CN112742603B - Automatic control method for wet-type electric precipitator of thermal power generating unit - Google Patents
Automatic control method for wet-type electric precipitator of thermal power generating unit Download PDFInfo
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Abstract
The invention discloses an automatic control method for a wet-type electric precipitator of a thermal power generating unit, which comprises the following steps: obtaining a dynamic characteristic model through a wet electric precipitator disturbance test; respectively reading the operation parameters of the unit, the operation parameters of the wet electric dust remover and the operation parameters of the preceding stage dry electric dust remover; solving a feedforward adjusting instruction for adjusting the secondary current and/or the secondary voltage according to the operation parameters of the dry electric dust collector and the operation parameters of the wet electric dust collector; sending a feedback adjusting instruction of secondary current and/or secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric dust collector; and adjusting the secondary current and/or the secondary voltage according to the feedforward adjusting instruction and the feedback adjusting instruction, so as to realize closed-loop automatic control of the wet electric dust collector. The embodiment of the invention has better anti-interference capability and energy-saving effect, and can realize the closed-loop automatic control of the wet electric dust remover.
Description
Technical Field
The invention belongs to the technical field of dedusting environmental protection control of thermal power generating units, and particularly relates to an automatic control method for a wet-type electric precipitator of a thermal power generating unit.
Background
Thermal power generation accounts for 73 percent of the power generation proportion of China, and is the most power generation mode, but the coal-fired power station inevitably discharges pollutants such as smoke dust and the like, and the atmospheric environment of China is influenced. Electrostatic dust collection is one of the technologies for effectively restraining smoke dust pollution of a thermal power plant, and is widely applied at present. Along with the country to environmental standard's constantly improvement, electrostatic precipitator emission concentration also requires the step-down, and the reduction of electrostatic precipitator emission concentration requires that electrostatic precipitator increase is handled to lead to the promotion of electrostatic precipitator station service electricity. Usually, the power consumption of the electric dust collector needs to be 3-5% of the power consumption of the power plant, so the energy-saving problem of the electric dust collector causes the attention of the personnel in the power plant.
At present, most of domestic electric dust removal systems are from a dry electric dust remover to a desulfurization spray tower and then to a wet electric dust remover. The wet electric dust collector is directly related to the smoke outlet concentration index of environmental protection examination, and is very important. Meanwhile, the wet-type electric dust collector is also the one most affected by various parameters of the preceding stage, and the electric dust collection system is a complex cascade nonlinear system affected by multivariable, and a mechanism model is difficult to establish and cannot be regulated and controlled through the mechanism model. Under the condition, how to estimate the disturbance quantity and execute feedforward compensation according to the known information of the preceding stage link is an important starting point for solving the problem of large concentration disturbance quantity of the wet electric precipitation outlet. Although the idea of energy-saving optimization and control of outlet concentration of an electric dust collector is already proposed, the electric dust collector of the current thermal power plant generally adopts an open-loop control method, and operators regulate and control parameters such as secondary voltage/current of an electric field in real time through experience. Therefore, closed-loop feedback control considering outlet concentration is an urgent solution for wet electric dust removal systems.
Disclosure of Invention
Aiming at the defects, the invention provides the automatic control method of the wet-type electric precipitator of the thermal power generating unit, which adopts a control framework combining feedforward compensation and feedback regulation, can ensure better anti-interference capability and energy-saving effect, and realizes the closed-loop automatic control of the wet-type electric precipitator.
In order to solve the technical problem, the embodiment of the invention adopts the following technical scheme:
the embodiment of the invention provides an automatic control method for a wet-type electric precipitator of a thermal power generating unit, which comprises the following steps:
s1, obtaining a dynamic characteristic model through a wet electric precipitator disturbance test;
s2, respectively reading the operation parameters of the unit, the wet electric dust collector and the preceding stage dry electric dust collector;
s3, calculating a feedforward adjusting instruction for adjusting secondary current and/or secondary voltage according to the operation parameters of the dry electric dust collector and the operation parameters of the wet electric dust collector;
s4, sending a feedback regulation instruction of secondary current and/or secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric dust collector;
and S5, adjusting the secondary current and/or the secondary voltage according to the feedforward adjusting instruction and the feedback adjusting instruction, and realizing closed-loop automatic control of the wet electric dust collector.
Preferably, through wet-type electrostatic precipitator disturbance test, obtain the dynamic characteristic model, specifically include:
obtaining model parameters by adopting a test modeling method, and establishing a transfer function model of the secondary current of the high-frequency power supply of the wet electric dust remover to the smoke concentration of the wet electric dust removal outlet, wherein the model is selected from one of the following formulas (1) or (2):
in the formulae (1) and (2), C w (s) represents the concentration of smoke dust at the outlet of the wet electric precipitation; I.C. A w (s) represents the average value of the secondary currents of all the high-frequency power supplies of the wet electric dust collector; g w (s) represents an open-loop transfer function model of wet electrostatic precipitation, where s is the laplace operator; k, T 1 ，T 2 T, tau is the model parameter of the transfer function model, K is the transfer function gain, T 1 、T 2 T is an inertia time constant, and tau is a time lag constant.
Preferably, the operating parameters of the unit include a unit load; the operation parameters of the wet electric dust remover comprise secondary current and secondary voltage of the wet electric dust remover and smoke concentration at an electric dust removal outlet; the operation parameters of the dry type electric dust remover comprise the smoke concentration at the dry electric dust removal outlet.
Preferably, the solving of the feedforward adjustment instruction for adjusting the secondary current and/or the secondary voltage according to the operation parameters of the dry electric precipitator and the operation parameters of the wet electric precipitator specifically includes:
s301, collecting concentration signal y at electric dust removal outlet of dry dust collector d And outlet concentration signal y of electric dust remover of wet dust remover w (ii) a Outlet concentration y of dry electric dust collector d When the change is large and the wet electric dust collector runs under a stable working condition, the wet electric dust collector is subjected to test modeling to obtain a concentration signal y of an electric dust outlet of the dry type dust collector d Transfer function G to concentration interference d of wet-type electric precipitation outlet d The transfer function structure of which is
S302, according to a feedforward equation G ffd Realizing accurate feedforward compensation;
s303, adding G ffd And writing the transfer function equation into a control program of the application server, calculating the control action quantity of the electric field feedforward control link as a feedforward regulation instruction, and transmitting the control action quantity to the high-frequency power supply of the wet dust collector and the control system of the wet dust collector.
Preferably, said feed forward equation G ffd The specific equation is as follows:
situation one, when
Then
Situation two, when
Then
In general
Can also be selected as
The outlet concentration y of the dry electric dust collector at the front stage can be eliminated at the steady state d Concentration y of wet-type electric precipitation outlet w The interference generated;
in the formulae (3) and (4), G ffd Representing the feedforward adjustment transfer function, G d Representing the disturbance transfer function, G w Model representing transfer function of wet electric dust removal, K d K represents a gain constant, G w 、T 1 The expressions of T, s and τ are the same as those in the expressions (1) and (2), and T is d Representing the constant of inertia time, τ d Representing a time lag constant.
Preferably, the sending of the feedback adjustment instruction of the secondary current and/or the secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric precipitator specifically includes:
s401, collecting outlet concentration y of wet electric dust collector from high-frequency power supply of wet electric dust collector and control system of high-frequency power supply w Acquiring unit operation parameters from a unit main control DCS system by signals to obtain error items and errors y at the current moment r -calculating the controlled variable by means of a PID algorithm when the absolute value of y is greater than a set value; when error y r -when the absolute value of y is less than the set value, the feedback adjustment command remains unchanged at the current moment;
s402, determining a PID algorithm, and adaptively adjusting k in the PID algorithm by adopting a critical proportion method according to the unit operation parameters p 、k i 、k d Calculating to obtain a control quantity u (k); the PID algorithm comprises two schemes of an incremental PID algorithm and a position PID algorithm.
And S403, adjusting the control quantity u (k) through the amplitude limiting link to be used as a feedback adjustment instruction.
Preferably, the incremental PID algorithm specifically includes:
first, setting an initial value u (0) = k p e(0)+k i e(0)+k d ×0，
Second, to obtain
u(1)＝u(0)+Δu(1)
＝u(0)+k p [e(1)-e(0)]+k i e(1)+k d [e(1)-2e(0)+e(-1)],
Wherein the value of e (-1) is set to e (0);
thirdly, according to the values of e (0), e (1) and e (2), obtaining u (2) = u (1) + delta u (2); and the u (k) after the two steps is more than or equal to the two steps is solved according to e (k-2), e (k-1), e (k) and u (k-1).
The incremental PID algorithm is shown as the following formula:
Δu(k)＝u(k)-u(k-1)
＝k p [e(k)-e(k-1)]+k i T sam e(k)+k d /T sam [e(k)-2e(k-1)+e(k-2)] (4)
in the formula (4), k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Representing a differential coefficient with a proportional term P of k p [e(k)-e(k-1)]The integral term I is k i e (k), the differential term D is k d [e(k)-2e(k-1)+e(k-2)]，T sam Is the sampling time, u (k) represents the feedback control quantity of the k step, e (k) represents the systematic error term of the k step, and k represents the k time.
Preferably, the PID algorithm may also adopt a position-based PID algorithm, and the position-based PID algorithm specifically includes:
the position-based PID algorithm is shown as follows:
in the formula (5), k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Representing a differential coefficient, T sam Is the sampling time, u (k) represents the feedback control quantity of the k-th step, e (k) represents the systematic error term of the k-th step, and k represents the k-th time.
Preferably, the critical ratio method specifically includes:
according to the actual working condition, the wet-type electric precipitation control system is put into closed-loop operation, k i 、k d Are all set to 0, k is adjusted p The value of (1) is such that the concentration of the smoke dust at the outlet of the wet electric dust collector approaches critical oscillation, and then the critical proportion degree delta =1/k is obtained p Critical oscillation period T 1 ，T 1 The time for oscillating the smoke concentration output signal at the outlet of the wet electric dust collector back and forth once is adopted; according to delta, T 1 To set PID controller parameters, respectively k p ＝1.78δ，k i ＝0.5T 1 ，k d ＝0.125T 1 And further modifying according to the actual operation condition.
Compared with the prior art, the automatic control method for the wet-type electric precipitator of the thermal power generating unit adopts the control framework combining feedforward compensation and feedback regulation, can ensure better anti-interference capability and energy-saving effect, and realizes the closed-loop automatic control of the wet-type electric precipitator. The automatic control method for the wet electric precipitator of the thermal power generating unit comprises the following steps: obtaining a dynamic characteristic model through a wet electric precipitator disturbance test; respectively reading the operation parameters of the unit, the wet electric dust collector and the preceding stage dry electric dust collector; solving a feedforward adjusting instruction for adjusting the secondary current and/or the secondary voltage according to the operation parameters of the dry electric dust collector and the operation parameters of the wet electric dust collector; sending a feedback adjusting instruction of secondary current and/or secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric dust collector; and adjusting the secondary current and/or the secondary voltage according to the feedforward adjusting instruction and the feedback adjusting instruction, so as to realize closed-loop automatic control of the wet electric dust collector. The dust removal power consumption of a wet electric dust remover of the thermal power unit is reduced; a dynamic characteristic model of the wet electric dust collector is obtained based on a disturbance test, and on the basis, an automatic control method of the wet electric dust collector combining feedforward compensation and feedback regulation is provided, so that the problems that the system robustness is poor, the output smoke concentration oscillates and instantaneous standard exceeding occurs under the disturbance effects of large-range load variation of a unit, coal quality fluctuation, dry-electricity last-stage electrode vibration and the like are solved. And simultaneously, the energy-saving capability of the system is improved. Parameters required in modeling and control algorithms can be directly read from a main control DCS system or a power plant SIS system, expensive auxiliary equipment such as analysis or measuring instruments and the like is not required to be additionally arranged on site, and some power plants are considered to have no smoke dust measuring point at a dry-type electric precipitation outlet, and in this case, measuring equipment is only additionally arranged at the dry-type electric precipitation outlet, so that the cost is low.
Drawings
Fig. 1 is a schematic flow chart of an automatic control method for a wet-type electric precipitator of a thermal power generating unit according to an embodiment of the present invention;
FIG. 2 is a strategy block diagram of an automatic control method for a wet-type electric precipitator of a thermal power generating unit according to an embodiment of the invention;
fig. 3 is a specific system implementation structure diagram of the automatic control method for the wet-type electric precipitator of the thermal power generating unit according to the embodiment of the invention.
The figure shows that: the system comprises an operator station 1, an engineer station 2, an application server 3, a programmable logic controller 4, a dry-type electric dust collector high-frequency power supply and control system 5, a wet-type electric dust collector high-frequency power supply and control system 6, a redundant network 7, a serial port 8 and a serial port 9.
Detailed Description
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
As shown in fig. 1, an automatic control method for a wet electric precipitator of a thermal power generating unit according to an embodiment of the present invention includes the following steps:
s1, obtaining a dynamic characteristic model through a wet electric precipitator disturbance test;
s2, respectively reading the operation parameters of the unit, the wet electric dust collector and the preceding stage dry electric dust collector;
s3, calculating a feedforward adjusting instruction for adjusting secondary current and/or secondary voltage according to the operation parameters of the dry electric dust collector and the operation parameters of the wet electric dust collector;
s4, sending a feedback adjusting instruction of secondary current and/or secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric dust collector;
and S5, adjusting the secondary current and/or the secondary voltage according to the feedforward adjusting instruction and the feedback adjusting instruction, and realizing closed-loop automatic control of the wet-type electric dust collector.
The system comprises a set, a wet electric precipitator, a preceding stage dry electric precipitator, a disturbance experiment and a model, wherein the set, the wet electric precipitator and the preceding stage dry electric precipitator are operated according to the operation parameters, the disturbance experiment and the model are combined, the high-frequency power supply secondary current and/or secondary voltage of the wet electric precipitator are automatically adjusted, the outlet smoke concentration of the wet electric precipitator is smaller than a set value, the technical effect of reducing the energy consumption of electric precipitation is achieved, a control framework combining feed-forward compensation and feedback adjustment is adopted, the anti-interference capacity and the energy-saving effect are better, and the closed-loop automatic control of the wet electric precipitator is realized.
The step S3 and the step S4 correspond to an electric field feedforward control link and an electric field feedback control link of the wet electric dust remover respectively, and the two links are combined to form the wet electric dust removal automatic control method.
Fig. 2 shows the automatic control method for wet electric dust removal in the embodiment of the present disclosure, and describes the control structure of the automatic control method for wet electric dust removal. In FIG. 2, the electric field feedforward control link comprises the outlet concentration y of the dry electric dust collector d 、y d Transfer function G of concentration disturbance d of wet-type electric precipitation outlet d Feedforward equation G ffd . The electric field feedback control link comprises the outlet concentration y of the wet electric dust collector w Outlet concentration reference instruction y of wet electric precipitator r The device comprises a dead zone module, a PID algorithm module, an amplitude limiting value module and a master control working condition operation parameter. G w The model is identified according to the relevant data under the current working condition.
In the automatic control method for the wet electric precipitator of the thermal power generating unit according to the embodiment, preferably, the dynamic characteristic model is obtained through a disturbance test of the wet electric precipitator, and the method specifically includes:
obtaining model parameters by adopting a test modeling method, and establishing a transfer function model of the secondary current of the high-frequency power supply of the wet electric dust remover to the smoke concentration of the wet electric dust removal outlet, wherein the model is selected from one of the following formulas (1) or (2):
in the formulae (1) and (2), C w (s) represents the concentration of the smoke dust at the outlet of the wet electric dust removal; i is w (s) represents the average value of the secondary currents of all the high-frequency power supplies of the wet electric dust collector; g w (s) represents an open-loop transfer function model of wet electrostatic precipitation, where s is the laplacian operator; k, T 1 ，T 2 T, τ are model parameters of the transfer function model, K is the transfer function gain, T 1 、T 2 T is an inertia time constant, and τ is a time lag constant. In practice, either (1) or (2) is used as the model for recognition. The identification work content comprises two parts:
1. establishing a dynamic model Cw(s) of the wet electric dust collector under different operation conditions of a unit;
2. and carrying out parameter identification on the parameters of the K, T1, T2, T and tau model in the transfer function model, wherein the identification parameter interval is generally set as K belonged to < -1,1 >, T1 belonged to [0,100], T2 belonged to [0,100], T belonged to [0,100] and tau belonged to [1,35].
Preferably, the operating parameters of the unit include a unit load; the operation parameters of the wet electric dust remover comprise secondary current and secondary voltage of the wet electric dust remover and smoke concentration at an electric dust removal outlet; the operation parameters of the dry type electric dust remover comprise the smoke concentration at the dry electric dust removal outlet. And acquiring unit operation parameters from a unit main control DCS system and a power plant SIS system, wherein the unit operation parameters comprise unit load and the like. The operation parameters of the wet electric dust remover and the operation parameters of the dry electric dust remover can be read from a high-frequency power supply system of the wet electric dust remover and a high-frequency power supply system of the dry electric dust remover respectively.
Preferably, the calculating the feedforward adjustment instruction for adjusting the secondary current and/or the secondary voltage according to the operation parameters of the dry electric precipitator and the operation parameters of the wet electric precipitator specifically includes:
s301, collecting concentration signal y at electric dust removal outlet of dry dust collector d And outlet concentration signal y of electric dust collector of wet dust collector w (ii) a Outlet concentration y of dry electric dust collector d When the change is large and the wet electric dust collector runs under a stable working condition, the wet electric dust collector is subjected to test modeling to obtain a concentration signal y of an electric dust outlet of the dry type dust collector d Transfer function G to concentration interference d of wet-type electric precipitation outlet d The transfer function structure of which is
S302, according to a feedforward equation G ffd Realizing accurate feedforward compensation;
s303, adding G ffd The transfer function equation is written into a control program of the application server, and the control action quantity of the electric field feedforward control link is calculated and used as a feedforward adjusting instruction to be transferred to the high-frequency power supply of the wet dust collector and the control system of the wet dust collector.
In step S301, the high-frequency power of the dry dust collector and the outlet concentration y of the dry electric dust collector in the control system 5 are collected d Signal, high-frequency power supply of wet type dust collector and outlet concentration y of wet type electric dust collector in control system 6 of high-frequency power supply w Of the signal of (a). Ensuring the secondary current and the secondary voltage of the high-frequency power supply of the wet dust collector to be unchanged and ensuring the concentration y at the outlet of the dry electric dust collector d When a large range of variation (usually caused by final electric field rapping of dry electric dust collector) occurs, y is obtained by relevant identification method d Transfer function G of concentration disturbance d of wet-type electric precipitation outlet d ，G d The identified transfer function structure is
In step S303, G is added ffd The transfer function equation is set in the application server 3, the application server 3 calculates the control action amount of the electric field feedforward control link according to the steps, transmits the control action amount to the programmable logic controller 4, and finally instructs the control action amount to act on the wet dust collector high-frequency power supply and the control system 6 thereof to adjust the secondary current and/or the secondary current of the wet dust collector high-frequency power supplyAnd (4) secondary voltage. The electric field feedforward control link can effectively compensate the interference d on the outlet smoke concentration y of the wet electric dust collector w The influence of (c).
Preferably, the feed forward equation G ffd The specific equation is as follows:
situation one, when
Then
In the second case
Then
In general
Can also be selected as
The outlet concentration y of the dry electric dust collector at the front stage can be eliminated at the steady state d To wet type electric precipitation outlet concentration y w The interference generated;
in the formulae (3) and (4), G ffd Representing the feedforward adjustment transfer function, G d Representing the disturbance transfer function, G w Model representing transfer function of wet electric dust removal, K d K denotes a gain constant, G w 、T 1 The expressions of T, s and τ are the same as those in the expressions (1) and (2), and T is d Representing the constant of inertia time, τ d Representing a time lag constant.
Preferably, according to the operating parameters of the unit and the operating parameters of the wet-type electric dust collector, a feedback adjustment instruction of the secondary current and/or the secondary voltage is sent out, and the method specifically comprises the following steps:
s401, collecting outlet concentration y of wet electric dust collector from high-frequency power supply of wet electric dust collector and control system 6 of high-frequency power supply w Acquiring unit operation parameters from a unit main control DCS system by signals to obtain error items and errors y at the current moment r -calculating the controlled variable by means of a PID algorithm when the absolute value of y is greater than a set value; when error y r -when the absolute value of y is less than the set value, the feedback adjustment command remains unchanged at the current moment;
s402, determining a PID algorithm, and adaptively adjusting k in the PID algorithm by adopting a critical proportion method according to the unit operation parameters p 、k i 、k d Calculating to obtain a control quantity u (k); the PID algorithm comprises two schemes of an incremental PID algorithm and a position PID algorithm.
And S403, adjusting the control quantity u (k) through the amplitude limiting value link to serve as a feedback adjustment instruction.
In step S401, the setting value is usually a small setting value, such as 0.01; in step S402, a critical proportion method is adopted to set PID parameters, PID controller parameters under different working conditions are determined according to different unit operating conditions and the critical proportion method, the PID controller parameters are written into a PID controller, and the purpose that a system adaptively adjusts the PID parameter k according to the main control DCS unit operating parameters is achieved p 、k i 、k d . In step S403, in consideration of the characteristics of the wet-type electric dust removal high-frequency power supply, the lower or higher secondary current is not favorable for the long-term operation of the high-frequency power supply, so that the amplitude limiting value is required to be performed, the control amount is adjusted, and the lower or higher secondary current is not favorable for the long-term operation of the high-frequency power supply according to the characteristics of the wet-type electric dust removal high-frequency power supply, and the lower limit and the upper limit of the amplitude limiting value are set to 150mA and 800mA respectively.
Preferably, the incremental PID algorithm specifically includes:
in the first step, an initial value u (0) = k is set p e(0)+k i e(0)+k d ×0，
Second, to obtain
u(1)＝u(0)+Δu(1)
＝u(0)+k p [e(1)-e(0)]+k i e(1)+k d [e(1)-2e(0)+e(-1)],
Wherein the value of e (-1) is set to e (0);
thirdly, according to the values of e (0), e (1) and e (2), obtaining u (2) = u (1) + delta u (2); and the u (k) after the two steps is more than or equal to the two steps is solved according to e (k-2), e (k-1), e (k) and u (k-1).
The incremental PID algorithm is shown as the following formula:
Δu(k)＝u(k)-u(k-1)
＝k p [e(k)-e(k-1)]+k i T sam e(k)+k d /T sam [e(k)-2e(k-1)+e(k-2)] (4)
in the formula (4), k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Representing a differential coefficient, the proportional term P being k p [e(k)-e(k-1)]The integral term I is k i e (k), the differential term D is k d [e(k)-2e(k-1)+e(k-2)]，T sam Is the sampling time because of the T of the electric dust removal control system sam Often set to 1, and also set to 1 herein, simplifying the formulation; u (k) represents the feedback control amount in the k-th step, e (k) represents the systematic error term in the k-th step, and k represents the k-th time.
The incremental PID algorithm only takes values at nearly three moments in execution, and has the advantages of small occupied memory, small calculated amount and the like.
Preferably, the PID algorithm may also adopt a position PID algorithm, and the position PID algorithm specifically includes:
the position-based PID algorithm is shown as follows:
in the formula (5), k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Represents a differential coefficient, T sam Is the sampling time, u (k) represents the feedback control quantity of the k step, e (k) represents the systematic error term of the k step, and k represents the k time.
According to the actual working condition, a position type PID algorithm can be adopted, and the position type PID algorithm has better grasp on a proportional term, an integral term and a differential term of the control action.
Preferably, the critical ratio method specifically includes:
according to the actual working condition, the wet-type electric precipitation control system is put into closed-loop operation, k i 、k d Are all set to 0, k is adjusted p The value of (2) is that the concentration of the smoke dust at the outlet of the wet electric precipitator is close to critical oscillation, and then the critical proportion delta =1/k is obtained p Critical oscillation period T 1 ，T 1 The time for oscillating the smoke concentration output signal at the outlet of the wet electric dust collector back and forth once is adopted; according to delta, T 1 To set PID controller parameters, respectively k p ＝1.78δ，k i ＝0.5T 1 ，k d ＝0.125T 1 And further modifying according to the actual operation condition. And determining PID controller parameters under different working conditions according to the method under different unit operating conditions, and writing the parameters into the application server 3 to realize that the system adaptively adjusts the PID parameter k according to the main control DCS unit operating parameters p 、k i 、k d 。
Compared with the prior art, the automatic control method for the wet-type electric precipitator of the thermal power unit can reduce the electric consumption for dust removal of the wet-type electric precipitator of the thermal power unit; a dynamic characteristic model of the wet electric dust collector is obtained based on a disturbance test, and on the basis, an automatic control method of the wet electric dust collector combining feedforward compensation and feedback regulation is provided, so that the problems that the system robustness is poor, the output smoke concentration oscillates and instantaneous standard exceeding occurs under the disturbance effects of large-range load variation of a unit, coal quality fluctuation, dry-electricity last-stage electrode vibration and the like are solved. And meanwhile, the energy-saving capability of the system is improved. Parameters required in modeling and control algorithms can be directly read from a main control DCS system or a power plant SIS system, expensive auxiliary equipment such as analysis or measuring instruments and the like is not required to be additionally arranged on the site, and some power plants are considered to have no smoke dust measuring points at a dry electric dust removal outlet, and in the case, measuring equipment is additionally arranged at the dry electric dust removal outlet, so that the cost is low.
According to the embodiment of the invention, as shown in fig. 3, the hardware structure mainly used for implementation is operator station 1, engineer station 2, application server 3, programmable logic controller 4, dry dust collector high-frequency power supply and its control system 5, and wet dust collector high-frequency power supply and its control system 6. The programmable logic controller 4 comprises the link for acquiring the dynamic characteristic model of the wet electric precipitator, the link for acquiring the operating parameters of the thermal power unit and the link for acquiring the operating parameters of the dry and wet electric precipitators. The operation parameters are specifically acquired from a DCS or SIS system through communication modes such as OPC, modbus and the like. The acquired data is used by an automatic control system of the wet electric dust remover after being filtered. The application server 3 comprises the electric field feedforward optimization control link and the electric field feedback optimization control link. Specifically, the programmable logic controller 4 is connected to the unit main control DCS system and the application server 3 so that the application server 3 obtains unit operation data from the unit main control DCS system through the programmable logic controller 4, and meanwhile, the programmable logic controller 4 is connected to the dry dust collector high-frequency power supply and its control system 5 and the wet dust collector high-frequency power supply and its control system 6 so that the application server 3 obtains dry and wet high-frequency power supply operation data from the dry dust collector system 5 and the wet dust collector system 6 through the programmable logic controller 4 and sends control instructions to the wet dust collector high-frequency power supply and its control system 6. Therefore, the application server 3 can simultaneously acquire the unit operation data and the operation data of the dry-wet electric dust removal high-frequency power supply and the wet-wet electric dust removal high-frequency power supply and calculate a control instruction, and the control instruction is transmitted to the wet-wet electric dust removal high-frequency power supply and the control system 6 thereof through the programmable logic controller 4 so as to be put into an automatic operation mode.
More specifically, the wet type electric dust collector high-frequency power supply and the control system 6 thereof comprise a wet type electric dust collector high-frequency power supply control system and a wet type electric dust collector high-frequency power supply which are connected with each other, and the programmable logic controller 4 is connected with the dry type electric dust collector high-frequency power supply control system and the wet type electric dust collector high-frequency power supply control system. The programmable logic controller 4 respectively controls the DCS system, the dry-type electric dust removal high-frequency power supply operation data and the wet-type electric dust removal high-frequency power supply operation data from the unit and transmits the data to the application server 3 through the redundant network 7, and on one hand, the application server 3 calculates an electric field feedback control instruction of the wet-type electric dust remover according to the unit operation data and the wet-type electric dust removal high-frequency power supply operation data. On the other hand, the application server 3 calculates an electric field feedforward instruction of the wet electric dust collector according to the operation data of the dry electric dust collection high-frequency power supply and the operation data of the wet electric dust collection high-frequency power supply, so that the wet electric dust collector is subjected to comprehensive control of feedforward compensation and feedback adjustment. The automatic control system of the wet electric dust collector can better inhibit interference caused by the rapping of a dry electric final-stage electric field, enhance the anti-interference capability and instantaneous regulation performance of the system and have better energy-saving effect. In addition, the system can have a certain adaptive adjustment capability so as to realize adaptive adjustment of large-range variable load.
In addition, in the aspect of communication implementation, the operator station 1, the engineer station 2, the application server 3 and the programmable controller 4 are all connected to the redundant network 7, and the operator station 1, the engineer station 2, the application server 3 and the programmable controller 4 all perform information interaction through the redundant network 7. And the redundant network 7 here is preferably an ethernet network. Furthermore, the wet electric dust collector high-frequency power supply and the control system 6 thereof are in communication connection with the programmable logic controller 4 through the serial port 8 and the hard connecting line of the serial port 8. The dry-type electric dust collector high-frequency power supply and the control system 5 thereof are in communication connection with the programmable logic controller 4 through the serial port 9 and the hard connecting wires of the serial port 9. In addition, the programmable logic controller 4 is also connected with the unit main control DCS system through a serial port 8.
The embodiments described herein are merely illustrative of the spirit of the present invention, and provide an automatic control system framework for a wet electric dust collector, which is composed of a field feed-forward control unit and a field feedback control unit. Various modifications or additions may be made or substituted in a similar manner to the embodiments described herein by those skilled in the art, for example, the feedback loop may replace the PID control with a PI controller and the feedforward loop may replace the disturbance observer without departing from the spirit of the invention, which is either directly or indirectly connected, or beyond the scope of the invention as defined in the appended claims. Although the terms operator station 1, engineer station 2, application server 3, programmable logic controller 4, dry electrostatic precipitator high frequency power supply and its control 5, wet electrostatic precipitator high frequency power supply and its control 6, redundant net 7, serial port 8 and serial port 9 are used much here, the possibility of using other terms is not excluded. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed as being without limitation to the spirit of the present invention.
The embodiments of the present invention are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. That is, all equivalent changes and modifications made according to the content of the claims of the present invention should be regarded as the technical scope of the present invention.
Claims (8)
1. The automatic control method for the wet electric precipitator of the thermal power generating unit is characterized by comprising the following steps of:
s1, obtaining a dynamic characteristic model through a disturbance test of a wet electric precipitator;
s2, respectively reading the operation parameters of the unit, the wet electric dust collector and the preceding stage dry electric dust collector;
s3, solving a feedforward adjusting instruction for adjusting secondary current and/or secondary voltage according to the operation parameters of the dry electric dust collector and the operation parameters of the wet electric dust collector;
s4, sending a feedback adjusting instruction of secondary current and/or secondary voltage according to the operation parameters of the unit and the operation parameters of the wet electric dust collector;
s5, adjusting the secondary current and/or the secondary voltage according to the feedforward adjusting instruction and the feedback adjusting instruction, and realizing closed-loop automatic control of the wet electric dust collector;
according to the operating parameter of dry-type electrostatic precipitator and the operating parameter of wet-type electrostatic precipitator, solve and calculate the feedforward adjustment instruction of adjusting secondary current and/or secondary voltage, specifically include:
s301, collecting concentration signal y at electric dust removal outlet of dry dust collector d And outlet concentration signal y of electric dust collector of wet dust collector w (ii) a Outlet concentration y of dry electric dust collector d Large scale of occurrenceWhen the wet electric dust collector operates under a stable working condition, the concentration signal y of the electric dust outlet of the dry type dust collector is obtained by carrying out test modeling on the wet electric dust collector d Transfer function G to concentration interference d of wet-type electric precipitation outlet d The transfer function structure of which is
S302, according to a feedforward equation G ffd Realizing accurate feedforward compensation;
s303, adding G ffd The transfer function equation is written into a control program of the application server, and the control action quantity of the electric field feedforward control link is calculated and used as a feedforward adjusting instruction to be transferred to the high-frequency power supply of the wet dust collector and the control system of the wet dust collector.
2. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 1, wherein the dynamic characteristic model is obtained through a disturbance test of the wet-type electric precipitator, and the method specifically comprises the following steps:
obtaining model parameters by adopting a test modeling method, and establishing a transfer function model of the secondary current of the high-frequency power supply of the wet electric dust remover to the smoke concentration of the wet electric dust removal outlet, wherein the model is selected from one of the following formulas (1) or (2):
in the formulae (1) and (2), C w (s) represents the concentration of smoke dust at the outlet of the wet electric precipitation; I.C. A w (s) represents the average value of the secondary currents of all the high-frequency power supplies of the wet electric dust collector; g w (s) represents an open-loop transfer function model of wet electrostatic precipitation, where s is the laplacian operator; k, T 1 ，T 2 T, τ being the modulus of the model of the transfer functionType parameter, K is the transfer function gain, T 1 、T 2 T is an inertia time constant, and tau is a time lag constant.
3. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 1, wherein the operation parameters of the thermal power generating unit comprise unit load; the operation parameters of the wet electric dust remover comprise secondary current and secondary voltage of the wet electric dust remover and smoke concentration at an electric dust removal outlet; the operation parameters of the dry type electric dust remover comprise the smoke concentration at the dry electric dust removal outlet.
4. The automatic control method for wet-type electric precipitator of thermal power generating unit according to claim 1, wherein the feedforward equation G ffd The specific equation is as follows:
situation one, when
Then the
In the second case
Then
In general
Can also be selected as
The outlet concentration y of the dry electric dust collector at the front stage can be eliminated at the steady state d Concentration y of wet-type electric precipitation outlet w The interference generated;
in the formulae (3) and (4), G ffd Representing the feed-forward regulation transfer function, G d Representing the disturbance transfer function, G w Model representing transfer function of wet electric dust removal, K d K represents a gain constant, G w 、T 1 The expressions of T, s and τ are the same as those in the expressions (1) and (2), and T is d Representing the constant of inertia time, τ d Representing a time lag constant.
5. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 1, wherein the feedback adjusting instruction for the secondary current and/or the secondary voltage is sent according to the operation parameters of the thermal power generating unit and the operation parameters of the wet-type electric precipitator, and specifically comprises the following steps:
s401, collecting outlet concentration y of wet electric dust collector from high-frequency power supply of wet electric dust collector and control system of high-frequency power supply w Acquiring unit operation parameters from a unit main control DCS (distributed control System) by using signals to obtain error items and errors y at the current moment r -calculating the controlled variable by means of a PID algorithm when the absolute value of y is greater than a set value; when error y r -when the absolute value of y is less than the set value, the feedback adjustment command remains unchanged at the current moment;
s402, determining a PID algorithm, and adaptively adjusting k in the PID algorithm by adopting a critical proportion method according to the unit operation parameters p 、k i 、k d Calculating to obtain a control quantity u (k); the PID algorithm comprises two schemes of an incremental PID algorithm and a position PID algorithm;
and S403, adjusting the control quantity u (k) through the amplitude limiting link to be used as a feedback adjustment instruction.
6. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 5, wherein the incremental PID algorithm specifically comprises:
in the first step, an initial value u (0) = k is set p e(0)+k i e(0)+k d ×0，
Second, obtain
u(1)＝u(0)+Δu(1)
＝u(0)+k p [e(1)-e(0)]+k i e(1)+k d [e(1)-2e(0)+e(-1)],
Wherein the value of e (-1) is set to e (0);
a third step of obtaining u (2) = u (1) + Δ u (2) from the values of e (0), e (1) and e (2); solving u (k) after more than or equal to two steps according to e (k-2), e (k-1), e (k) and u (k-1); the incremental PID algorithm is shown as the following formula:
Δu(k)＝u(k)-u(k-1)
＝k p [e(k)-e(k-1)]+k i T sam e(k)+k d /T sam [e(k)-2e(k-1)+e(k-2)]
in the formula, k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Representing a differential coefficient, the proportional term P being k p [e(k)-e(k-1)]The integral term I is k i e (k), the differential term D is k d [e(k)-2e(k-1)+e(k-2)]，T sam Is the sampling time, u (k) represents the feedback control quantity of the k-th step, e (k) represents the systematic error term of the k-th step, and k represents the k-th time.
7. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 5, wherein the PID algorithm can also adopt a position PID algorithm, and the position PID algorithm specifically comprises:
the position-based PID algorithm is shown as follows:
in the formula (5), k p Denotes the proportionality coefficient, k i Representing the integral coefficient, k d Represents a differential coefficient, T sam Is the sampling time, u (k) represents the feedback control quantity of the k step, e (k) represents the systematic error term of the k step, and k represents the k time.
8. The automatic control method for the wet-type electric precipitator of the thermal power generating unit according to claim 5, wherein the critical proportion method specifically comprises the following steps:
according to the actual working condition, the wet-type electric precipitation control system is put into closed-loop operation, k i 、k d Are all set to 0, k is adjusted p The value of (2) is that the concentration of the smoke dust at the outlet of the wet electric precipitator is close to critical oscillation, and then the critical proportion delta =1/k is obtained p Critical oscillation period T 1 ，T 1 The time for the smoke concentration output signal at the outlet of the wet electric dust collector to oscillate back and forth once is used; according to delta, T 1 To set PID controller parameters, respectively k p ＝1.78δ，k i ＝0.5T 1 ，k d ＝0.125T 1 And further modifying according to the actual operation condition.
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