working fluid and the vaporous working fluid , that is

[0207] E x-wft,k = m fwt,k [u fwt,k - u 0 - T 0 (s fwt,k - s 0 )] + m dwt,k [u dwt,k - u 0 - T 0 (s dwt,k - s 0 )]

[0208] + m set,k [u set,k - u 0 - T 0 (s set,k - s 0 )]

[0209] In the formula: u fwt,k , u dwt,k and u set,k are the thermodynamic energies of the feed water side working fluid, the internal liquid working fluid and the vaporous working fluid of the extraction steam side of the kth regenerative heater in the steam turbine system, kJ / kg; s fwt,k , s dwt,k and s set,k are the specific entropies of the feed water side working fluid, the internal liquid working fluid and the vaporous working fluid of the kth regenerative heater in the boiler system steam turbine system, kJ / (kg·K).

[0210] Preferably, the feedforward command m coal,ff of the coal feeding amount in the boiler system is feedforwarded using the change rate of the total storage in the boiler system:

[0211]

[0212] In the formula: η ex,B is the boiler system Efficiency, %; LHV is the lower heating value of the actual coal type burned in the boiler system, kJ / kg.

[0213] Preferably, the PID algorithm for calculating the coal feeding amount control command of the boiler system adopts an incremental PID algorithm.

[0214] Figure 1 、 Figure 2 、 Figure 3 and Figure 4 respectively show the relative deviation of unit power, relative deviation of main steam pressure, main steam temperature and reheat steam temperature of a 330MW subcritical coal-fired generating unit in the above specific implementation cases during the 50%-75% rapid load increase process. The control effects of the original direct energy balance control method and the control method of the present invention are compared in the figure. The maximum allowable deviation values of unit power, main steam pressure, main steam temperature and reheat steam temperature during the load change process are 2.0%, 3.0%, 8°C and 10°C respectively.

[0215] Using the original direct energy balance control method, when the load increase rate is 2.0% Pe / min, the maximum deviation of the reheat steam temperature reaches 11.31°C, exceeding the maximum limit value of 10°C; using the control method of the present invention, when the load increase rate is the same 2.0% Pe / min, the maximum deviation of the reheat steam temperature is reduced to 9.62°C, meeting the limit requirements. Therefore, the load increase rate of the coal-fired generating unit during the 50%-75% load increase process is increased from 1.5% Pe / min to 2.0% Pe / min.

[0216] When the load increase rate is 2.0% Pe / min, the control method of the present invention reduces the maximum relative deviation of unit power, the maximum relative deviation of main steam pressure, the maximum deviation of main steam temperature and the maximum deviation of reheat steam temperature by 46.99%, 56.00%, 23.04% and 14.94% respectively; the control method of the present invention reduces the maximum overshoot of unit power, the maximum overshoot of main steam pressure and the maximum overshoot of main steam temperature by 87.93%, 87.50% and 27.27% respectively; the control method of the present invention reduces the cumulative deviation of unit power, the cumulative deviation of main steam pressure, the cumulative deviation of main steam temperature and the cumulative deviation of reheat steam temperature by 46.15%, 45.69%, 12.84% and 10.15% respectively.

[0217] In summary, after using the coal feeding amount control method of direct balance of the present invention, the control effects of unit power, main steam pressure, main steam temperature and reheat steam temperature are all significantly improved. Therefore, the coal feeding amount control method of a coal-fired generating unit based on direct #imgpt265# balance of the present invention greatly improves the operation flexibility of the coal-fired generating unit.

Claims

1. A direct A balanced coal-fired power generation unit coal feed control method, characterized in that: The coal feed control signal is from the boiler system Output and turbine system The deviation of demand is calculated; The calculation formula of the coal feeding control instruction is: m coal =f PID (EX t -EX b )+m coal,ff Where: m coal is the coal feeding control instruction, kg / s; f PID Based on steam turbine Demand and boiler systems Output deviation PID controller; EX t For steam turbine system Demand; EX b For boiler systems Output: m coal,ff is the feedforward instruction of coal feeding amount of boiler system, kg / s; Among them, the boiler system Output uses the net output working fluid of the boiler system Flow and boiler system total storage The rate of change is calculated: Where: The net output of the boiler system flow, MW; Total storage capacity of boiler system rate of change, MW; Steam Turbine System Net output of boiler system required Flow setting value and total storage capacity of steam turbine system The rate of change is calculated: Where: The net output of the boiler system flow setpoint, MW; Total storage capacity of the steam turbine system Rate of change, MW.

2. According to claim 1, based on direct A balanced coal-fired power generation unit coal feed control method, characterized in that: Net output of boiler system flow The specific calculation method is as follows: The total output working fluid of the boiler system Flow and total input working fluid The net output of the boiler system is obtained by subtracting the flow flow: Where: is the total output working fluid of the boiler system flow, MW; is the total input working fluid of the boiler system flow, MW; Among them, the output working fluid of the boiler system The flow includes m working fluids leaving the boiler system Flow, each of which leaves the boiler system Flow and the total output of the boiler system The flow calculation formula is as follows: Where: is the mass carried by the i-th working fluid flow leaving the boiler system Flow, MW; m out,i is the mass flow rate of the working fluid leaving the boiler system, kg / s; h out,i is the enthalpy of the working fluid leaving the boiler system, kJ / kg; s out,i is the entropy value of the working fluid leaving the boiler system, kJ / (kg·K); h0 is the environmental reference enthalpy value, kJ / kg; s0 is the environmental reference entropy value, kJ / (kg·K); T0 is the environmental reference temperature, K; where i = 1~m; Input fluid of boiler system The flow includes m working fluids entering the boiler system Flow, each of which enters the boiler system Flow and total input working fluid of boiler system The flow calculation formula is as follows: Where: is the mass carried by the i-th working fluid flow entering the boiler system Flow, MW; m in,i is the mass flow rate of the working fluid entering the boiler system, kg / s; h in,i is the enthalpy value of the working fluid entering the boiler system, kJ / kg; s in,i is the entropy value of the working fluid leaving the boiler system, kJ / (kg·K); where i=1~m.

3. According to claim 2, based on direct A balanced coal-fired power generation unit coal feed control method, characterized in that: The specific method for determining the mass flow rate of the working fluid entering the boiler system and the mass flow rate of the working fluid leaving the boiler system is as follows: The working medium mass flow rate entering the boiler system includes the feed water flow rate and the cold section reheat steam flow rate, and the working medium mass flow rate leaving the boiler system includes the main steam flow rate and the hot section reheat steam flow rate, wherein the cold section reheat steam flow rate is equal to the hot section reheat steam flow rate; the working medium flow rate collected and calculated by the coal-fired power generation unit itself is preferably used, and the working medium flow rate that cannot be directly collected from the unit is calculated using the Flugel formula; wherein, if the feed water flow rate cannot be obtained from the coal-fired power generation unit, the feed water flow rate is regarded as the same as the main steam flow rate; The main steam flow is calculated using the regulating stage pressure, temperature and high-pressure cylinder exhaust pressure: m in,1 =m fw =m ls Where: m out,1 and m in,1 are the mass flow rates of the first working fluid leaving the boiler system and entering the boiler system, kg / s; m ls and m ls0 They are real-time main steam flow and design main steam flow, kg / s; p tj and p tj0 They are real-time regulating stage pressure and design operating condition regulating stage pressure; p ehp and p ehp0 are the real-time high-pressure cylinder exhaust steam pressure and the design high-pressure cylinder exhaust steam pressure; T tj and T tj0 They are real-time regulating stage pressure and design operating condition regulating stage temperature, ℃; m fw is the unit feed water flow rate, kg / s; The reheat steam flow, i.e., the flow of the working fluid entering and leaving the boiler system, is calculated using the pressure and temperature of the working fluid leaving the boiler system and the second stage extraction pressure after the working fluid returns to the turbine: Where: m out,i and m out,i0 are the real-time mass flow rate of the working fluid leaving the boiler system and the mass flow rate under design conditions, kg / s; m in,i is the real-time mass flow rate of the working fluid entering the boiler system, kg / s; p out,i and p out,i0 are the real-time pressure of the working fluid leaving the boiler system and the pressure under design conditions; p out,i+2 and p out,(i+2)0 are the real-time pressure of the second-stage steam extraction after the i-th working fluid leaving the boiler system enters the turbine and the pressure under the design condition; T out,i0 and T out,i are the real-time pressure and the temperature of the i-th working fluid leaving the boiler system under the design condition, ℃, where i = 2~m; The mass flow rate m of the working fluid leaving the boiler system is calculated by the above out,i and the mass flow rate of the working fluid entering the boiler system m in,i All calculated.

4. The method according to claim 1 A balanced coal-fired power generation unit coal feed control method, characterized in that: About the total storage capacity of the boiler system Rate of change The specific calculation method is as follows: Boiler system total storage The formula for calculating the rate of change is: Where: E x,B Total storage capacity of boiler system , M.J.; The total storage capacity of the boiler system is It is used to store working fluid for each equipment in the boiler system. and metal storage The specific calculation formula is: AND x,B =∑E x-b,j =∑(E x-wfb,j +E x-mb,j ) E x-wfb,j =∑m wfb,j [u wfb,j -u0-T0(s wfb,j -s0)] Where: E x-b,j The storage capacity of the jth equipment in the boiler system , M.J.;E. x-wfb,j The working fluid storage unit for the jth equipment in the boiler system , M.J.;E. x-mb,j The metal storage device of the jth equipment in the boiler system ,MJ;m wfb,j is the mass of the working fluid stored in the jth device in the boiler system, kg; u wfb,j is the thermodynamic energy of the working fluid stored in the jth device in the boiler system, kJ / kg; s wfb,j is the entropy value of the working fluid stored in the jth device in the boiler system, kJ / (kg·K); c p,m is the specific heat capacity of metal, kJ / (kg·K); m mb,j is the metal mass of the jth equipment in the boiler system, kg; T mb,j is the average metal temperature of the jth equipment in the boiler system, K; s0 is the environmental reference entropy value, kJ / (kg·K); T0 is the environmental reference temperature, K; u0 is the environmental reference thermodynamic energy, kJ / kg.

5. The method according to claim 4 based on direct A balanced coal-fired power generation unit coal feed control method, characterized in that: Regarding the calculation of the working fluid quality and working fluid storage capacity in the jth device in the boiler system The specific method is as follows: According to the structural parameters, determine the working fluid volume V of H heat exchange equipment in the boiler system b,j and metal mass m b,j , j = 1 ~ H; There are two main types of working fluid storage inside the equipment of the boiler system. One is that the internal working fluid is single-phase, and the other is that the internal working fluid is two-phase. The quality calculation of the single-phase working fluid inside the equipment adopts the following formula: m wfbd,j =ρ wfbd,j V b,j Where: wfbd,j is the average density of the internal working fluid of the jth equipment in the boiler system, which is obtained by using the temperature and pressure of the internal working fluid of the jth equipment in the boiler system with the help of the thermophysical property function. If there is no working fluid temperature and pressure measurement point inside the jth equipment, the average density of the inlet and outlet working fluid of the jth equipment is used, kg / m 3 ; V b,j is the volume inside the jth equipment in the boiler system, m 3 ; The mass calculation of the two-phase working fluid inside the equipment is based on the relationship between the equipment liquid level and the working fluid volume. The following formula is used to calculate the mass of the working fluid in different phases: V wb,j =f (h-v)b,j (h wb,j ) V sb,j =V b,j -V wb,j m wb,j =ρ wb,j V wb,j m sb,j =ρ sb,j V sb,j Where: V wb,j and V sb,j are the volumes of the internal liquid medium and the vapor medium of the jth equipment in the boiler system, m 3 ;h wb,j is the internal liquid level of the jth equipment in the boiler system, m; f (h-v)bj is the functional relationship between the internal liquid level and the volume of liquid working medium of the jth equipment in the boiler system, which is related to the specific structure of the jth equipment; m wb,j and m sb,j are the masses of the internal liquid and vapor working fluids of the jth equipment in the boiler system, kg; ρ wb,j and ρ sb,j are the densities of the internal liquid and vapor working fluids of the jth equipment in the boiler system, respectively. They can be obtained by using the thermophysical property function according to the temperature or pressure of the internal working fluid of the jth equipment in the boiler system, kg / m 3 ; Therefore, the mass of the working fluid stored in the jth device in the boiler system is: When the internal working fluid is single-phase, the working fluid mass calculation formula is m wfb,j =m wfbd,j At this time, calculate the working fluid storage capacity of each equipment in the boiler system for: E x-wfb,j =m wfbd,j [u wfbd,j -u0-T0(s wfbd,j -s0)] Where: u wfbd,j is the thermodynamic energy of the internal single-phase working fluid of the jth equipment in the boiler system, kJ / kg; s wfbd,j is the specific entropy of the internal single-phase working medium of the jth equipment in the boiler system, kJ / (kg·K); When the internal working fluid is two-phase, the mass of liquid working fluid m wfb,j =m wb,j , gas working medium mass m wfb,j =m sb,j At this time, calculate the working fluid storage capacity of each equipment in the boiler system When the liquid working fluid and the vapor working fluid are stored Add and E x-wfb,j =m wb,j [u wb,j -u0-T0(s wb,j -s0)]+m sb,j [u sb,j -u0-T0(s sb,j -s0)] Where: u wb,j and u sb,j are the thermodynamic energies of the internal liquid and vapor working fluids of the jth equipment in the boiler system, kJ / kg; s wb,j and sb,j are the specific entropies of the internal liquid and vapor working fluids of the j-th equipment in the boiler system, kJ / (kg·K).

6. The method according to claim 1 A balanced coal-fired power generation unit coal feed control method, characterized in that: About the Net Output of Boiler System Flow rate setting value The specific calculation method is as follows: When the coal-fired generator set is operating in a steady state, the net output of the boiler system is Flow as the net output working fluid of the boiler system in the control system The set value of the flow is calculated as: Where: The total output working fluid of the boiler system when the coal-fired generator set is running in steady state flow, MW; The total input working fluid of the boiler system when the coal-fired power generation unit is running in steady state flow, MW; The total output working fluid of the boiler system when the coal-fired generator set is running in steady state The flow calculation formula is as follows: Where: is the mass carried by the i-th working fluid flow leaving the boiler system flow, MW; m out,i is the mass flow rate of the working fluid leaving the boiler system, kg / s; h out,i is the enthalpy of the working fluid leaving the boiler system, kJ / kg; s out,i is the entropy value of the working fluid leaving the boiler system, kJ / (kg·K); h0 is the environmental reference enthalpy value, kJ / kg; s0 is the environmental reference entropy value, kJ / (kg·K); T0 is the environmental reference temperature, K; Total input working fluid of boiler system when coal-fired generator set is running in steady state The flow calculation formula is as follows: Where: is the mass carried by the i-th working fluid flow entering the boiler system flow, MW; m in,i is the mass flow rate of the working fluid entering the boiler system, kg / s; h in,i is the enthalpy value of the working fluid entering the boiler system, kJ / kg; s in,i is the entropy value of the working fluid leaving the boiler system, kJ / (kg·K); The net output working fluid of the boiler system under steady-state conditions of coal-fired power generation units corresponding to different unit loads The flow rate setting value is fitted with the unit load to obtain the net output working fluid of the boiler system corresponding to different unit loads. Curve of flow setpoint: Where: LDC is the load command of the coal-fired generator set.

7. The method according to claim 1 A balanced coal-fired power generation unit coal feed control method, characterized in that: About the total storage capacity of steam turbine system Rate of change The specific calculation method is as follows: Steam turbine system total storage The formula for calculating the rate of change is: Where: E x,T Total storage capacity of the steam turbine system , M.J.; Among them, the total storage capacity of the steam turbine system is Contains the working fluid storage of each stage of the steam turbine system regenerative heater and metal storage The specific calculation formula is: AND x,T =∑E x-t,k =Σ(E x-wft,k +E x-mt,k ) E x-wft,k =Σm wft,k [u wft,k -u0-T0(s wft,k -s0)] Where: E x-t,k The kth stage regenerative heater in the steam turbine system is , M.J.;E. x-wft,k The working fluid storage for the kth stage regenerative heater in the steam turbine system , M.J.;E. x-mt,k The metal storage device of the kth stage regenerative heater in the steam turbine system ,MJ;m wft,k is the mass of the working fluid stored in the k-th stage regenerative heater in the steam turbine system, kg; u wft,k is the thermodynamic energy of the working fluid stored in the k-th stage regenerative heater in the steam turbine system, kJ / kg; s wft,k is the entropy value of the working fluid stored in the k-th stage regenerative heater in the steam turbine system, kJ / (kg·K); c p,m is the specific heat capacity of metal, kJ / (kg·K); m mt,k is the equivalent metal mass of the kth stage regenerator involved in heat exchange in the steam turbine system, kg; T mt,k is the average metal temperature of the k-th stage heat recovery heater inside the steam turbine system. When there is no measurement data, the average temperature of the working fluid on the feed water side and the extraction side of the k-th stage heat recovery heater inside the steam turbine system is used instead, K; s0 is the environmental reference entropy value, kJ / (kg·K); T0 is the environmental reference temperature, K; u0 is the environmental reference thermodynamic energy, kJ / kg.

8. The method according to claim 7 A balanced coal-fired power generation unit coal feed control method, characterized in that: Regarding the calculation of the working fluid quality and working fluid storage capacity in each stage of the steam turbine system regenerative heater The specific method is as follows: Determine the volume V of the working fluid in the Zth regenerative heater of the steam turbine system t,k and metal mass m t,k , k = 1 ~ Z; The regenerative heater contains two kinds of working fluids, namely the water supply side and the working fluid side. The calculation formula for the working fluid mass stored on the water supply side is: m fwt,k =ρ fwt,k V t,k Where: m fwt,k is the mass of the working fluid stored on the feedwater side of the k-th stage regenerative heater of the steam turbine system, kg; ρ fwt,k is the density of the working fluid stored on the feedwater side of the k-th stage regenerative heater of the steam turbine system, using the average density of the inlet and outlet working fluids of the k-th stage regenerative heater of the steam turbine system, kg / m 3 ; V fwt,k is the storage volume of the working fluid on the feedwater side of the k-th stage regenerative heater of the steam turbine system, m 3 ; The extraction side of the regenerative heater contains both liquid and vapor working fluids. Therefore, the internal water level information of each regenerative heater is required to calculate the mass of the liquid and vapor working fluids separately: V dwt,k =f (h-v)tk (h wt,k ) V set,k =V t,k -V dwt,k m dwt,k =ρ dwt,k V dwt,k m set,k =ρ set,k V set,k Where: V dwt,k and V set,k are the volumes of the internal liquid medium and vapor medium on the extraction side of the k-th stage regenerative heater of the steam turbine system, m 3 ;h wt,k is the internal liquid level on the extraction side of the k-th stage regenerative heater of the steam turbine system, m; f (h-v)tk is the functional relationship between the internal liquid level and the volume of liquid working medium on the extraction side of the k-th stage regenerative heater of the steam turbine system, and is related to the specific structure of the extraction side of the k-th stage regenerative heater; m dwt,k and m set,k are the masses of the internal liquid and vapor working fluids on the extraction side of the k-th stage regenerative heater of the steam turbine system, kg; ρ dwt,k and ρ set,k They are the average densities of the internal liquid working medium and the vapor working medium on the extraction side of the k-th stage regenerative heater of the steam turbine system, respectively. They can be obtained by using the thermophysical property function according to the temperature or pressure of the internal working medium on the extraction side of the k-th stage regenerative heater of the steam turbine system, kg / m 3 ; Therefore, the mass of the working fluid stored in the k-th stage regenerative heater inside the steam turbine system is: When calculating the working fluid inside the water supply side, the working fluid mass calculation formula is m wft,k =m fwt,k ; When calculating the internal working fluid on the extraction side, the mass of the liquid working fluid is m wft,k =m dwt,k , the mass of the vapor working medium is m wft,k =m set,k At this time, calculate the working fluid storage capacity of each equipment in the steam turbine system When the liquid working fluid and the vapor working fluid are stored Add and E x-wft,k =m fwt,k [u fwt,k -u0-T0(s fwt,k -s0)]+m dwt,k [u dwt,k -u0-T0(s dwt,k -s0)] +m set,k [u set,k -u0-T0(s set,k -s0)] Where: u fwt,k ,u dwt,k and u set,k are the thermodynamic energies of the working fluid on the feed water side, the internal liquid working fluid and the steam working fluid on the extraction side of the kth regenerative heater of the steam turbine system, kJ / kg; s fwt,k ,s dwt,k and set,k They are the specific entropies of the working medium on the feed water side, the internal liquid working medium on the extraction side, and the vapor working medium of the kth regenerative heater of the boiler system and the steam turbine system, kJ / (kg·K).

9. The method for controlling the coal supply amount of a coal-fired power generation unit according to claim 1 A balancing method, characterized in that: Boiler system coal feed rate feedforward instruction m coal,ff Utilize the total storage capacity of the boiler system Feed forward the rate of change: Where: η ex,B For boiler systems Efficiency, %; LHV is the lower calorific value of the coal actually burned in the boiler system, kJ / kg.

10. The method for controlling the coal supply amount of a coal-fired power generation unit according to claim 1 A balancing method, characterized in that: The PID algorithm for calculating the boiler system's coal feed control command adopts an incremental PID algorithm.

Images