Simplified model suitable for thermal power coordination control simulation verification

Abstract

The invention discloses a simplified model suitable for thermal power coordination control simulation verification, which successfully builds a coordination system simulation model for DCS (Distributed Control System) transformation by adopting a simplified two-input and two-output system taking total coal quantity mu b and steam turbine regulating valve opening mu t as inputs and taking main steam pressure Pst and unit power Ne as outputs. The coordination simulation control model can be built and adjusted relatively simply, the precision of the model meets variable load control logic and RB control logic for verifying a coordination control system in DCS transformation, the model can well serve DCS transformation, and the coordination logic reliability of DCS transformation is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of automatic control of thermal power units, and in particular relates to a simplified model suitable for simulation verification of thermal power coordinated control. Background Art

[0002] Each system of the thermal power unit is controlled in real time by a distributed control system (DCS).

[0003] While domestic DCS technology is maturing, some in-service DCS equipment is aging, leading to a surge in domestic DCS upgrades. Compared to new units, DCS retrofit projects are shorter and require greater logic translation and verification. While digital control systems can be verified through interlocking protection sheets, analog control systems, particularly coordinated control systems, involve the most crucial load commands, boiler commands, turbine commands, fuel commands, feedwater commands, and air volume commands for thermal power unit automation. These commands require system simulation for robust logic verification.

[0004] For single-loop analog control systems, a simple "command-feedback" model can be used for simulation. However, a coordinated control system is a relatively complex multivariable coupled system, the core of which lies in the coordination between the boiler and turbine sides. On the boiler side, the air volume, coal volume, and feedwater volume must be precisely matched: the coal volume determines the boiler load and must be properly proportioned with the primary and secondary air volumes to ensure adequate combustion; the feedwater volume must be matched to the coal volume to maintain the appropriate steam temperature. On the turbine side, the regulating valve opening controls the steam inlet flow, directly affecting the main steam pressure and generator power.

[0005] The industry is currently developing a mature model for coordinated model control systems. Current modeling methods are categorized into two types based on unit model usage. The first type is used for simulation research, operator training, and control algorithm performance evaluation. These simulation models are more comprehensive and typically employ more complex modeling methods. The second type is used for control system optimization and control algorithm design. These models reflect the unit's key dynamic characteristics and can be simple or complex depending on verification requirements.

[0006] However, even in the simplified form of the second method, its primary application is control optimization, so various optimization algorithms are used to achieve model accuracy. This results in a complex and difficult model. Furthermore, parameter optimization must be performed separately for each unit, making this process relatively difficult.

[0007] In addition, from the perspective of simplifying the simulation system, the simulation logic should be built in the DCS system. This also requires the simulation logic to be as simple as possible to facilitate the use of existing function blocks in the DCS to achieve coordinated simulation functions.

[0008] Considering the short duration of maintenance and DCS transformation, there is not much time for complex modeling. Therefore, a coordination model with simple and convenient modeling, easy parameter adjustment, and strong versatility is needed to verify the correctness of the coordinated control model. This model can relatively sacrifice modeling accuracy.

[0009] Therefore, in order to simulate and verify the coordination logic in the DCS transformation project to ensure the reliability of the coordination logic and the smooth completion of the DCS transformation, it is urgent to invent a coordination model that is easy to build in the DCS system, simple and convenient, highly versatile, and easy to adjust parameters. Summary of the Invention

[0010] Aiming at the problems that existing coordination models are difficult to model, not easy to implement in DCS, and cannot meet the needs of DCS transformation, the present invention provides a simplified model method suitable for simulation verification of thermal power coordinated control. Based on the simplified coordination model, the coordination logic is simulated and verified in the DCS transformation project to ensure the reliability of the coordination logic and the smooth completion of the DCS transformation.

[0011] In order to achieve the above object, the technical solution adopted by the present invention is:

[0012] A simplified model suitable for simulation verification of thermal power coordinated control, wherein the model construction method comprises the following steps:

[0013] S1: Construct a 2-input 2-output system with total coal quantity μb and turbine regulating valve opening μt as inputs and main steam pressure Pst and unit power Ne as outputs;

[0014] S2: Implement the coordination model framework based on DCS and perform parameter tuning;

[0015] S3: Carry out variable load simulation test and RUNBACK (auxiliary machine failure load reduction) test to verify the usability of the simulation model.

[0016] Furthermore, the coordination model framework is implemented in the DCS system in step S2, specifically: building a coordination model in the DCS system,

[0017] (1) The simulated unit load Ne increases with the increase of the turbine control valve opening μt and the main steam pressure Pst, as shown in the following formula:

[0018] Ne=P st ·K4·K2·μt

[0019] Where K2 is the steam flow conversion coefficient, and K4 is the steam pressure conversion coefficient;

[0020] (2) When the unit load Ne and the fuel quantity μb are unbalanced, the boiler energy is generated by cumulative integration and then converted into the steam pressure simulation value, as shown in the following formula:

[0021]

[0022] Among them, K3 is the boiler response speed, K1 is the coal calorific value coefficient, and K4 is the steam pressure conversion coefficient;

[0023] Furthermore, in step S2, the parameter setting is specifically as follows:

[0024] According to the unit parameters of the simulated power plant, the model parameters are adjusted:

[0025] (1) A1, output saturation upper limit; according to the maximum load of the unit, add a certain margin as the saturation upper limit;

[0026] (2) K1, coal calorific value coefficient; Among them F n is the coal quantity at full load, P n is the rated power of the unit;

[0027] (3) K2, steam flow conversion coefficient; where μt n For the best comprehensive valve position, it can be set to about 0.7;

[0028] (4) K3, boiler response coefficient; when the unit load and fuel are unbalanced, the steam pressure changes after integration. K3 is proportional to the boiler response speed. The empirical parameter is 0.03 and can be adjusted according to the commissioning needs;

[0029] (5) K4, steam pressure conversion coefficient; Where Tn is the full load main steam pressure, P n is the rated power of the unit;

[0030] When the initial parameters are set, fine-tune the parameters according to the actual simulation situation.

[0031] Furthermore, the model also includes an initialization loop for investment and withdrawal, adding an intermediate variable "coordinated simulation". When the simulation is put into operation, the "coordinated simulation" is set to 1; when the simulation is not put into operation, that is, when the "coordinated simulation" is 0, the integral output is switched to 0.

[0032] Furthermore, the model includes an anti-saturation circuit that adds a certain margin as a saturation upper limit based on the maximum load of the unit. When the integral output deviates from the saturation upper limit A1 by more than 10, a 3-second pulse is sent to switch back to the integral upper limit A1.

[0033] Furthermore, the model also includes simulation switching logic; when the simulation is put into operation, the simulated unit power and simulated main steam pressure output by the model are assigned to the unit power and main steam pressure in the DCS logic.

[0034] Furthermore, based on the conventional simulation loop design method, in addition to using simulation coordination models for unit power and steam pressure, the air supply and water supply instructions are assigned to feedback through a certain inertia to form a coordinated simulation control loop.

[0035] Furthermore, the DCS configuration controller is placed in simulation state, and the controller is compiled and downloaded.

[0036] Furthermore, the coordination simulation switch was turned on, the unit was adjusted to the coordination mode, and load swing test and RUNBACK test were carried out.

[0037] The technical solution of the present invention has the following beneficial effects:

[0038] The present invention adopts a simplified two-input two-output system with total coal quantity μb and turbine valve opening μt as input and main steam pressure Pst and unit power Ne as output, and successfully builds a coordinated system simulation model for DCS transformation. The basic framework diagram of coordinated simulation in DCS transformation is shown in the following figure. Figure 4 .

[0039] Based on this framework, a simplified coordination model can be quickly built, model parameters adjusted, and used to verify variable load test logic and unit RUNBACK (auxiliary unit failure load reduction, abbreviated as RB) test logic. This effectively solves the problem of difficult coordinated control system simulation during DCS transformation and improves the reliability of coordination logic during DCS transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a simplified structural diagram of a thermal power generator unit according to the present invention;

[0041] Figure 2 This is a simplified structural diagram of the thermal power generator unit coordination system model;

[0042] Figure 3 A simplified coordination simulation model for coordination logic verification;

[0043] Figure 4 Schematic diagram of the basic framework of coordinated simulation in DCS transformation of the present invention;

[0044] Figure 5 This is the coordination simulation model based on the central control DCS of the present invention;

[0045] Figure 6 This is a simulation of the variable load test of the present invention; in the figure: 1-unit target load 2-load instruction after speed limit 3-unit power 4-steam pressure target value after speed limit 5-steam pressure target value 6-main steam pressure 7-boiler instruction 8-total coal quantity 9-total water quantity 10-total air volume 11-turbine valve control instruction;

[0046] Figure 7 This is a simulation of the primary fan RB test of the present invention; in the figure: 1-unit target load 2-load instruction after speed limit 3-unit power 4-steam pressure target value after speed limit 5-steam pressure target value 6-main steam pressure 7-boiler instruction 8-total coal quantity 9-total water quantity 10-total air volume 11-steam turbine valve control order. DETAILED DESCRIPTION

[0047] To make the objectives, technical solutions, and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other implementations obtained by those of ordinary skill in the art without inventive effort are within the scope of protection of the present invention.

[0048] The simplified structure of a direct current boiler is as follows Figure 1 As shown, the mainstream once-through boiler coordination model constructs a three-input, three-output coordination model with total coal quantity μb, total water quantity Dfw, and turbine throttle opening μt as inputs, and unit power Ne, main steam pressure Pst, and intermediate point enthalpy hsep as outputs. Based on the conservation of energy and mass, and assuming that the mass change rate and energy change rate at each state point in the working fluid flow remain constant in proportion to the total mass change rate and energy change rate throughout the entire process, independent of unit load, a state equation is established. The model parameters are then dynamically optimized using unit data and advanced algorithms.

[0049] The model has complex parameters, difficult parameter optimization, and many nonlinear links. It is not convenient to build in DCS and is not suitable for lightweight use in DCS transformation.

[0050] Therefore, the coordination model of thermal power units is further simplified. Since steam temperature and feed water are relatively independent, the coordination model of thermal power units is further simplified into a 2-input 2-output system with total coal quantity μb and turbine control valve opening μt as input, and main steam pressure Pst and unit power Ne as output. This simplified model has a clear physical meaning: the total coal quantity, as the dominant variable of energy input on the boiler side, can drive the air volume and feed water volume to follow proportionally; the control valve opening is a direct means of controlling steam flow on the turbine side. Among the output variables, the main steam pressure reflects the balance between boiler steam production and turbine steam consumption, and the unit power is the ultimate control target of the system. This simplified model not only retains the basic characteristics of boiler-turbine coordination, but also highlights the core control requirements of the system, such as Figure 2 shown.

[0051] Implement the coordination model framework based on DCS and perform parameter tuning. Conduct variable load simulation tests to verify the reliability of the simulation model.

[0052] The specific implementation steps of the present invention are as follows:

[0053] (1) Build a coordination model in the DCS system, and the simulation model is as follows Figure 3 shown

[0054] a) The simulated unit load Ne increases with the increase of the turbine control valve opening μt and the main steam pressure Pst, where K2 is the steam flow conversion coefficient and K4 is the steam pressure conversion coefficient.

[0055] Ne=P st ·K4·K2·μt

[0056] b) When the unit load Ne is unbalanced with the fuel quantity μb, the boiler energy is generated by cumulative integration and then converted into the steam pressure simulation quantity, where K3 is the boiler corresponding speed, K1 is the coal calorific value coefficient, and K4 is the steam pressure conversion coefficient.

[0057]

[0058] c) Designed the initialization circuit for simulated deployment and withdrawal.

[0059] d) A steam pressure anti-saturation circuit is designed.

[0060] (2) Adjust the model parameters according to the unit parameters of the simulated power plant

[0061] a) A1, output saturation upper limit. Based on the unit's maximum load, add a certain margin as protection. For example, for a 660MW unit, A1 can be set to 700.

[0062] b) K1, coal calorific value coefficient. Among them F n is the coal quantity at full load, P n is the rated power of the unit.

[0063] c) K2, steam flow conversion coefficient. where μt n It is the best comprehensive valve position.

[0064] d) K3, boiler response coefficient. When the unit load and fuel are unbalanced, the steam pressure changes after integration. The empirical parameter of K3 is 0.03 and can be adjusted according to the commissioning needs.

[0065] e) K4, steam pressure conversion coefficient. Where Tn is the full load main steam pressure, P n is the rated power of the unit.

[0066] f) When the initial parameters are set, fine-tune the parameters according to the actual simulation situation. (3) Based on the conventional simulation loop design method, in addition to using the simulation coordination model for the unit power and steam pressure, the air supply and water supply instructions are assigned to the feedback through a certain inertia to form a coordinated simulation control loop.

[0067] The basic framework diagram of the coordinated simulation in the final DCS transformation is shown in Figure 5 .

[0068] The main structure of the system of the present invention is as follows Figure 4 As shown in the figure, the coordinated modeling part of the main part is shown in Figure 3 .

[0069] A 660MW supercritical thermal power unit was retrofitted with a DCS system from SUPCON. A coordinated simulation control system was built in the SUPCON DCS system. Figure 5 shown.

[0070] Adjust each parameter and finally determine the parameters as follows:

[0071] A1=700, K1=2.6, K2=0.012, K3=0.03, K4=25.

[0072] On this basis, a coordinated simulation control system is built to carry out the load-changing process, such as Figure 6 As shown in the figure, with the controller in simulation mode and the unit in coordinated mode, during the variable load test simulation, the load command increased from 500MW to 550MW. After the unit power was fully reached, the load command decreased from 550MW to 500MW, with a load increase and decrease rate of 12MW / min. During the variable load test, the changing trends of coal flow, air supply, and feedwater, as well as the final control of unit power and steam pressure, met the logical design requirements, demonstrating the model's usability in simulating variable load conditions.

[0073] On this basis, RUNBACK (auxiliary machine failure load reduction) logic verification is carried out, taking a fan RB test as an example. Figure 7 As shown in the figure, the controller is in simulation mode, the unit is in coordinated mode, the unit load is 600MW, and both primary fans are running. At this time, one primary fan is shut down, the primary fan RB is triggered, the target load is 330MW, the RB rate is 120% / min, and the steam pressure drop rate is 1.8MPa / min.

[0074] Ultimately, the RB-related logic operated correctly, the RB target and rate met requirements, and the unit parameters remained relatively stable, successfully verifying the correctness of the primary fan RB circuit. RB testing is a risky component of thermal control testing during DCS retrofits. Using a simplified coordination model effectively facilitates the completion of RB static testing, significantly contributing to improving unit safety during DCS retrofits.

[0075] Based on the above simulation applications, this coordinated simulation control model is relatively simple to build and adjust, and its accuracy meets the requirements for verifying the variable load control logic and RB control logic of the coordinated control system during DCS transformation. This model can effectively serve DCS transformation and improve the reliability of the coordinated logic.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A simplified model suitable for simulation verification of thermal power coordinated control, characterized in that: The method for constructing the model comprises the following steps: S1: Construct a two-input and two-output system with the total coal quantity μb and the turbine regulating valve opening μt as inputs and the main steam pressure Pst and the unit power Ne as outputs; S2: Implement the coordination model framework based on DCS and perform parameter tuning; S3: Carry out variable load simulation test and RUNBACK (auxiliary machine failure load reduction) test to verify the usability of the simulation model.

2. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 1, characterized in that: The step S2 implements the coordination model framework in the DCS system, specifically: building a coordination model in the DCS system, (1) The simulated unit load Ne increases with the increase of the turbine control valve opening μt and the main steam pressure Pst, as shown in the following formula: Ne=P st ·K4·K2·μt Where K2 is the steam flow conversion coefficient, and K4 is the steam pressure conversion coefficient; (2) When the unit load Ne and the fuel quantity μb are unbalanced, the boiler energy is generated by cumulative integration and then converted into the steam pressure simulation value, as shown in the following formula: Among them, K3 is the boiler response speed, K1 is the coal calorific value coefficient, and K4 is the steam pressure conversion coefficient.

3. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 1, characterized in that: In step S2, the parameter setting is specifically as follows: According to the unit parameters of the simulated power plant, the model parameters are adjusted: (1) A1, output saturation upper limit; according to the maximum load of the unit, add a certain margin as the saturation upper limit; (2) K1, coal calorific value coefficient; Among them F n is the coal quantity at full load, P n is the rated power of the unit; (3) K2, steam flow conversion coefficient; where μt n For the best comprehensive valve position, it can be set to about 0.7; (4) K3, boiler response coefficient; when the unit load and fuel are unbalanced, the steam pressure changes after integration. K3 is proportional to the boiler response speed. The empirical parameter is 0.03 and can be adjusted according to the commissioning needs; (5) K4, steam pressure conversion coefficient; Where Tn is the full load main steam pressure, P n is the rated power of the unit; When the initial parameters are set, fine-tune the parameters according to the actual simulation situation.

4. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 1, characterized in that: The model also includes an initialization loop for activation and deactivation, which adds an intermediate variable "coordinated simulation". When the simulation is activated, "coordinated simulation" is set to 1; when the simulation is not activated, that is, when "coordinated simulation" is 0, the integral is output.

5. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 1, characterized in that: The model also includes an anti-saturation circuit; according to the maximum load of the unit, a certain margin is added as the saturation upper limit; when the integral output, that is, the integral output deviates from the saturation upper limit by more than 10, a 3-second pulse is sent to switch the integral output back to the integral upper limit.

6. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 1, characterized in that: The model also includes simulation switching logic; when the simulation is put into operation, the simulated unit power and simulated main steam pressure output by the model are assigned to the unit power and main steam pressure in the DCS logic.

7. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 2, characterized in that: Based on the conventional simulation loop design method, in addition to the simulation coordination model for unit power and steam pressure, the air supply and water supply instructions are assigned to the feedback through a certain inertia to form a coordinated simulation control loop.

8. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 2, characterized in that: Place the DCS configuration controller in simulation state and compile and download the controller.

9. A simplified model suitable for simulation verification of thermal power coordinated control according to claim 2, characterized in that: Turn on the coordination simulation switch, adjust the unit to the coordination mode, and conduct load swing test and RUNBACK test.

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